Patent Application
20210348106
This disclosure relates to a gas dissolution device and an algae cultivation device.
A gas dissolution device has been known (e.g., Patent Literature 1). The conventional gas dissolution device supplies a part of culture solution stored in a culture vessel to a dissolution vessel together with high-concentration carbonic acid gas, and quickly dissolves the carbonic acid gas in the culture solution by generating a turbulent flow in the dissolution vessel. The culture solution in which the carbonic acid gas has been dissolved is then returned to the culture vessel from the dissolution vessel.
Patent Literature 1: JP 1994-153912 A
The conventional gas dissolution device dissolves carbonic acid gas in the dissolution vessel rapidly and with high concentration in response to the shortage of the carbonic acid gas in the culture vessel, and the culture solution in which the carbonic acid gas has been dissolved is returned to the culture vessel. With this, the concentration of carbonic acid gas in the culture solution recovers rapidly. However, there is a concern that the high-concentration carbonic acid gas which has been dissolved in the culture solution may be released into the atmosphere easily due to the turbulent flow generated by continuous stirring of the culture solution. Additionally, although the carbonic acid gas is supplied from a carbonic acid gas source, it is desirable from the environmental and economic aspects that the carbonic acid gas has a large dissolved amount with respect to the input amount. That is, an index of dissolution efficiency, i.e., a ratio of dissolved amount to input amount, can be used for evaluation, and it is desirable to achieve a high dissolution efficiency.
The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a gas dissolution device and an algae cultivation device capable of improving a gas dissolution efficiency with respect to liquid.
In order to achieve the above object, a gas dissolution device of the present disclosure comprises a dissolution vessel that stores a part of liquid stored in a main vessel, a gas supply pipe that is connected to a gas supply source and supplies gas through a tip part inserted into the liquid stored in the dissolution vessel, a gas discharger that is provided at the tip part of the gas supply pipe and turns the gas supplied from the tip part into bubbles, and a gas controller that controls a flowrate of the gas flowing in the gas supply pipe. A water depth from the gas discharger to a liquid level of the liquid stored in the dissolution vessel is set deeper than a water depth of the liquid stored in the main vessel.
Additionally, in order to achieve the above object, an algae cultivation device of the present disclosure comprises a culture vessel that stores culture solution for culturing algae, and a gas dissolution device that dissolves carbon dioxide in the culture solution. The gas dissolution device comprises a dissolution vessel that stores a part of the culture solution stored in the culture vessel, a first circulation pipe and a second circulation pipe that communicate between the culture vessel and the dissolution vessel, a first pump that delivers the culture solution stored in the culture vessel to the dissolution vessel through the first circulation pipe, a second pump that returns the culture solution stored in the dissolution vessel to the culture vessel through the second circulation pipe, a gas supply pipe that is connected to a carbon dioxide source and supplies carbon dioxide through a tip part inserted into the culture solution stored in the dissolution vessel, a gas discharger that is provided at the tip part of the gas supply pipe and turns the carbon dioxide supplied from the tip part into bubbles, and a gas controller that controls a flowrate of the carbon dioxide flowing in the gas supply pipe. A water depth from the gas discharger to a liquid level of the culture solution stored in the dissolution vessel is set deeper than a water depth of the culture solution stored in the culture vessel.
With the gas dissolution device and the algae cultivation device of the present disclosure, it is possible to improve the gas dissolution efficiency with respect to liquid.
Hereinafter, an embodiment for implementing a gas dissolution device and an algae cultivation device of the present disclosure will be described with reference to the accompanying drawings.
An algae cultivation device 1 of the first embodiment is a device for artificially culturing microalgae and includes a culture vessel 2 and a gas dissolution device 3.
It should be understood that algae herein mean photosynthetic organisms that generate oxygen excluding moss plants, fern plants, and seed plants, and collectively refers to plants with photosynthetic pigments that live in water. Algae are excellent in growth, have a high yield per area, and accumulate a large amount of useful substances such as fats and oils. Hence, algae have a high utility value so as to be used as raw materials for health foods, supplements, chemical raw materials, biofuels, etc. The microalgae cultivated by the algae cultivation device 1 are unicellular algae having a body length of several μm to several hundred and are of a size that the individual existence is hardly visible by a human naked eye. The examples of the microalgae include green algae such as Spirulina, Euglena, Chlorella, Dunaliella salina, and Botryococcus.
