Numerical study of single coal particle combustion in o2/n2 and o2/co2 atmospheres

Abstract

This paper reports a modelling work on the existing experimental data of single coal particles combustion process [1][2]. Two kinds of coal particles (a high-volatile bituminous coal / a lignite coal) are injected in a drop-tube furnace, ignited and burned in quiescent O2/N2 and O2/CO2 atmospheres with oxygen mole fraction varying from 20% to 100%. Ignition delay time, particle life time and particle surface temperature are calculated to analyse the combustion behaviour of the single coal particle. Transient simulations are carried out based on Discrete Phase Model (DPM). The predicted results are in good agreement with the experimental data and give the details of combustion process. Further, predictions of NOx emissions are made to understand the influence of different gas atmosphere and oxygen mole fraction. This includes both thermal-NOx and fuel-NOx formation mechanisms. It is argued that the NOx emissions in both O2/N2 and O2/CO2 atmospheres are the result of competitions between the maximum particle temperature and the burning time.