FR3118134A1 - Process and chemical looping combustion reactor comprising staged fluidization - Google Patents

Abstract

The present invention relates to a process and a CLC installation in which the combustion reactor (10) operates in a dense fluidized bed (5) for the combustion of the charge in contact with particles of an oxido-reducing active mass (3). The dense bed is formed by:- the injection of a primary gas (1) at the base of the reactor, at a rate such that the superficial gas velocity in the dense bed is between Umf and 0.8xUg (Umf: minimum fluidization velocity, Ug: superficial velocity of the operational gas of the dense bed), and - the injection of a secondary gas (2) within the dense bed by at least one injection point located above the injection of the primary gas and the injection of the particles of the active mass, and located at a height of between 0.05×H and 0.7×H, according to a flow rate complementary to the flow rate of the primary gas so as to reach Ug. Figure 2 to be published

Description

Process and chemical looping combustion reactor comprising staged fluidization

The present invention relates to the field of the combustion of hydrocarbon feedstocks by oxidation-reduction in a chemical loop (CLC for Chemical Looping Combustion according to the English terminology) operating in a fluidized bed, and more specifically relates to a CLC process and a CLC installation comprising injections of gas over several stages in the combustion reactor to form a dense fluidized bed of the reactor where the combustion takes place, and making it possible to limit the formation of large bubbles in the dense fluidized bed which are detrimental to the mechanical stability and to the burning quality.

A CLC process consists in implementing oxidation-reduction reactions of an active mass, typically a metal oxide, to break down 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 burning area.

The redox active mass, which releases part of the oxygen it contains on contact with the charge in the combustion zone, thus plays the role of oxygen carrier between said combustion zone and the oxidation zone. where it is oxidized again.

This solid material is in the form of fluidizable particles, belonging to groups A, B or D, or even C of the Geldart classification which is based on the size of the particles and on their difference in density with the gas, and often at group B, with a typical particle size between 50 and 500 µm. The particles are brought into contact in the reaction zones, with either the oxidant gas or the feed, in the form of fluidized beds at high temperature, and are generally transported from one zone to another in a fluidized form. The set of particles transported in a fluidized form is commonly called a circulating fluidized bed.

These particles are oxidized in contact with an oxidizing gas, typically air (or steam), in at least a first reaction zone, called oxidation reactor or air reactor. They are then transported to at least a second reaction zone called a reduction reactor or combustion reactor or fuel reactor, where they are brought into contact with a solid hydrocarbon feedstock (e.g. coal, coke, petroleum coke called "pet -coke” in English, biomass, oil sands, household waste), liquid (e.g.: fuel, bitumen, diesel, gasoline, shale oil, etc.) or gaseous (e.g.: natural gas, syngas, biogas , shale gas) whose combustion is desired. The oxygen transported by the particles of the active mass fuels the combustion of the charge. This results in a gaseous effluent formed by the combustion of the charge and a flow of reduced particles. The particles are sent back to the air reactor to be re-oxidized there, thus closing the loop.

The CLC process makes it possible to produce energy (steam, electricity, etc.) by recovering the heat given off by combustion reactions while facilitating the capture of carbon dioxide (CO ₂ ) emitted during combustion thanks to the production of fumes rich in CO ₂ . The capture of CO ₂ can in fact take place after condensation of the water vapor and compression of the fumes, and this can then be stored, for example in a deep aquifer, or be recovered, for example by using it for improve the performance of oil operations in enhanced oil recovery (EOR for Enhanced Oil Recovery in English) or gas (EGR for Enhanced Gas Recovery in English) processes.

The CLC process can also allow the production of synthesis gas, or even hydrogen, by controlling the combustion and implementing the purifications required downstream of the combustion process. This particular mode of combustion also has the advantage of producing a stream very rich in nitrogen, which is the depleted air obtained following the oxidation of the active mass in the air reactor. Depending on the degree of purity achieved, this nitrogen flow can be recovered in various applications, particularly in the field of the oil industry. It can for example be used in refineries as an inert gas in various petroleum refining processes or for the treatment of produced water, or as gas injected into the subsoil in EOR processes.

Different fluidization regimes can be implemented in the different units of the CLC installation. The fluidization regime applied depends on the operation to be carried out (combustion of the charge, oxidation of the particles of the oxygen carrier, transport of the particles, solid/solid separation, solid/gas separation) and the type of charge treated.

For example, the combustion of a solid charge itself in the form of particles, requires a longer contact time with the particles of the oxygen carrier than the combustion of a gaseous charge, which generally results in the setting implementation in the combustion reactor of a zone comprising a dense fluidized bed, operating according to a heterogeneous fluidization regime (containing by definition bubbles) corresponding to a so-called bubbling bed (also called bubbling regime) or turbulent (superficial velocity of gas greater than that of the bubbling bed, strong particulate agitation), in which the particles of the oxygen carrier and the solid charge are brought into contact for their combustion.

In the case of chemical loop combustion of gaseous feedstocks, the contact time necessary between the particles of the active mass and the feedstock being less important than in the case of solid or liquid feedstocks, a reactor or a reactor part of the type riser, forming a substantially elongated and vertical duct, and operating in a dilute fluidized bed (also called transported), may be sufficient to carry out the combustion of the charge, and transport the particles. Particle oxidation reactors of the active mass also generally operate in a transported fluidized bed.

Combustion reactors operating in a dense fluidized bed can suffer from high pressure fluctuations due to the formation of large bubbles. This problem particularly affects reactors of this type having a high height/diameter ratio, for example greater than 2 or 3.

In addition to the problems of pressure fluctuations and mechanical stability of the system, large bubbles can deteriorate the quality of the fluidization and lead to poor solid-gas contacting and low reaction efficiency.

The quality of the fluidization can be deteriorated, whether the solid particles present in the fluidized bed belong to group B or to group A of the Geldart classification, conventionally encountered in the field of CLC. For group B particles, unlimited growth of bubbles with height can result in bubbles occupying most of the cross-section of the reactor, resulting in "plugged" flow known as slugging. according to Anglo-Saxon terminology, resulting in poor gas-solid contact. The pistoning phenomenon appears at the transition between the bubbling regime and the turbulent regime: it occurs when the bubbles grow larger as they rise in the reactor and their diameter becomes comparable to the diameter of the reactor. In this case, ‘plug’ flows occur. The large bubbles burst on the surface of the bed or on the wall, with dense agglomerates of solids entrained in their wake, generating strong flow heterogeneities, and resulting in strong pressure fluctuations and vibrations. For group A particles and some group B particles (small size with low permeability), in reactors operating in a dense fluidized bed, with a high aspect ratio, there can also be gas bypass, that is that is to say the formation of preferential paths of the gas without fluidization of the particles, and therefore a poor quality of fluidization.

