A supercritical CO2 continuous extraction and separation method and its application

Abstract

The present invention provides a continuous supercritical carbon dioxide extraction and separation method, comprising using multiple extraction devices and at least one separation tower to perform loading, pressure raising, extraction, and pressure reduction. The multiple extraction devices include extraction devices A, B, and C. When extraction device A is extracting, extraction device B is pressurized while extraction device C is simultaneously loaded and / or pressure reduced. When extraction device B is extracting, extraction device C is pressurized while extraction device A is simultaneously pressure reduced and / or loaded. When extraction device C is extracting, extraction device A is pressurized while extraction device B is simultaneously pressure reduced and / or loaded. The method of the present invention can achieve continuous extraction using multiple extraction devices, has a wide range of applications, high extraction efficiency, and is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a supercritical CO2 continuous extraction and separation method and its application in separating polytetrafluoroethylene and paraffin. Background Art

[0002] Polytetrafluoroethylene (PTFE) is a high molecular weight polymer produced by polymerizing tetrafluoroethylene (TFE) as a monomer. Due to its excellent properties (such as chemical stability, corrosion resistance, and electrical insulation), it is widely used in various fields. In industry, PTFE is generally produced by suspension polymerization or emulsion polymerization. Emulsion polymerization is carried out in an aqueous phase. To control the particle size of PTFE, the amount of emulsifier added must be limited, causing the polymer emulsion to be in a metastable state. The strong stirring and shearing and poor heat dissipation during the polymerization process can easily lead to demulsification, coagulation, and ultimately polymerization failure. Therefore, paraffin wax is usually added as a stabilizer in the emulsion polymerization process. It is generally believed that paraffin wax can more easily wet PTFE in the aqueous phase and, together with the emulsifier, can wrap the PTFE particles to prevent coagulation between particles. In addition, paraffin wax can also reduce the adhesion of PTFE to the inner wall of the polymerization vessel and the stirring paddle.

[0003] After the emulsion polymerization process is complete, the paraffin contained in the aqueous emulsion must be removed and recovered. Currently, this method typically involves lowering the temperature below the paraffin's freezing point to coagulate and separate the paraffin from the aqueous emulsion. The remaining aqueous emulsion is then further coagulated and separated to produce wet PTFE resin. However, during the actual cooling, separation, and coagulation processes, an intermediate transition layer often remains where the PTFE and paraffin are tightly encapsulated and cannot be separated. This material is typically treated as solid waste, wasting resources and polluting the environment.

[0004] CN 101081908A discloses a method in which PTFE waste residue containing paraffin and water is sorted, washed, crushed, and then leached with an organic solvent (such as petroleum ether) (PTFE is insoluble in organic solvents, while paraffin is soluble in organic solvents). After filtration, the crude PTFE product and the solvent containing the paraffin are recovered, respectively. The crude PTFE product is dried and crushed to obtain finished PTFE, and the solvent containing the paraffin is separated by distillation. This method involves numerous unit operations and uses a large amount of flammable and explosive organic solvent, making it unsuitable for large-scale application.

[0005] CN 108239299A discloses a method: adding water to PTFE waste residue containing paraffin wax and water, heating until the paraffin wax melts, stirring and washing with water, and allowing the residue to stand for separation to obtain an upper layer of crude paraffin wax and a lower layer of PTFE resin (which sinks to the bottom of the water). The upper layer of crude paraffin wax is dried in a dryer and filtered to recover the paraffin wax. This method is simple and easy to control, and the recovered paraffin wax has a purity of ≥99%. However, the yield is low, the quality of the PTFE resin is unknown, and the economic benefits are poor.

[0006] CN 111073034A discloses a method in which paraffin-containing PTFE waste residue with a moisture content of no more than 10% (if the moisture content is greater than 10%, the residue is first dried and dehydrated) is continuously extracted (Soxhlet extractor) using an organic solvent such as a chlorinated hydrocarbon. The paraffin is extracted with the organic solvent, and the remaining material is dried to obtain a PTFE recovery material (paraffin content ≤5%, recovery rate ≥90%). This method is simple and easy to operate, but the quality of the resulting PTFE is unsatisfactory, and no subsequent recovery process for the paraffin is mentioned. The organic solvent used is highly environmentally polluting and flammable and explosive, posing a safety hazard.

[0007] CN 111234305A discloses a method in which PTFE waste residue containing paraffin and water is first subjected to one or more extractions using an organic extractant, such as a chlorinated hydrocarbon, to extract the majority of the paraffin from the residue until the paraffin content in the material is less than 10%. The extractant is then used for continuous reflux extraction of the residue with a lower paraffin content. This method avoids the problems of high solvent consumption during multiple extractions and low extraction efficiency when the paraffin content is low in the later stages. It also avoids the large processing volume and equipment required for direct continuous reflux extraction. However, this method is complex, making it unsuitable for industrialization, and also involves the same pollution and safety issues of the organic solvent.

[0008] CN 112708168 A discloses a method that first uses supercritical CO2 to continuously extract paraffin-containing PTFE waste residue. The extraction kettle can separate the paraffin-containing supercritical CO2 and PTFE recovery material. The paraffin-containing supercritical CO2 from the extraction kettle then enters a primary separation kettle to obtain paraffin recovery material and supercritical CO2 containing a small amount of paraffin. Finally, the supercritical CO2 containing a small amount of paraffin enters a secondary separation kettle to obtain paraffin recovery material and liquid CO2. The recovered PTFE has a paraffin content of less than 0.1wt%, a water content of less than 0.05wt%, and a water content of less than 0.5wt%. The purity of the recovered paraffin is greater than 99.5%. This method uses environmentally friendly, inexpensive, and readily available supercritical CO2 as an extractant, and no new substances are introduced during the separation process, which helps ensure the quality of the recovered product and achieves both environmental and economic benefits. However, this continuous extraction is not continuous in the traditional sense and has low production efficiency.

[0009] In general, among the existing PTFE dewaxing technologies, it is difficult to completely remove wax by adding water and high-temperature washing, organic solvent extraction is highly polluting, and there are safety risks of flammability and explosion. Traditional supercritical CO2 extraction is green, environmentally friendly and economical, but the current process often has low production efficiency.

[0010] The process apparatus disclosed in CN 112708168 A utilizes an extraction kettle and two separation kettles (two-stage separation). While the patent claims the entire process is continuous extraction, in reality, the extraction is essentially a batch operation. A batch of material is loaded into the extraction kettle, and the CO2 is initially pressurized to the extraction pressure using a compressor. After a certain "continuous" extraction time, the pressure is reduced, the residual PTFE is removed (discharged), and reloading is performed. During the loading, pressure increase, pressure reduction, and discharge times outside the extraction period, the removal of paraffin from the PTFE waste is interrupted.

[0011] CN1181989A discloses a supercritical carbon dioxide continuous extraction process, which includes three extraction kettles and two separation kettles. Extraction kettles 1 and 2 are connected in series for extraction, while extraction kettle 3 is prepared. Then, extraction kettles 2 and 3 are connected in series, while extraction kettle 1 is prepared. Finally, extraction kettles 1 and 3 are connected in series, while extraction kettle 2 is prepared. However, in this process, when the extraction of extraction kettles 1 and 2 is switched to extraction of extraction kettles 2 and 3, extraction of kettle 2 is repeated twice. When extraction of kettles 2 and 3 is switched to extraction of kettles 1 and 3, extraction of kettle 3 is also repeated twice. That is, during the extraction process, one kettle is always repeatedly extracted, which causes waste in the process. Moreover, the process does not mention the recovery of CO2 released by the extraction kettles when the pressure is reduced, resulting in great waste.

