Water treatment process and water treatment system

• US 9,969,629 B2
• Filed: 03/30/2015
• Issued: 05/15/2018
• Est. Priority Date: 07/05/2013
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Heavy Industries Engineering, Ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Eda, Masayuki, Okino, Susumu, Yoshiyama, Ryuji, Sakurai, Hideaki, Ukai, Nobuyuki, Suzuki, Hideo, Nakashoji, Hiroshi, Yoshioka, Shigeru
• Primary Examiner(s): Perrin, Clare M
• Application Number:
  US14/672,996
• Publication Number:
  US 20150203381A1
• Time in Patent Office: 1,142 Days
• Field of Search: None
• CPC Class Codes: B01D 19/0005 with one or more auxiliary substances
• CPC Class Codes: B01D 2311/04 Specific process operations in the feed stream; Feed pretreatment
• CPC Class Codes: B01D 2311/12 Addition of chemical agents
• CPC Class Codes: B01D 2311/18 pH control
• CPC Class Codes: B01D 2311/2642 Aggregation, sedimentation, flocculation, precipitation or coagulation
• CPC Class Codes: B01D 2311/2649 Filtration
• CPC Class Codes: B01D 2311/2657 Deaeration
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 61/04 Feed pretreatment
• CPC Class Codes: B01D 61/42 Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: B01D 9/0036 Crystallisation on to a bed of product crystals; Seeding
• CPC Class Codes: C02F 1/04 by distillation or evaporation
• CPC Class Codes: C02F 1/20 by degassing, i.e. liberation of dissolved gases degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D
• 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 1/442 by nanofiltration
• CPC Class Codes: C02F 1/4691 Capacitive deionisation
• CPC Class Codes: C02F 1/4693 electrodialysis
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 1/5281 : Installations for water purification using chemical agents
• 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 2001/007 : Processes including a sedimentation step
• CPC Class Codes: C02F 2001/5218 : Crystallization
• CPC Class Codes: C02F 2101/10 : Inorganic compounds
• CPC Class Codes: C02F 2101/101 : Sulfur compounds
• CPC Class Codes: C02F 2103/023 : Water in cooling circuits
• CPC Class Codes: C02F 2209/06 : pH
• CPC Class Codes: C02F 5/10 : using organic substances
• CPC Class Codes: C02F 9/00 : Multistage treatment of water, waste water or sewage
• CPC Class Codes: Y02A 20/124 : Water desalination
• CPC Class Codes: Y02A 20/131 : Reverse-osmosis

Abstract

Provided are a water treatment system and a water treatment process, which are capable of reproducing water containing salts with high water recovery. A water treatment system 100 comprises a second demineralizing section 210a, 210b that separates water to be treated containing Ca ions, SO₄ ions and carbonate ions into concentrated water in which the Ca ions and the SO₄ ions are concentrated and treated water; a crystallizing section which is positioned on a downstream side of the second demineralizing section 210a, 210b and which includes a second crystallizing tank 221a, 221b that crystallizes gypsum from the concentrated water and a seed crystal supplying section that supplies seed crystals of gypsum to the second crystallizing tank 221a, 221b; and a separating section that is positioned on a downstream side of the crystallizing section and separates the gypsum from the concentrated water.

Claims

1. A water treatment process comprising:

a scale inhibitor supplying step of supplying a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca²⁺ ions SO₄²⁻

ions and carbonate ions;

a first pH adjusting step of adjusting the water to a pH which is 10 or more;

a demineralizing step of separating the water in which a pH is 10 or more into concentrated water in which the Ca²⁺ ions, the SO₄²⁻

ions, and the carbonate ions are concentrated and treated water after the first pH adjusting step;

a second pH adjusting step of adjusting the concentrated water to a pH which is 6 or less after the demineralizing step;

a crystallizing step of supplying seed crystals of gypsum to the concentrated water in which a pH is 6 or less containing the calcium scale inhibitor so that gypsum is crystallized from the concentrated water; and

a separating step of separating the gypsum from the concentrated water after the crystallizing step.

2. The water treatment process according to claim 1, wherein among the gypsum crystallized in the crystallizing step, gypsum having a predetermined size is recovered in the separating step.

3. The water treatment process according to claim 1, wherein the gypsum separated in the separating step is used as the seed crystals of gypsum.

