KR20210076485A - Method for seawater desalination available of non-stop osmotic backwashing cleaning - Google Patents

Abstract

The present invention relates to a method for seawater deionization available of non-stop osmotic backwashing cleaning, in which the stoppage of a pump on a source water supply side is minimized during an osmotic backwashing cleaning process, so that the source water is supplied to a source water side of a reverse osmosis membrane at a certain pressure or higher. Thus, when a filtration process is executed after completion of the osmotic backwashing cleaning process, a pump in the source water supply side can be effectively restarted so that the operating costs can be reduced. In addition, damage to the reverse osmosis membrane can be prevented by minimizing the pressure of processing water supplied to a processing water side of the reverse osmosis membrane during the osmotic backwashing cleaning process. In a method for seawater deionization available of non-stop osmotic backwashing cleaning according to the present invention, a filtration process, an osmotic backwashing cleaning process, and a filtration test process are sequentially repeated. A seawater deionization apparatus for performing the seawater deionization method includes: a source water supply pump that distributes and supplies source water to a reverse osmosis high pressure pump and an energy recovery device; a reverse osmosis high-pressure pump that pressurizes source water at high pressure and supplies the source water to the reverse osmosis membrane module to enable the reverse osmosis process; and a booster pump that supplies the source water to the reverse osmosis membrane module using the pressure recovered from concentrated water by the energy recovery device. In the osmotic backwashing cleaning process, the source water supply pump and the booster pump are operated, and the operation of the reverse osmosis high pressure pump is stopped. The pressure of the source water supplied to the reverse osmosis membrane module by the source water supply pump and the booster pump during the osmotic backwashing cleaning process is smaller than the osmotic pressure of seawater, and the pressure of processing water of 1 bar or less acts on the processing water side of the reverse osmosis membrane module during the osmotic backwashing cleaning process.

Description

Method for seawater desalination available of non-stop osmotic backwashing cleaning

The present invention relates to a seawater desalination method capable of a non-stop osmotic reverse washing process, and more particularly, by minimizing the stoppage of the raw water supply side pump during the osmotic reverse washing process so that the raw water is supplied to the raw water side of the reverse osmosis membrane at a predetermined pressure or more. When the filtration process is executed after the completion of the reverse washing process, the operating cost can be reduced by effectively restarting the raw water supply side pump. At the same time, the reverse osmosis membrane is damaged by minimizing the pressure of the treated water supplied to the treated water side of the reverse osmosis membrane during the reverse osmosis washing process. It relates to a seawater desalination method capable of a non-stop osmotic reverse washing process that can prevent

Seawater desalination technology using reverse osmosis membrane is common. When seawater is supplied to the reverse osmosis membrane at a pressure greater than the osmosis pressure, pure water is separated from the seawater by the reverse osmosis phenomenon, and the seawater desalination technology using the reverse osmosis membrane applies this principle.

On the other hand, when the reverse osmosis membrane is continuously used for a long period of time, fouling is formed by contaminants, and such fouling acts as a factor to decrease the reverse osmosis efficiency. Therefore, it is necessary to remove the fouling formed on the reverse osmosis membrane at regular intervals, and chemical cleaning and/or physical cleaning are used as the reverse osmosis membrane cleaning method. Chemical cleaning is a cleaning method using chemicals, and physical cleaning uses methods such as back cleaning, air scrubbing, and water cleaning.

A reverse osmosis cleaning method has been proposed as a cleaning method for the reverse osmosis membrane. Back osmosis washing is a method of removing fouling formed on the raw water side of the reverse osmosis membrane by allowing pure water to move from the treated water side of the reverse osmosis membrane to the raw water side of the reverse osmosis membrane using the osmosis phenomenon.

US Patent No. 7658852 discloses a reverse osmotic cleaning method. In detail, by injecting NaCl into the raw water and supplying the raw water at the pressure during the filtration process, the treated water is instantly sucked into the raw water side of the reverse osmosis membrane by the osmosis phenomenon, thereby removing the contaminants formed on the membrane surface on the raw water side of the reverse osmosis membrane. is presenting

However, according to US Patent No. 7658852, there is a problem in that the osmotic pressure loss occurs due to the pressure applied during the filtration process, so that the osmotic backwash efficiency is not high.

Looking at Korean Patent No. 987294 proposed by the present applicant and the present inventor, a method of using concentrated water generated in the reverse osmosis process is proposed instead of using raw water injected with NaCl. This method has advantages in that it does not require a separate device for NaCl injection and that it can perform osmotic backwashing using existing chemical cleaning facilities, but there are various pumps for supplying raw water during the osmotic backwashing process. When the filtration process is performed after the completion of the osmotic backwash process due to the need to make the operation stop state, there is a problem in that the operation cost is increased due to the restart of the pump. In addition, the need to provide a separate osmotic backwash treated water tank unit for the treated water used during osmotic backwashing also causes device complexity.

