System for treating gases laden with carbon dioxide
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- GAZTRANSPORT & TECHNIGAZ SA
- Filing Date
- 2026-01-13
- Publication Date
- 2026-07-30
Smart Images
Figure FR2026050020_30072026_PF_FP_ABST
Abstract
Description
[0001] I
[0002] DESCRIPTION
[0003] Title: Carbon Dioxide-Laden Gas Treatment System
[0004] The present invention relates to the field of gases emitted by consumers, and more particularly to the methods implemented to treat such gases.
[0005] When a carbon dioxide (CO₂) emission source is in operation, carbon dioxide-laden gases are generated. These gases are generally released into the atmosphere, causing environmental damage, particularly due to their carbon dioxide content. It is therefore advisable to treat the carbon dioxide-laden gases from an emission source in order to extract the carbon dioxide for later use or commercialization, or for deep geological disposal.
[0006] The emission source is, for example, a reforming unit. Reforming units are notably used in applications for producing hydrogen from natural gas, either through steam methane reforming (SMR) or autothermal reforming (ATR). In the absence of carbon dioxide capture during these applications, the hydrogen produced is called "grey hydrogen." To reduce the carbon footprint of such hydrogen production, it is known to capture the carbon dioxide in the gases emitted by the reforming section; this is then referred to as "blue hydrogen." In steam methane reforming, the reforming unit consists of a combustion section and a reforming section, separate from each other, with the gases to be treated originating primarily from the reforming section.In the context of autothermal remelting, there is no distinction between combustion and reforming.
[0007] The present invention falls within this context by proposing a system for treating gas emitted by a reforming unit, by capturing the carbon dioxide contained in these gases in order to produce blue hydrogen.The present invention thus has as its main object a system for treating gases charged with carbon dioxide, comprising a reforming unit intended to be supplied with natural gas and comprising at least one reforming device emitting the gases charged with carbon dioxide, the treatment system comprising at least one drying unit, a unit for separating dihydrogen present in the gases charged with carbon dioxide and a carbon dioxide capture unit comprising at least one carbon dioxide condensation device, the treatment system being configured so that the condensation device is cooled using liquefied natural gas, the treatment system comprising a conduit configured to bring the liquefied natural gas from the carbon dioxide capture unit to the reforming unit.
[0008] According to an optional feature of the invention, the reforming unit is a steam reforming unit of methane, the reforming unit comprising the reforming device configured to emit carbon dioxide-laden gases and a combustion device.
[0009] According to an optional feature of the invention, the reforming unit is an autothermal reforming unit comprising the reforming device.
[0010] The treatment system according to the invention enables the capture of carbon dioxide present in gases emitted by a reforming unit. The gases emitted by the reforming unit are rich in carbon dioxide and under pressure. When the reforming unit is a steam reforming unit of methane comprising both a reforming device and a combustion device, the carbon dioxide capture occurs on the exhaust gases emitted by the reforming device. The treatment system enables the production of blue hydrogen, this hydrogen being produced within the reforming unit during a reaction of natural gas with steam. The hydrogen is therefore, along with carbon dioxide, present in a stream of various gases emitted by the reforming device. The hydrogen is extracted from the gases emitted by the reforming device using a hydrogen separation unit, for example, by adsorption within this hydrogen separation unit.The dihydrogen separation unit allows the separation of dihydrogen on the one hand and other gases contained in gases charged with carbon dioxide on the other hand.
[0011] Carbon dioxide is extracted from the gases emitted by the reforming unit using a carbon dioxide capture unit, here cryogenically within a condensing unit. This condensing unit is advantageously cooled, either directly or indirectly depending on the embodiment, using liquefied natural gas (LNG) which is also used to power the reforming unit. In other words, the LNG used for cryogenic carbon dioxide capture is returned, via a pipeline from the processing system, to the reforming unit to supply it, at least partially, with fuel. This allows the LNG to be reused within the processing system, as it has been at least partially heated by the carbon dioxide capture step.The energy required to evaporate the natural gas before it enters the reforming unit can also be reduced, thanks to the calories collected during the carbon dioxide capture stage.
[0012] According to an optional feature of the invention, the treatment system includes a return line connecting the dihydrogen separation unit to the reforming unit.
[0013] This return line allows for the reuse of at least some of the hydrogen produced by the reforming unit within that same reforming unit. When the reforming unit is a steam methane unit, the return line connects the separation unit to the combustion device to supply it.
