Surge in Savings

By Nick Wright

Dubal and GE Energy earn award for revamping smelter power generation system

September 2012 - Energy savings is always an area where aluminum mills can cut costs. Technology certainly makes that easier. Take Dubai Aluminum Co. Ltd., Dubai, known as Dubal, as a prime example. Working with GE Energy, Dubal revamped its entire power management and generation system for its massive smelting plant. Now, Dubal saves about $4 million in energy costs a year. In June, the upgrade earned GE and Dubal an award in the “Best Brownfield Technology” category of the American Metal Market’s Awards for Aluminum Excellence.

The award was presented to company representatives in June during the 2nd Annual Aluminum Summit in New York.

Dubal’s smelting plant in Jebel Ali, United Arab Emirates, produces billets, ingots and cast aluminum—about 1 million metric tons per year. It has reached that capacity with expansions over the last several years. The plant contains eight pot lines with about 200 pots each, says Ryan Derouin, North America metals leader for GE Energy, Atlanta.

“Pot lines are expandable,” he says. “Basically you create the network and make sure you can support it from an electrical distribution standpoint.”

At the heart of Dubal’s three-part power upgrade, which began in 2007, was the coupling of two key GE applications: the turbines and energy management system.

GE Energy installed its XA-21 SCADA energy management system and upgraded Dubal’s existing GE Frame 9B and 9E turbines. The XA-21 system is an overarching energy management system that sits on top of the existing infrastructure system of a plant. As the electrical nerve center of Dubal’s plant, the system connects the smelter, cast house and rolling facility to their support buildings and power distribution.

“It interconnects with all those touch points and sets up a universal monitoring system that does advanced load shedding and advanced diagnostics,” Derouin says. “When you turn on a pot line, you’re looking at plus or minus 200 megawatts, or potentially more.”

Think of the electrical system like a garden hose you wave with your hand, he says. The sine curve the water makes represents power spikes. The XA-21 filters and regulates those fluctuations to keep from reverberating to other parts of the plant and possibly bringing pot lines down.

“Say if a power generator goes down and they need to shut down the system,” Derouin explains. “They can do that sequentially just to support the smelting side, so you can prioritize the existing system and architecture to make sure that molten aluminum doesn’t sit in the pots and solidify them, which would be very detrimental.”

Tweaking turbines
On the hardware side, Dubal has 25 generators, 19 of which are GE turbines of varying generations. The powerful 9E and 9B natural gas turbines can handle the different qualities of gas Dubai may get from its fuel suppliers, making them robust and reliable.

“Those things will chew anything on the planet. They’re very heavy duty,” says Derouin. “They can take same type of gas turbine we use in steel for seam gas, down to 1/10th the heating value of natural gas.”

Now, Dubal’s power output has increased by 22.69 percent, or about an additional 75 megawatts, according to the company. The heat rate has increased by 10.44 percent (accounting for the yearly fuel cost savings of $4 million). Management of Dubal’s 2,350 megawatt power station is leaner and more reliable at 98.98 percent availability.

Attaining that reliability rate is, overall, the biggest challenge of these types of upgrades, says Derouin.

“If you don’t have that, it’s worthless to the customer,” he adds. “When you hit that button, it needs to fire and go.”

Dubal expects to recover its costs for the upgrade within three years. That sustainability strategy factored into its award.

“With the price of energy currently at its highest level in the past decade, and set to continue rising, these savings are pivotal to our sustainability strategy of remaining one of the world's lowest-cost primary aluminium producers,” said Abdulla Kalban, Dubal president and COO, in a statement.

As one of the largest smelter sites in the world, firing up a pot line with such a system has a profound affect on the industry, Derouin says.

“In order for them to compete effectively they need to be world class.” MM


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