Method for operating a stack assembly and stack assembly
By introducing recirculation lines and hydrogen filters into the fuel cell stack assembly, the problem of high ventilation costs is solved, low-cost and efficient gas exchange and cooling are achieved, and safety is improved.
Patent Information
- Application Number
- CN202510412914.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-04-03
- Filing Date
- 2025-04-03
- Publication Date
- 2025-10-14
AI Technical Summary
Existing fuel cell stack components consume a lot of energy and are costly in the ventilation process, especially under adverse environmental conditions, which require a large amount of pre-treated air, resulting in increased energy consumption.
By introducing a recirculation line in the fuel cell stack assembly, using valves to control the recirculation of gas or gas mixture, and combining hydrogen filters and heat exchangers, the gas can be reused and effectively cooled, reducing the demand for fresh air.
It reduces the consumption and cost of ventilation, improves safety, reduces the demand for fresh air, and effectively reduces energy consumption, especially in high temperature environments.
Smart Images
Figure CN120776387A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a method for operating a stack assembly. In addition thereto, the present application relates to a stack assembly suitable for carrying out the method.
[0002] A preferred field of application of the present application is an electrochemical device, in particular an electrolysis device for producing hydrogen gas or a fuel cell system based on hydrogen gas. Thus, at least one stack of the stack assembly can be an electrolysis stack or a fuel cell stack, in particular. BACKGROUND
[0003] Irrespective of whether the device is an electrolysis device or a fuel cell system, a stack is the core part of the electrochemical device. Because the electrochemical reactions for material conversion take place in the stack or, respectively, in the electrochemical cells which form the stack as a monolithic stack.
[0004] For example, in an electrolysis stack, an electrochemical reaction takes place in which water is split into hydrogen gas and oxygen gas. Here, different technologies can be applied, such as proton exchange membrane (PEM), anion exchange membrane (AEM), alkaline electrolysis (AEL) or solid oxide electrolysis cell (SOEC). The technologies have in common that the produced hydrogen gas accumulates in areas outside the stack due to leaks and / or diffusion. Since hydrogen gas can form an explosive gas mixture with air or oxygen, the stack, alone or in combination with at least one further stack, is enclosed by an outer shell. In addition thereto, the outer shell can accommodate components for the media supply and voltage supply of the one or more stacks, such as lines, sensor mechanisms or actuator mechanisms. If power electronics of the electrochemical device are located in the vicinity of the outer shell, the power electronics are desirably installed in a separate outer shell in order to prevent flashovers.
[0005] Since hydrogen gas not only escapes outwardly but also accumulates in the interior of the outer shell, the interior is usually constantly actively ventilated. The constant active ventilation leads to a continuous exchange of air and thus to a dilution of the escaping hydrogen gas. In this way, it is ensured that the hydrogen concentration in the interior of the outer shell does not exceed a safety-relevant limit value.
[0006] In addition, cooling can be achieved by means of the constant active ventilation of the interior of the outer shell. This prevents the interior of the outer shell from overheating due to the waste heat of the at least one stack.
[0007] The constant active ventilation requires a high air exchange rate and thus a high outlay. In addition, depending on the environmental conditions, in particular the ambient temperature, at the installation site of the stack assembly, a prior cooling of the air used for ventilation can be necessary. This is usually the case, for example, in hot countries. In addition, due to adverse environmental conditions, a pretreatment of the air in the form of a purification can be necessary. SUMMARY
[0008] The invention is directed to the task of reducing the outlay and costs in terms of ventilating a stack assembly having a housing.
[0009] To solve this task, the invention proposes a method and a stack assembly. Advantageous refinements are also proposed.
[0010] A method for operating a stack assembly is proposed, the stack assembly comprising at least one stack and a housing accommodating the at least one stack. The housing encloses a volume filled with gas, which is connected via a gas inlet to an inlet line (conduit) and via a gas outlet to a discharge line for gas exchange. According to the invention, gas or a gas mixture is conducted out of the volume and is conducted into the volume again via the recirculation line and the gas inlet by opening a valve integrated into the recirculation line.
