WO2014068205A1

WO2014068205A1 - Chemical looping combustion process using an oxidation/reduction mass comprising pyrolusite enriched with nickel oxide

Info

Publication number: WO2014068205A1
Application number: PCT/FR2013/052196
Authority: WO
Inventors: Tiago SOZINHO; Florent Guillou; Hélène STAINTON
Original assignee: IFP Energies Nouvelles; Total Sa
Priority date: 2012-10-31
Filing date: 2013-09-20
Publication date: 2014-05-08
Also published as: FR2997318A1

Abstract

The invention relates to an oxidation/reduction active mass comprising a pyrolusite natural manganese ore initially comprising at least 60% by weight of MnO₂, wherein said mass is enriched with nickel oxide and is in particle form. The invention also relates to a process for chemical looping combustion (CLC) of solid, liquid or gaseous hydrocarbon-based fillers by oxidation/reduction using such an oxidation/reduction active mass. Advantageously, the invention is applied in the CO₂ uptake field.

Description

CHEMICAL LOOP COMBUSTION PROCESS USING OXYDO-REDUCING MASS COMPRISING PYROLUSITE ENRICHED WITH OXIDE

NICKEL

Field of the invention

The field of the invention is that of the combustion of hydrocarbons by chemical redox oxidation (CLC) to produce energy, synthesis gas and / or hydrogen. The invention relates in particular to an oxido-reducing active mass for CLC process and a CLC process using this active mass.

General context

Process of Chemical Looping Combustion or CLC: In the remainder of the text, the term CLC (Chemical Looping Combustion) is understood to mean a process of oxidation-reduction in loop on active mass. It should be noted that, in general, the terms oxidation and reduction are used in relation to the respectively oxidized or reduced state of the active mass. The oxidation reactor is one in which the redox mass is oxidized and the reduction reactor is the reactor in which the redox mass is reduced.

In a context of increasing global energy demand, the capture of carbon dioxide for sequestration has become an unavoidable necessity in order to limit the emission of greenhouse gases that are harmful to the environment. The active-loop-based oxidation-reduction method, or Chemical Looping Combustion (CLC) in the English terminology, makes it possible to produce energy from hydrocarbon fuels while facilitating the capture of the carbon dioxide emitted during of combustion.

The CLC process consists in carrying out oxidation-reduction reactions of an active mass, typically a metal oxide, in order to decompose the combustion reaction into two successive reactions. A first oxidation reaction of the active mass, with air or a gas acting as an oxidant, makes it possible to oxidize the active mass. A second reduction reaction of the active mass thus oxidized by means of a reducing gas then makes it possible to obtain a reusable active mass and a gaseous mixture essentially comprising carbon dioxide and water, or even gas synthesis product containing hydrogen and nitric oxide. This technique therefore makes it possible to isolate carbon dioxide or synthesis gas in a gaseous mixture that is substantially free of oxygen and nitrogen.

As the combustion is generally exothermic, it is possible to produce energy from this process, in the form of steam or electricity, by having exchange surfaces in the circulation loop of the active mass or on the gaseous effluents downstream of combustion or oxidation reactions.

No. 5,447,024 discloses a chemical loop combustion process comprising a first reduction reactor of an active mass using a reducing gas and a second oxidation reactor for restoring the active mass in its state. oxidized by an oxidation reaction with moist air. Circulating fluidized bed technology is used to allow the continuous passage of the active mass from its oxidized state to its reduced state.

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

Thus, in the reduction reactor, the active mass (M _x O _y ) is first reduced to the state M _x O _y -2n- _m / 2, via a hydrocarbon C _n H _m , which is correlatively oxidized to CO ₂ and H ₂ O, according to reaction (1), or optionally in CO + H ₂ mixture according to the proportions used.

C _n H _m + M _x O _y n C0 ₂ + m / 2 H ₂ 0 + M _x O _: y-2n-m / 2 (1)

In the oxidation reactor, the active mass is restored to its oxidized state (M _x O _y ) in contact with the air according to reaction (2), before returning to the first reactor.

M _x O _y _ ■ _; 2n-m / 2 + (n + m / 4) 0 ₂ M _x O _y (2)

In the equations above, M represents a metal. The efficiency of the circulating fluidized bed chemical loop (CLC) combustion process relies to a large extent on the physicochemical properties of the oxidation-reduction active mass.

The reactivity of the oxidation-reduction pair (s) involved as well as the associated oxygen transfer capacity are parameters that influence the design of the reactors and the particle circulation speeds.

The lifetime of the particles as for it depends on the mechanical resistance of the particles as well as their chemical stability.

In order to obtain particles that can be used for this process, the particles used are generally composed of a pair or a set of oxido-reducing pairs chosen from CuO / Cu, Cu ₂ O / Cu, NiO / Ni, Fe ₂ 03 Fe ₃ O ₄ , FeO / Fe, Fe ₃ O ₄ / FeO, MnO ₂ / Mn ₂ O ₃ , Μη ₂ O ₃ / Μη ₃ θ ₄ , Mn ₃ O ₄ / MnO, MnO / Mn, Co ₃ 0 ₄ / CoO, CoO / Co, and a binder providing the necessary physicochemical stability.

The NiO / Ni pair is often cited as a reference active mass for the CLC process for its oxygen transport capacity and its rapid reduction kinetics, especially in the presence of methane. Since nickel oxide does not exist in the natural state in a sufficiently concentrated manner to obtain properties of interest for the CLC process, it is therefore generally used in a concentrated manner in synthetic active-mass particles.

The use of nickel, however, poses some problems because the nickel oxide is suspected of being carcinogenic which causes significant constraints on the smoke filtration system. It also loses its reactive capacities in the presence of sulfur compounds, which does not allow to consider for the use of fuels, such as coal, which contain it.

In a more general way, the main problem posed by the use of synthetic particles is their high manufacturing cost. Since the process requires the circulation of the solid in reactors where the gas velocities are relatively high, continuous consumption of solid by attrition can not be prevented. If the cost of active mass is relatively high, then the booster active mass can become a significant part of the operating cost. It is therefore important to find a low cost active mass in order to reduce the impact of the cost of the particles on the price of C0 ₂ capture by CLC. As such, the possibility of using a natural ilmenite ore (FeTiO ₃ ) has been disclosed by the Instituto de Catalisis y Petroleoquimica (CSIC), Madrid ("Titania-supported iron oxide as oxygen carrier for chemical-looping combustion"). of methane, Corbella, Beatriz M. Palacios, José Maria, Fuel (2006), Volume Date 2007, 86 (1-2), 1 13-122), however this ore has only a transport capacity of oxygen very low and very low reactivity.

In GB patent application 2,058,828, various metal oxides, including a natural manganese ore, are used as oxygen sources to gasify carbon species.

Natural manganese ores have also been tested as oxygen carriers in CLC processes by Fossdal et al. ("Study of inexpensive oxygen carriers for chemical looping combustion", A. Fossdal et al., International Journal of Greenhouse Gas Control 5, 201 1, pp. 483-488).

Although the use of manganese oxides from natural ores as an active mass in a CLC process can be a satisfactory solution in terms of cost, it is less suitable for methane combustion than for combustion. solid or liquid charges in terms of process performance.

Mixtures of natural metal oxides from ores with nickel oxide have also been studied.

