Ceramic nanofiltration membrane device and system for recovering ketone benzene dewaxing solvent

Abstract

The utility model discloses a kind of ceramic nanofiltration membrane device and system for recycling ketone benzene dewaxing solvent, tubular nanofiltration membrane is arranged in the device, the tubular nanofiltration membrane active separation layer pore size is 0.7nm, and active separation layer thickness is 50-200nm, so that the solvent recovery rate of the ceramic nanofiltration membrane system permeate is above 98%, and the lubricating oil fraction content in permeate is below 0.5wt%;Ketone benzene dewaxing solvent recovery operation can be efficiently and low-lossly completed;In the ceramic nanofiltration membrane device, tubular nanofiltration membrane is installed and fixed by flower plate with through hole, elastically deformable O-ring is arranged between tubular nanofiltration membrane and flower plate through hole, and the fixing and sealing between tubular nanofiltration membrane and flower plate are realized by plug compression O-ring deformation.

Description

Technical Field

[0001] This utility model relates to a membrane separation device for improving solvent recovery in a ketone-benzene dewaxing unit, specifically a ceramic nanofiltration membrane device and system for solvent recovery in lubricating oil after dewaxing in a ketone-benzene dewaxing unit. Background Technology

[0002] The recovery system is the most energy-intensive part of the ketone-benzene unit. Traditional processes often employ multi-effect evaporation and single-stage stripping. If a single heating method is used to flash-evaporate the vast majority of the solvent, very high temperatures are required, resulting in significant energy consumption. Therefore, multi-stage flash evaporation is employed. The remaining trace amounts of solvent in the oil and wax after flash evaporation are then stripped using nitrogen or steam. If steam stripping is used, water will be mixed into the solvent, requiring further water removal via a drying tower and a butanone removal tower. The recovered solvent is then condensed through heat exchange and sent to a refrigeration system for cooling and recycling. Traditional recovery schemes are too energy-intensive, necessitating the design of low-energy recovery solutions to further reduce production costs and enhance market competitiveness.

[0003] Membrane separation technology boasts advantages such as simple operation, high separation precision, significant separation effect, and low cost, and has enormous development potential in industries such as chemical, pharmaceutical, environmental protection, and food. Ceramic nanofiltration membranes have an average pore size of less than 1 nanometer, effectively removing multivalent ions, some monovalent ion salts, and organic compounds with a molecular weight greater than 200. Ceramic membranes also possess advantages such as resistance to acids, alkalis, organic solvents, pressure, and high temperatures.

[0004] A membrane device is a device that assembles membranes in a certain form within a basic unit to separate the components in a mixture under a certain driving force and membrane selectivity. In industrial membrane separation processes, membrane systems can contain several or even hundreds of membrane devices, depending on production needs. The membrane device is the smallest basic unit of a membrane system.

[0005] Currently, there are no specific membrane devices or systems for the recovery of ketone-benzene dewaxing solvent. The inventors have conducted in-depth research on the working characteristics of ketone-benzene devices and the specific properties of the materials to be separated, and have proposed a ceramic nanofiltration membrane device and system that can efficiently and cost-effectively recover ketone-benzene dewaxing solvent. Utility Model Content

[0006] To overcome the above problems, the inventors conducted intensive research and designed a ceramic nanofiltration membrane device and system for recovering solvents from ketone-benzene dewaxing. This device incorporates a tubular nanofiltration membrane with an active separation layer having a pore size of 0.7 nm and a thickness of 50-200 nm. This results in a solvent recovery rate of over 98% for the permeate and a lubricating oil fraction content of less than 0.5 wt% in the permeate. It can efficiently and with low loss complete the ketone-benzene dewaxing solvent recovery operation. In this ceramic nanofiltration membrane device, the tubular nanofiltration membrane is fixed by a perforated plate. An elastically deformable O-ring is arranged between the tubular nanofiltration membrane and the perforated plate. The O-ring is deformed by a plug, thus achieving fixation and sealing between the tubular nanofiltration membrane and the perforated plate, thereby completing this invention.

[0007] Specifically, the purpose of this invention is to provide a ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent, the device comprising a cylindrical shell 1.

[0008] Multiple tubular nanofiltration membranes 3 are arranged parallel to each other inside the housing 1.

