Hybrid energy recovery system

Abstract

A system is designed to recover energy from a fluid treatment operation that uses a membrane to remove impurities from a feed stream. Energy recovery devices, such as turbochargers, isobaric chambers, and multi-stage pumps are used to recover energy.

Description

[0001] Inter-references to related applications

[0002] This application is based on and claims the benefit of U.S. Provisional Patent Application No. 63 / 307,285, filed February 7, 2022, which is incorporated herein by reference in its entirety. Background Technology

[0003] Reverse osmosis (RO) processes use a set of membrane elements that allow solvents (such as water) to pass through the membrane but block dissolved solids (such as salts). RO is used for desalination of brackish water and seawater, where the feed stream is separated by the membrane into a freshwater stream (called permeate), while the remainder is discarded as a concentrated brine stream (called concentrate, brine, or wastewater), which exits the membrane at a pressure slightly lower than the feed pressure entering the membrane array. This discussion will focus on desalination, but it is equally applicable to all separation processes using membranes of any type of solvent.

[0004] Figure 1 illustrates an RO system comprising a source of brackish water or seawater (referred to as feed), which is connected via pipe 1 to a high-pressure pump (HPP) 2. The effluent from HPP 2 enters membrane 10 via pipe 4, whose flow rate is regulated by control valve 3. Permeate exits via pipe 11. Brine exits membrane 10 via pipe 16 to drain pipe 6. Control valve 8 regulates the brine flow rate.

[0005] The rate at which permeate is produced in the membrane (called flux) is determined by the net driving pressure (NDP), which is equal to the fluid pressure minus the average osmotic pressure of the feed in the membrane. Osmotic pressure is determined by the concentration of the dissolved solids. As the feed travels along the membrane length, it becomes increasingly concentrated, thus gradually acquiring higher osmotic pressure and lower NDP. Therefore, the permeate production decreases along the length of the membrane.

[0006] The amount of permeate produced divided by the feed rate is called the recovery rate. For example, if from 10m... 3 4m of feed is recovered 3 The permeate recovery rate is 40%. In a seawater reverse osmosis (SWRO) system, a single membrane can achieve a recovery rate of up to approximately 45%, while maintaining acceptable energy consumption and permeate quality.

[0007] If a higher recovery rate is desired, the existing membrane arrangement depicted in Figure 2 is used. Brine exits membrane 10 through conduit 5 and enters pump 7, which increases the pressure to restore NDP, and then enters the second membrane 15. Due to the increased NDP supplied by pump 7, additional permeate exits membrane 15 through conduit 12 and is collected by permeate manifold 13. Brine exits membrane 15 through conduit 16 to drain line 6. Control valve 8 regulates the brine flow rate.

[0008] Energy recovery devices (ERDs) are often used to recover hydraulic energy from the brine stream leaving the last stage. ERDs relevant to this disclosure include turbochargers and isobaric chambers.

[0009] The turbocharger uses the hydraulic energy of brine to pressurize another stream (typically the feed entering the membrane stage). For a turbocharger designed for high-pressure desalination, refer to Figure 2.1. The turbocharger 26 includes a pump section 47 and a turbine section 48. The pump section 47 has a feed inlet 32 ​​and a feed outlet 33, and the turbine section 48 has a brine inlet 34 and a brine outlet 35. The pump section includes a diffuser 37, which surrounds a pump impeller 36 with a wear-resistant ring 42 and is in fluid communication with the feed inlet 32 ​​and the feed outlet 33. The turbine section 48 includes a nozzle ring or volute 39, which surrounds the impeller 38 with the wear-resistant ring 43 and is in fluid communication with the brine inlet 34 and the brine outlet 35. The pump and turbine impeller are attached to a shaft 40, which is supported by a bearing 41. In operation, high-pressure brine enters brine inlet 34, passes through nozzle ring 39, where a high tangential velocity is imparted to the fluid, and then enters impeller 38, imparting torque to shaft 40. The brine exits through brine outlet 35. Feed enters inlet 32, passes through impeller 36, which rotates in response to the shaft torque generated by turbine impeller 38. The feed, now with a high tangential velocity, enters diffuser 37, which converts the velocity into static pressure. The feed exits through outlet 33.

