Microalgae cultivation raceway pond and microalgae cultivation method

Abstract

The application relates to a microalgae cultivation runway pool and a microalgae cultivation method. The microalgae cultivation runway pool comprises a pool body and multiple submersible pumps. The pool body has a circulating flow channel for circulating flow of algal liquid. The multiple submersible pumps are arranged in the pool body and are arranged at intervals along the circulating flow channel. During operation of the submersible pumps, a spiral upward flow field which is propelled in a horizontal direction and disturbed in a vertical direction can be formed, so that stratification of water and generation of dead angle zones are avoided. The spiral upward flow field can continuously lift the bottom algal liquid to the surface layer, and continuously sink the surface layer algal liquid to the bottom layer, so that three-dimensional circulation of the whole pool is formed, stratification of water is avoided, the algal liquid is kept in a uniform suspended state, and the algal cells can fully receive light. In addition, the flow field driven by the submersible pumps has uniform shear force distribution and low numerical value, so that mechanical damage to the algal bodies can be avoided, high-viscosity algal liquid can be effectively dispersed, and long filamentous algal strains are prevented from winding and knotting, and the method is particularly suitable for high-density cultivation of large algal strains such as nitrogen-fixing blue-green algae.

Description

Technical Field

[0001] This invention relates to the field of microalgae cultivation technology, and in particular to microalgae cultivation racetrack pools and methods for microalgae cultivation. Background Technology

[0002] Microalgae have significant applications in carbon dioxide fixation, biomass energy, aquatic feed, bio-fertilizer, and ecological restoration. Raceway ponds are currently the mainstream device for large-scale open cultivation of microalgae. Traditional microalgae cultivation raceway ponds use mechanical agitators as the driving device, combined with bottom micropore aeration to assist mixing, maintain the circulation and uniform suspension of algal solution, and ensure the normal photosynthesis of microalgae.

[0003] Traditional agitator-type racetrack pools propel water through impellers. This type of system has significant technical drawbacks: the impeller thrust is limited, the flow velocity at the bottom of the pool is low, which easily causes algal cells to settle and accumulate, forming a thick sediment layer. This results in insufficient light exposure for the bottom algae, reduced photosynthetic efficiency, and low light energy utilization. Mechanical agitation systems have many transmission components, resulting in high frictional losses, high energy consumption per unit of water, and the impellers are prone to wear and deformation, requiring frequent maintenance and high operating costs. The shear force generated by the impeller is relatively large, which can easily damage, entangle, and clump long filamentous and brittle algal plants, making it difficult to adapt to high-density algal solutions and large algal plants. Summary of the Invention

[0004] Therefore, it is necessary to provide a microalgae cultivation raceway pool and a microalgae cultivation method to solve the problems of low light energy utilization and significant damage to algae caused by traditional stirred paddle raceway pools.

[0005] A microalgae cultivation raceway pool, comprising:

[0006] The pool body has a circulation channel for the algae solution to circulate.

[0007] And multiple submersible pumps, which are installed in the pool and spaced apart along the circulation channel.

[0008] In one embodiment, the submersible pump is an oil-immersed submersible pump.

[0009] In one embodiment, the submersible pump employs an open impeller structure.

[0010] In one embodiment, the flow rate of a single submersible pump is 80 m³ / h. 3 / h~150m 3 / h.

[0011] In one embodiment, the submersible pump has a head of 3m to 8m.

[0012] In one embodiment, the submersible pump has a rated power of 10kW to 20kW.

[0013] In one embodiment, the spacing between adjacent submersible pumps is 8m to 15m.

[0014] In one embodiment, the submersible pump is provided with a carbon dioxide air intake component, which includes an air intake port disposed on the pump body and / or the water inlet pipe of the submersible pump.

[0015] In one embodiment, the microalgae cultivation raceway pool further includes:

[0016] A carbon dioxide supply device is connected to the air inlet to supply carbon dioxide to the submersible pump.

[0017] In one embodiment, the microalgae cultivation raceway pool further includes:

[0018] An ultrasonic cleaning device is installed inside the pump body of the submersible pump.