As another method of reverse osmosis cleaning, Korean Patent Registration No. 1928212 proposes a technology of providing a reverse osmosis cleaning pump (PMP2) that supplies the treated water used for reverse osmosis cleaning to the treated water side of the reverse osmosis membrane in order to increase the reverse osmosis cleaning efficiency. are doing Disclosed is a method of supplying treated water below 6 bar through an osmotic backwash pump (PMP2) and supplying concentrated water containing an osmotic agent to the raw water side. However, since the treated water is supplied at a pressure of up to 6 bar or less, stress acts on the reverse osmosis membrane, which inevitably causes damage to the reverse osmosis membrane. As in Korea Patent No. 987294, various pumps for supplying raw water during the reverse osmosis cleaning process When the filtration process is performed after the completion of the osmotic backwash process due to the need to make the operation stop state, there is a problem in that the operation cost is increased due to the restart of the pump.

US registered patent US 7658852 Korean Patent No. 987294 Korean Patent No. 1928212

The present invention has been devised to solve the above problems, by minimizing the stoppage of the raw water supply side pump during the osmotic reverse washing process so that the raw water is supplied to the raw water side of the reverse osmosis membrane at a certain pressure or higher after completion of the osmotic reverse washing process When the filtration process is executed, the raw water supply side pump can be effectively restarted to reduce operating costs, and at the same time, the pressure of the treated water supplied to the treated water side of the reverse osmosis membrane during the reverse osmosis cleaning process is minimized, thereby preventing the reverse osmosis membrane from being damaged. An object of the present invention is to provide a seawater desalination method capable of osmotic backwashing process.

In addition, another object of the present invention is to provide a seawater desalination method capable of a non-stop osmotic backwashing process capable of effectively removing fouling and increasing seawater desalination production efficiency by optimizing the execution and termination criteria of the osmotic backwashing process. .

The seawater desalination method capable of a nonstop osmotic backwashing process according to the present invention for achieving the above object is a seawater desalination method capable of a nonstop osmotic backwashing process in which a filtration process, an osmosis backwashing process, and a filtration test process are sequentially repeated. In the above, the seawater desalination device in which the seawater desalination method is performed is a raw water supply pump that distributes and supplies raw water to a reverse osmosis high-pressure pump and an energy recovery device; and pressurizes the raw water to a high pressure to enable the reverse osmosis process to form a reverse osmosis membrane module A reverse osmosis high pressure pump for supplying; and a booster pump for supplying raw water to the reverse osmosis membrane module using the pressure recovered from the concentrated water by the energy recovery device; and the reverse osmosis cleaning process includes a raw water supply pump and The booster pump is operated, and the operation of the reverse osmosis high pressure pump is in a stopped state, and the raw water pressure supplied to the reverse osmosis membrane module by the raw water supply pump and the booster pump during the osmosis reverse washing process is smaller than the osmotic pressure of seawater, It is characterized in that the treated water pressure of 1 bar or less acts on the treated water side of the reverse osmosis membrane module during the back washing process.

In the process of the filtration process, if any one or more of Cl, TDS, and conductivity of the treated water produced by the reverse osmosis membrane module exceeds 5 to 10% of the preset reference value, the filtration process is terminated and the osmosis reverse washing process is performed proceeds

In the course of the filtration process, when the pressure of the raw water supplied to the reverse osmosis membrane module through the reverse osmosis high pressure pump exceeds 5 to 10% of the preset reference value, the filtration process is terminated and the reverse osmosis cleaning process is performed.

In the course of the filtration process, when the flow rate of the treated water produced by the reverse osmosis membrane module decreases by 5 to 10% compared to the reference value, the filtration process is terminated and the reverse osmosis washing process is performed.

In the course of the filtration process, if the difference between the pressure of the raw water supplied to the reverse osmosis membrane module through the reverse osmosis high pressure pump and the pressure of the concentrated water discharged from the reverse osmosis membrane module is 1.1 bar or more, the filtration process is terminated and the osmosis The cleaning process is in progress.

In the course of the reverse osmosis washing process, if any one or more of Cl, TDS, and conductivity of the treated water produced by the reverse osmosis membrane module meets a preset reference value, the filtration test process is terminated and the filtration process is performed.

In the filtration process, the raw water supply pump distributes and supplies raw water to the reverse osmosis high pressure pump and the energy recovery device, and the reverse osmosis membrane module separates the supplied raw water into treated water and concentrated water, and concentrated water discharged from the raw water side of the reverse osmosis membrane. is moved to the concentrated water tank with the pressure recovered by the energy recovery device, and the booster pump is used to supply the raw water to the reverse osmosis membrane module using the pressure recovered from the concentrated water by the energy recovery device.

