JP7102597B1 - Microalgae culture equipment - Google Patents

Abstract

An object of the present invention is to provide a microalgae culture apparatus capable of increasing the dissolution rate of carbon dioxide. A microalgae culture apparatus has an internal space serving as a flow path for a culture solution containing microalgae, and includes a tank provided with a first opening and a second opening, and a tank extending in the vertical direction, a first channel having an upper portion connected to the first opening; a second channel extending vertically, having an upper portion connected to the second opening and a lower portion connecting to the lower portion of the first channel; an aeration device arranged below the second flow path and supplying a gas containing carbon dioxide to the culture solution in the second flow path from a supply port. The supply port is located below the liquid surface of the tank. The distance between the supply port and the liquid surface is 1.5 m or more. [Selection drawing] Fig. 2

Description

The present disclosure relates to a microalgae culture apparatus.

For example, microalgae that produce lipids and carbohydrates as raw materials such as biofuels are cultivated by photosynthesis. Microalgae absorb carbon dioxide dissolved in the culture medium during photosynthesis. Therefore, the conventional microalgae culture device includes a carbon dioxide supply device that supplies a gas containing carbon dioxide to the culture solution. In addition, conventionally, in order to make the distribution of microalgae in the culture solution uniform, or to make the concentration of carbon dioxide in the culture solution uniform, the culture solution has flowed through the flow path while maintaining a flow velocity of a certain level or higher. ..

In the microalgae culture apparatus of the following patent document, a part of the flow path in the tank is recessed downward and has a U shape. According to this U-shaped flow path, the culture solution flowing in the horizontal direction in the tank once flows downward. After that, it flows upward and returns to the inside of the tank. Further, carbon dioxide is supplied to the culture solution that flows upward on the U-shaped flow path.

Japanese Unexamined Patent Publication No. 2012-23978

In a general tank, the depth from the liquid surface to the bottom of the tank is as shallow as several tens of centimeters in order to absorb the light required for photosynthesis. Therefore, even if carbon dioxide is supplied near the bottom, the carbon dioxide is not sufficiently dissolved. Further, the microalgae culture apparatus of the patent document supplies carbon dioxide through a U-shaped flow path. However, in order to cause an air lift effect, the amount of carbon dioxide supplied through the U-shaped flow path is extremely large. Moreover, since the distance to the liquid surface is short, the dissolution rate of carbon dioxide is low.

The present disclosure provides a microalgae culture apparatus capable of increasing the dissolution rate of carbon dioxide.

In the microalgae culture apparatus on one side of the present disclosure, the internal space is a flow path for the culture solution containing microalgae, and extends in the vertical direction with a tank provided with a first opening and a second opening. A first flow path that connects the upper part to the first opening and a first flow path that extends in the vertical direction, the upper part connects to the second opening, and the lower part connects to the lower part of the first flow path. It includes two flow paths and an air diffuser that is arranged below the second flow path and supplies a gas containing carbon dioxide to the culture solution of the second flow path from a supply port. The supply port is located below the liquid level of the tank. The distance between the supply port and the liquid level is 1.5 m or more.

According to the present disclosure, the dissolution rate of carbon dioxide can be increased.

FIG. 1 is a plan view of the microalgae culture apparatus of the first embodiment as viewed from above. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a diagram showing a pipe according to the first modification. FIG. 4 is a partially enlarged view of the microalgae culture apparatus according to the modified example 2. FIG. 5 is a partially enlarged view of the microalgae culture apparatus according to the second embodiment. FIG. 6 is an overall view of the microalgae culture apparatus of the third embodiment.

Hereinafter, the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the embodiments for carrying out the following inventions (hereinafter referred to as embodiments). In addition, the components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, that is, those in a so-called equal range. Further, the components disclosed in the following embodiments can be appropriately combined.

(Embodiment 1)
FIG. 1 is a plan view of the microalgae culture apparatus of the first embodiment as viewed from above. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. As shown in FIGS. 1 and 2, the microalgae culture apparatus 100 includes a tank 1 for storing the culture solution 110, a water wheel 6, and two U-shaped pipes 10 (only one U-shaped pipe 10 is shown in FIG. 2). And two air diffusers 20 (only one air diffuser 20 is shown in FIG. 2).

