CATALYTIC METHANATION DEVICE WITH CATALYST CIRCULATION AND COOLING EXTERNAL TO THE METHANATION REACTOR

Abstract

TITLE OF THE INVENTION: CATALYTIC METHANATION DEVICE WITH CATALYST CIRCULATION AND COOLING EXTERNAL TO THE METHANATION REACTOR The methanation device (550) comprises: - a methanation reactor (558) having a single reaction fluidized bed (553) of catalytic methanation particles through which a reaction gas flow passes, - a means for extracting catalytic particles from the reaction bed, - a means for cooling (551) the catalyst particles extracted from the reaction bed, and - a means for injecting (555) the cooled catalytic particles into the reaction bed.The means for cooling the extracted catalyst particles comprises: - a secondary fluidized bed (568) for catalytic particles extracted from the reaction bed, - at least one injector (564 to 566) of a cooling fluid into the secondary fluidized bed, and - a solids-gas separator (552) configured to receive this gas from the cooling fluid and the catalytic particles transported in the cooling means, and to separate these catalytic particles. The means for injecting the cooled catalytic particles injects these catalytic particles, separated from the gas stream mixture, into the reaction bed. (See Figure 8 for abbreviations.)

Description

Title of the invention: CATALYTIC METHANATION DEVICE WITH CATALYST CIRCULATION AND COOLING EXTERNAL TO THE METHANATION REACTOR Technical field of the invention

[0001] The present invention relates to a catalytic methanation device with external catalyst circulation and cooling. In particular, it is applicable to reducing the complexity of a catalytic methanation reactor by eliminating the need for a heat exchanger integrated into the reactor or directly immersed in its catalytic (or reaction) layer. Prior art

[0002] The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section constitutes prior art simply because of its inclusion in this section.

[0003] In the fight against climate change and the reduction of greenhouse gas emissions, the production of low-carbon energy carriers is an essential alternative. The present invention relates to the production of synthetic methane by methanation of carbon monoxide, CO, and / or carbon dioxide, CO2. The following are examples of methanation: - Syngas (or synthesis gas or SNG) from the "Pyrogasification" process of biomass or waste or hydrocarbon materials. - of a mixture of carbon dioxide and dihydrogen (CO2 / H2) in a "Power-to-Methane" process, which consists of converting electricity ("power") into methane.

[0004] In the remainder of this document and for the sake of simplicity, the term "methane" shall refer to all types of synthetic methane produced by methanation of CO and / or CO2.

[0005] The first sector concerned by this invention is the pyrogasification sector. This family of processes makes it possible to produce numerous energy carriers (electricity, heat, liquid biofuels, chemicals, methane, hydrogen, etc.) while integrating into a circular economy approach. From low capacity (a few kWth to two MWth) to high capacity (greater than 100 MWth), these processes can also provide decentralized solutions for waste recovery. Indeed, only 30% of global waste is currently recovered (through recycling, incineration, or composting), with the remainder being buried in dedicated facilities or dumped in the environment, creating significant health and environmental problems. The first step in this process involves the thermal conversion of biomass or waste, which undergoes successive drying and devolatilization of organic matter to produce a carbonaceous residue (char), a synthesis gas (called syngas), and condensable or non-condensable compounds (tars). The carbonaceous residue can then be oxidized by the gasification agent (water vapor, air, oxygen, carbon dioxide) to produce a gas primarily composed of H2 and CO. Depending on its nature, this gasification agent may also react with the tars or the major gases.Thus, if it is water vapor (H2O), a WGS (Water Gas Shift) reaction occurs in the gasification reactor according to the following balanced reaction, called "WGS" (acronym for Water Gas Shift for water-gas conversion): . CO + H2O Û H2 + CO2 AG298K = - 41 kJ / mol (RI)

[0006] Char can also be extracted from the reactor for further processing, while syngas is produced by secondary and tertiary reactions of the pyrolysis products. Reactor pressure has little effect on this reaction; however, the equilibrium is strongly linked to the reactor temperature and the initial concentrations of the reactants. The gas resulting from these reactions is called syngas. It consists of a mixture of major gases (H2, CO, CO2, CH4, CxHy), condensable compounds (tars), particles (char, coke, elutriated bed material), and inorganic compounds (alkali metals, heavy metals, H2S, HCl, NH3, etc.). As a reminder, the term "elutriated" derives from Stokes' law. The term "elutriation" refers to a particle floating in a fluid flow. In process language, by extension, a particle is said to be "elutriated" when it is carried away by the flow of a fluid out of its initial reactor.

[0007] After the removal of impurities, the major gases can be transformed into numerous energy carriers, including methane. For the production of this methane, the H2 / CO concentration ratio in the syngas is a determining factor. At the outlet of the gasification reactor, this ratio generally does not exceed two.

[0008] Syngas can be converted into methane by the catalytic methanation reaction of CO, also known as the "Sabatier reaction". This catalytic reaction, which has rapid kinetics at the temperatures used, is characterized by very high exothermicity: CO + 3 H2 Û CH4 + H2O AG298K = -206 kJ / mol (R2)

[0009] To maximize CH4 production, H2 and CO should be in a stoichiometric ratio close to 3:1. This ratio is obtained by carrying out a complementary WGS reaction (RI). This can be performed prior to methanation in a dedicated reactor, in the presence of specific catalysts. It can also be carried out directly in the same reactor as the methanation, with an adapted catalyst. In both cases, this reaction requires the presence of steam, obtained, for example, by co-injection, with the syngas produced by pyrogasification. Even when maintaining the stoichiometric H2 / CO ratio, the reaction remains incomplete due to chemical equilibria that also depend on the operating conditions (temperature, pressure, etc.).

[0010] CO2 also present in the syngas or from an external source produces CH4 by CO2 methanation reaction: CO2 + 4 H2 Û CH4 + 2 H2O AG298K = -164 kJ / mol (R3)

[0011] Like reaction (R2), this reaction is strongly exothermic. To maximize CH4 production, H2 and CO2 should be in a stoichiometric ratio close to 4:1. As with CO methanation, even when maintaining the H2 / CO stoichiometric ratio, the reaction remains incomplete due to chemical equilibria.

[0012] Reaction (R3) can be carried out in conjunction with reaction (R2) in a single methanation reactor within a pyrogasification process if the H2 / (CO+CO2) ratio is sufficiently high (>7): this is then referred to as co-methanation. To achieve these high ratios, a prior WGS (RI) reaction or an external H2 supply may be necessary.

[0013] The CO2 (R3) methanation reaction can also be carried out independently, for example in the so-called "Power-to-Methane" process. This process involves utilizing CO2 streams (of industrial origin) by reacting them with hydrogen in a methanation device to form methane.

[0014] In both cases (Pyrogasification and Power-to-Methane), a final specification step separates certain constituents of the produced gas to obtain methane that meets the specifications for injection into the natural gas network or for use as methane for mobility. For example, in France, the CO2 content must be less than 2.5% and the H2 content must be less than 6% for injection into a natural gas network and less than 2% for use as natural gas for vehicles.

[0015] Managing the very high exothermicity of these reactions is the main challenge for implementing this process. To maximize conversion and protect the catalysts from hot spots that could lead to their deactivation by sintering, the reaction temperature must be precisely controlled at a specific temperature. The lowest possible temperature (within the catalyst's operating temperature range) is the determining factor. However, maintaining a relatively low reactor temperature (T<350°C), while the reaction releases significant thermal energy, requires a complex system of heat exchangers. Consequently, the complexity of the design and / or the increased number of heat exchangers leads to high investment costs. To manage the strong exothermicity of the reactions, other approaches have been proposed in the prior art, consisting of directly injecting liquid water into the catalytic layer (reaction layer) to benefit from cooling through evaporation.However, this leads to an increase in the partial pressure of water in the reaction medium, resulting in an unfavorable shift in chemical equilibria, leading to a decrease in conversion performance and an excess of H2 in the SNG, necessitating further downstream adjustment steps to meet more stringent specifications.

