JP2022160029A - Algae culture system and algae culture method - Google Patents

Abstract

To provide an algae culture system and an algae culture method in which energy loss does not occur in separating carbon dioxide.SOLUTION: An algae culture system comprises: a carbon dioxide supply source which supplies gas containing carbon dioxide; a carbon dioxide recovery part which brings carbon dioxide lean absorption liquid in contact with the gas containing carbon dioxide to obtain carbon dioxide rich absorption liquid; and an algae culture device which is provided adjacent to the carbon dioxide supply source and the carbon dioxide recovery part, is supplied with the carbon dioxide rich absorption liquid as a nutrient source from the carbon dioxide recovery part, and capable of culturing algae.SELECTED DRAWING: Figure 1

Description

The present invention relates to an algae culture system and an algae culture method capable of culturing algae.

A method of recycling carbon dioxide generated from a thermal power plant or the like is known (see Patent Document 1, for example). In this method, exhaust gas from a thermal power plant or the like is passed through the amine or the like to cause the amine or the like to absorb carbon dioxide. The carbon dioxide absorbed by the amine or the like is separated from the amine or the like by means of heating or the like and recovered. The collected carbon dioxide is added to a microalgae culture pond attached to a thermal power plant or the like. The microalgae cultured in the microalgae culture pond are dried after collection and used as fuel in thermal power plants and the like.

JP-A-9-276648

In Patent Document 1, in order to separate carbon dioxide from the amine or the like that has adsorbed carbon dioxide, it is necessary to raise the temperature of the amine or the like to a high temperature of 100° C. or higher, for example. For this reason, a huge energy loss has occurred when separating carbon dioxide from amines and the like.

Accordingly, an object of the present invention is to provide an algae culture system and an algae culture method that do not cause energy loss during carbon dioxide separation.

The above problems are solved by the present invention described below.

That is, the algae culture system of the present invention (1) includes a carbon dioxide supply source that supplies a carbon dioxide-containing gas,
a carbon dioxide recovery unit for obtaining a carbon dioxide-rich absorbent by contacting the carbon dioxide-containing gas with the carbon dioxide-lean absorbent;
an algae culture vessel capable of cultivating algae by receiving supply of the carbon dioxide-rich absorption liquid as a nutrient source from the carbon dioxide recovery unit;
Prepare.

Further, the algae culture system of the present invention (2) is the algae culture system according to (1), wherein the carbon dioxide-lean absorption liquid and the carbon dioxide-rich absorption liquid are absorption liquids containing an absorbent,
The absorbent is ammonia or an amine-based compound.

Also, in the algae culture system of the present invention (3), the absorbent is ammonia or an organic amine compound.

Further, the algae culture system of the present invention (4) is the algae culture system according to any one of (1) to (3),
An algae recovery device is provided for recovering the algae cultured in the algae incubator.

Further, the algae culture system of the present invention (5) is the algae culture system according to any one of (1) to (4), wherein the algae are photosynthetic algae.

The algae culture method of the present invention (6) supplies a carbon dioxide-containing gas from a carbon dioxide supply source,
A carbon dioxide-rich absorption liquid is obtained by bringing a carbon dioxide-lean absorption liquid into contact with the carbon dioxide-containing gas by a carbon dioxide recovery unit,
The carbon dioxide-rich absorption liquid is supplied from the carbon dioxide recovery unit to the algae culture vessel as a nutrient source, and algae are cultured in the algae culture vessel.

Further, the algae culture method of the present invention (7) is the algae culture method according to (6), wherein the carbon dioxide-lean absorption liquid and the carbon dioxide-rich absorption liquid are absorption liquids containing an absorbent. ,
The absorbent is ammonia or an amine-based compound.

Also, the algae culture method of the present invention (8) is the algae culture method according to (7), wherein the absorbent is ammonia or an organic amine compound.

Further, the algae culture method of the present invention (9) is the algae culture method according to any one of (6) to (8), wherein the algae are photosynthetic algae.

