Method and apparatus for separating a mixture containing co2 by partial condensation

Abstract

In a method for separating a CO2-containing mixture by partial condensation, said mixture (G) containing at least one impurity lighter than CO2 as well as at least one impurity in the form of SO2 or SO3, the mixture is washed in a washing column (Q), dried in a drying unit (A) and separated by partial condensation (15), a portion (25B) of the regeneration gas (25) of the drying unit being sent directly to the washing column (Q) in gaseous form.

Description

[0001] Method and apparatus for separating a mixture containing CO2 by partial condensation

[0002] Processes for capturing and purifying CO2 from the flue gases of fossil-fueled electricity production units or cement or lime production units include steps for managing impurities and contaminants. These impurities can be removed at different points in the process to be recycled to another point where they will be removed. The invention provides a solution for removing certain impurities efficiently. State of the art

[0003] There are many techniques for removing and removing impurities in CO2 capture processes. Typically, they are in the following order:

[0004] 1. Flue gas inlet water washing to remove some of the dust and water-soluble impurities such as strong acids (e.g. SO3, HCl, HF). The impurities are then discharged into the liquid condensates generated.

[0005] 2. Washing with a basic solution (e.g. sodium hydroxide) to break down acid molecules (e.g. strong acids and SO2). The impurities are then removed in the liquid condensates generated.

[0006] 3. Filtration of residual dust. The dust is evacuated by gravity.

[0007] 4. Successive compression and cooling of the fumes allowing the partial reduction of soluble molecules in the acid condensates generated during cooling in the intermediate heat exchangers or in the exchangers at the outlet of the compression stage, such as nitric acid for example. The impurities are then evacuated in the acid liquid condensates generated.

[0008] 5. Adsorption drying of compressed flue gases allowing at least partial stopping of adsorbed molecules such as water but also many other compounds such as SO2, BTEX, PAHs etc. The adsorbed impurities are evacuated with the generation gas which is recycled upstream of the dryer, in the compression and cooling chain. The impurities are then evacuated in the previous acidic liquid condensates. EP2404658 describes the sending of the NO2-enriched regeneration gas to the combustion. As there is an equilibrium NO2 content during combustion, sending the NO2-enriched gas there will imply that less NO2 is generated during combustion, which therefore allows them to be eliminated from the overall loop. But this effect is undergone because it results from the flame temperature and the composition in the combustion. In addition, this process requires a very long recycling line.The combustion process is affected since the flow rate in the combustion process is increased and the energy consumed as well (going through the combustion process there is more pressure loss compensated by a smoke fan) etc.

[0009] Problem solved by the invention

[0010] Some molecules are stopped by the adsorption dryer but are not necessarily soluble (or only slightly so) in the acid condensates generated during the flue gas compression and cooling steps. In this case, the state-of-the-art scheme, for example, that of WO2014 / 009449, is not suitable. Here the regeneration gas is returned to the flue gas compressor. The impurities in the regeneration gas will then follow a cycle of stopping (adsorption) and recycling (regeneration and return), then concentrating in the loop to high levels. This may involve:

[0011] • parasitic chemical reactions generating new impurities harmful to the process. For example, high concentrations of SO2 can be transformed into SO3 by reaction with oxygen and / or NOx. This SO3 is then present downstream of the washing with basic solution, therefore in the compression chain, requiring a more restrictive selection of materials.

[0012] • a breakthrough of the molecules concerned at the outlet of the dryer, the maximum adsorption capacity being reached. These impurities will therefore propagate in the rest of the process, generating other potential problems such as blockage of the cryogenic part for example.

[0013] Description of the invention

[0014] The invention consists of:

[0015] • increase the processing capacity of the water washing or basic solution washing steps • install a regeneration gas bypass valve at the dryer outlet in order to send at least part of the regeneration gas upstream of the water washing or basic solution washing step

[0016] • potentially perform an impurity analysis on the regeneration gas and regulation of the opening of the previous bypass valve based on the measured content.

