Desalination system and method

Abstract

This disclosure relates to a desalination system and a method for operating the desalination system. An exemplary embodiment includes a desalination system (100) comprising a separation container (101), a membrane container (104) housing a cross-flow semi-permeable membrane (105), a feed pump (108) for supplying brine, a recirculation pump (109), a main valve (110), a bypass valve (111), and a cleaning valve (112). The desalination system (100) operates in a first pressurization phase where brine is supplied by the feed pump (108) when the bypass valve (111) is open, a second pressurization phase where an upstream compartment (114) of the container (101) is filled therein, and a replenishment phase where the main valve (110) is closed and the concentrated brine is cleaned by the cleaning valve (112). A feed valve (116) may also be provided, which is closed during the first pressurization phase and open during the second pressurization phase and the replenishment phase.

Description

Technical Field

[0001] The present invention relates to a desalination system and a method of operating the desalination system. Background Technology

[0002] Desalination systems have many industrial applications. One application is separating drinking water from groundwater, which is saline and therefore unsuitable for drinking. Other applications include treating seawater and treating saline wastewater from textile mills.

[0003] In desalination applications, it is often necessary to maximize the recovery rate, which is the ratio of the volume of freshwater produced at the system output to the volume of brine supplied at the input. Higher recovery rates are required to maximize the system's useful output and minimize the required input.

[0004] WO 2020 / 039158A1 discloses a system and method for batch reverse osmosis that achieves high recovery rates (defined as the volume ratio between clean water output and feed water input) requiring only two pumps and three valves, avoiding some of the complexities of earlier designs. However, one issue is that the recovery rate of a batch reverse osmosis system is dependent on the size of the vessel in the system; higher recovery rates require larger pressure vessels. As the recovery rate approaches one, the vessel becomes impractically large, limiting practical implementation. Different techniques, such as semi-batch reverse osmosis, avoid the need for larger pressure vessels, but the disadvantage is that the energy requirement increases with the recovery rate. Therefore, it would be advantageous to provide a system and method that offers high recovery rates, low energy consumption, and a compact size. Summary of the Invention

[0005] According to the present invention, a desalination system is provided, comprising:

[0006] A partitioned container that contains a movable partition that divides the container into an upstream compartment and a downstream compartment, each having a variable volume. The partitioned container has a first inlet port at the upstream end of the container, a second inlet port at the downstream end of the container, and an outlet port at the downstream end of the container.

[0007] A membrane container that houses a cross-flow semipermeable membrane that divides the membrane container into a brine compartment and a desalination compartment. The brine compartment includes a first cross-flow port and a second cross-flow port, and the desalination compartment includes a desalination outlet port.

[0008] A feed pump, used to supply saline water, has an inlet and an outlet;

[0009] A recirculation pump having an inlet connected to a second crossflow port and an outlet connected to a second inlet port to supply brine to the downstream compartment;

[0010] The main valve is connected between the outlet port and the first cross-flow port;

[0011] A bypass valve is connected between the feed pump outlet and the second cross-flow port; and

[0012] The cleaning valve is connected to the first cross-flow port and the main valve on one side, and to the cleaning port on the other side.

[0013] The advantage of the desalination system is that the arrangement of the containers and valves allows the system to operate in both half-batch and batch modes, resulting in a hybrid mode that combines the advantages of both, achieving high recovery rates, low energy consumption, and a compact size.

[0014] The desalination system may also include a feed valve connected between the feed pump outlet and the first inlet port. However, the system can operate without a feed valve because, in practice, fluid from the feed pump tends to flow into the separator container preferentially through the bypass valve rather than through the first inlet port, provided the bypass valve and the first inlet port of the separator container are properly proportioned. The advantage of not having a feed valve is that fewer moving parts are required in the system, while the advantage of having a feed valve is that the operation of the desalination system has greater control.

[0015] The desalination system may include a controller connected to and configured to operate the desalination system, the controller being configured to:

[0016] During the first pressurization phase, in which the feed valve (if present) and the cleaning valve are closed while the bypass valve and the main valve are open, the recirculation pump is operated to recirculate the brine through the brine compartment, and the feed pump is operated to supply brine to the brine compartment.

