WO2019165689A1 - Microbubble photobioreactor for economic microalgae cultivation - Google Patents

Abstract

Disclosed is a microbubble photobioreactor (1) for economic microalgae cultivation. The microbubble photobioreactor comprises a photobioreactor body (5) having a pre-determined volume, a controllable particle size microbubble generation device (2), a flow guiding device (3) and an LED variable wave and frequency illumination system (7). The controllable particle size microbubble generation device (2) is arranged at the bottom of the photobioreactor body (5), and is used for providing a carbon mass transfer and cyclic power required for economic microalgae cultivation and resolving dissolved oxygen; the flow guiding device (3) is hung inside the photobioreactor body (5) and is used for facilitating liquid circulation and a microbubble mass transfer; and the LED variable wave and frequency illumination system (7) is arranged outside or inside the photobioreactor body (5), and is used for providing the optimal growth wavelength and a light-dark frequency for economic microalgae according to specific economic microalgae requirements. The microbubble photobioreactor (1) is simple in structure and easy to operate, and can be widely used in economic microalgae cultivation.

Description

Microbubble photobioreactor for economical microalgae cultivation Technical field

The invention belongs to the field of bioengineering, and in particular relates to a microbubble photobioreactor for economical microalgae cultivation.

Background technique

Economic microalgae is widely used in food, aquaculture, medicine, beauty, bioenergy and other industries because it is rich in a variety of biologically active substances. For example, chlorella can be applied to single-cell protein production; Trichosanthes elegans is used in sea cucumber breeding; while Haematococcus pluvialis is rich in astaxanthin and has strong antioxidant capacity in health products, cosmetics, The pharmaceutical industry has a broad market. Therefore, the economic microalgae biomass energy industry is a new type of industry that countries are striving to develop first. To achieve rapid development of the economic microalgae biomass energy industry, the first condition is to obtain high-density biomass at low cost and efficiently.

At present, the main cultivation methods of economic microalgae are open-air culture and photobioreactor culture. Traditional open-air cultures have led to the development of microalgae culture processes due to their low controllability, large footprint, and easy to stain bacteria. Compared with open-air culture, photobioreactor culture has the characteristics of high controllability, small footprint, flexible operation, high yield and suitable for single culture, especially favored by economical microalgae cultivation. However, traditional photobioreactor cultivation still faces technical bottlenecks such as insufficient carbon supply, dissolved oxygen accumulation, and low utilization rate of light energy. The specific embodiment is as follows:

(a) Low utilization rate of light energy: At higher cell concentrations, the inter-algae shielding effect is liable to occur, so that the utilization of the light source by the algae cells becomes very limited, and it is difficult to achieve high-density culture of economic microalgae.

(b) Insufficient supply of CO ₂ : The supply of carbon by microalgae is mainly achieved by introducing a certain proportion of CO ₂ gas, and in the actual cultivation process, the supply of CO ₂ cannot satisfy the requirement of optimal growth of microalgae. Studies have shown that the absorption rate of CO ₂ by microalgae is as high as 0.2 to 0.3×10 ^-4 mol/L/min. The conventional aeration mode CO ₂ mass transfer rate is only 0.4×10 ^-7 to 0.7×10 ^-5 mol/L/min, which is far from satisfying the demand of microalgae for dissolving CO ₂ . Therefore, even if the light is sufficient, if the reactor does not reach a sufficient supply of CO ₂ , the microalgae cannot be optimally grown.

(c) The accumulation of dissolved oxygen is serious: the photosynthetic oxygen evolution rate of microalgae can reach 0.3×10 ^-4 mol/L, while the conventional blown gas to O ₂ is only about 0.16×10 ^-4 mol/L/min. , less than the photosynthetic oxygen evolution rate of microalgae. Therefore, accumulation of dissolved oxygen easily occurs in the closed culture, causing supersaturation of dissolved oxygen to suppress algae growth.

