Experimental Simulation of NO_x Formation and Emission from Low-capacity Coal-fired Industrial Boilers

NO_x was the priority pollutant to be controlled during the Twelfth Five-Year Plan period, and coal-fired industrial boilers were its main sources. In order to study the rule of NO_x formation and emission from coal-fired industrial boilers, the raw coal/char firing method to simulate the combustion process of different kinds of coals was carried out in the laboratory. The reaction from volatiles-N and char-N to generate NO_x was studied and the rule of fuel-type NO_x formation and emission investigated. Difference of NO_x generation coefficient between experiment and field test was analyzed. The results indicated that NO conversion rate of bituminous, anthracite and char was 25.77%, 22.17% and 11.98%, respectively; and NO_x generation coefficient was 4.31 kg/t coal, 5.08 kg/t coal and 2.00 kg/t coal respectively, which was higher than field test. Fuel-type NO_x was the main source of NO_x from coal-fired industrial boilers. Fuel-type NO_x formation and emission was a very complex multi-phase procession formed by volatile-N oxidation and reduction reaction as well as char-N oxidation and reduction reaction. The coal types, temperature, air flow, grain size, oxygen content had influence on the four reactions to distinct extent.