Forced internal circulation type microbubble reactor with guide cylinder and reaction method

Abstract

The invention relates to a fermentation tank for microbial reaction, in particular to a forced internal circulation type microbubble reactor with a guide cylinder, which comprises a tank body (1), a cylindrical guide cylinder (3) is arranged in the tank body (1), an overflow weir (32) is arranged at the upper part of the guide cylinder, and more than one liquid outlet pipe is arranged at the lower part of the guide cylinder; the upper part of the tank body (1) is provided with a plug flow stirrer (2), the lower end of the plug flow stirrer is provided with a plug flow paddle (24), and the plug flow paddle is positioned at the upper part of the guide cylinder (3); and at least one microbubble generator (4) is arranged in the guide cylinder (3) and is communicated with the air guide pipe. By means of the built-in guide cylinder, the device is large in flow, small in power consumption, mild in flowing, small in shearing force on liquid, uniform in airflow mixing, convenient to distribute and more suitable for a biological fermentation system.

Description

Technical Field

[0001] The invention relates to a fermentation tank for microbial reaction, in particular to a forced internal circulation type micro-bubble reactor with a guide tube. Background Art

[0002] In order to fully mix the microorganisms and the reaction materials, the fermentation tanks used in existing microbial reactions mostly adopt the method of stirring inside the tank. In addition, the fermentation tanks also use centrifugal pumps to circulate the materials externally, but due to the high speed and strong shear force of centrifugal pumps, microorganisms are easily destroyed and the energy consumption is high.

[0003] For example, Chinese patent CN215924946U discloses a microbial reactor, which includes a tank body, a driving motor is provided at the upper end of the tank body, a stirring shaft is provided inside the tank body, a defoaming paddle is provided on the stirring shaft near the upper part of the tank body, a stirring paddle is provided in the middle and lower end of the stirring shaft, and the driving motor drives the stirring shaft to rotate; an observation window is provided on the side wall of the fermentation tank body; an installation port is provided on the side wall of the fermentation tank near the bottom of the fermentation tank, and a temperature detection device, a dissolved oxygen detection device and a pH value detection device are provided on the installation port. The microbial reactor of the utility model is convenient for controlling various conditions inside the microbial reactor to improve the efficiency of microbial fermentation, and it can be used as a supporting device for automatically monitoring the microbial reactor.

[0004] Another example is Chinese patent CN211170506U, which discloses a microbial fermentation stirring reactor, including a reaction tank, a feed port and a vent valve are provided at the upper end, a motor installation box is provided on the side wall, a stirring motor is provided on the side wall of the motor installation box, and a first gear connected to the output end of the stirring motor is provided inside, the first gear is connected to the active stirring shaft extending into the reaction tank, a driven stirring shaft is provided on the lower side of the active stirring shaft, and a second gear meshing with the first gear is provided at one end of the driven stirring shaft located in the inner cavity of the motor installation box; a heating chamber with a heating wire is provided at the bottom of the reaction tank, and a temperature sensor is provided at the lower part of the inner cavity side wall of the reaction tank. This device improves the stirring efficiency of microbial fermentation raw materials, heats the microbial fermentation raw materials through the heating wire in the heating chamber, and provides a better reaction and fermentation environment for the microbial fermentation raw materials.

[0005] The above patents all use stirring blades to drive the reaction solution to achieve the exchange of gas, liquid and solid in the solution. This stirring effect is good, but its disadvantages are that it has great force, is easy to destroy microorganisms, and has high energy consumption. Summary of the invention

[0006] In order to overcome the shortcomings of the above reactors, such as easy destruction of microorganisms and high energy consumption, the present invention provides a forced internal circulation microbubble reactor with a guide tube.

[0007] The present invention is achieved by the following measures A forced internal circulation type micro-bubble reactor with a draft tube comprises a tank body, wherein a cylindrical draft tube is arranged inside the tank body, an overflow weir is arranged at the upper part of the draft tube, and one or more liquid outlet pipes are arranged at the lower part; a plug flow agitator is arranged at the upper part of the tank body, a plug flow blade is arranged at the lower end of the plug flow agitator, and the plug flow blade is located at the upper part of the draft tube; at least one micro-bubble generator is arranged in the draft tube (3), and the micro-bubble generator is connected to the air guide pipe.

[0008] The above-mentioned forced internal circulation microbubble reactor with a guide tube is preferably: a transmission motor is provided on the plug flow agitator, and a measuring instrument for measuring the driving motor current is provided on the transmission motor; a defoaming paddle for mechanical defoaming is provided on the upper part of the plug flow agitator, and a defoaming agent adding device is provided on the upper part of the tank body, and a controller is respectively connected to the measuring instrument and the defoaming agent adding device, and controls the amount of defoaming agent added or stops adding according to the change of the driving current.

