CLC plant and process with recovery of gaseous oxygen produced by an oxygen carrier

Description

Technical field

[0001] The present invention relates to the field of combustion of hydrocarbon feedstocks by chemical looping oxidation-reduction ("CLC" for Chemical Looping Combustion according to English terminology) operating in a fluidized bed, and more particularly a CLC process and installation exploiting gaseous oxygen produced by an oxygen carrier by the CLOU effect. Prior art

[0002] The fight against greenhouse gas emissions involves, among the range of technical solutions proposed, the capture of gases resulting from the combustion of carbon feedstocks such as CO 2 . Chemical looping combustion is not only one of the technologies with one of the lowest capture energy penalties, but it is also a CO 2 capture technology particularly suited to the combustion of solid feedstocks that are difficult to treat using traditional combustion processes such as the combustion of pulverized solid feedstocks.

[0003] A CLC process consists of implementing oxidation-reduction reactions of an active mass, typically a metal oxide, to decompose the combustion reaction of a hydrocarbon charge into two successive reactions: a first oxidation reaction of the active mass in contact with an oxidizing gas, typically air, in at least one oxidation zone, and a second reduction reaction of the active mass in contact with the charge whose combustion is desired, in at least one combustion zone.

[0004] The redox active mass, which releases part of the oxygen it contains upon contact with the charge in the combustion zone, thus plays the role of oxygen transporter between the combustion zone and the oxidation zone where it is oxidized again. It is commonly referred to as an "oxygen carrier".

[0005] This solid material is in the form of fluidizable particles, typically between 50 and 500 µm in size. The particles are brought into contact in the reaction zones with either the oxidizing gas or the feedstock in the form of high-temperature fluidized beds and are generally transported from one zone to another in a fluidized form. The set of particles transported in a fluidized form is commonly referred to as a circulating fluidized bed.

[0006] These particles are oxidized upon contact with an oxidizing gas, typically air (or water vapor), in at least one first reaction zone, called the oxidation zone or oxidation reactor or air reactor. They are then transported to at least one second reaction zone called the reduction zone or reduction reactor, combustion reactor or fuel reactor, where they are brought into contact with a hydrocarbon feedstock that is to be combusted. The feedstock may be solid (e.g., coal), liquid (e.g., fuel oil), or gaseous (e.g., natural gas). The oxygen contained in the particles of the active mass, transported from the oxidation zone to the reduction zone, fuels the combustion of the feedstock. This results in a gaseous effluent formed by the combustion of the feedstock, commonly called combustion fumes, and a stream of reduced particles. The particles are returned to the air reactor to be re-oxidized, thus closing the loop.

[0007] Oxidation and combustion reactors operate in fluidized beds. They each include at least one system for injecting a fluidizing gas. In the combustion reactor, the fluidizing gas is typically CO2, which can be CO2 produced during combustion and recycled, or water vapor. In the oxidation reactor, the fluidizing gas is an oxidizing gas, typically air.

[0008] The CLC process allows energy to be produced (for example in the form of steam, electricity, etc.) by recovering the heat released by combustion reactions while facilitating the capture of carbon dioxide (CO 2 ) emitted during combustion thanks to the production of CO 2 -rich fumes. CO 2 capture can in fact be done after condensation of water vapor and compression of the fumes, and it can then be stored, for example in a deep aquifer, or be recovered, for example by using it to improve the efficiency of oil operations in enhanced oil recovery (EOR) or enhanced gas recovery (EGR) processes.

[0009] The CLC process can also allow the production of synthesis gas, or even hydrogen, by controlling combustion and implementing the required purifications downstream of the combustion process.

[0010] This particular chemical looping combustion method also has the advantage of producing a stream very rich in nitrogen, which is the depleted air obtained after the oxidation of the active mass in the air reactor. Depending on the degree of purity achieved, this nitrogen stream can be used in various applications, particularly in the oil industry. For example, it can be used in refineries as an inert gas in various oil refining processes or for the treatment of production water, or as a gas injected into the subsoil in EOR processes.

[0011] The conversion of gaseous hydrocarbon feedstocks in the fuel reactor involves a gas / solid reaction between said gaseous feedstocks and the oxygen carrier which can be limiting for the process. In the case of solid hydrocarbon feedstocks, an additional gasification step is required to transform the solid feedstock into gaseous species (production of synthesis gas CO and H 2 ) reacting with the oxygen carrier. If the feedstock used is therefore a solid feedstock, the gasification step can be limiting (in time). In the case of liquid hydrocarbon feedstocks, a step of vaporization of the liquid feedstock and formation of coke on the oxygen carrier generally occurs in the fuel reactor. Here again, this step of vaporization of the liquid and formation of coke, and the gasification of the coke can be limiting.

[0012] To overcome these limitations, particularly in the case of combustion of solid or gaseous hydrocarbon feedstocks, it has been proposed in the literature, for example by Mattisson et al. 2009 (“Chemical-looping with oxygen uncoupling for combustion of solid fuels”, Int. journal of greenhouse gas control 3, 2009, pp.11-19) to use oxygen carriers capable of releasing gaseous oxygen (dioxygen in gaseous form). Combustion processes using this type of oxygen carrier are called chemical looping combustion processes with oxygen uncoupling or CLOU for “Chemical Looping with Oxygen Uncoupling” according to English terminology.Typically, CLOU processes are based on chemical looping combustion (CLC) and involve three stages in two reactors, an air reactor where the oxygen carrier is oxidized upon contact with air (stage 1), and a fuel reactor where the carrier releases gaseous oxygen (stage 2) and where this gaseous oxygen reacts with the hydrocarbon feedstock (stage 3). Thus, with such oxygen carriers, it is possible to implement gas / gas reactions directly between the gaseous oxygen released by the oxygen carrier and the reactants in gaseous form (gaseous species produced by devolatilization and / or gasification of the hydrocarbon feedstock when it is solid or liquid) and thus increase the conversion rates of the hydrocarbon feedstock. In addition, in the case of combustion of solid hydrocarbon feedstocks, the released oxygen can react directly with the solid feedstocks before gasification (conventional combustion).

[0013] Perovskites, copper, cobalt or manganese oxides, mixed iron-cobalt or iron-manganese oxides, for example, are among the materials with good oxygen release properties, as described in Mattisson et al., 2009, or Shafiefarhood et al. 2015 “Iron-containing mixed-oxide composites as oxygen carriers for CLOU”, Fuel 139, 2015, pp.1-10). According to Mattisson et al., 2009 for example, the use of oxygen-carrying materials releasing gaseous oxygen would increase the conversion rate of solid hydrocarbon feedstocks by up to 50 times. The particularity of these oxygen carriers capable of releasing gaseous oxygen, which can be called here "CLOU effect oxygen carriers", is that only a portion of the oxygen available in the material is released in gaseous form.The remaining oxygen in the oxygen carrier reacts with the hydrocarbon feedstock brought into contact with the oxygen carrier, through a gas / solid reaction. The gaseous oxygen is released very quickly by the oxygen carrier when it is under an inert atmosphere, which is an undeniable advantage for its use in the combustion of a hydrocarbon feedstock.

[0014] In a conventional CLC process, the oxygen carrier may be exposed for a significant time, typically a few minutes, to an inert atmosphere, i.e. consisting of nitrogen, CO2 or water vapor, alone or in a mixture, between the air and fuel reactors. Depending on the nature of the oxygen carrier used, this exposure may result in the release of part of the oxygen from the oxygen carrier by the CLOU effect, which is not conventionally exploited in the CLC process.

[0015] Patent EP3158264 discloses a CLC process in which the oxygen carrier is sent to a heat exchanger operating in a dense fluidized bed, positioned between the air reactor and the fuel reactor, in which heat recovery is controlled by varying the level of the fluidized bed by applying a pressure drop to a fluidization gas outlet at the top of the heat exchanger. The residence time in the heat exchanger of the oxygen carrier from the air reactor can allow the spontaneous release of gaseous oxygen by CLOU effect if it is placed at low partial pressure of O 2 , this gaseous oxygen being able to be used in the reduction zone for the combustion of the load. However, it is not specified how this gaseous oxygen would be used. In addition, the control of the operating conditions in the heat exchanger is specific to the control of the bed level to ensure the desired heat exchange.The inventory of the solid oxygen carrier in the heat exchanger is therefore variable depending on the bed level. Similarly, the choice of the section of the exchanger enclosure is dictated by the heat exchange surface with the carrier, which can lead to the implementation of very significant fluidization and therefore to diluting the oxygen released by the CLOU effect, making its operation less efficient.

[0016] Patent US9004911 relates to a chemical looping combustion process for a solid hydrocarbon feedstock, using a specific fuel reactor to benefit from the CLOU effect of the oxygen-carrying material. According to this process, there is no direct contact between the oxygen carrier and the solid feedstock: the fuel reactor is divided into two parts separated by a porous wall allowing the passage of gas. The oxidized oxygen carrier is introduced into one of the parts, and the solid hydrocarbon feedstock is introduced into the other where it is volatilized, and possibly gasified by the introduction of a gasifying agent (CO2 and / or H2O). The reducing gases produced by gasification pass through the porous wall, thus creating a reducing atmosphere allowing the reduction of the oxygen carrier and thus ensuring the combustion of the gasified feedstock.At the same time, gaseous oxygen produced by the carrier can pass through the wall and ensure the combustion of the reducing gases in the part containing the solid charge. This creates an equilibrium allowing the conversion of the solid charge without direct contact with the oxygen carrier. However, the gasification of the solid charge requires a significant heat input, which, in a conventional CLC process, is provided by the oxygen carrier. The process according to patent US9004911, in which the oxygen carrier is not in contact with the solid charge, therefore has the major disadvantage of not fully exploiting the heat input by the oxygen carrier. Another disadvantage of this process lies in the use of a large porous wall at the core of a very high temperature reactor, which represents a technological challenge.

