A Review of Multi-Stage Allothermal Gasifiers

Abstract

A review of the present development of multi-stage allothermal gasifiers is given. These reactors obtain part or all heat necessary for endothermic gasification reactions outside of the reactor space, and are usually only a segment in complex systems for cogeneration and production of other biofuels and chemicals. Their purpose is to produce as clean as possible product gas with the composition adapted to the final use of the gas. In this way designed gasifiers, substantially improve the efficiency of biomass conversion and the economics of the systems since they require less expensive gas cleaning equipment downstream of the reactor. Different types of gasifiers that obtain heat for endothermic gasification reactions by the use of: preheated medium, chemically active or not hot bed material, high heat fluxes over the solid reactor surfaces, electrical and solar energy are presented. They have significant potential for the combine use of biomass energy together with solar energy, excess electricity and high temperature waste heat.