Integrated device and integrated method for single-stage membrane distillation and vacuum compression

Abstract

The invention discloses a single-stage membrane distillation and vacuum compression integrated device and method, and relates to the field of gas field water treatment.The integrated device comprises a membrane distillation unit which is used for allowing part of gas field water to pass through a membrane and be converted into water vapor to be conveyed to the downstream of the membrane; the vacuum compression unit is connected with the membrane distillation unit and is used for compressing water vapor at the downstream of the membrane to normal pressure and increasing the temperature and enthalpy value of the water vapor; and the heat exchange unit is connected with the membrane distillation unit and the vacuum compression unit at the same time, and the heat exchange unit is arranged to carry out heat exchange on the water vapor heated by the vacuum compression unit and the gas field water before entering the membrane distillation unit. By arranging the vacuum compression unit, the downstream of the membrane can be conveyed to the heat exchange unit for heat exchange with gas field water entering the membrane distillation unit, so that the purposes of saving energy consumption, improving efficiency and reducing cost are achieved.

Description

Technical Field

[0001] This invention relates to the field of gas field water treatment, specifically to an integrated device and method for single-stage membrane distillation and vacuum compression. Background Technology

[0002] Gas field water is a byproduct of natural gas extraction. Its composition is complex, typically characterized by high levels of impurities such as salts, petroleum hydrocarbons, suspended solids, and organic chemicals. Direct reinjection or discharge of gas field water can harm the formation and its surrounding ecosystem. Furthermore, gas field water contains associated resources such as lithium, bromine, and potassium at levels higher than the comprehensive evaluation grade. Previously, only wastewater discharge was addressed, with less attention paid to lithium recovery from gas field water, leading to resource waste and environmental pollution. The increasingly stringent national requirements for environmental protection and energy utilization have made gas field water treatment increasingly challenging. Therefore, developing and researching new technologies and processes to achieve resource-based treatment of produced gas water has become a crucial task in the production processes of various oilfields.

[0003] Direct treatment of produced water often involves flocculation, sedimentation, filtration, and reinjection, or treatment followed by compliant discharge. However, produced water reinjection treatment faces challenges such as insufficient reinjection capacity, limited remaining reinjection depth, and increased difficulty in obtaining approval for new reinjection projects. Compliant discharge treatment of produced water faces difficulties and high costs. These issues often limit the effective treatment of produced water, affecting the stable and efficient development of gas fields, and also leading to the waste of associated resources. To achieve the recovery of associated resources, current technologies often employ reverse osmosis membrane separation and evaporation concentration techniques.

[0004] Reverse osmosis membrane technology is generally suitable for salt ion concentrations of 10g. -1 The following salt solution concentration process has high requirements for operating conditions. The feed liquid pressure needs to be above 1 MPa. Furthermore, as the reverse osmosis process proceeds, the concentration polarization at the membrane surface becomes increasingly pronounced, necessitating a continuous increase in the upstream liquid pressure to maintain membrane flux. When the salt concentration in the solution reaches 70 g, -1 At this time, the required operating pressure will exceed the pressure withstand capability of existing membrane modules. Reverse osmosis membrane separation technology has relatively high requirements for the feed solution, generally requiring pretreatment operations such as adsorption and microfiltration, and its salt concentration capacity is limited. Evaporation technology, as a commonly used salt solution concentration technology, is suitable for solutions with salt ion concentrations around 40g. -1 The above-mentioned evaporation and concentration process of salt solution generally produces freshwater at a rate of 20 kg / ml. -2 ·h -1The desalination rate can reach 98%, and the solution can be concentrated to saturation. For energy conservation, multi-effect evaporation and mechanical vapor compression evaporation are generally chosen. Mechanical vapor compression technology enables the cascade utilization of steam; except for the start-up phase which requires steam, electricity can be used in the later stages. However, evaporation technologies share common problems such as high evaporation temperature, small evaporator mass transfer area, large equipment size, and poor corrosion resistance.

