A dual-circulation gaslift syngas bio-fermentation production device and process

Abstract

This invention discloses an internal and external dual-circulation airlift syngas bio-fermentation production device and process, relating to the field of bio-fermentation. The device includes a fermenter, an external circulation pump, an external circulation cooler, a membrane filter, a liquid distributor, a liquid-gas type jet emulsification device, a gas distributor, a guide tube, and an internal coil. This invention uses the external circulation pump to drive the fermentation broth into symmetrically distributed liquid-gas type emulsification devices within the fermenter, returning the reaction tail gas to the fermenter for reuse. The use of a rotating jet and guide tube design achieves thorough mixing of the gas and liquid phases during the jetting process, forming an innovative internal and external dual-circulation mode, significantly improving the volumetric mass transfer coefficient and syngas conversion rate, and substantially reducing syngas consumption per unit volume. Furthermore, by using the internal coil and external circulation cooler for temperature control, combined with a membrane filter to achieve cell reflux and product separation, the problems of heat accumulation and product inhibition during high-intensity fermentation are solved, significantly improving the production capacity of the fermentation device.

Description

Technical Field

[0001] This invention belongs to the field of syngas bio-fermentation technology, specifically involving an internal and external dual-circulation airlift syngas bio-fermentation production device and a supporting process for continuous fermentation to produce acetic acid and ethanol with by-product microbial protein. It is applicable to scenarios involving the anaerobic microbial conversion of industrial waste gas containing CO / CO2 / H2 and biomass gasification syngas into high-value oxygen-containing chemicals. Background Technology

[0002] With the growth of global energy demand and environmental pollution, utilizing industrial waste gas or biomass gasification syngas containing carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2) to convert into high-value chemicals such as fuel ethanol and acetic acid through microbial fermentation has become an important way to recycle resources.

[0003] However, the following technical bottlenecks still exist in the industrialization process of syngas bio-fermentation: (1) The gas-liquid mass transfer efficiency is extremely low, and the contradiction between energy consumption and cell damage is prominent: The main components of syngas, CO and H2, are both poorly soluble in water. While traditional stirred tank reactors (CSTRs) can improve mass transfer through high-speed stirring, they consume extremely high energy in large-scale production, and the high shear forces can easily damage microbial cells. Existing airlift reactors, although with lower energy consumption, suffer from large bubble diameters and short residence times when processing poorly soluble gases, leading to a low volumetric mass transfer coefficient (K0). L a) It is difficult to meet the requirements of high-intensity fermentation.

[0004] (2) Low single-pass conversion rate, high raw material gas consumption, and high tail gas treatment cost. Existing airlift reactors rely on a single gas-phase rise contact, resulting in limited contact time between syngas and fermentation broth. Unreacted CO and H2 are directly discharged with the tail gas, leading to a low single-pass conversion rate of syngas, only about 60%. This results in a large waste of raw material gas. At the same time, the combustible components in the tail gas increase the investment and operating costs of tail gas incineration, desulfurization, and decarbonization treatment. High raw material consumption also restricts economic benefits.

[0005] (3) Temperature control and product inhibition Syngas bio-fermentation is a strongly exothermic process, and the concentration of cells and products in the fermentation broth significantly affects fermentation efficiency. Existing equipment often lacks efficient heat removal mechanisms and in-situ product separation methods, resulting in large temperature fluctuations within the reactor. The inhibitory effect caused by product accumulation severely restricts further increases in production intensity.

[0006] Therefore, developing a syngas bio-fermentation device and production process that can significantly improve gas-liquid mass transfer efficiency, increase syngas utilization, reduce operating energy consumption, and possess good heat dissipation and product separation performance is of great practical significance for promoting the industrial application of this technology. Summary of the Invention

