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Dissertation
A study of physical water treatment methods for the mitigation of mineral fouling
Doctor of Philosophy (Ph.D.), Drexel University
2001
DOI:
https://doi.org/10.17918/00006306
Abstract
The objectives of the present study were to investigate the effectiveness of physical water treatment (PWT) technology in fouling reduction, to validate the performance of PWT technology at a high cycle of concentration in a cooling tower system, and to theoretically study the principle of PWT technology. The scope of the present study included a microscopic observation to investigate the process of scale formation under various test conditions. The technology of physical water treatment used magnetic, electromagnetic, and electric fields. It was hypothesized that the external fields precipitated dissolved mineral ions and formed a state of suspended clusters in solution, resulting in fouling mitigation at heat-transfer surfaces. The principle of physical water-treatment (PWT) technology was theoretically studied including a review of bulk precipitation by PWT, the characteristics of PWT devices, and the concept of nucleation work. PWT devices included both an electronic anti-fouling (EAF) device using a solenoid coil and a permanent magnetic device. A microscopic imaging technique was developed to visualize fouling process with an artificially-hardened water and recirculating cooling tower water. Using the new experimental technique, one could acquire valuable information on the time-dependent behavior of crystal growth during fouling processes such as nucleation sites, scale growth, number of crystals, scale layer formation, and removal process. This study examined the effect of PWT technology on fouling in a simulated cooling-tower system. It was found that the EAF technology could maintain high COC (5 to 10) of water when applied to a circulating cooling tower water. The EAF treatment was effective in reducing fouling resistances in a heat exchanger in a recirculating cooling system, even at high cycles of concentration. The runs for 5 COC, no blowdown, and 10 COC resulted in 70, 50, and 60% reductions in the fouling resistance, respectively. The study also demonstrated that a high flow velocity of approximately 6 m/s through a PM device was necessary to obtain the maximum performance of the PM device in mineral scale prevention. At this optimum operating condition, the PM device could substantially reduce mineral fouling in a heat exchanger using cooling-tower water even at 5-6 COC. SEM photographs revealed characteristics of crystal structures in scale deposition, suggesting that the scale was created through crystallization fouling in cases without PWT. On the contrary, SEM photographs obtained in cases with PWT did not show regular crystal structures, suggesting that the scales were formed by suspended particles as particulate fouling.
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Details
- Title
- A study of physical water treatment methods for the mitigation of mineral fouling
- Creators
- Won Tae Kim
- Contributors
- Young I. Cho (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvii, 248 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888801504721