According to the present invention, it is possible to provide an algae culture system and an algae culture method that do not cause energy loss during carbon dioxide separation.

1 is a system diagram showing an algae culture system of an embodiment; FIG. FIG. 2 is a schematic diagram showing a carbon dioxide recovery unit of the algae culture system shown in FIG. 1; FIG. 2 is a top view showing an open pond raceway type algae incubator of the algae culture system shown in FIG. 1; FIG. 4 is a front view showing a closed algae culture vessel of the algae culture system of the second embodiment.

An algae culture system of the present invention will be described with reference to FIG. The algae culture system 10 includes a carbon dioxide supply source 1 that supplies exhaust gas (carbon dioxide-containing gas), and a carbon dioxide recovery unit 2 that recovers carbon dioxide from the exhaust gas (carbon dioxide-containing gas) generated from the carbon dioxide supply source 1. , an algae incubator 5 provided at a position adjacent to or separated from the carbon dioxide supply source 1 and the carbon dioxide recovery unit 2, and an algae recovery device 6 for recovering the algae cultured in the algae incubator 5. have. The algae collection device 6 is composed of, for example, a power shovel or other heavy equipment capable of collecting the cultured algae from the bottom of the algae culture vessel 5 . The algae collection device 6 is not limited to a heavy machine or the like, and may be a pump or the like capable of pumping up the algae together with the culture solution.

The carbon dioxide supply source 1 is a factory or the like that emits a carbon dioxide-containing gas as an exhaust gas. , boilers, etc. Alternatively, the carbon dioxide supply source 1 may be the atmosphere.

As shown in FIG. 2, the carbon dioxide recovery section 2 is formed in a tower shape extending in the vertical direction. The carbon dioxide recovery unit 2 includes a cylindrical absorption tower 11 having a contact mechanism 19a provided therein and configured by a mesh filter (mesh) or the like, and a first a storage part 14a, a first flow path 21 connecting the upper part of the absorption tower 11 and the first storage part 14a, a second storage part 15a for storing the carbon dioxide-rich absorbent 4 after the carbon dioxide absorption reaction, an absorption It has a second flow path 22 connecting the lower part of the tower 11 and the second reservoir 15 a and a third flow path 23 connecting the carbon dioxide supply source 1 and the lower part of the absorption tower 11 .

The first flow path 21 can supply the carbon dioxide-lean absorbent 3 from the first reservoir 14 a to the absorption tower 11 . The second flow path 22 can flow the carbon dioxide-rich absorbent 4 from the absorption tower 11 toward the second reservoir 15a. The third flow path 23 can supply gaseous carbon dioxide from the carbon dioxide supply source 1 into the absorber tower 11 .

The carbon dioxide-lean absorbent 3 is an absorbent that does not absorb carbon dioxide. The carbon dioxide-lean absorbent 3 becomes the carbon dioxide-rich absorbent 4 after absorbing carbon dioxide.

Examples of absorbents contained in the carbon dioxide-lean absorbing liquid 3 include ammonia and all amine-based compounds such as alkanolamines such as monoethanolamine, diethanolamine, diisopropanolamine, dimethyldiethanolamine and triethanolamine, and aminodiethylene glycol. Amino alcohols such as amino alcohols, hindered amine compounds, piperazine compounds, piperidine compounds, polyalkylpolyamine compounds, amino acid compounds such as 5-aminolevulinic acid, amino acid salt compounds, derivatives thereof, organic amine compounds, etc. mentioned.

Preferably, the absorbent is ammonia or an organic amine-based compound. The absorbent may be of one type or a combination of two or more of the above at any mixing ratio. As the absorbent, it is preferable to use one that has a high absorption rate, a large amount of carbon dioxide absorption, and is thermally stable.