[0007] To address the shortcomings of existing stirred tank reactors and conventional airlift fermentation reactors, such as low mass transfer efficiency, insufficient syngas conversion rate, fermentation heat accumulation, product inhibition, cell loss, and high operating energy consumption, this invention provides an internal and external dual-circulation airlift syngas bio-fermentation production device and its supporting continuous fermentation process. An external circulation pump drives the fermentation broth into symmetrically distributed liquid-gas emulsification devices within the fermenter, returning the reaction tail gas to the fermenter for reuse. A rotary jet and guide tube design achieves thorough mixing of the gas and liquid phases during the jetting process, forming an innovative "internal and external dual circulation" mode. This significantly improves the volumetric mass transfer coefficient (kLa) and syngas conversion rate, and substantially reduces syngas consumption per unit volume. Furthermore, by using an internal coil and external circulation cooler for temperature control, combined with a membrane filter to achieve cell reflux and product separation, the problems of heat accumulation and product inhibition during high-intensity fermentation are solved, significantly increasing the production capacity of the fermentation device.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention proposes an internal and external dual-circulation airlift syngas bio-fermentation production device, including a fermenter, an external circulation pump, an external circulation cooler, a membrane filter, a liquid distributor, and a gas distributor; the fermenter is equipped with a liquid-gas type jet emulsification device, a guide tube, a raw material gas inlet, a vent pipe, a tail gas outlet, a raw material liquid inlet, an inner coil, a material outlet, and fixed components; The fermenter has a raw material gas inlet at the bottom, which is connected to a vent pipe at the bottom of the tank; the fermenter has a tail gas outlet and a raw material liquid inlet at the top, and a material outlet at the bottom. The material outlet is connected to the inlet of the external circulation pump. The outlet of the external circulation pump is divided into two branches. One branch is connected to the inlet of the external circulation cooler, and the other branch collects fermentation mash for post-treatment. The outlet of the external circulation cooler is connected to the inlet of the membrane filter, and the outlet of the membrane filter is connected to the liquid phase inlet of the distributor. The gas distributor has a gas phase inlet at the top and multiple gas phase branch pipes evenly distributed on its side, which respectively penetrate into the fermentation tank shell and connect to the gas phase inlet on the side of each liquid-gas type jet emulsification device; the liquid distributor has a liquid phase inlet at the bottom and multiple liquid phase branch pipes evenly distributed on its side, with the outlets of the liquid phase branch pipes respectively penetrating into the fermentation tank shell and connecting to the liquid phase inlet at the top of each liquid-gas type jet emulsification device.

[0009] The exhaust gas outlet is divided into two branches. One branch is connected to the gas phase inlet of the gas distributor, and a circulating gas pipeline regulating valve is installed on its pipeline. The other branch goes to the fermentation exhaust gas treatment, and an exhaust gas outlet venting pipeline regulating valve is installed on its pipeline.

[0010] The flow guide tubes are fixed inside the fermenter and include a primary flow guide tube, a secondary flow guide tube, supporting ribs, and a diffuser tube. The ratio of the primary flow guide tube's diameter to the fermenter's inner diameter is (0.4~0.8):1, and the ratio of the secondary flow guide tube's diameter to the fermenter's inner diameter is (0.3~0.5):1. The primary and secondary flow guide tubes are fixed together by supporting ribs. The primary flow guide tube is located at the lower end of the flow guide tube and has a bottom-larger, top-smaller or trumpet / frustum-shaped structure. Its function is to smoothly introduce the gas-liquid mixture from the bottom of the tank into the flow guide tube, reducing local resistance and dead zones at the inlet, while also providing a certain degree of contraction, acceleration, and rectification for the gas-liquid mixture. The secondary flow guide tube is the straight section in the middle and is the main channel for gas-lift circulation. After the gas enters, the gas content inside the flow guide tube is high and the apparent density is low, forming an upward lifting flow; the liquid outside the flow guide tube flows downward back, forming an internal circulation.

[0011] The primary guide tube is located at the lower end of the secondary guide tube and is arranged coaxially with the secondary guide tube. The upper end of the primary guide tube is connected to the lower end of the secondary guide tube or partially extends into its lower opening area. It is fixed and positioned by the support rib plate 804, so that a continuous gas-liquid upward guiding channel is formed between the two.

[0012] The guide tube divides the tank interior 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 within the guide tube, includes the channels formed inside 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.

[0013] 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.

[0014] The liquid-gas jet emulsification device is equipped with a guide pipe at its bottom, which is tangentially positioned to drive the liquid inside the tank to rotate and form an internal circulating flow field. The liquid-gas jet emulsification devices are centrally symmetrically distributed within the fermentation tank, with a quantity of 2, 4, 6, or 8 devices. The jet angles of the bottom guide pipes of adjacent liquid-gas jet emulsification devices are arranged accordingly at 180°, 90°, 60°, or 45°. The liquid-gas jet emulsification devices are fixedly connected to the fermentation tank shell or guide pipe via fasteners.

