A double circulation loop reactor, a preparation method thereof and a gas fermentation device

Abstract

The application provides a double circulation loop reactor, a preparation method thereof and a gas fermentation device. The double circulation loop reactor comprises an exhaust tank, a double loop circulation loop and a circulating pump. The double loop circulation loop comprises a center pipe and two circulation branch pipes, forming a double loop circulation channel. A center pipe branch pipe connected with the center pipe at one end is arranged on the center pipe. The other end of the center pipe branch pipe and the open ends of the two circulation branch pipes are in communication with the exhaust tank. The circulating pump is arranged at the position where the center pipe is connected with the center pipe branch pipe. An air inlet is arranged on the center pipe branch pipe near the circulating pump. The double circulation loop reactor provided by the application generates sub-millimeter micro-bubbles through "air intake shearing" to strengthen mass transfer. The double circulation channel is used for flow distribution and speed reduction to prolong the bubble residence time. The double circulation loop reactor has the advantages of uniform flow field, no dead zone, low operation energy consumption and no need of additional high-pressure micro-bubble generator. The gas utilization rate can be significantly improved, and the double circulation loop reactor has good industrial application prospect in the field of gas fermentation.

Description

Technical Field

[0001] This invention belongs to the field of gas fermentation technology, and relates to a dual-circulation loop reactor, and more particularly to a dual-circulation loop reactor and its preparation method and gas fermentation device. Background Technology

[0002] In gaseous fermentation processes such as single-cell protein (SCP), the solubility of gaseous substrates (such as methane, hydrogen, and carbon dioxide) in water is typically low. Therefore, gas utilization rate is a core indicator determining the economic efficiency of the process. Traditional reactors (such as stirred tank reactors and airlift reactors) or conventional U-shaped loop reactors generally suffer from the following problems: 1) Severe bubble coalescence: Bubbles gradually coalesce and enlarge during transport, leading to a decrease in specific surface area and reduced mass transfer efficiency; 2) Rapid gas escape: Bubbles have a short residence time in the liquid phase, resulting in a large amount of undissolved gas being discharged from the exhaust port, causing substrate waste; 3) Uneven fluid distribution: Single-channel structures are prone to short-circuit flow, with some liquid being discharged before fully contacting the bubbles, affecting fermentation efficiency.

[0003] CN108623116A discloses a gas-circulating stirred-flow anaerobic fermentation reactor, which relates to a biological fermentation device to solve the problems of high energy consumption in the current anaerobic fermentation of livestock and poultry manure, low feed concentration, poor mass transfer, and easy sedimentation and stratification in the plug-flow anaerobic digestion process. This gas-circulating stirred-flow anaerobic fermentation reactor includes a fermentation tank, a dehumidifier, a gas booster pump, a gas circulation pipeline, and multiple gas nozzles. The fermentation tank is at a certain angle to the horizontal plane and has a discharge port, a feed port, a gas outlet, and a gas collection port. Valves are installed at the feed port and the gas collection port has a gas collection device. One end of the gas circulation pipeline is connected to the gas outlet, and the other end of the gas circulation pipeline extends into the fermentation tank. Multiple gas holes are provided on the gas circulation pipeline extending into the fermentation tank, and each gas hole has a nozzle. A dehumidifier and a gas booster pump are installed on the gas circulation pipeline outside the fermentation tank.

[0004] CN111662812A discloses a large-scale, high-mass-transfer, circulating, ventilated fermenter, relating to the field of bio-fermentation technology. The fermenter includes a fermenter body with cooling jets inside. A circulation cylinder is also fixedly installed inside the fermenter, with openings at both the top and bottom. A ventilation pipe is connected to the bottom of the circulation cylinder, with one end located at the bottom of the circulation cylinder and the other end extending out of the fermenter body. The first end of the ventilation pipe faces downwards and is connected to an air distributor head. The top of the air distributor head communicates with the first end of the ventilation pipe, and an outlet is located at its bottom. A three-phase mixing disturbance is connected below the outlet. A three-phase mixing thruster and a three-phase mixing puller are connected to the sidewall of the air distributor head via a gas distribution pipe. The three-phase mixing thruster is located inside the circulation cylinder, and the three-phase mixing puller is located outside the circulation cylinder. This invention aims to provide favorable engineering conditions for ventilated bioreactors, completely eliminating mechanical stirring and improving energy efficiency in the fermentation process.

[0005] In summary, existing reactors for gas fermentation have certain drawbacks, including insufficient residence time of bubbles in the liquid phase, resulting in low mass transfer efficiency and low gas utilization. They also require the configuration of a high-pressure microbubble generator. Therefore, it is crucial to develop and design a novel dual-circulation loop reactor and its preparation method, as well as a gas fermentation device. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a dual-circulation loop reactor, its preparation method, and a gas fermentation device. The dual-circulation loop reactor provided by the present invention enhances mass transfer by generating sub-millimeter-level microbubbles through "inlet shearing," and extends the bubble residence time by diverting and reducing the flow rate through dual circulation channels. It has the advantages of uniform flow field without dead zones, low operating energy consumption, and no need for additional high-pressure microbubble generators, which can significantly improve gas utilization and has good prospects for industrial application in the field of gas fermentation.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a dual-circulation loop reactor, the dual-circulation loop reactor comprising an exhaust tank, a dual-loop loop pipe and a circulation pump; The dual-loop pipe includes a central pipe and two circulating branch pipes, forming a dual-loop circulation channel. A central pipe branch pipe is provided on the central pipe, with one end connected to the central pipe. The other end of the central pipe branch pipe and the opening ends of the two circulating branch pipes are all connected to the exhaust tank. A circulation pump is installed at the connection between the central pipe and the central pipe branch pipe. An air inlet is installed on the central pipe branch pipe near the circulation pump. Gas enters the central pipe branch pipe through the air inlet and then enters the circulation pump. Under the shearing force generated by the rotation of the impeller of the circulation pump, a group of microbubbles with an average size of less than 500μm is formed and then mixed with the liquid in the double-loop pipe.

