JP3456795B2 - Reciprocating pump power recovery system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a reciprocating pump to recover surplus energy generated in the process of producing pure water or fresh water using a membrane separation device such as a reverse osmosis membrane (RO membrane). The present invention relates to a reciprocating pump type power recovery system configured.

[0002]

2. Description of the Related Art Conventionally, a membrane separation device using a reverse osmosis membrane (RO membrane) is known as a means for purifying ordinary water or desalting seawater.

In this type of membrane separation device, generally, seawater or the like is pressurized by a pump device and supplied to the membrane separation device, whereby a part of the water can be desalinated. For example, when seawater was pressurized to 6 MPa with a pump device and supplied to a membrane separation device, about 40% was desalinated in one pass of the membrane, and the remaining about 60% having a pressure of 6 MPa was concentrated. Seawater is discarded as waste liquid. This results in an energy loss of about 60%.

Conventionally, for example, as shown in FIG. 10, raw water stored in a raw water storage tank 10 is supplied to a membrane separation device 14 by a pump device 12, and a required amount of pure water is obtained by passing the membrane once, and the rest is left. It is known that the system is configured to discharge the non-separated concentrated raw water of the above to the outside. in this case,
The raw water supply side pressure P1, the unseparated concentrated raw water outlet side pressure P2, and the pure water outlet side pressure P3 of the membrane separation device 14 can be set as follows as an example.

P1: 35 kgf / cm ² G P2 = P 1 -3 kgf / cm ² G P3 = low pressure In this case, the energy of the non-separated raw water outlet side pressure P 2 is consumed as a loss.

As this type of desalination system, a system in which a pump P and a motor M are connected by providing a shaft seal mechanism (staffin box) S is used, and the motor M is further provided with a shaft seal mechanism. Turbine T through S
11, the pump P and the turbine T configured as described above are connected to the raw water storage tank 10 and the membrane separation device 1 as shown in FIG.
A method has been proposed in which 4 and 4 are connected to a raw water supply system and a concentrated raw water reflux system that communicate with each other. With this configuration, the non-separated concentrated raw water that flows back can be partially converted as the operating energy of the pump P by passing through the turbine T.

[0007]

However [0005] In the energy recovery system described above, the addition or the like of the additional and turbine T of the shaft sealing mechanism S to the motor M, to large in size, both when it comes to mechanically complex, It is relatively advantageous in the case of a large-scale desalination system, but in the case of a small-scale desalination system, it takes time and labor to manufacture, the manufacturing cost increases, and the energy recovery efficiency also decreases. There is. Also, the energy generated by such a turbine
Gee recovery requires large residual momentum of the fluid.
Yes, in the case of desalination with low discharge flow,
Gee recovery is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a reciprocating pump type power recovery system which is compact and lightweight, has low noise and vibration, and is excellent in energy recovery efficiency.

[0009]

In order to achieve the above object, a reciprocating pump type power recovery system according to the present invention comprises:
A reciprocating pump unit in which pump chambers are formed in front of and behind the piston is a common rotary drive shaft via a crank mechanism.
Respectively connected to a predetermined comprises a multiple-reciprocating pump structure arranged comprising to work with a phase angle, the raw water supply system via respective to the main pumping chamber side suction valve and the discharge valve of each reciprocating pump units At the same time, the raw water supply system is connected to the membrane separation device so that the concentrated raw water discharge system is led out from the membrane separation device, and the concentrated raw water discharge system is mainly connected to the sub pump chamber side of each reciprocating pump unit. Corresponding to the pump operation by the piston of the pump chamber, it is connected in communication through the switching valve unit on the suction side and the switching valve unit on the discharge side that are sequentially switched and connected, and in the raw water discharge step of each of the main pump chambers, the concentration is performed. It is characterized in that the concentrated raw water energy is sequentially introduced into each of the sub-pump chambers through the raw water discharge system to be recovered.

