EP3728546A1

EP3728546A1 - Photo bioreactor

Info

Publication number: EP3728546A1
Application number: EP18826007.9A
Authority: EP
Inventors: Marie-Alix DALLE; Jérôme ARNAUDIS
Original assignee: Suez Groupe SAS
Current assignee: Suez International SAS
Priority date: 2017-12-22
Filing date: 2018-12-19
Publication date: 2020-10-28
Also published as: US20210179987A1; WO2019121933A1; FR3075815B1; FR3075815A1; US11639488B2; CA3085888A1; CN111511892A

Abstract

The invention relates to a photo bioreactor comprising: a first vessel and a second vessel, extending in a longitudinal direction; the second vessel extending inside the first vessel so as to delimit a first channel between the first vessel and the second vessel, and forming a second channel inside the second vessel; a first passage means, allowing a fluid to flow between the first channel and the second channel; a second passage means, allowing the fluid to flow between the first channel and the second channel, said second passage means being disposed above the first passage means; at least one light source; and a gas injection means configured to inject gas in the form of bubbles into the second channel. According to the invention, the flow of fluid can be exposed to a light source.

Description

photobioreactor

TECHNICAL FIELD OF THE INVENTION

The invention lies in the field of photobioreactors.

More particularly, the invention relates to a photobioreactor of intensive production, adapted to avoid a reduction of light diffusion to the algal solution disposed in the photobioreactor.

STATE OF THE ART

Micro-algae-type photosynthetic microorganisms tend to dominate many application sectors. Photosynthetic microorganisms are thus used for the solar production of bioenergies, the production of natural molecules of interest or even the pollution control of gaseous effluents (for example C0 ₂ from fumes) or liquids with the associated production of a plant biomass with multiple outlets (PRUVOST, Jérémy and CORNET, Jean-François and LE BORGNE, François and JENCK, Jean, February 10, 2017, "Industrial production of microalgae and cyanobacteria", Green chemistry and new energy management, in line, TI Publishing, 2017.

With regard to C0 ₂ gas pollution abatement technologies, it is called carbon sinks or carbon dioxide (C0 ₂ ) sinks: it is a natural or artificial reservoir that absorbs carbon. of the atmosphere and helps to reduce the amount of atmospheric carbon dioxide. Photosynthetic micro-organisms of the microalgae type are particularly interesting for this application.

The industrial production of photosynthetic micro-organisms requires dedicated technologies to conduct so-called photoprocessing methods of photography capable of allowing photosynthetic growth based on the assimilation, thanks to the light captured, of nutrients inorganic and mineral. Depending on the constraints and objectives of exploitation, the cultivation process can be conducted using a wide range of technological solutions ranging from open systems (such as open basins, eg shallow ponds exposed to sunlight) to closed systems and using either solar energy or an artificial source of light. We speak generically of photobioreactors.

Photobioreactors must make it possible to produce high productivity of photosynthetic micro-organisms. It is therefore a question of optimizing their operations in order to maximize their performances.

Open systems have a major disadvantage of being subject to contamination by dust, other microorganisms, insects and environmental pollutants. In addition, it is difficult to control the processes in open basins.

Closed systems typically include long pipes forming a circuit developed to allow maximum exposure of an algal solution flowing in the pipes to the light. They also allow the establishment of a thin layer of suspension culture combined with biological purity to cultivate the microorganisms in the best way. Many systems with different shapes and functions have been developed with the aim of being profitable on an industrial scale.

Photobioreactors are, however, subject to many weather events. For example, natural sunlight is not available during the night or would not be sufficient during weather events such as cloudy skies. In addition, natural light is not sufficient to establish an intensive microalgae culture. Other light sources have been used to overcome these disadvantages.

In addition, it is necessary to manage the cleaning of the pipes, according to the materials used, and according to the microorganisms generated, and this, in order to allow the light to be diffused correctly in time. For example, patent US495251 1 discloses a photobioreactor for the cultivation of photosynthetic microorganisms that uses a light reservoir or light cavity to distribute a high intensity light and uniformly in a vessel comprising microbial liquid culture compartments . In order to achieve such an objective, the light compartment must have at least one transparent wall having a portion extending into the tank.

A photobioreactor as described in US4952511 is designed to diffuse the light in the microbial liquid and the light scattering inside the tank can be optimized by decreasing the wall thickness of the culture vessels.

Conversely, a large thickness of the walls of the tank has the effect of reducing the intensity of the light.

In addition, a high turbidity value, reflecting a cloudy algal solution, and a high concentration of organic matter and / or microorganisms in the algal culture have the effect of reducing the intensity of light.

A simple solution to maintain diffusion under the adverse conditions presented above would be to increase the luminous intensity, beyond the luminous intensity required in a clear solution, so as to maintain a favorable absorption for the microorganisms phototrophic. Thus the light intensity must be sufficient even after its attenuation through the thickness of the tank, and / or after passing a given distance in cloudy solution, concentrated in organic matter and / or microorganisms.

