Method and apparatus for inerting an oxygen-containing gas

Abstract

Method for inerting an oxygen-containing first gas contained in a protective housing (4) surrounding a fuel cell (1), wherein a predetermined quantity of a hydrogen-containing second gas is introduced into the protective housing (4) and at least a part of the oxygen contained in the first gas is reduced by cold combustion, wherein the oxygen content in the first gas or the oxygen content in a gas mixture of the first and second gas present in the protective housing (4) is measured and the predetermined quantity of the second gas to be introduced is determined from this.

Description

[0001] The invention relates to a method and a device for inerting an oxygen-containing first gas which is contained in a protective housing surrounding a fuel cell.

[0002] A fuel cell is a device for generating electrical energy that is powered by a hydrogen-containing gas. An uncontrolled release of the hydrogen-containing gas into the environment poses a fire or explosion hazard. To counteract this, DE 10 2004 026 226 A1 discloses that the fuel cell is operated in a protective housing filled with inert gas.

[0003] DE 10 2012 023 531 A1 relates to a method for using the exhaust gas of a fuel cell, in particular the cathode and anode exhaust gas, as an inert gas in a protective housing surrounding the fuel cell. Cathode exhaust gas is oxygen-depleted air. The reduced oxygen content is flame-retardant. The anode exhaust gas does not contain oxygen. Anode exhaust gas is gas enriched with carbon dioxide and / or nitrogen.

[0004] DE 10 2005 053 692 B3 discloses a fire protection system for reducing the risk of fire in an aircraft. The system uses a fuel cell to generate nitrogen-enriched cathode exhaust air. Hydrogen or reformed hydrocarbons are used as fuel. The composition of the cathode exhaust air is controlled such that the oxygen content in the surrounding space is approximately 15 vol.% or below 12 vol.%. This significantly minimizes the risk of fire or ignition compared to normal air.

[0005] The disadvantage of the state of the art is that when the protective housing is filled with inert gas, air always remains in the protective housing.

[0006] US Pat. No. 6,372,983 B1 discloses a housing for an electrical component for installation in a location where a flammable gas or vapor is expected to be present. The housing for the electrical component contains a catalyst for generating a reaction to convert a flammable fluid into a non-flammable product, thereby reducing the concentration of the flammable fluid and reducing the likelihood of the flammable fluid being ignited. The housing preferably allows the free exchange of gas and vapor between the surrounding atmosphere and the interior of the housing.

[0007] From DE 10 2008 013 150 B4, a mixing system for inerting a gas volume is known, the mixing system comprising: a fuel cell for providing at least a first exhaust gas; a hydrogen reformer for providing at least a second exhaust gas; wherein the mixing system is configured such that the first exhaust gas and the second exhaust gas can be mixed to form an inert gas mixture; and wherein the mixing system is configured such that the inert gas mixture can be passed into the gas volume for inerting.

[0008] DE 10 2014 005 614 A1 discloses a fuel cell system comprising at least one fuel cell arranged in a housing. The fuel cell has an anode chamber and a cathode chamber. A catalytic unit for converting hydrogen and oxygen into water is arranged in the housing. The anode chamber can be supplied with hydrogen or a hydrogen-containing gas, and exhaust gas flows out of the anode chamber. The fuel cell system is characterized in that the housing has an inlet line and an outlet line, with at least a portion of the exhaust gas flowing from the anode chamber into the housing via the inlet line.

[0009] The object of the invention is to eliminate the disadvantages of the prior art. In particular, it is intended to provide a device and a method with which the residual oxygen content in the protective housing can be further reduced.

[0010] This object is achieved by the features of claims 1 and 8. Advantageous embodiments of the invention emerge from the features of claims 2 to 7 and 9 to 14.

[0011] According to the invention, a method for inerting an oxygen-containing first gas contained in a protective housing surrounding a fuel cell is proposed, wherein a predetermined amount of a hydrogen-containing second gas is introduced into the protective housing and at least a portion of the oxygen contained in the first gas is reduced by cold combustion.

[0012] In the context of the present invention, “inerting” means the production of an inert gas using the gas contained in the protective housing, in particular the binding of the residual oxygen.

[0013] A “protective housing” in the sense of the invention is a gas-tight housing which surrounds the fuel cell and, if applicable, other chemical reactors connected upstream or downstream of the fuel cell and, if applicable, other components, for example pipes, valves and the like.

