WO2015001889A1 - 水処理方法及び水処理システム - Google Patents
水処理方法及び水処理システム Download PDFInfo
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- WO2015001889A1 WO2015001889A1 PCT/JP2014/064519 JP2014064519W WO2015001889A1 WO 2015001889 A1 WO2015001889 A1 WO 2015001889A1 JP 2014064519 W JP2014064519 W JP 2014064519W WO 2015001889 A1 WO2015001889 A1 WO 2015001889A1
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- water
- gypsum
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 886
- 238000000034 method Methods 0.000 title claims abstract description 88
- 229910052602 gypsum Inorganic materials 0.000 claims abstract description 330
- 239000010440 gypsum Substances 0.000 claims abstract description 330
- 238000002425 crystallisation Methods 0.000 claims abstract description 326
- 230000008025 crystallization Effects 0.000 claims abstract description 326
- 239000002455 scale inhibitor Substances 0.000 claims abstract description 275
- 239000013078 crystal Substances 0.000 claims abstract description 250
- 229910001424 calcium ion Inorganic materials 0.000 claims abstract description 92
- 150000002500 ions Chemical class 0.000 claims abstract description 88
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 51
- 238000001139 pH measurement Methods 0.000 claims abstract description 36
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 237
- 238000011033 desalting Methods 0.000 claims description 192
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 160
- 238000001556 precipitation Methods 0.000 claims description 153
- 239000011575 calcium Substances 0.000 claims description 143
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 119
- 229910052791 calcium Inorganic materials 0.000 claims description 119
- 239000000377 silicon dioxide Substances 0.000 claims description 118
- 238000000926 separation method Methods 0.000 claims description 82
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 78
- 238000010979 pH adjustment Methods 0.000 claims description 61
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 38
- 230000008569 process Effects 0.000 claims description 35
- 238000005259 measurement Methods 0.000 claims description 32
- 230000002265 prevention Effects 0.000 claims description 22
- 239000003002 pH adjusting agent Substances 0.000 claims description 12
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- 238000010612 desalination reaction Methods 0.000 abstract description 26
- 238000011084 recovery Methods 0.000 abstract description 21
- 150000003839 salts Chemical class 0.000 abstract description 6
- 230000001939 inductive effect Effects 0.000 abstract 1
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- 239000011777 magnesium Substances 0.000 description 22
- 150000002736 metal compounds Chemical class 0.000 description 22
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 20
- 238000001223 reverse osmosis Methods 0.000 description 20
- 239000000126 substance Substances 0.000 description 18
- 239000002253 acid Substances 0.000 description 16
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 14
- 229910052749 magnesium Inorganic materials 0.000 description 14
- 239000002244 precipitate Substances 0.000 description 13
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 150000002681 magnesium compounds Chemical class 0.000 description 10
- 229910021645 metal ion Inorganic materials 0.000 description 10
- 239000003513 alkali Substances 0.000 description 9
- 238000001816 cooling Methods 0.000 description 9
- 239000011734 sodium Substances 0.000 description 9
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 8
- 235000011941 Tilia x europaea Nutrition 0.000 description 8
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- 239000003014 ion exchange membrane Substances 0.000 description 5
- 230000001172 regenerating effect Effects 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 229920006318 anionic polymer Polymers 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000012267 brine Substances 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 239000000498 cooling water Substances 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000007654 immersion Methods 0.000 description 4
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 4
- 239000000347 magnesium hydroxide Substances 0.000 description 4
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
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- 229940088417 precipitated calcium carbonate Drugs 0.000 description 4
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 4
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical compound OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
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- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
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- 150000001450 anions Chemical class 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
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- 238000007561 laser diffraction method Methods 0.000 description 2
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 2
- 239000000391 magnesium silicate Substances 0.000 description 2
- 229910052919 magnesium silicate Inorganic materials 0.000 description 2
- 235000019792 magnesium silicate Nutrition 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 238000004065 wastewater treatment Methods 0.000 description 2
- -1 Na + Chemical class 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 150000004645 aluminates Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 239000003112 inhibitor Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
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- 239000013049 sediment Substances 0.000 description 1
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- 229910002027 silica gel Inorganic materials 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- B01D61/025—Reverse osmosis; Hyperfiltration
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- C—CHEMISTRY; METALLURGY
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/06—Controlling or monitoring parameters in water treatment pH
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
- C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Definitions
- the present invention relates to a water treatment method and a water treatment system for regenerating treated water containing Ca ions (Ca 2+ ), sulfate ions (SO 4 2 ⁇ ), and carbonate ions.
- ⁇ Water containing a large amount of ions is released into the environment after being desalted.
- a reverse osmosis membrane device As a device for performing the desalting treatment, a reverse osmosis membrane device, a nanofiltration membrane device, an ion exchange device, and the like are known.
- monovalent cations such as Na + , K + and NH 4 + and anions such as Cl ⁇ and NO 3 ⁇ are ions having high solubility in water.
- divalent metal ions such as Ca 2+ and anions such as SO 4 2 ⁇ and CO 3 2 ⁇ are components constituting the scale. Since the salt of the component constituting the scale has low solubility in water, it tends to precipitate as a scale.
- the brine, industrial wastewater, and cooling tower blowdown water described above are rich in Ca 2+ , SO 4 2 ⁇ , and carbonate ions (CO 3 2 ⁇ , HCO 3 ⁇ ).
- the pH is 8, Na ion is 20 mg / L, K ion is 5 mg / L, Ca ion is 50 mg / L, Mg ion is 15 mg / L, HCO 3 ion is 200 mg / L, and Cl ion is 200 mg. / L, SO 4 ion is 120 mg / L, and PO 4 ion is 5 mg / L.
- Ca ion, Mg ion, SO 4 ion, and HCO 3 ion concentration are high, and scale (CaSO 4 , CaCO 3, etc.) is generated by reaction of these. When scale is generated in the apparatus for performing the desalting process, the processing capacity is reduced. For this reason, it is calculated
- a plant using a water-cooled cooling tower for example, power generation equipment (for power sales use, industrial power generation equipment using on-site power, power generation is thermal power, geothermal, etc.), power generation equipment And plants with cooling facilities.
- the plant include a general chemical plant, steel plant, mining plant, oil field plant, gas field plant, and mechanical plant.
- the lime soda method is known as a method for removing Ca ions.
- sodium carbonate is added to the water to be treated, and Ca ions in the water to be treated are precipitated and precipitated as calcium carbonate to be removed from the water.
- Patent Document 1 discloses a wastewater treatment apparatus in which a chemical softening apparatus, an ion exchange apparatus, a reverse osmosis membrane apparatus and the like using a lime soda method are combined.
- the lime soda method has a high processing cost because it is necessary to add sodium carbonate for the processing.
- the lime soda method when 1 mol of Ca ions is precipitated as calcium carbonate, 2 mol of Na + is generated.
- SO 4 2- is contained in the water to be treated, it is not removed by the lime soda method. That is, in the lime soda method, the number of moles of ions contained in the treated water increases.
- the system of patent document 1 performs the process which further removes an ion component by the reverse osmosis membrane apparatus after the water processed by the lime soda method and the ion exchange apparatus. For this reason, in the system of Patent Document 1, since the number of moles of ions is increased, there is a problem that the osmotic pressure in the reverse osmosis membrane device is increased and the processing load is increased. Further, in the apparatus of Patent Document 1, SO 4 2 ⁇ is not removed, and SO 4 2 ⁇ remains in the treated water, and it is difficult to obtain a high water recovery rate. Moreover, in the wastewater treatment apparatus of Patent Document 1, a large amount of chemicals is required to regenerate the ion exchange apparatus, and the treatment cost is high.
- An object of the present invention is to provide a water treatment method and a water treatment system capable of regenerating salt-containing water with a high water recovery rate.
- the first aspect of the present invention is a scale inhibitor supply step in which a calcium scale inhibitor that prevents precipitation of scales containing calcium is supplied to water to be treated containing Ca ions, SO 4 ions, and carbonate ions.
- the desalting step in which, after the scale inhibitor supply step, the water to be treated is separated into the concentrated water enriched with the Ca ions, the SO 4 ions, and the carbonate ions and the treated water, and the concentration A seed crystal of gypsum is supplied to water, and a crystallization step in which gypsum crystallizes from the concentrated water, a pH measurement step in which the pH of the concentrated water in the crystallization step is measured, and the measured pH is When it is in a pH range where the scale prevention function of the calcium scale inhibitor is reduced, the supply amount of the seed crystals of the gypsum is reduced, and when the measured pH is higher than the pH range, Increasing the supply amount of the seed crystals of the plaster is a water treatment method and a supply amount control process.
- a second aspect of the present invention is a scale inhibitor supply unit that supplies a calcium scale inhibitor that prevents precipitation of scale containing calcium to water to be treated containing Ca ions, SO 4 ions, and carbonate ions
- a desalting unit that is installed on the downstream side of the scale inhibitor supply unit and separates the water to be treated into concentrated water and treated water in which the Ca ions, SO 4 ions, and carbonate ions are concentrated; and
- a crystallization part provided on the downstream side of the desalting part and having a crystallization tank for crystallizing gypsum from the concentrated water, a seed crystal supply part for supplying a seed crystal of gypsum to the crystallization tank, and the crystal PH measurement unit for measuring the pH of the concentrated water in the analysis tank, and when the pH measured by the pH measurement unit is in a pH range in which the scale prevention function of the calcium scale inhibitor is reduced, Seed crystal supply The reduced, wherein, when pH measurement pH measured by the unit is higher than the pH range, a water treatment system comprising
- production in a desalination part and a desalting process can be prevented by the effect of a calcium scale inhibitor.
- the gypsum can be crystallized and separated from the water to be treated even if a scale inhibitor is present.
- the water to be treated containing Ca ions and SO 4 ions can be treated with a high water recovery rate, and the operating cost can be reduced.
- there is an effect that high-purity gypsum can be recovered.
- the gypsum seed crystals are efficiently supplied, the amount of gypsum seed crystals used can be reduced.
- a calcium scale inhibitor which is a scale inhibitor that prevents precipitation of scales containing calcium, is supplied to water to be treated containing Ca ions, SO 4 ions, carbonate ions, and silica.
- a first desalting step in which, after the adjustment step, the water to be treated is separated into a first concentrated water and treated water in which the Ca ions, the SO 4 ions, the carbonate ions, and the silica are concentrated;
- a first crystallization step in which gypsum seed crystals are supplied to the first concentrated water and the gypsum crystallizes from the first concentrated water, and the pH of the first concentrated water in the first crystallization step is measured.
- First pH measurement step When the measured pH is in a pH range in which the scale prevention function of the calcium scale inhibitor is reduced, the supply amount of the seed crystal of the gypsum is reduced, and the measured pH is lower than the pH range.
- a first supply amount control step of increasing the supply amount of the gypsum seed crystal when the amount is high.
- a fourth aspect of the present invention provides Ca ions, SO 4 ion, water to be treated containing carbonate ion and silica, calcium scale inhibitor is a scale inhibitor to prevent the precipitation of scale including calcium
- the first concentrated water which is installed on the downstream side of the first scale inhibitor supply unit and the first pH adjusting unit and in which the water to be treated is enriched with the Ca ions, the SO 4 ions, the carbonate ions and the silica.
- a first crystallization tank for separating gypsum from the first concentrated water and a first crystallization tank provided on the downstream side of the first desalting section.
- Supplying gypsum seed crystals to the tank The first crystallization part having a seed crystal supply part, the first pH measurement part for measuring the pH of the first concentrated water in the first crystallization tank, and the pH measured by the first pH measurement part are When the scale prevention function of the calcium scale inhibitor is in a pH range where the gypsum seed crystal supply amount is reduced and the pH measured by the first pH measurement unit is higher than the pH range.
- a first control unit that increases the supply amount of the seed crystal of the gypsum.
- the first desalting part and the first desalting part are performed. Scale generation in the salt process can be prevented. Further, by adding a gypsum seed crystal to the first concentrated water in the first crystallization part and the first crystallization step, the gypsum is crystallized and separated from the water to be treated even if a scale inhibitor is present. be able to. As a result, the water to be treated containing Ca ions, SO 4 ions, carbonate ions and silica can be treated with a high water recovery rate while preventing the generation of scale. In addition, the amount of chemicals required for processing and the power required for operation can be reduced, and maintenance can be facilitated, so that the operating cost can be reduced.
- a calcium scale inhibitor which is a scale inhibitor that prevents precipitation of scales containing calcium with respect to water to be treated containing Ca ions, SO 4 ions, carbonate ions, and silica;
- the water to be treated is the Ca ions
- a second desalting step in which the SO 4 ion, the carbonate ion and the silica are concentrated into a second concentrated water and a treated water; and a gypsum seed crystal is supplied to the second concentrated water
- a second crystallization step in which gypsum crystallizes from the second concentrated water, a second pH measurement step in which the pH of the second concentrated water in the second crystallization step is measured, and the measured pH is the calcium scale.
- the amount of the gypsum seed crystal is reduced when the scale preventing function of the inhibitor is reduced, and the gypsum seed crystal is reduced when the measured pH is higher than the pH range.
- a water treatment method including a second supply amount control step of increasing the supply amount.
- a calcium scale inhibitor that is a scale inhibitor that prevents precipitation of scale containing calcium with respect to water to be treated containing Ca ions, SO 4 ions, carbonate ions, and silica.
- a second scale inhibitor supply unit for supplying a silica scale inhibitor, which is a scale inhibitor for preventing precipitation, and a downstream side of the second scale inhibitor supply unit, the treated water being the Ca ions,
- a second desalting unit that separates the SO 4 ion and the silica-concentrated second concentrated water and treated water; and a downstream side of the second desalting unit, and gypsum from the second concentrated water.
- a second crystallization section having a second crystallization tank for crystallization, a second seed crystal supply section for supplying a seed crystal of gypsum to the second crystallization tank, and the second crystallization tank in the second crystallization tank.
- production in a 2nd desalting part and a 2nd desalting process can be prevented by the effect of a calcium scale inhibitor and a silica scale inhibitor.
- the gypsum seed crystal is added to the first concentrated water in the first crystallization part and the first crystallization step, the gypsum is crystallized and separated from the water to be treated even if a scale inhibitor is present. be able to.
- the water to be treated containing Ca ions, SO 4 ions and silica can be treated with a high water recovery rate, and the operating cost can be reduced. Furthermore, there is an effect that high-purity gypsum can be recovered.
- water treatment is carried out by combining the water treatment methods of the third and fifth aspects and the water treatment system of the fourth and sixth aspects in the direction of water to be treated. be able to.
- a second pH measurement step of measuring the pH of the second concentrated water in the second crystallization step, and the measured pH is within a pH range in which the scale prevention function of the calcium scale inhibitor is reduced.
- the gypsum separated in the first separation step is used as a seed crystal of the gypsum. It is preferable that the gypsum separated in the second separation step is used as a seed crystal of the gypsum.
- the first supply amount control step It is preferable to control the supply amount of the seed crystal of the gypsum according to at least one of the Ca ion concentration and the sulfate ion concentration measured in the first concentration measurement step.
- the method includes a second concentration measurement step for measuring at least one of the Ca ion concentration and the sulfate ion concentration in the second concentrated water, and the second supply amount control step includes the second crystallization step. It is preferable to control the supply amount of the seed crystal according to at least one of the Ca ion concentration and the sulfate ion concentration measured in the two concentration measurement step.
- the second pH measuring unit that measures the pH of the second concentrated water in the second crystallization tank, and the pH measured by the second pH measuring unit reduces the scale preventing function of the calcium scale inhibitor.
- the amount of gypsum seed crystals supplied is reduced, and when the pH measured by the first pH measurement unit is higher than the pH range, the amount of gypsum seed crystals supplied is reduced. It is preferable that the 2nd control part to increase is included.
- the gypsum separated in the first separation part is used as a seed crystal of the gypsum. It is preferable that the gypsum separated in the second separation part is used as a seed crystal of the gypsum.
- a first concentration measurement unit that measures at least one of the Ca ion concentration and the sulfate ion concentration in the first concentrated water is provided downstream of the first crystallization unit, and the first control unit includes: It is preferable to control the supply amount of the seed crystal of the gypsum according to at least one of the Ca ion concentration and the sulfate ion concentration measured by the first concentration measuring unit.
- a second concentration measurement unit that measures at least one of the Ca ion concentration and the sulfate ion concentration in the second concentrated water is provided downstream of the second crystallization unit, and the second control unit includes the second crystallization unit. It is preferable to control the supply amount of the seed crystal of the gypsum according to at least one of the Ca ion concentration and the sulfate ion concentration measured by the two concentration measuring unit.
- the amount of gypsum seed crystals used can be reduced.
- the second concentrated water includes a third pH adjustment step in which calcium carbonate is adjusted to a pH at which calcium carbonate can be dissolved, and the gypsum separated in the first separation step is the second crystallization step. It is preferable that the second concentrated water whose pH is adjusted in the third pH adjusting step is supplied.
- the second pH adjusting unit adjusts the second concentrated water to a pH at which calcium carbonate can be dissolved, and supplies the gypsum separated by the first separating unit to the second crystallization unit. It is preferable.
- high-purity gypsum can be recovered in the course of water treatment.
- Ca 2+ and SO 4 2 ⁇ can be removed from the water to be treated as gypsum while preventing the generation of scale such as calcium carbonate during the treatment.
- the rate can be increased.
- the present invention also has an effect that high-purity gypsum can be crystallized and recovered.
- the water to be treated (treated water) of the present invention contains Ca 2+ , SO 4 2 ⁇ , carbonate ions and silica.
- water to be treated is brine, sewage, factory wastewater, cooling tower blowdown water, and the like.
- the treated water may contain metal ions such as Mg ions.
- FIG. 1 is a schematic view of a water treatment system according to a first reference embodiment of the present invention.
- the water treatment system 1 of FIG. 1 has a configuration in which two water treatment units are connected in the flow direction of the water to be treated.
- the number of water treatment units may be one or three or more water treatment units may be connected depending on the properties of the water to be treated.
- Each water treatment unit includes a first desalting unit 10 (10a, 10b) and a first crystallization unit 20 (20a, 20b) in order from the upstream side of the water to be treated.
- the concentration side of the first desalting units 10a and 10b and the first crystallization units 20a and 20b are connected.
- a water treatment part is equipped with the 1st scale inhibitor supply part 30 (30a, 30b) and the 1st pH adjustment part 40 (40a, 40b) in the upstream flow path of each 1st desalination part 10 (10a, 10b). .
- the first scale inhibitor supply unit 30 (30a, 30b) includes a tank 31 (31a, 31b), a valve V1 (V1a, V1b), and a control unit 32 (32a, 32b).
- the control units 32a and 32b are connected to valves V1a and V1b, respectively.
- a scale inhibitor is stored in the tanks 31a and 31b.
- the scale inhibitor used in the present reference embodiment prevents the scale containing calcium from precipitating in the water to be treated.
- calcium scale inhibitor suppresses the formation of gypsum or calcium carbonate crystal nuclei in the water to be treated, and the gypsum or calcium carbonate crystal nuclei contained in the water to be treated (small-scale scales deposited beyond the seed crystals and saturation concentration). Etc.) and has a function of suppressing crystal growth of gypsum or calcium carbonate.
- some calcium scale inhibitors have a function of dispersing (preventing aggregation) particles in the water to be treated such as precipitated crystals.
- Examples of calcium scale inhibitors include phosphonic acid scale inhibitors, polycarboxylic acid scale inhibitors, and mixtures thereof.
- a specific example is FLOCON260 (trade name, manufactured by BWA).
- magnesium scale inhibitor When Mg ion is contained in the water to be treated, a scale inhibitor that prevents the scale containing magnesium (for example, magnesium hydroxide) from being precipitated in the water to be treated can be used. Hereinafter, it is referred to as “magnesium scale inhibitor”.
- magnesium scale inhibitors include polycarboxylic acid scale inhibitors. A specific example is FLOCON 295N (trade name, manufactured by BWA).
- first scale inhibitor supply unit 30a, 30b is shown at each position.
- first scale inhibitor supply units 30a, 30b are installed. It is preferable. In this case, the scale inhibitor is stored separately for each type in each tank.
- the first pH adjusting unit 40 (40a, 40b) includes a tank 41 (41a, 41b), a valve V2 (V2a, V2b), a control unit 42 (42a, 42b), and a pH meter 43 (43a, 43b). ing.
