CN117486325A - A method for treating high-salt and high-hard water - Google Patents

Abstract

The invention belongs to the technical field of water treatment, and specifically relates to a method for treating high-salt and high-hard water. In the present invention, Na-type concentrated brine and Cl-type concentrated brine obtained by electrodialysis salt separation treatment are concentrated to a concentration of 18% salt through an ED ion membrane concentration process, and then subsequent MVR evaporation is performed to produce salt, thereby reducing the amount of evaporated water and energy. consumption and cost savings, and the final ED concentrated brine is evaporated by MVR to produce salt, achieving zero discharge of high-salt and high-hard water and reducing the environmental harm of wastewater and waste salt.

Description

A method for treating high-salt and high-hard water

Technical field

The invention belongs to the technical field of water treatment, and specifically relates to a method for treating high-salt and high-hard water.

Background technique

A large amount of high-salt and high-hard waste liquid is generated during the production process in thermal power, petrochemical, steel, desalination and other fields. This huge amount of concentrated drainage directly leads to significant waste of water resources and economic losses. Zero-discharge desalination of salt water is a key technology. At present, the method of adding chemicals (such as hydrated lime and sodium carbonate) is often used to remove hardness (desalination). A ton of water consumes 7.7kg of hydrated lime, and a ton of water consumes 17kg of soda ash. Based on the calculation of slaked lime of 750 yuan/ton and soda ash of 3200 yuan/ton, the dehydration of water per ton The hard cost is about 60.2 yuan, which makes the cost of traditional dosing to precipitate hardness too high. In order to reduce costs, technicians use displacement dialysis (EDM) to desalt high-salt and high-hard wastewater, and the resulting concentrated brine is evaporated through MVR to produce salt. However, in this method, the concentrated brine is evaporated directly, which requires a large amount of evaporated water and high energy consumption.

Contents of the invention

In view of this, the object of the present invention is to provide a method for treating high-salt and high-hard water. The method provided by the present invention is to pass electrodialysis ( After ED) ion membrane concentration treatment, MVR evaporation is performed to produce salt, which can reduce the amount of evaporated water and reduce costs.

In order to achieve the above objects, the present invention provides the following technical solutions:

The invention provides a method for treating high-salt and high-hard water, which includes the following steps:

Provide effluent produced by electrodialysis and salt removal treatment of high-salt and high-hard water. The effluent is Na-type concentrated brine, Cl-type concentrated brine and EDM effluent;

The Na-type concentrated brine and Cl-type concentrated brine are respectively subjected to ED ion membrane concentration treatment to obtain ED concentrated brine and ED effluent respectively;

Conduct MVR evaporation of the ED concentrated brine to produce salt;

The EDM effluent and ED effluent are subjected to reverse osmosis membrane treatment to obtain product water.

Preferably, the TDS in the high-salt and high-hard water is 36000-44000 mg/L, SO ₄ ^2- is 720-880 mg/L, Ca ²⁺ is 810-990 mg/L, Mg ²⁺ is 900-1100 mg/L, and Na ⁺ is 9000-12000mg/L, Cl- is 23000-25000mg/L; the pH value of the high-salt and high-hard water is 6.0-7.8.

Preferably, the electrodialysis salt removal treatment is carried out with EDM electrodialysis equipment; the EDM electrodialysis equipment includes 40 anode and yang compartments formed by alternating cathode membranes and anode membranes, one located at the end of the anode and yang compartments and composed of anode membranes. anode and anode compartments and electrolyte formed by the anode membrane; every 4 anode and anode compartments among the 40 anode and yang compartments form a processing unit, with a total of 10 repeated processing units. Each processing unit consists of an anode membrane, a cathode membrane, an anode membrane, cathode membrane, and anode membrane are formed, and C1 compartment, D1 compartment, C2 compartment, and D2 compartment are formed in sequence. Two adjacent processing units share an anode membrane. Two membrane stacks in the EDM electrodialysis equipment Connect the positive and negative terminals respectively.

Preferably, the electrolyte is a sodium sulfate solution; the mass concentration of the sodium sulfate solution is 4.8-5.2%.

Preferably, the voltage of each pair of cathode membrane and anode membrane in the electrodialysis salt removal treatment is 0.8-1.2V, and the current density is 100-300A/m ² .

Preferably, the conditions for MVR evaporation and salt production include: the steam temperature in the evaporation chamber is 105-110°C and the absolute pressure is 143.3kPa; the steam temperature in the heating chamber is 125-130°C and the absolute pressure is 250-270.1kPa.

Preferably, the membrane used in the ED ion membrane concentration treatment is a homogeneous ion exchange membrane.

Preferably, the voltage of each pair of cathode membrane and anode membrane in the ED ion membrane concentration process is 0.8-1.2V.

