Airlift fermentation tank with ventilation propeller

Abstract

The airlift fermentation tank comprises a tank body, a rotating shaft, a guide cylinder and a driving motor, the guide cylinder is coaxially arranged outside the rotating shaft, the lower end of the rotating shaft is provided with the ventilation propeller, the ventilation propeller is located at the lower middle position in the guide cylinder, the ventilation propeller comprises a tubular shaft, and propelling blades are circumferentially arranged on the outer wall of the tubular shaft; the propulsion blade is provided with a hollow cavity, a plurality of exhaust holes are formed in the surface of the propulsion blade and communicated with the hollow cavity, the root of the propulsion blade is communicated with an inner hole of the tubular shaft, a rotational flow device is arranged at the bottom of the guide cylinder, and the air inlet pipe penetrates through the rotational flow device from the bottom of the guide cylinder to be inserted into the tubular shaft. The interior of the tubular shaft, the interior of the propelling blade and the exhaust hole form a continuous gas channel; the device is reasonable in structure, good in gas-liquid mixing effect, efficient, energy-saving, smooth in overall circulating flow of fermentation liquid, regular in flow field, adjustable in circulating flow speed and free of anoxic zones, forced internal circulation is achieved under extremely low mechanical input power, and a powerful guarantee is provided for high-requirement fermentation engineering bacterium production.

Description

Technical Field

[0001] This invention relates to the field of bio-fermentation equipment technology, specifically to an airlift fermenter, and more particularly to an airlift fermenter with an air propulsion device, applicable to large-scale aerobic fermenters requiring the absence of contaminants. Background Technology

[0002] Bio-fermentation processes require the introduction of large amounts of sterile air into the fermenter. With the increasing size of individual fermenters, the rising concentration of microorganisms, and the adoption of high-volume, high-inoculation-rate production processes, achieving a highly efficient and energy-saving fermenter is of paramount importance.

[0003] Traditional fermenters typically have air intake devices fixed to the bottom of the fermenter. These devices usually come in various forms, such as straight-through, umbrella-shaped, perforated coil, and jet pipe. The basic principle of these devices is to use the static pressure of compressed air to enter the fermenter and mix with the fermentation broth. Straight-through and umbrella-shaped air intake devices are too simple in structure and cannot achieve uniform gas-liquid mixing and distribution for large-diameter fermenters. Perforated coil devices have limited gas-liquid mixing capacity, and this static device is prone to clogging with high-viscosity fermentation broths. Jet pipe devices require high compressed air pressure, which is detrimental to overall energy efficiency during fermentation. Similarly, for high-viscosity fermentations, the nozzles are prone to clogging with prolonged use, making maintenance inconvenient.

[0004] A search revealed a Chinese patent (patent number 201921003762.1) entitled "A Production Equipment for Improving the Efficiency of Closed Isocyanate Preparation," which designs a stirring blade with vent holes. Active gas is first introduced into the inner cavity of a closed stirring support on the reactor. The stirring shaft is a tubular shaft with a hole on its surface within the support, communicating with the interior. Gas is introduced through this hole and the internal channel of the shaft to the corresponding position of the stirring blade in the deep liquid phase inside the reactor. The stirring blade has an internal cavity. Gas from inside the tubular shaft is introduced into the inner cavity of the stirring blade through a pipe and finally discharged from the vent holes on the surface of the stirring blade. Gas is introduced from outside the reactor into the deep liquid phase and discharged from the surface of the stirring blade. When stirring is activated, this invention is beneficial for improving gas-liquid mass transfer efficiency and extending the gas-liquid reaction time. This stirring blade is suitable for chemical production with relatively small gas flow rates, but not for large-scale fermentation production with high air volume, and its structure does not consider the requirements of aseptic production.

[0005] There are also some published patents for airlift fermenters, but their application is limited to large-scale 200m³ fermenters. 3 No technology has yet been discovered that can adapt to fermentation processes with high solid content and high viscosity, while saving stirring power and not increasing air pressure.

