JP2015053872A - Culture tank for photosynthetic microorganism and culture apparatus for photosynthetic microorganism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a culture tank for photosynthetic microorganisms and a culture apparatus for photosynthetic microorganisms which allow cost reduction.SOLUTION: A culture tank for photosynthetic microorganisms has a circulation water channel in which a culture solution M containing photosynthetic microorganisms circulates. A cross-sectional shape D of a water channel is formed by cutting the water channel by a plane which has a normal in a flow direction X of the culture solution M circulating in the circulation water channel. The width of the cross-sectional shape becomes narrower toward the lower side of the shape. A culture apparatus for photosynthetic microorganisms includes the culture tank for photosynthetic microorganisms, a circulation agitation device, a diffused gas supply device, a photosynthetic microorganism recovery device, and a control device. The control device controls the photosynthetic microorganism recovery device so that the rotating speed of a paddle during recovery operation is slower than that during culture operation.

Description

  The present invention relates to a photosynthetic microorganism culture tank and a photosynthetic microorganism culture apparatus used for culturing photosynthetic microorganisms.

In recent years, the concept of carbon neutral has permeated from the viewpoint of suppressing the emission of carbon dioxide (CO ₂ ), one of the greenhouse gases. In addition, as a carbon neutral energy source, the use of fuel (biofuel) produced from biomass-derived raw materials has begun in part.

  However, when edible plants such as soybeans, corn, and palm are used as raw materials, concerns about food shortages are a problem. Further, when a non-edible plant such as Jatropha or camelina is used as a raw material, the production amount per unit area is lower than that of an edible plant. For this reason, when plants are used as raw materials, there is a problem of deforestation that occurs in order to secure wide arable land. Thus, among these plants, attention has been focused on photosynthetic microorganisms that have about 10 times higher oil production capacity per unit area than palm, which has higher oil production capacity. As such photosynthetic microorganisms, for example, microalgae (including cyanobacteria) are known, biosynthesizes biofuel and components that can be a raw material for biofuel, and accumulates in cells.

  The following three types of reactors (culture tanks and bioreactors) for culturing photosynthetic microorganisms such as microalgae (including cyanobacteria) are often used. The first is a method using pounds (ponds) such as raceway pounds. Although this method requires a large installation area, there is an advantage that the initial cost can be kept low. The second is a plate reactor. The plate type reactor can increase the light receiving area, but the initial cost is increased. The third is a pipe reactor. The pipe type reactor can increase the light receiving area, though not as much as the plate type reactor, but it is not as good as the system using pounds (ponds) at a low initial cost.

  Patent Documents 1 to 3 are disclosed as reactors using raceway ponds (hereinafter referred to as “raceway type culture tanks”). Patent Document 1 (Japanese Patent Laid-Open No. 5-76343) discloses a raceway type algae culture device (raceway type culture tank) that draws sunlight into water with an optical fiber or the like to increase the light receiving area. . When aiming for a cheaper culture tank, introduction of a large amount of expensive optical fibers becomes a bottleneck. Patent Document 2 (JP-A-8-116965) discloses a carbon dioxide immobilization method using the Chlorella T-1 strain, and uses a raceway reactor (raceway type culture tank) as a culture means. (See FIG. 9). Patent Document 3 (Japanese Patent Laid-Open No. 10-57745) discloses a method for collecting and immobilizing carbon dioxide using carbon dioxide collected with an alkaline solution for algae growth. A raceway reactor (as a culture means) is disclosed. Raceway type culture tank) is used (see FIG. 2).

  Thus, in any of the patent documents, a raceway type culture tank that can keep the initial cost low is used as the culture tank. In addition, in these raceway type culture tanks of Patent Documents 1 to 3, the cross section of the water channel viewed in the flow direction is a rectangular cross section.

JP-A-5-76343 JP-A-8-116965 JP-A-10-57745

  When manufacturing such a raceway-type culture tank (photosynthetic microorganism culture tank) outdoors, it is common to produce concrete by hitting concrete at a key point and attaching a water shielding sheet such as a polyethylene or polyolefin sheet. It is. However, the raceway culture tank manufactured in this way has poor workability, and the production cost per culture tank may be high. Moreover, the material which can be used for a water-impervious sheet is also restricted.

  In addition, when collecting photosynthetic microorganisms cultured in a raceway type culture tank (photosynthetic microorganism culture tank), the culture solution containing the photosynthetic microorganisms is pulled out with a pump or the like. At this time, the concentration of the photosynthetic microorganisms is as high as possible. Is preferable. That is, the higher the concentration, the shorter the operation time of the pump for the photosynthetic microorganism, and the running cost at the time of recovery is reduced. Moreover, the cost of the concentration process at the time of concentrating the collect | recovered photosynthetic microorganisms reduces.

  Accordingly, an object of the present invention is to provide a photosynthetic microorganism culture tank and a photosynthetic microorganism culture apparatus that reduce costs.

