A fuel cell system for separating hydrogen gas from anode exhaust gas, a method of operating the same, and its use.

Abstract

A fuel cell system for separating hydrogen gas from anode exhaust gas, a method of operating the same, and its use. In a fuel cell system equipped with an HT-PEM fuel cell (2), hydrogen is separated from the anode exhaust gas and recycled back to the anode to improve efficiency. Instead of burning hydrogen in the reformer heater, the reformer is heated electrically or using a heat pump (12). Separating H2 from the anode exhaust gas provides the option of collecting residual CO2 after condensing water from the anode exhaust gas.

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system including a hydrogen separator for separating hydrogen gas (H2) from anode exhaust gas and recirculating the separated H2 gas to the anode. In particular, the present invention relates to the system described in the preamble of an independent claim, its use, and its operation method. [Background technology]

[0002] When supplying hydrogen gas (H2) or hydrocarbons to fuel cells, there are various options, including pressurized H2, methane, or alcohols such as methanol or ethanol. Typical gaseous fuels for fuel cells include ethane, propane, and natural gas. Alcohol fuels for fuel cells have the advantage of being able to reuse much of the existing liquid fuel infrastructure for diesel and gasoline, including transportation to fuel supply stations and storage of fuel in vehicles.

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

[0004] Fuel reforming produces synthesis gas, a mixture of gases containing H2 gas, carbon dioxide (CO2), carbon monoxide (CO), and some residual water (H2O). In fuel cells with polymer electrolyte membranes (PEMs) that operate at low temperatures below 100°C (hence the name LT-PEM fuel cells or simply PEM fuel cells), the catalyst is highly sensitive to CO gas at this temperature, so CO gas is converted to CO2 in the shift reactor before the synthesis gas enters the fuel cell. In the case of typical high-temperature PEM fuel cells, HT-PEM fuel cells, that operate at higher temperatures above 120°C and even up to 200°C, the system has greater resistance to CO gas, allowing the shift reactor and other gas cleanup processes to be omitted.

[0005] Fuel cells are attracting increasing attention, particularly in power production for vehicles such as electric cars and ships. There is a continuous demand to improve the efficiency of power production, and even an improvement of around 1 percent is attractive. Accordingly, improvements in the technological field are required.

[0006] For example, U.S. Patent Publication US2010 / 0266923A1 discloses an electrochemical hydrogen separator for separating H2 gas from the anode exhaust gas of a fuel cell and reintroducing it into the fuel cell to optimize the efficiency of the fuel cell. By monitoring the performance of the hydrogen separator, the performance of the fuel cell system can be determined. Once the H2 gas is separated from the anode exhaust gas flow and recirculated to the fuel cell anode, it is consumed as fuel for the reformer heater. This is not a problem for SOFC batteries operating in the temperature range of 750°C to 950°C, as disclosed in U.S. Patent Publication US2010 / 0266923A1, because the excess heat from the fuel cell can be used not only to heat the electrochemical H2 separator shown in the publication, but also to heat the reformer.

[0007] However, in the case of fuel cells that operate at lower temperatures, the fuel is conventionally used to heat the reformer, so separating H2 and reintroducing it to the anode does not provide any significant efficiency advantage.

[0008] This consideration is supported by a study of a system disclosed in German patent application DE102013009244A1, in which a membrane separator is used to separate H2 from the anode gas in order to recover the remaining CO2 in a storage tank after water has been removed by condensation. In this reference, the membrane is used to transport H2 from the gas stream to the H2O stream to enrich the fuel gas stream for the reformer heater with H2. This follows the conventional approach of using H2 in a cycle that introduces it to the reformer burner by flame or catalytic combustion to heat the reformer. As an additional option, DE102013009244A1 discloses the enrichment of H2 in the methane gas stream entering the catalytic reformer. However, a more detailed evaluation suggests that this is not optimal. This is because an increase in the H2 level in the gas flow at the reformer inlet is expected to decrease rather than improve the overall reforming efficiency, as the H2 production capacity within the reformer is not optimized until the H2 concentration in the gas is at its maximum, since the H2 concentration is already offset to a considerable level from the start. Thus, from the disclosure of DE102013009244A1, it is understood that the purpose of separating H2 from the anode exhaust gas is not the general purpose of improving the efficiency of the fuel cell system, but rather to find some meaningful use for the byproduct, the H2 gas separated from the anode exhaust gas, before recovering carbon from the exhaust gas flow, and carbon recovery is the main objective of DE102013009244A1.

