An energy recovery pump for reverse osmosis water treatment system

Abstract

The present invention relates to an energy recovery pump for a reverse osmosis water treatment system, which adopts a structure similar to a piston pump, and innovatively eliminates the sealing means between the water inlet chamber (11) and the drainage chamber (12), the boosting chamber (13) and the recovery chamber (14), and the upper working chamber (21) and the lower working chamber (31), thereby achieving the purpose of making the structure simpler and more reliable while ensuring the performance of the pump. Compared with energy recovery pumps with similar energy recovery efficiency, the present invention has the simplest structure and has the same reliability and cost as traditional plunger pumps, and can be widely used in high-pressure reverse osmosis water treatment systems such as seawater desalination systems and brackish water treatment systems.

Description

Technical Field

[0001] The invention relates to an energy recovery pump for a reverse osmosis water treatment system, in particular to a high-pressure reverse osmosis water treatment system such as a seawater desalination system and a brackish water treatment system. Background Art

[0002] my country is already facing a serious shortage of water resources, and the shortage is getting worse. In response to this situation, my country has also introduced the "strictest water resource management system". As an important means to alleviate the shortage of water resources, seawater desalination technology has received more and more attention. Among the many seawater desalination technologies, reverse osmosis has gradually become the mainstream technical means in the market due to its lower cost.

[0003] The reverse osmosis desalination technology uses a high-pressure pump to pressurize the raw seawater to a reverse osmosis operating pressure of 5.0-7.0 MPa (depending on the salinity of the seawater), and then allows the pressurized seawater to flow to the reverse osmosis membrane in the reverse osmosis membrane device. Part of it passes through the reverse osmosis membrane and becomes fresh water, while the other part becomes concentrated water and is discharged. Since the pressure in the concentrated water is still very high, if it is not used, the power consumption required to produce one ton of fresh water is more than 10KW.h.

[0004] In the early days, the seawater desalination system using reverse osmosis method mostly adopted the method of increasing the pressure before the reverse osmosis membrane to reduce the power consumption per ton of water production. However, this method is restricted by the maximum pressure of the reverse osmosis membrane, the limit recovery rate of insoluble salts, the limit recovery rate of concentration polarization and the head of the high-pressure pump, and the power consumption is still above 8KW.h. In the 1980s, energy recovery technology was widely used, which used reverse pumps and Pelton impeller type energy recovery devices, which can effectively recover the energy in the waste high-pressure seawater, thereby greatly reducing the power consumption; later, hydraulic turbine type energy recovery devices were developed to further reduce the power consumption per ton of water; in recent years, with the development of direct contact positive displacement technology of fluids, the energy recovery efficiency of a new generation of energy recovery devices represented by piston work exchangers and rotary pressure exchangers has reached more than 90%, thereby reducing the power consumption per ton of fresh water produced to less than 4KW.h.

[0005] There are four types of piston work exchanger technologies commonly used at present. The first is isobaric exchange, such as the DWEER piston work exchanger of Aqualink, which is an equal-area piston, so that the pressure of high-pressure concentrated water in the exchanger is equal to the pressure of raw water entering the chamber, thereby achieving the purpose of pressure energy recovery; the second is boost exchange, such as the boost energy recovery device developed by Tianjin Seawater Desalination and Comprehensive Utilization Research Institute, which is a single piston rod piston, high-pressure concentrated water acts on the side without piston rod and raw water acts on the side with piston rod, so that the pressure of raw water after pressurization is higher than that of high-pressure concentrated water, achieving energy recovery and boosting; the third is differential pressure exchange, such as the Clark pump of Spectra Company in the United States, which is similar to two piston rods connected to piston cylinders, and achieves the purpose of energy recovery and boosting by utilizing the piston area difference of the high-pressure part and the pressure difference of the low-pressure part. Among the above technologies, the first two require the use of a high-pressure pump and do not have a boosting function; although the third does not require a high-pressure pump, it still requires a higher-pressure raw water pump. Limited by the speed of piston movement (too fast will cause wear), the three technologies have a common disadvantage, that is, the piston cylinder is large in size: except for the Clark pump, the others are used in large and medium-sized seawater desalination projects; the Clark pump is also larger in size than other small seawater desalination pumps.

