CN111875139A - Comprehensive desalting and pure water recovery method and system for multi-element heavy metal salt-containing wastewater - Google Patents
Comprehensive desalting and pure water recovery method and system for multi-element heavy metal salt-containing wastewater Download PDFInfo
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Abstract
The invention belongs to the technical field of industrial wastewater recovery, and provides a comprehensive desalting and pure water recovery method and system for multi-element heavy metal salt-containing wastewater. No pollutant is discharged in the whole process flow, zero discharge of wastewater is realized, and the environmental pressure and the economic cost for treating the composite heavy metal salt-containing wastewater are reduced. The operation flow can be continuous operation or intermittent operation.
Description
Technical Field
The invention belongs to the technical field of industrial wastewater recovery, and relates to a comprehensive desalting and pure water recovery method and system for multi-element heavy metal salt-containing wastewater, in particular to a comprehensive separating, desalting and recovering method and system for multi-element heavy metal salt-containing wastewater generated in the mining and mineral processing production processes.
Background
In mining and mineral processing production processes, calcination, acid washing, etc. are often used to extract target components from minerals. Due to the complexity of the components of the minerals, the byproduct wastewater contains various inorganic salts and heavy metal ions which are difficult to treat, and the wastewater is directly discharged, so that the environmental pollution is great, and the waste of water resources is also great. In order to effectively save the production cost and meet the national requirements on green and environmental protection, it becomes more important to effectively treat the multi-element heavy metal salt-containing wastewater and recover high-value salt in the multi-element heavy metal salt-containing wastewater.
At present, the following treatment methods are mainly used for treating heavy metal wastewater in the metallurgical industry: physical treatment, chemical precipitation and electrochemical treatment. The physical treatment method generally refers to mixing porous materials such as activated carbon and molecular sieves with wastewater to make pollutants in the wastewater attach to the surfaces of microporous materials to achieve the purpose of water purification, for example, patent CN102974305A, which is often suitable for macromolecular organic materials or floccules, but cannot effectively remove inorganic salts with small molecular weight. The chemical precipitation method adopts a method of adding a precipitator into the wastewater, heavy metal ions are removed from the wastewater in a precipitation form through chemical reaction, for example, patent CN103332810A, heavy metal salts are enriched in a filter cake after filtration, and the filtrate is recycled to an acid washing section or directly distilled. The salt in the filtrate in a saturated or nearly saturated state is easy to scale in the pipeline through which the filtrate flows; meanwhile, the filter cake produced in the process is high in treatment cost, so that the process is poor in efficiency and economy. The electrochemical treatment method is to introduce the sewage into an electrochemical reactor and initiate electrode reaction by an additional electrode, thereby achieving the purpose of degrading and separating pollutants. For example, in patent CN110357338A, the electrochemical method has high treatment efficiency, simple process flow and large treatment capacity, but the application of this method is limited by the high operation cost and fixed cost.
In recent years, with the stricter environmental protection requirements of China on the heavy pollution industries such as mining, mineral processing and the like, the economic and environmental pressures of enterprises and society caused by adopting the traditional means to treat heavy metal wastewater are more and more severe. Some enterprises began to adopt comprehensive wastewater regeneration techniques: the heavy metal wastewater is primarily filtered and then sent into a Reverse Osmosis (RO) device, so that pure water and high-concentration brine meeting the recycling standard can be obtained, and salt in the concentrated brine can be further recovered through processes such as crystallization or distillation. However, because the concentration polarization near the surface of the RO membrane is severe, the concentration of the concentrate produced by RO cannot be too high in order to avoid membrane fouling caused by fouling, and further treatment of the concentrate by direct distillation results in extremely high energy consumption. In summary, excessive operating condition requirements and energy consumption have limited the development of this technology.
With the further development of membrane technology, membrane distillation technology has been gradually developed as a water treatment technology different from the principles of membrane processes such as reverse osmosis, ultrafiltration, nanofiltration and the like. The method is characterized in that the driving force is changed from osmotic pressure difference of the traditional membrane process to vapor pressure difference driving, and the separation effect does not depend on the molecular size but depends on the volatility of the solute of the raw material liquid. This provides the membrane distillation process with the advantages of lower operating costs and higher concentration of the solution that can be processed. At present, the patent reports that membrane distillation technology is used for treating heavy metal or salt-containing wastewater, such as CN102260006A, CN109942129A and CN110627284A, and the technology successfully recovers pure water from heavy metal waste liquid in a membrane distillation mode, but the energy consumption cannot be sufficiently reduced only by the membrane distillation technology, and the high-value salt recycling cannot be realized.
Therefore, in order to break through the key bottleneck of the existing heavy metal salt-containing wastewater treatment technology and the existing membrane distillation technology, the patent provides a membrane regulation and control salt separation-membrane distillation-cooling crystallization coupling method and system capable of effectively treating common heavy metal wastewater in a mineral processing process, relatively pure recycled water and inorganic salt crystals with specific high value can be obtained while heavy metal waste liquid is concentrated and recovered, the heavy metal wastewater treatment, water production and salt production are synchronously completed, zero discharge of industrial wastewater is realized, and the treatment efficiency and the comprehensive utilization value of the heavy metal salt-containing wastewater are improved.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a comprehensive separation, desalination and recovery method and system for multi-heavy metal salt-containing wastewater, which are used for treating the multi-heavy metal wastewater in the metallurgical industry and realizing the resource utilization of water and high-value salt.
