U.S. Coal-Fired Power Plants Weigh Options for Compliance with Mercury and Air Toxic Standards

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Researched by Industrial Info Resources (Sugar Land, Texas)--The Mercury and Air Toxic Standards (MATS), enforced by the U.S. Environmental Protection Agency (EPA), will have to be addressed in some way by the majority of U.S. coal-fired power plants. MATS limits toxic air pollutants, such as mercury, arsenic, acid gases and toxic metals, and requires power plant owners to install some combination of emission controls equipment to address these pollutants. Plants have to be in compliance with the standards by 2015.

U.S. power plants are addressing MATS in various ways, whether by planning equipment retrofit projects or by monitoring the existing mercury emissions so as not to exceed the current or future limits. The closing of a plant is a last resort, if it is not economically possible to carry out the retrofits.

Upgrade requirements for mercury controls can include changing the type of coal or coal blend in order to lower mercury at the back end of the boiler flue gas, or addressing the mercury level by either wet or dry flue gas treatment to achieve a level of mercury that complies with the MATS.

MATS compliance requires the average coal-fired plant to attain an outlet mercury concentration of no more than 1.2 pounds per ton/British thermal unit (lb/TBtu), and 4 lb/TBtu for lignite. This corresponds to a collection efficiency of about 90%, or 80% for lignite.

The upgrade options will depend on the type of coal being used, what type of existing pollution controls are already installed (flue gas desulfurization, selective catalytic reduction, electrostatic precipitator, fabric filter baghouse, etc.), and what is needed to lower the level of mercury in the flue gases. Options for retrofits include:

• Activated Carbon Injection System (ACIS), in which powdered activated carbon is injected into the flue gas and collected in a particulate collection device, such as a fabric filter (FF) or electrostatic precipitator (ESP).
• Halogen Injection, in which a halogen gas, such as chlorine or bromine, is injected into the flue gas to promote oxidation. The oxidized mercury is collected in a wet scrubber or other particulate collection equipment.
• Dry Sorbent Injection (DSI), in which a sorbent, such as hydrated lime, trona or sodium bicarbonate, is injected into the flue gas to absorb scavenging agents that complete for absorption sites on activated carbon, which would reduce ACIS performance.

Currently, Industrial Info is tracking more than $1.5 billion in mercury emission controls projects scheduled to start construction within the next three years at coal-fired power plants in North America.

Industrial Info Resources (IIR), with global headquarters in Sugar Land, Texas, and eight offices outside of North America, is the leading provider of global market intelligence specializing in the industrial process, heavy manufacturing and energy markets. Industrial Info's quality-assurance philosophy, the Living Forward Reporting Principle™, provides up-to-the-minute intelligence on what's happening now, while constantly keeping track of future opportunities.