An internal-external double circulation air-lift type aerobic fermentation device

Abstract

This invention discloses an internal and external dual-circulation airlift aerobic fermentation device, relating to the field of microbial aerobic fermentation. The device includes a gas conveying system, a fermenter, a circulating pump, a circulating cooler, a liquid distributor, a liquid-gas jet emulsification device, a gas distributor, a guide tube, an internal coil heat exchanger, and a circulating liquid suction device. This invention utilizes multiple centrally symmetrical liquid-gas jet emulsification devices within the fermenter, employing high-speed liquid flow to strongly shear and collide with the gas phase, breaking the air into micron-sized fine bubbles, thus significantly increasing the gas-liquid contact surface area. Simultaneously, the use of rotating jets and a guide tube design ensures thorough mixing of the gas and liquid phases during the jetting process, forming an innovative internal and external dual-circulation mode. This invention combines the advantages of traditional mechanical stirring and airlift fermenters, significantly improving the production capacity and oxygen utilization rate of the fermentation device while substantially reducing energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of microbial aerobic fermentation technology, specifically relating to an internal and external dual-circulation airlift aerobic fermentation device, which is particularly suitable for the aerobic fermentation production of high value-added products such as antibiotics, amino acids, enzyme preparations, organic acids and microbial proteins. Background Technology

[0002] Aerobic fermentation is a series of biological processes in which microorganisms utilize oxygen as an electron acceptor to convert substrates into target products under aerobic conditions. It is widely used in the production of high-value-added products such as antibiotics, amino acids, enzyme preparations, organic acids, and microbial proteins, and is one of the core technologies in modern bioengineering.

[0003] Efficient oxygen transport and mixing are crucial for successful aerobic fermentation. Due to the extremely low solubility of oxygen in the fermentation broth and the rapid oxygen consumption by microorganisms during growth, the fermentation unit must possess strong oxygen supply and mass transfer capabilities to ensure that the dissolved oxygen (DO) concentration in the fermentation broth meets the needs of the microorganisms. Currently, the mainstream aerobic fermentation units in industry are mechanically stirred fermenters (CSTRs) and airlift fermenters (ALRs).

[0004] Mechanically stirred fermenters achieve oxygen supply and mixing through bottom gas distribution and multi-layered stirring paddles installed inside the tank. However, they have the following obvious drawbacks: (1) The stirring paddle drive requires a large amount of electrical energy, and the stirring power accounts for a large proportion of the total energy consumption of fermentation; (2) The shaft seal, reducer and stirring system have high maintenance costs and there are risks of leakage and contamination; (3) As the tank size increases, it is difficult to maintain the mixing efficiency of oxygen and materials, and the scale-up effect is significant.

[0005] Traditional airlift fermenters rely primarily on the upward force of air bubbles for mixing and mass transfer. While they have lower energy consumption and less shear force, their gas-liquid contact area and mixing intensity are relatively low, and their oxygen utilization rate and volumetric mass transfer coefficient (kLa) are often lower than those of mechanically stirred tanks. For high-viscosity or high-density fermentation broths, they cannot effectively ensure uniform gas-liquid mixing, making it difficult to meet the requirements of high-density, high-aerobic fermentation.

[0006] Existing improved airlift equipment mostly only optimizes a single gas distribution structure or a single flow guiding structure, failing to systematically upgrade from the circulation mode, gas-liquid emulsification method, and overall temperature control, and thus cannot simultaneously achieve low energy consumption, high dissolved oxygen, strong mixing, and wide system adaptability.