[0019] In one embodiment, the microalgae cultivation raceway pool further includes:

[0020] A smart shading film is used to cover the top of the pool, and the light transmittance of the smart shading film can be adjusted within the range of 50% to 90%.

[0021] In one embodiment, the microalgae cultivation raceway pool further includes:

[0022] An online monitoring and control system includes a sensor and a control unit, wherein the control unit is electrically connected to the sensor and the submersible pump; the online monitoring and control system meets at least one of the following characteristics (1) to (3):

[0023] (1) The sensor includes a dissolved oxygen sensor, which is used to detect the dissolved oxygen concentration of the algal solution. The control unit is used to adjust at least one of the operating power, speed and carbon dioxide supply flow rate of the submersible pump to control the dissolved oxygen concentration of the algal solution within a set range.

[0024] (2) The sensor includes a pH sensor, which is used to detect the pH value of the algal solution. The control unit is used to adjust at least one of the operating power, speed and carbon dioxide supply flow rate of the submersible pump to control the pH value of the algal solution within a set range.

[0025] (3) The sensor includes a turbidity sensor, which is used to detect the turbidity of the algal solution. The control unit is used to adjust at least one of the operating power, speed and carbon dioxide supply flow rate of the submersible pump to control the turbidity of the algal solution within a set range.

[0026] A method for cultivating microalgae, using the microalgae cultivation racetrack pool described in any of the above embodiments, the method comprising the following steps:

[0027] Add algae solution to the pool;

[0028] Start the submersible pump to drive the algal solution to flow along the circulation channel.

[0029] Compared with traditional technologies, the above-mentioned microalgae cultivation raceway pool and microalgae cultivation method have the following beneficial effects:

[0030] The aforementioned microalgae cultivation raceway tank utilizes multiple submersible pumps spaced along the circulation channel, replacing the traditional agitator system. During operation, the submersible pumps create a spiral upward flow field that propels horizontally and agitates vertically, preventing water stratification and dead zones. This spiral upward flow field continuously elevates the algal solution from the bottom layer to the surface, while the surface algal solution continuously sinks back to the bottom, forming a three-dimensional circulation throughout the tank. This prevents water stratification, maintains a uniform suspension of the algal solution, and ensures that algal cells receive ample light, improving light energy utilization. Furthermore, the shear force distribution of the flow field generated by the submersible pumps is uniform and low, preventing mechanical damage to the algae. It also effectively disperses high-viscosity algal solutions, preventing filamentous algal cells from tangling and clumping, making it particularly suitable for high-density cultivation of large algal species such as nitrogen-fixing cyanobacteria. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a microalgae cultivation raceway pool according to one embodiment.

[0032] Explanation of reference numerals in the attached figures:

[0033] 100. Microalgae cultivation racetrack pool; 110. Pool body; 111. Circulation channel; 120. Submersible pump; 130. Carbon dioxide intake component; 140. Carbon dioxide supply device. Detailed Implementation

[0034] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] like Figure 1 As shown, a microalgae cultivation raceway tank 100 of one embodiment includes a tank body 110 and multiple submersible pumps 120. The tank body 110 has a circulation channel 111 for circulating algae solution. The multiple submersible pumps 120 are disposed in the tank body 110 and spaced apart along the circulation channel 111.

[0040] The aforementioned microalgae cultivation raceway tank 100 uses multiple submersible pumps 120 spaced along the circulation channel 111 to replace the traditional stirring paddle system. During operation, the submersible pumps 120 create a spiral upward flow field that propels horizontally and agitates vertically, preventing water stratification and dead zones. This spiral upward flow field continuously elevates the algal solution from the bottom layer to the surface, while the surface algal solution continuously sinks back to the bottom, forming a three-dimensional circulation throughout the tank. This prevents water stratification, maintains a uniform suspension of the algal solution, and ensures that algal cells receive ample light, improving light energy utilization. Furthermore, the shear force distribution of the flow field driven by the submersible pumps 120 is uniform and low, preventing mechanical damage to the algae and effectively dispersing high-viscosity algal solutions, preventing filamentous algal cells from tangling and clumping. This is particularly suitable for high-density cultivation of large algal species such as nitrogen-fixing cyanobacteria.