[0006] The fourth type is an energy recovery pump similar to a piston pump structure. When pressurized, the concentrated brine is recovered to the side chamber of the piston with a connecting rod, that is, the lower working chamber, so as to achieve the purpose of energy recovery. On this basis, US Patent US8021128B2 proposed an energy recovery pump using a novel valve and piston, and the Pearson pump product was developed by Spectra Corporation of the United States. However, the pump has the following problems:

[0007] 1. There needs to be functional requirements of connectivity and sealing between the water inlet and the upper working chamber, the upper working chamber and the boosting chamber, the upper working chamber and the recovery chamber, the recovery chamber and the lower working chamber, and the lower working chamber and the drainage chamber; therefore, in its actual product, five layers of plates are set up to achieve the above functions, making its structure and flow path more complicated.

[0008] 2. In the patent text description and drawing illustration, in order to achieve sealing between the water inlet chamber and the drainage chamber, and the boost chamber and the recovery chamber, seals are provided at the connecting rods of the water inlet and drainage valve and the boost recovery valve; since the water inlet and drainage valve and the boost recovery valve are both one-way valve type valves, they are more sensitive to friction damping, so this problem can only be avoided by increasing the valve force area, reducing the size of the connecting rod and the seal, and reducing the pump speed. However, this also brings about the problems of increased structural size, poor valve force conditions, and poor response.

[0009] 3. In the patent text description, the water inlet and discharge valve and the boost recovery valve used in the pump do not specify the valve sealing surface form. The patent drawing description indicates that the valve sealing surface is a plane; but when the two plane sealing pairs are linked, if there is a parallelism deviation, leakage will occur, which will lead to poor pump performance or even complete inability to increase pressure.

[0010] 4. In the patent text description and the drawings, the water inlet and outlet valve and the boost recovery valve are provided with mating surfaces and seals to facilitate the adjustment of the relative positions of the two valve cores along the valve axis during assembly. However, the seals themselves have weak vibration resistance and are prone to loosening during high-speed reciprocating motion of the valve, causing the relative position of the valve to change, which in turn leads to internal leakage of the valve, poor pump performance, or even complete inability to boost pressure.

[0011] 5. In order to avoid excessive pressure difference between the upper and lower parts of the piston, the pump adopts a movable piston and uses springs to correct it. Compared with the traditional piston form, its form is more complicated and noisier. Summary of the invention

[0012] The present invention provides an energy recovery pump for a reverse osmosis water treatment system, comprising a pump body (1), an upper cover (2), a base (3), a water inlet and drain valve (4), a pressure-boosting recovery valve (5), a piston assembly (6), a spring (7) and related accessories. The cavities on the pump body (1) connected to the water inlet, the drain, the pressure-boosting port and the recovery port are respectively the water inlet chamber (11), the drain chamber (12), the pressure-boosting chamber (13) and the recovery chamber (14). The cavity between the pump body (1) and the upper cover (2) is the upper action chamber (21), and the cavity between the pump body (1) and the base (3) is the lower action chamber (31). The upper part of the pump body (1) is connected to the upper cover (2), and the lower part is connected to the base (3). The middle cavity serves as a cylinder for the reciprocating motion of the piston assembly (6), and the cavities on both sides serve as cylinders for the reciprocating motion of the water inlet and drain valve (4) and the pressure-boosting recovery valve (5). The two springs (7) act on the corresponding spring mounting surfaces on the water inlet and outlet valve (4) and the pressure boost recovery valve (5) respectively, so that the valves remain closed in the absence of other forces.

[0013] The piston assembly (6) reciprocates in the pump body (1). When it moves toward the base (3), the water inlet and drain valve (4) opens and the pressurization recovery valve (5) closes under the action of pressure. Raw water enters the upper working chamber (21) through the water inlet chamber (11), and waste water is discharged from the lower working chamber (31) through the drain chamber (12). When it moves toward the upper cover (2), the water inlet and drain valve (4) closes and the pressurization recovery valve (5) opens under the action of pressure. After the raw water is pressurized, it flows through the pressurization chamber (13) to the external reverse osmosis membrane group to produce fresh water, and the remaining high-pressure concentrated water flows through the recovery chamber (14) to the lower working chamber (31).

