Floating structure comprising a system for treating carbon dioxide-laden gases emitted by a fuel cell

Abstract

The invention relates to a floating structure comprising: a tank for a gas in the liquid state; a first circuit (30) for supplying gas taken from the tank, which circuit extends to a point (40) for distributing the gas to at least one gas-consuming apparatus; a main supply line (31) connecting the at least one gas-consuming apparatus to the distribution point; a fuel cell (50) emitting CO2-laden gases; a system (60) for treating the gases emitted by the fuel cell, which system comprises a device (61) for condensing the CO2, and a heat exchanger (70) exchanging heat between the CO2-laden gases circulating in the condensation device and the gas circulating in the first supply circuit.

Description

[0001] DESCRIPTION

[0002] Title of the invention: Floating structure comprising a system for treating carbon dioxide-laden gases emitted by a fuel cell

[0003] The present invention relates to the field of treatment of gases emitted by consumers, and more particularly to a floating structure comprising a system for treating gases loaded with carbon dioxide.

[0004] When a carbon dioxide 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. Therefore, it is advisable to treat the carbon dioxide-laden gases from an emission source in order to extract the carbon dioxide for later use or commercialization.

[0005] The emission source can be a fuel cell. Fuel cells are devices capable of generating electricity from a redox reaction. Fuel cells typically consist of two electrodes, an anode and a cathode, separated by an electrolyte membrane. The anode is supplied with a reducing fuel, while the cathode is supplied with an oxidant, such as oxygen from the air. The electrolyte membrane allows oxygen ions to pass from the cathode to the anode.

[0006] Solid oxide fuel cells, also known by their English abbreviation SOFC, exist. In these solid oxide fuel cells, which generally operate at very high temperatures, the electrolyte membrane consists of solid oxides. These solid oxide fuel cells are used, for example, to generate electrical power.

[0007] Floating structures, such as liquefied gas storage and / or transport vessels, may incorporate a fuel cell as a replacement for, or in addition to, an electrical generator to provide electrical power within the floating structure in which it is installed. In such a configuration, the fuel cell is advantageously powered by a fuel produced from the liquefied gas stored in the tank.

[0008] The fuel cell consumes fuel and emits exhaust gases from its anode. These exhaust gases contain carbon dioxide, and it is therefore necessary to implement methods for treating these exhaust gases in order to limit carbon dioxide emissions.

[0009] A known method for treating these carbon dioxide-laden gases involves circulating the gas through a condensing device. Condensation is a physical phenomenon involving a change of state of matter from a gaseous state to a condensed state (liquid or solid). There are two types of condensation: liquid condensation, or liquefaction, which corresponds to the change of matter from the gaseous state to the liquid state; and solid condensation, which corresponds to the change of matter from the gaseous state to the solid state. The invention will be described below with an example of liquid condensation. However, a person skilled in the art will understand that the principle of the invention applies similarly to solid condensation, provided that the equipment and the quantities of heat exchanged are adapted. Likewise, the invention can be applied to a gas in a liquid state, such as liquefied natural gas (LNG).However, the invention is by no means limited to this and its principle can be applied by analogy to other gases in the liquid state.

[0010] As it circulates through the condensing unit, the carbon dioxide-laden gas is exposed to a cold source. More precisely, the condensing unit is the site of a thermal energy exchange between the carbon dioxide-laden gas and the cold source, such as a refrigerant. Within the condensing unit, the carbon dioxide-laden gas exchanges heat with the heat transfer fluid. The temperature of the carbon dioxide-laden gas decreases, leading to its condensation. After the carbon dioxide is separated from the remaining exhaust gases, it can be stored in liquid form. As a reminder, in such a system for processing carbon dioxide-laden gas generated by a fuel cell, the fuel cell is powered by a fuel produced from the liquid gas stored in the tank.In a well-designed fuel system, the fuel intended to power the fuel cell passes through the condenser. It acts as the cold source for the condenser. As the carbon dioxide-laden gas downstream of the fuel cell passes through the condenser, a heat exchange occurs within the condenser, heating the fuel and cooling the carbon dioxide-laden gas. Thus, the fuel cell supply line, in addition to providing the fuel cell with fuel, acts as a cold source, capturing carbon dioxide by condensation from the carbon dioxide-laden gas stream exiting the fuel cell.

[0011] While generally satisfactory, such a system for treating the carbon dioxide-laden gas generated by a fuel cell derives the thermal energy required for carbon dioxide capture by condensation solely from the fuel intended to power the fuel cell. In other words, the amount of cooling available for condensation is dependent on the fuel cell's fuel requirements.

[0012] Furthermore, within the condensing unit, the carbon dioxide-laden gases exchange heat either with natural gas in its liquid state only, with natural gas in its vapor state only, or with both. Natural gas in its liquid state has a temperature of approximately -160°C. Natural gas in its vapor state, for example, is a gas resulting from the natural evaporation of liquefied natural gas, also known as boil-off gas (BOG), and has a higher temperature than natural gas in its liquid state. When the fuel cell is powered solely by BOG, the thermal energy provided by the BOG in the condensing unit may be insufficient to achieve carbon dioxide capture by condensation. Such a treatment system proves to be less efficient in certain operating configurations.The present invention aims to overcome this drawback by proposing a floating structure comprising a consumer exhaust gas treatment system that optimizes the use of available thermal energy for carbon dioxide capture by condensation.