[0041] In some examples, the pool body 110 has an annular or U-shaped structure. The aforementioned annular or U-shaped structure forms a continuous circulation channel, allowing the algae solution to circulate continuously in a single direction under the drive of the submersible pump 120, avoiding dead zones and promoting uniform mixing of the algae solution.

[0042] In some examples, the length of the circulation channel 111 is 15m to 60m, specifically 15m, 18m, 20m, 25m, 30m, 35m, 40m, 45m, 50m, 55m, 60m, etc.

[0043] In some of these examples, the width of the circulation channel 111 is 4m to 12m, specifically 4m, 5m, 6m, 7m, 8m, 9m, 10m, 11m, 12m, etc.

[0044] In some examples, the operating water depth of the circulation channel 111 is 0.3m to 0.6m, specifically 0.3m, 0.35m, 0.4m, 0.45m, 0.5m, 0.55m, 0.6m, etc.

[0045] In some examples, the bottom of the pool 110 is sloped. This slope facilitates complete drainage of the water when cultivation is complete or when pool cleaning is required, and also facilitates the settling and removal of waste and pool cleaning. In some examples, the slope of the bottom of the pool 110 is 0.3% to 0.8%. The slope is the ratio of the height difference to the horizontal length. In specific examples, the slope of the bottom of the pool 110 is, for example, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, etc.

[0046] In some of these examples, the pool body 110 is made of high-density polyethylene (HDPE), which gives the pool body 110 excellent corrosion resistance and anti-aging ability, enabling it to withstand the corrosion of algal liquid and substances such as nutrients and carbon dioxide added during the cultivation process for a long time.

[0047] In some of these examples, the pool body 110 is integrally formed.

[0048] In some examples, the inner wall of the pool body 110 is polished. For example, the surface roughness Ra of the inner wall of the pool body 110 is less than 1.0 μm. In some specific examples, the surface roughness Ra of the inner wall of the pool body 110 is, for example, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, etc. A smooth inner wall can reduce the attachment and deposition of algae on the pool wall, which is beneficial to maintaining the suspension of the algae solution.

[0049] In this application, multiple submersible pumps 120 are arranged at intervals along the circulation channel 111 to drive the algae solution to flow continuously along the circulation channel 111.

[0050] In some examples, the submersible pump 120 is located at the bottom of the pool body 110. This enhances the flow of the bottom water, effectively driving the algae solution upwards, forming a three-dimensional flow field, and reducing the problem of algae settling.

[0051] In some of these examples, the submersible pump 120 is a high-flow, low-head submersible pump. This allows for the output of a large volume of water, suitable for circulating water in large, shallow pools, achieving high-flow-rate water delivery at a relatively low head, resulting in high hydraulic efficiency and low energy consumption.

[0052] In some of these examples, the flow rate of a single submersible pump 120 is 80 m³ / h. 3 / h~150m 3 / h. Furthermore, in some of these examples, the flow rate of a single submersible pump 120 is 90m³ / h. 3 / h~120m 3 / h. In some specific examples, the flow rate of a single submersible pump 120 is, for example, 80m³ / h. 3 / h、85m 3 / h、90m 3 / h、95m 3 / h、100m 3 / h, 105m 3 / h、110m 3 / h、115m 3 / h, 120m 3 / h, 125m 3 / h, 130m 3 / h, 135m 3 / h, 140m 3 / h, 145m 3 / h, 150m 3 / h, etc. Setting the submersible pump flow rate within the above range provides sufficient power for algal solution circulation and effectively prevents algal sedimentation.

[0053] In some examples, the head of the submersible pump 120 is 3m to 8m. Further, in some examples, the head of the submersible pump 120 is 4m to 6m. In some specific examples, the head of the submersible pump 120 is, for example, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m, 7.5m, 8m, etc. Since the microalgae raceway pool is relatively shallow, typically only 0.3m to 0.6m, a very high head is not required to drive water circulation. The head setting within the above range is sufficient to maintain a adequate flow velocity of the algae solution and is conducive to forming a stable and uniform flow field throughout the pool.

