JPS62220183A - Culture device for fine alga - Google Patents

Abstract

PURPOSE:To use a carbonic acid gas as a carbon source efficiently and to carry out stirring in a tank efficiently, by setting an air lift part at part of an endless circulating water channel. CONSTITUTION:A wafer tank which carries out culture of fine algae under light irradiation condition using a carbonic acid gas as a carbon source consists of an endless water channel comprising an open water channel 1 and a pipe water channel 2 which communicates an upper stream end b to a downstream end c of the open water channel by passing under the surface of the water prescribed by the open water channel. An air lift part a is set at part of the pipe water channel 2 and a carbonic acid gas is introduced from the bottom of the air lift part to the water tank. Consequently, a circulating flow is formed in the water channel. The carbonic acid gas is recovered from the top of the air lift part a and fed to the bottom of the part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for growing microalgae, and more specifically, the present invention relates to an apparatus for growing microalgae, and more specifically, it forms a flow of liquid that repeatedly circulates in an endless waterway by injecting carbon dioxide-containing gas, and at the same time efficiently generates carbon dioxide gas. This invention relates to a device that can be dissolved in a culture medium.

In the cultivation of microalgae using light and carbon dioxide gas, a shallow and wide culture tank is used, so simply venting from the bottom of the tank would result in poor carbon dioxide dissolution efficiency and poor stirring efficiency. It is difficult to achieve gas supply and tank agitation at the same time using the gas method, and a method of creating a flow of culture solution circulating in an endless waterway using mechanical means such as water wheels and pumps is used for tank agitation. It has been adopted. Regarding the supply of carbon dioxide gas, methods have been devised such as covering the entire device with a light-transmitting material and supplying the carbon dioxide gas therein, but water droplets and dust adhere to the surface of the light-transmitting material, resulting in a decrease in light transmittance. However, there are some drawbacks, such as carbon dioxide gas being used as a carbon source. For this reason, carbon dioxide gas is hardly used, and carbon sources rely on expensive organic substances such as acetic acid.

The present invention has been made in view of the above-mentioned drawbacks, and provides a microalgae culturing device that can efficiently use carbon dioxide gas as a carbon source and at the same time efficiently stir the tank.
The aim is to revitalize the microalgae production industry.

The present invention provides an apparatus for culturing microalgae under light irradiation conditions using carbon dioxide gas as a carbon source, the apparatus comprising (a
) An open channel in which the inside of the tank is irradiated with light and microalgae proliferate, and an upstream end and a downstream end of the open channel pass below the water surface defined by the open channel.

A culture tank configured as an endless waterway consisting of pipes passing through the tank, in which at least one part of the pipes is located below the water level defined by the open channel and has a unit aeration tank. It is configured as an air lift section installed vertically above the position to help obtain a sufficient amount of carbon dioxide gas dissolved and water pumped, and forms a flow of the culture solution toward the upstream end within the air lift section. A carbon dioxide-containing gas supply pipe for dissolving carbon dioxide in the culture solution was installed in an open manner, and the total area of the free water surface that received direct sunlight in the open channel was divided by the total volume of the channel in the endless channel. value is 0.7
m or less, (b) a blower connected to the carbon dioxide-containing gas supply pipe for sending the carbon dioxide-containing gas, (c
) A gas return channel that guides the gas released from the water surface above the air lift part back to the blower, and is surrounded by the partition wall and the water surface and communicates with the blower; This is an injection device for injecting carbon dioxide through a carbon dioxide gas injection pipe that connects the gas return flow path and a carbon dioxide source, a flow control valve installed in the carbon dioxide gas injection pipe, and a carbon dioxide gas injection pipe. (e) the injection device comprises means for forcibly feeding the carbon dioxide gas source, and a container for storing the carbon dioxide gas source; A microalgae culturing device characterized by comprising a means for controlling the gas concentration to a value equal to or lower than the gas concentration, and the control means is connected to the injection device, and the culture solution is repeatedly circulated in the water channel. The aquarium is configured as an endless waterway with a large and sufficient light-receiving surface.
A part of the waterway is configured as an air lift section, and a flow channel is provided that covers a small part of the water surface of the aquarium and is a channel for circulating and utilizing carbon dioxide released from the water surface above the air lift section. It is characterized in that an injection device for replenishing carbon dioxide gas is provided inside the air lift section, and a device is provided for controlling the injection amount so as to maintain the amount of carbon dioxide gas sent to the air lift section at a value below.