[0014] The "specified amount" of a hydrogen-containing second gas is preferably such that the hydrogen from the second gas can react stoichiometrically with the oxygen from the first gas. At the very least, the oxygen content of the first gas should be reduced to such an extent that the first gas becomes unreactive.

[0015] “Cold combustion” refers to slow oxidation that occurs without the formation of a flame or explosion.

[0016] Conveniently, the second gas is taken from a reactor connected to the fuel cell and located upstream of it. The reactor can, for example, be a reformer upstream of the fuel cell.

[0017] In another embodiment of the method, a purge gas from the fuel cell is used as the second gas. The purge gas contains hydrogen. For purging, gas is released from the anode by briefly opening a valve, e.g., a purge valve, to remove unwanted components from the reactors, especially the fuel cell.

[0018] In another embodiment of the process, the anode exhaust gas of the fuel cell is used as the second gas. In contrast to the aforementioned purge operation, the fuel cell is operated in such a way that hydrogen-containing gas is continuously passed through the anode. This leaves a residue of unconsumed hydrogen, which is contained in the anode exhaust gas. The anode exhaust gas can be used as the second gas.

[0019] In a further embodiment of the process, hydrogen is used as the second gas, which is fed to the fuel cell. In this case, it is not necessary to provide a reactor and / or reformer upstream of the fuel cell.

[0020] A catalyst, particularly a platinum sponge, is advantageously used to conduct cold combustion. The catalyst lowers the activation energy of the reaction between hydrogen and oxygen. This safely and reliably prevents the formation of a flame or even an explosion.

[0021] According to the invention, the oxygen content in the first gas or the oxygen content in a gas mixture of the first and second gases present in the protective housing is measured, and the predetermined amount of the second gas to be introduced is determined from this. By measuring the oxygen content, the predetermined amount of the second gas can be adjusted more precisely.

[0022] In a further embodiment of the method, the hydrogen content in a gas mixture of the first and second gases present in the protective housing is measured, and if hydrogen is detected, the introduction of the second gas is stopped. When the method is used in vehicles with high safety requirements, particularly aircraft, the hydrogen and oxygen content in the gas mixture present in the protective housing are expediently continuously monitored. If the protective housing becomes leaky and, as a result, oxygen penetrates the protective housing, the inerting can be maintained through continuous monitoring in combination with one of the aforementioned methods.

[0023] In a further embodiment of the method, the quantity and composition of the second gas are adjusted so that the pressure in the protective housing is maintained within a predetermined range. The volume of the gas mixture present in the protective housing is reduced by the reaction of hydrogen and oxygen to form water, which can at least partially condense. The pressure can be maintained within a predetermined range if, for example, two-thirds of the volume of the second gas is hydrogen and one-third is a gas other than hydrogen. The other gas replaces the volume of oxygen in the first gas in the protective housing. If the resulting water condenses, a higher hydrogen content in the second gas results in a negative pressure, and a lower hydrogen content results in an overpressure.

[0024] Conveniently, the second gas is mixed with a hydrogen-containing gas with a hydrogen content of more than 66.67 vol.% H2 and another hydrogen-containing gas with a hydrogen content of less than 66.67 vol.% H2, such that the second gas contains a hydrogen content of 60 to 70 vol.% H2. Depending on the ambient temperature, which is typically below 100°C, not all of the H2O will condense into water, but some of it may remain as water vapor. The inert gas in the protective housing is then a moist inert gas.

[0025] Furthermore, a device for inerting an oxygen-containing first gas contained in a protective housing surrounding a fuel cell is proposed. A controllable gas supply device for a hydrogen-containing second gas is provided in the protective housing, so that at least a portion of the oxygen contained in the first gas can be reduced by cold combustion. The gas supply device is particularly suitable for controlling or regulating a mass flow of the second gas. Furthermore, it advantageously prevents backflow of the oxygen-containing first gas.

[0026] Conveniently, a reactor connected to the fuel cell and located upstream of the fuel cell has a first gas extraction device for the second gas, which is connected to the gas supply device. The second gas can be a reaction product of a fuel gas formed in the reactor.

[0027] The advantage is that in this case no additional gas is required for inerting.

[0028] In a further embodiment, a second gas extraction device for a purge gas is provided at the fuel cell outlet, which is connected to the gas supply device for the second gas in the protective housing. The second gas extraction device is designed so that no gas from the protective housing enters the extraction device.