Examples of the carbon dioxide-lean absorbent 3 include an aqueous solution of an absorbent. The absorption liquid is an aqueous solution of ammonia or all amine compounds, preferably an aqueous solution of ammonia or an organic amine, and more preferably an aqueous solution of ammonia, alkanolamine or 5-aminolevulinic acid. When an aqueous solution of alkanolamine is used as the carbon dioxide-lean absorbent 3, an aqueous solution of alkanolamine having a concentration of 15 to 45% by mass is particularly preferred.

The carbon dioxide-lean absorption liquid 3 and the carbon dioxide-rich absorption liquid 4 are preferably harmless to algae, but there is no problem even if they are compounds that are harmful to algae to some extent. For example, by installing the algae culture vessel 5 outdoors as an open system and increasing the size to some extent (oval type circuit shape with a total length of 50 m to several km, open pond raceway shape), toxicity is reduced by the effect of dilution. can be lowered. As for ammonia, the action of naturally occurring nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) can convert ammonia into nitrate through nitrite. Nitrates can be absorbed by algae as a nutrient (nitrogen source). Similarly, other amine-based compounds (organic amine compounds) other than ammonia are also decomposed by naturally occurring fungi (for example, Bacillus bacteria living in the bottom mud in the algae incubator 5) and absorbed by the algae as nutrients. be done. As for 5-aminolevulinic acid, it is not toxic to algae, but rather is taken up by algae as it is and has the effect of promoting growth. Further, the toxicity to algae can be reduced by the effect of dilution by intermittently supplying the carbon dioxide-rich absorbent 4 at predetermined time intervals instead of constantly supplying it.

Algae incubator 5 may be provided at a position adjacent to carbon dioxide supply source 1 and carbon dioxide recovery unit 2 . Alternatively, if space cannot be secured adjacent to the carbon dioxide supply source 1 and the carbon dioxide recovery unit 2, the algae incubator 5 may be provided at a position physically separated from them. In that case, the carbon dioxide-rich absorption liquid 4 can be transported from the carbon dioxide recovery unit 2 to the algae culture vessel 5 by an appropriate transport means such as a vehicle such as a tank truck or a vessel such as a tanker. Alternatively, the carbon dioxide-rich absorption liquid 4 may be supplied from the carbon dioxide recovery unit 2 to the algae culture vessel 5 via a pipeline or the like.

As shown in FIG. 3, the algae culture vessel 5 includes a tank-shaped algae culture vessel body 31 filled with a culture solution, a water wheel mechanism 32 mounted on a float member, and a culture solution from the algae culture body 31. a water intake portion 33 for taking in; a mixing portion 34 for mixing the carbon dioxide-rich absorbent 4 with the culture solution taken in from the water intake portion 33; and a drain 35 for returning to the algae incubator main body 31 . The mixing section 34 is connected to the second storage section 15a in which the carbon dioxide-rich absorbent 4 is stored.

The algae culture vessel main body 31 is preferably installed in a sunny location so that algae to be propagated can efficiently perform photosynthesis. Also, the algae culture vessel main body 31 is preferably installed in a relatively warm land throughout the year. Various forms can be used for the algae incubator main body 31 . The algae culture vessel main body 31 can be formed by digging the ground and covering the bottom with a waterproof sheet, or it can be formed without covering the waterproof sheet. Alternatively, the algae culture vessel main body 31 can be formed by combining a plurality of concrete blocks and constructing them into a tank shape.

The water wheel mechanism 32 is connected to a drive source such as a motor (not shown), and rotates to agitate the culture solution in the algae culture vessel 5 to uniformly mix the culture solution. The position of the float member is preferably fixed with respect to the algae incubator main body 31 by a rope or the like. A plurality of water wheel mechanisms 32 may be provided.

Algae to be cultured are so-called green algae. The algae to be cultured contains chloroplasts and can grow and proliferate through photosynthesis using sunlight. Algae to be cultured can be rephrased as algae capable of photosynthesis. An appropriate culture medium can be selected and employed according to the type of algae to be grown. For example, when the algae to be propagated is chlorella, the known urea culture solution, nitrate culture solution (N-25), nitrate culture solution (N-30), nitrate culture solution (N- 50), etc. can be employed as the culture solution.

