JP2017029881A - Salt water desalination plant and method of remodeling the salt water desalination plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient salt water desalination plant by effectively utilizing energy while saving cost of installation.SOLUTION: A salt water desalination plant that includes a reverse osmosis membrane device 3 that separates salt water into permeable water and concentrated salt water, a high pressure pump 5 that boosts low pressure salt water to a predetermined pressure and supplies to the reverse osmosis membrane device 3, a pressure exchange device 6 that boosts the low pressure salt water with high pressure concentrated salt water exhausted from the reverse osmosis membrane device 3, and a booster pump 7 that boosts the salt water boosted by the pressure exchange device 6 to the predetermined pressure and supplies to the reverse osmosis membrane 3, and further includes a residual pressure recovery device 8 that recovers the residual pressure of the concentrated salt water exhausted from the pressure exchange device 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a salt water desalination apparatus for obtaining fresh water from salt water such as seawater and a method for remodeling the salt water desalination apparatus.

  As described in Patent Document 1, when salt water is distilled to obtain fresh water from salt water such as seawater, a large amount of energy is required with a phase change called evaporation. A saltwater desalination apparatus using an osmotic membrane apparatus has attracted attention.

  A desalination apparatus using a reverse osmosis membrane device includes a reverse osmosis membrane device that separates salt water into permeate and concentrated salt water, a high-pressure pump that boosts low-pressure salt water to a predetermined pressure and supplies the reverse osmosis membrane device to a reverse osmosis membrane device, A pressure exchanging device that boosts the low-pressure salt water with the high-pressure concentrated salt water discharged from the osmosis membrane device, and a booster pump that further boosts the salt water boosted by the pressure exchanging device to a predetermined pressure and supplies it to the reverse osmosis membrane device. I have.

  A pressure exchange device is incorporated to recover the pressure energy of the concentrated brine discharged from the reverse osmosis membrane device for boosting the brine.

  In Patent Document 1, for the purpose of providing a salt water fresh water device capable of reducing the load and power consumption of a salt water supply pump, salt water supplying means for supplying salt water to a reverse osmosis membrane member and the reverse osmosis membrane member are discharged. A normal osmosis membrane member to which concentrated salt water is supplied, and an auxiliary device to which the mixed water discharged from the forward osmosis membrane member is supplied and connected to the salt water supply means, Disclosed is a saltwater freshwater device that increases at least one of the power supplied to the saltwater supply means, the pressure applied to the saltwater supply means, and the rotational capacity of the saltwater supply means.

  In particular, in FIG. 8, a pressure exchange device is incorporated to recover the pressure energy of the concentrated salt water discharged from the reverse osmosis membrane device for boosting the salt water, and the concentrated salt water after the pressure exchange is supplied to the forward osmosis membrane member. A saltwater freshwater apparatus configured as described is disclosed.

JP 2014-200708 A

  In general, when salt water taken from the sea is desalinated, pre-treatment is performed with a filtration device equipped with a microfiltration membrane, ultrafiltration membrane, etc. to remove foreign substances from the salt water before being supplied to the reverse osmosis membrane device. There is a need.

  When the building where such a pretreatment device is installed and the building where the reverse osmosis membrane device is installed are different buildings, etc., a long pipeline for supplying saltwater after pretreatment to the reverse osmosis membrane device and When it is necessary to provide a long pipe for supplying salt water after pretreatment to the pressure exchange device and to provide a pump for each, there is a problem that the equipment cost for providing the piping increases.

  Therefore, the salt water supply pipeline from the building where the pretreatment device is installed to the building where the reverse osmosis membrane device is installed is shared, and the pipeline is branched at the building where the reverse osmosis membrane device is installed. It is constructed so that water is supplied to each of the reverse osmosis membrane device and the pressure exchange device, and furthermore, the cost of laying the pipe by combining the water supply pump that supplies water to the high-pressure pump and the water supply pump that supplies water to the pressure exchange device with one pump. It is conceivable to reduce equipment costs.

