CN110510712B - Electrodialysis system and method for desalting brackish water - Google Patents
Electrodialysis system and method for desalting brackish water Download PDFInfo
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- CN110510712B CN110510712B CN201910734161.6A CN201910734161A CN110510712B CN 110510712 B CN110510712 B CN 110510712B CN 201910734161 A CN201910734161 A CN 201910734161A CN 110510712 B CN110510712 B CN 110510712B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
- C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
Abstract
The invention provides an electrodialysis system and method for desalting bitter water, which comprises an electrodialysis membrane stack system, a raw water pump, a raw water tank, an electrode liquid pump, an electrode liquid tank and a direct-current stabilized power supply, wherein the electrodialysis membrane stack system comprisesThe device comprises a plurality of sectional type electrodialysis membrane stacks, a cathode chamber and an anode chamber, wherein the electrodialysis membrane stacks are sequentially connected, a cathode and a cation exchange membrane are arranged between the anode chamber and the cathode chamber, the anode chamber is provided with a concentrated water inlet, a fresh water inlet, an anolyte water inlet and an anolyte water outlet, and the cathode chamber is provided with a first water outlet, a second water outlet, a catholyte water inlet and a catholyte water outlet; the electrodialysis membrane stack is provided with a direct current stabilized voltage power supply. Aiming at typical brackish water, the system and the method provided by the invention can be not higher than 0.8kWh/m3The method provided by the invention optimizes the brackish water desalination process, and achieves the purposes of energy reduction and consumption reduction by adjusting voltage and current.
Description
Technical Field
The invention belongs to the field of water treatment, and particularly relates to a high-efficiency energy-saving electrodialysis system and method for brackish water desalination.
Background
Electrodialysis is a technology combining an electrochemical process and a dialysis diffusion process, and is not a differential pressure filtration type process, so that the electrodialysis technology has relatively strong pollution resistance and relatively low requirement on the quality of raw water, and is suitable for treating water with high concentration and high salt content. The electrodialysis technology has the advantages of small occupied area, low investment, easy realization of automation and the like, is widely applied to the aspect of concentrating and salt making, and has better effect in the fields of water production, industrial wastewater treatment, chemical industry and the like.
Electrodialysis is commonly used for desalting low-concentration brackish water, a multistage continuous desalting process is adopted in China, constant voltage operation is adopted, desalted feed water passes through a plurality of single-stage or multi-stage series electrodialyzers, one-time desalting meets the preset requirement, water is discharged continuously, the desalting rate is high, the operation is stable, but the operation flexibility is small, and the adaptability is poor when the salt content of the feed water changes.
In the existing electrodialysis desalination technology, the following common defects exist: (1) the middle electrode of the multi-stage electrodialysis system is a common electrode, the voltage and current of each stage can not be independently adjusted, and the concentration of the raw material liquid is gradually reduced from the water inlet side to the water outlet side of the electrodialysis, so that the voltage of the rear stage of the electrodialysis is too large under the condition that the voltages of all stages are equal, and unnecessary energy consumption is caused; (2) the number of membrane pairs of each stage and section of electrodialysis is equal, so that the linear flow velocity in single compartments of the front stage and the rear stage of electrodialysis and the linear flow velocity in single compartments of the front stage and the rear stage of electrodialysis are equal, but the concentration of the desalted water of the rear stage or the rear stage is lower than that of the desalted water of the front stage or the front stage, so that the limiting current density of the lower stage is lower than that of the desalted water of the front stage or the rear stage, the; (3) in conventional electrodialysis of brackish water, the solution resistance of the electrode compartment is still in proportion, thus generating considerable energy consumption of the electrode compartment.
Therefore, a novel energy-saving electrodialysis desalination system and method are urgently needed to be developed, corresponding voltages and currents at all levels are adjusted, and the energy consumption of the body is reduced to the minimum on the premise that the target water quality is achieved.
Disclosure of Invention
The invention aims to overcome the defects of the existing electrodialysis desalination technology, provides an energy-saving multistage multi-section electrodialysis continuous desalination system, solves the problems of low desalination efficiency, high energy consumption, long-term operation stability need to be improved and the like in the process of using reverse osmosis and conventional electrodialysis technologies for brackish water desalination, and promotes energy reduction and consumption reduction in the application of brackish water electrodialysis desalination.
