Installation for recovering CO2 contained in a feed gas stream

Abstract

The invention relates to an installation (1) for recovering CO2 contained in a feed gas stream (FG) containing at least 10 ppm NOX, 10% by volume to 50% by volume CO2, N2, water and O2, at a minimum concentration of 0.1 mol%, where NOX contains NO and NO2, the installation comprising: - a compression assembly (2) arranged to compress the feed gas stream, - a drying space (8), preferably placed downstream of the compression assembly, for drying the feed gas stream passed by the compression assembly to obtain a dry gas stream (FGS), - an adsorption treatment unit (4) comprising at least one adsorbent (9) selected to promote the oxidation of NO to NO2, the drying space (8) belonging to a dryer (3) placed upstream of the treatment unit (4), the treatment unit (4) being arranged to treat the dry gas stream coming from the dryer with the purpose of generating a gas stream enriched in CO2.

Description

[Technical field]

[0001] The present invention relates to an installation and process for recovering CO2 (carbon dioxide) contained in a feed gas stream. [Background technology]

[0002] NOX (nitrogen oxides) are present in the combustion gases in the form of NO (nitric oxide) and NO2 (nitrogen dioxide), with a typical ratio of 90% NO to 10% NO2. Most power plants are equipped with selective catalytic reduction (SCR) units in which NH3 (ammonia) reacts with NO and NO2 to produce N2 (molecular nitrogen) and water (H2O), thereby reducing NOX emissions to less than a few hundred ppm. These units must process large amounts of combustion gas.

[0003] Not all plants in the industry are equipped with SCR systems. For example, fluid catalytic cracking plants or cement plants emit around 200 ppm NOx. Steam methane reforming units (SMR) emit less than 100 ppm NOx. In relation to carbon capture, a solution obvious to the skilled person would be a CCUS (carbon dioxide capture, utilization and storage) post-treatment with a continuous reduction of NOx by SCR followed by the capture of CO2, for example with amines. This technology is, on the one hand, sensitive to NOx (deterioration of the solvent and generation of highly toxic by-products) and, on the other hand, prone to concentrating NOx, which is released into the atmosphere after the CO2 has been captured. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims in particular to propose the capture of CO2 in combustion gases with a simultaneous significant reduction of NOx. The invention is not limited to combustion gases but can be applied to any kind of feed gas stream, regardless of its origin, which contains CO2, NOx and at least one gas potentially less adsorptive than CO2, such as N2, O2, Ar, He, H2. [Means for solving the problem]

[0005] The subject of the present invention is therefore an installation for recovering CO2 contained in a feed gas stream comprising at least 10 ppm NOX, 10% by volume to 50% by volume CO2, N2, water and O2 at a minimum concentration of 0.1 mol%, preferably at a concentration of 1 mol% or more, in particular at a concentration of 2% to 5% or at a concentration of more than 10%, wherein NOX comprises NO and NO2, the installation comprising: a compression assembly arranged to compress a feed gas stream, in particular comprising a plurality of compression stages and a plurality of heat exchangers arranged to cool the gas stream compressed by the compression stages, arranged to compress the gas stream to a pressure of more than 1.5 bar abs, in particular to a pressure of between 3 and 15 bar abs or even to a pressure of between 4 and 12 bar abs (the abbreviation "bar abs" means "bar (absolute pressure)"), - a drying space, preferably located downstream of the compression assembly, for drying the feed gas stream that has passed through the compression assembly to obtain a dry gas stream; - an adsorption treatment unit comprising at least one adsorbent selected to promote the oxidation of NO to NO2, a. if the drying space is part of a dryer located upstream of the treatment unit, treating a dry gas stream coming from the dryer to produce a gas stream enriched in CO2, or - b. treating the pre-dried gas stream with a drying sorbent, where the drying space forms part of the treatment unit and includes a drying sorbent selected to adsorb HO and is disposed within the treatment unit upstream of an sorbent selected to promote the oxidation of NO to NO, to produce a gas stream enriched in CO. an adsorption treatment unit arranged to perform the above-mentioned

[0006] In addition to the compounds mentioned above, the feed gas stream may contain other trace components such as argon and various impurities depending on the upstream unit from which the gas stream originates. Additionally, a portion of the NOX may be present in the form of N2O4 (dinitrogen tetroxide, considered for the purposes of evaluation as equivalent to 2NO2).