[0015] The liquid-gas type jet emulsification device is configured such that when the external circulating fermentation liquid is injected at high speed from the liquid phase inlet, a negative pressure zone is formed inside the device and at the gas phase inlet, which draws in the circulating tail gas sent by the gas distributor and shears and emulsifies it with the liquid phase before spraying it out from the bottom guide pipe.

[0016] The inner coil is distributed between the guide tube and the inner wall of the fermenter; Furthermore, the height-to-diameter ratio of the fermenter is (2~6):1; the aeration pipe is a porous microporous tube aerator, and the material is selected from sintered metal, ceramic, EPDM or microporous metal tube; the external circulation cooler is one or a combination of a fixed tube sheet heat exchanger, a plate heat exchanger or a spiral tube heat exchanger, and its cooling medium is circulating water or chilled water.

[0017] On the other hand, the present invention also proposes a process for continuous bio-fermentation of syngas using the apparatus described above, comprising the following steps: S1: After sterilizing the fermenter, add the culture medium and seed liquid required for syngas fermentation into the fermenter through the raw material liquid inlet, then add ammonia water and pH adjuster. After reaching a certain liquid level, start the external circulation pump. After the fermentation liquid is circulating normally, introduce the cooling medium into the inner coil and the external circulation cooler. S2: Syngas from upstream enters the fermenter through the feed gas inlet and generates tiny bubbles via the vent pipe. The pressure inside the fermenter is controlled at 0.15~0.45MPa by the tail gas outlet venting pipeline regulating valve. Then, the circulating gas pipeline regulating valve is opened to return the unreacted syngas to the fermenter. At the same time, the fermentation temperature is controlled at 30~45℃ by the internal coil and external circulating cooler. S3: When the ammonium acetate concentration in the fermenter reaches 4% or higher, the clear liquid containing ammonium acetate and ethanol in the fermentation broth is continuously removed from the device through a membrane filter, and the filtered cells are returned to the fermenter. At the same time, culture medium, ammonia water and pH adjuster are added according to the liquid level and pH value in the fermenter to achieve continuous gas fermentation. The ammonium acetate concentration is generally measured by sampling at regular intervals or by online sampling and detection using high performance liquid chromatography.

[0018] S4: When the OD value in the fermenter is ≥0.6, a portion of the fermentation mash is collected through the external circulation outlet for subsequent microbial protein production.

[0019] Furthermore, the culture medium comprises 0.05-0.15 g / L ammonium chloride, 0.01-0.1 g / L potassium chloride, 0.05-0.15 g / L sodium chloride, 0.01-0.1 g / L calcium chloride, 0.01-0.08 g / L manganese chloride, 0.01-0.1 g / L ferrous sulfate, and trace amounts of biotin, folic acid, and sodium bicarbonate; the seed culture is the seed culture of a strain that produces acetic acid and ethanol.

[0020] Furthermore, the hourly flow rate of the external circulation pump is 2 to 10 times the fermentation volume ratio; the volume ratio of the circulating gas flow rate to the raw material gas flow rate is 1 to 5 times the volume ratio.

[0021] Furthermore, the membrane filter is one or a combination of ceramic membrane and nanofiltration membrane, with a membrane separation pressure difference of 0.1~0.5MPa and a membrane pore size of 20~100nm.

[0022] Furthermore, the concentration of ammonium acetate in the fermentation broth is 4-10%, and the concentration of ethanol is 0.5-5%; the concentration of microbial protein in the fermentation mash is 5-20 g / L; the volume of the fermentation liquid is controlled at 60-85% of the tank capacity, and the pH value is controlled at 4-6.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Significantly improves gas-liquid mass transfer efficiency This invention uses an external circulation pump to drive the fermentation broth, and employs a liquid-gas jet emulsification device and rotary jet to re-absorb and shear the fermentation tail gas. Combined with the guiding effect of the internal guide tube, this significantly increases the gas-liquid contact area and renewal rate, overcoming the problem of limited mass transfer in traditional airlift reactors when processing sparingly soluble syngas. Compared with existing airlift reactors, this invention achieves active mixing of the gas and liquid phases rather than passive contact through the negative pressure self-absorption structure of the liquid-gas jet emulsification device combined with rotary jet, significantly improving mass transfer efficiency. The high-flow-rate circulation of fermentation tail gas achieves a high proportion of syngas conversion, significantly reducing the consumption of raw material gas.

