Method and facility for treating combustion gases originating in particular from a fluidised-bed catalytic cracking (FCC) process regenerator operating in partial combustion mode

Abstract

The invention relates to a method for treating combustion gases originating from the combustion of coke deposited on catalytic particles, the method comprising: (a) a step of regenerating the catalytic particles in a regenerator (10), during which the coke present on the catalytic particles is combusted in the presence of an oxidising gas containing dioxygen under partial combustion conditions, and combustion gases containing at least CO2 and CO are produced; (b) a step of combusting the combustion gases from the regenerator (10) in a combustion device (20) in order to oxidise the CO into CO2 and produce CO2-enriched combustion gases. Furthermore, dioxygen and some of the CO2-enriched combustion gases leaving the combustion device (20) are added to the combustion gases leaving the regenerator (10), upstream of step (b).

Description

[0001] DESCRIPTION

[0002] TITLE: PROCESS AND PLANT FOR TREATING COMBUSTION GAS, IN PARTICULAR FROM A FLUIDIZED BED CATALYTIC CRACKING (FCC) PROCESS REGENERATOR OPERATING IN PARTIAL COMBUSTION MODE

[0003] Field of invention

[0004] The present invention lies in the field of capturing carbon dioxide emitted by fumes from the regeneration of catalytic particles in catalytic cracking units (abbreviated as FCC).

[0005] Prior art

[0006] Catalytic cracking units generate combustion fumes from the regeneration of the catalyst carried out in a reactor, called a regenerator. These combustion fumes contain CO2, but also generally SOx (sulfur oxides) and / or NOx (nitrogen oxides). The CO2 contained in these fumes is usually recovered by a capture process comprising various pretreatment systems to remove SOx and / or NOX (for example basic scrubbing systems, amine scrubbing systems), dust separation systems and CO2 liquefaction systems, thus allowing its storage. These different systems consume energy and also water vapor, the production of which also generates CO2. The overall energy consumption of CO2 capture processes is therefore generally very sensitive to the CO2 content of the combustion fumes.

[0007] Additionally, FCC regenerators sometimes operate in partial combustion mode. One problem associated with operating regenerators in partial combustion mode is the formation of dilute flue gas containing both CO and CO2. While CO2 can be removed from the flue gas stream by amine scrubbing, reducing CO emissions would require multiple downstream treatment units or changes in the operation of the FCC regenerator to effectively reduce CO emissions. For this reason, flue gas from a regenerator operating in partial combustion mode is typically sent to a CO burner to oxidize the CO to CO2, thereby concentrating the flue gas to CO2 while recovering energy from the treated flue gas by producing steam.Despite the effectiveness of this type of burner positioned downstream of a regenerator to concentrate the fumes into CO2, there is still a need to further concentrate the fumes from an FCC regenerator into CO2 and to optimize the size of a downstream CO2 capture and storage unit and / or to allow the recovery of fumes from other emitters of a petrochemical site whose fumes would be more diluted in CO2, in addition to the FCC fumes.

[0008] Summary of the invention

[0009] In order to overcome all or part of the aforementioned drawbacks, a method is proposed for treating combustion gases originating from the combustion of coke deposited on catalytic particles, comprising:

[0010] (a) a step of regenerating catalytic particles in a regenerator, during which the combustion of the coke present on the catalytic particles is carried out in the presence of an oxidizing gas containing dioxygen under partial combustion conditions and combustion gases containing at least CO2 and CO are produced,

[0011] (b) a step of combustion of the flue gases leaving the regenerator of step (a) in a combustion device, during which the CO is oxidized to CO2 and flue gases enriched in CO2 are produced.

[0012] The method according to the invention is characterized in that: dioxygen and a portion of the CO2-enriched combustion gases leaving the combustion device are added to the combustion gases leaving the regenerator of step (a), upstream of step (b).

[0013] This recirculation makes it possible to operate the combustion device of step (b) in an oxycombustion mode, which makes it possible to increase its combustion temperature and therefore the energy released, and to produce fumes consisting of water vapor and concentrated carbon dioxide (more than 20% by volume).

