The raw material or solution used as a starting medium determines the process and thus the conversion step and its intermediate product.
If the starting material is rich in magnesium ions, the crystallization plant for potassium sulfate or the overall process will proceed via the intermediate product schoenite (K₂Mg(SO₄)₂ 6H₂O).
If, on the other hand, the raw material is enriched with sodium ions, the crystallization plant will be implemented via the intermediate glaserite (K3Na(SO₄)₂).
In any case, a vacuum cooling crystallization plant is used in the crystallization of potassium sulfate (SOP).