Energy Recovery Device

Abstract

To provide an energy recovery device capable of suppressing the generation of impact sound when finishing a filling step at a lower cost.SOLUTION: An energy recovery device comprises: first and second cylinder devices 9A, 9B connected to a concentrated water pipe 4 via first or second flow channel switching mechanism 6A or 6B; a controlling unit C to control the flow-in and discharge of concentrated brine to the cylinder devices; and a flow channel direction regulation mechanism 11 where diluted brine is filled in the first and second cylinder devices and the pushed out diluted brine is returned to a membrane separation unit. The first and second flow channel switching mechanisms are provided with a valve device for switching the discharge and stop of the concentrated brine from the cylinder device. The valve device for switching has a concentration side valve 14 installed at a concentration side connection tube 13a and a discharge water side valve 15 installed at a discharge water side connection tube 13b. The controlling unit intercepts communication between the cylinder device and a discharge water pipe by slowly or gradually closing the discharge water side valve.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an energy recovery device for a water treatment system using a low-pressure reverse osmosis membrane method, which is used for desalination of brackish water or the like. [Background technology]

[0002] Reverse osmosis is known as one method for producing freshwater from seawater. In this method, high pressure, approximately the osmotic pressure of seawater (approximately 2.5 to 8 MPa), is applied to seawater in the direction opposite to the osmotic pressure, and the seawater is filtered through a semipermeable membrane (reverse osmosis membrane) to separate salts from freshwater. In this reverse osmosis method, the seawater from which the freshwater has been separated and the salts have been concentrated (concentrated brine) flows out of the reverse osmosis membrane module while retaining its high pressure energy. To effectively utilize the high pressure energy of this outflowing concentrated brine, various energy recovery devices have been put into practical use.

[0003] In this energy recovery system, seawater delivered from the intake pump is pressurized by a high-pressure pump and supplied to a reverse osmosis membrane module, and high-pressure concentrated seawater discharged from the reverse osmosis membrane module is supplied to a cylinder device to drive a piston that pushes out the seawater at high pressure, and high-pressure seawater is also sent from the cylinder device to the reverse osmosis membrane module via a booster pump. This operation of supplying high-pressure concentrated seawater discharged from the reverse osmosis membrane module to a cylinder device to drive a piston that pushes out the seawater at high pressure is called the pumping process (or energy recovery process). In addition, after the pumping process is completed, seawater is supplied from the water intake pump to the cylinder device via the flow path direction control device, and the operation of filling seawater while discharging concentrated seawater by driving the piston in the opposite direction to the pumping process is called the filling process (or water supply process). In this way, in this energy recovery device, when the piston of the cylinder device reaches the end of the cylinder, the flow path switching device controls so that high-pressure concentrated seawater from the reverse osmosis membrane module is alternately supplied to a pair of cylinder devices, and seawater is alternately filled into the pair of cylinder devices from the water intake pump.

[0004] For example, Patent Document 1 describes a conventional energy recovery device in which a control unit slows down the movement speed of the drain side piston of a switching cylinder device when one end of a first cylinder device or a second cylinder device is connected to a drain pipe to slowly initiate communication, and slows down the movement speed of the drain side piston of the switching cylinder device to slowly interrupt communication when one end of the first cylinder device or the second cylinder device is disconnected from the drain pipe. This device slowly releases residual pressure within the cylinder device when connecting to the drain pipe, and controls the movement speed of the drain side piston of the switching cylinder device to slowly reduce the discharge flow rate from the first cylinder device or the second cylinder device when disconnecting, thereby preventing the generation of impact noise caused by water hammer (pressure rise phenomenon (water hammer phenomenon)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6057348 Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned conventional techniques still have the following problems. That is, in the above-mentioned conventional technology, the generation of impact noise from the first cylinder device or the second cylinder device is prevented by controlling the moving speed of the discharge-side piston of a switching cylinder device having a cylinder and a piston, but there is a problem in that the switching cylinder device has a complex structure and is expensive, resulting in high costs. In particular, when desalination of salty water other than seawater, such as brackish water, groundwater, or industrial water, which has a low osmotic pressure of 2.5 MPa or less, a low-cost device that can recover energy even at low pressure (here referred to as medium pressure) is desired.