[0054] In some examples, the submersible pump 120 has a rated power of 10kW to 20kW. Further, in some examples, the submersible pump 120 has a rated power of 12kW to 18kW. In some specific examples, the submersible pump 120 has rated power of, for example, 10kW, 11kW, 12kW, 13kW, 14kW, 15kW, 16kW, 17kW, 18kW, 19kW, 20kW, etc. The rated power is matched with the flow rate and head parameters to ensure that the submersible pump 120 can operate stably within its high-efficiency range, improving overall energy utilization efficiency and reducing energy costs in the cultivation process.

[0055] In some examples, the submersible pump 120 operates at a speed of 2500 rpm to 3200 rpm. Further, in some examples, the submersible pump 120 operates at a speed of 2700 rpm to 3000 rpm. In some specific examples, the submersible pump 120 operates at speeds such as 2500 rpm, 2600 rpm, 2700 rpm, 2800 rpm, 2860 rpm, 2900 rpm, 3000 rpm, 3100 rpm, and 3200 rpm. Setting the speed within these ranges allows for sufficient thrust output while maintaining low shear force, preventing damage to algal cells from the strong shearing force generated by high-speed rotation.

[0056] In some examples, the outlet diameter of the submersible pump 120 is 100mm to 200mm. Further, in some examples, the outlet diameter of the submersible pump 120 is 125mm to 175mm. In some specific examples, the outlet diameter of the submersible pump 120 is, for example, 100mm, 125mm, 150mm, 175mm, 200mm, etc. A large-diameter outlet can reduce the water velocity, allowing the water to be pushed out smoothly at a lower speed, reducing local high-shear areas, while also reducing outlet resistance and improving hydraulic efficiency.

[0057] In a specific example, the flow rate of submersible pump 120 is 100 m³ / h. 3 The pump has a head of 5m, a speed of 2860 rpm, and an outlet diameter of 150mm.

[0058] In some of these examples, the submersible pump 120 has a protection rating of at least IP68.

[0059] In some of these examples, submersible pump 120 is an oil-immersed submersible pump. The motor of an oil-immersed submersible pump is filled with insulating cooling oil, which provides excellent heat dissipation, low motor temperature rise, and allows for continuous full-load operation for extended periods. This high reliability meets the requirements of microalgae cultivation.

[0060] In some of these examples, the submersible pump 120 employs an open impeller structure. The open impeller structure lacks front and rear cover plates, resulting in a wide flow channel that effectively prevents algae from entangled and clogging the impeller, ensuring long-term stable operation of the submersible pump 120 in high-concentration algae solutions and reducing the frequency of downtime for cleaning.

[0061] In some examples, the impeller diameter of the submersible pump 120 is 250mm~350mm, and the blade angle is 20°~30°. Further, in some examples, the impeller diameter is 280mm~320mm, and the blade angle is 22°~28°. In some specific examples, the impeller diameter is, for example, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, etc., and the blade angle is, for example, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, etc. The above impeller parameter design ensures that the submersible pump 120 has good hydraulic efficiency and anti-clogging performance, maintaining low shear force while outputting a large flow rate, thus avoiding mechanical damage to algal cells.

[0062] In some examples, the spacing between adjacent submersible pumps 120 is 8m to 15m. Further, in some examples, the spacing between adjacent submersible pumps 120 is 9m to 12m. In some specific examples, the spacing between adjacent submersible pumps 120 is, for example, 8m, 9m, 10m, 11m, 12m, 13m, 14m, 15m, etc. Setting the submersible pump spacing within the above range can create a continuous and uniform flow field throughout the entire circulation channel 111, avoiding flow dead zones and preventing localized algal sedimentation.

[0063] In some examples, the submersible pump 120 operates using variable frequency drive (VFD) control. VFD control allows for flexible adjustment of the submersible pump 120's rotational speed based on actual cultivation needs, such as algal solution concentration, algal species type, and growth stage, thereby regulating the output flow rate and thrust, and achieving dynamic adjustment of the algal solution flow rate. In some examples, the VFD control of the submersible pump 120 allows the horizontal flow velocity of the algal solution within the circulation channel 111 to be adjusted within the range of 0.3 m / s to 2.5 m / s. Specifically, when the algal solution concentration is low in the early stages of cultivation, the flow rate can be appropriately reduced to save energy; when the algal solution concentration increases in the later stages of cultivation, the flow rate can be increased to enhance the mixing effect and prevent algal sedimentation.

