High temperature PEM fuel cell system with a heat pump for heating the reformer, method of operation thereof and use thereof

Abstract

A fuel cell system, method and use thereof, comprising a fuel cell (1) including a reformer (6) for catalytically reforming a fuel to obtain a synthesis gas containing hydrogen, a fuel cell (2) for receiving the synthesis gas from the reformer (6), a reformer heater (27) for heating the reformer (6) to a predetermined reformer temperature, and a cooling circuit (7) including a coolant flow for maintaining the operating temperature of the fuel cell (2). The reformer heater (27) includes an electric heat pump (12) thermally connected to the cooling circuit (7) for extracting thermal energy from the coolant and transferring the extracted thermal energy to a heating fluid in a heating circuit (13) connected to the reformer (6).

Description

[Technical Field]

[0001] The present invention relates to a high temperature PEM fuel cell system including a reformer and a reformer heater, a method for operating the same, and uses thereof. In particular, the invention relates to a system as set forth in the preamble of the independent claim. [Background technology]

[0002] There are various options for supplying hydrogen gas (H2) or hydrocarbons to fuel cells, including pressurized H2, methane, or alcohols such as methanol or ethanol. Typical gas fuels for fuel cells include ethane, propane, and natural gas. Alcohol fuels for fuel cells are advantageous in that they can reuse much of the existing liquid fuel infrastructure for diesel and gasoline, including transportation to fuel stations and storage of the fuel on board the vehicle.

[0003] When methane or alcohol is used as fuel, it must be converted to H2 gas. The corresponding reforming reaction in a catalytic reformer is endothermic and requires energy. A reformer heater is provided in a fuel cell system to provide such energy by heating the reformer. Typically, the reformer heater is a burner that combusts fuel to provide thermal energy. The term burner is common in the art, regardless of whether the burner uses a conventional flame or catalytic consumption of fuel to generate the required thermal energy. Optionally, the burner consumes excess H2 gas from the fuel cell anode exhaust gas. When using methanol, the reforming temperature is typically 250°C. The reformer heater adds thermal energy at a rate sufficient to sustain the reforming process, specifically, 49 kJ / mol of thermal energy to the reaction of methanol and water reforming to obtain CO2 and H2.

[0004] Fuel reforming produces syngas, a mixture of gases containing H2 gas, carbon dioxide (CO2), carbon monoxide (CO), and some residual water (HO). In fuel cells with polymer electrolyte membranes (PEMs) that operate at low temperatures below 100°C (hence these types of fuel cells are called LT-PEM fuel cells or simply PEM fuel cells), the membrane is highly sensitive to CO gas, so CO gas is converted to CO2 in a shift reactor before the syngas enters the fuel cell. In typical high-temperature PEM fuel cells, HT-PEM fuel cells, which operate at higher temperatures above 120°C and even up to 200°C, the shift reactor can be omitted because the system is more tolerant of CO gas.

[0005] Fuel cells are gaining increasing attention for power generation in vehicles, particularly electric cars and ships, and there is a continuing demand to improve the efficiency of power generation, with even improvements of around 1% being attractive. This has led to corresponding improvements in the technology field.

[0006] For example, U.S. Patent Publication US2010 / 0266923A1 discloses an electrochemical hydrogen separator for separating H2 gas from a fuel cell anode exhaust and reintroducing it into the fuel cell to optimize fuel cell efficiency. Monitoring the performance of the hydrogen separator provides insight into fuel cell system performance. When H2 gas is separated from the anode exhaust stream and recycled to the fuel cell anode, it is lost as fuel for the reformer heater. This is not an issue with the SOFC cells disclosed in US2010 / 0266923A1, which operate in the temperature range of 750°C to 950°C. This is because excess heat from the fuel cell can be used to heat the reformer as well as the electrochemical H2 separator described in the publication.

[0007] However, for fuel cells operating at lower temperatures, the fuel is traditionally used to heat the reformer, so separating the H2 and reintroducing it to the anode does not provide any appreciable efficiency advantage.