The culture vessel 2 (main vessel) is a water vessel that stores culture solution 100 (liquid) in which microalgae are suspended. The culture vessel 2 shown in
The gas dissolution device 3 controls a carbon dioxide concentration of the culture solution 100 in the culture vessel 2. To that end, the gas dissolution device 3 dissolves carbon dioxide (gas) in a part of the culture solution 100 retrieved from the culture vessel 2, and returns the culture solution 100 in which the carbon dioxide has been dissolved to the culture vessel 2. Here, inputting an excess amount of carbon dioxide into the culture solution 100 may inhibit the culture of microalgae. On the other hand, it is possible to rapidly culture the microalgae which is rich in useful substances by appropriately controlling the carbon dioxide concentration of the culture solution 100.
The gas dissolution device 3 is installed on a trolly with wheels (not illustrated) and includes a dissolution vessel 10, a first circulation pipe 20, a second circulation pipe 30, a circulation mechanism 40, a gas supply pipe 50, a mass flow controller 60 (gas controller), and a pH monitor 70.
The dissolution vessel 10 is a vessel for storing a part of the culture solution 100 retrieved from the culture vessel 2 and dissolving carbon dioxide into the stored culture solution 100. The dissolution vessel 10 has a vertically extended tube shape having a bottom surface 11 and side surface 12, and the upper part of the dissolution vessel 10 is closed by an upper surface 13. In this embodiment, the bottom surface 11 is a curved surface, and the upper surface 13 is covered by a non-sealed lid.
The side surface 12 of the dissolution vessel 10 has a sufficient height such that a water depth H2 from a gas discharger 53 described later to a liquid level 10a of the culture solution 100 stored in the dissolution vessel 10 is adjustable to be deeper than the water depth H1 in the culture vessel 2. The liquid amount of the culture solution 100 stored in the dissolution vessel 10 is set to equal to or less than one-twentieth of the liquid amount of the culture solution 100 stored in the culture vessel 2, and in this embodiment, is set to 5 liters. A liquid level sensor 14 is installed on the upper surface 13 of the dissolution vessel 10 to monitor the amount of the culture solution 100 stored therein. The detected values of the liquid level sensor 14 are input to a pump controller 43 of the circulation mechanism 40.
The first circulation pipe 20 communicates the culture vessel 2 and the dissolution vessel 10 such that the culture solution 100 to be delivered from the culture vessel 2 to the dissolution vessel 10 passes through the first circulation pipe 20. As shown in
In the first circulation pipe 20, a first flowmeter 24 and a first pump 41 of the circulation mechanism 40 are provided. The first flowmeter 24 is placed downside of the first pump 41. With the first flowmeter 24, the flowrate of the culture solution 100 which is discharged by the first pump 41 and delivered into the dissolution vessel 10 is detected. The detected values of the first flowmeter 24 are input to the pump controller 43 of the circulation mechanism 40.
The second circulation pipe 30 communicates the culture vessel 2 and the dissolution vessel 10 such that the culture solution 100 to be returned from the dissolution vessel 10 to the culture vessel 2 passes through the second circulation pipe 30. As shown in
In the middle of the second circulation pipe 30, a monitoring vessel 71 of the pH monitor 70, a second flowmeter 34, and a second pump 42 of the circulation mechanism 40 are provided. The monitoring 71 is placed in the uppermost stream, and the second pump 42 and the second flowmeter 34 are placed downstream of the monitoring vessel 71 in this order. With the second flowmeter 34, the flowrate of the culture solution 100 which is discharged by the second pump 42 and returned to the culture vessel 2 is detected. The detected values of the second flowmeter 34 are input to the pump controller 43 of the circulation mechanism 40.
