T07073-LBH-SY-M001 Rev.A.pdf

A 08.11.25 S.W.KANG S.H.SONG S.C.SONGP 08.03.13 S.W.KANG S.H.SONG S.C.SONG

Rev. Date Prepared Coordinated Checked

Client :

Engineer :

Contractor :

Sub Suplier :

Project Title : Orig-Pc

Date Name Scale N/APrepared 08.11.25 S.W.KANG DOC. TITLE Contents

Coordinated Code

Checked 08.11.25 S.H.SONGApproved 08.11.25 S.C.SONGDept. Reg. No.

AT07073-LBH-SY-M001 1/43

Owner Document No. : TCE.5146A-510-00-1309

Second Issued First Issued

Details of Revision

COASTAL GUJARAT POWER LIMITEDA TATA POWER COMPANY

Doosan Heavy Industries &Construction Co. Ltd.

Document No. :

4000 MW ULTRA MEGA POWER PROJECTAT MUNDRA, GUJARAT, INDIA

STARTUP AND SHUT DOWNPROCEDUREBOILER BASIC

DESIGN TEAM

FOR INFORMATION

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Type

Dept. UNID Rev Version

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Steam Generator Start-Up and Shut-Down Procedure for MUNDRA UMPP

STEAM GENERATOR START-UP AND SHUT-DOWN PROCEDURE

FOR MUNDRA UMPP (5 x 800MW)

DOOSAN HEAVY INDUSTRIES & CONSTRUCTION CO. LTD

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TABLE OF CONTENTS TITLE PAGE NO. INTRODUCTION ...................................................................................................................... 1 PRE-OPERATIONAL PROCEDURES ...................................................................................... 1

Cleanup .......................................................................................................................... 1 Chemical Cleaning ........................................................................................................ 1 Steam Line Blowing ...................................................................................................... 1 Setting Safety Valves ................................................................................................... 1

COLD START -UP .................................................................................................................. 2 Cold Start Conditions ................................................................................................... 2 Preparations for Lighting Off ....................................................................................... 2 Warm Water Filling of the Boiler .................................................................................. 5 Water Recirculation via Boiler for Clean-up ............................................................... 6 Start of the Boiler Circulation Pump (BCP) ................................................................. 6 Initial Firing Precautions .............................................................................................. 6 Superheat Steam Temperature Control (Prior to Unit Synchronization) ................... 7 Air Pre-heater Protection During Unit Start-Ups On Oil ............................................. 7 Lighting Off .................................................................................................................... 8 Rolling and Synchronizing the Turbine ..................................................................... 13 Introducing Coal .......................................................................................................... 14 Initial Load Increase .................................................................................................... 15

NORMAL OPERATION -UNIT LOAD CHANGES ................................................................... 17

Decreasing Load ......................................................................................................... 17 Increasing Load ........................................................................................................... 18

NORMAL SHUTDOWN TO COLD .......................................................................................... 19 NORMAL SHUTDOWN TO HOT STANDBY .......................................................................... 21 WARM START -UP ................................................................................................................ 23

Warm Start Conditions ................................................................................................ 23 Preparations, Lighting Off, and Load Increase .......................................................... 23 Lighting Off .................................................................................................................. 23 Rolling and Synchronizing the Turbine ..................................................................... 26 Introducing Coal .......................................................................................................... 27 Initial Load Increase .................................................................................................... 28

HOT START -UP .................................................................................................................... 30

Hot Start Conditions ................................................................................................... 30 Preparations, Lighting Off, and Load Increase .......................................................... 30 Rolling and Synchronization the Turbine .................................................................. 32

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TITLE PAGE NO. EMERGENCY PROCEDURES ............................................................................................... 33

Reheater Protection .................................................................................................... 33 Master Fuel Trip .......................................................................................................... 34 Low Water wall Flow ................................................................................................... 35 High Water Wall Tube Temperature ........................................................................... 36 Tube Failures ............................................................................................................... 36

APPENDIX A- FEEDWATER SPECIFICATIONS FOR ONCE THROUGH BOILERS ............. 38 Figure 1: Typical Air Flow Curve .......................................................................................... 39

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INTRODUCTION

These procedures are intended to serve as a guide during the initial stages of operation. The described situations in this procedure can be modified by actual operational condition and circumstance at site during start-up and shutdown the boiler. They include precautions, which must be observed, and the proper operating sequences of the steam generator, fuel firing equipment and auxiliary equipment. Refer to the General Arrangement Drawings(DWG. No. T07073-GA-A001 ~ A013 in O&M manual). The sequential procedures do not include all detailed reference to equipment such as the feed pumps, condensate pumps, or the turbine.

Because the steam generator is only one part of a complex power station and all equipment must operate in unison, all specific procedures and detailed values cannot be included in this manual. As operating experience is gained and the controls are fine-tuned, the characteristics and operating requirements of the unit will become apparent. Refer to the manufacturer's instructions which are included in O&M manual for further operating details for specific equipment, including pre-operational and operational procedures.

PRE-OPERATIONAL PROCEDURES Cleanup

The furnace should be inspected and cleaned both internally and externally before initial firing and prior to each subsequent cold start-up after maintenance. Remove all foreign material from the pressure parts. Clear any grating, pipe lines and electric conduit which may restrict normal expansion of the steam generator. All personnel should be clear and the access doors closed. A complete check list should be prepared by operating personnel.

Chemical Cleaning

Specific pre-operational chemical cleaning procedures are included else where in this manual. The fuel firing and circulating pump operating procedures, outlined under COLD START-UP, Lighting Off, should be used as a guide when operating the fuel firing equipment.

Steam Line Blowing

Prior to starting up a new steam generator, or following a major pressure part repair, the main steam and reheat steam lines should be blown out to remove scale and other foreign matter. Steam line blowing, which prevents damage to the turbine, should be done after chemical cleaning. Refer to Steam Line Blowing Procedures for recommended operating procedures and precautions.

Setting Pneumatically Operated Safety Valves

The pneumatically operated SH safety valves serve the function of over-pressure protection of the SH sections. It is important the complete checkout and verification of the pneumatic power station operation and pressure sensing instrumentation be completed prior to firing the boiler.

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COLD START-UP Cold Start Conditions

1. Boiler separator metal temperature < 100℃ and

2. Boiler pressure = 0 kg/cm2 (g)

Preparations for Lighting Off Before lighting off the steam generator, verify that the following activities have been completed:

CAUTION: The differential temperature between the feed water and boiler metal must never exceed 200℉(111℃) (separator during initial filling or separator and superheater outlet header during filling for hydrostatic test). If the metal temperature is less than 100℉ (38℃) and the feed water temperature is higher, a minimum fill rate should be used.

1. The unit has been chemically cleaned, and the steam lines have been

blown(applicable for the first start-up only). 2. All control systems have been checked and are available for service.

All safety interlock systems should be checked prior to start-up to ensure proper functioning. Exercise the systems by creating the actual interlock actuating conditions. Simulate the activating condition if the actual condition cannot be created.

3. All instrumentation and associated mechanical equipment has been checked out

and is available for service.

4. The oil firing equipment has been checked out to ensure it is properly functioning. Recheck the following items to make sure that:

a. Warm-up oil guns are inserted and properly coupled. Check gaskets between

unions.

b. All oil gun quick-connect couplings are properly assembled.

c. All manual valves are open.

d. All control valves are closed.

5. The pulverizers and feeders have been checked out and are available for service. Recheck the following items to ensure that:

a. All pulverizer discharge gates are open.

b. All fuel air dampers are in closed position.

c. All Burner inlet knife gates are in open position.

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d. All hot air gates are closed and all hot air control dampers are closed.

e. All cold air gates are open and the cold air control dampers are open

approximately 5%.

f. All bunker outlet valves are open and coal is available to the feeders.

g. All pulverizer and feeder seal air valves are open.

h. All classifier vane settings are identical.

i. The pulverizer lube oil systems are available for service.

6. The windboxes have been checked for proper damper positioning and the tilts are set at horizontal.

7. The feedwater system and at least one feedwater pump, including the

instrumentation and equipment, has been checked out and is available for operation. During a start-up, the feedwater flow should be controlled remote-manually until a continuous flow is established.

8. The deaerator auxiliary steam supply is operational and de-aerated feedwater at

105℃ is available. To avoid oxygen corrosion in the boiler, the use of de-aerated feedwater with a temperature of greater than 102℃ is recommended. Refer to Water Treatment instructions.(Appendix A: Feedwater specifications for Once Thru Boilers)

9. The boiler circulating pump has been checked out, the suction and discharge

isolation valves are open, and all pump instrumentation is available for service. The pump differential pressure transmitters must be in service. Ensure that the proper trip settings have been made.

10. The steam generator start-up system valves are ready for operation (UG, WR, ZR valves), with isolation valve open. The separator level control for WR and ZR valves has been checked and is available for service.

11. The startup system drain transfer system is ready for operation. This system includes

WR and ZR valves, the flash tank, condensate drain transfer pump and connecting pipe to condenser.

12. Auxiliary steam is available from another operating boiler for supplying the deaerator,

feedwater tank, and heavy oil atomization. When auxiliary steam is available, the unit can be started with Heavy Fuel Oil firing. But even though the auxiliary steam is available the Light Diesel Oil is introduced as an ignition fuel before HFO supplied during Cold start-up. As soon as the steam parameters i. e. pressure and temperature are available for the above requirements, they shall be put into service.

13. Cooling water system is in operation.

CAUTION: Before starting an ID fan and before adjusting the ID fan inlet blade pitch, an airflow path through the unit must be established such as ESP is in service, GAH in service and GAH inlet gas stream damper open and maintained by placing other dampers in the system in the start-up positions indicated below. The ID fan inlet blade pitch must be kept closed or at the minimum open position until after the fan

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is started. This minimizes the possibility of developing excessive negative pressure in the unit during the starting procedure. Furnace draft must be maintained within safe limits at all times. Extreme care should be taken when draft and airflow controls are in the manual mode. Be alert for possible malfunctions of automatic control equipment resulting in abnormal excursions, negative or positive, in furnace pressure.

NOTE: If the unit is started with only one ID and FD fan, one PA fan in service, the following damper positions apply to the equipment to be started. Dampers associated with the idle equipment should be closed. Refer to the fan manufacturer's instructions for operating details.

14. All air and gas handling equipment has been checked out and is available for service.

Air and gas duct dampers should be in the start-up position as follows:

a. For the first draft group to be started (ID fan A and FD fan A), the fan outlet shutoff dampers are closed and the inlet blade pitch is at minimum.

b. For the second draft group (ID fan B and FD fan B), the outlet shutoff dampers

shall be kept closed to enable start up of the Fans.

c. The PA fan outlet shutoff dampers and inlet blade pitch is closed or at the minimum position.

d. All duct dampers are open.

e. The overfire air dampers are closed.

f. The windbox auxiliary (secondary) air dampers are open or modulating.

g. One pulverizer seal air fan inlet shutoff damper is open with the associated fan

ready.

h. The scanner air fans are ready for operation

15. The gas air heaters have been prepared for service and an adequate means of extinguishing a gas air heater fire is available and ready for use. Refer to gas air pre-heater protection during unit start-ups on oil, and to the gas air heater instructions for details.

