Patent Publication Number: US-2023163328-A1

Title: Test system, air mixture line and gas control unit

Description:
BACKGROUND 
     A test system for characterizing solid oxide cells, preferably at temperatures from 500° C. to 850° C., comprising at least one gas control unit for producing a uniform fuel gas mixture for the solid oxide cells, comprising at least one fuel gas mixture line, comprising at least one hydrogen gas line and in particular comprising at least one oxygen gas line, wherein the at least one gas control unit comprises at least three stack layers, at least one hydration unit, which is configured to humidify the uniform gas mixture, is in particular directly connected in a gas-conductive manner to the at least one hydrogen gas line and/or to the at least one oxygen gas line and is disposed in a hydration layer of the at least three stack layers, at least one mixing chamber which is directly connected in a gas-conductive manner to the fuel gas mixture line and the hydration unit, is configured for producing the uniform gas mixture and is disposed in a mixing layer of the at least three stack layers and at least one test station for a solid oxide cell which is disposed on a test layer of the at least three stack layers, has already been proposed. 
     SUMMARY 
     The invention relates to a test system for characterizing solid oxide cells, preferably at temperatures from 500° C. to 850° C., comprising at least one gas control unit for producing a uniform fuel gas mixture for the solid oxide cells, comprising at least one fuel gas mixture line, comprising at least one hydrogen gas line and in particular comprising at least one oxygen gas line, wherein the at least one gas control unit comprises at least three stack layers, at least one hydration unit, which is configured to humidify the uniform gas mixture, is in particular directly connected in a gas-conductive manner to the at least one hydrogen gas line and/or to the at least one oxygen gas line and is disposed in a hydration layer of the at least three stack layers, at least one mixing chamber which is directly connected in a gas-conductive manner to the fuel gas mixture line and the hydration unit, is configured for producing the uniform gas mixture and is disposed in a mixing layer of the at least three stack layers and at least one test station for a solid oxide cell which is disposed on a test layer of the at least three stack layers. 
     It is proposed that the gas control unit comprise at least one further test station for at least one further solid oxide cell which is disposed on the test layer. 
     The test system is preferably configured for characterizing, in particular simultaneously and/or with a time delay, similar and different solid oxide cells, whereby in particular at least two solid oxide cells can be held in the test system at the same time. Individual or all of the solid oxide cells can be configured as anode-supported, metal-supported, cathode-supported and/or electrolyte-supported solid oxide cells, for example. The test system is preferably configured for characterizing at least two solid oxide cells at the same time. A solid oxide cell can be configured as a solid oxide fuel cell or a solid oxide electrolysis cell, for example. The solid oxide cell is preferably configured to convert chemical energy, in particular of a fuel gas, such as a natural gas, into electrical energy, preferably at temperatures of 450° C. to 850° C., particularly preferably at temperatures from 500° C. to 850° C. The solid oxide cells, in particular at least one solid oxide cell, preferably comprise a gas-tight electrolyte that is permeable to oxygen ions. The solid oxide cells, in particular at least one solid oxide cell, preferably comprise at least one multilayer electrode, in particular anode and/or cathode. The test system is preferably configured for characterizing solid oxide cells in a temperature range from 500° C. to 850° C. The test system can in particular be configured for characterizing solid oxide cells in a temperature range from 650° C. to 850° C. without a catalyst. 
     The test system can include at least one gas supply unit. The at least one fuel gas mixture line, the at least one hydrogen gas line and/or the at least one oxygen gas line can be assigned to the gas supply unit. The fuel gas mixture line is preferably configured for supplying a fuel gas mixture comprising carbon monoxide, carbon dioxide, methane, water vapor, hydrogen, nitrogen, methanol, diesel reformate and/or argon components to the gas control unit, in particular to the mixing chamber. The fuel gas mixture line is preferably configured for supplying a fuel gas mixture comprising at least carbon monoxide, at least carbon dioxide and at least methane components, in particular with water vapor, to the gas control unit, in particular to the mixing chamber. The hydrogen gas line is preferably configured for supplying hydrogen, in particular with water vapor, to the gas control unit, preferably to the hydration unit and/or in particular to the mixing chamber. The oxygen gas line is preferably configured for supplying oxygen, in particular with water vapor, to the gas control unit, preferably to the hydration unit and/or in particular to the mixing chamber. 