Regarding the optimization of light energy utilization, the current main ideas include the improvement of the light source and the shortening of the optical path. For example, Bourgoin et al. (Patent No. US20130029404A1) placed an illumination barrier consisting of photovoltaic cells in the center of the photobioreactor to provide the wavelengths required for growth of different microalgae species. Bazaire et al. (Patent No. US20090203116A1) provides 360 degree illumination to the reactor through built-in fiber optics. Friederich et al. (Patent No. US20140073035A1) collects and introduces the light flux generated by an external LED light source through a light pipe into the interior of the photobioreactor to provide illumination for the culture. Huang Xuxiong et al. (patent number CN104651215A) achieves energy saving, shortened optical path, and improved utilization of light energy by reducing the inner diameter of the photobioreactor and incorporating LED strips. In addition, there are many similar designs that improve the light energy utilization of the reactor to some extent. However, these designs do not fundamentally solve the problem of inter-algae shielding at high concentrations. In addition, under the conditions that the traditional CO ₂ supply cannot meet the rapid growth of microalgae, the optimization of the light source or optical path can not really improve the light energy effectively. Utilization, on the contrary, excess light may cause microalgae photorespiration to affect biomass production.

For the problem of insufficient CO ₂ supply and dissolved oxygen accumulation, improving the gas-liquid mass transfer capability of the aeration device is the main solution. Zheng Fanxi et al. (Patent No. CN102776117) supplied CO ₂ to the hollow fiber membrane module external to the photobioreactor and mixed well with the medium to increase the CO ₂ saturation rate in the medium. The principle of this method is to increase the gas-liquid mass transfer efficiency by increasing the contact time between the gas and the liquid through the porous structure of the filler. However, the external gas-liquid mixing device (that is, the hollow fiber membrane module) in the invention patent also needs to be equipped with a liquid pump to pump the culture medium into the reactor body, which increases the system complexity and additional energy consumption. Shi Yunhai et al. (Patent No. CN105985910) passed the spray of the algae into the external absorption tower of the reactor by atomization spray to make full contact with the CO ₂ gas passing through the bottom of the tower to improve gas-liquid mass transfer. The algae liquid passing through the absorption tower contains a higher CO ₂ concentration and is pumped back into the reactor body via a liquid pump. This method utilizes the principle of increasing the gas-liquid specific surface area to increase CO ₂ mass transfer. However, the algae liquid is highly likely to cause cell damage through the spray atomization device, thereby affecting its growth. Compared with atomized algae liquid, a more reasonable and effective method for increasing the gas-liquid mass transfer specific surface area is atomizing bubbles, that is, microbubbles. At present, microbubbles are widely used in the water treatment industry, which can effectively improve the mass transfer of dissolved oxygen. However, its application in the microalgae cultivation neighborhood is less, even if the existing related patents are mainly used for microalgae harvesting, for example, Pan Kehou et al. (Patent No. CN105002086) continuously floats the algae cells in the running pool through microbubbles. . Using microbubbles as a carrier for CO ₂ gas can greatly increase the utilization of CO ₂ by microalgae to overcome the bottleneck of insufficient carbon supply. The Chengguang mold (patent number CN102978102A) uses an external microbubble generator to generate process water containing microbubbles, and supplies the process water to the photobioreactor for culturing the microalgae. Yang Weimin et al. (patent number CN106434326, etc.) cut the CO ₂ bubbles in the gas-liquid two fluids into tiny bubbles by the high-speed axial rotation of the rotor screw pump, and then pass the microbubble containing microbubbles into the tubular photobioreaction. The microalgae are cultured in the device. In principle, both methods improve the biomass production of microalgae through the efficient gas-liquid mass transfer of microbubbles. However, the principle of microbubbles is to inject CO ₂ gas into the spiral wound hose in the mixing chamber and soft. The water in the tube is mixed, and the CO _{2 is} dissolved in the liquid or retained in the form of tiny bubbles to form process water through a long residence time, and the process water is introduced into the culture system to provide the growth of the microalgae. The latter uses micro-bubble water to supply the culture system using the principle of mechanical shearing. However, the two only consider the mass transfer characteristics of the microbubbles, but ignore the advantages of the microbubble high-efficiency momentum conduction. They all adopt the method of external microbubble generator to make microbubble water. Therefore, it is necessary to use an additional liquid pump for photobioreaction. The body of the device supplies microbubble water and enhances liquid circulation. In addition, the size of the microbubbles generated by the two is uncontrollable, and there may be a problem of excess supply or insufficient supply for the carbon demand of different economic microalgae. At the same time, the generation of microbubble water is accompanied by large energy consumption and more complicated microbubble production process. In the industrialized expansion application, there may be problems of excessive maintenance cost, energy consumption cost, and construction cost.

