WO2016019880A1 - 一种膜元件、使用该膜元件的装置及水处理方法 - Google Patents

一种膜元件、使用该膜元件的装置及水处理方法 Download PDF

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Publication number
WO2016019880A1
WO2016019880A1 PCT/CN2015/086209 CN2015086209W WO2016019880A1 WO 2016019880 A1 WO2016019880 A1 WO 2016019880A1 CN 2015086209 W CN2015086209 W CN 2015086209W WO 2016019880 A1 WO2016019880 A1 WO 2016019880A1
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water
membrane element
membrane
pure water
electrode
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PCT/CN2015/086209
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English (en)
French (fr)
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侯贻直
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艾欧史密斯（南京）水处理产品有限公司
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Publication of WO2016019880A1 publication Critical patent/WO2016019880A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
    • 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
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis

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  • the invention relates to a novel electrochemical self-cleaning membrane element, a device using the membrane element and a water treatment method, in particular to a novel membrane element and device for dissolving inorganic salt scale and improving the service life of the membrane element.
  • the reverse osmosis membrane element is a core component of the membrane water treatment technology, and is capable of removing microorganisms, ions, and the like from a water source to obtain pure water.
  • the existing reverse osmosis membrane elements are mainly used for the preparation of pure water through a reverse osmosis membrane under a certain pressure.
  • the produced wastewater has a higher concentration and hardness at the water outlet end, resulting in the membrane element being prone to inorganic salt scaling and reducing the service life of the membrane element.
  • small and medium-sized reverse osmosis treatment systems it is common to reduce the fouling of the membrane surface by adding a scale inhibitor and reducing the recovery rate.
  • the addition of scale inhibitors leads to an increase in wastewater while reducing fouling.
  • the technical problem to be solved by the present invention is to solve the problem of inorganic salt scaling on the surface of the diaphragm in the reverse osmosis or nanofiltration membrane element, to prolong the life of the membrane element, and to improve the recovery rate of the membrane element to some extent.
  • the reverse osmosis/nanofiltration membrane element of the present invention is developed on the basis of the existing reverse osmosis/nanofiltration membrane elements, and electrochemically produces H + , which dissolves the scale generated on the surface of the membrane and prolongs the use of the membrane element. life.
  • the reverse osmosis/nanofiltration membrane element of the present invention incorporates electrodes at the influent and pure water ends of conventional reverse osmosis/nanofiltration membrane elements, respectively, which are located on either side of the reverse osmosis/nanofiltration membrane.
  • an electrochemical self-cleaning membrane element characterized in that the membrane element comprises a membrane, a water inlet into the inlet end of the membrane, and waste water flowing out of the membrane.
  • the water outlet end and pure water flow out of the pure water end of the membrane, the membrane element further comprising a water inlet end electrode disposed in the influent water and a pure water end electrode disposed in the pure water, the pure
  • the water terminal electrode is connected to the negative pole of the power source, and the inlet electrode is connected to the positive pole of the power source Further, the distance between the inlet end electrode region and the inlet water flowing into the inlet end of the membrane is greater than the distance between the inlet end electrode region and the waste water outlet end of the wastewater flowing out of the membrane.
  • the inlet end electrode is located on the inlet side of the membrane, and/or the pure water end electrode is located on the pure water side of the membrane.
  • the distance B or B' ⁇ 2 cm between the inlet end electrode region and the waste water outlet end is the distance B or B' ⁇ 2 cm between the inlet end electrode region and the waste water outlet end.
  • the length of the pure water end electrode region is 1/3 to 1/2 of the effective length of the membrane in the flow direction of the inlet body; the width of the pure water terminal electrode region is perpendicular to 1/2 to 1 of the effective diaphragm width in the flow direction of the inlet body.
  • the degree of coincidence of the pure water end electrode region and the water inlet end electrode region is 80% or more, preferably 90% or more, and more preferably substantially completely.
  • the membrane element further has a sealant region, and the inlet end electrode region and the pure water end electrode region avoid the sealant region of the membrane.
  • the membrane element further comprises a pure water guide cloth and a water inlet grid, the pure water end electrode being arranged on the pure water guide cloth, the water inlet end electrode being arranged in the Into the water grid.
  • the inlet end electrode and/or the pure water end electrode are independently a filament, a sheet, a plate or a mesh electrode.
  • the membrane is a reverse osmosis membrane or a nanofiltration membrane.
  • the membrane element is a wound membrane element, a folded membrane element, a hollow fiber membrane element or a plate and frame membrane element.
  • the pure water end electrode is drawn from a pure water center pipe, a water inlet end or a waste water end, and the pure water end electrode is insulated by passing water and/or waste water.
  • a water treatment apparatus comprising the above membrane element.
  • the water treatment device further includes a water storage device connected to the pure water outlet end, a pump and a pre-filter element sequentially connected to the water inlet end of the membrane element, and the pure water outlet end of the membrane element is provided A return line connected to the inlet end of the membrane element.
  • the conduit is connected between the pre-filter element and the pump.
  • a water treatment method characterized in that water is treated using the above membrane element, wherein the electrode is energized This is done when the membrane element stops the water production operation.