     The gas control unit is preferably made of a ceramic, preferably a full ceramic, in particular an oxide ceramic, such as preferably aluminum oxide, or also silicon nitride, aluminum nitride, zirconium oxide and/or silicon carbide. The stack layers of the gas control unit are preferably made of a ceramic, in particular an oxide ceramic, such as preferably aluminum oxide, or also silicon nitride, aluminum nitride, zirconium oxide and/or silicon carbide. 
     The hydration unit can comprise at least one bubbler, in particular at least one vapor pressure saturator, at least one evaporator or at least one reaction chamber. The at least one evaporator and/or the at least one bubbler can be integrally formed with at least one of the at least one fuel gas mixture line, the at least one hydrogen gas line and/or the at least one oxygen gas line. The hydration unit preferably comprises at least one reaction chamber, in particular for reacting hydrogen and oxygen. The hydration unit, in particular the reaction chamber, is preferably directly connected in a gas-conductive manner to the at least one hydrogen gas line and to the at least one oxygen gas line. The hydration unit, in particular the reaction chamber, is preferably directly connected in a gas-conductive manner to the mixing chamber, in particular on a different side than that to which the at least one hydrogen gas line and/or the at least one oxygen gas line is/are connected to the hydration unit, in particular the reaction chamber. The hydration unit preferably comprises at least one catalyst, preferably at least one noble metal catalyst. The at least one catalyst is preferably disposed in the at least one reaction chamber to catalyze the reaction of hydrogen and oxygen. The hydration unit is preferably disposed in the gas control unit. The hydration unit is preferably disposed in exactly one stack layer, in particular the hydration layer, of the gas control unit. The hydration layer is preferably configured differently than the mixing layer. The hydration layer is preferably configured differently than the test layer. The hydration layer and the mixing layer are preferably directly adjacent stack layers of the gas control unit. The hydration layer is preferably disposed on a side of the mixing layer which faces away from the test layer. The test layer preferably forms a penultimate layer of the gas control unit in the stacking direction, in particular on a test side of the mixing layer. The stacking direction is preferably oriented at least substantially perpendicular to the largest outer surfaces of the individual stack layers. The expression “substantially perpendicular” here is in particular intended to mean an orientation of a direction relative to a reference direction, wherein, in particular viewed in a projection plane, the direction and the reference direction enclose an angle of 90° and the angle has a maximum deviation of in particular less than 8°, advantageously less than 5° and particularly advantageously less than 2°. The hydration layer preferably forms a penultimate layer of the gas control unit in the stacking direction, in particular on a hydration side of the mixing layer. The mixing layer is preferably disposed between the hydration layer and the test layer. The hydration unit is preferably disposed upstream of the mixing chamber with respect to a gas flow from the at least one fuel gas mixture line, the at least one hydrogen gas line and/or the at least one oxygen gas line to the mixing chamber, is in particular connected to at least one of the at least one hydrogen gas line and/or the at least one oxygen gas line and/or is integrated into at least one of the at least one hydrogen gas line and/or the at least one oxygen gas line. The test layer and the mixing layer are preferably disposed spaced apart from one another by at least one stack layer. Respective adjacent stack layers are preferably connected to one another. Individual stack layers can be connected to one another in a gas-tight manner by strips, preferably gold strips, or mica strips, glass strips and/or ceramic strips, for example, which are at least 2 mm, preferably at least 5 mm, wide, in particular within a sealing region defined by the strips. Individual stack layers can be connected to one another in a gas-tight manner by strips, preferably gold strips, or mica strips, glass strips and/or ceramic strips, for example, which are preferably 100-500 μm thick, in particular within a sealing region defined by the strips. 
     Because of the configuration according to the invention of the test system, an advantageously uniform fuel gas mixture can be achieved for uniform characterization of at least two solid oxide cells at the same time under the same conditions. Data sets relating to characteristics of the solid oxide cells can in particular be measured more quickly and more consistently. Advantageously reliable data sets can be achieved, in particular for solid oxide cells measured under advantageously same conditions. Advantageously uniform test conditions can in particular be achieved, which advantageously provide comparable data sets for solid oxide cells. An advantageously uniformly humidified fuel gas mixture can be achieved. An advantageous environmental standard can be achieved by simultaneously measuring a plurality of solid oxide cells. 