In this case, each reciprocating pump unit forms a main pump chamber on the side of the main piston portion of the piston, forms a subordinate pump chamber on the insertion side of the rod portion, and connects the end portion of the rod portion to the crank mechanism. Via a common rotary drive shaft of a multiple reciprocating pump.

The suction valve and the discharge valve connected to the main pump chamber side of each reciprocating pump unit can be constituted by a ball valve, a wing valve, a flat valve or a solenoid valve, respectively.

Further, the suction side and discharge side switching valve units connected to the sub pump chamber side of each reciprocating pump unit are arranged such that the rotary valve body is housed in a cylinder type valve casing having the same structure. made, the number with Ru provided with a plurality of fluid discharge hole or fluid introduction hole communicating with the valve chamber and equiangularly spaced to correspond to the respective reciprocating pump unit to the outer circumferential portion of the valve casing, the valve casing one A single fluid introduction hole or a fluid discharge hole is provided in the side end surface portion, and a cutout portion is provided so as to be able to communicate across the fluid discharge hole or the fluid introduction hole provided in the circumferential portion of the rotary valve body. Further, the rotary shafts of the switching valve units are coupled to each other and are configured to rotate synchronously with the rotary drive shaft of the reciprocating pump unit, and the pump operation by the piston of each reciprocating pump unit is provided. It may be configured to correspond to perform switching operation of each switching valve unit.

[0013]

According to the reciprocating pump type power recovery system of the present invention, the multiple reciprocating pumps are used, and the raw water is supplied to the main pump chamber side of each reciprocating pump unit via the suction valve and the discharge valve, respectively. In addition to being connected to the supply system, this raw water supply system is connected to the membrane separation device so as to lead out the concentrated raw water discharge system from the membrane separation device, and the concentrated raw water discharge system is connected to the sub pump chamber of each reciprocating pump unit. Corresponding to the pump operation by the piston in the main pump chamber, the raw water in each of the main pump chambers is connected by communicating through the switching valve unit on the suction side and the switching valve unit on the discharge side that are sequentially switched and connected. In the discharge step, the energy of the concentrated raw water is sequentially introduced into each of the slave pump chambers through the concentrated raw water discharge system to be recovered, thereby effectively saving the driving energy of this type of reciprocating pump. It can be formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a reciprocating pump type power recovery system according to the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows a basic structure of a reciprocating pump type power recovery system according to the present invention. Reference numeral 20 indicates a reciprocating pump unit.
Is provided with a reciprocating piston 22 and a cylinder portion 24 that passes through the piston 22, and a main pump chamber 26 and a sub pump chamber 28 are provided in front of and behind the reciprocating cylinder portion 24 of the piston 22, respectively. . However,
The main pump chamber 26 has a main piston portion 2 having a diameter D.
2a, a rod portion 22b having a diameter d (d <D) is inserted through the sub-pump chamber 28 on the opposite side of the main piston portion 22a, and a crank portion is provided at an end portion of the rod portion 22b. A rotary drive shaft 32 is connected via a mechanism 30. Therefore, the main pump chamber 26 holds a large volume change, and the slave pump chamber 28 makes a relatively small volume change.

The pump unit 20 constructed in this way
By the operation of the rotary drive shaft 32.
The piston 22 reciprocates through 0, whereby the pump operation including the suction process and the discharge process can be alternately repeated in the pair of pump chambers 26 and 28.