In the reverse osmosis cleaning process, the supply of high-pressure raw water to the reverse osmosis membrane module through the reverse osmosis high-pressure pump is blocked, and the raw water is supplied to the raw water side of the reverse osmosis membrane module through the raw water supply pump and the booster pump, and between the reverse osmosis membrane module and the treatment tank valve is in an open state, the treated water pressure of 1 bar or less acts on the treated water side of the reverse osmosis membrane module, the raw water and the treated water exist on the raw water side and the treated water side of the reverse osmosis membrane, respectively, and the concentration of impurities including salt is treated with the raw water The osmotic pressure is higher than the number, and the treated water passes through the reverse osmosis membrane and moves to the raw water side by the osmotic pressure, and the fouling formed on the raw water side membrane surface of the reverse osmosis membrane is removed by the movement of the treated water to the raw water side.

A treated water transport pipe branched from the pipe between the reverse osmosis membrane module and the treated water tank and connected to the pipe in front of the raw water supply pump is further provided, and in the filtration test process, the first valve between the reverse osmosis membrane module and the treated water tank is blocked and treated In the open state, the second valve of the transport pipe proceeds under the same process conditions as the filtration process, and in the process of the reverse osmosis washing process, any of Cl, TDS, and conductivity of the treated water produced by the reverse osmosis membrane module When one or more of the preset reference values are satisfied, the filtration test process is terminated and the filtration process proceeds.

The pressure of raw water supplied to the reverse osmosis membrane module through the reverse osmosis high pressure pump during the filtration process exceeds 80 bar, and the pressure of the raw water supplied to the reverse osmosis membrane module through the raw water supply pump and booster pump during the reverse osmosis cleaning process is 3 to 15 bar, The pressure of the treated water acting on the treated water side of the reverse osmosis membrane module during the reverse osmosis washing process is 1 bar or less.

The seawater desalination method capable of non-stop osmotic reverse washing process according to the present invention has the following effects.

In performing the reverse osmosis cleaning process, the reverse osmosis cleaning process can be effectively performed in a state where additional device components are minimized, and damage to the reverse osmosis membrane during the reverse osmosis cleaning process can be prevented. In addition, during the reverse osmosis cleaning process, only the reverse osmosis high pressure pump among the 'raw water supply side pumps' is stopped and the raw water supply pump and booster pump are operated normally. can

1 is a block diagram of a seawater desalination apparatus using a reverse osmosis membrane according to an embodiment of the present invention.
Figure 2a is a reference diagram for explaining the filtration process.
Figure 2b is a reference diagram for explaining the osmotic back washing process.
Figure 2c is a reference diagram for explaining the filtration test process.

The present invention provides a technique for stably ensuring the cleaning effect of the reverse osmosis membrane by the reverse osmosis cleaning and preventing the re-operation efficiency of the filtration process from being lowered due to the reverse osmosis cleaning process.

As described above in 'Technology Background of the Invention', it is essential to periodically clean the reverse osmosis membrane to remove fouling in the seawater desalination device using the reverse osmosis membrane, and reverse osmosis cleaning is an effective method for removing fouling of the reverse osmosis membrane. to be.

In the osmosis backwash process, the following should be considered. First, fouling of the reverse osmosis membrane must be effectively removed through reverse osmosis washing; second, damage to the reverse osmosis membrane must be prevented by reverse osmosis washing; degradation should be minimized.

The principle of reverse osmosis cleaning is to remove fouling formed on the membrane surface on the raw water side of the reverse osmosis membrane by moving pure water from the treated water side of the reverse osmosis membrane to the raw water side of the reverse osmosis membrane. Therefore, the osmotic pressure should work smoothly between the treated water side and the raw water side of the reverse osmosis membrane.

The present invention is different from the three prior patents mentioned in 'Technical Background of the Invention' that supplies concentrated water or NaCl-injected raw water (filtering pressure applied) to the raw water side of reverse osmosis membrane during reverse osmosis washing, reverse osmosis membrane during reverse osmosis washing Supply raw water, that is, seawater to the raw water side of As described above, in supplying seawater to the raw water side of the reverse osmosis membrane, the osmotic pressure is smoothly operated between the treated water side and the raw water side of the reverse osmosis membrane by setting the seawater supply pressure to be lower than the osmotic pressure of the seawater.

In addition, in the present invention, seawater is supplied to the raw water side of the reverse osmosis membrane as described above, and treated water is supplied to the treated water side of the reverse osmosis membrane. It is possible to prevent the reverse osmosis membrane from being damaged by the pressure of the treated water.

