Combined device for circularly preparing acid and alkali from acid-alkali wastewater based on pulse energy recovery and super-efficient concentration

Abstract

The invention discloses a combined device for circularly preparing acid and alkali from acid-alkali wastewater based on pulse energy recovery and super-efficient concentration. The combined device comprises a nanofiltration salt separation unit, a front concentration unit, a bipolar membrane / electrodialysis unit, a rear concentration unit, a high-pressure reverse osmosis membrane unit and an electric control system. Any one of the nanofiltration salt separation unit, the concentration unit and the high-pressure reverse osmosis membrane unit comprises a water feeding pump, a security filter, a high-pressure pump, a reverse osmosis membrane or nanofiltration membrane assembly, a circulating pump, an energy storage tank assembly, a pulse generation unit, a flow sensor and a pressure sensor. The device is applied to the field of wastewater treatment, pretreated acid-alkali wastewater serves as a working medium, salt separation and concentration of materials are achieved through membrane filtration, acid and alkali are generated through a bipolar membrane / electrodialysis unit, and pressure energy recovery of the high-pressure side of the membrane unit is achieved through combination of an energy storage device and pulses; the membrane unit adopts periodic pulsating traveling wave filtration, membrane surface sediments are reduced, the operation efficiency of the device is improved, the operation cost is reduced, and waste is turned into wealth.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment applications, in particular to a combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and ultra-efficient concentration. Background Art

[0002] Wastewater treatment has become a bottleneck restricting the development of the industry. Membrane water treatment technology with reverse osmosis membrane or nanofiltration membrane as the core has excellent treatment effect, good system operation stability, lower investment and operating costs, and is an important water treatment and reuse technology, but there are problems of high system operation pressure and high energy consumption. In 2018, the total water consumption of thermal power plants was close to 6 billion tons, and the wastewater discharge was about 270 million tons. It is urgent for power plants to treat and recycle various types of wastewater, and their acid and alkaline wastewater discharge treatment technology has also received more and more attention. Membrane water treatment technology with reverse osmosis membrane or nanofiltration membrane as the core is an important technical means of wastewater zero discharge system.

[0003] The bipolar membrane is a new type of composite membrane, which is composed of a cation exchange layer and an anion exchange layer. Under the drive of a DC electric field, water can be dissociated to produce corresponding H + and OH - , used in conjunction with anion and cation exchange membranes, the brine obtained after purifying acid and alkali wastewater is regenerated into acid and alkali under the action of an electric field. The existing process route for preparing acid and alkali using bipolar membrane electrodialysis technology from wastewater is: pretreatment, nanofiltration salt separation, reverse osmosis concentration, secondary pretreatment, electrodialysis concentration, and bipolar membrane electrodialysis regeneration of acid and alkali. The reverse osmosis concentration of this process does not have an energy recovery function, and the electrodialysis concentration technology consumes a lot of electricity. The existing membrane system uses a graded treatment method to improve the water quality of the membrane permeate effluent and reduce the salt content of the produced water; the segmented treatment method is used to improve the recovery rate of the membrane system and increase the concentration of the working medium on the concentrated water side. The multi-stage and multi-segment membrane treatment form is a classic process form of reverse osmosis or nanofiltration membrane method. The system flow and system configuration criteria of the existing concentration technology suitable for reverse osmosis or nanofiltration membrane filtration system are consistent with the above, but in practice, the specific combination of several stages and segments needs to be determined according to the specific conditions of the working medium and the concentration requirements. In addition, the existing membrane concentration devices rarely have energy recovery functions, and the specific operation processes of membrane concentration filtration systems are also different. Therefore, the existing acid-base preparation system with membrane system as the main body has the problems of low working medium concentration, high operating pressure and no energy recovery technology, so the energy consumption is high and the system efficiency is low. It requires super-efficient concentration, energy recovery and high-efficiency membrane filtration process technology to improve the system operation efficiency.

[0004] Existing energy recovery devices are mainly used in large-scale seawater desalination due to their high cost. They include centrifugal turbine energy recovery devices, isobaric or positive displacement energy recovery devices, energy cycle or triple cluster energy recovery devices. Centrifugal turbine energy recovery device system configuration is as follows:Figure 6 As shown in the figure, a hydraulic turbine is used to convert pressure energy into mechanical energy, and then the mechanical energy is converted into seawater pressure energy to achieve energy recovery. There is a certain loss of pressure energy in the two-step conversion process, so its total energy recovery efficiency is below 90%. The low-pressure seawater enters the membrane assembly after being pressurized by the high-pressure pump. The high-pressure brine discharged by the membrane assembly is converted into rotational mechanical energy in the turbine. The centrifugal turbine is coaxial with the high-pressure pump motor and drives the high-pressure pump to operate together. The energy recovery device achieves energy saving and consumption reduction by inputting shaft work to the high-pressure pump motor. Compared with the single high-pressure pump pressurization method, the flow rate and lifting pressure of the fluid output remain unchanged. Another solution for the centrifugal turbine energy recovery device is to directly connect the hydraulic turbine to the high-pressure pump coaxially, and the centrifugal turbine directly drives the high-pressure pump to operate. Its essence is a hydraulically driven pump or turbocharger. The high-pressure brine of the centrifugal turbine energy recovery device undergoes a two-step conversion process of "pressure energy-mechanical energy-pressure energy". Its energy conversion efficiency is generally around 50-70% and it needs to be coaxially connected to the high-pressure pump to achieve energy recovery. Therefore, the device has the disadvantages of low energy conversion efficiency, large equipment size, and high requirements for device installation and positioning. The isobaric energy recovery device is also called a positive displacement energy recovery device. Its system configuration is as follows: Figure 7 As shown, it is the most widely used in existing energy recovery devices. Isobaric energy recovery devices can be divided into two categories in principle: valve-controlled type and rotor type. The low-pressure working medium is divided into two paths by the low-pressure pump and transported to the high-pressure pump and the isobaric energy recovery component respectively. One path of the low-pressure working medium is directly added to the high pressure by the high-pressure pump and then transported to the reverse osmosis membrane component. The other path of the low-pressure working medium first enters the isobaric energy recovery component (such as the rotor-type isobaric energy recovery component or the valve-controlled energy recovery component) to exchange pressure with the high-pressure working medium discharged from the membrane component, and then enters the membrane component after being boosted to high pressure by the booster pump, which greatly reduces the system's water production energy consumption. The valve-controlled energy recovery component includes three parts: an active switching valve, a pressure exchange chamber, and a check valve group. The active switching valve and the check valve group cooperate with each other to realize the orderly switching of the boosting and pressure relief processes, and the pressure energy exchange is carried out in the pressure exchange chamber. The most important feature of the rotor-type energy recovery component is that the high-speed rotation of the rotor realizes the rapid switching of the boosting and pressure relief processes, and the pressure exchange is realized in multiple axial channels set on the rotor. The flow rate of the high-pressure pump of the isobaric energy recovery device is basically consistent with the processing capacity of the membrane assembly, and the energy conversion efficiency is slightly higher than that of the centrifugal turbine energy recovery device. However, fine particles can easily cause the rotary valve core to get stuck or the sealing surface to be scratched. There are also problems such as low energy conversion efficiency, internal leakage of the device, and salinity mixing between the working medium stock solution and the concentrated fluid on the high-pressure side of the membrane assembly. This type of energy recovery device does not have products for small flow or smaller-scale systems. Energy recovery in large-scale systems requires multiple such energy recovery devices to be connected in parallel. The system configuration of an energy cycle or triple cluster energy recovery device is as follows: Figure 8As shown, it is basically similar to the isobaric energy recovery device. The flow rate of its high-pressure pump is basically consistent with the processing capacity of the membrane component. The high-pressure working medium of this type of energy recovery device can circulate and cross-flow, and has strong adaptability to the processing capacity of the membrane system. The energy circulation system is the core component of this type of energy recovery device, and there are many valve configurations and complex pipelines. The fluid is prone to produce sediments and contaminate the membrane surface under high concentration conditions, and it is easy to produce concentration polarization phenomenon, resulting in uneven flux when the membrane element is working. Therefore, the energy recovery efficiency of the device is reduced, and the separation performance of the membrane filtration system is reduced. Summary of the invention

