A concentric rotating hypergravity bed

Abstract

The application discloses a concentric circle rotary type supergravity bed, which comprises a shell, a rotor arranged in the shell, the rotor comprising an upper fixed disc and a lower rotating disc, a plurality of concentric baffle rings with different diameters being arranged on the upper fixed disc and the lower rotating disc, the upper baffle ring and the lower baffle ring being nested and staggered, a heating pipe being arranged on the inner side wall surface of each upper baffle ring, the inner side wall surface of the lower baffle ring being provided with arrayed protruding parts, liquid material entering into a liquid distributor in the center of the rotor through a liquid inlet pipe and then falling on the upper baffle ring and the lower baffle ring, and the liquid material flowing out from inside to outside through the baffle flow channel between the upper baffle ring and the lower baffle ring, in the process, liquid drops or liquid filaments colliding and splashing at the protruding parts of the lower baffle ring, forming fine liquid drops and thin liquid films with continuously renewed surfaces, and improving the gas-liquid contact efficiency. The supergravity bed has the advantages of compact and reasonable structure, high mass transfer efficiency, small pressure drop and low power consumption.

Description

Technical Field

[0001] This invention belongs to the field of hypergravity bed technology, specifically relating to a concentric rotating hypergravity bed. Background Technology

[0002] In the industrial production of biodiesel (fatty acid methyl esters), the feedstock oil must first undergo methyl esterification, including esterification and transesterification reactions, to obtain crude methyl ester. The equipment used in the methyl esterification process must ensure thorough mixing of the oil and methanol to increase the phase interface of the heterogeneous reaction and promote rapid reaction. Reacting at a higher methanol to oil molar ratio, with excess methanol, can improve the oil conversion rate.

[0003] Existing biodiesel industrial reactors mostly use mechanically stirred reactors, where mixing is primarily achieved by agitators. During stirring, small local circulation easily forms in the liquid, preventing sufficient contact and mixing between the oil and methanol catalyst, resulting in slow reaction rates and low efficiency. Furthermore, the stirred structure leads to a scale-up effect, further reducing efficiency. Hypergravity reactors effectively address these issues. Their principle utilizes a centrifugal force field to achieve contact and mass transfer between different phases of fluid, enhancing the "three-transfer-one-reaction" process in traditional equipment. Gas-liquid mass transfer in a hypergravity bed occurs within a hypergravity field, resulting in a large contact area between the gas and liquid phases and rapid phase interface renewal. Leveraging the highly enhanced micro-mixing characteristics of a hypergravity environment, chemical towers tens of meters high can be replaced by hypergravity machines less than two meters high; therefore, hypergravity rotating beds are hailed as the "transistors" of chemical equipment. After years of development, hypergravity rotating beds have been widely applied in petrochemical, energy, materials, environmental, and pharmaceutical fields.

[0004] Chinese patent CN117085617A discloses a hypergravity bed reactor equipped with a high-speed large rotor. This hypergravity bed utilizes the centrifugal force generated by the rotation of the large rotor to disperse gaseous reactants into a large number of microbubbles in the liquid reactants, significantly increasing the reaction area and enabling rapid reactions. The upper plate is stationary, eliminating the need for a dynamic seal between the rotor and the gas phase outlet, reducing the manufacturing difficulty of the equipment; it also facilitates the placement of the feed inlet at any position on the upper plate, enabling continuous operation of a single unit; simultaneously, multiple rotors can be easily installed on the shaft within the same housing, multiplying the theoretical plate number of a single unit. However, this hypergravity bed also suffers from high manufacturing difficulty, high energy consumption, and large pressure drop, limiting its application in certain industries. Summary of the Invention

[0005] In view of the problems existing in the above background technology introduction, the purpose of the present invention is to provide a concentric rotating hypergravity bed with a compact and reasonable structure, high mass transfer efficiency, low pressure drop and low power consumption.

