Purification method and integrated purification system for decoloring white oil and removing oil mist through membrane separation

Abstract

The invention discloses a purification method for white oil decoloration and membrane separation oil mist removal and an integrated purification system. The method comprises the following steps: heating the recovered oil by using a preheater; mixing the carclazyte and the recovered oil by using a premixing kettle, wherein one part of premixed liquid is used as reflux liquid; stirring and heating the premixed solution by using a decolorizing kettle to form a decolorized solution and decolorized tail gas; separating the decoloring solution by using a filter cake layer filter to form carclazyte waste residues, white oil and filter cake tail gas; separating the filter cake tail gas and the decolorized tail gas by using a pre-separator to form white oil and separated gas; condensing the separated gas by using a condenser to form white oil and non-condensable gas; separating the non-condensable gas by using membrane separation equipment to form white oil and discharged oil gas; and white oil particles in the white oil are filtered out through a white oil filter, and the white oil is recycled. According to the purification method and the integrated purification system provided by the invention, the recovered oil obtained after dichloromethane rectification can be subjected to decoloration treatment, and white oil components are recovered from tail gas generated in the decoloration process, so that white oil is obtained.

Description

Technical Field

[0001] The invention relates to a purification method for white oil decolorization and membrane separation oil mist removal, and also relates to an integrated purification system for realizing the purification method, belonging to the technical field of extraction recovery. Background Art

[0002] The white oil decolorization device is an auxiliary equipment for the wet process lithium battery separator production line and the extract recovery device. In the production process of lithium battery separators, white oil is used as a pore former and dichloromethane is used as an extractant. The resulting extract contains dichloromethane, white oil, a small amount of water and polyethylene impurities.

[0003] In the Chinese invention with patent number ZL 202210833314.4, a continuous white oil decolorization system and a continuous white oil decolorization method are disclosed. The technical scheme includes a decolorization tower and a continuous filtering and discharging device connected to the decolorization tower, wherein an oil inlet and a compressed air inlet are provided upstream of the continuous filtering and discharging device, and a cyclone separator, a clean oil outlet and a dirty oil outlet are connected downstream. The method is: fill filter tank one with oil, circulate to obtain clean oil, filter, then switch to filter tank two, blow dry the filter cake of filter tank one with compressed air, relieve pressure and discharge slag for standby use; at the same time, starting from switching to filter tank two, the corresponding operations mentioned above are circulated. The system adopts a coupling design with two filter tanks to change the original intermittent treatment process into a continuous process, and the oil inlet and oil outlet are carried out continuously and uninterruptedly.

[0004] In addition, in the Chinese invention with patent number ZL 201910681806.4, a bleaching clay mixing device for oil decolorization is disclosed. The device includes a stirring tank, a premixing tank is provided on one side of the stirring tank, a bleaching clay metering cylinder is provided on the top of the premixing tank, and the top and bottom of the bleaching clay metering cylinder are respectively connected to the bleaching clay tank and the premixing tank. A conical diffusion plate is provided at the connection between the bleaching clay metering cylinder and the premixing tank. A conical hopper is provided at the bottom of the premixing tank. An oil injection pipe is provided on one side of the premixing tank, and the oil injection pipe is connected to the premixing tank in a horizontal inward manner. The oil injection pipe is arranged diagonally with the bleaching clay metering cylinder. The premixing tank, the stirring tank, the conical diffusion plate, and the blades are all provided with an anti-adhesion coating. The bleaching clay is mixed and stirred in the premixing tank in a diffused manner, and the oil is injected into the premixing tank in a horizontal inward manner by using the pressure of the oil itself, and the stirring effect is improved by using vortex.

[0005] However, in the production process of white oil products, traditional white oil decolorization devices and oil mist removal equipment still have problems such as low decolorization efficiency and incomplete oil mist removal, which seriously affects production efficiency and product quality. Summary of the invention

[0006] The primary technical problem to be solved by the present invention is to provide a purification method for white oil decolorization and oil mist removal by membrane separation.

[0007] Another technical problem to be solved by the present invention is to provide an integrated purification system for implementing the above purification method.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: According to a first aspect of an embodiment of the present invention, a method for decolorizing white oil and removing oil mist by membrane separation is provided, comprising the following steps: Step S1: using a raw material tank to receive recovered oil from the main line, and using a preheater to heat the recovered oil; Step S2: using a premixing kettle to mix the clay and the recovered oil to form a premixed tail gas and a premixed liquid; using a portion of the premixed liquid as a reflux liquid to input into the premixing kettle; Step S3: using a decolorization kettle to stir and heat the premixed liquid and the premixed tail gas to decolorize the white oil component to form a decolorized liquid and a decolorized tail gas; Step S4: using a filter cake layer filter to separate the decolorized liquid to form white clay waste residue, white oil and filter cake tail gas; Step S5: using a pre-separator to separate the filter cake tail gas and the decolorized tail gas to form white oil and separated gas; Step S6: using a condenser to condense the separated gas to form white oil and non-condensable gas; Step S7: using a membrane separation device to separate non-condensable gas, forming white oil and discharging oil and gas; Step S8: using a white oil filter to filter out white clay particles in the white oil and recover the white oil; The fluid in the pre-separator spirals down at a rotation angle α with the horizontal plane, and the fluid in the condenser spirals down at a rotation angle β with the horizontal plane, and α<β is satisfied to ensure that the flow rates of the two are similar.

