A multi-stage stirred fermenter

Abstract

The present application relates to the technical field of bio-fermentation equipment, and particularly relates to a multi-stage stirring type fermentation tank. The multi-stage stirring type fermentation tank comprises a tank body, a hollow first stirring shaft coaxially arranged and a second stirring shaft sleeved in the first stirring shaft, a first motor and a second motor for driving the two shafts to independently rotate, a shaft flow type first stirrer connected to the first stirring shaft, a radial flow type second stirrer connected to the lower end of the second stirring shaft, a central flow guide cylinder fixed in the tank body, and a static ring-shaped gas distributor installed at the opening below the central flow guide cylinder. The central flow guide cylinder covers the shaft flow type stirrer, and the radial flow type stirrer is located at the opening below the central flow guide cylinder. The bottom of the second stirring shaft is provided with an elastic scraper rod which can scrape the wall. The outer wall of the tank body is provided with a spiral half-pipe jacket heat exchange device. The present application realizes the synergistic effect of macroscopic mixing and microscopic mass transfer through differential driving of the double shafts and the combined stirrer, optimizes the stirring conditions in different fermentation stages, and significantly improves the oxygen dissolution efficiency and the heat transfer effect.

Description

Technical Field

[0001] This invention relates to the field of bio-fermentation equipment technology, and in particular to a multi-stage stirred fermenter. Background Technology

[0002] Fermenters are core equipment in bioengineering used for microbial fermentation, and their performance directly affects the efficiency of the fermentation process and the quality of the product. Traditional mechanically stirred fermenters typically employ a single-shaft, single-paddle or twin-paddle stirring structure, which suffers from problems such as uneven mixing, low dissolved oxygen efficiency, and poor heat transfer. Especially in aerobic fermentation, the oxygen transfer rate is often a key factor limiting fermentation density; simultaneously, the metabolic heat generated during fermentation needs to be removed promptly, otherwise it will affect cell activity. Furthermore, for high-viscosity or easily adhered fermentation systems, deposits easily form on the tank walls, leading to deteriorated heat transfer and increased risk of contamination. Therefore, developing a fermenter that combines efficient mixing, enhanced mass transfer, excellent heat transfer, and self-cleaning functions is of great significance. Summary of the Invention

[0003] The present invention aims to provide a multi-stage stirred fermenter to solve the problems of uneven mixing, low dissolved oxygen efficiency, poor heat transfer effect and easy wall adhesion in the prior art.

[0004] The technical solution adopted in this invention is: a multi-stage stirred fermenter, comprising: The tank body has a sealed lid at the top and a discharge port at the bottom, with a feed port on the lid. A first stirring shaft and a second stirring shaft are coaxially arranged. The first stirring shaft is a hollow tubular structure, and the second stirring shaft is rotatably coaxially sleeved in the inner cavity of the first stirring shaft. The two can rotate independently. A sealed bearing is provided between the inner side of the bottom end of the first stirring shaft and the second stirring shaft. The drive mechanism includes a first motor mounted on the can lid and a second motor mounted on a mounting bracket fixed to the top of the can lid; the first motor is used to drive the first stirring shaft to rotate, and the second motor is used to drive the second stirring shaft to rotate. An axial-flow first agitator is fixedly connected to the outer wall of the first agitator shaft; A radial flow type second agitator is fixedly connected to the extension of the second agitator shaft extending out of the lower end of the first agitator shaft; The central guide tube is a cylindrical structure with openings at both ends. It is fixedly installed inside the tank and coaxially sleeved on the outside of the first and second stirring shafts. The central guide tube completely encloses the axial-flow first stirrer inside it, and the radial-flow second stirrer is located at the lower opening of the central guide tube. And a static annular gas distributor, which is fixedly installed at the opening below the central guide tube.

[0005] Furthermore, the output end of the first motor is provided with a bevel gear one, and the upper end of the first stirring shaft is provided with a bevel gear two, wherein the bevel gear one and the bevel gear two are meshed and connected.

[0006] Furthermore, the axial flow first agitator includes at least two layers of axial flow impellers, the chord line of the blades of the axial flow impellers is at an angle of 20° to 35° with the horizontal plane; the radial gap between the outer edge of the blades and the inner wall of the central guide tube is 1 / 50 to 1 / 20 of the diameter of the central guide tube.

[0007] Furthermore, the radial flow second agitator includes a hub fixedly sleeved on the lower end of the second agitator shaft, the hub being in the shape of a solid frustum, and a plurality of radial blades uniformly fixed circumferentially on the sidewall of the hub, the radial blades being used to generate radial shear flow.