The technical scheme of the invention is as follows:
a comprehensive desalination and pure water recovery system for multi-element heavy metal salt-containing wastewater comprises a first centrifugal pump 1, a second centrifugal pump 5, a third centrifugal pump 8, a fourth centrifugal pump 10, a fifth centrifugal pump 16, a sixth centrifugal pump 25, a first valve 2, a second valve 4, a third valve 11, a fourth valve 19, a microfiltration and ultrafiltration integrated membrane forming assembly 3, a nanofiltration membrane assembly 12, a first membrane distillation assembly 14, a second membrane distillation assembly 23, a raw material liquid storage tank 6, a neutralization tank 7, a penetrating fluid storage tank 21, a security filter 9, a first heat exchanger 13, a second heat exchanger 20, a condenser 22, a vacuum pump 18, a first crystallizer 15, a second crystallizer 17, a third crystallizer 24 and a fourth crystallizer 26; the first centrifugal pump 1, the first valve 2 and the microfiltration and ultrafiltration integrated membrane component 3 are sequentially connected, and incoming heavy metal wastewater is introduced from the first centrifugal pump 1; the concentrated water output end of the microfiltration and ultrafiltration integrated film forming component 3 is connected with a sedimentation tank, the fresh water output end of the microfiltration and ultrafiltration integrated film forming component 3 is connected with a raw material liquid storage tank 6, the input end of the raw material liquid storage tank 6 is connected with a pipeline for introducing dilute acid, the first output end of the raw material liquid storage tank 6 is sequentially connected with a second centrifugal pump 5, a second valve 4 and the microfiltration and ultrafiltration integrated film forming component 3, the second output end of the raw material liquid storage tank 6 is sequentially connected with a security filter 9, a fourth centrifugal pump 10, a third valve 11 and a nanofiltration film component 12, the fresh water output end of the nanofiltration film component 12 is sequentially connected with a first heat exchanger 13 and a first film distillation component 14, the concentrated water output end of the nanofiltration film component 12 is sequentially connected with a second heat exchanger 20 and a second film distillation component 23, the permeation side output end of the first film distillation component 14 and the permeation side output end of the second film, A permeate storage tank 21, a fourth valve 19 and a vacuum pump 18; the concentrated water output end of the first membrane distillation assembly 14 is sequentially connected with a first crystallizer 15, a fifth centrifugal pump 16 and a second crystallizer 17; the concentrated water output end of the second membrane distillation assembly 23 is sequentially connected with a third crystallizer 24, a sixth centrifugal pump 25 and a fourth crystallizer 26; the output end of the second crystallizer 17 and the output end of the fourth crystallizer 26 are combined and then sequentially connected with the third centrifugal pump 8 and the neutralization tank 7, the input end of the neutralization tank 7 is connected with a pipeline which can be introduced with strong alkali, and the output end of the neutralization tank 7 is connected with the raw material liquid storage tank 6.
The microfiltration and ultrafiltration integrated membrane component 3 comprises a microfiltration membrane component and an ultrafiltration membrane component which are connected in sequence.
The fresh water output end of the microfiltration and ultrafiltration integrated membrane component 3 and the valve and the pump are connected between the raw material liquid storage tanks 6, the raw material liquid storage tanks 6 and the valve are connected between the security filter 9, the valve is arranged on the dilute acid feed pipeline of the raw material liquid storage tanks 6, the first membrane distillation component 14 and the valve is connected between the first crystallizers 15, the second membrane distillation component 23 and the valve is connected between the third crystallizers 24, the fifth centrifugal pump 16 and the valve is connected between the second crystallizers 17, the valve is connected between the sixth centrifugal pump 25 and the fourth crystallizers 26, the neutralization tank 7 and the pump and the valve are connected between the raw material liquid storage tanks 6, and the valve is arranged on the strong base feed pipeline of the neutralization tank 7.
The concentrated water output end of the nanofiltration membrane component 12 and the first heat exchanger 13 can be sequentially connected with a first membrane distillation concentrated water temporary storage tank, a centrifugal pump and a valve, the fresh water output end of the nanofiltration membrane component 12 and the second heat exchanger 20 can be sequentially connected with the membrane distillation concentrated water temporary storage tank, the centrifugal pump and the valve, the concentrated water output end of the first membrane distillation component 14 can be sequentially connected with the valve and the first membrane distillation concentrated water temporary storage tank, and the concentrated water output end of the second membrane distillation component 23 can be sequentially connected with the valve and the second membrane distillation concentrated water temporary storage tank.
