A refrigerant cryogenic dehydration process

Abstract

A low-temperature dehydration process for refrigerants, belonging to the field of refrigerant processing technology, addresses the problem that in refrigerant dehydration processes, the refrigerant temperature at the top of the distillation column is high, resulting in a much lower water absorption rate of the adsorbent during the dehydration process in the dryer compared to its static water absorption rate. Furthermore, the refrigerant pressure in the storage tank after passing through the dryer is significantly affected by the storage tank pressure, leading to large pressure fluctuations and impacting the adsorbent water absorption rate. This invention includes steps for refrigerant cooling, refrigerant drying, pressure regulation, and refrigerant storage. The invention adds a refrigerant cooler at the front end of the dryer to lower the refrigerant temperature and adds a pressure regulating device at the dryer assembly outlet to lower the refrigerant temperature at the dryer inlet and maintain a constant refrigerant pressure at the dryer outlet. This increases the adsorbent dehydration rate from 5.7% to 12.1%. Since some refrigerant is lost with each dryer regeneration, increasing the water absorption rate of the adsorbent reduces the number of dryer regeneration cycles, thereby reducing formulation loss.

Description

Technical Field

[0001] This invention relates to the field of refrigerant processing technology, specifically a low-temperature dehydration process for refrigerants. Background Technology

[0002] Refrigerants are the medium through which energy conversion is accomplished in various heat engines. These substances typically increase power through reversible phase changes (such as gas-liquid phase changes), as seen in refrigerant in refrigeration machines. Refrigerant dehydration process: Refrigerant with high moisture content collected from the top of the distillation column is initially dehydrated in a dryer (filled with an adsorbent to remove high moisture content) before entering the next dryer (filled with an adsorbent to remove low moisture content) to remove moisture to below 5 ppm. It then enters the refrigerant storage tank, and after passing analysis (refrigerant moisture ≤ 5 ppm), it is transferred to the finished product spherical tank.

[0003] In existing refrigerant dehydration processes, the refrigerant drawn from the top of the distillation column is at a high temperature. When it enters the dryer for dehydration, the water absorption rate of the adsorbent is much lower than the static water absorption rate of the adsorbent. After the refrigerant passes through the dryer and enters the storage tank, the pressure of the dryer is affected by the pressure of the storage tank, resulting in large pressure fluctuations and affecting the water absorption rate of the adsorbent in the dryer. At the same time, some refrigerant remains in the dryer after passing through it, which leads to refrigerant waste and inconvenience in use.

[0004] To address the above issues, a low-temperature dehydration process for refrigerants is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature refrigerant dehydration process. Using this device, the invention solves the problems in the aforementioned refrigerant dehydration process, such as the high temperature of the refrigerant drawn from the top of the distillation column, the adsorbent's water absorption rate being much lower than its static water absorption rate during the dehydration process in the dryer, the large pressure fluctuations in the dryer caused by the pressure in the storage tank affecting the adsorbent's water absorption rate, and the residual refrigerant in the dryer leading to refrigerant waste and inconvenience.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a low-temperature dehydration process for refrigerants, comprising the following steps:

[0007] Refrigerant cooling: Prepare the refrigerant that needs to be dehydrated, add a heat exchanger at the front end of the dryer group inlet, and exchange heat with the high moisture refrigerant through the refrigerant provided by the utility in the heat exchanger to reduce the temperature of the high moisture refrigerant to 15-20℃.

[0008] Refrigerant drying: The cooled refrigerant is passed into the dryer and then through dryer A, which is filled with a high water molecule adsorbent, and dryer B, which is filled with a low water molecule adsorbent, for drying treatment.

[0009] Pressure regulation: A pressure regulating device is added at the dryer outlet pipeline. The working pressure of the dryer group is kept constant at 0.85 MPa by the pressure regulating device. Under this constant pressure condition, the dryer removes moisture from the refrigerant.

[0010] Refrigerant storage: The dehydrated refrigerant is introduced into the refrigerant storage tank, and after passing the analysis, it is transferred to the finished product spherical tank to complete the dehydration and storage of the refrigerant.

