CN212334888U - Multi-stage freezing crystallization salt separation system - Google Patents
Multi-stage freezing crystallization salt separation system Download PDFInfo
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- CN212334888U CN212334888U CN202020596381.5U CN202020596381U CN212334888U CN 212334888 U CN212334888 U CN 212334888U CN 202020596381 U CN202020596381 U CN 202020596381U CN 212334888 U CN212334888 U CN 212334888U
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- 150000003839 salts Chemical class 0.000 title claims abstract description 345
- 238000000926 separation method Methods 0.000 title claims abstract description 295
- 238000002425 crystallisation Methods 0.000 title claims abstract description 167
- 230000008025 crystallization Effects 0.000 title claims abstract description 167
- 230000008014 freezing Effects 0.000 title claims abstract description 132
- 238000007710 freezing Methods 0.000 title claims abstract description 132
- 239000007788 liquid Substances 0.000 claims abstract description 182
- 238000001728 nano-filtration Methods 0.000 claims abstract description 118
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000012452 mother liquor Substances 0.000 claims description 72
- 238000001704 evaporation Methods 0.000 claims description 27
- 230000008020 evaporation Effects 0.000 claims description 26
- 239000000155 melt Substances 0.000 claims description 10
- 239000012528 membrane Substances 0.000 claims description 7
- 239000012943 hotmelt Substances 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 6
- 239000002562 thickening agent Substances 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 238000000909 electrodialysis Methods 0.000 claims description 3
- 239000011552 falling film Substances 0.000 claims description 3
- 238000001223 reverse osmosis Methods 0.000 claims description 3
- 239000012141 concentrate Substances 0.000 claims description 2
- 239000013078 crystal Substances 0.000 description 42
- 239000012267 brine Substances 0.000 description 13
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 13
- 238000000034 method Methods 0.000 description 11
- 239000002351 wastewater Substances 0.000 description 6
- 238000005194 fractionation Methods 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910017053 inorganic salt Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
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Abstract
The utility model relates to a multistage freezing crystallization salt separating system, which comprises a concentration device and a multi-stage salt separating device, wherein each stage salt separating device comprises a freezing crystallization unit, a solid-liquid separation unit and a nanofiltration separation concentration unit, and in each stage salt separating device, the solid-liquid separation unit is communicated with the freezing crystallization unit, and a liquid inlet of the nanofiltration separation concentration unit is communicated with a liquid outlet of the solid-liquid separation unit; a freezing crystallization unit in the first salt grading device is communicated with a liquid outlet of the concentration device, and a liquid outlet of a solid-liquid separation unit in the first salt grading device is also communicated with a liquid inlet of the concentration device; in the two adjacent salt separation devices, a freezing crystallization unit in the next salt separation device is communicated with a nanofiltration concentrated water port of a nanofiltration separation concentration unit in the previous salt separation device, and a liquid outlet of a solid-liquid separation unit in the next salt separation device is also communicated with a liquid inlet of the nanofiltration separation concentration unit in the previous salt separation device.
Description
Technical Field
The utility model relates to a water treatment technical field especially relates to a multistage freezing crystallization divides salt system.
Background
The wastewater generated in the industries of electric power, coal chemical industry and the like has the characteristics of high hardness, high salt content, large water quantity, high treatment difficulty and the like. In order to meet the requirement of resource utilization protection, zero discharge of waste water becomes an industry trend. The zero discharge of the wastewater is a mode of cleaning wastewater generated in industry, separating out pollutants in the wastewater in a solid form, reducing products in the wastewater to be infinitely close to zero, and enabling the produced solids to have great utilization value.
At present, the main treatment method for salt is to divide the salt according to the quality, the main technologies are hot crystallization and cold crystallization, but the problems of low purity and low yield of the produced crystallized salt exist, the produced miscellaneous salt is classified as solid dangerous waste, the quantity of the miscellaneous salt is large, the resource utilization rate is low, and the expense for treating the miscellaneous salt is high. Therefore, the development of a process technology capable of improving the resource utilization rate and reducing the operation cost is urgently needed.
SUMMERY OF THE UTILITY MODEL
Therefore, a multi-stage freezing crystallization salt separation system capable of improving resource utilization rate and reducing operation cost is needed.
A multi-stage freeze crystallization salt separation system, comprising:
a concentration device; and
the multi-stage salt separation device comprises a freezing crystallization unit, a solid-liquid separation unit and a nanofiltration separation and concentration unit, wherein in each stage of salt separation device, the solid-liquid separation unit is communicated with the freezing crystallization unit and is used for carrying out solid-liquid separation on a mixture after freezing crystallization, and a liquid inlet of the nanofiltration separation and concentration unit is communicated with a liquid outlet of the solid-liquid separation unit; a freezing crystallization unit in the first salt separating device is communicated with a liquid outlet of the concentration device, and a liquid outlet of a solid-liquid separation unit in the first salt separating device is also communicated with a liquid inlet of the concentration device; in the two adjacent salt separation devices, a freezing crystallization unit in the next salt separation device is communicated with a nanofiltration concentrated water port of a nanofiltration separation concentration unit in the previous salt separation device, and a liquid outlet of a solid-liquid separation unit in the next salt separation device is also communicated with a liquid inlet of the nanofiltration separation concentration unit in the previous salt separation device.
