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Last metal from Søderberg cells

June 13, 2007, 01:00 CEST

Today marks the end of the road for the last Søderberg electrolytic cells in Årdal, Norway. The Å3 hall, which began operating in 1961 with 168 cells, has produced no less that two million tonnes of aluminium. Now this era is irrevocably over.

The closure of the Å3 hall has been planned since last autumn, and is the result of the environmental control authorities setting stricter requirements regarding emissions. During the initial phase, the main priority was to find alternative employment for the 100 or so employees at the plant. There seems to be widespread agreement within the community of Årdal that this process has gone well.

Now, in the final phase, the main challenge is to close down the Søderberg Å3 line in a way that ensures that the last aluminium is of as high quality as possible, that the cells produce as much metal as possible, that the materials used in the process can be re-used, and that the work is carried out safely.

"We can’t just switch off the electricity"

When the power was cut from the last Søderberg cells in Å3 on Wednesday 13 June, this was the fifth, the largest, and the final section to be closed down. Electrolysis manager Per Arinn Solli and operations manager Helge Rørvik feel confident that the closure will go well. But shutting down a Søderberg line is far more complicated than just cutting off the power supply.

"In reality this is an extensive process involving all levels of our organization. In addition to the shutdown being technically demanding and involving a lot of extra work, we also have to ensure that everything is carried out safely. Here, it helps for instance that we have carried out a series of "safe job analyses" before starting the task, and that we have involved all shifts and units in the planning work. It is also important that those doing the job feel motivated right up to their last working hour. In Å3, there haven’t been any signs of employees losing motivation – if anything, we have witnessed the opposite. They have made exceptional efforts," Solli stresses.

Good metal, new anodes

In order to shut down the electrolytic cells in the best possible way, the anodes are placed in a special pattern, and then the filling with Søderberg paste is gradually reduced. During the final shift before the closure of the line, the electrolyte is gradually tapped, the anodes are lowered down into the metal, the power supply to the entire hall is cut off, and then the individual section is uncoupled. This process is carried out for one section at a time in the hall.

"The aim of this procedure of metal tapping is to assure as much good-quality metal as possible, while being able to recycle what is left of the anodes, so that they can be used later in a prebake plant", Solli explains.

He adds that experiences from equivalent closures of Søderberg lines in Sunndal and Høyanger have been useful, even though the conditions in the Å3 hall have also necessitated some modifications quite unlike those in Sunndal and Høyanger. In Årdal, a new method of uncoupling has been used, where as much liquid electrolyte as possible has been tapped off the cells for possible re-use in Qatalum, Hydro's part-owned aluminium plant project in Qatar."

Per A. Solli calls the restructuring work for the 100 or so employees at Å3 a "well-run race".

"It has been an organizational challenge. The timing was good, since new businesses have been established – such as the door fabrication company Dooria and the solar energy company Norsun, and all along it has been a great advantage that the employee representatives have contributed in an extremely constructive way," he adds.

A double red-letter day

"The fact that the Søderberg line closes on the same day as the foundation stone is laid for Norsun makes 13 June a double red-letter day in Årdal," comments factory manager Wenche Agerup.

"Nowadays it’s not often that new industry is set up in Norway. We are very happy that this is happening in Årdal. At the same time, the closure of the Søderberg plant goes to show that it is an advantage to restructure when times are good: people have new jobs to go to. All along we have had as our ambition that no-one should become unemployed. That we should succeed so well in this aim is almost more than we had dared to hope was realistic," she says.