CN115626686B

CN115626686B - Cleaning system and cleaning method of ultrapure water equipment

Info

Publication number: CN115626686B
Application number: CN202210848270.2A
Authority: CN
Inventors: 巩泉雨; 区灿林; 周维
Original assignee: BYD Co Ltd; BYD Auto Co Ltd
Current assignee: BYD Co Ltd; BYD Auto Co Ltd
Priority date: 2022-07-19
Filing date: 2022-07-19
Publication date: 2023-07-14
Anticipated expiration: 2042-07-19
Also published as: CN115626686A

Abstract

The application provides a cleaning system and a cleaning method of ultrapure water equipment. This cleaning system has set up liquid medicine reservoir and pipeline that matches with it at reverse osmosis module and EDI module respectively for reverse osmosis module can possess the pickling process, EDI module can possess acid and alkali and synthesize the cleaning process, can fully clean the core module of ultrapure water equipment, thereby can guarantee that the inside cleanliness factor of core module is higher, improve the quality stability of producing water, extension core module's life.

Description

Cleaning system and cleaning method of ultrapure water equipment

Technical Field

The application relates to the technical field of water treatment, in particular to a cleaning system and a cleaning method of ultrapure water equipment.

Background

At present, the industry often adopts equipment with a reverse osmosis module and an Electrodeionization (EDI) module to manufacture ultrapure water (the resistivity of water is about 18MΩ & cm), but long-time operation can lead to the generation of carbonate, sulfate, colloid and other organic pollutants which remain and are indissoluble in metal ions in the reverse osmosis system and the EDI module, so that the water yield is reduced, the water quality is poor, and the production water requirement cannot be met. Generally, the method of replacing the core assembly or directly using acid liquor to circularly wash the core assembly is adopted in the industry to solve the above problems, but the former has high maintenance cost, and the latter has poor cleaning effect and is easy to erode the core assembly.

Disclosure of Invention

In view of this, the present application provides a cleaning system for an ultrapure water device. This cleaning system has set up liquid medicine reservoir and pipeline that matches with it at reverse osmosis module and EDI module respectively for reverse osmosis module can possess the pickling process, EDI module can possess acid and alkali and synthesize the cleaning process, can fully clean the core module of ultrapure water equipment, thereby can guarantee that the inside cleanliness factor of core module is higher, improve the quality stability of producing water, extension core module's life.

The first aspect of the application provides a cleaning system of an ultrapure water device, which comprises the ultrapure water device and a cleaning device, wherein the ultrapure water device comprises a reverse osmosis module and an electrodeionization EDI module which are connected, the cleaning device comprises a first pickling agent storage tank, a second pickling agent storage tank and an alkaline agent storage tank, the first pickling agent storage tank is communicated with the reverse osmosis module, and the second pickling agent storage tank and the alkaline agent storage tank are communicated with the EDI module;

wherein the first pickling agent is used for downstream cleaning of the reverse osmosis module; the second pickling agent is used for cleaning the EDI module in a downstream mode, and the alkaline cleaning agent is used for circularly cleaning the EDI module.

The cleaning system can be obtained by simply modifying the pipeline of the existing ultrapure water equipment, and has the advantages of simple equipment, low manufacturing cost, convenient operation and high cleaning efficiency.

Accordingly, a second aspect of the present application provides a cleaning method of an ultrapure water device, including:

(1) Sequentially adopting a first pickling agent and water to clean the reverse osmosis module in a downstream way; wherein the first pickling agent comprises at least one of hydrochloric acid and phosphoric acid, and the pH value of the first pickling agent is in the range of 1-5;

(2) Sequentially adopting a second pickling agent and water to clean the EDI module in a downstream way, and then adopting water circulation to clean the EDI module; the second pickling agent comprises an organic weak acid and does not contain strong acid, and the organic weak acid comprises at least one of citric acid, acetic acid and oxalic acid; wherein the volume fraction of the organic weak acid is in the range of 1.5% -3%;

sequentially adopting alkali lotion and water circulation to clean the EDI module; wherein the alkaline detergent comprises a mixed solution of an organic alkali and an inorganic strong alkali, the organic alkali comprises tetramethyl ammonium hydroxide, and the inorganic strong alkali comprises sodium hydroxide and/or potassium hydroxide; wherein the volume percent of the tetramethyl ammonium hydroxide is in the range of 1-3%, and the volume percent of the sodium hydroxide is in the range of 0.3-0.8%.

The dirt particles in the reverse osmosis module are relatively larger, the concentration of the first pickling agent is larger, the acidity is stronger, large-size particle dirt and impurities (refractory stains such as calcium and magnesium impurities and indissolvable organic matters) in the reverse osmosis module can be flushed away, and the large-size flushed particle dirt can be taken away by subsequent forward water flushing, so that secondary pollution is avoided. Therefore, the reverse osmosis module can be cleaned by adopting forward flow cleaning, so that the replacement frequency of the reverse osmosis membrane can be obviously reduced, the quality of water entering the EDI module is improved, and the workload of the EDI module is reduced. The traditional cyclic acid washing has larger flushing pressure on the pipeline inside the equipment, which can lead to the secondary adhesion of the intractable impurities under flushing, and the cyclic acid washing has larger corrosion on the module, which can damage the performance of the equipment and reduce the service life of the equipment.

