Preconcept of a filtration system for the recovery of solids from the overflow of thickeners (LA26)

ISSUE

A Niobium mine located in North America operates with using thickeners to collect Niobium oxide extracted from the ore. In order to limit the loss of Niobium oxide in the overflow of the thickeners which is sent directly to the tailing (estimated at $ 1.3M / year). The client was looking for a method to recover as much solids as possible from the overflow. After several in-house tests, the customer identified filtering the overflow as one of the best possible solutions to achieve the required recovery rate. However, the filtering properties of the overflow made it difficult to filter with a conventional filtration method.

TECHNOLOGICAL CHALLENGE

STS Canada has been contacted to identify an economically viable way to filter the overflow without the addition of product that could contaminate the Niobium oxide.

RECOMMENDED SOLUTION

STS Canada proposed to modify the filtration properties of the overflow by incorporating some of the sludge collected at the underflow. The performance of this solution was then evaluated using laboratory filtration tests performed on an overflow containing an increasing proportion of sludge. The filterability of the pulp formed as well as the clarity of the filtrate obtained could then be evaluated according to the ratio of overflow / underflow tested. In parallel with the experimental study, STS Canada identified, using internally developed analysis matrix, the most appropriate filtration technology for this application before using the data collected in the laboratory to size it. Finally, a technical-economic analysis of the proposed solution was carried out.

RESULTS

In a first step, this study demonstrated the effectiveness of using underflow sludge as bodyfeed in the overflow of the thickener to optimize the filterability of the overflow. The ideal ratio of overflow / underflow required to optimize the recovery of Niobium oxide in the overflow of the thickener could also be identified. In a second step, this study made it possible to identify the most suitable filtration technology for filtering the overflow and to size it. Based on the data provided by the mine, the proposed treatment method should allow the mine to realize additional gains of $ 1,000,000 / year.