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        2. Home > Operational Area > BOILER
          Regulation of Steam Pressure and Steam Temperature of 220 tons circulating fluidized bed boiler

          1. In the operation, the evaporation capacity of the boiler and superheated steam parameters shall be adjusted according to the requirement of steam turbine and the load distribution of the boilers operating in parallel. In order to ensure the stable combustion and normal water circulation of boiler, the evaporation of boiler shall not be less than the 50% of the rating. 

          2. In the operation, the steam pressure and steam temperature of boiler shall be properly adjusted according to the load change of  boiler, the boiler drum pressure does not exceed the design value (10.8 MPa), the outlet pressure of superheated steam is generally not more than 9.8 MPa, the outlet temperature of superheated steam is generally not more than 535 ℃. The rated pressure of steam turbine is 8.83 MPa and the rated temperature is 535 ℃. 

          3. The steam pressure and steam temperature of boiler can be adjusted correspondingly according to the requirement of steam turbine within the scope of the above. The allowable changing range of the outlet temperature of the superheated steam is ±  5 ℃ ( the above is the setting value for automatic control of  steam pressure and steam temperature). When the boiler is manually operated, the allowable changing range of boiler outlet steam pressure is ± 0.1 MPa, the allowable changing range of the superheated steam temperature is + 5 ℃ - 10 ℃. 

          4. The outlet temperature of superheated steam is automatically adjusted by Level Ⅰ and Level Ⅱ water-spraying attemperator. The Level-I attemperator guarantees the safety operation of the platen superheater, it is used for coarse adjustment, in order to ensure that the outlet steam temperature of the attemperator does not exceed 465 ℃; Level Ⅱ attemperator guarantees the safe operation of high-pressure superheater and the conformity of main steam temperature, it is used for fine adjustment; and for ensuring that the outlet steam temperature of high-pressure superheater is stabilized at about 535 ℃, and the temperature cooling of water- spraying attemperator is 30 ℃.When the boiler is manually operated, the desuperheating water flow shall be adjusted in less amount and in many times in order to avoid large fluctuation of steam temperature. 

          5. When the desuperheating water flow has been increased to the largest, and the superheated steam outlet temperature is still too high, the following measures shall be taken to reduce the outlet temperature of the superheater.

          (1) appropriately decrease the coal feed amount.

          (2) appropriately decrease the returning ash.

          (3) reduce the secondary air volume. 

          (4) increasing water supply temperature. 

          6. When the steam temperature change is not normal, it is required to check whether it is because the bed materials coke, the ash hopper is blocked, air leaks from the boiler, the combustion is not reasonable, the returns is not abnormal, the coal from the coal feeder is interrupted or blocked, measures shall be taken immediately to solve these problems. 

          7. If the parameters of steam supply are normal , the indication of steam pressure gauge and steam temperature gauge of the boiler and steam turbine shall be contrasted at least once per shift, the indication of each steam gauge of the boiler shall also be compared once per shift. If it is found that the indication is not abnormal, it is required to contact the thermal engineering persons to treat and make records. 

          8. When steam temperature exceeds 540 ℃, the following measures shall be immediately taken : 

          (1) check whether the working state of the attemperation water is abnormal or not; and the automatic operation shall be changed to manual operation. 

          (2) decreases the combustion, reduces load and reduce the outlet smoke temperature of boiler. 

          (3) check whether the return feeder runs normally or not. 

          9. When the steam temperature is lower than 525 ℃, the following measures shall be immediately taken: 

          (1) The attemperation water shall be adjusted manually instead of automatically adjusting. 

          (2) check whether the water level is too high or the boiler water quality is poor and priming occurs or not. When this phenomenon occurs, it shall be handled as emergency. 

          (3) adjust the combustion mode, improve the outlet smoke temperature, flow rate and increase the hot load of boiler. 

          10. When steam pressure changes exceeds ± 0.05 MPa (gauge pressure ), the fixed load boiler will actively cooperate to maintain normal steam pressure. When the steam pressure is not stable, it is required to check the fluidization, differential pressure of material layer, situation of returns, and to check whether the proportioning ratio of air and coal is reasonable and the flame color is normal or not. According to the actual situation, quickly take effective measures for stabilization. 

          11. when the boiler load changes, namely the circulation ratio changes, so when the loads increases, the air volume shall be firstly adjusted then the coal feed amount shall be adjusted and increased. When load decreases and vice versa( because the increasing of coal feeding can cause the increasing of calorific value in dense-phase zone and rising of carbon content of boiler bed, thus causing the temperature of material layer rise rapidly and causing the increasing of combustible to increase. The burning of combustible in returns feeder will cause the returns temperature to rise and exceed the ash melting point and make the hearth and returns feeder coke).When the load is increased and decreased, it is required to pay attention to the stability of steam pressure and steam temperature. 

          12. The mother tube operation mode is adopted, the isolating valves of steam mother tube among # 1, # 2, # 3 boiler are in fully open position. When load rejection occurs in a steam turbine, air bleeding to the atmosphere from three boilers at the same time can shorten the overpressure time of boiler and can make the safety valves of the boiler back to their seats as soon as possible. 


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