Preferably, the desalination rate of the reverse osmosis membrane treatment is 99.2-99.8%; the treatment water volume of the reverse osmosis membrane treatment is ^58-63m3 /h.

The invention also provides a system for treating high-salt and high-hard water, including EDM electrodialysis equipment, first ED ion membrane concentration equipment, second ED ion membrane concentration equipment, first MVR evaporation salt production equipment, and second MVR evaporation salt production equipment. Salt equipment and reverse osmosis membrane equipment;

The Na-type concentrated brine and Cl-type concentrated brine outlets of the EDM electrodialysis equipment are respectively connected to the first ED ion membrane concentration equipment and the second ED ion membrane concentration equipment, and the EDM water outlet of the EDM electrodialysis equipment is connected to the reverse osmosis membrane equipment. ;

The ED concentrated brine outlet of the first ED ion membrane concentration equipment is connected to the first MVR evaporation salt making equipment;

The ED concentrated brine outlet of the second ED ion membrane concentration equipment is connected to the second MVR evaporative salt production equipment;

The ED water outlet of the ED ion membrane concentration equipment is connected to the reverse osmosis membrane equipment.

The invention provides a method for treating high-salt and high-hard water, which includes the following steps: providing the effluent of high-salt and high-hard water treated by electrodialysis for salt removal, and the effluents are Na-type concentrated brine, Cl-type concentrated brine and EDM effluent; The Na-type concentrated brine and the Cl-type concentrated brine are subjected to ED ion membrane concentration treatment to obtain ED concentrated brine and ED effluent respectively; the ED concentrated brine is subjected to MVR evaporation to produce salt; the EDM effluent and ED effluent are subjected to Reverse osmosis membrane treatment to obtain produced water. The present invention concentrates the Na-type concentrated brine and Cl-type concentrated brine from high-salt and high-hard water through the ED ion membrane concentration process to a concentration of 18% salt, and then performs subsequent MVR evaporation to produce salt, thereby reducing evaporation. water, reduce energy consumption, and save costs. The final ED concentrated brine is evaporated by MVR to produce salt, achieving zero discharge of high-salt and high-hard water and reducing the harm of wastewater and waste salt to the environment.

Description of drawings

Figure 1 is a schematic diagram of the principle of electrodialysis salt removal treatment;

Figure 2 is a flow chart of a method for treating high-salt and high-hardness nanofiltration concentrated water in Embodiment 1 of the present invention;

Figure 3 is a flow chart of a method for treating high-salt and high-hardness nanofiltration concentrated water in Comparative Example 1 of the present invention.

Detailed ways

The invention provides a method for treating high-salt and high-hard water, which includes the following steps:

Provide effluent produced by electrodialysis and salt removal treatment of high-salt and high-hard water. The effluent is Na-type concentrated brine, Cl-type concentrated brine and EDM effluent;

The Na-type concentrated brine and Cl-type concentrated brine are respectively subjected to ED ion membrane concentration treatment to obtain ED concentrated brine and ED effluent respectively;

Conduct MVR evaporation of the ED concentrated brine to produce salt;

The EDM effluent and ED effluent are subjected to reverse osmosis membrane treatment to obtain product water.

Unless otherwise specified, the present invention has no special requirements on the source of the raw materials used, and commercially available products well known to those skilled in the art can be used.

The invention provides effluent produced by electrodialysis and salt removal treatment of high-salt and high-hard water. The effluent is Na-type concentrated brine, Cl-type concentrated brine and EDM effluent respectively. In the present invention, the TDS in the high-salt and high-hard water is preferably 36000-44000 mg/L, more preferably 37000-40000 mg/L, and the SO ₄ ^2- is preferably 720-880 mg/L, more preferably 750-800 mg/L. , Ca ²⁺ is preferably 810 to 990 mg/L, more preferably 850 to 900 mg/L, Mg ²⁺ is preferably 900 to 1100 mg/L, more preferably 950 to 1000 mg/L, and Na ⁺ is preferably 9000 to 12000 mg/L. , more preferably 10000 mg/L, Cl- is preferably 23000-25000 mg/L, more preferably 23998-24500 mg/L; the pH value of the high-salt, high-hard water is preferably 6.0-7.8, more preferably 7.0-7.5.