16. The soot blowing equipment has been checked for proper operation and the system

is in the start-up mode with all blowers retracted and the main steam supply valve closed. Refer to the soot blower instructions.

17. All desuperheater spray water control and block valves are closed.

CAUTION: Prevent possible water damage to the turbine by taking extreme care to eliminate all water from the main steam line(s), cold and hot reheat lines, and the superheater and reheater elements and headers before the turbine is rolled. Refer to the turbine manufacturer's instructions for proper drain valve settings.

18. All boiler, superheater, and reheater drain valves are open, and all vent valves are

closed. The economizer and furnace wall drain valves are closed, and economizer

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vent valves are open.

19. The auxiliary steam extraction line from the main steam line is isolated.

20. The warming system for the boiler start-up system is isolated (supply from economizer outlet links and discharge to the SH 1st desuperheater).

21. The furnace gas temperature probe(s) is in working order and available for service.

22. The HP and LP bypass stations are available for service, and hydraulic stations are

in operation. The water supply for desuperheating has been established. 23. The condenser is available for service, with circulation water flow, and vacuum has

been established to accept water flow from the condensate transfer pump and LP bypass (condenser pressure setpoint interlock of LP bypass).

24. The main steam stop cum control valve and hot reheat stop and control valves are

closed. (The valve type will be corrected after confirmation from valve supplier) Drain valves on the main steam, cold reheat, and hot reheat lines are open.

25. The condensate polishing plant is available for operation.

26. The turbine generator has been prepared and is available for service as described in

the turbine manufacturer's instructions. Warm Water Filling of the Boiler

The entire economizer, furnace wall, and separator system must be filled with warm de-aerated water (105℃) and be free of air. The following procedure shall be carried out to ensure the water system is free of air: 1. The economizer outlet vent valve is open. 2. BFP(T) for start-up operation is started at minimum speed and flow according to feed

pump operating procedures. 3. If the water system of the boiler is empty (economizer, furnace walls, separators), then

the system is to be filled with approximately 10% TMCR feedwater flow. Feedwater flow is preferably controlled using automatic feedwater control with a set point of 10% TMCR. When the level in the separator reaches set-point, the WR valve will begin to open. Ensure that the motorized isolation valve at common drain line is kept open prior to WR valve opening. When the WR valve reaches >30% open for approximately one minute, then increase feedwater flow set-point to 30%TMCR. As the drain flow increases, WR valve will reach full open and ZR valve will begin to open. The water system is considered full when:

a. The separator water level remains stable for two(2) minutes

and b. The WR valve is fully opened and ZR valve is >15% open for two(2) minutes.

4. After filling the water system, the feedwater pump is stopped. The water level in the

de-aerator must be re-established and maintained and water temperature at 105℃ re-established.

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5. Re-start the feedwater pump and establish feedwater flow of 10% TMCR to the boiler.

6. Close Economiser outlet vent valve 20 seconds later than detecting the Economiser inlet water flow reaches over 10T/hr.

Water Recirculation via Boiler for Clean-up 1. When the feedwater quality at the outlet of deaerator and separator is not within the

specified limits, a feedwater clean-up recirculation via the boiler is necessary. 2. During this time, constant feedwater flow of 10% TMCR or more is maintained. 3. Water flows through the economizer and evaporator, and discharges the boiler through

the WR valve to the flash tank and via condensate drain pump to the condenser. From the condenser, the water flows through the condensate polishing plant, which is in service to remove impurities, then returns to the feedwater tank.

4. The recirculation is continued until the water quality is within the specified limits.

Start of the Boiler Circulation Pump (BCP)

1. It is assumed that the following preparatory work has been completed:

a. Feed water quality within specified limits. b. Feed water flow set point at 10% TMCR. c. Separator water level stable at normal level. d. Cooling water flow to the HP cooler of the BCP adequate. e. Suction valves and discharge valves are open.

2. Set the UG valve at minimum position, and start BCP per pump operating instructions. 3. As soon as pump is running, open the UG valve to establish minimum waterwall flow

at 35% TMCR. 4. With BCP in operation, flow through the economizer and waterwall tubes increases

substantially. It is recommended that the water quality at the separator be rechecked.

Initial Firing Precautions To ensure a maximum safety margin during start-ups, at least 35% of the full load airflow must be maintained to produce the following conditions: 1. An air-rich furnace atmosphere. This prevents the accumulation of an explosive

mixture due to poor or delayed ignition after fuel is introduced to the furnace. 2. High excess air through the gas air heaters. This minimizes the dilution of combustion

air by inert gases carried over by the gas air heater rotors.

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Superheat Steam Temperature Control (Prior to Unit Synchronization)

The boiler will normally be started-up de-coupled from the turbine using the HP and LP bypass systems, which provide a steam flow path through the superheater, to the reheater, and to the condenser. This provides additional flexibility for adjusting steam temperatures to match turbine requirements at start-up. The primary methods for controlling steam temperature will be firing rate and airflow adjustment.

Gas Air Pre-heater Protection During Unit Start-Ups On Oil It is strongly recommended to have the gas air heater soot blowing system continuously in service when firing oil to start up a boiler. This measure is intended to help avoid gas air heater fires due to accumulation of oil vapors on heating surfaces or ash particles in the gas air heater baskets. A retractable soot blower is installed at the cold end of the gas air heater on the gas side, arranged close to the changeover of air to gas side when looking in direction of rotation, opposite the fire detection device. This soot blower is primarily designed to reduce (knock off) and/or control oil residue deposits and ash build-up in the gas air heater surface. It is not a cleaning device such as the stationary wash down nozzles. Steam is the preferred soot blowing media. However, on some units auxiliary steam sources are not available when starting a unit, and normal sootblowing steam requirements are not reached until a later stage in the start-up process. In those cases, compressed air is an acceptable alternate blowing media, though less effective than steam. If neither steam nor compressed air is available, then extra attention must be given to any possible fuel oil carryover which could deposit in the airheater. A device to identify such carryover would be a water-cooled lance, temporarily located in the gas path leading from the economizer outlet to the airheater gas inlet. This lance, maintained at 93℃ (200℉) or below, will cause any oil vapor in the flue gas to condense on it, If the lance is periodically withdrawn by a plant observer, it will indicate if corrective action to the oil firing system has to be taken. Additionally, for those units where neither auxiliary steam nor compressed air is available for cold starts on oil, the hot spot detection system must be in service. This system will identify any possible start of a fire in the airheater. Also, the top oil elevations should not be utilized since they are more prone to cause oil carryover. Special attention must be given to the readings of gas and air temperatures leaving the airheater. An unusual increase in any of these temperatures must be investigated immediately. Any indication of an airheater fire must be reacted to immediately because once a fire is well under way it can't be stopped before the airheater is severely damaged. For unit loads below 10% TMCR steam flow, excessive combustion air(more than the required 35% minimum of full load air flow) or unnecessarily high furnace draft (more negative than -12 mm w.g.) should be avoided. Burner tilts should not go above the horizontal position. Changes in the firing pattern should be closely observed in respect to possible carryover. Also, any steam that is available including saturated steam can and should be used for gas air heater soot blowing as long as sufficient steam pressure is available (at least 9 bar / 130 psig). When this minimum steam pressure has been reached, continuous cold end blowing should be initiated and continued until 10% TMCR steam flow is reached. After that gas air heater soot blowing can be reduced to intermittent operation, once every four to eight hours or as required, depending on the fuel being fired. Once the unit is above 10% TMCR steam flow, normal soot blowing can

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be followed using the units own auxiliary steam source as temperature and pressure is built up. The following minimum requirements as delineated in the vendor's "Operating Instructions" should be observed:

Blowing Pressure Temperature Enthalpy Saturation Superheated by

[kg/cm2g] [℃] [kcal/kg] [℃] [℃] 9 327 743 179 148

11 328 743 187 141 14 332 743 197 135 15 333 743 201 132 17 335 743 206 129

WARNING: The greatest danger, for developing an gas air heater fire, is in the initial stages of boiler operation, i.e. boiler chemical cleaning and boiler steam blowing. Experience has shown that during these stages more than the normal precautions need to be taken. This is because there is normally insufficient boiler steam capacity and/or soot blowers are not available for use. Therefore, continuous plant visual observations must be undertaken so the risk of a gas air heater fire can be kept to its very minimum. Once the unit has seasoned on coal, fly ash will have been deposited in various areas of the boiler (especially in the assemblies of the back pass). These ash deposits will absorb some of the vapor before it reaches the gas air heater surfaces so the risk of gas air heater fires will be somewhat diminished. It goes without saying that prolonged low Ioad operation firing oil without blowing the gas air heaters should always be avoided. Water washing has no positive effects in removing oil unburned particles / residue. Only soot blowing would be effective by knocking off these particles. Therefore, when firing oil when sufficient blowing steam is available, the gas air heater should be continuously cleaned utilizing its soot blowers. Gas air heater surfaces should only be water washed, during initial stages of boiler operation and/or subsequent load operations, if heater surfaces become plugged with fly ash (high delta-P) when soot blowing was either ineffective or not available for use. Gas air heater water washing must be in strict accordance with vendor's instructions. Frequent water washing of gas air heater surfaces is not a substitute for the soot blowing process and should be avoided. Frequent washing will decrease the life of gas air heater heating elements.

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Lighting Off

1. Start the gas air heaters. Refer to the gas air heater instructions for operating details.

CAUTION: The ID fans are capable of developing drafts that exceed the furnace design pressure. Therefore, an airflow path through the unit must be established and maintained before starting an ID fan and before opening the ID fan inlet blade pitch by ensuring that other dampers in the system are in the start-up positions indicated in Preparations for Lighting Off, page 2. The ID fan inlet blade pitch must be kept closed or at the minimum open position until after the fan is started. This minimizes the possibility of developing excessive negative pressure in the unit during start-up. Furnace draft must be maintained within safe limits at all times. Extreme care should be taken when draft and airflow controls are in the manual mode. Be alert for possible malfunctions of automatic control equipment resulting in abnormal excursions, negative or positive, in furnace pressure.

2. Start the first draft group: Start one ID fan, then the corresponding FD fan. Open the

outlet shut-off dampers. Adjust the ID fan for proper furnace draft, and set furnace pressure control to automatic. Adjust unit air flow to minimum 35% air flow, and set unit air flow control to automatic.

3. Start the selected scanner air fan.

4. Adjust the fan and wind box dampers to permit a purge airflow of at least 35% of total

airflow and a furnace draft of approximately -12.0 mmw.g. Refer to Initial Firing Precautions.