[0017] Patent CN102200277 also discloses a chemical looping combustion process for a solid hydrocarbon feedstock, in which gaseous oxygen is supplied to the feedstock, but without contact with the oxygen carrier, through the use of a porous wall. The disadvantages of such a process are substantially identical to those discussed above for the process according to patent US9004911: a complex technology to implement, in particular linked to the installation of one reactor within another, to high combustion temperatures, and a problem of supplying the heat necessary for gasification without direct contact between the oxygen carrier and the feedstock.

[0018] Another method of combustion of a hydrocarbon feedstock by chemical looping oxidation-reduction of the prior art is disclosed in document FR3004126A1.

[0019] There is a need to improve CLC processes, particularly with a view to providing CLC processes that can treat all types of feedstocks, including solid feedstocks for which complete combustion is more difficult to achieve, that are simple, efficient in terms of the feedstock conversion level, while reducing energy costs, and ultimately operating costs, and / or while limiting the residence time of the reactants in the reaction zones, which may in particular allow the use of more compact fuel reactors, and ultimately reduce investment costs.

[0020] For this purpose, it would be advantageous to provide a CLC process in which gaseous oxygen released from the oxygen carrier can be exploited. Objectives and Summary of the Invention

[0021] In this context, the present invention aims to overcome, at least in part, the problems of the prior art set out above.

[0022] The present invention generally aims to provide a CLC method and installation which make it possible to recover gaseous oxygen released by the oxygen carrier by the CLOU effect so as to be used in the CLC method and installation, while allowing the recycling of part of the combustion fumes for the fluidization of the fuel reactor.

[0023] The CLC process and installation according to the invention make it possible to reduce operating costs, in particular by limiting the need for external utilities, such as for example the oxygen used for the combustion of residual unburned species that may be found in the combustion fumes to be recycled, or the water vapor used as fluidization gas. The conversion of the hydrocarbon feedstock is also faster if the recovered gaseous oxygen is used in the fuel reactor. The CLC process and installation according to the present invention, although applicable to any type of hydrocarbon feedstock, whether in gas, solid or liquid form, are particularly well suited to the combustion of solid feedstocks producing solid unburned species, and combustion fumes that may more frequently contain residual unburned species.

[0024] Thus, to achieve at least one of the above-mentioned objectives, among others, the present invention proposes, according to a first aspect, a method for combustion of a hydrocarbon feedstock by oxidation-reduction in chemical looping in which an active oxidation-reduction mass in the form of particles circulates between an oxidation zone and a reduction zone operating in a fluidized bed, which comprises: combustion of the hydrocarbon feedstock by contacting it with the redox active mass in the reduction zone; oxidation of the redox active mass from said reduction zone by contacting it with an oxidizing gas, preferably air, in the oxidation zone; sending the oxidized redox active mass into at least one sealing device operating in a double fluidized bed, positioned downstream of said oxidation zone on a line for transporting said redox active mass to said reduction zone, the sealing device being supplied with at least one neutral fluidizing gas, so as to form at least a first flow comprising at least a portion of said redox active mass sent to said reduction zone and a second gaseous flow comprising a portion of the neutral fluidizing gas and gaseous oxygen released by the redox active mass;mixing the second gaseous flow with a portion of the combustion fumes so as to form a recycle flow of the combustion fumes sent at least in part, after having been successively cooled, compressed, and reheated, into said reduction zone for its operation in a fluidized bed.;

[0025] According to one or more embodiments of the invention, the part of the combustion fumes contains residual unburned species from the reduction zone, and the combustion of said residual unburned species is carried out in contact with the gaseous oxygen provided by the mixing of said second gaseous flow with said part of the combustion fumes.

[0026] According to one or more embodiments of the invention, the method comprises the injection of fresh oxygen into said part of the combustion fumes to complete the combustion of said residual unburned species.

[0027] According to one or more embodiments of the invention, the method comprises sending a portion of the recycled flow of combustion fumes, after its successive cooling, compression and heating, into the sealing device for the operation of said sealing device in a fluidized bed.

[0028] According to one or more embodiments of the invention, the recycle gas stream is cooled by passing through at least one first heat exchanger, then said cooled combustion flue gas recycle stream is compressed in a compressor, then said cooled and compressed combustion flue gas recycle stream is reheated by passing through said first heat exchanger before being sent at least in part to the reduction zone.

[0029] According to one or more embodiments of the invention, the recycled flow of combustion fumes is cooled by passing through a second heat exchanger positioned between the first heat exchanger and the compressor.

[0030] According to one or more embodiments of the invention, the combustion flue gas recycle stream is cooled to a temperature of between 70°C and 450°C, preferably between 70°C and 300°C, then compressed to a pressure of between 0.02 MPa and 0.3 MPa, then reheated to a temperature of between 300°C and 950°C.

[0031] According to one or more embodiments of the invention, the second gas flow from said sealing device comprises between 1% and 20% vol. of gaseous oxygen.

[0032] According to one or more embodiments of the invention, the redox active mass comprises at least one compound chosen from the list consisting of copper oxides, cobalt oxides, manganese oxides, mixed cobalt-iron or manganese-iron oxides, preferably in the form of spinels, perovskites, alone or as a mixture, and preferably the redox active mass comprises at least one copper or manganese oxide, preferably associated with a support of alumina, silica, alumino-silicic, feldspars such as celsiane, slawsonite, anorthite or feldspathoids such as kalsilite.

[0033] According to one or more embodiments of the invention, the neutral fluidization gas sent into the sealing device consists essentially of water vapor, CO 2 , or a mixture of CO 2 and water vapor comprising between 0 and 2% vol. of O 2 , preferably less than 2% vol. of O 2 .

[0034] According to one or more embodiments of the invention, the sealing device comprises an enclosure provided with a first zone and a second zone in fluid communication. The fluidization conditions are different in these first and second zones so as to create a separate fluidized bed in each of the first and second zones. The first zone receives particles of redox active mass from the oxidation reactor, and the second zone receives at least a portion of the particles of redox active mass from the first zone which release the gaseous oxygen discharged into the second gas flow via an outlet pipe located at the top of said second zone.

[0035] According to one or more embodiments of the invention, a third flow comprising a portion of said redox active mass is formed and extracted from the bottom of said sealing device to be sent again into the oxidation zone.

[0036] According to one or more embodiments of the invention, the redox active mass sent into the sealing device is previously separated from the oxygen-depleted oxidizing gas from the oxidation zone within a cyclone positioned between the oxidation zone and the sealing device.

[0037] According to one or more embodiments of the invention, the hydrocarbon feedstock is a solid feedstock in the form of particles, preferably chosen from the list consisting of coal, coke, petcoke, biomass, oil sands and household waste, and the method further comprises: the separation, in a solid / solid separator operating in a fluidized bed and positioned at the outlet of the reduction zone, between the particles of said redox active mass and unburned particles generated by the combustion of said solid hydrocarbon feedstock contained in a first gas-solid mixture from said reduction zone, the solid / solid separator operating in a fluidized bed, then the separation, in a gas / solid separator positioned downstream of the solid / solid separator, between the unburned particles and the gas phase contained in a second gas-solid mixture from the solid / solid separator, a flow comprising the unburned particles preferably being sent into said reduction zone, and the gas phase forming the combustion fumes.

[0038] According to a first aspect, the present invention proposes a method for carrying out the process for combustion of a hydrocarbon feedstock by chemical looping oxidation-reduction according to the invention, comprising: a reduction zone configured to operate in a fluidized bed and carry out the combustion of said hydrocarbon feedstock by contacting it with an active redox mass in the form of particles; an oxidation zone configured to operate in a fluidized bed and carry out the oxidation of the active redox mass from the reduction zone by contacting it with an oxidizing gas, preferably air;a line for transporting the redox active mass from the oxidation zone to the reduction zone, said transport line comprising a sealing device configured to operate in a double fluidized bed by means of a neutral fluidization gas and to form at least a first flow comprising at least a portion of the redox active mass destined for the reduction zone and a second gas flow comprising a portion of the neutral fluidization gas and gaseous oxygen released by the redox active mass, the sealing device comprising an outlet pipe for the second gas flow (6); a line for recycling a portion of the combustion fumes in the reduction zone, ; said recycle line being connected to the outlet pipe of the second gas flow from the sealing device so as to mix the second gas flow with said part of the combustion fumes and form a recycle flow of the combustion fumes, and the recycle line comprising a system for cooling, compressing and heating the recycle flow of the combustion fumes before sending it to the reduction zone.

[0039] Other objects and advantages of the invention will appear on reading the following description of particular examples of embodiments of the invention, given as non-limiting examples, the description being made with reference to the appended figures described below. List of figures

[0040] There figure 1 illustrates the CLC installation and method according to a first embodiment of the invention. The figure 2illustrates the CLC installation and method according to a second embodiment of the invention. The figure 3 is an example of a gaseous oxygen release profile by CLOU effect of a manganese oxide-based oxygen carrier.