[0007] According to one aspect of the invention, the feed gas stream is filtered before being introduced into the compression assembly to remove any particles or dust that may be present, since the feed gas stream before filtration may contain excessive amounts of particles or dust, if necessary, until the filtered gas stream reaches a threshold value selected to be compatible with downstream units.

[0008] The term "compatible with downstream units" is understood to mean that the residual particles do not cause clogging, deposition or maldistribution that may be detrimental to the proper functioning of the unit. In some cases, the selected threshold value may correspond to a concentration of particles with a size of less than 40 microns, optionally less than 5 microns, and / or of solid particles less than 1 mg / m3, optionally less than 0.01 mg / m3.

[0009] If the drying space is part of a dryer upstream of the treatment unit, the dryer may include a temperature swing adsorption (TSA) device.

[0010] Here, TSA refers to all units that separate gas by adsorption after an adsorption / regeneration cycle, in which a regeneration gas is used at least temporarily at a temperature higher than the adsorption temperature (heating step). The atmospheric pressure of the regeneration gas is optional and is greater than, equal to or preferably less than the adsorption pressure.

[0011] This dryer would be an additional device, e.g. a TSA with two dry adsorber and only four valves per adsorber. This embodiment of the invention has the advantage that there are no corrosion problems with PSA and the gas coming out of PSA is dry.

[0012] It should be noted that a dryer may be installed on the gas exiting the compression stage after refrigeration if this is economically advantageous.

[0013] According to one aspect of the invention, the dryer includes a TEG (triethylene glycol) unit for drying the gas stream.

[0014] If the drying space forms part of the treatment unit and contains a drying adsorbent, no additional equipment is added to the PSA, but since nitric acid may be present, measures must be taken against corrosion, for example the use of corrosion-resistant materials such as stainless steel is advisable.

[0015] According to one embodiment of the invention, the dry gas stream comprises less than 500 ppm H2O, in particular less than 10 ppm, such as less than 1 ppm.

[0016] The NOX essentially comprises, inter alia, 90% by volume NO and 10% by volume NO2 prior to passing through the compression assembly. These ratios may vary depending, inter alia, on the source of the feed gas stream and the treatment it has undergone.

[0017] In the present invention, the presence of a dryer before the treatment unit is particularly advantageous in order to avoid the formation of nitric acid in or downstream of this treatment unit, which can avoid damage to equipment such as PSA valves.

[0018] The invention makes it possible to limit both the amount of NO in the CO2-enriched gas stream coming from an adsorption treatment unit (for example PSA) and the amount of NO present in the nitrogen-enriched gas stream at the PSA outlet. To this end, the invention makes use of the catalytic effect of certain adsorbents, which in the presence of oxygen promote the reaction of NO to NO2. The invention makes it possible to establish favorable conditions for these adsorbents to be fully active for a satisfactory period of time. To this end, the invention makes it possible to ensure, by means of a dry space, the absence of H2O, since H2O can be at least partially adsorbed and reduces the activity of the adsorbent. Furthermore, the presence of NO2 in the presence of H2O leads to the formation of nitric acid, which, depending on the type of adsorbent, on the one hand is adsorbed and significantly reduces the desired catalytic activity, and on the other hand promotes the destruction of certain other adsorbents. The absence of nitric acid allows the use of conventional materials and avoids damage to sensitive equipment such as valves.

[0019] Thus, the present invention allows for significant reductions in NO while allowing for the capture of CO2 emanating from the feed gas stream.

[0020] The pressure provided by the compression assembly facilitates the conversion of NO to NO2.

[0021] According to one aspect of the invention, the adsorbent is selected from silica gel, zeolite, activated carbon, alumina or a combination of these elements.

[0022] According to one aspect of the invention, the adsorbent selected to promote the oxidation of NO to NO2 comprises a mixture of at least two different silica gels, and / or at least two different zeolites, and / or at least two different activated carbons.

[0023] Two adsorbents may differ non-exhaustively by their porosity, the nature of the active sites (especially zeolites), the binder (nature or amount), the impurities present (binders, activated carbon, etc.), post-treatments (ion exchange, impregnation, washing operations, etc.). Due to these differences, two adsorbents of the same type may have very different adsorptive or catalytic properties, especially if two parameters such as composition and porosity are different.