[0008] In the dual-circulation loop reactor provided by this invention, the air inlet is located on the branch pipe of the central pipe and adjacent to the circulation pump. After the gas enters the branch pipe of the central pipe, it is instantly sucked into the circulation pump. When the impeller of the circulation pump rotates at high speed, it generates strong shear force and turbulence, which directly breaks the gas into a group of microbubbles with an average size of less than 500μm. This "inlet shearing" mode makes the size of the microbubbles much smaller than that of traditional aeration methods (the size of microbubbles is usually 1mm~5mm), which greatly increases the specific surface area and improves the volumetric mass transfer coefficient (kLa) by 2 to 3 times compared with traditional reactors.

[0009] In the dual-circulation loop reactor provided by this invention, the circulating pump drives the reaction liquid to flow downward along the central pipe of the dual-loop loop, and then circulates upward along two circulating branch pipes. Fluid diversion is achieved through the dual circulation channels. Compared with the single-loop structure, the dual circulation channels can divert the fluid and reduce the flow rate of the liquid in the single channel. The lower flow rate means that the bubbles have a longer residence time in the liquid phase (extended by 30%~50%). The bubbles continue to dissolve during the rising process, which significantly reduces the content of unreacted gas in the tail gas (the concentration of unused gas in the tail gas is reduced by 40%-60%), and greatly improves the gas utilization rate.

[0010] The dual-circulation ring reactor provided by this invention has dual circulation channels, which eliminate the eccentric flow and dead zone of the single-tube structure and improve the uniformity of the fermentation broth in the whole reactor.

[0011] The dual-circulation loop reactor provided by this invention does not require an additional high-pressure microbubble generator; it can be achieved by the shearing action of the axial flow pump itself. Furthermore, the dual-channel diversion reduces the flow rate, thereby reducing the energy consumption of the circulation pump.

[0012] In summary, the dual-circulation loop reactor provided by this invention enhances mass transfer by generating sub-millimeter-level microbubbles through "inlet shearing" and extends bubble residence time by diverting and reducing velocity in the dual-circulation channel. It has the advantages of uniform flow field without dead zones, low operating energy consumption, and no need for additional high-pressure microbubble generators, which can significantly improve gas utilization and has good prospects for industrial application in the field of gas fermentation.

[0013] Preferably, the diameter of the exhaust canister is 220mm~280mm.

[0014] Preferably, the diameters of the central pipe and the two circulating branch pipes are each independently 70mm to 150mm.

[0015] Preferably, the two circulating branch pipes are symmetrically arranged, and the diameters of the two circulating branch pipes are the same.

[0016] Preferably, the circulating pump includes an axial flow pump.

[0017] Preferably, the dual-circulation loop reactor further includes a motor, which is electrically connected to the circulation pump and is used to drive the circulation pump to operate.

[0018] Preferably, both circulating branch pipes include a temperature control section, and a temperature control sleeve is provided on the outside of the temperature control section.

[0019] Preferably, the dual-loop pipe is provided with at least one monitoring port, and the monitoring port is provided with any one or a combination of at least two of the following: a pH sensor, a dissolved oxygen sensor, or a temperature sensor.

[0020] Preferably, the dual-loop pipe includes at least one observation segment, and each observation segment is provided with an observation window.

[0021] Preferably, the top of the exhaust tank is provided with an exhaust port and a liquid inlet.

[0022] Preferably, a sterilization steam inlet is provided at the bottom of the dual-loop pipe.

[0023] Preferably, the dual-circulation loop reactor includes a liquid outlet, which includes a first liquid outlet located at the bottom of the exhaust tank and a second liquid outlet located at the bottom of the dual-circulation loop; a feed pump is provided on the liquid inlet, and a discharge pump is provided on the second liquid outlet.

[0024] In a second aspect, the present invention provides a gas fermentation method using the dual-circulation loop reactor described in the first aspect, the gas fermentation method comprising: Gas is introduced into the inlet and passes through the circulation pump. Under the shearing force generated by the impeller rotation of the circulation pump, a group of microbubbles with an average size of less than 500μm is formed. The gas then mixes with the liquid in the double-loop pipe to form a gas-liquid mixture. The gas-liquid mixture then flows downward along the central pipe of the double-loop pipe under the action of the circulation pump, and then circulates and mixes along the two circulation branch pipes in a bottom-up path. Finally, the gas is separated in the exhaust tank and discharged.

[0025] Preferably, the flow velocity of the gas-liquid mixture during the circulating flow mixing in the dual-loop pipe is 0.6 m / s to 1.0 m / s.

[0026] Thirdly, the present invention provides a gas fermentation apparatus, the gas fermentation apparatus comprising the dual-circulation loop reactor described in the first aspect.

