Mintek in control at SA's largest ferrochrome furnaces

SCADA/HMI

January 2008 SCADA/HMI

The Mintek FurnStar Minstral control system for submerged-arc furnaces is being used to optimise the smelting process on many of South Africa's ferrochromium furnaces. Recent installations include the new No. 4 furnace at Hernic Ferrochrome, near Brits in the Northwestern Province.

Tapping molten ferrochromium from the No. 4 furnace at Hernic Ferrochrome

The furnace, a closed unit that employs Outokumpu technology, is the largest ferrochromium furnace in the southern hemisphere, with a power rating of 78 Megavolt-Amperes (MVA).

"All four of the furnaces at Hernic are under Minstral control," said Paul Brereton Stiles, manager of the Measurement and Control (MaC) Division at Mintek. "The first controller was installed on the 37 MVA No. 1 furnace in 1996, and subsequent installations followed on the second (37 MVA) and third (54 MVA) furnaces, with the fourth at the beginning of 2006."

Hernic, whose major shareholders are Mitsubishi Corporation and the Industrial Development Corporation (IDC), is the world's fourth-largest ferrochromium producer, with an annual capacity of 420 000 tons. "After 10 years' experience we had no doubt in trusting Minstral for controlling our newest and biggest furnace", said Hannes Visser, production manager at Hernic.

"With large transformers and restrictions on excessive electrode movement, the ability to carry out effective differential tapping is a major advantage of the Minstral system. For a furnace of this size under balanced load conditions, differentially tapping the transformers can increase the power input by up to 1,5 MW and under unbalanced conditions by more than 5 MW (10%), compared with conventional balanced tap-position control," explained Stiles.

The system optimises operation of submerged-arc furnaces by means of a patented resistance algorithm. Benefits include:

* Improved power input (MWh).

* Lower specific energy consumption (MWh/t).

* Improved power factor.

* Reduced electrode consumption and breakage.

* Increased recovery.

"The system uses measurements from the primary side of the transformers, which are inherently more accurate and avoid the need for electrode-to-earth voltage measurements that are problematic and inaccurate," concluded Stiles.

The FurnStar Minstral advanced process control (APC) system is one of a family of APC systems developed to enhance the operation of metallurgical operations.

Mintek currently supports more than a hundred APC installations worldwide, the largest concentration of which is on the African continent. Specific solutions have been developed to address applications in milling, flotation, furnaces and leaching.

Mintek has installed APC systems in 15 countries and has an overseas office in Australia.

For more information contact Dr Hans Alink, Mintek, +27 (0)11 709 4265, [email protected], www.mintek.co.za

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Mintek in control at SA's largest ferrochrome furnaces

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