[0041] In the figures, the same references designate identical or similar elements. Description of the embodiments

[0042] Embodiments of the invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0043] The present invention relates to a CLC process, and a CLC installation implementing such a process, comprising the recovery of gaseous oxygen released by the oxygen carrier in a sealing device positioned on the path of the carrier from the oxidation reactor to the combustion reactor. The recovered gaseous oxygen is mixed with a portion of the combustion fumes intended to be recycled to the combustion reactor. The gaseous oxygen then allows the combustion of residual unburned species resulting from the devolatilization / gasification of a solid feedstock or from the non-conversion of a fraction of the gaseous hydrocarbon feedstock, which the combustion fumes may contain, and / or the combustion of the hydrocarbon feedstock in the combustion reactor.

[0044] More specifically, the method according to the invention is a method for combustion of a hydrocarbon feedstock by chemical loop oxidation-reduction in which an active oxidation-reduction mass in the form of particles circulates between an oxidation zone and a reduction zone operating in a fluidized bed, which comprises: combustion of the hydrocarbon feedstock by contacting it with the redox active mass in the reduction zone; oxidation of the redox active mass from said reduction zone by contacting it with an oxidizing gas, preferably air, in the oxidation zone; sending the oxidized redox active mass into at least one sealing device operating in a double fluidized bed, positioned downstream of said oxidation zone on a line for transporting said redox active mass to said reduction zone, the sealing device being supplied with at least one neutral fluidizing gas, so as to form at least a first flow comprising at least a portion of said redox active mass sent to said reduction zone and a second gaseous flow comprising a portion of the neutral fluidizing gas and gaseous oxygen released by the redox active mass;mixing the second gaseous flow with a portion of the combustion fumes so as to form a recycle flow of the combustion fumes sent at least in part, after having been successively cooled, compressed, and reheated, into said reduction zone for its operation in a fluidized bed.;

[0045] In the present description, the expressions "oxygen carrier" or "redox active mass" or abbreviated as "active mass", "oxygen-carrying material", or "oxygen-carrying solid" are equivalent. The redox mass is said to be active in relation to its reactive capacities, in the sense that it is capable of playing its role as an oxygen carrier in the CLC process by capturing and releasing oxygen.

[0046] It should be noted that, generally speaking, the terms oxidation and reduction are used in relation to the oxidized or reduced state of the active mass, respectively. The oxidation reactor, also called an air reactor, is the one in which the redox active mass is oxidized, and the reduction reactor, also called a fuel reactor or combustion reactor, is the reactor in which the redox active mass is reduced. The reactors operate in a fluidized bed and the active mass circulates between the oxidation reactor and the reduction reactor. Circulating fluidized bed technology is used to allow the continuous passage of the active mass from its oxidized state in the oxidation reactor to its reduced state in the reduction reactor.

[0047] Gaseous oxygen means molecular oxygen or dioxygen (O 2 ).

[0048] In the remainder of the description and in the claims, the positions (“bottom”, “top”, “above”, “below”, “horizontal”, “vertical”, “lower half”, etc.) of the various elements are defined relative to the devices in their operating position. The CLC method and installation according to the invention

[0049] Before describing in more detail the CLC method and installation according to the invention, the principle of chemical loop combustion, which applies within the framework of the present invention, is recalled below.

[0050] In the CLC process, the oxygen carrier in particulate form circulates between at least one reduction zone and one oxidation zone, both operating in a fluidized bed.

[0051] The treated hydrocarbon feedstock can be a solid, liquid or gaseous hydrocarbon feedstock: gaseous fuels (e.g. natural gas, syngas, biogas, shale gas), liquids (e.g. fuel oil, bitumen, diesel, gasoline, shale oil, etc.), or solids (e.g. coal, coke, petroleum coke called "petcoke" in English, biomass, oil sands, household waste, etc.).

[0052] The CLC method and installation according to the invention are particularly well suited to the combustion of a solid hydrocarbon feedstock, although not limited to solid feedstocks. Indeed, the CLC method and installation according to the invention allow the recovery of gaseous oxygen which can be used to carry out the combustion of residual unburned species contained in the combustion fumes recycled in the reduction zone. These residual unburned species come from combustion which is not entirely complete in the reduction zone, which is more frequent in the case of the combustion of solid feedstocks.

[0053] The operating principle of the CLC process according to the invention is as follows: a solid carrier of reduced oxygen is brought into contact with a flow of air, or any other oxidizing gas, in a reaction zone called an oxidation zone or air reactor (or oxidation reactor). This results in a flow of depleted air (or oxygen-depleted oxidizing gas) and a flow of particles of the oxidized oxygen carrier. The flow of particles of oxidized oxygen carrier is transferred to a reduction zone also called a fuel reactor (or reduction reactor or combustion reactor). The flow of particles is brought into contact with a fuel, typically a hydrocarbon feedstock as described above. This results in a combustion effluent, also commonly called combustion fumes, and a flow of particles of reduced oxygen carrier.The CLC installation can include various equipment, for heat exchange, pressurization, gas sealing between the reduction and oxidation zones, separation or possible recirculation of material around the oxidation and reduction zones.

[0054] In the reduction zone, the hydrocarbon feedstock is brought into contact, preferably co-currently, with the oxygen carrier in the form of particles to achieve combustion of said feedstock by reduction of the oxygen carrier. The oxygen carrier is reduced via the hydrocarbon feedstock, which is correlatively oxidized to CO 2 and H 2 O, or possibly to a CO + H 2 mixture (synthesis gas) depending on the proportions of oxygen carrier and hydrocarbon feedstock used. The combustion of the feedstock in contact with the oxygen carrier is carried out at a temperature generally between 600°C and 1200°C, preferably between 750°C and 1100°C, and more preferably between 800°C and 1100°C. The contact time may vary depending on the type of hydrocarbon feedstock used. It can typically vary between 1 second and 10 minutes, preferably between 1 and 8 minutes for a solid or liquid load, and preferably from 1 to 20 seconds for a gaseous load.

[0055] A mixture comprising the gases resulting from combustion (combustion fumes) and the particles of the solid oxygen carrier is discharged, typically at the top of the reduction zone. Gas / solid separation means, such as a cyclone, make it possible to separate the combustion gases on the one hand and the solid particles of the oxygen carrier in their most reduced state on the other. The latter are sent to the oxidation zone to be re-oxidized, at a temperature generally between 600°C and 1200°C, preferably between 750°C and 1100°C, and more preferably between 800°C and 1100°C.

[0056] In the oxidation reactor, the oxygen carrier is restored to its oxidized state upon contact with air (or another oxidizing gas), before returning to the reduction zone, and after being separated from the oxygen-depleted air (or oxygen-depleted oxidizing gas) discharged at the top of the oxidation zone.

[0057] The oxygen-carrying solid, passing alternately from its oxidized form to its reduced form and vice versa, describes an oxidation-reduction cycle.

[0058] Reactions (1) and (2) below describe respectively the reduction of the oxygen carrier comprising a metal oxide (M x O y ) generally supported on a ceramic, M representing a metal, in contact with a hydrocarbon charge, e.g. a hydrocarbon of formula C n H m , and its oxidation in contact with an oxidizing gas, e.g. air. [Chem 1] C n H m + M x O y → n CO 2 + m / 2 H 2 O + M x O y-2n-m / 2 (1) [Chem 2] M x O y-2n-m / 2 + (n+m / 4) O 2 → M x O y (2)

[0059] In the reduction zone, the oxygen carrier is reduced to the state M x O y-2n-m / 2 in contact with the hydrocarbon feedstock which is correlatively oxidized to CO 2 and H 2 O, according to reaction (1), or possibly to a mixture of CO + H 2 depending on the nature of the oxygen carrier and the proportions used.

[0060] In the oxidation zone, the oxygen carrier is restored to its oxidized state M x O y upon contact with the oxidizing gas, e.g. air, according to reaction (2), before returning to the reduction zone.

[0061] In the case where the oxidation of the oxygen carrier is carried out by water vapor, a flow of hydrogen can be obtained at the outlet of the oxidation reactor, according to reaction (3). [Chem 3] M x O y-2n-m / 2 + (2n+m / 2) H 2 O → M x O y + (2n+m / 2) H 2 (3) The oxygen carrier

[0062] In addition to the redox properties required for redox reactions in contact with the hydrocarbon feedstock or the oxidizing gas, and the characteristics necessary for implementing fluidization, the oxygen carrier used in the CLC process and installation according to the invention has a capacity to release gaseous oxygen by the CLOU effect.

[0063] Such oxygen carriers, usable in the CLC process and installation according to the invention, are known, and examples thereof are described in Mattisson et al., 2009 or Shafiefarhood et al. 2015, already cited above, or in patent applications EP3558518 and EP3558515, or in the French patent application filed under number 20 / 08.189.

[0064] The oxygen carrier is preferably composed of metal oxides, such as oxides of Cu (eg CuO / Cu 2 O pair), Co (eg and Co 3 O 4 / CoO pair), Mn (eg Mn 2 O 3 / Mn 3 O 4 pair), mixed oxides Co-Fe or Mn-Fe for example in the form of spinels (specific crystalline structures of mixed oxides reproducing the structure of the mineral spinel MgAl 2 O 4 ), perovskites (specific crystalline structures of mixed oxides reproducing the structure of the mineral perovskite CaTiO 3 ) such as CaMnO 3 , alone or in a mixture.

[0065] Such compounds can be derived from ores (e.g. pyrolusite for Mn oxide) or synthetic (e.g. copper oxide particles supported on an alumina or silica-alumina matrix).