[0014] According to an optional feature of the invention, the carbon dioxide capture unit is arranged downstream of the dihydrogen separation unit in a direction of flow of gases charged with carbon dioxide.
[0015] In other words, the hydrogen separation unit is located between the reforming unit and the carbon dioxide capture unit. Thus, the carbon dioxide-laden gases from the reforming unit undergo successive hydrogen removal followed by carbon dioxide removal. Therefore, the same gases circulate within both the hydrogen separation unit and the carbon dioxide capture unit. This ensures that the hydrogen produced is "blue" hydrogen.
[0016] The dihydrogen separation unit is located between the drying unit and the carbon dioxide capture unit.
[0017] According to an optional feature of the invention, the processing system includes at least one liquefied natural gas storage tank and a feed line connecting the storage tank to the reforming unit.
[0018] The storage tank provides a reserve of fuel to supply the reforming unit. Liquefied natural gas flows from the storage tank to the reforming unit via a feed line, which may also carry various components to supply the natural gas at the appropriate temperature and pressure.
[0019] According to an optional feature of the invention, the reforming unit comprises a combustion device, the feed line including a first branch connected to the combustion device and a second branch parallel to the first branch and connected to the reforming device. The reforming unit is here a steam reforming unit for methane. The feed line then divides into two parallel branches, each dedicated to one of the devices forming the reforming unit. The presence of two branches allows for independent regulation of the natural gas flow received respectively by the combustion device and the reforming device. According to an optional feature of the invention, the pipeline extends from the condensing device to the reforming unit, the feed line including a bypass branch comprising at least the pipeline and a pass of the condensing device of the carbon dioxide capture unit.
[0020] Upstream of its separation into the first branch and the second branch which feed the reforming unit, the supply line has a branch off which helps to connect the storage tank to the condensation device.
[0021] In a first embodiment, the condensing device is directly cooled by liquefied natural gas from the storage tank. In this case, the liquefied natural gas is conveyed from the storage tank to the condensing device via the supply line and the bypass branch, it passes through a pass of the condensing device in which it exchanges heat with another pass channeling the gases laden with carbon dioxide, and then it returns to the reforming unit via the pipeline.
[0022] According to an optional feature of the invention, the treatment system includes an intermediate fluid loop comprising at least one heat exchanger and a pass of the condensation device, the supply line comprising a bypass branch comprising at least the conduit and a heat exchanger mat, the heat exchanger being configured to operate a heat exchange between the intermediate fluid and the bypass branch.
[0023] This is a second embodiment in which the condensing unit is indirectly cooled by liquefied natural gas (LNG). More specifically, the LNG exchanges heat with an intermediate fluid channeled in an intermediate fluid loop. This intermediate fluid then exchanges heat with the carbon dioxide-laden gases within the condensing unit. The intermediate fluid is thus cooled by the LNG and heated by the carbon dioxide-laden gases. The use of an intermediate fluid ensures that the carbon dioxide does not freeze within the condensing unit during its cooling by the LNG, which could potentially clog the unit. Furthermore, the use of an intermediate fluid provides a reserve of heat transfer fluid when the treatment system is started up.According to an optional feature of the invention, the processing system includes a liquefied natural gas connection terminal and a distribution line connecting the liquefied natural gas storage tank to the connection terminal.
[0024] At a connection terminal, or import terminal, liquefied natural gas (LNG) changes from a liquid to a gaseous state upon injection into a gas transmission network. The presence of a connection terminal within the processing system ensures the availability of LNG.
[0025] Depending on the embodiment variants, the supply line is connected to the distribution line or the supply line and the distribution line are both directly connected to the storage tank.
[0026] According to an optional feature of the invention, the carbon dioxide capture unit includes a device for pre-cooling the carbon dioxide-laden gases.
[0027] The pre-cooling device allows the temperature of the carbon dioxide-laden gases to be adjusted before they pass through the condensation unit. The pre-cooling device is therefore positioned between the hydrogen separation unit and the condensation unit.
[0028] According to an optional feature of the invention, the carbon dioxide capture unit includes at least one device for separating carbon dioxide from residual gases present in carbon dioxide-laden gases.
[0029] The separation device allows the carbon dioxide to be separated from residual gases at the outlet of the condensation device.
[0030] According to an optional feature of the invention, the separation device comprises a first separation device and a second purification device, the carbon dioxide capture unit including a pressure-reducing valve disposed between the first separation device and the second purification device. Separation in the first separation device occurs, for example, at a pressure of approximately 40 bar, while separation in the second purification device is carried out at a pressure of approximately 20 bar. "Approximately" here means plus or minus 10% of the pressure value. The presence of the pressure-reducing valve between the first separation device and the second purification device allows the gas to be reduced to a pressure suitable for the second purification device.
