Thesis
Electrochemical reduction of water hardness for the prevention of fouling in cooling water treatment
Master of Science (M.S.), Drexel University
Jun 2012
DOI:
https://doi.org/10.17918/00009707
Abstract
Scale deposition occurs along heat exchanger surfaces, resulting in a decrease in efficiency of heat transfer, a problem known as mineral fouling, which poses challenges in industrial applications. The prevalent form of scale is calcium carbonate (CaCO₃). The formation of this CaCO₃ scale on heat exchanger surfaces in industrial systems can be mitigated by reducing the concentration of calcium ions (Ca²⁺), bicarbonate ions (HCO₃⁻), or both, in the water utilized in the system. The common method of reducing this fouling ability is to reduce the concentration of calcium ions. In the present study, research and experiments were conducted for the purpose of reducing this concentration of calcium ions and the associated potential of CaCO₃ to cause precipitate fouling. To mitigate these effects, a direct current (DC) electric field was applied across electrodes placed in a stream of water, to electrochemically capture calcium ions and precipitate CaCO₃ before it could be deposited as scale along surfaces of a heat exchanger. The electrochemical system was applied at constant galvanostatic conditions of 0.4 A, and 0.3 A, in a stream of 5 gallons (19 liters) of hard water at a flow rate of 1 liter/minute. This system was also then applied in a fouling test setup at similar test conditions of 0.2 A, 0.5 A, and 1.5 A, and the fouling resistance was monitored over 48 hours to determine if the reduction of calcium ions indeed led to a decrease in mineral fouling in the system. The electrochemical system was successful at reducing hardness in water at an energy cost of 23kJ/Iiter per abatement of 100 ppm of hardness. The system was however not able to reduce fouling resistance during a fouling test. Electrochemical water softening is discussed and suggestions are proposed for how to modify the proposed system so that it can reduce fouling in addition to removing calcium ions.
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Details
- Title
- Electrochemical reduction of water hardness for the prevention of fouling in cooling water treatment
- Creators
- Kamau Wright
- Contributors
- Young I. Cho (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- x, 52 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) (1970-2026); Drexel University
- Other Identifier
- 991021888940304721