Development of a Bubbling Circulating Fluidized-Bed Reactor for Biomass and Waste Gasification

The Bubbling Circulating Fluidized-Bed (BCFB) gasifier described in this paper is based on a combination of the two fluidized-bed reactor types: a bubbling and a circulating fluidized-bed. The BCFB gasifier was originally developed in the early 2000s and designed for air-blown gasification of waste-derived feedstocks that have very high volatile matter content resulting in high tar concentration in the raw product gas. In an ongoing EU project FlexSNG, the BCFB gasification technology is now adapted for the co-production of biochar and synthesis-quality gas, using steam and oxygen as fluidizing gases. In this paper, the pilot-scale development of the BCFB gasifier in air-blown operation with wood residues and a waste-derived feedstock is firstly presented. Then, the use of this gasifier design for the co-production of biochar and synthesis gas is described and the results from preliminary process simulations are presented. Estimated process performances are shown for two operation modes. In the maximized synthesis gas mode, the gasifier is operated at 900 °C resulting in a similar performance to a conventional CFB gasifier. In co-production operation mode, the bottom section of the BCFB gasifier acts as the carbonization zone producing good-quality biochar, which is recovered from the bottom of the gasifier.