CN111979097A

CN111979097A - Photobioreactor for microalgae culture

Info

Publication number: CN111979097A
Application number: CN202010922312.3A
Authority: CN
Inventors: 张荣庆; 章真
Original assignee: Zhejiang Qingrong Biotechnology Development Co ltd; ZHEJIANG TSINGHUA YANGTZE RIVER DELTA RESEARCH INSTITUTE; Tsinghua University
Current assignee: Zhejiang Qingrong Biotechnology Development Co ltd; ZHEJIANG TSINGHUA YANGTZE RIVER DELTA RESEARCH INSTITUTE; Tsinghua University; Yangtze Delta Region Institute of Tsinghua University Zhejiang
Priority date: 2020-09-04
Filing date: 2020-09-04
Publication date: 2020-11-24

Abstract

The invention discloses a photobioreactor for microalgae culture, comprising: a photobioreactor body; the aeration and gas-liquid mixing device is arranged at the bottom of the photobioreactor main body; the flow guide device is arranged in the photobioreactor main body in a hanging manner, the interior of the photobioreactor main body is divided into a light area and a dark area, and the flow guide device is used for promoting liquid circulation and gas-liquid mass transfer; a light source disposed at the periphery of the photobioreactor main body; the stirring and axial flow propelling device comprises an upper stirring paddle and a lower stirring paddle, wherein the lower stirring paddle is used for providing vortex flow to realize gas-liquid exchange, carbon dioxide mass transfer and oxygen analysis, and the upper stirring paddle is used for promoting the shuttle circulation of the algae liquid between a light area and a dark area. The device has simple structure and convenient operation, can obviously improve the utilization efficiency of light energy aiming at the culture of different types of microalgae, and can be widely applied to the large-scale amplification culture of the microalgae.

Description

Photobioreactor for microalgae culture

Technical Field

The invention relates to the field of microalgae culture, in particular to a photobioreactor for microalgae culture.

Background

The microalgae is rich in high-value nutrient components such as protein, unsaturated fatty acid, algal polysaccharide, beta-carotene, various trace elements (such as Cu, Fe, Se, Mn, Zn and the like), vitamins and the like, and is widely applied to the fields of feeds, foods, medicines and the like. At present, the method plays an increasingly important role in the emerging fields of renewable energy sources, environmental governance and the like.

The application of the microalgae biotechnology is based on low cost and large-scale culture of microalgae, and the core of the large-scale culture of the microalgae is a photobioreactor, which mainly comprises an open culture device and a closed photobioreactor at present. Open culture is the oldest and most common mode of application, and is still used as a main mode for industrial culture of microalgae in all countries in the world, especially China. Among them, the use of a raceway type culture pond and a circular culture pond is the most common. The main advantages of the culture mode are simple structure, low cost and simple operation. The defects are that the light energy utilization rate is low, the influence of external environmental factors (temperature, illumination and other climatic conditions) is large, the pollution is easy to occur, the water evaporation is large, and the production efficiency is low.

Closed photobioreactors come in many forms, such as columns, tubes and plates. Compared with open culture, closed culture is less affected by external environment, is not easy to be polluted, saves water resources, has relatively high culture density and low harvesting cost, and has the defects of high investment cost and large energy consumption caused by temperature rise or temperature reduction and the like. In order to overcome the defect of high cost of closed culture, on one hand, the material and energy consumption cost required by culture need to be reduced; on the other hand, the cell density and yield in the algae liquid need to be greatly improved. Although the yield of closed culture is higher than that of open culture, the light energy utilization efficiency of microalgae is still low. The method for improving the utilization rate of microalgae cells to light energy is an important way for improving the yield and reducing the cost.

For photoautotrophic microalgae, illumination is a necessary condition for growth and product accumulation, and the growth of microalgae requires illumination of a certain intensity (light compensation point) and duration, otherwise, a light limitation phenomenon occurs, that is, the growth of microalgae is limited due to insufficient light intensity and illumination time, and the death of microalgae cells can be caused in severe cases. After the illumination intensity exceeds the light compensation point, the photosynthetic rate is gradually increased along with the increase of the illumination intensity, at the moment, the photosynthetic intensity exceeds the respiration intensity, and the algae cells divide and accumulate dry matters. However, when the light intensity is increased after reaching a certain value, the photosynthetic rate is not increased, which is the phenomenon of light saturation. If the illumination intensity is continuously increased, the phenomenon of light inhibition can occur, and the phenomenon that the algae cells are inhibited from growing until dying due to photo oxidation caused by that too many photons captured by cytochrome can not be quenched can occur. Therefore, the core of the photobioreactor is to make the microalgae cells in a range of suitable illumination intensity and time.

