Abstract
Subject of the invention is a carbon capture system onboard a vessel which comprises an internal combustion engine for producing power and an exhaust gas, a molten carbonate fuel cell, which comprises a cathode and an anode, for producing electric energy, a cathode outlet stream and an anode outlet stream, wherein the cathode is in fluid communication with the internal combustion engine for receiving at least a portion of the exhaust gas, and a CO.sub.2 separation means which is in fluid communication with the anode for receiving at least a portion of the anode outlet stream, wherein the CO.sub.2 separation means is configured to separate CO.sub.2 from the at least a portion of the anode outlet stream for producing a CO.sub.2 rich stream and a CO.sub.2 depleted stream wherein the molten carbonate fuel cell has an electric connection with the CO.sub.2 separation means for at least partially using the electric energy to at least partially operate the CO.sub.2 separation means.
Claims
1. A carbon capture system (1) onboard a vessel, comprising: an internal combustion engine (2) for producing power (3) and an exhaust gas (4), a molten carbonate fuel cell (5), which comprises a cathode (6) and an anode (7), for producing electric energy (8), a cathode outlet stream (9) and an anode outlet stream (10), wherein the cathode (6) is in fluid communication with the internal combustion engine (2) for receiving at least a portion of the exhaust gas (4), and a CO.sub.2 separation means (11) which is in fluid communication with the anode (7) for receiving at least a portion of the anode outlet stream (10), wherein the CO.sub.2 separation means (11) is configured to separate CO.sub.2 from the at least a portion of the anode outlet stream (10) for producing a CO.sub.2 rich stream (12) and a CO.sub.2 depleted stream (13), wherein the molten carbonate fuel cell (5) has an electric connection (14) with the CO.sub.2 separation means (11) for at least partially using the electric energy (8) to at least partially operate the CO.sub.2 separation means (11).
2. The system (1) according to claim 1, wherein the CO.sub.2 separation means (11) is in additional fluid communication with the anode (7) for at least partially recycling the CO.sub.2 depleted stream (13) to the anode (7) as an anode inlet stream (28).
3. The system (1) according to claim 1 or 2, wherein the CO.sub.2 separation means (11) is a low temperature separation unit which is additionally configured to separate water from the at least a portion of the anode outlet stream (10).
4. The system (1) according to any of the preceding claims, wherein the CO.sub.2 separation means (11) is in fluid communication with the internal combustion engine (2) for feeding at least a portion of the CO.sub.2 depleted stream (13) to the internal combustion engine (2).
5. The system (1) according to any of the preceding claims, wherein the CO.sub.2 separation means (11) is in fluid communication with a burner (15) for feeding at least a portion of the CO.sub.2 depleted stream (13) via the burner (15) to the cathode (6) of the molten carbonate fuel cell (5).
6. The system (1) according to any of the preceding claims, wherein the CO.sub.2 separation means (11) is in fluid communication with a hydrogen purification unit (16), preferably a membrane unit, for receiving at least a portion of the CO.sub.2 depleted stream (13) and for recovering hydrogen (17) therefrom by the hydrogen purification unit.
7. The system (1) according to any of the preceding claims, wherein the CO.sub.2 separation means (11) is in fluid communication with a steam generator (18) for feeding at least a portion of the CO.sub.2 depleted stream (13) to the steam generator (18) for generating steam (19).
8. The system (1) according to any of the preceding claims, further comprising a splitter (20) which is in fluid communication with the internal combustion engine (2) for splitting the exhaust gas (3) and controlling an amount of the exhaust gas (4) that is sent to the cathode, and/or further comprising a splitter (23) which is in fluid communication with the CO.sub.2 separation means (11) for controlling an amount of the CO.sub.2 depleted stream (13) which is recycled to the cathode (6) and/or to the anode (7).
9. The system (1) according to any of the preceding claims, further comprising a compressor (24) which is in fluid communication with the anode (7) for receiving and compressing at least a portion of the anode outlet stream (10) and for feeding a resulting compressed anode outlet stream (25) to the CO.sub.2 separation means (11), wherein the molten carbonate fuel cell (5) preferably has an electric connection (26) with the compressor (24) for partially using the electric energy (8) to at least partially operate the compressor (24).