When lighting off an elevation on manual control, the fuel-air dampers should be closed. Once ignition of the main fuel is established, the fuel-air dampers should be opened in proportion to the fuel elevation firing rate. When the fuel-air dampers are fully open, further damper adjustments should be made, if necessary, with the auxiliary air dampers only. When changing the damper positioning, an entire elevation should be treated simultaneously, that is, damper positioning at the same elevation should always be identical in all wind boxes.

When the steam generator reaches a firing rate at which additional air is required to maintain the design operating excess air, increase the airflow. Refer to the percent excess air versus load curve.

5. When the fans are started, the secondary air damper control should modulate the auxiliary air dampers to maintain a programmed set point differential pressure of 102mmw.g. between the wind box and furnace.

6. Check that all other purge permissives are satisfied. 7. Place the gas temperature probes in service. 8. Initiate a furnace purge.

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9. Upon completion of the purge cycle, check that all firing prerequisites are satisfied,

including the following control settings:

a. Feed water control is on automatic maintaining minimum feed water flow rate of approximately 5% TMCR.

b. Start-up system (BCP and UG valve) is on automatic maintaining minimum water

wall flow.

CAUTION: It is extremely important that minimum water wall flow be maintained at all times when firing the boiler to prevent tube damage due to overheating. If water wall flow falls below the low set point, all fuel must be automatically tripped with a maximum time delay of five(5) seconds.

c. Separator level control is on automatic, i.e. the WR, and ZR level control valves are all in automatic.

d. Furnace pressure control is on automatic.

e. Unit air flow is on automatic maintaining minimum 35% full load air flow.

f. Place HP bypass valve in operation:

(1) Set to "valve position control" and desired preset position of app. 10 - 12% open.

(2) HP bypass valve is set to be controlled along with the pressure rising of boiler.

(3) Pressure and temperature controls for HP bypass valves, HP bypass spray valves, and Spray water pressure reducing valves are on automatic.

g. Place LP bypass valve in operation:

(1) Open LP bypass stop valve after establishing sufficient condenser vacuum and

water supply for de-superheating.

(2) Adjust to pre-set minimum position.

(3) The minimum pressure (13 kg/cm²(g)) is automatically controlled.

(4) Place control on automatic.

h. Place SH and RH temperature controls on automatic, with the steam temperature to enter into the turbine acceptable temperature range.

i. Open LTSH outlet vent valves, SH backpass drain valves, and RH outlet vent

valves.

11. Start one of the PA fans. After fan is started, open the PA fan outlet damper. Bring the

primary hot air duct pressure up to set point by manually adjusting the PA fan inlet blade pitch. Then, transfer to automatic control.

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Airflow must be maintained through the pulverizers whenever the unit is being fired. Therefore, the PA fans must be in service.

If the pulverizers are out of service the pulverizer discharge gates must be fully open. The cold air inlet control dampers must be set to the minimum position. The pulverizer discharge gates are closed during pulverizer maintenance, or when the pulverizers are idle and full of coal and other pulverizers are being started after a unit trip. Refer to emergency procedures, Master Fuel Trip.

12. For cold start-ups, the fuel startup sequence should follow this table:

Sequence Step Elevation Notes 1 AB oil Light Diesel Oil 2 CD oil Heavy Fuel Oil 3 AB oil Heavy Fuel Oil 4 B coal If coal elevation B not available, start coal elevation A 5 C coal If coal elevation C not available, start coal elevation B 6 D coal 7 A coal 8 E coal

13. Initiate a light-off sequence of oil elevation AB start-up oil guns. Refer to the HEA

igniter, WRTE Retractable oil gun, and the Recommended Burner Management System instructions for details.

To minimize the possibility of adverse visible stack emission, it is desirable to use the warm-up oil guns until 35 kg/cm2(g) steam pressure is produced and 175℃ secondary air temperature before firing pulverized coal.

14. Set fuel oil flow(LDO) control to auto and adjust the set point to 7% of TMCR firing

rate. Stabilize the AB elevation for 35 minutes. 15. When elevation AB is in service, close the economizer vent valves. 16. Initiate an elevation start command for HFO elevation CD. Progressively increase

firing rate to 15%TMCR at a rate of 1.5% per minute for 5 minutes and Stabilize the CD elevation for 30 minutes.

17. Stop firing LFO elevation AB by operator stop command after HFO elevation CD

firing stable and substitute HFO for LDO at elevation AB. Firing rate is reduced to 8%TMCR by stopping LDO elevation AB.

18. Initiate an elevation start command for HFO elevation AB. Progressively increase

firing rate to 15%TMCR again. Maintain the firing rate with 15% TMCR until the introducing coal firing is stable.

19. To ensure stable operation of the water system and to ensure sufficient steam flow

through the superheater, firing rate should not be further increased until 8 kg/cm2g is measured in the water separator.

20. As the pressure is raised, first the WR and then the ZR valves will open when

separator water level increases due to boiler water swell. As pressure further increases, the WR and ZR valves will start to close as the water level decreases.

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21. During all start-ups, control the firing rate to keep the maximum furnace exit gas temperature below 1000 ℉ (538 ℃ ), as measured by the furnace outlet gas temperature probe(s) until approximately 10% TMCR steam generation or the turbine is synchronized. Sufficient steam flow must be maintained at all times to assure clearing the superheater and reheater elements of condensate. Do not close the startup drains completely until steam flow through the HP/LP bypass is established.

22. The superheat backpass drain valve can be closed when separator pressure

reaches 3.5 kg/cm2(g). The superheat backpass drain valve closing pressure can be extended from 3.5 kg/cm2(g) to satisfactory point which is convinced to no saturated water drain through drain valve.

23. Progressively increase LP bypass set point to 13 kg/cm²(g). As the HP bypass

opens, the reheater will be warmed and pressurized as steam is passed through the LP bypass and reheat vents. In parallel, close the reheat vent and drain valve to transfer flow and pressure control to the LP bypass station.

24. Close the RH outlet vent valves when RH pressure reaches 3.5 kg/cm2(g). 25. When steam pressure at HP bypass reaches 12 kg/cm2(g), the HP bypass valve is

released to "pressure ramp" mode. The valves will move to nominal 30%, then control the boiler pressure ramp-up to 84 kg/cm²(g).

26. The rate of pressure rise should follow the prescribed start-up curves. In parallel,

close SH vent valve to transfer flow and pressure control to the HP bypass station. 27. When boiler pressure reaches 84 kg/cm²(g), the HP bypass valve is released to

"pressure control" mode, and maintains a constant pressure during turbine rolling, synchronization, and initial loading.

28. After a pressure of 84 kg/cm2(g) is attained, the firing rate can be adjusted to

achieve the required steam temperature for turbine rolling. Target steam conditions are: 6.5% BMCR steam flow, SH = 360℃,RH = 370℃. In case actual produced steam flow is over 6.5% BMCR and 6.5% BMCR steam flow is required at the turbine synchronization, the surplus steam flow bypasses through HP bypass valve.

29. Do not exceed the furnace exit gas temperature limit of 1000℉(538℃) below 10%

TMCR load. Above 10% TMCR load automatic interlocks provide protection from over-firing. When ready to fire coal, the pulverizer serving a lower elevation of coal nozzles should be prepared for operation and started in accordance with Introducing Coal, steps 1 through 5. Adjacent warm-up oil guns supply the required ignition energy. The feeder should be set to keep the furnace exit gas temperature from exceeding 1000℉(538℃).

NOTE: The steam pressure should be increased slowly during the initial start of a new steam generator. This allows sufficient time for checking expansion movements and permits the operators to become familiar with the characteristics of the steam generator and auxiliary equipment. Once these characteristics have been established, subsequent start-ups may be made at the fastest possible rate consistent with maintaining the furnace exit gas temperature limitation of 1000ºF (538℃).

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30. While the unit is heating up, check the boiler expansion movements frequently. Special attention should be given to expansion of the boiler relative to the building steel. Expansion movements should be recorded for comparison with future start-ups. Refer to the pressure Parts Connection and Expansion Movement Diagrams.

31. Maintain separator water level at normal and check the boiler water concentrations

and constituents as frequently as necessary to maintain proper boiler water conditions.

Rolling and Synchronizing the Turbine

1. Confirm the steam conditions, i.e. pressure, temperature, and steam purity, at the turbine are correct for turbine roll. (See turbine manufacturer’s Steam Purity recommendations)

2. Turbine roll, synchronization, and initial loading are all carried out using reheat

steam. Roll the turbine by opening the reheat stop and control valves to the IP turbine per the Turbine manufacturer’s procedures. The HP turbine is maintained in reverse flow using steam from CRH line. During this time, the total steam production is passed through the HP bypass while it remains on "pressure control' mode.

3. SH and RH steam temperatures are maintained by adjusting firing rate and airflow. 4. Synchronize the generator and put on initial load of app. 6.5% according to

turbine/generator startup instructions. Initial load is produced by IP/LP sections of the turbine. The HP section is still in reverse-flow mode.

5. As steam is transferred to the IP turbine during turbine loading, the LP bypass will

close while maintaining RH pressure at 13 kg/cm2 (g).

6. As turbine conditions permit, put feed water heaters into service per manufacturer’s instructions.

7. De-aerator heating steam source is transferred from auxiliary steam system to LP

extraction when LP extraction pressure is adequate.

CAUTION: Operators should be alert to detect the symptoms of water carry-over from the boiler and introduction of water into the turbine, such as: a. A sudden, unexplained drop in steam temperature in either the

main steam or hot reheat line.

b. Vibration in the steam piping resulting from water hammer.

c. Abnormal vibration and differential expansion readings from the turbine supervisory instrumentation.

Operators must be prepared to take necessary steps to prevent turbine damage upon detecting the introduction of water. Refer to the turbine manufacturer's instructions for specific actions to be taken.

8. The firing rate should never exceed the rate necessary to match the total steam

generation.

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If the unit is put on line before design operating pressure is reached, a further increase of firing rate should be in accordance with a gradual rate of pressure increase consistent with increasing load. Do not allow steam temperature to exceed the values shown in the steam temperature versus load curve.

9. Start the second set of fans as required. Refer to the fan manufacturer's instructions

for operating details.

Introducing Coal

1. Coal firing can commence when steam flow reaches app. 15%TMCR and LP bypass is closed.

2. Pulverizer B or alternately pulverizer A, serving the lower elevations of coal nozzles,

should be prepared for operation at this time so that it can be readily started. The seal air fan must be placed in service at this time. Refer to the Recommended Burner Management System instructions for start-up sequences and controls. The condition may exist when an upper elevation of coal will be placed in service for start-up, with ignition by the associated elevation of oil guns. Start-up by this procedure is allowable, however, if utilized, care must be exercised not to exceed the furnace exit gas temperature limitation of 1000 ℉ (538 ℃ ), or the steam temperature values shown in the steam temperature versus load curve.

