METHOD AND INSTALLATION FOR TREATMENT OF COMBUSTION GAS, PARTICULARLY FROM A REGENERATOR IN A FLUIDIZED BED CATALYTIC CRACKING (FCC) PROCESS OPERATED IN TOTAL COMBUSTION MODE

Abstract

The invention relates to a process for treating combustion gases from the combustion of coke deposited on catalytic particles, comprising: (a) a step of regenerating the catalytic particles in a regenerator (10), during which the coke present on the catalytic particles is burned in the presence of an oxidizing gas containing dioxygen under conditions of complete combustion, producing combustion gases containing at least CO2 and CO; (b) a step of recovering heat from the combustion gases of the regenerator (10); (c) a step of purifying the combustion gases cooled in step (b), carried out in a purification unit (30). Furthermore, the oxidizing gas used in step (a) contains a portion of the purified combustion gases exiting the purification unit (30) of step (c), to which dioxygen is added. Figure 1

Description

Title of the invention: METHOD AND PLANT FOR TREATING COMBUSTION GAS, IN PARTICULAR FROM A FLUIDIZED BED CATALYTIC CRACKING (FCC) PROCESS REGENERATOR OPERATING IN TOTAL COMBUSTION MODE Field of invention

[0001] 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). Prior art

[0002] Catalytic cracking units in fact 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 thus generally very sensitive to the CO2 content of the combustion fumes.

[0003] In addition, FCC regenerators sometimes operate in a partial combustion mode. One problem associated with operating regenerators in a partial combustion mode is the formation of a 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 a 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.

[0004] When the regenerators operate in total combustion mode, the entire Coke is burned, and the flue gases leaving the regenerator are typically CO-free. Therefore, there is no need to burn the flue gases and the burner downstream of the regenerator is replaced by a heat recovery system to produce steam.

[0005] Despite a high CO2 content of the combustion gases of the regenerator operating in total combustion, there is still a need to concentrate these gases more in CO2 and to optimize the size of a downstream CO2 capture and storage unit and / or to allow the recovery, in addition to the FCC fumes, of fumes from other emitters of a petrochemical site whose fumes would be more diluted in CO2. In this mode of operation, the fumes leaving the regenerator already contain an excess of oxygen, typically from 0.5% vol O2 to 1.5% vol O2. Summary of the invention

[0006] 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:

[0007] (a) a step of regenerating catalytic particles in a regenerator, at 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 total combustion conditions and combustion gases containing at least CO2 and free of CO are produced,

[0008] (b) a step of recovering the heat from the combustion gases leaving the reg generator of step (a),

[0009] (c) a step of purifying the combustion gases cooled in step (b), carried out works in a purification unit.

[0010] The method according to the invention is characterized in that:

[0011] - the oxidizing gas used during step (a) contains, in particular consists of, a part of the purified combustion gases leaving the purification unit of step (c) to which dioxygen is added.

[0012] This recirculation makes it possible to operate the regenerator of step (a) 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 80% by volume).

[0013] Advantageously, the added oxygen can advantageously be mixed with the purified combustion gases leaving the purification unit of step (c) before they enter the regenerator of step (a).

[0014] Advantageously, the purification step (c) can implement one or more treatments chosen from a particle removal treatment, a treatment sulfur oxide removal, nitrogen oxide removal treatment.

[0015] Advantageously, in particular in order to limit corrosion, the oxygen / combustion gas volume ratio at the inlet of the regenerator of step (a) may be from 15 to 28%, preferably from 15 to 20%, more preferably from 17 to 19%.

[0016] The steam produced may in particular be used for downstream purification treatments using steam, for example NOx treatment, and / or for the various CO2 compression / absorption systems used in a treatment installation implementing the method of the present invention, and / or for other units on the site where the method according to the invention is implemented.

[0017] 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 cooled combustion gases in step (b), or to the purified combustion gases leaving the purification unit in step (c).

[0018] The invention also relates to a combustion gas treatment installation, in particular for implementing the method according to the invention, the installation comprising:

[0019] - a regenerator of a fluid catalytic cracking unit comprising a pipe oxidizing gas supply, a supply line for coked catalytic particles to be regenerated, a discharge line for regenerated catalytic particles and a combustion gas discharge line,

[0020] - a heat recovery device comprising a supply line connected to the regenerator flue gas discharge line and a cooled flue gas discharge line,

[0021] - a purification unit comprising an inlet connected to the pipe heat recovery device exhaust and a purified gas exhaust pipe.

[0022] According to the invention, the installation further comprises:

[0023] - a recirculation pipe connecting the discharge pipe of the puri unit connection to the regenerator's oxidant gas supply line or to a dedicated regenerator inlet,

[0024] - a dioxygen supply line connected to the inlet of the regenerator or to the second recirculation line.