[0009] In their paper "Electrochemical hydrogen pumping using a high-temperature polybenzimidazole (PBI) membrane," published in Journal of Power Sources 177 (2008) 478-484, Perry et al. described the electrochemical separation of hydrogen from a mixture of gases containing N2, H2, CO, and CO2 using a high-temperature (>100°C) polybenzimidazole (PBI) membrane. Specifically, the electrochemical pump operated at 160°C, approximately 1.2 times the stoichiometric requirement for pure hydrogen, without external humidification. While such a hydrogen pump operates at temperatures similar to the coolant temperature of an HT-PEM fuel cell, it has been noted that coolants from LT-PEM fuel cells, such as those disclosed in DE102013009244A, may not provide sufficiently high temperatures.

[0010] However, if a method for heating the reformer using a method different from that of a burner is found, and if this configuration is more efficient than conventional systems that burn H2 in a reformer heater, then separating H2 from the anode exhaust gas and recirculating it to the fuel cell is useful in fuel cell systems where the fuel cell operates at a temperature lower than the temperature required for fuel reforming. [Overview of the project]

[0011] The object of the present invention is to provide an improvement to the art, and in particular to improve the efficiency of an HT-PEM fuel cell system including a reformer. This object and further advantages are achieved by the fuel cell system and method of operation described below and in the claims.

[0012] In short, in fuel cell systems with HT-PEM fuel cells, hydrogen is separated from the anode exhaust gas and recycled back into the anode to improve efficiency. Instead of burning hydrogen or fuel in the reformer heater, the reformer is heated by an electric reformer heater, such as an electric heater or electric heat pump system. Separating H2 gas from the anode exhaust gas also ensures a means of collecting the CO2 remaining after the water has condensed.

[0013] The details are explained below.

[0014] HT-PEM fuel cells are typically supplied 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 opposite side. Hereafter, the abbreviations anode and cathode will be used in reference to fuel cells.

[0015] Fuel cell systems include a fuel supply device that typically mixes alcohols such as ethanol, especially methanol, with water, then evaporates and supplies them to a reformer, allowing H2 gas to be supplied to the fuel cell after fuel reforming. Catalytic reforming of the fuel produces not only H2 but also other gaseous byproducts such as CO2, water, and CO. As mentioned above, in the case of HT-PEM fuel cells, CO removal is typically not necessary.

[0016] The anode of a fuel cell has an inlet that is fluidly connected to a reformed gas outlet via a synthesis gas conduit, receiving synthesis gas from the reformer for the reaction in the fuel cell, while the cathode receives oxygen gas, for example, as part of the air. In an HT-PEM fuel cell, hydrogen ions traverse the ion-conducting membrane from the anode side to the cathode side, forming water at the cathode. The water exits the cathode as vapor along with other gaseous components, such as nitrogen from the supply air.

[0017] The anode consumes the primary portion of the H2 it receives to generate electricity, and releases a small amount of secondary H2 into the exhaust gas from the anode.

[0018] The operating temperature of HT-PEM fuel cells is in the range of 120°C to 200°C, typically in the range of 150°C to 180°C, which is lower than the minimum temperature required for catalytic reforming of the fuel (above 400°C for ethanol and above 200°C for methanol). Typically, for methanol, a given reformer temperature T ref It is in the range of 250°C to 300°C, which is higher.

[0019] Instead of burning H2 and / or fuel within the reformer burner as in conventional technology, the reformer heater for the reformer is electrically powered. For example, the reformer heater includes an electric heater, in which electricity heats the heating element by an electric current passing through it. Alternatively, the reformer heater includes an electric heat pump. The latter has been found to have special advantages, as will be explained below.

[0020] As a result of using an electric reformer heater, H2 gas and other fuels for the reformer burner are no longer needed, and H2 gas can be recovered from the anode exhaust and recirculated to the anode, thus optimizing system performance.

[0021] Therefore, for separation, a hydrogen separator is connected downstream of the anode to receive the anode exhaust gas and separate H2 gas from it. Downstream of the hydrogen separator, it is connected to a synthesis gas conduit that extends between the downstream side of the reformer and the upstream side of the anode. In this way, the H2 separated from the anode exhaust gas can be mixed with the synthesis gas from the reformer and then supplied back to the anode.

