Preliminary Estimates of Performance and Cost of Mercury Emission Control Technology Applications on Electric Utility Boilers: An Update

The Environmental Protection Agency has recently proposed a reduction in mercury emissions from coal-fired power plants. There are two broad approaches under development to controlling mercury emissions from coal-fired electric utility boilers: (1) powdered activated carbon (PAC) injection, and (2) multipollutant control, in which Hg capture is enhanced in existing and new sulfur dioxide (SO2), nitrogen oxides (NOX), and particulate matter (PM) control devices. To help inform the recent EPA rulemaking proposal, estimates of performance levels and related costs associated with the above mercury control approaches were developed. This work presents these estimates. Estimates of cost for PAC injection range from 0.03-3.096 mills/kWh. In general, the higher costs are associated with the plants using spray dryers and electrostatic precipitators (ESPs) or plants using hot-side ESPs, which represent a minority of power plants. Excluding these plants, cost estimates range between 0.03 and 1.903 mills/kWh. At the low end of the cost ranges, 0.03 mills/kWh, it is assumed that no additional control technologies are needed, but mercury monitoring will be necessary. In these cases, high mercury removal may be the result of the type of NOx and SO2 control measures currently employed, such as combinations of selective catalytic reduction and wet flue gas desulfurization on bituminous coal fired boilers. Since mercury control approaches are under development at present, cost and performance estimates are preliminary and are expected to be refined as mercury control technologies are matured to commercial status. Factors that may affect the performance of these technologies include speciation of mercury in flue gas, the characteristics of the sorbent, and the type(s) of PM, NOx and SO2 controls employed. The effect of these factors may not be entirely accounted for in the data points that form the basis for this work. Ongoing research is expected to address these issues.