Removing mercury from combustion flue gas by injecting coolant and sorbent into a convective pass

摘要

A coal-fired combustion plant includes a furnace 12 producing flue gases 46 containing carbon and elemental mercury; a convective pass 50 channelling the flue gases from the furnace; a coolant injector 70 reducing temperature of the gases in the convective pass; and a sorbent injector 60 injecting sorbent into the convective pass for oxidation of mercury. The sorbent can be activated carbon. Extra coal 38 introduced to a reburn area 22 can also create a high carbon content fly ash in the gases, so that sorbent may not be required. The coolant may be atomised water or ambient air. Following sorbent and coolant injection fly ash and sorbent are collected in a particulate control device (PCD) 14, such as an electrostatic precipitator (ESP) or baghouse. The coal may be bituminous, Powder River Basin or lignite. Heat exchangers 48 heated by the furnace may include fuel cells.