LU501102B1 - BIOLOGICAL METHANATION REACTOR USING MICROBIAL FLORA IN SUSPENSION AND METHOD FOR IMPLEMENTING SUCH A REACTOR - Google Patents

Abstract

The invention relates to a biological methanation reactor, comprising a tank (1) comprising a liquid or semi-liquid medium (2), an inlet (5) for anoxic gas to be treated, comprising in particular carbon dioxide, a microbial flora ( 20), at least one non-microporous tubular membrane (6) immersed at least partially in said liquid or semi-liquid medium, said at least one membrane comprising a conduit into which a gas can be injected, said reactor comprising at least one injector of gas (7) connected to said conduit of said membrane and an outlet (10) allowing the recovery of methane. The reactor is remarkable in that said flora is in suspension in said liquid or semi-liquid medium and comprises hydrogenotrophic methanogenic Archaea and/or comprises homo-acetogenic bacteria and acetotrophic methanogenic Archaea, in that the gas injector ( 7) is a pure dihydrogen injector, and in that the reactor comprises a space (3) for collecting and storing gas, said outlet (10) being connected to said space (3) and said gas injector (7) and said inlet of anoxic gas to be treated (5) being two independent gas inlets.

Description

BIOLOGICAL METHANATION REACTOR OPERATING FLORA LU501102

MICROBIAL IN SUSPENSION AND METHOD FOR IMPLEMENTING SUCH

REACTOR

FIELD OF THE INVENTION

The invention relates to a biological methanation reactor, of the ex situ type, which allows the biological conversion of carbon monoxide (CO), carbon dioxide (COz) and dihydrogen (Hz) into methane (CH4), the latter being able to be used as an energy source.

STATE OF THE ART

“Biological methanation” will be understood as a process for converting carbon dioxide and/or carbon monoxide to produce methane using highly specialized micro-organisms (Archaea) in a technical plant. Methanation should not be confused with (bio-)methanation which concerns the natural process of degradation of organic matter in the absence of oxygen.

Biological methanation thus makes it possible to industrially recover carbon dioxide, resulting from biogas or syngas for example, to produce methane.

To do this, it is necessary to supply dihydrogen to carbon dioxide.

This reaction can be carried out either thermochemically or biologically: the present invention relates only to the production of methane by biological means.

More specifically, she is interested in the conversion of dihydrogen and carbon dioxide into methane by anaerobic microorganisms (microbial flora) methanogenic hydrogenotrophic Archaea.

Biological methanation reactors must be able to face two technical challenges. On the one hand, the water solubility of dihydrogen is very low.

On the other hand, the methanogenic Archaea responsible for the methanation reaction have a very low turnover rate, i.e. they reproduce slowly.

This is why there are reactors in which membranes are placed, making it possible to fix a large quantity of microorganisms in the form of a biofilm in the reactor and which are crossed by a gaseous flow, containing carbon monoxide and dihydrogen, making it possible to deliver the components of the gas directly to the microorganisms contained in the biofilm which transforms them into ethanol and other soluble products: US patent application 8,058,058 describes a reactor of this type, which comprises a tank comprising an aqueous bath in which are immersed microporous or non-microporous tubular membranes, covered at least partially with a biofilm. A gaseous mixture comprising carbon monoxide, carbon dioxide and dihydrogen is introduced into the tubular membranes, at one end. The rest of the gas mixture is collected at the other end of the tubular membranes. The product transformed by the microorganisms making up the biofilm is obtained in the liquid product of the tank and extracted from the upper part of the tank. The processed product is thus also liquid.

Note that such a device uses carbon dioxide or monoxide as well as dihydrogen but does not aim to produce methane from these inputs. It is therefore not a methanation reactor, but a reactor using bacteria (and not Archaea) to generate biochemical reactions of acetogenesis leading to the production of compounds such as ethanol or acetic acid. It should nevertheless be noted that these compounds are produced in a soluble form in a liquid and not in a gaseous form.

There are many devices using membranes as a support for microbial biofilm to generate methane production by biological methanation.

Among these, some operate in situ, i.e. the biological methanation reaction takes place in a biomethanation reactor aimed at producing biogas (gas mixture containing methane, but also carbon dioxide ) via the anaerobic digestion of complex organic matter, most often in a non-hydrolyzed form (manure, slurry, bio-waste, primary sludge from wastewater treatment plants, etc.). Thus, patent EP 2 771 472 describes an in-situ biological methanation process making it possible to reduce the CO2 level of the biogas produced by a biomethanation reactor by injecting dihydrogen into the liquid content of the latter by means of fiber membranes hollow. This type of reactor has two drawbacks. On the one hand, it requires injecting an acid product into the reactor to maintain the pH value between 7 and 8 in the liquid medium, a consequence of the in-situ configuration of the methanation reactor which requires preserving all the microbial categories. included in the anaerobic digestion consortium, in particular hydrolytic bacteria,

acidogenic and acetogenic. On the other hand, the recommended LU501102 hollow fiber membranes are subject to the rapid colonization of their microporosity by the microorganisms contained in the liquid medium, which leads to a rapid decrease in the rate of gas permeation through this type of membrane, causing a rapid drop in the methanation yield of the reactor in the absence of regular replacement of its membranes. However, such a regular replacement involves significant operating expenses of the reactor, the bundles of hollow fiber membranes being very expensive, as well as the repeated disturbance of the anaerobic conditions favorable to biological methanation, given the need to open the reactor. during each of these operations.

There are also ex situ processes using membranes as a microbial attachment support for biological methanation. In these processes, the reactor where the methanation reaction takes place is a reactor entirely dedicated to the accomplishment of the latter, not to that of biomethanation. Ex-situ methanation reactors have a better yield than in-situ methanation reactors because they make it possible to generate conditions conducive to the development of methanogenic Archaea without having to preserve the other microbial categories involved in the anaerobic digestion consortium. Thus, the device described in patent EP 3 555 258 couples a biomethanation reactor to an ex situ biological methanation reactor of the MBfR type (biofilm and membrane reactor). In the MBfR reactor vessel, dihydrogen and carbon dioxide are injected as a mixture in a liquid medium via a bundle of membranes permeable to these gases on the surface of which is stimulated the development of a biofilm carrying out the reaction of ~~ methanation . The MBfR-type reactor described here has several limitations. Indeed, it must be traversed by a permanent flow of liquid to evacuate in dissolved form (or micro-bubbles) the methane it produces because it does not include a dedicated gas outlet. As methane is very poorly soluble in water, the flow rate of liquid passing through the reactor must be high, which requires significant investment and operating costs for the liquid pumps required, which are all the more important costs. that the pumped liquid is viscous. In addition, the flow of liquid sweeping the surface of the membranes prevents the exploitation of a liquid medium loaded with solid elements, which would risk damaging the membranes as well as the biofilm they contain. Finally, the reactor described requires a permanent liquid exchange with a biomethanization reactor,

which restricts its use to sites specifically dedicated to the production of LU501102 biogas or biomethane.

Interestingly, in a study evaluating an MBfR-type reactor using hollow fiber membranes for biological methanation purposes, the authors demonstrated that the biofilm formed on the membranes contributed to only 22-36% of the dihydrogen consumption of the reactor, most of the dihydrogen being therefore consumed by the microbial flora suspended in the liquid medium surrounding the membranes (Luo et al., 2013).

