Forced external circulation type microbubble reactor and reaction method thereof

Abstract

The invention belongs to the technical field of microbial fermentation, and particularly relates to a forced external circulation type microbubble reactor and a reaction method thereof. The reactor comprises a tank body (1), at least one group of circulating inlets (11) and circulating outlets (12) are respectively formed in the upper part and the lower part of the tank body (1), and a circulating system capable of enabling reaction liquid to circulate up and down is connected between each group of circulating inlets (11) and circulating outlets (12); the circulating system comprises a plug flow circulating pump (3), a circulating pipe (7), a microbubble generator (5) and an airflow mixing distributor (4) positioned at a circulating outlet (12); and more than one microbubble generator (5) is arranged at one point or more points in the circulating pipe. The plug-flow circulating pump is adopted, and the plug-flow paddles of the plug-flow circulating pump have the advantages of being large in construction flow, small in power consumption, mild in flowing, small in shearing force generated on liquid and the like, so that the reactor more suitable for microbial fermentation is constructed.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial fermentation, and in particular relates to a forced external circulation type microbubble reactor and a reaction method thereof. Background Art

[0002] In order to ensure sufficient mixing between microorganisms and reaction materials, there are currently two main ways to design microbial fermentation reactors. The first is a stirred reactor with a stirring device inside the fermenter. Through the synergistic effect of the stirrer and the gas distributor, large bubbles are sheared into small bubbles, thereby improving the gas-liquid mass transfer efficiency. This process not only promotes the uniform mixing of microorganisms and reaction materials, but also helps to enhance the reproduction efficiency of cells. However, the main challenge faced by stirred reactors in large-scale production is its high energy consumption. The second is an airlift reactor, which uses microporous aeration set at the bottom of the fermenter to drive the fermentation liquid to form an up and down circulation flow by the buoyancy of the rising bubbles to achieve material mixing. In order to further improve the mixing effect, the airlift fermentation reactor will adopt a centrifugal pump external circulation design. However, the centrifugal pump requires a faster speed to maintain the circulation, and the strong shear force generated by this will damage the microbial cells on the one hand, and on the other hand, it will generate higher energy consumption.

[0003] For example, Chinese patent application publication number CN108220136A discloses a stirred biogas fermentation tank, including a tank body, a circulation pump, a feed pipe and a discharge pipe; two groups of stirring mechanisms are arranged in the stirring mechanism, and the stirring mechanism includes a rotating shaft, a connecting rod, a stirring plate and an arc-shaped end, and a horizontal vibration plate is arranged below the stirring mechanism, the circulation pump is connected to a circulation pipe, and the other end of the circulation pipe is connected to a sampling box fixed on the outer wall of the tank body, and the bottom of the sampling box is connected to a booster pump; the sealing box is connected to a plurality of evenly distributed nozzles.

[0004] For example, Chinese patent application publication number CN108795706A discloses a light-sensitive heat-insulating fermentation stirring system, including a fermenter, a heat-insulating interlayer, a light-sensitive heating system, a heating plate, a ring tube jet system, a cross jet system and a circulation pump. The heat-insulating interlayer is wrapped around the outer wall of the fermenter, the light-sensitive heating system and the heating plate are both arranged in the heat-insulating interlayer, the light-sensitive heating system is located on the sunny side of the fermenter, and the heating plate is located on the shady side of the fermenter; the ring tube jet system and the cross jet system are both arranged at the bottom of the fermenter, and the cross jet system is located above the ring tube jet system; the liquid inlet pipe of the circulation pump penetrates into the upper part of the inner cavity of the fermenter, and the liquid outlet pipe of the circulation pump is connected to the ring tube jet system and the cross jet system at the same time.

[0005] The above-mentioned fermentation reactors or systems all have the problems of easily causing damage to microbial cells and high energy consumption.

