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Dubal, GE Energy team up to improve energy efficiency

Keywords: Tags  Dubai Aluminium Co., GE Energy, nitrogen oxide emissions, Keiran Coulton, Abdulla Kalban, dry low-nitrogen oxide combustion systems, Gulf Turbine Services Facility,

The price of energy has reached unprecedented levels in the past decade. In an effort to lower energy costs, many metal manufacturers are developing innovative solutions to reduce overall energy consumption. 

Aluminum, in particular, is especially costly to produce, with electricity accounting for nearly one-third of total production costs. One company, Dubai Aluminium Co. Ltd. (Dubal), has taken a proactive stance to save power in an energy-reduction initiative with GE Energy that focuses primarily on its fleet of gas turbines. 

State-owned Dubal’s production complex south of Dubai produces about 960,000 tonnes of aluminum annually for customers in 48 countries. The facility, expanded several times over the past 30 years, is currently powered by 23 gas turbines running 24 hours a day, 365 days a year to produce enough electricity to power the plant’s massive smelters. In all, the complex has a generation capacity of 2,350 megawatts, making the operation completely autonomous in terms of energy requirements. 

The process of manufacturing aluminum—converting alumina into metallic aluminum—requires a large amount of electricity. During the smelting process, a direct electrical current with extremely high amperage (usually 150,000 amperes or more) must be channeled through a cryolite/alumina mixture to achieve the desired chemical reactions. Additionally, the potline must run around the clock; any power interruptions can cause the pots to “freeze,” resulting in irreversible damage. The entire process uses so much energy that aluminum smelters accounted for nearly 3 percent of global energy consumption in 2011. 

In an effort to reduce its energy consumption and nitrogen oxide emissions, Dubal teamed up with GE to design a system that would drastically reduce the costs associated with electricity production and improve the overall reliability of its turbines. 

“Performance and reliability of our power supply are very important for the production of aluminum,” Dubal president and chief executive officer Abdulla Kalban said in 2009. “This service agreement with GE will help us reduce our cost of generating electricity, which will lead to a lower cost of aluminum production, positioning us more competitively in the global market.”

The $45-million service agreement signed in August 2009 tasked GE with implementing innovative solutions that would simultaneously allow Dubal to lower its energy consumption and reduce its nitrogen oxide emissions by up to 15 percent, all while maintaining normal production. “The Dubal site is one of the world’s largest producers of aluminum,” said Keiran Coulton, president of global industries for GE Energy. “Over the course of three years, Dubal worked with us to complete an overhaul of its power generation, which included reducing fuel costs and (nitrogen oxide) output.” 

GE said in a news release at the time that the agreement also would cover “the supply of parts, performance upgrades, repairs and field services for planned outages for the gas turbines over a period of seven years,” allowing Dubal to drastically reduce its on-site parts inventory, which was a major component of the company’s cost-cutting initiative, and for vital repairs to be handled by experts at Abu Dhabi’s Gulf Turbine Services Facility (GTS), a joint venture between GE and Abu Dhabi Aircraft Technologies.  

The agreement, while not entirely unusual, marked a major change in how GE Energy was lending its expertise to the metal manufacturing sector. “We will consult the power strategy of the entire plant,” Coulton said. “A lot of companies we work with will opt for this strategy. This is actually a growing area for us, and it’s a very informative and intensive process. It’s not just about the power anymore.” 

Coulton, who joined GE in 2011 after a career at Rockwell Automation Inc., said that implementing power-saving technologies has become an area of focus for GE Energy. “In the metals industry, we are getting into some really revolutionary technology. We are doing a lot of low-heat recovery. In aluminum production, you have to deal with low temperatures of waste gas. We are doing a good deal of research with how low you can go (in terms of heat) to get an equal recovery.” He said that GE Energy has been achieving unprecedented levels of recovery while continuing to lower the heat to decrease overall power consumption.   

Since designing a series of power-saving initiatives for the Dubal project three years ago, GE has been able to achieve a number of upgrades to the performance and reliability of the existing gas turbines at the plant, some of which have been operational for nearly 35 years.

“Dubal has always been a technical leader,” Coulton said. “Their level of operations has always been in the top quintile, and our main task with the turbines was to reduce the tremendous fuel cost.”

Coulton said that reducing this cost was achieved primarily by choosing the most economical power source to meet the forecast load while simultaneously taking into account a wide variety of constantly changing constraint variables. According to Dubal, the success of the project over the past three years has allowed the company to save enough on its electricity expenses to fully recover the cost of its service agreement with GE.

Another vital component of the service agreement included a complete overhaul of the plant’s nitrogen oxide emissions systems, including implementing GE’s dry low-nitrogen oxide (DLN) combustion systems for heavy-duty gas turbines to enable lower emissions for turbines during operation. In a paper detailing its DLN technology, GE engineers indicated that “traditional methods of reducing (nitrogen oxide) emissions from combustion turbines (water and steam injection) are limited in their ability to reach the extremely low levels required in many localities.” The paper added that “the lean pre-mixed DLN systems for gas and fuel have demonstrated their ability to meet the ever-lower emissions levels required today.” 

A second component of the DLN technology used in the Dubal plant allows for turbine operability and production to remain at consistently high levels. In 2011, engineers said that “GE’s design goal is to make the DLN system operate so the gas turbine operator does not know whether a DLN or conventional combustion system has been installed (i.e., its operation is ‘transparent to the user’).” This, according to GE, allowed for a seamless transition to the DLN system from the outdated systems that had previously been in place. 

Today, with a full integration of systems and updates in place at the Dubal plant, GE is able to maintain arm’s-length contact with operators at the facility. There are currently no GE employees on site, and in the rare event of an outage Dubal can contract support from GE engineers to handle any mechanical or electrical problems that relate to the existing fleet of turbines.

Moreover, the updated monitoring systems that were installed in 2009 allow GE engineers to control power substations remotely, enhancing turbine productivity and reliability while simultaneously troubleshooting events that have the potential to cause a shutdown or an unscheduled loss of power.

“Our relationship with Dubal continues today and our experience in establishing the power-saving systems has helped us to set up a global metals business,” Coulton said, citing myriad benefits of the Dubal project for GE Energy. “While we are not yet known as a major player in metals, the Dubal project helped us establish a lot of world-class offerings that we can now bring to other projects."

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