A disadvantage of such a solution is that it may be to the detriment of the profitability of the system (it is necessary to spend more light energy).

In addition, it may burn floating algae, especially algae located closer to the wall (the less light emission has traveled a distance in the solution, the more it is intense, this has to disadvantage of treating the solution in a non-homogeneous manner) and / or precipitating them. Such phenomena are counterproductive because the algae burned and / or precipitated do not participate in the development of the system: they do not consume nutrients, do not metabolize them. They also help to make the water more turbid and can aggregate in the system, potentially clogging all or part of the reactor.

Conversely, insufficient light intensity tends to attract algae to the walls of the pipes or tanks, further blocking the access of light beyond a layer formed on the inner wall of the tanks.

In addition, when the algal density within the solution increases, it actually decreases the penetration distance of the light within the reactor, and therefore the period of light intensity to which the algae are subjected.

It is therefore a question of finding a solution for submitting an optimal and homogeneous light intensity to the algal solution, whatever its turbidity, its algal density and its concentration of organic matter and / or other microorganisms.

European Patent EP1 169428 discloses a photobioreactor with an improved exchange surface leading to a better spatial distribution of light in the reactor and thus an optimization of the intensity of light in the reactor. Thus, the subject of the invention of the patent EP1 169428 is a rectangular cross section tank having a greater exchange surface than a tank of circular cross section. The patent also relates to a turbulent flow guiding means, allowing a "flash light effect" obtained by increasing the turbulence. This effect is based on the principle that algal cells can, during the dark phases, metabolize the energy they have accumulated during the light phases. This effect is created when the algal cells are exposed to significant light intensity and short distance from the reactor walls during the light phase. A cycle comprising a light phase and a dark phase must be no longer than one second.

However, such a photobioreactor will lead to a rapid and probably heterogeneous increase in said reactor of the algal density due to the high availability of light. Thus, light scattering in the algal culture will be affected by the creation of dark areas in the center of the culture vessel and algal growth will ultimately be reduced.

The lack of light availability for algae creates phenomena that may further accentuate the lack of availability, creating a vicious circle.

In particular in an intensive production reactor, the algal growth is strong and induces an increase in the algal density. This last increase has the effect of reducing the diffusion of light in the medium, which in turn induces areas of shade where algal growth will be reduced. These shaded areas will in turn cause an attraction of the algae for the more illuminated walls of the tanks, which reduces the exchange surfaces and reduces the diffusion of light again. In addition, algae are stressed due to lack of light, affecting the profitability of the system.

There is thus the need for a photobioreactor that overcomes these disadvantages, while allowing intensive production, a device that avoids the decrease in algal growth resulting from the reduction of light diffusion, and / or an algal density. growing, and / or the attraction of algae to the cell walls.

It is particularly sought a photobioreactor allowing a diffusion of light to the algal liquid that contains as uniform as possible. SUMMARY OF THE INVENTION

An object of the invention for achieving this goal is a photobioreactor adapted to contain at least one fluid, characterized in that it comprises:

a first container extending in a first longitudinal direction;

a second container extending in a second longitudinal direction;

the second container extending inside the first container, so as to define a first channel between an inner side surface of the first container and an outer side surface of the second container; and forming a second channel within said second container;

at least one first passage means adapted to allow the circulation of the fluid between the first channel and the second channel;

at least one second passage means adapted to allow the circulation of the fluid between the first channel and the second channel, and disposed above the at least one first passage means;

at least one light source;

gas injection means configured to inject gas in the form of bubbles into the second channel;

the first and second containers, the first and second passage means and the injection means being configured to allow a flow of fluid in the photobioreactor between the first channel and the second channel, and the circulating fluid being adapted to be exposed to the at least one light source.

There may be more than one second container: in this case, there is more than one second channel, and the first channel is formed by the space between the inner side surface of the first container and the outer side surfaces of the first container. second containers. Throughout the present application, the first and second containers respectively extend in a first and second longitudinal directions.

Throughout the present application, the terms "lower", "upper", "vertical", "horizontal", "below" and "above" are to be understood by taking as a reference a vertical longitudinal direction, it being understood that each longitudinal direction may not be vertical, but may be horizontal or inclined at another angle.