[0064] In some examples, the submersible pumps 120 create a spiral upward flow field within the pool. Multiple submersible pumps 120 are arranged along the bottom of the pool, with the water outlet direction tangential to the circulation channel 111 and at a certain upward angle. This propels the water horizontally while generating vertical disturbances, forming a spiral upward three-dimensional flow field. In some examples, the horizontal flow velocity of the bottom water is not less than 0.5 m / s, and the vertical flow velocity is not less than 0.2 m / s. The spiral upward flow field allows the algal solution at the bottom to be continuously lifted to the surface, while the algal solution at the surface continuously sinks to the bottom, forming a three-dimensional circulation throughout the pool. This avoids water stratification, maintains a uniform suspension of the algal solution, and allows algal cells to receive sufficient light, making it particularly suitable for high-density, large-scale algal cultivation (such as nitrogen-fixing cyanobacteria).

[0065] In some of these examples, the shear force of the flow field during operation of the submersible pump 120 is below 50 Pa. This low-shear flow field avoids mechanical shear damage to algal cells, especially structurally fragile cells and filamentous algal strains, maintaining cell integrity and high activity, reducing intracellular material release and algal solution contamination caused by cell damage, and improving culture stability.

[0066] In some examples, the submersible pump 120 is equipped with a carbon dioxide inlet component 130, which includes an inlet port located on the pump body and / or water inlet pipe of the submersible pump 120. After carbon dioxide gas enters the inlet port, it is automatically drawn into the pump body under negative pressure and enters the impeller area of ​​the submersible pump 120. Once in the impeller area, the carbon dioxide gas is thoroughly broken down and sheared into numerous microbubbles under the intense shearing and turbulence generated by the high-speed rotation of the impeller. Simultaneously, it undergoes mass transfer with the algal solution, significantly improving the dissolution efficiency and utilization rate of carbon dioxide, achieving mixing of carbon dioxide and algal solution, and meeting the continuous replenishment requirements of inorganic carbon sources during high-density microalgae cultivation.

[0067] Carbon dioxide gas is thoroughly broken up by the rotation of the impeller and the shearing action of the water flow within the pump chamber, resulting in bubbles with an average diameter of less than 1 mm. These microbubbles have a larger specific surface area, a larger gas-liquid contact area, and higher mass transfer efficiency, allowing them to dissolve rapidly into the algal solution, significantly improving carbon dioxide utilization efficiency and avoiding carbon source waste caused by the rapid escape of large bubbles. Simultaneously, the microbubbles diffuse along the circulation channel 111 with the water flow throughout the entire pool, achieving a uniform distribution of the carbon source throughout the pool.

[0068] In some examples, the carbon dioxide inlet flow rate of a single submersible pump 120 is 0.1 L / min to 2.0 L / min. Further, in some examples, the carbon dioxide inlet flow rate of a single submersible pump 120 is 0.3 L / min to 1.0 L / min. In some specific examples, the carbon dioxide inlet flow rate of a single submersible pump 120 is, for example, 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, 1.0 L / min, 1.2 L / min, 1.5 L / min, 1.8 L / min, and 2.0 L / min. The inlet flow rate is set within the above range to balance carbon source supply efficiency and gas-liquid mixing stability. When multiple submersible pumps are running in parallel, the total carbon dioxide supply is adjusted proportionally according to the volume of the raceway pool and the concentration of algae solution, so that the concentration of dissolved inorganic carbon in the pool 110 is maintained in a suitable range of 5mg / L~20mg / L (calculated as carbon dioxide).