[0016] In existing isothermal methanation devices, the co-methanation of CO / CO2 of a synthesis gas cannot be envisaged, because the exothermic effects of the two hydrogenations would be combined and this would require immersed exchanger surfaces that are too large in relation to the available sections. Summary of the invention

[0017] The present invention aims to remedy all or part of these drawbacks.

[0018] The present invention relates to a new concept of a fluidized bed methanation reactor that can operate without an internal heat exchanger immersed directly in the chamber where the Sabatier reactions take place. The objective of this invention is to avoid the drawbacks of a methanation device comprising an immersed heat exchanger (a catalyst volume greater than that required by the chemical reactions alone, a limitation of the pressure at the reactor core) and / or of a methanation device comprising the injection of liquid water directly into the catalytic reaction zone, by controlling its temperature by a catalytic particle circulation system.

[0019] The implementation of the invention thus allows: - the use of higher pressure in an isothermal fluidized bed, thus promoting the methanation reaction, - the reduction in the mass of catalyst required for the conversion of syngas or H2 / CO2 mixture, because there is no longer a coupling between heat transfer and catalyst volume across the necessary exchange surface, - for each of the embodiments, the possibility of carrying out co-methanation of CO and CO2 by increasing the H2 content of the gas injected into the device Methanation. Although the exothermicity of the two hydrogenations is combined, the cooling of the reaction bed occurs outside the reaction zone and therefore does not limit the exothermicity of the reaction bed, and - in embodiments or variants, to use the latent heat of vaporization of water to cool the system by injecting water in the liquid state, without negative effect on the conversion, i.e. without shifting the thermodynamic equilibrium in a direction unfavorable to the production of methane and the excess of residual hydrogen.

[0020] To this end, the present invention relates to a methanation device comprising a methanation reactor having a single reaction fluidized bed of methanation catalytic particles through which a reaction gas stream passes, comprising syngas and water vapor and / or a mixture of hydrogen and carbon dioxide, between a reaction gas stream inlet and a synthetic natural gas (or SNG) outlet, the device further comprising: - a means of extracting catalytic particles from the reaction bed, - a means of cooling the catalyst particles extracted from the reaction bed, and - a means for injecting the cooled catalytic particles into the reaction bed; a device in which the means for cooling the extracted catalyst particles comprises: - a secondary fluidized bed of catalytic particles extracted from the reaction bed, - at least one injector of a coolant in the secondary fluidized bed, configured so that, downstream of each coolant injector, in the direction of gas flow, the gas flow velocity is greater than the terminal settling velocity of the catalytic particles and puts the catalytic particles into a transported fluidization regime, and - a solids and gas separator configured to receive this gas from the cooling fluid and the catalytic particles transported in the cooling medium, and to separate these catalytic particles, the means of injecting the cooled catalytic particles injecting these catalytic particles, separated from the gas stream, into the reaction bed.

[0021] In optional embodiments, at least one said injector of a cooling fluid in the secondary fluidized bed is a cooling fluid injector comprising SNG, nitrogen or carbon dioxide.

[0022] In optional embodiments, the device of the invention includes at least one coolant fluid injector comprising water in liquid form.

[0023] In optional embodiments, the device of the invention comprises a temperature sensor for the reaction bed and a means for controlling the flow rate of cooling fluid in at least one fluid injector depending on the temperature of the reaction bed.

[0024] In optional embodiments, the means for extracting catalytic particles from the reaction bed comprises an inclined channel or a siphon connecting the reaction fluidized bed and the secondary bed.

[0025] In optional embodiments, the means for injecting the cooled catalytic particles into the reaction bed comprises an inclined channel or a siphon opening into the methanation reactor.

[0026] In optional embodiments, the methanation reactor surrounds the cooling reactor, a wall separating the secondary fluidized bed from the reaction fluidized bed, the secondary fluidized bed having a transported operating zone extending above said wall.

[0027] In optional embodiments, the device that is the subject of the invention further comprises: - at least one gas injector in the reaction bed, configured so that, downstream of this injector, in the direction of gas flow, the gas flow velocity is greater than the terminal settling velocity of the catalytic particles and puts the catalytic particles into a transported fluidization regime, - a solids and gas separator configured to receive the gas stream and the transported catalytic particles and to separate these catalytic particles from the gas stream and - an injection channel into the secondary bed of catalytic particles separated from the gas flow.

[0028] In optional embodiments, the gas injector in the reaction bed is configured to inject into the reaction bed a portion of the gas stream separated by the solids and gas separator.

[0029] In optional embodiments, the device of the invention includes a temperature sensor of the gas circulating in the gas injector in the reaction bed and a means of controlling the gas flow in this gas injector as a function of the temperature of the gas circulating in this gas injector.

[0030] In optional embodiments, the device of the invention includes a temperature sensor of the reaction bed and a means of controlling the gas flow in the gas injector in the reaction bed as a function of the temperature of the reaction bed.

[0031] In optional embodiments, the surface area of ​​the methanation reactor cross-section perpendicular to the direction of the gas flow decreases in the direction of this gas flow, the decrease in this surface area causing an increase in the gas flow velocity at least until this velocity is greater than the velocity terminal of falling catalytic particles and puts catalytic particles into fluidization regime transported to the extraction means, the device further comprising a solids and gas separator configured to receive the gas stream and the transported catalytic particles and to separate these catalytic particles from this gas stream to inject them into the secondary bed. Brief description of the figures

[0032] Other advantages, purposes and features of the present invention will become apparent from the following description, given for explanatory purposes and in no way limiting the effect of the accompanying drawings, in which: [Fig. 1] represents, in the form of a graph, hydrogen content as a function of methanation pressure, [Fig.2] schematically represents a first variant of a first embodiment of a catalytic methanation device of the invention, [Fig.3] schematically represents a second variant of the first embodiment of a catalytic methanation device of the invention, [Fig.4] schematically represents a first type of heat exchanger in the device illustrated in [Fig.2] or [Fig.3], [Fig.5] schematically represents a second type of heat exchanger in the device illustrated in [Fig.2] or [Fig.3], [Fig.6] schematically represents the device illustrated in [Fig.2] or [Fig.3] equipped with a reactor of particularly advantageous geometry, [Fig.7] schematically represents a FICFB-type steam pyrogasifier, [Fig.8] schematically represents a second embodiment of a catalytic methanation device that is the subject of the invention, [Fig.9] schematically represents a first variant of the second embodiment of a catalytic methanation device that is the subject of the invention, and [Fig. 10] schematically represents a second variant of the second embodiment of a catalytic methanation device that is the subject of the invention. Detailed description

[0033] The present description is given by way of non-limiting grammar, each feature of an embodiment being able to be advantageously combined with any other feature of any other embodiment.

[0034] It should be noted from the outset that the figures are not to scale.

[0035] As can be understood from reading the present description, various concepts Inventive features may be implemented by one or more methods or devices described below, several examples of which are provided here. The actions or steps carried out in implementing the method or device may be ordered in any appropriate manner. Consequently, it is possible to construct embodiments in which the actions or steps are executed in a different order than illustrated, which may include the execution of certain acts simultaneously, even if they are presented as sequential acts in the illustrated embodiments.

[0036] The expression "and / or", as used in this application, shall be understood as meaning "either or both" of the elements thus joined, that is to say, elements which are present conjunctively in some cases and disjunctively in others. The multiple elements listed with "and / or" shall be interpreted in the same way, that is to say, "one or more" of the elements thus joined. Other elements may possibly be present, other than the elements specifically identified by the "and / or" clause, whether or not they are related to those specifically identified elements.Thus, by way of non-limiting example, a reference to "A and / or B", when used in conjunction with an open language such as "including", may refer, in one embodiment, to A only (possibly including elements other than B); in another embodiment, to B only (possibly including elements other than A); in yet another embodiment, to A and B (possibly including other elements); etc.