[0009] Preferably, when the filter cake tail gas and the decolorized tail gas are input into the pre-separator, a venturi tube is used to increase the flow rate.

[0010] According to a second aspect of an embodiment of the present invention, an integrated purification system for white oil decolorization and membrane separation oil mist removal is provided, comprising a raw material tank, a preheater, a premixing kettle, a decolorization kettle, a cake layer filter, a white oil filter, a pre-separator, a condenser and a membrane separation device; wherein, The feed port of the raw material tank is connected to the upstream process pipeline, and the discharge port is connected to the feed port of the preheater; the discharge port of the preheater is connected to the first feed port of the premixing kettle; the second feed port of the premixing kettle is connected to the upstream process pipeline, the first discharge port is connected to the first feed port of the decoloring kettle and the reflux port of the premixing kettle, and the second discharge port is connected to the second feed port of the decoloring kettle; The first discharge port of the decolorization kettle is connected to the feed port of the filter cake layer filter and the reflux port of the decolorization kettle, and the second discharge port is connected to the feed port of the pre-separator; the first discharge port of the filter cake layer filter is connected to the downstream process pipeline, the second discharge port is connected to the feed port of the white oil filter, and the third discharge port is connected to the feed port of the pre-separator; The first outlet of the pre-separator is connected to the feed port of the white oil filter, and the second outlet is connected to the feed port of the condenser; the first outlet of the condenser is connected to the feed port of the white oil filter, and the second outlet is connected to the feed port of the membrane separation device; the first outlet of the membrane separation device is connected to the feed port of the white oil filter, and the second outlet is connected to the downstream oil and gas discharge pipeline; the outlet of the white oil filter is connected to the downstream white oil recovery tank; Wherein, the pre-separator comprises a separator and a guide plate; the guide plate is arranged on the inner wall of the separator, and is spiral from top to bottom, and the angle of rotation with the horizontal plane is α; The condenser includes a cylinder, a condenser tube and a baffle; the condenser tube is arranged in the cylinder along the vertical direction, and the baffle is arranged on the inner wall of the cylinder, spirally from top to bottom, with a rotation angle β with the horizontal plane, satisfying α<β to form a similar flow rate.

[0011] Preferably, the hand angle α=30°, and the hand angle β=42°.

[0012] Preferably, the pre-separator further comprises a venturi tube; wherein, The venturi tube includes an inlet, a contraction section, a throat, a diffusion section and an outlet; the inlet is connected to the feed port of the pre-separator, and the outlet is connected to the feed port of the separator; the diameter of the inlet is D, the diameter of the throat is D1, the diameter of the outlet is D2, the tapered tube angle of the contraction section is A1, and the tapered tube angle of the diffusion section is A2; then D>D2>D1, A1>A2.

[0013] Preferably, a starting point or a section of the guide plate is arranged directly below an outlet of the venturi tube.

[0014] Preferably, the outlet of the venturi tube is located at the top of the pre-separator and is arranged so that the fluid flowing out of the venturi tube flows directly along the spiral channel of the guide plate when entering the separator.

[0015] Preferably, the membrane separation device comprises a vacuum unit and a plurality of membrane separation units; wherein, A plurality of the membrane separation units are connected in parallel, and the vacuum unit is connected in series with the membrane separation unit; The air inlet of the membrane separation unit is connected to the feed inlet of the membrane separation device, the air outlet is connected to the second outlet of the membrane separation device, the concentrated gas outlet of the central tube is connected to the air inlet of the vacuum unit, and the air outlet of the vacuum unit is connected to the first outlet of the membrane separation device.

[0016] Preferably, the membrane separation unit comprises multiple layers of lipophilic separation membranes; wherein, The multiple layers of separation membranes are bent into multiple layers of concentric circles, which are arranged concentrically and at intervals in the membrane separation unit to form air channels and white oil channels; the air channels are connected to the air inlet and outlet of the membrane separation unit, and the white oil channels are connected to the concentrated gas outlet of the central tube of the membrane separation unit.