[0009] Two perforated plates 4 are also provided inside the housing 1; through holes are provided on the perforated plates 4, and the end of the tubular nanofiltration membrane 3 extends into the through holes;

[0010] In the through hole, an O-ring 5 and a washer 6 are fitted on the outside of the tubular nanofiltration membrane 3. The O-ring 5 and the washer 6 are pressed by the plug 7 extending into the through hole from the other side, so as to achieve fixation and sealing between the tubular nanofiltration membrane 3 and the tube sheet 4.

[0011] The inner wall of the through hole is divided into three sections along the axial direction: the inner side adjacent to the tubular nanofiltration membrane 3 is the aperture section 8, the adjacent section is the transition section 9, and the outermost section is the threaded section 10.

[0012] The tubular nanofiltration membrane 3 passes through the aperture section 8 and extends into the transition section 9, where the O-ring 5 and the plug 7 fix and seal the tubular nanofiltration membrane 3.

[0013] Wherein, the inner diameter of the aperture segment 8 is smaller than the inner diameter of the transition segment;

[0014] The inner diameter of the aperture section 8 is basically the same as the outer diameter of the tubular nanofiltration membrane 3, so that a predetermined gap is left between the part of the tubular nanofiltration membrane 3 that passes through the aperture section 8 and enters the transition section 9 and the inner wall of the transition section 9. The O-ring 5 and the washer 6 fill the gap and adhere tightly to the tubular nanofiltration membrane 3 and the through hole.

[0015] Two O-rings 5 ​​are provided, arranged on both sides of the washer 6.

[0016] The plug 7 is cylindrical with threads on its outer surface. These threads engage with the threaded section 10 of the through hole, allowing it to be screwed into the through hole to gradually compress the O-ring 5, thereby achieving fixation and sealing between the tubular nanofiltration membrane 3 and the tube sheet 4.

[0017] The housing 1 has end caps 2 at both ends. One end cap 2 has an inlet flange 11 connected to the inlet of the ceramic nanofiltration membrane device. The other end cap 2 has a permeate outlet flange 12 connected to the permeate outlet of the ceramic nanofiltration membrane device.

[0018] A concentrate outlet flange 13 is also provided in the middle of the housing 1, which is connected to the concentrate outlet of the ceramic nanofiltration membrane device.

[0019] The tubular nanofiltration membrane 3 includes a porous support layer, a transition layer, and an active separation layer, wherein the thickness of the active separation layer is 50-200 nm.

[0020] The active separation layer has a pore size of 0.7 nm.

[0021] This invention also provides a ceramic nanofiltration membrane system for recovering ketone-benzene dewaxing solvent, characterized in that the system includes multiple ceramic nanofiltration membrane devices as described above for recovering ketone-benzene dewaxing solvent.

[0022] Among them, at least three ceramic nanofiltration membrane devices are connected in series to form a ceramic nanofiltration membrane unit, and the ceramic nanofiltration membrane system includes multiple ceramic nanofiltration membrane units connected in parallel with each other;

[0023] The series connection means that the concentrate outlet of the preceding ceramic nanofiltration membrane device is connected to the inlet of the subsequent ceramic nanofiltration membrane device.

[0024] When four tubular nanofiltration membranes are set in a ceramic nanofiltration membrane device, the ceramic nanofiltration membrane device is a four-channel tubular nanofiltration membrane device; when nineteen tubular nanofiltration membranes are set in a ceramic nanofiltration membrane device, they are respectively called a type I nineteen-channel tubular nanofiltration membrane device and a type II nineteen-channel tubular nanofiltration membrane device according to the arrangement rules of the tubular nanofiltration membranes.

[0025] In the first type of nineteen-channel tubular nanofiltration membrane device, the arrangement of the tubular nanofiltration membranes is as follows: connecting the center lines of adjacent tubular nanofiltration membranes results in equilateral triangles and squares, with the side lengths of the triangles and squares being equal; in the second type of nineteen-channel tubular nanofiltration membrane device, the arrangement of the tubular nanofiltration membranes is as follows: a combination of evenly distributed in the center and evenly distributed across the middle, with the distance between the center lines of adjacent tubular nanofiltration membranes on the axis of symmetry being equal.

[0026] In the ceramic nanofiltration membrane unit, the inlet of a type 19-channel tubular nanofiltration membrane device is connected to an external feed pump, the concentrate outlet of a type 19-channel tubular nanofiltration membrane device is connected to the inlet of a type 29-channel tubular nanofiltration membrane device, and the concentrate outlet of a type 29-channel tubular nanofiltration membrane device is connected to the inlet of a four-channel tubular nanofiltration membrane device.

