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MEI Online: Pyrometallurgy: Latest News: October 10th 2003

:: Mintek Installs Minstral Furnace Controller at CCM, Brazil  

Mintek recently commissioned a second Minstral(tm) furnace-control system at Camargo Corra Metais' Tucurui silicon metal plant in Para State, Brazil.This installation brings the number of Minstral systems at silicon metal producers around the world to six, four of which are in Brazil.

Silicon furnaces are difficult to control because small changes in the metallurgical balance can lead to the build up of silicon carbide or slag over time. Minstral's unique resistance-based control algorithm helps to decouple the electrical characteristics of the smelting process from the metallurgical conditions. This results in a more consistent picture of the metallurgical conditions in the furnace and allows better-informed decisions to be made on the amount of carbonaceous reductant to be added.

Silicon furnaces also typically use pre-baked electrodes. These are expensive, and electrode consumption is an important issue. With resistance-based control, there is less electrode movement, and consequently reduced electrode consumption as well as a lower risk of electrode breaks.The Minstral electrode and tapchanger control system has been used successfully on submerged-arc furnaces in the ferro-alloys industry for more than a decade. The system uses resistance-based algorithm to balance the electrode penetration and optimise the power supplied to the furnace, thus decreasing specific energy consumption and improving productivity. Stable operation then provides the basis for further optimisation, for example by making improvements to the metallurgical recipe. The revised power-control algorithm on the latest OPC (OLE for Process Control) Minstrals can manipulate the transformer tappings for each phase of the circuit independently, enabling the furnace to work in a smaller power band and improving the electrical balance of the circuit.

There are now more than 80 Minstral systems installed worldwide. Over half of these are in South Africa, where the major application is on ferrochromium furnaces. Ferrochrome furnaces are notoriously difficult to control due to their inherent instability, particularly when large proportions of fine chromite constitute the feed material. Recent installations include three controllers at Samancor's Tubatse Ferrochrome, two on the 60 MVA furnaces at SA Chrome & Alloys' new greenfield smelter near Rustenburg, and the latest on a 75 MVA furnace at SA Calcium Carbide (previously Sentrachem).

Further Minstrals are in operation in India, Brazil, Zimbabwe, Australia, France, and Canada, on furnaces producing a variety of alloys, including ferrochromium, ferrosilicon, silicon metal, ferromanganese and ferrosilicomanganese, calcium carbide and calcium silicide.




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