[0010] Valve 44 can be opened to allow the addition of brine flow to the nozzle ring or volute 45, thereby increasing the brine flow rate or reducing the brine flow resistance through the turbine section 48. Figure 2.2 shows a typical process symbol for a turbocharger equipped with a brine-assisted nozzle as described above.

[0011] Please refer to Figure 3. The depicted system is similar to that in Figure 2, with the addition of turbochargers 21 and 26. Feed from HPP 2 enters the pump section 18 of turbocharger 21, which pressurizes the feed, which then passes through pipe 9 to the first membrane 10. High-pressure brine exits membrane 10 through pipe 5 and enters the pump section 27 of turbocharger 26, which increases the pressure of the flow stream, which then enters the second membrane 15. Permeate exits membrane 15 through pipe 12 and is collected by permeate manifold 13. Brine exits membrane 15 through pipe 16 to the turbine section 28 of turbocharger 26. Hydraulic energy is recovered and used to power pump section 27. Partially depressurized brine passes through pipe 29 to turbine section 20 of turbocharger 21 to power pump section 18. Brine exits turbine section 20 through pipe 17 to drain pipe 6.

[0012] The prior art depicted in Figure 3 represents a preferred method for achieving increased recovery rates when designing new facilities. Increasing the recovery rate of an RO system improves its economic performance. However, hundreds of RO systems are single-stage systems with limited recovery rates. If replacing the existing HPP and ERD is deemed too expensive, it means that a second stage needs to be added for higher recovery rates, while retaining as many existing system components as possible to reduce the overall cost of the retrofit.

[0013] The isobaric chamber pressurizes the feed stream to equal the brine flow and discharges the feed at a pressure slightly lower than the incoming brine flow. Therefore, the isobaric chamber acts as a high-pressure pump, pressurizing the feed stream to equal the brine flow. A separate high-pressure pump pressurizes the feed stream to equal the permeate flow. An additional pump is needed to increase the feed discharge rate from the isobaric chamber to compensate for the 2 to 4 bar pressure loss, thus matching the membrane pressure.

[0014] Figure 4 illustrates an isobaric chamber 112, which is used to recover hydraulic energy from high-pressure brine to pressurize the feed stream. Isobaric chambers and how they function are well known in the art and will not be disclosed in detail here.

[0015] The inherent hydraulic characteristics of the isobaric chamber include: the HP feed pressure leaving the unit is slightly lower than the HP brine pressure. Furthermore, the volume of HP brine entering the isobaric chamber is equal to the volume of HP feed leaving the isobaric chamber, neglecting leakage. It is crucial that the HP brine pressure is always higher than the HP feed pressure. Similarly, the feed charge for purging brine from the pump cylinder requires a feed pressure greater than the brine pressure leading to the drain line. Figure 4 illustrates the prior art use of an isobaric chamber 112 energy recovery unit and a booster pump 110 in an RO system. The isobaric chamber 112 receives high-pressure brine from the membrane 10 via pipe 16 and discharges low-pressure brine to the drain line 6 via pipe 17. A control valve 8 regulates the brine flow rate. The feed rate entering the isobaric chamber 112 via pipe 150 is the same as the brine flow rate entering the isobaric chamber 112 via pipe 16. The feed leaves the isobaric chamber 112 via pipe 148 and is pumped to pipe 4 via pump 110. The combined flow of HPP 2 and isobaric chamber 112 enters the membrane 10. Pump 110 typically provides a pressure boost of 2 to 4 bar.