[0007] The present invention has been made in consideration of the above-mentioned conventional problems, and has an object to provide an energy recovery device that can suppress the generation of impact noise at the end of the filling process at a lower cost. [Means for solving the problem]

[0008] The present invention employs the following configuration to solve the above problems. That is, the energy recovery device according to the first invention is an energy recovery device connected to a membrane separation device that separates medium-pressure diluted saltwater such as brackish water into fresh water and concentrated saltwater using a reverse osmosis membrane and discharges the fresh water into a fresh water pipe and the medium-pressure concentrated saltwater into a concentrated water pipe, the energy recovery device comprising: a first cylinder device having a first piston reciprocating within a first cylinder, one end of which is connected to the concentrated water pipe and the discharge pipe via a first flow path switching mechanism that connects and disconnects the concentrated water pipe and the discharge pipe for the concentrated saltwater; a second cylinder device having a second piston reciprocating within a second cylinder, one end of which is connected to the concentrated water pipe and the drain pipe via a second flow path switching mechanism that switches between connecting and blocking the connection with the drain pipe, and a control function that controls the first flow path switching mechanism and the second flow path switching mechanism to switch between the connection of the first cylinder device and the second cylinder device to the concentrated water pipe and the drain pipe, and to alternately flow the concentrated brine at medium pressure into the first cylinder device and the second cylinder device; a flow path direction regulating mechanism connected to the other end of the first cylinder device and the other end of the second cylinder device, and configured to alternately supply diluted brine to the first cylinder device and the second cylinder device, and return the diluted brine alternately pushed out at medium pressure from the first cylinder device and the second cylinder device to the membrane separation device via a pressure increasing means; the first flow path switching mechanism and the second flow path switching mechanism comprise a switching valve device that switches between supplying and stopping the concentrated brine to the first cylinder device or the second cylinder device, and discharging and stopping the concentrated brine from the first cylinder device or the second cylinder device, and the switching valve device has a concentration-side valve provided in a concentration-side connecting pipe that connects one end of the first cylinder device or the second cylinder device to the concentrated water pipe, and a discharge-side valve provided in a discharge-side connecting pipe that connects one end of the first cylinder device or the second cylinder device to the discharge pipe; and the control unit controls the first flow path switching mechanism or the second flow path switching mechanism,When communication between one end of the first cylinder device or the second cylinder device and the drain pipe is blocked, the drain side valve is closed gradually or in stages to block the communication.

[0009] In this energy recovery device, the control unit controls the first flow path switching device or the second flow path switching mechanism to gradually or gradually close the drain valve to cut off the communication between one end of the first cylinder device or the second cylinder device and the drain pipe, thereby gradually reducing the discharge flow rate from the cylinder device when the communication is cut off, thereby preventing the generation of impact noise due to water hammer.In particular, while conventional systems have been expensive because they have used switching cylinder devices that use cylinders and pistons, which are complex in structure, the present invention uses a switching valve device that uses a valve that is simpler in structure and less expensive than a cylinder device, thereby reducing costs.

[0010] The energy recovery device according to a second invention is the energy recovery device according to the first invention, characterized in that the discharge side valve and the concentrate side valve are ball valves. In other words, in this energy recovery device, the discharge side valve and the concentrated side valve are ball valves, so costs can be reduced by using inexpensive ball valves with a simple structure.In addition, ball valves used for air valves etc. can be used, and maintenance and inspection are easier than with conventional switching cylinder devices, and control can be easily achieved by simply opening and closing the solenoid valve.

[0011] The energy recovery device of the third invention is characterized in that, in the first or second invention, when the control unit gradually closes the drain side valve, it temporarily stops it at an intermediate opening degree while changing the opening degree from fully open to fully closed. In other words, in this energy recovery device, when the control unit gradually closes the drain side valve, it temporarily stops it at an intermediate opening while changing the opening from fully open to fully closed, so that the generation of impact noise can be prevented by simple control that changes the opening in two steps.

