Process Control of Heavy Media Systems for Coal Preparation Plants

The concurrent demand for both lower sulfur coal and lower priced coal has resulted in an increased interest in control of unit operations within the coal preparation plant. While equipment control is widely used, process control of liquid/solid mixtures is seldom used and is fraught with problems. The control of medium specific gravity in a heavy-media cyclone-separation process exemplifies many of the issues which must be addressed. These include sensor and sensing problems, control scheme selection, and process modeling constraints. This paper examines these issues, and describes a pilot circuit which was constructed to facilitate a better understanding of the problems.