Dec '10/Jan '11

Intensive energy efficiency

Aluminerie Alouette makes energy reduction an operational victory

By Heather Ednie

The Aluminerie Alouette smelter, located near Sept-Îles, Quebec, consists of nearly 600 pots, which together produce 570,000 tonnes of aluminum each year | Photo courtesy of Aluminerie Alouette

Aluminerie Alouette is a global leader for both what it produces and how smartly it consumes. The largest aluminum smelter in the Americas creates over 570,000 tonnes of ingots and sows annually. It is also boasts the lowest specific energy consumption for aluminum production worldwide.

Created in 1989, Alouette runs as an independent operating company, owned by a consortium composed of Rio Tinto Alcan, Austria Metall, Hydro Aluminium, SGF and Marubeni. A primary smelter, it imports alumina from Australia, Brazil and Guinea, and reduces it to aluminum using Pechiney electrolysis technology, which is based on the Hall-Héroult process. The reduction process requires carbon anodes, which are also produced on-site at the anode plant. In the first stage of the anode plant, the paste plant, anodes are created from petroleum coke and pitch before going to the baking furnace, and then to the rodding shop to have stems attached. The pot rooms consist of four halls, of approximately one kilometre in length, for a total of 594 pots constructed with steel shells lined with refractories.

Using the electrolysis process, alumina is dissolved in cryolite and electrolyzed around 960° Celsius. Liquid aluminum is siphoned into crucibles after settling, with each pot producing approximately 2.7 tonnes daily. The chemical reaction eats away at the anodes, leaving behind carbon butts to be recycled into new anode production when anode replacement is done, typically every 26 days. In the cast house, three carrousel casters produce 750-kilogram sows from the liquid aluminum.

Continuous improvement

Alouette’s first phase of construction, completed in 1992, included 264 pots (one production line) at a capacity of 215,000 tonnes, and a power contract for 395 MW. With funds available for expansion, the strategy was to improve capacity while using the same power consumption. By 2003, they had increased capacity to 245,000 tonnes.

The production increase was achieved by raising the pot current from 300 to 330 kA (between 1996 and 1999). During that time, the improvement of the cathode block material allowed the smelter to significantly reduce cell voltage drop. With the higher thermal conductivity of the new material, it was possible to keep the pot in thermal balance, even at the higher current. “Most of the smelters switched to the new cathode grade,” recalls Hugo Levesque, R&D superintendent, Aluminerie Alouette. “In that time, it was a question of speed. This new information was known all around the world, and the fastest smelter to switch was getting most of the benefit. Alouette made the decision to replace all of its pots in the production line.”

In 2004, the government of Quebec awarded Alouette with a power block of 500 MW. “We were recognized as the best value-added option in Quebec, with the best economic impact for the province,” says Jules Côté, vice-president of operations, Aluminerie Alouette. “With that award, our total power block grew to 895 MW.”

The major increase in power availability allowed for the Phase 2 plant expansion, completed in 2005 at a capital cost of $1.45 billion. A new line was installed in the plant, including 312 pots; as well, and a test section of 18 pots was created, for technology development.

A gate process allows Alouette R&D staff to run experiments in the test section and, when viable, scale up to the production line. “It’s a rigorous process, ensuring no interruptions to production,” says Côté. “The vision we had when installing our test section and developing our R&D department was to ensure we maintain our competitive edge.”

The six-person R&D department is fully integrated into the production side. They work closely with operations, holding daily meetings to ensure transparency. “R&D is part of our culture, part of our daily business,” says Côté. The primary R&D aim at Alouette is to produce more metals with less energy and is the key to a sustainable operation, he adds.

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