GAS FLOW DECARBONATION PROCESS

The present invention relates to the decarbonation, that is to say the separation of carbon dioxide (C0 2 ), a gas stream comprising said carbon dioxide, as for example in the gas streams of steelworks where carbon monoxide gas streams very often contain very large amounts of carbon dioxide.

[0002] Indeed, it is already well known that it is possible to find C0 2 present in greater or lesser proportions, for example ranging from 15% to 60% by volume, in gas streams, in particular those containing a high content of carbon monoxide (at least 10%) and possibly hydrogen sulphide (10 ppmv to 5000 ppmv).

Too large amounts of C0 2 cause many drawbacks, or even problems, such as for example limited adsorption capacities due to faster saturation, therefore more frequent regenerations and accelerated aging of the product. These large amounts of CO 2 also represent an additional constraint for membrane processes, but also for those using a solvent, a cryogenic distillation system, and others; the separation then becomes very energy intensive and therefore becomes very expensive.

[0004] More specifically and by way of example, there may be mentioned, among the gas streams to be decarbonized, steelworks gases which typically contain from 20% to 50% of C0 2 and 20% to 50% of CO, as well that possibly minority species such as H 2 , N 2 , CH 4 , H 2 S, H 2 O.

[0005] In order to produce iron (this also being valid for the production of other metals), iron oxides are contacted with a reducing gas, which is often a mixture consisting essentially of CO and H 2 . This reducing gas reacts with iron oxides forming elemental iron, C0 2 and H 2 0. The gas produced therefore consists of a mixture of C0 2 , H 2 0, CO and H 2 . Before it can be reused, this gas must be enriched again with CO and H 2 . One of the solutions can be the elimination of undesirable components, in particular the elimination of the impurities C0 2 and H 20, by separation, selective adsorption for example.

[0006] US Pat. No. 3,161,461 describes an absorption process for separating acid gases present in gas mixtures using specific solvents. The use of solvents is however difficult to implement industrially, and the regeneration of these solvents often requires extremely large amounts of energy, corrosion problems and enormous environmental constraints, so that this process does not is often not profitable and therefore little used.

[0007] US Pat. No. 8,192,524 describes a process for decarbonizing a gas stream having a volume rate of C0 2 greater than 10%, said process implementing at least one membrane unit comprising a plurality of polymer membranes in order to produce a permeate comprising at least 95% by volume of C0 2 and a gas flow depleted in C0 2 . However, to make this process fully effective, and in order to ensure a good degree of separation, several stages of membranes are necessary, which leads to complex and expensive processes which are difficult to use industrially.

US Pat. No. 4,459,142 discloses a cryogenic distillation process for the separation of C0 2 present in streams of C 3 -C 10 hydrocarbons . The processes implementing such cryogenic distillation systems however have the drawback of having to manage the formation of dry ice at very low temperature.

[0009] It is also known practice to implement fixed bed adsorption processes making it possible to decarbonize gas streams. For example, US Pat. No. 4,775,396 describes the selective adsorption of carbon dioxide present in non-acidic gases (such as N 2 , H 2 and CH 4 ) by a PSA (Modulated Pressure Adsorption or “Pressure Swing Adsorption” process). English language) using a fixed adsorption bed comprising a zeolitic aluminosilicate of Faujasite type containing at least 20% of at least one cationic species chosen from the group consisting of zinc, rare earths, hydrogen and ammonium , and containing not more than 80% of alkali metal or alkaline earth metal cations.

TSA (Temperature Modulated Adsorption or "Temperature Swing Adsorption") type processes are also known, generally suitable for the decarbonation of low C0 2 charged streams .

[0011] Patent US5531808 describes the decarbonation of gas streams mainly comprising gases less polar than C0 2 , by passing said gas stream through a bed of type X zeolitic adsorbent with an Si / Al atomic ratio of less than approximately 1, 15, at temperatures above 20 ° G

US Pat. No. 7,608,134 proposes the use of an X-type zeolite with an Si / Al atomic ratio of between 1.0 and 1.15, strongly exchanged with sodium, and agglomerated with a maximum binder content of 20%, to decarbonise gas streams, in particular air, polluted by C0 2 .

[0013] The patent US6143057 describes composite adsorbents composed of zeolites in the form of microparticles of size less than 0.6 μm and of an inert macroporous binder. These composite adsorbents are used to separate gaseous components present in gas mixtures, and in particular to separate nitrogen or C0 2 present in air.

US6537348 B1 patent discloses the use of beads of 0, 5-3.0 mm of NaLSX or LiLSX to decarbonize a gas having 50 mm Hg (67 mbar) of C0 2 .

An air prepurification process is proposed in US Pat. No. 5,906,675. This process uses a battery of three adsorbent beds operating in PSA, and containing at least two adsorbents, one composed of alumina to remove water and a little C0 2 , and the other composed of zeolite to adsorb the remaining C0 2 . While columns 1 and 2 are operating in the PSA regime, the 3rd is thermally regenerated, then column 1 is thermally regenerated while columns 2 and 3 are operating in the PSA regime, and so on.

