WO2024018162A1

WO2024018162A1 - Methane pyrolysis method with recirculation of the solid carbon produced

Info

Publication number: WO2024018162A1
Application number: PCT/FR2023/051136
Authority: WO
Inventors: Mathieu Haddad; Manuel HERNANDEZ-SHEK
Original assignee: Suez International
Priority date: 2022-07-22
Filing date: 2023-07-21
Publication date: 2024-01-25
Also published as: FR3138136A1

Abstract

Method for producing and recycling the solid carbon obtained from the pyrolysis of methane, comprising: (a) a step of supplying gas containing methane and pollutants; (b) a step of removing the pollutants from the gas from step (a) producing treated gas, in the course of which the gas is brought into contact with an adsorbent medium; (c) a step of pyrolyzing the treated gas from step (b) producing an effluent containing a dihydrogen-enriched gas phase and solid carbon; (d) a step of separating the effluent from step (c) in the course of which the solid carbon is separated from the dihydrogen-enriched gas phase; the method is characterized in that at least one portion of the solid carbon separated in step (d) is used as adsorbent medium in step (b).

Description

Methane pyrolysis process with recirculation of the solid carbon produced

[1] Field of the invention

[2] The invention relates to a process for recovering solid carbon produced during the pyrolysis of methane from gas, in particular biogas, produced in a wastewater treatment chain. The process includes a methane pyrolysis step to produce dihydrogen and solid carbon recirculated in the process.

[3] State of the art

[4] In general, wastewater treatment is a three-step process: a primary treatment step reducing the content of solids and/or organic matter likely to flocculate in the wastewater to be treated, a secondary treatment step making it possible to reduce the carbon and/or nitrogen and/or phosphorus content and a tertiary treatment step to further clean the water when discharged into a sensitive ecosystem or for reuse.

[5] The primary and secondary treatment stages produce sludge which is treated by anaerobic digestion to produce biogas, an energetic gas composed mainly of methane and carbon dioxide.

[6] The methane thus produced can then be pyrolyzed to produce dihydrogen and solid carbon.

[7] In the current energy and climate context, this reaction is increasingly interesting, because it allows on the one hand the production of carbon-free dihydrogen intended to be used as an energy vector in numerous applications (i.e. metallurgy, production ammonia, transport, etc.) and on the other hand the production of solid carbon that can be used in numerous applications (tires, shoe soles, rubber, etc.) while presenting an economic advantage.

[8] However, on an industrial scale, solid carbon is produced in too large quantities compared to current market demand, it is therefore necessary to study other ways of valorizing solid carbon.

[9] Other methane-containing gases can be pyrolyzed to produce dihydrogen, such as natural gas or syngas.

[10] In addition, the pyrolysis of gas resulting from methanization treatment, or any other gas containing methane, requires the elimination of pollutants such as hydrogen sulphide, volatile organic compounds and siloxanes, or even carbon dioxide oxides. sulfur and oxygenated compounds depending on the origin of the gas sent to pyrolysis. Currently, the elimination of these pollutants is carried out by oxidation in biological filters, by adsorption coupled with chemical oxidation, by absorption in the presence of a basic medium or by the use of filters containing activated carbon or oxide of iron. Despite the performance of these products, these materials are expensive and their use increases the cost of installation. [11] The invention aims to overcome at least partly the aforementioned drawbacks.

[12] Summary of the invention

[13] A first object of the invention relates to a process for the production and valorization of solid carbon resulting from the pyrolysis of methane, comprising:

(a) a step of supplying gas containing methane and pollutants, optionally carbon dioxide;

(b) a step of eliminating pollutants from the gas of step (a) producing treated gas, during which the gas is brought into contact with an adsorbent media capable of adsorbing at least part of the pollutants contained in gas;

(c) a step of pyrolysis of the treated gas of step (b) producing an effluent containing a gas phase enriched in dihydrogen and solid carbon, during which at least part of the methane contained in the treated gas is converted into dihydrogen and solid carbon;

(d) a step of separating the effluent from step (c) during which the solid carbon is separated from the gas phase enriched in dihydrogen;

(e) an optional step of shaping at least part of the solid carbon separated in step (d).

According to the invention, at least part of the solid carbon separated in step (d), optionally shaped in step (e), is used as adsorbent media in step (b).

[14] This sequence of steps makes it possible to produce solid carbon from the pyrolysis of methane and to recover it on site. The use of solid carbon as an adsorbent media makes it possible to avoid the use of adsorbents such as metal-organic structures also called MOFs (“metal-organic frameworks”) or zeolites which are more expensive. In addition, solid carbon is produced in large quantities on site, which eliminates transport costs and recycling of the adsorbent media. Its use also makes it possible to reduce the quantity of adsorbent necessary for the elimination of pollutants.

[15] Furthermore, upgraded solid carbon can contain particles with a magnetic iron core when produced by catalytic pyrolysis. So, unlike the use of a conventional adsorbent media such as activated carbon, the solid carbon used as an adsorbent media can be recovered more easily using a magnetic field when it is in an aqueous medium. The use of solid carbon as an adsorbent media therefore makes it possible to avoid the use of a filter at the outlet of step (b) of eliminating pollutants from the gas to recover the adsorbent media used.

[16] The process according to the invention thus makes it possible to produce dihydrogen and solid carbon, and to use the latter to purify the gas used for the production of dihydrogen and solid carbon, so that the overall costs of the process can be reduced and the solid carbon produced recovered. [17] Advantageously, step (d) of separating the solid carbon from the gaseous effluent can be chosen from a step (dl) of cyclonic separation, a step (d2) of separation by filtration or the succession of steps (dl ) and (d2).

[18] Advantageously, the gas supplied in step (a) can be chosen from biogas, synthesis gas and natural gas, alone or as a mixture. In a preferred embodiment, the gas is biogas.