Thus, a mixture of natural ilmenite and nickel oxide has been tested by Rydén et al. in the context of a CLC process, in particular for the combustion of methane (Rydén M. et al., Fuel 2010, 89, pp. 3523-3533) . It appears that important transformations of the ilmenite structure occur, including a decrease in density and an increase in the porosity of the metal oxide, which may affect the lifetime of the particles. Problems of agglomeration and sintering of the particles, leading to shutdowns of the CLC plant, have also been noted. These problems seriously question the value of using such a mixture as an oxygen carrier in a CLC process. The use of a mixture of natural hematite and nickel oxide has also been tested by Chen et al., ("Experimental investigation of hematite oxygen carrier decorated with niO for chemical-loopong combustion of coal", Chen D. et al., Journal of Fuel Chemistry and Technology 2012, 40, 267-272). However, this process is limited to the combustion of the coal, and the reactivity of the mixture differs according to the methods of preparation of the mixture, with the appearance of a blockage of the porosity in certain cases. According to this study, the mixture of natural hematite and nickel oxide is obtained either by mechanical mixing or by an impregnation method. In the case of the impregnation carried out with a solution of nickel nitrates on natural hematite, the mixture shows a low surface area suggesting that the effect on the performance of reactions can not be significant. Furthermore, the impregnation on the natural hematite particles, showing an 80% Fe ₂ 0 ₃ hematite content, makes it possible to form nickel oxide particles on the hematite particles, but also results in a reaction. with the elements already present to form a stable phase, such as spinel NiAI ₂ 0 ₄ . Another undesirable effect of the impregnation carried out is the dissolution of a fraction of the iron by the impregnating solution (the Fe / Si ratio is modified). These two effects, the appearance of a stable phase and the dissolution of the oxygen transport phase, result in the decrease of the mass concentration of active sites supplying oxygen to the system. In the case of a mechanical mixture of natural hematite and nickel oxide, problems of stability and sintering under reducing conditions, particularly related to the use of natural hematite, are expected. In all cases, the mixture studied by Chen et al. poses problems of chemical interaction with the refractory materials related to the diffusion of iron at the temperatures implemented in the CLC processes.

There is therefore a need to provide a high-performance CLC process which, in particular, allows high capture of C0 ₂ , suitable for treating any type of hydrocarbon feedstock, whether solid, liquid or gaseous, and which uses a material as an active mass. oxido-reducer inexpensive, and meeting environmental standards in terms of toxicity and reducing emissions.

Objectives and summary of the invention

Applicants have discovered that certain natural manganese ores commonly known as pyrolusite and usually used for metallurgical production, can, once enriched with small amounts of nickel oxide (NiO), and after an activation phase, be used in a redox loop combustion process that allows, in particular, the sequestration of C0 ₂ . The use of such a mixture makes it possible to meet, at least in part, the needs of the prior art as described above.

The invention consists in providing and using natural manganese ores containing mainly MnO ₂ originally, in combination with NiO, as an oxido-reducing active mass for a chemical-loop oxidation-reduction process. The redox active mass is in the form of particles whose size makes it possible to obtain easy flow and transport properties. It is activated by a rise in temperature under an oxidizing atmosphere, and is used in a chemical loop combustion plant comprising a reduction zone in which the fuel is oxidized by the oxygen supplied by reduction of the particles, and an oxidation zone. of these same particles in the presence of air, the particles circulating continuously between these two zones of reduction and oxidation.

The method makes it possible to carry out the combustion of the fuel and in particular to produce nitrogen-free concentrated C0 ₂ -free gases facilitating the C0 ₂ sequestration. The mixture of natural ore of manganese and NiO used according to the invention (active mass), once activated, is particularly interesting because it has a large oxygen transport capacity, kinetic properties allowing rapid reactions, it is not is not sensitive to sulfur that may be contained in the fuel, it meets the environmental standards for toxicity and emissions, and it provides a high performance process, particularly in terms of chemistry and thermomechanical resistance, for a wide range of types of hydrocarbon feeds, in particular for the combustion of gaseous feeds such as methane. In addition, the active mass according to the invention has a low tendency to agglomeration.

According to the invention, the gaseous hydrocarbon feedstocks comprise the hydrocarbon feeds in the form of gas, the liquid feeds after vaporization, and the volatile hydrocarbons of solid feedstocks.

The hydrocarbon feedstocks used as fuel in the combustion process according to the invention may be of fossil origin, come from biomass, or be synthetic fuels. In general, the invention relates to an oxido-reducing active mass for a chemical loop-redox process (CLC) comprising a natural pyrolusite-type manganese ore initially comprising at least 60% by mass of MnO ₂ , said mass being enriched with NiO and in the form of particles.

Preferably, the oxido-reducing active mass initially comprises from 0.1% to 10% by weight, preferably from 1% to 5% by weight of NiO.

Preferably, the initial MnO _{2 content} of the ore is between 70% and 90% by weight, more preferably between 76% and 82% by mass.

According to one embodiment of the invention, the redox active mass comprises a mixture of particles of the natural ore of pyrolusite-type manganese and NiO particles.

The NiO may be shaped on a support of alumina and / or silica.

In a preferred manner, the oxido-reducing active mass has a particle size such that more than 90% of the particles of the active mass have a size of between 100 μηι and 500 μηι, preferably between 150 μηι and 300 μηι.

The invention also relates to a process for the combustion of solid hydrocarbon feeds, liquid or gaseous by oxido-reduction in a chemical loop using this redox active mass.

Preferably, the active mass is formed into particles having a particle size adapted to implementation in a fluidized bed.

Advantageously, the natural manganese ore is previously ground and sieved in order to obtain particles of particle size compatible with a fluidized bed implementation, and the nickel oxide is chosen such that it is in the form of particles of granulometry also compatible with a fluidized bed implementation.

According to one embodiment of the method:

- In a first reaction zone operating in a dense fluidized bed, the hydrocarbon feeds are brought into contact with the particles of the oxido-reducing active mass;

in a second reaction zone, a combustion of the gaseous effluents from the first reaction zone is carried out in the presence of the particles of the oxido-reducing active mass;

in a first division zone operating in a fluidized bed, the particle stream of the active mass coming from the second reaction zone is divided into a first sub-flow going back into the second reaction zone and a second sub-flow going into an oxidation zone; the particles of the active mass are reoxidized in the oxidation zone before returning them to the zone;

in a second division zone operating in a fluidized bed, a division of the particle stream of the active mass coming from the oxidation zone into a third sub-flow going back into the oxidation zone and a fourth sub-flow going into the first reaction zone.

The particle size of the NiO particles may be different from the particle size of the natural manganese ore particles such that the size of the NiO particles is greater or smaller than that of the natural manganese ore particles.

In this case, the method may comprise the following steps:

- In a first reaction zone operating in a dense fluidized bed, the hydrocarbon feeds are contacted with the particles of natural ore of pyrolusite-type manganese and the NiO particles;

in a second reaction zone, a combustion of the gaseous effluents from the first reaction zone is carried out in the presence of particles of pyrolusite-type natural ore of manganese and particles of NiO;

- in a separation zone, particles of natural ore are separated from

pyrolusite-type manganese and NiO particles in a mixture from the zone comprising flue gas, pyrolusite-type natural ore particles and NiO particles;

the pyrolusite-type natural manganese ore particles are re-oxidized in an oxidation zone before being returned to the zone.

Preferably, the oxidation-reduction active mass is activated by a gradual rise in temperature under an oxidizing atmosphere to a temperature greater than or equal to 600 ° C., preferably greater than or equal to 800 ° C., still more preferably greater than or equal to 800 ° C. equal to 900 ^.

This gradual rise in temperature under an oxidizing atmosphere can be carried out at a speed of between 5 Oh and 100 ° C / h.

Preferably, the redox active mass is activated in a chemical loop combustion plant in which the process is implemented.

Preferably, the oxidation-reduction active mass can be used for the combustion of gaseous hydrocarbons.

