Performance Review of Simplified Cooling Water Treatment
By Colin Hogan, Ph.D.
Effective corrosion and deposit control in evaporative cooling circuits can generally be achieved by selection and formulation of a phosphate, phosphonate, polymer dispersant, and azole treatment, with the possible supplement of zinc for highly corrosive systems. Unfortunately, formulating for effective corrosion and deposit control without increasing treatment costs is not that simple. Faced with the manufacture and supply of safe, high performance, costeffective programs, the water treatment professional must choose from a wide array of formulation components. Often a water treatment chemical supplier is tempted to develop sophisticated, multifunctional formulations based on numerous components. However, increasing their number only adds to inventory and manufacturing costs. To assist with simplifying corrosion and deposit control formulation development, the water treater often relies on models. These models consist of: 1. prescriptions for a suite of starting-point formulations (1); 2. a combination of field experience and an understanding f saturation indices, silt, and iron contamination; and 3. computerized models for optimization of inhibitor ratios (2). Each modeling approach requires a good understanding of the performance envelope of individual scale and corrosion inhibitors, together with knowledge of the target cooling system operating range. With rising raw material costs, a more competitive water treatment market, and a customer base struggling with economic recovery and growth, water treatment companies have been forced to re-examine the cost and composition of their product formulations (1). Specifically, the need for the complexity of a large number of components, which in turn requires high product inventories, has come into question. Formulators are also challenged with responding to increasing sensitivity toward environmental discharge limits. As a result, they are turning toward the use of more environmentally benign corrosion and scale inhibitors in lieu of phosphates, zinc, and manganese. Instead, they are focused on the pursuit of formulation cost reductions that do not compromise environmental impact and product performance. New chemistries are therefore sought to form the basis of a simplified, flexible range of all-organic cooling circuit formulations that can also sustain high corrosion and deposit control performance.
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