CN216513294U - Multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater - Google Patents
Multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater Download PDFInfo
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- 238000001728 nano-filtration Methods 0.000 title claims abstract description 141
- 150000003839 salts Chemical class 0.000 title claims abstract description 84
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 title claims abstract description 72
- 238000000926 separation method Methods 0.000 title claims abstract description 61
- 239000002351 wastewater Substances 0.000 title claims abstract description 46
- 239000011780 sodium chloride Substances 0.000 title claims abstract description 36
- 238000004939 coking Methods 0.000 title claims abstract description 34
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 title claims abstract description 33
- 229910052938 sodium sulfate Inorganic materials 0.000 title claims abstract description 33
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- 229910001868 water Inorganic materials 0.000 claims abstract description 80
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- 238000001223 reverse osmosis Methods 0.000 claims abstract description 49
- 238000006115 defluorination reaction Methods 0.000 claims abstract description 33
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- 229920005989 resin Polymers 0.000 claims abstract description 29
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 18
- 238000002425 crystallisation Methods 0.000 claims description 27
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- 230000000903 blocking effect Effects 0.000 abstract description 2
- 238000000605 extraction Methods 0.000 abstract description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 12
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 5
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- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 230000008020 evaporation Effects 0.000 description 4
- -1 fluorine ions Chemical class 0.000 description 4
- 238000004065 wastewater treatment Methods 0.000 description 4
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- 238000012986 modification Methods 0.000 description 3
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- 239000002904 solvent Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 239000013043 chemical agent Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
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- 238000010992 reflux Methods 0.000 description 2
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- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000010802 sludge Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- TVEXGJYMHHTVKP-UHFFFAOYSA-N 6-oxabicyclo[3.2.1]oct-3-en-7-one Chemical compound C1C2C(=O)OC1C=CC2 TVEXGJYMHHTVKP-UHFFFAOYSA-N 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical group [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-BJUDXGSMSA-N carbon-11 Chemical class [11C] OKTJSMMVPCPJKN-BJUDXGSMSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
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- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
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Abstract
The invention discloses a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater, and particularly relates to the field of wastewater salt extraction. The system comprises a pretreatment system (A), a salt separation concentration system (B), a second activated carbon device (11), a second resin softening device (12), a second defluorination tank (13) and a clean water tank (16). The invention adopts a combined pretreatment process of chemical softening and resin softening to reduce the scaling of a nanofiltration system; an immersed ultrafiltration membrane and resin combined process is adopted for preventing the membrane system from being blocked; meanwhile, in order to prevent the nanofiltration membrane from being blocked, a preposed reverse osmosis membrane protection process is adopted; the scaling and blocking risks of the nanofiltration membrane are eliminated; in order to improve the recovery rate of salt and reduce miscellaneous salt, a multi-stage nanofiltration combined process is adopted, the rejection rate of sodium sulfate is improved, the reclamation of wastewater and waste salt is realized, and the cost of dangerous waste treatment is reduced.
Description
Technical Field
The invention relates to the field of wastewater and salt extraction, in particular to a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater.
Background
For many years, the problems of coking wastewater treatment and discharge are always a great problem which troubles the design, construction and operation management of a coking plant.
The zero discharge technology of the coking wastewater is widely concerned. The technology mainly recycles the wastewater and sewage generated in the coking production process after advanced treatment so as to reduce the consumption of water resources, improve the recovery utilization rate of resources to the maximum extent, achieve the purposes of near zero emission and even zero emission, and is the future development direction of wastewater treatment in the coking industry.
The traditional zero-discharge technology comprises pretreatment, membrane concentration and evaporative crystallization, salt separation is not involved in the whole process, only mixed salt is generated by evaporative crystallization, and the mixed salt is identified as dangerous waste and has no use value. In order to maximize resources, the sodium chloride and sodium sulfate solid salts are required to be recovered by a salt separation method.
Common methods are thermal salt separation and nanofiltration salt separation.