[0025] This purification unit may comprise one or more purification systems such as particle separation systems, NOx removal systems and SOx removal systems.

[0026] Advantageously, the installation may comprise a combustion gas supply pipe coming from another unit connected to the exhaust pipe of the flue gas from the heat recovery device or to the purified gas discharge line from the purification unit.

[0027] 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.

[0028] 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. Definitions

[0029] 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.

[0030] The notation “SOx” designates all the sulfur oxides possibly present in combustion fumes (e.g. SO2, SO3).

[0031] The notation “NOx” designates all the nitrogen oxides possibly present in combustion fumes (e.g. NO, NO2).

[0032] By "coked catalyst" or "coked catalytic particles" is meant any solid catalytic material on which coke is deposited, typically in amounts of 0.5 to 1% by mass. Preferably, the coked catalytic particles are produced during a fluid catalytic cracking step.

[0033] By "particle fines" is meant 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 less than the average diameter of the particles before attrition.

[0034] By "average diameter" is meant the diameter of a spherical particle of the same mass. This average diameter can be determined by any appropriate technique, in particular by optical diffraction techniques (for example by laser diffraction).

[0035] Downstream and upstream refer to the directions of circulation of fluids within the different zones of the installation. Detailed description of the invention Regeneration step (a)

[0036] During this step, the combustion of the coke present on catalytic particles is carried out in the presence of an oxidizing gas containing dioxygen under total combustion conditions and combustion gases containing at least CO2 and free of CO are produced.

[0037] 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.

[0038] The regeneration step is implemented in a regenerator, in particular a regenerator of an FCC unit, comprising a pipe for supplying oxidizing gas, a pipe for supplying coked catalytic particles to be regenerated, a pipe for discharging the regenerated catalytic particles and a pipe for discharging combustion gas.

[0039] 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 0.05% by mass, or even less than 0.01% by mass.

[0040] In total combustion, the regenerator is typically operated at a temperature of 680°C to 760°C and a pressure of 1.5 to 2.5 barg.

[0041] Flue gases generated by the total combustion of coke typically contain predominantly CO2, are CO-free, and generally also contain NOx and SOx depending on the cracked feedstock. They also generally also include particulate fines.

[0042] According to the invention, the oxidizing gas comprises, in particular is made up of, purified combustion gases enriched in dioxygen, these purified combustion gases coming from a subsequent purification step (c) described below.

[0043] The regenerator then operates in oxycombustion, 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.

[0044] The oxygen / oxidizing gas volume ratio at the inlet of the regeneration step (a) may advantageously be 15 to 28%, preferably 15 to 20%, more preferably 17 to 19%. The oxygen used to enrich the purified combustion gases entering the regenerator may be pure oxygen or having a purity degree of 90% by volume or more.

[0045] The oxygen may advantageously be added to the combustion gases before they enter the regenerator. Heat recovery step (b)

[0046] During this step, the heat from the combustion gases produced during step (a) is recovered in a heat recovery device, which cools the combustion gases.

[0047] Step (b) of heat recovery is thus typically implemented in a device generally called a “boiler” or “waste heat boiler” in English, comprising a series of tubes filled with water between which the combustion gases circulate.

[0048] Thus, according to one embodiment, the heat recovered during step (b) is used to produce steam from water. Purification step (c)

[0049] The cooled combustion gases leaving the heat recovery step (b) are sent to a purification step (c), in particular to remove the particles and / or NOx and / or SOx still present.

[0050] According to the invention, part of the purified combustion gases leaving step (c) are recycled so that they form part of the oxidizing gas used in step (a).

[0051] Typically, the purified combustion gases exiting combustion step (c) may have one or more of the following characteristics: - A particle content of less than 50 mg / Nm3, or even < 10 mg / Nm3, - A NOx content of less than 250 ppm vol, - A SOx content of less than 400 ppm vol.

[0052] This purification step may in particular comprise one or more treatments chosen from a particle removal treatment, a sulfur oxide removal treatment, a nitrogen oxide removal treatment.

[0053] The purification step can be implemented in a purification unit, comprising for example a particle removal device, generally an electrostatic precipitator, 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 for NOx reduction. 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.

[0054] It may also be possible to inject air only at the start of the process to start combustion, then to stop this injection. For example, the air can be injected into the purified combustion gases leaving the purification unit before they are returned to the regenerator. Optional capture and storage step

[0055] Downstream of the heat recovery device implementing step (b) or the purification unit implementing step (c), the method according to the invention may further comprise a step of capturing and storing CO2, which may comprise at least one step of liquefaction of the CO2, typically by compression, and a step of storage of the liquefied CO2. The liquefaction step may optionally be preceded by a drying step and / or a step of adsorption by pressure inversion or PSA (from the English acronym Pressure Swing Adsorption).

[0056] 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.

