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January 2007

EPA updates mercury and hydrocarbon emission limits for newer portland cement production

Lehigh cement kiln at Union Bridge, Maryland.

The United States Environmental Protection Agency (EPA) announced new emission limits for cement kilns that will help cut annual emissions of mercury and hydrocarbons. These limits will help protect public health from emissions from portland cement kilns, through amendments to an air toxics standard issued on December 8, 2006.

The amendments set mercury and hydrocarbon emission limits for all cement kilns built after December 2, 2005, and will reduce annual mercury emissions by about one ton and annual hydrocarbon emissions by about 1,100 tons. Kilns built before that time must meet work practice requirements, such as removing cement kiln dust when it no longer can be recycled and operating kilns properly to ensure complete combustion.

In addition, the amendments prohibit all cement kilns from using fly ash from utility boilers equipped with certain types of mercury emission controls, unless the cement kiln can demonstrate that use of that fly ash will not increase its mercury emissions.

In a separate action, EPA will reconsider the limits for new kilns and take immediate steps to obtain additional information about mercury reductions achieved at kilns equipped with wet scrubbers. EPA is taking this step to consider new information controls at cement kilns and will make this information available for review and comment.

Portland cement manufacturing is an energy-intensive process that produces cement by grinding and heating a mixture of materials such as limestone, clay, sand and fly ash in a rotary kiln. That product, called clinker, is cooled, ground and then mixed with a small amount of gypsum to produce cement.

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