* Fe: 1.0, Ca: 0.5, Zn: 0.1, Mn: 0.1, Cu: 0.02, Mo: 0.01 ppm

* Fe: 1.0, Ca: 0.5, Zn: 0.1, Mn: 0.1, Cu: 0.02, Mo: 0.01 ppm

For example, 1 to 30% by mass, preferably 5 to 10% by mass of the carbon dioxide-rich absorption liquid 4 is mixed as a nitrogen source and a carbon source with respect to the culture solution (urea culture solution, nitrate culture solution). , can be used as a modified culture medium.

Alternatively, when the algae to be grown is Euglena, for example, a known Cramer and Myers medium (CM medium) shown in Table 2 or the like can be employed as the culture solution.

A mixture obtained by mixing, for example, 1 to 30% by mass, preferably 5 to 10% by mass of carbon dioxide-rich absorption liquid 4 as a nitrogen source and a carbon source with respect to the culture medium (CM medium), is added to the modified culture. It can be used as a liquid.

When the algae to be grown is Euglena, for example, the known Koren and Hunter medium (KH medium) shown in Table 3 or the like can be used as the culture medium.

A mixture of, for example, 1 to 30% by mass, preferably 5 to 10% by mass of carbon dioxide-rich absorption liquid 4 as a nitrogen source and a carbon source is added to the culture medium (KH medium) for the modified culture. It can be used as a liquid. When the algae to be grown are other than the above, a known culture solution (medium) suitable for culturing it is appropriately adopted, and for example, 1 to 30% by mass, preferably 5 to 10% by mass. A mixed solution obtained by mixing the carbon dioxide-rich absorption solution 4 of as a nitrogen source and a carbon source can be used as a modified culture solution.

Next, the operation of the algae culture system 10 of this embodiment will be described with reference to FIGS. 1 to 3. FIG. Exhaust gas (gaseous carbon dioxide) is supplied from the carbon dioxide supply source 1 to the lower part of the absorption tower 11 via the third flow path 23 . By driving a pump or the like (not shown), the carbon dioxide-lean absorbent 3 in the first reservoir 14 a is supplied to the upper part of the absorber 11 via the second flow path 22 . The gaseous carbon dioxide thus flows upward in the absorber tower 11 . On the other hand, the carbon dioxide-lean absorbent 3 flows downward in the absorption tower 11 . As a result, the gaseous carbon dioxide and the carbon dioxide-lean absorbent 3 come into contact with each other in the absorption tower 11 in a countercurrent flow. At this time, the carbon dioxide in the gaseous carbon dioxide source 1 reacts with the absorbent in the carbon dioxide-lean absorbent 3 . As a result, carbon dioxide is reacted and absorbed by the carbon dioxide-lean absorbent 3 . As a result, a carbon dioxide-rich absorbent 4 is produced and accumulated at the bottom of the absorption tower 11 . The carbon dioxide-rich absorbent 4 accumulated at the bottom of the absorption tower 11 is sent to the second reservoir 15a through the second channel 22 by the action of gravity. Residual gas 7 in which carbon dioxide is recovered from gaseous carbon dioxide and purified is discharged into the atmosphere from the upper part of absorption tower 11 .

The carbon dioxide-rich absorbent 4 stored in the second reservoir 15a is supplied into the algae incubator 5 by driving a pump (not shown) or the like. The algae incubator 5 is filled with a known culture solution in advance. Algae to be propagated are put into the algae incubator 5 in advance.

When the alga to be cultured is chlorella, the culture solution may be urea culture solution or nitrate culture solution (N-25, N-30, N-50). When the alga to be cultured is Euglena, CM medium or KH medium can be used as the culture medium. 1 to 30% by mass, preferably 5 to 10% by mass of carbon dioxide-rich absorbent 4 is mixed as a nitrogen source with such a known culture solution. Further, in the algae culture vessel 5, when the carbon dioxide-rich absorption liquid 4 is decomposed by the action of microorganisms, carbon dioxide is appropriately released into the culture medium. Therefore, the algae to be cultured can use this carbon dioxide as a carbon source when growing through photosynthesis. When a 5-aminolevulinic acid aqueous solution is used as the carbon dioxide-rich absorption liquid 4, 5-aminolevulinic acid can be absorbed by algae together with carbon dioxide as it is before decomposition.