[0005] In view of the problems of low concentration efficiency and high energy consumption in the existing bipolar membrane electrodialysis technology for preparing acid and alkali, the present invention discloses a combined device for circulating acid and alkali from acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration. Compared with the existing acid and alkali wastewater treatment devices, the hardware configuration and system operation mode are different. The present invention combines nanofiltration and reverse osmosis membrane technology, bipolar membrane and electrodialysis technology. The membrane unit adopts a pulse generating unit combined with an energy storage tank assembly, and regenerates acid and alkali wastewater into recyclable acid and alkali solutions according to periodic pulsating traveling wave filtration, thereby realizing energy recovery and super-efficient concentration of the working medium, converting wastewater into regenerated acid and alkali, reducing system operation energy consumption and improving system operation efficiency.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is: a combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and ultra-efficient concentration, which is composed of a nanofiltration salt separation unit, a pre-concentrator unit, a post-concentrator unit, a bipolar membrane / electrodialysis unit, a second-stage high-pressure reverse osmosis membrane unit, a water tank, an acid tank, an alkali tank and an electronic control system; the working medium of the system is acid and alkali wastewater after coagulation sedimentation and ultrafiltration pretreatment.

[0007] In this device, the acid-base wastewater input pipeline is connected to the inlet of the nanofiltration salt separation unit, and the concentrated water side of the nanofiltration salt separation unit is connected to the concentrated waste liquid output interface; its water production side is connected in series with the concentrated water side of the pre-concentrating unit by means of water tanks, pipelines and valves, and after the permeate of the nanofiltration salt separation unit is concentrated, the concentrated brine is connected to the concentrated brine tank; the water production outlet of the pre-concentrating unit and the concentrated water inlet of the second-stage high-pressure reverse osmosis membrane unit are connected in series by means of pipelines, valves and water pumps; the concentrated water outlet of the second-stage high-pressure reverse osmosis membrane unit and the water production outlet of the post-concentrating unit are connected to the working medium inlet pipeline of the pre-concentrating unit by means of pipeline valves; the membrane permeate of the second-stage high-pressure reverse osmosis membrane unit is connected to the fresh water reuse outlet; the concentrated brine in the brine tank and the medium in the polar water tank are pumped to the bipolar membrane / electrodialysis unit; the acid and alkali solution pipelines of the bipolar membrane electrodialysis unit are connected to the acid tank and the alkali tank.

[0008] The nanofiltration salt separation unit, the pre-concentrator unit, the post-concentrator unit, and the second-stage high-pressure reverse osmosis membrane unit included in the device, any single membrane filtration unit includes a water supply pump, a safety filter, a high-pressure pump, an energy storage tank assembly, a circulation pump, a reverse osmosis membrane or a nanofiltration membrane assembly, a pressure safety valve, an exhaust valve, a pulse generating unit, a flow sensor, and a pressure sensor; the water supply pump and the safety filter are connected in series with a pipeline; the outlet of the safety filter is connected to the high-pressure pump with a branch pipe; the outlet pipeline of the high-pressure concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly is connected to the inlet pipeline of the circulation pump; the outlet pipeline of the high-pressure pump is connected to the outlet pipeline of the circulation pump with a three-way joint; the device also includes an energy storage tank assembly, a pressure safety valve, and a pulse generating unit component; The outlet of the safety filter is connected to the inlet of the energy storage tank assembly and the pulse generating unit by a branch pipe; the outlet pipeline of the circulation pump is connected to the inlet pipeline of the energy storage tank assembly, and the outlet pipeline of the energy storage tank assembly is connected to the inlet of the high-pressure concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly; a circulation pipeline is formed between the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly, the circulation pump and the energy storage tank assembly to realize the filtering and concentration functions of the membrane system; the outlet pipeline of the pulse generating unit is connected to the outlet main pipe of the energy storage tank assembly by a three-way joint; the high-pressure concentrated water inlet side pipeline of the reverse osmosis membrane or nanofiltration membrane assembly is connected to the pressure safety valve; valves are provided at the inlet and outlet of the water supply pump, safety filter, high-pressure pump, energy storage tank assembly, circulation pump, reverse osmosis membrane or nanofiltration membrane assembly and pulse generating unit.