[0031] The carbon dioxide capture unit includes, for example, a first separation device allowing separation between liquid carbon dioxide and non-condensables and a second separation device or second purification device allowing the removal of impurities from the carbon dioxide.
[0032] According to an optional feature of the invention, the carbon dioxide capture unit includes a reboiler associated with the second purification device.
[0033] The reboiler is configured to heat the liquid phase of carbon dioxide present in the separation device in order to evaporate the light residual gases dissolved in it.
[0034] According to an optional feature of the invention, the treatment system includes a residual gas return line connecting the separation device to the reforming unit.
[0035] when the reforming unit is a steam reforming unit of methane, the residual gas return line connects the separation device to the combustion device.
[0036] According to an optional feature of the invention, the residual gas return line includes an additional pass of the condensation device of the carbon dioxide capture unit.
[0037] According to an optional feature of the invention, the treatment system includes a diversion line connected at one end to the residual gas return line and at a second end between the drying limit and the dihydrogen separation limit.
[0038] The diversion line is configured to return a portion of the residual gases to the dihydrogen separation unit.
[0039] According to an optional feature of the invention, the pre-cooling device of the carbon dioxide capture unit is configured to operate heat exchanges between the residual gases circulating in the return line and the gases loaded with carbon dioxide.
[0040] This waste gas return line allows the cooling of these waste gases to be used within the treatment system. The return line passes through at least the pre-cooling device, or in some embodiments, both the condensing and pre-cooling devices, in order to cool the carbon dioxide-laden gases. According to an optional feature of the invention, the treatment system includes a storage tank for carbon dioxide in liquid form. The storage tank is, for example, connected to an outlet of the separation device. It allows the carbon dioxide to be stored in liquid form at a pressure, for example, between 7 and 15 bar. The carbon dioxide is, for example, stored in the storage tank prior to being exported to a permanent storage site.
[0041] According to an optional feature of the invention, the treatment system includes a cooling device disposed between the second purification device and the storage tank.
[0042] The cooling system is configured to cool the liquid carbon dioxide to a temperature suitable for its storage within the storage tank.
[0043] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the accompanying drawings on the other hand, in which:
[0044] [Fig. 1] illustrates, schematically, a treatment system according to the invention according to a first embodiment, in which a condensation device of a carbon dioxide capture unit of the treatment system is directly cooled by liquefied natural gas;
[0045] [Fig, 2] illustrates, schematically, the treatment system according to the invention according to a second embodiment, in which the condensation device of the carbon dioxide capture unit is indirectly cooled by liquefied natural gas using an intermediate fluid loop;
[0046] [Fig. 3] illustrates, schematically, a close-up view of the carbon dioxide capture unit of the treatment system according to the first embodiment;
[0047] [Fig. 4] illustrates, schematically, a close-up view of the carbon dioxide capture unit of the treatment system according to the second embodiment;
[0048] [Fig. 5] illustrates, schematically, the treatment system according to the invention in a third embodiment.
[0049] The features, variations, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variations of the invention may include only a selection of features, described hereafter in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from prior art.
[0050] In the figures, elements common to several figures retain the same reference.
[0051] Figures 1 to 5 thus schematically illustrate a treatment system 1 for gases charged with carbon dioxide, respectively according to a first embodiment in figures 1 and 3, according to a second embodiment in figures 2 and 4, and according to a third embodiment in figure 5. The treatment system 1 is used in the production of so-called "blue dihydrogen", that is to say, it allows the capture of carbon dioxide during the production of dihydrogen.
[0052] The treatment system 1 includes a reforming unit 2. This reforming unit 2 is a steam reforming unit for methane in the first and second embodiments of Figures 1 to 4, and an autothermal reforming unit in the third embodiment of Figure 5. In the case of a reforming unit 2 corresponding to a steam reforming unit for methane, this reforming unit 2 consists of at least one combustion device 4, or combustion chamber, and a reforming device 6, or reforming reactor. In the case of a reforming unit 2 corresponding to an autothermal reforming unit, the reforming unit 2 lacks the combustion device 4, a combustion operation being associated with the reforming.