[0006] At present, although conventional airlift fermentation reactors have the advantages of being friendly to microorganisms, not causing loss to microbial cells, and having low energy consumption, their main problem is that the buoyancy of the bubbles is limited, which makes the up and down circulation speed of the fermentation liquid low; and small bubbles are easy to aggregate into large bubbles during the rising process, resulting in low gas-liquid mass transfer efficiency. Summary of the invention

[0007] In order to overcome the problems of the above-mentioned fermentation reactor that easily causes microbial cell damage, high energy consumption and low gas-liquid mass transfer efficiency, the present invention provides a microbubble reactor with a plug flow circulation pump structure.

[0008] The present invention is achieved by the following measures: The invention discloses a forced external circulation type micro-bubble reactor, comprising a tank body, wherein at least one group of circulation inlet and circulation outlet are respectively arranged at the top and the bottom of the tank body, and a circulation system for allowing a reaction liquid to circulate up and down is connected between the circulation inlet and the circulation outlet of each group, and the circulation system comprises a plug flow circulation pump, a circulation pipe, a micro-bubble generator and an air flow mixing distributor located at the circulation outlet; the number of the micro-bubble generators is more than one, and they are respectively installed at one or more points in the circulation pipe.

[0009] The above technical solution adopts a plug flow circulation pump, and uses its plug flow blades to build a reactor more suitable for microbial fermentation, which has the characteristics of large flow, low power consumption, gentle flow, and small shear force on the liquid. The microbubble generator is placed in the circulation pipe, and the generated microbubbles are directly mixed with the high-speed circulating liquid and then distributed. The airflow is evenly mixed and distributed conveniently, which is more conducive to gas-liquid mass transfer in the reactor (fermentation tank).

[0010] In the above-mentioned forced external circulation microbubble reactor, preferably, the circulation pipe is divided into an aerated circulation pipe located at the top and a pressurized circulation pipe located at the bottom, the microbubble generator is installed in the tube body of the aerated circulation pipe, the aerated circulation pipe of the microbubble generator is in the same direction as the aerated circulation pipe, and the gas outlet direction of the microbubble generator is perpendicular to the liquid flow direction; the diameter ratio of the aerated circulation pipe and the pressurized circulation pipe is 1:0.8~0.9.

[0011] The above preferred technical solution has the following advantages: first, since the gas outlet direction of the microbubble generator is perpendicular to the liquid flow direction, the reaction liquid will shear the side wall of the gas adding tube during the flow process to form even smaller bubbles. Second, after the gas addition is completed, the reaction liquid enters the pressurized circulation tube with a smaller diameter, the volume of the microbubbles becomes smaller, the pressure becomes larger, and microbubbles with a certain pressure are formed. After the microbubbles enter the reaction tank, a certain cavitation effect will be formed in the reaction liquid, thereby improving the mixing effect of the reaction liquid. Third, since there is a certain pressure in the reaction liquid pressurized circulation tube, the lateral movement speed of the microbubbles is reduced, which can prevent the reunion of the microbubbles.

[0012] In the above-mentioned forced external circulation microbubble reactor, preferably, an overflow weir with an upper opening slightly lower than the reaction liquid surface is also provided at the circulation inlet; the side wall of the overflow weir is densely covered with gas-liquid separation holes, and the aperture of the gas-liquid separation holes is 0.2-0.6mm.

[0013] In the above preferred technical solution, the inlet of the forced circulation system is the overflow weir on the top of the tank, and the outlet is the airflow mixing distributor at the bottom of the tank. The system has low resistance and low energy consumption, and is easier to achieve efficient and uniform gas-liquid mass transfer. The side wall of the overflow weir is densely covered with gas-liquid separation holes to prevent microbubbles from entering the guide tube.

[0014] In the above-mentioned forced external circulation type microbubble reactor, preferably, the plug flow circulation pump comprises a pump housing, a motor and guide vanes; and a heat exchanger is also arranged in the tank body (1).

[0015] In the above-mentioned forced external circulation microbubble reactor, preferably, the blades are two or more plug flow blades.