  • the water-making operation process of the membrane element is divided into a plurality of operations, and at least one shutdown is performed after the completion of the water-making operation, and the energization time of the electrode is 10 to 50 minutes, preferably 20 to 40 minutes.
  • the electrode is energized in a plurality of times, and is energized for 5 to 15 minutes each time, and after each energization is completed, the water is operated for 1 to 3 minutes.
  • the water inlet side of the membrane is rinsed with pure water before the membrane element is shut down.
  • the novel electrochemical self-cleaning reverse osmosis/nanofiltration membrane element of the invention maintains the advantages of high salt rejection of the original membrane element, and can dissolve the surface of the membrane without applying any chemical agent by applying a certain current.
  • the formation of scale increases the service life of the membrane element; at the same time, the recovery rate can be improved to some extent.
  • Figure 1 is a schematic illustration of one embodiment of the present invention for use in a form of membrane element
  • Figure 2 is a schematic illustration of one embodiment of the present invention for use in another form of membrane element
  • Figure 3 is a schematic illustration of one embodiment of the present invention for use in another form of membrane element
  • Figure 4 is a schematic view of an electrochemical self-cleaning water treatment device
  • 1 denotes a diaphragm
  • 2 denotes a water inlet grid
  • 3 denotes a pure water guide cloth
  • 4 denotes a water collection tube
  • 5 denotes a pure water end electrode
  • 6 denotes a water inlet end electrode
  • 7 denotes a side glue and a seal Glue
  • 8 indicates the waterproof rubber zone.
  • A represents the effective length of the electrode wire or electrode sheet (plate) arrangement area in the direction of the main body of the influent water
  • B and B' represent the minimum distance of the electrode wire or the electrode sheet (plate) arrangement area from the waste water outlet in the direction of the discharge main body of the waste water. distance.
  • 1 denotes a pre-filter
  • 2 denotes a booster pump
  • 3 denotes a membrane element
  • 4 denotes a water storage tank
  • 5 denotes a pure water return valve.
  • the recovery rate pure water flow rate / influent water flow rate.
  • the standard flow rate is the pure water flow rate under standard conditions (25 ° C).
  • Static pressure external pressure - osmotic pressure.
  • Pure water flow rate is the ratio of standard flow to static pressure.
  • the pure water flow rate decay rate is a percentage of the current pure water flow rate decrease compared to the initial pure water flow rate.
  • the water flow enters the membrane element in the direction of the arrow, and after confluence in the membrane element, flows in a direction substantially perpendicular to the direction of water inlet (i.e., the direction of the arrow) (i.e., the length direction of the membrane element).
  • the main direction of the influent water flow refers to the longitudinal direction of the membrane element
  • A represents the distance between the arrangement area of the electrode wire or the electrode sheet (plate) in the flow direction of the main body of the influent water
  • B represents the electrode wire or the electrode sheet. (plate) The closest distance from the waste water outlet.
  • the wires connecting the pure water end electrodes are arranged through the water collecting pipe.
  • the water stream enters the membrane element in the direction of the arrow and then exits the membrane element in the direction of the arrow.
  • the main direction of the influent water flow refers to the width direction of the membrane element
  • A represents the distance of the arrangement area of the electrode wire or the electrode sheet (plate) in the flow direction of the main body of the influent water.
  • B' indicates the closest distance of the electrode wire or the electrode sheet (plate) from the waste water outlet end.
  • the water flow enters the membrane element in the direction of the arrow, and after confluence in the membrane element, flows in a direction substantially perpendicular to the direction of water inlet (i.e., the direction of the arrow) (i.e., the length direction of the membrane element).
  • the main direction of the influent water flow refers to the longitudinal direction of the membrane element
  • A represents the distance between the arrangement area of the electrode wire or the electrode sheet (plate) in the flow direction of the main body of the influent water
  • B represents the electrode wire or the electrode sheet. (plate) The closest distance from the waste water outlet.
  • a wire (not shown) connecting the pure water end electrode is not disposed through the water collecting pipe, and the pure water end electrode is in contact with the water and/or waste water portion for insulation treatment.
  • the influent water is filtered through the pre-filter 1 and then enters the membrane element 3 by the booster pump 2, and the pure water produced can be stored in a water storage tank, that is, the water storage tank 4, and the power is turned off.
  • the obtained pure water is rinsed back to the pump before returning to the pump to ensure that the concentration of the wastewater in the membrane element is low during the energization.
  • a pure water return valve 5 can be provided on the pure water return passage.
  • a control portion not shown in the drawing may be provided to control the time and current of energization and the like.
  • the electrodes are arranged in such a way that the inlet electrode is arranged on each of the inlet grids, adjacent to the wastewater outlet, such that the inlet electrode region and the influent flow into the membrane
  • the distance from the inlet end of the sheet is greater than the distance between the inlet end electrode region and the waste water outlet end of the waste water flowing out of the membrane, and the closest distance between the inlet end electrode region and the waste water outlet end is greater than or equal to 2 cm.
  • the pure water end electrode is arranged on each page of the pure water guide cloth, and the overlapping area of the pure water end electrode area and the inlet water electrode area is more than 25% to ensure a certain current intensity. If the overlap is too small, the resistance between the two electrodes will be too large, which will affect the descaling effect.
