FLOTATION CONCENTRATE FROM A POTLINING TREATMENT CENTER (LA1)

ISSUE

Spent Pot lining (SPL) are the residues coming from the cleaning of the refractory coating that covers the electrolysis tanks in the Aluminum Production. The SPL’s are composed of carbon, refractory brick and other products. SPL’s are usually pretreated and then buried with great precaution.

Our client has developed an SPL treatment process to make them inert. The treatment process works on flotation stages of the carbon by-products. During the development of the flotation process three concentrates will be generated (carbon, brick, mixed rejects), the customer wanted to identify the most suitable technology (s) to ensure the solid / liquid separation of the three concentrates. To address this issue, STS Canada was retained to conduct a pre-concept study to identify the Best Available Control Technologies (BACT) for these different concentrates.

The following activities made it possible to recommend the best separation technology and to identify a method for breaking the emulsion produced during the flotation of the carbon concentrate.

1. Characterizing the concentrates and substrates (filtrate, mud, overflow, underflow);
2. Drafting of an experimental protocol, validated by the client;
3. Selecting the best technology that meets the application specifications;
4. Validating the technology and conducting a pilot testing in the laboratory;
5. Evaluating of the analysis results;
6. Validating the design criteria of the selected technology;

TECHNOLOGICAL CHALLENGE

The first series of pilot tests in the laboratory failed to provide sufficient filtrate clarity to allow recirculation in the process. The second series of trials have included the addition of chemical additives (Polymers). The use of a polymers made it possible to filter the concentrates in one step and recirculate the filtrate in the process while eliminating the possibility of creating a loop of fine particles that would be detrimental to flotation.

RECOMMENDED SOLUTION

Meetings with the client to validate the various concepts and technologies made it possible to identify the best operational strategy and filtration of the new equipment. This strategical process has successfully contributed to achieve a design with an accurate actual equipment sizing and a cost-effective solution.

RESULTS

STS Canada recommended the addition of a pressure filtration step and the use of coagulant with the three (3) different types of concentrate, which allows recirculation of the filtrate to the flotation stages.