Throughout this application also:

• "Receptacle" means a hollow object intended to receive solid, liquid or gaseous products delimited by at least one lateral surface. The object may have no lower and / or higher closure;

• A "first means of passage" may also be called "lower passage means";

• A "second means of passage" may also be called "upper means of passage";

• "External lateral surface" (or "internal lateral surface") means the surface extending in the longitudinal direction and delimiting an object on its outermost periphery, (or on its innermost periphery). If the object has a plurality of walls, the outer side surface will be the outer surface of the eccentric wall, and the inner side surface will be the inner surface of the most centered wall. The terms "inside" and "outside" must be understood in relation to a radial direction, with respect to the longitudinal direction;

• "Circumferential ring" means a ring disposed on a circumference of a container, preferably cylindrical;

• "Crenel" means a set of horizontal segments, alternately low and high, connected by vertical segments, the lower segments forming solid (or protuberances) and the upper segments forming voids (or depressions); • "Lower part" means the part of an element comprising the lower end of said element and may extend above said lower end;

• "upper part" means the part of an element comprising the upper end of said element and may extend below said upper end;

• "Channel" means a hollow form able to allow and guide the flow of a fluid;

• By substantially circular, is meant a closed curve substantially defining a circle of radius r, with a standard deviation on the radius of +/- 10% of the radius.

The fluid contains microorganisms, for example microalgae. It can also be a mixture of fluid and solids. In addition, the fluid can be mixed with the injected gas or the injected gas / solid mixture.

The inventors have been able to highlight an important technical effect of the invention which makes it possible to improve the exposure of microorganisms (for example micro-algae) to light: the bubbles injected and circulating with the fluid diffract the light they receive, the light is better distributed within the photobioreactor.

Thus, the photobioreactor according to the invention makes it possible to solve the problem of allowing intensive production, while avoiding the reduction in algal growth resulting from the reduction of light scattering, and / or of a growing algal density, and or the attraction of algae for the cell walls.

In other words, the circulation of fluid and bubbles that cause the fluid, coupled with the diffusion of a light source, increases the exposure of microalgae to light. This allows a diffusion of the light towards the algal liquid as uniform as possible.

The air injection system, by the formation of bubbles and the entrainment of the fluid generates a high shear rate in the medium, homogenizing the medium, preventing algal deposits on the walls, and improving the contact between the micro algae with nutrients for said microalgae and C0 ₂ .

According to one embodiment, the first container is closed at its lower and upper ends.

This has the advantage of being able to better manage the pressure of the gas injected into the photobioreactor, the temperature of the fluid, and, when the injected gas comprises CO ₂ , to prevent the reduction of the CO ₂ concentration. In addition, it is also often important for security reasons, in order to prevent access to the fluid that may be contained in the photobioreactor.

According to an advantageous embodiment, the first and second longitudinal directions of the first and second containers are parallel, preferably combined.

According to a particularly advantageous embodiment, the first and second containers are first and second cylinders of revolution, preferably concentric.

The advantage of these two modes is that the width of the first channel is better distributed between the two containers along the longitudinal direction. Thus, the circulation of the fluid is more regular and less likely to undergo jolts.

In particular, when the rolls are concentric, a symmetry is obtained which makes it possible to obtain a width of the first regular channel between the two containers along the longitudinal direction. This allows an even more uniform fluid flow in the photobioreactor, improving trade and avoiding in particular dead zones and / or the risk of algae concentrations in certain areas of the photobioreactor.

In addition, the cylinder-shaped revolution allows to avoid dead zones which are areas of loss of retention of material, and therefore particularly more difficult to clean.

Alternatively, only one of the first container and the second container is a cylinder of revolution.

According to one embodiment, the at least one first passage means is formed by openings in the wall of the second container, preferably in the lower part of said second container.

According to a particular embodiment, the second container is a second cylinder of revolution and comprises a plurality of openings forming first passage means, arranged along at least one second circumferential ring in the wall of said second container, and preferentially in the lower part of said second container.

According to a particular embodiment, the openings are arranged along several first circumferential rings in the wall of the second cylinder.

If the second container comprises a plurality of walls, the openings must be made throughout the walls to allow the passage of fluid between the first and second channels.

Alternatively or in addition, the at least one first passage means may be formed by slots, and preferably arranged at the lower end of the second container.

First means of passage must allow the aspiration of the fluid from the first channel to the second channel, while avoiding the diffusion of bubbles emitted in the second channel to the first channel.

The openings and / or crenellations may advantageously be dimensioned to ensure this double constraint. According to one embodiment, the at least one first passage means is formed by a difference in height between the first container and the second container, the lower end of the second container being located above the lower end of the first container.

This mode makes it possible to easily adapt the dimensions of the first passage means, in particular as a function of the geometries of the photobioreactor, the characteristics of the algal liquid and / or the injected gas and in particular the bubble sizes in order to optimize the circulation of the fluid.

According to one embodiment, the at least one second passage means is formed by a difference in height between the first container and the second container, the upper end of the second container being located below the upper end of the first container.

This mode makes it easy to adapt the dimensions of the second passage means, in particular as a function of the geometries of the photobioreactor, the characteristics of the algal liquid and / or the injected gas and in particular the bubble sizes in order to optimize the flow of the fluid.

Alternatively or in addition, a second passage means is formed by openings in the wall of the second container, in the upper part of said second container.