[0017] Compared with the prior art, the present invention has the following technical effects: first, the recovered white oil is purified to a standard that can be used again through decolorization treatment, which effectively realizes the recycling of resources, reduces the raw material procurement cost of the enterprise, and improves the economic benefits; second, for the tail gas generated during the decolorization process, a multi-stage treatment process such as pre-separation, condensation and membrane separation is adopted, which can efficiently recover the white oil component in the tail gas, further improve the resource utilization rate, and ensure that the exhaust gas meets the standard and reduces environmental pollution; third, the special structural design of the pre-separator and the condenser, such as the spiral guide plate and the specific rotation angle, and the application of the Venturi tube in the pre-separator, significantly enhance the oil-gas separation effect and improve the processing efficiency and stability of the whole system; fourth, the use of multi-layer lipophilic separation membranes in the membrane separation equipment can efficiently separate white oil under low oil content, further ensure the recovery rate of white oil and the cleanliness of the exhaust gas, and solve the problems of low decolorization efficiency and incomplete oil mist removal in the traditional white oil decolorization device and oil mist removal equipment as a whole, which is particularly suitable for the scene with high requirements for white oil decolorization and oil mist removal in fine chemical production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of an integrated purification system for white oil decolorization and membrane separation and oil mist removal provided in the first embodiment of the present invention; Figure 2 for Figure 1 Schematic diagram of the structure of the membrane separation unit; Figure 3 for Figure 2 A schematic diagram of the structure of the membrane separation unit perpendicular to the longitudinal direction of the cross section; Figure 4 This is a schematic structural diagram of a pre-separator in the second embodiment of the present invention; Figure 5 for Figure 4 Schematic diagram of the structure of the venturi tube; Figure 6FIG. 1 is a schematic structural diagram of a condenser in the second embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The technical concept of the present invention is to decolorize and remove oil mist from the dichloromethane white oil extract (containing dichloromethane, white oil, a small amount of water and polyethylene impurities, etc.) produced by the wet lithium battery diaphragm production line, after dichloromethane distillation recovery, to recover the white oil therein and make it reach the standard for reuse. Specifically, the recovered oil is refined by comprehensive use of decolorization kettle, filter, demister and membrane separation equipment. In the decolorization process, the oxide is removed to make the white oil color transparent for reuse; at the same time, for the tail gas containing white oil mist generated in the decolorization process, the white oil component is recovered through a multi-stage treatment process to achieve efficient utilization of resources and standard emission. In particular, the present invention focuses on the recovery of white oil in the tail gas containing white oil mist. Even if the white oil content in the tail gas is lower than 500mg / m³, the problem of low recovery efficiency of conventional equipment can be overcome through innovative treatment methods to achieve economical and efficient recovery of white oil. First embodiment

[0021] like Figure 1 As shown, the first embodiment of the present invention provides an integrated purification system for white oil decolorization and membrane separation oil mist removal, including a raw material tank 1, a preheater 2, a premixing kettle 3, a decolorization kettle 4, a cake layer filter 5, a white oil filter 6, a pre-separator 7, a condenser 8 and a membrane separation device 9.

[0022] The feed port 11 of the raw material tank 1 is connected to the upstream process pipeline for receiving the upstream main line recovery oil. The discharge port 12 is connected to the feed port 21 of the preheater 2.

[0023] The preheater 2 is a heating device, including a material pipeline and a medium pipeline. The two ends of the material pipeline are the feed port 21 and the discharge port 22 of the preheater 2. The medium pipeline connects the upstream and downstream medium pipelines of the preheater 2 to pass a heat exchange medium, such as steam or thermal oil. The feed port 21 of the preheater 2 is connected to the discharge port 12 of the raw material tank 1, and the discharge port 22 is connected to the first feed port 31 of the premixing kettle 3.

[0024] The premixing kettle 3 is a mixing device for chemical raw materials, including a kettle body, a homogenizer, a reduction motor, a temperature sensor and multiple inlets and outlets. Among them, the first inlet 31 of the premixing kettle 3 is connected to the material outlet 22 of the preheater 2, the second inlet 32 ​​is connected to the upstream process pipeline, the first outlet 33 is connected to the first inlet 41 of the decoloring kettle 4 and the reflux port 35 of the premixing kettle 3, and the second outlet 34 is connected to the second inlet 42 of the decoloring kettle 4.

[0025] The decolorizing kettle 4 is a decolorizing device for chemical raw materials, including a kettle body, a homogenizer, a reduction motor, a temperature sensor, a medium pipeline and multiple inlets and outlets. Among them, the first inlet 41 of the decolorizing kettle 4 is connected to the first outlet 33 of the premixing kettle 3, the second inlet 42 is connected to the second outlet 34 of the premixing kettle 3, the first outlet 43 is connected to the inlet 51 of the cake layer filter 5 and the reflux port 45 of the decolorizing kettle 4, and the second outlet 44 is connected to the inlet 71 of the pre-separator 7. The medium pipeline of the decolorizing kettle 4 connects the upstream and downstream medium pipelines of the decolorizing kettle 4 to pass a heat exchange medium, such as steam or heat transfer oil.