A comprehensive desalting and pure water recovery method for multi-element heavy metal salt-containing wastewater comprises the following steps:
1, opening a first valve 2, boosting the pressure of heavy metal wastewater by a first centrifugal pump 1 for the first time, and conveying the heavy metal wastewater to a microfiltration and ultrafiltration integrated membrane component 3 for primary filtration; microorganisms, macromolecular organic matters and floccules in the wastewater are blocked by the microfiltration membrane and the ultrafiltration membrane and then sent to a sedimentation tank for sedimentation treatment, and micromolecular inorganic salts, metal ions and protons can reach a raw material liquid storage tank 6 through the microfiltration and ultrafiltration membrane-forming component 3; meanwhile, as the operation is carried out, when the membrane flux of the microfiltration and ultrafiltration integrated membrane component 3 is obviously reduced, the second centrifugal pump 5 and the second valve 4 are opened, and the solution stored in the raw material solution storage tank 6 is used for backwashing the filter membrane; due to the requirement of the ultrafiltration membrane on the pH value of the solution, an acid adding pipeline needs to be reserved for the raw material liquid to prepare acid;
2, in order to prevent the particles which are not intercepted from entering a subsequent membrane module, the raw material liquid needs to pass through a security filter 9 before entering the membrane module; the filtered liquid enters a nanofiltration membrane component 12 for salt separation after being boosted by a fourth centrifugal pump 10, wherein the permeation side is a salt solution rich in lower-valence metal cations, and the retentate side is a salt solution rich in higher-valence metal cations; then the two solutions are respectively subjected to heat exchange and then enter corresponding membrane assemblies for further concentration;
3, preheating the two solutions subjected to nanofiltration salt separation by a first heat exchanger 13 and a second heat exchanger 20 respectively, and then feeding the two solutions into a first membrane distillation component 14 and a second membrane distillation component 23 respectively for membrane distillation operation; when the temperature in the first membrane distillation assembly 14 and the second membrane distillation assembly 23 reaches a set value, opening the vacuum pump 18 and the fourth valve 19 to maintain the permeation sides of the first membrane distillation assembly 14 and the second membrane distillation assembly 23 in a vacuum state; the vapor generated by membrane distillation is condensed by a condenser 22 and then stored in a penetrating fluid storage tank 21;
when the concentration of the solution in the first membrane distillation assembly 14 and the second membrane distillation assembly 23 reaches near saturation or supersaturation, the solution is gradually introduced into the first crystallizer 15, the second crystallizer 17, the third crystallizer 24 and the fourth crystallizer 26, and crystals with different solubilities are gradually crystallized and separated in the secondary cooling crystallizer set to the target temperature;
5 because the acidity of the system can not be reduced in the process under certain systems, the crystallized barren solution needs to be conveyed back to the neutralization tank 7 by a third centrifugal pump 8 for the whole material balance, and is returned to the raw material solution storage tank 6 for recycling treatment after proper acidity adjustment.
The raw material liquid storage tank 6 and the neutralization tank 7 are both provided with temperature and pH measuring instruments, the addition amount of acid and alkali is accurately controlled, and the pH value in the raw material liquid storage tank 6 is kept at 1-3.
The feed sides of the microfiltration and ultrafiltration integrated membrane component 3, the nanofiltration membrane component 12 and the membrane distillation component are provided with conductivity meters for detecting concentration;
the microfiltration membrane component in the microfiltration and ultrafiltration integrated membrane component 3 adopts a hydrophilic polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a nylon membrane, a cellulose membrane, an ether sulfone membrane and other materials prepared by modifying hydrophilic polytetrafluoroethylene, polyvinylidene fluoride, nylon, cellulose or ether sulfone, and the pore diameter of the membrane surface is 0.1-1 mu m; the operating pressure of the microfiltration membrane component is 0.1-0.3 MPa;
the ultrafiltration membrane component in the microfiltration and ultrafiltration integrated membrane component 3 adopts a polyvinylidene fluoride membrane, a polycarbonate membrane, a polyacrylonitrile membrane, a polysulfonamide membrane and other materials prepared by modifying polyvinylidene fluoride, polycarbonate, polyacrylonitrile or polysulfonamide, and the average pore diameter of the membrane surface is 0.08-0.12 mu m; the operating pressure of the ultrafiltration membrane component is 0.1-0.3 MPa;
the nanofiltration membrane component 12 is made of an acetate fiber membrane, a polyamide membrane or a ceramic membrane and other materials prepared by modifying acetate fiber, polyamide or ceramic, and the pore diameter of the membrane surface is 1-2 nm; the operating pressure of the nanofiltration membrane component 12 is 0.2-1 Mpa;
the first membrane distillation component 14 and the second membrane distillation component 23 are made of hydrophobic polytetrafluoroethylene membranes, hydrophobic polyvinylidene fluoride membranes, polypropylene membranes and other materials prepared by modifying polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene, wherein the materials used for the membrane distillation components must simultaneously ensure that the membrane distillation components have hydrophobicity, the average pore diameter of the membrane surface is 0.1-0.12 mu m, the vacuum degree of the permeation side is 0.03-0.095 Mpa, and the porosity is 30-85%.