[0016] Figure 5 illustrates a prior art configuration using an isobaric chamber 112 that receives brine from a second membrane 15. This configuration uses an interstage pump 7 to increase the pressure between the first membrane 10 and the second membrane 15. As noted above, the isobaric chamber 112 discharges feed through pipe 148 at a pressure 2 to 4 bar lower than the brine pressure in pipe 16. Typically, the brine pressure in the second membrane 15 is about 25 bar higher than the feed pressure going to the first membrane 10. Subtracting the maximum loss of 4 bar in the pipes and the second membrane 15, the feed pressure in pipe 148 is 21 bar higher than required by membrane 10. This excessive pressure must be directed by control valve 149 or is wasted. This represents a significant energy loss that could otherwise be recovered for useful purposes. Summary of the Invention

[0017] A system is designed to recover energy from a fluid handling operation that uses a membrane to remove impurities from a feed stream. Energy recovery devices, such as turbochargers, isobaric chambers, and multistage pumps, are used to recover energy. Attached Figure Description

[0018] Figure 1 is a side front view.

[0019] Figure 2 is a side front view.

[0020] Figure 2.1 is a side front view.

[0021] Figure 2.2 is a side front view.

[0022] Figure 3 is a side front view.

[0023] Figure 4 is a side front view.

[0024] Figure 5 is a side front view.

[0025] Figure 6 This is a side front view.

[0026] Figure 7 is a side front view.

[0027] Figure 7A is a partial side front view.

[0028] Figure 8 This is a side front view.

[0029] Figure 9 This is a side front view.

[0030] Figure 10 This is a side front view.

[0031] Figure 11 is a side front view.

[0032] Figure 12 This is a side front view.

[0033] Figure 13 This is a side front view.

[0034] Figure 14 This is a flowchart of the operation parameters.

[0035] Figure 15 This is a flowchart of the operation parameters.

[0036] Figure 16 This is a flowchart of the operation parameters. Detailed Implementation

[0037] This invention relates to an energy recovery system. In particular, the system utilizes a turbocharger, an isobaric chamber, and a multi-stage high-pressure pump to achieve the desired energy recovery result.

[0038] Figure 6 A first embodiment of the invention is shown. The essence of the invention is to reduce the brine pressure leaving membrane 15 to a value lower than the feed pressure used for membrane 10 without wasting available brine hydraulic energy. Therefore, the inherent hydraulic characteristics of the isobaric chamber will not result in excessive feed pressures that must be wasted or removed from the system via the control valve described with respect to FIG. 5.

[0039] To better understand the operation, assume the feed pressure in pipe 9 is 50 bar, the brine pressure in pipe 16 is 70 bar, and the brine pressure in pipe 29 is 35 bar. The pressure in pipe 29 is a result of the pressure reduction caused by the use of fluid pressure in the turbine section 28 of the turbocharger 26 relative to the input pressure in pipe 16. For clarity, in Figure 6 The accompanying explanation includes pressure.

[0040] Turbocharger 26 provides a pressure boost from 49 bar to 71 bar between the first membrane 10 and the second membrane 15. Partially depressurized brine exits the turbine section 28 of turbocharger 26 at 35 bar and passes through conduit 29 to isobaric chamber 112 at 35 bar. Isobaric chamber 112 discharges the feed at a pressure 4 bar lower. Pump 110 needs to increase the feed pressure supplied to conduit 9 by 19 bar to match the 50 bar requirement of membrane 10. The main advantage of this embodiment is the elimination of energy wasted from feed throttling by valve 149 in FIG. 5, and the elimination of the cost, complexity, and energy consumption of a motor-driven interstage booster pump 7.

[0041] The advantage of this embodiment is that it utilizes brine energy to simultaneously provide interstage pressure boosting and brine pressure reduction, allowing the isobaric chamber to operate without generating excessive feed pressure.

[0042] Note that pump 110 has a high pressure differential, which requires a large motor, variable frequency drive (VFD), high-pressure mechanical seal, and heavy-duty bearings to operate under high inlet pressure. Such pumps have high capital costs, high maintenance costs, and limited efficiency. The next feature of the present invention eliminates the need for such a pump.

[0043] Figure 7 illustrates a prior art multistage high-pressure pump 120 typically used in an RO system. The pump housing 125 of pump 120 contains stages 126 stacked in series. A low-pressure feed enters through inlet port 122 in inlet housing 131 and is then passed to the stage array. As the fluid progresses from one stage to another, each stage increases the pressure on the fluid. The feed exits pump 120 through outlet port 132. A motor 121 rotates pump shaft 124. A shaft seal 123 prevents leakage.

