Heat and water recovery in a methanol reformer system or methanol reformer fuel cell system

Abstract

The invention relates to a methanol reformer system (1) comprising: a methanol reformer (2); a waste heat utilisation system (3) having a first heat exchanger (4); a water recovery system (5) having a second heat exchanger (6) and a water separator (15); and a cooling water system (7) which is connected to the waste heat utilisation system (3) and the water recovery system (5), wherein an exhaust gas line (8) of the methanol reformer (2) is connected to an inlet (9) on a primary side (10) of the first heat exchanger (4), an outlet (11) on the primary side (10) of the first heat exchanger (4) is connected to an inlet (12) on a primary side (13) of the second heat exchanger (6), and an outlet (14) on the primary side (13) of the second heat exchanger (6) leads into the water separator (15). The invention also relates to a methanol reformer fuel cell system. The invention also relates to a method for recovering heat and water in a methanol reformer system (1).

Description

Description JUEL Heat and water recovery in a methanol reformer or a methanol reformer fuel cell system TECHNICAL FIELD

[0001] Fuel cell technology is an innovative energy conversion technology based on the chemical reaction of hydrogen and oxygen to form water. This process releases electrical energy, which can be used, for example, to power vehicles or supply electricity to buildings. A key component in some fuel cell systems is the methanol reformer.

[0002] Methanol, a liquid alcohol, is easy to transport and store, making it an attractive energy source for fuel cells. However, the use of methanol in fuel cells requires pretreatment, as the cells are typically powered by hydrogen. This is where the methanol reformer comes into play.

[0003] The methanol reformer is a chemical device that feeds methanol and water into a high-temperature-resistant reaction vessel. There, under the influence of heat, methanol (CH3OH) is converted with water (H2O) to carbon dioxide (CO2) and hydrogen (H2). The produced hydrogen is then used to generate electricity in the fuel cell. The exhaust gas from a methanol reformer for a fuel cell contains mainly water vapor and carbon dioxide (CO2). The reaction in a methanol reformer is simplified as follows: BACKGROUND D

[0004] In order to avoid having to transport water as additional ballast on a ship, for example, water is sometimes recovered from the exhaust gases of the methanol reformer.

[0005] Another possible use of the exhaust gases from a methanol reformer is the utilization of the exhaust heat. The temperature of the exhaust gases is typically around 180°C.

[0006] Even if the use of exhaust gases seems sensible in principle, a major disadvantage of water recovery and heat recovery systems is their volume, which reduces the power density of such systems. SUMMARY OF THE INVENTION

[0007] The object of the invention is to improve the power density of such methanol reformer systems for the recovery of water and heat from the exhaust gases of methanol reformers. A further object of the invention is to provide a methanol reformer fuel cell system with improved water and heat recovery. The object of the invention is also to provide an improved method for heat and water recovery in such methanol reformer fuel cell systems.

[0008] The object directed to a methanol reformer system is achieved by a methanol reformer system, comprising a methanol reformer, a waste heat utilization system with a first heat exchanger, a water recovery system with a second heat exchanger and a water separator and a cooling water system which is connected to the waste heat utilization system and the water recovery system, wherein an exhaust gas line of the methanol reformer is connected to an inlet of a primary side of the first heat exchanger, wherein an outlet of the primary side of the first heat exchanger is connected to an inlet of a primary side of the second heat exchanger and wherein an outlet of the primary side of the second heat exchanger opens into the water separator. By arranging the heat exchangers of the heat recovery system and the water recovery system in series, volume can be saved for the overall system because part of the cooling required for water recovery is already performed in the heat recovery system. The second heat exchanger arranged in the water recovery system can thus be designed smaller without compromising the condensation of sufficient water for the methanol reformer. At the same time, the invention also enables the advantageous use of the high temperatures in the exhaust stream of the methanol reformer for heat recovery.

