5.Energy Audit of CW System.ppt

7/28/2019 5.Energy Audit of CW System.ppt

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ENERGY AUDIT OF CONDENSER AND

CONDENSER COOLING WATER

SYSTEM

Presented ByM.V.Pande

Dy.Director

NPTI, Nagpur


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Background

Condenser:The condenser is the most important component of the turbine cycle that

affects the turbine heat rate. The function of the condenser is to

condense exhaust steam from the steam turbine by rejecting the heat of

evaporation to the cooling water passing through the condenser.

Generally, twin shell- double pass- surface type condensers areemployed for higher capacity units

CW Pump

Hot Water

Condenser

Cooled

Water

Cooling

Tower AirAir

Make-up

Water

Hot

Water


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Background

Cooling towers:

Different types of

cooling towers are

used in the power

plants depending upon

the location, size,

infrastructure andwater resources etc.

Close cycle wet

cooling systems:

-Induced draft

-Forced draft

- Natural draftcooling

towers


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Background

Cooling water pumps:

Circulating water pumps supply cooling water at therequired flow rate and pressure to the power plant

condenser and the plant auxiliary cooling water heat

exchangers. These pumps are required to operate

economically and reliably over the life of the plant.

For once through systems, vertical wet pit pumps are in

common usage.

For re-circulating cooling systems, vertical wet pit and

horizontal dry pit are used about equally, with occasional

use of vertical dry pit pumps.


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Specifications of Typical Cooling Water Pump


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Steps Involved in Energy Audit

The major energy consuming equipments in the CW

systems are:

Cooling towers and fans

Cooling water pumps

Make up water pumps

Condensers

The steps involved in conducting energy audit of cooling

water and cooling tower are:

Data collection Observations and Analysis

Exploration for energy conservation measures

Report preparation


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Data Collection

Specifications of cooling towers:


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Data Collection

Specifications of cooling towers- contd:


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Specification of water pumps and motors:

Specification of water pumps and motors


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Specification of water pumps and motors- contd:

Data Collection

Rated kW of the pump


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Data Collection- Other Information

Performance characteristics of all pumps and motors

Compile design, P. G. Test, previous best and last energy

audit value with respect to cooling tower and cooling water

system along with the condensers

If the pumps are operated in parallel then it is advised to

collect the performance curve for the parallel operation

Schematic diagram of Water pumping network (which

depict the source, pumps in operation & stand by, line sizes

and users)

Water and pressure equipments at the users as per the

design requirements

Brief description of the system with the key specifications in

which pumps are used (for example, if pumps are used for

supplying water to condenser, then add a brief write up

about the cooling water system)


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Data Collection- Condenser Specifications

Heat load considered for design

Design inlet cooling water temperature/ Design TTD

Cleanliness factor/ Cooling water temperature raise

Condenser back pressure

Cooling water flow/ Cooling water side pressure drop

No of cooling water pass/ Total heat transfer area

No. of tubes - Condensing zone - Air cooling zone

Tube dimensions: - Tube OD x thickness - Length of

tube

Tube material: - Condensing zone - Air cooling zone

Water box design pressure


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Instruments Required

Power Analyzer: Used for measuring electricalparameters of motors such as kW, kVA, pf, V, A andHz

Temperature Indicator & Probe

Pressure Gauge: To measure operating pressureand pressure drop in the system

Stroboscope: To measure the speed of the drivenequipment and motor

Ultra sonic flow meter or online flow meter

Sling hygrometer or digital hygrometer Anemometer

In addition to the above calibrated online instrumentscan be used

PH meter


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Measurements & Observation Energy consumption pattern of pumps and cooling tower

fans

Motor electrical parameters (kW, kVA, Pf, A, V, Hz, THD)for pumps and cooling tower fans

Pump operating parameters to be measured/monitored foreach pump are: - Discharge, - Head (suction & discharge) -

Valve position Temperature - Load variation, Powerparameters of pumps - Pumps operating hours andoperating schedule

Pressure drop in the system (between discharge and userpoint)