  However, if the discharge pressure of the feed water pump is adjusted so that inconveniences such as cavitation do not occur with the high pressure pump, the pressure of the salt water supplied to the pressure exchange device will be higher than the minimum pressure required for the pressure exchange. Residual pressure is generated in the later concentrated brine.

  Therefore, conventionally, as shown in FIG. 5, a pressure reducing valve 9 is provided in the conduit of concentrated salt water after pressure exchange by the pressure exchange device 6, and water is discharged as it is after pressure reduction.

  An object of the present invention is to provide an efficient salt water desalination apparatus and a method for remodeling a salt water desalination apparatus that efficiently uses energy while reducing facility costs.

  In order to achieve the above object, the first characteristic configuration of the saltwater desalination apparatus according to the present invention is the reverse osmosis for separating the saltwater into permeate and concentrated saltwater as described in claim 1 of the claims. A membrane device, a high-pressure pump that boosts low-pressure salt water to a predetermined pressure and supplies the same to the reverse osmosis membrane device, and a pressure exchange device that boosts low-pressure salt water with high-pressure concentrated brine discharged from the reverse osmosis membrane device; A salt water desalination apparatus comprising a booster pump that further boosts the salt water boosted by the pressure exchange device to the predetermined pressure and supplies the boosted water to the reverse osmosis membrane device, and is discharged from the pressure exchange device A residual pressure recovery device that recovers the residual pressure of the concentrated salt water.

  The salt water pressurized by the high-pressure pump is supplied to the reverse osmosis membrane device to be desalinated, and the salt water supplied to the pressure exchange device is pressure-exchanged with the high-pressure concentrated salt water and supplied to the booster pump. Even if residual pressure is generated in the concentrated salt water discharged from the pressure exchange device, the residual pressure of the concentrated salt water is recovered by the residual pressure recovery device. This residual pressure recovery device can sufficiently reduce the energy loss accompanying the drainage of concentrated salt water.

  In the second feature configuration, as described in claim 2, in addition to the first feature configuration described above, the residual pressure recovery device is a reaction driven by concentrated salt water discharged from the pressure exchange device. It is in the point comprised with the water wheel.

  By using a reaction water turbine as the residual pressure recovery device, the residual pressure of the concentrated salt water is recovered by power conversion.

  In the third feature configuration, as described in the third aspect, in addition to the first or second feature configuration described above, the pressure exchanging device has a plurality of pressure exchanging channels around a predetermined axis. And a concentrated salt water supply / drainage section for supplying high-pressure concentrated brine discharged from the reverse osmosis membrane device from one end side of the flow path and draining low-pressure concentrated brine after pressure exchange, A salt water supply / drainage unit that supplies low-pressure salt water from the other end of the flow path and drains high-pressure salt water after pressure exchange, and the concentrated salt water supply / drainage unit and the salt water supply / drainage unit are relative to the cylindrical body. The point is that it is configured to be rotatable.

  When the rotary pressure exchanger described above is used, the concentrated salt water discharged from the concentrated salt water supply / drainage section of the pressure exchanger is stably maintained at a constant flow rate. Therefore, the residual pressure is recovered stably and efficiently by the residual pressure recovery device.

  In the fourth feature configuration, as described in claim 4, in addition to any of the first to third feature configurations described above, a feed water pump for supplying salt water to the high pressure pump and the pressure exchange device is provided. Furthermore, it is in the point provided.

  Salt water is supplied to each of the high-pressure pump and the pressure exchange device by the feed pump, and the salt water pressurized by the high-pressure pump is supplied to the reverse osmosis membrane device for desalination, and the salt water supplied to the pressure exchange device is high-pressure concentrated brine The pressure is exchanged with the booster pump. When the discharge pressure of the feed water pump is adjusted so that cavitation or the like does not occur in the high pressure pump, residual pressure is generated in the concentrated salt water discharged from the pressure exchange device. Even in such a case, the residual pressure is properly recovered by the residual pressure recovery device, and energy loss can be sufficiently reduced.