  • the overlapping portion is 80% or more, preferably 90% or more, and more preferably substantially completely coincident.
  • the length of the pure water end electrode is 1/3 to 1/2 of the effective length of the diaphragm in the flow direction of the water inlet body, thereby ensuring a certain current while ensuring the power supply period at the pure water end. generation of OH - to ensure that water pH to weakly alkaline range.
  • the electrodes can be located on both sides of the diaphragm and the electrodes can be mounted directly on the diaphragm.
  • the membrane element may further comprise a pure water guide cloth and a water inlet grid, and the electrodes may not be directly mounted on the membrane, but may be installed on the water inlet grid and the pure water guide cloth on both sides of the membrane.
  • the pure water end electrode is arranged on the pure water guide cloth, and the inlet end electrode is arranged on the water inlet grid.
  • the electrode material at the inlet end must be an inert electrode material, such as gold, platinum, silver, ruthenium coated titanium wire, platinum coated titanium wire, polymer conductive material, etc., and the pure water end electrode material can be a conductive material.
  • the electrode form of the influent water and the pure water end may be a filament, a sheet, a plate, a mesh, or the like.
  • the pure water terminal electrode should be connected to the negative pole of the power supply, and the inlet electrode should be connected to the positive pole of the power supply.
  • the membrane may be a reverse osmosis membrane or a nanofiltration membrane, or may be another semipermeable membrane.
  • the membrane element may have an encapsulation zone, and the inlet end electrode zone and the pure water end electrode zone should avoid the seal zone of the membrane.
  • the membrane element may further include a water collection tube.
  • the electrodes at the pure water end can be concentrated together and connected by the water collecting pipe to the pure water end of the membrane shell, or can be pulled out from the water inlet end or the wastewater end.
  • the portion of the pure water end electrode that passes through the influent and/or wastewater can be insulated.
  • the inlet electrode can be connected to the inlet end of the membrane shell.
  • the pure water end and the inlet end electrode are respectively connected to the negative electrode and the positive electrode of the direct current power source.
  • the membrane element may be a wound membrane element, a folded membrane element, a hollow fiber membrane element or a plate and frame membrane element. These membrane elements are known in the art.
  • the present invention also provides a water treatment device comprising the above membrane element. More specifically, as shown in FIG. 3, the apparatus further includes a pump and a pre-filter element sequentially connected to the inlet end of the membrane element, and the pure water outlet end of the membrane element is connected to the membrane element.
  • the water end conduit drains pure water to the inlet end of the membrane element to flush the remaining scale of the membrane element, preferably the line is connected between the pre-filter element and the pump.
  • the water outlet end includes a waste water outlet end and a pure water outlet end.
  • an anti-scaling electric power of 15 mA to 200 mA between the inlet end electrode and the pure water end electrode.
  • the flow and the anti-scaling current are preferably 20 to 100 mA. If the current is too small, sufficient anti-scaling effect cannot be guaranteed. Excessive current can cause ion accumulation and increase the tendency to foul.
  • the present invention also provides a water treatment method in which water is treated using a membrane element as described above.
  • the energization is carried out while the water is being produced.
  • the raw water end connected to the positive electrode generates H + , which dissolves the scale generated on the surface of the diaphragm and improves the service life of the membrane element.
  • the pure water end connected to the negative electrode produces OH - , and when water is produced, the water can be adjusted to be weakly alkaline.
  • the recovery rate can be improved to some extent.
  • the above technical solution has the following drawbacks: since the influent water contains a certain amount of Ca 2+ , Mg 2+ , etc., it is easy to accumulate on the surface of the diaphragm under the action of an electric field, thereby causing serious scaling near the electrode.
  • the membrane element is not energized during operation, and the energization is performed after the shutdown.
  • the Applicant has surprisingly found that the fouling near the electrode can be effectively avoided, and the pure water end can produce pure water with a high pH value. During operation, this part of the high pH pure water can adjust the water to be weakly alkaline.
  • the Applicant has found that high-concentration wastewater in the membrane element is cleaned by pure water before shutdown, and then an electric field is applied.
  • Flushing with pure water can replace the high-concentration wastewater in the element with water having a low ion content, thereby avoiding ion aggregation due to the presence of an electric field, and it is more preferable to avoid scale formation near the electrode.
  • the pure water can be directly used in the pure water produced in the present invention, that is, the pure water can be washed before it is returned to the membrane.
  • the electrode energization is performed when the membrane element stops the water production operation, that is, the shutdown is energized.
  • the water-making operation process of the membrane element can be divided into multiple runs, and the time of the water-making operation is determined according to the needs for water use, and is not particularly limited.
  • At least one shutdown energization may be performed after the end of the water production operation, and the energization time of the electrodes may be 10 to 50 minutes, preferably 20 to 40 minutes.
  • the flow of the water production method may be: water production - shutdown (power on) - water production - shutdown (power on) - water production - shutdown (power on) ..., in the process, the shutdown power is performed at least once, in some times After the water is produced, it can be stopped only and not powered. Therefore, with "stop (power on)", the energization is selectively performed as long as the energization is performed at least once. In addition, during the power-off process, the energization of the electrodes can be performed in multiple times, each time for 5 to 15 minutes, and after each power-on, the water is operated for 1 to 3 minutes.