[0007] Therefore, there is an urgent need to develop a new type of aerobic fermentation device that combines high oxygen utilization, high mixing efficiency, and low energy consumption to meet the needs of high-density, high-oxygen-consumption fermentation. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention aims to provide an internal and external dual-circulation airlift aerobic fermentation device. By setting multiple centrally symmetrical liquid-gas jet emulsification devices inside the tank, high-intensity gas-liquid contact and mixing are achieved, greatly improving mass transfer efficiency and oxygen utilization. Simultaneously, the use of rotary jetting and a guide tube design forms an innovative "internal and external dual-circulation" mode. This invention combines the advantages of traditional mechanical stirring and airlift fermenters, significantly improving the production capacity and oxygen utilization of the fermentation device while significantly reducing energy consumption, providing a more efficient and economical solution for microbial aerobic fermentation.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention proposes an internal and external dual-circulation airlift aerobic fermentation device, including a gas conveying device, a fermenter, a circulating conveying pump, a circulating cooler, a liquid distributor, and a gas distributor; The fermenter is equipped with a liquid-gas type jet emulsification device, a guide tube, an internal coil heat exchanger, and a circulating liquid suction device. The outlet of the gas conveying equipment is connected to the inlet of the gas distributor, and the gas phase branch pipe of the gas distributor passes through the fermentation tank shell and is connected to the gas phase inlet of the liquid-gas type jet emulsification device. The outlet of the circulating liquid suction device is connected to the inlet of the circulating delivery pump, the outlet of the circulating delivery pump is connected to the inlet of the circulating cooler, the outlet of the circulating cooler is connected to the liquid phase inlet of the liquid distributor, and the liquid phase branch pipe of the liquid distributor passes through the fermenter shell and is connected to the liquid phase inlet of the liquid-gas type jet emulsification device. The liquid-gas type jet emulsification device is centrally symmetrically distributed in the fermentation tank. The bottom of the liquid-gas type jet emulsification device is provided with a guide pipe, and adjacent guide pipes are arranged along the tangential direction. The guide tube divides the interior of the fermenter into an ascending and descending zone, achieving efficient internal circulation. The ascending and descending zones are defined by the guide tube; the ascending zone, located inside the guide tube, includes the channels formed within the primary guide tube, secondary guide tube, and diffuser tube. After gas enters from the bottom, the gas content inside the guide tube is high, and the apparent density of the gas-liquid mixture is low. Under the influence of buoyancy and gas lifting, it flows upwards along the inside of the guide tube, hence the name ascending zone. The descending zone is the annular area between the outer wall of the guide tube and the inner wall of the fermenter. After the gas-liquid mixture rises to the top within the guide tube, it diffuses through the diffuser tube, causing some gas to escape or disperse, while the liquid turns and enters the outer area of ​​the guide tube, flowing downwards along the annular gap between the tank wall and the guide tube, hence the name descending zone.

[0010] The guide tube is installed inside the tank and arranged coaxially with the tank. An ascending zone is formed inside the guide tube, and a descending zone is formed between the outer wall of the guide tube and the inner wall of the tank. The gas-liquid mixture flows upward along the ascending zone under the lifting action of the gas, diffuses at the top of the guide tube, enters the descending zone, and flows back downward. It then re-enters the guide tube inlet at the bottom of the tank, thus forming a stable internal circulation flow.

[0011] Furthermore, the number of liquid-gas type jet emulsification devices is 2, 4, 6 or 8, and the liquid-gas type jet emulsification devices are fixedly connected to the fermenter shell or guide tube through fasteners.

[0012] Furthermore, the injection angle of adjacent guide tubes is set to 180°, 90°, 60° or 45° depending on the number of guide tubes.

[0013] Furthermore, the downward-sloping cut at the outlet of the guide tube forms an angle of 30°-60° with the horizontal plane, preferably 45°.

[0014] Furthermore, the guide tube includes a primary guide tube, a secondary guide tube, a diffuser tube, and supporting ribs. The diameter ratio of the primary guide tube to the fermentation tank is (0.4-0.8):1, the diameter ratio of the secondary guide tube to the fermentation tank is (0.3-0.5):1, and the diffuser tube has a flared, funnel-shaped structure that is larger at the top and smaller at the bottom.

[0015] Furthermore, the height-to-diameter ratio of the fermentation tank is (3-8):1.

