JP2013220372A - Seawater desalting system, and energy recovery apparatus - Google Patents

Abstract

Provided is an energy recovery device capable of switching between concentrated seawater and supply / drainage of seawater to an energy recovery chamber at an accurate timing in an energy recovery chamber without a piston.
A plurality of chambers 11 and 12 for supplying and draining concentrated seawater and seawater to increase the pressure of seawater by the pressure energy of the concentrated seawater, and a first use for integrating the flow rates of seawater or concentrated seawater flowing into the chambers 11 and 12. 1 flow meter, a second flow meter used for integrating the flow rate of seawater or concentrated seawater discharged from the chambers 11, 12, inflow of concentrated seawater into the chambers 11, 12 and concentrated seawater from the chambers 11, 12 A switching device 20 for switching the discharge of the gas, and a control device 21 for controlling the switching device 20 based on the integrated flow rate by obtaining the integrated flow rate of the chambers 11 and 12 based on the flow rate of the first flow meter and / or the second flow meter. Prepared.
[Selection] Figure 2

Description

  The present invention relates to a seawater desalination system that desalinates seawater by removing salt from seawater, and an energy recovery device that is suitably used in the seawater desalination system.

  Conventionally, as a system for desalinating seawater, a seawater desalination system is known in which seawater is passed through a reverse osmosis membrane separator and desalted. In this seawater desalination system, the collected seawater is adjusted to a constant water quality condition by a pretreatment device, and then pressurized by a high-pressure pump and pumped to a reverse osmosis membrane separation device. A part of the high-pressure seawater is taken out as fresh water from which the salt content has been removed by overcoming the reverse osmosis pressure and passing through the reverse osmosis membrane. The other seawater is discharged as concentrated seawater (brine) from the reverse osmosis membrane separation device in a state where the salinity is increased and concentrated. Here, the maximum operating cost in the seawater desalination system is the power cost, and it greatly depends on the energy for raising the pretreated seawater to the pressure that can overcome the osmotic pressure, that is, the reverse osmotic pressure, that is, the pressurized energy by the high-pressure pump. To do.

  That is, more than half of the power cost in the seawater desalination plant is often spent on pressurization by the high-pressure pump. Therefore, the pressure energy possessed by the high salinity and high-pressure concentrated seawater discharged from the reverse osmosis membrane separator is used to boost a part of the seawater. Then, as means for using the pressure energy of the concentrated seawater discharged from the reverse osmosis membrane separation device to pressurize a part of the seawater, the inside of the cylinder is separated by a piston movably fitted in the cylinder. An energy recovery chamber is used that is separated into two spaces, and provided with a concentrated seawater port for entering and exiting concentrated seawater in one of the two spaces, and a seawater port for entering and exiting seawater on the other.

  FIG. 9 is a schematic diagram showing a configuration example of a conventional seawater desalination system. As shown in FIG. 9, seawater taken by a water intake pump (not shown) is adjusted to a predetermined water quality condition by removing suspended matters and the like by a pretreatment device 1, and then passed through a water supply pump 2 and a high pressure pump line. 3 and the energy recovery device seawater supply line 4. Seawater that has flowed into the high-pressure pump 5 is pressurized by the high-pressure pump 5, merged with the seawater that has been pressurized by the energy recovery device 10 and the booster pump 7, and then pumped to the reverse osmosis membrane separation device 8.

Part of the seawater introduced into the reverse osmosis membrane separation device 8 overcomes the reverse osmosis pressure and passes through the reverse osmosis membrane (RO membrane) 8a in the reverse osmosis membrane separation device 8 as demineralized water from which the salt content has been removed. It is taken out through a desalted water line. The other seawater has a high salinity, becomes concentrated concentrated seawater, and is introduced from the reverse osmosis membrane separation device 8 to the energy recovery device 10 through the concentrated seawater line 9.
In the energy recovery apparatus 10, with the operation of the control valve 14, in the two energy recovery chambers 11, 12, the introduction of seawater from the water supply pump 2 to the check valve module 15 and the high pressure by movement of the pistons 13, 13 are performed. The seawater is pressurized and discharged using concentrated seawater (reject).

  The seawater pressurized in the energy recovery chambers 11 and 12 is supplied from the check valve module 15 to the booster pump 7 via the booster pump seawater supply line 6. Here, the booster pump 7 boosts the pressure loss of the reverse osmosis membrane separation device 8 and piping, the pressure loss in the control valve 14, and the pressure loss generated in the energy recovery chambers 11 and 12 and the check valve module 15. The seawater is discharged from the high-pressure pump 5 and merged with the seawater, and is pumped to the reverse osmosis membrane separation device 8.

In the above-described conventional energy recovery chamber, the piston in the energy recovery chamber slides with the inner wall of the cylinder, and the sliding member of the piston wears. It was necessary to process the inner diameter of the cylinder accurately with the outer shape of the piston, and the processing cost was very expensive.
Therefore, the applicant of the present application uses a cylindrical long chamber as a pressure exchange chamber in Patent Document 1, and a plurality of partitioned flow paths are provided in the chamber to concentrate high pressure discharged from a reverse osmosis membrane (RO membrane). By adopting a method of pressurizing seawater directly with seawater, an energy recovery chamber without a piston was proposed.

JP 2010-284642 A

In a conventional energy recovery chamber equipped with a piston, a magnet is built in the piston, and a magnet switch for detecting magnetism is provided outside the chamber to detect the position of the piston. Since the piston moves while separating concentrated seawater and seawater, this magnet switch is provided near both ends of the chamber, and the piston moving direction is switched by a control valve etc. to reciprocate in the chamber. It was control to switch. Note that the position of the piston is also detected using a proximity sensor, a laser, a photo sensor, or the like.
On the other hand, since the energy recovery chamber without the piston does not have the piston, the amount of water supply / drainage cannot be controlled in the same manner. For this reason, it is necessary to perform control which switches supply and drainage of seawater and concentrated seawater by another means and method.

