Disclosure of Invention
The invention aims to avoid the defects of the prior art and provides a membrane stack regeneration method based on voltage control, which can fully regenerate a bipolar membrane, solve the problem of membrane stack performance attenuation, improve the desalination performance and prolong the service life of a membrane stack.
The object of the present invention is achieved by the following technical means.
The membrane stack regeneration method based on voltage control is provided, during the regeneration time period, the instantaneous regeneration voltage at least one moment is higher than the average voltage of the water production time period, and the instantaneous regeneration voltage at other moments is not lower than the average voltage of the water production time period.
Preferably, in the above membrane stack regeneration method based on voltage control, the regeneration voltage in all regeneration periods is higher than the average voltage in the water production period.
Preferably, in the above membrane stack regeneration method based on voltage control, the regeneration voltage is 1.1 to 30 times of the water production voltage.
Preferably, in the above membrane stack regeneration method based on voltage control, the regeneration voltage is 1.2 to 20 times of the water production voltage.
Preferably, the voltage-controlled membrane stack regeneration method performs regeneration according to the voltage-controlled membrane stack regeneration method for each regeneration.
In another preferred embodiment, the regeneration method of the membrane stack based on the voltage control performs regeneration according to the regeneration method of the membrane stack based on the voltage control in each regeneration process after the amount of produced water reaches the rated value.
In another preferred mode, in the regeneration process of the membrane stack based on the voltage control, after the water production amount reaches the rated value for 1 to N times, the regeneration is carried out according to the regeneration method of the membrane stack based on the voltage control, wherein N is a natural number and is more than or equal to 1 and less than or equal to 15;
then, the water production amount is reset to zero, the water production amount is calculated again, and regeneration is carried out according to a membrane stack regeneration method based on voltage control in the regeneration process of 1 to N times after the water production amount reaches a rated value next time, wherein N is a natural number and is more than or equal to 1 and less than or equal to 15; and repeating the steps in sequence.
Preferably, in the membrane stack regeneration method based on voltage control, N is more than or equal to 2 and less than or equal to 10.
Preferably, in the regeneration method of the membrane stack based on the voltage control, after water is produced every time, in all regeneration processes after M times, the regeneration is carried out according to the regeneration method of the membrane stack based on the voltage control, wherein M is a natural number, and M is more than or equal to 1 and less than or equal to 10000.
In another preferred mode, in the membrane stack regeneration method based on voltage control, after each water production, in the regeneration processes of 1 to N times after the interval of M times, the regeneration is carried out according to the membrane stack regeneration method based on voltage control, wherein N is more than or equal to 1 and less than or equal to 50.
In another preferred mode, in the regeneration process of the membrane stack based on the voltage control, after the desalination rate of the produced water is lower than the rated value for 1 to N times, the regeneration is carried out according to the membrane stack regeneration method based on the voltage control, wherein N is a natural number, and is more than or equal to 1 and less than or equal to 50;
in the regeneration process of 1 to N times after the desalination rate of the next produced water is lower than the rated value, regenerating according to a membrane stack regeneration method based on voltage control, wherein N is a natural number and is more than or equal to 2 and less than or equal to 50; and repeating the steps in sequence.
In another preferred mode, in the regeneration process of the membrane stack based on the voltage control, after the water making time reaches the rated time for 1 to N times, the regeneration is carried out according to the membrane stack regeneration method based on the voltage control, wherein N is a natural number and is more than or equal to 1 and less than or equal to 50;
then, the water making time is reset to zero, the water making time is calculated again, and regeneration is carried out according to a membrane stack regeneration method based on voltage control in the regeneration process of 1 to N times after the next water making time reaches the rated time, wherein N is a natural number and is more than or equal to 1 and less than or equal to 50; and repeating the steps in sequence.
In another preferred embodiment, the regeneration mode is manually activated by an external key, and the regeneration is performed according to the membrane stack regeneration method based on voltage control.
