- PURPOSE
The purpose of this report is to propose a Re-look at Beneficiation Processes of coal in South Africa
Advantages and Disadvantages will be discussed on all the Processes.
- BACKGROUND
In South Africa with depleting Coal Reserves and depleting Water Sources the Beneficiation of coal for the Domestic and Export markets with the usual Wet DMS processes is becoming a real challenge.
The Quality of Raw coal sources are becoming a problem due to the Oxidation of the coal and the mining of ‘Young coal” (Lignite)
The Oxidized coal/Young coal tends to react with the water in the wet processes and produce its own challenges.
These challenges are:
2.1 Wet screening of the fines is problematic due to the blocking of the screen apertures due to the formation of clay.
2.2 Oxidized coal tends to have high Inherent Moisture and the drying of coal to lower the Total Moisture of the Final Product becomes a Big Head ache.
The Wet Beneficiation process of Coal.
Wet Processing of Coal requires a large quantity of water and the waste generated ties up significant amount of water and solids (slimes and fine saleable coal).
Slurry ponds also provide a serious Environmental problem and a safety issue (dam brakeage) High Investment cost in the Construction and Building of Double-Stage DMS
plants. The recovery of the slimes and fine saleable coal is a possibility but it is high cost,
high investment exercise.
3.0 DRY BENEFICIATION PROCESSES ON COAL.
The Theory of dry Separators relevant to Coal beneficiation is driven by the Density differences between Coal and the Impurities associated with the Coal seam.
Dry Beneficiation Processes are based on the Physical Properties of Coal and its associated Mineral matter.
3.1 Air-Dense Medium Fluidised Bed Technology.
The Dry DMS beneficiation technology with air-dense medium fluidised bed utilises air-solid (Magnitite) suspension as beneficiation medium with controllable density of the bed properties to achieve a stable separation zone. The higher density Discard in the feed coal will sink (Density higher than the Bed`s density) and Product (Density lower than the Bed`s density) will float, thus stratifying the feed materials according to their density.
Dry Beneficiation of Coal by using dry Magnetite and Air in a Fluidised bed technology has been researched fro as early as 1926 in Germany. In 1984 Professor Chen Qingru from CUMT (China University of Mining and Technology) developed the dense phase, high concentration, micro-bubblequasi-dispersion fluidised bed, dry coal separation theory which fuelled the start of the first commercial Dry DMS Coal plants in China.
The fluidised bed technology is best demonstrated on You Tube video: Liquid Sand Hot Tub.
