CN110902923A - Treatment and recovery system for high-salinity wastewater in coal chemical industry - Google Patents
Treatment and recovery system for high-salinity wastewater in coal chemical industry Download PDFInfo
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- 239000002351 wastewater Substances 0.000 title claims abstract description 44
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 239000003245 coal Substances 0.000 title claims abstract description 29
- 238000005039 chemical industry Methods 0.000 title claims abstract description 23
- 238000011084 recovery Methods 0.000 title claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 54
- 238000001728 nano-filtration Methods 0.000 claims abstract description 47
- 239000012528 membrane Substances 0.000 claims abstract description 46
- FAPWRFPIFSIZLT-UHFFFAOYSA-M sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 42
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 41
- 239000011780 sodium chloride Substances 0.000 claims abstract description 38
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 33
- PMZURENOXWZQFD-UHFFFAOYSA-L na2so4 Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 22
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 22
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 22
- 238000002425 crystallisation Methods 0.000 claims abstract description 11
- 230000005712 crystallization Effects 0.000 claims abstract description 11
- 239000002253 acid Substances 0.000 claims abstract description 7
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 24
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 21
- 239000001187 sodium carbonate Substances 0.000 claims description 12
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N HCl Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 238000004064 recycling Methods 0.000 claims description 7
- 238000005273 aeration Methods 0.000 claims description 5
- 238000001914 filtration Methods 0.000 claims description 5
- 239000004902 Softening Agent Substances 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 14
- 238000005562 fading Methods 0.000 abstract description 3
- 150000003839 salts Chemical class 0.000 description 12
- 229910001425 magnesium ion Inorganic materials 0.000 description 10
- 239000000126 substance Substances 0.000 description 8
- JLVVSXFLKOJNIY-UHFFFAOYSA-N magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 238000004140 cleaning Methods 0.000 description 4
- 230000001112 coagulant Effects 0.000 description 4
- 239000000701 coagulant Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000010865 sewage Substances 0.000 description 4
- 239000002910 solid waste Substances 0.000 description 4
- 229910001424 calcium ion Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000003814 drug Substances 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 244000005700 microbiome Species 0.000 description 3
- VTHJTEIRLNZDEV-UHFFFAOYSA-L Magnesium hydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000000347 magnesium hydroxide Substances 0.000 description 2
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 241000276438 Gadus morhua Species 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000001488 breeding Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 235000019516 cod Nutrition 0.000 description 1
- 230000004059 degradation Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000008394 flocculating agent Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 230000000813 microbial Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 230000028327 secretion Effects 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/06—Preparation by working up brines; seawater or spent lyes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/16—Purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/101—Sulfur compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
-
- 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
Abstract
The invention discloses a treatment and recovery system of high-salinity wastewater in coal chemical industry, which comprises a softening unit, a high-pressure reverse osmosis unit, an ultrafiltration membrane unit and a nanofiltration unit, wherein the high-salinity wastewater is treated by the softening unit to obtain softened produced water, the softened produced water after acid adjustment is subjected to reverse osmosis concentration by the high-pressure reverse osmosis unit, the obtained high-pressure reverse osmosis produced water is discharged for reuse, the high-pressure reverse osmosis concentrated solution is filtered by the ultrafiltration membrane unit, the obtained ultrafiltration concentrated solution is subjected to incineration treatment, the obtained ultrafiltration produced water enters the nanofiltration unit for treatment, after the treatment of the nanofiltration unit, the nanofiltration produced water of the nanofiltration unit is crystallized to obtain sodium chloride crystals, and the nanofiltration concentrated solution which does not pass through the nanofiltration unit is subjected to evaporative crystallization to obtain sodium sulfate crystals. Through the method of combining softening process, membrane process and evaporative crystallization process, the softening, concentration, desilicification and fading of high-salinity wastewater with complex components are realized, and the resources of crystallized sodium chloride and sodium sulfate are obtained and can be directly recycled.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment in coal chemical industry, and particularly relates to a treatment and recovery system for high-salinity wastewater in coal chemical industry.
Background
The Chinese energy condition belongs to the type of rich coal and lean oil, and the coal chemical technology occupies a very important position in the regeneration and consumption of energy. The coal chemical industry is a process of converting coal into gas, liquid and solid raw materials by using coal as a raw material through chemical processing, and mainly comprises the steps of coal vaporization, liquefaction, dry distillation, tar processing and the like. The application development of the coal chemical industry inevitably generates a large amount of waste water, the waste water mainly contains a large amount of organic matters and inorganic salts, the water quality is complex, and the effective treatment of the waste water is the key of the sustainable development of coal chemical industry enterprises.