     It is further proposed that the test system comprise an exhaust gas line for discharging exhaust gas from the at least one test station and the at least one further test station, wherein the at least one exhaust gas line is disposed at least partly in at least one stack layer of the at least three stack layers different from the test layer. The at least one exhaust gas line is preferably disposed at least partly in the at least one mixing layer. The at least one exhaust gas line is preferably disposed at least partly in the at least one hydration layer. The at least one exhaust gas line preferably extends through the at least one mixing layer, in particular along the stacking direction. The at least one exhaust gas line preferably extends through the at least one hydration layer, in particular along the stacking direction. The at least one exhaust gas line is preferably disposed spaced apart from the at least one test layer. The at least one exhaust gas line is preferably disposed in the mixing layer spaced apart from the mixing chamber. The at least one exhaust gas line is preferably disposed in the hydration layer spaced apart from the reaction chamber. The at least one exhaust gas line is preferably configured to discharge exhaust gas from the at least one test station and from the at least one further test station. An advantageously uniformly temperature-controlled exhaust gas line can be achieved. In particular risks of unfavorable exhaust gas flows can advantageously be reduced. Advantageously uniform test conditions can be achieved for all test stations. Recondensation effects can advantageously be reduced. 
     It is also proposed that the at least one test station and the at least one further test station be disposed equidistantly from the mixing chamber at least in relation to a gas path from the mixing chamber to the respective test stations. All of the test stations are preferably disposed equidistantly from the mixing chamber in relation to a gas path from the mixing chamber to the respective test stations. All of the test stations are preferably disposed symmetrically to one another on the test layer around a gas outlet from the mixing chamber. The mixing chamber preferably comprises the gas outlet. The gas outlet is preferably disposed centrally on an outer side of the mixing chamber which faces toward the test layer. A gas path from the mixing chamber, in particular from the gas outlet of the mixing chamber, to each test station is preferably configured to be the same length. A gas path from the mixing chamber, in particular from the gas outlet of the mixing chamber, to each test station is preferably configured to have the same shape. An advantageously uniform supply of the uniform gas mixture to the test stations can be achieved. 
     It is further proposed that the gas control unit comprise at least one, preferably at least two, additional test stations which are disposed on the test layer. All of the test stations are preferably configured, in particular shaped, the same way. The at least one test station is preferably configured in the same way as the at least one further test station. The at least one additional test station is preferably configured in the same way as the at least one test station and/or as the at least one further test station. Each test station preferably comprises a gas inlet which, in relation to a gas path from the mixing chamber, is disposed equidistantly from the at least one mixing chamber, in particular from the gas outlet of the at least one mixing chamber. An advantageously cost-efficient characterization of solid oxide cells can be achieved. Advantageous reliable statistics from measurements relating to solid oxide cells can be achieved. 
     It is also proposed that the gas control unit comprise at least one further stack layer, in particular a feed gas distribution layer, which is disposed between the mixing layer and the test layer and delimits a feed gas line which connects the at least one test station and the at least one further test station equidistantly at least with respect to a gas path to the at least one mixing chamber. The at least one feed gas distribution layer is preferably disposed between the at least one mixing layer and the at least one test layer. The at least one feed gas distribution layer is preferably disposed directly adjacent to the mixing layer. The at least one feed gas distribution layer is preferably disposed spaced apart from the test layer by at least one stack layer, in particular an exhaust gas collector layer. The at least one feed gas distribution layer can be disposed directly adjacent to the at least one test layer. The at least one feed gas distribution layer can be disposed spaced apart from the mixing layer by at least one stack layer, in particular an exhaust gas collector layer. The gas outlet of the mixing chamber is preferably connected in a gas-conductive manner to the feed gas distribution layer, in particular to the feed gas line. The feed gas line is preferably configured to a symmetrical shape around a central feed gas connector recess for uniformly connecting the test stations to the mixing chamber with respect to the gas path from the mixing chamber to the test stations. The feed gas line is preferably connected to the mixing chamber at the feed gas connector recess, in particular by a straight gas line. An advantageously uniform supply of the uniform fuel gas mixture to the test stations can be achieved. It is in particular possible to achieve an advantageously uniform temperature control of the uniform gas mixture in the feed gas distribution layer. 