[19] Advantageously, the process can comprise, between step (b) of elimination and step (c) of pyrolysis, a step (f) of separating the methane contained in the treated gas, during which the Methane present in the treated gas is separated from the rest of the gas before being sent to step (c). This allows a gas with a higher methane content to be sent to step (c).

[20] Advantageously, when the gas comprises carbon dioxide, the process can comprise, between step (b) of elimination and step (c) of pyrolysis, a step (f) of separation of methane and carbon dioxide. carbon dioxide contained in the treated gas, during which the carbon dioxide present in the treated gas is separated and removed.

[21] This optional step (f) aims to obtain, as an input to step (c) of pyrolysis, a flow containing the vast majority of methane. Thus the flow rate can be reduced since a greater quantity of methane enters step (c) and the outgoing stream containing the dihydrogen will have greater purity since it will only contain the methane not converted during step ( vs).

[22] Advantageously, the process can comprise, upstream of the supply step, a step (g) of gas production by anaerobic digestion of a sludge resulting from a wastewater treatment process. The gas obtained is then biogas.

[23] The sludge entering the anaerobic digestion step (g) is a sludge that may come from a primary treatment or secondary treatment step of a wastewater treatment process.

[24] Step (g) produces biogas which can thus be treated during steps (a), (b), (c), and optionally (f).

[25] In one embodiment, step (g) can be carried out in the presence of a biomass support and at least part of the solid carbon separated in step (d), optionally shaped using step (e), can then be used as a biomass support.

[26] In a digester, the sludge is broken down by the biomass present. The solid carbon used during this step will allow the biomass to form and develop around the solid carbon particles, the biomass can thus be maintained within the digester.

[27] Advantageously, the method may comprise a step of eliminating contaminants from treated water coming from a wastewater treatment process, during which the content of micropollutants in the treated water is reduced by in contact with at least part of the solid carbon separated in step (d), optionally formatted in step (e).

[28] This treatment process is intended to clean water of municipal or industrial origin so that it can be discharged into a sensitive ecosystem or to be reused.

[29] The contaminant removal stage most often occurs after two treatment stages called primary and secondary stages as described previously.

The contaminant removal stage is generally a tertiary treatment stage designed to further clean the water. This step may involve the removal of micropollutants by adsorption by an adsorbent media. The adsorbent media chosen is then solid carbon produced by pyrolysis, which is economical and eliminates transport costs if the solid carbon is produced close to the water treatment system.

[30] The water treatment process can optionally be the one providing the sludge to produce gas.

[31] Advantageously, the process can comprise a step of treating the odors of a gaseous effluent during which the gaseous effluent is brought into contact with an adsorbent media. At least part of the solid carbon separated in step (d), optionally shaped in step (e), is then used as adsorbent media during this odor treatment step.

[32] The odor treatment step can be used to, for example, treat the odors of an effluent leaving the water or sludge treatment process steps. The use of solid carbon during this process makes it possible to adsorb odors economically as mentioned and explained previously.

[33] Another object of the invention relates to an installation for the production and valorization of solid carbon resulting from the pyrolysis of methane for the implementation of the process according to the invention, comprising:

- a pipe (A) for supplying gas containing methane and pollutants, and optionally carbon dioxide; a gas pollutant elimination unit (B) capable of implementing step (b) producing treated gas, comprising an adsorbent media capable of adsorbing pollutants, said elimination unit (B) is connected to the conduct (A) of supply;

- a pyrolysis unit (C) of the treated gas capable of implementing step (c) producing an effluent containing a gas phase enriched in di-hydrogen and solid carbon, said pyrolysis unit (C) is connected to the disposal unit (B);

- a separation unit (D) of solid carbon from the gas phase enriched in dihydrogen of the effluent produced by the pyrolysis unit, said separation unit (D) being connected to the pyrolysis unit (C); an optional unit (E) for shaping solid carbon supplied with at least part of the solid carbon coming from the separation unit (D); and at least part of the solid carbon leaving the separation unit (D), optionally leaving the shaping unit (E), is used as adsorbent media in the elimination unit. pollutants.

[34] Advantageously, the separation unit (D) of the solid carbon from the gaseous effluent can be chosen from a cyclonic separation unit (Dl), a filtration separation unit (D2) or the succession of units (Dl ) and (D2).

[35] The supply pipe (A) can be connected to a gas source chosen from biogas, synthesis gas and natural gas, alone or in a mixture. This gas source can be a gas production unit or a storage capacity for this gas.

[36] The installation may in particular comprise a separation unit (E) capable of separating the methane present in the gas to be treated or treated, this separation unit being connected to the elimination unit (B) to receive it. the treated gas and to the pyrolysis unit (C) to supply it with a separated gas having a higher methane content.

[37] When the gas contains carbon dioxide, the installation may in particular comprise a separation unit (E) capable of separating and removing the carbon dioxide present in the treated gas, this separation unit being connected to the elimination unit (B) to receive the treated gas and to the pyrolysis unit (C) to supply it with a treated gas from which the carbon dioxide has been separated and removed.

[38] The installation may also include at least one of the following units:

- a unit (G) for producing gas by anaerobic digestion of a sludge from a water treatment installation connected on the one hand to the supply pipe (A) to send the gas produced there and on the other hand supplied with at least part of the solid carbon coming from the separation unit (D), optionally from the shaping unit (E); a unit for eliminating (H) contaminants from treated water coming from a wastewater treatment installation, said elimination unit being capable of reducing the content of micropollutants in the treated water and being connected to the separation unit (D), optionally to the shaping unit (E), to receive at least part of the solid carbon coming from the separation unit (D), optionally from the shaping unit ( E) ; a unit (I) for treating odors from a gaseous effluent comprising an adsorbent media, at least part of the solid carbon leaving the separation unit (D), optionally leaving the shaping unit (E) , being used as an adsorbent media in the odor treatment unit.