[0012] The energy recovery device according to a fourth invention is the energy recovery device according to the first or second invention, characterized in that the medium-pressure diluted salt water is brackish water, groundwater, or industrial water. In other words, in this energy recovery device, the medium-pressure diluted salt water is brackish water, groundwater, or industrial water, so brackish water, groundwater, or industrial water with a relatively low inlet pressure of 2.5 MPa or less to the membrane separation device can be desalinated using a low-cost device. [Effects of the Invention]

[0013] According to the present invention, the following effects are achieved. In other words, according to the energy recovery device of the present invention, the control unit controls the first flow path switching device or the second flow path switching mechanism so that when communication between one end of the first cylinder device or the second cylinder device and the drain pipe is cut off, the drain side valve is closed gradually or gradually to cut off the communication, thereby preventing the generation of impact noise with a configuration that is lower cost than conventional configurations. Therefore, the energy recovery device of the present invention is suitable for low-cost desalination, particularly when the medium-pressure diluted salt water is brackish water, groundwater, or industrial water. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a state in which a first cylinder device is in a pressure-feeding process and a second cylinder device is in a filling process in one embodiment of the energy recovery device according to the present invention. FIG. [Figure 2] FIG. 10 is a schematic diagram illustrating a state in which the first cylinder device is in a pressure-feeding process and the second cylinder device is in a piston deceleration process during a filling process in this embodiment. [Figure 3] 10 is a schematic diagram showing a state in which the first cylinder device is in a filling process and the second cylinder device is in a pressure-feeding process in this embodiment. FIG. [Figure 4] FIG. 10 is a schematic diagram illustrating a state in which the first cylinder device is in a piston deceleration process during a filling process, and the second cylinder device is in a pressure-feeding process in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the energy recovery device of the present invention will be described with reference to FIGS.

[0016] As shown in Figures 1 to 4, the energy recovery device 1 in this embodiment is an energy recovery device that is connected to a supply pipe 2a for medium-pressure diluted brine, which is salt-containing water such as brackish water, groundwater, or industrial water, and is connected to a membrane separation device 5 that separates the medium-pressure diluted brine into fresh water and concentrated brine using a reverse osmosis membrane, and discharges the fresh water into a fresh water pipe 3 and the medium-pressure concentrated brine into a concentrated water pipe 4.

[0017] The energy recovery device 1 includes a first cylinder device 9A having a first piston 8A that reciprocates within a first cylinder 7A and is connected at one end to the concentrated water pipe 4 and the drain pipe 19 via a first flow path switching mechanism 6A that connects and disconnects the concentrated water pipe 4 and the drain pipe 19 for concentrated brine, and a second cylinder device 9B having a second piston 8B that reciprocates within a second cylinder 7B and is connected at one end to the concentrated water pipe 4 and the drain pipe 19 via a second flow path switching mechanism 6B that connects and disconnects the concentrated water pipe 4 and the drain pipe 19, and a second cylinder device 9B that controls the first flow path switching mechanism 6A and the second flow path switching mechanism 6B to connect and disconnect the concentrated water pipe 4 and the drain pipe 19 for concentrated brine. The apparatus is equipped with a control unit C that switches the connection of the first cylinder device 9A and the second cylinder device 9B to the membrane separation device 5, and has a control function for alternately flowing high-pressure concentrated brine into the first cylinder device 9A and the second cylinder device 9B and a control function for alternately discharging the concentrated brine from the first cylinder device 9A and the second cylinder device 9B, and a flow path direction regulating mechanism 11 that is connected to the other end of the first cylinder device 9A and the other end of the second cylinder device 9B, and alternately supplies seawater to the first cylinder device 9A and the second cylinder device 9B, and returns seawater that is alternately pushed out at high pressure from the first cylinder device 9A and the second cylinder device 9B to the membrane separation device 5 via the pressure boosting means 10.

