Using Iron to Inhibit Scale Formation

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Calcite (CaCO3) is one of the most prevalent of boiler and heat exchanger scale. Recent work has shown that trace concentrations of divalent iron (Fe2+) very strongly inhibit the growth of CaC03, suggesting that iron of the appropriate form and in sufficient concentration can lead to a significant reduction in the amount and tenacity of such scale deposits. It is proposed to examine how iron and other metal cations affect the nucleation and growth of a variety of scale-forming carbonate minerals, and how various solution parameters enhance or suppress crystallization. A model will be developed to predict carbonate crystal growth inhibition, and electrolytic and magnetic means of introducing the metal cations into solution will be examined. The build up of scale deposits inside cooling water pipes and boilers is a multimillion dollar problem. Scale significantly reduces heat transfer efficiency and can lead to blockage of water flow passages. Understanding the mechanisms by which metal ions inhibit crystal nucleation and growth can lead to cost effective means of maintaining peak performance of heat exchange equipment.