[0010] In an advantageous embodiment of the invention, the first heat exchanger is an evaporator and has a secondary side, downstream of which a turbine, a condenser, and a pump are arranged in the circulation direction, with a pump outlet connected to an inlet of the secondary side of the first heat exchanger. Such a thermodynamic cycle is also known as the Clausius-Rankine cycle and is used, for example, in steam power plants. In this process, a working fluid (usually water) is alternately evaporated in a closed circuit by the addition of heat at high pressure and, after expansion with the release of work, condensed by heat removal at low pressure.

[0011] The evaporator is particularly preferably an ORC evaporator. The use of an ORC evaporator (Organic Rankine Cycle) offers several advantages, especially in terms of energy efficiency and heat management. The ORC evaporator is part of an Organic Rankine Cycle, a process that converts heat into mechanical energy (often for electricity generation) by using an organic working fluid (e.g. ammonia or silicone oils) that evaporates at lower temperatures than water. This allows the use of heat sources that would otherwise remain unused. As with the Clausius-Rankine cycle, the secondary side of the The ORC evaporator is connected to a turbine, a condenser, and a pump connected downstream in a closed-loop arrangement. This means that the thermal energy absorbed by the working fluid in the ORC evaporator is used to drive the turbine. The turbine converts this thermal energy into mechanical energy. The condenser then condenses the working fluid back into a liquid, which is picked up by the pump and pumped back to the inlet of the secondary side of the first heat exchanger. This closed-loop process increases the efficiency of heat utilization and enables continuous energy generation. Connecting the pump outlet to the inlet of the secondary side of the first heat exchanger ensures that the working fluid continuously circulates through the system loop, further increasing the efficiency of the process and minimizing the need to add additional working fluid.It is advantageous if the turbine is connected to a generator for generating electrical energy. Connecting a turbine to a generator for generating electrical energy enables the efficient conversion of mechanical energy into electrical energy. This electrical energy can then either be used directly or fed into the power grid. This is particularly useful in industrial applications or power plants, where large amounts of waste heat are generated that would otherwise remain unused. By converting this waste heat into electrical energy, the overall efficiency of a system can be significantly increased.

[0013] It is advantageous if the condenser is connected to the cooling water system. A cooling water system can help efficiently lower the temperature of the working fluid in the condenser. This enables faster condensation of the working fluid and thus improves the efficiency of the entire circuit. A cooling water system can also help keep operating temperatures stable in the ORC circuit. This can increase component lifespan and reduce maintenance costs. Furthermore, the use of a cooling water system can help reduce the system's environmental impact, as less heat is lost to the environment.

[0014] It is advantageous if the second heat exchanger is designed to ensure the reliable condensation of sufficient water to operate the methanol reformer. In a methanol reformer, methanol is converted into hydrogen with water in a catalytic process. This process requires a sufficient and continuous supply of water. A condenser that can ensure this supply contributes to process reliability and the continuity of hydrogen production. An efficiently operating condenser can extract the required amount of water from the steam present in the system. This saves energy and resources compared to supplying external water, and operating costs are lower. Furthermore, the reuse of steam generated in the system contributes to reducing water consumption and thus to environmental protection.

[0015] In an advantageous embodiment of the invention, an inlet of a secondary side of the second heat exchanger is directly connected to the cooling water system, as this enables direct and rapid cooling. This can be particularly useful in situations where rapid heat dissipation is required. Furthermore, such a direct connection can contribute to increasing efficiency.

[0016] In an alternative embodiment of the invention, a cooling water line branches off from the cooling water system, and the condenser and the heat exchanger with its secondary side are connected in series into the cooling water line, allowing cooling in the waste heat recovery system and the water recovery system to take place in a single circuit. A single circuit is easier to design, install, and maintain. There are fewer components that could be prone to failure, and the system is less complex overall.

[0017] The object directed to a methanol reformer fuel cell system is achieved by a methanol reformer fuel cell system, comprising a methanol reformer system and a fuel cell connected to the methanol reformer via a hydrogen line, further comprising a third heat exchanger, the primary side of which is connected to a cooling system of the fuel cell and whose secondary side is connected either between the secondary side of the first heat exchanger and the turbine or between the pump and the secondary side of the first heat exchanger. By additionally coupling the fuel cell's cooling system to the waste heat recovery system, the entire waste heat of a methanol reformer fuel cell unit can be used for heat recovery. The coupling can occur directly or via an intermediate circuit.

