NH4Cl-CaCl2-H2O 三元体系在25℃, 50℃ 和75℃下的相平衡研究.docVIP

 n Phase Equilibrium of Ternary System NH4Cl-CaCl2-H2O at 25℃, 50℃ and 75℃# Yuan Junsheng, Zhang Jijun, Li Xia, Chen Jianxin* 5 10 15 20 25 30 35 40 (Engineering Research Center of Seawater Utilization Technology of Ministry of Education,Hebei University of Technology, TianJin 300130) Abstract: The equilibrium data on the ternary system of NH4Cl-CaCl2-H2O at 25℃, 50℃ and 75℃ were investigated using the wet-residue method. The experimental results show that there are two pure phase crystal areas of NH4Cl and CaCl2·6H2O and their mixture phase crystal areas at 25℃. There are three pure phase crystal areas of NH4Cl, 2NH4Cl·CaCl2·3H2O and CaCl2·2H2O, two mixture phase crystal areas of NH4Cl and 2NH4Cl·CaCl2·3H2O, and 2NH4Cl·CaCl2·3H2O and CaCl2·2H2O in the system at 50℃ and 75℃. A new hydration double salt (2NH4Cl·CaCl2·3H2O) was found in the ternary equilibrium system for the first time. Keywords: Chemical Engineering; Phase Equilibrium; NH4Cl-CaCl2-H2O; wet-residue; crystal areas; hydration double salt 0 Introduction For multicomponent systems the composition of the equilibrium solid phase can be determined indirectly by the so-called wet-residues method[1], first proposed by Schreinemakers (1983), in which the need for solid-liquid separation before analysis is avoided. The method of wet residues is based on the application of the straight-line mixture rule on a phase diagram. By virtue of the properties of a triangular phase diagram, the three points representing the compositions of equilibrium solubility, wet-residues and the equilibrium solid phase, must lie on a straight line. Therefore the point at which a line drawn through the solubility and wet-residue points and extended to meet the side of the triangle can give the composition of the equilibrium solid phase. Research on the phase equilibrium for the crystallization process, which can give basic data for the design and simulation of the crystallization process, is extremely important both in scientific