Continuous back extraction system

Abstract

The utility model provides a continuous back extraction system. A mixing module of the continuous back extraction system comprises a microchannel matrix, and an organic phase and a back extraction agent enter the mixing module through an inlet for mixing and mass transfer enhancement; the sectional temperature control mass transfer module is communicated with a liquid outlet of the mixing module, the front section of the sectional temperature control mass transfer module is communicated with the mixing module, and the rear section of the sectional temperature control mass transfer module is provided with a heating structure for heating a fluid consisting of a mixed organic phase and a stripping agent; the membrane coupling phase separation unit is communicated with the rear section of the sectional temperature control mass transfer module, a sedimentation flow channel of the membrane coupling phase separation unit is communicated with the sectional temperature control mass transfer module and the hydrophilic modified ceramic membrane respectively, and the sedimentation flow channel and the hydrophilic modified ceramic membrane are used for separating an organic phase and a stripping agent twice respectively; the backwashing unit is connected with the membrane coupling phase separation unit and is used for backwashing the continuous back extraction system. The mass transfer speed is increased, the energy consumption is reduced, the waste of a solvent is reduced, and the problem of blockage is solved by backwashing.

Description

Technical Field

[0001] This application relates to the field of chemical technology, and in particular to a continuous back-extraction system. Background Technology

[0002] Caprolactam is a key raw material in the production of nylon-6, and its purity directly affects the performance of the final product. In industrial production, crude caprolactam solutions require multi-step refining processes (such as extraction, back-extraction, and ion exchange) to remove impurities. Among these, the back-extraction process, by transferring caprolactam from the organic phase (such as benzene-hexane solution) to the aqueous phase (process condensate), achieves separation from oil-soluble impurities and is a core step in improving product quality.

[0003] Traditional back-extraction processes primarily employ pulsed or packed columns, using countercurrent contact to transfer caprolactam from the organic phase to the aqueous phase. The crude caprolactam solution enters from the top of the column, while process condensate enters from the bottom. After countercurrent contact, the aqueous phase containing caprolactam is discharged from the bottom, and the organic phase is discharged from the top. However, traditional back-extraction processes suffer from low mass transfer efficiency, high energy consumption, high solvent consumption, and large equipment size, limiting their further application and development. Although microchannel technology can improve mass transfer efficiency, it still faces challenges such as easy clogging. Utility Model Content

[0004] The purpose of this application is to provide a continuous back-extraction system.

[0005] The embodiments of this application adopt the following technical solution: a continuous back-extraction system, comprising:

[0006] A mixing module includes a microchannel matrix having an inlet through which an organic phase and a back-extractant enter the mixing module and are mixed and mass transfer enhanced within the mixing module;

[0007] The segmented temperature-controlled mass transfer module is connected to the liquid outlet of the mixing module. The segmented temperature-controlled mass transfer module has a double-layer microchannel structure and includes a front section and a rear section. The front section is connected to the mixing module. The fluid in the front section is kept in a neutral environment by circulating cooling water. The rear section is provided with a heating structure for heating the fluid composed of the organic phase and the stripping agent after mixing by the mixing module.

[0008] A membrane-coupled phase separation unit is connected to the downstream section of the segmented temperature-controlled mass transfer module. The membrane-coupled phase separation unit includes a settling channel and a hydrophilic modified ceramic membrane. The settling channel is connected to both the segmented temperature-controlled mass transfer module and the hydrophilic modified ceramic membrane. The settling channel performs a first separation of the organic phase and the stripping agent from the segmented temperature-controlled mass transfer module. The hydrophilic modified ceramic membrane performs a second separation of the organic phase and the stripping agent after the first separation.

[0009] A backwashing unit is connected to the membrane-coupled phase separation unit and backwashes the continuous back-extraction system.

[0010] In some embodiments, the microchannel substrate is Y-shaped, comprising a main channel, two branch channels, and a transition channel. The two branch channels each have an inlet and an outlet. The outlets of the two branch channels are connected to one end of the transition channel, and the other end of the transition channel is connected to the inlet of the main channel. The diameter of the two branch channels gradually decreases from the inlet to the outlet, so that the organic phase and the stripping agent form a shear force at the connection between the two branch channels and the transition channel.

[0011] In some embodiments, the inlets of the two branch channels have a circular cross-section, and the outlets of the two branch channels have an elliptical cross-section.

