CN114733355A - Cleaning device and method for ion exchange membrane in electrodialysis membrane stack - Google Patents
Cleaning device and method for ion exchange membrane in electrodialysis membrane stack Download PDFInfo
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Abstract
The invention relates to a device and a method for cleaning an ion exchange membrane in an electrodialysis membrane stack, wherein the device comprises a cleaning liquid box, the electrodialysis membrane stack internally provided with the ion exchange membrane to be cleaned and a rectifier, the cleaning liquid box is also respectively connected with a water tank, an acid medicine storage box, a metal ion complexing agent medicine storage box, an alkali medicine storage box, a hydrogen peroxide medicine storage box and a surfactant medicine storage box through a feeding pipeline, the outlet of the cleaning liquid box is also led out of two branches through a liquid outlet pipeline and is respectively connected with the inlet and the outlet of the electrodialysis membrane stack, and two ends of the electrodialysis membrane stack are also connected with two poles of the rectifier. Compared with the prior art, the invention improves the problems that the existing ion exchange membrane cleaning only adopts a single chemical reagent, the cleaning efficiency is low, and the membrane performance gradually declines.
Description
Technical Field
The invention belongs to the technical field of membrane cleaning, and relates to a cleaning device and a cleaning method for an ion exchange membrane in an electrodialysis membrane stack.
Background
The ion exchange membrane is a material with a unique selective permeability function, can effectively separate each component in fluid under the drive of an electric field, and is widely applied to the fields of seawater desalination, wastewater zero discharge, landfill leachate treatment, reclaimed water reuse, chemical wastewater treatment, material separation, purification, concentration and the like.
In the process of electrodialysis operation, various inorganic matters, microorganisms, organic matters and oils in raw water are concentrated and enriched on the surface of the membrane, and dirt blocks the surface of the membrane and even membrane pores, so that the desalination rate is reduced, the membrane pollution is serious and inevitable, and chemical cleaning is an effective method for recovering the membrane flux. However, researches show that the chemical stability and the filtration performance of the membrane can be irreversibly degraded (namely, "membrane aging") after long-term chemical cleaning, the service life of the membrane is shortened, the stable operation of the membrane is influenced, the operation cost is increased, and the further popularization and application of the electrodialysis technology are restricted. Therefore, the development of a green and efficient cleaning technology is urgently needed, which not only can meet the membrane cleaning requirement, but also can correctly control the membrane aging process.
At present, the membrane cleaning agent existing in the market is only applied to a certain pollutant or a certain class of pollutants (such as oil or organic matters), and the application scene is narrow. For complex composite pollution caused by oil, organic matters and inorganic matters at the same time, the effect is often not good only by chemical cleaning. The invention is also based on this.
Disclosure of Invention
The invention aims to provide a device and a method for cleaning an ion exchange membrane in an electrodialysis membrane stack, and aims to solve the problems that the existing cleaning of the ion exchange membrane only adopts a single chemical reagent, the cleaning efficiency is low, and the membrane performance is gradually degraded.
The purpose of the invention can be realized by the following technical scheme:
one of the technical schemes of the invention provides a cleaning device for an ion exchange membrane in an electrodialysis membrane stack, which comprises a cleaning solution box, the electrodialysis membrane stack internally provided with the ion exchange membrane to be cleaned and a rectifier,
the cleaning solution box is further respectively connected with a water tank, an acid medicine storage box, a metal ion complexing agent medicine storage box, an alkali medicine storage box, a hydrogen peroxide medicine storage box and a surfactant medicine storage box through a feeding pipeline, the outlet of the cleaning solution box is also led out two branches through a liquid outlet pipeline and respectively connected with the inlet and the outlet of the electrodialysis membrane stack, and the two ends of the electrodialysis membrane stack are also connected with the two poles of the rectifier. Two poles of the rectifier are respectively connected with the ports of the electrodialysis membrane stack so as to apply equidirectional electricity or reverse electricity to the electrodialysis membrane stack (the equidirectional electricity is that the current direction is from the positive electrode to the negative electrode of the electrodialysis, and the reverse electricity is that the current direction is changed so that the positive electrode and the negative electrode of the electrodialysis are reversed).
Furthermore, a discharge pump is arranged on the liquid outlet pipeline, and stop valves are respectively arranged on branches connecting the inlet and the outlet of the electrodialysis membrane stack.
Furthermore, a filter and a micro-nano bubble generator are arranged on a branch path connected with the inlet of the electrodialysis membrane stack. Through strengthening chemical cleaning with micro-nano bubble technology, can high-efficiently get rid of remain at ion exchange membrane surface and the downthehole all kinds of pollutants of membrane, improve ion exchange membrane's desalination, guarantee ion exchange membrane's steady operation.