  The present invention has been made in view of the above-mentioned circumstances, and in both an energy recovery chamber without a piston and an energy recovery chamber with a piston, switching between supply and drainage of concentrated seawater and seawater to the energy recovery chamber is performed. An object of the present invention is to provide an energy recovery apparatus that can be performed at an accurate timing.

  In order to achieve the above-mentioned object, the energy recovery device of the present invention is a seawater desalination method in which seawater pressurized by a pump is passed through a reverse osmosis membrane separation device and separated into fresh water and concentrated seawater to produce fresh water from seawater. In an energy recovery device that is provided in a system and uses the pressure energy of concentrated seawater discharged from the reverse osmosis membrane separator as energy for boosting a part of the seawater, the pressure of the concentrated seawater by supplying and draining the concentrated seawater and seawater A plurality of chambers that pressurize seawater by energy, a first flow meter used to integrate the flow rate of seawater or concentrated seawater flowing into the chamber, and to integrate the flow rate of seawater or concentrated seawater discharged from the chamber The second flow meter used for the operation, switching between the flow of concentrated seawater into the chamber and the discharge of concentrated seawater from the chamber And a control device for obtaining an integrated flow rate of the chamber based on the flow rate of the first flow meter and / or the second flow meter and controlling the switch device based on the integrated flow rate. Features.

  According to the present invention, the concentrated seawater discharged from the reverse osmosis membrane separation device is supplied to and drained from the plurality of chambers through the switching device, and the seawater is supplied to and drained from the plurality of chambers, whereby the seawater is supplied by the concentrated seawater in each chamber. The pressure can be increased and discharged (discharged). The flow rate of seawater or concentrated seawater flowing into the chamber is measured with the first flow meter to determine the integrated flow rate, and the flow rate of seawater or concentrated seawater discharged from the chamber is measured with the second flow meter to determine the integrated flow rate. Based on the obtained integrated flow rate, the switching device is controlled by grasping the amount of seawater or concentrated seawater flowing into the chamber and / or the amount discharged from the chamber, thereby switching the supply and drainage of the concentrated seawater and seawater to the chamber. It can be done with accurate timing.

According to a preferred aspect of the present invention, the control device controls the switching device to switch when the integrated flow rate of the chamber by the first flow meter or the second flow meter reaches a predetermined value. It is characterized by that.
According to the present invention, since the switching device is switched when the integrated flow rate reaches the predetermined value after the integration by the first flow meter or the second flow meter is started, the flow rate of the concentrated seawater into the chamber is predetermined. The inflow of concentrated seawater can be stopped when the value is reached. Therefore, concentrated seawater does not flow into the booster pump from the energy recovery device. In this case, the flow rate of the concentrated seawater into the chamber can be obtained from the integrated flow rate measured by the first flow meter. Also, when concentrated seawater flows into the chamber, the seawater in the chamber is discharged (discharged), so the seawater discharge amount (discharge amount) from the chamber is obtained from the integrated flow rate of seawater measured by the second flow meter, The inflow of concentrated seawater into the chamber can be determined.

According to a preferred aspect of the present invention, the switching device is switched at a value calculated from a predetermined ratio of the actual volume of the chamber.
According to the present invention, the flow of the concentrated seawater can be stopped when the flow rate of the concentrated seawater to the chamber reaches a predetermined ratio (for example, 80 to 90%) of the actual volume of the chamber. Does not flow into the booster pump from the energy recovery device. As described above, the flow rate of the concentrated seawater into the chamber may be obtained from the integrated flow rate of the first flow meter or from the integrated flow rate of the second flow meter.

According to a preferred aspect of the present invention, the control device compares the integrated value of the inflow amount of the concentrated seawater into the chamber with the integrated value of the discharge amount of the concentrated seawater from the chamber, and is discharged from the chamber. It is characterized by controlling the flow rate of concentrated seawater.
According to the present invention, the integrated value of the inflow amount of concentrated seawater into the chamber is compared with the integrated value of the discharge amount of concentrated seawater from the chamber, and the flow rate of the concentrated seawater discharged from the chamber is controlled. Since the amount of concentrated seawater discharged from the chamber is equal to the amount of seawater flowing into the chamber, the amount of seawater flowing into the chamber can be determined by determining the amount of concentrated seawater discharged from the chamber. Therefore, the balance between the inflow of concentrated seawater into the chamber and the inflow of seawater into the chamber is compared by comparing the integrated value of the inflow of concentrated seawater into the chamber and the integrated value of the discharge of concentrated seawater from the chamber. Can be taken. By appropriately balancing this, concentrated seawater does not flow from the energy recovery device into the booster pump.
According to the present invention, the amount of seawater flowing into the chamber and the amount of concentrated seawater flowing into the chamber can be freely adjusted by the control of the switching device.

According to a preferred aspect of the present invention, the control device is configured so that the integrated value of the inflow amount of seawater into the chamber is equal to or greater than the integrated value of the inflow amount of concentrated seawater into the chamber. The apparatus is controlled.
According to the present invention, the switching device is controlled so that the integrated value of the inflow amount of seawater into the chamber is equal to or greater than the integrated value of the inflow amount of concentrated seawater into the chamber. Will not flow into the booster pump.

According to a preferred aspect of the present invention, the control device controls the switching device so as to include a step of simultaneously discharging pressurized seawater from a plurality of chambers.
In a plurality of chambers, the process of inhaling seawater and the process of increasing the pressure of the inhaled seawater with concentrated seawater and discharging (discharging) are repeated. In this case, when one chamber completes the seawater ejection process, When the switching device is controlled so that the chamber of No. 1 starts the seawater discharge process, pulsation of the pressurized seawater occurs at the time of switching. Therefore, in the present invention, the pulsation of the pressurized seawater can be suppressed by controlling the switching device so that the pressurized seawater is simultaneously discharged from the plurality of chambers, that is, by overlapping the seawater discharging process of the plurality of chambers. it can.

