Cooling water scale and corrosion inhibition

• US 20050150839A1
• Filed: 12/21/2004
• Published: 07/14/2005
• Est. Priority Date: 01/09/2004
• Status: Active Grant

• Current Assignee: John L. Kubis, Water Conservation Technology International, Inc.
• Original Assignee: Water & Enviro Tech Company, Inc.
• Inventors: Duke, Dan A., Kubis, John L., Wetherell, John P.
• Granted Patent: US 7,122,148 B2
• Time in Patent Office: Days
• US Class Current: 210/696
• CPC Class Codes: C02F 1/042 Prevention of deposits
• CPC Class Codes: C02F 1/42 by ion-exchange ion-exchange in general B01J
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/4602 for prevention or elimination of deposits
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2103/023 Water in cooling circuits
• CPC Class Codes: C02F 2209/05 Conductivity or salinity
• CPC Class Codes: C02F 2303/08 Corrosion inhibition
• CPC Class Codes: C02F 5/00 Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents softening using ion-exchange C02F1/42
• CPC Class Codes: C23F 11/182 Sulfur, boron or silicon containing compounds
• CPC Class Codes: C23F 15/00 Other methods of preventing corrosion or incrustation

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.

Claims

1. A method for controlling silica or silicate scale formation in an aqueous water system with silica contributed by source water, the methods of the present invention comprising the steps:

a) removing hardness ions from said source water;

b) controlling the conductivity of said aqueous system water such that said aqueous system water possesses a conductivity from approximately 10,000 to 150,000 μ

mhos; and

c) elevating and maintaining the pH of said aqueous system water such that said aqueous system water possesses a pH of approximately 9.0 or greater.

2. The method of claim 1 wherein in step a), said hardness ions comprise ions of calcium and magnesium.

3. The method of claim 1 wherein said aqueous system water contains soluble SiO₂ in excess of 200 mg/L.

4. The method of claim 3 wherein said aqueous system water contains soluble SiO₂ in excess of 300 mg/L.

5. The methods of the present invention of claim 3 wherein in step a), said hardness ions are removed in amounts equal to or less than approximately 20% of the SiO₂ present within said source water.

6. The methods of the present invention of claim 3 wherein in step a), said hardness ions are removed in amounts equal to or less than approximately 5% of the SiO₂ present within said source water.

7. The method of claim 1 wherein in step c), said pH is maintained at 9.6 or higher.

8. The method of claim 1 wherein in step a), said hardness ions are removed via a method selected from the group consisting of ion exchange, selective ion removal with reverse osmosis, reverse osmosis, electro chemical removal, chemical precipitation, evaporation and distillation.

9. The method of claim 1 wherein in step c), said pH is increased by adding an alkali agent.

10. The method of claim 8 wherein said alkali agent comprises sodium hydroxide.

11. The method of claim 1 wherein in step c), said pH is elevated by evaporating a portion of said aqueous system water.

12. The method of claim 1 wherein in step c), said pH is elevated by distilling a portion of said aqueous system water.

13. The method of claim 1 wherein in step c), said source water comprises water utilized for cooling processes, water utilized for cooling tower systems, water utilized for evaporative cooling, water utilized for cooling lakes or ponds, water utilized for enclosed or secondary cooling and heating loops.

27. The method of claim 1 wherein prior to step a), said methods of the present invention comprises the step:

a) analyzing said source water to determine the concentration of SiO₂ present therein.

29. The method of claim 1 wherein in step b), said conductivity of said aqueous system water is controlled such that said aqueous system water possesses a conductivity from approximately 20,000 to 150,000 μ

mhos.

31. The method of claim 1, wherein said source water contains silica in an amount of 4000 mg/L or less.

14. A method for inhibiting corrosion of a metallic substance in an aqueous system wherein said aqueous system derives water from make-up source water, the methods of the present invention comprising the steps:

a) removing hardness ions from said source water;

b) controlling the conductivity of said aqueous system water such that said aqueous system water possesses a conductivity from approximately 10,000 to 150,000 μ

mhos; and

c) elevating and maintaining the pH of said aqueous system water such that said aqueous system water possesses a pH of approximately 9.0 or greater.

15. The method of claim 14 wherein in step a), said hardness ions comprise ions of calcium and magnesium.

16. The method of claim 14 wherein said aqueous system water contains soluble SiO₂ in excess of 200 mg/L.

17. The method of claim 14 wherein said aqueous system water contains soluble SiO₂ in excess of 300 mg/L.

18. The method of claim 14 wherein in step a), said hardness ions are removed in amounts equal to or less than approximately 20% of the SiO₂ present within said source water.

19. The method of claim 16 wherein in step a), said hardness ions are removed in amounts equal to or less than approximately 5% of the SiO₂ present within said source water.

20. The method of claim 14 wherein in step c), said pH is maintained at 9.6 or higher.

21. The method of claim 14 wherein in step a), said hardness ions are removed via a method selected from the group consisting of ion exchange, selective ion removal with reverse osmosis, reverse osmosis, electro chemical removal, chemical precipitation, evaporation and distillation.

22. The method of claim 14 wherein in step c), said pH is increased by adding an alkali agent.

23. The method of claim 22 wherein said alkali agent comprises sodium hydroxide.

24. The method of claim 14 wherein in step c), said pH is elevated by evaporating a portion of said aqueous system water.

25. The method of claim 14 wherein in step c), said pH is elevated by distilling a portion of said aqueous system water.

26. The method of claim 14 wherein said metallic substrate is selected from the group consisting of carbon steel, copper, copper alloy and stainless steel alloy.

28. The method of claim 14 wherein prior to step a), said methods of the present invention comprises the step:

a) analyzing said source water to determine the concentration of SiO₂ present therein.

30. The method of claim 14 wherein in step b), said conductivity of said aqueous system water is controlled such that said aqueous system water possesses a conductivity from approximately 20,000 to 150,000 μ

mhos.