Study of the technology for high-precision separation of washed middlings at a large-size coking coal plant

The problem with the operation of the plant′s middlings rewashing system currently used is the wide fluctuation of percentage of cleaned coal in middlings which can go up to 30% with the ash of the middlings being in a range of 30%～35%, causing a great loss of cleaned coal. To cope with this situation, work is made on optimization of the heavy medium washing process to enable it to make high-precision rewashing of the middlings product of the primary washing system. In the optimized washing system, the 2-stage 3-product process is changed to a 2-stage 4-product one, and the pressure-fed 3-product H. M. cyclone is employed to replace the 2-product version previously used. After optimization the clean coal with an ash of 10%～12% can be effectively recovered. Field application of the renovated washing system shows that the total yield of clean coal is noticeably increased, and the 3^# clean coal product has a final ash of 11% with a rise of yield by 1.12 percentage points, creating a remarkable economic result.