[0008] This observation is supported by the study of a system disclosed in German Patent Application DE102013009244A1, which uses a membrane separator to separate H2 from the anode gas, with the CO2 remaining after condensation to be collected in a storage tank. In this reference, a membrane is used to transport H2 from the gas stream to the H2O stream and enrich the fuel gas stream for the reformer heater. This follows the conventional approach of using H2 in a cycle, introduced by flame or catalytic combustion into the reformer burner to heat the reformer. As an additional option, DE102013009244A1 discloses enriching the methane gas stream entering the catalytic reformer with H2. However, upon more detailed evaluation, this appears to be suboptimal. This is because increasing the H2 level in the gas stream at the reformer inlet is expected to reduce rather than improve overall reforming efficiency, as the H2 concentration in the reformer is already offset to a significant concentration level from the start, and the H2 production capacity in the reformer will not be optimized until the H2 concentration in the gas is at its maximum. Thus, it can be seen from the disclosure of DE102013009244A1 that the purpose of separating H2 from the anode exhaust gas is not for the general purpose of improving the efficiency of the fuel cell system, but rather to find some meaningful use for the by-product H2 gas separated from the anode exhaust gas before recovering carbon from the exhaust gas stream, with carbon recovery being the primary purpose of DE102013009244A1.

[0009] However, particularly for fuel cell systems where the fuel cell operates at temperatures below the minimum temperature required for reforming, it is desirable to find a reformer heater, distinct from a reformer burner, to heat the reformer without burning H2 gas or other fuel within the reformer heater.

[0010] In a paper by Perry et al. in Journal of Power Sources 177 (2008) 478-484 entitled "Electrochemical hydrogen pumping using a high-temperature polybenzimidazole (PBI) membrane," the authors demonstrated the electrochemical separation of hydrogen from a gas mixture containing N2, H2, CO, and CO2 using a high-temperature (>100°C) polybenzimidazole (PBI) membrane. Specifically, the electrochemical pump was operated at 160°C, approximately 1.2 times the stoichiometric requirement for pure hydrogen, without external humidification. While such a hydrogen pump operates at 160°C, similar to the coolant temperature of an HT-PEM fuel cell, it was noted that the coolant from an LT-PEM fuel cell, such as that disclosed in the aforementioned DE102013009244A, would not provide a sufficiently high temperature because it is below 100°C.

[0011] EP1081781A2 discloses a multi-stage chemical heat pump (HP1+HP2) for removing heat to maintain the temperature of a solid polymer electrolyte fuel cell at 80°C and for raising the temperature of a heat transfer medium to 350°C to heat a reformer. To achieve efficient cooling through a radiator, a temperature increase from 80°C to 200°C for HP1 and from 80°C to 350°C for HP2 is desirable, allowing for a smaller radiator and a more compact hydrogenation reactor. This system is recommended for use in automobiles. This heat can be used to heat the reformer. However, this system is complex. Furthermore, it is dangerous in automobiles because a mixture of IPA, acetone, H2, and other chemicals is maintained at temperatures above 200°C, and other chemicals are maintained at even higher temperatures.

[0012] DE 10152233 A1 discloses an LT-PEM fuel cell operating at temperatures between 50 and 120°C. It explains that if the external temperature is 20°C, a large air cooler is required to operate at 80°C, but that the air cooler can be made smaller if the temperature is raised to 100°C by a heat pump. It is recommended that this system be used in automobiles. This heat can be used to heat a reformer. However, no specific type of heat pump is mentioned. Summary of the Invention

[0013] The object of the present invention is to provide an improvement over the art, in particular to provide a reformer heater for an HT-PEM fuel cell system which does not provide heat to the reformer by burning H2 or fuel. This object and further advantages are achieved by a fuel cell system and a method for operating the same as set out below and in the claims. In particular, the present invention relates to a fuel cell system as set out in claim 1 and a method for operating the same as set out in claim 6.

[0014] In short, in the fuel cell system shown below, a heat pump is used to transfer thermal energy from the cooling circuit to the reformer, heating the reformer to a predetermined temperature T, which is equal to or higher than the minimum temperature required for catalytic reforming. ref The reformer is maintained at a constant temperature. Because reformer heating does not require a reformer burner that consumes H and / or fuel, H gas from the anode exhaust gas is advantageously recycled to the fuel cell by mixing with the syngas. Separating H gas from the anode exhaust gas, for example by electrochemical separation, provides the option of collecting the remaining CO, for example as liquid CO, after condensing and removing the water.

[0015] Details are explained below.