[0026] The cake filter 5 is a solid-liquid separation device. The feed port 51 of the cake filter 5 is connected to the first discharge port 43 of the decolorization kettle 4, the first discharge port 52 is connected to the downstream process pipeline, the second discharge port 53 is connected to the feed port 61 of the white oil filter 6, and the third discharge port 54 is connected to the feed port 71 of the pre-separator 7.

[0027] The pre-separator 7 is a gas-liquid separation device, such as a cyclone separator, which is used to condense liquid droplets in the gas to separate the liquid droplets from the gas. The feed port 71 of the pre-separator 7 is connected to the third discharge port 54 of the filter cake layer filter 5, the first discharge port 72 is connected to the feed port 61 of the white oil filter 6, and the second discharge port 73 is connected to the feed port 81 of the condenser 8.

[0028] The condenser 8 is a gas condensing device, including a medium pipeline and a material pipeline. The medium pipeline connects the upstream and downstream medium pipelines of the condenser 8 to pass a heat exchange medium, such as cold water. The feed port 81 (material pipeline) of the condenser 8 is connected to the second discharge port 73 of the pre-separator 7, the first discharge port 82 (material pipeline) is connected to the feed port 61 of the white oil filter 6, and the second discharge port 83 (material pipeline) is connected to the feed port 91 of the membrane separation device 9.

[0029] The membrane separation device 9 is a semi-permeable membrane gas separation device, including a vacuum unit 94 and a plurality of membrane separation units 95. The feed port 91 of the membrane separation device 9 is connected to the second discharge port 83 of the condenser 8, the first discharge port 92 is connected to the feed port 61 of the white oil filter 6, and the second discharge port 93 is connected to the downstream oil and gas discharge pipeline. The plurality of membrane separation units 95 are connected in parallel, and the vacuum unit 94 is connected in series with the membrane separation unit 95, and the vacuum unit 94 provides a negative pressure environment for the membrane separation unit 95, so that the white oil component in the non-condensable gas passes through the separation membrane and is enriched to form white oil.

[0030] like Figure 2 and Figure 3As shown, the membrane separation device 9 provided in an embodiment of the present invention, the air inlet 951 of the membrane separation unit 95 is connected to the feed inlet 91 of the membrane separation device 9, the air outlet 952 is connected to the second outlet 93 of the membrane separation device 9, the central tube concentrated gas outlet 953 is connected to the air inlet of the vacuum unit 94, and the air outlet of the vacuum unit 94 is connected to the first outlet 92 of the membrane separation device 9.

[0031] The membrane separation unit 95 includes a plurality of lipophilic separation membranes 954, which can separate organic components and inorganic components in the gas. The plurality of separation membranes 954 are bent into a plurality of concentric circles, which are arranged concentrically and at intervals in the membrane separation unit 95 to form an air channel 954a and a white oil channel 954b. The air channel 954a is connected to the air inlet 951 and the air outlet 952, and the white oil channel 954b is connected to the concentrated gas outlet 953 of the central tube.

[0032] The white oil filter 6 is a solid-liquid separation device for removing white clay particles in the white oil. The feed port 61 of the white oil filter 6 is connected to the second discharge port 53 of the filter cake layer filter 5, the first discharge port 72 of the pre-separator 7, the first discharge port 82 of the condenser 8 and the first discharge port 92 of the membrane separation device 9, and the discharge port 62 is connected to the downstream white oil recovery tank.

[0033] The raw material tank 1 receives the recovered oil from the upstream through the feed port 11, inputs it into the material pipeline of the preheater 2 through the discharge port 12 and the feed port 21 of the preheater 2, and outputs it as a preheated mixed liquid from the discharge port 22 of the preheater 2. The heating medium in the medium pipeline of the preheater 2 exchanges heat with the recovered oil in the material pipeline, so that the recovered oil is heated to be a preheated mixed liquid. The main component of the recovered oil includes decolorized white oil.

[0034] The premixed kettle 3 is fed with preheated mixed liquid from the first feed port 31, and fed with bleaching clay from the second feed port 32, and mixed by a homogenizer to separate premixed tail gas and premixed liquid. Among them, the main components of the premixed tail gas include air and white oil mist, and the main components of the premixed liquid include white oil to be decolorized and bleaching clay. The premixed tail gas is fed into the decolorizing kettle 4 from the second discharge port 34 of the premixing kettle 3 and the second feed port 42 of the decolorizing kettle 4. The premixed liquid is output from the first discharge port 33 of the premixing kettle 3, a part of the premixed liquid is fed into the decolorizing kettle 4 from the first feed port 41 of the decolorizing kettle 4, and the other part is fed into the premixing kettle 3 from the reflux port 35 of the premixing kettle 3 to improve the premixing efficiency.