The EDI module is relatively more precise, the particles of the internal dirt are smaller, and the metal ion impurities are more. The EDI module is washed directly through by adopting the second pickling agent with the main component of organic weak acid in a downstream way, so that metal ions attached to an EDI module component can be chelated to form metal ion chelates, the metal ion chelates can be removed by subsequent alkaline detergents, metal oxides, iron-aluminum colloids, indissolvable carbonates and sulfates remained in the EDI module can be removed, the surface performance of an inner pipeline of the EDI module is improved, and an environment foundation is provided for subsequent alkaline washing, so that the purpose of thoroughly cleaning the EDI module is facilitated. The subsequent cyclic alkaline washing process is adopted, and the larger washing pressure brought by the cyclic washing can better wash down the metal ion chelate attached on the internal pipeline, and better neutralize the weak acid environment inside the EDI module. Likewise, the circulating water washing after the concurrent acid washing and the circulating alkali washing can take away the impurities washed by the acid washing and the alkali washing, so that secondary pollution is avoided.

In conclusion, according to the different characteristics of the reverse osmosis module and the EDI module, the reverse osmosis module is cleaned in a downstream pickling mode, and the EDI module is organically combined with a downstream pickling process and a circulating alkaline washing process, so that the cleaning effect can be considered, and the risk of damaging equipment is reduced.

Drawings

FIG. 1 is a schematic flow diagram of an apparatus for an ultrapure water plant;

FIG. 2 is a schematic diagram of an apparatus for a cleaning system for an ultrapure water device according to an embodiment of the present application.

Description of the drawings: 11-reverse osmosis module; 111-a first pickling agent storage tank; a 12-EDI module; 121-a second pickling agent storage tank; 122-alkaline detergent storage tank.

Detailed Description

Currently, the production of semiconductor devices and their raw materials (e.g., silicon carbide, etc.) requires the use of large amounts of ultrapure water (resistivity up to 18mΩ·cm). Referring to fig. 1, an ultrapure water apparatus commonly used in industry generally includes a pretreatment device, a reverse osmosis module, an EDI module and a polishing mixed bed, which are sequentially connected, wherein the pretreatment device generally includes a multi-stage filter, the reverse osmosis module generally includes a first-stage reverse osmosis module and a second-stage reverse osmosis module, each reverse osmosis module is internally provided with a Reverse Osmosis (RO) membrane and inner pipelines of each stage, the EDI module is an organic combination of electrodialysis and ion exchange, and has a multi-stage anion/cation exchange membrane therein, and an ion exchange resin filled between the multi-stage anion/cation exchange membrane and the inner pipelines of each stage (such as a concentrate pipeline, an ion exchange channel, a water production pipeline, etc.), and the polishing mixed bed further improves water quality by using the ion exchange resin. In the process of preparing ultrapure water, the pretreated water obtained by the pretreatment device is generally treated by a reverse osmosis module, an EDI module and a polished resin bed in sequence to obtain ultrapure water. But the pretreated water still contains various metal ions, such as calcium ions, magnesium ions, iron ions and the like, and also contains a certain amount of organic pollutants. Therefore, after the ultrapure water machine is used for a long time, pollutants are accumulated in the ultrapure water machine, and the pollutants comprise metal ions, calcium-magnesium precipitates, iron-aluminum colloid and other indissoluble organic pollutants. The accumulation of the pollutants can cause high-load operation of equipment, water yield reduction and water quality reduction, and cannot meet the requirements of industrial production.

As the reverse osmosis module and the EDI module of the ultra-pure water equipment core component, the cleaning degree of the interior determines the quality of produced water, and the quantity of dirt in the reverse osmosis module is relatively large and stubborn stains are relatively large according to the operation mechanism of the ultra-pure water equipment. The number of impurities inside the EDI module is relatively small, but the EDI module is more precise. In the traditional process, a single pickling cleaning reverse osmosis module and an EDI module are directly adopted, but impurities inside the EDI module cannot be cleaned by adopting a downstream cleaning process, equipment can be corroded by adopting cyclic pickling, and the service life of the equipment is seriously influenced. It is found that it is difficult to efficiently and thoroughly clean the ultrapure water system in a nondestructive state and to maintain high-load and high-quality operation of the ultrapure water system. In order to solve the above problems, an embodiment of the present application provides a cleaning system for an ultrapure water device.

Referring to fig. 2, an embodiment of the present application provides a cleaning system of an ultrapure water device, including an ultrapure water device and a cleaning apparatus, the cleaning apparatus includes a first pickling agent storage tank 111, a second pickling agent storage tank 121, and an alkaline cleaning agent storage tank 122, the first pickling agent storage tank 111 is communicated with a reverse osmosis module 11, and the second pickling agent storage tank 121, the alkaline cleaning agent 122 storage tank is communicated with an EDI module 12.