[0024] The sorbent is selected so that it is not substantially decomposed by chemical reaction with NOX, and therefore has a useful life of more than one year, preferably more than two or even three years, during which operation is possible.

[0025] The adsorbent of the treatment unit preferentially adsorbs CO2 and N2 is not preferentially adsorbed by the adsorbent, so that most of the nitrogen is extracted at high pressure in a cycle of CO2-depleted gas streams, and during regeneration of the adsorbent mass, one or more gas streams enriched in CO2 are obtained.

[0026] According to one aspect of the invention, NO2 is also preferentially adsorbed and NO is not, so that most of the NO2 exiting the unit is in a gas stream enriched in CO2 and most of the NO exiting the unit is in a gas stream enriched in N2.

[0027] According to one embodiment of the invention, the adsorbent of the treatment unit selected is silica gel, alumina or a combination of these two elements.

[0028] According to one aspect of the invention, the treatment unit comprises, in addition to the adsorbent promoting the oxidation of NO to NO2 described above, at least one additional adsorbent, which does not have the function of promoting the oxidation of NO to NO2 but is capable of adsorbing, for example, CO2 and / or NO2.

[0029] According to one aspect of the invention, at least one condensate separator may be provided, in particular after cooling at the outlet of a compression stage.

[0030] According to one aspect of the invention, the treatment unit includes a pressure swing adsorption (PSA) device.

[0031] The regeneration gas of a TSA dryer is a gas, usually enriched in N2, preferentially extracted from the feed gas stream, i.e. either a portion of the CO2-depleted gas stream directly from the PSA or a purge gas from a unit located downstream of the PSA, for example a cryogenic unit that processes the CO2-enriched gas stream, still containing a certain amount of N2, for further CO2 enrichment. The remaining N2 fraction is usually extracted at the top of the denitrification column and can be returned to the CO2 capture plant, which is the subject of the present invention.

[0032] According to one embodiment of the invention, the treatment unit comprises a VPSA adsorption device in which the adsorption takes place at a high pressure above atmospheric pressure, in particular between 1.5 and 6 bar abs, and the desorption takes place at a low pressure below atmospheric pressure, in particular below 600 mbar abs, in particular between 200 and 600 mbar abs and, where appropriate, for example in the case of a vacuum pump comprising several pump stages, can essentially reach 50 mbar abs.

[0033] According to one aspect of the invention, when the drying space is part of a dryer, the gas stream entering the dryer is cooled with suitable refrigerated water, such as cold water or ice water, preferably to between 3°C and 20°C, to facilitate adsorption.

[0034] According to one aspect of the invention, particularly when the drying space is within the treatment unit, the gas stream entering the treatment unit is cooled, preferably to between 3°C and 20°C, with suitable refrigerated water, such as cold water or ice water.

[0035] Furthermore, the subject of the invention is also a process for recovering CO2 contained in a feed gas stream containing at least 10 ppm NOX, 10% by volume to 50% by volume CO2, N2, water and O2, at a minimum concentration of 0.1 mol%, preferably at a concentration of 1 mol% or more, in particular at a concentration of 2% to 5% or at a concentration of more than 10%, wherein NOX comprises NO and NO2, the process comprising the following steps: - compressing the feed gas stream with a compression assembly; - thereafter drying the compressed feed gas stream through a drying space to obtain a dry gas stream comprising in particular less than 500 ppm H2O, in particular less than 10 ppm H2O, for example less than 1 ppm H2O, - using an adsorption treatment unit comprising at least one adsorbent selected to promote the oxidation of NO to NO2; - a. if the drying space is part of a dryer located upstream of the treatment unit, treating a dry gas stream coming from the dryer to produce a gas stream enriched in CO2, or - b. if the drying space forms part of the treatment unit and comprises a drying adsorbent selected for adsorbing HO and is located within the treatment unit upstream of an adsorbent selected for promoting the oxidation of NO to NO, treating the pre-dried gas stream with the drying adsorbent to produce a gas stream enriched in CO.

[0036] According to the invention, an overall conversion of NO to NO2 via oxidation of NO of more than 20%, in particular 30% or 50% or even more than 75% can be obtained.