[0008] Furthermore, a mounting base is installed at the bottom end of the second stirring shaft, and a plurality of connecting crossbars are provided on the mounting base extending radially, with an elastic scraper provided at the end of each connecting crossbar.

[0009] Furthermore, the elastic scraper is provided with an upper guide rod and a lower support rod that are telescopically coordinated at its upper and lower ends, respectively; the upper guide rod is provided with an upper damping spring, and the lower support rod is provided with a lower buffer spring; the connecting crossbar is sleeved on the lower support rod, and one end of the lower buffer spring abuts against the inside of the connecting crossbar.

[0010] Furthermore, a guide sleeve is fitted on the outer side of the upper guide rod, and the upper damping spring abuts against the inside of the guide sleeve; a rotatable rolling assembly is provided at the end of the guide sleeve, and an annular slide rail is provided on the outer side of the bottom end of the central guide tube, and the rolling assembly is limited to slide within the annular slide rail to form a rotational support.

[0011] Furthermore, the top of the central guide tube is fixedly connected to the inner wall of the can lid by multiple suspension support rods; a guide cone skirt is integrally formed or fixedly connected to the lower opening of the central guide tube, and the guide cone skirt is in the shape of a trumpet with a larger top and a smaller bottom.

[0012] Furthermore, the static annular gas distributor includes a horizontally arranged annular gas distribution pipe coaxial with the central guide tube and at least one air inlet pipe in fluid communication with the annular gas distribution pipe; the surface of the annular gas distribution pipe is provided with a plurality of air outlet holes; the air inlet pipe extends downward through the suspension support rod and the outer wall of the central guide tube and communicates with the annular gas distribution pipe.

[0013] Furthermore, it also includes a spiral semi-tube jacketed heat exchange device fixedly installed on the outer wall of the tank body. The spiral semi-tube jacketed heat exchange device is composed of a metal tube with a semi-circular cross-section that is continuously wound in a spiral manner and welded to the outer surface of the tank body.

[0014] The present invention also provides a method for operating the above-mentioned multi-stage stirred fermenter, comprising the following stages: Phase 1: Start-up and Cooling After Sterilization Initial state: The tank has been evacuated and the temperature is high. Start the first and second motors, both set to low speed. The axial-flow first agitator rotates at low speed, initiating initial circulation inside and outside the guide tube; the radial-flow second agitator rotates at low speed, and the elastic scraper begins to slide against the tank wall. Cooling water is introduced into the spiral semi-tube jacketed heat exchanger. Because the elastic scraper continuously scrapes the tank wall, it disrupts the laminar boundary layer between the cooling water and the fermentation broth, allowing the heat from the high-temperature medium inside the tank to be rapidly transferred to the tank wall and then carried away by the jacket. The heat exchange efficiency is far higher than that of ordinary smooth-walled tanks.

[0015] Phase Two: Inoculation and Microbial Growth Period The goal at this stage is to promote rapid bacterial growth, requiring uniform mixing while avoiding excessive shear force (especially for filamentous bacteria or cells). The upper layer speed (first agitator shaft speed) is set to medium-high for macroscopic mixing; the lower layer speed (second agitator shaft speed) is set to medium-low to avoid damaging the bacteria. Air is introduced through a static annular gas distributor and directly dispersed by the radial-flow second agitator. Fluid state: Inside the guide tube, the fluid is powerfully pumped down by the upper impeller; outside the guide tube, oxygen-rich fluid is pushed upwards. The entire tank exhibits a uniform turbidity state with no dead zones.

[0016] Phase 3: Product Synthesis and High-Density Fermentation This stage involves high bacterial concentration, high oxygen demand, and high metabolic heat, and is prone to foaming or adhering to the walls. Parameter settings leverage the advantage of differential speed: the upper layer's rotation speed is maintained or slightly reduced to ensure macroscopic circulation; the lower layer's rotation speed is set to high speed to provide high shear force, breaking up bubbles more and extending their residence time in the liquid, forming a gas-liquid emulsion state, greatly improving dissolved oxygen efficiency. Simultaneously, the lower layer's elastic scraper scrapes the tank wall at a higher frequency, promptly removing viscous deposits that easily form on the wall due to increased metabolic products, preventing them from denaturing or clogging heat transfer. Fluid state: The bottom is a high-speed shear zone with small, dense bubbles, appearing as a white emulsion; at the upper guide tube outlet, the gas-liquid mixture flows out, some small bubbles may merge, but macroscopic circulation remains strong, delivering dissolved oxygen to all areas.