[0009] The above-mentioned forced internal circulation microbubble reactor with a guide tube is preferably configured such that: the microbubble generator is located below the plug flow blade, and the metal membrane tube of the microbubble generator is arranged along the axial direction of the guide tube; the diameter of the guide tube at the microbubble generator becomes smaller and is 50-90% of the diameter of the guide tube.

[0010] The above-mentioned forced internal circulation microbubble reactor with a guide tube is preferably provided with an internal circulation gas-liquid distributor at the outlet of the guide tube, and the distributor is provided with more than 4 distribution pipes (ports) distributed around the guide tube and at the bottom of the fermentation tank, so that the circulating liquid of the guide tube is evenly distributed along the cross-section of the fermentation tank.

[0011] In the above-mentioned forced internal circulation microbubble reactor with a guide tube, preferably, a heat exchanger is provided on the tank body.

[0012] The above-mentioned forced internal circulation microbubble reactor with a guide tube is preferably: an auxiliary external circulation system is also arranged on the outside of the tank body, and the auxiliary external circulation system includes an auxiliary plug flow pump, a circulation pipe, an auxiliary microbubble generator, and an external circulation gas-liquid distributor, and the auxiliary plug flow pump includes a transmission mechanism, a transmission shaft, a pump casing, and a plug flow impeller.

[0013] The above-mentioned forced internal circulation microbubble reactor with a guide tube is preferably arranged axially along the guide tube (circulation tube) so that the circulating liquid flows axially along the aeration tube, and the microbubbles formed on the surface of the aeration tube can be carried away by the circulating liquid in time. The circulating liquid flow rate of the aeration membrane tube section of the guide tube is preferably 2-5m / s.

[0014] The above-mentioned forced internal circulation microbubble reactor with a guide tube is preferably: the internal circulation gas-liquid distributor and the external circulation gas-liquid distributor are both composed of a guide plate densely covered with guide holes; the microbubble generator and the auxiliary microbubble generator are both composed of a plurality of microfiltration membranes.

[0015] The reaction method of the forced internal circulation type microbubble reactor with a guide tube is adopted, and the circulation flow is powered by a plug flow pump, so the shear force on the microorganisms is small and the power consumption is low; the microbubbles formed by the joint action of the microbubble generator and the high-speed circulation flow are small in diameter and are evenly mixed with the fermentation liquid; the microbubbles are evenly distributed along the tank bottom and the tank cross section through the internal circulation gas-liquid distributor and the external circulation gas-liquid distributor; the forced tank internal circulation flow rate can be adjusted by the plug flow pump frequency conversion; the microbubble generator can be installed above the tank bottom to reduce the requirement for the fermentation tank inlet back pressure value, thereby reducing the gas supply energy consumption; the external circulation system can be used alone when the fermentation tank is at a low liquid level, that is, to provide gas-liquid mass transfer conditions when the fermentation system is running at a low liquid level during startup.

[0016] The above reaction method is characterized in that: the controller monitors the change of the driving motor current through a measuring instrument to determine the foam intensity information during the fermentation process, which serves as the basis for adding defoaming agent during the fermentation process, and the controller adjusts the amount of defoaming agent added through the defoaming agent adding device.

[0017] The above reaction method, wherein the gas produced by the microbubble generator is characterized by: mainly or only containing a mixture of CO, CO2, and H2; mainly or only containing a mixture of CO and CO2; mainly or only containing a mixture of CO2 and H2; mainly or only containing a mixture of CO and H2; mainly or only containing CO.

[0018] In the above reaction method, the microorganisms include at least one carbon-fixing and gas-eating microorganism.

[0019] The above method, wherein the carbon-fixing and gas-eating microorganism is selected from Clostridium jundal ( Clostridium ljungdahlii )、Clostridium autoethanogenum( Clostridium autoethanogenum ), Clostridium carbonmonoxide ( Clostridium carboxidivorans ), Clostridium ragsdalei ( Clostridium ragsdalei ), Clostridium perfringens ( Clostridium coskatii )、Acetobacter woodii( Acetobacterium woodii ) or any combination thereof.