[0016] Furthermore, the gas distributor is provided with a gas phase inlet at the top and multiple gas phase branch pipes are evenly distributed on the side of the gas distributor, with each gas phase branch pipe connected to the gas phase inlet on the side of each liquid-gas type jet emulsification device.

[0017] Furthermore, the liquid distributor is provided with a liquid phase inlet at the bottom, and multiple liquid phase branch pipes are evenly distributed on the side of the liquid distributor. The outlet of each liquid phase branch pipe is connected to the liquid phase inlet at the top of each liquid-gas type jet emulsification device.

[0018] Furthermore, the internal coil heat exchanger is distributed between the guide tube and the fermenter wall; the circulating cooler is one or a combination of a fixed tube sheet heat exchanger, a plate heat exchanger, or a spiral tube heat exchanger.

[0019] Furthermore, the fermenter is provided with a drain outlet at the bottom and a tail gas outlet and a raw material liquid inlet at the top.

[0020] The working principle of this invention is as follows: First, culture medium, seed liquid, and other fermentation raw materials are added to the fermenter. Once the liquid level in the fermenter reaches the designed level, the circulation pump is turned on. After being evenly distributed by the distributor, the circulating liquid enters each liquid-gas type jet emulsification device to form a high-speed jet, which returns to the fermenter and is sprayed out tangentially, driving the rotation of the material inside the tank and realizing the external circulation of the fermentation liquid and the radial mixing of the material inside the tank.

[0021] After the fermentation broth circulation is established, the gas delivery equipment is started to transport the raw material air to the gas distributor. After being evenly distributed, the air enters each liquid-gas type jet emulsification device. The gas and liquid phases are violently sheared and mixed in the liquid-gas type jet emulsification device to form an emulsion state. The air bubbles are broken into micron-sized fine bubbles, which are then injected into the fermentation tank through a rotating jet, which greatly increases the dissolved oxygen rate and prolongs the residence time of the bubbles in the liquid phase.

[0022] Meanwhile, due to the low density of the ejected gas-liquid mixture, it enters the inside of the guide tube (rising zone) and moves upward. After the gas content decreases at the top, the fermentation liquid sinks and enters the space between the guide tube and the outer shell (falling zone), thus realizing the internal circulation of the fermentation liquid between the guide tube and the tank wall.

[0023] Once the internal and external circulation is established, cooling medium is introduced into the internal coil heat exchanger and the circulating cooler. The internal coil heat exchanger provides a basic constant temperature environment, while the circulating cooler utilizes the high-speed flow of the liquid phase to achieve efficient heat exchange, solving the problem of heat accumulation during high-intensity fermentation and ensuring stable fermentation temperature.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly improved oxygen mass transfer efficiency. This invention utilizes a centrally symmetrically arranged liquid-gas jet emulsification device, which employs the strong shearing and mutual impact of high-speed liquid flow on the gas phase to break up air into micron-sized fine bubbles, greatly increasing the specific surface area of ​​gas-liquid contact. Production verification shows that compared with traditional airlift fermenters, dissolved oxygen is increased by more than 10%, and the volumetric mass transfer coefficient (kLa) is significantly improved, which can meet the oxygen demand of fermentation processes with high cell density and high oxygen consumption.

[0025] (2) Innovative "Dual Circulation" Mode. This invention combines rotary jetting, a guide tube, and an external circulation device to form an innovative "dual circulation" mode. The jetting emulsification device creates a highly turbulent mixing zone inside the guide tube, ensuring high-intensity mass transfer in a localized area; the macroscopic flow between the guide tube and the tank wall ensures uniform distribution of materials throughout the tank; and the external circulation system achieves efficient heat exchange and recycling of the fermentation broth. The internal and external circulations work together synergistically to ensure both high-intensity gas-liquid mixing in a localized area and uniform distribution of materials throughout the tank.

