[1]

1COMPANY PROFILE

Leader in Manufacturing Process Steam amp Power Generation Equipment Cheema Boilers Limited popularly known as CBL is a trusted name in the field of Indian Boiler Industry It is known for its commitment competence and compliance CBL was established in the year 1999 to provide complete solution to steam generation needs Its visionary Mr Harjinder Singh Cheema currently CBL Managing Director along with his three brothers now CBL Directors started this company with Boiler services and very soon CBL moved to manufacturing of full-fledged Process Boilers

CBL has got its own manufacturing facilities at Kurali 25 kms from Chandigarh near Ropar and Corporate Office at Mohali (Chandigarh)

11 PRODUCTS OF CHEEMA BOILERS

112 Deaerator

They have developed a very effective multinozzles deaeration system to remove the oxygen from feed water and feed the water 130 degree celsius to boiler feed pump

113 AFBC Boilers

INPAC OIL PAC ENERGY PAC HYPAC BOILERS

2 INTRODUCTION OF BOILERS

A steam generator or boiler is usually a closed vessel made of steel Its function is to transfer the heat produced by the combustion of fuel to water the ultimately to generate the steam

21 TYPE OF BOILERS

22 Fire Tube Boiler

In a fire tube boiler hot gases pass through the tubes and boiler feed water in the shell side is converted into steam Fire tube boilers are generally used for relatively small steam capacities and low to medium steam pressures

[2]

23 Water Tube Boiler

In a water tube boiler boiler feed water flows through the tubes and enters the boiler drum

24 Packaged Boiler

The packaged boiler is so called because it comes as a complete package Package boilers are generally of a shell type with a fire tube design so as to achieve high heat transfer rates by both radiation and convection

[3]

25 Fluidized Bed Combustion (FBC) Boiler

The fluidized bed boilers have a wide capacity range- 05 Thr to over 100 Thr

26 Atmospheric Fluidized Bed Combustion (AFBC) Boiler

Most operational boiler of this type is of the Atmospheric Fluidized Bed Combustion (AFBC) This involves little more than adding a fluidized bed combustor to a conventional shell boiler

27 Pressurized Fluidized Bed Combustion (PFBC) Boiler

In Pressurized Fluidized Bed Combustion (PFBC) type a compressor supplies the Forced Draft (FD) air and the combustor is a pressure vessel

28 Atmospheric Circulating Fluidized Bed Combustion Boilers (CFBC)

In a circulating system the bed parameters are maintained to promote solids elutriation from the bed

29 Stoker Fired Boilers

Stokers are classified according to the method of feeding fuel to the furnace and by the type of grate The main classifications are spreader stoker and chain-gate or traveling-gate stoker

291 Spreader stokers

Spreader stokers utilize a combination of suspension burning and grate burning

[4]

292 Chain-grate or traveling-grate stoker

Coal is fed onto one end of a moving steel grate As the grate moves along the length of the furnace the coal burns before dropping off at the end as ash

210 Pulverized Fuel Boiler

Most coal-fired power station boilers use pulverized coal and many of the larger industrial water-tube boilers also use this pulverized fuel

211 Waste Heat Boiler

Wherever the waste heat is available at medium or high temperatures a waste heat boiler can be installed economically

[5]

212 Thermic Fluid Heater

Thermic fluid heaters have found wide application for indirect process heating Employing petroleum - based fluids as the heat transfer medium these heaters provide constantly maintainable temperatures for the user equipment

3 ASSESSMENT OF A BOILER

This section describes the Performance evaluation of boilers (through the direct and indirectmethod including examples for efficiency calculations) boiler blow down and boiler watertreatment

31 Performance Evaluation of a Boiler

311 Heat balance

[6]

312 Boiler efficiency

313 Direct method of determining boiler efficiency

Methodology

This is also known as lsquoinput-output methodrsquo due to the fact that it needs only the useful output (steam) and the heat input (ie fuel) for evaluating the efficiency This efficiency canbe evaluated using the formula

314 Boiler Blow Down

Blow down is necessary to protect the surfaces of the heat exchanger in the boiler However blow down can be a significant source of heat loss if improperly carried out