[0020] The beneficial effects of the present invention are: The present invention uses a built-in guide tube and a plug flow blade to construct a reactor with large flow, low power consumption, gentle flow, and small shear force on the liquid. It is more suitable for biological fermentation systems and can realize the circulation and exchange of upper and lower liquids. The built-in microbubble generator can generate a large number of tiny bubbles, which are directly mixed with the high-speed circulating liquid and then distributed. The gas and liquid are evenly mixed and distributed conveniently. The gas and liquid are further evenly mixed by the built-in gas-liquid distributor, which is more conducive to the gas-liquid mass transfer of the reactor (fermentation tank). At the same time, the added external plug flow circulation pump further improves the adaptability of the fermentation system to the low liquid level condition at startup. When the fermentation system reaches the normal working liquid level, the auxiliary plug flow pump can stop working, and other components are operated in parallel with the internal circulation guide system to maintain the circulating liquid distribution function. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the structure of Example 2 of the present invention (normal liquid level working condition) Figure 3 This is a schematic diagram of the structure of Example 2 of the present invention (starting liquid level working condition) Figure 4 for Figure 2 EE cross-sectional structure diagram In the figure, there is a tank body 1; a plug flow agitator 2, a transmission mechanism 21, a transmission shaft 22, a defoaming paddle 23, and a plug flow blade 24; a guide cylinder 3, a guide cylinder body 31, an overflow weir 32, and an internal circulation gas-liquid distributor 33; a microbubble generator 4; a heat exchanger 5; an auxiliary external circulation system, an auxiliary plug flow pump 6, a transmission mechanism 61, a transmission shaft 62, a pump casing 63, an impeller 64, a circulation pipe 65, an auxiliary microbubble generator 42, and an external circulation gas-liquid distributor 69. DETAILED DESCRIPTION

[0022] Embodiment 1 The following is combined with Figure 1 The present invention is described in detail. (Without auxiliary external circulation system) 1. Equipment composition and main components introduction The microbubble reactor of the present invention is provided with a guide tube inside the tank body to realize forced internal circulation. Specifically, it comprises a tank body (1), a cylindrical guide tube (3) is provided inside, an overflow weir (32) is provided at the top of the guide tube, 16 lateral liquid outlet pipes and 1 bottom liquid outlet pipe are provided at the bottom; a gas-liquid distributor (33) is provided at the outlet of the liquid outlet pipe. The gas-liquid distributor is a liquid outlet plate with guide holes. The diameter is φ16 mm.

[0023] A plug flow agitator (2) is arranged at the upper part of the tank body (1), and a plug flow blade (24) is arranged at the lower end of the plug flow agitator, and the plug flow blade is located at the upper part of the guide tube (3); three micro bubble generators (4) are arranged in the guide tube (3), and the micro bubble generators (4) are connected to the air guide pipe.

[0024] 1. Tank: The tank (1) is a metal container that provides a place and conditions for the fermentation reaction. The structure should meet the requirements of fermentation reaction cleaning, air disinfection, actual disinfection, fermentation process, hygiene indicators and safe production. It includes the tank container, material inlet and outlet (A, B, C, etc.), installation port and manhole (M), heat exchanger (5), etc. The tank (1) has a specification of φ1400*4200mm (straight section) and a nominal volume of 7kL.

[0025] 2. Plug flow agitator: The main function of the plug flow agitator (2) is to provide power for the forced internal circulation of the fermentation liquid under normal fermentation conditions and to assist in the generation of microbubbles. Its auxiliary function is to mechanically defoam through a defoaming paddle (23) and to provide foam intensity sensing information (drive motor current changes) during the fermentation process, which serves as one of the bases for adding defoaming agents during the fermentation process.

[0026] 3. Draft tube: The main functions of the draft tube (3) are, firstly, under normal fermentation conditions, to introduce the fermentation liquid at the top of the fermentation tank into the draft tube through the overflow weir (32), and to increase the pressure through the plug flow agitator (2), so that the fermentation liquid passes through the microbubble generator (4) at high speed, impacts the surface of the microporous membrane, reduces bubble aggregation, and helps generate microbubbles. Finally, the fermentation liquid mixed with microbubbles is distributed as evenly as possible to the cross section close to the tank bottom through the built-in gas-liquid distributor (33) and the external circulation gas-liquid distributor (69) located at the bottom of the draft tube. Secondly, under fermentation start-up (low liquid level) conditions, the fermentation liquid is introduced into the draft tube and the auxiliary external circulation system through the built-in gas-liquid distributor (33) located at the bottom of the draft tube, and the auxiliary plug flow pump (6) provides power, and the auxiliary microbubble generator (42) provides microbubbles. The fermentation liquid mixed with microbubbles is distributed as evenly as possible to the cross section close to the tank bottom through the external circulation gas-liquid distributor (69). The guide tube (3) is arranged in the middle of the fermentation tank, preferably in the center of the fermentation tank. The microbubble generator (4) is arranged at one or more points in the guide tube, preferably at the upper part of the guide tube (3) and below the flow-pushing blade (24).