[0016] The fuel cell system includes a fuel supply device for supplying fuel to the reformer, so that H2 gas can be supplied to the fuel cell after the fuel is reformed. Examples of gaseous fuels are methane, ethane, propane, and natural gas, and examples of liquid fuels are alcohols such as methanol or ethanol.

[0017] The reformer receives fuel, for example after vaporizing a liquid fuel, and catalytically reforms the fuel to obtain H gas and other gas by-products such as CO, water, and CO. If desired, the CO can be further converted to CO by a shift converter. However, for HT-PEM fuel cells, CO removal is typically not required.

[0018] Fuel cells are typically provided as part of a fuel cell stack. A fuel cell has a membrane, an anode on one side of the membrane, and a cathode on the other side of the membrane. In the following, the abbreviations anode and cathode are used to refer to fuel cells.

[0019] The anode receives hydrogen gas from a reformer for reaction in the fuel cell, and the cathode receives oxygen gas, for example, as part of the air. In a PEM fuel cell, the supplied H2 gas crosses an ion-conducting membrane and forms water at the cathode. The water exits the cathode as steam, along with other gaseous components, such as nitrogen, from the supply air.

[0020] As already mentioned in the introduction, if the fuel cell is operated at a temperature lower than that required for the reforming process, the reformer is heated by a reformer heater to a temperature T ref It needs to be heated to

[0021] The fuel cell is an HT-PEM fuel cell operating at a temperature between 120°C and 200°C, e.g., between 150°C and 180°C. In the following example, the HT-PEM fuel cell operates at a temperature of approximately 170°C, which is the temperature of the coolant at the outlet of the coolant channels in the fuel cell stack. However, because slight variations throughout the fuel cell stack are normal, the operating temperature of the fuel cell stack is typically not determined to an accuracy of more than ±10°C around the predetermined temperature. If the operating temperature is set to 170°C, which is the temperature of the coolant exiting the fuel cell stack, the temperature of the fuel cell stack will vary between 160°C and 180°C. In particular, the coolant exiting the fuel cell at T2 = 170°C enters the fuel cell stack at a lower temperature T1, e.g., T1 = 160°C, which is one of the causes of temperature variations within the stack.

[0022] The minimum temperature for the reforming of methanol is about 200°C, but to reform at a sufficient rate, the operating temperature of the reformer is higher. The predetermined reformer temperature T for the reforming of methanol is ref is in the range of 250℃ to 300℃, and the temperature T ref =250°C is sufficient.

[0023] In contrast to the prior art, the reformer heater in the system described herein includes an electrically powered heat pump to provide the required high temperature. The heat pump does not burn fuel or recycled hot gas. Instead, it consumes electricity generated, for example, by a fuel cell. In this way, driving the heat pump requires additional electricity generation by the fuel cell, and therefore indirectly consumes H2. However, this is advantageous compared to the reformer burner because the fuel cell is more fuel-efficient than the reformer burner. Thus, instead of consuming fuel at a relatively low efficiency in the reformer burner, the fuel cell consumes fuel at a higher efficiency. This represents an option to improve the overall system efficiency. Furthermore, as will become more apparent below, waste heat from the fuel cell can be reused to heat the reformer.

[0024] In particular, efficiency gains of several percent can be achieved if H2 is separated from the anode exhaust gas and recycled to the anode, as will be described in more detail below.

[0025] With H2 separation and recycling, an efficiency gain of 7.5% is achieved. If the HT-PEM fuel cell is operated at 170°C, the heat pump can raise the temperature to 250°C with moderate energy consumption, resulting in a net gain of over 5% for the system. These estimates include the electricity consumption by the H2 separator.

[0026] The heat pump is thermally connected to the cooling circuit and extracts thermal energy from the coolant to reduce the coolant temperature. This is advantageous to the efficiency of the fuel cell system because heat, which is normally a waste product, is useful in the systems described herein. Thermal energy from the coolant downstream of the fuel cell is extracted from the coolant and transferred to a heating fluid in a heating circuit. The heating circuit is connected to the reformer and transfers thermal energy from the heating fluid to the reformer to heat the reformer to a reformer temperature T ref To compensate for the lower temperature in the cooling circuit, the temperature of the heating fluid in the heating circuit must be raised by a heat pump to a temperature above the minimum temperature required for reforming and above the temperature of the coolant.

[0027] In the above example, the HT-PEM operates at 170 °C and the temperature T ref = 250°C, the temperature of the heating fluid needs to be raised to above 250°C, even slightly higher.