[0029] In a particularly advantageous embodiment, a catalyst, in particular a platinum sponge, is provided at the outlet of the gas supply device to carry out the cold combustion.

[0030] The device comprises a first sensor for measuring the oxygen content in the first gas or the oxygen content in a gas mixture of the first and second gases present in the protective housing, which transmits a first signal to a control unit for controlling the predetermined amount of the second gas to be introduced. The control unit controls the gas supply device.

[0031] Conveniently, the device further comprises a second sensor for measuring the hydrogen content in a gas mixture of the first and second gases present in the protective housing, which second sensor transmits a second signal to a control unit for controlling the termination of the introduction of the second gas. The sensor(s) can monitor and / or adjust the composition, in particular the oxygen and / or hydrogen content, of the gas in the protective housing.

[0032] In a further advantageous embodiment, the device comprises a pressure sensor in the protective housing, which transmits a third signal to a control unit, which can control the quantity and composition of the second gas such that the pressure in the protective housing is maintained within a predetermined range. To control the composition, the control unit can, for example, control a gas mixing unit, with which the composition of the second gas can be adjusted.

[0033] Conveniently, the device comprises a gas mixing unit for producing the second gas, wherein a hydrogen-containing gas with a hydrogen content of more than 66.67 vol.% H2 is mixed with another hydrogen-containing gas with a hydrogen content of less than 66.67 vol.% H2 such that the second gas contains a hydrogen content of 60 to 70 vol.% H2. The gas mixing unit allows the pressure in the protective housing to be maintained within the specified range.

[0034] The inerting process described above can also be performed using other gases instead of hydrogen. The protective housing does not necessarily have to be the protective housing of a fuel cell. For example, a liquid fuel, particularly gasoline or diesel, can be used to inerte a protective housing housing a gasoline or diesel engine. In this case, the oxygen in the protective housing can be oxidized and thus bound by a controlled leak of gasoline or diesel using a suitable catalyst.

[0035] In a similar way, a protective housing can also be made inert by accommodating a gas-powered unit, for example natural gas.

[0036] The method according to the invention is not limited to the one-time creation of an inert atmosphere in a protective housing. The method can also be designed so that the inert atmosphere is maintained even if, for example, the oxygen content in the protective housing increases due to a leak or continuous gas exchange. For this purpose, the oxygen content in the housing can be maintained at a predetermined level using a suitable control system and an oxygen sensor provided in the protective housing.

[0037] In the following, expedient embodiments of the invention are explained with reference to the drawings. They show: Fig. 1 a device with a first gas extraction device and Fig. 2 a device with a second gas extraction device.

[0038] Fig. Figure 1 schematically shows a fuel cell 1 with a gas inlet 2 and a gas outlet 3. The fuel cell 1 is enclosed by a protective housing 4. The fuel cell 1 is connected upstream to a reactor R1. Between the reactor R1 and the fuel cell 1, a first extraction device 5a is provided, which is connected to a controllable gas supply device 6. A catalyst 8 is expediently located at the outlet of the gas supply device 6.

[0039] The controllable gas supply device 6 can be controlled by a control device 7. A first sensor 9a and / or a second sensor 9b is expediently arranged in the protective housing 4, with which the hydrogen content and / or oxygen content in the protective housing 4 is measured. Corresponding signals are transmitted to the control device 7. A hydrocarbon is introduced into the reactor R1 via the gas inlet 2. In the reactor R1, which is in particular a reformer, a hydrogen-containing second gas is produced. A portion of the second gas is withdrawn at the first withdrawal device 5a between the first reactor R1 and the fuel cell 1 and fed into the protective housing 4 via the controllable gas supply device 6. In this case, in particular the quantity but also the flow rate of the second gas is controlled. The control of the gas supply device 6 ensures that cold combustion takes place.In particular, the gas supply device 6 also ensures that no gas flows back from the protective housing 4 into the first extraction device 5a. A catalyst 8 is expediently mounted at the outlet of the gas supply device 6 so that cold combustion takes place on the catalyst 8. The first sensor 9a and / or the second sensor 9b determines the oxygen content and / or hydrogen content in the protective housing 4. The first sensor 9a transmits a first signal to the controller 7 of the gas supply device 6, and the second sensor 9b transmits a corresponding second signal.