  In the fifth feature configuration, as described in claim 5, in addition to the fourth feature configuration described above, a power transmission mechanism that transmits power obtained by the reaction water turbine as auxiliary power to the water supply pump is provided. It is in the point to have.

  Since the power collected by the reaction water turbine is used to assist the power of the feed water pump via the power transmission mechanism, the energy required for driving the feed water pump can be reduced.

  In the sixth feature configuration, in addition to any one of the second to fourth feature configurations described above, the power obtained by the reaction water turbine is used as auxiliary power for the booster pump. It is in the point provided with the power transmission mechanism which transmits.

  Since the power recovered by the reaction water turbine is used to assist the power of the booster pump via the power transmission mechanism, the energy required for driving the booster pump can be reduced.

  In the seventh feature configuration, as described in claim 7, in addition to any one of the second to fourth feature configurations described above, a generator that generates power using the power obtained by the reaction water turbine is provided. There is in point.

  When the generator is driven by the power recovered by the reaction water turbine and the recovered power is supplied to, for example, the salt water desalination apparatus, an energy saving apparatus can be constructed as the salt water desalination apparatus.

  The characteristic configuration of the method for remodeling a saltwater desalination apparatus according to the present invention includes a reverse osmosis membrane device that separates saltwater into permeate and concentrated saltwater, and a low-pressure saltwater to a predetermined pressure as described in claim 8. A high-pressure pump that supplies the reverse osmosis membrane device, a pressure exchange device that boosts low-pressure salt water with high-pressure concentrated brine discharged from the reverse osmosis membrane device, and salt water that has been pressurized by the pressure exchange device A booster pump that boosts the pressure and supplies the reverse osmosis membrane device to the reverse osmosis membrane device, wherein the salt water desalination device is remodeled, and the concentrated salt water remains in a piping line of the concentrated salt water discharged from the pressure exchange device. A step of attaching a residual pressure recovery device for recovering pressure, and transmitting the power obtained by the residual pressure recovered by the residual pressure recovery device to the feed water pump or the booster pump, or attached to the residual pressure recovery device In that it includes a step of incorporating a power transmission mechanism for driving a generator, a.

  Energy that has not been used in the existing salt water desalination apparatus can be recovered and reused, and can be remodeled into an efficient salt water desalination apparatus.

  As described above, according to the present invention, it is possible to provide an efficient salt water desalination apparatus and a method for remodeling a salt water desalination apparatus that efficiently uses energy while reducing facility costs. .

(A) is a schematic configuration diagram of a seawater desalination facility, (b) is a schematic configuration diagram of a pretreatment device. (A) is a side view showing an example of a pressure exchange device used in the present invention, (b) is a sectional view of the same. Explanatory drawing which shows the other example of the pressure exchange apparatus used for this invention Schematic configuration diagram of seawater desalination facility showing another embodiment Schematic configuration diagram of a conventional seawater desalination facility

Below, preferable embodiment of the salt water desalination apparatus by this invention is described.
As shown to Fig.1 (a), a salt water desalination apparatus is set as the water quality suitable for the reverse osmosis membrane apparatus 3 with the intake pump 1 which takes in seawater as the salt water which is the object of desalination, and the taken salt water. And a reverse osmosis membrane device 3 for separating the salt water pretreated by the pretreatment device 2 into permeated water and concentrated salt water to make fresh water. Fresh water discharged from the reverse osmosis membrane device 3 is used as drinking water or industrial water.

  As shown by a two-dot chain line in FIG. 1A, the pretreatment device 2 and the reverse osmosis membrane device 3 are installed in different buildings.

  As shown in FIG. 1B, the pretreatment device 2 includes a contaminant removal device 2A that removes contaminants in seawater, and a filtered seawater tank that stores seawater from which contaminants have been removed by the contaminant removal device 2A. 2B, a safety filter 2C, and a water feed pump 2D for supplying salt water stored in the filtered seawater tank 2B to the safety filter 2C. The safety filter 2C includes a microfiltration membrane and an ultrafiltration membrane for removing fine foreign matters in seawater, and is provided to prevent the reverse osmosis membrane device 3 from being clogged.

