A Study On Oxygen-enriched Combustion Of Coal Under CO₂/O₂

With the growing of global concern about carbon dioxide emissions, it is very important to develop and promote low-carbon technologies for China. Oxygen enriched combustion (OEC) is an advanced clean energy technology. OEC can reduce the cost of carbon dioxide reduction and improve energy efficiency. And how to combine the OEC and coal combustion effectively has become a hotspot and difficult issues in the coal research field.This paper selected several kinds of coal, did experiments in carbon fixed furnace and TGA under CO2/O2, and discussed the characteristics of coal in OEC.In the carbon fixed furnace, XIN'AN coal's ignition time and burnout time both decline from 270s and 665s, to 94s and 166s, while oxygen concentration increasing from 21% to 100%. Simultaneously, the peak of combustion temperature increases from 681℃to 1240℃. However, the decrease of ignition time and burnout time is not obvious when over 60%-Oxy. Compared with ordinary air combustion, carbon dioxide delays ignition of coal. Carbon dioxide accelerates the burning of coal under high oxygen concentrations, otherwise it is bad for coal's combustion.In TGA, NINGLU coal's ignition temperature and burnout temperature both drop from 780K and 965K, to 723K and 760K, while oxygen concentration increasing from 21% to 100%. And the rate of decrease is low after some oxygen concentration. High heating rate makes ignition temperature and burnout temperature reduced to an extreme value. And influence on OEC of carbon dioxide is different in various oxygen concentrations. Compared with nitrogen, carbon dioxide is helpful to coal's combustion under low oxygen concentrations in TGA experiments.Also in TGA, the ignition mode of coal transforms from heterogeneous to homogeneous, as long as oxygen concentration increase under CO2/O2 atmosphere. And that is not happened under N2/O2 atmosphere. The ignition mode of coal is more likely to be heterogeneous under high heating rate in OEC. Coal with different particle radius has different ignition mode. And the volatile containing affects ignition mode very much.