[0027] The beneficial effects of this utility model include:

[0028] (1) The ceramic nanofiltration membrane device and system for recovering ketone-benzene dewaxing solvent provided by the present invention has a pore size of 0.7 nm in the active separation layer of the tubular nanofiltration membrane in the device and system, which is significantly smaller than that of traditional organic membranes. It precisely matches the molecular size of ketone-benzene dewaxing solvent and can exude methyl ethyl ketone with a molecular size of about 0.5 nm and toluene with a molecular size of about 0.6 nm, thereby achieving highly selective separation.

[0029] (2) The ceramic nanofiltration membrane device and system for recovering ketone-benzene dewaxing solvent provided by this utility model uses a plug to press the O-ring, gasket, and O-ring into the reserved gap between the nanofiltration membrane and the tube sheet, thereby achieving firm fixation and reliable sealing, and ensuring the pressure resistance and mechanical strength of the membrane device.

[0030] (3) The ceramic nanofiltration membrane device and system for recovering ketone-benzene dewaxing solvent provided by the present invention has a structure that facilitates control of the flow state of the fluid inside the tubular nanofiltration membrane, so that the fluid inside the tube reaches a turbulent state, eliminates concentration polarization, improves mass transfer efficiency, and maintains good uniformity.

[0031] (4) The ceramic nanofiltration membrane device and system for recovering ketone-benzene dewaxing solvent provided by the present invention effectively reduces the pressure drop of the membrane device and improves the mechanical strength and sealing characteristics of the membrane device through a detachable perforated plate and plug; facilitates the installation, disassembly, replacement and cleaning of the membrane; and improves the anti-fouling ability of the membrane device. Attached Figure Description

[0032] Figure 1 This paper shows a schematic diagram of the overall structure of the ceramic nanofiltration membrane device in this application;

[0033] Figure 2 This paper shows a cross-sectional view of the perforated plate when four tubular nanofiltration membranes are installed in the ceramic nanofiltration membrane device of this application;

[0034] Figure 3 This paper shows a cross-sectional view of the perforated plate when nineteen tubular nanofiltration membranes are installed in the ceramic nanofiltration membrane device of this application;

[0035] Figure 4 This diagram illustrates the arrangement of the tubular nanofiltration membranes in a type of nineteen-channel tubular nanofiltration membrane device according to this application.

[0036] Figure 5 This diagram illustrates the arrangement of the tubular nanofiltration membranes in the Type II nineteen-channel tubular nanofiltration membrane device of this application.

[0037] Figure 6 This diagram shows a cross-sectional view of the tubular nanofiltration membrane when it is fixed and sealed by a plug.

[0038] Figure 7 This application shows a cross-sectional view of the through hole on the tube sheet;

[0039] Figure 8 The diagram shows the flow path of the ketone-benzene dewaxing solvent and the structural schematic of the processing system of this application.

[0040] Explanation of reference numerals in the attached figures

[0041] 1-Shell

[0042] 2-End cap

[0043] 3-Tube Nanofiltration Membrane

[0044] 4-Flower Plate

[0045] 5-O ring

[0046] 6-Washer

[0047] 7-Plug

[0048] 8-Aperture Section

[0049] 9-Transition Section

[0050] 10-Threaded section

[0051] 11-Inlet Flange

[0052] 12-Permeate outlet flange

[0053] 13-Concentrate Outlet Flange Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0055] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0056] This invention provides a ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent. The device includes a cylindrical shell 1 and end caps 2 disposed at both ends of the shell 1, as shown below. Figure 1 As shown in the image.

[0057] Multiple tubular nanofiltration membranes 3 are arranged parallel to each other inside the housing 1.

[0058] Two flower plates 4 are also provided inside the shell 1;

[0059] A through hole is provided on the tube sheet 4, and the end of the tubular nanofiltration membrane 3 extends into the through hole; an O-ring 5 and a washer 6 are fitted on the outside of the tubular nanofiltration membrane 3 in the through hole, and the O-ring 5 and the washer 6 are pressed by a plug 7 extending into the through hole from the other side, so as to achieve fixation and sealing between the tubular nanofiltration membrane 3 and the tube sheet 4.