[0011] Furthermore, the dryer used in the refrigerant dehydration process includes a drying chamber and connecting pipes that are respectively connected and fixedly installed at the middle of the top and bottom surfaces of the drying chamber. The drying chamber is circular in shape. An inner chamber is rotatably installed at the middle of the top surface of the inner cavity of the drying chamber. A driving component is fixedly installed on the outer wall of the upper periphery of the drying chamber. A scraper is attached to the inner wall of the inner cavity of the drying chamber, and the upper end of the scraper is slidably installed on the top surface of the inner cavity of the drying chamber.

[0012] Furthermore, a circular inner groove is provided in the middle of the inner cavity of the drying oven, an inlet is provided in the middle of the top surface of the drying oven, an outlet is provided in the middle of the bottom surface of the drying oven, an inclined circular groove is provided on the bottom surface of the inner cavity of the circular inner groove, an inner ring groove is provided on the inner circumference of the top surface of the inner cavity of the circular inner groove, an outer ring groove is provided on the outer circumference of the top surface of the inner cavity of the circular inner groove, a T-shaped circular hole is provided on the upper outer wall of the drying oven, and a baffle plate is fixedly installed on the inner wall of the inner cavity of the drying oven.

[0013] Furthermore, a first arc-shaped annular groove is provided on the outer circumference inner wall of the inner annular groove, and a second arc-shaped annular groove is provided on the outer circumference and inner circumference inner wall of the outer annular groove, respectively. A connecting bearing is installed in the inner cavity of the T-shaped circular hole.

[0014] Furthermore, the driving component includes a drive motor and a bevel gear fixedly mounted on the output end of the drive motor, and the output end of the drive motor is mounted through the connecting bearing.

[0015] Furthermore, the inner box includes a lower circular plate and an upper circular plate located at the upper end of the lower circular plate. The lower circular plate and the upper circular plate are fixedly connected by several connecting rods, and the connecting rods are respectively located on the outer periphery of the lower circular plate and the upper circular plate. A leak-proof net is installed between the lower circular plate, the upper circular plate and the connecting rods. A rotating ring is fixedly installed on the top surface of the upper circular plate. A bevel gear ring is fixedly sleeved on the upper outer periphery of the connecting rod, and the bevel gear and the bevel gear ring are meshed together.

[0016] Furthermore, a plurality of first rolling balls are evenly arranged on the outer circumferential wall of the rotating ring, and the first rolling balls are respectively rolled in the first arc-shaped ring groove. The conical gear ring includes a gear ring body and a plurality of triangular blocks evenly fixed on the outer circumferential wall of the gear ring body, and the triangular blocks are respectively arranged adjacent to each other.

[0017] Furthermore, the scraping plate includes a scraping plate body and an L-shaped slide bar fixedly installed on the inner outer wall of the upper end of the scraping plate body. A snap-fit ​​protrusion is also fixedly installed on the inner outer wall of the upper end of the scraping plate body, and the snap-fit ​​protrusion is located at the lower end of the scraping plate body.

[0018] Furthermore, the L-shaped slide bar includes an L-shaped connecting rod and an arc-shaped slider fixedly installed on the upper end of the L-shaped connecting rod, and second balls are respectively provided on both sides of the arc-shaped slider, and the second balls are respectively rolled in the second arc-shaped annular groove.

[0019] Furthermore, a receiving groove is provided on the middle outer wall of the outer end of the snap-fit ​​protrusion, and a trapezoidal snap-fit ​​block is elastically slidably installed at the inner cavity opening of the receiving groove through a connecting spring, and the trapezoidal snap-fit ​​block and the triangular snap-fit ​​block are movably snapped together.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: A refrigerant cooler is added at the front end of the dryer to reduce the refrigerant temperature; a pressure regulating device is added at the outlet of the dryer assembly to control the dryer pressure to a constant value. Experiments and practical applications have proven that reducing the refrigerant temperature at the dryer inlet and maintaining a constant refrigerant pressure at the dryer outlet increases the adsorbent dehydration rate from 5.7% to 12.1%. Since some refrigerant is lost during each dryer regeneration, the increased water absorption rate of the desiccant reduces the number of dryer regeneration cycles, thereby reducing formulation loss. Attached Figure Description

[0021] Figure 1 This is a flow chart of the refrigerant dehydration process of the present invention;

[0022] Figure 2 This is a schematic diagram of the overall structure of the dryer of the present invention;

[0023] Figure 3 This is a schematic cross-sectional view of the dryer of the present invention;