Due to the self-shading effect among algae cells, there is a severe light attenuation phenomenon along the illumination direction in the algae liquid in the photobioreactor. When a certain cell density is reached, the light ray can be quickly attenuated when propagating in the algae liquid, and the penetration distance (optical path) of the light is from several millimeters to several centimeters. The interior of the photobioreactor can be divided into two parts, namely a light area close to the inner wall surface on the side of illumination and a dark area outside the light area. When the microalgae cells shuttle back and forth between the light area and the dark area of the photobioreactor, the microalgae cells return to the light area in time to receive light again, so that the light quantum entering the photobioreactor can be fully utilized. Therefore, the total light energy utilization rate and the yield of the microalgae cells can be improved by enabling the microalgae cells to shuttle back and forth between the light area and the dark area at high frequency. It is therefore extremely important to promote the ordered cycling of algae cells between the light dark regions within the photobioreactor.

However, in the conventional photobioreactor, the algae cells are in the light area or the dark area for a long time, and cannot realize ordered circulation between the light area and the dark area, the algae cells are in the light area for a long time and can generate light inhibition or even light damage, and the algae cells far away from the light area are in a light restriction state for a long time, so that the light energy utilization rate is not high.

On the other hand, gas-liquid exchange in the algae liquid is very important, and photosynthesis absorbs carbon dioxide and releases oxygen, while respiration of microalgae cells is reversed. These all require a sufficient exchange between the algal solution and the outside air. In addition, the absorption of inorganic nutrient elements in the algae liquid and the discharge of cell metabolic wastes also require the algae liquid to be fully mixed. Since algae cells are usually slightly heavier than water, good mixing also avoids sedimentation of algae cells and the resulting growth retardation.

Disclosure of Invention

An object of an embodiment of the present invention is to provide a photobioreactor for microalgae cultivation, so as to solve the general problem of the existing photobioreactor: along with the increase of the density of algae cells, the light attenuation is enhanced, the light path is shortened, so that the algae cells in different areas in the reactor receive uneven light, when the volume of the reactor is increased, the volume ratio of a light dark area is rapidly reduced, the light energy utilization efficiency is low, and the growth of the algae cells is limited. The photobioreactor adopts a form of 'bubbling-airlift-stirring' integration, realizes the orderly shuttling circulation of microalgae between dark areas to improve the retention time of the microalgae in illumination areas, has sufficient gas-liquid exchange in culture solution and good mixing, and is especially suitable for microalgae culture solution with higher viscosity.

In order to achieve the above purpose, the technical solution adopted by the embodiment of the present invention is as follows:

the embodiment of the invention provides a photobioreactor for microalgae culture, which comprises:

a photobioreactor body;

a ventilation and gas-liquid mixing device arranged at the bottom of the photobioreactor main body and used for providing CO required by microalgae culture₂Mass transfer and gas-liquid exchange are realized, and dissolved oxygen is resolved at the same time;

the flow guide device is arranged in the photobioreactor main body in a hanging mode and divides the interior of the photobioreactor main body into a light area and a dark area, the light area is an area between the flow guide device and the inner wall of the photobioreactor main body, the dark area is an area in the flow guide device, and the flow guide device is used for promoting liquid circulation and gas-liquid mass transfer;

the light source is used for providing illumination for the microalgae;

stirring and axial flow advancing device, include the (mixing) shaft, install the upper portion stirring rake on (mixing) shaft upper portion and install the lower part stirring rake of (mixing) shaft lower part, the lower part stirring rake is used for providing the vortex in order to realize gas-liquid exchange, carbon dioxide mass transfer and the analysis of oxygen, the upper portion stirring rake is used for promoting the circulation of shuttling of algae liquid in light zone and dark interval, increases the dwell time of little algae in the light zone, improves little algae utilization efficiency to the light energy, avoids the production of light restriction and light inhibition phenomenon.

Furthermore, the photobioreactor main body is of a columnar structure, a detachable reactor sealing cover with an air outlet is arranged at the top of the photobioreactor main body, and a ventilation device is connected to the bottom of the photobioreactor main body.