315 Boiler Water SamplingA boiler water sample is only useful if it is representative of the conditions inside the boiler Therefore samples taken from the level gauge glass externally mounted level control chambers or close to the feed water inlet connection are likely to be very inaccurate

316 Two types of blow down

a) Intermittent blow down b) Continuous blow down

317 Benefits of blow down control1048707 Lower pretreatment costs1048707 Less make-up water consumption1048707 Reduced maintenance downtime1048707 Increased boiler life1048707 Lower consumption of treatment chemicals

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[2]

23 Water Tube Boiler

In a water tube boiler boiler feed water flows through the tubes and enters the boiler drum

24 Packaged Boiler

The packaged boiler is so called because it comes as a complete package Package boilers are generally of a shell type with a fire tube design so as to achieve high heat transfer rates by both radiation and convection

[3]

25 Fluidized Bed Combustion (FBC) Boiler

The fluidized bed boilers have a wide capacity range- 05 Thr to over 100 Thr

26 Atmospheric Fluidized Bed Combustion (AFBC) Boiler

Most operational boiler of this type is of the Atmospheric Fluidized Bed Combustion (AFBC) This involves little more than adding a fluidized bed combustor to a conventional shell boiler

27 Pressurized Fluidized Bed Combustion (PFBC) Boiler

In Pressurized Fluidized Bed Combustion (PFBC) type a compressor supplies the Forced Draft (FD) air and the combustor is a pressure vessel

28 Atmospheric Circulating Fluidized Bed Combustion Boilers (CFBC)

In a circulating system the bed parameters are maintained to promote solids elutriation from the bed

29 Stoker Fired Boilers

Stokers are classified according to the method of feeding fuel to the furnace and by the type of grate The main classifications are spreader stoker and chain-gate or traveling-gate stoker

291 Spreader stokers

Spreader stokers utilize a combination of suspension burning and grate burning

[4]

292 Chain-grate or traveling-grate stoker

Coal is fed onto one end of a moving steel grate As the grate moves along the length of the furnace the coal burns before dropping off at the end as ash

210 Pulverized Fuel Boiler

Most coal-fired power station boilers use pulverized coal and many of the larger industrial water-tube boilers also use this pulverized fuel

211 Waste Heat Boiler

Wherever the waste heat is available at medium or high temperatures a waste heat boiler can be installed economically

[5]

212 Thermic Fluid Heater

Thermic fluid heaters have found wide application for indirect process heating Employing petroleum - based fluids as the heat transfer medium these heaters provide constantly maintainable temperatures for the user equipment

3 ASSESSMENT OF A BOILER

This section describes the Performance evaluation of boilers (through the direct and indirectmethod including examples for efficiency calculations) boiler blow down and boiler watertreatment

31 Performance Evaluation of a Boiler

311 Heat balance

[6]

312 Boiler efficiency

313 Direct method of determining boiler efficiency

Methodology

This is also known as lsquoinput-output methodrsquo due to the fact that it needs only the useful output (steam) and the heat input (ie fuel) for evaluating the efficiency This efficiency canbe evaluated using the formula

314 Boiler Blow Down

Blow down is necessary to protect the surfaces of the heat exchanger in the boiler However blow down can be a significant source of heat loss if improperly carried out

315 Boiler Water SamplingA boiler water sample is only useful if it is representative of the conditions inside the boiler Therefore samples taken from the level gauge glass externally mounted level control chambers or close to the feed water inlet connection are likely to be very inaccurate

316 Two types of blow down

a) Intermittent blow down b) Continuous blow down

317 Benefits of blow down control1048707 Lower pretreatment costs1048707 Less make-up water consumption1048707 Reduced maintenance downtime1048707 Increased boiler life1048707 Lower consumption of treatment chemicals

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[3]

25 Fluidized Bed Combustion (FBC) Boiler

The fluidized bed boilers have a wide capacity range- 05 Thr to over 100 Thr

26 Atmospheric Fluidized Bed Combustion (AFBC) Boiler

Most operational boiler of this type is of the Atmospheric Fluidized Bed Combustion (AFBC) This involves little more than adding a fluidized bed combustor to a conventional shell boiler