10. The system (1) according to any of the preceding claims, further comprising a water-gas-shift reactor (27) which is in fluid communication with the anode (7) for receiving at least a portion of the anode outlet stream (10).
11. A vessel comprising a carbon capture system (1) according to any of claims 1 to 10.
12. Use of a carbon capture system (1) according to any of claims 1 to 10 for capturing CO.sub.2.
13. Use of an internal combustion engine (2) and/or a molten carbonate fuel cell (5) and/or a CO.sub.2 separation means (11) in a carbon capture system (1) according to any of claims 1 to 10.
14. A method of capturing CO.sub.2 onboard a vessel, comprising: feeding a fuel to an internal combustion engine (2) to produce power (3) and an exhaust gas (4), feeding at least a portion of the exhaust gas (4) to a cathode (6) of a molten carbonate fuel cell (5), operating the molten carbonate fuel cell (5) to produce electric energy (8), feeding at least a portion of an anode outlet stream (10) of the molten carbonate fuel cell (5) to a CO.sub.2 separation means (11), feeding at least a portion of the electric energy (8) to the CO.sub.2 separation means (11), and separating CO.sub.2 from the at least a portion of the anode outlet stream (10) by the CO.sub.2 separation means (11) to produce a CO.sub.2 rich stream (12) and a CO.sub.2 depleted stream (13).
15. CO.sub.2 captured with a carbon capture system (1) according to any of claims 1 to 10, or captured on a vessel according to claim 11, or captured by the use according to claim 12, or captured with a method according to claim 14.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] FIG. 1 shows a carbon capture system according to the invention which comprises an internal combustion engine, an MCFC and a CO.sub.2 separation means.
[0073] FIG. 2 shows a carbon capture system according to the invention in which the molten carbonate fuel cell has an electric connection with the CO.sub.2 separation means.
[0074] FIG. 3 shows a carbon capture system according to the invention in which the CO.sub.2 separation means is in fluid communication with the internal combustion engine.
[0075] FIG. 4 shows a carbon capture system according to the invention which comprises a burner in fluid communication with the CO.sub.2 separation means and in fluid communication with the cathode of the MCFC.
[0076] FIG. 5 shows a carbon capture system according to the invention which comprises a hydrogen purification unit in fluid communication with the CO.sub.2 separation means.
[0077] FIG. 6 shows a carbon capture system according to the invention which comprises a steam generator in fluid communication with the CO.sub.2 separation means.
[0078] FIG. 7 shows a carbon capture system according to the invention which comprises a first splitter in fluid communication with the internal combustion engine and a second splitter in fluid communication with the CO.sub.2 separation means.
[0079] FIG. 8 shows a carbon capture system according to the invention which comprises a compressor in fluid communication with the anode of the MCFC.
[0080] FIG. 9 shows a carbon capture system according to the invention which comprises a water-gas-shift reactor in fluid communication with the anode of the MCFC.
[0081] FIG. 10 shows a carbon capture system according to the invention in which the CO.sub.2 separation means is in additional fluid communication with the anode of the MCFC.
[0082] FIG. 11 shows a carbon capture system according to the invention which comprises a compressor in fluid communication with the anode of the MCFC and in which the CO.sub.2 separation means is in additional fluid communication with the anode of the MCFC.
[0083] FIG. 12 shows a carbon capture system according to the invention which comprises a compressor in fluid communication with the CO.sub.2 separation means.
EXEMPLARY EMBODIMENTS
[0084] The present invention is further described with reference to the accompanying figures. The present invention is directed to a carbon capture system 1 which is located on a vessel, i.e., which is a carbon capture system 1 onboard a vessel. The vessel itself is however not shown in the figures. Where arrows are used, the rectangular end represents the upstream side or position, while the arrow end represents the downstream side or position.