According to one embodiment, the second container is a second cylinder of revolution and the openings are disposed along at least one second circumferential ring in the wall of said second container, and in the upper part of said second container.

Alternatively or in addition, the at least one second passage means may be formed by slots arranged at the upper end of the second container. According to one embodiment, the injection means is capable of generating bubbles of average diameters, preferably less than or equal to 1 mm.

This makes it possible to obtain a better rate of dissolution of C0 ₂ in the fluid, as well as a better mixing of the fluid, with the consequence in particular of making the best use of the technical effect of diffraction of light by the bubbles within the fluid. algal liquid.

According to one embodiment, the injection means is capable of injecting a gas / solid mixture. This is particularly necessary for treating a gas / solid mixture injected into the photobioreactor: the mixture can in particular comprise fine particles contained in the gas to be treated.

According to one embodiment, the injection means is disposed below the second container.

According to one embodiment, the injection means comprises a membrane, preferably disposed inside and in the lower part of the second container. The function of such a membrane is to inject the gas in the form of bubbles of size (s) mastered (s) and / or calibrated.

According to another embodiment, the injection means may comprise a fine-bubble diffuser, a hydro-injector, porous stone or any other means capable of performing the function of injecting the gas in the form of bubbles and more precisely control the size (s) of said bubbles.

According to an advantageous embodiment, at least one light source comprises at least one illuminating wall among at least one wall of the first and second containers. This allows a better homogeneity of light diffusion, without disturbance of the flow of the fluid (no addition of dead zone).

According to one embodiment, the at least one light source comprises at least one first light source disposed inside the second container. According to one embodiment, the at least one light source comprises at least a second light source disposed between the first container and the second container.

According to one embodiment, at least one light source is disposed on an inner side surface of the second container.

According to one embodiment, at least one light source is disposed on an outer side surface of the second container.

According to one embodiment, at least one light source is disposed on an inner side surface of the first container.

According to one embodiment, the at least one light source comprises at least one third light source disposed outside the first container, for example on an outer lateral surface of the first container, or at a given distance from said first container.

According to one embodiment, at least one light source is formed by at least one light column extending along one of the first and second longitudinal directions of the first and second containers.

We can also talk about light tube in the following description.

According to one embodiment, at least one light source comprises a coil having a helical shape around an axis parallel to one of the first and second longitudinal directions of the first and second containers, the coil being preferably wound around the first and / or the second container.

According to one embodiment, at least one light source comprises LEDs.

According to one embodiment, the photobioreactor further comprises at least one recirculation pump configured to circulate the fluid from the lower part of the photobioreactor to the upper part of the photobioreactor. According to one embodiment, the photobioreactor comprises at least one helix.

According to one embodiment, at least one helix is arranged in the lower part of the photobioreactor, preferably in the second channel.

According to one embodiment, at least one helix is disposed in the first channel.

According to one embodiment, at least one wall of the first container is transparent to light.

According to one embodiment, at least one wall of the second container is transparent to light.

DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will become apparent with the aid of the description which follows, which is given by way of nonlimiting illustration, with reference to the appended figures among which:

Figure 1 illustrates a photobioreactor according to a first embodiment;

FIG. 2 illustrates a photobioreactor according to a second embodiment, comprising two recirculation pumps; FIG. 3 illustrates a photobioreactor according to a third embodiment, comprising several propellers;

FIGS. 4A and 4B show a photobioreactor according to a fourth embodiment;

FIG. 5 illustrates the flow direction of the fluid in the photobioreactor according to the different embodiments; FIG. 6 illustrates a first example of location of light sources; Figs. 7A and 7B illustrate a second example of location of light sources;

Figure 8 illustrates a third example of location of light sources;

Figure 9 illustrates a fourth example of location of light sources;

Figure 10 illustrates a fifth example of location of light sources;

Figure 11 illustrates a sixth example of location of light sources.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

Figure 1 illustrates a photobioreactor 1 according to a first embodiment.

The photobioreactor 1 comprises a first container 2 which is a first hollow cylinder extending in a first longitudinal direction Z ₂ and a second container 3 which is a second hollow cylinder extending in a second longitudinal direction Z ₃ and disposed at the Inside the first hollow cylinder 2. The two cylinders are cylinders of revolution. The axes of revolution of the first and second cylinders are merged, in other words, the cylinders are concentric. The space between the two cylinders forms a first channel 42. The space in the second cylinder 3 forms a second channel 43.

The first lower end, or base 21, of the first cylinder 2, closes the lower end of the photobioreactor 1.

The second lower end, or base 31, of the second cylinder 3 may be merged with the base 21 of the first cylinder 2.

The photobioreactor 1 may advantageously comprise means 9 for fixing the second cylinder 3 and / or positioning it relative to the first cylinder 2, for example so that the first channel 42 formed between the two cylinders is of stable shape.

