Microalgae cultivation system and microalgae cultivation method

Abstract

To provide a microalgae cultivation system capable of reducing carbon dioxide in gas discharged from a gas emission apparatus.SOLUTION: A microalgae cultivation system 20 comprises: a cultivation device 24 to which a gas is supplied, which is taken from a gas exhaust path 150 of a gas emission apparatus 10 discharging gas containing carbon dioxide and mercury, the cultivation device being configured to culture halophilic microalgae using the carbon dioxide contained in the gas; and a mercury recovery device 22 which is disposed between the gas exhaust path 150 and the cultivation device 24, the mercury recovery device being configured to recover mercury contained in the gas.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a microalgae culture system and a microalgae culture method for culturing halophilic microalgae. [Background technology]

[0002] Patent Document 1 discloses an algae culture system in which carbon dioxide is introduced into a dissolution tank from a carbon dioxide supply source to dissolve the carbon dioxide in a culture solution, and the culture solution containing carbon dioxide is supplied to the culture tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-65331 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, there has been a demand for reducing the amount of carbon dioxide in the gas discharged from equipment that discharges gas containing carbon dioxide (hereinafter referred to as gas discharge equipment). For this reason, it has been considered to reduce the amount of carbon dioxide in the gas by introducing the gas into a conventional algae cultivation system such as that disclosed in the above-mentioned Patent Document 1 and using the carbon dioxide in the gas for culturing algae. However, the inventors of the present application have found that the gas contains various components other than carbon dioxide, which may affect the cultivation of algae. In this case, the gas cannot be used for culturing algae, and the carbon dioxide in the gas cannot be reduced.

[0005] The present invention was made by the inventors of the present application by focusing on the above-mentioned problem, and aims to provide a microalgae cultivation system and a microalgae cultivation method that can reduce carbon dioxide in the gas discharged from a gas exhaust equipment. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a microalgae cultivation system according to one embodiment of the present invention includes a cultivation device that is supplied with gas extracted from a gas exhaust line of a gas exhaust equipment that exhausts gas containing carbon dioxide and mercury, and cultivates halophilic microalgae using the carbon dioxide contained in the gas, and a mercury recovery device that is disposed between the gas exhaust line and the cultivation device and recovers mercury contained in the gas.

[0007] According to this, the microalgae cultivation system includes a cultivation device for cultivating halophilic microalgae using carbon dioxide contained in the gas extracted from the gas exhaust path of the gas exhaust equipment, and a mercury recovery device disposed between the gas exhaust path and the cultivation device for recovering mercury contained in the gas. In this way, when the gas contains mercury, the mercury affects the cultivation of halophilic microalgae when the gas is supplied to the cultivation device, so the mercury contained in the gas going from the gas exhaust path to the cultivation device is recovered by the mercury recovery device. As a result, the cultivation device is supplied with the gas from which the mercury has been recovered, so that the cultivation device can cultivate halophilic microalgae using carbon dioxide while suppressing the influence of mercury on the cultivation of halophilic microalgae. Therefore, since carbon dioxide is used in the cultivation device, the amount of carbon dioxide in the gas discharged from the gas exhaust facility can be reduced in the microalgae cultivation system.

[0008] Furthermore, exhaust gas after coal combustion may be supplied as the gas to the culture apparatus, and the mercury recovery apparatus may recover mercury contained in the exhaust gas.

[0009] According to this, in the microalgae cultivation system, exhaust gas after coal combustion is supplied to the cultivation device, and the mercury recovery device recovers mercury contained in the exhaust gas. In other words, after the mercury recovery device recovers mercury contained in the exhaust gas after coal combustion, the cultivation device uses carbon dioxide in the exhaust gas. This makes it possible to reduce the amount of carbon dioxide in the gas discharged from the gas exhaust facility that burns coal in the microalgae cultivation system.

[0010] In addition, exhaust gas after combustion in an incinerator may be supplied as the gas to the culture apparatus, and the mercury recovery apparatus may recover mercury contained in the exhaust gas.

[0011] According to this, in the microalgae cultivation system, the cultivation device is supplied with exhaust gas after combustion in an incinerator, and the mercury recovery device recovers mercury contained in the exhaust gas. In other words, after the mercury recovery device recovers mercury contained in the exhaust gas after combustion in an incinerator, the cultivation device uses carbon dioxide in the exhaust gas. This makes it possible to reduce the amount of carbon dioxide in the gas discharged from the gas exhaust facility equipped with an incinerator in the microalgae cultivation system.

[0012] The mercury recovery device may be connected to a pipe branched off from the gas exhaust path leading to a chimney.

[0013] According to this, the mercury recovery device is connected to a pipe branching off from the gas exhaust path leading to the chimney, so that gas can be easily extracted from the gas exhaust path via the pipe and the mercury contained in the gas can be recovered.

[0014] The mercury recovery device may have an aqueous solution containing chloride ions, and may recover mercury contained in the gas by bringing the gas into contact with the aqueous solution.

[0015] Since mercury dissolves in an aqueous solution containing chloride ions, when a gas containing mercury is brought into contact with an aqueous solution containing chloride ions, the mercury in the gas dissolves in the aqueous solution, and the mercury can be recovered from the gas. Therefore, a mercury recovery device has an aqueous solution containing chloride ions, and can recover the mercury contained in the gas by bringing the gas into contact with the aqueous solution.

[0016] Moreover, seawater may be supplied to the mercury recovery apparatus as the aqueous solution.

[0017] According to this, by supplying seawater as an aqueous solution containing chloride ions to the mercury recovery apparatus, the aqueous solution containing chloride ions can be easily supplied to the mercury recovery apparatus.

[0018] The culture device may supply a culture medium as the aqueous solution to the mercury recovery device.