[0027] The metal film tube of the micro-bubble generator (4) is arranged along the axial direction of the injection tube; the diameter of the flow guide tube at the micro-bubble generator becomes smaller, with a diameter of 300 mm, and the diameter of the flow guide tube is 400 mm.

[0028] The smaller the diameter of the guide tube at the microbubble generator, the faster the fluid will be. The fluid is tangent to the metal film tube wall. The outlet direction of the microbubbles generated on the metal film tube wall is perpendicular to the direction of the fluid, allowing the generated microbubbles to quickly enter the fluid and prevent the generation of larger bubbles.

[0029] 4. Microbubble generator: The main function of the microbubble generator is to form tiny bubbles in the fermentation liquid by using the micropores of the metal membrane and the fermentation liquid outside the membrane to facilitate efficient gas-liquid mass transfer in the fermentation. The metal membrane tube is preferably arranged along the axis of the injection tube or the circulation tube.

[0030] 5. Heat exchanger: The heat exchanger 5 is placed in the fermentation tank to supplement or export the heat in the fermentation tank and control the temperature in the fermentation tank within a set range.

[0031] 2. Specific process flow The process flow and parameters are as follows: In the forced internal circulation microbubble reactor with a draft tube, the filamentous fungus Aspergillus niger fermentation reaction is carried out: Aspergillus niger in the logarithmic growth phase is heated to 5% ( v / v ) was inoculated into the microbubble reactor. The cell viability, gas holdup and mass transfer efficiency were monitored on the third day of the operation of the reactor. The results are shown in Table 1 below.

[0032] Comparative Example Under the same reaction conditions as in Example 1, Aspergillus niger in the logarithmic growth phase was treated with 5% ( v / v ) inoculated into a centrifugal pump external circulation airlift reactor of the same volume. The centrifugal pump drives the bubble circulation and drives the fermentation liquid to move rapidly to the top of the tank at a flow rate of 1 tank volume per minute. The cell survival rate, gas holdup and mass transfer efficiency were monitored on the third day of the operation of the reactor. The results are shown in Table 1 below.

[0033] Compared with the conventional centrifugal pump airlift reactor, the reaction method of the filamentous fungus Aspergillus niger of the present invention is compared in three aspects: liquid shear force (measured as a survival rate micro-indicator), gas-liquid mixing degree (measured as a gas holdup index), and mass transfer efficiency: Table 1 Embodiment 2 The following is combined with Figure 2-4 The present invention is described in detail. (An auxiliary external circulation system is added) 1. Equipment composition and main components introduction The microbubble reactor of the present invention is provided with a guide tube inside the tank body to realize forced internal circulation, and at the same time, an auxiliary external circulation is also provided outside the tank body. The combined forced internal circulation and auxiliary external circulation microbubble reactor with a guide tube (hereinafter referred to as a fermentation tank) mainly comprises a tank body (1), a plug flow agitator (2), a guide tube (3), a microbubble generator (4), a heat exchanger (5) and an auxiliary external circulation system (6) (see Figure 2 ).

[0034] Specifically, it comprises a tank body (1), a cylindrical flow guide tube (3) is arranged inside, an overflow weir (32) is arranged at the upper part of the flow guide tube, and an internal circulation gas-liquid distributor (33) is arranged at the lower part, the internal circulation gas-liquid distributor (33) comprises 16 lateral liquid outlets and 1 bottom liquid outlet, and the nominal size of the liquid outlet is 200; a plug flow agitator (2) is arranged at the upper part of the tank body (1), and a plug flow blade (24) is arranged at the lower end of the plug flow agitator, and the plug flow blade is located at the upper part of the flow guide tube (3); a micro bubble generator (4) is arranged in the flow guide tube (3), and the micro bubble generator (4) is connected to the air guide pipe.

[0035] 1. Tank: The tank (1) is a metal container that provides a place and conditions for the fermentation reaction. The structure should meet the requirements of fermentation reaction cleaning, air disinfection, actual disinfection, fermentation process, hygiene indicators and safe production. It includes the tank container, material inlet and outlet (A, B, C, etc.), installation port and manhole (M), heat exchanger (5), etc. The tank (1) has a specification of φ3000*9000mm (straight section) and a nominal volume of 60kL.

[0036] 2. Plug flow agitator: The main function of the plug flow agitator (2) is to provide power for the forced internal circulation of the fermentation liquid under normal fermentation conditions and to assist in the generation of microbubbles; its auxiliary function is to mechanically defoam through the defoaming paddle (23), and to provide foam intensity sensing information (drive motor current changes) during the fermentation process, which serves as one of the bases for adding defoamers during the fermentation process. Plug flow pump rated flow 3000m 3 / h, pressure increase 4kPa.