[0014] The water inlet and outlet valve (4) and the boost recovery valve (5) are double valve core linkage valves, comprising an upper valve core (41), a lower valve core (42), a connecting piece (43) connecting the two valve cores, and a related valve seat, wherein the connecting piece (43) can also be integrated into the upper valve core (41) or the lower valve core (42). The upper valve core (41) or the lower valve core (42) and the connecting piece (43) have a matching surface (44) for adjusting the relative position of the two valve cores along the valve axis, the axis of the matching surface (44) is consistent with the valve axis, and the shape is but not limited to a cylindrical shape.

[0015] The present invention innovatively provides a pressurization recovery channel (16) between the pressurization chamber (13) and the recovery chamber (14), thereby greatly simplifying the pump structure. Figure 1 As shown. In US Pat. No. 8,021,128B2 and other similar patents, the upper action chamber (21) is located between the boost chamber (13) and the recovery chamber (14); the seal between the upper action chamber (21) and the boost chamber (13), and between the upper action chamber (21) and the recovery chamber (14) is essential, otherwise the pump will not be able to increase pressure; the present invention changes the structure to directly connect the boost chamber (13) and the recovery chamber (14), thereby canceling the original seal with the upper action chamber (21), and simplifying the structure of the pump from the traditional five-layer plate to the three-layer plate; and only the middle pump body (1) of the three-layer plate is a functional plate, the top plate (2) only plays a role in preventing leakage, and the bottom plate (3) also only plays a role in preventing leakage and assisting the piston rod movement of the piston (6). While the pump structure is greatly reduced, the pump structure size is reduced, and the pump structure weight is also reduced.

[0016] The present invention is further innovative, as Figure 1 As shown, by allowing no seal between the water inlet and drainage channel (15) and the water inlet and drainage valve (4), and by allowing a small amount of leakage between the boost recovery channel (16) and the boost recovery valve (5), the water inlet and drainage valve (4) and the boost recovery valve (5) avoid friction damping caused by the seal, and can adapt to higher pump speeds, thereby reducing the size of the pump structure and reducing the weight of the pump structure. At the same time, since the water inlet pressure and drainage pressure, and the boost pressure and recovery pressure are not much different, when the gap is small, the impact on the fresh water production is very small.

[0017] The present invention is further innovative, as Figure 2As shown, by setting the two valve sealing surfaces of the water inlet and drain valve (4) and the boost recovery valve (5) to spherical sealing or spherical-conical sealing, the sealing failure problem caused by the parallelism deviation of the two plane sealing surfaces is effectively solved. Due to the constraint between the two spherical pairs, there is only the permissible degree of freedom of rotation along the axis, so this sealing form is reliable; correspondingly, if there is a parallelism deviation between the two valve core plane seals and it is assumed that the valve seat surfaces are completely parallel, theoretically at least one surface cannot be completely sealed, that is, leakage will occur in theory; similarly, two cone seals, one plane and one cone seal, one plane and one spherical seal, one cone and one spherical seal, etc. will theoretically cause leakage.

[0018] The present invention is further innovative in that the relative positions of the valve components can be effectively ensured by fixing the mating surface (44) of the double valve core linkage valve by means of adhesive bonding, welding or fasteners and their combination. As mentioned above, the method of using seals to ensure the relative position in U.S. Patent US8021128B2 has the problem of sealing failure caused by loosening of the seals during high-speed reciprocating motion, while the use of adhesive bonding, welding or fasteners and their combination can avoid the occurrence of such problems. In addition, since the adhesive structure or threaded connection structure is simpler and more reliable, it can not only improve reliability but also reduce costs. However, since the adhesive bonding or welding method generally requires one-time fixation, if there is a deviation, the entire valve core can only be scrapped; therefore, on this basis, a test seal or thread can be added to the mating surface (44), and adhesive bonding or welding can be performed after various tests are completed.

