| 电化学-微滤耦合工艺对循环水钙硬度的结晶分离 |
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| 引用本文： | 苏晴,颜薇,唐沂珍,刘迪,江波.电化学-微滤耦合工艺对循环水钙硬度的结晶分离[J].化工进展,2022,41(2):1036-1042. |
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| 作者姓名： | 苏晴 颜薇 唐沂珍 刘迪 江波 |
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| 作者单位： | 1.青岛理工大学环境与市政工程学院，山东 青岛 266033;2.黄岛海关综合业务二处征管科，山东 青岛 266000 |
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| 基金项目： | 山东省重点研发计划重大科技创新工程项目(2020CXGC011204) |
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| 摘 要： | 为解决工业冷却循环水系统中水垢沉积导致换热效率降低和管路腐蚀等问题，本文提出了一种电化学-微滤耦合反应体系，以Ti/SnO2-Sb2O5-RuO2-IrO2钛滤膜为阴极，利用电解过程营造的局域强碱性和本身的微滤功能，同步实现钙硬度的高效结晶与分离。在膜反洗阶段，倒极后钛滤膜为阳极，其原位电解产生的H+能够溶解附着在膜表面和孔道内的水垢，实现水垢的剥离。结果表明，膜孔径越小，钙硬度去除率越高，以孔径为2μm的钛滤膜作阴极时，钙硬度去除率可达79%。电流密度从1mA/cm2增加到5mA/cm2时，钙硬度去除率从28%增加至86%，但电流密度进一步增加至10mA/cm2后，钙硬度去除率下降至78%。碱度增加有利于钙硬度的去除，当HCO3-]/Ca2+]摩尔比从0.7∶1提升至1.4∶1时，钙硬度去除率从53%增加至83%。当流速从5mL/min增加到20mL/min时，钙硬度去除率从84%下降至46%，能耗由3.06kWh/kgCaCO3降为1.38kWh/kgCaCO3，远低于传统电化学除硬体系。膜表面滤饼形成和膜孔内堵塞是引起钛滤膜污染的主要机制，经极性反转后，膜通量可恢复至78%左右。XRD和SEM分析表明，钛滤膜表面富集的CaCO3主要为方解石晶型。电化学-微滤耦合除硬以及膜反洗过程主要由电子驱动，避免了大量膜清洗剂的使用，为循环水系统中硬度离子的去除提供了新思路。
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| 关 键 词： | 电化学 钛滤膜 钙硬度 分离 结晶 |
| 收稿时间： | 2021-04-05 |
Electrochemical-microfiltration coupling process for the crystal separation of calcium hardness in circulating cooling water |
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| SU Qing,YAN Wei,TANG Yizhen,LIU Di,JIANG Bo.Electrochemical-microfiltration coupling process for the crystal separation of calcium hardness in circulating cooling water[J].Chemical Industry and Engineering Progress,2022,41(2):1036-1042. |
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| Authors: | SU Qing YAN Wei TANG Yizhen LIU Di JIANG Bo |
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| Affiliation: | 1.School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, Shandong, China
2.Collection Management Section, Huangdao Customs Comprehensive Business Division Ⅱ, Qingdao 266000, Shandong, China |
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| Abstract: | The formation of scale in the industrial circulating cooling water system has caused a series of problems such as decreased heat transfer efficiency and pipeline corrosion. In this study, an electrochemical-microfiltration coupling process was developed for water softening. In this reaction system, Ti/SnO2-Sb-RuO2-IrO2 titanium filter membrane was used as the cathode for OH- production by H2O electrolysis and therefore created a basic environment at its surface, where CaCO3 would become highly supersaturated. Meanwhile, this titanium filter membrane served as a microfiltration unit to effectively separate CaCO3 particles. Polarity reversal strategy was applied in the membrane backwash phase. At this time the titanium filter membrane was used as the anode for in-situ generation of H+ by H2O electrolysis, which could dissolve the scale attached to the membrane surface and in the membrane pores. The experimental results indicated that the smaller the membrane pore size was, the more calcium hardness was removed. Specifically, the calcium hardness removal efficiency could reach 79% when membrane pore diameter was 2μm. The calcium hardness removal efficiency increased from 28% to 86% with increasing current density from 1mA/cm2 to 5mA/cm2, and then it dropped to 78% with further increasing current density to 10mA/cm2. In addition, increasing the alkalinity facilitated the removal of calcium hardness. The calcium hardness removal efficiency rose from 53% to 83% when elevating the HCO3-]/Ca2+] molar ratio from 0.7∶1 to 1.4∶1. In contrast, the calcium hardness removal efficiency reduced from 84% to 46% as the flow rate increased from 5mL/min to 20mL/min with the energy consumption decreasing from 3.06kWh/kgCaCO3 to 1.38kWh/kgCaCO3, which was much less than that in the conventional electrochemical waster softening system. It was found that the fouling was mostly due to the filter cake formation and internal pore blocking. And 78% membrane flux could be recovered after backwash with polarity reversal. The XRD and SEM analysis results showed that the crystal structure of CaCO3 on titanium filter membrane surface was mainly calcite form. The electrochemical-microfiltration and backwash processes were driven by electron and thus avoided the consumption of detergents, which provided new strategy for water softening in the circulating cooling water. |
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| Keywords: | electrochemistry titanium filter membrane calcium hardness separation crystallization |
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