[0026] (3) Significantly reduced energy consumption. This invention completely replaces the traditional mechanical stirring system, fundamentally solving the problems of high power consumption, easy shaft seal leakage, easy damage to the reducer, and high risk of bacterial contamination in traditional mechanical stirring tanks. Production practice shows that after adopting the technical solution of this invention, the total energy consumption is reduced from 850kW to 67kW, a reduction of more than 92.2%, while the air feed pressure is reduced from 0.32MPa to 0.005MPa, significantly reducing the energy consumption of air compression.

[0027] (4) Improved fermentation conversion rate. Due to the significant improvement in dissolved oxygen environment, the metabolic activity of microorganisms is enhanced, and the product conversion rate is significantly improved. Production verification showed that in the fermentation of a certain bacterial protein, the product conversion rate increased from 75.7% to 84.6%, an increase of 8.9%.

[0028] (5) Reliable structure and easy to scale up. This invention uses a static jet emulsification device to replace the traditional dynamic mechanical stirring, eliminating the need for moving sealing components and fundamentally eliminating the risk of leakage and contamination. At the same time, the device has a simple structure, small scale-up effect, and is suitable for large-scale industrial production.

[0029] In summary, this device significantly improves the production capacity and oxygen utilization rate of fermentation equipment, while significantly reducing energy consumption, providing a more efficient and economical solution for aerobic microbial fermentation. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the complete structure of an internal and external dual-circulation airlift aerobic fermentation device according to the present invention; Figure 2 This is a top view of the fermenter and its internal components of the present invention; Figure 3 This is a schematic diagram of the structure of the guide tube of the present invention.

[0031] The meanings of the markings in the diagram are as follows: 1. Gas conveying equipment; 2. Fermentation tank; 3. Circulating transfer pump; 4. Circulating cooler; 5. Liquid distributor; 501. Liquid inlet of liquid distributor; 502. Branch pipe of liquid distributor; 6. Liquid-gas type jet emulsification device; 601. Guide pipe; 7. Gas distributor; 701. Gas inlet of gas distributor; 702. Branch pipe of gas distributor; 8. Flow guide tube; 801. Primary flow guide tube; 802. Secondary flow guide tube; 803. Diffuser tube; 804. Support rib; 9. Fixed parts; 10. Internal coil heat exchanger; 11. Circulating liquid suction device; 12. Drain outlet; 13. Tail gas outlet; 14. Raw material liquid inlet. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] like Figures 1-3 As shown, an internal and external dual-circulation airlift aerobic fermentation device is used for the aerobic fermentation production of microbial proteins.

[0034] (I) Device Structure The apparatus includes a gas conveying device 1, a fermenter 2, a circulating pump 3, a circulating cooler 4, a liquid distributor 5, a gas distributor 7, and a circulating liquid suction device 11. The fermenter 2 has a height-to-diameter ratio of 5:1 and a nominal volume of 130 m³. 3 .

[0035] The fermenter 2 is equipped with a liquid-gas type jet emulsification device 6, a guide tube 8, an internal coil heat exchanger 10, a circulating liquid suction device 11, and a fixing component 9. The fermenter 2 has a drain port 12 at the bottom and a tail gas outlet 13 and a raw material liquid inlet 14 at the top.

[0036] The number of liquid-gas type jet emulsification devices 6 is 4, which are centrally symmetrically distributed in the fermentation tank 2. The jet angle of the adjacent guide pipes 601 is 90°, and they are set along the tangential direction. The outlet of the guide pipe 601 is a 45° downward cut.

[0037] The flow guide tube 8 includes a primary flow guide tube 801, a secondary flow guide tube 802, a diffuser tube 803, and a supporting rib plate 804. The diameter ratio of the primary flow guide tube 801 to the fermenter 2 is 0.6:1, and the diameter ratio of the secondary flow guide tube 802 to the fermenter 2 is 0.4:1. The internal coil heat exchanger 10 is distributed between the flow guide tube 8 and the tank wall of the fermenter 2.