  • the diaphragm can be rinsed with pure water after the end of energization, and a better anti-scaling effect can be obtained.
  • the water inlet side of the membrane may be rinsed with the purified pure water before the membrane element is shut down, wherein the pure water is flushed back to the membrane to rinse the inlet side of the membrane.
  • the reverse osmosis membrane element was filled with 7 10 cm long 0.5 mm diameter yttria-coated titanium wires as electrodes, pure water guide cloth. Seven 5cm long 0.5mm diameter yttria-coated titanium wires were added as electrodes, where A is the length of the short side of the pure water electrode arrangement area, which is 5cm, and B is the nearest electrode wire from the waste water outlet end. The distance between the ends is 5cm, and a new type of electrochemical self-cleaning roll membrane element is prepared.
  • the pure water end electrode wire is connected with the negative electrode of the DC power source, and the inlet electrode wire is connected with the positive electrode of the DC power source, and the pure water backflow is used before the shutdown.
  • the membrane element is cleaned. Specifically, the water-making operation process is divided into three times. After each water-making operation, the power-on cleaning is performed, and each time the power is turned off for about 30 minutes, and finally the water is made to be full. With this mode of operation, the pH of the pure water in the pressure tank can reach 7.9, and the pure water flow rate decay rate is 30% when the membrane element pure water reaches 10t.
  • a novel electrochemical self-cleaning roll membrane element is prepared, and the pure water end electrode wire is connected with the negative electrode of the DC power source, the inlet electrode wire is connected with the positive electrode of the DC power source, and the membrane element is cleaned by means of pure water reflux flushing before shutdown. .
  • the operation process is divided into 3 times. After each water-making operation, the power is cleaned, and each time the power is turned off for about 20 minutes, and finally the water is made until the water is full. With this mode of operation, the pH of the pure water in the pressure tank can reach 7.88, and the pure water flow rate decay rate is 30% when the membrane element pure water reaches 8t.
  • the membrane element was prepared as described in Example 1, and the membrane element was cleaned by means of pure water without reflux before shutdown.
  • the operation process was divided into 3 times, and each time the water was run, the power was cleaned, and each time the power was turned off for about 30 minutes. Finally, the water is made to fill the water.
  • the pH of the pure water in the pressure tank can reach 8.1, and the pure water flow rate decay rate has been reduced to 30% when the membrane element pure water reaches 4t.
  • the pure water flow rate is attenuated to 30%, the amount of water per little is small, and it can be seen that the pure water reflux cleaning effect is better than the non-reflow.
  • the membrane element was prepared as described in Example 1, when the water and pure water end electrode overlap area was 10%, the membrane element was cleaned by means of pure water reflux washing before shutdown, and the water production operation was divided into three times. After each water-making operation, the power is cleaned, and each time the power is turned off for about 40 minutes, and finally the water is made until the water is full. With this operation mode, the pH of the pure water in the pressure tank is 7, almost the same as the pH of the pure water when the electricity is not energized, and the pure water flow rate decay rate is 35% when the membrane element pure water reaches 4t.
  • the membrane element is prepared as described in the first embodiment, when the water and pure water terminal electrode overlap area is 80%, the membrane element is cleaned by means of pure water reflux washing before shutdown, and the water production operation process is divided into three times. After the second water production operation, the power is cleaned, the power is turned off for about 25 minutes, and finally the water is made to be full. With this mode of operation, the pH of the pure water in the water storage tank can reach 7.6, and the pure water flow rate decay rate is 35% when the membrane element pure water reaches 7t.
  • the membrane element is prepared as described in the first embodiment, when the water and pure water terminal electrode overlap area is 80%, the membrane element is cleaned by means of pure water reflux washing before shutdown, and the water production operation process is divided into three times. After each water-making operation, the power is turned off for about 25 minutes. The power-off is divided into two times. The first power-on is about 10 minutes, then the power is turned off, the water is made for 2 minutes, and the power is turned off for about 15 minutes. Finally, make water until the water is full. With this mode of operation, the pH of the pure water in the water storage tank can reach 7.8, and the pure water flow rate decay rate is 30% when the membrane element pure water reaches 8t.

