A multi-line guiding transcritical drying device and its drying method

Abstract

This application relates to the field of drying of nanomaterials, and particularly to a multi-line guiding transcritical drying device and its drying method. It includes a plunger booster pump, a preheater, a drying kettle, a separation kettle, and a circulating cooler. The plunger booster pump, the preheater, the drying kettle, the separation kettle, and the circulating cooler are sequentially connected to each other by pipelines. The drying kettle is internally provided with a material frame for placing the hollow sandwich plates to be dried, and a material cover is detachably connected to the material frame. An air inlet is opened at the bottom end of the drying kettle and is connected to the preheater through the air inlet. An air outlet is opened on the side wall of the drying kettle, and the opening height of the air outlet is greater than the height where the material cover is placed after installation. This application has the effect of improving the drying efficiency of the nano-porous thermal insulation material in the hollow sandwich plates.

Description

Technical Field

[0001] This application relates to the field of drying of nanomaterials, and particularly to a multi-line guiding transcritical drying device and a drying method thereof. Background Art

[0002] When the nanoporous thermal insulation material is not dried, it contains a large amount of solvents such as low molecular weight alcohols or ketones. Currently, the drying method for nanoporous thermal insulation materials is the supercritical drying method. The supercritical drying method is to place the nanoporous thermal insulation material to be dried in a drying kettle, and by controlling the internal pressure and temperature of the drying kettle, the solvent reaches its own critical point during the drying process, completing the supercritical transformation from liquid phase to gas phase.

[0003] With the development, the uses of nanoporous materials are more extensive. Refer to Figure 1 , which is a hollow sandwich panel with a sandwich structure. Specifically, metal plates or ceramic plates (metal plates are taken as an example in the figure) are arranged on both sides of the nanoporous thermal insulation material, and metal strips or ceramic strips for providing support strength are arranged between the two metal plates or ceramic plates. When the nanoporous thermal insulation material is dried by the supercritical drying method, the part of the nanoporous thermal insulation material exposed on the outside can be dried. However, due to the large overall area of the steel plate, the overflow of the solvent is restricted, and it will take a lot of time to dry the inside of the nanoporous thermal insulation material near the center. During the process, the internal pressure and temperature of the drying kettle need to be continuously controlled, resulting in low drying efficiency. Summary of the Invention

[0004] In order to improve the drying efficiency of the nanoporous thermal insulation material in the hollow sandwich panel, this application provides a multi-line guiding transcritical drying device and a drying method thereof.

[0005] In a first aspect, a multi-line guiding transcritical drying device provided by this application adopts the following technical solution:

[0006] A multi-line guiding transcritical drying device includes a plunger booster pump, a preheater, a drying kettle, a separation kettle, and a circulating cooler. The plunger booster pump, the preheater, the drying kettle, the separation kettle, and the circulating cooler are sequentially connected to each other through pipelines. A material frame for placing the hollow sandwich panel to be dried is arranged inside the drying kettle. A material cover is detachably connected to the material frame. An air inlet is opened at the bottom end of the drying kettle and is connected to the preheater through the air inlet. An air outlet is opened on the side wall of the drying kettle, and the opening height of the air outlet is greater than the height where the material cover is placed after installation.

[0007] By adopting the above technical solution, when it is necessary to dry the nano-porous thermal insulation material in the hollow sandwich panel, place the hollow sandwich panel in the material frame, then fix the lid of the material frame, place the material frame in the drying kettle, pre-open the circulating cooler, introduce liquid carbon dioxide into the plunger booster pump, pressurize the liquid carbon dioxide, and then introduce it into the preheater to heat up the liquid carbon dioxide to vaporize it into gaseous carbon dioxide. Then introduce the gaseous carbon dioxide into the drying kettle. Next, through the indirect heat exchange in the drying kettle, at this time, the cold solvent and the hot carbon dioxide gas are separated by the solid wall, flowing on one side respectively, and the heat is transferred from the hot carbon dioxide to the cold solvent through the solid wall for heat exchange. And the solvent and carbon dioxide form a miscible solution, and the carbon dioxide brings the solvent from the drying kettle into the separation kettle to separate the carbon dioxide and the solvent. Then, through the pre-opened circulating refrigerator for refrigeration, it is re-converted into carbon dioxide fluid, so that the carbon dioxide flows into the plunger booster pump again for secondary utilization. This cycle process is a process of one-time drying. The intermittent heat exchange and mutual solubility between the carbon dioxide gas and the solvent increase the fluidity of the solvent, thereby improving the drying efficiency.

