Energy saving measures for low load operation of t

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Energy saving measures for low load operation of pulverized coal fired boilers

the power market reform has put forward higher requirements for the peak shaving capacity of units. In recent years, with the continuous increase of peak valley difference, the peak shaving task of power plants has become increasingly intensified. When the boiler of 55MW unit is in the power trough, it needs to operate under 30MW load. From 2002 to 2004, during several low load operations of the 3; boiler in our plant, we repeatedly explored and summarized the operation of shutting down a set of forced draft fan in due time without adding oil for stable combustion when the load is between MW. A large amount of fuel and auxiliary power are saved, and the economic benefits are extremely significant

I. overview of boiler

the 3p unit of our plant was put into operation in 1997. The ng/-m16 single drum natural water circulation solid-state slag removal pulverized coal boiler produced by Hangzhou Boiler plant is used, equipped with 55MW steam turbine generator unit. Two sets of air supply and induced draft systems, steel ball mill intermediate storage type exhaust gas powder supply system and four corner tangential firing mode of DC burner are adopted. The burner arrangement is. The primary air outlet is divided into upper and lower layers. A combustion supporting oil gun with a flow rate of 637kg/h shall be arranged at the next primary air outlet at the 2

II. Measures

the key point of this operation is to prevent unstable combustion, fire extinguishing or other accidents of the boiler from affecting the operation quality of the unit

1. closely cooperate with other disciplines such as steam turbine, electrical, etc., prepare in advance, carefully adjust, and uniformly reduce the boiler evaporation. During the process of reducing boiler load from 40mW to 30MW, the load shall be reduced gradually and slowly, and the range of each load reduction shall be controlled within MW. After each load reduction, the air distribution shall be adjusted in time. After the combustion is stable, the load shall be further reduced. Avoid boiler fire extinguishing due to imbalance of air coal ratio in case of large and rapid load reduction

there is load stiffness in the experimental machine system. 2. gradually reduce the furnace air volume. On the premise of maintaining stable combustion, the primary and secondary air volume shall be reduced as far as possible, and the adjustment shall be based on the furnace combustion, air pressure at the outlet of forced draft fan and oxygen content. Generally, the primary and secondary air volume shall not be less than 30% of the full load, the air pressure at the fan outlet shall not be less than PA, and the oxygen content shall be 4%-6%

3. gradually stop the operation of forced draft fan and induced draft fan on one side according to the combustion and load conditions. The precondition is to ensure that the boiler furnace operates under negative pressure or micro positive pressure. During operation, the forced draft fan shall be stopped first, and the negative pressure of the combustion chamber shall be properly adjusted. The induced draft fan shall be stopped after it is normal. Generally, one forced draft fan 1 can be stopped when the load is lower than 40mW. Shore hardness (HS) = Brinell hardness (Bhn)/10 + 12. One induced draft fan can be stopped when the load is lower than 35mW

4. try to stop the operation of the pulverizing system. In case of low load, the output of the pulverizer decreases and the unit consumption of pulverizing increases, so the high pulverized coal level of the pulverized coal bunker shall be maintained before the low load operation. At the same time, prevent the pulverized coal system running at low load from affecting the stability of boiler combustion during adjustment

5. ensure high pulverized coal concentration in the lower primary air duct. When operating at a load of about 30MW, the lower discharge pulverized coal feeder shall have a high pulverized coal feeding volume, and the corresponding pulverized coal concentration shall be controlled at 0 7kg/m3. This requires that in the process of load reduction, the number of upper discharge pulverized coal feeders shall be gradually reduced according to the actual situation, and the stopped pulverized coal feeders shall be diagonal and switched regularly

6. according to the maintenance degree of Jinan gold testing machine for furnace combustion intensity, properly turn down the opening of boiler air valve once, shorten the ignition point distance of pulverized coal at the outlet of each burner, and ensure that FSSS flame detection can detect sufficient flame intensity. Prevent MFT protection action and boiler fire extinguishing due to the failure of FSSS fire detection to detect the flame intensity. The opening of primary air valve is generally 40%-50%, and each air valve can be slightly adjusted according to the actual situation

7. properly reduce the outlet air pressure of the upper and lower pulverized coal exhausters according to the pulverized coal level in the pulverized coal bunker and the feeding conditions of the pulverized coal feeder. Prevent the poor discharge of pulverized coal to the pulverized coal machine due to the low pulverized coal level in the pulverized coal bunker and the high air pressure at the outlet of the pulverized coal exhauster, which will affect the combustion stability of the boiler. Generally, when the pulverized coal level in the pulverized coal bunker is below 1.5m, the feeding of each pulverized coal feeder is abnormal, and the outlet air pressure of the upper and lower pulverized coal exhausters can be gradually reduced, but not lower than 2KPa

8. prevent furnace air leakage. The operator on duty shall closely monitor the water level of the water seal at the bottom of the boiler to prevent the water level of the water seal at the bottom of the boiler. At the same time, thank the users for their long-term support to our company. Too low water level causes furnace air leakage; At the same time, the patrol inspectors in the boiler control room shall timely close each hole door, fire door and inspection hole of the boiler body which are sprayed due to positive furnace negative pressure. Avoid unstable boiler combustion caused by a large amount of furnace air leakage, and the operation parameters are difficult to control

9. strengthen monitoring and carefully adjust. Under low load, the temperature level in the furnace is low and the fire-fighting capacity is poor. The operating personnel shall concentrate, carefully monitor and carefully adjust. The air distribution and powder feeding shall be adjusted stably

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