The invention therefore proposes an ex situ reactor making it possible to optimize the exploitation of microbial flora present in suspension in a liquid or semi-liquid medium for biological methanation. The reactor that is the subject of the invention uses membranes (non-microporous), not to promote the development of a biofilm, but to locally supply dihydrogen to all points of a volume of liquid or semi-liquid medium. liquid to compensate for its low solubility. It therefore has characteristics aimed at avoiding the loss of performance due to microbial clogging of the membranes. In addition, the reactor that is the subject of the invention makes it possible to recover methane in gaseous form, which avoids the need to maintain a continuous flow of liquid through the reactor and makes it possible to exploit a viscous liquid medium and/or loaded with solids.

Finally, the reactor that is the subject of the invention does not require the exchange of large volumes of liquid or semi-liquid medium with a biomethanation reactor, which makes it possible to install it on a site not dedicated to production. biogas or biomethane, such as an industrial site generating gaseous emissions containing carbon dioxide and/or carbon monoxide.

SUMMARY OF THE INVENTION

The invention relates to a biological methanation reactor, comprising a tank comprising: - a liquid or semi-liquid medium, - an anoxic gas inlet to be treated, comprising carbon dioxide and optionally carbon monoxide, - a microbial flora comprising methanogenic Archaea, - at least one non-microporous tubular membrane, permeable to dihydrogen, at least partially immersed in said liquid or semi-liquid medium and at least partially in contact with said microbial flora, said at least one membrane comprising a membrane duct in which an LU501102 gas can be injected, said reactor comprising at least one gas injector connected to said conduit of said at least one membrane and an outlet dedicated to the gas allowing the recovery of methane generated by said biological methanation produced in the tank by said methanogenic Archaea microbial flora in contact with said gas having passed through said at least one membrane.

In addition, said tank comprises a second inlet for supplying the liquid or semi-liquid medium with nutrients, as well as a second effluent discharge outlet.

The methanation reactor in accordance with the invention is remarkable in that said microbial flora exploited is an anaerobic microbial flora in suspension in said liquid or semi-liquid medium and comprises hydrogenotrophic methanogenic Archaea and/or comprises homo-acetogenic bacteria and Methanogenic acetotrophic archaea, in that the gas injector is a pure dihydrogen injector, and in that said reactor comprises a gas collection and storage space, said gas comprising methane resulting from the methanation reaction generated by said microbial flora in contact with said pure dihydrogen injected into the liquid or semi-liquid medium through said at least one membrane, said outlet allowing the recovery of methane being a gas outlet and being connected to said gas collection and storage space, and said gas injector and said inlet of anoxic gas to be treated being two independent gas inlets in said reactor.

The combined characteristics of a microbial flora in suspension and the separate injection of pure dihydrogen and the anoxic gas to be treated avoid the formation of a thick biofilm on the tubular membranes which could clog them and reduce efficiency. of their gas permeation. Indeed, the hydrogenotrophic methanogenic Archaea lack a local carbon source to grow on the outer surface of the membranes, which would not be the case if the anoxic gas to be treated (containing carbon dioxide or carbon monoxide) was injected in the liquid or semi-liquid medium mixed with dihydrogen via tubular membranes, as often practiced with MBfR type reactors. Thus, the reactor according to the invention makes it possible to maximize the rate of supply of dihydrogen to the microbial flora in suspension in the liquid or semi-liquid medium while being less expensive to maintain than current MBfR type reactors.

The methanation reactor in accordance with the invention may also comprise the following characteristics, taken separately or in combination:

Advantageously, the gas collection and storage space is included in said tank, between the surface of said liquid or semi-liquid medium and a tank top lid. This space for collecting and storing gas, not present on MBfR-type reactors, makes it possible to collect in gaseous form the biomethane produced by the microbial flora and to extract it from the reactor in this same form via the outlet dedicated to the treated gas . The presence of this gas collection and storage space therefore prevents the reactor that is the subject of the invention from having to be traversed by a continuous flow of liquid to extract in soluble form (or micro-bubbles) the biomethane produced, and makes it possible to operate a viscous liquid medium and/or loaded with solid elements, which is difficult with MBfR type reactors. In addition, the presence of this gas collection and storage space prevents the reactor that is the subject of the invention from requiring the exchange of large volumes of liquid or semi-liquid medium with a biomethanization reactor, which allows it to be installed on a site not dedicated to the production of biogas or biomethane, such as an industrial site generating gaseous emissions containing carbon dioxide and/or carbon monoxide. Finally, the presence of this gas collection and storage space makes it possible to increase the performance of the biological methanation of the reactor by increasing the residence time of the anoxic gas to be treated there, which has the effect of increasing the duration of availability of carbon dioxide and/or carbon monoxide for the microbial flora in suspension in the liquid or semi-liquid medium responsible for the conversion of this (these) gas into biomethane.

Preferably, the anoxic gas inlet to be treated opens into said gas collection and storage space.

Preferably again, the anoxic gas inlet to be treated and the outlet allowing the recovery of the methane, each comprise a non-return valve.

Furthermore and according to an advantageous embodiment, the methanation reactor in accordance with the invention comprises a stirrer device capable of generating stirring in said liquid or semi-liquid medium.

In the context of this embodiment, said stirrer device preferably comprises at least one gas diffuser immersed in the liquid or semi-liquid medium.

liquid, preferably provided in the bottom of said tank. By placing the LU501102 gas diffuser in the bottom of the tank, the diffused gas rises up the entire column of liquid or semi-liquid medium and thus comes into contact with all of the microbial flora: This promotes contact with the microbial flora and gas as well as effective solubilization of carbon dioxide and/or carbon monoxide in the liquid or semi-liquid medium.

Preferably, said agitator device comprises a recirculation pump which is connected on the one hand to the gas collection and storage space, to extract gas therein, and on the other hand to said gas diffuser to supply said gas diffuser. gas with said gas extracted from said gas collection and storage space. In this way, the anoxic gas to be treated is injected by the diffuser into the liquid or semi-liquid medium and the carbon dioxide (and possibly the carbon monoxide) is brought into contact with the microbial flora so that it can carry out the methanation reaction in the presence of dihydrogen. The fact of injecting the anoxic gas to be treated through the gas diffuser, and not through the membrane as is usual in known solutions, makes it possible to prevent the formation of biofilm on the membranes, thus preserving them from clogging. Indeed, thanks to the solution in accordance with the invention, the hydrogenotrophic methanogenic Archaea lack a local carbon source to develop on the surface of the tubular membranes and a local dihydrogen source to develop on the gas diffusers. rich in carbon dioxide.

Advantageously, said at least one diffuser is placed under said at least one tubular membrane.

It is further provided that said stirrer device preferably extends over substantially 0.05 m2 for 1m? of liquid or semi-liquid medium in said tank.

This allows distribution of the gas to be treated throughout the volume of the liquid or semi-liquid medium. In addition, the rise of gas bubbles prevents the local accumulation of dihydrogen on the surface of the tubular membranes, the local accumulation reducing the permeation rate of dihydrogen through the wall of the tubes.

According to an exemplary implementation of the invention, the reactor comprises at least one bundle of membranes comprising at least two tubular membranes, the axes of said at least two tubular membranes, included in said at least one bundle of membranes, being substantially parallel to each other, each of said at least two tubular membranes of said at least one bundle of membranes each comprising a membrane duct LU501102 supplied with pure dihydrogen by said gas injector.

The tank can accommodate one or more sets of bundles of tubular membranes, to optimize the methanation reaction. Depending on the arrangement of the sets of membrane bundles in the tank and according to their orientation, the tank can accommodate a greater or lesser length of tubular membrane, which promotes the methanation yield. The latter will be all the higher as the configuration of the network of tubular membranes makes it possible to supply dihydrogen locally at any point in the volume of liquid or semi-liquid medium (long length of the tubular membranes compared to the volume of liquid or semi-liquid medium). -liquid and homogeneous arrangement thereof). This dense and homogeneous configuration of the network of tubular membranes makes it possible to advantageously compensate for the low solubility of dihydrogen in the liquid or semi-liquid medium and to maximize its recovery by the microbial flora present in suspension in the latter.