[0053] The reforming unit 2 is configured to form, from fuel, a gas stream containing, in particular, dihydrogen and carbon dioxide. The fuels used to power the reforming unit 2 are natural gas and steam. To supply the reforming unit 2, which corresponds to a steam reforming unit for methane, with water and air, the treatment system 1 includes a water supply line 8 and an air supply line 9. The water supply line 8 is specifically configured to supply the reforming device 6, while the air supply line 9 is configured to supply the combustion device 4. Alternatively, to power the reforming unit 2, which corresponds to an autothermal reforming unit, the treatment system 1 can include an oxygen supply line instead of the air supply line 9.To supply the reforming unit 2 with natural gas, the processing system 1 includes a liquefied natural gas (LNG) storage tank 10. The storage tank 10 is connected to a connection terminal 11 via a distribution line 13. The storage tank 10 is connected to the reforming unit 2 by a feed line 12, which carries the LNG from the storage tank 10 to the reforming unit 2. The feed line 12 is connected to the distribution line 13 extending to the connection terminal 11, but other embodiments are possible in which both the feed line 12 and the distribution line 13 are connected directly to the storage tank 10.The reforming unit 2 uses natural gas in the form of vapor as fuel, the supply line 12 carries a pump 14 and a vaporization device 16 configured to vaporize the liquefied natural gas before its delivery to the reforming unit 2. This pump 14 and this vaporization device 16 are arranged in this order on the supply line 12 between the storage tank 10 and the reforming unit 2.
[0054] As can be seen in Figures 1 and 2, in the case of the reforming unit 2, which corresponds to a steam reforming unit for methane, the combustion device 4 and the reforming device 6 are supplied separately with natural gas that has been vaporized within the vaporization device 16. Thus, between the vaporization device 16 and the reforming unit 2, the supply line 12 is split into a first branch 18 dedicated to supplying the combustion device 4 and a second branch 20 dedicated to supplying the reforming device 6. The first branch 18 and the second branch 20 extend in parallel within the treatment system 1. The first branch 18 and the second branch 20 can be equipped with valves to regulate the flow of the natural gas they channel.On the contrary, in Figure 5 the reforming device 6 of the reforming unit 2 corresponding to an autothermal reforming unit is supplied by a supply line 12 having a single branch; in other words, in the case of the autothermal reforming unit the supply line 12 is not split into two branches.
[0055] Within the reforming unit 2, a chemical reaction between natural gas from storage tank 10, water from water supply line 8, and air from air supply line 9 or oxygen from oxygen supply line leads to the formation of, among other gases, dihydrogen and carbon dioxide. More specifically, at the outlet of reforming unit 2, the reforming device 6 emits gases laden with carbon dioxide which also contain dihydrogen as well as residual quantities of methane, carbon monoxide, and water. The treatment system 1 according to the invention is designed to treat said gases, in particular to extract carbon dioxide and dihydrogen.
[0056] For this purpose, as illustrated here, the treatment system 1 comprises, in this order, a drying unit 22, a dihydrogen separation unit 24 and a carbon dioxide capture unit 26. Herein, "in this order" means that the carbon dioxide-laden gases emitted by the reforming device 6 of the reforming unit 2 pass successively through the drying unit 22, then the dihydrogen separation unit 24, and then the carbon dioxide capture unit 26. However, without departing from the scope of the invention, alternative embodiments could be imagined in which the order of the drying unit 22, the dihydrogen separation unit 24 and the carbon dioxide capture unit 26 would be different, provided that the carbon dioxide capture unit 26 is downstream of the dihydrogen separation unit 24.
[0057] The drying unit 22 is configured to extract water from the carbon dioxide-laden gases exiting the reforming device 6 of the reforming unit 2. To this end, the drying unit 22 includes at least one drying device 28. The drying device 28 is shown here upstream of the hydrogen separation unit 24 but could alternatively be located downstream of this hydrogen separation unit 24, the arrangement of the drying unit 22 depending on the operating specifications of the hydrogen separation unit 24 with respect to the water content of the carbon dioxide-laden gas stream it receives. In some embodiments, the drying unit 22 may optionally include a water condenser and a separator, not shown here, located upstream of the hydrogen separation unit 24.The drying device 28 of the drying unit 22 is shown here as a molecular sieve, but could also be a membrane or a cryogenic scrubber. The drying device 28 is configured to retain the water present in the carbon dioxide-laden gases. The drying unit 22 comprises, for example, two molecular sieves operating alternately. The water is then discharged from the molecular sieve and the drying unit 22 via a water discharge line 30 of the treatment system 1.
