Combustion characteristics of refuse derived fuels in circulating fluidised bed combustor

Fluidised bed combustion (FBC) is a technology which can use waste materials and low quality fuels along with coal. Mixed with wastes, coal can burn more efficiently. The present study aimed at the co-combustion of refuse derived fuels (RDF) with coal in a bench scale circulating fluidised bed combustor (CFBC). Tests were carried out at different ratios of RDF/coal at temperatures from 830 to 960°C. Compared with coal alone, RDF–coal mixtures gave a more uniform temperature distribution in the combustor and the emissions were lower when burning. Improved efficiency and stability of co-combustion were attributed to the higher volatile matter content in RDF. However, the advantages could be lessened if a too high secondary air ratio was used. NOx and SO2 emissions were due to the presence of S (mainly in the coal) and fuel N (more than S) in both fuels. The SO2 concentration decreased with increasing RDF rich in Ca in the fuel. It was shown that CFBC units could burn RDF efficiently and cleanly.