[0037] As used in this patent application, the expression "at least one," with reference to a list of one or more elements, is to be understood as meaning at least one element chosen from one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the expression "at least one" refers, whether or not they are related to those specifically identified elements.Thus, by way of non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or, equivalently, "at least one of A and / or B") may refer, in one embodiment, to at least one, possibly including more than one, A, without B present (and possibly including elements other than B); in another embodiment, to at least one, possibly including more than one, B, without A present (and possibly including elements other than A); in yet another embodiment, to at least one, possibly including more than one, A, and at least one, possibly including more than one, B (and possibly including other elements); etc.

[0038] In this application, all transitional expressions such as "comprising", "including", "carrying", "having", "containing", "implying", "holding", "composed of", and others, shall be understood as being open-ended, that is to say as meaning including, but not limited to. Only the transitory expressions "consisting of" and "consisting essentially of" should be understood as closed or semi-closed transitory expressions, respectively.

[0039] The different embodiments of the methanation device of the invention described below are equally applicable to the pyrogasification process of hydrocarbon materials for the production of methane by the hydrogenation of CO and / or CO2, and to the power-to-methane process for the production of e-methane by the hydrogenation of CO2.

[0040] Each embodiment of the invention can be used to perform co-methanation of CO and CO2 by increasing the H2 content of the gas injected into the methanation device. This is an advantage of the invention: in existing isothermal devices, the co-methanation of CO / CO2 from a synthesis gas cannot be considered, because the exothermic effects of the two hydrogenations would be combined, and this would require excessively large submerged heat exchanger surfaces relative to the available cross-sections. In the present invention, this limitation is overcome since the cooling of the solid takes place outside the reaction zone.

[0041] Throughout the description, the term "dense" qualifying a fluidized bed means "dense or bubbling".

[0042] The methanation device of the invention implements a fluidized bed methanation reactor that can operate without an internal heat exchanger, and a circulation of catalytic particles and their cooling outside the reactive zone. As described above, the invention allows the use of higher pressure in an isothermal fluidized bed, thus promoting the methanation reaction and requiring a smaller quantity of catalyst. This offers an economic advantage in view of the cost of the catalyst required per MWh of SNG produced and reduces the environmental footprint, particularly that related to mining prior to catalyst production.

[0043] Being able to operate the reactor at higher pressures constitutes a considerable performance advantage. The conversion to methane is improved, leading to higher synthetic natural gas (SNG) production. Furthermore, the quality of the SNG exiting the reactor is better, with a lower residual H2 content, which contributes to simplifying the specification adjustment steps before injection into the networks. Figure 1 shows, in the form of a graph, the effect of the methanation reaction pressure on the residual hydrogen content in the SNG. These values ​​were calculated for a methanation temperature of 300°C in CO2 methanation mode. Operating the reactor at relatively low pressure results in a relatively high residual H2 content (2.14% at two bar, for example). The present invention, by eliminating the need for an internal heat exchanger, allows for an increase in reaction pressure. At 25 bar, for example, the residual H2 is only 0.58%, a 73% reduction compared to the value obtained at two bar. Furthermore, this ability to operate at higher pressures reduces the compression forces required for injecting SNG into the gas network. In addition, it allows for the use of a smaller methanation reactor for the same SNG production.

[0044] The first embodiment (Figures 2 to 6) has a circulating fluidized bed (CFB) catalytic reactor. The second embodiment (Figures 7 to 10) has a single- and dual-fluidized bed (DFB) catalytic reactor. Throughout the following description, valves, pumps, and compressors or blowers controlled by temperature sensors constitute means for controlling the flow of a fluid. Of course, other types of fluid flow control means can be substituted for them.

[0045] Circulating fluidized bed catalytic methanation reactor

[0046] The circulating fluidized bed (CFB) is a technology generally implemented for the combustion or thermal treatment (pyrogasification) of solid fuels (biomass, coal, waste, etc.). Unlike conventional dense or bubbling fluidized beds, which have a freeboard zone to reduce the entrainment of solids (particularly fluidized bed particles, char, ash) from the conversion zone, the CFB allows operation at higher speeds to achieve significant heat recovery efficiencies. However, these higher speeds inherently lead to the entrainment of some of the solids contained in the conversion zone and sometimes to incomplete conversions.To overcome this problem and increase conversion efficiency, it is known to integrate the recovery of the eluted solid (char and bed material) through equipment such as cyclones, filters, or disengagement chambers. After separation, the solid returns to the fluidized bed constituting the combustion chamber or the reactive zone.

[0047] Unlike the CFB, the purpose of the first embodiment of the methanation device of the invention is not to limit losses by elutriation but to take advantage of the intentionally induced elutriation to remove heat from the catalytic solid resulting from the conversion reactions outside the methanation reactor. The first embodiment of the methanation device of the invention incorporates physical principles of the CFB in order to control the very high exothermicity of the hydrogenation reactions (here, the methanation of CO2 or a syngas, a gaseous mixture comprising at least H2, CO, and CO2). In the case of CO / CO2 co-methanation, a single isothermal or nearly isothermal reaction zone is obtained, the temperature of which is controlled by cooling catalytic particles outside the methanation reactor. Thus, the catalyst not only promotes conversion under the conditions generally used (e.g., T < 350°C and P < 80 bar), but also plays an important role as a heat transfer fluid, extracting heat from the single reaction zone in the absence of a heat exchanger, which can sometimes be limiting in terms of size, particularly at high operating pressures.

[0048] Figures 2 and 3 present the schematic diagrams of two variants of the first embodiment of the catalytic methanation device which is the subject of the invention.

[0049] In both configurations, the reactive gas (syngas or H2 / CO2 mixture or syngas containing H2 / CO / CO2), with or without steam, is injected through an inlet pipe 512 at the bottom of a methanation reactor 501 via a diffuser 502. The velocity of the reactive gas in the reactor 501 is preferably between two and ten times the minimum fluidization velocity of the catalyst under the prevailing operating conditions. Under these conditions, the bottom of the reactor consists of a dense or bubbling fluidized bed 503.

[0050] From a predetermined height 504 in the dense or bubbling fluidized bed 503, an injection (possibly staged at several heights in the reactor) of a fluid is carried out through at least one fluid injection inlet 505.

[0051] The role of this injection is to increase the total gas flow rate to achieve velocities exceeding the terminal settling velocity of the catalytic particles, thereby causing the transport of these particles through zone 506. In the following description, a fluidized bed in transported flow is referred to as a "riser". The gas injection into the reaction bed is configured so that, downstream of the injection inlet 505, in the direction of gas flow, the gas flow velocity exceeds the terminal settling velocity of the catalytic particles, thus placing the catalytic particles in transported fluidization.

[0052] For example, the injected fluid may be SNG exiting reactor 501 and resulting from the conversion of the gas entering it.

[0053] If the injected flux is cold, its injection contributes to the cooling of the catalytic particles during their transport.

[0054] The injection of this fluid is carried out through at least one inlet 505 from a height 504. This height is defined such that the volume of catalyst located upstream of the inlet 505 allows conversion at thermochemical equilibrium under the operating conditions of Pressure and Temperature of the single reaction zone 503. The height (or volume) of catalyst must therefore be sufficient to allow maximum conversion of the syngas, corresponding to what is imposed by the equilibrium chemical. For example, for commercial Ni / Al2O3 type catalysts, a Volumetric Hourly (WH) between 3,000 h 1 and 100,000 h preferably between 10,000 h 1 and 50,000 h 1 and even more preferably between 15,000 h 1 and 25,000 h 1 allows to reach, in the 503 zone, a conversion to thermochemical equilibrium of the reactions involved.