[0016] In the above-mentioned forced external circulation microbubble reactor, preferably, the gas-liquid mixing distributor is composed of a plurality of guide plates or guide tubes with guide holes, the guide plates or guide tubes are located inside the gas circulation pipe, and the reaction liquid flows outside the guide plates or guide tubes. Alternatively, the following structure is adopted: the guide plates or guide tubes are located inside the gas circulation pipe, and the reaction liquid flows inside the guide plates or guide tubes.

[0017] In the above-mentioned forced external circulation microbubble reactor, preferably, the circulation inlet is located at the upper part of the tank body, and the circulation outlet is located at the bottom of the tank body.

[0018] The above-mentioned forced external circulation type microbubble reactor is preferably provided with two or more circulation systems, which are respectively located on both sides of the tank body or evenly distributed along the outer side of the tank body.

[0019] The reaction method of the forced external circulation microbubble reactor is adopted. The circulation system is provided with two respectively located on both sides of the tank body. The plug flow pump 3 provides power for the external circulation of the fermentation liquid. The boost pressure is 2-30KPa. The flow rate is lower than 1m / s when the pressure is increased in the pump body, and the flow rate in the circulation pipe is 1-2m / s. The fermentation liquid is pressurized by the plug flow pump and enters the microbubble generator at a speed of 1.5-3m / s through the circulation pipe; at the same time, the fermentation gas is aerated through the microfiltration membrane in the microbubble generator, and micron-sized bubbles are formed on the surface of the microbubble generator. The bubbles quickly leave the microfiltration membrane under the impact of the high-speed flow of the fermentation liquid, reducing the bubble aggregation and forming micron or millimeter-sized microbubbles; after the fermentation liquid is mixed with the fermentation gas, it enters the tank through the gas-liquid mixing distributor at the bottom of the tank and is evenly distributed, completing a forced external circulation reaction process, and driven by the forced circulation and the rising power of the bubbles, it moves rapidly to the top of the tank at a flow rate of 0.5-2 tank volumes per minute, realizing gas-liquid mass transfer during movement, and realizing gas-liquid separation at the gas-liquid interface on the upper part of the tank body.

[0020] In the above reaction method, preferably, the overall gas content of the reaction liquid in the tank is 10-25%.

[0021] The beneficial effects of the present invention are: The present invention adopts a plug-flow circulation pump, and utilizes the characteristics of its plug-flow blades, such as large flow rate, low power consumption, gentle flow, and small shear force on the liquid, to construct a reactor that is more suitable for microbial fermentation. The microbubble generator is placed in the circulation pipe, and the generated microbubbles are directly mixed with the high-speed flowing circulating liquid and then distributed. The airflow is evenly mixed and distributed conveniently, which is more conducive to gas-liquid mass transfer in the reactor (fermentation tank); the inlet of the forced circulation system is the overflow weir on the top of the tank, and the outlet is the airflow mixing distributor at the bottom of the tank. The system resistance is small, the energy consumption is low, and it is easier to achieve efficient and uniform mass transfer between gas and liquid. The microbubble generator of the present invention is placed to prevent the reunion of microbubbles, and provide microbubbles of a certain pressure, so that a certain cavitation effect is generated in the reaction tank, thereby improving the reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of an embodiment of the present invention; Figure 2 for Figure 1 Schematic diagram of the cross section of EE.

[0023] In the figure, 1 is a tank body, 2 is an overflow weir, 3 is a plug flow circulation pump, 4 is an air flow mixing distributor, 5 is a micro bubble generator, 6 is a heat exchanger, 11 is a circulation inlet, 12 is a circulation outlet, 31 is an aeration circulation pipe, 32 is a guide vane, and 33 is a pressurized circulation pipe. DETAILED DESCRIPTION

[0024] The following is combined with Figures 1 to 2 The technical solution of the present invention is described in detail.