[0037] 3. Draft tube: The nominal diameter of the draft tube (3) is 900 mm. Its main function is to introduce the fermentation liquid in the upper part of the fermentation tank into the draft tube through the overflow weir (32) under normal fermentation conditions, and to increase the pressure through the plug flow agitator (2) so that the fermentation liquid passes through the microbubble generator (4) at high speed, impacting the surface of the microporous membrane, reducing bubble aggregation, and assisting in the generation of microbubbles; finally, the fermentation liquid mixed with microbubbles is dispersed as much as possible through the internal circulation gas-liquid distributor (33) and the external circulation system gas-liquid distributor (69) located at the lower part of the draft tube. It can be evenly distributed to the cross section close to the bottom of the tank; secondly, under the fermentation start-up (low liquid level) condition, the fermentation liquid is introduced into the guide tube and the auxiliary external circulation system through the internal circulation gas-liquid distributor (33) located at the bottom of the guide tube, and the auxiliary plug flow pump (60) provides power, and the auxiliary microbubble generator (42) provides microbubbles, and the fermentation liquid mixed with microbubbles is distributed as evenly as possible to the cross section close to the bottom of the tank through the gas-liquid distributor (69); the guide tube (3) is arranged in the middle position of the fermentation tank, preferably in the center position of the fermentation tank. The microbubble generator (4) is arranged at one or more points in the guide tube, preferably arranged at the upper part of the guide tube (3) and below the plug flow blade (24).

[0038] The metal film tube of the micro-bubble generator (4) is arranged along the axial direction of the injection tube; the diameter of the injection tube at the micro-bubble generator becomes smaller, the nominal diameter is 700 mm, and the designed flow rate is ≥ 2 m / s.

[0039] The smaller the diameter of the guide tube at the microbubble generator, the faster the fluid will be. The fluid is tangent to the metal film tube wall. The outlet direction of the microbubbles generated on the metal film tube wall is perpendicular to the direction of the fluid, allowing the generated microbubbles to quickly enter the fluid and prevent the generation of larger bubbles.

[0040] 4. Microbubble generator: There are at least two groups of microbubble generators, namely the microbubble generator (4) and the auxiliary microbubble generator (42). The main function is to form microbubbles in the fermentation liquid by using the micropores of the metal membrane and the fermentation liquid outside the membrane to facilitate efficient gas-liquid mass transfer in the fermentation. The metal membrane tube is preferably arranged along the axis of the injection tube or the circulation tube. The microbubble generator (4) is designed to have a gas flow rate of 1200Nm 3 / h, auxiliary microbubble generator (42) designed gas flow rate 300Nm 3 / h, the diameter of the aeration membrane pores is 1μm.

[0041] The microbubble generator (4) is turned on at the normal working liquid level, and the auxiliary microbubble generator (42) is used when the fermentation tank is started or in other low liquid level conditions.

[0042] 5. Heat exchanger: The heat exchanger (5) is placed in the fermentation tank to supplement or remove the heat in the fermentation tank and control the temperature in the fermentation tank within a set range.

[0043] 6. Auxiliary external circulation system: An auxiliary external circulation system (6) is also provided on the outside of the tank body. The auxiliary external circulation system includes an auxiliary plug flow pump (60), a circulation pipe (65), an auxiliary micro bubble generator (42), and an external circulation gas-liquid distributor (69). The auxiliary plug flow pump (60) has a design flow rate of 600m 3 / h, with a pressure increase of 4 kPa, comprising a transmission mechanism (61), a transmission shaft (62), a pump casing (63), and a push-flow impeller (64).

[0044] The auxiliary external circulation system (6) is located outside the lower part of the fermenter, and the inlet (G1) is connected to the guide tube (3) in the fermenter. The inlet (G1) is located below the start-up liquid level of the fermenter. The auxiliary external circulation system mainly provides micro-bubble gas supply to the fermentation liquid during the fermenter startup or other low liquid level conditions, and distributes the micro-bubble gas as evenly as possible at the bottom of the tank through the external circulation gas-liquid distributor (69).