  The seawater desalination system of the present invention is the seawater desalination system in which seawater pressurized by a pump is passed through a reverse osmosis membrane separation device and separated into fresh water and concentrated seawater to produce fresh water from the seawater. The energy recovery apparatus according to any one of claims 1 to 6, wherein pressure energy of concentrated seawater discharged from the apparatus is used to boost a part of the seawater.

The present invention has the following effects.
1) Because it is possible to switch between concentrated seawater and seawater supply / drainage to multiple chambers at an accurate timing, seawater with high salt concentration will not be sent to the reverse osmosis membrane separator. The performance of the reverse osmosis membrane separation device can be sufficiently exerted without lowering, and the exchange cycle of the reverse osmosis membrane itself can be lengthened.
2) Since the step includes simultaneously discharging (discharging) pressurized seawater from a plurality of chambers, the flow rate and pressure pulsation of the pressurized seawater are small.
3) Since the amount of seawater flowing into the chamber can be controlled by controlling the amount of concentrated seawater discharged from the chamber, seawater is not discharged more than necessary from the chamber.
4) When the demand for fresh water changes in the seawater desalination system, the flow rate of the concentrated seawater supplied from the reverse osmosis membrane separation device to the energy recovery device changes, but this flow rate change can be followed quickly. .

FIG. 1 is a schematic diagram showing a configuration example of a seawater desalination system according to the present invention. FIG. 2 is a schematic diagram showing a configuration example of the energy recovery device of the present invention. FIG. 3 is a schematic diagram showing an energy recovery process in the energy recovery apparatus shown in FIG. FIG. 4 is a graph showing the relationship between the opening / closing operation of each switching valve in the energy recovery process shown in FIG. 3, the seawater intake flow rate into the energy recovery chamber, and the concentrated seawater intake flow rate into the energy recovery chamber. FIG. 5 is a graph showing the chamber water supply / drainage flow rate in each step of the energy recovery process shown in FIG. 3. FIG. 6 compares the integrated value of the supplied concentrated seawater to the energy recovery device and the integrated value of the supplied seawater (exhaust concentrated seawater) during a half cycle in the process operation of the switching valve, and automatically opens the opening of the switching valve. It is a graph which shows the process controlled to. FIGS. 7A and 7B are flowcharts showing the procedure of the control method for realizing the operation of the energy recovery apparatus as shown in FIGS. FIGS. 8A and 8B are flowcharts showing the procedure for setting the maximum opening of the switching valve shown in FIGS. 7A and 7B. FIG. 9 is a schematic diagram showing a configuration example of a conventional seawater desalination system.

  Hereinafter, an embodiment of a seawater desalination system according to the present invention will be described with reference to FIGS. 1 to 8. 1 to 8, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic diagram showing a configuration example of a seawater desalination system according to the present invention. As shown in FIG. 1, seawater taken by a water intake pump (not shown) is pretreated by a pretreatment device 1 and adjusted to a predetermined water quality condition, and then passed through a water supply pump 2 and the high pressure pump line 3 and energy. Branches to the recovery device seawater supply line 4. Seawater that has flowed into the high-pressure pump 5 is pressurized by the high-pressure pump 5, merged with the seawater that has been pressurized by the energy recovery device 10 and the booster pump 7, and then pumped to the reverse osmosis membrane separation device 8.

Part of the seawater introduced into the reverse osmosis membrane separation device 8 overcomes the reverse osmosis pressure and passes through the reverse osmosis membrane (RO membrane) 8a in the reverse osmosis membrane separation device 8 as demineralized water from which the salt content has been removed. It is taken out through a desalted water line. The other seawater has a high salinity, becomes concentrated concentrated seawater, and is introduced from the reverse osmosis membrane separation device 8 to the energy recovery device 10 through the concentrated seawater line 9.
In the energy recovery apparatus 10, the interface between the concentrated seawater and the seawater moves in the two energy recovery chambers 11 and 12 due to the pressure balance between the concentrated seawater and the seawater in accordance with the operation of the switching device 20. Thus, the introduction of seawater from the water pump 2 to the check valve module 15 and the pressurization and discharge of seawater using high-pressure concentrated seawater (reject) are performed.

  The seawater pressurized in the energy recovery chambers 11 and 12 is supplied from the check valve module 15 to the booster pump 7 via the booster pump seawater supply line 6. Here, the booster pump 7 increases the pressure loss of the reverse osmosis membrane separation device 8 and the piping, the pressure loss in the switching device 20, and the pressure loss generated in the energy recovery chambers 11 and 12 and the check valve module 15 and then increases the pressure. The seawater is discharged from the high-pressure pump 5 and merged with the seawater, and is pumped to the reverse osmosis membrane separation device 8.

  Next, as shown in FIG. 1, in an energy recovery apparatus having a plurality of energy recovery chambers in which the interface between concentrated seawater and seawater moves in the chamber by the pressure balance between both concentrated seawater and seawater, A configuration for controlling the concentrated seawater and the supply / drainage of seawater to the chamber will be described with reference to FIG. Although FIG. 2 shows an example in which two energy recovery chambers are provided, three or more energy recovery chambers may be provided.