[0019] When an aqueous solution containing chloride ions is used as the culture medium of the culture device, the culture medium can be used as the aqueous solution of the mercury recovery device. In this case, the culture device supplies the culture medium to the mercury recovery device as an aqueous solution containing chloride ions. This makes it possible to easily supply the aqueous solution containing chloride ions to the mercury recovery device while effectively utilizing the culture medium of the culture device.

[0020] The present invention can be realized not only as such a microalgae culture system, but also as a microalgae culture method including a characteristic process performed by the microalgae culture system. For example, a microalgae culture method according to one aspect of the present invention includes a culture step of supplying a gas extracted from a gas exhaust passage of a gas exhaust facility that exhausts a gas containing carbon dioxide and mercury to a culture device, and cultivating halophilic microalgae using the carbon dioxide contained in the gas, and a mercury recovery step of recovering the mercury contained in the gas by a mercury recovery device disposed between the gas exhaust passage and the culture device before the culture step. In this microalgae culture method, as in the microalgae culture system, carbon dioxide is used in the culture device, so that the amount of carbon dioxide in the gas exhausted from the gas exhaust facility can be reduced.

[0021] The present invention can also be realized as a microalgae cultivation facility equipped with a microalgae cultivation system. The present invention can also be realized as a program for causing a computer to execute the microalgae cultivation method, or as a computer-readable recording medium such as a CD-ROM (Compact Disc-Read Only Memory) on which the program is recorded. Such a program can be distributed via a recording medium such as a CD-ROM or a transmission medium such as the Internet. The present invention can also be realized as an integrated circuit equipped with a processing unit (control device) that performs the microalgae cultivation method. Effect of the Invention

[0022] According to the microalgae culture system etc. of the present invention, it is possible to reduce the carbon dioxide in the gas discharged from the gas exhaust equipment. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a microalgae culture facility according to an embodiment. FIG. [Diagram 2] FIG. 1 is a schematic diagram showing a configuration of a microalgae culture system according to an embodiment. [Diagram 3] 1 is a flowchart showing a microalgae culture method according to an embodiment. [Figure 4] FIG. 2 is a schematic diagram showing a configuration of a microalgae culture system according to a first modified example of the embodiment. [Diagram 5] FIG. 11 is a schematic diagram showing the configuration of a microalgae culture facility according to a second modified example of the embodiment. [Figure 6] FIG. 11 is a schematic diagram showing the configuration of a microalgae culture facility according to a third modified example of the embodiment. [Figure 7] FIG. 11 is a schematic diagram showing the configuration of a microalgae culture facility according to a fourth modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, a microalgae culture system and a microalgae culture method according to an embodiment and its modified examples of the present invention will be described with reference to the drawings. Note that the embodiment and its modified examples described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection of components, steps in the method, and the order of steps shown in the following embodiment and its modified examples are merely examples and are not intended to limit the present invention. In each drawing, the same or similar components are given the same reference numerals.

[0025] (Embodiment) [1 General description of microalgae cultivation facility 1] First, a schematic configuration of a microalgae culture facility 1 equipped with a microalgae culture system will be described. Fig. 1 is a schematic diagram showing a schematic configuration of a microalgae culture facility 1 according to the present embodiment.

[0026] The microalgae cultivation facility 1 is a facility that burns fuel in a boiler to discharge gas, and cultivates halophilic microalgae using the gas.

[0027] 1, the microalgae cultivation facility 1 includes a gas exhaust facility 10 and a microalgae cultivation system 20. The gas exhaust facility 10 includes a boiler 100, a denitrification device 110, a dust collection device 120, a desulfurization device 130, a chimney 140, and a gas exhaust path 150.

[0028] The boiler 100 is a device that burns fuel to heat water and generate hot water or steam. In this embodiment, the boiler 100 is supplied with fossil fuel, specifically, coal. For example, the boiler 100 has a storage facility (not shown) for storing coal, pulverizes the coal stored in the storage facility into pulverized coal, and combusts the pulverized coal. In addition, a gas exhaust passage 150 is connected to the boiler 100, and exhaust gas g after burning the fuel is sent through the gas exhaust passage 150 to the denitration device 110, the dust collector 120, the desulfurization device 130, and the chimney 140. The gas exhaust passage 150 is a flue that sends the exhaust gas g from the boiler 100 to the chimney 140. In this embodiment, since coal is burned in the boiler 100, the exhaust gas g discharged from the boiler 100 contains nitrogen oxides, soot, sulfur oxides, carbon dioxide, and mercury (metallic mercury). The mercury discharged from the boiler 100 is cooled while passing through the gas discharge passage 150 and adheres to the soot and dust.

[0029] The denitration device 110 is a device that denitrifies the exhaust gas g generated by burning fuel in the boiler 100. Specifically, the denitration device 110 is disposed between the boiler 100 and the dust collector 120, and removes nitrogen oxides in the exhaust gas g flowing through the gas exhaust passage 150 toward the dust collector 120. During this process, in the denitration device 110, metallic mercury in the exhaust gas g reacts with other components to produce divalent mercury (HgCl2, etc.) 2+ Therefore, the exhaust gas g discharged from the denitrification device 110 contains dust (ash), sulfur oxides, carbon dioxide, and mercury (metallic mercury, mercury attached to dust, and divalent mercury (Hg 2+ )) is included.

[0030] The dust collector 120 is a device that removes soot and dust from the flue gas g. For example, the dust collector 120 is a low-temperature type dry electrostatic precipitator (EP) that attracts and removes soot and dust from the flue gas g by electrostatic force. In other words, the dust collector 120 is disposed between the denitration device 110 and the desulfurization device 130, and removes soot and dust in the flue gas g that flows from the denitration device 110 to the desulfurization device 130, as well as mercury attached to the soot and dust. For this reason, the flue gas g discharged from the dust collector 120 contains sulfur oxides, carbon dioxide, and mercury (metallic mercury and divalent mercury (Hg 2+ )) is included.

