CN113233673A - Forward and reverse osmosis coupling crystallization system - Google Patents
Forward and reverse osmosis coupling crystallization system Download PDFInfo
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- CN113233673A CN113233673A CN202110281562.8A CN202110281562A CN113233673A CN 113233673 A CN113233673 A CN 113233673A CN 202110281562 A CN202110281562 A CN 202110281562A CN 113233673 A CN113233673 A CN 113233673A
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- 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
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- 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
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- C02F1/445—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by forward osmosis
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- C02F1/00—Treatment of water, waste water, or sewage
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- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/02—Softening water by precipitation of the hardness
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Abstract
The invention provides a forward and reverse osmosis coupling crystallization system, which comprises: the pretreatment device is used for removing calcium and magnesium ions in the salt-containing wastewater and enabling the chemical oxygen demand in the pretreated salt-containing wastewater to be smaller than a first preset threshold value; the forward and reverse osmosis coupling device is used for pre-concentrating the pretreated saline wastewater through reverse osmosis, reducing the Chemical Oxygen Demand (COD) of the pre-concentrated saline wastewater to be less than a second preset threshold value, and continuously concentrating the pre-concentrated saline wastewater through forward osmosis to obtain concentrated water with the Total Dissolved Solid (TDS) content being greater than a third preset threshold value; the cooling crystallization device is used for cooling the concentrated water to a first preset temperature threshold range, and crystallizing mirabilite of which the concentration is more than or equal to 99%; and the thermal crystallization device is used for heating the concentrated water with the TDS content larger than a third preset threshold value to crystallize sodium chloride with the concentration of more than or equal to 98.5 percent. The high-multiple membrane concentration with low energy consumption is realized, and the zero discharge of salt-containing wastewater and the recycling of crystallized salt are realized.
Description
Technical Field
The invention relates to the technical field of environmental protection, in particular to a forward and reverse osmosis coupling crystallization system.
Background
At present, the industries of coal chemical industry, electric power, steel, papermaking, nonferrous smelting and the like develop the near zero emission of salt-containing wastewater, so that the realization of the efficient reuse and the near zero emission of the wastewater becomes the self requirement and the external requirement of the development of various industries.
However, in the technical scheme of the zero-emission engineering which is already operated in China at present, the salt content of inlet water is relatively low, the Total Dissolved Solids (TDS) content TDS in general salt-containing wastewater is less than or equal to 40000mg/L, and the required water amount is large, so that the scale of evaporative crystallization treatment equipment is large, the operation cost is high, the engineering investment and the operation cost of the whole zero-emission project are high, the quality of crystallized product salt is low, and the crystallized product salt can be only treated according to solid waste, so that the utilization rate of evaporative crystallization devices of part of enterprises is relatively low.
Disclosure of Invention
In view of the problems in the related art, the present invention is directed to a forward and reverse osmosis coupled crystallization system.
As an aspect of an embodiment of the present invention, a forward and reverse osmosis coupled crystallization system is provided, comprising:
the device comprises a pretreatment device, a forward and reverse osmosis coupling device, a cooling crystallization device and a thermal crystallization device;
the forward and reverse osmosis coupling device is respectively connected with the pretreatment device, the cooling crystallization device and the thermal crystallization device;
the pretreatment device is used for removing calcium and magnesium ions in the salt-containing wastewater and enabling the chemical oxygen demand in the pretreated salt-containing wastewater to be smaller than a first preset threshold value;
the forward and reverse osmosis coupling device is used for pre-concentrating the pretreated saline wastewater through reverse osmosis, reducing the Chemical Oxygen Demand (COD) of the pre-concentrated saline wastewater to be less than a second preset threshold value, and continuously concentrating the pre-concentrated saline wastewater through forward osmosis to obtain concentrated water with the Total Dissolved Solid (TDS) content being greater than a third preset threshold value;
the cooling crystallization device is used for cooling the concentrated water with the TDS content larger than a third preset threshold value to a first preset temperature threshold value range, and crystallizing mirabilite with the TDS content larger than or equal to 99%;
and the thermal crystallization device is used for heating the concentrated water with the TDS content larger than a third preset threshold value to crystallize sodium chloride with the concentration of more than or equal to 98.5%.
In one or more alternative embodiments, the forward and reverse osmosis coupling device comprises: the device comprises a water inlet tank, a 1# booster pump, a 1# precision filter, a 1# high-pressure pump, a forward and reverse osmosis device, a 2# booster pump, a 2# precision filter, a high-concentration water tank and a feed pump;
the 1# booster pump is connected with the water inlet tank and the 1# precision filter respectively;
the No. 1 high-pressure pump is connected with the No. 1 precision filter;
the 2# booster pump is connected with the water inlet tank and the 2# precision filter respectively;
the forward and reverse osmosis device is respectively connected with the 1# high-pressure pump, the 2# precision filter and the high-concentration water tank;
the high-concentration water tank is connected with the feeding pump.
In one or more alternative embodiments, the forward and reverse osmosis apparatus comprises: a reverse osmosis unit and a forward osmosis unit;
the inlet of the reverse osmosis device is connected with the outlet of the 1# high-pressure pump, and the outlet of the reverse osmosis device is connected with the concentrated water inlet of the forward osmosis device;
and a drawing liquid inlet and outlet of the forward osmosis device are respectively connected with the No. 2 precision filter and the No. 1 high-pressure pump, and a concentrated water outlet of the forward osmosis device is connected with the high-concentration water tank.
In one or more alternative embodiments, the forward and reverse osmosis apparatus further comprises: the system comprises a No. 1 ozone catalytic reactor, a No. 2 ozone catalytic reactor, a concentrated water tank, a booster pump and a No. 2 high-pressure pump;
the outlet of the reverse osmosis device is connected with the concentrated water tank through the No. 1 ozone catalytic reactor and the No. 2 ozone catalytic reactor;
the booster pump is respectively connected with the concentrated water tank and the 2# high-pressure pump;
and a concentrated water inlet of the forward osmosis device is connected with the 2# high-pressure pump.
