EXTENDED PARTICLE-SIZE CONTROL OF AN INDUSTRIAL RUN-OF-MINE MILLING CIRCUIT

This paper describes the application of methods to extend product particle-size control on an industrial run-of-mine (ROM) milling circuit, controlled by a multivariable controller (MVC). The objective of these methods is to maximize the range over which the MVC can control particle size to a setpoint. Results from long-term tests indicate the mill inlet-water flow can be used as a 'steady-state' control action to increase the range over which the particle size can be controlled. A cyclone underflow-angle meter is used to increase the 'practical' range of feed flow to the cyclone, which in turn further increases the range over which the particle size can be controlled. The extensions in particle-size control are illustrated by means of a milling circuit 'operating window' in the particle-size/cyclone feed-density plane.