The carbon dioxide-rich absorbent 4 may be supplied to the algae culture vessel 5 intermittently at regular intervals, or may be constantly supplied at a constant rate. The culture solution mixed with the carbon dioxide-rich absorption liquid 4 becomes a modified culture solution enriched with nitrogen source and carbon source. When the 5-aminolevulinic acid aqueous solution is used as the carbon dioxide-rich absorption solution 4, the culture solution can promote the growth of algae as it is while enhancing the carbon source. The carbon dioxide-rich absorption liquid 4 is uniformly mixed with the original culture liquid by the action of the water wheel mechanism 32 . Algae are efficiently grown and cultured by photosynthesis in the modified culture medium enriched with nitrogen and carbon sources. The grown and cultured algae are recovered by an algae recovery device 6 composed of a power shovel, a pump, or the like, and used for various purposes. The collected algae can be extracted, for example, as a liquid fuel, or the active ingredient can be extracted as a supplement. The extracted residue can be used as biomass fuel in a thermal power plant or the like, or can be used as feed for livestock.

If the culture medium is depleted, it can be supplemented with appropriately modified culture medium. That is, with respect to the culture medium (urea culture medium, nitrate culture medium, CM medium, KH medium, other medium), for example, 1 to 30% by mass, preferably 5 to 10% by mass carbon dioxide-rich absorption liquid 4 as a nitrogen source and a carbon source is prepared as a modified culture solution, which can be replenished to the algae incubator 5 .

According to the first embodiment, the following can be said. A carbon dioxide algae culture system 10 includes a carbon dioxide supply source 1 that supplies a carbon dioxide-containing gas, and a carbon dioxide recovery that obtains a carbon dioxide-rich absorbent 4 by bringing a carbon dioxide-lean absorbent 3 into contact with the carbon dioxide-containing gas. Algae culture vessel 5 provided adjacent to unit 2, carbon dioxide supply source 1 and carbon dioxide recovery unit 2, and receiving supply of carbon dioxide-rich absorbing liquid 4 from carbon dioxide recovery unit 2 as a nutrient source, and an algae culture vessel 5 capable of culturing algae.

In the algae culture method, a carbon dioxide-containing gas is supplied by a carbon dioxide supply source 1, and a carbon dioxide-lean absorbent 3 is brought into contact with the carbon dioxide-containing gas by a carbon dioxide recovery unit 2 to obtain a carbon dioxide-rich absorbent 4, The carbon dioxide-rich absorption liquid 4 is supplied from the carbon dioxide recovery unit 2 to the algae incubator 5 as a nutrient source, and algae are cultured in the algae incubator 5 .

According to these configurations, carbon dioxide from the carbon dioxide supply source 1 can be absorbed by the carbon dioxide-lean absorbent 3 to obtain the carbon dioxide-rich absorbent 4 . In addition, the carbon dioxide-rich absorption liquid 4 can be used as a part (nitrogen source) of the algae culture liquid as it is without desorbing carbon dioxide. This makes it possible to eliminate the energy required for the heat treatment required when desorbing carbon dioxide from the carbon dioxide-rich absorbent 4 . As described above, a large amount of algae can be cultured efficiently at low cost.

In this case, the carbon dioxide-lean absorbent 3 and the carbon dioxide-rich absorbent 4 are absorbents containing an absorbent, and the absorbent is ammonia or an amine compound.

According to this configuration, carbon dioxide from the carbon dioxide supply source can be efficiently recovered by the ammonia or amine-based compound. This enables efficient cultivation of algae.

