FIRST EXPERIENCES WITH THE NEW CHALMERS GASIFIER
Paper in proceedings, 2009
During summer 2007 a 2-4 MWth indirect gasification section was integrated into the loop of the existing 8-12 MWth circulating fluidized bed boiler at Chalmers University. With help of a particle distributor the gasification unit is connected to the loop after the cyclone. Hot bed material entrained from the boiler is so transferred to the gasifier providing the heat for the production of a nearly nitrogen free product gas. Non gasified char is returned together with the bed material into the boiler and converted. Biomass can be fed into both sections; the boiler and the gasifier. The gasification is separated from the boiler via two loop seals and a particle distributer, directing particles either back to the boiler or into the gasification section. For that reason the CFB boiler can be operated even after the retrofit independently, just like before, or in combined combustion/gasification mode. This possibility keeps the risk for a retrofit low. As, furthermore, the investment costs for the integration are considerably lower than standalone gasification units of that size, the retrofit is an easy way to extend the potential of a CFB Boiler towards bi- and tri generation (heat, power, fuel) and enter new markets.
The first experimental season with the installation proved stable operation of both the boiler and the gasification. Furthermore, the full functionality in combustion only mode was shown. The gasifier was operated for 60 h with wood pellets and wood chips. First analysis of the producer gas composition shows high contents of methane, making the installation a good match for SNG production. The heating value of the gas is about 14,4 MJ/nm3.