Selection of four filtration equipment from a NEW SPENT POT LINING WASTE TREATMENT PLANT (LA31)

ISSUE

The Spent Pot Lining (SPL) is a carbon-based paste used to seal joints between cathode blocks and bricks, forming the walls of an aluminum electrolysis cell. The cathode blocks must be replaced once they are consumed. This operation, called de-lining the pots, generates waste containing fluoride and cyanide, that require pre-treatment before being buried with great caution.

An aluminum smelter in Quebec uses proprietary in-house technology to process yearly near 80,000 tonnes of SPL. This new process makes the SPL de-lining completely inert and thus provides a sustainable solution to the global aluminum industry.

For this, the carbon and fluorinated by-products of the SPL processing plant need filtration. To address this issue, STS Canada was assigned to conduct a concept study that aimed to identify the best filtration technologies to be used in four of the steps of this new process.

TECHNOLOGICAL CHALLENGE

The challenges of this project were to identify the for each of the four steps involved, the filtration technology best suited to the operating conditions providing excellent cake washing while managing the toxicological and operational risks associated with the generation of ammonia gas by the process.

RECOMMENDED SOLUTION

As a result of pilot testing, STS Canada was able to calculate the required filtration areas required for each process step, depending on whether the separation was done under vacuum or pressure. Based on these sizing, STS Canada was then able to propose the most optimal combinations of vacuum filters, pressure filters and centrifugal filters for each of the process steps.

RESULTS

Following STS Canada's studies and research, the best-suited filtration equipment associated with the current operating conditions was identified to each of the four process steps. Based on pilot-scale demonstrations by STS Canada, each of the proposed filters were sized. Finally, thanks to STS Canada's comprehensive supplier database, the manufacturers offering the best-value equipment were identified and presented to the customer.