[0058] At the outlet of the drying unit 22, the dried carbon dioxide-laden gases are directed to the hydrogen separation unit 24. The hydrogen separation unit 24 is configured to extract the hydrogen present in the carbon dioxide-laden gases. The hydrogen separation unit 24 includes, for example, at least one pressure swing adsorption (PSA) module 32. The hydrogen separation unit 24 includes, for example, two pressure swing adsorption modules 32 operating alternately. In alternative embodiments, the hydrogen separation unit 24 may include a different number of pressure swing adsorption modules 32, for example, four.As illustrated in Figures 1, 2, and 5, the treatment system 1 includes a return line 34 configured to channel the dihydrogen produced within the reforming unit 2 and extracted from the carbon dioxide-laden gases. This return line 34 connects the dihydrogen separation unit 24 to the reforming unit 2. More specifically, in the case of the reforming unit 2, which corresponds to a steam reforming unit for methane, the return line 34 connects the pressure reversal adsorption module 32 to the first branch 18 of the feed line 12, which, as a reminder, is dedicated to supplying the combustion device 4 of the reforming unit 2. It is understood here that the dihydrogen extracted from the carbon dioxide-laden gases in the dihydrogen separation unit 24 is recycled back to the reforming unit 2 as fuel, if necessary for the combustion device 4.The treatment system 1 also includes a branch line 36 connected to the return line 34. This branch line 36 is configured to convey the dihydrogen separated from the carbon dioxide-laden gases out of the treatment system 1.
[0059] At the outlet of the hydrogen separation unit 24, the carbon dioxide-laden gases, now free of hydrogen, are directed to the carbon dioxide capture unit 26, which is particularly visible in Figures 3 and 4. The carbon dioxide capture unit 26 is configured to extract the carbon dioxide present in the carbon dioxide-laden gases emitted by the reforming device 6 of the reforming unit 2. The carbon dioxide capture unit 26 includes a compression device 38. This compression device 38 is, for example, a multi-stage compression device comprising alternating heat exchangers and compressors. The compression device 38 is configured to raise the pressure of the carbon dioxide contained in the carbon dioxide-laden gases above its triple point. The compression device 38 compresses, for example, the carbon dioxide-laden gases to a pressure of 40 bar.
[0060] Upon exiting the compression device 38, the compressed carbon dioxide-laden gases are conveyed to a pre-cooling device 40. The pre-cooling device 40 is a heat exchanger which includes a primary pass 42 and a secondary pass 44, which are particularly visible in figures 3 and 4. The primary pass 42 is configured to channel the carbon dioxide-laden gases and to cool them by heat exchange with the secondary pass 44 which will be described later.
[0061] According to the invention, the carbon dioxide capture unit 26 of the treatment system 1 comprises a condensation device 46 configured to condense the carbon dioxide present in the carbon dioxide-laden gases. The condensation device 46 is connected to the pre-cooling device 40 and disposed downstream of the latter in a direction of carbon dioxide-laden gas flow. The condensation device 46 is a heat exchanger configured to cool the carbon dioxide-laden gases using liquefied natural gas, either directly in the case of the first embodiment of Figures 1 and 3, or indirectly in the case of the second embodiment of Figures 2 and 4 and the third embodiment of Figure 5. To this end, the condensation device 46 comprises at least a first pass 48 and a second pass 50, which are illustrated in Figures 3.4 and 5. In certain embodiments, and particularly in the embodiments illustrated in Figures 3 and 4, the condensation device 46 also includes a third pass 52, otherwise called an additional pass 52. The first pass 48 of the condensation device 46 is configured to channel the carbon dioxide-laden gases and to cool them by heat exchange with the second pass 50 and, where applicable, the third pass 52. These heat exchanges will be detailed later. It should be noted that if a condensation device 46 includes both the first pass 48,The second pass 50 and the third pass 52 are illustrated here in Figures 1 to 4 representing a reforming unit 2 corresponding to a steam reforming unit of methane, while a condensation device 46 comprising only the first pass 48 and the second pass 50 is illustrated in Figure 5 representing the reforming unit 2 corresponding to an autothermal reforming unit. The present invention is intended to cover alternative embodiments in which the condensation device 46 comprising both the first pass 48, the second pass 50 and the third pass 52 would be associated with the reforming unit 2 corresponding to an autothermal reforming unit, while the condensation device 46 comprising only the first pass 48 and the second pass 50 would be associated with the reforming unit 2 corresponding to a steam reforming unit of methane.