[0012] CN203183731U and CN2468555Y disclose an energy-saving device for supercritical carbon dioxide extraction equipment and a supercritical carbon dioxide multi-variable flow path extraction device, respectively. However, both patents only mention that the equipment has reserved pipelines and valves, and can be operated in series or in parallel, but do not specifically provide the operating step sequence. Summary of the Invention

[0013] To address the problems of the prior art, the present invention provides a method for continuous supercritical carbon dioxide extraction and separation. The method utilizes multiple extraction units in conjunction, allowing extraction and other processes, such as loading / unloading, pressure increase, and pressure reduction, to be performed alternately within the units. While one unit is extracting, the other units are also loading / unloading, pressure increase, and pressure reduction. When one unit finishes extraction and begins another process, another unit resumes extraction. This ensures that the substances to be separated from the material are continuously and uninterruptedly removed, making the entire extraction and separation process truly continuous, improving production efficiency and saving costs.

[0014] To achieve the above object, the present invention adopts the following technical solutions:

[0015] A first aspect of the present invention provides a continuous extraction and separation method of supercritical carbon dioxide, which includes using multiple extraction devices and at least one separation tower to carry out loading, pressurization, extraction and pressure reduction, wherein when one of the extraction devices is extracting, at least one extraction device is pressurized, and at the same time, at least one extraction device is pressure-reduced and / or loaded.

[0016] Preferably, the number of the extraction devices is 3 to 6, such as 3, 4, 5 or 6, preferably 3.

[0017] Further preferably, the plurality of extraction devices include extraction devices A, B and C.

[0018] In some embodiments, when extraction device A is extracting, the pressure of extraction device B is increased, and extraction device C is loaded and / or depressurized; when extraction device B is extracting, the pressure of extraction device C is increased, and extraction device A is depressurized and / or loaded; when extraction device C is extracting, the pressure of extraction device A is increased, and extraction device B is depressurized and / or loaded.

[0019] The extraction device of the present invention includes but is not limited to an extraction kettle, an extraction tower, an extractor, and the like.

[0020] According to some embodiments of the present invention, the plurality of extraction devices further include any one or more of extraction devices D, E and F.

[0021] According to some embodiments of the present invention, the plurality of extraction devices further include an extraction device D. In some embodiments, when extraction kettle A is extracting, the pressure of extraction kettle B is increased, while extraction kettle C is loaded / unloaded and / or depressurized, and extraction kettle D is depressurized; when extraction kettle B is extracting, the pressure of extraction kettle A is depressurized, while extraction kettle C is increased, while extraction kettle D is loaded / unloaded and / or depressurized; when extraction kettle C is extracting, the pressure of extraction kettle A is depressurized and / or loaded / unloaded, while extraction kettle B is depressurized and extraction kettle D is increased; when extraction kettle D is extracting, the pressure of extraction kettle A is increased, while extraction kettle B is depressurized and / or loaded / unloaded, and extraction kettle C is depressurized.

[0022] According to some embodiments of the present invention, the plurality of extraction devices further include extraction devices D and E. In some embodiments, when extraction kettle A is extracting, the pressure of extraction kettles B and C is increased, while extraction kettle D is loaded / unloaded and / or depressurized, and extraction kettle E is depressurized; when extraction kettle B is extracting, the pressure of extraction kettle A is depressurized, while extraction kettle C and extraction kettle D are increased, while extraction kettle E is loaded / unloaded and / or depressurized; when extraction kettle C is extracting, the pressure of extraction kettle A is decreased and / or loaded / unloaded, while extraction kettle B is decreased and extraction kettle D and extraction kettle E are increased; when extraction kettle D is extracting, the pressure of extraction kettle A is increased, while extraction kettle B is decreased and / or loaded / unloaded, while extraction kettle C is decreased and extraction kettle E is increased; when extraction kettle E is extracting, the pressure of extraction kettles A and extraction kettle B is increased, while extraction kettle C is loaded / unloaded and / or depressurized, and extraction kettle D is decreased.

[0023] According to some embodiments of the present invention, the plurality of extraction devices further comprises extraction devices D, E and F. In some embodiments, when extraction kettle A is extracting, extraction kettle B and extraction kettle C are pressurized, while extraction kettle D is loaded / unloaded and / or depressurized, and extraction kettle E and extraction kettle F are depressurized; when extraction kettle B is extracting, extraction kettle A and extraction kettle F are depressurized, extraction kettle D and extraction kettle C are pressurized, and extraction kettle E is loaded / unloaded and / or depressurized; when extraction kettle C is extracting, extraction kettle A and extraction kettle B are depressurized, extraction kettle D and extraction kettle E are pressurized, and extraction kettle F is depressurized and / or loaded / unloaded; when extraction kettle D is extracting, extraction kettle A is depressurized and / or loaded / unloaded, extraction kettle B and extraction kettle C are depressurized, and extraction kettle E and extraction kettle F are pressurized; when extraction kettle E is extracting, extraction kettle A and extraction kettle F are pressurized, extraction kettle B is loaded / unloaded and / or depressurized, and extraction kettle C and extraction kettle D are depressurized; when extraction kettle F is extracting, extraction kettle A and extraction kettle B are pressurized, extraction kettle C is depressurized and / or loaded / unloaded, and extraction kettle E and extraction kettle D are depressurized.

[0024] The loading of the present invention includes loading materials into the extraction device. The present invention does not impose any special limitation on the materials, and any materials that can be separated by supercritical CO2 fluid can be used, such as polytetrafluoroethylene waste containing paraffin.

[0025] According to some embodiments of the present invention, the extraction in the extraction device A is started simultaneously with the pressure increase in the extraction device B and the pressure decrease in the extraction device C.

[0026] According to some embodiments of the present invention, the extraction in the extraction device A is completed simultaneously with the pressurization of the extraction device B and the charging of the extraction device C.

[0027] According to some embodiments of the present invention, the extraction in the extraction device B is started simultaneously with the depressurization of the extraction device A and the pressure increase of the extraction device C.

[0028] According to some embodiments of the present invention, the extraction in the extraction device B is completed simultaneously with the pressurization of the extraction device C and the charging of the extraction device A.

[0029] According to some embodiments of the present invention, the extraction in the extraction device C is started simultaneously with the pressure increase in the extraction device A and the pressure decrease in the extraction device B.

[0030] According to some embodiments of the present invention, the extraction in the extraction device C is completed simultaneously with the pressurization of the extraction device A and the charging of the extraction device B.

[0031] According to some embodiments of the present invention, the pressurization comprises introducing a supercritical CO2 flow into the extraction device after loading to increase the pressure of the extraction device to the extraction pressure.

[0032] According to some embodiments of the present invention, the pressure increase includes connecting the extraction device that has finished loading with the extraction device that has finished extraction, thereby increasing the pressure of the extraction device that has finished loading to the same pressure as the extraction device that has finished extraction. For example, in the present invention, increasing the pressure of extraction device B can be achieved by: after loading of extraction device B is completed, the pressure of extraction device B is increased to the extraction pressure by passing a supercritical CO2 flow into extraction device B; or first connecting extraction device B with extraction device C to reduce the pressure of extraction device C, while simultaneously increasing the pressure of extraction device B to the same pressure as extraction device C, and then passing a supercritical CO2 flow into extraction device B to increase the pressure of extraction device B to the extraction pressure.

[0033] According to some embodiments of the present invention, the pressure reduction comprises the steps of connecting an extraction apparatus that has completed extraction with an extraction apparatus that has completed loading, reducing the pressure of the extraction apparatus that has completed extraction to the same pressure as the extraction apparatus that has completed loading, and further reducing the pressure of the extraction apparatus that has completed extraction to zero. For example, the pressure reduction of extraction apparatus A in the present invention can be achieved by: after extraction apparatus B has completed extraction, first connecting extraction apparatus A and extraction apparatus C to reduce the pressure of extraction apparatus A, while simultaneously increasing the pressure of extraction apparatus C to the same pressure as extraction apparatus A, and then venting extraction apparatus A and continuing to reduce the pressure to zero.

[0034] According to some embodiments of the present invention, when extraction device B starts extraction, extraction device A and extraction device C are connected to reduce the pressure of extraction device A and increase the pressure of extraction device C to the same pressure as extraction device A.

