JP2020110736A - Energy recovery apparatus - Google Patents

Abstract

To provide an energy recovery apparatus capable of simplifying a facility by using only one pressurization pump.SOLUTION: Provided is an energy recovery apparatus to be connected to a membrane separation device 5 that separates high-pressure seawater into fresh water and concentrated seawater. The energy recovery apparatus comprises: a water supply pump P1 for supplying seawater; a high-pressure pump P2 for supplying high-pressure seawater to the membrane separation device; a plurality of cylinder devices 7A and 7B; a flow channel direction regulating mechanism 11; and a control unit C having a control function for implementing a force-feed process and a filling process. The cylinder device includes: a cylinder 8 of which one end communicates with the water supply pump and to which seawater is introduced from the one end side, and of which the other end is connected to a concentrated water pipe and a drainage channel and to which the concentrated seawater is introduced from the other end side; a piston 9 which reciprocates inside the cylinder; and a piston rod 12 of which one end is connected to the piston and the other end projects from the other end of the cylinder to the outside.SELECTED DRAWING: Figure 1

Description

The present invention relates to an energy recovery device for a water treatment system by a reverse osmosis membrane method used for desalination of seawater and the like.

The reverse osmosis method is known as one of the methods for producing fresh water from seawater. In this reverse osmosis method, salt water and fresh water are separated by applying a high pressure equal to or higher than the osmotic pressure of seawater to the seawater in the direction opposite to the direction in which the osmotic pressure acts and filtering with a semipermeable membrane (reverse osmosis membrane: RO membrane). To do. In this reverse osmosis method, seawater in which fresh water is separated and salts are concentrated (concentrated seawater) flows out from the reverse osmosis membrane module while maintaining high pressure energy. Various energy recovery devices have been put to practical use in order to effectively utilize the high pressure energy of the flowing out concentrated seawater.

Conventionally, for example, Patent Document 1 proposes an example of an energy recovery device in a seawater desalination system by a reverse osmosis method. In Patent Document 1, one end of each of the pair of cylinder devices is communicated with a water feed pump and a pressure boosting pump via a flow path direction regulating device configured by two check valves. The other end of the cylinder device is communicated with the inflow/outflow port of the flow path switching device. Further, the inflow port of the flow path switching device is communicated with the high pressure concentrated seawater outlet of the reverse osmosis membrane module. Further, an outflow port is provided at one end of the flow path switching device.

In this energy recovery device, seawater sent from the water supply pump is pressurized by the high-pressure pump and supplied to the reverse osmosis membrane module, and high-pressure concentrated seawater discharged from the reverse osmosis membrane module is supplied to the cylinder device at high pressure. The piston that pushes out seawater is driven, and high-pressure seawater is also sent from the cylinder device to the reverse osmosis membrane module through the booster pump. The operation of supplying the high-pressure concentrated seawater discharged from the reverse osmosis membrane module to the cylinder device and driving the piston that pushes out the seawater at high pressure is referred to as a pressure feeding step.
In addition, after the completion of the pressure feeding process, seawater is supplied from the water supply pump to the cylinder device via the flow path direction regulating device, and the piston is driven in the direction opposite to the pressure feeding process to discharge the concentrated seawater and to fill the seawater. It is called a filling process.
As described above, in this energy recovery device, when the piston of the cylinder device reaches the end of the cylinder, the flow switching device alternately supplies the high-pressure concentrated seawater from the reverse osmosis membrane module to the pair of cylinder devices and the water supply pump. The control is performed so that the pair of cylinder devices are alternately filled with seawater.

This allows continuous filtration by repeatedly performing the seawater pressure feeding step and the filling step with the two cylinder devices. In this way, by using high-pressure energy of concentrated seawater discharged from the reverse osmosis membrane module to supply high-pressure seawater from the two cylinder devices to the reverse osmosis module via the pressure boosting pump, the energy consumption of the high-pressure pump is reduced. Be reduced.

