Experience with the combustion of alternate fuels in a CFB pilot plant

A circulating fluidized bed pilot plant has been operated for several years in Williamsport, Pennsylvania, by Tampella Power Corporation to test the combustion characteristics of many different types of fuels. The fuels tested at the facility include: bituminous and anthracite coals; bituminous (gob) and anthracite (culm) waste; fluid and delayed petroleum coke; Colorado and Israel oil shales; tire derived fuel (TDF); refuse derived fuel (RDF); paper mill sludge and bark; and refinery process off-gas. Each of these fuels presented special fuel and ash handling problems that needed to be addressed before successful testing could be accomplished; these problems are more urgent on the pilot scale than in the commercial scale due to the corresponding reduction in equipment size. Each of these fuels also behaved differently in terms of combustion characteristics and gaseous emissions, as would be expected on the basis of their vastly different physical and chemical properties. This paper describes the major experiences obtained during the pilot plant testing of each of these alternative fuels, including summaries of the tested fuels and their measured emissions, limestone performance when applicable, and practical considerations.