A freeze-out device for producing high-purity menthol and a production process

Abstract

This invention relates to the field of menthol production technology, and in particular to a freeze-drying apparatus and process for producing high-purity menthol. The apparatus includes a tank structure, with a crystallization cylinder at the top and a crystal growth cylinder at the bottom. A pre-cooling mechanism is located at the top of the crystallization cylinder, and a transfer mechanism is located inside. The pre-cooling mechanism includes a cooling cylinder with multiple pre-cooling tubes inserted inside. A first pipe for supplying a cooling medium is connected to the cooling cylinder. A second pipe for supplying a cooling medium is located inside the wall of the crystallization cylinder. A pad is installed at the top of the crystallization cylinder, and through holes are formed on the pad to mate with the multiple pre-cooling tubes. The cooling cylinder can rotate relative to the crystallization cylinder, allowing the pre-cooling tubes to connect to the through holes. The process includes pre-cooling, crystallization, and crystal growth. This invention enables continuous menthol production. By setting a temperature gradient, the overall temperature of the tank structure does not need to be adjusted, thus saving energy.

Description

Technical Field

[0001] This invention relates to the field of menthol production technology, specifically to a freeze-drying apparatus and production process for producing high-purity menthol. Background Technology

[0002] Menthol, as an important natural fragrance and pharmaceutical raw material, relies heavily on freeze-drying crystallization as a core step in its production process to purify L-menthol. The efficiency, crystallization uniformity, and energy consumption control of this step directly determine the purity, yield, and production cost of the menthol product. Currently, most existing menthol freeze-drying devices employ a single-tank structure, performing overall cooling and freeze-drying. This involves uniformly controlling the temperature of the entire tank to achieve the crystallization and growth process of crude menthol. This traditional structure has numerous technical shortcomings and struggles to meet the demands of continuous industrial production and energy conservation.

[0003] Specifically, in practical applications, traditional single-tank freeze-drying equipment requires overall temperature regulation of the entire tank to adapt to the different temperature requirements of peppermint crude oil from pre-cooling, preliminary crystallization to crystal growth. Each temperature regulation consumes a large amount of cooling energy, resulting in high energy consumption. At the same time, the single-tank structure cannot achieve zoned operations for pre-cooling, preliminary crystallization, and crystal growth. After pre-cooling, peppermint crude oil directly enters the tank for crystallization and crystal growth. The pre-cooling effect interferes with the crystallization and crystal growth processes, which can easily lead to uneven cooling of peppermint crude oil, resulting in problems such as local overcooling, fine crystal clustering, and severe oil encapsulation in crystals, thereby affecting the purity and crystal regularity of menthol.

[0004] In addition, the precooling mechanism of existing freeze-drying equipment is mostly a fixed structure, which makes it impossible to transfer the precooled menthol crude oil accurately and continuously, making it difficult to achieve continuous freeze-drying production. Most of them adopt an intermittent operation mode, resulting in low production efficiency. Moreover, after each operation, the tank needs to be cleaned and the temperature reset, which further increases labor costs and energy consumption, thus restricting the large-scale and efficient development of menthol freeze-drying production. Summary of the Invention

[0005] This invention provides a freeze-drying apparatus and process for producing high-purity menthol, in order to solve the problem of poor freeze-drying efficiency of existing apparatuses for producing menthol.

[0006] To alleviate the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] A freeze-drying apparatus for producing high-purity menthol includes a tank structure, wherein the upper part of the tank structure is a crystallization cylinder and the lower part is a crystal growth cylinder, and the upper part of the crystallization cylinder is provided with a pre-cooling mechanism and the interior is provided with a transfer mechanism. The precooling mechanism includes a cooling cylinder with multiple precooling pipes inserted inside. A first pipe for supplying a cooling medium is connected to the cooling cylinder. A second pipe for supplying a cooling medium is provided inside the wall of the crystallizing cylinder. A pad is installed on the upper part of the crystallizing cylinder, and a through hole is opened on the pad to cooperate with the multiple precooling pipes. The cooling cylinder can rotate on the crystallizing cylinder, so that the precooling pipes can be connected to the through hole, allowing the precooled peppermint crude oil to enter the transfer mechanism. After the peppermint crude oil undergoes preliminary crystallization in the transfer mechanism, the transfer mechanism transfers the pre-crystallized peppermint crude oil to the crystal growth cylinder.