  FIG. 2 is a schematic diagram showing a configuration example of the energy recovery apparatus 10 of the present invention. As shown in FIG. 2, the energy recovery apparatus 10 includes two energy recovery chambers 11 and 12. The concentrated seawater line 9 for discharging the concentrated seawater from the reverse osmosis membrane separation device 8 branches into two, and one branch line is connected to the concentrated seawater port P1 of the energy recovery chamber 11 via the switching valve VS-1. The other branch line is connected to the concentrated seawater port P1 of the energy recovery chamber 12 via the switching valve VS-2. The concentrated seawater port P1 of the energy recovery chamber 11 is connected to the concentrated seawater discharge line 16 via a switching valve VD-1, and the concentrated seawater port P1 of the energy recovery chamber 12 is concentrated via a switching valve VD-2. A seawater discharge line 16 is connected. In the concentrated seawater line 9, a flow meter FM1 is installed upstream of the switching valves VS-1 and VS-2. In the concentrated seawater discharge line 16, a flow meter FM2 is installed on the downstream side of the switching valves VD-1 and VD-2. The switching valves VS-1, VS-2, VD-1, and VD-2 constitute a switching device 20 (see FIG. 1). Each switching valve VS-1, VS-2, VD-1, VD-2 is connected to the control device 21, and the operation of each switching valve VS-1, VS-2, VD-1, VD-2 is controlled. It is controlled by the device 21. In FIG. 2, a configuration example in which an ON-OFF valve is used for the switching valves VS-1, VS-2, VD-1, and VD-2 will be described. Any valve such as a valve having a so-called fluid flow switching function may be used.

  On the other hand, the seawater port P2 of the energy recovery chamber 11 is connected to the booster pump seawater supply line 6 via a check valve module 15 including four check valves (check valves) and connected to the energy recovery apparatus seawater supply line 4. It is connected. The seawater port P2 of the energy recovery chamber 12 is also connected to the booster pump seawater supply line 6 and the energy recovery device seawater supply line 4 via a check valve module 15 comprising four check valves (check valves). Has been. The booster pump seawater supply line 6 is provided with a flow meter FM3. The energy recovery device seawater supply line 4 is provided with a flow meter FM4. Each flow meter FM1, FM2, FM3, FM4 is connected to the control device 21, and the control device 21 performs integration of measured values of the flow meters FM1, FM2, FM3, FM4.

FIG. 3 is a schematic diagram showing an energy recovery process in the energy recovery apparatus 10 shown in FIG.
In Step 1A, each switching valve is in a state in which VS-1 is started to open, VS-2 is opened, VD-1 is closed, and VD-2 is closed, and the supply of concentrated seawater to the energy recovery chamber 11 is performed. The discharge of high-pressure seawater from the energy recovery chamber 11 is started and the supply of concentrated seawater to the energy recovery chamber 12 is continued, and the discharge of high-pressure seawater from the energy recovery chamber 12 is continued. At this time, the interface between the concentrated seawater and the seawater moves from right to left in the energy recovery chamber 11 and moves from right to left in the energy recovery chamber 12. After step 1A is completed, the process proceeds to step 2A.

  In step 2A, each switching valve is in a state in which VS-1 is opened, VS-2 is closed, VD-1 is closed, and VD-2 is closed, and the supply of concentrated seawater to the energy recovery chamber 11 is performed. The discharge of high-pressure seawater from the energy recovery chamber 11 is continued, the supply of concentrated seawater to the energy recovery chamber 12 is stopped, and the discharge of high-pressure seawater from the energy recovery chamber 12 is stopped. At this time, the interface between the concentrated seawater and the seawater moves from the right to the left in the energy recovery chamber 11 and stops at the left end of the movable range in the energy recovery chamber 12. After step 2A is completed, the process proceeds to step 3A.

  In step 3A, each switching valve is in a state in which VS-1 is open, VS-2 is closed, VD-1 is closed, and VD-2 is opened, and the supply of concentrated seawater to the energy recovery chamber 11 is started. The discharge of high-pressure seawater from the energy recovery chamber 11 is continued, supply of low-pressure seawater to the energy recovery chamber 12 is started, and discharge of concentrated seawater from the energy recovery chamber 12 is started. At this time, the interface between the concentrated seawater and the seawater moves from right to left in the energy recovery chamber 11 and moves from left to right in the energy recovery chamber 12. After step 3A is completed, the process proceeds to step 4A.

  In step 4A, each switching valve is in a state in which VS-1 is open, VS-2 is closed, VD-1 is closed, and VD-2 is open, and the supply of concentrated seawater to the energy recovery chamber 11 is continued. Thus, the discharge of high-pressure seawater from the energy recovery chamber 11 is continued, the supply of low-pressure seawater to the energy recovery chamber 12 is continued, and the discharge of concentrated seawater from the energy recovery chamber 12 is continued. At this time, the interface between the concentrated seawater and the seawater moves from right to left in the energy recovery chamber 11 and moves from left to right in the energy recovery chamber 12. After T time has elapsed in this state, the process proceeds to step 5A. The setting of the time T will be described later.

  In step 5A, each switching valve is in a state in which VS-1 is open, VS-2 is closed, VD-1 is closed, and VD-2 is closed, and the supply of concentrated seawater to the energy recovery chamber 11 is started. The discharge of high-pressure seawater from the energy recovery chamber 11 is continued, the supply of low-pressure seawater to the energy recovery chamber 12 is stopped, and the discharge of concentrated seawater from the energy recovery chamber 12 is stopped. At this time, the interface between the concentrated seawater and the seawater moves from the right to the left in the energy recovery chamber 11 and stops at the right end of the movable range in the energy recovery chamber 12. After step 5A is completed, the process proceeds to step 1B.

  In step 1B, each switching valve is in a state where VS-1 is open, VS-2 is opened, VD-1 is closed, and VD-2 is closed, and the supply of concentrated seawater to the energy recovery chamber 11 is performed. The discharge of high-pressure seawater from the energy recovery chamber 11 is continued, supply of concentrated seawater to the energy recovery chamber 12 is started, and discharge of high-pressure seawater from the energy recovery chamber 12 is started. At this time, the interface between the concentrated seawater and the seawater moves from right to left in the energy recovery chamber 11 and moves from right to left in the energy recovery chamber 12. After step 1B is completed, the process proceeds to step 2B.

