Slurry is treated to separate and recover the finest particles of coal and shale.
|Taff Merthyr Colliery fines separation|
The coal, shale and water mixture is pumped from the slurry sump to a large conical settling tower. Clean water overflows into a vertical pipe for recycling in the washbox while the solid matter sinks to the bottom from where it is pumped to supply the slurry screens, any excess being returned to the slurry sump. The screens separate dry material over 0.5mm, which is passed to AA501, from that under 0.5mm and water which is piped to the froth flotation feed sump. Any overflow is returned to the slurry sump while the contents are pumped to the froth flotation cells (plate 11). The mix in the cells is agitated and oil is added, forming bubbles to which particles of coal adhere; as the bubbles rise, coal is carried to the surface from where it is skimmed off by rotating paddles. The coal slurry passes to four rotary vacuum filters (plate 12) to dry the coal, which then falls to AA501 below, while the filtrate water is piped to the slurry sump. The shalt' water (tailings) from the froth flotation cells is pumped to a large circular thickener tank. A flocculent is added to the tailings in this tank to assist separation of water from solids. Clean water flows over the inner lip for re-use in the washbox and the more concentrated material is piped via the tailings buffer tank to the filter presses (plate 13). Here, tailings are compressed to remove water, which is piped to the slurry sump, from the solid shale which is transported by AA601 and a dumper truck to the shale stockpile. Coal carried on AA501 is transferred to AA502, AA503 and AA312, thence to the clean-coal blending bunker.
|Taff Merthyr Colliery fines separation diagram|
1. Raising coal and stone extraction
2. Preliminary coal grading
3. Raw coal treatment (washing)
4. Fines separation
5. Preparation of treated coal for market
6. Shale disposal and reclamation of surface water
7. Identification of principal surface features
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