3. When placing the first pulverizer in service, make sure the pulverizer start

permissives are satisfied. Refer to the Recommended Burner Management System instructions. The coal fuel-air dampers should remain closed until ignition is established. Make sure the nozzle tilts are horizontal. PA fan/fans must be in service. If the unit start-up follows a master fuel trip, the pulverizer may not be empty. Operate the pulverizer to clear it of excess coal before starting the feeder. During the pulverizer clearing procedure, the pulverizer discharge gates of all other idle pulverizers must be closed. This prevents hot furnace gases from entering the coal piping and the idle pulverizers. (See emergency procedures) When most of the coal has been removed from the pulverizer, the pulveriser can be introduced as per normal procedure Be sure the ignition energy in the furnace is established before starting the pulverizer. If ignition does not take place within 5 seconds after coal appears at the coal nozzles, stop the feeder. Determine the cause of ignition failure before attempting to restart the feeder .

4. Start the pulverizer. Open the hot air shutoff gate, adjust pulverizer airflow to 100%

by opening the hot air damper, and bring the pulverizer up to the required operating temperature without coal. Place the pulverizer airflow and temperature control on automatic. When ready to fire coal, manually start the feeder at minimum rating. Ignition of the pulverized coal should take place immediately. When the pulverizer is proven in service, the fuel-air dampers should open automatically. Maintain the fuel feed at a minimum rate consistent with stable ignition. Watch the fires.

Pulverizer start-up will cause a sudden and sharp increase in steam pressure. The pressure will level out rapidly as the HP bypass station responds.

Check the pulverizer oil temperature. When the temperature approaches 150℉ (66℃) turn on the water to the oil cooler or adjust the lube oil control system. The oil

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temperature should never exceed 160℉ (71℃).

5. Maintain the proper coal/air temperature leaving the pulverizers. Regulate the hot and cold air dampers to keep the temperature between 77℃ and 82℃ at the pulverizer outlet. The pulverizer outlet mixed air temperature should be revised at site during commissioning period based on coal characteristics which will be using.

6. At the prescribed load per turbine manufacturer, the HP turbine is transferred to

forward flow. The HP turbine control valves are opened until sufficient flow is established through the HP section of the turbine. The HP bypass valve compensates by closing to control the steam pressure at the set-point.

7. Continue the transfer to forward-flow until the first three turbine valves are fully

opened and HP bypass valves are fully closed. 8. Start the second pulverizer when the HP bypass is closed. 9. When the feeder rating of the first pulverizer has reached approximately 80%, place

the second pulverizer, which supplies the adjacent elevation of coal nozzles, in service in a similar manner. When the second pulverizer is proven in service, equalize the feeder rating of both. The warm-up oil guns must remain in service until both feeders proven signal is achieved.

If the adjacent pulverizer is not available for service, place the pulverizer serving the next closest elevation of coal nozzles in service. Do not remove the warm-up oil guns from service until the two(2) adjacent coal elevations are in service with feeder ratings greater than 50%.

10. Increase total fuel firing rate to 43% TMCR with second pulverizer. Also decrease

total oil firing rate to 10% TMCR by the operator decreasing command. 11. After reaching 43% TMCR load and firing is stable, oil firing load is maintained 10%

TMCR for coal firing stabilization.

12. The Burner Management System and secondary air damper controls should close the auxiliary air dampers which serve compartments adjacent to the coal nozzles out of service when the unit load reaches 35% TMCR load. These controls should also gradually increase the windbox-to-furnace differential pressure to approximately 102 mm w.g. as load is increased per the prescribed curve.

13. The airflow to the furnace must be sufficient for the firing rate. Automatic control

equipment is normally arranged to maintain such a balanced draft condition. The operation of the O2 measuring devices at economizer outlet, often tied in with the airflow control, should be checked periodically.

Initial Load Increase

1. The third pulverizer can be started after steam flow reaches 30-35% TMCR. Place additional pulverizers in service in a similar manner. Pre-warm the pulverizer, and initiate an elevation start command. After the coal elevation is proven in service (signal from BMS), the feeder is put into automatic.

2. Increase total firing rate to 43% TMCR. Oil elevation CD is issued an elevation stop

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command by the operator. 3. After total firing rate reaching 65% TMCR load and firing is stable, oil elevation AB is

issued an elevation stop command by the operator . 4. Before and after oil elevation AB is stopped, ensure coal elevation A or B shows

flame through flame scanner indications. 5. After stable firing is established, put into service the second BFP(M) per the

manufacturer procedures.

NOTE: Before increasing the total firing rate above 35% TMCR, feedwater quality must be verified to be within the limits for normal firing as defined in Appendix A.

6. Start the ESP per manufacturer’s instructions. 7. During load increase in automatic load control, the BMS shall be given a signal to

start the next available coal elevation. After a coal elevation is proven in service (signal from BMS), the feeder is put into automatic.

8. The steam temperature at the separator inlet will reach a stable superheated

condition at app. 35% TMCR, causing the level in the separator to decrease and eventually disappear. The boiler is now in once-through mode(dry mode). The BCP(Boiler Circulating Pump) will be stopped automatically.

9. When the BCP stops, the warm-keeping system of the start-up system should be put

into operation. 10. The boiler/turbine is now ready for automatic load dispatch. The control system shall

monitor unit loading and will start/stop firing equipment by the automatic load program.

11. Place additional pulverizers in service as the unit load demand increases. The

pulverizer serving the lowest coal nozzle elevation not already in service should be started, if available, when the feeders in service reach the 50% rating. As each pulverizer is placed in service, the required ignition energy must be available. When the unit firing conditions are stabilized, all warm-up oil guns may be taken out of service. Refer to the Recommended Burner Management System instructions.

12. Place the steam temperature control and combustion control on automatic when

firing conditions are stable and the temperature and pressure control set points have been reached. Please refer to the steam temperature and combustion control logic, ABC Logic.

13. Make frequent visual observations of furnace conditions to ensure that no excessive

slag build-up is developing. This is especially important when burning coal with low ash fusion temperatures. Operate the soot blowers as required to keep the steam temperature control (nozzle tilts, desuperheaters) within operating range. If response to soot blowing is sluggish or insignificant, reduce unit load or increase excess air to assist in lowering steam temperature and take steps to eliminate the cause of the erratic steam temperatures.

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WARNING: Efforts shall be made to ensure that the furnace bottom is maintained clean such that a situation like hopper full of ash does not occur. Under no circumstances should the level of ash in the bottom ash hopper be allowed to reach the level of the coutant opening, thus blocking further removal of ash from the furnace. Under no circumstances should ash or slag be allowed to bridge across the coutant opening. If bridging starts to occur, load should be reduced in an attempt to shed the buildup. If complete bridging across the coutant opening does occur, immediate steps should be taken to shut the steam generator down to cold following normal shutdown procedures. The ash should then be removed by means which preclude damage to the water wall tubes. Refer to "Preventing Furnace Bottom Overloading" for additional operating recommendations. If excessive slagging of furnace walls is experienced, make sure that the bottom ash removal system is in good working condition to handle the increased quantity of bottom ash that accompanies higher slagging rates.

14. Overfire air is used for NOx control and is automatically controlled as a function of

total unit air flow. The effective starting load must be determined during initial unit operation. Refer to the CCOFA damper characteristics furnishing the unit air flow Vs OFA damper opening position under Tilting Tangential Firing system section in O & M manual.

NORMAL OPERATION UNIT LOAD CHANGES

The normal load range under automatic control is 35% to 100% TMCR. The boiler load change rates should not exceed 2% per minute (16 MW per minute) between 35% and 50% load, and should not exceed 3% per minute (24 MW per minute) above 50% load. These maximum load change rates can only be achieved if control actions are well coordinated and well tuned. Below 35% TMCR load, the change rates should not exceed that shown on the prescribed start-up curves. During normal operation, with the unit on the line, unit load changes may alter pulverizer loading rate and/or the number of pulverizers in service. A wide range of load control can be achieved with the pulverizers on automatic. Refer to the Recommended Burner Management System instructions for pulverizer start and stop sequences and ignition energy requirements.

Decreasing Load

If the unit load decreases to a point at which the feeder rating of the pulverizers in service is reduced to 40%, a pulverizer should be taken out of service. Normally the

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pulverizer serving the lower-most coal elevation is removed. To remove the pulverizer from service, proceed as follows:

1. Ensure that pulverizer ignition energy is available in the furnace. Start the oil gun

elevation associated with the coal elevation served by the selected pulverizer. 2. Gradually reduce the feeder rating of the selected pulverizer to minimum. 3. When the feeder rating is at minimum, close the coal shut off gate above the feeder,

run the feeder until the spout and feeder are empty, and then stop the feeder.

4. Make sure the pulverizer is completely empty by running it for at least 5 minutes.

5. Close the hot air shut off gate.

6. Allow the pulverizer coal/air temperature to drop to 50 ℃ , and then stop the pulveriser.

7. The associated warm-up oil guns may be shut down when the furnace conditions

have stabilized.

Additional pulverizers can be taken out of service in a similar manner when the feeder ratings again drop to 40%. Every effort should be made to keep adjacent pulverizers in service. If, due to maintenance, a pulverizer is not available, skipping the coal elevation served by that pulverizer is permissible. Skipping two(2) coal elevations is not recommended and is only permissible through the use of the associated oil guns. If the unit load is reduced to a point at which only two(2) pulverizers are required, the associated oil guns adjacent to the coal nozzles in service must be placed in service to ensure positive ignition when the feeder ratings drop to 65% or less. Auxiliary supporting fuel should be used whenever, in the operator's judgment, ignition stabilization is necessary.

Increasing Load

If, after several pulverizers have been taken out of service due to a load decrease, load increases again to a point at which the feeder rating of the pulverizers in service exceeds 50% of maximum, place an additional pulverizer in service as follows

1. Establish the ignition energy required for the coal elevation served by the selected

pulverizer . 2. Start the pulverizer . 3. Open the hot air shutoff gate and damper to 100% airflow and bring the pulverizer

up to operating temperature.

4. Start the coal feeder. The feeder control should be on manual and at minimum feeder rating.

5. When the pulverizer is grinding and coal ignition has been established, gradually

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increase the feeder rating until it equals that of the other pulverizers in service. Then, place the pulverizer on automatic control.

6. The associated oil guns may be taken out of service when the furnace conditions

have stabilized and at least two(2) pulverizers are in service, each with a feeder rating of at least 65%.

7. Place additional pulverizers in service in the same manner, as required.

NORMAL SHUTDOWN TO COLD The following procedures for normal shutdown assume that the unit is operating at full load on automatic control, and the intention is to reduce the unit pressure to zero and cool the boiler completely.