[0009] The circulating pump in the single membrane filtration unit pressurizes the high-pressure working medium at the outlet of the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly and mixes it with the high-pressure working medium from the high-pressure pump. The mixed working medium flows through the energy storage tank assembly and then flows through the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly. Part of the working medium permeates through the membrane surface to become permeate, and the remaining high-pressure and high-concentration working medium flows out of the membrane assembly and enters the inlet of the circulating pump. The working medium forms a high-pressure, large-flow, circulating cross-flow operation mode.

[0010] Before the monomer membrane filter unit is put into operation, it is first filled with liquid by the water supply pump. After the device is completely filled with the working medium, the high-pressure pump and the circulation pump are started, and the device is put into operation. The initial pressure of the operation is set by the control system, and the specific set value is reached by changing the operating frequency of the water supply pump motor. As the working medium operates in high pressure, large flow, and circulating cross-flow mode, the concentration of the working medium becomes higher and higher, and the osmotic pressure gradually rises. The electronic control system increases the operating frequency of the high-pressure pump unit, the output power of the high-pressure pump increases, the operating pressure of the working medium rises, and the output of the membrane filtration system remains unchanged. When the operating pressure of the working medium rises to the maximum set value, the device completes a working cycle. The maximum set value is determined according to the specific conditions of the working medium, generally 5.0~8.0MPa. The energy storage tank assembly is divided into two parts: the energy storage working group and the energy storage standby group, which alternately participate in the cyclic operation of the energy recovery device. When the operating pressure of the device reaches the maximum set value, the energy storage working group participating in the circulating operation in the energy storage tank assembly exits operation and switches to the energy storage standby group; the energy storage standby group in the energy storage tank assembly participates in the circulating operation and switches to the energy storage working group. After the energy storage tank that has been out of operation is drained and replenished, it becomes an energy storage standby group waiting for the next cycle to be put into operation. The cycle period is determined by the effective residence time of the working medium in the energy storage tank assembly or the effective energy storage volume and the maximum working pressure factor of the device design. The unit operates in a high-pressure, large-flow, and cyclic cross-flow cycle mode.

[0011] In each working cycle of the single membrane filtration unit, the pulse generating unit receives the replenishment fluid from the security filter, and quickly injects the replenishment fluid into the connecting pipe at the inlet of the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly under hydraulic or electric drive. The inlet pipe is also the outlet main pipe of the energy storage tank assembly; the output of the pulse generating unit changes the operating pressure of the reverse osmosis membrane or nanofiltration membrane assembly, and the concentrated water pressure pulsates with high pressure; the system realizes periodic pulsating traveling wave filtration. The number, time and pulse pressure of high-pressure pulses are preset by the system, and the electronic control system also compares the detection value of the pressure sensor with the set value, and excites the pulse after the preset conditions are met.

[0012] In this device, the pretreated acid and alkali wastewater is input to the nanofiltration salt separation unit. The nanofiltration membrane intercepts the macromolecular organic impurities and high-valent ions in the acid and alkali wastewater on the concentrated water side, and the nanofiltration salt separation unit discharges the concentrated waste liquid on the concentrated water side of the unit in each working cycle; the remaining acid and alkali wastewater flows through the concentrated water side of the pre-concentrator unit as the permeate of the nanofiltration salt separation unit, and after being concentrated by the nanofiltration membrane and reaching the preset concentration, the concentrated brine is connected to the brine tank; the water output outlet of the pre-concentrator unit is connected to the inlet of the concentrated water side of the second-stage high-pressure reverse osmosis membrane unit; the post-concentrator unit concentrates the brine discharged from the bipolar membrane / electrodialysis unit, and the concentrated liquid outlet is connected to the brine tank; the concentrated water of the second-stage high-pressure reverse osmosis membrane unit and the water output of the post-concentrator unit are refluxed to the working medium inlet of the pre-concentrator unit through pipelines. The permeate of the second-stage high-pressure reverse osmosis membrane unit is reused as fresh water. The brine in the brine tank and the medium in the polar water tank are pumped to the bipolar membrane / electrodialysis unit, and the acid and alkali solutions produced under the action of the bipolar membrane / electric field are pumped to the acid tank and the alkali tank.

[0013] In this device, the above-mentioned single membrane filter unit realizes the concentration and energy recovery of the working medium according to the periodic pulsating traveling wave filtration. The high-pressure pulse of the working medium increases the turbulence degree of the medium on the concentrated water side of the membrane, prevents impurities in the highly concentrated brine from being deposited on the membrane surface, reduces the concentration polarization phenomenon, and improves the flux balance of the membrane filtration, thereby improving the operating efficiency of the membrane system and the energy recovery efficiency of the pressure energy on the high-pressure side of the device.

[0014] The system configuration of the present invention is simple and compact, and can achieve concentration and energy recovery for systems of different scales for treating acid and alkali wastewater. The energy recovery efficiency is high and the adaptability is strong. The maximum concentration of the working medium after concentration is close to its saturation concentration at the temperature. The device can reduce the high energy consumption problem in the process of preparing acid and alkali by bipolar membrane method and improve the operation efficiency of the system. The present invention turns waste into treasure, recycles acid and alkali wastewater to prepare acid and alkali, promotes industrial upgrading, and realizes energy-saving, low-carbon and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a system flow chart of a combined device for preparing acid and alkali from acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration in the present invention; Figure 2 This is a system configuration diagram of a single membrane filtration unit of a combined device for preparing acid and alkali from acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration in the present invention; Figure 3 It is a schematic diagram of the operating pressure of a single membrane filtration unit of the combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration of the present invention; Figure 4 This is a structural diagram of the energy storage tank of the combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration of the present invention; Figure 5 This is a structural diagram of a pulse generating unit of a combined device for preparing acid and alkali from acid and alkali wastewater based on pulsation energy recovery and super-efficient concentration in the present invention; Figure 6 It is a system configuration diagram of a centrifugal turbine energy recovery device in the prior art; Figure 7 It is a system configuration diagram of an isobaric or positive displacement energy recovery device of the prior art; Figure 8 It is a system configuration diagram of an energy cycle or triple cluster energy recovery device of the prior art; Fig. 9 The present invention is a flow chart of a bipolar membrane / electrodialysis unit of a combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration.