[0017] In the second pressurization stage, where the bypass valve and purge valve are closed and the feed valve (if present) and main valve are open, the feed pump is operated to supply brine to the upstream compartment of the separator, causing the compartment to move so that brine flows from the downstream compartment into the brine compartment of the membrane vessel; and

[0018] During the recharge phase, in which the feed valve (if present), bypass valve, and cleaning valve are open while the main valve is closed, the recirculation pump and feed pump are operated to supply brine to the second inlet port of the separator and into the brine compartment of the membrane vessel via the second cross-flow port, so that the brine flows out through the cleaning port via the first cross-flow port.

[0019] The controller can be configured and connected to control the operation of one or more of the main valve, cleaning valve, feed valve (if present), and bypass valve, and optionally all of them.

[0020] The feed valve (if present) can be configured to open when the pressure between the feed pump and the feed valve rises above a threshold pressure level. The bypass valve can be configured to close when the pressure between the feed pump and the bypass valve rises above a threshold pressure level.

[0021] The controller can be configured to open the feed valve (if present) and close the bypass valve to end the first pressurization phase and begin the second pressurization phase. The end of the first pressurization phase and the start of the second pressurization phase can be determined in several ways. In a first embodiment, the desalination system includes a pressure sensor arranged to measure the pressure of the brine supplied by the feed pump, and the controller is configured to open the feed valve (if present) and close the bypass valve when the pressure between the feed pump and the feed valve or between the feed pump and the first inlet port rises above a threshold pressure level. In a second embodiment, the desalination system includes a conductivity sensor arranged to measure the conductivity of the brine flowing through the recirculation pump, and the controller is configured to open the feed valve (if present) and close the bypass valve when the conductivity of the brine flowing through the recirculation pump rises above a threshold conductivity level. In a third embodiment, the controller is configured to open the feed valve (if present) and close the bypass valve during the first pressurization phase when the feed pump has already supplied a threshold volume of brine. This can be determined by measuring the flow rate of the brine, for example, by knowing the pumping rate of the feed pump. For a known pumping rate, the threshold volume can be determined by a time threshold.

[0022] According to a second aspect, a method for operating a desalination system is provided, the desalination system comprising:

[0023] A partition container that houses a movable partition that divides the container into an upstream compartment and a downstream compartment, each having a variable volume, the partition container having a first inlet port at the upstream end of the container, a second inlet port at the downstream end of the container, and an outlet port at the downstream end of the container.

[0024] A membrane container that houses a cross-flow semipermeable membrane that divides the membrane container into a brine compartment and a desalination compartment. The brine compartment includes a first cross-flow port and a second cross-flow port, and the desalination compartment includes a desalination outlet port.

[0025] A feed pump, used to supply brine, has an inlet and an outlet;

[0026] A recirculation pump having an inlet connected to a second crossflow port and an outlet connected to a second inlet port to supply brine to the downstream compartment;

[0027] The main valve is connected between the outlet port and the first cross-flow port;

[0028] A bypass valve is connected between the feed pump outlet and the second cross-flow port; and

[0029] A cleaning valve, which is connected to the first cross-flow port and the main valve on one side, and to the cleaning port on the other side.

[0030] The method includes:

[0031] During the first pressurization phase, in which the cleaning valve is closed and the bypass valve and main valve are open, the recirculation pump is operated to recirculate the brine through the brine compartment, and the feed pump is operated to supply brine to the brine compartment.

[0032] In the second pressurization stage, where the bypass valve and purge valve are closed and the main valve is open, the feed pump is operated to supply brine to the upstream compartment of the separator, causing the compartment to move and allowing brine to flow from the downstream compartment into the brine compartment of the membrane vessel; and

[0033] During the replenishment phase, when the bypass valve and the cleaning valve are open and the main valve is closed, the recirculation pump and the feed pump are operated to supply brine to the second inlet port of the separator and into the brine compartment of the membrane container via the second cross-flow port, so that the brine flows out through the cleaning port via the first cross-flow port.

[0034] The desalination system may include a feed valve connected between the feed pump outlet and a first inlet port. The feed valve is closed during the first pressurization phase and open during the second pressurization phase and the replenishment phase.

[0035] The first pressurization phase, the second pressurization phase, and the replenishment phase can be repeated in sequence.