In the case of circulating fluidized beds where there is a continuous feed of solid particles into the reactor, the production of bubbles below the solid feed zone can produce high pressure points which propagate through the system.

The turbulent regime is particularly interesting for industrial processes because it presents a much more homogeneous mixing of the phases and a very significant mass and heat transfer, compared to the bubbling and swabbing regimes. It is a regime which corresponds to a strong agitation of the particles: as the fluidization speed increases, the size and the number of the bubbles increase progressively and the agitation of the suspension becomes more and more violent. This agitation is produced by the rise of the bubbles and by the fact that they carry part of the suspension in their wake. At high speeds, the shape of the bubbles becomes irregular. Nevertheless, even if the large bubbles formed do not reach the diameter of the reactor, these can cause large pressure fluctuations and vibrations within the bed, typically when they break within the bed, at the surface of the bed and in the walls of the reactor.

The formation of large bubbles in a dense fluidized bed, whether in a bubbling regime with the appearance of pistoning, or in a turbulent regime, is therefore undesirable for several reasons: the mixture of solid and gas is less good (less homogeneous), the homogeneity of the temperature of the reactor is no longer ensured, and the strong pressure fluctuations and vibrations on the walls and the bottom of the reactor are detrimental to the mechanical strength of the reactor.

Devices are known for reducing the swabbing phenomenon. For example, patent US9512364 B2 relating to a hydropyrolysis process for the transformation of biomass in the form of particles into liquid fuels using catalytic bubbling beds, discloses an anti-pistoning reactor comprising side inserts, which are elements of obstacle, obstruction or constriction placed at regular intervals in the bed in order to inhibit swabbing in the reactor. Such inserts are not always easy to implement, and this type of reactor may require significant maintenance linked to the possible coking of the inserts.

In the field of CLC, application WO2020/126704 discloses injections of fluidization gas to reduce the problems associated with the pistoning phenomenon. However, these injections are carried out in specific combustion reactors, in particular in order to limit the strong pressure fluctuations in the riser part of combustion reactors comprising a lower part operating in a dense fluidized bed surmounted by a riser. These injections are carried out at the top of the lower part of the reactor, which is connected to the upper riser part by a flat roof, to break up the large agglomerates of solid formed during the bursting of bubbles before they arrive in the riser.

Objects and Summary of the Invention

The present invention aims to overcome the problems of the prior art, and in particular aims to provide a CLC process and installation in which the harmful effects of the presence of large bubbles in a combustion reactor operating in a fluidized bed dense are reduced, e.g., significant pressure fluctuations and poor fluidization quality, thus contributing to better mechanical stability of the combustion reactor and better combustion efficiency.

The present invention also aims, by some of these embodiments, to achieve this objective while avoiding the use of inserts to break the bubbles of large dimensions. Indeed, any insert in a CLC combustion reactor, which operates at very high temperature, involves significant costs and complexity of the structures and materials to be used to form these inserts, as well as significant maintenance, particularly related to erosion. inserts in the fluidized bed, and risks of fouling of said inserts which can disturb the fluidization by a reduction in the section of the reactor.

The inventors have demonstrated that the formation of the dense fluidized bed in the CLC combustion reactor by means of a system of staged gas injections, with in particular at least one injection of secondary gas as detailed below having in particular the effect to reduce the formation of large bubbles, made it possible to achieve these objectives.

Thus, to achieve at least one of the aforementioned objectives, among others, the present invention proposes, according to a first aspect, a CLC process for a hydrocarbon feedstock in which:
- particles of an active redox mass are injected into a combustion reactor;
- the combustion of the hydrocarbon charge is carried out within the combustion reactor by bringing said particles of the redox active mass into contact with the hydrocarbon charge within a dense fluidized bed of height H, the dense fluidized bed being formed in the combustion reactor:
-- by the injection of a primary gas at the base of the combustion reactor, the flow rate of said primary gas being such that the superficial velocity of the gas in the dense fluidized bed is between U _mf and 0.8xU _g , U _mf being the minimum fluidization velocity of the particles and U _g being the superficial gas velocity operational of the dense fluidized bed, and
-- by the injection of a secondary gas within the dense fluidized bed by at least one injection point located above the injection of the primary gas and above an injection of the particles of the active mass redox, and located at a height of between 0.05xH and 0.7xH, according to a flow rate complementary to the flow rate of the primary gas so as to reach U _g ;
- the particles of the redox active mass which have stayed in the combustion reactor are sent to an oxidation reactor operating in a fluidized bed to oxidize them, before sending them back to the combustion reactor.

According to one or more implementations, the secondary gas injection rate is such that the contribution of the secondary gas to the superficial gas velocity in the dense fluidized bed is between 0.2xU _g and (U _g -U _mf ).

According to one or more implementations, the flow rate of said primary gas is such that the superficial gas velocity in the dense fluidized bed is between 5xU _mf and 0.6xU _g , preferably between 10xU _mf and 0.4xU _g , and the flow rate of the secondary gas is such that the contribution of the secondary gas to the superficial gas velocity in the dense fluidized bed is between 0.4xU _g and (U _g -5xU _mf ), preferably between 0.6xU _g and (U _g -10xU _mf ).

According to one or more implementations, U _g is such that the regime of the dense fluidized bed is turbulent or bubbling, preferably U _g is between 0.1 m/s and 3 m/s

According to one or more implementations, the injection of the secondary gas is carried out in the lower half of said combustion reactor.

According to one or more implementations, the injection of the secondary gas is carried out at a distance of between 0.1xD and 5xD above an opening of a line for injecting the particles of the redox active mass, D being the diameter of said injection line.

According to one or more implementations, the injection of the secondary gas is carried out according to several injection points distributed, preferably uniformly, around the combustion reactor.

According to one or more implementations, the injection of the secondary gas is carried out according to several injection points within the dense fluidized bed distributed according to crowns located at different heights along the combustion reactor.

According to one or more implementations, the height between the rings is between 0.1xD and 5xD, preferably between 0.5xD and 1.5xD.

According to one or more implementations, the injection of secondary gas is carried out perpendicular to the wall of the combustion reactor by means of at least one tube comprising at one of its ends an opening contained by the wall of the combustion reactor forming said at least one injection point, preferably by means of four tubes each comprising at one of their ends an opening contained by the wall of the combustion reactor.

According to one or more implementations, the injection of secondary gas is carried out tangentially to the wall of the combustion reactor by means of at least one tube comprising at one of its ends an opening contained by the wall of said combustion reactor forming said at least one injection point, preferably by means of four tubes each comprising at one of their ends an opening contained by the wall of the combustion reactor.