[0069] Furthermore, by coordinating the carbon dioxide intake flow rate and the submersible pump speed (120 rpm), the pH value of the algal solution can be controlled. The submersible pump speed (120 rpm) can be adjusted from 200 rpm to 800 rpm, and the pH value of the algal solution can be controlled from 6.5 to 8.5. Through this coordinated adjustment, the carbon source supply rate can be adjusted in real time according to the dynamic carbon source requirements of microalgae at different growth stages, including the growth initiation period, rapid proliferation period, and stable culture period, maintaining the optimal pH environment and carbon source concentration of the algal solution to meet the needs of microalgae at different growth stages.

[0070] In some of these examples, the microalgae cultivation raceway also includes a carbon dioxide intake component 140. The carbon dioxide intake component 140 is connected to an intake port, preferably via a pressure-resistant hose, for supplying carbon dioxide to the submersible pump 120.

[0071] In some examples, the microalgae cultivation raceway tank 100 also includes an ultrasonic cleaning device (not shown). The ultrasonic cleaning device is located inside the pump body of the submersible pump 120. The ultrasonic cleaning device generates high-frequency ultrasonic vibrations to prevent algae from adhering to and growing on the inner wall of the pump body, impeller surface, and other parts, avoiding flow channel blockage and pump efficiency reduction, reducing the frequency of manual disassembly and cleaning, and improving equipment lifespan and operational stability. The ultrasonic cleaning device can operate periodically, for example, by starting and running it for a period of time at regular intervals, reducing energy consumption while ensuring cleaning effectiveness.

[0072] In some examples, the ultrasonic cleaning device operates at a frequency of 20kHz to 40kHz. In some specific examples, the ultrasonic cleaning device operates at frequencies such as 20kHz, 22kHz, 25kHz, 28kHz, 30kHz, 35kHz, and 40kHz.

[0073] In some examples, the microalgae cultivation raceway pool 100 also includes a smart shading membrane (not shown in the figure). The smart shading membrane covers the top of the pool body 110, and its light transmittance can be adjusted within the range of 50% to 90%. The smart shading membrane can automatically adjust its light transmittance according to the light saturation point characteristics of different microalgae, the light requirements of different growth stages, and the changes in natural light intensity at different times of the day. When the light is too strong, it appropriately reduces the light transmittance to avoid photoinhibition or photooxidation damage to algal cells; when the light is weak, it increases the light transmittance to ensure that the algal solution receives sufficient light for photosynthesis, thereby improving light energy utilization efficiency and photosynthetic adaptability, and achieving efficient and stable growth of microalgae.

[0074] In some examples, the microalgae cultivation raceway tank 100 also includes an online monitoring and control system (not shown in the figure). The online monitoring and control system includes sensors and a control unit. The control unit is electrically connected to the sensors and the submersible pump 120. The online monitoring and control system includes multiple sensors and a control unit. The sensors are used to detect various physicochemical parameters of the algal solution and transmit the monitoring data to the control unit in real time. Based on the feedback from the sensor detection data, the control unit dynamically adjusts at least one of the following: the operating power, speed, and carbon dioxide supply flow rate of the submersible pump 120. This achieves automatic adjustment of the flow field intensity, dissolved oxygen level, and carbon source supply, improving the stability of system operation.

[0075] In some examples, the sensors include at least one of a dissolved oxygen (DO) sensor, a pH sensor, and a turbidity sensor. The dissolved oxygen sensor is used to detect the dissolved oxygen concentration of the algal solution. The control unit adjusts at least one of the operating power, speed, and carbon dioxide supply flow rate of the submersible pump 120 to control the dissolved oxygen concentration of the algal solution within a set range. The pH sensor is used to detect the pH value of the algal solution. The control unit adjusts at least one of the operating power, speed, and carbon dioxide supply flow rate of the submersible pump 120 to control the pH value of the algal solution within a set range. The turbidity sensor is used to detect the turbidity of the algal solution, thereby reflecting the algal cell concentration. The control unit adjusts at least one of the operating power, speed, and carbon dioxide supply flow rate of the submersible pump 120 to control the turbidity of the algal solution within a set range.