[0011] Thus, in the proposed method, gas or a gas mixture from the volume filled with gas is recirculated, so that the gas consumption is reduced. This means that less fresh gas needs to be conducted into the volume via the inlet line. The gas can be air, in particular, which is conducted into the volume for ventilation. By recirculating the gas or air discharged via the gas outlet, the amount of fresh air required and, if necessary, pre-treated, can be greatly reduced.
[0012] Since, by means of the gas inlet, not only recirculation, but also fresh gas or fresh air can be introduced into the volume, it is also ensured that released hydrogen is removed from the volume. Using a suitable sensor system, it can be monitored whether the hydrogen concentration has reached a critical range and, in this case, the recirculation must be interrupted. The gas or gas mixture conducted out of the volume is then completely conducted out via the discharge line.
[0013] The recirculation of the gas or gas mixture can be passive by means of the gas flow introduced into the volume via the inlet line and the gas inlet and / or active by means of a blower integrated into the recirculation line. The first variant has the advantage that the outlay for recirculating the gas or gas mixture is minimal. In addition, energy can be saved. The second variant has the advantage that the recirculation can be better controlled, in particular, it can be implemented independently of the gas flow in the inlet line. This means that only recirculation can also be introduced into the volume.
[0014] In an expansion of the application it is proposed that the recirculated gas or gas mixture is guided through a hydrogen filter before it is introduced into the volume again. This means that the hydrogen contained in the recirculation is completely or at least partially removed. Thus, the desired ventilation of the volume can be carried out - at least temporarily - exclusively by means of the recirculation. In this way the need for fresh gas or fresh air can be further reduced.
[0015] The hydrogen filter can be realized in various ways. For example, a filter with a palladium membrane can be used. The palladium membrane is warmed up by the gas or gas mixture which is guided out of the volume and recirculated, so that it reliably removes the hydrogen contained in the gas or gas mixture. Alternatively, the filter can be realized by means of a recombination catalyst with a gas dryer connected downstream, wherein the gas dryer can be embodied as a cold trap or a silicate dryer. This variant of the hydrogen filter has the advantage that the water content can be inferred by monitoring and taken into account for the regulation.
[0016] It is additionally proposed that the recirculated gas or gas mixture is tempered, preferably cooled, before it is introduced into the volume again. Thus, an effective cooling can be achieved at the same time by means of the ventilation of the stack assembly. The cooling of the recirculation can be realized, for example, by means of a heat exchanger integrated into the recirculation line.
[0017] The valve integrated into the recirculation line can be opened in a time-controlled manner and / or depending on the gas composition in the volume and / or depending on the gas composition of the recirculation. For example, a fixed time interval can be defined in which the valve is opened and the gas or gas mixture guided out is recirculated. The opening of the valve depending on the gas composition in the volume and / or the gas composition of the recirculation enables a need-based control of the recirculation. However, the knowledge of the gas composition is a prerequisite, so that this variant requires a gas sensor, in particular a hydrogen sensor. When recirculating, the amount of hydrogen in the recirculation is measured and this value is then used, for example, to switch off the recirculation.
[0018] Advantageously, the recirculation is only active in stable, previously defined operating states and in other cases, in particular in the case of a change in operating state (start-up -> operation, operation -> standby, operation -> shutdown), the valve integrated into the recirculation line remains closed. If a blower for active recirculation is present, it can be decided whether the ventilation should be achieved exclusively by means of the recirculation or exclusively by means of the introduction of fresh gas or fresh air. It is also possible to ventilate by means of recirculation in combination with fresh gas or fresh air and, in addition to this, no blower is required.
[0019] As an extension measure, it is proposed to introduce an inert gas, preferably nitrogen, into the volume via the inlet line. In this way, at least partial inerting of the atmosphere in the interior of the housing is achieved. By means of the introduced inert gas, the air fraction in the volume is reduced, so that a higher hydrogen fraction can be achieved without forming an explosive gas mixture. Accordingly, the gas flow can be reduced.
[0020] In combination with the proposed recirculation, the amount of inert gas introduced into the volume of the housing for ventilation can be kept low, so that the outlay and costs for this can be further reduced. Furthermore, not only the inlet line, but also the outlet line can have a smaller size.