In the case of applying the osmotic backwashing process in the seawater desalination device, as the osmotic backwashing process is performed after the filtration process is completed, all the 'raw water supply side pumps' operated during the filtration process are stopped (Korean Patent No. 987294 and See Korean Patent No. 1928212). For reference, US Patent No. 7658852 discloses a method of supplying raw water injected with NaCl at the same pressure as in the filtration process during osmotic backwashing, but due to this, the osmotic backwashing efficiency is inevitably low. If all the pumps on the raw water supply side are stopped during osmotic backwashing, an increase in operating costs is inevitable as the raw water supply side pumps must be restarted in the stopped state during the filtration process after osmotic backwashing.

The 'raw water supply side pump' includes a raw water supply pump, a reverse osmosis high pressure pump, and a booster pump, and the raw water supply pump serves to supply raw water stored in a raw water storage tank to the reverse osmosis high pressure pump, and reverse osmosis. The high-pressure pump serves to apply raw water at high pressure to the reverse osmosis membrane to enable the reverse osmosis phenomenon, and the booster pump serves to supply concentrated water at a predetermined pressure to the raw water side of the reverse osmosis membrane through a pressure recovery device.

In Korean Patent No. 987294 and Korean Patent No. 1928212, the reverse osmosis cleaning process is performed while all 'raw water supply side pumps' are stopped, and in US Patent No. 7658852, the reverse osmosis high pressure pump is a filtration process during reverse osmosis cleaning. It operates under the same conditions as the city. As described above, as in Korean Patent No. 987294 and Korean Patent No. 1928212, if all of the 'raw water supply side pump' is stopped during reverse osmosis washing, the operating cost increases when the filtration process is restarted, and as in US Patent No. 7658852, If a reverse osmosis high pressure pump is used for back osmosis washing, the efficiency of back osmosis washing is reduced.

The present invention stops only the operation of the reverse osmosis high pressure pump among the 'raw water supply side pump' during reverse osmosis washing so that the raw water is supplied to the raw water side of the reverse osmosis membrane at a constant pressure (3 to 15 bar). It is possible to effectively reduce operating costs by increasing the restart efficiency. In addition, since the pressure (3-15 bar) supplied to the raw water side of the reverse osmosis membrane is lower than the osmotic pressure (25-30 bar) of seawater, reverse osmosis washing by osmosis can proceed smoothly.

In addition, the present invention can increase the process efficiency of the seawater desalination apparatus by presenting the conditions for the execution and termination of the osmosis backwash process in sequentially proceeding the filtration process and the osmosis backwash process. The operating conditions and termination conditions of the osmotic backwashing process will be described in detail through Examples to be described later.

Hereinafter, a seawater desalination method capable of a nonstop osmotic reverse washing process according to an embodiment of the present invention will be described in detail with reference to the drawings. Before describing the reverse osmosis washing method of the seawater desalination device using the reverse osmosis membrane according to an embodiment of the present invention, a seawater desalination device in which the osmotic reverse washing method of the present invention is implemented will be described.

1, the seawater desalination apparatus using a reverse osmosis membrane according to an embodiment of the present invention includes a raw water supply pump 11, a reverse osmosis high pressure pump 12, a reverse osmosis membrane module 120, an energy recovery device 130, and a booster. It comprises a pump (13).

The raw water supply pump 11 serves to supply raw water stored in the raw water storage tank 110 to the reverse osmosis high pressure pump 12 and the booster pump 13 . That is, part of the raw water is supplied to the reverse osmosis high pressure pump 12 , and the other part of the raw water is supplied to the booster pump 13 . Here, the raw water refers to seawater, and the seawater to which a predetermined pretreatment process is applied may be stored in the raw water storage tank 110 . The reason for supplying raw water to the booster pump 13 other than the reverse osmosis high pressure pump 12 is to supply the reverse osmosis membrane module 120 by utilizing the pressure recovered by the energy recovery device 130, which will be described later. do it with

The reverse osmosis high pressure pump 12 serves to supply the reverse osmosis membrane module 120 by pressurizing the raw water delivered through the raw water supply pump 11 to a high pressure of about 80 bar. The reverse osmosis membrane module 120 serves to separate the high-pressure seawater supplied through the reverse osmosis high-pressure pump 12 into pure water and concentrated water through reverse osmosis. Pure water, that is, treated water is moved to the treated water tank 140 , and the concentrated water is moved to the concentrated water tank 150 through the energy recovery device 130 . The reverse osmosis membrane module 120 is configured to include a reverse osmosis membrane 121 , and a space on the raw water side 122 and the treated water side 123 space of the reverse osmosis membrane 121 . Raw water is supplied to the raw water side 122 of the reverse osmosis membrane 121, the treated water separated by the reverse osmosis phenomenon is moved to the treated water side 123 of the reverse osmosis membrane 121, and the concentrated water from which the treated water is separated is the reverse osmosis membrane 121 ) is left on the raw water side 122 and is moved to the energy recovery device 130 .