[0016] Figure numerals: 1: water feed pump; 2: safety filter; 3: high-pressure pump; 4: energy storage tank assembly; 5: circulation pump; 6: reverse osmosis membrane or nanofiltration membrane assembly; 7: pressure safety valve; 8: pulse generating unit; 9: end cover; 10: fixed orifice plate; 11: shell; 12: thin-walled energy storage tube; 13: floating orifice plate; 14: actuator; 15: piston rod; 16: cylinder body; 17: piston; 18: centrifugal turbine; 19: booster pump; 20: isobaric energy recovery assembly; 21: energy circulation system; 22: exhaust valve; 23: pressure sensor; 24: flow sensor; 25: pressure sensor; 26: flow sensor; 27: pressure sensor; 28: flow sensor; 29: flow sensor; 30: positive electrode; 31: negative membrane; 32: positive membrane; 33: bipolar membrane; 34: negative electrode. DETAILED DESCRIPTION

[0017] The function of the combined device for preparing acid and alkali from acid and alkali wastewater based on pulsating energy recovery and ultra-efficient concentration is to treat acid and alkali wastewater after coagulation sedimentation, filtration, and ultrafiltration pretreatment, and to further separate and purify the acid and alkali wastewater by using a comprehensive technology combining nanofiltration membranes and reverse osmosis membranes, bipolar membranes, and electrodialysis, and to regenerate the acid and alkali wastewater into recyclable acid and alkali solutions after concentration, thus turning waste into treasure. Any single membrane filtration unit in the device adopts a periodic pulsating traveling wave operation mode to minimize energy consumption during system operation, and combines high-pressure pulsation technology to improve system operation efficiency, recover the pressure energy of the high-pressure working medium on the concentrated water side of the reverse osmosis or nanofiltration membrane filtration system, increase the working medium concentration, and reduce operating energy consumption and operating costs. The system flow of the present invention is as follows: Figure 1 As shown, it consists of a nanofiltration salt separation unit, a pre-concentrator unit, a post-concentrator unit, a bipolar membrane / electrodialysis unit, a second-stage high-pressure reverse osmosis membrane unit, a water tank, an acid tank, an alkali tank and an electronic control system; the system working medium is acid and alkali wastewater that has been pre-treated by coagulation sedimentation, filtration and ultrafiltration.

[0018] This device first performs salt separation and purification on the acid-base wastewater after pretreatment. The input pipeline of the acid-base wastewater is connected to the inlet of the nanofiltration salt separation unit. After the water supply pump 1 infuses and the high-pressure pump 3 pressurizes, the high-pressure acid-base wastewater flows into the concentrated water side of the nanofiltration membrane. The nanofiltration membrane intercepts the macromolecular organic impurities and high-valent ions in the acid-base wastewater on the concentrated water side. Part of the acid-base wastewater passes through the surface of the nanofiltration membrane and flows to the water tank to be concentrated. The remaining part of the working medium flows out of the concentrated water side of the nanofiltration membrane and enters the circulating pump 5 of the nanofiltration salt separation unit. Under the action of the circulating pump 5, the working medium and the acid-base wastewater from the high-pressure pump 3 are mixed in the pipeline. The mixed working medium is periodically circulated and salted and purified on the concentrated water side of the nanofiltration membrane. In each working cycle, the nanofiltration salt separation unit regularly discharges the concentrated waste liquid on the concentrated water side.

[0019] In the pre-concentration stage of the device, the water feed pump 1 conveys the permeate of the nanofiltration salt separation unit to the pre-concentration unit high-pressure pump 3 for pressurization. The high-pressure pump 3 pressurizes the working medium and pumps it to the nanofiltration / reverse osmosis membrane concentrated concentrated water side of the pre-concentration unit for concentration. Part of the working medium permeates the membrane surface, and the remaining part of the working medium flows out of the nanofiltration / reverse osmosis membrane concentrated concentrated water side and enters the circulation pump 5 of the pre-concentration unit. Under the action of the circulation pump 5, the working medium and the acid and alkaline wastewater from the high-pressure pump 3 of the concentrator unit are mixed in the pipeline. The mixed working medium is cyclically concentrated in the pre-concentration unit. In each working cycle, the concentrated brine is regularly discharged to the concentrated brine tank; the water outlet of the pre-concentration unit and the inlet of the concentrated water side of the second-stage high-pressure reverse osmosis membrane unit are connected in series by pipelines and valves; the membrane permeate of the second-stage high-pressure reverse osmosis membrane unit is connected to the fresh water reuse outlet.

[0020] In the acid and alkali production stage of this device, the brine in the brine tank and the medium in the polar water tank are pumped to the bipolar membrane / electrodialysis unit; the acid and alkali solutions produced under the action of the bipolar membrane / electric field are connected to the acid tank and alkali tank. The brine outlet of the bipolar membrane / electrodialysis unit is connected to the inlet pipeline of the post-concentration unit, and the post-concentration unit concentrates the brine discharged from the bipolar membrane / electrodialysis unit, and the concentrated liquid is collected in the brine tank; the water outlet of the post-concentration unit and the concentrated water outlet of the second-stage high-pressure reverse osmosis membrane unit are connected to the inlet of the pre-concentration unit through pipeline valves, and these two working media are mixed with the permeate of the salt separation unit and enter the pre-concentration process.