[0021] To solve the task mentioned at the outset, furthermore, an electrical stack assembly for an electrochemical device, in particular an electrolysis device or a fuel cell system, is proposed. The electrical stack assembly comprises at least one electrical stack and a housing accommodating the at least one electrical stack. The housing encloses a volume, which is connected via a gas inlet to an inlet line and via a gas outlet to an outlet line. A connection of the gas outlet or outlet line to the gas inlet or inlet line can be established via a recirculation line with an integrated valve.
[0022] The proposed electrical stack assembly is particularly suitable for carrying out or can be operated in accordance with the previously described method according to the invention, so that the same advantages can be achieved. In particular, an effective gas exchange in the volume of the housing can be achieved with low outlay and over low costs.
[0023] The recirculation line can be connected to the gas outlet directly or indirectly via the outlet line. Similarly, the recirculation line can be connected to the gas inlet directly or indirectly via the inlet line. The indirect connection of the recirculation line can be achieved via a T-piece, respectively.
[0024] The recirculation can be passive and / or active. In the case of passive recirculation, the gas flow supplied to the gas inlet via the inlet line is used as driving force. To achieve passive recirculation, it is proposed that the gas inlet or inlet line has a cross-sectional constriction according to the type of a Venturi nozzle, into the region of which the recirculation line opens. The cross-sectional constriction generates a negative pressure, which sucks the recirculation from the recirculation line.
[0025] It is further proposed that a hydrogen filter is integrated into the recirculation line. This hydrogen filter reduces the hydrogen fraction in the recirculation, so that less fresh gas or fresh air needs to be introduced for ventilating the volume. The hydrogen filter can be implemented, for example, as a palladium membrane or as a reforming catalyst with a gas dryer connected downstream. The implementation as a reforming catalyst with a gas dryer connected downstream offers the advantage that, on the one hand, hydrogen can be converted into water and, on the other hand, the water produced can be removed from the system relatively easily by means of the gas dryer. For this purpose, the gas dryer can be designed as a cold trap that promotes condensation or as a silicate dryer, in which drying takes place by means of adsorption. Here, not only the hydrogen contained in the recirculation is reacted, but also the oxygen contained, so that both are removed from the recirculation. This is advantageous, in particular, if not fresh air, but an inert gas is supplied to the volume via the inlet line in order to inert the atmosphere. If air or oxygen still enters the volume that needs to be ventilated, the amount of air or oxygen that enters the volume of the housing can be counteracted by means of the reforming catalyst with a gas dryer connected downstream. An inert atmosphere in the interior of the housing allows a higher fraction of hydrogen. Thereby, on the one hand, the safety increases. On the other hand, in the case of active recirculation, the required blower power and the outlay for air pretreatment (temperature and particle content) can be reduced.
[0026] Advantageously, a heat exchanger is integrated into the recirculation line. By means of the heat exchanger, the recirculation can be cooled before it is introduced into the volume. In this way, an effective cooling can be achieved at the same time by means of ventilation. It is further proposed that the heat exchanger is thermally coupled with a further heat exchanger integrated into the inlet line. Then, the gas or gas mixture in the inlet line can be tempered, in particular heated, by means of the heat of the recirculation before it is introduced into the volume.
[0027] Preferably, a blower is integrated into the recirculation line. By means of the blower, the recirculation can be actively controlled. In addition, the recirculation can be operated independently of the introduction of fresh gas or fresh air, unlike in the case of passive recirculation. Preferably, the blower is arranged downstream of the hydrogen filter and / or the heat exchanger. In this way, the blower is traversed by recirculation that contains no or only a small amount of hydrogen. The proposed arrangement of the blower thus increases the safety.