Advantageously, the oxido-reducing active mass can be reduced in contact with the hydrocarbon feedstocks in a reduction zone of the chemical loop, and the flow rate of the oxido-reducing active mass measured at the inlet of said reduction zone. can be between 30 and 100 kg / h per kg / h of oxygen consumed in the reduction zone.

Advantageously, the reduction of the oxido-reducing active mass in contact with the hydrocarbon feeds is carried out at a temperature of between 600 ° C. and 1400 ° C. The process according to the invention is advantageously used for the capture of C0 ₂ .

The present invention will be better understood and its advantages will appear more clearly on reading the description and examples below, in no way limiting, and illustrated by the appended figures.

Brief description of the figures

Figure 1 is a diagram illustrating the implementation of the CLC method according to a first embodiment of the invention.

FIG. 2 is a diagram illustrating a second embodiment of the CLC method according to the invention.

FIG. 3 is a diagram illustrating a third embodiment of the CLC method according to the invention.

Fig. 4 is a diagram showing the normalized conversion rate Xc of methane versus the number N of oxidation reduction rings in a CLC process using pyrolusite particles alone as the redox active mass (Example 1).

FIG. 5 is a diagram showing the evolution as a function of time of the measured gas concentrations (CH ₄ , CO, CO ₂ ) at the outlet of the reactor during the reduction phase at CH ₄ of the tenth oxidation reduction cycle; reduction, in the case of the use of pyrolusite particles alone as oxido-reducing active mass (Example 1).

FIG. 6 is a diagram representing the standardized conversion rate Xc of methane as a function of the number N of oxidation-reduction cycles in a CLC process using an active mass according to the invention based on pyrolusite and nickel oxide ( example 2).

FIG. 7 is a diagram showing the evolution as a function of time of the measured gas concentrations (CH ₄ , CO, CO ₂ ) at the outlet of the reactor during the reduction phase at CH ₄ of the tenth oxidation reduction cycle; reduction, in the case of the use of an active mass according to the invention based on pyrolusite and nickel oxide (Example 2). FIG. 8 is a diagram representing the standardized conversion rate Xc of methane as a function of the number N of oxidation-reduction cycles in a CLC process using an active mass according to the invention based on pyrolusite and nickel oxide ( example 3). In the figures, the same references designate identical or similar elements.

Description of the invention

The invention relates to an oxido-reducing active mass for a chemical-based oxidation-reduction process based on a natural manganese ore of the pyrolusite type initially comprising at least 60% by weight of MnO ₂ , and enriched with NiO. The active mass is in the form of particles.

The initial amount of nickel oxide in the active mass may vary from 0.1 wt.% To 10 wt.% In the natural manganese / NiO ore mixture, preferably from 0.1 wt.% To 5 wt. more preferably from 0.5 wt% to 5 wt%, even more preferably from 1 wt% to 5 wt%, and still more preferably from 0.5 wt% to 2 wt%.

Preferably, the initial MnO _{2 content} (before introduction of the particles into the chemical loop) is between 70% and 90% by mass, and very preferably between 76% and 82% by mass, which corresponds to metallurgical grade pyrolusite. commercially available.

In the case of the conversion of gaseous hydrocarbon feedstocks in a CLC process, two steps can be distinguished. Firstly, the hydrocarbon molecule is converted into a synthesis gas on the oxygen carrier according to equation (3), and then the synthesis gas formed is oxidized on the CO and H ₂ oxygen carrier. according to equations (4) and (5).

Synthesis gas conversion reactions (equations (4) and (5)) exhibit very high kinetics compared to the formation reaction of this synthesis gas (equation (3)).

C _n H _m + nMn _x O _{y → n} CO + -H ₂ + nMn _x O _y _ ₁ (3)

CO + Mn _x O _y → C0 ₂ + Μη _χ Ο _γ ,, (4)

H ₂ + Mn _x O _y → H ₂ 0 + Mn _x O _y _ ₁ (5)

Enriching the active mass with small amounts of NiO accelerates the synthesis gas formation reaction according to equations (6) and (7) below. C _n H _m + nH ₂ 0 ^^ → nCO + (n + -) H ₂ (6)

777

C _n H _m + nC0 ₂ ^ ^L → 2nCO + - H ₂ (7)

Active mass preparation and activation for CLC process according to the invention

Natural Manganese Ore

Manganese is naturally present in the form of ores. More than 300 ores are now known to contain manganese, but only about thirty are exploited for the manganese they contain. The table below lists the most commonly used, their chemical formula, as well as their average manganese content in%:

Pyrolusite is therefore a natural variety of manganese dioxide, MnO ₂ , also known as manganese oxide (IV). In general, the MnO ₂ concentration of the natural pyrolusite extracted from the pyrolusite mines currently exploited is greater than or equal to a concentration of about 60% by mass of Mn0 ₂ .

Several commercial grades of natural Mn0 ₂ are available:

pyrolusite (ore and concentrate) of metallurgical grade (MnO ₂ 76% to 82%);

- Mn0 ₂ chemical quality (Mn0 ₂ 82% to 85%);

- Mn0 ₂ high purity (93%) for the manufacture of standard batteries. According to the invention, the pyrolusite may be used in combination with NiO as an oxido-reducing active mass for a chemical loop redox process. In order to obtain properties of reactivity and of sufficient oxygen transport capacity for the process, the latter must initially comprise at least 60% by mass of MnO ₂ . Preferably, the initial MnO _{2 content} is between 70% and 90% by mass, and very preferably between 76% and 82% by mass.

Enrichment of the active mass with nickel oxide

The enrichment of the active mass with NiO can be carried out in different ways. Preferably, the active mass comprises a mixture of particles of natural ore of pyrolusite-type manganese and NiO particles. The enrichment consists in this case in mechanically mixing pyrolusite particles and nickel oxide particles. The NiO may in this case be shaped on a solid support of alumina and / or silica, for example in the form of a spinel NiO / NiAl ₂ O ₄ . In addition to alumina, where spinel is advantageously formed, which stabilizes the support with respect to the migration of NiO, it is also possible to use supports based on cerium oxide, zirconium, silica or rutile. of cordierite or a structure resulting from the above-mentioned oxides with NiO. These supports advantageously have the common points of good temperature resistance and good behavior with respect to attrition.

Alternatively, the active mass comprising the natural ore of manganese can be enriched with NiO by forming the NiO directly on the manganese oxide or by synthesizing a mixed manganese oxide material of the pyrolusite / nickel oxide type, according to several techniques well known to those skilled in the art. By way of non-limiting examples, mention may be made of the following techniques:

- Dry or excess impregnation using nickel precursors. The method of dry impregnation (or "incipient wetness" according to the English terminology) can be used advantageously to maintain the initial particle size distribution, but any other type of impregnation can be used, including impregnation in excess.