Further, a one end 35a of a discharge pipe 35 is connected to a part of the second circulation pipe 30 between the monitoring vessel 71 and the second pump 42. The discharge pipe 35 is a pipe to return the culture solution 100 discharged from the dissolution vessel 10 to the culture vessel 2 while bypassing the monitoring vessel 71. The other end 35b of the discharge pipe 35 is connected to a liquid discharge opening 36 formed on the bottom surface 11 (bottom part) of the dissolution vessel 10. Accordingly, the culture solution 100 stored in the dissolution vessel 10 flows into the discharge pipe 35 through the liquid discharge opening 36. Further, a switching valve 37 is provided in the discharge pipe 35. The switching valve 37 is a normally closed valve and allows the culture solution 100 in the discharge pipe 35 to directly flow into the second circulation pipe 30 when open. The opening and closing of the switching valve 37 are operated manually.
The circulation mechanism 40 delivers a part of the culture solution 100 stored in the culture vessel 2 to the dissolution vessel 10 through the first circulation pipe 20 and returns the culture solution 100 stored in the dissolution vessel 10 to the culture vessel 2 through the second circulation pipe 30. In this embodiment, the circulation mechanism 40 continuously circulates the culture solution 100 between the culture vessel 2 and the dissolution vessel 10. The circulation mechanism 40 includes the first pump 41, the second pump 42, and the pump controller 43.
The first pump 41 is provided in the first circulation pipe 20. The first pump 41 is a magnet pump which sucks and discharges the culture solution 100 in the culture vessel 2 to deliver the culture solution 100 from the culture vessel 2 to the dissolution vessel 10. The second pump 42 is provided in the second circulation pipe 30. The second pump 42 is a magnet pump which sucks and discharges the culture solution in the dissolution vessel 10 to deliver the culture solution 100 from the dissolution vessel 10 to the culture vessel 2. In this embodiment, the first pump 41 has better performance than the second pump 42.
It should be noted that the first pump 41 may be set to have similar performance to the second pump 42. In such a case, a mechanism for adjusting the output may be provided in order to adjust the performance of the pumps similar to each other. It should also be noted that the first pump 41 and the second pump 42 are not limited to magnet pumps but may be diaphragm pumps or turbo pumps such as centrifugal pumps, mixed flow pumps and axial flow pumps.
The pump controller 43 controls the operation of the first pump 41 and the second pump 42 to circulate one-twentieth or less of the liquid amount (in this embodiment, 1 to 2 liters) of the culture solution 100 stored in the culture vessel 2. The pump controller 43 includes a Central Processing Unit (CPU), a memory, and the like, and the detected values of the liquid level sensor 14, the detected values of the first flowmeter 24, and the detected values of the second flowmeter 34 are input to the pump controller 43. The pump controller 43 controls the operation of the first and second pumps 41, 42 to maintain a constant liquid amount of the culture solution 100 stored in the dissolution vessel 10 based on the detected values of the liquid level sensor 14. Additionally, the pump controller 43 controls the operation of the first pump 41 and the second pump 42 based on the detected values of the first flowmeter 24 and the second flowmeter 34, such that the flowrate of the culture solution 100 which is discharged by the first pump 41 in the first circulation pipe 20 and the flowrate of the culture solution 100 which is discharged by the second pump 42 in the second circulation pipe 30 become equal to each other.
The gas supply pipe 50 is a pipe through which the carbon dioxide (gas) is input to the dissolution vessel 10 from a carbon dioxide cylinder B (gas source or carbon dioxide source). A one end 51 of the gas supply pipe 50 is connected to the carbon dioxide cylinder B. The other end 52 (tip part) of the gas supply pipe 50 penetrates the side surface 12 of the dissolution vessel 10 and is inserted inside the culture solution 100 stored in the dissolution vessel 10. Further, the gas discharger 53 is fixed to the other end 52 of the gas supply pipe 50 in the dissolution vessel 10.
The gas discharger 53 turns the carbon dioxide supplied from the gas supply pipe 50 into fine bubbles (e.g., microbubbles and nanobubbles. Hereinafter, collectively referred to as “bubbles”) inside the culture solution 100 stored in the dissolution vessel 10. In this embodiment, the gas discharger 53 has a cylindrical shape and is formed of a porous ceramic material, a sintered alloy, a polymer compound, or the like. The pore diameters of the gas discharger 53 is 1 to 100 μm.