CAUTION: Exercise care to prevent water from entering the turbine through the main steam line(s), the hot reheat line(s), or the cold reheat line(s) during and after the shutdown process. This prevents water damage to the turbine during a subsequent restart. Possible water sources are: a. Overflow from the separator into the superheater when a high

water level exists.

b. Water entering the superheater or reheater through the desuperheaters due to open desuperheater control valves or valve leakage with the feed pumps running.

1. Reduce the unit load at a rate of 2% per minute following the prescribed sliding

pressure vs. load curve. Hold pressure constant at app. 125 kg/cm2g until the turbine is taken off line. Reduce the firing rate in line with the decreasing steam flow. Reduce the steam temperature at the rate prescribed by the turbine manufacturer.

Leave the steam temperature, combustion and feedwater controls on automatic until better control can be obtained on manual.

2. When the feeder rating on all pulverizers is reduced to 40% put the upper elevation

of oil guns in service. Place the pulverizer supplying the upper coal elevation on manual control. Gradually reduce the feeder rating. When minimum rating is reached, close the coal shutoff gate above the feeder, run the feeder until the spout and feeder are empty, and then stop the feeder. Make sure the pulverizer is completely empty by running it for at least Five (5) minutes. Close the hot air shutoff gate. When the coal/air temperature has dropped to approximately 50℃,then, stop the pulverizer. Unless an emergency condition exists, the pulverizer should always be emptied before being stopped.

3. As pulverizers are taken out of service, the secondary air damper control system should close the associated windbox damper and adjust the other dampers to compensate for the reduced firing rate.

4. Take the second pulverizer supplying the next highest elevation of coal nozzles out

of service when the feeder rating on all remaining pulverizers reaches 40%. Continue taking additional pulverizers out of service in the same manner. When only two(2) pulverizers remain in service, the adjacent oil guns must be placed in service

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prior to reducing the feeder rating of either pulverizer to below 65%.

It is recommended that this consecutive elevation shutdown sequence be followed. Firing coal at separated/non-adjacent coal nozzle elevations without auxiliary supporting fuel is not permitted.

5. Overfire air will be reduced automatically as the unit load drops per the prescribed control curve. Stop admitting overfire air when the unit load drops below the predetermined starting load. Keep the overfire air dampers at minimum open position to prevent the nozzles from overheating.

6. Operate all soot blowers. Refer to the soot blowing philosophy section and to the

soot blower manufacturer's instructions. 7. Reduce the airflow in line with the fuel reduction until 35% BMCR airflow is reached.

Do not reduce the airflow below this rating until all fires are out and the unit is off the line (Refer to Figure 1, typical air flow curve of this section, and the percent excess air versus load curve. To avoid firing instability during this period of high airflow, the auxiliary air dampers at all elevations should open and the windbox-to-furnace differential pressure reduced to its lower setting per the prescribed control curve. Refer to the auxiliary air damper characteristics furnishing the unit load Vs windbox to furnace differential pressure under Tilting Tangential Firing System section in O & M manual.

8. Check the boiler expansion movements as the load is reduced. 9. At app. 35% steam flow, open the HP and LP bypass valves. Remove the turbine

from service following the turbine operating instructions. Boiler steam production will be transferred to HP/LP bypass operation.

10. At app. 35% TMCR steam flow, the steam temperature at the separator inlet will fall

below the superheated region, and a water level will develop in the separator. The boiler must now be returned to recirculation mode, and the BCP must be started to provide minimum water wall flow when a water level in the separator reaches over 3 meters.

11. After the last pulverizer is shut down, remove the oil guns from service. Shut off the

cooling water to the pulverizers. All fires should be extinguished when the unit is off the line. With no pulverizers in service, the PA fans and the pulverizer seal air fans may also be shut down. The PA fans should not be shut down if the gas air heater gas inlet temperature is above 400℉(205℃).

12. After all fuel firing is removed, close the HP and LP bypass valves. 13. Immediately after closing the HP/LP bypass valves, open all superheater outlet

vents and drains and all reheater vent and drains. Open the steam line and turbine drains per the turbine manufacturer's instructions.

14. Close the de-superheater isolating valves. 15. Do not exceed the following cool down rates referenced to saturation temperature in

the separator: For pressure above 35 bar: 83℃per 15 minutes; for pressure less than 35 bar: 42℃ per 15 minutes.

16. If the steam generator will not be entered during the shutdown period, a slower rate

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of pressure and temperature decay may be desirable. This can be accomplished as follows:

a. Purge the unit by running the ID and FD fans for at least Five(5) minutes at 35%

TMCR airflow after the fires are extinguished. b. Reduce the airflow through the unit to minimum. Keep the fans and gas air

heaters in service until the unit has cooled to the desired temperature. Gas air heaters and fans should not be taken out of service until the gas air heater gas inlet temperatures have dropped below 400℉ (205℃).

c. Keep the boiler circulating pump in service until the boiler water temperature is reduced to the desired point ( 300 ℃ i.e. app. 15 ℃ less than the saturation temperature corresponding to the SHO pressure at 35 % TMCR load). Keep the water level near normal in the separator, adding makeup water as required.

17. If the cooling process must be accelerated to permit entry into the steam generator

for maintenance, proceed as in step 16, except:

a. Continue running the fans at the desired rate to cool the unit. The gas air heaters may be shut down when the gas entering temperature has dropped below 400℉ (205℃). Refer to the gas air heater instructions.

With the gas air heaters stopped and the fans running, deposits of fly ash may accumulate in the gas air heater and cause a rotor unbalance. Therefore before stopping the GAHs, fans should be stopped.

b. Keep the boiler circulating pump in service to increase recirculation. Keep the

water level near normal in the separator. Shut down the pump when the boiler water temperature is reduced to the desired level, which is differential temperature, 20˚C, between separator outlet water temperature and economizer inlet water temperature.

18. Do not shut down the scanner air fan until the furnace temperature has dropped to

below 140℉ (60˚C). 19. If the boiler is to be laid up wet, refer to Lay-up Procedures. 20. If the boiler is to be emptied, the boiler water temperature should be reduced to at

least 200℉ (93℃) before draining. NORMAL SHUTDOWN TO HOT STANDBY

CAUTION: Exercise care to prevent water from entering the turbine through the main steam line(s), the hot reheat line(s), or the cold reheat line(s) during and after the shutdown process. This prevents water damage to the turbine during a subsequent restart. Possible water sources are: a. Overflow from the separator into the superheater when a high

water level exists. b. Water entering the superheater or reheater through the

desuperheaters due to open desuperheater control valves or valve

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leakage with the feed pumps running.

During a shutdown to hot standby, it is assumed that the unit will be shut down for a relatively short period of time and that the existing pressure and temperature conditions will be substantially maintained. A procedure similar to that for normal shutdown should be used, with the following exceptions: 1. Reduce steam pressure in line with unit load reduction, following the prescribed

sliding pressure curve. After the turbine is off the line and fires removed and HP/LP bypass closed, the boiler may be bottled up by closing all superheater drains and vents. Reheater drains and vents are kept open. If the unit will be restarted soon enough to prevent turbine metal temperatures from decreasing appreciably, it may be desirable to cool the turbine metal to below 800℉ (427℃) by reducing the steam temperature and pressure, while the unit load is being reduced. This will reduce the steam/turbine metal differential temperature upon restart.

2. It is not necessary to close the feeder inlet gates and run the spouts and feeders

empty. As each pulverizer is taken out of service, gradually reduce the feeder rating. To minimum and then stop the feeder. Make sure the pulverizer is completely empty by running it for at least Five (5) minutes. Close the hot air shutoff gate. When the coal/air temperature has dropped to approximately 50℃,then, stop the pulverizer.

3. The boiler circulating pump should be kept in operation to ensure adequate boiler

water circulation. This will prevent possible local overheating due to hot slag deposits.

WARNING: If the fans are shut down with an gas air heater gas inlet temperature above 400℉ (205℃), the gas air heater must be kept rotating. However, running an gas air heater with the gas inlet temperature above 400℉(205℃) and no air flow through it will cause seal damage followed by excessive leakage during operation. (Refer to gas air heater instructions.) The decision to bottle up the unit above 400℉ (205℃) must be made with this in mind.

CAUTION: If combustible deposits are present in the gas air heater elements, the gas air heater gas inlet temperature ,must be reduced to 400℉ (205℃) before the FD fans, ID fans and gas air heaters are shut down. The gas air heaters must be thoroughly cleaned to remove any combustible products before they are shut down.

4. After the fires are extinguished, keep the ID, FD and PA fans and gas air heaters

running until the gas air heater gas inlet temperatures have dropped to below 400℉ (205℃). Close all gas duct and secondary air duct dampers after the gas air heaters and fans are shut down. Keep the scanner air fan running.

5. Shut down the boiler circulating pump after the unit has been bottled up. However, if

an immediate hot restart is anticipated, keep the boiler circulating pump in service for more effective warm-up circulation.

CAUTION: The differential temperature between the feed water and boiler metal must never exceed 200℉(111℃) (separator during initial filling or separator and superheater outlet header during filling for hydrostatic test).

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6. The operator should observe the separator level periodically so that he is always

aware of the actual level and can take the appropriate action to re-establish the water level when the unit is being restarted.

When the boiler circulating pump is shut down, the water level will rise. As the unit cools and the water shrinks, makeup water should be added intermittently to prevent the water from dropping below normal level. Adding relatively cold feed water will establish a reservoir of cooler water in the system. If a boiler circulating pump is then started, this cooler water will produce a cycle of cool and hot temperature transients to the pump casing and other pressure parts of the boiler. At least one pump should be operating when makeup water is added.

WARM START-UP

Assuming that the unit has been down for a short period of time (less than app. 36 hours), the unit can be re-started in a similar sequence to Cold Start-up procedure as outlined below:

Warm Start Conditions 1 Boiler separator metal temperature > 100℃ and 2 Boiler pressure < 30 kg/cm2 (g)

Preparations, Lighting Off, and Load Increase

1. Make a general inspection of the steam generator and check the points outlined in the Preparations for Lighting Off for Cold Start-Ups.

2. Verify that the boiler is filled with water and properly vented of air per the points

outlined for Cold Start-ups. 3. Verify that the boiler water quality is within specified limits per the points outlined for

Cold Start ups. 4. Start the Boiler Circulating Pump per the points outlined for Cold Start-ups. 5. Observe the initial firing precautions and gas air heater protection per the procedure

for Cold Start-ups.

Lighting Off

1. Start the gas air heaters. Refer to the gas air heater instructions for operating details. 2. Start the first draft group: Start one ID fan, then the corresponding FD fan. Open the

outlet shut-off dampers. Adjust the ID fan for proper furnace draft, and set furnace pressure control to automatic. Adjust unit airflow to minimum 35% TMCR air flow, and place unit air flow control to automatic.