[39] The installation can advantageously comprise at least one circuit comprising at least one solid carbon storage device, such as a tank or the like, and at least one transport device, such as a train, truck or other, for the transport of solid carbon leaving the separation unit, or leaving the optional shaping unit, towards the at least one storage device, and the transport of the carbon solid from the at least one storage device to the pollutant elimination unit (B), and optionally to at least one unit chosen from the unit (G) for gas production by anaerobic digestion, the unit d elimination (H) of contaminants from treated water and the unit (I) for treating odors from a gaseous effluent.

[40] Description of figures

[41] Other particularities and advantages of the invention will emerge on reading the description given below of several particular embodiments of the invention, given for information only but not limitation, with reference to the appended drawings in which :

[42] Figure 1 is a schematic representation of the solid carbon production and recovery installation according to one embodiment of the invention.

[43] Figure 2 is a schematic representation of the production and recovery installation according to another embodiment of the invention.

[44] Figure 3 is a schematic representation of the production and recovery installation according to another embodiment of the invention.

[45] Detailed description of the invention

[46] Process

[47] The process according to the invention is a process for the production and valorization of solid carbon resulting from the pyrolysis of methane.

[48] The method comprises a step (a) of supplying gas containing carbon dioxide, methane and pollutants, a step (b) of removing pollutants from the gas of step (a) producing treated gas , a step (c) of pyrolysis of the treated gas from step (b) producing an effluent containing a gas phase enriched in dihydrogen and solid carbon, a step (d) of separating the effluent from step (c) during which the solid carbon is separated from the gas phase enriched in dihydrogen.

[49] The process can also include an optional step (e) of shaping at least part of the solid carbon separated in step (d).

[50] In this process, at least part of the solid carbon separated in step (d), optionally shaped in step (e), is used as adsorbent media during step (b).

[51] The configurations of the different stages of the process presented below can be combined depending on the treatment objective decided.

[52] Step (a) of gas supply

[53] Supply step (a) is a gas supply step which is a gaseous effluent containing methane and pollutants, and optionally carbon dioxide.

[54] Depending on its origin, the gas can contain up to 90% by volume of methane, preferably from 45 to 90%, from 45% to 80% or from 55 to 70% by volume of methane, which can be revalorized in particular to produce energy or dihydrogen by pyrolysis. [55] The gas supplied can come from different sources such as methanization or the fermentation of organic waste such as sludge, the gasification of carbonaceous material or be natural gas.

[56] Pollutants may include one or more of the following compounds:

- sulfur compounds: such as hydrogen sulphide (H2S) and sulfur oxides (SOx), or other sulfur compounds,

- volatile organic compounds (VOC),

- tars,

- halogenated compounds, such as hydrochloric acid (HCl) and hydrofluoric acid (HF), etc.,

- siloxanes.

[57] When the gas is biogas from methanization or fermentation, it may contain methane, carbon dioxide and pollutants. It can in particular contain approximately 45 to 80% by volume, in particular 55 to 70% by volume, of methane. Pollutants may include sulfur compounds, including hydrogen sulfide (H2S), volatile organic compounds, ammonia, siloxanes. Hydrocarbons and nitrogen gas may also be present.

[58] When the gas is synthesis gas, also called syngas, coming from the gasification of carbonaceous material, typically biomass, it may contain methane, carbon dioxide and pollutants. It generally typically includes methane, carbon monoxide (CO), hydrogen, carbon dioxide and dinitrogen. Syngas can notably contain up to 5% by volume of methane. It can also contain 5 to 15% by volume of carbon dioxide, 10 to 25% by volume of hydrogen, 30 to 50% by volume of dinitrogen, 15 to 30% by volume of carbon monoxide. Pollutants may include sulfur compounds (H2S, COS, CS2), ammonia, halogenated compounds or halogens (HCl, Cl,...), metals (sodium, potassium,...), tar .

[59] When the gas is natural gas it may contain methane and pollutants, and optionally carbon dioxide. Syngas can notably contain up to 90% by volume of methane. It may also contain other hydrocarbons containing 2 to 5 carbon atoms. Pollutants may include sulfur compounds, including H2S.

[60] Step (b) of removing pollutants from the gas

[61] The gas supplied in step (a) is then treated in a pollutant removal step then producing treated gas. During step (b), the gas is brought into contact with an adsorbent media capable of adsorbing at least part of the pollutants contained in the gas. These pollutants include sulfur compounds, and in particular hydrogen sulfide and/or sulfur oxides, volatile organic compounds, halogenated compounds, and in particular hydrochloric acid (HCl) and hydrofluoric acid (HF), and siloxanes, alone or in mixture. [62] In general, the use of biogas from methanization treatments requires the elimination of pollutants such as hydrogen sulfide (H2S) which can have concentrations between 50 and 8000 ppm _v , volatile organic compounds (VOCs) which can have concentrations between 50 and 250 ppm _v , and siloxanes which can have concentrations between 1 and 10 mg Si m ^-3 . In the specific case of thermal biogas valorization processes, these corrosive pollutants can damage cogeneration installations, and in the specific case of catalytic pyrolysis, they play a parasitic role and can inhibit the action of the catalyst. The other aforementioned pollutants present in biogas, syngas or natural gas can also prove problematic for the implementation of pyrolysis.

[63] The pollutants present in the gas are then eliminated, at least in part, by adsorption using filters filled with an adsorbent media. Removal is typically carried out in a fixed bed reactor filled with an adsorbent media. The gas to be treated is then injected through the bottom of the reactor and it will pass through the reactor while being in contact with the adsorbent media. Then the treated gas will exit through the top of the reactor. When the adsorbent media is no longer effective and has lost its adsorbent power, then the filter is changed.