The present invention will be explained below using examples.

FIGS. 1 and 2 are explanatory diagrams showing one embodiment of the present invention. FIG. 1 is a plan view, and FIG. 2 is a longitudinal sectional view taken along line X-X.

The device is constructed as an endless waterway consisting of an open waterway 1 that bends and returns to almost its original position, and a pipe waterway 2 that communicates between its two ends. The carbon dioxide-containing gas supply pipe 3 is configured as an open air lift section a, and the upper end of the air lift section a is directly connected to the upstream end at the bottom below the water surface. A gas return channel d is constituted by the partition wall 4 covering the water surface at the upstream end, the pipe 5, and the gas trap 6 in the pipe 5.

The blower 7 is connected to the carbon dioxide-containing gas supply pipe 3 and the pipe 5. Gas cylinder 8 containing liquefied carbon dioxide under high pressure
A carbon dioxide gas injection pipe 9 is provided which communicates the gas return flow path d with the inside of the gas cylinder 8. A flow rate control valve 10 is provided in the carbon dioxide gas injection pipe 9 to constitute a carbon dioxide gas injection device. Pipe 1 connecting gas return flow path d and carbon dioxide analyzer 11
2, a dehumidifier 13 and a pump 14 are provided.

The carbon dioxide analyzer 11 is connected to the flow rate control valve 10 via a recording controller 15.

Carbon dioxide analyzer 11, recording controller 15 and flow control valve 1
In the operation circuit of the flow rate control valve 10 consisting of 0, a carbon dioxide gas analyzer 11 continuously measures and analyzes carbon dioxide in the gas drawn from inside the gas trap 6 by the pump 14.

The carbon dioxide gas analyzer 11 is, for example, an infrared carbon dioxide gas analyzer, which has a quick response and can be connected online. - In an example, an infrared carbon dioxide gas analyzer consists of an analysis sample chamber through which a sample gas passes continuously and an analysis comparison chamber filled with nitrogen gas, and infrared rays are emitted equally into both chambers.

The infrared rays passing through the sample chamber are absorbed by carbon dioxide gas in the sample, and the amount of infrared light transmitted therethrough decreases depending on the concentration of carbon dioxide gas.Since no carbon dioxide gas is present in the comparison chamber, the amount of transmission does not decrease. The energy difference of the infrared rays passing through each chamber is detected as an electric current, which is amplified to a standard signal range suitable for a standard controller. The recording controller 15 consists of the above controller combined with a recorder, and continuously indicates and records the carbon dioxide concentration.

The controller in the recording controller 15 compares the input signal with a predetermined set value, and if the carbon dioxide concentration is lower than the set value, it sends a signal to the flow rate control valve 10 to open, and vice versa. It is.

In FIGS. 1 and 2, one pipe channel 2 and one open channel 1 are connected, and a part of the pipe channel 2 is provided with an air lift section atfi. The number of open channels 1 and pipe channels 2 is not limited to one, and a plurality of them may be alternately connected as necessary, such as when the total channel length becomes long. In this case, it is sufficient to communicate the respective gas return channels d with each other and control the carbon dioxide gas injection group with one control system.If multiple endless channels are used, carbon dioxide gas injection can be performed with one control system in the same way. Just control the amount. Both ends of the pipe channel 2 are opened at the bottom below the water surface, and the air lift section a functions as an air lift pump that has almost no lifting head and can lift a large amount of water. FIGS. 3 and 4 are explanatory longitudinal cross-sectional views showing another aspect of the connection between the pipe waterway 2 and the upstream end of the open waterway 1. FIG.

In FIG. 3, a pipe channel 2 is opened between the bottom of the open channel 1 and the water surface. In Fig. 4, the pipe channel 2 is partially opened below the water surface through the side wall of the open channel 1, but in this case, the horizontal part of the pipe channel 2 has a free water surface that is continuous with the water surface of the open channel 1. Therefore, in the present invention, it is regarded as an open channel. The same applies to other connected parts. Therefore, the embodiments shown in FIGS. 3 and 4 are substantially the same, and both ends of the pipe channel 2 are opened below the water surface.