Pressure drop and temperatures across the users (heatexchangers, condensers, etc)

Cooling water flow rate to users - Pump /Motor speed

Actual pressure at the user end

User area pressure of operation and requirement


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Measurements & Observation

Cooling tower parameters to be monitored

Inlet temperature

Outlet temperature

Dry bulb temperature

Wet bulb temperature or relative humidity

Water flow to cooling towerAir flow rate of cooling tower

Range, oC

L/G ratio

Approach, oC

Fan speed, rpm

Fan power consumption (kW/cell)


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Observations and Analysis

System familiarization and operational details

Energy consumption Pattern

The energy consumption of cooling water : kWh/day and

associated system

Total auxiliary power consumption : kWh/Day

O ti Effi i d P f


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Operating Efficiency and Performance

Evaluation of the Pumps

Water flow rate and pressure of pumps / headers

Velocity in the main headers and pumps and major lines (to

verify adequacy of line sizes)

Power consumption of pumps (for estimating the operating

efficiency of the pumps) Monitor present flow control system and frequency of

control valve variation if any (for application of variable

speed drives)

Fill up the following data sheet for every pump forcomparison with the design / PG test values



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Investigations & Recommendations Compare the actual values with the design / performance

test values if any deviation is found, investigate for the

contributing factors and arrive at appropriate suggestions The investigations for abnormality are to be carried out for

problems. Enlist scope of improvement with extensivephysical checks / observations.

Based on the actual operating parameters, enlistrecommendations for action to be taken for improvement, ifapplicable such as

Replacement of pumps/ Impeller replacement/ trimming

Variable speed drive application, etc

Compare the specific energy consumption with similar typeof pumps and latest energy efficient pumps

Cost analysis with savings potential for taking improvementmeasures.


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Flow Distribution

Measure the flow at the individual pump discharge side,

main header, at the users (for the major and large users) along with the

pressure and

velocity. Depict these values in schematic diagram

Ensure Line adequacy by measuring the velocity in themajor pipe lines

Pressure drop in the distribution network

Specific water flow rate


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CONDENSERS


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Performance of Condensers

Parameters for condenser performance


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Parameters for condenser performance- contd


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The following needs to be computed:

1. Condenser heat load = Q x T x Cp

Parameter Details Unit

Q Water flow rate Kg/h

T Average CW temperature rise oC

Cp Specific heat kcal/kg oC

2. Calculated condenser vacuum =

Atmospheric pressure Condenser back-pressure

3. Deviation in condenser vacuum =Expected condenser vacuum - Measured condenser vacuum

4. Condenser TTD =Saturation temperature Cooling water outlet temperature


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5. Condenser Effectiveness =

Rise in cooling water temperature

Saturation temperature - Cooling water inlet temperature

6. Condenser heat duty in kcal/h =

Heat added by main steam + heat added by reheater + heat

added by SH attemperation + heat added by RHattemperation + heat added by BFP - 860 x (Pgen + Pgen

losses + heat loss due to radiation)

7. Condenser tube velocity (m/s) =

Cooling water flow rate (m3/h) x 106

3600 x tube area (mm2) x ( no. of tubes per pass - no. of

tubes plugged per pass )


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8. Determination of actual LMTD

Tsat - ToutLn

LMTD =

Tout - Tin

Tsat -Tin

9. LMTD expected = LMTD test x ft x fw x fq

(Saturation Temperature during test LMTD during test

Saturation Temperature design LMTD design)ft=

0.25

fw = Tube velocity during test Tube velocity design( )0.50

fq = Condenser design duty

Condenser duty during test( )

fw: correction forwater flow rate

fq: correction for

cooling water heat load

ft: Correction for cooling water inlet temperature


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Observations During Condenser Energy Audit Tubes in operation Vs total installed

Cleaning system operation

Filtering system for cooling water Regular monitoring system for performance

Comparison of LMTD, TTD, heat load, condenser vacuum, flow,temperatures, pressures with design / PG test- arriving the factorscausing deviation

