Abstract
Desalination, the separation of water from its dissolved constituents, is currently practiced by three commercial processes: electrodialysis, reverse osmosis, and distillation, most commonly by multiple stage flash evaporation, called MSF. Accounting for more than 7.7 million m3/d of the total, worldwide desalting capacity of approximately 10 million m3/d, MSF distillation is the leading process today. The major problem in the design and operation of MSF systems is the potential for alkaline and calcium sulfate scale deposition on critical heat transfer surfaces throughout the unit. Currently, there are three scale control methods, mineral acid dosing, antiscalant treatment, and concurrent addition of reduced amounts of both acid and inhibitor. Laboratory and field studies were conducted to develop successive generation antiscalants which effectively and efficiently minimize alkaline and calcium sulfate scaling in MSF units. Field operating results are presented which establish the efficacy of the first generation antiscalant. Both static and dynamic threshold studies in the laboratory have led to the development of a blend of sulfonic acid/acrylic acid copolymer and a phosphorus containing compound which evidences outstanding inhibitory properties in seawater brines at elevated temperatures. Projected field results will confirm the new product’s superiority.