[0085] An exemplary embodiment of a carbon capture system 1 is shown in FIG. 1. The carbon capture system 1 comprises an internal combustion engine 2 for producing power 3 and an exhaust gas 4. The internal combustion engine 2 is preferably a Diesel engine, an Otto engine or a gas turbine. The internal combustion engine 2 is fed with a fuel which comprises hydrocarbons, typically including methane, for combustion in the engine proper of the combustion engines (not shown). By combusting the fuel, the internal combustion engine 2 produces the power 3 and the exhaust gas 4. The power 3 produced by the internal combustion engine 2 is typically used for propelling the vessel in which the carbon capture system 1 is installed, but may also be used for other applications. The exhaust gas 4 produced by the internal combustion engine 2 typically contains carbon-based fuel waste such as carbon oxides, nitrogen oxides and sulfur oxides. The exhaust gas 4 typically contains carbon dioxide (CO.sub.2), and the present invention aims at capturing and potentially using CO.sub.2 onboard the vessel in order to avoid an emission of the CO.sub.2 to the atmosphere, thereby preventing a pollution of the environment by such emitted CO.sub.2. In order to further concentrate the CO.sub.2, the carbon capture system 1 further comprises an MCFC 5 downstream of the internal combustion engine 2. The MCFC comprises two electrodes, namely a cathode 6 and an anode 7. In the embodiment of FIG. 1, both these electrodes are made of nickel. The MCFC 5 further comprises an electrolyte between the two electrodes. In the embodiment of FIG. 1, the electrolyte is a blend of Li.sub.2CO.sub.3 and K.sub.2CO.sub.3. The MCFC 5 is preferably operated at a temperature in the range of 540 to 750 C., more preferably in the range of 550 to 700 C., and still more preferably in the range of 580 C. to 675 C. The MCFC 5 is further operated such that it generates electricity, i.e., the MCFC 5 produces electric energy 8. A resulting typical cell voltage is about 0.7 V. The exhaust gas 4 is used as an inlet stream for the MCFC 5 and is more specifically sent to the cathode 6 of the MCFC 5 (the cathode inlet stream). This cathode inlet stream typically has a high CO.sub.2 concentration. At the same time a fuel comprising methane is used as a further inlet stream for the MCFC 5 and is more specifically sent to the anode 7 of the MCFC 5 (the anode inlet stream). During the operation of the MCFC 5, CO.sub.2 is transferred from the cathode 6 to the anode 7. As a result, the cathode outlet stream 9 has a lower CO.sub.2 concentration than the cathode inlet stream, while the anode outlet stream 10 has a higher CO.sub.2 concentration than the anode inlet stream. The anode outlet stream 10 is subsequently sent to another unit for separating CO.sub.2 from that anode outlet stream 10. This can also be seen as a further purification of the CO.sub.2 exiting the anode 7 in order to provide a purified CO.sub.2 stream for subsequent storage or further use. The unit for separating CO.sub.2 from that anode outlet stream 10, or for purifying this CO.sub.2 outlet stream, is combinedly referred to herein as a CO.sub.2 separation means. In the embodiment of FIG. 1, the CO.sub.2 separation means 11 is a low temperature phase change separation unit which liquifies CO.sub.2 contained in the anode outlet stream 10 and allows to separate liquified CO.sub.2 therefrom. In the embodiment of FIG. 1, this low temperature phase change separation unit is operated under typical conditions of a temperature of 53 to 56 C. and an absolute pressure of 1 to 2 MPa, for example 55 C. and 2 MPa. The CO.sub.2 separation means 11 thereby produces a basically liquid CO.sub.2 rich stream 12 and a basically gaseous CO.sub.2 depleted stream 13. In the embodiment of FIG. 1, a purity of the CO.sub.2 rich stream 12 of at least 95 mol % is achieved. Further, compared to the originally produced exhaust gas 4, the carbon capture system 1 of FIG. 1 achieves an avoidance rate of CO.sub.2 emission of at least 80 wt. %, i.e., at most 20 wt. % of the CO.sub.2 produced by the internal combustion engine 2 are emitted to the atmosphere. The carbon capture system 1 of FIG. 1 may further achieve an avoidance rate of CO.sub.2 emission of at least 90 wt. % and even up to 100 wt. %. The carbon capture system 1 of FIG. 1 can thereby prevent a respective pollution of the environment. In the embodiment of FIG. 1, the captured CO.sub.2 is sent to one or more not shown containers for onboard storage of the CO.sub.2. For this, the CO.sub.2 separation means 11 is in fluid communication with the one or more containers. In an unshown alternative, the captured CO.sub.2 is further used onboard the vessel, in particular as a cathode feed for a second, auxiliary molten carbonate fuel cell onboard which produces additional electric energy.