[0012] In some embodiments, the inner wall of the main channel is provided with multiple rows of grooves with the tip protruding towards the outlet of the main channel. Each row of grooves includes multiple grooves, and the multiple grooves are arranged in a circumferential ring around the main channel so that the organic phase and the back-extraction agent form a periodic vortex in the main channel.

[0013] The inner wall of the main channel is coated with polytetrafluoroethylene, and the surface roughness of the coating is between 0.05 micrometers and 0.15 micrometers.

[0014] In some embodiments, each of the grooves is V-shaped with a helical orientation within a plane in which the main channel extends axially.

[0015] In some embodiments, the microchannel substrate is made of silicon carbide.

[0016] In some embodiments, the heating structure of the segmented temperature control mass transfer module is an electric heating wire.

[0017] In some embodiments, the settling channel is inclined downward along the direction of fluid flow.

[0018] In some embodiments, the hydrophilic modified ceramic membrane uses α-alumina ceramic as a substrate and has a pore size of 0.2 micrometers.

[0019] In some embodiments, the front-end circulating cooling water temperature of the segmented temperature-controlled mass transfer module is 25°C, and the rear-end electric heating wire heating temperature is 40°C.

[0020] The beneficial effects of the embodiments of this application are as follows:

[0021] By incorporating a heating structure into the segmented temperature-controlled mass transfer module, the mass transfer rate was improved. Maintaining a neutral environment through circulating cooling water at the front end of the module reduced side reactions and prevented energy waste. The microchannel matrix of the mixing module enabled efficient fluid mixing, minimizing energy consumption increases due to incomplete mixing. Furthermore, the separation of the organic and inorganic phases was achieved using a hydrophilic-modified ceramic membrane, reducing energy input for subsequent processing and improving solvent recovery, thus minimizing solvent waste. Backwashing via a backwashing unit resolved the clogging issue. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a structural block diagram of the continuous back-extraction system of this application;

[0024] Figure 2 This is a schematic diagram of the microchannel matrix structure of this application;

[0025] Figure 3 for Figure 2 A cross-sectional schematic diagram of BB;

[0026] Figure 4 for Figure 2 Schematic diagram of the cross section of AA;

[0027] Figure 5 This is a schematic diagram of the structure of the main channel of this application extending along the axial direction;

[0028] Figure 6 For this application Figure 5 A schematic diagram of the structure of one of the grooves.

[0029] Reference numerals: 1. Main channel; 101. Groove; 1011. Tip; 2. Branch channel; 3. Transition channel. Detailed Implementation

[0030] Various embodiments and features of this application are described herein with reference to the accompanying drawings.

[0031] It should be understood that various modifications can be made to the embodiments described herein. Therefore, the above description should not be considered as limiting, but merely as an example of embodiments. Other modifications within the scope and spirit of this application will be apparent to those skilled in the art.

[0032] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the present application and, together with the general description of the present application given above and the detailed description of the embodiments given below, serve to explain the principles of the present application.

[0033] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0034] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application.

[0035] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0036] Specific embodiments of this application are described thereafter with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that could obscure the application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in a variety of substantially any suitable detailed structures.

[0037] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0038] This application provides a continuous back-extraction system, combined with... Figure 1 The system includes a mixing module (A), a segmented temperature-controlled mass transfer module (B), a membrane coupling phase separation unit (C), and a backwashing unit (not shown in the figure). The components can be connected by corrosion-resistant stainless steel pipelines, and flange sealing structures can be used to ensure the leak-free operation of the entire system.

[0039] The mixing module includes a microchannel substrate with an inlet. The organic phase and the stripping agent enter the mixing module through the inlet and undergo mixing and enhanced mass transfer within the mixing module. During system operation, the organic phase (benzene solution) and the stripping agent (pure water or neutral aqueous solution) are injected into the inlet of mixing module A via a metering pump at a specified ratio and flow rate.

[0040] In some embodiments, combined with Figure 2 , Figure 3 and Figure 4 The microchannel substrate is Y-shaped, comprising a main channel 1, two branch channels 2, and a transition channel 3. The two branch channels 2 each have an inlet and an outlet. An organic phase (benzene solution) and a back-extraction agent (pure water or neutral aqueous solution) are introduced into the inlets of the two branch channels 2 via metering pumps. Within the Y-shaped microchannel, the two phases achieve highly efficient micro-mixing and enhanced mass transfer. Subsequently, the mixture enters the segmented temperature-controlled mass transfer module B.