In the present invention, the source of the high-salt and high-hard water is preferably nanofiltration concentrated water; the preparation method of the nanofiltration concentrated water is preferably: subjecting raw water to pretreatment and nanofiltration in sequence to obtain nanofiltration concentrated water and nanofiltration concentrated water, respectively. Strain the water. In the present invention, the TDS in the raw water is preferably 36000-44000 mg/L, more preferably 37000-40000 mg/L, SO ₄ ^2- is preferably 720-880 mg/L, more preferably 750-800 mg/L, Ca ^{2 +} is preferably 810 to 990 mg/L, more preferably 850 to 900 mg/L, Mg ²⁺ is preferably 900 to 1100 mg/L, more preferably 950 to 1000 mg/L, and Na ⁺ is preferably 9000 to 12000 mg/L, more preferably is 10000-11000mg/L, ^Cl- is preferably 23000-25000mg/L, more preferably 23500-23998mg/L; the pH value of the raw water is preferably 6.0-7.8, more preferably 7-7.5; the flow rate of the raw water Preferably it is ^3600-4400m3 /d, More preferably, it is ^3700-4000m3 /d.

In the present invention, the pretreatment is preferably carried out with a PVDF ultrafiltration membrane; the filtration area of a single membrane element of the PVDF ultrafiltration membrane is preferably 78m ² ; the treatment water volume of a single set of the PVDF ultrafiltration membrane is preferably 130m ³ /h; the number of PVDF ultrafiltration membranes is preferably 2 sets; 2 sets of PVDF ultrafiltration membranes are arranged in parallel; the turbidity of the water obtained from the pretreatment is preferably ≤0.5NTU. The present invention removes suspended solids in water through pretreatment and provides guaranteed water inlet conditions for subsequent membrane systems.

In the present invention, the nanofiltration membrane used in the nanofiltration is preferably an aromatic polyamide composite membrane; the molecular weight cutoff of the aromatic polyamide composite membrane is preferably 100,000; the single membrane area of the aromatic polyamide composite membrane is preferably 400ft ² ; the water production volume of a single set of the aromatic polyamide composite membrane is preferably 150m ³ /h; the number of the aromatic polyamide composite membrane is preferably 1 set; the recovery rate of the aromatic polyamide composite membrane is preferably 75% . The invention uses a nanofiltration device to separate high-priced ions in water, remove hardness, and solve the problem of excessive cost of traditional dosing to precipitate hardness.

After obtaining the nanofiltration effluent, the present invention preferably processes the nanofiltration effluent with the first reverse osmosis membrane to obtain the first reverse osmosis membrane produced water and the first reverse osmosis membrane concentrated water respectively.

In the present invention, the desalination rate of the first reverse osmosis membrane treatment is preferably 99.2 to 99.8%, more preferably 99.5 to 99.8%; the treatment water volume of the first reverse osmosis membrane treatment is preferably 58 to 63m ³ /h , more preferably 60 to 63m ³ /h; the membrane used for the first reverse osmosis membrane treatment is preferably a PVDF ultrafiltration membrane; the membrane flux of the membrane used for the first reverse osmosis membrane treatment is preferably 20 to 40L/m ² /h, more preferably 25-35L/ ^m2 /h; the water permeability of the membrane used for the first reverse osmosis membrane treatment is preferably 30-45%, more preferably 30-35%; the first reverse osmosis membrane The pH value of the treated incoming water is preferably 6.0 to 7.8, more preferably 7 to 7.5; the incoming water temperature treated by the first reverse osmosis membrane is preferably 10 to 30°C, more preferably 20 to 30°C; the first reverse osmosis membrane The operating pressure of reverse osmosis membrane treatment is preferably 8.0 to 10.0 MPa, more preferably 8.5 to 9.0 MPa.

In the present invention, the concentration of TDS in the produced water of the first reverse osmosis membrane is preferably 400-600 mg/L, more preferably 450-550 mg/L, and the pH value is preferably 6.0-7.8, more preferably 7.0-7.5. The fresh water produced by the first reverse osmosis membrane can be used for industrial water.

After obtaining the first reverse osmosis membrane concentrated water, the present invention preferably performs the first MVR evaporation on the first reverse osmosis membrane concentrated water to produce salt. In the present invention, the conditions for the first MVR evaporation salt production include: the steam temperature of the evaporation chamber is preferably 105-110°C, more preferably 110°C, and the absolute pressure is preferably 143.3kPa; the steam temperature of the heating chamber is preferably 125 ~130°C, more preferably 130°C, and the absolute pressure is preferably 250-270.1kPa, more preferably 260-270.1kPa.