[0040] Fig.2 shows a device with a second gas extraction device 5b, which is provided at the outlet of the fuel cell 1. This second gas extraction device 5b is in turn connected to a controllable gas supply device 6, which introduces the hydrogen-containing second gas via a catalyst 8 into the protective housing 4. The hydrogen and oxygen content in the protective housing 4 can be determined via a first sensor 9a and a second sensor 9b. The first sensor 9a and / or the second sensor 9b transmit first and / or second signals to the control unit 7, which regulates the gas supply device 6. By means of the second gas extraction device 5b, the purge gas or the hydrogen-containing anode exhaust gas is extracted from the fuel cell 1 and introduced into the protective housing 4 via the controllable gas supply device 6. LIST OF REFERENCE SYMBOLS 1 fuel cell 2 Gas inlet 3 Gas outlet 4 protective housings 5a first withdrawal device 5b second withdrawal device 6 Gas supply device 7 Control unit 8 Catalyst 9a first sensor 9b second sensor R1 reactor

Claims

[1] Method for inerting an oxygen-containing first gas which is contained in a protective housing (4) surrounding a fuel cell (1), wherein a predetermined amount of a hydrogen-containing second gas is introduced into the protective housing (4) and at least part of the oxygen contained in the first gas is reduced by cold combustion, wherein the oxygen content in the first gas or the oxygen content in a gas mixture of the first and second gas present in the protective housing (4) is measured and the predetermined amount of the second gas to be introduced is determined therefrom. [2] Method according to claim 1, wherein the second gas is taken from a reactor (R1) connected to the fuel cell (1) and located upstream of the fuel cell. [3] Method according to claim 1, wherein a purge gas or an anode exhaust gas of the fuel cell (1) is used as the second gas. [4] Method according to one of the preceding claims, wherein a catalyst (8), in particular a platinum sponge, is used to carry out the cold combustion. [5] Method according to one of the preceding claims, wherein the hydrogen content in a gas mixture of the first and second gas present in the protective housing (4) is measured, and upon detection of hydrogen, the introduction of the second gas is stopped. [6] Method according to one of the preceding claims, wherein the quantity and composition of the second gas are adjusted so that a pressure in the protective housing (4) is maintained within a predetermined range. [7] A process according to claim 6, wherein, to produce the second gas, a hydrogen-containing gas having a hydrogen content of more than 66.67 vol.% H2 is mixed with another hydrogen-containing gas having a hydrogen content of less than 66.67 vol.% H2 such that the second gas contains a hydrogen content of 60 to 70 vol.% H2. [8] Device for inerting an oxygen-containing first gas which is contained in a protective housing (4) surrounding a fuel cell (1), wherein a controllable gas supply device (6) for a hydrogen-containing second gas is provided in the protective housing (4), so that at least part of the oxygen contained in the first gas can be reduced by cold combustion, comprising a first sensor (9a) for measuring the oxygen content in the first gas or the oxygen content in a gas mixture consisting of the first and second gases present in the protective housing (4), which first sensor transmits a first signal to a control unit (7) for controlling the predetermined amount of the second gas to be introduced. [9] Device according to claim 8, wherein a reactor (R1) connected to the fuel cell (1) and located upstream of the fuel cell (1) has a first gas extraction device (5a) for the second gas, which is connected to the gas supply device (6). [10] Device according to claim 8, wherein a second gas extraction device (5b) for a purge gas or an anode exhaust gas is provided at the outlet of the fuel cell (1), which is connected to the gas supply device (6). [11] Device according to one of claims 8 to 10, wherein a catalyst (8), in particular a platinum sponge, is provided at the outlet of the gas supply device (6) for carrying out the cold combustion. [12] Device according to one of claims 8 to 11, comprising a second sensor (9b) for measuring the hydrogen content in a gas mixture of the first and second gas present in the protective housing, which second sensor transmits a second signal to a control unit for controlling (7) a termination of the introduction of the second gas. [13] Device according to one of claims 8 to 12, comprising a pressure sensor in the protective housing (4) which transmits a third signal to a control unit (7) which can control the quantity and composition of the second gas so that the pressure in the protective housing (4) is maintained within a predetermined range. [14] Device according to one of claims 8 to 13, which comprises a gas mixing unit for producing the second gas, wherein a hydrogen-containing gas having a hydrogen content of more than 66.67 vol.% H2 is mixed with another hydrogen-containing gas having a hydrogen content of less than 66.67 vol.% H2 such that the second gas contains a hydrogen content of 60 to 70 vol.% H2.

Images