[0005] Membrane distillation, as a novel membrane desalination technology, integrates the advantages of membrane separation and evaporation technologies, and can handle salt ion concentrations ranging from 1g. -1 Up to 200g of new -1 Both are applicable. During membrane distillation, water in the feed solution evaporates on the membrane surface under the action of a hydrophobic porous membrane, forming gas that passes through the membrane pores and is ultimately condensed and enriched downstream of the membrane. Inorganic salt ions in the feed solution are retained upstream of the membrane, thus achieving desalination. Membrane distillation can be carried out at normal pressure and temperature, achieving a desalination rate of 99.9%-100%, with a retention rate of over 99% for organic matter, and a purified water flux of 5-80 kg / m³. -2 ·h -1 The concentration factor can reach 8-10 times. Membrane distillation is relatively stable; changes in the salt ion concentration in the feed solution have little impact on membrane distillation dehydration, allowing for long-term stable operation. However, the vaporization of water during membrane distillation requires the absorption of a large amount of heat, necessitating preheating of the feed solution to provide heat for the membrane distillation unit. To achieve steam recovery under vacuum conditions, low-temperature refrigeration is often used, but this method requires high energy consumption, increasing the cost of clean water recovery.

[0006] In view of the above, this application is hereby submitted. Summary of the Invention

[0007] The purpose of this invention is to provide an integrated device and method for single-stage membrane distillation and vacuum compression. By setting up a vacuum compression unit, the downstream of the membrane can be transported to the heat exchange unit to exchange heat with the gas field water entering the membrane distillation unit, thereby solving the problems of high energy loss and high cost in the prior art.

[0008] The embodiments of the present invention are achieved through the following technical solution: First, the embodiments of the present invention provide an integrated device for single-stage membrane distillation and vacuum compression, comprising:

[0009] The membrane distillation unit is designed to allow a portion of gas field water to pass through the membrane and be converted into water vapor, which is then transported downstream of the membrane.

[0010] The vacuum compression unit, connected to the membrane distillation unit, functions to compress water vapor downstream of the membrane to atmospheric pressure, thereby increasing the temperature and enthalpy of the water vapor.

[0011] A heat exchange unit is connected to both a membrane distillation unit and a vacuum compression unit. The heat exchange unit is configured to exchange heat between the water vapor heated by the vacuum compression unit and the gas field water before entering the membrane distillation unit.

[0012] The gas field water absorbs heat before entering the membrane distillation unit. After being heated by the vacuum compression unit, the water vapor releases heat and is converted into liquid water for recycling.

[0013] Preferably, the vacuum compression unit includes a vacuum compressor, which is capable of providing a vacuum compression environment for water vapor downstream of the membrane;

[0014] The heat exchange unit includes a heat exchanger.

[0015] Preferably, the vacuum compressor is a single-stage vacuum compressor or a vacuum compressor unit.

[0016] Preferably, the inlet of the vacuum compressor is connected to the outlet pipeline of the membrane distillation unit, and its outlet is connected to the heat exchanger pipeline;

[0017] The inlet of the membrane distillation unit is connected to the heat exchanger piping;

[0018] The heat exchanger is also connected to a circulating pump via pipeline, and the circulating pump is connected to a feed tank via pipeline. The circulating pump is used to transport the gas field water in the feed tank to the heat exchanger for heat absorption before entering the membrane distillation unit.

[0019] The membrane distillation unit is also connected to a concentrate tank, which is used to collect the gas field water concentrate that has not been converted into water vapor in the membrane distillation unit.

[0020] The heat exchanger is also connected to a clear liquid tank, which is used to collect the liquid water converted from water vapor after heat release in the heat exchanger.

[0021] Preferably, the membrane distillation unit includes a membrane module, which includes one of the following structures: flat sheet, spiral wound, butterfly, hollow fiber, and plate and frame.

[0022] Preferably, the membrane assembly includes a filter membrane, which comprises one of PVDF, PTFE and PP microporous membrane structures.

[0023] Preferably, the pore size of a single micropore in the microporous structure is 0.1 to 1 μm.

[0024] Preferably, the heat exchanger is a partition wall type heat exchange structure.