- alkali is stored as a pH adjuster.
- the alkali is, for example, calcium hydroxide or sodium hydroxide.
- calcium hydroxide is preferable because Ca ions are collected as gypsum in the crystallization step described later, and the amount of ions reaching the downstream desalting portion is reduced.
- the controllers 42a and 42b are connected to valves V2a and V2b and pH meters 43a and 43b, respectively.
- the first desalting units 10a and 10b are reverse osmosis membrane devices.
- the first desalting units 10a and 10b include an electrodialyzer (ED), a polarity-changing electrodialyzer (EDR), an electroregenerative pure water device (EDI), an ion exchange device (IEx), an electrostatic device.
- ED electrodialyzer
- EDR polarity-changing electrodialyzer
- EDI electroregenerative pure water device
- IEx ion exchange device
- electrostatic device an electrostatic device.
- a desalting apparatus (CDI), a nano filter (NF), an evaporator, or the like can be employed.
- NF nano filter
- ED electrodialyzer
- EDR polarity switching electrodialyzer
- EDI electric regenerative pure water device
- CDl electrostatic desalting device
- the scale component (2 Valent ions such as Ca 2+ and Mg 2+ are selectively removed, and monovalent ions such as Na + and Cl ⁇ are permeated. If these desalting apparatuses are used, the concentration of ions, which are scale components in the concentrated water, is suppressed from being concentrated, so that it is possible to improve the water recovery rate and save energy (for example, reduce pump power).
- the reclaimed water does not need to be pure water, and scale components (divalent ions, Ca 2+ , Mg 2+, etc.) need only be removed.
- scale components divalent ions, Ca 2+ , Mg 2+, etc.
- FIG. 1 shows only one first desalting unit 10a, 10b, but a plurality of desalting apparatuses may be connected in parallel or in series in the flow direction of the water to be treated.
- the first crystallization unit 20 (20a, 20b) includes a first crystallization tank 21 (21a, 21b) and a first seed crystal supply unit 22 (22a, 22b).
- the first seed crystal supply units 22a and 22b are connected to the first crystallization tanks 21a and 21b, respectively.
- the first seed crystal supply units 22a and 22b include a seed crystal tank 23 (23a and 23b), a valve V3 (V3a and V3b), and a control unit 24 (24a and 24b).
- the control units 24a and 24b are connected to valves V3a and V3b, respectively.
- the seed crystal tanks 23a and 23b store gypsum particles as seed crystals.
- the 1st precipitation part 50 (50a, 50b) may be installed in the downstream of each of the 1st crystallization part 20a, 20b.
- Each of the first precipitation units 50a and 50b includes a first precipitation tank 51 (51a and 51b) and a first filtration device 52 (52a and 52b).
- the water treatment system 1 includes a downstream desalting unit 60 on the downstream side of the water to be treated of the first crystallization unit 20b located on the most downstream side.
- the downstream desalting unit 60 is a reverse osmosis membrane device.
- the downstream desalting unit 60 includes an electrodialyzer (ED), a polarity-changing electrodialyzer (EDR), an electric regeneration pure water device (EDI), an ion exchange device, an electrostatic desalting device (CDI), and a nano filter. (NF), an evaporator or the like can be employed.
- a precipitation tank 71 and a filtration device 72 are installed as a first upstream precipitation unit 70 upstream of the first scale inhibitor supply unit 30 a and the first pH adjustment unit 40 a located at the most upstream of the water to be treated. Is done.
- the settling tank 71 and the filtration device 72 have the same configuration as the first settling tank 51 and the first filtration device 52 of the first settling unit 50.
- the first upstream sedimentation section can adopt a configuration in which a plurality of sedimentation tanks 71 are connected in series in the flow direction of the water to be treated.
- a first deaeration unit 73 may be provided on the upstream side of the first upstream sedimentation unit 70.
- the 1st deaeration part 73 is a deaeration tower provided with the filler which removes a carbon dioxide, or a separation membrane.
- a pH adjustment unit (not shown) that adjusts the water to be treated to a pH at which carbonate ions exist in the state of CO 2 may be installed on the upstream side of the water to be treated of the first degassing unit 73.
- the 1st deaeration part 73 may be installed in the to-be-processed water downstream of the 1st upstream sedimentation part 70, and the upstream of the 1st scale inhibitor supply part 30a and the 1st pH adjustment part 40a.
- the deaeration part having the same configuration as the first deaeration part 73 is a flow path between the first demineralization part 10 and the first crystallization part 20, and between the first crystallization part 20 and the first precipitation part 50. You may install in the flow path and the flow path between the 1st desalination part 10b or the downstream desalination part 60 in the downstream of the 1st sedimentation part 50.
- FIG. 1st desalination part 10b or the downstream desalination part 60 in the downstream of the 1st sedimentation part 50.
- an ion exchange device (not shown) is provided downstream of the filtration device 72 and upstream of the first scale inhibitor supply unit 30a and the first pH adjustment unit 40a located at the most upstream. May be installed.
- the ion exchange device is, for example, an ion exchange resin tower or an ion exchange membrane device.
- the gypsum in the for-treatment water flowing into the first desalting unit 10a is already supersaturated, the ions are further concentrated in the first desalting unit 10a, so that the gypsum concentration is further increased.
- a large amount of calcium scale inhibitor needs to be added, and the gypsum concentration becomes higher than the calcium scale inhibitor exhibits its effect, and scale may be generated in the first desalting unit 10a. Therefore, when the gypsum in the raw water (treated water) is supersaturated, the above-described first crystallization tanks 21a and 21b are disposed upstream of the most upstream first scale inhibitor supply unit 30a and the first pH adjustment unit 40a.
- An upstream crystallization part (not shown) having the same configuration as that described above may be provided, and the water to be treated may be supplied to the first desalting part 10a after reducing the gypsum concentration.
- FIG. 2 is a simulation result of the pH dependence of the amount of gypsum deposited.
- FIG. 3 is a simulation result of the pH dependency of the precipitated amount of calcium carbonate.
- the horizontal axis represents pH
- the vertical axis represents the amount of precipitation (mol) of gypsum or calcium carbonate, respectively.
- the simulation was performed using simulation software manufactured by OLI under the condition that 0.1 mol / L of each solid component was mixed in water and H 2 SO 4 as an acid and Ca (OH) 2 as an alkali were added.
- FIG. 4 is a graph showing the pH dependency of silica dissolution (source: FIG. 4 of US Pat. No. 7,815,804).
- the horizontal axis represents pH
- the vertical axis represents the amount of silica dissolved (mg / L).
- ⁇ Pretreatment> When the water to be treated is industrial waste water or the like, before the water to be treated flows into the first upstream sedimentation section 70, a process of removing oil or suspended particles in the water to be treated, biological treatment or chemical oxidation treatment The step of removing organic substances is performed by the above.
- Second degassing step> In the water treatment system 1 of FIG. 1, the water to be treated before flowing into the first degassing unit 73 is adjusted to a low pH. Carbonic acid in the water to be treated is in the following equilibrium state depending on the pH of the water to be treated. When the pH is as low as 6.5 or less, it exists mainly in the state of HCO 3 ⁇ and CO 2 in the treated water.
- the water to be treated containing CO 2 flows into the first deaeration unit 73.
- CO 2 is removed from the water to be treated in the first deaeration unit 73.
- carbonate ions if it is adjusted water to be treated pH present as CO 2, can be efficiently removed carbon dioxide.
- the treated water in which the carbonate ion concentration has been reduced by the first degassing step is fed to the first upstream sedimentation unit 70.
- Second upstream precipitation step> In the 1st upstream sedimentation part 70, Ca ion and carbonate ion are partially removed from to-be-processed water beforehand as calcium carbonate.
- the metal ions are roughly removed from the water to be treated in advance as a metal compound having low solubility in water in the first upstream precipitation unit 70.
- This metal compound is mainly a metal hydroxide, but may also contain carbonates.
- the settling tank 71 Ca (OH) 2 and an anionic polymer (Mitsubishi Heavy Industries Mechatronics Systems Co., Ltd., trade name: Hishiflock H305) are introduced into the water to be treated, and the pH in the settling tank 71 is 4 to 12, preferably Is controlled to be 8.5 or more and 12 or less.
- Ca (OH) 2 and an anionic polymer Mitsubishi Heavy Industries Mechatronics Systems Co., Ltd., trade name: Hishiflock H305
- the solubility of calcium carbonate is low in this pH region.
- calcium carbonate becomes supersaturated calcium carbonate is deposited and settles at the bottom of the settling tank 71.
- the solubility of the metal compound depends on the pH.
- the solubility of metal ions in water increases with acidity. In the above pH range, the solubility of many metal compounds is low.
- the metal compound having low solubility in water aggregates in the precipitation tank 71 and precipitates at the bottom of the precipitation tank 71. The precipitated calcium carbonate and metal compound are discharged from the bottom of the precipitation tank 71.
- Mg ions form a salt that is hardly soluble in water, it is a component that tends to precipitate as scale. Mg (OH) 2 precipitates at pH 10 or higher.
- the pH of the water to be treated in the precipitation tank 71 is adjusted to a pH at which a magnesium compound (mainly magnesium hydroxide) is precipitated.
- the pH of the water to be treated is adjusted to 10 or more, preferably pH 10.5 or more, more preferably pH 11 or more. By doing so, the magnesium compound is precipitated from the water to be treated and is precipitated and removed at the bottom of the precipitation tank 71.
- the water to be treated after being discharged from the first upstream sedimentation section 70 is preferably adjusted to a pH at which the magnesium compound can be dissolved. Specifically, the pH is adjusted to less than 10. By doing so, it is possible to prevent scale generation in the downstream apparatus and process, particularly in the first desalting unit 10a and the first desalting process.
- Mg ions in the for-treatment water can be surely removed, and the Mg ion concentration in the for-treatment water fed downstream can be reduced.
- the supernatant liquid in the settling tank 71 which is the water to be treated is discharged from the settling tank 71.
- FeCl 3 is added to the discharged water to be treated, and solids such as calcium carbonate and metal compounds in the supernatant liquid aggregate with Fe (OH) 3 .
- the treated water is supplied to the filtration device 72.
- the solid content aggregated by Fe (OH) 3 is removed by the filtration device 72.
- the pH of the water to be treated is adjusted to a pH at which carbonate ions can exist as CO 2 , specifically 6.5 or lower. .
- the first degassing step and the first upstream precipitation step may be omitted depending on the properties of the water to be treated.
- gypsum seed crystals are introduced into the water to be treated in the upstream crystallization section installed immediately after the filtration device 72, and the gypsum crystallizes to increase the gypsum concentration in the water to be treated.
- Reduce Water to be treated with a reduced gypsum concentration is fed to the first desalting unit 10a.
- the control unit 32a of the first scale inhibitor supply unit 30a opens the valve V1a and supplies a predetermined amount of calcium scale inhibitor from the tank 31a to the water to be treated.
- the control unit 32a adjusts the opening of the valve V1a so that the concentration of the calcium scale inhibitor becomes a predetermined value set according to the properties of the water to be treated.
- the magnesium scale inhibitor is supplied to the water to be treated by the same method as described above in the first scale inhibitor supply step.
- the calcium scale inhibitor and the magnesium scale inhibitor are respectively stored in the tanks of the plurality of first scale inhibitor supply units, and each control unit adjusts the supply amounts of the calcium scale inhibitor and the magnesium scale inhibitor.
- the control unit 42a of the first pH adjusting unit 40a manages the pH of the water to be treated at the inlet of the first desalting unit 10a to a value at which silica can be dissolved in the water to be treated. Specifically, the pH of the water to be treated fed to the first desalting unit 10a is adjusted to 10 or more, preferably 10.5 or more, more preferably 11 or more.
- the pH meter 43a measures the pH of the water to be treated at the inlet of the first desalting unit 10a.
- the controller 42a adjusts the opening of the valve V2a so that the measured value of the pH meter 43a becomes a predetermined pH control value, and causes alkali to be introduced from the tank 41a into the water to be treated.
- the to-be-processed water in which pH was adjusted is processed.
- the 1st desalination part 10a is a reverse osmosis membrane apparatus
- the water which passed the reverse osmosis membrane is collect
- other desalting apparatuses such as an electrostatic desalting apparatus are used, the water to be treated is separated into treated water and concentrated water (first concentrated water) having a high ion concentration.
- silica is contained in the first concentrated water in a state of being dissolved in the water to be treated as shown in FIG. Even when the gypsum and calcium carbonate in the first concentrated water are concentrated to a saturation concentration or more, the scale generation is suppressed by the calcium scale inhibitor.
- Mg ion is contained in the water to be treated, the concentration of Mg ions contained in the first concentrated water is increased by the first desalting step. However, the generation of scales containing magnesium is suppressed by the magnesium scale inhibitor.
- the first concentrated water is fed toward the first crystallization part 20a.
- the first concentrated water discharged from the first desalting unit 10a is stored in the first crystallization tank 21a of the first crystallization unit 20a.
- the control unit 24a of the first seed crystal supply unit 22a opens the valve V3a and adds the gypsum seed crystal from the tank 23a to the first concentrated water in the first crystallization tank 21a.
- the first concentrated water from the first desalting unit 10a has a pH of 10 or more. As described above, gypsum is in a dissolved state in water in a high pH region where a calcium scale inhibitor is present. However, if the seed crystal is sufficiently present, gypsum crystallizes with the seed crystal as a nucleus even if the scale inhibitor is present.
- gypsum having a large diameter for example, a particle diameter of 10 ⁇ m or more, more preferably 20 ⁇ m or more
- the precipitated gypsum is discharged from the bottom of the first crystallization tank 21a.
- the silica exists in a dissolved state in the first concentrated water in the first crystallization tank 21a. Even when the silica concentration in the first concentrated water exceeds the saturation solubility, there is no silica seed crystal, so that it precipitates as a small floating substance such as a colloid and is not easily precipitated. According to FIG. 3, calcium carbonate tends to precipitate at pH 10 or higher. However, since the calcium scale inhibitor is added, the precipitation of calcium carbonate is suppressed in the first crystallization tank 21a. Moreover, when providing a 1st upstream sedimentation part and a 1st deaeration part, the density
- FIG. 5 shows that when the scale inhibitor (FLOCON260) is added to simulated water (including Ca 2+ , SO 4 2 ⁇ , Na + , Cl ⁇ ) in which the gypsum is supersaturated, the pH of the simulated water is changed. It is the result of conducting a gypsum precipitation experiment.
- the experimental conditions are as follows.
- Simulated water gypsum supersaturation (25 ° C): 460%, Scale inhibitor addition amount: 2.1 mg / L, pH: 6.5 (condition 1), 5.5 (condition 2), 4.0 (condition 3), 3.0 (condition 4), Seed crystal addition amount: 0 g / L.
- the Ca concentration in the simulated water treated under each condition was measured using an atomic absorption analyzer (manufactured by Shimadzu Corporation, AA-7000). As shown in FIG. In the figure, the vertical axis represents the degree of supersaturation (%).
- the crystallization rate increases as the pH is lowered even under conditions where there is no seed crystal. From this, when seed crystals exist, gypsum crystallizes under condition 1 (pH 6.5), and the relationship between the crystallization speeds is that the lower the pH as shown in FIG. 5, the higher the crystallization speed. Understandable.
- the first crystallization step when the first crystallization step is performed under a low pH condition, the high-purity gypsum crystallizes due to the low content of calcium carbonate and silica, and is recovered from the bottom of the first crystallization tank 21a. It will be.
- an acid as a pH adjusting agent is added to the flow path between the first crystallization tank 21a or the first desalting unit 10a and the first crystallization tank 21a.
- a third pH adjusting unit (not shown) to be supplied is installed.
- the said pH adjustment part is the same structure as the 2nd pH adjustment part mentioned later.
- FIG. 6 shows the results of a gypsum precipitation experiment in which the amount of seed crystals added was changed when a calcium scale inhibitor (FLOCON 260) was added to simulated water.
- the experimental conditions in FIG. 5 were the same except that the pH was 4.0 and gypsum (CaSO 4 .2H 2 O) was added as a seed crystal in the following amounts.
- Seed crystal addition amount 0 g / L (condition 3), 3 g / L (condition 5), 6 g / L (condition 6), 3 g / L (condition 7).
- seed crystals and sulfuric acid for pH adjustment were added to the simulated water to which the scale inhibitor was added.
- condition 7 seed crystals previously immersed in the scale inhibitor were added to the simulated water to which the scale inhibitor was added, and sulfuric acid was added for pH adjustment.
- the Ca concentration in the simulated water treated under each condition was measured by the same method as in FIG. In FIG. 6, the vertical axis represents the degree of supersaturation (%).
- the supersaturation degree was 215% in condition 3 where no seed crystal was added, but the supersaturation degree was 199% (condition 5) and 176% (condition 6) as the seed crystal concentration increased. It can be understood that the gypsum deposition rate increases. Even under high pH conditions, the gypsum deposition rate tends to increase as the seed crystal input amount increases.
- Conditions 5 and 7 are the same test conditions except that a seed crystal not immersed in the scale inhibitor and a seed crystal immersed therein are used. The supersaturation degree was 199% even under condition 7 in which the scale inhibitor was previously attached to the seed crystal, and it was confirmed that gypsum of the same degree as that in condition 5 was precipitated. That is, from the results of Conditions 5 and 7, it was shown that the function of the scale inhibitor is reduced by lowering the pH to 4.0 regardless of the immersion time of the seed crystal in the calcium scale inhibitor.
- FIG. 7 and 8 are micrographs of gypsum obtained by crystallization.
- FIG. 7 shows the result of Condition 5 (with seed crystal addition)
- FIG. 8 shows the result of Condition 3 (without seed crystal addition).
- condition 5 gypsum larger than condition 3 was deposited.
- the larger the precipitated gypsum the lower the water content. If the moisture content is low, the gypsum is highly pure.
- the average particle size is 10 ⁇ m or more, preferably 20 ⁇ m or more, gypsum having a sufficiently reduced water content can be obtained.
- the “average particle diameter” in the present invention is a particle diameter measured by a method (laser diffraction method) defined in JIS Z 8825.
- First precipitation step The supernatant liquid (first concentrated water) of the first crystallization part 20a is fed to the first precipitation part 50a.
- Ca (OH) 2 and an anionic polymer (Hishiflock H305) are charged into the first concentrated water after the crystallization step, and the pH in the first precipitation tank 51a is 4 or more and 12 or less, preferably It is managed from 8.5 to 12 inclusive.
- the first precipitation tank 51a calcium carbonate and a metal compound are precipitated and removed from the first concentrated water. The precipitated calcium carbonate and the metal compound having low solubility in water are discharged from the bottom of the first precipitation tank 51a.
- Water to be treated which is a supernatant liquid in the first sedimentation tank 51a is discharged from the first sedimentation tank 51a.
- FeCl 3 is added to the discharged water to be treated, and solids such as calcium carbonate and metal compounds in the water to be treated aggregate with Fe (OH) 3 .
- the treated water is fed to the first filtration device 52a.
- the solid content aggregated by Fe (OH) 3 is removed by the first filtration device 52a.
- Silica in the supernatant of the first crystallization part 20a may be removed from the first concentrated water in the first precipitation step, or may be fed downstream without being removed. Whether or not silica is removed in the first precipitation step is determined according to the properties of the water to be treated and the first concentrated water.
- the first precipitation step is performed without supplying the silica seed crystal and the silica precipitant to the first precipitation tank 51a.
- the silica is separated from the treated water in the desalting unit (the first desalting unit 10b or the downstream desalting unit 60) located on the downstream side.
- a silica seed crystal and a silica precipitant is supplied from a supply unit (not shown) into the first concentrated water in the first precipitation unit 50a.
- the silica seed crystal is, for example, silica gel
- the silica precipitant is, for example, MgSO 4 or aluminate Na (Na [Al (OH) 4 ]).
- the first concentrated water in the first sedimentation tank 51a is preferably adjusted to pH 8 or more and 10 or less.
- silica seed crystal silica is crystallized using the seed crystal as a nucleus.
- MgSO 4 is used as a silica precipitant
- magnesium silicate is precipitated. Crystallized silica and magnesium silicate are precipitated at the bottom of the first precipitation tank 51a and discharged from the bottom of the first precipitation tank 51a.
