Evaluation of combustion characteristics in thermogravimetric analyzer and drop tube furnace for Indian coal blends

Availability of low ash coals is diminishing in India very fast. As such, trend of utilization of high-ash coals by blending with low ash coals is rapidly growing in Indian power plants with the growing demand of coal and with emerging environmental strictures to reduce green house gas emission and to restrict the ash limit to a targeted value. Quick decision on acceptance of certain blends in power stations very often leads to various operational problems/uncertainties. To address such uncertainties in coal combustion, three blend combinations of high-ash-low-ash coals have been examined in this study through lab- and bench-scale combustion experiments. Combustion parameters are found to be mostly non-additive. Both synergistic and anti-synergistic combustion characteristics were noticed at different combustion-stages. This study reveals necessity of pre-assessment of certain blends through lab/bench scale studies before those are adopted in power plant. This work also attempts estimation of low rank intertinite (i.e., reactive component of inertinite having Rr ≤ 1.30) followed by 'total reactive content' for prediction of burn out characteristics in TGA/DTF. Here, total reactive content is the sum of low rank inertinite and other traditional reactive macerals viz., vitrinite, semi-vitrinite and liptinite. Interestingly, satisfactory correlations between 'combustion parameters' and the 'total reactive maceral content' were found.