  The pipe L is laid from the building where the pretreatment device 2 is installed to the building where the reverse osmosis membrane device 3 is installed, and the salt water pretreated by the pretreatment device 2 is sent through the pipe L.

  In the building where the reverse osmosis membrane device 3 is installed, the high-pressure pump 5 supplies the reverse osmosis membrane device 3 with the low-pressure salt water increased to a predetermined pressure, and the high-pressure concentrated salt water discharged from the reverse osmosis membrane device 3 There are provided a pressure exchanging device 6 for boosting low-pressure salt water and a booster pump 7 for further boosting the salt water boosted by the pressure exchanging device 6 to a predetermined pressure and supplying it to the reverse osmosis membrane device 3.

  A water supply pump 4 is provided in the pipe L, and the pretreated salt water is boosted by the water supply pump 4 and branched and supplied to the high pressure pump 5 and the pressure exchange device 6. The reverse osmosis membrane device 3 is a device that exudes fresh water from which various salts in seawater have been removed to the other side of the reverse osmosis membrane by applying pressure to the seawater on one side of the reverse osmosis membrane. In order to filter with, seawater is pressure | voltage-risen to the predetermined pressure more than an osmotic pressure.

  The salt water having a salt concentration of about 4%, which has been boosted to 2 to 4 bar by the feed water pump 4, is boosted to about 40 to 80 bar by the high pressure pump 5 and supplied to the reverse osmosis membrane device 3, and about 40% is desalinated and discharged. , 60% is discharged as salt water concentrated to a salt concentration of about 8%. The concentrated seawater discharged from the reverse osmosis membrane device 3 is supplied to the pressure exchange device 6 while maintaining a pressure of about 40 to 80 ba. The concentrated seawater supplied to the pressure exchange device 6 is pressure-exchanged with 2 to 4 bar salt water branched and supplied from the feed pump 4 to the pressure exchange device 6, and the salt water is increased to a pressure of about 58 to 78 bar. At the same time, the concentrated seawater is depressurized to a pressure of about 1.4 to 3.4 bar.

  The salt water that has been boosted to a pressure of about 58 to 78 bar by the pressure exchange device 6 is boosted to a pressure of about 60 to 80 bar by the booster pump 7, and then merges with the salt water in the discharge side piping of the high pressure pump 5. 3 is supplied.

  The discharge pressure of the feed water pump 4 is set to 2 to 4 bar so that inconvenience such as cavitation does not occur in the high pressure pump 5. The required pressure of the salt water supplied to the pressure exchange device 6 is, for example, about 0.6 bar, which is sufficiently lower than the discharge pressure of the feed water pump 4. Therefore, a residual pressure of about 1.4 to 3.4 bar is held in the low-pressure concentrated salt water that is pressure-exchanged and discharged by the pressure exchange device 6.

  In order to recover this residual pressure, a residual pressure recovery device 8 for recovering the residual pressure of the concentrated salt water discharged from the pressure exchange device 6 is provided.

  Salt water is supplied to the high-pressure pump 5 and the pressure exchange device 6 by the feed water pump 4, and the salt water pressurized by the high-pressure pump 5 is supplied to the reverse osmosis membrane device 3 to be desalinated, and the salt water supplied to the pressure exchange device 6 is The pressure is exchanged with high-pressure concentrated brine and supplied to the booster pump 7.

  Since the discharge pressure of the feed water pump 4 is adjusted so that cavitation or the like does not occur in the high pressure pump 5, residual pressure is generated in the concentrated salt water discharged from the pressure exchange device 6, but the residual pressure is reduced by the residual pressure recovery device. Since it is recovered, the energy loss when the concentrated salt water is discharged can be sufficiently reduced.

  The residual pressure recovery device 8 includes a reaction water turbine 8a driven by concentrated salt water discharged from the pressure exchange device 6, and is connected to an electric motor 8c for driving the booster pump 7 via a mechanical coupler 8b. Furthermore, the motor 8c and the rotating shaft of the booster pump 7 are connected via a mechanical coupler 8d.