In the prior art, the treatment steps of the wastewater generated in the coal chemical industry are mainly as follows: the method comprises the steps of microbial aerobic-anaerobic treatment, chemical oxidation and reverse osmosis membrane separation, clear water generated after reverse osmosis membrane separation is directly discharged to the discharge standard, reverse osmosis concentration water contains about 6% of inorganic salt and a small amount of COD, and at present, aiming at the high-salt reverse osmosis concentration water, an enterprise adopts a treatment method of directly evaporating the high-salt reverse osmosis concentration water to dryness so as to greatly reduce the amount of wastewater for outsourcing, but inorganic salt solid waste generated after evaporation to dryness is difficult to treat, and the method is a difficult problem for coal chemical enterprises to treat.
For example: the reverse osmosis concentrated solution is generated by a chemical enterprise at 60t per hour, the inorganic miscellaneous salt solid waste materials generated each year after being treated by the method are up to 3000t, the inorganic miscellaneous salt solid waste materials can be only treated according to dangerous chemicals, and the economic angle also increases a lot of cost burden on the chemical enterprise. However, when the content ratios of sodium chloride and sodium sulfate in the incoming water of the sewage are close to each other, it is difficult to perform the salt separation treatment on the sodium chloride and sodium sulfate in the incoming water, and only the treatment of crystallization into mixed salt can be realized.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a treatment and recovery system for high-salinity wastewater in coal chemical industry, and solves the problems that inorganic salt solid waste is difficult to treat and simple salt separation treatment cannot be carried out in the production process of coal chemical industry enterprises in the prior art.
The purpose of the invention can be realized by the following technical scheme:
a treatment and recovery system for high-salinity wastewater in coal chemical industry comprises a softening unit, a high-pressure reverse osmosis unit, an ultrafiltration membrane unit and a nanofiltration unit, wherein the high-salinity wastewater is treated by the softening unit to obtain softened product water, and then acid is added to adjust the pH of the softened product water to 8.5-10.0;
and performing reverse osmosis concentration on the softened produced water after acid adjustment through a high-pressure reverse osmosis unit, discharging the obtained high-pressure reverse osmosis produced water for reuse, adjusting the pH of the other part of the formed high-pressure reverse osmosis concentrated solution to 6.0-6.5, filtering the high-pressure reverse osmosis concentrated solution through an ultrafiltration membrane unit, crystallizing the obtained ultrafiltration concentrated solution, then performing incineration treatment, allowing the obtained ultrafiltration produced water to enter a nanofiltration unit for treatment, performing nanofiltration unit treatment, crystallizing the nanofiltration produced water passing through the nanofiltration unit to obtain sodium chloride crystals, and performing evaporative crystallization on the nanofiltration concentrated solution not passing through the nanofiltration unit to obtain sodium sulfate crystals.
Furthermore, a heat source of a heat exchanger in the softening unit is from condensed water in the crystallization of the first evaporative crystallization unit and the second evaporative crystallization unit, and the heating temperature of the heat exchanger is controlled to be 25-28 ℃.
Furthermore, the softening agent added by the dosing mechanism in the softening unit is formed by combining 30% by mass of sodium hydroxide and 10% by mass of sodium carbonate, and the sodium carbonate is continuously added into the softening unit at a time interval of 40 min.
Further, acid is added into the high-salinity wastewater treated by the softening unit, and a hydrochloric acid solution with the volume fraction of 30% is adopted.
Furthermore, the solid content in the water body before the high-salinity wastewater passes through the softening unit is controlled to be 1-6%, and CODcr is less than or equal to 1000 mg/L.
Furthermore, the filter membrane of the high-pressure reverse osmosis unit adopts a reverse osmosis membrane with a spiral winding structure, and the operating pressure is controlled between 70 and 120 bar.
Furthermore, the molecular weight cut-off of the membrane element in the ultrafiltration membrane unit is 10000-50000D, a tubular or roll-type ultrafiltration membrane is selected, and the inlet pressure of the ultrafiltration membrane unit is controlled to be 5 bar.