[0017] Voiding: After fermentation is complete, open the discharge port to drain the fermentation liquid.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. It adopts coaxial dual-shaft independent drive, combining axial flow and radial flow agitators to achieve synergistic effect of macroscopic mixing in the upper layer and microscopic mass transfer in the lower layer. The speed can be independently adjusted according to different fermentation stages to meet the differentiated needs of cell growth and product synthesis.

[0019] 2. A central guide tube is set up to guide the fluid to form a regular circulation and improve the mixing uniformity; at the same time, the guide tube covers the axial flow impeller, which enhances the pumping effect.

[0020] 3. The radial flow second agitator is equipped with an elastic scraper, which can break up air bubbles to enhance dissolved oxygen, continuously scrape the tank wall, disrupt the heat transfer boundary layer, significantly improve heat exchange efficiency, and prevent material from sticking to the wall.

[0021] 4. The static annular gas distributor is closely matched with the lower agitator, resulting in uniform gas distribution, good bubble refinement, large gas-liquid contact area, and high oxygen dissolution rate.

[0022] 5. The spiral semi-tube jacketed heat exchange device works in synergy with the elastic scraper to significantly improve the heat transfer coefficient, making it especially suitable for high-density fermentation processes. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the structure above the can lid; Figure 3 This is a schematic diagram of the internal structure of the tank. Figure 4 A schematic diagram of the internal structure of the central guide tube; Figure 5 A schematic diagram showing the fit between the upper and lower ends of the elastic scraper; Figure 6 This is a schematic diagram of the bottom structure of the central guide tube.

[0024] In the diagram: 10-Tank body; 11-Tank cover; 12-Discharge port; 13-Inlet port; 20-First stirring shaft; 21-Sealed bearing; 22-Bevel gear II; 30-Second stirring shaft; 31-Mounting base; 40-First motor; 41-Bevel gear I; 50-Second motor; 60-Mounting frame; 70-Axial flow first agitator; 71-Axial flow impeller; 80-Radial flow second agitator; 81-Hub; 82-Radial blades; 90-Central guide tube ; 91-Suspension support rod; 92-Guide cone skirt; 93-Annular slide rail; 100-Static annular gas distributor; 101-Annular gas distribution pipe; 102-Inlet pipe; 103-Outlet; 110-Elastic scraper; 111-Upper guide rod; 112-Lower support rod; 113-Upper damping spring; 114-Lower buffer spring; 115-Guide sleeve; 116-Rolling assembly; 117-Connecting crossbar; 120-Spiral half-pipe jacketed heat exchanger. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0026] As shown in the figure, a multi-stage stirred fermenter includes a tank body 10, a first stirring shaft 20 and a second stirring shaft 30 arranged coaxially, a drive mechanism, an axial flow first stirrer 70, a radial flow second stirrer 80, a central guide tube 90, a static annular gas distributor 100, and a spiral half-pipe jacketed heat exchange device 120.

[0027] The tank body 10 is a vertical cylindrical structure with a tank cover 11 sealed to the top and a discharge port 12 at the bottom. The tank cover 11 has a feed port 13. The tank cover 11 and the tank body 10 can be sealed together using flanges and gaskets.

[0028] The first stirring shaft 20 is a hollow tubular structure, vertically mounted on the central axis of the tank body 10, with its upper end supported on the tank cover 11 by a bearing. The second stirring shaft 30 is a solid shaft, rotatably coaxially sleeved within the inner cavity of the first stirring shaft 20, and the two rotate independently. A sealing bearing 21 is provided between the inner bottom end of the first stirring shaft 20 and the second stirring shaft 30 to ensure the sealing of their relative rotation and prevent material from entering the gap between the shafts.

[0029] The drive mechanism includes a first motor 40 and a second motor 50. The first motor 40 is mounted on the tank lid 11, and its output end is equipped with a first bevel gear 41. A second bevel gear 22 is located at the upper end of the first stirring shaft 20. The first bevel gear 41 and the second bevel gear 22 mesh with each other, thereby enabling the first motor 40 to drive the first stirring shaft 20. The second motor 50 is mounted on a mounting bracket 60 fixed to the top of the tank lid 11. Its output shaft is directly connected to the upper end of the second stirring shaft 30 via a coupling, and it drives the second stirring shaft 30 to rotate. Both the first motor 40 and the second motor 50 are variable frequency speed control motors, allowing their speeds to be independently adjusted according to the fermentation process requirements.

