Fire protection system and procedures for reducing fire hazards in a shelter

Abstract

Fire protection system (1) for reducing the risk of fire in a shelter, wherein the fire protection system (1) comprises: - a fuel cell (3) with a cathode exhaust outlet (25) strictly separated from an anode outlet (27) for providing an oxygen-reduced cathode exhaust gas with an oxygen content of at most 15.0 vol% at the cathode exhaust outlet (25), - a drying system (35) connected downstream of the cathode exhaust outlet (25) for drying the oxygen-reduced cathode exhaust before the oxygen-reduced cathode exhaust is introduced into the protective chamber (54), and - a control system (51) configured to determine the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) and to introduce the dried oxygen-reduced cathode exhaust gas into the protective space (54) only when the current dew point is below an adjustable maximum dew point, wherein the control system (51) has at least one controllable shut-off valve (55), wherein the control system (51) is configured to control the at least one shut-off valve (55) and to close it towards the protective space (54) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point.

Description

[0001] The present invention relates to a fire protection system and a method for reducing the risk of fire in a shelter. Such a system and method can also be used for firefighting or to support firefighting efforts.

[0002] From DE 10 2005 053 692 B3, it is known that oxygen-reduced cathode exhaust from a fuel cell can be used to reduce the risk of fire in a space, such as an aircraft. It has been found that such fire protection systems using oxygen-reduced cathode exhaust from a fuel cell can be used particularly effectively where conventional fire protection systems, such as water sprinklers, cannot be used. This applies especially to very large shelters with a volume of 100,000 m³. 3or more. In particular, semi-automated or fully automated high-bay warehouses with high packing densities cannot be equipped with sprinkler systems to effectively reduce the risk of fire. The same applies to deep-freeze warehouses, where water pipes would freeze. Even in archive and server rooms, a fire protection system based on the oxygen-reduced cathode exhaust of a fuel cell can be advantageous compared to conventional fire protection systems.

[0003] However, a problem arises when a high amount of moisture is introduced into the protective chamber via the oxygen-reduced cathode exhaust. In a deep-freeze warehouse, this moisture could condense as snow or ice, which is undesirable. In archives, condensed moisture could lead to unwanted mold growth. In automated high-bay warehouses or server rooms, condensed moisture could lead to corrosion or short circuits.

[0004] US Patent 2020 / 0102087 A1 describes a system and method for providing a dried inert gas in a protective enclosure. German Patent DE 10343342 A1 describes a method and a device for air-conditioning at least one room with an air mixture that has a reduced oxygen particle pressure compared to ambient air, while maintaining a total pressure essentially equivalent to ambient air pressure. German Patent DE 102005053692 B3 discloses the ability to dry the water-containing, oxygen-reduced cathode exhaust gas using a condenser and to use the condensed water for other purposes. However, it remains unclear whether the oxygen-reduced cathode exhaust gas is dry enough for use in the protective enclosure.

[0005] It is therefore the object of the present invention to provide a fire protection system and method for reducing the risk of fire in a shelter, which ensures that the oxygen-reduced cathode exhaust gas is dry enough for the shelter, depending on the application.

[0006] This problem is solved by a fire protection system and a method for reducing the risk of fire in a protected area according to the independent claims. Preferred embodiments of the invention can be found in the dependent claims, the description, and the figures.

[0007] According to a first aspect of the present invention, a fire protection system is provided to reduce the risk of fire in a shelter, wherein the fire protection system comprises: - a fuel cell with a cathode exhaust outlet strictly separated from an anode outlet to provide an oxygen-reduced cathode exhaust gas with an oxygen content of no more than 15.0 vol.% at the cathode exhaust outlet, - a drying system connected downstream of the cathode exhaust outlet for drying the oxygen-reduced cathode exhaust before the oxygen-reduced cathode exhaust is introduced into the protective chamber, and - a control system designed to determine the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system and to introduce the dried oxygen-reduced cathode exhaust gas into the protective space only if the current dew point is below an adjustable maximum dew point.