If the distance from the opening in the airlift part a of the carbon dioxide gas supply pipe 3 to the plane containing the water surface defined by the open channel 1 is the same in FIGS. 2, 3, and 4, the present invention The amount of water pumped is almost the same within the range. This is because, in FIG. 2, a gas-liquid mixing system is also formed in the open channel section directly above the air lift section aK1, and the carbon dioxide gas supply pipe 3 is connected to the open channel 1 in the pipe channel 2 below the open channel 1.
This is because the pipe is provided in a manner that is isolated from the inside, ensuring flow from the pipe waterway 1 to the upstream end, and providing a pumping effect. The distance from the opening in the air lift section a of the carbon dioxide gas supply pipe 3 to the plane defined by the open channel 1 that includes the water surface is the amount of water pumped per unit aeration power required for fluid agitation in the open channel 1. It is determined from the viewpoint of increasing the amount of carbon dioxide gas dissolved per unit amount of aeration power, and in practical terms, a length of 1 m or more is required. It is desirable that the distance from the opening in the air lift section C of the carbon dioxide-containing gas supply pipe 3 to the plane defined by the open channel 1 including the water surface be as long as possible within the range of the above conditions. Normally, air lift pumps have a immersion depth of 1~
Under conditions of 5 m and a lifting head of 0, the amount of water pumped is 20 to 4 times the airflow rate.
It is in the range of 0 times. It is desirable that the gas be injected as fine bubbles.

The flow cross-sectional area of the pipe channel 2 in which the air lift section a is provided must be greater than or equal to the average flow cross-sectional area of the open channel 1 in order to eliminate sudden changes in the flow cross section of the flow channel from the open channel 1 to the pipe channel 2. It is said that The end of the pipe channel 2 that opens at a point other than the upstream end C must be opened at the bottom of the open channel 1 or slightly above it to ensure a sufficient flow rate from the open channel 1 to the pipe channel 2. A pipe without an air lift section is not necessary, but if one is provided for construction reasons, the water flow cross-sectional area of the pipe channel 2 without an air lift section is equal to the average flow cross-sectional area of the open channel 1. Consideration should be given to increasing the resistance by 0.8 to 1.2 times to reduce the pipe resistance of the pipe waterway 2 and to reduce sudden changes in the flow cross section at the joint between the open waterway 1 and the pipe waterway 2. These ensure that the flow velocity in the open channel 1 depends on the amount of ventilation.

The amount of growth of microalgae depends on the amount of light received and the light receiving area once a certain algae concentration is reached, so the total area of the free water surface that receives direct sunlight in open channel 1 is the total volume of the channel in the endless channel. The divided value may be 0.7 m or less, and preferably 0.1 to 0.2 m.

As the carbon dioxide source, boiler exhaust gas, fermentation exhaust gas, liquefied carbon dioxide, etc. can be used. Carbon dioxide source is oxygen,
If gases such as nitrogen gas that are difficult to dissolve in water are included, oxygen and nitrogen gas, etc. will be accumulated under pressure in the gas return channel d due to the injection of this carbon dioxide gas source, and this will eventually be released into the atmosphere outside the gas return channel d. In this case, unnecessary loss of carbon dioxide from the carbon dioxide source occurs. If liquefied carbon dioxide gas is used as a carbon source, this loss will be minimal because liquefied carbon dioxide gas does not contain gases that are poorly soluble in water.

Since bubbles have negative effects such as scattering light, it is undesirable for bubbles to move to the water surface of the open channel. The partition wall 4 provides a gas return flow path d and prevents the movement of bubbles.

This foam will disappear naturally if the partition wall 4 is sufficiently high, but it may be eliminated using a water spray device or the like. The lower end of the partition wall 4 may be provided 1 to 2 cm below the liquid level.