[0025] Embodiment 1: This embodiment is an external circulation reactor, which is mainly composed of a tank body 1, an overflow weir 2, a plug flow circulation pump 3, an air flow mixing distributor 4, a micro bubble generator 5, a heat exchanger 6, a circulation pipe and other components. The flow rate of the plug flow circulation pump 3 is 400m 3 / h, boost 4kPa, shaft power 0.75kw, the diameter of the gas circulation pipe is DN350, and the diameter of the pressurized circulation pipe is DN300.

[0026] Tank 1: including tank container, material inlet and outlet (A, B, C, etc.), circulation inlet 11, circulation outlet 12, instrument and sensor port M1 (T, PH, L, etc.), installation port and manhole M2, heat exchanger 6, etc. The specification of tank 1 is φ1400*4200mm (straight section), nominal volume 7KL, the diameter of circulation inlet 11 is DN350, and the diameter of circulation outlet 12 is DN300.

[0027] Overflow weir 2: It is placed below the gas-liquid interface and close to the gas-liquid interface. Its main function is to evenly guide the upper liquid into the weir and the inlet of the plug flow circulation pump. The side wall of the overflow weir is densely covered with gas-liquid separation holes, and the aperture of the gas-liquid separation holes is 0.3mm.

[0028] Plug flow circulation pump 3: There are two plug flow circulation pumps 3, which are respectively located on both sides of the tank body 1. They are mainly composed of two guide blades 32, a motor, a reducer, a transmission shaft, a seal, a pump housing and a guide pipe 31, which are used to pressurize the liquid in the overflow weir 2 so that the circulating liquid overcomes the resistance of the circulation pipe 7, the microbubble generator 5 and the gas-liquid mixing distributor 4 to form liquid circulation and air flow mixing. The plug flow circulation pump 3 has a simple structure and low system resistance, which is convenient for arranging multiple circulation systems in a single reactor or fermentation tank to form a forced external circulation system with a large circulation volume, low energy consumption, and easier to achieve efficient and uniform gas-liquid mass transfer.

[0029] The gas-liquid mixing distributor 4 is mainly composed of a guide plate with a plurality of guide holes, which is used to promote uniform mixing of gas and liquid and evenly distribute the gas-liquid mixture along the cross section of the tank body 1.

[0030] Microbubble generator 5: It is mainly composed of several microfiltration membranes. Its main function is to distribute the gas in the form of tiny bubbles into the high-speed flowing liquid. The microbubbles are directly mixed with the high-speed flowing circulating liquid and then distributed to form a uniform gas-liquid mixture, which is more conducive to gas-liquid mass transfer in the reactor. The above-mentioned microbubble generator is divided into two types. One is an external flow microbubble generator 5B. The guide tube is located inside the gas circulation tube 31, and the reaction liquid flows outside the guide tube. The other is an internal flow microbubble generator 5A. The guide tube is located inside the gas circulation tube 31, and the reaction liquid flows inside the guide tube.

[0031] Reaction process and steps: In the tank body 1, the fermentation liquid uniformly mixed with microbubbles enters the tank from the gas-liquid mixing distributor 4 at the bottom of the tank, and moves rapidly to the top of the tank at a flow rate of about 1 tank volume per minute driven by forced circulation and bubble rising power, realizing gas-liquid mass transfer during movement, and realizing gas-liquid separation at the gas-liquid interface on the upper part of the tank body. The fermentation liquid enters the inlet 11 of the external circulation pipe through the overflow weir 2, and the plug flow pump 3 provides power for the external circulation of the fermentation liquid. The fermentation liquid is pressurized by the plug flow pump 3. When the pressure is increased in the pump body, the flow rate is lower than 1m / s, and the flow rate in the circulation pipe is 1~2m / s. The fermentation liquid is pressurized by the plug flow pump 3 and enters the microbubble generator 5 at a speed of 1.5~3m / s through the circulation pipe. At the same time, the fermentation gas is aerated through the microfiltration membrane in the microbubble generator 5, forming micron-level bubbles on the surface of the microbubble generator 5, and quickly leaves the microfiltration membrane under the impact of the high-speed flowing fermentation liquid, reducing bubble aggregation, and forming micron or millimeter-level microbubbles. After the fermentation liquid is mixed with the fermentation gas, it enters the tank through the gas-liquid mixing distributor 4 at the bottom of the tank and is evenly distributed, completing a forced external circulation reaction process.