In the present invention, the electrodialysis salt separation treatment is preferably carried out using EDM electrodialysis equipment; the EDM electrodialysis equipment preferably includes 40 anode and yang compartments formed by alternating cathode membranes and anode membranes, and one at the end of the anode and yang compartments. And the anode and anode compartments and electrolytes formed by the anode membrane and the anode membrane; every 4 anode and yang compartments among the 40 anode and yang compartments form a processing unit, with a total of 10 repeated processing units. Each processing unit is composed of an anode membrane, A cathode film, an anode film, a cathode film, and an anode film are formed, and C1 compartment, D1 compartment, C2 compartment, and D2 compartment are formed in sequence. Two adjacent processing units share an anode membrane. The EDM electrodialysis equipment The two ends of the middle membrane stack are connected to the positive and negative electrodes respectively; the high-salt and high-hard water is sent to the EDM electrodialysis equipment from the D1 compartment; the Na-type concentrated brine flows out of the C1 compartment and enters the ED ion membrane for concentration treatment; the Cl-type concentrated brine is The salt water effluent from the C2 compartment enters the ED ion membrane for concentration treatment; the EDM effluent enters the reverse osmosis membrane from the D1 compartment for treatment; the present invention preferably adds a replacement liquid in the electrodialysis salt removal treatment; the replacement liquid is preferably from D2 The addition is performed in the compartment; the replacement liquid is preferably a sodium chloride solution; the mass concentration of the sodium chloride solution is preferably 4.8 to 5.2%, more preferably 5%; the added amount of the sodium chloride solution is preferably 0.2 to 0.25 times of the high salt and high hard water, more preferably 0.2 times.

In the present invention, the negative electrode is preferably made of stainless steel; the positive electrode is preferably made of alloy; the electrolyte is preferably sodium sulfate solution; the mass concentration of the sodium sulfate solution is preferably 4.8 to 5.2%, more preferably 5 %; the voltage of each pair of cathode membrane and anode membrane in the electrodialysis salt removal treatment is preferably 0.8~1.2V, more preferably 0.9~1.0V; the current density of the electrodialysis salt removal treatment is preferably 100~300A/ m ² is more preferably 200 to 300 A/m ² .

In the present invention, the principle of EDM electrodialysis salt removal treatment is shown in Figure 1. As can be seen from Figure 1, high-salt and high-hard water is used as the raw material liquid. This water has the characteristics of high calcium, magnesium and high sulfate. NaCl solution is used as the replacement liquid, and a four-compartment electrodialysis ion recombination reactor is used to ionize the high-salt and high-hard water. Split and recombine, split the sulfate, calcium ion, and magnesium ion system into two materials: one is sodium sulfate liquid (i.e., Na-type concentrated brine), and the other is magnesium chloride, calcium chloride liquid (i.e., Cl type concentrated brine), in which the D1 compartment is the raw material liquid, the D2 compartment is the sodium chloride solution, the C1 compartment is the split sulfuric acid salt solution (i.e. Na type concentrated brine), and the C2 compartment is the split Calcium-magnesium salt solution (i.e. Cl-type concentrated salt water); the specific principle is: under the action of a DC electric field, the anion and cation sinks move to the electrodes in opposite directions respectively. Driven by the current, the anions then pass through the anion exchange membrane and the cations Through the cation exchange membrane, in the middle compartment of the two membranes, the concentration of salt will be reduced due to the directional migration of ions, and the two compartments close to the electrode are the concentration chambers for anions and cations, and finally in the middle The purpose of desalination is achieved in the desalination chamber. The present invention uses EDM electrodialysis equipment (electrodialysis ion recombination reactor) to perform ion separation and recombination of high-salt and high-hard water to obtain two high-solubility concentrated brine, Na-type concentrated brine and Cl-type concentrated brine. The problem of easy scaling of ions during the concentration process is solved, and high-rate concentration is achieved simultaneously.

After obtaining the Na-type concentrated brine and Cl-type concentrated brine, the present invention conducts ED ion membrane concentration treatment on the Na-type concentrated brine and Cl-type concentrated brine respectively to obtain ED concentrated brine and ED effluent respectively.

In the present invention, the membrane used in the ED ion membrane concentration treatment is preferably a homogeneous ion exchange membrane; the voltage of each pair of cathode membranes and anode membranes in the ED ion membrane concentration treatment is preferably 0.8 to 1.2V, more preferably 0.9 ~1.1V; the concentration of TDS in the ED concentrated brine is preferably 170000~185000mg/L, more preferably 175000~180000mg/L; the pH value of the ED concentrated brine is preferably 6.0~7.8, more preferably 7.0~7.5 .

Electrically driven membrane separation technology, represented by electrodialysis, can achieve desalination and salt concentration of various wastewaters. Because its working principle is completely different from that of the pressure membrane process, it only achieves the directional and selective migration of solutes such as charged ions under the joint action of electric field driving and the selective permeation mechanism of the ion membrane, regardless of the osmotic pressure of the solution. Therefore It can operate under normal pressure, and the concentration of concentrated salt solution it can obtain is much higher than that of the conventional pressure membrane process, and it is easy to be applied on a large scale. After the ED ion membrane concentration process is added, only displacement dialysis is needed to separate the high-salt and high-hard water into Na-type concentrated brine and Cl-type concentrated brine. There is no need to continue to concentrate (during the continued concentration process, water will pass through the displacement dialysis membrane with the migration of ions). , leading to an increase in the amount of subsequent distilled water and an increase in operating costs), the present invention concentrates the Na-type concentrated brine and Cl-type concentrated brine after desalting through the ED ion membrane concentration process until the concentration salt content is 18%, and then performs subsequent MVR Evaporate salt to reduce the amount of evaporated water, reduce energy consumption, and save costs.