[0025] To better address the aforementioned problems, embodiments of the present invention also provide an integrated method for single-stage membrane distillation and vacuum compression, implemented by the aforementioned integrated device, comprising the following steps:

[0026] S1: Collect the gas field water into the feed tank, turn on the circulation pump to transport the gas field water to the heat exchanger, and then turn on the membrane distillation unit and vacuum compressor. The water vapor after vacuum compression by the vacuum compressor will be transported to the heat exchanger to exchange heat with the gas field water in the heat exchanger.

[0027] S2: The circulating pump, heat exchanger, membrane distillation unit and vacuum compressor operate in continuous circulation. The gas field water concentrate that has not been converted into water vapor in the membrane distillation unit is collected by the concentrate tank, and the liquid water converted into liquid water after the water vapor in the heat exchanger is collected by the clear liquid tank.

[0028] S3: Turn off the circulating pump, membrane distillation unit, and vacuum compressor.

[0029] This integrated method, through a rationally designed process, achieves efficient treatment and clean water recovery of gas field water. By combining vacuum compression and heat exchange, it maximizes energy utilization efficiency and reduces system energy consumption.

[0030] Preferably, the operating temperature of the membrane distillation unit is 40–60°C;

[0031] The vacuum compressor is a screw or Roots type structure. The vacuum compressor can provide an environment of less than 10 kPa for water vapor downstream of the membrane, and the temperature of the water vapor after vacuum compression is 80-120°C.

[0032] Specifically, the operating temperature of the membrane distillation unit is set at 40–60°C. This temperature range is suitable for the evaporation of gas field water and effective membrane separation, which helps to improve the steam generation efficiency. The screw-type vacuum compressor has high efficiency and good flow characteristics, making it suitable for high-flow and high-pressure applications. The Roots-type vacuum compressor has a simple structure and is easy to maintain, making it suitable for applications requiring stable flow. The vacuum compressor can provide a low-pressure or vacuum environment below 10 kPa for the steam downstream of the membrane, which helps to effectively compress the steam and improve the efficiency of subsequent heat exchange. The steam temperature after vacuum compression is 80–120°C, ensuring that the steam can effectively exchange heat with the gas field water in the heat exchanger, thereby increasing the temperature of the gas field water and promoting the membrane distillation process.

[0033] Preferably, after the gas field water and water vapor exchange heat in the heat exchanger, the inlet temperature of the gas field water entering the membrane distillation unit is equal to the temperature required by the membrane distillation unit during membrane distillation operations. This arrangement ensures optimal operating conditions for the gas field water during the membrane distillation process, promotes the effective generation and separation of water vapor, and thus achieves efficient treatment of gas field water and recovery of clean water.

[0034] Preferably, the gas field water passes through the membrane distillation unit once, the concentration factor of the membrane distillation unit is 2 to 10, and the recovery rate of liquid water in the clear liquid tank is 45% to 90%.

[0035] Preferably, the gas field water includes one of the following: raw brine from gas field produced water, water sample of raw brine after hardening removal from gas field produced water, tailings of gas field produced water after lithium adsorption and extraction, and desorption and extraction solution.

[0036] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects:

[0037] 1. The embodiments of the present invention operate under mild conditions, and can achieve the concentration of gas field water and the recovery of clean water at normal temperature and pressure, which reduces the requirements for the mechanical performance of system equipment and improves the operational safety factor.

[0038] 2. The embodiments of the present invention can exchange heat between high-temperature steam and gas field water, eliminating the need for distillation heat in the membrane distillation process and the use of low-temperature refrigeration equipment for water recovery, thus saving energy consumption.

[0039] 3. In this embodiment of the invention, a vacuum compression unit is provided to provide a low-pressure environment of vacuum or near vacuum for water vapor downstream of the membrane, so that water vapor can be compressed in a vacuum or near vacuum environment, thereby increasing the temperature and enthalpy. This operation can be carried out at a lower temperature, reducing the heat generated by compression and improving the compression efficiency.

[0040] 4. The embodiments of the present invention can achieve efficient heat utilization through only one membrane distillation, which greatly saves the number of equipment and the length of the process flow. Moreover, the concentration factor of the membrane distillation unit can reach 2 to 10, and the recovery rate of liquid water in the clear liquid tank can reach 45% to 90%.