[0016] The patent US7309378 describes a process for purifying synthesis gas of the H 2 / CO OR H 2 / N 2 type , consisting in removing the C0 2 as well as other impurities, using an adsorbent of the NaLSX type and then by desorbent during a regeneration step which can be carried out by raising the temperature (TSA) and / or reducing the pressure (VSA, for “Volume Swing Adsorption” or PSA).

However, it is difficult to decarbonize certain gas streams heavily loaded with C0 2 , in particular when the gas stream to be purified contains CO in high concentration because the separation system used must have high C0 2 separation capacities and selectivities as well as suitable regenerability

US6027545 discloses a directly reduced iron production process using a gas composed of CO and H 2 (with impurities of C0 2 , H 2 0 and CH 4 ) with a PSA unit which adsorbs C0 2 (and a little CO) to produce H 2 of high purity, without however specifying the solids used.

International application WO2017 / 042466 proposes a process for decarbonating natural gas using a type A molecular sieve highly exchanged with calcium and agglomerated with a fibrous magnesian clay. This process, however, is only suitable for the elimination of low C0 2 contents , typically less than 2% by volume of C0 2 in natural gas.

[0020] Besides zeolites, other solids have been tested for the decarbonation of gas streams, and for example silica gels, as described for example in patent US8298986. The costs of manufacturing effective silica gels

are however relatively high, so that there remains a need for adsorbents exhibiting high capacities and selectivity for C0 2 adsorption .

Thus, an objective of the present invention is the provision of a method allowing the decarbonation of gas streams containing a large amount of C0 2 , typically more than 15% of C0 2 , by volume relative to the total volume of the stream gas to be decarbonated.

Another objective of the invention is to provide a process for decarbonating a gas flow leading to a final CO 2 content of less than 5%, better still less than 3%, and better still a final CO 2 content of 'order of a few ppm, by volume relative to the total volume of said gas stream.

Yet another objective is to provide a process for decarbonating a gas stream containing a large amount of CO 2, typically between 15% and 60%, or even between 20% and 50%, for example between 25% and 40% , by volume relative to the total volume of gas flow to be decarbonated, said process leading to a final C0 2 content of less than 5%, better still less than 3%, and better still a final C0 2 content of the order of a few ppm, by volume relative to the total volume of said gas stream.

Another objective is to provide a process for the decarbonation of gas streams using efficient and economical means that are compatible with profitable industrial operation, and in particular with reduced energy costs and improved selectivity.

[0025] Other technical problems will appear in the description of the present invention which follows. It has now been surprisingly discovered that the objectives presented are achieved, in whole or at least in part, thanks to the method of the invention which is now detailed in what follows.

[0026] Thus, and according to a first aspect, the present invention relates to a process for decarbonating a gas stream, said method comprising at least the steps of: a) providing a gas stream containing from 15% to 60% of carbon dioxide, expressed as a volume relative to the total volume of gas flow,

b) passing said gas stream over a zeolitic agglomerate, and

c) recovery of a gas flow depleted in C0 2 ,

process in which the zeolitic agglomerate comprises at least one binder and at least one zeolite, and has a mesoporous volume of between 0.02 cm 3 .g _1 and 0.15 cm 3 .g _1 and a mesoporous volume fraction of between 0 , 1 and 0.5, preferably between 0.15 and 0.45.

The zeolitic adsorbent in the form of agglomerates of the invention comprises both macropores, mesopores and micropores. By "macropores" is meant

pores with an opening greater than 50 nm. By “mesopores” is meant pores whose opening is between 2 nm and 50 nm, limits not included. By “micropores” is meant pores whose opening is less than 2 nm, typically greater than strictly than 0 and less than or equal to 2 nm.

In the description of the present invention, "V ma" denotes the macroporous volume expressed in cm 3 .g _1 of adsorbent, by "V me" the mesoporous volume expressed in cm 3 .g _1 of adsorbent and by "V mi" the microporous volume expressed in cm 3 .g _1 of adsorbent.

The macroporous l / ma and mesoporous volumes l / me are measured by mercury intrusion porosimetry. A Micromeritics Autopore ® 9500 mercury porosimeter is used to analyze the pore volume distribution in macropores and mesopores.

The experimental method, described in the operating manual of the apparatus with reference to standard ASTM D4284-83, consists in placing a sample of adsorbent (zeolitic adsorbent in the form of agglomerates to be measured) (loss on ignition known) weighed beforehand, in a cell of the porosimeter, then, after a preliminary degassing (discharge pressure of 30 pm Hg for at least 10 min), to fill the cell with mercury at a given pressure (0.0036 MPa) , and then applying an increasing pressure in stages up to 400 MPa in order to gradually penetrate the mercury into the porous network of the sample, taking at least 15 pressure stages up to 0.2 MPa, and applying then increments of 0.1 MPa up to 1 MPa, then 0.5 MPa up to 10 MPa, then 2 MPa up to 30 MPa,then 5 MPa up to 180 MPa, and finally 10 MPa up to 400 MPa.