After obtaining the ED concentrated brine, the present invention performs MVR evaporation on the ED concentrated brine to produce salt.

In the present invention, the conditions for MVR evaporation and salt production include: the steam temperature in the evaporation chamber is preferably 105-110°C, more preferably 110°C, the absolute pressure is preferably 143.3kPa, and the steam temperature in the heating chamber is preferably 125-130°C. ° C, more preferably 130 ° C, and the absolute pressure is preferably 250 to 270.1 kPa, more preferably 260 to 270.1 kPa.

The present invention uses MVR for evaporation and salt production, with low energy consumption, and the energy consumption per ton of water is less than 50 kilowatt hours of electricity.

After obtaining the EDM effluent and ED effluent, the present invention performs reverse osmosis membrane treatment on the EDM effluent and ED effluent to obtain product water and reverse osmosis membrane concentrated water respectively.

In the present invention, the desalination rate of the reverse osmosis membrane treatment is preferably 99.2-99.8%, more preferably 99.5-99.8%; the treatment water volume of the reverse osmosis membrane treatment is preferably ^58-63m3 /h, more preferably 60～63m ³ /h; the membrane used for reverse osmosis membrane treatment is preferably a PVDF ultrafiltration membrane; the membrane flux of the membrane used for reverse osmosis membrane treatment is preferably 20～40L/m ² /h, more preferably 25～ 35L/m ² /h; the water permeability of the membrane used in the reverse osmosis membrane treatment is preferably 30 to 45%, more preferably 35 to 40%; the inlet water pH value for the reverse osmosis membrane treatment is preferably 6.0 to 7.8. More preferably, it is 7.0-7.5; the inlet temperature of the reverse osmosis membrane treatment is preferably 10-30°C, more preferably 20-30°C; the operating pressure of the reverse osmosis membrane treatment is preferably 1.0-3.0MPa, more preferably is 1.6~2.8MPa.

In the present invention, the concentration of TDS in the reverse osmosis membrane concentrated water is preferably 14000-16000 mg/L, more preferably 14500-15000 mg/L; the pH value of the reverse osmosis membrane concentrated water is preferably 6.0-7.8, more preferably is 7.0 to 7.5; the reverse osmosis membrane concentrated water is preferably returned to nanofiltration for continued treatment; part of the produced water is preferably returned to the C1 compartment and C2 compartment of the EDM electrodialysis equipment for supplementary water, and part is used for industrial water.

In the present invention, the nanofiltration effluent and the first reverse osmosis concentrated water are mixed as the source of sodium chloride in the D2 compartment in the electrodialysis salt removal treatment to provide the required chloride ions. This method does not require the addition of sodium chloride. It saves costs and can be recycled.

The invention also provides a system for treating high-salt and high-hard water, including EDM electrodialysis equipment, first ED ion membrane concentration equipment, second ED ion membrane concentration equipment, first MVR evaporation salt production equipment, and second MVR evaporation salt production equipment. Salt equipment and reverse osmosis membrane equipment;

The Na-type concentrated brine and Cl-type concentrated brine outlets of the EDM electrodialysis equipment are respectively connected to the first ED ion membrane concentration equipment and the second ED ion membrane concentration equipment, and the EDM water outlet of the EDM electrodialysis equipment is connected to the reverse osmosis membrane equipment. ;

The ED concentrated brine outlet of the first ED ion membrane concentration equipment is connected to the first MVR evaporation salt production equipment;

The ED concentrated brine outlet of the second ED ion membrane concentration equipment is connected to the second MVR evaporative salt production equipment;

The ED water outlet of the ED ion membrane concentration equipment is connected to the reverse osmosis membrane equipment.