JP, 2013-86043, A

In the above-mentioned conventional technique, the following problems remain.
That is, in the above conventional technique, high-pressure seawater is sent to the membrane separation device by a high-pressure pump that directly pressurizes the seawater sent from the water supply pump and a pressure-increasing pump that pressurizes the seawater sent from the cylinder device. Since two pressure increasing paths using two pumps are required, the equipment becomes complicated and the equipment cost increases.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an energy recovery device that requires only one pressurizing pump and can simplify equipment.

The present invention adopts the following configurations in order to solve the above problems. That is, the energy recovery apparatus according to the first aspect of the invention is a membrane separation that separates high-pressure seawater into fresh water and concentrated seawater with a reverse osmosis membrane, discharges the freshwater to a freshwater pipe, and discharges the high-pressure concentrated seawater to a concentrated water pipe. An energy recovery device connected to the device, a water supply pump for supplying seawater, a high-pressure pump for pressurizing the seawater to supply the high-pressure seawater to the membrane separation device, and one end communicating with the water supply pump, A plurality of ends each connected to the concentrated water pipe and the drainage channel through a flow path switching mechanism that communicates with and blocks the concentrated water channel and also communicates with and blocks the drainage channel of the concentrated seawater. Of the cylinder device and one end of the plurality of cylinder devices, the seawater is alternately supplied to the plurality of cylinder devices, and the seawater that is alternately extruded at high pressure from the plurality of cylinder devices is the membrane separation device. To control the flow channel direction control mechanism and the flow channel switching mechanism to switch the connection of the plurality of cylinder devices to the concentrated water pipe and the drainage channel, and to supply the concentrated seawater of high pressure to the cylinder device. Control function to perform a pressure-feeding step of pushing out the seawater at high pressure, and a filling step of supplying the seawater from the water supply pump to the cylinder device after the pressure-feeding step to discharge the concentrated seawater inside, and the seawater. The cylinder device, the other end is connected to the concentrated water pipe and the drainage channel, the concentrated seawater is introduced from the other end side, and one end communicates with the water supply pump From which the seawater is introduced, a piston reciprocating in the cylinder, and a piston rod having one end connected to the piston and the other end protruding outward from the other end of the cylinder. And

In this energy recovery device, the cylinder device includes a piston that reciprocates in the cylinder, and a piston rod that has one end connected to the piston and the other end that protrudes outward from the other end of the cylinder. The cross-sectional area on one end side of the piston and the cross-sectional area on the other end side of the piston differ depending on the (cross-sectional area), and it is possible to set the seawater sent out from the cylinder device to the desired pressure and flow rate. ..
That is, according to Pascal's principle, the input/output ratio of the pressure and flow rate of seawater in the cylinder device is the cross-sectional area of one end side of the piston (cross-sectional area inside the cylinder) and the cross-sectional area of the other end side of the piston in the cylinder. Since it is proportional to the area ratio with (the area obtained by subtracting the cross-sectional area of the piston rod from the cross-sectional area of the inside of the cylinder), only the flow rate and pressure on the other end side of the piston into which the concentrated seawater is introduced need be controlled. The control system can be easily constructed. In addition, the pressure energy recovered from the concentrated seawater entering the other end of the piston is transmitted to the seawater entering the one end of the piston and supplied to the suction side of the high-pressure pump, so that the high-pressure pump discharges only the amount corresponding to the pushing pressure. It becomes possible to raise the pressure.
In this way, seawater pressure is further added by pushing out seawater from the cylinder device and supplying it to the high-pressure pump side at the pressure and flow rate set on the other end side of the piston and the one end side of the piston in the cylinder. Can be supplied to the membrane separation device, and the seawater from the water supply pump is boosted and supplied to the high-pressure pump to compensate for the head loss of each part such as the semipermeable membrane (reverse osmosis membrane: RO membrane) and each pipe. Eliminates need for pressure pump. That is, the amount of pressure discharged from the cylinder device becomes the pushing pressure of the high-pressure pump, and the total lifting height of the high-pressure pump can be lowered by the pushing pressure. Since the head loss of each portion such as the RO membrane and each pipe may be added to the head of the high pressure pump, the booster pump becomes unnecessary.
Further, since the flow rate and the pressure ratio associated with the energy transfer are always constant, the control of the entire system including the present device may be performed only for the flow rate and the pressure on the other end side of the piston, which facilitates the control.