It is advantageously provided that the injector supplies pure dihydrogen to the duct of each of said tubular membranes by means of a set of connecting tubes, each of the connecting tubes being connected to a main injection duct of said injector. The fact of multiplying the dihydrogen injection modules makes it possible to close the arrival of dihydrogen to one of them, in the event of a leak for example. A single large dihydrogen injection module could be implemented in the reactor without departing from the scope of the invention, but the slightest leak would imply the total stoppage of dihydrogen injection. This would result in a significant loss of revenue for the operator. With a large number of modules, the process can remain profitable in the event of a leak on one or more modules, as defective modules can be replaced during an annual maintenance operation.

Also preferably, the tank has a tank volume dedicated to the liquid or semi-liquid medium, said at least two membranes of said at least one set of membranes have a total specific length at least equal to 1000 m per cubic meter of said volume dedicated to the liquid medium and they occupy a specific volume less than substantially 0.2 m3 per 1 m3 of said volume dedicated to the liquid or semi-liquid medium (or less than 0.2 m3 per 1 m3 of said volume dedicated to the liquid or semi-liquid medium) .

Furthermore, said at least one membrane comprises silicone. Indeed, this material LU501102 has a high permeability to gas (in particular to dihydrogen).

For example, a 1 meter length of silicone tubing with an inside diameter of 8 mm and a wall thickness of 1 mm subjected to a difference in partial pressure of hydrogen of 1 bar between the membrane duct and the outside of this makes it possible to diffuse a dihydrogen flow of ~1.4 L/day.

Silicone also has excellent durability, a reduced cost compared to that of hollow fiber membranes and a dense, non-micro-porous structure, offering a low attachment surface to micro-organisms. This last characteristic allows a good temporal stability of the rate of gas permeation through the membrane, the efficiency of which does not risk being reduced by the development of a thick biofilm opposing a physical barrier to the passage of gas.

In the context of an advantageous embodiment, the membrane comprises at least one silicone tube or several silicone tubes aligned relative to each other and held by their tube ends in gas distributor elements, the gas distributor elements gas and the ends of the tubes being embedded in a polyurethane or polyepoxide resin.

Preferably again, said duct of said tubular membrane is subjected to an internal pressure of between substantially 0.5 and 1.5 bar (or between 0.5 and 1.5 bar), an intramembrane pressure range allowing an adequate flow rate of supply of dihydrogen to the microbial flora present in suspension in the liquid or semi-liquid medium. In addition, subjecting said tubular membrane duct to a pressure regulated in this range makes it possible to avoid contamination of the hydrogen circuit with gases such as ammonia (NH3) or hydrogen sulphide (H2S), potentially toxic to the microbial flora.

Preferably again, the methanation reactor comprises several levels each comprising at least one tubular membrane and in that the internal ducts of the tubular membranes of each level are subjected to different pressures. Indeed, this configuration makes it possible, in the case of a high reactor, to compensate for the negative effect of the hydrostatic pressure (due to the column of liquid or semi-liquid medium) on the rate of permeation of dihydrogen through the wall of the tubular membranes, by subjecting the most deeply immersed membranes to an intramembrane pressure greater than that to which the less deeply immersed membranes are subjected.

Advantageously, the methanation reactor comprises a first flowmeter-flow regulator device which is connected to said dihydrogen injector.

Advantageously, the methanation reactor comprises a second flowmeter-flow regulator device, connected to said inlet of anoxic gas to be treated.

The reactor preferably also comprises, according to one embodiment, a control module for one or the other or of the two first and second flowmeter-flow regulator devices.

In addition, the reactor preferably includes an apparatus for analyzing the composition of the gas at said gas outlet and the composition of the gas at said inlet of anoxic gas to be treated opening into said gas collection and storage space.

These last features allow the implementation of a method in accordance with the invention, for a methanation reactor as defined above, which comprises the following steps: - measurement of a first composition of the anoxic gas to be treated at said inlet of anoxic gas to be treated by means of said analysis apparatus, said first composition of the anoxic gas to be treated comprising a concentration of carbon dioxide and/or carbon monoxide, - measurement of a second gas composition at said gas outlet , said second gas composition comprising a concentration of methane and dihydrogen, and - comparison of said methane concentration with a predetermined threshold value of methane and comparison of said concentration of dihydrogen with a predetermined threshold value of dihydrogen, - comparison of said concentration in carbon dioxide and/or carbon monoxide with a predetermined threshold value of carbon dioxide and/or carbon monoxide, and increase of a first set value of said first flow meter device - flow regulator and/or decrease of a second setpoint value of said second flow meter device - flow regulator and/or increase in a service life of said recirculation pump if said concentration of carbon dioxide and/or carbon monoxide is greater than said predetermined threshold value carbon dioxide and/or carbon monoxide, and vice versa, or - reduction of said first setpoint value of said first flowmeter device - flow regulator and/or increase of a second setpoint value of said second flowmeter device - regulator flow rate and/or increase in a service life of said recirculation pump if said concentration of dihydrogen at said outlet is greater than said one predetermined threshold value of dihydrogen, and vice versa.

The invention also relates to a computer program comprising instructions, which when executed by computer, implement all the steps of the method defined above.

FIGURES

Other advantages and characteristics of the invention will appear on examination of the detailed description of a non-limiting mode of implementation, and of the appended drawings, in which: [Fig. 1] is a schematic representation of a biological methanation reactor in accordance with the invention, seen in section, [Fig. 2] shows a reactor according to a first embodiment according to the invention, seen in perspective, [Fig. 3] shows the reactor of figure 2, seen in perspective, from which a cover has been removed and from which a tank is illustrated in transparency, in order to better distinguish the elements which it comprises, [Fig. 4] shows the reactor of FIG. 2, seen in perspective, from which the tank, the cover and a pump have been removed, [Fig. 5] shows the vessel of the reactor of FIG. 2, seen in perspective, as well as a stirring device connected to the pump, a pipe for supplying the reactor with anoxic gas to be treated, as well as the presence of a space collection and storage of gas located above the level of the liquid or semi-liquid medium in the tank, [Fig. 6] shows an example of a membrane that the vessel of the reactor according to the invention may comprise, seen in perspective and in longitudinal section, [Fig. 7] is an enlargement of zone VII shown in FIG. 6, [Fig. 8] shows an alternative embodiment of a reactor in accordance with the invention, illustrating a vessel seen in section, with a deformable membrane which is not very permeable to gas forming a lid,

[Fig. 9] illustrates a top view of the tank shown in FIG. 8, and LU501102 [Fig. 10] shows part of the reactor illustrated in FIGS. 8, seen in perspective.

DESCRIPTION OF AN EMBODIMENT

Figure 1 schematically illustrates an embodiment of a biological methanation reactor according to the invention.

It comprises a tank 1 which contains a liquid or semi-liquid medium 2.

The liquid or semi-liquid medium 2 comprises a microbial flora 20 comprising hydrogenotrophic methanogenic Archaea and/or comprising homo-acetogenic bacteria and acetotrophic methanogenic Archaea suspended in said medium (2).

The level of the liquid or semi-liquid medium 2, comprising said flora in suspension, is such that there is a free volume of liquid above the liquid or semi-liquid medium in the tank: in other words, the liquid or semi-liquid medium - liquid 2 comprising said microbial flora 20 in suspension does not fill the entire volume of tank 1.

