Picked up a small story in the Montreal Gazette, which reports that Rio Tinto Alcan’s smelter in Alma Canada is experiencing problems with excess iron and silicon in the metal.
The newspaper story focuses on the (temporary) loss of jobs for about 60 workers. The workers are from the pot relining centre, and are being laid off because the equipment they would normally use for pot relining is being diverted to address the impurities problem.
That is interesting. The equipment normally used in the relining centre consists of jackhammers, tamping guns, molten iron heaters and crucibles and overhead cranes. I am no specialist, but my guess is that it is the cranes that are being diverted. First of all, not much else in relining can be useful in solving an iron/silicon problem. Second, I suspect that the potrooms people need to make use of extra crane time the daily cycle.
Iron and silicon can’t come from too many places. One obvious source is the anode, but they should be able to isolate and identify that without needing to use equipment from the relining centre. Another and more likely source is the alumina itself. The problem with getting impurities in your alumina stream is that it’s hard to divert out of the problem. You need a lot of alumina and a whole alternate delivery system, depending on how your alumina silos are configured.
My guess is that the cranes are being used to deliver top-ups of high purity alumina into the pots. If you are doing that, then your crane time goes up exponentially, and you’ve no time for anything else.
The article says that metal production levels are unaffected, only the quality is a problem. But if the pot relining centre is down for two weeks, then one hopes that there isn’t a failure of more than a few pots in the next 4 – 5 weeks.
The fact that they expect to work their way out of the problem in 2 weeks tells me it’s an alumina problem.
But I am no smelting specialist. If you have better information or knowledge, please send us a comment.