Simulation of dewatering devices for predicting the moisture content of coals

The coal specifications for coal-burning power plants usually contain a requirement for a maximum moisture content in order to prevent coal handling problems and to minimize evaporative losses in the boiler. As most coal cleaning processes are water-based, dewatering and sometimes thermal drying are required to meet moisture specifications. Screens are often used for dewatering and are followed often by centrifuges or filters to reduce the moisture content further. Algorithms for predicting the moisture content of coal dewatered by screens, centrifuges, and filters were developed for a project that developed a flowsheet simulator running under ASPEN PLUS^TM sponsored by the U.S. Department of Energy and the Electric Power Research Institute. These algorithms include size separation in the devices to account for losses in effluents, size reduction where appropriate, and calculation of moisture content for the products based on the size and specific gravity distribution. This paper discusses these algorithms and gives comparison of the predicted moisture contents versus published moisture contents where available.