[0086] FIG. 2 shows a supplementing exemplary embodiment of a carbon capture system 1 in which the electric energy 8 is used for operating the CO.sub.2 separation means 11, in particular a low temperature phase change separation unit. This is realized by the electric connection 14 of the MCFC 5 with the CO.sub.2 separation means 11, established by wiring. In order to achieve the typical conditions of the low temperature phase change separation unit of a temperature of 53 to 56 C. and an absolute pressure of 1 to 2 MPa, especially 55 C./2 MPa, simultaneous cooling and pressurising is required. Such cooling and pressurising typically requires electric energy, for example for circulating a cooling fluid or moving a pressure exerting element. For this purpose, the CO.sub.2 separation means 11 of FIG. 2 uses the electric energy produced by the MCFC 5. There is thus no (or reduced) need to feed additional electric energy from the outside to the carbon capture system 1. The carbon capture system 1 thereby advantageously becomes a self-supporting system. Even if not shown, an electric connection 14 of the MCFC 5 with the CO.sub.2 separation means 11 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 and 3 to 9.
[0087] FIG. 3 shows a supplementing exemplary embodiment of a carbon capture system 1 in which the CO.sub.2 depleted stream 13 is recirculated to the internal combustion engine 2. In a first case, the internal combustion engine 2 of FIG. 3 is a volumetric engine, in particular a Diesel engine or an Otto engine. In this case, the CO.sub.2 depleted stream 13 becomes an additional inlet stream for the internal combustion engine. The CO.sub.2 depleted stream 13 typically contains H.sub.2 and/or CO, which is mixed with the fuel fed to the internal combustion engine 2. The combustion reactions occurring within the internal combustion engine 2 thereby become more complete, so that the efficiency of the combustion reactions is improved and less methane contained in the fuel slips unreacted (or unburnt) through the internal combustion engine 2. Accordingly, the combustion properties of the internal combustion engine 2 of the carbon capture system according to FIG. 3 are improved, and simultaneously the methane slip occurring in the system is reduced. In a second case the internal combustion engine 2 of FIG. 3 is a gas turbine. In this case, the CO.sub.2 separation means is more specifically in fluid communication with a post-firing device of the gas turbine (not shown). The post-firing device is in fluid communication with the gas turbine and receives exhaust gas produced by the gas turbine. In this scenario, the CO.sub.2 depleted stream 13 is more specifically sent to the post-firing device. Valuable components of the CO.sub.2 depleted stream 13, in particular H.sub.2, CO and/or unburnt CH.sub.4, are thereby recycled and mixed with the exhaust gas produced by the gas turbine. The combustion reactions occurring in the post-firing device thereby become more complete and thus more efficient. Accordingly, the combustion properties of the post-firing device and hence of the overall internal combustion engine 2 are also improved in this scenario. Although not shown, a recirculation of the CO.sub.2 depleted stream 13 to the internal combustion engine 2 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1, 2 and 4 to 9.
[0088] FIG. 4 shows a supplementing exemplary embodiment of a carbon capture system 1 in which the CO.sub.2 depleted stream 13 is recirculated to the cathode 6 of the MCFC 5 via a burner 15. Additionally, the burner 15 receives at least a part of the exhaust gas 4 (in FIG. 4, all exhaust gas 4 is sent to the burner 15; alternatively, exhaust gas 4 may be split to be partly fed to the burner 15 and partly directly to cathode 6). The exhaust gas 4 regularly contains some air which is the used for an oxidisation in the burner 15. The burner 15 is thus a device which allows for an oxidisation of gases in the CO.sub.2 depleted stream 13 which are different from CO.sub.2, for example residual hydrocarbons, especially CH.sub.4, and/or H.sub.2 and/or CO. By burning these gases, the burner 15 increases the CO.sub.2 concentration in the CO.sub.2 depleted stream 13 which is thereafter sent to the cathode 6. Accordingly, the cathode inlet stream will have an even higher CO.sub.2 concentration, thereby rendering the electric energy producing reactions in the MCFC 5 more effective, which adds to the self-supporting properties of carbon capture system 1. At the same time, the burner 15 generates additional heat which can be used onboard the vessel and in particular within the carbon capture system 1 itself. For example, the MCFC 5 requires elevated temperatures for its operation due to the need of a molten carbonate electrolyte. The heat generated by the burner 15 can be used to heat up the MCFC 5 as required, which further adds to the self-supporting properties of carbon capture system 1. Additionally, by burning residual CH.sub.4, the burner 15 contributes to an overall reduction of potential methane slip of the internal combustion engine 2, and the burner 15 further increases the CO.sub.2 concentration in the stream sent to the cathode 6. Although not shown, a burner 15 including a recirculation of the CO.sub.2 depleted stream 13 to the cathode 6 of the MCFC 5 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 to 3 and 5 to 9.