According to the multi-stage freezing crystallization salt separation system, the multi-stage salt separation device is multi-stage freezing separation crystallization, and hydrated crystal salts with different application values can be obtained through fractional freezing crystallization. Compared with the traditional process of completely circulating the mother liquor in a freezing crystallization system, the multistage freezing crystallization salt separation system further processes the mother liquor subjected to solid-liquid separation, further separates out divalent and high-valent ions remained in the mother liquor, and performs freezing crystallization to separate out crystal salt, so that the purity and yield of the crystal salt are improved, and the problems of low purity and no application value of the crystal salt produced by long-time operation due to continuous accumulation of impurities such as inorganic salt, organic matters and the like in the mother liquor in the traditional process are solved; meanwhile, mother liquor is classified, separated by nanofiltration and discharged from a multi-stage salt separation device in a nanofiltration water production mode, high-purity monovalent salt can be further prepared, the amount of final miscellaneous salt is greatly reduced, and the problem of high miscellaneous salt treatment cost is avoided. The multi-stage freezing crystallization salt separation system improves the purity and the yield of the crystallized salt, greatly reduces the amount of final miscellaneous salt, improves the resource utilization rate, does not need to adopt a medicine-adding crystallization mode for crystallization, and reduces the operation cost.
In some embodiments, the multistage freezing, crystallizing and salt separating system further comprises a monovalent salt evaporative crystallization device which is communicated with the nanofiltration water production port of each nanofiltration separation and concentration unit of each stage of salt separating device.
In some embodiments, the monovalent salt evaporative crystallization device is any one of a falling film evaporator, a forced circulation evaporator and an MVR evaporator, or a combination of a plurality of evaporators in series or in parallel.
In some embodiments, the multistage freezing crystallization salt separation system further comprises a mixed salt evaporation crystallization device and a mixed salt solid-liquid separation device, the mixed salt evaporation crystallization device is communicated with a nanofiltration concentrated water port of a nanofiltration separation concentration unit in the last stage salt separation device, and the mixed salt solid-liquid separation device is communicated with the mixed salt evaporation crystallization device for carrying out solid-liquid separation on the mixed salt after evaporation crystallization.
In some embodiments, the miscellaneous salt evaporative crystallization device comprises a crystallizer, a heat exchanger and a circulating pump, wherein the heat exchanger is used for carrying out heat exchange on the crystallizer, and the circulating pump is used for circulating a heat exchange medium in the heat exchanger.
In some embodiments, the multistage freezing crystallization salt separation system further comprises a mixed salt mother liquor tank, wherein a liquid inlet of the mixed salt mother liquor tank is communicated with a liquid outlet of the mixed salt solid-liquid separation device, and a liquid outlet of the mixed salt mother liquor tank is communicated with a liquid inlet of the mixed salt evaporation crystallization device.
In some embodiments, each of the salt separating devices further comprises a salt separating mother liquor tank, and in each salt separating device, a liquid inlet of the nanofiltration separation and concentration unit is communicated with a liquid outlet of the solid-liquid separation unit through the salt separating mother liquor tank.
In some embodiments, the liquid outlet of the salt separation mother liquid tank in the next salt separation device is also communicated with the liquid inlet of the salt separation mother liquid tank in the last salt separation device.
In some of these embodiments, each of the fractional salt apparatuses further comprises a melt crystallization unit for melt crystallizing the hydrated crystalline salt separated by the solid-liquid separation unit within each fractional salt apparatus.
In some embodiments, the melt crystallization unit is any one of a hot melt crystallizer, a hot melt heat exchanger, an evaporative crystallizer, or a combination of a plurality of the above in series or in parallel.
In some of these embodiments, the concentration device is any one of an MVR evaporation device, a multi-effect evaporation device, a high pressure reverse osmosis device, and an electrodialysis device, or a combination of multiple devices in series or parallel.
In some of these embodiments, the solid-liquid separation unit comprises a cyclone separator, a thickener, a centrifuge, and a dryer connected in series.
In some embodiments, the freezing and crystallizing unit is any one of a freezing crystallizer, a freezing heat exchanger, a refrigerating unit and a heat exchanger, or a combination of a plurality of the freezing crystallizers, the freezing heat exchanger, the refrigerating unit and the heat exchanger in series or in parallel.
In some embodiments, the nanofiltration separation concentration unit is any one of roll-type nanofiltration and high-pressure flat nanofiltration membranes, or a combination of multiple nanofiltration membranes connected in series or in parallel.