  In step 2B, each switching valve is in a state in which VS-1 is closed, VS-2 is opened, VD-1 is closed, and VD-2 is closed, and the supply of concentrated seawater to the energy recovery chamber 11 is performed. The discharge of high-pressure seawater from the energy recovery chamber 11 is stopped, the supply of concentrated seawater to the energy recovery chamber 12 is continued, and the discharge of high-pressure seawater from the energy recovery chamber 12 is continued. At this time, the interface between the concentrated seawater and the seawater stops at the left end of the movable range in the energy recovery chamber 11 and moves from right to left in the energy recovery chamber 12. After step 2B is completed, the process proceeds to step 3B.

  In step 3B, each switching valve is in a state in which VS-1 is closed, VS-2 is opened, VD-1 is opened, and VD-2 is closed, so that low-pressure seawater is supplied to the energy recovery chamber 11. Then, the discharge of the concentrated seawater from the energy recovery chamber 11 is started, the supply of the concentrated seawater to the energy recovery chamber 12 is continued, and the discharge of the high-pressure seawater from the energy recovery chamber 12 is continued. At this time, the interface between the concentrated seawater and the seawater moves from left to right in the energy recovery chamber 11 and moves from right to left in the energy recovery chamber 12. After step 3B is completed, the process proceeds to step 4B.

  In step 4B, each switching valve is in a state in which VS-1 is closed, VS-2 is open, VD-1 is open, and VD-2 is closed, and the supply of low-pressure seawater to the energy recovery chamber 11 is continued. Then, the discharge of the concentrated seawater from the energy recovery chamber 11 is continued, the supply of the concentrated seawater to the energy recovery chamber 12 is continued, and the discharge of the high-pressure seawater from the energy recovery chamber 12 is continued. At this time, the interface between the concentrated seawater and the seawater moves from left to right in the energy recovery chamber 11 and moves from right to left in the energy recovery chamber 12. After T time has elapsed in this state, the process proceeds to step 5B. The setting of the time T will be described later.

  In step 5B, each switching valve is in a state where VS-1 is closed, VS-2 is opened, VD-1 is closed, and VD-2 is closed, and the supply of low-pressure seawater to the energy recovery chamber 11 is performed. The discharge of the concentrated seawater from the energy recovery chamber 11 is stopped, the supply of the concentrated seawater to the energy recovery chamber 12 is continued, and the discharge of the high-pressure seawater from the energy recovery chamber 12 is continued. At this time, the interface between the concentrated seawater and the seawater stops at the right end of the movable range in the energy recovery chamber 11 and moves from right to left in the energy recovery chamber 12. After step 5B is completed, the process proceeds to step 1A.

4 shows the opening / closing operation of each switching valve VS-1, VS-2, VD-1, VD-2 in the energy recovery process shown in FIG. 3, the flow rate of the intake seawater to the energy recovery chambers 11, 12, and the energy recovery chamber. 11 is a graph showing the relationship with the flow rate of suction concentrated seawater to 11 and 12;
The upper graph in FIG. 4 shows the opening / closing operation of the switching valves VS-1, VS-2, VD-1, and VD-2 in each step.
As shown by the thick solid line, the switching valve VS-1 starts to open in Step 1A, continues to open until Steps 2A to 1B are completed, starts to close in Step 2B, and starts to Steps 3B to 3B. The closed state is continued until step 5B is completed.
As shown by the thick dotted line, the switching valve VS-2 starts the closing operation in Step 2A, continues the closing state until Step 3A to Step 5A are completed, starts the opening operation in Step 1B, and starts from Step 2B to Step 2B. The open state is continued until step 1A is completed.
As shown by the thick solid line, the switching valve VD-1 starts to open in step 3B, continues to open until time T elapses in step 4B, and starts to close in step 5B. The closed state is continued until step 2B is completed.
As shown by the thick dotted line, the switching valve VD-2 starts the opening operation in step 3A, continues the opening state until the time T elapses in step 4A, starts the closing operation in step 5A, and steps 1B to The closed state is continued until step 2A is completed.

  The middle graph in FIG. 4 shows the intake seawater flow rate into the energy recovery chambers 11 and 12 when the switching valves VS-1, VS-2, VD-1, and VD-2 are in the above-described open / closed state at each step. . In steps 1A to 2A, the intake seawater flow rate into the energy recovery chambers 11 and 12 is 0. In step 3A, seawater intake into the energy recovery chamber 12 is started, and in step 4A, the seawater intake into the energy recovery chamber 12 is a constant flow rate. In step 5A, the seawater suction into the energy recovery chamber 12 is terminated. In steps 1B to 2B, the flow rate of the intake seawater into the energy recovery chambers 11 and 12 is 0. In step 3B, the intake of seawater into the energy recovery chamber 11 is started. In step 4B, the intake of seawater into the energy recovery chamber 11 is The flow rate becomes constant, and seawater suction into the energy recovery chamber 11 is terminated in step 5B.

  The lower graph of FIG. 4 shows the flow rate of the suction concentrated seawater to the energy recovery chambers 11 and 12 when the switching valves VS-1, VS-2, VD-1, and VD-2 are in the above open / closed state at each step. Show. In step 1A, concentrated seawater is sucked into the energy recovery chambers 11 and 12 at the same time, and concentrated seawater is sucked into the energy recovery chamber 11 in steps 2A to 5A. In step 1B, concentrated seawater is simultaneously sucked into the energy recovery chambers 11 and 12, and concentrated seawater is sucked into the energy recovery chamber 12 in steps 2B to 5B. As shown in the drawing, in all steps 1A to 5B of one cycle, the flow rate of the suction concentrated seawater into the chamber is constant.