This volume left free above the level of the liquid or semi-liquid medium constitutes a gas collection and storage space 3. This volume is closed in the upper part of the tank 1 by a lid 4 at the top, advantageously of curved shape ( see figure 2 for example) to increase the volume of the gas collection and storage space 3.

The tank 1 of the methanation reactor comprises an inlet 5 for gas to be treated which also opens into the gas collection and storage space 3: the gas to be treated is anoxic (that is to say devoid of oxygen) and includes carbon dioxide (CO) and optionally carbon monoxide (CO).

The anoxic gas inlet 5 to be treated is equipped with a non-return valve (reference 50).

The reactor in accordance with the invention further comprises a set of non-microporous tubular membranes 6, immersed in the liquid or semi-liquid medium 2 comprising the microbial flora 20: the non-microporous tubular membranes 6 are thus in contact with the liquid medium or semi-liquid 2 and also with the microbial flora 20 suspended in the medium.

Each tubular membrane 6 comprises an internal duct 60, otherwise called LU501102 "membrane duct", which is blind (that is to say that one of the ends of the tubular membrane is closed).

Each membrane duct 60 is supplied with dihydrogen (Hz) by a supply duct 70 connected to a pure dihydrogen injector 7.

“Pure” dihydrogen will be understood to mean a gas comprising at least 95% dihydrogen, or even less: the volume concentration of dihydrogen at the level of the injector is at least 80%, the remaining 20% (or substantially 20%) including neither carbon dioxide nor carbon monoxide.

Each membrane 60 is permeable to dihydrogen so that the dihydrogen injected into the membrane ducts 60 passes through the wall of each membrane 60 to penetrate into the liquid or semi-liquid medium 2 comprising the microbial flora in suspension 20.

This is how the microbial flora 20 finds itself in contact with dihydrogen.

The microbial flora 20 generates the methanation reaction which consists of transforming carbon dioxide and possibly carbon monoxide (present in the anoxic gas to be treated) in the presence of dihydrogen, into methane and water, respectively according to the reactions (1) and (2) following:

CO2 + 4H2 > CH4 + 2H20 (1)

CO+3H2+> CHa + H2O (2).

So that the microbial flora 20 is also in contact with the anoxic gas to be treated, the methanation reactor according to the invention comprises at least one gas diffuser 8, provided in the bottom of the tank 2, which takes the gas from the gas collection and storage space 3 to reinject it in the form of fine bubbles into the liquid or semi-liquid medium 2 by means of a pump 9 external to the tank 1. Indeed, the anoxic gas to be treated is , in the context of this embodiment, injected into the gas collection and storage space 3.

It is therefore in this space 3 that the gas to be treated is withdrawn by the pump 9 to supply the gas diffuser 8 which injects it into the liquid or semi-liquid medium 2 comprising the microbial flora in suspension.

In doing so, the gas diffuser 8 also constitutes a device which creates agitation in the liquid or semi-liquid medium, the gas reinjected by the diffuser 8 ascending the entire column of liquid 2 and creating movement in the microbial flora 20, this which prevents this flora from stagnating in the liquid or semi-liquid medium and being deposited on the membranes 6, to prevent LU501102 from forming a biofilm on the membranes 6.

The advantage of avoiding the formation of a biofilm is to avoid the clogging of the membranes 6, partially preventing the diffusion of dihydrogen into the liquid or semi-liquid medium. Thus, by avoiding the formation of biofilm, the presence of dihydrogen in the liquid or semi-liquid medium is favored and, consequently, the methanation reaction by the microbial flora in suspension therein.

The gas diffuser 8 thus has a dual function: to introduce the anoxic gas to be treated into the liquid or semi-liquid medium comprising the microbial flora in suspension (at the origin of the methanation reaction) and to best prevent the formation of biofilm on membranes 6.

The formation of biofilm is also avoided due to the fact that the gas injected by the membranes into the liquid or semi-liquid medium does not contain carbon dioxide (only dihydrogen) - in the absence of carbon dioxide diffused through the membrane, and by creating agitation in the liquid or semi-liquid medium, the microbial flora does not develop either on the membranes 6 or on the gas diffuser 8.

Thus, the reactor according to the invention, comprising an inlet of dihydrogen independent of the inlet of anoxic gas to be treated, makes it possible to avoid the formation of biofilm and to optimize the exploitation of the microbial fore in suspension. for the accomplishment of methanation.

The methanation reaction by the microbial flora in suspension takes place as follows:

The methane generated by the methanation reaction is collected in the gas collection and storage space 3, above the liquid or semi-liquid medium 2. It is evacuated from the reactor vessel 1 through an outlet 10, provided in the lid 4 in the context of this example.

Outlet 10 is equipped, like inlet 5 of anoxic gas to be treated, with a non-return valve 100.

In order to maintain the richness and activity of the microbial flora 20 in suspension in the liquid or semi-liquid medium 2, a second inlet 22 is provided in the tank 1, to supply the liquid or semi-liquid medium 2 with nutrients. . If the source of these nutrients is anaerobic sludge from a methanization digester, the inlet 22 also makes it possible to supply the liquid or semi-liquid medium with healthy microbial flora as well as additional soluble inorganic carbon (HCOz, COs? and H>COs) that can be converted into methane by the LU501102 methanation reaction.

The second inlet 22, serving for the supply of nutrients, is made in the side wall of the tank 1, in the upper part of the latter.

The tank also has a second outlet 21, to evacuate the liquid/semi-liquid effluents from the reactor. This is fitted at the bottom of the tank so as to allow evacuation of the effluents by the effect of gravity.

Unlike MBfR type reactors (biofilm and membrane reactors), the reactor that is the subject of the invention does not require any permanent liquid medium exchange with another reactor or a gas extractor. This characteristic makes it possible to adopt a high hydraulic residence time of the liquid or semi-liquid medium in the reactor ensuring the maintenance of a high density of methanogenic Archaea in suspension in the liquid or semi-liquid medium despite the low rate of reproduction. inherent in this microbial category. The nutrients can moreover be introduced into the reactor in dried or freeze-dried form, which makes it possible to maximize the hydraulic residence time of the reactor by minimizing the flow of liquid or semi-liquid medium between the inlet 22 and the outlet 21.

Figures 2 to 5 show a particular embodiment of a reactor according to the invention and will now be described.

The tank 1 shown in Figure 2 is substantially cylindrical in shape and has a capacity of substantially 800 L (liters).

The wall of the tank can be equipped with heating means, making it possible to increase the temperature of the liquid or semi-liquid medium 2 that it comprises, in order to promote the reaction.

The temperature of the liquid or semi-liquid medium 2 is ideally between substantially 35° C. and 42° C. (or between 35° C. and 42° C.), or else between substantially 50° C. and 65° C. (or between 50° C. C and 65°C).

The tank 1 is insulated from the ground by being mounted on four feet 11.

The tank 1 encloses a set of membranes 6 which are all tubular, extending along rectilinear directions and whose axes are substantially all parallel to one another.

The cover 4 is substantially dome-shaped and is fixed to the edge of the upper end of the tank 1, open, by means of a bolted double flange 40 comprising an EPDM seal.

FIG. 5 illustrates the position of the bolted double flange 40 with respect to the level of the liquid or semi-liquid medium 2 in the tank, without the cover 4, in order to better distinguish the distance separating the level of the liquid or semi-liquid medium in the tank from the level of the opening (upper end) of the tank 1. It is thus observed that the double bolted flange 40 is at a distance d above the level of the liquid or semi-liquid medium 2.

It is also observed that the inlet 5 of anoxic gas to be treated takes place through the side wall of the tank, at a level located between the level of the liquid or semi-liquid medium 2 and the level of the upper end of the tank. 1.