[0021] The present invention is based on energy recovery technology to achieve low energy consumption and ultra-efficient concentration of the working medium. Existing energy recovery devices mainly include centrifugal turbine energy recovery devices, isobaric energy recovery devices, and energy circulation energy recovery devices. The system configuration of the centrifugal turbine energy recovery device is as follows: Figure 6As shown, it is composed of a water supply pump 1, a security filter 2, a high-pressure pump 3, a centrifugal turbine 18, a reverse osmosis membrane or a nanofiltration membrane assembly 6, an instrument, a valve, and an electronic control system. The low-pressure seawater is pressurized by the high-pressure pump 3 and enters the reverse osmosis membrane or the nanofiltration membrane assembly 6. The high-pressure brine discharged from the reverse osmosis membrane or the nanofiltration membrane assembly 6 is converted into rotational mechanical energy in the centrifugal turbine 18. The centrifugal turbine 18 is coaxial with the motor of the high-pressure pump 3 and drives the high-pressure pump 3 to operate together. Another scheme of the centrifugal turbine energy recovery device is to directly connect the centrifugal turbine 18 to the high-pressure pump 3 coaxially, and the centrifugal turbine 18 directly drives the high-pressure pump 3 to operate. Its essence is a hydraulically driven pump or a turbocharger. The high-pressure brine of the centrifugal turbine energy recovery device undergoes a two-step conversion process of "pressure energy-mechanical energy-pressure energy". Its energy conversion efficiency is generally about 50-70% and needs to be coaxially connected with the high-pressure pump 3 to realize energy recovery and utilization. Therefore, the device has the disadvantages of low energy conversion efficiency, large equipment volume, and high requirements for device installation and positioning. Isobaric energy recovery device is also called positive displacement energy recovery device. Its system configuration is as follows: Figure 7 As shown, it is composed of a water supply pump 1, a security filter 2, a high-pressure pump 3, a booster pump 19, an isobaric energy recovery component 20, a reverse osmosis membrane or a nanofiltration membrane component 6, an instrument, a valve, and an electronic control system. This device is the most widely used in existing energy recovery devices. Isobaric energy recovery devices can be divided into two categories in principle: valve-controlled type and rotor type. The low-pressure working medium is divided into two paths by the water supply pump 1 and is respectively delivered to the high-pressure pump 3 and the isobaric energy recovery component 20. One path of the low-pressure working medium is directly added to the high pressure by the high-pressure pump 3 and then delivered to the reverse osmosis membrane or the nanofiltration membrane component 6. The other path of the low-pressure working medium first enters the isobaric energy recovery component 20 (such as a rotor-type isobaric energy recovery component or a valve-controlled energy recovery component) and exchanges pressure with the high-pressure working medium discharged from the reverse osmosis membrane or the nanofiltration membrane component 6, and then enters the reverse osmosis membrane or the nanofiltration membrane component 6 after being raised to high pressure by the booster pump 19. The system's water production energy consumption is greatly reduced. The device has internal leakage and mixing problems between the working medium raw liquid and the concentrated fluid on the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly 6. The system configuration of the energy cycle or triple cluster energy recovery device is as follows Figure 8 As shown, it is composed of a water supply pump 1, a security filter 2, a high-pressure pump 3, an energy circulation system 21, a reverse osmosis membrane or a nanofiltration membrane assembly 6, instruments, valves, and an electronic control system. The high-pressure working medium of this type of energy recovery device can circulate and cross-flow, which is consistent with the working mode of the existing closed-loop reverse osmosis membrane filtration system and has strong adaptability to the processing capacity of the membrane system. However, its core component, the energy circulation system, has the problems of a large number of valve configurations and complex pipelines; the fluid is prone to sediment contamination of the membrane surface under high-concentration circulating flow conditions, and is prone to concentration polarization, resulting in uneven flux when the membrane element is working, thereby affecting the energy recovery efficiency of the device and reducing the separation performance of the membrane filtration system.

[0022] The existing technology of membrane system usually adopts graded treatment to improve the water quality of membrane permeate effluent, and graded treatment can reduce the salt content of produced water; segmented treatment is adopted to improve the recovery rate of membrane system and increase the concentration of working medium on the concentrated water side. Multi-stage and multi-segment membrane treatment process is the classic process form of reverse osmosis or nanofiltration membrane method. The principles of existing membrane concentration technology are consistent with the above-mentioned classic membrane process form, but in practice, the specific combination of several stages and segments needs to be determined according to the specific conditions of the working medium and the concentration requirements. Existing membrane concentration devices rarely use energy recovery methods, and the specific operation process of membrane concentration filtration systems is also different. The present invention is as follows Figure 3 As shown, a periodic pulsating traveling wave operation mode is adopted, combined with an energy storage tank assembly 4, to achieve concentration of the working medium, recover the pressure energy of the high-pressure working medium on the concentrated water side of the reverse osmosis or nanofiltration membrane concentration system, and improve the concentration effect.

[0023] Among the nanofiltration salt separation unit, pre-concentration unit, post-concentration unit and second-stage high-pressure reverse osmosis membrane unit included in this device, the system configuration of any of the above membrane filtration units is as follows: Figure 2 As shown, it is composed of a water supply pump 1, a security filter 2, a high-pressure pump 3, an energy storage tank assembly 4, a circulation pump 5, a reverse osmosis membrane or a nanofiltration membrane assembly 6, a flow sensor 24, a flow sensor 26, a flow sensor 28, a flow sensor 29, a pressure sensor 23, a pressure sensor 25, and a pressure sensor 27. The system working medium is seawater, reverse osmosis concentrated water, other high-concentration salt water or solution. Figure 2 As shown in FIG. 1 , PI represents a pressure gauge; PIT represents a pressure sensor; and FIT represents a flow sensor. The energy storage tank assembly 4 is composed of a plurality of energy storage tanks connected in parallel. The energy storage tank monomer structure is as follows: Figure 4 As shown, it is composed of an end cover 9, a fixed orifice plate 10, a shell 11, a thin-walled energy storage tube 12, and a floating orifice plate 13. One end of the thin-walled energy storage tube 12 is connected to the fixed orifice plate 10, and the other end is connected to the floating orifice plate 13 to form an assembly. The assembly is fixed to one end of the shell 11 by the fixed orifice plate 10 and the end cover 9, and is installed in the shell 11 by the floating orifice plate 13; the other end of the shell 11 is fixed by the end cover 9; the thin-walled energy storage tube 12 is a thin-walled seamless straight tube, and can also be a thin-walled corrugated steel tube, and the material is corrosion-resistant material. The structure of the pulse generating unit 8 is shown in FIG. Figure 5 As shown, it is composed of an actuator 14, a piston rod 15, a cylinder body 16, and a piston 17. The actuator 14 adopts a hydraulic cylinder or an electric push rod. In the pulse generating unit 8, one end of the piston rod 15 is connected to the actuator 14, and the other end is connected to the piston 17. The piston 17 is installed in the cylinder body 16; the actuator 14 drives the piston 17 to reciprocate in the cylinder body 16 through the piston rod 15 under the drive of the electronic control system.