In one or some optional embodiments, the forward and reverse osmosis coupling device is further configured to use the pretreated saline wastewater as a draw solution, discharge fresh water obtained in a process of concentrating the pretreated saline wastewater by reverse osmosis as produced water, and continuously concentrate the concentrated water by forward osmosis to finally obtain concentrated water with a total dissolved solids TDS content greater than a third preset threshold.
In one or some alternative embodiments, the pretreatment device comprises a chemical reaction tank, a tubular microfiltration membrane, ion exchange resin, a decarbonization tower and an ozone oxidation device which are connected in sequence;
the chemical reaction tank is used for carrying out chemical reaction on the salt-containing wastewater to obtain calcium and magnesium ion reaction precipitates;
the tubular microfiltration membrane is used for filtering suspended matters and calcium and magnesium ion reaction precipitates in the salt-containing wastewater after reaction to obtain the salt-containing wastewater with the calcium and magnesium ion content smaller than a fourth preset threshold;
the ion exchange resin is used for removing the residual calcium and magnesium hardness in the salt-containing wastewater with the calcium and magnesium ion content smaller than a fourth preset threshold;
the decarbonizing tower is used for removing carbonate and bicarbonate ions in the salt-containing wastewater;
the ozone oxidation device is used for enabling COD (chemical oxygen demand) in the salt-containing wastewater to be smaller than a first preset threshold value, so that the pretreated salt-containing wastewater is obtained.
In one or some alternative embodiments, the cooling crystallization device is connected with the thermal crystallization device;
the thermal crystallization device is also used for heating and dissolving the mirabilite more than or equal to 99 percent and recrystallizing anhydrous sodium sulphate more than or equal to 99.5 percent.
In one or some optional embodiments, the cooling crystallization device is further configured to make the TDS content in the cooling mother liquor generated in the mirabilite crystallization process less than a fifth preset threshold, and introduce the cooling mother liquor with the TDS content less than the fifth preset threshold into the pretreatment device.
In one or some alternative embodiments, the cooling crystallization device comprises: the system comprises a precooler, a cooling crystallizer, a circulating pump, a cooler, a refrigerator, a salt outlet pump, a liquid cyclone, a centrifuge, a cold mother liquor tank, a cold mother liquor pump and a dissolving tank;
the inlet of the circulating pump is respectively connected with the precooler and the cooling crystallizer, and the outlet of the circulating pump is connected with the cooling crystallizer through the cooler;
the inlet and the outlet of the refrigerator are respectively connected with the cooler and used for controlling the temperature in the cooling crystallizer within the first preset temperature threshold range;
the salt outlet pump is respectively connected with the cooling crystallizer and the liquid cyclone;
the cyclone is respectively connected with the cooling crystallizer and the centrifuge;
the centrifuge is respectively connected with the dissolving tank and the cold mother liquor tank;
and the inlet of the cold mother liquor pump is connected with the cold mother liquor tank, and the outlet of the cold mother liquor pump is connected with the pretreatment device through the precooler.
In one or some alternative embodiments, the coolant of the chiller is ethylene glycol.
The invention has the beneficial technical effects that:
in the forward and reverse osmosis coupling crystallization system provided by the embodiment of the invention, calcium and magnesium ions in the salt-containing wastewater are removed and COD is reduced through a pretreatment mode to obtain the pretreated salt-containing wastewater, then the pretreated salt-containing wastewater is used as a drawing liquid through a forward and reverse osmosis coupling device to realize concentration of the salt-containing wastewater, so that concentrated water with TDS content larger than a third preset threshold and COD smaller than a second preset threshold is obtained, and for the concentrated water mainly containing sodium sulfate obtained after concentration, more than or equal to 99% of mirabilite can be crystallized through a cooling crystallization device, no phase change exists in the cooling crystallization process, and the energy consumption in the cooling crystallization process is reduced; and for the concentrated water which is obtained after concentration and is concentrated by high times and mainly contains sodium chloride, anhydrous sodium sulphate which is more than or equal to 99.5 percent can be crystallized by a thermal crystallization device. Because the absorption liquid without a forward osmosis membrane and the absorption liquid recovery device with high energy consumption are not needed when the salt-containing wastewater is concentrated, the absorption liquid is not needed to be recovered and supplemented, the high-multiple membrane concentration with low energy consumption can be realized, the energy consumption for concentrating the salt-containing wastewater is reduced, the sewage discharge is reduced, a large amount of water resources are saved, the operation cost is reduced, the problem of water resource shortage is solved, and the pollution and damage to the environment and the ecology can be reduced; and the concentrated water is crystallized through the cooling crystallization device or the thermal crystallization device, so that the load of an evaporation crystallization section is reduced, the comprehensive treatment cost can be reduced, and the purity of mirabilite or sodium chloride obtained by crystallization meets the quality requirement, so that the recycling of high-purity crystal salt is realized, the industrial utilization value of the high-purity crystal salt is high, the high-purity crystal salt can be sold as a product, the high-purity crystal salt can be used as a raw material for inorganic chemical industry, and the income of salt-containing wastewater treatment is increased.