The outlet 10 for recovering a gas enriched in methane is formed through the lid 4: the non-return valve 10 is shown alone in Figure 5, at a distance from the edge of the tank located between the edge of the tank and its center, in a position diametrically opposite to the position of the anoxic gas inlet to be treated.

The pure dihydrogen injector 7 is a canister which is placed close to the tank 1, which supplies (thanks to the supply conduit 70) a network of tubes connected to the internal conduits of the membranes 6. This source of dihydrogen can be replaced by the pressurized hydrogen tank of a water electrolyser.

All of the ducts supplying the membranes 6 are illustrated in more detail in Figures 3 and 4.

Each internal membrane duct is connected by a supply tube 72 to a main injection (distribution) duct 71, of toroidal shape which extends around the tank and which, itself, is fed by the duct injection 70.

It is observed in Figure 3 that each tube is connected to the main conduit 71 by opening and closing devices 73, which can be controlled independently of each other. Also, if a leak were detected on a connection tube, it is possible to stop the supply of dihydrogen to the membrane associated with it without however having to stop the supply of the other tubes connected to the other membranes.

The gas reintroduction pump 9 is also placed close to the tank.

It makes it possible to supply seven gas diffusers 8, fitted to the bottom of the tank 1.

It should be understood that the invention is not limited to the presence of seven gas diffusers and that the reactor could comprise more or less.

Preferably, the gas diffusers extend over an area greater than LU501102 substantially 0.05 m? for 1m? of liquid or semi-liquid medium contained in said tank, to create sufficient agitation to prevent the formation of biofilms and so that all of the microbial flora in suspension can be in contact with the carbon dioxide and carbon monoxide of the injected anoxic gas to be treated. In the context of the example shown, the gas diffusers 8 cover 34% of the surface of the bottom of the tank 1.

The gas diffusers 8 are placed under the tubular membranes shown in more detail in figures 3 and 4.

A first pipe 90 takes the gas contained in the gas collection and storage space 3 and a second pipe 91 reinjects the gas taken from the gas diffuser 8.

Figure 5 shows in more detail the ducts 90, 91 and the gas diffusers 8 placed at the bottom of the tank 1.

The methanation reactor according to the invention and shown in Figures 2 to 5 comprises thirty-seven non-microporous tubular membranes 6.

An example illustrating a membrane 6 in more detail is shown in Figures 6 and 7.

Each membrane 6 is actually composed of a bundle of thirty-six silicone tubes 61, each tube itself being a membrane, the tubes 61 being positioned vertically and parallel to each other, held together by an upper element of distribution 62 and a lower end element 63. A central stiffening rod 64 is also provided within each bundle of membrane 6, in the middle of the silicone tubes 61 to hold together the upper distribution element 62 and the element lower end 63, in particular by screwing the ends of the rod 64 into the distribution element 62 and end 63.

The distribution 62 and end 63 elements as well as the ends of the silicone tubes which are connected thereto are embedded in a polyurethane resin sealing the connection between the silicone tubes and the distribution elements 62 and end 63 (see reference 69 in Figure 6).

The lower end of the silicone tubing is connected to lower end member 63 by castellated nipples 65 (Figure 7).

The upper distribution element 62 of each bundle of membranes has an inlet 66 for connecting a supply tube 71, to introduce pure dihydrogen into the membrane duct of each of the 36 silicone tubes included in the bundle of membrane. To do this, the upper distribution element 62 comprises a hollow space 67 connected to the inlet 66, having 36 outlets allowing the pure dihydrogen to be diffused into the membrane duct of each silicone tube 61 via a crenellated nipple 65.

The upper distribution elements 62 and the lower end elements 63 can be produced by 3D printing.

The pressure obtained by injecting gas into the membrane duct of each silicone tube 61 is between 0.5 and 1.5 bar (the diffusion of pure dihydrogen through the wall of each tubular membrane 61 being dependent on the internal pressure in the membrane duct: the higher this pressure, the higher the permeation rate of dihydrogen through the wall of the silicone tube).

It will be understood from the preceding description that the membrane duct into which the dihydrogen is injected can be produced by a single duct (passage with walls of its own) or by other means such as spaces defined between tubes of parallel silicones, positioned against each other, and this without departing from the scope of the invention.

In the context of the example presented, the silicone tube included in the thirty-seven bundles of membranes 6 has a total specific length of 1000 m for 1 m3 of volume of dedicated liquid or semi-liquid medium comprising the microbial flora in suspension . However, the specific volume occupied by the silicone tube is less than 0.2 M3 for 1 m3 of volume dedicated to the liquid or semi-liquid medium comprising the microbial flora in suspension.

Note in Figures 3 and 4 that all the tubular membranes 61 are oriented in the same way, parallel to the axis of the tank.

Reference will now be made to other elements of the reactor in accordance with the invention and illustrated in FIGS. 1 to 7, which make it possible to further optimize its operation.

Provision is made to equip the supply conduit 70 with pure dihydrogen with a first device 31 which performs both the functions of flow meter and flow regulator.

The anoxic gas inlet to be treated is also equipped with a second device 32 which also performs the functions of flow meter and flow regulator.

The first and second flow meter/flow regulator devices 31 and 32 are LU501102 associated in their operation with a control module 30 that also includes the methanation reactor according to the invention.

Provision is also made for the gas collection and storage space to be equipped with an apparatus 33 for analyzing the composition of the gas at the inlet of the anoxic gas to be treated and that the outlet (for extracting the gas enriched in methane) is also equipped with an apparatus 34 for analyzing the composition of the gas in methane.

The apparatus 33 makes it possible to identify the proportion of carbon dioxide and carbon monoxide in the anoxic gas to be treated introduced into the reactor.

The apparatus 34 makes it possible to identify the proportion of dihydrogen and methane in the gas extracted from the reactor.

The control mode makes it possible to control the flow rates of pure dinhydrogen introduced and of anoxic gas to be treated introduced according to the composition data provided by the devices 33 and 34.

In particular, the control module 30 implements a computer program which includes instructions which, when executed, implement all the steps of the method which will now be described:

Using the device 33, a first measurement of the composition of the anoxic gas to be treated at said gas inlet is obtained: the first measurement of the composition of the anoxic gas comprising a concentration of carbon dioxide and/or carbon monoxide.

In parallel and/or simultaneously, using the device 34, a second measurement of the composition of the gas is obtained at said gas outlet 10, the second measurement of gas composition comprising a concentration of methane and dihydrogen.

Two comparisons are made by the control module:

D) The methane concentration of the second measurement of gas composition is compared with a predetermined threshold value of methane and the dihydrogen concentration of the second measurement of gas composition is compared with a predetermined threshold value of dihydrogen.

ID) The carbon dioxide and/or carbon monoxide concentration of the first anoxic gas composition measurement to be processed is compared with a predetermined threshold value of carbon dioxide and/or carbon monoxide.

If this comparison leads to the observation that the concentration of dihydrogen in LU501102 leaving the reactor is greater than said predetermined threshold value of dihydrogen, then said first setpoint value of said first flow meter-regulator device 31 is decreased and/or the second is increased. set point value of said second device 32 flow meter - flow regulator and/or the service life of said recirculation pump 9 is increased, and vice versa.

If this comparison leads to the observation that said concentration of carbon dioxide and/or carbon monoxide is greater than said predetermined threshold value of carbon dioxide and/or carbon monoxide, then the first set point value of said first device is increased 31 flow meter - flow regulator and/or the second set point value of said second device 32 flow meter - flow regulator is decreased and/or the service life of said recirculation pump 9 is increased.

