Before raw coal can be used in power plants or in industrial processes, it goes through a process called coal washing. Also known as coal beneficiation, the process involves a series of steps to remove impurities from coal which is comes straight from the mines.

Crushing & Screening: Coal in its raw form comes in varying sizes, ranging from huge boulders to small particles. To make it easier to process and transport, it is first crushed into smaller, more uniform sizes. The size of the coal can be adjusted to meet the specific requirements of the processing plant or the applications in which it will be used. Particles of a similar size are usually processed together.

Dense Medium Separation: This is an effective method to separate coal from shale, stone and other impurities based on their different densities. Coal is mixed with a medium – usually magnetite or ferrosilicon mixed with water. This medium has a specific gravity between coal and the impurities. So when mixed with the medium, the lighter coal floats to the top while the heavier impurities sink to the bottom, enabling easy separation. 

Froth Flotation: This method is used to separate coal from ash-forming minerals based on their difference in surface properties or hydrophobicity. The addition of chemicals to a coal-water mixture creates a froth which separates coal from impurities. This froth which contains coal is then skimmed off, leaving behind unwanted impurities

Gravity Separation: This versatile method uses techniques such as jigging and spiral concentration to separate coal particles from ash based on their density, size and shape. It relies on gravitational force to separate lighter particles from heavier ones and is often used in combination with Froth Flotation.

Dewatering: After coal has undergone processes such as Dense Medium Separation, Froth Flotation and Gravity Separation, the separated coal contains some amount of water. The Dewatering process reduces the moisture content of the cleaned coal, facilitating easier transportation, storage as well as its utilization in various processes.

Coal Washing increases the coal’s energy content per unit weight, resulting in cost savings through greater efficiency and enables industry-specific customization. By improving the quality of coal by reducing its sulfur and ash content, coal washing also reduces the environmental impact of coal combustion.