[0008] Furthermore, a cylinder is installed on the upper part of the cooling cylinder, and an annular cover is installed on the cylinder. A feed pipe for supplying peppermint crude oil is connected to the annular cover. A press valve is provided on the feed pipe and installed at the port of the crystallizing cylinder. A protrusion is provided on the outer wall of the cooling cylinder. When the cooling cylinder rotates to the point where the precooling pipe is coaxial with the through hole, the protrusion can touch the press valve, thereby supplying peppermint crude oil into the cylinder through the feed pipe. At the same time, the precooled peppermint crude oil in the precooling pipe is discharged under pressure to the transfer mechanism.

[0009] Furthermore, a rotating shaft is coaxially fixedly connected to the cooling cylinder, and the rotating shaft is connected to an external servo motor.

[0010] Furthermore, the transfer mechanism includes a transfer cylinder, a scraping bracket is installed at the port of the transfer cylinder, a hydraulic rod is connected to the middle of the scraping bracket, the cylinder of the hydraulic rod is fixed in the workshop, and a hole is opened in the middle of the rotating shaft to cooperate with the cylinder of the hydraulic rod. When the hydraulic rod extends, it can drive the transfer cylinder to move from the crystallization cylinder to the crystal growth cylinder.

[0011] Furthermore, a conical plate is axially slidably connected inside the crystallization cylinder, a guide cylinder is fixedly connected to the bottom wall of the crystallization cylinder, a guide rod is fixedly connected to the lower surface of the conical plate, a slider is provided on the outer wall of the guide rod, the guide rod is inserted into the guide cylinder, and a guide groove that cooperates with the slider is opened on the inner wall of the guide cylinder. The guide groove is composed of a vertical slide groove and a spiral slide groove, and the tail end of the vertical slide groove is connected to the head end of the spiral slide groove. When the transfer cylinder moves downward, the cone plate can slide upward relative to the transfer cylinder, thereby scraping away the crystals on the inner wall of the transfer cylinder. After the cone plate contacts the scraping support, the transfer cylinder continues to move downward, and the slider can slide into the spiral groove, thereby moving the cone plate relative to the scraping support, thereby scraping away the crystals on the surface of the cone plate.

[0012] Furthermore, an annular protrusion is provided at the bottom port of the transfer cylinder to prevent the cone plate from detaching.

[0013] Furthermore, the inner diameter of the crystal growth cylinder is larger than that of the crystallization cylinder. When the hydraulic rod is extended to its maximum length, the transfer cylinder can be completely moved into the crystal growth cylinder, and the cone plate can be moved to contact the scraping support, so that crystallization and mother liquor can overflow from the port of the transfer cylinder into the crystal growth cylinder.

[0014] Furthermore, the outer wall of the crystal growth cylinder is equipped with a low-temperature jacket and a high-temperature jacket from top to bottom; The freeze-drying apparatus further includes a post-processing mechanism, which includes a filter screen and a piston plate. The piston plate is located below the filter screen, and the filter screen is located inside the crystal growth cylinder at the bottom of the low-temperature jacket. Both the filter screen and the piston plate have holes in their middle portions that cooperate with the guide cylinder. A drain pipe is connected to the piston plate, and a one-way valve and a switching valve are installed on the drain pipe. A first cylinder for driving the piston plate to move vertically is installed on the bottom wall of the crystal growth cylinder. When the first cylinder is shortened, the mother liquor can pass through the filter screen and be discharged through the drain pipe.

[0015] Furthermore, a second cylinder for driving the filter screen to move vertically is installed on the bottom wall of the crystal growth cylinder, and a hole for cooperating with the second cylinder is opened on the piston plate; A door is installed on the crystal growth cylinder at the lower part of the high-temperature jacket. After both the first cylinder and the second cylinder are shortened, the filter screen can be moved down to the door position.

