Fine screening with electrically heated screen decks

Financed by LKAB/Minelco, Mineral Processing at LTU built a test station for a screen with heated decks. Screening of moist material <1 mm normally leads to a coating of fine material on the screen decks resulting in blinding. One way to counter-act the problem is to heat the decks by electricity. By heating the screen decks, the build-up of a wet surface coating on the metal wires is avoided. It is this wet covering that traps the fine material.

Objectives

The goal is, for a select number of representative materials, to establish the screen's work envelope for varying feed and moisture levels.

It should also give LKAB the tools for evaluating if this type of screen is the solution for certain severe screening problems.

Approach

The tests are for each type of material done according to a statistical research plan, where mainly the feed rate and the moisture content are varied.

For each run, key parameters are calculated for each screen deck as well as for combinations of products from the screen decks: solids split, recovery by size fraction, d50, Imperfection and screen efficiency.

The results from the runs are evaluated based on: the loss in per cent of the correct size fraction compared to what is available in the feed, and the percentage of unwanted fractions in the product produced.

Conclusions

Fine screening with heated screen decks might be an alternative to wet processes for sites, where there is a lock of water or when discharge of water is not tolerated.