[0024] Figure 4 This is a three-dimensional cross-sectional view of the drying oven of the present invention;

[0025] Figure 5 For the present invention Figure 4 Enlarged view of point A;

[0026] Figure 6 This is a schematic diagram of the three-dimensional structure of the inner box of the present invention;

[0027] Figure 7 This is a top view of the bevel gear ring structure of the present invention;

[0028] Figure 8 This is a three-dimensional structural diagram of the driving component of the present invention;

[0029] Figure 9 This is a schematic diagram of the planar structure of the scraping plate portion of the present invention;

[0030] Figure 10 This is a schematic cross-sectional view of the inner end of the snap-fit ​​protrusion of the present invention.

[0031] In the diagram: 1. Drying oven; 11. Circular inner groove; 12. Inlet; 13. Outlet; 14. Inclined circular groove; 15. Inner annular groove; 151. First arc-shaped annular groove; 16. Outer annular groove; 161. Second arc-shaped annular groove; 17. T-shaped circular hole; 171. Connecting bearing; 18. Baffle plate; 2. Connecting pipe; 3. Driving component; 31. Drive motor; 32. Bevel gear; 4. Inner chamber placement; 41. Lower circular plate; 42. Upper... 43. Circular plate; 44. Connecting rod; 45. Leak-proof mesh; 46. Rotating ring; 47. First ball bearing; 48. Conical gear ring; 49. Gear ring body; 40. Triangular locking block; 50. Scraping plate; 51. Scraping plate body; 52. L-shaped slide bar; 521. L-shaped connecting rod; 522. Arc-shaped slider; 523. Second ball bearing; 53. Snap-fitting protrusion; 54. Receiving groove; 55. Trapezoidal locking block; 56. Connecting spring. Detailed Implementation

[0032] 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.

[0033] To address the technical problem in refrigerant dehydration processes where the refrigerant temperature at the top of the distillation column is high, and during the dehydration process in the dryer, the water absorption rate of the adsorbent is much lower than the static water absorption rate, and the refrigerant enters the storage tank after passing through the dryer, the dryer pressure is affected by the storage tank pressure, resulting in large pressure fluctuations that affect the water absorption rate of the adsorbent in the dryer, such as... Figure 1 As shown, the following preferred technical solutions are provided:

[0034] A low-temperature dehydration process for refrigerants includes the following steps:

[0035] Refrigerant cooling: Prepare the refrigerant that needs to be dehydrated, add a heat exchanger at the front end of the dryer group inlet, and exchange heat with the high moisture refrigerant through the refrigerant provided by the utility in the heat exchanger to reduce the temperature of the high moisture refrigerant to 15-20℃.

[0036] Refrigerant drying: The cooled refrigerant is passed into the dryer and then through dryer A, which is filled with a high water molecule adsorbent, and dryer B, which is filled with a low water molecule adsorbent, for drying treatment.

[0037] Pressure regulation: A pressure regulating device is added at the dryer outlet pipeline. The working pressure of the dryer group is kept constant at 0.85 MPa by the pressure regulating device. Under this constant pressure condition, the dryer removes moisture from the refrigerant.

[0038] Refrigerant storage: The dehydrated refrigerant is introduced into the refrigerant storage tank, and after passing the analysis, it is transferred to the finished product spherical tank to complete the dehydration and storage of the refrigerant.

[0039] Specifically, a refrigerant cooler is added at the front end of the dryer to lower the refrigerant temperature, and a pressure regulating device is added at the outlet of the dryer assembly to control the dryer pressure to a constant value. Experiments and practical applications have proven that lowering the refrigerant temperature at the dryer inlet and maintaining a constant refrigerant pressure at the dryer outlet increases the adsorbent dehydration rate from 5.7% to 12.1%. Since some refrigerant is lost with each dryer regeneration, the number of dryer regenerations is reduced by increasing the water absorption rate of the desiccant, thereby reducing the loss of the adsorbent.

