Fundamental drying experiments with processed residual municipal solid waste materials
Waste management companies and municipalities in southwestern Hungary aim the fulfillment of the EU's target, namely to decrease landfilling below 10 % and increase recycling above 65 % of municipal solid wastes. However selective collection is continuously improved there is still high amount of residual MSW is generated. A new mechanical RMSW processing plant (20 t/h) and an experimental RDF pyrolysis plant (200 kg/h) had been built (Faitli et al. 2020) and now extensive research is being carried out to solve the local utilization of the bio-fraction and the RDF. This is the reason why this fundamental drying research was necessary. Dryer classification and the selection of the best solid waste drying techniques vary significantly due to the vast range of waste to be dried and the inherent challenges of dealing with non-standardized systems. In general, biomass dryers may be categorized according to their heat transmission technique and the physical qualities of wet particles.
The EU's circular economy concept necessitates the increasing of the recycling ratioof municipal solid wastes. There are many existing mechanical – biological processing plantsin Hungary for the preparation of residual municipal solid wastes (RMSW). The two most importantproducts of these plants are the so called bio-fraction and the RDF (refuse derived fuel).Currently there are problems with both of these material streams in Hungary, namely most ofthe bio-fraction is still landfilled and the local thermal utilisation of the RDF is not solved yet. Thehigh moisture content of the produced bio-fraction and RDF causes difficulties for the downstreamoperations; therefore drying of these materials has a recent engineering interest to improve.Authors have carried out a systematic drying experimental series where the effect of thematerial, material composition, mass (volume or surface) of material and particle size distributionon drying intensity were studied in a 1 m3 oven. The initial slope of the relative moisture lossas function of time was determined. Process engineering design methods of convective hot air drying can be further developed taking into account the research results.