[0028] In an expansion of the application it is proposed that at least one cooling unit is arranged externally on the housing. The cooling unit effects an additional cooling of the gas-filled volume in the interior of the housing. As a result, the temperature of the gas or gas mixture which is conducted out of the volume is less hot. Accordingly, the outlay for cooling the gas or gas mixture which is conducted back into the volume via the recirculation line is reduced. Furthermore, in the case of a high ambient temperature at the installation site of the stack assembly, an excessively strong temperature change in the interior of the housing can be suppressed. The embodiment with at least one external cooling element is therefore particularly suitable for hot regions. BRIEF DESCRIPTION OF DRAWINGS
[0029] Preferred embodiments of the application are explained in more detail below with reference to the drawings. These show:
[0030] Figure 1 a schematic diagram of a first stack assembly according to the application,
[0031] Figure 2 a schematic diagram of a second stack assembly according to the application,
[0032] Figure 3 a schematic diagram of a third stack assembly according to the application,
[0033] Figure 4 a schematic diagram of a fourth stack assembly according to the application,
[0034] Figure 5a ) and Figure 5b ) respectively show a schematic diagram of a hydrogen filter for a stack assembly according to the application,
[0035] Figure 6 a preferred first flow of a method according to the application, and
[0036] Figure 7 a preferred second flow of a method according to the application. DETAILED DESCRIPTION
[0037] From Figure 1A cell stack assembly 1 can be seen in the figure, which comprises a cell stack 2 and a housing 3. The housing 3 surrounds a volume 4, in which the cell stack 2 is accommodated together with a medium line 17 for connecting the necessary media for the cell stack 2. By way of example, the cell stack 2 represents one or more (more than two) cell stacks 2, wherein the one cell stack 2 or the multiple cell stacks 2 can in particular be electrolytic cell stacks for producing hydrogen. The volume 4 accommodating at least one cell stack 2 is filled with gas, for example with air. Due to the leakiness, hydrogen can enter the volume 4, which then forms an explosive gas mixture together with the air present there. Therefore, for safety reasons, the volume 4 needs to be ventilated. To this end, the housing 3 has a gas inlet 5 connected to the inlet line 6 and a gas outlet 7 connected to the outlet line 8, so that ventilation can be carried out. By ventilation, not only gas exchange can be achieved, but also cooling can be achieved if the gas introduced into the volume 4 is cooler than the gas or gas mixture in the volume 4. If necessary, the fresh gas or fresh air needs to be cooled beforehand.
[0038] Figure 1 The illustrated stack assembly 1 furthermore has a recirculation line 9, which connects the discharge line 8 to the gas inlet 5. For this purpose, the recirculation line 9 is connected to the gas inlet 5 at the other end - in parallel with the inlet line 6. A valve 10 is integrated into the recirculation line 9. If this valve is opened, the gas or gas mixture discharged from the volume 4 via the gas outlet 7 can be recirculated. In addition, a hydrogen filter 11 is integrated into the recirculation line 9, which removes hydrogen from the gas or gas mixture or reduces the hydrogen content before the gas or gas mixture is introduced back into the volume 4. Thus, ventilation can be achieved solely with the aid of recirculated material, so that only in the case of a high hydrogen load is it necessary to additionally supply fresh gas or fresh air via the inlet line 6.
[0039] Furthermore, a heat exchanger 12 is integrated into the recirculation line 9. Before the recirculation material is introduced back into the volume 4, it can be cooled by means of the heat exchanger 12. Thus, effective cooling can be achieved simultaneously with the recirculation material.
[0040] exist Figure 2 Shown in Figure 1 A variation of the stack assembly 1. Figure 1 The difference of the stack assembly of is the additional blower 14, which is integrated into the recirculation line 9 downstream of the hydrogen filter 11 and the heat exchanger 12. With the help of the blower 14, the recirculation via the recirculation line 9 can be actively controlled when necessary. In addition, Figure 2In the embodiment of the present invention, the recirculation line 9 is not connected directly to the gas inlet 5, but indirectly via the inlet line 6. For example, the connection can be realized via a T-piece. In order to save electricity costs, the blower 14 can remain switched off, and the recirculation can be realized only passively by means of the gas flow in the inlet line 6.
[0041] Figure 3 Show Figure 1 Another variant of the stack assembly 1 of FIG. Here, a heat exchanger 12 integrated into the recirculation line 9 is thermally coupled to a further heat exchanger 13 integrated into the inlet line 6. By thermally coupling the two heat exchangers 12 and 13, the heat of the recirculated material can be used to heat the fresh gas or fresh air that is introduced into the volume 4 via the inlet line 6. At the same time, the recirculated material is cooled. In addition, Figure 3 The stack assembly 1 has a gas concentration sensor 16 integrated into the discharge line 8, which is in particular a hydrogen sensor, making it possible to measure the hydrogen concentration in the discharged gas or gas mixture. In this case, the introduction of fresh gas or fresh air and recirculated material into the volume 4 can be demand-dependent, more precisely, dependent on the measured hydrogen concentration in the discharged gas or gas mixture.