According to one or more implementations, the injection of secondary gas is carried out parallel to the wall of the combustion reactor by means of at least one vertical tube arranged at the base of the reactor, extending into said reactor and opening by said at least one injection point within the dense fluidized bed in said reactor.

According to one or more implementations, the hydrocarbon feedstock is a solid hydrocarbon feedstock in the form of particles, and the injection of the secondary gas comprises the injection of the solid hydrocarbon feedstock.

According to one or more implementations, the hydrocarbon charge is a gaseous hydrocarbon charge and the injection of the primary and/or secondary gas, preferably the injection of the secondary gas, comprises the injection of said hydrocarbon charge.

According to a second aspect, the invention relates to a CLC installation for carrying out the combustion of a hydrocarbon feedstock according to the CLC process, the CLC installation comprising:
- a combustion reactor capable of comprising a dense fluidized bed of height H comprising particles of an oxido-reducing active mass and said hydrocarbon charge, and provided with a fluidization system to form said dense fluidized bed,
the fluidization system comprising:
-- first means for injecting a primary gas positioned at the base of said combustion reactor located below an opening of the line for injecting the particles of the active mass, and
-- second means for injecting a secondary gas comprising at least one injection point in said reactor situated above the first injection means and above the opening of a line for injecting particles of the redox active mass in said combustion reactor, and located at a height of between 0.05xH and 0.7xH, and
- an oxidation reactor configured to receive the particles of the redox active mass having stayed in the combustion reactor, to oxidize said particles within a fluidized bed, and to return them to the combustion reactor.

According to one or more embodiments, at least one injection point of the second secondary gas injection means is located in the lower half of the combustion reactor.

According to one or more embodiments, the second secondary gas injection means are located at a distance between 0.1xD and 5xD, preferably between 0.5xD and 1.5xD, above said opening of the injection line for the particles of the redox active mass, D being the diameter of said injection line.

According to one or more embodiments, the second secondary gas injection means comprise several injection points distributed, preferably uniformly, around the combustion reactor.

According to one or more embodiments, the second secondary gas injection means comprise several injection points within the dense fluidized bed distributed according to crowns located at different heights along the combustion reactor, the height between said crowns preferably being between 0.1xD and 5xD.

According to one or more embodiments, the second secondary gas injection means comprise at least one tube perpendicular to the wall of the combustion reactor at the injection point and comprising at one of its ends an opening contained by the wall said combustion reactor and forming said at least one injection point, the second secondary gas injection means preferably comprising four of said tubes perpendicular to the injection wall.

According to one or more embodiments, the second secondary gas injection means comprise at least one tube tangential to the wall of the combustion reactor at the injection point and comprising at one of its ends an opening contained by the wall said combustion reactor forming said at least one injection point, said second secondary gas injection means preferably comprising four of said tangential tubes.

According to one or more embodiments, the second secondary gas injection means comprise at least one vertical tube arranged at the base of said reactor, extending into said reactor and opening via said at least one injection point within dense fluidized bed in said reactor.

Other objects and advantages of the invention will appear on reading the following description of examples of particular embodiments of the invention, given by way of non-limiting examples, the description being made with reference to the appended figures described below. -After.

List of Figures

There is a block diagram for implementing a CLC process.

There is a block diagram of the operation of a combustion reactor in the CLC process and installation according to the invention.

There schematically represents a first embodiment of the CLC combustion reactor used according to the invention, according to a perspective view (A) and according to a top view (B).

There schematically represents a second embodiment of the CLC combustion reactor used according to the invention, according to a perspective view (A) and according to a top view (B).

There schematically represents a third embodiment of the CLC combustion reactor used according to the invention, according to a perspective view.

There is a set of images representing the distribution of solid particles in section at a given height in an example of a CLC reactor used according to the prior art (images (6.A), (6.B), and (6.C) ) and in example of reactor used according to the invention (images (6.D), (6.E), and (6.F)).

There is a diagram showing the pressure fluctuations in an example of a CLC reactor used according to the prior art and in an example of a reactor used according to the invention.

There shows 3D images of the simulated solid/gas distribution in an example of a CLC reactor used according to the prior art (image 8.A) and in an example of a reactor used according to the invention (image 8.B)

In the figures, the same references designate identical or similar elements.

Before describing in more detail the operation of the combustion reactor used in the installation and the CLC process according to the invention, said installation and said CLC process according to the invention are described below in general terms, in relation to the .

In the present description, the expressions “redox active mass” or, for abbreviated form, “active mass”, “oxygen carrier material”, “oxygen carrier solid” or “oxygen carrier” 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 of oxygen carrier in the CLC process by capturing and releasing oxygen.

It should be noted that generally the terms oxidation and reduction are used in relation to the respectively oxidized or reduced state of the active mass. The oxidation reactor, also called air reactor, is the one in which the redox mass is oxidized and the reduction reactor, also called fuel reactor or combustion reactor, is the reactor in which the redox 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.

In the following description and in the claims, the positions ("bottom", "top", "above", "below", "horizontal", "vertical", "lower half", etc.) of the various elements are defined with respect to the reactor in the operating position.

Installation and CLC process

There is a diagram representing the general operating principle of chemical loop combustion. It is in no way limiting of the combustion reactor used in the installation and of the CLC process of the invention.

A reduced oxygen carrier 25 is brought into contact with an air stream 20 in a reaction zone 11 previously defined as the oxidation reactor (or air reactor). This results in a depleted air flow 21 and a flow of re-oxidized particles 24. The flow of oxidized oxygen carrier particles 24 is transferred to the reduction zone 100 previously defined as the combustion reactor (or reduction). The flow of particles 24 is brought into contact with a fuel 22, which is a hydrocarbon feedstock. This results in a combustion effluent 23 and a reduced oxygen carrier particle flux 25. For simplicity, the representation of the does not include the various equipment that may be part of the CLC unit, for solid/gas separation, solid/solid separation, heat exchange, pressurization, sealing of gases between reactors (e.g.: siphons), solid storage, control of solid flows (eg mechanical or pneumatic valves) or any recirculation of material around the oxidation and combustion reactors.

In the combustion zone 10, the hydrocarbon charge 22 is brought into cocurrent contact with the redox active mass in the form of particles to carry out the combustion of said charge by reduction of the redox active mass.

The redox active mass M _x O _y , M representing a metal, is reduced to the state M _x O _y-2n-m/2 , via the hydrocarbon charge C _n H _m , which is correlatively oxidized in CO ₂ and H ₂ O, according to reaction (1) below, or optionally in a CO + H ₂ mixture according to the proportions used.

