Structure of reaction zone of normal temperature air flameless combustion in a 2 ton/h coal-fired boiler furnace

Abstract

By injecting normal temperature air into a coal-fired boiler furnace at an evaporation capacity of 2 ton/h, flameless combustion with little noise is achieved. Numerical simulations and experimental research shows that the combustion takes place in a wide and broad area, almost the whole furnace, resulting in a voluminal reaction. For this normal temperature air flameless combustion (NTAFC), when the excess air coefficient approaches 1, the fuel combusts fully. The concentrations of NO _x and CO in flue gas are relatively low and are hardly affected by either an excess air coefficient or thermal load. In front of the jet is a low-temperature gas-mixing zone whose diameter is equivalent to that of the jet, and the temperature of this zone increases with the distance from the jet tip. A mild stable combustion reaction without a visible flame takes place in the part of the furnace where the temperature value is higher and the amplitude of variation is not large. In addition to the advantages shared with high-temperature air combustion (e.g. uniform temperature distribution, low NO _x and CO emission, high combustion efficiency, and so on), NTAFC does not require a high-temperature air-preheating system and is easier to actualize.