Scale Formation and Mitigation of Mixed Salts in Horizontal Tube Falling Film Evaporators for Seawater Desalination
Krömer K, Will S, Loisel K, Nied S, Detering J, Kempter A, Glade H (2015)
Publication Language: English
Publication Status: Published
Publication Type: Journal article
Publication year: 2015
Journal
Publisher: Taylor & Francis
Book Volume: 36
Pages Range: 750-762
Journal Issue: 7-8
DOI: 10.1080/01457632.2015.954961
Abstract
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 degrees C, 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 CO2 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 Mg2+ ion concentration in the solution results in an increase in the mass of calcium carbonate as aragonite in the scale layer. Results suggest that Mg2+ ions retard the calcium carbonate crystallization.
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APA:
Krömer, K., Will, S., Loisel, K., Nied, S., Detering, J., Kempter, A., & Glade, H. (2015). Scale Formation and Mitigation of Mixed Salts in Horizontal Tube Falling Film Evaporators for Seawater Desalination. Heat Transfer Engineering, 36(7-8), 750-762. https://dx.doi.org/10.1080/01457632.2015.954961
MLA:
Krömer, Kerstin, et al. "Scale Formation and Mitigation of Mixed Salts in Horizontal Tube Falling Film Evaporators for Seawater Desalination." Heat Transfer Engineering 36.7-8 (2015): 750-762.
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