OA20824A - Reactor with optimized lighting device. - Google Patents

Abstract

The present invention relates to a reactor including a tank (1) intended to contain: • a mass to be treated, and • at least one lighting device (2a, 2b) intended to promote the treatment of this mass, remarkable in that each lighting device (2a, 2b) comprises a light diffuser including at least one micro-engraved plate (211) transparent to light radiation.

Description

REACTOR WITH OPTIMIZED LIGHTING SYSTEM

FIELD OF THE INVENTION

The present invention relates to the general technical field of reactors with integrated lighting, in particular for the cultivation of photosensitive microorganisms.

It can be a bioreactor but also a chemical or physico-chemical reactor.

BACKGROUND OF THE INVENTION

The notion of bioreactor, or biological reactor, denotes here a reactor within which biological phenomena develop, such as growth of cultures of pure microorganisms or of a consortium of microorganisms (in particular microalgae), in very varied fields such as the treatment of effluents, the production of biomass containing biomolecules of interest (that is to say biomolecules that we know how to valorize). This notion therefore encompasses in particular reactors called fermenters.

A bioreactor typically comprises a tank (cylindrical or parallelepipedal) containing a culture medium for biological species (yeasts, bacteria, microscopic fungi, algae, animal and plant cells) for:

your production of biomass, or for the production of a metabolite, or for

- the bioconversion of a molecule of interest.

Various types of operating conditions may be necessary for the growth of biological species within such a bioreactor; we thus know, in particular, autotrophic (or photo-autotrophic) growth regimes with an input of light (we also speak of photosynthesis) or mixotrophic growth (with a combined input of carbon source and light). It should also be noted that light can act on cell metabolism by inducing or repressing the production of certain compounds, independent of growth and photosynthesis. A supply of light during culture can therefore be useful even when the microorganisms are heterotrophic.

In the following, we will focus more specifically on photo-bioreactors, that is to say the 30 bioreactors in which a supply of light (continuous, cyclically, or in the form of pulses) is implemented. .

We have already proposed photo-bioreactors in which the light supply is carried out by the inside of the tank. Document US 3,986,297 proposes in particular a photo-bioreactor in which the supply of light is produced by immersion, in the culture medium, of illumination means (such as xenon lamps). A disadvantage of this solution is that the efficiency of the photo-bioreactor is inversely proportional to its dimensions. Thus, the more the dimensions of the photo-bioreactor increase, the more its efficiency decreases.

Photo-bioreactors have also been proposed in which light is supplied from the outside of the tank. In particular, a well-controlled configuration consists in providing the tank with portholes allowing the penetration of light generated from outside the tank (natural or artificial light). A disadvantage of such a configuration is that the windows limit the illumination surface and absorb or reflect a significant part of the photons emitted by the lighting source.

Whether the light supply is made from inside or outside the tank, the productivity of a photo-bioreactor (production of biomass per unit volume) is directly linked to its specific surface ( ratio of illuminated area to culture volume). It is therefore necessary for the photo-bioreactor to have a large illuminated specific surface.

Whether they are flat or cylindrical, a disadvantage of current photo-bioreactors is that they must occupy a large floor area for their productivity to be acceptable.

Moreover, whatever the light source chosen to illuminate the culture medium (Neons, LEDs, Natural Light), its photonic energy supply is carried out in a very localized manner, so that:

most of the photons emitted by the light source cannot be biologically consumed by the micro-organism due to an energy overload, the dissipation of the heat generated by the light source is poorly controlled,

- It is complex and expensive to produce large photo-bioreactors.

An object of the present invention is to provide an economical photo-bioreactor, both in terms of investments and operating costs, and whose land area is reduced.

Another object of the invention is to provide a large capacity photo-bioreactor (tank of 1000 liters or more) in which the yield in quantity of photons (pmol-ph-s') provided by a luminous surface per unit of power (Watt) is optimized.

BRIEF DESCRIPTION OF THE INVENTION

To this end, the invention proposes a reactor including a tank intended to contain: o a mass to be treated, and o at least one lighting device intended to promote the treatment of this mass, remarkable in that each lighting device understand :

a light diffuser, the diffuser including at least one micro-etched plate transparent to light radiation, said plate having opposite rear and front faces and at least two slices between the rear and front faces, the area of each face being greater than the area of each slice, the back side including a plurality of micropatterns,

- a light source to generate the light radiation, the light source being arranged on at least one edge of the plate and being oriented so that the light radiation it generates propagates in the plate.

This solution makes it possible to obtain a photo-bioreactor with better yields (energy on the one hand, and biomass production on the other) than existing photo-bioreactors.

Indeed, the use of one (or more) micro-engraved plate(s) allows the homogeneous conduction of the light radiation generated by the light source. The photon energy is guided through the entire micro-etched plate and emerges from it over the entire surface of its front face, which improves the ratio of illuminated surface to illuminated volume directly in contact with the culture medium.

Thus, the invention makes it possible to increase the ratio pmol-photons s ⁻¹ W ¹ per unit volume, which ensures a reduction in the environmental footprint of the photo-bioreactor and reduces the costs associated with its operation.