[0016] A process for producing high-purity menthol, using a freeze-drying apparatus for high-purity menthol production, includes the following steps: Open the annular cylinder cover and add peppermint crude oil into the cylinder. The peppermint crude oil flows into the pre-cooling pipe. The first pipe is connected to a cooling medium at 10℃-15℃. The peppermint crude oil is kept warm in the first pipe for 2-3 hours. Control the rotation of the cooling cylinder so that the precooling pipe is connected to the through hole. At this time, the precooled peppermint crude oil flows into the transfer cylinder. The second pipe in the side wall of the transfer cylinder is filled with a cooling medium at a temperature of 0-5℃ and maintained for 2-3 hours, so that the peppermint crude oil in the transfer cylinder can initially crystallize. The hydraulic rod is extended to move the transfer cylinder down into the crystal growth cylinder. At this time, the cone plate moves up relative to the crystal growth cylinder, so that the crystal and mother liquor in the transfer cylinder are discharged into the crystal growth cylinder and are located above the filter screen. A cooling medium of -10℃ to -30℃ is introduced into the low temperature jacket to keep the crystal above the filter screen warm for 2-4 hours, so that the crystal continues to grow and become larger. After the heat preservation is completed, first control the first cylinder to shorten and discharge the remaining mother liquor. Then control both the first and second cylinders to shorten, so that the filter screen moves down to the position of the high temperature jacket. A heating medium of 35℃-40℃ is introduced into the high temperature jacket to loosen the crystals and facilitate their discharge. The remaining crystals adhering to the inner wall of the crystal growth cylinder are manually scraped off.

[0017] The beneficial effects of this invention are analyzed as follows: A freeze-drying apparatus for producing high-purity menthol includes a tank structure. The upper part of the tank structure is a crystallization cylinder, and the lower part is a crystal growth cylinder. The outer wall of the crystal growth cylinder is equipped with support legs. A pre-cooling mechanism is provided at the upper part of the crystallization cylinder, and a transfer mechanism is provided inside. The pre-cooling mechanism includes a cooling cylinder with multiple pre-cooling pipes inserted inside. A first pipe for supplying cooling medium is connected to the cooling cylinder. A second pipe for supplying cooling medium is provided inside the cylinder wall of the crystallization cylinder. A pad is installed at the upper part of the crystallization cylinder. The pad has through holes that cooperate with the multiple pre-cooling pipes. The cooling cylinder can rotate around the crystallization cylinder, so that the pre-cooling pipes can be connected to the through holes, allowing the pre-cooled menthol crude oil to enter the transfer mechanism. After the menthol crude oil undergoes preliminary crystallization in the transfer mechanism, the transfer mechanism transfers the pre-crystallized menthol crude oil to the crystal growth cylinder.

[0018] The tank structure consists of a crystallization cylinder and a crystal growth cylinder. The crystallization cylinder is mainly responsible for the initial crystallization of peppermint crude oil, while the crystal growth cylinder is used for further crystal growth. The cooling cylinder in the precooling mechanism introduces a cooling medium through the first pipe to precool the peppermint crude oil in the precooling tube, lowering its temperature to a suitable range to prepare for the subsequent crystallization process. After precooling to the required time and temperature, the cooling cylinder is controlled to rotate. When the cooling cylinder rotates and connects the precooling tube with the through hole on the pad, the precooled peppermint crude oil flows into the transfer mechanism. After crystallizing in the transfer mechanism, the peppermint crude oil is transferred to the crystal growth cylinder for subsequent crystal growth. This device can continuously produce menthol through freeze-drying. By setting the tank structure to a stepped temperature change, the temperature of the entire tank structure does not need to be changed each time, thus saving energy. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a cross-sectional view of the present invention; Figure 3 This is a schematic diagram of the structure of the press valve of the present invention; Figure 4 This is a schematic diagram of the structure of the cylindrical part of the present invention; Figure 5 This is a schematic diagram of the transfer mechanism of the present invention; Figure 6 This is a schematic diagram of the structure of the slider in this invention; Figure 7This is a schematic diagram of the structure of the transfer cylinder of the present invention; Figure 8 This is a schematic diagram of the structure of the filter screen in this invention.