In order to solve the technical problems, the invention adopts the technical scheme that: the device comprises an electrodialysis membrane stack system, a raw water pump, a raw water tank, an anolyte pump, an anolyte tank and a direct-current stabilized voltage power supply, wherein the electrodialysis membrane stack system is formed by sequentially connecting a plurality of sectional electrodialysis membrane stacks, an anode chamber and a cathode chamber are arranged on the electrodialysis membrane stacks, anion and cation exchange membranes are arranged between the anode chamber and the cathode chamber, the anode chamber is provided with a concentrated water inlet, a fresh water inlet, an anolyte water inlet and an anolyte water outlet, and the cathode chamber is provided with a first water outlet, a second water outlet, a catholyte water inlet and a catholyte water outlet; the water outlet of the raw water tank is divided into two water flows, namely a first water outlet and a second water outlet, wherein the first water outlet and the second water outlet are respectively connected to a concentrated water inlet and a fresh water inlet in the electrodialysis membrane stack system, the first water outlet is connected with an external discharge pipeline, and the second water outlet is connected with a water user pipeline; the effluent of the anolyte tank is divided into two anolyte flows which are anolyte and catholyte respectively, the anolyte and the catholyte are connected to an anolyte water inlet and a catholyte water inlet respectively through anolyte pipelines, and a catholyte water outlet and an anolyte water outlet are connected with the anolyte tank through pipelines; the electrodialysis membrane stack is provided with a direct current stabilized voltage power supply.
Further, the polar chamber of the electrodialysis membrane stack is made of a resin packed bed type ultrathin electrode plate frame; the resin packed bed type ultrathin electrode plate frame comprises a resin packed bed ultrathin anode plate frame and a resin packed bed ultrathin cathode plate frame, and the anode chamber and the cathode chamber are respectively made of the resin packed bed ultrathin anode plate frame and the resin packed bed ultrathin cathode plate frame; the resin packed bed ultrathin anode plate frame and the resin packed bed ultrathin cathode plate frame both comprise an electrode plate and an electrode frame, the thickness of the resin packed bed type ultrathin electrode plate frame is 1-3mm, and strong acid and strong base mixed bed anion and cation exchange resin with the volume ratio of 1:1 is filled between the electrode plate and the electrode frame.
Furthermore, the electrodialysis membrane stack system is formed by sequentially connecting three sectional electrodialysis membrane stacks, namely a first-stage electrodialysis membrane stack, a second-stage electrodialysis membrane stack and a third-stage electrodialysis membrane stack; wherein the thickness of an electrode plate frame in the first-stage electrodialysis membrane stack is 1-3 mm; the thickness of an electrode plate frame in the second-stage electrodialysis membrane stack is 1-3 mm; and the thickness of an electrode plate frame in the third-stage electrodialysis membrane stack is 1-3 mm.
Further, the electrodialysis membrane stack is designed by using inter-stage asymmetric membrane pairs, wherein the inter-stage asymmetric membrane pairs comprise inter-stage asymmetric membrane pairs and each inter-stage asymmetric membrane pair; the membrane stack is designed by the interstage asymmetrical membrane logarithm, wherein each stage of membrane stack unit adopts different membrane logarithms, and the total membrane logarithms are counted in 360 pairs.
Further, the number of membrane pairs in the first-stage electrodialysis membrane stack is 120-160 pairs; the number of membrane pairs in the second-stage electrodialysis membrane stack is 100-140 pairs; the number of membrane pairs in the third electrodialysis membrane stack is 80-120.
Furthermore, each stage of electrodialysis membrane stack with asymmetric membrane logarithm design among the sections is provided with a reversing partition plate, and the number of membrane logarithms in front of the reversing partition plate is more than that behind the reversing partition plate; and the film log ratio of the two sides of the reversing partition board is between 1 and 1.3.
Furthermore, the membrane stacks are connected by a non-common electrode, and each electrodialysis membrane stack is provided with a direct current stabilized voltage supply; the first electrodialysis membrane stack, the second electrodialysis membrane stack and the third electrodialysis membrane stack are respectively connected with a first direct-current stabilized power supply, a second direct-current stabilized power supply and a third direct-current stabilized power supply; an insulation board with the thickness of 3, 5, 7, 9 or 10mm is arranged between the cathode plate of the first-stage electrodialysis membrane stack and the anode plate of the second-stage electrodialysis membrane stack; an insulating plate with the thickness of 3, 5, 7, 9 or 10mm is arranged between the cathode plate of the second-stage electrodialysis membrane stack and the anode plate of the third-stage electrodialysis membrane stack.
