Thesis for the Degree of Licentiate of Technology


Year 1996
Mikko Ruonala

The Use of Electrochemical Mixed Potential Measurements for the Process Control and Expert System Development at Hitura Concentrator

In flotation processes many parameters can change occasionally and affect process control. These effects usually derive from the differences in chemical and physical properties of different ore types. At concentrators the type of ore in the process is usually unknown. When the mineralogy of the feed in the process is changed it is normally impossible to have the correct set points for the different basic controllers, because the process situation is unknown and normally there is not enough time to find optimal set point values for each controller. In such a situation economic results cannot reach the maximum value.

The aim of the study at the Hitura concentrator was to design an expert system with which it is possible to find the ideal set points for basic controllers for each type of ore.

Different ore types at the concentrator feed were detectetd using cluster analysis as a mathematical classification method. The variables in the calculation were measured directly from the process on-line. Results of the classidication analysis were compared with the co-ordinates of different delfs in the mine. A good correlaton was obseved. Electrochemical potential measurements improve the accuracy of mathemeatical classification analysis because electrochemical potential measurements are a tool to detect the mineral surface chemistry directly from the pulp.

In this work it is also shown how to improve the economic reslults of the process using potential measurements in process control. The amount of sulphuric acid was controlled based on the potential value of the synthetic nickelsulphide electrode.

As a result of work an expert systems based on ore type classification should be progammed at the Hitura concentrator. With such an expert system it is possible to find better set point values for basic controllers for each type of ore.

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