[64] The invention is not limited to a single fixed bed reactor with a filter but in alternative embodiments, several fixed bed reactors can be had in parallel and/or in series.

[65] This step can also be implemented in a reactor containing a liquid phase containing the adsorbent media in which the gas to be purified is bubbled, or in a fluidized bed reactor or even in a washing tower.

[66] The adsorbent media used during this step is solid carbon produced during the pyrolysis step (c) or during the optional shaping step (f). The carbon is then recovered from this step (c) or (f) and it is injected as a gas filtering medium into the fixed bed reactors or other usable reactors or enclosures. The recovered solid carbon is generally stored before use since the use of the filter media is generally not continuous. Preferably, solid carbon is stored in a dry place, away from water, to prevent it from losing its adsorbent power by adsorbing the humidity present.

[67] Step (c) of pyrolysis of the treated gas

[68] The gas treated in step (b) is then pyrolyzed in a pyrolysis step (c), thus producing an effluent containing a gas phase enriched in dihydrogen and solid carbon. Depending on the composition of the gas, and in particular its CO2 content, the gas phase produced may also include CO2 and/or CO2 pyrolysis products. During stage (c) of pyrolysis, at least part of the methane contained in the treated gas is converted into dihydrogen and solid carbon.

[69] Methane pyrolysis is an endothermic reaction that results in the production of hydrogen and solid carbon according to the following chemical equation: CH4 -> 2H2+Csoiide. Methane pyrolysis is carried out at a temperature between between 750 and 2100 °C and at a pressure between 1 and 8 bars. The residence time is typically of the order of a second, for example from 1 to 4 seconds.

[70] The pyrolysis process may be a plasma or thermal pyrolysis process, for example carried out at a temperature of 1100 to 2000°C, or be a catalytic pyrolysis process, for example carried out at a temperature of approximately 900 °C and a pressure of approximately 8 bars. The catalysts used in the catalytic pyrolysis process are generally iron oxide granules (Fe2O3/Fe3O4) or molten metal catalysts with Nickel (Ni) and Bismuth (Bi) as presented in the following publication: Catalytic Hydrogen Production from Methane: A Review on Recent Progress and Prospect, Chen et al, Catalysts 2020, 10, 858.

[71] The pyrolysis step can for example be implemented in a reactor adapted to the pyrolysis of a gas. We can use a plasma reactor or a catalytic reactor such as a fluidized bed reactor, adapted to the treatment of a gas.

[72] The solid carbon produced during the pyrolysis of methane can present different structures, physicochemical properties and purity depending on the catalyst used and the pyrolysis operating conditions.

[73] Among the most common forms, solid carbon can be in the form of carbon black or “Carbon black” which comes from thermal pyrolysis carried out between 1100 and 2000 °C or even in the form of graphite when the process is carried out for example at a temperature of 900 °C, a pressure of 8 bars and with iron oxide granules (Fe2O3/Fe3O4). Graphite then forms around the catalyst, making it magnetic. These two forms are partially active and are therefore potentially usable in the treatment of water and air as a means of adsorption of pollutants. Although less effective than some adsorbents such as zeolites, the solid carbon formed is produced in large quantities by the pyrolysis reaction and can be used to change the filter more frequently at lower cost. Its use therefore reduces costs compared to the costs of purchasing and moving a more efficient adsorbent. In addition, the solid carbon produced and valorized during stage (c) of pyrolysis can advantageously come from a clean process: the methanization of organic waste or the gasification of biomass, it therefore does not come from a polluting process resulting from processing of fossil products.

[74] Step (d) of separation of the effluent from step (c)

[75] The effluent produced during step (c) is then sent to a separation step (d) during which the solid carbon is separated from the gas phase enriched in dihydrogen.

[76] The separation step (d) is chosen from a cyclonic separation step (dl), a filtration separation step (d2) or the succession of steps (dl) and (d2).

[77] Step (dl) is a cyclonic separation step. This step uses at least one separation cyclone to separate the solid carbon from the produced dihydrogen.

[78] The separation cyclone used is a device for separating a gas from the fine solid particles mixed with it. It imposes a rapid rotation on the gas which throws the particles to the sides of the cyclone by centrifugal force. These then fall into a bin thanks to the force of friction. The clean gas, freed from part of its particle charge, escapes through the outlet tube. It then forms a second vortex in the center of the first, in the opposite direction. This process cannot be applied to very fine particles because their mass is too low but is suitable for separating most solid carbon particles produced by pyrolysis.

[79] Cyclones are devices with essentially cylindrical-conical bodies in which the gyratory movement is obtained by causing the fluid to enter tangentially to the circumference, in the vicinity of the wall. Under the effect of centrifugal force, the solid particles caught in the vortex move towards the wall, lose their speed there through friction and fall into the lower part of the conical-shaped device, before exiting through the top of the cone. . The fluid follows the wall until near the top, and once free of particles, rises to the upper part to exit through an axial opening. Thus, for the separation to be effective, the time taken by a particle to reach the wall must be less than the average residence time of an element of fluid in the cyclone.

[80] Step (d2) is a filtration separation step during which the solid carbon particles are separated from the gaseous effluent by filtration. There are two principles of gaseous effluent filtration which are cake filtration and depth filtration.

[81] Cake filtration corresponds to surface filtration which implies that particles are retained mainly on the surface of a filter media forming a layer of solid particles which increases the efficiency or fineness of the particles retained. The gas stream containing the particles passes through a porous media which retains the particles, but allows the gas to pass. As filtration continues, a cake (of solid particles) builds up on the porous media. This cake has a complex pore structure determined by the nature of the solid carbon particles. This structure removes additional particles by simple sieving mechanism. When a specified cake thickness is reached, usually monitored by the loss of pressure around the filter media, the cake is removed before another filtration cycle begins. This type of filtration refers to the group of dust collectors using fabric, ceramic or metal filter media.

