Coal preparation plant

A coal preparation plant (CPP; also known as a coal handling and preparation plant (CHPP), coal handling plant, prep plant, tipple, or wash plant) is a facility that washes coal of soil and rock, crushes it into graded sized chunks (sorting), stockpiles grades preparing it for transport to market, and more often than not, also loads coal into rail cars, barges, or ships. The more of this waste material that can be removed from coal, the lower its total ash content, the greater its market value and the lower its transportation costs.

Run-of-mine (ROM) coal

The run-of-mine (ROM) coal is the raw material that comes from the mine. It consists of coal, rocks, middlings, minerals, and contamination. Contamination is usually introduced by the mining process and may include machine parts, used consumables, and parts of ground engaging tools. ROM coal can have a large variability of moisture and ash content.

Coal handling

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

Stockpiles

Stockpiles provide surge capacity to various parts of the CPP. 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.

Stacker

A stacker is a large machine used in bulk material handling. Its function is to pile bulk material such as coal, limestone, ores, and cereals on to a stockpile. A reclaimer can be used to recover the material.

Reclaimer

A reclaimer is a large machine used in bulk material handling applications. A reclaimer's function is to recover bulk material such as ores and cereals from a stockpile.

Coal washing

Coal washing is a process that is undertaken in a coal preparation plant to remove impurities from coal. The process involves crushing the coal to a manageable size and then washing it. During the washing process, the coal is separated from the impurities using a variety of techniques, including gravity separation, flotation, and magnetic separation.

Gravity separation

Gravity separation methods make use of the different relative densities of different grades of coal, and the reject material. Jigs, dense medium baths, and dense medium cyclones are used to separate the coal from the waste material.

Flotation

Flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries. Historically this was first used in the mining industry, where it was one of the great enabling technologies of the 20th century.

Magnetic separation

Magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using a magnetic force. This separation technique can be useful in mining iron as it is attracted to a magnet.

Dewatering

Dewatering is an important step in the coal preparation process. After washing, the coal is wet and needs to be dried before it can be transported. Dewatering screens, centrifuges, and thickeners are used to remove excess water from the coal.

Control and instrumentation

Control and instrumentation is a very important part of a CPP. Measurement of flow, density, levels, ash and moisture are inputs to the control system. The control system is typically a distributed control system (DCS) but the level of automation varies according to the individual plant.

Also see

• Coal mining
• Coal breaker
• Coal washing
• Mineral processing
• Bulk material handling