[0042] from Figure 4 A further preferred embodiment of the fuel cell stack assembly 1 according to the invention can be found in . In this embodiment, a blower 14 is also provided for active recirculation. However, the blower is arranged upstream of the hydrogen filter 11 and the heat exchanger 12 in the recirculation line 9. In addition, the fuel cell stack assembly 1 has a cooling element 15, which is arranged on the outside (of the housing 3) on the housing 3. With the aid of the cooling element 15, further cooling can be achieved, which prevents overheating of the assembly. This is advantageous in particular when the fuel cell stack assembly 1 is to be used in hot areas.
[0043] from Figure 5a ) and 5b) can be found in embodiments for the hydrogen filter 11. Figure 5a ), the hydrogen filter 11 is exemplarily implemented as a palladium membrane. Figure 5b ), the recombination catalyst 11.1 together with the downstream gas dryer 11.2 forms the hydrogen filter 11. Furthermore, a gas concentration sensor 16 is integrated into the recirculation line 9 in order to monitor the filter function or to measure the hydrogen concentration in the recirculated material. As an alternative to measuring with the aid of a gas concentration sensor, it is possible to infer the gas concentration from the temperature at the recombination catalyst and / or from the temperature change at the recombination catalyst and / or from the amount of condensed water (in the case of cooling) and / or from the weight increase in the case of a silicate dryer.
[0044] Irrespective of the specific configuration of the stack assembly 1, the volume 4 enclosed by the housing 3 can also be filled with an inert gas or at least partially with an inert gas instead of air. Here, the volume 4 is ventilated with the aid of an inert gas which is introduced into the volume 4 via the inlet line 6 and the gas inlet 5. The inert gas can be nitrogen, in particular. The inert atmosphere in the interior of the housing 3 allows a higher concentration of hydrogen, so that the gas exchange can be reduced. This means that ventilation is not necessary at all or can be reduced in terms of time and / or in terms of the amount of gas introduced for ventilation, without increasing the safety risk.
[0045] It can be gathered from Figure 6 that a flow chart for regulating the ventilation with fresh air and / or recirculated air. The regulation follows a multi-stage procedure. First, in step S1, it is ensured that there is a suitable operating state for recirculation. This includes, for example: the operating state is not subject to change and / or there is an operating state with low expected impermeability. Because otherwise recirculation should preferably not be carried out. If the operating state is not subject to change or there is a defined operating state ("+"), it is checked in step S2 with the aid of suitable sensors whether the hydrogen concentration and / or the temperature and / or the pressure in the volume 4 is fluctuating in a previously defined non-critical range. If this is the case ("+"), the valve 10 integrated into the recirculation line 9 is opened in step S3 and the gas or gas mixture drawn from the volume 4 is recirculated passively and / or actively with the aid of the blower 14. In step S4, the hydrogen content in the recirculation is determined, for example, from the temperature development in the reforming catalyst 11.1 and / or from the amount of water subsequently separated from the gas stream in the gas dryer 11.2. If the hydrogen content is low or is in the expected range, ventilation can be carried out in step S5 only with the recirculation. If the hydrogen content requires an increased gas exchange, fresh air can be introduced into the volume 4 in addition to the recirculation in step S6. In step S7, if the check in step S1 results in the operating state being subject to change or there is a defined operating state ("-"), or the check in step S2 results in the hydrogen concentration and / or the temperature and / or the pressure in the volume 4 having reached a critical range ("-"), the recirculation is stopped or the valve 10 in the recirculation line 9 is closed. The same applies if the determination of the hydrogen content in step S4 results in the recirculation carrying too much hydrogen, in particular more than expected: the recirculation is stopped or the valve 10 in the recirculation line 9 is closed. In this case or these cases, ventilation is only achieved with fresh air in order to achieve the maximum gas exchange.