[0027] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0028] Compared with the prior art, the present invention has the following beneficial effects: In the dual-circulation loop reactor provided by this invention, the air inlet is located on the branch pipe of the central pipe and adjacent to the circulation pump. After the gas enters the branch pipe of the central pipe, it is instantly sucked into the circulation pump. When the impeller of the circulation pump rotates at high speed, it generates strong shear force and turbulence, which directly breaks the gas into a group of microbubbles with an average size of less than 500μm. This "inlet shearing" mode makes the size of the microbubbles much smaller than that of traditional aeration methods (the size of microbubbles is usually 1mm~5mm), which greatly increases the specific surface area and improves the volumetric mass transfer coefficient (kLa) by 2 to 3 times compared with traditional reactors. In the dual-circulation loop reactor provided by this invention, the circulating pump drives the reaction liquid to flow downward along the central pipe of the dual-loop loop, and then circulates along two circulating branch pipes in an upward path. The fluid is split through the dual circulation channels. Compared with the single-loop structure, the dual circulation channels can split the fluid and reduce the flow rate of the liquid in the single channel. The lower flow rate means that the bubbles have a longer residence time in the liquid phase (extended by 30%~50%). The bubbles continue to dissolve during the rising process, which significantly reduces the content of unreacted gas in the tail gas (the concentration of unused gas in the tail gas is reduced by 40%-60%), and greatly improves the gas utilization rate. The dual-circulation loop reactor provided by this invention has dual circulation channels. The dual circulation channels eliminate the eccentric flow and dead zone of the single-tube structure and improve the uniformity of the fermentation broth in the entire reactor. The dual-circulation loop reactor provided by this invention does not require an additional high-pressure microbubble generator; it can be achieved by the shearing action of the axial flow pump itself. Furthermore, the dual-channel diversion reduces the flow rate, thereby reducing the energy consumption of the circulation pump. Attached Figure Description

[0029] Figure 1 This is a front structural schematic diagram of a dual-circulation loop reactor provided in a specific embodiment of the present invention.

[0030] Figure 2 This is a side view of a dual-circulation loop reactor provided in a specific embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the back structure of a dual-circulation loop reactor provided in a specific embodiment of the present invention.

[0032] Among them, 1-exhaust tank; 2-dual loop ring pipe; 3-axial flow pump; 4-motor; 5-temperature control sleeve; 6-observation window; 7-air inlet; 8-liquid inlet; 9-air outlet; 10-liquid outlet; 11-sterilization steam inlet; 12-water inlet; 13-water outlet; 14-monitoring port. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0034] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0035] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0036] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0037] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0038] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0040] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0041] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0042] In one embodiment, the present invention provides a dual-circulation loop reactor, the dual-circulation loop reactor comprising an exhaust tank 1, a dual-loop loop 2, and a circulation pump; The double-loop ring pipe 2 includes a central pipe and two circulating branch pipes to form a double-loop circulation channel. A central pipe branch pipe is provided on the central pipe, and the other end of the central pipe branch pipe and the opening ends of the two circulating branch pipes are all connected to the exhaust tank 1. A circulation pump is installed at the connection between the central pipe and the central pipe branch pipe. An air inlet 7 is installed on the central pipe branch pipe near the circulation pump. Gas enters the central pipe branch pipe through the air inlet 7 and then enters the circulation pump. Under the shearing force generated by the rotation of the impeller of the circulation pump, a group of microbubbles with an average size of less than 500μm is formed and then mixed with the liquid in the double-loop ring pipe 2.

[0043] In the dual-circulation loop reactor provided by this invention, the air inlet 7 is located on the central pipe branch pipe and adjacent to the circulation pump. After the gas enters the central pipe branch pipe, it is instantly sucked into the circulation pump. When the impeller of the circulation pump rotates at high speed, it generates strong shear force and turbulence, which directly breaks the gas into a group of microbubbles with an average size of less than 500μm. This "inlet shearing" mode makes the size of the microbubbles much smaller than that of traditional aeration methods (the size of microbubbles is usually 1mm~5mm), which greatly increases the specific surface area and improves the volumetric mass transfer coefficient (kLa) by 2 to 3 times compared with traditional reactors.

[0044] In the dual-circulation loop reactor provided by this invention, the circulating pump drives the reaction liquid to flow downward along the central pipe of the dual-loop loop 2, and then circulates along two circulating branch pipes in a bottom-up path. The fluid is split through the dual circulation channels. Compared with the single loop structure, the dual circulation channels can split the fluid and reduce the flow rate of the liquid in the single channel. The lower flow rate means that the bubbles have a longer residence time in the liquid phase (extended by 30%~50%). The bubbles continue to dissolve during the rising process, which significantly reduces the content of unreacted gas in the tail gas (the concentration of unused gas in the tail gas is reduced by 40%-60%), and greatly improves the gas utilization rate.

[0045] The dual-circulation ring reactor provided by this invention has dual circulation channels, which eliminate the eccentric flow and dead zone of the single-tube structure and improve the uniformity of the fermentation broth in the whole reactor.

[0046] The dual-circulation loop reactor provided by this invention does not require an additional high-pressure microbubble generator; it can be achieved by the self-shearing of the axial flow pump 3. Furthermore, the dual-channel diversion reduces the flow rate, and the corresponding energy consumption of the circulation pump is also reduced.

