Self-cleaning bio-membrane reactor for microalgae cultivation

Abstract

The invention relates to the technical field of cooling towers, in particular to a self-cleaning bio-membrane reactor for microalgae cultivation. Comprising a culture sleeve, a support, a liquid inlet pipe, a liquid discharge pipe, an air inlet pipe and an exhaust pipe, two sets of cleaning mechanisms are arranged in the culture sleeve in an array mode, the cleaning mechanisms are communicated with the air inlet pipe, and the cleaning mechanisms are used for cleaning microalgae attached to the inner wall of the culture sleeve in the culture stage. Microalgae attached to the inner wall of the culture sleeve are scraped through rotation of the scraper, outer air holes in different positions of the scraper are alternately opened by means of periodic reciprocating movement of the air guide arc plate, directional release of air is achieved, the air released from the outer air holes can disperse the scraped microalgae, the microalgae are diffused into algae liquid, the situation that the local concentration is too high is avoided, and therefore the microalgae can be effectively degraded. And moreover, the released air can be located deep in the algae liquid, the air floating path is prolonged, the retention time is prolonged, and the disturbance effect on the algae liquid is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of cooling tower technology, and more specifically, to a self-cleaning biofilm reactor for microalgae cultivation. Background Technology

[0002] Microalgae can fix a large amount of CO2 during photoautotrophic cultivation. On Earth, organisms fix 1010 × 102 tons of carbon and produce 14.6 × 102 tons of biomass annually through photosynthesis, with more than half of this attributable to algal photosynthesis. Injecting CO2 into microalgae and converting it into biofuel through photosynthesis represents a major breakthrough in renewable energy over the past decade. Photobioreactor microalgae cultivation devices, through recyclable photosynthesis, achieve continuous synthesis of microalgal lipids, laying the foundation for high-throughput production of microalgal lipids.

[0003] Traditional photobioreactors can be broadly classified into four categories: raceway tanks, tubular photobioreactors, flat-plate photobioreactors, and airlift photobioreactors.

[0004] As for bioreactors, there are many existing technologies, such as: Chinese Patent Publication No. CN102586075A discloses a self-cleaning tubular photobioreactor, comprising an air inlet structure, an exhaust structure, and a transparent sleeve. Both ends of the transparent sleeve are provided with flanges that are sealed to them. One flange of the transparent sleeve is provided with a liquid inlet, and the other flange of the transparent sleeve is provided with a liquid outlet. A spiral shaft is provided inside the transparent sleeve, which is supported on the flanges at both ends of the transparent sleeve, and one end is connected to a driving device. The transparent sleeve is provided with a track parallel to its center line, and a T-shaped slider is mounted on the track. A cleaning head is fixed on the T-shaped slider, and the cleaning head is adapted to be installed in the spiral groove of the spiral shaft.

[0005] Therefore, the aforementioned structure, which incorporates a spiral shaft within a transparent sleeve and a cleaning component on the spiral shaft, prevents microalgae from adhering to the wall and growing during microalgae cultivation, thus achieving a self-cleaning function. Secondly, by employing a structure with hollow channels and radial guide holes on the spiral shaft, gas is directly and uniformly dispersed into the interior of the photobioreactor through these channels and holes. This aeration method allows the gas exiting through the radial guide holes on the spiral shaft to flush its surface.