An energy recovery device according to a second invention is the energy recovery device according to the first invention, wherein the concentrated water pipe and the drainage channel are connected to the other end of the cylinder or a peripheral surface in the vicinity of the other end to introduce and discharge the concentrated seawater. It is characterized in that a concentrated seawater inlet for operation is provided.
That is, in this energy recovery device, on the peripheral surface of the other end of the cylinder or in the vicinity of the other end, since the concentrated seawater inlet for introducing and discharging the concentrated seawater is provided, which is connected to the concentrated water pipe and the drainage channel, Regardless of the outer diameter of the piston rod, a concentrated seawater inlet can be provided near the other end of the cylinder, and the concentrated seawater can be stably introduced and discharged.

In the energy recovery device according to a third aspect of the present invention, in the first or second aspect of the present invention, a through hole through which the piston rod penetrates is formed at the other end of the cylinder, and the concentration is on the inner peripheral surface of the through hole. It is characterized in that a rod seal for preventing leakage of seawater to the outside is provided.
That is, in this energy recovery device, a through hole through which the piston rod penetrates is formed at the other end of the cylinder, and a rod seal that prevents leakage of concentrated seawater to the outside is provided on the inner peripheral surface of the through hole. Therefore, the concentrated seawater can be prevented from leaking out around the piston rod protruding from the other end of the cylinder.

The present invention has the following effects.
That is, according to the energy recovery device of the present invention, the cylinder device includes the piston that reciprocates in the cylinder, and the piston rod that has one end connected to the piston and the other end that projects outward from the other end of the cylinder. , The cross-sectional area on one end side of the piston and the cross-sectional area on the other end side of the piston in the cylinder are different depending on the thickness (cross-sectional area) of the piston rod, and the pressure and flow rate of seawater sent out from the cylinder device are set. It will be possible.
Therefore, in the energy recovery device of the present invention, seawater can be sent to the membrane separation device at a high pressure and a sufficient flow rate only by the high-pressure pump, and the pressure boosting pump that was required in the past becomes unnecessary, and the facility can be simplified. It is possible to reduce the equipment cost.

It is a schematic diagram which shows 1st Embodiment of the energy recovery apparatus which concerns on this invention. It is a schematic diagram of the principal part which shows 2nd Embodiment of the energy recovery apparatus which concerns on this invention.

Hereinafter, a first embodiment of the energy recovery device according to the present invention will be described with reference to FIG.

As shown in FIG. 1, the energy recovery device 1 according to the present embodiment separates high-pressure seawater into fresh water and concentrated seawater by a reverse osmosis membrane, discharges the freshwater to a freshwater pipe 3, and feeds the high-pressure concentrated seawater to a concentrated water pipe 4. It is an energy recovery device connected to the discharging membrane separation device 5.

The energy recovery device 1 includes a water supply pump P1 for supplying seawater, a high pressure pump P2 for pressurizing seawater to supply high pressure seawater to the membrane separation device 5, one end of which communicates with the water supply pump P1 and a concentrated water pipe 4. A plurality of cylinders, the other ends of which are connected to the concentrated water pipe 4 and the drainage path 19 respectively, via flow path switching mechanisms 6A and 6B that perform communication and cutoff and communication and cutoff with the drainage path 19 of the concentrated seawater. Device 7A, 7B and one end of the plurality of cylinder devices 7A, 7B, seawater is alternately supplied to the plurality of cylinder devices 7A, 7B, and seawater is alternately extruded at high pressure from the plurality of cylinder devices 7A, 7B. To control the flow direction control mechanism 11 for returning the water to the membrane separation device 5 and the flow path switching mechanisms 6A and 6B to switch the connection of the plurality of cylinder devices 7A and 7B to the concentrated water pipe 4 and the drainage path 19 to obtain high-pressure concentrated seawater. Is supplied to the cylinder devices 7A, 7B to push out the internal seawater at high pressure, and after the pressure feeding process, the seawater from the water supply pump P1 is supplied to the cylinder devices 7A, 7B to discharge the concentrated seawater inside the seawater. It is provided with a filling process for filling and a control unit C having a control function to perform.