[0006] A search revealed a Chinese patent with patent number 202021502364.7, entitled "A Large-Scale High-Mass Transfer Circulating Ventilated Fermentation Tank." This tank is essentially a non-stirred, airlift-type fermentation tank. The internal circulation power of the fermentation broth comes from the aforementioned "three-phase mixing thruster" and "three-phase mixing puller." Essentially, it uses a Venturi tube. High-speed compressed air jets enter the Venturi tube, drawing the fermentation broth in, and then ejecting it from the tail end. The fermentation tank also includes a circulation tank, which physically isolates the counter-current flow of the fermentation broth inside and outside the tank; this is often referred to as a flow guide. While the Venturi tube provides good multiphase mixing, using it as a propulsion device in deep fermentation broth (large fermentation tanks are typically 10 meters deep) is challenging. Large-scale circulation is difficult to achieve inside and outside the flow guide, and although there are many localized small circulations, material accumulation and blockage at the bottom of the fermentation tank are common when the solid content of the fermentation broth is high. The drawback of this structure is that the Venturi tube requires a considerably high inlet air pressure, and it also causes significant shear damage to the producing bacteria; therefore, it is gradually being phased out. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an airlift fermenter with a reasonable structure and good gas-liquid mixing effect, which is in response to the above-mentioned technical status quo.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: an airlift fermenter with an aeration propeller, comprising a tank body, a rotating shaft and a drive motor, wherein an air inlet pipe is provided at the lower end of the tank body and an exhaust pipe is provided at the top of the tank body, characterized in that: a guide tube is provided inside the tank body, the guide tube is coaxially arranged outside the rotating shaft, an aeration propeller is coaxially installed at the lower end of the rotating shaft, the aeration propeller is located in the lower middle part of the guide tube, the aeration propeller includes a tubular shaft, the outer wall of the tubular shaft is circumferentially arranged with propulsion blades, the propulsion blades have hollow cavities, the surface of the propulsion blades is provided with multiple exhaust holes communicating with the hollow cavities, the root of the propulsion blades is connected to the inner hole of the tubular shaft, a swirling device is provided at the bottom of the guide tube, the air inlet pipe passes through the swirling device from the bottom of the guide tube and is inserted into the tubular shaft of the aeration propeller, the interior of the tubular shaft, the interior of the propulsion blades and the exhaust holes form a continuous gas channel.

[0009] As an improvement, the guide tube is a variable diameter cylindrical structure with a small upper diameter and a large lower diameter, and the length of the upper part is greater than the length of the lower part. The upper and lower parts are connected by a conical transition. An enlarged diameter opening is formed at the upper opening of the guide tube. The upper end of the rotating shaft passes through the top of the tank and is connected to the drive motor for transmission. The lower end of the rotating shaft is inserted into the guide tube and located below the conical transition.

[0010] Furthermore, the ventilated thruster is installed at the lower end of the rotating shaft via a flange connection. The shaft end flange at the lower end of the rotating shaft is a plate flange or a clamp coupling. The upper end of the tubular shaft of the ventilated thruster is a reduced-diameter section connected to the rotating shaft. At the end of the reduced-diameter section, a blind flange is provided that mates with the shaft end flange of the rotating shaft.

[0011] Furthermore, the propulsion blade is a spiral curved blade as a whole, and the outer wall of the tubular shaft is uniformly provided with blade slots for installing the propulsion blade along the circumference. The root of the propulsion blade is inserted into the blade slot and fixedly connected to the tubular shaft by welding or special flange.

[0012] Furthermore, the root thickness of the propulsion blade is the greatest and gradually decreases outwards; correspondingly, the root height of the hollow cavity inside the propulsion blade is the greatest and gradually decreases outwards.

[0013] Furthermore, the number of exhaust holes on the upper and lower surfaces of the propulsion blades is different, with the lower surface having a large number of exhaust holes and the upper surface having a small number of exhaust holes.

[0014] Furthermore, the diameter of the intake pipe is smaller than the diameter of the inner hole of the tubular shaft, the radial gap between the intake pipe and the inner wall of the tubular shaft is 20mm~40mm, the lower end face of the tubular shaft is provided with a convex ring extending horizontally outward, and a circular ring corresponding to the convex ring is welded at the pipe opening of the exhaust pipe. The convex ring and the circular ring are coaxially installed and the overlapping part forms a gap sealing structure. The circumferential gap height between the circular ring and the convex ring is 8mm~20mm, and the gap width is 50mm~100mm.