     It is further proposed that the gas control unit comprise at least one further stack layer, in particular a, in particular the already mentioned, exhaust gas collector layer, which is disposed between the mixing layer and the test layer and delimits an exhaust gas section line which connects the at least one test station and the at least one further test station equidistantly at least in relation to a gas path to the at least one exhaust gas line. The at least one exhaust gas collector layer is preferably disposed between the at least one mixing layer and the at least one test layer. The at least one exhaust gas collector layer is preferably disposed directly adjacent to the test layer. The at least one exhaust gas collector layer is preferably disposed spaced apart from the mixing layer by at least one stack layer, in particular the at least one feed gas distribution layer. The at least one exhaust gas collector layer can be disposed directly adjacent to the at least one mixing layer. The at least one exhaust gas collector layer can be spaced apart from the test layer by at least one stack layer, in particular the at least one feed gas distribution layer. The at least one exhaust gas line is preferably connected in a gas-conductive manner to the exhaust gas collector layer, in particular to the exhaust gas section line. The exhaust gas section line is preferably configured to a symmetrical shape about a central exhaust gas connector recess for uniformly connecting the test stations to the exhaust gas line with respect to the gas path and/or an effective gas path, in particular a combination of the length of the gas path and the geometry of the gas path, from the test stations to the exhaust gas line. The exhaust gas section line is preferably connected to the test stations at exhaust gas recesses which are spaced apart from the exhaust gas connector recess, in particular by a straight gas line. An advantageously uniform discharge of exhaust gas from the test stations can be achieved. It is in particular possible to achieve an advantageously uniform temperature control of the exhaust gas, as a result of which in particular backflow effects can advantageously be reduced. 
     It is also proposed that the gas control unit comprise at least one further stack layer, in particular a gas distribution layer, which is disposed between the mixing layer and the test layer and delimits a feed gas line which connects the at least one test station and the at least one further test station equidistantly at least with respect to a gas path to the at least one mixing chamber and delimits an exhaust gas section line which connects the at least one test station and the at least one further test station equidistantly at least in relation to a gas path to the at least one exhaust gas line. The gas distribution layer is preferably configured as a one-piece variant of the exhaust gas collector layer with the feed gas distribution layer. “In one piece” is in particular intended to be understood to mean formed in one piece, whereby the one piece is preferably produced from a single blank, a mass and/or a casting, preferably from a single solid material in a milling process and/or sintering process. The feed gas line can be delimited by the gas distribution layer at a different level than the exhaust gas section line, in particular with respect to the stacking direction. The feed gas line can be delimited by the gas distribution layer at the same level as the exhaust gas section line, in particular with respect to the stacking direction. The feed gas line and the exhaust gas line are preferably disposed spaced apart from one another by at least 5 mm of material of the gas distribution layer. The feed gas distribution layer and/or the exhaust gas collector layer can be configured in one piece with the test layer. An advantageously cost-efficient gas control unit can be achieved. It is in particular possible to achieve an advantageously compact gas control unit. 
     It is also proposed that the test system comprise at least one air mixture line for supplying the at least one test station and the at least one further test station with an air mixture, which comprises at least one common rail unit for uniformly supplying the at least one test station and the at least one further test station with the air mixture. The air mixture line is preferably disposed entirely outside the gas control unit. The air mixture is preferably at a pressure of at least 1.5 bar. The air mixture is preferably at a pressure between 1.5 bar to 5 bar. 
     The common rail unit preferably comprises at least one high-pressure pump. The high-pressure pump can actively be regulated to a pressure. For pressure control in unregulated pumps, the common rail unit can comprise at least one pressure control valve. The air mixture is preferably configured as a mixture of at least nitrogen and at least oxygen. It is possible to achieve an advantageously uniform air mixture supply to the test stations, in particular for a cathode supply to the solid oxide cells. 
     An air mixture line of a test system according to the invention is proposed as well. An advantageous compatibility of the air mixture line to the gas control unit can be achieved. It is in particular possible to achieve an advantageous interchangeability of air mixture lines. 