[0017] Incidentally, the the ratio of the volume change in each pump chamber 26, 28 is thus set to the ratio of the supply amount and the non-separation of the concentrated raw water quantity of the raw water which is determined by the performance of which will be described later membrane separator You can

Therefore, in the present invention, in order to supply the raw water and discharge the non-separated concentrated raw water to the pump chambers 26 and 28, the pump chambers 26 and 28 are connected to each other so as to communicate with each other. Connected. That is, in this case, the main pump chamber 26 connects the raw water supply system 36 to the membrane separation device 34 via the suction valve VA and the discharge valve VB, respectively,
Similarly, in the secondary pump chamber 28, the concentrated raw water discharge system 38 derived from the membrane separation device 34 can be discharged to the outside through the suction side switching valve (distribution valve) Va and the discharge side switching valve (discharge valve) Vb. Connect the pipe so that In FIG. 1, reference numeral 40 indicates a pure water extraction system for extracting pure water or fresh water obtained in the membrane separation device 34.

However, as one embodiment of the reciprocating pump type power recovery system according to the present invention, as shown in FIG. 2, three pump units 20 having the above-mentioned structure are connected and arranged. . That is, the first
Pump unit 20 (1) and second pump unit 2
0 (2) and the third pump unit 20 (3) to the common rotary drive shaft 32 via the crank mechanism 30, respectively.
They are connected with a predetermined phase difference (120 °).

Each main pump chamber (2 of each pump unit)
For 6), a common raw water supply system 3 via suction valves VA1, VA2, VA3 and discharge valves VB1, VB2, VB3, respectively.
6 is communicatively connected to a predetermined membrane separation device 34. in this case,
Suction valves VA1, VA2, VA3 and discharge valves VB1, VB2, VB3
A known check valve such as a ball valve, a wing valve, a flat valve, a solenoid valve, or the like can be used.

Also, for each slave pump chamber (28),
Concentrated raw water discharge system 38 derived from the membrane separator 34
Is connected to the suction side switching valve (distribution valve) Va and the discharge side switching valve (discharging valve) Vb through a pair of switching valve units 42 and 44, respectively, so that external discharge is possible. Connected.

FIG. 3 is a cross-sectional view showing an embodiment of the switching valve units 42 and 44. FIGS. 4A and 4B show the suction side switching valve () of one switching valve unit 42, respectively. Distribution valve) Va rotary valve body 43, and discharge side switching valve (discharging valve) in the other switching valve unit 44
The structure with the rotary valve body 45 of Vb is shown. However, Fig. 3
And in FIG. 4, a pair of switching valve units 42, 44
Have basically the same configuration.

One of the switching valve units 42 is provided with a cylinder type valve casing 46, and one fluid introduction hole 48 communicating with the inside of the valve chamber 47 is provided at one end surface portion of the valve casing 46, and at the outer peripheral portion thereof. Three fluid discharge holes 50 (1), 50, which are separated by an angle (120 °) and communicate with the inside of the valve chamber 47.
(2) and 50 (3) are provided. In the valve chamber 47 thus configured, a notch 43a is provided so as to communicate with each other across two adjacent fluid discharge holes, and the other portion can be hermetically sealed. A rotary valve body 43 having a cylindrical body configured as described above is provided. Therefore, the rotary valve body 43 is rotatably mounted on the rotary shaft 52. In FIG. 3, reference numeral 54 indicates a bearing mechanism that pivotally supports the rotary shaft 52, and reference numeral 55 indicates a drain hole provided at the bottom of the valve casing 46.

The other switching valve unit 44 has basically the same structure as the switching valve unit 42. That is, the switching valve unit 44 includes a cylinder type valve casing 56, and three fluid introduction holes 60 (1) that communicate with the inside of the valve chamber 57 at an equal angle (120 °) apart from the outer peripheral portion of the valve casing 56. , 60 (2), 60 (3), and one fluid discharge hole 58 communicating with the inside of the valve chamber 57 is provided at one end face portion. And the valve chamber 5 configured in this way
A notch 45a is provided in the inside of 7 so as to be able to communicate with each other across two adjacent fluid introduction holes, and the other part is formed of a cylindrical body configured to be hermetically sealed. A shaped valve body 45 is provided. Therefore, the rotary valve body 45 is rotatably mounted on the rotary shaft 62. In FIG. 3, reference numeral 64 indicates a bearing mechanism that pivotally supports the rotary shaft 62, and reference numeral 65 indicates a drain hole provided at the bottom of the valve casing 56.