Figure 2 is a flow chart of a method for treating high-salt and high-hard water according to an embodiment of the present invention. As shown in Figure 2, the present invention performs nanofiltration on raw water after pretreatment, and the resulting concentrated water (i.e., high-salt and high-hard water) enters electrodialysis for salt removal treatment. The EDM electrodialysis equipment has 10 repeated processing units, each of which The processing unit is composed of four adjacent yin and yang compartments: C1 compartment, D1 compartment, C2 compartment, and D2 compartment. The nanofiltration concentrated water enters the EDM electrodialysis equipment from the D1 compartment, and consists of the C1 compartment and the C2 compartment. Na-type concentrated brine and Cl-type concentrated brine are produced respectively and enter the ED ion membrane for concentration treatment. The obtained ED concentrated water enters the MVR for evaporation to produce salt. The obtained ED effluent and EDM effluent enter the reverse osmosis membrane for treatment to obtain product water and reverse osmosis membrane concentrated water respectively. ; Part of the concentrated water from the reverse osmosis membrane is returned to the nanofiltration for continued processing, and part is returned to the C1 compartment and C2 compartment. Part of the nanofiltration effluent enters another set of reverse osmosis membranes for treatment to obtain product water and concentrated water, and part of the concentrated water enters the MVR for evaporation For salt production, part of the concentrated water and the other part of the nanofiltration effluent enter the D2 compartment as a source of sodium chloride. The method provided by the invention realizes zero discharge of high-salt and high-hard water, and reduces the harm of waste water and waste salt to the environment.

The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but they should not be understood as limiting the scope of the present invention.

Example 1

The raw water with a TDS content of 400000mg/L is pretreated by ultrafiltration to remove suspended solids in the water as a guarantee condition for the subsequent membrane system; the pretreatment system is 2 sets of PVDF ultrafiltration membranes, and the water treatment capacity of a single set is 130m ³ /h , Product water quality requirements: turbidity ≤ 0.5NTU, TDS content in the water obtained from pretreatment is 39919mg/L;

The water obtained from the pretreatment is subjected to nanofiltration to obtain nanofiltration concentrated water and nanofiltration effluent respectively. The nanofiltration membrane is an aromatic polyamide composite membrane with a molecular weight cutoff of 100,000, a single membrane area of 400ft ² , and a water production capacity of 150m ³ /h. Quantity 1 set, the recovery rate is 75%; the TDS content in the nanofiltration concentrated water is 52171mg/L, and the TDS content in the nanofiltration effluent is 35832mg/L;

The nanofiltration effluent was subjected to the first reverse osmosis membrane treatment. The desalination rate of the first reverse osmosis membrane treatment was 99.8%. The water treatment volume was 63m ³ /h. The membrane used was a PVDF ultrafiltration membrane, and the membrane flux was 30L/m ² /h, the water permeability is 40%, the inlet water pH is 7.0, the inlet water temperature is 25°C, and the operating pressure is 9.0MPa. The first reverse osmosis membrane water production is 80m ³ /h, and the TDS concentration is 503mg/L. The pH value is 7.0 and can be used for industrial water; the concentrated water obtained from the first reverse osmosis membrane enters the first MVR for evaporation and salt production. The steam temperature of the evaporation chamber in the first MVR for evaporation and salt production is preferably 110°C, and the absolute pressure is preferably 143.3kPa. The steam temperature in the heating chamber is preferably 130°C, and the absolute pressure is preferably 270.1kPa;

The TDS content in the nanofiltration concentrated water is 52171mg/L, and enters the EDM electrodialysis equipment for electrodialysis salt removal treatment; the EDM electrodialysis equipment includes 40 yin and yang compartments formed by cathode membranes and anode membranes alternately arranged, and one in the yin and yang compartment. The anode and anode compartments and electrolytes are formed at the end of the chamber and are formed by anode membranes and anode membranes; every 4 anode and yang compartments among the 40 anode and yang compartments form a processing unit, with a total of 10 repeated processing units. Each processing unit is composed of an anode. membrane, cathode membrane, anode membrane, cathode membrane, and anode membrane are formed, and C1 compartment, D1 compartment, C2 compartment, and D2 compartment are formed in sequence. Two adjacent processing units share an anode membrane, and the EDM circuit The two ends of the membrane stack in the dialysis equipment are connected to the positive electrode and the negative electrode respectively; the negative electrode is made of stainless steel; the positive electrode is made of alloy, the electrolyte is sodium sulfate solution, the mass concentration of the sodium sulfate solution is 5%, the voltage is 20V, and the current density is 300A/m ² , to obtain Na-type concentrated brine, Cl-type concentrated brine and EDM effluent. The 4 adjacent yin and yang compartments form a processing unit, forming a total of 10 repeated processing units; the 4 adjacent yin and yang compartments are counted as C1 respectively. Compartments, D1 compartment, C2 compartment, D2 compartment; the nanofiltration concentrated water is carried out from the D1 compartment to the EDM electrodialysis equipment; the replacement liquid 5wt.% sodium chloride solution, sodium chloride is added from the D2 compartment The added amount of the solution is 0.2 times that of the nanofiltration concentrated water. The Na-type concentrated brine flows out of the C1 compartment and enters the ED ion membrane for concentration; the Cl-type concentrated brine flows out of the C2 compartment and enters the ED ion membrane for concentration; so The EDM effluent enters the reverse osmosis membrane from the D1 compartment for treatment. The TDS contents of the Na-type concentrated brine (C1) and Cl-type concentrated brine (C2) after electrodialysis salt removal treatment are 54116mg/L and 48727mg/L respectively;