[0030] An axial-flow first agitator 70 is fixedly connected to the outer wall of the first agitator shaft 20 and located in the upper middle part of the tank body 10. In this embodiment, the axial-flow first agitator 70 includes two layers of axial-flow impellers 71. The angle between the chord line of the blades of each layer of axial-flow impellers 71 and the horizontal plane is 20° to 35°, preferably 30°, to generate a strong axial thrust and drive the fluid to flow axially. The radial gap between the outer edge of the blades and the inner wall of the central guide tube 90 is 1 / 50 to 1 / 20 of the diameter of the central guide tube 90. This gap ensures smooth fluid flow and prevents material from accumulating at the gap.

[0031] A radial flow second agitator 80 is fixedly connected to the extension of the second agitator 30 extending from the lower end of the first agitator 20. The agitator includes a hub 81 fixedly sleeved on the lower end of the second agitator 30 and a plurality of radial blades 82 uniformly fixed circumferentially to the sidewall of the hub 81. The radial blades 82 are used to generate a radial shear flow, breaking up bubbles from the gas distributor below and throwing them out radially.

[0032] The central guide tube 90 is a cylindrical structure with openings at both ends. Its top is fixedly connected to the inner wall of the tank cover 11 by multiple suspension support rods 91, thus suspending it inside the tank body 10. The central guide tube 90 is coaxial with the first stirring shaft 20 and the second stirring shaft 30, and completely encloses the axial flow first stirrer 70 inside it. The radial flow second stirrer 80 is located at the lower opening of the central guide tube 90. A guide cone skirt 92 is integrally formed or fixedly connected to the lower opening of the central guide tube 90. The guide cone skirt 92 is funnel-shaped, wider at the top and narrower at the bottom, which helps to guide the fluid to flow smoothly out from the bottom of the guide tube and avoid eddies and dead zones.

[0033] A static annular gas distributor 100 is fixedly installed at the opening below the central guide tube 90. It includes a horizontally arranged annular gas distribution pipe 101 coaxial with the central guide tube 90 and at least one air inlet pipe 102. The surface of the annular gas distribution pipe 101 has several air outlets 103, preferably downwards or obliquely downwards, to prevent material backflow. The air inlet pipe 102 passes through the suspension support rod 91 and extends downwards through the outer wall of the central guide tube 90, communicating with the annular gas distribution pipe 101. External air or oxygen-enriched gas enters the annular gas distribution pipe 101 through the air inlet pipe 102 and is then evenly sprayed out from the air outlets 103.

[0034] A mounting base 31 is installed at the bottom end of the second stirring shaft 30. Several connecting crossbars 117 are arranged radially on the mounting base 31. Each connecting crossbar 117 is provided with an elastic scraper 110 at its end. The elastic scraper 110 is used to scrape the inner wall of the tank 10 during rotation, remove adhering substances and enhance heat transfer.

[0035] Furthermore, the elastic scraper 110 is equipped with an upper guide rod 111 and a lower support rod 112 at its upper and lower ends, respectively, which are telescopically coordinated. An upper damping spring 113 is mounted on the upper guide rod 111, and a lower buffer spring 114 is mounted on the lower support rod 112. A connecting crossbar 117 is sleeved on the lower support rod 112, and one end of the lower buffer spring 114 abuts against the interior of the connecting crossbar 117. This structure gives the elastic scraper 110 a certain radial floating capability, ensuring close contact between the scraper and the tank wall while avoiding rigid impacts caused by tank roundness errors or vibrations.

[0036] A guide sleeve 115 is fitted around the outer side of the upper guide rod 111, and an upper damping spring 113 abuts against the inside of the guide sleeve 115. A rotatable rolling assembly 116 (such as a roller or bearing) is provided at the end of the guide sleeve 115, and an annular slide rail 93 is provided on the outer side of the bottom end of the central guide cylinder 90. The rolling assembly 116 slides within the annular slide rail 93 to form a rotational support. In this way, when the elastic scraper 110 rotates with the second stirring shaft 30, its top slides within the annular slide rail 93 through the rolling assembly 116, which not only ensures the positioning of the scraper but also reduces frictional resistance and enhances the stability of the scraper.

[0037] A spiral semi-tube jacketed heat exchanger 120 is fixedly installed on the outer wall of the tank body 10. This device consists of a metal tube with a semi-circular cross-section continuously wound in a spiral and welded to the outer surface of the tank body 10. Cooling water or steam can be introduced into the spiral semi-tube jacket for heating or cooling the material inside the tank. Due to the guiding effect of the spiral channel, the heat exchange medium has a high flow velocity and a large heat transfer coefficient. Combined with the scraping of the inner wall of the tank by the elastic scraper 110, the heat transfer efficiency is significantly improved.

