Study on the combustion kinetics and combustion processes of four coals in a W-shaped boiler furnace

摘要

The kinetic parameters of chemical reaction, apparent pre-exponential factor A and activation energy E according to the Arrhenius formulation, are usually calculated from experimental data using the method of linear regression. But in this paper, A and E are taken as variables changed with burnout degree, and they can be obtained from TG and DTG curves of thermo-gravimetric analysis (TGA) of a coal at two heating rates of 15K/min and 20K/min.Four coals in which two are pure coals and the others are their blended coals, were tested by this method, and their varied E and A were obtained. Under three constant temperatures of 773K, 1273K and 1773K, the combustion rates of four coals were predicted using these kinetic parameters, indicating the combustion reaction transforming from the kinetic-control zone to the diffusion-control zone. The kinetic parameters calculated were given into a simulation code as reactivity parameters to investigate the combustion processes of four coals in a W-shaped boiler furnace. The simulation results show that the surrounding scare of oxygen relatively inhibits the further burnout of pulverized coals during the rise of main flue-gas flow. It is probably one of the origins of high carbon in fly ash for this type of boilers. The technology on Over Fired Air for W-shaped boilers (OFAW) is proposed to improve the burnout of pulverized coals.