[0057] Typically, if the CO2 content at the inlet of the capture and storage unit is less than 45-50% by volume, a PSA will advantageously be used to concentrate the fumes. If the CO2 content is greater than 45-50% by volume, a PSA is not useful.

[0058] The capture and storage of CO2 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 the 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] Alternatively, the method according to the invention can receive, downstream of the heat recovery 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 from other petrochemical units. To the extent that the present invention makes it possible to enrich the combustion gases produced by the regenerator 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.

[0063] In particular, the CO2 content of the dry gases entering a capture and storage unit can advantageously be 15 to 20% CO2 by volume on a dry basis. It will thus be possible to adjust the ratios of the combustion gases coming from step (b) or (c) and the combustion gases coming from other units to obtain a CO2 content of this order. For example, combustion gases coming from furnaces typically contain 7 to 10% CO2 by volume. Treatment facility

[0064] The method according to the invention can be implemented in a treatment installation as previously described.

[0065] Furthermore, this installation may include a CO2 capture and storage unit as described above.

[0066] As previously described with reference to the method, this installation can receive combustion gases from other units via dedicated pipes. These pipes can be connected to the installation downstream of the heat recovery device or downstream of the purification unit, and in particular upstream of the CO2 capture and storage unit. Description of figures

[0067] The invention is now described with reference to the accompanying non-limiting drawings, in which:

[0068] [Fig.l] [Fig.l] represents an exemplary embodiment of an installation implementing the method according to an embodiment of the invention.

[0069] [Fig. 1] schematically represents a treatment installation 1 according to one embodiment of the invention. The installation shown comprises a regenerator 10, a heat recovery device 20, a purification unit 30, and in the example shown a CO2 capture and storage unit 40.

[0070] 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.

[0071] The heat recovery device 20 comprises a supply line 201 connected to the flue gas discharge line 103 of the regenerator, and a discharge line 202 for cooled flue gas. The heat recovery device 20 further comprises an inlet 20a for water and an outlet 20b for steam. Such a heat recovery device 20 is generally called a "boiler".

[0072] The purification unit 30 comprises an inlet 301 connected to the discharge pipe 202 of the heat recovery device, and a discharge pipe 302 for the purified gases.

[0073] According to the invention, a recirculation line 303 connects the discharge line 302 of the purification unit to the oxidizing gas supply line 102 of the regenerator. In addition, a dioxygen supply line 106 is connected to the oxidizing gas supply line 102 of the regenerator.

[0074] Thus, the oxidizing gas entering the regenerator 10 consists of the cooled combustion gases brought in via the pipe 303 and of oxygen brought in via a pipe 106.

[0075] In the example shown, the installation also comprises a compressor 2 between the heat recovery device 20 and the purification unit 30, a compressor 3 on the pipe 302 between the purification unit 30 and the recirculation pipe 303, and another compressor 4 on the pipe 302 between the recirculation pipe 303 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 pipes may further be equipped with valves and / or pumps for the circulation of fluids.

[0076] 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.

Claims

Claims

1. A method for treating flue 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 coke present on the catalytic particles is burned in the presence of an oxidizing gas containing dioxygen under total combustion conditions and flue gases containing at least CO2 and free of CO are produced, (b) a step of recovering heat from the flue gases leaving the regenerator (10) of step (a), (c) a step of purifying the flue gases cooled in step (b), carried out in a purification unit (30), characterized in that: the oxidizing gas used in step (a) contains a portion of the purified flue 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 their entry into 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 regenerator of step (a) is 15 to 28%, preferably 15 to 20%, more preferably 17 to 19%.

5. Treatment method according to any one of claims 1 to 4, characterized in that other combustion gases containing CO2 are added to the cooled combustion gases in step (b), or to the purified combustion gases leaving the purification unit of step (c).

6. 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, characterized in that it implements the treatment method according to any one of claims 1 to 5.

7. Installation (1) 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 gases, - a heat recovery device (20) comprising a supply line (201) connected to the discharge line (103) for combustion gases of the regenerator and a discharge line (202) for cooled combustion gases, - a purification unit (30) comprising an inlet connected to the discharge line (202) of the heat recovery device and a discharge line (302) for purified gases,characterized in that it further comprises: - a recirculation pipe (303) connecting the discharge pipe (302) of the purification unit to the oxidizing gas supply pipe (102) of the regenerator or to a dedicated inlet of the regenerator, - a dioxygen supply pipe (106) connected to the inlet of the regenerator or to the recirculation pipe.,

8. Treatment installation (1) according to claim 7, characterized in that it comprises a combustion gas supply line from another unit connected to the combustion gas discharge line of the heat recovery device or to the purified gas discharge line of the purification unit.

9. 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 the treatment installation according to claim 7 or 8, the regenerator of which receives the coked catalytic particles from the fluid catalytic cracking reactor.

Images