The gas discharger 53 generates bubbles having a sphere-equivalent diameter of 2.5 mm or smaller, preferably 1.0 mm or smaller. The number of bubbles which are generated by the gas discharger 53 and pass through a unit cross-section area per unit time is 35/min/cm2 or more.
The gas discharger 53 is arranged at a position such that the water depth H2 to the liquid level 10a of the culture solution 100 stored in the dissolution vessel 10 (i.e., depth from gas discharger 53 to liquid level 10a) is deeper than the water depth H1 of the culture solution 100 stored in the culture vessel 2. In this embodiment, the gas discharger 53 is positioned such that the water depth H2 becomes 450 mm or deeper. However, in case where the gas discharger 53 generates bubbles having the sphere-equivalent diameter of 1.4 mm or smaller, the water depth H2 may be set to 350 mm or deeper.
In the gas dissolution device 3, the pore diameter of the gas discharger 53, the water depth H2, as well as the liquid amount and the setting values of the dissolution vessel 10 are adjusted in order to control the dissolved amount of carbon dioxide in the culture solution 100 stored in the dissolution vessel 10 to be 200 mg/L or less in terms of dissolved inorganic carbon weight.
The mass flow controller 60 measures the flowrate of carbon dioxide flowing in the gas supply pipe 50 and controls the flowrate of carbon dioxide. The mass flow controller 60 receives a control command from a pH controller 72 provided in the pH monitor 70. The mass flow controller 60 controls the flowrate of carbon dioxide flowing in the gas supply pipe 50 based on the control command from the pH controller 72.
The pH monitor 70 monitors a pH value of the culture solution 100 stored in the dissolution vessel 10. The pH monitor 70 includes the monitoring vessel 71, the pH controller 72, and a pH sensor 73.
The monitoring vessel 71 is provided in the middle of the second circulation pipe 30. The monitoring vessel 71 communicates with the dissolution vessel 10 through the second circulation pipe 30 and stores a part of the culture solution 100 flowing out of the dissolution vessel 10. The monitoring vessel 71 has a vertically extended tube shape having a bottom surface 71a and a side surface 71b, and the upper part of the monitoring vessel 71 is closed by an upper surface 71c. In this embodiment, the bottom surface 71a is a curved surface, and the upper surface 71c is covered by a non-sealed lid. The liquid amount of the culture solution 100 stored in the monitoring vessel 71 can be arbitrary determined, and in this embodiment, set to 1 liter.
An inlet 74a through which the culture solution 100 is flown into the monitoring vessel 71 via the second circulation pipe 30 is formed on the bottom surface 71a. An outlet 74b through which the culture solution 100 is flown out of the monitoring vessel 71 is formed on the side surface 71b. The monitoring vessel 71 is positioned such that the height of the liquid level 71d of the culture solution 100 stored in the monitoring vessel 71 is equal to the height of the liquid level 10a of the culture solution 100 stored in the dissolution vessel 10.
The pH controller 72 includes, for example, a Central Processing Unit (CPU) and a memory, and the detected values of the pH sensor 73 are input to the pH controller 72. The pH controller 72 outputs the control command to the mass flow controller 60 based on the detected value of the pH sensor 73 such that the pH value falls within an appropriate range according to a required dissolved amount of carbon dioxide for algae cultivation. For example, the pH controller 72 outputs a control command to stop the inflow of carbon dioxide to the dissolution vessel 10 when the detected pH value becomes a predetermined value or less.
The pH sensor 73 is installed on the upper surface 71c of the monitoring vessel 71, and the sensor part thereof is inserted into the culture solution 100 stored in the monitoring vessel 71. The pH value of the culture solution 100 stored in the monitoring vessel 71 is detected by the pH sensor 73.
A problem of a conventional gas dissolution device will be explained below.