[0047] In some embodiments, the diameter of the exhaust tank 1 is 220mm to 280mm, for example, it can be 220mm, 225mm, 230mm, 235mm, 240mm, 245mm, 250mm, 255mm, 260mm, 265mm, 270mm, 275mm or 280mm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] In some embodiments, the diameters of the central pipe and the two circulating branch pipes are independently 70mm to 150mm, for example, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm or 150mm, but are not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] In some embodiments, the central tube is a vertical tube.

[0050] In some embodiments, the two circulating branch pipes are symmetrically arranged, and the two circulating branch pipes have the same diameter.

[0051] In this invention, the two circulating branch pipes are symmetrically arranged, and the diameters of the two circulating branch pipes are the same, which further improves the mass transfer efficiency and gas utilization rate.

[0052] In some embodiments, the circulating pump includes an axial flow pump 3.

[0053] In some embodiments, the dual-circulation loop reactor further includes a motor 4, which is electrically connected to the circulation pump for driving the circulation pump.

[0054] In some embodiments, both of the circulating branch pipes include a temperature control section, and a temperature control sleeve 5 is provided outside the temperature control section.

[0055] In this invention, the temperature control sleeve 5 is used to introduce a heating medium or a cooling medium to adjust the temperature of the gas-liquid mixture in the dual-loop pipe 2.

[0056] The dual-circulation loop reactor provided by this invention, through the temperature control sleeve 5 and the dual circulation flow of gas-liquid mixed fluid, enables the temperature control accuracy of the gas-liquid mixed fluid to reach ±0.2℃, meeting the stringent temperature requirements of high-density fermentation.

[0057] In some embodiments, the temperature control sleeve 5 includes a heating sleeve and / or a cooling sleeve.

[0058] In some embodiments, the temperature control sleeve 5 is provided with an inlet 12 and an outlet 13, with the outlet 13 located above the inlet 12.

[0059] In some embodiments, the dual-loop pipe 2 is provided with at least one monitoring port 14, and the monitoring port 14 is provided with any one or a combination of at least two of the following: a pH sensor, a dissolved oxygen sensor, or a temperature sensor.

[0060] In some embodiments, the central pipe includes a monitoring port 14 near the circulation pump, and the two circulation branch pipes each include a monitoring port 14 near the temperature control section.

[0061] In some embodiments, the dual-loop pipe 2 includes at least one observation segment, and each observation segment is provided with an observation window 6.

[0062] In some embodiments, the central pipe includes an observation section near the circulation pump, and the two circulation branch pipes each include an observation section between the temperature control section and the exhaust tank 1.

[0063] In some embodiments, the observation window 6 is formed by a portion of the tube body of the double-loop tube 2, and the tube body material of the double-loop tube 2 at the position corresponding to the observation window 6 is a transparent material.

[0064] In some embodiments, the top of the exhaust tank 1 is provided with an exhaust port 9 and a liquid inlet 8.

[0065] In some embodiments, a sterilization steam inlet 11 is provided at the bottom of the dual-loop pipe 2.

[0066] In some embodiments, the dual-circulation loop reactor includes an outlet 10, which includes a first outlet located at the bottom of the exhaust tank 1 and a second outlet located at the bottom of the dual-circulation loop 2; a feed pump is provided on the inlet 8, and a discharge pump is provided on the second outlet.

[0067] In this invention, the inlet flow rate of the feed pump is the same as the outlet flow rate of the outlet pump, so as to maintain a constant liquid volume in the dual-circulation loop reactor.

[0068] In another embodiment, the present invention provides a gaseous fermentation method employing the above-described dual-circulation loop reactor, the gaseous fermentation method comprising: Gas is introduced into the air inlet 7. The introduced gas passes through the circulation pump. Under the shearing force generated by the rotation of the circulation pump impeller, it forms a group of microbubbles with an average size of less than 500μm. Then, it mixes with the liquid in the double-loop ring pipe 2 to form a gas-liquid mixture. The gas-liquid mixture then flows downward along the central pipe of the double-loop ring pipe 2 under the action of the circulation pump. After that, it circulates and mixes along the two circulation branch pipes in a bottom-up path. Finally, it is separated in the exhaust tank 1 and discharged as gas.

[0069] In some embodiments, the flow velocity of the gas-liquid mixture during circulating flow mixing in the dual-loop annular pipe 2 is 0.6 m / s to 1.0 m / s, for example, it can be 0.6 m / s, 0.62 m / s, 0.64 m / s, 0.66 m / s, 0.68 m / s, 0.7 m / s, 0.72 m / s, 0.74 m / s, 0.76 m / s, 0.78 m / s, 0.8 m / s, 0.82 m / s, 0.84 m / s, 0.86 m / s, 0.88 m / s, 0.9 m / s, 0.92 m / s, 0.94 m / s, 0.96 m / s, 0.98 m / s, or 1.0 m / s, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0070] In another embodiment, the present invention provides a gas fermentation apparatus comprising the aforementioned dual-circulation loop reactor.

