Computational study on the effect of gasification reaction on pulverized coal MILD combustion diluted by N2 and CO2

Abstract

The behavior of pulverized coal gasification reaction under MILD combustion regime will be significant, and then it affects pulverized coal combustion. This work performs a computational study on the effects of gasification reaction on pulverized coal MILD combustion with N2 and CO2 dilution. Results show that, regardless of at air or O2/CO2 atmospheres, the proportion of char consumed by gasification reaction exceeds 50%. The gasification reaction makes a decrease in flame temperature about 80 K at O2/CO2 and about 50 K at air. The delayed ignition time affected by the gasification reaction is 1.38 ms at air while 3.29 ms at O2/CO2 due the formation of CO. The presence of gasification reaction shortens the char burnout time at air and O2/CO2 atmospheres. The reactions of H2O and CO2 with char destroy the char surface structures and create additional porosity, which prompts the char burnout. The significant decrease in the NOx emission affected by gasification reaction at air and O2/CO2 atmospheres can be attributed to the enhancement of NO reburning and the suppression of fuel-NOx conversion, i.e., NH3 + O2 → NO + products.