[82] Depth filtration, on the other hand, refers to a thicker or multi-layered filter media, forming a tortuous path to retain solid particles. This type of media ideally retains coarser dust on the surface and increasingly finer dust as the gas penetrates deeper into the media. The solid gas feed stream passes through a porous medium which retains solid particles, but allows gas to pass through. As the flow continues, dust particles accumulate in the filter media which gradually blocks it. When a loss of pressure determined on the filter media is reached, the filter media is usually replaced.

[83] At the end of filtration, the solid carbon captured by the filters can be recovered in the usual way, for example by vibration and/or circulation of a reverse flow of inert gas, for example dinitrogen.

[84] The succession of steps (dl) and (d2) makes it possible to obtain a dihydrogen having greater purity and also to recover a maximum of solid carbon formed. Thus, step (d2) of separation by filtration is generally placed after step (dl) of cyclonic separation to be able to recover the particles which have not been separated by the cyclone and in particular the particles having a small diameter.

[85] Once the solid carbon has been recovered during this step, at least part of this solid carbon can either be stored in a closed enclosure before use in the process according to the invention, preferably, the solid carbon is kept in a dry place protected from water, where the solid carbon can be recovered directly in another unit.

[86] The solid carbon produced during pyrolysis and thus separated can advantageously be used directly as an adsorbent media and/or biomass support, without the need to be shaped, and without the need for heat treatment. . This further reduces the costs associated with its use.

[87] In certain embodiments, shaping can be carried out, without however requiring heat treatment.

[88] Optional step (e) of shaping the solid carbon

[89] At least part of the solid carbon recovered during separation step (d) can optionally be shaped during step (f).

[90] The solid carbon shaping step is typically a granulation step also called pelletization.

[91] This step, as opposed to grinding technology, consists of assembling or agglomeration of fine solid particles in order to form larger elements such as spheres, briquettes or even cylindrical pellets. Preferably, the solid carbon is put in the form of cylindrical pellets.

[92] There are two main methods of granulation. The first method is wet granulation. During this method, the cohesion of the particles is obtained thanks to the addition of a liquid binder, most generally water but also molasses or chemical agents such as lignosulfonate, and thanks to mechanical action a suitable device such as a pelletizing plate, a granulator mixer, etc. For this method, no compression is carried out to ensure the granules hold together.

[93] The second method is dry granulation: the granules are obtained by compression, their cohesion thus being ensured by the combined effect of the reduction in the spacing of the particles and the increase in their surface area. contact. This granulation is carried out with or without the addition of binder. The methods of implementation are through briquetting presses for iron ores, for example, or even granulating presses with extrusion dies for fuel production, for example.

[94] The main advantages of granulation are densification of the material, which allows a reduction in storage or transport costs, ensures easier handling of the material, or even improves its flowability.

[95] Preferably, step (e) of shaping the solid carbon is carried out by a granulating press, that is to say by dry granulation.

[96] Once shaped during optional step (e), either the solid carbon is used directly or it is stored. Since the pelletization process is generally a batch process, the solid carbon leaving step (d) is typically stored before being shaped.

[97] The optional shaping can be adapted to the application of carbon black.

[98] For example, when used as a gas adsorbent media, before entering the pyrolysis reactor or during the treatment of odors from a gaseous effluent, particles of 2 to 8 mm can advantageously be used. in diameter, optionally impregnated with a basic solution containing for example NaOH or an acid, for example HCl or H2SO4 in order to improve the adsorption of pollutants such as H2S or NH3, but preferably without impregnation of a chemical compound.

[99] For example, in use for the treatment of liquids, for example as an adsorbent to eliminate micropollutants from water to be treated or as a biomass support for a digester, we can either use particles of 0, 5 to 2 mm in diameter in fixed bed filters, or use particles less than 100 micrometers for fluidized bed or bubbled systems.

[100] Optional step (f) of separation of methane, and optionally carbon dioxide, contained in the treated gas

[101] Between step (b) of eliminating pollutants and step (c) of pyrolysis, the process of production and valorization of solid carbon can also include a step (f) of separation of methane, and optionally of carbon dioxide, contained in the treated gas.

[102] This step thus makes it possible to concentrate the gas into methane and purify it in order to obtain a gas flow with a higher methane content before sending it to step (c).

[103] This step can be chosen from several gas separation processes, for example the pressure inversion adsorption process or the membrane separation process and/or from other separation and/or purification processes. Advantageously, this step can make it possible to separate and remove carbon dioxide and/or other contaminants present in the gas. [104] Pressure swing adsorption, also called "Pressure Swing Adsorption", is a process for separating gas mixtures during which the adsorption of a gas by a solid or a liquid alternately takes place. a given pressure, then its desorption at a lower pressure. It consists of removing a gas from a gas mixture, using its chemical affinity and its particular characteristics with respect to a solid material, an adsorbent exposed to a rigorously controlled pressure oscillation. Selective adsorption occurs through different equilibrium capacities (equilibrium adsorbent) or by differences in absorption rates (kinetic adsorbent). The pressure inversion adsorption technique thus uses solid adsorbents to capture carbon dioxide and thus obtain an effluent enriched in methane.

[105] Membrane separation consists of separating several compounds from a gas by sending a gaseous effluent through a module comprising a membrane. Depending on the difference in permeability of the membrane with respect to the compounds in the gaseous effluent, certain compounds will pass through the membrane more quickly while others will pass through it slowly. Thus, in the case of the invention, on one side or the other of the module, there will be different concentrations of methane, an effluent will be enriched in methane and will be used during step (c) of pyrolysis of the methane while the other effluent will be depleted in methane.