[0006] The microalgae scraped off the inner wall of the casing will flow with the algae solution, which will flow from the inlet to the outlet along the spiral shaft. Because there is a certain distance between the guide hole and the inner wall of the casing, when the gas is sprayed radially downwards from the guide hole towards the algae solution, it is blocked by the algae solution. The disturbance effect of the gas on the algae solution near the inner wall of the casing is significantly weakened. Due to insufficient disturbance in this area, the microalgae in the algae solution cannot be fully moved. Compared with other areas, the microalgae are more likely to adhere to the surface of the spiral shaft here, thus affecting the cleaning effect of the equipment and the efficiency of microalgae recovery. Summary of the Invention

[0007] This invention provides a self-cleaning biofilm reactor for microalgae cultivation. By periodically reciprocating the movement of an arc plate, external vents at different positions on the scraper are alternately opened, enabling the directional release of air to agitate the algal solution, thereby solving the problems mentioned in the background art. To achieve the above objectives, a self-cleaning biofilm reactor for microalgae cultivation includes a culture sleeve, a support, an inlet pipe, a outlet pipe, an air inlet pipe, and an exhaust pipe. The culture sleeve is equipped with a cleaning mechanism arranged in an array of two sets. The cleaning mechanism is connected to the air inlet pipe and is used to clean the microalgae attached to the inner wall of the culture sleeve during the cultivation stage. It also guides the detached microalgae towards the axis of the culture sleeve through rotation. An air guiding mechanism is movably installed inside the cleaning mechanism. During the rotation stage, the air guiding mechanism releases the introduced gas towards the detached microalgae through periodic reciprocating movement, thereby disturbing the algal solution at different depths.

[0008] First, in order to further improve the distribution of scraped microalgae in the algal solution, there is a mixing channel between the scraper and the culture sleeve. The mixing channel can realize the communication between the algal solution on both sides of the scraper. The scraper is arc-shaped, with the thin end bent in the direction of rotation. In this way, during the rotation of the scraper, the curved scraper works with the horizontal flow of algal solution to guide the microalgae towards the axis. The inner side of the curved scraper is the water-facing side, and the outer side is the water-repelling side. Based on the above, the air guiding mechanism includes an air guiding arc plate fitted inside the air conveying channel. The air guiding arc plate corresponds to the water-facing surface. The air guiding arc plate is provided with a number of internal air holes. When the internal air holes coincide with the external air holes, they guide the air in the air conveying channel to the water-facing surface to disturb the scraped microalgae. Secondly, in Figure 6 Based on and then combined Figure 7 As shown, a guide groove is provided on the inner side wall of the scraper, and a slider is fixedly provided on the air guide arc plate corresponding to the guide groove. The slider extends into the guide groove and slides in the guide groove to keep the slider sliding against the inner wall of the air delivery channel. Furthermore, when in Figure 4In this state, the scraper located below the rotating shaft is upright. The inner and outer air holes near the thin end of the scraper are aligned, while the inner and outer air holes away from the thin end of the scraper are misaligned. In this way, when the outer air hole near the thin end of the scraper releases air, it impacts the microalgae scraped off the water-facing surface, causing the microalgae to mix evenly in the algae solution and preventing the concentration of scraped microalgae in the local algae solution from being too high.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In this self-cleaning biofilm reactor for microalgae cultivation, the microalgae attached to the inner wall of the cultivation sleeve are scraped off by a rotating scraper. Then, the external air holes at different positions on the scraper are opened alternately by the periodic reciprocating movement of the air guide arc plate, so as to achieve directional release of air. The air released from the external air holes can not only disperse the scraped microalgae and diffuse them into the algal solution to avoid excessive local concentration, but also keep the released air deep in the algal solution, prolonging the air's upward path and residence time, and significantly improving the disturbance effect on the algal solution.

[0010] 2. In this self-cleaning biofilm reactor used for microalgae cultivation, the cleaning is carried out by an arc-shaped scraper. The rotation action promotes the flow of algae in the algae solution along the water-facing surface. The scraped algae diffuse in the algae solution. In other words, the distribution of microalgae is optimized through the fluid action of the flow, so that it can contact the nutrient source in the culture medium more evenly and avoid growth inhibition caused by local nutrient depletion. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a front view of the internal structure of the culture sleeve of the present invention (cut section). Figure 3 This is an exploded view of the scraper and rotating shaft of the present invention; Figure 4 This is a schematic diagram illustrating the cleaning principle of the scraper in this invention; Figure 5 For the present invention Figure 3 Enlarged structural diagram at point A in the diagram; Figure 6 This is a schematic diagram illustrating the principle of alternating air disturbance on algal liquid in this invention; Figure 7 For the present invention Figure 3 Enlarged structural diagram at point B in the diagram; Figure 8 This is a schematic diagram of air floating in the algal solution according to the present invention.