[0031] The desulfurization device 130 is a device that removes sulfur oxides from the flue gas g. For example, the desulfurization device 130 is a wet desulfurization device in which makeup water is supplied to an absorption tower (not shown) and wet desulfurization treatment is performed. In other words, the desulfurization device 130 is disposed between the dust collector 120 and the chimney 140, and removes sulfur oxides from the flue gas g that flows from the dust collector 120 to the chimney 140. Here, metallic mercury is insoluble in water, but divalent mercury (Hg 2+ ) is water-soluble, so it dissolves in the makeup water in the desulfurization device 130 and is removed by the desulfurization device 130 together with the sulfur oxides. For this reason, the flue gas g discharged from the desulfurization device 130 contains carbon dioxide and mercury (metallic mercury). In this way, nitrogen oxides, soot and dust, sulfur oxides, mercury attached to the soot and dust, and the like are removed from the flue gas g discharged from the boiler 100, and the flue gas g containing carbon dioxide and mercury (metallic mercury) is discharged from the desulfurization device 130.

[0032] The microalgae culture system 20 is connected to a gas discharge passage 150, and is a system for cultivating halophilic microalgae using the gas discharged from the gas discharge passage 150. The microalgae culture system 20 includes a pipe 21 branched from the gas discharge passage 150, and cultivates halophilic microalgae using the gas discharged from the pipe 21. In this embodiment, the pipe 21 is a pipe that is thinner (has a smaller cross-sectional area of ​​the flow path) than the gas discharge passage 150, and is connected between the desulfurizer 130 and the chimney 140 in the gas discharge passage 150 (branched from between the desulfurizer 130 and the chimney 140). Therefore, the gas discharged from the pipe 21 contains carbon dioxide and mercury (metallic mercury). The configuration of the microalgae culture system 20 for cultivating halophilic microalgae using this gas will be described in detail below.

[0033] [2 Explanation of Microalgae Cultivation System 20] Fig. 2 is a schematic diagram showing the configuration of a microalgae culture system 20 according to the present embodiment. As shown in Fig. 2, in addition to the above-mentioned piping 21, the microalgae culture system 20 includes a mercury recovery device 22, a piping 23, and a culture device 24.

[0034] The mercury recovery device 22 is disposed between the gas exhaust path 150 and the culture device 24, and recovers mercury contained in the gas (exhaust gas g) extracted from the gas exhaust path 150. Specifically, the mercury recovery device 22 is connected to a pipe 21 branching off from the gas exhaust path 150 leading to the chimney 140, thereby being connected to the gas exhaust path 150. The mercury recovery device 22 is connected to the culture device 24 by being connected to a pipe 23 connected to the culture device 24. In this way, the mercury recovery device 22 is connected to the gas exhaust path 150 and the culture device 24 between the gas exhaust path 150 and the culture device 24.

[0035] The mercury recovery device 22 recovers mercury (metallic mercury) contained in the exhaust gas g supplied from the pipe 21. Specifically, the mercury recovery device 22 has an aqueous solution 22a containing chloride ions, and recovers mercury (metallic mercury) contained in the gas (exhaust gas g) by contacting the aqueous solution 22a with the gas. More specifically, the mercury recovery device 22 has a configuration in which the aqueous solution 22a is accommodated in a container, and the pipe 21 is inserted into the aqueous solution 22a in the container, and the exhaust gas g is released from the pipe 21, so that the mercury (metallic mercury) contained in the exhaust gas g dissolves in the aqueous solution 22a. The aqueous solution 22a is an aqueous solution containing chloride ions, such as a sodium chloride aqueous solution, an ammonium chloride aqueous solution, a potassium chloride aqueous solution, a calcium chloride aqueous solution, an iron (II) chloride aqueous solution, an iron (III) chloride aqueous solution, or a magnesium chloride aqueous solution. In this embodiment, seawater (aqueous sodium chloride solution: NaCl) is supplied to the mercury recovery device 22 as the aqueous solution 22a. Specifically, the mercury recovery device 22 has a pipe 22b, and seawater (NaCl) is supplied as the aqueous solution 22a from the pipe 22b. In this way, the mercury recovery device 22 converts metallic mercury (Hg) contained in the exhaust gas g supplied from the pipe 21 into mercury tetrachloride ions (HgCl4 2- ) and other divalent mercury (Hg 2+ The mercury is recovered by dissolving it in the aqueous solution 22a in the form of mercury salt. The aqueous solution 22a may be supplied to the mercury recovery device 22 with high-concentration salt water, which is an aqueous solution having a higher salt concentration (containing a high concentration of chloride ions) than seawater.

[0036] In this embodiment, the mercury recovery device 22 dissolves metallic mercury contained in the exhaust gas g into the aqueous solution 22a by bubbling. That is, the mercury recovery device 22 has a pipe 21 inserted up to the bottom of the aqueous solution 22a, and sends the exhaust gas g from the pipe 21 into the aqueous solution 22a to generate bubbles of the exhaust gas g in the aqueous solution 22a. In this way, the mercury recovery device 22 dissolves metallic mercury contained in the exhaust gas g into the aqueous solution 22a. Specifically, the mercury recovery device 22 dissolves metallic mercury contained in the exhaust gas g into the aqueous solution 22a by generating bubbles (bubbles with a diameter of about 100 μm or more). The mercury recovery device 22 may dissolve metallic mercury into the aqueous solution 22a by generating microbubbles (very small bubbles with a diameter of about 1 μm to 100 μm) or ultrafine bubbles (very small bubbles with a diameter of less than 1 μm). In this manner, the mercury recovery device 22 dissolves the metallic mercury contained in the exhaust gas g into the aqueous solution 22a by a bubbling method such as bubbles, and thus can effectively dissolve the metallic mercury into the aqueous solution 22a.