When gas is pressurized through the opening of the carbon dioxide-containing gas supply pipe 3, a gas-liquid mixed system is formed within the air lift section a, and the internal density is reduced. Due to this decrease in density and the rising force of the bubbles, a flow of the culture solution occurs in the pipe channel 2 from the downstream end C to the upstream end, and this causes the culture solution to flow from the upstream end to the downstream end C in the open channel 1. A flow of culture solution is formed in the opposite direction, and the inside of the water channel is agitated. When the culture solution passes through the open channel 1 with microalgae, the microalgae are irradiated with light and proliferate, and when passing through the air lift section a, the microalgae are supplied with carbon dioxide gas. The pressurized gas is released into a closed space formed by the partition wall 4 and the water surface, and is guided by the pipe 5 to the air lift section a through the opening of the carbon dioxide-containing gas supply pipe 3. It is press-fitted. A gas cylinder 8 is fed into the gas return channel d formed by the partition wall 4 and the pipe 5 at a flow rate controlled by the flow rate control valve 10.
The liquefied carbon dioxide gas inside is injected through the carbon dioxide gas injection pipe 9, and a part of this gas is pumped into the gas trap 6 by the pump 14.
The water passes through a pipe 12, is dehumidified by a dehumidifier 13, and is continuously sent to a carbon dioxide gas analyzer 11, where its carbon dioxide concentration is analyzed. The signal from the carbon dioxide gas analyzer 11 is recorded by the controller 1.
2, the recording controller 12 records the carbon dioxide concentration and adjusts the flow rate control valve 10.

If the carbon dioxide concentration is lower than the set value, the flow rate control valve 10
is further opened, and if the carbon dioxide concentration is higher than the set value, the flow rate control valve 10 is further closed, and the amount of carbon dioxide gas pressurized into the air lift section -d is regulated.

Setting values of the recording controller 15 can be changed as necessary. The set value is determined by considering the ventilation amount, the distance from the opening in the airlift part a of the carbon dioxide gas supply pipe 3 to the plane defined by the open channel 1 that includes the water surface, the light receiving area, weather conditions, etc. Usually, the carbon dioxide concentration is 0.2 to 0.2 in volume percentage.
It may be set within a range of 2%.

Since the apparatus of the present invention is constructed as described above, it has the following advantages compared to the conventional apparatus. (a) The structure is simple. (a) The aeration method allows stirring inside the tank and supplying carbon dioxide gas at the same time and efficiently. (1) Since ventilation is conducted from a deep region, the gas-liquid contact time is long, and the amount of carbon dioxide gas dissolved per unit amount of ventilation is large and stable, allowing for stable control of the amount of carbon dioxide gas supplied. (1) Since the carbon dioxide gas is cyclically reused, almost all of the supplied carbon dioxide gas can be dissolved, resulting in little loss. (e)
There is no need to cover the entire device with transparent material, allowing full use of sunlight. (Power) There is almost no scattering of light by the bubbles.

FIG. 5 is an explanatory view showing a longitudinal section of another embodiment, and the second
It is almost the same as the figure. It differs from the one in FIG. 2 in that the upstream end side end of the pipe waterway 2 provided with the air lift section a is opened above the water surface defined by the open waterway 1. In the apparatus of this embodiment, the amount of water pumped per unit meter of ventilation is smaller than in the apparatuses shown in Figs. The advantage is that the gas concentration can be set low, and the loss of carbon dioxide gas when excess gas is released into the atmosphere outside the gas return channel d when using the aforementioned boiler exhaust gas or fermentation exhaust gas is reduced. be. In practice, the length of the part of the near rift 1 part a defined by the open channel 1 below the water surface is 10 times the distance from the opening above the water surface to the water surface, that is, the lift height.
It is sufficient if it is twice or more. Normally, with an air lift pump, the pumping amount is in the range of 6 to 8 times the ventilation amount under the condition that the immersion depth is 1 to 5 rr + the lifting head is 0.1 times that amount.

As described above, according to the apparatus of the present invention, it is possible to mass-produce microalgae using inexpensive carbon dioxide gas. The apparatus of the present invention can also be used in wastewater treatment for the purpose of microalgae production and wastewater purification, such as the high-rate oxidation pond method.

[Brief explanation of drawings]

FIG. 1 is a plan view, FIG. 2 is a longitudinal cross-sectional view taken along the line X-X in FIG. FIG. 2 is a longitudinal cross-sectional view showing another embodiment of the present invention. 1 is an open channel, 2 is a pipe channel, 3 is a carbon dioxide gas supply pipe,
4 is a bulkhead, 5 is a pipe, 6 is a gas trap, 7 is a blower, 8
1 is a gas cylinder, 9 is a carbon dioxide gas injection pipe, 10 is a flow rate control valve, 11 is a carbon dioxide gas analyzer, 12 is a pipe, 13 is a dehumidifier, 1
4 is a pump, 15 is a recording controller, a is an air lift part, b
- is the upstream end, and C is the downstream end. Arrows indicate the direction of flow.