[0006] The technical solution adopted in this invention is as follows:

[0007] A concentric rotating hypergravity bed includes a shell and a rotor disposed within the shell. The rotor includes an upper fixed plate and a lower rotating plate. Each of the upper fixed plate and the lower rotating plate is provided with a plurality of concentric baffles of different diameters, namely upper baffles and lower baffles. The upper and lower baffles are nested and staggered. The lower rotating plate is connected to a shaft that drives its rotation. A heating tube is provided on the inner wall of each upper baffle. A liquid inlet pipe is provided at the upper end of the middle of the upper fixed plate, and a liquid distributor communicating with the liquid inlet pipe is provided at the lower end. An array of protrusions is provided on the inner wall of the lower baffle. This invention enables liquid dispersion within the rotor via a liquid distributor at the rotor center. Liquid material enters through a liquid inlet pipe and flows into the liquid distributor at the rotor center. Under centrifugal force, it is accelerated and thrown out, flowing out from the inside to the outside through the baffle channel between the upper and lower baffle rings. During this process, droplets or liquid filaments collide and splash at the protrusions of the lower baffle ring, reducing the thickness of the liquid film on the lower rotating disk, increasing the gas flow space, and reducing the pressure drop. At the same time, the liquid collides with the protrusions, forming fine droplets and a thin liquid film that is constantly renewed on the surface. The surface renewal rate of the liquid film and the gas-liquid contact area increase, improving the gas-liquid contact efficiency.

[0008] Furthermore, the protrusion has a semi-circular protrusion structure, and the protrusion covers the inner wall surface of the lower deflector ring and is distributed in a concentric array.

[0009] Furthermore, the lower end of the upper deflector ring and the upper end of the lower deflector ring have a horizontally overlapping area.

[0010] Furthermore, the heights of the upper deflector rings are the same, the heights of the lower deflector rings are the same, and the heights of both the upper and lower deflector rings are less than the distance between the upper fixed disk and the lower rotating disk.

[0011] Furthermore, a gas inlet pipe is provided on the side of the housing, a liquid outlet pipe is provided at the bottom of the housing away from the gas inlet pipe, and a gas outlet branch pipe is provided at the center of the top of the housing, with the gas outlet branch pipe located outside the liquid inlet pipe.

[0012] Furthermore, the liquid distributor includes a liquid distribution tube, the upper end of which is connected to a liquid inlet tube, the bottom of which is closed, and several liquid outlet holes are evenly distributed along the circumference on the lower side wall.

[0013] Furthermore, the rotating shaft extends out of the housing and is connected to the output shaft of an external motor, and a mechanical seal is provided at the connection between the rotating shaft and the housing.

[0014] Furthermore, the heating tubes arranged on the inner wall of the upper deflector include several ring-shaped heating tubes arranged from top to bottom, and several vertical heating tubes evenly spaced along the circumference. The vertical heating tubes are welded together with the ring-shaped heating tubes, and their internal spaces are connected. The resistance wire passes through the first vertical heating tube into the first ring-shaped heating tube, and runs along its internal space until it reaches the last vertical heating tube of the first ring. Then, it passes through the last vertical heating tube of the first ring into the second ring-shaped heating tube, and so on, until the resistance wire completes all the loops and exits from the bottom of the corresponding vertical heating tube. The two ends of the resistance wire then pass upward along the wall of the upper deflector and out of the upper fixed plate, and are connected to the power supply.

[0015] Furthermore, the diameter of both the vertical heating tube and the annular heating tube is 3-8mm, and the inner diameter of both the vertical heating tube and the annular heating tube is larger than the diameter of the resistance wire. After the resistance wire is routed inside the heating tube, magnesium oxide powder is filled into the heating tube, and the port of the vertical heating tube is sealed.

[0016] Furthermore, the height of each of the upper or lower deflector rings is 3 to 20 cm, and the thickness is 1 to 3 mm; the height of each of the upper or lower deflector rings is 0.5 to 10 cm smaller than the distance between the upper fixed plate and the lower rotating plate.

[0017] Compared with the prior art, the significant advantages of this invention include:

[0018] 1) The liquid distributor at the center of the rotor can disperse the liquid within the rotor; the lower baffle is vertically arranged on the lower rotating disk, and the inner side of the lower baffle is covered with semi-circular small protrusions, which reduces the thickness of the liquid film on the lower rotating disk, increases the gas flow space, reduces the pressure drop, and increases the surface renewal rate of the liquid film and the gas-liquid contact area; both the upper and lower baffles of the rotor have the function of accelerating the liquid, resulting in less liquid kinetic energy loss and lower power consumption.