Drawings
FIG. 1 is a schematic structural diagram of a multi-stage freezing crystallization salt separation system according to an embodiment.
Detailed Description
In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the accompanying drawings. The preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The traditional salt separation crystallization is one-time integral salt discharge, the purity of the produced crystallized salt is poor, the particle size is uneven, the produced frozen crystallization mother liquor completely flows back to the system to circulate in the system, the content of organic matters in the mother liquor exceeds the standard, the long-time operation can cause the purity of the separated crystallized salt to be low and the amount of miscellaneous salt to be large, and the economic value of the crystallized salt is reduced.
Based on this, the utility model discloses an embodiment provides a multistage freezing crystallization divides salt system, and a corresponding embodiment still provides a multistage freezing crystallization divides salt method, and this multistage freezing crystallization divides salt method can adopt above-mentioned multistage freezing crystallization to divide salt system to go on. The multi-stage freezing crystallization salt separation method is described in more detail below in conjunction with a multi-stage freezing crystallization salt separation system.
Referring to fig. 1, one embodiment of the present invention provides a multi-stage freezing crystallization salt separation system 10 for multi-stage salt separation of brine to be treated. The multi-stage freezing crystallization salt separation system 10 includes a concentration device 100 and a multi-stage salt separation device 200. The multi-stage salt fractionation device 200 includes at least a two-stage salt fractionation device 200.
Each of the fractional salt apparatuses 200 (not shown) includes a freezing and crystallizing unit 210, a solid-liquid separation unit 220, and a nanofiltration separation and concentration unit 230 connected in this order. In each grade salt separating device 200, a solid-liquid separation unit 220 is communicated with a freezing crystallization unit 210 for performing solid-liquid separation on a mixture after freezing crystallization, and a liquid inlet of a nanofiltration separation concentration unit 230 is communicated with a liquid outlet of the solid-liquid separation unit 220.
The freezing and crystallizing unit 210 in the first salt separating device 200 is communicated with the liquid outlet of the concentrating device 100, so that the brine is concentrated by the concentrating device 100, enters the freezing and crystallizing unit 210 of the salt separating system 200 for freezing and crystallizing, and then enters the solid-liquid separating unit 220 for solid-liquid separation of the mixture after freezing and crystallizing to obtain hydrated crystal salt and mother liquor; a part of mother liquor enters a liquid inlet of the nanofiltration separation concentration unit 230 from a liquid outlet of the solid-liquid separation unit 220 to be subjected to nanofiltration separation concentration treatment. The liquid outlet of the solid-liquid separation unit 220 in the first salt separating device 200 is also communicated with the liquid inlet of the concentration device 100, and the other part of mother liquor returns from the liquid outlet of the solid-liquid separation unit 220 to the concentration device 100 from the liquid inlet of the concentration device 100 for secondary concentration treatment, so that the amount of the mother liquor entering the nanofiltration separation and concentration unit 230 is reduced, the yield of the hydrated crystalline salt obtained by solid-liquid separation is increased, and the purity of the hydrated crystalline salt is not influenced.
In the two adjacent salt separation devices 200, the freezing crystallization unit 210 in the next salt separation device 200 is communicated with the nanofiltration concentrated water port of the nanofiltration separation concentration unit 230 in the previous salt separation device 200, so that the nanofiltration concentrated water generated by the nanofiltration separation concentration unit 230 in the previous salt separation device 200 enters the next salt separation device 200 again for treatment, the salt separation devices 200 respectively obtain hydrated crystal salt through the solid-liquid separation unit 220, the further hydrated crystal salt can be melted and crystallized to remove the crystal water to obtain anhydrous crystal salt, meanwhile, the salt separation devices 200 respectively obtain nanofiltration product water through the nanofiltration separation concentration unit 230, and the nanofiltration product water can be further evaporated and crystallized to obtain monovalent salt.
In the two adjacent salt separation devices 200, the liquid outlet of the solid-liquid separation unit 220 in the next salt separation device 200 is also communicated with the liquid inlet of the nanofiltration separation concentration unit 230 in the previous salt separation device 200. The mother liquor generated by the solid-liquid separation unit 220 in the next salt separating device 200 is returned to the nanofiltration separation and concentration unit 230 in the previous salt separating device 200 for further separation and concentration, the mother liquor is circularly treated, monovalent salt is separated by the nanofiltration separation and concentration unit 230 as much as possible, and further hydrated crystal salt is separated through freezing crystallization and solid-liquid separation, so that the yield of subsequent miscellaneous salt is reduced after the treatment of each salt separating device 200.