Further, the height-diameter ratio of the photobioreactor body is 1-10: 1, the ratio of the diameter (inner diameter) of the guide cylinder to the diameter (inner diameter) of the photobioreactor body is 0.2-0.8: 1; the diameter (inner diameter) of the tank body of the photobioreactor body is 0.01-0.5 m.

Further, the bottom of the photobioreactor main body is flat-bottomed.

Further, the stirring and axial flow propelling device is made of stainless steel or polytetrafluoroethylene organic material.

Further, the diameter of the bubbles generated by the aeration and gas-liquid mixing device is 10-100 μm.

Further, the light source is arranged on the periphery of the photobioreactor main body and comprises a power-adjustable ring-shaped light source.

Further, the ring-shaped light source is perpendicular to the flow direction of the microalgae culture solution.

Furthermore, the length of the luminous section of the annular light source is 0.5-5 m.

Further, the cross section of the circular ring type light source may be circular or square, preferably circular. Implementations of the ring-type light source include, but are not limited to, implementations with multiple point light sources arranged on a strip or tube, and/or light from an external light source directed into a segmented-emitting light pipe or light bar.

Further, the plurality of point light sources may be implemented by Light Emitting Diodes (LEDs), preferably light-condensing LEDs, in a manner of being arranged on a belt or a tube; in this case, a transparent light source sleeve needs to be inserted into the belt or tubular light source, and the light source sleeve is fixed on the periphery of the column reactor.

Further, the number of the ring-shaped light sources is calculated according to the following principle: the total light energy of the culture solution per unit volume in the photoreactor is 4-10 kw m^-3. Wherein the light energy emitted by each ring-shaped light source is measured by a common standard method.

Furthermore, the flow guide device is suspended in the cavity of the main body of the photobioreactor through supporting points arranged at the upper end and the lower end of the flow guide device. The fulcrum can adopt a guide shell pillar and a reactor side support frame to respectively fix the guide shell in the axial direction and the radial direction.

Further, the flow guide device, the ventilation and gas-liquid mixing device and the stirring and axial flow propelling device jointly divide the interior of the cavity of the photobioreactor main body into an ascending region and a descending region, the ascending region refers to the cavity part of the photobioreactor main body located inside the flow guide device, the descending region refers to the cavity part of the photobioreactor main body located outside the flow guide device, and the ascending region and the descending region correspond to a dark region and a light region respectively.

Furthermore, the photobioreactor body can be further provided with a jacket, a window and a sensor socket, the sealing cover can be further provided with an exhaust port, a sensor socket and the like, and the photobioreactor body, the guide cylinder and the sealing cover can be made of any transparent material which is harmless to algae cells and can be processed and molded, such as glass, organic glass and the like.

Further, the aeration and gas-liquid mixing device may be a gas distributor, and a gas distributor material of a general airlift reactor may be used, and a stainless steel porous sintered plate is preferable.

Further, the aeration rate (ratio) of the photobioreactor body is the aeration rate of a general airlift reactor, and preferably 0.01 to 1 vvm.

Further, the stirring and axial flow propelling means is preferably a combination of a pitched blade paddle (upper paddle) and a rashton paddle (lower paddle) made of stainless steel or teflon. Other possible combinations of paddles include any combination of turbine paddles and propeller paddles.

According to the technical scheme, the invention has the following beneficial effects: the shuttle circulation of the algae cells in the light area and the dark area is remarkably accelerated, the flow speed in the dark area is high, and the retention time is short. The light energy utilization rate of microalgae mass culture is improved, the yield of unit illumination area is improved, the illumination area is large, liquid mixing is good, the gas-liquid mass transfer intensity is high, the shearing force is low, the damage to cells is small, and the operation is simple and convenient. The cultured algae has high cell density and is convenient for the next working procedures such as harvesting and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic perspective view of a photobioreactor for microalgae cultivation according to an embodiment of the present invention;

FIG. 2 is a top view of a photobioreactor for microalgae cultivation according to an embodiment of the present invention;

FIG. 3 is a comparison of the results of the dry weight of algal cells at the end of the culture in the examples of the present invention and the control examples;

FIG. 4 is a diagram illustrating a velocity profile of an internal flow field of a photobioreactor for culturing microalgae according to an embodiment of the present invention;

the attached drawings are as follows: 1. a photobioreactor body; 2. a draft tube; 3. a gas distributor; 41. a stirring motor; 42 stirring shaft; 43. an upper stirring paddle; 44. a lower stirring paddle; 5. sealing the cover; 6. a ring-shaped light source; 7. a light area; 8. dark areas.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The reactor of the present invention will be further described with reference to the accompanying drawings.