  In order to solve such problems, a photosynthetic microorganism culture tank according to the present invention has a circulation channel through which a culture solution containing a photosynthetic microorganism circulates, and the flow direction of the culture solution flowing through the circulation channel is normal. The cross-sectional shape of the water channel cut along the surface is characterized in that the width becomes narrower as it goes down.

  In addition, the photosynthetic microorganism culture apparatus according to the present invention includes a photosynthetic microorganism culture tank having a circulation channel through which a culture solution containing the photosynthetic microorganism circulates, and a paddle to rotate the culture liquid in the photosynthetic microorganism culture tank. A circulation agitator that circulates along the circulation channel and agitates the culture solution; an aeration gas supply device that diffuses aeration gas to the culture solution in the photosynthetic microorganism culture tank; and a photosynthetic microorganism culture tank A photosynthetic microorganism collection device that collects the photosynthetic microorganism together with the culture solution, a circulating stirring device, the aeration gas supply device, and a photosynthetic microorganism collection device that controls the culture operation for culturing the photosynthetic microorganism and the photosynthetic microorganism A control device for executing a recovery operation for recovery, wherein the control device determines the rotation speed of the paddle during the recovery operation, Characterized by lower than the rotational speed of the paddles during rotation.

  ADVANTAGE OF THE INVENTION According to this invention, the photosynthetic microorganism culture tank and photosynthetic microorganism culture apparatus which reduce cost can be provided. Thereby, the cost required for the production of photosynthetic microorganisms can be reduced, and consequently the production cost of biofuel produced using the photosynthetic microorganisms as raw materials can be reduced.

1 is a schematic configuration diagram of a photosynthetic microorganism culturing apparatus according to the present embodiment. It is a perspective view of the photosynthetic microorganism culture tank concerning this embodiment. It is sectional drawing of the photosynthetic microorganism culture tank which concerns on this embodiment. (A) is the relationship between the water depth of the photosynthetic microorganism culture tank according to the present embodiment and the velocity applied to the fluid, and (b) is a diagram showing the relationship between the water depth and the velocity applied to the fluid. It is longitudinal direction sectional drawing at the time of collection | recovery operation | movement of the photosynthetic microorganism culture tank which concerns on this embodiment. It is a flowchart explaining the driving | operation of the photosynthetic microorganism culture apparatus which concerns on this embodiment. It is a perspective view of the photosynthetic microorganism culture tank concerning a modification. It is a perspective view of the photosynthetic microorganism culture tank concerning a comparative example. It is sectional drawing of the photosynthetic microorganism culture tank which concerns on a comparative example.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

≪Photosynthetic microorganism culture device 1≫
A photosynthetic microorganism culturing apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a photosynthetic microorganism culturing apparatus 1 according to the present embodiment. In addition, the photosynthetic microorganism culture tank 2 of FIG. 1 has shown the state seen from upper direction. As shown in FIG. 1, the photosynthetic microorganism culture device 1 includes a photosynthetic microorganism culture tank 2, an aeration gas supply device 3, a circulation stirring device 4, a photosynthetic microorganism recovery device 5, and a control device 6. Yes.

  The photosynthetic microorganism culture tank 2 is a raceway type culture tank formed by an endless open channel (open pond). The culture microorganism M contains the photosynthetic microorganism M, and contains the culture medium M containing the photosynthetic microorganism. It can be circulated along the water channel. An arrow X shown in FIG. 1 indicates the circulation direction (flow direction) of the culture solution M. The structure of the photosynthetic microorganism culture tank 2 will be described later with reference to FIGS.

  Moreover, the photosynthetic microorganism culture tank 2 is provided with a pit 29 which is a recess lower than the surrounding bottom at the downstream bottom of the circulation stirring device 4 described later (see FIG. 5 described later). In addition, although illustration and detailed description are abbreviate | omitted, the culture solution supply means (not shown) for keeping the water level of the photosynthetic microorganism culture tank 2 constant is provided.

The diffused gas supply device 3 includes a gas tank (or a gas supply source) 31, a blower 32, and a diffuser pipe 33. The gas tank 31 is filled with an aeration gas that is a gas containing CO ₂ . The blower 32 can pump the diffused gas (CO ₂ -containing gas) in the gas tank 31 to the diffuser pipe 33. The aeration tube 33 is disposed in the pit 29 of the photosynthetic microorganism culture tank 2, and diffuses a diffused gas (for example, CO ₂ -containing gas) into the culture liquid M of the photosynthetic microorganism culture tank 2. The CO ₂ can be enriched. In addition, the control apparatus 6 mentioned later can control the whole diffused gas supply apparatus 3 by controlling the air blower 32. FIG.

  The circulation stirring device 4 includes a paddle 41 that rotates about a rotation shaft 41 a and a motor 42 that rotates the paddle 41. The rotating shaft 41a of the circulation stirring device 4 is disposed on the water channel of the photosynthetic microorganism culture tank 2, and the paddle 41 rotates to stir the culture medium M and to mix the culture medium M with the photosynthetic microorganism culture tank 2. It can be circulated along the water channel. In addition, the control apparatus 6 mentioned later can control the whole circulation stirring apparatus 4 by controlling the motor 42 now.

