Coal is treated in processes called “beneficiation” to prepare a material that meets the certain requirements. These processes may result in low ash quantity and low sulphur content. They include the following:
- Sizing, controlled by a crushing and screening process
- increasing heating value, by removing non-combustible ash and rock by gravity separation
- Removing or controlling undesirable mineral and chemical components (sulfur, sodium, and trace elements) by a combination of gravity separation and blending.
Traditionally, most coal preparation was primarily concerned with sulfur and ash reduction. Today, however, much more sophisticated processes have more narrow and complex physical and chemical requirements for coal stock.