Circulating fluidized bed

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Circulating Fluid Bed

The first CFB process was developed at the University of Western Ontario in the late 1970s and early 1980s. The principle is shown on the right side. Biomass is screwed into a (riser or fast fluidization) reactor, where extensive contacting between inert particles (sand) and biomass takes place. Together with the char, sand is entrained out of the reactor, and sent to a combustor chamber where the char is combusted. The main advantage of the CFB system compared to fluid bed and ablative is the direct heat supply to the biomass by recirculation of hot sand, generated by combustion of the char from the pyrolysis. In the beginning of the nineties, Ensyn Technologies Inc. in Ottawa, Canada offered the technology indicated as “rapid thermal processing”, or RTP. The Canadian Ensyn Technologies Inc. developed industrial applications for their so-called Rapid Thermal Processing, in which woody biomass is converted to pyrolysis liquids as a source of valuable chemicals and fuel. Commercialization for mainly wood flavors is done through Red Arrow Food Products Company Ltd. Ensyn and Red Arrow have been producing large quantities of bio-oil for the production of specialty products since 1990. A larger circulating fluid bed pilot plant of 625 kg/hr throughput capacity has been built in Bastardo, Italy. ENEL retains this unit, and operates on request only.

By 2007, eight RTP™ plants are in commercial operation, ranging from 1 to 100 t/day. Details of the operation (or operational performance) are unknown. Recently, Ensyn stepped into a joint venture with UOP, under the name Envergent Technologies LCC to commercialize the pyrolysis technology for fuel substitution and electricity generation. Another joint venture to develop bio-oil production is established between the Finnish companies Metso and UPM. Their development is based on the integration of conventional biomass-based fluidized bed boiler with a pyrolysis reactor (in cooperation with VTT). The pyrolysis unit utilizes the circulating hot sand from the boiler as a heat source. Test production began at Metso’s test unit in Tampere (Finland) in 2009. Recently Metso (now Valmet) and Fortum Power announced the delivery of a demonstration plant with a planned annual production of 50,000 tons bio-oil. The plant is started-up in the autumn of 2013.