[0013] The present invention thus has as its principal object a floating structure comprising a storage tank for a gas in liquid state, at least one gas-consuming appliance intended to be supplied with gas taken from the tank, a first gas supply circuit taken in liquid or gaseous state from the tank extending from the tank to a gas distribution point to at least one gas-consuming appliance, a main supply line connecting at least one gas-consuming appliance to the distribution point, a fuel cell configured to be supplied with a fuel produced from the gas in liquid state stored in the tank and to emit gases charged at least with carbon dioxide, a gas treatment system charged at least with carbon dioxide and emitted by the fuel cell, said treatment system comprising at least one device for condensing the carbon dioxide present in the carbon dioxide-charged gases,and a heat exchanger configured to perform heat exchange between the carbon dioxide-laden gases circulating in the condensing device and the gas circulating in the first supply circuit.

[0014] As indicated, the gas drawn from the tank can be in liquid or gaseous form. Advantageously, the gas is drawn in gaseous form; this is the BOG (Boiling Oil Gas) that needs to be treated. The invention will be described based on this configuration.

[0015] However, the invention is not limited to this and it is also possible to collect the gas in liquid form and regasify it using a regasification device on the first supply circuit and located downstream of the heat exchanger, or an auxiliary device fluidly connected to the first supply circuit.

[0016] The first gas supply circuit helps meet the fuel requirements of at least one consuming appliance. The gas from the tank flows through the first gas supply circuit from the tank to the distribution point, from which the gas will be directed to at least one gas consuming appliance via the main line.

[0017] The distribution point is a connection point between the first supply circuit and the main line. An output of the first supply circuit is thus connected to an input of the main supply line.

[0018] The heat exchanger defines a heat exchange zone between the carbon dioxide-laden gases emitted by the fuel cell and the gas from the tank circulating in the first supply circuit to the gas-consuming appliances. The carbon dioxide-laden gases are hot, while the gas circulating in the first supply circuit acts as a cold source. Within the heat exchanger, the carbon dioxide-laden gases transfer some of their thermal energy to the gas circulating in the first supply circuit. Following this heat exchange between the carbon dioxide-laden gases circulating in the condensing unit and the gas circulating in the first supply circuit, the gas circulating in the first supply circuit heats up and the carbon dioxide-laden gases cool down. The resulting decrease in the temperature of the carbon dioxide-laden gases allows the carbon dioxide to condense.

[0019] The heat exchange between the carbon dioxide-laden gases circulating in the condensation unit and the gas circulating in the first feed circuit within the heat exchanger allows the floating structure's treatment system to make optimal use of all available cold sources within the floating structure to contribute to carbon dioxide capture. This results in a higher carbon dioxide capture rate compared to prior art solutions. According to an optional feature of the invention, the gas treatment system includes a device for compressing the carbon dioxide-laden gases, a device for drying these carbon dioxide-laden gases, and a device for separating the carbon dioxide present in the gases emitted by the fuel cell.The treatment system compresses, dries, and condenses the carbon dioxide-laden gases emitted by the consumer, respectively, using the decompression device, the drying device, and the condensation device. The carbon dioxide is then separated from the remaining carbon dioxide-laden gases using the carbon dioxide separation device. This separation device may include a purification device, such as a distillation column. Its role is to extract any gases dissolved in the liquid phase of the carbon dioxide. The components of the treatment system and their arrangement within the system are described herein by way of illustration and shall not limit the scope of the claimed invention. The treatment system may include other components involved in the condensation and separation of carbon dioxide from the carbon dioxide-laden gas stream.The physical and fluidic arrangement of the elements within the treatment system relative to one another may differ, provided that these elements meet the carbon dioxide capture requirements of the treatment system. The description will clearly show that the invention applies to any treatment system comprising at least one condensation device.

[0020] According to an optional feature of the invention, the floating structure includes an auxiliary supply line connecting the fuel cell to the distribution point. The fuel cell is supplied with fuel by gas in a gaseous state, produced from the gas in the tank and directed to the distribution point. This gas flows through the auxiliary line to power the fuel cell.

[0021] According to an optional feature of the invention, at least one gas-consuming device is a high-pressure gas-consuming device and the floating structure includes at least one low-pressure gas-consuming device, the main supply line connecting the high-pressure gas-consuming device to the distribution point, and the auxiliary supply line connecting the low-pressure gas-consuming device to the distribution point.

[0022] In this configuration, the distribution point is a connection point between the primary supply circuit and the main and auxiliary supply lines. In other words, the main and auxiliary supply lines are seamlessly connected to the primary supply circuit at the distribution point. An output of the primary supply circuit is thus connected to an input of the main supply line and an input of the auxiliary supply line.

[0023] According to an optional feature of the invention, the floating structure includes a second gas supply circuit taken in liquid form from the tank extending from the tank to the point of distribution of the gas to at least one gas-consuming appliance, the second supply circuit including a pumping element disposed in the tank and configured to pump the gas taken in liquid form, the heat exchanger being configured to operate a heat exchange between the carbon dioxide-laden gases circulating in the condensation device and the gas circulating in the second supply circuit.

[0024] It is thus understood that the distribution point is a connection point between the first and second power supply circuits and the main and auxiliary power lines. At the distribution point, the main and auxiliary power lines are seamlessly connected to the first and second power supply circuits. One output from the first power supply circuit and one output from the second power supply circuit converge at the distribution point, connected to the input of the main power line and the input of the auxiliary power line.

[0025] The second gas supply circuit also contributes to meeting the fuel requirements of the high-pressure and low-pressure gas-consuming appliances. The gas from the tank is pumped in liquid form by the pumping unit located at the bottom of the tank. It flows through the second gas supply circuit from the tank to the distribution point, from where the gas is directed to the high-pressure and / or low-pressure gas-consuming appliances via the main and / or auxiliary lines.