Total combustion of the hydrocarbon charge is generally targeted.

The combustion of the charge in contact with the active mass is carried out at a temperature generally between 600°C and 1400°C, preferably between 800°C and 1000°C. The contact time varies according to the type of combustible charge used. It typically varies between 1 second and 20 minutes, for example preferably between 1 minute and 10 minutes, and more preferably between 1 minute and 8 minutes for a solid or liquid load, and for example preferably from 1 to 20 seconds for a load carbonated.

A mixture comprising the gases resulting from the combustion and the particles of the active mass is evacuated at the top of the reduction zone 10. Gas/solid separation means (not shown), such as a cyclone, make it possible to separate the combustion gas 23 of the solid particles of the active mass in their most reduced state 25. In the case of the presence of unburned matter which may occur if the hydrocarbon charge is solid, a solid/solid separation device making it possible to separate the particles of unburned particles of the active mass can be implemented at the outlet of the combustion reactor. This type of separator can be associated with one or more gas/solid separators arranged downstream of the solid/solid separator. The particles of the active mass having stayed in the combustion reactor, and separated from the combustion gases, are sent to the oxidation zone 11 to be re-oxidized. The unburnt can be recycled to the reduction reactor 10.

In the oxidation reactor 11, the active mass is restored to its oxidized state M _x O _y in contact with an oxidizing gas 20, typically air or steam, and preferably air. , according to reaction (2) below, before returning to the reduction reactor 10, and after having been separated from the oxygen-depleted gas 21, typically so-called "depleted" air, evacuated at the top of the oxidation 11.

Where n and m represent respectively the number of carbon and hydrogen atoms having reacted with the active mass in the combustion reactor.

The temperature in the oxidation reactor is generally between 600°C and 1400°C, preferably between 800°C and 1000°C.

The active mass, passing alternately from its oxidized form to its reduced form and vice versa, describes an oxidation-reduction cycle.

The hydrocarbon feedstocks (or fuels) treated can be solid, gaseous or liquid hydrocarbon feedstocks, and preferably solid or gaseous feedstocks. The solid fillers can be chosen from among coal, coke, pet-coke, biomass, bituminous sands and household waste. The gaseous feeds are preferably composed essentially of methane, for example natural gas or a biogas. The liquid fillers can be chosen from oil, bitumen, diesel, gasoline. Preferably, the hydrocarbon feedstock treated is a solid or gaseous feedstock, as stated above.

The redox mass may be composed of metal oxides, such as for example oxides of Fe, Ti, Ni, Cu, Mn, Co, V, alone or as a mixture, which may come from ores (for example ilmenite or pyrolusite) or be synthetic (for example particles of copper oxide supported on alumina CuO/Al ₂ O ₃ or particles of nickel oxide supported on alumina NiO/Al ₂ O ₄ , preferably particles of oxide of copper supported on CuO/Al ₂ O ₃ alumina), with or without a binder, and has the required oxidation-reduction properties and the characteristics necessary for the implementation of fluidization. The oxygen storage capacity of the redox mass is advantageously comprised, depending on the type of material, between 0.5% and 15% by weight. Advantageously, the quantity of oxygen actually transferred by the metal oxide is between 0.5% and 3% by weight, which makes it possible to use only a fraction of the total oxygen transfer capacity, ideally less than 30% of it in order to limit the risks of mechanical aging or particle agglomeration. The use of only a fraction of the oxygen transport capacity also has the advantage that the fluidized bed acts as a thermal ballast and thus smooths the temperature variations on the path of the oxygen carrier.

The active mass is in the form of fluidizable particles, belonging to groups A, B, C or D of the Geldart classification, preferably to groups A, B, or D, alone or in combination. Preferably, the particles of the redox active mass belong to group B of the Geldart classification. By way of example, and in a non-limiting way, the particles of group B used have a particle size such that more than 90% of the particles have a size of between 100 μm and 500 μm, preferably between 150 μm and 300 μm.

Preferably, the particles of the redox active mass, which may be metal oxides, synthetic or natural minerals, supported or not, have a density of between 1000 kg/m ³ and 5000 kg/m ³ and preferentially between 1200 kg /m ³ and 4000 kg/m ³ .
For example, nickel oxide particles supported on alumina (NiO/NiAl ₂ O ₄ ) generally have a grain density of between 2500 kg/m ³ and 3500 kg/m ³ depending on the porosity of the support and the the nickel oxide content, typically approximately 3200 kg/m ³ .
Ilmenite, an ore combining titanium and iron (iron oxide and titanium), has a density of 4700 kg/m ³ .

The redox active mass can undergo an activation phase so as to increase its reactive capacities, which can consist of a temperature rise phase, preferably progressive, and preferably under an oxidizing atmosphere (for example under air).

The oxidation and combustion reactors operate in fluidized beds. They each comprise at least one fluidization gas injection system. In the combustion reactor, the fluidization gas can be CO ₂ , which can be CO ₂ produced during combustion and recycled, or steam. In the oxidation reactor, the fluidizing gas is an oxidizing gas, preferably air.

The oxidation reactor 11 preferably comprises a transported fluidized bed. Advantageously, the gas velocity (gas phase of the bed) is between 2 m/s and 15 m/s, and preferably between 3 m/s and 10 m/s. By way of example, such an oxidation reactor can have a diameter of between 1 m and 6 m for a height of between 10 m and 30 m.

The oxidation reactor is thus configured to receive the particles of the redox active mass having stayed in the combustion reactor, to oxidize said particles within the transported material, and to return them to said combustion reactor.

The combustion reactor 10 is configured to include a dense fluidized bed. Preferably, the superficial velocity of the gas in the dense fluidized bed of the reactor, which is also referred to here as the superficial velocity of the operational gas U _g , is between 0.1 m/s and 3 m/s, preferably between 0. 3m/s and 2m/s.
By way of example, the combustion reactor 10 can have a diameter D _R of between 1 m and 10 m. According to the invention, the combustion reactor preferably has a height H _R to diameter D _R ratio of between 0.5 and 8, preferably between 1 and 5, even more preferably between 2 and 4. same for the ratio of the height of the dense fluidized bed in the reactor to the diameter of the reactor.

By dense fluidized bed is meant a bubbling bed (bubbling regime also called bubble regime or bubbling) or a turbulent bed (turbulent regime). The volume fraction of solid in such a dense fluidized bed is generally between 0.25 and 0.50.

By dilute fluidized bed is meant a transported bed. The volume fraction of solid is generally less than 0.25.