Salt separation by a thermal method: the method is a treatment process which utilizes the difference of solubility of each component in the mixture in the same solvent or the obvious difference of solubility in cold and hot conditions and adopts a crystallization method for separation. The process principle of the method is divided into a cooling heat saturated solution crystallization method and an evaporation solvent crystallization method, wherein the cooling heat saturated solution crystallization method is suitable for substances with the solubility which is obviously increased along with the rise of the temperature, and the evaporation solvent crystallization method is suitable for substances with the solubility which is not changed much along with the temperature.
And (3) nanofiltration salt separation: the nanofiltration membrane can effectively remove organic matters and divalent salts in high-concentration salt water, more than 90% of sodium chloride can be dialyzed, and simultaneously, a large amount of concentrated solution of sulfate radicals is enriched, so that the process for separating the sulfate radicals from chloride ions is realized.
At present, chinese patent CN112830618A discloses a multistage salt purification processing system of chlor-alkali industry waste water, the system includes 1 equalizing basin, 2 softening reaction tank, 3 middle water tank, 4 medium filter, 5 ozone contact oxidation tank, 6 antipollution pressure type ultrafiltration system, 7 one-level nanofiltration salt separating system, 8 one-level RO desalination system, 9 two-level nanofiltration salt separating system, 10 one-level DTRO concentration system, 11 one-level evaporative crystallization system, 12 one-level produced water recycling water tank, 13 two-level RO desalination system, 14 two-level DTRO concentration system, 15 two-level evaporative crystallization system, 16 two-level produced water recycling water tank, 17 sludge concentration filter pressing system, 18 sludge outward transport system. The system realizes the analysis of monovalent sodium chloride and divalent sodium sulfate, but the process flow is too complex, the internal combination collocation is not reasonable enough, the equipment cost is relatively high, and the use limitation is large.
Chinese patent CN108059213A discloses a combined nanofiltration salt separation process and system with high recovery rate and high sulfate retention rate. The process comprises a nanofiltration system A, a nanofiltration system B, a nanofiltration system C, a water production tank and a concentrated water tank. The system successfully realizes sulfate radical interception, neglects chloride ion recovery, has higher chloride ion concentration in produced water, and cannot be used for recycling circulating water.
Disclosure of Invention
Therefore, the invention provides a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater, which aims to solve the problems of complex process flow, high equipment cost, limited use, incomplete salt removal and the like in the prior art.
In order to achieve the above purpose, the invention provides the following technical scheme:
according to one aspect of the invention, a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater is provided, and the system comprises a pretreatment system, a salt separation concentration system, a second activated carbon device, a second resin softening device, a second defluorination tank and a clean water tank;
the pretreatment system is connected with the salt separation concentration system; one outlet end of a second reverse osmosis device in the salt separation concentration system is connected with the clean water tank, and the other outlet end of the second reverse osmosis device is connected with a second defluorination tank; the second defluorination tank is connected with the first evaporative crystallization device; one outlet of the second nanofiltration device in the salt separation concentration system is connected with the second activated carbon device, and the other outlet of the second nanofiltration device and the other outlet of the first nanofiltration device are merged into the third nanofiltration device; the second active carbon device is connected with the second evaporative crystallization device through a second resin softening device.
Further, the pretreatment system comprises a first activated carbon device, a high-density tank, a first defluorination tank, an ultrafiltration device and a first resin softening device.
Further, the salt separation and concentration system comprises a first reverse osmosis device, a first nanofiltration device, a second nanofiltration device, a third nanofiltration device and a second reverse osmosis device.
Furthermore, in the pretreatment system, a first activated carbon device is connected with a first defluorination tank through a high-density pool, the first defluorination tank is connected with an ultrafiltration device, and the ultrafiltration device is connected with a first resin softening device.
Further, in the salt separation and concentration system, a first reverse osmosis device is connected with a first nanofiltration device, one outlet of the first nanofiltration device is connected with a second nanofiltration device, the other outlet of the first nanofiltration device is connected with a third nanofiltration device, one outlet of the second nanofiltration device is connected with a second activated carbon device, and the other outlet of the second nanofiltration device and the first nanofiltration device are merged into the third nanofiltration device; the third nanofiltration device is connected with the second reverse osmosis device.