In the multi-stage freezing crystallization salt separation system, the multi-stage salt separation device 200 is a multi-stage freezing separation crystallization device, and hydrated crystal salts with different application values can be obtained through fractional freezing crystallization. Compared with the traditional process of completely circulating the mother liquor in a freezing crystallization system, the multistage freezing crystallization salt separation system further processes the mother liquor subjected to solid-liquid separation, further separates out divalent and high-valent ions remained in the mother liquor, and performs freezing crystallization to separate out crystal salt, so that the purity and yield of the crystal salt are improved, and the problems of low purity and no application value of the crystal salt produced by long-time operation due to continuous accumulation of impurities such as inorganic salt, organic matters and the like in the mother liquor in the traditional process are solved; meanwhile, mother liquor is classified, separated by nanofiltration and discharged from the multi-stage salt separation device 200 in the form of nanofiltration water production, high-purity monovalent salt can be further prepared, the amount of final miscellaneous salt is greatly reduced, and the problem of high expense in miscellaneous salt treatment is avoided. The multi-stage freezing crystallization salt separation system improves the purity and the yield of the crystallized salt, greatly reduces the amount of final miscellaneous salt, improves the resource utilization rate, does not need to adopt a medicine-adding crystallization mode for crystallization, and reduces the operation cost.
In some of the embodiments, the concentration device 100 may be any one of an MVR evaporation device, a multi-effect evaporation device, a high-pressure reverse osmosis device and an electrodialysis device, or a combination of a plurality of devices connected in series or in parallel, for performing deep concentration on the saline water to be treated.
In some embodiments, the freezing and crystallizing unit 210 can be any one of a freezing crystallizer, a freezing heat exchanger, a refrigerating unit and a heat exchanger, or a combination of a plurality of series or parallel connection. Further, the freezing crystallizer may be selected from OSLO crystallizer, DTB crystallizer, FC crystallizer.
In some of these embodiments, the solid-liquid separation unit 220 includes a cyclone separator, a thickener, a centrifuge, and a dryer connected in series. Specifically, the mother liquor outlet of the freezing and crystallizing unit 210 is connected to the inlet of the cyclone separator, the outlet of the cyclone separator is connected to the inlet of the thickener, the outlet of the thickener is connected to the inlet of the centrifuge, and the outlet of the centrifuge is connected to the inlet of the dryer.
Further, the centrifuge may be a pusher centrifuge, a scraper centrifuge or a decanter centrifuge.
In some embodiments, nanofiltration separation concentration unit 230 may be any one of roll-to-roll nanofiltration and high-pressure flat nanofiltration membranes, or a combination of multiple nanofiltration membranes connected in series or in parallel. Wherein the operating pressure of the high-pressure flat nanofiltration membrane is 40-160 bar.
In some of the embodiments, the multistage freezing, crystallizing and salt separating system 10 further comprises a monovalent salt evaporative crystallization apparatus 300, wherein the monovalent salt evaporative crystallization apparatus 300 is communicated with the nanofiltration water production port of each nanofiltration separation and concentration unit 230 of each stage salt separating apparatus 200.
Further, the monovalent salt evaporative crystallization apparatus 300 may be any one of a falling film evaporator, a forced circulation evaporator and an MVR evaporator, or a combination of a plurality of evaporators in series or in parallel.
In some embodiments, the multi-stage freezing crystallization salt separation system 10 further includes a mixed salt evaporation crystallization device 400 and a mixed salt solid-liquid separation device 500, the mixed salt evaporation crystallization device 400 is communicated with the nanofiltration concentrate port of the nanofiltration separation concentration unit 230 in the last stage salt separation device 200, and the mixed salt solid-liquid separation device 500 is communicated with the mixed salt evaporation crystallization device 400 for performing solid-liquid separation on the mixed salt after evaporation crystallization.
Further, the miscellaneous salt evaporation crystallization device 400 comprises a crystallizer, a heat exchanger and a circulating pump, wherein the heat exchanger is used for carrying out heat exchange on the crystallizer, and the circulating pump is used for circulating a heat exchange medium in the heat exchanger.
In some embodiments, the multi-stage freezing crystallization salt separation system 10 further comprises a mixed salt mother liquor tank 600, a liquid inlet of the mixed salt mother liquor tank 600 is communicated with a liquid outlet of the mixed salt solid-liquid separation device 500, and a liquid outlet of the mixed salt mother liquor tank 600 is communicated with a liquid inlet of the mixed salt evaporation crystallization device 400.
Further, the mixed salt solid-liquid separation device 500 may be any one of a cyclone separator, a refrigerated centrifuge, a thickener, and a dryer, or a combination of a plurality of them connected in series or in parallel.
In some of the embodiments, each of the salt separating and concentrating devices 200 further comprises a salt separating mother liquor tank 240, and in each salt separating and concentrating device 200, a liquid inlet of the nanofiltration separation and concentration unit 230 is communicated with a liquid outlet of the solid-liquid separation unit 220 through the salt separating mother liquor tank 240. In other words, the liquid inlet of the salt separation mother liquor tank 240 is communicated with the liquid outlet of the solid-liquid separation unit 220, and the liquid outlet of the salt separation mother liquor tank 240 is communicated with the liquid inlet of the nanofiltration separation concentration unit 230.