[0014] The method according to the invention can be used to modify an existing installation in which the regenerator operates in total combustion to operate the regenerator in partial combustion. In this configuration, the fumes leaving the regenerator can have a CO content of between 5 and 10% vol CO, the initial system of heat extraction and steam production by boiler is then converted into a combustion device such as a CO boiler, called CO Boiler, in which the CO is converted into CO2.

[0015] Advantageously, the proportion of CO2-enriched combustion gases leaving the combustion device and recycled to the combustion device inlet can represent 10 to 35% of the total volume of gases entering the combustion device (including O2).

[0016] Advantageously, the treatment method according to the invention may further comprise:

[0017] (c) a step of purifying the CO2-enriched combustion gases leaving the combustion device of step (b) carried out in a purification unit, and the oxidizing gas used during step (a) then contains, in particular consists of, a portion of the purified combustion gases leaving the purification unit of step (c) to which dioxygen is added.

[0018] In this embodiment, both the combustion device of step (b) and the regenerator of step (a) can be operated in oxycombustion mode, for an even greater CO2 concentration of the combustion gases produced.

[0019] In this embodiment, the added oxygen may advantageously be mixed with the purified combustion gases leaving the purification unit of step (c) before their entry into the regenerator of step (a).

[0020] In this embodiment, the proportion of purified combustion gases leaving the purification unit and recycled to the inlet of the regenerator may represent 60 to 85%, preferably 70 to 80%, of the total volume of gases leaving the regenerator.

[0021] Advantageously, the purification step (c) can implement one or more treatments chosen from a particle removal treatment, a sulfur oxide removal treatment, a nitrogen oxide removal treatment.

[0022] In a preferred embodiment, the purification step (c) may implement the following treatments from upstream to downstream with respect to the circulation of the CO2-enriched combustion gases leaving the combustion device of step (b): a treatment for removing nitrogen oxides, in particular in an SCR device for catalytic reduction of NOx, followed by a treatment for removing particles, in particular via an electrostatic precipitator, preferably dry, followed by a treatment for removing sulfur oxides, in particular in a washing device with a basic solution.

[0023] Advantageously, in particular in order to limit corrosion, the oxygen / combustion gas volume ratio at the inlet of the combustion device of combustion step (b) may be 5 to 10%, so as to reduce the additional formation of NOx. Advantageously, in particular in order to limit corrosion, the oxygen / oxidizing gas volume ratio at the inlet of the regenerator of combustion step (a) may be 22 to 28%, preferably 24 to 28%, more preferably 26 to 28%. Such a ratio may be obtained by adding oxygen to a gas which may be air or the purified combustion gases leaving the purification unit of step (c) previously mentioned.

[0024] Advantageously, in order to optimize energy consumption, during step (b), the heat generated by the combustion of the flue gases produced by step (a) can be recovered to heat water and produce steam. The steam produced may in particular be used for downstream purification treatments using steam, for example an amine absorption treatment, and / or for the various compression systems used in a treatment installation implementing the method of the present invention, and / or for other units of the site where the method according to the invention is implemented.

[0025] Advantageously, other combustion gases containing CO2, in particular combustion gases containing CO2 from other combustion systems, such as those from steam production or other petrochemical units, may be added to the CO2-enriched combustion gases leaving the combustion device of step (b), or to the purified combustion gases leaving the purification unit of step (c).

[0026] The invention also relates to a combustion gas treatment installation, in particular for implementing the method according to the invention, the installation comprising: a regenerator of a fluid catalytic cracking unit comprising a supply line for oxidizing gas, a supply line for coked catalytic particles to be regenerated, a discharge line for the regenerated catalytic particles and a combustion gas discharge line, a combustion device capable of oxidizing CO to CO2, said device comprising a supply line connected to the combustion gas discharge line of the regenerator and a discharge line for CO2-enriched combustion gases.

[0027] According to the invention, the installation further comprises: a recirculation pipe connecting the discharge pipe of the combustion device to the supply pipe of the latter, a dioxygen supply pipe connected to the supply pipe of the combustion device or to the recirculation pipe.

[0028] Advantageously, the installation may further comprise: a purification unit comprising an inlet connected to the exhaust pipe of the combustion device and an exhaust pipe for the purified gases, a second recirculation pipe connecting the exhaust pipe of the purification unit to the oxidizing gas supply pipe of the regenerator or to a dedicated inlet of the regenerator, a second oxygen supply pipe connected to the inlet of the regenerator or to the second recirculation pipe.

