Co-firing wastes with coal has been investigated since the late ‘90s as a promising and cost efficient alternative for materials which are non-recyclable or too costly to recycle. Various waste derived fuels such as waste wood, animal waste, paper sludge or the organic fraction of MSW (Municipal Solid Waste) have been utilised or at least tested at demonstration scale for their co-combustion behaviour. An overview of the results attained up to date in the co-firing power plants is described and the main interest focuses on the utilisation of Solid Recovered Fuels (SRF) derived from the waste treatment. Its energy exploitation through co-firing becomes gradually important for the European coal sector, since it is promoted by the 1999/31 EC waste landfill Directive, which prohibits the disposal of untreated MSW to landfill. The use of secondary fuels as substitute for coal in large scale power plants leads to additional revenues for the the plant operators, since SRF is considered to be at least 50% biogenic and therefore CO2 emissions can be saved.
The co-combustion of SRF with brown coal has been demonstrated in two pulverised coal boilers at RWE Power’s power plant site in Weisweiler, Germany in the framework of the EU-funded project RECOFUEL. During the experimental campaign the share of SRF in the overall thermal input was adjusted to approximately 2%thermal input , resulting into a feeding rate of about 25 tons per hour. The measurement campaign included boiler measurements in different locations, fuel and ash sampling and its characterisation. The corrosion rates were monitored by dedicated corrosion probes. The overall results showed no significant influence of SRF co-combustion on boiler operation, emissions behaviour and residues quality for the thermal shares applied. Also no effect of the increased chlorine concentration of the recovered fuel was observed in the flue gas path after the desulphurization unit. As a consequence, co-firing SRF with coal can be considered beneficial following European Directive 2001/77/EC on electricity from renewable energy sources (RES-E directive). Future research should address to the development of reliable process-specific fuel qualification methods to predict the environmental and economic potential or impact by the SRF energy exploitation
Keywords:Waste Wood, Solid Recovered Fuels (SRF), Emissions