[0019] 2) The present invention uses a method of placing a resistance wire and filling it with magnesium oxide powder inside the heating tube. On the one hand, the arrangement of the heating tubes on the inner wall surface of the upper baffle ring makes the wall surface of the upper baffle ring uneven, increasing the contact area of ​​the reactants. On the other hand, heating through the heating tube can also effectively stabilize the temperature of the reaction liquid. In contrast, if a hot fluid is introduced into the heating tube, the diameter of the heating tube needs to be larger, occupying more space, which is not conducive to the nesting of the upper and lower baffle rings, and also significantly increases the resistance of the reaction liquid on the surface of the upper baffle ring. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the concentric rotating supergravity bed of the present invention;

[0021] Figure 2 This is a schematic diagram of the single-layer structure of the upper baffle ring of the present invention;

[0022] Figure 3 This is a diagram showing the distribution of the resistance wires in the heating tube of the present invention;

[0023] Figure 4 This is a top view of the lower deflector structure of the present invention;

[0024] Figure 5 This is a partial structural unfolded view of the lower baffle coil of the present invention;

[0025] Figure 6 This is a schematic diagram of the liquid distributor, gas outlet pipe, and liquid inlet pipe of the present invention.

[0026] Explanation of reference numerals in the attached drawings: 1. Gas outlet pipe; 2. Liquid inlet pipe; 3. Lower baffle; 4. Upper baffle; 5. Liquid outlet pipe; 6. Lower rotating disk; 7. Rotating shaft; 8. Liquid distributor; 9. Gas inlet pipe; 10. Upper fixed disk; 11. Several bolts; 12. Upper mechanical seal; 13. Lower mechanical seal; 14. Housing; 15. Heating tube; 151. Annular heating tube; 152. Vertical heating tube; 16. Liquid outlet hole; 17. Protrusion. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0028] Example 1:

[0029] See Figures 1-6 This embodiment provides a concentric rotating hypergravity bed, including a housing 14 and a rotor disposed within the housing 14. The rotor includes an upper fixed plate 10 and a lower rotating plate 6. Each of the upper fixed plate 10 and the lower rotating plate 6 has several concentric baffles of different diameters, namely an upper baffle 4 and a lower baffle 3. The upper and lower baffles are nested and staggered. The lower rotating plate 6 is connected to a rotating shaft 7 that drives its rotation. The rotating shaft 7 passes through the bottom surface of the housing 14 and is connected to the output shaft of an external motor. A lower mechanical seal 13 is provided at the connection between the rotating shaft 7 and the housing 14. A liquid inlet pipe 2 is provided at the upper end of the middle of the upper fixed plate, and a liquid distributor 8 communicating with the liquid inlet pipe 2 is provided at the lower end. The liquid distributor 8 includes a liquid distribution pipe, the upper end of which is connected to the liquid inlet pipe 2. The bottom of the liquid distribution pipe is closed, and several liquid outlet holes 16 are evenly distributed along the circumference of the lower side wall. A gas inlet pipe 9 is provided on the side of the housing 14, and a liquid outlet pipe 5 is provided at the bottom of the housing 14 away from the gas inlet pipe 9. A gas outlet branch pipe 1 is provided at the center of the top of the housing 14, and the gas outlet branch pipe 1 is located outside the liquid inlet pipe 2. An upper mechanical seal 12 is provided at the connection between the liquid inlet pipe 2 and the housing 14.

[0030] like Figure 1 and Figure 6 As shown, the liquid distributor 8 in this embodiment has several uniform small holes. The height of the hole area is less than the height of the lower baffle ring 3. The number of holes can be increased or decreased according to actual working needs.

[0031] The side of the housing 14 is provided with a gas inlet pipe 9, and the bottom of the housing 14 is provided with a liquid outlet pipe 5 away from the gas inlet pipe 9. The top center of the housing is provided with a gas outlet main pipe, which is connected to the inner cavity of the rotor and is located outside the liquid inlet pipe 2. The side of the gas outlet main pipe is connected to the gas outlet branch pipe 1.

[0032] The upper plate 10 is fixed to the housing 14 by several bolts 11, and a mechanical seal is provided at the connection between the gas outlet main pipe and the upper plate 10.