[0012] The meanings of the labels in the diagram are as follows: 100. Culture tube; 101. Support; 102. Liquid inlet pipe; 103. Liquid outlet pipe; 104. Air inlet pipe; 105. Exhaust pipe; 106. Mixing channel; 107. Exhaust trough; 110. Cleaning mechanism; 111. Scraper; 112. Rotating shaft; 113. Motor; 114. Through groove; 115. Partition; 116. Air supply channel; 117. External air vent; 120. Air guiding mechanism; 121. Air guiding arc plate; 122. Top plate; 123. Tension spring; 124. Guide groove; 125. Slider; 126. Horizontal plate; 127. Internal air hole; 130. Stop wheel. Detailed Implementation

[0013] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0014] Because there is a certain distance between the guide hole and the inner wall of the sleeve, when the gas is sprayed radially downwards from the guide hole towards the algae liquid, it is blocked by the algae liquid. The disturbance effect of the gas on the algae liquid near the inner wall of the sleeve is significantly weakened. Due to insufficient disturbance in this area, the microalgae in the algae liquid cannot be fully moved. Compared with other areas, the microalgae are more likely to adhere to the surface of the spiral shaft, thus affecting the cleaning effect of the equipment and the efficiency of microalgae recovery.

[0015] Therefore, in view of the above-mentioned problems, the present invention discloses a self-cleaning biofilm reactor for microalgae cultivation, referencing... Figure 1-3 As shown, the system includes a culture sleeve 100, a support 101, an inlet pipe 102, a drain pipe 103, an air inlet pipe 104, and an exhaust pipe 105. The culture sleeve 100 is made of a transparent material, such as glass. During microalgae cultivation, a light source system (not shown in the figure) installed outside the culture sleeve 100 provides light to the cultured microalgae. The culture medium is injected through the inlet pipe 102, and air is injected into the culture medium inside the culture sleeve 100 through the air inlet pipe 104 and then discharged through the exhaust pipe 105. The culture medium after the reaction is discharged through the drain pipe 103. During microalgae cultivation, microalgae proliferate and attach to the inner wall of the cultivation sleeve 100. To clean the attached microalgae and disturb any detached microalgae, a cleaning mechanism 110 is installed inside the cultivation sleeve 100. Two sets of cleaning mechanisms 110 are arranged in an array. The cleaning mechanisms 110 are connected to the air inlet pipe 104 and are used to clean the microalgae attached to the inner wall of the cultivation sleeve 100 during the cultivation stage. They also guide the detached microalgae towards the axis of the cultivation sleeve 100 through rotation. Then, based on the above diagram, and combined with... Figure 4 As shown, the cleaning mechanism 110 is equipped with an air guiding mechanism 120. During the rotation phase, the air guiding mechanism 120 releases the introduced gas to the detached microalgae through periodic reciprocating movement, so as to disturb the algal liquid at different depths.