Further, the liquid outlet of the salt separation mother liquor tank 240 in the next salt separation device 200 is also communicated with the liquid inlet of the salt separation mother liquor tank 240 in the previous salt separation device 200, so that the liquid outlet of the solid-liquid separation unit 220 in the next salt separation device 200 is communicated with the liquid inlet of the nanofiltration separation concentration unit 230 in the previous salt separation device 200, so that the mother liquor generated by the solid-liquid separation unit 220 in the next salt separation device 200 is firstly returned to the salt separation mother liquor tank 240 in the previous salt separation device 200, and then returned to the nanofiltration separation concentration unit 230 in the previous salt separation device 200 through the salt separation mother liquor tank 240 for further separation and concentration.
In some of these embodiments, each of the fractional salt apparatuses 200 further comprises a melt crystallization unit 250, and within each fractional salt apparatus 200, the melt crystallization unit 250 is used to melt crystallize the hydrated crystalline salt separated by the solid-liquid separation unit 220. Specifically, by further controlling the concentration of the fed materials and selecting different freezing and crystallizing devices in the freezing and crystallizing unit 210, the crystallized salts with different purities and different particle sizes can be obtained, the purities of the crystallized salts are gradually reduced from top to bottom, and the crystallized salts with different purities have different application values.
Further, the melt crystallization unit 250 may be any one of a hot melt crystallizer, an evaporative crystallizer, and a hot melt heat exchanger, or a combination of a plurality of them in series or in parallel.
It will be appreciated that in the particular example shown in fig. 1, the multi-stage freeze crystallization salt fractionation system 10 includes an N-stage salt fractionation device, where N may be any integer greater than or equal to 2, and in this particular example, N is an integer greater than 3, e.g., N is 4, 5, 6, etc., depending on the flow direction of the material.
Specifically, the first-stage salt separation device 200 comprises a freezing crystallization unit 1, a solid-liquid separation unit 1, a salt separation mother liquor tank 1, a nanofiltration separation concentration unit 1 and a melting crystallization unit 1. The freezing and crystallizing unit 1 is communicated with a liquid outlet of the concentration device. The solid-liquid separation unit 1 communicates with the freeze crystallization unit 1. The liquid inlet of the salt separation mother liquor tank 1 is communicated with the liquid outlet of the solid-liquid separation unit 1, and the liquid outlet of the salt separation mother liquor tank 1 is respectively communicated with the liquid inlet of the nanofiltration separation concentration unit 1 and the liquid inlet of the concentration device. The melt crystallization unit 1 is used for melt crystallization of the hydrated crystalline salt separated by the solid-liquid separation unit 1.
The second-stage salt separation system 200 comprises a freezing crystallization unit 2, a solid-liquid separation unit 2, a nanofiltration separation concentration unit 2 and a melting crystallization unit 2. The freezing and crystallizing unit 2 is communicated with a nanofiltration concentrated water port of the nanofiltration separation and concentration unit 1. The solid-liquid separation unit 2 communicates with the freeze crystallization unit 2. A liquid inlet of the salt separation mother liquor tank 2 is communicated with a liquid outlet of the solid-liquid separation unit 2, and a liquid outlet of the salt separation mother liquor tank 2 is respectively communicated with a liquid inlet of the nanofiltration separation concentration unit 2 and a liquid inlet of the salt separation mother liquor tank 1. The melt crystallization unit 2 is used for melt crystallization of the hydrated crystalline salt separated by the solid-liquid separation unit 2.
The third salt separation system 200 comprises a freezing crystallization unit 3, a solid-liquid separation unit 3, a nanofiltration separation concentration unit 3 and a melting crystallization unit 3. The freezing and crystallizing unit 3 is communicated with a nanofiltration concentrated water port of the nanofiltration separation and concentration unit 2. The solid-liquid separation unit 3 communicates with the freeze crystallization unit 3. A liquid inlet of the salt separation mother liquor tank 3 is communicated with a liquid outlet of the solid-liquid separation unit 3, and a liquid outlet of the salt separation mother liquor tank 3 is respectively communicated with a liquid inlet of the nanofiltration separation concentration unit 3 and a liquid inlet of the salt separation mother liquor tank 2. The melt crystallization unit 3 is used for melt crystallization of the hydrated crystalline salt separated by the solid-liquid separation unit 3.
