Circulate Water Lines.
Most power plants stand on the shore of river, lake, bay or ocean so that they have access to large volumes of cooling water. To prevent sea water debris or trash come through suction of circulating water pumps, they have to installed trash rake and travelling screen with spray pump. And to prevent the metal corrosion, cathodic protection has to install. Also Hypo chlorination could be injection at suction of circulating water pump to prevent biota growth inside the circulating water line and water box of condenser.
Seawater Booster Pump
Suction of Sea Water Booster is tapping from circulating water line to cooling close cooling heat exchanger.
Close Cycle Cooling Water Pump
All equipment the plant is to be cooled by close cycled, use close cooling system and heat transfer it by sea water by heat exchanger. The suction pressure of close cooling pump is to be maintained by head tank to prevent pump cavitation. The level head tank is to be maintained by make up booster pump from water treatment plant.
Before start CCCW Pump, do flushing and priming of CCCW lines. Fill CCCW line and drain until TSS <200 ppb (2ppm) by open head tank make up valve and open drain valve. After TSS < 200 ppb, close drain valve and open venting valve.
After water coming out from venting valve, close venting valve and start the pump.
Start chemical dosing with hydrazine until 5 – 200 ppm residual content and ammonia until pH 9.2 – 9.9.
Flushing Hot Well, Feed Water Tank and Steam Drum
Top up and drain hot well by make up water twice for flushing,
Start Condensate Extraction Pump (CEP) circulation to hot well only
Open Condenser blow out valve for 10%, monitor level sump pit.
After hot well TSS < 200 ppb
Top Up and drain out from system of De-aerator / feed water tank twice for flushing.
Fill De-aerator / feed water tank and circulate back to hot well.
After TSS de-aerator < 100 ppb
Top Up and drain Steam Drum twice for flushing through Boiler Filling Valve.
Start NH3 & N2H4 Pump, inject to CEP discharge line.
Target pH 9.2 – 10 and residual eliminox 200 – 250 ppm
Fill Steam Drum.
Seal Oil system of Generator.
Before Generator is filled by H2, seal oil system should be in service first to prevent H2 come out through shaft and bearing of generator. And oil which contaminated with H2 will be separated by vacuum and spray treatment. Oil vapour which contaminated with H2 will vent out and pure oil with re circulating again to generator.
Fill H2 to Generator.
Rotor cooling is using gas H2 due to high efficiency compare to other gas but it has content explosive danger. The particular thing is avoid air direct contact with H2 by special procedure.
Principle the procedure is using density method between highest density CO2, air and lowest density H2. After maintenance, inside generator is containing air. Remove air by use CO2 supplied through bottom side of generator, and air will remove from upper side of generator. After air content inside generator is zero, H2 ready to supply to generator through upper side and CO2 will release from bottom side of generator.
Generator Stator Cooling Pump.
Stator cooling is using primary water, that is demineralise water from water treatment plant and circulate it through ion exchanger to reduce conductivity. Lowest conductivity needs to avoid electrical short at generator stator.
Main Oil In service.
Vapour Extractor Fan for release oil which contaminated with steam, and Main Suction Oil Pump (MSOP) for supply oil to turbine bearing, Turning Gear Oil Pump (TGOP) and Turning Device for make turbine blade warming uniform. Also Jacking oil pump to make oil film between turbine shaft and bearing.
Preparation Generator Thyristor
Generator Thyristor Cooling Fan.
Select Automatic Voltage Rrgulator channel A or B.
Lube Oil in service on Boiler area.
Force Drive (FD) Fan lube oil pump.
Primary Air (PA) Fan lube oil pump.
Induce Drive (ID) Fan lube oil pump,
all pulverizer lube oil pump.
pulverizer hydraulic power unit.
all pulverizer classifier lube oil pump.
Warm Up Auxiliary Steam line:
Auxiliary steam is using for warm up feed water tank also start 1st BFP for circulation. Propose to avoid low DT between lower and upper of steam drum during firning.
Condenser Vacuum Master.
After condenser is in service, do vacuum up by start gland steam from aux steam, start gland steam exhaust fan, close condenser vacuum breaker and start vacuum pump.
HP Turbine pre-warming
To reduce DT between CV and Turbine blade, before CV warming, do HP Turbine warming by aux steam
Warm Electrostatic Precipitator Heater. After pulverizer is in service or flue gas temperature above 90oC is time to start ESP
Preparation Bottom Ash System.
Fill Submerged Scraper Chain Conveyor.