Reference will now be made to the operation of the methanation reactor which has just been described:

The tank is previously filled with a volume of 800L of anaerobic liquid or semi-liquid medium comprising a hydrogenotrophic methanogenic Archaea microbial flora and/or homo-acetogenic bacteria and acetotrophic methanogenic Archaea.

The volume of the remaining gas collection and storage space is approximately 200

L: it thus corresponds substantially to a quarter of the volume dedicated to the liquid or semi-liquid medium, or to a fifth of the total volume of the tank.

The vessel is heated or maintained at a temperature of substantially 37°C or substantially 55°C.

The anoxic gas to be treated is introduced into the gas collection and storage space 3 of the tank 1 through the gas inlet 5, this gas comprising carbon dioxide and optionally carbon monoxide.

The recirculation pump 9 takes the gas present in the gas collection and storage space 3 to supply the gas diffusers 8 at the bottom of the tank and the diffusers 8 inject this gas into the liquid or semi-liquid medium 2 comprising the microbial flora in suspension: the microbial flora is thus brought into contact with carbon dioxide and possibly carbon monoxide.

In parallel, pure dihydrogen is introduced into each of the bundles of membranes 6.

The tubular membranes 61 included in the bundles of membranes 6 diffuse LU501102 the dihydrogen into the liquid or semi-liquid medium 2 comprising the microbial flora 20: the latter is thus also brought into contact with the dihydrogen necessary for the methanation reaction.

The microbial flora 20 then generates methane (CH4) from the carbon dioxide (and possibly from the carbon monoxide) and dihydrogen supplied to it independently.

Methane, which is not very soluble in water, rises naturally in gaseous form to the surface of the liquid or semi-liquid medium and enriches the gaseous medium of the gas collection and storage space 3.

The methane-enriched gas is evacuated through outlet 10.

The composition analysis devices 33 and 34 inform the control module 30 on, respectively, the composition of the carbon dioxide gas (and possibly carbon monoxide) introduced into the gas collection and storage space and the composition of the gas in dihydrogen and methane which is evacuated by outlet 10.

The control module 30 compares permanently, or at regular intervals, these compositions of carbon dioxide (and possibly carbon monoxide), methane and dihydrogen with threshold values which condition the operation of devices 31 and 32 (operating flow meter and flow regulator) to regulate the flow of anoxic gas to be treated introduced into the gas collection and storage space and that of hydrogen introduced into the conduits of tubular membranes.

Depending on whether the concentration of the anoxic gas to be treated introduced into the gas collection and storage space increases or decreases, and depending on whether the concentration of methane and dihydrogen in the methane-enriched gas increases or decreases, the control module modifies the setpoints of the devices 31 and 32 to increase or decrease the flow rate of anoxic gas to be treated introduced or that of dihydrogen introduced.

The control module also acts on the mode of operation of the pump 9 to increase or reduce the diffusion of gas (withdrawn from the gas storage space) in the liquid or semi-liquid medium 2.

It is understood from the preceding description how the invention promotes the methanation reaction, in particular by avoiding the formation of biofilm on the tubular membranes 61 and by controlling the flow rate of the two gases (anoxic to be treated and dihydrogen) introduced separately into the liquid or semi-liquid medium LU501102 comprising the microbial flora in suspension.

It should however be understood that the invention is not specifically limited to the embodiment presented in the figures and that it extends to the implementation of any equivalent means.

For example, the inlet of anoxic gas to be treated 5 could be made at another place: indeed, the inlet of anoxic gas to be treated can be provided at any point of the gas recirculation loop.

For example again, it could be provided to connect additional pumps, a first whose delivery pipe is connected to the inlet 5 and a second whose suction pipe is connected to the outlet 10, without departing from the scope of the 'invention.

In addition, Figures 8 and 9 illustrate an alternative embodiment according to which the tank can contain 125 m? of liquid or semi-liquid medium 2:

A preferred application for a reactor of this scale is the upgrading of biogas (i.e. obtaining biomethane which can be injected into the natural gas network from biogas) produced by a small biogas production facility (i.e. producing 100 to 150 Nm3 of biogas per day). The enclosure of the reactor described has the characteristics of those fitted to the most widespread design of digester or post-digester for the production of biogas (cylindrical reactor with vertical axis). Therefore, a post-digester equipping a biomethanation installation can be easily transformed into a methanation reactor in accordance with the invention, which saves the cost of installing a new reactor on the site.

Such a reactor is shown in Figures 8 and 9: the cylindrical tank 1 has an internal diameter of 6100 mm and an internal height of 6200 mm, as well as a flat bottom. It is constructed of reinforced concrete and hermetically sealed at its top by an extensible and removable membrane 12 made of an elastomer chosen for its low gas permeability (for example Butyl).

A preferred method of implementation consists of burying the tank in the ground over part of its height. This buried configuration allows both to benefit from the thermal insulation of the ground and to allow easy access to the interior of the vessel from its top once the membrane has been removed, the format of the reactor allowing internal access with a machine. of building site. This facilitates the initial installation of the internal elements of the reactor as well as their handling during LU501102 maintenance operations.

The reactor is heated by means of a coil of piping traversed by a coolant and embedded in the concrete of the side wall of the vessel (not illustrated). The upper part of the tank, above ground, is provided with thermal insulation 13 placed on the outer face of its reinforced concrete wall and protected by a rigid envelope.

The 125m3 capacity of the reactor corresponds to a height of substantially 4250 mm of liquid or semi-liquid medium 2 conducive to the development of anaerobic microbial flora comprising a population of hydrogenotrophic methanogenic Archaea and/or a population comprising both bacteria homoacetogens and acetotrophic methanogenic Archaea.

This medium can be digestate from a digester intended for the production of biogas.

The content of the reactor in nutrients, microbial flora and soluble inorganic carbon (HCOz, CO3* and H2COz) can be regenerated via the introduction of new liquid or semi-liquid medium via a dedicated inlet pierced in the side wall, just at the above the level 14 of the liquid or semi-liquid medium 2 in the reactor.

The pipe 15 leading to this inlet includes a pump 16 with a nominal flow rate of approximately 10 m3/day.

The liquid or semi-liquid effluents can be evacuated via a dedicated outlet 17 pierced in the side wall and placed as close as possible to the bottom of the reactor.

This outlet 17 is connected to a vertical pipe 18 allowing the effluents to rise above ground level.

Lines 15 and 18 dedicated to the circulation of liquid or semi-liquid medium are stainless steel pipes.

The volume of the concrete tank corresponding to the upper 1950 millimeters of its interior height does not contain any liquid or semi-liquid medium and constitutes a gas collection and storage space 3 with a volume of substantially 58 m3, equivalent to approximately 46% of the volume dedicated to the liquid or semi-liquid medium.

In this space, the side wall of the vessel comprises an inlet through which gas containing CO/CO₂ to be converted into methane can be introduced into the reactor. The gas line to be treated 5 leading to this inlet comprises a gas pump LU501102 with a nominal flow rate of 150 Nm3/day (at atmospheric pressure) and a cut-off solenoid valve placed in series.

The space for collecting and storing gas 3 comprises two outlets dedicated to gas.

The first outlet allows the evacuation of the gas enriched in methane from the reactor and is connected to an evacuation pipe fitted with a second gas pump with a nominal flow rate of 150 Nm3/day (at atmospheric pressure) 92 allowing actively evacuate treated gas from the reactor as well as from a cut-off solenoid valve 93.

The second outlet makes it possible to suck the gas contained in the gas collection and storage space via a suction line 51 connected to the inlet of a third gas pump 52 with a nominal flow rate of +35 Nm3 /min (at atmospheric pressure). The outlet of this pump delivers the gas via a pipe 53 connected to an inlet pierced in the side wall of the concrete tank, below the level of the liquid or semi-liquid medium, 75 mm above the bottom of the tank.