[0076] The aforementioned microalgae cultivation raceway pool 100 allows for flexible adjustment of the number and spacing of submersible pumps based on site conditions and cultivation scale. It supports modular expansion and is suitable for large-scale microalgae cultivation under different climatic conditions, algae species, and application scenarios, including carbon sequestration, feed, fertilizer, or ecological restoration.

[0077] Furthermore, this application also provides a method for cultivating microalgae.

[0078] One embodiment of the microalgae cultivation method of this application uses the microalgae cultivation raceway pool 100 of any of the above embodiments for microalgae cultivation, and includes the following steps:

[0079] Inject a culture medium containing microalgae seeds into pool 110;

[0080] Multiple submersible pumps 120 are started to drive the algae solution to flow along the circulation channel 111.

[0081] In some of these examples, the horizontal flow rate of the algal solution is controlled at 0.5 m / s to 2 m / s to keep the algal cells in suspension.

[0082] In some examples, during cultivation, carbon dioxide is supplied to the algal solution via a carbon dioxide intake module integrated into a submersible pump 120. The pH of the algal solution is controlled within the range of 6.5 to 8.5 by adjusting the carbon dioxide intake flow rate and the submersible pump speed. In some examples, the dissolved inorganic carbon concentration is maintained at 5 mg / L to 20 mg / L during cultivation to meet the carbon source requirements of microalgae photosynthesis.

[0083] In some of these examples, during the cultivation process, an ultrasonic cleaning device is activated periodically to clean the inside of the submersible pump 120 and prevent algae from adhering and clogging it.

[0084] In some of these examples, at least one parameter of the algal solution, such as dissolved oxygen, pH, and turbidity, is monitored in real time by sensors. Based on the monitoring results, the control unit automatically adjusts at least one of the following: the operating power, speed, and carbon dioxide supply flow rate of the submersible pump 120, so as to keep the relevant parameters of the algal solution within the set range.

[0085] In some of these examples, the light transmittance of the smart shading membrane on the pool roof is adjusted according to changes in light intensity to provide suitable light conditions for microalgae growth, avoid light inhibition, and improve light energy utilization.

[0086] In some of these examples, the microalgae include nitrogen-fixing cyanobacteria. Furthermore, the concentration of microalgae in the culture solution is above 5 g / L during the cultivation process. The microalgae cultivation method of this application, due to the use of a low-shear submersible pump, produces a uniform and gentle flow field, effectively avoiding the entanglement, clumping, and mechanical damage of filamentous nitrogen-fixing cyanobacteria, thus achieving long-term, stable, and high-density cultivation of large algal strains such as nitrogen-fixing cyanobacteria.

[0087] In summary, compared with traditional impeller systems, this application has the following technical advantages:

[0088] (1) High mixing efficiency, effectively preventing algal settling. By arranging multiple submersible pumps at intervals along the bottom of the pool and forming a spiral upward three-dimensional flow field, the entire pool is circulated in a three-dimensional manner, resulting in a bottom flow velocity greater than 0.5 m / s and a vertical flow velocity of more than 0.3 m / s, which effectively inhibits algal settling and maintains the algal solution in a uniform suspension state. It is particularly suitable for the cultivation of high-density, large algal strains such as nitrogen-fixing cyanobacteria.

[0089] (2) Optimize lighting conditions and significantly improve light energy utilization. By enhancing vertical disturbance, the algae periodically enter the surface lighting area, improving the uniformity of light distribution, avoiding local light saturation or light blind spots, significantly improving the light energy utilization efficiency of algae, and thus increasing the yield per unit area.

[0090] (3) Effectively reduce energy consumption and maintenance costs. Under the premise of achieving the same or even better mixing effect as traditional agitator systems, this application can significantly reduce unit energy consumption due to less mechanical friction, higher transmission efficiency and higher hydraulic efficiency; and avoids problems such as blade wear and entanglement; combined with ultrasonic self-cleaning function, it greatly reduces long-term maintenance costs and maintenance workload.

[0091] (4) Reduce mechanical damage to algae and improve algal adaptability. Traditional stirring paddle systems generate high shear force in the blades, which can easily cause damage to the structure of filamentous or brittle algae. However, the shear force generated by the submersible pump is less than 50 Pa, and the water flow is more stable and gentle, which significantly reduces the risk of cell breakage, clumping, entanglement and other problems, and improves the activity and growth stability of algae.