In algae cultivation, it is important to control the carbon dioxide concentration of culture solution within an appropriate range, as described above. In conventional devices, the dissolution of carbon dioxide in culture solution is generally performed by directly inserting an air diffusing tube (air diffuser) into the culture solution. However, when the air diffusing tube is directly inserted into the culture solution, the dissolution amount of carbon dioxide is heavily influenced by the water depth of a culture vessel and/or the size of the diffused bubbles. Further, a mixed air containing 1-5% of carbon dioxide is often used as the gas to be diffused, and thus it is difficult to dissolve the carbon dioxide efficiently.
With a standard culture vessel having a shallow water depth of about 20-30 cm, it is generally difficult to retain carbon dioxide in culture solution until the carbon dioxide is sufficiently dissolved. Therefore, using one of the main dissolution methods, “a method of directly inserting an air diffuser into a culture vessel” may result in the dissolution efficiency of the input carbon dioxide of one-hundredth or less. Further, it is not desirable to release a large amount of undissolved carbon dioxide into the atmosphere due to the aspect of environmental protection. However, the amount of undissolved carbon dioxide released into the atmosphere will increase if the dissolution efficiency of carbon dioxide is low. Additionally, if the dissolution efficiency of carbon dioxide is low, the cultivation period will be prolonged due to the lack of carbon dioxide and thereby the costs of the cultivation will also increase.
To overcome the above deficiencies, a part of or the entire water depth of a culture vessel may be deepened to prolong the time period to retain carbon dioxide in the culture solution. In this case, however, the closer to the bottom surface of the culture vessel, the lower the culture efficiency due to insufficient light. Additionally, it may become difficult to install the culture vessel as the water depth of the culture vessel increases.
Alternatively, nanobubbles or microbubbles may be used as a high-efficiency dissolution method of carbon dioxide. However, aerating the micro-bubbled carbon dioxide into the culture solution will reduce the apparent absorbance of the culture solution. Therefore, it may not be suitable for algae cultivation.
It is also necessary to minimize a physical load on algae in order to avoid damaging the algae cells. To that end, it is desirable not to circulate the culture solution with a high pressure and high flowrate pump, not to generate swirling flow using such a pump, and not to generate bubbles with a Venturi tube. That is, although the importance of dissolving carbon dioxide in the culture solution has been recognized for algae cultivation, there is still a room to improve the dissolution method.
Hereinafter, a condition for inputting carbon dioxide and the dissolution efficiency of carbon dioxide with the gas dissolution device 3 of the first embodiment will be described.
As indicated by the relations shown in
As shown in
As shown in
It is also possible to calculate the number of bubbles passing through a cross-section area per unit time based on the relation between the average number of the generated bubbles and the cross-section area of the dissolution vessel 10. The number of bubbles passing through the cross-section area per unit time varies depending on the size of the pore diameter of the gas discharger 53. That is, as shown in
Hereinafter, results of carbon dioxide dissolution experiments with the gas dissolution device 3 of the first embodiment, a first comparative example, and a second comparative example will be described.
In the experiment, a raceway-type vessel shown in
In the gas dissolution device 3 of the first embodiment, a constant amount (1-2 L/min.) of the liquid (tap water) is supplied to the dissolution vessel 10 (liquid amount of 5 liters) from the raceway-type culture vessel 2 (liquid amount of 150 liters) shown in
In the experiment, the dissolved mount of carbon dioxide is measured in the culture vessel 2 as the dissolved inorganic carbon weight. In the gas dissolution device 3 of the first embodiment, when the pH value detected in the monitoring vessel 71 became a predetermined value or less, the supply of carbon dioxide was terminated.
As shown in
The gas dissolution device 3 of the first embodiment includes the first circulation pipe 20 that supplies the culture solution 100 stored in the culture vessel 2 to the dissolution vessel 10. The liquid ejection port 23 of the first circulation pipe 20 is positioned higher than the gas discharger 53 fixed to the other end of the gas supply pipe 50. Therefore, the culture solution 100 ejected from the first circulation pipe 20 flows down toward the bottom surface 11 of the culture vessel 2. On the other hand, the carbon dioxide discharged from the gas discharger 53 flows upward in the dissolution vessel 10.