As described above, the photosynthetic microorganism culture apparatus 1 is configured to agitate and circulate the culture solution M in the photosynthetic microorganism culture tank 2 with the circulation agitator 4 while using the aeration gas supply apparatus 3 with a diffused gas (a gas containing CO ₂ ). Aerating. Moreover, nutrient salts, such as a nitrogen source, a phosphorus source, and a mineral, are added to the culture solution M. As a result, the photosynthetic microorganism biosynthesizes biofuel and components that can be a raw material of the biofuel by photosynthesis and accumulates them in the cell, and the number thereof grows.

  The photosynthetic microorganism collection device 5 includes a water intake pipe 51, a liquid pump 52, and a precipitation tank 53. The intake pipe 51 has an opening 51 a which is one end disposed in the pit 29 of the photosynthetic microorganism culture tank 2, and the other end connected to the suction port of the liquid pump 52. The liquid pump 52 can take the culture solution M containing the photosynthetic microorganism from the opening 51 a of the intake pipe 51 and send it to the sedimentation tank 53. The sedimentation tank 53 precipitates the photosynthetic microorganisms from the culture solution M containing the photosynthetic microorganisms and separates them into a supernatant M1 and a precipitate M2. The supernatant liquid M1 can be reused in the photosynthetic microorganism culture tank 2 to reuse the nutrient salts and the photosynthetic microorganisms of the culture liquid M contained in the supernatant liquid M1. In addition, the precipitate M2 containing a large amount of photosynthetic microorganisms is collected from the precipitation tank 53, further concentrated by centrifugation or the like, and used as a raw material for biofuel. The control device 6 to be described later can control the entire photosynthetic microorganism collection device 5 by controlling the liquid pump 52.

  The control device 6 controls the whole of the photosynthetic microorganism culture device 1 by controlling the blower 32 of the diffused gas supply device 3, the motor 42 of the circulation stirring device 4, and the liquid pump 52 of the photosynthetic microorganism recovery device 5. It can be controlled.

<Photosynthetic microorganism>
An example of a photosynthetic microorganism that can be used in the present embodiment is Euglena. Euglena is a group of flagellates, including Euglena, which is famous as a motile algae. Most Euglena has a chloroplast and photosynthetizes for an autotrophic life, but some are predatory and some are absorptive.
Euglena is a genus classified into both zoology and botany.
In zoology, there are Euglenida in the eyes belonging to Protozoa's Mastigophorea and Phytomastigophorea, which are three sub-Euglenoidina, Peranemoidina It consists of Petalomonadoidina.
Euglenoidina includes Euglena, Trachelemonas, Strombonas, Phacus, Lepocinelis, Astasia and Colacium as genera.
In botany, Euglenophyta is the Euglenophyta, followed by Euglenophyceae and Euglenales, and the genera included in this eye is similar to that of the Euglena and the animal taxonomy. is there.
In addition to this, one or two species from cyanobacteria, green algae and treboxya, plastino algae (green algae), primordial red algae, diatoms, round stone algae, dinoflagellate algae, golden spot algae, etc. The above can be selected and used.

Examples of cyanobacteria include Chroococcacae, Stigonematacae, Mastigocladacae, and Oscillatroriacae. In addition, Synechococcus such as Synechococcus lividus and Synechococcus elongatus; Synechocystis such as Synechocystis minervae; Mastigocladus such as Mastigocladus laminosus; Phormidium such as Phormidium laminosus; , Fisherella and the like.
Furthermore, Anabanena variabilis ATCC 29413 belonging to the genus Anabaena, Cyanothece sp. ATCC 51142 belonging to the genus Cyanothece, Synechococcus sp. PCC 7942 belonging to the genus Synechococcus and Anasis Anacystis nidulans belonging to the genus (Anacystis), thermophilic cyanobacteria and the like can be used.

  Examples of green algae and treboxya include aerial algae such as chlorella (including phylogenetically separated parachlorella), Chlamydomonas, Donariella, Senedesmus, Botryococcus, Sticococcus, Nannochloris, and Desmodemus Can do. Specifically, the basic properties of Chlorella vulgaris and Chlorella saccharophila (Chlorella), Dunaliella salina, Dunaliella tertiolecta, etc., and photosynthesis are the same, but they are classified as treboxya algae by molecular phylogenetic analysis. Parachlorella kessleri (Chlorella kessleri). In addition, Chlamydomonas reinhardtii, Chlamydomonas moewusii, Chlamydomonas eugametos, Chlamydomonas eugametos, Chlamydomonas genus, Slams・ Senedesmus obliquus, Stichococcus ampliformis belonging to the genus Stichococcus, Nannochloris bacillaris belonging to the genus Nannochloris, and Desmodesmus Examples include Desmodesmus subspicatus belonging to the genus.