The relationship between the applied pressure and the characteristic dimension of the pore entry threshold (corresponding to an apparent pore diameter) is established using the Laplace-Young equation and assuming a cylindrical pore opening, a contact angle between the mercury and the pore wall of 140 ° and a surface tension of the mercury of 485 dynes / cm. The volume increments AVi of mercury introduced at each pressure step Pi are recorded, which then makes it possible to plot the cumulative volume of mercury introduced as a function of the applied pressure l / (Pi), or as a function of the apparent diameter of the pores V (li).

The value from which the mercury fills all the inter-granular voids is fixed at 0.2 MPa, and it is considered that beyond the mercury penetrates into the pores of the adsorbent. The macroporous volume V ma of the adsorbent is defined as being the cumulative volume of mercury introduced at a pressure of between 0.2 MPa and 30 MPa, corresponding to the volume contained in the pores with an apparent diameter greater than 50 nm.

The mesoporous volume V me of the adsorbent is defined as being the cumulative volume of mercury introduced at a pressure of between 30 MPa and 400 MPa.

The method of measuring the pore volume by mercury intrusion does not allow access to the microporous volume, the total pore volume V tot as measured by mercury intrusion, corresponds to the sum of the macroporous volumes V ma and mesoporous V me .

In the present description, the macroporous and mesoporous volumes V ma and V me , as well as their sum (total pore volume V tot ), of the zeolitic adsorbents, expressed in cm 3 .g _1 , are thus measured by intrusion porosimetry of mercury and related to the mass of the sample in anhydrous equivalent, that is to say the mass of said adsorbent corrected for loss on ignition.

The mesoporous volume fraction (FVM) is the quotient of the mesoporous volume Vme by the total pore volume, or FVM = V me / (V ma + V me ).

By "decarbonation", within the meaning of the present invention, is meant the process for removing a gas stream containing C0 2 , and by "removal" is meant that the gas stream at the end of the process no longer contains C0 2 , or contains a quantity of C0 2 , less than 5%, better still less than 3%, and better still a final C0 2 content of the order of a few ppm, by volume relative to the total volume of said gas stream. The term “CO 2 depleted” gas flow denotes the gas flow at the end of the process, as described above.

The process of the present invention is particularly suitable for the decarbonation of a gas stream containing from 15% to 60% of carbon dioxide (C0 2 ), preferably from 20% to 50%, more preferably from 25 % to 40%, by volume relative to the total volume of said gas stream.

According to one embodiment of the method of the present invention, the gas flow depleted in C0 2 , comprises a quantity of C0 2 generally between a few ppmv and 10%, preferably from 0.01% to 5%, typically from 2 to 4%, but higher or lower values ​​can be obtained depending on the applications envisaged.

The process of the present invention is also particularly suitable for the decarbonation of gas streams comprising hydrogen sulphide (H2S), for example in concentrations of between 10 ppmv to 5000 ppmv.

Such gas streams with high C0 2 contents are present in a large number of industrial fields, and in particular can be found in biogas, which may contain for example up to 50% of C0 2 , in gases combustion, in steelworks where said gas streams may contain CO contents for example between 10% and 50%,

by volume relative to the total volume of said gas stream, in natural gas which may contain up to 50% of C0 2 , but also synthesis gases, such as for example those resulting from the gasification of coal and which contain approximately 20 % C0 2 and about 20% to 50% CO, to name only the most common gas streams with high C0 2 contents .

Thus, the gas streams which are the most suitable for the process of the present invention are the gas streams containing a C0 2 content ranging from 15% to 60%, preferably from 20% to 50%, more preferably from 25% to 40%, more preferably about 35% by volume relative to the total volume of the gas stream.

These particularly suitable gas streams additionally and preferably contain one or more of the following gases:

- carbon monoxide (CO), generally from 20% to 50%, more generally from 30% to 45% by volume relative to the total volume of said gas stream, typically around 40%,

- hydrogen (H 2 ), generally from 15% to 25% by volume relative to the total volume of said gas stream, typically around 20%,

- nitrogen (N 2 ) and / or argon (Ar), generally from 5% to 15% by volume relative to the total volume of said gas stream, typically around 10%,

- methane (CH 4 ), generally from 0.5% to 50% by volume relative to the total volume of said gas stream, preferably from 1% to 20%, more preferably from 1% to 10%, typically about 1 % to 2%,

- water (H 2 0), generally from a few ppm (by volume, or ppmv) to 4%, typically around 3%,

- hydrogen sulphide (H 2 S), generally from 80 ppmv to 100 ppmv.

