Pelletization of Refuse-Derived Fuel Fluff to Produce High Quality Feedstock

Abstract

Municipal solid waste (MSW) may be a suitable feedstock for thermochemical conversion. Current technologies process the MSW into refuse-derived fuel (RDF) fluff before conversion. Bench- and pilot-scale densification trials were conducted to determine the parameters required to produce a high quality feedstock from the MSW-RDF material in pellet form. The RDF was densified, as well as the biodegradable (paper and wood) fraction of the RDF stream to compare quality of pellets for the two material compositions. A single pelleting trial was conducted to examine the compaction parameters that would produce high quality pellets: sample material, grind size, moisture content, temperature, and pelleting pressure. It was determined that quality pellets, for both materials, were formed at a grind size of 6.35 mm at 16% moisture under pelleting conditions of 90 °C and 4000 N applied load. Pilot-scale pelleting was then completed to emulate industrial pelleting process utilizing the parameters from the single pelleting trials that were deemed to produce quality pellets. All of the samples produced durable pellets (88–94%), with the ash content around 20%. A techno-economic feasibility study determined that 6.35 mm diameter pellets could be produced for an average cost of $38/Mg, although the aggressive process of the size reduction required indicates that it may not be a technically feasible option.