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ABB Boosts Energy Efficiency At Aluminum Smelters

Posted on August 13, 2009

The high power converters (also known as rectiformers) are the biggest and most powerful ever built and are part of extensive ABB power and automation solutions for the Sohar aluminum smelter in the Sultanate of Oman and the Qatalum smelter in Qatar. Both smelters are setting new records for size and production capacity. Sohar, which started production in June 2008, has the world’s largest potline, which consists of 360 pots and produces up to 360,000 tons of aluminum a year; and Qatalum will be the world’s largest aluminum smelter with a production capacity of 585,000 tons a year and 704 pots when the plant starts up in late 2009.

At the heart of each smelter are five uniquely large and powerful ABB rectiformers, each weighing more than 400 tons and each designed to enable the plants to operate in all conditions, including worst-case scenarios. Rectiformers are critical components in the aluminum production process. They control and convert the alternating current delivered by the power grid or onsite power plant into the required direct current that powers the electrolytic process and produces the molten aluminum in the pots.

The potlines have to be constantly supplied with power. If the power conversion station fails, the lines will shut down and the molten aluminum in the pots will solidify and incur massive costs of as much as $100 million or more. For many years the voltage limit of rectiformers was stuck at 1200 volts DC. In the past few years ABB has extended the voltage limit first to 1500 V DC, then to 1650 V DC for Sohar and soon after to 2000 V DC for Qatalum (although the plant will operate at 1750 V DC).

This groundbreaking achievement enables the rectiformers to convert and deliver substantially more power than was previously possible. As a result, each smelter requires only five rectiformers instead of the six that would have been necessary at the lower voltage limit. In addition to the huge cost saving in eliminating the need for a sixth rectiformer, the increase in energy efficiency achieved by the ABB solution is equivalent to 18 percent – an enormous saving for plants that consume as much electrical energy in a year as 300,000 homes. The rectiformers are part of extensive ABB power and automation solutions designed to make both Sohar and Qatalum the most energy efficient, productive and environmentally sound aluminum plants in the world.

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