[0071] Example 1 This embodiment provides a dual-circulation loop reactor, which includes an exhaust tank 1 with a pipe diameter of 250 mm, a dual-loop loop 2, and a circulation pump; The double-loop ring pipe 2 includes a central pipe (vertical pipe) with a diameter of 100mm and two circulating branch pipes with a diameter of 100mm arranged symmetrically on the axis, forming a double-loop circulation channel. A central pipe branch pipe is provided on the central pipe, and the other end of the central pipe branch pipe and the opening ends of the two circulating branch pipes are connected to the exhaust tank 1. An axial flow pump 3 is installed at the connection between the central pipe and the central pipe branch pipe. An air inlet 7 is installed on the central pipe branch pipe near the axial flow pump 3. The gas enters the central pipe branch pipe through the air inlet 7 and then enters the circulation pump. Under the action of the shear force generated by the rotation of the impeller of the axial flow pump 3, a group of microbubbles with an average size of 350μm is formed and then mixed with the liquid in the double loop ring pipe 2. The dual-circulation loop reactor also includes a motor 4, which is electrically connected to the circulation pump and is used to drive the circulation pump to operate. Both of the circulating branch pipes include a temperature control section, and a temperature control sleeve 5 is provided on the outside of the temperature control section. The temperature control sleeve 5 is used to introduce a heat medium or a cold medium to adjust the temperature of the gas-liquid mixture in the dual-loop pipe 2 (temperature control accuracy is ±0.2℃). The temperature control sleeve 5 is provided with an inlet 12 and an outlet 13, and the outlet 13 is located above the inlet 12.

[0072] The dual-loop pipe 2 is provided with at least one monitoring port 14, and the monitoring port 14 is provided with any one or a combination of at least two of the following: pH sensor, dissolved oxygen sensor or temperature sensor. The central pipe includes a monitoring port 14 near the circulation pump, and the two circulation branch pipes each include a monitoring port 14 near the temperature control section. The dual-loop pipe 2 includes at least one observation segment, and each observation segment is provided with an observation window 6; The central pipe includes an observation section near the circulation pump, and the two circulation branch pipes each include an observation section between the temperature control section and the exhaust tank 1. The observation window 6 is formed by a portion of the tube body of the double-loop ring tube 2, and the tube body material of the double-loop ring tube 2 at the position corresponding to the observation window 6 is a transparent material; The top of the exhaust tank 1 is provided with an air outlet 9 and a liquid inlet 8; The bottom of the dual-loop pipe 2 is provided with a sterilization steam inlet 11; The dual-circulation loop reactor includes an outlet 10, which includes a first outlet located at the bottom of the exhaust tank 1 and a second outlet located at the bottom of the dual-loop pipe 2. A feed pump is installed on the inlet 8, and a discharge pump is installed on the second outlet. The inlet flow rate of the feed pump is the same as the outlet flow rate of the discharge pump to maintain a constant liquid volume in the dual-circulation loop reactor.

[0073] This embodiment also provides a gas fermentation method using the above-described dual-circulation loop reactor, the gas fermentation method comprising: Gas is introduced into the air inlet 7. The introduced gas passes through the circulation pump driven by the motor 4 (the motor 4 drives the axial flow pump 3 at a speed of 400-800 rpm). Under the shear force generated by the rotation of the impeller of the circulation pump, a group of microbubbles with an average size of 350 μm is formed. The microbubbles then mix with the liquid in the double-loop ring pipe 2 to form a gas-liquid mixture. The gas-liquid mixture is then driven by the circulation pump and flows downward along the central pipe of the double-loop ring pipe 2 at a flow rate of 1.0 m / s. After that, it circulates and mixes along the two circulation branch pipes in a bottom-up path. Finally, the gas is separated in the exhaust tank 1 and discharged. After fermentation, the remaining liquid is discharged from the bottom of the second liquid outlet.

[0074] Example 2 This embodiment provides a dual-circulation loop reactor, which includes an exhaust tank 1 with a pipe diameter of 280 mm, a dual-loop loop 2, and a circulation pump; The double-loop ring pipe 2 includes a central pipe (vertical pipe) with a diameter of 150mm and two symmetrically arranged circulating branch pipes with a diameter of 150mm, forming a double-loop circulation channel. A central pipe branch pipe is provided on the central pipe, and the other end of the central pipe branch pipe and the opening ends of the two circulating branch pipes are connected to the exhaust tank 1. An axial flow pump 3 is installed at the connection between the central pipe and the central pipe branch pipe. An air inlet 7 is installed on the central pipe branch pipe near the axial flow pump 3. After the gas enters the central pipe branch pipe through the air inlet 7, it enters the circulation pump. Under the shear force generated by the rotation of the impeller of the axial flow pump 3, it forms a group of microbubbles with an average size of 300μm and then mixes with the liquid in the double loop ring pipe 2. The dual-circulation loop reactor also includes a motor 4, which is electrically connected to the circulation pump and is used to drive the circulation pump to operate. Both of the circulating branch pipes include a temperature control section, and a temperature control sleeve 5 is provided on the outside of the temperature control section. The temperature control sleeve 5 is used to introduce a heat medium or a cold medium to adjust the temperature of the gas-liquid mixture in the double-loop pipe 2. The temperature control sleeve 5 is provided with an inlet 12 and an outlet 13, and the outlet 13 is located above the inlet 12.