The invention has the following advantages:
the invention relates to a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater, which adopts a combined pretreatment process of chemical softening and resin softening in order to reduce scaling of a nanofiltration system; in order to prevent the membrane system from being blocked, an immersed ultrafiltration membrane and resin combined process is adopted; meanwhile, in order to prevent the nanofiltration membrane from being blocked, a preposed reverse osmosis membrane protection process is adopted; and the scaling and blocking risks of the nanofiltration membrane are eliminated. And finally, in order to improve the recovery rate of salt and reduce miscellaneous salt, a multi-stage nanofiltration combined process is adopted, and the retention rate of sodium sulfate is improved, so that the reclamation of wastewater and waste salt is realized, and the cost of dangerous waste treatment is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.
FIG. 1 is a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride from coking wastewater provided by the invention 1;
in the figure: a is a pretreatment system, B is a salt separation concentration system; the first activated carbon 1 is a first activated carbon device, the high-density tank 2 is a high-density tank, the first defluorination tank 3 is a first defluorination tank, the ultrafiltration 4 is an ultrafiltration device, the first resin softening 5 is a first resin softening device, the first reverse osmosis 6 is a first reverse osmosis device, the first nanofiltration 7 is a first nanofiltration device, the second nanofiltration 8 is a second nanofiltration device, the third nanofiltration 9 is a third nanofiltration device, the second reverse osmosis 10 is a second permeation device, the second activated carbon 11 is a second activated carbon device, the second resin softening 12 is a second resin softening device, the second defluorination tank 13 is a second defluorination tank, the first evaporative crystal 15 is a first evaporative crystallization device, the second evaporative crystal 14 is a second evaporative crystallization device, and the clear water tank 16 is a clear water tank.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Embodiment 1 a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater
A multi-stage nano-filtration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater, which is shown in figure 1; the system comprises a pretreatment system A, a salt separation concentration system B, a second activated carbon device 11, a second resin softening device 12, a second defluorination tank 13 and a clean water tank 16;
the pretreatment system A is connected with the salt separation concentration system B; one outlet end of a second reverse osmosis device 10 in the salt separation and concentration system B is connected with a clean water tank 16, and the other outlet end of the second reverse osmosis device is connected with a second defluorination tank 13; the second defluorination tank 13 is connected with the first evaporative crystallization device 15; one outlet of the second nanofiltration device 8 in the salt separation concentration system B is connected with an activated carbon device 11, and the other outlet of the first nanofiltration device 7 are merged into a third nanofiltration device 9; the second activated carbon device 11 is connected with a second evaporative crystallization device 14 through a second resin softening device 12.
Preferably, the pretreatment system a comprises a first activated carbon device 1, a high density tank 2, a first defluorination tank 3, an ultrafiltration device 4 and a first resin softening device 5.
Preferably, the salt separation concentration system B includes a first reverse osmosis device 6, a first nanofiltration device 7, a second nanofiltration device 8, a third nanofiltration device 9 and a second reverse osmosis device 10.
Preferably, in the pretreatment system A, the first activated carbon device 1 is connected with the first defluorination tank 3 through the high-density tank 2, the first defluorination tank 3 is connected with the ultrafiltration device 4, and the ultrafiltration device 4 is connected with the first resin softening device 5.
Preferably, in the salt separation and concentration system B, the first reverse osmosis device 6 is connected with the first nanofiltration device 7, one outlet of the first nanofiltration device 7 is connected with the second nanofiltration device 8, the other outlet of the first nanofiltration device 7 is connected with the third nanofiltration device 9, one outlet of the second nanofiltration device 8 is connected with the second activated carbon device 11, and the other outlet of the second nanofiltration device 8 and the first nanofiltration device 7 are merged into the third nanofiltration device 9; the third nanofiltration device 9 is connected to a second reverse osmosis device 10.