The zeolitic agglomerate useful for the process of the present invention typically comprises crystals of zeolite (s) agglomerated with a binder, which is preferably a clay binder. The amount of clay binder is generally between 1% and 30% by weight, preferably between 5% and 20% by weight, relative to the total weight of the zeolitic adsorbent.

According to a preferred aspect, the clay binder of the zeolitic agglomerate useful for the process of the invention preferably comprises at least one clay chosen from magnesian clays, and typically magnesian clay and a fibrous magnesian clay. By "fibrous magnesian clays" is meant fibrous clays containing magnesium and preferably hormites, the main representatives of which are sepiolite and attapulgite (or palygorskite). Sepiolite and attapulgite are the preferred hormites in the context of the present invention.

A zeolitic adsorbent material is also preferred, the binder of which comprises only one or more clays of the hormite family. According to another embodiment, the binder comprises a mixture of clay (s) consisting of at least one fibrous magnesian clay, for example a hormite, and at least one other clay, for example chosen from montmorillonites, for example bentonite. According to another preferred embodiment, binders comprising at least 50% by weight of at least one hormite relative to the total weight of the binder are preferred. The preferred clay mixtures are sepiolite / bentonite and attapulgite / bentonite mixtures, more preferably attapulgite / bentonite,

Said at least one zeolite of the zeolitic agglomerate defined above is a zeolite in the form of crystals and preferably crystals of Faujasite type zeolite, for example crystals of zeolite chosen from zeolites X, LSX, MSX, Y and their mixtures. Said zeolite crystals are preferably present in sodium form, and generally a sodium content, expressed as sodium oxide (Na 2 O) greater than 9.0% by weight of oxide relative to the total mass of the agglomerate. The zeolites described above all have an Si / Al atomic ratio of between 1 and 3, limits included.

The zeolite crystal content (s) is generally between 70% and 99% by weight, preferably between 80% and 95% by weight relative to the total weight of the adsorbent.

The zeolitic agglomerate defined above can also comprise one or more additives and / or fillers well known to those skilled in the art, such as for example a pore-forming agent, carboxymethylcellulose (CMC), an agent of reinforcement in general, fibers (such as glass fibers, carbon, Kevlar ® and the like), carbon nanotubes (CNT), colloidal silica, polymer, fabrics and the like. The additive (s) and / or filler (s) represent at most 10% by weight, preferably at most 5% by weight relative to the total weight of the zeolitic adsorbent material which can be used in the context of the present invention.

As indicated above, the zeolitic adsorbent useful for the decarbonation process of the present invention has a very particular porous profile, characterized by:

- a mesoporous volume of between 0.02 cm 3 .g _1 and 0.15 cm 3 .g _1 , (<50 nm) Hg, and

- a mesoporous volume fraction of between 0.1 and 0.5, preferably 0.15 and 0.45. The zeolitic agglomerate which can be used in the process of the present invention can be of any form known to those skilled in the art and for example in the form of yarns, beads, trilobes, for example and without limitation. It is however preferred to use an adsorbent in the form of beads, and most particularly beads with a particle size of between 0.5 mm and 5 mm, preferably between 1 mm and 3 mm, and more preferably between 1.6 mm and 2.5. mm. Preference is thus given to agglomerated and shaped zeolitic adsorbent materials produced according to any techniques known to those skilled in the art such as extrusion, compacting, agglomeration on a granulating plate, granulating drum, atomization and others.

This adsorbent zeolitic agglomerate can be obtained according to techniques well known to those skilled in the art, and in particular by agglomeration of zeolite crystals with one or more clay (s) and optionally additives and other agglomeration auxiliaries and formatting. The specific porous profile of the zeolitic agglomerate used in the process of the invention can also be obtained according to conventional techniques and well known to those skilled in the art, and for example by introducing one or more pore-forming agent (s). ) able (s) to create mesoporosity by burning during the calcination of the zeolitic agglomerate.

The zeolitic agglomerate described above can be used alone or in combination or in admixture with one or more other zeolitic agglomerate (s) and / or other adsorbents. One can for example use the zeolitic agglomerate described above in one or more bunk beds, alternating or sequenced. By way of illustrative but non-limiting example, it is possible to combine the zeolitic agglomerate defined above with one or more activated aluminas or other zeolitic agglomerates, upstream, for drying the gas stream.

Thus, the process of the present invention allows the elimination of large amounts of C0 2 , in particular large amounts of C0 2 present in a flow rich in CO, by means of an agglomerated zeolitic adsorbent as defined above. above. The characteristics of said zeolitic adsorbent confer in particular a strong affinity for C0 2 and rapid adsorption kinetics.