[0017] In this way, if an impurity tends to concentrate in the regeneration loop (being stopped by the dryer) and this impurity is at least partially removed during the basic solution washing step, it will be removed more easily from the overall system via the washing condensates and its concentration will then be limited.

[0018] A notable example is the SO2 molecule. Indeed, in the case of a thorough but not absolute reduction during the basic solution washing step, levels of several ppmv or even tens of ppmv are possible at the inlet of the compression and cooling steps. Since the condensate conditions are acidic, the residual SO2 will be very little reduced and will therefore reach the dryer. In the dryer, a very significant portion of this SO2 will be stopped and therefore sent to regeneration. If this regeneration gas is recycled upstream of compression, the SO2 will therefore concentrate to levels leading to a breakthrough through the dryer or even to levels promoting oxidation to SO3. If at least part of the regeneration gas is sent upstream of the basic solution washing step, the SO2 will be largely evacuated, thus limiting their concentration in the loop.

[0019] It is also possible to open the bypass valve only when the concentration of impurities to be removed is high and to close it when it is low. This saves compression energy when the regeneration is recycled intermediate to the compression stage or even at the outlet of the compression stage before the final cooling.

[0020] In the case of the invention, the process where the gas is sent aims to remove the molecule in question in a controlled manner. The SO2 are sent in part to where they are specifically removed by a chemical reaction mechanism with the scrubbing liquid. Sending to the scrubbing column is necessary to avoid accumulating SO2 to infinity. The invention makes it possible to purify a gas mixture containing at least 10 mol% of carbon dioxide, or even at least 50 mol% of carbon dioxide, or even at least 75 mol% of carbon dioxide to produce a flow enriched in carbon dioxide compared to the mixture. The percentages cited relate to the dry base gas mixture, which very often contains water.

[0021] All percentages relating to purities in this document are molar percentages.

[0022] Cryogenic CO2 capture and purification uses partial condensation of CO2, which can be supplemented by one or more distillations and / or solidification to increase the CO2 purity of the final product. To ensure these partial condensations and distillations, the gases to be purified must be compressed, dried and then cooled to form a liquid phase enriched in CO2 and a gas phase enriched in non-condensable gases, which will be separated in one or more partial condensation pots. Thanks to this type of process, capture efficiencies of between 80 and 95% are achievable. The term "non-condensable gases" refers to gases that condense at lower temperatures than that at which CO2 condenses and may include nitrogen, oxygen, methane, carbon monoxide, and argon.

[0023] In some cases, the CO2 content of the gas to be partially condensed is increased by at least one adsorption or permeation separation step.

[0024] Non-condensable gases are usually heated against the gases to be purified, which cool before being released into the atmosphere. Before being released into the ambient air, they can also be used to regenerate the capture unit's dryers.

[0025] In order to maximize the CO2 capture efficiency, membranes can also be used on the non-condensable gases coming from the partial condensation pot(s). A method of this kind is known from EP-A-2404656.

[0026] Two important parameters allow the sizing of membranes and quantification of their performance: the efficiency per membrane and the CO2 selectivity. The higher the CO2 efficiency, the less it will be necessary to add membrane modules to increase the overall efficiency of the unit. The initial investment is then reduced. The higher the CO2 selectivity, the less other gases will pass through the membrane. High CO2 selectivity makes it possible to obtain a purer CO2 permeate and to reduce the energy consumption of the gas compressor to be purified.

[0027] The membrane used can operate at ambient (not shown) or subambient temperature, as shown in Figure 1. The preferred solution is to use the membrane separation units to separate a partially heated gas, either at the hot end of the exchanger 12, preferably with a cold bypass circuit, or at the intermediate outlet of the exchanger 12.