The Na-type concentrated brine and the Cl-type concentrated brine are respectively subjected to ED ion membrane concentration treatment to obtain ED concentrated brine and ED effluent respectively; the voltage of the ED ion membrane concentration treatment is 450V, and the concentration of TDS in the ED concentrated brine is 180000 mg/L. The pH value of ED concentrated brine is 7.0;

The Na-type concentrated brine (C1) and Cl-type concentrated brine (C2) are concentrated to an ion content of 18% through ED ion membrane concentration and then enter MVR evaporation to produce salt. At this time, the total amount of distilled water is 20m ³ /h; MVR evaporation In salt production, the steam temperature in the evaporation chamber is 110°C and the absolute pressure is 143.3kPa. The steam temperature in the heating room is 130°C and the absolute pressure is 270.1kPa;

The EDM effluent and ED effluent are subjected to reverse osmosis membrane treatment to obtain produced water and reverse osmosis membrane concentrated water respectively. The desalination rate of the reverse osmosis membrane treatment is 99.8%, the water treatment volume is 63m ³ /h, and the membrane used is PVDF ultrafiltration membrane , the membrane flux is 30L/m ² /h, the water permeability is 40%, the inlet water pH is 7.0, the inlet water temperature is 20°C, and the operating pressure is 2.0MPa; the concentration of TDS in the reverse osmosis membrane concentrated water is 15000mg /L, the pH value is 7.0, the concentrated water from the reverse osmosis membrane is returned to nanofiltration for continued treatment, the reverse osmosis water production is 40m ³ /h, part of it is reused to supplement water in the C1 compartment and C2 compartment, and part is used for industrial water. The filtered water and the first reverse osmosis concentrated water are mixed as the source of sodium chloride for the D2 compartment in the electrodialysis salt removal treatment. This process achieves zero discharge of high-salt and high-hard water and reduces the harm of wastewater and waste salt to the environment.

The specific composition of the nanofiltration concentrated water is shown in Table 1, and the TDS content in the inlet and outlet water of each process section in the process is shown in Table 2.

Table 1 Specific components of nanofiltration concentrated water

Table 2 TDS content in the inlet and outlet water of each process section

In this method, the evaporated water volume of each set of MVR for evaporating salt is 10m ³ /h, the total evaporated water volume is 20m ³ /h, and the water production volume is 40m ³ /h.

Comparative example 1

The difference from Example 1 is that the Na-type concentrated brine and Cl-type concentrated brine obtained by the electrodialysis salt separation treatment are no longer subjected to ED ion membrane concentration treatment, but are directly subjected to MVR evaporation to produce salt. The remaining contents are consistent with Example 1. The specific method is as follows As shown in Figure 3.

In this method, the evaporated water volume of each set of MVR for evaporating salt is 20m ³ /h, the total evaporated water volume is 40m ³ /h, and the water production volume is 20m ³ /h.

Performance Testing

(1) Select control experiments under the conditions of current density of 200A/m ² and 300A/m ² to study the rules of ion mobility. The specific experiments are: put 4kg of pure water into the C1 tank corresponding to displacement dialysis, and put C2 into Add 4kg of pure water, 5kg of nanofiltration concentrated water in D1, 5kg of 1mol/L sodium chloride solution in D2, 5kg of 5wt.% sodium sulfate solution in the extreme liquid tank, set the voltage to 20V and the current to 15.3A , at this time the current density is 200A/m ² or 300A/m ² , start the test, and record the inter-membrane voltage, current C1, C2, D1, and D2 conductance during the process. The results are shown in Table 3.

Table 3 Changes in ion mobility with time in electrodialysis salt removal treatment

It can be seen from Table 3 that under high chloride ion conditions, chloride ion migration is dominant in the early stage. After the chloride ion concentration decreases, the sulfate ion migration rate accelerates.

(2) At the same time, the scaling tendency of the two feed liquids (Na type concentrated brine and Cl type concentrated brine) produced in the C1 compartment and the C2 compartment was studied. The specific experiments were as follows: C1 obtained after splitting the salt was studied. The Na-type concentrated brine in the compartment and the chlorine-type concentrated brine in the C2 compartment are placed in the electrodialysis tank. Both D1 and D2 remain unchanged (the nanofiltration concentrated water is placed in D1 and the sodium chloride solution is placed in D2). Turn on EDM device, voltage 20V, current density 300A/ ^m2 , continue to carry out concentration experiments, concentration multiple = total TDS content at the end of the experiment / total TDS content in the raw material solution at the beginning, by calculating the ionic strength at different concentration multiples, thus The corresponding Ksp values under different ionic strength conditions are obtained to determine the structural tendency. The results are shown in Tables 4 to 5.

