Circulating fluidized bed combustion of pitches derived from heavy oil upgrading

Combustion trials were conducted with two pitch materials in the University of British Columbia pilot scale (152 mm × 152 mm × 7.3 m) circulating fluidized bed combustion unit. The pitches, which were bottom end by-products of heavy oil upgrading processes containing high concentrations of sulphur, heavy metals and asphaltenes, were fed to the combustor in liquid form and atomized in the combustion chamber. Limestone was fed also to capture sulphur in situ. The combustion efficiency was always above 99%. NO_x emissions increased as the Ca:S ratio increased. The heavy metal elements present in the pitch were found to remain essentially in the solid residue.