[0028] To optimize both the efficiency and selectivity of the membranes, using them at subambient temperatures (or even at temperatures <-10°C) can nevertheless prove relevant. A process of this type is described in WO-A- 2014 / 009449 and in WO-A-2014 / 009643. They will thus be placed directly downstream of the partial condensation pot(s) with or without expansion of the non-condensable gases. If the temperature of the pot is too low to ensure the proper functioning and especially the feasibility of the membranes, the non-condensable gases can be partially heated before sending them to the membranes, up to temperatures between -45 and -10°C. However, when putting these membranes into operation, it is necessary to control the cooling of these membranes gradually: in fact, a direct supply of cold gas to the membranes could induce strong mechanical stresses on this equipment and lead to their degradation.

[0029] Furthermore, it is necessary to ensure good regulation of the operating conditions of these membranes (particularly temperature) during normal operation to ensure optimal performance and also ensure the integrity of the materials that make up the membranes.

[0030] According to one subject of the invention, there is provided a method for separating a mixture containing CO2 by partial condensation, the mixture containing at least one impurity lighter than CO2 as well as at least one impurity chosen from the list: SO2, SO3, the method comprising the following steps: i) washing the mixture in a washing column allowing the partial reduction of the at least one impurity chosen from the list: SO2, SO3, ii) compression of the washed mixture, iii) cooling of the compressed washed mixture, iv) drying and purification of the at least one impurity chosen from the list: SO2, SO3, of the washed, compressed and cooled mixture in a temperature-swing adsorption unit which is regenerated by a regeneration gas, v) separation of the dried and purified mixture in the adsorption unit at least by at least one partial condensation step and optionally by distillation and / or adsorption and / or solidification,partial condensation producing a gas depleted in carbon dioxide compared to the dried and purified mixture and a liquid enriched in carbon dioxide compared to the dried and purified mixture, and vi) recycling a portion of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, to the inlet of the washing column to be washed there, the regeneration gas being a) the gas depleted in carbon dioxide compared to the dried and purified mixture produced by partial condensation, or b) formed by separating the gas depleted in carbon dioxide compared to the dried and purified mixture produced by partial condensation and / or by at least one adsorption and / or permeation step or c) a portion of a product rich in carbon dioxide formed by separating the liquid enriched in carbon dioxide by distillation and / or adsorption and / or solidification,optionally after a vaporization or sublimation step vii) the regeneration gas having carried out the regeneration containing CO2, water and at least one impurity chosen from the list: SO2, SO3, water and at least one impurity coming from the temperature swing adsorption unit and viii) recycling of a part of the regeneration gas containing the water and at least one impurity chosen from the list: SO2, SO3, is sent downstream of the washing column to be compressed with the mixture washed in step ii) and / or cooled with the compressed washed mixture in step iii).,

[0031] According to other optional aspects:

[0032] • the at least one other part of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, is sent to be compressed with the washed mixture in step ii) and / or cooled with the washed mixture compressed in step iii) has a larger flow rate than the part of the regeneration gas sent to the inlet of the tower.

[0033] • the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas downstream of the adsorption unit is measured and at least part of the regeneration gas is sent to the inlet of the washing column if, preferably only if, the content is above a first threshold.

[0034] • the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas downstream of the adsorption unit is measured and at least part of the regeneration gas is sent to be compressed with the washed mixture in step ii) and / or cooled with the washed mixture compressed in step iii) if the content is below the first threshold or below a second threshold lower than the first threshold.

[0035] • the washing of step i) is carried out in a gas / liquid contactor with a basic washing liquid containing NaOH and / or Na2CO3 and / or NaHCO3.

[0036] • the washed, compressed and purified mixture is separated first by adsorption and then by partial condensation, a CO2-enriched gas being produced by separating the mixture by adsorption and this CO2-enriched gas being partially condensed and separated in at least one phase separator.

[0037] • the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas downstream of the adsorption unit is measured and at least part of the regeneration gas is sent to the air if, preferably only if, the content is above a third threshold, higher than the first threshold.

[0038] • the regeneration gas is formed by membrane separation of the carbon dioxide depleted gas from the dried and purified mixture to produce a permeate having a richer carbon dioxide content than the carbon dioxide depleted gas.