[0038] The working process of the fermenter of the present invention is described below in conjunction with the above structure: Phase 1: Start-up and Cooling After Sterilization After the fermenter has undergone sterilization, the internal temperature is high. The first motor 40 and the second motor 50 are started, both set to low speed. The axial-flow first agitator 70 rotates at low speed, creating a downward pumping flow within the central guide tube 90, initiating initial circulation inside and outside the guide tube. The radial-flow second agitator 80 rotates at low speed, causing the elastic scraper 110 to slide against the wall. Simultaneously, cooling water is introduced into the spiral semi-tube jacketed heat exchanger 120. The elastic scraper 110 continuously scrapes the tank wall, disrupting the laminar boundary layer adhering to the wall, allowing the heat from the high-temperature medium inside the tank to be rapidly transferred to the tank wall and then carried away by the cooling water in the jacket, achieving rapid cooling.

[0039] Phase Two: Inoculation and Microbial Growth Period After the material cools to a suitable temperature, it is inoculated and replenished through inlet 13. During this stage, the bacteria are in their growth and reproduction phase and are sensitive to shear force. The speed of the first motor 40 is adjusted to a medium-high value to enhance macroscopic mixing; the speed of the second motor 50 is kept at a medium-low value to avoid excessive shear force damaging the bacteria. Air is introduced into the static annular gas distributor 100 through the air inlet pipe 102 and is evenly sprayed out from the air outlet 103 of the annular air distribution pipe 101. It is immediately initially dispersed by the low-speed rotating radial-flow second agitator 80, forming fine bubbles. Under the pumping action of the axial-flow first agitator 70, the fluid in the guide tube moves downwards, carrying bubbles into the lower part of the guide tube, and then flows out from the bottom of the guide tube, moving upwards along the annular gap between the tank wall and the guide tube, forming an overall circulation. The material in the entire tank is uniformly mixed, and the dissolved oxygen distribution is consistent.

[0040] Phase 3: Product Synthesis and High-Density Fermentation As fermentation progresses, the cell concentration increases, oxygen demand rises, metabolic heat increases, and foam or viscous substances may be produced. At this point, the speed of the first motor 40 is maintained or slightly reduced to maintain macroscopic circulation; the speed of the second motor 50 is adjusted to high speed to provide high shear force. The high-speed rotating radial blades 82 further cut the bubbles ejected from the gas distributor into extremely fine microbubbles, forming a gas-liquid emulsion state, which greatly increases the gas-liquid contact area and significantly improves the dissolved oxygen mass transfer coefficient. At the same time, the elastic scraper 110 scrapes the tank wall at a higher frequency to promptly remove any viscous wall deposits that may form due to the increase in metabolic products, keeping the tank wall clean and ensuring that the heat transfer efficiency does not decrease. The bottom high-speed shear zone has dense bubbles, appearing as a white emulsion; at the outlet of the upper guide tube, the gas-liquid mixture flows out, and some small bubbles may merge, but the macroscopic circulation remains strong, delivering the dissolved oxygen-rich fluid to all parts of the tank.

[0041] After fermentation is complete, open outlet 12 to discharge the fermentation liquid. Throughout the fermentation process, the rotation speed of the two shafts can be adjusted as needed to adapt to the process requirements at different stages.

[0042] In summary, this invention achieves efficient mixing, enhanced mass transfer, excellent heat transfer, and self-cleaning functions through the synergistic effect of coaxial dual-shaft independent drive, combined stirrer, guide tube, elastic scraper, and spiral half-tube jacket, making it particularly suitable for high-density aerobic fermentation processes.