27 Pressurized Fluidized Bed Combustion (PFBC) Boiler

In Pressurized Fluidized Bed Combustion (PFBC) type a compressor supplies the Forced Draft (FD) air and the combustor is a pressure vessel

28 Atmospheric Circulating Fluidized Bed Combustion Boilers (CFBC)

In a circulating system the bed parameters are maintained to promote solids elutriation from the bed

29 Stoker Fired Boilers

Stokers are classified according to the method of feeding fuel to the furnace and by the type of grate The main classifications are spreader stoker and chain-gate or traveling-gate stoker

291 Spreader stokers

Spreader stokers utilize a combination of suspension burning and grate burning

[4]

292 Chain-grate or traveling-grate stoker

Coal is fed onto one end of a moving steel grate As the grate moves along the length of the furnace the coal burns before dropping off at the end as ash

210 Pulverized Fuel Boiler

Most coal-fired power station boilers use pulverized coal and many of the larger industrial water-tube boilers also use this pulverized fuel

211 Waste Heat Boiler

Wherever the waste heat is available at medium or high temperatures a waste heat boiler can be installed economically

[5]

212 Thermic Fluid Heater

Thermic fluid heaters have found wide application for indirect process heating Employing petroleum - based fluids as the heat transfer medium these heaters provide constantly maintainable temperatures for the user equipment

3 ASSESSMENT OF A BOILER

This section describes the Performance evaluation of boilers (through the direct and indirectmethod including examples for efficiency calculations) boiler blow down and boiler watertreatment

31 Performance Evaluation of a Boiler

311 Heat balance

[6]

312 Boiler efficiency

313 Direct method of determining boiler efficiency

Methodology

This is also known as lsquoinput-output methodrsquo due to the fact that it needs only the useful output (steam) and the heat input (ie fuel) for evaluating the efficiency This efficiency canbe evaluated using the formula

314 Boiler Blow Down

Blow down is necessary to protect the surfaces of the heat exchanger in the boiler However blow down can be a significant source of heat loss if improperly carried out

315 Boiler Water SamplingA boiler water sample is only useful if it is representative of the conditions inside the boiler Therefore samples taken from the level gauge glass externally mounted level control chambers or close to the feed water inlet connection are likely to be very inaccurate

316 Two types of blow down

a) Intermittent blow down b) Continuous blow down

317 Benefits of blow down control1048707 Lower pretreatment costs1048707 Less make-up water consumption1048707 Reduced maintenance downtime1048707 Increased boiler life1048707 Lower consumption of treatment chemicals

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[4]

292 Chain-grate or traveling-grate stoker

Coal is fed onto one end of a moving steel grate As the grate moves along the length of the furnace the coal burns before dropping off at the end as ash

210 Pulverized Fuel Boiler

Most coal-fired power station boilers use pulverized coal and many of the larger industrial water-tube boilers also use this pulverized fuel

211 Waste Heat Boiler

Wherever the waste heat is available at medium or high temperatures a waste heat boiler can be installed economically

[5]

212 Thermic Fluid Heater

Thermic fluid heaters have found wide application for indirect process heating Employing petroleum - based fluids as the heat transfer medium these heaters provide constantly maintainable temperatures for the user equipment

3 ASSESSMENT OF A BOILER

This section describes the Performance evaluation of boilers (through the direct and indirectmethod including examples for efficiency calculations) boiler blow down and boiler watertreatment

31 Performance Evaluation of a Boiler

311 Heat balance

[6]

312 Boiler efficiency

313 Direct method of determining boiler efficiency

Methodology

This is also known as lsquoinput-output methodrsquo due to the fact that it needs only the useful output (steam) and the heat input (ie fuel) for evaluating the efficiency This efficiency canbe evaluated using the formula

314 Boiler Blow Down

Blow down is necessary to protect the surfaces of the heat exchanger in the boiler However blow down can be a significant source of heat loss if improperly carried out

315 Boiler Water SamplingA boiler water sample is only useful if it is representative of the conditions inside the boiler Therefore samples taken from the level gauge glass externally mounted level control chambers or close to the feed water inlet connection are likely to be very inaccurate

