Circulating fluidized bed repowering to reduce SOx and NOx emissions from industrial and utility boilers

摘要

Repowering industrial and utility boilers (60) with a circulating fluidized bed combustor (22) to reduce SOx and NOx emissions emanating from the boilers by:   combusting high sulfur-containing carbonaceous solid fuel in a circulating fluidized bed combustor (20) in admixture with limestone and air at about 1600°F;   combusting a carbonaceous fuel, such as coal, oil or gas in an industrial or utility boiler (60);   mixing the flue gases generated in the circulating fluidized bed combustor (20) from which particulates were removed with the exhaust gases produced in the industrial or utility boiler (60) so that about 70 % of the flue gases from the circulating fluidized bed combustor (20) is mixed with about 30 % of the exhaust gases from the industrial or utility boiler (60);   controlling the total heat generation by maintaining the circulating fluidized bed heat input to the boiler furnace from about 70 to 90 % and the heat input of the boiler furnace from about 30 to 10 %.;Saturated steam generated in heat exchangers (80, 82) located in the circulating fluidized bed combustor (20) and in the boiler furnace (60) are mixed and superheated in a primary and a secondary superheater (100) prior to being supplied to a steam turbine to generate electricity.