According to a preferred embodiment, the method of the invention uses conventional and well-known adsorption techniques, and in particular techniques by adsorption modulated in volume, pressure, temperature, volume and pressure. or in pressure and temperature. These techniques are better known by their acronyms in English VSA, PSA, TSA, VPSA and PTSA, respectively. It is particularly preferred to use the process according to the VSA, VPSA, PSA or PTSA technique, and better still according to the V SA, PSA or VPSA technique, in particular for the decarbonation of gases rich in C0 2 and CO, such as gases from steelworks.

The method of the present invention can be implemented under the temperature and pressure conditions well known to those skilled in the art.

Typically, the process of the invention can be carried out at a temperature between 0 ° C and 100 ° C, preferably between OC and 80 ° C, more preferably between 10 ° C and 60 ° C, typically between 20 ° C and 50 ° C, panœmple at room temperature.

The pressure applied throughout the process of the present invention can also vary widely. However, it is preferred to operate with a pressure generally between 200 kPa and 400 kPa, more preferably at a pressure equal to approximately 300 kPa.

The process of the invention can be carried out in any type of process reactor known to those skilled in the art, capable of withstanding the operating conditions defined above, in particular in terms of temperature and pressure, to achieve Adsorption / regeneration cycles, typically of the VSA, PSA, TSA, VPSA and PTSA type, and for example and without limitation, reactor, column with or without filling, tubular reactor, and others. The process of the invention can be carried out in one or more of the reactors defined above, placed in series or in parallel, in any suitable configuration, vertical and / or horizontal. For example, one or more column reactors can be provided in parallel for the adsorption phases and one or more column reactors in parallel for the regeneration phases.

It is also possible and often advantageous to provide a step of drying the gas stream to be decarbonized, for example on an alumina bed, before engaging said gas stream in the decarbonation process according to the present invention.

The invention also relates to the use, for the decarbonation of a gas stream, of a zeolitic agglomerate as defined above, that is to say comprising at least one binder and at least one zeolite, and exhibiting a mesoporous volume between 0.02 cm 3 .g _1 and 0.15 cm 3 .g _1 and a mesoporous volume fraction between 0.1 and 0.5, preferably between 0.15 and 0.45, such as previously defined.

Thus, the zeolitic agglomerate comprises a binder, which is preferably a clay binder in an amount generally between 1% and 30% by weight, preferably between 5% and 20% by weight, relative to the total weight of the zeolitic adsorbent.

As indicated above, this clay binder preferably comprises at least one clay chosen from magnesian clays, and typically magnesian clay and a fibrous magnesian clay, chosen from sepiolite and attapulgite (or palygorskite), optionally from mixture with at least one other clay, for example chosen from montmorillonites, in particular bentonite. When the binder is a mixture of clay, it is preferred that the binder comprises at least 50% by weight of at least one hormite relative to the total weight of the binder. The preferred clay mixtures are sepiolite / bentonite and attapulgite / bentonite mixtures, more preferably attapulgite / bentonite,

The zeolite crystals (s) of the zeolitic agglomerate are preferably zeolite crystals of the Faujasite type, for example zeolite crystals chosen from zeolites X, LSX, MSX, Y and their mixtures. Said zeolite crystals are preferably present in sodium form, and generally a sodium content, expressed as sodium oxide (Na 2 O) greater than 9.0% by weight of oxide relative to the total mass of the agglomerate. The zeolites described above all have an Si / Al atomic ratio of between 1 and 3, limits included.

The zeolite crystal content is generally between 70% and 99% by weight, preferably between 80% and 95% by weight relative to the total weight of the adsorbent.

The zeolitic agglomerate defined above can also comprise one or more additives and / or fillers well known to those skilled in the art, such as for example a pore-forming agent, carboxymethylcellulose (CMC), an agent of reinforcement in general, fibers (such as glass fibers, carbon, Kevlar ® and the like), carbon nanotubes (CNT), colloidal silica, polymer, fabrics and the like. The additive (s) and / or filler (s) represent at most 10% by weight, preferably at most 5% by weight relative to the total weight of the zeolitic adsorbent material which can be used in the context of the present invention.

The zeolitic agglomerate which can be used in the process of the present invention can be of any form known to those skilled in the art, as indicated above.

The zeolitic agglomerate described above can be used alone or in combination or as a mixture with one or more other zeolitic agglomerate (s) and / or other adsorbents. One can for example use the zeolitic agglomerate described above in one or more bunk beds, alternating or sequenced. By way of illustrative but non-limiting example, it is possible to combine the zeolitic agglomerate defined above with one or more activated aluminas or other zeolitic agglomerates, upstream, for drying the gas stream.

The use of the zeolitic agglomerate defined above for the decarbonation of a gas stream, and most particularly of a gas stream containing from 15% to 60%

(volume) of carbon dioxide (C0 2 ), preferably from 20% to 50%, more preferably from 25% to 40% relative to the total volume of gas flow to be treated, has many advantages.

It has thus been observed that the zeolitic adsorbent of the invention has a very high capacity as well as a very high selectivity, and this, in particular because of the specific porous profile described above.