[0060] In a preferred embodiment, the perforated plate 4 has a certain thickness, preferably 32.7 mm, that is, the length of the through hole is 32.7 mm; the inner wall of the through hole is divided into three sections, the side adjacent to the tubular nanofiltration membrane 3 is the smooth section 8, the side adjacent to the end cap 2 is the threaded section 10, and the section between the smooth section 8 and the threaded section 10 is the transition section 9.

[0061] More preferably, the inner diameter of the aperture section 8 is smaller than the inner diameter of the transition section, thus making the through hole a stepped hole structure; the inner diameter of the aperture section 8 is basically the same as the outer diameter of the tubular nanofiltration membrane 3, so that a predetermined gap is left between the part of the tubular nanofiltration membrane 3 that passes through the aperture section 8 and enters the transition section 9 and the inner wall of the transition section. The O-ring 5 and the washer 6 fill the gap and adhere tightly to the tubular nanofiltration membrane 3 and the through hole, thereby achieving fixation and sealing between the tubular nanofiltration membrane 3 and the perforated plate 4.

[0062] In a preferred embodiment, two O-rings 5 ​​are provided and arranged on both sides of the gasket 6. The inner O-ring 5 is close to the side of the stepped hole, and the outer O-ring has at least a part of its structure located outside the tubular nanofiltration membrane 3, so that when the plug 7 presses the O-ring, the O-ring compression deformation can fully fix and seal the tubular nanofiltration membrane 3 and the perforated plate 4.

[0063] In a preferred embodiment, the plug 7 is cylindrical with threads on its outer surface. These threads engage with the threaded section of the through hole, allowing it to be screwed into the through hole. By screwing the plug 7 into the through hole, it gradually extends into the through hole, thereby gradually compressing the O-ring 5 and achieving fixation and sealing between the tubular nanofiltration membrane 3 and the perforated plate 4.

[0064] The plug 7 and the perforated plate 4 are detachably fastened, making the maintenance and replacement of the tubular nanofiltration membrane 3 more convenient.

[0065] In a preferred embodiment, the length, diameter, and channel inner diameter of the tubular nanofiltration membrane can vary depending on the membrane type; for example, in a four-channel tubular nanofiltration membrane device, the tubular nanofiltration membrane has a length of 1200 mm, a diameter of 20.6 mm, a channel inner diameter of 6.1 mm, and an outer diameter of 70 mm for the device cylinder. In a nineteen-channel tubular nanofiltration membrane device, the tubular nanofiltration membrane has a length of 1200 mm, a diameter of 25 mm, a channel inner diameter of 3.5 mm, and an outer diameter of 180 mm for the device cylinder.

[0066] In a preferred embodiment, connecting flanges are provided on the end caps 2 at both ends. One connecting flange is an inlet flange 11, which is connected to the inlet of the ceramic nanofiltration membrane device. The other connecting flange is a permeate outlet flange 12, which is connected to the permeate outlet of the ceramic nanofiltration membrane device. A third flange is also provided in the middle of the housing 1. This flange is a concentrate outlet flange 13, which is connected to the concentrate outlet of the ceramic nanofiltration membrane device.

[0067] In a preferred embodiment, the tubular nanofiltration membrane structure includes a porous support layer, a transition layer, and an active separation layer, wherein the thickness of the active separation layer is 50-200 nm.

[0068] In a preferred embodiment, the active separation layer of the tubular nanofiltration membrane has a pore size of 0.5-2 nm, preferably 0.7 nm, and an organic solvent swelling rate of less than 1%. This pore size allows methyl ethyl ketone (MEK) and toluene to permeate, forming a permeate, while retaining lubricating oil fractions to form a concentrate, achieving a good permeation effect.

[0069] Preferably, the tubular nanofiltration membrane is made of aluminum oxide (Al2O3), zirconium dioxide (ZrO2), or titanium dioxide (TiO2).

[0070] More preferably, the tubular nanofiltration membrane described in this application is a TiO2 ceramic membrane from Inopor, Germany.

[0071] In a preferred embodiment, the surface of the tubular nanofiltration membrane is hydroxylated, and its permeation selectivity for butanone or toluene is 20-100 times that for lubricating oil fractions, thereby further improving its permeation effect.

[0072] Preferably, the active separation layer of the tubular nanofiltration membrane is doped with 1-5 wt% nano-silica (SiO2) particles, more preferably with 1-3 wt% nano-silica (SiO2) particles; after immersion in a methyl ethyl ketone (MEK) or toluene environment at 25°C for 48 hours, the swelling rate is less than 1%; preferably, after immersion in a methyl ethyl ketone (MEK) or toluene environment at 25°C for 48 hours, the swelling rate is less than 0.5%.