[0022] For example, different types of H2 separators involved in pressure swing adsorption, amine absorption, and electrochemical separation can be used, the latter of which is particularly advantageous and will be described in more detail below.

[0023] In this regard, it is necessary to compare with the aforementioned reference document DE102013009244A1. According to the comparison, it can be seen that the only example of directly recycling H2 to the anode is shown in FIG. 3 of DE102013009244A1. However, in this example, in contrast to the system described herein, the anode does not receive syngas. Instead, in DE102013009244A1, the recycled H2O vapor containing recycled H2 receives additional H2 from the syngas by the H2 separation membrane, and the obtained H2-enriched recycled vapor is used to supply not only the anode but also the reformer burner after splitting the flow into separate conduits respectively. This is a different system with a different function from that described herein.

[0024] In comparison, in the HT-PEM system described herein equipped with an electric reformer heater instead of a reformer burner, the H2 separator acts only on the anode exhaust gas and does not act on the syngas from the reformer. This point is in contrast to DE102013009244A1. Therefore, the required capacity of the H2 separator in the system described herein can be designed to be much smaller than the H2 membrane separator in DE102013009244A1. This is another advantage over DE102013009244A1.

[0025] For example, in contrast to the LT-PEM fuel cell disclosed in the aforementioned reference document DE102013009244A1, a high-concentration H2O vapor is not required in the gas supply to the anode of the HT-PEM fuel cell. Therefore, the principle of DE102013009244A1 of using the recycled H2O vapor flow on one side of the H2 separation membrane to force the transport of H2 across the H2 separation membrane does not seem to be useful for the HT-PEM fuel cell system, because the high-concentration vapor may be harmful to the function of the HT-PEM fuel cell, especially the catalyst used therein, and thus is not desirable.

[0026] Instead, it has been found that the electrochemical separation of hydrogen gas is superior to the membrane separation system of DE102013009244A1.

[0027] As an option for the electrochemical separation of hydrogen gas, the type of hydrogen pump 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 the references therein can be used as a H2 separator. As already mentioned in the introduction, this paper discloses the electrochemical separation of hydrogen from a gas mixture containing N2, H2, CO, and CO2 using a high-temperature (>100°C) polybenzimidazole (PBI) membrane. In particular, the electrochemical pump was operated at 160°C, about 1.2 times the stoichiometric requirement of pure hydrogen, without external humidification. A relatively low voltage of less than 1V was required to operate the hydrogen pump over a wide range of hydrogen flow rates.

[0028] Such a hydrogen pump operates at a temperature of 160°C, similar to the temperature of the coolant of the HT-PEM fuel cell, but it has been pointed out that the coolant from the LT-PEM fuel cell as disclosed in the aforementioned DE102013009244A is less than 100°C and will not supply a sufficiently high temperature.

[0029] In contrast to the passive membranes such as the membrane in DE102013009244A, a significant advantage of the electrochemical separation of H2 is that the performance of the H2 separator, particularly the power consumption, which can be used to understand the performance of the fuel cell system, can be monitored. In some embodiments of the present invention described herein, such monitoring of the performance of the fuel cell system is performed. For example, the amount of H2 generation can be monitored and the fuel supply lambda value can be determined.

[0030] After separating H2 from the anode exhaust gas by the H2 separator and typically removing moisture by condensation, the remaining gas contains almost only CO2. As an option, as a carbon recovery means, this can be liquefied and stored in a tank.

[0031] As mentioned earlier, HT-PEM fuel cells have the advantage of being robust against CO in the gas from the reformer, thus eliminating the need for a shift gas reactor. As a result, a relatively small and lightweight reformer can be used, which is advantageous because it leads to the miniaturization of electric reformer heaters, such as heat pump systems. Heat pumps may be advantageous in various ways for various types of fuel cell systems, but HT-PEM fuel cell systems in particular are likely to benefit from using a heat pump or electric heater to heat the reformer.