     Proceeding from a test system for characterizing solid oxide cells, preferably at temperatures from 500° C. to 850° C., comprising at least one gas control unit for producing a uniform fuel gas mixture for the solid oxide cells, comprising at least one fuel gas mixture line, comprising at least one hydrogen gas line and comprising at least one oxygen gas line, wherein the at least one gas control unit comprises at least three stack layers, at least one hydration unit, which is directly connected in a gas-conductive manner to the at least one hydrogen gas line and/or to the at least one oxygen gas line to humidify the uniform gas mixture and is disposed in a hydration layer of the at least three stack layers, at least one mixing chamber which is directly connected in a gas-conductive manner to the fuel gas mixture line and the hydration unit, is configured for producing the uniform gas mixture and is disposed in a mixing layer of the at least three stack layers and at least one test station for a solid oxide cell which is disposed on a test layer of the at least three stack layers, it is also proposed that the at least one hydration unit comprise a reaction chamber for reacting hydrogen and oxygen and at least one catalyst, preferably a noble metal catalyst, which is disposed upstream of the at least one mixing chamber with respect to a gas flow and is directly connected in a gas-conductive manner to the at least one hydrogen gas line and to the at least one oxygen gas line. The test system is preferably configured for characterizing solid oxide cells in a temperature range from 500° C. to 850° C. 
     The catalyst is preferably configured as a platinum catalyst, in particular in the form of at least one mesh. The catalyst is preferably at least partially, preferably at least for the most part, made of platinum. 
     Because of the configuration according to the invention of the test system, an advantageously uniform fuel gas mixture can be achieved for uniform characterization of solid oxide cells under the same conditions. It is in particular possible to achieve an advantageously uniformly humidified fuel gas mixture. In particular a risk of coking, in particular of the gas control unit, can be reduced. 
     It is further proposed that the test system comprise an exhaust gas line for discharging exhaust gas from the at least one test station, wherein the at least one exhaust gas line is disposed at least partly in at least one stack layer of the at least three stack layers different from the test layer. The at least one exhaust gas line can be the same as the already mentioned exhaust gas line. The at least one exhaust gas line is preferably configured to discharge exhaust gas from the at least one test station. An advantageously uniformly temperature-controlled exhaust gas line can be achieved. In particular risks of unfavorable exhaust gas flows can advantageously be reduced. Advantageously uniform test conditions can be achieved for all test stations. 
     A gas control unit of a test system according to the invention is proposed as well. An improved availability of the gas control unit can be achieved, in particular for measuring a plurality of solid oxide cells at the same time. An advantageously short production time, in particular delivery time, of the gas control unit can be achieved, in particular for measuring a plurality of solid oxide cells at the same time. Advantageously standardized gas control units can be achieved, which in particular make it possible to achieve advantageously comparable measurement conditions. Standardized measurement conditions can advantageously be achieved. It is in particular possible to achieve advantageously reliable, in particular comparable, data sets from different gas control units. An advantageously high safety standard for gas control units can be achieved. 
     The test system(s) according to the invention, the air mixture line according to the invention and/or the gas control unit according to the invention is/are not intended to be limited to the above-described application and embodiment. In order to fulfill a herein described function, the test system according to the invention, the air mixture line according to the invention and/or the gas control unit according to the invention can in particular comprise a number of individual elements, components and units that deviates from a herein mentioned number. Moreover, for the ranges of values indicated in this disclosure, values lying within the mentioned limits are also intended to be considered disclosed and usable as desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages will become apparent from the following description of the drawing. The drawing shows two design examples of the invention. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations. 
       The figures show: 
         FIG.  1    a test system according to the invention comprising a gas control unit according to the invention and an air mixture line according to the invention in a schematic illustration, 
         FIG.  2    the gas control unit according to the invention in a schematic partially transparent illustration, 
         FIG.  3    a part of the gas control unit according to the invention in a schematic illustration, 
         FIG.  4    a part of the gas control unit according to the invention in a schematic illustration, 
         FIG.  5    a part of the gas control unit according to the invention in a schematic illustration, 
         FIG.  6    the air mixture line according to the invention in a schematic illustration and 
         FIG.  7    a part of an alternative gas control unit according to the invention of an alternative test system in a schematic illustration. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a test system  10   a . The test system  10   a  is configured for characterizing solid oxide cells. The test system  10   a  is configured for characterizing solid oxide cells at temperatures from 500° C. to 850° C. The test system  10   a  can be configured for characterizing solid oxide cells at temperatures from 650° C. to 850° C., in particular without a catalyst  44   a.    