- Mg ion When Mg ion is contained in the water to be treated, Mg ions and silica in the first concentrated water react and precipitate in the first precipitation step. Depending on the balance between the content of Mg ions in the first concentrated water in the first sedimentation tank 51a and the content of silica, the steps for removing silica and Mg ions are different.
- the first concentrated water in the first precipitation step has a Mg ion concentration lower than the silica content
- Mg ions are consumed for precipitation with silica.
- a silica precipitating agent MgSO 4
- the supply amount of the silica precipitating agent is supplied in accordance with the silica content and the Mg ion content in the first precipitation step as much as the excess silica is consumed.
- the first concentrated water in the first precipitation step has a high Mg ion concentration relative to the silica content, Mg ions remain as a result of precipitation of Mg ions and silica.
- the first concentrated water is discharged from the first sedimentation tank 51a in a state where the residual Mg ion concentration is high, in the case of the subsequent desalination part (in FIG. 1, the first desalination part 10b, the most downstream first precipitation part) May precipitate a scale containing Mg in the downstream desalting section 60). Therefore, the first concentrated water in the first precipitation tank 51a is adjusted to a value at which a magnesium compound (mainly magnesium hydroxide) can be precipitated.
- a magnesium compound mainly magnesium hydroxide
- a magnesium compound precipitates in the 1st sedimentation tank 51a, and Mg ion concentration of the 1st concentrated water in the 1st sedimentation tank 51a is reduced. Further, after the first precipitation step, the first concentrated water discharged from the first precipitation tank 51a is adjusted to a pH at which the magnesium compound can be dissolved. Specifically, the pH is less than 10. By carrying out like this, precipitation of the scale containing Mg in a desalting part can be suppressed.
- the first concentrated water that has passed through the first filtration device 52a of the first water treatment section at the front stage flows into the water treatment section at the rear stage as treated water.
- the first precipitation step is performed from the first scale inhibitor supply step described above.
- the concentrated water (first concentrated water) that has passed through the first precipitation unit 50 b located on the most downstream side of the water to be treated is supplied to the downstream desalting unit 60.
- the water that has passed through the downstream desalting unit 60 is recovered as treated water.
- the concentrated water in the downstream desalting unit 60 is discharged out of the system.
- ions are concentrated in the first desalting unit 10, but gypsum, calcium carbonate, silica, and the like are removed in the first crystallization unit and the first precipitation unit. .
- the number of moles of ions in the water flowing into the downstream desalting unit 60 is reduced as compared with that before the treatment.
- the osmotic pressure in the 1st desalination part 10b located downstream and the downstream desalination part 60 becomes low, and required motive power is reduced.
- An evaporator (not shown in FIG. 1) may be installed downstream of the downstream desalting unit 60 on the concentrated water side.
- water is evaporated from the concentrated water, and ions contained in the concentrated water are precipitated as a solid and recovered as a solid. Since water is collected on the upstream side of the evaporator and the amount of concentrated water is significantly reduced, the evaporator can be made smaller and the energy required for evaporation can be reduced.
- FIG. 9 is a schematic view of a water treatment system according to a second reference embodiment of the present invention.
- the same components as those in the first reference embodiment are denoted by the same reference numerals.
- the first separation unit 180 180a, 180b
- the water treatment system 100 of FIG. 9 has a configuration in which two water treatment units are connected in the flow direction of the water to be treated.
- the number of water treatment units may be one or three or more water treatment units may be connected according to the properties of the water to be treated.
- FIG. 9 the same components as those in the first reference embodiment are denoted by the same reference numerals.
- the first separation unit 180 180a, 180b
- the water treatment system 100 of FIG. 9 has a configuration in which two water treatment units are connected in the flow direction of the water to be treated.
- the number of water treatment units may be one or three or more water treatment units may be connected according to the properties of the water to be treated.
- the first separation unit 180 (180a, 180b) includes a classifier 181 (181a, 181b) and a dehydrator 182 (182a, 182b).
- the classifiers 181a and 181b are, for example, liquid cyclones.
- the dehydrators 182a and 182b are, for example, belt filters.
- only one classifier is installed in the first separation unit 180, but a plurality of classifiers may be connected in series in the flow direction of the water to be treated.
- the water to be treated is treated in the same process as in the first reference embodiment, except that the first separation process is performed immediately after the first crystallization process.
- the first concentrated water in the first crystallization tanks 21a and 21b is conveyed to the first separation units 180a and 180b.
- the 1st concentrated water conveyed here is water containing the solid substance which precipitated in the 1st crystallization tank 21a, 21b.
- the first concentrated water discharged from the first crystallization tanks 21a and 21b contains calcium carbonate and silica that have precipitated because the concentration exceeds the saturation concentration, in addition to gypsum having various particle sizes. Since calcium carbonate and silica are not precipitated in the presence of seed crystals, they are small-diameter or colloidal floating substances.
- gypsum having a predetermined size for example, an average particle size of 10 ⁇ m or more settles at the bottom of the classifiers 181a and 181b, and gypsum, calcium carbonate and silica having a small particle size are It remains in the supernatant.
- the gypsum settled on the bottoms of the classifiers 181a and 181b is further dehydrated and collected by the dehydrators 182a and 182b.
- the supernatant liquid containing gypsum having a small particle diameter, calcium carbonate, and silica is fed to the first precipitation sections 50a and 50b.
- gypsum having an average particle size of 10 ⁇ m or more is mainly precipitated, and the proportion of small-diameter gypsum is reduced.
- gypsum having a low water content and no impurities that is, high purity
- a part of the gypsum collected by the first separation units 180a and 180b may be circulated to the seed crystal tanks 23a and 23b as seed crystals.
- the water to be treated (treated water) of the present invention contains Ca 2+ , SO 4 2 ⁇ and carbonate ions.
- water to be treated (raw water) is brine, sewage, factory wastewater, cooling tower blowdown water, and the like.
- the treated water may contain metal ions such as Mg ions.
- FIG. 10 is a schematic view of a water treatment system of a first reference example of the third reference embodiment of the present invention.
- the water treatment system 201 in FIG. 10 has a configuration in which two water treatment units are connected in the flow direction of the water to be treated.
- One water treatment part may be sufficient according to the property of to-be-processed water, and three or more water treatment parts may be connected.
- One water treatment unit in the water treatment system 201 of the first reference example of the third reference embodiment is a second desalting unit 210 (210a, 210b) and a second crystallization unit 220 in order from the upstream side of the water to be treated. (220a, 220b).
- the concentration side of the second desalting units 210a and 210b and the second crystallization units 220a and 220b are connected.
- the water treatment unit includes a second scale inhibitor supply unit 230 (230a, 230b) in the upstream flow path of each second desalting unit 210 (210a, 210b).
- the second scale inhibitor supply units 230a and 230b are composed of a tank 231 (231a and 231b), a valve V4 (V4a and V4b), and a control unit 232 (232a and 232b), respectively.
- the control units 232a and 232b are connected to the valves V4a and V4b.
- the scale inhibitor is stored in the tanks 231a and 231b of the second scale inhibitor supply units 230a and 230b.
- the scale inhibitor used in the first reference example of the present embodiment prevents precipitation of calcium-containing scale in the water to be treated.
- calcium scale inhibitor suppresses the formation of gypsum or calcium carbonate crystal nuclei in the water to be treated, and the gypsum or calcium carbonate crystal nuclei contained in the water to be treated (small-scale scales deposited beyond the seed crystals and saturation concentration). Etc.) and has a function of suppressing crystal growth of gypsum or calcium carbonate.
- some calcium scale inhibitors have a function of dispersing (preventing aggregation) particles in the water to be treated such as precipitated crystals.
- Examples of calcium scale inhibitors include phosphonic acid scale inhibitors, polycarboxylic acid scale inhibitors, and mixtures thereof.
- a specific example is FLOCON260 (trade name, manufactured by BWA).
- FIG. 10 shows tanks 231a and 231b, and calcium scale inhibitors are stored in the tanks 231a and 231b.
- the second desalting units 210a and 210b are reverse osmosis membrane devices.
- the second desalting units 210a and 210b include an electrodialyzer (ED), a polarity switching electrodialyzer (EDR), an electric regenerative deionized water device (EDI), an ion exchange device (IEx), an electrostatic device.
- ED electrodialyzer
- EDR polarity switching electrodialyzer
- EDI electric regenerative deionized water device
- IEx ion exchange device
- electrostatic device an electrostatic device.
- a desalting apparatus (CDI), a nano filter (NF), an evaporator, or the like can be employed.
- NF nano filter
- ED electrodialyzer
- EDR polarity switching electrodialyzer
- EDI electric regenerative pure water device
- CDl electrostatic desalting device
- the scale component (2 Valent ions such as Ca 2+ and Mg 2+ are selectively removed, and monovalent ions such as Na + and Cl ⁇ are permeated. If these desalting apparatuses are used, the concentration of ions, which are scale components in the concentrated water, is suppressed from being concentrated, so that it is possible to improve the water recovery rate and save energy (for example, reduce pump power).
- the reclaimed water does not need to be pure water, and scale components (divalent ions, Ca 2+ , Mg 2+, etc.) need only be removed.
- scale components divalent ions, Ca 2+ , Mg 2+, etc.
- FIG. 10 only one second desalting unit 210 a and 210 b is shown, but a plurality of desalting apparatuses may be connected in parallel or in series in the direction of water to be treated.
- the second crystallization unit 220 (220a, 220b) includes a second crystallization tank 221 (221a, 221b) and a second seed crystal supply unit 222 (222a, 222b).
- the second seed crystal supply units 222a and 222b are connected to the second crystallization tanks 221a and 221b.
- the second seed crystal supply units 222a and 222b include seed crystal tanks 223 (223a and 223b), valves V5 (V5a and V5b), and control units 224 (224a and 224b).
- the control units 224a and 224b are connected to the valves V5a and V5b.
- the seed crystal tanks 223a and 223b store gypsum particles as seed crystals.
- the second precipitation unit 250 may be installed on the downstream side of the second crystallization units 220a, 220b.
- Each of the second precipitation units 250a and 250b includes a second precipitation tank 251 (251a and 251b) and a second filtration device 252 (252a and 252b).
- the water treatment system 201 includes a downstream desalting unit 60 on the downstream side of the water to be treated of the second crystallization unit 220b located on the most downstream side.
- the downstream desalting unit 60 is a reverse osmosis membrane device.
- the downstream desalting unit 60 includes an electrodialyzer (ED), a polarity-changing electrodialyzer (EDR), an electric regeneration pure water device (EDI), an ion exchange device, an electrostatic desalting device (CDI), and a nano filter. (NF), an evaporator or the like can be employed.
- An evaporator (not shown in FIG. 10) may be installed downstream of the downstream desalting unit 60 on the concentrated water side.
- water is evaporated from the concentrated water, and ions contained in the concentrated water are precipitated as a solid and recovered as a solid. Since water is collected on the upstream side of the evaporator and the amount of concentrated water is significantly reduced, the evaporator can be made smaller and the energy required for evaporation can be reduced.
- the second pH adjusting unit 240 (240a, 240b) may be installed between the second desalting unit 210 and the second crystallization unit 220.
- the second pH adjusting unit 240 includes a tank 241 (241a, 241b), a valve V6 (V6a, V6b), a pH meter 243 (243a, 243b), and a control unit 242 (242a, 242b).
- An acid is stored in the tank 241 as a pH adjuster. Examples of the acid that can be used include hydrochloric acid, sulfuric acid, and nitric acid.
- the control unit 242 is connected to the valve V6 and the pH meter 243.
- the pH meter 243 may be installed in the flow path between the second desalting unit 210 and the second crystallization unit 220 as shown in FIG. 10, or may be installed in the second crystallization tank 221.
- a settling tank 271 and a filtration device 272 are installed as a second upstream settling unit 270 on the upstream side of the second scale inhibitor supply unit 230a located in the uppermost stream of the water to be treated.
- the second upstream sedimentation unit 270 has the same configuration as the first sedimentation tank 251 and the first filtration device 252 of the first sedimentation unit 250.
- the second upstream sedimentation section 270 can employ a configuration in which a plurality of sedimentation tanks 271 are connected in series in the flow direction of the water to be treated.
- the water treatment system 201 may be provided with a second deaeration unit 273 upstream of the second upstream precipitation unit 270.
- the second degassing unit 273 is a degassing tower or a separation membrane provided with a filler for removing carbon dioxide.
- a pH adjustment unit (not shown) that adjusts the water to be treated to a pH at which carbonate ions are CO 2 may be installed on the upstream side of the water to be treated of the second degassing unit 273.
- the 2nd deaeration part 273 may be installed in the to-be-processed water downstream of the 2nd upstream sedimentation part 270, and the upstream of the 2nd scale inhibitor supply part 230a.
- the deaeration part having the same configuration as the second deaeration part 273 is a flow path between the second demineralization part 210 and the second crystallization part 220, and between the second crystallization part 220 and the second precipitation part 250. And the downstream side of the second sedimentation part 250 and between the second desalting part 210b or the downstream desalting part 60.
- an ion exchange device (not shown) is installed downstream of the filtration device 272 and upstream of the second scale inhibitor supply unit 230a located at the uppermost stream. good.
- the ion exchange device is, for example, an ion exchange resin tower or an ion exchange membrane device.
- the ions are further concentrated in the second desalting unit 210a, so that the gypsum concentration is further increased.
- a large amount of calcium scale inhibitor needs to be added, and the gypsum concentration becomes higher than the calcium scale inhibitor exhibits its effect, and scale may be generated in the second desalting unit 210a. Therefore, when the gypsum in the raw water (treated water) is supersaturated, upstream crystallization having the same configuration as the second crystallization units 221a and 221b is arranged upstream of the second scale inhibitor supply unit 230a in the uppermost stream. A portion (not shown) may be provided to reduce the gypsum concentration before supplying the water to be treated to the second desalting unit 210a.
- the second separation unit 280 (280a, 280b) is installed on the downstream side of the second crystallization unit 220 as shown in FIG.
- the second separation unit 280 has the same configuration as the first separation unit 180, and includes a classifier 281 (281a, 281b) and a dehydrator 282 (282a, 282b).
- the classifiers 281a and 281b are, for example, liquid cyclones.
- the dehydrators 282a and 282b are, for example, belt filters.
- only one classifier is installed in the second separation unit 280, but a plurality of classifiers may be connected in series in the flow direction of the water to be treated.
- FIG. 2 is a simulation result of the pH dependence of the amount of gypsum deposited.
- FIG. 3 is a simulation result of the pH dependency of the precipitated amount of calcium carbonate.
- the horizontal axis represents pH
- the vertical axis represents the amount of precipitation (mol) of gypsum or calcium carbonate, respectively.
- the simulation was performed using simulation software manufactured by OLI under the condition that 0.1 mol / L of each solid component was mixed in water and H 2 SO 4 as an acid and Ca (OH) 2 as an alkali were added.
- ⁇ Pretreatment> When the water to be treated is industrial wastewater or the like, before the water to be treated flows into the second upstream sedimentation section 270, a process for removing oil or suspended particles in the water to be treated, biological treatment or chemical oxidation treatment The step of removing organic substances is performed by the above.
- ⁇ Second degassing step> In the water treatment system 201 of FIG. 10, the water to be treated before flowing into the second degassing unit 273 is adjusted to a low pH. Carbonic acid in the water to be treated is in the following equilibrium state depending on the pH of the water to be treated. When the pH is as low as 6.5 or less, it exists mainly in the state of HCO 3 ⁇ and CO 2 in the treated water.
- the water to be treated containing CO 2 flows into the second degassing unit 273.
- CO 2 is removed from the water to be treated in the second degassing unit 273.
- carbonate ions if it is adjusted water to be treated pH present as CO 2, can be efficiently removed carbon dioxide.
- the water to be treated whose carbonate ion concentration has been reduced by the second degassing step is fed to the second upstream sedimentation unit 270.
- ⁇ Second upstream precipitation step> In the second upstream sedimentation section 270, Ca ions and carbonate ions are roughly removed from the treated water in advance as calcium carbonate.
- the metal ions are roughly removed from the water to be treated in advance as a metal compound having low solubility in water in the second upstream precipitation portion 270.
- This metal compound is mainly a metal hydroxide, but may also contain carbonates.
- Ca (OH) 2 and an anionic polymer are introduced into the water to be treated, and the pH in the sedimentation tank 271 is 4 or more and 12 or less, preferably Is managed in the range of 8.5 to 12.
- the solubility of calcium carbonate is low in this pH region.
- calcium carbonate becomes supersaturated calcium carbonate is deposited and settles at the bottom of the settling tank 271.
- the solubility of the metal compound depends on the pH.
- the solubility of metal ions in water increases with acidity. In the above pH range, the solubility of many metal compounds is low.
- the metal compound having low solubility in water aggregates in the precipitation tank 271 and precipitates at the bottom of the precipitation tank 271. The precipitated calcium carbonate and metal compound are discharged from the bottom of the precipitation tank 271.
- Mg ions form a salt that is hardly soluble in water, it is a component that tends to precipitate as scale. Mg (OH) 2 precipitates at pH 10 or higher.
- the magnesium to be treated (mainly magnesium hydroxide) is deposited in the second upstream precipitation unit 270. Adjust to pH. Specifically, the pH of the water to be treated is adjusted to 10 or more, preferably pH 10.5 or more, more preferably pH 11 or more. By doing so, the magnesium compound is precipitated from the water to be treated and is precipitated and removed at the bottom of the precipitation tank 271.
- the water to be treated after being discharged from the second upstream precipitation section 270 is adjusted to a pH at which the magnesium compound can be dissolved. Specifically, the pH is adjusted to less than 10. By doing so, it is possible to prevent scale generation in the downstream apparatus and process, particularly the second desalting unit 210 and the second desalting process.
- Mg ions in the water to be treated can be reliably removed, and the Mg ion concentration in the water to be treated fed downstream can be reduced.
- the supernatant liquid in the settling tank 271 that is the water to be treated is discharged from the settling tank 271.
- FeCl 3 is added to the discharged water to be treated, and solids such as calcium carbonate and metal compounds in the supernatant liquid aggregate with Fe (OH) 3 .
- the water to be treated is supplied to the filtration device 272.
- the solid content aggregated by Fe (OH) 3 is removed by the filtration device 272.
- the pH of the water to be treated is adjusted to a pH at which carbonate ions can exist as CO 2 , specifically 6.5 or lower. .
- the second degassing step and the second upstream precipitation step can be omitted.
- ⁇ Second scale inhibitor supply step> The controller 232a of the second scale inhibitor supply unit 230a opens the valve V4a and supplies a predetermined amount of calcium scale inhibitor from the tank 231a to the water to be treated.
- the controller 232a adjusts the opening of each valve V4a so that the concentration of the calcium scale inhibitor becomes a predetermined value set according to the properties of the water to be treated.
- Mg ion is contained in the water to be treated
- the magnesium scale inhibitor is supplied to the water to be treated by the same method as described above in the second scale inhibitor supply step.
- the calcium scale inhibitor and the magnesium scale inhibitor are respectively stored in the tanks of the plurality of second scale inhibitor supply units, and each control unit adjusts the supply amounts of the calcium scale inhibitor and the magnesium scale inhibitor.
- the pH adjustment of the water to be treated immediately before flowing into the second desalting unit 210 is arbitrarily performed.
- the pH of the water to be treated becomes about 5 to 6 by adding FeCl 3 and flows into the second desalting unit 210a.
- the pH of the water to be treated is 6.5 or less, calcium carbonate has high solubility in water.
- carbonic acid exists mainly in the state of HCO 3 ⁇ and CO 2 in water.
- the treated water flowing into the second desalting unit 210a has a low calcium carbonate concentration.
- the pH adjustment part of the same structure as a 2nd pH adjustment part is installed upstream of the 2nd desalination part 210a, and pH adjustment is carried out.
- the treated water may be supplied to the second desalting unit 210a.
- ⁇ Second desalting step> In the 2nd desalination part 210a, the to-be-processed water into which the scale inhibitor was thrown in is processed.
- the 2nd desalination part 210a is a reverse osmosis membrane apparatus
- the water which passed the reverse osmosis membrane is collect
- the water to be treated is separated into treated water and concentrated water (second concentrated water) having a high ion concentration.
- the second concentrated water is fed toward the second crystallization part 220a.
- the pH of the water to be treated is adjusted by the second pH adjusting unit 240a between the second desalting unit 210a and the second crystallization unit 220a. Also good.