In summary, in recent years, a lot of research has been done on the culture process of economic microalgae at home and abroad, but the above technical bottlenecks have not been effectively solved. Most of the research is still in the laboratory stage, and only a few companies and research institutions have established The industrial production mode has inevitably formed a monopoly on production technology and product prices. Therefore, how to break through these technical bottlenecks and achieve high-density culture of economic microalgae is still the focus of research on microalgae biotechnology neighborhood at home and abroad.

Summary of the invention

In view of the above problems, an object of the present invention is to provide a microbubble photobioreactor (MPBR) for economical microalgae cultivation, which can solve the main technical bottleneck faced by traditional culture and stimulate the growth potential of microalgae in one stop. Improve the economic microalgae biomass production, suitable for laboratory and large-scale cultivation.

In order to achieve the above object, the present invention adopts the following technical solution: a microbubble photobioreactor for economical microalgae cultivation, characterized in that it comprises a photobioreactor body having a predetermined volume, and a controllable particle size microbubble a generating device, a flow guiding device, and an LED wave frequency double-change illumination system; the controllable particle size microbubble generating device is disposed at a bottom of the photobioreactor body for providing carbon mass transfer required for economical microalgae cultivation And circulating power, while dissolving dissolved oxygen; the flow guiding device is suspended inside the photobioreactor body for promoting liquid circulation and microbubble mass transfer; the LED wave frequency double variable illumination system is disposed in the The outside or inside of the photobioreactor body is used to provide its optimal growth wavelength and light-dark frequency according to the needs of specific economic microalgae.

The photobioreactor body has a tubular or plate-like structure, and a detachable reactor cover with an air outlet is disposed at a top thereof, and the bottom bolt is connected to the controllable particle size microbubble generating device.

The bottom of the photobioreactor main body is provided in a funnel shape, but is not limited thereto.

The controllable particle size microbubble generating device comprises a detachable base, a microporous ceramic membrane and an annular fixing piece; the detachable base comprises a substrate and a cavity disposed on the substrate, the substrate is provided with a base threadedly coupled to a bottom wall of the photobioreactor main body, the cavity being provided with a discharge end thread for connection with the discharge valve; a central portion of the upper portion of the cavity is provided with a conical groove An air inlet penetrating through the upper and lower ends of the cavity is disposed in a middle portion of the conical groove, and a lower end of the air inlet is connected to a variable diameter air inlet provided in a middle portion of the substrate, and the variable diameter is The other end of the gas nozzle is connected to the CO ₂ mixed gas through the intake valve and the intake pipe in sequence; the microporous ceramic diaphragm is fixedly disposed on the cone groove through the annular fixing piece, the microporous ceramic An arcuate air cavity for gas accumulation pressurization is formed between the lower surface of the diaphragm and the cone groove, and a gas passage is reserved between a side surface of the microporous ceramic diaphragm and the cone groove Clearance.

The upper surface of the microporous ceramic membrane is provided with a plurality of micropores for gas circulation, and the microporous ceramic membrane is internally provided with a plurality of drainage channels for uniformly distributing incident gas, and each of the drainage channels The inlet is located on the side of the microporous ceramic membrane.

The pore diameter of the upper surface of the microporous ceramic membrane is 0.01 to 10 μm. The gap between the side surface of the microporous ceramic membrane and the groove of the cone is 1 to 2 mm.

