Advantages and disadvantages of low NOx burners
Advantages of Low NOx Burners
Due to the stretching of the combustion zone, some of the combustion intensity is weakened, and the composition of NOx is suppressed for a certain period of time. Low load stable combustion. Due to a decrease in the amount of air in the lower part, 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 already full. The water-cooled wall absorbs heat evenly.
Disadvantages of Low NOx Burners
Due to the location of the burned out air, many supply air does not participate in combustion when leaving the furnace. This 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 air inlet in the lower furnace, the support of the lower secondary air may weaken, resulting in an increase in slag discharge volume and carbon content, especially when the load is high. 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 the lack of oxygen combustion in the lower part of the furnace, a large amount of reducing gas is generated, which reduces the ash melting point and even forms coking in the cold slag hopper. Due to the extension of the combustion zone, overheating of the superheater and insufficient desuperheating 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, the middle and lower parts of the water-cooled wall are severely coking. There may be fire extinguishing, deflagration, and damage to the slag conveyor caused by 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 presence of NOx in the lower part of the furnace increases 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" → evaporation combustion → coke combustion → in the case of ash peeling, evaporation fraction "in the lower part of the furnace and the theory of" evaporation part "in the upper part of the combustion of coke and coal powder combustion. 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 added fly ash carbon content.