Modifications carried out in the recent past Cooling water flow

Pressure drop on water side and choking

Affect of present performance of cooling tower

Accurate metering of vacuum

Absolute back pressure deviation from expected value Sub cooling of air steam mixture and condensate

Circulation water temperature raise

Effectiveness of cleaning the tubes

Circulating water velocity in tubes


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COOLING TOWERS


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Performance of Cooling Towers


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Performance of Cooling TowersWhile conducting the cooling tower, visual observations

need to be made with respect to:

Adequate water level in the trough Cross flow air from other cooling towers (which are under

maintenance)

Nozzle condition and operation

Fill condition Change of blade angles during change of seasons

The CT airflow shall be measured using an anemometerand compared with calculated airflow derived from fan

characteristic curves of CT fans with actual powermeasurements.

Calculate range, approach, L/G (Liquid to gas) ratio andeffectiveness for design and operating conditions for eachtower


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1. C.T. Range = Water inlet temperature Water outlet temp.

2. C.T. Approach = Water outlet temperature Wet bulb temp.

3. Effectiveness % = Range x 100( range + approach )

Fan actual airflow (Nm3) / cell =

Fan rated airflow (Nm3) / h x ( Fan input kW actual )

( Fan input rated )

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4.

5. Air mass flow / cell = flow x density of air


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5. Evaporation losses =CW flow (m3/ h) x CT range in 0C

675

6. Makeup water consumption = Evaporation losses(COC 1)

The above readings may be taken on daily basis for three

days on different atmospheric conditions say during mid

summer, winter & monsoon period. Once in the mid day and

once in the mid night time and a record duly maintained.

Collect unit load (MW), frequency, and condenser vacuum

condition while taking the cooling tower measurement


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Power consumption of CT fans

Exploration of Energy Conservation Possibilities:

Condenser Possibility of Improvement in condenser vacuum

Turbine heat rate Reduction possibilities

Improving the effectiveness of condenser and TTD Cooling water flow adequacy and flow optimization

Air ingress

Increasing the TTD of the condenser


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Exploration of Energy Conservation Possibilities

Water pumping and cooling tower

Improvement of systems and drives Use of energy efficient pumps Correcting inaccuracies of the Pump sizing / Trimming of impellers Use of high efficiency motors

Integration of variable speed drives into pumps: The integration ofadjustable speed drives (VFD) into compressors could lead toenergy efficiency improvements, depending on load characteristics

High Performance Lubricants: The low temperature fluidity and hightemperature stability of high performance lubricants can increaseenergy efficiency by reducing frictional losses

Improvements in condenser performance Improvement in cooling tower performance Application potential for energy efficient fans for cooling tower fans Measuring and tracking system performance


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Measuring water use and energy consumption is essentialin determining whether changes in maintenance practices

or investment in equipment could be cost effective

In this case it is advised to monitor the water flow rate andcondenser parameters, cooling tower parameters

periodically i.e. at least once in a three months and energyconsumption on daily basis. This will help in identifying the -

- Deviations in water flow rates

- Heat duty of condenser and cooling towers

- Measures to up keep the performance


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System Effect Factors

Equipment cannot perform at its optimum capacity if fans,

pumps, and blowers have poor inlet and outlet conditions

Correction of system effect factors (SEFs) can have asignificant effect on performance and energy savings

Elimination of cavitation: Flow, pressure, and efficiency arereduced in pumps operating under cavitation. Performance

can be restored to manufacturers specifications through

modifications. This usually involves inlet alterations and

may involve elevation of a supply tank

f C


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Internal Running Clearances: The internal runningclearances between rotating and non-rotating elements

strongly influence the turbo machine's ability to meet ratedperformance. Proper set-up reduces the amount of leakage

(re-circulation) from the discharge to the suction side of the

impeller

Reducing work load of pumping: Reducing of obstructionsin the suction / delivery pipes thereby reduction in frictional

losses. This includes removal of unnecessary valves of the

system due to changes. Even system and layout changes

may help in this including increased pipe diameter.Replacement of components deteriorated due to wear and

tear during operation, modifications in piping system


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5.Energy Audit of CW System.ppt

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