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Capturing Mercury Emissions

August 11, 2014

Coal-fired power plants emit 772 million pounds of toxic chemicals into the atmosphere every year—more than 2.5 lb for every person in the United States. As a result, the U.S. Environmental Protection Agency (EPA) and other organizations around the globe have tightened regulations on emissions of hazardous chemicals, such as mercury.
    Mercury is a naturally occurring element that is found in the environment and exists in several forms, including elemental mercury and mercury compounds. Mercury is emitted into the air from a variety of sources as a neurotoxin, a chemical that is destructive to the nervous system.
    Mercury cycles in the environment as a result of human activities, and the environmental cycle of mercury presents threats both to human health and the earth. Most mercury in the atmosphere is elemental mercury vapor, which can circulate in the air for up to a year and thus can be widely dispersed and transported thousands of miles from the source of the emissions. Once released, mercury eventually settles into bodies of water or into the earth, where it can be washed into lakes, rivers and streams. After it is deposited, mercury can be converted into methylmercury, a highly toxic form of the element that builds up in the gills of fish. The larger the fish, the more mercury it absorbs, leading states to release advisories on the consumption of fish and seafood.
    Mercury can be emitted in a variety of ways, such as burning hazardous wastes, breaking products that contain mercury, and the improper treatment of disposal of mercury-contaminated wastes. Coal-burning power plants are the largest human-caused source of mercury emissions in the U.S., accounting for more than 50 percent of the mercury released into the air.
    Exposure to mercury can have devastating effects on the human nervous system and damage the brain, heart, kidneys, lungs, and immune system. To combat the threat of mercury exposure, the U.S. Environmental Protection Agency (EPA) has established and tightened regulations on mercury emissions over the past 20 years.
    The Mercury Export Ban Act of 2008 (MEBA) prohibits the export of elemental mercury from the U.S. This prohibition is designed to limit the availability of elemental mercury in the global market. The European Union established a similar ban on the exportation of mercury and mercury compounds in 2007.
    The Clean Air Mercury Rule, which the EPA issued in 2005, created “performance standards and established permanent, declining caps on mercury emissions” (U.S. EPA, 2005). This regulation marked the first time the EPA has regulated mercury emissions from coal-fired power plants. The goal of the Clean Air Mercury Rule is to reduce utility emissions of mercury from 48 to 15 tn/year, a 70 percent reduction.
    In May 2011, the EPA proposed the National Emission Standard for Hazardous Air Pollutants (NESHAP). This regulation was created to reduce toxic air pollutant emissions, such as mercury, from coal-fired and oil-fired electricity generating utilities. In the past 15 years, many states have also established regulations limiting mercury emissions from coal-fired power plants. Between 1999 and 2009, emissions decreased by almost 27 percent.
    Another contributor to mercury emissions is the Portland cement industry. Portland cement manufacturing is an energy-intensive process that grinds and heats a mixture of raw materials—such as limestone, clay, sand and iron ore—in a rotary kiln. The product of this process is known as “clinker” and is used to make cement, which is then mixed with aggregate and water to create concrete.
    A variety of pollutants, including mercury, are released from the burning of fuels and heating of the raw materials used to make cement. The EPA aims to reduce the harmful air pollution from the Portland cement industry through regulations that depend on current technology to limit the emissions of toxic air pollutants such as mercury. The newest mercury regulations from the EPA are designed to limit emissions from cement kilns to 55 lb/million tn of clinker.
    Fortunately, mercury can be removed from contaminated substrates through the use of thermal desorption. In this process, intense heat is applied to the material to volatize the mercury without damaging the material itself.
    Through its Vulcan Systems, Worldwide Recycling Equipment Sales LLC (WWR) in Moberly, MO, aids those in the industry in the removal of mercury and mercury products from contaminated materials. WWR has developed technology that is able to remove mercury from substrates on a continuous basis. This custom-designed and manufactured thermal equipment includes vapor recovery for the collection of vaporized mercury and has been demonstrated on both a pilot plant and a commercial basis. WWR is capable of designing systems to remove mercury from any industrial powders, such as activated carbon, fluorescent lamp powder, sludges, and soil contaminated with mercury and mercury compounds. Vulcan Systems custom designs and manufactures drying, calcining, and thermal desorption equipment. Each system is custom-built to suit the client’s specific needs. Services include setup, commissioning, training, and maintenance support services over the lifetime of your project. For more information, visit www.getavulcan.com or call 660-263-7575.