And by analogy, the Nth-level salt separation system comprises a freezing crystallization unit N, a solid-liquid separation unit N, a nanofiltration separation concentration unit N and a melting crystallization unit N. The freezing crystallization unit N is communicated with a nanofiltration concentrated water port of the nanofiltration separation concentration unit N-1. The solid-liquid separation unit N is communicated with the freezing and crystallizing unit N. A liquid inlet of the salt separation mother liquor tank N is communicated with a liquid outlet of a solid-liquid separation unit N of the solid-liquid separation unit N, and a liquid outlet of the salt separation mother liquor tank N is respectively communicated with a liquid inlet of the nanofiltration separation concentration unit N and a liquid inlet of the salt separation mother liquor tank N-1. And the melt crystallization unit N is used for carrying out melt crystallization on the hydrated crystalline salt separated by the solid-liquid separation unit N.
In this embodiment, one monovalent salt evaporative crystallization apparatus 300 is used to perform evaporative crystallization on the nanofiltration product water of the nanofiltration separation concentration units 1 to N, but it is understood that in other embodiments, a plurality of monovalent salt evaporative crystallization apparatuses 300 may be used, for example, one monovalent salt evaporative crystallization apparatus may perform evaporative crystallization on the nanofiltration product water of each nanofiltration separation concentration unit 230.
The utility model discloses a multistage freezing crystallization salt separating method of embodiment can adopt above-mentioned arbitrary multistage freezing crystallization salt separating system to go on, include following step S10 ~ S20:
and step S10, performing concentration treatment on the brine to be treated to obtain concentrated brine.
Step S20, the concentrated brine is sequentially subjected to multi-stage salt treatment.
Wherein, the salt treatment of each stage in the step S20 includes steps S21 to S23 which are performed in sequence:
step S21, freezing and crystallizing;
step S22, performing solid-liquid separation treatment on the mixture after the freezing crystallization treatment to obtain hydrated crystal salt and mother liquor; and
step S23, in the first stage salt separation treatment, the mother liquor obtained by the solid-liquid separation treatment is shunted, nanofiltration separation and concentration treatment are respectively carried out to obtain nanofiltration product water and nanofiltration concentrated water, and the nanofiltration product water and the nanofiltration concentrated water are returned to the concentration treatment; in other salt treatment of each fraction except the first salt treatment, the mother liquor obtained by the solid-liquid separation treatment is shunted, and is respectively subjected to nanofiltration separation and concentration treatment and returned to the last salt treatment for nanofiltration separation and concentration treatment to obtain nanofiltration product water and nanofiltration concentrated water;
in the salt treatment of two adjacent fractions, the nanofiltration concentrated water after the nanofiltration separation and concentration treatment of the previous stage is transferred to the freezing crystallization treatment of the next stage, so that the steps S21-S23 are repeated.
It is understood that the nanofiltration concentrated water obtained in step S23 is water containing divalent and higher ions, such as sodium sulfate and/or sodium carbonate, and the nanofiltration concentrated water is transferred to a next freezing crystallization treatment, and the hydrated crystal salt obtained from the freezing crystallization treatment is further removed by a subsequent melting crystallization treatment to obtain anhydrous crystal salt, such as sodium sulfate and/or sodium carbonate.
The fractional salt separation method improves the purity and the yield of the crystallized salt, greatly reduces the amount of final miscellaneous salt, improves the resource utilization rate, does not need to adopt a drug-adding crystallization mode for crystallization, and reduces the operation cost.
In some of the embodiments, the multi-stage freezing crystallization salt separation method further comprises the following step S30: and (4) evaporating and crystallizing nanofiltration produced water obtained by nanofiltration separation and concentration treatment in salt treatment of each fraction to obtain monovalent salt. Wherein, the nanofiltration water produced in the step S30 is water containing monovalent ions, and the water is subjected to evaporation crystallization to obtain high-purity monovalent salt, and the monovalent salt is sodium chloride generally.
In some of the embodiments, the multi-stage freezing crystallization salt separation method further comprises the following step S40: and carrying out melt crystallization on the hydrated crystal salt obtained by the solid-liquid separation treatment in the salt treatment of each fraction, and removing crystal water to obtain anhydrous crystal salt.
In some of the embodiments, the multi-stage freezing crystallization salt separation method further comprises the following step S52: the multi-stage freezing crystallization salt separation method also comprises the following steps: and (4) carrying out evaporative crystallization on nanofiltration concentrated water obtained by nanofiltration separation and concentration treatment in the last stage salt separation treatment, and carrying out solid-liquid separation to obtain the miscellaneous salt.
Further, the multistage freezing crystallization salt separation method further comprises the following step S54: carrying out evaporation crystallization on nanofiltration concentrated water obtained by nanofiltration separation and concentration treatment in the last stage salt separation treatment, and carrying out solid-liquid separation to obtain mother liquor; and returning the mother liquor to the evaporation and crystallization step of nanofiltration concentrated water.