Further, the filter has a filtration accuracy of less than 10 microns.
Furthermore, a circulating cleaning pump is arranged on a branch connected with the inlet or the outlet of the electrodialysis membrane stack.
Furthermore, a stirrer is further arranged in the cleaning liquid tank.
Furthermore, the inlet of the electrodialysis membrane stack comprises a material inlet, an electrode chamber inlet and a concentration chamber inlet during desalination of the electrodialysis membrane stack, the outlet of the electrodialysis membrane stack comprises a material outlet, an electrode chamber outlet and a concentration chamber outlet during desalination of the electrodialysis membrane stack, and each inlet and each outlet are respectively connected into a branch of the electrodialysis membrane stack through an independently controlled stop valve.
The second technical scheme of the invention provides a cleaning method of an ion exchange membrane in an electrodialysis membrane stack, which is based on the cleaning device, and the cleaning method comprises water cleaning, primary acid cleaning, alkali cleaning and secondary acid cleaning which are sequentially carried out, wherein,
the water cleaning process specifically comprises the following steps: and (3) delivering water in the water tank into a cleaning liquid tank, pumping into the electrodialysis membrane stack, circularly cleaning, and discharging to finish the operation, wherein the temperature during circular cleaning is preferably 25-35 ℃, and the time for circular cleaning is 20-30 min, so as to obtain the water-washed membrane.
The primary pickling process comprises the following specific steps: pumping water in a water tank, an acidic reagent in an acid medicine storage tank and a metal ion complexing agent in a metal ion complexing agent medicine storage tank into a cleaning liquid tank, stirring, pumping into an electrodialysis membrane stack, circularly cleaning and discharging to finish. Specifically, the circulating cleaning time is 60-90 min, the pH value of the cleaning liquid in the primary acid cleaning process is controlled to be 2-3, and the content of the metal ion complexing agent is 0.2-2 wt%. The acidic cleaning agent used for adjusting the pH can be hydrochloric acid, oxalic acid or citric acid, etc. The metal ion complexing agent may be disodium edetate.
The alkali washing process specifically comprises the following steps: pumping water in a water tank, an alkaline reagent in an alkaline medicine storage tank, hydrogen peroxide in a hydrogen peroxide medicine storage tank and a surfactant in a surfactant medicine storage tank into a cleaning liquid tank, stirring, pumping into an electrodialysis membrane stack, circularly cleaning and discharging to finish. Specifically, the alkaline washing time is 60-90 min. The pH value of the alkaline cleaning solution is preferably 11-12, and an alkaline reagent used for adjusting the pH value can be sodium hydroxide or sodium carbonate. The surfactant is preferably sodium dodecyl benzene sulfonate and/or sodium dodecyl sulfate, and more preferably, the content of the sodium dodecyl benzene sulfonate in the alkaline cleaning solution is 0.05-0.1 wt%, and the content of the sodium dodecyl sulfate in the alkaline cleaning solution is 0.05-0.1 wt%. The content of hydrogen peroxide is 5-10 wt%.
The secondary acid washing process comprises the following specific steps: pumping water in the water tank and an acidic reagent in the acid medicine storage tank into a cleaning liquid tank, stirring, pumping into the electrodialysis membrane stack, circularly cleaning, and discharging to finish. Similarly, the pH of the cleaning solution with secondary acidity is controlled to be 2-3, and the acidic reagent can be hydrochloric acid, oxalic acid or citric acid.
Through repeated research, the components and the contents in the acidic cleaning solution and the alkaline cleaning solution are selected, the cleaning effect is not ideal when the using amount of each component of the acidic cleaning solution and the alkaline cleaning solution is too high or too low, the desalination rate of the ion exchange membrane can be obviously improved within the range, the resistance of the ion exchange membrane is reduced, and the stable operation of an electrodialysis system is ensured. An additional acid wash is added after the alkaline wash in order to restore the change in ion exchange membrane exchange groups caused by the alkaline wash.
Further, one or the combination of two of the processes of forward washing and back washing is independently adopted in water washing, primary acid washing, alkali washing and secondary acid washing respectively, wherein,
the forward washing process is to control the washing liquid in the circulating washing process to enter from the inlet of the electrodialysis membrane stack and then to be discharged from the outlet of the electrodialysis membrane stack, and the process is circulated;
and the backwashing process is to control the cleaning liquid in the circulating cleaning process to enter from the outlet of the electrodialysis membrane stack and then to be discharged from the inlet of the electrodialysis membrane stack, and the circulation is carried out.