[0035] The premixed liquid and premixed tail gas input into the decoloring kettle 4 are mixed and stirred by a homogenizer to decolorize the white oil component, and the decolorized tail gas and decolorized liquid are separated. Among them, the main components of the decolorized tail gas include air and white oil mist, and the main components of the decolorized liquid include decolorized white oil and white clay waste residue. The decolorized tail gas is input into the pre-separator 7 through the second discharge port 44 of the decoloring kettle 4 and the feed port 71 of the pre-separator 7. The decolorized liquid is output from the first discharge port 43 of the decoloring kettle 4, a part of the decolorized liquid is input into the filter cake layer filter 5 through the feed port 51 of the filter cake layer filter 5, and the other part is input into the decolorizing kettle 4 through the reflux port 45 input into the decolorizing kettle 4 to improve the decolorization efficiency. The heating medium in the medium pipeline of the decolorizing kettle 4 performs heat exchange with the decolorized material to maintain the decolorized material in the decolorizing kettle 4 at the design temperature and improve the decolorization efficiency.

[0036] The decolorized liquid input into the filter cake layer filter 5 is separated into white clay waste residue (filter cake), white oil and filter cake tail gas. Among them, the main components of the filter cake tail gas include air and white oil mist. The white clay waste residue is transported to the downstream pipeline through the first discharge port 52, the white oil is input into the white oil filter 6 through the second discharge port 53 and the feed port 61 of the white oil filter 6, and the filter cake tail gas is input into the pre-separator 7 through the third discharge port 54 and the feed port 71 of the pre-separator 7.

[0037] The filter cake tail gas and decolorized tail gas input into the pre-separator 7 are subjected to the action of the pre-separator 7, and the white oil mist droplets therein are condensed and separated to form white oil and separated gas. Among them, the main components of the separated gas include air and white oil mist. The white oil is input into the white oil filter 6 through the first discharge port 72 and the feed port 61 of the white oil filter 6, and the separated gas is input into the condenser 8 through the second discharge port 73 and the feed port 81 of the condenser 8.

[0038] The medium pipeline and material pipeline of the condenser 8 are fully heat exchanged to condense the separated gas in the material pipeline to form white oil and non-condensable gas. Among them, the main components of the non-condensable gas include air and white oil mist. The white oil is input into the white oil filter 6 through the first discharge port 82 and the feed port 61 of the white oil filter 6, and the separated gas is input into the membrane separation device 9 through the second discharge port 83 and the feed port 91 of the membrane separation device 9.

[0039] The vacuum unit 94 of the membrane separation device 9 provides a negative pressure environment for the membrane separation unit 95, that is, the pressure of the white oil channel 954b is lower than the pressure of the air channel 954a, and the non-condensable gas is input from the feed port 91 of the membrane separation device 9 (the air inlet 951 of the membrane separation unit 95), separated and enriched by the separation membrane 954, and separated into white oil and discharged oil gas. Due to the negative pressure of the vacuum unit 94, the white oil is discharged from the concentrated gas outlet 953 of the central tube, and is input into the white oil filter 6 through the vacuum unit 94. The discharged oil gas is discharged through the air outlet 952 and the second outlet 93.

[0040] After multiple separations and oil removals, the oil content in the oil mist has been greatly reduced, and the lower oil content environment is more conducive to the separation membrane 954 to exert its selective permeation advantage, thereby further improving the oil removal rate. In addition, after the upstream equipment speeds up and cooperates with the pressure regulating device at the inlet of the membrane separation device 9, the oil mist reaches the most suitable pressure and wind speed for separation by the separation membrane 954.

[0041] The white oil filter 6 filters and removes the white clay particles that may be present in the white oil, and outputs the white oil from the discharge port 62 to the white oil recovery tank. Second embodiment

[0042] The present embodiment is different from the above-mentioned embodiment in that the structures of the pre-separator 7 and the condenser 8 provided in the embodiment of the present invention are further optimized to improve the recovery efficiency.

[0043] like Figure 4 and Figure 5 As shown, the pre-separator 7 includes a venturi tube 710, a separator 720 and a guide plate 730. Among them, the separator 720 is a separation device of the pre-separator 7. The guide plate 730 is arranged on the inner wall of the separator 720, and is spiral from top to bottom, with a rotation angle α with the horizontal plane. The venturi tube 710 is a feeding device of the pre-separator 7, and its outlet is located at the top of the pre-separator 7, and is arranged so that the fluid flowing out of the venturi tube 710 can flow directly along the spiral channel of the guide plate 730 when entering the separator 720. In other words, the starting point or one section of the guide plate 730 should be installed directly below the outlet of the venturi tube 710 to ensure smooth transition of the fluid, directly enter the spiral channel, reduce local resistance, and utilize the fluid dynamic effect generated by the venturi tube 710. In addition, the installation angle and position of the guide plate 730 and the venturi tube 710 need to be precisely adjusted to optimize the fluid flow path.