Preferred but non-limiting aspects of the assembly according to the invention are the following:

- each plate can be substantially planar and comprise four slices, each light source including a piurality of light-emitting diodes arranged on at least one of the slices of smaller dimensions;

- each plate may be cylindrical and comprise two slices, each light source including a plurality of light-emitting diodes arranged on at least one of the two slices;

- The diodes of the plurality of light-emitting diodes can be arranged on the edge of the plate furthest from the bottom of the tank;

- each light diffuser can comprise a pair of micro-engraved plates arranged so that their rear faces extend facing each other;

- each light diffuser may further comprise at least one layer of material reflecting the light radiation, each layer of reflecting material extending over the rear face of a respective plate;

each light diffuser may further comprise at least one transmission layer, each layer of transmission material extending over the front face of a respective plate;

the first reactor may comprise a plurality of light diffusers, two adjacent light diffusers being spaced apart by a distance of between 2 and 10 centimeters, preferably between 4 and 8 centimeters, and even more preferably substantially equal to 6 centimeters;

- the light source of each lighting device can be adapted to generate continuous light radiation;

- the reactor may comprise a plurality of light diffusers, two adjacent light diffusers being spaced apart by a distance of between 8 and 150 centimeters, preferably between 10 and 50 centimeters, and even more preferably substantially equal to 11 centimeters;

- the light source of each lighting device can be adapted to generate discontinuous light radiation in the form of flashes composed of alternating dark phases and lighted phases, for example at a frequency between 10 and 50 kHz;

- the tank can have a capacity of 100m ³ , the surface covered by your light diffuser plates being between 2000 and 3000m ² , preferably between 2250 and 2750m ^z , preferably substantially equal to 2500m ² ;

- your lighting devices can consist of:

o of a first group of lighting devices of a first height, and o of a second group of lighting devices of a second height lower than the first height, a lighting device of the second group being arranged between two successive lighting devices of the first group;

- the reactor may further comprise an injection system including a plurality of diffusion units, each diffusion unit:

o extending between two adjacent light diffusers, and o being separated from the other diffusion units by at least two successive light diffusers;

- each lighting device can be independently connected to an electrical power supply module so that each lighting device can be removed individually from the reactor during its operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics of the reactor according to the invention will emerge better from the following description of several variant embodiments, given by way of non-limiting examples, from the appended drawings in which:

Figure 1 is a schematic representation in perspective of a first variant of photo-bioreactor according to the invention;

Figure 2 is a schematic representation in perspective of a lighting device;

- Figure 3 is a schematic representation in cross section of a first embodiment of the lighting device;

Figure 4 is a schematic representation in cross section of a second embodiment of the lighting device;

Figure 5 is a schematic representation of an experimental photobioreactor variant;

- Figure 6 is a curve illustrating the biomass production yield (as a function of various parameters) obtained from the experimental variant of photobioreactor illustrated in Figure 5;

- Figure 7 is a partial cross-sectional view of a second photobioreactor variant;

- Figure 8 is a curve illustrating the maximum concentration of microalgae as a function of a spacing between two adjacent lighting devices;

- Figure 9 is a block diagram illustrating the difference between continuous lighting and discontinuous lighting;

- Figure 10 shows curves of microalgae concentration as a function of a distance between two adjacent lighting devices in the case of continuous lighting on the one hand and in the case of discontinuous lighting on the other.

DETAILED DESCRIPTION OF THE INVENTION

We will now describe various examples of photo-bioreactors according to the invention with reference to the figures. In these various figures, the equivalent elements are designated by the same reference numeral.

1. General

Referring to Figure 1, the bioreactor comprises:

A tank 1 intended to receive a mass to be treated,

- A plurality of lighting devices 2a, 2b, and

An injection system including a plurality of diffusion units 3 of carbon dioxide (COa) in the form of gas bubbles or in the form of a fluid consisting of CO ₂ dissolved in an aqueous medium.

Each lighting device is intended to be integrated into the tank for the treatment of the medium contained in the tank. These lighting devices are intended to be totally immersed in the culture medium. In the following, the bioreactor will be described with reference to the treatment of a biomass formed of microorganisms, for example microalgae. It is however understood that the following description also applies to other types of reactors, chemical or physico-chemical.

As illustrated in Figure 1, the lighting devices 2a, 2b are arranged at a non-zero distance from the bottom of the tank. The lighting devices 2a, 2b can be of different heights. In particular, the bioreactor may comprise:

- a first group 2a of lighting devices having a first height h _a , and

- A second group 2b of lighting devices having a second height h _b lower than the first height h _a , a lighting device of the second group 2b being arranged between two successive lighting devices of the first group 2a. This makes it possible to promote mixing and homogenization of the mass to be treated.