The flow guiding device is suspended inside the photobioreactor main body by a guiding fulcrum disposed at upper and lower ends thereof, and the guiding device divides the interior of the photobioreactor main body into a rising zone and a descending zone, the rising zone refers to the photobioreactor body cavity portion located inside the flow guiding device, and the descending zone refers to the photobioreaction located outside the flow guiding device The body cavity portion.

When the external illumination is used, the flow guiding device is made of a specular reflective material, and the inner wall of the photoreactor body is made of a transparent plexiglass material; when the built-in illumination is used, the flow guiding device adopts a lens plexiglass material, and the The inner wall of the photoreactor body is made of a mirror reflective material.

The LED wave frequency double-variation illumination system comprises a preset number and proportion of white, red and blue LED lamp beads, a frequency conversion system and a time relay; the frequency conversion system is used for controlling the LED lamp bead according to actual cultivation requirements. Realizing white, red, blue and combined illumination of any two or more wavelengths, and adjusting the illumination intensity; the time relay is used to control the LED lamp bead according to actual cultivation requirements, and realize illumination time and dark processing time adjustment .

The invention adopts the above technical solutions, and has the following advantages: 1. The invention provides a controllable particle size microbubble generating device at the bottom of the microbubble photobioreactor body, and utilizes the efficient mass transfer and momentum conduction capability of the microbubbles to provide economy. The microalgae rapidly grows the carbon source needed, and at the same time drives the algae cells to enter the descending zone to receive light, which improves the utilization rate of light energy and photosynthetic efficiency, reduces process complexity and maintenance cost, reduces floor space, and is one-stop. Solve the bottleneck of traditional technology. 2. The present invention provides a microporous gas outlet surface at the top of the microporous ceramic membrane in the controllable particle size microbubble generating device, and a drainage channel is arranged inside the membrane, so that the generated microbubbles are evenly distributed, the flux is large, and the gas resistance is small. It can be adjusted in size and flexible in application. 3. In the present invention, since the microbubble photobioreactor is used, it is possible to accurately control the internal culture solution of the microbubble photobioreactor by using a single dose of carbonate and continuous microbubble ventilation without using additional pH monitoring and regulating equipment. The pH is in the optimum range, reducing process complexity and maintenance costs. The present invention can be widely applied to economical microalgae cultivation.

DRAWINGS

1(a) is a schematic view showing the structure of a microbubble photobioreactor for economical microalgae cultivation according to the present invention;

Figure 1 (b) is a 3D schematic view of a microbubble photobioreactor for economical microalgae cultivation of the present invention;

2(a) is a schematic structural view of a microbubble generator of the present invention;

Figure 2 (b) is a 3D schematic view of the microbubble generator of the present invention;

Figure 2 (c) is a schematic view of the microbubble generator base 3D of the present invention;

Figure 3 is a schematic view showing the cultivation of economic microalgae using a microbubble photobioreactor;

4(a) is a schematic view showing a plurality of unit ring-type joint structures of a microbubble photobioreactor according to the present invention;

4(b) is a schematic view showing a plurality of unit line type joint structures of the microbubble photobioreactor of the present invention;

Figure 5 (a) is a diagram showing the particle size distribution of microbubbles generated by different pore microporous ceramic membranes of the present invention;

Figure 5 (b) is a test result of the mass transfer coefficient of the microbubble photobioreactor under different conditions of the present invention;

The reference numerals referred to in the drawings are as follows: 1. Microbubble photobioreactor (MPBR); 2. Controllable particle size microbubble generator; 3. Built-in diversion tube; 4. Guide device fulcrum; , photobioreactor main body; 6, reactor cover; 7, LED wave frequency double variable illumination system; 8, unloading valve; 9, intake valve; 10, microporous ceramic diaphragm; 11, diversion channel; 12, annular fixed piece; 13, base; 14, base fastening thread; 15, unloading end thread; 16, curved air cavity; 17, annular fixing piece first fastening nut; 18, annular fixing piece second tight Solid nut; 19, variable diameter air inlet; 20, microbubble photobioreactor bracket; 21, fixed clamp; 22, fixed bottom; 23, intake pipe; 24, algae liquid; 25, CO ₂ mixture ; 26, air outlet.