[0035] According to some embodiments of the present invention, when extraction device C starts extraction, extraction device B and extraction device A are connected to reduce the pressure of extraction device B and increase the pressure of extraction device A to the same pressure as extraction device B.

[0036] According to some embodiments of the present invention, when extraction device A starts extraction, extraction device C and extraction device B are connected to reduce the pressure of extraction device C and increase the pressure of extraction device B to the same pressure as extraction device C.

[0037] According to some embodiments of the present invention, the method comprises the steps of:

[0038] (1) CO2 flow is introduced into the extraction device A loaded with material to increase the pressure of the extraction device A to the extraction pressure. At the end of the pressure increase of the extraction device A, the extraction device B begins to be loaded with material, so that the pressure increase of the extraction device A and the loading of the extraction device B are completed at the same time;

[0039] (2) Extraction unit A is performing extraction, while a CO2 flow is introduced into extraction unit B to increase the pressure of extraction unit B to the extraction pressure. At the end of extraction in extraction unit A and the end of pressure increase in extraction unit B, loading of extraction unit C begins, and the extraction in extraction unit A, pressure increase in extraction unit B, and loading of extraction unit C are completed simultaneously;

[0040] (3) Extraction device B is performing extraction, while extraction devices A and C are connected, so that the pressure of extraction device A is reduced and the pressure of extraction device C is increased to the same pressure as that of extraction device A;

[0041] (4) A CO2 flow is introduced into the extraction device C to increase the pressure of the extraction device C to the extraction pressure. At the same time, the extraction device A continues to reduce the pressure to 0, then unloads and reloads, so that the loading of the extraction device A, the extraction of the extraction device B, and the pressure increase of the extraction device C are completed at the same time;

[0042] (5) Extraction is carried out in extraction device C, while extraction devices B and A are connected, so that the pressure of extraction device B is reduced and the pressure of extraction device A is increased to the same pressure as that of extraction device B;

[0043] (6) CO2 flow is introduced into extraction device A to increase the pressure of extraction device A to the extraction pressure, while extraction device B continues to reduce the pressure to 0, then unloads and reloads, so that extraction device A is pressurized, extraction device B is loaded, and extraction device C is completed at the same time;

[0044] (7) Extraction device A is performing extraction, while extraction devices B and C are connected, so that the pressure of extraction device C is reduced, and the pressure of extraction device B is increased to the same pressure as that of extraction device C;

[0045] (8) CO2 flow is introduced into the extraction unit B to increase the pressure to the extraction pressure, while the extraction unit C continues to reduce the pressure to 0, then unloads and reloads, so that the extraction of the extraction unit A, the pressure increase of the extraction unit B, and the loading of the extraction unit C are completed at the same time;

[0046] (9) Same as step (3); repeat this process.

[0047] In some embodiments, the material comprises polytetrafluoroethylene containing paraffin wax.

[0048] According to some embodiments of the present invention, the content of paraffin in the polytetrafluoroethylene is 5 to 60 wt %.

[0049] According to some embodiments of the present invention, the water content in the polytetrafluoroethylene is 2 to 40 wt %.

[0050] According to some embodiments of the present invention, the flow rate of the supercritical CO2 is 250 to 600 L / h.

[0051] Preferably, the flow rate of the supercritical CO2 is 300-400 L / h.

[0052] According to some embodiments of the present invention, the extraction pressure is 20-40 MPa, for example, 22 MPa, 25 MPa, 28 MPa, 30 MPa, 32 MPa, 35 MPa, or 38 MPa.

[0053] Preferably, the extraction pressure is 25-30 MPa.

[0054] According to some embodiments of the invention, the extraction temperature is 50-90°C, for example 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C.

[0055] Preferably, the extraction temperature is 65-75°C.

[0056] According to some embodiments of the present invention, the extraction time is 2 to 6 hours.

[0057] Preferably, the extraction time is 3 to 4 hours.

[0058] In a second aspect, the present invention provides use of the method described in the first aspect in separating polytetrafluoroethylene and paraffin.

[0059] According to some embodiments of the present invention, the using comprises loading a polytetrafluoroethylene material containing paraffin wax into the extraction device.

[0060] The beneficial effects of the present invention are: (1) by using a plurality of extraction devices in combination, the extraction in one of the extraction devices and the loading and unloading, pressure increase, pressure reduction and other processes in the other extraction devices are carried out simultaneously, and the extraction steps are carried out alternately in different extraction devices, which can realize uninterrupted extraction operation in the entire separation process and high extraction efficiency; (2) by connecting the two extraction devices, the CO2 pressure reduction of one extraction device is used for the CO2 pressure increase of the other extraction device, which can realize full utilization of CO2 and save resources and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is the process flow chart of traditional supercritical CO2 extraction.

[0062] Figure 2 This is a process flow chart of continuous extraction and separation of supercritical CO2 using three towers in accordance with an embodiment of the present invention, wherein 1, 2, and 3 represent compressor boost valves, 4, 5, and 6 represent pressure equalizing valves between extraction kettles, 7, 8, and 9 represent connecting valves between the extraction kettle and the separator, 10, 11, and 12 represent connecting valves between the extraction kettle and the CO2 recovery tank, and 13, 14, 15, 16, and 17 represent extraction kettle vent valves.

[0063] Figure 3This is a process flow chart of continuous extraction and separation of supercritical CO2 using four towers in accordance with an embodiment of the present invention, wherein 1, 2, 3, and 4 represent compressor boost valves, 5 and 6 represent pressure equalizing valves between extraction kettles, 7, 8, 9, and 10 represent connecting valves between the extraction kettle and the separator, 11, 12, 13, and 14 represent connecting valves between the extraction kettle and the CO2 recovery tank, and 15, 16, 17, 18, 19, and 20 represent extraction kettle vent valves.

[0064] Figure 4 According to the process flow chart of the continuous extraction and separation of supercritical CO2 using five towers in an embodiment of the present invention, 1, 2, 3, 4, and 5 represent compressor boost valves, 6, 7, 8, 9, and 10 represent pressure equalizing valves between extraction kettles, 11, 12, 13, 14, and 15 represent connecting valves between the extraction kettle and the separator, 16, 17, 18, 19, and 20 represent connecting valves between the extraction kettle and the CO2 recovery tank, and 21, 22, 23, 24, 25, 26, and 27 represent extraction kettle vent valves.

[0065] Figure 5 According to the process flow chart of the continuous extraction and separation of supercritical CO2 using six towers in accordance with an embodiment of the present invention, 1, 2, 3, 4, 5, and 6 represent compressor boost valves, 7, 8, and 9 represent pressure equalizing valves between extraction kettles, 10, 11, 12, 13, 14, and 15 represent connecting valves between the extraction kettle and the separator, 16, 17, 18, 19, 20, and 21 represent connecting valves between the extraction kettle and the CO2 recovery tank, and 22, 23, 24, 25, 26, 27, 28, and 29 represent extraction kettle vent valves. DETAILED DESCRIPTION

[0066] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the following embodiments and accompanying drawings. These embodiments and accompanying drawings are intended only to illustrate the present invention and are not intended to limit the present invention in any way. The actual scope of protection of the present invention is set forth in the claims.

[0067] It should be noted that the present invention Figures 2 to 5In the text, the "boost valve" refers to the valve connecting the compressor and the extraction device. Opening the valve allows the supercritical CO2 fluid introduced through the compressor to enter the extraction device, thereby increasing the pressure of the extraction device. The "equalizing valve" refers to the valve connecting two extraction devices. Opening the valve allows one of the extraction devices to reduce pressure and the other extraction device to increase pressure, so that the pressures of the two connected extraction devices are the same, that is, "equalizing pressure" is achieved. The "vent valve" refers to an ordinary valve that can evacuate pressurized gas or liquid in a non-working state. For example, after the extraction device completes the extraction and / or equalizing and reducing pressure operations, opening the vent valve connected to the extraction device can directly and completely vent the pressure in the extraction device. The above-mentioned valves in the present invention can all be conventional valves in the field, and are not specifically limited here.