Example 2 method for treating wastewater by using a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride from coking wastewater
The method for treating the wastewater by using the multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in the coking wastewater comprises the steps of pretreating the coking wastewater by a pretreatment device A to obtain pretreated product water; concentrating the pretreated produced water by a first reverse osmosis device 6 to obtain reverse osmosis concentrated water 6; carrying out first nanofiltration device 7 treatment on the reverse osmosis concentrated water 6 to obtain nanofiltration produced water 7 and nanofiltration concentrated water 7; carrying out treatment on the nanofiltration concentrated water 7 by a second nanofiltration device 8 to obtain nanofiltration produced water 8 and nanofiltration concentrated water 8; carrying out adsorption by a second activated carbon device 11 and treatment by a second resin softening device 12 on the nanofiltration concentrated water 8 to obtain sodium sulfate concentrated water, and then carrying out evaporative crystallization on the sodium sulfate concentrated water; carrying out third nanofiltration device 9 treatment on the nanofiltration water production 7 and the nanofiltration water production 8 to obtain nanofiltration water production 9 and nanofiltration concentrated water 9, and enabling the nanofiltration concentrated water 9 to enter the nanofiltration device 7 for treatment; concentrating the nanofiltration produced water 9 by a second reverse osmosis device 10 to obtain reverse osmosis concentrated water 10; and carrying out chemical defluorination treatment on the reverse osmosis concentrated water 10 by using a second defluorination tank 13 to obtain sodium chloride concentrated water, and then carrying out evaporative crystallization on the sodium chloride concentrated water.
Preferably, the method for pretreating the coking wastewater by the pretreatment device A comprises the steps of adding powdered activated carbon into the coking wastewater in a first activated carbon 1 device, continuously stirring, adsorbing COD in the wastewater, and removing carbon powder adsorbing the COD by precipitation; chemically softening the coking wastewater subjected to COD removal in a high-density tank 2, adding a required chemical agent, continuously stirring, and removing calcium ions, magnesium ions, fluorine ions and soluble silicon in the wastewater in a precipitation form to primarily soften the coking wastewater; the coking wastewater after primary softening enters a first defluorination tank 3 for defluorination treatment, fluoride ions in the wastewater are removed by adding defluorination agents, particles which are not settled are removed through an ultrafiltration membrane in an ultrafiltration device 4, and the coking wastewater after defluorination is subjected to resin exchange in a first resin softening device 5 so as to further reduce the hardness in the wastewater.
Preferably, the chemical agent comprises one or more of calcium hydroxide, sodium carbonate, polyaluminium chloride, anionic polyacrylamide and hydrochloric acid; the defluorination agent comprises one or more of polyaluminium chloride, ferrous sulfate, polyaluminium chloride and calcium chloride; the resin adopts sodium ion exchange resin.
Preferably, the total hardness of the coking wastewater is less than or equal to 3000mg/L, the soluble silicon is less than or equal to 50mg/L, the COD is less than or equal to 700mg/L, the fluorine ions are less than or equal to 300mg/L, and the total soluble solids are less than or equal to 50000 mg/L.