316 Two types of blow down

a) Intermittent blow down b) Continuous blow down

317 Benefits of blow down control1048707 Lower pretreatment costs1048707 Less make-up water consumption1048707 Reduced maintenance downtime1048707 Increased boiler life1048707 Lower consumption of treatment chemicals

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[5]

212 Thermic Fluid Heater

Thermic fluid heaters have found wide application for indirect process heating Employing petroleum - based fluids as the heat transfer medium these heaters provide constantly maintainable temperatures for the user equipment

3 ASSESSMENT OF A BOILER

This section describes the Performance evaluation of boilers (through the direct and indirectmethod including examples for efficiency calculations) boiler blow down and boiler watertreatment

31 Performance Evaluation of a Boiler

311 Heat balance

[6]

312 Boiler efficiency

313 Direct method of determining boiler efficiency

Methodology

This is also known as lsquoinput-output methodrsquo due to the fact that it needs only the useful output (steam) and the heat input (ie fuel) for evaluating the efficiency This efficiency canbe evaluated using the formula

314 Boiler Blow Down

Blow down is necessary to protect the surfaces of the heat exchanger in the boiler However blow down can be a significant source of heat loss if improperly carried out

315 Boiler Water SamplingA boiler water sample is only useful if it is representative of the conditions inside the boiler Therefore samples taken from the level gauge glass externally mounted level control chambers or close to the feed water inlet connection are likely to be very inaccurate

316 Two types of blow down

a) Intermittent blow down b) Continuous blow down

317 Benefits of blow down control1048707 Lower pretreatment costs1048707 Less make-up water consumption1048707 Reduced maintenance downtime1048707 Increased boiler life1048707 Lower consumption of treatment chemicals

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[6]

312 Boiler efficiency

313 Direct method of determining boiler efficiency

Methodology

This is also known as lsquoinput-output methodrsquo due to the fact that it needs only the useful output (steam) and the heat input (ie fuel) for evaluating the efficiency This efficiency canbe evaluated using the formula

314 Boiler Blow Down

Blow down is necessary to protect the surfaces of the heat exchanger in the boiler However blow down can be a significant source of heat loss if improperly carried out

315 Boiler Water SamplingA boiler water sample is only useful if it is representative of the conditions inside the boiler Therefore samples taken from the level gauge glass externally mounted level control chambers or close to the feed water inlet connection are likely to be very inaccurate

316 Two types of blow down

a) Intermittent blow down b) Continuous blow down

317 Benefits of blow down control1048707 Lower pretreatment costs1048707 Less make-up water consumption1048707 Reduced maintenance downtime1048707 Increased boiler life1048707 Lower consumption of treatment chemicals

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[7]

4BOILER FEED WATER TREATMENT

Producing quality steam on demand depends on properly managed water treatment to control steam purity deposits and corrosion A boiler is the sump of the boiler system41 Deposit control

Deposits in boilers may result from hardness contamination of feed water and corrosion products from the condensate and feed water system

There are two main groups of impurities causing deposits

411 Hard salts of calcium and magnesium

The most important chemicals in water that influence the formation of deposits in boilers are the salts of calcium and magnesium which are known as hardness salts

42 Silica

The presence of silica in boiler water can rise to formation of hard silicate scales

43 Internal water treatment

Internal treatment involves adding chemicals to a boiler to prevent the formation of scale Scale-forming compounds are converted to free-flowing sludge which can be removed by blow down

44 External Water Treatment

External treatment is used to remove suspended solids dissolved solids (particularly the calcium and magnesium ions which are major a cause of scale formation) and dissolved gases (oxygen and carbon dioxide)The external water treatment processes are described below

441 Ion-exchange process (Softener Plant)

442 De-aerationDe-aeration can be done by

Mechanical de-aeration Chemical de-aeration

443 Reverse osmosisReverse osmosis uses the fact that when solutions of differing concentrations are separated by a semi-permeable membrane water from a less concentrated solution passes through the membrane to dilute the liquid of high concentration444 Recommended boiler and feed water quality

The impurities found in boiler water depend on the untreated feed water quality the treatment process used and the boiler operating procedures

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[8]