[0055] The injection rate through inlet 505 of this transport fluid is generally a function of the characteristics of the catalyst used. The lower the density and particle size of the catalyst, the lower the required flow rate of transport gas.

[0056] Once in transport mode, the catalytic particles leave the zone (or riser) 506 via a pipe 507 to feed a solids-gas separator 508 (for example, a cyclone separator, a filter separator, or a disengagement volume separator that reduces the gas velocity below the terminal settling velocity of the solid particles, thus causing their gravitational separation from the gas stream that transported them to this separation zone). From this separator, the gas, almost free of catalytic particles, is sent to a device 514 that performs steps downstream of the methanation stage (cooling, compression, optionally separation of H2O, H2O+CO2, H2O+CO2+H2, and adjustment to injection specifications for the networks, etc.). The catalytic particles recovered by the separator 508 are cooled by a cooler 509 to a temperature TIS1 detected by a temperature sensor 519 ([Fig. 2]).The cooler 509 includes, for example, a solid / fluid heat exchanger and / or a coolant injector. Then the catalytic particles cooled to temperature TIS1 return to the dense or bubbling part 503 of the fluidized bed, via a pipe 510.

[0057] Thus, the continuous extraction of hot catalytic particles and their return, once cooled, allows for quasi-isothermal control of the temperature of the reaction zone 503 and thereby promotes maximum conversion of the syngas or H2 / CO2 mixture entering the reactor 501 through an inlet 512, in a single step. The temperature of the dense bed 503 is a function of the flow rate of the cooled catalytic particles and their temperature TIS1.

[0058] Thanks to this circulation of catalytic particles, the heat produced by the methanation reactions in reactor 501 is continuously released from reactor 501 to be transferred by direct or indirect convection to a secondary fluid in the cooler 509.

[0059] Figures 4 and 5 show two alternative solutions for cooling the solid (catalytic particles) to a temperature TIS1 (areas outlined with dashed lines). In the first solution, shown in [Fig. 4], the cooler 509 is a shell-and-tube heat exchanger 511 in which a cold fluid circulates through the tubes while the The solid from the separator 508 passes into the calender (the reverse is also possible). In the second solution, shown in [Fig. 5], the heat exchanger is a dense or bubbling fluidized bed 521 supplied with a cold fluid (e.g., N2, CO2, SNG). As it passes through the fluidized bed 521, this cooling fluid is heated by contact with the catalytic particles.

[0060] The temperature TIS1 of the cooled catalytic particles can be adjusted by controlling the flow rate of the cooling fluid, based on the measured temperature. This flow control can be achieved by a valve 513 controlled by the sensor 519 measuring the temperature of the catalytic particles at the outlet of the cooler 509, as shown in [Fig. 2]. Alternatively, this control of the cooling fluid flow rate can be achieved by a valve 513 controlled based on the temperature of the fluidized bed 503 measured by a sensor 522, as illustrated in [Fig. 3].

[0061] Beyond the principle of the overall arrangement of the main elements constituting the present invention, Figures 2 and 3 show two methods of controlling the temperature of the reaction zone 503. The first, illustrated in [Fig. 2], consists of regulating the temperature of the reaction zone 503 by adjusting the flow rate of fluid injected through the inlet 505, between the dense fluidized bed 503 and the zone 506, while the temperature of the solid at the outlet of the cooler 509 is fixed. [Fig. 2] thus shows, on a gas line 515 exiting the device 514 and leading to the injection inlet 505, a valve 516. The flow rate through this valve 516 is controlled according to an increasing function of the temperature measured by a sensor 517 in the dense fluidized bed 503.

[0062] In this first mode of temperature control of the single reaction zone 503, an increase in the gas flow rate through the inlet 505 increases the circulation rate of solid catalytic particles. Thus, at equal exothermicity and temperature TIS1, the temperature of the reaction zone 503 decreases when these flow rates increase. Conversely, with a decrease in the gas flow rate through the inlet 505, at equal exothermicity and temperature TIS1, the temperature of the reaction zone 503 increases, due to a decrease in the circulation rate of the catalytic particles. Unless the surface area of ​​the methanation reactor cross-section at the level of the dense zone surface of the fluidized bed is sufficiently reduced, as shown opposite [Fig.6], a minimum gas flow rate through inlet 505 is required and must allow the transport of catalytic particles, i.e., ensure a gas flow velocity in zone 506 greater than the terminal settling velocity of the catalytic particles (and preferably less than twice this velocity). The corresponding flow rate (or velocity) is a function of the physico-chemical characteristics (composition, particle size, density, size and shape, i.e. i.e. sphericity) of the catalytic particles used and of the geometry of reactor 501.

[0063] The second method of regulating the temperature of the single reaction zone 503 consists of adjusting the temperature TIS1 of the cooled catalytic particles, while the flow rate of the transport gas through the inlet 505 is fixed. The temperature TIS1 is modulated by varying the flow rate of the cooling fluid circulating inside the cooler 509. Thus, this flow rate of cooling fluid circulating in the cooler 509 is controlled by the temperature of the reaction zone 503, via the temperature sensor 522 [Fig. 3] and the valve 513, which is controlled according to the temperature of the fluidized bed 503.

[0064] These two modes of regulation can be implemented independently or in combination.

[0065] As mentioned previously, the temperature control of the single reaction zone 503 depends on the flow rate of the catalytic particles and their return temperature TIS1 in the methanation reactor after cooling. The value of the catalytic particle flow rate is directly correlated to the physical characteristics of the solid catalytic particles (density, particle size, and shape) and to the velocity reached in zone 506. Thus, one way to increase the flow rate of the solid catalytic particles is to increase, for example, the flow rate of transport gas injected through inlet 505, between the dense fluidized bed 503 and zone 506. However, this injection has the effect of modifying the composition of the SNG exiting reactor 501.In order to reduce these effects and have a controlled composition of the SNG solely dependent on the temperature of the reaction zone 503, the composition of the syngas feed (or H2 / CO2 ratio) at the inlet 512 and the operating pressure of zone 503, preferably, the flow rate of the injection through the inlet 505 is limited so as to keep the velocity through zone 506 less than twice the terminal free fall velocity of the catalytic particles.

[0066] Figure 6 shows a design of a reactor 526 implemented in a variant 525 of the device of the invention. In the reactor 526, an appropriate reduction in the cross-section of the transport zone is achieved. In other words, the methanation reactor has a cross-section perpendicular to the direction of the gas flow located, in the direction of gas flow, downstream of the gas injection inlet 505, the surface area of ​​which is smaller than the surface area of ​​a cross-section perpendicular to the direction of the gas flow located upstream of the gas injector.

[0067] By this means, the gas flow rate through inlet 505, required to ensure transport, is reduced, or even eliminated. Thus, for a given syngas (or H2 / CO2) capacity, the reduction in the surface area of ​​the horizontal cross-section of the transport zone (related to its diameter, in the case of a cylindrical zone) makes it possible to obtain 1.2 to 2.5 times the The terminal settling velocity of the catalytic particles used results in a reduced requirement for the gas flow rate through inlet 505. In this case, the temperature regulation of the reaction zone 503 is entirely controlled by the capacity of the cooler 509 to cool the catalytic solid before its return to the dense fluidized bed 503. Another advantage associated with this reactor design concerns the design of the equipment located downstream of the pipeline 507. Indeed, the reduction, or complete elimination, of the gas flow rate through inlet 505 inherently leads to smaller equipment sizes up to the point of gas intake, if this intake point is located downstream of the methanation reactor.

[0068] It is noted that the methanation device 525 illustrated in [Fig.6] can operate without gas injection through the inlet 505, because the shape of the methanation reactor 526 implies an increase in the velocity of the gas flow towards the top of the methanation reactor 526, which makes it possible to exceed the terminal falling velocity of the catalytic particles.

