At a glance
Coal preparation plants clean raw coal by separating it from rock, shale, and other rejects. The equipment scope follows the unit operations: raw coal handling, sizing, dense-medium cleaning, fine coal cleaning, dewatering, medium recovery, and tailings management.
Process flow and equipment
A typical coal preparation plant routes raw coal through six unit operations. Each operation has its own equipment scope and selection criteria. Integration between operations — surge capacity, water balance, medium balance — is where engineering effort concentrates.
Raw coal handling and sizing
Raw coal is received, broken to a manageable top size with primary crushers or sizers, and screened into size fractions matched to the cleaning circuits. Typical splits are coarse (above about 13 mm), small (1–13 mm), and fine (below 1 mm). The split sizes vary with feed coal characteristics and the cleaning technology chosen for each fraction.
Coarse coal cleaning
Coarse coal is cleaned in dense-medium baths or vessels, or in jigs. Dense-medium cleaning uses a magnetite-water suspension with a controlled density between coal and reject. Modern plants favor dense-medium cyclones for both coarse and small coal because of their high efficiency over a wide size range.
Fine coal cleaning
Fine coal (below 1 mm) is cleaned by dense-medium cyclones (small dia), spirals, teeter-bed separators, or flotation. The choice depends on coal characteristics, target product, and economic considerations.
Dewatering
Coarse product is dewatered on dewatering screens. Small and fine product use centrifuges, with filter presses for ultra-fine fractions where recovery is justified.
Medium and water recovery
Magnetite is recovered from dilute medium streams by wet drum magnetic separators. Process water is clarified in thickeners and recycled to the plant. Make-up water and make-up magnetite are added to maintain inventory.
Tailings management
Tailings are dewatered by filter press, thickener, or paste plant. Modern plants increasingly use filter presses to produce stackable tailings, avoiding wet tailings dams.