The invention also provides a bipolar membrane electrodeionization device which regenerates according to the membrane stack regeneration method based on voltage control.
In the regeneration method of the membrane stack based on voltage control, in the regeneration time period, the instantaneous regeneration voltage at least one moment is higher than the average voltage of the water production time period, and the instantaneous regeneration voltages at other moments are not lower than the average voltage of the water production time period. Preferably, the regeneration voltage is 1.1 to 30 times the water production voltage. The method of the invention can effectively regenerate the membrane stack, solve the problem of membrane stack performance attenuation, improve the desalination performance and prolong the service life of the membrane stack.
According to the bipolar membrane electrodeionization device, the bipolar membrane is regenerated by adopting the above means, so that the membrane stack can be effectively regenerated, the problem of membrane stack performance attenuation is solved, the desalting performance is improved, and the service life of the membrane stack is prolonged.
Detailed Description
The invention is further illustrated by the following examples.
Unless clearly defined otherwise herein, the scientific and technical terms used have the meaning commonly understood by those of skill in the art to which this application pertains. As used in this application, the terms "comprising," "including," "having," or "containing" and similar referents to shall mean that the content of the listed items is within the scope of the listed items or equivalents thereof.
In the specification and claims, the singular and plural of all terms are not intended to be limiting unless the context clearly dictates otherwise. The use of "first," "second," and similar language in the description and claims of this application does not denote any order, quantity, or importance, but rather the intention is to distinguish one material from another, or embodiment.
Unless the context clearly dictates otherwise, the term "or", "or" does not mean exclusively, but means that at least one of the mentioned items (e.g. ingredients) is present, and includes the case where a combination of the mentioned items may be present.
References in the specification to "some embodiments" or the like indicate that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the invention is included in at least one embodiment described in the specification, and may or may not be present in other embodiments. In addition, it is to be understood that the described inventive elements may be combined in any suitable manner.
Reference herein to "deionization" is to the removal of ions from the liquid to be treated, including anions and cations in various valence states. In most cases, "deionization" has the same meaning as "desalination". In some cases, deionization is also referred to as demineralization.
Example 1.
A membrane stack regeneration method based on voltage control adopts a method of increasing regeneration voltage to regenerate. During the regeneration period, the instantaneous regeneration voltage at least one moment is higher than the average voltage of the water making period.
In desalination and regeneration processes, the voltage applied to the membrane stack during water production and regeneration is the same, as is conventional in the art. In the embodiment, the technical scheme that the regeneration voltage is higher than the water making voltage is selected, so that the membrane stack can be fully regenerated.
In the regeneration time period, at least one moment of instant regeneration voltage is higher than the average voltage of the water making time period, and the other moments of regeneration voltage are not lower than the average voltage of the water making time period. The method can be realized in a mode that the instantaneous regeneration voltage at a certain moment is higher than the average voltage of the water making time period, or can be realized in a mode that the regeneration voltage in certain time periods is controlled to be higher than the average voltage of the water making time period, or can be realized in a mode that the regeneration voltage in all regeneration time periods is higher than the average voltage of the water making time period.
Preferably, the regeneration voltage is 1.1 to 30 times of the water making voltage, and the regeneration voltage is 1.2 to 20 times of the water making voltage, so that the regeneration effect of the membrane stack is better.
In the membrane stack regeneration method based on voltage control, regeneration is performed according to a method of increasing the regeneration voltage during each regeneration. The regeneration voltage is increased, the energy of H + and OH-generated by hydrolysis of the bipolar membrane interface is increased, the ion exchange efficiency is improved, and the regeneration degree of the bipolar membrane is improved. The regeneration time of the membrane stack is prolonged, and the performance of the membrane stack can be effectively recovered.
The method of the embodiment can effectively regenerate the membrane stack, solve the problem of membrane stack performance attenuation, improve the desalination performance and prolong the service life of the membrane stack.