[0037] The exhaust gas g from which metallic mercury has been recovered is supplied from the mercury recovery device 22 to the culture device 24 through the piping 23. Specifically, the piping 23 is inserted into the upper part of the container of the mercury recovery device 22 so that the tip of the piping 23 is positioned above the aqueous solution 22a. As a result, the exhaust gas g from which metallic mercury has been recovered by the aqueous solution 22a and from which carbon dioxide remains moves above the aqueous solution 22a and is sent from the mercury recovery device 22 to the culture device 24 through the piping 23.

[0038] The culture device 24 is supplied with gas extracted from the gas exhaust line 150 of the gas exhaust equipment 10 that exhausts gas containing carbon dioxide and mercury, and is used to culture halophilic microalgae using the carbon dioxide contained in the gas. As described above, the culture device 24 is supplied with exhaust gas g after coal combustion as the gas. That is, the culture device 24 is supplied with exhaust gas g extracted from the gas exhaust line 150 by the pipe 21 and passed through the pipe 21, the mercury recovery device 22, and the pipe 23. The exhaust gas g extracted from the gas exhaust line 150 by the pipe 21 contains carbon dioxide and mercury (metallic mercury), but as described above, the mercury (metallic mercury) is recovered by the mercury recovery device 22. Therefore, the exhaust gas g supplied to the culture device 24 through the pipe 23 contains almost no mercury (metallic mercury) and contains carbon dioxide.

[0039] Halophilic microalgae are unicellular algae with a body length of several μm to several hundred μm, and live in seawater (natural seawater or artificial seawater; the same applies below) or high-saline water with a higher salinity than seawater. Among halophilic microalgae, marine microalgae that live in seawater include, but are not limited to, phytoplankton such as Odontella, Isochrysis, Nitzschia, Chaetoceros, Nannochloropsis, Pavlova, Porphyridium, Phaeodactylum, and Skeltonema. Since marine microalgae live in seawater, it is preferable to use seawater for the liquid medium. Among halophilic microalgae, Dunaliella is an example of a microalgae that lives in high-saline water such as the Dead Sea, salt lakes, and salt fields. For Dunaliella, it is preferable to use a medium with a higher salinity than seawater. For this reason, the culture device 24 has a pipe 24a, and seawater or high-concentration salt water (aqueous sodium chloride solution: NaCl) is supplied from the pipe 24a as a culture medium. Here, metallic mercury does not dissolve in water, but dissolves in the seawater or high-concentration salt water serving as the culture medium and exists in the form of mercury tetrachloride ions, which affect the growth of halophilic microalgae. For this reason, by not including metallic mercury in the exhaust gas g supplied to the culture device 24, it is possible to suppress the dissolution of metallic mercury in the culture medium and to suppress the influence of metallic mercury on the growth of halophilic microalgae.

[0040] Furthermore, since the exhaust gas g supplied to the culture device 24 contains carbon dioxide, the culture device 24 cultures the halophilic microalgae using the carbon dioxide. The halophilic microalgae fix carbon dioxide by photosynthesis. Since lipids that can be used as raw materials for diesel fuel and aviation fuel called SAF (short for "Sustainable Aviation Fuel" in Japanese) can be extracted from the cultured halophilic microalgae, it is possible to establish a carbon recycling technology using the halophilic microalgae. In addition to carotenoids such as β-carotene, which is said to have antioxidant properties, highly unsaturated fatty acids such as docosahexaenoic acid (DHA), which is known to have the function of activating brain nerve cell processes, and eicosapentaenoic acid (EPA), which is used as a treatment for arteriosclerosis and hyperlipidemia, can also be extracted. The type of halophilic microalgae is not particularly limited as long as it is a microalgae that grows with carbon dioxide in a culture medium such as seawater or highly concentrated salt water.

[0041] [3 Explanation of microalgae cultivation method] Next, a detailed description will be given of the process (microalgae culture method) performed by the microalgae culture facility 1. Fig. 3 is a flowchart showing the microalgae culture method according to the present embodiment.

[0042] As shown in FIG. 3, in the mercury recovery step (S102), before the culture step (S104), mercury contained in the gas (exhaust gas g) is recovered by the mercury recovery device 22 disposed between the gas exhaust path 150 and the culture device 24. That is, the mercury recovery device 22 receives the exhaust gas g from the pipe 21 branched from the gas exhaust path 150 toward the chimney 140, and recovers the mercury (metallic mercury) contained in the exhaust gas g. Specifically, the mercury recovery device 22 is supplied with seawater as the aqueous solution 22a containing chloride ions, and recovers the mercury (metallic mercury) contained in the exhaust gas g by contacting the aqueous solution 22a with the exhaust gas g. Then, the exhaust gas g from which the metallic mercury has been recovered is supplied from the mercury recovery device 22 to the culture device 24 by the pipe 23. The mercury recovery device 22 may be supplied with highly concentrated salt water as the aqueous solution 22a.

[0043] Thereafter, in the culture step (S104), gas extracted from the gas exhaust path 150 of the gas exhaust equipment 10, which exhausts gas containing carbon dioxide and mercury, is supplied to the culture device 24, and halophilic microalgae are cultured using the carbon dioxide contained in the gas. As described above, exhaust gas g after coal combustion is supplied to the culture device 24 as the gas. Since the exhaust gas g supplied to the culture device 24 contains almost no mercury (metallic mercury) but contains carbon dioxide, the halophilic microalgae fix the carbon dioxide through photosynthesis while suppressing the effects of mercury. In this way, the culture device 24 cultures the halophilic microalgae.