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Abstract

一种膜元件、使用该膜元件的装置及水处理方法。该膜元件包含膜片（1）、进水流入膜片（1）的进水端、废水流出膜片（1）的废水出水端和纯水流出膜片（1）的纯水端，膜元件还包括设于进水中的进水端电极（6）和设于纯水中的纯水端电极（5），纯水端电极（5）与电源负极相连，进水端电极（6）与电源正极相连，进水端电极区域与进水流入膜片（1）的进水端的距离大于进水端电极区域与废水流出膜片（1）的废水出水端的距离。

Description

一种膜元件、使用该膜元件的装置及水处理方法 技术领域
本发明涉及一种新型的电化学自清洗膜元件、使用该膜元件的装置及水处理方法，特别是一种新型的溶解无机盐结垢，提高膜元件使用寿命的膜元件和装置。
背景技术
反渗透膜元件是膜法水处理技术的核心部件，能够去除水源中的微生物、离子等，得到纯水。目前已有的反渗透膜元件主要是在一定压力下通过反渗透膜达到纯水制备的目的。在使用反渗透膜元件对自来水进行处理的实际过程中，发现产生的废水出水端具有较高的浓度和硬度，导致膜元件易于发生无机盐结垢，降低膜元件的使用寿命。在中小规模的反渗透处理系统中，通常采用投加阻垢剂、降低回收率的方式来减少膜片表面的结垢。但投加阻垢剂在减少结垢的同时，又导致了废水的增加。
发明内容
技术问题
本发明所要解决的技术问题是解决反渗透或纳滤膜元件中膜片表面的无机盐结垢问题，延长膜元件寿命，并在一定程度上提高膜元件回收率。
技术方案
本发明的反渗透/纳滤膜元件的开发是在现有反渗透/纳滤膜元件的基础上，采用电化学的方法产生H+，溶解膜片表面产生的结垢，延长膜元件的使用寿命。本发明反渗透/纳滤膜元件是在传统的反渗透/纳滤膜元件的进水和纯水端分别加入了电极，所述电极分别位于反渗透/纳滤膜片两侧。
根据本发明的第一方面，提供了一种电化学自清洗膜元件，其特征在于所述膜元件包含膜片、进水流入所述膜片的进水端、废水流出所述膜片的废水出水端和纯水流出所述膜片的纯水端，所述膜元件还包括设于所述进水中的进水端电极和设于所述纯水中的纯水端电极，所述纯水端电极与电源负极相连，所述进水端电极与电源正极相 连，所述进水端电极区域与所述进水流入所述膜片的进水端的距离大于所述进水端电极区域与所述废水流出所述膜片的废水出水端的距离。
在上述膜元件中，所述进水端电极位于所述膜片上的进水侧，和/或所述纯水端电极位于所述膜片上的纯水侧。
在上述膜元件中，所述进水端电极区域与所述废水出水端的距离B或B’≥2cm。
在上述膜元件中，所述纯水端电极区域的长度为所述膜片在进水主体流动方向上有效长度的1/3～1/2；所述纯水端电极区域的宽度为垂直于进水主体流动方向上有效膜片宽度的1/2～1。
在上述膜元件中，所述纯水端电极区域与所述进水端电极区域的重合度为80％以上，优选为90％以上，更优选基本完全重合。
在上述膜元件中，所述膜元件还具有封胶区，所述进水端电极区域和所述纯水端电极区域避开所述膜片的封胶区。
在上述膜元件中，所述膜元件还包括纯水导布和进水格网，所述纯水端电极排布在所述纯水导布上，所述进水端电极排布在所述进水格网上。
在上述膜元件中，所述进水端电极与所述纯水端电极之间形成15mA～200mA，优选20～100mA的抗垢电流。
在上述膜元件中，所述进水端电极和/或纯水端电极独立地为丝状、片状、板状或网状电极。
在上述膜元件中，所述膜片为反渗透膜或纳滤膜。
在上述膜元件中，所述膜元件为卷式膜元件、折叠式膜元件、中空纤维膜元件或板框式膜元件。
在上述膜元件中，所述纯水端电极从纯水中心管、进水端或废水端牵引出，并对纯水端电极经过进水和/或废水的部分进行绝缘处理。
根据本发明的第二方面，提供了一种水处理装置，所述装置包含上述膜元件。
在上述水处理装置中，还包括与纯水出水端相连接的储水装置、与膜元件进水端依次相连接的泵和前置过滤元件，在所述膜元件的纯水出水端设有连接到膜元件进水端的回流管路。
在上述水处理装置中，所述管路连接至所述前置过滤元件和所述泵之间。
一种水处理方法，其特征在于，使用上述膜元件对水进行处理，其中，电极通电 在所述膜元件停止制水运行时进行。
在上述方法中，所述膜元件的制水运行过程分成多次运行，在制水运行结束后进行至少一次停机通电，所述电极的通电时间为10～50分钟，优选为20～40分钟。
在上述方法中，电极通电分为多次进行，每次通电5～15分钟，在每次通电结束后，制水运行1～3分钟。
在上述方法中，在所述膜元件停机前，用纯水冲洗所述膜片的进水侧。
在上述方法中，纯水以回流的方式回到膜前冲洗所述膜片的进水侧。
技术效果
本发明的新型电化学自清洗反渗透/纳滤膜元件保持了原膜元件高脱盐率的优点，并可以通过施加一定的电流，能够在不投加任何化学试剂的情况下，溶解膜片表面形成的结垢，增加膜元件使用寿命；同时，可以在一定程度上提高回收率。