Further, in the primary acid washing process, the rectifier is started and used for applying equidirectional electricity to the electrodialysis membrane stack;
during the alkaline washing process, the rectifier is turned on and used to apply a reverse current to the electrodialysis membrane stack.
According to the invention, through the synergistic effect of the micro-nano bubbles and the chemical agent, the contact area between the chemical agent and the pollutant is increased, and the active oxygen and the pollutant are generated due to high interface charges and cavitation, so that the analysis of the organic pollutant is promoted, and the using amount of the chemical agent is reduced.
Drawings
Fig. 1 is a schematic structural diagram of an ion exchange membrane cleaning apparatus according to the present invention.
The symbols in the figure illustrate:
the device comprises a 1-acid medicine storage box, a 2-metal ion complexing agent medicine storage box, a 3-alkali medicine storage box, a 4-hydrogen peroxide medicine storage box, a 5-surfactant medicine storage box, a 6-water tank, a 7-stirrer, an 8-cleaning liquid box, a 9-water pump, a 10-medicine feeding pump, an 11-discharging pump, a 12-filter, a 13-micro-nano bubble generator, a 14-electrodialysis membrane stack, a 15-rectifier and a 16-circulation cleaning pump.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
Electrodialysis pollution is mainly divided into inorganic pollution and organic pollution, wherein the inorganic pollution is caused by that high-salinity wastewater contains a large amount of calcium and magnesium ions which react with sulfate radicals, hydroxyl radicals and carbonate radicals in a solution to form scale on the surface of an ion exchange membrane, so that voltage is increased, and normal operation is influenced. Most of the organic matters are electronegative and are accumulated on the surface of an anion exchange membrane or enter the anion exchange membrane during the operation process of electrodialysis, so that organic pollution is caused. Ordinary acid and alkali washing can usually wash away the scale deposit on ion exchange membrane surface, organic deposit, and the inside partial scale deposit of positive membrane on the one hand, and the inside organic pollution of negative membrane can not be solved, can lead to the inside pollutant accumulation of ion exchange membrane more and more, makes ion exchange membrane's life-span significantly reduce, and on the other hand, the ion exchange group of ion exchange membrane can change after alkali washing, for example the quaternary ammonium group of negative membrane can change into tertiary ammonium group, and this can seriously influence ion exchange membrane's desalination ability.
In order to solve at least one of the above problems, the present invention provides a novel method and apparatus for cleaning an electrodialysis membrane stack 14.
The invention provides a cleaning device for an ion exchange membrane in an electrodialysis membrane stack, which is shown in figure 1 and comprises a cleaning solution box 8, an electrodialysis membrane stack 14 with an ion exchange membrane to be cleaned arranged inside, and a rectifier 15,
the cleaning solution box 8 is also respectively connected with a water tank 6, an acid medicine storage box 1, a metal ion complexing agent medicine storage box 2, an alkali medicine storage box 3, a hydrogen peroxide medicine storage box 4 and a surfactant medicine storage box 5 through a feeding pipeline, the outlet of the cleaning solution box 8 is also led out of two branches through a liquid outlet pipeline and is respectively connected with the inlet and the outlet of the electrodialysis membrane stack 14, and two ends of the electrodialysis membrane stack 14 are also connected with two electrodes of the rectifier 15. The two poles of the rectifier 15 are respectively connected with the ports of the electrodialysis membrane stack 14, so as to apply the same direction electricity or reverse direction electricity to the electrodialysis membrane stack 14 (the same direction electricity, namely the current direction, is from the positive pole to the negative pole of the electrodialysis, and the reverse direction electricity, namely the current direction is changed, so that the positive pole and the negative pole of the electrodialysis are reversed).
In some specific embodiments, the liquid outlet pipeline is further provided with a discharge pump 11, and the branches connecting the inlet and the outlet of the electrodialysis membrane stack 14 are further provided with a stop valve respectively.
In some specific embodiments, a filter 12 and a micro-nano bubble generator 13 are further disposed on a branch connecting an inlet of the electrodialysis membrane stack 14. Through strengthening chemical cleaning with micro-nano bubble technology, can high-efficiently get rid of remain at ion exchange membrane surface and the downthehole all kinds of pollutants of membrane, improve ion exchange membrane's desalination, guarantee ion exchange membrane's steady operation.
Further, the filter 12 has a filtration accuracy of less than 10 microns.