Drawings
FIG. 1 is a first schematic structural diagram of a forward and reverse osmosis coupled crystallization system according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a forward and reverse osmosis coupled crystallization system according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a forward/reverse osmosis apparatus of a forward/reverse osmosis coupled crystallization system according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a pretreatment device of a forward and reverse osmosis coupled crystallization system according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings, and various specific embodiments of a forward and reverse osmosis coupled crystallization system provided by the embodiments of the present disclosure will be described in detail. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
An embodiment of the present invention provides a forward and reverse osmosis coupled crystallization system, as shown in fig. 1, including:
the device comprises a pretreatment device 1, a forward and reverse osmosis coupling device 2, a cooling crystallization device 3 and a thermal crystallization device 4;
the forward and reverse osmosis coupling device 2 is respectively connected with the pretreatment device 1, the cooling crystallization device 3 and the thermal crystallization device 4;
the pretreatment device 1 is used for removing calcium and magnesium ions in the salt-containing wastewater and enabling the chemical oxygen demand in the pretreated salt-containing wastewater to be smaller than a first preset threshold value;
the forward and reverse osmosis coupling device 2 is used for pre-concentrating the pretreated saline wastewater through reverse osmosis, reducing the Chemical Oxygen Demand (COD) of the pre-concentrated saline wastewater to be less than a second preset threshold value, and continuously concentrating the pre-concentrated saline wastewater through forward osmosis to obtain concentrated water with the Total Dissolved Solid (TDS) content being greater than a third preset threshold value;
the cooling crystallization device 3 is used for cooling the concentrated water with the TDS content larger than a third preset threshold value to a first preset temperature threshold value range, and crystallizing mirabilite with the TDS content larger than or equal to 99%;
and the thermal crystallization device 4 is used for heating the concentrated water with the TDS content larger than a third preset threshold value to crystallize sodium chloride with the concentration of more than or equal to 98.5%.
In the embodiment of the present invention, the salt-containing wastewater may be salt-containing wastewater containing impurities such as reverse osmosis concentrated water with TDS content not less than 30000mg/L, desulfurization wastewater, concentrated nanofiltration dilute water, nanofiltration concentrated water, and the like, which contain calcium, magnesium, carbonate, bicarbonate plasma, Suspended Solids (SS), Chemical Oxygen Demand (COD), and the like.
In the embodiment of the present invention, the first preset threshold, the second preset threshold, and the third preset threshold may be set according to actual use requirements. The first preset threshold may be in the range of 20mg/L to 45mg/L, for example, 25mg/L, 30mg/L, 35 mg/L; the second preset threshold may be in the range of 25mg/L to 50mg/L, for example, 30mg/L, 35mg/L, 40 mg/L; the third predetermined threshold may be 150000mg/L to 200000mg/L, for example, 160000mg/L, 180000mg/L, 200000 mg/L.
In the embodiment of the present invention, the size of the first preset temperature threshold range may also be set according to the actual use requirement, for example, the first preset temperature threshold range may be 0 ℃ to 5 ℃ (celsius).
In the embodiment of the invention, the 99% of mirabilite can be 99% of mirabilite by mass, or can be written as 99 wt% of mirabilite; similarly, the above-mentioned 98.5% sodium chloride may be 98.5% by mass sodium chloride, or may be written as 98.5% by weight sodium chloride.
In the embodiment of the invention, because the salt-containing wastewater contains impurities such as calcium, magnesium, carbonate, bicarbonate ions, SS, COD and the like, in order to ensure the continuous and stable operation of the forward and reverse osmosis coupling device, reduce the cleaning times and ensure the purity of crystal salts such as mirabilite or sodium chloride obtained by crystallization treatment of the cooling crystallization device or the thermal crystallization device, the impurities such as calcium, magnesium, carbonate, bicarbonate ions, SS and the like in the salt-containing wastewater are removed by the pretreatment device 1, and the COD is reduced to be less than a first preset threshold value.
In the forward and reverse osmosis coupling crystallization system provided by the embodiment of the invention, calcium and magnesium ions in the salt-containing wastewater are removed and COD is reduced through a pretreatment mode to obtain the pretreated salt-containing wastewater, then the pretreated salt-containing wastewater is used as a drawing liquid through a forward and reverse osmosis coupling device to realize concentration of the salt-containing wastewater to obtain concentrated water with TDS content larger than a third preset threshold, and for the concentrated high-multiple sodium sulfate-based concentrated water obtained after concentration, more than or equal to 99% of mirabilite can be crystallized through a cooling crystallization device, no phase change exists in a cooling crystallization process, and energy consumption in the cooling crystallization process is reduced; and for the concentrated water which is obtained after concentration and is concentrated by high times and mainly contains sodium chloride, the sodium chloride with the concentration of more than or equal to 98.5 percent can be crystallized by a thermal crystallization device. Because the absorption liquid without a forward osmosis membrane and the absorption liquid recovery device with high energy consumption are not needed when the salt-containing wastewater is concentrated, the absorption liquid is not needed to be recovered and supplemented, the high-multiple membrane concentration with low energy consumption can be realized, the energy consumption for concentrating the salt-containing wastewater is reduced, the sewage discharge is reduced, a large amount of water resources are saved, the operation cost is reduced, the problem of water resource shortage is solved, and the pollution and damage to the environment and the ecology can be reduced; and the concentrated water is crystallized through the cooling crystallization device or the thermal crystallization device, so that the load of an evaporation crystallization section is reduced, the comprehensive treatment cost can be reduced, and the purity of mirabilite or sodium chloride obtained by crystallization meets the quality requirement, so that the recycling of high-purity crystal salt is realized, the industrial utilization value of the high-purity crystal salt is high, the high-purity crystal salt can be sold as a product, the high-purity crystal salt can be used as a raw material for inorganic chemical industry, and the income of salt-containing wastewater treatment is increased.
In an embodiment, the forward and reverse osmosis coupling device 2 is further configured to use the pretreated saline wastewater as a draw solution, discharge fresh water obtained in a process of concentrating the pretreated saline wastewater by reverse osmosis as produced water, and continuously concentrate the concentrated water by forward osmosis to finally obtain concentrated water with a total dissolved solids TDS content greater than a third preset threshold.
In one embodiment, referring to FIG. 2, the forward and reverse osmosis coupling device 2 comprises: a feed water tank 201, a 1# booster pump 202, a 1# precision filter 203, a 1# high-pressure pump 204, a forward and reverse osmosis device 205, a 2# booster pump 206, a 2# precision filter 207, a high-concentration water tank 208 and a feed pump 209;
the 1# booster pump 202 is respectively connected with the water inlet tank 201 and the 1# precision filter 203;
the # 1 high-pressure pump 204 is connected with the # 1 precision filter 203;
the 2# pressurizing pump 206 is respectively connected with the water inlet tank 201 and the 2# precision filter 207;
the forward and reverse osmosis device 205 is respectively connected with the # 1 high-pressure pump 204, the # 2 precision filter 207 and the high-concentration water tank 208;
the high-concentrate tank 208 is connected to the feed pump 209.