[0020] In the diagram: 100, Tank body; 110, Crystallizing cylinder; 111, Second pipe; 120, Crystal growth cylinder; 121, Low-temperature jacket; 122, High-temperature jacket; 130, Support leg; 200, Pre-cooling mechanism; 210, Cooling cylinder; 211, First pipe; 220, Rotating shaft; 230, Pre-cooling pipe; 240, Pad plate; 250, Through hole; 260, Cylinder; 261, Annular cover; 270, Feed pipe; 271, Press valve ; 272, protrusion; 300, transfer mechanism; 310, hydraulic rod; 320, scraping bracket; 330, transfer cylinder; 340, cone plate; 350, guide rod; 360, guide cylinder; 361, vertical slide; 362, spiral slide; 370, slider; 400, post-processing mechanism; 410, piston plate; 411, drain pipe; 420, first cylinder; 430, filter screen; 440, second cylinder; 450, box door. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Examples, such as Figures 1-8 As shown, a freeze-drying apparatus for producing high-purity menthol includes a tank structure 100. The upper part of the tank structure 100 is a crystallization cylinder 110, and the lower part is a crystal growth cylinder 120. Support legs 130 are installed on the outer wall of the crystal growth cylinder 120. A pre-cooling mechanism 200 is provided on the upper part of the crystallization cylinder 110, and a transfer mechanism 300 is provided inside. The pre-cooling mechanism 200 includes a cooling cylinder 210, with multiple pre-cooling pipes 230 inserted inside. A first pipe 211 for supplying a cooling medium is connected to the cooling cylinder 210. The cylinder wall is provided with a second pipe 111 for supplying cooling medium. A pad 240 is installed on the upper part of the crystallizing cylinder 110. The pad 240 has through holes 250 that cooperate with multiple pre-cooling pipes 230. The cooling cylinder 210 can rotate on the crystallizing cylinder 110, so that the pre-cooling pipes 230 can be connected to the through holes 250, so that the pre-cooled peppermint crude oil enters the transfer mechanism 300. After the peppermint crude oil is initially crystallized in the transfer mechanism 300, the transfer mechanism 300 transfers the initially crystallized peppermint crude oil to the crystal growth cylinder 120.

[0023] The working mechanism of the cryoablation apparatus for producing high-purity menthol provided in this embodiment is as follows: The tank structure 100 consists of a crystallization cylinder 110 and a crystal growth cylinder 120. The crystallization cylinder 110 is mainly responsible for the initial crystallization of peppermint crude oil, while the crystal growth cylinder 120 is used for further crystal growth. The cooling cylinder 210 in the precooling mechanism 200 introduces a cooling medium through the first pipe 211 to precool the peppermint crude oil in the precooling pipe 230, reducing its temperature to a suitable range to prepare for the subsequent crystallization process. After precooling to the required time and temperature, the cooling cylinder 210 is controlled to rotate. When the cooling cylinder 210 rotates and connects the precooling pipe 230 with the through hole 250 on the pad 240, the precooled peppermint crude oil will flow into the transfer mechanism 300. After crystallizing in the transfer mechanism 300, the peppermint crude oil is transferred to the crystal growth cylinder 120 for subsequent crystal growth. This device can continuously freeze-dry produce menthol. By setting the tank structure 100 to a stepped temperature change, it is not necessary to change the temperature of the tank structure 100 as a whole each time, thereby saving energy.

[0024] Among the optional methods in this embodiment, the more preferred one is: A cylinder 260 is installed on the upper part of the cooling cylinder 210. An annular cover 261 is installed on the cylinder 260. A feed pipe 270 for supplying peppermint crude oil is connected to the annular cover 261. A press valve 271 is installed on the feed pipe 270. The press valve 271 is installed at the port of the crystallizing cylinder 110. A protrusion 272 is provided on the outer wall of the cooling cylinder 210. When the cooling cylinder 210 rotates to the point where the precooling pipe 230 is coaxial with the through hole 250, the protrusion 272 can touch the press valve 271, so that the feed pipe 270 supplies peppermint crude oil into the cylinder 260. At the same time, the precooled peppermint crude oil in the precooling pipe 230 is discharged under pressure to the transfer mechanism 300.

[0025] The cylinder 260 is used to contain menthol crude oil, and multiple pre-cooling pipes 230 are connected to the cylinder 260. After the menthol crude oil is discharged into the cylinder 260, it will naturally flow into each pre-cooling pipe 230. When the menthol crude oil in the pre-cooling pipe 230 is cooled to the required temperature, the cooling cylinder 210 is controlled to rotate. When the cooling cylinder 210 rotates to connect with the through hole 250, the protrusion 272 simultaneously applies pressure to the press valve 271. At this time, the menthol crude oil is pumped into the cylinder 260, and the feed pipe 270 is opened to supply new menthol crude oil into the cylinder 260. Meanwhile, the menthol crude oil that has been pre-cooled in the pre-cooling pipe 230 is discharged to the transfer mechanism 300 under pressure. The newly injected menthol crude oil is in the pre-cooling pipe 230. Then the cooling cylinder 210 rotates in the opposite direction, so that the newly injected menthol crude oil is pre-cooled. Through the above settings, continuous production of menthol cryopreservation is realized.