In a specific example, the step S20 sequentially performs 2-stage salt treatment on the concentrated brine, and can be specifically performed by using the multi-stage freezing crystallization salt separating system 10 with the 2-stage salt separating device. Further, when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the fraction 1 is 50-85%, the mother liquor obtained in the solid-liquid separation treatment in the salt treatment of the fraction 1 is transferred to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the 1 st-2 nd-fraction salt treatment is 85-96%, transferring the mother liquor obtained by the solid-liquid separation treatment in the 2 nd-fraction salt treatment to a nanofiltration separation concentration treatment step. Wherein, the crystallization rate refers to the mass percentage of anhydrous crystallized salt in the total salt mass of the treated brine, and is the same as below.
In another specific example, the step S20 sequentially performs 3-stage salt treatment on the concentrated brine, and can be specifically performed by using the multi-stage freezing crystallization salt separating system 10 with the 3-stage salt separating device. Further, when the mass of the hydrated crystal salt subjected to cold crystal freezing treatment in the salt treatment of the 1 st fraction is 40-75% of the total salt mass of the treated brine, the mother liquor obtained by solid-liquid separation treatment in the salt treatment of the 1 st fraction is transferred to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the 1 st-2 nd-fraction salt treatment is 75-86%, transferring the mother liquor obtained by the solid-liquid separation treatment in the 2 nd-fraction salt treatment to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the 1 st to 3 rd fractions is 86-96%, transferring the mother liquor obtained by the solid-liquid separation treatment in the salt treatment of the 3 rd fraction to a nanofiltration separation concentration treatment step.
In another specific example, the step S20 sequentially performs 4-stage salt treatment on the concentrated brine, and can be specifically performed by using the multi-stage freezing crystallization salt separating system 10 with the 4-stage salt separating device. Further, when the mass of the hydrated crystal salt subjected to cold crystal freezing treatment in the salt treatment of the 1 st fraction is 35-60% of the total salt mass of the treated brine, the mother liquor obtained by solid-liquid separation treatment in the salt treatment of the 1 st fraction is transferred to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the 1 st-2 nd-fraction salt treatment is 60-75%, transferring the mother liquor obtained by the solid-liquid separation treatment in the 2 nd-fraction salt treatment to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the 1 st to 3 rd fractions is 75 to 85 percent, transferring the mother liquor obtained by the solid-liquid separation treatment in the salt treatment of the 3 rd fraction to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the 1 st to 4 th fractions is 85 to 96 percent, transferring the mother liquor obtained by the solid-liquid separation treatment in the salt treatment of the 4 th fraction to a nanofiltration separation concentration treatment step.
In another specific example, the step S20 sequentially performs 5-stage salt treatment on the concentrated brine, and can be specifically performed by using the multi-stage freezing crystallization salt separating system 10 with the 5-stage salt separating device. Further, when the mass of the hydrated crystal salt subjected to cold crystal freezing treatment in the salt treatment of the 1 st fraction is 30-50% of the total salt mass of the treated brine, the mother liquor obtained by solid-liquid separation treatment in the salt treatment of the 1 st fraction is transferred to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the 1 st-2 nd-fraction salt treatment is 50-65%, transferring the mother liquor obtained by the solid-liquid separation treatment in the 2 nd-fraction salt treatment to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the 1 st to 3 rd fractions is 65-75%, transferring the mother liquor obtained by the solid-liquid separation treatment in the salt treatment of the 3 rd fraction to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the 1 st to 4 th fractions is 75 to 85 percent, transferring the mother liquor obtained by the solid-liquid separation treatment in the salt treatment of the 4 th fraction to a nanofiltration separation concentration treatment step. And when the crystallization rate of the cold crystal freezing treatment in the salt treatment of the fraction 1-5 is 85-96%, transferring the mother liquor obtained by the solid-liquid separation treatment in the salt treatment of the fraction 5 to a nanofiltration separation concentration treatment step.
Further, in the specific example of performing the 5-stage salt treatment, the purity of the crystalline salt obtained by the cold crystal freezing treatment in the 1-stage salt treatment is 99.5% to 99.8%, the purity of the crystalline salt obtained by the cold crystal freezing treatment in the 2-stage salt treatment is 99.2% to 99.7%, the purity of the crystalline salt obtained by the cold crystal freezing treatment in the 3-stage salt treatment is 99% to 99.5%, the purity of the crystalline salt obtained by the cold crystal freezing treatment in the 4-stage salt treatment is 98.6% to 99.2%, and the purity of the crystalline salt obtained by the cold crystal freezing treatment in the 5-stage salt treatment is 98.5% to 99%.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.