[0039] • the part of the regeneration gas sent to the inlet of the washing column constitutes between 5 and 25% of the regeneration gas having carried out the regeneration.

[0040] • the part of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, is sent downstream of the washing column to be compressed with the mixture washed in step ii) and / or cooled with the washed mixture compressed in step iii) constitutes between 75 and 95% of the regeneration gas having carried out the regeneration

[0041] • the washed mixture is compressed by a multi-stage compressor and the other part of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, is sent downstream of the washing column and upstream of the compressor or upstream of at least one stage of the compressor.

[0042] • the washed mixture is compressed by a multi-stage compressor and the other part of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, is sent between the last stage of the compressor and the last cooler of the compressor.

[0043] • the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3 is at a pressure between 5 and 25 bars abs.

[0044] According to another object of the invention, there is provided an apparatus for separating a mixture containing CO2 by partial condensation, the mixture containing at least one impurity lighter than CO2 as well as at least one impurity chosen from the list: SO2, SO3 comprising: a washing column, means for sending the mixture to be washed in the washing column allowing the partial reduction of the at least one impurity chosen from the list: SO2, SO3, a compressor connected to the washing column to compress the washed mixture, means for cooling the compressed washed mixture in the compressor, a temperature-swing adsorption unit, means for sending the compressed and cooled mixture to be dried and purified of the at least one impurity chosen from the list: SO2, SO3, to the temperature-swing adsorption unit, means for sending a regeneration gas to the temperature-swing adsorption unit,at least one phase separator for separating the dried and purified mixture in the adsorption unit at least by at least one partial condensation step and optionally means of separation by distillation and / or adsorption and / or solidification, the at least one phase separator being capable of producing by partial condensation a gas depleted in carbon dioxide compared to the dried and purified mixture as well as a liquid enriched in carbon dioxide compared to the dried and purified mixture and a pipe connected to the temperature-swing adsorption unit for recycling a portion of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, to the inlet of the washing column to be washed there, means for using as the regeneration gas a) the gas depleted in carbon dioxide compared to the dried and purified mixture of the at least one phase separator,or b) the gas formed by separating the carbon dioxide-depleted gas from the dried and purified mixture produced by partial condensation and / or by at least one adsorption and / or permeation step or c) a portion of a carbon dioxide-rich product formed by separating the carbon dioxide-enriched liquid by distillation and / or adsorption and / or solidification, optionally after a vaporization or sublimation step and means for sending a portion of the regeneration gas containing water and the at least one impurity chosen from the list: SO2, SO3 to be compressed with the washed mixture in step ii) and / or cooled with the compressed washed mixture in step iii).,

[0045] According to other optional aspects, the apparatus comprises:

[0046] • means for measuring the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas downstream of the adsorption unit

[0047] • means for varying the flow rate of the part of the regeneration gas sent to be compressed with the washed mixture in step ii) and / or cooled with the washed mixture compressed in step iii) as a function of the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas downstream of the adsorption unit.

[0048] • means for separation by distillation, means for using as the regeneration gas a portion of a carbon dioxide-rich product formed by separating the carbon dioxide-enriched liquid by distillation, these means comprising a vaporizer for vaporizing the carbon dioxide-enriched liquid to form the regeneration gas.

[0049] • means for sending a portion of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3 to the atmosphere The invention will be described in more detail with reference to the figures where [FIG.1] represents a separation process according to the invention.

[0050] [FIG.2] represents the part of a separation process according to the invention which is carried out at a temperature above 0°C.

[0051] [FIG.3] represents another separation method according to the invention.

[0052] In the variant of figure 1, the device comprises a single multi-fluid heat exchanger, called main exchanger 13.