Further, each switching valve unit 42, 44
The rotary shafts 52, 62 provided on the valve casing 46,
Coupled by a coupling 66 on the outside of 56,
It is configured to rotate synchronously. As shown in FIG. 2, the coupling 66 includes a rotary drive shaft 32 for driving the reciprocating pump units 20 (1), 20 (2), 20 (3) and a timing belt 68. The switching valve units 42 and 44 are connected via the switching valve units 42 and 44 in synchronization with the pumping operation of the reciprocating pump units. The rotary shafts 52 and 62 of the switching valve units 42 and 44 are coupled to each other by a coupling 66.
And the rotary drive shaft 32 may be directly connected.

The rotary valve body 43 of the switching valve unit 42
The configuration will be described in detail. As shown in FIG. 4A, the fluid discharge holes 50 (1), 50 provided on the outer peripheral portion of the inner peripheral surface of the valve casing 46 of the switching valve unit 42.
(2) Fluid discharge chambers 51 (1), 51 communicating with 50 (3)
(2) and 51 (3) are the required opening width α (30 °)
And are spaced apart by an equal angle (120 °). Then, these fluid discharge chambers 51 (1), 51 (2), 51
Corresponding to (3), the rotary valve body 4 provided in the valve chamber 47.
3, the notch 43a is provided on the outer peripheral surface thereof over a required angle β (150 °), and the other outer peripheral surface is configured to be in sliding contact with the inner peripheral surface of the valve chamber 47.

Similarly, with respect to the structure of the rotary valve body 45 of the switching valve unit 44, as shown in FIG. 4B, the inner peripheral surface of the valve casing 56 of the switching valve unit 44 has an outer periphery thereof. Fluid introduction holes 60 (1), 60 (2)
, 60 (3), fluid introduction chambers 61 (1), 61 (2)
, 61 (3) are provided with a required opening width α (30 °) and at an equal angle (120 °). Then, these fluid introduction chambers 61 (1), 61 (2), 61 (3)
Corresponding to, the rotary valve body 45 provided in the valve chamber 57
Is provided with a notch 45a on its outer peripheral surface over a required angle β (150 °), and the other outer peripheral surface is configured to be in sliding contact with the inner peripheral surface of the valve chamber 57.

That is, in this case, the fluid discharge chamber 51
(1) to (3) and opening width α of the fluid introduction chambers 61 (1) to (3)
And the angle β of the cutouts 43a, 45a of the rotary valve bodies 43, 45 are β = 180 ° -α . In addition, each of the fluid discharge holes 50 and the fluid chamber 51 and the fluid introduction hole 6 are provided.
The set positions of 0 and its fluid chamber 61 are equal (360 ° / number of multiple stations) to multiple stations (including a single station) [see (a) and (b) of FIG. 4].

Next, the operation of the reciprocating pump type power recovery system of the present embodiment constructed as described above will be explained.

Each main pump chamber 26 by the reciprocating pump units 20 (1), 20 (2), 20 (3) of the embodiment shown in FIG.
The suction valves VA1 to VA along with the operation of the piston 22 in
A3 and the discharge valves VB1 to VB3 are sequentially opened and closed to perform a predetermined pump operation for supplying raw water to the membrane separation device 34. The operation of the piston 22 in each main pump chamber 26 in this case is as shown in FIG. 5, and the pump operation (discharging step and suction step) in each main pump chamber 26 at this time is as shown in FIG. Is.

On the other hand, in each of the sub pump chambers 28, the operation of the piston 22 closes the switching valve Va on the suction side during the suction process in each of the main pump chambers 26.
The switching valve Vb on the discharge side is set to open. The operation of each of the switching valves Va and Vb will be described in detail later.