In this case, the absorbent is ammonia or an organic amine compound. According to this configuration, carbon dioxide from the carbon dioxide supply source can be efficiently recovered by ammonia or the organic amine compound. This enables efficient cultivation of algae.

In this case, an algae recovery device 6 for recovering the algae cultured in the algae incubator 5 is provided. According to this configuration, algae grown in the algae incubator 5 can be efficiently recovered and used by the algae recovery device 6 .

In this case, said algae are photosynthetically capable algae. According to this configuration, the carbon dioxide contained in the carbon dioxide-rich absorbent 4 is appropriately released when the carbon dioxide-rich absorbent 4 is decomposed by the action of naturally occurring microorganisms in the algae incubator 5. be done. Therefore, algae can grow using this carbon dioxide as a carbon source during photosynthesis. As described above, a large amount of algae can be cultured efficiently at low cost.

In the following embodiment, portions different from the first embodiment will be mainly described, and illustration or description of portions common to the first embodiment will be omitted.
[Second embodiment]

The algae culture system 10 of this embodiment will be described with reference to FIG. In this embodiment, the configuration of the algae incubator 5 is different from that of the first embodiment, but other parts are common to those of the first embodiment. Therefore, the algae incubator 5 will be mainly described.

The algae culture vessel 5 of this embodiment may be provided at a position adjacent to the carbon dioxide supply source 1 and the carbon dioxide recovery section 2 . Alternatively, if space cannot be secured adjacent to the carbon dioxide supply source 1 and the carbon dioxide recovery unit 2, the algae incubator 5 may be provided at a position physically separated from them. In that case, the carbon dioxide-rich absorption liquid 4 can be transported from the carbon dioxide recovery unit 2 to the algae culture vessel 5 by an appropriate transport means such as a vehicle such as a tank truck or a vessel such as a tanker. Alternatively, the carbon dioxide-rich absorption liquid 4 may be supplied from the carbon dioxide recovery unit 2 to the algae culture vessel 5 via a pipeline or the like. The algae culture vessel 5 is preferably installed in a sunny location so that the algae to be propagated can efficiently photosynthesise. Also, the algae incubator 5 is preferably installed in relatively warm land throughout the year.

The algae culture vessel 5 is composed of a closed culture system that is cut off from the outside world. The algae culture vessel 5 includes a processing unit 51 connected to the second storage unit 15a of the carbon dioxide recovery unit, a filter unit 52 for filtering the liquid processed by the processing unit 51 in a sterile state, and a filter unit 52 for filtering the liquid. A tank 53 to which the liquid is supplied and the algae culture solution and the algae are stored; a pipe portion 54 extending from the tank 53 and formed in a cylindrical shape from a translucent plastic material; and the pipe portion 54 is supported. and a pump 56 provided in the middle of the pipe portion 54 . The position of the pump 56 is arbitrary, and may be provided at any position as long as the culture solution and algae to be cultured can be circulated with respect to the pipe portion 54 .

The processing unit 51 is formed in the shape of a closed tank, and stores water in which an aquatic microbial ecosystem such as nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria), bacillus, etc. has been established. Water in which an aquatic microbial ecosystem has been established can be prepared, for example, by allowing water containing soil and organic matter (bonito broth or corn steeping liquid) to stand for 2 to 4 weeks while being aerated. The processing unit 51 can appropriately decompose ammonia or an amine compound in the carbon dioxide-rich absorbent 4 supplied from the second storage unit 15a. That is, when an aqueous ammonia solution is used as the carbon dioxide-rich absorbent 4, the ammonia is nitrified into nitrate via nitrite by nitrifying bacteria. As the ammonia is so decomposed, carbon dioxide is released from the carbon dioxide-rich absorbent. Although part of the carbon dioxide is released into the air in the tank 53, most of it is retained dissolved in the liquid.