[0053] A gas mixture 1 containing carbon dioxide (for example containing at least 10 mol% carbon dioxide, or even at least 50 mol% carbon dioxide, or even at least 75 mol% carbon dioxide), moisture and at least one other gas, chosen from the list: hydrogen, nitrogen, oxygen, argon, carbon monoxide is sent to a five-stage compressor 5A, 5B, 5C, 5D, 5E, stage 5A being followed by cooler R1, stages 5B and 5C by cooler R2 and stages 5D and 5E by a cooler R3. After being cooled by the final cooler R3, the mixture 7 is stripped of water by the temperature swing adsorption unit A to form the dried stream 9. The mixture is stripped in bed 10 during the regeneration of bed 12 and vice versa. The dried flow 9 is compressed in the compressor 5F, cooled by the cooler R4, partially condenses in the plate and fin heat exchanger 13 and is sent to the phase separator 15.

[0054] The first system operating at low temperature here comprises a single phase separator 15, as well as a stripping column 31, also known as a stripping column.

[0055] Alternatively, the gas from a first phase separator may be cooled in a heat exchanger and partially condense to form a two-phase flow. This two-phase flow may be sent to a second phase separator. The liquids from both separators may feed the top of column 31.

[0056] The overhead gas 33 from column 31 is heated in heat exchanger 13 and is recompressed in compressor 5F with flow rate 9. The bottom liquid 35 from column 31 is divided into two. One part 37 vaporizes in heat exchanger 13 and is divided into two. The other part 43 of the bottom liquid 35 is expanded in a valve 36, is sent to exchanger 13, vaporized, sent to a compressor C5 to C8, is cooled by cooler R8, is condensed by cooler R9 and then pumped by pump P to form a pressurized liquid product rich in carbon dioxide.

[0057] A portion 41 of the flow 37 is sent between stages C5, C6. The remainder 39 of the flow 37 is heated to the hot end of the exchanger 13 and is returned to the column 31 in the tank, without having been cooled, to provide reboiling heat.

[0058] The overhead gas 19 from the phase separator 15 is enriched with non-condensable gases, for example hydrogen, carbon monoxide, nitrogen, argon or oxygen. This gas may come from a second phase separator as described above, if there is one or from both phase separators including the separator 15. This gas is sent to a membrane separation unit 21 producing a permeate 25 enriched in CO2 and a non-permeate 23 depleted in CO2. The non-permeate 23 will be strongly heated before being sent to the atmosphere. The non-permeate 23 may be expanded in a turbine after heating in a heater.

[0059] The flow supplying the membrane system M is here at a temperature below -10°C. However, it is not essential that the membrane system M operates at a temperature other than ambient temperature.

[0060] The permeate 25, enriched in carbon dioxide compared to the flow 19, is heated in E1, E2 and used to regenerate the beds 10, 12 of adsorbent A, in turn. The permeate 25 leaving the bed of adsorbents is enriched in water but also in SO2 and / or SO3 accumulated in the bed 10, 12 and is sent at least in part to a washing tower Q operating at no more than 1.5 bar abs by the flow 25B in gaseous form to be purified there. Sending the flow 25B just upstream of the tower Q makes it possible to reduce the length of the recycle line, to reduce the impact on the upstream process (with lower flow in the combustion process which could be bottlenecked) and lower energy consumption (by passing through the combustion process there is more pressure loss compensated by a smoke fan).

[0061] Flow rate 25B preferably constitutes between 5 and 25% of the permeate flow rate leaving the adsorbent bed with a pressure between 5 and 25 bar abs. Flow rate 25A preferably constitutes between 75 and 95% of the permeate flow rate leaving the adsorbent bed with a pressure between 5 and 25 bar abs. Flow rate 25A is sent between stages 5A and 5B of the compressor, which avoids oversizing tower Q and avoids losing the regeneration gas pressure.

[0062] Flow rate 25B has a lower flow rate than flow rate 25A.

[0063] Figure 2 shows in more detail the compressor 5A to 5E of Figure 1, as well as the adsorbent beds 10, 12 of the adsorption unit A, the compressor being preceded by a washing tower Q with an alkaline liquid. The tower Q in which the washing takes place is a gas / liquid contactor with a basic washing liquid preferably containing NaOH and / or Na2CO3 and / or NaHCO3.