3. Start the second draft group: After closing the outlet shut-off dampers, start the

other ID fan, then the corresponding FD fan. Open the shutoff dampers and adjust

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blade pitch to balance with the first group, and place on automatic control. 4. Start the selected scanner air fan. 5. Place the gas air pre heater temperature control (steam coil air pre heaters) to

automatic. 6. Adjust the fan and wind box dampers to permit a purge airflow of at least 30% of

BMCR airflow and a furnace draft of approximately negative 12.0 mmwg. Refer to Initial Firing Precautions.

7. When the fans are started, the secondary air damper control should modulate the

auxiliary air dampers to maintain a programmed set point differential pressure between the wind box and furnace.

8. Check that all other purge permissive is satisfied. 9. Place the gas temperature probes in service. 10. Initiate a furnace purge. Upon completion of the purge cycle, check that all firing

prerequisites are satisfied, including the following:

a. Feed water control is on automatic maintaining minimum feed water flow rate of approximately 5% TMCR.

b. Start-up system (BCP and UG valve) is on automatic maintaining minimum

water wall flow. c. Separator level control is on automatic, i.e. the WR, and ZR level control valves

are all on automatic. d. Furnace pressure control is on automatic. e. Unit air flow is on automatic maintaining minimum 35% TMCR air flow. f. Place HP bypass valve in operation: 1) Set to "valve position control" and desired preset position of app. 10 - 12% open. 2) HP bypass valve is set to be controlled along with the pressure rising of boiler. 3) Pressure and temperature controls for HP bypass valves with safety function, HP

bypass spray valves, and Spray water pressure reducing valves are on automatic.

g. Place LP bypass valve in operation:

1) Open LP bypass stop valve after establishing sufficient condenser vacuum and

water supply for de-superheating. 2) Adjust to pre-set minimum position. 3) The minimum pressure 13 kg/cm2(g) is automatically controlled. 4) Place control on automatic.

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h. Place SH and RH temperature controls on automatic, with set-points of 400℃ for

SH and 410℃ for RH (or at least 50℃ over saturation). i. Open LTSH vent valves, and RH outlet vent valves.

j. SH backpass drain valves are open after 10 minutes from light-up.

11. Start two(2) PA fans per the points outlined for Cold start up. 12. For warm start-ups, the fuel startup sequence should follow this table:

Sequence

Step Elevation Notes

1 CD oil Heavy Fuel Oil 2 AB oil Heavy Fuel Oil 3 B coal If coal elevation B not available, start coal elevation A 4 C coal If coal elevation C not available, start coal elevation A 5 D coal 6 A coal 7 E coal

13. Initiate a light-off sequence of oil elevation CD warm-up oil guns by using HFO in

case of atomizing steam is available. Refer to the HEA igniter, WRTE Retractable oil gun, and the Recommended Burner Management System instructions for details.

To minimize the possibility of adverse visible stack emission, it is desirable to use the warm-up oil guns until 35 kg/cm²(g) steam pressure is produced and 175℃ secondary air temperature before firing pulverized coal.

14. Set fuel oil flow control to auto and adjust the set-point to 1.5% of TMCR firing rate.

Stabilize the CD elevation for 15 minutes.

15. When elevation CD is in service, close the economizer vent valves.

16. To ensure stable operation of the water system and to ensure sufficient steam flow through the superheater, firing rate should not be further increased until 8kg/cm²(g) is measured in the water separator.

17. Initiate an elevation start command for oil elevation AB. Stabilize the AB elevation.

The total oil firing rate will be kept for coal firing support.

18. As the pressure is raised, the WR and ZR valves will open when separator water level increases due to boiler water swell. As pressure further increases, the WR and ZR valves will start to close as the water level decreases.

19. During all start-ups, control the firing rate to keep the maximum furnace exit gas

temperature below 1000 ℉ (538 ℃ ), as measured by the furnace outlet gas temperature probe(s) until approximately 10% steam generation or the turbine is synchronized. Sufficient steam flow must be maintained at all times to assure clearing the superheater and reheater elements of condensate. Do not close the startup drains completely until steam flow through the HP/LP bypass is established.

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20. The superheat backpass drain valve can be closed when separator pressure

reaches 5 kg/cm2g. The superheat backpass drain valve closing pressure can be extended from 5 kg/cm2g to satisfactory pressure which is convinced to no saturated water drain through drain valve.

21. Progressively increase LP bypass setpoint to 13 kg/cm²(g). As the HP bypass opens,

the reheater will be warmed and pressurized as steam is passed through the LP bypass and reheat vents. In parallel, close the reheat vents and drains to transfer flow and pressure control to the LP bypass station.

22. Close the RH outlet vent valves when RH pressure reaches 3.5 kg/cm²(g). 23. When steam pressure at HP bypass reaches 12 kg/cm²(g), the HP bypass valve is

released to "pressure ramp" mode. The valves will move to nominal 30%, then control the boiler pressure ramp-up to 84 kg/cm2(g). Firing rate is maintained as a stable load until coal firing point.

24. The rate of pressure rise should follow the prescribed start-up curves. In parallel,

progressively throttle the SH outlet vents to transfer flow and pressure control to the HP bypass station.

25. When boiler pressure reaches 84 kg/cm²(g), the HP bypass valve is released to


26. After a pressure of 84 kg/cm²(g) is attained, the firing rate can be adjusted to

achieve the required steam temperature for turbine rolling. Target steam conditions are: 6.5%TMCR steam flow, SH = 400℃, RH = 410℃. In case actual produced steam flow is over 6.5% BMCR and 6.5% BMCR steam flow is required at the turbine synchronization, the surplus steam flow bypasses through HP bypass valve.

27. Do not exceed the furnace exit gas temperature limit of 1000℉(538℃) below 10%

boiler load. Above 10% boiler load automatic interlocks provide protection from over-firing.

28. While the unit is heating up, check the boiler expansion movements frequently. 29. Maintain separator water level at normal and check the boiler water concentrations

and constituents as frequently as necessary to maintain proper boiler water conditions.

Rolling and Synchronizing the Turbine

1. Confirm the steam conditions, i.e. pressure, temperature, and steam purity, at the turbine are correct for turbine roll. (See turbine manufacturer’s Steam Purity recommendations)


steam. Roll the turbine by opening the Reheat Stop and Control Valves to the IP turbine per the Turbine manufacturer’s procedures. The HP turbine is maintained in reverse flow using steam from CRH line. During this time, the total steam production is passed through the HP bypass while it remains on "pressure control' mode.

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turbine/generator startup instructions. Initial load is produced by IP/LP sections of the turbine. The HP section is still in reverse-flow mode.

5. As steam is transferred to the IP turbine during turbine loading, the LP bypass will

close while maintaining RH pressure at 13kg/cm²(g). 6. As turbine conditions permit, put feedwater heaters into service per manufacturer’s

instructions. 7. De-aerator heating steam source is transferred from auxiliary steam system to LP

extraction when LP extraction pressure is adequate. 8. The firing rate should never exceed the rate necessary to match the total steam

generation. 9. If the unit was started with one set of fans in service, start the second set of fans as

required. Refer to the fan manufacturer's instructions for operating details. Introducing Coal

1. Coal firing can commence when steam flow reaches app. 8%TMCR and HP bypass and LP bypass should be regulated in order that the turbine can accept the produced steam conditions.

2. Pulverizer B or alternately pulverizer A, serving the lower elevations of coal nozzles,

should be prepared for operation at this time so it can be readily started. The selected pulverizer seal air fan must be placed in service at this time. Refer to the Control Logic of Burner Management System for start-up sequences and controls.

3. When placing the first pulverizer in service, make sure the pulverizer start

permissives are satisfied. Refer to the Recommended Burner Management System instructions. The coal fuel-air dampers should remain closed until ignition is established. Make sure the nozzle tilts are horizontal. Both PA fans must be in service. If the unit start-up follows a master fuel trip, the pulverizer may not be empty. Operate the pulverizer to clear it of excess coal before starting the feeder. During the pulverizer clearing procedure, the pulverizer discharge gates of all other idle pulverizers must be closed. This prevents hot furnace gases from entering the coal piping and the idle pulverizers. (See EMERGENCY PROCEDURES) When most of the coal has been removed from the pulverizer, the pulveriser can be introduced as per normal procedure. Be sure the ignition energy in the furnace is established before starting the pulverizer. If ignition does not take place within five(5) seconds after coal appears at the coal nozzles, stop the feeder. Determine the cause of ignition failure before attempting to restart the feeder.

4. Start the pulverizer. Open the hot air shutoff gate, adjust the hot air damper to 100%

pulverizer airflow, and bring the pulverizer up to the required operating temperature

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without coal. Place the pulverizer airflow and temperature control on automatic. When ready to fire coal, manually start the feeder at minimum rating. Ignition of the pulverized coal should take place immediately. When the pulverizer is proven in service, the fuel-air dampers should open automatically. Maintain the fuel feed at a minimum rate consistent with stable ignition. Watch the fires.

Pulverizer start-up will cause a sudden and sharp increase in steam pressure. The pressure will level out rapidly as the HP bypass station responds. Check the pulverizer oil temperature. When the temperature approaches 150℉ (66℃) turn on the water to the oil cooler or adjust the lube oil control system. The oil temperature should never exceed 160℉ (71℃).

5. Maintain the proper coal/air temperature leaving the pulverizers. Regulate the hot

and cold air dampers to keep the temperature between 77℃ and 82℃ at the pulverizer outlet. The pulverizer outlet mixed air temperature should be revised at site during commissioning period based on coal characteristics which will be using.

6. At the pre-scribed load per turbine manufacturer, the HP turbine is transferred to

forward-flow. The first three turbine control valves are opened until sufficient flow is established through the HP section of the turbine. The HP bypass valve compensates by closing to control the steam pressure at the set point.


opened and HP bypass valves are fully closed. 8. Start the second pulverizer when the HP bypass is closed. 9. When the feeder rating of the first pulverizer has reached approximately 50%, place

the second pulverizer, which supplies the adjacent elevation of coal nozzles, in service in a similar manner. When the second pulverizer is proven in service, equalize the feeder rating of both. The warm-up oil guns must remain in service until both feeders proven signal is achieved.

If the adjacent pulverizer is not available for service, place the pulverizer serving the next closest elevation of coal nozzles in service. Do not remove the warm-up oil guns from service until the two(2) adjacent coal elevations are in service with feeder ratings greater than 50%.

10. Increase total firing rate to 45% TMCR. 11. The Burner Management System and secondary air damper controls should close

the auxiliary air dampers which serve compartments adjacent to the coal nozzles out of service when the unit load reaches 30% of TMCR load. These controls should also gradually increase the wind box-to-furnace differential pressure to approximately 102 mm w.g.

12. The airflow to the furnace must be sufficient for the firing rate. Automatic control

equipment is normally arranged to maintain such a balanced draft condition. The operation of the O2 measuring devices at economizer outlet, often tied in with the airflow control, should be checked periodically.