[0008] The invention is characterized in particular by the fact that the oxygen-reduced cathode exhaust gas of the fuel cell is first dried, and then the current dew point of the dried, oxygen-reduced cathode exhaust gas is determined. The dried, oxygen-reduced cathode exhaust gas is then only directed into the protective chamber if the current dew point is below an adjustable maximum dew point. Monitoring the current dew point of the dried, oxygen-reduced cathode exhaust gas has the advantage that the fire protection system or method according to the invention is independent of the temperature of the dried, oxygen-reduced cathode exhaust gas. Therefore, cooling of the dried, oxygen-reduced cathode exhaust gas can be dispensed with regardless of the application.The cathode exhaust gas can have a much higher temperature than the protective chamber if its dew point is sufficiently low, without introducing significant heat into the chamber. For example, in a deep-freeze storage application, the maximum dew point can be set to -20°C, allowing cathode exhaust gas with a dew point below -20°C to be introduced into the cold storage at a temperature of +50°C or higher. The heat input from the cathode exhaust gas is negligible at such a low dew point.

[0009] According to the invention, the control system comprises at least one controllable shut-off valve, the control system being configured to control the at least one shut-off valve and close it towards the protective chamber when the current dew point of the dried, oxygen-reduced cathode exhaust gas is at or above the adjustable maximum dew point. The shut-off valve can be open in its normal state and close when the current dew point rises above the set maximum dew point. Alternatively, the shut-off valve can have a closed normal state and only open when the current dew point falls below the set maximum dew point.

[0010] Optionally, the control system can include at least one actuated opening valve, configured to actuate and open this valve to the environment when the dew point of the dried, oxygen-reduced cathode exhaust gas is at or above the adjustable maximum dew point. It is important to prevent a pressure increase at the cathode exhaust outlet that could cause irreparable damage to the fuel cell. Therefore, it is advantageous for the at least one shut-off valve and / or, in particular, the at least one opening valve to be a fast-acting solenoid valve. To prevent a pressure increase at the cathode exhaust outlet, the at least one opening valve can be opened during or before the at least one shut-off valve closes.

[0011] Optionally, at least one shut-off valve and at least one opening valve can be separately controllable valves and / or be integrated together in at least one 3 / 2-way valve.

[0012] Optionally, the fire protection system can include at least one safety valve located upstream of the drying system. This valve opens automatically and / or via the control system to the ambient air when the pressure of the oxygen-reduced cathode exhaust exceeds a maximum value. The safety valve thus protects the fuel cell, if necessary, from an excessive pressure increase at the cathode exhaust outlet. Preferably, the fire protection system includes a pressure sensor located upstream of the drying system that transmits the current pressure of the oxygen-reduced cathode exhaust to the control system.

[0013] Optionally, the drying system can be configured to increase its drying capacity if the current dew point of the oxygen-reduced cathode exhaust gas being dried by the system is at or above the adjustable maximum dew point. This is particularly useful if the drying system still has capacity to increase its drying capacity and the current dew point is still relatively far above the set maximum dew point. The drying capacity of the system can be increased, for example, by adding another drying stage.

[0014] The drying system can optionally have one or more drying stages. Multiple drying stages can be particularly advantageous for applications using a deep-freeze storage facility as a protective layer, in order to reduce the dew point to a sufficiently low value, for example, below -20°C. For a high-bay warehouse operating in the range of 10°C to 30°C, a single-stage drying system may suffice.

[0015] Optionally, the drying system can include an adsorption dryer, which is designed as a rotary dehumidifier with a heated regeneration airflow flowing in the opposite direction to the cathode exhaust gas flow. Preferably, the heating power for the regeneration airflow is provided at least partially by the waste heat from the fuel cell. An adsorption dryer is particularly advantageous in a second drying stage for applications using a deep-freeze storage facility as a protective chamber. This is because an adsorption dryer can achieve a particularly high degree of dryness and a correspondingly low dew point of, for example, -20°C. To operate the adsorption dryer with maximum efficiency, it is advantageous to derive at least some of the heating power for the regeneration airflow from the waste heat of the fuel cell.