- the second pH adjusting unit 240a manages the pH of the second concentrated water so that the function of the calcium scale inhibitor is reduced and the gypsum in the second concentrated water can be precipitated.
- the pH meter 243a measures the pH of the second concentrated water.
- the controller 242a adjusts the opening degree of the valve V6a so that the measured value of the pH meter 243a becomes a predetermined pH management value.
- the second concentrated water discharged from the second desalting unit 210a is stored in the second crystallization tank 221a of the second crystallization unit 220a.
- the control unit 224a of the second seed crystal supply unit 222a opens the valve V5a and adds the gypsum seed crystal from the seed crystal tank 223a to the second concentrated water in the second crystallization tank 221a.
- the second concentrated water from the second desalting unit 210a has a pH of 10 or more. As described above, gypsum is in a dissolved state in water in a high pH region where a calcium scale inhibitor is present.
- gypsum crystallizes with the seed crystal as a nucleus even if the scale inhibitor is present.
- gypsum having a large diameter for example, a particle size of 10 ⁇ m or more, more preferably 20 ⁇ m or more
- the precipitated gypsum is discharged from the bottom of the second crystallization tank 221a.
- calcium carbonate tends to precipitate at pH 10 or higher.
- the calcium scale inhibitor is added, the precipitation of calcium carbonate is suppressed in the second crystallization tank 221a.
- concentration of calcium carbonate is reduced previously.
- calcium carbonate is difficult to crystallize using gypsum seed crystals as nuclei.
- FIG. 5 shows that when the scale inhibitor (FLOCON260) is added to simulated water (including Ca 2+ , SO 4 2 ⁇ , Na + , Cl ⁇ ) in which the gypsum is supersaturated, the pH of the simulated water is changed. It is the result of conducting a gypsum precipitation experiment.
- the experimental conditions are as follows.
- Simulated water gypsum supersaturation (25 ° C): 460%, Scale inhibitor addition amount: 2.1 mg / L, pH: 6.5 (condition 1), 5.5 (condition 2), 4.0 (condition 3), 3.0 (condition 4), Seed crystal addition amount: 0 g / L.
- the Ca concentration in the simulated water treated under each condition was measured using an atomic absorption analyzer (manufactured by Shimadzu Corporation, AA-7000). As shown in FIG. In the figure, the vertical axis represents the degree of supersaturation (%).
- the crystallization rate increases as the pH is lowered even under conditions where there is no seed crystal. From this, when seed crystals exist, gypsum crystallizes under condition 1 (pH 6.5), and the relationship between the crystallization speeds is that the lower the pH as shown in FIG. 5, the higher the crystallization speed. Understandable.
- an acid as a pH adjusting agent is added to the flow path between the second crystallization tank 221a or the second desalting unit 210a and the second crystallization tank 221a.
- a third pH adjusting unit (not shown) to be supplied is installed.
- the said pH adjustment part is the same structure as a 2nd pH adjustment part.
- FIG. 6 shows the results of a gypsum precipitation experiment in which the amount of seed crystals added was changed when a calcium scale inhibitor (FLOCON 260) was added to simulated water.
- the experimental conditions in FIG. 5 were the same except that the pH was 4.0 and gypsum (CaSO 4 .2H 2 O) was added as a seed crystal in the following amounts.
- Seed crystal addition amount 0 g / L (condition 3), 3 g / L (condition 5), 6 g / L (condition 6), 3 g / L (condition 7).
- seed crystals and sulfuric acid for pH adjustment were added to the simulated water to which the scale inhibitor was added.
- condition 7 seed crystals previously immersed in the scale inhibitor were added to the simulated water to which the scale inhibitor was added, and sulfuric acid was added for pH adjustment.
- the Ca concentration in the simulated water treated under each condition was measured by the same method as in FIG. In FIG. 6, the vertical axis represents the degree of supersaturation (%).
- the supersaturation degree was 215% in condition 3 where no seed crystal was added, but the supersaturation degree was 199% (condition 5) and 176% (condition 6) as the seed crystal concentration increased. It can be understood that the gypsum deposition rate increases. Even under high pH conditions, the gypsum deposition rate tends to increase as the seed crystal input amount increases.
- Conditions 5 and 7 are the same test conditions except that a seed crystal not immersed in the scale inhibitor and a seed crystal immersed therein are used. The supersaturation degree was 199% even under condition 7 in which the scale inhibitor was previously attached to the seed crystal, and it was confirmed that gypsum of the same degree as that in condition 5 was precipitated. That is, from the results of Conditions 5 and 7, it was shown that the function of the scale inhibitor is reduced by lowering the pH to 4.0 regardless of the immersion time of the seed crystal in the calcium scale inhibitor.
- FIG. 7 and 8 are micrographs of gypsum obtained by crystallization.
- FIG. 7 shows the result of Condition 5 (with seed crystal addition)
- FIG. 8 shows the result of Condition 3 (without seed crystal addition).
- condition 5 gypsum larger than condition 3 was deposited.
- the larger the precipitated gypsum the lower the water content. If the moisture content is low, the gypsum is highly pure.
- the average particle size is 10 ⁇ m or more, preferably 20 ⁇ m or more, gypsum having a sufficiently reduced water content can be obtained.
- the “average particle diameter” in the present invention is a particle diameter measured by a method (laser diffraction method) defined in JIS Z 8825.
- condition 7 (pH 4.0) adds seed crystals previously immersed in the calcium scale inhibitor to simulated water to which the calcium scale inhibitor has been added. Then, sulfuric acid was added for pH adjustment. The conditions other than the above were the same in conditions 5 and 7, and a gypsum precipitation experiment was performed. After 2 hours from pH adjustment, the Ca concentration in the simulated water was measured by the same method as in FIG. As a result, as shown in FIG. 6, in both conditions 5 and 7, the degree of supersaturation was 199% or less. From this, it can be said that the function of the calcium scale inhibitor is lowered when the pH is lowered to 4.0 regardless of the immersion time of the seed crystal in the calcium scale inhibitor.
- the pH of the second concentrated water is adjusted to 6.0 or less, preferably 5.5 or less, more preferably 4.0 or less by the second pH adjustment step.
- the function of the calcium scale inhibitor can be significantly reduced.
- the pH range in the second pH adjustment step is appropriately set according to the type of scale inhibitor.
- calcium carbonate dissolves in water at pH 6.0 or lower. From the above, high-purity gypsum can be recovered in the second crystallization tank 221a of the second water treatment unit.
- ⁇ Second separation step> The second concentrated water in the second crystallization tanks 221a and 221b is conveyed to the second separation units 280a and 280b.
- the 2nd concentrated water conveyed here is water containing the solid substance which precipitated in the 2nd crystallization tank 221a, 221b.
- the gypsum settled on the bottoms of the classifiers 281a and 281b is further dehydrated and collected by the dehydrators 282a and 282b.
- the supernatant liquid containing gypsum having a small particle diameter, calcium carbonate, and silica is fed to the second precipitation sections 250a and 250b.
- gypsum having an average particle size of 10 ⁇ m or more mainly precipitates, and the proportion of small-diameter gypsum decreases.
- gypsum having a low water content and no impurities (ie, high purity) can be separated and recovered at a high recovery rate.
- Some of the gypsum collected by the second separation units 280a and 280b may be circulated to the seed crystal tanks 223a and 223b as seed crystals.
- ⁇ Second precipitation step> The supernatant liquid (second concentrated water) or the supernatant liquid (second concentrated water) discharged from the second separation section 280a is fed to the second precipitation section 250a.
- Ca (OH) 2 and an anionic polymer (Hishifloc H305) are added to the second concentrated water after the crystallization step, and the pH in the second precipitation tank 251a is 4 or more and 12 or less, preferably It is managed from 8.5 to 12 inclusive.
- the second settling tank 251a calcium carbonate and a metal compound are precipitated and removed from the second concentrated water. The precipitated calcium carbonate and the metal compound having low solubility in water are discharged from the bottom of the second precipitation tank 251a.
- Water to be treated which is a supernatant liquid in the second sedimentation tank 251a, is discharged from the second sedimentation tank 251a.
- FeCl 3 is added to the discharged water to be treated, and solids such as calcium carbonate and metal compounds in the water to be treated aggregate with Fe (OH) 3 .
- the treated water is supplied to the second filtration device 252a.
- the solid content aggregated by Fe (OH) 3 is removed by the second filtration device 252a.
- the second concentrated water that has passed through the second filtration device 252a of the second water treatment section at the front stage flows into the water treatment section at the rear stage as treated water.
- the second precipitation step is performed from the second scale inhibitor supply step.
- ⁇ Downstream desalting process> The second concentrated water that has passed through the second sedimentation section 250b located on the most downstream side of the water to be treated is treated by the downstream desalting section 60.
- the water that has passed through the downstream desalting unit 60 is recovered as treated water.
- the concentrated water in the downstream desalting unit 60 is discharged out of the system.
- the downstream desalting unit 60 When the downstream desalting unit 60 is installed, the treated water can be further recovered from the water that has been treated by the water treating unit, so that the water recovery rate is improved.
- an evaporator (not shown) may be installed downstream of the downstream desalting unit 60 on the concentrated water side.
- the second crystallization is performed as the third pH adjusting step.
- the pH of the second concentrated water may be adjusted so that the calcium scale inhibitor can exert its function.
- the pH is preferably 4.0 or higher, preferably 5.5 or higher, more preferably 6.0 or higher.
- the third pH adjustment step is performed after the second crystallization step and before the second desalting step, or after the second crystallization step and before the downstream desalting step.
- ions are concentrated in the second desalting unit 210a, but gypsum, calcium carbonate, etc. are used in the second crystallization unit 220a, the second precipitation unit 250a, and the like. Has been removed. For this reason, the number of moles of ions in the water flowing into the second desalting unit 210b and the downstream desalting unit 60 is lower than that before treatment. For this reason, the osmotic pressure in the 2nd desalination part 210b located downstream and the downstream desalination part 60 becomes low, and required motive power is reduced.
- the water treatment system 201 of the first reference example of the present embodiment has a second crystallization part and a second desalting part immediately thereafter (the second crystallization part 220a in FIG. 10).
- the third pH adjusting unit (not shown in FIG. 10) having the same configuration as the second pH adjusting unit between the second desalting unit 210b and, in particular, between the second precipitation unit 250a and the second desalting unit 210b). Is installed.
- a third pH adjusting unit (not shown in FIG. 10) having the same configuration as the second pH adjusting unit is installed between the most downstream second precipitation unit 250b and the downstream desalting unit 60.
- the water to be treated containing ions can be treated with a high water recovery rate.
- gypsum is mainly deposited in the second crystallization unit 220, so that the gypsum recovery rate in the second crystallization unit 220 is high, and the mole of ions fed downstream. The number is further reduced.
- the purity of the gypsum recovered by the second crystallization unit 220 can be increased.
- FIG. 11 is a schematic diagram of a water treatment system of a second reference example of the third reference embodiment of the present invention.
- the water treatment system 200 in FIG. 11 has a configuration in which two water treatment units are connected in the flow direction of the water to be treated.
- One water treatment part may be sufficient according to the property of to-be-processed water, and three or more water treatment parts may be connected.
- One water treatment unit in the water treatment system 200 of the second reference example of the third reference embodiment is a second desalting unit 210 (210a, 210b) and a second crystallization unit 220 in order from the upstream side of the water to be treated. (220a, 220b).
- the concentration side of the second desalting units 210a and 210b and the second crystallization units 220a and 220b are connected.
- the water treatment unit includes a second scale inhibitor supply unit 230 (230a, 230b) in the upstream flow path of each second desalting unit 210 (210a, 210b).
- the second scale inhibitor supply units 230a and 230b are composed of a tank 231 (231a and 231b), a valve V4 (V4a and V4b), and a control unit 232 (232a and 232b), respectively.
- the control units 232a and 232b are connected to the valves V4a and V4b.
- the scale inhibitor is stored in the tanks 231a and 231b of the second scale inhibitor supply units 230a and 230b.
- the scale inhibitor used in the second reference example of the third reference embodiment is the calcium scale inhibitor described in the first reference embodiment, and prevents the silica from being precipitated as scale in the water to be treated ( It is called “silica scale inhibitor”.
- silica scale inhibitors include phosphonic acid scale inhibitors, polycarboxylic acid scale inhibitors, and mixtures thereof.
- FLOCON260 trade name, manufactured by BWA.
- FIG. 11 shows two tanks 231a. For example, a calcium scale inhibitor is stored in one tank 231a, and a silica scale inhibitor is stored in the other tank 231a.
- the second desalting unit 210 is a reverse osmosis membrane device.
- the second desalting unit 210 includes an electrodialyzer (ED), a polarity switching electrodialyzer (EDR), an electric regeneration pure water device (EDI), an ion exchange device, and an electrostatic desalting device (CDI). ), A nano filter (NF), an evaporator, or the like can be employed.
- ED electrodialyzer
- EDR polarity switching electrodialyzer
- EDI electric regeneration pure water device
- CDI electrostatic desalting device
- NF nano filter
- evaporator or the like can be employed.
- FIG. 11 only one second desalting unit 210 is shown, but a plurality of desalting apparatuses may be connected in parallel or in series in the flow direction of the water to be treated.
- the second crystallization unit 220 (220a, 220b) includes a second crystallization tank 221 (221a, 221b) and a second seed crystal supply unit 222 (222a, 222b).
- the second seed crystal supply unit 222 is connected to the second crystallization tank 221.
- the second seed crystal supply unit 222 includes a seed crystal tank 223 (223a, 223b), a valve V5 (V5a, V5b), and a control unit 224 (224a, 224b).
- the control unit 224 is connected to the valve V5.
- the seed crystal tank 223 stores gypsum particles as seed crystals.
- the second pH adjusting unit 240 (240a, 240b) may be installed between the second desalting unit 210 and the second crystallization unit 220.
- the second pH adjusting unit 240 includes a tank 241 (241a, 241b), a valve V6 (V6a, V6b), a pH meter 243 (243a, 243b), and a control unit 242 (242a, 242b).
- An acid is stored in the tank 241 as a pH adjuster. Examples of the acid that can be used include hydrochloric acid, sulfuric acid, and nitric acid.
- the control unit 242 is connected to the valve V6 and the pH meter 243.
- the pH meter 243 may be installed in the flow path between the second desalting unit 210 and the second crystallization unit 220 as shown in FIG. 11, or may be installed in the second crystallization tank 221.
- a sedimentation tank 271 and a filtration device 272 are installed as a second upstream sedimentation unit 270 on the upstream side of the second scale inhibitor supply unit 230a located in the uppermost stream of the water to be treated.
- the second upstream sedimentation section 270 has the same configuration as the first upstream sedimentation section 70.
- a plurality of stages of settling tanks 271 may be connected in series in the direction of water to be treated.
- the water treatment system 200 may be provided with a second deaeration unit 273 upstream of the second upstream precipitation unit 270.
- the 2nd deaeration part 273 is the same structure as the 1st deaeration part 73 of 1st reference embodiment.
- the 2nd deaeration part 273 may be installed in the to-be-processed water downstream of the 2nd upstream sedimentation part 270, and the upstream of the 2nd scale inhibitor supply part 230a.
- the deaeration part having the same configuration as the second deaeration part 273 is a flow path between the second demineralization part 210a and the second crystallization part 220a, and between the second crystallization part 220 and the second precipitation part 250. And the downstream side of the second sedimentation part 250 and between the second desalting part 210b or the downstream desalting part 60.
- an ion exchange device may be installed downstream of the filtration device 272 and upstream of the second scale inhibitor supply unit 230a located at the uppermost stream. Further, even if an upstream crystallization part (not shown) having the same configuration as the second crystallization part is installed upstream of the most upstream second scale inhibitor supply part 230a according to the gypsum concentration in the water to be treated. good.
- the second separation unit 280 (280a, 280b) may be installed on the downstream side of the second crystallization unit 220 as shown in FIG.
- the second separation unit 280 has the same configuration as the first separation unit 180, and includes a classifier 281 (281a, 281b) and a dehydrator 282 (282a, 282b).
- the second precipitation unit 250 (250a, 250b) may be installed on the downstream side of the second crystallization unit 220.
- the 2nd sedimentation part 250 is the structure similar to the 1st sedimentation part 50, and is provided with the 2nd sedimentation tank 251 (251a, 251b) and the 2nd filtration apparatus 252 (252a, 252b).
- the water treatment system 200 includes a downstream desalting unit 60 on the downstream side of the water to be treated of the first water treatment unit.
- An evaporator (not shown in FIG. 11) may be installed downstream of the downstream desalting unit 60 on the concentrated water side.
- Pretreatment The pretreatment described in the first reference embodiment is performed on the water to be treated.
- ⁇ Second upstream precipitation step> In the second upstream sedimentation section 270, Ca ions and carbonate ions are roughly removed from the treated water in advance as calcium carbonate. When metal ions other than Ca ions are contained in the water to be treated, the metal compound having low solubility in water is roughly removed from the water to be treated in advance in the second upstream precipitation portion 270.
- the second upstream precipitation step is performed in the same step as the first upstream precipitation step.
- the water to be treated containing Mg ions is treated in the water treatment system 200 of the second reference example of the present embodiment, the water to be treated is a magnesium compound in the second upstream sedimentation section 270 as in the first embodiment.
- the pH is adjusted to precipitate, and rough removal of Mg ions in the water to be treated is performed. Thereafter, the pH is preferably adjusted to a pH at which the magnesium compound can be dissolved on the downstream side of the second upstream precipitation portion 270. Specifically, the pH is adjusted to less than 10. By doing so, it is possible to prevent scale generation in the downstream apparatus and process, particularly the second desalting unit 210 and the second desalting process.
- the pH of the water to be treated is adjusted to a pH at which carbonate ions can exist as CO 2 , specifically 6.5 or lower. .
- the second degassing step and the second upstream precipitation step can be omitted.
- the controller 232a of the second scale inhibitor supply unit 230a opens the valve V4a and supplies a predetermined amount of calcium scale inhibitor from the tank 231a to the water to be treated.
- the control unit 232b of the second scale inhibitor supply unit 230b opens the valve V4b and supplies a predetermined amount of silica scale inhibitor from the tank 231b to the water to be treated.
- the control unit 232a and the control unit 232b adjust the opening degrees of the valve V4a and the valve V4b so that the concentrations of the calcium scale inhibitor and the silica scale inhibitor have predetermined values set according to the properties of the water to be treated. adjust.
- the pH adjustment of the water to be treated immediately before flowing into the second desalting unit 210 is arbitrarily performed.
- the pH of the water to be treated becomes about 5 to 6 by adding FeCl 3 and flows into the second desalting unit 210a.
- the pH of the water to be treated is 6.5 or less, calcium carbonate has high solubility in water.
- carbonic acid exists mainly in the state of HCO 3 ⁇ and CO 2 in water.
- the treated water flowing into the second desalting unit 210a has a low calcium carbonate concentration.
- the pH adjustment part of the same structure as the 1st pH adjustment part of 1st reference embodiment is upstream in the 2nd desalination part 210a.
- the treated water whose pH is adjusted may be installed and supplied to the second desalting unit 210a.
- ⁇ Second desalting step> In the 2nd desalination part 210a, the to-be-processed water into which the scale inhibitor was thrown in is processed.
- the 2nd desalination part 210a is a reverse osmosis membrane apparatus
- the water which passed the reverse osmosis membrane is collect
- Water containing ions and scale inhibitors is discharged as concentrated water (second concentrated water) from the non-permeating side of the reverse osmosis membrane.
- the gypsum and silica in the second concentrated water are concentrated by the treatment in the second desalting unit 210a, but scale generation is suppressed by the calcium scale inhibitor and the silica scale inhibitor.
- the water to be treated is separated into treated water and concentrated water (second concentrated water) having a high ion concentration.
- the second concentrated water is fed toward the second crystallization part 220a.
- the pH of the water to be treated is adjusted by the second pH adjusting unit 240a between the second desalting unit 210a and the second crystallization unit 220a. Also good.
- the second pH adjusting unit 240a manages the pH of the second concentrated water so that the function of the calcium scale inhibitor is reduced and the gypsum in the second concentrated water can be precipitated.
- the pH meter 243a measures the pH of the second concentrated water.
- the controller 242a adjusts the opening degree of the valve V6a so that the measured value of the pH meter 243a becomes a predetermined pH management value.