[0062] Within the treatment system 1, the condensation device 46 is connected to at least one separation device 54 responsible for separating the condensed carbon dioxide from residual gases. At the outlet of the separation device 54 and the carbon dioxide capture unit 26, the carbon dioxide is stored in liquid form in a storage tank 56 of the treatment system 1. The carbon dioxide is, for example, stored in the storage tank 56 at a pressure between 7 and 15 bar.
[0063] As can be clearly seen in Figures 3 and 4, the separation device 54 of the carbon dioxide capture unit 26 comprises a first separation device 54A and a second purification device 54B arranged in that order within the carbon dioxide capture unit 26. The first separation device 54A is, for example, a separator such as a separation flask. The first separation device 54A is configured to separate a liquid phase consisting mainly of carbon dioxide from a vapor phase consisting mainly of residual gases. The second separation device 54B, or second purification device 54B, is, for example, a purifier such as a purification column or a distillation column.The second purification device 54B is configured to extract residual gases dissolved in the liquid phase of carbon dioxide from the first separation device 54A. The carbon dioxide capture unit 26 also includes a pressure-reducing valve 55 configured to adjust the pressure between the first separation device 54A and the second purification device 54B.
[0064] Within the carbon dioxide capture unit 26, a reboiler 57 is associated with the second purification device 54. This reboiler 57 is configured to heat the liquid phase of carbon dioxide so as to evaporate the light residual gases dissolved therein. The reboiler 57 is arranged here on a bypass line 59 of the pre-cooling device 40. This bypass line 59 is connected at one end between the compression device 38 and the pre-cooling device 40, and at the other end between this pre-cooling device 40 and the condensing device 46. The bypass line 59 is configured to divert a portion of the carbon dioxide-laden gases in order to use them to heat the liquid phase of carbon dioxide present in the second purification device 54B.Notably, the treatment system 1 includes a return line 58 configured to channel the residual gases from the separation device 54 to the reforming unit 2. More specifically, the return line 58 here connects each of the first separation device 54A and the second purification device 54B to the reforming unit 2, where appropriate by the first branch 18 of the feed line 12 configured to supply fuel to the combustion device 4 of the reforming unit 2 when the reforming unit 2 corresponds to a steam reforming unit of methane. The treatment system 1 includes a diversion line 60 connected to the return line 58. The diversion line 60 includes a first end connected to the return line 58 between the separation device 54 and the reforming unit 2, and a second end connected to the treatment system 1 between the drying unit 22 and the dihydrogen separation unit 24.In other words, the second end of the diversion line 60 is connected upstream of the hydrogen separation unit 24. It is understood here that a portion of the waste gas is recycled to the hydrogen separation unit 24. This notably improves the performance of this hydrogen separation unit 24. If necessary, the flow of waste gas to the reforming unit 2 or to the hydrogen separation unit 24 can be regulated by the presence of valves positioned on the return line 58 and / or the diversion line 60.
[0065] As can be clearly seen in Figures 3 and 4, the return line 58 is split into a first portion connecting the first separation device 54A to the reforming unit 2, and a second portion connecting the second purification device 54B to the reforming unit 2. The first portion of the return line 58 from the first separation device 54A participates in a heat exchange with the carbon dioxide-laden gases emitted by the reforming device 6 of the reforming unit 2. In fact, the first portion of the return line 58 forms the third pass 52 of the condensing device 46 and the secondary pass 44 of the pre-cooling device 40. It is understood from the above that the residual gases are used to cool the carbon dioxide-laden gases before they are sent to the reforming unit 2, both in the pre-cooling device 40 and in the condensing device 46.In the embodiment illustrated in Figure 5, the first portion of the return line 58 forms the secondary pass 44 of the pre-cooling device 40 and bypasses the condensation device 46. In other words, the residual gases are used in the pre-cooling device 40 to cool the carbon dioxide-laden gases before they are sent to the reforming unit 2, without passing through the condensation device 46.
[0066] As mentioned above, the condensing unit 46 is configured to cool the carbon dioxide-laden gases using liquefied natural gas, directly in the first embodiment illustrated in Figures 1 and 3, and indirectly in the second embodiment illustrated in Figures 2, 4, and 5. For this purpose, the treatment system 1 includes a bypass branch 62 configured to channel liquefied natural gas. This bypass branch 62 is connected to the supply line 12 between the storage tank 10 and the vaporization unit 16.