[0026] Among the optional methods in this embodiment, the more preferred one is: A rotating shaft 220 is coaxially fixedly connected to the cooling cylinder 210, and the rotating shaft 220 is connected to an external servo motor.

[0027] A pulley is provided on the rotating shaft 220. An external servo motor drives the cooling cylinder 210 to rotate through the pulley belt drive, or the external servo motor drives the rotating shaft 220 to rotate through gear drive, thereby rotating the cooling cylinder 210.

[0028] Among the optional methods in this embodiment, the more preferred one is: The transfer mechanism 300 includes a transfer cylinder 330, a scraping bracket 320 installed at the port of the transfer cylinder 330, a hydraulic rod 310 connected to the middle of the scraping bracket 320, the cylinder of the hydraulic rod 310 being fixed in the workshop, and a hole for cooperating with the cylinder rod of the hydraulic rod 310 being opened in the middle of the rotating shaft 220. When the hydraulic rod 310 extends, it can drive the transfer cylinder 330 to move from the crystallization cylinder 110 to the crystal growth cylinder 120.

[0029] The transfer cylinder 330 is located below the pad 240. The pre-cooled peppermint crude oil can flow into the transfer cylinder 330. A low-temperature cooling medium is introduced into the side wall of the transfer cylinder 330 through the second pipe 111, so that the peppermint crude oil can initially crystallize in it. When the hydraulic rod 310 extends, the transfer cylinder 330 will move smoothly from the crystallization cylinder 110 to the crystal growth cylinder 120 under its drive.

[0030] Among the optional methods in this embodiment, the more preferred one is: A conical plate 340 is axially slidably connected inside the crystallization cylinder 110. A guide cylinder 360 is fixedly connected to the bottom wall of the crystal growth cylinder 120. A guide rod 350 is fixedly connected to the lower surface of the conical plate 340. A slider 370 is provided on the outer wall of the guide rod 350. The guide rod 350 is inserted into the guide cylinder 360. A guide groove that mates with the slider 370 is opened on the inner wall of the guide cylinder 360. The guide groove is composed of a vertical sliding groove 361 and a spiral sliding groove 362. The tail end of groove 361 is connected to the head end of spiral groove 362; when transfer cylinder 330 moves down, cone plate 340 can slide up relative to transfer cylinder 330, thereby scraping off the crystals on the inner wall of transfer cylinder 330. After cone plate 340 contacts scraping support 320, transfer cylinder 330 continues to move down, and slider 370 can slide into spiral groove 362, thereby moving cone plate 340 relative to scraping support 320, thereby scraping off the crystals on the surface of cone plate 340.

[0031] When the hydraulic rod 310 is in its shortest state, the transfer cylinder 330 is in its highest state. At this time, the cone plate 340 is at the bottom of the transfer cylinder 330, thus the cone plate 340 blocks the bottom wall of the transfer cylinder 330. After the hydraulic rod 310 extends, the transfer cylinder 330 moves down. At this time, the transfer cylinder 330 drives the cone plate 340 to move down synchronously. The slider 370 on the side wall of the guide rod 350 at the bottom of the cone plate 340 first slides in the vertical slide groove 361, and then the slider 370 can slide in the spiral slide groove 362. At this time, the cone plate 340 can rotate. The guide cylinder 360 is pre-filled with compressible inert gas (to ensure airtightness, the guide rod 350 can be set to a longer length, a sealing ring is set at the part of the guide rod 350 that exceeds the spiral groove 362, and the lower part is filled with gas). When the transfer cylinder 330 moves down, the cone plate 340 can move up relative to the transfer cylinder 330. Finally, after the cone plate 340 contacts the scraping bracket 320, the sliding of the slider 370 in the spiral groove 362 can make the cone plate 340 rotate relative to the scraping bracket 320, thereby scraping off the crystals attached to the surface of the cone plate 340 and the inner wall of the transfer cylinder 330.

[0032] Among the optional methods in this embodiment, the more preferred one is: An annular protrusion is provided at the bottom port of the transfer cylinder 330 to prevent the cone plate 340 from disengaging.

[0033] The annular protrusion ensures that the cone plate 340 will not detach from the lower part of the transfer cylinder 330 when the hydraulic rod 310 is shortened to its shortest length.