[0019] The present invention is further innovative, as Figure 3 As shown, by adopting a piston form without seals, the piston structure is greatly simplified while reducing the pressure difference on both sides of the piston. The mechanism of this type of pump is that the piston rod enters the pump, resulting in a reduction in the system volume, so that the same volume of working fluid is "squeezed" out of the reverse osmosis membrane in the form of fresh water. Ideally, the system can also work without a piston. Therefore, the system can work normally without a seal between the pistons, and the simulation and test results both prove that when the size of the fluid passage (piston) is small, the impact on the pump performance is very small. Since there is no seal, the piston structure is simpler than the traditional piston structure, and is greatly simplified compared with the piston with a complex anti-pressure differential device in US Patent US8021128B2. The piston fluid passage (61) can be a gap between the piston assembly (6) and the middle cavity of the pump body (1), or a gap or hole between the upper action chamber (21) and the lower action chamber (31) on the piston assembly (6), or a gap or hole between the upper action chamber (21) and the lower action chamber (31) on the pump body (1), or a combination of the three.

[0020] The present invention is further innovative, as Figure 4and Figure 7 As shown, by integrating a one-way valve, an orifice plate or a combination of the two at the outlet of the drainage chamber (12) or connecting it to the outside, the working medium in the lower working chamber (31) can be effectively prevented from vaporizing. When the piston moves toward the upper working chamber (21) and the boost recovery valve (5) is not opened, the volume of the lower working chamber (31) increases and the pressure of the working medium therein decreases rapidly; when the pressure decreases to the point where vaporization occurs inside the lower working chamber (31), violent vibrations will occur in the pump, and the system boost pressure, flow rate, etc. will decrease accordingly. In severe cases, the system may even be unable to boost pressure. Adding a one-way valve, an orifice plate or a combination of the two at the drainage port or outside can increase the drainage back pressure, making it difficult for the working medium in the lower working chamber (31) to reach the vaporization conditions, thereby avoiding the occurrence of vaporization.

[0021] The present invention is further innovative, as Figure 1 and Figure 5 As shown, by providing a split valve seat connected to the pump body (1), installation and testing are facilitated. The split valve seat is an inlet valve seat (101), a drain valve seat (102), a boost valve seat (103) and a recovery valve seat (104), and only one or more of them may be provided, which are connected to the relevant parts by means of adhesive connection, screw connection, welding, fastener connection or a combination thereof.

[0022] The present invention is further innovative, as Figure 6 As shown, by setting the corresponding spring mounting surfaces on the water inlet and drain valve (4) and the boost recovery valve (5) at any position of the valve that can keep it closed in the absence of other forces, it is convenient to flexibly apply it according to the actual structure during design.

[0023] The present invention is further innovative in that the pump system is more integrated by integrating the water inlet pump and the safety valve.

[0024] The present invention can further be expanded to a multi-piston energy recovery pump to increase flow and reduce pressure fluctuations, such as a three-piston pump, a five-piston pump, a nine-piston pump, etc.

[0025] In addition, the pump body (1), the upper cover (2), the base (3), the water inlet and outlet valve (4), the boost recovery valve (5), and the piston assembly (6) can be made of plastic materials in addition to conventional seawater corrosion-resistant metal materials. The plastic materials include but are not limited to PEEK, POM, PTFE, and PE.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. The structure is the simplest among all similar devices with energy recovery efficiency above 90%;

[0028] 2. It has the same reliability as the traditional plunger pump;

[0029] 3. The cost is the lowest among similar equipment, and it is possible to reduce the cost to the same level as ordinary plunger pumps for non-seawater desalination.

[0030] The present invention can be widely applied to high-pressure reverse osmosis water treatment systems such as seawater desalination systems and brackish water treatment systems.