[0036] When the pressure in the brine supplied by the feed pump rises to the threshold pressure level, the first pressurization phase can end and the second pressurization phase can begin.

[0037] When the conductivity of the brine flowing through the recirculation pump rises to the threshold conductivity level, the first pressurization phase can end and the second pressurization phase can begin.

[0038] The first pressurization phase can end and the second pressurization phase can begin when the threshold volume of brine supplied by the feed pump is reached during the first pressurization phase. Attached Figure Description

[0039] The invention is further described in detail below with reference to examples and the accompanying drawings, wherein:

[0040] Figure 1 This is a schematic diagram of an exemplary desalination system;

[0041] Figure 2 This is a schematic diagram of an exemplary desalination system in the first operational stage;

[0042] Figure 3 This is a schematic diagram of an exemplary desalination system in the second operational stage;

[0043] Figure 4 This is a schematic diagram of an exemplary desalination system in the third stage of operation;

[0044] Figure 5 This is a schematic flowchart illustrating an exemplary method for operating a desalination system;

[0045] Figure 6 These are graphs showing the pressure change over time in different types of desalination systems; and

[0046] Figure 7 It is a contour map showing the batch volume of a hybrid desalination system and a conventional batch reverse osmosis system. Detailed Implementation

[0047] exist Figure 1 The desalination system shown includes a first separator container 101 and a second membrane container 104. Separator container 101 is divided into an upstream compartment 114 and a downstream compartment 115 by a movable partition or piston 102. A feed pump 108 provides a pressurized brine supply, supplying desalinated water at a desalinated water outlet port 113. A semi-permeable membrane 105 divides membrane container 104 into a brine compartment 131 and a desalination compartment 132. Separator container 101 may be a cylindrical container housing piston 102, wherein piston 102 is slidably mounted within cylindrical container 101. Container 101 may be made of glass-reinforced plastic, stainless steel, or some other pressure- and salt-resistant material. The inner diameter of container 101 is typically 4 inches (approximately 10.2 cm). Piston 102 may be machined to a diameter just less than 4 inches, allowing it to slide freely within cylindrical container 101. To prevent water leakage between the compartments on either side of the piston, the piston may be fitted with an O-ring seal 103. Alternatively, piston 102 can be machined to a tolerance close enough to prevent significant leakage and therefore eliminate the need for any seals.

[0048] The container 104 containing the membrane 105 can be in the form of a second cylindrical container that houses a semi-permeable membrane element 105 that allows cross-flow, as it is important to sweep the concentrated brine solution from the surface of the membrane 105. A first cross-flow port 106 and a second cross-flow port 107 allow cross-flow to enter and exit the container 104 in two directions, i.e., inflow through the second cross-flow port 107 and outflow through the first cross-flow port 106, and vice versa. The membrane element 105 used can be a spirally wound reverse osmosis type, such as those commonly used in desalination industries. Hollow fiber or flat sheet reverse osmosis membranes can also be used.

[0049] The desalination system 100 includes a first high-pressure feed pump 108 and a second low-pressure recharge or recirculation pump 109. The feed pump 108 supplies brine to the first inlet 121 of the cylindrical container 101 via a feed valve 116 and / or to the recharge or recirculation loop via a bypass valve 111. As described above, the feed valve 116 can be omitted without affecting the operation of the desalination system 100. The bypass valve 111 is connected between the outlet 129 of the feed pump 108 and the second cross-flow port 107, and when open, allows brine from the feed pump 108 to bypass the cylindrical container 101 and flow into the recirculation loop comprising the brine compartment 131 of the membrane container 104 and the recirculation pump 109. A cleaning valve 112, connected between the first cross-flow port 106 and the cleaning port 123, allows concentrated brine from the brine compartment 131 of the membrane container 104 to flow from the first cross-flow port 106 to the cleaning port 123 when open. A main valve 110, connected between the first cross-flow port 106 and the outlet port 124 of the separator 101, allows brine to flow from the outlet port 124 to the first cross-flow port 106 of the membrane vessel 104 when open. Valves 110, 111, 112, and 116 (if present) may be solenoid valves. To minimize power consumption when actuating the valves, the main valve 110 and the feed valve 116 (if present) may be normally-open, while the bypass valve 111 and the purge valve 112 may be normally-closed. Valves 110, 111, and 112 may be electrically or pneumatically actuated, or in some cases, particularly for the bypass valve 111, the main valve 110, and the feed valve 116, may be pressure-actuated, for example, as disclosed in WO 2020 / 039158A1.