[0034] Among the optional methods in this embodiment, the more preferred one is: The inner diameter of the crystal growth cylinder 120 is larger than that of the crystallization cylinder 110. When the hydraulic rod 310 is extended to its maximum length, the transfer cylinder 330 can be completely moved into the crystal growth cylinder 120, and the cone plate 340 can be moved to contact the scraping support 320, so that the crystallization and mother liquor can overflow from the port of the transfer cylinder 330 into the crystal growth cylinder 120.

[0035] When the transfer cylinder 330 moves into the crystal growth cylinder 120, the mother liquor and crystals can overflow from the port of the transfer cylinder 330 into the crystal growth cylinder 120, thereby completing the transfer of crystals and facilitating subsequent crystal growth.

[0036] Among the optional methods in this embodiment, the more preferred one is: The outer wall of the crystal growth cylinder 120 is equipped with a low-temperature jacket 121 and a high-temperature jacket 122 from top to bottom. The freeze-drying device also includes a post-processing mechanism 400, which includes a filter screen 430 and a piston plate 410. The piston plate 410 is located below the filter screen 430, which is located inside the crystal growth cylinder 120 at the bottom of the low-temperature jacket 121. Both the filter screen 430 and the piston plate 410 have holes in the middle that cooperate with the guide cylinder 360. A drain pipe 411 is connected to the piston plate 410. A one-way valve and a switch valve are provided on the drain pipe 411. A first cylinder 420 for driving the piston plate 410 to move vertically is installed on the bottom wall of the crystal growth cylinder 120. When the first cylinder 420 is shortened, the mother liquor can pass through the filter screen 430 and be discharged through the drain pipe 411.

[0037] The filter screen 430 and piston plate 410 are initially in the cooling range of the low temperature jacket 121. At this time, the crystals that fall on the surface of the filter screen 430 grow in the low temperature environment provided by the low temperature jacket 121. After growing for a set time, the first cylinder 420 is shortened, so the piston plate 410 moves down. Then the valve switch on the drain pipe 411 is opened. With the help of the one-way valve on the drain pipe 411, when the piston plate 410 moves down, the mother liquor passes through the filter screen 430 and is on the surface of the piston plate 410. When the piston plate 410 moves up, the positive pressure generated at the top allows the mother liquor to be discharged. Alternatively, after the first cylinder 420 is slightly shortened, a negative pressure pump can be connected to the end of the drain pipe 411 to directly filter the mother liquor.

[0038] Among the optional methods in this embodiment, the more preferred one is: The bottom wall of the crystal growth cylinder 120 is equipped with a second cylinder 440 for driving the filter screen 430 to move vertically. The piston plate 410 has a hole that cooperates with the second cylinder 440. A door 450 is installed on the crystal growth cylinder 120 at the lower part of the high temperature jacket 122. After the first cylinder 420 and the second cylinder 440 are shortened, the filter screen 430 can be moved down to the position of the door 450.

[0039] After the mother liquor is discharged, the first cylinder 420 and the second cylinder 440 are shortened, so that the filter screen 430 moves down to the heating range of the high temperature jacket 122, so that the crystals adhering to the filter screen 430 can fall off under the heating condition, and the fallen crystals can be taken out by opening the box door 450. In addition, during continuous production, the scraping frequency of crystals adhering to the inner wall of the crystal growth cylinder 120 is determined according to the concentration of peppermint crude oil. After the continuous production is completed, the crystals adhering to the inner wall of the crystal growth cylinder 120 are thoroughly cleaned.

