Controlling the percent solids of concentration plant No.1 hydrocyclones overflow by a soft sensor at the Sarcheshmeh Copper Complex

The primary grinding of the concentration plant No.1 at the Sarcheshmeh copper complex includes eight ball mills working in a closed circuit with hydrocyclones. Due to the importance of the density of hydrocyclones in the classification process, the overflow density control loop was included in the initial plant design. Because of high cost, additional maintenance efforts, safety issues and constraints of nuclear density meters, this control loop never became operational. In this research, the percent solids was determined based on the mass balance equations in a format of a soft sensor. These sensors are computer programs that are used as an inexpensive alternative to hardware sensors and their use has increased in the material processing industry in the recent years. After transferring of the measured data to the control room, a program based on mass balances of solid and water the calculations for all 8 ball mills was prepared. To start the overflow density control loop, a control valve was installed on the inlet of the hydrocyclones feed tank. With the installation of hardware and the use of a soft sensor, the hydrocyclones overflow density control loop made operational for one of the ball mills. The monitoring of the circuit showed that the percent solids fluctuation of hydrocyclones overflow decreased from the range of 30.4 ± 4.5 when the percentage of solids was not displayed to a range of 28 ± 0.5 when using the percent solids control loop was operational. Furthermore, the measurement of the size distribution indicated that the percent of material finer than 75 microns of the overflow increased from 63.5% to 67% on account of installation of the control loop.