1. Optimization and adjustment of flue gas
Under the condition of satisfying the performance guarantee of NOx removal rate and ammonia escape rate, the SCR system is designed to have the lowest continuous operation temperature of 315℃ and the highest continuous operation temperature of 420℃. Ammonia spraying should be stopped when SCR reactor inlet is below 315℃. The pre-smoke temperature of SCR reactor was controlled to be less than 450℃.
2. Optimize and adjust the amount of ammonia injection
According to the boiler load, fuel amount, SCR inlet NO concentration and outlet NO concentration to adjust the amount of ammonia injection. Influenced by the uneven concentration distribution in the ammonia injection reaction zone and the poor characteristics of the ammonia injection valve, when the load change is relatively large, the regulator timely manually interferes with the operation of the ammonia injection valve and adjusts the adjustment range according to the operation situation of the ammonia injection valve and the NOx concentration value at the SCR reactor outlet. If the differential pressure at the SCR inlet and outlet exceeds 750Pa, the soot blowing frequency should be increased until the differential pressure is normal, otherwise ammonia spraying should be stopped.
3. Optimization and adjustment of dilution air flow
The dilution air flow rate is set according to the maximum ammonia injection amount corresponding to the denitrification efficiency, so that the ammonia volume concentration in the ammonia/air mixture is less than 5%. In the ammonia air mixer, ammonia and air should be evenly mixed and maintained at a certain pressure. The dilution air volume on each side shall not be less than 3200Nm3/h.
4. Optimization of operation mode of pulverizing system
When the unit is running normally, keep the lower pulverizing system running for a long time. The NOx concentration at the SCR inlet of the lower mill was lower than that of the upper mill. Under the condition of ensuring the normal operation of the coal mill, and the high melting point of coal ash, it is not easy to reduce the primary air pressure when the burner mouth cokes, which can effectively reduce the concentration of nitrogen oxides at the denitrification SCR inlet.
5. Adjustment and optimization of burnout air opening
In order to adapt to the load change, the opening of SOFA wind baffle should be adjusted in time to ensure that the high temperature and low oxygen in the burning area, the low temperature and rich oxygen in the burning area, and the generation of NOx should be reduced. Through the burnout air optimization adjustment test, SOFA damper opening (H layer 20%,I layer, G layer opening are in 70%) and fully closed G layer SOFA damper, fully open I, H layer SOFA damper, denitrification device spraying ammonia reduced 14.13kg/ H. When the load changes, adjust the opening of SOFA wind baffle in time according to the NOx concentration of SCR inlet.
6. Adjustment and optimization of oxygen capacity
A slightly higher oxygen content at low load is beneficial to the stability of boiler combustion, while a slightly lower oxygen content at high load is beneficial to the reduction of fan power consumption. Under the premise of ensuring the stability of boiler combustion, maintaining the appropriate oxygen amount is beneficial to reduce the generation of NOx. Oxygen content above 500MW load was maintained at about 3.0%, 400 ~500MW at about 3.5%, 350 ~450MW at 4.0%, and 300MW at about 4.5%.
7. Adjustment and optimization of soot blowing
The denitration area uses the sonic soot blower to blow soot regularly, and the steam soot blower is used as the standby. The test shows that in order to ensure the best soot blowing effect in the denitrification area, the following soot blowing operation mode is developed: 2 sonic soot blowers in the same layer are set as one group, and 2 soot blowers on both sides of the reactor are set as one group, and the soot cleaning is performed simultaneously in the group. Each group of acoustic soot blowers will sound 10s when blowing soot, and the next group will sound 40s.
8. Strictly control the quality of coal
Affected by the tight supply of coal market, the power plant takes the way of mixing and burning to reduce the cost of power generation. Most of the time, the coal source is unstable, can not meet the requirements of the design of coal. It is found through the test that the coal ash content in the furnace is high, the dust content of the flue gas is increased, and the maintenance of the same load will increase the amount of ammonia injection, which is not conducive to the control of nitrogen oxides. Therefore, the coal ash content should be strictly controlled and not exceed the design value as far as possible.
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