[0070] Furthermore, the zeolitic adsorbent, in the use claimed in the present invention, has a very advantageous lifetime, and in particular longer than most that observed with the other known decarbonation systems of the prior art.

Thanks to these excellent properties both in terms of mechanical strength and in terms of selectivity and adsorption capacity, the zeolitic agglomerate used in the process of the invention allows the creation of decarbonation units a lot. compact, in terms of size, and much more energy efficient.

The use according to the present invention moreover makes it possible to observe relatively short adsorption times, compared to those known from the prior art, and for example adsorption times of the order of 5 sec. to 10 min, preferably 5 sec to 4 min and typically 10 to 60 seconds.

Another very interesting advantage is the fact that it is possible, thanks to the zeolitic agglomerate of the present invention, to carry out the regeneration steps under less reduced vacuum conditions than those required with the other decarbonation systems described. in the prior art.

The CO 2 concentrations of the gas stream at the end of the process can thus easily be around 5%, or even 3%, by volume, and even only a few ppmv.

Without wishing to be bound by theory, it has been observed that the use of the zeolitic agglomerate described above allows rapid diffusion of C0 2 , thus making the mass transfer fronts extremely narrow.

The zeolitic agglomerate which can be used in the process of the present invention also proves to be a very versatile product and which can therefore be used for a very wide variety of applications, in particular in the field of liquid or gaseous hydrocarbons. , such as for example operations in drying, decarbonation, desulfurization, or in the fields of industrial gases, for example air decarbonation operations, nitrogen / oxygen separation, and others.)

METHODS OF ANALYSIS

Chemical analysis of zeolitic agglomerates

The elemental chemical analysis of the zeolitic agglomerate which can be used in the process of the invention can be carried out according to various analytical techniques known to those skilled in the art. Among these techniques, mention may be made of the technique of chemical analysis by X-ray fluorescence as described in standard NF EN ISO 12677: 201 1 on a wavelength dispersive spectrometer (WDXRF), for example the Tiger S8 spectrometer. from the Bruker company.

X fluorescence is a non-destructive spectral technique using the photoluminescence of atoms in the X-ray field, to establish the elemental composition of a sample. The excitation of atoms, which is most often and generally carried out by an X-ray beam or by bombardment with electrons, generates specific radiations after returning to the ground state of the atom. In a conventional manner, after calibration, a measurement uncertainty of less than 0.4% by weight is obtained for each oxide.

The X-ray fluorescence spectrum has the advantage of depending very little on the chemical combination of the element, which offers a precise determination, both quantitative and qualitative. In a conventional manner, after calibration, for each oxide Si0 2 and Al 2 O 3 , as well as Na 2 0, a measurement uncertainty of less than 0.4% by weight is obtained .

Other analysis methods are for example illustrated by the methods by atomic absorption spectrometry (AAS) and atomic emission spectrometry with induced plasma by high frequency (ICP-AES) described in the NF EN ISO standards. 21587-3 or NF EN ISO 21079-3 on a device such as Perkin Elmer 4300DV.

The elementary chemical analyzes described above make it possible both to verify the Si / Al atomic ratio of the zeolite used within the zeolitic agglomerate and the Si / Al atomic ratio of said agglomerate. In the description of the present invention, the measurement uncertainty of the Si / Al atomic ratio is ± 5%. The measurement of the Si / Al atomic ratio of the zeolite present in the zeolitic agglomerate can also be measured by solid Nuclear Magnetic Resonance (NMR) spectroscopy of silicon.

Qualitative and quantitative analysis by X-ray diffraction

The zeolite content in the zeolitic adsorbent material is evaluated by X-ray diffraction analysis (XRD), according to methods known to those skilled in the art.

job. This identification can be carried out using a DRX device of the Bruker brand.

This analysis makes it possible to identify the different zeolites present in the zeolitic adsorbent material because each of the zeolites has a unique diffractogram defined by the positioning of the diffraction peaks and by their relative intensities.

The zeolitic adsorbent materials are ground and then spread and smoothed on a sample holder by simple mechanical compression.

The conditions for acquiring the diffractogram produced on the D5000 Bruker device are as follows:

• Cu tube used at 40 kV - 30 mA;

• size of the slits (divergent, diffusion and analysis) = 0.6 mm;

• filter: Ni;

• rotating sample device: 15 rpm -1 ;

• measuring range: 3 ° <2Q <50 °;

• step: 0.02 °;

• counting time per step: 2 seconds.

The interpretation of the diffractogram obtained is carried out with the EVA software with identification of the zeolites using the ICDD PDF-2 database, release 201 1.

The amount of zeolite fractions, by weight, is measured by XRD analysis on the D5000 device of the Bruker brand, then the amount by weight of the zeolitic fractions is evaluated using the TOPAS software from the Bruker company.

The invention will be better understood in the light of the following examples, which are given for illustrative purposes only and in no way limit the scope of the invention.