[0008] Optionally, a pressure buffer assembly is connected to the air inlet of the drying kettle. One end of the pressure buffer assembly away from the air inlet is connected to one end of the pipeline away from the preheater. The pressure buffer assembly includes a plurality of spherical crowns installed at the air inlet and a buffer pipe passing through the plurality of spherical crowns at the same time. The plurality of spherical crowns are communicated with each other.

[0009] By adopting the above technical solution, before the carbon dioxide enters the drying kettle, it first enters the spherical crown for buffering. The shape of the spherical crown enables the carbon dioxide to enter the drying kettle at a reduced speed, and the plurality of spherical crowns are stacked, so as to achieve multiple buffering, thereby reducing the impact of sudden pressure changes on the nano-porous thermal insulation material.

[0010] Optionally, the diameter of the spherical crown decreases as the distance from the drying kettle increases.

[0011] By adopting the above technical solution, as the diameter of the spherical crown decreases, the movement area of the carbon dioxide gradually increases, so that the pressure buffering can be reduced along a stepped decrease, so that the pressure of the carbon dioxide can buffer the nano-porous thermal insulation material step by step, thereby further reducing the impact of sudden pressure changes on the nano-porous thermal insulation material.

[0012] Optionally, a plurality of reflux pipes are installed on the part of the buffer pipe placed in the spherical crown, and the plurality of reflux pipes are all inclined downward.

[0013] By adopting the above technical solution, during operation, carbon dioxide gas is introduced into the buffer tube. Since the density of carbon dioxide is less than that of air, the carbon dioxide gas overflows from multiple reflux tubes and then enters the drying kettle through the spherical crown body, shunting the high-pressure carbon dioxide gas, thereby reducing the impact of the high-pressure carbon dioxide gas on the nano-porous thermal insulation material at one time and causing damage.

[0014] Optionally, a tower-shaped guide column is arranged inside the material frame. The diameter of the tower-shaped guide column gradually decreases from near the bottom of the material frame to away from the bottom of the material frame, and air holes are formed at the bottom of the tower-shaped guide column.

[0015] By adopting the above technical solution, the setting of the tower-shaped guide column can prevent carbon dioxide from diffusing in the drying kettle and reduce the drying efficiency. The tower-shaped guide column gathers carbon dioxide gas into the material frame and transports it to the nano-porous thermal insulation material for heat exchange, thereby further improving the drying efficiency and making the drying effect better.

[0016] Optionally, a gas guide plate is arranged between the air inlet and the material frame. The gas guide plate includes a circular plate and a plurality of hollow plates connected to the outside of the circular plate. The hollow plates are also circular and concentric with the circular plate. The spaces between the plurality of hollow plates increase proportionally along the outside of the circular plate. A plurality of air-permeable holes are formed on both the circular plate and the hollow plates.

[0017] By adopting the above technical solution, the setting of the gas guide plate enables carbon dioxide gas to pass through the air-permeable holes of the gas guide plate, guides the carbon dioxide gas into the material frame, dries the nano-porous thermal insulation material in the hollow sandwich panel in the material frame, and guides the dried carbon dioxide gas around the hollow sandwich panel, thereby forming an orderly flow and improving the drying efficiency.

[0018] Optionally, the circular plate is folded from the axis of symmetry, the plurality of hollow plates are inclined, the inclination directions of adjacent two hollow plates are opposite, and both the folding angle of the circular plate and the connection angle of adjacent two hollow plates are obtuse angles.

[0019] By adopting the above technical solution, the folding setting of the gas guide plate enables carbon dioxide gas to be guided and flow in different directions, so that the carbon dioxide gas can flow not only in the same direction but also from all directions to the material frame, dissolve with the solvents everywhere, and thus can reduce the possibility of the generation of flow dead angles.

[0020] Optionally, the air holes at the bottom of the tower-shaped guide column and the air-permeable holes of the gas guide plate are in a normal distribution.

[0021] By adopting the above technical solution, since the outer side of the nano-porous heat insulation material is exposed to the outside and the inside is clamped by the steel plate on the outer side, the drying time required for the outer side and the inside is different. To ensure the drying efficiency, more air-permeable holes and air-passage holes in a normal distribution are opened inside and sparsely opened at the edge, thereby balancing the drying time required.