[0075] The dual-loop pipe 2 is provided with at least one monitoring port 14, and the monitoring port 14 is provided with any one or a combination of at least two of the following: pH sensor, dissolved oxygen sensor or temperature sensor. The central pipe includes a monitoring port 14 near the circulation pump, and the two circulation branch pipes each include a monitoring port 14 near the temperature control section. The dual-loop pipe 2 includes at least one observation segment, and each observation segment is provided with an observation window 6; The central pipe includes an observation section near the circulation pump, and the two circulation branch pipes each include an observation section between the temperature control section and the exhaust tank 1. The observation window 6 is formed by a portion of the tube body of the double-loop ring tube 2, and the tube body material of the double-loop ring tube 2 at the position corresponding to the observation window 6 is a transparent material; The top of the exhaust tank 1 is provided with an air outlet 9 and a liquid inlet 8; The bottom of the dual-loop pipe 2 is provided with a sterilization steam inlet 11; The dual-circulation loop reactor includes an outlet 10, which includes a first outlet located at the bottom of the exhaust tank 1 and a second outlet located at the bottom of the dual-loop pipe 2. A feed pump is installed on the inlet 8, and a discharge pump is installed on the second outlet. The inlet flow rate of the feed pump is the same as the outlet flow rate of the discharge pump to maintain a constant liquid volume in the dual-circulation loop reactor.

[0076] This embodiment also provides a gas fermentation method using the above-described dual-circulation loop reactor, the gas fermentation method comprising: Gas is introduced into the air inlet 7. The introduced gas passes through the circulation pump. Under the shear force generated by the rotation of the impeller of the circulation pump, it forms a group of microbubbles with an average size of 300μm. Then, it mixes with the liquid in the double-loop ring pipe 2 to form a gas-liquid mixture. The gas-liquid mixture is then driven by the circulation pump and flows downward along the central pipe of the double-loop ring pipe 2 at a flow rate of 0.8m / s. After that, it circulates and mixes along the two circulation branch pipes in a bottom-up path. Finally, it is separated in the exhaust tank 1 and discharged as gas. After the fermentation is completed, the remaining liquid is discharged from the bottom of the second liquid outlet.

[0077] Example 3 This embodiment provides a dual-circulation loop reactor, which includes an exhaust tank 1 with a pipe diameter of 220 mm, a dual-loop loop 2, and a circulation pump; The double-loop ring pipe 2 includes a central pipe (vertical pipe) with a diameter of 70mm and two symmetrically arranged circulating branch pipes with a diameter of 70mm, forming a double-loop circulation channel. A central pipe branch pipe is provided on the central pipe, and the other end of the central pipe branch pipe and the opening ends of the two circulating branch pipes are connected to the exhaust tank 1. An axial flow pump 3 is installed at the connection between the central pipe and the central pipe branch pipe. An air inlet 7 is installed on the central pipe branch pipe near the axial flow pump 3. After the gas enters the central pipe branch pipe through the air inlet 7, it enters the circulation pump. Under the action of the shear force generated by the rotation of the impeller of the axial flow pump 3, a group of microbubbles with an average size of 480μm is formed and then mixed with the liquid in the double loop ring pipe 2. The dual-circulation loop reactor also includes a motor 4, which is electrically connected to the circulation pump and is used to drive the circulation pump to operate. Both of the circulating branch pipes include a temperature control section, and a temperature control sleeve 5 is provided on the outside of the temperature control section. The temperature control sleeve 5 is used to introduce a heat medium or a cold medium to adjust the temperature of the gas-liquid mixture in the double-loop pipe 2. The temperature control sleeve 5 is provided with an inlet 12 and an outlet 13, and the outlet 13 is located above the inlet 12.

[0078] The dual-loop pipe 2 is provided with at least one monitoring port 14, and the monitoring port 14 is provided with any one or a combination of at least two of the following: pH sensor, dissolved oxygen sensor or temperature sensor. The central pipe includes a monitoring port 14 near the circulation pump, and the two circulation branch pipes each include a monitoring port 14 near the temperature control section. The dual-loop pipe 2 includes at least one observation segment, and each observation segment is provided with an observation window 6; The central pipe includes an observation section near the circulation pump, and the two circulation branch pipes each include an observation section between the temperature control section and the exhaust tank 1. The observation window 6 is formed by a portion of the tube body of the double-loop ring tube 2, and the tube body material of the double-loop ring tube 2 at the position corresponding to the observation window 6 is a transparent material; The top of the exhaust tank 1 is provided with an air outlet 9 and a liquid inlet 8; The bottom of the dual-loop pipe 2 is provided with a sterilization steam inlet 11; The dual-circulation loop reactor includes an outlet 10, which includes a first outlet located at the bottom of the exhaust tank 1 and a second outlet located at the bottom of the dual-loop pipe 2. A feed pump is installed on the inlet 8, and a discharge pump is installed on the second outlet. The inlet flow rate of the feed pump is the same as the outlet flow rate of the discharge pump to maintain a constant liquid volume in the dual-circulation loop reactor.

[0079] This embodiment also provides a gas fermentation method using the above-described dual-circulation loop reactor, the gas fermentation method comprising: Gas is introduced into the air inlet 7. The introduced gas passes through the circulation pump. Under the shear force generated by the rotation of the impeller of the circulation pump, it forms a group of microbubbles with an average size of 480μm. Then, it mixes with the liquid in the double-loop ring pipe 2 to form a gas-liquid mixture. The gas-liquid mixture is then driven by the circulation pump and flows downward along the central pipe of the double-loop ring pipe 2 at a flow rate of 0.6m / s. After that, it circulates and mixes along the two circulation branch pipes in a bottom-up path. Finally, it is separated in the exhaust tank 1 and discharged as gas. After the fermentation is completed, the remaining liquid is discharged from the bottom of the second liquid outlet.

