Advantages and disadvantages of low NOx burners

Advantages and disadvantages of low NOx burners
The advantages of low NOx burners
Due to the stretching of the combustion zone, some combustion intensity is weakened, and the composition of NOx is suppressed for a certain period of time. Low load stable combustion. Due to the decrease in air volume in the lower part, the fuel is also very stable when burned at low concentrations. It can even achieve stable combustion at 40% load. When the load is low, the furnace flame is full. The water-cooled wall uniformly absorbs heat.
Disadvantages of Low NOx Burners
Due to the location of the burned air, many supply air do not participate in combustion when leaving the furnace. This part of the hot air also absorbs a large amount of heat from the air preheater, which will lead to the phenomenon of low exhaust gas temperature. Especially under low loads. Due to the weakening of the lower furnace air inlet, the support of the lower secondary air may weaken, resulting in an increase in slag discharge volume and carbon content, especially at high loads. Because it weakens the air inlet of the lower furnace, weakens the rigidity of the air, and expands the combustion area. When the load is high, the water-cooled wall only coking. Due to oxygen deficient combustion in the lower part of the furnace, a large amount of reducing gas is produced, which reduces the ash melting point and even causes coking in the cold slag hopper. Due to the extension of the combustion zone, overheating of the superheater and insufficient cooling water will occur during high load periods. In severe cases, it may even form coking on the sieve. Due to the expansion of many restorative gases and combustion areas, severe coking occurs in the middle and lower parts of the water-cooled wall. Fire extinguishing, explosion, and damage to the slag conveyor may occur due to decoking. The coking under high load affects the heat absorption of the water-cooled wall, leading to an increase in temperature in the lower part of the furnace. Due to its position, the overheated air can only cool the flue gas in the upper part of the furnace and has no effect on the temperature in the lower furnace. Therefore, the NOx appearing in the lower part of the furnace increased coking. The longer the duration of high load, the smaller the reduction effect of NOx, even exceeding the original NOx amount. The theory of "continuous separation of ash peeling from the situation" does not match the theory of "evaporation part" in the lower part of the furnace combustion and the theory of "evaporation part" in the upper part of the combustion of coke and coal powder combustion → evaporation combustion → coke combustion → in the case of ash peeling, the evaporation fraction). Therefore, when the load is high, the combustion time of a large amount of coal powder is prolonged, and the partially burned coal powder enters the flue. The formation of carbon content in added fly ash.