The at least one first passage means comprises a plurality of first passage means, or lower passage means, formed by openings 331, each opening having a substantially circular section, being formed in the wall of the second cylinder 3 at the lower portion. 3a of said second cylinder. The openings 331 allow passage between the first channel 42 and the second channel 43.

In the illustrated example, the openings 331 are made regularly along a first circumferential ring 33 of the wall of the second cylinder.

The difference in height H between the upper ends of the first and second cylinders defines a second means of passage, or upper passage means 52.

A fluid can flow in the photobioreactor 1, in particular in the second channel 43 and in the first channel 42.

In this embodiment, the injection means 7 comprises several elements capable of injecting gas in the form of bubbles into the second channel 43. The injection means 7 comprises a compressor 72 for sending gas and a membrane 71 adapted to receive the gas and inject it in the form of bubbles. The membrane 71 is disposed inside the second cylinder 3. The compressor 72 is disposed below the photobioreactor 1.

The second cylinder 3 and the injection means 7 thus form an air lift system capable of injecting into the photobioreactor a gas, or a mixture of gases, or a gas / solid mixture, and in doing so, circulating the fluid present in the second channel 43.

According to the applications, and in particular the type of photobioreactor, the gas / solid mixture can be:

a gaseous mixture air / C0 ₂ and / or a gaseous mixture comprising solids, in particular fine particles, and in particular microparticles to be treated.

The gas can be urban air or industrial fumes, containing pollutants, including NO _x , which can pass in aqueous form (just like C0 ₂ ) and contribute to the feeding of micro-algae.

In the remainder of the present description, we will speak of gas, it being understood that it may be a gas mixture, or a gas / solid mixture.

The fluid is in particular a liquid, more particularly an aqueous solution comprising microalgae, also called "algal solution". But the fluid can also define the mixture between the fluid and the gas, the gas mixture or the gas / solid mixture.

In the remainder of the present description, the term "fluid" will be used, it being understood that it may be either the algal solution alone, or the mixture of said algal solution with the gas, or with the gaseous mixture, or with the mixture gas / solid.

The main function of the membrane 71 is to inject the gas in the form of bubbles and especially to control more precisely the size (s) of said bubbles, the gas thus being diffused in the second channel 43 in the form of bubbles, allowing and in particular to dissolve gas, for example C0 ₂ , in the liquid. This can also contribute to increase agitation in the reactor.

Alternatively to a membrane, it may be a fine bubble diffuser, a grid, a porous stone, a hydro injector or any other means capable of injecting the gas in the form of bubbles and more precisely control the size (s) of said bubbles.

There may be several membranes and / or other means capable of injecting the gas in the form of bubbles. All are preferably arranged in the lower part 3a of the second cylinder 3, and / or at several levels in said second cylinder in the longitudinal direction Z _{3 of} said second cylinder. Figure 5 illustrates the flow direction of the fluid. The bubbles from the injection means 7, and in particular the membrane 71, back in the second channel 43 by driving the fluid present in said second channel. The fluid thus driven back into the second channel 43. Once the upper end of said second channel reached (corresponding in the example shown at the high end 32 of the second cylinder 3), the fluid flows into the first channel 42 through the at least one upper passage means 52, for example formed by the space due to a difference in height between the first and second cylinders 2 and 3 at the upper ends 22 and 32 of said first and second cylinders. Then the fluid goes down to the lower end of the first channel 42. At the lower end of the first channel 42, the at least one lower passage means 51, for example openings 331 in the second cylinder 3, allow the suction of the descending fluid in the first channel 42 to the second channel 43 through the upward flow of the second channel, the passage of the fluid again in the second channel 43, and again a fluid entrainment movement by the bubbles since the lower part towards the upper part of the second channel 43, when the gas is injected.

The injection means 7 can inject gas bubbles continuously into the second channel 42.

Alternatively, the injection means 7 can inject gas bubbles in batch mode.

Thus, a movement of the fluid is thus created, corresponding to a forced convection movement according to the direction of circulation described above and illustrated in FIG.

In addition, the photobioreactor comprises several light sources 8 represented in FIG. 1 in the form of several first light columns 810 disposed on the wall inside the second cylinder 3 and extending in the longitudinal direction Z _{3 of} said second cylinder. . Sure the example shown, there are eight light columns 810 arranged regularly on the wall inside the second cylinder 3.

Other arrangements of light sources are presented more precisely with FIGS. 6, 7A, 7B, 8 to 1 1. All these arrangements can be combined with the photobioreactor illustrated in FIG. 1, or with the other embodiments presented below. after.

FIG. 2 illustrates a photobioreactor 1 according to a second embodiment, which differs from the first mode in that it furthermore comprises at least one recirculation pump 10.