[0033] The upper fixed plate 10 is provided with several upper deflector rings 4 of different diameters and concentrically arranged, and the lower rotating plate 6 is provided with several lower deflector rings 3 of different diameters and concentrically arranged. The lower deflector rings 3 and the upper deflector rings 4 are arranged in an alternating nested manner. The inner wall surface of the lower deflector rings 3 has an array of protrusions 17. The protrusions 17 have a semi-circular protrusion structure and cover the inner wall surface of the deflector rings in a concentric circular array.

[0034] In this embodiment, the upper and lower baffle rings are nested together. All upper baffle rings 4 have the same height, and all lower baffle rings 3 have the same height. The height of both upper and lower baffle rings is less than the distance between the upper fixed disk and the lower rotating disk. There is a horizontal overlap between the lower end of the upper baffle ring 4 and the upper end of the lower baffle ring 3.

[0035] The reactor bed height in this embodiment is 0.5m, the bed diameter is 0.8m, the shell thickness is 5mm, the upper and lower baffles are both 20cm high and 2mm thick, and the distance between the upper fixed plate and the lower rotating plate is 30cm.

[0036] Comparison Figure 2 and Figure 3 In this invention, each upper deflector ring 4 has a heating tube 15 disposed on its inner wall surface, including several annular heating tubes 151 arranged from top to bottom, and several vertical heating tubes 152 evenly spaced along the circumference. The vertical heating tubes 152 are welded together with the annular heating tubes 151, and their internal spaces are connected. The resistance wire passes through the first vertical heating tube 152 into the first ring of annular heating tubes 151, and runs along its internal space until it reaches the last vertical heating tube 152 of the first ring. Then, it passes through the last vertical heating tube 152 of the first ring into the second ring of annular heating tubes 151, and so on, until the resistance wire completes all the rings and exits from the corresponding vertical heating tubes 152 (see the circuit diagram of the resistance wire for details). Figure 3(The dotted part in the text); the two ends of the resistance wire pass through the upper fixed plate 10 along the wall of the upper deflector 4 and are connected to the power supply.

[0037] The inner diameters of both the vertical heating tube 152 and the annular heating tube 151 are larger than the diameter of the resistance wire. After the resistance wire is routed inside the heating tube, magnesium oxide powder is filled into the heating tube, and the port of the vertical heating tube 152 is sealed. The diameter of both the vertical heating tube 152 and the annular heating tube 151 is 6mm. The vertical heating tube 152 of this invention is made of high-temperature resistant stainless steel, and the reaction temperature is controlled by heating through the resistance wire inside the high-temperature resistant stainless steel tube.

[0038] Comparison Figure 3 The resistance wire routing generally runs from top to bottom. The upper end of the first vertical heating tube 152 can pass directly upwards through the upper fixed plate 10, allowing one end of the resistance wire to extend beyond the housing 14 and connect to the power supply. From Figure 3 As can be seen, the other end of the resistance wire passes through the lower end of one of the vertical heating tubes. Then, the lower end port of the vertical heating tube 152 can be sealed. A protective sleeve is wrapped around the outer surface of the resistance wire. The protective sleeve goes down along the inner side of the upper baffle 4 to the bottom of the upper baffle 4, then goes around the bottom of the upper baffle 4 and fits against its outer side to pass through the upper fixed plate 10, so that the other end of the resistance wire extends out of the housing 14 under insulation and is connected to the power supply.

[0039] The working process of this embodiment is as follows: After the gas enters the shell 14 through the gas inlet pipe 9, under the action of pressure difference, the gas will flow in a tortuous manner from the outermost layer to the center through the gap between the upper baffle ring 4 and the lower baffle ring 3, so the gas movement trajectory is S-shaped, and finally leaves the hypergravity bed through the gas outlet branch pipe 1. The liquid enters the liquid distributor 8 through the liquid inlet pipe 2. The liquid is accelerated by the liquid distributor 8 and dispersed by the small holes on it. It impacts the innermost lower baffle ring 3 and begins to flow outward along the tortuous S-shaped channel. During this process, droplets or liquid filaments collide and splash at the protrusion 17 of the lower baffle ring 3, forming fine droplets and a constantly renewed liquid film on the surface. Under the action of centrifugal force, they are thrown to the upper baffle ring 4 and come into contact with the heating tube 15. Then, they are accelerated away from the heating tube 15 of the upper baffle ring 4 as fine droplets or liquid filaments. Under the action of gravity and centrifugal force, the liquid is accelerated away from the upper baffle ring 4 and moves to the adjacent second layer of the lower baffle ring 3 to enter the next cycle until it leaves the rotor. The liquid leaving the rotor is collected by the shell 14 and discharged from the liquid outlet pipe 5.