[0028] Current heat pumps used in systems with LT-PEM fuel cells operating below 100°C are not expected to provide any efficiency gains compared to using a reformer burner.

[0029] The heat pump includes a multi-stage gas piston compressor that uses a working medium for heat pumping. refThe COP for heating is greater than 2. There are various working media, and some efficient heat pumps use helium as the working medium.

[0030] Examples of heat pumps capable of increasing temperature are found in the commercial market. For example, Spilling Technologies® GmbH in Germany manufactures heat pumps that use a modular multi-stage vapor compressor with up to six cylinders, can heat up to 280°C, and have an effective coefficient of performance (COP) of over 2. At temperatures below 250°C, the COP is higher; for example, from a source temperature of 175°C to an output temperature of 215°C, the COP is 8 or higher. For higher output temperatures, such as 250°C, the COP is lower, but is expected to be 5.

[0031] With current cutting-edge heat pump technology, T2=170°C to T ref = 250 °C, it is possible to use a heat pump, which is particularly useful for methanol reforming and HT-PEM cells. For such HT-PEM systems, where the reformer is heated using a heat pump and H2 gas from the anode is recirculated, an overall efficiency improvement of over 5% has been found compared to current state-of-the-art fuel cell systems, where the reformer is heated by a fuel burner as a reformer heater. This very beneficial efficiency improvement occurs when the fuel cell is heated to the reforming temperature T ref This is made possible by operating at a relatively high temperature that is lower than, but relatively close to, the COP. In these calculations, a COP of 5 was assumed. Simple scaling revealed an efficiency gain of 4% at COP of 4, a 3% efficiency gain at COP of 3, and a 2% efficiency gain at COP of 2. Thus, even at COPs lower than the expected COP of 5, say in the range of 2-4, there is still a gain when using a heat pump compared to using a burner and recycling H2 to the anode.

[0032] Of particular interest is the use of large fuel cell systems, such as those designed for ships, and also for stationary power plants with an electrical generating capacity of at least 1 MW.

[0033] By using large heat pumps with multi-stage compressors, the efficiency gains can offset the depreciation of the additional investment relatively quickly. For example, the aforementioned Spilling Technologies® GmbH offers heat pumps with capacities ranging from 1 MW to 15 MW and weighing between 15,000 and 45,000 kg. Needless to say, such heat pumps are required for large-scale installations such as ships, especially container cargo ships, or power plants or large-scale energy storage systems, such as those described in connection with the so-called Power-to-X (PtX) option for converting and storing green energy.

[0034] Another potential application for heat pumps is the Enerin® machine from Energy Engineering. In this machine, the heat pump uses a Stirling cycle, a closed, single-phase system with double-acting pistons for compression and expansion, and is expected to have a COP of 2.5. This heat pump can raise temperatures by 200 degrees, but its minimum heat source temperature is limited to 100°C, making it suitable for HT-PEM but not LT-PEM. Heat supply capacities range from 0.3 MW to 10 MW, and the weight is 10,000 kg.

[0035] In the fuel cell systems described herein, a flow of coolant through a fuel cell is provided, with the coolant entering the fuel cell at a first temperature T1, e.g., 160°C, and the coolant exiting the fuel cell at a second elevated temperature T2, e.g., 170°C, that is higher than the first temperature T1. To maintain a stable, optimal operating temperature for the fuel cell, the heat pump receiving the coolant downstream of the fuel cell should not reduce the temperature of the coolant at the downstream end of the heat pump system to a temperature T3 that is lower than T1. This can be achieved by appropriately adjusting the heat pump flow rate and design, for example, by selecting a heat pump with appropriate specifications as described above.

[0036] In the example of a fuel cell system including a reformer for reforming an alcohol such as methanol, the methanol is mixed with water and fed to the reformer as evaporated steam. The heat required for evaporation is advantageously extracted from the coolant in the cooling circuit. For example, the required thermal energy can be extracted from a cold branch of the cooling circuit, which has a temperature close to the coolant temperature T1 supplied to the fuel cell, e.g., 160°C. Alternatively, the required thermal energy can be extracted from a hot branch of the cooling circuit, which has a coolant temperature T2 at the outlet of the fuel cell, e.g., T2=170°C. A heat pump can be used to raise the temperature to the reforming temperature T ref Bearing in mind that the temperature needs to be raised to, say, 250°C, it is optimal to supply the heat pump with the refrigerant with the highest available temperature. As a result, the evaporator needs to be connected to the low-temperature branch of the refrigeration circuit downstream from where the heat pump system extracts thermal energy from the refrigeration circuit.