Accordingly, the flow direction of the culture solution 100 supplied to the dissolution vessel 10 and the moving direction of carbon dioxide input to the dissolution vessel 10 are opposite to each other, thereby improving the dissolution efficiency of carbon dioxide.
The gas dissolution device 3 of the first embodiment includes the second circulation pipe 30 that returns the culture solution 100 stored in the dissolution vessel 10 to the culture vessel 2. The liquid suction port 33 of the second circulation pipe 30 is open to the side surface 12 of the dissolution vessel 10 and is positioned lower than the gas discharger 53. As described above, the carbon dioxide discharged through the gas discharger 53 flows upward in the dissolution vessel 10. Accordingly, the carbon dioxide discharged through the gas discharger 53 seldomly flows into the second circulation pipe 30. Therefore, it is possible to keep the input carbon dioxide in the dissolution vessel 10 in order to sufficiently dissolve the carbon dioxide, thereby further improving the dissolution efficiency of carbon dioxide.
Further, the gas dissolution device 3 of the first embodiment includes the pH monitor 70 that monitors the pH value of the culture solution 100 stored in the dissolution vessel 10. The mass flow controller 60 that controls the flowrate of the carbon dioxide input to the dissolution vessel 10 controls the carbon dioxide flowing through the gas supply pipe 50 based on the monitoring result of the pH monitor 70.
With this, it is possible to promptly detect the change in the pH value due to the change in the flowrate of the carbon dioxide. Accordingly, it is possible to appropriately control the input amount of carbon dioxide compared to the case where the flowrate of carbon dioxide input to the dissolution vessel 10 is controlled based on, for example, the pH value of culture solution 100 stored in the culture vessel 2.
Additionally, the pH monitor 70 includes the monitoring vessel 71 that communicates with the dissolution vessel 10 and the pH sensor 73 that measures the pH value of the culture solution 100 stored in the monitoring vessel 71. With this, the pH value of the culture solution 100 stored in the dissolution vessel 10 is measured outside the dissolution vessel 10, thereby preventing the bubbles of the carbon dioxide from adhering to the pH sensor 73. Accordingly, it is possible to suppress the occurrence of an error in the pH measurement and to improve the measurement accuracy of the pH value. Additionally, the culture solution 100 flown into the monitoring vessel 71 has an even carbon dioxide concentration since it is a liquid after dissolving the carbon dioxide. Therefore, it is possible to further suppress the occurrence of an error in the pH measuring and to improve the measurement accuracy of the pH value.
In the first embodiment, the height of the liquid level 71d of the culture solution 100 stored in the monitoring vessel 71 is equal to the height of the liquid level 10a of the culture solution 100 stored in the dissolution vessel 10. That is, the monitoring vessel 71 is provided at a position to allow the heights of the liquid levels 71d, 10a to be equal to each other. With this, it is possible to store the culture solution 100 up to the vicinity of each upper surface 13, 71d without overflowing the culture solution 100 from the corresponding vessel 10, 71. Therefore, it is possible to reduce the size of the device since there is no need to enlarge the dissolution vessel 10 and the monitoring vessel 71 unnecessarily.
In the gas dissolution device 3 of the first embodiment, the liquid discharge opening 36 is formed on the bottom surface 11 (bottom part) of the dissolution vessel 10, and the liquid discharge opening 36 is connected to the discharge pipe 35 having the switching valve 37. Once the switching valve 37 is open, the culture solution 100 in the dissolution vessel 10 flows into the discharge pipe 35 through the liquid discharge opening 36 and returns to the culture vessel 2 while bypassing the monitoring vessel 71. Accordingly, it is possible to discharge sediment such as algae that have been settled in the vicinity of the bottom surface 11 of the dissolution vessel 10 from the dissolution vessel 10 together with the culture solution 100.
The algae cultivation device 1 of the first embodiment uses the gas dissolution device 3 of the first embodiment to dissolve carbon dioxide in the culture solution 100. With this, it is possible to efficiently input carbon dioxide required for the algae cultivation to the culture vessel 2. Further, in the first embodiment, the carbon dioxide is dissolved in the culture solution 100 stored in the dissolution vessel 10, and then the culture solution 100 in which the carbon dioxide has been dissolved is returned to the culture vessel 2. Therefore, it is possible to prevent a sudden change in the pH value of the culture solution 100 stored in the culture vessel 2, and to prevent the bubbles of carbon dioxide from contacting the algae cells thereby suppressing damage on the algae cells in the culture solution 100.