  A Francis turbine is preferably used as the reaction turbine 8a, and the rotational power of the Francis turbine driven by concentrated salt water is used as power to assist the electric motor 8c. As a result, the power consumed by the electric motor 8c can be reduced. The mechanical coupler 8b serves as a power transmission mechanism that transmits the power obtained by the reaction water turbine 8a to the booster pump 7 via the electric motor 8c. The reaction water turbine 8a and the mechanical coupler 8b constitute a device that assists the driving force for the pump.

  FIG. 2 shows an example of a positive displacement and rotary pressure exchange device 6. The pressure exchange device 6 includes a cylindrical body 40 in which a plurality of pressure exchange channels 41 and 42 are formed around a predetermined axis, and a high pressure discharged from the reverse osmosis membrane device at one end of the cylindrical body 40. Concentrated salt water is supplied to one end side of the flow path and the concentrated salt water supply / drainage sections 16 and 17 for discharging the low pressure concentrated salt water after pressure exchange, and the low pressure salt water is supplied to the other end side of the flow path and after pressure exchange. Salt water supply / drainage sections 15 and 18 for draining the high-pressure salt water.

  The pressure exchanging device 6 includes a cylindrical casing 12 provided between a first end cover 20 and a second end cover 30 fastened via a connecting member 11. The casing 12 accommodates a first side member 50 and a second side member 60 connected to the first side member 50 via the support shaft 13 and the holding member 14. Further, between the first side member 50 and the second side member 60, the cylindrical body 40 described above is sandwiched so as to be rotatable around the support shaft 13.

  The first side member 50 is supplied with the first fluid inflow passage 51 to which the high-pressure concentrated brine drained from the reverse osmosis membrane device is supplied, and the pressurized high-pressure salt water Ho is discharged to the reverse osmosis membrane device 6. A second fluid outflow passage 52, a second fluid inflow passage 53 to which low-pressure salt water before being pressurized to be supplied to the reverse osmosis membrane device is supplied, and a low-pressure concentrated salt water that has finished transmitting pressure is discharged. One fluid outflow passage 54 is formed in the thickness direction.

  In the cylindrical body 40, a plurality of first flow paths 41 and second flow paths 42 are disposed around the rotation axis so as to penetrate in the rotation axis direction. When high-pressure concentrated salt water is supplied from the first fluid inflow path 51 to the first flow path 41, the low-pressure salt water is pressurized in the cylindrical body 40 to become high-pressure salt water, and the high-pressure salt water is supplied from the second flow path 42 to the second fluid. It flows out to the outflow path 52. When the low-pressure salt water is supplied from the second fluid inflow path 53 to the second flow path 42, the high-pressure concentrated salt water that has transmitted pressure to the low-pressure salt water in the rotating body 40 is transferred from the first flow path 41 to the first fluid outflow path 54. And leaked.

  The cylindrical body 40 has the first side member 50, the second side member 60, and the holding by the energy of each fluid flowing from the first side member 50 and the energy of each fluid flowing out to the first side member 50. It is configured to rotate around the support shaft 13 in a space defined by the member 14. Along with the rotation of the rotating body 40, the plurality of first flow paths 41 communicate with the first fluid inflow path 51 and the first fluid outflow path 54 in order, and the plurality of second flow paths 42 in order with the second fluid inflow path 53. The second fluid outflow passage 52 communicates with each other, and the inflow and outflow of each fluid to the rotating body 40 are continuously performed. That is, the 1st end cover 20 provided with the concentrated salt water supply / drainage parts 16 and 17 and the salt water supply / drainage parts 15 and 18 and the cylindrical body 40 are comprised so that relative rotation is possible.

  The high-pressure concentrated brine supplied from one end of the partial flow path formed in the tubular body 40 is pressurized and discharged from the other end of the flow path, and the other partial flow Concentration discharged from the concentrated salt water supply / drainage section of the pressure exchange device by continuously performing the operation of discharging the concentrated salt water after pressure exchange by the low-pressure salt water supplied from the other end of the path by the relative rotation described above. The salt water is stably maintained at a constant flow rate, and the residual pressure is recovered stably and efficiently by the residual pressure recovery device 8.