[0032] According to the external circulation flow rate 400m 3 / h calculation, the circulating flow pump 3 of the present application has a boost pressure of 4KPa and a shaft power of less than 0.75kw. Compared with the IH type chemical flow pump (minimum head 20m, shaft power 27.58kw), when it is used in a fermentation system with the same nominal volume as the present invention, its agitator shaft power is about 1.5kw (without gas distribution paddle) ~ 5.5kw (with gas distribution paddle).

[0033] The fermentation reaction of filamentous fungus Aspergillus niger in the forced external circulation microbubble reactor was carried out: Aspergillus niger in the logarithmic growth phase was inoculated into a forced external circulation microbubble reactor containing 5KL fermentation medium at a 5% (V / V) inoculation rate. The continuous airflow of compressed air was aerated through the microbubble generator 5, mixed with the high-speed flowing fermentation liquid, and entered the tank through the gas-liquid mixing distributor 4 at the bottom of the tank and was evenly distributed. Driven by the forced circulation and the rising power of microbubbles, the fermentation liquid moved rapidly to the top of the tank at a flow rate of 1 tank volume per minute, and efficient gas-liquid mass transfer was achieved during the movement. The cell survival rate, gas holdup and mass transfer efficiency were monitored on the third day of the operation of the reactor, and the results are shown in the following table.

[0034] Comparative Example: Under the same reaction conditions as in Example 2, Aspergillus niger in the logarithmic growth phase was inoculated into a centrifugal pump external circulation airlift reactor containing 5KL fermentation medium at an inoculum amount of 5% (V / V). The centrifugal pump drives the air bubble external circulation and drives the fermentation liquid to move rapidly toward 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, and the results are shown in the following table.

[0035] The reaction method of the filamentous fungus Aspergillus niger in the forced external circulation microbubble reactor of the present invention is compared with the traditional centrifugal pump external circulation airlift reactor in terms of liquid shear force (measured as a micro-survival rate indicator), gas-liquid mixing degree (measured as a gas holdup indicator), and mass transfer efficiency: Comparison of liquid shear force: The filamentous fungus Aspergillus niger exists in the form of mycelium and is not resistant to high shear equipment. Excessive shear force will lead to a decrease in survival rate. When using a traditional centrifugal pump, the survival rate of the entire culture system was 65% after 3 days of continuous operation; when using the forced external circulation microbubble reactor of the present invention for cultivation, the survival rate of the entire culture system was 90% after 3 days of continuous operation. This shows that the external plug flow circulation plug flow blade method of the present invention has less liquid shear force and is more suitable for use in biological fermentation systems.

[0036] Comparison of gas-liquid mixing: When using a traditional centrifugal pump, the overall gas content is 8%. When using the forced external circulation microbubble reactor of the present invention, the overall gas content is 18%. This shows that the forced external circulation microbubble reactor of the present invention is more uniform for gas-liquid mixing and is more suitable for use in gas fermentation systems.

[0037] Comparison of mass transfer efficiency: The volume mass transfer coefficient of the forced external circulation microbubble reactor of the present invention is increased by 63.67% compared with that of the traditional centrifugal pump, which indicates that the forced external circulation microbubble reactor of the present invention has a more uniform gas-liquid mixing, a higher mass transfer efficiency, and is more suitable for use in a gas fermentation system.

Claims

1. A forced external circulation microbubble reactor, comprising a tank (1), characterized in that: At least one group of circulation inlets (11) and circulation outlets (12) are respectively arranged at the top and the bottom of the tank body (1), and a circulation system is connected between each group of circulation inlets (11) and circulation outlets (12) to allow the reaction liquid to circulate up and down, and the circulation system comprises a plug flow circulation pump (3), a circulation pipe, a micro bubble generator (5) and an air flow mixing distributor (4) located at the circulation outlet (12); there are more than one micro bubble generator (5), which are respectively installed at one or more points in the circulation pipe.