In some specific embodiments, a circulation cleaning pump 16 is further arranged on a branch connected with the inlet or the outlet of the electrodialysis membrane stack 14.
In some embodiments, the cleaning solution tank 8 is further provided with an agitator 7.
In some specific embodiments, the inlets of the electrodialysis membrane stack 14 include a material inlet, an electrode compartment inlet and a concentration compartment inlet when the electrodialysis membrane stack 14 is operated for desalination, and the outlets of the electrodialysis membrane stack 14 include a material outlet, an electrode compartment outlet and a concentration compartment outlet when the electrodialysis membrane stack 14 is operated for desalination, and each inlet and each outlet are respectively connected into a branch of the electrodialysis membrane stack 14 through a stop valve which is controlled independently.
The invention also provides a cleaning method of the ion exchange membrane in the electrodialysis membrane stack, which is based on the cleaning device and comprises water cleaning, primary acid cleaning, alkali cleaning and secondary acid cleaning which are sequentially carried out, wherein,
the water cleaning process specifically comprises the following steps: and (3) delivering water in the water tank 6 into a cleaning solution tank 8, pumping into the electrodialysis membrane stack 14, circularly cleaning, and discharging, wherein the temperature during circular cleaning is preferably 25-35 ℃, and the time for circular cleaning is 20-30 min, so as to obtain the water-washed membrane.
The primary pickling process comprises the following specific steps: pumping water in the water tank 6, an acidic reagent in the acid medicine storage box 1 and a metal ion complexing agent in the metal ion complexing agent medicine storage box 2 into a cleaning solution box 8, stirring, pumping into the electrodialysis membrane stack 14, circularly cleaning and discharging to finish. Specifically, the circulating cleaning time is 60-90 min, the pH value of the cleaning liquid in the primary acid cleaning process is controlled to be 2-3, and the content of the metal ion complexing agent is 0.2-2 wt%. The acidic cleaning agent used for adjusting the pH can be hydrochloric acid, oxalic acid or citric acid, etc. The metal ion complexing agent may be disodium edetate.
The alkali washing process specifically comprises the following steps: pumping water in the water tank 6, an alkaline reagent in the alkaline medicine storage box 3, hydrogen peroxide in the hydrogen peroxide medicine storage box 4 and a surfactant in the surfactant medicine storage box 5 into the cleaning liquid box 8, stirring, pumping into the electrodialysis membrane stack 14, circularly cleaning and discharging to finish. Specifically, the alkaline washing time is 60-90 min. The pH value of the alkaline cleaning solution is preferably 11-12, and the alkaline reagent used for adjusting the pH value can be sodium hydroxide or sodium carbonate. The surfactant is preferably sodium dodecyl benzene sulfonate and/or sodium dodecyl sulfate, and more preferably, the content of the sodium dodecyl benzene sulfonate in the alkaline cleaning solution is 0.05-0.1 wt%, and the content of the sodium dodecyl sulfate in the alkaline cleaning solution is 0.05-0.1 wt%. The content of hydrogen peroxide is 5-10 wt%.
The secondary acid washing process comprises the following specific steps: pumping the water in the water tank 6 and the acid reagent in the acid medicine storage tank 1 into the cleaning liquid tank 8, stirring, pumping into the electrodialysis membrane stack 14, circularly cleaning, and discharging to finish. Similarly, the pH of the cleaning solution with secondary acidity is controlled to be 2-3, and the acidic reagent can be hydrochloric acid, oxalic acid or citric acid.
Through repeated research, the components and the contents in the acidic cleaning solution and the alkaline cleaning solution are selected, the cleaning effect is not ideal when the using amount of each component of the acidic cleaning solution and the alkaline cleaning solution is too high or too low, the desalination rate of the ion exchange membrane can be obviously improved within the range, the resistance of the ion exchange membrane is reduced, and the stable operation of an electrodialysis system is ensured. An additional acid wash is added after the alkaline wash to restore the change in ion exchange membrane exchange groups caused by the alkaline wash.
In some embodiments, one or a combination of two forward washing and reverse washing processes are independently used in the water washing, the primary acid washing, the alkali washing and the secondary acid washing respectively, wherein,
the forward washing process is to control the washing liquid in the circulating washing process to enter from the inlet of the electrodialysis membrane stack 14 and then to be discharged from the outlet of the electrodialysis membrane stack, and the circulation is carried out;
the backwashing process is to control the cleaning liquid in the circulating cleaning process to enter from the outlet of the electrodialysis membrane stack 14 and then to be discharged from the inlet of the electrodialysis membrane stack, and the circulation is carried out.