[0038] The primary guide tube 801 is located at the lower end of the guide tube 8 and has a shape that is wider at the bottom and narrower at the top, or a trumpet / frustum shape. Its function is to introduce the gas-liquid mixture at the bottom of the tank into the interior of the guide tube more smoothly, reduce local resistance and dead zones at the inlet, and at the same time play a certain role in contracting, accelerating and rectifying the gas-liquid mixture.

[0039] The secondary guide tube 802 is the straight section in the middle, which is the main channel for the gas-lift circulation. After the gas enters, the gas content inside the guide tube is high and the apparent density is low, forming an upward lifting flow; the liquid outside the guide tube flows downward back, forming an internal circulation.

[0040] The primary guide tube 801 is located at the lower end of the secondary guide tube 802 and is arranged coaxially with the secondary guide tube 802. The upper end of the primary guide tube 801 is connected to the lower end of the secondary guide tube 802 or partially extends into its lower opening area. It is fixed and positioned by the supporting stiffener 804, so that a continuous gas-liquid upward guiding channel is formed between the two.

[0041] The outlet of the gas conveying device 1 is connected to the inlet of the gas phase main pipe of the gas distributor 7. The gas phase branch pipe of the gas distributor 7 passes through the fermentation tank shell and is connected to the gas phase inlet of the liquid-gas type jet emulsification device 6. The outlet of the circulating liquid suction device 11 is connected to the inlet of the circulating transfer pump 3. The outlet of the circulating transfer pump 3 is connected to the inlet of the circulating cooler 4. The outlet of the circulating cooler 4 is connected to the liquid phase inlet of the liquid distributor 5. The liquid phase branch pipes of the liquid distributor 5 pass through the fermentation tank shell and are connected to the liquid phase inlet of the liquid-gas type jet emulsification device 6. The circulating cooler 4 is a plate heat exchanger.

[0042] The liquid-gas type jet emulsification device 6 and the guide tube 8 are fixedly connected to the fermenter shell through the fastener 9.

[0043] (II) Work Process First, culture medium and seed liquid are added to fermenter 2. When the liquid level reaches the designed level, the circulation pump 3 is turned on. After being evenly distributed by the distributor 5, the circulating liquid enters each liquid-gas type jet emulsification device 6 to form a high-speed jet, which is sprayed into fermenter 2 tangentially, causing the material in the tank to rotate, thus realizing external circulation and radial mixing.

[0044] After the fermentation broth circulation is established, the gas delivery device 1 is started to deliver sterile air to the gas distributor 7, which then distributes it evenly and enters each liquid-gas type jet emulsification device 6. The gas and liquid phases are violently sheared and mixed in the liquid-gas type jet emulsification device 6 to form an emulsion. The air is broken into micron-sized fine bubbles, which are then injected into the fermentation tank 2 through a rotating jet.

[0045] The ejected gas-liquid mixture enters the interior of the guide tube 8 (rising zone) and moves upward. After reaching the top, the fermentation liquid sinks into the space between the guide tube 8 and the tank wall (falling zone), achieving internal circulation. At the same time, cooling medium is introduced into the internal coil heat exchanger 10 and the circulating cooler 4 to maintain a constant fermentation temperature.

[0046] Example 1

[0047] This dual-circulation airlift aerobic fermentation device was applied to the fermentation of cell protein, replacing the manufacturer's existing 130m mechanically stirred fermentation unit. 3The fermenter was replaced. The original fermenter used a multi-stage combined agitator with a stirring power of 220 kW. To meet the dissolved oxygen rate requirements, a jet nozzle was used at the bottom, and the air had to be compressed before entering the tank, with a feed pressure of 0.32 MPa. The technical solution provided by this invention replaced the original mechanically stirred fermenter. The energy consumption parameters and conversion rate indicators are shown in Table 1.