Next, a control method for realizing the operation of the energy recovery apparatus as shown in FIGS. 3 and 4 in the energy recovery apparatus 10 of the present invention will be described.
(1) The switching valves (VS-1, VS-2, VD-1, VD-2) are opened and closed in a total of 10 steps per cycle (steps 1A to 5A and 1B to 5B).
In step 1A and step 1B in FIG. 3, the contact interface between the concentrated seawater and the seawater becomes a seawater pressurization step at the same time.
This makes it possible to suppress the pulsation of the pressurized seawater discharged from the energy recovery device to the booster pump.
(2) The adjustment (control) of the opening degree of the switching valves VD-1 and VD-2 on the concentrated seawater discharge side (seawater supply side) is supplied to the energy recovery device. The integrated flow rate of seawater is set, and the difference between the integrated flow rates can be adjusted.
As a result, the following is realized.
1) Concentrated seawater does not flow from the energy recovery device to the booster pump.
2) Seawater is not discharged more than necessary from the energy recovery device.
In addition, it becomes possible by adjusting the opening degree of the switching valves VD-1 and VD-2 to freely adjust the integrated flow rate of the concentrated seawater supplied to the energy recovery device and the integrated flow rate of the seawater supplied to the energy recovery device.

Next, the control method will be specifically described.
(1) Switching valve opening / closing sequence and time setting method The switching valve opening / closing time in each step and the time T (see FIG. 4) or step transition time setting in steps 4A and 4B are as follows. There are two types.
Here, the significance of setting the time T will be described. As shown in the upper graph of FIG. 4, any one of the switching valves performs an opening / closing operation in steps 1A, 2A, 3A, and 5A as shown in the upper graph of FIG. This is the switching valve opening / closing time. In this switching valve opening / closing time, the flow rate of the concentrated seawater (or seawater) sucked (supplied) into the chamber is not constant, so the time for the chamber to be filled with concentrated seawater (or seawater) based on this non-constant flow rate is set. It cannot be predicted. However, in step 4A, none of the switching valves are open or closed, and the opening / closing operation is not performed. Therefore, the flow rate of the concentrated seawater (or seawater) sucked (supplied) into the chamber is constant, and based on this constant flow rate, the time when the chamber is filled with the concentrated seawater (or seawater) can be predicted. The same applies to step 4B in the next half cycle.

1) First mode of setting of switching valve opening / closing time and time T i) The switching valve opening / closing time (see FIG. 4) is set to a predetermined value.
ii) The time T in steps 4A and 4B is set by calculating in advance the time until the energy recovery chamber is filled with concentrated seawater from the volume of the energy recovery chamber and the inflow of concentrated seawater.
At this time, in order to reliably avoid the inflow of the concentrated seawater into the booster pump, for example, the volume of the energy recovery chamber is reduced by several to several tens of percent from the actual volume at the time of calculation, or the number of calculated times is For example, the time may be set to a time shorter by several tens of percent.

2) Second mode of setting method of switching valve opening / closing time and step transition time i) The switching valve opening / closing time is set to a predetermined value.
ii) The step transition time is automatically set according to the concentrated seawater flow rate measured by the flow meter FM1.
The step transition time is set as follows.
The integration of the measured value of the flow meter FM1 is started from the time when the switching valve VS-1 or VS-2 starts to open (in FIG. 4, the concentrated seawater flow rate integration start point), and the integration value is the actual volume of the energy recovery chamber. When a predetermined ratio (80-90%) (initial setting value) is reached, the process proceeds to the next step. Since the suction concentrated seawater flow rate measured by the flow meter FM1 and the discharge seawater flow rate measured by the flow meter FM3 are equal, the flow meter FM3 may be used.
The operation is as follows.
Integration of the concentrated seawater flow rate from step 1A to the chamber 11 is started, and when the integrated value reaches a predetermined ratio (80-90%) of the actual volume of the energy recovery chamber, the process proceeds to step 2B.
Integration of the concentrated seawater flow rate from step 1B to the chamber 12 is started, and when the integrated value reaches a predetermined ratio (80-90%) of the actual volume of the energy recovery chamber, the process proceeds to step 2A.

(2) About the adjustment (control) method of the opening degree of the switching valves VD-1 and VD-2 on the concentrated seawater discharge side (seawater supply side) The opening degree of the switching valves VD-1 and VD-2 is automatically adjusted. This is a method of balancing the amount of supplied concentrated seawater to the energy recovery chamber and the amount of supplied seawater.
The upper and middle graphs in FIG. 4 show the relationship between the opening / closing of the switching valve and the flow rate of the seawater supplied to the energy recovery chamber in each step.
As shown in the figure, in the switching valve opening / closing steps 1A, 2A, 3A, 5A and the switching valve opening / closing steps 1B, 2B, 3B, 5B, the intake seawater flow rate to the energy recovery chamber decreases, and in particular, the switching valve VD-1 In steps 1A and 2A and steps 1B and 2B where VD-2 is fully closed, the intake seawater flow rate becomes zero.
Moreover, the upper and lower graphs in FIG. 4 show the relationship between the opening / closing of the switching valve and the flow rate of the supplied concentrated seawater to the energy recovery chamber in each step.
As shown, the flow rate of the suction concentrated seawater into the energy recovery chamber is constant.
Here, as a condition that the concentrated seawater supplied to the energy recovery device does not flow into the booster pump, the amount of the concentrated seawater introduced and led out into each chamber needs to be the same as the amount of seawater.

  FIG. 5 is a graph showing the chamber water supply / drainage flow rate in each step of the energy recovery process shown in FIG. 3. As shown in FIG. 5, in steps 1A to 5A (1/2 cycle), concentrated seawater is sucked into the chamber, and the integrated value of the suction concentrated seawater flow rate at this time becomes a rectangular area A. On the other hand, in steps 3A to 5A, seawater is sucked into the chamber, and the integrated value of the flow rate of the sucked seawater at this time becomes a trapezoidal area B. As a condition that the concentrated seawater supplied to the energy recovery device does not flow into the booster pump, it is necessary to make the area A and the area B equal. The same applies to Steps 1B to 5B (1/2 cycle). If this measure is not taken, the energy recovery chamber will gradually fill with concentrated seawater, and eventually the concentrated seawater will flow into the booster pump and be introduced into the reverse osmosis membrane (RO membrane), reducing the desalination rate or The deterioration of the osmotic membrane (RO membrane) is promoted.