As shown in fig. 1 and 2, an embodiment of the present invention provides a photobioreactor for microalgae culture, including a photobioreactor body 1, a ventilation and gas-liquid mixing device, a flow guiding device, a light source, and a stirring and axial flow propelling device, wherein the ventilation and gas-liquid mixing device is disposed at the bottom of the photobioreactor body and is used for providing CO required by microalgae culture₂Mass transfer and gas-liquid exchange are realized, and dissolved oxygen is resolved at the same time; the flow guide device is arranged in the photobioreactor main body in a hanging mode, the interior of the photobioreactor main body is divided into a light area 7 and a dark area 8, the light area 7 is an area between the flow guide device and the inner wall of the photobioreactor main body, the dark area 8 is an area in the flow guide device, and the flow guide device is used for promoting liquid circulation and gas-liquid mass transfer; the light source is arranged at the periphery of the photobioreactor main body and is used for providing illumination for the microalgae; the stirring and axial flow propelling device comprises a stirring shaft 42 (driven by a stirring motor 41), an upper stirring paddle 43 arranged on the upper part of the stirring shaft 42 and a lower stirring paddle 44 arranged on the lower part of the stirring shaft 42, wherein the lower stirring paddle 44 is used for providing vortex flow to realize gas-liquid exchange, carbon dioxide mass transfer and oxygen desorption, and the upper stirring paddle 43 is used for promoting the shuttle circulation of algae liquid between a light area and a dark area.

The guide device in this embodiment adopts the guide cylinder 2, and the components are limited to the illustrated structure.

In the present embodiment, the gas distributor 3 is used as the aeration and gas-liquid mixing device, and the components are not limited to those shown in the drawings.

In this embodiment, the photobioreactor main body is a columnar structure, and a detachable reactor cover 5 with an air outlet is arranged at the top of the photobioreactor main body.

In this embodiment, the light source comprises a power-adjustable ring-shaped light source 6.

The photobioreactor for microalgae culture is applied to a microalgae culture process and mainly comprises the steps of preparing a culture medium with a specific volume according to a formula, filtering and sterilizing, inoculating, detecting the process, harvesting algae liquid and the like.

Comparative example

Comparative experiments were conducted in a pilot scale reactor, using a glass material for the 1L bubble column reactor, with the following specification and dimensions; an inner diameter of 46mm, a wall thickness of 2mm and a height of 600 mm. The liquid loading amount was 700 mL. Double-side light irradiation, the intensity of the light on the surface of the reactor is 400 mu E m^-2s^-1. Bubbling aeration was carried out by extending a stainless steel tube having a diameter of 2mm into the bottom of the reactor.

The marine microalgae Porphyridium cruentum is cultured in the reactor, and the culture solution is ASW culture medium taking potassium nitrate as nitrogen source. The liquid loading amount is 700mL, and the inoculation density is 0.8g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 5%, and ventilation amount of 0.14L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 13.85g L^-1Volume yield 0.87g L^-1d^-1。

EXAMPLE one (Whole)

The photobioreactor body 1 is made of high-light-transmission organic glass, the thickness is 5mm, the inner diameter is 180mm, and the height of the reactor is 500 mm; the guide cylinder is made of organic glass, the thickness is 5mm, the inner diameter is 120mm, the height is 360mm, and the distance from the lower edge to the bottom of the body is 20 mm; is fixed on the bottom surface through a support rod; the diameter of the ring-shaped light source is 220mm, 3 ring-shaped light sources are distributed at equal intervals from top to bottom, each luminous ring belt is 700mm in length and comprises 2 circles of LEDs, and 35 LED patches which are of double-core 3528 type and have the maximum power of 0.15W are distributed in each circle. Actually, the light energy emitted from each rod-shaped light source was measured to be 10.5W, and the total light energy entering the culture solution was measured to be 31.5W. The illumination intensity of the outer surface of the reactor is 400 mu E m^-2s^-1. The outer shell of the bottom gas distributor is made of stainless steel, the ventilation surface is a stainless steel sintered perforated plate with the diameter of 40mm, and the average pore diameter is 60 mu m. The total volume of the reactor was 12L, and the effective volume (liquid loading) was 10L. The stirring motor is fixed on the top of the reactor, and the stirring shaft and the stirring paddle vertically extend into the liquidBelow the surface, the lower stirring paddle is a six-blade Lahston paddle, and the upper stirring paddle is a four-blade inclined blade paddle. The power of the stirring motor is 500W, and the stretching diameter of the stirring paddle is 90 mm. The stirring speed was set at 400 rpm.