[0016] Optionally, all the electrical energy required for the fire protection system can be supplied by the fuel cell. This allows the fire protection system to operate completely autonomously without a connection to an external power grid. This is particularly advantageous for mobile shelters, for example, in the form of a container, trailer, or van.

[0017] Optionally, the fire protection system can also include a fan arranged downstream of at least one drying stage of the drying system and configured to increase the pressure of the oxygen-reduced cathode exhaust gas downstream of the fan. This has the advantage of reducing the pressure in the upstream drying stage and increasing it in a downstream drying stage or towards the containment area. For example, if an adsorption dryer is used as a second drying stage, the increased pressure in the second drying stage ensures that no regeneration air is drawn into the cathode exhaust gas stream. Therefore, a regeneration air blower is preferably arranged in the regeneration air stream downstream of the adsorption dryer so that the regeneration air blower draws the regeneration air into the adsorption dryer rather than pushing it out.This reduces the pressure of the regeneration airflow in the adsorption dryer, thus also preventing regeneration air from being forced into the cathode exhaust gas flow.

[0018] Optionally, the fire protection system can include a hydrogen catalyst designed to chemically convert any residual hydrogen present in the dried, oxygen-reduced cathode exhaust gas before it is introduced into the shelter. This prevents any residual hydrogen from entering the shelter.

[0019] Preferably, the fuel cell of the fire protection system is a proton exchange membrane fuel cell (PEMFC). The fuel cell can have an anode outlet that is either closed or openable. Without an anode outlet, or with a closed anode outlet, the fuel cell can be operated in a so-called dead-end mode. However, the more common operating mode of a fuel cell is a flow-through mode, in which the anode outlet can be opened to allow the fuel supplied to the anode, for example, hydrogen, to be discharged as needed. This protects the fuel cell from harmful anode overpressure and allows residual components of unreacted fuel to be discharged. This occurs at regular intervals, sometimes several times per minute, depending on the operating conditions. This is also known as anode fuel purge.

[0020] There are fuel cells in which the anode fuel purge is routed into the cathode exhaust outlet, meaning that discharged fuel residues are mixed with the cathode exhaust. Such fuel cells cannot be used for the fire protection system according to the invention. For the fire protection system according to the invention, only a fuel cell can be used in which the cathode exhaust outlet is strictly separated from an anode outlet, i.e., an anode outlet is not connected to the cathode exhaust outlet, or there is no anode outlet at all. In any case, no anode fuel purge may be routed into the cathode exhaust outlet. Operating a fuel cell in a dead-end mode is suitable for the fire protection system according to the invention, since with the anode outlet closed, no anode fuel purge takes place and / or the fuel cell does not have an anode outlet in the first place.Although a PEMFC is preferably used for the fire protection system according to the invention, other types of fuel cells can also be used in principle, such as Alkaline Fuel Cell (AFC), Phosphoric Acid Fuel Cell (PAFC), Molten Carbonate Fuel Cell (MCFC), Solid Oxide Fuel Cell (SOFC), or Direct Alcohol / Methanol Fuel Cell (DAFC / DMFC).

[0021] According to a further aspect of the present invention, a mobile or stationary protective space is provided with a previously described fire protection system, wherein the protective space is preferably a storage and / or deep-freeze room, which is preferably at least partially operable with electrical energy supplied by the fuel cell. In particular, mobile containers or refrigerated vehicles carrying frozen goods can form such protective spaces. Preferably, the fuel cell provides all the electrical energy for operating the fire protection system. The thermal energy provided by the fuel cell in the form of waste heat can also be used by the drying system of the fire protection system.

[0022] According to another aspect of the present invention, a method is provided for reducing the risk of fire in a shelter, comprising the following steps: - Generating an oxygen-reduced cathode exhaust gas with an oxygen content of at most 15.0 vol.% at a cathode exhaust gas outlet of a fuel cell, wherein the cathode exhaust gas outlet is strictly separated from an anode outlet, - Drying of the oxygen-reduced cathode exhaust gas by means of a drying system connected downstream of the cathode exhaust gas outlet, - Determining the current dew point of the dried, oxygen-reduced cathode exhaust gas, and - Only introduce the dried, oxygen-reduced cathode exhaust gas into the protective chamber if the current dew point is below an adjustable maximum dew point.

