Cooling water scale and corrosion inhibition

Abstract A methods of the present invention for inhibiting silica scale formation and corrosion in aqueous systems where soluble silica residuals (SiO2) are maintained in excess of 200 mg/L, and source water silica deposition is inhibited with silica accumulations as high as 4000 mg/L (cycled accumulation) from evaporation and concentration of source water. The methods of the present invention also provides inhibition of corrosion for carbon steel at corrosion rates of less than 0.3 mpy (mils per year), and less than 0.1 mpy for copper, copper alloy, and stainless steel alloys in highly concentrated (high dissolved solids) waters. The methods of the present invention comprise pretreatment removal of hardness ions from the makeup source water, maintenance of electrical conductivity, and elevating the pH level of the aqueous environment. Thereafter, specified water chemistry residual ranges are maintained in the aqueous system to achieve inhibition of scale and corrosion. Other References   Strumm, et al.; “Formation of Polysilicates as Determined by Coagulation Effects”; Environmental Science and Technology; 1967; Vo. 1, 21-227. Rozenfield, I.L.; “Corrosion Inhibitors”; 1981; McGraw Hill; 171-174. The NALCO Water Handbook; 1979; Chapter 3, p. 14 and 16. Drew; Principles of Industrial Water Treatment; Sixth Edition; 1983; Chapter 3, pp. 43 and 64. Boffardi, Bennett P., PhD; Calgon Internal Publication; 1988; Chapter 4; pp. 30-31.

Field of Search

159/47.1 , PROCESSES 159/47.3 , Involving waste liquid 203/10 , WATER PURIFICATION ONLY 210/652 , Hyper filtration (e.g., reverse osmosis, etc.) 210/687 , Calcium or magnesium (e.g., hardness, water softening, etc.) 210/696 , Preventing, decreasing, or delaying precipitation, coagulation or flocculation 210/697 , Utilizing inorganic phosphorus agent 210/698 , Utilizing organic agent 210/699 , Phosphorus containing 210/700 , Nitrogen containing 210/701 , Acrylic polymer 210/702 , Making an insoluble substance or accreting suspended constituents 210/743 , pH Sensing 210/746 , Electrical property sensing 210/748 , Utilizing electrical or wave energy (directly applied to liquid or material being treated) 210/96.1 , CONSTITUENT MIXTURE VARIATION RESPONSIVE 422/13 Aqueous alkali environment (i.e., pH £ 4.1)

US Patent References

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