In an embodiment, the above # 1 booster pump 202 is connected to the water inlet tank 201 and the # 1 precision filter 203 respectively, specifically, an inlet of the # 1 booster pump 202 is connected to an outlet of the water inlet tank 201, and an outlet of the # 1 booster pump 202 is connected to an inlet of the # 1 precision filter 203;
the # 1 high-pressure pump 204 is connected to the # 1 precision filter 203, and specifically, an inlet of the # 1 high-pressure pump 204 may be connected to an outlet of the # 1 precision filter 203;
the 2# booster pump 203 is connected to the water inlet tank 201 and the 2# precision filter 207 respectively, specifically, an inlet of the 2# booster pump 203 may be connected to an outlet of the water inlet tank 201, and an outlet of the 2# booster pump 203 may be connected to an inlet of the 2# precision filter 207;
the forward and reverse osmosis device 205 with 1# high-pressure pump 204, 2# precision filter 207 with high enriched water jar 208 is connected respectively, forward and reverse osmosis device 205 and 1# high-pressure pump 204's exit linkage, and forward and reverse osmosis device 205's dense water export is connected with high enriched water jar 208, and forward and reverse osmosis device 205's the draw liquid entry and 2# precision filter 207's exit linkage, forward and reverse osmosis device 205's the draw liquid export and 1# high-pressure pump 204's entry linkage, high enriched water jar 208's export with the entry linkage of charge pump 209.
In one embodiment, the forward osmosis apparatus 205 may comprise: a reverse osmosis unit 2051 and a forward osmosis unit 2057;
the inlet of the reverse osmosis device 2051 is connected with the outlet of the # 1 high-pressure pump 204, and the outlet of the reverse osmosis device 2051 is connected with the concentrated water inlet of the forward osmosis device 2057;
the inlet and the outlet of the draw solution of the forward osmosis device 2057 are respectively connected with the # 2 precision filter 207 and the # 1 high-pressure pump 204, and the concentrated water outlet of the forward osmosis device 2057 is connected with the high-concentration water tank 208.
In one embodiment, the forward osmosis device, the reverse osmosis device and the ozone catalytic reactor are coupled into a whole, and for a part of pretreated saline wastewater obtained after pretreatment, a part of pretreated saline wastewater is concentrated by the reverse osmosis device, then COD is reduced by the ozone catalytic reactor, and then enters the forward osmosis device, and the produced water in the reverse osmosis process is discharged through the reverse osmosis device; the other part of pretreated salt-containing wastewater directly enters the liquid drawing side of the forward and reverse osmosis device, the salt-containing wastewater subjected to preconcentration by the reverse osmosis device is subjected to auxiliary pressurization concentration, and the diluted pretreated salt-containing wastewater can be mixed with the pretreated salt-containing wastewater and then enters the reverse osmosis device of the forward and reverse osmosis coupling device again to be subjected to concentration.
In one embodiment, referring to FIG. 3, the forward and reverse osmosis apparatus 205 comprises: a reverse osmosis device 2051, a # 1 ozone catalytic reactor 2052, a # 2 ozone catalytic reactor 2053, a concentrate tank 2054, a booster pump 2055, a # 2 high-pressure pump 2056, and a forward osmosis device 2057;
the inlet of the reverse osmosis device 2051 is connected with the outlet of the # 1 high-pressure pump 204, and the outlet of the reverse osmosis device 2051 is connected with the concentrated water tank 2054 through the # 1 ozone catalytic reactor 2052 and the # 2 ozone catalytic reactor 2053;
the booster pump 2055 is connected with the concentrated water tank 2054 and the # 2 high-pressure pump 2056 respectively;
an inlet and an outlet of a draw solution of the forward osmosis device 2057 are respectively connected with the # 2 ultrafilter 207 and the # 1 high-pressure pump 204, and an inlet and an outlet of a concentrated water of the forward osmosis device 2057 are respectively connected with the # 2 high-pressure pump 2056 and the high-concentrated water tank 208.
In one embodiment, the reverse osmosis unit 2051 further comprises a product water outlet for discharging product water, which may be used as recycled water station makeup water or desalinated water station makeup water.
In one embodiment, referring to fig. 4, the pretreatment apparatus 1 comprises a chemical reaction tank 101, a tubular microfiltration membrane 102, an ion exchange resin 103, a decarbonization column 104 and an ozone oxidation apparatus 105, which are connected in sequence;
the chemical reaction tank 101 is used for carrying out chemical reaction on the salt-containing wastewater to obtain calcium and magnesium ion reaction precipitates;
the tubular microfiltration membrane 102 is used for filtering suspended matters and calcium and magnesium ion reaction precipitates in the salt-containing wastewater after reaction to obtain the salt-containing wastewater with the calcium and magnesium ion content smaller than a fourth preset threshold;
the ion exchange resin 103 is used for removing the residual calcium and magnesium hardness in the saline wastewater with the calcium and magnesium ion content smaller than a fourth preset threshold;
the decarbonizing tower 104 is used for removing carbonate ions and bicarbonate ions in the salt-containing wastewater;
the ozone oxidation device 105 is used for enabling COD (chemical oxygen demand) in the salt-containing wastewater to be smaller than a first preset threshold value, so that the pretreated salt-containing wastewater is obtained.
In a specific embodiment, sodium hydroxide, sodium carbonate, polyaluminum chloride PAC, polyacrylamide PAM, and other agents may be added to the chemical reaction tank 101 to perform a chemical reaction with the salt-containing wastewater.
In a specific embodiment, the fourth preset threshold value for characterizing the calcium and magnesium ion threshold value of the saline wastewater filtered by the tubular microfiltration membrane 102 may be set according to actual requirements, for example, the magnitude of the fourth preset threshold value may be between 5mg/L and 15mg/L, such as 10 mg/L.