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Initial Load Increase 1. The third pulverizer can be started after steam flow reaches 35-40% TMCR. Place

additional pulverizers in service in a similar manner. Pre-warm the pulverizer and Initiate an elevation start command. After the coal elevation is proven In service (signal from BMS), the feeder is put on automatic.

2. Increase total firing rate to 55% TMCR. 3. After reaching 45% TMCR of steam load and firing is stable, oil elevation CD is

issued an elevation stop command by the operator. 4. After oil elevation CD is stopped, ensure coal elevation C or D shows flame through

flame scanner indications.

5. The forth pulverizer is started along with steam load increase.

6. Reduce oil firing to minimum after starting pulverizer A. Oil elevation AB is issued an elevation stop command by the operator.

7. After stable firing is established, put into service the second BFP(M) per the

manufacturer procedures.

NOTE: Before increasing the total firing rate above 35% TMCR, feed water quality must be verified to be within the limits for normal firing as defined in Appendix A.

8. Start the ESP per manufacturer’s instructions. 9. During load increase, the BMS shall be given a signal to start the next available coal

elevation. After a coal elevation is proven in service (signal from BMS), the feeder is put on automatic.

10. The steam temperature at the separator inlet will reach a stable superheated

condition at app. 35% TMCR, causing the level in the separator to decrease and eventually disappear. The boiler is now in once-through mode. The BCP will be stopped automatically.

11. When the BCP stops, the warm-keeping system of the start-up system should be put

into operation. 12. The boiler/turbine is now ready for automatic load dispatch. The control system shall

monitor unit loading and will start/stop firing equipment by the automatic load program.

13. Place additional pulverizers in service as the unit load demand increases. The

pulverizer serving the lowest coal nozzle elevation not already in service should be started, if available, when the feeders in service reach the 50% rating. As each pulverizer is placed in service, the required ignition energy must be available. When the unit firing conditions are stabilized, all warm-up oil guns may be taken out of service. Refer to the Control Logic of Burner Management System for start-up sequences and controls.

14. Place the steam temperature control and combustion control on automatic when

firing conditions are stable and the temperature and pressure control set points have

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been reached. Refer to the control system manufacturer's instructions for specific procedures.

15. Make frequent visual observations of furnace conditions to ensure that no excessive

slag build-up is developing. This is especially important when burning coal with low ash fusion temperatures. Operate the soot blowers as required to keep the steam temperature control (nozzle tilts, de-superheaters) within operating range. If response to soot blowing is sluggish or insignificant, reduce unit load or increase excess air to assist in lowering steam temperature and take steps to eliminate the cause of the erratic steam temperatures. Refer to Soot Blowing O&M manual.

If excessive slagging of furnace walls is experienced, make sure that the bottom ash removal system is in good working condition to handle the increased quantity of bottom ash that accompanies higher slagging rates.

16. Overfire air is used for NOx control and is automatically controlled as a function of

total unit air flow. The effective starting load must be determined during initial unit operation.

HOT START-UP

Assuming the unit has been down for a comparatively short period of time (<8 hours) and considerable steam pressure has been maintained, use the following procedures to restart the unit:

Hot Start Conditions 1. SH outlet header metal temperature >= 300℃ and 2.Main steam pressure ≥ 30 kg/cm2(g) and < 120 kg/cm2(g)

Preparations, Lighting Off, and Load Increase

1. Make a general inspection of the steam generator and check the points outlined in the Preparations for Lighting Off for Cold Start Ups.

2. The boiler circulating pump should still be in service. 3. If the gas air heaters and fans were shut down at reduced temperature(see

NORMAL SHUTDOWN TO HOT STANDBY, step 4), start the gas air heaters and fans as outlined under COLD START -UP, Lighting Off. If the unit was bottled up hot with the gas air heaters still running start the fans in the normal sequence.

CAUTION: Prevent possible water damage to the turbine by using extreme care to eliminate all water from the main steam line(s), cold and hot reheat lines, and superheater and reheater elements and headers before the turbine is rolled. Refer to the turbine manufacturer's instructions for the proper drain valve settings.

4. Open wide all superheater drains to allow complete draining of superheater headers

and/or elements. After draining, close all drains the start-up drains (main steam line vents and drains). Keep the start-up drains open. Reheater drains and vents are open. Open the de-superheater isolating valves (de-superheater control valves must be closed). SH backpass drain valves are open after 5 minutes from light-up and close after 10

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minutes from valve opening. 5. Set the HP and LP bypass control set-point to the existing pressure in auto mode. 6. For hot start-ups, the fuel startup sequence should follow this table:

Sequence Step

Elevation Notes

1 CD oil Heavy Fuel Oil 2 AB oil Heavy Fuel Oil 3 B coal If coal elevation B not available, start coal elevation A 4 C coal If coal elevation C not available, start coal elevation A 5 D coal 6 A coal 7 E coal

7. Initiate a furnace purge and a normal light off sequence of the warm-up oil guns

following the sequence noted above. 8. Set fuel oil flow control to auto and increase oil flow set point to 8% of TMCR firing

rate.

9. Initiate an elevation start command for CD oil elevation. 10. Progressively increase firing rate to 15% TMCR at a rate of 1.5% per minute.

Stabilize the CD elevation for 5 minutes. 11. When steam pressure at HP bypass begins to increase, the HP bypass valve is

released to "pressure ramp" mode. The valves will then control the boiler pressure ramp-up to 84 kg/cm²(g).

12. As the HP bypass opens, the reheater will be pressurized as steam is passed

through the reheat vents and drains. Set the LP bypass station to minimum set-point in auto mode. The LP bypass will open in response to increasing reheat pressure. Close the reheat vents and drains to transfer flow and pressure control to the LP bypass station.

13. Initiate an elevation start command for oil elevation AB and stabilize.

14. Progressively increase coal firing rate to 25% TMCR at a rate of 1% per minute. 15. Increase the firing rate, as prescribed, to raise the pressure and steam production.

The rate of pressure rise should follow the prescribed start-up curves. 16. When boiler pressure reaches 84 kg/cm²(g), the HP bypass valve is released to


17. After a pressure of 84 kg/cm²(g) is attained, the firing rate can be adjusted to

achieve the correct steam temperature for turbine rolling. Target steam conditions are: 15%TMCR steam flow, SH = 450℃,RH = 460℃. In case actual produced steam flow is over 6.5% BMCR and 6.5% BMCR steam flow is required at the turbine synchronization, the surplus steam flow bypasses through HP bypass valve.

18. When steam is admitted to roll the turbine, there should be a minimum steam-to-

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turbine metal temperature differential. This can be achieved by raising boiler load while on HP/LP bypass.

Rolling and Synchronization the Turbine

1. Confirm the steam conditions, i.e. pressure, temperature, and steam purity (See turbine manufacturer’s Steam Purity recommendations), at the turbine are correct for turbine roll.


steam. Roll the turbine by opening the Combined Reheat Valves to the IP turbine per the Turbine manufacturers procedures. The HP turbine is maintained in reverse flow using steam from CRH line.


turbine/generator startup instructions. Initial load is produced by IP/LP sections of the turbine. The HP section is still in reverse-flow mode. During this time period, boiler steam production is passed through the HP bypass.

During a hot start, the turbine metal temperature will normally require a rapid reloading of the unit.

5. As steam is transferred to the IP turbine, the LP bypass will close while maintaining

RH pressure at 13 kg/cm²(g). 6. As turbine conditions permit, put feed water heaters into service per manufacturer’s

instructions. 7. De-aerator heating steam source is transferred from auxiliary steam system to LP

extraction when LP extraction pressure is adequate. 8. At the prescribed load per turbine manufacturer, the HP turbine is transferred to

forward-flow. The first three turbine control valves are opened until sufficient flow is established through the HP section of the turbine. The HP bypass valve compensates by closing to control the steam pressure at the set-point.


opened and HP bypass valves are fully closed. 10. Commence coal firing as required to support load increase. 11. Coal firing and load increases generally follow the procedures outlined for cold start-

ups and normal load changes.

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EMERGENCY PROCEDURES Reheater Protection

Stopping or significantly reducing steam flow through the reheater when the entering gas temperature is above 1000℉ (538℃) can cause overheating and damage to the reheater tubing. To prevent this condition, the following measures are taken with the automatic reheat protection interlocks:

RH FLOW MONITORING If excessive steam flow is extracted upstream of the reheater, causing flow through the reheater to be dangerously low, all fuel should be tripped automatically with a maximum time delay of 10 seconds. Extreme care should be exercised when bringing in feedwater heaters or when extracting auxiliary steam from the cold reheat lines. TURBINE VALVE CLOSURE If a loss of load should cause the turbine valves to close, the HP/LP bypass stations will automatically open to allow the boiler to stay on-line. If the HP/LP bypass stations do not open within 10 seconds to provide a flow path through the superheater and reheater, all fuel should be tripped. When a master fuel trip is caused by turbine control valve closure, an immediate restart is feasible in most instances because the turbine is still rolling and will be available to take steam as soon as the governor has the turbine speed under control. (Refer to turbine manufacturer's instructions for no-load operating procedures and limitations.) If an immediate turbine restart is not possible and the turbine is tripped, the reheater condensate drains should be opened (refer to Turbine Trip below).

TURBINE TRIP If a loss of load occurs in which the turbine is tripped, the HP/LP bypass stations will automatically open to provide a steam flow path for the superheater and reheater, allowing the boiler to stay on-line. The reheater safety valves will protect against overpressure in the reheater. The reheater condensate drains should be opened to evacuate the steam in the reheater . POST -TRIP PROCEDURES The furnace must be purged immediately following a master fuel trip. Empty any pulverizer containing coal as soon as possible. Refer to Master Fuel Trip, page 35. To permit firing during start-up, the initiating fuel trip circuits must be disarmed before opening the turbine valves. They must then be rearmed at a suitable point in the start-up sequence, such as when synchronizing the turbine.

CAUTION: Operators should be alert to detect the symptoms of water carry-over from the boiler and introduction of water into the turbine, such as: a. A sudden, unexplained drop in steam temperature in either the main steam or hot reheat line. b. Vibration in the steam piping resulting from water hammer . c. Abnormal vibration and differential expansion readings from the turbine supervisory instrumentation.

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Operators must be prepared to take necessary steps to prevent turbine damage upon detecting the introduction of water. Refer to the turbine manufacturer's instructions for specific actions to be taken.

TURBINE PROTECTION UPON LOSS OF LOAD Extreme care must be taken following a trip of the turbine and boiler to prevent water from entering the turbine during a unit restart. Condensation may cause water to collect in the main steam line(s) and cold reheat lines. Water may be introduced into the superheater due to overflow from the separator (inadvertent high water level). Water may be introduced into the superheater and/or reheater through the desuperheaters due to open or leaking spray water control valves. Inadvertent introduction of water into the steam lines must be prevented. The lines must be drained prior to opening the turbine stop valves. Refer to the turbine manufacturer's instructions.

