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        2. Home > Operational Area > BOILER
          Shutdown of the boiler

          Preparation of boiler:

          1. After the monitor receives  the shift chief-operator's order, he will inform the stoker to make preparation of shutdown of the boiler, and explain the mode and time of shutdown of the boiler. 

          2. Inform the expected time of shutdown of the boiler to the steam turbine, electricity, chemical water and fuel operators on-duty. 

          3. Before the boiler is shutdown, the boiler equipment shall be completely inspected, and the defects found shall be recorded in the book for maintenance and processing. (when necessary , the exhaust test of the safety door shall be carried out). 

          4. Boiler overhaul or standby for a long time, before the boiler is stopped, the bituminous coal in the original coal hopper shall be burnt out. If the boiler shutdown time is within one week, less amount of coal can be stored.  

          Procedures of boiler shutdown: 

          1. Contact with the adjacent boiler operator. According to the thermal load situation of the system, transfer the load and keep the pressure and  steam temperature of mother tube  normal.

          2. Change the system from automatic operating to manual operating. According to the decreasing of steam flow, decrease the coal-feeding amount and the primary and secondary air flow in order to reduce the boiler load by 50%. (During the process of load decreasing, the temperature difference of upper wall and lower wall of the steam drum shall be ensured not to exceed 50 ℃ and the steam temperature shall be kept.)

          3. In the process of boiler shutdown, the operation of soot blower shall be maintained. 

          4. The procedures of Load decreasing shall not be too fast, generally the coal feeding amount shall be reduced at the speed of no more than 10% per minute. 

          5. After the bed temperature is below 700 ℃, stop the operating of coal feeder. Before the coal-feeder is stopped, firstly close the entry shutter of coal feeder. After the coal in the coal feeder is consumed, then the operation of coal feeder is stopped .

          6. According to the  rate of descending of flue gas temperature of cyclone separator and metal temperature of boiler drum, the output of boiler  shall be reduced at the rate not more than 100 ℃ and 50 ℃ / h. 

          7. When load is reduced to of 50% of rated load, stop the secondary  fan and close the entrance control damper. 

          8. After the bed temperature has dropped below 600 ℃, stop the primary fan and the induced draft fan, close the inlet control damper of each fan. Close the coal-spreading damper and close the returns damper. 

          9. Appropriately open the draining valve of each superheater in order to cool the  steam superheater. According to the load and main steam, adjust the air bleeding valve in order to avoid that that safety valve acts and the steam pressure drops too fast. 

          10. According to the main steam pressure situation, shut off the electric main steam valve, open the water draining valve in front of the main steam and the draining valve of the header of  superheater. 

          11. Strengthen water-feeding to + 200 mm or so of steam drum water level, then close the water supply valve, open the recirculation valve of the coal economizer, stop the operation of precipitator. After the ash is completely discharged from the ash hopper, the ash conveying system shall be stopped. (The specific operation shall be conducted according to the regulations of ESP and bag filters). 

          12. After the boiler is stopped, report to the chief-operator on duty and make detail record of shutdown of boiler. Procedures of emergency shutdown of the boiler: 

          1. Immediately stop coal-feeding, stop the operation of the secondary fan, returns fan, the primary fan and the induced draft fan. At the same  time, inform the man on-duty of the electricity of the steam turbine to emergency stop the boiler and rapidly reduce the load or shut down the steam turbine.  

          2. If the tube on heating surface blasts, then the induced draft fan is not stopped. Turn down the damper baffle of the induced draft fan to keep the hearth under negative pressure. 

          3. In case the leakage is serious, then stop feeding water to the boiler. 

          4. According to the accident situation, maintain the water level of steam drum, if water is in acute shortage, it is strictly prohibited to feed water to the boiler. 

          5. If the water-cooling wall tube (including water-cooling panel), the platen superheater tube is damaged, then the primary fan is not stopped, the bed materials shall be immediately discharged. 

          6. Other operation shall be conducted according to normal operation of boiler shutdown.  


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