[0032] The following example shows an HT-PEM fuel cell operating at a temperature of approximately 170°C, which is the temperature of the coolant at the outlet of the fuel cell stack. However, because slight temperature fluctuations are normal throughout the fuel cell stack, the operating temperature of the fuel cell stack is typically not fixed with an accuracy of ±10°C or more of 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 fluctuate within the range of 160-180°C. In particular, the coolant exiting the fuel cell at T2=170°C enters the fuel cell stack at a lower temperature T1, for example, T1=160°C, which is one of the causes of temperature fluctuations within the stack.

[0033] The minimum temperature required for methanol reforming is 200°C, and typically, a given temperature T ref It is in the range of 250°C to 300°C, and the temperature or T ref =250℃ is useful.

[0034] The above objectives are also achieved by the provided method, which is Electricity is used for the electric reformer heater, and the reformer heater is used to bring the catalytic reformer to a predetermined reformer temperature T that is above the minimum temperature required to catalytically reform the fuel and obtain synthesis gas containing hydrogen (H2). ref (For example, in the case of methanol reforming, a predetermined reformer temperature T ref Heating to a temperature in the range of 250°C to 300°C, This involves operating a fuel cell, for example, an HT-PEM fuel cell, at an operating temperature in the range of 120°C to 200°C, or optionally in the range of 150°C to 180°C. The cooling circuit, which includes the flow of coolant, maintains the operating temperature of the fuel cell. A reformer is used to reform a fuel containing alcohol such as methanol to obtain synthesis gas containing hydrogen (H2), the synthesis gas is supplied to the anode of a fuel cell, the fuel cell consumes the first portion of the H2 to generate electricity, and the second portion of the H2 is released from the anode as part of the anode exhaust gas. The system includes receiving the anode exhaust gas with an H2 separator, separating the residual H2 from the anode exhaust gas, mixing the separated H2 with synthesis gas from a reformer, and then recirculating it to the anode.

[0035] In contrast to the prior art, the reformer heaters in the systems described herein include electric reformer heaters. In some embodiments, the reformer heater is an electric heater in which electricity is converted into heat by ohmic resistance; this type of heating is also called ohmic heating. When reforming methanol to obtain synthesis gas, the HT-PEM fuel cell systems described herein with electric heaters have been found to be 1% more efficient when recirculating H2 compared to reformer heaters for fuel and / or anode exhaust gas.

[0036] Alternatively, an electric reformer heater, including an electric heat pump, improves efficiency by more than 5% in an HT-PEM fuel cell system as described herein. This is quite remarkable, and for the following reasons: The heat pump does not burn fuel or recirculated hot gas. Instead, it consumes electricity generated, for example, by the fuel cell. In this way, driving the heat pump indirectly consumes H2, as it requires additional electricity generation by the fuel cell. However, this is advantageous compared to the reformer burner because the fuel cell is more fuel-efficient. Therefore, instead of consuming fuel with relatively low efficiency in the reformer burner, fuel is consumed with higher efficiency in the fuel cell. This means an option to improve the overall efficiency of the system. Furthermore, as will become clearer below, waste heat from the fuel cell is reused to heat the reformer.

[0037] By separating and recirculating H2, an efficiency gain of 7.5% is achieved. In the case of an electric heater, most of it is reused. However, when the HT-PEM fuel cell is driven at 170°C, a heat pump can raise the temperature to 250°C with moderate energy consumption, and the net gain of the system is more than 5%. These estimates include the electricity consumption by the H2 separator. A heat pump system is best suited to the HT-PEM system, which will be discussed in more detail below.

[0038] In actual embodiments, a heat pump is thermally connected to a cooling circuit to extract thermal energy from the coolant and lower its temperature. This is advantageous for the efficiency of the fuel cell system because heat, which is normally waste, is useful in the system described herein. The thermal energy from the coolant downstream of the fuel cell is extracted from the coolant and transferred to the heating fluid in a heating circuit. The heating circuit is connected to a reformer and transfers thermal energy from the heating fluid to the reformer. To offset the lower temperature in the cooling circuit, the temperature of the heating fluid in the heating circuit needs to be raised by the heat pump to a temperature higher than the coolant temperature required for reforming.

[0039] The above example shows the HT-PEM operating at 170°C, and a predetermined reformer temperature T for methanol reforming. ref Referring to the example of 250°C, in order to maintain the temperature inside the reformer at 250°C, the temperature of the heated fluid needs to rise to 250°C or higher, and in some cases slightly higher.