Example 2.
A membrane stack regeneration method based on voltage control is the same as the embodiment 1 in other characteristics, and is different from the embodiment 1 in that: and in each regeneration process after the water production amount reaches the rated value, regenerating according to a membrane stack regeneration method based on voltage control.
The rated value of the water production can be set as the sum of 5-10 times of single water production or other quantity according to actual conditions.
The membrane stack regeneration method based on voltage control can regenerate by a method of increasing voltage when the water quantity of the membrane stack reaches a rated value and is rapidly failed or fails, and is high in efficiency, good in effect and less in waste.
The membrane stack regeneration method based on voltage control enables the membrane stack to be effectively regenerated, solves the problem of membrane stack performance attenuation, improves the desalination performance, and prolongs the service life of the membrane stack.
Example 3.
A membrane stack regeneration method based on voltage control is characterized by the following steps in the same way as the embodiment 3: in the regeneration process of 1 to N times after the water production amount reaches the rated value, regeneration is carried out according to a membrane stack regeneration method based on voltage control, wherein N is a natural number and is more than or equal to 1 and less than or equal to 15;
then, the water production amount is reset to zero, the water production amount is calculated again, and regeneration is carried out according to a membrane stack regeneration method based on voltage control in the regeneration process of 1 to N times after the water production amount reaches a rated value next time, wherein N is a natural number and is more than or equal to 1 and less than or equal to 15; and repeating the steps in sequence.
The rated value of the water production can be set according to the requirement, such as two tons or one ton or other quantities, and the rated value can be a fixed value or a non-fixed value and is set according to the specific use scene of the user.
The specific quantity of N can be flexibly set according to the actual water production requirement, if N is set to be 3, the regeneration is carried out according to the membrane stack regeneration method based on voltage control in the 1 st, 2 nd and 3 rd regeneration processes after the water production reaches the rated value. After the three times of prolonged regeneration are finished, the water production amount is reset to zero, the water production amount is calculated again, and regeneration is carried out according to a membrane stack regeneration method based on voltage control in the 1 st, 2 nd and 3 rd regeneration processes after the water production amount reaches the rated value next time; and repeating the steps in sequence.
Experiments show that when N is more than or equal to 3 and less than or equal to 10, the regeneration performance is good.
When N is 1, the regeneration is performed by a method of extending the life of the membrane stack in 1 regeneration process after the water production amount reaches the rated value.
The membrane stack regeneration method based on voltage control can regenerate by a method of increasing voltage when the water quantity of the membrane stack is rapidly failed or fails after reaching a rated value, can perform regeneration control according to the needs of the membrane stack, and is high in efficiency, good in effect and less in waste.
The membrane stack regeneration method based on voltage control enables the membrane stack to be effectively regenerated, solves the problem of membrane stack performance attenuation, improves the desalination performance, and prolongs the service life of the membrane stack.
In addition to the embodiment, other methods may be used for regeneration.
One way may be: in all regeneration processes after M times of water production, regeneration is carried out according to a membrane stack regeneration method based on voltage control, wherein M is a natural number, and is more than or equal to 1 and less than or equal to 10000.
Another way may be: and after water is produced every time, in the regeneration process of 1 to N times after the interval of M times, regeneration is carried out according to a membrane stack regeneration method based on voltage control, wherein N is more than or equal to 1 and less than or equal to 50.
Another way may be: in the regeneration process of 1 to N times after the desalination rate of the produced water is lower than the rated value (such as 90 percent and 80 percent), regeneration is carried out according to a membrane stack regeneration method based on voltage control, wherein N is a natural number, and is more than or equal to 1 and less than or equal to 50;
in the regeneration process of 1 to N times after the desalination rate of the next produced water is lower than the rated value, regenerating according to a membrane stack regeneration method based on voltage control, wherein N is a natural number and is more than or equal to 2 and less than or equal to 50; and repeating the steps in sequence.