[0016] First, after microalgae cultivation for a period of time, a layer of microalgae will adhere to the inner wall of the cultivation sleeve 100, blocking light penetration and causing a decrease in the light intensity inside the cultivation sleeve 100, thus reducing the photosynthetic rate of the algal solution inside the cultivation sleeve 100. Therefore, the specific structure of the cleaning mechanism 110 is disclosed below. The cleaning mechanism 110 includes a scraper 111 with its thin end attached to the inner wall of the cultivation sleeve 100, and a rotating shaft 112 coaxial with the cultivation sleeve 100 fixedly connected to the thick end of the scraper 111. Both ends of the rotating shaft 112 are rotatably connected to the cultivation sleeve 100, and a motor 113 is coaxially fixedly connected to one end. The motor 113 is located outside the cultivation sleeve 100. In this way, when it is necessary to clean the attached microalgae, the motor 113 is started to drive the rotating shaft 112 to rotate clockwise. The rotating shaft 112 and the scraper 111 rotate synchronously, that is, as shown below. Figure 4 As indicated by the middle arrow, during the rotation process, the scraper 111 scrapes off the microalgae attached to the inner wall of the culture sleeve 100, reducing microalgae attachment, improving light transmittance, and facilitating photosynthesis by the microalgae. Secondly, the rotation of scraper 111 also rotates the algal solution, causing the scraped microalgae to mix with the solution, promoting the dispersion of microalgae within the solution, preventing excessive local microalgae concentration, and maintaining a stable growth environment for the microalgae. Returning to... Figure 2 As shown, the direction of algal liquid flow is from the inlet pipe 102 to the outlet pipe 103, forming a flow path in the horizontal direction parallel to the rotation axis 112. Combined with the clockwise rotation of the scraper 111, it can be seen that the scraper 111 shears the algal liquid during the rotation process. To further improve the distribution of scraped microalgae in the algal solution, a mixing channel 106 is provided between the scraper 111 and the culture sleeve 100. The mixing channel 106 allows the algal solution on both sides of the scraper 111 to communicate with each other. The scraper 111 is arc-shaped, with the thin end bent in the direction of rotation. Thus, during the rotation of the scraper 111, the curved scraper 111, together with the horizontal flow of algal solution, guides the microalgae towards the axis. The inner side of the curved scraper 111 is the water-facing side, and the outer side is the water-repelling side. That is, the algal solution carries the microalgae and flows on the water-facing side, allowing the scraped microalgae to diffuse in the algal solution. In other words, the distribution of microalgae is optimized through the fluid action of the flow, so that it can contact the nutrient source in the culture medium more evenly and avoid growth inhibition caused by local nutrient depletion.

[0017] Because air needs to be introduced into the culture sleeve 100 when disturbing the scraped microalgae, the algal solution is agitated by the gas. The buoyancy generated by the rising bubbles drives the culture medium and microalgae to mix and flow within the culture sleeve 100, thereby improving the efficiency of nutrient absorption by the microalgae; therefore, the following is based on Figure 4 Based on and combined Figure 5 As shown, the air inlet end of the air inlet pipe 104 is fixed to the culture sleeve 100. The air inlet pipe 104 passes through the rotating shaft 112, which has a cavity for accommodating gas. Several exhaust grooves 107 are provided on the air inlet pipe 104, and the exhaust grooves 107 communicate with the through grooves 114 on the rotating shaft 112. On the other hand, the scraper 111 has a hollowed-out middle section forming a gas delivery channel 116 for gas to flow through. The gas delivery channel 116 corresponds to the through groove 114, and the gas delivery channel 116 gradually narrows from the thick end to the thin end. Furthermore, several external air holes 117 communicating with the gas delivery channel 116 are provided along the water-facing surface of the scraper 111 (see reference). Figure 6 As shown in the diagram, the external vent 117 retracts inward from the air delivery channel 116 towards the water-facing side; therefore, the specific working principle described above is as follows: Before the gas is introduced, one end of the air inlet pipe 104 is connected to the air supply device (not shown in the figure) via a flange. Air is introduced into the air inlet pipe 104 through the air supply device. The air flows into the air delivery channel 116 through the exhaust groove 107 and the through groove 114, and finally exits from the external air hole 117. The air exiting from the air delivery channel 116 disturbs the algal liquid; specifically, refer to Figure 6 As shown, Figure 6 The image shows the effect of air disturbance on the algal solution when air is introduced into the algal solution by the two sets of scrapers 111 in this state. For ease of understanding, it should also be considered in conjunction with... Figure 4 To understand, among them, Figure 6 The diagram on the left corresponds to... Figure 4 The lower scraper 111, Figure 6 The diagram on the right corresponds to scraper 111 above the image; It should be understood that by narrowing the air supply channel 116 towards the water-facing side through the external air vent 117 and by gradually narrowing the air supply channel 116 from the thick end to the thin end, the speed of the ejected air can be increased when air is ejected from the external air vent 117, thereby increasing the disturbance effect on the algal solution and making the microalgae mix evenly in the algal solution.

