An Advanced Control System for Fine Coal Floatation

A model-based flotation control scheme is being implemented to achieve optimal performance in the handling and treatment of fine coal. The control scheme monitors flotation performance through on-line analysis of ash content. Then, based on the economic and metallurgical performance of the circuit, variables such as collector dosage, frother dosage, and pulp level are adjusted using model-based control algorithms to compensate for feed variations and other process disturbances. Recent developments in sensor technology are being applied for on-line determination of slurry ash content. During the eighth quarter of this project, the analysis of data collected during Task 2 (Sampling and Data Analysis) was completed, and significant progress was made on Task 3 (Model Building and Computer Simulation). Previously, a plant sampling campaign had been conducted at Pittston�s Moss No. 3 preparation plant to provide data for the development of a mathematical process model and a model-based control system. During this campaign, a one-half factorial design experiment, blocked into low and high feed rates, was conducted to investigate the effects of collector, frother, and pulp level on model parameters. In addition, samples were collected during the transient period following each change in the manipulated variables to provide data for confirmation of the dynamic process simulator. A residence time distribution (RTD) test was also conducted to estimate the mean residence time. This is a critical piece of information since no feed flowrate measurement is available, and the mean residence time can be used to estimate the feed flowrate. Feed samples were taken at timed intervals and floated in a laboratory flotation cell to investigate the magnitude of feed property disturbances and their duration