Another way may be: in the regeneration process of 1 to N times after the water production time reaches the rated time, regeneration is carried out according to a membrane stack regeneration method based on voltage control, wherein N is a natural number, and is more than or equal to 1 and less than or equal to 50;
then, the water making time is reset to zero, the water making time is calculated again, and regeneration is carried out according to a membrane stack regeneration method based on voltage control in the regeneration process of 1 to N times after the next water making time reaches the rated time, wherein N is a natural number and is more than or equal to 1 and less than or equal to 50; and repeating the steps in sequence.
Another way may be: and manually starting a regeneration mode through an external key, and regenerating according to a membrane stack regeneration method based on voltage control.
All of the above methods enable control of the regeneration process. It should be noted that the specific method may not be limited to the case of the present embodiment.
Example 4.
A bipolar membrane electrodeionization unit having an extended stack life in accordance with the method of any one of embodiments 1 to 3.
As shown in fig. 1 and 2, the bipolar membrane electrodeionization device is provided with an electrode 100, an electrode 200, and two bipolar membranes 300 located between the electrode 100 and the electrode 200, each bipolar membrane 300 being composed of a cation exchange membrane 310 and an anion exchange membrane 320 which are combined together.
In this embodiment, the electrode is a conventional metal electrode such as a ruthenium yttrium electrode, a carbon electrode, a graphite electrode, etc., and the bipolar membrane is a commercially available bipolar membrane.
The desalting process by the bipolar membrane electrodeionization device is shown in FIG. 1. When desalination is carried out for a while, reverse-polarity regeneration is required to release ions in water adsorbed on the bipolar membrane, as shown in FIG. 2.
According to the bipolar membrane electrodeionization device, the membrane stack is regenerated by a method of increasing voltage, so that the membrane stack can be effectively regenerated, the problem of membrane stack performance attenuation is solved, the desalting performance is improved, and the service life of the membrane stack is prolonged.
Example 5.
A bipolar membrane electrodeionization unit having an extended stack life in accordance with the method of any one of embodiments 1 to 3.
In this embodiment, the bipolar membrane electrodeionization device includes at least one pair of electrode assemblies, where the at least one pair of electrode assemblies includes a porous electrode and one or more bipolar membranes, each bipolar membrane is composed of a cation exchange membrane and an anion exchange membrane that are attached together, and there is no flow channel between the cation exchange membrane and the anion exchange membrane that constitute the same bipolar membrane.
A pair of electrode sets may be formed by two porous electrodes. A pair of electrode sets may be formed of a porous electrode and a common electrode. Common electrodes such as metal electrodes, titanium electrodes with ruthenium-yttrium coatings, ruthenium-yttrium electrodes, carbon electrodes, graphite electrodes, etc.
Among them, the porous electrode may be composed of a porous material, or a porous material and a current collector laminated, or a current collector, a porous material, and an ion exchange membrane laminated in this order. The ion exchange membrane is an anion exchange membrane or a cation exchange membrane, and when the ion exchange membrane is contained, the ion exchange membrane in the porous electrode is close to the bipolar membrane. The cation exchange membrane or the anion exchange membrane in the porous electrode can be flexibly selected according to actual needs.
The porous material may be any electrically conductive material having a large specific surface, e.g. a specific surface of more than 100m2Conductive material per gram. In some embodiments, the porous material is a hydrophobic, electrically conductive material. The porous material has a porous structure with pore sizes between 0.5 and 50 nanometers. The porous material can be activated carbon, carbon black, carbon nanotube, graphite, carbon fiber, carbon cloth, carbon aerogel, metal powder (such as nickel), metal oxide (such as ruthenium oxide), and/or carbon-containing materialAn electrical conductor made from one or more of the conductive polymers. In one embodiment, the porous material is a sheet or plate structure made of activated carbon and having a thickness in the range of 100 to 5000 micrometers, preferably 200 to 2,500 micrometers, and the pore size of the activated carbon sheet structure is between 0.5 to 20 nanometers, preferably 1 to 10 nanometers.