[0041] The outlets of the two branch channels 2 are respectively connected to one end of the transition channel 3, and the other end of the transition channel 3 is connected to the inlet of the main channel 1. The diameter of the two branch channels 2 gradually decreases from the inlet to the outlet so that the organic phase and the stripping agent form a shear force at the connection between the two branch channels 2 and the transition channel 3.

[0042] Combined again Figure 3 The cross-section of the inlet of the two branch channels 2 can be circular, and the cross-section of the outlet of the two branch channels 2 can be elliptical.

[0043] The Y-shaped microchannel substrate can be made of silicon carbide (SiC). For example, the dimensions of the Y-shaped microchannel substrate can be 50mm × 20mm × 5mm (length × width × height). The diameter of the main channel 1 is 400-600μm (preferably 500μm), and the diameter of the branch channel 2 can be 150-250μm (preferably 200μm). The branch channel 2 and the main channel 1 are connected by a tapered transition, i.e., the inlet end is a pure circular cross-section, and the diameter of the confluence area (transition channel 3) can be 280-360μm (preferably 320μm) with an elliptical transition cross-section and a major-to-minor axis ratio of 1.1-1.3:1 (preferably 1.2:1). The length of the transition channel 3 can be 1.5-2.0mm (preferably 1.8mm) to ensure a smooth flow velocity transition. This design, through precise bi-branch symmetrical layout and three-dimensional angle control, achieves efficient mixing under low turbulence (turbulence intensity <5%), while avoiding the backflow defects of traditional Y-shaped structures.

[0044] Combination Figure 4 and Figure 5 The inner wall of the main channel 1 is provided with multiple rows of grooves 101 with pointed ends 1011 protruding towards the outlet of the main channel 1. The grooves 101 are similar to V-shapes. That is, in the plane extending along the axial direction of the main channel 1, each groove 101 is V-shaped with a spiral orientation. Each row of grooves 101 includes multiple grooves 101, which are arranged in a circumferential ring around the main channel 1 to form a periodic vortex between the organic phase and the stripping agent within the main channel 1.

[0045] The trenches are located within the main channel 1, with a depth of 40-60 μm (preferably 50 μm) and a spacing of 80-120 μm (preferably 100 μm). Combined Figure 5 and Figure 6 The V-shaped tips 1011 of these grooves are designed to be 10°-20° (preferably 15°) opposite to the direction of fluid flow in the main channel 1, which matches the helix angle of 20-30° (preferably 25°) of the spiral arrangement, forming a continuous vortex-induced structure.

[0046] The inner wall of the main channel 1 is coated with a polytetrafluoroethylene (PTFE) coating, with a surface roughness between 0.05 μm and 0.15 μm. Specifically, the inner wall of the main channel 1 can be coated with a 60-100 μm (preferably 80 μm) thick PTFE coating using a plasma spraying process, with a surface roughness Ra ≤ 0.05-0.15 μm (preferably ≤ 0.1 μm) to optimize fluid flow characteristics. At the confluence of the two-phase fluids in the Y-shaped microchannel, shear force is generated due to the velocity difference, and the grooves induce periodic eddies, effectively breaking the laminar boundary layer and achieving a mixing uniformity of over 93%. The special design of the Y-shaped microchannel substrate, such as the tapered transition connection and the grooves within the main channel 1, enables efficient mixing under low turbulence, breaking the laminar boundary layer and reducing the energy consumption increase caused by insufficient mixing.

[0047] The segmented temperature-controlled mass transfer module is connected to the outlet of the mixing module. This module features a double-layer microchannel structure and consists of a front section and a rear section. The front section is connected to the mixing module, and the fluid within it is maintained in a neutral environment by circulating cooling water. This is because the cooling water absorbs the heat generated during the reaction, preventing localized overheating and thus avoiding changes in the solution's acidity or alkalinity due to temperature increases. When the solution temperature rises, it may accelerate certain chemical reactions, including side reactions that could alter the solution's acidity or alkalinity. Precise temperature control via circulating cooling water effectively suppresses these side reactions, thereby maintaining the neutral environment of the solution. Maintaining a neutral environment is crucial for improving mass transfer efficiency and ensuring product quality during the back-extraction of caprolactam. A neutral environment facilitates the stable transfer of caprolactam, reducing the risk of denaturation or reactions with other impurities caused by acidic or alkaline conditions. The use of cooling water achieves this purpose, creating a stable neutral environment for the caprolactam back-extraction process through precise temperature control, thereby improving the overall process efficiency and product quality.