[0018] Furthermore, in order to achieve the effect of the air ejected by the scraper 111 disturbing the algae liquid at different depths, it is necessary to disclose the structure of the air guiding mechanism 120. The air guiding mechanism 120 includes an air guiding arc plate 121 that is fitted into the air conveying channel 116. The air guiding arc plate 121 corresponds to the water-facing surface. The air guiding arc plate 121 is provided with a number of internal air holes 127. When the internal air holes 127 coincide with the external air holes 117, they are used to guide the air in the air conveying channel 116 to the water-facing surface, so as to disturb the scraped microalgae. Secondly, in Figure 6 Based on and then combined Figure 7 As shown, a guide groove 124 is provided on the inner wall of the scraper 111. A slider 125 is fixedly provided on the air guide arc plate 121 corresponding to the guide groove 124. The slider 125 extends into the guide groove 124 and slides within the guide groove 124 to keep the slider 125 sliding against the inner wall of the air delivery channel 116; secondly, when in Figure 4 In this state, the scraper 111 located below the rotating shaft 112 is upright. The inner air hole 127 near the thin end of the scraper 111 coincides with the outer air hole 117, while the inner air hole 127 away from the thin end of the scraper 111 is misaligned with the outer air hole 117. In this way, when the outer air hole 117 near the thin end of the scraper 111 releases air, the air impacts the microalgae scraped off the water-facing surface, so that the microalgae are evenly mixed in the algae solution, avoiding excessively high concentrations of scraped microalgae in local algae solutions. At the same time, the scraper 111 located above the rotating shaft 112 is inverted. The inner air hole 127 near the thin end of the scraper 111 is misaligned with the outer air hole 117, while the inner air hole 127 away from the thin end of the scraper 111 is aligned with the outer air hole 117. At this time, since the ejected air is located deep in the algal liquid, that is, the ejected air is closer to the axis, the air floating path is extended, thereby increasing the time the air stays in the algal liquid and improving the disturbance effect of the air on the algal liquid and microalgae.

[0019] Next, in achieving the above process, the air guide arc plate 121 needs to periodically reciprocate to switch the external air vents 117. That is, an additional power source is needed to drive the air guide arc plate 121 to reciprocate. This power comes from: a tension spring 123 elastically connected between the air guide arc plate 121 and the inner wall of the scraper 111; a horizontal plate 126 fixedly installed on the air guide arc plate 121 near the thick end of the scraper 111, the horizontal plate 126 extending away from the water-facing side; then, the air inlet pipe 1 Several stop wheels 130 are fixedly installed on the 04. The stop wheels 130 have concave and convex surfaces. An L-shaped top plate 122 is slidably installed on the stop wheels 130. The top of the top plate 122 overlaps with the horizontal plate 126. A partition block 115 is slidably connected to the top plate 122. The partition block 115 is fixed to the rotating shaft 112. By rotating the stop wheels 130, the top plate 122 slides alternately on the concave and convex surfaces, and works with the tension spring 123 to make the outer air hole 117 and the inner air hole 127 coincide and misalign. It should be understood that the return Figure 3 As shown, since the stop wheel 130 needs to apply a thrust to the top plate 122 when it rotates, the thrust needs to overcome the influence of gravity and elastic potential energy. Therefore, the end away from the intake pipe 104 is inserted into the rotating shaft 112 so that both ends of the intake pipe 104 can be supported, thereby increasing the strength of the intake pipe 104 and avoiding the state where one end of the intake pipe 104 is supported while the other end is suspended.

