Study on the similarity of the parameters of biomass and solid waste fuel combustion for the needs of thermal power engineering

The topic raised in this paper concerns an important aspect regarding the possibilities of the combustion and co-combustion of biomass substrates (energetic willow/sewage sludge), in light of the renewable energy source (RES) regulations, with fuel from waste defined here as RDF. Particular interest in these fuels and their mixtures results from a search by the thermal power engineering sector for fuels whose combustion will be associated with benefits, e.g., the acquisition of energy origin licenses, availability and lower cost of obtaining fuel (RDF), as well as moderate investment contributions using the existing base of coal grate boilers. This article indicates the possible variants of the combustion and co-combustion of the abovementioned fuels, referring to the use of technical and technological capabilities of coal grate furnaces. It was possible by comparing the mechanical and thermal load of grates, as well as so-called indicators for the quantitative assessment of combustion (i.e., ignition rate and mass loss rate). The result of the combustion of the fuel as above in a laboratory-scale furnace (samples weighing up to 1 kg), as well as their thermogravimetric analysis, indicates a great similarity of the mass loss curve, temperature profiles and combustion phases, as well as indicators of a quantitative assessment in the process of biomass and RDF oxidation. The obtained results of the mechanical and thermal load capacity of the grates constitute the basis for further analyses of fuel conversion, without the risk of thermal and/or mechanical grate overload. Relying on the research of the indicators for the quantitative assessment of combustion, it was found that the combustion process of the tested fuels could be carried out while maintaining the quality of burning the fuel layer. Based on the conducted research, it can be assumed that it is possible to replace coal fuels with biomass, RDF fuel, sewage sludge using coal furnaces for their combustion, which means a hybrid nature of the furnace due to the type of fuel.