In addition, examples of the plasino algae (green algae) include tetracermis, and examples of the primordial red algae include cyanidiozone, cyanidium, gardi area, porphyridium, and the like.
In addition, the photosynthetic microorganism that can be used in the present embodiment can generate biofuel and a component that can be a raw material of biofuel by photosynthesis, accumulate in the cell, and can improve sedimentation by the dissolved oxygen reduction treatment Can be used as long as they are not limited to those described above.

<Culture medium M>
When Euglena is used as the photosynthetic microorganism, examples of the culture medium M include modified Cramer-Myers medium ((NH ₄ ) ₂ HPO ₄ 1.0 g / L, KH ₂ PO ₄ 1.0 g / L, MgSO ₄ .7H ₂ O 0.2 g / L, CaCl ₂ · 2H ₂ O 0.02 g / L, Fe ₂ (SO ₂ ) ₃ · 7H ₂ O 3 mg / L, MnCl ₂ · 4H ₂ O 1.8 mg / L, CoSO ₄ · 7H ₂ O 1.5 mg / L, ZnSO ₄ .7H ₂ O 0.4 mg / L, Na ₂ MoO ₄ .2H ₂ O 0.2 mg / L, CuSO ₄ .5H ₂ O 0.02 mg / L, thiamine hydrochloride (vitamin B1) 0.1 mg / L, cyanocobalamin (vitamin B12) 0.0005 mg / L, (pH 3.5)) can be used. Note that (NH ₄ ) ₂ HPO ₄ can be converted to (NH ₄ ) ₂ SO ₄ or NH ₃ aq.
In addition, the culture solution M should just use the culture medium suitable for the photosynthetic microorganism to be used, and it cannot be overemphasized that it is not limited to this.

<Aeration gas (CO ₂ containing gas)>
The diffused gas filled in the gas tank 31 and diffused from the diffuser tube 33 to the culture solution M in the photosynthetic microorganism culture tank 2 may be any gas containing CO ₂ , for example, discharged from a factory or a thermal power plant. Fuel exhaust gas may be used. In addition, when using a fuel exhaust gas as an aeration gas, it is preferable to remove fuel exhaust gas dust, NOx (nitrogen oxide), and SOx (sulfur oxide) with a dust collector, a denitration device, and a desulfurization device.

≪Photosynthetic microorganism culture tank 2≫
Next, the structure of the photosynthetic microorganism culture tank 2 according to the present embodiment will be further described with reference to FIGS. FIG. 2 is a perspective view of the photosynthetic microorganism culture tank 2 according to the present embodiment. FIG. 3 is a cross-sectional view of the photosynthetic microorganism culture tank 2 according to the present embodiment cut along a plane whose normal is the direction in which the culture solution M flows. In FIG. 2, the pit 29, the diffused gas supply device 3 (aeration tube 33), the circulation stirring device 4 (paddle 41), and the photosynthetic microorganism collection device 5 (water intake tube 51) are not shown.

  As shown in FIG. 2, the photosynthetic microorganism culture tank 2 according to the present embodiment includes an outer peripheral wall 21 composed of two semicircles and two straight lines when viewed from above, and a central longitudinal length in a range surrounded by the outer peripheral wall 21. It has the center wall 22 provided in the direction, and the bottom face 23, and is formed as a water channel with the upper side opened. And the channel cross-sectional shape D cut | disconnected by the surface which makes the normal direction the flow direction (refer arrow X of FIG. 1) of the culture solution M which flows through a water channel becomes a shape where a width | variety becomes narrow as water depth becomes deep. . That is, the channel cross-sectional shape D has a shape in which the width on the bottom surface side (lower side) of the water channel is narrower than the width on the water surface side (upper side). Incidentally, in the example of FIG. 2, the upper base (bottom side on the water surface side (upper side)) has an inverted trapezoidal shape longer than the lower base (bottom side on the water channel bottom surface side (lower side)).

  As shown in FIG. 3, the photosynthetic microorganism culture tank 2 includes a concrete retaining wall 21A having a tapered portion 21Aa, a concrete retaining wall 22A having a tapered portion 22Aa, a concrete weight 23A, protective mats 24 and 24, and a water shielding Sheets 25 and 26 and a crushed stone 27 are provided.

  The concrete retaining wall 21 </ b> A becomes the outer peripheral wall 21. Moreover, the protective mat 24 laid on the taper portion 21Aa of the concrete retaining wall 21A and the crushed stone 27 forms a slope inclined toward the center of the water channel. The concrete retaining wall 22 </ b> A becomes the central wall 22. Further, the protective mat 24 laid on the taper portion 22Aa of the concrete retaining wall 22A and the crushed stone 27 forms a slope inclined toward the center of the water channel.

  In the construction of the photosynthetic microorganism culture tank 2, first, the concrete retaining wall 21 </ b> A and the concrete retaining wall 22 </ b> A are constructed, and the slope is constructed with the crushed stone 27 and the protective mat 24. A water shielding sheet 25 is laid on the slope formed in this way, and a concrete weight 23A for pressing (tensioning) the water shielding sheet 25 is disposed at the center of the water channel. The end portion of the water shielding sheet 25 is fixed to the concrete retaining wall 21A with an anchor or the like. Then, a water shielding sheet 26 is attached to the upper surface of the concrete weight 23 </ b> A that becomes the bottom surface 23.