Conveying to-be-treated raw materials of the system by adopting centrifugal pumps, controlling the flow rate to be 0.2-3 m/s and controlling the temperature of the to-be-treated raw materials to be 20-60 ℃;
temperature adjusting devices are arranged in the crystallizers of the system, and the temperature is controlled to be 5-80 ℃ according to needs;
the system mainly comprises a microfiltration ultrafiltration, nanofiltration and membrane distillation three-stage membrane process and a cooling crystallization process;
the membrane distillation process adopts a vacuum membrane distillation process;
the vacuum degree value of the vacuum membrane distillation permeation side of the system is 0.01-0.09 MPa, and the outlet temperature of the condenser 22 is 5-15 ℃;
if necessary, adding crystal seeds of the target product into the crystallization kettle, wherein the mass of the added crystal seeds is 3-5% of that of the mother liquor;
the kind of the composite metal cation in the raw material to be treated is Na+、Ca2+、Mg2+、Cu2+、Zn2+、Fe2+、Ni2+、Ba2 +、K+、Li+；
In the crystallization process, the temperature difference between the solution inlet and the solution outlet of the first crystallizer 15, the second crystallizer 17, the third crystallizer 24 or the fourth crystallizer 26 is 5-50 ℃.
The microfiltration and ultrafiltration integrated membrane component 3, the nanofiltration membrane component 12, the first membrane distillation component 14 and the second membrane distillation component 23 adopt a multi-section parallel connection mode according to the treatment requirement;
when the feeding pH value of the nanofiltration membrane component 12 is less than 3, the rejection rate of the nanofiltration membrane component 12 on divalent ions is 90%, and the rejection rate of the nanofiltration membrane component on monovalent ions is 20%; in the first membrane distillation assembly 14 and the second membrane distillation assembly 23, the concentration multiple of the fed material is 3-15 times according to the concentration of the raw material until the concentrated solution reaches a saturated state.
The invention has the beneficial effects that:
(1) the concentration range of the treated raw materials is wide, and the concentration degree is high;
(2) the operation cost is low, and energy is saved;
(3) crystals can be selectively recovered, and resources can be maximally regenerated;
(4) the recovery rate of pure water is high, and the discharge capacity is greatly reduced;
(5) the membrane assembly has high integration level, small volume, convenient operation and easy cleaning of the microporous membrane.
Drawings
FIG. 1 is a schematic diagram of integrated membrane separation system coupled with multistage cooling crystallization for treating heavy metal salt-containing wastewater
In the figure: 1 a first centrifugal pump; 2, a first valve, 3, a microfiltration and ultrafiltration integrated membrane component; 4a second valve;
5a second centrifugal pump; 6, a raw material liquid storage tank; 7, a neutralization tank; 8a third centrifugal pump;
9a cartridge filter; 10a fourth centrifugal pump; 11 a third valve; 12 a nanofiltration membrane module;
13 a first heat exchanger; 14 a first membrane distillation assembly; 15 a first crystallizer; 16 a fifth centrifugal pump;
17 a second crystallizer; 18 a vacuum pump; 19 a fourth valve; 20 a second heat exchanger;
21 a permeate storage tank; 22 a condenser; 23 a second membrane distillation assembly; 24 a third crystallizer;
25 a sixth centrifugal pump; 26 a fourth crystallizer.
Detailed Description
The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.
Example 1
The method of the invention is adopted to treat the potassium (K) with the concentration of 33.5g/L+) 23.95g/L Nickel (Ni)2+) 20.71g/L calcium (Ca)2+) And 99.49g/L chlorine (Cl)-) The acid waste liquid contains a small amount of microorganisms and organic matters, and the flow speed of conveying the raw materials is 2 m/s.
The method comprises the following specific steps: (1) opening a first centrifugal pump and a first valve to enable the raw material liquid to enter a microfiltration and ultrafiltration membrane component so as to remove contained microorganisms and macromolecular organic matters; (2) the raw material liquid after the impurities are removed is stored in a raw material liquid storage tank, and when the liquid level of the storage tank meets the requirement, a fourth centrifugal pump and a third valve are opened to convey the raw material liquid to a nanofiltration membrane component for salt separation; (3) in the nanofiltration membrane component, the raw material liquid is divided into two streams, and the salt concentrations are respectively as follows: 26.8g/L K+、2.39g/L Ni2+、2.07g/L Ca2 +、32.56g/L Cl-And 21.56g/L Ni2+、18.64g/L Ca2+、6.7g/L K+、66.88g/L Cl-. The two solutions reach 80 ℃ after being subjected to heat exchange by the first heat exchanger and the second heat exchanger respectively, and then enter the first membrane distillation assembly and the second membrane distillation assembly respectively for concentration. (4) Opening a fourth valve, a vacuum pump and a condenser, maintaining the membrane module to permeate and measure the vacuum degree to be 0.085-0.095MPa, and keeping the outlet temperature of the condenser to be 5 ℃; because hydrochloric acid is volatile, the liquid collected in the permeate storage tank is a dilute hydrochloric acid solution with high purity. The feed liquid reaches a nearly saturated state after being concentrated by about ten times, and then is sent into a crystallization kettle for cooling and crystallization. (5) Cooling the solution to 10 deg.C in the first and second crystallization vessels to produce a plurality of crystals, and filtering to remove 40% of K in the feed solution+Recovering in the form of potassium chloride crystal, returning the residual liquid to a neutralization tank to adjust pH, and returning the residual liquid to a raw material liquid storage tank for circular treatment; cooling the solution to 30 ℃ in a third crystallization kettle, and recovering 21 percent of Ni in the solution in the form of nickel chloride hexahydrate crystals2+The temperature is reduced to 10 ℃ in a fourth crystallization kettle, and 10.7 percent of Ni is recovered in the form of mixed salt of nickel chloride hexahydrate and calcium chloride hexahydrate2+And 36.3% of Ca2+The residual liquid is returned to the neutralization tank to adjust the pH value and then returned to the raw material liquid storage tank for circular treatment
Example 2
The method of the invention is adopted to treat the potassium (K) with the concentration of 12.03g/L+) 16.52g/L sodium (Na)+) 15.56g/L copper (Cu)2+) 17.69g/L Zinc (Zn)2+) And 148.89g/L Sulfate (SO)4 2-) The waste liquid contains a small amount of microorganisms and organic mattersThe flow rate of the raw material was 2 m/s.
