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首页> 外文期刊>Heat Transfer Engineering >Scale Formation and Mitigation of Mixed Salts in Horizontal Tube Falling Film Evaporators for Seawater Desalination
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Scale Formation and Mitigation of Mixed Salts in Horizontal Tube Falling Film Evaporators for Seawater Desalination

机译：水平管降膜蒸发器中用于海水淡化的水垢形成和缓和混合盐

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摘要

Scale formation on heat transfer surfaces is one of the most severe problems in multiple-effect distillers for seawater desalination. A horizontal tube falling film evaporator in pilot-plant scale was used to study crystallization fouling under conditions close to those prevailing in industrial multiple-effect distillers. Experiments were performed with artificial seawater and model solutions based on artificial seawater under various process conditions. In experiments with artificial seawater, the surface of copper-nickel 90/10 tubes was covered with a two-layer scale comprising a thin, flaky magnesium-rich and calcium-free base layer underneath a thick layer of calcium carbonate crystals in the form of aragonite. Analyses indicated Mg(OH)_2 (brucite) and iowaite in the thin base layer. The magnesium-rich scale layer was formed even at a low evaporation temperature of 50℃, which promotes the assumption of locally high pH values at the metal-solution interface. A shift of pH to high values in the thin seawater film due to CO_2 release and, additionally, cathodic reactions may promote a high degree of supersaturation of Mg(OH)_2. Once the tube surface is completely covered with the thin Mg-rich scale layer, it seems that the growth of the Mg-rich layer ceases and aragonite crystals start to precipitate. A decrease in the Mg~(2+) ion concentration in the solution results in an increase in the mass of calcium carbonate as aragonite in the scale layer. Results suggest that Mg~(2+) ions retard the calcium carbonate crystallization.
机译：在用于海水淡化的多效蒸馏器中，传热表面上的水垢形成是最严重的问题之一。中试规模的水平管降膜蒸发器用于研究在接近工业多效蒸馏器的条件下的结晶结垢。实验是在各种工艺条件下使用人造海水和基于人造海水的模型解决方案进行的。在使用人造海水的实验中，铜镍90/10管的表面覆盖了两层水垢，该水垢包括一层薄的片状，富含镁且不含钙的碱层，该碳酸钙晶体的厚层位于碳酸钙晶体的下面，文石。分析表明在薄的基层中有Mg（OH）_2（微晶石）和碘。即使在50℃的低蒸发温度下仍会形成富镁垢层，这促进了金属-溶液界面处局部pH值较高的假设。由于CO_2的释放，海水薄膜中的pH值移至高值，此外，阴极反应可能会促进Mg（OH）_2的高度过饱和。一旦管子表面完全被薄薄的富含Mg的氧化皮层覆盖，似乎富含Mg的层停止生长，文石晶体开始沉淀。溶液中Mg〜（2+）离子浓度的降低导致水垢层中作为文石的碳酸钙的质量增加。结果表明，Mg〜（2+）离子阻碍了碳酸钙的结晶。

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  • 来源
    《Heat Transfer Engineering》 |2015年第8期|750-762|共13页
  • 作者

    KERSTIN KROEMER; STEFAN WILL; KATELL LOISEL; STEPHAN NIED; JUERGEN DETERING; ANDREAS KEMPTER; HEIKE GLADE;

  • 作者单位

    Technical Thermodynamics, University of Bremen, Bremen, Germany;

    Institute of Engineering Thermodynamics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany;

    BASF SE, Ludwigshafen, Germany;

    BASF SE, Ludwigshafen, Germany;

    BASF SE, Ludwigshafen, Germany;

    BASF SE, Ludwigshafen, Germany;

    Universitaet Bremen, Fachbereich Produktionstechnik, Technische Thermodynamik, Badgasteiner Str. 1, D-28359 Bremen, Germany;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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