To further increase the mixing and the homogenization of the mass to be treated, the diffusion units 3 of the injection system can be arranged periodically downstream of each lighting device of the first group 2a (the reactor being devoid of a broadcast 3 downstream of the lighting device of the second group 2b). Thus, after having circulated under the lighting device of the first group 2a, the mass to be treated is driven vertically upwards from the tank 1 (ie, direction opposite to the bottom) by the bubbles of CO ₂ (or the fluid containing the dissolved COa) emitted (or emitted) by the diffusion units 3. The mass to be treated passes over the lighting device of the second group 2b and falls back towards the bottom of the tank by gravity. This creates a circulation of the mass to be treated through the tank, which improves mixing and homogenization of the mass to be treated.

As a variant, the lighting devices 2a, 2b of the bioreactor can all be of identical height. This simplifies the installation of lighting devices by an operator. In this case, the diffusion units 3 are arranged every two lighting devices so that two successive diffusion units 3 are separated by two adjacent lighting devices 2a, 2b.

LL Tank

Tank 1 is intended to contain the mass to be treated. It comprises a bottom and at least one side wall.

In the embodiment illustrated in Figure 1, the tank 1 is substantially parallelepipedic. It is composed of a bottom, four side walls and a ceiling (or cover) at least partially removable.

In other embodiments, the tank 1 can be cylindrical and comprise a lower base forming a bottom, an upper base forming a lid, and a side wall between the lower and upper bases.

The material constituting the walls of the tank 1 can be stainless steel or equivalent. Of course, other materials can be chosen depending on the intended application (Plexiglass®, Polypropylene, Concrete, etc.). In all cases, the tank is preferably made of a material resistant to cleaning products (bleach, peroxide, etc.).

1.2. lighting device

Referring to Figure 2, each lighting device 2a, 2b comprises:

one (or more) light diffusers 21, and one (or more) light source(s) 22.

The light source 22 allows the generation of a luminous flux. The light diffuser 21 allows:

to guide the luminous flux generated by the light source, and

- to redisperse it in a homogeneous way towards the mass to be treated.

Advantageously, each light source 22 can be independently connected to an electrical power supply module. The module makes it possible to supply the electrical energy necessary for the generation of the luminous flux. The fact that each light source is independently connected to an electrical power supply module makes it possible to individually remove each lighting device 2a, 2b from the bioreactor during operation of the latter.

L 2.1. light diffuser

The light diffuser 21 comprises one (or more) textured plate(s) 211(s). Each plate 211 can be substantially flat and rectangular (suitable in the case of a parallelepipedal tank) or tubular (suitable in the case of a cylindrical tank). Each plate 211 comprises a rear face 2113, a front face 2114 and:

- four side edges (or edges) 2111 in the case of a rectangular plate 211, or - two side edges (or edges) 2111 in the case of a tubular plate 211.

Each side edge 2111 can be polished, and at least one of the side edges 2111 is intended to come into contact with the light source 22 to allow the transmission of the luminous flux through the plate 211.

The material constituting each plate 211 can be polymethyl methacrylate (PMMA) or another transparent material known to those skilled in the art which allows the plate 211 to conduct - by total internal reflection on its front and rear faces - the luminous flux emitted by the light source 22, such as for example:

another transparent methacrylic resin such as methyl methacrylate, ethyl ethacrylate, butyl methacrylate, propyl or isopropyl methacrylate, or a transparent resin such as polystyrene, polycarbonate, polyacrylate, or a glass/silica fondue.

1.2.1.1. Micro-patterns

Referring to Figure 3, each plate 211 comprises a plurality of micro-patterns 2112 on its front face 2113. The micro-patterns 2112 make it possible to intercept the radiation 23 of the luminous flux circulating through the plate 211 and to direct them towards the front face 2114 so as to facilitate their transmission out of the plate 211. More precisely, the radiation 23 which strikes each micro-pattern 2112 is redispersed. Each radiation 23 is re-emitted at an angle such that it can leave the plate 211 via the front face 2114 opposite the rear face 2113 comprising the micro-patterns 2112.

Each micro-pattern 2112 can consist of a cavity - point or furrow - having a shape chosen from a conical shape, a (poly)pyramidal shape, a quadrangular shape, or any other shape known to those skilled in the art and allowing each micro-pattern 2112 to deflect the radiation 23 from the luminous flux. In particular in the example illustrated in Figure 3, the micro-patterns 2112 consist of fine grooves parallel to the side edge 2111 in contact with the light source 22.

Of course, the micro-patterns 2112 can consist of deflection elements other than cavities, such as:

light scattering particles disposed in the material constituting the plate 211, or surface texturing components disposed on the rear face 2113, such as emergent hemispherical structures, bumps extending outward from the rear face 2113, emerged pyramidal structures or combinations comprising at least one of the preceding structures.

The height (i.e. dimension along an axis perpendicular to the rear face) of each micro-pattern 2112 can be between 0.15 and 0.5 μm, and the pitch between two adjacent micro-patterns can be between 20 and 900 μm, and in particular greater than or equal to 100 μm.

Advantageously, the micro-patterns 2112 can be arranged on the rear face 2113 according to a consecutive spacing inversely proportional to the distance of said micro-patterns 2112 from the side edge 2111 in contact with the light source 22. Such an arrangement makes it possible to obtain a constant light intensity over the entire surface of the rear face 2113. Indeed, the intensity of the light flux which penetrates the plate 211 decreases as a function of its distance relative to the light source 22. By varying the density of micro- patterns 2112 on the rear face 2113, it is possible to compensate for the loss of intensity by increasing the density of micro-patterns 2112.