With this structure, the raw water sequentially delivered from each of the main pump chambers 26 through the raw water supply system 36 is introduced into the membrane separation device 34 to convert the raw water into pure water or fresh water. The purified water or fresh water thus obtained is separated and collected through the pure water extraction system 40 . On the other hand, the unseparated concentrated raw water is introduced from the concentrated raw water discharge system 38 into each of the sub pump chambers 28 together with the switching operation of the switching valves Va and Vb to discharge the piston 22 to each of the main pump chambers 26. sequentially discharged is divided by a line while assisting the operation. That is, the energy of the concentrated raw water derived from the membrane separator 34 is supplied to each sub pump chamber 28.
It can be effectively recovered as the pump operation energy for each main pump chamber 26 for supplying the raw water to the membrane separation device 34 .

Therefore, in the basic structure of the reciprocating pump unit shown in FIG. 1, the discharge amount of raw water in the main pump chamber 26 is Q and the discharge pressure is p, and the amount of separated water obtained in the membrane separator 34, that is, the amount of pure water is obtained. Q2, non-separated concentrated raw water amount Q1, main piston portion 22a diameter D, rod portion 22b diameter d, piston 22 reciprocating length (stroke length) L, and crank mechanism 30 rotation speed N. , R is the radius of the circle that rotates the crank mechanism 30.

As a result, the discharge amount Q of raw water is expressed by the following equation (1).

[0035]

[Equation 1] In this case, for the required concentrated raw water amount Q1, the following formula (2)
Thus, the diameter d of the rod portion 22b can be set.

[0036]

[Equation 2] From the equation (2)

[0037]

[Equation 3] Is obtained, and the following equation (4) is obtained.

[0038]

[Equation 4] At this time, if Q1 = 0.6Q, it can be calculated as follows from the equation (4).

[0039]

[Equation 5]

When carrying out, some leakage , non-separated water
Concentrated raw water due to fluctuations and slight pulsations unique to reciprocating pumps
Concentrated raw water discharge system 3 to cope with changes in the flow rate of discharge system 38
8 Accumulator (accumulator) and relief valve (relief)
Valve) or pressure regulating valve, etc., and the diameter d of the rod portion 22b
And the diameter D of the main piston portion 22a is d> 0.6
It may be determined on a case-by-case basis so that it becomes 3D.

In this way, the unseparated concentrated raw water whose pressure has been increased to a high pressure is guided to the sub pump chamber 28 while keeping the high pressure as much as possible to assist the power in the discharge process of the piston 22 in the main pump chamber 26. In the suction process of the piston 22 in the main pump chamber 26, the pressure of the sub pump chamber 28 is released, so that the energy of the concentrated raw water can be recovered with high efficiency.

Next, the operation of the switching valve units 42 and 44 in this embodiment described above will be described in detail.

That is, (a) to (h) of FIG.
Return pump units 20 (1), 20 (2), 20 (3)
Switching valve unit for introducing concentrated raw water into the slave pump chamber 28
Of the rotary valve body 43 in the0 °(A),Thirty
°(B),60 °(C),120 °(D),180 °
(E),240 °(F),300 °(G),360 °
The operation state at each position in (h) is shown.

Further, FIGS. 8A to 8G show each sub-pond.
Switching unit for discharging concentrated raw water from the pump chamber 28
Of the rotary valve body 45 in0 °(A),60 °
(B),120 °(C),180 °(D),240 °
(E),300 °(F),360 °At each position of (g)
It shows the operating state.

