Co-combustion of biomass in lignite-fired power plants

Power generation in the eastern part of Germany is mainly based on lignite as a domestic fuel. More than 90% of lignite is converted into electricity in large-scale power plants. The remaining portion is used for heating homes and in decentralised plants. With a specific CO2-emission of 0.40 kg/kWh per fuel used, CO2 makes up the biggest problem as regards the acceptance of lignite used for a further long-term power generation. For this reason power stations were completely modernised during the last five years. Besides increasing the efficiency, co-combustion of biomass offers another important possibility to improve the CO2-balance of lignite-fired power stations. In Schwarze Pumpe power station which is part of VEAG Vereinigte Energiewerke AG Berlin, co-combustion of biomass as wood chips has been tested for some time. The lecture deals with both development work carried out by VEAG (logistics, operation management, emission behaviour with co-combustion) and development work about the co-combustion of biomass in smaller plants for the decentralized heat supply market. At the chair "Power Station Technology" of Brandenburg University of Technology Cottbus and in the Energy Resource Institute Cottbus, E. cycloidal firing system (cyclone firing) for use on the decentralised heat supply market was developed in co-operation with partners from the industry such as LAUBAG and BBP Environment. Lusatian fluidised-bed lignite is used as primary fuel. Combustion in applying cycloidal firing takes place in an upwardly directed rotational flow. The application of this technique makes a highly-efficient co-combustion of biomass (wood chips) possible. Besides the reduction Of CO2-emissions, fuel substitution offers the possibility to reduce SO2-emissions in such a way that existing boundary value requirements regarding the emission of pollutants can be met without any additional desulphurisation of flue gas.