Furthermore, the molecular weight cut-off of the membrane element in the nanofiltration unit is 100-600D, and the outlet pressure of the nanofiltration unit is controlled to be 20-60 bar.
Further, the purity of the sodium chloride crystal is more than or equal to 98.5 percent; the content of sodium sulfate crystals is more than or equal to 99 percent.
The invention has the beneficial effects that:
1. softening, concentrating, removing silicon and fading high-salinity wastewater with complex components are realized by a method of mutually combining a softening process, a membrane process and an evaporative crystallization process, and resources of crystallized industrial-grade sodium chloride and sodium sulfate are obtained.
2. The softening unit adds sodium hydroxide with the mass fraction of 30% and sodium carbonate with the mass fraction of 10% to the solution earlier in this application, forms the magnesium ion in the water and deposits to the process that the magnesium ion formed the deposit is endothermic reaction, can accelerate the sedimentation velocity of magnesium ion, and the input of flocculating agent/coagulant in the reducible traditional sewage treatment in-process of the combined reagent that adds in this application simultaneously reduces energy consumption and cost.
3. According to the invention, the ultrafiltration membrane unit and the nanofiltration unit are used in a matched manner, and the filtration parameters are set, so that the sodium chloride monovalent salt and the sodium sulfate divalent salt are effectively separated, and the purity of sodium chloride crystals is more than or equal to 98.5%; the content of the sodium sulfate crystal is more than or equal to 99 percent, and the sodium sulfate crystal can be directly applied to industry.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
Fig. 1 is an overall structural block diagram of an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
As shown in fig. 1, an embodiment of the present invention provides a system for treating and recycling high-salt wastewater from coal chemical industry, which comprises a softening unit, a high-pressure reverse osmosis unit, an ultrafiltration membrane unit, and a nanofiltration unit, wherein the high-salt wastewater passes through the softening unit, the softening unit is of a combined structure, a heat exchanger is disposed in the softening unit (the heat source is condensed water that flows back when the nanofiltration unit is crystallized, the temperature of the condensed water is controlled to be 25-28 ℃, calcium and magnesium ions are contained in total hardness in a water body, magnesium hydroxide formed by magnesium ions is an endothermic reaction, and the heating speed can accelerate the sedimentation speed of the magnesium ions at the temperature during softening), a dosing mechanism (an added softening agent is formed by combining 30% by mass of sodium hydroxide and 10% by mass of sodium carbonate, and the sodium hydroxide is prepared into a solution, and the solution is added into incoming water through a dosing pump and a pipeline mixer, participate in NaOH + Mg2+＝Mg(OH)2↓; sodium carbonate is dissolved by the alkali dissolving platform and is directly fed into the reaction tank by the dosing pump, and is added into the high-salinity wastewater in the softening unit according to the time interval of 40min, and the total Mg in the water body is waited2+After the content is reduced, adding sodium carbonate to precipitate Ca2+。CO3 2-+Ca2+＝CaCO3↓, purpose, reduction of Mg2+To CO3 2-The consumption of the method is reduced, the magnesium ions are removed by adding the flocculant/coagulant during the original sewage treatment, the actual cost is higher by about 0.25 yuan/ton of water, the energy consumption is high, equipment needs to be cleaned regularly when the magnesium ions are removed by adopting the flocculant/coagulant, the flocculant/coagulant is prevented from being excessively accumulated on the inner wall of a pipeline to influence the discharge of the sewage, and the combined medicament provided by the application is directly adoptedNot only obtaining water reduced to about 0.22 yuan/ton to a certain extent from the price cost, but also reducing the cleaning times of pipelines and prolonging the service life of equipment), and an aeration mechanism carries out aeration operation on the high-salinity wastewater in the softening unit to realize the full mixing of the high-salinity wastewater and a softening medicament, and meanwhile, the aeration can obviously reduce the using amount of the sodium carbonate medicament and prevent excessive introduction of sodium carbonate, thereby reducing the content of newly introduced sodium carbonate in the high-salinity wastewater. And then discharging the softened water through a filtering mechanism, wherein the solid content in the discharged softened water is controlled within the range of 1-6%, and CODcr is less than or equal to 1000 mg/L. The hardness and silicon content of the softened water produced after the softening treatment are reduced.