Although the gas dissolution device and the algae cultivation device of the present disclosure have been described based on the first embodiment, it should not be limited thereto. It should be appreciated that variations or modifications may be made in the embodiment by persons skilled in the art without departing from the scope of the present invention as defined by the following claims.
In the first embodiment, the gas dissolution device 3 is exemplarily installed on a trolly with wheels. In this case, it is possible to move the gas dissolution device 3 as needed by disconnecting the one end 21 of the first circulation pipe 20 and the one end 31 of the second circulation pipe 30 from the culture solution 100 stored in the culture vessel 2. It is also possible to retrofit the gas dissolution device 3 to the culture vessel 2. However, it is not limited thereto. The first and the second circulation pipes 20, 30 may be fixed to the culture vessel 2 to integrate the gas dissolution device 3 and the culture vessel 2.
In the first embodiment, the culture vessel 2 and the dissolution vessel 10 are connected to each other through the first and the second circulation pipes 20, 30. Carbon dioxide is input to the culture solution 100 in the dissolution vessel 10, and the culture solution 100 is continuously circulated between the culture vessel 2 and the dissolution vessel 10 by the circulation mechanism 40. However, it is not limited thereto. The culture vessel 2 and the dissolution vessel 10 may be independently installed. In this case, a certain amount of culture solution 100 may be pumped out from the culture vessel 2 to the dissolution vessel 10, and the culture solution 100 may be pumped out from the dissolution vessel 10 to return to the culture vessel 2 after dissolving carbon dioxide to the culture solution 100 in the dissolution vessel 10.
In the first embodiment, the one end 35a of the discharge pipe 35 connected to the bottom surface 11 of the dissolution vessel 10 is connected to a part of the second circulation pipe 30 between the monitoring vessel 71 and the second pump 42. The culture solution 100 that has been settled at the bottom of the culture vessel 2 is flown into the discharge pipe 35 and is returned to the culture vessel 2 while bypassing the monitoring vessel 71. However, it is not limited thereto. For example, the one end 35a of the discharge pipe 35 may be inserted into a container such as a bucket, such that the sediment settled at the bottom of the culture vessel 2 is not returned to the culture vessel 2. Alternatively, the one end 35a of the discharge pipe 35 may directly be inserted to the culture vessel 2, such that the sediment is returned to the culture vessel 2 while bypassing the second pump 42. This configuration may be advantageous since it is possible to prevent the second pump 42 from being clogged by the sediment contained in the culture solution 100 flowing in the discharge pipe 35.
In the first embodiment, the water depth H2 from the gas discharger 53 to the liquid level 10a of the culture solution 100 stored in the dissolution vessel 10 is set to 450 mm or deeper. However, it is not limited thereto. Algae cultivation is often carried out in a relatively shallow environment where the water depth H1 of the culture vessel 2 is commonly set to about 200-300 mm, whereas the water depth H1 of the culture vessel 2 of the first embodiment is set to 130-135 mm. Therefore, the water depth H2 may be set to twice or more the water depth H1 of the culture solution 100 stored in the culture vessel 2.
In the first embodiment, the liquid stored in the culture vessel 2 or in the dissolution vessel 10 is used as the culture solution 100 in which microalgae are suspended, and carbon dioxide is used as the gas to be dissolved in the culture solution 100. However, it is not limited thereto. For example, oxygen, ozone, hydrogen, nitrogen, or the like may be dissolved in water. Alternatively, oxygen or another gas may be dissolved in industrial wastewater. Further, a plurality of gas dissolution devices 3 may be installed on the main vessel, namely the culture vessel 2.
The present application is based on and claims priority to Japanese Patent Application No. 2018-201899, filed on Oct. 26, 2018, the disclosure of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-201899 | Oct 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/041493 | 10/23/2019 | WO | 00 |