[0044] [4. Description of Effects] As described above, the microalgae culture system 20 according to the present embodiment includes the culture device 24 that cultures halophilic microalgae using carbon dioxide contained in the gas (exhaust gas g) extracted from the gas exhaust path 150 of the gas exhaust equipment 10. The microalgae culture system 20 further includes the mercury recovery device 22 that is disposed between the gas exhaust path 150 and the culture device 24 and recovers mercury contained in the gas. In this manner, when the gas (exhaust gas g) contains mercury, the mercury affects the culture of the halophilic microalgae when the gas is supplied to the culture device 24. Therefore, the mercury recovery device 22 recovers the mercury contained in the gas flowing from the gas exhaust path 150 to the culture device 24. As a result, the culture device 24 is supplied with the gas from which the mercury has been recovered, and the culture device 24 can culture the halophilic microalgae using carbon dioxide while suppressing the influence of mercury on the culture of the halophilic microalgae. Therefore, since carbon dioxide is used in the culture device 24, it is possible to reduce the amount of carbon dioxide in the gas discharged from the gas discharge equipment 10 in the microalgae culture system 20. In addition, since the microalgae culture system 20 has a simple configuration, it is possible to reduce the size of the system.

[0045] Furthermore, in the microalgae cultivation system 20, exhaust gas g after coal combustion is supplied to the cultivation device 24, and the mercury recovery device 22 recovers mercury contained in the exhaust gas g. In other words, after the mercury recovery device 22 recovers mercury contained in the exhaust gas g after coal combustion, the cultivation device 24 uses carbon dioxide in the exhaust gas g. This makes it possible to reduce the amount of carbon dioxide in the gas discharged from the gas discharge facility 10 that burns coal in the microalgae cultivation system 20.

[0046] In addition, the mercury recovery device 22 is connected to a pipe 21 branched off from a gas exhaust path 150 leading to the chimney 140. This allows the mercury recovery device 22 to easily extract gas (exhaust gas g) from the gas exhaust path 150 via the pipe 21 and recover the mercury contained in the gas.

[0047] In addition, since mercury dissolves in an aqueous solution containing chloride ions, when a gas containing mercury is brought into contact with an aqueous solution containing chloride ions, the mercury in the gas dissolves in the aqueous solution, and the mercury can be recovered from the gas. Therefore, the mercury recovery device 22 has an aqueous solution 22a containing chloride ions, and can recover the mercury contained in the gas by bringing the gas (exhaust gas g) into contact with the aqueous solution 22a.

[0048] Moreover, seawater is supplied as the aqueous solution 22a containing chloride ions to the mercury recovery apparatus 22. This makes it possible to easily supply the aqueous solution 22a containing chloride ions to the mercury recovery apparatus 22. High-concentration salt water may be supplied to the mercury recovery apparatus 22 as the aqueous solution 22a.

[0049] In addition, the microalgae cultivation equipment 1 and the microalgae cultivation method can also achieve the same effects as those of the microalgae cultivation system 20 described above, such as reducing the carbon dioxide in the gas discharged from the gas exhaust equipment 10.

[0050] [5. Explanation of Variations] Although the microalgae culture facility 1, the microalgae culture system 20, and the microalgae culture method according to the present embodiment have been described above, the present invention is not limited to the above embodiment. The embodiment disclosed herein is illustrative and not restrictive in all respects, and the scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

[0051] (Variation 1) In the above embodiment, the aqueous solution 22a is supplied to the mercury recovery device 22 from the pipe 22b, but the aqueous solution 22a may be supplied from the culture device 24. Fig. 4 is a schematic diagram showing the configuration of a microalgae culture system 20a according to Modification 1 of this embodiment.

[0052] As shown in FIG. 4, the microalgae culture system 20a in this modification includes a pipe 25 between the mercury recovery device 22 and the culture device 24. The pipe 25 is connected to the mercury recovery device 22 and the culture device 24, and connects the mercury recovery device 22 and the culture device 24. The culture device 24 supplies a medium (seawater or high-concentration salt water) to the mercury recovery device 22 through the pipe 25. That is, the culture device 24 supplies the medium to the mercury recovery device 22 as an aqueous solution 22a. For example, the culture device 24 supplies the seawater or high-concentration salt water that has been used as the medium to the mercury recovery device 22 and no longer used, thereby reusing the medium. Alternatively, the culture device 24 may supply the seawater or high-concentration salt water that has not been used (before use) as the medium to the mercury recovery device 22. Other configurations of this modification are similar to those of the above embodiment, and therefore detailed description will be omitted.

[0053] As described above, the microalgae culture system 20a according to this modified example can achieve the same effects as those of the above-described embodiment. In particular, when an aqueous solution containing chloride ions is used as the culture medium of the culture device 24, the culture medium can be used as the aqueous solution 22a of the mercury recovery device 22. In this case, the culture device 24 supplies the culture medium to the mercury recovery device 22 as the aqueous solution 22a containing chloride ions. This makes it possible to easily supply the aqueous solution 22a containing chloride ions to the mercury recovery device 22 while effectively utilizing the culture medium of the culture device 24.

[0054] In the above-mentioned first modification, the mercury recovery apparatus 22 has the pipe 22b, and the aqueous solution 22a is also supplied to the mercury recovery apparatus 22 from the pipe 22b, but the mercury recovery apparatus 22 may not have the pipe 22b. In other words, the mercury recovery apparatus 22 may be configured so that the aqueous solution 22a is supplied to the mercury recovery apparatus 22 only from the culture apparatus 24.

[0055] (Variation 2) In the above embodiment, the hot water or steam generated by the boiler 100 may be used for any purpose. In other words, the gas used by the microalgae culture system 20 to culture halophilic microalgae may be gas discharged from the boiler 100 used for any purpose. An example of this is described below. Figure 5 is a schematic diagram showing the configuration of a microalgae culture facility 2 according to a second modification of this embodiment.

[0056] 5, the microalgae cultivation equipment 2 in this modification includes a gas exhaust equipment 11 instead of the gas exhaust equipment 10 included in the microalgae cultivation equipment 1 in the above embodiment. In addition to the components included in the gas exhaust equipment 10 in the above embodiment, the gas exhaust equipment 11 in this modification further includes a steam turbine 160 and a generator 170. The other components of this modification are similar to those in the above embodiment, and therefore will not be described in detail.

