Biomass and fossil fuel conversion by pressurised fluidised bed gasification using hot gas ceramic filters as gas cleaning

Abstract

Gasification of biomass and fossil fuels, hot gas cleanup using a ceramic filter and combustion of LCV product gas in a combustor were performed using a 1.5 MWth test rig (pressurised bubbling fluidised bed gasifier) at Delft University and a 10– 50 kWth system at Stuttgart University (DWSA) in the framework of experimental research on efficient, environmentally acceptable large-scale power generators based on fluidised bed gasification. The influence of operating conditions (pressure, temperature, stoichiometric ratio) on gasification (gas composition, conversion grades) was studied. The gasifiers were operated in a pressure range of 0.15– 0.7 MPa and maximum temperatures of ca. 900°C. The Delft gasifier has a 2 m high bed zone (diameter: 0.4 m ) followed by a freeboard approximately 4 m high (diameter: 0.5 m ). The IVD gasifier has a diameter of 0.1 m and a reactor length of 4 m . Carbon conversions during wood, miscanthus and brown coal gasification experiments were well above 80%. Fuel-nitrogen conversion to ammonia was above ca. 50% and the highest values were observed for biomass. The results are in line with other investigations with biomass bottom feeding. Deviation occurs compared with top feeding. Measurements are compared with simulation results of a reaction-kinetics-based model, using ASPEN PLUS, related to emission of components like fuel-nitrogen-derived species. Data from literature regarding initial biomass flash pyrolysis in the gasification process are used in the gasifier model and will be compared with simulation results from the FG-DVC model. Measurements and model predictions were in reasonably good agreement with each other.