[0064] A gas mixture G containing carbon dioxide, carbon (for example containing at least 10 mol% carbon dioxide, or even at least 50 mol% carbon dioxide, or even at least 75 mol% carbon dioxide), at least one component lighter than carbon dioxide, and SO2 and / or SO3 is sent to tower Q operating at a maximum of 1.5 bar abs where it is washed, producing condensates C in the bottom of the tower and a gas 1 at the top of tower Q, enriched in CO2 compared to mixture 1 and depleted in SO2 and / or SO3 but still containing it. Gas 1 is filtered by a filter F, compressed by the stages in series 5A to 5E of compressor 5, and is sent to adsorption unit A to be dried, forming a dried gas 9, knowing that a portion of the water W has already been removed by the compression stages. In the adsorption unit, a very significant portion of this SO2 and / or SO3 will be stopped and therefore sent to the regeneration gas 25.

[0065] The permeate 25, having been used to regenerate the beds of unit A, leaves it loaded with water and can be sent as flow 25A to compressor 5, for example between stages 5A and 5B or between stage 5E and cooler 7 and / or as flow 25B through valve V at the inlet of tower Q while being mixed with gas G. If this regeneration gas 25 is recycled only upstream of compression (one of stages 5A to 5E), the SO2 will therefore concentrate to levels leading to a breakthrough through adsorption unit A, or even to levels promoting oxidation to SO3. If at least part of the regeneration gas 25 is sent upstream of the washing step Q with the basic solution, the SO2 will be strongly evacuated, thus limiting their concentration in the loop.

[0066] The flow rate 25B preferably constitutes between 5 and 25% of the permeate flow rate leaving the adsorbent bed with a pressure between 5 and 25 bar abs. The flow rate 25A preferably constitutes between 75 and 95% of the permeate flow rate leaving the adsorbent bed with a pressure between 5 and 25 bar abs.

[0067] Flow rate 25B has a lower flow rate than flow rate 25A.

[0068] It is therefore possible to open valve V only when the concentration of an impurity to be removed, for example SO2, is high and to close it when it is low. This saves compression energy when the regeneration is recycled intermediate to the compression stage or even at the outlet of the compression stage before the last cooling.

[0069] For example, if the impurity content, for example SO2, of the permeate 25 having regenerated the adsorption unit A is below a threshold, all of the permeate 25 is sent to the compressor 5 at a point between two of the stages or after the last stage and the last cooler. If the content of this impurity, for example SO2, in the permeate having regenerated the adsorption unit A is above a threshold, which may be the threshold mentioned before or a threshold higher than this threshold, at least a part of the permeate 25 is sent as flow 25B in gaseous form to the bottom of the tower Q to be washed there, the remainder (if any) of the permeate 25 being sent to the compressor as for the previous case.

[0070] Figure 3 differs from Figure 1 in that the gas mixture G contains between 15 and 50 mol% CO2 9 as well as at least one impurity which is nitrogen. The gas 9 dried in the temperature swing adsorption unit A is separated in an adsorption unit 16, of the pressure swing type or a permeation apparatus to form a higher pressure stream 14 depleted in CO2 and enriched in nitrogen and a lower pressure stream 11 enriched in CO2 and depleted in nitrogen. It is this flow 11, preferably compressed, which is partially condensed in the heat exchanger 13 and separated in the phase separator 15, forming a liquid 17 enriched in CO2 to feed the column 21 and a gas depleted in CO2 25 compared to the mixture 1. The gas 25 is used to regenerate the adsorption unit A and comes out loaded with water and SO2 and / or SO3. It is at a pressure between 5 and 25 bars abs.Flow rate 25B preferably constitutes between 5 and 25% of the permeate flow rate leaving the adsorbent bed with a pressure between 5 and 25 bar abs. Flow rate 25A preferably constitutes between 75 and 95% of the permeate flow rate leaving the adsorbent bed with a pressure between 5 and 25 bar abs. Flow rate 25A is sent after the last stage of the compressor and upstream of the last cooler.