- Binder type charge forming nickel particles and / or pyrolusite. This method consists, for example, in bringing the particles of nickel and / or pyrolusite into the presence of a suspension also containing one or more organic or inorganic species whose function is to ensure the cohesion of the building. resulting from the shaping and subsequent calcination, hence the name of binder given to these species. This suspension is generally, but not exclusively, aqueous. The solvent content, in general of the water, depends on the chosen shaping: extrusion, "oil drop", atomization ("spray drying" in English). The object resulting from the shaping usually requires cooking or calcination to have its full thermomechanical properties. The cooking conditions depend on the binder used. In general, we can use the peptized bohemite as inorganic binder.

co-precipitation of nickel particles and pyrolusite. According to this synthesis route, precursors of each of the targeted phases are dissolved, for example, but not exclusively, in aqueous solution. The use of other media such as ethanol is possible. Precursors such as manganese salts and nickel salts can be selected. It is preferable that the counterions be as close as possible. It is for example advantageous to dissolve nitrate salts of each of the chosen species. These salts may be chosen from the following list given by way of examples and not limited to: chlorides, nitrates, sulphates, carbonates. Preferably, and for better dispersion of the phases formed, and therefore a better homogeneity of the material, it will be attempted to dissolve these species in the same aqueous solution. It is also possible to carry out this synthesis using separate solutions. The solution (s) comprising the salts of the dissolved precursors are gradually added in a medium whose pH and composition are adjusted so that each of the species in solution precipitates, for example in the form of hydroxide. When species rush together, there is co-precipitation. The precipitates formed can be recovered by filtration and then treated in temperature to reveal the desired phases. This synthetic route can be carried out by bringing into contact a natural pyrolusite-type manganese ore and a nickel precipitate to form a nickel-manganese compound after heat treatment.

- Resin synthesis, called "soft chemistry". This synthetic route consists in forming organometallic resins by chelating metals with protic organic compounds. It is thus possible, for example, to dissolve a metal or a metal salt in an organic acid of citric acid type whose carboxylic oxide function (in carboxylate form after dissolution of the metal or of the salt) has the capacity to induce the chelation of a metal ion. We then speak more specifically of "citrate way". This results in the formation of a resin whose viscosity increases as the excess of acid evaporates. The target phase is obtained by heat treatment in air of the resin at a temperature such that the organic component of the resin will be removed, leaving only the inorganic species, ie the metals, which will subsequently react to form the desired phase. This synthetic route can be done by bringing into contact a natural ore of pyrolusite type manganese with a nickel resin to form a nickel-manganese compound.

- ceramic synthesis. According to this synthetic route, precursor oxide powders of the targeted phases, such as pyrolusite and nickel oxide according to the invention, are finely ground then intimately mixed before undergoing heat treatment under air at high temperature (typically 800 to 1200 °). The high temperature favors the atomic mobility of the metals in the presence, which allows the formation of mixed oxide phase.

Particle size of the active mass

The process of extracting natural manganese ore usually involves a crushing step. Advantageously, the fines produced during this initial crushing can be used for the application targeted by the invention. These fines generally have a particle size less than or equal to 10 mm.

To allow optimal use in the CLC process, in particular to facilitate the transport and flow of the particles of the redox active mass, the natural manganese ore of the pyrolusite type is advantageously milled and sieved to obtain a particle size compatible with its implementation in a fluidized bed. When the active mass comprises a mixture of distinct pyrolusite and NiO particles, the nickel oxide, generally of synthetic origin, is advantageously chosen so that it is in the form of particles of particle size which is also compatible with a use in fluidized bed.

In the case of a NiO shaping directly on the pyrolusite or the synthesis of a mixed manganese ore material of the pyrolusite / nickel oxide type according to the aforementioned methods, the particle size of the particles at the end of the setting in form or synthesis may not be the one sought, unless a spray drying technique, to obtain a material in the form of powder to a desired particle size, is used. In the case where the particles formed are smaller than the desired particle size, the solids formed can be pelletized, then crushed and sieved and / or elutriated. to obtain the desired particle size. In the case where the particles have a larger size than the desired particle size, sieving and / or elutriation can improve the dispersibility.

The particle size of implementation of the active mass in the chemical loop combustion process is indeed important for the proper operation of the process.

As a result, it is preferable to divide the manganese ore into fine particles which can then be mixed with fine NiO particles, or which can be doped with NiO by, for example, an impregnation technique or any other technique permitting to synthesize a mixed MnO ₂ / NiO material from natural pyrolusite ore. The division of manganese ore into fine particles can be carried out for example by grinding the ore using the ore grinding technologies well known to those skilled in the art.

In the chemical loop combustion process, it is necessary to control the circulation of solids between the various oxidation and reduction chambers, to control the supply of oxygen by the active mass and the temperature gradient between the different enclosures. . The use of non-mechanical valves such as L-shaped valves, the principle of which is described in patent FR 2 948 177, makes it possible to effectively control the circulation at high temperature while minimizing the presence of internal elements in the flow. The use of these non-mechanical valves is preferable with relatively large particles, in order to obtain in the L-shaped valves a sufficiently large range of gas / particle slip rates to control the circulation in a relatively wide range. In addition, in the chemical loop process with solid charges, it is necessary to separate the unburnt particles from the metal oxides in the reduction reactor.

It is therefore advantageous to limit the content of fine particles of metal oxides with a diameter of less than 100 micrometers in the installation in order to have optimal operation of the non-metallic valves controlling the circulation, but also to limit the entrainment of metal oxides with unburnt coal in the gaseous effluents of the reactor after separation.

Large particles are more difficult to transport and require high transport speeds. To limit the transport speeds in the transfer lines and inside the reactors, and thus to limit the pressure losses in the process as well as the abrasion and erosion phenomena, it is therefore preferable to limit the size of the particles to a maximum value close to 500 micrometers.

Preferably, the particle-type oxido-reducing active mass introduced into the chemical loop combustion plant therefore has a particle size such that more than 90% of the particles have a size of between 100 micrometers and 500 micrometers.

More preferably, the particle-forming oxido-reducing active mass introduced into the plant has a particle size such that more than 90% of the particles have a particle diameter of between 150 micrometers and 300 micrometers.

Even more preferably, the particle-forming oxido-reducing active mass introduced into the plant has a particle size such that more than 95% of the particles have a diameter of between 150 micrometers and 300 micrometers.

According to a preferred embodiment of the invention, the particle size of the particles of natural ore of pyrolusite-type manganese is different from the particle size of the NiO particles, so as to be able to separate the NiO particles from those of the natural manganese ore during of the CLC process. Advantageously, the NiO particles are shaped to a particle size smaller or larger than that of the particles of natural manganese ore. Thus, the particles of natural manganese ore and NiO do not follow the same circuit in the chemical loop, and only the particles of manganese ore requiring to be reoxidized are sent to the oxidation reactor, which allows optimize the utilities and energy costs of the CLC process. This specific circuit also makes it possible to lower the degree of oxidation of the nickel compound, by changing from the oxidized form NiO to the reduced form Ni, and consequently to increase its catalytic power.

According to another embodiment of the invention, the particle size of the particles of natural ore of pyrolusite-type manganese and that of the NiO particles is substantially identical.

The active mass according to the invention is preferably activated by a phase of gradual rise in temperature under an oxidizing atmosphere. In order to be able to increase the reactive capacities of the redox mass, and according to the invention, the solid in the form of particles advantageously undergoes an activation phase comprising a gradual rise in temperature under an oxidizing atmosphere, constituted for example by the air. The temperature reached is generally greater than or equal to 535 ° C., advantageously greater than or equal to 600 ° C., preferably greater than or equal to 800 ° C., and very preferably greater than or equal to 900 ° C. The activation phase is preferably carried out in the chemical loop combustion plant in the combustion reactor.