5 ENERGY EFFICIENCY OPPORTUNITIESThis section includes energy efficiency opportunities related to combustion heat transfer avoidable losses auxiliary power consumption water quality and blow downThe various energy efficiency opportunities in a boiler system can be related to51 Stack Temperature ControlThe stack temperature should be as low as possible However it should not be so low that water vapor in the exhaust condenses on the stack walls52 Feed Water Preheating using EconomizersTypically the flue gases leaving a modern 3-pass shell boiler are at temperatures of 200 to 300 oC Thus there is a potential to recover heat from these gases53 Combustion Air PreheatingCombustion air preheating is an alternative to feed water heating In order to improve thermal efficiency by 1 percent the combustion air temperature must be raised by 20 C54 Incomplete CombustionIncomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel55 Excess Air ControlThe table below gives the theoretical amount of air required for combustion of various types of fuel56 Radiation and Convection Heat Loss MinimizationThe external surfaces of a shell boiler are hotter than the surroundings The surfaces thus lose heat to the surroundings depending on the surface area and the difference in temperature between the surface and the surroundings57 Reduction of Scaling and Soot LossesIn oil and coal-fired boilers soot buildup on tubes acts as an insulator against heat transfer Any such deposits should be removed on a regular basis Elevated stack temperatures may indicate excessive soot buildup58 Reduction of Boiler Steam PressureThis is an effective means of reducing fuel consumption if permissible by as much as 1 to 2 percent59 Variable Speed Control for Fans Blowers and PumpsVariable speed control is an important means of achieving energy savings Generally combustion air control is affected by throttling dampers fitted at forced and induced draft fans510 Controlling Boiler LoadingThe maximum efficiency of the boiler does not occur at full load but at about two-thirds of the full load511 Proper Boiler SchedulingSince the optimum efficiency of boilers occurs at 65-85 percent of full load it is usually more efficient on the whole to operate a fewer number of boilers at higher loads than to operate a large number at low loads 512 Boiler ReplacementThe potential savings from replacing a boiler depend on the anticipated change in overall Efficiency

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[9]

6 OPTION CHECKLISTThis section includes the most common options for improving a boilerrsquos energy efficiency

61 Periodic tasks and checks outside of the boiler62 Boilers extra items for steam raising and hot water boilers63 Boiler rooms and plant rooms64 Water and steam65 Boiler water66 Blow down (BD) procedure

7 GENERAL RULES THERE ARE THE FOLLOWING GENERAL RULES

71 General rules (ldquoRules of Thumbrdquo)

1048707 5 percent reduction in excess air increases boiler efficiency by 1 percent (or 1 percent reduction of residual oxygen in stack gas increases boiler efficiency by 1 percent)

1048707 22 degC reduction in flue gas temperature increases the boiler efficiency by 1 percent

72 Boiler Dorsquos and Donrsquots

Boiler dos and donrsquots Dorsquos Donlsquots

1 Soot blowing regularly2 Clean blow down gauge glass once a shift3 Check safety valves once a week4 Blow down in each shift to requirement5 Keep all furnace doors closed6 Control furnace draughts7 Clear discharge ash hoppers every shift8 Watch chimney smoke and control fires9 Check auto controls on fuel by stopping feed water for short periods occasionally10 Attend to leakages periodically11 Check all valves dampers etc for correct operation once a week12 Lubricate all mechanisms for smooth functioning13 Keep switchboards neat and clean and indication systems in working order14 Keep area clean dust free15 Keep fire fighting arrangements at readiness always Rehearsals to be carried out once a month16 All log sheets must be truly filled

1 Donrsquot light up torches immediately after a fire-out (purge)2 Donrsquot blow down unnecessarily3 Donrsquot keep furnace doors open unnecessarily4 Donrsquot blow safety valves frequently (control Operation)5 Donrsquot over flow ash hoppers6 Donrsquot increase firing rate beyond that permitted7 Donrsquot feed raw water8 Donrsquot operate boiler blind fold9 Donrsquot overload boiler as a practice10 Donrsquot keep water level too high or too low11 Donrsquot operate soot blowers at high loads12 Donrsquot trip the ID fan while in operation13 Donrsquot look at the fire in furnace directly use tinted safety glasses14 Avoid thick fuel bed15 Donrsquot leave boiler to untrained operatorstechnicians16 Donrsquot overlook unusual observation (sound change change in performance control

