Troubleshooting of boiler induced draft fan in thermal power plant during use

To ensure the safe and stable operation of the boiler in the event of induced draft fan failure, and to prevent secondary safety hazards, the following handling plans and precautions are formulated based on the actual operating mode, operating conditions, and unit characteristics. Operators are required to strictly implement them and handle emergency situations in case of abnormal situations.
1. Treatment plan for tripping of a single boiler induced draft fan.
When the unit is operating normally, boiler personnel and the unit supervisor must understand the RB input, and each unit personnel should understand the RB action process of the unit.
When the induced draft fan trips due to a fault, it should be possible to check the RB action and manually operate it in a timely manner if any abnormal action is found.
After the RB action, check the following linkage conditions. If there are no abnormalities, there is no need to interfere with the RB action process:
Stop the corresponding side air supply fan, trip the -3 coal mill, and adjust the capacity air door of the -2 coal mill in the automatic position (automatically adjusted according to the fuel control command corresponding to the unit load after RB action). Activate the AA layer # 1 and # 3 angle oil guns (AA layer 2.4 angle oil gun is activated after a 5-second delay for # 4 boiler), close the corresponding secondary air door: S-OFA1.S-OFA2 is fully closed, C-OFA30%，EF.FF60%。
DE30%, D.E10% (# 4 furnace OFA2-OFA3 fully closed, OFA120%，EF10%，DE30%)， The induced draft fan on the other side automatically adjusts and closes the superheater.
The regulating valves of each cooling water in the reheater and the connecting valve of the induced draft fan are automatically fully opened, and the soot blowing system is locked; After the RB is triggered, it automatically switches to the operation mode of machine following furnace and sliding pressure mode, and the RB action ends in about 7 minutes.
RB action precautions:
1) Pay attention to the linkage of the tripping fan's inlet and outlet baffles to ensure that the fan does not reverse.
When winter recirculation is put into operation, close the secondary air and hot air recirculation door on the trip side (the boiler with recirculation fan running needs to shut down the inlet and outlet baffles in case of emergency shutdown).
2) RB operation is normal, and the unit load has decreased to around 220MW.
Stable combustion.
If the oxygen level is normal, RB can be manually adjusted.
If the fan output allows, the unit load does not need to be reduced too much.
3) After the cooling water is connected, it should be opened in a timely manner according to the temperature and wall temperature of the superheater to ensure that the heating surface does not exceed the temperature limit.
4) When RB occurs in the heating conditions of the unit, special attention should be paid to changes in the heating flow rate of the unit, and the heating butterfly valve should be opened in a timely manner. If necessary, contact the dispatch to remove the heating.
5) After the RB action, the control of the steam drum water level is the key, and improper control can easily lead to the expansion of the steam drum water level protection action and accidents.
When RB action is required, the team immediately arranges an experienced water level adjustment employee to monitor and control the water level of the steam drum.
When RB is activated, the water level in the steam drum will drop sharply.
At this time, the water supply pump should automatically adjust and release the water supply according to the water level reversal situation, and be manually controlled.
When the water level stops dropping, immediately release the automatic feedwater system, reduce the speed of the feedwater pump, and make the feedwater flow rate correspond to the steam flow rate.
When the water level rises rapidly, open the emergency drainage valve in advance to prevent the water level from being too high as much as possible.
Meanwhile, the water supply flow rate should not be reduced too much.
According to the situation, contact the personnel on the machine side in a timely manner to remove the water supply pump, and then it will automatically circulate, opening about 10%.
If RB is not triggered, handle it according to the following method:
(1) Immediately manually activate the AA layer 1.3 # angle oil gun to stabilize combustion;
(2) Release the RB function of the unit, release CCS, and quickly reduce the output of the -3 coal mill to the lowest level (pay attention to the operation of the coal feeder to prevent blockage of the coal mill);
(3) Check that the inlet connection door of the induced draft fan is fully opened, and that the output of the induced draft fan on the operating side automatically increases. Otherwise, manually increase the output of the induced draft fan, paying attention to the motor not flowing and bearing temperature.
Vibration is within the allowable range, reduce the unit load to around 220MW, and adjust the furnace negative pressure as soon as possible.
The oxygen level is normal.
(4) When winter recirculation is put into operation, close the secondary air hot air recirculation door (emergency stop of recirculation fan operation and close the inlet and outlet baffles), check that the outlet baffle of the tripped blower is fully closed and the fan does not reverse.
(5) Adjust the air distribution in a timely manner to prevent the secondary air box pressure from being too low and affecting combustion.
(6) Strengthen the monitoring of air preheater current.
To prevent excessive deviation in exhaust gas temperature after the shutdown of the single-sided induced draft fan on both sides of the boiler, a throttle damper is used to reduce the deviation in exhaust gas temperature on both sides.
(To be determined based on the actual situation)
(7) Strengthen the normal control of the steam drum water level during the processing.
The personnel on the machine side should strengthen the monitoring of various parameters such as pumping pressure, lubricating oil temperature, shaft vibration, tile vibration, and axial displacement.
The heating unit should adjust the heating butterfly valve in a timely manner to prevent the heating main pipe from returning steam.
2、 Trip handling plan for two induced draft fans.
The MFT should be activated when two induced draft fans trip.
Furnace side:
1) Firstly, check and confirm each coal mill.