[0057] Thus, the gas discharge facility 11 is a coal-fired power plant, which burns fuel (coal) in the boiler 100 to generate steam, which rotates the steam turbine 160 to generate electricity in the generator 170. The microalgae cultivation system 20 cultivates halophilic microalgae using the exhaust gas g discharged from the boiler 100 of the coal-fired power plant. The gas discharge facility 11 may further include an air preheater that preheats the combustion air with the exhaust gas g before sending it to the boiler 100 in order to increase the thermal efficiency of the boiler 100.

[0058] Specifically, the boiler 100 is, for example, a constant pressure once-through boiler. The boiler 100 has a main steam pipe 101, and sends steam (main steam) generated by burning fuel (coal) to a steam turbine 160 through the main steam pipe 101. A bottom ash treatment facility (not shown) for treating ash (coal ash) generated by burning fuel in the boiler 100 may be provided at the bottom of the boiler 100.

[0059] The steam turbine 160 is a turbine that rotates by the energy of steam generated in the boiler 100. In this modification, the steam turbine 160 has a high-pressure turbine 161, an intermediate-pressure turbine 162, and a low-pressure turbine 163. In this modification, the low-pressure turbine 163, the intermediate-pressure turbine 162, and the high-pressure turbine 161 are arranged coaxially in this order from the side closer to the generator 170. That is, high-temperature, high-pressure steam (main steam) generated in the boiler 100 is sent to the high-pressure turbine 161 through the main steam pipe 101 to rotate the high-pressure turbine 161. In addition, the steam that has left the high-pressure turbine 161 is sent to the intermediate-pressure turbine 162 to rotate the intermediate-pressure turbine 162. In addition, the steam that has left the intermediate-pressure turbine 162 is sent to the low-pressure turbine 163 to rotate the low-pressure turbine 163. Note that the steam turbine 160 may be configured not to have any of the turbines among the high-pressure turbine 161, the intermediate-pressure turbine 162, and the low-pressure turbine 163. Alternatively, steam turbine 160 may include turbines other than those discussed above.

[0060] The generator 170 is a turbine generator that generates electricity by converting the rotational force of the steam turbine 160 into electric power. Specifically, the generator 170 is arranged coaxially with the steam turbine 160 and on the side of the low-pressure turbine 163 (opposite the intermediate-pressure turbine 162), and generates electricity by converting the rotational forces of the high-pressure turbine 161, the intermediate-pressure turbine 162, and the low-pressure turbine 163 into electric power.

[0061] As described above, the microalgae culture facility 2 according to this modification can achieve the same effects as the above embodiment. In particular, even when the gas discharge facility 11 is a large-scale facility such as a coal-fired power plant, the microalgae culture facility 2 according to the modification can achieve the same effects as the above embodiment, such as reducing the carbon dioxide in the gas discharged from the gas discharge facility 11.

[0062] (Variation 3) In the above embodiment, the gas exhaust equipment 10 includes the denitrification device 110, the dust collection device 120, and the desulfurization device 130 in the gas exhaust passage 150 between the boiler 100 and the chimney 140, but any of them may not be included. Fig. 6 is a schematic diagram showing the configuration of a microalgae culture facility 3 according to a third modification of this embodiment.

[0063] 6, the microalgae culture equipment 3 in this modification includes a gas exhaust equipment 12 instead of the gas exhaust equipment 10 included in the microalgae culture equipment 1 in the above embodiment. The gas exhaust equipment 12 in this modification does not include the denitrification device 110 and the desulfurization device 130 included in the gas exhaust equipment 10 in the above embodiment. The other configurations of this modification are similar to those of the above embodiment, so detailed description will be omitted.

[0064] As in the above embodiment, the exhaust gas g discharged from the boiler 100 contains nitrogen oxides, soot, sulfur oxides, carbon dioxide, and mercury (metallic mercury). The mercury discharged from the boiler 100 is cooled while passing through the gas exhaust passage 150, and adheres to the soot. The dust collector 120 removes the soot in the exhaust gas g flowing from the boiler 100 to the chimney 140, and the mercury adhered to the soot. Therefore, the exhaust gas g discharged from the dust collector 120 contains nitrogen oxides, sulfur oxides, carbon dioxide, and mercury (metallic mercury). That is, the gas (exhaust gas g) taken out from the gas exhaust passage 150 contains carbon dioxide and mercury (metallic mercury) as in the above embodiment. The microalgae culture system 20 uses this gas to culture halophilic microalgae.

[0065] As described above, the microalgae culture equipment 3 according to this modified example can achieve the same effects as those of the above-described embodiment. In particular, even in the case of a small-scale facility in which the gas exhaust equipment 12 does not include the denitrification device 110 and the desulfurization device 130, the same effects as those of the above-described embodiment can be achieved, such as reducing the amount of carbon dioxide in the gas exhausted from the gas exhaust equipment 12.

[0066] In this modification, the gas discharge equipment 12 may include a denitration device 110 or a desulfurization device 130 in addition to the dust collector 120, or may include at least one of the denitration device 110 and the desulfurization device 130 instead of the dust collector 120. The gas discharge equipment 12 does not need to include all of the denitration device 110, the dust collector 120, and the desulfurization device 130. Even in this case, the gas (exhaust gas g) taken out from the gas discharge path 150 contains carbon dioxide and mercury (metallic mercury, etc.) as in the above embodiment. The mercury in this gas is recovered by the mercury recovery device 22 of the microalgae culture system 20. The microalgae culture system 20 uses the carbon dioxide in this gas to cultivate halophilic microalgae.

[0067] (Variation 4) In the above embodiment, the gas used by the microalgae culture system 20 to culture the halophilic microalgae does not have to be the gas discharged from the boiler 100. Fig. 7 is a schematic diagram showing the configuration of a microalgae culture facility 4 according to a fourth modification of the present embodiment.