1.2.1.2. reflective layer

The light diffuser 21 may also include a layer of material 212 that reflects the light flux.

This layer of reflective material 212 preferably extends over the entire rear face 2113 of the plate 211 including the plurality of micro-patterns 2112.

The layer of reflective material 212 may consist of a film of reflective material such as a metallized aluminum film. As a variant, the layer of reflective material 212 can consist of a paint made of material with a refractive index lower than that of the material 211 constituting each plate 21.

1.2.1.3. Transmission layer

The light diffuser 21 may also include a transmission layer 213 on the front face 2114 of the plate 211.

This transmission layer 213 makes it possible to promote the transmission of the radiation 23 of the luminous flux towards the outside of the plate 211.

This transmission layer 213 also makes it possible to smooth the illumination effect obtained with the light diffuser 21.

The transmission layer 213 finally makes it possible to protect the plate 21 against possible mechanical attacks (scratches due to friction, etc.).

The transmission layer 213 can for example consist of a protective varnish with a refractive index close to the refractive index of the material constituting the plate 211.

1.2.2. Light source

Each light source 22 may comprise one (or more) light-emitting diode(s) (LED) 221. Preferably, each diode 221 is a power light-emitting diode (HPLED), that is to say an LED power greater than 1 watt. For example, each diode 221 can be a light-emitting diode directly mounted on chips (also known as “COB” LEDs, an acronym for the English expression “Chip On Board”). In this case, the light source 22 may comprise a COB LED module composed of several LED chips fixed to a substrate (for example) of ceramic. This makes it possible to generate a more powerful and dense luminous flux.

The diodes 221 of the light source 22 can be individual, or be arranged “in a strip” or “in a ribbon” (see patent application FR1050015). The use of diodes arranged in a ribbon makes it possible to facilitate the manufacture of the lighting device, each light source 22 being intended to come into contact with a lateral edge of the to be arranged on a lateral edge 2111 of the plate 211 of the diffuser light 21. The diodes 221 can be supplied with electrical energy via one (or more) connection cable(s) electrically connected to a source of electrical energy.

Whatever the arrangement chosen, the diodes 221 of the light source 22 can all be identical with the same excitation regime, or be different. In particular, your diodes 221 of a light source 22 can have:

- distinct excitation regimes (for example continuous regime for some, and flash regime at a frequency between 1 and 150 kHz for others), and/or

- distinct emission spectra (for example in white light for some and blue light for others), etc.

Each light source 22 may also include one (or more) reflectors (not shown) to reflect, direct and focus the light produced by the diodes 221.

Each light source is intended to come into contact with a side edge of the plate 211 so that the radiation 23 of the luminous flux generated by the light source propagates inside the plate 211. Advantageously, the diodes 221 and the connection cable(s) can be embedded/cast in a resin to seal each light source.

In the embodiment illustrated in FIG. 3, the lighting device comprises a light source 22 intended to come into contact with a lateral edge 2111 of the plate 211. As a variant, each lighting device can comprise two light sources. light 22 intended to come into contact with a respective opposite side edge 2111 of the plate 211. As a further variant, each lighting device may comprise four light sources 22 intended to come into contact with a respective side edge 2111 of the plate 211 .

1.3. Injection system

The injection system makes it possible to supply the bioreactor with nutrients, in particular CO ₂ , In particular, the injection system makes it possible:

- to provide the carbon dioxide necessary for the development of the biomass and to suspend the support particles of microorganisms contained in the culture medium of the biomass.

The supply of carbon dioxide can be continuous or discontinuous in response to certain criteria such as time or pH. As mentioned above, carbon dioxide can be introduced: in the form of gas bubbles, or

- in the form of an aqueous solution pumped or pushed into the bioreactor.

The introduction of carbon dioxide in the form of gas bubbles allows a better distribution of CO ₂ in the tank.

The injection system may include:

- a CO ₂ supply unit - such as a booster (in the case of gaseous CO ₂ ) or a pump (of the turbine type in the case of fluid CO ₂ ) - preferably fitted with a check valve in order to avoid the rise of sludge or effluent at the level of the CO _{2 supply unit]}

- a plurality of broadcast units 3 forming:

o in the case of gaseous CO ₂ , micro-bubbling heads for the diffusion of bubbles of different diameters, o in the case of CO ₂ dissolved in an aqueous medium, fluid ejection nozzles for (a diffusion of the fluid containing dissolved CO ₂ .

The diffusion units can be of different types known to those skilled in the art, for example diffusers made of microporous composite materials, with a membrane (EPDM, silicone, etc., preferably EPDM), ceramic or slotted, etc.

Each diffusion unit is preferably arranged in the immediate vicinity of the bottom of the tank. Furthermore, each diffusion unit 3 is arranged between two adjacent lighting devices 2a, 2b, the different diffusion units 3 being arranged so that each diffusion unit 3 is surrounded by lighting devices distinct from the lighting devices 2a, 2b surrounding the other diffusion units 3. In other words, each diffusion unit 3 is separated from the nearest diffusion unit 3 (or the nearest units) by two lighting devices 2a, 2b.