[0040] This invention employs a rotor structure of "upper fixed disk and lower rotating disk". The liquid distributor 18 at the center of the rotor can disperse the liquid within the rotor. The lower baffle ring 3 is vertically arranged on the lower rotating disk 6 and has uniform semi-circular small protrusions, which reduces the thickness of the liquid film on the lower rotating disk 6, increases the gas flow space, reduces the pressure drop, and increases the surface renewal rate of the liquid film and the gas-liquid contact area. In addition, both the upper and lower baffle rings of the rotor have the function of accelerating the liquid, resulting in less liquid kinetic energy loss and lower power consumption.

[0041] When used in gas-liquid reactions, the preheated reaction raw material gas enters the supergravity bed through the gas inlet pipe 9. Under the action of pressure difference, it flows from the outer edge of the rotor along the gap between the upper baffle ring 4 of the upper fixed plate 10 and the lower baffle ring 3 of the lower rotating plate 6, moving from the outside to the center plate by plate, making countercurrent contact with the liquid, and finally being discharged through the gas outlet pipe 1. The reaction raw material liquid enters through the liquid inlet pipe 2 and is directly introduced into the liquid distributor 8 at the center of the rotor. Under the action of centrifugal force, it is accelerated and thrown out, impacting the innermost baffle ring. Starting from the innermost baffle ring, it flows from the outer edge along the tortuous S-shaped channel, making countercurrent contact with the gas, and carrying out mass transfer. The liquid leaving the rotor is finally collected by the shell 14 and discharged through the liquid outlet pipe 5.

[0042] For example Figures 1-6 The concentric rotating hypergravity bed described above is used for the esterification reaction of methanol and oleic acid. The specific operation process is as follows:

[0043] A sulfonated carbon solid acid catalyst is dispersed in oleic acid at 10% of the oleic acid mass, forming a liquid-phase reaction slurry. Methanol is fed at a molar ratio of 12:1 to oleic acid, and the reaction temperature is controlled at 65°C. Preheated methanol gas enters the shell 14 of the high-gravity bed through gas inlet pipe 9. Under the influence of pressure difference, it flows from the outer edge of the rotor along the gap between the upper baffle 4 of the upper fixed plate 10 and the lower baffle 3 of the lower rotating plate 6, meandering from the outside to the center plate by plate. It comes into countercurrent contact with the liquid and finally exits through gas outlet pipe 1.

[0044] The reaction slurry, composed of sulfonated carbon solid acid catalyst and oleic acid, is preheated to 65°C and then enters the liquid distributor 8 at the center of the rotor through the liquid inlet pipe 2. It then falls onto the innermost upper baffle ring 4 and lower baffle ring 3. At a rotor speed of 1000 rpm, the liquid flows outward along a tortuous S-shaped channel from the channel between the innermost upper baffle ring 4 and lower baffle ring 3, contacting the gas in a counter-current flow for mass transfer. The liquid leaving the rotor is finally collected by the shell 14 and discharged from the liquid outlet pipe 5. The residence time of the reaction slurry composed of sulfonated carbon solid acid catalyst and oleic acid on the rotor is 0.2 h. After 2 h of stable operation according to the above experimental procedure, the yield of biodiesel collected at the liquid outlet pipe reaches 96.3%.

[0045] Example 2:

[0046] The inner wall of the lower baffle ring does not have a semi-circular protrusion, and everything else is the same as in Example 1. The experimental results of sampling and analysis after 2 hours of stable operation showed that the biodiesel yield was 85.7%.

[0047] Example 3:

[0048] No heating tube was installed inside the upper baffle ring; everything else was the same as in Example 1. The experimental results of sampling and analysis after 2 hours of stable operation showed that the biodiesel yield was 77.8%.

[0049] The above description is only a partial embodiment of the present invention and is not intended to limit the present invention. Any equivalent changes and modifications made based on the content of this invention are within the protection scope of this invention.