[0045] 2. Working Principle 1. Fermentation tank startup and low liquid level conditions: When the fermentation tank is in the startup or low liquid level condition, the fermentation liquid cannot form an internal circulation through the guide tube (3). At this time, the auxiliary external circulation system (6) is started, and the fermentation liquid enters the guide tube (3) from the bottom of the fermentation tank through the internal circulation gas-liquid distributor (33), and enters the auxiliary external circulation system (6) from the inlet (G1) of the auxiliary external circulation system through the guide tube (3). After the fermentation liquid is pressurized by the auxiliary plug flow pump (60), it passes through the auxiliary bubble generator (43), and forms a gas-liquid mixture with the microbubbles generated by the auxiliary bubble generator (43), and then is sent to the bottom of the fermentation tank by the gas-liquid distributor (69), and is distributed as evenly as possible along the tank cross section. The fermentation liquid gas-liquid mixture transfers mass and supplements fermentation nutrients in the fermentation tank, and the fermentation liquid forms a natural internal circulation in the fermentation tank. After degassing, it enters the guide tube (3) from the bottom of the tank through the internal circulation gas-liquid distributor (33), forming an external circulation of microbubble distribution of the fermentation liquid. When the liquid level in the fermentation tank rises to the normal working level, the system switches to the normal working condition, the auxiliary plug flow pump (60) and the auxiliary bubble generator (43) stop running, and the auxiliary external circulation system (6) as a part of the circulation pipe and the guide tube, together with the guide tube (3), performs the transmission and distribution of the microbubble fermentation liquid under the forced internal circulation state.

[0046] 2. Normal liquid level conditions: When the fermentation liquid level reaches the normal operating condition or is above the designed level, the plug flow agitator (2) and the micro bubble generator (4) are turned on to operate in a forced internal circulation mode. When the fermentation liquid flows from bottom to top in the fermentation tank to the gas-liquid separation interface, the gas phase overflows to the top of the tank, and the liquid phase enters the guide tube (3) through the overflow weir (32). After being pressurized by the plug flow agitator (2) located at the top of the guide tube, it passes through the micro bubble generator (4) at high speed (the guide tube of the micro bubble generator section can be reduced in diameter to facilitate the formation of high-speed flow of the fermentation liquid in the local area). Under the flushing of the metal microporous membrane of the micro bubble generator (4) and the fermentation liquid, the fermentation liquid and the micro bubbles are evenly mixed and divided into two paths downward along the guide tube. Most of the gas flows into the micro bubble generator (4). The liquid mixture continues to flow downward along the guide tube (3) and is distributed to the bottom of the fermentation tank by the internal circulation gas-liquid distributor (33). A small portion of the gas-liquid mixture is distributed to the bottom of the fermentation tank via the auxiliary external circulation system (6) and the external circulation gas-liquid distributor (69). The gas-liquid mixture distributed to the bottom of the tank is evenly distributed along the tank cross section. Under the action of the forced circulation force jointly formed by the plug flow agitator (2) and the micro-bubble flow, the fermentation liquid flows toward the upper part of the fermentation tank and enters the guide tube (3) through the overflow weir (32), thereby forming an orderly forced circulation of the fermentation liquid.

[0047] When excessive foam is generated during the fermentation process and reaches or submerges the defoaming paddle (23), the rotation of the defoaming paddle (23) can achieve mechanical defoaming and eliminate or partially eliminate the excessive foam. At the same time, since the defoaming paddle consumes energy when working, the workload of the plug flow agitator (2) increases, the current of the driving motor increases, and the signal of the increase in the current of the driving motor can be used as one of the important bases for adding defoaming agent to the tank.

[0048] 3. Main innovations 1. High gas-liquid mass transfer efficiency: the plug flow blade (24) is used as the forced circulation working mechanism, the forced circulation flow rate is large, the internal circulation gas-liquid distributor (33) and the external circulation gas-liquid distributor (69) are conventionally designed, and it is easy to achieve uniform distribution of the gas-liquid mixture along the cross section of the fermentation tank; the guide tube (3) has a simple structure and small resistance to liquid flow, the micro bubble generator (4) uses metal membrane micropores for aeration, the guide tube (3) is designed with a reduced diameter in the aeration section to increase the flow rate, and the axis of the metal membrane tube is parallel to the flow direction of the fermentation liquid, so that the formed micro bubbles are separated from the metal membrane in time, reducing the bubble aggregation phenomenon, and the formed bubbles have a smaller diameter and are evenly mixed with the fermentation liquid; the gas content in the air flow mixed liquid is high.

[0049] 2. Low energy consumption: The fermentation liquid can achieve a large circulation with low energy consumption and adjustable circulation volume in the fermentation tank: a simple structure, low resistance guide tube (3) and auxiliary external circulation system (6) are designed, and a plug flow pump (plug flow agitator 2, auxiliary plug flow pump 60) is used as the forced circulation power. Compared with stirring type and centrifugal pump external circulation fermentation tanks, the efficiency is significantly improved and the power consumption is significantly reduced; the micro bubble generator (4) is installed on the upper part of the fermentation tank, and the required air source back pressure is lower than that of the bottom aeration of the general fermentation tank; by adjusting the speed of the plug flow blade (24) and the plug flow impeller (64) of the forced circulation power mechanism by means of frequency conversion of the plug flow defoamer (2) or the auxiliary plug flow pump (60), the flow rate of the forced circulation can be conveniently adjusted according to the process requirements.