<Photosynthetic microorganism culture tank 2C according to comparative example>
Here, the structure of the photosynthetic microorganism culture tank 2C according to the comparative example will be further described with reference to FIGS. FIG. 8 is a perspective view of a photosynthetic microorganism culture tank 2C according to a comparative example. FIG. 9 is a cross-sectional view of the photosynthetic microorganism culture tank 2C according to the comparative example.

  The photosynthetic microorganism culture tank 2C (see FIGS. 8 and 9) according to the comparative example is compared with the photosynthetic microorganism culture tank 2 (see FIGS. 2 and 3) according to the present embodiment (D, DC). ) Are different, and the construction method is different due to this. Other configurations are the same, and the description is omitted.

  As shown in FIG. 8, the photosynthetic microorganism culture tank 2C according to the comparative example includes an outer peripheral wall 21C composed of two semicircles and two straight lines when viewed from above, and a central longitudinal direction of a range surrounded by the outer peripheral wall 21C. A water channel having an upper opening is formed by the central wall 22C and the bottom surface 23C provided on the upper surface. And the channel cross-sectional shape DC cut | disconnected by the surface which makes the flow direction of the culture solution M which flows through a water channel normal is a rectangular cross section, It is characterized by the above-mentioned.

  As shown in FIG. 9, the photosynthetic microorganism culture tank 2C includes a concrete retaining wall 21CA, a concrete retaining wall 22CA, concrete weights 23CA and 23CA, a protective mat 24C, water shielding sheets 25C, 26C and 26C, and a crushed stone 27C. And is configured.

  The concrete retaining wall 21CA becomes the outer peripheral wall 21C. The concrete retaining wall 22CA becomes the central wall 22C. Further, the protective mat 24C laid on the crushed stone 27C is disposed so as to be horizontal and forms a bottom surface 23C.

  In the construction of the photosynthetic microorganism culture tank 2C, first, the concrete retaining wall 21CA and the concrete retaining wall 22CA are constructed, and a horizontal bottom surface is constructed by the crushed stone 27C and the protective mat 24C. The water shielding sheet 25C is laid on the horizontal bottom surface thus formed, and concrete weights 23CA and 23CA for pressing (tensioning) the water shielding sheet 25C are disposed at both ends of the water channel. The end portion of the water shielding sheet 25C is fixed to the concrete retaining wall 21CA with an anchor or the like. And the water shielding sheets 26C and 26C are affixed on the upper surfaces of the concrete weights 23CA and 23CA.

<Operation and effect of the photosynthetic microorganism culture tank 2 according to the present embodiment>
The operation and effect of the photosynthetic microorganism culture tank 2 (see FIGS. 2 and 3) according to the present embodiment will be described in comparison with the photosynthetic microorganism culture tank 2C (see FIGS. 8 and 9) according to the comparative example.

  In the photosynthetic microorganism culturing tank 2C according to the comparative example, as shown in FIG. 9, two concrete weights 23CA and 23CA for pressing (tensioning) the water shielding sheet 25C are disposed at both ends of the water channel. Further, in order to insulate the two concrete weights 23CA and 23CA, the water shielding sheets 26C and 26C are stuck on the respective parts. That is, there are two pasting operations.

  On the other hand, in the photosynthetic microorganism culture tank 2 according to the present embodiment, as shown in FIG. 3, the concrete weight 23 </ b> A for pressing (tensioning) the water shielding sheet 25 is arranged at one place in the center of the water channel. . Moreover, in order to insulate the concrete weight 23A at one place, one place of the water shielding sheet 26 is pasted. Thereby, the installation cost of the concrete weight 23A (23CA) and the cost of attaching the water shielding sheet 26 (26C) can be reduced, and the production cost per unit of the photosynthetic microorganism culture tank 2 can be reduced. it can.

  Further, the photosynthetic microorganism culture tank 2 according to the present embodiment does not have to be bent at right angles when constructing the water shielding sheet 26 (26C), as compared with the photosynthetic microorganism culture tank 2C according to the comparative example. Therefore, for example, even when a plurality of culture tanks are arranged in parallel, it can be applied at a time.

  Further, the length of the wet edge (the length in which the culture solution M and the water shielding sheets 25 and 26 are in contact with each other in the cross-sectional view of FIG. 3) is longer than the photosynthetic microorganism culture tank 2C according to the comparative example. The culture tank 2 can be shortened. Thereby, since the resistance when the culture solution M circulates decreases, the culture solution M can be circulated efficiently.

  FIG. 4A shows the relationship between the water depth of the photosynthetic microorganism culture tank 2 according to this embodiment and the speed given to the fluid, and FIG. 4B shows the relationship between the water depth and the speed given to the fluid. is there.