[0066] They may or may not be associated with a binder or a support, such an association making it possible in particular to ensure good reversibility of the oxidation and reduction reactions, and to improve the mechanical resistance of the particles. Indeed, metal oxides, chosen for example from the redox couples of Cu, Mn, Co, or their mixtures, used pure, that is to say without binder or support, can show a significant and rapid decrease in their oxygen transfer capacity, due to the sintering of the metal particles, due to the successive oxidation / reduction cycles at high temperature. Many types of binders and supports have been studied in the literature, in order to increase the mechanical resistance of the particles. Among these, we can cite alumina, metallic aluminate spinels, titanium dioxide, silica, zirconia, ceria, kaolin, bentonite, perovskites, etc.

[0067] Advantageously, the oxygen carrier may comprise at least one manganese or copper oxide, or mixtures thereof, and preferably at least one copper oxide, and more preferably associated with a binder or a support, for example a support of alumina (Al 2 O 3 ), silica (SiO 2 ), alumino-silicic (mixture of alumina Al 2 O 3 and silica SiO 2 ), metal aluminates, silicates, aluminum silicates, aluminosilicates, titanium dioxide, perovskites, zirconia, tectosilicates such as feldspars chosen from celsiane, slawsonite, anorthite, or feldspathoids such as kalsilite, or a mixture of a tectosilicate as previously mentioned with an oxide as previously mentioned (alumina, metal aluminates, silica, silicates, aluminum silicates, aluminosilicates, titanium dioxide, perovskites, zirconia).

[0068] According to one or more embodiments, the oxygen carrier may comprise at least one manganese or copper oxide, and preferably at least one copper oxide, preferably associated with a support, and more preferably a support of alumina (Al 2 O 3 ), silica (SiO 2 ), alumino-silicic (mixture of alumina Al 2 O 3 and silica SiO 2 ), feldspars such as celsiane, slawsonite, anorthite or feldspathoids such as kalsilite.

[0069] According to one or more embodiments, the oxygen carrier may comprise at least one manganese oxide, and is for example constituted by pyrolusite, which is a natural variety (ore) of manganese dioxide, MnO 2 , also known as manganese (IV) oxide.

[0070] According to one or more embodiments, the oxygen carrier may comprise, and preferably may consist of, copper oxide supported on alumina (CuO / Al 2 O 3 ).

[0071] Oxygen carrier particles combining one or more metal oxides and a support may have a specific initial porosity (before any use in the CLC process) playing a role in the performance of the oxygen carrier, in particular improving the lifetime of the particles in the CLC process. This is the case, for example, for the oxygen carriers disclosed in patent applications EP3558515 and EP3558518, and described below.

[0072] According to one or more embodiments, the oxygen carrier may comprise, and preferably may consist of, as described in patent application EP3558515, copper oxide, preferably forming between 5% and 75% by weight of said oxygen carrier, and a ceramic support within which the copper oxide is dispersed, preferably forming between 25% and 95% by weight of said oxygen carrier, and consisting of calcium aluminate (CaAl 2 O 4 ), silica (SiO 2 ), titanium dioxide (TiO 2 ), perovskite (CaTiO 3 ), alumina (Al 2 O 3 ), zirconia (ZrO 2 ), yttrium dioxide (Y 2 0 3 ), barium zirconate (BaZrO 3 ), magnesium aluminate (MgAl 2 O 4 ), magnesium silicate (MgSi 2 O 4 ), or lanthanum oxide (La 2 O 3 ), preferably alumina or a mixture of alumina and silica.Such a carrier has a porosity such that the total pore volume is between 0.05 and 1.2 ml / g, and preferably between 0.1 and 0.85 ml / g, the pore volume of the macropores constitutes at least 10%, and preferably at least 40%, of the total pore volume of the oxygen carrier; and the size distribution of the macropores within the oxygen carrier is between 50 nm and 7 µm, preferably between 50 nm and 3 µm. Such an oxygen carrier is efficient in terms of oxygen transfer capacity, reactivity with the various hydrocarbon feedstocks capable of being treated, and mechanical strength. In particular, it has a long service life, making it possible to reduce the investment and / or operating costs for such processes.

[0073] According to one or more embodiments, the oxygen carrier may comprise, and preferably may consist of, as described in patent application EP3558518, copper oxide, preferably forming between 5% and 75% by weight of said oxygen carrier, and a ceramic support within which the copper oxide is dispersed, preferably forming between 25% and 95% by weight of said oxygen carrier, and comprising between 60% and 100% by weight of at least one feldspar or feldspathoid having a melting temperature above 1500°C, preferably chosen from celsiane, slawsonite, anorthite, and kalsilite, more preferably celsiane, and between 0% and 40% of at least one oxide chosen from alumina, metal aluminates, silica, silicates, aluminosilicates, titanium dioxide, perovskites, zirconia.Such a carrier has a porosity such that the total pore volume is between 0.05 and 0.9 ml / g, and preferably between 0.1 and 0.5 ml / g, the pore volume of the macropores constitutes at least 10%, and preferably at least 50%, of the total pore volume of the oxygen carrier; and the size distribution of the macropores within the oxygen carrier is between 50 nm and 7 µm, preferably between 50 nm and 4 µm. Such an oxygen carrier is also efficient in terms of oxygen transfer capacity, reactivity with the various hydrocarbon feedstocks capable of being treated, and mechanical strength. In particular, it has a long service life, making it possible to reduce the investment and / or operating costs for such processes.

[0074] It should be remembered that according to the IUPAC nomenclature, we speak of micropores for pores whose size (opening) is less than 2 nm, of mesopores for pores whose size is between 2 nm and 50 nm, and of macropores for pores with a size greater than 50 nm. The total pore volume is understood to be the volume measured by intrusion with a mercury porosimeter according to the ASTM D4284-83 standard, (measurement of the volume of mercury injected when the pressure exerted increases from 0.22 MPa to 413 MPa). The volume of macropores is measured by mercury intrusion porosimetry according to the same standard (the value from which the mercury fills all the intergranular voids is set at 0.2 MPa, and it is considered that beyond this the mercury penetrates into the pores of the sample). The size distribution of macropores within the particles is measured by mercury porosimetry.

[0075] According to one or more embodiments, the oxygen carrier may comprise, and preferably may consist of, as described in the French patent application filed under number 20 / 08.189, copper with a total content X of between 5% and 39% expressed by weight of copper oxide relative to the total weight of the oxygen carrier in its oxidized form, and a ceramic support within which the copper is dispersed, the support comprising a first sub-stoichiometric spinel of formula Mg a Al b O4, and / or a second sub-stoichiometric spinel of formula Cu c Mg d Al e O 4 , with a, b, c, d, and e described according to the following formulas: a= 4 / [ 1 + ( 3 * ( ( ( 100 - X ) / Y ) - 1) ) x M MgO / M Al2O3 ], b = (8 * (100-XY)) / [ Y * M Al2O3 / M MgO + 3 x ( 100 - X - Y) ], c = (4 * X) / [ M CuO * ( (X / M CuO ) + (Y / M MgO ) + 3 * ( 100 - X - Y ) / M Al2O3 )), d = (4 * Y) / [ M MgO * ( ( Al2O3 * ( (X / M CuO ) + ( Y / M MgO ) + 3 * ( 100 - X - Y ) / M Al2O3 )],.

[0076] M MgO , M CuO , M Al2O3 being the respective molar masses of MgO, CuO and Al 2 O 3 , Y being the quantity of MgO in percentage by weight of the oxygen carrier, with X between 5% and 39%, Y between 1% and 23%, and Y < -0.6342X + 26.223. Such an oxygen carrier is another example of an oxygen carrier with good mechanical strength, which allows it to have a long service life and thus reduce the investment and / or operating costs of the process, while being efficient in terms of oxygen transfer capacity and reactivity with the different types of hydrocarbon feedstocks to be treated.

[0077] The oxygen storage capacity of the oxygen carrier can advantageously be understood, depending on the type of material, between 1% and 15% by weight. It is understood as the mass of oxygen corresponding to the transition between the most reduced state of the oxygen carrier and its most oxidized state; it is, for example, 10% when related to the mass of CuO used in the case of the CuO / Cu 2 O couple. In the case where the oxygen carrier is supported on an inert support, the storage capacity is reduced to the mass of the assembly formed by the support and the active phase, i.e. 3% for the CuO / Cu 2 O example if this active phase represents 30% of CuO dispersed in a support.Advantageously, the quantity of oxygen actually transferred by the metal oxide is between 1 and 3% by weight, typically 2% by weight, which makes it possible to use only a fraction of the oxygen storage capacity, ideally less than 30% of it in order to limit the risks of mechanical aging or agglomeration of the particles. In the case of oxygen carriers composed of a supported active phase, the degradation of the mechanical properties and the agglomeration of the particles are limited, and it is possible to go higher in the use of oxygen, up to 100% of the capacity. The use of only a fraction of the oxygen storage capacity also has the advantage that the fluidized bed acts as a thermal ballast and thus smooths out the temperature variations along the path of the bed.

[0078] According to the invention, the oxygen carrier is capable of releasing a portion of the oxygen it contains in the form of gaseous oxygen under certain conditions in the CLC process, typically when subjected to an atmosphere with low partial pressure of oxygen for a sufficient time. The other portion of the oxygen in atomic form in the oxygen carrier can be used during reduction reactions in contact with the hydrocarbon feedstock. This is what is referred to herein as the capacity to release gaseous oxygen by the CLOU effect.