Claims (1)

[Scope of Claims] 1. An apparatus for culturing microalgae under light irradiation conditions using carbon dioxide gas as a carbon source, which apparatus includes: It is a culture tank configured as an endless waterway consisting of a waterway and a pipe waterway in which the upstream end and downstream end of the open waterway pass below the water surface defined by the open waterway and communicate with each other, and in the pipe waterway, A portion of at least one pipe channel is located below the water level defined by the open channel, and is erected vertically above the location to help obtain a sufficient amount of carbon dioxide gas dissolved and water pumped for a unit ventilation amount. A carbon dioxide-containing gas supply pipe for forming a flow of the culture solution toward the upstream end and dissolving carbon dioxide in the culture solution is provided in the air lift section, A culture tank in which the value obtained by dividing the total area of the free water surface that receives direct sunlight in the waterway by the total volume of the flow path in the endless waterway is 0.7 m or less, (b) connected to the carbon dioxide-containing gas supply pipe. (c) a gas flow path that guides the gas released from the water surface above the airlift portion back to the blower; a gas return flow path that is surrounded by a partition wall and the water surface and communicates with the blower; , (d) An injection device for injecting carbon dioxide into the gas return flow path, a carbon dioxide gas injection pipe that connects the gas return flow path and the carbon dioxide source, and a flow rate provided in the carbon dioxide gas injection pipe. said injection device comprising a control valve, a means for forcibly sending carbon dioxide gas through a carbon dioxide gas injection pipe, and a container for storing a carbon dioxide gas source; and (e) an air lift section via said carbon dioxide gas supply pipe. A microalgae culturing device, characterized in that it is a means for controlling the carbon dioxide concentration of the gas to be pressurized to a certain value lower than the carbon dioxide concentration of the carbon dioxide source, and the control means is connected to the injection device. 2. The means for controlling the carbon dioxide concentration of the gas pressurized into the air lift section via the carbon dioxide-containing gas supply pipe to a certain value lower than the carbon dioxide concentration of the carbon dioxide source is configured to control the gas in the gas return flow path. The carbon dioxide analyzer is equipped with means for continuously drawing out carbon dioxide gas and is effective for measuring and analyzing carbon dioxide gas in the gas, and the carbon dioxide gas analyzer The microalgae culturing device according to claim 1, wherein the microalgae culturing device is connected to a controller for controlling the flow rate of carbon dioxide gas injected into the microalgae, and the controller is connected to the flow rate control valve. 3. Claim 1, wherein the carbon dioxide source is liquefied carbon dioxide, and the liquefied carbon dioxide is stored in a pressure-resistant container.
The microalgae culturing device according to item 1 or 2. 4. A claim in which the air lift section is directly connected to the upstream end of the open channel, and the distance from the opening in the air lift section of the carbon-containing gas supply pipe to the plane defined by the open channel that includes the water surface is 1 m or more. The microalgae culture tank according to item 1, item 2, or item 3. 5. The microalgae according to claim 1 or 2 or 3 or 4, wherein the water flow cross-sectional area of the pipe waterway in which the air lift portion is provided is greater than or equal to the average flow water cross-sectional area of an open channel. Culture device. 6. Each end of the pipe channel is opened below the water level defined by the open channel, and the ends other than the end on the upstream end side of the pipe channel where the air lift part is provided are at the bottom of the open channel or Claim 1, 2, or 3 opens slightly above the endless waterway, and the various parts of the endless waterway are communicated with each other.
5. The microalgae culturing device according to item 4 or 5. 7. The upstream end of the pipe waterway where the airlift part is provided is opened at or above the water level defined by the open channel, and the other end is below the water level defined by the open channel. and the open channel is opened at the bottom of the open channel or slightly above it, and each part of the endless channel is communicated with each other when gas is pressurized. The microalgae culture device described. 8. A portion where the upstream end side end of the pipe waterway in which the air lift section is provided is opened at or above the water surface defined by an open channel, and is below the water surface defined by the open channel of the air lift section. 8. The microalgae culturing device according to claim 7, wherein the length is at least 10 times the distance from the opening to the water surface, that is, the lifting height.