Desulphurized gypsum, also known as smoke desulphurized gypsum, sulfur gypsum or FGD gypsum, the main composition and natural gypsum, the same as calcium sulfate dihydrate CaSO₄ · H₂O, content ≥93%. Desulphurized gypsum is an industrial by-product gypsum obtained by coal burning or oil burning industrial enterprises after treating sulfur dioxide in flue gas, and its processing and utilization is very significant. It not only effectively promotes the further development of the national environmental protection circular economy, but also greatly reduces the mining amount of gypsum and protects resources.

The gypsum raw material used in the general production line is dihydrate gypsum (grade > 90%) and desulfurized gypsum with surface water content below 15%.