[0023] According to the invention, the method further comprises the following steps: - Actuating at least one shut-off valve, and - Closing of at least one shut-off valve towards the protective chamber when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system is at or above the adjustable maximum dew point.

[0024] Optionally, the procedure may also include the following steps: - Activating at least one opening valve, and - Opening of the at least one opening valve to the environment when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system is at or above the adjustable maximum dew point. Preferably, the at least one opening valve is opened first, and then the at least one shut-off valve is closed, when the current dew point is at or above the adjustable maximum dew point, in order to avoid an undesirable pressure increase at the cathode exhaust gas outlet.

[0025] Optionally, the process can also include the opening of a safety valve if the pressure of the oxygen-reduced cathode exhaust gas downstream of the fuel cell exceeds a maximum value. This protects the fuel cell cathode from harmful overpressure.

[0026] Optionally, the process can also include increasing the drying capacity of the drying system if the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system is at or above the adjustable maximum dew point. This is advantageous in order to lower the current dew point below the maximum dew point more quickly, thus enabling the oxygen-reduced cathode exhaust gas to be fed into the protective chamber more rapidly. Preferably, the drying capacity of the drying system is increased by adding an additional drying stage.

[0027] Preferably, the drying process can be carried out in one or more drying stages. For applications with storage in a temperature range of 10°C to 30°C, one drying stage may suffice. For applications with a deep-freeze storage facility, where the maximum dew point is set to, for example, -20°C, two or more drying stages may be advantageous.

[0028] Optionally, drying in at least one drying stage can be carried out using an adsorption dryer designed as a rotary dehumidifier, whereby a regeneration air stream flowing in the opposite direction to the cathode exhaust gas stream is heated, with the waste heat from the fuel cell preferably providing at least part of the heating power for heating the regeneration air stream. Preferably, the adsorption dryer is used in a second drying stage to lower the current dew point sufficiently so that the fire protection system can be used in a deep-freeze storage facility, where, for example, a maximum dew point of -20°C is set.

[0029] Optionally, all the required electrical energy can be supplied by the fuel cell. This is particularly useful for applications with mobile shelters that do not have a connection to an external electrical power supply.

[0030] Optionally, the process can further include the operation of a fan located downstream of at least one drying stage of the drying system, thereby increasing the pressure of the oxygen-reduced cathode exhaust gas downstream of the fan. This has the advantage that the pressure is reduced in an upstream drying stage and increased in a downstream drying stage and / or towards the containment area. This is particularly useful with a downstream adsorption dryer, where it must be ensured that no regeneration air is drawn into the cathode exhaust gas stream.

[0031] Optionally, any residual hydrogen present in the dried, oxygen-reduced cathode exhaust gas can be chemically converted using a hydrogen catalyst before it is introduced into the protective chamber. This ensures that any residual hydrogen is not introduced into the protective chamber.

[0032] Preferably, the process is used with a storage and / or deep-freeze room as a protective enclosure. If the protective enclosure is a storage room with temperatures of, for example, 10°C to 30°C, one drying stage may be sufficient. For applications using a deep-freeze room as a protective enclosure, two drying stages are preferably used.

[0033] The invention is explained in more detail below with reference to the accompanying figures. These show: Fig. 1 a first part of an embodiment of a fire protection system according to the invention; Fig. 2 a first embodiment of a second part of the fire protection system, which is attached to the one in Fig. connects to the first part of the fire protection system shown in section 1; and Fig. 3 a second embodiment of a second part of the fire protection system, which is attached to the one in Fig. connects to the first part of the fire protection system shown in section 1.

