Coal preparation plant
This is the raw material for the CPP, and consists of coal, rocks, middlings, minerals and contamination.
Coal needs to be stored at various stages of the preparation process, and conveyed around the CPP facilities.
ROM coal is delivered with large variations in production rate of tonnes per hour (tph).
Taller and wider stockpiles reduce the land area required to store a set tonnage of coal.
Larger coal stockpiles have a reduced rate of heat loss, leading to a higher risk of spontaneous combustion.
Travelling, luffing boom stackers that straddle a feed conveyor are commonly used to create coal stockpiles.
Tunnel conveyors can be fed by a continuous slot hopper or bunker beneath the stockpile to reclaim material.
A "cross cut" sampler mimics the "stop belt" sampling method specified by a standard originally published by the American Society for Testing and Materials (ASTM).
The sampler is set according to Tons per hour, Feet per minute and top size of the product on the actual belt.
[citation needed] Crushing reduces the overall top size of the ROM coal so that it can be more easily handled and processed within the CPP.
Gravity separation methods make use of the different relative densities of different grades of coal, and the reject material.
Different types of DMB include: A cyclone is a conical vessel in which coal along with finely ground magnetite (media) is pumped tangentially to a tapered inlet and short cylindrical section at a predetermined flowrate and pressure followed by a conical section where the separation takes place.
The higher specific gravity fractions being subject to greater centrifugal forces pull away from the central core and descend downwards towards the apex along the wall of cyclone body and pass out as rejects/middlings through the underflow orifice discharge, also known as the spigot.
The lighter particles are caught in an upward stream and pass out as clean coal through the cyclone overflow outlet via the vortex finder.
The Heavy Media Cyclone may be lined with very high quality ceramic tiles or manufactured from Ni-hard (a very hard alloy of cast iron containing nickel) with a specially designed helical profile.
It is produced as a by-product is typically placed in a coal slurry impoundment, which can be sources of environmental disasters.
A thickener is a large circular tank that is used to settle out the solid material from the water in the feed slurry.
Measurement of flow, density, levels, ash and moisture are inputs to the control system.
Other instrumentation found in plants include density gauges and online elemental coal analyzers.