[0079] It is generally possible to experimentally establish a profile of gaseous oxygen release as a function of time for a given oxygen carrier, when it is subjected, in its most oxidized form, to an inert atmosphere, typically composed of nitrogen or rare gases, by measuring the oxygen produced as a function of time. figure 3illustrates for example the release profile of gaseous oxygen from an oxygen carrier formed from manganese oxides, detailed in example 1.

[0080] Typically, the oxygen carrier used in the CLC process and installation according to the invention is capable of releasing gaseous oxygen, under an atmosphere with low partial oxygen pressure, i.e. containing between 0 and 2% vol. of oxygen, preferably less than 2% vol. of O 2 , and more preferably less than 1% vol. of O 2 , for example pure nitrogen, CO 2 , water vapor, or a mixture of CO 2 and water vapor, at the temperature and pressure conditions of the CLC process, as is the case, for example, for recycled combustion fumes.

[0081] Under these conditions, the oxygen carrier used in the CLC process and installation according to the invention is preferably capable of releasing gaseous oxygen very quickly.

[0082] Typically, most, or even more than 80% or even 90%, of the gaseous oxygen that it is capable of releasing can be reached after a few minutes, for example between 1 minute and 15 minutes, preferably between 1 minute and 10 minutes, and more preferably between 1 minute and 5 minutes.

[0083] By "neutral" or "inert" atmosphere with respect to the oxygen carrier, we mean an atmosphere which does not present any possibility of spontaneous chemical reaction, under the conditions of the test, of the gases which compose it with the oxygen carrier.

[0084] The shape and size of the particles are advantageously adapted to implementation in a fluidized bed. The oxygen carrier may be in the form of fluidizable particles, belonging to groups A, B or C of the Geldart classification, based on the size of the particles and their density difference with the gas, (D. Geldart. “Types of gas fluidization”. Powder Technol. 7(5), 1973, p.285-292). Preferably the particles of the oxygen carrier belong to group A or group B, and more preferably to group B, of the Geldart classification.

[0085] Preferably, the particles of the carrier solid are substantially spherical, or may be of any similar shape.

[0086] Preferably, the particles of the oxygen carrier have a particle size such that more than 90% of the particles have a size between 50 µm and 600 µm, more preferably a particle size such that more than 90% of the particles have a size between 80 µm and 400 µm, even more preferably a particle size such that more than 90% of the particles have a size between 100 µm and 300 µm, and even more preferably a particle size such that more than 95% of the particles have a size between 100 µm and 300 µm.

[0087] Particle size can be measured by laser particle size analysis. The particle size distribution of the oxygen-carrying solid is preferably measured using a laser particle size analyzer, e.g. Malvern Mastersizer 3000 ®< , preferably in liquid form, and using Fraunhofer theory.

[0088] Preferably, the particles of the oxygen carrier have a grain density of between 500 kg / m 3< and 5000 kg / m 3< , preferably a grain density of between 800 kg / m 3< and 4000 kg / m 3< , and even more preferably a grain density of between 1000 kg / m 3< and 3000 kg / m 3< . Use of gaseous oxygen released by the CLOU effect

[0089] The CLC method and installation according to the invention are notably described below in relation to the figures 1 And 2 , which schematically represent two non-limiting embodiments of the invention.

[0090] There figure 1is a diagram illustrating the CLC installation and process according to a first embodiment of the invention. Only part of the CLC installation is shown for the sake of simplification: the oxidation zone is not shown because it is not necessary for a better understanding of the invention, the present invention relating more specifically to the fluidic connection between said oxidation zone and the combustion reactor, and the operation of the combustion reactor comprising recycling of the combustion fumes. The diagram of the figure 1 is a schematic diagram, in which, for example, the locations of the flows relative to each other do not presuppose their spatial location on an actual CLC installation, unless specifically mentioned in the description.

[0091] There figure 1represents an embodiment of the invention in which the hydrocarbon feedstock 8 is solid, and for example chosen from the list consisting of coal, coke, petcoke, biomass, oil sands and household waste. However, the present invention is not limited to the combustion of solid feedstocks. The invention includes other embodiments more suited to the combustion of gaseous or liquid feedstocks, which do not necessarily include all the elements represented in the figure 1 , or on the contrary which include elements not represented in the figure 1 but well known to those skilled in the art. For example, the solid / solid separator S2 is not necessary in the case of combustion of gaseous or liquid charges.

[0092] The CLC process according to the invention comprises the combustion of a hydrocarbon feedstock 8 by contacting it with the oxygen carrier 7 in the reduction zone R0, and the oxidation of the oxygen carrier from the reduction zone R0 by contacting it with an oxidizing gas, preferably air, in the oxidation zone (not shown).

[0093] According to the invention, the oxidized oxygen carrier 3 is sent to at least one sealing device S1 operating in a double fluidized bed, positioned downstream of the oxidation zone on a line for transporting the oxygen carrier to said reduction zone R0. The sealing device S1 in fact ensures gas sealing between the oxidation zone and the reduction zone. It is a non-mechanical gas-sealing device, described in detail below. The oxygen carrier 3 is in its oxidized state because it comes from the oxidation zone. The sealing device S1 is supplied with at least one neutral fluidization gas 4, so as to form at least a first flow 7 comprising at least a portion of the oxygen carrier, said flow 7 being sent to the reduction zone R0, and a second flow 6 which is gaseous and which comprises a portion of the neutral fluidization gas 4 and gaseous oxygen released by the oxygen carrier.

[0094] The gaseous flow 6, containing gaseous oxygen released by the carrier, is mixed with a portion 16 of the combustion fumes 15 to form a combustion fume recycle flow 9 sent at least in part, after having been successively cooled, compressed, and reheated, into the reduction zone R0 for its operation in a fluidized bed.

[0095] The recycling of part of the combustion fumes in the reduction zone R0 allows it to operate in a fluidized bed, without it being necessary to use another fluidization gas, or at least by reducing the need for an additional fluidization gas, in particular additional water vapor.

[0096] The combustion fumes 15 may contain residual unburned species, which are gaseous species, typically CO and / or H 2 and / or CH 4 , originating from the reduction zone R0. The mixing of the gas flow 6 with a portion 16 of said fumes 15 in this case makes it possible to carry out the combustion of said residual unburned species of the fumes 15.

[0097] Residual unburned species are understood to mean the gaseous compounds produced during incomplete combustion of the feedstock, mainly unburned gaseous compounds, e.g. CO and / or H2, resulting from the conversion of the feedstock in contact with water (devolatilization / gasification of a solid or liquid feedstock and reforming of methane, producing CO and H2) or a fraction of the unconverted gaseous hydrocarbon feedstock, e.g. CH4.

[0098] The residual unburned species that the fumes may contain are in fact likely to damage the compressor C1 used for recycling the combustion fumes in the reduction zone R0. The recycle compressor has the function of increasing the pressure of the fumes resulting from the combustion so as to bring them to a pressure sufficient to overcome the pressure drop of the fuel reactor (mainly induced by the fluidized bed and the distributors) and thus to be able to introduce them into the fuel reactor as fluidization gas. Thus, the combustion of the residual unburned species by means of the gaseous oxygen recovered in the device S1 makes it possible to protect said compressor, without having to resort to an oxygen flow external to the process, or at least by reducing the requirements for such an external oxygen flow 17 to the CLC process, thus contributing to limiting the operating costs of the CLC process.

[0099] In addition to carrying out, at least in part, the combustion of the residual unburned species that the fumes may contain, the gaseous oxygen of the gaseous flow 6 mixed with a portion 16 of the combustion fumes 15 can also participate in the combustion of the charge in the reduction zone if it has not been entirely consumed during the combustion of the residual unburned species in the combustion fume recycling circuit. The gaseous oxygen that can thus remain in the combustion fume recycle flow 9 sent to the reduction zone R0 reacts with the hydrocarbon charge, improving the combustion performance in particular due to the speed of the gas / gas reactions.Furthermore, since gaseous oxygen accelerates the gasification of the feedstock (faster gasification with O2 than with H2O), it is possible to reduce the residence time of the feedstock in the reduction zone, which can result in a smaller sizing of the fuel reactor requiring a smaller volume for the dense bed, and ultimately limit the investment costs for the CLC installation.

[0100] In the reduction zone R0, the flow 7 of oxygen carrier coming from the device S1, as well as the hydrocarbon feedstock 8, are therefore brought into contact within a fluidized bed by a fluidization gas comprising at least part of the conditioned combustion fumes recycle flow 9, also ensuring the gasification of the solid hydrocarbon feedstock.

[0101] The reduction zone R0 is configured so that complete combustion of the hydrocarbon feedstock, in particular of the gaseous species of the feedstock, is sought. The combustion fumes are thus essentially composed of a mixture of CO2 and H2O. However, the combustion fumes may also contain a small quantity of residual unburned species as explained above, in particular CO + H2 (synthesis gas), from the reduction zone, formed during the incomplete combustion of a part of the feedstock, which can particularly occur in the case of the use of solid hydrocarbon feedstocks.

[0102] The reduction zone R0 can operate as a dense fluidized bed or a transported fluidized bed or in an arrangement of beds consisting of a dense phase and a transported phase. Advantageously, the gas velocity in the upper part of the reduction zone R0 is between 1 m / s and 10 m / s.