[0050] An electrical control unit or controller 125 is connected and configured to operate valves 110, 111, 112, and 116, which can be done in response to sensors 126 and 127 arranged to detect the position of piston 102. A first sensor 126 may be located at the first inlet 121 to detect when piston 102 has moved back to its initial position, i.e., upstream of the first inlet 121 of container 101. A second sensor 127 may be located at the second inlet port 122 to detect when piston 102 has moved to the downstream end of container 101. Sensors 126 and 127 can be pressure sensors or flow sensors. For pressure sensors, when piston 102 reaches either end of container 101, it will cause a pressure rise in the upstream compartment 114 or the downstream compartment 115, which can be detected by the corresponding sensor 126 or 127. The pressure difference between sensors 127 and 126, located at or near outlet port 124 and inlet 121 respectively, can be used to detect when piston 102 reaches either end of container 101. For the flow sensor, when piston 102 reaches either end of container 101, it will cause a decrease in flow rate. The first sensor 126 could be, for example, a pressure sensor, since a greater pressure is available from feed pump 108. The second sensor 127 could be a flow sensor, since the pressure change will be smaller when piston 102 has returned to the upstream end of container 101. In an alternative arrangement, sensors 126 and 127 could be proximity sensors configured to provide a signal when piston 102 approaches the sensor, thereby detecting when piston 102 is located at the upstream or downstream end of the separating container 101.

[0051] Another pressure sensor 130, disposed between the feed pump outlet 129 and the feed valve 116 (if present), may be configured to sense the pressure of the liquid supplied to the desalination system 100 via the feed pump 108. This pressure may be used to trigger the system to switch from a first stage to a second stage, as described in more detail below. Alternatively or additionally, a conductivity sensor 133 may be provided, the output of which may be used to detect the salt concentration within the recirculation loop and trigger the system to switch from a first stage to a second stage, as described in further detail below. The conductivity sensor 133 may be located on either side of the recirculation pump 109 or the main valve 110 to measure the conductivity of the brine flowing through the recirculation pump 109.

[0052] Various components of the desalination system 100 can be connected via pressure pipes and corrosion-resistant pipes, such as... Figure 1 As shown by the solid lines in the diagram. These pipes are typically made of PVC or stainless steel and are connected via threads or flanges using techniques familiar to those skilled in the field of designing and building desalination systems.

[0053] The saline feed water enters the system at inlet 128 of the feed pump 108 and is separated into demineralized water that exits through demineralized water outlet port 113, and concentrated brine that exits through purge valve 112 and purge port 123. The operation method for achieving this separation includes three stages: a first pressurization stage, a second pressurization stage, and then a purge-refill stage, which are described in detail below. Figure 2 , 3 Explanation of section 4. In these diagrams, pipes carrying water flow are represented by solid lines, while pipes without flow are represented by dashed lines. Flow is opened and closed by valves 110, 111, 112, and 116, whether by pressure actuation or controlled by controller 125. The closed position of valves 110, 111, and 112 is indicated by solid shading, while the open position is indicated by an unshaded outline of the valve.

[0054] In the first stage, such as Figure 2 As shown, feed valve 116 and cleaning valve 112 are closed, while main valve 110 and bypass valve 111 are open. In some embodiments, feed valve 116 may be omitted because without feed valve 116, the flow supplied by feed pump 108 will tend to flow preferentially through bypass valve 111. Feed pump 108 and recirculation pump 109 are operated, with feed pump 108 supplying brine to the circulation loop, which includes a brine compartment 131 of membrane vessel 104 and a conduit connecting a second cross-flow port 107 to a first cross-flow port 106 via recirculation pump 109 and main valve 110. The recirculation loop also includes a portion of the downstream compartment 115 of vessel 101 as flow enters compartment 115 through second inlet port 122 and exits compartment 115 through outlet port 124. Because feed valve 116 is closed, or because the flow from feed pump 108 preferentially flows through bypass valve 111, piston 102 is stationary during the first stage, and the amount of salt in the recirculation loop gradually increases with increasing pressure. Demineralized water is discharged via demineralized water outlet port 113 during the first stage.