[0034] The figures show two embodiments of a fire protection system 1 according to the invention. A first part 1a of the fire protection system 1 is the same for both embodiments and is in Fig. 1 shown. The embodiments therefore differ only in a second part 1b of the fire protection system 1, wherein Fig. 2 shows the second part 1b for the first embodiment and Fig. 3 the second part 1b for the second embodiment. The two embodiments differ essentially in that the first embodiment according to Fig. 2. One embodiment has a drying system with only one drying stage, and the second embodiment has a drying system with two drying stages. The first embodiment with single-stage drying is preferably used for fire protection in warehouses that are operated, for example, in a temperature range of 10°C to 30°C. The second embodiment with two-stage drying can be used for fire protection in deep-freeze warehouses that are operated at temperatures below 0°C.

[0035] As in Fig. As shown in Figure 1, the fire protection system 1 includes a fuel cell 3 in the form of a PEMFC. The PEMFC 3 has an anode 5 and a cathode 7. The anode 5 of the fuel cell 3 is supplied with fuel from a fuel supply 9. The fuel supply 9 is a hydrogen supply, which in turn can be supplied with hydrogen as fuel from one or more fuel sources 11a, 11b, 11c. For example, the fuel source 11a can be a hydrogen storage tank, which can be filled or completely replaced, for example, via an on-site electrolyzer or via delivery. Additionally or alternatively, a hydrogen pipeline 11b can serve as a hydrogen source. Alternatively or additionally, a methanol storage tank 11c can be used, wherein the methanol is separated into hydrogen and carbon dioxide in a downstream reformer 13, with the carbon dioxide being discharged through a carbon dioxide outlet 15.

[0036] When operating, the fuel cell 3 provides electrical power 17 and thermal power 19 in the form of waste heat. The cathode 7 of the fuel cell 3 has a cathode inlet 23 through which the cathode 7 can be supplied with ambient air 21. Furthermore, the cathode 7 has a cathode exhaust outlet 25, from which oxygen-reduced cathode exhaust with an oxygen content of at most 15.0 vol% is discharged. In the illustrated embodiment, the anode 5 also has an outlet 27, which, however, is strictly separated from the cathode exhaust outlet 25, i.e., they are not connected. In a flow-through operating mode, the anode exhaust outlet 27 serves as a hydrogen purge 29, which may be necessary to protect the anode 5 from hydrogen overpressure and to discharge residual hydrogen components. The hydrogen is then released into the environment 31.In the fire protection system 1 according to the invention, it is essential that the hydrogen is not introduced into the exhaust gas output 33 of the cathode 7, but that the cathode exhaust gas outlet 25 is strictly separated from the anode exhaust gas outlet 27.

[0037] The oxygen-reduced cathode exhaust gas is fed via lines 33 to a drying system 33 connected downstream of the cathode exhaust gas outlet 25 for drying the oxygen-reduced cathode exhaust gas. Fig. Figure 1 shows a first drying stage 35a of the drying system 35. Upstream of the first drying stage 35a of the drying system 35, a safety valve 37 is arranged, which opens automatically and / or under control to the ambient air when the pressure of the oxygen-reduced cathode exhaust gas at the cathode exhaust gas outlet 25 exceeds a maximum value. Since the cathode exhaust gas may already contain water in droplet form, this can be discharged via a water drain 39 and a siphon 41 upstream of the first drying stage 35a of the drying system 35.

[0038] The first drying stage 35a is operated here via an open-air cooler 43 and / or a chiller 45, whereby water 47 is extracted from the cathode exhaust gas and drains off via a siphon 49. The oxygen-reduced cathode exhaust gas dried in the first drying stage 35a is then fed to the second part 1b of the fire protection system 1 via the piping system 33.

[0039] In the Fig. In the first embodiment of the second part 1b of the fire protection system 1 shown in Figure 2, the drying system 35 does not have a further drying stage. The oxygen-reduced cathode exhaust gas dried in the single drying stage 35a of the drying system 35 is fed to a control system 51 downstream of the drying system 35. The control system 51 is configured to determine the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system 35 using a dew point sensor 53 and to allow the dried, oxygen-reduced cathode exhaust gas to pass through to a protective chamber 54 only if the current dew point is below an adjustable maximum dew point. For this purpose, the control system 51 has a controllable shut-off valve 55 in the form of a 3 / 2-way valve, which can be controlled to close the cathode exhaust gas flow to the protective chamber 54 and to discharge the cathode exhaust gas to the environment 57. Since the 3 / 2-way valve 55 may be used...Since the control system 51 cannot open or close quickly enough, an opening valve 59 in the form of a fast-switching solenoid valve is provided to quickly open the cathode exhaust gas flow to the environment 57 before the closing of the shut-off valve 55 creates an overpressure in the cathode exhaust line 33, which can be harmful to the cathode 7 of the fuel cell 3.