[0048] The downstream section includes a heating structure for heating the fluid composed of the organic phase and the stripping agent after mixing in the mixing module. The heating structure can be an electric heating wire or other heating methods. The electric heating wire is embedded in the downstream section to enhance the mass transfer rate, ensuring stable transfer and efficient mass transfer of caprolactam.

[0049] In some embodiments, the front-end circulating cooling water temperature of the segmented temperature-controlled mass transfer module is 25°C, and the rear-end electric heating wire heating temperature is 40°C.

[0050] The segmented temperature-controlled mass transfer module can employ a dual-layer microchannel structure, consisting of an outer layer and an inner layer. The outer layer can be made of 316L stainless steel with an internal spiral flow channel. The inner layer can be a silicon carbide microchannel (with a liquid holding capacity of 10 mL / m). 2 The system is divided into a front section and a rear section. The front section maintains a neutral environment through circulating cooling water to reduce side reactions and avoid energy waste caused by side reactions; the rear section embeds electric heating wires to improve the mass transfer rate, ensure the stable transfer and efficient mass transfer of caprolactam, and avoid unnecessary energy loss.

[0051] The membrane-coupled phase separation unit is connected to the downstream section of the segmented temperature-controlled mass transfer module. The membrane-coupled phase separation unit includes a sedimentation channel and a hydrophilic modified ceramic membrane. The sedimentation channel is connected to both the segmented temperature-controlled mass transfer module and the hydrophilic modified ceramic membrane. The sedimentation channel performs the first separation of the organic phase and the back-extraction agent from the segmented temperature-controlled mass transfer module, that is, preliminary phase separation occurs in the sedimentation channel, with the aqueous phase settling and the benzene phase floating.

[0052] The settling channel can employ a wide-diameter settling channel structure. The overall shape of the wide-diameter settling channel is rectangular, with a length of up to 1 meter. This longer channel length provides sufficient residence time for the fluid, allowing ample time for the different phases to separate. The cross-section is rectangular, with a height of 1.5 mm and a width of 20 mm. The larger width and smaller height result in a higher surface area to volume ratio, which enhances mass and heat transfer within the channel. The channel can be made of transparent polycarbonate (PC) material to facilitate observation of the phase separation process. The settling channel is inclined downwards along the fluid flow direction. That is, the settling channel can be installed at an angle, for example, at 5°, with the direction of fluid flow. This inclined design helps utilize gravity to promote the separation of phases of different densities, making the aqueous phase settle more easily and the benzene phase float more easily. The 5° inclination angle is optimized to ensure smooth fluid flow while fully utilizing gravity to enhance the phase separation effect. An excessively large tilt angle may result in excessively high flow rates, affecting the phase separation effect; while an excessively small tilt angle may prevent the effective use of gravity to promote phase separation.

[0053] Hydrophilic modified ceramic membranes are used for the re-separation of the organic phase and the back-extractant after the initial separation. The hydrophilic modified ceramic membrane module preferentially permeates the aqueous phase (containing caprolactam), achieving highly efficient membrane separation and significantly improving recovery rates, thus reducing the energy input required for subsequent processing. Furthermore, the use of hydrophilic modified ceramic membrane modules enables effective separation of the organic and aqueous phases, improving solvent recovery and utilization rates. Overall, solvent efficiency is improved compared to existing technologies, thereby reducing solvent waste.

[0054] After the mixture enters the wide-bore settling channel, the flow velocity rapidly decreases to 0.01 m / s due to the large cross-sectional area of ​​the channel. Under these low flow velocity conditions, the aqueous and benzene phases mainly separate by gravity due to their density difference. The density of the aqueous phase is 1.0 g / cm³. 3 The density is greater than that of the benzene phase, which is 0.87 g / cm³. 3 Therefore, the aqueous phase gradually sinks to the bottom of the channel under the influence of gravity, while the benzene phase gradually rises to the top of the channel. At the same time, the inclined channel design helps to accelerate this phase separation process, causing the aqueous phase to accumulate towards the bottom of the channel along the inclined direction, while the benzene phase accumulates towards the top of the channel along the inclined direction.