附图说明
图1是本发明用于一种形式的膜元件中的一个实施方式的示意图；
图2是本发明用于另一种形式的膜元件中的一个实施方式的示意图；
图3是本发明用于另一种形式的膜元件中的一个实施方式的示意图；
图4是一种电化学自清洗水处理装置示意图；
在上述附图中，①表示膜片；②表示进水格网；③表示纯水导布；④表示集水管；⑤表示纯水端电极；⑥表示进水端电极；⑦表示边胶和封口胶；⑧表示防水胶区。A表示电极丝或电极片(板)布置区域在进水水流主体方向上的有效长度；B和B’表示电极丝或电极片(板)布置区在废水主体出水方向上距离废水出水口的最小距离。
在图4中，1表示前置滤芯；2表示增压泵；3表示膜元件；4表示储水桶；5表示纯水回流阀门。
具体实施方式
在本发明中，回收率＝纯水流量/进水流量。
标准流量为在标准条件下(25℃)的纯水流量。
静压力＝外压力-渗透压。
纯水流率为标准流量与静压力之比。纯水流率衰减率为相比于初始的纯水流率，当前纯水流率下降的百分比。
不同形式的膜元件，水流方向不同。如图1中所示，水流沿箭头方向进入膜元件，在膜元件中汇合后，沿与进水方向(即箭头方向)基本垂直的方向(即膜元件的长度方向)流动。在此情况下，进水水流主体方向就是指膜元件的长度方向，A表示电极丝或电极片(板)布置区域在进水水流主体流动方向上的距离，同时，B表示电极丝或电极片(板)距离废水出水端最近的距离。在图1中，连接纯水端电极的导线穿过集水管布置。
在图2中，水流沿箭头方向进入膜元件，然后沿箭头方向流出膜元件。在此情况下，进水水流主体方向就是指膜元件的宽度方向，A表示电极丝或电极片(板)布置区域在进水水流主体流动方向上的距离。B’表示电极丝或电极片(板)距离废水出水端的最近距离。
在图3中，水流沿箭头方向进入膜元件，在膜元件中汇合后，沿与进水方向(即箭头方向)基本垂直的方向(即膜元件的长度方向)流动。在此情况下，进水水流主体方向就是指膜元件的长度方向，A表示电极丝或电极片(板)布置区域在进水水流主体流动方向上的距离，同时，B表示电极丝或电极片(板)距离废水出水端最近的距离。在图3中，连接纯水端电极的导线(未示出)未穿过集水管布置，此时纯水端电极接触进水和/或废水的部分进行绝缘处理。
在图4中，进水通过前置滤芯1过滤后，在增压泵2的作用下进入到膜元件3中，产生的纯水可以储存到一个储水容器，即储水桶4中，停机通电前，采用得到的纯水以回流的方式回到泵前对膜元件3进行冲洗，保证通电过程中膜元件中的废水浓度较低。在纯水回流通路上，可以设置纯水回流阀门5。
另外，在本发明的膜元件或装置中，可以具有图中未示出的控制部，以控制通电的时间和电流等。
针对不同形式的膜元件，电极的安置方式为：进水端电极布置在每一页进水格网上，靠近废水出水端布置，使得所述进水端电极区域与所述进水流入所述膜片的进水端的距离大于所述进水端电极区域与所述废水流出所述膜片的废水出水端的距离，进水端电极区域与废水出水端的最近距离大于或等于2cm。通过该特征，可以保证停机通电过程中，进水端电极产生的H+可以直接溶解膜片废水出水端产生的无机盐结垢。 纯水端电极布置在每一页纯水导布上，纯水端电极区域与进水电极区域重叠面积在25％以上，以保证一定的电流强度。重叠部分过小，会导致两电极之间的电阻过大，从而影响除垢效果。该重叠部分为80％以上，优选为90％以上，更优选基本完全重合。
在本发明中，所述纯水端电极的长度为所述膜片在进水主体流动方向上有效长度的1/3～1/2，从而保证一定的电流，同时确保通电期间在纯水端产生的OH-能够保证纯水pH达到弱碱性范围。
电极可以位于膜片两侧，并且电极可以直接安装膜片上。另外，所述膜元件还可以包括纯水导布和进水格网，电极也可以未直接安装在膜片上，而是安装在膜片两侧的进水格网和纯水导布上。纯水端电极排布在纯水导布上，进水端电极则排布在进水格网上。对进水端的电极材料，必须为惰性电极材料，如金、铂、银、铱涂层钛丝、铂涂层钛丝、高分子导电材料等，纯水端电极材料为可导电材料即可，优选使用惰性材料。进水和纯水端的电极形式可以是丝状、片状、板状、网状等。纯水端电极应与电源负极相连，进水端电极与电源正极相连。所述膜片可以为反渗透膜或纳滤膜，也可以是其他半透膜。
所述膜元件可以具有封胶区，所述进水端电极区域和所述纯水端电极区域应当避开所述膜片的封胶区。
在本发明中，所述膜元件还可以包括集水管。纯水端的电极可以集中在一起由集水管穿出与膜壳纯水端相连，也可以由进水端或废水端牵引出来。对纯水端电极经过进水和/或废水的部分可以进行绝缘处理。进水端电极可以与膜壳进水端相连。纯水端和进水端电极分别与直流电源的负极和正极相连。
所述膜元件可以为卷式膜元件、折叠式膜元件、中空纤维膜元件或板框式膜元件。这些膜元件是本领域已知的。