Claims

1. A multi-stage stirred fermenter, characterized in that, include: The tank body (10) has a sealed lid (11) at the top and a discharge port (12) at the bottom. The lid (11) has a feed port (13). A first stirring shaft (20) and a second stirring shaft (30) are coaxially arranged. The first stirring shaft (20) is a hollow tubular structure, and the second stirring shaft (30) is rotatably coaxially sleeved in the inner cavity of the first stirring shaft (20). The two can rotate independently. A sealed bearing (21) is provided between the inner side of the bottom end of the first stirring shaft (20) and the second stirring shaft (30). The driving mechanism includes a first motor (40) mounted on the can lid (11) and a second motor (50) mounted on a mounting bracket (60) fixed on the top of the can lid (11); the first motor (40) is used to drive the first stirring shaft (20) to rotate, and the second motor (50) is used to drive the second stirring shaft (30) to rotate. An axial flow first agitator (70) is fixedly connected to the outer wall of the first agitator shaft (20); A radial flow second agitator (80) is fixedly connected to the extension of the second agitator shaft (30) extending out of the lower end of the first agitator shaft (20); The central guide tube (90) is a cylindrical structure with openings at both ends. It is fixedly installed inside the tank (10) and coaxially sleeved on the outside of the first stirring shaft (20) and the second stirring shaft (30). The central guide tube (90) completely covers the axial flow first stirrer (70) inside it, and the radial flow second stirrer (80) is located at the lower opening of the central guide tube (90). And a static annular gas distributor (100), which is fixedly installed at the opening below the central guide tube (90).

2. The multi-stage stirred fermenter according to claim 1, characterized in that: The output end of the first motor (40) is provided with a bevel gear one (41), and the upper end of the first stirring shaft (20) is provided with a bevel gear two (22). The bevel gear one (41) and the bevel gear two (22) are meshed and connected.

3. The multi-stage stirred fermenter according to claim 1, characterized in that: The axial flow first agitator (70) includes at least two layers of axial flow impellers (71), the angle between the blade chord of the axial flow impeller (71) and the horizontal plane is 20° to 35°; the radial gap between the outer edge of the blade and the inner wall of the central guide tube (90) is 1 / 50 to 1 / 20 of the diameter of the central guide tube (90).

4. A multi-stage stirred fermenter according to claim 1, characterized in that: The radial flow second agitator (80) includes a hub (81) fixedly sleeved on the lower end of the second agitator shaft (30), the hub (81) being in the shape of a solid frustum, and a plurality of radial blades (82) uniformly fixed along the circumferential sidewall of the hub (81), the radial blades (82) being used to generate radial shear flow.

5. A multi-stage stirred fermenter according to claim 1, characterized in that: The bottom end of the second stirring shaft (30) is equipped with a mounting base (31), and a plurality of connecting crossbars (117) are provided on the mounting base (31) extending radially, and each of the connecting crossbars (117) is provided with an elastic scraper (110) at its end.

6. A multi-stage stirred fermenter according to claim 5, characterized in that: The elastic scraper (110) is provided with an upper guide rod (111) and a lower support rod (112) with telescopic cooperation at its upper and lower ends respectively; the upper guide rod (111) is provided with an upper damping spring (113), and the lower support rod (112) is provided with a lower buffer spring (114); the connecting crossbar (117) is sleeved on the lower support rod (112), and one end of the lower buffer spring (114) abuts against the inside of the connecting crossbar (117).

7. A multi-stage stirred fermenter according to claim 6, characterized in that: The upper guide rod (111) is fitted with a guide sleeve (115) on its outer side, and the upper damping spring (113) abuts against the inside of the guide sleeve (115); the end of the guide sleeve (115) is provided with a rotatable rolling assembly (116), and the bottom outer side of the central guide tube (90) is provided with an annular slide rail (93). The rolling assembly (116) slides within the annular slide rail (93) to form a rotational support.

8. A multi-stage stirred fermenter according to claim 1, characterized in that: The top of the central guide tube (90) is fixedly connected to the inner wall of the can lid (11) by multiple suspension support rods (91); a guide cone skirt (92) is integrally formed or fixedly connected at the lower opening of the central guide tube (90), and the guide cone skirt (92) is in the shape of a trumpet with a larger top and a smaller bottom.

9. A multi-stage stirred fermenter according to claim 1, characterized in that: The static annular gas distributor (100) includes a horizontally arranged annular gas distribution pipe (101) coaxial with the central guide cylinder (90) and at least one air inlet pipe (102) in fluid communication with the annular gas distribution pipe (101); the surface of the annular gas distribution pipe (101) is provided with a plurality of air outlet holes (103); the air inlet pipe (102) extends downward through the suspension support rod (91) and the outer wall of the central guide cylinder (90) and communicates with the annular gas distribution pipe (101).

10. A multi-stage stirred fermenter according to claim 1, characterized in that: It also includes a spiral semi-tube jacketed heat exchange device (120) fixedly installed on the outer wall of the tank (10). The spiral semi-tube jacketed heat exchange device (120) is composed of a metal tube with a semi-circular cross section continuously wound in a spiral manner and welded to the outer surface of the tank (10).

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