索尔维工艺生产纯碱(碳酸钠，Na2CO3)，每吨纯碱将产生10 m³CaCl2废液。按此计算，年产量100万吨纯碱厂每年就排放废液1000万m³。除环境要求迫切需要减少排放外，其实纯碱CaCl2废液(每升含CaCl2：100克，NaCl：50克)是可利用的资源。针对传统蒸发工艺得到的氯化钙价值很低的缺点，申请人提出利用纯碱CaCl2废液制备ɑ型高强石膏的新工艺，即浓氯化钙与硫酸铝反应直接得到ɑ型高强石膏(CaSO4·0.5H2O)和六水氯化铝两个高附加值产品。本课题将深入开展该工艺应用基础的研究，包括：固-液相平衡热力学与反应结晶动力学的实验和模拟计算，以及整个工艺的验证和过程模拟。为新工艺工业化提供设计基础，项目的完成将对纯碱工业节能减排解决关键科学问题，具有显著的理论价值和实际意义。

There has been growing interest in the recovery and reutilization of CaCl2 generated from Solvay’s process to help combat environmental pollution. Here a novel, eco-friendly process aimed for the direct production of high strength, α-Hemihydrate from the discharged CaCl2 waste stream is proposed. The scope of this project includes, the reactive crystallization of alpha-calcium sulfate hemihydrate by the adding aluminum sulfate into CaCl2-contained liquor, as well as the crystallization kinetics of aluminum chloride hexahydrate from the filtrated slurry. Basic researches of the new process, such as the solid-liquid phase equilibrium of the reaction system, the crystallization kinetics, experimental verification and simulation of the whole process, will provide data and theoretical support for the industrial application of the new technique. The main research contents are as follows: the experimental determination and modeling of the stability and solubility of the calcium sulfate hydrate in the mixed aqueous solutions; the nucleation and crystallization kinetics study of alpha-calcium sulfate hemihydrate; and lastly, the simulation, scale-up, cost-benefit analysis and optimization of the new proposed process in whole.