[0041] In general, the integrated device and method for single-stage membrane distillation and vacuum compression provided in this invention, by setting up a vacuum compression unit, can transport downstream of the membrane to the heat exchange unit for heat exchange with the gas field water entering the membrane distillation unit, thereby achieving the purpose of saving energy, improving efficiency, and reducing costs. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the structure and process flow of the integrated device provided in an embodiment of the present invention.

[0044] The attached diagram shows the markings and corresponding component names:

[0045] 1-Feed tank, 2-Circulation pump, 3-Heat exchanger, 4-Membrane distillation unit, 5-Vacuum compressor, 6-Clear liquid tank, 7-Concentrate tank. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0049] In the description of this invention, it should be noted that the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0050] Example

[0051] Example 1: As Figure 1 As shown, an embodiment of the present invention provides an integrated device for single-stage membrane distillation and vacuum compression, comprising:

[0052] Membrane distillation unit 4 is designed to allow some gas field water to pass through the membrane and be converted into water vapor and transported downstream of the membrane. Specifically, gas field water enters membrane distillation unit 4, and through the separation of the membrane, water molecules are converted into water vapor, while other components such as salt and impurities are left on the upstream side of the membrane. The water vapor is sent to the downstream side of the membrane, while the concentrated gas field water (containing a high concentration of salt and other impurities) is collected or sent to subsequent treatment sections.

[0053] The vacuum compression unit, connected to the membrane distillation unit 4, is configured to compress water vapor downstream of the membrane to atmospheric pressure, thereby increasing the temperature and enthalpy of the water vapor. Specifically, the water vapor generated by the membrane distillation unit 4 enters the vacuum compression unit. Under vacuum conditions, the water vapor is compressed to atmospheric pressure. The compression process increases the temperature and enthalpy of the water vapor, providing thermal energy for the subsequent heat exchange process.

[0054] The heat exchange unit connects both the membrane distillation unit 4 and the vacuum compression unit. The heat exchange unit is configured to exchange heat between the water vapor heated by the vacuum compression unit and the gas field water before it enters the membrane distillation unit 4. Specifically, the heat exchange unit connects both the membrane distillation unit 4 and the vacuum compression unit. The water vapor heated by the vacuum compression unit exchanges heat with the gas field water before it enters the membrane distillation unit 4 in the heat exchange unit. The gas field water absorbs the heat released by the water vapor, and its temperature rises, providing the necessary thermal energy for the membrane distillation process. The released water vapor is converted into liquid water, which can be effectively recovered and utilized.

[0055] In this embodiment of the invention, through the arrangement and unique connection method of the vacuum compression unit and the heat exchange unit, the integrated device can recover and reuse heat, reduce dependence on external energy, and reduce energy consumption. The integrated device integrates multiple processing steps into one system, simplifies the process flow, reduces the number of equipment, and saves space and cost. The device can operate under normal pressure, reducing the risk of system accidents and improving operational safety.

[0056] Exemplarily, the vacuum compression unit includes a vacuum compressor 5, which provides a vacuum compression environment for water vapor downstream of the membrane; the heat exchange unit includes a heat exchanger 3. The vacuum compressor 5 provides a vacuum environment for the water vapor generated by the membrane distillation unit 4, allowing the water vapor to be compressed at a lower temperature. This compression process increases the temperature and enthalpy of the water vapor, providing heat energy for subsequent heat exchange processes. The heat exchanger 3 facilitates heat exchange between the water vapor and the gas field water. In the heat exchanger 3, the heated water vapor, after being processed by the vacuum compression unit, exchanges heat with the cooler gas field water before entering the membrane distillation unit 4. This process can be parallel flow, counter-flow, or cross-flow, and is not limited here. This integrated device makes the gas field water treatment process more efficient and energy-saving. By increasing the temperature and pressure of the water vapor through the vacuum compression unit and then transferring this heat energy to the gas field water to be treated using the heat exchanger, the system's energy utilization efficiency is improved, and the demand for external energy is reduced. Furthermore, by effectively recovering and reusing heat, this device helps reduce operating costs while minimizing environmental impact.