As shown in FIG. 1, the tank 1 is a raceway type tank. Specifically, the tank 1 includes a bottom wall 2 extending in the horizontal direction, an annular side wall 3, and a partition wall 4 provided at the center of the side wall 3. Therefore, the inside of the tank 1 is a circulation flow path 5 in which the culture solution 110 flows in the horizontal direction and the culture solution 110 circulates around the partition wall 4.

The water turbine 6 rotates by transmitting power from a motor (not shown). As a result, the culture solution 110 moves the circulation flow path 5 in the direction of the arrow shown in FIG. 1 and circulates in the circulation flow path 5. As a result, the distribution of microalgae in the culture solution becomes uniform. In addition, the concentration of carbon dioxide dissolved in the culture solution becomes uniform.

As shown in FIG. 2, the tank 1 does not have a top wall covering the upper part of the circulation flow path 5. That is, the tank 1 is a so-called open pond (open system) tank. Therefore, the oxygen discharged from the microalgae by photosynthesis is discharged upward (outside the system) from the circulation flow path 5.

The bottom wall 2 of the tank 1 is relatively shallow. As a result, the microalgae distributed under the circulation flow path 5 can easily absorb sunlight. Further, the bottom wall 2 of the tank 1 is provided with two first openings 7 and two second openings 8.

The first opening 7 and the second opening 8 have a square shape when viewed from above as shown in FIG. 1, but in the present disclosure, they may have other shapes such as a circle. The first opening 7 is a hole for flowing the culture solution 110 from the circulation flow path 5 into the U-shaped pipe 10. The second opening 8 is a hole for allowing the culture solution 110 to flow out from the U-shaped pipe 10 to the circulation flow path 5. Therefore, the first opening 7 and the second opening 8 are a set of two.

As shown in FIG. 1, one set of the first opening 7 and the second opening 8 and another set of the first opening 7 and the second opening 8 are arranged apart from each other. Further, in a set of the first opening 7 and the second opening 8, the second opening 8 is arranged on the upstream side of the circulation flow path 5 with respect to the first opening 7.

As shown in FIG. 2, the U-shaped pipe 10 includes a first pipe 11 and a second pipe 12. The first pipe 11 and the second pipe 12 extend in the vertical direction. The upper part of the first pipe 11 is connected to the first opening 7. The upper part of the second pipe 12 is connected to the second opening 8. The lower part of the first pipe 11 and the lower part of the second pipe 12 are bent and connected to each other. As a result, the first flow path 11a of the first pipe 11 and the second flow path 12a of the second pipe 12 are continuous to form a U-shaped flow path.

The air diffuser 20 is a carbon dioxide supply device that supplies a gas containing carbon dioxide to the culture solution. The carbon dioxide concentration in the gas is not particularly limited. The gas supplied from the supply port 21 of the air diffuser 20 becomes bubbles 22 in the culture solution 110, but it is desirable that the diameter of the bubbles 22 is, for example, 5 mm or less in order to facilitate dissolution. Further, the amount of gas in the cross-sectional area of the flow path of the second pipe 12 supplied from the air diffuser 20 to the culture solution is preferably 2.0 NL (normal liter) / cm ² / min or less, for example. It is more preferably 0 NL (normal liter) / cm ² / min or less.

Further, the gas supplied from the air diffuser 20 may be an exhaust gas generated when the fossil fuel is burned. Since the exhaust gas contains carbon dioxide, the amount of carbon dioxide released into the atmosphere can be reduced. Further, the concentration of oxygen contained in the exhaust gas is preferably 10% or less.

The supply port 21 of the air diffuser 20 is arranged in the lower part of the second flow path 12a. That is, fine bubbles 22 are generated in the lower part of the second flow path 12a. Then, when the generated bubbles 22 rise, the culture solution 110 in the second flow path 12a receives an upward propulsive force. Therefore, the culture solution 110 in the second flow path 12a rises and flows into the circulation flow path 5. On the other hand, the culture solution 110 in the first flow path 11a is drawn toward the second flow path 12a. Therefore, in the first flow path 11a, the culture solution 110 flows downward. Further, since the culture solution 110 flows downward in the first flow path 11a, a part of the culture solution 110 flowing through the circulation flow path 5 is drawn into the first flow path 11a. As a result, a part of the culture solution 110 that has returned from the second flow path 12a to the circulation flow path 5 is drawn into the U-shaped pipe 10 again.