[0044] As illustrated in Figure 7-A, shaft 124 drives impeller 127 in each stage 126. Diffuser 128 converts dynamic pressure into static pressure, and return channel 129 guides the flow to the next stage. Arrow 130 illustrates the flow path through the stage.

[0045] Figure 8An embodiment of the multistage pump of the present invention is illustrated, which overcomes the limitations of the previous embodiment in terms of wasted energy (energy cannot be recovered and used to provide feed pressure for the first and second membranes). A motor 121 is connected to a pump shaft 124. A shaft seal 123 prevents leakage. Feed enters the pump 140 through inlet port 122 in a first inlet housing 131. Stage stack 126-A generates a specified feed pressure. A second inlet port 135 in a second inlet housing 136 receives additional feed from another source, which mixes with the feed leaving stage stack 126-A. The combined flow is passed to a second stage stack 138-A, which increases the pressure to a specified value and exits through a discharge port 139. Note that the stages in stage stack 138-A can be larger than the stages in stage stack 126-A to accommodate higher flow rates.

[0046] Figure 9 The functionality of the improved pump 140 within this invention is illustrated. Feed from pipe 1 enters pump 140 through inlet port 122. The feed pressure is increased by stage stack 126-A to a specified value at inlet housing 136. Feed from pump 110 enters through inlet port 135 and mixes with the feed from stage stack 126-A. The combined flow passes through stage stack 138-A and through pipe 4 to membrane 10.

[0047] Pump 140 receives flow from isobaric chamber 112 via second inlet port 135, which supplies flow to pump 110. The combined flow entering pump 140 through first inlet port 122 and second inlet port 135 exits through outlet port 139 and is delivered to first membrane 10 via conduit 4. Motor 145 includes VFD 144 to allow adjustment of pump speed to obtain the required pressure for first membrane 10.

[0048] A booster pump 110 with motor 146 and VFD 147 may be required to provide precise control of the pressure from the feed outlet pipe 148 of the isobaric chamber 112. Note that pump 110 must be rated for operation at high inlet pressures, which necessitates expensive and faulty high-pressure shaft seals and high-capacity bearings. If precise pressure control at inlet port 135 is not required, booster pump 110 and associated equipment may not be necessary.

[0049] Integrating the turbocharger and isobaric chamber into the same system requires novel control logic. Control data is provided by flow meters 190, 191, and 192. Flow meter 190 measures the feed flow rate in pipe 148, which supplies feed from isobaric chamber 112 to pump 140; flow meter 191 measures the brine discharge through pipe 17; and flow meter 192 measures the total permeate flow rate in permeate manifold 13. Flow data is processed by PLC 160. PLC 160 controls flow control valve 8 via control line 168, VFD 147 via control line 164, and VFD 144 via control line 165.

[0050] Figure 10 The illustration shows another embodiment where pump 110 and associated equipment are replaced with pressure reducing valve 151. The pressure in the second inlet port 135 will be designed to be a few bar lower than the minimum expected pressure of the feed discharge line 148 of the isobaric chamber 112. Adjustment of valve 151 provides flow regulation. Stage stack 138-A will be designed to provide the pressure required by membrane 10. VFD 144 can be used to adjust motor speed 145, thereby controlling the pump discharge pressure at outlet port 139.

[0051] Integrating a turbocharger and an isobaric chamber into the same system requires novel control logic. (Reference) Figure 10 Control data is provided by flow meters 190, 191, and 192. Flow meter 190 measures the feed flow rate in pipe 148, which supplies feed from the isobaric chamber 112 to the pump 140. Flow meter 191 measures the brine discharge through pipe 17, while flow meter 192 measures the total permeate flow rate in the permeate manifold 13. Flow data is processed by PLC 160. PLC 160 controls flow control valve 8 via control line 168, control valve 151 via control line 164, and VFD 144 via control line 165.