Detailed ways

The invention will now be described in detail in conjunction with the drawings and embodiments.

As shown in FIG. 1(a) and FIG. 1(b), the present invention provides a microbubble photobioreactor for economical microalgae cultivation, comprising: a microbubble photobioreactor 1, the microbubble photobio The reactor 1 comprises a photobioreactor body 5 having a predetermined volume, a controllable particle size microbubble generating device 2, a flow guiding device 3, and an LED wave frequency dimorphic illumination system 7. Wherein, the controllable particle size microbubble generating device 2 is disposed at the bottom of the photobioreactor main body 5 for providing carbon mass transfer and circulating power required for economical microalgae cultivation, and simultaneously analyzing dissolved oxygen; the flow guiding device 3 is suspended at The inside of the photobioreactor body 5 is used to promote liquid circulation and microbubble mass transfer and can adjust the suspension height according to actual needs; the LED wave frequency double-variation illumination system 7 is disposed outside or inside the photobioreactor body 5 for Provide optimal growth wavelength and light-dark frequency according to the demand of specific economic microalgae.

The photobioreactor body 5 is of a tubular or plate-like structure, the top of which is provided with a detachable reactor cover 6 with an air outlet 26, and the bottom bolt is connected to the controllable particle size microbubble generating device 2.

As shown in FIGS. 2(a) to 2(c), the controllable particle size microbubble generating device 2 includes a detachable base 13, a microporous ceramic diaphragm 10, and an annular fixing piece 12. The detachable base 13 includes a substrate and a cavity disposed on the substrate, and the base is provided with a base fastening thread 14 for bolting to the bottom side wall of the photobioreactor body 5, and the cavity is provided with a connection for unloading a discharge end thread 15 of the valve 8; a conical groove is arranged in the center of the upper portion of the cavity, and an air inlet is formed in the middle of the conical groove through the upper and lower ends of the cavity, and the lower end of the inlet is disposed in the middle of the substrate The variable diameter air inlet nozzle 19 is connected, and the other end of the variable diameter air inlet nozzle 19 is sequentially connected to the CO ₂ mixed gas 25 through the intake valve 9 and the intake duct 23; the microporous ceramic diaphragm 10 is fixedly disposed by the annular fixing piece 12 An arcuate air chamber 16 for gas accumulation pressurization is formed on the upper surface of the detachable base 13 and between the lower surface of the microporous ceramic diaphragm 10 and the cone recess of the detachable base 13, the microporous ceramic diaphragm 10 A gap of 1 to 2 mm for gas circulation is reserved between the side surface and the cone groove.

The upper surface of the microporous ceramic membrane 10 is provided with a plurality of micropores for gas circulation, and the pore diameter of the micropores is 0.01 to 10 micrometers; the microporous ceramic membrane 10 is provided with a plurality of diversion channels 11 inside, and each diversion flow The inlet of the canal 11 is located on the side of the microporous ceramic membrane 10 for distributing the incident gas to prevent microbubble accumulation in a certain area of the microporous gas outlet surface, thereby ensuring uniform distribution of the microbubbles.

The flow guiding device 3 is suspended from the cavity of the photobioreactor main body 5 by a baffle fulcrum 4 disposed at the upper and lower ends thereof, and the flow guiding device 3 divides the interior of the photobioreactor main body 5 into a rising region and The descending zone refers to the cavity portion of the photobioreactor body 5 located inside the flow guiding device 3, and the descending zone refers to the cavity portion of the photobioreactor body 5 located outside the flow guiding device 3. Wherein, the flow guiding device 3 can adopt a hollow draft tube or a baffle according to the structure of the photobioreactor main body 5. When the photobioreactor main body 5 has a tubular structure, a hollow diversion tube is used, when photobioreaction When the main body 5 is a plate-like structure, a baffle is used. In addition, the flow guiding device 3 can be replaced, position adjusted, cleaned, etc. according to actual cultivation needs.

