Algae recovery apparatus and algae recovery method

Abstract

To provide an efficient algae collection apparatus and an algae collection method in which generation of clog in a filter when filtering culture solution of microalgae by the filter.SOLUTION: An algae collection apparatus collects cultured microalgae and culture solution, where the algae collection apparatus 12 comprises: a collection pipe 14 which collects microalgae and culture solution from a culture tank; a tank 18 which stores microalgae and culture solution collected via a collection pipe 14; a filter mechanism 16 which is provided for a downstream side of the collection pipe 14, and has a filter 32 which filters culture solution. A settling part 15 which settles microalgae is formed on the collection pipe 14. In the algae collection method, microalgae are settled in the settling part 15, culture solution is filtered by the filter 32, and concentrated microalgae and culture solution are stored in the tank 18.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an algae recovery device and an algae recovery method for recovering cultured microalgae and a culture solution.

Background Art

[0002] Conventionally, efforts aimed at mitigating or reducing the impact of climate change have been continued, and research and development on reducing carbon dioxide emissions have been conducted towards this realization. A culture device for culturing microalgae is expected to contribute to mitigating or reducing the impact of climate change.

[0003] For example, in the culture system disclosed in Patent Document 1 below, a filter for filtering the culture solution is disclosed in order to recycle the culture solution used in the culture tank.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the culture system of Patent Document 1, clogging occurs in the filter by filtering the culture solution. In the culture system of Patent Document 1, there is room for improvement regarding the efficient recovery of microalgae.

[0006] An object of the present invention is to solve the above-described problems.

Means for Solving the Problems

[0007] A first aspect of the present invention is an algae recovery apparatus for recovering cultured microalgae and culture solution, comprising: a recovery pipe for recovering the microalgae and culture solution from a culture tank; a tank for storing the microalgae and culture solution recovered via the recovery pipe; and a filtration mechanism provided downstream of the recovery pipe and having a filter for filtering the culture solution, wherein a settling section is formed in the recovery pipe for allowing the microalgae to settle.

[0008] A second aspect of the present invention is an algae recovery method for recovering cultured microalgae and culture solution, wherein the microalgae and culture solution are recovered from a culture tank by a recovery pipe, the microalgae are allowed to settle in a settling section formed in the recovery pipe, the culture solution is filtered by a filter provided downstream of the recovery pipe, and the recovered microalgae and culture solution are stored in a tank. [Effects of the Invention]

[0009] According to the present invention, since microalgae settle in the settling section provided in the recovery piping, clogging of the filter located downstream of the settling section by microalgae can be suppressed. By performing the settling of microalgae in the settling section and the filtration of the culture solution with the filter simultaneously, the process is consolidated, allowing for efficient recovery of microalgae. The microalgae liquid (microalgae and culture solution) that has passed through the recovery piping is further filtered by a filtration mechanism to obtain an algae concentrate, thus allowing for efficient recovery of microalgae. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a flowchart of the process for culturing, harvesting, and concentrating microalgae. [Figure 2] Figure 2 is a schematic diagram of an algae recovery device according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] In Figure 1, the culture apparatus 10 supplies light and gas to microalgae in a culture medium containing water to cultivate the microalgae (cultivation step S1). Although not shown in detail, the culture apparatus 10 includes a culture tank capable of containing the culture medium and microalgae. For example, carbon dioxide gas or a carbon dioxide-containing gas (for example, air) is supplied to the culture tank containing the culture medium and microalgae. As a result, the microalgae grow in the culture apparatus 10 while performing photosynthesis. Preferably, the culture medium contains water as well as nutrients necessary for culturing microalgae (for example, at least one selected from nitrogen, phosphorus, and potassium). Preferably, the gas contains, for example, carbon dioxide gas emitted from a factory.

[0012] The microalgae that can be cultured using the culture device 10 are not particularly limited. When using the cultured microalgae to produce biofuels such as ethanol, it is preferable to culture microalgae classified as Chlorophyta (e.g., Chlamydomonas and Chlorella), Prasinophyta, Cryptofophyta, and Cyanobacteria (e.g., Spirulina) using the culture device 10. An example of a suitable microalgae to be cultured using the culture device 10 is the "HondaDREAMO strain" (deposit date April 22, 2016, accession number FERM BP-22306), which has been deposited with the National Institute of Technology and Evaluation Patent Organism Depositary Center (Room 120, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture).