An efficient energy-saving electrodialysis method for brackish water desalination adopts a means of parallel flow of cathode and anode electrode liquids and countercurrent flow of concentrated and fresh water, and forms a continuous energy-saving electrodialysis technology for brackish water desalination by integrating and optimizing multi-stage systems with independently adjustable stages; the cathode and anode electrode solutions are in parallel flow and are respectively conveyed to the cathode and anode chambers of each stage, so that the cathode and anode solutions are not mutually connected in series; the concentrated fresh water flows reversely, concentrated fresh water inlets of the membrane stacks are positioned on two sides of the respective membrane stacks, so that the membrane stack concentrated chamber liquid flow and the membrane stack dilute chamber liquid flow in opposite directions, and the method comprises the following specific implementation steps:
step 1: starting the electrode solution pump, respectively conveying the electrode solution in the electrode solution tank to a cathode chamber and an anode chamber of each stage of the electrodialysis membrane stack through the electrode solution pump, and circulating the electrode solution to the electrode solution tank after the electrode solution is converged at an outlet of each electrode chamber;
step 2: starting the raw water pump, dividing the raw water in the raw water tank into two branches of effluent, and respectively conveying the effluent to a concentrated water inlet and a fresh water inlet through the raw water pump so as to enter a first-stage electrodialysis membrane stack for flowing; in the flowing process, the concentrated water enters a concentrated water inlet of a next-stage electrodialysis membrane stack from a first water outlet of the previous-stage electrodialysis membrane stack and continuously flows in the next-stage electrodialysis membrane stack, the fresh water enters a fresh water inlet of the next-stage electrodialysis membrane stack from a second water outlet of the previous-stage electrodialysis membrane stack and continuously flows in the next-stage electrodialysis membrane stack, wherein the concentrated water at the front section of each-stage membrane stack flows from top to bottom, the fresh water flows from bottom to top, and the concentrated water at the second section of each-stage membrane stack flows from bottom to top and the fresh water flows from top to bottom under the action of a reversing partition plate; concentrated water of the last stage of electrodialysis membrane stack, namely the third stage of electrodialysis membrane stack is discharged out of the equipment through the first water outlet, and fresh water is connected with a water user through a pipeline through the second water outlet;
and step 3: in the operation process of the step 2, the voltage and the current of the direct-current stabilized voltage power supply connected with each stage of electrodialysis membrane stack are adjusted, so that the voltage and the current of each stage of electrodialysis membrane stack are independently adjusted, and the energy consumption of the operation body is further reduced.
The invention has the advantages and positive effects that:
1. the invention adopts the non-common electrode connection, the electrodialysis membrane stacks of each stage are controlled by a direct current stabilized voltage supply, the voltage and the current of the electrodialysis membrane stacks of each stage can be adjusted at any time according to the concentration change of the raw material liquid of each stage, and the energy consumption of the desalination system can be further reduced by reasonably adjusting the voltage and the current of the electrodialysis membrane stacks of each stage under the condition of ensuring the desalination rate in a certain range.
2. The thickness of the electrode chamber of each stage of electrodialysis membrane stack provided by the invention is not more than 3mm, the difficulty of mould formation is small, and the large-scale industrial production is easy to realize; the asymmetric membrane logarithm design among the sections can improve the membrane surface flow rate of the next section of the concentration chamber, so that the concentration diffusion and concentration polarization of the next section are reduced, and the operation energy consumption of the whole membrane stack is further reduced; the water quality of the produced water of the whole energy-saving electrodialysis desalination system can be flexibly adjusted, the operation is simple and convenient, and the running stability is high.
3. The electrodialysis system for desalting the brackish water can be not higher than 0.8kWh/m3The body of the device can continuously produce the desalted water with movable and adjustable quality (TDS is between 132 and 241 mg/L).