Claims

1. A concentric rotating supergravity bed, comprising a shell (14) and a rotor disposed within the shell (14), the rotor comprising an upper fixed disk (10) and a lower rotating disk (6), each of the upper fixed disk (10) and the lower rotating disk (6) being provided with a plurality of concentric baffles of different diameters, namely an upper baffle (4) and a lower baffle (3), the upper baffles and the lower baffles being nested to each other and arranged alternately, the lower rotating disk being connected to a rotating shaft that drives its rotation, characterized in that: Each upper baffle ring (4) has a heating tube on its inner wall. The upper end of the middle of the upper plate is provided with a liquid inlet pipe (2), and the lower end is provided with a liquid distributor (8) that communicates with the liquid inlet pipe (2). The inner wall of the lower baffle ring is provided with arrayed protrusions (17). The liquid material enters through the liquid inlet pipe (2) and flows into the liquid distributor (8) in the center of the rotor, and then falls onto the upper baffle ring (4) and the lower baffle ring (3). It flows out from the inside to the outside through the baffle channel between the upper baffle ring (4) and the lower baffle ring (3). During this process, the droplets or liquid filaments collide and splash at the protrusions (17) of the lower baffle ring (3), forming fine droplets and a thin liquid film that is constantly renewed on the surface, thereby improving the gas-liquid contact efficiency. The heating tubes arranged on the inner wall of the upper deflector (4) include several ring heating tubes (151) arranged from top to bottom, and several vertical heating tubes (152) arranged at even intervals along the circumference. The vertical heating tubes (152) are welded together with the ring heating tubes (151) and their internal spaces are connected. The resistance wire passes through the first vertical heating tube (152) into the first ring heating tube (151), and runs along its internal space until it reaches the last vertical heating tube (152) of the first ring. Then it passes through the last vertical heating tube (152) of the first ring into the second ring heating tube (151), and so on, until the resistance wire completes all the rings and passes out from the corresponding vertical heating tube (152). The two ends of the resistance wire pass through the upper fixed plate (10) along the wall of the upper deflector (4) and are connected to the power supply; the inner diameters of the vertical heating tube (152) and the annular heating tube (151) are both larger than the diameter of the resistance wire. After the resistance wire is completed in the heating tube, magnesium oxide powder is filled into the heating tube and the port of the vertical heating tube (152) is sealed.

2. The concentric rotating supergravity bed as described in claim 1, characterized in that... The protrusion (17) has a semi-circular protrusion structure, and the protrusion (17) covers the inner wall of the lower deflector ring and is distributed in a concentric circle array.

3. The concentric rotating supergravity bed as described in claim 1, characterized in that... The lower end of the upper deflector ring and the upper end of the lower deflector ring have a horizontally overlapping area.

4. The concentric rotating supergravity bed as described in claim 1, characterized in that... The heights of the upper deflector rings are the same, and the heights of the lower deflector rings are the same. The heights of the upper and lower deflector rings are both less than the distance between the upper fixed disk (10) and the lower rotating disk (6).

5. A concentric rotating supergravity bed as described in claim 1, characterized in that... The side of the housing (14) is provided with a gas inlet pipe (9), and the bottom of the housing (14) is provided with a liquid outlet pipe (5) away from the gas inlet pipe (9). The top center of the housing is provided with a gas outlet branch pipe (1), which is located outside the liquid inlet pipe (2).

6. The concentric rotating supergravity bed as described in claim 1, characterized in that... The liquid distributor (8) includes a liquid distribution tube, the upper end of which is connected to the liquid inlet tube (2). The bottom of the liquid distribution tube is closed, and several liquid outlet holes are evenly distributed along the circumference on the lower side wall.

7. A concentric rotating supergravity bed as described in claim 1, characterized in that... The rotating shaft extends out of the housing and connects to the output shaft of an external motor. A mechanical seal is provided at the connection between the rotating shaft and the housing.

8. A concentric rotating supergravity bed as described in claim 1, characterized in that... The diameters of both the vertical heating tube (152) and the annular heating tube (151) are 3~8mm.

9. A concentric rotating supergravity bed as described in claim 1, characterized in that... The height of each of the upper or lower baffle rings is 3-20cm and the thickness is 1-3mm; the height of each of the upper or lower baffle rings is 0.5-10cm smaller than the distance between the upper fixed plate and the lower rotating plate.

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