[0022] On the other hand, the present application also provides a multi-line guiding transcritical drying device and its drying method, including the following steps:

[0023] S1. Temperature measurement: Check whether the temperature of the drying kettle is lower than 25°C. If so, the kettle can be opened for drying; if the temperature is higher than 25°C, start the cold water pump and the cold circulation pump, turn on the refrigerator, and start the circulation of the chilled circulating water. Stop the circulation after the temperature reaches 25°C;

[0024] S2. Plate placement: After the drying kettle shows zero pressure, open the exhaust valve at the bottom of the drying kettle, so that the drying kettle is connected to the outside. Then tilt and vertically place the hollow sandwich panel into the material frame, fix the material frame and the material cover, and then lift the material frame and put it into the drying kettle, and close the drying kettle;

[0025] S3. Preparation: Start the cold water pump and the cold circulation pump, and turn on the refrigerator;

[0026] S4. Parameter setting: Set the pressure at the air outlet of the drying kettle to 8 - 20 MPa, the temperature to 35 - 60°C, set the pressure of the separation kettle to 3 - 7 MPa, the temperature to 30 - 50°C, set the temperature of the refrigerator to 5 - 20°C, and the temperature of the preheater to 30 - 50°C;

[0027] S5. Circulation: Adjust the frequency of the plunger booster pump to reciprocate within a certain range, so as to adjust the pressure in the drying kettle to reciprocate within a certain range and maintain for a certain period of time;

[0028] S6. Pressure relief: After the drying time reaches 40 - 200 h, turn off the plunger booster pump, and set the valve opening degrees of the two pneumatic valves before and after the drying kettle to 0;

[0029] S7. Unloading from the kettle: Open the exhaust valve of the drying kettle, press the kettle opening button. After the kettle cover is opened, lift the material frame out of the drying kettle.

[0030] By adopting the above technical solution, during drying, the temperature of the drying kettle is first detected to avoid the influence of excessive temperature in the drying kettle on subsequent drying after the previous cycle. Then, the hollow sandwich panel to be dried is placed in the material frame, and then the drying kettle is closed. Next, the refrigerator is turned on to prepare for the subsequent recycling of carbon dioxide. Then, by adjusting the frequency of the pump, it is easier for carbon dioxide to extract the solvent. After a period of time, the drying is completed, and the hollow sandwich panel can be taken out. The pressure and temperature of the carbon dioxide gas are changed at a certain frequency, making the extraction of the solvent faster and improving the drying efficiency.

[0031] Optionally, the frequency of the plunger booster pump is adjusted to reciprocate within a certain range, thereby adjusting the pressure in the drying kettle to reciprocate within a certain range and maintaining for a certain period of time, including the steps of: dividing the drying cycle into five stages. The first stage: the frequency of the plunger booster pump reciprocates between 5 - 25 Hz, so that the pressure in the drying kettle reciprocates between 9 - 16 MPa and maintains for 5 - 50 h; the second stage: the frequency of the plunger booster pump reciprocates between 10 - 35 Hz, so that the pressure in the drying kettle reciprocates between 9 - 18 MPa and maintains for 5 - 60 h; the third stage: the frequency of the plunger booster pump reciprocates between 15 - 50 Hz, so that the pressure in the drying kettle reciprocates between 9 - 20 MPa and maintains for 5 - 80 h; the fourth stage: the frequency of the plunger booster pump reciprocates between 10 - 30 Hz, so that the pressure in the drying kettle reciprocates between 6 - 9 MPa and maintains for 5 - 70 h; the fifth stage: the frequency of the plunger booster pump reciprocates between 15 - 40 Hz, so that the pressure in the drying kettle reciprocates between 6.5 - 9.5 MPa and maintains for 5 - 60 h.

[0032] By adopting the above technical solution, the change in the frequency of the plunger booster pump changes the pressure in the drying kettle. Within a certain period of time, the change in frequency generates a pressure difference, so that the carbon dioxide fluid extracts the solvent in the form of pulses, making it easier to extract the internal solvent and improving the drying efficiency.

[0033] In summary, the present application includes at least one of the following beneficial technical effects:

[0034] 1. By setting a plunger booster pump, a preheater, a drying kettle, a separation kettle, a circulating cooler, a material frame, a material cover, an air inlet and an air outlet, when it is necessary to dry the nano-porous thermal insulation material in the hollow sandwich panel, place the hollow sandwich panel in the material frame, then fix the material cover of the material frame, place the material frame in the drying kettle, pre-open the circulating cooler, introduce liquid carbon dioxide into the plunger booster pump, pressurize the liquid carbon dioxide, and then introduce it into the preheater to heat up the liquid carbon dioxide to vaporize it into gaseous carbon dioxide. Then introduce the gaseous carbon dioxide into the drying kettle. Next, through the partition heat exchange in the drying kettle, at this time, the cold solvent and the hot carbon dioxide gas are separated by the solid wall, and each flows on one side. The heat is transferred from the hot carbon dioxide to the cold solvent through the solid wall for heat exchange, and the solvent and carbon dioxide form a mutual solution. Carbon dioxide extracts the solvent from the drying kettle and brings it into the separation kettle to separate the carbon dioxide and the solvent. Then, through the pre-opened circulating refrigerator for refrigeration, it is re-converted into carbon dioxide fluid, so that the carbon dioxide flows into the plunger booster pump again for secondary use. This cycle process is a process of one-time drying. The intermittent heat exchange and mutual solubility between the carbon dioxide gas and the solvent increase the fluidity of the solvent, thereby improving the drying efficiency;

[0035] 2. By setting a pressure buffer assembly, a spherical crown body, a buffer tube and a reflux tube, before the carbon dioxide enters the drying kettle, the carbon dioxide gas is introduced through the buffer tube. Since the density of carbon dioxide is less than that of air, the carbon dioxide gas overflows from multiple reflux tubes and then enters the spherical crown body for buffering. The shape of the spherical crown body enables the carbon dioxide to enter the drying kettle at a reduced speed, and multiple spherical crown bodies are stacked to achieve multiple buffering, shunting the high-pressure carbon dioxide gas, thereby reducing the impact of the high-pressure carbon dioxide gas on the nano-porous thermal insulation material at one time and causing damage;

[0036] 3. By setting a gas guide plate, a circular plate, a hollow plate and air holes, the setting of the gas guide plate enables the carbon dioxide gas to pass through the air holes of the gas guide plate, guides the carbon dioxide gas to the inside of the material frame, dries the nano-porous thermal insulation material in the hollow sandwich panel in the material frame, and guides the dried carbon dioxide gas around the hollow sandwich panel, thereby forming an orderly flow and improving the drying efficiency; and the gas guide plate is folded, so that the carbon dioxide gas is guided to flow in different directions, so that the carbon dioxide gas can not only flow in the same direction, but flow from all directions to the material frame and dissolve with the solvent everywhere, thereby reducing the possibility of generating flow dead angles. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram for explaining the hollow sandwich panel.

[0038] Figure 2 It is a schematic diagram of the overall structure of this application.

[0039] Figure 3 It is a partial sectional structure schematic diagram for showing the internal structure of the drying kettle of this application.

[0040] Figure 4 It is a schematic diagram for showing the structure of the gas deflector plate.

[0041] Figure 5 It is a flow chart of the drying method of this application.

[0042] Explanation of reference numerals: 1, plunger booster pump; 2, preheater; 3, drying kettle; 4, separation kettle; 5, circulating cooler; 6, material frame; 7, material cover; 8, air inlet; 9, air outlet; 10, pressure buffer assembly; 101, spherical crown body; 102, buffer pipe; 103, reflux pipe; 11, tower-shaped deflector column; 12, air passing hole; 13, gas deflector plate; 131, circular plate; 132, hollow plate; 14, air permeable hole. Specific embodiments

[0043] The following will Figures 2-5 further describe this application in detail with reference to the attached drawings.

[0044] The embodiments of this application disclose a multi-line guiding transcritical drying device.

[0045] Referring to Figure 2 and Figure 3 , a multi-line guiding transcritical drying device includes a plunger booster pump 1, a preheater 2, a drying kettle 3, a separation kettle 4 and a circulating cooler 5. Among them, the plunger booster pump 1, the preheater 2, the drying kettle 3, the separation kettle 4 and the circulating cooler 5 are all connected to each other in sequence by pipelines. A material frame 6 for placing the hollow sandwich board to be dried is arranged inside the drying kettle 3, a material cover 7 is detachably connected to the material frame 6, an air inlet 8 is opened at the bottom end of the drying kettle 3, and the air inlet 8 is connected to the preheater 2, an air outlet 9 is opened on the side wall of the drying kettle 3, and the opening height of the air outlet 9 is greater than the height where the material cover 7 is placed after installation.