Drawings
FIG. 1 is a schematic diagram of the construction of an electrodialysis membrane stack system in an electrodialysis system and method for desalinating brackish water according to the present invention;
FIG. 2 is a process experimental flow diagram of an electrodialysis system and method for desalinating brackish water according to the present invention;
in the figure: 1-resin packed bed ultrathin anode plate frame, 2-cathode, the device comprises a cation exchange membrane, a 3-reversing partition plate, a 4-resin packed bed ultrathin cathode plate frame, a 5-insulating plate, a 6-first-stage electrodialysis membrane stack, a 7-second-stage electrodialysis membrane stack, an 8-third-stage electrodialysis membrane stack, a 9-raw water tank, a 10-concentrated water inlet, a 11-fresh water inlet, a 13-first-stage direct current stabilized power supply, a 14-second-stage direct current stabilized power supply, a 15-third-stage direct current stabilized power supply, a 16-anolyte water inlet, a 17-catholyte water inlet, an 18-anolyte water outlet, a 19-catholyte water outlet, a 20-first water outlet, a 21-second water outlet, a 22-anolyte tank, a 23-anolyte pump and a 24-raw water pump.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
As shown in fig. 1 and 2, an electrodialysis system for desalinating brackish water comprises an electrodialysis membrane stack system, a raw water pump 24, a raw water tank 9, an electrode liquid pump 23, an electrode liquid tank 22 and a direct current stabilized voltage power supply, and is characterized in that the electrodialysis membrane stack system is formed by sequentially connecting a plurality of sectional type electrodialysis membrane stacks, an anode chamber and a cathode chamber are arranged on each electrodialysis membrane stack, a cathode-cation exchange membrane 2 is arranged between each anode chamber and each cathode chamber, the anode chamber is provided with a concentrated water inlet 10, a fresh water inlet 11, an anolyte water inlet 16 and an anolyte water outlet 18, and the cathode chamber is provided with a first water outlet 20, a second water outlet 21, a catholyte water inlet 17 and a catholyte water outlet 19; the water outlet of the raw water tank 9 is divided into two water flows, namely a first water outlet and a second water outlet, wherein the first water outlet and the second water outlet are respectively connected to a concentrated water inlet 10 and a fresh water inlet 11 in the electrodialysis membrane stack system, the first water outlet 20 is connected with an external discharge pipeline, and the second water outlet 21 is connected with a water user pipeline; the effluent of the anolyte tank 22 is divided into two anolyte flows, namely anolyte and catholyte, which are respectively connected to the anolyte water inlet 16 and the catholyte water inlet 17 through anolyte pipelines, and the catholyte water outlet 19 and the anolyte water outlet 18 are connected to the anolyte tank 22 through pipelines; the electrodialysis membrane stack is provided with a direct current stabilized voltage power supply. Wherein, the cathode and the anode liquid in the anolyte tank 22 are respectively transported to the cathode chamber and the anode chamber by pipelines under the action of the anolyte pump 23, the raw water in the raw water tank 9 is divided into two water flows, and the raw water is respectively transported to the anode chamber by the concentrated water inlet 10 and the fresh water inlet 11 by pipelines under the action of the raw water pump 24.
Further, the polar chamber of the electrodialysis membrane stack is made of a resin packed bed type ultrathin electrode plate frame; the resin packed bed type ultrathin electrode plate frame comprises a resin packed bed ultrathin anode plate frame 1 and a resin packed bed ultrathin cathode plate frame 4, and the anode chamber and the cathode chamber are respectively made of the resin packed bed ultrathin anode plate frame 1 and the resin packed bed ultrathin cathode plate frame 4; the resin packed bed ultrathin anode plate frame 1 and the resin packed bed ultrathin cathode plate frame 4 comprise an electrode plate and an electrode frame, the thickness of the resin packed bed type ultrathin electrode plate frame is 1-3mm, and strong acid and strong base mixed bed anion and cation exchange resin with the volume ratio of 1:1 is filled between the electrode plate and the electrode frame. Anolyte water inlet 16, anolyte delivery port 18, catholyte water inlet 17 and catholyte delivery port 19 all are provided with the moisturizing groove that moisturizing gap width is 0.1/0.2/0.3/0.4 or 0.5mm, and the interval of adjacent moisturizing gap is 2.0/2.2/2.4/2.6/2.8 or 3.0mm, and simultaneously, the plate electrode is less than utmost point frame 1.0/2.0 or 3.0mm in order to do benefit to the resin and fill.