[0040] Current heat pumps used in systems with LT-PEM fuel cells operating below 100°C are not expected to improve system efficiency compared to similar systems using reformer burners. Therefore, heat pumps do not seem attractive for such systems. However, future developments may make the use of heat pumps attractive in such LT-PEM fuel cell systems in terms of improved energy efficiency. Regardless, heat pumps may be used in such LT-PEM fuel cell systems due to other advantages, such as simplicity and benefits. Therefore, the idea of ​​using a heat pump to heat the reformer in an LT-PEM fuel cell system is justified to be extended to systems with other types of fuel cells, such as LT-PEM fuel cell systems.

[0041] For example, a heat pump includes a multi-stage gas piston compressor that uses a working fluid for heat pumping. Various working fluids exist, and some efficient heat pumps use vapor or helium as the working fluid.

[0042] Examples of heat pumps capable of increasing temperature can be found in the commercial market. For instance, Spilling Technologies (registered trademark) GmbH in Germany manufactures heat pumps that can heat up to 280°C and have a coefficient of performance (COP) of more than 2, using a modular, multi-stage steam compressor with up to six cylinders. Below 250°C, the COP is high; for example, from a heat source temperature of 175°C to an output temperature of 215°C, the COP is 8 or higher. At higher output temperatures, such as 250°C, the COP is lower, but is expected to be around 5.

[0043] With current state-of-the-art heat pump technology, T2 = 170°C to T ref Because the temperature can be raised to 250°C, it is possible to use a heat pump, which is particularly useful for methanol reforming and HT-PEM batteries. As already mentioned, in such an HT-PEM system where the reformer is heated using a heat pump and H2 gas from the anode is recirculated, the overall efficiency has been found to be more than 5% higher compared to the current state-of-the-art fuel cell system where the reformer is heated by a fuel burner as a reformer heater. This very beneficial efficiency improvement is due to the fuel cell being able to reform at a temperature of T ref This is made possible by operating at a relatively high temperature, lower than but relatively close to the expected COP. These calculations assumed COP=5. Simple scaling revealed that the efficiency gain is 4% at COP=4, 3% at COP=3, and 2% at COP=2. Therefore, even at COPs lower than the expected COP=5, such as in the range of 2-4, a gain can be obtained when using a heat pump compared to using a burner and recirculating H2 to the anode.

[0044] Of particular interest is the use of large-scale fuel cell systems, such as those designed for ships. There is also considerable interest in fuel cell systems for stationary power plants with an electricity generation capacity of at least 1 MW.

[0045] By using large heat pumps employing multi-stage compressors, the depreciation of additional investments can be offset relatively quickly by efficiency gains. For example, Spilling Technologies® GmbH, mentioned above, offers heat pumps with capacities ranging from 1 MW to 15 MW and weighing 15,000 to 45,000 kg. Needless to say, such heat pumps are required in large-scale installations such as ships, particularly container ships, or power plants, or large-scale energy storage systems, as described in relation to so-called Power-to-X (PtX) options for converting and storing green energy.

[0046] Another potential application for the heat pump is a machine offered by Enerin® Energy Engineering. This machine features a sealed single-phase system using a Stirling cycle and double-acting pistons for compression and expansion, with an expected COP of 2.5. While this heat pump can raise the temperature by 200 degrees, its minimum heat source temperature is limited to 100 degrees, making it suitable for HT-PEM but not for LT-PEM. Its heat supply capacity ranges from 0.3 MW to 10 MW, and its weight is 10,000 kg.

[0047] In the fuel cell system described herein, a flow of coolant is provided through the fuel cell, with the coolant entering the fuel cell at a first temperature T1, e.g., 160°C, and the coolant leaving the fuel cell at a second temperature rise T2, e.g., 170°C, which is higher than the first temperature T1. To maintain a stable and optimal operating temperature for the fuel cell, the heat pump receiving the coolant downstream of the fuel cell should not lower the temperature of the coolant at the downstream end of the heat pump system to a third temperature T3, which is lower than the first temperature T1. This can be achieved by appropriately adjusting the flow rate and design of the heat pump, for example, by selecting a heat pump with the appropriate specifications as described above.

