Biomass to Fuels: Impact of Reaction Medium and Heating Rate

摘要

We have recently reported on the impact of CO_2 on biomass gasification and its ability to more effectively gasify biomass than steam. Continuing this investigation has led to understanding the impact of heating rates and different reaction environments. This paper will present the results from the gasification of various biomass feedstocks. The heating rates were varied from 1℃ min~(-1) to 100 ℃ min~(-1) to ballistic rates (～ 500℃ min~(-1)). The gasification mediums investigated include H_20/N_2, CO_2, CO_2/N_2/H_20, and O_2/N_2.rnGlobal activation energies for pyrolysis were found to be significantly higher than for gasification while those for the grasses were significantly lower than the woods, possibly indicating a catalytic effect during pyrolysis of the high mineral content herbaceous feedstocks. CO_2 pyrolysis (110-450℃) activation energy values for lignin, cellulose and biomass were 22-49, 202-230, and 28-72 kJ mol~(-1) and CO_2 gasification (500-700℃) values for lignin and biomass were 12-38 and 9-57 kJ mol"1, though cellulose did not exhibit significant gasification behavior. Using a least squares fit on the rate of mass loss fraction, the global decomposition reaction during pyrolysis for lignin in either medium was found to be third order while that for cellulose was first order and for the various biomass samples either first or second order.rnGC analysis has shown the effect of CO_2 on the product distribution. Data will be presented focusing on the relation between gasification medium, feedstock selection and major chemical species evolution.