[0018] The object directed to a method is achieved by a method for heat and water recovery in a methanol reformer fuel cell system, wherein an exhaust gas stream from a methanol reformer is first cooled in a waste heat utilization system and then in a water recovery system and the water obtained from the water recovery system is used to produce a methanol-water mixture required for the methanol reformer.

[0019] Advantageously, a fluid is circulated in the waste heat recovery system, whereby the fluid in liquid form absorbs heat from the exhaust gas flow, evaporates and is then expanded in a turbine, whereby the expanded fluid is cooled and condenses.

[0020] It is useful if the turbine drives a generator to produce electrical energy.

[0021] Advantageously, cooling water from a cooling water system flows through a condenser in the waste heat recovery system and a second heat exchanger in the water recovery system either sequentially or in parallel.

[0022] It is also advantageous if cooling water from a fuel cell cooling system transfers at least part of its heat to the evaporated fluid in the waste heat recovery system. SHORT DESCRIPTION OF THE SIGNS

[0023] FIG 1 shows schematically a methanol reformer system according to the invention, in which the heat exchanger in the water recovery system is indirectly connected to a cooling water system via the waste heat utilization system

[0024] FIG 2 shows schematically a methanol reformer system according to the invention, in which the heat exchanger in the water recovery system is directly connected to a cooling water system,

[0025] FIG 3 shows schematically a methanol reformer fuel cell system comprising the methanol reformer system of FIG 1 with an additional heat coupling from the cooling system of a fuel cell into the waste heat utilization system and

[0026] FIG 4 shows schematically a methanol reformer fuel cell system comprising the methanol reformer system of FIG 2 with an additional heat coupling from the cooling system of a fuel cell into the waste heat utilization system. DESCRIPTION OF THE EMBODIMENTS

[0027] FIG. 1 shows a methanol reformer system 1 according to the invention. It comprises a methanol reformer 2, a waste heat recovery system 3, and a water recovery system 5.

[0028] An exhaust gas stream 31 from the methanol reformer 2 is fed to a first heat exchanger 4 of the waste heat utilization system 3 and from there forwarded to a second heat exchanger 6 in the water recovery system 5. For this purpose, an exhaust gas line 8 of the methanol reformer 2 is connected to an inlet 9 of a primary side 10 of the first heat exchanger 4. In the exemplary embodiment of FIG. 1, three methanol reformers 2 are shown, whose exhaust gas streams 31 are combined and fed to the first heat exchanger 4 via a common exhaust gas line 8. Furthermore, an outlet 11 of the primary side 10 of the first heat exchanger 4 is connected to an inlet 12 of a primary side 13 of the second heat exchanger 6 and finally opens an outlet 14 of the primary side 13 of the second heat exchanger 6 into a water separator 15. The second heat exchanger s is designed such that it enables reliable condensation of sufficient water for the operation of the methanol reformer 2.

[0029] A cooling water system 7 is connected to the waste heat recovery system 3 via a condenser 18 and to the water recovery system 5 via the second heat exchanger 6. In the exemplary embodiment of Figure 1, a cooling water line 34 branches off from the cooling water system 7, and the condenser 18 and the heat exchanger 6 with its secondary side 24 are connected in series into the cooling water line 34. During operation, the cooling water first flows through the condenser 18 and then through the second heat exchanger s. Depending on the design of the methanol reformer system 1, however, flow through the condenser 18 and the second heat exchanger s in the reverse order may also be expedient. The waste heat utilization system 3 of the exemplary embodiment in FIG. 1 is typically constructed according to the principle of an Organic Rankine Cycle (ORC) due to the expected temperatures of approximately 150°C. Such an organic Rankine cycle is a thermodynamic process that converts heat into mechanical work, which is then often used to generate electricity. The organic Rankine cycle is very similar to the traditional Rankine cycle, but uses organic fluids with a lower evaporation temperature instead of water and steam. The organic Rankine cycle is therefore particularly advantageous for utilizing comparatively low-temperature heat sources that would otherwise remain unused, such as industrial waste heat, geothermal heat, solar energy, or waste heat from a methanol reformer 2.

