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Coal Washery equipment

Coal Washery

A coal washery is also called coal preparation plant (CPP), it is a facility that washes coal of soil and rock, preparing it for transport to market. A coal washery may also be called a "coal handling and preparation plant" (CHPP), "prep plant," "tipple," or "wash plant".

Run-of-mine (ROM) coal

The coal delivered from the mine that reports to the coal preparation plant is called run-of-mine, or ROM, coal. This is the raw material for the coal washery, and consists of coal, rocks, middlings, minerals and contamination.

Coal handling equipment used in coal washery

Coal needs to be stored at various stages of the preparation process, and conveyed around the Washery facilities. Coal handling is part of the larger field of bulk material handling, and is a complex and vital part of the Coal Washery.

Stockpiles provide surge capacity to various parts of the Coal washery. ROM coal is delivered with large variations in production rate of tonnes per hour (tph). A ROM stockpile is used to allow the washplant to be fed coal at lower, constant rate.

Travelling, lugging boom stackers that straddle a feed conveyor are commonly used to create coal stockpiles.

Reclaiming

Tunnel conveyors can be fed by a continuous slot hopper or bunker beneath the stockpile to reclaim material. Front-end loaders and bulldozers can be used to push the coal into feeders.

Coal sampling

Sampling of coal is an important part of the process control in the CPP. A grab sample is a one-off sample of the coal at a point in the process stream, and tends not to be very representative.

Washability

The washability characteristics of a coal reserve are provided by obtaining liberation data on the raw coal. Liberation refers to the amount of physical breakage required to separate material of different material densities. Low density material is clean coal whereas high density material is reject (rock). The intermediate density material is called middlings.

Coal Crushing equipment used in Coal washery

Crushing reduces the overall topsize of the ROM coal so that it can be more easily handled and processed withe Coal washery. Crushing requirements are an important part of Coal washery design, and a number of different types.

Coal Screening Equipment used in Coal washery

Screens are used to group process particles into ranges by size. These size ranges are also called grades. Dewatering screens are used to remove water from the product. Screens can be static, or mechanically vibrated. Screen decks can be made from different materials such as high tensile steel, stainless steel, or polyethelene.

Gravity separation

Gravity separation methods make use of the different relative densities of different grades of coal, and the reject material.

Jigs are a gravity separation method for coarse coal. Different types of jig include:

Dense medium process

Dense medium gravity separation methods use a material such as magnetite to form a medium denser than water to assist in separation.

Dense medium baths (DMBs)

Dense medium cyclones

A mixture of raw coal and dense medium enters the cyclone at a predetermined flowrate and pressure. A vortex is formed, and the high density reject forced to the outside to the underflow orifice discharge, also called the spigot.

Fine coal methods

Fine coal is cleaned using froth flotation methods. Denver cells and Jameson cells are two flotation methods used. Spirals perform a simple, low cost and reasonably efficient separation of finer sized material, based on particle density and size.

Dewatering product coal

Water is removed from the product to reduce the mass, and runoff on the stockpile.

Dewatering tailings

Water is removed from tailings to recycle water. Filters, centrifuges and thickeners are used in this part of the process.

Thickeners

Thickeners are used for dewatering slurries of either tailings or product. A thickener is a large circular tank that is used to settle out the solid material from the water in the feed slurry.

Control and instrumentation

Control and instrumentation is a very important part of a coal washery. Measurement of flow, density, levels, ash and moisture are inputs to the control system.