[0069] The second embodiment of the methanation device of the invention is based on a general principle known as dual fluidized beds (hereafter referred to as DFB, for Dual Fluidized Bed). Several DFB reactors have been developed for different applications (combustion, pyrogasification, hydrocarbon cracking), under the names FICFB (acronym for "Fast Internally Circulating Fluidized Bed"), a-DFB, MILENA, FERCO Silvagas, registered trademarks.

[0070] The second embodiment uses a double fluidized bed, but adapts it for a methanation application of syngas or an H2 / CO2 mixture. The usual operation of these different reactors is described below.

[0071] First, a detailed description of the FICFB reactor in its usual operation is given, then the modifications to be made to adapt this reactor to the application of catalytic methanation will be presented in a preferred, but non-exclusive, configuration.

[0072] The FICFB is generally used, like the CFB, in the field of pyrogasification of solid carbonaceous materials (biomass, waste, etc.) for the production of an N2-free syngas for downstream use in methanation or any other process where the presence of N2 is undesirable. Figure 7 shows a schematic diagram of the FICFB steam pyrogasifier.

[0073] The main equipment constituting the FICFB pyrogasification reactor 540 is a dense / boiling fluidized bed gasifier 543, a transported fluidized bed combustor 541, a solids and fume separator 542 and two pipes 544 and 545 allowing the circulation of the bed material between the two reaction zones (gasifier 543 and combustor 541).

[0074] In this system, the solid fuel to be converted (biomass, waste, etc.) feeds, via an inlet 539, a dense / boiling fluidized bed 543 containing a solid (sand, olivine, dolomite, etc.) at around 800-900°C. This bed 543 is fluidized by an injection of steam 546, which also serves as a gasifying agent. During its conversion, the solid fuel undergoes high-temperature heat treatment and secondary reactions to produce a nitrogen-free syngas (N2) and a char (carbonaceous residue) resulting from the incomplete conversion of the solid input.

[0075] Since pyrogasification reactions are highly endothermic (they require a heat input), the heat contained in the bed material 543 is consumed. To compensate for the drop in enthalpy contained in the bed material 543, the latter is transferred mixed with the residual char to the combustor 541, into which air is injected. Upon contact with atmospheric oxygen, combustion of the char is initiated, releasing heat that reheats the bed material before its return to the gasifier 543. In industrial operation, the temperature of the gasifier 543 is controlled by the combustion (char and recirculated syngas) carried out within the fluidized bed in the transported flow regime of the combustor 541.

[0076] Air or the oxidation and transport agent from a source 547 is injected at the bottom of the combustor 541. A fluidizing gas can be injected through a pipe 548 into the return pipe 545 of the solid material to the gasifier 543. The syngas exits the gasifier 543 through an outlet 549.

[0077] In conclusion, in the original application of the FICFB, the gasifier 543 constitutes a cold pole consuming heat and the combustor 541 a hot pole producing heat.

[0078] On the contrary, in the double fluidized bed catalytic methanation device 550 shown in [Fig.8], the methanation reactor is exothermic and the transported fluidized bed catalyst cooling reactor (“riser”) serves to cool the catalytic particles coming from and returning to the methanation reactor 558. Thus, the heat produced by the methanation is extracted from the single reaction zone 553 to be released by the solid catalytic particles transported in an external zone without implanting an exchanger immersed in the single reaction zone 553 of the methanation reactor 558.

[0079] In [Fig.8], in the device 550, we observe a methanation reactor 558 comprising a dense or bubbling fluidized bed 553 through which a reaction flow enters via the inlet 556 at the bottom of the reactor, a cooling reactor 551 with a fluidized bed catalyst in transported regime.

[0080] In this device 550, the reaction flow, syngas and / or mixture of CO2 and H2, optionally supplemented with steam, feeds the dense or bubbling fluidized bed 553 containing a catalyst. The velocity of the reaction gas flow is The flow rate is preferably between one and twelve times the minimum fluidization velocity and, even more preferably, between two and eight times the minimum fluidization velocity of the catalyst. The produced SNG exits the reactor through a pipe 559 at the top of the reactor 558. To control the temperature of the reaction layer 553, the catalyst circulates between the methanation reactor 558 and the fluidized bed cooling reactor 551 in a transported flow regime. For this purpose, an inclined channel 554 (or a siphon) connects the lower parts of the two reactors 558 and 551, allowing a continuous flow of catalytic particles from the methanation reactor 558 to the cooling reactor 551. Similarly, the channel 555 may be inclined or include a siphon.

[0081] In the bottom of the cooling reactor 551, at least one fluid is injected by at least one injector 564 to cool the bed of catalytic particles and ensure its fluidization and then the transport of the catalytic particles to the top of the cooling reactor 551. In the embodiment shown in [Fig.8], to ensure a gas seal between the cold and hot poles of the cooling reactor 551, this reactor 551 has a dense or bubbling zone 568 at the bottom, above a distributor overlooking the outlet of the injector 564.

[0082] At least one coolant injector, positioned further downstream than injector 564 in reactor 551, contributes to both the cooling of the catalytic particles and their transport, if the horizontal cross-section of reactor 551 is not sufficiently small to achieve the transport velocities (1.2 to two times the terminal settling velocity of the solid particles to be transported). In device 550, the fluid injection is staged via three injectors 564, 565, and 566. In variants, one, two, or more than three coolant injectors are used. Several different types of fluid can be used to perform both functions: cooling and transport. In [Fig.8] N2, CO2 or less preferably SNG is injected into the cooling reactor 551 via a compressor or blower 563 and injectors 564 and 565.Optionally, and as illustrated in [Fig.8], liquid water is injected into the cooling reactor 551 via a pump 562 and injector 566. In normal operation, the cooling fluid is not air, oxygen, or H2, but during the activation or passivation phases of the catalyst, these fluids can also be used to enable: . - regenerate the catalyst by burning the coke that may be formed during methanation reactions and be present in the catalytic bed (injection of water in vapor form or air or oxygen or a mixture of these fluids). - reactivate the catalyst in case of loss of catalytic activity (injection of H2 or an N2 / H2 mixture).

[0083] The injection of fluids into the secondary bed 568 is configured so that, after possible vaporization of the water, downstream of the last injector, in the direction of movement of the gas flow, the speed of the gas flow is greater than the terminal settling speed of the catalytic particles and puts the catalytic particles into transported fluidization regime.

[0084] At the top of the cooling reactor 551, the cooled catalyst is separated from the gas stream by a solids and gas separator 552 before recirculating into the methanation reactor 558, via a pipe 555. This circulation of catalyst, cooled in the cooling reactor 551, allows the temperature of the reaction zone 553 to be controlled to a temperature setpoint. The flow rate of the pump 562 and / or the compressor or blower 563 is controlled according to the temperature measured in the reaction zone 553 by a sensor 561. Thus, the control of the temperature of the reaction bed 553 can, for example, be carried out solely by controlling the flow rate of water in the liquid state injected into the cooling reactor 551 by the injector 566 according to the temperature of the reaction bed 553, the flow rate of gas injected by at least one gas injector, 564 and / or 565, being dedicated solely to transport.This control can also, according to a second example, be carried out with a constant flow rate of water injected in liquid state by injector 566, and a control of the flow rate of gas injected by at least one injector, 564 and / or 565, as a function of the temperature of the reaction bed 553.

[0085] The gas exiting the separator 552 is conveyed, via a pipe 567, to a heat exchanger 560 which cools it and allows, if the injected cooling fluid contains water, the separation of the condensed water, if any, in liquid form, on the one hand, and the SNG, N2 or CO2, in gaseous form, on the other hand, into at least one tank 557 supplying the pump 562 and the compressor or blower 563. If no fluid in liquid form is injected into the cooling reactor 551, the device does not include a liquid tank, a pump 562, or a liquid injector 566.

