Biomass combustion for power generation

An overview is given of the state of the art of biomass combustion power generation technologies with a capacity of more than 10 MWe. Biomass combustion technologies have been compared on a qualitative basis and a selection of individual biomass combustion power plants has been compared on a quantitative basis. Collected data were modified for comparison of the various power plants in the quantitative analysis. The qualitative analysis focused on the following technologies: pile, grate, suspension and fluidised-bed combustion. Fluidised-bed systems are found to have relatively high efficiencies and are also flexible with regard to fuel properties. Both fluidised-bed systems and vibrating grates are successful in limiting thermal NOx formation. Some recently built plants and some planned concepts are compared quantitatively on the basis of efficiency, investment costs and emissions. All electric efficiencies are close to or above 30% (at lower heating value). Of the plants fired solely by biomass, vibrating grates and circulating fluidised beds turn out to have the highest efficiency at the moment. Co-firing of 4.5% biomass in a pulverised coal boiler has an efficiency of about 37% (LHV). Expected efficiencies for large-scale (100 to 250 MWe) promising concepts are in the 39–44% (LHV) range. Investment costs range from 1200 to 2900 (1992)US$/kWe. High costs are often caused by additional features such as the firing of difficult fuels or combined heat and power production. None of the existing technologies is found to be superior with respect to all the criteria selected.