[0052] The isobaric chamber 112 requires that the feed flow rate through pipe 148 must be equal to the brine flow rate through pipe 17. This control functionality also allows for adjustment of the brine and feed flow rates as needed for process control.

[0053] The turbocharger 26 is equipped with an auxiliary brine nozzle 25. Opening the nozzle 25 increases the brine flow rate and / or decreases the pressure differential, while closing the nozzle decreases the brine flow rate and / or increases the pressure differential. Since the brine flow rate can be kept constant by adjusting the control valve 8 of the isobaric chamber 112, the pressure differential across the turbine section 28 is controlled by adjusting the brine nozzle 25. When open, the pressure differential decreases, which reduces the pressure boost from the pump section 27. Conversely, when closed, the pressure differential increases, resulting in a greater pressure boost. If the pressure boost is high, the permeate production from the second membrane 15 increases, while if the pressure boost is low, the permeate production decreases. The position of the brine nozzle 25 can be set to any value between fully open and fully closed to achieve a desired intermediate pressure boost value.

[0054] Figure 14 The control logic used in this invention is described.

[0055] Figure 11 illustrates the prior art of functionally replacing the isobaric chamber using a turbocharger 21. Turbochargers offer numerous advantages, such as higher reliability compared to isobaric chambers due to their significantly less complex design and lower capital costs. The turbo exchanger (TX) 21 replaces the isobaric chamber as described in the prior art. A significant difference is that, instead of the pump 110 used to raise the pressure downstream of the isobaric chamber feed outlet, the booster pump 110 raises the pressure upstream of the turbocharger feed inlet. The feed enters through pipe 1. A portion of the feed flows through pipe 19, through HPP 2, through control valve 3 to membrane 10. The remaining feed flows through pipe 150, through booster pump 110 to pump section 18 of turbocharger 21. Pump section 18 raises the feed pressure to a level sufficient to match the pressure downstream of control valve 3. As previously disclosed, partially depressurized brine from turbocharger 26 passes through pipe 29 to turbine section 20 of turbocharger 21, drives pump section 18, and then leaves under low pressure through pipe 17 to reach drain pipe 6.

[0056] The significant difference from the isobaric chamber is that the feed flow rate through pipe 150 can be greater than, equal to, or less than the brine flow rate through pipe 29. This expands the system's operational flexibility.

[0057] Pump 110 requires its own motor, VFD, power supply, base plate, etc., resulting in significantly increased capital and maintenance costs.

[0058] Figure 12An embodiment of the invention based on the use of TX 21 is shown. Pump 140 is similar to the previous embodiment, but with several key differences. The total feed flow rate enters inlet port 122 through conduit 1. Stage stack 126-A increases the pressure to slightly above the pressure required at the feed inlet of pump section 18 of turbocharger 21 (the pressure increase ranges from 4 bar to 8 bar as needed) to suppress cavitation in pump section 18 of turbocharger 21. A portion of the feed leaves pump 140 through outlet 135, passes through control valve 151 to pump section 18 of turbocharger 21. The feed leaves pump section 18 at a pressure matching the pressure required for membrane 10. Referring to pump 140, the feed that does not leave at outlet 135 continues through stage stack 138-A, where the pressure is increased to match the pressure required for membrane 10. The flow from pump 140 and pump section 18 combines in conduit 4 and enters membrane 10.

[0059] Adjust control valve 151 to maintain the feed flow rate at the desired value. PLC 160 is used to control the fluid flow rate, as previously mentioned. Figure 10 As described.

[0060] Figure 15 The control functions of the above embodiments are limited.