[0037] The term "total conversion" is understood to mean that an evaluation is made between the amount of incoming NO measured in the feed gas at the inlet of the compression assembly (possibly adding the amount of NO contained in the recycle coming from units other than the CO2 capture unit of the installation of the invention) and the amount discharged from the adsorption treatment unit.

[0038] Please note that the exit evaluation must be performed over at least a full cycle of the PSA.

[0039] According to one aspect of the invention, CO2 is present in the feed gas stream in a proportion of more than 10% by volume, in particular more than 15% or more than 20% by volume, calculated on a moisture-free basis.

[0040] The moisture-free composition is defined as the composition when moisture is removed from the gas. For example, if there is 15 mole % water in a gas stream, all other compositions where water is present must be divided by 0.85 to ultimately add up to 100% without considering HO.

[0041] According to one embodiment of the invention, NOX is contained in the feed gas stream at a rate of less than 1000 ppmv, in particular less than 500 ppmv or less than 100 ppmv.

[0042] According to one embodiment of the invention, the NO2 / (NO+NO2) ratio (in molar ppm) in the feed gas stream to be treated is less than 50%, in particular less than 20% or 10%, or even less than 5% or 1%.

[0043] The CO2-enriched gas stream obtained from the adsorption processing unit (e.g., PSA or VPSA) can be processed in a downstream unit to further enrich the CO2, and the CO2-depleted gas from this downstream unit can be recycled upstream of the adsorption processing unit (e.g., PSA or VPSA) or directly to the adsorption processing unit (e.g., PSA or VPSA) to increase the CO2 extraction yield.

[0044] The CO2 composition of the CO2-rich stream from the adsorption processing unit (e.g., PSA or VPSA) can be between 45% and 90% CO2 depending on the application.

[0045] According to one aspect of the invention, the combustion gas stream is exhaust gas produced by the combustion of hydrocarbons.

[0046] These exhaust gases originate, for example, from cement kilns or SMR (Steam Methane Reforming) furnaces.

[0047] According to one embodiment of the invention, a portion of the CO2 contained in the combustion gas may originate from the starting material introduced into the furnace and converted, for example, the CO2 may originate from CaCO3.

[0048] The invention will be better understood on reading the following detailed description and on referring to the accompanying figures, which are given for illustrative purposes only and do not in any way limit the invention. [Brief description of the drawings]

[0049] [Figure 1] FIG. 1 is a block diagram showing an example of equipment according to the present invention. [Diagram 2] FIG. 2 is a schematic curve showing the test results for measuring the conversion rate of NO to NO2. [Diagram 3] FIG. 3 is a block diagram showing equipment according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] FIG. 1 shows an installation for recovering CO2 contained at a minimum concentration of 0.1 mol %, preferably at a concentration of 1 mol % or more, in a feed gas stream containing at least 10 ppm NOX, 10% to 50% by volume CO2, N2, water and O2, where NOX includes NO and NO2, and the installation comprises: a compression assembly 2 arranged to compress a feed gas stream FG, the compression assembly comprising in particular a plurality of compression stages, a plurality of heat exchangers arranged to cool the gas stream compressed by the compression stages and, optionally, a plurality of items of equipment for removing condensate, the compression assembly being arranged to compress the gas stream to a pressure of more than 1.5 bar abs, in particular to a pressure between 3 and 15 bar abs or even to a pressure between 4 and 12 bar abs, a dryer 3 located downstream of the compression assembly 2 for drying the feed gas stream that has passed through the compression assembly to obtain a dry gas stream FGS, said dryer 3 forming a drying space 8 within the meaning of the present invention, - an adsorption treatment unit 4 arranged to treat the dry gas stream FGS to produce a gas stream F1 enriched in CO2, the adsorption treatment unit 4 being placed downstream of the dryer 3 and comprising at least one adsorbent 9 selected to promote the oxidation of NO to NO2.

[0051] The feed gas stream FG is formed, for example, by exhaust gas coming from a cement kiln or an SMR (Steam Methane Reforming) furnace.

[0052] In addition to the compounds listed above, the feed gas stream may contain other trace components such as argon and various impurities depending on the upstream unit from which the gas stream originates. Additionally, some of the NOX may be present in the form of N2O4 (dinitrogen tetroxide).