There are two recirculation pumps 10 disposed outside the first cylinder 2. Said pumps make it possible to accentuate the flow rate of the fluid. They are configured to suck the fluid from the lower part of the photobioreactor, for example in the lower part of the first channel 42 and reinject it into the upper part of the photobioreactor, for example in the upper part of the first channel 42, accentuating the phenomenon of air lift.

The number of pumps and the arrangement of the pump or pumps can be adapted to allow to increase the flow rate of the fluid.

Although not all elements of the photobioreactor have been shown in FIG. 2, it should be considered that the photobioreactor of the second embodiment may comprise all or some of the elements described for the first mode.

FIG. 3 illustrates a photobioreactor according to a third embodiment which differs from the first mode in that it comprises at least one helix 11.

According to the example shown, the photobioreactor comprises three propellers 1 1. A propeller is arranged in the lower part of the second channel 43. The arrangement and the orientation of a propeller are made in such a way that the propeller can apply upward movement to the fluid from the lower end to the upper end of said second channel. Two other propellers are arranged in the first channel 42 so as to apply a downward movement to the fluid in said first channel from the upper end to the lower end of said first channel.

The propellers, driven by a motor disposed outside the photobioreactor 1, rotate and agitate the fluid inside the photobioreactor. The propellers create a stirring which makes it possible to accentuate the stirring of the fluid in the photobioreactor.

The number of propellers and the arrangement of the propeller (s) in the photobioreactor can be adapted to obtain the same effect.

Although not all elements of the photobioreactor have been shown in FIG. 3, it should be considered that the photobioreactor of the third embodiment may comprise all or some of the elements described for the first mode.

FIGS. 4A and 4B show an example of a photobioreactor according to a fourth embodiment.

FIG. 4A illustrates a photobioreactor 1 comprising a first cylinder 2 of revolution of first external diameter D2 extending in a first longitudinal direction Z ₂ on a first height H2 and a second cylinder 3 of revolution of second outer diameter D3 extending according to a second longitudinal direction Z ₃ on a second height H3. Both cylinders are cylinders of hollow revolution and are concentric.

The space between the two cylinders forms a first channel 42. The first channel 42 has a cylindrical sleeve shape of height equal to the height H3 of the second cylinder 3 and whose width corresponds to (D2-D3) / 2 (and (D2-D31) / 2 at the base 31 of the second cylinder, as explained later).

The height H between the two cylinders forming a second passage means 52 is equal to H2-H3. The photobioreactor 1 comprises holding means 9 able to position and / or hold the second cylinder 3 relative to the first cylinder 2.

By way of example, and as illustrated, the holding means 9 comprise holding tabs 91 arranged at the level of the upper part 3b, preferably at the upper end 32 of the second cylinder 3, and capable of positioning the second cylinder 3 with respect to the first cylinder 2.

In addition, they comprise centering lugs 92 fixed to the base 21 of the first cylinder 2 and able to center the second cylinder 3 relative to the first cylinder 2.

The side wall of the first cylinder 2 is made of transparent PVC, and its thickness is for example 10 mm.

The base 21 of the first cylinder 2 is non-transparent PVC and its thickness is for example 10 mm.

The base 21 of the first cylinder 2 is traversed by two passages 26, for example tappings, allowing the arrival and / or the exit of a fluid or a fluid / solid mixture within said first cylinder.

The second cylinder 3 is disposed on the base 21 of the first cylinder 2, and is centered with respect to said first cylinder by means of the centering lugs 92.

The base 31 of the second cylinder has a diameter D31 greater than the diameter D3 and comprises a crenellated lower end 31 1, the protruding portions 31 1b are in contact with the base 21 of the first cylinder. The height of the lower end is equal to H31. Each depression of a slot 31 1a may have a length L31 1a and a height H31 1a.

The depressions 31 1 has slots can form first passage means for the fluid.

The injection means 7 comprises several elements capable of injecting gas in the form of bubbles into the second channel 43. In this embodiment, the injection means 7 comprises a compressor 72 for sending gas and a membrane 71 capable of receiving the gas and injecting it in the form of bubbles and diffusing it in the second channel 43. The compressor 72 is disposed below the photobioreactor 1.

The membrane 71 is disposed in the base 31 of the second cylinder 3. It is in the form of a flat disc of diameter D71.

FIG. 4B illustrates more precisely the second revolution cylinder 3.

The side wall of the second cylinder 3 is made of transparent PVC, and its thickness is for example 5 mm.

The second cylinder 3 further comprises first passage means in the form:

first openings 331 of diameters D331, arranged and uniformly distributed along a first circumferential ring 33 in the wall of the second cylinder, at a height equal to H33 with respect to the point of contact of the base 31 of said second cylinder with the base 21 of the first cylinder, and

second openings 331 'of diameters D331', arranged and evenly distributed along a second circumferential ring 33 'in the wall of the second cylinder, at a height equal to H33' with respect to the point of contact of the base 31 of said second cylinder with the base 21 of the first cylinder.