[0046] When it is necessary to dry the nano-porous thermal insulation material in the hollow sandwich panel, place the hollow sandwich panel in the material frame 6, then fix the lid 7 of the material frame 6, place the material frame 6 in the drying kettle 3, pre-open the circulating cooler 5, introduce liquid carbon dioxide into the plunger booster pump 1, pressurize the liquid carbon dioxide, and then introduce it into the preheater 2 to heat up the liquid carbon dioxide to vaporize it into gaseous carbon dioxide. Then introduce the gaseous carbon dioxide into the drying kettle 3. Next, through the wall-type heat exchange in the drying kettle 3, at this time, the cold solvent and the hot carbon dioxide gas are separated by the solid wall surface and flow on one side respectively. The heat is transferred from the hot carbon dioxide to the cold solvent through the solid wall surface for heat exchange, and the solvent and carbon dioxide form a mutual solution. The carbon dioxide brings the solvent from the drying kettle 3 into the separation kettle 4 to separate the carbon dioxide and the solvent, and then refrigerate through the pre-opened circulating refrigerator to become carbon dioxide fluid again, so that the carbon dioxide flows into the plunger booster pump 1 again for secondary utilization. This cycle process is the process of one-time drying. The intermittent heat exchange and mutual solution between the carbon dioxide gas and the solvent increase the fluidity of the solvent, thereby improving the drying efficiency.

[0047] Refer to Figure 3 , a pressure buffer assembly 10 is connected to the air inlet 8 of the drying kettle 3. One end of the pressure buffer assembly 10 away from the air inlet 8 is connected to one end of the pipeline away from the preheater 2. The pressure buffer assembly 10 includes a plurality of spherical crown bodies 101 installed at the air inlet 8 and a buffer pipe 102 passing through the plurality of spherical crown bodies 101 at the same time. The plurality of spherical crown bodies 101 are connected and communicated. The diameter of the spherical crown body 101 decreases as the distance from the drying kettle 3 increases.

[0048] As the diameter of the spherical crown body 101 decreases, the movement area of the carbon dioxide gradually increases, so that the buffer of the pressure can decrease along a stepped reduction, so that the pressure of the carbon dioxide can buffer the nano-porous thermal insulation material step by step, thereby further reducing the impact of the sudden change in pressure on the nano-porous thermal insulation material. Before the carbon dioxide enters the drying kettle 3, it first enters the spherical crown body 101 for buffering. The shape of the spherical crown body 101 enables the carbon dioxide to enter the drying kettle 3 at a reduced speed, and the plurality of spherical crown bodies 101 are superimposed, so as to achieve multiple buffering, thereby reducing the impact of the sudden change in pressure on the nano-porous thermal insulation material.

[0049] A plurality of reflux pipes 103 are fixedly connected to the portion of the buffer pipe 102 placed inside the spherical crown body 101. The reflux pipes 3 are distributed on both sides of the buffer pipe 102 and are communicated with the buffer pipe 102. The plurality of reflux pipes 103 are all inclined downward. During operation, carbon dioxide gas is introduced into the buffer pipe 102. Since the density of carbon dioxide is less than that of air, the carbon dioxide gas overflows from the plurality of reflux pipes 103 and then enters the drying kettle 3 through the spherical crown body 101, shunting the high-pressure carbon dioxide gas, thereby reducing the impact of the high-pressure carbon dioxide gas on the nanoporous thermal insulation material at one time and causing damage.

[0050] Referring to Figure 3 , a tower-shaped flow guide column 11 is lapped inside the material frame 6. The diameter of the tower-shaped flow guide column 11 gradually decreases from near the bottom of the material frame 6 to far from the bottom of the material frame 6. A through-hole 12 is opened at the bottom of the tower-shaped flow guide column 11. The through-holes 12 at the bottom of the tower-shaped flow guide column 11 are normally distributed.

[0051] The setting of the tower-shaped flow guide column 11 can prevent carbon dioxide from diffusing in the drying kettle 3 and reduce the drying efficiency. Since the outside of the nanoporous thermal insulation material is exposed to the outside and the inside is clamped by the outer steel plate, the drying time required for the outside and the inside is different. In order to ensure the drying efficiency, the through-holes 12 are normally distributed. The tower-shaped flow guide column 11 gathers the carbon dioxide gas into the material frame 6 and transports it to the nanoporous thermal insulation material for heat exchange, thereby further improving the drying efficiency and making the drying effect better.

[0052] Referring to Figure 3 and Figure 4 , a gas flow guide plate 13 is lapped between the air inlet 8 and the material frame 6. The gas flow guide plate 13 includes a circular plate 131 and a plurality of hollow plates 132 fixedly connected to the outside of the circular plate 131. In this application, two are taken as examples for illustration. The hollow plates 132 are also circular and concentric with the circular plate 131. The spaces between the plurality of hollow plates 132 increase proportionally along the outside of the circular plate 131. A plurality of air-permeable holes 14 are opened on both the circular plate 131 and the hollow plates 132. The air-permeable holes 14 are normally distributed.

