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摘要
The solid-liquid equilibrium (SLE) of Na2SO4 + N, N'-bis (2-hydroxypropyl) piperazine (HPP?0.5H2SO4) + H2O system were investigated at 0, 25, 50 and 70℃ by the isothermal dissolution method. The equilibrium solid phase was determined by wet slag method. Based on the solid-liquid equilibrium data, isothermal phase diagrams were drawn at 0, 25, 50 and 70℃.The results show that the phase diagrams at 0℃ and 25℃ were similar, both contained the crystalline region of Na2SO4 and Na2SO4?10H2O, the mixed crystalline region of Na2SO4 and Na2SO4?10H2O, one co-saturated point and an unsaturated solution region. The crystallization area of Na2SO4?10H2O is larger and its solubility is smaller at 0℃, while the crystallization area of Na2SO4? 10H2O is larger and its solubility is smaller at 25℃. The phase diagrams at 50℃ and 70℃are similar. There is only one crystallization region of Na2SO4 and an unsaturated solution region in the phase diagrams at 50℃ and 70℃.There is no existence of HPP?0.5H2SO4 crystallization region observed in any of the phase diagrams, which is beneficial to the recycling of amine solution. The phase equilibrium data and phase diagram at four temperatures provide theoretical basis for separating Na2SO4 from HPP?0.5H2SO4 system. ? 2020, Editorial Office of CHEMICAL ENGINEERING (CHINA). All right reserved.
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