[0080] Example 4 This embodiment provides a dual-circulation loop reactor. Except for the central pipe (vertical pipe) of the dual-loop loop 2 having a diameter of 200mm and the two axially symmetrically arranged circulation branch pipes having a diameter of 200mm, the rest are the same as in Embodiment 1.

[0081] Example 5 This embodiment provides a dual-circulation loop reactor. Except that the diameter of the central pipe (vertical pipe) of the dual-loop loop 2 is 50 mm and the diameter of the two axially symmetrically arranged circulation branch pipes is 50 mm, the rest is the same as in embodiment 1.

[0082] Comparative Example 1 This comparative example provides a reactor, which includes an exhaust tank 1, a U-shaped ring pipe and a circulation pump, wherein the two open ends of the U-shaped reaction pipe with a diameter of 100 mm are respectively connected to the exhaust tank 1; An air inlet 7 is provided near one open end of the U-shaped ring pipe, and an axial flow pump 3 is connected to the bottom of the U-shaped ring pipe. This comparative example also provides a gaseous fermentation method using the aforementioned reactor, the gaseous fermentation method comprising: Gas is introduced into the air inlet 7. The introduced gas enters the U-shaped ring pipe and initially mixes with the liquid in the U-shaped ring pipe to form a gas-liquid mixture. The gas-liquid mixture is circulated under the action of the axial flow pump 3 to achieve further flow and mixing, thus completing the fermentation.

[0083] Comparative Example 2 This comparative example provides a reactor that is identical to Example 1, except that the circulating pump is located at the end of the central tube away from the branch tube of the central tube and connected to the two double-loop ring tubes 2.

[0084] Microbial fermentation was carried out using the reactors and gas fermentation methods provided in the above embodiments and comparative examples. Tests were conducted under the same aeration rate, initial fermentation conditions, and operating load. The results of the tests, including the average size of microbubbles, the average residence time of bubbles in the liquid phase, the volumetric mass transfer coefficient, the gas utilization rate, and the cell yield per unit gas substrate, are shown in Table 1.

[0085] The method for testing the average size of microbubbles is as follows: using high-speed camera image analysis, after the reactor has reached a stable gas-liquid two-phase circulation state, bubble images in the circulation branch pipe are acquired through the observation window 6 on the loop pipe. The bubble size in the acquired images is identified and statistically analyzed using image processing software, and the average particle size of the microbubbles is calculated. The results are shown in Table 1.

[0086] The method for testing the average residence time of bubbles in the liquid phase is as follows: using the gas phase pulse tracer method, after the reactor has reached a stable gas-liquid two-phase circulation state, a quantitative inert tracer gas is injected instantaneously at the inlet 7. Simultaneously, the concentration of tracer gas in the exhaust gas is continuously detected over time at the outlet 9 at the top of the exhaust tank 1. The residence time distribution curve is plotted and the average residence time of bubbles in the liquid phase is calculated. The results are shown in Table 1.

[0087] The test method for the volumetric mass transfer coefficient is as follows: The dynamic dissolved oxygen electrode method is adopted. After the microbubble loop reactor reaches the stable state of gas and liquid two phases, the gas supply is stopped and the dissolved oxygen electrode is used to record the change curve of dissolved oxygen concentration in the reaction liquid with time in real time. The volumetric mass transfer coefficient (kLa) of the reactor is calculated by the dissolved oxygen decrease rate. The results are shown in Table 1.

[0088] The gas utilization rate was tested using the tail gas composition quantitative analysis method. Gas samples were collected from the reactor inlet 7 and outlet 9 respectively. The volume concentration of the target substrate gas in the inlet and tail gas was detected by gas chromatography. Combined with the volume flow rate of the inlet and tail gas, the gas utilization rate was calculated as the proportion of the substrate gas consumption to the total inlet gas. The results are shown in Table 1.

[0089] The method for testing the cell yield per unit gas substrate is as follows: After fermentation, the fermentation broth is taken, centrifuged, washed and dried to constant weight, the cell dry weight is measured, and the initial cell dry weight is subtracted to obtain the net cell increment. The cell yield per unit gas substrate is then calculated, and the results are shown in Table 1.

[0090] Table 1 Table 2 From Table 1, we can obtain: (1) When using the dual-circulation loop reactor provided in Examples 1-3 and carrying out microbial gas fermentation using the gas fermentation method provided in Examples 1-3, it simultaneously exhibits a smaller average microbubble size, a longer average residence time, a higher volumetric mass transfer efficiency, a higher gas utilization rate, and a higher cell yield per unit gas substrate. (2) By comparing Example 1 with Examples 4 and 5, it can be seen that in this invention, when the diameters of the central pipe and the two circulating branch pipes are independently 70mm~150mm, the gas fermentation method exhibits better overall performance. This is because when the pipe diameter is too small, the flow resistance of the pipe increases significantly, the circulation energy consumption increases, and strong shearing easily damages the microbial cells; when the pipe diameter is too large, the liquid velocity in the pipe is low, the liquid phase turbulence is insufficient, the bubbles are easy to aggregate, and the mass transfer efficiency decreases; the pipe diameter range of 70mm~150mm can take into account the circulation flow rate, the bubble dispersion effect and the operating energy consumption, and is suitable for the microbial fermentation working conditions. (3) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that in the dual-circulation loop reactor provided by the present invention, the air inlet 7 is set on the central pipe branch and is close to the circulation pump. After the gas enters the central pipe branch, it is instantly sucked into the circulation pump. When the impeller of the circulation pump rotates at high speed, it generates strong shear force and turbulence, which directly breaks the gas into a group of microbubbles with an average size of less than 500 μm. This "inlet shearing" mode makes the size of the microbubbles much smaller than that of the traditional aeration method (the size of the microbubbles is usually 1 mm to 5 mm), and the specific surface area is greatly improved. The volumetric mass transfer coefficient (kLa) is 2 to 3 times higher than that of the traditional reactor.