Therefore, each switching valve unit 42, 44 is
Each reciprocating pump unit 20 (1), 20 (2), 20 (3)
The opening / closing operation of each sub pump chamber 28 is as shown in FIG. Therefore, as is clear from FIG.
When a pump is in the discharge process, be sure to
The chamber is almost the same as the main pump chamber (only the pressure loss due to the flow is
(Low) pressure is applied, so power is not significantly recovered.
You can save money. That is, in FIG.
No. 0 to 180 ° phase angle, 1 in the discharge process
In this pump, the switching valve Va of this pump is opened, and the switching valve
Vb is closed, open on the membrane separator side and open on the exhaust side.
Since it is closed, the secondary pump chamber is under pressure. Well
Also, within the same phase angle range, 120 to 180 °
Between the pump No. Since 2 is also in the discharging process at the same time,
The switching valve Va of the pump also opens and the switching valve Vb closes.
Pump No. The secondary pump chamber of 2 is also pressurized
It Further, within the same phase angle range, the pump N
o. 2 is in the suction process between 0 and 120 °
The switching valve Va of the valve is closed and communicates with the membrane separation device.
Since Vb is opened to the discharge system by opening the valve,
The discharge pressure is not applied.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and for example, the reciprocating pump unit may have a multi-unit structure including two or more stations. Not only can it be driven by cam
Main pump chamber and slave pump respectively using different diameter cylinders
It is also possible to use a dual pump corresponding to the room
In addition, various design changes can be made without departing from the spirit of the present invention.

[0047]

As is apparent from the above-described embodiments, according to the power recovery type pump of the present invention, the reciprocating pump unit having the pump chambers formed in front of and behind the piston is provided.
It is equipped with multiple reciprocating pumps configured and arranged so as to interlock with a common rotary drive shaft through a crank mechanism at a predetermined phase angle. It is connected to a raw water supply system via a discharge valve, the raw water supply system is connected to a membrane separation device, and a concentrated raw water discharge system is led out from the membrane separation device, and the concentrated raw water discharge system is reciprocally moved. Corresponding to the pump operation by the piston of the main pump chamber to the sub-pump chamber side of the pump unit, the intake side switching valve unit and the discharge side switching valve unit, which are sequentially switched and connected, are communicatively connected, In the raw water discharge process of the pump chamber, the energy of the concentrated raw water is sequentially introduced into the respective sub pump chambers through the concentrated raw water discharge system to be recovered, whereby each reciprocating pump The energy provided during the supply of raw water in the main pump chamber of the unit is effectively recovered by introducing the energy retained in the concentrated raw water overflowing from the membrane separator into the corresponding sub pump chamber. Savings in the drive energy of the reciprocating pump can be achieved.

In particular, according to the present invention, in the structure of a small-sized pump device, the device can be lightened and low noise and low vibration can be maintained, so that the energy recovery device can be widely used as an extremely economical and efficient energy recovery device. It has the advantage that it can be applied.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram showing a basic configuration of a reciprocating pump type power recovery system according to the present invention.

FIG. 2 is a schematic system diagram showing an embodiment of a reciprocating pump type power recovery system according to the present invention.

FIG. 3 is a schematic side sectional view showing an embodiment of a switching valve unit used in the reciprocating pump type power recovery system according to the present invention.

4A and 4B show a structure of a main part of the switching valve unit shown in FIG. 3, in which FIG. 4A is a sectional view of a main part taken along line IV (a) -IV (a) of FIG. 3 and FIG. IV (b) -IV (b) line main part sectional view of FIG.

5 is a waveform diagram showing a pump operation in a main pump chamber of each reciprocating pump unit of the embodiment shown in FIG. 2 when the reciprocating pump unit shown in FIG. 1 is used.

6 is an explanatory view showing a pump operation in a main pump chamber of each reciprocating pump unit shown in FIG.

7 (a) to 7 (h) are explanatory views showing respective operating states of the switching valve unit shown in FIG. 4 (a).

8 (a) to (g) are explanatory views showing respective operating states of the switching valve unit shown in FIG. 4 (b).

9 is an explanatory diagram showing a switching operation in relation to the slave pump chamber of each reciprocating pump unit of each switching valve unit shown in FIGS. 7 and 8. FIG.