[0057] Vacuum compressor 5 can be a single-stage vacuum compressor 5 or a group of vacuum compressors 5, which is not limited here. The inlet of vacuum compressor 5 is connected to the outlet pipeline of membrane distillation unit 4, and its outlet is connected to the pipeline of heat exchanger 3; the inlet of membrane distillation unit 4 is connected to the pipeline of heat exchanger 3; heat exchanger 3 is also connected to a circulation pump 2, which is connected to a feed tank 1. The circulation pump 2 is used to transport the gas field water in feed tank 1 to heat exchanger 3 for heat absorption before entering membrane distillation unit 4; membrane distillation unit 4 is also connected to a concentrate tank 7, which is used to collect the gas field water concentrate that has not been converted into water vapor in membrane distillation unit 4; heat exchanger 3 is also connected to a clear liquid tank 6, which is used to collect the liquid clear water converted into water vapor after heat release in heat exchanger 3.

[0058] Specifically, the inlet of the vacuum compressor 5 is connected to the outlet pipe of the membrane distillation unit 4 to receive the water vapor generated by the membrane distillation unit 4. Its outlet is connected to the pipe of the heat exchanger 3 to send the compressed, heated, and pressurized water vapor into the heat exchanger 3. The inlet of the membrane distillation unit 4 is connected to the pipe of the heat exchanger 3 to receive the gas field water that has been heated by the heat exchanger 3. The membrane distillation unit 4 converts the gas field water into water vapor through the membrane distillation process. The water vapor enters the vacuum compressor 5, and the concentrate that has not been converted into water vapor is collected in the concentrate tank 7. Heat exchanger 3 is connected to the outlet pipe of vacuum compressor 5 to receive heated and pressurized water vapor, and is also connected to the inlet pipe of membrane distillation unit 4 to send gas field water, after heat exchange, into membrane distillation unit 4. Simultaneously, heat exchanger 3 is also connected to circulation pump 2 and feed tank 1. Circulation pump 2 is responsible for transporting gas field water from feed tank 1 to heat exchanger 3. Feed tank 1 is a container for storing gas field water. Circulation pump 2 ensures continuous flow of gas field water between heat exchanger 3 and membrane distillation unit 4. Clear liquid tank 6 collects the liquid water converted from the released heat of water vapor in heat exchanger 3, which can be used for irrigation, washing, or other purposes. This structure achieves efficient treatment and resource recovery of gas field water.

[0059] It should be noted that the membrane distillation unit 4 includes a membrane module, which includes one of the following structures: flat plate, spiral wound, butterfly, hollow fiber, and plate and frame. The membrane module includes a filter membrane, which includes one of the following microporous membrane structures: PVDF, PTFE, and PP. These are not limited here. As a preferred embodiment of the present invention, the pore size of a single micropore in the microporous structure is 0.1 to 1 μm. This pore size range can effectively separate water molecules from other solutes, ensuring the high efficiency of the membrane distillation process. The heat exchanger 3 is a partition wall heat exchange structure. The partition wall heat exchanger 3 has a large heat exchange area, which can improve the heat exchange efficiency and is suitable for transferring heat from water vapor to the gas field water to be treated during the membrane distillation process.

[0060] Example 2: Using the integrated device from Example 1, a total ion concentration of 59.665g was treated with single-stage membrane distillation-vacuum compression integrated technology. -1 The lithium ion concentration is 153 mg / g -1 Produced water from the gas field. Details are as follows:

[0061] Gas field produced water is fed by feed pump 2 at a rate of 100-120L as follows: -1The water flow rate is delivered to heat exchanger 3, where it exchanges heat with the compressed steam. Once the temperature reaches 60°C, it enters membrane distillation unit 4. In membrane distillation unit 4, water evaporates within the membrane pores and enters the downstream membrane as steam, flowing into vacuum compressor 5. After compression, the pressure is increased to atmospheric pressure and the temperature to 80°C. The water is then transported to heat exchanger 3 for preheating, releasing heat and condensing before entering the clarified liquid tank 6. The feed liquid from the completed membrane distillation process is collected in concentrate tank 7. The maximum membrane distillation flux reaches 27 kg / m³. -2 ·h -1 Lithium ions are concentrated 6 times, the total ion rejection rate is >99%, and the downstream water recovery rate reaches 90%.

