Author:Site Editor Publish Time: 2018-05-21 Origin:Site
1. What are the rules for the coal position and silo level of the coal bunker when the furnace is shut down? Why should this be the case?
(1) Where the standby or shutdown of the boiler is over seven days, the coal in the original coal bin shall be used up.
(2) When the standby time or overhaul time exceeds three days, the pulverized coal in the pulverized coal bunker should be used up. When the shutdown time is less than three days, the pulverized coal bunker should be reduced as far as possible, and the sealing of the pulverized coal bunker should be carefully done to strictly monitor the temperature of the pulverized coal bunker.
The above regulations are mainly intended to prevent spontaneous combustion and explosions due to agglomeration of raw coal and the agglomeration or long-term deposition of pulverized coal.
2. Why does the temperature of the pulverizer sometimes rise after the furnace is shut down? The
In the process of pulverized coal accumulation, due to the lack of tightness of the silo or the weak shut-off of the moisture absorption valve of the silo and the oxidation of the pulverized coal pipe leaking into the air, heat is released slowly, and the heat dissipation conditions in the silo are poor, and the fuel temperature will also be low. Gradually, the increase in temperature causes the oxidation to increase, and the increase in oxidation causes the temperature to rise until it rises to its ignition point. Therefore, after the shutdown, the temperature of the silo must be monitored. Once the temperature of the silo is found to be increasing, measures should be taken in time.
3. Hot water how to operate?
Take the SG400/13.7 boiler as an example:
(1) Before the boiler stops to stall, the pressure of the steam drum should be no more than 1.5 MPa, the water level of the steam drum should be maintained in the range of 0-50 mm, the steam pressure after fire extinguishing should be reduced to 1 MPa, and the superheater trap door should be opened to notify the turbine to shut off the first and second levels. bypass.
(2) The dampers, baffles, manhole doors, and fire doors after the boiler is shut down shall all be closed tightly.
(3) The wall temperature of each point of the steam drum is recorded before the boiler turns off, and every other half thereafter. It should be recorded once, until 4h after the vapor pressure has dropped to zero.
(4) 60min after the boiler is extinguished, open the large-diameter descent pipe to release the water (open the first door, open the door for 1/4 of a turn), open the accident water release door slightly to discharge the water, and discharge the water to the electric contact water level indicator as -250mm. Then continue to put 30min, then close the water release door, so that the water inside the drum is basically discharged.
(5) 4 hours after the flameout of the boiler, the smoke temperature after the screen superheater shall not exceed 400°C, the pressure of the steam drum shall be less than 0.8MPa, and the temperature at each measuring point of the upper and lower walls of the steam drum shall not exceed 200°C, and the boiler water wall and coal shall be saved. Water is discharged.
(6) Open the water-cooled wall lower connection box, large-diameter drop pipe water release door (open the first door, open the door by 1/4 turn), accident water release door, and open the economizer water release door 1/8 laps. The time required to strictly control the pressure relief rate of the boiler from 0.8 to 0.3 MPa is generally 2 to 2.5 hours; the time required from 0.3 to OMPa is generally 3 hours.
(7) When the pressure of the steam drum drops to zero, all air doors and micro-opening headers are opened to the air exhaust valves, and at the same time, the water supply console and the desuperheating water system discharge valve are opened.
(8) In the process of discharging water with pressure cooker, the maximum temperature difference between the upper and lower walls of the steam drum must not exceed 40°C. When the temperature difference reaches 40°C, the water discharge should be suspended until the temperature difference is stable and then the water is released again.
(9) When there is a large mass of coke in the furnace to envelop the furnace tube or the fire-retardant belt laid on the furnace, the time for water release should be appropriately delayed and the water release rate should be slowed down to prevent overheating of the furnace tube.
(10) Before shutting down the furnace, check whether the economizer recirculation door is closed tightly so as not to allow the water to enter the steam drum and cause the temperature of the drum bottom wall to decrease.
(11) After the furnace is shut off, the heater shall be discharged to the empty exhaust valve and the cold section hydrophobic door.
(12) During the discharge of the boiler, it should be checked that the expansion is normal.
4. After the boiler stops running, why do I need to run the primary and secondary bypasses for 10-15 minutes?
After the boiler stops running, the residual heat of the boiler is still high. On the one hand, it is possible to make the steam pressure rise. On the other hand, it may cause overheating of the superheater and reheater tubes. This phenomenon is especially noticeable after the higher parameters are out of service. This unfavorable cooling of heating surfaces and steam drums also delays the shutdown of boilers. Therefore, after the boilers are stopped, the unit-generators are generally required to re-run the steam turbine for 10 to 15 minutes (depending on the steam pressure and steam temperature). Does not return to principle).
5. After the turbine shuts off the primary and secondary bypasses, why does it need to open the cold section of the reheater and discharge it to the air?
After the turbine shuts off the primary and secondary bypasses, the pressure of the reheater is quite low at this time. If the reheater is drained and the reheater is discharged to the air exhaust heater until the hot water is discharged, the reheater uses its own pressure to drain the remainder. Steam and water are quite difficult, and they may not be able to be stored. They will stay in the pipe and cause corrosion to the pipe. The stagnant water in the pipe causes a water plug, which causes difficulty in the next startup and easily causes overheating of the pipe wall. Therefore, after the boiler is extinguished, the first and second bypasses of the steam turbine are shut down for a period of time and the reheater cold end should be opened immediately. Hydrophobic and vent to the air.
6. After the boiler goes out of flame, why does the fan need to continue to ventilate for 5 minutes before it can be stopped?
Because in the process of shutting down the furnace, due to the lowering of the furnace temperature and unstable combustion, the incomplete combustion of combustibles is increased. These combustibles are retained in the furnace and the flue, and will be reburned under the heating of the residual heat in the furnace. , Directly threaten the safety of boiler equipment. Therefore, after the boiler is turned off, the fan continues to ventilate for a period of time to remove the combustibles from the furnace. However, the ventilation time should not be too long. Otherwise, the large amount of cold air directly enters the furnace, causing the furnace, the flue, and the heat receiving surfaces to cool down and shrink. damage. Therefore, after the boiler is turned off, the fan will continue to ventilate for 5 minutes to stop operation. Then, the smoke damper is closed so that the furnace and the flue gas ducts are in a confined state, and the temperature of the flue gas must be continuously monitored to prevent re-combustion of the unburnt combustibles.