Furthermore, the electrodialysis membrane stack system is formed by sequentially connecting three sectional electrodialysis membrane stacks, namely a first-stage electrodialysis membrane stack 6, a second-stage electrodialysis membrane stack 7 and a third-stage electrodialysis membrane stack 8; wherein the thickness of an electrode plate frame in the first-stage electrodialysis membrane stack 6 is 1-3 mm; the thickness of an electrode plate frame in the second-stage electrodialysis membrane stack 7 is 1-3 mm; the thickness of the electrode plate frame in the third-stage electrodialysis membrane stack 8 is 1-3 mm.
Further, the electrodialysis membrane stack is designed by using inter-stage asymmetric membrane pairs, wherein the inter-stage asymmetric membrane pairs comprise inter-stage asymmetric membrane pairs and each inter-stage asymmetric membrane pair; each level of film stack of the interstage asymmetric film logarithm design, wherein each level of film stack unit adopts different film logarithms, and the total film logarithms are counted in 360 pairs; the number of membrane pairs in the first-stage electrodialysis membrane stack 6 is 120-160 pairs; the number of membrane pairs in the second-stage electrodialysis membrane stack 7 is 100-140 pairs; the number of membrane pairs in the third electrodialysis membrane stack 8 is 80-120.
Furthermore, each stage of electrodialysis membrane stack with asymmetric membrane logarithm design among the sections is provided with a reversing partition plate 3, and the number of membrane logarithms in front of the reversing partition plate 3 is more than that behind the reversing partition plate; and the film log ratio of the two sides of the reversing partition plate 3 is between 1 and 1.3.
Furthermore, the membrane stacks are connected by a non-common electrode, and each electrodialysis membrane stack is provided with a direct current stabilized voltage supply; the first-stage electrodialysis membrane stack 6, the second-stage electrodialysis membrane stack 7 and the third-stage electrodialysis membrane stack 8 are respectively connected with a first-stage direct-current stabilized power supply 13, a second-stage direct-current stabilized power supply 14 and a third-stage direct-current stabilized power supply 15; an insulating plate 5 with the thickness of 3, 5, 7, 9 or 10mm is arranged between the cathode plate of the first-stage electrodialysis membrane stack 6 and the anode plate of the second-stage electrodialysis membrane stack 7; an insulating plate 5 with the thickness of 3, 5, 7, 9 or 10mm is arranged between the cathode plate of the second electrodialysis membrane stack 7 and the anode plate of the third electrodialysis membrane stack 8.
An efficient energy-saving electrodialysis method for brackish water desalination adopts a means of parallel flow of cathode and anode electrode liquids and countercurrent flow of concentrated and fresh water, and forms a continuous energy-saving electrodialysis technology for brackish water desalination by integrating and optimizing multi-stage systems with independently adjustable stages; the cathode and anode electrode solutions are in parallel flow and are respectively conveyed to the cathode and anode chambers of each stage, so that the cathode and anode solutions are not mutually connected in series; the concentrated fresh water flows reversely, concentrated fresh water inlets of the membrane stacks are positioned on two sides of the respective membrane stacks, so that the membrane stack concentrated chamber liquid flow and the membrane stack dilute chamber liquid flow in opposite directions, and the method comprises the following specific implementation steps:
step 1: starting an electrode liquid pump 23, and then respectively conveying the electrode liquid in the electrode liquid tank 22 to a cathode chamber and an anode chamber of each stage of the electrodialysis membrane stack through the electrode liquid pump 23, wherein the electrode liquid is merged at an outlet of each electrode chamber and then circulated to the electrode liquid tank 22;
step 2: starting the raw water pump 24, dividing the raw water in the raw water tank 9 into two effluent streams, and respectively delivering the effluent streams to the concentrated water inlet 10 and the fresh water inlet 11 through the raw water pump 24 so as to enter the first-stage electrodialysis membrane stack 6 for flowing; in the flowing process, the concentrated water enters the concentrated water inlet 10 of the next-stage electrodialysis membrane stack from the first water outlet 20 of the previous-stage electrodialysis membrane stack and continues to flow in the next-stage electrodialysis membrane stack, the fresh water enters the fresh water inlet 11 of the next-stage electrodialysis membrane stack from the second water outlet 21 of the previous-stage electrodialysis membrane stack and continues to flow in the next-stage electrodialysis membrane stack, wherein the previous-stage concentrated water of each-stage membrane stack flows from top to bottom, the fresh water flows from bottom to top, and the second-stage concentrated water of each-stage membrane stack flows from bottom to top and the fresh water flows from top to bottom under the action of the reversing partition plate; concentrated water of the last electrodialysis membrane stack, namely the third electrodialysis membrane stack 8 is discharged out of the equipment through a first water outlet 20, and fresh water is connected with a water user through a pipeline through a second water outlet 21;
and step 3: in the operation process of the step 2, the voltage and the current of the direct-current stabilized voltage power supply connected with each stage of electrodialysis membrane stack are adjusted, so that the voltage and the current of each stage of electrodialysis membrane stack are independently adjusted, and the energy consumption of the operation body is further reduced.
