RELATION BETWEEN COMBUSTION EFFICIENCY AND COAL RANK IN FLUIDIZED-BED COMBUSTORS

The relative combustion performance of a range of coals varying in rank from subbituminous to semi-anthracite has been investigated in a technical-scale bubbling fluidized bed combustor. Two coal-rank-dependent combustion efficiency relationships based on coal fixed carbon content and organic carbon content are identified. In the preferred relationship the single-pass combustion efficiency, eta(sp,d), is shown to vary linearly with the coal organic carbon content, C(oc), according to: eta(sp,d) = K(oc,d) - 1.30C(oc), where K(oc,d) is a constant related to the particular fluidized bed combustor design and coal feed size. Combustion efficiency data in fluidized beds from other sources is also shown to conform to this type of relationship.