Experience of Indirect Cofiring of Biomass and Coal
AUTHOR: Rohan Fernando
DATE: October 2002
There has been increasing interest in the use of biomass for power generation in recent years. The principal reason for this is that the use of biomass can significantly reduce net CO2 emissions. Other advantages of utilising biomass are that it diversifies the power plant's fuel portfolio, it can lead to reductions in SO2 and NOx emissions and that such use can help to dispose of a solid waste.
There are some disadvantages of firing biomass which relate to its supply, transportation and composition and these can be reduced if the biomass is cofired with coal. Cofiring can be direct, where the biomass and coal are fired in the same boiler, or indirect, where the combustion or gasification of biomass occurs in a separate unit.
This report concentrates on indirect cofiring which is taken to mean technologies in which the ash from the coal and biomass are kept separate. Direct cofiring is relatively straightforward but can lead to several technical concerns. Indirect cofiring incurs greater costs and is particularly suitable for biomass containing troublesome components or when the quality of the ash is of importance. Indirect cofiring is less common than direct cofiring.
The report discusses the relative advantages and disadvantages of direct and indirect cofiring. It then describes the following plants which indirectly cofire biomass: Aabenraa in Denmark, Amergas in the Netherlands, Avedore 2 in Denmark, Kymijarvi in Finland, Zeltweg in Austria and Vasteras in Sweden.