Further, in the primary acid washing process, the rectifier 15 is turned on and is used for applying the same-direction electricity to the electrodialysis membrane stack 14;
during the alkaline washing process, the rectifier 15 is turned on and used to apply a reverse current to the electrodialysis membrane stack 14.
In the electrodialysis operation process, the generated inorganic scaling reaction is mainly concentrated in the concentration chamber and the polar chamber, and the organic pollution is mainly generated on the surface (the dilute chamber or the material chamber side) or inside the anion exchange membrane.
And electrifying in the same direction in the acid washing process, on one hand, the disodium ethylene diamine tetraacetate can complex calcium and magnesium metal ions to weaken the compactness of inorganic dirt, then hydrogen ions permeate the cationic membrane to clean magnesium hydroxide or calcium hydroxide precipitate generated by hydroxyl generated by electrolysis in membrane pores in the migration process of calcium and magnesium, and positive washing and back washing can clean scales generated on the surfaces of the anodic membrane and the polar chamber.
The alkali wash process can be through reverse circular telegram, make the dense-dilute room exchange, the hydroxyl can see through the negative membrane from original dense-dilute room and migrate to the dilute room, simultaneously because the existence of hydrogen peroxide and surfactant, can realize degrading, dissolving, peeling off and cleaing away organic pollutant with three's synergistic effect, and then accomplish the recovery to polluting the membrane performance in the short time, have high efficiency, convenient, the weak point's of consuming time advantage.
And a step of acid washing is added after the alkali washing, so that the ion groups on the ion exchange membrane are changed after the alkali washing, and the desalting performance of the ion exchange membrane can be recovered after the acid washing. Meanwhile, the cleaning process is always accompanied with the cooperative operation of the micro-nano bubble generator 13, the high mass transfer efficiency of the micro-nano bubbles not only improves the utilization rate of chemical agents, but also can generate hydroxyl radicals when the bubbles collapse, so that the hydroxyl radicals can indirectly and non-selectively react with organic pollutants, and the synergistic effect of the hydroxyl radicals and the chemical agents also promotes the degradation rate of the pollutants. Based on the technical scheme, the invention provides a novel cleaning technology which is characterized in that micro-nano bubbles and a chemical cleaning agent work cooperatively to control the aging process of the membrane on the basis of achieving the cleaning efficiency. The cleaning method can solve the problem of membrane surface and internal pollution, recover the membrane performance, and reduce the period of membrane replacement, thereby reducing the operating cost.
The following describes the method and apparatus for cleaning the electrodialysis membrane stack 14 in detail with reference to the accompanying drawings and specific examples.
Example 1:
the embodiment provides a cleaning device for an ion exchange membrane in an electrodialysis membrane stack, please refer to fig. 1, which includes a cleaning solution tank 8, an electrodialysis membrane stack 14 with an ion exchange membrane to be cleaned inside, and a rectifier 15,
the cleaning solution box 8 is also respectively connected with a water tank 6, an acid medicine storage box 1, a metal ion complexing agent medicine storage box 2, an alkali medicine storage box 3, a hydrogen peroxide medicine storage box 4 and a surfactant medicine storage box 5 through a feeding pipeline, the outlet of the cleaning solution box 8 is also led out of two branches through a liquid outlet pipeline and is respectively connected with the inlet and the outlet of the electrodialysis membrane stack 14, and two ends of the electrodialysis membrane stack 14 are also connected with two electrodes of the rectifier 15.
Referring to fig. 1 again, the liquid outlet pipeline is further provided with a discharge pump 11, and the branches connecting the inlet and the outlet of the electrodialysis membrane stack 14 are further provided with a stop valve respectively. A water pump 9 is arranged between the water tank 6 and the cleaning liquid tank 8, and a dosing pump 10 is arranged between each medicine storage tank and the cleaning liquid tank 8. And a circulating cleaning pump 16 is also arranged on a branch connected with the inlet or the outlet of the electrodialysis membrane stack 14, and a circulating cleaning loop for the electrodialysis membrane stack 14 is formed by the circulating cleaning pump 16 and the two branches connected with the electrodialysis membrane stack 14 in a matching manner.
Meanwhile, the discharge pump 11, the water pump 9, the dosing pump 10 and the like in the embodiment can all adopt fluoroplastic chemical pumps.