The method comprises the following specific steps: (1) opening a first centrifugal pump and a first valve to enable the raw material liquid to enter a microfiltration and ultrafiltration membrane component so as to remove contained microorganisms and macromolecular organic matters; (2) the raw material liquid after the impurities are removed is stored in a raw material liquid storage tank, and when the liquid level of the storage tank meets the requirement, a fourth centrifugal pump and a third valve are opened to convey the raw material liquid to a nanofiltration membrane component for salt separation; (3) in the nanofiltration membrane component, the raw material liquid is divided into two streams, and the salt concentrations are respectively as follows: 9.61g/L K+、13.22g/L Na+、1.56g/L Cu2 +、1.77g/L Zn2+And 2.40g/L K+、3.30g/L Na+、14.01g/L Cu2+、15.93g/L Zn2+. The two solutions reach 80 ℃ after being subjected to heat exchange by the first heat exchanger and the second heat exchanger respectively, and then enter the first membrane distillation assembly and the second membrane distillation assembly respectively for concentration. (4) Opening the fourth valve, the vacuum pump and the condenser, maintaining the membrane module at a penetration vacuum degree of 0.085-0.095MPa and a condenser outlet temperature of 5 ℃, condensing the generated steam and collecting the condensed steam in the storage tank. The feed liquid reaches a nearly saturated state after being concentrated by about ten times, and then is sent into a crystallization kettle for cooling and crystallization. (5) In the first crystallization vessel, the solution was cooled to 30 ℃ to produce a large amount of crystals, and after filtration 39.2% of the K in the feed solution was obtained+Recovering in the form of potassium sulfate crystals, cooling the solution to 10 deg.C in a second crystallization kettle, and adding 72.5% Na in the feed solution+And 18.2% of K+Recovering in the form of mixed salt of sodium sulfate and potassium sulfate, returning the residual liquid to a neutralization tank to adjust pH, and returning the residual liquid to a raw material liquid storage tank for circular treatment; cooling the solution to 40 deg.C in a third crystallizing kettle, and recovering 48.2% Cu in the solution as copper sulfate pentahydrate crystal2+The temperature is reduced to 20 ℃ in a fourth crystallization kettle, and 22.3 percent of Zn is recovered in the form of mixed salt of zinc sulfate heptahydrate and copper sulfate pentahydrate2+And 14.7% of Cu2+The residual liquid is returned to the neutralization tank to adjust the pH value and then returned to the raw material liquid storage tank for circular treatment
Example 3
The method of the invention is adopted to treat the potassium (K) with the concentration of 12.01g/L+) 19.06g/L sodium (Na)+) 4.76g/L magnesium (Mg)2+) 23.96g/L Nickel (Ni)2+) 55.642g/L sulfate radical (SO)4 2-) And 42.83g/L of chlorine (Cl)-) The acid waste liquid contains a small amount of microorganisms and organic matters, and the flow speed of conveying the raw materials is 2 m/s. The method comprises the following specific steps: (1) opening a first centrifugal pump and a first valve to enable the raw material liquid to enter a microfiltration and ultrafiltration membrane component so as to remove contained microorganisms and macromolecular organic matters; (2) the raw material liquid after the impurities are removed is stored in a raw material liquid storage tank, and when the liquid level of the storage tank meets the requirement, a fourth centrifugal pump and a third valve are opened to convey the raw material liquid to a nanofiltration membrane component for salt separation; (3) in the nanofiltration membrane component, the raw material liquid is divided into two streams, and the salt concentrations are respectively as follows: 9.61g/L K+、15.68g/L Na+、0.48g/L Mg2+、2.40g/L Ni2+、44.51g/L SO4 2-、4.28g/LCl-And 2.4g/L K+、3.92g/L Na+、4.29g/L Mg2+、21.56g/L Ni2+、11.13g/L SO4 2-、38.54g/LCl-. The two solutions reach 80 ℃ after being subjected to heat exchange by the first heat exchanger and the second heat exchanger respectively, and then enter the first membrane distillation assembly and the second membrane distillation assembly respectively for concentration. (4) And opening a fourth valve, a vacuum pump and a condenser, maintaining the penetration vacuum degree of the membrane assembly to be 0.085-0.095MPa, and the outlet temperature of the condenser to be 5 ℃, wherein the hydrochloric acid is volatile, so that the liquid collected in the penetrating fluid storage tank is a high-purity dilute hydrochloric acid solution. The feed liquid reaches a nearly saturated state after being concentrated by about ten times, and then is sent into a crystallization kettle for cooling and crystallization. (5) In the first crystallization kettle, the solution is cooled to 50 ℃, and 22.4 percent of K in the feeding liquid can be obtained after