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CN-122003746-A - Method for operating an air system, air system and fuel cell system

CN122003746ACN 122003746 ACN122003746 ACN 122003746ACN-122003746-A

Abstract

The invention relates to a method for operating an air system (1), comprising at least one air supply path (2) for supplying air to at least one fuel cell stack (3), and at least one exhaust path (4) for discharging exhaust gases flowing out of the fuel cell stack (3), wherein the air supplied to the at least one fuel cell stack (3) is humidified by means of the exhaust gases of the same fuel cell stack (2) or of a further fuel cell stack (2), and wherein liquid water (5) contained in the exhaust gases is separated beforehand by means of a water separator (6). The invention further relates to an air system (1) and to a fuel cell system having an air system (1) according to the invention.

Inventors

  • J. BRAUN

Assignees

  • 罗伯特·博世有限公司

Dates

Publication Date
20260508
Application Date
20241008
Priority Date
20231010

Claims (13)

  1. 1. A method for operating an air system (1), comprising: -at least one air supply path (2) for supplying air to at least one fuel cell stack (3), and At least one exhaust path (4) for discharging exhaust gases flowing out of the fuel cell stack (3), Wherein the air supplied to the at least one fuel cell stack (3) is humidified by means of the exhaust gas of the same fuel cell stack (2) or a further fuel cell stack (2), and wherein the liquid water (5) contained in the exhaust gas is separated beforehand by means of a water separator (6).
  2. 2. The method according to claim 1, Characterized in that the liquid water (5) separated by means of the water separator (6) is collected in a container (7), which is preferably freeze-proof and/or which can be heated and/or emptied in the event of a freeze hazard, for example by purging with air or exhaust gas.
  3. 3. The method according to claim 2, Characterized in that the water (5) collected in the container (7) is sprayed into the at least one air supply path (2) for moistening and/or cooling the air, wherein the water (5) is preferably sprayed upstream of a heat exchanger (8) integrated into the air supply path (2) and/or between two compression stages (9.1, 9.2) of a multi-stage air compressor (9) integrated into the air supply path (2).
  4. 4. The method according to any of the preceding claims, It is characterized in that the water separator (6) is cooled passively or actively by means of a cooling device (11) in order to increase the separation rate, wherein preferably the cooling device (11) is flown through by the coolant of the cooling circuit (10).
  5. 5. The method according to any of the preceding claims, The exhaust gas is introduced tangentially in order to increase the separation rate of the water separator (6).
  6. 6. An air system (1) for a fuel cell system, comprising: -at least one air supply path (2) through which air can be supplied to at least one fuel cell stack (3), and At least one exhaust gas path (4) through which exhaust gas flowing out of the fuel cell stack (3) can be discharged, Wherein the at least one air supply path (2) is connected or connectable to the at least one air discharge path (4) or to a further air discharge path (4) via a connecting line (12) having an integrated shut-off valve (13) and an integrated water separator (6).
  7. 7. An air system (1) according to claim 6, The water separator (6) is characterized in that it has a container (7) for collecting the separated liquid water (5), wherein the container (7) is preferably embodied in a freeze-proof manner and/or can be heated.
  8. 8. An air system (1) according to claim 7, Characterized in that the container (7) is connected or connectable to a water spraying device (14), an extraction line (15) and/or a drainage line (16), wherein preferably the water spraying device (14) is arranged at the at least one air supply path (2).
  9. 9. An air system (1) according to claim 8, Characterized in that the water spraying device (14) is arranged at the at least one air supply path (2) upstream of the connecting line (12), preferably upstream of a heat exchanger (8) integrated into the air supply path (2), or between two compression stages (9.1, 9.2) of an air compressor (9) integrated into the air supply path (2).
  10. 10. An air system (1) according to any of claims 6 to 9, Characterized in that the connecting line (12) opens into the supply air path (2) upstream or at the same level as a bypass path (17) which connects the at least one supply air path (2) with the at least one exhaust air path (4) for bypassing the fuel cell stack (3).
  11. 11. An air system (1) according to any of claims 6 to 10, Characterized in that the water separator (6) has a cooling device (11) for passive or active cooling, wherein preferably the cooling device (11) is integrated into a cooling circuit (10) with circulating coolant.
  12. 12. An air system (1) according to any one of claims 6 to 11, Characterized in that the water separator (6) is connected to the connecting line (12) via an inlet (6.1) and an outlet (6.2), wherein preferably the inlet (6.1) is arranged tangentially.
  13. 13. A fuel cell system having at least one fuel cell stack (2) and an air system (1) according to any one of claims 6 to 12.