[0089] FIG. 5 shows a supplementing exemplary embodiment of a carbon capture system 1 which comprises a hydrogen purification unit 16 which is in fluid communication with the CO.sub.2 separation means 11. In the embodiment of FIG. 5, the hydrogen purification unit 16 is a ceramic membrane unit (alternatives are a palladium membrane unit, a carbon membrane unit, and a polymeric membrane unit), which separates hydrogen 19 contained in the CO.sub.2 depleted stream 13. The separated hydrogen 19 is then preferably sent to an auxiliary fuel cell onboard the vessel as an anode inlet stream for this auxiliary fuel cell (not shown). The auxiliary fuel cell produces additional electric energy which can be used to operate different means, devices, units, etc. of the carbon capture system 1 and which can in particular be used to operate the CO.sub.2 separation means 11. The hydrogen purification unit 16 used in the system of FIG. 5 thereby fosters the self-supporting properties of carbon capture system 1. Although not shown, a hydrogen purification unit 16 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 to 4 and 6 to 9.
[0090] FIG. 6 shows a supplementing exemplary embodiment of a carbon capture system 1 which comprises a steam generator 18 which is in fluid communication with the CO.sub.2 separation means 11. Like the burner 15, the steam generator 18 makes use of residual components in the CO.sub.2 depleted stream 13, in particular of yet unreacted (unburnt) hydrocarbons, especially CH.sub.4, and/or H.sub.2 and/or CO in a further oxidation process which generates heat. For the oxidation process, additional air is regularly fed to the steam generator 18 (not shown). The generated heat actually heats up water to produce steam. The steam can especially be used as an additional inlet stream of anode 7 of the MCFC 5 to initiate a reforming reaction like CH.sub.4+H.sub.2O=3H.sub.2+CO. The steam generator 18 used in the carbon capture system 1 of FIG. 6 thereby fosters the self-supporting properties of that carbon capture system 1. Although not shown, a steam generator 18 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 to 5 and 7 to 9.
[0091] FIG. 7 shows a supplementing exemplary embodiment of a carbon capture system 1 which comprises a first splitter 20 in fluid communication with the internal combustion engine 2. The first splitter 20 splits the exhaust gas 4 into two different streams, a first split stream 21 and a second split stream 22. Accordingly, the flow of exhaust gas from the internal combustion engine 2 is controlled by the splitter 20. A controlled portion of the exhaust gas 4 is thereby brought into contact with the cathode 6 at which CO.sub.2 is selectively extracted according to the electrochemical reactions described herein. That is, the flowrate of the first split stream 21 is controlled. The first split stream 21 corresponds to the amount of the exhaust gas 4 that is sent to the cathode. The control of the flowrate of the first split stream 21 is used to control the electric output of MCFC 5, i.e., to control the electric energy produced by MCFC 5. The use of the produced electric energy within the carbon capture system 1 itself is then controlled according to demand for such energy within the system. The first splitter 20 used in the carbon capture system 1 of FIG. 7 thereby fosters the self-supporting properties of that carbon capture system 1. The carbon capture system 1 of FIG. 7 further comprises a second splitter 23 which is in fluid communication with the CO.sub.2 separation means. The second splitter 23 splits the CO.sub.2 depleted stream 13 into two streams which are sent to the cathode 6 and the anode 7, i.e., they are recycled to the cathode 6 and/or to the anode 7 as CO.sub.2 depleted partial stream 13a and CO.sub.2 depleted partial stream 13b. In the embodiment of FIG. 7, the second splitter 23 controls the split between the two recycled streams in response to the concentration of CH.sub.4 in the CO.sub.2 depleted stream 13. By setting the split between the two recycled streams accordingly, the second splitter 23 controls the power outlet of the MCFC 5. The second splitter 23 used in the carbon capture system 1 of FIG. 7 thereby also fosters the self-supporting properties of that carbon capture system 1 and enhances the versatility thereof. Although not shown, a carbon capture system 1 of FIG. 7 comprising only one of splitter 20 or splitter 23 is also disclosed herein. Although not shown, a splitter 20 and/or a splitter 23 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 to 6, 8 and 9.