In a specific embodiment, sulfuric acid or hydrochloric acid may be added to the decarbonizing tower 104 in advance to make the pH of the salt-containing wastewater acidic, so as to remove carbonate ions and bicarbonate ions from the salt-containing wastewater.
In one embodiment, referring to FIG. 1, the cooling crystallization device 3 is coupled to the thermal crystallization device 4; the thermal crystallization device 4 is also used for heating the mirabilite more than or equal to 99 percent and recrystallizing anhydrous sodium sulphate more than or equal to 99.5 percent.
In one embodiment, the cooling crystallization device 3 is further configured to make the TDS content in the cooling mother liquor generated in the mirabilite crystallization process smaller than a fifth preset threshold, and introduce the cooling mother liquor with the TDS content smaller than the fifth preset threshold into the pretreatment device 1.
In the embodiment of the invention, the TDS content in the saline wastewater to be treated is generally more than or equal to 30000 mg/L. Therefore, the setting of the fifth preset threshold value can be set by referring to the TDS content in the saline wastewater to be treated, and a specific numerical range can be selected according to actual needs, which is not specifically limited herein.
In one embodiment, as shown with reference to fig. 2, the cooling crystallization device 3 comprises: a precooler 301, a cooling crystallizer 302, a circulating pump 303, a cooler 304, a refrigerator 305, a salt outlet pump 306, a hydrocyclone 307, a centrifuge 308, a cold mother liquor tank 309, a cold mother liquor pump 310 and a dissolving tank 311;
the feed pump 209 is respectively connected with the high-concentration water tank 208 and the precooler 301;
the inlet of the circulating pump 303 is respectively connected with the precooler 301 and the cooling crystallizer 302, and the outlet of the circulating pump 303 is connected with the cooling crystallizer 302 through the cooler 304;
the inlet and the outlet of the freezer 305 are respectively connected to the cooler 304 for controlling the temperature in the cooling crystallizer 302 within the first preset temperature threshold range;
the salt outlet pump 306 is respectively connected with the cooling crystallizer 302 and the liquid cyclone 307;
the cyclone 307 is connected to the cooling crystallizer 302 and the centrifuge 308 respectively;
the centrifuge 308 is respectively connected with the dissolving tank 311 and the cold mother liquor tank 309;
the inlet of the cold mother liquor pump 310 is connected to the cold mother liquor tank 309, and the outlet of the cold mother liquor pump 310 is connected to the pretreatment apparatus 1 via the precooler 301.
As a specific implementation manner of the embodiment of the present invention, the cooling crystallization device 3 may be connected in a manner that an inlet of the feed pump 209 is connected to the high-concentration water tank 208, and an outlet of the feed pump 209 is connected to the precooler 301; the inlet of the circulating pump 303 is respectively connected with the precooler 301 and the cooling crystallizer 302, and the outlet of the feeding pump 301 is connected with the cooling crystallizer 302 through the cooler 304; the inlet and the outlet of the refrigerator 305 are respectively connected with the cooler 304 to control the temperature in the cooling crystallizer 302 to be 0-5 ℃; the inlet of the salt outlet pump 306 is connected with the cooling crystallizer 302, and the outlet of the salt outlet pump 306 is connected with the inlet of the hydrocyclone 307; a clear liquid outlet of the cyclone 307 is connected with the cooling crystallizer 302, and a slurry outlet of the cyclone 307 is connected with the centrifuge 308; the outlet of the centrifuge 308 is connected with the dissolving tank 311, and the cold mother liquor outlet of the centrifuge 308 is connected with the cold mother liquor tank 309; the inlet of the cold mother liquor pump 310 is connected to the cold mother liquor tank 309, and the outlet of the cold mother liquor pump 310 is connected to the pretreatment apparatus 1 via the precooler 301.
In the embodiment of the present invention, the coolant used for cooling the crystallization device 3 may be a coolant in the prior art, such as a glycol solvent, and the specific choice of the coolant is not limited herein.
In one particular embodiment, the thermal crystallization device 4 comprises a three-effect forced circulation crystallizer or a Mechanical Vapor Recompression (MVR) forced circulation crystallizer.
In the embodiment of the invention, if the salt-containing wastewater is high-salt-containing wastewater such as desulfurization wastewater mainly containing sodium sulfate, the thermal crystallization device 4 is connected with the dissolving tank 311 of the cooling crystallization device 3, and the mirabilite which is crystallized by the cooling crystallization device 3 and is greater than or equal to 99% is heated and dissolved, and the anhydrous sodium sulphate which is greater than or equal to 99.5% is recrystallized; if the salt-containing wastewater is high-salt-containing wastewater mainly containing sodium chloride, the thermal crystallization device 4 is directly connected with the outlet of the feed pump 209 of the forward and reverse osmosis coupling device 2, and the concentrated water obtained by the forward and reverse osmosis coupling device 2 is heated without passing through the cooling crystallization device 3, so that sodium chloride with the concentration of more than or equal to 98.5% is crystallized.
The saline wastewater treatment process of the forward and reverse osmosis coupled crystallization system provided by the embodiment of the present invention is described in detail by two specific examples, example 1 and example 2, below:
example 1
The salt-containing wastewater described in the embodiment of the present invention is catalytic cracking flue gas desulfurization wastewater, wherein table 1 is an example of a water quality table of the catalytic cracking flue gas desulfurization wastewater.