[0024] 2. Achieve high-intensity continuous fermentation This invention employs a membrane filter to achieve cell filtration and reflux, maintaining a consistently high cell concentration (OD value) in the fermentation broth, thus solving the problem of low production intensity caused by cell loss in traditional processes. Simultaneously, by continuously removing the product-containing supernatant, the feedback inhibition of microorganisms by the fermentation products is eliminated, achieving continuous and efficient bio-fermentation of syngas.

[0025] 3. Highly efficient temperature control By utilizing a combined temperature control process of "internal coil + external circulation cooling," the internal coil provides a basic constant temperature environment, while the external circulation cooler achieves efficient heat exchange using a high-speed flowing liquid phase, thus solving the problem of heat accumulation during high-intensity fermentation. Compared with the single jacket or coil heat exchange in existing technologies, the combined temperature control method of this invention has higher heat exchange efficiency and more uniform temperature distribution.

[0026] 4. Low energy consumption and high bacterial cell activity By replacing traditional high-energy-consuming mechanical stirring with external circulation power, the device not only significantly reduces operating power consumption, but also generates a gentle shear force in the rotating flow field, effectively protecting the integrity of anaerobic cells. Combined with specific culture medium formulations and control strategies, the selectivity and yield of the target product are further improved. Attached Figure Description

[0027] Figure 1 This invention provides a schematic diagram of an internal and external dual-circulation airlift syngas bio-fermentation production device and process. Figure 2 This is a top view of the liquid distributor, gas distributor, fermenter, and internal components of the present invention. Figure 3 This is a schematic diagram of the structure of the guide tube of the present invention.

[0028] In the diagram: 1. Fermentation tank, 2. External circulation pump, 3. External circulation cooler, 4. Membrane filter, 5. Liquid distributor, 6. Gas distributor, 7. Liquid-gas type jet emulsification device, 8. Guide tube, 9. Fixed component, 10. Inner coil, 11. Raw material gas inlet, 12. Vent pipe, 13. Material outlet, 14. Tail gas outlet, 15. Raw material liquid inlet, 501. Liquid phase inlet, 502. Liquid distributor branch pipe, 601. Gas phase inlet, 602. Gas distributor branch pipe, 701. Guide tube, 801. Primary guide tube, 802. Secondary guide tube, 803. Diffuser, 804. Support rib. Detailed Implementation

[0029] 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.

[0030] Example 1

[0031] In this embodiment, the syngas comes from methanol production off-gas. The pressure of this syngas stream is 4.5 MPa, which needs to be reduced to 0.45 MPa before use. The composition of the syngas is as follows: H₂ 28.0%, CO 18.8%, CO₂ 12%, CH₄ 10.9%, N₂ 27.8%, with the remaining H₂O, Ar, methanol, etc., accounting for approximately 2.5%. The culture medium used mainly consists of ammonium chloride 0.08 g / L, potassium chloride 0.02 g / L, sodium chloride 0.15 g / L, calcium chloride 0.01 g / L, manganese chloride 0.05 g / L, ferrous sulfate 0.03 g / L, and trace amounts of biotin, folic acid, sodium bicarbonate, etc. The application of this invention to the continuous production fermentation of this syngas mainly includes the following steps: (1) Sterilize the fermenter 1. After sterilization, add the prepared culture medium and seed liquid to the fermenter, and then add 15% ammonia water and pH adjuster. After the fermenter reaches 50% liquid level, start the external circulation pump 2. After the circulating liquid is uniformly distributed by the liquid distributor 5, it enters the liquid-gas type spray emulsification device 7 for spraying. A negative pressure zone is formed at the gas phase inlet of the liquid-gas type spray emulsification device 7. Then, the inner coil 10 and the external circulation cooler 3 are cooled by passing 7°C chilled water. (2) Syngas from upstream, depressurized to 0.45 MPa, is introduced into the fermenter through raw material gas inlet 11 and vent pipe 12 to produce ammonium acetate and ethanol. The back pressure in the fermenter is controlled to 0.3 MPa by the tail gas outlet venting pipeline regulating valve. Then, the circulating gas pipeline regulating valve is opened to return the unreacted syngas to the fermenter. The density difference generated by the gas lift principle drives the fermentation liquid to form an internal circulation flow field along the guide tube. Combined with the rotary jet process, microbubbles are induced to rise in a spiral path, which significantly prolongs the gas phase residence time. At the same time, the fermentation temperature is maintained at 37°C by controlling the flow rate of the chilled water in the inner coil and the outer circulation cooler. The hourly flow rate of the outer circulation pump is 4:1 to the fermentation volume. The volume ratio of the circulating gas flow rate to the raw material gas flow rate is 2:1. (3) When the ammonium acetate concentration in the fermenter reaches 4% or more, the clear liquid containing ammonium acetate and ethanol in the fermentation broth is continuously removed from the device through the membrane filter 4. The ammonium acetate concentration in the fermentation clear liquid is 6.5% and the ethanol concentration is 1.5%. The filtered cells are returned to the fermenter 1. The membrane filter 4 is a ceramic membrane with a membrane separation pressure difference of 0.3MPa and a membrane pore size of 40nm. While collecting the fermentation clear liquid, culture medium, ammonia water and pH adjuster are added according to the liquid level and pH value in the fermenter to control the volume of the fermentation liquid at 75% of the tank capacity and the pH value at 4.7 to achieve continuous gas fermentation. (4) When the OD value in the fermenter is ≥0.6, a portion of the fermentation mash is collected through the external circulation outlet. The concentration of microbial protein in the fermentation mash is 12g / L.

