By Eric J. Adams
Photographs by Darren England/Getty Corporate Assignment
There is no tree on earth quite like the finicky mangrove. It’s a saltwater tree that needs fresh water to survive. It draws nutrients from the sea but can only take root near the mouths of rivers or along shores protected from high waves. Yet, despite their fragility, mangrove trees are home to an incredible variety of animals, from mud crabs (a local delicacy) to osprey, and these trees give life to large regions of mud flats that otherwise might be barren. It’s no surprise, then, that the mangrove tree and its surrounding environment were primary concerns when Comalco Aluminium Limited proposed the construction of an alumina refinery near a mangrove-rich area just northwest of the port city of Gladstone in central Queensland, Australia.
The Comalco Alumina Refinery is designed to extract alumina from bauxite, a red-orange, pebbly rock. The refining process involves dissolving alumina with caustic soda under high temperatures and then precipitating it from the liquid and heating it to white powder. The resulting alumina is shipped to aluminum smelters, where an electrolytic process is used to turn it into pure aluminum. Four tonnes of bauxite yield two tonnes of alumina, which yield one tonne of aluminum.
“This refinery is central to the company’s strategy of expanding upstream from aluminum production and remaining a globally competitive producer,” says Ron Douglas, Comalco’s general manager for engineering and construction. “We needed to build it in a very sustainable way, but because of the competitive marketplace for alumina and aluminum, we also had to make the project very cost-effective.”
“But when we kicked off this project, there was a fair amount of skepticism in the international community about whether we could meet the budget and schedule,” Douglas adds.
The Gladstone site was selected because of its port facilities, proximity to raw materials, availability of skilled labor, strong national and regional support, and the cost of energy. Comalco’s contract with Bechtel Australia covers construction of refinery processing and production facilities; a steam generation plant; a bauxite residue storage area; a port facility; and materials handling, transportation, and associated stockpile areas.
When completed in November 2004, the refinery will be the first of its kind built in the past 20 years, and it will boast operating costs significantly below the industry average. The first stage of the project will enable the refinery to produce 1.4 million tonnes of alumina a year. Additional stages will increase capacity to 4.2 million tonnes.
Bechtel’s global resources came into play early in the project. Engineering was performed at project offices in Brisbane and Melbourne, as well as in India. “It made good sense, because our engineers in New Delhi had experience using software for the design of these types of projects,” says Norm Smith, Bechtel’s project engineering manager.
Bechtel also employed some ingenuity during the project, particularly when it came to meeting stringent environmental standards. Rather than build steel tanks for the highly corrosive caustic soda, for example, Bechtel engineers came up with the idea of using a more protective polypropylene bladder.
The storage bladder is 150 meters long by 80 meters wide and 4 meters high, and it can hold 40,000 cubic meters of 50-percent liquid caustic soda. It is contained inside an earth embankment capable of holding the total storage volume if necessary. “Polypropylene is easier to put together and there is minimal chance of leaks or rupture,” says Jim Connor, Bechtel’s project manager. “This is the only refinery that’s ever been built using this type of technology—and it has resulted in savings of US$4 million.”
Another cost-saving decision was to shift some manufacturing off-site. “When you build large components off-site, you have the opportunity to improve quality control, build components in parallel, and save work-hours in the process,” says Connor. “We’ve been able to put pieces together at 90 percent of the hours it would have taken on-site.”
Because of drought conditions in the Gladstone area, the Bechtel team worked to tweak the cooling system. “We had to ask ourselves, ‘How are we going to run this plant when we don’t have enough water?’” says Smith. “The answer is with either fresh or sea water, so we designed the cooling towers to accommodate both.”
The refinery design incorporates highly efficient gas-cleaning technology and energy efficiency to limit fuel use and greenhouse emissions. Bechtel and Comalco deployed innovative technology with seven washing stages to recover potentially hazardous caustic soda.
To protect the environment, the two companies engineered a heating system ideally suited for the type of bauxite shipped in from Comalco’s Weipa mine, all in an effort to minimize waste. “The site has been designed for zero discharge and we’re very proud of that,” says Douglas.
To ensure the safety of the mangrove trees and surrounding ecosystem, the project developed a detailed environmental management plan, created in consultation with the government and local community. Special care was taken to move selected plants to a nursery to make room for the refinery. Natural vegetation that could not be saved was turned into mulch and used to prevent erosion in surrounding areas. Comalco also reserved a 110-hectare buffer of natural vegetation for a wildlife corridor.
The same environmental and cost-efficient principles are being applied to necessary infrastructure improvements, including expanded wharf facilities at nearby Fisherman’s Landing, a 4-kilometer conveyor system between Fisherman’s Landing and the refinery for transporting alumina and bauxite, a rail loop for the delivery of coal, a bauxite residue management and storage area, and a service corridor between the refinery and remote locations.
Bechtel’s partnership with Comalco dates back to more than 20 years ago, when Bechtel was the prime contractor for construction of Comalco’s Boyne Island and Tiwai smelters in the late 1970s, and the expansion of those smelters in the mid-1990s.
“We have a lot of common ground with Bechtel,” says Comalco’s Douglas. “From project execution to safety and leadership, we have very similar cultures, work ethics, and work practices. Our reporting systems are very similar, so we work well together, but that’s to be expected after all these years.”