It will be appreciated that a communication pipe is provided between each storage tank and the water inlet of each module, and that a valve may be provided on the pipe. Communication pipelines are also arranged between the modules and between the structures of all levels in the modules.

In this application, the reverse osmosis module 11 includes a first-stage reverse osmosis module and a second-stage reverse osmosis module, and the inlet water of the reverse osmosis module 11 is pretreated water, and the inlet water of the EDI module 12 is second-stage reverse osmosis water obtained after reverse osmosis treatment.

In this application, above-mentioned reverse osmosis module's belt cleaning device can set up in one-level reverse osmosis module department, also can set up in second grade reverse osmosis module department, can also all set up in one-level, second grade reverse osmosis module department.

The first pickling agent is used for downstream cleaning of the reverse osmosis module 11; the second pickling agent is used for downstream cleaning of the EDI module 12, and the alkaline cleaning agent is used for circulating cleaning of the EDI module 12.

Wherein, downstream cleaning specifically means: from the water inlet (I) of the reverse osmosis module 11 or EDI module 12, water or liquid medicine lotion ₁ Or I ₂ ) Pumping water or lotion along the pipeline inside the module by a certain flushing water pump, and discharging water from the water outlet (O) ₁ Or O ₂ ) And discharging the waste liquid into a waste liquid collecting device. The cyclic cleaning specifically means: after the water outlet of the EDI module is closed, water or alkali detergent is taken from the water inlet I of the EDI module ₂ Pumping with a certain flushing water, and closing the water inlet I of the EDI module when a preset amount is reached ₂ The water or alkaline detergent circularly flows in the EDI module under a certain water pressure, and after a certain time, the waste liquid is discharged from the water outlet O ₂ Pumped out and discharged into a waste liquid collecting device.

In some embodiments of the present application, the second pickling agent storage tank 121 communicates with the EDI module 12 through a first conduit, and the alkaline cleaning agent storage tank 122 communicates with the EDI module 12 through a second conduit.

In other embodiments of the present application, the second pickling agent storage tank 121 and the alkaline agent storage tank 122 are in communication with the EDI module 12 via a first conduit that is remote from the EDI module water inlet I ₂ The first branch communicates with the second pickling agent storage tank 121 and the second branch communicates with the alkaline detergent storage tank 122.

In some cases, the second pickling agent and alkaline agent may be stored in the same tank in stages. At this time, when the lotion is replaced, the liquid storage tank may be washed with water first.

In this application, in some cases, other medical fluid storage tanks, for example, a non-oxidative sterilizing agent storage tank, may be additionally provided to the reverse osmosis module 11 and/or the EDI module 12.

Accordingly, the embodiment of the application also provides a cleaning method of the ultra-pure water device, which comprises the steps of cleaning the reverse osmosis module 11 and the EDI module 12. In the present application, the cleaning sequence of the reverse osmosis module 11 and the EDI module 12 is not particularly limited. The reverse osmosis module 11 may be cleaned first, or the EDI module 12 may be cleaned first, or even the reverse osmosis module 11 and the EDI module 12 may be cleaned simultaneously.

The step of cleaning the reverse osmosis module 11 includes: the reverse osmosis module 11 is cleaned by adopting a first pickling agent and water in sequence; wherein the first pickling agent comprises at least one of hydrochloric acid and phosphoric acid, and the pH value of the first pickling agent is in the range of 1-5. The first pickling agent (hydrochloric acid, phosphoric acid aqueous solution) is adopted for downstream cleaning, so that insoluble stains such as calcium carbonate, calcium sulfate and most insoluble organic matters in the reverse osmosis module 11 (RO membrane and the inner pipeline of the module) can be removed simply and efficiently, and the residual acid can be washed away by subsequent downstream water through cleaning, and the effect of physical flushing can be achieved, so that the reverse osmosis module 11 is cleaned more fully. In addition, the pH value of the first pickling agent is controlled within the range of 1-5, so that the impurities can be effectively cleaned, and the acid excessively-strong corrosion of equipment can be avoided. In addition, the corrosion damage to equipment caused by concurrent acid washing is small.

In this application, the pH of the first pickling agent may be, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.

In this application, the water for cleaning the reverse osmosis module 11 may be pretreated water obtained from the ultrapure water device or produced water from other modules in the ultrapure water device, or even may be introduced water from other places, so long as the water quality reaches the standard, and the introduced water may be temporarily stored in the first pickling agent storage tank 111 or another storage device in communication with the reverse osmosis module 11 is additionally provided. In particular, if water introduced elsewhere and temporarily stored in the first pickling agent storage tank 111 is used, the first pickling agent storage tank 111 needs to be cleaned before storing water.