[0055] After initial phase separation, the mixture enters the hydrophilic modified ceramic membrane module. The hydrophilic modified ceramic membrane, based on α-alumina ceramic, has a pore size of 0.2 μm, a hydroxylated surface, and a contact angle of less than 30°, exhibiting excellent hydrophilicity and aqueous phase permeation selectivity. Under a pressure of 0.2 MPa, the hydrophilic membrane preferentially permeates the aqueous phase (containing caprolactam), achieving efficient separation of the aqueous and benzene phases, with an aqueous phase recovery rate exceeding 97%.

[0056] The feed inlet of the membrane-coupled phase separation unit is located on the upper side of the unit's housing, used to introduce the mixture into the hydrophilic modified ceramic membrane module. The permeate outlet of the membrane-coupled phase separation unit is located on the lower side of the housing, used to remove the aqueous phase (containing caprolactam) that has permeated through the membrane. The design of the feed inlet and permeate outlet allows the fluid to smoothly enter and exit the membrane module, achieving the separation process.

[0057] The backwashing unit is connected to the membrane coupled phase separation unit. Specifically, the backwashing unit is connected to the backwash port of the membrane coupled phase separation unit, which is located at the bottom of the outer shell of the membrane coupled phase separation unit and can be connected to a pneumatic diaphragm pump. A pulse backwash is initiated every 15 minutes (or other set time) to effectively remove contaminants adhering to the membrane surface by impacting the membrane surface with high-pressure gas, thus maintaining stable membrane flux.

[0058] In the membrane separation unit, the organic phase and the aqueous phase are effectively separated and directed to the organic phase (benzene phase) recycling system and the aqueous phase (containing caprolactam) purification and crystallization system for subsequent processing, respectively.

[0059] To clearly describe this application, comparative examples and different embodiments of this application are described below.

[0060] Comparative Example: The traditional pulse tower for caprolactam back-extraction is characterized by its large equipment size and low mass transfer efficiency. When processing the same amount of crude caprolactam solution, the mass transfer efficiency is only 65%, the energy consumption per unit product is as high as 2 kWh / kg, the solvent recovery rate is only 80%, and the equipment occupies a large area, frequently experiencing blockages during operation, severely impacting production efficiency and cost control.

[0061] Example 1:

[0062] This invention employs a continuous caprolactam back-extraction system and method based on a microchannel reactor. The system consists of three core modules connected in series: a mixing module (A), a segmented temperature-controlled mass transfer module (B), and a membrane-coupled phase separation unit (C). During operation, the organic phase (benzene-caprolactam solution) and the back-extraction agent (pure water or neutral aqueous solution) are injected into the inlet of the micro-mixing module (A) via a metering pump at a specified ratio and flow rate. Within the Y-shaped microchannel, the two phases achieve efficient micro-mixing and enhanced mass transfer. Subsequently, the mixture enters the segmented temperature-controlled mass transfer module (B), where a neutral environment is maintained at the front end by circulating cooling water to reduce side reactions, and an electric heating wire is embedded at the rear end to increase the mass transfer rate. Afterward, the mixture enters the membrane-coupled phase separation unit (C), where initial phase separation occurs in a wide-diameter settling channel. The hydrophilic modified ceramic membrane module preferentially permeates the aqueous phase (containing caprolactam), achieving efficient membrane separation. The system initiates a pulse backwash every 15 minutes to ensure stable membrane flux.

[0063] In practical operation, the mixing module (A) adopts a Y-shaped microchannel substrate made of silicon carbide (SiC). The main channel 1 has a diameter of 500 μm, the branch channel 2 has a diameter of 200 μm, and they are connected by a tapered transition. The inlet end has a pure circular cross-section, the confluence area has a diameter of 320 μm, an elliptical transition cross-section, a major-minor axis ratio of 1.2:1, and a connection transition section length of 1.8 mm. The main channel 1 has grooves with a depth of 50 μm and a spacing of 100 μm. The V-shaped tip 1011 forms a 15° angle with the fluid flow direction in the main channel 1, and the spiral arrangement has an inclination angle of 25°. The inner wall of the main channel 1 is coated with an 80 μm thick PTFE coating with a surface roughness Ra≤0.1 μm.

[0064] The segmented temperature and mass transfer module (B) adopts a double-layer microchannel structure. The temperature of the circulating cooling water in the front section is controlled at 25°C, and the temperature of the electric heating wire in the back section is controlled at 40°C.