  FIG. 3 shows another example of the positive and rotary pressure exchange device 6. The pressure exchange device 6 includes a cylindrical body 40 in which a plurality of flow paths for pressure exchange are formed around a predetermined axis, and high-pressure concentrated brine discharged from the reverse osmosis membrane device at the end of the cylindrical body 40. Is supplied to one end of the flow path and drains the low-pressure concentrated salt water after pressure exchange, and the low-pressure salt water is supplied to the other end side of the flow path and the high-pressure after pressure exchange. And salt water supply / drainage sections 15 and 18 for draining the salt water. And the concentrated salt water supply / drainage parts 16 and 17 and the salt water supply / drainage parts 15 and 18 and the cylindrical body 40 are comprised so that relative rotation is possible.

  As the pressure exchange device, a method of directly exchanging pressure between salt water and concentrated salt water without using a rotating body such as the cylindrical body 40, for example, a piston type pressure exchange device or the like can be used.

  However, when a rotating body is not provided, it is necessary to provide a switching valve that introduces fluid into each flow path to switch between inflow and outflow of the fluid, which causes fluctuations in the flow and pressure of the concentrated drainage. As a result, the residual pressure cannot be recovered stably. In addition, there is a pressure exchange device that employs a configuration in which pressure is exchanged between salt water and concentrated salt water via a member, but friction loss of the member occurs. Therefore, it is optimal to use a pressure exchange device as shown in FIGS. 2 and 3 in which the salt water and the concentrated salt water directly exchange the pressure without rotating through the other members by the rotation of the cylindrical body 40.

  Furthermore, although a pressure exchange device using a water wheel is applicable to the present application, since the residual pressure of the concentrated waste water is low, the amount of residual pressure recovered by the residual pressure recovery device is small, and the effect is not as high as that of a positive displacement and rotary pressure exchange device .

  As shown in FIG. 4, for the same purpose, a power transmission mechanism 8b for transmitting the energy recovered by the residual pressure recovery device 8, that is, the power obtained by the reaction water turbine 8a, as auxiliary power for the feed water pump 4 may be provided. Good.

  Furthermore, you may comprise with the generator which generate | occur | produces with the motive power obtained by the reaction water turbine 8a, and it may comprise so that it may supply electric power to the various electrical equipment with which the salt water desalination apparatus was equipped.

  In addition, the reaction water turbine is excellent in the ability to collect pressure with the impeller of the water wheel, and when the residual pressure remains like the positive displacement type rotary pressure recovery device, the impulse is excellent in the ability to recover the speed. This is a device for recovering the residual pressure more suitable than the water wheel.

  In the embodiment described above, the configuration in which the water supply pump 4 is provided in the vicinity of the reverse osmosis membrane device 3 has been described. However, the water supply pump 2D provided in the pretreatment device 2 may be used instead of the water supply pump.

  In this case, it is necessary to supply the pressure required for the booster pump 7 with the water pump 2D, and the cost increases due to the increased capacity of the water pump 2D, and the piping L from the pretreatment device 2 to the booster pump 7 can withstand high pressure. Thus, since the material is changed or the tube thickness is increased, the cost is increased. Therefore, it is preferable to provide the water supply pump 4 in the vicinity of the reverse osmosis membrane device 3 as in the above-described embodiment.

  A reverse osmosis membrane device that separates salt water into permeate and concentrated salt water, a high-pressure pump that boosts low-pressure salt water to a predetermined pressure and supplies the reverse osmosis membrane device, and high-pressure concentration discharged from the reverse osmosis membrane device Existing salt water fresh water comprising a pressure exchanging device that boosts low-pressure salt water with salt water, and a booster pump that further boosts the salt water boosted by the pressure exchanging device to the predetermined pressure and supplies it to the reverse osmosis membrane device By remodeling the above-described saltwater desalination apparatus, the energy that has not been used can be recovered and reused, and can be remodeled into an efficient saltwater desalination apparatus. It becomes like this.