As shown in FIG. 4 (b), the paddle 41 (paddle type circulation stirring device 4) has different speeds given to the fluid (culture medium M) depending on the water depth, and the higher the water depth is, the higher the speed (speed V _H ). The shallower it is, the slower (velocity V _L , V _H > V _L ). For this reason, the paddle type circulation stirring device 4 has an effect of not only giving a flow to the fluid (culture medium M) but also mixing the upper and lower fluids by the difference in fluid speed. However, like the photosynthetic microorganism culture tank 2C according to the comparative example, when the channel cross-sectional shape DC is a rectangular cross-section, the place where the channel is replaced is limited, and the stirring effect is small.

On the other hand, in the photosynthetic microorganism culture tank 2 according to the present embodiment, the channel cross-sectional shape D and the paddle 41 have inverted trapezoidal shapes, so the speed applied to the fluid (culture medium M) is as shown in FIG. As shown. The magnitude relationship among the speeds V _H , V _MH , V _ML , and V _L is “V _H > V _MH > V _ML > V _L ”.

  As described above, in the photosynthetic microorganism culture tank 2 according to the present embodiment, the channel cross-sectional shape D and the paddle 41 are inverted trapezoidal, so that the space between the bottom and the water surface (upper and lower in FIG. 4A). ), A speed difference also occurs between the central part and both bank parts (between the left and right in FIG. 4A). Thereby, even if the circulation stirring apparatus 4 is the same power, the photosynthetic microorganism culture tank 2 according to the present embodiment can perform more effective stirring than the photosynthetic microorganism culture tank 2C according to the comparative example.

  Further, when the channel cross-sectional shape DC has a rectangular cross section as in the photosynthetic microorganism culture tank 2C according to the comparative example, the water shielding sheet extends between the adjacent photosynthetic microorganism culture tanks 2C from the bending limit of the water shielding sheet 25C. It was difficult to construct the sheet 25C. On the other hand, when the channel cross-sectional shape D becomes an inverted trapezoid like the photosynthetic microorganism culture tank 2 according to the present embodiment, the water shielding sheet 25C is gently bent, so that the adjacent photosynthetic microorganism culture tanks 2 are adjacent to each other. It is possible to construct the water shielding sheet 25C over the two. Thereby, the workability | operativity at the time of constructing the several photosynthetic microorganism culture tank 2 improves, and the manufacturing cost per unit | set of the photosynthetic microorganism culture tank 2 can be reduced.

≪Operation of photosynthetic microorganism culture device 1≫
Next, operation | movement of the photosynthetic microorganism culture apparatus 1 which concerns on this embodiment is demonstrated using FIG. 5 and FIG. FIG. 5 is a longitudinal cross-sectional view of the photosynthetic microorganism culture tank 1 according to the present embodiment during the recovery operation. FIG. 6 is a flowchart for explaining the operation of the photosynthetic microorganism culturing apparatus 1 according to this embodiment.

First, operation | movement of the photosynthetic microorganism culture apparatus 1 which concerns on this embodiment is demonstrated using FIG.
In step S101, the control device 6 performs a culture operation for culturing photosynthetic microorganisms. Specifically, the control device 6 operates the blower 32 (blower: ON) to diffuse a diffused gas (for example, CO ₂ -containing gas) to the culture solution M in the photosynthetic microorganism culture tank 2. Further, the control device 6 controls the motor 42 to rotate the paddle 41 at the rotational speed R ₁ (motor rotational speed: R ₁ ), thereby circulating and stirring the culture medium M in the photosynthetic microorganism culture tank 2. In the culture operation, the liquid pump 52 is stopped (liquid pump: OFF).

  In step S102, the control device 6 determines whether or not to start the recovery operation (recovery start determination). When the collection operation is started (S102, Yes), the process of the control device 6 proceeds to step S103. On the other hand, when the collection operation is not started (No in S102), the process of the control device 6 returns to Step S101. The determination as to whether or not to start the recovery operation is not limited, and any method may be used. For example, a photosynthetic microorganism concentration sensor that detects the concentration of photosynthetic microorganisms in the culture solution M of the photosynthetic microorganism culture tank 2 may be provided, and it may be determined that the recovery operation is started when the photosynthetic microorganism concentration exceeds a predetermined threshold. Further, a timer may be provided, and it may be determined that the recovery operation is started when a predetermined time has elapsed since the end of the previous recovery operation.

In step S103, the control device 6 performs a recovery operation for recovering photosynthetic microorganisms. Specifically, the control device 6 stops the blower 32 (blower: OFF). In addition, the control device 6 controls the motor 42 to rotate the paddle 41 at a rotational speed R ₂ lower than the rotational speed R ₁ during the culture operation (motor rotational speed: R ₂ ). Further, the control device 6 operates the liquid pump 52 (liquid pump: ON) to take the culture solution M containing the photosynthetic microorganisms from the opening 51 a of the intake pipe 51 and send it to the sedimentation tank 53.