- the second concentrated water is stored in the second crystallization tank 221 of the second crystallization unit 220a.
- the control unit 224a of the second seed crystal supply unit 222a opens the valve V5 and adds the gypsum seed crystal from the seed crystal tank 223a to the second concentrated water in the second crystallization tank 221a.
- a calcium scale inhibitor is contained in the second concentrated water, but when a seed crystal is introduced, gypsum crystallizes and grows.
- the supersaturation degree is 460%, and even after 6 hours, there is no change from the initial supersaturation degree.
- condition 1 the scale inhibitor exhibits a function and the precipitation of gypsum is suppressed.
- conditions 2 to 4 the degree of supersaturation is reduced. That is, even when no seed crystal was added, it was confirmed that when the pH was reduced, the function of the scale inhibitor was reduced and the gypsum crystallized.
- the result that the precipitation rate was so large that pH was low was obtained.
- condition 7 (pH 4.0) adds seed crystals previously immersed in the calcium scale inhibitor to simulated water to which the calcium scale inhibitor has been added. Then, sulfuric acid was added for pH adjustment. The conditions other than the above were the same in conditions 5 and 7, and a gypsum precipitation experiment was performed. After 2 hours from pH adjustment, the Ca concentration in the simulated water was measured by the same method as in FIG. As a result, as shown in FIG. 6, in both conditions 5 and 7, the degree of supersaturation was 199% or less. From this, it can be said that the function of the calcium scale inhibitor is lowered when the pH is lowered to 4.0 regardless of the immersion time of the seed crystal in the calcium scale inhibitor.
- the pH of the second concentrated water is adjusted to 6.0 or less, preferably 5.5 or less, more preferably 4.0 or less by the second pH adjustment step.
- the function of the calcium scale inhibitor can be significantly reduced.
- the pH range in the second pH adjustment step is appropriately set according to the type of scale inhibitor.
- the silica when the pH is low, the silica may have a saturation solubility or higher.
- the silica scale inhibitor is introduced in the second water treatment unit, the precipitation of silica is suppressed even when the pH is low. Even if silica is precipitated in the second crystallization tank 221a, it is present as small-diameter particles or colloidal suspended matter.
- calcium carbonate dissolves in water at pH 6.0 or lower. From the above, high-purity gypsum can be recovered in the second crystallization tank 221a of the second water treatment unit.
- the second concentrated water in the second crystallization step may be adjusted to a pH at which silica can be dissolved in the second concentrated water by the second pH adjusting step. By doing so, silica precipitation from the second concentrated water is suppressed in the second crystallization tank 221a. As a result, when the second concentrated water discharged from the second crystallization tank 221a is classified by the second separation unit 280a, the purity of the recovered gypsum can be increased.
- the classifier 281a of the second separation unit 280a is composed of gypsum having a predetermined size (for example, an average particle size of 10 ⁇ m or more) and small-diameter precipitates (gypsum, silica).
- the supernatant liquid containing is separated.
- the large-diameter gypsum is further dehydrated and collected by the dehydrator 282a. According to the second reference example of this reference embodiment, it is possible to collect high-purity gypsum. A part of the collected gypsum may be circulated to the seed crystal tank 223a as a seed crystal.
- ⁇ Second precipitation step> The supernatant liquid (second concentrated water) or the supernatant liquid (second concentrated water) discharged from the second separation section 280a is fed to the second precipitation section 250a.
- the calcium carbonate and the metal compound in the second concentrated water are removed by the second precipitation tank 251a and the second filtration device 252a in the same manner as the first precipitation step described in the first reference embodiment.
- At least one of a silica seed crystal and a silica precipitation agent may be added to the second precipitation tank 251a in the same manner as in the first precipitation step, and the silica may be removed from the second concentrated water.
- the second concentrated water that has passed through the second filtration device 252a of the second water treatment section at the front stage flows into the water treatment section at the rear stage as treated water.
- the second precipitation step is performed from the second scale inhibitor supply step.
- ⁇ Downstream desalting process> The second concentrated water that has passed through the second sedimentation section 250b located on the most downstream side of the water to be treated is treated by the downstream desalting section 60.
- the water that has passed through the downstream desalting unit 60 is recovered as water to be treated.
- the concentrated water in the downstream desalting unit 60 is discharged out of the system.
- an evaporator (not shown) may be installed downstream of the downstream desalting unit 60 on the concentrated water side.
- the second crystallization is performed as the third pH adjusting step.
- the pH of the second concentrated water may be adjusted so that the calcium scale inhibitor can exert its function.
- the pH is preferably 4.0 or higher, preferably 5.5 or higher, more preferably 6.0 or higher.
- the third pH adjustment step is performed after the second crystallization step and before the second desalting step, or after the second crystallization step and before the downstream desalting step.
- the water treatment system 200 has a second crystallization part and a second desalting part immediately thereafter (the second crystallization part 220a in FIG. 11).
- the third pH adjusting unit (not shown in FIG. 11) having the same configuration as the second pH adjusting unit between the second desalting unit 210b and in particular, between the second precipitation unit 250a and the second desalting unit 210b). Is installed.
- a third pH adjusting unit (not shown in FIG. 11) having the same configuration as the second pH adjusting unit is installed between the second precipitation unit 250b on the most downstream side and the downstream desalting unit 60.
- silica is concentrated by the treatment in the second water treatment unit. If the silica concentration in the second concentrated water is equal to or higher than the concentration at which the silica scale inhibitor works effectively, silica may be generated as scale from the second concentrated water. For example, when FLOCON260 is used as a silica scale inhibitor, the scale generation prevention effect is obtained up to a silica concentration of about 200 mg / L. Therefore, the number of stages of the second water treatment unit is set until the silica scale inhibitor is concentrated to a concentration at which the effect can be exerted.
- the water to be treated containing ions can be treated with a high water recovery rate.
- gypsum is mainly precipitated in the second crystallization unit 220, so that the gypsum recovery rate in the second crystallization unit 220 is high, and the mole of ions fed downstream. The number is further reduced.
- the purity of the gypsum recovered by the second crystallization unit 220 can be increased.
- FIG. 12 is a schematic view of a water treatment system according to a fourth reference embodiment of the present invention.
- the water treatment system 300 of the fourth reference embodiment is provided with the water treatment unit described in the first reference embodiment.
- the water treatment unit described in the third reference embodiment is installed on the downstream side of the water to be treated of the water treatment unit.
- the first separation unit 180 is installed on the downstream side of the first crystallization unit 20.
- a second separation unit 280 similar to the first separation unit 180 is installed on the downstream side of the second crystallization unit 220.
- a downstream desalting unit 60 is installed on the downstream side of the water to be treated of the second crystallization unit 220 located on the most downstream side.
- the water treatment system 300 of the fourth reference embodiment has the first scale described in the first reference embodiment on the upstream side of the first scale inhibitor supply unit 30 and the first pH adjustment unit 40 located in the uppermost stream of the water to be treated.
- An upstream sedimentation section 70 is provided.
- the water treatment system 300 of the fourth reference embodiment has a first deaeration unit 73 similar to that of the first reference embodiment on the upstream side of the first upstream sedimentation unit 70 as shown in FIG.
- the first degassing unit 73 may be installed on the downstream side of the water to be treated of the first upstream sedimentation unit 70 and upstream of the first scale inhibitor supply unit 30 and the first pH adjustment unit 40.
- the deaeration part of the same structure as the 1st deaeration part 73 is the flow path between the 1st demineralization part 10 and the 1st crystallization part 20, the 1st crystallization part 10 and the 1st precipitation part 50, Installed between the first crystallization unit 220 and the second precipitation unit 250, and between the first precipitation unit 50 and the second desalination unit 210. good.
- an ion exchange device (not shown) and an upstream crystallization part (not shown) are provided upstream of the first scale inhibitor supply unit 30 and the first pH adjustment unit 40. May be.
- water treatment units from the first scale inhibitor supply unit 30 to the first precipitation unit 50 and the water treatment units from the second scale inhibitor supply unit 230 to the second precipitation unit 250 are shown one by one.
- a plurality of water treatment units may be connected to each other.
- first, water to be treated is treated by the water treatment method described in the first reference embodiment and the second reference embodiment.
- the first concentrated water after being treated by the method of the first reference embodiment and the second reference embodiment is treated water, and the second precipitation process from the second scale inhibitor supply process described in the third reference embodiment. Is processed.
- the second concentrated water that has passed through the most downstream second precipitation section 250 is processed by the downstream desalting section 60.
- the water that has passed through the downstream desalting unit 60 is recovered as treated water.
- the concentrated water in the downstream desalting unit 60 is discharged out of the system.
- an evaporator (not shown) may be installed downstream of the concentrated water side of the downstream desalting unit 60.
- the third pH adjustment step described in the third reference embodiment is performed. May be.
- FIG. 13 is a schematic view of a water treatment system according to a fifth reference embodiment of the present invention.
- the water treatment system 400 of the fifth reference embodiment is provided with the water treatment unit described in the third reference embodiment.
- the water treatment unit described in the first reference embodiment is installed on the downstream side of the water to be treated of the water treatment unit.
- a first separation unit 180 and a second separation unit 280 are installed.
- a downstream desalting unit 60 is installed on the downstream side of the water to be treated of the first crystallization unit 20 located on the most downstream side.
- the water treatment system 400 of the fifth reference embodiment includes the second upstream sedimentation unit 270 described in the third reference embodiment on the upstream side of the second scale inhibitor supply unit 230 located in the uppermost stream of the water to be treated.
- the water treatment system 400 of 5th reference embodiment has the 2nd deaeration part 273 similar to 3rd reference embodiment in the upstream of the 2nd upstream sedimentation part 270, as shown in FIG.
- the second deaeration unit 273 may be installed on the downstream side of the water to be treated of the second upstream sedimentation unit 270 and upstream of the second scale inhibitor supply unit 230.
- the deaeration part of the same structure as the 2nd deaeration part 273 is the flow path between the 2nd demineralization part 210 and the 2nd crystallization part 220, the 1st crystallization part 20, the 1st precipitation part 50, May be installed in the flow path between the second crystallization part 220 and the second precipitation part 250 and the flow path between the second precipitation part 250 and the first desalting part 10. good.
- an ion exchange device (not shown) and an upstream crystallization part (not shown) may be provided upstream of the second scale inhibitor supply part 230.
- the water treatment units from the second scale inhibitor supply unit 230 to the second precipitation unit 250 and the water treatment units from the first scale inhibitor supply unit 30 to the first precipitation unit 50 are shown one by one.
- a plurality of water treatment units may be connected to each other.
- first, water to be treated is treated by the water treatment method described in the third reference embodiment.
- the second concentrated water after being treated by the method of the third reference embodiment is treated water, as the water to be treated, from the first scale inhibitor supply step described in the first reference embodiment and the second reference embodiment to the first precipitation step. Is processed.
- the first concentrated water that has passed through the most downstream first sedimentation unit 50 is processed by the downstream desalting unit 60.
- the water that has passed through the downstream desalting unit 60 is recovered as treated water.
- the concentrated water in the downstream desalting unit 60 is discharged out of the system.
- an evaporator (not shown) may be installed downstream of the concentrated water side of the downstream desalting unit 60.
- the third pH adjustment step described in the third reference embodiment is performed. May be.
- the water treatment system 300 of the fourth reference embodiment and the water treatment system 400 of the fifth reference embodiment can also treat the water to be treated containing ions at a high water recovery rate.
- gypsum is mainly precipitated in the second crystallization unit 220 on the upstream side of the water to be treated, so that the gypsum recovery rate in the second crystallization unit 220 is high and the gypsum is sent downstream.
- the number of moles of ions supplied is further reduced.
- the purity of the gypsum recovered by the second crystallization unit 220 can be increased.
- the amount of gypsum seed crystals supplied to the first crystallization tank 21 and the second crystallization tank 221 is controlled in the first to fifth reference embodiments.
- a configuration in which the seed crystal supply amount to the first crystallization tank 21 is controlled will be described with reference to FIG. The same configuration is applied to the second crystallization tank 221.
- a first pH measurement unit 543 that measures the pH of the first concentrated water in the first crystallization tank 21 is installed.
- the first pH measurement unit 543 may be installed in a flow path connecting the first desalting unit 10 and the first crystallization tank 21, or may be installed directly in the first crystallization tank 21.
- the first pH measurement unit 543 is connected to the control unit 24 of the seed crystal supply unit 22.
- a pH adjusting unit 540 is installed as shown in FIG.
- the pH adjustment unit 540 includes a tank 541, a control unit 542, and a valve V7.
- the first pH measurement unit 543 is connected to the control unit 542 of the pH adjustment unit 540.
- the pH adjustment unit 540 manages the pH of the first concentrated water in the first crystallization tank 21 to a predetermined value based on the measurement value of the first pH measurement unit 543.
- the pH meter 243a described in the third reference embodiment corresponds to the second pH measuring unit
- the control unit 242 corresponds to the control unit 542.
- the seed crystal stored in the seed crystal tank 23 of the first seed crystal supply unit 22 may be a new chemical. However, when the first separation unit 180 is installed, the seed crystal is larger than the predetermined particle size separated by the classifier 181. Gypsum and gypsum after being dehydrated by the dehydrator 182 may be stored in the seed crystal tank 23.
- Control of the seed crystal supply amount according to the first embodiment is performed in the following steps.
- the first pH measuring unit 543 measures the pH of the first concentrated water in the first crystallization tank 21.
- the measured pH value is transmitted to the control unit 24 of the seed crystal supply unit 22.
- the control unit 24 stores a pH range in which the scale prevention function of the calcium scale inhibitor is reduced.
- the pH range in which the scale prevention function of the calcium scale inhibitor is reduced is 6.0 or less, preferably 5.5 or less, more preferably 4.0. It is as follows.
- the control unit 24 compares the measured value of the first pH measuring unit 543 with the pH range. When the measured value is in the above pH range, the control unit 24 reduces the amount of gypsum seed crystals supplied by reducing the opening of the valve V3. When the measured value is higher than the pH range, the control unit 24 increases the opening amount of the valve V3 to increase the supply amount of the gypsum seed crystal.
- the seed crystal If the seed crystal is present, gypsum precipitates, but if the calcium scale inhibitor is functioning, the crystallization rate is slowed down. For this reason, the amount of seed crystals is increased to promote crystallization. On the other hand, when the function of the calcium scale inhibitor is reduced, a sufficient crystallization rate can be obtained even if there are few seed crystals. Thus, if the seed crystal supply amount is adjusted according to pH, it becomes possible to reduce the amount of seed crystal used.
- the seed crystal can be intermittently supplied by measuring pH periodically during continuous operation.
- a change with time of pH may be acquired during a test operation of the system, and the seed crystal supply amount may be increased or decreased based on the acquired change with time.
- the second embodiment of the present invention is a water treatment system 600 including at least one of a first separation unit 180 and a second separation unit 280.
- the water treatment system 600 is different from the first embodiment in that the gypsum separated in the separation unit is directly supplied to the first crystallization tank or the second crystallization tank as a seed crystal.
- a configuration in which the seed crystal supply amount to the first crystallization tank 21 according to the present embodiment is controlled will be described with reference to FIG. The same configuration is applied to the second crystallization tank 221.
- a first circulation line 601 is installed so that a part of gypsum settled on the bottom of the classifier 181 of the first separation unit 180 is fed directly to the first crystallization tank 21.
- a second circulation line 602 is provided that conveys part of the gypsum after being dehydrated by the dehydrator 182 so as to be directly supplied to the first crystallization tank 21.
- a valve V8 is installed in the first circulation line 601 and a valve V9 is installed in the second circulation line 602. In the present embodiment, either one of the first circulation line 601 and the second circulation line 602 may be installed.
- the control unit 610 is connected to the first pH measurement unit 543, the valve V8, and the valve V9 that are the same as those in the first embodiment.
- the first pH measurement unit 543 measures the pH of the first concentrated water in the first crystallization tank 21.
- the measured pH value is transmitted to the control unit 610.
- the controller 610 stores a pH range in which the scale prevention function of the calcium scale inhibitor is reduced.
- the control unit 610 compares the measured value of the first pH measuring unit 543 with the pH range in the same process as in the first embodiment, and adjusts the opening degrees of the valve V8 and the valve V9.
- a seed crystal concentration measurement unit (not shown) that measures the gypsum seed crystal concentration in the first concentrated water in the first crystallization tank 21 is installed in the first crystallization tank 21. May be.
- the seed crystal concentration measurement unit measures the seed crystal concentration in the first crystallization tank 21.
- the measured concentration value is transmitted to the control unit 24 or the control unit 610.
- the control unit 24 or the control unit 610 stores a threshold value of the seed crystal concentration, and increases the seed crystal supply amount when the seed crystal concentration is equal to or lower than the threshold value.
- a first concentration measurement unit (not shown) is installed downstream of the first crystallization tank 21 and upstream of the first precipitation unit 50.
- the first concentration measurement unit is preferably installed on the downstream side of the first separation unit 180, but may be on the upstream side of the first separation unit 180.
- the first concentration measurement unit is connected to the control unit 24 or the control unit 610.
- a second concentration measurement unit is installed instead of the first concentration measurement unit.
- the first concentration measuring unit measures at least one of the Ca ion concentration and the sulfate ion concentration in the first concentrated water discharged from the first crystallization tank 21.
- the measured concentration is transmitted to the control unit 24 or the control unit 610.
- the Ca ion concentration and the sulfate ion concentration measured by the first concentration measuring unit depend on the crystallization speed in the first crystallization tank 21. In the case of the same residence time, the lower the Ca ion concentration and the sulfate ion concentration, the faster the crystallization rate.
- the control unit 24 and the control unit 610 store at least one threshold value of the Ca ion concentration and the sulfate ion concentration.
- the control unit 24 increases the opening amount of the valve V3 to increase the supply amount of the seed crystal. .
- the control unit 24 reduces the opening of the valve V3 to reduce the supply amount of the seed crystal. .
- the control unit 610 increases the opening of the valve V8 and the valve V9 to supply the seed crystal supply amount. Increase.
- the control unit 610 reduces the opening of the valve V8 and the valve V9 to supply the seed crystal supply amount. Reduce.
- the supply amount of the seed crystal is controlled in the same process as described above. As described above, when the supply amount of the seed crystal is controlled by at least one of the Ca ion concentration and the sulfate ion concentration after the crystallization step, the seed crystal usage amount can be reduced.
- FIG. 16 is a partial schematic view of a water treatment system according to a third embodiment of the present invention.
- the water treatment system 700 of FIG. 16 collects the gypsum separated from the first concentrated water in the first crystallization unit 20 in the water treatment system of the fifth reference embodiment, and the second crystallization of the second crystallization unit 220. It is configured to be supplied to the tank 221. The same configuration can be adopted in the water treatment system of the fourth reference embodiment.
- the pH of the concentrated water (first concentrated water) in the first crystallization tank 21 of the first crystallization unit 20 is not particularly limited. It is advantageous to perform the first crystallization step without changing the pH from the 1 desalting step. In this case, the first crystallization step is performed at a pH (10 or more) at which silica can be dissolved, but the solubility of calcium carbonate is low in this pH region.
- the second crystallization unit 220 (second crystallization step) crystallizes gypsum in a lower pH region.
- the pH range of the second crystallization step (6.0 or less, more preferably 4.0 or less)
- calcium carbonate can be dissolved in water.
- the gypsum containing calcium carbonate recovered in the first crystallization unit 20 is supplied to the second crystallization tank 221 of the second crystallization unit 220, the calcium carbonate which is an impurity dissolves in the second concentrated water and the gypsum. Is present in the second concentrated water as a solid. If the water treatment system 300 of 3rd Embodiment is used, while being able to process to-be-processed water with a high water recovery rate, it becomes possible to collect
- FIG. 17 is a partial schematic view of a water treatment system according to a sixth reference embodiment of the present invention.
- the same components as those of the second reference embodiment are denoted by the same reference numerals.
- the sixth reference embodiment has been described using the water treatment method having the first separation step and the water treatment system having the first separation unit, but the second separation step and the second separation unit have the same configuration. Applicable.
- the water treatment system 800 includes a plurality of classifiers (first classifiers) 181 in the flow direction of the water to be treated with respect to one first crystallization unit 20.
- first classifiers classifiers
- two first classifiers 181a and 181b are installed.