Embodiment 3a multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater and a method for treating wastewater by using the same
The system comprises a first activated carbon device 1, a high-density tank 2, a first defluorination tank 3, an ultrafiltration 4, a first resin softening device 5, a first reverse osmosis device 6, a first nanofiltration device 7, a second nanofiltration device 8, a third nanofiltration device 9, a second reverse osmosis device 10, a second activated carbon device 11, a second resin softening device 12, a second defluorination tank 13, a second evaporative crystallization device 14, a first evaporative crystallization device 15 and a clean water tank 16, wherein the pretreatment system comprises the first activated carbon device 1, the high-density tank 2, the first defluorination tank 3, the ultrafiltration device 4 and the first resin softening device 5 which are sequentially connected in series; the salt separating and concentrating system comprises a first reverse osmosis device 6 and a first nanofiltration device 7, the system comprises a second nanofiltration device 8, a third nanofiltration device 9 and a second reverse osmosis device 10, wherein reverse osmosis produced water 6 in the first reverse osmosis device 6 enters a clean water tank for recycling, reverse osmosis concentrated water 6 enters a first nanofiltration device 7 for primary salt separation, nanofiltration fresh water 7 enters the third nanofiltration device 9, nanofiltration concentrated water 7 enters the second nanofiltration device 8, nanofiltration concentrated water 8 directly enters a sodium sulfate second evaporative crystallization device 14, nanofiltration fresh water 8 also enters the third nanofiltration device 9 and is subjected to further salt separation treatment through the third nanofiltration device 9, nanofiltration fresh water 9 enters the second reverse osmosis device 10 for concentration, concentrated water in the second reverse osmosis device 10 enters a sodium chloride first evaporative crystallization device 15, and nanofiltration concentrated water 9 flows back to a water inlet of the first nanofiltration device 7 for salt separation treatment again; the water outlet of a first resin softening device 5 of the pretreatment system is communicated with the water inlet of a salt separation concentration system to form a first reverse osmosis device 6, the water outlet of nanofiltration concentrated water 9 of the salt separation concentration system is communicated with the water inlet of a sodium sulfate second evaporative crystallization device 14, the concentration water outlet of a second reverse osmosis device 10 of the salt separation concentration system is communicated with the water inlet of a sodium chloride first evaporative crystallization device 15.
The nanofiltration membranes and reverse osmosis membranes used by the first nanofiltration device 7, the second nanofiltration device 8, the third nanofiltration device 9, the first reverse osmosis device 6 and the second reverse osmosis device 10 in the nanofiltration concentration system are common commercial nanofiltration membranes and reverse osmosis membranes, so that the operation cost and the technical requirements are greatly reduced; the pretreatment of the prepositive first reverse osmosis device 6 protects the first nanofiltration device 7, the second nanofiltration device 8 and the third nanofiltration device 9, avoids the blockage problem of nanofiltration membranes and reduces the wastewater treatment capacity at the same time. The unique design realizes the reflux circulation treatment through the internal arrangement and combination of the system, can simultaneously improve the purity of sodium chloride in the concentrated water of the second reverse osmosis device 10 and the rejection rate of sodium sulfate by nanofiltration, the water recovery rate of the system reaches more than 80 percent, the concentration of sodium chloride in the separated sodium chloride concentrated water reaches more than 98 percent, and the rejection rate of sulfate ions of the system reaches more than 99 percent. The method realizes the thorough separation of sodium sulfate and sodium chloride, effectively improves the purity of the crystallized salt, reduces the difficulty of subsequent salt separation, ensures the quality and the yield of the crystallized salt and reduces the yield of miscellaneous salt.
Example 4 specific wastewater treatment method
By utilizing the nano-filtration salt separation process with high water, sodium sulfate and sodium chloride recovery rates of the coking wastewater performed in the embodiment 3, the coking wastewater inlet water quality indexes are as follows: COD 719mg/L, total hardness 2824mg/L, TDS 31733mg/L, chloride 9359mg/L, fluoride 208mg/L, sulfate 5692mg/L, water inflow 54m3H; conveying the coking wastewater to a pretreatment water inlet for pretreatment, removing hardness, fluoride ions and COD in the wastewater, and obtaining the index of the pretreated water quality: COD is 129mg/L, total hardness is 14mg/L, TDS is 29049mg/L, chloride ion is 10014mg/L, fluoride ion is 8.3mg/L, sulfate ion is 5350 mg/L; the pretreated wastewater entersThe salt separating concentration system carries out treatment, and after salt separating concentration, the water quality indexes of a concentrated water outlet of the third nanofiltration device 9 are as follows: COD is 112mg/L, total hardness is 7mg/L, TDS is 252704mg/L, chloride ion is 28039mg/L, fluoride ion is 17mg/L, sulfate ion is 94557mg/L, effluent flow is 2.2m3H; the quality indexes of the concentrated water outlet of the second reverse osmosis device 10 are as follows: COD is 59mg/L, total hardness is 1mg/L, TDS is 93879mg/L, chloride ion is 56077mg/L, fluoride ion is 33mg/L, sulfate ion is 229mg/L, effluent flow is 8.4m3/h。
The water recovery rate of the salt separation concentrated water system is 80.4 percent, the sulfate radical rejection rate is 99.5 percent, the chloride ion rejection rate is 99.1 percent, and the produced water of the system is conveyed to a clean water tank for recycling; conveying the concentrated water of the third nanofiltration device 9 to a sodium sulfate crystallization evaporation system, wherein the purity of the sodium sulfate is 55.3%; the concentrated water of the second reverse osmosis device 10 is conveyed to a sodium chloride crystallization evaporation system, and the purity of the sodium chloride in the water is 98.4%. The system recovery is shown in table 1; the salt separation effect of the salt separation concentration system is shown in table 2.