When an aqueous solution of any of the amine compounds is used as the carbon dioxide-rich absorption liquid 4, it is appropriately decomposed by Bacillus, and carbon dioxide is released from the carbon dioxide-rich absorption liquid upon decomposition. Decomposition products of nitrates and amine compounds are absorbed by algae to be cultured as nitrogen sources (nutrients). Note that providing the processing unit 51 and the filter unit 52 is optional. For example, when a 5-aminolevulinic acid aqueous solution is used as the carbon dioxide-rich absorption liquid 4, the carbon dioxide-rich absorption liquid 4 is not harmful to algae, but rather has the effect of promoting the growth thereof. The carbon dioxide-rich absorbent 4 can be supplied to the tank 53 as it is without passing through the .

The filter part 52 includes a bacteria filter and can remove microorganisms, bacteria, etc. in the liquid. A cellulose ester membrane having micropores of 0.2 mm or less can be suitably used as the bacterial filter. In order to prevent clogging of the bacterial filter, a plurality of preliminary filters having a coarser mesh than the bacterial filter may be provided upstream of the bacterial filter.

The pipe portion 54 is formed as one long pipe line by repeating a straight portion and a curved portion. The pipe portion 54 is transparent. By passing the culture solution and the algae to be cultured inside the pipe portion 54, the algae to be cultured can undergo photosynthesis in this interior, and the algae can be propagated and cultured.

The pillar 55 is placed on the ground 57 , but the lower portion thereof may be embedded in the ground 57 .

Next, the action of the algae culture system 10 of this embodiment will be described. A carbon dioxide-rich absorbent 4 is produced in the same manner as in the first embodiment. The carbon dioxide-rich absorbent 4 stored in the second storage portion 15a of the carbon dioxide recovery portion 2 is treated with an aquatic microbial ecosystem such as nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) and bacillus. It is mixed with water in part 51 . In the processing section 51, when the mixture of the carbon dioxide-rich absorbing liquid 4 and the water in the processing section 51 is left for several days to several weeks, the carbon dioxide-rich absorbing liquid 4 is decomposed by the action of bacteria in the underwater microbial ecosystem. . When the carbon dioxide-rich absorption liquid 4 is composed of an aqueous solution of ammonia, it is nitrified into nitrate via nitrite by the action of nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) and the like. When the carbon dioxide-rich absorption liquid 4 is composed of an aqueous solution of any of the amine compounds, it is appropriately decomposed by the action of bacillus or the like. When the carbon dioxide-rich absorbent 4 is decomposed, the carbon dioxide retained in the carbon dioxide-rich absorbent is appropriately released into the liquid.

The liquid processed by the processing unit 51 is supplied to the filter unit 52 and filtered. The filter section 52 removes the nitrifying bacteria, bacillus, and other bacteria. When an aqueous ammonia solution is used as the carbon dioxide-rich absorbing liquid 4, the nitrate (nitrate ion) and carbon dioxide in the liquid are supplied to the tank 53 together with the filtrate.

When any aqueous solution of an amine-based compound is used as the carbon dioxide-rich absorption liquid 4, the amine decomposed product and carbon dioxide in the liquid are supplied to the tank 53 together with the filtrate. When the 5-aminolevulinic acid aqueous solution is used as the carbon dioxide-rich absorbing liquid 4, it is directly supplied to the tank 53 without passing through the processing section 51 and the filter section 52. The carbon dioxide-rich absorbent 4 (decomposition treatment liquid of the carbon dioxide-rich absorbent 4) may be constantly supplied to the tank 53, or may be intermittently supplied to the tank 53 at predetermined time intervals. you can

The algae to be cultured are put into the tank 53 in advance, and the algae culture solution is stored therein. When the alga to be cultured is chlorella, the culture solution may be a known urea culture solution or nitrate culture solution (N-25, N-30, N-50). When the alga to be cultured is Euglena, a known CM medium or KH medium can be employed as the culture medium.