- the first classifier 181a located on the most upstream side and the first classifier 181b located on the downstream side differ in the size of the gypsum to be separated.
- the size of the gypsum separated by the first classifier 181b is smaller than the gypsum separated by the first classifier 181a.
- the first classifier 181a is a classifier that separates particles having an average particle diameter of 10 ⁇ m or more
- the first classifier 181b is a classifier that separates particles having an average particle diameter of 5 ⁇ m or more.
- the size of the gypsum separated by each first classifier 181 is designed so as to decrease in order from the upstream side toward the downstream side.
- the number of first classifiers installed in the distribution direction to be processed and the particle size of solids that can be separated by each classifier are appropriately set in consideration of the water recovery rate, gypsum recovery rate, processing cost, and the like.
- the following treatment is performed in the first separation step.
- the first classifier 181a located at the uppermost stream gypsum having an average particle size of 10 ⁇ m or more is classified and settles to the bottom of the first classifier 181a.
- the settled gypsum is discharged from the first classifier 181a and fed to the dehydrator 182.
- the supernatant liquid of the first classifier 181a is fed to the first classifier 181b on the downstream side.
- This supernatant liquid mainly contains particles (gypsum, calcium carbonate, silica, etc.) having a particle diameter of less than 10 ⁇ m.
- gypsum having an average particle size of 5 ⁇ m or more is classified and settles to the bottom of the first classifier 181b.
- the supernatant liquid of the first classifier 181b is fed to the first sedimentation unit 50.
- the settled gypsum is discharged from the first classifier 181b.
- the discharged gypsum is fed to the first crystallization tank 21 through the solids circulation line 801 and is supplied to the first concentrated water in the first crystallization tank 21.
- the circulated gypsum functions as a seed crystal in the first crystallization tank 21, and the circulated gypsum grows by crystallization.
- the circulating gypsum having an average particle size of 10 ⁇ m or more is fed together with the first concentrated water from the first crystallization tank 21 to the first classifier 181a, separated from the first concentrated water by the first classifier 181a, and dehydrated. To the machine 182.
- the supernatant liquid of the first classifier 181b contains particles having a relatively small diameter of less than 5 ⁇ m, for example, about 2 to 3 ⁇ m.
- the gypsum is discharged from the first crystallization tank 21 before growing to a sufficient size in the first crystallization tank 21 and flows into the first precipitation tank 51.
- the amount of gypsum increases.
- the sediment in the first sedimentation tank 51 contains a large amount of gypsum.
- a circulation line 802 that connects the bottom of the first precipitation tank 51 and the first crystallization tank 21 is provided, and a solid substance containing gypsum precipitated at the bottom of the first precipitation tank 51 is provided.
- the first crystallization tank 21 may be circulated.
- this reference embodiment it is possible to increase the amount of gypsum recovered in the first separation unit and to reduce the moisture content of the recovered gypsum.
- Using the water treatment process and the water treatment system of the present embodiment leads to a reduction in the amount of gypsum particles with a relatively small diameter flowing out to the downstream side. The amount of waste generated can be reduced.
- First desalting unit 20 First crystallization unit 21 First crystallization tank 22 First seed crystal supply unit 23,223 Seed crystal Tanks 24, 32, 42, 224, 232, 242, 542, 610 Control unit 30 First scale inhibitor supply unit 31, 41, 231, 241, 541 Tank 40 First pH adjustment unit 43, 243 pH meter 50 First precipitation Unit 51 first sedimentation tank 52 first filtration device 60 downstream demineralization unit 70 first upstream sedimentation unit 71 sedimentation tank 72 filtration device 73 first degassing unit 180 first separation unit 181, 181a, 181b, 281 classifier 182, 282 Dehydrator 210 Second desalting unit 220 Second crystallization unit 221 Second crystallization tank 222 Second seed crystal supply unit 230 Second scale inhibitor supply unit 240 Second pH adjustment unit 25 0 second sedimentation unit 251 second sedimentation tank 252 second filtration device 280 second separation unit 540 pH adjustment unit 543 first pH measurement unit 601 first circulation line 602 second circulation line 80
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Abstract
Description
また、特許文献1の廃水処理装置ではイオン交換装置を再生するに当たり多量の薬品が必要となり、処理コストが高いことも問題となっていた。
また、前記第1晶析工程の後に、前記第1濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第1濃度計測工程を含み、前記第1供給量制御工程が、前記第1濃度計測工程で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御することが好ましい。前記第2晶析工程の後に、前記第2濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第2濃度計測工程を含み、前記第2供給量制御工程が、前記第2濃度計測工程で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記種結晶の供給量を制御することが好ましい。
また、前記第1晶析部の下流側に、前記第1濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第1濃度計測部を備え、前記第1制御部が、前記第1濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御することが好ましい。前記第2晶析部の下流側に、前記第2濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第2濃度計測部を備え、前記第2制御部が、前記第2濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御することが好ましい。
上記態様において、前記第2pH調整部が、前記第2濃縮水を炭酸カルシウムが溶解可能なpHに調整し、前記第1分離部で分離された前記石膏を、前記第2晶析部に供給することが好ましい。
図1は、本発明の第1参考実施形態に係る水処理システムの概略図である。図1の水処理システム1は、被処理水の流通方向に2つの水処理部が連結された構成となっている。本参考実施形態の水処理システム1では、被処理水の性状に応じて水処理部が1つであっても良いし、3つ以上の水処理部が連結されても良い。
カルシウムスケール防止剤は、被処理水中で石膏または炭酸カルシウムの結晶核生成を抑制するとともに、被処理水中に含まれる石膏または炭酸カルシウムの結晶核(種結晶や飽和濃度を超えて析出した小径のスケールなど)の表面に吸着して、石膏または炭酸カルシウムの結晶成長を抑制する機能を有するものである。あるいは、カルシウムスケール防止剤は、析出した結晶などの被処理水中の粒子を分散させる(凝集を防止する)機能を有するタイプのものもある。
カルシウムスケール防止剤としては、ホスホン酸系のスケール防止剤、ポリカルボン酸系のスケール防止剤、及びこれらの混合物等がある。具体例としては、FLOCON260(商品名、BWA社製)が挙げられる。
マグネシウムスケール防止剤としては、ポリカルボン酸系のスケール防止剤等がある。具体例としては、FLOCON 295N(商品名,BWA社製)が挙げられる。
ここで、ナノフィルター(NF)、電気透析装置(ED)、極性転換式電気透析装置(EDR)、電気再生式純水装置(EDI)、静電脱塩装置(CDl)では、スケール成分(2価イオン、Ca2+、Mg2+等)を選択的に除去し、Na+及びCl-等の1価イオンは透過する。これらの脱塩装置を使用すれば濃縮水中のスケール成分となるイオンのイオン濃度の濃縮を抑制するので、水回収率の向上、省エネルギー化(例えばポンプ動力の削減等)を図ることができる。
また、被処理水が冷却塔ブローダウン水の場合では、再生水は純水である必要は無く、スケール成分(2価イオン、Ca2+、Mg2+等)が除去されていればよいので、ナノフィルター(NF)等を利用する利点がある。
特に被処理水にMgイオンが含まれる場合には、第1上流側沈殿部は複数の沈殿槽71が被処理水の流通方向に直列に接続される構成を採用することができる。
第1脱気部73は、第1上流側沈殿部70の被処理水下流側であって、第1スケール防止剤供給部30a及び第1pH調整部40aの上流側に設置されていても良い。
そこで、原水(被処理水)中の石膏が過飽和である場合には、最上流の第1スケール防止剤供給部30a及び第1pH調整部40aの上流に、上述の第1晶析槽21a,21bと同じ構成の上流側晶析部(不図示)を設け、石膏濃度を低減させてから被処理水を第1脱塩部10aに送給しても良い。
まず、水中での石膏、シリカ、及び炭酸カルシウムの析出挙動を説明する。図2は、石膏析出量のpH依存性のシミュレーション結果である。図3は、炭酸カルシウム析出量のpH依存性のシミュレーション結果である。同図において、横軸はpH、縦軸はそれぞれ、石膏または炭酸カルシウムの析出量(mol)である。シミュレーションはOLI社製シミュレーションソフトを用い、水中に各固体成分が0.1mol/Lずつ混合され、酸としてH2SO4、アルカリとしてCa(OH)2が添加される条件で行った。
図4は、シリカ溶解量のpH依存性を示すグラフ(出典:米国特許第7815804号明細書の図4)である。同図において、横軸はpH、縦軸はシリカの溶解量(mg/L)である。
被処理水が工業廃水などである場合は、被処理水が第1上流側沈殿部70に流入する前に、被処理水中の油分や浮遊粒子等を除去する工程や、生物処理あるいは化学酸化処理により有機物を除去する工程が実施される。
図1の水処理システム1では、第1脱気部73に流入する前の被処理水が、低pHに調整される。被処理水中の炭酸は、被処理水のpHに応じて以下の平衡状態となっている。
pHが6.5以下と低い場合には、被処理水中では主としてHCO3 -及びCO2の状態で存在する。
第1脱気工程により炭酸イオン濃度が低減された被処理水が、第1上流側沈殿部70に送給される。
第1上流側沈殿部70において、Caイオン及び炭酸イオンは炭酸カルシウムとして予め被処理水から一部除去される。
被処理水にCaイオン以外の金属イオンが含まれる場合は、第1上流側沈殿部70において、金属イオンが水への溶解性が低い金属化合物として予め被処理水から粗除去される。この金属化合物は主として金属水酸化物であるが、炭酸塩も含まれる場合がある。
沈殿槽71で被処理水にCa(OH)2及びアニオン系ポリマー(三菱重工メカトロシステムズ(株)製、商品名:ヒシフロックH305)が投入され、沈殿槽71内のpHは4以上12以下、好ましくは8.5以上12以下に管理される。
金属化合物の溶解度はpHに依存する。金属イオンの水への溶解度は酸性になるほど高くなる。上記のpH領域では多くの金属化合物の溶解度が低くなる。上記pH領域では水への溶解度が低い金属化合物は沈殿槽71内で凝集し、沈殿槽71の底部に沈殿する。
沈殿した炭酸カルシウム及び金属化合物は沈殿槽71の底部から排出される。
本参考実施形態の水処理システム1でMgイオンを含む被処理水を処理する場合、沈殿槽71での被処理水のpHが、マグネシウム化合物(主として水酸化マグネシウム)が析出するpHに調整する。具体的には、被処理水のpHが10以上、好ましくはpH10.5以上、より好ましくはpH11以上に調整される。こうすることにより、マグネシウム化合物が被処理水から析出し、沈殿槽71の底部に沈殿して除去される。この結果、被処理水中のMgイオンが粗除去され、被処理水中のMgイオン濃度が低減する。
上記の場合、第1上流側沈殿部70から排出された後の被処理水が、上記のマグネシウム化合物が溶解可能なpHに調整されることが好ましい。具体的に、pH10未満に調整される。こうすることにより、下流側の装置及び工程、特に第1脱塩部10a及び第1脱塩工程でのスケール生成を防止することが可能となる。
被処理水はろ過装置72に送給される。ろ過装置72によりFe(OH)3により凝集した固形分が除去される。
第1スケール防止剤供給部30aの制御部32aはバルブV1aを開放し、タンク31aから所定量のカルシウムスケール防止剤を被処理水に供給する。制御部32aは、カルシウムスケール防止剤の濃度が被処理水の性状に応じて設定された所定値となるようにバルブV1aの開度を調整する。
第1pH調整部40aの制御部42aは、第1脱塩部10a入口での被処理水のpHを、シリカが被処理水中に溶解可能な値に管理する。具体的に、第1脱塩部10aに送給される被処理水のpHは10以上、好ましくは10.5以上、より好ましくは11以上に調整される。
pH計43aは、第1脱塩部10a入口での被処理水のpHを計測する。制御部42aは、pH計43aでの計測値が所定のpH管理値になるようにバルブV2aの開度を調整し、タンク41aからアルカリを被処理水に投入させる。
第1脱塩部10aにおいて、pHが調整された被処理水が処理される。第1脱塩部10aが逆浸透膜装置である場合、逆浸透膜を通過した水は処理水として回収される。被処理水に含まれるイオン及びスケール防止剤は、逆浸透膜を透過することができない。従って、逆浸透膜の非透過側はイオン濃度が高い濃縮水となる。例えば静電脱塩装置など他の脱塩装置を用いた場合も、被処理水は処理水と、イオン濃度が高い濃縮水(第1濃縮水)とに分離される。
被処理水にMgイオンが含まれている場合、第1脱塩工程により第1濃縮水中に含まれるMgイオン濃度が増加する。しかし、マグネシウムスケール防止剤によりマグネシウムを含むスケールの発生が抑制されている。
第1濃縮水は、第1晶析部20aに向かって送給される。
第1脱塩部10aから排出された第1濃縮水が、第1晶析部20aの第1晶析槽21aに貯留される。第1種結晶供給部22aの制御部24aは、バルブV3aを開放し、タンク23aから石膏の種結晶を第1晶析槽21a内の第1濃縮水に添加する。
第1脱塩部10aからの第1濃縮水はpH10以上である。前述したようにカルシウムスケール防止剤が存在する高pH領域の水中で石膏は溶解状態である。しかし、種結晶が十分に存在すると、スケール防止剤が存在していても種結晶を核として石膏が晶析する。図1の水処理システム1においては、結晶成長した大径(例えば粒径が10μm以上、より好ましくは20μm以上)の石膏が第1晶析槽21aの底部に沈殿する。沈殿した石膏は第1晶析槽21aの底部から排出される。
図3に依ればpH10以上で炭酸カルシウムは析出する傾向がある。しかし、カルシウムスケール防止剤が添加されているために、第1晶析槽21a内では炭酸カルシウムの析出は抑制されている。また、第1上流側沈殿部や第1脱気部を設ける場合は、予め炭酸カルシウムの濃度が低減されている。この結果、第1晶析槽21aでは炭酸カルシウムは石膏の種結晶を核として晶析しにくい。
図5は、石膏が過飽和状態にある模擬水(Ca2+,SO4 2-,Na+,Cl-を含む)に、スケール防止剤(FLOCON260)を添加した場合において、模擬水のpHを変えて石膏析出実験を行った結果である。実験条件は以下のとおりである。
模擬水の石膏過飽和度(25℃):460%、
スケール防止剤添加量:2.1mg/L、
pH:6.5(条件1)、5.5(条件2)、4.0(条件3)、3.0(条件4)、
種結晶添加量:0g/L。
図6は、模擬水にカルシウムスケール防止剤(FLOCON260)を添加した場合において、種結晶の添加量を変えて石膏析出実験を行った結果である。pHを4.0として、種結晶として石膏(CaSO4・2H2O)を以下の添加量とした以外は、図5の実験条件と同じとした。
種結晶添加量:0g/L(条件3)、3g/L(条件5)、6g/L(条件6)、3g/L(条件7)。
条件5,6では、スケール防止剤が添加された模擬水に、種結晶とpH調整のための硫酸とを添加した。条件7では、スケール防止剤が添加された模擬水に予め上記スケール防止剤に浸漬した種結晶を添加し、pH調整のため硫酸を添加した。
条件5と条件7とは、スケール防止剤に浸漬していない種結晶と浸漬した種結晶を使用している以外は同じ試験条件である。予め種結晶にスケール防止剤を付着させた条件7でも過飽和度が199%となっており、条件5と同程度の石膏が析出することが確認できた。すなわち、条件5,7の結果から、種結晶のカルシウムスケール防止剤中の浸漬時間に依らず、pH4.0と低下させることによってスケール防止剤の機能が低減されることが示された。
第1晶析部20aの上澄み液(第1濃縮水)は、第1沈殿部50aに送給される。第1沈殿部50aにおいて、晶析工程後の第1濃縮水にCa(OH)2及びアニオン系ポリマー(ヒシフロックH305)が投入され、第1沈殿槽51a内のpHが4以上12以下、好ましくは8.5以上12以下に管理される。第1沈殿槽51a内で、炭酸カルシウム及び金属化合物が沈殿し、第1濃縮水から除去される。沈殿した炭酸カルシウム及び水への溶解性が低い金属化合物は、第1沈殿槽51aの底部から排出される。
被処理水は第1ろ過装置52aに送給される。第1ろ過装置52aによりFe(OH)3により凝集した固形分が除去される。
第1沈殿工程でシリカを除去するか否かは、被処理水や第1濃縮水の性状に応じて決定される。
そこで、第1沈殿槽51a内の第1濃縮水が、マグネシウム化合物(主として水酸化マグネシウム)が析出可能な値に調整される。こうすることにより、第1沈殿槽51a内でマグネシウム化合物が沈殿し、第1沈殿槽51a内の第1濃縮水のMgイオン濃度を低減させる。更に、第1沈殿工程の後で、第1沈殿槽51aから排出された第1濃縮水が、マグネシウム化合物が溶解可能なpHに調整される。具体的に、pH10未満である。こうすることにより、脱塩部でのMgを含むスケールの析出を抑制することができる。