[0040] If the dried, oxygen-reduced cathode exhaust gas has a sufficiently low dew point, the shut-off valve 55 is or will be opened, and a downstream fan 61 pushes the dried, oxygen-reduced cathode exhaust gas into the protective chamber 54. An optional hydrogen catalyst 63 is interposed between the fan 61 and the protective chamber 54. This catalyst is designed to chemically react any residual hydrogen present in the dried, oxygen-reduced cathode exhaust gas before it is introduced into the protective chamber 54.

[0041] A monitoring system 65 is located in shelter 54, which monitors the atmosphere within shelter 54. The monitoring system 65 can, for example, measure the oxygen, nitrogen, and / or carbon dioxide concentrations of the atmosphere in shelter 54 and regulate the supply of dried, oxygen-reduced cathode exhaust gas. This allows a desired oxygen concentration to be continuously maintained in the atmosphere of shelter 54. Preferably, the fire protection system 1 is operated only when required, as triggered by the monitoring system 65. The fire protection system 1 can remain inactive as long as the oxygen content in the atmosphere of shelter 54 is sufficiently low. Alternatively, the fuel cell 3 of the fire protection system 1 can be operated to provide electrical and / or thermal power when no cathode exhaust gas is required for fire protection.The cathode exhaust is then simply released into the surrounding area 57. Shelter 54 is located in the [location omitted]. Fig. In the embodiment shown in 2, preferably a storage room that is operated in a temperature range of 10°C to 30°C.

[0042] Fig. Figure 3 shows a second embodiment in which the second part 1b of the fire protection system 1 has a second drying stage 35b of the drying system 35. The protected space 54 is a deep-freeze storage facility operated at temperatures below freezing. Downstream of the second drying stage 35b is the Fig. The embodiment shown in 3 is identical to the one shown in Fig. 2 first embodiment shown with the exception of the position of the fan 61. Here, the fan 61 is connected between the first drying stage 35a and the second drying stage 35b.

[0043] The second drying stage 35b of the drying system 35 here includes an adsorption dryer 67 in the form of a rotary dehumidifier, the operation of which is shown in the dashed box of Fig. Figure 3 illustrates this. The rotary dehumidifier 67 is driven to rotate by a motor 69. The fan 61 forces the oxygen-reduced cathode exhaust gas, pre-dried in the first drying stage 35a, axially through the rotating rotary dehumidifier 67 as a cathode exhaust gas stream 73. Within the rotary dehumidifier, the cathode exhaust gas releases moisture onto the internal surfaces of the rotary dehumidifier 67 by adsorption. In a segment 75 of the rotary dehumidifier 67, which is tightly separated from the cathode exhaust gas stream 73, the internal surfaces are dried by a regeneration air stream 77. The regeneration air stream 77 flows in the opposite direction to the cathode exhaust gas stream and is drawn into the rotary dehumidifier 67 by a regeneration air blower 79. The humidified regeneration air is then released into the surroundings 81.To increase the drying capacity of the adsorption dryer 67, the regeneration air is heated or preheated by a heater 83 before entering the rotary dehumidifier 67. Additionally or alternatively to the heater 83, the thermal output 19 of the fuel cell can be used, at least partially, to heat the regeneration air stream 77. To further increase the drying capacity, the regeneration air taken from the environment 85 can be dried in a dryer 87 using a chiller 89 before being heated in the heater 83 and / or by the waste heat 19 of the fuel cell 3.