In the case of the combustion of solid hydrocarbon feedstocks, a sufficiently long contact time of the feedstock with the particles of the active mass is generally necessary to tend towards total combustion, and involves a first phase of gasification of the solid feedstock, followed by of a combustion of the gasified charge. Both phases can be carried out in the dense fluidized bed of the combustion reactor. According to another configuration, the first phase can be carried out in the dense fluidized bed of the combustion reactor, and the second phase can be carried out in another combustion zone, for example within the same reactor in a zone overcoming the dense bed and operating in a dilute fluidized bed or in a separate reactor receiving the gasified charge and bringing it into contact with the active mass, within a dense or dilute fluidized bed.

The geometry of the reactors can be parallelepipedic, typically a rectangular parallelepiped, cylindrical or any other three-dimensional geometry preferably comprising a symmetry of revolution. Cylindrical refers to a cylinder of revolution. For example, the combustion reactor is cylindrical or has the shape of a rectangular parallelepiped. In the latter case, the diameter D _R of the reactor must be understood as an equivalent diameter, defined as the diameter of the circle inscribed in the section of the reactor.

The materials used to make the reactors and their constituent elements (intake(s), evacuation(s), outlet(s), etc.) can be chosen from refractory materials, for example of the refractory concrete, refractory brick or ceramic type, high temperature steels, for example of the Hastelloy®, Incoloy®, Inconel® or Manaurite® type, or conventional steels, for example of the stainless steel or carbon steel type combined with refractory materials or combined with cooling means such as tubes in which a heat transfer fluid circulates.

Combustion stage in the CLC staged fluidization combustion reactor

The operation of the combustion reactor is now described in more detail, in relation to Figures 2 to 8.

There is a non-limiting block diagram of the combustion reactor of the installation and of the CLC process according to the invention, and of its operation.

The combustion reactor 10 is configured to comprise a dense fluidized bed 5 of height H.

The dense fluidized bed comprises the particles of the active mass, as well as the hydrocarbon feedstock, which may be in the form of solid particles, in liquid form or in gaseous form.

The reactor 10 thus comprises a line for injecting the particles of the active mass 3 coming from the oxidation reactor, said line comprising an opening in the combustion reactor, located at the base of the reactor. This particle injection line 3 has a diameter D. To give an order of magnitude, D can range from a few centimeters to 2 or 3 meters. The reactor also includes an inlet for the hydrocarbon charge.

The combustion reactor 10 is configured to carry out the combustion of the hydrocarbon charge within the dense fluidized bed, and therefore is thus configured to evacuate gas (fluidization gas and gas resulting from the combustion of the hydrocarbon charge and possibly part of the feed not converted into gas form) and solid particles (active mass and possibly unburned matter and ash in the case of solid hydrocarbon feed) from the dense fluidized bed 5. It thus advantageously comprises an outlet for the gas 7, preferably at the top of the reactor, an evacuation for the particles of active mass 6, said outlet 7 and evacuation 6 being able to form a single and same conduit for evacuating gas and solid, preferably at the top of the reactor.

The combustion reactor 10 is provided with a fluidization system to form the dense fluidized bed 5, said system comprising:
- first means for injecting a primary gas 1 positioned at the bottom of the reactor 10, below an opening of the line for injecting the particles of the active mass 3, and
- second means for injecting a secondary gas 2 comprising at least one injection point in the reactor. Said at least one injection point is located above the primary gas injection means 1 and also above the opening of the active mass particle injection line 3. Said at least one point injection is also located at a height of between 0.05xH and 0.7xH.

Thus the gas making it possible to fluidize the solid particles and form the dense bed comprises the primary gas 1 and the secondary gas 2, injected at different heights into the combustion reactor 10, thus taking the form of a staged fluidization.

The entry for the hydrocarbon charge into the reactor 10 is advantageously made by the means for injecting the primary gas 1 and/or the means for injecting the secondary gas 2.
In the case of a solid hydrocarbon feedstock, said feedstock advantageously enters through the secondary gas injection means 2. In this case, the secondary gas injection means 2 preferably comprise a multi-phase line (solid/gas) pneumatic transport.

In the case of a gaseous hydrocarbon feedstock, said feedstock may enter through the primary gas injection means 1, through the secondary gas injection means 2, or through both, and preferably through the secondary gas injection means 2 in order in particular to further limit the formation of bubbles at the bottom of the reactor at the level of the injection line for the particles of the active mass 3 if an increase in the gas flow occurs due to the combustion of the load.

In the case of a liquid hydrocarbon feed, the feed is injected into the reactor, and is preferably atomized within the fluidized bed to form fine droplets. The entry of said liquid feedstock can be done by dedicated injection means, which may include means for mixing the liquid feedstock with an atomizing gas and means for atomizing the liquid feedstock. These atomization means making it possible to form small-sized droplets on high flow rates of liquid in the presence of gas are well known to those skilled in the art, and are for example described in patent FR2936301. One can for example use venturi-type injectors, impact-type injectors, or other more complex systems already well described in the literature. These injectors make it possible to form droplets whose size is close to 100 microns or less over high unit flows. Several injectors can be arranged around the reactor to inject the droplets in a jet directed towards the center of the reactor, above the particle injection line 3.

The combustion reactor 10 may also comprise one or more pipes for recycling unburnt particles connected to solid/solid separation systems (devices for separation by elutriation) and/or gas/solid (e.g. cyclones), in the case combustion of a solid hydrocarbon charge. For reasons of simplicity, these elements are not represented on the .

In the CLC system and process according to the invention, the particles of the redox active mass 3 are therefore injected into the combustion reactor 10, typically continuously, and the combustion of the hydrocarbon charge is carried out, which can be introduced with the primary gas injection means 1 and/or with the secondary gas injection means 2, within the reactor 10 by bringing the particles of the redox active mass into contact with the hydrocarbon charge at the within the dense fluidized bed 5.

The dense fluidized bed 5 is formed in the reactor 10:
- on the one hand by the injection of the primary gas 1 at the bottom of the combustion reactor, the flow rate of the primary gas being such that the superficial velocity of the gas in the dense fluidized bed is between U _mf and 0.8xU _g , and
- on the other hand by the injection of the secondary gas 2 within the dense fluidized bed 5 by said at least one injection point located above the injection of the primary gas 1 and above the injection of the particles of the redox active mass 3, and located at a height comprised between 0.05×H and 0.7×H, according to a flow rate complementary to the flow rate of the primary gas so as to reach U _g .

U _mf is the minimum fluidization velocity of the particles, and it is recalled that U _g is the superficial velocity of the operational gas of said dense fluidized bed.

The injection of the primary gas 1 at the bottom of the combustion reactor is of course carried out below the opening of the injection line for the particles of the active mass 3.

