Simulation Investigation on NOx Emission Characteristics and Mechanisms During Co-combustion of Fossil Fuels with Different Fuel-Nitrogen Distributions via CHEMKIN

There are over 100 million tons of semi-coke produced in China every year, and use of the semi-coke in utility coal-fired boilers is a promising approach. In this paper, a blending model of semi-coke and bituminous coal was established via CHEMKIN. The NOx emission was investigated by analyses of sensitivity and production rate, while the effects of stoichiometric ratio of main combustion zone, blending ratio, and combustion temperature on migration of fuel nitrogen were further elucidated. The simulation results showed that the conversion ratio of NOx increased monotonically with an increase in the stoichiometric ratio of main combustion zone. The temperature of plug flow reactor (PFR) I exhibited a significant effect on NOx emission, but other reactors had limited influences. The NOx conversion ratio was enlarged with the increase of semi-coke blending ratio. The influence of blending proportion on NOx emission was significant when the stoichiometric ratio of main combustion zone was small. Compared with high blending ratio, the main reactions with low blending ratio had stronger inhibitory effect on the formation of NO. The present study was of guiding significance for reducing NOx emission in the utility boilers co-firing semi-coke.