[0029] This purification unit may include one or more purification systems such as particle separation systems, NOx removal systems and SOx removal systems.

[0030] In a preferred embodiment, the purification unit may comprise, from upstream to downstream with respect to the circulation of CO2-enriched combustion gases leaving the combustion device of step (b): a nitrogen oxide removal system, such as an SCR device for catalytic reduction of NOx, followed by a particulate removal system, such as an electrostatic precipitator, preferably dry, followed by a sulfur oxide removal system, such as a washing device with a basic solution.

[0031] Advantageously, the combustion device may comprise a heat exchanger which comprises an inlet for water and an outlet for steam. Such a combustion device is also called a carbon monoxide boiler, or "CO Boiler" in English.

[0032] Advantageously, the installation may comprise a combustion gas supply line from another unit connected to the combustion gas discharge line of the combustion device or to the purified gas discharge line of the purification unit.

[0033] Advantageously, the installation may further comprise: a control system configured to control the proportion of CO2-enriched combustion gases leaving the combustion device and recycled at the inlet of the combustion device, and in particular configured to set this proportion at 10 to 35% of the total volume of gases entering the combustion device (including O2), and / or

[0034] - a control system configured to control the proportion of purified combustion gases leaving the purification unit and recycled to the inlet of the regenerator, and in particular configured to set this proportion at 60 to 85%, preferably 70 to 80%, of the total volume of gases leaving the regenerator, and / or

[0035] - a system for controlling the oxygen / oxidizing gas volume ratio at the inlet of the regenerator, configured to set this ratio at a value ranging from 22 to 28%, preferably from 24 to 28%, more preferably from 26 to 28%.

[0036] This control system(s) may be a mixing valve or any other mixing device capable of controlling the ratio of a mixture of streams.

[0037] The invention also relates to a fluid catalytic cracking process comprising a step of fluid catalytic cracking of a hydrocarbon feedstock in the presence of catalytic particles producing a cracked hydrocarbon feedstock and coked catalytic particles, and a step of regenerating the coked catalytic particles, the process implementing the treatment process according to the invention.

[0038] The invention also relates to a fluid catalytic cracking unit comprising a fluid catalytic cracking reactor in which a step of fluid catalytic cracking of a hydrocarbon feedstock is carried out in the presence of catalytic particles producing a cracked hydrocarbon feedstock and coked catalytic particles, the unit further comprising the treatment installation according to the invention, the regenerator of which receives the coked catalytic particles coming from the fluid catalytic cracking reactor.

[0039] Definitions

[0040] By "hydrocarbon feedstock" or "hydrocarbon stream" is meant a mixture of hydrocarbon compounds, a hydrocarbon compound containing carbon and hydrogen, and possibly heteroatoms such as sulfur, nitrogen, metals, etc.

[0041] The notation “SOx” designates all the sulfur oxides possibly present in combustion fumes (e.g. SO2, SO3).

[0042] The term "NOx" refers to all nitrogen oxides that may be present in combustion fumes (e.g., NO, NO2). "Coked catalyst" or "coked catalytic particles" refers to any solid catalytic material on which coke is deposited, typically in quantities of 0.5 to 1% by mass. Preferably, the coked catalytic particles are produced during a fluid catalytic cracking step.

[0043] The term "fine particles" means particles whose average diameter has been reduced by abrasion, due to the friction of the particles against each other, in other words by attrition. Such particles therefore have an average diameter smaller than the average diameter of the particles before attrition.

[0044] By "mean diameter" is meant the diameter of a spherical particle of the same mass. This mean diameter can be determined by any suitable technique, in particular by optical diffraction techniques (e.g. laser diffraction).

[0045] Downstream and upstream refer to the directions of circulation of fluids within the different areas of the installation.

[0046] Detailed description of the invention

[0047] Regeneration step (a)

[0048] In this step, the coke present on catalytic particles is burned in the presence of an oxidizing gas containing dioxygen under partial combustion conditions and combustion gases containing at least CO2 and CO are produced.