[0055] Once a threshold is reached, which could be when the brine pressure measured by pressure sensor 130 has risen to the threshold level, when the salt concentration in the recirculation loop has reached the threshold level measured by conductivity sensor 133, or when a predetermined volume of brine determined by volume or time measurement has been pumped into the system by feed pump 108, the system switches from the first stage to the second stage, such as... Figure 3As shown. In this stage, bypass valve 111 and cleaning valve 112 are closed, while feed valve 116 (if present) and main valve 110 are open. Feed pump 108 and recirculation pump 109 continue to operate. Therefore, the transition from the first stage to the second stage is achieved by closing the bypass valve and opening feed valve 116 (if present). This can be done using controller 125 (see...). Figure 1 This can be achieved by actuating valves 111 and 116, or if feed valve 116 is not present, bypass valve 111 can be actuated alone.

[0056] As the second stage proceeds, the feed pump 108 provides more brine. In this stage, the brine is not added to the recirculation loop, but instead fills the upstream compartment 114 of the separator container 101, causing the piston 102 to move to the right, as... Figure 3 As shown, the size of downstream compartment 115 is reduced and its contents are added to the recirculation loop. This results in additional demineralized water being discharged from demineralized water outlet port 113, and the pressure further increases.

[0057] Once piston 102 has reached the end of compartment 101, i.e., when upstream compartment 114 is maximized and downstream compartment 115 is minimized, the second stage ends. At this point, the third stage begins, as... Figure 4 As shown. In the third stage, feed valve 116 (if present), bypass valve 111, and purge valve 112 are open, while main valve 110 is closed. Therefore, the transition from the second to the third stage involves opening bypass valve 111, opening purge valve 112, and closing main valve 110. Feed pump 108 and recirculation pump 109 continue to operate. Brine from feed pump 108 is supplied to brine compartment 131 of membrane vessel 104 via bypass valve 111, flushing concentrated brine out of first cross-flow port 106 and through purge port via purge valve 112. Simultaneously, recirculation pump 109 supplies brine to downstream compartment 115 of separator vessel 101, causing the volume of upstream compartment 114 to decrease as downstream compartment 115 fills with brine. Once downstream compartment 115 is maximized and upstream compartment 114 is minimized, the third stage ends, and the process can then be repeated by going back to the first stage.

[0058] Figure 5An example operation of the desalination system of the type described above is illustrated schematically. In the first step 501, the feed valve 116 (if present) and the rinsing valve 112 are closed, and the bypass valve 111 and the main valve 110 are opened. In the second step 502, the feed pump 108 and the recirculation pump 109 are operated to supply brine to the recirculation loop. As the pressure within the loop increases, desalinated water is output from the desalinated water outlet port 113. In the third step 503, checks are performed to determine whether pressure, salt concentration, brine volume, or time thresholds have been reached. In one embodiment, pressure is monitored (e.g., by measuring pressure with pressure sensor 130) and checked against a pressure threshold. In another embodiment, the salinity of the water in the recirculation loop is measured by conductivity sensor 133 and checked against a conductivity threshold. In other embodiments, the volume of water supplied by the feed pump may be checked against a volume threshold, or a time threshold may be checked. This is repeated until the threshold is reached, at which point the method proceeds to step 504, where the bypass valve 111 is closed and the feed valve 116 (if present) is opened. Feed pump 108 and recirculation pump 109 then continue operation (step 505), and in step 506, the position of piston 102 within separator container 101 is checked. Once piston 102 has reached the downstream end of separator container 101 and upstream compartment 114 is maximized, the method proceeds to step 507, at which point purge valve 112 is opened, main valve 110 is closed, and bypass valve 111 is opened. Feed pump 108 and recirculation pump 109 continue operation (step 508). A check (step 509) is performed to determine when piston 102 has reached the upstream end of separator container 101, i.e., when upstream compartment 114 is minimized and downstream compartment is maximized. Once this occurs, the process is repeated by returning to step 501.