[0068] It should be noted that "pressure equalization" as used in the present invention refers to connecting two extraction kettles via a pressure equalizing valve, using the CO2 pressure reduction in one extraction kettle to increase the CO2 pressure in the other extraction kettle, so that the pressures in the two connected extraction kettles are the same. For example, if extraction kettles A and C are connected, and the pressure reduction in extraction kettle A is used to increase the pressure in extraction kettle C, the pressure reduction in extraction kettle A is called "pressure equalization," and the pressure increase in extraction kettle C is called "pressure equalization."

[0069] The present invention provides a supercritical carbon dioxide continuous extraction and separation method, which comprises using multiple extraction devices and at least one separation tower to carry out loading, pressure increase, extraction and pressure reduction, wherein when one of the extraction devices is extracting, at least one extraction device is pressurized, and at the same time at least one extraction device is pressure reduced and / or loaded.

[0070] In the present invention, the number of the plurality of extraction devices is preferably 3 to 6, for example 3, 4, 5 or 6.

[0071] As a specific embodiment of the present invention, the method includes using three extraction kettles A, B and C, a separator and a CO2 recovery tank for loading / unloading, pressurization, extraction and pressure reduction. The process flow of the supercritical CO2 continuous extraction and separation using the three towers is as follows: Figure 2 As shown in the figure, during the extraction operation, the extraction kettle and the separation kettle are continuous, which is different from the traditional supercritical CO2 extraction process (such as Figure 1 The three-column combined supercritical CO2 continuous extraction and separation process consists of six steps: 1. Loading / unloading, 2. Pressure equalization and boosting, 3. Compressor boosting, 4. Extraction, 5. Pressure equalization and reduction, and 6. Pressure reduction to zero. The operation steps for each extraction reactor are shown in Table 1.

[0072] Table 1

[0073]

[0074] When extraction kettle A is extracting, the pressure of extraction kettle B is increased, and extraction kettle C is loaded and / or depressurized at the same time; when extraction kettle B is extracting, the pressure of extraction kettle C is increased, and extraction kettle A is depressurized and / or loaded at the same time; when extraction kettle C is extracting, the pressure of extraction kettle A is increased, and extraction kettle B is depressurized and / or loaded at the same time.

[0075] Preferably, the operation of the continuous extraction and separation of supercritical CO2 using the three towers is as follows:

[0076] When the device is turned on for the first time and the extraction kettle A is charged (step 1), the boost valve 1 is opened, and the compressor compresses the continuous CO2 flow to the operating pressure of the extraction kettle (step 3, since the B kettle has not started running at this time, the pressure equalization cannot be carried out temporarily) and passes it into the extraction kettle A. At this time, the connecting valve 7 is opened to connect the separator with the extraction kettle A and control its pressure value to be lower than a certain pressure of the extraction kettle. At the end of the pressure increase of kettle A, kettle B starts to be charged (step 1), and the pressure increase of kettle A and the charging of kettle B are completed at the same time. Immediately afterwards, kettle A starts to extract, and the separator starts to extract paraffin and water continuously (step 4). At the same time, the boost valve 2 is opened and kettle B starts to be pressurized (step 3). At the end of the extraction of kettle A and the pressure increase of kettle B, kettle C starts to be charged (step 1). A still extracts, B still boosts, and C still charges and finishes simultaneously. Then A still starts to depressurize, B still starts to extract (step 4), and C still starts to boost. Now, open the equalizing valve 5 between A still and C still, depressurize A still (step 5) and realize the boost of C still (step 2) simultaneously. When A and C two stills have the same pressure, close A and C equalizing valve 5, and the equalizing pressure depressurization of A still and the equalizing pressure boost of C still finish synchronously. Open the connecting valve 10 of extraction still A and CO2 recovery tank, so that A still continues to depressurize (step 6). Meanwhile, open boosting valve 3, and C still continues to carry out compressor boost to extraction pressure (step 3). When A still is the same as CO2 recovery tank pressure, close the connecting valve 10 between them, open A still vent valve 13, make its pressure thoroughly vent, after A still is depressurized to 0, start unloading, and recharge (step 1). A still charges (step 1), B still extracts (step 4), and C still boosts (step 3) and completes synchronously. Then, open the equalizing valve 4 between B still and A still, make B still reduce pressure (step 5), A still boost (step 2), while C still starts extraction (step 4).After pressure equalization is completed, close A, B equalizing valve 4, B still continues pressure reduction (step 6), and A still starts compressor boost (step 3). After B still is depressurized to 0, start unloading, charging (step 1). The compressor boost (step 3) of A still, the charging (step 1) of B still, the extraction (step 4) of C still are completed synchronously. Now, A still enters extraction process (step 4), and B, C still realize equalizing pressure by opening equalizing valve 6. After the pressure equalization of B, C still ends, B still continues compression boost (step 3), and C still continues pressure reduction (step 6), unloading, charging (step 1). The extraction of kettle A, the pressure increase of kettle B and the loading of kettle C are completed simultaneously, followed by the extraction of kettle B (step 4), the pressure equalization of kettles A and C, and the cycle continues.

[0077] As a specific embodiment of the present invention, the method includes using four extraction kettles A, B, C and D, a separator and a CO2 recovery tank for loading / unloading, pressurization, extraction and pressure reduction. The process flow of the four-tower combined supercritical CO2 continuous extraction and separation is as follows: Figure 3As shown in Table 2, the extraction separation process is divided into 6 steps: 1. loading / unloading, 2. equalizing pressure and increasing pressure, 3. compressor pressure increasing, 4. extraction, 5. equalizing pressure and decreasing pressure, 6. decreasing pressure to 0. The step operation of each extraction kettle is shown in Table 2.

[0078] Table 2

[0079]

[0080]

[0081] When extraction kettle A is extracting, the pressure of extraction kettle B is increased, and at the same time, extraction kettle C is loaded / unloaded and / or depressurized, and extraction kettle D is depressurized; when extraction kettle B is extracting, the pressure of extraction kettle A is depressurized, and at the same time, extraction kettle C is increased, and extraction kettle D is loaded / unloaded and / or depressurized; when extraction kettle C is extracting, the pressure of extraction kettle A is depressurized and / or loaded / unloaded, and at the same time, extraction kettle B is depressurized and extraction kettle D is increased; when extraction kettle D is extracting, the pressure of extraction kettle A is increased, and at the same time, extraction kettle B is depressurized and / or loaded / unloaded, and extraction kettle C is depressurized.

[0082] Preferably, the operation of the above four-tower combined supercritical CO2 continuous extraction and separation is as follows:

[0083] When the device is turned on for the first time and the extraction kettle A is charged (step 1), the boost valve 1 is opened, and the compressor compresses the continuous CO2 flow to the operating pressure of the extraction kettle (step 3, since the B kettle has not started running at this time, the pressure equalization cannot be carried out temporarily) and passes it into the extraction kettle A. At this time, the connecting valve 7 is opened to connect the separator with the extraction kettle A and control its pressure value to be lower than a certain pressure of the extraction kettle. At the end of the pressure increase of kettle A, kettle B starts to be charged (step 1), and the pressure increase of kettle A and the charging of kettle B are completed at the same time. Immediately afterwards, kettle A starts to extract, and the separator starts to extract paraffin and water continuously (step 4). At the same time, the boost valve 2 is opened and kettle B starts to be pressurized (step 3). At the end of the extraction of kettle A and the pressure increase of kettle B, kettle C starts to be charged (step 1). A still extraction, B still boost, C still charging end simultaneously, immediately followed by A still start depressurization, B still starts extraction (step 4), C still starts boosting, now open the equalizing valve 5 between A still and C still, A still is depressurized (step 5) and realizes the boosting (step 2) of C still simultaneously. When A, C two still pressures are identical, close A, C equalizing valve 5, the equalizing pressure depressurization of A still and the equalizing pressure boosting of C still end synchronously. Open the connecting valve 11 of extraction still A and CO2 recovery tank, A still is continued depressurization (step 6). Meanwhile, open boosting valve 3, C still proceeds to compressor boost to extraction pressure (step 3), D still starts charging (step 1), B still extraction, C still compressor boost, D still charging end simultaneously. Open the equalizing valve 6 of B still and D still, B still is depressurized and realizes the boosting of D still simultaneously, C still extracts. When the pressure of A kettle is the same as that of CO2 recovery tank, close the connecting valve 11 between them, then open the A kettle vent valve 15 to completely vent its pressure, and the venting of A kettle, the pressure reduction of B kettle, and the pressure increase of D kettle are completed simultaneously. Immediately afterwards, A kettle starts to unload and reload, and B kettle starts to reduce pressure (step 6), and D kettle starts compressor boost (step 3). A kettle is loaded, C kettle is extracted, and D kettle is boosted and ends simultaneously. Open the equalizing valve 5 between A kettle and C kettle again, so that A kettle and C kettle are achieved. D kettle starts to extract. A kettle, C kettle are equalized and B kettle is depressurized and completed simultaneously, and A kettle enters the compressor boost stage (step 3), B kettle is unloaded, loaded, and C kettle continues to reduce pressure. A kettle is boosted, B kettle is loaded, and D kettle extracts and ends simultaneously. A kettle enters the extraction stage, and pressure is equalized between B kettle and D kettle. This equalizing process ends simultaneously with the pressure reduction of C kettle. Then, kettle C enters the unloading / loading stage, kettle B continues to increase the pressure by the compressor, and kettle C continues to reduce the pressure, and the cycle continues.

[0084] As another specific embodiment of the present invention, the method includes using five extraction kettles A, B, C, D and E, a separator and a CO2 recovery tank to load / unload, increase pressure, extract and reduce pressure. The process flow of the five-tower combined supercritical CO2 continuous extraction and separation is as follows: Figure 4As shown in Table 3, the extraction separation process is divided into 6 steps: 1. loading / unloading, 2. equalizing pressure and increasing pressure, 3. compressor pressure increasing, 4. extraction, 5. equalizing pressure and decreasing pressure, 6. decreasing pressure to 0. The step operation of each extraction kettle is shown in Table 3.

[0085] Table 3

[0086]

[0087] When extraction kettle A is extracting, the pressure of extraction kettle B and extraction kettle C is increased, and extraction kettle D is loaded / unloaded and / or depressurized, and extraction kettle E is depressurized; when extraction kettle B is extracting, the pressure of extraction kettle A is depressurized, and extraction kettle C and extraction kettle D are increased, and extraction kettle E is loaded / unloaded and / or depressurized; when extraction kettle C is extracting, the pressure of extraction kettle A is decreased and / or loaded / unloaded, and extraction kettle B is depressurized, and extraction kettle D and extraction kettle E are increased; when extraction kettle D is extracting, the pressure of extraction kettle A is increased, extraction kettle B is depressurized and / or loaded / unloaded, extraction kettle C is depressurized, and extraction kettle E is increased; when extraction kettle E is extracting, the pressure of extraction kettle A and extraction kettle B is increased, extraction kettle C is loaded / unloaded and / or depressurized, and extraction kettle D is depressurized.

[0088] As another specific embodiment of the present invention, the method includes using six extraction kettles A, B, C, D, E and F, a separator and a CO2 recovery tank to load / unload, increase pressure, extract and reduce pressure. The process flow of the six-tower combined supercritical CO2 continuous extraction and separation is as follows: Figure 5 As shown in Table 4, the extraction separation process is divided into 6 steps: 1. loading / unloading, 2. equalizing pressure and increasing pressure, 3. compressor pressure increasing, 4. extraction, 5. equalizing pressure and decreasing pressure, 6. decreasing pressure to 0. The step operation of each extraction kettle is shown in Table 4.

[0089] Table 4

[0090]

[0091] When extraction kettle A is extracting, the pressure of extraction kettles B and extraction kettle C is increased, and extraction kettle D is loaded / unloaded and / or depressurized, and extraction kettles E and extraction kettle F are depressurized; when extraction kettle B is extracting, the pressure of extraction kettles A and extraction kettle F is depressurized, and extraction kettle D and extraction kettle C are increased, and extraction kettle E is loaded / unloaded and / or depressurized; when extraction kettle C is extracting, the pressure of extraction kettles A and extraction kettle B is decreased, and extraction kettle D and extraction kettle E are increased, and extraction kettle F is depressurized and / or loaded / unloaded; when extraction kettle D is extracting, the pressure of extraction kettle A is decreased and / or loaded / unloaded, extraction kettle B and extraction kettle C are decreased, and extraction kettle E and extraction kettle F are increased; when extraction kettle E is extracting, the pressure of extraction kettles A and extraction kettle F is increased, extraction kettle B is loaded / unloaded and / or depressurized, and extraction kettle C and extraction kettle D are depressurized; when extraction kettle F is extracting, the pressure of extraction kettles A and extraction kettle B is increased, extraction kettle C is decreased and / or loaded / unloaded, and extraction kettle E and extraction kettle D are depressurized.

[0092] Example 1

[0093] This embodiment provides a method for continuous extraction and separation of supercritical CO2 using three towers. The material used is PTFE waste residue containing paraffin (containing 10.04% wax and 14.03% water). The specific operation of extraction and separation is as follows:

[0094] 15 kg of PTFE waste residue was loaded into Extraction Vessel A. A high-pressure pump continuously introduced CO2 into Extraction Vessel A, and pressure was increased. The final conditions for the extraction vessel were set to 30 MPa, 65°C, and 300 L / h. The separator was now connected to Extraction Vessel A, and the set conditions were 60°C and 6 MPa. At the end of the pressure increase in Vessel A, 15 kg of PTFE waste residue was loaded into Extraction Vessel B. The pressure increase in Vessel A and the loading of Vessel B were completed simultaneously. Once the extraction and separation vessels reached the set conditions, the separator valve was opened, and extraction began in Vessel A. Paraffin wax and liquid CO2 continuously flowed out of the separator (this CO2 was purified and recycled in the recovery system). Meanwhile, Vessel B was in the high-pressure pump-increased stage (30 MPa, 65°C, and 300 L / h). At the end of the extraction in Vessel A and the pressure increase in Vessel B, 15 kg of PTFE waste residue was loaded into Extraction Vessel C. The extraction in Vessel A (3 hours), the pressure increase in Vessel B, and the loading of Vessel C were completed simultaneously. Open the equalizing valves between Kettles A and C, where extraction has concluded, to reduce the pressure in Kettle A while simultaneously increasing the pressure in Kettle C. Simultaneously, connect Kettle B to the separator and begin extraction in Kettle B. When the pressures in Kettles A and C are the same (approximately 15 MPa), close the equalizing valves and open the valve connecting Kettle A to the CO2 recovery tank (the recovery tank is at room temperature and approximately 3 MPa; the CO2 is recovered and purified for recycling). Continue reducing the pressure in Kettle A while simultaneously increasing the pressure in Kettle C using the high-pressure pump (30 MPa, 65°C, 300 L / h). When the pressures in Kettles A and C are the same, close the connecting valve and open the vent valve in Kettle A to completely vent the pressure. Once Kettle A's pressure drops to zero, begin unloading and reloading. Loading Kettle A, extracting Kettle B (for 3 hours), and increasing the pressure in Kettle C are completed simultaneously. Open the equalizing valves between Kettles B and A to reduce the pressure in Kettle B and increase the pressure in Kettle A, while simultaneously beginning extraction in Kettle C. After the pressure equalization is completed, close the A and B pressure equalizing valves, and the B kettle continues to reduce the pressure, and the A kettle starts to increase the pressure with the high-pressure pump. When the pressure of the B kettle is reduced to 0, unloading and loading begin. The A kettle high-pressure pump increases the pressure, the B kettle is loaded, and the C kettle extraction (3 hours) is completed simultaneously. The A kettle enters the extraction process again, and the B and C kettles achieve pressure equalization through the pressure equalizing valve. After the pressure equalization of the B and C kettles is completed, the B kettle continues to compress and increase the pressure, and the C kettle continues to reduce the pressure, unload, and load. The extraction (3 hours) of the A kettle and the pressure increase of the B kettle and the loading of the C kettle are completed simultaneously, followed by the extraction of the B kettle again and the pressure equalization of the A kettle and the C kettle, and so on.