In some embodiments of the present application, the rinse pressure of the first pickling agent and the water is independently in the range of 0.1MPa to 0.3MPa. Preferably, the flushing pressure of the first pickling agent and the water is independently 0.1MPa to 0.2MPa. Illustratively, the rinse pressures of the first pickling agent and the water may be independently 0.1MPa, 0.12MPa, 0.13MPa, 0.14MPa, 0.15MPa, 0.16MPa, 0.17MPa, 0.18MPa, 0.19MPa, 0.2MPa, 0.25MPa, 0.3MPa, and the like. The flushing pressure is controlled within a proper range, so that the cleaning effect can be ensured, and the risk of equipment damage can be effectively reduced.

The step of cleaning the reverse osmosis module 11 includes: 1) Sequentially adopting a second pickling agent and water to clean the EDI module 12 in a downstream way, and then adopting water circulation to clean the EDI module 12; the second pickling agent comprises organic weak acid and does not contain strong acid, and the organic weak acid comprises at least one of citric acid, acetic acid and oxalic acid; wherein the volume fraction of the organic weak acid is in the range of 1.5% -3%. 2) Sequentially adopting alkali lotion and water circulation to clean the EDI module 12; wherein the alkaline detergent comprises a mixed solution of organic alkali and inorganic alkali, the organic alkali comprises tetramethyl ammonium hydroxide, and the inorganic alkali comprises sodium hydroxide and/or potassium hydroxide; wherein the volume percent of the tetramethylammonium hydroxide is in the range of 1-3 percent and the volume percent of the sodium hydroxide is in the range of 0.3-0.8 percent.

The second pickling agent containing weak organic acids (citric acid, oxalic acid, phosphoric acid) can be used as a chelating agent to form chelates with metal ions attached to the internal pipeline of the EDI module 12 and the ion exchange membrane (partial chelate precipitates and partial soluble chelates exist), can remove metal oxides, iron-aluminum colloids, the chelate precipitates and insoluble matters of calcium and magnesium ions (magnesium carbonate, calcium sulfate and the like) to a certain extent, and can also provide a proper weak acid environment to lay a foundation for subsequent alkaline washing. In the present application, the second pickling agent does not contain a strong acid, and is not limited to a strong acid in an absolute sense that hydrochloric acid, sulfuric acid, perchloric acid, and the like are not contained and can be completely ionized in water, but a medium strong acid in a strict sense such as phosphoric acid may be regarded as the "strong acid" described above. The structure of the EDI module is more precise, the second pickling agent does not contain the strong acid, the cleaning effect can be effectively improved, and corrosion to equipment can be avoided. In addition, concurrent cleaning also significantly reduces the risk of acid corrosion of the EDI module 12, and subsequent concurrent and circulating water washes remove portions of the second pickling agent in the pipeline while more completely carrying away the solid impurities.

In the alkaline detergent circulation washing step in the step 2), the alkaline detergent is a mixed solution obtained by mixing an organic alkali (tetramethylammonium hydroxide) and a strong base (potassium hydroxide and/or sodium hydroxide) in a certain proportion, and the two bases are matched with each other in a certain concentration so as to sufficiently precipitate the soluble chelate formed in the acid washing step. In addition, the proper concentration ratio of the alkali-washing agent and the alkaline-washing agent can improve the alkali-washing effect, is beneficial to saving the cost, and can also avoid damage to equipment caused by over-strong alkalinity. On the other hand, the reaction time of the alkaline detergent and the dirt is relatively long, and the contact time of the alkaline detergent and the internal pipelines of the module and the cleaning pressure are required to be increased in a circulating cleaning mode. In addition, the alkali lotion is a mixture of inorganic alkali and organic alkali, and the two reagents can be further ensured to be fully mutually dissolved by adopting circulating cleaning, so that the combined effect of the two reagents can be fully exerted, and further, the metal ion chelate attached to the inner wall of the pipeline can be more fully precipitated and washed down. Moreover, before the alkaline washing process is started, the inner wall of the pipeline is in a weak acid environment, and the equipment is not irreversibly damaged by adopting circulating alkaline washing. Finally, the circulating water washing is combined, so that the cleanliness of the inside of the pipeline can be fully ensured, and the aim of thoroughly cleaning the water equipment is fulfilled.

According to the characteristics of different modules of the ultra-pure water equipment, the cleaning method adopts different process schemes to clean, so that the ultra-pure water equipment has the advantages of simple process, high cleaning efficiency, low cost, less damage to the equipment and good cleaning effect, the cleaning frequency of the ultra-pure water equipment can be obviously reduced, the water purifying capability of the reverse osmosis module 11 and the EDI module 12 can be maintained to be higher for a long time after cleaning, the work load of a subsequent polishing mixed bed is reduced, the replacement frequency of ion exchange resin in the polishing mixed bed is reduced, the cost is reduced, the ultra-pure water equipment can be operated with high load and high quality for a long time, and the service life of the ultra-pure water can be prolonged.