[0040] A process for producing high-purity menthol, using a freeze-drying apparatus for high-purity menthol production, includes the following steps: Open the annular cover 261, add peppermint crude oil into the cylinder 260, the peppermint crude oil flows into the precooling pipe 230, the first pipe 211 is connected to a cooling medium of 10℃-15℃, and the peppermint crude oil is kept warm in the first pipe 211 for 2-3 hours; The cooling cylinder 210 is rotated so that the precooling pipe 230 is connected to the through hole 250. At this time, the precooled peppermint crude oil flows into the transfer cylinder 330. The second pipe 111 in the side wall of the transfer cylinder 330 is filled with a cooling medium at a temperature of 0-5℃ and maintained for 2-3 hours, so that the peppermint crude oil in the transfer cylinder 330 initially crystallizes. The hydraulic rod 310 is extended, causing the transfer cylinder 330 to move down into the crystal growth cylinder 120. At this time, the cone plate 340 moves up relative to the crystal growth cylinder 120, so that the crystals and mother liquor in the transfer cylinder 330 are discharged into the crystal growth cylinder 120 and are located above the filter screen 430. A cooling medium of -10℃ to -30℃ is introduced into the low temperature jacket 121 to keep the crystals above the filter screen 430 warm for 2-4 hours, so that the crystals continue to grow and become larger. After the heat preservation is completed, first control the first cylinder 420 to shorten and discharge the remaining mother liquor. Then control both the first cylinder 420 and the second cylinder 440 to shorten, so that the filter screen 430 moves down to the position of the high temperature jacket 122. A heating medium of 35℃-40℃ is introduced into the high temperature jacket 122 to loosen the crystals and facilitate their discharge. The remaining crystals adhering to the inner wall of the crystal growth cylinder 120 are manually scraped off.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A freeze-drying apparatus for producing high-purity menthol, characterized in that: It includes a tank structure (100), the upper part of which is a crystallization cylinder (110) and the lower part is a crystal growth cylinder (120). The upper part of the crystallization cylinder (110) is provided with a pre-cooling mechanism (200) and the interior is provided with a transfer mechanism (300). The precooling mechanism (200) includes a cooling cylinder (210), in which a plurality of precooling pipes (230) are inserted. A first pipe (211) for supplying cooling medium is connected to the cooling cylinder (210). A second pipe (111) for supplying cooling medium is provided in the cylinder wall of the crystallization cylinder (110). A pad (240) is installed on the upper part of the crystallization cylinder (110). A through hole (250) is opened on the pad (240) to cooperate with the plurality of precooling pipes (230). The cooling cylinder (210) can rotate on the crystallization cylinder (110), so that the precooling pipes (230) can be connected to the through hole (250) so that the precooled peppermint crude oil enters the transfer mechanism (300). After the peppermint crude oil is initially crystallized in the transfer mechanism (300), the transfer mechanism (300) transfers the initially crystallized peppermint crude oil to the crystal growth cylinder (120).

2. The freeze-drying apparatus for producing high-purity menthol according to claim 1, characterized in that: A cylinder (260) is installed on the upper part of the cooling cylinder (210). An annular cover (261) is installed on the cylinder (260). A feed pipe (270) for supplying peppermint crude oil is connected to the annular cover (261). A press valve (271) is provided on the feed pipe (270). The press valve (271) is installed at the port of the crystallizing cylinder (110). A protrusion (272) is provided on the outer wall of the cooling cylinder (210). When the cooling cylinder (210) rotates to the point where the precooling pipe (230) is coaxial with the through hole (250), the protrusion (272) can touch the press valve (271), so that the feed pipe (270) supplies peppermint crude oil into the cylinder (260). At the same time, the precooled peppermint crude oil in the precooling pipe (230) is discharged under pressure to the transfer mechanism (300).

3. The freeze-drying apparatus for producing high-purity menthol according to claim 2, characterized in that: A rotating shaft (220) is coaxially fixedly connected to the cooling cylinder (210), and the rotating shaft (220) is connected to an external servo motor.

4. The freeze-drying apparatus for producing high-purity menthol according to claim 3, characterized in that: The transfer mechanism (300) includes a transfer cylinder (330), a scraping bracket (320) is installed at the port of the transfer cylinder (330), a hydraulic rod (310) is connected to the middle of the scraping bracket (320), the cylinder body of the hydraulic rod (310) is fixed in the workshop, and a hole is opened in the middle of the rotating shaft (220) to cooperate with the cylinder rod of the hydraulic rod (310). When the hydraulic rod (310) is extended, it can drive the transfer cylinder (330) to move from the crystallization cylinder (110) to the crystal growth cylinder (120).

5. The freeze-drying apparatus for producing high-purity menthol according to claim 4, characterized in that: The crystallization cylinder (110) is axially slidably connected to a conical plate (340), the bottom wall of the crystal growth cylinder (120) is fixedly connected to a guide cylinder (360), the lower surface of the conical plate (340) is fixedly connected to a guide rod (350), the outer wall of the guide rod (350) is provided with a slider (370), the guide rod (350) is inserted into the guide cylinder (360), the inner wall of the guide cylinder (360) is provided with a guide groove that cooperates with the slider (370), the guide groove is composed of a vertical slide groove (361) and a spiral slide groove (362), the tail end of the vertical slide groove (361) is connected to the head end of the spiral slide groove (362); When the transfer cylinder (330) moves downward, the cone plate (340) can slide upward relative to the transfer cylinder (330), thereby scraping away the crystals on the inner wall of the transfer cylinder (330). After the cone plate (340) contacts the scraping bracket (320), the transfer cylinder (330) continues to move downward, and the slider (370) can slide into the spiral groove (362), thereby moving the cone plate (340) relative to the scraping bracket (320), thereby scraping away the crystals on the surface of the cone plate (340).

