Water treatment process and water treatment system

Patent metadata

Field	Value
Publication number	US-10160671-B2
Application number	US-201514673483-A
Country	US
Kind code	B2
Filing date	Mar 30, 2015
Priority date	Jul 5, 2013
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

A water treatment system includes a first demineralizing section that separates water to be treated including Ca ions, SO4 ions, and carbonate ions into concentrated water and treated water; a crystallizing section including a first crystallizing tank 21 that crystallizes gypsum from the concentrated water and a first seed crystal supplying section 22 that supplies seed crystals of gypsum to the first crystallizing tank 21; a first pH measuring section 543 that measures the pH of the first concentrated water in the first crystallizing tank 21; and a first controlling section that reduces the amount of the seed crystals of the gypsum to be supplied when the measured pH falls within a pH range in which a scale inhibition function of the calcium scale inhibitor is reduced, and increases the amount of the seed crystals of the gypsum to be supplied when the measured pH is beyond the pH range.

First claim

The invention claimed is:

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 Ca 2+ ions, SO 4 2− ions, and carbonate ions;
a demineralizing step of separating the water fed from the scale inhibitor supplying step into concentrated water in which the Ca 2+ ions, the SO 4 2− ions, and the carbonate ions are concentrated and treated water after the scale inhibitor supplying step;
a crystallizing step of supplying seed crystals of gypsum to the concentrated water so that gypsum is crystallized from the concentrated water;
a pH measuring step of measuring the pH of the concentrated water in the crystallizing step; and
a supplied amount controlling step of reducing the amount of the seed crystals of gypsum to be supplied when the measured pH falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increasing the amount of the seed crystals of gypsum to be supplied when the measured pH is greater than the pH range.

2. The water treatment process according to claim 1 , comprising a separating step of separating the gypsum from the concentrated water after the crystallizing step, wherein the gypsum separated in the separating step is used as the seed crystals of gypsum.

3. The water treatment process according to claim 1 , comprising a concentration measuring step of measuring at least one of the concentration of the Ca 2+ ions and the concentration of sulfate ions in the concentrated water after the crystallizing step,
wherein the supplied amount controlling step controls the amount of the seed crystals of gypsum to be supplied according to at least one of the concentration of the Ca 2+ ions and the concentration of sulfate ions measured in the concentration measuring step.

4. 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 Ca 2+ ions, SO 4 2− ions, and carbonate ions;
a demineralizing section that is positioned on a downstream side of the scale inhibitor supplying section and separates the water fed from the scale inhibitor supplying step into concentrated water in which the Ca 2+ ions, the SO 4 2− ions, and the carbonate ions are concentrated and treated water;
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 and a seed crystal supplying section that supplies seed crystals of gypsum to the crystallizing tank;
a pH measuring section that measures the pH of the concentrated water in the crystallizing tank; and
a controlling section that reduces the amount of the seed crystals of gypsum to be supplied when the pH measured in the pH measuring section falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increases the amount of the seed crystals of gypsum to be supplied when the pH measured in the pH measuring section is greater than the pH range.

5. The water treatment system according to claim 4 , comprising, on a downstream side of the crystallizing section, a separating section that separates the gypsum from the concentrated water, wherein the gypsum separated in the separating section is used as the seed crystals of gypsum.

6. The water treatment system according to claim 4 , comprising, on a downstream side of the crystallizing section, a concentration measuring section that measures at least one of the concentration of the Ca 2+ ions and the concentration of sulfate ions in the concentrated water,
wherein the controlling section controls the amount of the seed crystals of gypsum to be supplied according to at least one of the concentration of the Ca 2+ ions and the concentration of sulfate ions measured in the concentration measuring section.

7. 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 Ca 2+ ions, SO 4 2− ions, carbonate ions and silica;
a first pH adjusting step of adjusting the water fed from the first scale inhibitor supplying step to a pH of 10 or more at which the silica is soluble in the water,
a first demineralizing step of separating the water fed from the first pH adjusting step into first concentrated water in which the Ca 2+ ions, the SO 4 2− 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 first crystallizing step of supplying seed crystals of gypsum to the first concentrated water so that gypsum is crystallized from the first concentrated water;
a first pH measuring step of measuring the pH of the first concentrated water in the first crystallizing step; and
a first supplied amount controlling step of reducing the amount of the seed crystals of gypsum to be supplied when the measured pH falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increasing the amount of the seed crystals of gypsum to be supplied when the measured pH is greater than the pH range.

8. The water treatment process according to claim 7 , 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 fed from the first crystallizing step;
a second demineralizing step of separating the water fed from the second scale inhibitor supplying step into second concentrated water in which the Ca 2+ ions, the SO 4 2− 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.

9. The water treatment process according to claim 8 , comprising:
a second pH measuring step of measuring the pH of the second concentrated water in the second crystallizing step; and
a second supplied amount controlling step of reducing the amount of the seed crystals of gypsum to be supplied when the measured pH falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increasing the amount of the seed crystals of gypsum to be supplied when the measured pH is greater than the pH range.

10. The water treatment process according to claim 9 , comprising a second separating step of separating the gypsum from the second concentrated water after the second crystallizing step, wherein the gypsum separated in the second separating step is used as the seed crystals of gypsum.

11. The water treatment process according to claim 9 , comprising a second concentration measuring step of measuring at least one of the concentration of the Ca 2+ ions and the concentration of sulfate ions in the second concentrated water after the second crystallizing step,
wherein the second supplied amount controlling step controls the amount of the seed crystals to be supplied according to at least one of the concentration of the Ca 2+ ions and the concentration of sulfate ions measured in the second concentra

Assignees

• Mitsubishi Heavy Ind Ltd
• Mitsubishi Heavy Ind Eng Ltd

Inventors

• Eda Masayuki
• Okino Susumu
• Yoshiyama Ryuji
• Sakurai Hideaki
• Ukai Nobuyuki
• Suzuki Hideo
• Nakashoji Hiroshi
• Yoshioka Shigeru

Classifications

• Y02A20/134

  Cross-Sectional Technologies · mapped topic

• C02F2101/10

  Inorganic compounds · CPC title

• B01D19/0005

  with one or more auxiliary substances · CPC title

• B01D2311/04

  Specific process operations in the feed stream; Feed pretreatment · CPC title

• B01D2311/2657

  Deaeration · CPC title