[0026] The heat exchanger thus defines a heat exchange zone between the carbon dioxide-laden gases emitted by the fuel cell and the gas from the tank circulating in the first and second supply circuits, which feed gas-consuming appliances. The gas circulating in the second supply circuit is a cold source. Being a liquid gas, it is a cooling agent with even greater cooling power than gas in its gaseous state. Within the heat exchanger, the carbon dioxide-laden gases also transfer some of their thermal energy to the gas circulating in the second supply circuit. This heat exchange between the carbon dioxide-laden gases circulating in the condensing unit and the gas circulating in the second supply circuit results in the heating of the gas circulating in the second supply circuit.A phase change occurs, and the gas circulating in the second supply circuit leaves the heat exchanger in a gaseous state. It is then directed to the distribution point to supply the gas-consuming appliances.

[0027] As explained previously, the carbon dioxide-laden gases are cooled in the heat exchanger by the cold source from the first and second supply circuits, and carbon dioxide capture by condensation takes place within the treatment system.

[0028] The amount of gas flowing in the first supply circuit and the amount flowing in the second supply circuit vary according to the fuel requirements of the gas-consuming appliances. According to the embodiments detailed in the description, the fuel supply to the gas-consuming appliances can be achieved via the first gas supply circuit or via both the first and second gas supply circuits.

[0029] The second gas supply circuit carries the gas in liquid form to the heat exchanger, thus delivering a significant cooling power.

[0030] The heat exchanger is thus able to perform heat exchange between the carbon dioxide-laden gases circulating in the condensing unit and the gas circulating in the second supply circuit, based on this cooling capacity. The cooling source used within the condensing unit makes the treatment system even more efficient than existing systems. The floating structure can therefore utilize the cooling of the gas in its liquid and / or gaseous state from the tank to supply gas-consuming appliances, thereby improving carbon dioxide capture performance. This available cooling is captured from the gas supply circuits and used by the condensing unit to capture carbon dioxide.

[0031] According to an optional feature of the invention, the heat exchanger comprises a first pass, the first pass being a portion of the second feed circuit, and the first pass passes through the condensing device. In other words, the portion of the second feed circuit passes through the condensing device. The condensing device forms the heat exchanger. The carbon dioxide-laden gases directly transfer their thermal energy to the gas circulating in the second feed circuit within the condensing device. According to an optional feature of the invention, the heat exchanger comprises a second pass, the second pass being a portion of the first feed circuit, and the second pass passes through the condensing device. In other words, the portion of the first feed circuit passes through the condensing device. The condensing device forms the heat exchanger.Carbon dioxide-laden gases directly transfer their thermal energy to the gas circulating in the first feed circuit within the condensing unit. This is referred to as the heat exchanger integrated into the condensing unit. The cold passes of this heat exchanger are formed by the first and second feed circuits.

[0032] According to an optional feature of the invention, the heat exchanger comprises a primary pass, the primary pass being a portion of the first supply circuit, and a cooling pass through which the heat transfer fluid is intended to circulate. The cooling pass passes through the condensing unit. According to another optional feature of the invention, the heat exchanger comprises a secondary pass, the secondary pass being a portion of the second supply circuit. In this architecture, the heat exchanger is remote. The first and second gas supply circuits pass through the heat exchanger, which is remote from the condensing unit. A cooling loop connects the heat exchanger to the condensing unit. The cooling loop contains the heat transfer fluid.The heat transfer fluid carries the heat recovered from the carbon dioxide-laden gases in the condensing unit to the heat exchanger. In the heat exchanger, heat exchange occurs between the heat transfer fluid and the gas circulating in the gas supply circuit(s). The heat transfer fluid cools, and the gas circulating in the gas supply circuit(s) heats up. The heated gas circulating in the gas supply circuit(s) is directed to the distribution point to supply gas-consuming appliances with gas in its gaseous state. The cooled heat transfer fluid is then directed to the condensing unit, where heat exchange takes place between the heat transfer fluid, acting as the cold source, and the carbon dioxide-laden gases, which are thereby cooled.After this heat exchange between the heat transfer fluid and the carbon dioxide-laden gases in the condensing unit, the next stage of the process can take place, and the carbon dioxide is captured by condensation. The heated heat transfer fluid is then directed to the heat exchanger to recover the coolness of the gases destined to supply the gas-consuming appliances.

[0033] According to an optional feature of the invention, the floating structure includes a liquid carbon dioxide storage device. The storage device is located downstream of the treatment system. For example, the storage device is connected directly to the separation device or connected to a subcooling device which is itself connected to the separation device.

[0034] According to an optional feature of the invention, the first supply circuit includes a compression element located downstream of the heat exchanger, and the auxiliary supply line includes an expansion element. The compression element and the expansion element, respectively, are configured to compress and expand the gas to the operating pressure of the gas-consuming devices, respectively. The compression element located on the first supply circuit is responsible for drawing gas in its gaseous state from the headspace of the tank in order to both supply the gas-consuming devices and regulate the pressure within the tank. The compression element may be a low-pressure compressor. If the high-pressure gas-consuming device is a ME-GI type propulsion engine, the gas supplying this gas-consuming device must be compressed to a very high pressure of up to 300 bar.In this case, the compression unit is a high-pressure compressor. The low-pressure gas-consuming device could, for example, be an auxiliary motor such as an electric generator. It does not require high pressure. The auxiliary line is therefore equipped with its own expansion valve to reduce the gas to the operating pressure of the low-pressure gas-consuming device.

[0035] According to an optional feature of the invention, the second supply circuit includes a pump located upstream of the gas treatment system. This pump is a high-pressure pump. The gas in its liquid state is first pumped by the pumping element into the second supply circuit. In series with the pumping element, i.e., downstream of the pumping element, the pump increases the pressure of the gas in its liquid state in the second supply circuit. After its pressure has been increased, the gas in its liquid state is directed to the heat exchanger to cool the carbon dioxide-laden gases.

