Investigation into co-gasifying Indian coal and biomass in a down draft gasifier - Experiments and analysis

Gasification is an energy efficient and environmentally clean process to generate heat and electricity, and biomass and coal have found wide usage as fuels. In India, biomass gasification has received significant attention, while, coal gasification has been less studied due to its lower reactivity and the potential difficulty in handling arisen due to high ash contents of domestic coals. In the current study, coal and biomass were co-gasified in a downdraft reactor, and the challenges originating due to the varying thermo-physical properties of both the fuels: like density, volatile fraction, ash content, etc. to achieve an engine quality gas are addressed. A fundamental study was undertaken and the fuels for flaming and glowing times were characterized. Further, the overall conversion time was estimated. Gasification studies were conducted using an open top downdraft gasification system of 10 kg/h capacity, with different fuel blends and varying reactants (air, air + steam), and it was observed that the fuel blend with higher percentage of coal generated severe clinker due to ash fusion. Steam was found beneficial in increasing the carbon conversion, reducing clinkers and also improving gas quality. The best performance was achieved with biomass to coal ratio of 85:15 on weight basis. With 94% carbon conversion and 65% cold gas efficiency, the present study successfully establishes the optimum operating condition's for stable operation with multi-fuel feed. (C) 2015 Elsevier B.V. All rights reserved.