ABB rectiformers help aluminum smelters increase energy efficiency
Advances in high-power conversion technology increase the energy efficiency of aluminum smelters in Oman and Qatar by 18%.
David Greenfield -- Control Engineering, 8/18/2009
For several months now, automation vendors have been noting an increased interest in energy efficiency in Middle East countries. Considering the global manufacturing focus on energy efficiency, this news is not that surprising. However, considering that the Middle East is growing so fast industrially and that energy is cheaper there than most everywhere else in the world, it is a bit eye-opening to see how manufacturers in this region embrace energy efficiency--even in the absence of government mandates. As one vendor representative expressed earlier this year, "Considering the commodity products most of the manufacturers in these areas produce, their margins are extremely thin. Anything that cuts into those margins--like unnecessary energy expenditures--is a direct impact to their bottom line."
 The ABB power conversion station at Sohar, in Oman, features powerful converters, capable of handling up to 1650 volts of dc power. |
A recently announced example of how this energy efficient focus in the Middle East is being put into action comes from ABB, which has installed high-power converters (also known as rectiformers) in 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, according to ABB.
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 ABB rectiformers, each weighing more than 400 tons and each designed to enable the plants to operate in all conditions. 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.
 One of two potrooms at Qatalum, in Qatar. Each is more than one kilometer long, and holds 704 electrolytic cells or 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 voltage increase 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 is equivalent to 18 percent-an enormous saving for plants that consume as much electrical energy in a year as 300,000 homes.
See other Control Engineering content about energy efficient automation applications:
- Webcast: Energy Efficiency Strategy & Tactics
- Energy Management: First Steps Toward Greater Efficiency
- Motor energy- efficiency developments: recycling, efficiency classes
- By David Greenfield, editorial director
Control Engineering Sustainable Engineering News Desk
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