Thesis for the Degree of Master of Science


Year 2005
Teemu Mattila

Mass balancing in hydrometallurgical leaching process

This work is related to the Outokumpu HydroCopperTM Process, based on leaching of copper concentrate in cupric chloride media. The aim of he work was to develop a tool that facilitates the calculation of reconciled mass balances in different leaching stages of the process for varying time periods. Using reconciled mass flows that comply to the law of mass conservation it is possible to get information from the process that helps to follow and understand it. The tool was developed and tested using historical data, obtained from the demonstration run carried out in autumn 2004.

The mass balances were calculated using flow measurements and laboratory analyses. Only the main components, copper, iron and sulphur, ere considered. Because there are always random errors and gross (systematic) errors included in the measurements mass balabces don’t comply with the law of mass conservation. The work was mainly done using Excel. Matlab was used in the data reconciliation part. The tool was realized keeping it feasible to modify it later easily to function also as on on-line process monitoring application.

Using reconciled mass balances the tool gives valuable information about dissolution of the main components, solid rates of thickener underflows and rates of reaction. Also gross errors of measurements were estimated. The results revealed some treatable matters in the process. Improvements that should be done during the next demonstration run include experimental determination of the solution and solid densities in each leaching stage, addition of some flow measurements and analyses, and calibration of instruments used to define the density in thickener underflows.

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