[0037] However, in this case, since the evaporator removes heat from the coolant, which comes from the heat pump and has a temperature T3, the temperature T3 of the coolant at the inlet of the evaporator must be slightly higher, for example 2-4 degrees higher, than the temperature T1 of the coolant used at the cooling inlet of the fuel cell. Therefore, when using an evaporator, the heat pump must reduce the temperature of the coolant, for example from level T2, to temperature T3, which is higher than T1 at which the coolant is supplied to the fuel cell.

[0038] As a result of using a heat pump, H gas and other fuels for the reformer burner are not required, and H gas can be recovered from the anode exhaust gas and recycled to the anode. Therefore, for separation, an H separator is connected downstream of the anode to receive the anode exhaust gas and separate H gas from the anode exhaust gas. The hydrogen separator is then connected downstream to a conduit between the downstream side of the reformer and the upstream side of the anode, and the separated H gas is mixed with the synthesis gas from the reformer and then sent back to the anode.

[0039] In this regard, a comparison should be made with the aforementioned reference DE102013009244A1, where it can be seen that the only example of direct H recirculation to the anode is shown in FIG. 3 of DE102013009244A1. However, in this example, the anode does not receive synthesis gas, in contrast to the system described herein. Instead, in DE102013009244A1, the recycled H2O vapor containing recycled H2 receives additional H2 from the synthesis gas via an H2 separation membrane, and the resulting H2-enriched recycled vapor is used to supply not only the anode but also the reformer burner after splitting the streams into separate conduits. This is a different system with a different function from that described herein.

[0040] By comparison, in the HT-PEM system described herein with an electric heat pump system instead of a reformer burner, the H separator operates only on the anode exhaust gas, not on the synthesis gas from the reformer. This is in contrast to DE 10 2013 009 244 A1. Therefore, the required capacity of the H separator in the system described herein can be designed to be much smaller than the H membrane separator in DE 10 2013 009 244 A1. This is another advantage over DE 10 2013 009 244 A1.

[0041] For example, in contrast to the LT-PEM fuel cells disclosed in the aforementioned reference DE102013009244A1, high concentrations of H2O vapor are not required in the gas supply to the anode of an HT-PEM fuel cell. Therefore, the principle of DE102013009244A1 of using a recycled H2O vapor flow on one side of the H2 separation membrane to force H2 across the membrane does not appear to be useful for HT-PEM fuel cell systems, and high concentrations of vapor are undesirable as they may be detrimental to the function of the HT-PEM fuel cell, and in particular the catalysts used therein.

[0042] Instead, electrochemical separation of hydrogen gas has been found to be superior to the membrane separation system of DE 10 2013 009 244 A1.

[0043] As an option for electrochemical separation of hydrogen gas, a hydrogen pump of the type described in the paper "Electrochemical hydrogen pumping using a high-temperature polybenzimidazole (PBI) membrane" by Perry et al. in Journal of Power Sources 177 (2008) 478-484 and references therein can be used as an H separator. As mentioned in the introduction, this paper demonstrated the electrochemical separation of hydrogen from a gas mixture containing N, H, CO, and CO using a high-temperature (>100 °C) polybenzimidazole (PBI) membrane. Notably, the electrochemical pump was operated at 160 °C, approximately 1.2 times the stoichiometric requirement for pure hydrogen, without external humidification. A relatively low voltage of less than 1 V was required to operate the hydrogen pump over a wide range of hydrogen flow rates.

[0044] It has been pointed out that such a hydrogen pump operates at a temperature of 160°C, similar to the temperature of the coolant in an HT-PEM fuel cell, but would not provide a sufficiently high temperature since the coolant from an LT-PEM fuel cell, such as that disclosed in the aforementioned DE102013009244A, is below 100°C.

[0045] A significant advantage of electrochemical separation of H, as opposed to passive membranes such as those in DE 102013009244A, is the ability to monitor the performance of the H separator, particularly the electrical consumption, which provides insight into the performance of the fuel cell system. In some embodiments of the invention described herein, such monitoring of fuel cell system performance is provided. For example, H production can be monitored to determine the fuel supply lambda value.