[0044] The venturi tube 710 includes an inlet 711, a contraction section 712, a throat 713, a diffusion section 714 and an outlet 715. Due to its physical properties, it can accelerate the flow rate of the fluid flowing therethrough. Among them, the inlet 711 is connected to the feed port 71 of the pre-separator 7, and the outlet 715 is connected to the feed port of the separator 720. The diameter of the inlet 711 is D, the diameter of the throat 713 is D1, the diameter of the outlet 715 is D2, the tapered tube angle of the contraction section 712 is A1, and the tapered tube angle of the diffusion section 714 is A2. Then D>D2>D1, A1>A2. According to Bernoulli's principle, an increase in flow rate will lead to a decrease in pressure, thereby forming a low-pressure area in the contraction part (contraction section 712) of the venturi tube. In the low-pressure area, liquid dissolved or entrained in the gas is more likely to form droplets.

[0045] A venturi tube 710 is provided at the feed port 71 of the pre-separator 7, and the separation of oil droplets is achieved by utilizing its speed increasing and outlet adsorption. Since the white oil droplets have a greater specific gravity than the air, the speed increasing rate is slower than that of the air during the speed increasing stage through the throat 713, so they can be separated from the air, thus achieving a primary separation. When passing through the outlet 715, due to the adsorption effect, the white oil droplets, which are also heavier, are subjected to less adsorption, and are more likely to sink and separate under the action of gravity, thus achieving a secondary separation. Preferably, in order to make it easier for the separated oil droplets to flow and accumulate on the tube wall and be discharged, and not to stay on the tube wall due to the viscosity of the white oil, thus affecting the airflow velocity, an oil-proof smooth coating is added to the tube wall and the guide plate 730.

[0046] Preferably, D2 = 0.65D, D1 = 0.3D, A1 = 24°, A2 = 10.5°. According to experimental analysis, when the design parameters of the venturi tube 710 meet the above parameters, the oil-gas separation efficiency of the pre-separator 7 is the highest and the energy loss is the lowest.

[0047] It is worth noting that the venturi tube 710 is used to significantly accelerate the fluid. When the fluid flows at high speed, the flow direction is suddenly changed, and the droplets in the fluid (vaporized white oil) will continue to move in the original direction due to inertia and separate from the gas (because the gas can easily change the flow direction). The pre-separator 7 uses this feature to condense and separate the white oil mist droplets in the filter cake tail gas and the decolorized tail gas (the tail gas mixed into the white oil mist), and adsorb them on the guide plate 730 to form white oil and separated gas. The structural characteristics of the venturi tube 710 increase the flow rate of the filter cake tail gas and the decolorized tail gas entering the pre-separator 7, thereby enhancing the separation efficiency.

[0048] Specifically, the mass of the oil droplets is much greater than that of the gas molecules. Therefore, when the airflow accelerates, the inertia of the oil droplets is greater, and it is difficult for them to change their motion state quickly with the airflow. Due to their small mass, gas molecules can quickly respond to changes in flow rate and follow the airflow. When the airflow passes through the venturi throat 713, the gas flow rate increases sharply, while the oil droplets increase more slowly due to their large inertia. This speed difference causes relative motion between the oil droplets and the gas, and the oil droplets gradually "lag behind" from the airflow and are separated.

[0049] The oil droplets in the airflow are mainly affected by inertia, drag and gravity. In the acceleration stage of the throat 713, the drag of the airflow increases rapidly, but due to the large inertia of the oil droplets, the change of its motion state lags behind the gas. When the airflow speed is high enough, the drag force on the oil droplets is not enough to overcome the inertia, causing the oil droplets to "break away" from the airflow. The escaping oil droplets settle under the action of gravity, or are adsorbed by the wall of the venturi tube 710 and the guide plate 730 to achieve separation.

[0050] The spiral guide plate 730 prolongs the path of the fluid entering the pre-separator 7, thereby increasing the residence time of the fluid in the pre-separator 7, which provides more time for the sedimentation of the droplets. The droplets have more opportunities to settle in the spiral path, reducing the possibility of being taken away by the gas again, thereby improving the separation efficiency. The guide plate 730 enhances the eddy effect in the pre-separator 7, promotes the collision and aggregation between the droplets, thereby improving the sedimentation efficiency of the droplets, making it easier for the droplets to settle to the bottom of the pre-separator 7.

[0051] like Figure 6 As shown, the condenser 8 includes a cylinder 810, a condenser tube 820 and a baffle 830. The condenser tube 820 is connected to the medium pipeline and is arranged in the cylinder 810 along the vertical direction, so that the heat exchange medium in the condenser tube 820 cools the separated gas in the cylinder 810. The baffle 830 is arranged on the inner wall of the cylinder 810, and is spiral from top to bottom, and the angle of rotation with the horizontal plane is β.