In this application, similarly, the water used to clean the EDI module 12 may be secondary reverse osmosis water in an ultrapure water plant, or may be water of standard quality introduced elsewhere. The water introduced elsewhere may be temporarily stored in the second pickling agent storage tank 121 and/or the alkaline cleaning agent storage tank 122, or may be stored in another storage device that may be additionally provided in communication with the EDI module 12, and it should be noted that the second pickling agent storage tank 121 and/or the alkaline cleaning agent storage tank 122 needs to be cleaned before storing water.

In this application, the volume fraction of the organic weak acid may be, for example, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, etc. Preferably, in some embodiments of the present application, the volume fraction of the weak acid is in the range of 1.5% -2%, which is favorable for removing impurities inside the EDI module, and can sufficiently chelate metal ions attached in the EDI module, so that the risk of corrosion of the second pickling agent on the equipment can be further reduced while the cleaning effect is better, thereby being favorable for prolonging the service life of the ultrapure water equipment.

In some embodiments of the present application, the second pickling agent is citric acid. The citric acid has better chelation effect on metal ions in the EDI module 12, and can better remove carbonate dirt, calcium sulfate, metal oxide and iron-aluminum colloid attached on the inner pipeline of the EDI module 12.

In some embodiments of the present application, after the second pickling agent and the water circulation wash the EDI module, that is, before the alkaline cleaning agent is used to wash the EDI module, the pH of the droplet on the surface of the pipeline is maintained in the range of 2-5, which is more favorable for the subsequent alkaline cleaning process.

In the present application, the mass percentage of the tetramethylammonium hydroxide in the alkaline wash may be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5%, 3%, etc., by way of example; the mass percentage of the strong alkali in the alkali lotion can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% and the like.

In some embodiments of the present application, preferably, the mass percent of tetramethylammonium hydroxide in the alkaline wash is in the range of 1% -2%.

In some embodiments of the present application, preferably, the mass percentage of the strong base in the alkaline lotion is in the range of 0.4% -0.7%. In this application, the pH of the alkaline lotion is not particularly limited in general. Illustratively, the pH of the alkaline lotions described above can be in the range of 8-11. Illustratively, the pH of the alkaline cleaner may be 8, 9, 10, 11, etc.

The following describes the specific operation steps of the concurrent purge and the cyclic purge in conjunction with fig. 2, taking the purge of the EDI module 12 as an example: (a) downstream pickling EDI module 12: first, valve C between the reverse osmosis module and the EDI module is closed, valve G at the water outlet of the water inlet valve D, EDI module of the valve E, EDI module of the second pickling agent storage box is opened, so that the second pickling agent enters the EDI module 12 along the pipeline and washes the anion/cation exchange membrane and the internal pipeline inside the EDI module in a downstream manner, and the second pickling agent flows out of the outlet O of the EDI module ₂ Flows out into a waste liquid collecting device. (b) downstream water wash EDI module 12: immediately after opening valve C, the second-stage reverse osmosis water (other water with the quality reaching the standard can be taken) flows into the EDI module 12 in a downstream way, so that the water flows into the EDI module 12 along the pipeline and washes the anion/cation exchange membrane and the internal pipeline inside the EDI module in the downstream way, and flows out of the outlet O of the EDI module ₂ And the water flows out and is discharged into the waste liquid collecting device, and when the flushing water quantity reaches the preset water quantity, the valve C is closed. (c) circulating water washing EDI module 12: closing the valve G and opening the valve C to enable the secondary reverse osmosis water to enter and be stored in the EDI module 12, closing the valves D and C after reaching the preset water quantity, and opening a circulation mode to enable the secondary reverse osmosis water to be circularly cleaned along the inner pipeline of the EDI module 12, and opening the valve G after cleaning for a certain time to drain the waste liquid into the waste liquid collecting device. After the cleaning is finished, the ultrapure water equipment is operated, the operation parameters of the equipment and the water quality of each water consumption point are detected, and the resistivity of the final produced water is more than or equal to 18MΩ & cm, so that the cleaning effect reaches the standard. And if the final produced water does not reach the standard, starting a new round of cleaning until the cleaning effect reaches the standard.

In other embodiments, the second pickle tank may be rinsed with water prior to rinsing the second pickle tank, either with concurrent or cyclic rinsing, and then into EDI module 12 for rinsing.

Similarly, the specific operation method of the downstream cleaning of the reverse osmosis module 11 and the alkaline cleaning process of the EDI module 12 can be finely tuned by referring to the above downstream cleaning and circulating cleaning processes, and will not be described herein. It will be appreciated that the water used to clean the reverse osmosis module 11 may be pre-treated water or may be other water that meets the water quality requirements.

In some embodiments of the present application, the above steps may be repeated several times by water circulation washing and/or concurrent washing. In general, it may be repeated 2 times.

