Patent ID: 8088348

Claim:
An air pollution control system for a coal combustion boiler, the air pollution control system comprising: a NOx removing apparatus that removes nitrogen oxide contained in flue gas emitted from the coal combustion boiler; an air pre-heater that recovers heat in the gas after the nitrogen oxide is removed; a precipitator that reduces particulates from the gas after the heat is recovered; a liquid-gas contact type desulfurizer that removes sulfur oxide by way of a limestone-gypsum method and reduces mercury oxide in the gas after the particulates are reduced; and a stack that releases gas after SOx removal, wherein the system further comprises a solid-liquid separator suitable for extracting limestone-gypsum containing slurry from the desulfurizer to the exterior and performing a solid-liquid separation where water separated in the solid-liquid separator is removed and concentrated slurry is sent back to the bottom of the desulfurizer in order to keep a gypsum concentration in slurry equal to or higher than 10 percent in the desulfurizer.