[0052] The separated gas separated by the pre-separator 7 is condensed by the condenser 820 and is acted upon by the baffle 830 to descend in a spiral in the condenser 8, thereby utilizing the centrifugal force to further enhance the oil-gas separation effect.

[0053] Preferably, α<β. The guide plate 730 and the baffle plate 830 are both spiral devices. Due to the obstruction of the condenser 820, the rotation angle of the baffle plate 830 needs to be greater than the rotation angle of the guide plate 730, forming a similar flow rate, thereby achieving a higher gas-liquid separation effect.

[0054] More preferably, α = 30°, β = 42°. According to experimental verification, when the rotation angle is α = 30° and β = 42°, the separation effect of gas and oil droplets is the best. Third embodiment

[0055] The third embodiment of the present invention provides a method for decolorizing white oil and removing oil mist by membrane separation, which at least includes the following steps.

[0056] Step S1: using the raw material tank 1 to receive the recovered oil from the main line, and using the preheater 2 to heat the recovered oil; Step S2: using the premixing kettle 3 to mix the clay and the recovered oil to form a premixed tail gas and a premixed liquid; using a portion of the premixed liquid as a reflux liquid to input into the premixing kettle 3; Step S3: using the decolorization kettle 4 to stir and heat the premixed liquid and the premixed tail gas to decolorize the white oil component to form a decolorized liquid and a decolorized tail gas; Step S4: using the filter cake layer filter 5 to separate the decolorized liquid to form white clay waste residue, white oil and filter cake tail gas; Step S5: using the pre-separator 7 to separate the filter cake tail gas and the decolorized tail gas to form white oil and separated gas; The fluid in the pre-separator 7 has a rotation angle α with the horizontal plane, and spirals downward.

[0057] Step S6: using the condenser 8 to condense the separated gas to form white oil and non-condensable gas; The fluid in the condenser 8 has a rotation angle β with the horizontal plane, spirally descending. Preferably, α<β. More preferably, α=30°, β=42°.

[0058] Step S7: using the membrane separation device 9 to separate the non-condensable gas, forming white oil and discharging oil and gas; Step S8: using the white oil filter 6 to filter out the clay particles in the white oil and recover the white oil.

[0059] In summary, the embodiment of the present invention provides a method and integrated purification system for decolorizing white oil and removing oil mist by membrane separation, which decolorizes the recovered white oil to meet the standards for reuse, thereby achieving effective recycling and utilization of resources and reducing the raw material procurement costs of enterprises. The tail gas formed during the decolorization process is separated, condensed and membrane separated to further recover the white oil in the tail gas, thereby improving economic benefits.

[0060] It should be noted that the above embodiments are only examples, and the technical solutions of the various embodiments can be combined, all within the protection scope of the present invention.

[0061] It should be noted that the term "formation" in the present invention means that it can be obtained by one of a variety of processes and is not limited to the processes listed in the embodiments. The order of steps in the present invention can be changed according to actual needs, the order of steps can be changed, and serial processing can also be changed to parallel processing, which is not limited to the order of steps listed in the embodiments.

[0062] The orientation or position relationship indicated by the terms "upper", "lower", "horizontal", "vertical", "top", "bottom", etc. is based on the orientation or position relationship shown in the drawings and is only for the convenience of describing the present invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0063] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0064] The above is a detailed description of a purification method and an integrated purification system for white oil decolorization and membrane separation oil mist removal provided by the present invention. For a person skilled in the art, any obvious changes made to it without departing from the essence of the present invention will constitute an infringement of the patent right of the present invention and will bear the corresponding legal liability.

Claims

1. A method for decolorizing white oil and removing oil mist by membrane separation, characterized in that The following steps are involved: Step S1: using a raw material tank to receive recovered oil from the main line, and using a preheater to heat the recovered oil; Step S2: using a premixing kettle to mix the clay and the recovered oil to form a premixed tail gas and a premixed liquid; using a portion of the premixed liquid as a reflux liquid to input into the premixing kettle; Step S3: using a decolorization kettle to stir and heat the premixed liquid and the premixed tail gas to decolorize the white oil component to form a decolorized liquid and a decolorized tail gas; Step S4: using a filter cake layer filter to separate the decolorized liquid to form white clay waste residue, white oil and filter cake tail gas; Step S5: using a pre-separator to separate the filter cake tail gas and the decolorized tail gas to form white oil and separated gas; Step S6: using a condenser to condense the separated gas to form white oil and non-condensable gas; Step S7: using a membrane separation device to separate non-condensable gas, forming white oil and discharging oil and gas; Step S8: using a white oil filter to filter out white clay particles in the white oil and recover the white oil; The fluid in the pre-separator spirals down at a rotation angle α with the horizontal plane, and the fluid in the condenser spirals down at a rotation angle β with the horizontal plane, and α<β is satisfied to ensure that the flow rates of the two are similar.