[0091] In the dual-circulation loop reactor provided by this invention, the circulating pump drives the reaction liquid to flow downward along the central pipe of the dual-loop loop 2, and then circulates along two circulating branch pipes in a bottom-up path. The fluid is split through the dual circulation channels. Compared with the single loop structure, the dual circulation channels can split the fluid and reduce the flow rate of the liquid in the single channel. The lower flow rate means that the bubbles have a longer residence time in the liquid phase (extended by 30%~50%). The bubbles continue to dissolve during the rising process, which significantly reduces the content of unreacted gas in the tail gas (the concentration of unused gas in the tail gas is reduced by 40%-60%), and greatly improves the gas utilization rate.

[0092] The dual-circulation ring reactor provided by this invention has dual circulation channels, which eliminate the eccentric flow and dead zone of the single-tube structure and improve the uniformity of the fermentation broth in the whole reactor.

[0093] The dual-circulation loop reactor provided by this invention does not require an additional high-pressure microbubble generator; it can be achieved by the self-shearing of the axial flow pump 3. Furthermore, the dual-channel diversion reduces the flow rate, and the corresponding energy consumption of the circulation pump is also reduced.

[0094] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A dual-circulation loop reactor, characterized in that, The dual-circulation loop reactor includes an exhaust tank, a dual-loop loop, and a circulation pump. The dual-loop pipe includes a central pipe and two circulating branch pipes, forming a dual-loop circulation channel. A central pipe branch pipe is provided on the central pipe, with one end connected to the central pipe. The other end of the central pipe branch pipe and the opening ends of the two circulating branch pipes are all connected to the exhaust tank. A circulation pump is installed at the connection between the central pipe and the central pipe branch pipe. An air inlet is installed on the central pipe branch pipe near the circulation pump. Gas enters the central pipe branch pipe through the air inlet and then enters the circulation pump. Under the shearing force generated by the rotation of the impeller of the circulation pump, a group of microbubbles with an average size of less than 500μm is formed and then mixed with the liquid in the double-loop pipe.

2. The dual-circulation loop reactor according to claim 1, characterized in that, The diameter of the exhaust tank is 220mm~280mm; And / or, the diameter of the central pipe and the two circulating branch pipes are independently 70mm~150mm; And / or, the two circulating branch pipes are symmetrically arranged, and the diameters of the two circulating branch pipes are the same.

3. The dual-circulation loop reactor according to claim 1, characterized in that, The circulating pump includes an axial flow pump; And / or, the dual-circulation loop reactor further includes an electric motor electrically connected to the circulation pump for driving the circulation pump.

4. The dual-circulation loop reactor according to claim 1, characterized in that, Both of the circulating branch pipes include a temperature control section, and a temperature control sleeve is provided on the outside of the temperature control section.

5. The dual-circulation loop reactor according to claim 4, characterized in that, The dual-loop pipe is provided with at least one monitoring port, and the monitoring port is provided with any one or a combination of at least two of the following: a pH sensor, a dissolved oxygen sensor, or a temperature sensor.

6. The dual-circulation loop reactor according to claim 4, characterized in that, The dual-loop pipe includes at least one observation segment, and each observation segment is provided with an observation window.

7. The dual-circulation loop reactor according to any one of claims 1 to 6, characterized in that, The top of the exhaust tank is provided with an air outlet and a liquid inlet; And / or, a sterilization steam inlet is provided at the bottom of the dual-loop pipe; And / or, the dual-circulation loop reactor includes a liquid outlet, the liquid outlet including a first liquid outlet disposed at the bottom of the exhaust tank and a second liquid outlet disposed at the bottom of the dual-circulation loop; a feed pump is disposed on the liquid inlet and a discharge pump is disposed on the second liquid outlet.

8. A gaseous fermentation method using a dual-circulation loop reactor as described in any one of claims 1 to 7, characterized in that, The gas fermentation method includes: Gas is introduced into the inlet and passes through the circulation pump. Under the shearing force generated by the impeller rotation of the circulation pump, a group of microbubbles with an average size of less than 500μm is formed. The gas then mixes with the liquid in the double-loop pipe to form a gas-liquid mixture. The gas-liquid mixture then flows downward along the central pipe of the double-loop pipe under the action of the circulation pump, and then circulates and mixes along the two circulation branch pipes in a bottom-up path. Finally, the gas is separated in the exhaust tank and discharged.

9. The gas fermentation method according to claim 8, characterized in that, The flow velocity of the gas-liquid mixture during its circulating flow and mixing in the dual-loop pipe is 0.6 m / s to 1.0 m / s.

10. A gas fermentation apparatus, characterized in that, The gas fermentation apparatus includes the dual-circulation loop reactor as described in any one of claims 1 to 7.

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