Coal/biomass co-gasification in a pressurised fluidised bed reactor

Biomass and coal co-gasification is performed using a 1.5 MWth pressurised bubbling fluidised bed gasifier in the framework of a 3 year multinational EU JOULE project concerning research on efficient, environmentally acceptable large scale power generation systems based on IGCC technology. Influences of feedstock (biomass component and coal/biomass ratio) and operating conditions (temperature, stoichiometric ratio, steam/air ratio) on specific gasification characteristics (gas composition, fuel element conversion grades) are studied. Maximum gasification pressure and temperature are 10 bar and 900 °C, respectively. The gasifier has a 2 m deep bed zone with a diameter of 0.4 m followed by a 4 m high freeboard with a diameter of 0.5 m. The low calorific product gas is cleaned by a high temperature cleaning unit and subsequently combusted in a pressurised combustor. The operating envelope of the installation has been determined and the results of further experiments will be used to validate a mathematical model for the emission of environmentally harmful components like fuel-nitrogen derived species. Results obtained within the project are presented and analysed. A fuel gas of a heating value acceptable for combustion in a gas turbine combustion chamber is obtained at stoichiometric ratio's as low as circa 0.4. Carbon conversions measured are well above 80%. The fuel-nitrogen conversion to ammonia is in-line with other investigations.