Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was...Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.展开更多
1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate ...1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate is known as a major展开更多
1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also inc...1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also increase the scaling of vacuum evaporation tanks and brine reusing pipes.Additives have certain impacts on the crystallization dynamics(Randolph et al.,1971).The crystallization展开更多
The microstructures of gypsum board and gypsum particleboard were observed by SEM. The effects of retarder and waterproof agent on the shape and the average dimension of the gypsum crystal were discussed. The mechanis...The microstructures of gypsum board and gypsum particleboard were observed by SEM. The effects of retarder and waterproof agent on the shape and the average dimension of the gypsum crystal were discussed. The mechanism was investigated as well. Four typical instances, i e, the gypsum crystal shape, the gypsum combined with particles on the particles surface, the gypsum combined with particles on the wood cross section and the gypsum combined with particles inside the wood cell cavity were selected and observed. Furthermore, the agglomeration and cementation mechanism between gypsum and particle were studied.展开更多
基金Project(50974018)supported by the National Natural Science Foundation of ChinaProject(108007)supported by Key Project of the Ministry of Education of China
文摘Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.
基金financial support of National Nature Science Foundation (21376178)TIDA giant growth plan (2011-XJR13020)+3 种基金Tianjin Science and technology support program (12ZCDZSF06900)Tianjin University of Science and Technology fund for scientific research (20120119)Tianjin education commission program (20130509)Research fund for the doctoral program of higher education of China(20131208120001)
文摘1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate is known as a major
基金financial support of National Nature Science Foundation (21376178)TIDA giant growth plan (2011-XJR13020)+3 种基金Tianjin Science and technology support program (12ZCDZSF06900)Tianjin University of Science and Technology fund for scientific research (20120119)Tianjin education commission program (20130509)Research fund for the doctoral program of higher education of China (20131208120001)
文摘1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also increase the scaling of vacuum evaporation tanks and brine reusing pipes.Additives have certain impacts on the crystallization dynamics(Randolph et al.,1971).The crystallization
基金Supported by the National High Technology Research and Development Program of China（2006AA06Z385） the Science Foundation of Wuhan University of Science and Technology（2008RC06）
基金Funded by the National Natural Science Foundation of China (No. 30371130) the NSFU and KOSEF cooperation research in 2004
文摘The microstructures of gypsum board and gypsum particleboard were observed by SEM. The effects of retarder and waterproof agent on the shape and the average dimension of the gypsum crystal were discussed. The mechanism was investigated as well. Four typical instances, i e, the gypsum crystal shape, the gypsum combined with particles on the particles surface, the gypsum combined with particles on the wood cross section and the gypsum combined with particles inside the wood cell cavity were selected and observed. Furthermore, the agglomeration and cementation mechanism between gypsum and particle were studied.