And a filter 12 and a micro-nano bubble generator 13 are also arranged on a branch path connected with the inlet of the electrodialysis membrane stack 14. Through strengthening chemical cleaning with micro-nano bubble technology, can high-efficiently get rid of remain at ion exchange membrane surface and the downthehole all kinds of pollutants of membrane, improve ion exchange membrane's desalination, guarantee ion exchange membrane's steady operation. The filter 12 has a filtration accuracy of less than 10 microns. And a stirrer 7 is also arranged in the cleaning liquid tank 8.
The inlet of the electrodialysis membrane stack 14 comprises a material inlet, an electrode chamber inlet and a concentration chamber inlet during desalination operation of the electrodialysis membrane stack 14, the outlet of the electrodialysis membrane stack 14 comprises a material outlet, an electrode chamber outlet and a concentration chamber outlet during desalination operation of the electrodialysis membrane stack 14, and each inlet and each outlet are respectively connected into a branch of the electrodialysis membrane stack 14 through an independently controlled stop valve.
The embodiment also provides a cleaning method of an ion exchange membrane in an electrodialysis membrane stack, which is based on the cleaning device, and the cleaning method comprises water cleaning, primary acid cleaning, alkali cleaning and secondary acid cleaning which are sequentially carried out, wherein,
the water cleaning process specifically comprises the following steps: and (3) feeding the water in the water tank 6 into a cleaning solution tank 8, pumping into the electrodialysis membrane stack 14, circularly cleaning, and discharging, wherein the temperature during circular cleaning is preferably 30 ℃, and the time for circular cleaning is 25min, so as to obtain the water-washed membrane.
The primary pickling process comprises the following specific steps: pumping water in the water tank 6, an acidic reagent in the acid medicine storage box 1 and a metal ion complexing agent in the metal ion complexing agent medicine storage box 2 into a cleaning solution box 8, stirring, pumping into the electrodialysis membrane stack 14, circularly cleaning and discharging to finish. Specifically, the time of circulating cleaning is 78min, the pH value of the cleaning solution in the primary acid cleaning process is controlled to be about 2.5, and the content of the metal ion complexing agent is 1 wt%. And the acidic cleaning agent used for adjusting the pH can be oxalic acid. The metal ion complexing agent is disodium ethylene diamine tetraacetate.
The alkali washing process specifically comprises the following steps: pumping water in the water tank 6, an alkaline reagent in the alkaline medicine storage box 3, hydrogen peroxide in the hydrogen peroxide medicine storage box 4 and a surfactant in the surfactant medicine storage box 5 into the cleaning liquid box 8, stirring, pumping into the electrodialysis membrane stack 14, circularly cleaning and discharging to finish. Specifically, the time of alkaline washing is 75 min. The pH value of the alkaline cleaning liquid is preferably about 11-12, and the alkaline reagent used for adjusting the pH value adopts sodium hydroxide. The surfactant is preferably sodium dodecyl benzene sulfonate and sodium dodecyl sulfate, and meanwhile, in the alkaline cleaning solution, the content of the sodium dodecyl benzene sulfonate is 0.08 wt%, and the content of the sodium dodecyl sulfate is 0.08 wt%. The hydrogen peroxide content was 8 wt%.
The secondary acid washing process comprises the following specific steps: pumping the water in the water tank 6 and the acid reagent in the acid medicine storage tank 1 into the cleaning liquid tank 8, stirring, pumping into the electrodialysis membrane stack 14, circularly cleaning, and discharging to finish. Similarly, the pH of the cleaning solution with secondary acidity is controlled to be 2.5, and the acidic reagent can be hydrochloric acid.
Through repeated research, the components and the contents in the acidic cleaning solution and the alkaline cleaning solution are selected, the cleaning effect is not ideal when the using amount of each component of the acidic cleaning solution and the alkaline cleaning solution is too high or too low, the desalination rate of the ion exchange membrane can be obviously improved within the range, the resistance of the ion exchange membrane is reduced, and the stable operation of an electrodialysis system is ensured. An additional acid wash is added after the alkaline wash in order to restore the change in ion exchange membrane exchange groups caused by the alkaline wash.