[0053] The dry gas stream FGS contains less than 500 ppm H2O, in particular less than 10 ppm, for example less than 1 ppm.

[0054] The NOX essentially comprises, inter alia, 90% by volume NO and 10% by volume NO2 prior to passing through the compression assembly.

[0055] In the present invention, the presence of a dryer prior to the treatment unit is particularly advantageous in order to avoid the formation of nitric acid in or downstream of this treatment unit.

[0056] Thus, the present invention allows for significant reduction of NO while enabling capture of CO2 from the feed gas stream.

[0057] The adsorbent 9 is selected from silica gel, zeolite, activated carbon, alumina or a combination thereof.

[0058] For example, the adsorbent 9 selected to promote the oxidation of NO to NO2 may include a mixture of at least two different silica gels, and / or at least two different zeolites, and / or at least two different activated carbons.

[0059] The sorbent 9 is selected such that it is not substantially decomposed by chemical reaction with NOX, and therefore has a useful life of more than one year, preferably more than two or even three years of operable time.

[0060] The adsorbent 9 of the treatment unit 4 preferentially adsorbs CO2 and N2 is not preferentially adsorbed by this adsorbent, so that most of the nitrogen is extracted at high pressure in the cycle of a gas stream F2 depleted in CO2, and during regeneration of the adsorbent mass one or more gas streams F1 enriched in CO2 are obtained.

[0061] NO2 is also preferentially adsorbed and NO is not so preferentially adsorbed, so that most of the NO2 exiting the treatment unit 4 is in the CO2 enriched gas stream and most of the NO exiting the unit is in the N2 enriched gas stream.

[0062] For example, processing unit 4 may include a pressure swing adsorption (PSA) device.

[0063] As a variant, the treatment unit 4 comprises a VPSA adsorption device in which the adsorption takes place at a high pressure above atmospheric pressure, in particular at 1.5 to 6 bar abs, and the desorption takes place at a low pressure below atmospheric pressure, in particular at 200 to 600 mbar abs or even possibly down to 50 mbar abs.

[0064] Dryer 3 includes a temperature swing adsorption (TSA) device.

[0065] The gas stream entering the dryer 3 is cooled, preferably to 3-20° C., with suitable cooling water, such as cold water or ice water, to facilitate adsorption.

[0066] The gas stream entering the treatment unit 4 has been cooled, preferably to 3-20° C., with suitable cooling water, such as cold water or ice water.

[0067] This installation 1 makes it possible to carry out the following steps: - compressing the feed gas stream using a compression assembly 2; - thereafter drying the compressed feed gas stream using a dryer 3 to obtain a dry gas stream, in particular the dryer being arranged such that it produces a dry gas stream comprising less than 500 ppm, in particular less than 10 ppm, for example less than 1 ppm HO, - treating the dry gas stream using an adsorption treatment unit 4 to produce a gas stream enriched in CO2, the treatment unit being located downstream of the dryer and comprising at least one adsorbent 9 selected to promote the oxidation of NO to NO2.

[0068] According to the invention, an overall conversion of NO to NO2 via oxidation of NO of more than 20%, in particular 30% or 50% or even more than 75% can be obtained.

[0069] The term "total conversion" is intended to be understood to mean that an evaluation is made between the amount of incoming NO measured at the inlet of the compression assembly and the amount exhausted from the adsorption treatment unit.

[0070] CO2 is present in the feed gas stream at a level of more than 10% by volume, especially more than 15% or more than 20% by volume, calculated on a moisture-free basis.

[0071] NOX is contained in the feed gas stream FG at less than 1000 ppmv, in particular less than 500 ppmv or less than 100 ppmv.

[0072] The NO2 / (NO+NO2) ratio (mol ppm) in the feed gas stream FG to be treated is less than 50%, in particular less than 20% or 10% or even less than 5% or 1%.

[0073] The CO2-enriched gas stream F1 obtained from the adsorption unit 4 (e.g., PSA or VPSA) can be treated in a downstream unit to further enrich the CO2, and the CO2-depleted gas from this downstream unit can be recycled upstream of the adsorption unit 4 (e.g., PSA or VPSA) or directly to the adsorption unit (e.g., PSA or VPSA) to increase the CO2 extraction yield.

