Biomass to Fuels: Impact of Reaction Medium and Heating Rate

摘要

We have recently reported on the impact of CO2 on biomass gasification and its ability to more effectively gasifynbiomass than steam. Continuing this investigation has led to understanding the impact of heating rates andndifferent reaction environments. This article presents the results from the gasification of various biomass feedstocks.nHeating rates were varied from 1 to 1008C minu00011 to ballistic rates (*5008C minu00011). Gasification medianinvestigated include H2O=N2, CO2, CO2=N2=H2O, and O2=N2. Global activation energies for pyrolysis werenfound to be significantly higher than for gasification, whereas those for the grasses were significantly lower thannthe woods, possibly indicating a catalytic effect during pyrolysis of the high mineral content herbaceous feedstocks.nCO2 pyrolysis (110–4508C) activation energy values for lignin, cellulose, and biomass were 22–49, 202–n230, and 28–72 kJ molu00011, respectively, and CO2 gasification (500–7008C) values for lignin and biomass weren12–38 and 9–57 kJ molu00011, although cellulose did not exhibit significant mass loss in the gasification interval 500–n7008C. Using a least squares fit on the rate of mass loss fraction, the global decomposition reaction duringnpyrolysis for lignin in either medium was found to be third order, whereas that for cellulose was first order andnfor the various biomass samples either first or second order. The most significant difference in biomass processingnin CO2, when compared with steam gasification, occurred above 7508C where nearly all of the biomassnwas converted to volatiles with less than 2% ash remaining after CO2 gasification. Only when pure CO2 wasnused as the gasification medium under a slow heating rate did complete processing of the components to volatilenproducts occur. Gas chromatography analysis has shown the effect of CO2 on product distribution. Data arenpresented focusing on the relation between gasification medium, feedstock selection, and major chemical speciesnevolution.sustainable systems engineering;