The LED wave frequency double-change illumination system 7 includes white, red, and blue three-color LED lamp beads, a frequency conversion system, and a time relay of a preset number and proportion. The frequency conversion system is used to realize the combined illumination of white, red, blue and any two or more wavelengths according to the actual culture requirements, and adjust the illumination intensity; the time relay is used to adjust the illumination time and dark processing time according to the actual culture requirements. To achieve "light flash effect" and improve photosynthetic efficiency.

As a preferred embodiment, the bottom of the photobioreactor body 5 can be arranged in a funnel shape for reducing cell sedimentation buildup by structural dead angles while promoting fluid circulation. It will be appreciated that the photobioreactor body 5 can employ other structures that are effective in reducing structural dead angles.

As a preferred embodiment, the photobioreactor body 5 employs a higher aspect ratio for increasing the residence time of the gas phase in the photobioreactor body 5 and reducing the footprint. The specific value of the aspect ratio of the photobioreactor main body 5 can be determined according to the specific culture scale and the target mass transfer value.

As a preferred embodiment, in the controllable particle size microbubble generating device 2, the lower surface of the annular fixing piece 12 is provided with a groove for placing a 0-shaped rubber ring, and the annular fixing piece 12 passes through the annular fixing piece first, The second fastening nuts 17, 18 achieve a point pressure seal.

As a preferred embodiment, in practical applications, the controllable particle size microbubble generating device 2 can adopt an integrated design in consideration of the convenience of engineering operation, wherein the microporous ceramic diaphragm 10 and the microbubble generator base 13 and The annular fixing piece 12 is bonded by superglue or other means to form a microbubble generator having a fixed aperture, and the target microbubble particle size is obtained directly by replacing the microbubble generators of different apertures.

As a preferred embodiment, when external illumination is used, the flow guiding device 3 adopts a specular reflective material that can increase the light reflection to improve the utilization of light energy, and the photobioreactor main body 5 is made of a transparent plexiglass material, when the built-in illumination is used. When the flow guiding device 3 is made of a transparent plexiglass material, the photobioreactor main body 5 is made of a mirror reflective material.

As a preferred embodiment, when the flow guiding device 3 adopts a hollow draft tube, the ratio of the inner diameter to the inner diameter of the cavity of the photobioreactor body 5 is determined according to the actual culture scale to increase the interior of the photobioreactor body 5. The flow rate of the liquid in the ascending and descending zones and reduces the residence time.

As a preferred embodiment, the microbubble photobioreactor for economical microalgae cultivation of the present invention further comprises a microbubble photobioreactor support 20, which is a rectangular parallelepiped frame, the cuboid frame A fixing base 22 is disposed on one side of the bottom portion for fixing the bottom of the photobioreactor main body 5, and a fixing clamp 21 is disposed on one side of the upper portion of the rectangular parallelepiped frame for fixing the upper portion of the photobioreactor main body 5, and each side of the rectangular parallelepiped frame It is used to fix the three-color LED lamp bead in the LED wave frequency double-change illumination system 7.

The method for using the microbubble photobioreactor for economical microalgae cultivation of the present invention is further described below, and specifically includes the following steps:

As shown in FIG. 3, when the microbubble photobioreactor 1 is used to carry out single unit culture of economic microalgae, the microbubble photobioreactor 1 is placed in the microbubble photobioreactor holder 20, by fixing the bottom tray 22 and The fixing clip 21 fixes it. The LED wave frequency double growth lamp in the illumination system is placed around the microbubble photobioreactor 1 or fixed to the reactor holder 20. During the cultivation, the CO ₂ mixed gas 25 is supplied from a high pressure gas cylinder and enters the controllable particle size microbubble generating device 2 through the intake pipe 23. The CO ₂ mixed gas enters the curved air chamber 16 through the variable diameter nozzle 19 to accumulate the pressure, and enters the internal guide channel 11 from the side of the microporous ceramic diaphragm 10, and is generated on the microporous gas outlet surface of the microporous ceramic diaphragm 10. Uniformly distributed microbubbles. The microbubbles ejected by the controllable particle size microbubble generating device 2 enter the photobioreactor main body 5. In the case of external illumination, the inside of the diversion device 3 is a dark area, and the outside is a light area, a dark area, and a micro area. The bubble rise causes the liquid to rise. Based on the fluid continuity, the rising liquid drops in the light zone, thereby achieving alternating circulating flow of the liquid in the dark zone and the light zone (as indicated by the arrow in Fig. 1(a)). Considering the high gas stagnation rate of the microbubbles, the liquid surface of the algae liquid 24 in the photobioreactor main body 5 and the reactor cover 6 reserve a space to prevent the liquid surface from overflowing, and the exhaust gas is discharged through the gas outlet port 26.