[0032] Results of Example 1

[0033] According to the method steps of this invention, the concentration of ammonium acetate in the fermentation product reaches 45 g / L, the concentration of ethanol reaches 12.6 g / L, and the concentration of bacterial protein reaches 12 g / L. Before using the device and process provided by this invention, the single-pass conversion rate of syngas using the same culture medium and strain was only 60%. This invention solves the problem of limited mass transfer of sparingly soluble syngas (CO, H2) by combining internal and external dual circulation with rotary jet. Through high-flow circulation of fermentation tail gas and continuous separation of products by membrane filter, the total conversion rate of syngas is increased to 82.5%, and the consumption of raw material gas is reduced by about 27.3% compared with traditional processes.

[0034] Example 2

[0035] The difference between this embodiment and Embodiment 1 is that the height-to-diameter ratio of the fermenter is 4:1, the number of liquid-gas type jet emulsification devices is 6, and the jet angle between adjacent guide pipes is 60°. The syngas composition is 30.5% H2, 22.3% CO, 8.5% CO2, 5.2% CH4, 30.5% N2, and the remainder 3.0%. The back pressure inside the fermenter is controlled at 0.45 MPa, the fermentation temperature is controlled at 35℃, the hourly flow rate of the external circulation pump is 6:1 to the fermentation volume, and the volume ratio of the circulating gas flow rate to the raw material gas flow rate is 3:1. A nanofiltration membrane is used as the membrane filter, with a membrane separation pressure difference of 0.2 MPa and a membrane pore size of 30 nm. The concentration of ammonium acetate in the fermentation broth is 7.2%, the concentration of ethanol is 2.1%, and the concentration of microbial protein in the fermentation mash is 15 g / L. The total conversion rate of syngas was measured to be 85.3%.

[0036] Example 3

[0037] The difference between this embodiment and Embodiment 1 is that the height-to-diameter ratio of the fermenter is 3:1, the number of liquid-gas type jet emulsification devices is 4, and the jet angle between adjacent guide pipes is 90°. The syngas comes from biomass gasification gas, with the following composition: H2 25.0%, CO2 0.5%, CO2 15.0%, CH4 8.0%, N2 28.5%, and the remainder 3.0%. The back pressure inside the fermenter is controlled at 0.25 MPa, the fermentation temperature is controlled at 40℃, the hourly flow rate of the external circulation pump is 8:1 to the fermentation volume, and the volume ratio of the circulating gas flow rate to the raw material gas flow rate is 4:1. The membrane filter uses a combination of ceramic membrane and nanofiltration membrane, with a membrane separation pressure difference of 0.35 MPa. The concentration of ammonium acetate in the fermentation broth is 5.8%, the concentration of ethanol is 1.8%, and the concentration of microbial protein in the fermentation mash is 10 g / L. The total conversion rate of syngas was measured to be 80.6%.