In some embodiments of the present application, the rinse pressures of the second pickling agent, the alkaline washing agent, and each water in steps 1) -2) are independently in the range of 0.1MPa to 0.3MPa when the EDI module 12 is cleaned. Preferably, the second pickling agent, the alkaline washing agent and the washing pressure of each water are independently in the range of 0.2MPa to 0.25 MPa. Illustratively, the rinse pressures of the second pickling agent, the alkaline washing agent, and each water may be independently 0.1MPa, 0.15MPa, 0.2MPa, 0.21MPa, 0.22MPa, 0.23MPa, 0.24MPa, 0.25MPa, 0.3MPa, and the like. The flushing pressure is controlled within the range, so that the cleaning effect can be ensured, and the risk of equipment damage can be effectively reduced.

In some embodiments of the present application, when cleaning the EDI module, after cleaning with alkaline wash and water circulation, an optional step (3) is further included: the EDI module 12 is sequentially rinsed with a non-oxidizing sterilant rinse and water circulation. In some embodiments, the main components of the non-oxidizing sterilant may be chlorophenol-based agents and anionic polyacrylamides. The use of the non-oxidizing sterilant wash cycle to remove microorganisms from the EDI module 12 facilitates long-term operation of the ultrapure water device and further extends the cleaning cycle of the ultrapure water device to one month.

In some embodiments of the present application, the non-oxidizing sterilant in the non-oxidizing sterilant wash is in the range of from 5% to 10% by mass. Illustratively, the non-oxidizing sterilant may comprise 5%, 6%, 7%, 8%, 9%, 10% by mass of the non-oxidizing sterilant wash.

In the present application, the non-oxidizing sterilizing agent washing liquid may be stored in the second pickling agent storage tank, may be stored in the alkaline washing agent storage tank, and may even be stored in a non-oxidizing sterilizing washing liquid storage tank provided separately. It should be noted that if the non-oxidizing sterilant wash is stored in the second acid wash tank or the alkaline wash tank, the tank needs to be rinsed with water prior to the injection of the liquid.

In some embodiments of the present application, when the EDI module is cleaned, in the step 1), the step 2), and the optional step (3), each cycle cleaning time is independently 15min to 30min. Preferably, the time for each cycle of cleaning is independently 20min-30min. The sufficient cycle wash time can fully react the metal ion chelate with the alkaline cleaner, and in addition, the sufficient cycle wash time is more favorable for taking away impurity residues in the EDI module 12, thereby improving the final cleaning effect.

The following describes the technical scheme of the present application with reference to examples.

Example 1

(1) The hydrochloric acid solution is disposed in the first pickling agent storage tank so that the pH of the first pickling agent is about 2, the reverse osmosis module is washed downstream with a washing pressure of 0.1MPa, and the waste liquid is discharged into the waste liquid collecting device. And then 500L of pretreatment water is taken, the reverse osmosis module is cleaned by downstream direct flow under the flushing pressure of 0.2MPa, and the water flushing process is repeated twice.

(2) 200L of 1.5% citric acid is added in a second pickling agent storage tank, the EDI module is washed in a downstream manner under a flushing pressure of 0.1MPa, and the waste liquid is discharged into a waste liquid collecting device. Then 200L of second-stage reverse osmosis water is taken, the washing is carried out in a downstream and direct way under the washing pressure of 0.2MPa, and the water washing process is repeated twice.

(3) The EDI module is cleaned by adopting 200L of two-stage reverse osmosis water circulation, the flushing pressure is 0.25MPa, and the water flushing process is repeated twice.

(4) 200L of alkaline lotion is proportioned in an alkaline lotion storage tank, wherein the alkaline lotion is 0.5% sodium hydroxide and 2% tetramethylammonium hydroxide, the EDI module is circularly cleaned at a flushing pressure of 0.1MPa, and the waste liquid is discharged into a waste liquid collecting device. The EDI module is cleaned by adopting 200L of two-stage reverse osmosis water circulation, the flushing pressure is 0.2MPa, and the water flushing process is repeated twice.

Example 2

The only differences from example 1 are: further comprising the step (5): 200L of 5% non-oxidizing sterilizing agent (containing chlorophenol agent and anionic polyacrylamide as main components) washing solution is mixed in a non-oxidizing sterilizing agent washing solution storage tank, and the washing solution is circularly washed at a washing pressure of 0.1MPa, and the waste solution is discharged into a waste solution collecting device. And then 200L of second-stage reverse osmosis water circulation is adopted to clean the EDI module, the flushing pressure is 0.2MPa, and the water flushing process is repeated twice.

Example 3

The only differences from example 2 are: in step (1), the pH of the first pickling agent is 5; in the step (2), the second pickling agent is 1.5% citric acid; in the step (4), the alkali lotion is 0.3 percent sodium hydroxide and 2 percent tetramethyl ammonium hydroxide; in step (5), 3% of a non-oxidizing sterilant.

Example 4

The only differences from example 2 are: in the step (1), the pH of the first pickling agent is 1; in the step (2), the second pickling agent is 2% citric acid; in the step (4), the alkali lotion is 0.8% sodium hydroxide and 2% tetramethylammonium hydroxide; in step (5), 7% of a non-oxidizing sterilant.