[0020] The above can be summarized as follows: during the rotation of scraper 111, stop wheel 130 remains stationary. When top plate 122 slides from concave to convex, top plate 122 overcomes the elastic potential energy of tension spring 123 and pushes horizontal plate 126 upward. Air guide arc plate 121 slides against the inner wall of air delivery channel 116. During this process, with... Figure 6 For example, the scraper 111 corresponding to the convex surface of the stop wheel 130 is in an upright state, and the inner air hole 127 at the thin end of the scraper 111 coincides with the outer air hole 117. Air is released from the outer air hole 117. Conversely, the scraper 111 corresponding to the concave surface of the stop wheel 130 is in an inverted state, and the inner air hole 127 at the thin end of the scraper 111 is misaligned with the outer air hole 117. The open outer air hole 117 is close to the axis, so that the air released from the outer air hole 117 is deep in the algae liquid, the air floating time is increased, and the mixing effect is improved.

[0021] In other words, the scraper 111 rotates to scrape off the microalgae attached to the inner wall of the culture sleeve 100, and then the air guide arc plate 121 moves back and forth periodically to alternately open the external air holes 117 at different positions on the scraper 111, so as to achieve directional release of air. The air released from the external air holes 117 can not only disperse the scraped microalgae and make them diffuse into the algal solution to avoid excessive local concentration, but also keep the released air deep in the algal solution, prolonging the air's upward path and residence time, and significantly improving the disturbance effect on the algal solution.

[0022] In addition, combined Figure 8 As shown, when the scraper 111 below the rotating shaft 112 is in Figure 8 In the state shown, the air released from the lower external vent 117 disturbs the algal solution, while the air injected into the algal solution forms bubbles. These bubbles move upwards due to buoyancy. Figure 8 The bubbles float from point a to point b, and then float to point c. In this way, the bubbles float radially upward from the water-facing side of the lower scraper 111. At the same time, the algae liquid moves horizontally in the opposite direction (equivalent to lateral movement), which achieves multi-directional disturbance of the algae liquid. Then, after passing the outer surface of the rotating shaft 112, the bubbles move to the back water surface of the upper scraper 111, thereby disturbing the algae liquid around the outer surface of the rotating shaft 112 and the back water surface of the upper scraper 111, preventing microalgae from attaching.

[0023] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A self-cleaning biofilm reactor for microalgae cultivation, comprising a culture sleeve (100), a support (101), an inlet pipe (102), a drain pipe (103), an air inlet pipe (104), and an exhaust pipe (105), characterized in that: The culture sleeve (100) is equipped with a cleaning mechanism (110). Two sets of cleaning mechanisms (110) are arranged in an array. The cleaning mechanism (110) is connected to the air inlet pipe (104). The cleaning mechanism (110) is used to clean the microalgae attached to the inner wall of the culture sleeve (100) during the culture stage. It also guides the detached microalgae to the axis of the culture sleeve (100) by rotating. The cleaning mechanism (110) is equipped with a gas guiding mechanism (120). During the rotation stage, the gas guiding mechanism (120) releases the gas into the detached microalgae by periodically reciprocating, so as to disturb the algal liquid at different depths.

2. The self-cleaning biofilm reactor for microalgae cultivation according to claim 1, characterized in that: The cleaning mechanism (110) includes a scraper (111) with its thin end attached to the inner wall of the culture sleeve (100). The thick end of the scraper (111) is fixedly connected to a rotating shaft (112) coaxial with the culture sleeve (100). Both ends of the rotating shaft (112) are rotatably connected to the culture sleeve (100), and one end is coaxially fixedly connected to a motor (113). The motor (113) is located outside the culture sleeve (100).