[0053] The setting of the gas flow guide plate 13 enables the carbon dioxide gas to pass through the air-permeable holes 14 of the gas flow guide plate, guiding the carbon dioxide gas into the inside of the material frame 6 to dry the nanoporous thermal insulation material in the hollow sandwich panel in the material frame 6. Since the outside of the nanoporous thermal insulation material is exposed to the outside and the inside is clamped by the outer steel plate, the drying time required for the outside and the inside is different. In order to ensure the drying efficiency, the air-permeable holes 14 with a normal distribution have more air-permeable holes 14 opened inside than outside, and are sparse at the edges, thereby balancing the drying time required and guiding the dried carbon dioxide gas around the hollow sandwich panel, thereby forming an orderly flow and improving the drying efficiency.

[0054] The circular plate 131 is folded from the axis of symmetry, and a plurality of hollow plates 132 are arranged obliquely. The inclination directions of two adjacent hollow plates 132 are opposite, and the folding angle of the circular plate 131 and the connection angle between two adjacent hollow plates 132 are both obtuse angles. The folding setting of the gas deflector 13 enables the carbon dioxide gas to be guided and flow in different directions, so that the carbon dioxide gas can flow not only in the same direction, but flow from all directions to the material frame 6, and be miscible with the solvent everywhere, thereby reducing the possibility of the formation of flow dead zones.

[0055] The implementation principle of a multi-line guiding transcritical drying device according to an embodiment of the present application is as follows: When it is necessary to dry the nano-porous thermal insulation material in the hollow sandwich panel, the hollow sandwich panel is placed in the material frame 6, and then the lid 7 of the material frame 6 is fixed. The material frame 6 is placed in the drying kettle 3. The circulating cooler 5 is pre-opened, and liquid carbon dioxide is introduced into the plunger booster pump 1 to pressurize the liquid carbon dioxide, and then it is introduced into the preheater 2 to heat up the liquid carbon dioxide to vaporize it into gaseous carbon dioxide. Then the gaseous carbon dioxide is introduced into the drying kettle 3. The carbon dioxide gas is introduced from the buffer pipe 102. Since the density of carbon dioxide is less than that of air, the carbon dioxide gas overflows from a plurality of reflux pipes 103 and then enters the drying kettle 3 through the spherical crown body 101 to divide the high-pressure carbon dioxide gas, and the solvent and carbon dioxide form a miscible solution. The carbon dioxide brings the solvent from the drying kettle 3 into the separation kettle 4 to separate the carbon dioxide and the solvent, and then refrigerate it through the pre-opened circulating refrigerator to become carbon dioxide fluid again, so that the carbon dioxide flows into the plunger booster pump 1 again for secondary utilization. This circulation process is the process of one-time drying.

[0056] Refer to Figure 5 , the present application also discloses a multi-line guiding transcritical drying device and its drying method, including the following steps:

[0057] S1. Temperature measurement: Check whether the temperature of the drying kettle 3 is lower than 25°C. If so, the kettle can be opened for drying; if the temperature is higher than 25°C, start the cold water pump and the cold circulation pump, turn on the refrigerator, and start the refrigerated circulating water for circulation. Stop the circulation after the temperature reaches 25°C;

[0058] S2. Plate placement: After the drying kettle 3 shows zero pressure, open the exhaust valve at the bottom of the drying kettle 3, so that the drying kettle 3 is connected to the outside. Then tilt and vertically place the hollow sandwich panel into the material frame 6, fix the material frame 6 and the lid 7, and then lift the material frame 6 and put it into the drying kettle 3, and close the drying kettle 3;

[0059] S3. Preparation: Start the cold water pump and the cold circulation pump, and turn on the refrigerator;

[0060] S4. Parameter setting: Set the pressure at the outlet 9 of the drying kettle 3 to be 8 - 20 MPa and the temperature to be 35 - 60 °C, set the pressure of the separation kettle 4 to be 3 - 7 MPa and the temperature to be 30 - 50 °C, set the temperature of the refrigerator 5 to be -20 °C, and the temperature of the preheater 2 to be 30 - 50 °C;

[0061] S4. Circulation: Adjust the frequency of the plunger booster pump 1 to reciprocate within a certain range, so as to adjust the pressure inside the drying kettle 3 to reciprocate within a certain range and maintain for a certain period of time;

[0062] S5. Pressure relief: After the drying time reaches 40 - 200 h, turn off the plunger booster pump 1 and set the valve openings of the two pneumatic valves before and after the drying kettle 3 to 0;

[0063] S6. Unloading from the kettle: Open the exhaust valve of the drying kettle 3, press the kettle opening button, and after the kettle lid is opened, lift out the material frame 6 from the drying kettle 3.