[0024] In any membrane filtration unit monomer of the present invention, the original working medium inlet is connected to the inlet of the water supply pump 1 through a pipeline valve, and the outlet of the water supply pump 1 is connected to the inlet of the security filter 2 through a pipeline valve; the water supply pump 1 and the security filter 2 are connected in series by pipelines; the outlet of the security filter 2 is divided into three branches, which are respectively connected to the inlets of the high-pressure pump 3, the energy storage tank assembly 4, and the pulse generating unit 8 by pipelines; the outlet pipeline of the high-pressure concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly 6 is connected to the inlet pipeline of the circulation pump 5, the outlet pipeline of the circulation pump 5 is connected to the inlet main pipe pipeline of the energy storage tank assembly 4, and the outlet main pipe pipeline of the energy storage tank assembly 4 is connected to the inlet of the high-pressure concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly 6; a circulation pipeline is formed between the reverse osmosis membrane or nanofiltration membrane assembly 6, the circulation pump 5 and the energy storage tank assembly 4; the outlet pipeline of the high-pressure pump 3 is connected to the circulation pump 5 by a three-way joint. outlet pipeline; the outlet pipeline of the pulse generating unit 8 is connected to the outlet main pipe of the energy storage tank assembly 4 by a three-way joint; the high-pressure concentrated water inlet side pipeline of the reverse osmosis membrane or nanofiltration membrane assembly 6 is connected to the pressure safety valve 7; the outlet pipeline of the high-pressure pump 3 is installed with a flow sensor 26 and a pressure sensor 25; the high-pressure concentrated water inlet side main pipe pipeline of the reverse osmosis membrane or nanofiltration membrane assembly 6 is respectively installed with a flow sensor 24 and a pressure sensor 23; the high-pressure concentrated water outlet side main pipe pipeline of the reverse osmosis membrane or nanofiltration membrane assembly 6 is respectively installed with a flow sensor 28 and a pressure sensor 27; the water outlet main pipe of the reverse osmosis membrane or nanofiltration membrane assembly 6 is installed with a flow sensor 29; the water supply pump 1, the security filter 2, the high-pressure pump 3, the energy storage tank assembly 4, the circulation pump 5, the reverse osmosis membrane or nanofiltration membrane assembly 6 and the pulse generating unit 8, the inlet and outlet of the above-mentioned components are all provided with valves. The exhaust valve 22 and the pipeline are connected at the highest position of the working medium high-pressure circulation main pipe. The energy storage tank assembly 4, the reverse osmosis membrane or nanofiltration membrane assembly 6, and the pulse generating unit 8 are respectively connected with the emptying valve and pipeline. The reverse osmosis membrane or nanofiltration membrane assembly 6 is skid-assembled together to form a membrane frame assembly.

[0025] In any membrane filtration unit monomer of the present invention, the circulation pump 5 pressurizes the high-pressure working medium at the outlet of the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly 6 and mixes it with the high-pressure working medium stock solution from the high-pressure pump 3. The mixed working medium flows through the energy storage tank assembly 4 and then flows through the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly 6. Part of the pure water passes through the membrane surface to become the produced water effluent, and the remaining high-pressure and high-concentration working medium flows out of the reverse osmosis membrane or nanofiltration membrane assembly 6 and enters the inlet of the circulation pump 5. The working medium operates in a high-pressure, large-flow, and circulating cross-flow form, and the flow rate of the circulation pump 5 is about 1 to 5 times the flow rate of the high-pressure pump 3.

[0026] In any monomer of the membrane filtration unit of the present invention, the water supply pump 1, the high-pressure pump 3 and the circulation pump 5 are connected to the variable frequency motor, and the operating frequency thereof is adjusted by the corresponding frequency converter of the electric control system. Before being put into operation, the water supply pump 1 is first filled with liquid. After the device is completely filled with the working medium, the high-pressure pump 3 and the circulation pump 5 are started, and the device is put into operation. Only 1 to 4 membrane elements are installed in each reverse osmosis membrane or nanofiltration membrane shell. At the initial stage of the operation of the membrane filtration unit, the pressure of the working medium is set by the control system, and the specific set value is reached by changing the operating frequency of the water supply pump 1 motor. As the working medium operates in the high-pressure, large-flow, and circulating cross-flow mode, the concentration of the working medium becomes higher and higher, and the osmotic pressure gradually rises. The electric control system increases the operating frequency of the high-pressure pump 3 unit, the output power of the high-pressure pump 3 increases, and the operating pressure of the working medium rises. Under the control of the electric control system, the output of the membrane filtration system is kept unchanged. When the operating pressure of the working medium rises to the maximum set value, the device completes a working cycle. The maximum set value is determined according to the specific conditions of the working medium, generally 5.0 to 8.0 MPa. The energy storage tank assembly 4 is composed of multiple energy storage tanks connected in parallel. A thin-walled energy storage tube 12 is arranged inside the energy storage tank. The thin-walled energy storage tube 12 is installed between the orifice plates at both ends, one of which is a fixed orifice plate 10 and the other end is a floating orifice plate 13. The working medium flows in the thin-walled energy storage tube 12. When the pressure of the working medium is higher, the thin-walled energy storage tube 12 undergoes greater free elastic deformation and stores pressure energy; the pressure inside the thin-walled energy storage tube is consistent with the pressure of the working medium inside it, and the pressure of the outer shell of the tube is consistent with the atmospheric pressure. The inside of the energy storage tank assembly 4 can be divided into two parts: an energy storage working group and an energy storage standby group. The two parts alternately participate in the circulation operation of the working medium according to the operating pressure of the device. During the operation of the system, when the pressure value of the pressure sensor 23 detected by the electronic control system reaches the maximum working pressure set by the system, the opening and closing status of the inlet and outlet valves of the energy storage tank are changed, and the energy storage working group in the running energy storage tank assembly 4 is switched to the energy storage standby group to exit the system operation, and the energy storage standby group is switched to the energy storage working group to participate in the system operation. During the switching process, the two energy storage tanks are first connected, and part of the elastic deformation energy of the thin-walled energy storage tube in the energy storage working group is released and converted into the working medium pressure energy in the energy storage standby group. When the working medium pressures in the two are equal, the energy conversion is completed, and then the working state of the two energy storage tanks is switched through the valve action. The original energy storage working group that has exited operation becomes the energy storage standby group after drainage and rehydration, waiting to be put into operation in the next cycle. Its cycle is determined by the effective residence time or effective energy storage volume of the working medium in the energy storage tank assembly 4, and the maximum working pressure factor of the device design. The electronic control system detects the pressure values ​​of the pressure sensor 23, the pressure sensor 27 and the pressure difference between the two. When the pressure difference reaches the set value, the electronic control system drives the actuator 14 to act, and the pulse generating unit 8 outputs the pulse flow of the working medium, and the reverse osmosis or nanofiltration membrane filtration system realizes pulsating filtration.As described above, the membrane filtration unit unit operates periodically in a high pressure, large flow, and circulating cross-flow mode, and the flow of the circulating pump 5 is about 1 to 5 times the flow of the high pressure pump 3 .

