Planning for the Utility MACT

By Mike Durham, ADA Environmental Solutions

On March 16, Environmental Protection Agency (EPA) proposed Mercury and Air Toxics Standards (“Air Toxics Rule”) for coal-fueled electric power generating plants. The rule was based upon the Maximum Achievable Control Technology (MACT) provisions of the Clean Air Act Amendments. The MACT process involves establishing emissions limitations on 187 listed hazardous air pollutants (HAP) based upon the average emissions of best performing 12 percent of plants. The rule is scheduled to be finalized by November 2011. Power plants will then have 36 months to specify and install control equipment to meet a compliance deadline of November 2014.

Planning for the upcoming MACT in combination with other regulations such as the Clean Air Transport Rule (CATR) will require significant effort to minimize risks and costs. ADA Environmental Solutions (ADA) is assisting plant owners to analyze existing emissions and develop potential compliance scenarios. The most significant aspect of these evaluations is determining which plants may require the addition of large capital equipment such as scrubbers and baghouses and which plants can achieve compliance with low-capital cost technology such as activated carbon injection (ACI) for mercury and dry sorbent injection (DSI) for SO₂, acid gases, and condensable particulate matter. This is determined by an analysis of the capabilities of the existing equipment at each plant and the new emissions standards. Now that the proposed rule is released, operators can narrow the potential compliance options and refine their decision deadlines. The incremental cost per kW of retrofitting emission control equipment is inversely proportional to the size of the plant. An additional consideration for small units, especially older, less efficient plants, is the capital breakeven point between retrofitting and replacing the power with other options such as new gas combined cycle plants. Therefore, for many older plants and/or smaller power plants, an approach that avoids large capital expenditures is often preferred and could lead to a reduced number of forced retirements.

With tight compliance deadlines, decisions for all levels of capital projects must be made early to provide sufficient time for procurement, construction, and startup of the new equipment. Due to competition for resources during periods prior to regulatory implementation, plants should start the evaluation of options as soon as possible. Some plants began initial planning efforts before the proposed rule was announced to make sure there was sufficient time for thoughtful planning and implementation. For this multi-pollutant regulation, retrofits must be designed to meet compliance levels for several pollutants, leading to more than one configuration change; such as the addition of both a scrubber and a fabric filter. Retrofitting a unit with a scrubber will require higher capital investments and a longer timeline than other retrofits such as a fabric filter for particulate control, dry sorbent injection for acid gas, and condensable particulate control, or an activated carbon injection system for mercury control.

EPA proposed emission limits on three subcategories of pollutants and a work-based standard on a fourth:

• Mercury – limits should prevent 91 percent of mercury in coal from being released to the air
• Acid gases, using HCl as a surrogate for units without scrubbers
• Non-mercury metals such as arsenic and chromium
• Organic air toxics (including dioxins) will be addressed with a work practice standard.