[0040] To address the technical problem of refrigerant residue remaining in the dryer after refrigerant passes through, leading to refrigerant waste and inconvenience, such as... Figures 2-10 As shown, the following preferred technical solutions are provided:

[0041] The dryer used in the dehydration process of the refrigerant includes a drying chamber 1 and connecting pipes 2 that are fixedly installed at the middle of the top and bottom surfaces of the drying chamber 1. The connecting pipes 2 are respectively set at the input end and the output end of the drying chamber 1. The drying chamber 1 is circular in shape. An inner chamber 4 is rotatably installed at the middle of the top surface of the inner cavity of the drying chamber 1. A driving component 3 is fixedly installed on the outer wall of the upper periphery of the drying chamber 1. A scraping plate 5 is attached to the inner wall of the inner cavity of the drying chamber 1, and the upper end of the scraping plate 5 is slidably installed on the top surface of the inner cavity of the drying chamber 1.

[0042] A circular inner groove 11 is provided in the middle of the inner cavity of the drying oven 1. An inlet 12 is provided in the middle of the top surface of the drying oven 1, and an outlet 13 is provided in the middle of the bottom surface of the drying oven 1. The inlet 12 and outlet 13 are respectively connected to the circular inner groove 11. An inclined circular groove 14 is provided on the bottom surface of the inner cavity of the circular inner groove 11, and the outlet 13 is connected to the middle of the inclined circular groove 14. An inner ring groove 15 is provided on the inner circumference of the top surface of the inner cavity of the circular inner groove 11, and an outer ring groove 15 is provided on the outer circumference of the top surface of the inner cavity of the circular inner groove 11. The outer ring groove 16 and the upper outer wall of the drying chamber 1 are provided with T-shaped round holes 17. The inner wall of the inner cavity of the drying chamber 1 is fixedly installed with a baffle plate 18. By setting the inclined round groove 14, the refrigerant flowing to the bottom surface of the inner cavity of the circular inner groove 11 can be concentrated at the discharge port 13 to flow out, which improves the discharge effect of the dryer. The upper and lower ends of the baffle plate 18 are respectively connected to the top and bottom surfaces of the inner cavity of the circular inner groove 11. The connecting pipe 2 is fixedly installed at the outer opening positions of the inlet 12 and the outlet 13.

[0043] A first arc-shaped annular groove 151 is provided on the outer periphery of the inner cavity of the inner annular groove 15, and a second arc-shaped annular groove 161 is provided on the outer periphery and inner periphery of the inner cavity of the outer annular groove 16, respectively. A connecting bearing 171 is installed in the inner cavity of the T-shaped circular hole 17.

[0044] The drive unit 3 includes a drive motor 31 and a bevel gear 32 fixedly mounted on the output end of the drive motor 31, and the output end of the drive motor 31 is mounted through the connecting bearing 171.

[0045] The inner box 4 includes a lower circular plate 41 and an upper circular plate 42 located at the upper end of the lower circular plate 41. The lower circular plate 41 and the upper circular plate 42 are fixedly connected by several connecting rods 43, which are respectively located on the outer periphery of the lower circular plate 41 and the upper circular plate 42. A leak-proof net 44 is installed between the lower circular plate 41, the upper circular plate 42, and the connecting rods 43. By setting the leak-proof net 44, the water molecule adsorbent can be contained within the inner box 4. Workers can fill the inner box 4 with water molecule adsorbent through the connecting pipe 2. A rotating ring 45 is fixedly installed on the top surface of 42. A bevel gear ring 46 is fixedly sleeved on the outer periphery of the upper end of the connecting rod 43. The bevel gear 32 and the bevel gear ring 46 are meshed and connected. A number of first balls 451 are evenly arranged on the outer periphery of the rotating ring 45, and the first balls 451 are respectively rolled in the first arc-shaped ring groove 151. The bevel gear ring 46 includes a gear ring body 461 and a number of triangular blocks 462 evenly fixedly installed on the outer periphery of the gear ring body 461, and the triangular blocks 462 are arranged adjacent to each other.

[0046] Specifically, the inner chamber 4 is filled with water molecule adsorbent. When the refrigerant is introduced into the connecting pipe 2 and enters the inner chamber 4 through the connecting pipe 2, the refrigerant can be dehydrated by passing through the water molecule adsorbent. Then the refrigerant will be continuously discharged from the leak-proof net 44 and enter the next step through the discharge port 13, thereby completing the dehydration treatment of the refrigerant.