  In step S104, the control device 6 determines whether or not to end the recovery operation (recovery end determination). When the collection operation is terminated (S104, Yes), the process of the control device 6 returns to step S101. On the other hand, when the collection operation is not terminated (No at S104), the process of the control device 6 returns to Step S103. The determination as to whether or not to end the recovery operation is not limited, and any method may be used. For example, a photosynthetic microorganism concentration sensor that detects the concentration of the photosynthetic microorganism in the culture solution M of the photosynthetic microorganism culture tank 2 may be provided, and it may be determined that the recovery operation is started when the concentration of the photosynthetic microorganism becomes less than a predetermined threshold. Further, a timer may be provided, and it may be determined that the collection operation is terminated when a predetermined time has elapsed from the start of the collection operation.

During the collection operation, the rotation speed of the motor 42 is set to a rotation speed R ₂ that is lower than the rotation speed R ₁ during the culture operation. More specifically, the rotation speed R ₂ is set to be equal to or less than a speed at which the photosynthetic microorganisms in the culture solution M start to sink as the stirring of the culture solution M decreases. As a result, as shown in FIG. 5, a culture solution MU having an increased concentration of photosynthetic microorganisms is formed on the bottom side. As a guideline for the rotation speed, the average flow rate generated by the rotation speed R ₁ during the culture operation is preferably 0.25 m / s or more, and the average flow speed generated by the rotation speed R ₂ during the recovery operation is 0. .1 m / s or less is preferable.

  Further, the culture liquid MU in which the concentration of the photosynthetic microorganisms is increased by the paddle 41 rotating gently is guided to the pits 29 formed in the photosynthetic microorganism culture tank 2. Then, the culture solution MU containing a large amount of photosynthetic microorganisms is taken from the opening 51 a of the intake pipe 51 provided in the pit 29 and sent to the sedimentation tank 53.

  Thereby, since the photosynthetic microorganism culturing apparatus 1 according to the present embodiment can take in the culture solution MU containing a large amount of photosynthetic microorganisms during the recovery operation, the photosynthetic microorganisms can be efficiently recovered.

  In addition, by stopping the blower 32 during the recovery operation and stopping the aeration from the aeration tube 33 provided in the pit 29, it is possible to prevent the photosynthetic microorganisms flowing into the pit 29 from being wound up by the aeration gas, Efficiently recover photosynthetic microorganisms.

  On the other hand, during the culture operation, the photosynthetic microorganisms that have flowed into the pit 29 are wound up by the aeration gas by aeration from the aeration tube 33 provided in the pit 29. Thereby, it is possible to prevent the photosynthetic microorganisms from staying and precipitating in the pits 29 during the culture operation.

≪Modification≫
The photosynthetic microorganism culture apparatus 1 (photosynthetic microorganism culture tank 2) according to the present embodiment is not limited to the configuration of the above embodiment, and various modifications can be made without departing from the spirit of the invention. .

  Although the diffused gas supply device 3 has been described as being diffused by the blower 32 from the diffuser pipe 33, the present invention is not limited to this. For example, the diffused gas may be diffused from the diffuser pipe 33 by the gas pressure of the diffused gas filled in the gas tank 31. In such a configuration, an opening / closing valve and a flow rate adjusting valve may be used instead of the blower 32.

  Although the photosynthetic microorganism recovery device 5 has been described as recovering the culture solution M containing the photosynthetic microorganisms by the liquid pump 52, the invention is not limited to this. For example, the culture solution M containing the photosynthetic microorganisms may be allowed to flow from the photosynthetic microorganism culture tank 2 to the sedimentation tank 53 by providing a height difference between the photosynthetic microorganism culture tank 2 and the sedimentation tank 53. In such a configuration, an on-off valve and a flow rate adjustment valve may be used instead of the liquid pump 52.

  Although the water channel cross-sectional shape D of the photosynthetic microorganism culture tank 2 has been described as an inverted trapezoid (see FIGS. 2 and 3), it is not limited thereto. FIG. 7 is a perspective view of a photosynthetic microorganism culture tank 2B according to a modification.

  As shown in FIG. 7, the photosynthetic microorganism culture tank 2B according to the modification includes an outer peripheral wall 21B composed of two semicircles and two straight lines when viewed from above, and a central longitudinal direction of a range surrounded by the outer peripheral wall 21B. A water channel having an open upper side is formed by the central wall 22B provided on the upper side. And the channel cross-sectional shape DB cut | disconnected by the surface which makes the flow direction of the culture solution M which flows through a water channel the normal line becomes an inverted triangle whose liquid surface side is a base.

  Thus, the channel cross-sectional shape D of the photosynthetic microorganism culture tank 2 is not limited to the inverted trapezoid (see FIGS. 2 and 3), and may be an inverted triangle (see FIG. 7).