[0095] The steps of each extraction kettle are shown in Table 5 below:

[0096] Table 5

[0097]

[0098] Paraffin wax was continuously discharged from the separation kettle in a columnar form. Sampling and analysis revealed a paraffin purity of 99.2% and a water content of 0.52%. The PTFE material discharged from the extraction kettle appeared as a loose white powder. Sampling and analysis revealed a paraffin content of 0.04% and a water content of 0.03%. After the cycle began, 45 kg of material was processed in 9 hours.

[0099] Example 2

[0100] This embodiment provides a method for continuous extraction and separation of supercritical CO2 using three towers. The material used is PTFE waste residue containing paraffin (containing 22.15% wax and 10.52% water). The specific operation of extraction and separation is as follows:

[0101] 12 kg of PTFE waste residue was loaded into Extraction Vessel A. A high-pressure pump continuously introduced CO2 into Extraction Vessel A, and pressure was increased. The final conditions of the extraction vessel were set to 25 MPa, 75°C, and 400 L / h. The separator was now connected to Extraction Vessel A, and the set conditions were 50°C and 5 MPa. At the end of the pressure increase in Vessel A, 12 kg of PTFE waste residue was loaded into Extraction Vessel B. The pressure increase in Vessel A and the loading of Vessel B were completed simultaneously. Once the extraction and separation vessels reached the set conditions, the separator valve was opened, and extraction began in Vessel A. Paraffin wax and liquid CO2 continuously flowed out of the separator (this CO2 was purified and recycled in the recovery system). Meanwhile, Vessel B was in the high-pressure pump pressure increase phase (25 MPa, 75°C, and 400 L / h). At the end of the extraction in Vessel A and the pressure increase in Vessel B, 12 kg of PTFE waste residue was loaded into Extraction Vessel C. The extraction in Vessel A (4 hours), the pressure increase in Vessel B, and the loading of Vessel C were completed simultaneously. Open the equalizing valves between Kettles A and C, where extraction has concluded, to reduce the pressure in Kettle A while simultaneously increasing the pressure in Kettle C. Simultaneously, connect Kettle B to the separator and begin extraction in Kettle B. When the pressures in Kettles A and C are the same (approximately 12.5 MPa), close the equalizing valves and open the valve connecting Kettle A to the CO2 recovery tank (the recovery tank is at room temperature and approximately 3 MPa; the CO2 is recovered and purified for recycling). Continue reducing the pressure in Kettle A while simultaneously increasing the pressure in Kettle C using the high-pressure pump (25 MPa, 75°C, 400 L / h). When the pressures in Kettles A and C are the same, close the connecting valve and open the vent valve in Kettle A to completely vent the pressure. Once Kettle A's pressure drops to zero, begin unloading and reloading. Loading Kettle A, extracting Kettle B (4 hours), and increasing the pressure in Kettle C are completed simultaneously. Open the equalizing valves between Kettles B and A to reduce the pressure in Kettle B and increase the pressure in Kettle A. Simultaneously, begin extraction in Kettle C. After the pressure equalization is completed, close the A and B pressure equalizing valves, and the B kettle continues to reduce the pressure, and the A kettle starts to increase the pressure with the high-pressure pump. When the pressure of the B kettle is reduced to 0, unloading and loading begin. The A kettle high-pressure pump increases the pressure, the B kettle is loaded, and the C kettle is extracted (4 hours) and completed simultaneously. The A kettle enters the extraction process again, while the B and C kettles achieve pressure equalization through the pressure equalizing valve. After the pressure equalization of the B and C kettles is completed, the B kettle continues to compress and increase the pressure, and the C kettle continues to reduce the pressure, unload, and load. The extraction (4 hours) of the A kettle and the pressure increase of the B kettle and the loading of the C kettle are completed simultaneously, followed by the extraction of the B kettle again and the pressure equalization of the A kettle and the C kettle, and so on.

[0102] The operation steps of each extraction kettle are shown in Table 6.

[0103] Table 6

[0104]

[0105]

[0106] Paraffin wax was continuously discharged from the separation kettle in a columnar form. Sampling and analysis revealed a paraffin purity of 99.5% and a water content of 0.47%. The PTFE material discharged from the extraction kettle appeared as a loose white powder. Sampling and analysis revealed a paraffin content of 0.02% and a water content of 0.05%. After the cycle began, 36 kg of material was processed in 12 hours.

[0107] Example 3

[0108] This embodiment provides a method for continuous extraction and separation using supercritical CO2 in a four-tower combination. The material used is paraffin-containing PTFE waste residue (containing 10.04% wax and 14.03% water). The specific operation of the extraction and separation is as follows:

[0109] 15 kg of PTFE waste slag is loaded into Extraction Vessel A. A high-pressure pump continuously introduces CO2 into Extraction Vessel A, and pressure increases are initiated, setting the final conditions for the extraction vessel to 30 MPa, 65°C, and 300 L / h. The separator is now connected to Extraction Vessel A, and the set conditions are 60°C and 6 MPa. At the end of the pressure increase in Vessel A, 15 kg of PTFE waste slag is loaded into Extraction Vessel B. The pressure increase in Vessel A and the loading of Vessel B are completed simultaneously. Once the extraction and separation vessels reach the set conditions, the separator valve is opened, and extraction begins in Vessel A. Paraffin wax and liquid CO2 continuously flow out of the separator (this CO2 is purified and recycled in the recovery system). Meanwhile, Vessel B is in the high-pressure pump pressure increase phase (30 MPa, 65°C, and 300 L / h). At the end of the extraction in Vessel A and the pressure increase in Vessel B, 15 kg of PTFE waste slag is loaded into Extraction Vessel C. The extraction in Vessel A (3 hours), the pressure increase in Vessel B, and the loading of Vessel C are completed simultaneously. Open the equalizing valves between Kettles A and C, where extraction has concluded, to reduce the pressure in Kettle A while simultaneously increasing the pressure in Kettle C. Simultaneously, connect Kettle B to the separator, and Kettle B begins extraction. When the pressures in Kettles A and C are the same (approximately 15 MPa), close the equalizing valves. Open the valve connecting Kettle A to the CO2 recovery tank (the recovery tank is at room temperature and approximately 3 MPa; the CO2 is recovered and purified for recycling), allowing Kettle A to continue to reduce its pressure. Simultaneously, Kettle C continues to increase its pressure using the high-pressure pump (30 MPa, 65°C, 300 L / h). Begin loading Kettle D (15 kg). The extraction in Kettle B, the compressor pressure increase in Kettle C, and the loading of Kettle D are simultaneously completed. Open the equalizing valves between Kettles B and D, reducing the pressure in Kettle B while simultaneously increasing the pressure in Kettle D. When the pressures in Kettle A and the CO2 recovery tank are the same, close the connecting valve between them and open the vent valve in Kettle A to completely vent it. This completes the venting of Kettle A and the equalization of pressures in Kettle B and D simultaneously. Then, Kettle A begins to unload and reload, Kettle B begins to reduce pressure (15→3→0MPa), and Kettle D begins to increase pressure with the high-pressure pump. The loading of Kettle A, the extraction of Kettle C, and the pressure increase of Kettle D end simultaneously. Kettles A and C begin to equalize pressure, and Kettle D begins to extract. The equalization of pressures in A and C and the reduction of pressure in Kettle B are completed simultaneously, and Kettle A enters the high-pressure pump pressure increase stage, Kettle B unloads and loads, and Kettle C continues to reduce pressure. The pressure increase of Kettle A, the loading of Kettle B, and the extraction of Kettle D end simultaneously. Kettle A enters the extraction stage, and the pressure equalization between Kettles B and D begins, and the pressure equalization process ends simultaneously with the pressure reduction of Kettle C. Then, Kettle C enters the unloading and loading stage, Kettle B continues to increase pressure with the high-pressure pump, and Kettle C continues to reduce pressure, and the cycle continues.

