Ultra-High Temperature Steam Gasification of Biomass and Solid Wastes

摘要

This paper presents experimental results on the gasification of several wastes using high temperature steam. Four cellulose-rich surrogate wastes (paper, cardboard, and wood pellets) were gasified with preheated steam at different temperatures in the range of 700 to 1100℃. Gasification is an efficient method for clean conversion of waste to hydrogen rich gas with moderate heating value product gas stream containing negligible soot and tars. Although the gasification is a relatively old technique, it has not been examined at ultra high gasification temperatures. Paper, cardboard and other cellulose-rich wastes represent their considerable shares in Municipal Solid Wastes. A basic chemistry of gasification and main reactions propelling the process are presented. The experimental facility used provided pure steam or steamoxygen mixtures from the combustion of hydrogen and oxygen at very high temperatures. The role of feedstock property (ultimate analysis, chemical formulas, steam/feedstock ratio) and gasifying agent property (flow rate, temperatures) have been determined. The results obtained have been compared with the equilibrium calculations using Equil software-part of Chemkin software. The experimental results for hydrogen and carbon monoxide yield are compared with the numerical simulation results. The results reveal information on the operating parameters for high hydrogen yield from cellulose-rich wastes. The results show high hydrogen yield of over 36% at 1000℃ gasification temperatures using paper. At higher gasification temperatures the yield of hydrogen decreased due to its dissociation. For other biomass wastes, only 24% hydrogen was obtained at 900℃. The heating value of the gases produced was high at higher gasification temperatures for all wastes. Although the experimental results showed good comparison with calculations, the experimentally determined magnitude of hydrogen and CO obtained was smaller than the calculation results.