[0074] The CO2 composition of the CO2-rich stream from the adsorption processing unit (e.g., from a PSA or VPSA) can be between 45% and 90% depending on the application.

[0075] That the adsorbent is capable of promoting the oxidation of NO to NO2 can be confirmed, for example, by a test including the following steps. - regenerating the particles by flushing with dry nitrogen (containing up to 1 ppm water) at 250°C (or the maximum recommended temperature if necessary); - passing a dry nitrogen stream containing up to 1 ppm water, 50 ppm NO and 2 mol % O2 through a tube packed with glass beads at a temperature and pressure representative of the process according to the invention (e.g. 20°C and 8 bar abs for a PSA operating at high pressure cycle of 8 bar abs and at ambient temperature), the N2 flow rate and the dimensions of the adsorber being selected so that the contact time of the gas with the glass beads (contact time is defined below) is about 5 seconds, - continuing the flushing until a stable NO content is obtained at the outlet; - calculating the conversion of NO to NO2; - filling the same tube with the same amount of sorbent as the sorbent to be tested and carrying out these steps; - measuring the NO content at the outlet when the NO content has stabilized; - calculating the conversion rate; - if the conversion rate in the tube packed with the adsorbent is greater than the conversion rate in the tube packed with glass beads, concluding that the adsorbent is capable of promoting the oxidation of NO to NO2, and preferentially retaining adsorbents having conversion rates at least 10 percentage points greater than the conversion rate obtained with the glass beads.

[0076] Here, "contact time" means the time it takes for the gas to pass through the useful area of ​​the tube (the area filled with particles) when the tube is free of any material. This accurately sets the gas flow rate to be used during the test. Under these conditions, a contact time of 5 seconds corresponds to an actual residence time of about 3 seconds of the gas during the test.

[0077] The conversion rate in the chemical reaction of oxidizing NO to NO2 is defined as follows. There are N moles of NO at the inlet (per unit time), and M moles of NO at the outlet. When M < N, the conversion rate is (N - M) / N, that is, the number of moles converted to NO2 divided by the number of moles at the inlet.

[0078] In the case of the test defined as above, the gas flow rate can be considered constant between the inlet and the outlet, and the ppm values of NO between the inlet and the outlet can be directly compared.

[0079] Figure 2 shows the results of the test conducted under the above conditions. The contents (NO and optionally NO2) at the outlet of the tube are shown on the y-axis, and time is shown on the x-axis.

[0080] The curve of reference numeral 11 corresponds to glass beads or an adsorbent having no specific catalytic effect. The NO that is not adsorbed is rapidly discharged and then remains in a substantially stable state. Since this type of product is not a catalyst or is very poor as a catalyst for the oxidation reaction, the content at the outlet is in the range of, for example, 47 to 49.5 ppm. Although not shown, the NO2 content can be determined within the range of measurement uncertainty. The conversion rate is in the range of 1% to 6%.

[0081] Curves 12 and 13 show the breakthroughs of NO and NO2 on the adsorbent according to the present invention, respectively. Since NO reacts strongly with oxygen to form NO2 and the NO2 is adsorbed, a stabilized system is obtained when the adsorbent saturates at the reference time (ts). In this case, the conversion rate from NO to NO2 after the adsorbent saturation is 60%. The adsorbent can be considered to have a significant effect on the conversion rate when the conversion rate determined in this way is 20% or more, that is, about 15 points higher than that of a substantially inert material.

[0082] Curve 12 also shows that by adsorbing the NO2 produced before saturation, a higher conversion of NO is obtained than the NO obtained afterwards. From this it can be concluded that, on the one hand, making the layer corresponding to the adsorbent which promotes the conversion reaction larger increases the average conversion, and, on the other hand, said adsorbent mass can advantageously be composed of a material which promotes the reaction and of a material which has a high capacity for adsorbing NO2. These two materials can be in the form of particles intimately mixed in an optimal ratio determined by tests. If appropriate, these two materials can be mixed in powder form and shaped to obtain particles which include both catalytic and NO2 adsorption functions. The catalytic function can be assumed, for example, by a binder. The mixture of the two substances is then called "adsorbent".

[0083] Generally, according to one aspect of the invention, the treatment unit employs an adsorbent, as defined above, that has a conversion of NO to NO2 of 20% or greater.