[0047] Furthermore, after the dehydration is complete, the staff can start the drive motor 31. The output end of the drive motor 31 will drive the bevel gear 32 to rotate rapidly. The bevel gear 32 will then drive the bevel gear ring 46 to rotate rapidly, thereby causing the entire inner box 4 to rotate rapidly. Under the action of centrifugal force, the refrigerant remaining in the inner box 4 will be thrown out, thereby reducing the refrigerant residue and preventing the refrigerant waste.

[0048] The scraping plate 5 includes a scraping plate body 51 and an L-shaped slide rod 52 fixedly installed on the inner outer wall of the upper end of the scraping plate body 51. A snap-fit ​​protrusion 53 is also fixedly installed on the inner outer wall of the upper end of the scraping plate body 51, and the snap-fit ​​protrusion 53 is located at the lower end of the scraping plate body 51. The L-shaped slide rod 52 includes an L-shaped connecting rod 521 and an arc-shaped slider 522 fixedly installed on the upper end of the L-shaped connecting rod 521. A second ball bearing 523 is provided on both sides of the arc-shaped slider 522, and the second ball bearing 523 is rolled in the second arc-shaped annular groove 161. A receiving groove 531 is provided on the middle outer wall of the outer end of the snap-fit ​​protrusion 53. A trapezoidal locking block 532 is elastically slidably installed at the inner opening of the receiving groove 531 through a connecting spring 533, and the trapezoidal locking block 532 is movably locked with the triangular locking block 462.

[0049] The drive motor 31 is designed to rotate in both directions. When the output of the drive motor 31 rotates in the forward direction, the trapezoidal locking block 532 and the triangular locking block 462 cannot engage. After the refrigerant remaining in the inner casing 4 is thrown onto the inner wall of the circular inner groove 11, the operator can start the drive motor 31 in the reverse direction. The output of the drive motor 31 will then drive the bevel gear 32 to rotate in the reverse direction, which in turn will drive the bevel gear ring 46 to rotate in the reverse direction. At this time, the trapezoidal locking block 532 will engage with the triangular locking block 462. The scraper plate 51 rotates along the inner wall of the circular inner groove 11, thus scraping off the refrigerant on the inner wall of the circular inner groove 11 until the scraper plate body 51 moves to the position of the baffle plate 18. By the scraper plate body 51 adhering to the surface of the baffle plate 18, all the refrigerant can be squeezed off and collected. The structure is ingeniously designed and multi-functional. It is not only highly automated, eliminating the need for manual processing and collection of the remaining refrigerant in the dryer, but also prevents refrigerant waste and is convenient to use.