[0092] FIG. 8 shows a supplementing exemplary embodiment of a carbon capture system 1 which further comprises a compressor 24 in fluid communication with the anode 7. The compressor 24 receives the anode outlet stream 10 and subsequently compresses the received anode outlet stream 10. The result of the compression is the compressed anode outlet stream 25, which is sent to the CO.sub.2 separation means 11, which is a low temperature phase change separation unit as in the embodiment of FIG. 1. The low temperature phase change separation unit can now work under reduced pressure compared to the embodiment of FIG. 1 because the received stream is here the compressed anode outlet stream 25. Hence, less additional compression work has to be invested by the CO.sub.2 separation means 11 in order to liquify the CO.sub.2. As the received stream is pre-compressed, the separation of CO.sub.2 within the CO.sub.2 separation means 11 can occur quicker and more efficiently. The CO.sub.2 captured with the carbon capture system 1 of FIG. 8 may consequently have an even higher concentration than the CO.sub.2 captured by the carbon capture system 1 of FIG. 1. The carbon capture system 1 of FIG. 8 thereby effectively prevents a pollution of the environment by the CO.sub.2 thus captured. Further, in the carbon capture system 1 of FIG. 8, the MCFC 5 has an electric connection 26 (wiring) with the compressor 24. The electric energy 8 produced by the MCFC 5 is partially used to operate the compressor 24. No (or less) electricity input from the outside is thus required for operating the compressor 24. The electric connection 26 between MCFC 5 and compressor 24 therefore contributes to the self-supporting characteristics of the carbon capture system 1. Additionally, in the carbon capture system 1 of FIG. 8, the MCFC 5 has an electric connection 14 (wiring) with the CO.sub.2 separation means 11. No (or less) electricity input from the outside is thus required for operating the compressor 24. The electric connection 14 between MCFC 5 and CO.sub.2 separation means 11 therefore contributes to the self-supporting characteristics of the carbon capture system 1. Although not shown, a carbon capture system 1 of FIG. 7 comprising only one of electric connection 26 or electric connection 14 is also disclosed herein. Similarly, while also not shown, a carbon capture system 1 of FIG. 7 comprising neither electric connection 26 nor electric connection 14 is also disclosed herein. Further, although not shown, a compressor 24 and/or an electric connection 26 and/or an electric connection 14 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 to 7 and 9.
[0093] FIG. 9 shows a supplementing exemplary embodiment of a carbon capture system 1 which comprises a water-gas-shift reactor 27 in fluid communication with the molten carbonate fuel cell 5. The water-gas-shift reactor 27 receives the anode outlet stream 10 which typically contains residual CO and H.sub.2O. The water-gas-shift reactor converts the CO and the H.sub.2O into CO.sub.2 and H.sub.2. The converted stream is then sent to the CO.sub.2 separation means 11, which can capture the additional CO.sub.2 produced by the water-gas-shift reactor. The additionally captured CO.sub.2 is thereby also prevented from polluting the environment. Although not shown, a water-gas-shift reactor 27 can additionally and analogously be a feature of the carbon capture system 1 according to any of FIGS. 1 to 8.
[0094] FIG. 10 shows a supplementing exemplary embodiment of a carbon capture system 1 in which the CO.sub.2 separation means 11 has an additional (or second) fluid communication with the anode 7. Via this additional fluid communication, the CO.sub.2 depleted stream 13 is recycled to the anode 7 and thereby becomes an anode inlet stream 28. Of course, the anode is further fed with some fuel so that there is at least one further anode inlet stream (not shown). Although in FIG. 10 the entire CO.sub.2 depleted stream 13 is recycled to the anode 7, it is also contemplated that the CO.sub.2 depleted stream 13 is only partially recycled to the anode 7. By recycling, or returning, at least a part of the CO.sub.2 depleted stream 13 to the anode 7 unreacted components of the reformable fuel sent to the anode 7 are recirculated within the system. Accordingly, these regularly valuable components are not lost, but are utilized in an improved manner, making the overall system more economic.