[0013] The culture apparatus 10 is installed in an environment where the microalgae can be irradiated with light of wavelengths necessary for their growth (e.g., 400-700 nm). Such an environment could be, for example, outdoors where sunlight can be irradiated onto the microalgae. However, the culture apparatus 10 may also be installed indoors where sunlight can be irradiated onto the microalgae. Alternatively, the culture apparatus 10 may also be installed indoors where artificial light of the above wavelengths can be irradiated onto the microalgae.

[0014] The microalgae cultivated in the culture device 10 are sent to the algae recovery device 12 along with the culture medium. Hereinafter, the mixture of microalgae and culture medium will also be referred to as "microalgae solution ML". The algae recovery device 12 recovers the cultivated microalgae and culture medium. The algae recovery device 12 recovers and settles the microalgae and filters the culture medium (recovery, settling, and filtration process S2). The algae recovery device 12 further concentrates the microalgae (algae concentration process S3). The filtered culture medium is subjected to predetermined processing and then reused in the culture device 10. In other words, the culture medium is recycled. The details of the algae recovery device 12 will be described below.

[0015] As shown in Figure 2, the algae recovery device 12 includes a recovery pipe 14 for recovering microalgae liquid ML (microalgae and culture solution) from the culture tank, a filtration mechanism 16 having a filter 32 for filtering the culture solution, and a tank 18 for storing the microalgae and culture solution recovered via the recovery pipe 14.

[0016] The recovery piping 14 has an introduction pipe section 20 into which microalgae liquid ML is introduced from the culture tank, and a U-shaped sedimentation pipe section 22 that is convex downwards. An inlet 201 is formed at one end of the introduction pipe section 20. Microalgae liquid ML (microalgae and culture solution) flows into the introduction pipe section 20 through the inlet 201. One end (upstream end) of the U-shaped sedimentation pipe section 22 is connected to the other end (downstream end) of the introduction pipe section 20. The introduction pipe section 20 extends, for example, in a horizontal direction.

[0017] The sedimentation pipe section 22 includes a first vertical pipe 221, a curved pipe 222 connected to the first vertical pipe 221, and a second vertical pipe 223 connected to the curved pipe 222. The sedimentation pipe section 22 can be a single piping member in which the first vertical pipe 221, the curved pipe 222, and the second vertical pipe 223 are continuously connected without any breaks.

[0018] The upper end of the first vertical pipe 221 is connected to the downstream end of the introduction pipe portion 20. The first vertical pipe 221 extends in the vertical direction. One end (the upstream end) of a curved pipe 222 is connected to the lower end (the downstream end) of the first vertical pipe 221. The curved pipe 222 forms the lower part of the sedimentation pipe portion 22. The curved pipe 222 is curved in an arc shape so as to face downward from one end (the upstream end) of the curved pipe 222 and change its direction upward at an intermediate position of the curved pipe 222, and is formed in a shape that reaches the other end (the downstream end) upward.

[0019] A sedimentation portion 15 for sedimenting the microalgae in the microalgae liquid ML is formed in the recovery pipe 14. The sedimentation portion 15 is formed at the U-shaped lower end of the sedimentation pipe portion 22. That is, the sedimentation portion 15 is constituted by the curved shape at the bottom in the sedimentation pipe portion 22. A discharge port 151 is formed at the lowermost end of the sedimentation portion 15 (the lowermost end of the recovery pipe 14). An on-off valve 28 is arranged in an outlet pipe 26 connected to the discharge port 151. The lower end (the upstream end) of a second vertical pipe 223 is connected to the other end of the curved pipe 222.

[0020] The second vertical pipe 223 extends in the vertical direction parallel to the first vertical pipe 221. The upper end of the second vertical pipe 223 is connected to the filtration mechanism 16 via a connecting pipe 24. The connecting pipe 24 is formed in a U-shaped configuration that protrudes upward, for example, as shown in FIG. 2.

[0021] The filtration mechanism 16 is provided on the downstream side of the recovery pipe 14. The culture solution that has passed through the recovery pipe 14 flows into the filtration mechanism 16. The filtration mechanism 16 includes a housing 30 and a filter 32 disposed inside the housing 30. The upper end of the housing 30 has an inlet 300 for taking in the microalgae liquid ML to be filtered (the microalgae that did not sediment in the sedimentation portion 15 and the culture solution). The lower end of the housing 30 has a first outlet 301 and a second outlet 302. The first outlet 301 discharges the liquid (the concentrated liquid) that has not passed through the filter 32. The second outlet 302 discharges the liquid (the permeate) that has passed through the filter 32. A discharge pipe 34 is connected to the second outlet 302.