[0049] The coked catalytic particles typically originate from a fluid catalytic cracking step carried out in one or more suitable reactors. This regeneration step thus makes it possible to regenerate the catalyst and return it to the fluid catalytic cracking step in a manner known per se.

[0050] The regeneration step is carried out in a regenerator, in particular a regenerator of an FCC unit, comprising an oxidizing gas supply line, a supply line for coked catalytic particles to be regenerated, a discharge line for the regenerated catalytic particles and a combustion gas discharge line.

[0051] Typically, the catalytic particles enter the regenerator with a coke content of 0.5 to 1% by mass and exit with a coke content of 0.1 to 0.5% by mass when the regenerator is operated in partial combustion. In partial combustion, the regenerator is typically operated at a temperature of 680 to 760 °C and a pressure of 1.5 to 2.5 barg.

[0052] Flue gases generated by partial combustion of coke typically contain mainly CO2 and CO, and usually also NOx and SOx depending on the cracked feedstock. They also usually include particulate fines.

[0053] Typically, flue gases contain CO2 and CO, as well as nitrogen compounds, such as HCN, NH3, and sulfur compounds, such as sulfur oxides, COS, CS2, and H2S.

[0054] Typically, the CO content of flue gases can be 0.5 to 10% by volume.

[0055] The oxidizing gas may be air, oxygen-enriched air, or purified oxygen-enriched combustion gases, these purified combustion gases coming from a subsequent purification step (c) described below.

[0056] When it is oxygen-enriched air or oxygen-enriched purified combustion gases, the oxygen / oxidant gas volume ratio at the inlet of the regeneration step (a) may be 22 to 28%, preferably 24 to 28%, more preferably 26 to 28%, for example 27.5. The oxygen used to enrich the air or purified combustion gases entering the regenerator may be pure oxygen or having a purity degree of 90% by volume or more.

[0057] Dioxygen can advantageously be added to the oxidizing gas before it enters the regenerator.

[0058] It may also be possible to use only air as the oxidizing gas, in particular when only the combustion device implementing step (b) operates in oxycombustion.

[0059] Combustion step (b)

[0060] In this step, the combustion gases produced in step (a) are combusted in a combustion device during which the CO is oxidized to CO2 and CO2-enriched combustion gases are produced. In addition, generally, most of the nitrogen compounds present in the combustion gases are then converted to NOx and most of the sulfur compounds present in the combustion gases are converted to SOx. The combustion gases leaving the combustion device are thus enriched in CO2 and typically contain nitrogen oxides and sulfur oxides. This step is implemented in a combustion device capable of oxidizing CO to CO2, this device comprising an inlet connected to the combustion gas discharge pipe of the regenerator and a CO2-enriched combustion gas discharge pipe.

[0061] The combustion step is preferably carried out with recovery of the heat generated by the combustion of the flue gases produced by the step

[0062] (a), this heat being recovered to heat water and produce steam.

[0063] Treatment step (b) is thus typically implemented in a carbon monoxide boiler, comprising a combustion chamber in which the CO is oxidized to CO2, and a heat exchanger recovering the combustion heat to produce steam from water.

[0064] According to the invention, combustion step (b) is carried out by adding to the combustion gases produced by step (a), upstream of step (b), dioxygen and a portion of the CO2-enriched combustion gases leaving the combustion device. These CO2-enriched combustion gases are preferably taken directly from the outlet of the combustion device and returned directly upstream of step

[0065] (b), optionally after compression, without having undergone purification treatment. It is thus possible to implement this recycling in a simple and inexpensive manner.

[0066] Dioxygen may be pure dioxygen or having a purity of 90% by volume or more.

[0067] Typically, step (b) may be implemented with the addition of a marginal quantity of make-up fuel (e.g. Fuel Gas) so as to stabilize the thermal load of the combustion device and avoid destabilization of the latter in the event of a significant change in the composition of the fumes.

[0068] It may also be possible to inject air only at the start of the process to initiate the CO combustion reactions, then to stop this injection by gradually recycling more and more of the fumes taken from the outlet of the combustion device. For example, air can be injected into the CO2-enriched combustion gases leaving the combustion device and returned to the inlet of the latter.

[0069] Preferably, step (b) can be implemented with a dioxygen / combustion gas volume ratio at the inlet of combustion step (b) of 5 to 10%.