The following is an experiment for desalting seawater nanofiltration water of typical brackish water quality using the electrodialysis system described above:
example 1:
the thickness of a reversing partition plate 3 in the electrodialysis membrane stack is 0.9mm, the electrode plate is 3mm lower than the electrode frame, the width of the water distribution tank is 6mm, the width of a water replenishing gap of the water distribution tank is 0.3mm, and the distance between adjacent water replenishing gaps is 2.6 mm; fully and uniformly mixing anion-cation exchange resin and cation-exchange resin according to the volume ratio of 1:1, and filling the mixture into an electrode chamber in a wet state, wherein the thickness of the electrode chamber is 3 mm; the area of the ion exchange membrane is 400 x 800mm, and the area of the effective membrane is 340 x 620 mm; the number of membrane pairs of the electrodialysis system is 360 pairs in total, the number of membrane pairs of the three-stage electrodialysis membrane stack is sequentially set to be 140 pairs, 120 pairs and 100 pairs, and the number of membrane pairs of the later section of the same membrane stack is reduced by 7 percent compared with that of the former section. The specific operating parameters and the water quality of inlet and outlet water are shown in the following table 1:
table 1 operating parameters and inlet and outlet water quality 1 of example 1
Specifically, in the embodiment, the water yield of electrodialysis is 18L/min, namely 1.08t/h, the conductivity of the produced water is as low as 187 mu S/cm, the TDS is as low as 132.6 mg/L, the desalination rate is more than 95%, and the power consumption per ton of water is 0.759KWh/m3。
Based on example 1, by adjusting the voltage or current of each stage, example 2 can be obtained, and the specific operating parameters and the water quality of inlet and outlet water are shown in table 2 below:
example 2
Table 2 operating parameters and inlet and outlet water quality 2 of example 2
In the experiment, by properly reducing the working voltage and current of each stage of the electrodialysis desalination system, the conductivity of fresh water is 410 mu S/cm, the TDS is 241 mg/L, the desalination rate can still reach more than 90 percent, and the power consumption per ton of water is reduced to 0.52KWh/m3(ii) a Compared with the embodiment 1, the water inlet flow and the pressure of the embodiment 2 are the same, the electric conductivity of the water inlet is the same, the desalination rate can still reach more than 90% only by properly adjusting the voltage and the current of each stage of electrodialysis membrane stack, and the electricity consumption of each ton of water is saved by 0.25KWh/m compared with the electricity consumption of each ton of water in the embodiment 13。
Obviously, by reasonably adjusting the voltage and current of each stage of electrodialysis membrane stack, the body energy consumption of the desalination system can be further reduced under the condition of ensuring a certain range of desalination rate.
The thickness of the electrode chamber of each stage of electrodialysis membrane stack provided by the invention is not more than 3mm, the difficulty of mould formation is small, and the large-scale industrial production is easy to realize; the water quality of the produced water of the whole energy-saving electrodialysis desalination system can be flexibly adjusted, the operation is simple and convenient, and the running stability is high.
Through the operation and comparison of the above embodiments, the present invention can achieve the following beneficial effects:
1. the invention adopts the non-common electrode connection, the electrodialysis membrane stacks of each stage are controlled by a direct current stabilized voltage supply, the voltage and the current of the electrodialysis membrane stacks of each stage can be adjusted at any time according to the concentration change of the raw material liquid of each stage, and the energy consumption of the desalination system can be further reduced by reasonably adjusting the voltage and the current of the electrodialysis membrane stacks of each stage under the condition of ensuring the desalination rate in a certain range.