The marine microalgae Porphyridium cruentum is cultured in the reactor, and the culture solution is ASW culture medium taking potassium nitrate as nitrogen source. The liquid loading amount is 10L, and the inoculation density is 0.8g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 5%, and ventilation volume of 2L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 12.32g L^-1Volume yield 0.77g L^-1d^-1。

EXAMPLE two (volume enlargement)

The photobioreactor body 1 is made of high-light-transmission organic glass, the thickness is 8mm, the inner diameter is 180mm, and the height of the reactor is 1.5 m; the guide cylinder is made of organic glass, the thickness is 5mm, the inner diameter is 120mm, the height is 1.35m, and the distance from the lower edge to the bottom of the body is 20 mm; is fixed on the bottom surface through a support rod; the diameter of the ring-shaped light source is 220mm, 7 ring-shaped light sources are distributed at equal intervals from top to bottom, each luminous ring belt is 700mm in length and comprises 2 circles of LEDs, and 35 LED patches which are of double-core 3528 type and have the maximum power of 0.15W are distributed in each circle. Actually, the light energy emitted from each rod-shaped light source was measured to be 10.5W, and the total light energy entering the culture solution was measured to be 73.5W. Average light intensity on the outer surface of the reactor is 400 mu E m^-2s^-1. The outer shell of the bottom gas distributor is made of stainless steel, the ventilation surface is a stainless steel sintered perforated plate with the diameter of 40mm, and the average pore diameter is 60 mu m. The total volume of the reactor was 36L, and the effective volume (liquid loading) was 30L. The stirring motor is fixed on the top of the reactor, the stirring shaft and the stirring paddles vertically extend below the liquid level, the lower stirring paddle is a six-blade Lashiton paddle, and the upper stirring paddle is a four-blade inclined-blade paddle. The power of the stirring motor is 1.5kw, and the stretching diameter of the stirring paddle is 90 mm. The stirring speed was set at 400 rpm.

The marine microalgae Porphyridium cruentum is cultured in the reactor, and the culture solution is ASW culture medium taking potassium nitrate as nitrogen source. The liquid loading amount is 30L, and the inoculation density is 0.8g L^-1. Introducing CO₂Air dioxide with volume fraction of 5%The ventilation rate of carbon mixed gas is 6L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 12.01g L^-1Volume yield 0.75g L^-1d^-1。

EXAMPLE III (aeration agitation type)

The photobioreactor body 1 is made of high-light-transmission organic glass, the thickness is 5mm, the inner diameter is 180mm, and the height of the reactor is 500 mm; the inside is not provided with a guide shell. The diameter of the peripheral ring-shaped light source is 220mm, 3 ring-shaped light sources are distributed at equal intervals from top to bottom, each luminous ring band is 700mm in length and comprises 2 circles of LEDs, and 35 LED patches which are of a double-core 3528 type and have the maximum power of 0.15W are distributed in each circle. Actually, the light energy emitted from each rod-shaped light source was measured to be 10.5W, and the total light energy entering the culture solution was measured to be 31.5W. The illumination intensity of the outer surface of the reactor is 400 mu E m^-2s^-1. The outer shell of the bottom gas distributor is made of stainless steel, the ventilation surface is a stainless steel sintered perforated plate with the diameter of 40mm, and the average pore diameter is 60 mu m. The total volume of the reactor was 12L, and the effective volume (liquid loading) was 10L. The stirring motor is fixed on the top of the reactor, the stirring shaft and the stirring paddles vertically extend below the liquid level, the lower stirring paddle is a six-blade Lashiton paddle, and the upper stirring paddle is a four-blade inclined-blade paddle. The power of the stirring motor is 500W, and the stretching diameter of the stirring paddle is 90 mm. The stirring speed was set at 400 rpm.