The base of the dense bed is formed substantially at the same level as the injection of the particles of active mass 3.

The surface velocity of the operational gas U _g in the dense bed of the combustion reactor 10 is such that the bed regime is that of a bubbling bed, or a bed in a turbulent regime corresponding to a higher gas velocity. The superficial velocity of the operational gas U _g depends on the particles to be fluidized (size and density) and on the operating conditions. Preferably, U _g is between 0.1 m/s and 3 m/s, more preferably between 0.3 m/s and 2 m/s.

In such heterogeneous fluidization regimes, the formation of large bubbles, possibly approaching the size of the flow section of the reactor (pistoning phenomenon at the transition between the bubbling bed regime and the turbulent), can pose problems of pressure fluctuation, vibration, temperature heterogeneity and poor solid/gas mixture as already described, and harmful to the integrity of the CLC installation and the performance of the CLC process.

According to the invention, the formation of the dense bed by the stepped gas injection system makes it possible to reduce the formation of large bubbles, and thus limit the pressure fluctuations in the reactor and improve the contact between the hydrocarbon charge and the active mass, allowing better mechanical stability of the CLC installation and better combustion performance.

The primary gas 1 can be injected into the reactor by any type of gas distributor known to those skilled in the art. The primary gas distributor 1 can comprise, without being limiting, perforated plates, valve plates (“bubble cap” according to the English terminology), porous plates, diffusers (“spargers” in English) such as network tubes provided with orifices and/or slots, ring gas dispersion tubes. For example, the primary gas is introduced by perforated plates arranged downstream of a distributor which may be a wind box supplied by a gas supply conduit. Preferably, these plates are arranged horizontally. In some cases, these plates can be inclined at an angle generally between 30° and 70° relative to the horizontal. This can be advantageous in particular in the case of combustion of solid loads, because thus the plates can leave in the central part a free space for the flow of the particles, making it possible to extract through the distributor part of the particles sedimenting in this zone and mainly made up of agglomerated ashes.

The flow rate of primary gas 1 must be sufficient to fluidize the particles; it is such that the superficial gas velocity in the dense fluidized bed is between U _mf and 0.8xU _g , and preferably such that the superficial gas velocity in the dense fluidized bed is between 5xU _mf and 0.6xU _g , and more preferably between 10×U _mf and 0.4×U _g .

The operational speed U _g in the dense fluidized bed is reached thanks to the complementary gas flow provided by the injection of secondary gas 2.

Thus, the flow rate of secondary gas 2 is such that the contribution of the secondary gas to the superficial gas velocity in the fluidized bed is between 0.2xU _g and (U _g -U _mf ), preferably between 0.4xU _g and (U _g -5xU _mf ), and more preferably between 0.6xU _g and (U _g -10xU _mf ).

The injection of the secondary gas 2 into the dense fluidized bed 5 can comprise several injection points, either at the same height in the reactor, or at different heights in the reactor, or both. For example, the secondary gas injection means 2 comprise several injection points, typically 2 to 8 injection points, and preferably 2 to 4 injection points, distributed, preferably uniformly, around the combustion reactor . An example of such an embodiment is illustrated in Figures 3 and 4 detailed below. The secondary gas injection means 2 can also comprise several injection points distributed according to crowns located at different heights along the combustion reactor, preferably 2 to 4 crowns each comprising between 2 and 8 injection points, and preferably between 2 to 4 injection points. In all cases, the injection of the secondary gas is carried out in the dense fluidized bed 5, at a height comprised between 0.05×H and 0.7×H, and more preferably comprised 0.05×H and 0.5×H.

Preferably, the injection of the secondary gas is carried out in the lower half of the combustion reactor 10. For this, the secondary gas injection point(s) 2 are located in the lower half of the combustion reactor. Preferably, the secondary gas injection point(s) 2 are located at a height of between 0.05×H _R and 0.7×H _R , and more preferably between 0.05×H _R and 0.5×H _R .

Advantageously, the injection of the secondary gas 2 is carried out at a distance comprised between 0.1xD and 5xD, preferably comprised between 0.5xD and 1.5xD, above the opening of the injection line of the particles of the active mass 3 (D= diameter of the particle injection line 3). For this, the secondary gas injection point(s) 2 are located at a distance between 0.1xD and 5xD, preferably between 0.5xD and 1.5xD, above the opening of the line d injection of the particles of the active mass 3. In the case where the injection of the secondary gas comprises several injection points distributed according to crowns located at different heights along the combustion reactor, the height between said crowns is preferably between 0.1xD and 5xD, and more preferably between 0.5xD and 1.5xD.

The secondary gas 2 can be injected into the reactor 10 by any suitable means known to those skilled in the art. The secondary gas injection means 2 may comprise one or more tubes which penetrate into the dense fluidized bed 5, or which, preferably, open into the bed without entering it, the tube(s) then comprising on one from their ends an opening contained by the wall of the combustion reactor. The tube or tubes are supplied with secondary gas 2. The tube or tubes can be horizontal, inclined with respect to the vertical, or vertical (angle α formed, in a vertical plane, between the axis of the tube and the tangent to the wall of the reactor at the injection point). The tube or tubes can also form an angle with the wall of the reactor at the injection point, defined in the horizontal plane (angle β formed between the axis of the tube and the tangent to the wall at the injection point, defined in a horizontal plane), and for example be perpendicular to the wall of the reactor 10 at the injection point (β = 90°) so as to form a jet in the bed which is perpendicular to the wall (jet in a radial direction ), or even be inclined with respect to the wall of the reactor 10 at the injection point so as to form a jet in the bed which is tangential to the wall.

There schematically and non-limitingly illustrates a combustion reactor 100 according to an example embodiment (perspective view (A) and top view (B)), in which the fluidization system comprises an injection of secondary gas 2 by means of four tubes 200 distributed uniformly around the cylindrical combustion reactor 100, above the injection of the primary gas 1, not shown, and above and close to the opening of the injection line for the particles of the oxido-active mass. reducer 3. The four tubes 200 each have an opening contained in the wall of the reactor 100, ie they do not penetrate inside the reactor, constituting four secondary gas injection points 2 in the dense fluidized bed 5. The four tubes are horizontal, and each form an angle β of 90° with respect to the wall of the reactor at the point of injection so as to form jets of secondary gas 2 in the dense fluidized bed 5 radially. Gas and solid particles are evacuated through a common pipe at the top of reactor 10.

There illustrates, schematically and in a non-limiting way, in the same way a combustion reactor 110 according to another embodiment, in all respects identical to that of the except for the fact that the four tubes 210 are inclined in the horizontal plane (angle β different from 90°) so as to form secondary gas jets 2 in the dense fluidized bed 5 tangentially to the wall.