The cylinder device 7A, 7B is a cylinder in which the other end is connected to the concentrated water pipe 4 and the drainage channel 19, concentrated seawater is introduced from the other end side, and one end communicates with the water supply pump P1 and seawater is introduced from one end side. 8, a piston 9 that reciprocates in the cylinder 8, and a piston rod 12 having one end connected to the piston 9 and the other end protruding outward from the other end of the cylinder 8.
A piston seal (not shown) for preventing leakage is provided on the outer peripheral surface of the piston 9.

At the other end of the cylinder 8 or on the peripheral surface near the other end, a concentrated seawater inlet 8a is provided which is connected to the concentrated water pipe 4 and the drainage channel 19 to introduce and discharge the concentrated seawater.
The concentrated seawater inlet 8a is connected to one end of the connecting pipe 13e, and the other end of the connecting pipe 13e is connected to the inflow/outflow port 13c. That is, the cylinder 8 is connected to the inflow/outflow port 13c via the concentrated seawater inlet 8a and the connecting pipe 13e.
Further, a through hole 8b through which the piston rod 12 penetrates is formed at the other end of the cylinder 8, and a rod seal (not shown) for preventing leakage of concentrated seawater to the outside is formed on the inner peripheral surface of the through hole 8b. It is provided.

Further, the flow path direction regulating mechanism 11 is set so as to supply the seawater pushed out from each of the cylinder devices 7A and 7B to the suction side of the high pressure pump P2. That is, the flow path direction regulation mechanism 11 is set to send the seawater pushed out from each of the cylinder devices 7A and 7B to the connecting pipe 11e connected to the suction side of the high-pressure pump P2.

The cylinder devices 7A and 7B have one end connected to the concentrated water pipe 4 through the first flow path switching mechanism 6A which communicates with and cuts off the concentrated water pipe 4 and also communicates with and cuts off the concentrated seawater drainage pipe 19. The first cylinder device 7A connected to the pipe 19 communicates with and shuts off the concentrated water pipe 4, and at the same time one end concentrates via a second flow path switching mechanism 6B that communicates with the drain pipe 19 and shuts off. The second cylinder device 7B connected to the water pipe 4 and the drain pipe 19 is provided.

That is, the control unit C controls the first channel switching mechanism 6A and the second channel switching mechanism 6B to switch the connection between the concentrated water pipe 4 and the drain pipe 19 between the first cylinder device 7A and the second cylinder device 7B. , And has a control function of alternately flowing the high-pressure concentrated seawater into the first cylinder device 7A and the second cylinder device 7B and a control function of alternately discharging the concentrated seawater from the first cylinder device 7A and the second cylinder device 7B. ing.

Further, a water supply pump P1 is connected to the seawater supply pipe 2a, and the seawater is sent from the supply pipe 2a to the flow path direction regulation mechanism 11 by the water supply pump P1.
The flow path direction regulation mechanism 11 supplies seawater to the first cylinder device 7A and the second cylinder device 7B alternately, and at the same time, the seawater is alternately pushed out at high pressure from the first cylinder device 7A and the second cylinder device 7B. Is returned to the membrane separation device 5 via the connecting pipe 11e.

The concentrated water pipe 4 is branched midway and connected to the first flow path switching mechanism 6A and the second flow path switching mechanism 6B.
The first flow channel switching mechanism 6A and the second flow channel switching mechanism 6B are configured to supply and stop concentrated seawater to the first cylinder device 7A or the second cylinder device 7B, and stop the first cylinder device 7A or the second cylinder device 7B. A switching cylinder device 13 for switching between discharging the concentrated seawater from the tank and stopping it, and a drive device 14 for driving the switching cylinder device 13.