This inlet supplies gas to one hundred and twenty bubble diffusers 80 of the disc type with a microperforated EPDM membrane via a distribution network 81 inscribed in a plane parallel to the bottom of the tank, in direct proximity to the latter.

The total effective area of these gas diffusers is 6.832 m2, which is 0.055 m? per m3 of liquid or semi-liquid medium.

The assembly comprising the gas collection and storage space, the outlet, the gas suction line 51, the third pump 52, the discharge line 53, the inlet, the distribution network 81, the gas diffusers 80 and the liquid or semi-liquid medium 2 form a recirculation loop making it possible to improve the contacting of the CO/CO2 fraction of the gas to be treated with the microbial flora in suspension in the liquid or semi-liquid medium. liquid 2.

The pipe 5 for introducing the gas to be treated into the reactor, the pipe network 51, 53, 81 allowing its recirculation in the liquid or semi-liquid medium 2 and the pipe for discharging the treated gas are PVC pipes of 100mm outer diameter and 2.5mm thick.

To the fixed gas collection and storage volume 3 is added a variable volume 40 delimited by the top of the tank and the extensible membrane 12 isolating it from the environment outside the reactor.

The volume of this space 40 can vary between 0 m3 (membrane 12 loose) and approximately LU501102 59 m3 (membrane 12 stretched forming a half-sphere - see figure 8), this maximum volume corresponding to approximately 47% of the volume dedicated to the liquid medium or semi-liquid.

This variable-volume space 40 makes it possible to maximize the methane content of the treated gas by varying the residence time of the gas in the reactor in proportion to the carbon monoxide/carbon dioxide content in the gas to be treated or to the injection rate. of the latter in the reactor.

Its volume can be increased by injecting gas to be treated into the reactor by activating the gas injection pump, or decreased by evacuating treated gas from the reactor by activating the gas extraction pump 92.

This device also makes it possible to process volumes of gas in the reactor in successive cycles using the extensible membrane 12 like a lung - Inflating the extensible membrane 12 with gas containing carbon monoxide/carbon dioxide; - Waiting for the time necessary to obtain a methane level compatible with injection of the treated gas into the natural gas network (case of use of the reactor to upgrade biogas); - Deflation of the extensible membrane 12 and discharge of the biomethane into the natural gas network; - Restart of the cycle.

Another embodiment for this variable-volume gas collection space is to place in the gas recirculation loop one or more reservoir(s) containing a volume of (incompressible) liquid surmounted by a free space of liquid. The gas storage capacity of this (these) tank(s) can be increased by reducing the share of the volume occupied by the liquid in the tank(s) using a first pump sucking liquid in and pushing it back. in a liquid storage tank independent of the variable volume gas storage tank(s). Conversely, the gas storage capacity of the latter(s) can be reduced by injecting liquid into them using a second pump drawing liquid into the independent liquid storage tank and pushing it back into the (s) variable volume gas storage tank(s).

Pure dihydrogen, which can be produced by a water electrolyser (not shown), LU501102 is injected into the liquid or semi-liquid medium 2 by means of tubular membranes 6, operating on the same principle and having the same method of manufacture than that shown schematically in Figure 6 and described above.

The upper and lower end elements 62 and 63, fitted to each membrane 6, have a parallelepipedal shape in the context of this example and accommodate one hundred and fifty-seven silicone tubes 61 of 8 mm and 10 mm inside and outside diameter, respectively.

The connection tubes 71 of the dihydrogen injection modules are arranged so that the axes of the tubular membranes 6 are oriented in a horizontal direction (see FIG. 10), which allows better vertical diffusion of the gas bubbles containing hydrogen monoxide. carbon/carbon dioxide in the entire volume of liquid or semi-liquid medium 2.

Indeed, the end elements 62 and 63 of the membranes 6 are less of an obstacle to the rise of the gas bubbles in the liquid or semi-liquid medium 2 because they are inscribed in planes that are no longer perpendicular but parallel to the vertical path of the bubbles. gas.

The hydrogen injection modules are divided into twelve vertical, radial, hydrogen injection units 100, each of which comprises a stainless steel trapezoidal section frame 101 supporting one hundred and eight hydrogen injection modules.

Each vertical unit 100 is suspended via chains from two metal crosspieces 102, one end of which rests on the upper edge of the side wall of the tank, and the other end rests on the top of a central reinforced concrete post.

Within a vertical dihydrogen injection unit 100, the one hundred and eight injection modules are divided into 2 subunits A and B superimposed vertically (i.e. 1 upper subunit A and 1 lower subunit B) each comprising six stages each comprising nine injection modules (or membranes 6) of different formats corresponding to nine lengths of silicone tubing.

These nine injection module formats correspond to 240, 340, 500, 630, 760, 890, 1020, 1150 and 1280 millimeters of silicone tubing length, respectively (see references M1 to M9 in Figure 10).

The distribution network that supplies dihydrogen to the membranes 6 included LU501102 in the 12 upper subunits A is independent of that which supplies the membranes 6 in the 12 lower subunits B.

This feature makes it possible to compensate for the negative effect of hydrostatic pressure on the permeation rate of dihydrogen through the wall of the silicone tubes by subjecting the membranes included in the 12 lower subunits B, immersed between 2 and 4 meters deep , at an intramembrane pressure greater than that to which the membranes 6 included in the 12 upper subunits A are subjected, submerged between 0 and 2 meters deep.

The reactor must be fed by a pressurized source of dihydrogen, which can be the dihydrogen tank of a water electrolyser. The pressurized dihydrogen tank supplies a general pipe on which the following control devices are mounted in series: A general dihydrogen supply cut-off valve, a first safety valve, a first pressure sensor, a general pressure regulator (first expansion valve), a second safety valve, a second pressure sensor, a mass flow meter-regulator device, a third pressure sensor.

The main pipe supplies dihydrogen as many secondary pipes as subunits A or B superimposed in each vertical dihydrogen injection unit (two secondary pipes in the present case where two subunits are present).

Each secondary pipe includes, in series, the following control devices: A secondary cut-off valve, a secondary pressure regulator (second expansion valve) making it possible to adapt the intra-membrane pressure of the membranes 6 to the immersion depth of the subunit A or B including the latter, a pressure sensor.

Each secondary pipe supplies dihydrogen as many tertiary pipes as subunits A or B included in each level of immersion depth (twelve tertiary pipes in the present case). Each tertiary pipe includes the following control devices as standard: A tertiary shut-off valve, a safety valve, a mass flow rate meter-regulator device, a pressure sensor.

Each tertiary pipe supplies dihydrogen to the injection modules included in an A or B subunit via: A rigid pipe crossing the wall of the reactor and fitted with a connector at each of its ends; an internal flexible pipe in LU501102 stainless steel, an internal distribution network made of rigid stainless steel pipes.

The reactors which are the subject of the invention can be used jointly. For example, several reactors can be used with their gas collection space mounted in parallel on the pipe for anoxic gas containing carbon dioxide to be treated, which makes it possible to multiply the value of the flow rate of treatable gas by the number of reactors used. . To maximize the level of methane in the treated gas (case of an injection of the treated gas into the natural gas network), it is also possible to use several reactors which are the subject of the invention mounted in series.