[0086] Initially, a reservoir 557 preferably contains liquid water and a gaseous headspace. The gaseous headspace is circulated to, on the one hand, allow the transport of the catalytic particles and, on the other hand, to cool them. If, for example, at maximum circulation of the compressor or blower 563, the target temperature in the reaction layer 553 (measured by the temperature sensor 561) is exceeded, liquid water is injected through the injector 566, in addition to the gaseous headspace. In other operating modes, the cooling reactor 551 operates, in a steady state controlled by the temperature of the reaction layer 553, with an injection Gas is used for transport, and liquid water is injected to provide the majority of the cooling. The advantage of this method is that it reduces the gas volumes to be managed in the separator 552, the pipe 567, and the heat exchanger 560, because very little liquid water is needed to extract a significant amount of heat from the catalyst. This is due to the evaporation of the liquid water upon contact with the hot catalytic particles (thanks to the high latent heat of vaporization of water). The temperature of the reaction bed can be controlled both by the flow rate of catalytic particles and by the temperature difference between the cold end (the outlet of the cooling reactor) and the hot end (the reaction bed).

[0087] The same principle as that described opposite Figures 7 and 8 for the FICFB can be applied to adapt all types of double fluidized bed (DFB) reactors to the application of catalytic methanation. The principle is based on the following modifications to the usual operation of these reactors: - The first fluidized bed is the site of the methanation reactions (exothermic), - The first bed is fluidized by syngas or an H2 / CO2 mixture, both of which may or may not contain water vapor, or be co-injected with a water vapor stream, - The second fluidized bed serves not as an exothermic pole (combustor), but as an endothermic pole used to cool the transported catalytic particles, - This second bed is fluidized by a cooling fluid (SNG, CO2, steam, liquid water, etc.), - The material of the beds is a methanation catalyst. - At least one of the two reactors containing the two fluidized beds operates in transported fluidization mode, - The methanation reaction is isothermal or quasi-isothermal due to the circulation and cooling of the catalytic particles.

[0088] In the double fluidized bed catalytic methanation device 570 shown in [Fig.9], the methanation reactor 578 is exothermic and surrounds the transported fluidized bed cooling reactor 571 which serves to cool the catalyst coming from and returning to the methanation reactor 578. Thus, the heat produced by the methanation is extracted from the single reaction zone 573 to be released via the transported solid catalytic particles, without implanting an exchanger immersed in the methanation reactor.

[0089] In [Fig. 9], device 570 includes a methanation reactor 578 comprising a dense fluidized bed 573 through which a reaction flow enters via the inlet 576 at the bottom of reactor 578, and a fluidized bed catalyst cooling reactor 571 operating in transport mode. In this device 570, the reaction flow, syngas and / or a mixture of CO2 and H2, possibly supplemented by water vapor, feeds the dense / boiling fluidized bed 573 containing a catalyst. The reaction fluidized bed 573 of solid catalytic particles is in a boiling state. The gas velocity of the reaction flow is preferably between one and twelve times the minimum fluidization velocity of the catalyst 573 and, even more preferably, between two and eight times the minimum fluidization velocity of the catalyst 573. The SNG produced in the methanation reactor 578 exits through a pipe 579 at the top of this reactor.

[0090] To control the temperature of the reaction bed 573, the catalytic particles circulate between two reactors: the methanation reactor 578 and the cooling reactor 571, a fluidized bed reactor in transported flow mode, which is surrounded by the methanation reactor 578. For this purpose, openings 572 at the bottom of reactors 578 and 571 allow the passage of catalytic particles from the reaction bed 573 to the cooling reactor 571. These catalytic particles originate from the dense zone of the fluidized bed 573 and enter a dense zone of the secondary fluidized bed 575 of the cooling reactor 571. In the device 570, fluid injection into the cooling reactor 571 is staged, for example, via three injectors 584, 585, and 586. As described previously, a number of injectors other than three can be used.

[0091] Several fluids of different natures can be used to perform the two functions of cooling and transport. In [Fig. 9], N2, CO2, or, less preferably, SNG, is injected into the cooling reactor 571 via a compressor or blower 583 and injectors 584 and 585. Optionally, and as illustrated in [Fig. 9], liquid water is injected into the cooling reactor 571 via a pump 582 and injector 586.

[0092] The flow rates of the pump 582 and the compressor or booster 583 are controlled according to the temperature measured in the reaction zone 573 by a sensor 581.

[0093] The gas injection into the secondary bed 575 is configured so that, after possible vaporization of the water downstream of the last injector, in the direction of gas flow, the gas flow velocity is greater than the terminal settling velocity of the catalytic particles, thus placing the catalytic particles in a transported fluidization regime. As with the device 550 shown in [Fig. 8], the injection of the transport fluid is carried out partly in the dense zone of the secondary bed 575, to put it into dense or boiling fluidization, and partly above this dense zone, to put the solid catalytic particles into a transported regime while cooling them.

[0094] The transported catalytic particles then follow the path indicated by arrows in [Fig. 9] until, once cooled, they return to the dense zone of the fluidized bed 573. The methanation reactor 578 surrounds the cooling reactor 571. A wall separates the secondary fluidized bed 575 of the cooling reactor 571 from the reaction fluidized bed 573. The secondary fluidized bed 575 has a transported zone extending above the wall separating the fluidized beds, so that the transported catalytic particles pass from the top of the cooling reactor 571 to the dense fluidized bed of the methanation reactor 578.

[0095] At the top of the cooling reactor 571, the gas from the injection of fluids through the injectors 584, 585 and 586, heated during the cooling of the catalytic particles present in the reactor 571, is discharged by a pipe 574. This gas is conveyed, by the pipe 574 to a heat exchanger 580 which cools it and, if a fluid in liquid state has been injected into the cooling reactor, allows the separation of the water by condensation, in liquid form and the gas injected into the cooling reactor 571, in gaseous form, in at least one tank 577 supplying the pump 582 and the compressor or blower 583.

[0096] In the double-fluidized bed catalytic methanation device 600 shown in [Fig. 10], the methanation reactor 608 is exothermic, and the transported fluidized bed cooling reactor 601 serves to cool the catalytic particles coming from and returning to the methanation reactor 608. Both reactors 601 and 608 are fluidized beds with an upper zone operating in transport mode and each has a dense or bubbling zone 603 and 625, respectively, at the bottom of the reactor. Thus, the heat produced by methanation is extracted from the single reaction zone 603 and released via the transported solid catalytic particles to an external zone without the need for an immersed heat exchanger in the methanation reactor 608.The originality of the 600 system lies in the fact that the 608 reactor and the 601 cooling reactor each contain a fluidized bed operating in transported mode.

[0097] The methanation reactor 608 operates as described opposite [Fig. 3], except that the cooler is a cooling reactor 601. The methanation reactor 608 thus receives an injection of gas (preferably SNG from the separator 618) by a gas injector 624, in a zone separating the dense fluidized bed 603 from a transported fluidized bed 623. In the lower part, the dense fluidized bed 603 is traversed by a reaction flow entering it through the inlet 606 at the bottom of the reactor 608.

[0098] The gas injector 624 in the reaction bed 603 is configured so that, downstream of this injector 624, in the direction of gas flow, the flow velocity gaseous is greater than the terminal settling velocity of the catalytic particles and puts the catalytic particles into a transported fluidization regime.