[0046] If nitrogen is introduced into the volume 4, use can be made of the flow chart according to Figure 7The method is explained as follows. First, the introduction in step 10 takes place according to a volume predefinition and / or a pressure predefinition. In step Sll, during the ongoing operation of the stack assembly, the hydrogen concentration in the volume 4 of the housing 3 increases due to the imperfection. Therefore, in step S12, in a time-controlled manner and / or according to the hydrogen concentration in the volume 4, the valve 10 integrated into the recirculation line 9 is opened and the gas or gas mixture drawn from the volume 4 is recirculated. If the recirculation is actively induced, the blower 14 has to be switched on. In step 13, the hydrogen content in the recirculation is determined. Here, this can take place as in step S4 of the above-described method. The further processing then depends on the hydrogen content. If this is below a predefined limit value, the recirculation can be stopped in step S14 by closing the valve 10 and, if necessary, by switching off the blower 14. If the hydrogen content fluctuates within a lower and an upper limit value, the recirculation can be continued in step S15. If the upper limit value is exceeded, fresh nitrogen can be introduced into the volume 4 in step S16. The gas or gas mixture drawn from the volume 4 is then discharged via the discharge line 8.
Claims
1. A method for operating a fuel cell stack assembly, the fuel cell stack assembly comprising at least one fuel cell stack (2) and a housing (3) for accommodating the at least one fuel cell stack (2), wherein: The housing (3) encloses a gas-filled volume (4), which is connected via a gas inlet (5) to an inlet line (6) and via a gas outlet (7) to an outlet line (8) for gas exchange. It is characterized in that by opening a valve (10) integrated into the recirculation line (9), gas or a gas mixture is discharged from the volume (4) and introduced back into the volume (4) via the recirculation line (9) and the gas inlet (5).
2. The method according to claim 1, It is characterized in that The gas or gas mixture is recirculated passively by means of a gas flow introduced into the volume (4) via the inlet line (6) and the gas inlet (5); and / or actively by means of a blower (14) integrated into the recirculation line (9).
3. The method according to claim 1 or 2, It is characterized by: The recirculated gas or gas mixture is passed through a hydrogen filter (11) before being introduced back into the volume (4).
4. The method according to any one of the preceding claims, It is characterized by: The recirculated gas or gas mixture is temperature-controlled, preferably cooled, before being introduced again.
5. The method according to any one of the preceding claims, It is characterized in that A valve (10) integrated into the recirculation line (9) is opened in a time-controlled manner and / or as a function of the gas composition in the volume (4) and / or as a function of the gas composition of the recirculated material.
6. The method according to any one of the preceding claims, It is characterized by: An inert gas, preferably nitrogen, is introduced into the volume (4) via the inlet line (6).
7. A stack assembly (1) for an electrochemical device, wherein the electrochemical device is particularly an electrolysis device or a fuel cell system, the stack assembly comprising at least one stack (2) and a housing (3) for accommodating the at least one stack (2), wherein: The housing (3) encloses a volume (4) which is connected via a gas inlet (5) to an inlet line (6) and via a gas outlet (7) to an outlet line (8), wherein a connection of the gas outlet (7) or the outlet line (8) to the gas inlet (5) or the inlet line (6) can be established via a recirculation line (9) having an integrated valve (10).
8. The battery stack assembly (1) according to claim 7, It is characterized in that The gas inlet (5) or the inlet line (6) has a cross-sectional constriction in the manner of a Venturi nozzle, into the region of which the recirculation line (9) opens.
9. The fuel cell stack assembly (1) according to claim 7 or 8, It is characterized by: A hydrogen filter (11) is integrated into the recirculation line (9), wherein the hydrogen filter (11) is preferably designed as a palladium membrane or as a recombination catalyst (11.1) with a downstream gas dryer (11.2).
10. The fuel cell stack assembly (1) according to any one of the preceding claims, It is characterized by: A heat exchanger (12) is integrated into the recirculation line (9), which is preferably thermally coupled to a further heat exchanger (13) integrated into the inlet line (6).
11. The battery stack assembly (1) according to any one of the preceding claims, It is characterized by: A blower (14) is integrated into the recirculation line (9), the blower being preferably arranged downstream of the hydrogen filter (11) and / or the heat exchanger (12).
12. The fuel cell stack assembly (1) according to any one of the above claims, characterized in that: At least one cooling unit (15) is arranged externally on the housing (3).