|
Mercury Emissions Control Technologies |
|
The AEO2006 reference case assumes that States will comply with the requirements of the EPA’s new CAMR regulation. CAMR is a two-phase program, with a Phase I cap of 38 tons of mercury emitted from all U.S. power plants in 2010 and a Phase II cap of 15 tons in 2018. Mercury emissions in the electricity generation sector in 2003 are estimated at around 50 tons. Generators have a variety of options to meet the mercury limits, such as: switching to coal with a lower mercury content, relying on flue gas desulfurization or selective catalytic reduction equipment to reduce mercury emissions, or installing conventional activated carbon injection (ACI) technology. The reference case assumes that conventional ACI technology will be available as an option for mercury control. Conventional ACI has been shown to be effective in removing mercury from bituminous coals but has not performed as well on subbituminous or lignite coals. On the other hand, brominated ACI—a relatively new technology—has shown promise in its ability to control mercury emissions from subbituminous and lignite coals. Therefore, an alternative mercury control technology case was developed to analyze the potential impacts of brominated ACI technology. Preliminary tests sponsored by DOE indicate that brominated ACI can achieve high efficiencies in removing mercury (approximately 90 percent or higher for subbituminous coal and lignite, compared with about 60 percent for conventional ACI) at relatively low carbon injection rates [77]. For the sensitivity case, the mercury removal efficiency equations were revised to reflect the latest brominated ACI data available from DOE-sponsored tests [78]. Brominated ACI is about 33 percent more expensive than conventional ACI, and this change was also incorporated in the alternative case. Other than the change in mercury removal efficiency and the higher cost of brominated ACI, the mercury emissions case uses the reference case assumptions. Figure 20 compares mercury emissions in the reference and mercury control technology cases. Both cases show substantial reductions in mercury emissions, with the greatest reductions occurring around 2010 to 2012, when the CAMR Phase I cap has to be met. The availability of brominated ACI results in slightly greater reductions in mercury emissions in the 2010-2012 period, as generators are able to utilize the technology to overcomply and bank allowances for later use. In the reference case, mercury emissions from U.S. power plants total 37 tons in 2012, compared with 31 tons in the mercury control technology case. In 2030, emissions are approximately the same in the two cases, at 15.3 and 15.6 tons. Figure 21 shows mercury allowance prices in the reference and mercury control technology cases. When brominated ACI is assumed to be available, it has a substantial impact on mercury allowance prices in the early years of the projection. In 2010, mercury allowance prices are reduced from $23,400 per pound in the reference case to $8,700 per pound in the mercury control technology case, a reduction of 63 percent. The mercury control technology case incorporates improved ACI performance data for a limited number of plant configurations (those for which data were available from the DOE-sponsored tests), because not all plant configurations had been tested with brominated ACI technology at the time [79]. In the alternative case, the difference in allowance prices between the reference and mercury control technology cases narrows over the forecast horizon. Mercury allowance prices have a substantial impact on the market for pollution control equipment. The mercury control technology case shows that, as expected, increased use of brominated ACI would greatly influence the ACI equipment market. Figure 22 compares the amounts of coal-fired capacity expected to be retrofitted with ACI systems in the reference and mercury control technology cases. The impact is significant in the alternative case throughout the projection period. In the reference case, about 125 gigawatts of coal-fired capacity is retrofitted with ACI by 2030. In the mercury control technology case, as a result of more effective mercury removal with brominated ACI, only about 88 gigawatts of coal-fired capacity is retrofitted with ACI by 2030. The mercury control technology case assumes that brominated ACI will be commercially available before 2010 (CAMR Phase I), and that the cost and performance levels seen in the initial DOE-sponsored tests will be replicable in the systems being offered commercially. Under these assumptions, comparison of the reference and mercury control technology cases highlights several important points. The mercury emissions levels are similar in the two cases, but allowance prices are much lower in the alternative case, through 2020. Corresponding to the difference in allowance prices, significantly less coal-fired capacity is retrofitted with ACI in the mercury control technology case than in the reference case. Overall, electricity generators are able to comply with the CAMR requirements more easily when they have access to the brominated ACI technology, while achieving the same reductions in mercury emissions as in the reference case and complying with the CAMR caps.
[77] Approximately 2 to 3 pounds of brominated ACI per million metric actual cubic feet of flue gas. [78] A.P. Jones, J.W. Hoffman, T.J. Feeley, III, and J.T. Murphy, DOE/NETL Mercury Control Technology Cost Estimate Report – 2005 Update (National Energy Technology Laboratory, June 2005). [79] Configuration refers to the type of air pollution control device at a plant, such as cold-side electrostatic precipitator, fabric filter, or flue gas desulfurization unit.
Contact: Robert Smith |