filtration+Recovering as potassium sulfate crystals, cooling the solution to 20 deg.C in a second crystallization kettle, and adding 76.8% Na to the feed solution+And 17.2% of K+Recovering in the form of mixed salt of sodium sulfate and potassium sulfate, returning the residual liquid to a neutralization tank to adjust pH, and returning the residual liquid to a raw material liquid storage tank for circular treatment; cooling the solution to 30 ℃ in a third crystallization kettle, and recovering 21.1 percent of Ni in the solution in the form of nickel chloride hexahydrate crystals2+The temperature was reduced to 100 ℃ in a fourth crystallization vessel and 2.5% of Mg was recovered as a mixed salt of magnesium chloride hexahydrate and nickel chloride hexahydrate2+And 10.7% of Ni2+The residual liquid is returned to the neutralization tank to adjust the pH value and then returned to the raw material liquid storage tank for circular treatment
The processing method and system disclosed and proposed by the present invention have been described in terms of preferred embodiments, and those skilled in the art can implement the processing steps with appropriate modifications according to the contents of the present disclosure. It is expressly intended that all such modifications are included within the spirit, scope and content of the present invention.
Claims (10)
1. The utility model provides a comprehensive desalination and pure water recovery system of many first heavy metals salt waste water, characterized in that, this comprehensive desalination and pure water recovery system of many first heavy metals salt waste water includes first centrifugal pump (1), second centrifugal pump (5), third centrifugal pump (8), fourth centrifugal pump (10), fifth centrifugal pump (16), sixth centrifugal pump (25), first valve (2), second valve (4), third valve (11), fourth valve (19), integrated membrane module of microfiltration and ultrafiltration (3), receive filter membrane module (12), first membrane distillation subassembly (14), second membrane distillation subassembly (23), raw materials liquid storage tank (6), neutralization tank (7), penetrant storage tank (21), safety filter (9), first heat exchanger (13), second heat exchanger (20), condenser (22), vacuum pump (18), first crystallizer (15), A second crystallizer (17), a third crystallizer (24) and a fourth crystallizer (26); the first centrifugal pump (1), the first valve (2) and the microfiltration and ultrafiltration integrated membrane component (3) are sequentially connected, and incoming heavy metal wastewater is introduced from the first centrifugal pump (1); the concentrated water output end of the microfiltration and ultrafiltration integrated membrane component (3) is connected with a sedimentation tank, the fresh water output end of the microfiltration and ultrafiltration integrated membrane component (3) is connected with a raw material liquid storage tank (6), the input end of the raw material liquid storage tank (6) is connected with a pipeline for introducing dilute acid, the first output end of the raw material liquid storage tank (6) is sequentially connected with a second centrifugal pump (5), a second valve (4) and the microfiltration and ultrafiltration integrated membrane component (3), the second output end of the raw material liquid storage tank (6) is sequentially connected with a security filter (9), a fourth centrifugal pump (10), a third valve (11) and a nanofiltration membrane component (12), the fresh water output end of the nanofiltration membrane component (12) is sequentially connected with a first heat exchanger (13) and a first membrane distillation component (14), and the concentrated water output end of the nanofiltration membrane component (12) is sequentially connected with a second heat exchanger (20, the output end of the permeation side of the first membrane distillation assembly (14) and the output end of the permeation side of the second membrane distillation assembly (23) are combined and then sequentially connected with a condenser (22), a penetrating fluid storage tank (21), a fourth valve (19) and a vacuum pump (18); the concentrated water output end of the first membrane distillation assembly (14) is sequentially connected with a first crystallizer (15), a fifth centrifugal pump (16) and a second crystallizer (17); the concentrated water output end of the second membrane distillation assembly (23) is sequentially connected with a third crystallizer (24), a sixth centrifugal pump (25) and a fourth crystallizer (26); the output end of the second crystallizer (17) and the output end of the fourth crystallizer (26) are combined and then sequentially connected with a third centrifugal pump (8) and a neutralization tank (7), the input end of the neutralization tank (7) is connected with a pipeline which can be filled with strong base, and the output end of the neutralization tank (7) is connected with a raw material liquid storage tank (6).