The energy recovery device 130 serves to recover the pressure energy of the concentrated water discharged from the raw water side 122 of the reverse osmosis membrane 121 . As described above, the reverse osmosis high-pressure pump 12 pressurizes the raw water to a high pressure of about 80 bar and supplies it to the raw water side 122 of the reverse osmosis membrane 121, which is concentrated even after separation of the treated water and the concentrated water by the reverse osmosis phenomenon. A constant pressure remains in the water. The energy recovery device 130 serves to recover the pressure remaining in the concentrated water, and may be configured as a positive displacement energy recovery device 130 having a piston pump structure as an embodiment. The concentrated water discharged from the raw water side 122 of the reverse osmosis membrane 121 is moved to the concentrated water tank 150 after the pressure is recovered by the energy recovery device 130, and the pressure recovered by the energy recovery device 130 is It is used to operate the booster pump 13 .

The booster pump 13 serves to supply the raw water to the raw water side 122 of the reverse osmosis membrane 121 by using the pressure recovered by the energy recovery device 130 to pressurize the raw water. The path through which raw water is supplied to the reverse osmosis membrane module 120 is divided into a path supplied to the reverse osmosis membrane module 120 through the reverse osmosis high pressure pump 12 and a path supplied to the reverse osmosis membrane module 120 through the booster pump 13 do. The former path can be called a main raw water supply path, and the latter path is an auxiliary raw water supply path that recycles pressure energy. Branched in the path between the raw water supply pump 11 and the reverse osmosis high pressure pump 12, a part of the raw water is supplied to the booster pump 13 through the energy recovery device 130, and the booster pump 13 is an energy recovery device The raw water is pressurized through the pressure recovered by 130 and supplied to the raw water side 122 of the reverse osmosis membrane 121 .

In addition to the above configuration, a treated water transport pipe 60 branched from the pipe between the reverse osmosis membrane module 120 and the treated water tank 140 and connected to the pipe at the front end of the raw water supply pump 11 is further provided, and the treated water transport pipe Reference numeral 60 serves to return the treated water to the raw water supply pump 11 during the filtration test process.

In addition, a first pressure gauge 21 is provided between the reverse osmosis high pressure pump 12 and the reverse osmosis membrane module 120 , and a second pressure gauge 22 is provided between the reverse osmosis membrane module 120 and the energy recovery device 130 . , a flow meter 30 is provided between the reverse osmosis membrane module 120 and the treatment water tank 140 . At the same time, a first water quality meter 41 is provided between the reverse osmosis membrane module 120 and the treatment water tank 140 , and a second water quality meter 42 is provided between the energy recovery device 130 and the concentrated water tank 150 . do. A first valve 51 is provided between the reverse osmosis membrane module 120 and the treatment water tank 140 , and a second valve 52 is provided at the treatment water transport pipe 60 .

Above, the seawater desalination apparatus using a reverse osmosis membrane according to an embodiment of the present invention has been described. Next, a seawater desalination method according to an embodiment of the present invention will be described.

The seawater desalination method capable of non-stop osmotic reverse washing process according to an embodiment of the present invention is carried out on the basis of the seawater desalination apparatus using the above-described reverse osmosis membrane, and the filtration process, the osmosis reverse washing process and the filtration test process are repeated. do.

The filtration process is a process in which treated water is produced by the reverse osmosis membrane module 120, and the reverse osmosis washing process is a process of washing the reverse osmosis membrane 121 using the osmotic reverse washing principle after completion of the filtration process, and the filtration test process is an osmosis process This is a process of testing whether the filtration performance of the reverse osmosis membrane module 120 satisfies the target water quality after the completion of the cleaning process and before the implementation of the filtration process.

First, the filtration process proceeds as follows.

As shown in FIG. 2A , raw water in the raw water storage tank 110 , that is, seawater is supplied to the reverse osmosis high pressure pump 12 by the raw water supply pump 11 . The reverse osmosis high pressure pump 12 pressurizes raw water to a high pressure of about 80 bar and supplies it to the raw water side 122 space of the reverse osmosis membrane module 120 , that is, the raw water side 122 of the reverse osmosis membrane 121 . By the reverse osmosis phenomenon, seawater is separated into treated water and concentrated water with the reverse osmosis membrane 121 interposed therebetween. The treated water moved to the treated water side 123 of the reverse osmosis membrane 121 is moved to the treated water tank 140 , and the concentrated water remaining on the raw water side 122 of the reverse osmosis membrane 121 is moved to the energy recovery device 130 . . The pressure retained by the concentrated water is recovered by the energy recovery device 130 , and the concentrated water is moved to the concentrated water tank 150 . At this time, the second valve 52 of the treated water transport pipe 60 forms a blocked state.