Master Fuel Trip

When a master fuel trip occurs automatically through normal interlocks, or is initiated manually by an operator, all fuel should be tripped instantaneously. If coal is being fired, the pulverizers should be tripped immediately. Tripping the pulverizers will automatically trip the feeders and close the hot air shutoff gates. If oil was being fired, the fuel trip valves and individual nozzle shutoff valves should be closed immediately. The following steps should be taken immediately following an emergency fuel trip: 1. Maintain the unit airflow at the pre-trip value for at least 5 minutes to purge the

system. If a hot restart is anticipated, the airflow may be gradually reduced to a light-off airflow (35% of TMCR load airflow) during the purge. The boiler circulating pumps should be started to maintain uniform temperatures throughout the boiler circulation system and to facilitate lighting off. (Refer to Boiler Circulating Pump manufacturer's Operating Procedures).

2. Procedure after Master Fuel Trip when all ID and FD Fans are off:

The ID and FD fans discharge dampers shall be opened to allow natural ventilation of the unit. Opening of fan(s) dampers shall be timed or controlled to avoid excessive furnace pressure excursions during fan(s) coast-down. The fans discharge dampers shall remain open for a period of at least 15 minutes. During this 15-minute period, the ID and FD fans shall not be started. At the end of the 15-minute period, the ID/FD fans may be started in accordance with ID/FD fan(s) start-up procedures. If the unit is not possible to restart for an extended time, a flow of air through the unit shall be maintained.

3. If oil guns were in service when the fuel trip occurred, make sure the individual nozzle shutoff valves are closed. If an immediate restart is anticipated, the oil guns will not require cleaning. Otherwise, the oil guns should be retracted, removed, cleaned and then re-installed. Refer to the Recommended Burner Management System instructions for emergency oil gun shutdown sequencing.

4. If all auxiliaries are lost during a fuel trip, refer to the Boiler Circulating Pump

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manufacturer's Operating Procedures for handling the low pressure cooling water. The cooling flow must be maintained.

5. If all auxiliary power sources were lost during a trip, start the fans and gas air

heaters when power is restored to purge the furnace for five(5) minutes. Observe the hot restart precautions in the gas air heater instructions. The boiler circulating pump, if available, should be placed in service during the purge. (See Boiler Circulating Pump manufacturer's Operating Procedures for restarting procedures).

6. If pulverizers are in service when the fuel trip occurs, successively clear all

pulverizers containing coal, as soon as possible in the following manner

a. Close the pulverizer discharge gates on all other idle pulverizers containing coal. This prevents hot furnace gases from being carried back into the pulverizers in the event of a furnace pressure rise when a pulverizer is started.

b. Establish the ignition energy required to start a pulverizer. Refer to COLD

START -UP, page 2, and to the Recommended Burner Management System instructions for ignition energy requirements and permissives.

c. Clear the pulverizer .

If, due to load conditions and/or requirements to the Burner Management System, it is impossible to establish ignition permissives for all pulverizers and clear them of coal, the discharge gates of any idle pulverizer (including those still containing coal) should be opened to allow a flow of cooling air through the pulverizer. Keep the discharge gates open until the pulverizer is ready to be unloaded and/or restarted. Each time an additional pulverizer is placed in service or unloaded, any idle pulverizer containing coal should be temporarily isolated again (see item a).

(1) If the pulverizer will be retained in service, start the associated feeder when the pulverizer amps begin to falloff .When the feeder is started, open the hot air shutoff gate and bring the pulverizer up to normal operating temperature.

Following a pulverizer trip under load, the pulverizer should be operated with cold air only until the associated feeder is started.

(2) If the pulverizer will not be retained in service, stop it after completely clearing

the coal. The pulverizer discharge gates should remain open to allow a flow of cooling air through the empty pulverizer.

d. An emergency trip subjects residual fuel in the pulverizers to conditions which

may cause spontaneous combustion. If the unit cannot be refired within a reasonable time (45 minutes) to clear the pulverizers, then the pulverizers should be cooled to ambient temperature and manually unloaded. If this is not possible, isolate the pulverizers and remove all doors to prevent gases from entering the furnace.

Low Water Wall Flow

If the water wall flow drops below the minimum set point due to failure of the BCP, UG valve, feed water supply, controls, or operator neglect, automatically trip the fuel following a maximum 15 second time delay. The time delay allows for momentary

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fluctuations due to valve transfers, etc. Low flow subjects the water wall tubing to overheating, and potential for failures: 1. Trip all fuel immediately. 2. Shut off all steam being discharged from the unit (trip turbine, steam driven

auxiliaries, and such). 3. Leave the boiler circulating pump in service as long as it is operating normally.

CAUTION: The differential temperature between feed water and boiler metal must never exceed 200℉(111℃) (separators during initial filling or separators and superheater outlet header during filling for hydrostatic test.)

4. If the problem is rectified, re-establish minimum water wall flow. 5. If the boiler circulating pump cannot be kept in service, do not admit feed water to

the unit. 6. Maintain a high airflow at first to hasten the cooling process. 7. If pressure part damage is suspected, reduce the steam pressure gradually by

opening the superheater start-up drains. As the boiler cools, reduce the airflow. Shut down the gas air heaters and fans as soon as the unit is cool enough to enter. When the separator metal temperature is 200℉ (93℃), drain the boiler following normal draining procedures. Determine the cause of low water flow and examine the boiler for signs of overheating, such as leaks and distorted pressure parts.

8. Repair any leaks. 9. Hydrostatically test the boiler at operating pressure before putting the unit back in

service. High Water Wall Tube Temperature

If water wall tube metal temperatures exceed the set point, automatically trip the fuel following a maximum 3 second time delay. This trip protects the tubes from overheating, and potent failure, and therefore immediate action is required. High water wall tube temperatures are an indication of over-firing, low water wall flow, or a combination of both. Over-firing could be a result of extreme load change rates. Low water wall flow could be a result of excessive SH spray flow. Investigate these parameters and their control before re-firing the boiler .

Tube Failures

If any water or steam carrying tube fails, the best shutdown method will be dictated by the size of the failure, the ability to maintain a normal water level and the demand for the unit to remain in service. The following instructions are general since most of the conditions will require the judgment of the operators.

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WATERWALL TUBES If a leak or tube failure does not involve a serious drain on the feed water supply, the water level should be maintained and the unit taken out of service in the normal manner: 1. Operate the soot blowers if conditions permit.

2. Switch the combustion control equipment to manual control and proceed to reduce

the firing rate and air flow in a normal manner.

3. When all fires are extinguished continue the air flow through the unit at a reduced rate to purge all combustible gases, vapors, etc. Shut down the fans when the unit is cooled sufficiently.

4. Feed water to the boiler by manual. To hasten cooling, boiler pressure can be

reduced by opening the superheater outlet drains.

5. Allow the boiler to cool at least to 200℉ (93℃) (separator metal temperature); before draining.

If there is a serious water loss and the water level cannot be maintained with the feedwater supply available. use the following method: 1. Trip all fuel.

2. Shut off the feed water to the boiler .

3. Maintain only enough airflow to carry the escaping steam up the stack.

4. Leave the fans and gas air heaters in service until pressure is off the unit.

5. Once the unit is cool enough to enter, inspect the pressure parts for damage caused

by the loss of water level. After the necessary repairs have been carried out, apply a hydrostatic test and obtain the approval of the proper authorities before putting the unit back in service.

ECONOMIZER TUBES An economizer tube leak can be detected by sound and/or increased makeup water requirements. Check the leak as soon as possible. Water leaks in the economizer can cause considerable erosion damage to adjacent tubes. Water carried over from an economizer tube leak may cause plugging of hoppers and gas air heaters. Any decision to continue operation with known leaks should be made with this in mind. The unit should be shut down in a normal manner. SUPERHEATER AND REHEATER TUBES A small leak in a superheater or reheater element should be checked as soon as possible. Steam leaks in the superheater or reheater can cause considerable erosion damage to adjacent tubes. Any decision to continue operation with known leaks should be made with this in mind. The unit should be shut down in a normal manner . A major superheater or reheater tube failure may require an emergency unit shutdown. The operator must judge the degree of failure, its consequences, and then decide what type of shut down is required.

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APPENDIX A FEEDWATER SPECIFICATIONS FOR ONCE THRU BOILERS

Normal Operation Short Periods

Units Alkaline Water Treatment

Combined Water Treatment

Start-up Procedures (1)

Conductivity at 25℃ measured After cation-exchanger in H+ form and after Co2 removal (2)

㎲/㎝ max. 0.2 max. 0.5 max. 1.0

pH-VALUE(25℃) (3) min. 9.0 8.0-8.5 min. 9.0 Oxygen (4) ppb max. 100 30-150 max.100 Silica (5) ppb max. 20 max.20 max.100 Iron (susp. + dissolv.) ppb max. 20 max.20 max.50 Copper (susp.+ dissolv) ppb max. 3 max.3 max.10 Sodium ppb max. 10 max.10 max.50 General requirements clear and

colorless clear and colorless

clear and colorless

(1) Values specified in this column may be tolerated for max. 2 hours. However, they

must approach the limits for normal operation and should attain them within 6 hours after ignition.

(2) If the contamination measured with the conductivity in the feed water are only soluble

salts such as sodium chlorides, sodium sulfates etc., they will concentrate in the (circulating) water and dissolve in the steam in the evaporating area. They have a corrosive effect only, if they can settle into the pores of deficient magnetite layers or already existing corrosion pits formed e.g. through oxygen corrosion during shutdown. The case is different when the contamination in the feed water consist of hardness constituents (calcium and magnesium compounds) or free acids from cooling water leakage. Therefore, observance of the conductivity limit value of 0.2 ㎲/㎝ is still no guarantee for a proper feed water quality. Rather care should be taken that the conductivity can be kept at the practically lowest possible level, and at each increase of this value the reason for the conductivity increase should be sought.

(3) If copper materials are present in the water/steam circuit, the pH-value should be

kept within the limits of 9.1 ± 0.2 in order to prevent undue copper corrosions. (4) If Combined Water Treatment is practiced the specified oxygen level is controlled by

oxygen dosing into the condensate line between the condensate polishing plant(CPP) and the low-pressure pre heaters.

(5) The max. allowable silica content should in any case not be higher than the limits

specified by the turbine manufacturer for the turbine steam.

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AIR FLOW CURVEFOR COLD START-UP

0

10

20

30

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60

70

80

90

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0 10 20 30 40 50 60 70 80 90 100 110

BOILER LOAD - % OF MAX. DESIGN

AIR

FLO

W -

% O

F M

AX.

DES

IGN

PURGEAIRFLOW

LIGHTINGOFF

WARMINGUP

ON THELINE

Figure 1. Airflow Curve

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T07073-LBH-SY-M001 Rev.A.pdf

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