[0050] 3. The power mechanism operates gently and causes little damage to microorganisms: The forced circulation power mechanism plug flow blades (24) and plug flow impellers (64) have little shear force when operating, and are more friendly to microorganisms than centrifugal pumps.

[0051] 4. Strong adaptability to the working liquid level of the fermentation tank: By configuring the auxiliary external circulation system (6), the fermentation tank can still perform micro-bubble gas-liquid mass transfer, forced circulation stirring and other operations when the fermentation tank is below the normal working liquid level and above the starting liquid level, thereby meeting the basic needs of gas supply and gas-liquid mass transfer during the fermentation tank startup.

[0052] 5. Particularly suitable for continuous fermentation conditions: The fermentation tank works under normal liquid level conditions. Compared with stirred fermentation, it has the advantages of low energy consumption, better gas-liquid mass transfer effect, large circulation volume and uniform mixing; compared with airlift fermentation tank, it has the advantages of better gas-liquid mass transfer effect, large circulation volume and high yield per unit fermentation volume.

[0053] 6. It has both the defoaming and foaming sensing functions of the traditional paddle fermenter during the fermentation process.

[0054] 4. Specific process flow 60m 3 Taking the (φ3000×9000) fermentation tank as an example, describe the equipment structure and operating process parameters.

[0055] Normal working condition: three-blade push flow impeller, impeller diameter φ900, circulation flow 3000m 3 / h, boost pressure of about 4kPa, power consumption of about 5.5kW, motor installed power of 18.5kW (of which the defoaming paddle power is 10kW); gas flow rate of 1200Nm 3 / h, the pore size of the metal microporous membrane is 1μm, the fermentation liquid flow rate in the aeration section is 2-3m / s, and the circulation pipe is about 1-1.5m / s.

[0056] Start-up condition: circulation flow 600m 3 / h, motor 1.5kW; metal microporous membrane pore size 1μm.

[0057] In the forced internal circulation microbubble reactor with a draft tube (with an auxiliary external circulation system), the filamentous fungus Aspergillus niger fermentation reaction is carried out: Aspergillus niger in the logarithmic growth phase is heated to 5% ( v / v ) inoculated into the microbubble reactor. The cell viability, gas holdup and mass transfer efficiency were monitored on the third day of the operation of the reactor. The results are shown in Table 2 below.

[0058] Comparative Example Under the same reaction conditions as in Example 2, Aspergillus niger in the logarithmic growth phase was treated with 5% ( v / v ) inoculated into a centrifugal pump external circulation airlift reactor of the same volume. The centrifugal pump drives the bubble circulation and drives the fermentation liquid to move rapidly to the top of the tank at a flow rate of 1 tank volume per minute. The cell survival rate, gas holdup and mass transfer efficiency were monitored on the third day of the operation of the reactor. The results are shown in Table 2 below.

[0059] Compared with the conventional centrifugal pump airlift reactor, the reaction method of the filamentous fungus Aspergillus niger of the present invention is compared in three aspects: liquid shear force (measured as a survival rate micro-indicator), gas-liquid mixing degree (measured as a gas holdup index), and mass transfer efficiency: Table 2 Embodiment 3 A microbubble reactor with a forced internal circulation and auxiliary external circulation combined with a guide tube was used as a fermentation tank to ferment gas substrates containing CO, CO2 and H2. 40kL of culture medium was added to the reactor. The reactor was sterilized at 115℃ for 30 minutes. After the sterilization was completed, nitrogen was continuously passed to make the inside of the reactor an anaerobic environment. Clostridium aerogenes in the logarithmic growth phase was added at 5% ( v / v ) inoculated into the reactor, and nitrogen was kept flowing during the inoculation process. After the inoculation was completed, the inoculation was continued at 500Nm 3 / h of gas flow rate to introduce a mixture of CO, CO2 and H2. As the biomass increases, the gas flow rate is gradually increased to 1000Nm 3 / h. The pH is adjusted by ammonia and acetic acid during the process.

[0060] Results: The biomass was maintained at about 3 g / L, the acetic acid concentration was maintained at about 30 g / L, and the acetic acid productivity was 30 g / L / d.

Claims

1. A forced internal circulation microbubble reactor with a guide tube, comprising a tank body (1), characterized in that: A cylindrical flow guide tube (3) is arranged inside the tank body (1), an overflow weir (32) is arranged at the upper part of the flow guide tube, and one or more liquid outlet pipes are arranged at the lower part; a plug flow agitator (2) is arranged at the upper part of the tank body (1), a plug flow blade (24) is arranged at the lower end of the plug flow agitator, and the plug flow blade is located at the upper part of the flow guide tube (3); at least one micro bubble generator (4) is arranged in the flow guide tube (3), and the micro bubble generator (4) is connected to the air guide pipe.