[0068] 7, the microalgae cultivation equipment 4 in this modification includes a gas exhaust equipment 13 instead of the gas exhaust equipment 10 included in the microalgae cultivation equipment 1 in the above embodiment. The gas exhaust equipment 13 in this modification includes an incinerator 200, a cooling tower 210, a bag filter 220, a chimney 230, and a gas exhaust path 240. The other configurations of this modification are similar to those of the above embodiment, and therefore detailed description thereof will be omitted.

[0069] In this way, the gas discharge facility 13 is an incineration facility of a waste incineration plant, etc. The microalgae cultivation system 20 cultivates halophilic microalgae using the exhaust gas g1 discharged from the incineration facility of a waste incineration plant, etc.

[0070] The incinerator 200 is a device that burns household waste. A gas exhaust line 240 is connected to the incinerator 200, and exhaust gas g1 after burning household waste is sent through the gas exhaust line 240 to the temperature reducing tower 210, the bag filter 220, and the chimney 230. The gas exhaust line 240 is a flue that sends the exhaust gas g1 from the incinerator 200 to the chimney 230. In this modification, when items containing mercury, such as fluorescent lamps, dry batteries, and mercury sphygmomanometers, are burned in the incinerator 200, the exhaust gas g1 discharged from the incinerator 200 contains carbon dioxide and mercury (metallic mercury).

[0071] The temperature reducing tower 210 is a device for lowering the temperature of the exhaust gas g1. In the temperature reducing tower 210, almost all of the metallic mercury in the exhaust gas g1 reacts with other components to form divalent mercury (HgCl2, etc.). 2+ ) is generated. Therefore, the exhaust gas g1 discharged from the temperature reducing tower 210 contains carbon dioxide and divalent mercury (HgCl2, etc.). 2+ ) are included.

[0072] The bag filter 220 is a filter-type dust collector that removes a portion of HgCl2 in the exhaust gas g1. Therefore, the exhaust gas g1 discharged from the bag filter 220 contains carbon dioxide and the remaining divalent mercury (Hg 2+ In other words, the gas (exhaust gas g1) extracted from the gas exhaust line 240 contains carbon dioxide and divalent mercury (HgCl2, etc.). 2+ The microalgae cultivation system 20 uses this gas to cultivate halophilic microalgae.

[0073] The configuration of the microalgae culture system 20 in this modification is the same as that of the microalgae culture system 20 in the above embodiment. That is, the microalgae culture system 20 in this modification includes a mercury recovery device 22 and a culture device 24. The mercury recovery device 22 is disposed between the gas exhaust path 240 and the culture device 24, and recovers mercury contained in the gas (exhaust gas g1) extracted from the gas exhaust path 150. Specifically, the mercury recovery device 22 recovers mercury (divalent mercury) contained in the exhaust gas g1 after combustion in the incinerator 200. The mercury recovery device 22 is connected to a pipe 21 branched from the gas exhaust path 240 toward the chimney 230, and is thereby connected to the gas exhaust path 240. Specifically, the mercury recovery device 22 has an aqueous solution 22a containing chloride ions, and recovers mercury (divalent mercury) contained in the gas (exhaust gas g1) by contacting the aqueous solution 22a with the gas. The mercury recovery device 22 is supplied with seawater or high-concentration salt water (aqueous sodium chloride solution: NaCl) as the aqueous solution 22a. The mercury recovery device 22 recovers divalent mercury (HgCl2, etc.) contained in the exhaust gas g1 supplied from the pipe 21. 2+ ) to mercury tetrachloride ion (HgCl4 2- ) and other divalent mercury (Hg 2+ ) in the aqueous solution 22a and recovered.

[0074] The culture device 24 is supplied with gas extracted from the gas exhaust passage 240 of the gas exhaust equipment 13 that exhausts gas containing carbon dioxide and mercury, and cultivates halophilic microalgae using the carbon dioxide contained in the gas. The culture device 24 is supplied with exhaust gas g1 after combustion in the incinerator 200 as the gas. The exhaust gas g1 extracted from the gas exhaust passage 240 through the piping 21 contains carbon dioxide and mercury (divalent mercury), but as described above, the mercury (divalent mercury) is recovered by the mercury recovery device 22. Therefore, the exhaust gas g1 supplied to the culture device 24 contains almost no mercury (divalent mercury) but contains carbon dioxide, and the halophilic microalgae fix the carbon dioxide by photosynthesis while suppressing the influence of mercury. In this way, the culture device 24 cultivates halophilic microalgae.

[0075] As described above, the microalgae culture equipment 4 according to this modification can achieve the same effects as those of the above-mentioned embodiment. In particular, in this modification, in the microalgae culture system 20, the culture device 24 is supplied with the exhaust gas g1 after combustion in the incinerator 200, and the mercury recovery device 22 recovers the mercury contained in the exhaust gas g1. In other words, after the mercury recovery device 22 recovers the mercury contained in the exhaust gas g1 after combustion in the incinerator 200, the culture device 24 uses the carbon dioxide in the exhaust gas g1. This makes it possible to reduce the amount of carbon dioxide in the gas discharged from the gas discharge equipment 13 equipped with the incinerator 200 in the microalgae culture system 20.

[0076] (Other variations) In the above embodiment and its modified examples, various facilities other than those described above can be exemplified as the gas exhaust equipment. For example, the gas exhaust equipment may be a cement manufacturing facility, a steelworks, a non-ferrous metal manufacturing facility, a ferroalloy manufacturing facility, a petroleum-related facility, a carbon black manufacturing facility, a lime product manufacturing facility, a pulp and paper manufacturing facility, a biomass power generation heat supply facility, an oil combustion facility, an LNG combustion facility, etc. In other words, the gas used by the microalgae cultivation system 20 or 20a to cultivate halophilic microalgae may be a gas extracted from a gas exhaust path of a gas exhaust equipment used for any purpose.