[0031] Like the Rankine cycle, the organic Rankine cycle consists of four main processes: a) Evaporation: The organic fluid is converted into a gaseous state by adding heat (here heat from the exhaust gas stream 31 of the methanol reformer 2), b) Expansion: The gaseous fluid drives a turbine 17 or an expander, which generates mechanical work, c) Condensation: The gaseous fluid is condensed back into a liquid by releasing heat, and d) Pumping: The liquid fluid is increased back to the pressure at which it can be evaporated, closing the cycle. The waste heat recovery system 3 of FIG. 1 therefore comprises the first heat exchanger 4, which is an ORC evaporator. This has a secondary side 16, downstream of which, in the cycle direction, are the turbine 17 connected to a generator 22 for generating electrical energy, the condenser 18, and a pump 19. A pump outlet 20 is connected to an inlet 21 of the secondary side 16 of the first heat exchanger 4.

[0032] FIG. 2 shows a slightly modified embodiment of a methanol reformer system 1 according to the invention. While in the embodiment shown in FIG. 1, an inlet 23 of a secondary side 24 of the second heat exchanger 6 is indirectly connected to the cooling water system 7 via the condenser 18, the embodiment shown in FIG. 2 shows that the inlet 23 of the secondary side 24 of the second heat exchanger 6 can also be directly connected to the cooling water system 7.

[0033] FIG. 3 shows an embodiment of the methanol reformer fuel cell system 32 according to the invention. Starting from the exemplary embodiment of an inventive methanol reformer system 1 in FIG. 1, the methanol reformer fuel cell system 32 of FIG. 3 further comprises a fuel cell 30, which is connected to the methanol reformer 2 via a hydrogen line 29. In the exemplary embodiment of FIG. 3, the methanol reformer 2 and the fuel cell 30 are integrated into a methanol reformer fuel cell unit 33. FIG. 3 shows three methanol reformer fuel cell units 33. Alternatively, a coupling between a separate methanol reformer 2 and a separate fuel cell 30 would of course also be possible.

[0034] In order to utilize the waste heat of the fuel cell, a third heat exchanger 25 is provided, the primary side 26 of which is connected to a cooling system 27 of the fuel cell 30 and the secondary side 28 of which is connected between the secondary side 16 of the first heat exchanger 4 and the turbine 17. Alternatively, the third heat exchanger 25 could also be connected between the pump 19 and the secondary side 16 of the first heat exchanger 4, depending on the design of the methanol reformer fuel cell system 32. In the embodiment of FIG 3, analogous to the exhaust gas flow 31 in the exhaust line 8, the cooling water from the three fuel cells 30 is collected and fed to the third heat exchanger 25 and then distributed again to the fuel cells 30.

[0036] FIG. 4, analogous to FIG. 3 but based on FIG. 2, also shows an exemplary embodiment of a methanol reformer fuel cell system 32, which has a third heat exchanger 25, the primary side 26 of which is connected to a cooling system 27 of the fuel cell 30 and the secondary side 28 of which is connected between the secondary side 16 of the first heat exchanger 4 and the turbine 17. Here, too, the third heat exchanger 25 can alternatively be arranged in the circuit upstream of the first heat exchanger 4, depending on the design of the methanol reformer fuel cell system 32. REFERENCE NUMBER LIST 1 methanol reformer system 2 methanol reformers 3 Waste heat recovery system 4 first heat exchanger 5 Water recovery system 6 second heat exchanger 7 Cooling water system 8 exhaust pipe 9 Input of a primary side of the first heat exchanger 10 Primary side of the first heat exchanger 11 Output of the primary side of the first heat exchanger 12 Input of a primary side of the second heat exchanger 13 Primary side of the second heat exchanger 14 Output of the primary side of the second heat exchanger 15 water separators 16 Secondary side of the first heat exchanger 17 turbines 18 Capacitor 19 Pump 20 Pump outlet 21 Input of the secondary side of the first heat exchanger 22 Generator 23 Input of the secondary side of the second heat exchanger 24 Secondary side of the second heat exchanger 25 third heat exchanger 26 Primary side of the third heat exchanger 27 Fuel cell cooling system 28 Secondary side of the third heat exchanger 29 Hydrogen pipeline 30 fuel cells 31 Exhaust gas flow 32 Methanol reformer fuel cell system 33 Methanol reformer fuel cell unit 34 Cooling water pipe