Once the redox mass has been shaped, for example after mixing the NiO particles with those of natural manganese ore obtained following a possible grinding and sieving step, the non-activated solid (particles of the redox mass ) is preferably introduced into an area of the plant containing an excess of oxygen, namely the oxidation reactor, for its activation. The chemical loop combustion plant comprises an oxidation reaction zone in which the active mass is oxidized, and a reduction reaction zone in which the active mass is reduced. At start-up, before initiating the oxidation-reduction cycles by introducing fuel into the process, the non-activated solid at room temperature can be introduced at the bottom of the oxidation zone, which is advantageously at a temperature of between 400 ° C and 550 ° C under an oxidizing atmosphere, for example air. This preferential temperature range of the oxidation zone at the time of introduction of the redox mass into the installation makes it possible, for example, to minimize the air to be introduced into the process. The redox mass then equilibrates thermally with the oxidizing atmosphere in the oxidation zone where it is introduced, almost instantaneously. The charging time of the cold solid in the oxidation zone is for example between 12h and 72h, depending on the flow rate of the solid introduced and the dimensions of the installation. The redox mass then undergoes a rise ramp under this oxidizing atmosphere to a temperature generally greater than or equal to 535 ° C, preferably greater than or equal to ΘΟΟ'Ό, preferably greater than or equal to 800 ° Ό , and very preferably greater than or equal to 900 'Ό. During the activation of the active mass, the temperature rise in an oxidizing atmosphere can be done in a progressive manner, preferably at a speed of between 5 Oh and 100 Oh, more preferably at a speed of between 10 ° C./h and 50 ° C / h. The temperature rise of the oxidation reactor can be done by introducing hot air, possibly by the use of gas burners, or a combination of both. The temperature rise of the installation by increasing the Preheating air temperature, by starting gas burners, or a combination of both, allows the circulation of the solid between the reaction zone of reduction and that of oxidation. During this phase of starting and activation of the solid, the oxygen concentration in the oxidation zone is preferably at least 5% excess of O ₂ .

Once the mass is activated, it is possible to initiate the oxidation-reduction cycles by introducing the fuel into the reduction zone.

Preferably, the NiO of the redox mass itself undergoes an activation in order to maximize its catalytic power. The activation of the NiO consists of reducing the degree of oxidation of the nickel compound, that is to say of passing from the form of NiO metal oxide to the Ni metal form, which can be achieved when the particles of the NiO 2 active mass pass into the reduction reactor.

Preferably, the combustion reaction (reduction of the active mass) is carried out in the presence of steam. In the case of using solid or liquid charges, the injection of water vapor is inherent to the process. Indeed to promote the contact between a liquid charge and the metal oxide, it is preferable to atomize the liquid charge and this can be effected effectively in two-phase atomizers in the presence of water vapor. On the other hand, water vapor promotes the gasification of hydrocarbons, and it is preferable in the case of liquid or solid feeds to maintain in the reduction reactor a high pressure of water vapor favoring the gasification reactions. In the case of a gaseous feed, it is advantageous to inject steam with the fluidization gas in order to avoid the formation of agglomerates of the oxygen-bearing solid.

The invention also relates to a method of combustion of solid hydrocarbon feeds, liquid or gaseous by oxidation-reduction in a chemical loop using an active mass according to the invention.

Fluidized bed chemical hydrocarbon combustion process

The active compounds according to the invention act as oxygen carriers for the oxidation-reduction loop combustion process and can be used to treat gaseous fuels (eg natural gas, syngas, biogas), liquids (eg fuel, bitumen, diesel, species, etc.), or solids (eg coal, coke, petcoke, biomass, oil sands, waste etc.) in a circulating fluidized bed.

The general scheme of an oxidation-reduction chemical loop combustion plant according to the invention is as follows: the plant comprises an oxidation reaction zone and a reduction reaction zone. The solid particles of the active mass are oxidized, at least in part, in an oxidation zone comprising at least one fluidized bed at a temperature generally between 600 ° C. and 1400 ° C., preferably between 800 and 1000 ° C. These are then transferred to a reduction zone comprising at least one fluidized bed reactor where the active mass is brought into contact with the fuel at a temperature generally of between 600 ° C. and 1400 ° C., preferably between 800 ° C. and 1000 ° C. The contact time varies depending on the type of fuel load used. It typically varies between 1 seconds and 10 minutes, for example preferably between 1 and 5 minutes for a solid or liquid charge, and for example preferably from 1 to 20 seconds for a gaseous charge. The ratio between the amount of active mass in circulation and the quantity of oxygen to be transferred between the two reaction zones is advantageously between 30 and 100, preferably between 40 and 70.

The combustion can be partial or total.

In the case of partial combustion, the active mass / fuel ratio is adjusted so as to achieve partial oxidation of the fuel, producing a synthesis gas in the form of a mixture rich in CO + H ₂ .

The process can therefore be used for the production of synthesis gas. This synthesis gas can be used as a feedstock for other chemical transformation processes, for example the Fischer Tropsch process making it possible to produce liquid hydrocarbons with long hydrocarbon chains which can subsequently be used as fuel bases from synthesis gas.

In the case where the fluidization gas used is water vapor or a mixture of water vapor and other gas (s), the reaction of CO gas with water (or water gas shift in English terms) Saxons, CO + H ₂ O ^" '* - C0 ₂ + H ₂ ) can also take place, resulting in the production of a C0 ₂ + H ₂ mixture at the reactor outlet. In this case, the flue gas can be used for energy production purposes given its calorific value.

It is also possible to use this gas for the production of hydrogen, for example to supply hydrogenation units, hydrotreating units for refining or a hydrogen distribution network (after reaction of water gas shift).

In the case of total combustion, the gas flow at the outlet of the reduction reactor is composed essentially of CO ₂ and water vapor. A flow of C0 ₂ ready to be sequestered is then obtained by condensation of the water vapor. The energy production is integrated in the Chemical Looping Combustion process by heat exchange in the reaction zone and on the fumes which are cooled.

The invention therefore also relates to a process for capturing CO ₂ by total combustion in a chemical loop in a process according to the invention.

In the case of the use of sulfur-containing fuels, the sulfur oxides that could be produced during the total combustion of sulfur-containing fuels can be separated, depending on the implementation of the chosen process, of the concentrated C0 ₂ stream by a conventional method such as absorption on solvent or by the addition of a desulfurization reagent (lime or limestone). Thus, the use according to the invention of the active mass based on pyrolusite and NiO makes it possible not to reject sulfur oxide in the flow leaving the oxidation reactor, thus advantageously limiting the flow to be treated, in the a case where the redox mass consists of a mixture of particles of natural manganese ore and NiO particles that can be separated so that the majority of the NiO particles are recycled to the reduction reactor and do not circulate in the oxidation reactor. In this case, the sulfur oxides produced by the process during the use of sulfur-containing fuels are thus advantageously recovered only on the outflow of the reduction reactor ("fuel" reactor).

Depending on the use of the flue gases, the process pressure is adjusted. Thus, to achieve total combustion, it is advantageous to work at low pressure to minimize the energy cost of gas compression and thus maximize the energy efficiency of the installation. To produce synthesis gas, it is advantageously possible in certain cases to work under pressure, in order to avoid compression of the synthesis gas upstream of the downstream synthesis process: the Fischer Tropsch process working for example with pressures between 20 bar and 40 bar, it may be advantageous to produce the gas at a higher pressure.

In the case where the active mass comprises a mixture of particles of natural manganese ore and NiO particles, with a particle size of NiO particles different from that of particles of natural manganese ore such that the particle size of NiO is greater than or less than that of the particles of natural manganese ore, the process according to the invention can be implemented as illustrated in FIGS. 1 and 2. According to these embodiments, it is possible to carry out a separation of the particles of NiO that of manganese oxide. This separation advantageously makes it possible to send to the oxidation zone only the particles requiring reoxidation, that is to say the particles of natural ore of manganese, which constitutes a significant energy and financial gain for the whole. of the process. In addition, this configuration allows the initial dopant NiO of the redox mass to remain mainly in the active form Ni. In the case of solid hydrocarbon feedstock combustion, these embodiments can furthermore make it possible to separate the unburnt particles and the ash from the remainder of the effluents leaving the reduction zone.