[0067] In the first embodiment illustrated in Figures 1 and 3, the bypass branch 62 comprises a pipe 64 extending from the supply line 12 to the condensing unit 46, the second pass 50 of the condensing unit 46, and a conduit 66 extending from the condensing unit 46 to the supply line 12. It is thus understood that the bypass branch 62 forms a loop between the supply line 12 and the condensing unit 46. Therefore, in this first embodiment, within the condensing unit 46, the first pass 48, which carries the carbon dioxide-laden gases, is cooled both by the second pass 50, which carries liquefied natural gas, and by the third pass 52, which carries residual gases. This is a direct cooling by the liquefied natural gas, as it flows within one of the passes of the condensing unit 46.
[0068] After cooling the carbon dioxide-laden gases in the condensation device 46, the natural gas is in a gaseous state and is conveyed to the supply line 12 via the pipe 66. The natural gas in a gaseous state can then be used to supply fuel to the reforming unit 2, where appropriate either by the first branch 18 for the combustion device 4 or by the second branch 20 for the reforming device 6.
[0069] In the second and third embodiments illustrated in Figures 2, 4, and 5, the carbon dioxide capture unit 26 includes an intermediate fluid loop 68. The intermediate fluid loop 68 is arranged between the bypass branch 62 on one side and the condensing device 46 on the other. The intermediate fluid loop 68 is configured to channel an intermediate fluid whose temperature is regulated to prevent the carbon dioxide from freezing within the condensing device 46. The temperature of the intermediate fluid is, for example, ~56 °C at its inlet to the condensing device 46.
[0070] The intermediate fluid loop 68 carries a heat exchanger 70 which comprises a first layer 72 and a second layer 74, the first layer 72 being configured to channel the intermediate fluid. Thus, in the second embodiment, the branch 62 comprises the pipe 64 which extends between the supply line 12 and the heat exchanger 70 of the intermediate fluid loop 68, the second layer 74 of this heat exchanger 70, and the conduit 66 which extends between said heat exchanger 70 and the supply line 12. The intermediate fluid loop 68 also includes the second pass 50 of the condensation device 46.
[0071] It is understood that in the second embodiment, the liquefied natural gas from the storage tank 10 circulates in the supply line 12, in the pipeline 64 and then in the second layer 74 of the heat exchanger 70 of the intermediate fluid loop 68, within which it exchanges heat with the intermediate fluid channeled in the first layer 7 of the heat exchanger 70 and vaporizes. The natural gas in gaseous state then flows from the heat exchanger 70 to the feed line 12 via the pipe 66, and then it feeds the reforming unit 2. When the reforming unit 2 is a steam reforming unit of methane, the natural gas in vapor state passes through the first branch 18 and / or the second branch 20 in order to supply fuel respectively to the combustion device 4 and / or the reforming device 6 of the reforming unit 2.
[0072] During the heat exchange between the intermediate fluid circulating in the first layer 72 of the heat exchanger 70 and the liquefied natural gas circulating in its second layer 74, the intermediate fluid cools and contributes to the evaporation of the liquefied natural gas. This is indirect cooling by the liquefied natural gas because it does not circulate within one of the passes of the condensing unit 46; rather, the treatment system 1 uses the intermediate fluid as a heat carrier. Within the intermediate fluid loop 68, the intermediate fluid, having exchanged heat with the liquefied natural gas, is channeled to the second pass 50 of the condensing unit 46, where it exchanges heat with the carbon dioxide-laden gases circulating in the first pass 48, the intermediate fluid then vaporizing.The intermediate fluid, having exchanged heat with the carbon dioxide-laden gases, is then recirculated via the intermediate fluid loop 68 to the heat exchanger 70.
[0073] In both the first and second embodiments, the treatment system 1 may also include a cooling device 76 disposed between the second purification device 54B and the storage tank 56. The cooling device 76 is configured to cool the liquid carbon dioxide to a temperature suitable for its storage in the storage tank 56. The cooling device 76 cools the liquid carbon dioxide using a cooling loop 78 which, in the first embodiment, is connected to the line 66 between the condensing device 46 and the supply line 12, and which, in the second embodiment, is connected to the intermediate fluid loop 68 between the condensing device 46 and the heat exchanger 70.The present invention thus proposes a system for treating carbon dioxide-laden gases from a reforming unit, the treatment system using liquefied natural gas both to power the reforming unit, to participate in the cryogenic capture of carbon dioxide and to produce dihydrogen.
[0074] The present invention is not limited to the means and configurations described and illustrated herein, and also extends to any equivalent means and configuration as well as any technically operative combination of such means.