[0071] As for Figure 1, this Figure 3 presents the risk of accumulation of SO2 and / or SO3 in the adsorption unit A, if at least part of the gas 25 is not sent at least occasionally to the washing tower Q, as explained in relation to Figure 2, which applies to both Figure 3 and Figure 1.

[0072] A fraction of the regeneration gas loaded with water and SO2 and / or SO2 can be sent to the air to avoid too much accumulation of impurities.

[0073] In Figures 1 and 3, a portion of the product 35 can serve as regeneration gas for the adsorption unit A after vaporization in the exchanger 13 in a dedicated vaporizer.

Claims

AMENDED CLAIMS received by the International Bureau on May 2, 2025 (02.05.2025) 1. A method for separating a mixture containing CO2 by partial condensation, the mixture (G) containing at least one impurity lighter than CO2 as well as at least one impurity chosen from the list: SO2, SO3, the method comprising the following steps: i) washing the mixture in a washing column (Q) allowing the partial reduction of the at least one impurity chosen from the list: SO2, SO3 ii) compression (5A, 5B, 5C, 5D, 5E) of the washed mixture iii) cooling (R2, 53) of the compressed washed mixture, iv) drying and purification of the at least one impurity chosen from the list: SO2, SO3, of the washed, compressed and cooled mixture in a temperature-swing adsorption unit (A) which is regenerated by a regeneration gas (25) v) separation of the dried and purified mixture in the adsorption unit at least by at least one partial condensation step (15) and optionally by distillation (31) and / or adsorption and / or solidification,partial condensation producing a gas (19, 25) depleted in carbon dioxide compared to the dried and purified mixture as well as a liquid (17) enriched in carbon dioxide compared to the dried and purified mixture and vi) recycling a portion (25B) of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, to the inlet, preferably directly to the inlet, of the washing column to be washed therein, the regeneration gas being a. the gas (25) depleted in carbon dioxide compared to the dried and purified mixture produced by partial condensation, or b. formed by separating the gas (19) depleted in carbon dioxide compared to the dried and purified mixture produced by partial condensation and / or by at least one adsorption and / or permeation step or c. a portion of a carbon dioxide-rich product (17, 35) formed by separating the carbon dioxide-enriched liquid (35, 37, 43) by distillation and / or adsorption and / or solidification,possibly after a vaporization or sublimation step, vii) the regeneration gas having carried out the regeneration containing CO2, water and the at least one impurity chosen from the list: SO2, SO3, and the at least one impurity chosen from the list comes from the temperature swing adsorption unit and viii) recycling another part (25A) of the regeneration gas containing the water and the at least one impurity chosen from the list: SO2, SO3 downstream of the washing column to be compressed with the mixture washed in step ii) and / or cooled with the compressed washed mixture in step iii).

2. Method according to one of claims 1 in which the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas (25) downstream of the adsorption unit (A) is measured and at least part of the regeneration gas (Q) is sent to the inlet of the washing column if, preferably only if, the content is above a first threshold.

3. Method according to one of claims 1 or 2 in which the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas (25) downstream of the adsorption unit (A) is measured and the part of the regeneration gas is sent to be compressed with the washed mixture in step ii) and / or cooled with the washed mixture compressed in step iii) if the content is below the first threshold or below a second threshold lower than the first threshold.

4. Method according to one of the preceding claims in which the washing of step i) is carried out in a gas / liquid contactor (Q) with a basic washing liquid (N) containing NaOH and / or Na2CO3 and / or or NaHCO3.

5. Method according to one of the preceding claims in which the washed, compressed and purified mixture is separated first by adsorption and then by partial condensation, a CO2-enriched gas being produced by separating the mixture by adsorption and this CO2-enriched gas being partially condensed and separated in at least one phase separator.

6. Method according to one of the preceding claims, in which the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas (25) downstream of the adsorption unit (A) is measured and at least part of the regeneration gas is sent to the air if, preferably only if, the content is above a third threshold, higher than the first threshold.