By way of example, the aforementioned dimensions can be:

- D2 = 400 mm

- H2 = 3000 mm

- D3 = 200 mm

- H3 = 2525 mm

- H = H2-H3 = 475 mm

- D31 = 280 mm - H31 = 50 mm

- D331 = D331 '= 30 mm

- H33 = 100 mm

- H33 '= 200 mm

- L311 a = 75 mm

- H31 1 a = 22 mm

- D71 = 270 mm

In addition, the photobioreactor comprises a plurality of light sources 8 shown as columns or tubes 810 in Figs. 4A and 4B, but which may be otherwise configured as shown hereinafter.

Several light sources 8 can create a uniform light pattern by being spaced 10 cm apart from each other.

According to an embodiment not shown, which may especially apply to all of the preceding embodiments, there may be several second containers 3 inside the first container 2. In this case, there may be several seconds. channels 43.

This makes it possible to improve the uniformity of light diffusion within the algal liquid, to increase the flow rate of the fluids (reduction of the sections) and thus to improve the homogenization of the medium, to prolong the residence time of the bubbles of CO ₂ in the medium and thus improve the rate of dissolution of CO ₂ in the medium.

As indicated above, FIGS. 6, 7A, 7B, 8, 9, 10, 1 1 illustrate several arrangements of light sources.

The light sources are preferably spaced apart from each other by a maximum of 10 cm.

In the illustrated examples, the first container 2 is shown as being a cylinder of revolution, of longitudinal direction Z ₂ and the second container 3 is shown as being a cylinder of revolution, of longitudinal direction Z ₃ .

For ease of reading, in FIGS. 6, 7A, 7B, 8, 9, 10, 1 1 are represented cylinders of revolution and the corresponding description expresses first and second cylinders, it being understood that this may be containers that are not necessarily cylinders, and not necessarily cylinders of revolution.

The different arrangements of light sources can be combined with each other.

In addition, they can be combined with each of the various embodiments presented in connection with FIGS. 1 to 4B.

The lighting is preferably made by LEDs, but other sources of light can be envisaged. This can be spots, or garlands or light ribbons. Other modes are presented below.

The bubbles themselves can be sources of light because they can diffract the light and send it back to the fluid.

The intensity of the light sources must be adapted: an intensity too high may grill the micro-algae, and on the contrary, too low intensity makes them stick to the walls of the reactor.

FIG. 6 illustrates a first example in which the light sources 8 comprise first light sources 81 disposed inside the second cylinder 3.

They are illustrated in the form of first light columns 810 extending in the longitudinal direction Z ₃ of the second cylinder 3.

The first light columns 810 are positioned on the inner side surface of said second cylinder, and are distributed evenly. In this example, eight light columns 810 are shown, but there may be fewer, or more.

The first light columns 810 may be attached to a wall of the second cylinder 3, for example by a latching system. In a photobioreactor whose cylindrical walls are opaque, especially those of the second cylinder, it is important that the light sources can diffuse the light 360 ° and therefore they are not glued to the walls of the cylinders.

Thus, alternatively or in addition, the first light columns 810 can be positioned inside the second cylinder 3, but not on a lateral surface of said cylinder, as illustrated in FIGS. 7A (in 3D view) and 7B (in view of FIG. above): second example of location.

The spacing of the first light columns 810, and more broadly the spacing of the first light sources 81, with the inner side surface of the second cylinder 3 depends on the turbidity of the medium, the concentration of algae, but also the light intensity. issued.

Alternatively or in addition, second light columns 820 can be positioned between the first and the second cylinder, on the outer lateral surface of the second cylinder 3 as illustrated in Figure 8 in top view (third example of location).

Alternatively or in addition, second light columns 820 can be positioned between the first and second rolls, but not necessarily on the outer side surface of the second roll.

FIG. 9 illustrates a fourth example of location of light sources 8, seen from above.

In this example, first light sources 81 are disposed inside the second cylinder 3 and third light sources 83 are disposed outside the first cylinder 2. The first light sources 81 are in the form of light columns 810 disposed inside the second cylinder 3.

The first light columns 810 extend in the longitudinal direction Z ₃ and are positioned at a given distance from the inner side surface of the second cylinder 3. They can be arranged alternately according to one of the first and third examples presented, or according to a combination of the first to third location examples.

The third light sources 83 are in the form of several second light columns 830 extending along the longitudinal direction Z ₂ of the first cylinder 2. They can be positioned against the wall of the first cylinder 2 or at a distance D83 of the first cylinder 2 .

The distance D83 between the third light columns 830 and the outer lateral surface of the first cylinder 2, and more widely between the third light sources 83 and said wall, depends on the turbidity of the medium, the concentration of algae, but also the luminous intensity delivered.

Figure 10 illustrates a fifth example of location of light sources.

