The application of Baleen Filter microscreening technology at BECSA’s South Export Plant
S Tshikhudo, V Shikwambana
This paper outlines an investigation into the recovery of saleable fractions
of coal from ‘as-arising’ South Export Plant effluent streams, using Baleen
microscreening technology. South Export Plant, a subdivision of BHP
Billiton Energy Coal SA (BECSA) Coal Processing, is a two-module plant
treating 2000 t/h. The nominally -150 µm coal is untreated and is therefore
passed from classifying cyclones to the thickeners for process water
recovery. The thickened underflow is pumped into a series of slurry cells
for further settling and recovery of supernatant water. The marginal
quality, moisture content, and handlebility of this settled material renders
it unsuitable for inclusion into saleable products and it is thus stockpiled
and trucked to designated pits for disposal.
Over the years, stockpiling and trucking has become an overly
expensive exercise. In an effort to recover some of this cost, a task team
was assigned to investigate less costly options to process slurry across
BECSA plants. Various technologies such as froth flotation, sieve bends,
and Reflux Classifier were considered, although the results were generally
not beneficial – this could be attributed to weathered/oxidized coal.
A decision was made to pursue an alternative approach by testing the
suitability of the new ‘Baleen Filter’. The concept is to screen out the
higher-grade fraction (+50 µm) as saleable product and reject the finer
fractions to the slurry ponds.
The Baleen Filter was found to effectively screen at an acceptable
efficiency between 94% and 99.99%, with a very sharp cut-point (d50 and
Ep). The actual yields from the screening results were better than the
predicted yields in terms of both mass and energy as predicted from
feedstock analysis.
Keywords: Fine coal, coal slurry, upgrading, screening, Baleen Filter, thickener feed.