As shown in Fig. 4(a) and Fig. 4(b), in the actual industrialized expansion culture process, a plurality of reactor units can also be connected in a circular or linear shape to achieve a large-scale culture volume requirement. Compared to single reactor unit amplification, multiple reactor units operate in parallel with better controllability and flexibility while facilitating maintenance.

Embodiment 1:

As shown in FIG. 5(a) and FIG. 5(b), in the present embodiment, four kinds of microporous ceramic membranes with different pore diameters are used to form a microbubble photobioreactor, and the particle size distribution of the microbubble photobioreactor is as follows. Mass transfer performance was tested.

[Correct according to Rule 26 05.06.2018]
As shown in Fig. 5(a), it is the result of microbubble particle size distribution of the microbubble photobioreactor. In a 500 ml culture solution, a 1% CO ₂ mixed gas was introduced at a flow rate of 50 ml min ⁻¹ to generate microbubbles composed of four different pore size microporous ceramic membranes (type 1, species 2, species 3, species 4). The average particle diameter d ₃₂ of the microbubbles produced was 554 μm, 464 μm, 333 μm, and 115 μm, respectively. Among them, the type 1 ceramic diaphragm produces larger microbubbles, and about 30% of the microbubbles have a particle size of 400-500 um, which can be used for pre-cultivation of most economical microalgae or pre-cultivation of laboratory algae. Among the microbubbles produced by the type 2 and type 3 ceramic diaphragms, the number of microbubbles with a particle size of 100-200 μm accounts for about 35% and 65%, respectively, and can be used for the early stage or laboratory algae species of economic microalgae logarithmic growth. Expanded. The type 4 ceramic diaphragm produces the smallest microbubbles, about 65% of the microbubbles have a particle size of less than 100 μm, and 25% of the microbubbles have a particle size of less than 50 μm, which can be used for the middle or late stage of economical microalgae logarithmic growth or high scale. Density culture.

As shown in Fig. 5(b), the mass transfer performance of the four microbubble generators composed of different pore microporous ceramic membranes under different gas fluxes and different reactor height to diameter ratios was tested. In general, for the same type of microporous ceramic membrane, the mass transfer coefficient K _L a increases with the increase of gas flux or height to diameter ratio; for the same gas flux and high aspect ratio conditions, the mass transfer coefficient K _L a increases as the average particle size of the microbubbles decreases. The mass transfer coefficient of the microbubble generator composed of the above four different pore microporous ceramic membranes can reach 0.0035min ^-1 -1.92min ^-1 , which is about 200 ^{~ of the} mass transfer performance of traditional bubbles (for example, particle size 3mm). 30000 times, can meet the carbon demand of different economic microalgae in different growth periods. On the other hand, combined with the above test results and theoretical derivation of microbubble particle size and mass transfer performance, the present invention provides the main factors affecting mass transfer performance (bubble particle size, reactor height to diameter ratio, gas flux) and mass transfer coefficient. The mathematical model between them provides a theoretical basis for the preferred method of microbubble photobioreactor structure and operating parameters.