FIG. 10 is a schematic system diagram showing a basic configuration of a conventional membrane separation device.

FIG. 11 is a schematic system diagram of a power recovery type pump system applied to a conventional membrane separation device.

[Explanation of symbols]

20, 20 (1) ~ 20 (3) Reciprocating pump unit 22 pistons 22a Main piston part 22b Rod part 24 Cylinder 26 Main pump room 28 Secondary pump room 30 crank mechanism 32 rotary drive shaft 34 Membrane separation device 36 Raw water supply system 38 Concentrated raw water discharge system 40 Pure water extraction system 42,44 Switching valve unit 43, 45 rotary valve body 43a, 45a Notch 46, 56 valve casing 47, 57 valve chamber 48 fluid inlet 50 (1), 50 (2), 50 (3) Fluid discharge hole 51 (1), 51 (2), 51 (3) Fluid discharge chamber 52, 62 rotating shaft 54, 64 bearing mechanism 55, 65 drain hole 58 Fluid discharge hole 60 (1), 60 (2), 60 (3) Fluid introduction hole 61 (1), 61 (2), 61 (3) Fluid introduction chamber 66 Coupling 68 Timing belt VA (VA1 to VA3) Suction valve VB (VB1 to VB3) Discharge valve Va switching valve (distribution valve) Vb switching valve (discharge valve)

Claims (4)

(57) [Claims] 1. A reciprocating pump unit in which pump chambers are formed in front of and behind a piston, respectively , through a crank mechanism.
Each reciprocating pump unit is equipped with multiple reciprocating pumps that are configured and arranged so as to interlock with each other through a predetermined rotary drive shaft, and a suction valve and a discharge valve are provided to the main pump chamber side of each reciprocating pump unit. The raw water supply system is connected to the raw water supply system, and the raw water supply system is connected to a membrane separation device. The concentrated raw water discharge system is led out from the membrane separation device, and the concentrated raw water discharge system is used as a sub-pump for each reciprocating pump unit. Corresponding to the pump operation by the piston of the main pump chamber to the chamber side, the intake side switching valve unit and the discharge side switching valve unit, which are sequentially switched and connected, are connected in communication and the raw water discharge of each main pump chamber is performed. In the step, the reciprocating pump type power recovery system is configured so that the energy of the concentrated raw water is sequentially introduced into each of the slave pump chambers through the concentrated raw water discharge system and recovered. Temu. 2. A reciprocating pump unit, wherein a main pump chamber is formed on a main piston portion side of a piston, a subordinate pump chamber is formed on an insertion side of a rod portion, and an end portion of the rod portion is interposed by a crank mechanism. The reciprocating pump type power recovery system according to claim 1, wherein the reciprocating pump type power recovery system is connected to a common rotary drive shaft of a multiple reciprocating pump. 3. The reciprocating pump type power recovery system according to claim 1, wherein the suction valve and the discharge valve connected to the main pump chamber side of each reciprocating pump unit are ball valves or solenoid valves, respectively. system. 4. The suction-side and discharge-side switching valve units connected to the sub-pump chamber side of each reciprocating pump unit are arranged such that a rotary valve body is housed in a cylinder type valve casing having the same structure. And a plurality of fluid discharge holes or fluid introduction holes communicating with the valve chamber at equal angular intervals in the outer peripheral portion of the valve casing in correspondence with the number of the reciprocating pump units. A single fluid introduction hole or a fluid discharge hole is provided in the end face portion, and a cutout portion is provided so as to be able to communicate across the fluid discharge hole or the fluid introduction hole provided in the circumferential portion of the rotary valve body. Further, the rotary shafts of the switching valve units are coupled to each other and are configured to rotate synchronously with the rotary drive shaft of the reciprocating pump unit, which corresponds to the pump operation by the piston of each reciprocating pump unit. The reciprocating pump type power recovery system according to claim 1, wherein the switching valve unit is configured to perform a switching operation.