The porous electrode can reduce the scaling risk of the bipolar membrane electrodeionization device. Since the ion exchange membrane contains or is adsorbed with ion charge units, when the amount of ions at the porous electrode is insufficient to complete the desorption process, the excess charge on the electrode is buffered by releasing the ions in the ion exchange membrane to help complete the desorption process. In this way, the risk of fouling of the electrochemical deionization unit is greatly reduced.
The current collector is used to connect to a wire or power source, also referred to as a "current collector". The current collector is formed of one or more materials selected from the group consisting of metals, metal alloys, graphite, graphene, carbon nanotubes, and conductive plastics. The current collector may be in any suitable form such as a plate, mesh, foil or sheet. In some embodiments, the current collector may be made of a metal or metal alloy, suitable metals include titanium, platinum, iridium or rhodium, etc., preferably titanium, and suitable metal alloys may be stainless steel, etc. In other embodiments, the current collector may be made of a conductive carbon material, such as graphite, graphene, carbon nanotubes, and the like. In other embodiments, the current collector is made of a conductive plastic material, such as a polyolefin (e.g., polyethylene), and conductive carbon black or metal particles, etc., may be mixed therein. In some embodiments, the current collector is a sheet or plate-like structure and may have a thickness in the range of 50 micrometers to 5 millimeters. In some embodiments, the current collector and the porous electrode have substantially the same shape and/or size.
When the porosity and conductivity of the porous material are sufficient, the current collector may not be provided when the porous material itself functions as the current collector.
The bipolar membrane electrodeionization device of the present embodiment may be configured by a plurality of electrode groups, and when the bipolar membrane electrodeionization device includes a plurality of electrode groups, the electrode groups may be connected to each other through flow channels in series or in parallel or in a series-parallel manner. In the present specification, the terms "in series" and "in parallel" are defined in consideration of the flow direction of the flow path liquid flow output liquid. For example, if two electrode sets are connected in series, the product fluid from the flow channel of the previous electrode set enters the flow channel of the next electrode set. For another example, if two electrode sets are connected in parallel, it means that the flow channels of the two electrode sets receive the same liquid. The series set of electrodes is used to further remove ions from the liquid, while the parallel set of electrodes is used to increase the throughput of the device.
The technical solution of the present invention will be described below by taking the bipolar membrane electrodeionization device shown in FIGS. 3 and 4 as an example.
The bipolar membrane electrodeionization device comprises,
an electrode pair composed of a pair of porous electrodes 100, 200;
two bipolar membranes 300 arranged between the electrode pairs, wherein each bipolar membrane 300 is composed of a cation exchange membrane 310 and an anion exchange membrane 320 which are attached together, no flow channel is arranged between the cation exchange membrane 310 and the anion exchange membrane 320 which form the same bipolar membrane 300, and the arrangement modes of the two bipolar membranes 300 are the same;
and a flow channel formed between the electrode and the membrane stack or between the membrane stack and the membrane stack.
In the present embodiment, the porous electrode 100 is formed by laminating the current collector 130 and the porous material 110, and the porous electrode 100 is a cathode film electrode. The porous electrode 200 is formed by sequentially laminating a current collector 230 and a porous material 210, and the porous electrode 200 is an anode membrane electrode. The porous electrode can be formed by laminating and clamping a current collector and a porous material together without using a binder; or may be fixed by thermal bonding or bonded by an adhesive. The cation exchange membrane or the anion exchange membrane in the porous electrode can be flexibly selected according to actual needs.