[0036] According to an optional feature of the invention, the fuel cell is a solid oxide fuel cell (SOFC). Alternatively, another possible type of fuel cell is a molten carbonate fuel cell (MCFC).

[0037] The fuel cell is supplied with air, which is delivered to the cathode, and fuel stored in the tank, which is delivered to the anode. The fuel cell produces electrical energy through redox reactions, resulting in the formation of effluents at both the anode and the cathode. It is the carbon dioxide-laden gases emitted by the anode that are treated by the treatment system.

[0038] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:

[0039] [Fig. 1] illustrates, schematically, a floating structure comprising a system for treating gases charged with carbon dioxide emitted by a fuel cell according to the invention in a first embodiment;

[0040] [Fig. 2] illustrates, schematically, a floating structure according to the invention in a second embodiment;

[0041] [Fig. 3] illustrates, schematically, a floating structure according to the invention in a third embodiment;

[0042] [Fig. 4] illustrates, schematically, a floating structure according to the invention in a fourth embodiment;

[0043] [Fig. 5] illustrates, schematically, a floating structure according to the invention in a fifth embodiment.

[0044] 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.

[0045] In the figures, elements common to several figures retain the same reference. The terms "upstream" and "downstream" used in the following description are used to express the positions of components within gas circuits in liquid or vapor state and refer to the direction of flow of said gas within said circuit.

[0046] Figures 1 to 5 thus schematically illustrate a floating structure 1 according to the invention which incorporates within it a storage tank 10 of a gas in liquid state 11, as well as at least one gas-consuming device. The floating structure 1 of the invention may comprise a single gas-consuming device, for example, the high-pressure gas-consuming device 21. Or, as shown in the figures, the floating structure 1 of the invention may comprise several gas-consuming devices, for example, the high-pressure gas-consuming device 21, and at least one low-pressure gas-consuming device 22. The gas-consuming devices 21, 22 are intended to be supplied with gas in liquid or gaseous state 11, 12 taken from the tank 10. In addition, the floating structure 1 comprises a fuel cell 50 configured to be supplied with a fuel produced from the liquid gas 11 stored in the tank 10.

[0047] Figure 1 schematically illustrates such a floating structure 1 comprising a system for treating gases charged with carbon dioxide emitted by a fuel cell according to the invention in a first embodiment.

[0048] The floating structure 1 can, for example, be a vessel capable of storing and / or transporting gas in liquid form, such as LNG. In this case, the liquid gas that the floating structure stores and / or transports is used to power at least one gas consumer. As shown in Figure 1, but not limiting the invention, the gas drawn from the tank powers the high-pressure gas consumer 21, which can, for example, be a propulsion engine, and the low-pressure gas consumer 22, which is an electric generator supplying electricity to the floating structure. As illustrated, the low-pressure gas consumer 22 comprises two electric generators 221, 222 and a fuel cell 50. Each of these components is designed to produce electrical energy.Of course, the number of electric generators and fuel cells indicated here is by way of non-limiting example, and the invention applies analogously regardless of that number. For the purposes of the invention, the floating structure 1 comprises at least one gas-consuming device and at least one fuel cell. This is one configuration of the invention.

[0049] In another configuration, the floating structure 1 may include a high-pressure gas-consuming device 21 and at least one low-pressure gas-consuming device 22, and a fuel cell 50. The invention applies similarly to either of these two configurations. Within these configurations, the invention can be implemented in various ways. Although not limited to them, the invention will be described below on the basis of a floating structure comprising a high-pressure gas-consuming device 21 and at least one low-pressure gas-consuming device 22, and a fuel cell 50.A person skilled in the art will understand, based on the description in this document, that the invention relies on supplying gas to at least one gas-consuming device and a fuel cell, and on the judicious use of the coldness of this supply gas to capture the carbon dioxide emitted by the fuel cell. In this respect, a person skilled in the art will understand that the low-pressure gas-consuming device 22, although generally present on a floating structure, is optional here.

[0050] In the first embodiment shown in Figure 1, the gas-consuming devices 21, 22 are supplied with gas in a gaseous state from the tank 10.

[0051] The floating structure 1 includes a first gas supply circuit 30, which draws gas from tank 10 in its gaseous state (or, as explained previously, from a liquid state and then converted to a gaseous state by a suitable device). This first supply circuit 30 extends from tank 10 to a gas distribution point 40 for supplying gas-consuming appliances 21 and 22. The first supply circuit 30 is designed to circulate the gas in its gaseous state from the gas head of tank 10 to the distribution point 40 in order to supply gas in its gaseous state to gas-consuming appliances 21 and 22. In addition to supplying gas to the appliances 21 and 22, the circulation of the gas in its gaseous state in the first supply circuit 30 allows for pressure management within tank 10 following the evaporation of the gas in its liquid state during transport and / or its storage.

[0052] The floating structure 1 includes a main supply line 31 connecting the high-pressure gas-consuming device 21 to the distribution point 40. It also includes an auxiliary supply line 32 connecting the low-pressure gas-consuming device 22 to the distribution point 40. The gas in its gaseous state thus flows through the first supply line 30 to the distribution point 40, and once at the distribution point 40, the gas in its gaseous state is distributed to the high-pressure gas-consuming device 21 and / or to the low-pressure gas-consuming device 22. The gas distribution at the distribution point 40 is conventionally achieved by means of a control system (not shown) that takes into account the propulsion requirements of the floating structure and the electrical power requirements within the floating structure. This aspect is known from the prior art and will not be described in further detail.