[0073] Preferably, after continuous operation in a methyl ethyl ketone / toluene mixed solvent for 1000 hours, the permeate flux decay rate of the tubular nanofiltration membrane is less than 15%; preferably, after continuous operation in a methyl ethyl ketone / toluene mixed solvent for 1200 hours, the permeate flux decay rate of the tubular nanofiltration membrane is less than 10%.

[0074] This invention also provides a ceramic nanofiltration membrane system for recovering ketone-benzene dewaxing solvent, such as... Figure 8 As shown, the recycling system includes a buffer tank, a feed pump, multiple ceramic nanofiltration membrane devices, and a ketone-benzene dewaxing device; wherein the ceramic nanofiltration membrane device is the ceramic nanofiltration membrane device described above.

[0075] The buffer tank is used to temporarily store the mixed solvent generated after the ketone-benzene unit performs ketone-benzene dewaxing. The buffer tank is connected to the feed pump, which draws the mixed solvent from the buffer tank and injects it into the ceramic nanofiltration membrane unit. The feed pump can adjust the flow rate of the mixed solvent pumped in according to the working pressure and internal flow rate required by the ceramic nanofiltration membrane system. Preferably, the recovery system is also equipped with a control module that can detect the flow rate and pressure in the ceramic nanofiltration membrane unit and can be electrically connected to the feed pump, so that the control module can automatically control the feed flow rate of the feed pump.

[0076] In a preferred embodiment, when four tubular nanofiltration membranes are arranged in the ceramic nanofiltration membrane device, such as Figure 2 As shown, the ceramic nanofiltration membrane device is a four-channel tubular nanofiltration membrane device; when nineteen tubular nanofiltration membranes are arranged in the ceramic nanofiltration membrane device, as... Figure 3 As shown, based on the arrangement of the tubular nanofiltration membranes, they are respectively called a type I nineteen-channel tubular nanofiltration membrane device and a type II nineteen-channel tubular nanofiltration membrane device.

[0077] In this type of 19-channel tubular nanofiltration membrane device, the arrangement of the tubular nanofiltration membranes is as follows: connecting the center lines of adjacent tubular nanofiltration membranes forms a pattern of equilateral triangles and squares, with the side lengths of the triangles and squares being equal. Preferably, the side length is 36 mm. Figure 4 As shown in the diagram; the arrangement of the tubular nanofiltration membranes in the two types of nineteen-channel tubular nanofiltration membrane devices is a combination of centered and cross-sectional uniform distribution, and the distance between the center lines of adjacent tubular nanofiltration membranes on the axis of symmetry is equal. Preferably, the center-to-center distance of the membranes on this axis is 35 mm. Figure 5 As shown;

[0078] This arrangement pattern can also be described as follows: the tubular nanofiltration membranes are evenly arranged in a three-layer ring structure. The innermost layer contains only one tubular nanofiltration membrane, the middle layer has six tubular nanofiltration membranes evenly distributed around the innermost layer, and the outermost layer has twelve tubular nanofiltration membranes evenly distributed around the middle layer. The distance between each layer is equal. Draw a line connecting the center line of the innermost tubular nanofiltration membrane to the center line of any tubular nanofiltration membrane in the middle layer, and extend it outward. If this extended line passes between the two outermost tubular nanofiltration membranes and is equidistant from the distance between those two tubular nanofiltration membranes, then the ceramic nanofiltration membrane device is as follows: Figure 4 The image shows a type of nineteen-channel tubular nanofiltration membrane device; if the extension line passes through the center line of the outermost tubular nanofiltration membrane, then the ceramic nanofiltration membrane device is as follows. Figure 5 The two types of nineteen-channel tubular nanofiltration membrane devices shown are illustrated.

[0079] In this application, at least three ceramic nanofiltration membrane devices are connected in series to form a ceramic nanofiltration membrane unit. The ceramic nanofiltration membrane system includes multiple ceramic nanofiltration membrane units connected in parallel. The series connection means that the concentrate outlet of the preceding ceramic nanofiltration membrane device is connected to the inlet of the subsequent ceramic nanofiltration membrane device.