[0095] FIG. 11 shows a supplementing exemplary embodiment of a carbon capture system 1 which is basically a combination of the exemplary embodiments of FIGS. 8 and 10. That is, in this embodiment the carbon capture system 1 further comprises a compressor 24 in fluid communication with the anode 7. Additionally, the CO.sub.2 separation means 11 has an additional (or second) fluid communication with the anode 7. The same elements as described separately for FIG. 8 and for FIG. 10 above are jointly present in this embodiment and lead to the same effects. Accordingly, the MCFC 5 produces electric energy 8 which is used to operate both, the CO.sub.2 separation means 11 and the compressor 24. The compressor 24 supports the CO.sub.2 separation means 11 in that pre-compressed CO.sub.2 is sent to the CO.sub.2 separation means 11 where the CO.sub.2 separation can occur quicker and more efficiently. The CO.sub.2 separation means 11 at least partially recirculates the CO.sub.2 depleted stream 13 to the anode 7, wherein the CO.sub.2 depleted stream 13 contains unreacted and hence still usable fuel components. Accordingly, the CO.sub.2 separation means 11 supports the MCFC 5. It is thus seen that the MCFC 5, the CO.sub.2 separation means 11 and the compressor 24 mutually support each other, thereby adding to the self-supporting characteristics of the carbon capture system 1.
[0096] FIG. 12 shows a supplementing exemplary embodiment of a carbon capture system 1 In this embodiment the carbon capture system 1 further comprises a (nother) compressor 29 in fluid communication with the CO.sub.2 separation means 11. Here, the MCFC 5 produces electric energy 8 which is used to operate both, the CO.sub.2 separation means 11 and the further compressor 29. The compressor 29 receives a CO.sub.2 rich stream 12 from the CO.sub.2 separation means 11 and compresses the received CO.sub.2 such that the CO.sub.2 is liquified and can subsequently be conveniently stored onboard the vessel.
LIST OF REFERENCE SIGNS
[0097] 1: carbon capture system [0098] 2: internal combustion engine [0099] 3: power [0100] 4: exhaust gas [0101] 5: molten carbonate fuel cell [0102] 6: cathode [0103] 7: anode [0104] 8: electric energy [0105] 9: cathode outlet stream [0106] 10: anode outlet stream [0107] 11: CO.sub.2 separation means [0108] 12: CO.sub.2 rich stream [0109] 13: CO.sub.2 depleted stream [0110] 13a: CO.sub.2 depleted partial stream [0111] 13b: CO.sub.2 depleted partial stream [0112] 14: electric connection [0113] 15: burner [0114] 16: hydrogen purification unit [0115] 17: hydrogen [0116] 18: steam generator [0117] 19: steam [0118] 20: splitter [0119] 21: first split stream [0120] 22: second split stream [0121] 23: splitter [0122] 24: compressor [0123] 25: compressed anode outlet stream [0124] 26: electric connection [0125] 27: water-gas-shift reactor [0126] 28: anode inlet stream [0127] 29: a (nother) compressor [0128] 30: compressed CO.sub.2 rich stream
FURTHER DISCLOSURE
[0129] The present invention further provides the following items:
[0130] 1. A carbon capture system (1) onboard a vessel, comprising: [0131] an internal combustion engine (2) for producing power (3) and an exhaust gas (4), [0132] a molten carbonate fuel cell (5), which comprises a cathode (6) and an anode (7), for producing electric energy (8), a cathode outlet stream (9) and an anode outlet stream (10), wherein the cathode (6) is in fluid communication with the internal combustion engine (2) for receiving at least a portion of the exhaust gas (4), and [0133] a CO.sub.2 separation means (11) which is in fluid communication with the anode (7) for receiving at least a portion of the anode outlet stream (10), wherein the CO.sub.2 separation means (11) is configured to separate CO.sub.2 from the at least a portion of the anode outlet stream (10) for producing a CO.sub.2 rich stream (12) and a CO.sub.2 depleted stream (13).