2. The comprehensive desalination and pure water recovery system for multi-element heavy metal salt-containing wastewater as claimed in claim 1, wherein the microfiltration and ultrafiltration integrated membrane module (3) comprises a microfiltration membrane module and an ultrafiltration membrane module which are connected in sequence.
3. The comprehensive desalination and pure water recovery system for multi-element heavy metal salt-containing wastewater as claimed in claim 1 or 2, wherein a valve and a pump are connected between the fresh water output end of the microfiltration and ultrafiltration integrated membrane module (3) and the raw material liquid storage tank (6), a valve is connected between the raw material liquid storage tank (6) and the security filter (9), a valve is arranged on the dilute acid feed pipeline of the raw material liquid storage tank (6), a valve is connected between the first membrane distillation module (14) and the first crystallizer (15), a valve is connected between the second membrane distillation module (23) and the third crystallizer (24), a valve is connected between the fifth centrifugal pump (16) and the second crystallizer (17), a valve is connected between the sixth centrifugal pump (25) and the fourth crystallizer (26), and a pump and a valve are connected between the neutralization tank (7) and the raw material liquid storage tank (6), and a valve is arranged on a strong alkali feeding pipeline of the neutralization tank (7).
4. The comprehensive desalination and pure water recovery system for multi-element heavy metal salt-containing wastewater as claimed in claim 1 or 2, wherein a first membrane distillation concentrated water temporary storage tank, a centrifugal pump and a valve can be sequentially connected between the concentrated water output end of the nanofiltration membrane component (12) and the first heat exchanger (13), a membrane distillation concentrated water temporary storage tank, a centrifugal pump and a valve can be sequentially connected between the fresh water output end of the nanofiltration membrane component (12) and the second heat exchanger (20), a valve and a first membrane distillation concentrated water temporary storage tank can be sequentially connected between the concentrated water output end of the first membrane distillation component (14), and a valve and a second membrane distillation concentrated water temporary storage tank can be sequentially connected between the concentrated water output end of the second membrane distillation component (23).
5. The comprehensive desalination and pure water recovery system for multi-element heavy metal salt-containing wastewater as claimed in claim 3, wherein a first membrane distillation concentrated water temporary storage tank, a centrifugal pump and a valve can be sequentially connected between the concentrated water output end of the nanofiltration membrane component (12) and the first heat exchanger (13), a membrane distillation concentrated water temporary storage tank, a centrifugal pump and a valve can be sequentially connected between the fresh water output end of the nanofiltration membrane component (12) and the second heat exchanger (20), a valve and a first membrane distillation concentrated water temporary storage tank can be sequentially connected between the concentrated water output end of the first membrane distillation component (14), and a valve and a second membrane distillation concentrated water temporary storage tank can be sequentially connected between the concentrated water output end of the second membrane distillation component (23).
6. A comprehensive desalting and pure water recovery method for multi-element heavy metal salt-containing wastewater is characterized by comprising the following steps:
(1) firstly, opening a first valve (2), and carrying out primary pressure boosting on heavy metal wastewater by a first centrifugal pump (1) and conveying the heavy metal wastewater to a microfiltration and ultrafiltration integrated membrane component (3) for primary filtration; microorganisms, macromolecular organic matters and floccules in the wastewater are blocked by the microfiltration membrane and the ultrafiltration membrane and then sent to a sedimentation tank for sedimentation treatment, and micromolecular inorganic salts, metal ions and protons can reach a raw material liquid storage tank (6) through the microfiltration and ultrafiltration integrated membrane component (3); meanwhile, along with the operation, when the membrane flux of the microfiltration and ultrafiltration integrated membrane component (3) is obviously reduced, a second centrifugal pump (5) and a second valve (4) are opened, and the solution stored in a raw material solution storage tank (6) is used for backwashing the filter membrane; due to the requirement of the ultrafiltration membrane on the pH value of the solution, an acid adding pipeline needs to be reserved for the raw material liquid to prepare acid;
(2) in order to prevent the particles which are not intercepted from entering a subsequent membrane module, the raw material liquid needs to pass through a security filter (9) before entering the membrane module; the filtered liquid is pressurized by a fourth centrifugal pump (10) and then enters a nanofiltration membrane component (12) for salt separation, wherein the permeation side is a salt solution rich in lower-valence metal cations, and the retentate side is a salt solution rich in higher-valence metal cations; then the two solutions are respectively subjected to heat exchange and then enter corresponding membrane assemblies for further concentration;
(3) the two solutions after the salt separation by nanofiltration are respectively preheated by a first heat exchanger (13) and a second heat exchanger (20) and then respectively sent into a first membrane distillation component (14) and a second membrane distillation component (23) for membrane distillation operation; when the temperature in the first membrane distillation assembly (14) and the second membrane distillation assembly (23) reaches a set value, opening a vacuum pump (18) and a fourth valve (19) to maintain the permeation sides of the first membrane distillation assembly (14) and the second membrane distillation assembly (23) in a vacuum state; the vapor generated by membrane distillation is condensed by a condenser (22) and then stored in a penetrating fluid storage tank (21);
(4) when the concentration of the solution in the first membrane distillation assembly (14) and the second membrane distillation assembly (23) reaches near saturation or supersaturation, the solution is gradually introduced into a first crystallizer (15), a second crystallizer (17), a third crystallizer (24) and a fourth crystallizer (26), and crystals with different solubilities are gradually crystallized and separated in a secondary cooling crystallizer set to a target temperature;
(5) because the acidity of the system cannot be reduced in the process under certain systems, the crystallized barren solution needs to be conveyed back to the neutralization tank (7) by a third centrifugal pump (8) for integral material balance, and is returned to the raw material solution storage tank (6) for recycling treatment after proper acidity adjustment.