Adding 30% hydrochloric acid solution by volume fraction into the high-salinity wastewater passing through the high-pressure reverse osmosis unit to adjust the pH to 8.5-10.0, and selecting a reverse osmosis membrane with a spiral wound structure, wherein the operation pressure is controlled to be 70-120 bar. And then the softened produced water passing through the high-pressure reverse osmosis unit is discharged for reuse in a high-pressure reverse osmosis water production mode, the other part of the softened produced water forms high-pressure reverse osmosis concentrated solution, the pH value of the high-pressure reverse osmosis concentrated solution is adjusted to 6.0-6.5, and the high-pressure reverse osmosis concentrated solution after the pH value adjustment flows into the ultrafiltration membrane unit. The pollution of the ultrafiltration membrane is reduced by adjusting the pH value for many times, the cleaning frequency of the ultrafiltration membrane is reduced, and meanwhile, as is known, the waste water contains more organic matters, so that the permeability of the ultrafiltration membrane is influenced, and the degradation rate of the membrane is accelerated due to the secretion of microorganisms. The adoption of the acidity and the alkalinity of adjusting the pH value for multiple times can reduce the breeding of microorganisms in the wastewater, thereby reducing the adhesion of the microorganisms on the nanofiltration membrane, reducing the replacement and cleaning times of the nanofiltration membrane and prolonging the service life of the nanofiltration membrane.
The membrane element in the ultrafiltration membrane unit adopts a tubular ultrafiltration membrane or a spiral type ultrafiltration membrane, the molecular weight cut-off of the membrane element is 10000-50000D, and the inlet pressure of the ultrafiltration membrane unit is controlled to be 5 bar; after the high-pressure reverse osmosis concentrated solution flowing into the ultrafiltration membrane unit is treated, the obtained ultrafiltration concentrated solution is crystallized and then is incinerated, the obtained ultrafiltration product water flows into the nanofiltration unit for treatment, the interception molecular weight of a membrane element in the nanofiltration unit is 100-600D, the outlet pressure of the nanofiltration unit is controlled to be 20-60bar, after the nanofiltration unit is treated, the nanofiltration product water passing through the nanofiltration unit is crystallized to obtain sodium chloride crystals, and the nanofiltration concentrated solution not passing through the nanofiltration unit is evaporated and crystallized to obtain sodium sulfate crystals; at the moment, the solute mass ratio of the sodium chloride solution to the sodium sulfate solution is controlled to be more than 60:1 through the solution on the water production side through nanofiltration, so that the sodium chloride solution can be separated out high-content industrial sodium chloride in the concentration process, and the purity of sodium chloride crystals is more than or equal to 98.5%; and the solute mass ratio of sodium sulfate to sodium chloride of the solution on the side where the nanofiltration water is not permeated is controlled to be 10:1, so that the high-content industrial sodium sulfate is separated out from the sodium sulfate solution in the concentration process, and the content of sodium sulfate crystals is more than or equal to 99%.
Example (b):
3000kg of high-salinity wastewater is obtained from a certain chemical plant, wherein the content ratio of sodium chloride to sodium sulfate in the incoming water is 1: (0.75-1.5), wherein the total hardness of the wastewater obtained by detection is 2835.7mg/L, and Ca is2+The content is 255.6mg/L, heat exchange is carried out through a heat exchanger, the temperature is raised to 26 ℃, a softening agent is added while aeration is carried out, a sodium hydroxide solution with the mass fraction of 30% is added into high-salinity wastewater, a small amount of sodium carbonate solution with the mass fraction of 10% is added after 40min, the produced water of a softening unit is connected into a softening produced water buffer tank, the total hardness of the produced water obtained after softening is 29.4mg/L, Ca is added2+The content is 7.74mg/L, which is greatly reduced. Adding hydrochloric acid into softened produced water until the pH value is 9.2, feeding the softened produced water into a high-pressure reverse osmosis unit for concentration, feeding concentrated solution of the high-pressure reverse osmosis unit into a high-pressure reverse osmosis concentrated solution buffer tank, then adding hydrochloric acid into the high-pressure reverse osmosis concentrated solution until the pH value is 6.7, feeding the high-pressure reverse osmosis concentrated solution into an ultrafiltration membrane unit, directly feeding the produced water of the ultrafiltration membrane unit into a nanofiltration unit for salt separation, crystallizing the nanofiltration produced water of the nanofiltration unit to obtain sodium chloride crystals, and evaporating and crystallizing the nanofiltration concentrated solution which does not pass through the nanofiltration unit to obtain sodium sulfate crystals.