  That is, the salt water desalination device is modified by attaching a residual pressure recovery device for recovering the residual pressure of the concentrated salt water to the piping line of the concentrated salt water discharged from the pressure exchange device, and the residual pressure recovered by the residual pressure recovery device. The power obtained by pressure is transmitted to a feed water pump or a booster pump, or a power transmission mechanism for driving a generator attached to the residual pressure recovery device is incorporated.

  When the residual pressure recovery device 8 is configured to include the above-described reaction water turbine 8a, the mechanical coupler 8b and the like serve as a power transmission mechanism.

  It is needless to say that the specific configuration of the salt water desalination apparatus described above is not limited to the description of the embodiment, and can be appropriately changed and designed within the scope of the effects of the present invention.

3: Reverse osmosis membrane device 4: Water supply pump 5: High pressure pump 6: Pressure exchange device 7: Booster pump 8: Residual pressure recovery device 8a: Reaction water turbine

Claims (8)

A reverse osmosis membrane device that separates salt water into permeate and concentrated salt water, a high-pressure pump that boosts low-pressure salt water to a predetermined pressure and supplies the reverse osmosis membrane device, and high-pressure concentration discharged from the reverse osmosis membrane device Salt water desalination comprising: a pressure exchanging device that boosts low-pressure salt water with salt water; and a booster pump that further boosts the salt water boosted by the pressure exchanging device to the predetermined pressure and supplies it to the reverse osmosis membrane device. A device,
A salt water desalination apparatus comprising a residual pressure recovery device for recovering a residual pressure of concentrated salt water discharged from the pressure exchange device.   The salt water desalination apparatus according to claim 1, wherein the residual pressure recovery apparatus includes a reaction water turbine driven by concentrated salt water discharged from the pressure exchange device.   The pressure exchange device supplies a cylindrical body in which a plurality of flow channels for pressure exchange are formed around a predetermined axis, and high-pressure concentrated salt water discharged from the reverse osmosis membrane device from one end of the flow channel. And a salt water supply / drainage section for draining low-pressure concentrated salt water after pressure exchange, and a salt water supply / drainage section for feeding low-pressure salt water from the other end of the flow path and draining high-pressure salt water after pressure exchange. The salt water desalination apparatus according to claim 1 or 2, wherein the concentrated salt water supply / drainage unit and the salt water supply / drainage unit are configured to be rotatable relative to the cylindrical body.   The salt water desalination apparatus in any one of Claim 1 to 3 further equipped with the feed water pump which supplies salt water to the said high pressure pump and the said pressure exchange apparatus.   The salt water desalination apparatus of Claim 4 provided with the power transmission mechanism which transmits the motive power obtained by the said reaction water turbine as auxiliary power of the said water supply pump.   The salt water desalination apparatus in any one of Claim 2 to 4 provided with the power transmission mechanism which transmits the motive power obtained by the said reaction water turbine as auxiliary power of the said booster pump.   The salt water desalination apparatus in any one of Claim 2 to 4 provided with the generator which produces electric power with the motive power obtained by the said reaction water turbine. A reverse osmosis membrane device that separates salt water into permeate and concentrated salt water, a high-pressure pump that boosts low-pressure salt water to a predetermined pressure and supplies the reverse osmosis membrane device, and high-pressure concentration discharged from the reverse osmosis membrane device Salt water desalination comprising: a pressure exchanging device that boosts low-pressure salt water with salt water; and a booster pump that further boosts the salt water boosted by the pressure exchanging device to the predetermined pressure and supplies it to the reverse osmosis membrane device. A method of remodeling the device,
Attaching a residual pressure recovery device for recovering the residual pressure of the concentrated salt water to a piping line of the concentrated salt water discharged from the pressure exchange device;
A step of transmitting power obtained by the residual pressure recovered by the residual pressure recovery device to the feed water pump or the booster pump, or incorporating a power transmission mechanism for driving a generator attached to the residual pressure recovery device. Remodeling method of salt water desalination equipment.

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