7. Method according to one of the preceding claims in which the regeneration gas is formed by membrane separation (21) of the depleted gas in carbon dioxide (19) relative to the dried and stripped mixture to produce a permeate (25) having a richer carbon dioxide content than the carbon dioxide depleted gas.

8. Method according to one of the preceding claims in which the part of the regeneration gas sent to the inlet of the washing column constitutes between 2 and 25% of the regeneration gas having carried out the regeneration.

9. Method according to one of the preceding claims in which the washed mixture is compressed by a multi-stage compressor and the other part (25A) of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, is sent downstream of the washing column and upstream of the compressor or upstream of at least one stage of the compressor.

10. Method according to one of the preceding claims in which the washed mixture is compressed by a multi-stage compressor and the other part (25A) of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, is sent between the last stage of the compressor and the last cooler of the compressor.

11. Method according to one of the preceding claims in which the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3 is at a pressure between 5 and 25 bars abs.

12. Apparatus for separating a mixture containing CO2 by partial condensation capable of operating according to the method of claim 1, the mixture containing at least one impurity lighter than CO2 as well as at least one impurity chosen from the list: SO2, SO3 comprising: a washing column (Q), means for sending the mixture (G) to be washed in the washing column allowing the partial reduction of the at least one impurity chosen from the list: SO2, SO3, a compressor (5A, 5B, 5C, 5D) connected to the washing column to compress the washed mixture, means (R1, R2, R3) for cooling the washed mixture compressed in the compressor, a temperature-swing adsorption unit (A), means for sending the compressed and cooled mixture (7) to be dried and purified of the at least one impurity chosen from the list: SO2, SO3, to the temperature-swing adsorption unit,means for sending a regeneration gas (25) to the temperature-swing adsorption unit, at least one phase separator (15) for separating the dried and purified mixture in the adsorption unit at least by at least one partial condensation step and, optionally means of separation by distillation (31) and / or adsorption and / or solidification, the at least one phase separator being capable of producing by partial condensation a gas depleted in carbon dioxide (19) compared to the dried and purified mixture as well as a liquid (17) enriched in carbon dioxide compared to the dried and purified mixture and a pipe connected to the temperature-swing adsorption unit to recycle a portion (25B) of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3, to the inlet of the washing column to be washed there, means for using as the regeneration gas: a) the gas depleted in carbon dioxide compared to the dried and purified mixture of the at least one phase separator,or b) a gas (25) formed by separating the carbon dioxide-depleted gas from the dried and purified mixture produced by partial condensation and / or by at least one adsorption and / or permeation step (21) or c) a portion of a carbon dioxide-rich product (17, 35) formed by separating the carbon dioxide-enriched liquid by distillation and / or adsorption and / or solidification, optionally after a vaporization or sublimation step and means for sending a portion (25A) of the regeneration gas containing water and the at least one impurity chosen from the list: SO2, SO3 downstream of the washing column to be compressed with the washed mixture in step ii) and / or cooled with the compressed washed mixture in step iii)., 13. Apparatus according to claim 12 comprising means for measuring the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas (25) downstream of the adsorption unit (A) and means for varying the flow rate of the part (25A) of the regeneration gas sent to be compressed with the washed mixture in step ii) and / or cooled with the washed mixture compressed in step iii) as a function of the content of at least one impurity chosen from the list: SO2, SO3, in the regeneration gas downstream of the adsorption unit.

14. Apparatus according to claim 12 or 13 comprising the means for separating by distillation (31), the means for using as the regeneration gas a part of a product (17, 35) rich in carbon dioxide formed by separating the liquid (35, 37, 43) enriched in carbon dioxide by distillation, these means comprising a vaporizer (13) for vaporizing the carbon dioxide enriched liquid to form the regeneration gas.

15. Apparatus according to one of claims 12 to 14 comprising means for sending a portion of the regeneration gas containing water and at least one impurity chosen from the list: SO2, SO3 to the atmosphere.

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