Claims (14)
1. A multi-stage freezing crystallization salt separation system is characterized by comprising:
a concentration device; and
the multi-stage salt separation device comprises a freezing crystallization unit, a solid-liquid separation unit and a nanofiltration separation and concentration unit, wherein in each stage of salt separation device, the solid-liquid separation unit is communicated with the freezing crystallization unit and is used for carrying out solid-liquid separation on a mixture after freezing crystallization, and a liquid inlet of the nanofiltration separation and concentration unit is communicated with a liquid outlet of the solid-liquid separation unit; a freezing crystallization unit in the first salt separating device is communicated with a liquid outlet of the concentration device, and a liquid outlet of a solid-liquid separation unit in the first salt separating device is also communicated with a liquid inlet of the concentration device; in the two adjacent salt separation devices, a freezing crystallization unit in the next salt separation device is communicated with a nanofiltration concentrated water port of a nanofiltration separation concentration unit in the previous salt separation device, and a liquid outlet of a solid-liquid separation unit in the next salt separation device is also communicated with a liquid inlet of the nanofiltration separation concentration unit in the previous salt separation device.
2. The multi-stage freezing crystallization salt separation system according to claim 1, further comprising a monovalent salt evaporative crystallization device in communication with the nanofiltration water production port of each nanofiltration separation concentration unit of each salt separation device.
3. The multi-stage freezing crystallization salt separation system according to claim 2, wherein the monovalent salt evaporation crystallization device is any one of a falling film evaporator, a forced circulation evaporator and an MVR evaporator, or a combination of a plurality of evaporators in series or in parallel.
4. The multi-stage freezing crystallization salt separation system according to claim 1, further comprising a mixed salt evaporation crystallization device and a mixed salt solid-liquid separation device, wherein the mixed salt evaporation crystallization device is communicated with a nanofiltration concentrate port of the nanofiltration separation concentration unit in the last stage salt separation device, and the mixed salt solid-liquid separation device is communicated with the mixed salt evaporation crystallization device for solid-liquid separation of the mixed salt after evaporation crystallization.
5. The multi-stage freezing crystallization salt separation system according to claim 4, wherein the miscellaneous salt evaporation crystallization device comprises a crystallizer, a heat exchanger and a circulating pump, the heat exchanger is used for carrying out heat exchange on the crystallizer, and the circulating pump is used for circulating a heat exchange medium in the heat exchanger.
6. The multi-stage freezing crystallization salt separation system according to claim 4, further comprising a mixed salt mother liquor tank, wherein a liquid inlet of the mixed salt mother liquor tank is communicated with a liquid outlet of the mixed salt solid-liquid separation device, and a liquid outlet of the mixed salt mother liquor tank is communicated with a liquid inlet of the mixed salt evaporative crystallization device.
7. The multi-stage freezing crystallization salt separation system of claim 1, wherein each of the salt separation devices further comprises a salt separation mother liquor tank, and in each of the salt separation devices, a liquid inlet of the nanofiltration separation concentration unit is communicated with a liquid outlet of the solid-liquid separation unit through the salt separation mother liquor tank.
8. The multi-stage freezing crystallization salt separation system of claim 7, wherein the liquid outlet of the salt separation mother liquid tank in the next-stage salt separation device is further communicated with the liquid inlet of the salt separation mother liquid tank in the previous-stage salt separation device.
9. The multi-stage freezing crystallization salt separation system according to any one of claims 1 to 8, wherein each of the salt separation devices further comprises a melt crystallization unit for melt-crystallizing the hydrated crystalline salt separated by the solid-liquid separation unit in each of the salt separation devices.
10. The multi-stage freezing crystallization salt separation system according to claim 9, wherein the melting crystallization unit is any one of a hot melt crystallizer, a hot melt heat exchanger, an evaporative crystallizer, or a combination of a plurality of serial or parallel connection.
11. The multi-stage freezing crystallization salt separation system according to any one of claims 1 to 8, wherein the concentration device is any one of an MVR evaporation device, a multi-effect evaporation device, a high-pressure reverse osmosis device and an electrodialysis device, or a combination of a plurality of devices connected in series or in parallel.
12. The multi-stage freezing crystallization salt separation system according to any one of claims 1 to 8, wherein the solid-liquid separation unit comprises a cyclone separator, a thickener, a centrifuge and a dryer connected in sequence.
13. The multi-stage freezing crystallization salt separation system according to any one of claims 1 to 8, wherein the freezing crystallization unit is any one of a freezing crystallizer, a freezing heat exchanger, a refrigerating unit and a heat exchanger, or a combination of a plurality of the freezing crystallizers, the freezing heat exchanger, the refrigerating unit and the heat exchanger in series or in parallel.
14. The multi-stage freezing crystallization salt separation system according to any one of claims 1 to 8, wherein the nanofiltration separation concentration unit is any one of roll-type nanofiltration and high-pressure flat nanofiltration membranes, or a combination of multiple nanofiltration membranes connected in series or in parallel.
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Denomination of utility model: Multi stage freezing crystallization salt separation system Granted publication date: 20210112 Pledgee: Ordos Rural Commercial Bank Co.,Ltd. Pledgor: INNER MONGOLIA JIUKE KANGRUI ENVIRONMENTAL TECHNOLOGY Co.,Ltd. Registration number: Y2024980046867 |