pH | Ca2+ | Mg2+ | Na+ | Cl- | SO4 2- |
8.52 | 33.2mg/L | 13.8mg/L | 23090mg/L | 186mg/L | 47000mg/L |
HCO3 - | CO3 2- | TDS | CODcr | SS | |
929mg/L | 26.5mg/L | 77000mg/L | 182mg/L | 70mg/L |
TABLE 1
The catalytic cracking desulfurization wastewater firstly enters a chemical reaction tank 101 of a pretreatment device 1, and reactants such as sodium hydroxide, PAC, PAM and the like which are added in advance in the chemical reaction tank 101 react with calcium, magnesium, carbonate, bicarbonate and the like in the catalytic cracking desulfurization wastewater to generate reaction precipitates such as calcium carbonate, magnesium hydroxide and the like;
filtering the precipitated reaction precipitate by a tubular microfiltration membrane 102, and then, allowing the filtered salt-containing wastewater to enter an ion exchange resin 103 to remove the residual calcium and magnesium hardness;
then, the desulfurization wastewater without calcium and magnesium ions enters a decarbonizing tower 104, the pH of the salt-containing wastewater is adjusted to be acidic through dilute sulfuric acid which is added in advance in the decarbonizing tower 104, carbonate ions are converted into carbon dioxide, and after the carbon dioxide is removed, sodium hydroxide is added in the decarbonizing tower 104 to adjust the pH of the salt-containing wastewater to be neutral;
and finally, the salt-containing wastewater with the neutral pH value is fed into an ozone oxidation device 105, sodium sulfite in the desulfurization wastewater is thoroughly oxidized to obtain pretreated salt-containing wastewater, and the pretreated salt-containing wastewater is the desulfurization wastewater.
The pretreated desulfurization wastewater enters a water inlet tank 201 of a forward and reverse osmosis coupling device, enters a 1# precision filter 203 after being pressurized by a 1# booster pump 202, adopts a 5 micron filter element for the 1# precision filter 203 to remove impurities which influence the stable operation of the forward and reverse osmosis device 205, such as residues, suspended matters and the like in the desulfurization wastewater, the desulfurization wastewater after being subjected to impurity removal enters a reverse osmosis device 2051 of the forward reverse osmosis device 205 after being pressurized again by a 1# high-pressure pump 204 for preconcentration, and then directly enters a forward osmosis device 2057 (because the concentration of organic COD in the desulfurization wastewater is very low), the auxiliary pressure concentration is continuously carried out to obtain concentrated water with the total dissolved solid TDS content being more than a third preset threshold value, and the concentrated water enters a high-concentration water tank 208, the produced water in the process is discharged out of the forward and reverse osmosis coupling device 2, wherein the produced water can be used as the water replenishing of a circulating water station or the water replenishing of a desalted water station.
The other pretreated desulfurization wastewater is subjected to pressure boosting by the 2# booster pump 206 and then enters the 2# precision filter 207, the 2# precision filter 207 adopts a 5-micrometer filter element to remove impurities which influence the stable operation of the forward and reverse osmosis device 205, such as residues, suspended matters and the like in the desulfurization wastewater, the desulfurization wastewater after impurity removal enters the suction liquid inlet side of the forward osmosis device 2057 and is diluted by the desulfurization wastewater on the other side, the diluted desulfurization wastewater returns to the 1# high-pressure pump 204 and is mixed with the original desulfurization wastewater, and then enters the 1# high-pressure pump 204 again for pressure boosting, and then enters the reverse osmosis device 2051 of the forward and reverse osmosis device 205 to be continuously pre-concentrated.
In the whole forward and reverse osmosis device 205, in the process of high-multiple concentration of the desulfurization wastewater, the drawing liquid and high-energy consumption drawing liquid recovery device of the traditional forward osmosis membrane are omitted, the drawing liquid recovery and supplement are not needed, and the operating cost and the engineering investment are greatly reduced.
The obtained concentrated water (i.e. high-concentration desulfurization wastewater) with the total dissolved solid TDS content larger than a third preset threshold enters a precooler 301 through a feed pump 209, exchanges cold with the cold mother liquor of the shell pass, enters a circulating pump 303, is mixed with the circulating high-concentration desulfurization wastewater in a cooling crystallizer 302, and then enters the circulating pump 303. The circulating high-concentration desulfurization wastewater passes through a tube pass of the cooler 304, is cooled by coolant such as ethylene glycol and the like in a shell pass, enters the cooling crystallizer 302 for cooling crystallization, and an inlet and an outlet of the refrigerator 305 are respectively connected with the cooler 304 so as to control the temperature in the cooling crystallizer 302 to be 0-5 ℃.
When the temperature of the high-concentration desulfurization wastewater is reduced to 0-5 ℃, sodium sulfate in the high-concentration desulfurization wastewater is saturated and separated out in a sodium sulfate decahydrate form, the sodium sulfate decahydrate concentration is higher and higher in the circulation process between the cooler 304 and the cooling crystallizer 302 through the circulating pump 303, when the sodium sulfate decahydrate concentration reaches a certain concentration, the sodium sulfate decahydrate enters the hydrocyclone 307 through the salt outlet pump 306, suspension is separated, clear liquid returns to the cooling crystallizer 302 for continuous cooling and crystallization, slurry enters the centrifuge 308, 99% of mirabilite is centrifuged and can be sold as a product or enter the dissolving tank 311, the mirabilite is redissolved into a high-purity sodium sulfate saturated solution and then enters the thermal crystallization device 4, and anhydrous sodium sulphate which is more than or equal to 99.5% is crystallized through the three-effect forced circulation crystallizer or the MVR forced circulation crystallizer. The cold mother liquor centrifuged by the centrifuge 308 enters a cold mother liquor tank 309, enters the shell pass of the precooler 301 through a cold mother liquor pump 310, exchanges cold with the high-concentration desulfurization wastewater in the tube pass, returns to the pretreatment device 1, and is mixed with the saline wastewater to remove impurities.
In the embodiment of the present invention, the process for treating other concentrated nanofiltration concentrated water mainly containing sodium sulfate or wastewater containing sodium sulfate and other salt-containing wastewater is similar to the process flow in the above embodiment 1, and those skilled in the art can refer to the description in the above embodiment 1 to implement the process, and details in the embodiment of the present invention are not repeated herein.