[0015] Furthermore, the drive motor is a variable frequency synchronous motor, which is installed at the top of the tank, with the upper end of the rotating shaft extending out of the tank and connected to the motor shaft for transmission.

[0016] Finally, the number of propulsion blades is 2 to 4.

[0017] Compared with existing technologies, the advantages of this invention are as follows: A guide tube and an aeration propeller are installed inside the tank. The aeration propeller is connected to the lower end of the rotating shaft and rotates with the shaft. The aeration propeller includes a tubular shaft and propulsion blades. The propulsion blades have hollow cavities and exhaust holes. An air inlet pipe is inserted into the tubular shaft of the aeration propeller. The interior of the tubular shaft, the interior of the propulsion blades, and the exhaust hole form a continuous gas channel, allowing the gas to mix thoroughly with the fermentation broth when the aeration propeller rotates. This invention has a reasonable structure, excellent gas-liquid mixing effect, and is highly efficient and energy-saving. The fermentation broth circulates smoothly and regularly, with an adjustable circulation speed. It avoids the anoxic zone common in airlift tanks and achieves forced internal circulation with extremely low mechanical input power, providing a strong guarantee for the production of high-requirement fermentation engineered bacteria. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the fermenter according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of a ventilated thruster;

[0020] Figure 3 for Figure 2 Sectional view of line AA (after linearization). Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] like Figures 1-3 As shown, an airlift fermenter with an aeration propeller includes a tank body 1, a rotating shaft 2, a drive motor 8, a guide tube 3, and an aeration propeller 4. An air inlet pipe 6 is located at the lower side of the tank body 1, and an exhaust pipe 7 is located on one side of the top of the tank body 1. The guide tube 3 is vertically installed inside the tank body 1 and coaxially positioned outside the rotating shaft 2. The aeration propeller 4 is installed at the lower end of the rotating shaft 2, located in the lower-middle part of the guide tube 3. The aeration propeller 4 includes a tubular shaft 41, and propulsion blades 42 are evenly distributed circumferentially on the outer wall of the tubular shaft 41. The propulsion blades 42 have… There is a hollow cavity 422. The surface of the propulsion blade 42 is provided with multiple exhaust holes 421 that communicate with the hollow cavity 422. The root of the propulsion blade 42 is connected to the inner hole of the tubular shaft 41. In order to make the fermentation liquid flowing downward from the outlet of the guide tube 3 more smoothly turn upward after encountering the bottom of the fermentation tank, the bottom of the guide tube 3 is provided with a swirling device 5. The air inlet pipe 6 passes through the swirling device 5 from the bottom of the guide tube 3 and is inserted into the tubular shaft 41 of the air propulsion device 4. The interior of the tubular shaft 41, the interior of the propulsion blade 42, and the exhaust holes 421 form a continuous channel for gas.

[0023] The specific structure is as follows: the guide tube 3 is a variable diameter cylindrical structure with a small upper diameter and a large lower diameter, and the length of the upper part is greater than the length of the lower part. The upper and lower parts are transitioned by a conical surface 32. The upper opening of the guide tube 3 is formed with an enlarged diameter port 31. The upper end of the rotating shaft 2 passes through the top of the tank and is connected to the drive motor 8 for transmission. The lower end of the rotating shaft 2 is inserted into the guide tube 3 and is located below the transition of the conical surface 32. For easy disassembly and assembly, the venting thruster 4 is installed at the lower end of the rotating shaft 2 by means of a flange connection. The shaft end flange 21 at the lower end of the rotating shaft 2 adopts a plate flange or a clamp coupling. The upper end of the tubular shaft 41 of the venting thruster 4 is a reduced diameter section connected to the rotating shaft 2. At the end of the reduced diameter section, there is a blind flange 412 that mates with the shaft end flange 21 of the rotating shaft 2.