The marine microalgae Porphyridium cruentum is cultured in the reactor, and the culture solution is ASW culture medium taking potassium nitrate as nitrogen source. The liquid loading amount is 10L, and the inoculation density is 0.8g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 5%, and ventilation volume of 2L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 6.16g L^-1Volume yield 0.39g L^-1d^-1。

EXAMPLE four (airlift type)

The photobioreactor body 1 is made of high-light-transmission organic glass, the thickness is 5mm, the inner diameter is 180mm, and the height of the reactor is 500 mm; the guide cylinder is made of organic glass, the thickness is 5mm, the inner diameter is 120mm, the height is 360mm, and the distance from the lower edge to the bottom of the body is 20 mm; is fixed on the bottom surface through a support rod; circular ring type light source diameter 220mm3 circular ring type light sources are distributed at equal intervals from top to bottom, each luminous circular ring band is 700mm in length and is composed of 2 circles of LEDs, and 35 light emitting diode patches which are of a double-core 3528 type and have the maximum power of 0.15W are distributed in each circle. Actually, the light energy emitted from each rod-shaped light source was measured to be 10.5W, and the total light energy entering the culture solution was measured to be 31.5W. The illumination intensity of the outer surface of the reactor is 400 mu E m^-2s^-1. The outer shell of the bottom gas distributor is made of stainless steel, the ventilation surface is a stainless steel sintered perforated plate with the diameter of 40mm, and the average pore diameter is 60 mu m. The total volume of the reactor was 12L, and the effective volume (liquid loading) was 10L. The stirring motor, the stirring shaft and the stirring paddle are not arranged.

The marine microalgae Porphyridium cruentum is cultured in the reactor, and the culture solution is ASW culture medium taking potassium nitrate as nitrogen source. The liquid loading amount is 10L, and the inoculation density is 0.8g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 5%, and ventilation volume of 2L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 7.01g L^-1Volume yield 0.44g L^-1d^-1。

EXAMPLE five (bubbling type)

The photobioreactor body 1 is made of high-light-transmission organic glass, the thickness is 5mm, the inner diameter is 180mm, and the height of the reactor is 500 mm; the guide cylinder is not arranged; the diameter of the peripheral ring-shaped light source is 220mm, 3 ring-shaped light sources are distributed at equal intervals from top to bottom, each luminous ring band is 700mm in length and comprises 2 circles of LEDs, and 35 LED patches which are of a double-core 3528 type and have the maximum power of 0.15W are distributed in each circle. Actually, the light energy emitted from each rod-shaped light source was measured to be 10.5W, and the total light energy entering the culture solution was measured to be 31.5W. The illumination intensity of the outer surface of the reactor is 400 mu E m^-2s^-1. The outer shell of the bottom gas distributor is made of stainless steel, the ventilation surface is a stainless steel sintered perforated plate with the diameter of 40mm, and the average pore diameter is 60 mu m. The total volume of the reactor was 12L, and the effective volume (liquid loading) was 10L. The stirring motor, the stirring shaft and the stirring paddle are not arranged.

The marine microalgae Porphyridium cruentum is cultured in the reactor, and the culture solution is ASW culture medium taking potassium nitrate as nitrogen source. Liquid loading amount of 10L, inoculation densityIs 0.8g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 5%, and ventilation volume of 2L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 2.85g L^-1Volume yield 0.18g L^-1d^-1。

EXAMPLE six (application to other algae cultures)

The same reactor as used in example 1 and described in the present invention was used to culture fresh water Chlorella vulgaris in the culture medium NaNO₃BG-11 medium as nitrogen source. The liquid loading amount is 10L, and the inoculation density is 0.3g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 3%, and ventilation volume of 2L min^-1The culture temperature is controlled to be 25 +/-1 ℃. The final density of algae cells reaches 3.5g L after 7 days of culture^-1Volume yield 0.46g L^-1d^-1。

In the reactor, Isochrysis galbana is cultured as marine bait, microalgae ball, etc. the culture solution is 2f seawater culture medium with NaNO3 as nitrogen source. The liquid loading is 10 liters, and the inoculation density is 0.2g L^-1. Introducing CO₂Air and carbon dioxide mixture with volume fraction of 3%, and ventilation volume of 2L min^-1The culture temperature was controlled at 25. + -. 1 ℃ and the stirring speed was reduced to 150rpm (to reduce the effect of the paddle on the flagella due to flagella in the alga). The final density of algae cells reaches 1.5g L after 7 days of culture^-1Volume yield 0.19g L^-1d^-1。

It is seen from the results of examples 1 and 2 and comparative example that the combination of the internal structure of the column reactor and the aeration stirring device according to the present invention improves the light energy utilization rate of the microalgae scale culture, and the final density and volume yield of the algae cells are greatly improved, which is close to the results under ideal illumination and mixing conditions in the pilot plant reactor (see fig. 3 for details), indicating that the volume amplification of the photobioreactor according to the present invention is feasible.

