Abstract
High phosphate-based cooling water treatment programs have been used extensively throughout industry over the past 8-10 years. Although corrosion protection and deposit control can be achieved at a cost-effective level, a primary drawback of these treatments has been the necessity of very tight system control. Cycles of concentration must be maintained to limit calcium and iron levels in the water, pH must be controlled within acceptable parameters and the concentration of phosphate corrosion inhibitor and deposit control agent must also be tightly controlled in order to achieve low corrosion rates and deposit-free heat transfer surfaces. While the exact control parameters vary based on factors such as the makeup water quality and the degree of system control, these parameters typically reflect calcium concentration of 100-1000 mg/l as CaCO3, pH guidelines ranging from 6.5 to 7.5, total inorganic phosphate of 10-20 mg/l as PO4, iron concentrations of <3.0 mg/l as Fe and polymer feed varying from 5-15 mg/l. A new phosphate deposit control agent has recently been made available which exhibits excellent control of phosphate sludge problems which may occur under typical cooling water environments. However, the real advantage of this new technology is its ability to perform under upset conditions which may often occur in a cooling water system. In this paper, laboratory data is provided on the ability of this new technology to control fouling under conditions of high cycles, high iron levels, high temperature, pH excursions, low flow conditions and over and under feed of treatment chemicals. In addition, various formulations of phosphate corrosion inhibitors are evaluated from an inhibition point of view as well as their deposit potential.