On the other hand, a portion of the raw water in the raw water storage tank 110 is supplied to the booster pump 13 through the energy recovery device 130 by the raw water supply pump 11 . The booster pump 13 supplies raw water to the raw water side 122 of the reverse osmosis membrane 121 using the pressure recovered from the concentrated water by the energy recovery device 130 . That is, the raw water transferred from the reverse osmosis high pressure pump 12 and the raw water transferred from the booster pump 13 are introduced into the raw water side 122 of the reverse osmosis membrane 121 , and the reverse osmosis process is performed on them.

Through the above operation, the filtration process using the reverse osmosis membrane 121 is performed. During the filtration process, the quality of raw water, the pressure of the raw water path, and the pressure of the treated water path are continuously checked. If the measured quality of the raw water, the pressure of the raw water path, and the pressure of the treated water path are out of the preset reference values, It is determined that the reverse osmosis membrane 121 is contaminated, the filtration process is terminated, and the reverse osmosis washing process is performed.

The criteria for carrying out the osmotic backwashing process are as follows, and when any one of the following criteria is met, the filtration process is terminated and the osmotic backwashing process is performed. The first criterion is that Cl, TDS, and conductivity of the treated water measured by the first water quality meter 41 provided in the treated water path between the reverse osmosis membrane module 120 and the treated water tank 140 are 5 to 10% compared to the preset reference value. Whether or not it exceeds the standard value, the osmotic backwash process is performed. The second criterion is whether the pressure measured by the first pressure gauge 21 provided between the reverse osmosis high pressure pump 12 and the reverse osmosis membrane module 120 exceeds 5 to 10% of the reference value. A cleaning process is carried out. The third criterion is whether the treated water flow rate measured by the flow meter 30 provided in the treated water path between the reverse osmosis membrane module 120 and the treated water tank 140 decreases by 5 to 10% compared to the reference value, and if this is met, the osmosis A cleaning process is carried out. The fourth criterion is that if the difference between the first pressure gauge 21 and the second pressure gauge 22 is 1.1 bar or more, the osmotic backwashing process is performed. If any one of the above four criteria is satisfied, it is determined that the reverse osmosis membrane 121 is contaminated, and the filtration process is terminated and the reverse osmosis washing process is performed.

The osmotic backwash process proceeds as follows (see FIG. 2b).

During the reverse osmosis cleaning process, the raw water supply pump 11 and the booster pump 13 of the 'raw water supply side pump' operate normally, and the reverse osmosis high pressure pump 12 is stopped. Accordingly, the supply of high-pressure raw water to the reverse osmosis membrane module 120 through the reverse osmosis high pressure pump 12 is blocked, and the raw water through the raw water supply pump 11 and the booster pump 13 is the reverse osmosis membrane module 120 . It is supplied to the raw water side (122). During the filtration process, the pressure of raw water supplied to the reverse osmosis membrane module 120 through the reverse osmosis high pressure pump 12 is about 80 bar, and it is supplied to the reverse osmosis membrane module 120 through the raw water supply pump 11 and the booster pump 13. The raw water pressure is about 3 to 15 bar.

At the same time, the first valve 51 between the reverse osmosis membrane module 120 and the treated water tank 140 is in an open state, and accordingly, the treated water pressure of 1 bar or less is applied to the treated water side 123 of the reverse osmosis membrane module 120 . works At this time, a separate pump for supplying the treated water from the treated water tank 140 to the reverse osmosis membrane module 120 is not provided, and the treated water side 123 of the reverse osmosis membrane module 120 and the It is maintained only in a state in which the treatment water tank 140 is spatially connected.

Under the above conditions, a raw water pressure of about 3 to 15 bar acts on the raw water side 122 of the reverse osmosis membrane 121 , and a treated water pressure of 1 bar or less acts on the treated water side 123 of the reverse osmosis membrane 121 . Raw water and treated water are present on the raw water side 122 and the treated water side 123 of the reverse osmosis membrane 121, respectively, and the osmotic pressure acts because the raw water has a higher concentration of impurities including salt than the treated water. Accordingly, the treated water passes through the reverse osmosis membrane 121 and moves to the raw water side 122 , and by this movement of the treated water to the raw water side 122 , fouls formed on the membrane surface on the raw water side 122 of the reverse osmosis membrane 121 . The ring is removed, and the removed fouling is included in the concentrated water and moved to the concentrated water tank 150 . That is, as opposed to the movement of treated water from the raw water side 122 to the treated water side 123, which is the forward direction of the filtration process, the treated water moves from the treated water side 123 to the raw water side 122 by osmotic pressure, and by this osmotic pressure, the raw water The so-called back osmosis cleaning process is performed so that fouling on the membrane surface of the side 122 is removed.