[0059] Figure 6The pressure changes over time are shown in different types of desalination processes. A minimum pressure of approximately 250 kPa is required 601 for the desalinated water to pass through the membrane. In batch processes, pressure 602 rises from just over 500 kPa to approximately 800 kPa after approximately 300 seconds, at which point the process ends. In semi-batch processes, such as those described in WO 2020 / 039158A1, pressure 603 rises approximately linearly from the same starting point to approximately 3100 kPa. In the process described herein, pressure 604 initially rises in a similar manner to batch process 602 because the brine is supplied directly to the brine compartment 131 of membrane vessel 104. In practice, the pressure may be slightly higher at this stage than in the semi-batch process, but the difference is not significant in terms of total energy consumption. Once the pressure has risen to a threshold level of approximately 800 kPa, which is the end of the first pressurization stage, the second stage begins as described above, and the pressure continues to rise until it reaches a maximum value similar to that of a half-batch process, such as approximately 3100 kPa. At this point, the process enters the third stage for flushing and recharging.

[0060] The advantages of the methods and systems described in this paper are the low total energy consumption per cycle. The energy used is comparable to... Figure 6 The area under each pressure curve is related to the area under pressure curve 604. The area under pressure curve 604 is significantly smaller than the area under pressure curve 603. Compared to systems of the type described in WO 2020 / 039158A1, using systems of the type described herein, the container size for equivalent efficiency can be more than halved, for example, reducing the container size from approximately 135 liters to approximately 60 liters, with approximately 0.38 kWh / m³. 3 With a similar specific energy, the feed water at 25 °C contains 3 g of salt per liter, with a recovery rate of 90%.

[0061] As another embodiment, to illustrate the relationship between the size and specific energy consumption of the present invention compared to previous systems, Figure 7 The contour plot in the image shows the batch volume V of the hybrid system described in this paper relative to a conventional batch reverse osmosis (RO) system. b0The horizontal axis shows the container size in the batch RO system described in WO 2020 / 039158A1, and the vertical axis shows the container size in the hybrid system of the type described herein. The batch system design is located on the diagonal 701, which gives the maximum container size. The exemplary semi-batch system design based on US498330 is located on the horizontal axis, resulting in a container size of zero. The hybrid design is defined by a lower triangle at these two extremes, with specific energy consumption represented by contour lines. The contour lines show that a significant reduction in container size will only result in a small loss in energy consumption. For example, at a 95% recovery rate, reducing the container size from 275.7 liters to 97.1 liters will result in a batch RO system (0.2079 kWh / m³) 3 The specific energy consumption (SEC) of the product increases by only 0.0107 kWh / m³. 3 Despite being three times smaller in size, the energy loss of the hybrid process is very small (less than 5%). The SEC of the hybrid system is 0.2184 kWh / m³. 3 , compared to 0.6921 kWh / m³ for the semi-batch process 3 In comparison, this is quite low.

[0062] The exemplary desalination system 100 according to this disclosure is constructed with a separator container 101 having an inner diameter of 24 cm. This separator container houses a piston 102, which provides a swept length of 155 cm, thereby generating a displaced volume of 70 liters. A membrane container 104 has an inner diameter of 20 cm and an internal length of 1 m, accommodating a surface area of ​​40 m². 2 A semi-permeable membrane 105. Other components of the system are provided in the embodiments described herein, wherein a conductivity sensor 133 is provided in the recirculation loop.