[0027] In each circulating filtration cycle of any membrane filtration unit in the present invention, the branch pipeline at the outlet of the security filter 2 replenishes the pulse generating unit 8. The electronic control system detects the pressure values ​​of the pressure sensor 23 and the pressure sensor 27 and the pressure difference between the two. When the pressure difference reaches the set value, or according to the system preset time as a trigger condition and sends a control signal, the hydraulic or electric actuator 14 of the pulse generating unit 8 can drive the replenishing liquid in its cylinder 16 to quickly press into the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly 6, change the operating pressure of the reverse osmosis membrane or nanofiltration membrane assembly 6, and the concentrated water pressure will pulsate under high pressure. The system realizes periodic pulsating traveling wave filtration, as shown in the following example. Figure 3 As shown in the figure, the number of high-voltage pulses in each working cycle is 0 to 5 times, the duration of the high-voltage pulse is 10 to 30 seconds, and the pulse pressure is 0.5 to 0.95 times the maximum working pressure set by the system. Figure 3 The high-pressure pulsating traveling wave operation shown in the figure reduces the accumulation of deposits on the membrane surface, reduces the concentration polarization phenomenon on the membrane surface, improves the flux balancing performance of the membrane element, and improves the system operation efficiency.

[0028] The bipolar membrane / electrodialysis unit is composed of a positive electrode 30, a negative membrane 31, a positive membrane 32, a bipolar membrane 33, and a negative electrode 34. The system flow is as follows: Fig. 9 As shown. The bipolar membrane / electrodialysis unit has a water chamber, a brine chamber, an alkali chamber, an acid chamber, and a water chamber arranged in sequence. Among them, the brine chamber, the alkali chamber, and the acid chamber form a group, and the group is arranged in multiple groups between the two water chambers. The bipolar membrane 33 is a new type of ion exchange resin composite membrane, which is composed of a cation exchange membrane, an intermediate interface hydrophilic layer, and an anion exchange membrane. Under the action of the DC electric field, water dissociates at the interface of the bipolar membrane anion and cation membrane layers, and the generated H + , OH - They migrate in opposite directions through the positive membrane layer and the negative membrane layer respectively. On the migration path, H + Ions in the acid chamber react with the acid radical ions from the brine chamber to form acid solution, OH - In the alkali chamber, the sodium ions from the brine chamber form an alkaline solution, and the interfacial hydrophilic layer sandwiched between the bipolar membrane 33 continuously absorbs water to replenish the consumed water. The bipolar membrane continuously absorbs water, dissociating water into H + OH -Ions, which combine with corresponding anions and cations, eventually produce acid and alkali solutions. Acid and alkali solutions circulate between the acid and alkali boxes and the acid chamber and alkali chamber of the bipolar membrane / electrodialysis unit under the action of the pump. With the operation of the bipolar membrane / electrodialysis unit, the concentration of acid and alkali solutions continues to increase. During this period, the polar water circulates in the polar water chamber under the action of the pump, and the concentrated brine flows into the brine chamber of the bipolar membrane / electrodialysis unit under the action of the pump. The ions in the concentrated brine flow in the reverse direction to the acid and alkali chamber under the action of the electric field, and the concentration of the brine decreases; the brine chamber outlet of the bipolar membrane / electrodialysis unit is connected to the post-concentration unit, and the brine is concentrated and then merged into the concentrated brine tank to enter the brine circulation. When the concentration in the acid and alkali tank reaches the preset value, a working cycle of the bipolar membrane / electrodialysis unit ends, the prepared acid and alkali solution is discharged, and the acid and alkali tank is re-injected with the produced water from the secondary high-pressure reverse osmosis, and the bipolar membrane / electrodialysis unit enters the next working cycle. The temperature of the working medium rises during the circulation cycle and is cooled by a heat exchanger.

