Use of biomass materials and bio-waste in existing power and combined heat and power plants is widely recognized as representing an important way to achieve internationally agreed overall targets for reduction of green-house gas emissions. The RECOMBIO project currently in progress under the Seventh Framework Program is concerned with developments and demonstrations of innovative approaches to the high efficient co-utilization of low quality biomasses and Solid Recovered Fuels (SRF) produced from high calorific fractions derived from municipal solid waste for electricity production and combined heat and power usage, at competitive costs, high plant availability and advanced energy efficiency. Different technologies such as circulating and bubbling fluidized beds or continuous grate firings, meeting best available techniques standards are incorporated to demonstrate the highly efficient utilization chain for the intelligent co-utilization of low quality biomass together with SRF. Accompanying R&D activities at KIT are focused on combustion behavior in continuous grate systems. In May 2011 a number of tests in the pilot scale (500kW) grate system Tamara were performed for evaluation of slagging, corrosion risk, emissions and assessment of ash utilization. Several fuel blends based on wood chips (taken as reference fuel) and two different solid recovered fuels produced and delivered by REMONDIS GmbH were fired. During the test campaign a number of process parameters were measured along the grate, in the furnace and in gas cleaning system to provide data for balancing. Additionally a test with sulfur addition was carried out for firing of both above mentioned SRFs. Bottom ash and fly ashes were then sampled for further analysis concentrated on chlorides and sulfides content. In order to assess corrosion and slagging risk a corrosion probe provided by IFK at University of Stuttgart was installed in the furnace.
A relationship between combustion behavior of blends of both SRFs with wood chips has been found and described, which can help a power plant operator to choose the right mixture for a given grate parameters. It has been also shown, that firing the right biomass/SRF mixture helps to protect the firing against slagging. Last but not least, it has been proved that adjusting sulfur-to-chlorine factor by adding elemental sulfur to the fuel during co-firing has a corrosion reducing potential under certain conditions.