Therefore, in the present invention, the switching valves VD-1 and VD are set so that the integrated value of the supplied concentrated seawater and the integrated value of the supplied seawater in each chamber in the process of supplying and discharging the concentrated seawater and seawater in the energy recovery device satisfy the following conditions. -2 is controlled.
Integrated value of supply seawater flow rate to energy recovery device ≧ integrated value of supply concentrated seawater flow rate to energy recovery device Thereby, concentrated seawater does not always flow into the booster pump.
In order to prevent loss of energy (pressure, flow rate) of the supply concentrated seawater to the energy recovery device, the opening degree of the switching valves VS-1 and VS-2 on the supply concentration seawater side of the energy recovery device is basically set. Fully open.
Regardless of the above conditions, the supply seawater flow rate to the energy recovery device and the supply concentrated seawater flow rate to the energy recovery device can be adjusted by controlling the opening degree of the switching valves VD-1 and VD-2. It is.

FIG. 6 compares the integrated value of the supplied concentrated seawater to the energy recovery device and the integrated value of the supplied seawater (exhaust concentrated seawater) during a half cycle in the process operation of the switching valve, and switches the switching valves VD-1, VD-. It is a graph which shows the process of controlling the opening degree of 2 automatically.
The upper graph of FIG. 6 shows the opening / closing operation of the switching valves VS-1, VS-2, VD-1, and VD-2. The opening / closing operations of the switching valves VS-1, VS-2, VD-1, and VD-2 are as described in FIG.

The lower graph of FIG. 6 shows the intake concentrated seawater flow rate and the intake seawater flow rate to the energy recovery device in each step.
1) In step 1A, from the time when the switching valve VS-1 starts to open, integration of the measured value of the flow meter FM1 that measures the suction concentrated seawater flow rate to the energy recovery device is started. Since the suction concentrated seawater flow rate measured by the flow meter FM1 and the discharge seawater flow rate measured by the flow meter FM3 are equal, the flow meter FM3 may be used.
At the same time, integration of the measured values of the flow meter FM4 that measures the intake seawater flow rate to the energy recovery device is started. Since the intake seawater flow rate measured by the flow meter FM4 and the exhaust concentrated seawater flow rate measured by the flow meter FM2 are equal, the flow meter FM2 may be used.
2) At the end of step 5A, that is, at the end of the half cycle (A) consisting of steps 1A to 5A, the integration of the intake concentrated seawater flow rate and the integration of the intake seawater flow rate are ended. The integrated value of the intake concentrated seawater flow rate at this time is a rectangular area, and the integrated value of the intake seawater flow rate is a trapezoidal area. Similarly, the integrated value is obtained in the next half cycle (B) including Steps 1B to 5B.
3) Next, the integrated value of the intake concentrated seawater flow rate is compared with the integrated value of the intake seawater flow rate, and the integrated value of the supplied seawater flow rate to the energy recovery device ≧ the integrated value of the supply concentrated seawater flow rate to the energy recovery device. Thus, the opening degree of the switching valves VD-1 and VD-2 is automatically adjusted in the next 1/2 cycle.
That is, the integrated value comparison result of 1/2 cycle (A) is reflected in the next 1/2 cycle (A). That is, the opening degree of the switching valve VD-2 is controlled based on the integrated value comparison result.
The integrated value comparison result of 1/2 cycle (B) is reflected in the next 1/2 cycle (B). That is, the opening degree of the switching valve VD-1 is controlled based on the integrated value comparison result.
4) In the opening / closing process of the switching valve, the controls 1) to 3) are performed during each ½ cycle from the opening start to the closing end of the switching valves VS-1 and VS-2.
In order to reliably satisfy the condition in step 3), the above condition may be set after multiplying the integrated value of the supply concentrated seawater flow rate to the energy recovery device by a preset coefficient.

FIGS. 7A and 7B are flowcharts showing the procedure of the control method for realizing the operation of the energy recovery apparatus as shown in FIGS.
In the 1st mode shown in Drawing 7 (a), operation control of an energy recovery device (ERD) is started, the counter of flow meter FM1 which measures the supply concentration seawater flow rate to an energy recovery device is reset, and integration is carried out. Start. The flow meter FM1 may be replaced with the flow meter FM3. In addition, the counter of the flow meter FM4 that measures the supply seawater flow rate to the energy recovery device is reset and integration is started. The flow meter FM4 may be replaced with the flow meter FM2. Then, steps 1A to 4A described in FIG. 3 are sequentially performed to determine whether the set time T has been reached since the start of step 4A. When the set time T has been reached, the process proceeds to step 5A.
When step 5A is completed, the maximum opening of the switching valve VD-2 is set (described later), the ½ cycle is completed, and the process returns to the first integrating step with the flow meter. Thereafter, Steps 1A to 5A in FIG. 7A are changed to Steps 1B to 5B, and the maximum opening setting of the switching valve VD-2 is set to the maximum opening setting of the switching valve VD-1. Run the cycle.

  The mode shown in FIG. 7B is obtained by replacing the step of determining the set time of the mode shown in FIG. 7A with a step of determining the integrated value of the flow meter FM1. That is, in the embodiment shown in FIG. 7B, the integrated value of the supply concentrated seawater flow rate to the energy recovery device measured by the flow meter FM1 is set to a predetermined ratio (80-90%) of the actual volume of the energy recovery chamber. It is determined whether or not it has been reached, and if it has been reached, the process proceeds to step 5A. Other steps are the same as those in FIG. Note that the integrated value of the flow meter FM3 may be obtained by replacing the flow meter FM1 with the flow meter FM3.

