A cost effective concept for generation of heat, electricity and transport fuel from biomass in fluidized bed boilers – using existing energy infrastructure
Conference contribution, 2007
Poly-generation of various energy carriers from biomass is a cost effective option to initiate production of transport fuels from lignocellulosic biomass. Traditionally, the routs for this option have been trough greenfield gasification reactors. Here, on the other hand, the infrastructure of existing boilers is used for introduction of the gasification technology, which lowers cost and minimizes risks. The concept is based on adding a gasifier to existing fluidized bed boilers. An evaluation indicates the possibility of producing between 25 to 50 % of syngas, based on fuel input, without reducing the power output of the boiler. The process uses the thermal flywheel of the fluidized bed as a means to devolatilise the biomass. Only in Sweden there are around 100 fluidized bed boilers, which are potentially appropriate to be retrofitted with the proposed concept, whereof around 40 are large enough to give a low risk option for production of transport fuels within the present energy infrastructure. To demonstrate the concept, the Chalmers 12 MWth circulating fluidized bed boiler will be retrofitted according to this concept, resulting in co-generation of around 2 MWth product gas. The gas will be used temporarily for production of heat and electricity. The unit will, however, be prepared in such a way that the gas in a later stage can produce any Fischer-Tropsch fuel or synthetic natural gas. The retrofit is planed for the summer of 2007 and the plant is planned to be in operation in October 2007. This paper presents and discusses an evaluation of the concept.