[0048] In an example of a fuel cell system including a reformer that reforms an alcohol such as methanol, the methanol is mixed with water and supplied to the reformer as evaporated vapor. 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 low-temperature branch of the cooling circuit having a temperature close to the temperature T1 of the coolant supplied to the fuel cell, for example, T1 = 160°C. Alternatively, the required thermal energy can be extracted from a high-temperature branch of the cooling circuit having a temperature T2 of the coolant at the outlet of the fuel cell, for example, T2 = 170°C. Keeping in mind that the heat pump needs to raise the temperature to the reforming temperature T ref For example, 250°C, it is optimal to supply the coolant having the highest available temperature to the heat pump. As a result, the evaporator needs to be connected to a low-temperature branch of the cooling circuit downstream of the position where the heat pump system extracts thermal energy from the cooling circuit.

[0049] However, in this case, since the evaporator extracts heat from the coolant, the temperature T3 of the coolant at the inlet of the evaporator, which has a temperature T3 coming from the heat pump, needs to be slightly higher than the temperature T1 of the coolant used at the cooling inlet of the fuel cell, for example, 2 to 4 degrees higher. Therefore, when using an evaporator, the heat pump needs to lower the temperature of the coolant from, for example, level T2 to a temperature T3 higher than T1 where the coolant is supplied to the fuel cell.

[0050] Optionally, by using an additional heat exchanger between the evaporator and the fuel cell, the temperature of the coolant before entering the fuel cell can be finely adjusted.

[0051] The present invention will be described in more detail with reference to the drawings.

Brief Description of the Drawings

[0052] [Figure 1] It is a schematic diagram of a fuel cell system.

Modes for Carrying Out the Invention

[0053] Figure 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 fuel tank 3 and water from water tank 4 are mixed and evaporated in evaporator 5. The evaporated methanol-water mixture is fed to the inlet 6A of catalytic reformer 6, which produces synthesis gas as reformed gas. Such synthesis gas contains carbon dioxide CO2, carbon monoxide CO, hydrogen gas H2, and some residual water. The synthesis gas is fed from the reformed gas outlet 6B to the anode inlet 22 of fuel cell 2, as indicated by arrow 21A, and the H2 is used for electricity generation by fuel cell 2.

[0054] In the example provided, fuel cell 2 is an HT-PEM fuel cell, which is not sensitive to CO, does not require a shift reactor, and does not require a high water vapor content in the synthesis gas, in contrast to an LT-PEM battery.

[0055] Other alcohols can be used instead of methanol, but the reformer temperature will need to be adjusted accordingly.

[0056] Since the HT-PEM fuel cell 2 is operated at temperatures in the range of 170°C to 180°C, for example, the coolant in the cooling circuit 7, which is delivered towards the fuel cell stack by the coolant pump 8 in the directions indicated by arrows 17A and 17B, is heated from T1=160°C to T2=170°C. The HT-PEM fuel cell 2 can be operated at slightly different temperatures in the range of 120°C to 200°C, but is typically operated at temperatures in the range of 150°C to 180°C. Advantageously, the polymer electrolyte membrane PEM of the HT-PEM fuel cell is mineral acid-based and is typically a polymer membrane, such as phosphoric acid-doped polybenzimidazole (PBI).

[0057] The reformer 6 is heated by the reformer heater 27, shown by the dotted line in Figure 1. The components of the reformer heater 27 will be described in more detail below.

[0058] As indicated by arrow 17B, the coolant flowing from the fuel cell 2 at temperature T2 transfers thermal energy in the heat transfer / heat exchanger 9 to the heat transfer fluid in the heat transfer circuit 10, which is then transported by the heat transfer pump 11.

[0059] The heat transfer circuit 10 is thermally connected to the electric heat pump 12. The heat pump 12 transfers thermal energy from the heat transfer fluid in the heat transfer circuit 10 to the heating fluid circulating in the heating circuit 13, which is driven by a corresponding heating fluid pump 14, and the heating fluid heats the reformer 6.

[0060] The advantage of the heat transfer circuit 10 is that it allows for easy adjustment of the temperature of the fluid entering the heat pump 12 and the temperature of the coolant in the cooling circuit 7 located downstream of the heat transfer / heat exchanger 9.