[0062] Example 3: Using the integrated device from Example 1, a total ion concentration of 72.229 g·L⁻¹ was treated with single-stage membrane distillation-vacuum compression integrated technology. -1 The lithium ion concentration is 32 mg·L⁻¹ -1 Produced water from the gas field. Details are as follows:

[0063] Produced water from the gas field is fed by feed pump 2 at a rate of 100-120 L / h -1 The water flow rate is delivered to heat exchanger 3, where it exchanges heat with the compressed steam. Once the temperature reaches 60°C, it enters membrane distillation unit 4. In membrane distillation unit 4, water evaporates within the membrane pores and enters the downstream membrane as steam, flowing into vacuum compressor 5. After compression, the pressure is increased to atmospheric pressure and the temperature to 80°C. The compressed water is then sent to heat exchanger 3 for preheating, releasing heat and condensing before entering the clarified liquid tank 6. The feed liquid from the completed membrane distillation process is collected in concentrate tank 7. The membrane distillation flux reaches a maximum of 15 kg·m³. -2 ·h -1 Lithium ions are concentrated three times, with a total ion rejection rate of >99.6%, and the downstream water recovery rate reaches 66%.

[0064] Example 4: Using the integrated device from Example 1, a total ion concentration of 74.190 g·L⁻¹ was treated with single-stage membrane distillation-vacuum compression integrated technology. -1 The lithium ion concentration is 68 mg·L⁻¹ -1 The produced water from the gas field meets the standards for external drainage. Details are as follows:

[0065] Produced water from the gas field is fed by feed pump 2 at a rate of 100–120 L / h. -1The water flow rate is delivered to heat exchanger 3, where it exchanges heat with the compressed steam. Once the temperature reaches 60°C, it enters membrane distillation unit 4. In membrane distillation unit 4, water evaporates within the membrane pores and enters the downstream membrane as steam, flowing into vacuum compressor 5. After compression, the pressure is increased to atmospheric pressure, and the temperature is raised to 120°C. The compressed water is then sent to heat exchanger 3 for preheating, releasing heat and condensing before entering the clarified liquid tank 6. The feed liquid from the completed membrane distillation process is collected in concentrate tank 7. The membrane distillation flux reaches a maximum of 17.5 kg·m³. -2 ·h -1 Lithium ions are concentrated by 2 times, the total ion rejection rate is >99.7%, and the downstream water recovery rate reaches 49%.

[0066] In general, in order to reduce system energy consumption, the embodiments of the present invention propose a single-stage membrane distillation-vacuum compression technology. Specifically, the steam in the vacuum state downstream of the membrane distillation first enters the compressor and is compressed to atmospheric pressure. After its temperature and enthalpy are increased, it enters the heat exchange unit to exchange heat with the gas field water feed liquid. At the same time, the energy supply of the membrane distillation unit and the low-energy recovery of clean water are realized, saving the use of steam and low-temperature refrigeration equipment and reducing system energy consumption.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. It should be noted that the structures or components illustrated in the accompanying drawings are not necessarily drawn to scale, and descriptions of well-known components, processing techniques, and processes have been omitted to avoid unnecessarily limiting the invention.

Claims

1. An integrated device for single-stage membrane distillation and vacuum compression, characterized in that, include: The membrane distillation unit (4) is designed to allow some gas field water to pass through the membrane and be converted into water vapor and transported downstream of the membrane. The vacuum compression unit is connected to the membrane distillation unit (4) and its function is to compress the water vapor downstream of the membrane to atmospheric pressure, thereby increasing the temperature and enthalpy of the water vapor. The heat exchange unit is connected to both the membrane distillation unit (4) and the vacuum compression unit. The heat exchange unit is configured to exchange heat between the water vapor heated by the vacuum compression unit and the gas field water before entering the membrane distillation unit (4). The gas field water absorbs heat before entering the membrane distillation unit (4), and the water vapor heated by the vacuum compression unit releases heat and is converted into liquid water for recycling.