[0065] The membrane-coupled phase separation unit (C) uses a hydrophilic modified ceramic membrane module with a pore size of 0.2 μm and a membrane area of ​​10 m². 2 .

[0066] When processing the same amount of crude caprolactam solution, the mass transfer efficiency reaches 95%, the energy consumption per unit product is only 0.75 kWh / kg, the solvent recovery rate exceeds 97.5%, the equipment volume is only 1 / 8 of that of traditional equipment, and the flux decay is less than 5% after 1200 hours of continuous operation.

[0067] Example 2: Compared to Example 1, the main channel 1 of the mixing module (A) has a diameter of 400 μm, the branch channel 2 has a diameter of 150 μm, and other conditions are the same. When processing the same amount of crude caprolactam solution, the mass transfer efficiency reaches 92%, the energy consumption per unit product is 0.8 kWh / kg, the solvent recovery rate is 97%, the equipment volume is 1 / 7 of the conventional equipment, and the flux decay is 4% after 1200 hours of continuous operation.

[0068] Example 3: Compared with Example 1, the segmented temperature-controlled mass transfer module (B) maintains the front-end circulating cooling water temperature at 20°C and the rear-end electric heating wire temperature at 35°C, with other conditions remaining the same. When processing the same amount of crude caprolactam solution, the mass transfer efficiency reaches 94%, the unit product energy consumption is 0.78 kWh / kg, the solvent recovery rate is 97.3%, the equipment volume is 1 / 8 of the traditional equipment, and the throughput decay is 4.5% after 1200 hours of continuous operation.

[0069] Example 4: Compared with Example 1, the membrane coupling phase separation unit (C) uses a hydrophilic modified ceramic membrane module with a membrane pore size of 0.1 μm and a membrane area of ​​8 m². 2 Under the same conditions, the mass transfer efficiency reached 93% when processing the same amount of crude caprolactam solution, the energy consumption per unit product was 0.76 kWh / kg, the solvent recovery rate was 97.2%, the equipment volume was 1 / 8 of that of traditional equipment, and the throughput decay was 3.8% after 1200 hours of continuous operation.

[0070] Example 5: Compared to Example 1, the system initiated a pulse backwash every 30 minutes, with other conditions remaining the same. When processing the same amount of crude caprolactam solution, the mass transfer efficiency reached 94%, the energy consumption per unit product was 0.77 kWh / kg, the solvent recovery rate was 97.4%, the equipment volume was 1 / 8 of the conventional equipment, and the flux decay was 4.2% after 1200 hours of continuous operation.

[0071] Example 6: Compared to Example 1, the trench depth of the mixing module (A) was 40 μm, the spacing was 80 μm, and other conditions were the same. When processing the same amount of crude caprolactam solution, the mass transfer efficiency reached 91%, the energy consumption per unit product was 0.82 kWh / kg, the solvent recovery rate was 96.8%, the equipment volume was 1 / 7 of the conventional equipment, and the throughput decay was 5% after 1200 hours of continuous operation.

[0072] Example 7: Compared to Example 1, the segmented temperature-controlled mass transfer module (B) maintains the front-end circulating cooling water temperature at 30°C and the rear-end electric heating wire temperature at 45°C, with other conditions remaining the same. When processing the same amount of crude caprolactam solution, the mass transfer efficiency reaches 93%, the unit product energy consumption is 0.79 kWh / kg, the solvent recovery rate is 97.1%, the equipment volume is 1 / 8 of the traditional equipment, and the throughput decay is 4.8% after 1200 hours of continuous operation.

[0073] Example 8: Compared with Example 1, the membrane coupling phase separation unit (C) uses a hydrophilic modified ceramic membrane module with a membrane pore size of 0.3 μm and a membrane area of ​​12 m². 2 Under the same conditions, the mass transfer efficiency reached 92% when processing the same amount of crude caprolactam solution, the energy consumption per unit product was 0.76 kWh / kg, the solvent recovery rate was 97.3%, the equipment volume was 1 / 8 of that of traditional equipment, and the throughput decay was 4.5% after 1200 hours of continuous operation.

