Research on Oxy-Fuel Combustion Characteristics of Two Typical Chinese Coals

Oxy-fuel (O-2/CO2) combustion technology shows great potential for carbon reduction. However, difference in the combustion atmosphere would affect coal combustion characteristics and pollutant emissions. In order to explore oxy-fuel combustion characteristics, two typical Chinese coals, sub-bituminous and lean coal, were utilized. Based on thermogravimetry and pilot-scale test, the ignition and burnout characteristics under oxy-fuel and air combustion atmosphere were investigated. Besides, the NOx emission characteristics were also investigated on the pilot-scale test. Through experimental results, these two kinds of coal showed different combustion characteristics, mainly due to differences in coal quality. Compared with air combustion, oxy-fuel combustion affected the coal combustion process. Firstly, the ignition temperature of sub-bituminous and lean coal decreased from 418 and 477 degrees C to 405 and 415 degrees C, respectively; the burnout temperature also decreased from 855 and 985 degrees C to 808 and 838 degrees C, respectively. Then, coal combustion performance was evaluated by comprehensive combustion characteristics (S); with an increase in S from, respectively, 3.659 and 2.013 to 4.826 and 3.545 x 10(-8)(min(-2) x K-3), the combustion performance significantly improved. Then, the char burnout time was advanced for 1 similar to 3 min. Similar results were obtained on the pilot-scale test. The ignition temperatures decreased from 505 and 552 to 490 and 512 degrees C, respectively. Moreover, the char burnout rate increased by 0.5 similar to 5% and 2 similar to 11%, respectively. Lastly, the NOx concentration in flue gas was 2.2 similar to 2.6 and 2.0 similar to 2.3 times higher for the two kinds of coal under oxy-fuel combustion.