[0053] The floating structure of the invention comprises a fuel cell 50 configured to be powered by a fuel produced from the liquid gas 11 stored in the tank 10. Such a fuel cell 50 emits gases containing at least carbon dioxide during operation. As illustrated in Figure 1, the auxiliary supply line 32 connects the fuel cell 50 to the distribution point 40. The fuel cell 50 is here a solid oxide fuel cell, but could alternatively be a molten carbonate fuel cell. It consists of a cathode 4 and an anode 6, which correspond to the two electrodes of the fuel cell 50 and are separated from each other by an electrolyte membrane, which is here a solid oxide. In order to provide electrical energy, the fuel cell 50 is supplied with air on the one hand and with a fuel on the other.More specifically, the cathode 4 of the fuel cell 50 is supplied with air, for example, ambient air within the floating structure. The fuel supplies the anode 6 of the fuel cell 50. The fuel used to supply the anode 6 is, for example, gas previously stored in the storage tank 10 of the floating structure. This could be the gas in its liquid state stored in the tank 10. Alternatively, the fuel used to supply the anode 6 is a gas in its gaseous state, resulting from the evaporation of the gas in its liquid state stored in the storage tank 10. The different embodiments will be shown by means of Figures 1 to 5.

[0054] The conduits which carry the gas in liquid or vapor state from the storage tank 10 to the anode 6 consist of the first supply circuit 30 (extending from the tank 10 to the distribution point 40) and the auxiliary supply line 32 (extending from the distribution point 40 to the low pressure gas consuming device 22, and in particular the fuel cell 50).

[0055] The floating structure 1 also includes a gas treatment system 60 charged at least with carbon dioxide and emitted by the fuel cell 50. These gases flow from the anode 6 to the treatment system 60 in a treatment circuit 14. Thus, the treatment circuit 14 is dedicated to the evacuation of gases charged at least with carbon dioxide from an outlet of this fuel cell 50 to the gas treatment system 60 to be treated there.

[0056] The treatment system 60 includes at least one condensing device 61 for the carbon dioxide present in the carbon dioxide-laden gases. The condensing device 61 is configured to cool the carbon dioxide present in the carbon dioxide-laden gases so that it changes state from a vapor to a liquid. For this purpose, the carbon dioxide-laden gases are cooled within the condensing device 61.

[0057] The gas treatment system 60 may include a device for compressing gases charged with carbon dioxide 62, a device for drying these gases charged with carbon dioxide 63, and a device for separating carbon dioxide 64 from the gases emitted by the fuel cell 50.

[0058] At the outlet of the treatment circuit 14, the carbon dioxide-laden gases are conveyed to the carbon dioxide-laden gas compression device 62 to increase their pressure, for example, from approximately 1 bar to 30 bar. The compression device 62 is connected to the drying device 63 of the treatment system 60, for example, a molecular sieve, from which the remaining water present in the compressed carbon dioxide-laden gases is removed. It can be understood from the above that an outlet of the compression device 62 is connected to an inlet of the drying device 63. Between the compression device 62 and the drying device 63, the carbon dioxide-laden gases have a pressure of approximately 30 bar and a temperature of approximately 40 °C. At the outlet of the drying device 63, the gases charged with carbon dioxide are composed of carbon dioxide, hydrogen, carbon monoxide and nitrogen, the water having been previously removed.These carbon dioxide-laden gases are then conveyed from the drying unit 63 to the condensing unit 61. Within the condensing unit 61, the carbon dioxide-laden gases are cooled; upon exiting the condensing unit 61, they can have a pressure of approximately 15 to 30 bar and a temperature between -40 and -55 °C. From the condensing unit 61, the carbon dioxide-laden gases are conveyed to a separation unit 64 to separate a liquid phase of carbon dioxide from a vapor phase of the residual gases. The separation unit 64 can be, for example, a separation vessel.

[0059] In one embodiment of the invention, the floating structure 1 comprises a storage device 90 for liquid carbon dioxide. The storage device 90 is located downstream of the treatment system 60 and is intended to collect the liquid carbon dioxide resulting from the treatment of carbon dioxide-laden gases in the treatment system 60. For storage purposes, the carbon dioxide is thus brought by the treatment system 60 to a temperature compatible with the operation of the storage device 90, for example, a temperature between -50 °C and -25 °C.

[0060] In the foregoing, the treatment system 60 was described according to an exemplary embodiment comprising a compression device 62, a drying device 63, a condensation device 61, and a separation device 64, arranged in that order successively within the treatment system 60. The invention is not limited to this, and the treatment system 60 of the floating structure according to the invention may comprise the same elements arranged in a different order, and / or it may comprise additional elements to operate another compression or drying stage as required for the gas treatment to be carried out. As will become apparent in the remainder of the description of the invention, the invention is based on a treatment system 60 comprising at least the condensation device 61. Therefore, the arrangement of the elements within the treatment system 60 will not be described further.

[0061] According to the invention, the floating structure includes a heat exchanger 70 configured to operate a heat exchange between the carbon dioxide-laden gases circulating in the condensation device 61 and the gas circulating in the first supply circuit 30.