According to these embodiments, in a first reaction zone R 1 operating in a dense fluidized bed, the hydrocarbon feeds are contacted with the particles of natural ore of pyrolusite-type manganese and the NiO particles. In a second reaction zone R2, a combustion of the gaseous effluents from the first reaction zone R1 is carried out in the presence of the particles of natural ore of pyrolusite-type manganese and NiO particles. In a separation zone S3, the particles of natural pyrolusite-type manganese ore and the NiO particles are separated in a mixture from zone R2 comprising flue gas, the particles of natural manganese ore from Pyrolusite type and NiO particles. The majority of the NiO particles are returned to the first reaction zone R1, and the majority of the natural manganese ore particles are reoxidized in an oxidation zone R4 before returning them to the zone R1.

A first embodiment illustrated in Figure 1, is adapted to the case where the NiO particles are smaller than the particles of natural manganese ore. The installation used is similar to that described in the patent application FR 2 960 740. According to this first embodiment, a hydrocarbon feedstock is contacted with the particles in a first reaction zone R 1 operating in a dense fluidized bed. of natural ore of pyrolusite-type manganese and NiO particles, introduced through a conduit 3. The conduit 1 through which the fuel is introduced can be penetrated inside the reactor R1. The reaction zone R1 is also fed by a fluidization gas fed via a pipe 2. The fluidization means (not shown) are well known to those skilled in the art and are, for example, flat or frustoconical distribution grids, distribution crowns or "spargers". The injected fluidization gas is, for example, water vapor, optionally a steam and CO ₂ mixture, or consists of the gaseous hydrocarbon feedstock which is reduced in the reduction reactor. The temperature in the reaction zone R1 is substantially homogeneous in view of the fluidization conditions leading to the formation of a dense phase. The temperature is preferably between 600 and 1400, preferably between 800 and 1000 ° C. From the reaction zone R1 come out, through a line 4, the particles of the active mass accompanied by the combustion gases that may contain water vapor, nitrogen, hydrogen, CO and / or CO ₂ or a mixture of these gases. The duct 4 transfers the gaseous mixture containing the particles to a second reaction zone R2. The duct 4 is preferably a duct of variable section so as to join the reaction zones R1 and R2. A pipe 5 can extract in the lower part of the reaction zone R1, in the case of a combustion of solid hydrocarbon feeds producing ash and unburnt particles, said ash formed and agglomerated with each other in the reactor as well as possibly oxygen carrier particles and unburnt particles. In the reaction zone R1, the average residence time of the fuel and of the oxido-reducing active mass is, for example, between 1 minute and 5 minutes if a solid or liquid combustible charge is used, and for example between 1 second and 20 seconds in the case of a gaseous fuel charge. The superficial gas velocity is generally between 0.3 and 3 m / s (at the reaction conditions at the outlet of the reaction zone (R1)).

The concentration of metal oxides in the reaction zone (R1) is at least 10% by volume.

In a second reaction zone R2, a combustion of the gaseous effluents from the first reaction zone R1 is carried out in the presence of the particles of natural ore of pyrolusite-type manganese and NiO particles. In order to promote total combustion, it may be envisaged to introduce a certain amount of fresh oxido-reducing mass completely oxidized by a pipe 6. It is also possible to inject oxygen directly via a pipe 7. At the outlet of the second reaction zone R2, a mixture comprising combustion gas, the particles of pyrolusite-type natural ore of manganese and the NiO particles is extracted via a pipe 8 to be sent to a separation zone S3 in which takes place a rapid separation between the lightest particles, that is to say mainly the NiO particles of smaller size than the other particles of the mass, extracted by the conduit 10 with the gas, and the particles the heaviest - mostly particles of natural manganese ore - extracted in the lower part of the separation zone S3 by a conduit 13 feeding an enclosure F4. This enclosure F4 serves as a buffer zone, and may be materialized by a concentric fluid bed and peripheral to the second reaction zone R2, the fluidization being obtained by injecting a gas supplied by a pipe 14. Advantageously, the latter participates in the separation in the separation zone S3 by being channeled to it by a pipe 17. In this fluidized bed of the buffer zone, it is advantageous to have heat exchange means 16 which can be tubes in wall or in the fluidized bed to recover a variable part generally representing 5 to 60% of the heat produced in the chemical loop combustion process. A conduit 15 makes it possible to extract the particles of the active mass constituted, for the most part, by the natural manganese ore from the buffer zone to an oxidation zone R4 to re-oxidize the latter, and then send them back to the reaction zone R 1 by the conduit 3.

In the separation zone S3, it is also possible to introduce via a pipe 9 a gas coming from an external source. This gas may contain oxygen or an oxidizing gas to continue the combustion reactions of CO and hydrogen in the separator S3. From the separation zone S3, a part of the decanted heavy particles (mainly particles of natural manganese ore) is extracted via a pipe 1 1 to be recycled to the reaction zone R1. It is thus possible to promote the temperature homogeneity in the reaction zones R1, R2 and in the separation zone S3.

At the exit of the separation zone S3, the pipe 10 conveys the gas stream containing the lighter particles - mainly NiO particles and possibly a minor fraction of particles of natural manganese ore - to at least one gas separation stage. -solid, for example two gas-solid separation stages (S5, S6), for example cyclones, as shown in FIG. These devices make it possible to recover almost all the particles contained in the gas stream of the pipe 10 which are then recycled to the reaction zone R1 respectively by the pipes 19 and 20. At the outlet of the first cyclone S5, the gas stream is extracted by a pipe 17 to be sent to the second cyclone S6 and at the outlet of this cyclone S6, the substantially particle-free gas is extracted via a pipe 18, the latter no longer containing that a particle content generally between 100 mg / m ³ and 1 g / m ³ .

A dense fluidized bed is understood to mean a fluidized bed in which the gas fraction ε ₉ is less than 0.9, preferably less than 0.8.

Diluted fluidized bed means a fluidized bed in which the volume fraction of the particles of the redox active mass is less than 10% by volume.

According to this first embodiment, the majority of the NiO is activated once within the second reaction zone R2.

In the case of the injection of a solid fuel into the reactor R1, the flow of the solid fuel particles can be either continuous or intermittent with an injection frequency corresponding to a period equal to at least half the time average residence time of all the solid fuel particles in the reaction zone R1. The solid fuel undergoes, on contact with the particles of the active mass, a devolatilization of the volatile compounds, which generally represent from 5 to 50% by weight of the solid fuel according to its origin. The temperature in the reaction zone R 1 is preferably greater than 800% and preferably between 900% and 6%, so as to minimize the time required to gasify the solid fuel. From the reaction zone R1 exits through the pipe 4, in addition to the particles of the active mass and the combustion gas, a unburned solid fuel fraction. In the separation zone S3, unburnt particles and possibly fly ash can be extracted together with the NiO particles and sent to the separators S5 and S6 via the line 10. The solid particles passing through S5 and S6 can then be recovered almost completely, after possible removal of fly ash by fluidized bed elutriation, for example.