[0048] By adopting the technical solution of this invention, the high-power agitator of the original fermenter is replaced with a 35kW circulating pump. The raw material gas only needs to be pressurized using a low-pressure blower, reducing the air feed pressure to 0.005MPa, which significantly reduces air compression energy consumption. Production verification shows that the product conversion rate is increased by 8.9%, dissolved oxygen is increased by more than 10%, and production power consumption is reduced by more than 92.2%. A summary table of relevant energy consumption parameters is shown in Table 1.

[0049] Table 1. Summary of energy consumption parameters for different fermentation equipment used in the production of bacterial protein.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dual-circulation airlift aerobic fermentation device, characterized in that, It includes a gas conveying device (1), a fermenter (2), a circulating conveying pump (3), a circulating cooler (4), a liquid distributor (5), and a gas distributor (7). The fermenter (2) is equipped with a liquid-gas type jet emulsification device (6), a guide tube (8), an internal coil heat exchanger (10), and a circulating liquid suction device (11). The outlet of the gas conveying device (1) is connected to the inlet of the gas distributor (7), and the gas phase branch pipe of the gas distributor (7) passes through the shell of the fermenter (2) and is connected to the gas phase inlet of the liquid-gas type jet emulsification device (6). The outlet of the circulating liquid suction device (11) is connected to the inlet of the circulating transfer pump (3), the outlet of the circulating transfer pump (3) is connected to the inlet of the circulating cooler (4), the outlet of the circulating cooler (4) is connected to the liquid phase inlet of the liquid distributor (5), and the liquid phase branch pipe of the liquid distributor (5) passes through the shell of the fermenter (2) and is connected to the liquid phase inlet of the liquid-gas type jet emulsification device (6). The liquid-gas type jet emulsification device (6) is centrally symmetrically distributed in the fermentation tank (2). The bottom of the liquid-gas type jet emulsification device (6) is provided with a guide pipe (601), and adjacent guide pipes (601) are arranged along the tangential direction. The guide tube (8) divides the interior of the fermenter into an ascending zone and a descending zone.

2. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The number of liquid-gas type jet emulsification devices (6) is 2, 4, 6 or 8, and the liquid-gas type jet emulsification devices (6) are fixedly connected to the shell of the fermenter (2) or the guide tube (8) through the fastener (9).

3. The dual-circulation airlift aerobic fermentation device according to claim 2, characterized in that, The injection angle of adjacent guide tubes (601) is set to 180°, 90°, 60° or 45° depending on the number of guide tubes.

4. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The downward-sloping cut at the outlet of the guide tube (601) forms an angle of 30°-60° with the horizontal plane.

5. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The guide tube (8) includes a primary guide tube (801), a secondary guide tube (802), a diffuser tube (803), and a supporting rib (804). The diameter ratio of the primary guide tube (801) to the fermenter (2) is (0.4-0.8):1, the diameter ratio of the secondary guide tube (802) to the fermenter (2) is (0.3-0.5):1, and the diffuser tube (803) is a flared structure with a larger upper part and a smaller lower part.

6. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The height-to-diameter ratio of the fermentation tank (2) is (3-8):

1.

7. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The gas distributor (7) is provided with a gas phase inlet (701) at the top and multiple gas phase branches (702) are evenly distributed on the side of the gas distributor. Each gas phase branch (702) is connected to the gas phase inlet on the side of each liquid-gas type jet emulsification device (6).

8. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The liquid distributor (5) is provided with a liquid phase inlet (501) at the bottom and multiple liquid phase branches (502) are evenly distributed on the side of the liquid distributor. The outlet of each liquid phase branch (502) is connected to the liquid phase inlet at the top of each liquid-gas type jet emulsification device (6).

9. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The inner coil heat exchanger (10) is distributed between the guide tube (8) and the tank wall of the fermenter (2); the circulating cooler (4) is one or a combination of a fixed tube sheet heat exchanger, a plate heat exchanger or a spiral tube heat exchanger.

10. The dual-circulation airlift aerobic fermentation device according to claim 1, characterized in that, The fermenter (2) has a drain outlet (12) at the bottom and a tail gas outlet (13) and a raw material liquid inlet (14) at the top.

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