[0077] In the above embodiment and its modified examples, the microalgae cultivation system 20 or 20a may include various devices such as a denitrification device, a dust collection device, and a desulfurization device in addition to the above-mentioned configuration.

[0078] In the above embodiment and its modified examples, the mercury recovery apparatus 22 dissolves metallic mercury contained in the exhaust gas into the aqueous solution 22a by a bubbling method such as bubbles. However, the mercury recovery apparatus 22 may dissolve metallic mercury into the aqueous solution 22a by a shower method. That is, the mercury recovery apparatus 22 may dissolve metallic mercury contained in the exhaust gas into the aqueous solution 22a by spraying (showering) the aqueous solution 22a into the exhaust gas and bringing the exhaust gas into contact with the aqueous solution 22a. The mercury recovery apparatus 22 may recover mercury contained in the gas by any other method.

[0079] In the above embodiment and its modified examples, seawater or high-concentration salt water is supplied as the aqueous solution 22a to the mercury recovery apparatus 22. However, the mercury recovery apparatus 22 may be supplied with an aqueous solution containing chloride ions at a concentration different from that of seawater or high-concentration salt water, or may be supplied with an aqueous solution having a different temperature, such as a higher temperature, than that of seawater or high-concentration salt water. This allows the mercury recovery apparatus 22 to effectively recover mercury contained in the exhaust gas. In this way, the mercury recovery apparatus 22 may be supplied with any aqueous solution containing chloride ions as the aqueous solution 22a, or may be supplied with any aqueous solution other than an aqueous solution containing chloride ions as long as it can recover mercury.

[0080] In the above embodiment and its modified example, the mercury recovery device 22 has the pipe 22b, and the aqueous solution 22a is supplied from the pipe 22b. However, the mercury recovery device 22 may not have the pipe 22b, and the aqueous solution 22a may be periodically replaced.

[0081] In the above embodiment and its modified example, the culture device 24 has the piping 24a, and the culture medium is supplied from the piping 24a. However, the culture device 24 may not have the piping 24a, and the culture medium may be replaced periodically.

[0082] In the above embodiment and its modified examples, the culture device 24 uses an aqueous solution containing chloride ions, such as seawater or highly concentrated salt water, as a culture medium. However, the culture device 24 may use any culture medium as long as it is capable of supporting halophilic microalgae.

[0083] In the above embodiment and its modified examples, the boiler 100 is configured to burn coal. However, the boiler 100 is not limited to burning coal, and may burn any fuel as long as it emits gases containing carbon dioxide and mercury. The boiler 100 may also burn a mixture of coal and another fuel.

[0084] The present invention can also be realized as a microalgae culture facility including the microalgae culture system 20 or 20a. The present invention can also be realized as a program for causing a computer (processor) to execute the microalgae culture method, or as any medium such as a computer (processor) readable non-transitory recording medium on which the program is recorded, such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray (registered trademark) Disc), semiconductor memory, flash memory, magnetic storage device, optical disk, paper tape, etc. Such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet. The present invention can also be realized as an integrated circuit including a processing unit (control device) that performs the microalgae culture method.

[0085] Any combination of the components included in the above-described embodiment and modified examples is also included within the scope of the present invention. [Industrial Applicability]

[0086] The present invention can be applied to a microalgae culture system that cultures halophilic microalgae using carbon dioxide contained in a gas. [Explanation of symbols]

[0087] 1, 2, 3, 4 Microalgae culture equipment 10, 11, 12, 13 Gas exhaust equipment 20, 20a Microalgae Cultivation System 21, 22b, 23, 24a, 25 Piping 22 Mercury recovery equipment 22a Aqueous solution 24 Culture device 100 Boiler 101 Main steam pipe 110 Denitration equipment 120 Dust collector 130 Desulfurization equipment 140, 230 Chimney 150, 240 Gas exhaust duct 160 Steam Turbine 161 High Pressure Turbine 162 Intermediate Pressure Turbine 163 Low Pressure Turbine 170 Generator 200 Incinerator 210 Cooling Tower 220 Bag Filter g, g1 Exhaust gas

Claims

1. A culture device that is supplied with a gas extracted from a gas exhaust passage of a gas exhaust facility that exhausts a gas containing carbon dioxide and mercury, and that cultivates halophilic microalgae using the carbon dioxide contained in the gas; a mercury recovery device disposed between the gas exhaust path and the culture device and configured to recover mercury contained in the gas; A microalgae culture system comprising:

2. The culture apparatus is supplied with exhaust gas after coal combustion as the gas, The mercury recovery device recovers mercury contained in the exhaust gas. The microalgae culture system according to claim 1 .

3. The culture apparatus is supplied with exhaust gas after combustion in an incinerator as the gas, The mercury recovery device recovers mercury contained in the exhaust gas. The microalgae culture system according to claim 1 .

4. The mercury recovery device is connected to a pipe branched off from the gas exhaust path leading to a chimney. The microalgae culture system according to any one of claims 1 to 3.

5. The mercury recovery device has an aqueous solution containing chloride ions, and recovers mercury contained in the gas by bringing the gas into contact with the aqueous solution. The microalgae culture system according to any one of claims 1 to 3.

6. Seawater is supplied to the mercury recovery device as the aqueous solution. The microalgae culture system according to claim 5 .

7. The culture device supplies a culture medium as the aqueous solution to the mercury recovery device. The microalgae culture system according to claim 5 .

8. A culture step of supplying the gas extracted from a gas exhaust line of a gas exhaust facility that exhausts gas containing carbon dioxide and mercury to a culture device and culturing halophilic microalgae using carbon dioxide contained in the gas; a mercury recovery step of recovering mercury contained in the gas by a mercury recovery device disposed between the gas exhaust path and the culture device before the culture step; A method for culturing microalgae comprising the steps of:

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