Example 2
The salt-containing wastewater described in the embodiment of the present invention is salt-containing wastewater mainly containing sodium chloride, wherein table 2 is an example of a water quality table of salt-containing wastewater mainly containing sodium chloride.
pH | Ca2+ | Mg2+ | Na+ | Cl- | SO4 2- |
7.75 | 68.4mg/L | 94.1mg/L | 15331mg/L | 21400mg/L | 320mg/L |
HCO3 - | CO3 2- | TDS | CODcr | SS | |
768mg/L | Not detected out | 41000mg/L | 188mg/L | 16mg/L |
TABLE 2
Firstly, salt-containing wastewater mainly containing sodium chloride enters a chemical reaction tank 101 of a pretreatment 1 device, and reagents such as sodium hydroxide, PAC (polyaluminium chloride), PAM (polyacrylamide) and the like which are added in advance in the chemical reaction tank 101 react with calcium, magnesium, bicarbonate radical plasma in the salt-containing wastewater mainly containing sodium chloride to generate reaction precipitates such as calcium carbonate and magnesium hydroxide;
filtering the precipitated reaction precipitate by a tubular microfiltration membrane 102, and then, allowing the filtered salt-containing wastewater mainly containing sodium chloride to enter an ion exchange resin 103 to remove the residual calcium and magnesium hardness;
then, the salt-containing wastewater from which the calcium and magnesium ions are removed enters a decarbonizing tower 104, the pH is adjusted to be acidic by adding hydrochloric acid into the decarbonizing tower 104 in advance, carbonate ions are converted into carbon dioxide, the carbon dioxide is removed by the decarbonizing tower 104, and after the carbon dioxide is removed, sodium hydroxide is added into the decarbonizing tower 104 to adjust the pH of the salt-containing wastewater to be neutral;
and finally, the salt-containing wastewater with the neutral pH value enters an ozone oxidation device 105, and COD in the salt-containing wastewater is reduced to be less than a first preset threshold value, so that the pretreated salt-containing wastewater is obtained.
The pretreated saline wastewater enters a water inlet tank 201 of a forward and reverse osmosis coupling device, enters a 1# precision filter 203 after being pressurized by a 1# booster pump 202, the 1# precision filter 203 adopts a 5 micron filter element to remove impurities such as residues and suspended matters in the saline wastewater and affecting the stable operation of the forward and reverse osmosis device 205, the saline wastewater after being subjected to impurity removal is subjected to secondary pressurization by a 1# high-pressure pump 204, enters a reverse osmosis device 2051 of the forward and reverse osmosis device 205 for preconcentration, passes through a 1# ozone catalytic reactor 2052 and a 2# ozone catalytic reactor 2053, enters a concentrated water tank 2054 after the COD after concentration is reduced to be less than a second preset threshold value, enters a forward osmosis 2057 after being pressurized by a booster pump 2055 and a 2# high-pressure pump 2056, and continues to pressurize and concentrate the concentrated water with the total dissolved solid TDS content being more than a third preset threshold value, so that the concentrated water enters a high-concentration water tank 208, and the produced water in the process is discharged from the forward and reverse osmosis coupling device 2, wherein, the produced water can be used as the water replenishing of a circulating water station or the water replenishing of a desalted water station.
The other pretreated saline wastewater enters the 2# precision filter 207 after being boosted by the 2# booster pump 206, the 2# precision filter 207 adopts a 5-micrometer filter element, impurities which affect the stable operation of the forward and reverse osmosis device 205, such as residues and suspended matters in the saline wastewater, are removed, the saline wastewater after the impurities are removed enters the suction liquid inlet side of the forward osmosis device 2057 and is diluted by the saline wastewater on the other side, the diluted saline wastewater returns to the inlet of the 1# high-pressure pump 204 and is mixed with the original saline wastewater, and then the saline wastewater enters the 1# high-pressure pump 5 again for boosting, and then enters the reverse osmosis device 2051 of the forward and reverse osmosis device 205 to be continuously pre-concentrated.
In the whole forward and reverse osmosis device 205, in the process of carrying out high-fold concentration on the pretreated saline wastewater, the absorption liquid and high-energy consumption absorption liquid recovery device of the traditional forward osmosis membrane are eliminated, the absorption liquid recovery and supplement are not needed, and the operating cost and the engineering investment are greatly reduced.
The obtained concentrated water (namely the high-concentration saline wastewater) with the total dissolved solid TDS content larger than a third preset threshold value enters a thermal crystallization device 4 through a feed pump 209, and sodium chloride with the concentration larger than or equal to 98.5% is crystallized through a triple-effect forced circulation crystallizer or an MVR forced circulation crystallizer.
In the embodiment of the present invention, the process for treating other concentrated nanofiltration fresh water mainly containing sodium chloride or wastewater containing sodium chloride and other salt-containing wastewater is similar to the process flow in the above embodiment 2, and a person skilled in the art can refer to the description in the above embodiment 1 to implement the process, which is not described herein again in the embodiment of the present invention.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solutions of the present disclosure, not to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present disclosure.
Claims (10)
1. A forward and reverse osmosis coupled crystallization system, comprising:
the device comprises a pretreatment device (1), a forward and reverse osmosis coupling device (2), a cooling crystallization device (3) and a thermal crystallization device (4);
the forward and reverse osmosis coupling device (2) is respectively connected with the pretreatment device (1), the cooling crystallization device (3) and the thermal crystallization device (4);
the pretreatment device (1) is used for removing calcium and magnesium ions in the salt-containing wastewater and enabling the chemical oxygen demand in the pretreated salt-containing wastewater to be smaller than a first preset threshold value;
the forward and reverse osmosis coupling device (2) is used for pre-concentrating the pretreated saline wastewater through reverse osmosis, reducing the Chemical Oxygen Demand (COD) of the pre-concentrated saline wastewater to be less than a second preset threshold value, and continuously concentrating the pre-concentrated saline wastewater through forward osmosis to obtain concentrated water with the total dissolved solid TDS content being greater than a third preset threshold value;
the cooling crystallization device (3) is used for cooling the concentrated water with the TDS content larger than a third preset threshold value to a first preset temperature threshold value range, and crystallizing mirabilite with the TDS content larger than or equal to 99%;
and the thermal crystallization device (4) is used for heating the concentrated water with the TDS content larger than a third preset threshold value to crystallize sodium chloride with the concentration of more than or equal to 98.5%.
