Patent ID: 7427384

Claim:
A method of reducing sulfur dioxide emissions of a circulating fluidized bed boiler, comprising the steps of: (a) feeding a first stream comprising a sulfur-containing carbonaceous fuel to a furnace of the boiler; (b) feeding a second stream comprising calcium carbonate to the furnace at a rate relative to the first stream such that the molar ratio of calcium in the second stream to sulfur in the first stream (the Ca/S molar ratio) is at most about 1.0; (c) combusting the fuel so that the sulfur is oxidized to form sulfur dioxide and ashes are produced in the furnace; (d) calcining the calcium carbonate to form calcium oxide in the furnace and utilizing the calcium oxide to sulfate the sulfur dioxide to form calcium sulfate; (e) discharging flue gases and particles entrained in the flue gases from the furnace; (f) separating the particles from the flue gases using a hot loop separator, and returning the separated particles to the furnace; (g) discharging the ashes from the boiler; and (h) further reducing the sulfur content of the flue gases in a sulfur-reduction stage downstream of the furnace.