[0103] A mixture 11 comprising the gases resulting from the combustion (including any residual unburned gaseous species) and the particles of the oxygen carrier, as well as fluidization gas and solid particles of unburned material resulting from the unconverted solid feedstock (unburned material particles), is discharged at the top of the reduction zone R0 to be sent to a solid / solid separator S2, fluidized by a fluidization gas 12, making it possible to isolate the reduced oxygen carrier from the other compounds. In particular, the solid / solid separator S2 makes it possible to separate the particles of unburned material from the particles of the oxygen carrier. Such a solid / solid separator is known and for example described in international application WO2011151535.It preferably comprises an enclosure with a mixture inlet pipe 11 opening into a diluted phase in the upper part of the enclosure, an outlet pipe located in the lower part of the enclosure and an outlet pipe located in the upper part of the enclosure. The inlet and outlet / outlet parameters are chosen to create in the enclosure a dense phase in the lower part and the diluted phase in the upper part (solid content generally less than 5%, or even 1%). In the separator S2, the superficial velocity of the gas flow is advantageously greater than the terminal fall velocity of the unburned fuel particles to allow them to be entrained with the gas, thus allowing a "rapid" separation between the heavy particles (oxygen carrier) and the light particles (unburned particles).By rapid separation is meant a separation taking place in less than 1 minute and preferably in less than 20 seconds, this duration corresponding to the residence time of the light particles in the dilute phase of the separator. A flow 13 of reduced oxygen carrier separated in the separator S2 is sent to the air reactor, while another flow 14 comprising the other compounds, including the unburned particles, is sent to a gas / solid separator S3, typically a cyclone, making it possible to separate the gases from the unburned particles, and to form a flow 10 of said unburned particles sent to the reduction zone R0, for their combustion. One or more other gas / solid separators may be arranged downstream of the separator S3 to carry out a more thorough separation.

[0104] The mixing of the gas flow 6 with a portion 16 of the fumes 15 leaving the gas / solid separator S3, forming the flue gas recycle flow 9, is preferably carried out before the compression of the recycle flow in the compressor C1, in order to burn the residual unburned species, e.g. the synthesis gas, possibly contained in the fumes to preserve said compressor, and preferably before any cooling of the recycle flow before its passage into the compressor C1, so as to carry out combustion under the best temperature conditions.

[0105] Advantageously, the gaseous flow of flue gas recycling 9 is cooled by passing through at least one first heat exchanger E1, then said cooled flow of flue gas recycling is compressed in the compressor C1, then said cooled and compressed flow of combustion flue gas recycling 18 is reheated by passing through the heat exchanger E1 before being sent at least in part to the reduction zone R0.

[0106] Preferably, the recycled flue gas stream 9 is cooled by passing through a second heat exchanger E2 positioned between the first heat exchanger E1 and the compressor C1. The function of the exchanger E2 is to bring the recycled flue gas stream to a temperature compatible with the operation of the selected compressor. In this case, it is possible to mix the gas stream 6 with the portion 16 of the combustion flue gases 15 between the first heat exchanger E1 and the second heat exchanger E2.

[0107] Preferably, the flue gas recycle stream 9 is cooled to a temperature of between 70°C and 450°C, preferably between 70°C and 300°C, and more preferably between 150°C and 300°C, upstream of the compressor C1, then compressed to a pressure of between 0.02 MPa and 0.3 MPa, then reheated to a temperature of between 300°C and 950°C. Preferably, the maximum temperature reached during heating of the compressed flue gases is 50°C lower than the temperature of the mixture of streams 6 and 16, preferably lower than 20°C.

[0108] Preferably, the fumes are compressed by the compressor C1 to a pressure approximately 0.03 MPa higher than that of the reduction zone, in particular in order to compensate for the pressure drop of the distributor.

[0109] According to the invention, the gaseous oxygen released by the oxygen carrier in the sealing device S1 may be sufficient to carry out the combustion of the residual unburned species, e.g. CO and / or H 2 , of the part 16 of the fumes 15 which will form the flue gas recycle flow 9. However, an injection of fresh dioxygen 17, oxygen external to the CLC process, may be carried out in the part 16 of the combustion fumes 15 to complete the combustion of said residual unburned species carried out with the gaseous oxygen supplied by the second gas flow 6.

[0110] Preferably, the gas stream 6 from the sealing device S1 comprises between 1% and 20% vol. of gaseous oxygen, preferably between 1% and 16% vol., and more preferably between 2% and 16% vol. The oxygen carrier 3 sent into the sealing device S1 preferably comes from a stream 1 containing the carrier directly from the oxidation zone (not shown) and transported by air, or another oxidizing gas, preferably containing between 2% and 10% oxygen, and sent into a gas / solid separator S0, typically a cyclone. The gas / solid separator S0 separates the gaseous and solid species into a predominantly gaseous flow 2, consisting of depleted air also called depleted air (or oxygen-depleted oxidizing gas if an oxidizing gas other than air is used in the oxidation zone), and a predominantly solid flow comprising the oxidized oxygen carrier 3.

[0111] The sealing device S1 can make it possible to separate the oxygen carrier into two parts: one part forming the first flow 7, and a second complementary part forming a second flow 5, preferably extracted from the bottom of the sealing device S1, and which is again sent to the oxidation zone. This recycle 5 makes it possible to increase the average residence time of the oxygen carrier in the air reactor by increasing the average number of passes. The desired effect is to maximize the degree of oxidation of the carrier and thus approach the theoretical equilibrium determined between the solid oxygen carrier and the partial pressure of oxygen in the gaseous atmosphere at the outlet of the air reactor. It is thus possible to maximize the degree of oxidation of the oxygen carrier, and in fact maximize its CLOU effect potential.

[0112] The sealing device S1 makes it possible to ensure maximum gas sealing between the oxidation zone and the reduction zone, while allowing the release of gaseous oxygen from the oxygen carrier forming the gas flow 6 also containing fluidization gas 4, preferably extracted by a pipe located in the upper part of the sealing device S1. The fluidization gas 4 used is not air, but is essentially composed of water vapor, CO 2 , for example taken from a CO 2 compression chain downstream of the process, or a mixture of CO 2 and water vapor between 0% and 2% vol. of O 2 , preferably less than 2% vol. of O 2 . During its stay in the device S1, which is not fluidized by air, the oxygen carrier releases a large part of its oxygen by CLOU effect.The partial pressure of oxygen is in fact very low, or even zero, which allows this release of gaseous oxygen from the oxygen carrier, under the temperature conditions within the device S1, which are close to those of the oxidation and reduction zones, typically, depending on the oxygen carrier and the feedstock chosen, between 600°C and 1200°C. Preferably, the temperature operated in the device S1 is 50°C lower than the temperature operated in the oxidation zone.

[0113] The sealing device S1 and its operation are such that the release of gaseous oxygen by the oxygen carrier is achieved, in particular by a residence time of the oxygen carrier in the sealing device S1 suitable. The residence time of the carrier is typically between 20 and 900 seconds, preferably between 40 and 300 seconds.

[0114] The gas tightness enabled by the sealing device S1, thanks to the fluidization by means of the fluidization gas 4, is important to, on the one hand, guarantee the best possible CO2 capture rate, and on the other hand to guarantee the highest possible quality for the captured CO2. Indeed, it is important that the oxidizing gas used in the oxidation zone does not contaminate, or as little as possible, the reduction zone. For example, the tightness can in particular make it possible to comply with the standards for non-condensables in the CO2 flow in the combustion fumes, for its transport and / or storage, typically less than 5% mol.

[0115] The sealing device S1 operates in a double fluidized bed, that is to say that it comprises two different fluidized beds within the same device, more precisely two beds operating under different fluidization conditions. Typically, to operate in a double fluidized bed, the sealing device comprises two communicating zones, each configured to operate in a fluidized bed under its own operating conditions.

[0116] The sealing device S1 preferably comprises an enclosure provided with a first zone S1a and a second zone S1b in fluid communication, the fluidization conditions being different in the first and second zones S1a and S1b so as to create a separate fluidized bed in each of the first and second zones. The first zone S1a receives particles of the oxygen carrier 3 from the oxidation zone. The second zone S1b receives at least a portion of the particles of the oxygen carrier from the first zone S1a which release gaseous oxygen discharged into the gas flow 6 via an outlet pipe located at the top of the second zone S1b.

[0117] The injection of the fluidizing gas 4 into the sealing device S1 can be carried out in the form of multiple injections (not shown).

[0118] The sealing device S1 may also be a siphon (“loop seal” in English) configured to evacuate the gas flow 6. Such a siphon comprises a descending leg (“downleg” in English) having the same function as the first zone S1a, connected, preferably by a substantially horizontal conduit, to an ascending leg (“uplgeg” in English) having the same function as the zone S1b. The ascending leg comprises a first part in the form of a substantially vertical conduit extending by a second part in the form of an inclined conduit descending towards the downstream capacity, i.e. the fuel reactor. The siphon S1 comprises an evacuation conduit for the gas, preferably positioned at the top of the first part of the ascending leg, at the junction with the second inclined part of the ascending leg.Thus, the siphon S1 allows the gas flow 6 to be evacuated, unlike a classic siphon configuration where the ascending leg ("upleg") would take the entire mixture formed by the solid and the gas to the downstream capacity.