The distance L from the supply port 21 to the liquid level 5a of the circulation flow path 5 is 1.5 m or more, preferably 1.5 m or more and less than 6 m, and more preferably 1.5 m or more and less than 2.5 m. According to this, when the bubble size is 5 mm or less, the dissolution rate of carbon dioxide is 90% or more, and efficient dissolution is possible.

Next, the effect of the microalgae culture apparatus 100 of the first embodiment will be described. In the microalgae culture apparatus 100, the distance L from the supply port 21 to the liquid level 5a of the circulation flow path 5 is 1.5 m or more. Therefore, a sufficient distance is secured for the bubbles 22 to reach the liquid level 5a. Therefore, the amount of carbon dioxide dissolved in the culture solution 110 is significantly increased as compared with the conventional case.

Further, the first pipe 11 and the second pipe 12 are not inclined with respect to the vertical direction. Therefore, the rising air bubbles 22 are unlikely to adhere to the inner peripheral surface of the second pipe 12. If the bubbles 22 adhere to the inner peripheral surface of the second pipe 12, the bubbles 22 come into contact with each other to generate bubbles 22 having a larger diameter. Such bubbles 22 having a large diameter are difficult to dissolve in the culture solution 110. Therefore, in the present embodiment, since the second pipe 12 is not inclined with respect to the vertical direction, the rising air bubbles 22 adhere to the inner peripheral surface of the second pipe 12 to reduce the carbon dioxide dissolution rate. That is avoided.

Further, the second opening 8 is arranged on the upstream side of the circulation flow path 5 with respect to the first opening 7. As a result, a part of the culture solution 110 that has returned from the second flow path 12a to the circulation flow path 5 is drawn into the U-shaped pipe 10 again, so that the concentration of carbon dioxide in the culture solution 110 increases.

As described above, in the microalgae culture apparatus 100 of the first embodiment, the internal space is a flow path of the culture solution 110 containing the microalgae, and the tank 1 provided with the first opening 7 and the second opening 8 A first flow path 11a extending in the vertical direction and having an upper portion connected to the first opening 7, and a first flow path 11a extending in the vertical direction and extending in the vertical direction, having an upper portion connected to the second opening 8 and a lower portion of the first flow path 11a. A second flow path 12a connecting the lower part and an air diffuser 20 arranged in the lower part of the second flow path 12a to supply a gas containing carbon dioxide to the culture solution 110 of the second flow path 12a from the supply port 21. , Equipped with. The supply port 21 is located below the liquid level 5a of the tank 1. The distance L between the supply port 21 and the liquid level 5a is 1.5 m or more.

According to the first embodiment, most of the supplied carbon dioxide is dissolved. Therefore, the dissolution rate is higher than that of the conventional microalgae culture apparatus.

Further, in the first embodiment, the first opening 7 is arranged downstream of the flow of the culture solution 110 than the second opening 8.

According to this, a part of the culture solution 110 is repeatedly drawn into the U-shaped pipe 10, and the concentration of carbon dioxide in the culture solution 110 is increased.

Although the first embodiment has been described above, the present disclosure is not limited to this. For example, in the first embodiment, the U-shaped pipe 10 and the air diffuser 20 are each provided, but the present disclosure may have one or three or more.

FIG. 3 is a diagram showing a pipe according to the first modification. Further, the lower ends of the first pipe 11 and the second pipe of the first embodiment have an R shape (arc shape), but in the present disclosure, the lower ends of the first pipe 11 and the second pipe are bent at a right angle. It may be, and is not particularly limited. Further, in the present disclosure, one of the first pipe 11 and the second pipe 12 may be a straight pipe, and the other may be a spiral pipe that orbits around the straight pipe. Further, in the present disclosure, as shown in FIG. 3, the lower end of the first pipe 11 may be connected in the middle of the vertical direction of the second pipe 12. Further, in this modification 1, the air diffuser 20 may be arranged in the second pipe 12 below the portion where the first pipe 11 joins.

The supply of gas by the air diffuser 20 may be continuous or intermittent, and is not particularly limited.

Further, in the present disclosure, the first pipe 11 and the second pipe 12 may be inclined with respect to the vertical direction. However, when the second pipe 12 is inclined, the dissolution rate of carbon dioxide drops. Therefore, the example of the first embodiment is a preferable state.

