Part 3: Performance of Polymers, Phosphonates, and Polymer/Phosphonate Blends as Gypsum Scale Inhibitors
By Zahid Amjad, Ph.D.
The deposition of unwanted materials on equipment surfaces causes serious operational challenges in various industrial water systems (e.g., evaporative cooling, boiler, thermal, membrane-based desalination, and geothermal). The deposits normally consist of mineral scales, suspended matter, corrosion products, and microbiological mass. In evaporative cooling systems, calcium sulfate dihydrate (gypsum) is the most commonly encountered calcium sulfate scale; whereas, calcium sulfate hemihydrate and calcium sulfate anhydrite are the most frequently formed scales in high-temperature processes (e.g., high-temperature boiler, multi-flash distillation, and geothermal). The deposits that form can markedly reduce heat transfer, causing energy losses or material damage, especially when coupled with corrosion. Additionally, scaling is often accompanied with corrosion that leads to damage of the metallic parts, including pumps, pipes, and heat exchangers. In many cases, the removal of deposits results in discontinuous operation of the system, leading to higher operation costs.
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