[0029] The water supply pump 1, the security filter 2, the high-pressure pump 3, the energy storage tank assembly 4, the circulation pump 5, the reverse osmosis membrane or nanofiltration membrane assembly 6 and the pulse generating unit 8 in the device can be constructed by a unit system, or by a mother pipe system, or by other combinations. The replenishment and drainage of the energy storage tank assembly 4 can be achieved by setting up a separate water pump, and the replenishment of the pulse generating unit 8 can also be achieved by setting up a separate water pump. Figure 1 , Figure 2 The system configuration is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration, characterized in that The device consists of a nanofiltration salt separation unit, a front concentrator unit, a bipolar membrane / electrodialysis unit, a rear concentrator unit, a second-stage high-pressure reverse osmosis membrane unit, a water tank, an acid tank, an alkali tank and an electronic control system; the acid-alkali wastewater input pipeline is connected to the inlet of the nanofiltration salt separation unit; the water production side of the nanofiltration salt separation unit is connected in series with the nanofiltration or reverse osmosis membrane concentrated water side of the front concentrator unit, the concentrated brine tank, and the concentrated brine pipe inlet of the bipolar membrane / electrodialysis unit by pipelines; the brine outlet pipeline of the bipolar membrane / electrodialysis unit is connected to the rear concentrator unit, and the concentrated brine outlet pipeline on the concentrated water side of the rear concentrator unit merges into the concentrated brine tank at the inlet of the bipolar membrane / electrodialysis unit; the water production pipeline of the front concentrator unit is connected to the second-stage high-pressure reverse osmosis membrane unit, and its concentrated water pipeline reflux merges into the water inlet pipeline of the front concentrator unit, and its water production pipeline is connected to the fresh water reuse outlet.

2. The combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration as claimed in claim 1, characterized in that Among the nanofiltration salt separation unit, pre-concentration unit, post-concentration unit, and second-stage high-pressure reverse osmosis membrane unit, any membrane filtration unit monomer comprises a water supply pump (1), a safety filter (2), a high-pressure pump (3), a circulation pump (5), a reverse osmosis membrane or nanofiltration membrane assembly (6), a flow sensor (24, 26, 28, 29), a pressure sensor (23, 25, 27), an energy storage tank assembly (4), and a pulse generating unit (8); the water supply pump (1), the safety filter (2) and the high-pressure pump (3) are connected in series by pipelines; the outlet of the high-pressure pump (3) is connected to the inlet main pipe of the concentrated water side of the membrane system; the inlet and outlet of the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly (6) are connected to the circulation pump (5) by pipelines to form a high pressure Circulation loop; the electronic control system is electrically connected to the water supply pump (1), the high-pressure pump (3), the circulation pump (5), the flow sensor (24, 26, 28, 29), and the pressure sensor (23, 25, 27); the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly (6) and the circulation pump (5) are connected by a high-pressure circulation pipeline; the unit realizes the mutual conversion of the pressure energy of the working medium and the mechanical energy of the energy storage tank assembly (4); the pulse generating unit (8) excites the pulsation of the flow and pressure of the working medium; the energy storage tank assembly (4), the pulse generating unit (8) and the electronic control system are electrically connected; the circulation pump (5), the concentrated water side of the reverse osmosis membrane or nanofiltration membrane assembly (6) and the energy storage tank assembly (4) are connected by a high-pressure circulation pipeline.

3. The combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration as claimed in claim 2, characterized in that In any of the membrane filtration units, the outlet of the safety filter (2) is connected to the inlet main pipe of the energy storage tank assembly (4) by a branch pipe; the outlet main pipe of the energy storage tank assembly (4) is connected to the high-pressure concentrated water side inlet of the membrane assembly (6); the energy storage tank assembly (4) is composed of a plurality of energy storage tanks and valves at both ends thereof connected in parallel by pipelines; the energy storage tank assembly (4) is divided into an energy storage working group and an energy storage standby group, and the electronic control system switches the energy storage tank assembly (4) into groups to participate in system operation by changing the opening and closing states of the inlet and outlet valves of the energy storage tanks.

4. The combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration as claimed in claim 3, characterized in that In any of the membrane filtration units, the energy storage tank in the energy storage tank assembly (4) is composed of an end cover (9), a fixed orifice plate (10), a shell (11), a thin-walled energy storage tube (12), and a floating orifice plate (13); one end of the thin-walled energy storage tube (12) is connected to the fixed orifice plate (10), and the other end is connected to the floating orifice plate (13) to form an assembly; the assembly is fixed to one end of the shell (11) by means of the fixed orifice plate (10) and the end cover (9), and is installed in the shell (11) by means of the floating orifice plate (13); the other end of the shell (11) is fixed by means of the end cover (9); the thin-walled energy storage tube (12) is a thin-walled seamless straight tube or a thin-walled corrugated steel tube, and is made of corrosion-resistant material.

5. The combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration as claimed in claim 4, characterized in that In any of the membrane filtration units, the outlet of the safety filter (2) is connected to the inlet of the pulse generating unit (8) by a branch pipe; the outlet of the pulse generating unit (8) is connected to the outlet main pipe of the energy storage tank assembly (4); the pulse generating unit (8) is composed of an actuator (14), a piston rod (15), a cylinder body (16), and a piston (17); one end of the piston rod (15) is connected to the actuator (14), and the other end is connected to the piston (17), and the piston (17) is installed in the cylinder body (16); the actuator (14) is driven by the electronic control system to push the piston (17) through the piston rod (15) to move back and forth in the cylinder body (16).

6. The combined device for preparing acid and alkali by circulating acid and alkali wastewater based on pulsating energy recovery and super-efficient concentration as claimed in claim 5, characterized in that In any of the membrane filtration units, the electronic control system detects the flow value of the flow sensor (29) and changes the operating frequency of the motor of the high-pressure pump (3) so that the flow value of the flow sensor (29) is consistent with the set value of the water production output; it is characterized in that during the operation of the membrane filtration unit, when the electronic control system detects that the pressure value of the pressure sensor (23) reaches the maximum working pressure set by the system, the opening and closing conditions of the inlet and outlet valves of the energy storage tank are changed, the energy storage working group in the running energy storage tank assembly (4) is switched to the energy storage standby group to exit the system operation, and the energy storage standby group is switched to the energy storage working group to participate in the system operation; the electronic control system detects the pressure values ​​of the pressure sensors (23, 27) and the pressure difference between the two. When the pressure difference reaches the set value, the electronic control system drives the actuator (14) to operate, and the pulse generating unit (8) outputs the pulse flow of the working medium, so that the reverse osmosis or nanofiltration membrane filtration system realizes pulsating filtration.

Images