The switching cylinder device 13 reciprocates in the switching cylinder 20 and the switching cylinder 20 connected to one end of the first cylinder device 7A or the second cylinder device 7B, the drainage pipe 19 and the concentrated water pipe 4. A drain side piston 20a capable of communicating and blocking one end of the first cylinder device 7A or the second cylinder device 7B with the drain pipe 19 and the concentrated water pipe 4, and reciprocates integrally with the drain side piston 20a in the switching cylinder 20. The supply-side piston 20b and the drain-side piston 20a are provided at one end, the supply-side piston 20b is provided at an intermediate portion, and the other end projects from the other end of the switching cylinder 20 to the outside and is connected to the drive device 14. And a switching piston rod 22.

The switching cylinder 20 includes an outflow port 13a connected to the concentrated seawater drainage pipe 19 and provided on one end side, an inflow port 13b connected to the concentrated water pipe 4 and provided in an intermediate portion, and the first cylinder device 7A or It has an inflow/outflow port 13c connected to the second cylinder device 7B and provided between the outflow port 13a and the inflow port 13b.

The control unit C is provided at each of a plurality of positions including, for example, the vicinity of the other end of the cylinder 8 of each of the cylinder devices 7A and 7B, and can detect the position of the piston 9, in particular, the fact that the piston 9 has reached the vicinity of the other end of the cylinder 8. A position detector (not shown) is provided at the position, and has a function of controlling the first flow path switching mechanism 6A and the second flow path switching mechanism 6B based on the detection signals of these position detectors.
It should be noted that the position detector may be installed at a position other than the above on the cylinder 8.

Further, even if the position detector attached to the cylinder 8 is not provided, the piston rod 12 projects from the cylinder 8 in this embodiment, and the position of the piston 9 can be determined from the amount of projection. Therefore, when the piston rod 12 reaches a predetermined protrusion amount, a function of issuing a signal to control the first flow path switching mechanism 6A and the second flow path switching mechanism 6B may be adopted.

The first flow path switching mechanism 6A and the second flow path switching mechanism 6B include the drive device 14 that drives the switching cylinder device 13.
The drive unit 14 is configured by using, for example, a hydraulic piston connected to a hydraulic pump, an electric actuator, and the like.
The control unit C has a function of operating a drive device 14 by controlling a hydraulic servo valve or a servo motor (not shown) based on the detection signal.

The other end of each of the first cylinder device 7A and the second cylinder device 7B is in communication with the water feed pump P1 via the flow path direction regulation mechanism 11 including a pair of check valves 11.
One end of the first cylinder device 7A is communicated with the inflow/outflow port 13c of the switching cylinder device 13 in the first flow path switching mechanism 6A, and one end of the second cylinder device 7B is used for switching in the second flow path switching mechanism 6B. It communicates with the inflow/outflow port 13c of the cylinder device 13.

The inflow port 13 b of the switching cylinder device 13 is connected to the concentrated water pipe 4. Further, at one end of the switching cylinder device 13, an outflow port 13a connected to the drain pipe 19 is provided. The drain side piston 20 a and the supply side piston 20 b arranged in the switching cylinder 20 are connected to the switching piston rod 22. Further, one end of the switching piston rod 22 is connected to the driving device 14 and reciprocates in the switching cylinder 20 in conjunction with the driving device 14.

The flow path direction regulating mechanism 11 has a pair of branch pipes 11c connected to the supply pipe 2a, and one end of the corresponding first cylinder device 7A and second cylinder device 7B is provided in the middle of these branch pipes 11c. It is connected through a cylinder connecting pipe 11d. In the branch pipe 11c, a pair of check valves 11 are provided on both sides of the connecting portion of the cylinder connecting pipe 11d. The other ends of the pair of branch pipes 11c are connected to the connecting pipe 11e.

Next, the operation of the energy recovery system 1 of this embodiment will be described with reference to the drawings.
First, as shown in FIG. 1, when the piston 9 of the first cylinder device 7A in the pressure feeding step moves in the direction of the arrow Y1, the seawater in the cylinder 8 is pushed out to the side of the branch pipe 11c. The seawater pushed out to the branch pipe 11c is supplied to the high-pressure pump P2 via the connecting pipe 11e.
On the other hand, when the piston 9 of the second cylinder device 7B in the filling step moves in the direction of the arrow Y2, the concentrated seawater in the cylinder 8 is discharged to the drain pipe 19 via the concentrated seawater inlet 8a and the inflow/outflow port 13c. ..