[0044] The upstream arrangement of the fan 61 in the cathode exhaust gas stream with respect to the rotary dehumidifier 67 and the downstream arrangement of the regeneration air blower 79 in the regeneration air stream with respect to the rotary dehumidifier 67 ensure that the pressure in the cathode exhaust gas stream 73 is higher than in the regeneration air stream 77, so that no regeneration air can enter the cathode exhaust gas stream 73 through any leaks.

[0045] The second drying stage 35b dries the cathode exhaust gas to such an extent that the dew point can be below, for example, a set value of -20°C, which can be monitored by the dew point sensor 53 of the control system 51. Due to the low dew point, the cathode exhaust gas carries only a very small amount of heat, even though its temperature can reach 50°C or higher. Therefore, feeding the relatively hot but very dry cathode exhaust gas stream into the deep-freeze storage facility 54 does not result in a high heat input into the facility. Cooling the cathode exhaust gas stream is therefore unnecessary. The operation of the control system 51 is described in the following. Fig. The second embodiment shown in 3 is identical to the operating principle of the control system 51 described above in the first embodiment according to Fig. 2. Reference symbol list 1 Fire protection system 1a first part of the fire protection system 1b second part of the fire protection system 3 Fuel cell 5 Anode 7 Cathode 9 Fuel supply 11a Hydrogen storage 11b Hydrogen pipeline 11c Methanol storage 13 reformers 15 Carbon dioxide output 17 electrical power 19 thermal performance 21 Ambient air 23 Cathode input 25 Cathode exhaust outlet 27 Anode exhaust outlet 29 Hydrogen Purge 31 Surroundings 33 Cathode exhaust line 35 Drying system 35a first drying stage 35b second drying stage 37 Safety valve 39 Water outlet 41 Siphon 43 outdoor coolers 45 Cold water set 47 Water 49 Siphon 51 Control system 53 Dew point sensor 54 Shelter 55 Shut-off valve 57 surroundings 59 Opening valve 61 Fan 63 Hydrogen catalyst 65 Monitoring system 67 Adsorption dryer / rotary dehumidifier 69 Engine 73 Cathode exhaust stream 75 segments of the rotary dehumidifier 77 Regeneration airflow 79 Regeneration air blowers 81 Surroundings 83 Heating 85 Ambient air 87 dryers 89 Chiller