It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not limited thereto; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that The technical solutions described in the foregoing embodiments are modified, or some of the technical features are equivalently substituted, and the modifications or substitutions do not deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

A microbubble photobioreactor for economical microalgae cultivation, characterized in that it comprises a photobioreactor body with a predetermined volume, a controllable particle size microbubble generating device, a flow guiding device, and an LED wave frequency double a variable-lighting system; the controllable particle size microbubble generating device is disposed at the bottom of the photobioreactor body for providing carbon mass transfer and circulating power required for economical microalgae cultivation, and simultaneously analyzing dissolved oxygen; a flow device suspension disposed inside the photobioreactor body for promoting liquid circulation and microbubble mass transfer; the LED wave frequency double variable illumination system is disposed outside or inside the photobioreactor body for Specific economic microalgae requirements provide optimal growth wavelengths and light-dark frequencies. The microbubble photobioreactor for economical microalgae cultivation according to claim 1, wherein the photobioreactor body has a tubular or plate-like structure, and a top portion thereof is provided with an air outlet. The reactor cover is removed, and the bottom bolt is connected to the controllable particle size microbubble generating device. A microbubble photobioreactor for economical microalgae cultivation according to claim 2, wherein the bottom of the photobioreactor body is arranged in a funnel shape. A microbubble photobioreactor for economical microalgae culture according to claim 1, wherein said controllable particle size microbubble generating device comprises a detachable base, a microporous ceramic membrane and a ring fixing sheet; The detachable base includes a substrate and a cavity disposed on the substrate, and the substrate is provided with a base fastening thread for bolting to a bottom wall of the photobioreactor main body, and the cavity is disposed on the cavity a discharge end thread for connecting to the discharge valve; a central portion of the upper portion of the cavity is provided with a conical groove, and a central portion of the conical groove is provided with an air inlet opening through the upper and lower ends of the cavity. The lower end of the inlet port is connected to the variable diameter inlet nozzle disposed in the middle of the substrate, and the other end of the variable diameter inlet nozzle is sequentially connected to the CO 2 mixed gas through an intake valve and an intake duct; The microporous ceramic membrane is fixedly disposed on the cone groove by the annular fixing piece, and a gas accumulation pressure is formed between the lower surface of the microporous ceramic membrane and the cone groove. A curved air cavity, a gap for gas circulation is reserved between the side surface of the microporous ceramic diaphragm and the cone groove. The microbubble photobioreactor for economical microalgae cultivation according to claim 4, wherein the upper surface of the microporous ceramic membrane is provided with a plurality of micropores for gas circulation. The microporous ceramic diaphragm is internally provided with a plurality of guiding channels for uniformly distributing the incident gas, and an inlet of each of the guiding channels is located at a side of the microporous ceramic diaphragm. A microbubble photobioreactor for economical microalgae culture according to claim 5, wherein the microporous ceramic membrane has a micropore pore diameter of 0.01 to 10 μm. A microbubble photobioreactor for economical microalgae culture according to claim 4, wherein a gap between the side of the microporous ceramic membrane and the cone recess is 1 to 2 mm. A microbubble photobioreactor for economical microalgae culture according to claim 1, wherein said flow guiding means is suspended at said fulcrum by means of a flow guiding device disposed at upper and lower ends thereof Inside the photobioreactor main body, the flow guiding device divides the interior of the photobioreactor main body into an ascending zone and a descending zone, and the ascending zone refers to the light located inside the diversion device Bioreactor body cavity portion, said drop zone refers to the photobioreactor body cavity portion external to said flow guiding device. A microbubble photobioreactor for economical microalgae cultivation according to claim 8, wherein said flow guiding means is made of a specularly reflective material when external illumination is employed, said photoreactor The inner wall of the main body adopts a transparent plexiglass material; when the built-in illumination is used, the flow guiding device adopts a lens plexiglass material, and the inner wall of the photoreactor body adopts a specular reflective material. A microbubble photobioreactor for economical microalgae cultivation according to claim 1, wherein said LED wave frequency double-variation illumination system comprises a predetermined number and proportion of white, red and blue colors. LED lamp bead, frequency conversion system and time relay; the frequency conversion system is used for controlling the LED lamp bead according to actual cultivation requirements, realizing white, red, blue and combined illumination of two or more wavelengths, and performing illumination intensity Adjusting; the time relay is used to control the LED lamp bead according to actual cultivation requirements, and realize illumination time and dark processing time adjustment.

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