[0031] Figure 1 Schematic diagram of the energy recovery pump system

[0032] Figure 2 Schematic diagram of the structure of three types of double spherical linkage valves

[0033] Figure 3 Schematic diagram of the fluid path structure between three types of pistons and cavities

[0034] Figure 4 Schematic diagram of the energy recovery pump system with integrated drain check valve

[0035] Figure 5 Schematic diagram of the energy recovery pump system with integrated partial valve seat

[0036] Figure 6 Schematic diagram of the energy recovery pump system with the spring position changed

[0037] Figure 7 Schematic diagram of a reverse osmosis water treatment system using an energy recovery pump

[0038] In the figure: 1- pump body; 2- upper cover; 3- base; 4- water inlet and drain valve; 5- boost recovery valve; 6- piston assembly; 7- spring; 8- discharge port one-way valve; 11- water inlet chamber; 12- drain chamber; 13- boost chamber; 14- recovery chamber; 15- water inlet and drain channel; 16- boost recovery channel; 21- upper action chamber; 31- lower action chamber; 61- piston fluid passage; 101- water inlet valve seat; 102- drain valve seat; 103- boost valve seat; 104- recovery valve seat; 201- water inlet pipe; 202- drain pipe; 203- boost pipe; 204- recovery pipe; 205- raw water pipe; 206- raw water pump; 207- reverse osmosis membrane group; 208- produced water pipe; 209- external one-way valve. DETAILED DESCRIPTION

[0039] Combine the following Figure 7 Specific embodiments of the present invention will be described.

[0040] In addition to the energy recovery pump, the reverse osmosis water treatment system also includes an inlet pipe (201), a drain pipe (202), a booster pipe (203), a recovery pipe (204), a raw water pipe (205), a raw water pump (206), a reverse osmosis membrane group (207), a water production pipe (208), an external one-way valve (209), and related filter components, valves, pipes and accessories. The inlet pipe (201), the drain pipe (202), the booster pipe (203), and the recovery pipe (204) are respectively connected to the energy recovery pump water inlet, the drain port, the booster port, and the external one-way valve (209). The external one-way valve (209) is connected to the recovery port; the external one-way valve (209) can also be integrated in the drain pipe (202). The inlet of the raw water pump (206) is connected to the raw water pipe (205), and the outlet is connected to the inlet pipe (201). The inlet of the reverse osmosis membrane group (207) is connected to the boosting pipe (203), the water production port is connected to the water production pipe (208), and the outlet is connected to the recovery pipe (204).

[0041] After the system is in operation, the raw water enters the raw water pump (206) from the raw water pipe (205), and then enters the energy recovery pump for pressurization through the water inlet pipe (201). The pressurized raw water enters the reverse osmosis membrane group (207) through the pressurization pipe (203), and a part of it becomes produced water and flows out from the produced water pipe (208), and the remaining part becomes high-pressure concentrated water from the recovery pipe (204) to the recovery port of the energy recovery pump to recover its high-pressure energy. After being recovered, the high-pressure concentrated water becomes low-pressure waste water, and then passes through the drain port, the external one-way valve (209), and the drain pipe (202) in sequence to be discharged out of the system.