DESCRIPTION OF SYMBOLS 1 Photosynthesis microorganism culture apparatus 2, 2B Photosynthesis microorganism culture tank 21 Outer peripheral wall 22 Central wall 23 Bottom surface 21A, 22A Concrete retaining wall (retaining wall)
21Aa, 22Aa Taper part 23A Concrete weight (weight)
24 Protective mats 25 and 26 Water shielding sheet 27 Crushed stone 29 Pit 3 Aeration gas supply device 31 Gas tank (gas supply source)
32 Blower 33 Aeration pipe 4 Circulating stirrer 41 Paddle 41a Rotating shaft 42 Motor 5 Photosynthetic microorganism recovery device 51 Intake pipe 51a Opening part (intake part)
52 Liquid pump 53 Precipitation tank 6 Controller D, DB Channel cross-sectional shape M, MU Culture medium M1 Supernatant liquid M2 Precipitate

Claims (10)

A circulation channel through which a culture solution containing photosynthetic microorganisms circulates;
The photosynthetic microorganism culture tank, wherein the cross-sectional shape of the water channel cut along a plane whose normal is the flow direction of the culture fluid flowing through the circulation water channel becomes a shape that becomes narrower toward the lower side. 2. The photosynthetic microorganism culture tank according to claim 1, wherein the channel cross-sectional shape is an inverted trapezoidal shape in which the width on the bottom surface side of the water channel is narrower than the width on the liquid surface side. The photosynthetic microorganism culture tank according to claim 1, wherein the cross-sectional shape of the water channel is an inverted triangular shape having a liquid surface side as a base. The circulation channel is
Retaining walls arranged on both banks of the circulation channel;
A weight disposed at the center bottom of the circulation channel;
The photosynthetic microorganism culture tank according to claim 1, comprising a water shielding sheet. The photosynthetic microorganism culture tank according to claim 1,
Circulating the culture medium in the photosynthetic microorganism culture tank along the circulation channel by rotating a paddle, and a circulation stirring device for stirring the culture liquid;
A diffused gas supply device for aspirating a diffused gas to the culture solution of the photosynthetic microorganism culture tank;
A photosynthetic microorganism recovery apparatus for recovering the photosynthetic microorganism together with the culture solution from the photosynthetic microorganism culture tank;
A control device for controlling the circulating agitator, the aeration gas supply device, the photosynthetic microorganism recovery device, and performing a culture operation for culturing the photosynthetic microorganism and a recovery operation for recovering the photosynthetic microorganism;
The controller is
The photosynthetic microorganism culturing apparatus, wherein the rotational speed of the paddle during the recovery operation is lower than the rotational speed of the paddle during the culture operation. During the culture operation, the control device diffuses the culture solution in the photosynthetic microorganism culture tank by the aeration gas supply device,
6. The photosynthetic microorganism culturing apparatus according to claim 5, wherein, during the recovery operation, the control device stops the aeration to the culture solution of the photosynthetic microorganism culture tank by the aeration gas supply device. The photosynthetic microorganism culture tank has a pit that is a recess that is lower than the surrounding bottom at the bottom of the circulation channel,
The pit
An air diffuser for the air diffuser gas to diffuse the diffused gas to the culture solution of the photosynthetic microorganism culture tank;
The photosynthetic microorganism culturing apparatus according to claim 6, wherein the photosynthetic microorganism collecting apparatus includes a water intake unit that collects the photosynthetic microorganism together with the culture solution from the photosynthetic microorganism culture tank. A photosynthetic microorganism culture tank having a circulation channel through which a culture solution containing the photosynthetic microorganism circulates;
Circulating the culture medium in the photosynthetic microorganism culture tank along the circulation channel by rotating a paddle, and a circulation stirring device for stirring the culture liquid;
A diffused gas supply device for aspirating a diffused gas to the culture solution of the photosynthetic microorganism culture tank;
A photosynthetic microorganism recovery apparatus for recovering the photosynthetic microorganism together with the culture solution from the photosynthetic microorganism culture tank;
A control device for controlling the circulating agitator, the aeration gas supply device, the photosynthetic microorganism recovery device, and performing a culture operation for culturing the photosynthetic microorganism and a recovery operation for recovering the photosynthetic microorganism;
The controller is
The photosynthetic microorganism culturing apparatus, wherein the rotational speed of the paddle during the recovery operation is lower than the rotational speed of the paddle during the culture operation. During the culture operation, the control device diffuses the culture solution in the photosynthetic microorganism culture tank by the aeration gas supply device,
9. The photosynthetic microorganism culturing apparatus according to claim 8, wherein, during the recovery operation, the control device stops aeration to the culture solution in the photosynthetic microorganism culture tank by the aeration gas supply device. The photosynthetic microorganism culture tank has a pit that is a recess that is lower than the surrounding bottom at the bottom of the circulation channel,
The pit
An air diffuser for the air diffuser gas to diffuse the diffused gas to the culture solution of the photosynthetic microorganism culture tank;
The photosynthetic microorganism culture device according to claim 9, wherein the photosynthetic microorganism collection device comprises a water intake unit that collects the photosynthetic microorganism together with the culture solution from the photosynthetic microorganism culture tank.

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