Further, in the first embodiment, the first opening 7 and the second opening 8 are provided on the bottom wall 2 of the tank 1, but in the present disclosure, it is sufficient that the culture solution 110 can flow in. Therefore, the positions of the first opening 7 and the second opening 8 may be lower than the liquid level 5a of the culture solution 110 flowing through the circulation flow path 5.

As shown in FIG. 4, the first opening 7 may be arranged on the upstream side of the circulation flow path 5 with respect to the second opening 8. According to the microalgae culture apparatus 100A of the second modification, the culture solution 110 flowing out from the U-shaped pipe 10 is not immediately drawn into the U-shaped pipe 10.

(Embodiment 2)
FIG. 5 is a partially enlarged view of the microalgae culture apparatus according to the second embodiment. Next, the microalgae culture apparatus 100B of the second embodiment is different from the first embodiment in that the tank 1B is used instead of the tank 1 as shown in FIG. The tank 1B has a shape in which one end and the other end of a transparent tube through which light can be transmitted are connected. That is, the tank 1B has a top wall 9 that covers the upper part of the circulation flow path 5, and the cross-sectional shape of the circulation flow path 5 is annular.

Even with such a microalgae culture apparatus 100B, most of the supplied carbon dioxide is dissolved in the same manner as in the first embodiment. Further, along with this, the amount of carbon dioxide accumulated above the circulation flow path 5 is reduced. Therefore, the gas phase space M (see FIG. 5) in the tank 1B is also reduced. If the gas phase space M becomes large, the space of the culture solution 110 becomes relatively small, and the amount of the culture solution 110 also decreases. Therefore, according to the second embodiment, it is possible to avoid the disadvantage that the amount of the culture solution 111 is reduced.

(Embodiment 3)
FIG. 6 is an overall view of the microalgae culture apparatus of the third embodiment. The microalgae culture apparatus 100C of the third embodiment is a photobioreactor. Specifically, as shown in FIG. 6, the microalgae culture apparatus 100C of the third embodiment is different from the first embodiment in that the tank 1C is used instead of the tank 1. Further, the microalgae culture apparatus 100C is different from the first embodiment in that the pump 6C is used instead of the water wheel 6. Further, the microalgae culture device 100C is different from the first embodiment in that it includes a buffer tank 30, a pH measuring device 40, and a control device 50.

The tank 1C is a pipe in which a plurality of straight pipes 60 extending in the horizontal direction are connected by a plurality of bending pipes 61, and the culture solution 110 is flowed in the vertical direction while swirling. The straight tube 60 and the bent tube 61 are made of a transparent material to enable photosynthesis. The tank 1C may be supported by a dedicated support base that supports the tank 1C, or may be fixed to a wall surface that is irradiated with sunlight all day long in the building.

In the third embodiment, the culture solution 110 flows upward by the pump 6C. Therefore, the inflow port 62 of the tank 1C is located on the lower side, and the outflow port 63 is located on the upper side. The inflow port 62 of the tank 1C is connected to the lower part of the buffer tank 30 via the lower connecting pipe 70. The outlet 63 of the tank 1C is connected to the upper part of the buffer tank 30 via the upper connecting pipe 71.

The U-shaped pipe 10 is provided on the upper connecting pipe 71. Therefore, carbon dioxide is supplied to the culture solution 110 flowing from the tank 1C to the buffer tank 30. The U-shaped pipe 10 is arranged between the upper connecting pipe 71 and the lower connecting pipe 70. Therefore, the space between the upper connecting pipe 71 and the lower connecting pipe 70 is effectively utilized.

The buffer tank 30 temporarily stores the culture solution 110. A degassing hole 31 is provided in the upper part of the buffer tank 30. As a result, oxygen generated from microalgae, carbon dioxide supplied from the air diffuser 20 and not dissolved, nitrogen gas in the exhaust gas, and the like are discharged from the gas vent hole 31.

The pH measuring device 40 is a device for measuring the hydrogen ion concentration in the culture solution 110. The pH measuring device 40 is an upper connecting pipe 71 and is arranged on the upstream side of the U-shaped pipe 10. The control device 50 is a device that adjusts the amount of gas supplied from the air diffuser 20 based on the measurement result of the pH measuring device 40. According to this, the amount of gas supplied to the culture solution 110 becomes an appropriate amount. Further, when carbon dioxide is directly supplied to the tank 1C, the space of the gas phase becomes large, and the space of the culture solution 110 becomes relatively small. Therefore, also in the present embodiment, the disadvantage that the amount of the culture solution 111 is reduced can be avoided as in the second embodiment.