[0024] The number of propulsion blades 42 is 2 to 4. Each propulsion blade 42 is a helical curved blade. The outer wall of the tubular shaft 41 has uniformly spaced circumferential slots for mounting the propulsion blades 42. The root of the propulsion blade 42 is inserted into the slot and fixedly connected to the tubular shaft 41 by welding or a shaped flange. The root of the propulsion blade 42 has the greatest thickness, gradually decreasing outwards. Correspondingly, the root height of the hollow cavity 422 inside the propulsion blade 42 has the greatest height, gradually decreasing outwards. Because the lower part of the aeration propulsion device 4 is oxygen-rich and the upper part is relatively oxygen-deficient when the fermentation broth flows downwards, the number of exhaust holes 421 on the upper and lower surfaces of the propulsion blade 42 is different. The exhaust holes 421 are mainly distributed on the lower surface of the propulsion blade 42, with a small number of exhaust holes 421 distributed on the upper surface, allowing sterile air to escape upwards, creating a micro-oxygen zone.

[0025] The diameter of the intake pipe 6 is smaller than the diameter of the inner hole of the tubular shaft 2. The radial clearance between the intake pipe 6 and the inner wall of the tubular shaft 2 must be greater than the shaft swing amplitude. In this embodiment, it is 20mm~40mm. The lower end face of the tubular shaft 2 is provided with a horizontally extending convex ring 411. A circular ring 61 corresponding to the convex ring 411 is welded to the pipe opening of the exhaust pipe 6. The convex ring 411 and the circular ring 61 are coaxially installed and their overlapping parts form a gap sealing structure. The height h of the circumferential gap 10 is 8mm~20mm and the gap width w is 50mm~100mm. In this way, the large radial clearance between the intake pipe 6 and the tubular shaft 2 is transformed into a closer circumferential gap 10. Moreover, the radial clearance between the intake pipe 6 and the inner wall of the tubular shaft 2 can be appropriately lengthened to 50mm~100mm. This ensures that the air-permeable propeller 4 does not scrape against the fixed intake pipe 6 when rotating, and also ensures that the gas flow rate leaking from the gap is negligible. The airflow resistance through this gap achieves the function of controlling the gas flow rate in this path.

[0026] The drive motor 8 is a variable frequency synchronous motor. The drive motor 8 is installed at the top of the tank 1, and the upper end of the rotating shaft 2 extends out of the tank 1 and is connected to the motor shaft for transmission.

[0027] The specific working principle is as follows:

[0028] The sterile air exiting from the intake pipe 6 is mainly discharged through the numerous exhaust holes 421 on the lower surface of the propeller blade 42, with a small amount of air discharged from the circumferential gap 10. To address the issue of insufficient dissolved oxygen in the fermentation broth above the aeration propeller 5 within the guide tube, several exhaust holes 421 are also provided on the upper surface of the propeller blade 42 to supply oxygen to the fermentation broth above it. This structural design ensures that air enters the fermentation broth in a more ideal state: small bubble diameter, good dispersion, good gas-liquid mixing (emulsification) effect, and balanced dissolved oxygen distribution.

[0029] When stationary, air can be discharged as long as the air pressure is greater than the static pressure of the liquid layer where the exhaust port 421 is located. When rotating, a relatively low-pressure zone is formed at the moment the fermentation liquid separates from the propeller blade 42, allowing air to enter the fermenter at a lower pressure.

[0030] The forced circulation direction inside the fermentation broth is as follows: downward inside the guide tube; after passing through the swirling device at the bottom of the guide tube, the fermentation broth forms a swirling flow, which has both axial and radial flow, and the flow direction changes at the bottom of the fermenter, spiraling upward along the outside of the guide tube; after reaching the top of the guide tube at the liquid surface, it turns inward again, thus achieving circulation.

[0031] From a macroscopic perspective of the fermenter, under the action of the aeration propeller 4, the fermentation liquid flows downward in the guide tube 3. At the bottom of the guide tube 3, as it passes the guide device 5, the axial flow changes to a swirling flow, possessing both axial and radial components. The swirling flow can smoothly change direction at the bottom of the fermenter, and then flows upward around the guide tube 3. It continues upward until it reaches the height of the expanded diameter port 31 at the upper end of the guide tube 3, after which it flows back into the interior. This achieves forced internal circulation of the fermentation liquid. To accommodate different gas contents in different areas, the guide tube 3 is designed with a variable diameter structure, with a smaller upper diameter and a larger lower diameter.