[0119] There figure 2 schematically illustrates the CLC installation and method according to a second embodiment of the invention. This second embodiment is in all respects identical to the first embodiment shown in figure 1and described above, except that only a part of the combustion flue gas recycle flow 9 is sent to the reduction zone R0, another part 19, preferably minor, being sent, after its successive cooling, compression and heating, to the sealing device S1 to be used as fluidization gas, replacing or supplementing the neutral fluidization gas 4, preferably as a replacement.In particular, the flue gas recycle stream 9 is cooled by passing through at least one first heat exchanger E1, and preferably then by passing through a second heat exchanger E2, then said cooled flue gas recycle stream is compressed in the compressor C1, then said cooled and compressed combustion flue gas recycle stream 18 is reheated by passing through the heat exchanger E1, before a portion, preferably a major portion, is sent to the reduction zone R0, and another portion 19, preferably a minor portion, is sent to the sealing device S1.

[0120] The CLC installation has been described above, alongside the description of the CLC process. It is recalled that it includes: the reduction zone R0 configured to operate in a fluidized bed and carry out the combustion of the hydrocarbon feedstock by contacting it with the oxygen carrier in the form of particles; the oxidation zone (not shown in the figures) configured to operate in a fluidized bed and carry out the oxidation of the oxygen carrier from the reduction zone R0, by contacting it with an oxidizing gas, preferably air;a line for transporting the oxygen carrier from the oxidation zone to the reduction zone R0, said transport line comprising the sealing device S1 configured to operate in a double fluidized bed by means of a neutral fluidizing gas (4, 19) and to form at least the flow 7 comprising at least the part of the oxygen carrier destined for the reduction zone R0 and the gaseous flow 6 comprising a part of the neutral fluidizing gas (4, 19) and of the gaseous dioxygen released by the oxygen carrier, the sealing device S1 comprising an outlet pipe for the gaseous flow 6;a line for recycling a portion 16 of the combustion fumes 15 into the reduction zone R0, the fumes possibly containing residual unburned species from the reduction zone R0, e.g. CO and / or H2 and / or CH4, into said reduction zone R0. The recycle line is connected to the outlet pipe of the gas flow 6 of the sealing device S1 so as to mix the gas flow 6 with the portion 16 of the combustion fumes 15 and form a recycle flow of the combustion fumes 9. The recycle line comprises a system for cooling, compressing and heating the recycle flow of the combustion fumes 9 before sending it into the reduction zone R0. ; Examples

[0121] The following examples aim to show certain performances of the CLC process and installation according to the invention, in particular the reduction of the need for water vapor to ensure the fluidization of the reduction zone and the reduction of the need for external oxygen for the combustion of the unburned gases CO and H 2 present in the combustion fumes to be recycled. Example 1

[0122] This example concerns the experimental measurement of the oxygen release rate of an example of an oxygen carrier exhibiting a CLOU effect.

[0123] It uses a batch fluidized bed (the oxygen-carrying solid does not circulate) whose temperature can be controlled by an external device such as heating shells and whose fluidization gas composition can be controlled to alternately supply the reactor with an oxidizing, inert or reducing atmosphere. The gaseous effluents are collected and a sample is analyzed by gas chromatography. The operation is carried out in cycles with a temperature setpoint maintained constant on each of the phases.

[0124] The first phase of the cycle consists of fluidizing the reactor with an oxidizing gas (N2 / O2 mixture at 20% vol. of O2). The end of this cycle is characterized by an O2 content downstream equal to that upstream of the reactor, reflecting complete oxidation of the material.

[0125] The second phase consists of fluidizing the reactor with an inert atmosphere. It is during this phase that the CLOU effect will be measured. The end of this cycle is characterized by an O2 content that tends towards zero, i.e. the exhaustion of the CLOU effect.

[0126] The third phase consists of fluidizing the reactor with a reducing atmosphere, typically methane CH 4 . The aim is to exhaust the residual oxygen contained in the structure of the oxygen carrier. The end of the cycle is the measurement of a reducing species content at the outlet equal to that at the inlet.

[0127] After a new inerting phase to avoid mixing the oxidizing and reducing atmospheres, a new cycle can begin.

[0128] Here we present the monitoring of a material during the second phase of the cycle.

[0129] The manganese oxide oxygen carrier is exposed to air until complete oxidation at 940°C, then it is abruptly exposed to a neutral atmosphere by flushing with pure nitrogen and the oxygen release profile is recorded as a function of time. The oxygen carrier is a natural manganese ore, pyrolusite, which is a naturally occurring variety of manganese dioxide, MnO 2 , also known as manganese(IV) oxide. The redox couple is Mn 2 O 3 / Mn 3 O 4 , and the carrier particles have a size between 150 µm and 300 µm.

[0130] The results are presented at the figure 3The x-axis represents time (in seconds), and the y-axis the O 2 flux per kg of oxygen carrier (in mol / kg / s). The oxygen carrier is first exposed to air until complete oxidation at 940°C. It is then abruptly exposed to a neutral atmosphere by flushing with pure nitrogen, and the oxygen release profile is recorded as a function of time. Example 2 (comparative)

[0131] An example of a pilot CLC plant, fueled with petcoke as solid fuel, is loaded with a manganese oxide-based oxygen carrier as described in Example 1. This oxygen carrier exhibits a CLOU effect.

[0132] The pilot CLC installation according to this example 2 is similar to that shown in figure 1, except that it is not configured to exploit the gaseous oxygen released by the oxygen carrier by CLOU effect in the sealing device S1 and to carry out the mixing of the flow 6 with the part of the fumes to be recycled: it does not include a connection between the sealing device S1 and the recycle line of a part 16 of the combustion fumes 15. The elements S0, S2, S3 are not detailed in this example.

[0133] For this example of a 3MW pilot CLC installation, the estimated residence time of the oxygen carrier in the sealing device S1 is 160 s. By integrating the oxygen release profiles as a function of the residence time, it is thus possible to estimate the total quantity of oxygen released in the sealing device S1.

[0134] The gas flow leaving the sealing device S1 operating in a double fluidized bed is combined with the main flow of depleted air leaving the air reactor. The composition of the combination of these two flows is given in the following table 1: [Table 1] Composition in mol% H 2 0.0% H2O 8.7% CO 0.0% CO2 1.8% CH 4 0.0% O 2 2.7% N 2 86.8% SOx 0.0% NOx 0.0%

[0135] In the chemical composition tables given in this example, values ​​are rounded to one decimal place.

[0136] The fumes leaving the fuel reactor R0 are partly recycled to serve as fluidization gas 9 injected into the fuel reactor.

[0137] The composition of the fumes at the fuel reactor outlet is given in the following table 2: [Table 2] Composition in mol% H 2 1.0% H2O 43.6% CO 1.0% CO2 53.4% CH 4 0.0% O 2 0.0% N 2 0.4% SOx 0.2% NOx 0.3%

[0138] Since these fumes contain unburned gases CO and H2, combustion in air or oxygen, also called "air or oxygen polishing" is necessary to burn these gases.

[0139] The portion of fumes leaving the fuel reactor at 950°C, which is intended to be recycled into the fuel reactor as fluidization gas, is a flow with a flow rate of 1690 Nm 3 < / h which must be mixed with a flow of pure oxygen external to the CLC process, in order to completely burn the CO and H 2 compounds present.

[0140] The flow of pure O2 required to remove CO and H2 is 17 Nm3 / h.

[0141] Downstream of the mixing zone with the external pure O 2 flow, the flow is cooled to 150°C by successive exchange with the cooled flue gases and then with cooling water tubes. The flue gas flow has the composition given in the following table 3 (identical composition before and after cooling): [Table 3] Composition in mol% H 2 0.0% H2O 44.7% CO 0.0% CO2 54.5% CH 4 0.0% O 2 0.0% N 2 0.4% SOx 0.2% NOx 0.3%

[0142] This cooled flue gas stream passes into a recycle compressor and is then reheated to a temperature of 300°C by exchange with the hot flue gas stream, then injected into the fuel reactor, after mixing with 135 kg / h of water vapor. The composition of the gas injected into the fuel reactor is given in Table 4 below: [Table 4] Composition in mol% H 2 0.0% H2O 49.6% CO 0.0% CO2 49.5% CH 4 0.0% O 2 0.0% N 2 0.3% SOx 0.2% NOx 0.3% Example 3 (according to the invention)

[0143] Another example of a pilot CLC plant, fueled with petcoke as solid fuel, is loaded with a manganese oxide-based oxygen carrier as described in Example 1. This oxygen carrier exhibits a CLOU effect.

[0144] The pilot CLC installation according to this example 3 is similar to that shown in figure 1 , and is configured to exploit the gaseous oxygen released by the oxygen carrier by CLOU effect in the sealing device S1 and to carry out the mixing of the flow 6 with the part of the fumes to be recycled. The elements S0, S2, S3 are not detailed in this example.

[0145] Unlike example 2, the gas flow leaving the sealing device S1 operating in a double fluidized bed is not combined with the main flow of depleted air leaving the air reactor, but it is mixed with part of the flow of fumes leaving the fuel reactor.

[0146] The composition of the depleted air at the outlet of the air reactor is given in the following table 5: [Table 5] Composition in mol% H 2 0.0% H2O 0.1% CO 0.0% CO2 2.0% CH 4 0.0% O 2 2.3% N 2 95.5% SOx 0.0% NOx 0.0%

[0147] The composition of the fumes at the fuel reactor outlet is given in the following table 6: [Table 6] Composition in mol% H 2 1.0% H2O 43.6% CO 1.0% CO2 53.4% CH 4 0.0% O 2 0.0% N 2 0.4% SOx 0.2% NOx 0.3%

[0148] The portion of fumes leaving the fuel reactor at 950°C, which is intended to be recycled into the fuel reactor as fluidization gas 9, is a flow with a flow rate of 1550 Nm 3 < / h.