[0099] A pipeline 604 transports catalytic particles and SNG from the top of the reactor 608 to a solids and gas separator 618. The gas exiting the separator 618 is routed to a device 619 that performs steps downstream of the methanation stage (cooling, compression, adjustment to injection specifications into the networks, etc.) to supply SNG to the outlet pipeline 609. SNG, collected upstream, during, or downstream of these steps, feeds a valve 620 connected to the gas injector 624. A flow sensor 621 downstream of the valve 620 controls the flow rate through this valve 620 to keep it constant. Alternatively, the device 600 includes a temperature sensor (not shown) for the reaction bed 603, with the valve 620 controlling the gas flow in the gas injector 624 into the reaction bed 603 as a function of the reaction bed temperature.

[0100] The solid catalytic particles exiting the separator 618 are transported, by a pipe 622 into the dense or bubbling zone of the fluidized bed at the bottom of the cooling reactor 601.

[0101] In this device 600, the reaction flow, syngas and / or a mixture of CO2 and H2, optionally supplemented with steam, feeds the dense or bubbling fluidized bed 603 containing a catalyst. The reaction flow velocity is preferably between one and twelve times the minimum fluidization velocity and, even more preferably, between two and eight times the minimum fluidization velocity of the catalyst.

[0102] The cooling reactor 601 is a fluidized bed reactor, dense or bubbling at the bottom, and in transport mode at the top. In the bottom of the cooling reactor 601, at least one fluid is injected by at least one injector 614 to cool the catalytic particles and ensure the fluidization of the bed 625 and / or the transport of these particles to the top of the cooling reactor 601. In the device 600, the fluid injection is staged via three injectors 614, 615 and 616. Several fluids of different natures can be used to ensure the three functions: fluidization (dense or bubbling), cooling and transport. In [Fig. 10], N2, CO2 or, less preferably, SNG, is injected into the cooling reactor via a compressor or blower 613 and injectors 614 and 615. Optionally, and as shown in [Fig.

[10] , liquid water is injected into the cooling reactor 601 via a pump 612 and injector 616.

[0103] The injection of fluids into the secondary bed 625 is configured so that, after possible vaporization of the water, downstream of the last injector, in the direction of gas flow, the gas flow velocity is greater than the velocity terminal settling velocity of catalytic particles and preferably between 1.5 times and two times the terminal settling velocity of catalytic particles and puts catalytic particles into transported fluidization regime.

[0104] At the top of the cooling reactor 601, the cooled catalytic particles are separated from the gas stream by a solids and gas separator 602 before recirculating into the dense or bubbling zone of the fluidized bed 603 of the methanation reactor 608, via the pipe 605. This circulation of catalyst, cooled in the cooling reactor 601, allows the temperature of the reaction zone 603 to be controlled.

[0105] The flow rates of the pump 612 and the compressor or blower 613 are controlled according to the temperature measured in the reaction zone 603 by a sensor 611. The gas exiting the separator 602 is conveyed, by a pipe 617 to a heat exchanger 610 which cools it and, if water in the liquid state is injected into the cooling reactor 601, allows the separation of the water by condensation, in liquid form, and the gas, N2, CO2, or less preferably SNG, in tanks 607 supplying the pump 612 and the compressor or blower 613.

[0106] In conclusion, in the second embodiment, the methanation device of the invention comprises at least two fluidized bed reactors, at least one of which is in transported fluidization mode, between which solid particles of methanation catalyst circulate. At least one of the reactors is a methanation reactor fed and fluidized by a syngas or an H2 / CO2 mixture, both of which may or may not contain steam or be co-injected into the reactor with steam.

[0107] The exothermic methanation reaction takes place within this reactor. At least one other reactor is a cooling reactor used to cool catalytic particles heated by the methanation reaction in the methanation reactor. This cooling reactor is cooled by a cold fluid (SNG, CO2, steam, liquid water, etc.). A gas / solids separator is used to separate the gas from the catalytic particles, either upstream or downstream of this cooling reactor.

[0108] For each methanation reactor, a pipeline returns the hot catalytic particles to at least one cooling reactor. At least one other pipeline circulates the cooled catalytic particles from each cooling reactor to the methanation reactor. The methanation reaction can take place in either a dense or bubbling fluidized bed reactor or a transported flow reactor. The cooling reactor is preferably a fluidized bed reactor in transported flow mode, particularly to facilitate the injection of liquid water. This liquid water can be advantageously used for The catalytic particles are efficiently cooled thanks to its high latent heat of vaporization. The injection of liquid water does not hinder the conversion to methane, as the water injection occurs outside the methanation zone.

[0109] Various DFB reactor configurations have been described in this document, but these configurations are given by way of example and are not intended to be an exhaustive list of possible implementations of the invention. Depending on the numerous possible variations, different equipment may or may not be used (siphon, channel, overflow, cyclone, filter, disengagement zone) for gas / solid separation, sealing between the two reactors, or the transfer lines for catalytic particles from one reactor to the other. Other means, depending on the variations, contribute to sealing between the two reactors (pressure differential control of the fluidized beds, pressure control at the top of the reactors, siphon-type solid valve, L-shaped solid valve, J-shaped solid valve, etc.).Various methods can be used to cool the catalyst: injecting cold fluid into the methanation reactor, cooling the catalyst in the cooling reactor via a fluid / solid heat exchanger and / or by injecting cold fluid or liquid fluid with phase change. This concept allows the methanation reaction to take place in a quasi-isothermal reactor. The exothermicity of the reaction is managed by the circulation of catalytic particles between the methanation reactor and the cooling reactor.

[0110] The implementation of the invention eliminates the need for an immersed heat exchanger within the catalytic bed fed by the gas mixture to be converted into SNG. It completely, or partially if necessary, eliminates the need for an internal heat exchanger within the methanation reactor. By removing this constraint, the two embodiments described opposite the figures allow operation at higher pressures, thus shifting the chemical equilibrium towards greater CH4 production, a reduction in residual H2 content, and a smaller catalyst volume, since it is not constrained by a catalyst volume-to-exchange surface ratio as is the case in prior art isothermal fluidized bed methanation devices. Consequently, the unit's efficiency is improved, and the SNG output chain is simplified.

[0111] The invention makes it possible to achieve thermodynamic equilibrium at temperatures greater than or equal to 260°C with, for example, a nickel catalyst supported on alumina. The performance of the present invention offers the possibility of operating at higher pressures. This makes it possible to increase the conversion to methane and reduce the residual hydrogen content (and therefore the need for upgrading, i.e., the steps following methanation to achieve a higher quality of SNG in terms of, in particular, Wobbe index, PCS, and residual H2).

[0112] Preferably, the device of the invention uses a catalyst highly resistant to attrition. Its mechanical properties are therefore an important factor for the device's performance. The use of a fluidized bed in transported flow increases the number and force of collisions between catalytic particles. Under the effect of these collisions, catalysts with low resistance would undergo significant attrition, resulting in the loss of catalyst in the form of dust. A substantial addition of fresh catalyst would then be necessary.

[0113] Other embodiments of the device of the invention may have architectures similar to the reactors described below, but with a combination of a fluidized bed methanation reactor and a means for extracting catalytic particles. These extracted catalytic particles are cooled in a cooling reactor replacing the combustor, or the reactor in which the intended chemical reaction takes place, of the reactors described below. This cooling reactor has a fluidized bed comprising a dense zone and a zone operating in transport mode, allowing the separation of gases originating from the cooling fluids injected into the cooling reactor for cooling, on the one hand, and the catalytic particles, which are returned (or recirculated) to the methanation reactor.

[0114] The TNEE reactor, used for the pyrogasification of solid fuel, is another DFB reactor. This device is very similar to the FICFB: it consists of a bubbling fluidized bed gasifier, a pipeline connecting the gasifier to the combustor through which the bed particles and char circulate, a transported fluidized bed combustor heating the bed material by oxidizing the char, a gas / solid separator separating the char from the syngas downstream of the gasifier, a pipeline connecting this separator to the combustor recirculating the char to it, a gas / solid separator separating the flue gases from the hot bed material at the outlet of the combustor and a pipeline returning the hot bed material to the gasifier.The unique features of this reactor compared to the FICFB are: (1) the pipe through which the bed flows from the gasifier to the combustor is placed at the top of the bubbling fluidized bed (and not at the bottom) and operates in overflow; (2) once separated from the flue gases, the hot bed material is returned to the top of the gasifier onto a rotary distributor which distributes the hot particles onto a particle shower packed heat exchanger, acting as a counter-current contactor between the syngas and the hot bed particles.