L4. Biomass processing

The biomass cultured in the reactor according to the invention can be harvested by any technique known to those skilled in the art such as sedimentation, filtration, flotation or centrifugation techniques.

The biomass harvest can be implemented continuously or semi-continuously, in particular in the case where the bioreactor is installed on an industrial site. For this purpose, the bioreactor can be associated with a separation unit - decanter and/or centrifuge and/or filter etc. - allowing a portion of the contents of the tank to be taken to separate the biomass from the culture medium.

The biomass thus extracted can then be packaged (vacuum freezing, etc.) for subsequent use. The culture medium, once separated from the biomass, can be reintroduced into the tank of the bioreactor.

1.5. Other features of the bioreactor

The reactor can also comprise a control module including one (or more) sensor(s) to check the parameters of the bioreactor. In particular, the control module may include:

- one (or more) pH probe(s),

- one (or more) sensor(s) for measuring the CO ₂ level,

- one (or more) light sensor(s), one (or more) POm, and/or NO3, and/or NhL sensor(s),

- one (or more) temperature sensor(s).

The various sensors and probes of the control module make it possible to maintain optimal values for the parameters of the bioreactor influencing the growth of the biomass.

In particular, the control module can adapt the quantity of CO ₂ injected into the culture medium according to the measurements made by the pH probe and/or by the sensor(s) for measuring the CO ₂ level, etc. . For example, if the measured CO ₂ rate is below a threshold, the control module can control the injection of a greater quantity of CO ₂ into the tank (relative to a set quantity). Conversely, if the measured pH is lower than a predetermined threshold, the control module can control the injection of a lower quantity of CO ₂ (relative to a set quantity).

Similarly, if the measured temperature is lower (respectively higher) than a threshold temperature, the control module can control the activation of a heat exchanger - such as a plate exchanger - integrated into the tank of the bioreactor to heat (respectively cool) the culture medium.

Also, depending on the measurements taken by the POsm, NO ₃ , NH ₄ sensor(s), the control module can adapt a quantity of nutrient (phosphorus, nitrogen, etc.) injected into the medium of culture (by acting on the activation/deactivation of a pump connected to a source of nutrients, etc.).

Finally, the measurement of information representative of the luminosity inside the culture medium allows an estimation of the biomass concentration inside the tank. Thus, it is possible to regulate the biomass harvesting step. In particular, if the light measurement inside the tank is representative of too low a biomass concentration, the control module can suspend biomass harvesting. Conversely, if the light measurement inside the tank is representative of too high a concentration of biomass, the control module can initiate biomass harvesting.

2. Characteristics of the photo-biofeactor

2.1. Case of continuous light radiation

We will now describe various aspects relating to a dimensioning of the bioreactor allowing the optimal use of the luminous flux resulting from the lighting devices. This sizing of the bioreactor is carried out by considering a continuous supply of light, that is to say by considering that each light source 22 generates continuous light radiation of constant intensity over time.

2.1.1. Photon capture model

To understand if the flux of photons from the lighting devices is used optimally by the mass to be treated, we propose to use a model on the capture of photons by microalgae as a function of an emission surface and a geometry of the reactor.

The following representation shows the adjustable parameters for deducing productivities in a photo-bioreactor. Here it will be preferable to reduce the unlit fraction of the reactor as much as possible and to increase the surface receiving the photon flux.

The global model of the surface yield of a photo-bioreactor is as follows:

=(ΐ-ΰΛ

OR :

- f _d is the volume fraction unlit by design of the reactor (f _d = 0 if the entire surface of the reactor is lit);

- pM is the maximum energy efficiency of conversion of light energy into physico-chemical energy;

φ is the molar quantum yield of photosynthesis;

u is the linear diffusion modulus;

- aiight is the illuminated specific surface of the reactor on the volume;

K corresponds to a half-saturation constant of photosynthesis (depends on the microorganism);

- ή corresponds to the average degree of collimation of the incident radiation,

- Q _n is the average flux density on the surface of the photo-bioreactor.

The maximum performance of a photo-bioreactor can be characterized by some simplifications of the constants in an ideal case. Therefore production will depend on the following:

- The dark fraction "Sx", which corresponds to the unlit volume ratio (fd=O):

Sx = (1 - fd) read (1 + J) in kg /m ² !J

Where q is expressed in pmolphotons/s/m ^a , and where K is the half-saturation constant of photosynthesis (30000 pmol/kgx/s),

The surface production "P _x " due to the capture of the surface photon flux captured:

Px - Sx * aLight in kg /m ³ /1 With correction factor of 20%

The volume production according to the captured surface photon flux compared to the total volume:

Light to Light — ~

By applying the previous calculation rules for: an acrylic plate 0.2m wide and 0.4m long an incident light of 250pmol/m2/s, - a total reactor volume of 0.008 m ³ , no shadow zone (fd=O), then the maximum theoretical volume productivity is estimated at 100 mg/L/J, as illustrated by the table below.