[0050] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0051] 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 low-temperature dehydration process for refrigerants, characterized in that: Includes the following steps: Refrigerant cooling: Prepare the refrigerant that needs to be dehydrated, add a heat exchanger at the front end of the dryer group inlet, and exchange heat with the high moisture refrigerant through the refrigerant provided by the utility in the heat exchanger to reduce the temperature of the high moisture refrigerant to 15~20℃. Refrigerant drying: The cooled refrigerant is passed into the dryer and then through dryer A, which is filled with a high water molecule adsorbent, and dryer B, which is filled with a low water molecule adsorbent, for drying treatment. Pressure regulation: A pressure regulating device is added at the dryer outlet pipeline. The working pressure of the dryer group is kept constant at 0.85 MPa by the pressure regulating device. Under this constant pressure condition, the dryer removes moisture from the refrigerant. Refrigerant storage: The dehydrated refrigerant is introduced into the refrigerant storage tank, and after passing the analysis, it is transferred to the finished product spherical tank to complete the dehydration and storage of the refrigerant; The dryer used in the dehydration process of the refrigerant includes a drying box (1) and a connecting pipe (2) that is fixedly installed on the top and bottom of the drying box (1). The drying box (1) is circular in shape. An inner box (4) is rotatably installed on the top of the inner cavity of the drying box (1). A driving component (3) is fixedly installed on the outer wall of the upper periphery of the drying box (1). A scraping plate (5) is attached to the inner wall of the inner cavity of the drying box (1), and the upper end of the scraping plate (5) is slidably installed on the top surface of the inner cavity of the drying box (1). A circular inner groove (11) is provided in the middle of the inner cavity of the drying box (1), an inlet (12) is provided in the middle of the top surface of the drying box (1), an outlet (13) is provided in the middle of the bottom surface of the drying box (1), an inclined circular groove (14) is provided on the bottom surface of the inner cavity of the circular inner groove (11), an inner ring groove (15) is provided on the inner circumference of the top surface of the inner cavity of the circular inner groove (11), an outer ring groove (16) is provided on the outer circumference of the top surface of the inner cavity of the circular inner groove (11), a T-shaped circular hole (17) is provided on the upper outer wall of the drying box (1), and a baffle plate (18) is fixedly installed on the inner wall of the inner cavity of the drying box (1). The inner wall of the inner circumference of the inner ring groove (15) is provided with a first arc-shaped ring groove (151), and the outer circumference and inner wall of the inner circumference of the outer ring groove (16) are respectively provided with a second arc-shaped ring groove (161). The connecting bearing (171) is installed in the inner cavity of the T-shaped round hole (17). The drive unit (3) includes a drive motor (31) and a bevel gear (32) fixedly mounted on the output end of the drive motor (31), and the output end of the drive motor (31) is mounted through the connecting bearing (171); The inner box (4) includes a lower circular plate (41) and an upper circular plate (42) located at the upper end of the lower circular plate (41). The lower circular plate (41) and the upper circular plate (42) are fixedly connected by several connecting rods (43). The connecting rods (43) are respectively located on the outer periphery of the lower circular plate (41) and the upper circular plate (42). A leak-proof net (44) is installed between the lower circular plate (41), the upper circular plate (42) and the connecting rods (43). A rotating ring (45) is fixedly installed on the top surface of the upper circular plate (42). A bevel gear ring (46) is fixedly sleeved on the upper outer periphery of the connecting rod (43). The bevel gear (32) and the bevel gear ring (46) are meshed and connected. The inner box (4) is filled with water molecule adsorbent so that the refrigerant is dehydrated by the water molecule adsorbent. Then the refrigerant is continuously discharged from the leak-proof net (44). When the dehydration is completed, the drive motor (31) is started. The output end of the drive motor (31) drives the bevel gear (32) to rotate rapidly. The bevel gear (32) drives the bevel gear ring (46) to rotate rapidly, so that the entire inner box (4) rotates rapidly. Under the action of centrifugal force, the refrigerant remaining in the inner box (4) is thrown out. A plurality of first balls (451) are evenly arranged on the outer periphery of the rotating ring (45), and the first balls (451) are rolled in the first arc-shaped ring groove (151). The conical gear ring (46) includes a gear ring body (461) and a plurality of triangular blocks (462) evenly fixed on the outer periphery of the gear ring body (461), and the triangular blocks (462) are arranged adjacent to each other. The scraping plate (5) includes a scraping plate body (51) and an L-shaped slide bar (52) fixedly installed on the inner outer wall of the upper end of the scraping plate body (51). A snap-fit ​​protrusion (53) is also fixedly installed on the inner outer wall of the upper end of the scraping plate body (51), and the snap-fit ​​protrusion (53) is located at the lower end of the scraping plate body (51). The L-shaped slide bar (52) includes an L-shaped connecting rod (521) and an arc-shaped slider (522) fixedly installed on the upper end of the L-shaped connecting rod (521). The two ends of the arc-shaped slider (522) are respectively provided with second balls (523), and the second balls (523) are respectively rolled in the second arc-shaped annular groove (161). A receiving groove (531) is provided on the outer wall of the middle part of the outer end of the snap-fit ​​protrusion (53), and a trapezoidal snap-fit ​​block (532) is elastically slidably installed at the inner cavity opening of the receiving groove (531) through the connecting spring (533), and the trapezoidal snap-fit ​​block (532) and the triangular snap-fit ​​block (462) are movably snap-fitted together. When the output end of the drive motor (31) rotates in the forward direction, the trapezoidal block (532) and the triangular block (462) cannot be engaged. When the refrigerant remaining in the inner box (4) is thrown onto the inner wall of the circular inner groove (11), the drive motor (31) is started in the reverse direction. The output end of the drive motor (31) drives the bevel gear (32) to rotate in the reverse direction. The bevel gear (32) drives the bevel gear ring (46) to rotate in the reverse direction. At this time, the trapezoidal block (532) and the triangular block (462) are engaged, thereby driving the scraping plate (5) to rotate along the inner wall of the circular inner groove (11) and scrape off the refrigerant on the inner wall of the circular inner groove (11).

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