Description

Method for operating an air system, air system and fuel cell system Technical Field The invention relates to a method for operating an air system for supplying air to at least one fuel cell stack. The invention further relates to an air system for a fuel cell system having at least one fuel cell stack and to a fuel cell system having an air system according to the invention. Background Fuel cells convert fuel, such as hydrogen and oxygen, into electrical energy, heat and water. Typically, air, generally ambient air, is used as the oxygen supply source. The air supply is performed by an air system including an air supply path for delivering air and an exhaust path for exhausting exhaust gas flowing from the fuel cell. Because the electrochemical reaction in a fuel cell requires a certain air mass flow and a certain pressure level, air is compressed in advance. For this purpose, a compressor is integrated in the air supply path. The air heats up very drastically during compression, so that it must be cooled. Thus, the cooling device is integrated into the air supply path downstream of the compressor. Means for moistening the air can be provided for further conditioning the air in the air supply path. The wetting of the air is intended to prevent drying of the membrane of the fuel cell. Because the proton conductivity of the membrane is to a large extent dependent on the storage of a sufficient amount of water in its structure. Various solutions for moistening the air in the air supply path of an air system are known from the prior art. Wetting can be brought about, for example, by means of a gas-membrane humidifier arranged in the gas supply path, which transports water in the form of water vapor generated during operation from the gas discharge side to the gas supply side via the membrane. However, such membrane humidifiers require a large structural space, which is limited, especially in mobile applications. In addition, membrane humidifiers are relatively slow in terms of heat and can produce pressure losses. Other solutions for moistening the air provide for the moist exhaust gases to be led back and mixed with the dry air in the air supply path. In systems with a plurality of fuel cell stacks, the exhaust gases of other fuel cell stacks can also be used for this purpose. In this case, exhaust gas recirculation is also mentioned below. Furthermore, solutions are known in which water is sprayed into the air supply path. Disclosure of Invention The object of the invention is to optimize the wetting of the air in the air supply path of an air system, more precisely in such a way that components arranged in the air supply path are protected from liquid water droplets. To achieve this object, a method having the features of claim 1 and an air system having the features of claim 6 are proposed. Advantageous developments of the invention result from the respective dependent claims. Furthermore, a fuel cell system having an air system according to the invention is proposed. A method for operating an air system is presented, comprising: at least one air supply path for supplying air to at least one fuel cell stack, and At least one exhaust path for discharging exhaust gases flowing from the fuel cell stack. The air supplied to at least one fuel cell stack is humidified by means of exhaust gases of the same fuel cell stack or of a further fuel cell stack. The liquid water contained in the exhaust gas is separated beforehand by means of a water separator. In the proposed method, moist exhaust gas is used to moisten the air in the air supply path. However, liquid water contained in the exhaust gas is removed in advance, wherein product water is involved, which is produced as a by-product in the electrochemical reaction in the fuel cells of the fuel cell stack. Thus, the exhaust gases returned to the air supply path no longer contain, or at least approximately do not contain, liquid water, so that optimum component protection is achieved. For example, the compressor integrated into the gas supply path can be protected from droplet impact. In addition, liquid water is prevented from entering the fuel cell stack and adversely affecting the electrochemical reaction in the fuel cells. The liquid water is separated in the water separator, so that the water vapor contained in the exhaust gas is returned to the gas supply path together with the exhaust gas. The air in the air supply path is then wetted by means of water vapor. In a development of the invention, it is proposed to collect liquid water separated by means of a water separator in a container. The water collected in the container can then be supplied to the utilization, so that less water needs to be drained or output to the surroundings. The container is preferably freeze-proof and/or heatable, so that damage due to ice pressure is avoided in the event of freezing hazards. The freeze protection embodiment of the container can, for example, comprise a funnel-shape