[0092] (5) Strong anti-clogging and anti-pollution capabilities. It adopts an open impeller structure and integrates an ultrasonic self-cleaning module, which effectively prevents algae from attaching and clogging, ensuring smooth water flow and stable equipment operation. It is especially suitable for cultivation scenarios where algal secretions are abundant and easily adhered.

[0093] (6) Provides an inorganic carbon source to improve carbon dioxide utilization efficiency. This application sets up a carbon dioxide intake module to provide an inorganic carbon source for algae. The carbon dioxide is fully sheared and dispersed into microbubbles in the submersible pump impeller area and during the subsequent transportation process, and is evenly diffused throughout the raceway pool with the water flow. This avoids the problems of concentrated floating of bubbles, low local mass transfer efficiency, and impact on algae in traditional bottom aeration or independent bubbling methods, while improving the utilization efficiency of carbon dioxide.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A microalgae cultivation racetrack pool, characterized in that, include: The pool body has a circulation channel for the algae solution to circulate. as well as Multiple submersible pumps are installed in the pool and spaced apart along the circulation channel.

2. The microalgae cultivation racetrack pool as described in claim 1, characterized in that, It meets at least one of the following characteristics (1) to (2): (1) The submersible pump is an oil-immersed submersible pump; (2) The submersible pump adopts an open impeller structure.

3. The microalgae cultivation racetrack pool as described in claim 1, characterized in that, It meets at least one of the following characteristics (1) to (3): (1) The flow rate of a single submersible pump is 80 m³ / h. 3 / h~150m 3 / h; (2) The head of the submersible pump is 3m~8m; (3) The rated power of the submersible pump is 10kW~20kW.

4. The microalgae cultivation raceway pool as described in claim 1, characterized in that, The distance between adjacent submersible pumps is 8m to 15m.

5. The microalgae cultivation raceway pool as described in any one of claims 1 to 4, characterized in that, The submersible pump is equipped with a carbon dioxide intake component, which includes an intake port located on the pump body and / or the water inlet pipe of the submersible pump.

6. The microalgae cultivation racetrack pool as described in claim 5, characterized in that, Also includes: A carbon dioxide supply device is connected to the air inlet to supply carbon dioxide to the submersible pump.

7. The microalgae cultivation raceway pond according to any one of claims 1 to 4 and 6, characterized in that, Also includes: An ultrasonic cleaning device is installed inside the pump body of the submersible pump.

8. The microalgae cultivation raceway pool as described in any one of claims 1 to 4 and 6, characterized in that, Also includes: A smart shading film is used to cover the top of the pool, and the light transmittance of the smart shading film can be adjusted within the range of 50% to 90%.

9. The microalgae cultivation raceway pond according to any one of claims 1 to 4 and 6, characterized in that, Also includes: An online monitoring and control system includes a sensor and a control unit, wherein the control unit is electrically connected to the sensor and the submersible pump; the online monitoring and control system meets at least one of the following characteristics (1) to (3): (1) The sensor includes a dissolved oxygen sensor, which is used to detect the dissolved oxygen concentration of the algal solution. The control unit is used to adjust at least one of the operating power, speed and carbon dioxide supply flow rate of the submersible pump to control the dissolved oxygen concentration of the algal solution within a set range. (2) The sensor includes a pH sensor, which is used to detect the pH value of the algal solution. The control unit is used to adjust at least one of the operating power, speed and carbon dioxide supply flow rate of the submersible pump to control the pH value of the algal solution within a set range. (3) The sensor includes a turbidity sensor, which is used to detect the turbidity of the algal solution. The control unit is used to adjust at least one of the operating power, speed and carbon dioxide supply flow rate of the submersible pump to control the turbidity of the algal solution within a set range.

10. A method for cultivating microalgae, characterized in that, The microalgae cultivation raceway pool according to any one of claims 1 to 9, the microalgae cultivation method includes the following steps: Algae solution was added to the pool; and Start the submersible pump to drive the algal solution to flow along the circulation channel.

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