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[10]

17 Trip FD fan if ID fan trips18 CO2 or O2 recorder must be checkedcalibrated once in three months19 Traps should be checked and attended to periodically20 Quality of steam water should be checked once a day or once a shift as applicable21 Quality of fuel should be checked once aweek22 Keep sub heater drain open during start up23 Keep air cocks open during start and close

difficulties) investigate17 Donrsquot skip annual maintenance18 Donrsquot prime boilers19 Donrsquot allow steam formation in economizer (watch temps)20 Donrsquot expose grate (spread evenly)21 Donrsquot operate boiler with water tube leaking

8 FANS AND BLOWERS

81 IntroductionFans and blowers provide air for ventilation and industrial process requirements82 Difference between Fans Blowers and CompressorsFans blowers and compressors are differentiated by the method used to move the air and by the system pressure they must operate against83 Fan TypesFan and blower selection depends on the volume flow rate pressure type of material handled space limitations and efficiency Fan efficiencies differ from design to design and also by types84 Centrifugal Fan TypesThe major types of centrifugal fan are radial forward curved and backward curvedRadial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams Because of their simple design radial fans are well suited for high temperatures and medium blade tip speeds85 Axial Flow Fan TypesThe major types of axial flow fans are tube axial vane axial and propeller

Tubeaxial fans have a wheel inside a cylindrical housing with close clearance between blade and housing to improve airflow efficiency

9 TYPES OF AXIAL FANS

91 Tube Axial

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[11]

92 Vane Axial

93 Propeller

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[12]

94 Common Blower Types

Blowers can achieve much higher pressures than fans as high as 120 kgcm2 They are also used to produce negative pressures for industrial vacuum systems

10 FAN PERFORMANCE EVALUATION AND EFFICIENT SYSTEM OPERATION

101 System CharacteristicsThe term system resistance is used when referring to the static pressure The system resistance is the sum of static pressure losses in the system102 Fan CharacteristicsFan characteristics can be represented in form of fan curve(s) The fan curve is a performance curve for the particular fan under a specific set of conditions103 System Characteristics and Fan CurvesIn any fan system the resistance to air flow (pressure) increases when the flow of air is increased As mentioned before it varies as the square of the flow 104 Fan LawsThe fans operate under a predictable set of laws concerning speed power and pressure A change in speed (RPM) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[13]

11 FAN DESIGN AND SELECTION CRITERIA

Precise determination of air-flow and required outlet pressure are most important in proper selection of fan type and size The air-flow required depends on the process requirements normally determined from heat transfer rates or combustion air or flue gas quantity to be handled111 Fan Performance and EfficiencyFan performance characteristics and efficiency differ based on fan and impeller type

Figure 22 Fan Performance Characteristics Based on Fans Impellers

112 Safety marginThe choice of safety margin also affects the efficient operation of the fan In all cases where the fan requirement is linked to the processother equipment the safety margin is to be decided based on the discussions with the process equipment supplier

12 FLOW CONTROL STRATEGIES Typically once a fan system is designed and installed the fan operates at a constant speed There may be occasions when a speed change is desirable ie when adding a new run of duct that requires an increase in air flow (volume) through the fan121 Pulley Change

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[14]

When a fan volume change is required on a permanent basis and the existing fan can handle the change in capacity the volume change can be achieved with a speed change122 Damper ControlsSome fans are designed with damper controls Dampers can be located at inlet or outlet Dampers provide a means of changing air volume by adding or removing system resistance123 Inlet Guide VanesInlet guide vanes are another mechanism that can be used to meet variable air demand124 Variable Speed DrivesAlthough variable speed drives are expensive they provide almost infinite variability in speed control Variable speed operation involves reducing the speed of the fan to meet reduced flow requirements125 Series and Parallel OperationParallel operation of fans is another useful form of capacity control126 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power is shown in Figure 514 All methods of capacity control mentioned above have turn-down ratios (ratio of maximumndashtondashminimum flow rate) determined by the amount of leakage (slip) through the control elements For example even with dampers fully closed the flow may not be zero due to leakage through the damper127 Factors to be considered in the selection of flow control methodsComparison of various volume control methods with respect to power consumption () required power13 FAN PERFORMANCE ASSESSMENTThe fans are tested for field performance by measurement of flow head temperature on the fanside and electrical motor kW input on the motor side131 Air flow measurement1311 Static pressure

