Phosphogypsum contains soluble phosphorus, eutectic phosphorus, fluorine, organic matter and other harmful impurities, which deteriorate the performance of phosphogypsum, which is the main factor that cannot be used directly. Soluble phosphorus, fluorine and organic matter are distributed on the surface of phosphogypsum crystals. Impurities such as soluble phosphorus, eutectic phosphorus, and fluorine affect the hardening of cementitious materials and the bonding between crystals.

In the production of gypsum products, the calcination is the key step for product quality control. The one-step process, two-step process, Si De calciner, Si De dryer and inside & outside boiling furnace developed by Dongda Powder Company are the processes and equipment which are applicable to different heat sources and different products, and they has formed a complete industrialized system. In selection of calcination system, the purpose of manufactured products, the local heat source, the power conditions, the automation level and the production scale etc should be taken into account so as to determine the calcination method and supporting system.

The calcination process system worked out and process calciner determined in accordance with coal series clay, soft and hard soil characteristics can realize the fast decomposition, slow redox and drying use of heat source. Small land covering area, it can produce double-90 soil and calcinate modified soil, and it gives good performance in the use and is better than the traditional method. 

Calcined calcium carbonate to make calcium oxide adopts dynamic calcination process, which is a new process of calcium carbonate calcination. . Due to the rapid calcination and uniform heat transfer, it is an advanced process for producing activated calcium oxide and an advanced process for decomposing caustic lime.