本发明还提供了一种水处理装置，所述装置包含上述膜元件。更具体而言，如图3所示，所述装置还包括与膜元件进水端依次相连接的泵和前置过滤元件，在所述膜元件的纯水出水端设有连接到膜元件进水端的管路，将纯水引流至膜元件的进水端以冲洗膜元件残存的垢，优选所述管路连接至所述前置过滤元件和所述泵之间。另外，出水端包括废水出水端和纯水出水端。
在本发明中，进水端电极与纯水端电极之间需要形成15mA～200mA的抗垢电 流，抗垢电流优选20～100mA。电流过小，则无法保证足够的抗垢效果。电流过大，可能会导致离子积聚，增加结垢倾向。
本发明还提供了一种水处理方法，其中使用如上述的膜元件对水进行处理。
一般而言，通电是在制水时进行。在通电条件下，连接正极的原水端产生H+，从而溶解膜片表面产生的结垢，提高膜元件使用寿命。另外，连接负极的纯水端产生OH-，制水时，可以调节出水为弱碱性。同时，可在一定程度上提高回收率。但是，上述技术方案存在以下缺陷：由于进水中含有一定量的Ca2+和Mg2+等，使其易于在电场作用下在膜片表面聚集，从而导致电极附近的结垢较为严重。运行时外加电场容易造成电极附近较为严重的结垢现象。与此相反，在本发明中，膜元件在运行过程中电极不通电，通电在停机后进行。采用该方式，申请人惊讶地发现，可以有效避免电极附近结垢，同时纯水端可以产生高pH值的纯水，运行时此部分高pH值的纯水可调节出水为弱碱性。同时，申请人发现，通过停机前采用纯水对膜元件中的高浓度废水进行清洗，然后再后施加电场。采用纯水进行冲洗可以将元件中的高浓度废水置换为离子含量低的水，从而避免了因电场存在而引起的离子聚集，可以更好地避免电极附近结垢，因此更加优选。所述纯水可以直接使用本发明中制得的纯水，即可以使纯水回流至膜片之前对膜片进行清洗。
即，根据本发明的方法，电极通电在所述膜元件停止制水运行时进行，即为停机通电。所述膜元件的制水运行过程可以分成多次运行，制水运行的时间根据用于用水需要而定，不进行特别限定。在制水运行结束后可以进行至少一次停机通电，电极的通电时间可以为10～50分钟，优选为20～40分钟。即，制水方法的流程可以为：制水-停机(通电)-制水-停机(通电)-制水-停机(通电)…，在该过程中，停机通电至少进行一次，在某些次制水之后，可以只停机，不通电。因此，用“停机(通电)”表示，通电是选择性进行的，只要满足进行至少一次停机通电即可。另外，在停机通电过程中，电极的通电可以分多次进行，每次通电5～15分钟，每次通电结束后，制水运行1～3分钟。采用这种运行方式，可以在通电结束后，用制得的纯水冲洗一下膜片，可以取得更好的防结垢效果。在所述膜元件停机前，可以用制得的纯水冲洗所述膜片的进水侧，其中纯水以回流的方式回到膜前冲洗所述膜片的进水侧。
实施例
实施例1
在1810-75G-ss侧流式(图1所示膜元件结构)反渗透膜元件的进水格网中加入7根10cm长的0.5mm直径氧化铱涂层钛丝作为电极，纯水导布中加入7根5cm长的0.5mm直径的氧化铱涂层钛丝作为电极，其中A为纯水电极布置区域短边的长度，即为5cm，B为离废水出水端最近的电极丝距离废水出水端的距离，为5cm，制备新型电化学自清洗的卷式膜元件，将纯水端电极丝与直流电源负极相连，进水端电极丝与直流电源正极相连，采用停机前纯水回流冲洗的方式对膜元件进行清洗。具体而言，制水运行过程分为3次进行，在每次制水运行后进行通电清洗，每次停机通电约30min，最后制水至水满。采用该运行方式，压力桶中的纯水pH可达到7.9，膜元件纯水过水量达到10t时，纯水流率衰减率为30％。
实施例2
在1810-75G(图2所示膜元件结构)反渗透膜元件的进水格网中加入7根10cm长的0.5mm直径氧化铱涂层钛丝作为电极，纯水导布中加入7根10cm长的0.5mm直径的氧化铱涂层钛丝作为电极，其中A为纯水电极布置区域短边的长度，即为10cm，B为离废水出水端最近的电极丝距离废水出水端的距离，为5cm，制备新型电化学自清洗的卷式膜元件，将纯水端电极丝与直流电源负极相连，进水端电极丝与直流电源正极相连，采用停机前纯水回流冲洗的方式对膜元件进行清洗。运行过程分为3次进行，每次制水运行后进行通电清洗，每次停机通电约20min，最后制水至水满。采用该运行方式，压力桶中的纯水pH可达到7.88，膜元件纯水过水量达到8t时，纯水流率衰减率为30％。
实施例3
如实施案例1所述制备膜元件，采用停机前纯水不回流冲洗的方式对膜元件进行清洗，运行过程分为3次进行，每次制水运行后进行通电清洗，每次停机通电约30min，最后制水至水满。采用该运行方式，压力桶中的纯水pH可达到8.1，膜元件纯水过水量达到4t时，纯水流率衰减率已降为30％。与实施例1相比，其纯水流率衰减到30％时，过水量较少，可以看出纯水回流清洗效果比不回流好。
实施例4