EXAMPLES

The examples below show adsorption tests for C0 2 included in a gas stream rich in CO, according to a VPSA type process, using different adsorbents.

The adsorbents tested are listed below:

- Sample A: A2AW ® silica gel from KD Corporation in the form of 2-5 mm granulometry beads.

- Sample B: zeolitic agglomerate whose mesoporous volume is equal to 0.065 cm 3 .g _1 , and the mesoporous volume fraction is equal to 0.31 comprising approximately 20% of attapulgite binder and approximately 80% of FAU type zeolite with ratio Si / Al of 1, 19, the zeolitic agglomerate is in the form of beads with a particle size of 1.6-2.5 mm.

- Sample C: zeolitic agglomerate similar to sample B, but in which the agglomeration binder is sepiolite.

The load in an adsorption column of a pilot plant is identical with each sample and is equal to 379 g. the adsorption pilot column has a diameter of 2.2 cm and a height of 2 m. The height of the load in the column varies for each sample depending on the density of each sample:

- height for sample A: 1.45 m;

- height for sample B: 1.59 m;

- height for sample C: 1.49 m.

The gas mixture which feeds the adsorption column has a volume composition of 35% CO, 35% C0 2 , 10% N 2 and 20% H 2 . The feed rate is fixed at 8 NL.min _1 and 16 NL.min -1 at a temperature of 40 ° C and a pressure of 300kPa.

At the end of the adsorption step, the regeneration is carried out for 100 seconds by reducing the pressure to a vacuum level of 20 - 30 kPa, comprising a purge step of 50 seconds under vacuum at using a gas with a volume composition of about 62% CO, 2.7% C0 2 and the remainder to 100% N2.

Example 1:

The total C0 2 adsorption capacities of sample A and sample B are compared in order to study the difference between a silica gel and a zeolitic agglomerate. The gas mixture which feeds the column is as described above. The feed rate is fixed at 8 NL.min _1 at a temperature of 40 ° C and a pressure of 300 kPa. As previously indicated, the same amount of adsorbent of 379 g is used for each sample.

The adsorption phase is stopped when the samples are completely saturated with C0 2 , that is to say that the concentrations of the constituents of the incoming gas stream are identical to those of the outgoing gas stream. The adsorption time required for each sample in order to obtain its full saturation is as follows:

- Sample A: 450 seconds;

- Sample B: 1055 seconds.

The piercing time to achieve a volume concentration of 0.1% of C0 2 , for each sample, is:

- Sample A: 63 seconds;

- Sample B: 747 seconds.

These results clearly show that, for an equal amount, sample B (zeolitic agglomerate according to the invention) has a total adsorption capacity of C0 2 , more than 2 times higher than that observed with sample A (silica gel, comparative sample). If adsorption is stopped at the start of piercing, the performance of sample B is approximately 12 times better than that of sample A.

This example clearly shows that the use of sample B (zeolitic agglomerate according to the invention) leads to a much longer duration of use than when silica gel is used, if the same amount of The adsorbent is used or the adsorption unit can be made more compact by using a zeolitic agglomerate rather than a silica gel, which makes it possible to reduce both the investment and operating costs.

Example 2:

Using the same operating conditions as in Example 1, this example compares the dynamic adsorption capacities of C0 2 of samples A and C in order to study the differences between a silica gel and a molecular sieve. The feed rate is fixed at 16 NL.min _1 , at a temperature of 40 ° C and a pressure of 300 kPa. The amount of each sample used is 379 g.

The adsorption phase is stopped when the volume concentration of C0 2 in the outgoing gas stream reaches 2.6% (concentration at the piercing).

At the end of the adsorption step, the regeneration is carried out for 100 seconds by reducing the pressure to a vacuum level of 20 kPa, comprising a purge step of 50 seconds under vacuum at the using a gas with a volume composition of about 62% CO, 2.7% C0 2 and the remainder to 100% N 2 . Fifteen (15) adsorption / desorption cycles are performed to achieve a stable piercing time for each sample.

The drilling time to achieve a volume concentration of 2.6% of C0 2 , for each sample, is:

- Sample A: 15 seconds;

- Sample C: 38 seconds.

These results clearly show that, for an equal amount, sample C (zeolitic agglomerate according to the invention) exhibits a performance of 2.5 times more compared to sample A (silica gel, comparative sample) and therefore that by using a zeolitic agglomerate the duration of use will be longer than with a silica gel, if the same amount of adsorbent is used, because of the possibility of reducing the number of regeneration cycles.

Example 3:

Under the same operating conditions as in Example 1, this example compares the dynamic adsorption capacities of C0 2 of samples A and C in order to study the differences between a silica gel and a molecular sieve. The feed rate is fixed at 16 NL.min _1 , the temperature at 40 ° C and the pressure at 300 kPa. The amount of each sample used is 379 g. The regeneration of each of samples A and C is compared in order to study the differences between a silica gel and a zeolitic agglomerate. The gas mixture entering the adsorption column at a volume composition of 35% CO, 35% C0 2 , 10% N 2 and 20% H 2 . The feed rate is fixed at 8 NL.min_1 , the temperature at 40 ° C and the pressure at 300 kPa. The amount of adsorbent is identical for each sample and is 379 g.