Although the third embodiment has been described above, the present disclosure does not have to include the control device 50. That is, the operator may confirm the measurement result of the pH measuring device 40, and the operator may adjust the supply amount from the air diffuser 20. In the tank 1C of the present embodiment, the culture solution 110 flows upward, but the present disclosure may allow the culture solution 110 to flow downward, and there is no particular limitation. Further, when the culture solution 110 flows downward in the tank 1C, the U-shaped pipe 10 may be connected to the lower connecting pipe 70 or the upper connecting pipe 71.

Further, although the microalgae culture device 100C of the third embodiment includes a pH measuring device 40, the present disclosure measures the concentration of carbon dioxide dissolved in the culture solution 110 instead of the pH measuring device 40. Equipped with a measuring device. Then, the control device 50 may adjust the amount of gas supplied from the air diffuser 20 based on the measurement result of the carbon dioxide concentration measuring device. Alternatively, both the pH measuring device 40 and the carbon dioxide concentration measuring device may be provided. In such a case, the control device 50 adjusts the amount of gas supplied from the air diffuser 20 based on the measurement result of the pH measuring device 40 and the measurement result of the carbon dioxide concentration measuring device.

1, 1B, 1C tank 6 Water wheel 6C Pump 5 Circulation flow path 7 1st opening 8 2nd opening 10 U-shaped pipe 11 1st pipe 12 2nd pipe 11a 1st flow path 12a 2nd flow path 20 Air diffuser 21 Supply port 22 Bubbles 30 Buffer tank 31 Degassing hole 40 pH measuring device 50 Control device 60 Straight pipe 61 Bending pipe 70 Lower connecting pipe 71 Upper connecting pipe 100, 100A, 100B, 100C Microalgae culture device 110 Culture solution

Claims (5)

The internal space serves as a circulation channel for the culture solution containing microalgae, and a tank provided with a first opening and a second opening, and a tank.
A first flow path extending in the vertical direction and having an upper portion connected to the first opening,
A second flow path that extends in the vertical direction, the upper part of which connects to the second opening, and the lower part of which connects to the lower part of the first flow path.
An air diffuser arranged in the lower part of the second flow path and supplying a gas containing carbon dioxide to the culture solution in the second flow path from a supply port.
With
The tank is
A tube through which light can pass and the culture solution flowing inside can be photosynthesized.
A connecting tube connected to the outlet of the photosynthetic tube,
At least
The first opening and the second opening are provided in the connecting pipe.
The supply port is located below the liquid level of the tank and is located below.
The distance between the supply port and the liquid level is 1.5 m or more.
The second opening is a microalgae culturing device arranged closer to the outlet of the photosynthetic tube than the first opening. A pH measuring device for measuring the pH value of the culture solution and
A control device that adjusts the amount of gas supplied from the air diffuser based on the measurement results of the pH measuring device, and
With
The microalgae culturing device according to claim 1, wherein the pH measuring device is arranged closer to the outlet of the photosynthetic tube than the second opening. A carbon dioxide concentration measuring device for measuring the concentration of the carbon dioxide dissolved in the culture solution, and
A control device that adjusts the amount of gas supplied from the air diffuser based on the measurement results of the carbon dioxide concentration measuring device, and
With
The microalgae cultivating device according to claim 1, wherein the carbon dioxide concentration measuring device is arranged closer to the outlet of the photosynthetic tube than the second opening. A pH measuring device for measuring the pH value of the culture solution and
A carbon dioxide concentration measuring device for measuring the concentration of the carbon dioxide dissolved in the culture solution, and
A control device that adjusts the amount of gas supplied from the air diffuser based on the measurement result of the pH measuring device and the measurement result of the carbon dioxide concentration measuring device.
With
The microalgae cultivating device according to claim 1, wherein the pH measuring device and the carbon dioxide concentration measuring device are arranged closer to the outlet of the photosynthetic tube than the second opening. The gas supplied from the air diffuser is an exhaust gas generated by combustion of fossil fuel.
The microalgae cultivating apparatus according to any one of claims 1 to 4, wherein the exhaust gas contains carbon dioxide and oxygen, and the concentration of oxygen in the exhaust gas is 10% or less.

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