When the piston 9 of the first cylinder device 7A reaches the position of the predetermined position detector, a detection signal is transmitted from the position detector to the control unit C, and when the control unit C receives this detection signal, the control unit C The drive device 14 of the second flow path switching mechanism 6B is controlled to switch the flow path.
At this time, the inflow port 13b and the outflow/outflow port 13c of the switching cylinder device 13 in the second flow path switching mechanism 6B are communicated with each other, and high-pressure concentrated seawater is supplied from the membrane separation device 5 to the second cylinder device 7B. The communication between the inflow/outflow port 13c and the outflow port 13a is blocked, and the pressure feeding process of the second cylinder device 7B is started.
The flow paths are switched in this way, and the first cylinder device 7A and the second cylinder device 7B alternately repeat the pressure feeding process and the filling process.

In the present embodiment, the flow rate of seawater sent to the high-pressure pump P2 by the cylinder devices 7A and 7B is
Q ₁ : Flow rate of concentrated seawater sent from the piston in the cylinder to the other end side Q ₂ : Flow rate of seawater sent from one end side in the cylinder piston A ₁ : Cross-sectional area of the other end side of the piston in the cylinder (cylinder Area obtained by subtracting the cross-sectional area of the piston rod from the inner cross-sectional area of, that is, the ring-shaped area on the outer circumference of the piston rod)
A _2: (inside sectional area of the cylinder) the cross-sectional area of the one end side of the piston in the cylinder,
Then, the relation between the flow rate and the area is determined by the following relational expression.
Flow ratio: area ratio _{= Q 2 / Q 1: A} 2 / A 1

For example, when the ratio of the cross-sectional area A ₁ on the other end side of the piston 9 in the cylinder 8 to the cross-sectional area A ₂ on the one end side of the piston 9 in the cylinder 8 is A ₁ :A ₂ =1:2. Will be described below.
In this case, in the first cylinder device 7A in the pressure feeding step, if the introduction flow rate of the concentrated seawater on the other end side of the piston 9 in the cylinder 8 is 5,000 m ³ /d and the pressure is 4.0 MPa, the piston in the cylinder 8 The discharge flow rate of seawater on one end side from 9 is 10,000 m ³ /d, and the pressure is 2.0 MPa.

At this time, the high pressure pump P2, the pressure in the flow from the first cylinder device 7A is 10,000 m ³ / d is sent seawater 2.0 MPa, flow rate membrane separation device 5 is at 10,000 m ³ / d When it is desired to send in seawater having a pressure of 4.0 MPa, it is sufficient to increase the pressure by 2.0 MPa in the high-pressure pump P2.
Therefore, in the conventional technology, high-pressure seawater is sent to the membrane separation device by a high-pressure pump that directly pressurizes the seawater sent from the water supply pump and a pressure-increasing pump that pressurizes the seawater sent from the cylinder device. It was necessary to have two lines of pressure increasing path using two. In the present embodiment, the entire amount of seawater sent from the cylinder device is sent to the suction side of the high-pressure pump, and the loss head of each part such as the RO membrane and each pipe that the booster pump has supplemented is taken into account in the total head of the high-pressure pump. No need for a pump.

In the membrane separation device 5, the concentrated seawater is sent to the first cylinder device 7A at a flow rate of 5,000 m ³ /d and a pressure of 4.0 MPa, and fresh water (permeate) is sent at a flow rate of 5,000 m ³ /d to a fresh water pipe. Sent to 3.
At this time, in the second cylinder device 7B, which is the filling step, the flow rate of seawater from one end of the cylinder 8 is 10,000 m ³ /d, and the discharge amount of concentrated seawater from the other end side of the cylinder 8 is 5 m ^2. 1,000 m ³ /d.

As described above, in the energy recovery device 1 of the present embodiment, the cylinder devices 7A and 7B have the piston 9 that reciprocates in the cylinder 8 and one end connected to the piston 9 and the other end protruding outside from the other end of the cylinder 8. Since the piston rod 12 is provided, the cross-sectional area on one end side of the piston 9 and the cross-sectional area on the other end side of the piston 9 in the cylinder 8 differ depending on the thickness (cross-sectional area) of the piston rod 12. It is possible to set the pressure and flow rate of seawater delivered from the devices 7A and 7B.