Static pressure is the potential energy put into the system by the fan1312 Velocity pressure

Velocity pressure is the pressure along the line of the flow that results from the air flowing through the duct

1313 Total pressureTotal pressure is the sum of the static and velocity pressure Velocity pressure and static pressure can change as the air flows though different size ducts accelerating and decelerating the velocity

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[15]

Figure 29 Static Total and Velocity Pressure

1314 Measurement by Pitot tube

The Figure 30 shows how velocity pressure is measured using a pitot tube and a manometer Total pressure is measured using the inner tube of pitot tube and static pressure is measured using the outer tube of pitot tube

132 Measurements and Calculations

1321 Velocity pressurevelocity calculation1322 Air density calculation

14 ENERGY SAVING OPPORTUNITIES

141 Minimizing demand on the fan1 Minimising excess air level in combustion systems to reduce FD fan and ID fan load2Minimising air in-leaks in hot flue gas path to reduce ID fan load especially in case of kilns boiler plants furnaces etc

15 BIBLOGRAPHY

1 Agriculture and Agri-Food Canada Heat recovery for Canadian food and beverage industries 2001 wwwagrgccacalepub5181e5181-0007_ehtml

2 BIB Cochran 2003 wwwbibcochrancomenglishindexhtm Considine Douglas M Energy Technology Handbook McGraw Hill Inc New York 1977 Department of Coal Publications Government of India Fluidised Bed Coal-Fired Boilers Department of

[16]

Coal India prepared by National Productivity Council Coal ndash Improved Techniques for Efficiency 1985

3 Elonka Jackson M and Alex Higgins Steam Boiler Room Questions amp Answers Third Edition

4 Energy Machine India Energy Machine Products Thermic Fluid Heater Flowtherm series

5 wwwwarmstreamcoinprod-em-thermic-fluid-heatershtml

6 Gunn D and Horton R Industrial Boilers Longman Scientific amp Technical New York India Energy Bus Project Industrial Heat Generation and Distribution NIFES Training Manual Issued for CEC

7 IS 10392 19828 Jackson J James Steam Boiler Operation Prentice-Hall Inc New Jersey 1980 Light

Rail Transit Association Trams for Bath DC Power stations ndash Boilers9 wwwbathtramorgtfbtT111htm

10 National Coal Board Fluidised Combustion of Coal London National Productivity Council Efficient Operation of Boilers Pincus Leo I Practical Boiler Water Treatment McGraw Hill Inc New York 1962

11 Sentry Equipment Corp Continuous Blowdown Heat Recovery Systems for boilers rated 35 to 250 PSIG Installation Operating and Maintenance Instructions SD 170 Rev 4 26 wwwsentry-equipcomPDF20filesBlowdown20173020Rev204PDF 2006

12 Shields Carl D Boilers McGraw Hill Book Company US 1961

13 Spirax Sarco Module 3 of Spirax Sarcorsquos web based Learning Centre wwwspiraxsarcocomlearn

14 Technical Papers Boiler Congress - 2000 Seminar 11 amp 12 January 2000

15 TERI GTZ and EMC Steam Generation Distribution and Utilisation Thermax Babcock amp Wilcox Limited CFBC Boilers 2001

16 wwwtbwindiacomboilercfbc_systemasp University of Missouri Colombia Energy Management ndash Energizing Mizzou 2004

17 wwwcfmissourieduenergy YourDictionarycom Water tube boiler 2004

18 wwwyourdictionarycomimagesahdjpgA4boilerjpg

19 Websites

[17]

20 wwwerendoegov

21 wwwoitdoegovbestpractices

22 wwwpcraorg23 wwwenergy-efficiencygovuk

24 wwwactionenergyorguk

25 wwwciaorguk

26 wwwaltenergycom