2. The method for decolorizing white oil and removing oil mist by membrane separation as claimed in claim 1, characterized in that: When the filter cake tail gas and the decolorized tail gas are input into the pre-separator, a venturi tube is used to increase the flow rate.

3. An integrated purification system for white oil decolorization and membrane separation and oil mist removal, characterized in that It includes a raw material tank, a preheater, a premixing kettle, a decolorizing kettle, a cake layer filter, a white oil filter, a pre-separator, a condenser and a membrane separation device; among which, The feed port of the raw material tank is connected to the upstream process pipeline, and the discharge port is connected to the feed port of the preheater; the discharge port of the preheater is connected to the first feed port of the premixing kettle; the second feed port of the premixing kettle is connected to the upstream process pipeline, the first discharge port is connected to the first feed port of the decoloring kettle and the reflux port of the premixing kettle, and the second discharge port is connected to the second feed port of the decoloring kettle; The first discharge port of the decolorization kettle is connected to the feed port of the filter cake layer filter and the reflux port of the decolorization kettle, and the second discharge port is connected to the feed port of the pre-separator; the first discharge port of the filter cake layer filter is connected to the downstream process pipeline, the second discharge port is connected to the feed port of the white oil filter, and the third discharge port is connected to the feed port of the pre-separator; The first outlet of the pre-separator is connected to the feed port of the white oil filter, and the second outlet is connected to the feed port of the condenser; the first outlet of the condenser is connected to the feed port of the white oil filter, and the second outlet is connected to the feed port of the membrane separation device; the first outlet of the membrane separation device is connected to the feed port of the white oil filter, and the second outlet is connected to the downstream oil and gas discharge pipeline; the outlet of the white oil filter is connected to the downstream white oil recovery tank; Wherein, the pre-separator comprises a separator and a guide plate; the guide plate is arranged on the inner wall of the separator, and is spiral from top to bottom, and the angle of rotation with the horizontal plane is α; The condenser includes a cylinder, a condenser tube and a baffle; the condenser tube is arranged in the cylinder along the vertical direction, and the baffle is arranged on the inner wall of the cylinder, spirally from top to bottom, with a rotation angle β with the horizontal plane, satisfying α<β to form a similar flow rate.

4. The integrated purification system for white oil decolorization and membrane separation and oil mist removal according to claim 3, characterized in that: The hand-in angle α=30°, and the hand-in angle β=42°.

5. The integrated purification system for white oil decolorization and membrane separation oil mist removal according to claim 4, characterized in that The pre-separator also includes a venturi tube; wherein, The venturi tube includes an inlet, a contraction section, a throat, a diffusion section and an outlet; the inlet is connected to the feed port of the pre-separator, and the outlet is connected to the feed port of the separator; the diameter of the inlet is D, the diameter of the throat is D1, the diameter of the outlet is D2, the tapered tube angle of the contraction section is A1, and the tapered tube angle of the diffusion section is A2; then D>D2>D1, A1>A2.

6. The integrated purification system for white oil decolorization and membrane separation and oil mist removal according to claim 5, characterized in that: The starting point of the guide plate or a section thereof is arranged directly below the outlet of the venturi tube.

7. The integrated purification system for white oil decolorization and membrane separation and oil mist removal according to claim 6, characterized in that: The outlet of the venturi tube is located at the top of the pre-separator and is arranged so that the fluid flowing out of the venturi tube directly flows along the spiral channel of the guide plate when entering the separator.

8. The integrated purification system for white oil decolorization and oil mist removal by membrane separation according to any one of claims 3 to 7, characterized in that The membrane separation device comprises a vacuum unit and a plurality of membrane separation units; wherein, A plurality of the membrane separation units are connected in parallel, and the vacuum unit is connected in series with the membrane separation unit; The air inlet of the membrane separation unit is connected to the feed inlet of the membrane separation device, the air outlet is connected to the second outlet of the membrane separation device, the concentrated gas outlet of the central tube is connected to the air inlet of the vacuum unit, and the air outlet of the vacuum unit is connected to the first outlet of the membrane separation device.

9. The integrated purification system for white oil decolorization and membrane separation oil mist removal according to claim 8, characterized in that The membrane separation unit comprises multiple layers of lipophilic separation membranes; wherein, The multiple layers of separation membranes are bent into multiple layers of concentric circles, which are arranged concentrically and at intervals in the membrane separation unit to form air channels and white oil channels; the air channels are connected to the air inlet and outlet of the membrane separation unit, and the white oil channels are connected to the concentrated gas outlet of the central tube of the membrane separation unit.

Images