[106] Other possible separation and/or purification processes include:

[107] - chemical absorption processes using a selective solvent to absorb unwanted gases such as carbon dioxide (CO2), nitrogen (N2) and sulfur compounds, leaving methane unabsorbed in the gas stream ,

[108] - activated carbon adsorption processes using activated carbon to adsorb impurities such as CO2, sulfur compounds and volatile organic compounds, and allowing methane to pass through,

[109] - cryogenic processes in which the gas stream is cooled to very low temperatures to liquefy and separate unwanted components such as CO2 and water, leaving the methane in gaseous form,

[110] - processes using selective separation membranes to separate methane from other undesirable gases such as CO2, nitrogen and sulfur compounds depending on their size and permeability,

[H l] - adsorption processes on molecular sieves having a porous structure, capable of adsorbing large molecules such as CO2 and water, and allowing methane to pass through,

[112] - ion exchange processes using ion exchange resins to remove charged ions such as sulfate, chloride and ammonium ions, thereby reducing impurities in the gas stream,

[113] - cryogenic distillation processes using a combination of cooling and distillation to separate undesirable components such as CO2, water and sulfur compounds from methane, [114] - alternate hydrotr processes implementing chemical hydrogenation reactions to remove sulfur compounds and other impurities from the gas, producing a purer stream of methane.

[115] Optional step (g) of gas production by anaerobic digestion

[116] The solid carbon production and valorization process may include an optional step (g) of gas production by anaerobic digestion. This unit may be a unit present on the same site as the process according to the invention. Preferably, the optional step (g) is located upstream of the gas supply step (a) and it produces the gas used during step (a) and in the remainder of the process according to the invention.

[117] Anaerobic digestion or methanization corresponds to a cascade of biochemical reactions allowing methanogenic microorganisms to convert organic matter such as sludge present in a digester into gas corresponding mainly to a mixture of carbon dioxide and methane. The remaining materials are called digestate. The conditions for implementing this step (c), in particular the temperature, pH and residence time, can advantageously be chosen in order to maximize gas production.

[118] The sludge used in the digester is typically sludge coming from a primary treatment and/or secondary treatment stage of a wastewater treatment process. The primary treatment stage generally makes it possible to reduce the solids and/or organic matter content of the wastewater to be treated. This is typically a settling stage, possibly assisted by a prior addition of coagulant and flocculant, during which the wastewater is placed in a holding tank or a settling basin. The secondary treatment step, for its part, makes it possible to reduce the carbon and/or nitrogen and/or phosphorus content of the effluent having a reduced solids content leaving the first treatment step. During this stage, organic matter, nitrogen compounds and/or phosphorus compounds are assimilated or decomposed by aerobic and/or anaerobic and/or anoxia bacteria. It is therefore a biological treatment step, most often implemented in free culture reactors (so-called “activated sludge” process).

[119] In a digester, the sludge is broken down by the biomass present. A biomass support is generally used to allow biomass to form and grow around the particles of the support, the biomass can thus be maintained within the digester.

[120] In one embodiment, the biomass support corresponds to at least part of the solid carbon separated in step (d), optionally shaped in step (e).

[121] From the point of view of solid carbon, step (g) can be a continuous or discontinuous step. Preferably, it is a continuous step in which the solid carbon leaving step (d) is directly introduced into the digester progressively. as the solid carbon used leaves it.

[122] Optional step of removing contaminants from treated water

[123] In one embodiment, the solid carbon produced, preferably when containing a magnetized iron core, can be used for the removal of contaminants such as micropollutants in water. Thus, the process may include an optional step of eliminating contaminants from treated water coming from a wastewater treatment process, during which the content of micropollutants in the treated water is reduced.

[124] This step is designed to further clean water when it is released into a sensitive ecosystem or to reuse it.

[125] The optional contaminant removal step typically involves placing the water in a decanter containing a bed of adsorbent media. According to one embodiment of the invention, the adsorbent media is the solid carbon separated during step (d), optionally shaped during step (e). The water will pass through the bed of adsorbent media in which the adsorption of contaminants such as micropollutants or even organic matter takes place. Once the solid carbon is saturated with contaminants, it is removed from the pool and replaced. This step is a discontinuous step from the point of view of the adsorbent media because it must be saturated before replacing it. So, before use, solid carbon is generally stored in a dry place.

[126] At the output of the optional contaminant removal step, solid carbon can be recovered using a magnetic field. For example, using a magnetic field cyclone.

[127] Optional odor treatment step

[128] The solid carbon produced recovered during separation step (d) or optionally during shaping step (e) can also be used for odor treatment. Thus in one embodiment, the method can comprise a step of treating the odors of a gaseous effluent during which the gaseous effluent is brought into contact with an adsorbent media. The adsorbent media being the solid carbon recovered or optionally shaped.

[129] The odorous compounds to be treated are often sulfur compounds such as hydrogen sulfide but also nitrogen compounds such as ammonia or even acidic compounds. Legislation thus orders the emission of these odorous compounds to be limited so as not to disturb or annoy homes located around the installation.

[130] This step is typically a treatment of odors by adsorption on an adsorbent media on which the odorous compounds are trapped by adsorption. This process is recommended for installations with low flow rates and low polluting loads.

[131] The adsorbent media used is typically placed in filter cartridges through which the gas to be treated circulates. This process is a batch process, thus, the solid carbon produced is generally stored upstream in a dry location.

[132] Description of the installation

[133] In the various figures described below, the solid lines correspond to a continuous line in which the flow circulates continuously in the pipe, while the dotted lines mean that the flow circulates discontinuously in a circuit which may include a step of storing solid carbon in a storage device (tank or other) and a device for transporting solid carbon (train, truck, or other) to and from the storage device, not shown in the figures. The storage step is carried out in a storage unit comprising at least one enclosure allowing the solid carbon to be kept in a dry place. The different embodiments and their variants described with reference to the figures can be combined depending on the desired results.