     The test system  10   a  comprises a gas control unit  12   a . The gas control unit  12   a  is configured for producing a uniform fuel gas mixture for the solid oxide cells. The test system  10   a  comprises a furnace  14   a . The gas control unit  12   a  is disposed in the furnace  14   a . The test system  10   a  comprises a fuel gas mixture line  16   a . The test system  10   a  comprises a hydrogen gas line  18   a . The test system  10   a  comprises an oxygen gas line  20   a.    
     As an example, the gas control unit  12   a  here comprises seven stack layers  22   a.    
     The gas control unit  12   a  comprises a hydration unit  24   a . The hydration unit  24   a  is configured to humidify the uniform gas mixture. In this example, the hydration unit  24   a  is directly connected in a gas-conductive manner to the at least one hydrogen gas line  18   a  and to the at least one oxygen gas line  20   a . The hydration unit  24   a  is disposed in a hydration layer  26   a  of the seven stack layers  22   a.    
     The gas control unit  12   a  comprises a mixing chamber  28   a . The mixing chamber  28   a  is directly connected in a gas-conductive manner to the fuel gas mixture line  16   a . The mixing chamber  28   a  is directly connected in a gas-conductive manner to the hydration unit  24   a.    
     The mixing chamber  28   a  is configured for producing the uniform gas mixture. The mixing chamber  28   a  is disposed in a mixing layer  30   a  of the seven stack layers  22   a.    
     The gas control unit  12   a  comprises a test station  32   a ,  36   a ,  38   a ,  38 ′ a . The test station  32   a ,  36   a ,  38   a ,  38 ′ a  is configured for a solid oxide cell. The test station  32   a ,  36   a ,  38   a ,  38 ′ a  is disposed on a test layer  34   a  of the seven stack layers  22   a.    
     The gas control unit  12   a  comprises at least one further test station  32   a ,  36   a ,  38   a ,  38 ′ a . The further test station  32   a ,  36   a ,  38   a ,  38   a ′ is configured for a solid oxide cell. The further test station  32   a ,  36   a ,  38   a ,  38   a ′ is disposed on the test layer  34   a  of the seven stack layers  22   a . The gas control unit  12   a  comprises two additional test stations  32   a ,  36   a ,  38   a ,  38 ′ a . The additional test stations  32   a ,  36   a ,  38   a ,  38 ′ a  are configured for one respective solid oxide cell. The additional test stations  32   a ,  36   a ,  38   a ,  38 ′ a  are disposed on the test layer  34   a  of the seven stack layers  22   a . All of the test stations  32   a ,  36   a ,  38   a ,  38   a ′ are preferably configured, in particular shaped, the same way. The test station  32   a ,  36   a ,  38   a ,  38   a ′ is configured in the same way as the further test station  32   a ,  36   a ,  38   a ,  38   a ′. The additional test stations  38   a ,  38 ′ a  are configured in the same way as the test station  32   a ,  36   a ,  38   a ,  38   a ′ and as the further test station  32   a ,  36   a ,  38   a ,  38   a′.    
     Each test station  32   a ,  36   a ,  38   a ,  38 ′ a  comprises a gas inlet  40   a  (see  FIG.  2   ). The gas inlets  40   a  are disposed equidistantly from the at least one mixing chamber  28   a , in particular from a gas outlet  54   a  of the mixing chamber  28   a , in relation to a gas path from the mixing chamber  28   a . Each test station  32   a ,  36   a ,  38   a ,  38 ′ a  comprises a gas outlet  41   a.    
     The test system  10   a  is configured for characterizing similar and different solid oxide cells simultaneously and with a time delay. Individual or all of the solid oxide cells can be configured as anode-supported, metal-supported, cathode-supported and/or electrolyte-supported solid oxide cells, for example. The test system  10   a  is configured for characterizing up to four solid oxide cells at the same time. A solid oxide cell can be configured as a solid oxide fuel cell or a solid oxide electrolysis cell, for example. 
     The test system  10   a  is configured for characterizing solid oxide cells in a temperature range from 500° C. to 850° C. 