[0032] Compared with traditional mechanically stirred fermenters, this invention can reduce stirring power by 50% to 90% without increasing the inlet air pressure; compared with unstirred simple airlift fermenters, the inlet air pressure can be reduced by 0.01 MPa to 0.05 MPa, and the inlet pressure can even be lower than the static pressure of the liquid layer at the air inlet. Both can bring significant direct energy-saving benefits and indirect benefits from improved production stability.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An airlift fermenter with an aeration propulsion device, comprising a tank body, a rotating shaft, and a drive motor, wherein an air inlet pipe is provided at the lower end of the tank body, and an exhaust pipe is provided at the top of the tank body, characterized in that: The tank is equipped with a guide tube, which is coaxially mounted outside the rotating shaft. A ventilating thruster is coaxially mounted at the lower end of the rotating shaft. The ventilating thruster is located in the lower middle part of the guide tube. The ventilating thruster includes a tubular shaft, and propulsion blades are arranged circumferentially on the outer wall of the tubular shaft. The propulsion blades have hollow cavities, and multiple exhaust holes on the surface of the propulsion blades communicate with the hollow cavities. The root of the propulsion blades is connected to the inner hole of the tubular shaft. A swirl device is provided at the bottom of the guide tube. The air inlet pipe passes through the swirl device from the bottom of the guide tube and is inserted into the tubular shaft of the ventilating thruster. The interior of the tubular shaft, the interior of the propulsion blades, and the exhaust holes form a continuous channel for gas.

2. The airlift fermenter according to claim 1, characterized in that: The guide tube is a variable diameter cylindrical structure with a small upper diameter and a large lower diameter, and the length of the upper part is greater than the length of the lower part. The upper and lower parts are connected by a conical transition. The upper opening of the guide tube has an enlarged diameter opening. The upper end of the rotating shaft passes through the top of the tank and is connected to the drive motor. The lower end of the rotating shaft is inserted into the guide tube and located below the conical transition.

3. The airlift fermenter according to claim 2, characterized in that: The ventilated thruster is installed at the lower end of the rotating shaft via a flange connection. The shaft end flange at the lower end of the rotating shaft is a plate flange or a clamp coupling. The upper end of the tubular shaft of the ventilated thruster is a reduced-diameter section connected to the rotating shaft. At the end of the reduced-diameter section, a blind flange is provided that mates with the shaft end flange of the rotating shaft.

4. The airlift fermenter according to claim 3, characterized in that: The propulsion blade is a spiral curved blade. The outer wall of the tubular shaft is uniformly provided with blade slots for installing the propulsion blades along the circumference. The root of the propulsion blade is inserted into the blade slot and fixedly connected to the tubular shaft by welding or a special-shaped flange.

5. The airlift fermenter according to claim 4, characterized in that: The root of the propulsion blade has the greatest thickness, which gradually decreases outward. Correspondingly, the root height of the hollow cavity inside the propulsion blade has the greatest height, which gradually decreases outward.

6. The airlift fermenter according to claim 5, characterized in that: The number of exhaust holes on the upper and lower surfaces of the propulsion blades is different, with the lower surface having a large number of exhaust holes and the upper surface having a small number of exhaust holes.

7. The airlift fermenter according to any one of claims 1 to 6, characterized in that: The diameter of the intake pipe is smaller than the diameter of the inner hole of the tubular shaft. The radial gap between the intake pipe and the inner wall of the tubular shaft is 20mm~40mm. The lower end face of the tubular shaft is provided with a convex ring extending horizontally outward. A circular ring corresponding to the convex ring is welded at the pipe opening of the exhaust pipe. The convex ring and the circular ring are coaxially installed and the overlapping part forms a gap sealing structure. The circumferential gap height between the circular ring and the convex ring is 8mm~20mm and the gap width is 50mm~100mm.

8. The airlift fermenter according to any one of claims 1 to 6, characterized in that: The drive motor is a variable frequency synchronous motor, which is installed at the top of the tank. The upper end of the rotating shaft extends out of the tank and is connected to the motor shaft for transmission.

9. The airlift fermenter according to any one of claims 1 to 6, characterized in that: The number of propulsion blades is 2 to 4.

Images