[0070] Furthermore, combustion step (b) can typically be carried out at a temperature of 900 to 1300 °C and a pressure of 0.02 to 0.3 barg. Due to the addition of oxygen, step (b) is thus carried out under oxycombustion conditions with increased heat production and a CO2 content of the flue gases leaving step (b) typically of 20 to 25% by volume.

[0071] Combustion step (b) can be carried out in the presence of a reducing agent, and optionally a catalyst, making it possible to transform the NOx present in the fumes into N2 and water, and possibly into CO2. This reducing agent can be urea or NH3 in the gaseous or aqueous phase, preferably NH3 in the gaseous phase (ammonia). The usual catalysts are based on tungsten and vanadium in oxidized form: tungsten (III) oxide W2O3 or vanadium (V) oxide V2O5. The catalyst is generally deposited on a support based on titanium oxide (TiCh). The invention is of course not limited to a specific catalyst and any catalyst usually used to catalyze the selective reduction of nitrogen oxides can be considered.

[0072] The combustion device is then equipped with an "SCR" system ("Selective Catalytic Reduction"). It is generally inserted at the outlet of the CO Boiler convection outlet and upstream of the CO Boiler economizer in order to optimize the operating conditions of the SCR in terms of temperature.

[0073] Optional purification step (c)

[0074] Most often, the CO2-enriched flue gases leaving combustion step (b) are sent to a purification step (c), in particular to remove the particles and / or NOx and / or SOx still present. The purified gases leaving step (c) thus have a reduced content of particles and / or NOx and / or SOx compared to the CO2-enriched flue gases leaving step (b).

[0075] In this case, provision may be made to recycle part of the purified combustion gases leaving step (c) so that they form part of the oxidizing gas used in step (a). These purified combustion gases are preferably taken directly from the outlet of purification step (c) and returned directly to step (a), optionally after compression, without having undergone any other treatment.

[0076] Typically, the purified flue gases exiting purification step (c) and returned to step (a) may have one or more of the following characteristics:

[0077] - A particle content of less than 50 mg / Nm 3 , or even less than 10 mg / Nm 3 , for example from 0.01 to 50 mg / Nm 3 , - A NOx content of less than 250 ppm vol, for example from 1 to 250 ppm vol,

[0078] - A SOx content of less than 400 ppm vol, for example from 1 to 400 ppm vol.

[0079] This purification step may in particular comprise, or consist of, one or more treatments chosen from a particle removal treatment, a sulfur oxide removal treatment, a nitrogen oxide removal treatment.

[0080] The purification step can be implemented in a purification unit, comprising for example, or consisting of, a particle removal device, generally an electrostatic precipitator, in particular dry (operating without adding liquid), a SOx removal device, for example a washing device with a basic solution, a NOx removal device, for example an SCR device for catalytic reduction of NOx or an ozone injection device. The invention is of course not limited by the number and nature of these devices, which are otherwise well known to those skilled in the art.

[0081] The SCR device for catalytic reduction of NOx typically operates in the presence of a reducing agent and optionally a catalyst as previously described with reference to step (b) in order to transform the NOx present in the fumes into N2 and water. In particular, the reducing agents and catalysts described with reference to step (b) may be used.

[0082] In a preferred embodiment, the purification unit implementing the purification step can advantageously comprise, or consist of, from upstream to downstream: an SCR device for catalytic reduction of NOx, an electrostatic precipitator (in particular dry) and a washing device with a basic solution.

[0083] The SCR device can in particular be integrated into a carbon monoxide boiler implementing step (b) as previously described.

[0084] Optional capture and storage step

[0085] Downstream of the combustion device implementing step (b) or the purification unit implementing step (c), the method according to the invention may further comprise a CO2 capture and storage step, which may comprise at least one CO2 liquefaction step, typically by compression, and a liquefied CO2 storage step. The liquefaction step may optionally be preceded by a drying step and / or a pressure swing adsorption step or PSA (from the English acronym Pressure Swing Adsorption).

[0086] This step can be implemented in a CO2 capture and storage unit comprising at least one liquefaction system, typically by compression, and at least one liquefied CO2 storage system. This capture and storage unit can also comprise, upstream of the liquefaction system, a drying system, and / or a pressure inversion adsorption system to further concentrate the gases into CO2.