Coal feeder.
The fan trips and each fuel angle valve closes.
Supply.
Quickly close the valve.
Each coal mill inlet quick closing valve.
Each coal mill outlet quick closing valve closes, cutting off all fuel, causing the turbine generator to jump, and reporting to the unit leader.
The shift supervisor extinguished the boiler fire, promptly reset the tripping equipment, checked the jumping of the two fans, checked that all the inlet and outlet baffles of the induced draft fan were open, ventilated for about 5 minutes, and stopped the operation of the electrostatic precipitator;
2) Check if two steam pumps have tripped and the electric pump has successfully snatched water. Otherwise, manually fetch water to maintain the normal water level in the steam drum, and switch the main feedwater to the auxiliary feedwater.
Check the superheater.
The hydraulic valves of each cooling water in the reheater are tightly closed.
3) Send someone to check the cause of the fan tripping and restore it as soon as possible.
4) Contact the reset fan frequency converter and send someone to inspect the fan, sealing fan, powder production system, and fuel system on site.
5) Send someone to start the slow transmission motor of the coal mill in sequence.
6) After the fault is eliminated, send someone to inspect the induced draft fan on site and start blowing as soon as possible.
7) After receiving the ignition command, ignite the AA layer oil gun.
Start the fan once.
Gradually activate various powders to increase temperature and pressure.
Cooperate with the turbine to drive and load.
8) Contact the machine side to put the steam pump into operation as soon as possible.
When the load rises to 150MW and the two steam pumps are in parallel, the electric pump is shut down and put into standby 180MW, and the auxiliary feedwater is switched to the main feedwater.
9) After the working conditions stabilize, the oil guns are dismantled one by one and put into operation for main protection and electrostatic precipitator.
Machine side: 1) Check that the high and medium pressure main valves, regulating valves, high exhaust check valves, all extraction check valves, heating butterfly valves are closed, and the unit speed has decreased.
2) Start the AC lubricating oil pump and release the interlock of the high-pressure starting oil pump.
Adjust the shaft seal pressure and maintain the vacuum of the unit.
3) Release the low water pressure interlock of the condenser pump outlet main pipe, start spraying water to cool down the rear cylinder, protect the water curtain, and adjust the deaerator water level.
The water level in the condenser hot well is normal.
Close # 3, drain the water normally to the deaerator regulating valve, and drain the high and low water to the condenser.
The gas source of the deaerator is poured into the auxiliary gas.
4) Send someone to open the high and low pressure bypass drainage and heating pipes on site, and assist steam to the small heating pipes.
Contact the thermal department to remove the relevant protection for the large and small machines.
Adjust the oil temperature to normal.
When the unit speed drops to 1200r/min, check that the top shaft oil pump is connected, otherwise start manually.
5) After the unit speed drops to 0 and the auxiliary steam header temperature returns to normal, use auxiliary steam to flush a small machine to 3000r/min for backup.
6) After the boiler is ignited, the high and low pressure bypass is put into operation to increase the temperature and pressure.
After reaching the starting conditions, start the high-pressure starting oil pump and the unit will trip and start.
After setting the speed, check for any abnormalities, connect the unit to the grid, and increase the load as soon as possible after grid connection to prevent further decrease in cylinder temperature.
Put in high and low gas filling side.
Gradually exit the high and low pressure bypass.
Pour the steam source from the deaerator into four pumps.
7) When the load reaches around 180MW, use four pumps to start another small unit, pour the load of the electric pump into the steam pump, stop the operation of the electric pump, and gradually restore the unit to normal load.
8) If two induced draft fans trip and MFT does not move, manual MFT should be used.
3. Precautions during the operation of a single induced draft fan.
When the unit needs to stop any induced draft fan for maintenance work, the RB protection must be released before stopping, otherwise the corresponding RB will be triggered when the fan stops.
2. When the unit load drops to around 230MW, try not to stop producing powder.
During the shutdown of the fan, the operating personnel should strengthen the monitoring of various operating parameters of the fan, temporarily change the inspection cycle to once per hour, and strictly prohibit the fan from exceeding its output.
3. Release CCS manual adjustment during fan shutdown.
4. In non special circumstances, the operation of the desulfurization system shall be temporarily suspended, the fan shall resume operation, and the maintenance switch shall be activated after the induced draft fan is powered off.
5. Maintain guidance after the fan is stopped.
The fan inlet contact door remains fully open.
To prevent excessive temperature deviation of exhaust gas on both sides of the boiler after the shutdown of the single-sided fan, a throttle damper is used to reduce the temperature deviation of exhaust gas on both sides.
(To be determined based on the actual situation).
6. After the fan is shut down, the parameters of the induced draft fan should be monitored by the industrial television, and any abnormalities should be promptly reported and dealt with.
7. After one fan is shut down, try not to arrange maintenance work for the other fan as much as possible.
If there is maintenance work, it is necessary to classify the maintenance work category for a long time and contact the leadership for supervision.
8. If the fan stops for a short period of time, try not to affect the combustion during the shift.
During the process of stopping and before starting the induced draft fan, the operator should strengthen the monitoring of the operating parameters of the induced draft fan.
It is strictly prohibited to operate the fan beyond its output, and a dedicated person should be assigned to inspect and monitor it until the induced draft is reached.