TG-FTIR study on co-combustion of bituminous coal semicoke and lignite

Abstract

The combustion behaviors and pollutants emission characteristics during co-combustion of bituminous coal semicoke and lignite were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR). Results showed the addition of lignite could lower the ignition and burnout temperature and also enhance the comprehensive combustion performance of blends. High heating rate could improve the combustion intensity and corresponding combustion characteristic indexes. The activation energy analysis by distributed activation energy model (DAEM) and Ozawa–Flynn–Wall (OFW) methods at lignite blend ratio of 40% indicated its distribution was consistent with the combustion process of blends. An obvious activation energy jump occurred at conversion rate range of 0.4–0.55 due to the poor ignition performance of semicoke. The average activation energy obtained by DAEM and OFW methods was 101.69 kJ mol−1 and 109.12 kJ mol−1, respectively. With the increase of lignite blend ratios, CO and CO2 emission gradually decreased. Meanwhile, NO emission increased, while NO2 and SO2 emission ascended after an initial decline. Semicoke had certain suppression effect on NOx and SO2 emission. The minimum NO2 and SO2 emission was obtained at lignite blend ratio of 20%.