Reactor geometry case Length 0.40 m Width 0.20 m Illuminated area 0.08 ^m2 Qn 250.00 pmol/ ^m2 /s K 30000.00 pmol/kg _x /s Vr 0.008 m ³ 3 light 10 me fd 0.00 n/a Sx 0.01 Kg/m ² /d Price 0.08 Kg/m ³ /d P _x correction 0.099585634 Kg/m ³ /d Theoretical maximum production 100 mg/L/D

This is confirmed during an experiment using the reactor shown in Figure 5, in which the lighting device comprises an acrylic plate placed under the bottom of a tank with transparent walls. An average production is 102 mg/L/D over 140 hours is obtained (minimum: 60 mg/L/D, maximum: 130 mg/L/D), as shown in Figure 6.

Adding air with 2% CO? provides mixing and brings carbon to the mass to be treated.

2.1.2. Determination of an optimal plate area for reactor lighting devices

The objective is to determine the optimal area of diffusion of the luminous flux for the reactor. Of course, the number and arrangement of lighting devices can vary depending on the amount of biomass that one wishes to produce.

If one wishes to produce 1 kg of biomass per m ³ of culture in a volume of 100 m ³ by applying the formulas of the global modeling described in point 2.1, the lighting devices must include 2500 m ² of light plates ( light diffusers) emitting 1000 pmol/m ² /s (light sources).

This number is directly related to the desired output, volume, geometry and light intensity.

We get the following table:

Surface light 2,500 ^m2 Qn 1000.00 pmol/ ^m2 /s K 30000.00 μΓηοΙ/kgx/s Vr 100.00 m ³ 3 lights 25.00 m ¹ fd 0.00 n/a Sx 0.03 Kg/m71 P _x continuous 0.82 Kg/m ³ /d Yield corrected 0.98 Kg/m ³ /d

2.1.3. Determination of a maximum quantity of biomass not to be exceeded

The objective is to determine the maximum concentration not to be exceeded so as not to have a dark zone in the medium (i.e. to maintain a fo=O),

Assume a reactor as shown in Figure 7 and comprising:

- a tank having the following dimensions: 17 meters x 2 meters x 3 meters (Length x width x Height in meters), and a volume of 100 m ³

- lighting devices including plates having dimensions of 3 meters x 2 meters x 0.01 meter (Length x width x Thickness).

To have a luminous surface of 2500m ² , the number of plates must be 2500/(3x2) = 417 plates, for a total thickness of 4.17 meters (the thickness of each plate being 1 centimeter).

In order to minimize the size relating to the introduction of the plates into the tank, each lighting device can comprise two plates joined by their rear faces so that their front faces are opposite each other (the rear faces of the two plates extending opposite and being in contact). An example of such a lighting device is shown in Figure 4. The spacing between the different lighting devices is then given by the following formula: d = (L-Etal) i (½ X Nbplates) d = (17-4.17)/ (%χ417).

Or :

- d is the free distance between the front faces of two successive lighting devices,

L corresponds to the length of the tank,

- Βω corresponds to the total thickness of the plates of the lighting devices (i.e., sum of the thicknesses of the plates),

Nbpiaques corresponds to the number of plates required to have a luminous surface of 2500m ² .

The following tables summarize the different results above.

Characteristic reactor Length -m 17 Width - m 2 Depth -m 3 Volume - m3 100

Characteristics of the plates Number of single plates 417 Thickness "Ae" of a plate - m 0.01 Total thickness - m 4.17 Distance "D" between the rear faces of two successive lighting devices - m 0.08 Free space “d” between plates - m 0.06

In order not to have a dark zone in the middle (i.e. to maintain an fd-O), it is necessary to have a sufficient flux of photons (F) up to the middle zone (B) between two adjacent lighting devices .

The luminous intensity as a function of the distance Z can be expressed from the following formula. l(z)=loe ^haBï

Or :

lo corresponds to the incident light,

Ka is an absorption coefficient,

B corresponds to the biomass concentration, Z corresponds to the length of the tank.

FIG. 8 illustrates the maximum concentration of microalgae as a function of a spacing between two adjacent lighting devices. If it is considered that from 50 pmol/m ² /s, the quantity of light is insufficient to obtain satisfactory yields, it is possible to determine the maximum concentration not to be exceeded.

In the case of the device illustrated in figure 7 (and considering a free space "d" of 6 centimeters between the lighting devices), with an adjoining zone B located at 0.03 meters from each lighting device, the maximum concentration at do not cross is 1.5 g/L.

This concentration can be measured via suspended solids sensors such as . 5 6131 Blue-Green Algae Sensor or ALS-OD4.

2.1.4. Determination of a CO2 exchange

The quantity of CO ₂ must be procured so as to correspond to the proportion of photons supplied (Provide as much CO2 as photons supplied by the reactor).

Consequently, the flow rate of the mix (Air/COs) must be adjusted to the light choice selected.

fO Here for 1 kg/m ³ /J, 90% CO2 is needed with a flow rate of 4.77 m ³ /h.