A second embodiment illustrated in FIG. 2 is adapted to the case where the NiO particles have a size greater than that of the particles of natural manganese ore. The reaction zones R1, R2, R4 function in a manner similar to that described with reference to FIG. 1. With reference to FIG. 2, the following steps are performed:

the mixture of particles brought by the pipe 205 is brought into contact with the combustible charge introduced via the pipe 1 into a first reaction zone R 1 operating in a dense fluidized bed; a combustion of the gaseous effluents from the first reaction zone R1 is carried out by the pipe 4 in the presence of the particles of the active mass in a second reaction zone R2;

in a separation zone S3, the natural pyrolusite-type manganese ore particles and the NiO particles are separated in a mixture coming from the zone R2 by the pipe 8 and comprising combustion gas, the particles of pyrolusite-type natural manganese ore and NiO particles. Larger and heavier NiO particles are mostly returned to reaction zone R1 via line 11, and the rest of the particles - mostly natural manganese ore particles - are sent with combustion by the pipe 10 in a solid-gas separation zone S5, for example a cyclone, for separating the combustion gas that escapes through a pipe 18 and a flux composed mainly of particles of manganese oxide sent by a pipe 201 to an oxidation zone R4 to be re-oxidized;

the particles of manganese oxide are re-oxidized in the oxidation zone R4 by means of an oxidizing gas such as air introduced via a pipe 22. The re-oxidized particles are then returned to the first reduction zone R1;

after a solid-gas separation in a cyclone separator S6, the solid particles from the oxidation reactor R4 are sent via a pipe 203 to a solid-solid division zone R5, operating in a fluidized bed, which allows to divide the partially oxidized solid stream leaving the oxidation reactor R4, composed mainly of a major fraction of particles of natural manganese ore and a minor fraction of NiO particles, into two sub-streams. A first sub-flow returns via a pipe 204 to the oxidation reactor R4 to be further oxidized, and a second sub-flow is conveyed to the reduction reactor R1 through a pipe 205 to provide the oxygen required for the combustion of the charges. fuels introduced into R1. In addition, the solid-solid division zone R5 can also be used to recover the heat produced by the oxidation of methane, for example by integrating heat exchange means. As in the first embodiment, the majority of the NiO is activated once within the second reaction zone R2.

A CLC installation making it possible to implement the method according to the first and second embodiments of the invention thus comprises:

at least one first reaction zone R1 operating in a dense fluidized bed and making it possible to bring into contact the gaseous, solid or liquid hydrocarbon feedstock with the particles of the redox active mass. In the case of solid fuels, this first reaction zone R1 makes it possible to gasify the particles of the solid fuel in the presence of particles of the redox mass.

a second combustion or reduction reaction zone R2 preferably operating in a diluted fluidized bed and making it possible to carry out the combustion of the gaseous effluents originating from the first reaction zone R1 in the presence of the particles of the oxido-reducing active mass;

a separating zone S3 effecting a separation in a mixture containing gas, particles of natural ore of pyrolusite-type manganese and NiO particles, said mixture coming from the second reaction zone R2, and said zone separation device comprising an enclosure in which the admission of the mixture of particles to be separated is carried out in a dilute phase in which a gas flows at an ascending speed which is imposed;

an oxidation zone R4 of the particles of the oxido-reducing active mass, in particular particles of natural ore of manganese, making it possible to re-oxidize said particles before returning them to the reaction zone R1.

FIG. 3 illustrates a third embodiment for implementing the method according to the invention. This embodiment is particularly adapted to the case where the particle size of the particles of natural ore of pyrolusite-type manganese and that of the NiO particles is similar, and in the case where the active mass is not a mixture of distinct particles of NiO and of manganese ore, but comprises particles formed from the same material comprising NiO-doped pyrolusite-type natural ore of manganese. According to this third embodiment, the hydrocarbon feedstocks coming from a pipe 1 are brought into contact with the particles of the oxido-reducing active mass arriving via a pipe 308 in an oxidized state, in a first reaction zone R 1 operating in dense fluidized bed. Next, combustion of the gaseous effluents from the first reaction zone R1 in the presence of the particles of the redox active mass in a second reaction zone R2. The gaseous effluent resulting from the combustion and containing the particles of the active mass is then sent via a pipe 8 into a first gas-solid separator S1, for example a cyclone, from which the combustion gas is extracted via a pipe 18 and a flow of particles through a conduit 301. The latter is divided into a first division zone R3 operating in a fluidized bed in a first sub-flow returned by a pipe 302 to the second reaction zone R2 where it is advantageously recycled, and a second sub-flow going in a zone d R4 oxidation by 303. The recycling of the first sub-flow makes it possible to increase the activated form Ni of the dopant in the reaction zone R2. The particles of the second sub-flux are reoxidized in the oxidation zone R4 and then returned to the reduction zone R1. For this, the particles of the active mass are first recovered by means of a solid-gas separator S2 of the cyclone type, which are then sent through line 306 to a second division zone R5 operating in a fluidized bed. In this zone R5, the particle flow of the active mass from the oxidation zone R4 is divided into a third sub-flow going back into the oxidation zone R4 via a pipe 307, to be further re-oxidized. , and a fourth sub-flow going into the first reaction zone R1 via a pipe 308.

According to this third embodiment, the NiO of the redox mass is activated at each passage within the second reaction zone R2 when said mass comes from the oxidation zone R4.

Examples

EXAMPLE 1 Combustion of methane at 890 ° C. in the presence of pyrolusite particles (example given for comparison)

A compound charge, by volume, of 50% methane, 33.3% of nitrogen and 16.7% of water vapor, which corresponds to a nominal power of 0.6 kW heat, is treated in a reactor of 40 mm diameter working in batch.

For the chemical loop combustion, pyrolusite-based oxygen-carrying particles having the following properties are used:

density: 3250 kg / m ³

oxygen transfer capacity: 6.7%

particle diameter: 208 μηι

The pyrolusite utilization rate, ROAx, is 2%, which means that for every 100 grams of oxide, 2 grams of oxygen are used.

The temperature of the oxygen carrier in the reactor varies between 870 ° C and 900 ° C, the average temperature being 890 ° C.

The apparent residence time of the gas in the reactor is 1 second. This calculated residence time does not take into account the hydrodynamics of the fluidized bed, and corresponds to the ratio between the height of the bed and the superficial velocity of the gas.

The redox mass is activated by a rise in temperature of 20 ^q C / minute in air, up to a temperature of 900 'Ό. FIG. 4 represents the evolution of the conversion of methane Xc (%) over the first 35 oxidation-reduction cycles of the process (Number of cycles N on the abscissa).

The conversion rate of methane Xc corresponds to the ratio between the amount of C0 ₂ formed

(in moles), and the quantity of CH ₄ injected (in moles), standardized to take account of the carbon footprint.

Initially, the conversion of methane is about 40%, then decreases to about 20% for the last four cycles.

Figure 5 illustrates gas profiles CH _4, CO and C0 ₂ measured obtained at the reactor outlet during the reduction phase of the 10 ^th redox cycle.

The gases at the outlet are analyzed with the Rosemount NGA2000 analyzer.

CO ₂ , CO and CH ₄ are measured with a non-dispersive infra-red spectrometer

(NDIR), the oxygen is measured using a paramagnetic cell, and the dihydrogen is measured with a katharometer.

At the beginning of the reduction, a C0 ₂ peak is observed and then a constant decrease in CH ₄ conversion.

Example 2: Combustion of methane at 890 ° C in the presence of a mixture comprising 99% pyrolusite and 0.59% NiO.

A compound charge, by volume, of 50% methane, 33.3% of nitrogen and 16.7% of water vapor, which corresponds to a nominal power of 0.6 kW heat, is treated in a 40 mm reactor of diameter working in batch.

For the chemical loop combustion are implemented pyrolusite-based oxygen carrier particles having the following properties:

density: 3250 kg / m ³

oxygen transfer capacity: 6.7%

particle diameter: 208 μηι

Pyrolusite mass tested: 131 g

The pyrolusite utilization rate, ROAx, is 2%, that is to say that for each 100 grams of oxide, 2 grams of oxygen are used.