7. The comprehensive desalination and pure water recovery method according to claim 6, wherein the raw material liquid storage tank (6) and the neutralization tank (7) are both provided with temperature and pH measuring instruments, the addition amount of acid and alkali is accurately controlled, and the pH value in the raw material liquid storage tank (6) is kept between 1 and 3.
8. The integrated desalination and pure water recovery method according to claim 6 or 7,
the feed sides of the microfiltration and ultrafiltration integrated membrane component (3), the nanofiltration membrane component (12) and the membrane distillation component are provided with conductivity meters for detecting concentration;
the microfiltration membrane component in the microfiltration and ultrafiltration integrated membrane component (3) adopts a hydrophilic polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a nylon membrane, a cellulose membrane, an ether sulfone membrane and other materials prepared by modifying hydrophilic polytetrafluoroethylene, polyvinylidene fluoride, nylon, cellulose or ether sulfone, and the pore diameter of the membrane surface is 0.1-1 mu m; the operating pressure of the microfiltration membrane component is 0.1-0.3 MPa;
the ultrafiltration membrane component in the microfiltration and ultrafiltration integrated membrane component (3) adopts a polyvinylidene fluoride membrane, a polycarbonate membrane, a polyacrylonitrile membrane, a polysulfonamide membrane and other materials prepared by modifying polyvinylidene fluoride, polycarbonate, polyacrylonitrile or polysulfonamide, and the average pore diameter of the membrane surface is 0.08-0.12 mu m; the operating pressure of the ultrafiltration membrane component is 0.1-0.3 MPa;
the nanofiltration membrane component (12) is made of an acetate fiber membrane, a polyamide membrane or a ceramic membrane and other materials prepared by modifying acetate fiber, polyamide or ceramic, and the pore diameter of the membrane surface is 1-2 nm; the operating pressure of the nanofiltration membrane component (12) is 0.2-1 Mpa;
the first membrane distillation assembly (14) and the second membrane distillation assembly (23) are made of hydrophobic polytetrafluoroethylene membranes, hydrophobic polyvinylidene fluoride membranes, polypropylene membranes and other materials prepared by modifying polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene, wherein the materials used for the membrane distillation assemblies must simultaneously ensure that the membranes have hydrophobicity, the average pore diameter of the membrane surface is 0.1-0.12 mu m, the vacuum degree of a permeation side is 0.03-0.095 Mpa, and the porosity is 30-85%.
9. The integrated desalination and pure water recovery method according to claim 8,
conveying to-be-treated raw materials of the system by adopting centrifugal pumps, controlling the flow rate to be 0.2-3 m/s and controlling the temperature of the to-be-treated raw materials to be 20-60 ℃;
temperature adjusting devices are arranged in the crystallizers of the system, and the temperature is controlled to be 5-80 ℃ according to needs;
the system mainly comprises a microfiltration ultrafiltration, nanofiltration and membrane distillation three-stage membrane process and a cooling crystallization process;
the membrane distillation process adopts a vacuum membrane distillation process;
the vacuum degree value of the vacuum membrane distillation permeation side of the system is 0.01-0.09 MPa, and the outlet temperature of the condenser (22) is 5-15 ℃;
if necessary, adding crystal seeds of the target product into the crystallization kettle, wherein the mass of the added crystal seeds is 3-5% of that of the mother liquor;
the kind of the composite metal cation in the raw material to be treated is Na+、Ca2+、Mg2+、Cu2+、Zn2+、Fe2+、Ni2+、Ba2+、K+、Li+；
In the crystallization process, the temperature difference between the solution inlet and the solution outlet of the first crystallizer (15), the second crystallizer (17), the third crystallizer (24) or the fourth crystallizer (26) is 5-50 ℃.
10. The integrated desalination and pure water recovery method according to claim 9,
the microfiltration and ultrafiltration integrated membrane component (3), the nanofiltration membrane component (12), the first membrane distillation component (14) and the second membrane distillation component (23) adopt a multi-section parallel connection mode according to the treatment requirement;
when the pH value of the feed material of the nanofiltration membrane component (12) is less than 3, the rejection rate of the nanofiltration membrane component on bivalent ions is 90 percent, and the rejection rate of the nanofiltration membrane component on univalent ions is 20 percent; in the first membrane distillation assembly (14) and the second membrane distillation assembly (23), the concentration multiple of the fed materials is 3-15 times according to the concentration of the raw materials until the concentrated solution reaches a saturated state.
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