[0110] The steps of each extraction kettle are shown in Table 7 below:

[0111] Table 7

[0112]

[0113] Paraffin wax was continuously discharged from the separation kettle in a columnar form. Sampling and analysis revealed a paraffin purity of 99.2% and a water content of 0.53%. The PTFE material discharged from the extraction kettle appeared as a loose white powder. Sampling and analysis revealed a paraffin content of 0.04% and a water content of 0.04%. After the cycle began, 60 kg of material was processed in 12 hours.

[0114] Example 4

[0115] This embodiment provides a method for continuous extraction and separation using supercritical CO2 in a five-tower combination. The material used is paraffin-containing PTFE waste residue (containing 10.04% wax and 14.03% water). The specific operation of the extraction and separation is as follows:

[0116] 15 kg of PTFE waste slag was loaded into Extraction Reactor A. A high-pressure pump continuously introduced CO2 into Extraction Reactor A, and the pressure began to increase. The final conditions of the extraction reactor were set to: 30 MPa, 65°C, and 300 L / h. The separator was now connected to Extraction Reactor A, and the set conditions were: 60°C, 6 MPa. While the pressure of Extraction Reactor A was increasing, 15 kg of PTFE waste slag was loaded into Extraction Reactor B, and the pressure began to increase. At the end of the pressure increase of Extraction Reactor A and while the pressure of Extraction Reactor B was increasing, Extraction Reactor C began to be loaded (15 kg). The pressure increase of Extraction Reactor A and the loading of Extraction Reactor C were completed simultaneously. At this time, the separator valve was opened, and Extraction Reactor A began to extract. Paraffin wax and liquid CO2 continuously flowed out of the separator (this CO2 was purified and recycled by the recovery system). The high-pressure pump for Extraction Reactor C began to increase the pressure (30 MPa, 65°C, and 300 L / h). At the end of the extraction of Extraction Reactor A and the pressure increase of Extraction Reactor B, and while the pressure of Extraction Reactor C was increasing, Extraction Reactor D began to be loaded (15 kg). The extraction (3 hours) in Kettle A, the pressure increase in Kettle B, and the loading of Kettle D are completed simultaneously. The pressure-equalizing valves of Kettles A and D, which have completed extraction, are opened to reduce the pressure in Kettle A while simultaneously increasing the pressure in Kettle D. Simultaneously, Kettle B is connected to the separator, and Kettle B begins extraction. At the end of the pressure-equalizing phases in Kettles A and D, the extraction in Kettle B, and the pressure increase in Kettle C, the loading of Kettle E (15 kg) begins. When the pressures in Kettles A and D are the same (approximately 15 MPa), the pressure-equalizing valves in Kettles A and C are closed, and the connecting valve between Kettle A and the CO2 recovery tank (the recovery tank is at room temperature and has a pressure of approximately 3 MPa; the CO2 is recycled and purified) is opened. Kettle A continues to reduce its pressure, while Kettle D continues to increase its pressure with the high-pressure pump (30 MPa, 65°C, 300 L / h). The extraction (3 hours) in Kettle B, the pressure increase in Kettle C, and the loading of Kettle E are completed simultaneously. Kettles B and E begin to equalize their pressures, and Kettle C enters the extraction phase. When the pressure in Kettle A and the CO2 recovery tank is the same, close the connecting valve between them and open Kettle A's vent valve to completely vent the pressure. Once Kettle A is vented, it is unloaded and reloaded. After pressure equalization is completed between Kettles B and E, Kettle B continues to reduce pressure while Kettle E's high-pressure pump increases pressure. Loading Kettle A, extraction in Kettle C, and pressure increase in Kettle D are completed simultaneously. Kettles A and C begin pressure equalization, and Kettle D begins extraction. After Kettle B is completely depressurized, unloading and loading begin. After pressure equalization is completed between Kettle A and C, Kettle A continues to increase pressure with its high-pressure pump, while Kettle C continues to reduce pressure. Loading Kettle B, extraction in Kettle D, and pressure increase in Kettle E are completed simultaneously. Open the pressure equalization valves between Kettles B and D to equalize the pressures between the two, and Kettle E enters the extraction stage. After pressure reduction is completed, Kettle C enters the unloading and loading stages. After pressure equalization is completed between Kettle B and D, the high-pressure pump between Kettle B increases pressure while Kettle D continues to reduce pressure. Pressure increase in Kettle A, loading in Kettle C, and extraction in Kettle E are completed simultaneously. Pressure equalization between Kettle C and E begins, and Kettle A begins extraction again, repeating the cycle.

[0117] The operation steps of each extraction kettle are shown in Table 8 below.

[0118] Table 8

[0119]

[0120]

[0121] Paraffin wax was continuously discharged from the separation kettle in a columnar form. Sampling and analysis revealed a paraffin purity of 99.6% and a water content of 0.36%. The PTFE material discharged from the extraction kettle appeared as a loose white powder. Sampling and analysis revealed a paraffin content of 0.03% and a water content of 0.05%. After the cycle began, 75 kg of material was processed in 15 hours.

[0122] Comparative Example 1

[0123] This comparative example provides a method for continuous extraction and separation of supercritical CO2 using a double-tower combination. The material used is PTFE waste residue containing paraffin (containing 10.04% wax and 14.03% water). The specific operation of extraction and separation is as follows:

[0124] Extraction vessel A is loaded with 15 kg of PTFE waste residue (for 1 hour). A high-pressure pump continuously introduces CO2 into extraction vessel A, starting to increase the pressure. The final conditions of the extraction vessel are set to 30 MPa, 65°C, and 300 L / h. The separator is now connected to extraction vessel A, and the set conditions are 60°C and 6 MPa. Once the extraction and separation vessels reach the set conditions (2 hours), the separator valve is opened, and extraction begins in vessel A. Paraffin wax and liquid CO2 continuously flow out of the separator (this CO2 is purified and recycled in the recovery system). After 2 hours of extraction, 15 kg of PTFE waste residue is loaded into vessel B (for 1 hour). The extraction of vessel A (3 hours) and the loading of vessel B are completed simultaneously. Open the equalizing valves between kettles A and B, reducing the pressure in kettle A while simultaneously increasing the pressure in kettle B. When the pressures in kettles A and B are the same (approximately 15 MPa), close the equalizing valve and open the valve connecting kettle A to the CO2 recovery tank (the recovery tank is at room temperature and has a pressure of approximately 3 MPa; the CO2 is recovered and purified for recycling). Continue to reduce the pressure in kettle A. Simultaneously, continue to increase the pressure in kettle B using the high-pressure pump (30 MPa, 65°C, 300 L / h). After increasing the pressure for 1 hour, kettle B is connected to the separator and enters the extraction state (3 hours). When the pressures in kettles A and the CO2 recovery tank are the same, close the connecting valve between them and open the vent valve in kettle A to completely vent the pressure. After kettle A's pressure drops to 0 (3 hours), begin unloading and reloading. The loading of kettle A and the extraction of kettle B are completed at the same time. The pressure of the two kettles is equalized again (1 hour). After the equalization is completed, kettle A enters the compressor pressure increase stage (1 hour) and the extraction stage (3 hours). Kettle B enters the pressure reduction stage (the pressure reduction process is the same as that of kettle A, 3 hours). The materials are unloaded and reloaded. The extraction of kettle A and the loading of kettle B are completed simultaneously. The cycle continues.

[0125] The operation steps of each extraction kettle are shown in Table 9.