The bipolar membrane 300 is composed of a cation exchange membrane 310 and an anion exchange membrane 320 which are attached together, and the cation exchange membrane 310 and the anion exchange membrane 320 which form the same bipolar membrane are clamped tightly without a binder; the cation exchange membrane 310 and the anion exchange membrane 320 may be formed by thermal lamination. There is no flow channel between the cation exchange membrane 310 and the anion exchange membrane 320, and a flow channel is formed between the bipolar membrane or between the bipolar membrane and the electrode. The bipolar membranes sold in the market can be used as the bipolar membranes in the scheme, and the details are not repeated.
In this embodiment, there are two bipolar membranes 300 between the porous electrodes 100 and 200, the arrangement directions of the two bipolar membranes 300 are the same, and the same arrangement direction means that the cation exchange membranes 310 of each bipolar membrane 300 are oriented in the same direction, and certainly the corresponding anion exchange membranes 320 of each bipolar membrane 300 are also oriented in the same direction. It should be noted that the number of the bipolar membranes 300 is not limited to two in this embodiment, and can be flexibly set according to actual needs, and the number of the bipolar membranes 300 between the general electrode pairs is 1-50, or even more.
FIG. 3 shows a bipolar membrane electrodeionization device in a desalination process. When desalination is carried out for a while, reverse-polarity regeneration is required to release ions in water adsorbed on the bipolar membrane, as shown in FIG. 4.
According to the bipolar membrane electrodeionization device, when water is produced, all single channels simultaneously produce water, and no concentrated water is produced. During regeneration, the regeneration can be realized by reversing the poles, and the regeneration process is also carried out in a single channel. Therefore, the bipolar membrane electrodeionization device has a simple water path structure. The membrane area of the bipolar membrane is repeatedly utilized, and the speed and the efficiency of ion exchange are greatly improved by the electrolytic ion exchange mode. The bipolar membrane electrodeionization device does not generate gas in polar water and scale formation. This bipolar membrane electrodeionization device adopts the structure of porous electrode and bipolar membrane, can avoid among the prior art the problem that the pole water hydrolysis produced gas and scale deposit, and can improve the desalination, has the characteristics that the system water rate is high, the water waste is few.
According to the bipolar membrane electrodeionization device, the membrane stack is regenerated by a method of increasing voltage, so that the membrane stack can be effectively regenerated, the problem of membrane stack performance attenuation is solved, the desalting performance is improved, and the service life of the membrane stack is prolonged.
Example 6.
A bipolar membrane electrodeionization apparatus having the same other features as in example 5 except that: as shown in fig. 5 and 6, in the present embodiment: the porous electrode 100 is formed by stacking a current collector 130, a porous material 110, and an anion exchange membrane 120 in this order, and the porous electrode 100 is a cathode electrode. The porous electrode 200 is formed by stacking a current collector 230, a porous material 210, and a cation exchange membrane 220 in this order, and the porous electrode 200 is an anode membrane electrode. The porous electrode can be formed by overlapping and clamping a current collector, a porous material and an ion exchange membrane together without using a binder; or may be fixed by thermal bonding or bonded by an adhesive.
The desalting process of the bipolar membrane electrodeionization device of the present embodiment is shown in FIG. 5. When desalination is carried out for a while, reverse-polarity regeneration is required to release ions in water adsorbed on the bipolar membrane, as shown in FIG. 6.
Experiments show that the porous electrode not only solves the problem of gas generation of the metal electrode, but also can realize the design of independent water outlet of the electrode chamber flow passage. And compared with the common electrode, the whole desalting efficiency of the electrodeionization device adopting the porous electrode can be improved by more than 10 percent. This is because the porous electrode can adsorb ions of raw water, and this adsorption efficiency is higher than the ion exchange efficiency of the bipolar membrane.
According to the bipolar membrane electrodeionization device, the membrane stack is regenerated by a method of increasing voltage, so that the membrane stack can be effectively regenerated, the problem of membrane stack performance attenuation is solved, the desalting performance is improved, and the service life of the membrane stack is prolonged.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.