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Boiler Slag

Photo of Boiler Slag
Courtesy of the American Coal Ash Association

Boiler slag is the molten bottom ash collected at the base of slag tap and cyclone type furnaces that is quenched with water. When the molten slag comes in contact with the quenching water, it fractures, crystallizes, and forms pellets. This boiler slag material is made up of hard, black, angular particles that have a smooth, glassy appearance.

Boiler slag is generally a black granular material. Boiler slag particles are uniform in size, hard, and durable with a resistance to surface wear. In addition, the permanent black color of this material is desirable for asphalt applications and aids in the melting of snow. Boiler slag is in high demand for beneficial use applications however, supplies are decreasing because of the removal from service of aging power plants that produce boiler slag.

Boiler slag applications include its use as a:

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