One or the combination of two of forward washing and back washing is independently adopted in water washing, primary acid washing, alkali washing and secondary acid washing respectively, wherein,
the forward washing process is to control the washing liquid in the circulating washing process to enter from the inlet of the electrodialysis membrane stack 14 and then to be discharged from the outlet of the electrodialysis membrane stack, and the circulation is carried out; specifically, referring to fig. 1, through valve cutting, the prepared cleaning solution is pumped into a filter 12, after the cleaning solution is filtered by a 10um filter 12, the cleaning solution enters a micro-nano bubble generator 13, a large amount of micro-nano bubbles are generated and pumped into an inlet of an electrodialysis membrane stack 14 along with the cleaning solution, at this time, each cut-off valve arranged at the inlet of the electrodialysis membrane stack 14 is opened, that is, the material, a polar chamber and a dense chamber during desalination operation of the membrane stack flow into the membrane stack from outlets of the membrane stack, then each cut-off valve at the outlet of the electrodialysis membrane stack 14 is opened, that is, the material, the polar chamber and the dense chamber during desalination operation of the membrane stack flow out of the membrane stack from outlets of the membrane stack, and then the material, the polar chamber and the dense chamber are recycled in the electrodialysis membrane stack 14 through a circulation loop and a circulation cleaning pump 16 formed by two branches. The remaining non-mentioned valves are closed. And the washing is finished and the washing can be discharged by opening the discharge valve.
The backwashing process is to control the cleaning liquid in the circulating cleaning process to enter from the outlet of the electrodialysis membrane stack 14 and then to be discharged from the inlet of the electrodialysis membrane stack, and the circulation is carried out. Specifically, the prepared cleaning solution is pumped into a circulating cleaning pump 16, a valve at the outlet of an electrodialysis membrane stack 14 is opened, the cleaning solution enters a material, a polar chamber and a concentration chamber during desalination operation of the membrane stack, then the valve at the inlet of the electrodialysis membrane stack 14 is opened, namely the cleaning solution flows out of the membrane stack from the material, the polar chamber and the concentration chamber during desalination operation of the membrane stack, is filtered by a micro-nano bubble generator 13 and a 10um filter 12, and is recycled in the electrodialysis membrane stack 14 through a circulating loop formed by two branches and the circulating cleaning pump 16. The remaining non-mentioned valves are closed. After the cleaning is finished, the cleaning liquid can be discharged by opening a discharge valve.
In addition, during one pickling process, the rectifier 15 is turned on and used to apply a co-current to the electrodialysis membrane stack 14 for 60s, for 10 cycles.
During the alkaline washing process, the rectifier 15 is turned on and used to apply a reverse current to the electrodialysis membrane stack 14 for 60s, with 10 cycles. During the secondary pickling process, the rectifier 15 does not need to be opened.
Example 2
After an electrodialysis membrane module for power plant desulfurization wastewater treatment is continuously operated for one month, serious irreversible pollution is generated, the desalination rate is reduced by 50%, and the device and the process method in the embodiment 1 are utilized for cleaning. Evaluation of cleaning performance: determination of salt rejection rate;
under the same measurement conditions, the salt rejection rates of the ion exchange membranes after the untreated desulfurization waste water, the treated desulfurization waste water and the cleaning were measured, respectively.
Comparative example 1:
compared with the embodiment 2, most of the cleaning steps are the same, and the functional part of the micro-nano bubble generator is omitted. The cleaning performance was evaluated in the same manner as in example 2.
Comparative example 2:
compared with example 2, most of the cleaning steps are the same, except that the secondary acid cleaning step is omitted. The cleaning performance was evaluated in the same manner as in example 2.
The results of evaluating the cleaning performance of example 2 and comparative examples 1 to 2 are shown in table 1.
TABLE 1 evaluation of cleaning Performance of example 2 and comparative examples 1 to 2
| D1 | D2 | D3 | Recovery ratio (%) | |
| Example 2 | 96.2 | 45.7 | 95.1 | 98.8 |
| Comparative example 1 | 96.2 | 46.1 | 75.9 | 78.9 |
| Comparative example 2 | 96.2 | 45.2 | 69..6 | 72.3 |
Remarking: d1 (%): the desalination rate of the ion exchange membrane without performing electrodialysis treatment on the desulfurization wastewater; d2 (%): the desalination rate of the ion exchange membrane for performing electrodialysis treatment on the desulfurization wastewater;
d3 (%): carrying out electrodialysis treatment on the desulfurization wastewater and the desalination rate of the cleaned ion exchange membrane;
recovery (%). D3/D1. multidot.100%
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. A cleaning device for an ion exchange membrane in an electrodialysis membrane stack is characterized by comprising a cleaning solution box, the electrodialysis membrane stack internally provided with the ion exchange membrane to be cleaned and a rectifier,
the cleaning solution box is further respectively connected with a water tank, an acid medicine storage box, a metal ion complexing agent medicine storage box, an alkali medicine storage box, a hydrogen peroxide medicine storage box and a surfactant medicine storage box through a feeding pipeline, the outlet of the cleaning solution box is also led out two branches through a liquid outlet pipeline and respectively connected with the inlet and the outlet of the electrodialysis membrane stack, and the two ends of the electrodialysis membrane stack are also connected with the two poles of the rectifier.