[0126] Table 9

[0127]

[0128]

[0129] Paraffin wax was continuously discharged from the separation kettle in a columnar form. Sampling and analysis revealed a paraffin purity of 99.1% and a water content of 0.49%. The PTFE material discharged from the extraction kettle appeared as a loose white powder. Sampling and analysis revealed a paraffin content of 0.05% and a water content of 0.05%. After the cycle began, since there were only two extraction kettles, to achieve pressure balance between them, there was a period of time when neither kettle was in the extraction state. This prevented the two-tank operation from achieving a true process cycle (one kettle was always in the extraction phase), significantly reducing extraction efficiency, and only 30 kg of material could be processed in 10 hours.

[0130] Comparative Example 2

[0131] This comparative example provides a method for supercritical CO2 extraction and separation in a single extraction kettle. The material used is PTFE waste residue containing paraffin (containing 10.04% wax and 14.03% water). The specific operation of extraction and separation is as follows:

[0132] 15 kg of paraffin-containing PTFE waste was added to an extraction kettle. A high-pressure pump continuously introduced CO2 into the extraction kettle. The extraction kettle was set at 30 MPa, 65°C, and 300 L / h. The extraction kettle was connected to a separator, and the separator was set at 60°C and 6 MPa. The operating steps are shown in Table 10.

[0133] Finish to spend 3.5 hours altogether from loading and unloading to boosting, after extraction starts, paraffin is discharged in a continuous column from separating still, sampling and analysis, paraffin purity is 99.0%, and water content is 0.48%, recycles after reclaiming carbon dioxide system reclaiming purification, stops feeding supercritical CO after 3 hours , in addition with 2.5 hours with CO in the still emptying (first discharge to CO recovery tank, recovery tank pressure is about 3MPa, this CO can be recycled after reclaiming purification). The PTFE material outward appearance of unloading in the extraction still is white loose powder, sampling and analysis, paraffin content is 0.06%, and water-content is 0.04%. Process 15kg material in 9 hours, extraction efficiency is far not as good as 2-6 still operation, and extraction still boosts and relies entirely on compressor, does not have pressure-equalizing mode between still, and CO recovery and utilization degree is also not as good as multi-still operation.

[0134] Table 10

[0135]

[0136] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A supercritical CO2 continuous extraction and separation method, comprising using multiple extraction devices and at least one separation tower to perform loading, pressurization, extraction, and pressure reduction. in, When one of the extraction devices is extracting, at least one extraction device is pressurized at the same time, and at least one extraction device is depressurized and / or loaded at the same time.

2. The method according to claim 1, characterized in that The number of the multiple extraction devices is 3 to 6.

3. The method according to claim 2, characterized in that The multiple extraction devices include extraction devices A, B and C, wherein when extraction device A is extracting, the pressure of extraction device B is increased, and extraction device C is loaded and / or depressurized; when extraction device B is extracting, the pressure of extraction device C is increased, and extraction device A is depressurized and / or loaded; when extraction device C is extracting, the pressure of extraction device A is increased, and extraction device B is depressurized and / or loaded.

4. The method according to claim 3, characterized in that The extraction in the extraction device A starts simultaneously with the pressure increase in the extraction device B and the pressure decrease in the extraction device C, and / or the extraction in the extraction device A ends simultaneously with the pressure increase in the extraction device B and the loading of the extraction device C.

5. The method according to claim 4, characterized in that The extraction in the extraction device B starts simultaneously with the depressurization of the extraction device A and the pressure increase of the extraction device C, and / or the extraction in the extraction device B ends simultaneously with the pressure increase of the extraction device C and the charging of the extraction device A.

6. The method according to claim 4, characterized in that The extraction in the extraction device C starts simultaneously with the pressure increase in the extraction device A and the pressure decrease in the extraction device B, and / or the extraction in the extraction device C ends simultaneously with the pressure increase in the extraction device A and the loading of the extraction device B.

7. The method according to any one of claims 1 to 6, characterized in that The pressure increase includes introducing a supercritical CO2 flow into the extraction device at the end of loading to increase the pressure of the extraction device to the extraction pressure, and / or connecting the extraction device at the end of loading with the extraction device at the end of extraction to increase the pressure of the extraction device at the end of loading to the same pressure as that of the extraction device at the end of extraction.

8. The method according to any one of claims 1 to 6, characterized in that The depressurization comprises the steps of connecting the extraction device that has finished extraction with the extraction device that has finished loading, depressurizing the extraction device that has finished extraction to the same pressure as that of the extraction device that has finished loading, and further depressurizing the extraction device that has finished extraction to 0.

9. The method according to any one of claims 3 to 6, characterized in that When extraction device B starts extraction, extraction device A and extraction device C are connected, so that the pressure of extraction device A is reduced and the pressure of extraction device C is increased to the same pressure as extraction device A; and / or when extraction device C starts extraction, extraction device B and extraction device A are connected, so that the pressure of extraction device B is reduced and the pressure of extraction device A is increased to the same pressure as that of extraction device B; And / or when extraction device A starts extraction, extraction device C and extraction device B are connected, so that the pressure of extraction device C is reduced and the pressure of extraction device B is increased to the same as that of extraction device C.

10. The method according to any one of claims 3 to 6, comprising the following steps: (1) A CO2 flow is introduced into the extraction device A loaded with material to increase the pressure of the extraction device A to the extraction pressure. At the end of the pressure increase of the extraction device A, the extraction device B starts to be loaded with material, so that the pressure increase of the extraction device A and the loading of the extraction device B are completed at the same time; (2) Extraction device A is extracting, while CO2 flow is introduced into extraction device B to increase the pressure of extraction device B to the extraction pressure. At the end of extraction in extraction device A and the end of pressure increase in extraction device B, extraction device C starts to be loaded, and the extraction in extraction device A, pressure increase in extraction device B, and loading in extraction device C are completed at the same time; (3) Extraction device B is performing extraction, while extraction devices A and C are connected, so that the pressure of extraction device A is reduced, and the pressure of extraction device C is increased to the same pressure as that of extraction device A; (4) CO2 flow is introduced into the extraction device C to increase the pressure of the extraction device C to the extraction pressure. At the same time, the extraction device A continues to reduce the pressure to 0, then unloads and reloads, so that the loading of the extraction device A, the extraction of the extraction device B, and the pressure increase of the extraction device C are completed at the same time; (5) Extraction device C is performing extraction, while extraction devices B and A are connected, so that the pressure of extraction device B is reduced, and the pressure of extraction device A is increased to the same pressure as that of extraction device B; (6) CO2 flow is introduced into the extraction device A to increase the pressure of the extraction device A to the extraction pressure. At the same time, the extraction device B continues to reduce the pressure to 0, then unloads and reloads, so that the pressure of the extraction device A is increased, the extraction device B is loaded, and the extraction of the extraction device C is completed at the same time; (7) Extraction device A is performing extraction, while extraction devices B and C are connected, so that the pressure of extraction device C is reduced, and the pressure of extraction device B is increased to the same pressure as that of extraction device C; (8) A CO2 flow is introduced into the extraction device B to increase the pressure to the extraction pressure. At the same time, the extraction device C continues to reduce the pressure to 0, then unloads and reloads, so that the extraction of the extraction device A, the pressure increase of the extraction device B, and the loading of the extraction device C are completed at the same time.

11. The method according to claim 10, characterized in that The material comprises polytetrafluoroethylene containing paraffin wax.

12. The method according to any one of claims 1 to 6, characterized in that The flow rate of the supercritical CO2 is 250-600 L / h; and / or the pressure of the extraction is 20-40 MPa.

13. The method according to claim 12, characterized in that The flow rate of the supercritical CO2 is 300-400 L / h.

14. The method according to claim 12, characterized in that The extraction pressure is 25-30 MPa.

15. The method according to any one of claims 1 to 6, characterized in that The extraction temperature is 50-90° C.; and / or the extraction time is 2-6 hours.

16. The method according to claim 15, characterized in that The extraction temperature is 65-75°C.

17. The method according to claim 15, characterized in that The extraction time is 3 to 4 hours.

18. Use of the method according to any one of claims 1 to 17 in separating polytetrafluoroethylene and paraffin.

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