[0038] Comparative Example

[0039] Using the same culture medium and bacterial strain, syngas fermentation was carried out in a conventional airlift fermenter. The back pressure inside the fermenter was controlled at 0.3 MPa, the fermentation temperature at 37℃, and no exhaust gas recycling system or membrane filtration cell return system was installed. The results showed that the single-pass conversion rate of syngas was only 60%, the ammonium acetate concentration in the fermentation broth was only 25 g / L, and the ethanol concentration was 6.5 g / L.

[0040] As can be seen from the comparison of Examples 1-3 and the comparative examples, the present invention significantly improves the total conversion rate of syngas and the concentration of fermentation products by combining the internal and external dual circulation airlift structure with the liquid-gas type jet emulsification device, the guide tube design and the membrane filtration microbial reflux system.

[0041] As can be seen, this invention solves all the pain points of industrialization at once by using a triple-coupled internal circulation system of gas lift, liquid external circulation, and tail gas gas phase circulation, combined with a multi-stage guide tube, tangential rotary jet emulsification, internal and external linkage cooling, and in-situ membrane separation integrated structure. This enables low-energy consumption, high conversion rate, continuous and stable fermentation production of ammonium acetate and ethanol, while simultaneously producing by-product microbial protein.

[0042] 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 syngas bio-fermentation production device, characterized in that, It includes a fermenter (1), an external circulation pump (2), an external circulation cooler (3), a membrane filter (4), a liquid distributor (5), a gas distributor (6), a liquid-gas type jet emulsification device (7), a guide tube (8), and an inner coil (10). The fermenter (1) has a raw material gas inlet (11) at the bottom and is connected to a ventilation pipe (12) at the bottom of the tank. The fermenter (1) has a tail gas outlet (14) and a raw material liquid inlet (15) at the top and a material outlet (13) at the bottom. The material outlet (13) is connected to the inlet of the external circulation pump (2). The outlet of the external circulation pump (2) is divided into two branches. One branch is connected to the inlet of the external circulation cooler (3), and the other branch collects fermentation mash for post-processing. The outlet of the external circulation cooler (3) is connected to the inlet of the membrane filter (4), and the outlet of the membrane filter (4) is connected to the liquid phase inlet (501) of the distributor (5). The exhaust outlet is divided into two branches. One branch is connected to the gas phase inlet (601) of the gas distributor (6), and the other branch is used for fermentation exhaust gas treatment. The guide tube (8) is fixed inside the fermenter (1) and divides the tank into an ascending zone and a descending zone. The bottom of the liquid-gas type jet emulsification device (7) is provided with a guide pipe (701). The guide pipe (701) is set along the tangential direction to drive the liquid in the tank to rotate and form an internal circulation flow field. The inner coil (10) is distributed between the guide tube (8) and the inner wall of the fermenter (1); The liquid-gas type jet emulsification device (7) is configured such that when the external circulating fermentation liquid is injected at high speed from the liquid phase inlet, a negative pressure zone is formed inside the device and at the gas phase inlet, which draws in the circulating tail gas sent by the gas distributor (6) and emulsifies it with the liquid phase before being sprayed out from the bottom guide pipe (701).

2. The dual-circulation airlift syngas bio-fermentation production device according to claim 1, characterized in that, The liquid-gas type jet emulsification device (7) is centrally symmetrically distributed in the fermentation tank (1), with a quantity of 2, 4, 6 or 8; the bottom guide pipe (701) of adjacent liquid-gas type jet emulsification devices (7) is arranged with a jet angle of 180°, 90°, 60° or 45°, set along the tangential direction, thereby driving the liquid in the tank to rotate; the liquid-gas type jet emulsification device (7) is fixedly connected to the shell of the fermentation tank (1) or the guide tube (8) through the fastener (9).