[0046] As an alternative to electrochemical separation, pressure swing adsorption techniques or amine absorption can be useful for H2 separation.

[0047] After separating the H2 from the anode exhaust gas using an H2 separator and removing the water, typically by condensation, the remaining gas contains almost exclusively CO2, which can be liquefied and stored in tanks as a means of carbon capture.

[0048] As mentioned above, HT-PEM fuel cells are advantageous in that they are robust to CO in the gas from the reformer, allowing the shift gas reactor to be omitted. As a result, a relatively small and lightweight reformer can be used, which is advantageous for minimizing the heat consumption of the reforming process and for properly sizing the heat pump system. Therefore, while heat pumps can be advantageous in various ways for various types of fuel cell systems, HT-PEM fuel cell systems in particular could benefit from using a heat pump to heat the reformer.

[0049] The invention will now be explained in more detail with reference to the drawings. [Brief explanation of the drawings]

[0050] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell system. DETAILED DESCRIPTION OF THE INVENTION

[0051] FIG. 1 shows a fuel cell system 1 including multiple fuel cells 2 arranged in parallel as a fuel cell stack, as typically illustrated. Methanol as fuel from a fuel tank 3 and water from a water tank 4 are mixed and evaporated in an evaporator 5. The evaporated methanol-water mixture is supplied to an inlet 6A of a catalytic reformer 6, which produces synthesis gas as a reformed gas. Such synthesis gas contains carbon dioxide CO, carbon monoxide CO, hydrogen gas H, and some residual water. The synthesis gas is supplied from a reformed gas outlet 6B to an anode inlet 22 of the fuel cell 2, as indicated by arrow 21A, and the H is used to generate electricity by the fuel cell 2.

[0052] Fuel cell 2 is a HT-PEM fuel cell, which is insensitive to CO and, in contrast to LT-PEM cells, does not require a shift reactor and does not require a high water vapor content in the syngas.

[0053] Other alcohols can be used in place of methanol, but the reformer temperature will need to be adjusted accordingly.

[0054] The HT-PEM fuel cell 2 is operated at a temperature in the range of, for example, 170°C to 180°C, so that the coolant in the cooling circuit 7, which is pumped towards the fuel cell stack by a coolant pump 8 in the direction shown by arrows 17A and 17B, is heated to T1=160°C to T2=170°C. The HT-PEM fuel cell 2 is typically operated at a temperature in the range of 150°C to 180°C, although it can be operated at slightly different temperatures in the range of 120°C to 200°C. Advantageously, the polymer electrolyte membrane PEM of the HT-PEM fuel cell is mineral acid based, and is typically a polymer membrane, for example phosphoric acid doped polybenzimidazole (PBI).

[0055] The reformer 6 is heated by a reformer heater 27, shown in dotted lines in FIG. 1, the components of which are described in more detail below.

[0056] As shown by arrow 17B, coolant flowing from fuel cell 2 at temperature T2 transfers thermal energy in heat transfer / heat exchanger 9 to a heat transfer fluid in heat transfer circuit 10, which is transported by heat transfer pump 11.

[0057] The heat transfer circuit 10 is thermally connected to an electric heat pump 12. The heat pump 12 transfers thermal energy from the heat transfer fluid in the heat transfer circuit 10 to a heating fluid circulating in a heating circuit 13 driven by a corresponding heating fluid pump 14, which heats the reformer 6.

[0058] The advantage of the heat transfer circuit 10 is that it allows easy regulation of the temperature of the fluid entering the heat pump 12 and of the temperature of the coolant in the cooling circuit 7 downstream of the heat transfer and heat exchanger 9 .

[0059] In the illustrated system, the coolant in the low-temperature branch 7A of the cooling circuit 7, downstream of the heat transfer / heat exchanger 9, is used to heat the fuel-water mixture in the evaporator 5. After heating, the coolant temperature must be T1, e.g., T1 = 160 °C, to maintain a stable operating temperature of the fuel cell 2. The temperature can be fine-tuned to T1 using a regulating heat exchanger 18. Depending on the heat requirement of the evaporator 5, which varies depending on the load and the corresponding fuel consumption by the fuel cell 2, the temperature of the coolant in the cooling circuit 7 can be adjusted by adjusting the transfer of thermal energy in the heat transfer / heat exchanger 9 upstream of the evaporator 5. The electrical consumption of the heat pump 12 is adjusted depending on the temperature of the heat transfer fluid in the heat transfer circuit 10 and the heat requirement of the reformer 2.

