Fast pyrolysis (ultrapyrolysis) of cellulose and wood components

Abstract

A fast pyrolysis process, termed Ultrapyrolysis, has been developed at the University of Western Ontario in order to exploit the high heating rates, short residence times, high temperature and rapid quenching which are required to produce valuable non-equilibrium chemical intermediates (i.e. olefins, BTX, etc.) from carbonaceous feedstocks. The first phase of the work was conducted primarily to develop a novel reactor system which could accommodate the rapid and severe process requirements, and which could also serve as a conceptual design for a continuous commercial process. The first phase of work also demonstrated the chemistry of fast pyrolysis. Trials with cellulose, lignin and wood were conducted at temperatures between 750 and 900°C and residence times between 250 and 450 ms. Maximum ethylene yields, expressed as mass percentages of the product gas, were 8.2, 7.3 and 6.3% for cellulose, wood and lignin trials, respectively, at 900°C. The second phase of the work, which is currently in progress, was initiated to refine the operation of the pilot plant in order to generate data suitable for kinetic studies and process optimization. Several system components were replaced or modified, the mass balance and analytical procedures have been improved, and studies on the effect of Thermofor (heat carrier) type and proportion (i.e. with respect to feedstock) have been completed.