Advantages of Low NOx Burners
Because the combustion zone is stretched, part of the combustion intensity is weakened, and the composition of NOx is suppressed within a certain time. Smooth combustion at low load. Because the air volume at the lower part is reduced, the fuel is also very stable when burning at low concentration. It can even achieve stable combustion at 40% load. When the load is low, the furnace flame is full. The water wall absorbs heat evenly.
Disadvantages of Low NOx Burners
Because of the location of the burn-out air, a lot of the supply air does not participate in the combustion when it leaves the furnace, and this part of the hot air also absorbs a lot of heat from the air preheater, which will cause the phenomenon of low exhaust gas temperature. Especially at low loads. Because of the weakening of the air intake in the lower furnace, the support of the lower secondary air can be weakened, and the amount of slag discharged is increased, and the carbon content of the discharged slag is increased, especially when the load is high. Because it weakens the air intake in the lower furnace, the rigidity of the wind is weakened, and the combustion area is expanded. When the load is high, the water wall is simply coking. Because of the oxygen-deficient combustion in the lower part of the furnace, a lot of restorative gas is generated, which reduces the ash melting point, and even the formation of a cold slag bucket has the phenomenon of coking. Because of the stretching of the combustion zone, during the high load period, the phenomenon of overheating of the superheater and lack of desuperheating water will be formed. In severe cases, it will even form over-screen coking. Because of the expansion of many restorative gases and the combustion area, the middle and lower parts of the water wall are severely coked. The phenomenon of fire extinguishing, deflagration, and damage to the slag conveyor caused by decoking will occur. The coking under high load affects the heat absorption of the water wall, causing The temperature of the lower part of the furnace rises, and the overfire air can only cool the flue gas in the upper part of the furnace because of its position, and has no effect on the temperature of the lower furnace. Therefore, the occurrence of NOx in the lower part of the furnace is added with coking. The longer the high load duration, the reduction The effect of NOx is smaller, and even exceeds the original NOx amount. The lower part of the furnace burns the evaporation fraction and the upper part burns the coke theory, and the theory of pulverized coal combustion "evaporation fraction → evaporative combustion → coke combustion → case ash peeling, evaporation fraction) The theory of "continuous separation with the peeling of the ash from the case" does not match. Therefore, when the load is high, the burning time of a lot of pulverized coal is prolonged, and the incompletely burned pulverized coal is brought into the flue. The formation of fly ash carbon content is added.
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