6. The freeze-drying apparatus for producing high-purity menthol according to claim 5, characterized in that: The bottom port of the transfer cylinder (330) is provided with an annular protrusion for restricting the cone plate (340) from disengaging.

7. The freeze-drying apparatus for producing high-purity menthol according to claim 5, characterized in that: The inner diameter of the crystal growth cylinder (120) is larger than that of the crystallization cylinder (110). When the hydraulic rod (310) is extended to its maximum length, the transfer cylinder (330) can be completely moved into the crystal growth cylinder (120), and the cone plate (340) can be moved to contact the scraping support (320), so that crystallization and mother liquor can overflow from the port of the transfer cylinder (330) into the crystal growth cylinder (120).

8. The freeze-drying apparatus for producing high-purity menthol according to claim 7, characterized in that: The outer wall of the crystal growth cylinder (120) is equipped with a low-temperature jacket (121) and a high-temperature jacket (122) from top to bottom. The freeze-drying apparatus further includes a post-processing mechanism (400), which includes a filter screen (430) and a piston plate (410). The piston plate (410) is located below the filter screen (430), and the filter screen (430) is located inside the crystal growth cylinder (120) at the bottom of the low-temperature jacket (121). Both the filter screen (430) and the piston plate (410) have holes in the middle that cooperate with the guide cylinder (360). A drain pipe (411) is connected to the piston plate (410). A one-way valve and a switch valve are provided on the drain pipe (411). A first cylinder (420) for driving the piston plate (410) to move vertically is installed on the bottom wall of the crystal growth cylinder (120). When the first cylinder (420) is shortened, the mother liquor can pass through the filter screen (430) and be discharged through the drain pipe (411).

9. The freeze-drying apparatus for producing high-purity menthol according to claim 8, characterized in that: The bottom wall of the crystal growth cylinder (120) is equipped with a second cylinder (440) for driving the filter screen (430) to move vertically, and the piston plate (410) is provided with a hole that cooperates with the second cylinder (440); A door (450) is installed on the crystal growth cylinder (120) at the lower part of the high temperature jacket (122). After the first cylinder (420) and the second cylinder (440) are shortened, the filter screen (430) can be moved down to the position of the door (450).

10. A process for producing high-purity menthol, using the freeze-drying apparatus for producing high-purity menthol as described in claim 9, characterized in that, Includes the following steps: Open the annular cylinder cover (261), add peppermint crude oil into the cylinder (260), the peppermint crude oil flows into the precooling pipe (230), the first pipe (211) is connected to a cooling medium of 10℃-15℃, and the peppermint crude oil is kept warm in the first pipe (211) for 2-3 hours; The cooling cylinder (210) is rotated so that the precooling pipe (230) is connected to the through hole (250). At this time, the precooled peppermint crude oil flows into the transfer cylinder (330). The second pipe (111) in the side wall of the transfer cylinder (330) is filled with a cooling medium at a temperature of 0-5℃ and maintained for 2-3 hours so that the peppermint crude oil in the transfer cylinder (330) can initially crystallize. The hydraulic rod (310) is extended, causing the transfer cylinder (330) to move down into the crystal growing cylinder (120). At this time, the cone plate (340) moves up relative to the crystal growing cylinder (120), so that the crystal and mother liquor in the transfer cylinder (330) are discharged into the crystal growing cylinder (120) and are located above the filter screen (430). A cooling medium of -10℃ to -30℃ is introduced into the low temperature jacket (121) to keep the crystal above the filter screen (430) warm for 2-4 hours, so that the crystal continues to grow and become larger. After the heat preservation is completed, the first cylinder (420) is shortened to discharge the remaining mother liquor. Then, the first cylinder (420) and the second cylinder (440) are shortened to move the filter screen (430) down to the position of the high temperature jacket (122). A heating medium of 35℃-40℃ is introduced into the high temperature jacket (122) to loosen the crystals and facilitate their discharge. The remaining crystals adhering to the inner wall of the crystal growth cylinder (120) are manually scraped off.

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