[0064] During drying, first detect the temperature of the drying kettle 3 to avoid the influence of excessive temperature inside the drying kettle 3 on subsequent drying after the previous cycle. Then place the hollow sandwich board to be dried into the material frame 6, and then close the drying kettle 3. Next, turn on the refrigerator to prepare for the subsequent recycling of carbon dioxide. Then, by adjusting the frequency of the pump, it is easier for carbon dioxide to extract the solvent. After a period of time, the drying is completed, and the hollow sandwich board can be taken out. The pressure and temperature of the carbon dioxide gas are changed at a certain frequency, making the extraction of the solvent faster and improving the drying efficiency.

[0065] Adjust the frequency of the plunger booster pump 1 to reciprocate within a certain range, so as to adjust the pressure inside the drying kettle 3 to reciprocate within a certain range and maintain for a certain period of time, including the steps: Divide the drying cycle into five stages. The first stage: The frequency of the plunger booster pump 1 reciprocates between 5 - 25 Hz, so that the pressure in the drying kettle 3 reciprocates between 9 - 16 MPa and maintains for 5 - 50 h; The second stage: The frequency of the plunger booster pump 1 reciprocates between 10 - 35 Hz, so that the pressure in the drying kettle 3 reciprocates between 9 - 18 MPa and maintains for 5 - 60 h; The third stage: The frequency of the plunger booster pump 1 reciprocates between 15 - 50 Hz, so that the pressure in the drying kettle 3 reciprocates between 9 - 20 MPa and maintains for 5 - 80 h; The fourth stage: The frequency of the plunger booster pump 1 reciprocates between 10 - 30 Hz, so that the pressure in the drying kettle 3 reciprocates between 6 - 9 MPa and maintains for 5 - 70 h; The fifth stage: The frequency of the plunger booster pump 1 reciprocates between 15 - 40 Hz, so that the pressure in the drying kettle 3 reciprocates between 6.5 - 9.5 MPa and maintains for 5 - 60 h.

[0066] The change in the frequency of the plunger booster pump 1 changes the pressure in the drying kettle 3. Within a certain period of time, the change in frequency generates a pressure difference, so that the carbon dioxide fluid performs solvent extraction in the form of pulses, making the internal solvent easier to be extracted and improving the drying efficiency.

[0067] The above are all preferred embodiments of this application, and the protection scope of this application is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application shall be covered within the protection scope of this application.

