1. Oxidation process
It mainly uses hydrogen peroxide, various chloric acids, nitrogen dioxide and some high valent iron salts with oxidation to selectively oxidize minerals and sulfur in coal to turn them into soluble salts, and finally wash them with water to remove them.
2. Acid treatment
Demineralization of coal with acid. Among them, fluoric acid is the most, because fluoric acid can dissolve almost all minerals in coal.
3. Alkali acid treatment
The coal is leached with alkali and then washed with acid solution.
4. Solution extraction
Ultrapure coal can be obtained by extracting coal with various solvents and separating the extract from the solvent