2. The system according to claim 1, wherein the apparatus (2) comprises: a water inlet tank (201), a 1# booster pump (202), a 1# precision filter (203), a 1# high-pressure pump (204), a forward and reverse osmosis device (205), a 2# booster pump (206), a 2# precision filter (207), a high-concentration water tank (208) and a feed pump (209);
the 1# booster pump (202) is respectively connected with the water inlet tank (201) and the 1# precision filter (203);
the # 1 high-pressure pump (204) is connected with the # 1 precision filter (203);
the 2# booster pump (206) is connected with the water inlet tank (201) and the 2# precision filter (207) respectively;
the forward and reverse osmosis device (205) is respectively connected with the 1# high-pressure pump (204), the 2# precision filter (207) and the high-concentration water tank (208);
the high-concentration water tank (208) is connected with the feeding pump (209).
3. The system of claim 2, wherein the forward and reverse osmosis unit (205) comprises: a reverse osmosis unit (2051) and a forward osmosis unit (2057);
the inlet of the reverse osmosis device (2051) is connected with the outlet of the No. 1 high-pressure pump (204), and the outlet of the reverse osmosis device (2051) is connected with the concentrated water inlet of the forward osmosis device (2057);
an inlet and an outlet of a drawing liquid of the forward osmosis device (2057) are respectively connected with the 2# precision filter (207) and the 1# high-pressure pump (204), and a concentrated water outlet of the forward osmosis device (2057) is connected with the high-concentration water tank (208).
4. The forward-reverse osmosis coupled crystallization system according to claim 3, wherein the forward-reverse osmosis device (205) further comprises: a 1# ozone catalytic reactor (2052), a 2# ozone catalytic reactor (2053), a concentrated water tank (2054), a booster pump (2055) and a 2# high-pressure pump (2056);
the outlet of the reverse osmosis device (2051) is connected with the concentrated water tank (2054) through the No. 1 ozone catalytic reactor (2052) and the No. 2 ozone catalytic reactor (2053);
the booster pump (2055) is respectively connected with the concentrated water tank (2054) and the # 2 high-pressure pump (2056);
the concentrated water inlet of the forward osmosis device (2057) is connected with the # 2 high-pressure pump (2056).
5. The reverse osmosis coupled crystallization system of any one of claims 1-4,
and the forward and reverse osmosis coupling device (2) is also used for taking the pretreated saline wastewater as a drawing liquid, discharging fresh water obtained in the process of pre-concentrating the pretreated saline wastewater as produced water through reverse osmosis, continuously concentrating the concentrated water through forward osmosis, and finally obtaining the concentrated water with the total dissolved solid TDS content being greater than a third preset threshold value.
6. The forward and reverse osmosis coupled crystallization system according to any one of claims 1-4, wherein the pretreatment device (1) comprises a chemical reaction tank (101), a tubular microfiltration membrane (102), an ion exchange resin (103), a decarbonization tower (104) and an ozone oxidation device (105) which are connected in sequence;
the chemical reaction tank (101) is used for carrying out chemical reaction on the salt-containing wastewater to obtain calcium and magnesium ion reaction precipitates;
the tubular microfiltration membrane (102) is used for filtering suspended matters and calcium and magnesium ion reaction precipitates in the salt-containing wastewater after reaction to obtain the salt-containing wastewater with the calcium and magnesium ion content smaller than a fourth preset threshold;
the ion exchange resin (103) is used for removing the residual calcium and magnesium hardness in the saline wastewater with the calcium and magnesium ion content smaller than a fourth preset threshold value;
the decarbonization tower (104) is used for removing carbonate and bicarbonate ions in the salt-containing wastewater;
and the ozone oxidation device (105) is used for enabling COD (chemical oxygen demand) in the salt-containing wastewater to be smaller than a first preset threshold value to obtain the pretreated salt-containing wastewater.
7. The forward-reverse osmosis coupled crystallization system according to any one of claims 1 to 3, wherein the cooling crystallization device (3) and the hot crystallization device (4) are connected;
the thermal crystallization device (4) is also used for heating and dissolving the mirabilite more than or equal to 99 percent and recrystallizing anhydrous sodium sulphate more than or equal to 99.5 percent.
8. The forward-reverse osmosis coupled crystallization system according to claim 7, wherein the cooling crystallization device (3) is further configured to make the TDS content in the cooling mother liquor generated in the mirabilite crystallization process smaller than a fifth preset threshold, and to introduce the cooling mother liquor with the TDS content smaller than the fifth preset threshold into the pretreatment device (1).
9. The forward-reverse osmosis coupled crystallization system according to claim 8, wherein the cooling crystallization device (3) comprises: the system comprises a precooler (301), a cooling crystallizer (302), a circulating pump (303), a cooler (304), a refrigerator (305), a salt pump (306), a cyclone (307), a centrifuge (308), a cold mother liquor tank (309), a cold mother liquor pump (310) and a dissolving tank (311);
the inlet of the circulating pump (303) is respectively connected with the precooler (301) and the cooling crystallizer (302), and the outlet of the circulating pump (303) is connected with the cooling crystallizer (302) through the cooler (304);
the inlet and the outlet of the refrigerator (305) are respectively connected with the cooler (304) and used for controlling the temperature in the cooling crystallizer (302) within the first preset temperature threshold range;
the salt outlet pump (306) is respectively connected with the cooling crystallizer (302) and the cyclone (307);
the cyclone (307) is respectively connected with the cooling crystallizer (302) and the centrifuge (308);
the centrifuge (308) is respectively connected with the dissolving tank (311) and the cold mother liquor tank (309);
the inlet of the cold mother liquor pump (310) is connected with the cold mother liquor tank (309), and the outlet of the cold mother liquor pump (310) is connected with the pretreatment device (1) through the precooler (301).
10. The system of claim 9, wherein the coolant of the cooler (304) is ethylene glycol.
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