In the process of removing the fouling formed on the membrane surface on the raw water side 122 of the reverse osmosis membrane 121 by the action of osmosis, the pressure of the treated water acting on the treated water side 123 of the reverse osmosis membrane 121 is 1 bar or less. (121) does not cause damage such as detachment. However, the raw water pressure of about 3 to 15 bar acts on the raw water side 122 of the reverse osmosis membrane 121, which may act as a factor in the loss of osmotic pressure. As the osmotic pressure of seawater is 25 to 30 bar, the osmotic reverse washing process proceeds smoothly there is no problem in In consideration of this point, the pressure supplied to the raw water side 122 of the reverse osmosis membrane 121 through the raw water supply pump 11 and the booster pump 13 should be lower than the osmotic pressure of seawater.

The reverse osmosis cleaning process according to the present invention as described above has the following differences compared to the prior patent mentioned in 'Technology Background of the Invention'. In the case of the prior patent, the reverse osmosis washing process proceeds while all 'raw water supply side pumps' are stopped, whereas in the present invention, only the reverse osmosis high pressure pump 12 of the 'raw water supply side pumps' is stopped and the raw water supply pump 11 ) and the booster pump 13 are operated in the same way as during the filtration process. Therefore, when performing the filtration process again after the end of the reverse osmosis washing process, only the reverse osmosis high pressure pump 12 needs to be restarted, thereby reducing operating costs. However, the premise that the pressure of the raw water supplied to the raw water side 122 of the reverse osmosis membrane 121 through the raw water supply pump 11 and the booster pump 13 should be smaller than the osmotic pressure of seawater for the smooth progress of the osmotic reverse washing process. do.

In addition, as the pressure of the treated water acting on the treated water side 123 of the reverse osmosis membrane 121 is 1 bar or less, the reverse osmosis membrane 121 is not damaged, such as detached.

When the back osmosis washing process is completed, a subsequent filtration test process is performed. At the end of the back osmosis washing process, it is determined whether the turbidity value measured by the second water quality meter 42 meets a reference value. Specifically, the turbidity value of the concentrated water is measured by the second water quality meter 42 provided in the concentrated water path between the energy recovery device 130 and the concentrated water tank 150 during the osmotic backwashing process, If the measured turbidity value is lower than the preset reference value, the osmotic backwash process is completed.

After completion of the osmotic backwashing process, the filtration test process proceeds as follows.

As described above, the filtration test process is a process of testing whether the treated water produced by the reverse osmosis membrane module 120 meets a preset target water quality before performing a normal filtration process in a state in which the reverse osmosis washing process is completed.

In the filtration test process, the first valve 51 between the reverse osmosis membrane module 120 and the treated water tank 140 is blocked, and the second valve 52 of the treated water transport pipe 60 is opened. Except for the blocking of the first valve 51 and the opening of the second valve 52 , all process conditions are the same as those of the filtration process.

Specifically, as shown in FIG. 2c, the raw water is supplied to the reverse osmosis membrane module 120 through the raw water supply pump 11 and the reverse osmosis high pressure pump 12, the raw water supply pump 11 and the booster pump 13. It is supplied to the reverse osmosis membrane module 120 through a path supplied to the reverse osmosis membrane module 120 through the reverse osmosis membrane module 120, and the reverse osmosis membrane module 120 separates the supplied raw water into treated water and concentrated water. The concentrated water is moved to the concentrated water tank 150 after the pressure is recovered by the energy recovery device 130 , and the pressure recovered by the energy recovery device 130 is used to operate the booster pump 13 . At this time, the treated water is returned to the raw water supply pump 11 through the treated water transport pipe 60, and the raw water supply pump 11 mixes the treated water returned through the treated water transport pipe 60 with the raw water. It is supplied to the reverse osmosis high pressure pump 12 and the booster pump 13 side.

In the process of the above process, the first water quality meter 41 provided in the treated water path measures Cl, TDS, and conductivity of the treated water, and when the measured values meet the preset target water quality value, the filtration test process This ends.

When the filtration test process is completed, the filtration process proceeds, and the filtration process, the osmotic backwash process, and the filtration test process as described above are repeated again.

11: raw water supply pump 12: reverse osmosis high pressure pump
13: booster pump 21: first pressure gauge
22: second pressure gauge 30: flow meter
41: first water quality meter 42: second water quality meter
51: first valve 52: second valve
60: treated water transport pipe 110: raw water storage tank
120: reverse osmosis membrane module 121: reverse osmosis membrane
122: raw water side 123: treated water side
130: energy recovery device 140: treatment tank
150: concentration tank

Claims (10)