[0062] The condensation device 61 is traversed by carbon dioxide-laden gases from the fuel cell 50 and is configured to cool them in order to capture carbon dioxide by condensation. In the floating structure of the invention, the heat exchanger 70 corresponds to a heat exchange zone between the gases to be condensed in the condensation device 61 and the gas in its gaseous state circulating in the first supply circuit 30. Thanks to the heat exchanger 70, the gas in its gaseous state from the tank 10, intended to supply the high-pressure gas-consuming device 21 and / or the low-pressure gas-consuming device 22, is used to cool the carbon dioxide-laden gases passing through the condensation device 61.The gas in the gaseous state of the tank 10 is used in the heat exchanger 70 to provide cooling to the carbon dioxide-laden gases in the condensation device 61, before being used as fuel in the gas-consuming devices 21, 22. This means that the cooling of the carbon dioxide-laden gases in the condensation device 61 is achieved by the combination of the gas from the tank 10 intended to supply the fuel cell 50 and the gas from the tank 10 intended to supply the high-pressure gas-consuming device 21 and / or the electric generator(s) 221, 222 of the low-pressure gas-consuming device 22.Making this quantity of cold from the gas circulating in the first supply circuit 30 available for heat exchange with the carbon dioxide-laden gases circulating in the condensing unit 61 allows the available cold on board the floating structure 1 to be used as an additional cooling source for capturing the carbon dioxide contained in the carbon dioxide-laden gases by condensation. Using the cold from the first supply circuit thus increases the carbon dioxide capture rate. The performance of the treatment system is thereby improved.

[0063] The first supply circuit 30 includes a compression element 130 located downstream of the heat exchanger 70. The compression element 130 is intended to compress the gas in the gaseous state circulating in the first supply circuit 30 up to the operating pressure of the high-pressure consumer device 31. In the architecture shown in Figure 1, this pressure can, for example, be on the order of 13 bar.

[0064] The pressure in the first supply circuit 30 downstream of the compression member 130 has been raised to the operating pressure of the high-pressure consumer unit 31. The auxiliary supply line 32 includes a pressure-reducing member 131. The pressure-reducing member 131 is therefore positioned between the distribution point 40 and the low-pressure gas consumer unit 22. The pressure-reducing member 131 is configured to reduce the gas coming from the distribution point 40 to an operating pressure of the low-pressure gas consumer unit 22. In the architecture shown in Figure 1, this pressure can, for example, be on the order of 6 to 8 bar.

[0065] Figure 2 schematically illustrates a floating structure according to the invention in a second embodiment. The floating structure of the second embodiment is a floating structure in which the propulsion engine is powered by gas drawn from tank 10. The propulsion engine is the high-pressure gas-consuming device 21. It can be partially powered by gas in its gaseous state from tank 10 in order to equalize the pressure in the tank. Its power supply is supplemented by gas in its liquid state drawn from tank 10. The floating structure thus includes a second supply circuit 35, which will be described below. In its architecture, the second embodiment is identical to the first embodiment. This refers to a floating structure with a low-pressure fuel system.In addition to the elements of the first embodiment already presented, the floating structure 1 in the second embodiment includes a second gas supply circuit 35, drawing gas from the liquid state 11 in the tank 10. The second supply circuit 35 extends from the tank 10 to the gas distribution point 40 for the gas-consuming appliances 21, 22. In order to draw the gas from the liquid state in the tank 10, the second supply circuit 35 includes a pumping element 36 located in the tank, advantageously near a bottom wall of the tank 10. The pumping element 36 is configured to pump the gas from the liquid state 11 in the tank in order to circulate it in the second supply circuit 35.

[0066] According to the invention, the heat exchanger 70 is configured to perform a heat exchange between the carbon dioxide-laden gases circulating in the condensation device 61 and the gas circulating in the second supply circuit 35. It is understood from the above that the heat exchanger 70 has at its disposal the cold from the gas stored in the tank 10, either in the gaseous state in the first supply circuit 30, or in the liquid state in the second supply circuit 35, or the combination of the two, that is to say the cold from the gas in the gaseous state in the first supply circuit 30 and the cold from the gas in the liquid state in the second supply circuit 35.

[0067] In the second embodiment, the heat exchanger 70 includes a first pass 75. The first pass 75 is a portion of the second supply circuit 35. And the first pass 75 passes through the condensation device 61. In other words, the heat exchange carried out within the heat exchanger 70 is carried out at the first pass 75 in the condensation device 61.

[0068] In the first and second embodiments, the heat exchanger 70 includes a second pass 76. The second pass 76 is a portion of the first supply circuit 30. The second pass 76 flows through the condensing device 61. As with the first pass 75, the heat exchange within the heat exchanger 70 is carried out at the second pass 76 in the condensing device 61. When the first pass 75 and / or the second pass 76 flow through the condensing device 61, as is the case in the first, second, and third embodiments, the cold sources from the gas drawn from the tank 10 (in liquid and / or gaseous form) are directed directly to the condensing device 61. The cold from these cold sources is delivered to the carbon dioxide-laden gases within the condensing device 61 at the first pass 75 and / or the second pass 76.The heat exchanger 70 is formed by the condensation device 61, which, due to the passage of the first and second supply circuits in the condensation device 61, becomes the site of the heat exchange between the cold source formed by the gases from the tank 10 and intended to supply the gas-consuming devices 21, 22 and the gases charged with carbon dioxide.

[0069] This architecture is particularly advantageous because it allows the needs of gas-consuming appliances 21, 22 to be met while guaranteeing the desired carbon dioxide capture rate. The gas in its gaseous state is drawn from the tank 10 and circulates in the first supply circuit 30. The first supply circuit 30 passes through the condensing device 61. The portion of the first supply circuit 30 located within the condensing device 61 constitutes the second pass 76. Depending on the application of the gas-consuming appliances 21, 22, the demand for gas in its gaseous state, and therefore the amount of cooling available for carbon dioxide capture by condensation in the condensing device 61, may not be sufficient to achieve the desired carbon dioxide capture rate.In other words, there may not be enough cooling circulating in the first supply circuit 30 to capture carbon dioxide. In this case, the gas in its liquid state is drawn from the tank 10 by pumping using the pumping unit 36. The liquid gas then flows into the second supply circuit 35. The second supply circuit 35 passes through the condensing unit 61. The portion of the second supply circuit 35 located within the condensing unit 61 constitutes the first pass 75. The amount of cooling made available for carbon dioxide capture by condensation in the condensing unit 61 by the first pass 75 supplements the amount of cooling made available by the second pass 76. The gas in its liquid state has a greater cooling capacity than the gas in its gaseous state.By transferring their thermal energy to the liquid gas, the carbon dioxide-laden gases have their temperature lowered, allowing the carbon dioxide to condense. Conversely, the temperature of the liquid gas increases, and a phase change from liquid to gas occurs. This ensures the condensation of carbon dioxide from the carbon dioxide-laden gases passing through the condensation device 61.

