Abstract: A solid powder reactor includes: a reaction kettle, including a hollow kettle body and covers; an agitating device, including an agitating shaft and blades, wherein the agitating shaft is arranged in the kettle body and the blades are fixed on the agitating shaft; and a heating system, including a kettle body heater and an agitating heater, wherein the kettle body heater is fixed on the kettle body and the agitating heater is arranged on the agitating device. While the agitating device and the kettle body are driven to agitate, by a driving device fixedly arranged outside the reaction kettle, the heating system heats materials in the reactor. The present invention is applicable to solid reaction of solid powders. The materials containing attached water or not are both feasible, and the materials can directly enter the reactor and react. Compared with conventional solid reactors, the present invention increases the production efficiency.

Abstract: A method for preparing ?-calcium sulfate hemihydrate with calcium sulfate dihydrate includes steps of: uniformly mixing the calcium sulfate dihydrate with an additive solution, and obtaining a mixture, wherein weight percentages of the calcium sulfate dihydrate and the additive solution in the mixture are respectively 90.00-95.00% and 5.00-10.00%, and the additive solution contains water, inorganic salt, organic salt, organic acid, surfactant, and seed crystal; rising a temperature of the mixture to 130-150° C., keeping for 20-120 minutes, and the calcium sulfate dihydrate in the mixture transforming to the ?-calcium sulfate hemihydrate; drying the mixture after reaction at 105-160° C., and thereafter obtaining ?-calcium sulfate hemihydrate product. The used calcium sulfate dihydrate can be natural raw materials and industrial by-products. The industrial by-products can be directly applied.