Example 5

The only differences from example 2 are: in step (2), the second pickling agent is 3% citric acid.

Example 6

The only differences from example 2 are: in step (4), the alkaline cleaner is 0.5% sodium hydroxide+1% tetramethylammonium hydroxide.

Example 7

The only differences from example 2 are: in step (4), the alkaline cleaner is 0.5% sodium hydroxide+3% tetramethylammonium hydroxide.

Example 8

The only differences from embodiment 1 are: in the step (1), the flushing pressure of the first pickling agent is 0.05MPa; in the step (2), the flushing pressure of the second pickling agent is 0.05MPa; in the step (4), the washing pressure of the alkaline lotion is 0.05MPa; in the step (5), the washing pressure of the non-oxidizing sterilant washing liquid is 0.05MPa.

Example 9

The only differences from example 2 are: in the steps (1) - (5), all cleaning pressures are 0.3MPa in each concurrent cleaning or cyclic cleaning process.

Example 10

The only differences from example 1 are: in step (2), the second pickling agent is 1.5% oxalic acid.

To highlight the beneficial effects of the embodiments of the present application, the following comparative examples are set forth.

Comparative example 1

(1) The reverse osmosis module was washed downstream with 500L of 0.5% hydrochloric acid in the first pickling agent storage tank at a washing pressure of 0.1MPa, and the waste liquid was discharged into the waste liquid collecting device. And then 500L of pretreatment water is taken, the reverse osmosis module is cleaned by downstream direct flow under the flushing pressure of 0.2MPa, and the water flushing process is repeated twice.

(2) 200L of a mixed acid solution of 1.5% citric acid and 0.5% hydrochloric acid is prepared in a second pickling agent storage tank, the EDI module is washed in a downstream manner under a washing pressure of 0.1MPa, and the waste liquid is discharged into a waste liquid collecting device. Then 200L of second-stage reverse osmosis water is taken, the washing is carried out in a downstream and direct way under the washing pressure of 0.2MPa, and the water washing process is repeated twice.

(5) 200L of 5% non-oxidizing sterilizing agent (containing chlorophenol agent and anionic polyacrylamide as main components) washing solution is mixed in a non-oxidizing sterilizing agent washing solution storage tank, and the washing solution is circularly washed at a washing pressure of 0.1MPa, and the waste solution is discharged into a waste solution collecting device. And then 200L of second-stage reverse osmosis water circulation is adopted to clean the EDI module, the flushing pressure is 0.2MPa, and the water flushing process is repeated twice.

Comparative example 2

The only differences from comparative example 1 are: step (2): 200L of hydrochloric acid with the pH value of 2 is matched in a second pickling agent storage tank, the EDI module is circularly cleaned under the flushing pressure of 0.1MPa, and the waste liquid is discharged into a waste liquid collecting device. Then 200L of second-stage reverse osmosis water is taken, the washing is carried out in a downstream and direct way under the washing pressure of 0.2MPa, and the water washing process is repeated twice.

Comparative example 3

The only differences from example 2 are: in the step (1), the pH of the first pickling agent is 1; in step (2), the second pickling agent is 0.1% citric acid.

Comparative example 4

The only differences from example 2 are: in the step (1), the pH of the first pickling agent is 1; in step (2), the second pickling agent is 3.5% citric acid.

Comparative example 5

The only differences from example 2 are: in step (4), the alkaline lotion is 0.5% ammonia water+2% tetramethylammonium hydroxide.

Comparative example 6

The only differences from example 2 are: in step (4), the alkaline cleaner is 1% sodium hydroxide+0.5% tetramethylammonium hydroxide.

Comparative example 7

The only differences from comparative example 1 are: in the step (1), the pH value of the first pickling agent is 6.

The performance parameters of the ultrapure water equipment and the off-line water quality detection parameters of the water point are summarized in table 1, and the water quality standards to be achieved by the water produced by the ultrapure water equipment are also summarized in table 1 before the ultrapure water equipment is cleaned according to the steps of each example and each comparative example.

The reverse osmosis module and the EDI module of the ultrapure water device to be cleaned were cleaned according to the cleaning steps of the above examples and comparative examples. And detecting all parameters of the cleaned ultrapure water equipment and the quality of the product water in all process nodes.

Resistivity test: the online resistance meter is adopted for testing, so that the resistance condition of the water quality can be accurately tested, and the resistance of the water quality reflects the content of impurities such as metal ions and the like in the water; on the other hand, the obvious decrease of the resistance after cleaning can reflect the corrosion damage condition of the cleaning module.

And (3) detecting the impurity content of particles: off-line detection was performed using Japanese Liyin KS42-AF equipment, with a hundred-grade clean zone at the sampling point, and a soluble Polytetrafluoroethylene (PFA) clean bottle was used for sampling. The result can reflect the impurity content of water quality particles.

The results are summarized in table 2.