[0070] After passing through the heat exchanger 70, i.e. at the outlet of the condensation device 61, the first supply circuit 30 and the second supply circuit 35 converge towards the distribution point 40. Downstream of the distribution point 40, the gas supplies the gas-consuming appliances 21, 22 according to their needs.

[0071] Figure 3 schematically illustrates a floating structure according to the invention in a third embodiment. This third embodiment is identical to the second embodiment. It is a floating structure with a high-pressure fuel system due to the type of propulsion engine requiring a high-pressure gas supply. The high-pressure gas-consuming device 21 can be an ME-GI engine. To power this type of engine, the gas must be compressed to very high pressure by compressors capable of compressing the gas up to 300 bar.

[0072] In addition to the elements of the second embodiment already presented, the second supply circuit 35 of the third embodiment includes a pump 135 located upstream of the gas treatment system 60. The pump 135 is a high-pressure pump. The pump 135 is installed on the supply circuit 35, downstream of the pumping unit 36 ​​located at the bottom of the tank 10. The gas in its liquid state is pumped by the pumping unit 36 ​​out of the tank 10 into the second supply circuit 35. The pump 135 increases the pressure of the gas in its liquid state in the second supply circuit, which reaches a pressure of approximately 150 to 400 bar abs. The gas in its liquid state then passes through the condensing device 61 according to the principle described previously in Figure 2.

[0073] Given the high-pressure gas-consuming device 21, the compression element 130 of the first supply circuit 30 is in this embodiment a high-pressure compressor in order to increase the pressure of the gas in the gaseous state at the outlet of the treatment system 60 to the operating pressure of the high-pressure gas-consuming device 21, i.e. of the order of 300 bar in the example mentioned above.

[0074] Figure 4 schematically illustrates a floating structure according to the invention in a fourth embodiment. The fourth embodiment is identical to the first embodiment. The difference between the fourth embodiment and the first embodiment lies in the positioning of the heat exchanger configured to perform the heat exchange between the carbon dioxide-laden gases circulating in the condensation device 61 and the gas circulating in the first supply circuit 30. In the first embodiment, the heat exchanger (referenced as 70) is formed by the condensation device 61. In the fourth embodiment, as illustrated in Figure 4, the heat exchanger (referenced as 80) is located away from the condensation device 61.

[0075] To facilitate heat exchange between the carbon dioxide-laden gases circulating in the condensing unit 61 and the gas circulating in the first supply circuit 30, the heat exchanger 80 includes a primary pass 81. The primary pass 81 is a portion of the first supply circuit 30. The primary pass forms the cold source in the heat exchanger 80. The heat exchanger 80 includes a cooling pass 83 through which heat transfer fluid from a cooling loop 84 is intended to circulate. The cooling loop 84 comprises the cooling pass 83 that passes through the condensing unit 61 and a condensing pass 85 that corresponds to the portion of the cooling loop 84 that passes through the condensing unit 61.Advantageously, the cooling loop 84 includes a pump 86 disposed between the cooling pass 83 and the condensation pass 85 to pump the heat transfer fluid from the outlet of the heat exchanger 80 to the inlet of the condensation device 61. The cooling loop 84 is a closed loop which passes through the heat exchanger 80 and the condensation device 61.

[0076] The gas in its gaseous state is drawn from tank 10 and flows through the first supply circuit towards the gas-consuming appliances 21, 22. According to the invention, the gas in its gaseous state passes through the heat exchanger 80 in its primary pass 81. A transfer of thermal energy takes place within the heat exchanger 80. The heat transfer fluid circulating in the cooling pass 83, the hot source, transfers thermal energy to the gas in its gaseous state within the heat exchanger 80. The temperature of the gas in its gaseous state increases while the temperature of the heat transfer fluid decreases. The heated gaseous gas leaves the heat exchanger 80 and is directed to the distribution point 40 to supply the gas-consuming appliances 21, 22. The heat transfer fluid circulates in the cooling loop 84, it leaves the heat exchanger 80 and passes through the condensation device 61.In the condensation device 61, the heat transfer fluid is in turn the cold source which enables the capture of carbon dioxide by condensation within the condensation device 61.

[0077] Figure 5 schematically illustrates a floating structure according to the invention in a fifth embodiment. The fifth embodiment is identical to the second embodiment and applies the principle of a remote heat exchanger from the fourth embodiment.