[0087] Typically, if the CO2 content at the inlet of the capture and storage unit is less than 45-50% by volume, a PSA is advantageously used to concentrate the fumes. If the CO2 content is greater than 45-50% by volume, a PSA is not useful.

[0088] The CO2 capture and storage step can also be carried out, not in the liquid phase but in the gas phase or supercritical phase, typically at room temperature and pressure between 20 barg and 170 barg. In this configuration, the CO2 liquefaction step, allowing in particular ultimate purification of the CO2, can either be maintained with a CO2 revaporization step, or carried out by alternative treatments such as absorption by amine solvents.

[0089] The CO2 capture and storage unit may then comprise at least one liquefaction system followed by a revaporization system, or at least one CO2 extraction system, typically using an amine solvent, followed by a water and oxygen extraction system, and a compression system in gaseous or supercritical form.

[0090] The CO2 enrichment of the regenerator flue gases can be, on a dry basis, from 16% vol CO2 to 95% vol CO2.

[0091] The invention can in particular make it possible to obtain an energy gain of 5 to 70% of energy per tonne of CO2 captured.

[0092] The method according to the invention can make it possible to obtain combustion gases having a CO2 content in dry fumes of 20 to 30% by volume, typically 25% by volume, at the outlet of step (b) or (c).

[0093] The implementation of the method according to the invention thus makes it possible to produce combustion gases with a higher concentration of CO2, which then makes it possible to reduce the size of the purification unit implementing step (c) and / or of the capture and storage unit implementing the capture and storage step, and consequently to reduce their operating cost.

[0094] Alternatively, the method according to the invention may receive, downstream of the combustion device implementing step (b) or of the purification unit implementing step (c), and in particular upstream of a CO2 capture and storage step, combustion gases containing CO2 originating from other petrochemical units. Insofar as the present invention makes it possible to enrich the combustion gases produced with CO2, it is possible to envisage adding external combustion gases without having to modify the dimensions and / or conditions of implementation of a purification step and / or a CO2 capture and storage step located downstream.

[0095] In particular, the CO2 content of dry gases entering a capture and storage unit can advantageously be 15 to 20% CO2 by volume on a dry basis. The ratios of combustion gases from step (b) or (c) and combustion gases from other units can thus be adjusted to obtain a CO2 content of this order. For example, combustion gases from furnaces typically contain 7 to 10% CO2 by volume.

[0096] Treatment facility

[0097] The method according to the invention can be implemented in a treatment installation as previously described.

[0098] Furthermore, this installation may include a CO2 capture and storage unit as described above.

[0099] As previously described with reference to the process, this installation can receive combustion gases from other units via dedicated pipes. These pipes can be connected to the installation downstream of the combustion device or downstream of the purification unit, and in particular upstream of the CO2 capture and storage unit.

[0100] Description of figures

[0101] The invention is now described with reference to the accompanying non-limiting drawings, in which:

[0102] [Fig. 1] Figure 1 represents an exemplary embodiment of an installation implementing the method according to an embodiment of the invention.

[0103] [Fig. 2] Figure 2 represents an exemplary embodiment of an installation implementing the method according to another embodiment of the invention. In the figures, the same elements are designated by the same references.

[0104] Figure 1 schematically represents a treatment installation 1 according to one embodiment of the invention. The installation shown comprises a regenerator 10, a combustion device 20, a purification unit 30, and in the example shown a CO2 capture and storage unit 40.

[0105] The regenerator 10 has a coked catalytic particle feed line 101, an oxidizing gas feed line 102, a combustion gas discharge line 103, and a regenerated catalytic particle discharge line 104. The coked catalytic particles come from a catalytic cracking reactor (not shown) into which the regenerated catalytic particles are returned.

[0106] The combustion device 20 comprises a supply line 201 connected to the exhaust line 103 for combustion gases from the regenerator, and an exhaust line 202 for CO2-enriched combustion gases. In this example, the combustion device 20 is equipped with a heat exchanger 203 comprising an inlet 203a for water and an outlet 203b for steam. Such a combustion device 20 is generally called a “carbon monoxide boiler”.

[0107] The purification unit 30 comprises an inlet 301 connected to the discharge pipe 202 of the combustion device, and a discharge pipe 302 for the purified gases.

