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U.S. Patents 6,998,092

Cooling water scale and corrosion inhibition

US Patent Issued on February 14, 2006




No. 11018732 filed on 2004-12-21


Attorney, Agent or Firm




A methods for inhibiting silica scale formation and corrosion in aqueous systems where soluble silica (SiO2) can be maintained at residuals below 200 mg/L, but more preferably maintained at greater than 200 mg/L as SiO2, without silica scale and with control of deposition of source water silica accumulations as high as 4000 mg/L (cycled accumulation) from evaporation and concentration of source water. The methods of the present invention also provide highly effective inhibition of corrosion for carbon steel, copper, copper alloy, and stainless steel alloys. 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
  • 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.
  • Strumm, et al.; ‚??Formation of Polysilicates as Determined by Coagulation Effects‚?Ě; Environmental Science and Technology; 1967; vol. 1, 221-227.
  • Rozenfeld, I.L.; ‚??Corrosion Inhibitors‚?Ě; 1981; McGraw Hill; 171-174.

Current US Class

422/3 , Process control in response to analysis 159/47.1 , PROCESSES 203/10 , WATER PURIFICATION ONLY 210/652 , Hyperfiltration (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 422/13 , Aqueous alkali environment (i.e., pH £ 4.1) 422/14 Essentially pure water environment

US Patent References

    Silica scale inhibition
    Issued on: January 11, 1994
    Inventor: Hann, et al.
    Blow system and a method of use therefor in controlling the quality of recycle cooling water in a cooling tower
    Issued on: April 4, 1995
    Inventor: Takahashi

WAM ZLD Presentation *.pdf



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