An overview of fast pyrolysis of biomass

Biomass fast pyrolysis is of rapidly growing interest in Europe as it is pe rceived to offer significant logistical and hence economic advantages over other thermal conversion processes. This is because the liquid product can be stored until required or readily transported to where it can be most eff ectively utilised. The objective of this paper is to review the design cons iderations faced by the developers of fast pyrolysis, upgrading and utilisa tion processes in order to successfully implement the technologies. Aspects of design of a fast pyrolysis system include feed drying; particle size; p retreatment; reactor configuration; heat supply; heat transfer; heating rat es; reaction temperature; vapour residence time; secondary cracking; char s eparation; ash separation; liquids collection. Each of these aspects is rev iewed and discussed. A case study shows the application of the technology t o waste wood and how this approach gives very good control of contaminants. Finally the problem of spillage is addressed through respirometric tests o n bio-oils concluding with a summary of the potential contribution that fas t pyrolysis can make to global warming. (C) 1999 Elsevier Science Ltd. All rights reserved.