Claims (23)

CLAIMS LU501102 1. Biological methanation reactor, comprising a tank (1) comprising: - a liquid (2) or semi-liquid medium, - an inlet (5) for anoxic gas to be treated, comprising carbon dioxide and optionally carbon monoxide , - a microbial flora (20) comprising methanogenic Archaea, - at least one non-microporous tubular membrane (6), permeable to dihydrogen, immersed at least partially in said liquid or semi-liquid medium (2) and at least partially in contact with said microbial flora (20), said at least one membrane (6) comprising a membrane duct into which a gas can be injected, said reactor comprising at least one gas injector (7) connected to said duct of said at least one membrane (6) and an outlet (10) allowing the recovery of methane generated by said biological methanation produced in the tank (1) by said microbial flora (20) methanogenic Archaea in contact with said gas having passed through said at least one membrane (6) , - said tank (1) comprising a second inlet (21) for supplying the liquid or semi-liquid medium with nutrients and comprising a second effluent discharge outlet (22), characterized in that said microbial flora (20) exploited for the methanation reaction is an anaerobic microbial flora in suspension in said liquid or semi-liquid medium (2) and comprises hydrogenotrophic methanogenic Archaea and/or comprises homoacetogenic bacteria and acetotrophic methanogenic Archaea, in that the gas injector (7) is a pure dihydrogen injector, and in that said reactor comprises a space (3) for collecting and storing gas, said gas comprising methane resulting from the methanation reaction generated by said microbial flora ( 20) in contact with said pure dihydrogen injected into the liquid or semi-liquid medium (2) through said at least one membrane (6), said outlet (10), allowing the recovery of methane, being a gas outlet and being connected to said gas collection and storage space (3), and said gas injector (7) and said inlet of anoxic gas to be treated (5) being two independent gas inlets in said reactor. 2. Biological methanation reactor according to claim 1, characterized in that the space (3) for collecting and storing gas is included in said tank, between the surface of said liquid or semi-liquid medium (2) and a lid (4) tank top. 3. Biological methanation reactor according to claim 1 or 2, characterized in that said inlet of anoxic gas to be treated (5) opens into said space (3) for collecting and storing gas. 4. Biological methanation reactor according to claim 1, 2 or 3, characterized in that said inlet of anoxic gas to be treated (5) and said outlet (10), allowing the recovery of methane in gaseous form, each comprise a check valve (50, 100). 5. Biological methanation reactor according to claim 1, 2, 3 or 4, characterized in that said inlet of anoxic gas to be treated (5) and said outlet (10), allowing the recovery of methane, each comprise a pump. 6. Biological methanation reactor according to any one of the preceding claims, characterized in that it comprises a stirring device (8, 9) capable of generating stirring in said liquid or semi-liquid medium (2). 7. Methanation reactor according to claim 6, characterized in that said stirrer device (8, 9) comprises at least one gas diffuser (8) immersed in the liquid or semi-liquid medium. 8. Methanation reactor according to claim 7, characterized in that said stirrer device (8, 9) comprises a recirculation pump (9) which is connected, on the one hand, to said space (3) for collecting and storing gas to extract gas therefrom and which is connected, on the other hand, to said gas diffuser (8) to supply said gas diffuser (8) with said gas extracted from said space (3) for collecting and storing gas. 9. Methanation reactor according to claim 7 or 8, characterized in that said at least one gas diffuser (8) is placed under said at least one tubular membrane (6). 10.Methanation reactor according to claim 6 or any one of claims 7 or 8 dependent on claim 6, characterized in that said stirrer device (8, 9) extends over substantially 0.05 m2 for LU501102 1m? liquid or semi-liquid medium contained in said tank. 11.Methanation reactor according to any one of the preceding claims, characterized in that it comprises at least one bundle of membranes (6) comprising at least two tubular membranes, the axes of said at least two tubular membranes, included in said at least at least one bundle of membranes (6), being substantially parallel to each other, each of said at least two tubular membranes of said at least one bundle of membranes (6) each comprising a membrane duct (60) supplied with pure dihydrogen by said injector gas (7). 12. Methanation reactor according to claim 11, characterized in that said gas injector (7) supplies pure dihydrogen to the conduit of each of said tubular membranes (6) by means of a set of connecting tubes (71), each connection tubes (71) being connected to a main injection duct (72). 13. Methanation reactor according to claim 11 or 12, characterized in that said tank (1) has a tank volume dedicated to the liquid or semi-liquid medium (2), in that said at least two membranes (6) of said at least one set of membranes have a total specific length at least equal to 1000 m per cubic meter of said volume dedicated to the liquid or semi-liquid medium and occupy a specific volume less than substantially 0.2 m3 for 1 m3 of said volume dedicated to the medium liquid or semi-liquid. 14. Methanation reactor according to any one of the preceding claims, characterized in that said membrane (6) comprises at least one silicone tube. 15. Methanation reactor according to any one of the preceding claims, characterized in that said membrane comprises several silicone tubes (61) aligned relative to each other and held by their tube ends in gas distributor elements (62 , 63), said gas distributor elements (62, 63) and the tube ends being embedded in a polyurethane or polyepoxide resin. 16. Methanation reactor according to any one of the preceding claims, characterized in that said conduit of said tubular membrane (6) is subjected to an internal pressure of between substantially LU501102 0.5 and 1.5 bar. 17. Methanation reactor according to any one of the preceding claims, characterized in that it comprises several levels each comprising at least one tubular membrane and in that the internal ducts of the tubular membranes (6) are subjected to different pressures. 18. Methanation reactor according to any one of the preceding claims, characterized in that it comprises a first device (31) flow meter - flow regulator which is connected to said dihydrogen injector (7). 19. Methanation reactor according to any one of the preceding claims, characterized in that it comprises a second device (32) flow meter - flow regulator connected to said inlet of anoxic gas to be treated (5). 20. Methanation reactor according to claim 18 or 19, characterized in that it comprises a module (30) for controlling one or the other or the two first and second devices (31, 32) flowmeters - regulators of debt. 21. Methanation reactor according to claim 3 or according to any one of the preceding claims dependent on claim 3, characterized in that it comprises a first apparatus (34) for analyzing the composition of the gas at said outlet (10 ) of gas and a second apparatus (33) for analyzing the composition of the gas at said inlet (5) of anoxic gas to be treated opening into said space (3) for collecting and storing gas. 22. Method for implementing a methanation reactor according to claims 8 and 21, associated with the characteristics of claims 18 to 20, characterized in that it comprises the following steps: - obtaining a first measurement of the composition of the anoxic gas to be treated to be treated at said inlet (5) of anoxic gas by means of said second analysis device (33), said first measurement of the composition of the anoxic gas to be treated comprising a concentration of carbon dioxide and/or carbon monoxide , - obtaining a second gas composition measurement at said gas outlet (10), by means of said first apparatus (34), said second gas composition measurement comprising a concentration of methane and dihydrogen, and LU501102 - comparison of said methane concentration with a predetermined threshold value of methane and comparison of said concentration of dihydrogen with a predetermined threshold value of dihydrogen, - comparison of said concentration of carbon dioxide and/or carbon monoxide with a predetermined threshold value of dihydrogen of carbon and/or carbon monoxide, and increase of a first setpoint value of said first device (31) flowmeter - flow regulator and/or decrease of a second setpoint value of said second device (32) flowmeter - regulator flow rate and/or increase in a service life of said recirculation pump (9) if said concentration of carbon dioxide and/or carbon monoxide is higher than said predetermined threshold value of carbon dioxide and/or monoxide of carbon, and vice versa, or decrease of said first setpoint value of said first device (31) flowmeter - flow regulator and/or increase of a second setpoint value of said second device (32) flowmeter - flow regulator and/or increasing a service life of said recirculation pump (9) if said dihydrogen concentration at said outlet (10) is greater than said one predetermined dihydrogen threshold value, and vice versa. 23. Computer program comprising instructions, which when executed by computer, implement all the steps of the method according to claim 22.