In a seawater desalination method capable of a non-stop osmotic backwashing process in which the filtration process, the osmosis backwash process, and the filtration test process are sequentially repeated,
The seawater desalination device in which the seawater desalination method proceeds,
A raw water supply pump that distributes and supplies raw water to the reverse osmosis high-pressure pump and the energy recovery device; and a reverse osmosis high-pressure pump that supplies the reverse osmosis membrane module by pressurizing the raw water at high pressure to enable the reverse osmosis process; and by the energy recovery device A booster pump for supplying raw water to the reverse osmosis membrane module using the pressure recovered from the concentrated water;
The osmotic backwash process is,
The raw water supply pump and the booster pump are operated, and the operation of the reverse osmosis high pressure pump is in a stopped state,
The pressure of the raw water supplied to the reverse osmosis membrane module by the raw water supply pump and the booster pump during the osmotic reverse washing process is smaller than the osmotic pressure of seawater,
Seawater desalination method capable of nonstop osmotic backwashing process, characterized in that the treated water pressure of 1 bar or less acts on the treated water side of the reverse osmosis membrane module during the osmotic backwashing process.
The method of claim 1, wherein in the process of the filtration process,
Non-stop osmosis station, characterized in that when any one or more of Cl, TDS, and conductivity of the treated water produced by the reverse osmosis membrane module exceeds 5 to 10% of the preset reference value, the filtration process is terminated and the osmosis reverse washing process proceeds Seawater desalination method capable of washing process.
The method of claim 1, wherein in the process of the filtration process,
When the pressure of the raw water supplied to the reverse osmosis membrane module through the reverse osmosis high-pressure pump exceeds 5 to 10% of the preset reference value, the filtration process is terminated and the osmotic reverse washing process is performed. desalination method.
The method of claim 1, wherein in the process of the filtration process,
When the flow rate of the treated water produced by the reverse osmosis membrane module decreases by 5 to 10% compared to the reference value, the filtration process is terminated and the osmosis reverse washing process is performed.
The method of claim 1, wherein in the process of the filtration process,
If the difference between the pressure of the raw water supplied to the reverse osmosis membrane module through the reverse osmosis high pressure pump and the pressure of the concentrated water discharged from the reverse osmosis membrane module is 1.1 bar or more, the filtration process is terminated and the osmosis reverse washing process is performed, characterized in that Seawater desalination method capable of non-stop osmotic reverse washing process.
The method according to claim 1, wherein during the osmotic backwashing process,
When any one or more of Cl, TDS, and conductivity of the treated water produced by the reverse osmosis membrane module meets a preset reference value, the filtration test process is terminated and the filtration process is performed. Way.
According to claim 1, wherein the filtration process,
The raw water supply pump distributes and supplies raw water to the reverse osmosis high pressure pump and the energy recovery device, and the reverse osmosis membrane module separates the supplied raw water into treated water and concentrated water, and the concentrated water discharged from the raw water side of the reverse osmosis membrane is supplied to the energy recovery device. It is moved to the concentrated water tank with the pressure recovered by the energy recovery device, and the booster pump uses the pressure recovered from the concentrated water by the energy recovery device to supply raw water to the reverse osmosis membrane module. Possible seawater desalination methods.
The method of claim 1, wherein the osmotic backwash process comprises:
The supply of high-pressure raw water to the reverse osmosis membrane module through the reverse osmosis high pressure pump is blocked, and the raw water is supplied to the raw water side of the reverse osmosis membrane module through the raw water supply pump and the booster pump,
The valve between the reverse osmosis membrane module and the treated water tank is in an open state, and the treated water pressure of 1 bar or less acts on the treated water side of the reverse osmosis membrane module,
Raw water and treated water exist on the raw water side and the treated water side of the reverse osmosis membrane, respectively, and the concentration of impurities including salts in the raw water is higher than that of the treated water, so osmotic pressure works. A seawater desalination method capable of a nonstop osmosis reverse washing process, characterized in that it proceeds as a process in which fouling formed on the membrane surface on the raw water side of the reverse osmosis membrane is removed by movement to the raw water side.
According to claim 1, wherein the treatment water transport pipe branched from the pipe between the reverse osmosis membrane module and the treatment water tank and connected to the pipe in front of the raw water supply pump is further provided,
The filtration test process is
The first valve between the reverse osmosis membrane module and the treated water tank is blocked, and the second valve of the treated water transport pipe is opened under the same process conditions as the filtration process,
In the process of the osmotic backwashing process,
When any one or more of Cl, TDS, and conductivity of the treated water produced by the reverse osmosis membrane module meets a preset reference value, the filtration test process is terminated and the filtration process is performed. Way.
According to claim 1, wherein the pressure of the raw water supplied to the reverse osmosis membrane module through the reverse osmosis high pressure pump during the filtration process exceeds 80 bar, the pressure of the raw water supplied to the reverse osmosis membrane module through the raw water supply pump and the booster pump during the reverse osmosis washing process is 3 to 15 bar, and the pressure of the treated water acting on the treated water side of the reverse osmosis membrane module during the reverse osmosis washing process is 1 bar or less.

Images