The comparison results of examples 1 and 2 and examples 3 to 5 show that the yield of the microalgae cells in the photobioreactor is 2 to 4 times that of the culture result of the conventional culture device. And the yield times are increased more along with the enlargement of the reactor volume.

By comparison between the results of examples 4 and 5, the photobioreactors of the present invention are feasible to scale up in height, with the final cell density of the culture not being significantly affected by the volume scaling, due to the division of the light and dark zones and the rapid shuttling cycles of the microalgae in the two zones, especially in the dark zone with a greater average velocity along the axis, and therefore a shorter residence time in this zone (see in detail fig. 4). While the scale-up of photoreactors is a bottleneck for large-scale cultivation. The reactor of the present invention is expected to provide reference for the scale-up of other types of photobioreactors.

Example 6 demonstrates the use of the photobioreactor of the invention in the culture of other microalgae (including freshwater and seawater algae, dinoflagellates and dinoflagellates), with higher cell yields for the cultured microalgae compared to the existing publicly available data. The invention has wide application value.

Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.

Claims

1. A photobioreactor for microalgae culture, comprising: the method comprises the following steps:

a photobioreactor body;

a ventilation and gas-liquid mixing device arranged at the bottom of the photobioreactor main body and used for providing CO required by microalgae culture₂Mass transfer and gas-liquid exchange are realized;

the light source is used for providing illumination for the microalgae;

the stirring and axial flow propelling device comprises a stirring shaft, an upper stirring paddle arranged on the upper part of the stirring shaft and a lower stirring paddle arranged on the lower part of the stirring shaft, wherein the lower stirring paddle is used for providing vortex flow to realize gas-liquid exchange, carbon dioxide mass transfer and oxygen analysis, and the upper stirring paddle is used for promoting the shuttle circulation of algae liquid between a light area and a dark area.

2. The photobioreactor for culturing microalgae according to claim 1, wherein: the photobioreactor main body is of a columnar structure, a detachable reactor sealing cover with an air outlet is arranged at the top of the photobioreactor main body, and a ventilation device is connected at the bottom of the photobioreactor main body.

3. A photobioreactor for microalgae cultivation as claimed in claim 2, wherein: the bottom of the photobioreactor main body is flat-bottomed.

4. The photobioreactor for culturing microalgae according to claim 1, wherein: the stirring and axial flow propelling device is made of stainless steel materials or polytetrafluoroethylene organic materials.

5. The photobioreactor for culturing microalgae according to claim 1, wherein: the diameter of the bubbles generated by the aeration and gas-liquid mixing device is 10-100 μm.

6. The photobioreactor for culturing microalgae according to claim 1, wherein: the light source comprises a power-adjustable annular light source, so that the total light energy of the culture solution in unit volume in the photobioreactor body is 4-10 kw m^-3。

7. The photobioreactor for culturing microalgae according to claim 6, wherein: the ring-shaped light source is vertical to the flowing direction of the microalgae culture solution.

8. The photobioreactor for culturing microalgae according to claim 1, wherein: the flow guide device is suspended in the cavity of the main body of the photobioreactor through supporting points arranged at the upper end and the lower end of the flow guide device.

9. The photobioreactor for culturing microalgae according to claim 1, wherein: the flow guide device, the ventilation and gas-liquid mixing device and the stirring and axial flow propelling device jointly act to divide the interior of the cavity of the photobioreactor main body into a fluid ascending region and a fluid descending region, the fluid ascending region is the cavity part of the photobioreactor main body located in the flow guide device, the fluid descending region is the cavity part of the photobioreactor main body located outside the flow guide device, and the fluid ascending region and the fluid descending region correspond to a dark region and a light region respectively, or the rotation direction of the stirring shaft is changed to enable the fluid ascending region and the fluid descending region to correspond to the light region and the dark region respectively.