[0074] Table 1. Experimental results under different treatment conditions:

[0075]

[0076]

[0077]

[0078] By incorporating a heating structure into the segmented temperature-controlled mass transfer module, the mass transfer rate is improved. Maintaining a neutral environment through circulating cooling water at the front end of the module reduces side reactions and avoids energy waste caused by them. The microchannel matrix of the mixing module achieves efficient fluid mixing, reducing energy consumption increases due to insufficient mixing. Furthermore, the separation of the organic and inorganic phases is achieved using a hydrophilic modified ceramic membrane, reducing energy input required for subsequent processing and improving solvent recovery, thus minimizing solvent waste. Backwashing via a backwashing unit solves the clogging problem. Additionally, the use of microchannel reactor technology significantly reduces the equipment size due to its small scale effect. Compared to the bulky equipment in existing technologies, this application is more integrated and modular, facilitating installation and maintenance and reducing the requirements for production sites.

[0079] The foregoing has described in detail several embodiments of this application, but this application is not limited to these specific embodiments. Those skilled in the art can make various variations and modifications based on the concept of this application, and all such variations and modifications should fall within the scope of protection claimed in this application.

Claims

1. A continuous back-extraction system, characterized in that, include: A mixing module includes a microchannel matrix having an inlet through which an organic phase and a back-extractant enter the mixing module and are mixed and mass transfer enhanced within the mixing module; The segmented temperature-controlled mass transfer module is connected to the liquid outlet of the mixing module. The segmented temperature-controlled mass transfer module has a double-layer microchannel structure and includes a front section and a rear section. The front section is connected to the mixing module. The fluid in the front section is kept in a neutral environment by circulating cooling water. The rear section is provided with a heating structure for heating the fluid composed of the organic phase and the stripping agent after mixing by the mixing module. A membrane-coupled phase separation unit is connected to the downstream section of the segmented temperature-controlled mass transfer module. The membrane-coupled phase separation unit includes a settling channel and a hydrophilic modified ceramic membrane. The settling channel is connected to both the segmented temperature-controlled mass transfer module and the hydrophilic modified ceramic membrane. The settling channel performs a first separation of the organic phase and the stripping agent from the segmented temperature-controlled mass transfer module. The hydrophilic modified ceramic membrane performs a second separation of the organic phase and the stripping agent after the first separation. A backwashing unit is connected to the membrane-coupled phase separation unit and backwashes the continuous back-extraction system.

2. The continuous back-extraction system according to claim 1, characterized in that, The microchannel substrate is Y-shaped, comprising a main channel, two branch channels, and a transition channel. The two branch channels each have an inlet and an outlet. The outlets of the two branch channels are connected to one end of the transition channel, and the other end of the transition channel is connected to the inlet of the main channel. The diameter of the two branch channels gradually decreases from the inlet to the outlet, so that the organic phase and the stripping agent form a shear force at the connection between the two branch channels and the transition channel.

3. The continuous back-extraction system according to claim 2, characterized in that, The inlets of the two branch channels have circular cross-sections, and the outlets of the two branch channels have elliptical cross-sections.

4. The continuous back-extraction system according to claim 2, characterized in that, The inner wall of the main channel is provided with multiple rows of grooves with the tips protruding towards the liquid outlet of the main channel. Each row of grooves includes multiple grooves, and the multiple grooves are arranged in a circumferential ring around the main channel so that the organic phase and the back-extraction agent form a periodic vortex in the main channel. The inner wall of the main channel is coated with polytetrafluoroethylene, and the surface roughness of the coating is between 0.05 micrometers and 0.15 micrometers.

5. The continuous back-extraction system according to claim 4, characterized in that, Within the plane extending axially along the main channel, each groove is V-shaped with a spiral orientation.

6. The continuous back-extraction system according to claim 1, characterized in that, The microchannel substrate is made of silicon carbide.

7. The continuous back-extraction system according to claim 1, characterized in that, The heating structure of the segmented temperature control and mass transfer module is an electric heating wire.

8. The continuous back-extraction system according to claim 1, characterized in that, The settling channel is inclined downward along the direction of fluid flow.

9. The continuous back-extraction system according to claim 1, characterized in that, The hydrophilic modified ceramic membrane uses α-alumina ceramic as a substrate and has a pore size of 0.2 micrometers.

10. The continuous back-extraction system according to claim 1, characterized in that, The front-end circulating cooling water temperature of the segmented temperature-controlled mass transfer module is 25°C, and the rear-end electric heating wire heating temperature is 40°C.

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