[0115] The a-DFB reactor used for the same application is similar in its approach to the FICFB and the TNEE reactor. The main difference with the TNEE reactor lies in the syngas / bed material contactor system on the upper part of the gasifier. In the a-DFB reactor, the hot bed material exiting the combustor does not return at the very top of the gasifier, but below a disengagement zone located in the upper part of the gasifier. Contact between the hot bed material and the syngas is achieved via contactors positioned along the length of the gasifier. Another difference from the TNEE reactor is that the pipeline through which the bed flows from the gasifier to the combustor is located at the bottom of the gasifier.

[0116] Fluid Catalytic Cracking (FCC) is used in a completely different context than solid fuel valorization, in the field of hydrocarbon refining. It is based on physical principles very similar to those of combustion-based fuel bed (CFB) or pyrogasification. In an FCC, the role of the solid bed is not to ensure combustion, but to promote a catalytic reaction that cracks heavy hydrocarbons into lighter molecules (gasoline, diesel, gas). This operation also relies on the fluidization of solid particles, in this case catalytic particles (alumina, zeolites), which are suspended in a hydrocarbon vapor stream. The cracking takes place in a reactor (vertical pipe) in which the fluidized bed reaction occurs under transported flow conditions.The catalyst, loaded with coke as the reactions progress, is then separated from the gases (cyclone, filter or disengagement) and sent to a regenerator where it is burned (oxidation of the coke) to be reactivated and then returned to the "main" reactive zone. Despite very different objectives (combustion or chemical transformation), the combustion or pyrogasification of solids in CFB and FCC share a fairly similar architecture: - a circulating fluidized solid bed (to increase conversion efficiency in the case of CFB and to regenerate a solid catalyst in the case of FCC). - a separation of solids and gases. - a recirculation of the solid towards the "main" reactive zone.

[0117] Of course, the variants and particular features of the first embodiment can be implemented in the second embodiment, for example the use of a reactor whose cross-sectional area perpendicular to the gas flow decreases in the direction of movement of the gas flow, and vice versa, in particular the use of a cooling reactor in which at least one area of ​​the fluidized bed operates in transported mode.

[0118] In particular, all the reactors described above can be such that the surface area of ​​the methanation reactor cross-section perpendicular to the direction of the gas flow decreases in the direction of this gas flow, the decrease in this surface area causing an increase in the gas flow velocity at least until this velocity exceeds the terminal settling velocity of the catalytic particles and puts the catalytic particles into a fluidization regime, transporting them until their extraction from the reactor. The device then further comprises a solids separator and of gas configured to receive this mixture of gas stream and the transported catalytic particles and to separate these catalytic particles.

Claims

Demands

1. A methanation device (550, 570, 600) comprising a methanation reactor (558, 578, 608) having a single reaction fluidized bed (553, 573, 603) of methanation catalytic particles through which a reaction gas stream flows, comprising syngas and water vapor and / or a mixture of hydrogen and carbon dioxide, between a reaction gas stream inlet (556, 576, 606) and a synthetic natural gas outlet (559, 579, 604), characterized in that it further comprises: - a means for extracting (554, 572, 604, 624) catalytic particles from the reaction bed, - a means for cooling (551, 564 to 566, 584, 586, 601) the catalyst particles extracted from the reaction bed, and - a means for injecting (555, 605) the cooled catalytic particles into the reaction bed; a device in which the means for cooling the extracted catalyst particles comprises: - a secondary fluidized bed (568, 575,625) of catalytic particles extracted from the reaction bed (553, 573, 603) by the extraction means (554, 572, 604, 624), - at least one injector (564 to 566, 584 to 586, 614 to 616) of a cooling fluid into the secondary fluidized bed, configured so that, downstream of each cooling fluid injector, in the direction of gas flow, the gas flow velocity is greater than the terminal settling velocity of the catalytic particles and puts the catalytic particles into a transported fluidization regime, and - a solids-gas separator (552, 602) configured to receive this gas from the cooling fluid and the catalytic particles transported in the cooling means and to separate these catalytic particles from this gas, the particle injection means (555, 605) cooled catalytic converters inject these catalytic particles, separated from this gas, into the reaction bed.

2. A methanation device (550, 570, 600) according to claim 1, wherein at least one said injector (564, 565, 584, 585, 614, 615) of cooling fluid into the secondary fluidized bed is a coolant injector containing SNG, nitrogen or carbon dioxide.

3. Methanation device (550, 570, 600) according to any one of claims 1 or 2, comprising at least one injector (566, 586, 616) of coolant fluid comprising water in the liquid state.

4. Methanation device (550, 570, 600) according to any one of claims 1 to 3, comprising a temperature sensor (561, 581, 611) of the reaction bed (553, 573, 603) and a control means (562, 563, 582, 583, 612, 613) of the flow rate of cooling fluid in at least one fluid injector (564 to 566, 584 to 586, 614 to 616) as a function of the reaction bed temperature.

5. Methanation device (550) according to any one of claims 1 to 4, wherein the means for extracting catalytic particles from the reaction bed comprises an inclined channel (554) or a siphon connecting the reaction fluidized bed (553) and the secondary bed (568).

6. Methanation device (550) according to any one of claims 1 to 5, wherein the injection means (555) for the cooled catalytic particles into the reaction bed (553) comprises an inclined channel or a siphon opening into the methanation reactor (558).

7. Methanation device (570) according to any one of claims 1 to 4, wherein the methanation reactor (578) surrounds the cooling reactor (571), a wall separating the secondary fluidized bed (575) from the reaction fluidized bed (573), the secondary fluidized bed having a transported operating zone extending above said wall.

8. Methanation device (600) according to any one of claims 1 to 4, further comprising: - at least one gas injector (624) into the reaction bed (603) configured so that, downstream of this injector, in the direction of movement of the gas flow, the velocity of the gas flow is greater than the terminal settling velocity of the catalytic particles and puts the catalytic particles into a transported fluidization regime, - a solids and gas separator (618) configured to receive the gas flow and the transported catalytic particles and to separate these catalytic particles from the gas flow and - an injection channel (622) into the secondary bed (625) of the catalytic particles separated from the gas flow.

9. Methanation device (600) according to claim 8, wherein the gas injector (624) into the reaction bed (603) is configured to inject into the reaction bed a portion of the gas stream separated by the solids and gas separator (618).

10. Methanation device (600) according to any one of claims 8 or 9, which includes a temperature sensor (621) of the gas flowing in the gas injector (624) into the reaction bed (603) and a control means (620) of the gas flow in this gas injector as a function of the temperature of the gas flowing in this gas injector.

11. Methanation device (600) according to any one of claims 8 to 10, which includes a temperature sensor of the reaction bed (603) and a control means (620) of the gas flow in the injector (624) of gas into the reaction bed as a function of the temperature of the reaction bed.

12. A methanation device according to any one of claims 1 to 7, wherein the surface area of ​​the methanation reactor cross-section perpendicular to the direction of the gas flow is decreasing in the direction of this gas flow, the decrease in this surface area causing an increase in the velocity of the gas flow at least until this velocity is greater than the terminal settling velocity of the catalytic particles and puts the catalytic particles into a fluidization regime transported to the extraction means, the device further comprising a solids and gas separator configured to receive this gas flow and the transported catalytic particles and to separate these catalytic particles from this gas flow for injection into the secondary bed.

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