[0084] According to another aspect of the invention, the treatment unit uses an adsorbent, as defined above, with a conversion rate of NO to NO2 of at least 30%, preferentially at least 50%.

[0085] Figure 3 shows a CO2 capture installation 10 according to another example embodiment of the invention, which differs from the example installation of Figure 1 in that a drying space 80 forms part of a treatment unit 40 (in this case of the PSA type). This drying space 80 comprises a drying adsorbent selected to adsorb H2O and is arranged in the treatment unit 40 upstream of an adsorbent 9 selected to promote the oxidation of NO to NO2. The treatment unit 40 is arranged to treat a gas stream previously dried in the drying space 80, producing a gas stream enriched in CO2.

Claims

1. At least 10 ppm NOX, 10% to 50% CO by volume ２ , N ２ , water and O ２ CO contained in a feed gas stream containing the compound at a minimum concentration of 0.1 mol %, preferably at a concentration of 1 mol % or more, in particular at a concentration of 2% to 5% or at a concentration of more than 10%. ２ The NOx recovery system (1) comprises NO and NO ２ The facility includes: a compression assembly (2) arranged to compress said feed gas stream, in particular comprising a plurality of compression stages and a plurality of heat exchangers arranged to cool said gas stream compressed by said compression stages, arranged to compress said gas stream to a pressure above 1.5 bar abs, in particular to a pressure between 3 and 15 bar abs or even to a pressure between 4 and 12 bar abs, a drying space (8; 80), preferably located downstream of said compression assembly, for drying the feed gas stream passed by said compression assembly to obtain a dry gas stream (FGS); - NO of said NO ２ and an adsorption treatment unit (4; 40) comprising at least one adsorbent (9) selected to promote the oxidation of CO to CO, said drying space (8) being part of a dryer (3) located upstream of said treatment unit (4), said treatment unit (4; 40) treating the dry gas stream coming from said dryer to ２ an adsorption treatment unit (4; 40) arranged to produce an enriched gas stream; The equipment (1).

2. The dry gas stream (FGS) has a H content of less than 500 ppm, in particular less than 10 ppm, for example less than 1 ppm. ２ The facility of claim 1 , comprising:

3. The above NO ２ 3. The installation according to claim 1 or 2, wherein the adsorbent (9) selected to promote oxidation to is selected from silica gel, zeolites, activated carbon, alumina or a combination of these elements.

4. The above NO ２ 4. The system of claim 3, wherein the adsorbent selected to promote oxidation to comprises a mixture of at least two different silica gels, and / or at least two different zeolites, and / or at least two different activated carbons.

5. The plant of any one of claims 1 to 4, wherein the treatment unit comprises a pressure swing adsorption apparatus.

6. 5. The installation according to claim 1 , wherein the treatment unit comprises a VPSA adsorption device in which the adsorption takes place at a high pressure above atmospheric pressure, in particular 1.5 to 6 bar abs, and the desorption takes place at a low pressure below atmospheric pressure.

7. The installation according to any one of claims 1 to 6, wherein the dryer (3) comprises a temperature swing adsorption (TSA) device.

8. At least 10 ppm NOX, 10% to 50% CO by volume ２ , N ２ , water and O ２ CO contained in a feed gas stream containing the compound at a minimum concentration of 0.1 mol %, preferably at a concentration of 1 mol % or more, in particular at a concentration of 2% to 5% or at a concentration of more than 10%. ２ A process for recovering NOx, wherein the NOx is NO and NO ２ said process comprising: - compressing said feed gas stream using a compression assembly; - thereafter, through a drying space (8; 80), said compressed feed gas stream is dried, in particular to a concentration of less than 500 ppm H ２ O, especially H less than 10 ppm ２ O, e.g. less than 1 ppm H ２ obtaining a dry gas stream (FGS) comprising O; - NO of said NO ２ and wherein the drying space (8; 80) is part of a dryer (3) located upstream of the treatment unit (4), the drying gas stream coming from the dryer (3) is treated with an adsorption treatment unit (4; 40) comprising at least one adsorbent (9) selected to promote the oxidation of CO to CO. ２ generating a gas stream enriched with The process includes:

9. NO via the oxidation of NO ２ 9. The process according to claim 8, wherein the overall conversion to is more than 20%, in particular 30% or 50% or even more than 75%.

Images