Case Culture condition CO2

CO2 input 90.00% % Debit 4.77 m ³ /h__________ CO2 load 202.38 Kg CO2/D Assimilation 2,059 kg CO ₂ /kg biomass_______ Max output 98.30 Kg acute/J___ Volume 100.00 m ³ __________ Max yield 0.983 kg/m ³ /d

2.1.5. Plate specificity

Those skilled in the art will know how to choose the right type of plate for each light diffuser. It will prioritize:

. The type of engraving (type V, etc.) which allows photons to be transmitted as well as possible over the entire plate,

- The material with the best light propagation rate for the transmission panel that receives the engravings (acrylic, polycarbonate, etc.), An optimal reflective material to obtain the strongest luminosity,

- The most effective material for the homogenization of the photon flux.

The person skilled in the art will choose the positioning of the LEDs on one, two, three or four sides of each plate, as well as the shape (rectangle, square, cylindrical) of each plate according to the culture conditions. He will favor the most uniform LEDs in order to fill the entire edge of the engraved plate.

2.2. Case of discontinuous light radiation

We will now describe various aspects relating to a dimensioning of the bioreactor by considering a discontinuous supply of light, that is to say by considering that each light source 22 generates a discontinuous light radiation composed of a close alternation of dark phases and of illuminated phases (flashes), for example at a frequency of between 10 and 50 kHz.

As an indication, Figure 9 illustrates the difference between discontinuous lighting 31 and continuous lighting 32.

Such a discontinuous supply of light makes it possible to act positively on crop yield in terms of biomass. As illustrated below, the transition from a continuous light supply to a discontinuous light supply makes it possible to increase the distance between two adjacent light diffusers 21 (between 2 and 10 centimeters, preferably between 4 and 8 centimeters, and even more preferably substantially equal to 6 centimeters), while maintaining the other parameters identical to those calculated above.

2.2.1. Calculation of an optimal distance between adjacent lighting devices

Consider a system endowed with a continuous average intensity of 1000 pmol.m′ ^z .s′ ¹ at the level of the light diffusers 21.

When this average intensity (continuous) is parameterized in “flashes” while maintaining an average irradiance of 1000 pmol.m'Z.s' ¹ , it is then possible to obtain flash waves of 10000 pmol.m ^-2 .s' ¹ :

- The cycle time t _cyc ie is such that:

w = tüght + tdark (s) / or the frequency (Hz) where tüght corresponds to a lighted phase and U* corresponds to a dark phase;

The luminous fraction φ is such that: φ = (tüght ! (iiight ⁺ tdark ))

Integrated irradiance: l _m = lr φ with φ = 10%;

U = 1000 pmol.nT ^z .s' ¹ l _m = l _f φ pmoLm'Zs ¹ h = 10000 pmol.m'Zs ¹

This wave of photons makes it possible to increase the entry distance of the photons into the medium, and therefore to increase the distance between the light scatterers 21 with an identical biomass concentration.

As shown in Figure 10 illustrating microalgae concentration curves 33, 34 as a function of a spacing between two adjacent lighting devices:

- in the case of continuous lighting on the one hand (curve referenced 33), and in the case of discontinuous lighting (curve referenced 34) on the other hand, the dividing distance can then be extended to 0.055 meters in flash with a concentration of 1.5 g/L. In other words, the lighting devices can be arranged so that the distance between two adjacent light diffusers 21 is substantially equal to 11 centimeters.

3. Other embodiments

In the preceding description, different variants of bioreactors have been described, in particular bioreactors intended for industrial applications allowing the treatment of the gases emitted. Of course, the teachings of the present invention are not limited to large bioreactors intended for industrial applications.

In particular, in a variant embodiment, the bioreactor can be of smaller dimensions. For example, the bioreactor may include:

- a tank with transparent or translucent walls: o between 1 and 10 meters long, o between 50 centimeters and 5 meters wide, o between 4 and 30 centimeters thick, a single lighting device integrated into the tank,

- an injection system including one (or more) diffusion units.

Such a bioreactor can in particular be used in urban applications to replace certain existing panels such as one (or more) wall(s) of a Bus Shelter®, or of any bus shelter type.

Of course, the shape of the tank is not necessarily parallelepipedal, and depends on the intended application (cylindrical shape, etc.). Similarly, for some applications the walls of the tank may not be transparent or translucent.

In all cases, the lighting device is preferably arranged in the tank so as to extend;

- parallel to the side walls of the larger tank, (including a light diffuser made up of a pair of plates, and

- At equal distance from said side walls of larger dimensions.

Such a lighting device comprises a light diffuser preferably composed of a pair of micro-engraved plates joined by their rear faces, said plates having substantially the same shapes and dimensions as the side walls of larger dimensions of the tank ( plate dimensions = 90-100% side wall dimensions of larger dimensions). The lighting device also comprises a light source as described previously. Preferably, the dimensions of the tank are adapted so that the illumination of the mass to be treated by the lighting device is optimal. In particular, the distance separating:

- the light diffuser and

- Each side wall of larger dimensions of the tank can be between 1 and 15 centimeters, preferably between 2 and 10 centimeters, and even more preferably between 3 and 6 centimeters.