[0063] An exemplary desalination system 100 is used to desalinate brine containing sodium chloride at a concentration of 0.85 g / L. A feed pump 108 supplies water to the system at a flow rate of 12 liters per minute. The recirculation flow provided by a recirculation pump 109 is set to a significantly larger flow rate of 42 liters per minute. Initially, during the first pressurization phase (i.e., half-batch mode), the rinsing valve 112 and feed valve 116 are closed, while the main valve 110 and bypass valve 111 are open. Permeate flows out of the system at a rate of 12 liters per minute. The salt concentration in the system's recirculation loop gradually increases, causing a corresponding increase in system pressure. A controller 125 monitors this concentration using a conductivity sensor 133 and detects when it exceeds a threshold level of 4 g / L. The controller 125 then switches the system to the second pressurization phase (i.e., batch mode) by closing the bypass valve 111 and opening the feed valve 116. This causes piston 102 to move in the direction of downstream compartment 115, while permeate continues to be discharged at a rate of 12 liters per minute. The concentration in the recirculation loop then increases more rapidly until piston 102 reaches the end of its stroke, at which point controller 125 opens purge valve 112 and bypass valve 111, and closes main valve 110 (while feed valve 116 remains open), thus initiating the replenishment phase. During the replenishment phase, brine is collected, with a salinity measured at 15.1 g / L, 17.8 times that of the feed water. A total of 363 liters of permeate were collected during the test, compared to the 379 liters of feed water supplied. This equates to a 96% recovery rate. The hydraulic work required to power the system, based on the displacement and average pressure provided by each pump, was also measured as the total work of feed pump 108 and recirculation pump 109. Therefore, the specific energy consumption of desalination system 100 was determined to be 0.5 kWh per cubic meter of permeate output.

[0064] Other embodiments are intentionally within the scope of the invention as defined by the appended claims.

Claims

1. A desalination system (100), comprising: A partition container (101) is provided with a movable partition (102) that divides the container (101) into an upstream compartment (114) and a downstream compartment (115) each having a variable volume. The partition container (101) has a first inlet port (121) at the upstream end of the container (101), a second inlet port (122) at the downstream end of the container (101), and an outlet port (124) at the downstream end of the container (101). A membrane container (104) contains a cross-flow semipermeable membrane (105) that divides the membrane container (104) into a brine compartment (131) and a desalination compartment (132). The brine compartment (131) includes a first cross-flow port (106) and a second cross-flow port (107). The desalination compartment (132) includes a desalination water outlet port (113). A feed pump (108) is used to supply brine and has an inlet (128) and an outlet (129). A recirculation pump (109) having an inlet connected to the second crossflow port (107) and an outlet connected to the second inlet port (122) to supply brine to the downstream compartment (115); A main valve (110) is connected between the outlet port (124) and the first cross-flow port (106); A bypass valve (111) is connected between the feed pump outlet (129) and the second cross-flow port (107); and A cleaning valve (112) is connected to the first cross-flow port (106) and the main valve (110) on one side and to the cleaning port (123) on the other side. The desalination system (100) further includes a controller (125) connected to and configured to operate the desalination system (100), the controller (125) being configured to: During the first pressurization phase in which the feed valve (116), if present, and the cleaning valve (112) are closed while the bypass valve (111) and the main valve (110) are open, the recirculation pump (109) is operated to recirculate the brine through the brine compartment (131), and the feed pump (108) is operated to supply brine to the brine compartment (131); In the second pressurization phase, when the bypass valve (111) and cleaning valve (112) are closed and the feed valve (116), if present, and the main valve (110) are open, the feed pump (108) is operated to supply brine to the upstream compartment (114) of the separator container (101), causing the compartment (102) to move, thereby allowing brine to flow from the downstream compartment (115) into the brine compartment (131) of the membrane container (104); and During the replenishment phase where the feed valve (116) is present, the bypass valve (111) and the cleaning valve (112) are open and the main valve (110) is closed, the recirculation pump (109) and the feed pump (108) are operated to supply brine to the second inlet port (122) of the separator container (101) and into the brine compartment (131) of the membrane container (104) via the second cross-flow port (107), so that the brine flows out through the cleaning port (123) via the first cross-flow port (106).

2. The desalination system (100) according to claim 1 further includes a feed valve (116) connected between the feed pump outlet (129) and the first inlet port (121).

3. The desalination system (100) according to claim 1, wherein, The controller (125) is configured and connected to control the operation of one or more of the main valve (110), the cleaning valve (112), the feed valve (116), if present, and the bypass valve (111).

4. The desalination system (100) according to claim 2, wherein, The feed valve (116) is configured to open when the pressure between the feed pump (108) and the feed valve (116) rises above a threshold pressure level.

5. The desalination system (100) according to claim 4, wherein, The bypass valve (111) is configured to close when the pressure between the feed pump (108) and the bypass valve (111) rises above the threshold pressure level.