2. The thickness of the electrode chamber of each stage of electrodialysis membrane stack provided by the invention is not more than 3mm, the difficulty of mould formation is small, and the large-scale industrial production is easy to realize; the asymmetric membrane logarithm design among the sections can improve the membrane surface flow rate of the next section of the concentration chamber, so that the concentration diffusion and concentration polarization of the next section are reduced, and the operation energy consumption of the whole membrane stack is further reduced; the water quality of the produced water of the whole energy-saving electrodialysis desalination system can be flexibly adjusted, the operation is simple and convenient, and the running stability is high.
3. The electrodialysis system for desalting the brackish water can be not higher than 0.8kWh/m3The body of the device can continuously produce the desalted water with movable and adjustable quality (TDS is between 132 and 241 mg/L).
The two embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (7)
1. An electrodialysis system for desalting brackish water comprises an electrodialysis membrane stack system, a raw water pump (24), a raw water tank (9), an electrode liquid pump (23), an electrode liquid tank (22) and a direct-current stabilized voltage power supply, and is characterized in that the electrodialysis membrane stack system is formed by sequentially connecting a plurality of sectional type electrodialysis membrane stacks, an anode chamber and a cathode chamber are arranged on the electrodialysis membrane stack, anion and cation exchange membranes (2) are arranged between the anode chamber and the cathode chamber, the anode chamber is provided with a concentrated water inlet (10), a fresh water inlet (11), an anolyte water inlet (16) and an anolyte water outlet (18), and the cathode chamber is provided with a first water outlet (20), a second water outlet (21), a catholyte water inlet (17) and a catholyte water outlet (19); the water outlet of the raw water tank (9) is divided into two water flows, namely a first water outlet and a second water outlet, wherein the first water outlet and the second water outlet are respectively connected to a concentrated water inlet (10) and a fresh water inlet (11) in the electrodialysis membrane stack system, the first water outlet (20) is connected with an external discharge pipeline, and the second water outlet (21) is connected with a water user pipeline; the water outlet of the anolyte tank (22) is divided into two anolyte flows, namely anolyte and catholyte, the anolyte and the catholyte are respectively connected to an anolyte water inlet (16) and a catholyte water inlet (17) through anolyte pipelines, and a catholyte water outlet (19) and an anolyte water outlet (18) are connected with the anolyte tank (22) through pipelines;
the electrodialysis membrane stack is designed by adopting inter-stage asymmetric membrane pairs, wherein the inter-stage asymmetric membrane pairs comprise inter-stage asymmetric membrane pairs and inter-stage asymmetric membrane pairs; each level of film stack of the interstage asymmetric film logarithm design, wherein each level of film stack unit adopts different film logarithms, and the total film logarithms are counted in 360 pairs;
and the membrane stacks are connected by a non-common electrode, and each electrodialysis membrane stack is provided with a direct current stabilized voltage supply.
2. Electrodialysis system for desalinating brackish water according to claim 1, characterized in that the polar compartments of the electrodialysis membrane stack are made of resin-packed bed type ultra thin electrode plate frames; the resin packed bed type ultrathin electrode plate frame comprises a resin packed bed ultrathin anode plate frame (1) and a resin packed bed ultrathin cathode plate frame (4), and the anode chamber and the cathode chamber are respectively made of the resin packed bed ultrathin anode plate frame (1) and the resin packed bed ultrathin cathode plate frame (4); the resin packed bed ultrathin anode plate frame (1) and the resin packed bed ultrathin cathode plate frame (4) both comprise an electrode plate and an electrode frame, the thickness of the resin packed bed type ultrathin electrode plate frame is 1-3mm, and strong-base strong-acid mixed bed anion-cation exchange resin with the volume ratio of 1:1 is filled between the electrode plate and the electrode frame.
3. Electrodialysis system for desalinating brackish water according to claim 2, characterized in that the electrodialysis membrane stack system is formed by three segmented electrodialysis membrane stacks connected in series, respectively a first electrodialysis membrane stack (6), a second electrodialysis membrane stack (7) and a third electrodialysis membrane stack (8); wherein the thickness of an electrode plate frame in the first-stage electrodialysis membrane stack (6) is 1-3 mm; the thickness of an electrode plate frame in the second-stage electrodialysis membrane stack (7) is 1-3 mm; the thickness of an electrode plate frame in the third-stage electrodialysis membrane stack (8) is 1-3 mm.