[0042] The above description of the embodiments is to facilitate the understanding and use of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. An energy recovery pump for a reverse osmosis water treatment system, comprising a pump body (1), an upper cover (2), a base (3), a water inlet and drain valve (4), a boost recovery valve (5), a piston assembly (6), a spring (7) and related accessories, wherein the cavities on the pump body (1) connected to the water inlet, the drain, the boost port and the recovery port are respectively the water inlet chamber (11), the drain chamber (12), the boost chamber (13) and the recovery chamber (14), the cavity between the pump body (1) and the upper cover (2) is the upper action chamber (21), and the cavity between the pump body (1) and the base (3) is the lower action chamber (31); the upper part of the pump body (1) is connected to the upper cover (2), and the lower part is connected to the base (3); the middle cavity serves as a cylinder for the reciprocating motion of the piston assembly (6), and the cavities on both sides serve as cylinders for the reciprocating motion of the water inlet and drain valve (4) and the boost recovery valve (5); the two springs are connected to the upper cover (2), and the lower part of the pump body (1) is connected to the upper cover (2). The spring (7) acts on the corresponding spring mounting surfaces on the water inlet and drain valve (4) and the boost recovery valve (5) respectively, so that the water inlet and drain valve (4) and the boost recovery valve (5) remain closed in the absence of other forces; the piston assembly (6) reciprocates in the pump body (1), and when it moves toward the base (3), the water inlet and drain valve (4) is opened and the boost recovery valve (5) is closed under the action of pressure, and the raw water enters the upper working chamber (21) through the water inlet chamber (11), and the waste water is discharged from the lower working chamber (31) through the drain chamber (12); when it moves toward the upper cover (2), the water inlet and drain valve (4) is closed and the boost recovery valve (5) is opened under the action of pressure, and the boosted raw water flows through the boost chamber (13) to the external reverse osmosis membrane group, a part of which becomes fresh water, and the remaining part becomes high-pressure concentrated water, flows out of the external reverse osmosis membrane group, and then flows through the recovery chamber (14) to the lower working chamber (31); it is characterized in that The water inlet chamber (11) and the water discharge chamber (12) are communicated through a water inlet and water discharge channel (15), the pressurization chamber (13) and the recovery chamber (14) are communicated through a pressurization recovery channel (16), and there is no sealing member between the water inlet and water discharge channel (15) and the water inlet and water discharge valve (4), and between the pressurization recovery channel (16) and the pressurization recovery valve (5); The water inlet and outlet valve (4) and the boost recovery valve (5) are both double valve core linkage valves, comprising an upper valve core (41), a lower valve core (42), a connecting piece (43) connected to the two valve cores, and a related valve seat, wherein the connecting piece (43) is integrated into the upper valve core (41) or the lower valve core (42), the sealing surfaces of the two valve cores are both spherical, and the sealing surface of the valve seat in contact with them is a spherical or conical surface; The upper valve core (41) or the lower valve core (42) and the connecting piece (43) have a mating surface (44) for adjusting the relative positions of the two valve cores along the valve axis. The axis of the mating surface (44) is consistent with the valve axis and is cylindrical in shape. The mating surface (44) is fixed by gluing, welding or fasteners and a combination thereof, or on this basis, a test seal or thread is added to the mating surface (44).

2. An energy recovery pump for a reverse osmosis water treatment system according to claim 1, characterized in that The upper action chamber (21) and the lower action chamber (31) have a piston fluid passage (61) in communication and are free of sealing components.

3. An energy recovery pump for a reverse osmosis water treatment system according to claim 2, characterized in that The piston fluid passage (61) is a gap between the piston assembly (6) and the intermediate cavity of the pump body (1), or a gap or hole between the upper action chamber (21) and the lower action chamber (31) on the piston assembly (6), or a gap or hole between the upper action chamber (21) and the lower action chamber (31) on the pump body (1), or a combination of the three.

4. The energy recovery pump for a reverse osmosis water treatment system according to claim 1, characterized in that A device for preventing the working medium in the lower working chamber (31) from vaporizing is integrated at the outlet of the drainage chamber (12), i.e., the drainage port, or connected to the outside thereof. The device is a one-way valve, an orifice plate, or a combination of the two.

5. The energy recovery pump for a reverse osmosis water treatment system according to claim 1, characterized in that A split valve seat connected to the pump body (1) is provided, wherein the split valve seat is one or more of an inlet valve seat (101), a drain valve seat (102), a booster valve seat (103) or a recovery valve seat (104), and is connected to relevant parts by means of adhesive connection, screw connection, welding, fastener connection or a combination thereof.

6. The energy recovery pump for a reverse osmosis water treatment system according to claim 1, characterized in that The corresponding spring mounting surfaces on the water inlet and outlet valve (4) and the pressure boost recovery valve (5) are located at any position of the valve that enables the valve to remain closed in the absence of other forces.

7. The energy recovery pump for a reverse osmosis water treatment system according to claim 1, characterized in that It integrates water inlet pump and safety valve.

8. The energy recovery pump for a reverse osmosis water treatment system according to claim 1, characterized in that The pump body (1), the upper cover (2), the base (3), the water inlet and outlet valve (4), the boost recovery valve (5), and the piston assembly (6) are made of conventional seawater corrosion-resistant metal materials or plastic materials; the plastic materials include PEEK, POM, PTFE, and PE.

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