In this way, 1 to 30% by mass, preferably 5 to 10% by mass of the carbon dioxide-rich absorption liquid 4 is mixed with the culture solution containing the algae to be cultured, and the modified culture solution is placed in the tank 53. create. More specifically, the carbon dioxide-rich absorbent 4 is a filtrate that has been decomposed by the processing section 51 and filtered by the filter section 52 .

A mixture of the culture solution containing algae to be cultured and the carbon dioxide-rich absorption liquid 4 is sent into the pipe section 54 by driving the pump 56 . By irradiating the pipe portion 54 with sunlight, the algae in the pipe portion 54 perform photosynthesis and proliferate. Nitrates (nitrate ions) are then absorbed by the algae as a nitrogen source. Amine degradation products are likewise absorbed by algae as a nitrogen source. Carbon dioxide is also absorbed by algae as a carbon source. 5-Aminolevulinic acid is absorbed as such by algae to promote their growth.

This liquid mixture is circulated in the pipe portion 54, and after the algae have grown sufficiently after the lapse of a predetermined period, the algae are recovered together with the culture solution. At that time, an algae collection device (not shown) can be used. An example of an algae recovery device is a filter device (filter) capable of picking up algae from a culture solution.

The collected algae are used for various purposes. The collected algae can be extracted, for example, as a liquid fuel, or the active ingredient can be extracted as a supplement. The extracted residue can be used as biomass fuel in a thermal power plant or the like, or can be used as feed for livestock.

When the culture medium is depleted, it can be supplemented with the culture medium modified as described above. That is, with respect to the culture medium (urea culture medium, nitrate culture medium, CM medium, KH medium, other medium), for example, 1 to 30% by mass, preferably 5 to 10% by mass carbon dioxide-rich absorption liquid 4 Alternatively, a mixed solution is prepared as a modified culture solution by mixing the filtrate obtained by decomposing the carbon dioxide-rich absorption liquid 4 in the processing unit 51 and filtering it in the filter unit 52 . The tank 53 can be replenished with the culture medium thus modified.

The above-described embodiments can be implemented with various replacements and modifications.

1 carbon dioxide supply source 2 carbon dioxide recovery unit 3 carbon dioxide-lean absorbent 4 carbon dioxide-rich absorbent 5 algae incubator 6 algae recovery device 10 algae culture system

Claims (9)

a carbon dioxide source that supplies a carbon dioxide-containing gas;
a carbon dioxide recovery unit for obtaining a carbon dioxide-rich absorbent by contacting the carbon dioxide-containing gas with the carbon dioxide-lean absorbent;
an algae culture vessel capable of cultivating algae by receiving supply of the carbon dioxide-rich absorption liquid as a nutrient source from the carbon dioxide recovery unit;
An algae culture system comprising: The carbon dioxide-lean absorbent and the carbon dioxide-rich absorbent are absorbent-containing absorbents,
The algae culture system according to claim 1, wherein the absorbent is ammonia or an amine-based compound. The algae culture system according to claim 2, wherein the absorbent is ammonia or an organic amine compound. The algae culture system according to any one of claims 1 to 3, comprising an algae recovery device for recovering the algae cultured in the algae culture vessel. The algae culture system according to any one of claims 1 to 4, wherein the algae are algae capable of photosynthesis. supplying a carbon dioxide-containing gas with a carbon dioxide source;
A carbon dioxide-rich absorption liquid is obtained by bringing a carbon dioxide-lean absorption liquid into contact with the carbon dioxide-containing gas by a carbon dioxide recovery unit,
An algae culture method comprising supplying the carbon dioxide-rich absorption liquid from the carbon dioxide recovery unit to an algae culture vessel as a nutrient source and culturing algae in the algae culture vessel. The carbon dioxide-lean absorbent and the carbon dioxide-rich absorbent are absorbent-containing absorbents,
The method for culturing algae according to claim 6, wherein the absorbent is ammonia or an amine compound. The algae culture method according to claim 7, wherein the absorbent is ammonia or an organic amine compound. The algae culture method according to any one of claims 6 to 8, wherein the algae are algae capable of photosynthesis.

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