Triboelectrostatic Cleaning of Coal In-Line Between Pulverizers and Burners at Utilities

Pulverized coal combustors are the principal means for converting coal to electricity in the United States. Coals used in these combustors have to be beneficiated because of escalating specifications on fuel quality that help to increase boiler efficiency and decrease acid gas emmissions. Because coal is pulverized before its combustion in PC boilers, during which time substantial mineral liberation occurs, it may be beneficial to remove mineral matter from the combustibles by using dry beneficiation techniques after the pulverizers and within the burner pipes leading to the coal burners. One such technique is based on triboelectrostatics. It relies on establishing a differential charge on coal and mineral matter and then separating this charged mixture in an electrostatic field. This paper presents data obtained at a utility site that quantify the charge imparted on coal during pulverization and transport in a burner pipe, and compares these values to data obtained within a laboratory setting. The electrostatic separation of differentially charged coal and mineral matter is also presented and discussed using data obtained at a utility site and within an analytical laboratory separator system. Triboelectrostatic separation may present unique opportunities to coal beneficiation within commonly practiced utility operations.