4. The water treatment process according to claim 1,

wherein the separating step is carried out a plurality of times in sequence along a flow direction which is associated with a single crystallizing step,

wherein the size of the gypsum separated in a later separating step produces smaller gypsum particles than in the first of the plurality of separating steps, and

the gypsum separated in the later separating step is supplied into the concentrated water in the crystallizing step.

5. A water treatment system comprising:

a scale inhibitor supplying section that supplies a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca²⁺ ions SO₄²⁻

ions and carbonate ions;

a first pH adjusting section that supplies a pH adjuster to the water to adjust the pH of the water to 10 or more;

a demineralizing section that is positioned on a downstream side of the scale inhibitor supplying section and separates the water in which a pH is 10 or more into concentrated water in which the Ca²⁺ ions, the SO₄²⁻

ions and the carbonate ions are concentrated and treated water;

a second pH adjusting section that adjusts the pH of the concentrated water separated in the demineralizing section to 6 or less;

a crystallizing section which is positioned on a downstream side of the demineralizing section and which includes a crystallizing tank that crystallizes gypsum from the concentrated water in which a pH is 6 or less containing the calcium scale inhibitor and a seed crystal supplying section that supplies seed crystals of gypsum to the crystallizing tank; and

a separating section that is positioned on a downstream side of the crystallizing section and separates the gypsum from the concentrated water.

6. The water treatment system according to claim 5, wherein the separating section separates and recovers the gypsum having a predetermined size.

7. The water treatment system according to claim 5, wherein the gypsum separated in the separating section is used as the seed crystals of gypsum.

8. The water treatment system according to claim 5, wherein the separating section includes a plurality of classifiers in a flowing direction of the water associated with the crystallizing section,

wherein the size of the gypsum separated in a classifier positioned downstream from a first classifier of the plurality of classifiers is smaller than the gypsum separated in the first classifier, and

the gypsum separated in the classifier positioned downstream from the first classifier is supplied to the concentrated water in the crystallizing section.

9. A water treatment process comprising:

a first scale inhibitor supplying step of supplying a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca²⁺ ions, SO₄²⁻

ions, carbonate ions and silica;

a first pH adjusting step of adjusting the water to a pH of 10 or more at which the silica is soluble in the water;

a first demineralizing step of separating the water in which a pH is 10 or more into first concentrated water in which the Ca²⁺ ions, the SO₄²⁻

ions, the carbonate ions and the silica are concentrated and treated water after the first scale inhibitor supplying step and the first pH adjusting step;

a second pH adjusting step of adjusting the first concentrated water to a pH which is 6 or less after the first demineralizing step;

a first crystallizing step of supplying seed crystals of gypsum to the first concentrated water in which a pH is 6 or less containing the calcium scale inhibitor so that gypsum is crystallized from the first concentrated water; and

a first separating step of separating the gypsum from the first concentrated water after the first crystallizing step.

10. The water treatment process according to claim 9, comprising, after the first crystallizing step:

a second scale inhibitor supplying step of supplying the calcium scale inhibitor and a silica scale inhibitor which is a scale inhibitor for inhibiting the deposition of the silica to the water;

a second demineralizing step of separating the water into second concentrated water in which the Ca ions, the SO₄ ions, the carbonate ions and the silica are concentrated and treated water after the second scale inhibitor supplying step; and

a second crystallizing step of supplying seed crystals of gypsum to the second concentrated water so that gypsum is crystallized from the second concentrated water.

11. The water treatment process according to claim 10, comprising a second separating step of separating the gypsum from the second concentrated water after the second crystallizing step.

12. The water treatment process according to claim 11, wherein among the gypsum crystallized in the second crystallizing step, gypsum having a predetermined size is recovered in the second separating step.

13. The water treatment process according to claim 11, wherein the gypsum separated in the second separating step is used as the seed crystals of the gypsum.

14. The water treatment process according to claim 11,

wherein the second separating step is carried out a plurality of times in sequence along a flow direction which is associated with a single crystallizing step,

wherein the size of the gypsum separated in a later separating step produces smaller gypsum particles than in the first of the plurality of separating steps, and

the gypsum separated in the later separating step is supplied into the second concentrated water in the second crystallizing step.