The adsorption phase is stopped when the volume concentration of C0 2 reaches 2.6% (piercing concentration). At the end of this adsorption step, the regeneration is carried out for 100 seconds by reducing the pressure to a certain specific vacuum level, comprising a stage of purging of 50 seconds under vacuum using a gas. with a volume composition of about 62% CO, 2.7% C0 2 and the balance 100% N 2 . The specific vacuum level mentioned above varies depending on the sample to achieve the same 36 second pierce time (stable after a multitude of cycles) to achieve an output volume concentration of 2.6% in C0 2for each sample. Fifteen (15) adsorption / desorption cycles are performed to achieve a stable piercing time for each sample.

[0106] The vacuum level required for each sample is:

- Sample A: 20 kPa;

- Sample C: 40 kPa.

These results clearly show that, for an equal amount of adsorbent and identical adsorption performance, sample C (zeolitic agglomerate according to the invention) requires a quantity of vacuum 2 times less than that required for the sample. A (silica gel, comparative sample) and therefore by using a zeolitic agglomerate (sample C), it is possible to reduce operational costs during regeneration.

CLAIMS

1. A process for decarbonating a gas stream, said process comprising at least the steps of:

a) supply of a gas stream containing 15% to 60% carbon dioxide, expressed as a volume relative to the total volume of the gas stream,

b) passing said gas stream over a zeolitic agglomerate, and

c) recovery of a gas flow depleted in C0 2 ,

process in which the zeolitic agglomerate comprises at least one binder and at least one zeolite, and has a mesoporous volume of between 0.02 cm 3 .g _1 and 0.15 cm 3 .g _1 and a mesoporous volume fraction of between 0 , 1 and 0.5, preferably between 0.15 and 0.45.

2. Method according to claim 1, wherein the gas stream to be decarbonated contains from 15% to 60% of carbon dioxide, preferably from 20% to 50%, more preferably from 25% to 40%, by volume relative to to the total volume of said gas stream.

3. Method according to claim 1 or claim 2, wherein the gas stream to be decarbonated contains a C0 2 content ranging from 15% to 60%, preferably from 20% to 50%, more preferably from 25% to 40 %, more preferably about 35% by volume relative to the total volume of the gas stream, and additionally contains one or more of the following gases:

- carbon monoxide (CO), generally from 20% to 50%, more generally from 30% to 45% by volume relative to the total volume of said gas stream, typically around 40%,

- hydrogen (H 2 ), generally from 15% to 25% by volume relative to the total volume of said gas stream, typically around 20%,

- nitrogen (N 2 ) and / or argon (Ar), generally from 5% to 15% by volume relative to the total volume of said gas stream, typically around 10%,

- methane (CH 4 ), generally from 0.5% to 50% by volume relative to the total volume of said gas stream, preferably from 1% to 20%, more preferably from 1% to 10%, typically about 1 % to 2%,

- water (H 2 0), generally from a few ppm (by volume, or ppmv) to 4%, typically around 3%,

- hydrogen sulphide (H 2 S), generally from 80 ppmv to 100 ppmv.

4. Method according to any one of the preceding claims, wherein the zeolite agglomerate comprises crystals of zeolite (s) agglomerated with between 1% and 30% by weight, preferably between 5% and 20% by weight, relative to to the total weight of the zeolitic adsorbent of a clay binder.

5. Method according to any one of the preceding claims, in which the clay binder of the zeolitic agglomerate comprises at least one clay chosen from among fibrous magnesian clays.

6. Process according to any one of the preceding claims, in which said at least one zeolite of the zeolitic agglomerate is a zeolite in the form of crystals of Faujasite type zeolite, chosen from zeolites X, LSX, MSX, Y and theirs. mixtures.

7. Method according to any one of the preceding claims, wherein said at least one zeolite of the zeolitic agglomerate is a zeolite in the form of crystals present in sodium form, with a sodium content, expressed as sodium oxide (Na 2 0) greater than 9.0% by weight of oxide relative to the total mass of the agglomerate.

8. Method according to any one of the preceding claims, said method being carried out at a temperature between 0 ° C and 100 ° C, preferably between 0 ° C and 80 ° C, more preferably between 10 ° C and 60. ° C, typically between 20 ° C and 50 ° C, for example at room temperature.

9. Method according to any one of the preceding claims, said method being carried out at a pressure of between 200 kPa and 400 kPa, preferably at a pressure equal to approximately 300 kPa.

10. Use, for the decarbonation of a gas stream, of a zeolitic agglomerate defined in any one of claims 1 to 7