That is, the input/output ratio between the pressure and the flow rate of seawater in the cylinder devices 7A and 7B is such that the cross-sectional area on one end side of the piston 9 (the cross-sectional area on the inner side of the cylinder 8) and the cross-sectional area on the other end side of the piston 9 are Since it is proportional to the area ratio with the area (area obtained by subtracting the cross-sectional area of the piston rod 12 from the cross-sectional area of the inside of the cylinder 8), only the flow rate and pressure on the other end side of the piston 9 into which the concentrated seawater is introduced are controlled. Therefore, the control system can be easily constructed. Further, the pressure energy recovered from the concentrated seawater entering the other end side of the piston 9 is transmitted to the seawater entering the one end side of the piston 9 and is supplied to the suction side of the high pressure pump P2, so that the high pressure pump corresponds to the pushing pressure. It becomes possible to raise the discharge pressure.

In this way, by extruding seawater from the cylinder devices 7A and 7B at the pressure and flow rate set on the other end side of the piston 9 and the one end side of the piston 9 in the cylinder 8 and supplying the seawater to the high pressure pump P2 side, The pressure of seawater can be further added and supplied to the membrane separation device 5, and seawater from the water supply pump P1 is boosted and supplied to the high-pressure pump P2 to compensate for the head loss of each part such as the RO membrane and each pipe. No need for booster pump.
That is, the amount of pressure from the one end side of the piston 9 in the cylinder 8 becomes the pushing pressure of the high-pressure pump P2, and the total head of the high-pressure pump P2 can be lowered by the pushing pressure. The head loss of the high pressure pump P2 may be added to the head loss of each part such as the RO membrane and each pipe, so that the booster pump is not required.
Further, since the flow rate and the pressure ratio associated with the energy transfer are always constant, the control of the entire system including the present device may be performed only for the flow rate and the pressure on the other end side of the piston, which facilitates the control.

Further, since the concentrated seawater inlet port 8a for introducing and discharging the concentrated seawater, which is connected to the concentrated water pipe 4 and the drainage channel 19, is provided on the other end of the cylinder 8 or in the vicinity of the other end, the piston rod Regardless of the outer diameter of 12, the concentrated seawater inlet 8a can be provided near the other end of the cylinder 8, and the concentrated seawater can be stably introduced and discharged.
Further, a through hole 8b through which the piston rod 12 penetrates is formed at the other end of the cylinder 8, and a rod seal that prevents the concentrated seawater from leaking to the outside is provided on the inner peripheral surface of the through hole 8b. It is possible to prevent the concentrated seawater from leaking around the piston rod 12 protruding from the other end of the cylinder 8.

Next, 2nd Embodiment of the energy recovery apparatus in this invention is described based on FIG. In the following description of the embodiments, the same components as those described in the above embodiments will be designated by the same reference numerals, and the description thereof will be omitted.

The difference between the second embodiment and the first embodiment is that the first embodiment is provided with two cylinder devices 7A and 7B, whereas the energy recovery device 21 of the second embodiment is shown in FIG. As shown, three cylinder devices 7A, 7B and 7C are provided.
That is, in the second embodiment, the cylinder device includes the first cylinder device 7A, the second cylinder device 7B, and the third cylinder device 9C.

In the second embodiment, the branch pipe 11c is branched into three corresponding to the three cylinder devices, and is divided into the first cylinder device 7A, the second cylinder device 7B, and the third cylinder device 7C via the check valves 11a, respectively. It is connected.
The flow path switching mechanism is also composed of three first flow path switching mechanism 6A, second flow path switching mechanism 6B, and third flow path switching mechanism 6C corresponding to the three cylinder devices.
The third cylinder device 7C also has the same cylinder structure as the first cylinder device 7A and the second cylinder device 7B.

