A coastal based power station which is a captive power project of 63.75 MW near Chennai found blending of coal technically and economically to be suitable. Different types of imported and Indian coal brought via sea are available at port from the coal suppliers. Coal is transported to the plant site, which is about 50 Kilometers, by means of trucks from port.
Different blends of coal were tried. One blend gave very high furnace exit temperature. Another blend gave high unburnt carbon in the fly ash making ash disposal difficult as disposal was through supply to the cement industries and there is a restriction that unburnt carbon content in the fly ash should be less that 2%.
Attempt is made here to study the reactivity of blended coals by using simple experimental techniques from a chemical kinetics point of view.
The focus is on finding the activation energy and reactivity of coal chars component coals and also a blend which has been successful. Using muffle furnace and TGA the mass loss rate during char conversion rate is found for a particle size, Mathematical equation in Arrhenius form is derived for two coals and also of the blend which is proved working satisfactorily using first order kinetics.
Studies on weight loss against time and temperature of Char and Volatile matter for Indian coal, imported coal and a blends of these two in ratio of 1:2,1:3, 1:4 with increasing proportion of imported content was done. Non Isothermal TGA run and constant temperature run in TGA was done for two component coals and for the three blends mentioned above. It was found that activation energy of Indian char was found to be 77 KJ/mole and that of Indonesian char as 61 KJ/ Mole. Averaged reactivity parameters and Rate constants has been found.
Additivity and non additivity has been mentioned using the plant data and conclusions from the experiments are listed.
Keywords: Combustion, coal, char, blend, Activation energy.