The Study of Combustion of Municipal Waste in a Fluidised Bed Combustor

The combustion behaviour of municipal solid waste was studied in a pilot fluidised bed combustor. The waste was pelletised prior to its use. Both co-firing with coal and combustion of waste alone were under taken. The combustion studies were carried out on the pilot installation of INETI. The fluidised bed combustor is square in cross section with each side being 300 mm long. Its height is 5000 mm. There is a second air supply to the freeboard at different heights to deal with high volatile fuels. There was a continuous monitoring of the temperatures in the bed, as well as the composition of the combustion gases. The combustion gases leaving the reactor were let go through the recycling cyclone first to capture most of particulates elutriated out of the combustor. There was a second cyclone which was employed with the aim of increasing the overall efficiency of collecting solid particles. The gaseous pollutants leaving the stack were sampled under iso-kinetic conditions for particulate matter, chlorine compounds and heavy metals. The ash streams were characterised for heavy metals. The results obtained were compared with national legislation. The results obtained suggest that i) the combustion efficiency was very high, ii) there was an enrichment of ashes with heavy metals in the cyclones compared to the bed material, iii) in general, the gaseous pollutants were below the permited limits, and iv) for the compliance with the new European Directive for stricter emission limits adequate control devices, like bag filters, should be integrated with RDF combustion.