[0134] 2. The system (1) according to item 1, wherein the molten carbonate fuel cell (5) has an electric connection (14) with the CO.sub.2 separation means (11) for at least partially using the electric energy (8) to at least partially operate the CO.sub.2 separation means (11).
[0135] 3. The system (1) according to item 1 or 2, wherein the CO.sub.2 separation means (11) is a low temperature separation unit which is additionally configured to separate water from the at least a portion of the anode outlet stream (10).
[0136] 4. The system (1) according to any of the preceding items, wherein the CO.sub.2 separation means (11) is in fluid communication with the internal combustion engine (2) for feeding at least a portion of the CO.sub.2 depleted stream (13) to the internal combustion engine (2).
[0137] 5. The system (1) according to any of the preceding item, wherein the CO.sub.2 separation means (11) is in fluid communication with a burner (15) for feeding at least a portion of the CO.sub.2 depleted stream (13) via the burner (15) to the cathode (6) of the molten carbonate fuel cell (5).
[0138] 6. The system (1) according to any of the preceding items, wherein the CO.sub.2 separation means (11) is in fluid communication with a hydrogen purification unit (16), preferably a membrane unit, for receiving at least a portion of the CO.sub.2 depleted stream (13) and for recovering hydrogen (17) therefrom by the hydrogen purification unit.
[0139] 7. The system (1) according to any of the preceding items, wherein the CO.sub.2 separation means (11) is in fluid communication with a steam generator (18) for feeding at least a portion of the CO.sub.2 depleted stream (13) to the steam generator (18) for generating steam (19).
[0140] 8. The system (1) according to any of the preceding items, further comprising a splitter (20) which is in fluid communication with the internal combustion engine (2) for splitting the exhaust gas (3) and controlling an amount of the exhaust gas (4) that is sent to the cathode, and/or further comprising a splitter (23) which is in fluid communication with the CO.sub.2 separation means (11) for controlling an amount of the CO.sub.2 depleted stream (13) which is recycled to the cathode (6) and/or to the anode (7).
[0141] 9. The system (1) according to any of the preceding items, further comprising a compressor (24) which is in fluid communication with the anode (7) for receiving and compressing at least a portion of the anode outlet stream (10) and for feeding a resulting compressed anode outlet stream (25) to the CO.sub.2 separation means (11), wherein the molten carbonate fuel cell (5) preferably has an electric connection (26) with the compressor (24) for partially using the electric energy (8) to at least partially operate the compressor (24).
[0142] 10. The system (1) according to any of the preceding items, further comprising a water-gas-shift reactor (27) which is in fluid communication with the anode (7) for receiving at least a portion of the anode outlet stream (10).
[0143] 11. A vessel comprising a carbon capture system (1) according to any of items 1 to 10.
[0144] 12. Use of a carbon capture system (1) according to any of items 1 to 10 for capturing CO.sub.2.
[0145] 13. Use of an internal combustion engine (2) and/or a molten carbonate fuel cell (5) and/or a CO.sub.2 separation means (11) in a carbon capture system (1) according to any of items 1 to 10.
[0146] 14. A method of capturing CO.sub.2 onboard a vessel, comprising: [0147] feeding a fuel to an internal combustion engine (2) to produce power (3) and an exhaust gas (4), [0148] feeding at least a portion of the exhaust gas (4) to a cathode (6) of a molten carbonate fuel cell (5), [0149] operating the molten carbonate fuel cell (5) to produce electric energy (8), [0150] feeding at least a portion of an anode outlet stream (10) of the molten carbonate fuel cell (5) to a CO.sub.2 separation means (11), and [0151] separating CO.sub.2 from the at least a portion of the anode outlet stream (10) by the CO.sub.2 separation means (11) to produce a CO.sub.2 rich stream (12) and a CO.sub.2 depleted stream (13).
[0152] 15. CO.sub.2 captured with a carbon capture system (1) according to any of items 1 to 10, or captured on a vessel according to item 11, or captured by the use according to item 12, or captured with a method according to item 14.