[0108] According to the invention, a recirculation line 204 connects the discharge line 202 of the combustion device to the supply line 201 of the latter. In addition, a dioxygen supply line 205 is connected to the supply line 201 of the combustion device to supply it with dioxygen.

[0109] In the example shown, the recirculation line 204 also includes an air supply 206 intended to be used only when starting the installation.

[0110] The recirculation line 204 also includes in this example a compressor 207 for compressing the recycled gases.

[0111] In the example shown, the oxidizing gas entering the regenerator 10 consists of air supplied via a pipe 105 and oxygen supplied via a pipe 106.

[0112] In the example shown, the installation also comprises a compressor 2 on the air supply line 105, a compressor 3 between the combustion device 20 and the purification unit 30 and another compressor 5 between the purification unit 30 and the CO2 capture and storage system 40. The invention is of course not limited by the number and position of the compressors which may vary depending on the needs of the installation. The different lines may also be equipped with valves and / or pumps for the circulation of fluids.

[0113] The installation further includes here different control systems configured to control the proportions of gas coming from the different lines, such as mixing valves V1, V2, V3, V4.

[0114] The capture and storage unit 40 typically comprises a CO2 liquefaction system and a liquefied CO2 storage system. This capture and storage unit may also correspond to an extraction of CO2 by an amine solvent followed by a step of extraction of water and oxygen and final compression of the CO2 in the form of gas or supercritical fluid.

[0115] Figure 2 represents an installation T which differs from that shown in Figure 1 only by the presence of a second recirculation pipe 303 connecting the discharge pipe 302 of the purification unit 30 to the oxidizing gas supply pipe 102 of the regenerator. Furthermore, in this embodiment, the oxidizing gas consists solely of the purified combustion gases supplied by the recirculation pipe 303 and by oxygen supplied by the pipe 106. In other words, in this embodiment, the regenerator is not supplied with air. It will also be possible in this embodiment to provide an additional air supply pipe 304 at the outlet of the purification unit 30 to inject air at the start of the process so that the oxidizing gas entering the regenerator contains sufficient oxygen. Another compressor 305 may be arranged between the air supply 304 and the recirculation pipe 303.

[0116] The installation further includes here different control systems configured to control the proportions of gas coming from the different lines, such as mixing valves V1, V2, V3, V4, V5.

[0117] Example

[0118] If we define the efficiency of a CO2 capture process from the energy demand required to carry out the capture, for example using the following calculation method: - We measure or estimate the quantity of CO2 emitted by the installation and the quantity of CO2 recovered by the CO2 capture installation. Generally, the captured CO2 corresponds to 90-95% of the CO2 emitted by the installation,

[0119] - The steam consumption required to carry out the capture is measured or estimated, expressed in tonnes of steam / tonnes of CO2 captured, and converted into tonnes of CO2 / h emitted from the quantity of CO2 produced for the production of steam. This corresponds to the so-called "scope 1" emissions linked to the fact that fuel is burned and therefore CO2 is emitted to produce steam.

[0120] - We measure or estimate the electricity consumption required to carry out the capture expressed in KWh / Ton CO2 captured and we convert it into Ton CO2 / h emitted from the CO2 footprint on electricity. This corresponds to so-called "scope 2" emissions. We consider all the electrical installations required to carry out the CO2 capture.

[0121] - The CO2 avoided (noted: CO2 avoided “Scope 1” in table 1) then corresponds to the formula CO2 avoided = CO2 captured - CO2 scope 1 - CO2 scope 2

[0122] - the ratio between CO2 avoided and CO2 emitted (noted: CO2 avoided Scope 1 + 2 in table 1) makes it possible to judge the overall energy and environmental performance of the installation.

[0123] Table 1 thus brings together an estimate of the gains for an installation according to figure 1 but without the recycling of the invention (base case), an installation according to figure 1 and an installation according to figure 2.