[0061] 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 temperature of the coolant needs to be T1, for example T1 = 160°C, in order to maintain a stable operating temperature for the fuel cell 2. The temperature can be fine-tuned to T1 using the regulating heat exchanger 18. Depending on the amount of heat required by the evaporator 5, which changes according to 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 electricity consumption of the heat pump 12 is adjusted according to the temperature of the heat transfer fluid in the heat transfer circuit 10 and the amount of heat required by the reformer 2.

[0062] The temperature of the heat transfer fluid is changed from a temperature in the range of 120°C to 200°C to at least T ref In an example of a heat pump that raises the temperature of the heating fluid to 220°C, the temperature of the heat transfer fluid can optionally be raised from a temperature in the range of 150°C to 180°C to at least T ref = Raise the temperature of the heating fluid to 250°C.

[0063] By using the reformer heater 27 as 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, fuel or H2 gas is not required for the reformer burner. 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 supplied through an H2 conduit 20 to a synthesis gas 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 is added to the synthesis gas flowing from the reformer (6) into the synthesis gas conduit 21, as indicated by arrow 20A and arrow 21A, creating a mixed flow in the synthesis gas conduit 21 upstream of the anode inlet 22 of the fuel cell 2, as indicated by the thick arrow 21B.

[0064] Furthermore, since H2 gas is separated from the anode exhaust gas in the exhaust gas conduit 18 by the H2 separator 19, the remaining gases, mainly water vapor and CO2 gas, can, in principle, be discarded. However, optionally, water can be separated from the CO2 gas in the condenser 15, collected in the water reservoir 16, and reused for mixing with fuel. Optionally, residual CO2 in the CO2 conduit 23 can be compressed, for example, in the compressor 24, condensed in the heat exchanger 25, and then collected as liquid in the CO2 tank 26.

[0065] Furthermore, since H2 separation and H2 recirculation to fuel cells rather than burners, as well as additional elements for water recirculation and potential carbon capture, all benefit from the use of heat pump 12, the overall result of adding these elements is not merely an aggregate, but a synergistic combination of elements that leads to an overall improved environmentally friendly system.

Claims

1. A fuel supply device (3) that supplies fuel, A reformer (6) catalytically reforms the aforementioned fuel to obtain synthesis gas containing hydrogen (H2), A fuel cell (2) is fluidly connected to the reformed gas outlet (6B) of the reformer (6) and has an anode equipped with an anode inlet (22) that receives the H2, and generates electricity using the H2, The reformer (6) is set to a predetermined reformer temperature T that is at or above the minimum temperature required for the catalytic reforming of the fuel. ｒｅｆ A reformer heater (27) that heats the reformer, A cooling circuit (7) including a flow of coolant to maintain the operating temperature of the fuel cell (2), In a fuel cell system (1) comprising: an H2 separator (19) connected to an anode exhaust gas conduit (18) downstream of the anode, which receives anode exhaust gas and separates H2 from the anode exhaust gas, the H2 separator (19) being fluidly connected to a synthesis gas conduit (21) connecting the reformed gas outlet (6B) and the anode inlet (22), which mixes the separated H2 gas with the synthesis gas from the reformer (6) and then recirculates it to the anode, The fuel contains alcohol, the fuel cell (2) is an HT-PEM fuel cell, the operating temperature of the fuel cell (2) is in the range of 120°C to 200°C, and the predetermined reformer temperature T ｒｅｆ The fuel cell system (1) is characterized in that the reformer heater is an electric reformer heater (27), and is lower than the specified value.

2. The system according to claim 1, wherein the H2 separator is an electrochemical H2 separator (19).

3. The system according to any of the prior claims, further comprising: a water separator (15) located downstream of the H2 separator (19) for separating water from the anode exhaust gas after H2 separation; CO2 liquefaction units (24, 25); and a CO2 storage tank (26) for storing residual CO2 in liquid form.

4. The electric reformer heater (27) includes an electric heat pump (12), which is thermally connected to the cooling circuit (7), extracts thermal energy from the coolant to lower the temperature of the coolant, and transfers the extracted thermal energy to the heating fluid in the heating circuit (13) to heat the heating fluid, so that the temperature reaches the predetermined reformer temperature T ｒｅｆ The system according to any of the prior claims, wherein the heating fluid described above is provided, the heating circuit (13) is connected to the reformer (6), and thermal energy is transferred from the heating fluid to the reformer (6).