[0018] A pressure pump 33 is connected to the base end of the supply pipe 2a, and a water intake pump 12 is connected to the base end of the water supply pipe 2b connected to the supply pipe 2a. The concentrated water pipe 4 is branched midway and connected to a first flow path switching mechanism 6A and a second flow path switching mechanism 6B. The first flow path switching mechanism 6A and the second flow path switching mechanism 6B are equipped with a switching valve device 13 that switches between supplying and stopping concentrated salt water to the first cylinder device 9A or the second cylinder device 9B and discharging and stopping concentrated salt water from the first cylinder device 9A or the second cylinder device 9B.

[0019] The switching valve device 13 has a concentration side valve 14 provided on a concentration side connecting pipe 13a that connects one end of the first cylinder device 9A or the second cylinder device 9B to the concentrated water pipe 4, and a drainage side valve 15 provided on a drainage side connecting pipe 13b that connects one end of the first cylinder device 9A or the second cylinder device 9B to the drainage pipe 19. In this embodiment, a switching valve device 13 is connected to one end of each of the first cylinder device 9A and the second cylinder device 9B.

[0020] The control unit C has the function of controlling the first flow path switching mechanism 6A or the second flow path switching mechanism 6B to gradually or gradually close the drain side valve 15 to block communication between one end of the first cylinder device 9A or the second cylinder device 9B and the drain pipe 19 when communication between them is blocked. This control unit C is equipped with a pair of first position detectors S1 that are provided near the other ends of the first cylinder 7A and the second cylinder 7B and detect when the first piston 8A or the second piston 8B has reached the vicinity of the other end of the corresponding first cylinder 7A or second cylinder 7B, and a pair of third position detectors S3 that are provided near one end of the first cylinder 7A and the second cylinder 7B and detect when the first piston 8A or the second piston 8B has reached the vicinity of one end of the corresponding first cylinder 7A or second cylinder 7B. The control unit C also 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 the pair of first position detectors S1 or the pair of third position detectors S3.

[0021] The discharge side valve 15 and the concentration side valve 14 are, for example, ball valves. Furthermore, when closing the drain valve 15 in stages, the control unit C performs control to temporarily stop the valve at an intermediate opening degree while changing the opening degree from fully open to fully closed. For example, the intermediate opening of the drain valve 15 is set in the range of 15 to 30%, and is set to 30% in this embodiment. That is, the control unit C controls the valve opening of the discharge side valve 15, which is a two-stage opening / closing ball valve, by repeating the operation of "fully closed - fully open - slightly open (30%) - fully closed." Note that the concentration side valve 14 is controlled by repeating the operation of "fully open - fully closed - fully open - fully closed."

[0022] The other ends of the first cylinder device 9A and the second cylinder device 9B are connected to a water intake pump 12 and a pressure boosting means 10 via a flow path direction regulating mechanism 11 consisting of four check valves 11a. The pressure boosting means 10 is, for example, a pressure boosting pump. One end of the first cylinder device 9A is connected to the concentration side connecting pipe 13a of the switching valve device 13 in the first flow path switching mechanism 6A, and one end of the second cylinder device 9B is connected to the discharge side connecting pipe 13b of the switching valve device 13 in the second flow path switching mechanism 6B.

[0023] The flow path direction regulating mechanism 11 has an annular pipe 11c connected to the water supply pipe 2b via a connecting pipe 11b, and the other ends of the first cylinder device 9A and the second cylinder device 9B are connected to this annular pipe 11c via cylinder connecting pipes 11d. A pair of check valves 11a is provided on each side of the connecting portion of the annular pipe 11c to the cylinder connecting pipe 11d. In addition, a connecting pipe 11e connects the annular pipe 11c between the connecting portions of the two cylinder connecting pipes 11d and the supply pipe 2a via a pressure boosting means 10. A high-pressure pump 33 is connected between the connection part of the water supply pipe 2b with the flow path direction regulation mechanism 11 and the connection part of the supply pipe 2a with the connecting pipe 11e.

[0024] A first position detector S1 and a second position detector S2 are disposed on the outer peripheral walls of the first cylinder device 9A and the second cylinder device 9B on the side of the flow path direction regulating mechanism 11 (the other end side), and a third position detector S3 is disposed on the outer peripheral wall on the side of the switching valve device 13 (one end side). The first position detector S1 and the second position detector S2 are disposed at an appropriate interval in the direction of movement of the corresponding first piston 8A or second piston 8B.