[0124] Table 1

Claims

CLAIMS 1. Method for treating combustion gases from the combustion of coke deposited on catalytic particles, comprising: (a) a step of regenerating catalytic particles in a regenerator (10), during which the combustion of the coke present on the catalytic particles is carried out in the presence of an oxidizing gas containing dioxygen under partial combustion conditions and combustion gases containing at least CO2 and CO are produced, (b) a step of combustion of the combustion gases leaving the regenerator (10) of step (a) in a combustion device (20), during which the CO is oxidized to CO2 and CO2-enriched combustion gases are produced, in which dioxygen and a portion of the CO2-enriched combustion gases leaving the combustion device (20) are added to the combustion gases leaving the regenerator of step (a), upstream of step (b), characterized in that it further comprises c) a step of purification of the CO2-enriched combustion gases leaving the combustion device of step (b) carried out in a purification unit (30), and in that the oxidizing gas used during step (a) contains a portion of the purified combustion gases leaving the purification unit (30) of step (c) to which dioxygen is added.

2. Treatment method according to claim 1, characterized in that the added oxygen is mixed with the purified combustion gases leaving the purification unit (30) of step (c) before they enter the regenerator of step (a).

3. Treatment method according to claim 1 or 2, characterized in that step (c) implements one or more purification treatments chosen from a particle removal treatment, a sulfur oxide removal treatment, a nitrogen oxide removal treatment.

4. Treatment method according to any one of claims 1 to 3, characterized in that the oxygen / combustion gas volume ratio at the inlet of the combustion device of step (b) is 5 to 10%.

5. Treatment method according to any one of claims 1 to 4, characterized in that the oxygen / oxidizing gas volume ratio at the inlet of the regenerator of step (a) is 22 to 28%, preferably 24 to 28%, more preferably 26 to 28%.

6. Treatment method according to any one of claims 1 to 5, characterized in that, during step (b), the heat generated by the combustion of the combustion gases leaving the regenerator (10) of step (a) is recovered to heat water and produce steam.

7. Treatment method according to any one of claims 1 to 6, characterized in that other combustion gases containing CO2 are added to the CO2-enriched combustion gases leaving the combustion device of step (b), or to the purified combustion gases leaving the purification unit of step (c).

8. Fluid catalytic cracking process comprising a step of fluid catalytic cracking of a hydrocarbon feedstock in the presence of catalytic particles producing a cracked hydrocarbon feedstock and coked catalytic particles, and a step of regenerating the coked catalytic particles, characterized in that it implements the treatment process according to any one of claims 1 to 7.

9. Installation (1, T) for treating combustion gases comprising: - a regenerator (10) of a fluid catalytic cracking unit comprising a supply line (102) for oxidizing gas, a supply line (101) for coked catalytic particles to be regenerated, a discharge line (104) for the regenerated catalytic particles and a discharge line (103) for combustion gas, - a combustion device (20) capable of oxidizing CO into CO2, said device comprising a supply line (201) connected to the combustion gas discharge line (103) of the regenerator and a discharge line (202) of combustion gases enriched in CO2, - a recirculation pipe (204) connecting the discharge pipe (202) of the combustion device to the supply pipe (201) of the latter, - a dioxygen supply line (205) connected to the supply line (201) of the combustion device or to the recirculation line (204), characterized in that it further comprises: - a purification unit (30) comprising an inlet connected to the discharge pipe (202) of the combustion device and a discharge pipe (302) for the purified gases, - a second recirculation pipe (303) connecting the pipe discharge (302) from the purification unit to the oxidizing gas supply line (102) of the regenerator or to a dedicated inlet of the regenerator, - a second oxygen supply line (106) connected to the inlet of the regenerator or to the second recirculation line.

10. Treatment plant (1, T) according to claim 9, characterized in that the combustion device (20) comprises a heat exchanger (203) which comprises an inlet for water and an outlet for steam.

11. Treatment installation (1, T) according to claim 9 or 10, characterized in that it comprises a combustion gas supply line coming from another unit connected to the combustion gas discharge line of the combustion device or to the purified gas discharge line of the purification unit.

12. Fluid catalytic cracking unit comprising a fluid catalytic cracking reactor in which a step of fluid catalytic cracking of a hydrocarbon feedstock is carried out in the presence of catalytic particles producing a cracked hydrocarbon feedstock and coked catalytic particles, characterized in that it further comprises a treatment installation according to any one of claims 9 to 11, the regenerator of which receives the coked catalytic particles from the fluid catalytic cracking reactor.

Images