Claims
DEMANDS 1. Carbon dioxide-laden gas treatment system (1), comprising a reforming unit (2) intended to be supplied with natural gas and comprising at least one reforming device (6) emitting carbon dioxide-laden gases, the treatment system (1) comprising at least one drying unit (22), a dihydrogen separation unit (24) present in the carbon dioxide-laden gases and a carbon dioxide capture unit (26) comprising at least one carbon dioxide condensation device (46), the treatment system (1) being configured so that the condensation device (46) is cooled using liquefied natural gas, the treatment system (1) comprising a pipeline (66) configured to bring the liquefied natural gas from the carbon dioxide capture unit (26) to the reforming unit (2).
2. Processing system (1) according to claim 1, comprising a return line (34) connecting the dihydrogen separation unit (24) to the reforming unit (2).
3. Processing system (1) according to any one of claims 1 and 2, wherein the carbon dioxide capture unit (26) is arranged downstream of the dihydrogen separation unit (24) in a direction of flow of the gases charged with carbon dioxide.
4. Processing system (1) according to any one of claims 1 to 3, wherein the dihydrogen separation unit (24) is arranged between the drying unit (22) and the carbon dioxide capture unit (26).
5. Processing system (1) according to any one of claims 1 to 4, comprising at least one liquefied natural gas storage tank (10) and a feed line (12) connecting the storage tank (10) to the reforming unit (2).
6. Processing system (1) according to claim 5, wherein the reforming unit (2) comprises a combustion device (4), the feed line (12) comprising a first branch (18) connected to the combustion device (4) and a second branch (20) parallel to the first branch (18) and connected to the reforming device (6), 7. Processing system (1) according to any one of claims 5 and 6, wherein the conduit (66) extends from the condensation device (46) to the reforming unit (2), the feed line (12) comprising a bypass branch (62) comprising at least the conduit (66) and a pass (50) of the condensation device (46) of the carbon dioxide capture unit (26).
8. Processing system. (1) according to any one of claims 5 and 6, comprising an intermediate fluid loop (68) including at least one heat exchanger (70) and a pass (50) of the condensation device (46), the supply line (12) including a bypass branch (62) including at least the conduit (66) and a sheet (74) of the heat exchanger (70), the heat exchanger (70) being configured to perform heat exchange between the intermediate fluid and the bypass branch (62), 9. Processing system (1) according to any one of claims 1 to 8 in combination with claim 5, comprising a liquefied natural gas connection terminal (11) and a distribution line (13) connecting the liquefied natural gas storage tank (10) to the connection terminal (11). w. Processing system (1) according to any one of claims 1 to 9, wherein the carbon dioxide capture unit (26) includes a pre-cooling device (40) for carbon dioxide-laden gases.
11. Processing system (1) according to any one of claims 1 to 10, wherein the carbon dioxide capture unit (26) comprises at least one device for separating carbon dioxide from residual gases present in the carbon dioxide-laden gases (54, 54A, 54B).
12. Treatment system (1) according to claim 11, wherein the separation device (54, 54A, 54B) comprises a first separation device (54A) and a second purification device (548), the carbon dioxide capture unit (26) comprising a pressure relief valve (55) disposed between the first separation device (54A) and the second purification device (54B).
13. Treatment system (1) according to claim 12, wherein the carbon dioxide capture unit (26) comprises a reboiler (57) associated with the second purification device (54B).
14. Processing system (1) according to any one of claims 11 to 13, comprising a residual gas return line (58) connecting the separation device (54, 54A, 54B) to the reforming unit (2).
15. Treatment system. (1) according to claim 14, wherein the residual gas return line (58) comprises an additional pass (52) of the condensation device (46) of the carbon dioxide capture unit (26).
16. Treatment system (1) according to any one of claims 14 or 15, comprising a diversion line (60) connected at one end to the residual gas return line (58) and at a second end, between the drying unit (22) and the dihydrogen separation unit (24).
17. Treatment system (1) according to claim 12 in combination with claim 10, wherein the pre-cooling device (40) of the carbon dioxide capture unit (26) is configured to operate heat exchanges between the residual gases flowing in the return line (58) and the carbon dioxide-laden gases.
18. Treatment system (1) according to any one of claims 1 to 14, comprising a storage tank (56) for carbon dioxide in liquid form.
19. Processing system (1) according to claim 18 in combination with claim 12. comprising a cooling device (76) disposed between the second purification device (54B) and the storage tank (56).