[0061] Figure 13 An embodiment of the invention based on the use of TX 21 with an attached motor 172 and VFD 173 is shown. Shaft 171 directly connects motor 172 to shaft 40 depicted in FIG. 2.1. The rotational speed of shaft 171 is adjusted by adjusting the VFD 173 driving motor 172, thereby adjusting the pressure and flow rate in pipe 148 to match the flow and pressure requirements of membrane 10. This control method eliminates Figure 12 Valve 151 and associated wasted hydraulic energy. Furthermore, pump 140 no longer requires a VFD for speed control, such as... Figure 12 As shown, feed flow and pressure regulation are provided by TX 21 with an attached motor 172 and VFD 173. Eliminating this large VFD can reduce capital costs, maintenance costs, and energy consumption by eliminating energy losses that would otherwise occur in the VFD. Note that VFD 173 has a... Figure 12 The VFD 144 used in conjunction with the motor 145 is approximately 10% to 15% of its rating.

[0062] Figure 16 The control scheme used to regulate the motor is defined.

[0063] The above description is provided for the purpose of explaining the present invention. Various modifications and substitutions may be made without departing from the scope of the following claims.

Claims

1. A fluid handling system, comprising: A first membrane for treating fluids, the first membrane having an inlet for the fluid to be treated, an outlet for the treated fluid, and a discharge opening for the untreated fluid; A source of fluid under pressure to be processed, the source of fluid under pressure to be processed being operatively connected to the inlet of the first membrane; A second membrane for treating fluids, the second membrane having an inlet for the fluid to be treated, an outlet for the treated fluid, and a discharge opening for the untreated fluid; An energy recovery turbocharger has a pump section and a turbine section, the pump section having a feed inlet and a feed outlet, the turbine section having a brine inlet and a brine outlet, a discharge opening of a first membrane being operatively connected to the feed inlet of the pump section, the feed outlet of the pump section being operatively connected to the inlet of a second membrane, and a discharge opening of the second membrane being operatively connected to the brine inlet on the turbine section; An isobaric chamber having an inlet opening, a discharge opening, a feed inlet opening, and a feed outlet opening, the inlet opening being operatively connected to the brine outlet of the turbocharger, the feed inlet opening being operatively connected to a source of fluid under pressure, and the feed outlet opening being operatively connected to the inlet of the first membrane.

2. The system according to claim 1, wherein, A pump is connected to the feed outlet, and the pump is used to increase the pressure of the fluid from the feed outlet to the pressure required for the operation of the first membrane.

3. The system according to claim 2, wherein, A feed pump is operatively connected to a source of fluid at the pressure described above, and the feed pump provides at least a portion of the pressure required for the operation of the first membrane.

4. The system according to claim 3, wherein, The feed pump is a multistage pump having a first stage stack and a second stage stack. The first stage stack has an inlet port and an outlet port. The inlet port is operatively connected to a source of fluid at the pressure. The outlet port is operatively connected to a first inlet opening for the second stage stack. The second inlet opening for the second stage stack is operatively connected to the feed outlet opening of the isobaric chamber.

5. The system according to claim 4, wherein, A motor is used to drive the feed pump, and a frequency converter is connected to the motor to drive the feed pump to provide control over the pressure of the fluid supplied to the inlet of the first membrane.

6. The system according to claim 5, wherein, A motor is used to operate a pump connected to the feed outlet of the isobaric chamber, and a frequency converter is connected to the motor for operating the pump connected to the feed outlet of the isobaric chamber to provide control over the pressure of the fluid supplied to the second inlet opening of the multistage pump.

7. The system according to claim 6, wherein, A first flow meter is operatively connected to the outlet of the first membrane, a second flow meter is operatively connected to the outlet of the second membrane, a third flow meter is operatively connected to the discharge opening of the isobaric chamber, and a fourth flow meter is operatively connected to the feed outlet of the isobaric chamber.

8. The system according to claim 7, wherein, The controller is operatively connected to the first flow meter, the second flow meter, the third flow meter, and the fourth flow meter, and to a variable frequency drive for the feed pump and a variable frequency drive for the pump connected to the feed outlet of the isobaric chamber. The controller regulates the flow rate and pressure in the system to achieve the desired pressure of the fluid feed supplied to the inlets of the first membrane and the second membrane.

9. The system according to claim 1, wherein, A pressure reducing valve is operatively connected to the feed outlet of the isobaric chamber, and the pressure reducing valve regulates the flow rate of fluid from the feed outlet of the isobaric chamber.

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