[0022] Filter 32 removes proteins from the culture solution. As the filter 32, for example, a nanofiltration membrane (NF membrane) is used. The filter 32 is arranged so as to partition the inside of the housing 30 into a first chamber 311 and a second chamber 312. The first chamber 311 is a space on the side of the supplied liquid. The second chamber 312 is a space on the side of the permeate. The filtration mechanism 16 supplies the supplied liquid parallel to the filter 32, and the permeate permeates the filter 32 in a direction perpendicular thereto. That is, the filtration mechanism 16 is a cross-flow type filtration device.

[0023] The tank 18 is arranged below the sedimentation section 15 and the filtration mechanism 16. The recovery pipe 14 and the filtration mechanism 16 are fixed to the upper part of the tank 18. The algae recovery device 12 is a processing unit in which the recovery pipe 14, the filtration mechanism 16, and the tank 18 are integrated.

[0024] The microalgae sedimented in the sedimentation section 15 and the culture solution that has passed through the filtration mechanism 16 are stored in the tank 18. Specifically, the tank 18 has a storage section 19 capable of storing microalgae and the culture solution. The microalgae (algae concentrate M1) discharged from the sedimentation section 15 flows down and is stored in the storage section 19 of the tank 18. The concentrate (algae concentrate M2) discharged from the first outlet 301 of the filtration mechanism 16 flows down and is stored in the storage section 19 of the tank 18. An outlet 180 is formed at the lowermost end of the tank 18. An on-off valve 38 is arranged in the discharge pipe 36 connected to the outlet 180.

[0025] The algae recovery device 12 operates as follows.

[0026] The microalgae liquid ML (cultured microalgae and culture solution) is sent from the culture device 10 (see FIG. 1) to the recovery pipe 14 through the inlet 201 at a low flow rate and high pressure. The flow rate and pressure during the feeding of the microalgae liquid ML are set so that the sedimentation of microalgae in the sedimentation section 15 and the filtration of the culture solution in the filtration mechanism 16 can be performed well. The microalgae liquid ML is sent to the recovery pipe 14 at a pressure of, for example, several hundred kPa to several MPa.

[0027] As the microalgae liquid ML flows through the recovery pipe 14, microalgae with settling characteristics settle in the settling section 15 and accumulate as concentrated microalgae (algae concentrate M1). When a certain amount of microalgae has accumulated in the settling section 15, the on / off valve 28 is opened. The algae concentrate M1 is transferred from the settling section 15 to the tank 18 via the outlet 151 of the settling section 15.

[0028] The microalgae solution ML that has passed through the recovery pipe 14 flows into the filtration mechanism 16 via the connecting pipe 24. In the filtration mechanism 16, the culture solution permeates through the filter 32 and flows into the second chamber 312. Microalgae do not permeate through the filter 32. Proteins are removed from the culture solution as it passes through the filter 32. The culture solution from which proteins have been removed (protein-removed solution) is discharged to the outside of the algae recovery device 12 via the second outlet 302 and the discharge pipe 34. The protein-removed solution is recycled as culture solution after undergoing predetermined processing (see Figure 1).

[0029] In the filtration mechanism 16, the microalgae liquid ML that does not pass through the filter 32 becomes a concentrated liquid of microalgae containing culture medium (algae concentrate M2), which is discharged through the first outlet 301 and stored in the tank 18.

[0030] In the storage section 19 of tank 18, a liquid (algae concentrate M3) is stored, which is a mixture of the algae concentrate M1 discharged from the settling section 15 and the algae concentrate M2 discharged from the filtration mechanism 16. In tank 18, the algae concentrate M3 is further concentrated and accumulated in the lower part of tank 18. As a result, a high-concentration algae concentrate M4 is obtained in the lower part of tank 18. When a predetermined amount of high-concentration algae concentrate M4 has accumulated, the on-off valve 38 is opened. The algae concentrate M4 is discharged to the outside of tank 18 via the outlet 180 and discharge pipe 36 provided in the lower part of tank 18 and recovered.

[0031] This embodiment provides the following effects.