For this example, nickel oxide is used to dope the redox mass comprising pyrolusite. The NiO is shaped under a NiO / NiAl ₂ ₄ spinel (60% / 40% by mass), the properties of which are as follows: density: 2217 kg / m ³

particle diameter: 186 μηι

Mass of NiO / NiAl ₂ 0 ₄ tested: 1.3 g

The temperature of the oxygen carrier in the reactor varies between 870 ° and 900 ° C, the average temperature being 890 ° C.

The redox mass is activated by a rise in temperature of 20% per minute in air, up to a temperature of 900%.

FIG. 6 describes the evolution of the methane conversion Xc (%) over the first 35 oxidation-reduction cycles of the process (Number of cycles N on the abscissa).

The conversion rate of methane Xc corresponds to the ratio between the amount of C0 ₂ formed (in moles), and the amount of CH ₄ injected (in moles), standardized to take account of the carbon footprint.

Initially, the conversion of methane amounts to about 50%, then increases to stabilize around 70%.

Figure 7 illustrates the profiles of CH _4, CO and C0 ₂ obtained at the reactor outlet during the reduction phase of the 10 ^th redox cycle.

The gases at the outlet are analyzed with the Rosemount NGA2000 analyzer.

At the beginning of the reduction, a C0 ₂ peak is observed and then a constant decrease in CH ₄ conversion. After 40 seconds of reduction, there is an increase in the conversion of CH ₄ .

Example 3: Combustion of methane at 880 ° C in the presence of a mixture comprising 95% pyrolusite and 2.53% NiO.

A compound charge, by volume, of 50% methane, 33.3% of nitrogen and 16.7% of water vapor, which corresponds to a nominal power of 0.6 kW heat, is treated in a 40 mm reactor. diameter working in batch. For the chemical loop combustion are implemented pyrolusite-based oxygen carrier particles having the following properties:

density: 3250 kg / m ³

oxygen transfer capacity: 6.7%

particle diameter: 208 μηι

Pyrolusite mass tested: 150 g

For this example, nickel oxide is used to dope the redox mass comprising pyrolusite. The NiO is shaped under a NiO / NiAl ₂ ₄ spinel (60% / 40% by mass), the properties of which are as follows:

density: 2217 kg / m ³

particle diameter: 186 μηι

Mass of NiO / NiAl ₂ O ₄ tested: 6.6 g

The temperature of the oxygen carrier in the reactor varies between 870 ° C and 900 ° C, the average temperature being 880 ° C.

The redox mass is activated by a rise in temperature of 20 ^q C / minute in air, up to a temperature of 900 'Ό.

FIG. 8 describes the evolution of the methane conversion Xc (%) over the first 35 oxidation-reduction cycles of the process (Number of cycles N on the abscissa).

The conversion rate of methane Xc corresponds to the ratio between the amount of C0 ₂ formed (in moles), and the amount of CH ₄ injected (in moles), standardized to take account of the carbon footprint. The same measuring devices as those described for the other examples are used.

Initially, the conversion of methane amounts to about 50%, then increases to stabilize to 80%.

Claims

1. Oxidoreducing active mass for a chemical loop-redox process comprising a natural pyrolusite-type manganese ore initially comprising at least 60% by weight of MnO ₂ , said mass being enriched with nickel oxide (NiO) and in the form of particles.

2. Redox active mass according to claim 1, initially comprising from 0.1% to 10% by weight, preferably from 1% to 5% by weight of NiO.

3. Redox active mass according to one of claims 1 and 2, wherein the initial MnO _{2 content} of the ore is between 70% and 90% by weight, preferably between 76% and 82% by mass.

4. Redox active mass according to one of the preceding claims, comprising a mixture of particles of the natural ore of pyrolusite-type manganese and NiO particles.

5. Redox active mass according to claim 4, wherein the NiO is shaped on a support of alumina and / or silica.

6. Redox active mass according to one of the preceding claims, having a particle size such that more than 90% of the particles of the active mass have a size between 100 μηι and 500 μηι, preferably between 150 μηι and 300 μηι .

7. A process for the combustion of solid hydrocarbon feeds, liquid or gaseous by chemical redox oxidation using an oxido-reducing active mass according to any one of claims 1 to 6.

8. The method of claim 7, wherein the active mass is shaped particles having a particle size suitable for implementation in a fluidized bed.

9. The method of claim 8, wherein the natural manganese ore is previously milled and sieved to obtain grain size particles. compatible with implementation in a fluidized bed, and in which the nickel oxide is chosen such that it is in the form of particle size distribution also compatible with a fluidized bed implementation.

10. Method according to one of claims 7 to 9, wherein:

- In a first reaction zone (R1) operating in a dense fluidized bed, the hydrocarbon feeds are brought into contact with the particles of the redox active mass;

in a second reaction zone (R2), combustion of the gaseous effluents from the first reaction zone (R1) in the presence of the particles of the oxido-reducing active mass;

in a first division zone (R3) operating in fluidized bed, a division of the particle stream of the active mass from the second reaction zone (301) into a first sub-flow going back into the second reaction zone (R2) and a second sub-flow going into an oxidation zone (R4);

the particles of the active mass are reoxidized in the oxidation zone (R4) before returning them to the zone (R1);

in a second division zone (R5) operating in a fluidized bed, a division of the particle stream of the active mass coming from the oxidation zone (R4) into a third sub-flow going back into the zone an oxidation step (R4) and a fourth sub-flow going to the first reaction zone (R1).

1 1. The method of claim 9 wherein the particle size of the NiO particles is different from the particle size of the natural manganese ore particles such that the particle size of NiO is higher or lower than that of the natural manganese ore particles.

The method of claim 11, wherein:

- In a first reaction zone (R1) operating in a dense fluidized bed, the hydrocarbon feeds are contacted with the particles of natural ore of pyrolusite-type manganese and the NiO particles;

in a second reaction zone (R2), combustion of the gaseous effluents from the first reaction zone (R1) is carried out in the presence of natural pyrolusite type ore particles and NiO particles; separating, in a separation zone (S3), the particles of natural pyrolusite-type manganese ore and the NiO particles in a mixture originating from the zone (R2) comprising flue gas, the particles of pyrolusite-type natural manganese ore and NiO particles;

the pyrolusite-type natural manganese ore particles are re-oxidized in an oxidation zone (R4) before being returned to the zone (R1).

13. Method according to one of claims 7 to 12, wherein the active redox active mass is activated by a gradual rise in temperature under an oxidizing atmosphere to a temperature greater than or equal to 600 'Ό, preferably greater or equal to 800 'Ό, still more preferably greater than or equal to 900 ^< €.

14. The method of claim 13, wherein the gradual rise in temperature in an oxidizing atmosphere is carried out at a speed between 5 ° C / h and 100 ^< € / h.

15. Method according to one of claims 7 to 14, wherein the redox active mass is activated in a chemical loop combustion plant in which the method is implemented.

16. Method according to one of claims 7 to 15, in the active redox active mass is used for the combustion of gaseous hydrocarbons.

17. Method according to one of claims 7 to 16, wherein the redox active mass is reduced in contact with the hydrocarbon feedstock in a reduction zone of the chemical loop, and wherein the flow rate of the active oxide mass -reductor measured at the entrance of said reduction zone is between 30 and 100 kg / h per kg / h of oxygen consumed in the reduction zone.

18. The process as claimed in one of claims 7 to 17, in which the reduction of the oxido-reducing active mass in contact with the hydrocarbon feeds is carried out at a temperature of between 600 ° and 1400 °.

19. Method according to one of claims 7 to 18 for the capture of C0 ₂ .