The Centre for Renewable Energy Sources, CRES, began a project on flash pyrolysis of biomass in spring 1990 as a consequence of the considerable European interest generated in direct production of liquid fuels from the work of Alten and Bio-Alternative. This was one of six activities started at the same time in the EEC JOULE programme (22) — the others were Egemin, INETl, Union Fenosa, University of Aston and University of Twente, all of which are described in this paper.

5.6.1 Description

The process has a nominal capacity of 10 kg dry wood per hour and is based on the principle that the by-product char from flash pyrolysis liquid production has to be used to provide process heat to drive the process. This is derived by burning the char in a conventional bubbling bed to heat sand which is then carried through a recirculating bed with the hot combustion gases to carry out flash pyrolysis in the riser section of the recirculating fluid bed (23). Instead of having two separate reactors as usually practised in steam and pyrolytic gasification processes, these are integrated into one vessel as shown in Figure 5.5. The design is in line with the recommendations of the IEA Bioenergy Agreement liquefaction group of integrating char combustion into the flash pyrolysis reactor.

A cold model has been constructed to understand the hydrodynamics of the system and a hot unit has been built, commissioned and tested. Although some liquids have been produced, no reliable heat or mass balance data is yet available.