Burning profile of high ash Indian coals in oxy-fuel environment

Oxy-fuel combustion is one of the emerging technologies to capture and store CO2 emissions generated from thermal power plants. Research programs are in full swing to find out the possibility of retrofitting existing coal fired power plants with oxy-fuel mode combustion. Most of the Indian thermal power plants are pulverized coal based and use sub-bituminous Indian coals. These coals differ from the foreign coals in respect of maceral composition, ash content and combustion kinetics. It is imperative to understand the burning characteristics of Indian coals in oxy-fuel environment to evolve the suitable design for the retrofit of Indian boilers with oxy-fuel mode for the efficient and economic carbon capture without losing thermal efficiency. The present study involves the assessment of the kinetics of pyrolysis and char oxidation of three different Indian coals with varying ash contents viz. 33 to 44% in normal air and in oxy-fuel environment with three different CO 2/O2 concentrations (60:40, 70:30 and 80:20) by Thermo Gravimetric method (TGA). The results are compared in respect of weight loss pattern, peaking temperatures and weighted mean activation energy. The results have shown that the combustion kinetics of the selected high ash Indian coals in normal air combustion is more comparable with 70:30 and 80:20 than 60:40 CO2/O2 concentrations. The methodology adopted in the present study is found useful for comparing the combustion kinetics of various types of coals in normal air and oxy-fuel environment. Copyright © 2008 by ASME.