Start SSCC Re-circulating Pump for cooling SSCC water.
Start Pyrites Sluice Pump.
Open SSCC sump suction valve of jet pump at dirty side.
Preparation Start Fans Group
Scanner Cooling Air Blower, and Air Heater include guide and support bearing and then start fans group.
Induce Draft Fan for maintain furnace pressure negative and Forced Draft Fan or secondary air is to support air combustion, its flow control with opening secondary air dampers.
Target Purging boiler furnace is to removal combustible material inside furnace with 25% air flow for five minutes is operation standard before light off burners.
Target of light off is main steam pressure minimum set point reach 85 bars.Increase rate of saturation temperature for protection thermal shock at riser tube 0.93 C/min.
Protection of economizer very little water, if any is added to the drum-type boiler during the pressure rising period, consequently, there is no feed water flow through the economizer. Economizer is located in relative low temperature zone. Nevertheless some economizers generate steam during the pressure raising period. This steam remains trapped until feed water is fed through the economizer. It not only makes the control of steam drum water level difficult but it causes water hammer. This difficulty is overcome by supplying feed water continuously by venting the economizer of steam or by recirculation water through the economizer. If recirculation line is used, the valve in line must remain open until feed water is being fed continuously through the economizer to the boiler.
During start up, re-heater tubes get insufficient steam flow as long HP by-pass is still close or a little bit open. Insert thermo-probe at re-heater area to make sure re-heater tubes is not over-heating > 482C.
Next Guide is using Steam Drum Pressure or Main Steam Pressure for reference. Target is minimum pressure set point of main steam and the temperature suitable for turbine blade temperature.
Rate of firing like we called cold, warm, hot and very hot start up is depend to 1st stage inner metal temperature.
Steam Drum Pressure 15bar.
1st BFP in service
Close Boiler filling valve.
Aux steam supply to De aerator put to auto.
Monitor economizer line for steaming
Steam Drum pressure 20bar.
Warm up Aux steam its self unit.
2nd BFP start circulation (for S/H spray next)
Steam Drum pressure 30bar.
HP bypass down stream warming
Preparation warming sootblow system, Air Heater is to be sootblow first.
1st stage inner metal temperature satisfied
HP Pre warming complete.
Start CV warming manually, target CV chest temperature satisfied.
Main Steam pressure 85 bar.
HP bypass auto
CV Warming complete.
CV Chest outer metal temperature satisfied
1st stage inner metal temperature satisfied
IP upper casing inner metal temp satisfied
Turbine Start Rolling.
Turbine speed Up 800 rpm
Low speed heat soak.
Stop MSOP & TGOP when turbine speed 3000 RPM due to self lubrication of turbine shaft already created.
Start 1st PA Fan.
Primary Air Fan is used for transport pulverized of coal to furnace.
1st Pulveriser in service
Superheater & Reheater spray in service
After 1 pulverizer in service usually main steam temperature rapid increase, that is way spray temperature control should be ready
Generator Synchronize for frequency and amplitude to grid.
BFP Discharge Valve Conversion Master
Ii is change steam drum level control at low load and high load. During low load, steam drum pressure always fix, control level only by control valve. After high load, steam drum pressure is increase proportionally with load, so BFP speed maintain discharge pressure 10 bar above steam drum and feed water valve go to full open and control valve go to shut.
Start Extraction steam master at 10% Load.
Extraction steam from HP Turbine, IP Turbine and LP Turbine is to increase efficiency cycle by pre-heating condensate and feed water line before enter the boiler.
ALR set to 178 MW,.
Electro Hydraulic Control of main steam control valve from manual start select to follow Unit Control System.
Turbine speed control by governor is change to load control
Turbine Master auto, Unit Mode is Boiler Follow.
Air flow trim auto and O2 trim auto. Excees air and excess O2 follow to load.
Boiler master auto, Unit Mode is between Boiler and Turbine.
HP bypass close at Load 186 MW
When the starting Up the unit, Boiler and Turbine are running by manual mode, the Unit is set to control main steam pressure to minimum pressure set point or fix pressure set point. The boiler capacity is set a little bit higher than demand by monitoring the opening HP by-pass around 15 to 20%.
After HP bypass close, the unit is coordination mode and main steam pressure is increase follow the load.
Load up depend on silica content base on drum pressure.
When Unit trip, the value of Low Cycle Fatique Index is increasing. LCFI is indicated of turbine material stress.
Click here for example power station shut down chart.