Oxy-fuel combustion of pulverized coal in an industrial boiler with a tangentially fired furnace

Abstract

Numerical studies of the processes of oxy-fuel combustion of pulverized coal (PC) in an industrial boiler BKZ 500–140–1 (with a capacity of about 400 MW) were carried out in this work. The proposed comprehensive mathematical model was tested based on data from a full-scale experiment (2.4 MW laboratory stand) of oxy-fuel combustion of PC. The conducted comparison has shown a good agreement of the calculation results with the experimental data. A detailed comparative analysis of the effect of the operating modes of the BKZ 500–140–1 industrial boiler during oxy-fuel combustion of coal on physical and chemical processes and the level of harmful emissions (NOx, CO2) was performed for the first time. The effect of oxygen concentration and CO2/H2O ratio in the blast on the processes of ignition and combustion of fuel in a nitrogen-free environment has been studied. It is shown that when nitrogen in the blast composition is replaced with flue gases without changing the oxygen concentration in the boiler under study, the average temperature in the furnace volume declines, as well as the average heat flux at the walls decreases from 87.35 to 70.32 kW/m2. To achieve the standard operating parameters of the BKZ 500–140–1 industrial boiler, it is necessary to increase the oxygen concentration in the blast from 15.4 to 19.7 vol.% (i.e. by 28%). The implementation of the oxy-fuel combustion technology on a steam boiler leads to a decrease in the NOx concentration in flue gases from 480 to 273 mg/m3.