5. The fuel (2) comprises methanol and water, the system (1) includes an evaporator (5) that receives and evaporates the fuel for reforming in the reformer (6), the cooling circuit (7) is configured to maintain the operating temperature of the HT-PEM fuel cell (2) in the range of 150°C to 180°C, and the predetermined reformer temperature T ｒｅｆ The system according to claim 4, wherein the temperature range is 250°C to 300°C.

6. The heat pump (12) includes an electric multi-stage gas piston compressor, and the heat pump raises the reformer to the predetermined reformer temperature T ｒｅｆ The system according to claim 4 or 5, wherein the COP to be heated is 2 or more.

7. The reformer heater (27) raises the catalytic reformer (6) to a predetermined reformer temperature T that is above the minimum temperature required to catalytically reform the fuel and obtain synthesis gas containing hydrogen H2. ｒｅｆ To heat, The cooling circuit (7), which includes the flow of coolant, maintains the operating temperature of the fuel cell (2), The fuel is reformed by the reformer to obtain synthesis gas containing hydrogen H2, the synthesis gas is supplied to the anode of the fuel cell (2), the fuel cell (2) generates electricity by consuming the first portion of the H2, and the second portion of the H2 is released from the anode as part of the anode exhaust gas. A method for operating a fuel cell system, comprising: receiving the anode exhaust gas with an H2 separator (19), separating H2 from the anode exhaust gas, and recirculating the separated H2 to the anode, The fuel comprises alcohol, the system comprises a fuel evaporator (5), the fuel cell (2) is an HT-PEM fuel cell, the reformer heater is an electric reformer heater (27), the method involves receiving and evaporating the fuel in the evaporator (5), supplying the evaporated fuel into the reformer (6), operating the fuel cell at an operating temperature in the range of 120°C to 200°C, and using the reformer heater (27) to bring the fuel to a predetermined reformer temperature T that is above the minimum temperature required for the catalytic reforming of the fuel. ｒｅｆ The method, characterized by including maintaining

8. The method according to claim 7, comprising adding the separated H2 gas to the synthesis gas from the reformer (6) in a synthesis gas conduit (21) connecting the reformed gas outlet (6B) of the reformer (6) and the gas inlet (22) of the anode of the fuel cell (2).

9. The method according to claim 7 or 8, wherein the H2 separator is an electrochemical H2 separator (19).

10. The method according to claim 7, 8, or 9, further comprising separating H2O from the anode exhaust gas after H2 separation, recovering carbon by liquefying the residual CO2, and storing the CO2 as a liquid in a storage tank.

11. The reformer heater (27) includes an electric heat pump (12) thermally connected to the cooling circuit (7), and the method involves driving the heat pump (12) electrically, extracting thermal energy from the coolant in the cooling circuit (7) by the heat pump (12) to lower the temperature of the coolant, transferring the extracted thermal energy to the heating fluid in the heating circuit (13) to heat the heating fluid, and raising the temperature to the predetermined reformer temperature T ｒｅｆ The method according to any one of claims 7 to 10, comprising providing the heating fluid described above and transferring thermal energy from the heating fluid to the reformer (6).

12. The method according to claim 11, comprising maintaining the operating temperature of the fuel cell (2) in the range of 150°C to 180°C using the cooling circuit, and heating the reformer to a temperature in the range of 250°C to 300°C using the heat pump (12).

13. The method according to claim 11 or 12, comprising 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 temperature T2 higher than the first temperature T1, for example, T1 = 160°C and T2 = 170°C, the heat pump (12) receiving the coolant whose temperature has been raised to T2 by the fuel cell (2), and the method comprising using the heat pump (12) to extract thermal energy from the coolant to lower the temperature of the coolant to a third temperature T3 lower than T2 but higher than the first temperature T1.

14. The method according to claim 13, comprising: using the heat pump (12) to lower the temperature of the coolant to a third temperature T3 which is lower than T2 but higher than the first temperature T1; supplying the coolant to the evaporator (5) downstream of the reformer heater (27); transferring thermal energy from the coolant to the fuel in order to evaporate the fuel in the evaporator (5) before the fuel enters the reformer (6); and lowering 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 greater than the first temperature T1.

15. Use of the system according to any one of claims 1 to 6 or the method according to any one of claims 7 to 14 in generating electricity in an electric vessel.

Images