[134] With reference to Figure 1, the installation 100 for producing and recovering solid carbon from the pyrolysis of methane comprises a gas supply pipe A, a pollutant elimination unit B capable of implementing step (b), a pyrolysis unit C capable of implementing step (c) and a separation unit D adapted to implement step (d) of the process.

[135] The gas pollutant elimination unit B comprises, for example, at least one fixed bed reactor capable of receiving an adsorbent media or any other suitable reactor. In an alternative embodiment, several fixed bed reactors in parallel and/or series can be installed. The elimination unit B is fluidly connected to the gas supply pipe A and it includes a pipe 1 for evacuating the treated gas.

[136] The pyrolysis unit C of the treated gas comprises at least one reactor capable of carrying out pyrolysis. In an alternative embodiment, several reactors in parallel and/or in series can be installed. The pyrolysis unit C is fluidly connected to the elimination unit B via the evacuation pipe 1 and it comprises a pipe 2 for evacuating an effluent containing a gas phase enriched in dihydrogen and solid carbon.

[137] The separation unit D of the effluent leaving unit C can be a cyclonic separation unit (Dl), a filtration separation unit (D2) or the succession of units (Dl) and (D2 ). In a particular embodiment, the cyclonic separation unit (Dl) comprises one or more cyclones in parallel and/or in series. Likewise, in another particular embodiment, the filtration separation unit (D2) comprises one or more filters in parallel and/or in series. The separation unit D is fluidly connected to the pyrolysis unit C via the evacuation line 2 and includes a circuit 3 for evacuating the solid carbon and a line 4 for evacuating the gas phase enriched with dihydrogen.

[138] With reference to Figure 1, at least part of the solid carbon included in the evacuation pipe 4 is sent to the elimination unit B to be used as adsorbent media via circuit 5.

[139] Figure 2 presents an embodiment of the installation, including in particular as an option, a separation unit F for implementing a separation between the elimination unit B and the pyrolysis unit C , and, optionally, a shaping unit E for implementing step (e) of shaping downstream of the separation unit D. The installation 200 thus comprises a pipe (A) supply of gas, a pollutant elimination unit B capable of implementing step (b), a pyrolysis unit C capable of implementing step (c) and a separation unit D adapted to implement implement step (d) of the process.

[140] Installation 200 further includes:

[141] - between unit B and unit C, the separation unit E capable of separating the methane present in the treated gas, and optionally of removing the carbon dioxide, and

[142] - downstream of the separation unit D, the optional unit E for shaping solid carbon capable of carrying out the optional step (e) of the process.

[143] Note that the installation could include only one of these optional units E and F.

[144] The separation unit F of the gas leaving unit B makes it possible to purify the gas in order to concentrate it into methane. In one embodiment, this unit F makes it possible to separate the carbon dioxide present from methane to obtain treated gas enriched in methane. The separation unit F is fluidly connected to the elimination unit B via the evacuation pipe 1 and comprises a pipe 19 for evacuating a gaseous effluent depleted in methane, for example enriched in carbon dioxide or in another component of the gas, and a pipe 6 for evacuating the treated gas enriched in methane, and depleted in carbon dioxide or in another component of the gas.

[145] The solid carbon shaping unit E leaving the separation unit D is a unit operating discontinuously, that is to say that the solid carbon does not enter continuously at a flow rate fixed in the unit (same for the output of this unit). The shaping unit E is connected to the separation unit D by an evacuation circuit 3 and includes a circuit 8 for evacuating the shaped solid carbon.

[146] With reference to Figure 2, circuit 8 means that at least part of the solid carbon shaped in unit E, all of it in the example shown, is sent to the elimination unit B to be used as an adsorbent media.

[147] Figure 3 shows another embodiment of the installation.

[148] The installation 300 shown firstly comprises a unit G for producing gas by anaerobic digestion of a sludge. The gas production unit G is connected to a pipe 9 for supplying a sludge from a water treatment installation 400 and the unit G is connected to the supply pipe A to send the gas there. product. The unit G is also supplied with at least part of the solid carbon coming from the separation unit (D), optionally from the shaping unit (E), via a circuit 10. The gas production unit G also includes a pipe 11 for evacuating sludge and solid carbon used.

[149] Gas supply line A is connected to unit B for eliminating gas pollutants. Elimination unit B includes a pipe 1 for evacuating the treated gas.

[150] Then, the optional separation unit E is here connected to unit B via evacuation pipe 1. Unit E also includes a pipe 19 for evacuating a gaseous effluent depleted in methane, and enriched in carbon dioxide or other gas component, and a pipe 6 for evacuating the treated gas enriched in methane and depleted in carbon dioxide or other gas component.

[151] The pyrolysis unit C, for its part, is connected to the optional unit E by the evacuation pipe 6. The unit C also includes an evacuation pipe 2 of an effluent containing a gas phase enriched with dihydrogen and solid carbon. Line 2 connects unit C to separation unit D. The separation unit D includes a circuit 3 for evacuating solid carbon and a pipe 4 for evacuating the gas phase enriched with dihydrogen.

[152] In a first variant, unit D includes a circuit 5-1 and 5-2 for recovering solid carbon. Circuit 5-1 supplies circuit 10 for supplying unit G with solid carbon and a circuit 12 for supplying unit B with solid carbon as adsorbent media. Circuit 5-2, for its part, supplies solid carbon to a circuit 13 for supplying an elimination unit H of contaminants from treated water and a circuit 14 for supplying a treatment unit I for odors of a gaseous effluent.

[153] In the example shown, the contaminant elimination unit H receives treated water coming from a wastewater treatment installation 400. Unit H thus comprises a pipe 15 for supplying treated water and a pipe 16 for evacuating water depleted in contaminants.