2. The forced external circulation microbubble reactor according to claim 1, characterized in that: The circulation pipe is divided into an aeration circulation pipe (31) located at the top and a pressurized circulation pipe (33) located at the bottom. The microbubble generator (5) is installed in the pipe body of the aeration circulation pipe (31). The aeration pipe of the microbubble generator (5) is in the same direction as the aeration circulation pipe (31). The gas outlet direction of the microbubble generator (5) is perpendicular to the liquid flow direction. The diameter ratio of the aeration circulation pipe (31) to the pressurized circulation pipe (33) is 1:0.8-0.

9.

3. The forced external circulation microbubble reactor according to claim 1, characterized in that: The circulation inlet is also provided with an overflow weir (2) whose upper opening is slightly lower than the reaction liquid surface; the side wall of the overflow weir (2) is densely covered with gas-liquid separation holes, and the aperture of the gas-liquid separation holes is 0.2-0.6 mm.

4. The above-mentioned forced external circulation microbubble reactor is characterized by: The plug-flow circulation pump (3) comprises a pump casing, a motor and guide vanes (32); a heat exchanger (6) is also arranged in the tank body (1).

5. The forced external circulation microbubble reactor according to claim 1, characterized in that: The blades (32) are two or more push-flow blades.

6. The forced external circulation microbubble reactor according to claim 1, characterized in that: The gas-liquid mixing distributor (4) is composed of a plurality of guide plates or guide tubes with guide holes. The guide plates or guide tubes are located inside the gas circulation pipe (31), and the reaction liquid flows outside the guide plates or guide tubes.

7. The forced external circulation microbubble reactor according to claim 1, characterized in that: The gas-liquid mixing distributor (4) is composed of a plurality of guide plates or guide tubes with guide holes. The guide plates or guide tubes are located inside the gas circulation pipe (31), and the reaction liquid flows inside the guide plates or guide tubes.

8. The forced external circulation microbubble reactor according to claim 1, characterized in that: The circulation inlet (11) is located at the upper part of the tank body (1), and the circulation outlet (12) is located at the bottom of the tank body (1); the circulation system is provided with two or more, which are respectively located on both sides of the tank body (1) or evenly distributed along the outer side of the tank body (1).

9. The reaction method using the forced external circulation microbubble reactor of claim 1, characterized in that: The circulation system is provided with two plug flow pumps (3) respectively located on both sides of the tank body (1). The plug flow pump (3) provides power for the external circulation of the fermentation liquid. The boost pressure is 2-8 KPa. When the pressure is increased in the pump body, the flow rate is less than 1 m / s, and the flow rate in the circulation pipe is 1-2 m / s. The fermentation liquid is pressurized by the plug flow pump (3) and enters the micro bubble generator (5) through the circulation pipe at a speed of 1.5-3 m / s. At the same time, the fermentation gas is aerated through the microfiltration membrane in the micro bubble generator (5), and micron-sized bubbles are formed on the surface of the micro bubble generator (5). The bubbles quickly leave the microfiltration membrane under the impact of the high-speed flow of the fermentation liquid, thereby reducing the bubble aggregation and forming micron or millimeter-sized micro bubbles. After the fermentation liquid and the fermentation gas are mixed, they enter the tank through the gas-liquid mixing distributor (4) at the bottom of the tank and are evenly distributed, completing a forced external circulation reaction process. Driven by the forced circulation and the rising power of the bubbles, the fermentation liquid quickly moves toward the top of the tank at a flow rate of 0.5-2 tank volumes per minute, realizing gas-liquid mass transfer during movement, and realizing gas-liquid separation at the gas-liquid interface on the upper part of the tank body.

10. The reaction method according to claim 9, characterized in that: The overall gas content of the reaction liquid in the tank is 10-25%.

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