[0025] Next, the operation of the energy recovery device 1 of this embodiment will be described with reference to the drawings. 1, when the first piston 8A of the first cylinder device 9A in the pumping process is moving in the direction of the solid arrow, the control unit C fully opens the concentrate-side valve 14 of the switching valve device 13 of the first flow path switching mechanism 6A and fully closes the discharge-side valve 15. The control unit C also fully closes the concentrate-side valve 14 of the switching valve device 13 of the second flow path switching mechanism 6B and fully opens the discharge-side valve 15. At this time, the discharge-side valve 15 of the switching valve device 13 of the second flow path switching mechanism 6B is fully open, and concentrated brine is discharged from the second cylinder device 9B to the discharge pipe 19 at a constant flow rate.

[0026] 2, when the second piston 8A of the second cylinder device 9B reaches the position of the third position detector S3, a detection signal is sent from the third position detector S3 to the control unit C. When the control unit C receives this detection signal, a signal is sent from the control unit C to the switching valve device 13 of the second flow path switching mechanism 6B, and the drain side valve 15 is set to a slightly open state, and the opening degree is narrowed to, for example, 30%. This reduces the amount of drainage flow from the drain valve 15 to the drain pipe 19, slowing down the operating speed of the second piston 8B and suppressing the pressure rise phenomenon (water hammer phenomenon) that occurs when the second piston 8B reaches the end of the second cylinder 7B. In this way, the second cylinder device 9B enters a piston deceleration process at the end of the filling process.

[0027] The pressure rise is proportional to the square of the water flow velocity (v 2 / (2×g):v=flow velocity (m / s), g=gravitational acceleration (9.8m / s 2 )) and therefore the pressure rise can be suppressed by slowing down the flow velocity. After a certain time has elapsed since the second piston 8B reached the end of the second cylinder 7B after the valve was slightly opened, the control section C brings the drain valve 15 into a fully closed state.

[0028] 1 and 2 show the case where the first cylinder device 9A is in the pressure-feeding process and the second cylinder device 9B is in the filling process and then the piston deceleration process. However, conversely, after the second cylinder device 9B has completed the filling process and the piston deceleration process, the states of the first cylinder device 9A and the second cylinder device 9B are switched as shown in FIGS. 3 and 4. That is, FIGS. 3 and 4 show a case where the second cylinder device 9B is in the pressure-feeding process, and the first cylinder device 9A is in the piston deceleration process from the filling process.

[0029] Therefore, rather than closing the discharge valve 15 from fully open to fully closed all at once, the discharge valve 15 is stopped at an intermediate opening position midway through the transition from fully open to fully closed, thereby gradually stopping the flow rate of concentrated brine into the discharge pipe 19. By gradually reducing the discharge rate in this way, the stable, continuous flow in the discharge pipe 19 does not suddenly stop, preventing water hammer and the occurrence of impact noise at the end of the filling process.

[0030] In this way, in the energy recovery device 1 of this embodiment, when the communication between one end of the first cylinder device 9A or the second cylinder device 9B and the drain pipe 19 is cut off, the control unit C gradually or gradually closes the drain side valve 15 to cut off the communication, so that when the communication is cut off, the discharge flow rate from the cylinder device is gradually reduced, thereby preventing the generation of impact noise caused by water hammer.

[0031] In particular, conventionally, switching cylinder devices using cylinders and pistons, which are complex in structure and expensive, have been used, resulting in high costs. However, the present invention employs a switching valve device using valves, which have a simpler structure and are less expensive than cylinder devices, thereby reducing costs. Furthermore, because the discharge side valve 15 and the concentration side valve 14 are ball valves, the cost can be further reduced by using inexpensive ball valves with a simple structure. Furthermore, the ball valves can be those used for air valves, etc., and are easier to maintain and inspect than conventional switching cylinder devices, and can be easily controlled by simply opening and closing the solenoid valve.

