MAGNASAT is a bench top device, which determines the magnetic susceptibility of materials by measuring the changes that these materials cause to an alternating current magnetic field. The magnitude of these changes is dependent on the material’s magnetic and electrical properties, sample geometry and quantity of material presented for measurement.
The physical principle on which MAGNASAT is based relies on tried and tested technology; if a magnet is moved through a coil an electrical current is generated, conversely if an electrical current is passed through a coil a magnetic field is produced. In this way an absolute measurement of magnetic susceptibility is provided.
Ultra-Dynamics has supplied a MAGNASAT system to Xstrata Copper Limited, Mount Isa Mines copper smelter. Mount Isa Mines (MIM) is a major copper producer located in North West Queensland producing over 230,000 tonnes of anode copper per annum.
Copper smelter operation details
In the MIM copper smelter there are 3 main stages; the Isamelt furnace which produces matte copper of 58% to 62% copper content; 4 converters which produce blister copper of approximately 97% copper content; anode furnaces which produce anode quality copper at 99.7% copper content.
Converter operation is a batching process during which air is blown through the matte for a certain time following which further matte is added together with additional silica to act as a fluxing agent to remove magnetite created during the blowing (oxidation) cycle. Correct silica addition is important because if too little silica is added (under fluxing) insufficient magnetite is removed resulting in a viscous slag; if too much silica is added (over fluxing) then the excess silica also results in a viscous slag. Both conditions can result in significant losses.
The previous method of assessing the oxidation state of the matte was to use a magnet to determine the magnetite content. This method was subjective and hence inaccurate. A rapid method of determining the magnetite content was needed to improve converter operation. Laboratory analysis is too slow to be of use to the operations personnel. A field tool was required for use by the operators adjacent to the converters. A MAGNASAT system was purchased from Ultra-Dynamics and installed in the plant.
MAGNASAT sample preparation and operation
The requirement was to keep the sample preparation and analysis as simple as possible. The following sampling and analysis regime has been adopted; a sample of slag is obtained by dipping a cold bar into the slag stream as it is skimmed off. This is then cooled and crushed. A flail mill is used to provide acceptable sample sizing. A measuring cylinder is then filled to overflowing with a sample of the slag and the top leveled off. The fixed sample volume is then transferred to a sample bottle and the sample presented to the MAGNASAT system for analysis.
The MAGNASAT system has proved to be able to provide an accurate slag magnetite measurement in just a few minutes so that the correct flux addition can be made during operation of the converters.