Facing the increasingly serious situation of air pollution

to realize high efficient low NO_x combustion of pulverized coal

the technical route of combustion with fuel preheating was put forward and developed. In this technology

the pulverized coal particles are preheated to over 800 ℃ in a CFB by partial combustion with equivalence ratio air

and then the resulting fuel gas and char particles are burned out in the furnace under air-staging conditions. Part of fuel nitrogen is removed at high temperature and in strong reducing atmosphere in the preheating process

and the NO_x generation can be further decreased by staged air distribution in the furnace. The results of industrial tests on a pulverized coal preheating combustion 40 t/h boiler showed that

this boiler could realize collaborative control of efficient operation and low NO_x emissions. The NO_x emission mass concentration increased with the boiler operating load

increasing the internal secondary air ratio and delaying the use of the tertiary air could both reduce the NO_x emission mass concentration. The NO_x emission mass concentration reached the lowest when the equivalent ratio of the secondary air was 0.4. Generally

the thermal efficiency of the boiler could reach 93.08% and the original NO_x emission mass concentration could be controlled below 119 mg/m~3(φ(O_2)=6%) in the range of 50%～100% operating load.