4. Conclusions

The solution described above makes it possible to increase the energy and biomass production yields of the reactor, in particular thanks to a homogeneous conduction of light, and to an optimal dimensioning of the various components of the reactor according to the maximum quantity of biomass desired in the reactor.

This is valid for cultures in mixotrophy, in autotrophy on photo-synthetic organisms but also for cultures in predominantly heterotrophic mixotrophy where light is not important for photosynthetic activity but for example for the induction of molecules of interest as pigments (WO2017050917), and/or oil.

The invention presented above has numerous applications, and can for example be used to create a carbon sink making it possible, by absorbing the carbon contained in the atmosphere (carbon monoxide/dioxide), to reduce the quantity of carbon dioxide. atmospheric carbon.

The reader will have understood that many modifications can be made to the invention described above without materially departing from the new teachings and advantages described here.

For example, in the preceding description, the lighting and heating device was integrated into a reactor including a rotating assembly intended to ensure mixing of this mass of microorganisms. It is obvious to those skilled in the art that the lighting and heating device described above could be integrated into a reactor without a rotating assembly.

Accordingly, all such modifications are intended to be incorporated within the scope of the appended claims.

Claims (15)

1. Reactor including a tank (1) intended to contain: o a mass to be treated, and o at least one lighting device (2a, 2b) intended to promote the treatment of this mass, characterized in that each lighting device (2a, 2b) comprises . - a light diffuser (21), the diffuser (21) including at least one micro-etched plate (211) transparent to light radiation (23), said plate (211) having opposite rear and front faces (2113, 2114) and at least two slices (2111) between the rear and front faces (2113, 2114), the area of each face being greater than the area of each slice, the rear face (2113) including a plurality of micro-patterns (2112 ), - a light source (22) for generating the light radiation (23), the light source (22) being arranged on at least one edge of the plate (211) and being oriented so that the light radiation (23) qu 'it generates propagates in the plate (211). 2. Reactor according to claim 1, wherein each plate (211) is substantially flat and comprises four slices (2111), each light source (22) including a plurality of light emitting diodes arranged on at least one of the more slices small dimensions. 3. Reactor according to claim 1, in which each plate (211) is cylindrical and comprises two slices, each light source (22) including a plurality of light-emitting diodes arranged on at least one of the two slices. 4. Reactor according to one of claims 2 or 3, wherein the diodes of the plurality of light-emitting diodes are arranged on the edge of the plate (211) furthest from the bottom of the tank (1). 5. Reactor according to any one of claims 1 to 4, wherein each light diffuser (21) comprises a pair of micro-etched plates (211) arranged so that their rear faces (2113) extend opposite the each other. 6. Reactor according to any one of claims 1 to 5, wherein each light diffuser (21) further comprises at least one layer of reflective material (212) the light radiation (23), each layer of reflective material (212 ) extending over the rear face (2113) of a respective plate (211). 7. Reactor according to any one of claims 1 to 6, wherein each light diffuser (21) further comprises at least one transmission layer (213), each layer of transmission material (213) extending over the front face (2114) of a respective plate (211). 8. Reactor according to any one of claims 1 to 7, which comprises a plurality of light diffusers (21), two adjacent light diffusers (21) being spaced apart by a distance of between 2 and 10 centimeters, preferably between 4 and 8 centimeters, and even more preferably substantially equal to 6 centimeters. 9. Reactor according to claim 8, in which the light source (22) of each lighting device (2a, 2b) is adapted to generate continuous light radiation. 10. Reactor according to any one of claims 1 to 7, which comprises a plurality of light diffusers (21), two adjacent light diffusers (21) being spaced apart by a distance of between 8 and 150 centimeters, preferably between 10 and 50 centimeters, and even more preferably substantially equal to 11 centimeters. 11. Reactor according to claim 10, in which the light source (22) of each lighting device (2a, 2b) is adapted to generate discontinuous light radiation in the form of flashes composed of an alternation of dark phases and illuminated phases, for example at a frequency between 10 and 50 kHz. 12. Reactor according to any one of claims 1 to 11, in which the tank has a capacity of 100m ³ , the surface covered by the plates of the light diffusers (21) being between 2000 and 3000m ² , preferably between 2250 and 2750m ² , preferably substantially equal to 2500m ^z . 13. Reactor according to any one of claims 1 to 12, in which the lighting devices are composed: © of a first group (2a) of lighting devices of a first height (h _a ), and o of a second group (2b) of lighting devices of a second height (h _b ) less than the first height (h _a ), a lighting device of the second group (2b) being placed between two successive lighting devices of the first group (2a). 14. Reactor according to any one of claims 1 to 13, which further comprises an injection system including a plurality of diffusion units (3), each diffusion unit (3): o extending between two adjacent light diffusers (21), and 10 o being separated from the other diffusion units (3) by at least two successive light diffusers (21). 15. Reactor according to any one of the preceding claims, in which each lighting device (2a, 2b) is independently connected to an electrical energy supply module so that each lighting device (2a, 2b) ) can be individually removed from the reactor during operation of the reactor.