[0032] Furthermore, when the control unit C closes the drain side valve 15 in stages, it temporarily stops the valve at an intermediate opening while changing the opening from fully open to fully closed, thereby preventing the generation of impact noise with simple control that changes the opening in two steps. In particular, since the medium-pressure diluted salt water is brackish water, groundwater, or industrial water, brackish water, groundwater, or industrial water having a relatively low inlet pressure to the membrane separation device can be desalinated using a low-cost device.

[0033] The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0034] For example, although the above embodiment shows the case where there are two cylinder devices, it may also be applied to the case where there are three cylinder devices. In this case, while the first cylinder device and the second cylinder device are operating, the piston of the remaining third cylinder device is stopped at the end on the switching valve device 13 side. [Explanation of symbols]

[0035] REFERENCE SIGNS LIST 1...energy recovery device, 2a...supply pipe, 2b...water 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, 7A...first cylinder, 7B...second cylinder, 8A...first piston, 8B...second piston, 9A...first cylinder device, 9B...second cylinder device, 10...pressure boosting means, 11...flow path direction regulating mechanism, 13...switching valve device, 13a...concentration side connecting pipe, 13b...discharge side connecting pipe, 14...concentration side valve, 15...discharge side valve, C...control section

Claims

1. An energy recovery device connected to a membrane separation device that separates medium-pressure diluted brine, which has an osmotic pressure of 2.5 MPa or less and contains salt other than seawater, into fresh water and concentrated brine using a reverse osmosis membrane, discharges the fresh water into a fresh water pipe, and discharges the medium-pressure concentrated brine, which has an osmotic pressure of 2.5 MPa or less, into a concentrated water pipe, a first cylinder device having one end connected to the concentrated water pipe and the drain pipe via a first flow path switching mechanism that connects and disconnects the concentrated water pipe and the drain pipe for the concentrated brine, and having a first piston that reciprocates within a first cylinder; a second cylinder device having one end connected to the concentrated water pipe and the drain pipe via a second flow path switching mechanism that connects and disconnects the concentrated water pipe and the drain pipe, and having a second piston that reciprocates within a second cylinder; a control unit having a control function of controlling the first flow path switching mechanism and the second flow path switching mechanism to switch the connection between the first cylinder device and the second cylinder device and the concentrated water pipe and the drain pipe, and alternately flowing the concentrated salt water at medium pressure into the first cylinder device and the second cylinder device, and alternately discharging the concentrated salt water from the first cylinder device and the second cylinder device; a flow path direction regulating mechanism connected to the other end of the first cylinder device and the other end of the second cylinder device, for alternately supplying diluted brine to the first cylinder device and the second cylinder device, and returning the diluted brine alternately pushed out at medium pressure from the first cylinder device and the second cylinder device to the membrane separation device via a pressure boosting means; The first flow path switching mechanism and the second flow path switching mechanism include a switching valve device that switches between supplying and stopping the concentrated salt water to the first cylinder device or the second cylinder device and discharging and stopping the concentrated salt water from the first cylinder device or the second cylinder device, the switching valve device includes a concentrated-side valve provided in a concentrated-side connecting pipe that connects one end of the first cylinder device or the second cylinder device to the concentrated water pipe; a drainage side valve provided in a drainage side connecting pipe that connects one end of the first cylinder device or the second cylinder device to the drainage pipe, The control unit controls the first flow path switching device or the second flow path switching mechanism to gradually or gradually close the drain side valve when communication between one end of the first cylinder device or the second cylinder device and the drain pipe is blocked, thereby blocking the communication; 10. An energy recovery device, wherein the discharge side valve and the concentrated side valve are ball valves.

2. 2. The energy recovery device according to claim 1, An energy recovery device characterized in that, when the control unit closes the drain side valve in stages, it temporarily stops the valve at an intermediate opening degree while changing the opening degree from fully open to fully closed.

3. 3. The energy recovery device according to claim 1, 10. An energy recovery system according to claim 9, wherein the medium-pressure diluted salt water is brackish water, groundwater, or industrial water.

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