In the second embodiment, of the three cylinder devices 7A, 7B, and 7C, for example, when the first cylinder device 7A is the pressure feeding process and the third cylinder device 9C is the filling process, the second cylinder device 7B is In the state where the piston 9 has reached the other end of the second cylinder device 7B, the process switching of the cylinder devices 7A, 7B, 7C is set so that the second cylinder device 7B becomes the standby process. That is, by using one of the three cylinder devices 7A, 7B, and 7C as a pressure feed process, one as a filling process, and one as a standby process, seawater is constantly supplied from the water supply pump P1 to supply water. The pulsation of the pump P1 can be suppressed.

As described above, also in the energy recovery device 21 of the second embodiment, the three cylinder devices 7A, 7B, and 7C include the piston 9 that reciprocates in the cylinder 8, and one end of which is connected to the piston 9 and the other end of which is the cylinder 8. Since the piston rod 12 projecting from the end to the outside is provided, the cross-sectional area on one end side of the piston 9 and the cross-sectional area on the other end side of the piston 9 in the cylinder 8 are determined according to the thickness (cross-sectional area) of the piston rod 12. Unlike the above, it becomes possible to set the pressure and flow rate of seawater sent from the cylinder devices 7A, 7B, 7C.

It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

1, 21... Energy recovery device, 2a... Supply pipe, 3... Fresh water pipe, 4... Concentrated water pipe, 5... Membrane separation device, 6A... First flow path switching mechanism, 6B... Second flow path switching mechanism, 6C... 3 flow path switching mechanism, 7A... 1st cylinder device, 7B... 2nd cylinder device, 7C... 3rd cylinder device, 8... Cylinder, 8a... Concentrated seawater inlet, 8b... Through hole, 9... Piston, 11... Flow Road direction regulation mechanism, 12... Piston rod, 19... Drainage channel of concentrated seawater, P1... Water supply pump, P2... High pressure pump, C... Control section

Claims (3)

An energy recovery device that is connected to a membrane separation device that separates high-pressure seawater into fresh water and concentrated seawater with a reverse osmosis membrane and discharges the freshwater to a freshwater pipe and discharges the high-pressure concentrated seawater to a concentrated water pipe,
A water supply pump for supplying seawater,
A high-pressure pump that pressurizes the seawater to supply the high-pressure seawater to the membrane separation device,
One end communicates with the water supply pump, communicates with the concentrated water pipe and blocks it, and at the other end connects with the concentrated water pipe through a flow path switching mechanism that communicates with and blocks the drainage channel of the concentrated seawater. A plurality of cylinder devices connected to the drainage channel,
A flow path direction that is connected to one end of the plurality of cylinder devices and alternately supplies the seawater to the plurality of cylinder devices, and sends the seawater alternately extruded at high pressure from the plurality of cylinder devices to the membrane separation device. A regulatory mechanism,
A pressure feeding step of controlling the flow path switching mechanism to switch the connection of the plurality of cylinder devices to the concentrated water pipe and the drainage channel, supplying the concentrated seawater of high pressure to the cylinder device to push out the seawater inside at high pressure. And a control unit having a control function of performing a filling step of filling the seawater while supplying the seawater from the water supply pump to the cylinder device after discharging the concentrated seawater inside the pumping step,
A cylinder in which the other end of the cylinder device is connected to the concentrated water pipe and the drainage channel, the concentrated seawater is introduced from the other end side, and one end communicates with the water supply pump and the seawater is introduced from one end side; ,
A piston that reciprocates in the cylinder,
An energy recovery device, comprising: a piston rod, one end of which is connected to the piston, and the other end of which extends outward from the other end of the cylinder. The energy recovery device according to claim 1,
Energy characterized in that a concentrated seawater inlet for introducing and discharging the concentrated seawater, which is connected to the concentrated water pipe and the drainage channel, is provided on the peripheral surface of the other end of the cylinder or in the vicinity of the other end. Recovery device. The energy recovery device according to claim 1 or 2,
At the other end of the cylinder, a through hole through which the piston rod penetrates is formed,
An energy recovery device characterized in that a rod seal for preventing leakage of the concentrated seawater to the outside is provided on the inner peripheral surface of the through hole.

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