6. The desalination system (100) according to claim 3, wherein, The controller (125) is configured to open the feed valve (116), if present, and close the bypass valve (111) to end the first pressurization phase and begin the second pressurization phase.

7. The desalination system (100) according to claim 6, comprising a pressure sensor (130) arranged to measure the pressure of brine supplied by the feed pump (108), wherein the controller (125) is configured to open the feed valve (116) when the pressure at the pressure sensor (130) rises above a threshold pressure level, and if present, close the bypass valve (111).

8. The desalination system (100) according to claim 6, comprising a conductivity sensor (133) arranged to measure the conductivity of brine flowing through the recirculation pump (109), wherein the controller (125) is configured to open the feed valve (116) when the conductivity of the brine flowing through the recirculation pump (109) rises above a threshold conductivity level, and, if present, close the bypass valve (111).

9. The desalination system (100) according to claim 6, wherein, The controller (125) is configured to: open the feed valve (116) and, if present, close the bypass valve (111) when the feed pump (108) has provided a threshold volume of brine during the first pressurization phase.

10. A method of operating a desalination system (100), the desalination system (100) comprising: A partition container (101) is provided with a movable partition (102) that divides the container (101) into an upstream compartment (114) and a downstream compartment (115) each having a variable volume. The partition container (101) has a first inlet port (121) at the upstream end of the container (101), a second inlet port (122) at the downstream end of the container (101), and an outlet port (124) at the downstream end of the container (101). A membrane container (104) contains a cross-flow semipermeable membrane (105) that divides the membrane container (104) into a brine compartment (131) and a desalination compartment (132). The brine compartment (131) includes a first cross-flow port (106) and a second cross-flow port (107). The desalination compartment (132) includes a desalination water outlet port (113). A feed pump (108) is used to supply brine and has an inlet (128) and an outlet (129). A recirculation pump (109) having an inlet connected to the second crossflow port (107) and an outlet connected to the second inlet port (122) to supply brine to the downstream compartment (115); A main valve (110) is connected between the outlet port (124) and the first cross-flow port (106); A bypass valve (111) is connected between the feed pump outlet (129) and the second cross-flow port (107); and A cleaning valve (112) is connected to the first cross-flow port (106) and the main valve (110) on one side and to the cleaning port (123) on the other side. The method includes: During the first pressurization phase, in which the cleaning valve (112) is closed and the bypass valve (111) and the main valve (110) are open, the recirculation pump (109) is operated to recirculate brine through the brine compartment (131), and the feed pump (108) is operated to supply brine to the brine compartment (131); In the second pressurization phase, where the bypass valve (111) and cleaning valve (112) are closed and the main valve (110) is open, the feed pump (108) is operated to supply brine to the upstream compartment (114) of the separator container (101), causing the compartment (102) to move, thereby allowing brine to flow from the downstream compartment (115) into the brine compartment (131) of the membrane container (104); and During the replenishment phase, in which the bypass valve (111) and the cleaning valve (112) are open and the main valve (110) is closed, the recirculation pump (109) and the feed pump (108) are operated to supply brine to the second inlet port (122) of the separator container (101) and into the brine compartment (131) of the membrane container (104) via the second cross-flow port (107), so that the brine flows out through the cleaning port (123) via the first cross-flow port (106).

11. The method according to claim 10, wherein, The desalination system (100) further includes a feed valve (116) connected between the feed pump outlet (129) and the first inlet port (121), the feed valve (116) being closed during the first pressurization phase and open during the second pressurization phase and the replenishment phase.

12. The method of claim 10, wherein the first pressurization phase, the second pressurization phase, and the replenishment phase are repeated in sequence.

13. The method according to any one of claims 10 to 12, wherein, When the pressure in the brine supplied by the feed pump (108) rises to the threshold pressure level, the first pressurization phase ends and the second pressurization phase begins.

14. The method according to any one of claims 10 to 12, wherein, When the conductivity of the brine flowing through the recirculation pump (109) rises to the threshold conductivity level, the first pressure increase phase ends and the second pressure increase phase begins.

15. The method according to any one of claims 10 to 12, wherein, When the threshold volume of brine supplied by the feed pump (108) during the first pressurization phase is reached, the first pressurization phase ends and the second pressurization phase begins.

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