Patent ID: 8703080

Claim:
An apparatus for removing mercury in exhaust gas, in which mercury in exhaust gas discharged from combustion equipment is removed, said apparatus comprising: (a) a denitrification apparatus located downstream from said combustion equipment, said denitrification apparatus having a denitrification catalyst adapted to convert metallic mercury in said exhaust gas to mercury chloride; (b) a scrubber including: (1) a cooling tower with an aqueous alkali absorbing solution and a first electrometer that measures the oxidation-reduction potential of the absorbing solution in said cooling tower (2) a desulfurization absorption tower with an aqueous alkali absorbing solution and a second electrometer that measures the oxidation-reduction potential of the absorbing solution in said desulfurization absorption tower, wherein said desulfurization absorption tower is separate from the cooling tower and located downstream from said cooling tower, and wherein said desulfurization absorption tower is adapted to remove the mercury chloride from the exhaust gas by contacting said exhaust gas with said absorbing solution, (3) a first introduction pipe that provides a first amount of blown air, said first introduction pipe bifurcates to feed a first portion of said first amount of blown air to said cooling tower and also feeds a second portion of said first amount of blown air to said desulfurization absorption tower, said first introduction pipe has a first valve located between the bifurcation section and the cooling tower, and said first introduction pipe has a second valve located between the bifurcation section and the desulfurization absorption tower, wherein the first valve is opened or closed in response to the first electrometer measurements and the second valve is opened or closed in response to the second electrometer measurements; (c) a mist eliminator located downstream from the desulfurization absorption tower, said mist eliminator includes a contact area where a cleaning solution contacts said exhaust gas; (d) a cleaning solution tank connected to recirculate cleaning solution with the mist eliminator, wherein said cleaning solution tank comprising cleaning solution and a third electrometer, wherein resulting liquid remaining after cleaning solution contacts exhaust gas in the mist eliminator is sent to the cleaning solution tank, said third electrometer continuously measures the oxidation-reduction potential of said cleaning solution; and, (e) a second introduction pipe that provides a second amount of blown air to said cleaning solution tank, said second introduction pipe includes a third valve, wherein the third valve is opened or closed in response to the third electrometer measurements.