[0080] In the ceramic nanofiltration membrane unit, the inlet of a type 19-channel tubular nanofiltration membrane device is connected to an external feed pump, the concentrate outlet of a type 19-channel tubular nanofiltration membrane device is connected to the inlet of a type 29-channel tubular nanofiltration membrane device, and the concentrate outlet of a type 29-channel tubular nanofiltration membrane device is connected to the inlet of a four-channel tubular nanofiltration membrane device.

[0081] This invention also provides a method for using a ceramic nanofiltration membrane system for recovering ketone-benzene dewaxing solvent, the method comprising the following steps:

[0082] Step 1: Pass the low-temperature mixture containing lubricating oil fraction and ketone-benzene dewaxing solvent into the ceramic nanofiltration membrane system. The ketone-benzene dewaxing solvent is a mixture of butanone and toluene.

[0083] Preferably, the low-temperature mixture is an unheated raw material liquid produced in the dewaxing section, with a temperature of -20°C to 40°C. More specifically, the temperature is -20°C to 20°C. This application can directly process the low-temperature mixture, avoiding the energy consumption caused by heating / cooling in traditional processes.

[0084] The recovery method and system described in this application are applied in a ketone-benzene dewaxing unit, which includes a dewaxing section. This section generates a low-temperature mixture containing lubricating oil fraction and ketone-benzene dewaxing solvent. The mass fraction of the ketone-benzene dewaxing solvent in the mixture is 70-95%. By implementing the method and system described in this application, the separation of the lubricating oil fraction and the ketone-benzene dewaxing solvent can be achieved without temperature adjustment.

[0085] Preferably, the operating temperature in step 1 is 0-40℃ and the operating pressure is 0.5-3.0 MPa;

[0086] Preferably, the operating temperature in step 1 is 10-30℃, which is close to room temperature and relatively easy to control, thus reducing costs and increasing efficiency in industrial production.

[0087] Preferably, the operating pressure in step 1 is 1.0-2.5 MPa; in step 1, the low-temperature mixture is fed into the ceramic nanofiltration membrane system by a feed pump, and the operating pressure in the ceramic nanofiltration membrane system is adjusted by controlling the working rate of the feed pump to ensure that the ceramic nanofiltration membrane system can perform permeation operations efficiently.

[0088] Preferably, the mixture needs to be pretreated before performing step 1, including filtering to remove particles with a diameter greater than 1 μm and controlling the temperature to the target operating range.

[0089] Step 2: The ceramic nanofiltration membrane system allows methyl ethyl ketone and toluene to permeate to form a permeate, while retaining the lubricating oil fraction to form a concentrate.

[0090] In step 2, the ceramic nanofiltration membrane system employs a cross-flow filtration mode, with a membrane surface flow velocity of 0.5-3 m / s and a solvent permeation flux of not less than 20 L / (m²). 2 ·h·bar).

[0091] In step 2, the solvent recovery rate of the permeate is above 98%, and can even reach above 99%, and the lubricating oil fraction content in the permeate is below 0.5 wt%. The solvent purity in the permeate is high enough to allow it to be directly recycled to the dewaxing section without further processing, thus improving recycling efficiency and reducing recovery costs.

[0092] Step 3: Collect methyl ethyl ketone (MEK) and toluene from the permeate and control the return of MEK and toluene to the dewaxing section for recycling; collect and process the concentrate.

[0093] In step 3, the butanone and toluene in the permeate are directly returned to the dewaxing section for recycling at a temperature below 40°C, without the need for additional refrigeration. Since solvent recovery via the ceramic nanofiltration membrane system does not require heating, and the recovered products do not require cooling for application, overall energy consumption is significantly reduced.

[0094] In step 3, the collected concentrate is circulated to a buffer tank so that the concentrate and the mixture to be treated can be transported to the ceramic nanofiltration membrane system for further processing.

[0095] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and serve only an illustrative purpose. Based on this, various substitutions and improvements can be made to the present invention, all of which fall within the protection scope of the present invention.

Claims

1. A ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent, characterized in that, The device includes a cylindrical housing (1). Multiple tubular nanofiltration membranes (3) are arranged in parallel to each other inside the housing (1). Two perforated plates (4) are also provided inside the shell (1); through holes are provided on the perforated plates (4), and the end of the tubular nanofiltration membrane (3) extends into the through holes; In the through hole, an O-ring (5) and a washer (6) are fitted on the outside of the tubular nanofiltration membrane (3). The O-ring (5) and the washer (6) are pressed by a plug (7) that extends into the through hole from the other side, thereby achieving fixation and sealing between the tubular nanofiltration membrane (3) and the tube sheet (4).

2. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 1, characterized in that, The inner wall of the through hole is divided into three sections along the axial direction. The inner side adjacent to the tubular nanofiltration membrane (3) is the aperture section (8), the adjacent section is the transition section (9), and the outermost section is the threaded section (10). The tubular nanofiltration membrane (3) passes through the aperture section (8) and extends into the transition section (9), where the O-ring (5) and the plug (7) fix and seal the tubular nanofiltration membrane (3).

3. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 2, characterized in that, The inner diameter of the aperture section (8) is smaller than the inner diameter of the transition section; The inner diameter of the aperture section (8) is consistent with the outer diameter of the tubular nanofiltration membrane (3), so that a predetermined gap is left between the part of the tubular nanofiltration membrane (3) that passes through the aperture section (8) and enters the transition section (9) and the inner wall of the transition section (9). The O-ring (5) and the gasket (6) fill the gap and adhere tightly to the tubular nanofiltration membrane (3) and the through hole.

4. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 1, characterized in that, Two O-rings (5) are provided and arranged on both sides of the washer (6).

5. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 1, characterized in that, The plug (7) is cylindrical and has threads on its outer surface. The threads cooperate with the threaded section (10) of the through hole, so that it can be screwed into the through hole to gradually compress the O-ring (5) and achieve fixation and sealing between the tubular nanofiltration membrane (3) and the tube sheet (4).

6. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 1, characterized in that, Both ends of the housing (1) are provided with end caps (2). An inlet flange (11) is provided on one end cap (2), which is connected to the inlet of the ceramic nanofiltration membrane device. A permeate outlet flange (12) is provided on the other end cap (2), which is connected to the permeate outlet of the ceramic nanofiltration membrane device. A concentrate outlet flange (13) is also provided in the middle of the housing (1), which is connected to the concentrate outlet of the ceramic nanofiltration membrane device.

7. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 1, characterized in that, The tubular nanofiltration membrane (3) includes a porous support layer, a transition layer and an active separation layer, wherein the thickness of the active separation layer is 50-200 nm.

8. The ceramic nanofiltration membrane device for recovering ketone-benzene dewaxing solvent according to claim 7, characterized in that, The active separation layer has a pore size of 0.7 nm.

9. A ceramic nanofiltration membrane system for recovering ketone-benzene dewaxing solvent, characterized in that, The system includes multiple ceramic nanofiltration membrane devices for recovering ketone-benzene dewaxing solvent as described in any one of claims 1 to 8.

10. The ceramic nanofiltration membrane system for recovering ketone-benzene dewaxing solvent according to claim 9, characterized in that, At least three ceramic nanofiltration membrane devices are connected in series to form a ceramic nanofiltration membrane unit, and the ceramic nanofiltration membrane system includes multiple ceramic nanofiltration membrane units connected in parallel. The series connection means that the concentrate outlet of the preceding ceramic nanofiltration membrane device is connected to the inlet of the subsequent ceramic nanofiltration membrane device. When four tubular nanofiltration membranes are set in a ceramic nanofiltration membrane device, the ceramic nanofiltration membrane device is a four-channel tubular nanofiltration membrane device; when nineteen tubular nanofiltration membranes are set in a ceramic nanofiltration membrane device, they are respectively called a type I nineteen-channel tubular nanofiltration membrane device and a type II nineteen-channel tubular nanofiltration membrane device according to the arrangement rules of the tubular nanofiltration membranes. In the first type of nineteen-channel tubular nanofiltration membrane device, the arrangement of the tubular nanofiltration membranes is as follows: connecting the center lines of adjacent tubular nanofiltration membranes results in equilateral triangles and squares, with the side lengths of the triangles and squares being equal; in the second type of nineteen-channel tubular nanofiltration membrane device, the arrangement of the tubular nanofiltration membranes is as follows: a combination of evenly distributed in the center and evenly distributed across the middle, with the distance between the center lines of adjacent tubular nanofiltration membranes on the axis of symmetry being equal. In the ceramic nanofiltration membrane unit, the inlet of a type 19-channel tubular nanofiltration membrane device is connected to an external feed pump, the concentrate outlet of a type 19-channel tubular nanofiltration membrane device is connected to the inlet of a type 29-channel tubular nanofiltration membrane device, and the concentrate outlet of a type 29-channel tubular nanofiltration membrane device is connected to the inlet of a four-channel tubular nanofiltration membrane device.

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