[0149] The mixing of this flue gas flow with the gas flow with a flow rate of 230 Nm 3 < / h exiting at 1000°C from the sealing device S1 causes the combustion of the CO and H 2 compounds present in the flue gas. A flow of pure O 2 external to the CLC process, of 1 Nm 3 < / h, must be injected to completely eliminate the residual CO and H 2 compounds.

[0150] Downstream of the mixing zone with the gas flow from the sealing device S1 and the external pure O 2 flow, the smoke flow is cooled to 150°C by successive exchange with the cooled smoke then with cooling water tubes, and has the composition given in the following table 7: [Table 7] Composition in mol% H 2 0.0% H2O 49.7% CO 0.0% CO2 49.7% CH 4 0.0% O 2 0.0% N 2 0.3% SOx 0.2% NOx 0.2%

[0151] This cooled flue gas stream passes through a recycle compressor and is then reheated to a temperature of 300°C by exchange with the hot flue gas stream, then injected into the fuel reactor. It has the required composition in terms of water vapor concentration, and therefore it is not necessary to add a water vapor stream before its injection into the bottom of the fuel reactor.

[0152] The chemical looping combustion operation according to the invention thus makes it possible to significantly reduce the costs of the process, thanks to the reduction or even absence of the use of additional water vapor, and the reduction of the flow rate of pure oxygen external to the CLC process used for the combustion of unburned gases CO and H 2 in the combustion fumes to be recycled. Table 8 below compares these different flow rates during the operation according to example 2 and according to example 3: [Table 8] Additional steam flow rate to be injected into the bottom of the fuel reactor (kg / h) Flow rate of pure oxygen to burn CO and H2 (Nm3 / h) Example 2 (comparative) 135 17 Example 3 (according to the invention) 0 1

Claims

1. Process for the combustion of a hydrocarbon feedstock (8) by chemical looping oxidation / reduction in which an oxidation / reduction active mass in the form of particles circulates between an oxidation zone and a reduction zone (R0) operating as a fluidized bed, comprising: - the combustion of said hydrocarbon feedstock (8) by bringing it into contact with said oxidation / reduction active mass in the reduction zone (R0); - the oxidation of said oxidation / reduction active mass resulting from said reduction zone (R0) by bringing it into contact with an oxidizing gas, preferably air, in said oxidation zone; characterized by the following process stages: - sending said oxidized oxidation / reduction active mass into at least one sealing device (S1) operating as a double fluidized bed, positioned downstream of said oxidation zone on a line for transportation of said oxidation / reduction active mass to said reduction zone (R0), said sealing device being fed with at least a neutral fluidizing gas (4, 19), so as to form at least a first stream (7) comprising at least a portion of said oxidation / reduction active mass sent to said reduction zone (R0) and a second gas stream (6) comprising a portion of said neutral fluidizing gas (4) and gaseous molecular oxygen released by said oxidation / reduction active mass; - mixing said second gas stream (6) with a portion (16) of the combustion flue gases (15) so as to form a combustion flue gases recycle stream (9) sent, at least in part, after having been successively cooled, compressed and reheated, into said reduction zone (R0) for its operation as a fluidized bed.

2. Process according to Claim 1, in which the portion (16) of the combustion flue gases (15) contains residual unburned entities resulting from the reduction zone (R0), and in which the combustion of said residual unburned entities is carried out in contact with the gaseous molecular oxygen supplied by the mixing of said second gas stream (6) with a portion (16) of the combustion flue gases (15).

3. Process according to Claim 2, additionally comprising the injection of fresh molecular oxygen (17) into said portion (16) of the combustion flue gases (15) in order to complete the combustion of said residual unburned entities.

4. Process according to one of the preceding claims, comprising sending a portion (19) of said combustion flue gases recycle stream (9), after its successive cooling, compression and reheating, into said sealing device (S1) for the operation of said sealing device (S1) as a fluidized bed.

5. Process according to one of the preceding claims, in which said one gases recycle stream (9) is cooled by passing through at least a first heat exchanger (E1), then said one cooled combustion flue gases recycle stream is compressed in a compressor (C1), then said one cooled and compressed combustion flue gases recycle stream is reheated by passing through said first heat exchanger (E1) before being sent, at least in part, to the reduction zone (R0).

6. Process according to Claim 5, in which said combustion flue gases recycle stream (9) is cooled by passing through a second heat exchanger (E2) positioned between the first heat exchanger (E1) and the compressor (C1).

7. Process according to either of Claims 5 and 6, in which said combustion flue gases recycle stream (9) is cooled to a temperature of between 70°C and 450°C, preferably of between 70°C and 300°C, then compressed to a pressure of between 0.02 MPa and 0.3 MPa, then reheated to a temperature of between 300°C and 950°C.

8. Process according to one of the preceding claims, in which said second gas stream (6) resulting from said sealing device (S1) comprises between 1 vol% and 20 vol% of gaseous molecular oxygen.

9. Process according to one of the preceding claims, in which said oxidation / reduction active mass comprises at least one compound chosen from the list consisting of copper oxides, cobalt oxides, manganese oxides, cobalt-iron or manganese-iron mixed oxides, preferably in the form of spinels, perovskites, alone or as a mixture, and preferably said oxidation / reduction active mass comprises at least one copper or manganese oxide, preferably combined with an alumina, silica, alumina / silica, feldspar, such as celsian, slawsonite or anorthite, or feldspathoid, such as kalsilite, support.

10. Process according to one of the preceding claims, in which said neutral fluidizing gas (4, 19) sent into said sealing device (S1) consists essentially of steam, of CO2 or of a mixture of CO2 and of steam comprising between 0 vol% and 2 vol% of O2, preferably less than 2 vol% of O2.

11. Process according to one of the preceding claims, in which said sealing device (S1) comprises a chamber provided with a first zone (Sla) and with a second zone (S1b) in fluidic communication, the fluidization conditions being different in said first and second zones, so as to create a separate fluidized bed in each of the first and second zones, said first zone (Sla) receiving oxidation / reduction active mass particles resulting from the oxidation reactor, and said second zone (S1b) receiving at least a portion of said oxidation / reduction active mass particles resulting from said first zone (Sla) which release gaseous molecular oxygen discharged in said second gas stream (6) via an outlet pipe located at the top of said second zone (S1b).

12. Process according to Claim 11, in which a third stream (5) comprising a portion of said oxidation / reduction active mass is formed and extracted from said bottom of said sealing device (S1) in order to be again sent into said oxidation zone.

13. Process according to one of the preceding claims, in which said oxidation / reduction active mass sent into said sealing device (S1) is separated beforehand from the oxygen-depleted oxidizing gas resulting from the oxidation zone within a cyclone (S0) positioned between said oxidation zone and said sealing device (S1).

14. Process according to one of the preceding claims, in which said hydrocarbon feedstock (8) is a solid feedstock in the form of particles, preferably chosen from the list consisting of coal, coke, petcoke, biomass, oil sands and household waste, said process additionally comprising: - the separation, in a solid / solid separator (S2) operating as a fluidized bed and positioned at the outlet of the reduction zone (R0), between the particles of said oxidation / reduction active mass and particles of unburned matter generated by the combustion of said solid hydrocarbon feedstock (8) which are contained in a first gas / solid mixture (11) resulting from said reduction zone (R0), said solid / solid separator operating as a fluidized bed, then - the separation, in a gas / solid separator (S3) positioned downstream of said solid / solid separator (S2), between the particles of unburned matter and the gas phase which are contained in a second gas / solid mixture (14) resulting from the solid / solid separator (S2), a stream (10) comprising said particles of unburned matter being preferably sent into said reduction zone (R0), and said gas phase forming the combustion flue gases (15).

15. Plant for carrying out the process for the combustion of a hydrocarbon feedstock by chemical looping oxidation / reduction according to any one of the preceding claims, comprising: - a reduction zone (R0) configured to operate as a fluidized bed and to carry out the combustion of said hydrocarbon feedstock by bringing it into contact with an oxidation / reduction active mass in the form of particles; - an oxidation zone configured to operate as a fluidized bed and to carry out the oxidation of said oxidation / reduction active mass resulting from said reduction zone (R0) by bringing it into contact with an oxidizing gas, preferably air; - a line for transportation of said oxidation / reduction active mass from said oxidation zone to said reduction zone (R0), characterized in that said transportation line comprises a sealing device (S1) configured to operate as a double fluidized bed by means of a neutral fluidizing gas (4, 19) and to form at least a first stream (7) comprising at least a portion of said oxidation / reduction active mass destined for said reduction zone (R0) and a second gas stream (6) comprising a portion of said neutral fluidizing gas (4, 19) and gaseous molecular oxygen released by said oxidation / reduction active mass, said sealing device (S1) comprising an outlet pipe for said second gas stream (6); - a line for recycling a portion (16) of the combustion flue gases (15) in said reduction zone (R0), said recycling line being connected to said outlet pipe for said second gas stream (6) of the sealing device (S1) so as to mix said second gas stream (6) with said portion (16) of the combustion flue gases (15) and form a combustion flue gases recycling stream (9), and said recycling line comprising a system for cooling, compressing and heating said combustion flue gases recycle stream (9) before it is sent into said reduction zone (R0).