2. A device for cleaning ion exchange membranes in electrodialysis membrane stacks as claimed in claim 1, wherein the liquid outlet pipeline is further provided with a discharge pump, and the branches connecting the inlet and the outlet of the electrodialysis membrane stack are further provided with a stop valve respectively.
3. The device for cleaning the ion exchange membrane in the electrodialysis membrane stack as claimed in claim 1, wherein a filter and a micro-nano bubble generator are further provided on a branch connecting the inlet of the electrodialysis membrane stack.
4. A cleaning device for ion exchange membranes in electrodialysis membrane stack according to claim 3, wherein the filtration precision of the filter is less than 10 μm.
5. The device for cleaning the ion exchange membranes in the electrodialysis membrane stack as claimed in claim 1, wherein a circulation cleaning pump is further provided on a branch connecting the inlet or the outlet of the electrodialysis membrane stack.
6. An apparatus for cleaning ion exchange membranes in electrodialysis membrane stack according to claim 1, wherein the cleaning solution tank is further provided with a stirrer.
7. The device for cleaning the ion exchange membrane in the electrodialysis membrane stack according to claim 1, wherein the inlets of the electrodialysis membrane stack comprise a material inlet, an electrode compartment inlet and a concentration compartment inlet during desalination operation of the electrodialysis membrane stack, the outlets of the electrodialysis membrane stack comprise a material outlet, an electrode compartment outlet and a concentration compartment outlet during desalination operation of the electrodialysis membrane stack, and each inlet and each outlet are respectively connected into the branches of the electrodialysis membrane stack through a stop valve which is independently controlled.
8. A method for cleaning an ion exchange membrane in an electrodialysis membrane stack, which is based on the cleaning device as claimed in any one of claims 1 to 7, characterized in that the cleaning method comprises water cleaning, primary acid cleaning, alkali cleaning and secondary acid cleaning which are sequentially carried out, wherein,
the water cleaning process specifically comprises the following steps: water in the water tank is sent into a cleaning liquid tank, then pumped into the electrodialysis membrane stack, circularly cleaned and discharged, and then the operation is finished;
the primary pickling process comprises the following specific steps: pumping water in a water tank, an acidic reagent in an acid medicine storage tank and a metal ion complexing agent in a metal ion complexing agent medicine storage tank into a cleaning solution tank, stirring, pumping into an electrodialysis membrane stack, circularly cleaning and discharging to finish;
the alkali washing process specifically comprises the following steps: pumping water in a water tank, an alkaline reagent in an alkaline medicine storage tank, hydrogen peroxide in a hydrogen peroxide medicine storage tank and a surfactant in a surfactant medicine storage tank into a cleaning liquid tank, stirring, pumping into an electrodialysis membrane stack, circularly cleaning and discharging to finish;
the secondary acid washing process comprises the following specific steps: pumping water in the water tank and an acidic reagent in the acid medicine storage tank into a cleaning liquid tank, stirring, pumping into the electrodialysis membrane stack, circularly cleaning, and discharging to finish.
9. The method for cleaning the ion exchange membrane in the electrodialysis membrane stack as claimed in claim 8, wherein one or a combination of two of the forward washing and the back washing is independently adopted in the water cleaning, the primary acid cleaning, the alkali cleaning and the secondary acid cleaning respectively,
the forward washing process is to control the washing liquid in the circulating washing process to enter from the inlet of the electrodialysis membrane stack and then to be discharged from the outlet of the electrodialysis membrane stack, and the process is circulated;
and the backwashing process is to control the cleaning liquid in the circulating cleaning process to enter from the outlet of the electrodialysis membrane stack and then to be discharged from the inlet of the electrodialysis membrane stack, and the circulation is carried out.
10. The method for cleaning the ion exchange membranes in the electrodialysis membrane stack according to claim 8, wherein in one acid washing process, the rectifier is turned on and used for applying equidirectional electricity to the electrodialysis membrane stack;
during the alkaline washing process, the rectifier is turned on and used to apply a reverse current to the electrodialysis membrane stack.
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| CN115253686A (en) * | 2022-08-23 | 2022-11-01 | 同舟纵横（厦门）流体技术有限公司 | Impurity removal and desalination system and method for betaine feed liquid |
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| CN115253686A (en) * | 2022-08-23 | 2022-11-01 | 同舟纵横（厦门）流体技术有限公司 | Impurity removal and desalination system and method for betaine feed liquid |
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