According to another embodiment, the tube or tubes may be vertical and arranged at the base of the reactor, extending into the reactor 10 and opening within the dense fluidized bed 5 by one of their ends constituting the point or points of injection of the secondary gas 2. Said vertical tubes can have different heights to make injections at different heights in the dense bed 5. The vertical tubes are preferably distributed at the bottom of the reactor in a uniform manner. The number of vertical tubes can be such that the tubes cover from 0.1 to 0.7 times the section of the reactor. For example, the reactor comprises between 1 and 8 tubes, preferably between 2 and 4 tubes, covering such a surface.
There illustrates schematically and in a non-limiting way a combustion reactor 120 according to such an embodiment, in which the fluidization system comprises an injection of secondary gas 2 by means of three vertical tubes 220 fixed to the bottom of the cylindrical combustion reactor 120, aligned and distributed equidistant from each other. The three tubes 220, fed by the secondary gas 2, open into the dense fluidized bed 5 at the same height, above the opening of the line for injecting the particles of the redox active mass 3, thus forming three injection points above the opening of said line and the injection of primary gas 1, not shown. Gas and solid particles are evacuated through a common conduit at the top of reactor 120.

The secondary gas injection 2 can comprise a combination of these different tube geometries. For example, injections can be made by means of a combination of tubes perpendicular and tubes tangential to the wall of the combustion reactor at the point of injection. Other combinations are still possible.

The embodiments comprising tubes that do not penetrate into the reactor have the advantage of avoiding wear of the secondary gas injection means 2, and thus of limiting the maintenance costs, or even the investment costs of the system.

Preferably, the secondary gas 2 is injected into the dense fluidized bed 5 at a speed of between 3 m/s and 90 m/s, and more preferably between 5 m/s and 30 m/s. This is typically the speed at the exit of the tube(s).

In the case where the hydrocarbon charge is solid, one or more tubes of the secondary gas injection means can be used to introduce said charge mixed with the secondary gas 2. The solid charge in the form of particles is then to be transported in a manner pneumatic, in the form of dense or dilute pneumatic transport. Preferably, the velocity of the secondary gas in the tube(s) for the pneumatic transport of the solid hydrocarbon feedstock is from 0.05 to 10 times the saltation velocity U _salt of the particles of the hydrocarbon feedstock.

The primary gas 1 and the secondary gas 2 comprise a fluidization gas which can be CO ₂ , for example the CO ₂ produced during combustion and recycled, or steam, or a mixture of the two.

In the case of the combustion of a gaseous hydrocarbon feedstock, the primary gas and/or the secondary gas can comprise said feedstock, and preferably the secondary gas because the secondary gas injection means are preferred for injecting such a feedstock into reactor 10.

In the case of the combustion of a solid or liquid hydrocarbon feedstock, the primary gas 1 and the secondary gas 2 can consist of CO ₂ or water vapour.

In the CLC process according to the invention, the particles of the redox active mass which have stayed in the combustion reactor 10 are sent to the oxidation reactor (not shown in the figure). ) operating in a fluidized bed to oxidize them, before returning them to the combustion reactor 10.

The following example aims to show certain performances of the CLC process and installation according to the invention, in particular the effectiveness of the staged fluidization system forming the dense fluidized bed to limit the formation of large bubbles and reduce the pressure fluctuations in a dense fluidized bed reactor.

According to this example, we compare the distribution of solid ( ), normalized pressure fluctuations ( ), and the distribution and dimensions of the imaged bubbles ( ) in the dense fluidized bed, for an example of an RI reactor in which the fluidization is staged to form the dense bed and an example of an RPA reactor according to the prior art in which the fluidization of the dense bed is only carried out by the injection of gas at the base of the reactor.

This example is carried out by simulation using the Barracuda software of a dense fluidized bed in the two reactors.

The geometric characteristics of the reactors are the same in both cases, with the exception of the fluidization system:

The R _I and R _PA reactors have a height/diameter ratio equal to 4, and the dense fluidized bed occupies the entire reactor. The diameter of the reactors is 1.5 m. The fluidizing gas is water vapour. The outlet pressure is 0.11 MPa, the temperature 950° C., the operational superficial gas velocity U _g 1 m/s.

In the R _PA reactor, all the fluidization gas is injected at the base of the reactor.

In the R _I reactor, 30% (0.147 kg/s) of the fluidization gas is injected at the base of the reactor and 70% (0.34 kg/s) is injected through four tubes distributed uniformly around the reactor as shown to the , 0.1 m above the opening of the solid particle arrival line 3.

There illustrates, by 2D images, the distribution of solid particles and gas in the fluidized bed at 3 different heights of the reactor, respectively at 1 m (images 6.A and 6.D), 2 m (images 6.B and 6 .E) and 4 m (images 6.C and 6.F) from the opening of the solid particle arrival line, for the RPA reactor (according to prior art) on the top images 6.A, 6. B, and 6.C, and for the RI reactor (according to the invention) in the bottom images 6.D, 6.E, 6F. The grayscale scale gives the value of C which is the volumetric fraction of the solid. On the scale, the higher the density (from white to black), the less solid there is (maximum value at the top of the scale, in white, corresponding to a state of minimum fluidization, and minimum value, at the bottom of the scale, in black, corresponding to a vacuum). It is observed that the solid volume fraction is more uniform across the cross section of the column in the case of the RI reactor.

There is a diagram illustrating the normalized pressure fluctuations (Delta P/mean Delta P on the ordinate) over the entire height of the reactor (height z in meters in the reactor). The RI reactor (dotted curve) shows less significant pressure fluctuations than those of the RPA reactor (solid line curve).

There gives a 3D image of the bubbles in the RPA reactor (8.A) and in the RI reactor (8.B). The presence of large bubbles is significantly reduced in the case of the RI reactor. On image 8.A, horizontal tubes are visible but not implemented for the injection of the fluidization gas which is injected entirely at the base of the reactor.