Claims

1. A multi-line guided transcritical drying device, characterized in that: It includes a plunger booster pump (1), a preheater (2), a drying kettle (3), a separation kettle (4) and a circulating cooler (5). The plunger booster pump (1), the preheater (2), the drying kettle (3), the separation kettle (4) and the circulating cooler (5) are sequentially connected to each other by pipelines. A material frame (6) for placing the hollow sandwich panels to be dried is arranged inside the drying kettle (3). A material cover (7) is detachably connected to the material frame (6). An air inlet (8) is opened at the bottom end of the drying kettle (3), and it is connected to the preheater (2) through the air inlet (8). An air outlet (9) is opened on the side wall of the drying kettle (3), and the opening height of the air outlet (9) is greater than the height where the material cover (7) is placed after installation; A pressure buffer assembly (10) is connected to the air inlet (8) of the drying kettle (3). The end of the pressure buffer assembly (10) far from the air inlet (8) is connected to the end of the pipeline between the preheater (2) and the drying kettle (3) far from the preheater (2). The pressure buffer assembly (10) includes a plurality of spherical crown bodies (101) installed at the air inlet (8) and a buffer pipe (102) simultaneously passing through the plurality of spherical crown bodies (101). The plurality of spherical crown bodies (101) are communicated with each other; The diameter of the spherical crown body (101) decreases as the distance from the drying kettle (3) increases; A plurality of reflux pipes (103) are installed on the part of the buffer pipe (102) placed inside the spherical crown body (101), and the plurality of reflux pipes (103) are all inclined downward; 2. The multi-line guiding transcritical drying equipment according to claim 1, characterized in that: A tower-shaped guide column (11) is arranged inside the material frame (6). The diameter of the tower-shaped guide column (11) gradually decreases from near the bottom of the material frame (6) to far from the bottom of the material frame (6). An air passing hole (12) is opened at the bottom of the tower-shaped guide column (11); 3. The multi-line guiding transcritical drying equipment according to claim 2, characterized in that: A gas guide plate (13) is arranged between the air inlet (8) and the material frame (6). The gas guide plate (13) includes a circular plate (131) and a plurality of hollow plates (132) connected to the outside of the circular plate (131). The hollow plates (132) are also circular and concentric with the circular plate (131). The plurality of hollow plates (132) increase in proportion along the outside of the circular plate (131). A plurality of air permeation holes (14) are opened on both the circular plate (131) and the hollow plates (132); 4. A multi-line guiding transcritical drying device according to claim 3, characterized in that: The circular plate (131) is folded from the axis of symmetry. The plurality of hollow plates (132) are inclined. The inclination directions of adjacent two hollow plates (132) are opposite. The folding angle of the circular plate (131) and the connection angle of adjacent two hollow plates (132) are both obtuse angles; 5. A multi-line guided transcritical drying device according to claim 4, characterized in that: The air passing holes (12) at the bottom of the tower-shaped guide column (11) and the air permeation holes (14) of the gas guide plate (13) are in a normal distribution; 6. A drying method for a multi-line guided transcritical drying device according to any one of claims 1-5, characterized in that: It includes steps: S1. Temperature measurement: Check whether the temperature of the drying kettle (3) is lower than 25°C. If so, open the kettle for drying. If the temperature is higher than 25°C, start the cold water pump and the cold circulation pump, turn on the refrigerator, and start the frozen circulating water for circulation. Stop the circulation after the temperature reaches 25°C. S2. Plate placement: After the drying kettle (3) shows zero pressure, open the exhaust valve at the bottom of the drying kettle (3) so that the drying kettle (3) is connected to the outside. Then tilt and vertically place the hollow sandwich panel into the material frame (6), fix the material frame (6) and the material cover (7), and then lift the material frame (6) and put it into the drying kettle (3), and close the drying kettle (3). S3. Preparation: Start the cold water pump and the cold circulation pump, and turn on the refrigerator. S4. Parameter setting: Set the pressure at the air outlet (9) of the drying kettle (3) to 8 - 20 MPa and the temperature to 35 - 60°C, set the pressure of the separation kettle (4) to 3 - 7 MPa and the temperature to 30 - 50°C, set the temperature of the refrigerator to 5 - 20°C, and the temperature of the preheater (2) to 30 - 50°C. S5. Circulation: Adjust the frequency of the plunger booster pump (1) to reciprocate within a certain range, so as to adjust the pressure in the drying kettle (3) to reciprocate within a certain range and maintain for a certain period of time. S6. Pressure relief: After the drying time reaches 40 - 200 h, turn off the plunger booster pump (1), and set the valve opening degrees of the two pneumatic valves before and after the drying kettle (3) to 0. S7. Unloading from the kettle: Open the exhaust valve of the drying kettle (3), press the kettle opening button. After the kettle cover is opened, lift the material frame (6) out of the drying kettle (3).

7. A drying method for a multi-line guided transcritical drying device according to claim 6, characterized in that: Adjust the frequency of the plunger booster pump (1) to reciprocate within a certain range, so as to adjust the pressure in the drying kettle (3) to reciprocate within a certain range and maintain for a certain period of time, including the steps: Divide the drying cycle into five stages. The first stage: The frequency of the plunger booster pump (1) reciprocates between 5 - 25 Hz, so that the pressure in the drying kettle (3) reciprocates between 9 - 16 MPa and maintains for 5 - 50 h. The second stage: The frequency of the plunger booster pump (1) reciprocates between 10 - 35 Hz, so that the pressure in the drying kettle (3) reciprocates between 9 - 18 MPa and maintains for 5 - 60 h. The third stage: The frequency of the plunger booster pump (1) reciprocates between 15 - 50 Hz, so that the pressure in the drying kettle (3) reciprocates between 9 - 20 MPa and maintains for 5 - 80 h. The fourth stage: The frequency of the plunger booster pump (1) reciprocates between 10 - 30 Hz, so that the pressure in the drying kettle (3) reciprocates between 6 - 9 MPa and maintains for 5 - 70 h. The fifth stage: The frequency of the plunger booster pump (1) reciprocates between 15 - 40 Hz, so that the pressure in the drying kettle (3) reciprocates between 6.5 - 9.5 MPa and maintains for 5 - 60 h.

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