15. The water treatment process according to claim 10, comprising a third pH adjusting step of adjusting the second concentrated water to a pH of 6 or less at which calcium carbonate is soluble,

wherein in the second crystallizing step, the gypsum separated in the first separating step is supplied into the second concentrated water after the adjustment of the pH in the third pH adjusting step.

16. The water treatment process according to claim 9, wherein among the gypsum crystallized in the first crystallizing step, gypsum having a predetermined size is recovered in the first separating step.

17. The water treatment process according to claim 9, wherein the gypsum separated in the first separating step is used as the seed crystals of the gypsum.

18. The water treatment process according to claim 9,

wherein the first separating step is carried out a plurality of times in sequence along a flow direction which is associated with a single crystallizing step,

wherein the size of the gypsum separated in a later separating step produces smaller gypsum particles than in the first of the plurality of separating steps, and

the gypsum separated in the later separating step is supplied into the first concentrated water in the first crystallizing step.

19. A water treatment system comprising:

a first scale inhibitor supplying section that supplies a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca²⁺ ions, SO₄²⁻

ions, carbonate ions and silica;

a first pH adjusting section that supplies a pH adjuster to the water to be treated to adjust the pH of the water to a pH of 10 or more at which the silica is soluble in the water;

a first demineralizing section that is positioned on a downstream side of the first scale inhibitor supplying section and the first pH adjusting section and separates the water into first concentrated water in which the Ca²⁺ ions, the SO₄²⁻

ions, the carbonate ions and the silica are concentrated and treated water;

a second pH adjusting section that adjusts the pH of the first concentrated water separated in the first demineralizing section to 6 or less;

a first crystallizing section which is positioned on a downstream side of the first demineralizing section and which includes a first crystallizing tank that crystallizes gypsum from the first concentrated water in which a pH is 6 or less containing the calcium scale inhibitor and a first seed crystal supplying section that supplies seed crystals of gypsum to the first crystallizing tank; and

a first separating section that is positioned on a downstream side of the first crystallizing section and separates the gypsum from the first concentrated water.

20. The water treatment system according to claim 19, comprising, on a downstream side of the water in the first crystallizing section:

a second scale inhibitor supplying section that supplies the calcium scale inhibitor and a silica scale inhibitor which is a scale inhibitor for inhibiting the deposition of silica to the water;

a second demineralizing section that is positioned on a downstream side of the second scale inhibitor supplying section and separates the water into second concentrated water in which the Ca²⁺ ions, the SO₄²⁻

ions, the carbonate ions and the silica are concentrated and treated water; and

a second crystallizing section which is positioned on a downstream side of the second demineralizing section and which includes a second crystallizing tank that crystallizes gypsum from the second concentrated water and a second seed crystal supplying section that supplies seed crystals of gypsum to the second crystallizing tank.

21. The water treatment system according to claim 20, comprising a second separating section that is positioned on a downstream side of the second crystallizing section and separates the gypsum from the second concentrated water.

22. The water treatment system according to claim 21, wherein the second separating section separates and recovers the gypsum having a predetermined size.

23. The water treatment system according to claim 21, wherein the gypsum separated in the second separating section is used as the seed crystals of gypsum.

24. The water treatment system according to claim 21,

wherein the second separating section includes a plurality of classifiers in a flowing direction of the water associated with the second crystallizing section,

wherein the size of the gypsum separated in a classifier positioned downstream from a first classifier of the plurality of classifiers is smaller than the gypsum separated in the first classifier, and

the gypsum separated in the classifier positioned downstream from the first classifier is supplied to the second concentrated water in the second crystallizing section.

25. The water treatment system according to claim 20, wherein the second pH adjusting section adjusts the second concentrated water to a pH of 6 or less at which calcium carbonate is soluble, and supplies the gypsum separated in the first separating section to the second crystallizing section.

26. The water treatment system according to claim 19, wherein the first separating section separates and recovers the gypsum having a predetermined size.

27. The water treatment system according to claim 19, wherein the gypsum separated in the first separating section is used as the seed crystals of gypsum.

28. The water treatment system according to claim 19, wherein the first separating section includes a plurality of classifiers in a flowing direction of the water associated with the first crystallizing section,

wherein the size of the gypsum separated in a classifier positioned downstream from a first classifier of the plurality of classifiers is smaller than the gypsum separated in the first classifier, and

the gypsum separated in the classifier positioned downstream from the first classifier is supplied to the first concentrated water in the first crystallizing section.