4. Electrodialysis system for desalinating brackish water according to claim 3, wherein the number of membrane pairs in the first electrodialysis membrane stack (6) is 120-160 pairs;
the number of membrane pairs in the second-stage electrodialysis membrane stack (7) is 100-140 pairs;
the number of membrane pairs in the third electrodialysis membrane stack (8) is 80-120.
5. Electrodialysis system for desalinating brackish water according to claim 3, wherein each electrodialysis membrane stack of the interstage asymmetric membrane pair design is provided with a reversing partition (3), and the number of membrane pairs before the reversing partition (3) is greater than the number of membrane pairs after the reversing partition; and the film log ratio of the two sides of the reversing partition plate (3) is between 1 and 1.3.
6. Electrodialysis system for desalinating brackish water according to claim 3, wherein the first (6), second (7) and third (8) electrodialysis membrane stacks are connected to a first (13), second (14) and third (15) regulated DC supply, respectively;
an insulating plate (5) with the thickness of 3, 5, 7, 9 or 10mm is arranged between the cathode plate of the first-stage electrodialysis membrane stack (6) and the anode plate of the second-stage electrodialysis membrane stack (7);
an insulating plate (5) with the thickness of 3, 5, 7, 9 or 10mm is arranged between the cathode plate of the second-stage electrodialysis membrane stack (7) and the anode plate of the third-stage electrodialysis membrane stack (8).
7. An efficient and energy-saving electrodialysis method for brackish water desalination, which uses the electrodialysis system for brackish water desalination as claimed in any one of claims 1 to 6, and is characterized in that the method adopts a co-current and counter-current method of cathode and anode liquid and a counter-current method of dense and fresh water, and forms a continuous type energy-saving electrodialysis technology facing brackish water desalination through integration and optimization of a multi-stage system with independently adjustable voltage of electrodialysis membrane stacks; the cathode and anode electrode solutions are in parallel flow and are respectively conveyed to the cathode and anode chambers of each stage, so that the cathode and anode solutions are not mutually connected in series; the concentrated fresh water flows reversely, concentrated fresh water inlets of the membrane stacks are positioned on two sides of the respective membrane stacks, so that the membrane stack concentrated chamber liquid flow and the membrane stack dilute chamber liquid flow in opposite directions, and the method comprises the following specific implementation steps:
step 1: when the polar liquid pump (23) is started, the electrode liquid in the polar liquid tank (22) is respectively conveyed to the cathode chamber and the anode chamber of each electrodialysis membrane stack through the polar liquid pump (23), and the electrode liquid is merged at the outlet of each polar chamber and then circulated to the polar liquid tank (22);
step 2: starting a raw water pump (24), dividing raw water in a raw water tank (9) into two branches of effluent, and respectively conveying the effluent to a concentrated water inlet (10) and a fresh water inlet (11) through the raw water pump (24) so as to enter a first-stage electrodialysis membrane stack (6) for flowing; in the flowing process, the concentrated water enters a concentrated water inlet (10) of a next-stage electrodialysis membrane stack from a first water outlet (20) of the previous-stage electrodialysis membrane stack and continuously flows in the next-stage electrodialysis membrane stack, the fresh water enters a fresh water inlet (11) of the next-stage electrodialysis membrane stack from a second water outlet (21) of the previous-stage electrodialysis membrane stack and continuously flows in the next-stage electrodialysis membrane stack, wherein the concentrated water at the front section of each-stage membrane stack flows from top to bottom, the fresh water flows from bottom to top, and the concentrated water at the second section of each-stage membrane stack flows from bottom to top and the fresh water flows from top to bottom under the action of a reversing partition plate; concentrated water of the last electrodialysis membrane stack, namely a third electrodialysis membrane stack (8), is discharged out of the equipment through a first water outlet (20), and fresh water is connected with a water user through a second water outlet (21) through a pipeline;
and step 3: in the operation process of the step 2, the voltage and the current of the direct-current stabilized voltage power supply connected with each stage of electrodialysis membrane stack are adjusted, so that the voltage and the current of each stage of electrodialysis membrane stack are independently adjusted, and the energy consumption of the operation body is further reduced.
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| CN114436377B (en) * | 2022-04-08 | 2022-07-08 | 中国科学院生态环境研究中心 | Electrodialysis equipment and method for selectively removing target ions of drinking water |
| US11502322B1 (en) | 2022-05-09 | 2022-11-15 | Rahul S Nana | Reverse electrodialysis cell with heat pump |
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