如实施案例1所述制备膜元件，其进水和纯水端电极重叠面积为10％时，采用停机前纯水回流冲洗的方式对膜元件进行清洗，制水运行过程分为3次进行，每次制水运行后进行通电清洗，每次停机通电约40min，最后制水至水满。采用该运行方式，压力桶中的纯水pH为7，几乎与未通电时纯水pH相同，膜元件纯水过水量达到4t时，纯水流率衰减率为35％。
实施例5
如实施案例1所述制备膜元件，其进水和纯水端电极重叠面积为80％时，采用停机前纯水回流冲洗的方式对膜元件进行清洗，制水运行过程分为3次进行，在第二次制水运行后进行通电清洗，停机通电约25min，最后制水至水满。采用该运行方式，储水桶中的纯水pH可达到7.6，膜元件纯水过水量达到7t时，纯水流率衰减率为35％。
实施例6
如实施案例1所述制备膜元件，其进水和纯水端电极重叠面积为80％时，采用停机前纯水回流冲洗的方式对膜元件进行清洗，制水运行过程分为3次进行，每次制水运行结束后停机通电约25min，该停机通电分为2次进行，第一次通电约10min，然后停止通电，制水2分钟，再停机通电约15分钟。最后制水至水满。采用该运行方式，储水桶中的纯水pH可达到7.8，膜元件纯水过水量达到8t时，纯水流率衰减率为30％。

Claims (20)

  1. 一种膜元件，其特征在于，所述膜元件包含膜片、进水流入所述膜片的进水端、废水流出所述膜片的废水出水端和纯水流出所述膜片的纯水端，所述膜元件还包括设于所述进水中的进水端电极和设于所述纯水中的纯水端电极，所述纯水端电极与电源负极相连，所述进水端电极与电源正极相连，所述进水端电极区域与所述进水流入所述膜片的进水端的距离大于所述进水端电极区域与所述废水流出所述膜片的废水出水端的距离。
  2. 如权利要求1所述的膜元件，其中，所述进水端电极位于所述膜片上的进水侧，和/或所述纯水端电极位于所述膜片上的纯水侧。
  3. 如权利要求1所述的膜元件，其中，所述进水端电极区域与所述废水出水端的距离B或B’≥2cm。
  4. 如权利要求1或2所述的膜元件，其中，所述纯水端电极区域的长度为所述膜片在进水主体流动方向上有效长度的1/3～1/2；所述纯水端电极区域的宽度为垂直于进水主体流动方向上有效膜片宽度的1/2～1。
  5. 如权利要求1或2所述的膜元件，其中，所述纯水端电极区域与所述进水端电极区域的重合度为80％以上，优选为90％以上，更优选基本完全重合。
  6. 如权利要求1或2所述的膜元件，其中，所述膜元件还具有封胶区，所述进水端电极区域和所述纯水端电极区域避开所述膜片的封胶区。
  7. 如权利要求1或2所述的膜元件，其中，所述膜元件还包括纯水导布和进水格网，所述纯水端电极排布在所述纯水导布上，所述进水端电极排布在所述进水格网上。
  8. 如权利要求1或2所述的膜元件，其中，所述进水端电极与所述纯水端电极之间形成15mA～200mA，优选20～100mA的抗垢电流。
  9. 如权利要求1或2所述的膜元件，其中，所述进水端电极和/或纯水端电极独立地为丝状、片状、板状或网状电极。
  10. 如权利要求1或2所述的膜元件，其中，所述膜片为反渗透膜或纳滤膜。
  11. 如权利要求1或2所述的膜元件，其中，所述膜元件为卷式膜元件、折叠式膜元件、中空纤维膜元件或板框式膜元件。
  12. 如权利要求1或2所述的膜元件，其中，所述纯水端电极从纯水中心管、进水端或废水端牵引出，并对纯水端电极经过进水和/或废水的部分进行绝缘处理。
  13. 一种水处理装置，其特征在于，所述装置包含权利要求1～12任一项所述的膜元件。
  14. 如权利要求13所述的水处理装置，其特征在于，还包括与纯水出水端相连接的储水装置、与膜元件进水端依次相连接的泵和前置过滤元件，在所述膜元件的纯水出水端设有连接到膜元件进水端的回流管路。
  15. 如权利要求14所述的水处理装置，其特征在于，所述管路连接至所述前置过滤元件和所述泵之间。
  16. 一种水处理方法，其特征在于，使用如权利要求1～12任一项所述的膜元件对水进行处理，其中，电极通电在所述膜元件停止制水运行时进行，即为停机通电。
  17. 如权利要求16所述的方法，其中，所述膜元件的制水运行过程分成多次运行，在制水运行结束后进行至少一次停机通电，所述电极的通电时间为10～50分钟，优选为20～40分钟。
  18. 如权利要求17所述的方法，其中，电极通电分为多次进行，每次通电5～15分钟，在每次通电结束后，制水运行1～3分钟。
  19. 如权利要求16或17所述的方法，其中，在所述膜元件停机前，用纯水冲洗所述膜片的进水侧。
  20. 如权利要求16或17所述的方法，其中，纯水以回流的方式回到膜前冲洗所述膜片的进水侧。
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