[0060] The heat pump is designed to convert the temperature of the heat transfer fluid from a temperature in the range of 120°C to 200°C to at least T ref = 220 °C, and optionally, increase the temperature of the heat transfer fluid from a temperature in the range of 150 °C to 180 °C to at least T ref The temperature of the heating fluid is increased to 250°C.

[0061] By using the reformer heater 27 shown herein, which includes a heat exchanger 9, a heat transfer circuit 10 with a pump 11, a heating circuit 13 with a pump 14, and a heat pump 12, no fuel or H2 gas is required for the reformer burner, and the H2 gas remaining in the anode exhaust gas conduit 18 is separated by an H2 separator 19, for example an electrochemical H2 separator, and fed through an H2 conduit 20 to a syngas conduit 21 connecting the reformed gas outlet 6B of the reformer 6 to the anode inlet 22 of the fuel cell 2. The flow of H2 gas in the H2 conduit 20 downstream of the separator 19, as shown by arrow 20A, is added to the syngas flowing in the syngas conduit 21 from the reformer (6), as shown by arrow 21A, to produce a mixed flow in the syngas conduit 21 upstream of the anode inlet 22 of the fuel cell 2, as shown by the thick arrow 21B.

[0062] Furthermore, since H gas has been separated from the anode exhaust gas in exhaust gas conduit 18 by H separator 19, the remaining gases, mainly water vapor and CO gas, can in principle be discarded. However, optionally, water can be separated from the CO gas in condenser 15, collected in water reservoir 16, and reused for mixing with fuel. Optionally, the remaining CO in CO conduit 23 is collected as a liquid in CO tank 26, for example after being compressed in compressor 24 and condensed in heat exchanger 25.

[0063] It should be noted that the additional elements for H2 separation and recirculation to the fuel cell rather than the burner, as well as water recirculation and potential carbon capture, all benefit from the use of heat pump 12, so the overall result of adding these elements is not just the sum of its parts, but a synergistic combination of elements that leads to an overall improved environmentally friendly system.

Claims

1. a fuel supply device (3) for supplying fuel; a reformer (6) for catalytically reforming the fuel to obtain a synthesis gas containing hydrogen H2; a fuel cell (2) fluidly connected to the reformed gas outlet (6B) of the reformer (6) and having an anode for receiving the synthesis gas, the fuel cell using the H2 to generate electricity; The reformer (6) is heated to a predetermined reformer temperature T that is equal to or higher than the minimum temperature required for the catalytic reforming of the fuel. ｒｅｆ a reformer heater (27) for heating the The predetermined reformer temperature T ｒｅｆ a cooling circuit (7) containing a flow of coolant to maintain an operating temperature of the fuel cell (2) below The reformer heater (27) includes an electric heat pump (12) thermally connected to the cooling circuit (7) and adapted to extract thermal energy from the coolant to reduce the temperature of the coolant and transfer the extracted thermal energy to a heating fluid in a heating circuit (13) to heat the heating fluid, the temperature of which reaches the predetermined reformer temperature T ｒｅｆ A fuel cell system (1) that provides the above-mentioned heating fluid, and the heating circuit (13) is connected to the reformer (6) and transfers thermal energy from the heating fluid to the reformer (6), The fuel cell is a HT-PEM fuel cell with an operating temperature in the range of 120°C to 200°C, and T ｒｅｆ is in the range of 250°C to 300°C, and the heat pump (12) includes an electrically driven multi-stage gas piston compressor, and the reformer is heated by the heat pump to T ｒｅｆ The fuel cell system (1) is characterized in that the COP for heating is 2 or more.

2. 2. The system of claim 1, wherein the fuel (2) comprises methanol and water, and the system (1) comprises an evaporator (5) that receives and evaporates the fuel for reforming in the reformer (6).

3. 10. The system of claim 9, further comprising: an H separator (19) connected to an anode exhaust gas conduit (18) downstream of the anode for receiving the anode exhaust gas and separating H from the anode exhaust gas, the H separator (19) being fluidly connected to a synthesis gas conduit (21) connecting a reformed gas outlet (6B) of the reformer (6) to an anode inlet (22), and for recycling the separated H gas to the anode after mixing it with synthesis gas from the reformer (6).