2. The integrated device for single-stage membrane distillation and vacuum compression according to claim 1, characterized in that, The vacuum compression unit includes a vacuum compressor (5), which is capable of providing a vacuum compression environment for water vapor downstream of the membrane; The heat exchange unit includes a heat exchanger (3).

3. The integrated device for single-stage membrane distillation and vacuum compression according to claim 2, characterized in that, The vacuum compressor (5) is a single-stage vacuum compressor or a vacuum compressor unit.

4. The integrated device for single-stage membrane distillation and vacuum compression according to claim 2, characterized in that, The inlet of the vacuum compressor (5) is connected to the outlet pipe of the membrane distillation unit (4), and its outlet is connected to the pipe of the heat exchanger (3). The inlet of the membrane distillation unit (4) is connected to the pipeline of the heat exchanger (3); The heat exchanger (3) is also connected to a circulation pump (2) via a pipeline. The circulation pump (2) is connected to a feed tank (1) via a pipeline. The circulation pump (2) is used to transport the gas field water in the feed tank (1) to the heat exchanger (3) for heat absorption and then into the membrane distillation unit (4). The membrane distillation unit (4) is also connected to a concentrate tank (7), which is used to collect the gas field water concentrate that has not been converted into water vapor in the membrane distillation unit (4); The heat exchanger (3) is also connected to a clear liquid tank (6), which is used to collect the liquid water converted from water vapor after the heat is released in the heat exchanger (3).

5. The integrated device for single-stage membrane distillation and vacuum compression according to claim 1, characterized in that, The membrane distillation unit (4) includes a membrane module, which includes one of the following structures: flat sheet, spiral wound, butterfly, hollow fiber, and plate and frame.

6. The integrated apparatus for single-stage membrane distillation and vacuum compression according to claim 5, characterized in that, The membrane module includes a filter membrane, which includes one of PVDF, PTFE and PP microporous membrane structures.

7. The integrated apparatus for single-stage membrane distillation and vacuum compression according to claim 6, characterized in that, The pore size of a single micropore in the microporous structure is 0.1 to 1 μm.

8. The integrated apparatus for single-stage membrane distillation and vacuum compression according to claim 2, characterized in that, The heat exchanger (3) is a partition wall type heat exchange structure.

9. An integrated method for single-stage membrane distillation and vacuum compression, implemented by the integrated apparatus according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Collect the gas field water into the feed tank, turn on the circulation pump to transport the gas field water to the heat exchanger, and then turn on the membrane distillation unit and vacuum compressor. The water vapor after vacuum compression by the vacuum compressor will be transported to the heat exchanger to exchange heat with the gas field water in the heat exchanger. S2: The circulating pump, heat exchanger, membrane distillation unit and vacuum compressor operate in continuous circulation. The gas field water concentrate that has not been converted into water vapor in the membrane distillation unit is collected by the concentrate tank, and the liquid water converted into liquid water after the water vapor in the heat exchanger is collected by the clear liquid tank. S3: Turn off the circulating pump, membrane distillation unit, and vacuum compressor.

10. The integrated method of single-stage membrane distillation and vacuum compression according to claim 9, characterized in that, The operating temperature of the membrane distillation unit is 40–60°C; The vacuum compressor is a screw or Roots type structure. The vacuum compressor can provide an environment of less than 10 kPa for water vapor downstream of the membrane, and the temperature of the water vapor after vacuum compression is 80-120°C.

11. The integrated method of single-stage membrane distillation and vacuum compression according to claim 10, characterized in that, After the gas field water and water vapor exchange heat in the heat exchanger, the temperature of the gas field water entering the membrane distillation unit is equal to the temperature required by the membrane distillation unit in the membrane distillation operation.

12. The integrated method for single-stage membrane distillation and vacuum compression according to claim 9, characterized in that, The gas field water passes through the membrane distillation unit once, and the concentration factor of the membrane distillation unit is 2 to 10. The recovery rate of liquid water in the clear liquid tank is 45% to 90%.

13. The integrated method for single-stage membrane distillation and vacuum compression according to claim 9, characterized in that, The gas field water includes one of the following: raw brine from gas field produced water, raw brine sample after impurity removal, adsorption tailings from gas field produced water, and desorption liquid.

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