Rice husk gasification in a two-stage fixed-bed gasifier: Production of hydrogen rich syngas and kinetics

•Production of hydrogen in syngas increases from 2.96 to 25.01 (vol%) in the gasifier.•Air as gasification medium was more effective for secondary gaseous yield.•FTIR study indicates homogeneous tar cracking in two-stage gasifier.•Activation energies were significantly more for DAEM than single-reaction model.

The purpose of this study is to evaluate the products of homogeneous cracking of rice husk tars and to investigate the conditions for production of hydrogen rich syngas. Experiments were performed in a two-stage downdraft fixed-bed gasifier as a function of temperature and residence times. Tars were generated with a medium heating rate of 25 K/min in a pyrolysis section of the gasifier. Generated tars were subsequently cracked by secondary reactions in gasification section. Tar conversion of about 91% was achieved. Tar cracking at higher temperatures resulted in the formation of hydrogen rich syngas. Secondary product yields and their kinetics were studied for tar cracking and individual gas formed by single-reaction model and distributed activation energy model. A good fit of the data was obtained with the single-reaction model; however distributed activation energy model correlated the tar cracking kinetic parameters more closely than single-reaction model.