The precipitation mechanism of calcium carbonate in the gas-liquid-solid three phase at alkalescency condition

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• 作者：Jianxin Chen ; Xiangchao Zhang ; Yueyue Ge ; Min Su and Zhaolong Zhong
• 刊名：Crystal Research and Technology
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：52
• 期：2
• 全文大小：1079K
• ISSN：1521-4079

文摘

The precipitation of calcium carbonate in heat exchanger is a serious problem in seawater desalination which results in significant decrease of heat exchange efficiency and tedious cleaning. Decalcification pretreatment by acidic flue gas provides an efficient and economical solution to this problem, but few literature has been reported about the crystallization mechanism of CaCO<sub>3sub>, including the supersaturation ratio, the relationship between the supersaturation ratio of the reaction solution and the crystallization growth rate of CaCO<sub>3sub> in the CO<sub>2sub>-CaCl<sub>2sub>-H<sub>2sub>O system. In this study, the crystallization of CaCO<sub>3sub> was studied by combing the dynamic method and the static method to ensure the accuracy in measuring the carbonate ion concentration by chemical titration at pH = 8.0 in the CO<sub>2sub>-CaCl<sub>2sub>-H<sub>2sub>O system. It was found that there existed an ion competition between HCO<sub>3sub><sup>−sup> and CO<sub>2sub> (aq) in the CO<sub>2sub>-CaCl<sub>2sub>-H<sub>2sub>O system, which led to fluctuations of CO<sub>2sub> absorption rate. The supersaturation ratio of the reaction solution still increased when the reaction crystallization rate was reduced. The variations of the concentration of HCO<sub>3sub><sup>−sup>, CO<sub>3sub><sup>2−sup> and Ca<sup>2+sup> ions with time were investigated. The growth process of the vaterite was monitored and described on mesoscale.