And experimental data as shown in table 1 were obtained:
TABLE 1
In conclusion, the invention realizes softening, concentration, desilicification and fading of high-salinity wastewater with complex components by a method of combining a softening process, a membrane process and an evaporative crystallization process, obtains resources of crystallized sodium chloride and sodium sulfate, and simultaneously the purity of sodium chloride crystals is more than or equal to 98.5%; the content of the sodium sulfate crystal is more than or equal to 99 percent and can be recycled.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.
Claims (10)
1. A treatment and recovery system for high-salinity wastewater in coal chemical industry comprises a softening unit, a high-pressure reverse osmosis unit, an ultrafiltration membrane unit and a nanofiltration unit, and is characterized in that the high-salinity wastewater is treated by the softening unit to obtain softened product water, and then acid is added to adjust the pH of the softened product water to 8.5-10.0;
and performing reverse osmosis concentration on the softened produced water after acid adjustment through a high-pressure reverse osmosis unit, discharging the obtained high-pressure reverse osmosis produced water for reuse, adjusting the pH of the other part of the formed high-pressure reverse osmosis concentrated solution to 6.0-6.5, filtering the high-pressure reverse osmosis concentrated solution through an ultrafiltration membrane unit, crystallizing the obtained ultrafiltration concentrated solution, then performing incineration treatment, allowing the obtained ultrafiltration produced water to enter a nanofiltration unit for treatment, performing nanofiltration unit treatment, crystallizing the nanofiltration produced water passing through the nanofiltration unit to obtain sodium chloride crystals, and performing evaporative crystallization on the nanofiltration concentrated solution not passing through the nanofiltration unit to obtain sodium sulfate crystals.
2. The system for treating and recycling high-salinity wastewater in coal chemical industry according to claim 1, characterized in that the softening unit is of a combined structure, and a heat exchanger, a dosing mechanism, an aeration mechanism and a filtering mechanism are arranged in the softening unit to soften the high-salinity wastewater passing through the softening unit.
3. The system for treating and recycling high-salinity wastewater in coal chemical industry according to claim 2, characterized in that the heat source of the heat exchanger in the softening unit is derived from condensed water refluxed during the crystallization of the nanofiltration unit, and the heating temperature of the heat exchanger is controlled to be 25-28 ℃.
4. The system for treating and recycling high-salinity wastewater in coal chemical industry according to claim 2, characterized in that the softening agent added by the dosing mechanism in the softening unit is composed of 30% by mass of sodium hydroxide and 10% by mass of sodium carbonate, and the sodium carbonate is added into the softening unit at a time interval of 40 min.
5. The system for treating and recycling high-salinity wastewater in coal chemical industry according to claim 2, characterized in that the high-salinity wastewater treated by the softening unit is added with acid by adopting a hydrochloric acid solution with a volume fraction of 30%.
6. The system for treating and recycling high-salinity wastewater in the coal chemical industry according to claim 1, wherein the solid content in the water body before the high-salinity wastewater passes through the softening unit is controlled to be 1-6%, and the CODcr is less than or equal to 1000 mg/L.
7. The system for treating and recycling coal chemical industry high-salt wastewater as claimed in claim 6, wherein the filter membrane of the high-pressure reverse osmosis unit is a reverse osmosis membrane with a spiral-wound structure, and the operating pressure is controlled to be 70-120 bar.
8. The system for treating and recovering high-salinity wastewater in coal chemical industry according to claim 1, wherein the molecular weight cut-off of the membrane elements in the ultrafiltration membrane unit is 10000-50000D, and a tubular or spiral type ultrafiltration membrane is selected, and the inlet pressure of the ultrafiltration membrane unit is controlled to be 5 bar.
9. The system for treating and recovering high-salinity wastewater in coal chemical industry according to claim 1, wherein the molecular weight cut-off of the membrane element in the nanofiltration unit is 100-600D, and the outlet pressure of the nanofiltration unit is controlled to be 20-60 bar.
10. The system for treating and recovering high-salinity wastewater in coal chemical industry according to claim 1, wherein the purity of the sodium chloride crystal is more than or equal to 98.5%; the content of sodium sulfate crystals is more than or equal to 99 percent.
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