Claims (22)

Process for the combustion of a hydrocarbon charge by oxidation-reduction in a chemical loop, in which:
- particles of an active redox mass (3) are injected into a combustion reactor (10);
- combustion of said hydrocarbon charge is carried out within the combustion reactor (10, 100, 110, 120) by bringing said particles of the redox active mass (3) into contact with said hydrocarbon charge within a dense fluidized bed (5) of height H, said dense fluidized bed (5) being formed in said combustion reactor:
-- by injecting a primary gas (1) at the base of said combustion reactor, the flow rate of said primary gas being such that the superficial gas velocity in the dense fluidized bed is between U _mf and 0.8xU _g , U _mf being the minimum fluidization velocity of the particles and U _g being the surface velocity of the operational gas of said dense fluidized bed (5), and
-- by the injection of a secondary gas (2) within said dense fluidized bed (5) by at least one injection point located above the injection of the primary gas (1) and an injection particles of said redox active mass (3), and located at a height comprised between 0.05×H and 0.7×H, according to a flow rate complementary to the flow rate of the primary gas so as to reach U _g ;
- the particles of the redox active mass which have stayed in the combustion reactor are sent to an oxidation reactor (11) operating in a fluidized bed to oxidize them, before returning them to the combustion reactor (10, 100, 110, 120). Method according to claim 1, wherein the rate of said injection of the secondary gas (2) is such that the contribution of the secondary gas to the superficial gas velocity in the dense fluidized bed (5) is between 0.2xU _g and ( U _g -U _mf ). Process according to Claim 2, in which the flow rate of said primary gas (1) is such that the superficial gas velocity in the dense fluidized bed (5) is between 5xU _mf and 0.6xU _g , preferably between 10xU _mf and 0 .4xU _g , and the flow rate of the secondary gas (2) is such that the contribution of the secondary gas to the superficial gas velocity in the dense fluidized bed (5) is between 0.4xU _g and (Ug-5xU _mf ), preferably between 0.6xU _g and (U _g -10xU _mf ). Process according to any one of the preceding claims, in which U _g is such that the regime of the dense fluidized bed (5) is turbulent or bubbling, preferably U _g is between 0.1 m/s and 3 m/s. Method according to any of the preceding claims, wherein the injection of the secondary gas (2) is carried out in the lower half of said combustion reactor (10). Process according to any one of the preceding claims, in which the injection of the secondary gas (2) is carried out at a distance of between 0.1xD and 5xD above an opening of a line for injecting the particles of the redox active mass (3), D being the diameter of said injection line. Method according to any one of the preceding claims, in which the injection of the secondary gas (2) is carried out at several injection points distributed, preferably uniformly, around the combustion reactor (10). Method according to any one of the preceding claims, in which the injection of the secondary gas (2) is carried out according to several injection points within the dense fluidized bed (5) distributed according to crowns located at different heights along the combustion reactor (10). A method according to claim 8, wherein the height between said crowns is between 0.1xD and 5xD, preferably between 0.5xD and 1.5xD. Process according to any one of the preceding claims, in which the injection of secondary gas (2) is carried out perpendicular to the wall of the combustion reactor (100) by means of at least one tube (200) comprising at one from its ends an opening contained by the wall of said combustion reactor (100) forming said at least one injection point, preferably by means of four tubes (200) each comprising at one of their ends an opening contained by the wall of said combustion reactor (100). Process according to any one of the preceding claims, in which the injection of secondary gas (2) is carried out tangentially to the wall of the combustion reactor (110) by means of at least one tube (210) comprising at one from its ends an opening contained by the wall of said combustion reactor (110) forming said at least one injection point, preferably by means of four tubes (210) each comprising at one of their ends an opening contained by the wall of said combustion reactor (110). Process according to any one of Claims 1 to 6, in which the injection of secondary gas (2) is carried out parallel to the wall of the combustion reactor (120) by means of at least one vertical tube (220) arranged at the base of the reactor, extending into said reactor (120) and opening via said at least one injection point within the dense fluidized bed (5) in said reactor (120). Process according to any one of the preceding claims, in which the hydrocarbon feedstock is a solid hydrocarbon feedstock in the form of particles, and the injection of the secondary gas (2) comprises the injection of the said solid hydrocarbon feedstock. Process according to any one of the preceding claims, in which the hydrocarbon feedstock is a gaseous hydrocarbon feedstock and the injection of the primary (1) and/or secondary (2) gas, preferably the injection of the secondary gas (2), comprises the injection of said hydrocarbon charge. Installation for carrying out the process for the combustion of a hydrocarbon charge by oxidation-reduction in a chemical loop according to any one of the preceding claims comprising:
- a combustion reactor (10, 100, 110, 120) capable of comprising a dense fluidized bed (5) of height H comprising particles of an oxido-reducing active mass (3) and said hydrocarbon charge, and provided with a fluidization system for forming said dense fluidized bed,
said fluidization system comprising:
-- first means for injecting a primary gas (1) positioned at the base of said combustion reactor located below an opening of the line for injecting the particles of the active mass (3), and
-- second means for injecting a secondary gas (2, 200, 210, 220) comprising at least one injection point in said reactor located above the first injection means and above the opening of a line for injecting particles of the redox active mass (3) into said combustion reactor, and located at a height of between 0.05xH and 0.7xH, and
- an oxidation reactor (11) configured to receive the particles of the redox active mass having stayed in the combustion reactor, to oxidize said particles within a fluidized bed, and to return them to said combustion reactor (10, 100, 110, 120). Installation according to claim 15, wherein said at least one injection point of the second secondary gas injection means (2) is located in the lower half of the combustion reactor. Installation according to any one of claims 15 and 16, in which the second secondary gas injection means (2) are located at a distance of between 0.1xD and 5xD, preferably between 0.5xD and 1.5xD , above said opening of the line for injecting the particles of the redox active mass (3), D being the diameter of said injection line. Installation according to any one of Claims 15 to 17, in which the second means (2) for injecting the secondary gas comprise several injection points distributed, preferably uniformly, around the combustion reactor. Installation according to any one of Claims 15 to 18, in which the second means for injecting the secondary gas (2) comprise several injection points within the dense fluidized bed (5) distributed according to crowns located at different heights along the combustion reactor, the height between said rings preferably being between 0.1xD and 5xD. Installation according to any one of claims 15 to 19, in which the second secondary gas injection means (2) comprise at least one tube (200) perpendicular to the wall of the combustion reactor at the injection point and comprising at one of its ends an opening contained by the wall of said combustion reactor (100) and forming said at least one injection point, said second secondary gas injection means (2) preferably comprising four of said perpendicular tubes ( 200). Installation according to any one of Claims 15 to 20, in which the second means for injecting the secondary gas (2) comprise at least one tube (210) tangential to the wall of the combustion reactor (110) at the point of injection and comprising at one of its ends an opening contained by the wall of said combustion reactor (110) forming said at least one injection point, said second secondary gas injection means (2) preferably comprising four of said tubes tangential (210). Installation according to any one of claims 15 to 17, in which the second secondary gas injection means (2) comprise at least one vertical tube (220) arranged at the base of the said reactor (120), extending into said reactor and opening via said at least one injection point within the dense fluidized bed (5) in said reactor (120).