The higher the cleaning degree of the inside of the ultrapure water device is, the smaller the water inlet pressure of the water inlet of the device is. In addition, after the inner pipeline of the ultrapure water device is unblocked, the water yield of the ultrapure water device can reach the maximum value (the rated water yield of the ultrapure water device is 1T/H, the actual water yield can reach 1.1T/H), and the resistivity of the finally obtained water can reach 18MΩ & cm. On the other hand, the smaller the concentrated water discharge amount of the EDI module is, the higher the cleaning degree of the inside of the EDI module is, the water quality stabilizing time of the produced water after the ultra-pure water equipment is cleaned is generally controlled within 15 hours, and the excessive chemical liquid medicine residue in the equipment is indicated when the water quality stabilizing time exceeds 15 hours, so that the equipment can be corroded after the water is cleaned for many times, the performance of the EDI module is reduced, and the service life of the EDI module is damaged.

Table 1 parameter summary of water quality standards before and after cleaning by ultrapure water device

Table 2 summary of parameters after cleaning of ultrapure water plant

It should be noted that, after cleaning, a certain buffer time is required for the ultrapure water device, in other words, even if the water quality detection of the water produced by the device after cleaning reaches the standard, the situation that the water quality is occasionally unstable (peculiar smell and the like appears) or the device cannot operate stably may exist, and the continuous and stable water production can be realized after the buffer for a certain time. Therefore, the recovery of normal operation within 15 hours noted in the remarks column means that water can be stably supplied within 15 hours after the end of cleaning of the ultrapure water device according to the post-cleaning detection standard. Similarly, the stable water quality within 30 hours noted in each of the above comparative examples means that the water having no odor could be stably and continuously produced after the apparatus was operated for 30 hours after cleaning, but the quality of the produced water still could not meet the standard of ultrapure water.

As can be seen from the data in table 1, after the pure water apparatus was cleaned according to the procedure of each example, the water inlet pressure of the total water inlet of the apparatus was significantly smaller than that of the comparative example, and the water yield was significantly larger than that of the comparative example. Also, the resistivity of the comparative example produced water did not reach the ultra pure water standard. In addition, the EDI module concentrate yield was lower than the comparative example. The data can fully demonstrate that the cleaning method provided by the application has better cleaning effect.

The foregoing is illustrative embodiments of the present application, and it will be appreciated by those skilled in the art that various modifications and adaptations can be made thereto without departing from the principles of the present application, and such modifications and adaptations are intended to be comprehended within the scope of the present application.

Claims

1. A method for cleaning an ultrapure water device, comprising:

(2) Sequentially adopting a second pickling agent and water to clean the EDI module in a downstream way, and then adopting water circulation to clean the EDI module; the second pickling agent comprises an organic weak acid and does not contain strong acid, and the organic weak acid comprises at least one of citric acid, acetic acid and oxalic acid; wherein the volume percent of the organic weak acid is in the range of 1.5% -3%;

sequentially adopting alkali lotion and water circulation to clean the EDI module; wherein the alkaline detergent comprises a mixed solution of an organic alkali and an inorganic strong alkali, the organic alkali comprises tetramethyl ammonium hydroxide, and the inorganic strong alkali comprises sodium hydroxide and/or potassium hydroxide; wherein the volume percent of the tetramethyl ammonium hydroxide is in the range of 1-3%; the volume percent of the sodium hydroxide and/or potassium hydroxide is in the range of 0.3-0.8%.

2. The cleaning method of claim 1, wherein the organic weak acid is present in a volume percentage in the range of 1.5% -2%.

3. The cleaning method according to claim 1 or 2, wherein the weak organic acid is citric acid.

4. The cleaning method of claim 1, wherein the volume percent of tetramethyl ammonium hydroxide is in the range of 1% -2%.

5. The method of claim 1, wherein the pH of the interior conduit surface droplets of the EDI module is in the range of 2-5 prior to washing the EDI module with the alkaline cleaner.

6. The cleaning method according to claim 1, wherein the rinse pressures of the first pickling agent, the second pickling agent, the alkaline washing agent, and each water are independently in the range of 0.1MPa to 0.3MPa.

7. The cleaning method according to claim 1, wherein the time of the cyclic cleaning is independently 15min to 30min.

8. The cleaning method according to claim 1, further comprising (3): and washing the EDI module by sequentially adopting non-oxidizing sterilizing agent washing liquid and water circulation.

9. The cleaning method according to claim 1, wherein the cleaning method is implemented by a cleaning system of an ultrapure water device, wherein the cleaning system comprises an ultrapure water device and a cleaning apparatus, the ultrapure water device comprises the reverse osmosis module and the EDI module which are connected, the cleaning apparatus comprises a first pickling agent storage tank, a second pickling agent storage tank and an alkaline cleaning agent storage tank, the first pickling agent storage tank is communicated with the reverse osmosis module, and the second pickling agent storage tank and the alkaline cleaning agent storage tank are communicated with the EDI module.

10. The cleaning method of claim 9, wherein the second pickling agent reservoir communicates with the EDI module via a first conduit and the alkaline agent reservoir communicates with the EDI module via a second conduit.