2. The forced internal circulation microbubble reactor with a draft tube according to claim 1, characterized in that: The plug-flow agitator (2) is provided with a transmission motor (21), and the transmission motor is provided with a measuring instrument for measuring the current of the driving motor; a defoaming paddle 23 for mechanical defoaming is provided on the upper part of the plug-flow agitator (2), and a defoaming agent adding device is provided on the upper part of the tank body; a controller is respectively connected to the measuring instrument and the defoaming agent adding device, and controls the amount of defoaming agent added or stops adding according to changes in the driving current.

3. The forced internal circulation microbubble reactor with a draft tube according to claim 1, characterized in that: The microbubble generator (4) is located below the flow-pushing blade, and the metal film tube of the microbubble generator is arranged along the axial direction of the guide tube; the diameter of the guide tube at the microbubble generator becomes smaller and is 50-90% of the diameter of the guide tube.

4. The forced internal circulation microbubble reactor with a draft tube according to claim 1, characterized in that: An internal circulation gas-liquid distributor (33) is provided at the outlet of the guide tube. The distributor (33) is provided with more than four distribution pipes distributed around the guide tube and at the bottom of the fermentation tank, so that the circulating liquid in the guide tube is evenly distributed along the cross section of the fermentation tank. A heat exchanger (5) is provided on the tank body.

5. The forced internal circulation microbubble reactor with a draft tube according to claim 1, characterized in that: An auxiliary external circulation system is also provided on the outside of the tank body, the auxiliary external circulation system comprising an auxiliary plug flow pump (6), a circulation pipe (65), an auxiliary micro bubble generator (42), and an external circulation gas-liquid distributor (69), the auxiliary plug flow pump (6) comprising a transmission mechanism (61), a transmission shaft (62), a pump housing (63), and a plug flow impeller (64).

6. The forced internal circulation microbubble reactor with a draft tube according to claim 1, characterized in that: The aeration membrane tube is arranged axially along the guide tube so that the circulating liquid flows axially along the aeration tube. The microbubbles formed on the surface of the aeration tube can be taken away by the circulating liquid in time. The circulating liquid flow rate of the aeration membrane tube section of the guide tube is preferably greater than 2-5m / s.

7. The forced internal circulation microbubble reactor with a draft tube according to claim 1, characterized in that: The inner circulation gas-liquid distributor (33) and the outer circulation gas-liquid distributor (69) are both composed of guide plates densely covered with guide holes; the microbubble generator (4) and the auxiliary microbubble generator 42 are both composed of a plurality of microfiltration membranes.

8. The reaction method using the above-mentioned forced internal circulation microbubble reactor with a draft tube is characterized by: The plug flow pump provides power for the circulation flow, which produces little shear force on the microorganisms and low power consumption; the combined action of the microbubble generator and the high-speed circulation flow forms microbubbles with a small diameter, which are evenly mixed with the fermentation liquid; the microbubbles are evenly distributed along the tank bottom and tank cross-section through the gas-liquid distributor (33) (69); the circulation flow rate in the tank can be adjusted by the plug flow pump; the microbubble generator can be installed above the tank bottom to reduce the fermentation tank inlet back pressure requirement, thereby reducing the gas supply energy consumption; the external circulation system can be used alone when the fermentation tank is at low liquid level, that is, to provide gas-liquid mass transfer conditions when the fermentation system is running at low liquid level during startup.

9. The reaction method according to claim 9, characterized in that: The controller measures the driving motor current through a measuring instrument, and determines the foam intensity information during the fermentation process through the driving motor current change, which serves as the basis for adding defoaming agent during the fermentation process. The controller adjusts the amount of defoaming agent added through the defoaming agent adding device.

10. The reaction method according to claim 9, characterized in that: The gas generated by the microbubble generator comprises one or a mixture of CO, CO2, H2; the fermentation microorganism comprises at least one carbon-fixing and gas-eating microorganism, wherein the carbon-fixing and gas-eating microorganism is selected from Clostridium jundal ( Clostridium ljungdahlii )、Clostridium autoethanogenum( Clostridium autoethanogenum ), Clostridium carbonmonoxide ( Clostridium carboxidivorans ), Clostridium ragsdalei ( Clostridium ragsdalei ), Clostridium perfringens ( Clostridium coskatii ) and Acetobacter woodii ( Acetobacterium woodii ) or a combination of them.

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