TABLE 1 System recovery
TABLE 2 salt separation effect of salt separation concentration system
As can be seen from tables 1 and 2, the purity of sodium chloride in the concentrated water of the second reverse osmosis device 10 and the rejection rate of sodium sulfate by nanofiltration can be simultaneously improved by the internal arrangement and combination of the reflux circulation treatment, the recovery rate of wastewater is more than 80%, the concentration of sodium chloride in the concentrated water of sodium chloride is more than 98%, and the rejection rate of sulfate radicals of the system is more than 99%; the sodium sulfate and the sodium chloride can be thoroughly separated, the concentrated water of the second reverse osmosis device 10 is mainly chloride ions, and the concentrated water of the third nanofiltration device 9 is mainly sulfate ions, so that the purity of the crystallized salt is effectively improved, the subsequent salt separation difficulty is reduced, and the quality and the yield of the crystallized salt are ensured.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (5)
1. A multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater is characterized by comprising a pretreatment system (A), a salt separation concentration system (B), a second activated carbon device (11), a second resin softening device (12), a second defluorination tank (13) and a clean water tank (16);
the pretreatment system (A) is connected with the salt separation and concentration system (B); one outlet end of a second reverse osmosis device (10) in the salt separation concentration system (B) is connected with a clean water tank (16), and the other outlet end is connected with a second defluorination tank (13); the second defluorination tank (13) is connected with the first evaporative crystallization device (15); one outlet of the second nanofiltration device (8) in the salt separation concentration system (B) is connected with the second activated carbon device (11), and the other outlet of the first nanofiltration device (7) are merged into the third nanofiltration device (9); the second activated carbon device (11) is connected with the second evaporative crystallization device (14) through a second resin softening device (12).
2. The multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater according to claim 1, wherein the pretreatment system (A) comprises a first activated carbon device (1), a high-density tank (2), a first defluorination tank (3), an ultrafiltration device (4) and a first resin softening device (5).
3. The multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride from coking wastewater according to claim 1, wherein the salt separation concentration system (B) comprises a first reverse osmosis device (6), a first nanofiltration device (7), a second nanofiltration device (8), a third nanofiltration device (9) and a second reverse osmosis device (10).
4. The multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater according to claim 2, wherein in the pretreatment system (A), the first activated carbon device (1) is connected with the first defluorination tank (3) through the high density tank (2), the first defluorination tank (3) is connected with the ultrafiltration device (4), and the ultrafiltration device (4) is connected with the first resin softening device (5).
5. The multi-stage nanofiltration salt separation system for separating sodium sulfate and sodium chloride in coking wastewater according to claim 3, wherein in the salt separation and concentration system (B), the first reverse osmosis device (6) is connected with the first nanofiltration device (7), one outlet of the first nanofiltration device (7) is connected with the second nanofiltration device (8), the other outlet of the first nanofiltration device (7) is connected with the third nanofiltration device (9), one outlet of the second nanofiltration device (8) is connected with the second activated carbon device (11), and the other outlet of the second nanofiltration device (8) is combined with the first nanofiltration device (7) into the third nanofiltration device (9); the third nanofiltration device (9) is connected with the second reverse osmosis device (10).
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