4. The system of claim 3, wherein the H2 separator (19) is an electrochemical H2 separator.

5. 5. The system according to claim 3 or 4, further comprising a water separator (15) located downstream of the H separator (19) for separating water from the anode exhaust gas after H separation, a CO liquefier (24, 25), and a CO storage tank (26) for storing residual CO in liquid form.

6. A method of operating a fuel cell system including a fuel cell (2), comprising: The reformer heater (27) heats the catalytic reformer (6) to a predetermined reformer temperature T that is equal to or higher than the minimum temperature required to catalytically reform the fuel to obtain synthesis gas containing hydrogen H2. ｒｅｆ and Maintaining the operating temperature of the fuel cell (2) by a cooling circuit (7) containing a flow of coolant, said operating temperature being maintained at said predetermined reformer temperature T ｒｅｆ and Reforming fuel by the reformer to obtain synthesis gas containing hydrogen H2, supplying the synthesis gas to an anode of the fuel cell (2), consuming a first portion of the H2 by the fuel cell (2) to generate electricity, and discharging a second portion of the H2 from the anode as part of an anode exhaust gas, The reformer heater (27) includes an electric heat pump (12) thermally connected to the cooling circuit (7), and the method includes electrically driving the heat pump (12), extracting thermal energy from the coolant in the cooling circuit (7) by the heat pump (12) to reduce the temperature of the coolant, and transferring the extracted thermal energy to a heating fluid in a heating circuit (13) to heat the heating fluid, so that the temperature reaches the predetermined reformer temperature T ｒｅｆ providing the heating fluid and transferring thermal energy from the heating fluid to the reformer (6), The fuel cell is a HT-PEM fuel cell, and the method includes operating the fuel cell at a temperature in the range of 120°C to 200°C, and T ｒｅｆ is in the range of 250°C to 300°C, and the electric heat pump (12) includes an electric multi-stage gas piston compressor, and the heat pump drives the reformer to T ｒｅｆ The method is characterized in that the COP of the heated water is 2 or more.

7. 7. The method of claim 6, wherein the fuel comprises alcohol, the system includes a fuel evaporator (5), and the method includes receiving and evaporating the fuel in the evaporator (5), supplying the evaporated fuel into the reformer (6), catalytically reforming the fuel by the reformer (6) to produce gaseous H2, and supplying the H2 from the reformer (6) to the anode of the fuel cell (2).

8. 8. The method of claim 6 or 7, wherein the method includes providing a flow of coolant through the fuel cell (2), the coolant entering the fuel cell (2) at a first temperature T1 and exiting the fuel cell (2) at a second elevated temperature T2 higher than the first temperature T1, the heat pump (12) receiving the coolant whose temperature has been elevated to T2 by the fuel cell (2), and the method includes extracting thermal energy from the coolant using the heat pump (12) to reduce the temperature of the coolant to a third temperature T3 lower than T2 but equal to or greater than the first temperature T1.

9. 9. The method of claim 8, wherein the method includes reducing a temperature of the coolant by the heat pump (12) to a third temperature T3 lower than T2 but higher than the first temperature T1, supplying the coolant to an evaporator (5) downstream of the reformer heater (27), transferring thermal energy from the coolant to the fuel to evaporate the fuel in the evaporator (5) before the fuel enters the reformer (6), and reducing the temperature from the third temperature T3 to a fourth temperature T4 by transferring thermal energy in the evaporator (5), wherein the fourth temperature T4 is equal to or higher than the first temperature T1.

10. 10. The method of claim 6, further comprising providing a hydrogen separator (19) connected to an anode exhaust gas conduit (18) downstream of the anode, receiving the anode exhaust gas, separating H gas from the anode exhaust gas by the hydrogen separator (19), and recycling the separated H gas to the anode.

11. 11. The method of claim 10, further comprising adding the separated H2 gas to the synthesis gas from the reformer (6) in a synthesis gas conduit (21) connecting a reformed gas outlet (6B) of the reformer (6) and a gas inlet (22) of the anode of the fuel cell (2).

12. Use of a system according to any one of claims 1 to 5 or a method according to any one of claims 6 to 11 in the generation of electricity on an electric vessel.

Images