[0078] To simplify the description of this embodiment, the floating structure of the fifth embodiment can be said to be identical to that of the fourth embodiment shown in Figure 4. In addition, the heat exchanger 80 includes a secondary pass 82. The secondary pass 82 is a portion of the second feed circuit 35. In this embodiment, in addition to what has been shown in Figure 4, the liquid gas drawn from the tank 10 by pumping circulates in the second feed circuit 35 and passes through the heat exchanger 80 in the secondary pass 82. The liquid gas is the cold source in the heat exchanger 80. It transfers heat to the heat transfer fluid circulating in the cooling pass 83 within the heat exchanger 80. The temperature of the liquid gas increases, causing it to change to a gaseous state.The gas, initially in a liquid state, leaves the heat exchanger 80 in a gaseous state and is directed to the distribution point 40 to supply the gas-consuming appliances 21 and 22. Following the heat exchange in the heat exchanger 80, the heat transfer fluid's temperature decreases. The heat transfer fluid circulates in the cooling loop 84, leaving the heat exchanger 80 and passing through the condenser 61. In the condenser 61, the heat transfer fluid releases heat to the carbon dioxide-laden gases from the fuel cell. Carbon dioxide capture is achieved by condensation within the condenser 61.

[0079] The present invention thus proposes a floating structure in which carbon dioxide is captured by condensation within a condensation device of a treatment system. The carbon dioxide capture by condensation utilizes the cooling energy of the gases intended to power the propulsion engine of the floating structure and, if present, the electric generator(s) supplying electrical power on board the floating structure. According to the principle of the invention, all available cooling sources in the gas supply circuit(s) are used to condense the carbon dioxide contained in the carbon dioxide-laden gases released at the anode of the fuel cell. In other words, the invention uses the gas from the tank, intended to power at least one gas-consuming device, as a supplementary cooling source to improve the performance of the carbon dioxide capture by condensation.Thanks to the principle of the invention, it is not necessary to install a refrigeration unit on the floating structure to generate the cold required to maintain or increase the carbon dioxide capture rate. However, 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 feasible combination of such means.

Claims

DEMANDS 1- Floating structure (1) comprising a storage tank (10) for a gas in liquid state (11), at least one gas-consuming appliance (21, 22) intended to be supplied with gas (11, 12) taken from the tank (10), a first supply circuit (30) for gas taken in liquid or gaseous state (12) from the tank (10) extending from the tank (10) to a distribution point (40) for the gas to at least one gas-consuming appliance (21, 22), a main supply line (31) connecting at least one gas-consuming appliance (21, 22) to the distribution point (40), a fuel cell (50) configured to be supplied with a fuel produced from the gas in liquid state (11) stored in the tank (10) and to emit gases containing at least carbon dioxide, a gas treatment system (60) charged at least with carbon dioxide and emitted by the fuel cell (50),said treatment system (60) comprising at least one condensing device (61) for the carbon dioxide present in the carbon dioxide-laden gases, and a heat exchanger (70, 80) configured to perform a heat exchange between the carbon dioxide-laden gases circulating in the condensing device (61) and the gas circulating in the first supply circuit (30). 2- Floating structure (1) according to claim 1, comprising an auxiliary supply line (32) connecting the fuel cell (50) to the distribution point (40). 3- Floating structure (1) according to claim 2, wherein at least one gas-consuming device is a high-pressure gas-consuming device (21) and the floating structure (1) further comprises at least one low-pressure gas-consuming device (22), the main supply line (31) connecting the high-pressure gas-consuming device (21) to the distribution point (40), and the auxiliary supply line (32) connecting the low-pressure gas-consuming device (22) to the distribution point (40). 4- Floating structure (1) according to any one of claims 1 to 3, comprising a second supply circuit (35) for gas taken in liquid form (11) from the tank (10) extending from the tank (10) to the distribution point (40) of the Tl gas to at least one gas-consuming appliance (21, 22), the second supply circuit (35) comprising a pumping unit (36) disposed in the tank and configured to pump the gas taken from the liquid state (11), the heat exchanger (70) being configured to operate a heat exchange between the carbon dioxide-laden gases circulating in the condensation device (61) and the gas circulating in the second supply circuit (35). 5- Floating structure (1) according to claim 4, in which the heat exchanger (70) comprises a first pass (75), the first pass (75) being a portion of the second supply circuit (35), and the first pass (75) passes through the condensation device (61). 6- Floating structure (1) according to any one of claims 1 to 5, in which the heat exchanger (70) comprises a second pass (76), the second pass (76) being a portion of the first supply circuit (30), and the second pass (76) passes through the condensation device (61). 7- Floating structure (1) according to any one of claims 1 to 3, wherein the heat exchanger (80) comprises a primary pass (81), the primary pass (81) being a portion of the first supply circuit (30), and a cooling pass (83) through which heat transfer fluid is intended to circulate, and the cooling pass (83) passes through the condensation device (61). 8- Floating structure (1) according to claim 7 in combination with claim 4, wherein the heat exchanger (80) comprises a secondary pass (82), the secondary pass (82) being a portion of the second feed circuit (35). 9- Floating structure (1) according to any one of claims 1 to 8, comprising a storage device (90) for carbon dioxide in liquid form. 10- Floating structure (1) according to any one of claims 1 to 9 in combination with claim 3, wherein the first supply circuit (30) comprises a compression member (130) disposed downstream of the heat exchanger (70, 80) and the auxiliary supply line (32) comprises an expansion member (131), the compression member (130), respectively the expansion member (131), being configured to compress, respectively expand, the gas up to an operating pressure of the gas-consuming devices (21, 22). 11- Floating structure (1) according to any one of claims 1 to 10 in combination with claim 4, wherein the second supply circuit (35) comprises a pump (135) disposed upstream of the gas treatment system (60). 12- Floating structure (1) according to any one of claims 1 to 11, wherein the fuel cell is a solid oxide fuel cell or a molten carbonate fuel cell. 13- Floating structure (1) according to any one of claims 1 to 12, in which the gas treatment system (60) comprises a device for compressing (62) the gases charged with carbon dioxide, a device for drying (63) these gases charged with carbon dioxide, and a device for separating (64) the carbon dioxide present in the gases emitted by the fuel cell (50).

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