3. The dual-circulation airlift syngas bio-fermentation production device according to claim 1, characterized in that, The guide tube (8) includes a primary guide tube (801), a secondary guide tube (802), a supporting rib (804), and a diffuser (803). The ratio of the inner diameter of the primary guide tube (801) to that of the fermenter (1) is (0.4~0.8):1, and the ratio of the inner diameter of the secondary guide tube (802) to that of the fermenter (1) is (0.3~0.5):

1. The primary guide tube (801) and the secondary guide tube (802) are fixed together by the supporting rib (804).

4. The dual-circulation airlift syngas bio-fermentation production device according to claim 1, characterized in that, The height-to-diameter ratio of the fermenter (1) is (2~6)∶1; the aeration pipe (12) is a porous microporous tube aerator, and the material is selected from sintered metal, ceramic, EPDM or microporous metal tube; the external circulation cooler (3) is one or a combination of a fixed tube sheet heat exchanger, a plate heat exchanger or a spiral tube heat exchanger, and its cooling medium is circulating water or chilled water.

5. The dual-circulation airlift syngas bio-fermentation production device according to claim 1, characterized in that, The gas distributor (6) is provided with a gas phase inlet (601) at the top and multiple gas phase branch pipes (602) are evenly distributed on the side of the gas distributor (6), which are respectively inserted into the shell of the fermentation tank (1) and connected to the gas phase inlet on the side of each liquid-gas type spray emulsification device (7); the liquid distributor (5) is provided with a liquid phase inlet (501) at the bottom and multiple liquid phase branch pipes (502) are evenly distributed on the side of the liquid distributor, and the outlet of the liquid phase branch pipes are respectively inserted into the shell of the fermentation tank (1) and connected to the liquid phase inlet at the top of each liquid-gas type spray emulsification device (7).

6. A process for continuous bio-fermentation of syngas using the apparatus according to any one of claims 1-5, characterized in that, Includes the following steps: S1: After the fermenter (1) is emptied, the culture medium and seed liquid required for syngas fermentation are added into the fermenter through the raw material liquid inlet (15), and then ammonia water and pH adjuster are added. After reaching a certain liquid level, the external circulation pump (2) is started. After the fermentation liquid is in normal circulation, the inner coil (10) and the external circulation cooler (3) are circulated with cooling medium. S2: Syngas enters the fermenter through the raw material gas inlet (11) and generates tiny bubbles through the vent pipe (12) to react. The pressure inside the fermenter is controlled to be 0.15~0.45MPa through the tail gas outlet venting pipeline regulating valve. Then, the circulating gas pipeline regulating valve is opened to return the unreacted syngas to the fermenter. At the same time, the fermentation temperature is controlled to be 30~45℃ through the inner coil and the outer circulating cooler. S3: When the ammonium acetate concentration in the fermenter reaches 4% or more, the clear liquid containing ammonium acetate and ethanol in the fermentation liquid is continuously removed from the device through the membrane filter (4), and the filtered bacteria are returned to the fermenter. At the same time, culture medium, ammonia water and pH adjuster are added according to the liquid level and pH value in the fermenter to achieve continuous gas fermentation. S4: When the OD value in the fermenter is ≥0.6, a portion of the fermentation mash is collected through the external circulation outlet for subsequent microbial protein production.

7. The syngas biological continuous fermentation process according to claim 6, characterized in that, The culture medium comprises 0.05-0.15 g / L ammonium chloride, 0.01-0.1 g / L potassium chloride, 0.05-0.15 g / L sodium chloride, 0.01-0.1 g / L calcium chloride, 0.01-0.08 g / L manganese chloride, 0.01-0.1 g / L ferrous sulfate, and trace amounts of biotin, folic acid, and sodium bicarbonate; the seed culture is the seed culture of a strain that produces acetic acid and ethanol.

8. The syngas biological continuous fermentation process according to claim 7, characterized in that, The ratio of the hourly flow rate of the external circulation pump to the fermentation volume is 2~10:1; the ratio of the circulating gas flow rate to the raw material gas flow rate is 1~5:

1.

9. The syngas biological continuous fermentation process according to claim 7, characterized in that, The membrane filter (4) is one or a combination of ceramic membrane or nanofiltration membrane, with a membrane separation pressure difference of 0.1~0.5MPa and a membrane pore size of 20~100nm.

10. The syngas bio-continuous fermentation process according to claim 7, characterized in that, The concentration of ammonium acetate in the fermentation broth is 4-10%, and the concentration of ethanol is 0.5-5%; the concentration of microbial protein in the fermentation mash is 5-20 g / L; the volume of the fermentation liquid is controlled at 60-85% of the tank capacity, and the pH value is controlled at 4-6.

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