被処理水最下流に位置する第1沈殿部50bを通過した濃縮水(第1濃縮水)は、下流側脱塩部60に送給される。下流側脱塩部60を通過した水は、処理水として回収される。下流側脱塩部60の濃縮水は系外に排出される。下流側脱塩部60が設置されると、水処理部で処理された後の水から更に処理水を回収することができるので、水回収率が向上する。
図9は、本発明の第2参考実施形態の水処理システムの概略図である。図9において第1参考実施形態と同じ構成には同一の符号を付す。第2参考実施形態の水処理システム100は、第1晶析部20a,20bの下流側に第1分離部180(180a,180b)が設置される。図9の水処理システム100は、被処理水の流通方向に2つの水処理部が連結された構成となっている。本参考実施形態の水処理システム100では、被処理水の性状に応じて水処理部が1つであっても良いし、3つ以上の水処理部が連結されても良い。
図9では、第1分離部180(180a,180b)は分級機181(181a,181b)と脱水機182(182a,182b)とで構成される。分級機181a,181bは、例えば液体サイクロンとされる。脱水機182a,182bは例えばベルトフィルタとされる。
<第1分離工程>
第1晶析槽21a,21b内の第1濃縮水が第1分離部180a,180bに搬送される。ここで搬送される第1濃縮水は、第1晶析槽21a,21b内で析出した固形物を含む水である。
分級機181a,181bに第1濃縮水が流入すると、所定の大きさ、例えば平均粒径10μm以上の石膏は分級機181a,181bの底部に沈降し、小さい粒径の石膏、炭酸カルシウム及びシリカは上澄み液に残留する。分級機181a,181bの底部に沈降した石膏は、脱水機182a,182bで更に脱水されて回収される。小さい粒径の石膏、炭酸カルシウム及びシリカを含む上澄み液は、第1沈殿部50a,50bに送給される。
本発明の処理対象となる水(被処理水)はCa2+、SO4 2-及び炭酸イオンを含む。具体的に、被処理水(原水)はかん水、下水、工場廃水、冷却塔のブローダウン水などである。また、被処理水は、Mgイオンなどの金属イオンを含む場合がある。
図10は、本発明の第3参考実施形態の第1参考例の水処理システムの概略図である。図10の水処理システム201は、被処理水の流通方向に2つの水処理部が連結された構成となっている。被処理水の性状に応じて、水処理部は1つであっても良いし、3つ以上の水処理部が連結されていても良い。
カルシウムスケール防止剤は、被処理水中で石膏または炭酸カルシウムの結晶核生成を抑制するとともに、被処理水中に含まれる石膏または炭酸カルシウムの結晶核(種結晶や飽和濃度を超えて析出した小径のスケールなど)の表面に吸着して、石膏または炭酸カルシウムの結晶成長を抑制する機能を有するものである。あるいは、カルシウムスケール防止剤は、析出した結晶などの被処理水中の粒子を分散させる(凝集を防止する)機能を有するタイプのものもある。
カルシウムスケール防止剤としては、ホスホン酸系のスケール防止剤、ポリカルボン酸系のスケール防止剤、及びこれらの混合物等がある。具体例としては、FLOCON260(商品名、BWA社製)が挙げられる。
図10にはタンク231a,231bが示され、タンク231a,231bにカルシウムスケール防止剤が収納される。
ここで、ナノフィルター(NF)、電気透析装置(ED)、極性転換式電気透析装置(EDR)、電気再生式純水装置(EDI)、静電脱塩装置(CDl)では、スケール成分(2価イオン、Ca2+、Mg2+等)を選択的に除去し、Na+及びCl-等の1価イオンは透過する。これらの脱塩装置を使用すれば濃縮水中のスケール成分となるイオンのイオン濃度の濃縮を抑制するので、水回収率の向上、省エネルギー化(例えばポンプ動力の削減等)を図ることができる。
また、被処理水が冷却塔ブローダウン水の場合では、再生水は純水である必要は無く、スケール成分(2価イオン、Ca2+、Mg2+等)が除去されていればよいので、ナノフィルター(NF)等を利用する利点がある。
図10では、第2脱塩部210a,210bを1つのみ示しているが、複数の脱塩装置が被処理水の流通方向に並列または直列に連結される構成とされても良い。
特に被処理水にMgイオンが含まれる場合には、第2上流側沈殿部270は複数の沈殿槽271が被処理水の流通方向に直列に接続される構成を採用することができる。
第2脱気部273は、第2上流側沈殿部270の被処理水下流側であって第2スケール防止剤供給部230aの上流側に設置されていても良い。
そこで、原水(被処理水)中の石膏が過飽和である場合には、最上流の第2スケール防止剤供給部230aの上流に、第2晶析部221a,221bと同じ構成の上流側晶析部(不図示)を設け、石膏濃度を低減させてから被処理水を第2脱塩部210aに送給しても良い。
まず、水中での石膏及び炭酸カルシウムの析出挙動を説明する。図2は、石膏析出量のpH依存性のシミュレーション結果である。図3は、炭酸カルシウム析出量のpH依存性のシミュレーション結果である。同図において、横軸はpH、縦軸はそれぞれ、石膏または炭酸カルシウムの析出量(mol)である。シミュレーションはOLI社製シミュレーションソフトを用い、水中に各固体成分が0.1mol/Lずつ混合され、酸としてH2SO4、アルカリとしてCa(OH)2が添加される条件で行った。
被処理水が工業廃水などである場合は、被処理水が第2上流側沈殿部270に流入する前に、被処理水中の油分や浮遊粒子等を除去する工程や、生物処理あるいは化学酸化処理により有機物を除去する工程が実施される。
図10の水処理システム201では、第2脱気部273に流入する前の被処理水が、低pHに調整される。被処理水中の炭酸は、被処理水のpHに応じて以下の平衡状態となっている。
pHが6.5以下と低い場合には、被処理水中では主としてHCO3 -及びCO2の状態で存在する。
第2脱気工程により炭酸イオン濃度が低減された被処理水が、第2上流側沈殿部270に送給される。
第2上流側沈殿部270において、Caイオン及び炭酸イオンは炭酸カルシウムとして予め被処理水から粗除去される。被処理水にCaイオン以外の金属イオンが含まれる場合は、第2上流側沈殿部270において金属イオンが水への溶解性が低い金属化合物として予め被処理水から粗除去される。この金属化合物は主として金属水酸化物であるが、炭酸塩も含まれる場合がある。
沈殿槽271で被処理水にCa(OH)2及びアニオン系ポリマー(三菱重工メカトロシステムズ(株)製、商品名:ヒシフロックH305)が投入され、沈殿槽271内のpHは4以上12以下、好ましくは8.5以上12以下に管理される。
金属化合物の溶解度はpHに依存する。金属イオンの水への溶解度は酸性になるほど高くなる。上記のpH領域では多くの金属化合物の溶解度が低くなる。上記pH領域では水への溶解度が低い金属化合物は沈殿槽271内で凝集し、沈殿槽271の底部に沈殿する。
沈殿した炭酸カルシウム及び金属化合物は沈殿槽271の底部から排出される。
本参考実施形態の第1参考例の水処理システム201でMgイオンを含む被処理水を処理する場合、第2上流側沈殿部270において被処理水がマグネシウム化合物(主として水酸化マグネシウム)が析出するpHに調整する。具体的には、被処理水のpHが10以上、好ましくはpH10.5以上、より好ましくはpH11以上に調整される。こうすることにより、マグネシウム化合物が被処理水から析出し、沈殿槽271の底部に沈殿して除去される。この結果、被処理水中のMgイオンが粗除去され、被処理水中のMgイオン濃度が低減する。
上記の場合、第2上流側沈殿部270から排出された後の被処理水が、上記のマグネシウム化合物が溶解可能なpHに調整されることが好ましい。具体的に、pH10未満に調整される。こうすることにより、下流側の装置及び工程、特に第2脱塩部210及び第2脱塩工程でのスケール生成を防止することが可能となる。
被処理水はろ過装置272に送給される。ろ過装置272によりFe(OH)3により凝集した固形分が除去される。
原水中の石膏が過飽和である場合は、ろ過装置272直後に設置される上流側晶析部で被処理水に石膏の種結晶が投入され、石膏が晶析して被処理水中の石膏濃度を低減させる。石膏濃度が低減した被処理水が第2脱塩部210aに送給される。
第2スケール防止剤供給部230aの制御部232aはバルブV4aを開放し、タンク231aから所定量のカルシウムスケール防止剤を被処理水に供給する。制御部232aは、カルシウムスケール防止剤の濃度が被処理水の性状に応じて設定された所定値となるように、それぞれバルブV4aのバルブの開度を調整する。
被処理水にMgイオンが含まれる場合、第2スケール防止剤供給工程において上記と同様の方法にてマグネシウムスケール防止剤が被処理水に供給される。この場合、複数の第2スケール防止剤供給部のタンクにそれぞれカルシウムスケール防止剤及びマグネシウムスケール防止剤が収納され、各制御部がカルシウムスケール防止剤及びマグネシウムスケール防止剤の供給量を調整する。
例えば図10の構成では、FeCl3が添加されることにより被処理水のpHが5から6程度となって第2脱塩部210aに流入することになる。図3に示すように、被処理水のpHが6.5以下では炭酸カルシウムは水中への溶解度が高い。また、式(1)のように、上記pH領域では水中で炭酸は主としてHCO3 -及びCO2の状態で存在する。第2脱塩部210aに流入する被処理水は、炭酸カルシウム濃度が低くなっている。このような場合には、第2脱塩部210aの直前でpHを調整しなくても良い。
なお、第2脱塩工程で処理される被処理水のpHを調整する場合には、第2脱塩部210aの上流において第2pH調整部と同じ構成のpH調整部を設置し、pH調整された被処理水を第2脱塩部210aに送給しても良い。
第2脱塩部210aにおいて、スケール防止剤が投入された被処理水が処理される。第2脱塩部210aが逆浸透膜装置である場合、逆浸透膜を通過した水は処理水として回収される。被処理水に含まれるイオン及びスケール防止剤は、逆浸透膜を透過することができない。従って、逆浸透膜の非透過側はイオン濃度が高い濃縮水(第2濃縮水)となる。
第2脱塩部210aでの処理により、第2濃縮水中の石膏及び炭酸カルシウムは飽和濃度以上に濃縮されている場合でも、カルシウムスケール防止剤によりスケール発生が抑制されている。
被処理水にMgイオンが含まれている場合、第2脱塩工程により第2濃縮水中に含まれるMgイオン濃度が増加する。しかし、マグネシウムスケール防止剤によりマグネシウムを含むスケールの発生が抑制されている。
本参考実施形態の第1参考例では、第2脱塩部210aと第2晶析部220aとの間で、第2pH調整部240aにより被処理水(第2濃縮水)のpHが調整されても良い。
第2pH調整部240aは、第2濃縮水のpHを、カルシウムスケール防止剤の機能が低減されて第2濃縮水中の石膏が析出可能な値に管理する。pH計243aは、第2濃縮水のpHを計測する。制御部242aはpH計243aでの計測値が所定のpH管理値になるように、バルブV6aの開度を調整する。
第2脱塩部210aから排出された第2濃縮水は、第2晶析部220aの第2晶析槽221aに貯留される。第2種結晶供給部222aの制御部224aは、バルブV5aを開放し、種結晶タンク223aから石膏の種結晶を第2晶析槽221a内の第2濃縮水に添加する。
第2脱塩部210aからの第2濃縮水はpH10以上である。前述したようにカルシウムスケール防止剤が存在する高pH領域の水中で石膏は溶解状態である。しかし、種結晶が十分に存在すると、スケール防止剤が存在していても種結晶を核として石膏が晶析する。図10の水処理システム201においては、結晶成長した大径(例えば粒径が10μm以上、より好ましくは20μm以上)の石膏が第2晶析槽221aの底部に沈殿する。沈殿した石膏は第2晶析槽221aの底部から排出される。
図5は、石膏が過飽和状態にある模擬水(Ca2+,SO4 2-,Na+,Cl-を含む)に、スケール防止剤(FLOCON260)を添加した場合において、模擬水のpHを変えて石膏析出実験を行った結果である。実験条件は以下のとおりである。
模擬水の石膏過飽和度(25℃):460%、
スケール防止剤添加量:2.1mg/L、
pH:6.5(条件1)、5.5(条件2)、4.0(条件3)、3.0(条件4)、
種結晶添加量:0g/L。
以上の結果から、pHが低い条件で第2晶析工程を行うと、炭酸カルシウムの含有量が低いために純度の高い石膏が晶析し、第2晶析槽221a底部から回収されることになる。低いpHで第2晶析工程を行う場合には、第2晶析槽221a内または第2脱塩部210aと第2晶析槽221aとの間の流路に、pH調整剤としての酸を供給する第3pH調整部(不図示)が設置される。当該pH調整部は、第2pH調整部と同じ構成である。
図6は、模擬水にカルシウムスケール防止剤(FLOCON260)を添加した場合において、種結晶の添加量を変えて石膏析出実験を行った結果である。pHを4.0として、種結晶として石膏(CaSO4・2H2O)を以下の添加量とした以外は、図5の実験条件と同じとした。
種結晶添加量:0g/L(条件3)、3g/L(条件5)、6g/L(条件6)、3g/L(条件7)。
条件5,6では、スケール防止剤が添加された模擬水に、種結晶とpH調整のための硫酸とを添加した。条件7では、スケール防止剤が添加された模擬水に予め上記スケール防止剤に浸漬した種結晶を添加し、pH調整のため硫酸を添加した。
条件5と条件7とは、スケール防止剤に浸漬していない種結晶と浸漬した種結晶を使用している以外は同じ試験条件である。予め種結晶にスケール防止剤を付着させた条件7でも過飽和度が199%となっており、条件5と同程度の石膏が析出することが確認できた。すなわち、条件5,7の結果から、種結晶のカルシウムスケール防止剤中の浸漬時間に依らず、pH4.0と低下させることによってスケール防止剤の機能が低減されることが示された。
この結果、図6に示すように、条件5と条件7は共に、過飽和度が199%以下であった。このことから、種結晶のカルシウムスケール防止剤中の浸漬時間に依らず、pHを4.0と低下させるとカルシウムスケール防止剤の機能が低下されると言える。
以上のことから、第2水処理部の第2晶析槽221aでは、高純度の石膏が回収できる。
第2晶析槽221a,221b内の第2濃縮水は、第2分離部280a,280bに搬送される。ここで搬送される第2濃縮水は、第2晶析槽221a,221b内で析出した固形物を含む水である。
分級機281a,281bに第2濃縮水が流入すると、所定の大きさ、例えば平均粒径10μm以上の石膏は分級機281a,281bの底部に沈降し、小さい粒径の石膏、炭酸カルシウム及びシリカは上澄み液に残留する。分級機281a,281bの底部に沈降した石膏は、脱水機282a,282bで更に脱水されて回収される。小さい粒径の石膏、炭酸カルシウム及びシリカを含む上澄み液は、第2沈殿部250a,250bに送給される。
第2晶析部220aの上澄み液(第2濃縮水)または第2分離部280aから排出された上澄み液(第2濃縮水)は、第2沈殿部250aに送給される。
第2沈殿部250aにおいて、晶析工程後の第2濃縮水にCa(OH)2及びアニオン系ポリマー(ヒシフロックH305)が投入され、第2沈殿槽251a内のpHが4以上12以下、好ましくは8.5以上12以下に管理される。第2沈殿槽251a内で、炭酸カルシウム及び金属化合物が沈殿し、第2濃縮水から除去される。沈殿した炭酸カルシウム及び水への溶解性が低い金属化合物は、第2沈殿槽251aの底部から排出される。
被処理水は第2ろ過装置252aに送給される。第2ろ過装置252aによりFe(OH)3により凝集した固形分が除去される。
被処理水最下流に位置する第2沈殿部250bを通過した第2濃縮水は、下流側脱塩部60で処理される。下流側脱塩部60を通過した水は、処理水として回収される。下流側脱塩部60の濃縮水は系外に排出される。下流側脱塩部60が設置されると、水処理部で処理された後の水から更に処理水を回収することができるので、水回収率が向上する。
本参考実施形態の第1参考例においても、下流側脱塩部60の濃縮水側の下流に、蒸発器(不図示)が設置されても良い。
特に第3参考実施形態の第1参考例では第2晶析部220で主として石膏を析出させるので、第2晶析部220での石膏回収率が高く、下流側へ送給されるイオンのモル数がより低減される。また、第2晶析部220で回収される石膏の純度を高めることができる。
図11は、本発明の第3参考実施形態の第2参考例の水処理システムの概略図である。図11の水処理システム200は、被処理水の流通方向に2つの水処理部が連結された構成となっている。被処理水の性状に応じて、水処理部は1つであっても良いし、3つ以上の水処理部が連結されていても良い。
図11にはタンク231aが2つ示されているが、例えば一方のタンク231aにカルシウムスケール防止剤が収納され、他方のタンク231aにシリカスケール防止剤が収納される。
図11では、第2脱塩部210を1つのみ示しているが、複数の脱塩装置が被処理水の流通方向に並列または直列に連結される構成とされても良い。
第2脱気部273は、第2上流側沈殿部270の被処理水下流側であって第2スケール防止剤供給部230aの上流側に設置されていても良い。
被処理水に対し、第1参考実施形態で説明した前処理が実施される。
第1参考実施形態で説明した第1脱気工程と同様にして、第2脱気部273で被処理水中のCO2が除去されることにより、被処理水中の炭酸イオン濃度が低減される。
第2上流側沈殿部270において、Caイオン及び炭酸イオンは炭酸カルシウムとして予め被処理水から粗除去される。被処理水にCaイオン以外の金属イオンが含まれる場合は、第2上流側沈殿部270において水への溶解性が低い金属化合物が予め被処理水から粗除去される。
第2上流側沈殿工程は、第1上流側沈殿工程と同工程で実施される。
本参考実施形態の第2参考例の水処理システム200でMgイオンを含む被処理水を処理する場合、第1参考実施形態と同様に、第2上流側沈殿部270において被処理水がマグネシウム化合物が析出するpHに調整され、被処理水中のMgイオンの粗除去が実施される。この後、第2上流側沈殿部270の下流側で、上記のマグネシウム化合物が溶解可能なpHに調整されることが好ましい。具体的に、pH10未満に調整される。こうすることにより、下流側の装置及び工程、特に第2脱塩部210及び第2脱塩工程でのスケール生成を防止することが可能となる。
上流側晶析部が設置された場合は、上流側晶析部において第1参考実施形態と同様の工程により被処理水中の石膏濃度が低減される。
第2スケール防止剤供給部230aの制御部232aはバルブV4aを開放し、タンク231aから所定量のカルシウムスケール防止剤を被処理水に供給する。第2スケール防止剤供給部230bの制御部232bはバルブV4bを開放し、タンク231bから所定量のシリカスケール防止剤を被処理水に供給する。制御部232a及び制御部232bは、カルシウムスケール防止剤及びシリカスケール防止剤の濃度が被処理水の性状に応じて設定された所定値となるように、それぞれバルブV4a及びバルブV4bバルブの開度を調整する。
例えば図11の構成では、FeCl3が添加されることにより被処理水のpHが5から6程度となって第2脱塩部210aに流入することになる。図3に示すように、被処理水のpHが6.5以下では炭酸カルシウムは水中への溶解度が高い。また、式(1)のように、上記pH領域では水中で炭酸は主としてHCO3 -及びCO2の状態で存在する。第2脱塩部210aに流入する被処理水は、炭酸カルシウム濃度が低くなっている。このような場合には、第2脱塩部210aの直前でpHを調整しなくても良い。
なお、第2脱塩工程で処理される被処理水のpHを調整する場合には、第2脱塩部210aの上流において第1参考実施形態の第1pH調整部と同じ構成のpH調整部を設置し、pH調整された被処理水を第2脱塩部210aに送給しても良い。
第2脱塩部210aにおいて、スケール防止剤が投入された被処理水が処理される。第2脱塩部210aが逆浸透膜装置である場合、逆浸透膜を通過した水は処理水として回収される。イオン及びスケール防止剤を含む水は、逆浸透膜の非透過側から濃縮水(第2濃縮水)として排出される。
第2脱塩部210aでの処理により、第2濃縮水中の石膏及びシリカは濃縮されているが、カルシウムスケール防止剤及びシリカスケール防止剤によりスケール発生が抑制されている。
本参考実施形態の第2参考例では、第2脱塩部210aと第2晶析部220aとの間で、第2pH調整部240aにより被処理水(第2濃縮水)のpHが調整されても良い。
第2pH調整部240aは、第2濃縮水のpHを、カルシウムスケール防止剤の機能が低減されて第2濃縮水中の石膏が析出可能な値に管理する。pH計243aは、第2濃縮水のpHを計測する。制御部242aはpH計243aでの計測値が所定のpH管理値になるように、バルブV6aの開度を調整する。
第2濃縮水が、第2晶析部220aの第2晶析槽221に貯留される。第2種結晶供給部222aの制御部224aは、バルブV5を開放し、種結晶タンク223aから石膏の種結晶を第2晶析槽221a内の第2濃縮水に添加する。第2濃縮水中にカルシウムスケール防止剤が含まれているが、種結晶が投入されると石膏が晶析し結晶成長する。
すなわち、種結晶を投入していなくても、pHを低減させるとスケール防止剤の機能が低減されて石膏が晶析することが確認できた。また、図5の結果によると、pHが低い程析出速度が大きいとの結果が得られた。
この結果、図6に示すように、条件5と条件7は共に、過飽和度が199%以下であった。このことから、種結晶のカルシウムスケール防止剤中の浸漬時間に依らず、pHを4.0と低下させるとカルシウムスケール防止剤の機能が低下されると言える。
また、図3によると、pH6.0以下では炭酸カルシウムは水中に溶解する。
以上のことから、第2水処理部の第2晶析槽221aでは、高純度の石膏が回収できる。
第2分離部280aが設置される場合、第2晶析槽221a内で析出した固形物を含む第2濃縮水が、第2分離部280aに搬送される。第2晶析槽221a内の第2濃縮水中には、晶析により析出した石膏が存在する。この他に、原水の水質変動や濃縮によりシリカスケール防止剤の機能が発揮する以上にシリカ濃度が高くなったために析出したシリカが含まれる可能性がある。シリカは小径粒子やコロイド状浮遊物として第2濃縮水中に存在する。
第2晶析部220aの上澄み液(第2濃縮水)または第2分離部280aから排出された上澄み液(第2濃縮水)は、第2沈殿部250aに送給される。
第2沈殿工程では、第1参考実施形態で説明した第1沈殿工程と同様にして、第2沈殿槽251a及び第2ろ過装置252aにより第2濃縮水中の炭酸カルシウム及び金属化合物が除去される。
被処理水最下流に位置する第2沈殿部250bを通過した第2濃縮水は、下流側脱塩部60で処理される。下流側脱塩部60を通過した水は、被処理水として回収される。下流側脱塩部60の濃縮水は系外に排出される。
本参考実施形態の第2参考例においても、下流側脱塩部60の濃縮水側の下流に、蒸発器(不図示)が設置されても良い。
特に第3参考実施形態の第2参考例では第2晶析部220で主として石膏を析出させるので、第2晶析部220での石膏回収率が高く、下流側へ送給されるイオンのモル数がより低減される。また、第2晶析部220で回収される石膏の純度を高めることができる。
図12は、本発明の第4参考実施形態の水処理システムの概略図である。図12において第1参考実施形態乃至第3参考実施形態と同じ構成には同一の符号を付す。
第4参考実施形態の水処理システム300は、第1参考実施形態で説明した水処理部が設置される。この水処理部の被処理水下流側に、第3参考実施形態で説明した水処理部が設置される。
最下流の第2沈殿部250を通過した第2濃縮水は、下流側脱塩部60で処理される。下流側脱塩部60を通過した水は、処理水として回収される。下流側脱塩部60の濃縮水は系外に排出される。
