Method of mercury removal in a wet flue gas desulfurization system

A method for controlling an amount of mercury discharged to an environment in a flue gas generated by combustion of a fuel source, said method comprising:

• subjecting said flue gas to a wet scrubbing operation to decrease an amount of sulfur oxides present in said flue gas, said wet scrubbing operation comprising contacting said flue gas with an aqueous alkaline slurry to absorb said sulfur oxides from said flue gas, wherein at least a portion of gaseous ionic mercury species present in said flue gas are dissolved in said aqueous alkaline slurry and thereby removed from the flue gas;
• measuring an amount of gaseous elemental mercury emitted from a scrubber tower to provide a signal indicative of the measured amount of gaseous elemental mercury;
• and
• adjusting a redox potential of the aqueous alkaline slurry used in the wet scrubbing operation using the signal, thereby controlling the amount of ionic mercury present in flue gas that can be reduced to elemental mercury by the slurry.

A system for controlling an amount of mercury discharged to an environment in a flue gas generated by combustion of a fuel source, said system comprising:

• a scrubbing tower in which the flue gas is subjected to an aqueous alkaline slurry to decrease an amount of sulfur oxides present in said flue gas, wherein at least a portion of gaseous ionic mercury species present in said flue gas are dissolved in the aqueous alkaline slurry and thereby removed from the flue gas, the scrubbing tower including a collecting tank to collect the aqueous alkaline slurry used in the wet scrubbing operation;
• a measuring device coupled to the collecting tank and configured to provide a signal indicative of a redox potential of the aqueous alkaline slurry used in the wet scrubbing operation;
• and
• a means for controlling the amount of ionic mercury present in the flue gas that can be reduced to elemental mercury by the slurry, whereby the redox potential of the aqueous alkaline slurry used in the wet scrubbing operation is adjusted in response to the signal.