In this example also, second light sources 82 are disposed outside the second cylinder 3 and third light sources 83 are disposed outside the first cylinder 2.

As in the previous example, the third light sources 83 are in the form of third light columns 830 extending along the longitudinal direction Z ₂ of the first cylinder 2. They can be positioned against the outer lateral surface of the first cylinder 2 or at a distance D83 from the first cylinder 2.

Alternatively, the third light sources 83 may not be integrated.

The second light sources 82 comprise a second light coil 821 forming a helix whose axis corresponds to the longitudinal direction Z ₃ of the second cylinder 3, disposed around the outer lateral surface of said second cylinder.

Alternatively or in addition, a first light coil may be disposed inside the second cylinder 3.

Alternatively or in addition, a third light coil may be disposed outside the first cylinder 2.

The second, or first, light coil may be positioned on the outer or inner side surface of said second cylinder or positioned at a given distance from said side surface.

The third light coil may be positioned on the outer side surface of the first cylinder or positioned at a given distance from said side surface.

FIG. 11 illustrates a sixth example of a location of light sources, which differs from the fifth example in that the third light sources 83 comprise segments of light bars 832 extending along the longitudinal direction Z ₂ of the first cylinder 2 and positioned outside said first cylinder.

The third light sources 83 may be positioned against the wall outside the first cylinder 2 or at a distance D83 from the first cylinder 2.

The different modes presented can be combined with each other.

In addition, the present invention is not limited to the previously described embodiments but extends to any embodiment within the scope of the claims.

Claims

Photobioreactor (1) capable of containing at least one fluid, characterized in that it comprises:

a first container (2) extending in a first longitudinal direction (Z ₂ );

a second container (3) extending in a second longitudinal direction (Z ₃ );

the second container (3):

- extending inside the first container (2), so as to define a first channel (42) between an inner side surface (25) of the first container (2) and an outer side surface (35) of the second container (3); and

forming a second channel (43) inside said second container;

- At least a first passage means (51, 331, 31 1 a) adapted to allow the flow of fluid between the first channel (42) and the second channel (43);

at least one second passage means (52) able to allow the circulation of the fluid between the first channel (42) and the second channel (43) and arranged above the at least one first passage means (51, 331, 31 1 a);

at least one light source (8);

gas injecting means (7) configured to inject bubble gas into the second channel (43); the first and second containers, the first and second passage means and the injection means being configured to allow a flow of fluid in the photobioreactor between the first channel (42) and the second channel (43), and the fluid circulating being able to be exposed to the at least one light source (8).

2. photobioreactor (1) according to claim 1, the first container (2) being closed at its lower and upper ends. 3. Photobioreactor (1) according to claim 1 or 2, the first and second longitudinal directions (Z ₂ , Z ₃ ) of the first and second containers (2,

3) being parallel, preferably merged.

4. Photobioreactor (1) according to claim 3, the first and second containers (2, 3) being cylinders of revolution, preferably concentric.

The photobioreactor (1) according to any one of the preceding claims, the at least one first passage means being formed by at least one aperture (331) in the wall of the second container

(3), preferably in the lower part (3a) of said second container.

6. Photobioreactor (1) according to claim 5, the second container (3) being a cylinder of revolution comprising a plurality of openings (331, 331 ') forming first passage means, arranged along at least one second circumferential ring (33, 33 ') in the wall of said second container, and preferably at the lower end (31) of the second container (3).

7. photobioreactor (1) according to any one of the preceding claims, a first passage means being formed by slots (31 1) disposed in the wall of said second container, and preferably at the lower end (31) of the second container (3).

8. Photobioreactor (1) according to any one of the preceding claims, the at least one second passage means (52) being formed by a difference in height between the first container (2) and the second container (3), the upper end of the second container being located below the upper end of the first container.

9. Photobioreactor (1) according to any one of the preceding claims, the injection means (7) being capable of generating bubbles with diameters preferably less than or equal to 1 mm.

10. Photobioreactor (1) according to one of the preceding claims, the injection means (7) being configured to inject a gas / solid mixture.

1. Photobioreactor (1) according to one of the preceding claims, the injection means (7) being disposed below the second container (3).

12. photobioreactor (1) according to one of the preceding claims, the injection means (7) comprising means by means capable of diffusing calibrated sized bubbles, for example a membrane (71), preferably arranged at the inside and in the lower part (3a) of the second container (3)

13. Photobioreactor (1) according to one of the preceding claims, the at least one light source (8) comprising at least one illuminating wall among at least one wall of the first and / or second containers.

Photobioreactor (1) according to one of the preceding claims, further comprising at least one recirculation pump (10). configured to circulate fluid from the lower portion of the photobioreactor (1) to the upper portion of the photobioreactor (1).

15. Photobioreactor (1) according to one of the preceding claims, the photobioreactor comprising at least one helix (1 1).