Claims

[1] Fire protection system (1) for reducing the risk of fire in a shelter, wherein the fire protection system (1) comprises: - a fuel cell (3) with a cathode exhaust outlet (25) strictly separated from an anode outlet (27) for providing an oxygen-reduced cathode exhaust gas with an oxygen content of at most 15.0 vol% at the cathode exhaust outlet (25), - a drying system (35) connected downstream of the cathode exhaust outlet (25) for drying the oxygen-reduced cathode exhaust before the oxygen-reduced cathode exhaust is introduced into the protective chamber (54), and - a control system (51) configured to determine the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) and to introduce the dried oxygen-reduced cathode exhaust gas into the protective space (54) only when the current dew point is below an adjustable maximum dew point, wherein the control system (51) has at least one controllable shut-off valve (55), wherein the control system (51) is configured to control the at least one shut-off valve (55) and to close it towards the protective space (54) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point. [2] Fire protection system (1) according to claim 1, wherein the control system (51) has at least one controllable opening valve (59), wherein the control system (51) is configured to control the at least one opening valve (59) and open it to the environment (31) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point. [3] Fire protection system (1) according to claim 2, wherein the at least one shut-off valve (55) and the at least one opening valve (59) are separately controllable valves and / or are integrated into at least one 3 / 2-way valve. [4] Fire protection system (1) according to one of the preceding claims, comprising at least one safety valve (37) arranged upstream of the drying system (35) and opened to the ambient air automatically and / or controlled by the control system (51) when the pressure of the oxygen-reduced cathode exhaust gas exceeds a maximum value. [5] Fire protection system (1) according to one of the preceding claims, wherein the drying system (35) is configured to increase the drying capacity of the drying system (35) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point. [6] Fire protection system (1) according to one of the preceding claims, wherein the drying system (35) has one or more drying stages (35a, 35b). [7] Fire protection system (1) according to one of the preceding claims, wherein the drying system (35) comprises an adsorption dryer, wherein the adsorption dryer is designed as a rotary dehumidifier (67) with a regeneration air stream (77) opposite to the cathode exhaust gas stream (73) and heated, wherein preferably a heating power for heating the regeneration air stream (77) is provided at least partially by the waste heat of the fuel cell (3). [8] Fire protection system (1) according to one of the preceding claims, wherein all electrical energy required for the fire protection system can be provided by the fuel cell (3). [9] Fire protection system (1) according to one of the preceding claims, further comprising a fan (61) which is arranged downstream of at least one drying stage (35a, 35b) of the drying system (35) and is configured to increase the pressure of the oxygen-reduced cathode exhaust gas downstream of the fan (61). [10] Fire protection system (1) according to one of the preceding claims, further comprising a hydrogen catalyst (63) which is configured to chemically convert residual hydrogen present in the dried, oxygen-reduced cathode exhaust gas before it is introduced into the protective space (54). [11] Fire protection system (1) according to one of the preceding claims, wherein the fuel cell (3) is a proton exchange membrane fuel cell (3), PEMFC. [12] Mobile or stationary shelter (54) with a fire protection system (1) according to one of the preceding claims, wherein the shelter (54) is preferably a storage and / or deep-freeze room, which is preferably at least partially operable with electrical energy that can be provided by the fuel cell (3). [13] Method for reducing the risk of fire in a shelter (54) comprising the steps: - Generating an oxygen-reduced cathode exhaust gas having an oxygen content of at most 15.0 vol% at a cathode exhaust outlet (25) of a fuel cell (3), wherein the cathode exhaust outlet (25) is strictly separated from an anode outlet (27), - Drying of the oxygen-reduced cathode exhaust gas by means of a drying system (35) connected downstream of the cathode exhaust gas outlet (25), - Determining the current dew point of the dried, oxygen-reduced cathode exhaust gas, - Introduce the dried, oxygen-reduced cathode exhaust gas into the protective chamber (54) only if the current dew point is below an adjustable maximum dew point, - Actuating at least one shut-off valve (55), and - Closing the at least one shut-off valve (55) to the protective space (54) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point. [14] Method according to claim 13, further comprising: - Controlling at least one opening valve (59), and - Opening of at least one opening valve (59) to the environment (31) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point. [15] Method according to claim 13 or 14, further comprising: - Opening of a safety valve (37) when the pressure of the oxygen-reduced cathode exhaust gas downstream of the fuel cell (3) exceeds a maximum value. [16] Method according to any one of claims 13 to 15, further comprising: - Increasing the drying capacity of the drying system (35) when the current dew point of the oxygen-reduced cathode exhaust gas dried by the drying system (35) is at or above the adjustable maximum dew point. [17] Method according to any one of claims 13 to 16, wherein the drying takes place in one or more drying stages (35a, 35b). [18] Method according to any one of claims 13 to 17, wherein the drying in at least one drying stage (35a, 35b) is carried out by means of an adsorption dryer designed as a rotary dehumidifier (67), wherein a regeneration air stream (77) opposite to the cathode exhaust gas stream (73) is heated, wherein preferably the waste heat of the fuel cell (3) provides at least part of a heating power for heating the regeneration air stream (77). [19] Method according to any one of claims 13 to 18, wherein all electrical energy required for the method is provided by the fuel cell (3). [20] Method according to any one of claims 13 to 19, further comprising: - Operating a fan (61) arranged downstream of at least one drying stage (35a, 35b) of the drying system (35), thereby increasing the pressure of the oxygen-reduced cathode exhaust gas downstream of the fan (61). [21] Method according to one of claims 13 to 20, wherein, prior to introducing the dried, oxygen-reduced cathode exhaust gas into the protective space (54), residual hydrogen present in the dried, oxygen-reduced cathode exhaust gas is chemically reacted by means of a hydrogen catalyst (63). [22] Method according to any one of claims 13 to 21, wherein the protective space (54) is a storage and / or deep-freeze room.

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