3. The self-cleaning biofilm reactor for microalgae cultivation according to claim 2, characterized in that: There is a mixing channel (106) between the scraper (111) and the culture sleeve (100). The scraper (111) is arc-shaped, with the thin end bent in the direction of rotation. The curved scraper (111) works with the horizontal flow of algal solution to guide the microalgae towards the axis. The inner side of the curved scraper (111) is the water-facing side, and the outer side is the water-repelling side.

4. The self-cleaning biofilm reactor for microalgae cultivation according to claim 2, characterized in that: The air inlet end of the air inlet pipe (104) is fixed to the culture sleeve (100). The air inlet pipe (104) is inserted into the rotating shaft (112). The rotating shaft (112) has a cavity for containing gas. Several exhaust grooves (107) are provided on the air inlet pipe (104). The exhaust grooves (107) are connected to the through grooves (114) on the rotating shaft (112).

5. The self-cleaning biofilm reactor for microalgae cultivation according to claim 3, characterized in that: The scraper (111) has a hollowed-out air delivery channel (116) for gas to flow through. The air delivery channel (116) corresponds to the through groove (114), and the air delivery channel (116) gradually narrows from the thick end to the thin end. Several external air holes (117) communicating with the air delivery channel (116) are opened along the water-facing surface of the scraper (111).

6. The self-cleaning biofilm reactor for microalgae cultivation according to claim 5, characterized in that: The air guiding mechanism (120) includes an air guiding arc plate (121) fitted inside the air conveying channel (116). The air guiding arc plate (121) corresponds to the water-facing side. The air guiding arc plate (121) is provided with a plurality of internal air holes (127). The internal air holes (127) are used to guide the air in the air conveying channel (116) to the water-facing side when they coincide with the external air holes (117), so as to disturb the scraped microalgae.

7. The self-cleaning biofilm reactor for microalgae cultivation according to claim 5, characterized in that: A guide groove (124) is provided on the inner side wall of the scraper (111). A slider (125) is fixedly provided on the air guide arc plate (121) corresponding to the guide groove (124). The slider (125) extends into the guide groove (124) and slides in the guide groove (124) to keep the slider (125) sliding against the inner wall of the air delivery channel (116).

8. The self-cleaning biofilm reactor for microalgae cultivation according to claim 6, characterized in that: The scraper (111) located below the rotating shaft (112) is upright. The inner air hole (127) near the thin end of the scraper (111) is in the same state as the outer air hole (117), while the inner air hole (127) away from the thin end of the scraper (111) is in the opposite state to the outer air hole (117). The air impacts the microalgae scraped off the water-facing surface. The scraper (111) located above the rotating shaft (112) is inverted. The inner air hole (127) near the thin end of the scraper (111) is misaligned with the outer air hole (117), while the inner air hole (127) far from the thin end of the scraper (111) is overlapped with the outer air hole (117). The ejected air is located deep in the algal liquid to extend the air floating path.

9. The self-cleaning biofilm reactor for microalgae cultivation according to claim 6, characterized in that: A tension spring (123) is elastically connected between the air guide arc plate (121) and the inner wall of the scraper (111). A horizontal plate (126) is fixedly installed on the air guide arc plate (121) near the thick end of the scraper (111), and the horizontal plate (126) extends away from the water-facing side.

10. The self-cleaning biofilm reactor for microalgae cultivation according to claim 9, characterized in that: A number of stop wheels (130) are fixedly installed on the air intake pipe (104). The stop wheels (130) have concave and convex surfaces. An L-shaped top plate (122) is slidably installed on the stop wheels (130). The top of the top plate (122) overlaps with the horizontal plate (126). A partition (115) is slidably connected on the top plate (122). The partition (115) is fixed to the rotating shaft (112). By rotating the stop wheels (130), the top plate (122) slides alternately on the concave and convex surfaces. The tension spring (123) works together to make the outer air hole (117) and the inner air hole (127) coincide and misalign.

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