Table 4 Concentration times and structural tendencies of C1 compartment

Table 5 Concentration times and structural tendencies of the C2 compartment

It can be seen from Tables 4 to 5 that the separated sodium-type water and chlorine-type water [Ca ²⁺ ] [SO ₄ ^2- ] are both smaller than the Ksp value at the corresponding salinity, and there is no risk of scaling. And all are better than the raw material liquid.

Although the above embodiments describe the present invention in detail, they are only some of the embodiments of the present invention and not all of them. People can also obtain other embodiments based on this embodiment without any inventive step. These embodiments are all It belongs to the protection scope of the present invention.

Claims (10)

1. A method for treating high-salt and high-hard water, characterized in that it includes the following steps: Provide effluent produced by electrodialysis and salt removal treatment of high-salt and high-hard water. The effluent is Na-type concentrated brine, Cl-type concentrated brine and EDM effluent; The Na-type concentrated brine and Cl-type concentrated brine are respectively subjected to ED ion membrane concentration treatment to obtain ED concentrated brine and ED effluent respectively; Conduct MVR evaporation of the ED concentrated brine to produce salt; The EDM effluent and ED effluent are subjected to reverse osmosis membrane treatment to obtain product water. 2. The method according to claim 1, characterized in that TDS in the high-salt and high-hard water is 36000-44000 mg/L, SO ₄ ^2- is 720-880 mg/L, and Ca ²⁺ is 810-990 mg/L. , Mg ²⁺ is 900 to 1100 mg/L, Na ⁺ is 9000 to 12000 mg/L, and Cl- is 23000 to 25000 mg/L; the pH value of the high-salt and high-hard water is 6.0 to 7.8. 3. The method according to claim 1, characterized in that the electrodialysis salt removal treatment is carried out with EDM electrodialysis equipment; the EDM electrodialysis equipment includes 40 cathode membranes and anode membranes formed by alternating arrangements of cathode and anode membranes. chamber, an anode and yang compartment located at the end of the anode and yang compartments and formed by an anode membrane and an anode membrane, and an electrolyte; every 4 of the 40 anode and yang compartments form a processing unit, with a total of 10 repeated processing units. Each processing unit is composed of an anode film, a cathode film, an anode film, a cathode film, and an anode film, and forms C1 compartment, D1 compartment, C2 compartment, and D2 compartment in sequence. Two adjacent processing units share an anode. Membrane, the two ends of the membrane stack in the EDM electrodialysis equipment are respectively connected to the positive electrode and the negative electrode. 4. The method according to claim 3, characterized in that the electrolyte is sodium sulfate solution; the mass concentration of the sodium sulfate solution is 4.8-5.2%. 5. The method according to claim 1 or 3, characterized in that the voltage of each pair of cathode membranes and anode membranes in the electrodialysis salt removal treatment is 0.8-1.2V, and the current density is 100-300A/ ^m2 . 6. The method according to claim 1, characterized in that the conditions for the MVR evaporation salt production include: the steam temperature of the evaporation chamber is 105-110°C, and the absolute pressure is 143.3kPa; the steam temperature of the heating chamber is 125-110°C. 130℃, absolute pressure is 250~270.1kPa. 7. The method according to claim 1, characterized in that the membrane used in the ED ion membrane concentration treatment is a homogeneous ion exchange membrane. 8. The method according to claim 1 or 7, characterized in that the voltage of each pair of cathode membrane and anode membrane in the ED ion membrane concentration process is 0.8-1.2V. 9. The method according to claim 1, characterized in that the desalination rate of the reverse osmosis membrane treatment is 99.2-99.8%; the treatment water volume of the reverse osmosis membrane treatment is ^58-63m3 /h. 10. A system for treating high-salt and high-hard water, including EDM electrodialysis equipment, first ED ion membrane concentration equipment, second ED ion membrane concentration equipment, first MVR evaporation salt production equipment, second MVR evaporation salt production equipment and Reverse osmosis membrane equipment; The Na-type concentrated brine and Cl-type concentrated brine outlets of the EDM electrodialysis equipment are respectively connected to the first ED ion membrane concentration equipment and the second ED ion membrane concentration equipment, and the EDM water outlet of the EDM electrodialysis equipment is connected to the reverse osmosis membrane equipment. ; The ED concentrated brine outlet of the first ED ion membrane concentration equipment is connected to the first MVR evaporation salt making equipment; The ED concentrated brine outlet of the second ED ion membrane concentration equipment is connected to the second MVR evaporative salt production equipment; The ED water outlet of the ED ion membrane concentration equipment is connected to the reverse osmosis membrane equipment.