本参考実施形態においても、下流側脱塩部60の濃縮水側の下流に、蒸発器(不図示)が設置されても良い。
図13は、本発明の第5参考実施形態の水処理システムの概略図である。図13において第1参考実施形態乃至第3参考実施形態と同じ構成には同一の符号を付す。
第5参考実施形態の水処理システム400は、第3参考実施形態で説明した水処理部が設置される。この水処理部の被処理水下流側に、第1参考実施形態で説明した水処理部が設置される。
更に、第5参考実施形態の水処理システム400は、図13に示すように第2上流側沈殿部270の上流側に、第3参考実施形態と同様の第2脱気部273を有する。第2脱気部273は、第2上流側沈殿部270の被処理水下流側であって、第2スケール防止剤供給部230の上流側に設置されていても良い。
最下流の第1沈殿部50を通過した第1濃縮水は、下流側脱塩部60で処理される。下流側脱塩部60を通過した水は、処理水として回収される。下流側脱塩部60の濃縮水は系外に排出される。
本参考実施形態においても、下流側脱塩部60の濃縮水側の下流に、蒸発器(不図示)が設置されても良い。
特に第5参考実施形態の構成では、被処理水上流側の第2晶析部220で主として石膏を析出させているので、第2晶析部220での石膏回収率が高く、下流側へ送給されるイオンのモル数がより低減されている。更に、第2晶析部220で回収される石膏の純度を高めることができる。
本発明の第1実施形態は、第1参考実施形態から第5参考実施形態において、第1晶析槽21及び第2晶析槽221に供給される石膏の種結晶の量が制御される。図14を用いて、第1晶析槽21への種結晶供給量が制御される構成を説明する。第2晶析槽221についても同様の構成が適用される。
なお、第2晶析槽221に供給される石膏の種結晶の量を制御する場合には、第3参考実施形態で説明したpH計243aが第2pH計測部に相当し、第2pH調整部の制御部242が制御部542に相当する。
第1pH計測部543は第1晶析槽21内の第1濃縮水のpHを計測する。計測されたpHの値は、種結晶供給部22の制御部24に送信される。
このように、pHに応じて種結晶供給量を調整すれば、種結晶使用量を低減させることが可能となる。
本発明の第2実施形態は、第1分離部180及び第2分離部280の少なくとも一方を備える水処理システム600である。水処理システム600は、分離部で分離された石膏を種結晶として第1晶析槽または第2晶析槽に直接供給する点で第1実施形態と異なる。
図15では、第1分離部180の分級機181の底部に沈降した石膏の一部が、第1晶析槽21に直接供給されるように搬送する第1循環ライン601が設置される。また、脱水機182で脱水された後の石膏の一部が、第1晶析槽21に直接供給されるように搬送する第2循環ライン602が設置される。第1循環ライン601にバルブV8が設置され、第2循環ライン602にバルブV9が設置される。なお、本実施形態では、第1循環ライン601及び第2循環ライン602のいずれか一方が設置される構成でも良い。
制御部610が、第1実施形態と同様の第1pH計測部543、バルブV8、及び、バルブV9に接続する。
第1pH計測部543は、第1晶析槽21内の第1濃縮水のpHを計測する。計測されたpHの値は、制御部610に送信される。
制御部610は、カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲を格納している。制御部610は、第1実施形態と同様の工程にて、第1pH計測部543の計測値と上記pH範囲とを比較し、バルブV8及びバルブV9の開度を調整する。
第2晶析槽221の場合は、第1濃度計測部に代えて第2濃度計測部が設置される。
制御部610は、第1濃度計測部で計測されるCaイオンの濃度及び硫酸イオン濃度の少なくとも一方が閾値以上になる場合に、バルブV8及びバルブV9の開度を増大して種結晶の供給量を増大させる。制御部610は、第1濃度計測部で計測されるCaイオンの濃度及び硫酸イオン濃度の少なくとも一方が閾値未満である場合に、バルブV8及びバルブV9の開度を低減して種結晶の供給量を低減させる。
このように晶析工程後のCaイオンの濃度及び硫酸イオンの濃度の少なくとも一方により種結晶の供給量を制御すると、種結晶使用量を低減させることが可能となる。
図16は、本発明の第3実施形態の水処理システムの部分概略図である。図16において第1参考実施形態乃至第3参考実施形態と同じ構成には同一の符号を付す。
図16の水処理システム700は、第5参考実施形態の水処理システムにおいて第1晶析部20で第1濃縮水から分離された石膏が回収され、第2晶析部220の第2晶析槽221に供給される構成となっている。第4参考実施形態の水処理システムにおいても、同様の構成を採用することができる。
図17は、本発明の第6参考実施形態の水処理システムの部分概略図である。図17において第2参考実施形態と同じ構成には同一の符号を付す。
なお、以下では第6参考実施形態を第1分離工程を有する水処理方法及び第1分離部を有する水処理システムを用いて説明したが、第2分離工程及び第2分離部でも同様の構成を適用可能である。
最上流に位置する第1分級機181aでは、平均粒径10μm以上の石膏が分級され、第1分級機181aの底部に沈降する。沈降した石膏は、第1分級機181aから排出され、脱水機182に送給される。第1分級機181aの上澄み液は、下流側の第1分級機181bに送給される。この上澄み液には、主として粒径10μm未満である粒子(石膏、炭酸カルシウム、シリカ等)が含まれている。
循環された石膏は、第1晶析槽21内で種結晶として機能し、循環された石膏は晶析により結晶成長する。平均粒径10μm以上に結晶成長した循環石膏は、第1濃縮水とともに第1晶析槽21から第1分級機181aに送給され、第1分級機181aにより第1濃縮水から分離され、脱水機182に搬送される。
10 第1脱塩部
20 第1晶析部
21 第1晶析槽
22 第1種結晶供給部
23,223 種結晶タンク
24,32,42,224,232,242,542,610 制御部
30 第1スケール防止剤供給部
31,41,231,241,541 タンク
40 第1pH調整部
43,243 pH計
50 第1沈殿部
51 第1沈殿槽
52 第1ろ過装置
60 下流側脱塩部
70 第1上流側沈殿部
71 沈殿槽
72 ろ過装置
73 第1脱気部
180 第1分離部
181,181a,181b,281 分級機
182,282 脱水機
210 第2脱塩部
220 第2晶析部
221 第2晶析槽
222 第2種結晶供給部
230 第2スケール防止剤供給部
240 第2pH調整部
250 第2沈殿部
251 第2沈殿槽
252 第2ろ過装置
280 第2分離部
540 pH調整部
543 第1pH計測部
601 第1循環ライン
602 第2循環ライン
801,802 固形物循環ライン
Claims (38)
- Caイオン、SO4イオン及び炭酸イオンを含む被処理水に対して、カルシウムを含むスケールの析出を防止するカルシウムスケール防止剤が供給されるスケール防止剤供給工程と、
前記スケール防止剤供給工程の後で、前記被処理水が、前記Caイオン、前記SO4イオン及び前記炭酸イオンが濃縮された濃縮水と処理水とに分離される脱塩工程と、
前記濃縮水に石膏の種結晶が供給されて、前記濃縮水から石膏が晶析する晶析工程と、
前記晶析工程での前記濃縮水のpHを計測するpH計測工程と、
前記計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる供給量制御工程と、
を含む水処理方法。 - 前記晶析工程の後に、前記濃縮水から前記石膏を分離する分離工程を含み、前記分離工程で分離された前記石膏が、前記石膏の種結晶として用いられる請求項1に記載の水処理方法。
- 前記晶析工程の後に、前記濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する濃度計測工程を含み、
前記供給量制御工程が、前記濃度計測工程で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項1または請求項2に記載の水処理方法。 - Caイオン、SO4イオン及び炭酸イオンを含む被処理水に対して、カルシウムを含むスケールの析出を防止するカルシウムスケール防止剤を供給するスケール防止剤供給部と、
前記スケール防止剤供給部の下流側に設置され、前記被処理水を、前記Caイオン、前記SO4イオン及び前記炭酸イオンが濃縮された濃縮水と処理水とに分離する脱塩部と、
前記脱塩部の下流側に設けられ、前記濃縮水から石膏を晶析させる晶析槽と、前記晶析槽に石膏の種結晶を供給する種結晶供給部とを有する晶析部と、
前記晶析槽内の前記濃縮水のpHを計測するpH計測部と、
前記pH計測部で計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記pH計測部で計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる制御部と、
を含む水処理システム。 - 前記晶析部の下流側に、前記濃縮水から前記石膏を分離する分離部を備え、前記分離部で分離された前記石膏が、前記石膏の種結晶として用いられる請求項4に記載の水処理システム。
- 前記晶析部の下流側に、前記濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する濃度計測部を備え、
前記制御部が、前記濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項4または請求項5に記載の水処理システム。 - Caイオン、SO4イオン、炭酸イオン及びシリカを含む被処理水に対して、カルシウムを含むスケールの析出を防止するスケール防止剤であるカルシウムスケール防止剤が供給される第1スケール防止剤供給工程と、
前記被処理水が、前記シリカが前記被処理水中に溶解可能なpHに調整される第1pH調整工程と、
前記第1スケール防止剤供給工程及び前記第1pH調整工程の後で、前記被処理水が、前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第1濃縮水と処理水とに分離される第1脱塩工程と、
前記第1濃縮水に石膏の種結晶が供給されて、前記第1濃縮水から石膏が晶析する第1晶析工程と、
前記第1晶析工程での前記第1濃縮水のpHを計測する第1pH計測工程と、
前記計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第1供給量制御工程と、
を含む水処理方法。 - 前記第1晶析工程の後に、
前記被処理水に対して、前記カルシウムスケール防止剤と、シリカの析出を防止するスケール防止剤であるシリカスケール防止剤とが供給される第2スケール防止剤供給工程と、
前記第2スケール防止剤供給工程の後で、前記被処理水が前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第2濃縮水と処理水とに分離される第2脱塩工程と、
前記第2濃縮水に石膏の種結晶が供給されて、前記第2濃縮水から石膏が晶析する第2晶析工程とを含む請求項7に記載の水処理方法。 - 前記第1晶析工程の後に、前記第1濃縮水から前記石膏を分離する第1分離工程を含み、前記第1分離工程で分離された前記石膏が、前記石膏の種結晶として用いられる請求項7に記載の水処理方法。
- 前記第1晶析工程の後に、前記第1濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第1濃度計測工程を含み、
前記第1供給量制御工程が、前記第1濃度計測工程で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項7または請求項9に記載の水処理方法。 - 前記第2晶析工程での前記第2濃縮水のpHを計測する第2pH計測工程と、
前記計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第2供給量制御工程とを含む請求項8に記載の水処理方法。 - 前記第2晶析工程の後に、前記第2濃縮水から前記石膏を分離する第2分離工程を含み、前記第2分離工程で分離された前記石膏が、前記石膏の種結晶として用いられる請求項11に記載の水処理方法。
- 前記第2晶析工程の後に、前記第2濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第2濃度計測工程を含み、
前記第2供給量制御工程が、前記第2濃度計測工程で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項11または請求項12に記載の水処理方法。 - 前記第2濃縮水が、炭酸カルシウムが溶解可能なpHに調整される第3pH調整工程を含み、
前記第1分離工程で分離された前記石膏が、前記第2晶析工程において前記第3pH調整工程でpHが調整された前記第2濃縮水中に供給される請求項8に記載の水処理方法。 - Caイオン、SO4イオン、炭酸イオン及びシリカを含む被処理水に対して、カルシウムを含むスケールの析出を防止するスケール防止剤であるカルシウムスケール防止剤と、シリカの析出を防止するスケール防止剤であるシリカスケール防止剤とが供給される第2スケール防止剤供給工程と、
前記第2スケール防止剤供給工程の後で、前記被処理水が前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第2濃縮水と処理水とに分離される第2脱塩工程と、
前記第2濃縮水に石膏の種結晶が供給されて、前記第2濃縮水から石膏が晶析する第2晶析工程と、
前記第2晶析工程での前記第2濃縮水のpHを計測する第2pH計測工程と、
前記計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第2供給量制御工程と、
を含む水処理方法。 - 前記第2晶析工程の後に、
前記被処理水に対して、前記カルシウムスケール防止剤が供給される第1スケール防止剤供給工程と、
前記被処理水が、前記シリカが前記被処理水中に溶解可能なpHに調整される第1pH調整工程と、
前記第1スケール防止剤供給工程及び前記第1pH調整工程の後で、前記被処理水が、前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第1濃縮水と処理水とに分離される第1脱塩工程と、
前記第1濃縮水に石膏の種結晶が供給されて、前記第1濃縮水から石膏が晶析する第1晶析工程とを含む請求項15に記載の水処理方法。 - 前記第2晶析工程の後に、前記第2濃縮水から前記石膏を分離する第2分離工程を含み、前記第2分離工程で分離された前記石膏が、前記石膏の種結晶として用いられる請求項15に記載の水処理方法。
- 前記第2晶析工程の後に、前記第2濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第2濃度計測工程を含み、
前記第2供給量制御工程が、前記第2濃度計測工程で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項15または請求項17に記載の水処理方法。 - 前記第1晶析工程での前記第1濃縮水のpHを計測する第1pH計測工程と、
前記計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第1供給量制御工程とを含む請求項16に記載の水処理方法。 - 前記第1晶析工程の後に、前記第1濃縮水から前記石膏を分離する第1分離工程を含み、前記第1分離工程で分離された前記石膏が、前記石膏の種結晶として用いられる請求項19に記載の水処理方法。
- 前記第1晶析工程の後に、前記第1濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第1濃度計測工程を含み、
前記第1供給量制御工程が、前記第1濃度計測工程で計測された前記前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項19または請求項20に記載の水処理方法。 - 前記第2濃縮水が、炭酸カルシウムが溶解可能なpHに調整される第3pH調整工程を含み、
前記第1分離工程で分離された前記石膏が、前記第2晶析工程における前記第2濃縮水中に供給される請求項20に記載の水処理方法。 - Caイオン、SO4イオン、炭酸イオン及びシリカを含む被処理水に対して、カルシウムを含むスケールの析出を防止するスケール防止剤であるカルシウムスケール防止剤を供給する第1スケール防止剤供給部と、
前記被処理水にpH調整剤を供給して、前記シリカが前記被処理水中に溶解可能な値に前記被処理水のpHを調整する第1pH調整部と、
前記第1スケール防止剤供給部及び前記第1pH調整部の下流側に設置され、前記被処理水を、前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第1濃縮水と処理水とに分離する第1脱塩部と、
前記第1脱塩部の下流側に設けられ、前記第1濃縮水から石膏を晶析させる第1晶析槽と、前記第1晶析槽に石膏の種結晶を供給する第1種結晶供給部とを有する第1晶析部と、
前記第1晶析槽内の前記第1濃縮水のpHを計測する第1pH計測部と、
前記第1pH計測部で計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記第1pH計測部で計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第1制御部と、
を備える水処理システム。 - 前記第1晶析部の前記被処理水の下流側に、
前記被処理水に対して、前記カルシウムスケール防止剤と、シリカの析出を防止するスケール防止剤であるシリカスケール防止剤とを供給する第2スケール防止剤供給部と、
前記第2スケール防止剤供給部の下流側に設置され、前記被処理水を前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第2濃縮水と処理水とに分離する第2脱塩部と、
前記第2脱塩部の下流側に設けられ、前記第2濃縮水から石膏を晶析させる第2晶析槽と、前記第2晶析槽に石膏の種結晶を供給する第2種結晶供給部とを有する第2晶析部とを備える請求項23に記載の水処理システム。 - 前記第1晶析部の下流側に、前記第1濃縮水から前記石膏を分離する第1分離部を備え、前記第1分離部で分離された前記石膏が、前記石膏の種結晶として用いられる請求項23に記載の水処理システム。
- 前記第1晶析部の下流側に、前記第1濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第1濃度計測部を備え、
前記第1制御部が、前記第1濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項23または請求項25に記載の水処理システム。 - 前記第2晶析槽内の前記第2濃縮水のpHを計測する第2pH計測部と、
前記第2pH計測部で計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記第2pH計測部で計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第2制御部とを含む請求項24に記載の水処理システム。 - 前記第2晶析部の下流側に、前記第2濃縮水から前記石膏を分離する第2分離部を備え、前記第2分離部で分離された前記石膏が、前記石膏の種結晶として用いられる請求項27に記載の水処理システム。
- 前記第2晶析部の下流側に、前記第2濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第2濃度計測部を備え、
前記第2制御部が、前記第2濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項27または請求項28に記載の水処理システム。 - 前記第2pH調整部が、前記第2濃縮水を炭酸カルシウムが溶解可能なpHに調整し、
前記第1分離部で分離された前記石膏を、前記第2晶析部に供給する請求項25に記載の水処理システム。 - Caイオン、SO4イオン、炭酸イオン及びシリカを含む被処理水に対して、カルシウムを含むスケールの析出を防止するスケール防止剤であるカルシウムスケール防止剤とシリカの析出を防止するスケール防止剤であるシリカスケール防止剤とを供給する第2スケール防止剤供給部と、
前記第2スケール防止剤供給部の下流側に設置され、前記被処理水を前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第2濃縮水と処理水とに分離する第2脱塩部と、
前記第2脱塩部の下流側に設けられ、前記第2濃縮水から石膏を晶析させる第2晶析槽と、前記第2晶析槽に石膏の種結晶を供給する第2種結晶供給部とを有する第2晶析部と、
前記第2晶析槽内の前記第2濃縮水のpHを計測する第2pH計測部と、
前記第2pH計測部で計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記第2pH計測部で計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第2制御部と、
を含む水処理システム。
を備える水処理システム。 - 前記第2晶析部の前記被処理水の下流側に、
前記被処理水に対して、前記カルシウムスケール防止剤を供給する第1スケール防止剤供給部と、
前記被処理水にpH調整剤を供給して、前記シリカが前記被処理水中に溶解可能な値に前記被処理水のpHを調整する第1pH調整部と、
前記第1スケール防止剤供給部及び前記第1pH調整部の下流側に設置され、前記被処理水を、前記Caイオン、前記SO4イオン、前記炭酸イオン及び前記シリカが濃縮された第1濃縮水と処理水とに分離する第1脱塩部と、
前記第1脱塩部の下流側に設けられ、前記第1濃縮水から石膏を晶析させる第1晶析槽と、前記第1晶析槽に石膏の種結晶を供給する第1種結晶供給部とを有する第1晶析部とを備える請求項31に記載の水処理システム。 - 前記第2晶析部の下流側に、前記第2濃縮水から前記石膏を分離する第2分離部を備え、前記第2分離部で分離された前記石膏が、前記石膏の種結晶として用いられる請求項31に記載の水処理システム。
- 前記第2晶析部の下流側に、前記第2濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第2濃度計測部を備え、
前記第2制御部が、前記第2濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項31または請求項33に記載の水処理システム。 - 前記第1晶析槽内の前記第1濃縮水のpHを計測する第1pH計測部と、
前記第1pH計測部で計測されたpHが前記カルシウムスケール防止剤のスケール防止機能が低減されるpH範囲である場合に、前記石膏の種結晶の供給量を低減させ、前記第1pH計測部で計測されたpHが前記pH範囲よりも高い場合に、前記石膏の種結晶の供給量を増大させる第1制御部とを含む請求項32に記載の水処理システム。 - 前記第1晶析部の下流側に、前記第1濃縮水から前記石膏を分離する第1分離部を備え、前記第1分離部で分離された前記石膏が、前記石膏の種結晶として用いられる請求項35に記載の水処理システム。
- 前記第1晶析部の下流側に、前記第1濃縮水中の前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方を計測する第1濃度計測部を備え、
前記第1制御部が、前記第1濃度計測部で計測された前記Caイオンの濃度及び硫酸イオンの濃度の少なくとも一方に応じて、前記石膏の種結晶の供給量を制御する請求項35または請求項36に記載の水処理システム。 - 前記第2pH調整部が、炭酸カルシウムが溶解可能な値に前記第2濃縮水のpHを調整し、
前記第1分離部で分離された前記石膏を、前記第2晶析部に供給する請求項36に記載の水処理システム。
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