Claims

Claims What is claimed:

1. A methanol reformer system (1) comprising a methanol reformer (2), a waste heat utilization system (3) with a first heat exchanger (4), a water recovery system (5) with a second heat exchanger (6) and a water separator (15), and a cooling water system (7) which is connected to the waste heat utilization system (3) and the water recovery system (5), characterized in that an exhaust gas line (8) of the methanol reformer (2) is connected to an inlet (9) of a primary side (10) of the first heat exchanger (4), that an outlet (11) of the primary side (10) of the first heat exchanger (4) is connected to an inlet (12) of a primary side (13) of the second heat exchanger (6), and that an outlet (14) of the primary side (13) of the second heat exchanger (6) opens into the water separator (15).

2. The methanol reformer system (1) according to claim 1, wherein the first heat exchanger (4) is an evaporator and wherein the first heat exchanger (4) has a secondary side (16) downstream of which a turbine (17), a condenser (18) and a pump (19) are connected in the circulation direction, wherein a pump outlet (20) is connected to an inlet (21) of the secondary side (16) of the first heat exchanger (4).

3. The methanol reformer system (1) according to claim 2, wherein the first heat exchanger (4) is an ORC evaporator.

4. The methanol reformer system (1) according to one of claims 2 or 3, wherein the turbine (17) is connected to a generator (22) for generating electrical energy.

5. The methanol reformer system (1) according to one of claims 2 to 4, wherein the condenser (18) is connected to the cooling water system (7).

6. The methanol reformer system (1) according to claim 5, wherein the second heat exchanger (6) is designed to enable reliable condensation of sufficient water for the operation of the methanol reformer (2).

7. The methanol reformer system (1) according to one of the preceding claims, wherein an inlet (23) of a secondary side (24) of the second heat exchanger (6) is directly connected to the cooling water system (7).

8. The methanol reformer system (1) according to one of claims 1 to 6, wherein a cooling water line (34) branches off from the cooling water system (7) and the condenser (18) and the heat exchanger (6) with its secondary side (24) are connected one behind the other in the cooling water line (34).

9. A methanol reformer fuel cell system (32), comprising a methanol reformer system (1) according to one of the preceding claims and a fuel cell (30) connected to the methanol reformer (2) via a hydrogen line (29), further comprising a third heat exchanger (25), the primary side (26) of which is connected to a cooling system (27) of the fuel cell (30) and the secondary side (28) of which is connected either between the secondary side (16) of the first heat exchanger (4) and the turbine (17) or between the pump (19) and the secondary side (16) of the first heat exchanger (4).

10. A method for heat and water recovery in a methanol reformer fuel cell system (32), characterized in that an exhaust gas stream (31) from a methanol reformer (2) is first cooled in a waste heat utilization system (3) and then in a water recovery system (5) and the water obtained from the water recovery system (5) is used to produce a methanol-water mixture required for the methanol reformer (2).

11. The method according to claim 10, wherein a fluid is circulated in the waste heat utilization system (3), wherein the fluid in liquid form absorbs heat from the exhaust gas stream (31), is evaporated in the process and is then expanded in a turbine (17), the expanded fluid being cooled and condensed in the process.

12. The method according to claim 11, wherein the turbine (17) drives a generator (22) for generating electrical energy.

13. The method according to any one of claims 10 to 12, wherein cooling water from a cooling water system (7) flows through a condenser (18) in the waste heat utilization system (3) and a second heat exchanger (6) in the water recovery system (5) either sequentially or in parallel.

14. The method according to any one of claims 10 to 13, wherein cooling water from a cooling system (27) of a fuel cell (30) transfers at least part of its heat to the fluid in the waste heat utilization system (3).

Images