[154] The treatment unit I, whose adsorbent media is the solid carbon produced, comprises a pipe 17 for supplying a gaseous effluent comprising odorous compounds and a pipe 18 for evacuating a gaseous effluent depleted in compounds odorous.

[155] In a second variant, in combination or not with the first variant, at least part of the solid carbon leaving the unit D is shaped in the unit E, connected to the separation unit D by a circuit 3 of evacuation. Unit E also includes an 8-1 and 8-2 solid carbon recovery circuit. Circuit 8-1 supplies circuit 10 for supplying unit G with solid carbon and circuit 12 for supplying unit B with solid carbon as adsorbent media.

Circuit 8-2, for its part, supplies circuit 13 for supplying an elimination unit H of contaminants from treated water and circuit 14 for supplying a treatment unit I for odors from a gaseous effluent. [156] Preferably, the installation includes the solid carbon shaping unit E as well as its recovery circuit 8-1 and 8-2.

[157] In the embodiments previously described with reference to Figures 1-3, each of the circuits 3, 5, 5-1, 5-2, 8-1, 8-2, 10, 12, 13, 14 can comprise at least one storage device (tank or other) and at least one device for transporting solid carbon (train, truck, or other) to and from the storage device.

Claims

[Claim 1] Process for the production and valorization of solid carbon from the pyrolysis of methane, comprising:

(a) a step of supplying gas containing methane and pollutants;

(b) a step of eliminating pollutants from the gas of step (a) producing treated gas, during which the gas is brought into contact with an adsorbent media capable of adsorbing at least part of the pollutants contained in the gas ;

(d) a step of separating the effluent from step (c) chosen from a step (dl) of cyclonic separation, a step (d2) of separation by filtration or the succession of steps (dl) and (d2) , during which the solid carbon is separated from the gas phase enriched in dihydrogen;

(e) an optional step of shaping at least part of the solid carbon separated in step (d), the process is characterized in that at least part of the solid carbon separated in step (d) ), optionally shaped in step (e), is used as adsorbent media in step (b).

[Claim 2] Valorization process according to claim 1, characterized in that the gas supplied in step (a) is chosen from biogas, synthesis gas and natural gas, alone or as a mixture.

[Claim 3] Valorization process according to any one of claims 1 to 2, characterized in that the process comprises, between step (b) of elimination and step (c) of pyrolysis, a step (f) separation of the methane contained in the treated gas, during which the methane present in the treated gas is separated before being sent to step (c).

[Claim 4] Valorization process according to any one of claims 1 to 3, characterized in that the process comprises, upstream of the supply step, a step (g) of gas production by anaerobic digestion of a sludge from a wastewater treatment process.

[Claim 5] Valorization process according to claim 4, characterized in that step (g) is carried out in the presence of a biomass support and in that at least part of the solid carbon separated in step ( d), optionally shaped in step (e), is used as a biomass support.

[Claim 6] Valorization process according to any one of claims 1 to 5, characterized in that the process comprises a step of eliminating contaminants from treated water coming from a wastewater treatment process, during of which the micropollutant content of the treated water is reduced by bringing it into contact with at least part of the solid carbon separated in step (d), optionally shaped in step (e).

[Claim 7] Valorization process according to any one of claims 1 to 6, characterized in that the process comprises a step of treating the odors of a gaseous effluent during which the gaseous effluent is brought into contact with a adsorbent media, and in that at least part of the solid carbon separated in step (d), optionally shaped in step (e), is used as adsorbent media during this odor treatment step.

[Claim 8] Installation for the production and valorization of solid carbon resulting from the pyrolysis of methane for the implementation of the process according to any one of the preceding claims, comprising:

- a gas supply pipe (A) containing methane and pollutants;

- a gas pollutant elimination unit (B) capable of implementing step (b) producing treated gas, comprising an adsorbent media capable of adsorbing pollutants, said elimination unit

(B) is connected to the supply line (A);

- a pyrolysis unit (C) of the treated gas capable of implementing step (c) producing an effluent containing a gas phase enriched in dihydrogen and solid carbon, said pyrolysis unit

(C) is connected to the elimination unit (B);

- a separation unit (D) of solid carbon from the gas phase enriched in dihydrogen of the effluent produced by the pyrolysis unit, said separation unit (D) being connected to the pyrolysis unit (C) and chosen among a cyclonic separation unit (Dl), a filtration separation unit (D2) or the succession of units (Dl) and (D2); - an optional unit (E) for shaping solid carbon supplied with at least part of the solid carbon coming from the separation unit (D); the installation is characterized in that at least part of the solid carbon leaving the separation unit (D), optionally leaving the shaping unit (E), is used as adsorbent media in the unit elimination of pollutants.

[Claim 9] Installation according to claim 8, characterized in that it comprises a separation unit (F) capable of separating the methane present in the treated gas, this separation unit being connected to the unit (B) d elimination to receive the treated gas and to the pyrolysis unit (C) to supply it with a separated gas having a higher methane content.

[Claim 10] Installation according to any one of claims 8 or 9, characterized in that it comprises at least one of the following units:

- a unit (G) for producing gas by anaerobic digestion of a sludge from a water treatment installation connected on the one hand to the supply pipe (A) to send the gas produced there and on the other hand supplied with at least part of the solid carbon coming from the separation unit (D), optionally from the shaping unit (E); a unit (H) for eliminating contaminants from treated water coming from a wastewater treatment installation, said elimination unit being capable of reducing the content of micropollutants in the treated water and being connected to the separation unit (D), optionally to the shaping unit (E), to receive at least part of the solid carbon coming from the separation unit (D), optionally from the shaping unit ( E);

- a unit (I) for treating odors from a gaseous effluent comprising an adsorbent media, at least part of the solid carbon leaving the separation unit (D), optionally leaving the shaping unit (E ), being used as an adsorbent media in the odor treatment unit.