[0032] Since microalgae settle in the settling section 15 provided in the recovery pipe 14, clogging of the filter 32 located downstream of the settling section 15 by microalgae can be suppressed. By performing the settling of microalgae in the settling section 15 and the filtration of the culture solution in the filter 32 simultaneously, the processes are consolidated, allowing for efficient recovery of microalgae. The microalgae solution ML that has passed through the recovery pipe 14 is further filtered by the filtration mechanism 16 to obtain the algae concentrate M2, thus allowing for efficient recovery of microalgae.

[0033] In the settling section 15, the microalgae are allowed to settle, and the microalgae liquid ML that has passed through the recovery pipe 14 is further filtered by the filtration mechanism 16 and stored in the tank 18, thereby obtaining a highly concentrated algae solution M4.

[0034] The recovery pipe 14 has a U-shaped sedimentation tube section 22 that is convex downwards. A sedimentation section 15 is formed at the lower end of the U-shape of the sedimentation tube section 22. Because the sedimentation section 15 is formed at the lower end of the U-shaped sedimentation tube section 22, microalgae can be settled effectively, preventing clogging of the filter 32.

[0035] The microalgae that settle in the settling section 15 and the culture solution that has passed through the filtration mechanism 16 are stored in the tank 18. This allows the filtered culture solution and microalgae to settle and concentrate in the tank 18 while suppressing clogging of the filter 32.

[0036] Filter 32 removes proteins from the culture medium, allowing the culture medium to be recycled.

[0037] This embodiment allows for the efficient harvesting of cultured microalgae, and therefore contributes to mitigating or reducing the impact of climate change.

[0038] The above embodiments can be summarized as follows:

[0039] The above embodiment discloses an algae recovery device (12) for recovering cultured microalgae and culture solution, comprising: a recovery pipe (14) for recovering the microalgae and culture solution from a culture tank; a tank (18) for storing the microalgae and culture solution recovered via the recovery pipe; and a filtration mechanism (16) provided downstream of the recovery pipe and having a filter (32) for filtering the culture solution, wherein a settling section (15) for settling the microalgae is formed in the recovery pipe.

[0040] The recovery piping has a U-shaped sedimentation tube section (22) that is convex downwards, and the sedimentation section is formed at the lower end of the U-shape of the sedimentation tube section.

[0041] The tank is positioned below the sedimentation section and the filtration mechanism, and the tank stores the microalgae that have settled in the sedimentation section and the culture solution that has passed through the filtration mechanism.

[0042] The filter removes proteins from the culture medium.

[0043] The above embodiment discloses an algae recovery method for recovering cultured microalgae and culture solution, wherein the microalgae and culture solution are recovered from a culture tank by a recovery pipe (14), the microalgae are allowed to settle in a sedimentation section (15) formed in the recovery pipe, the culture solution is filtered by a filter (32) provided downstream of the recovery pipe, and the recovered microalgae and culture solution are stored in a tank (18).

[0044] Furthermore, the present invention is not limited to the embodiments described above, and various configurations can be taken without departing from the spirit of the invention. [Explanation of symbols]

[0045] 12…Algae recovery device 14…Recovery piping 18...Tank 16...Filtration mechanism 15...Sedimentation section 32...Filter

Claims

1. An algae recovery device for recovering cultured microalgae and culture solution, A recovery pipe for recovering the microalgae and the culture solution from the culture tank, A tank for storing the microalgae and culture solution recovered via the recovery piping, A filtration mechanism is provided downstream of the aforementioned recovery piping and has a filter for filtering the culture medium, The recovery pipe has a settling section formed therein, which allows the microalgae having settling characteristics to settle. An algae recovery device that stores the microalgae that have settled in the sedimentation section and the culture solution that has passed through the filtration mechanism in the tank.

2. In the algae recovery apparatus according to claim 1, The recovery piping has a U-shaped sedimentation pipe section that is convex downwards, An algae harvesting device in which the settling section is formed at the lower end of the U-shaped part of the settling tube.

3. In the algae recovery apparatus according to claim 1 or 2, Algae recovery device in which the tank is positioned below the sedimentation section and the filtration mechanism.

4. In the algae recovery apparatus according to any one of claims 1 to 3, The filter is an algae recovery device that removes proteins from the culture medium.

5. A method for recovering cultured microalgae and culture solution, The microalgae and culture solution are recovered from the culture tank using the recovery piping. The microalgae having settling characteristics are allowed to settle in the settling section formed in the aforementioned recovery pipe. The culture medium is filtered by a filter located downstream of the aforementioned recovery piping. A method for recovering algae, comprising storing the microalgae and culture solution recovered via the recovery piping in a tank.

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