FIGS. 8A and 8B are flowcharts showing the procedure for setting the maximum opening of the switching valves VD-1 and VD-2 shown in FIGS. 7A and 7B.
In FIG. 8A, the maximum opening setting of the switching valve VD-1 is started, and the integrated value (Vbi) of the flow meter FM1 that measures the supply concentrated seawater flow rate to the energy recovery device and the energy recovery device. The integrated value (Vsi) of the flow meter FM4 that measures the supply seawater flow rate is compared, and it is determined whether or not Vbi−Vsi <0. When Vbi−Vsi <0 is not satisfied (in the case of NO), the maximum opening degree of the switching valve VD-1 is increased by a predetermined degree (%), and the setting of the maximum opening degree of the switching valve VD-1 is completed. When Vbi-Vsi <0 (in the case of YES), it is determined whether or not the absolute value of Vbi-Vsi is out of the predetermined range. If out of the range (in the case of YES), the switching valve VD is determined. -1 is decreased by a predetermined degree (%) to complete the setting of the maximum opening of the switching valve VD-1, and when it is within the range (in the case of NO), the switching valve VD-1 The maximum opening setting of the switching valve VD-1 is finished while leaving the maximum opening as it is.

  In FIG. 8B, the maximum opening degree setting of the switching valve VD-2 is started, and the integrated value (Vbi) of the flow meter FM1 that measures the supply concentrated seawater flow rate to the energy recovery device and the supply to the energy recovery device The integrated value (Vsi) of the flow meter FM4 that measures the seawater flow rate is compared to determine whether or not Vbi−Vsi <0. When Vbi−Vsi <0 is not satisfied (in the case of NO), the maximum opening degree of the switching valve VD-2 is increased by a predetermined degree (%), and the setting of the maximum opening degree of the switching valve VD-2 is ended. When Vbi-Vsi <0 (in the case of YES), it is determined whether or not the absolute value of Vbi-Vsi is out of the predetermined range. If out of the range (in the case of YES), the switching valve VD is determined. -2 is decreased by a predetermined degree (%) to complete the setting of the maximum opening of the switching valve VD-2. If the switching valve VD-2 is within the range (in the case of NO), the switching valve VD-2 The maximum opening setting of the switching valve VD-2 is finished while leaving the maximum opening as it is. As described above, the flowmeter FM1 may be replaced with the flowmeter FM3 and the flowmeter FM4 may be replaced with the flowmeter FM2 in FIGS.

  Although the embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention may be implemented in various forms within the scope of the technical idea. For example, the present invention can be applied to an energy recovery chamber having a piston as shown in FIG. As for the opening / closing operation of the switching valve, when one switching valve (for example, VS-1) is performing the opening operation (or closing operation), the other switching valve (for example, VS-2) is closed (or Control may be performed so that the charts at the time of opening and closing of the two switching valves cross each other.

DESCRIPTION OF SYMBOLS 1 Pretreatment device 2 Water pump 3 High pressure pump line 4 Energy recovery device seawater supply line 5 High pressure pump 6 Booster pump seawater supply line 7 Booster pump 8 Reverse osmosis membrane separation device 8a Reverse osmosis membrane (RO membrane)
9 Concentrated seawater line 10 Energy recovery device 11, 12 Energy recovery chamber 15 Check valve module 16 Concentrated seawater discharge line 20 Switching device 21 Controller FM1, FM2, FM3, FM4 Flowmeter P1 Concentrated seawater port P2 Seawater port VS-1, VS -2, VD-1, VD-2 selector valve

Claims (7)

Concentrated seawater discharged from the reverse osmosis membrane separator is provided in a seawater desalination system that generates fresh water from seawater by passing seawater pressurized by a pump through a reverse osmosis membrane separator and separating it into fresh water and concentrated seawater. In the energy recovery device that uses the pressure energy of the energy for boosting a part of the seawater,
A plurality of chambers for supplying and draining the concentrated seawater and seawater to pressurize the seawater by the pressure energy of the concentrated seawater;
A first flow meter used for integrating the flow rate of seawater or concentrated seawater flowing into the chamber;
A second flow meter used for integrating the flow rate of seawater or concentrated seawater discharged from the chamber;
A switching device that switches inflow of concentrated seawater into the chamber and discharge of concentrated seawater from the chamber;
An energy recovery system comprising: a control device that obtains an integrated flow rate of the chamber based on the flow rate of the first flow meter and / or the second flow meter and controls the switching device based on the integrated flow rate. apparatus.   2. The control device according to claim 1, wherein the switching device is controlled to be switched when an integrated flow rate of the chamber by the first flow meter or the second flow meter reaches a predetermined value. Energy recovery equipment.   The energy recovery device according to claim 2, wherein the switching device is switched at a value calculated from a predetermined ratio of the actual volume of the chamber.   The control device controls the flow rate of the concentrated seawater discharged from the chamber by comparing the integrated value of the inflow amount of the concentrated seawater into the chamber and the integrated value of the discharge amount of the concentrated seawater from the chamber. The energy recovery device according to claim 1.   The control device controls the switching device so that an integrated value of the inflow amount of seawater into the chamber is equal to or greater than an integrated value of the inflow amount of concentrated seawater into the chamber. The energy recovery apparatus according to claim 1.   The energy recovery device according to claim 1, wherein the control device controls the switching device so as to include a step of simultaneously discharging pressurized seawater from a plurality of chambers. In a seawater desalination system that generates fresh water from seawater by passing seawater pressurized by a pump through a reverse osmosis membrane separator and separating it into freshwater and concentrated seawater.
The energy recovery device according to any one of claims 1 to 6, wherein the pressure energy of the concentrated seawater discharged from the reverse osmosis membrane separation device is used to boost a part of the seawater. Seawater desalination system.

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