     The fuel gas mixture line  16   a  is configured for supplying a fuel gas mixture comprising at least carbon monoxide, at least carbon dioxide and at least methane components to the gas control unit  12   a , in particular to the mixing chamber  28   a . The hydrogen gas line  18   a  is configured for supplying hydrogen to the gas control unit  12   a , in particular to the hydration unit  24   a . The oxygen gas line  20   a  is configured for supplying oxygen to the gas control unit  12   a , in particular to the hydration unit  24   a.    
     The gas control unit  12   a  is made of a ceramic, preferably a full ceramic, in particular an oxide ceramic, such as aluminum oxide. The stack layers  22   a  of the gas control unit  12   a  are preferably in particular made of the ceramic, in particular the oxide ceramic, such as aluminum oxide. 
     The hydration unit  24   a  comprises a reaction chamber  42   a , in particular for reacting hydrogen and oxygen. The reaction chamber  42   a  is directly connected in a gas-conductive manner to the at least one hydrogen gas line  18   a  and to the at least one oxygen gas line  20   a.    
     The hydration unit  24   a , in particular the reaction chamber  42   a , is preferably directly connected in a gas-conductive manner to the mixing chamber  28   a , in particular on a different side than that to which the at least one hydrogen gas line  18   a  and/or the at least one oxygen gas line  20   a  is/are connected to the hydration unit  24   a , in particular the reaction chamber  42   a.    
     The hydration unit  24   a  comprises a catalyst  44   a , in particular a noble metal catalyst. The catalyst  44   a  is disposed in the reaction chamber  42   a  to catalyze the reaction of hydrogen and oxygen. The hydration unit  24   a  is preferably disposed in the gas control unit  12   a . The hydration unit  24   a  is disposed in exactly one stack layer  22   a , in particular in the hydration layer  26   a , of the gas control unit  12   a . The catalyst  44   a  is configured as a platinum catalyst, in particular in the form of at least one mesh. The hydration layer  26   a  is configured differently than the mixing layer  30   a . The hydration layer  26   a  is configured differently than the test layer  34   a . The hydration layer  26   a  and the mixing layer  30   a  are preferably directly adjacent stack layers  22   a  of the gas control unit  12   a . The hydration layer  26   a  is disposed on a side of the mixing layer  30   a  which faces away from the test layer  34   a.    
     The test layer  34   a  is a penultimate layer of the gas control unit  12   a  in the stacking direction  48   a , in particular on a test side  46   a  of the mixing layer  30   a . The stacking direction  48   a  is oriented perpendicular to the largest outer surfaces of the individual stack layers  22   a . The hydration layer  26   a  is a penultimate layer of the gas control unit  12   a  in the stacking direction  48   a , in particular on a hydration side  50   a  of the mixing layer  30   a . The test layer  34   a  and the mixing layer  30   a  are disposed spaced apart from one another by at least one stack layer  22   a.    
     The hydration side  50   a  of the mixing layer  30   a  is a side of the mixing layer  30   a  which faces toward the hydrogen gas line  18   a , the fuel gas mixture line  16   a  and the oxygen gas line  20   a . The test side  46   a  of the mixing layer  30   a  is a side of the mixing layer  30   a  which faces away from the hydrogen gas line  18   a , the fuel gas mixture line  16   a  and the oxygen gas line  20   a . The mixing layer  30   a  is disposed between the hydration layer  26   a  and the test layer  34   a.    
     The hydration unit  24   a  is disposed upstream of the mixing chamber  28   a  with respect to a gas flow from the fuel gas mixture line  16   a , the hydrogen gas line  18   a  and the oxygen gas line  20   a  to the mixing chamber  28   a.    
     The hydration unit  24   a  is connected to the hydrogen gas line  18   a  and the oxygen gas line  20   a  with respect to a gas flow from the fuel gas mixture line  16   a , the hydrogen gas line  18   a  and the oxygen gas line  20   a  to the mixing chamber  28   a.    
     Respective adjacent stack layers  22   a  are connected to one another. Individual stack layers  22   a  are connected to one another in a gas-tight manner by gold strips  88   a  which are at least 100, in particular at most 500 μm, thick, in particular within a sealing region  86   a  defined by the gold strips  88   a . Individual stack layers  22   a  are connected to one another in a gas-tight manner by gold strips  88   a  which are at least 2 mm wide, in particular within a sealing region  86   a  defined by the gold strips  88   a.    
     The test system  10   a  comprises an exhaust gas line  52   a  for discharging exhaust gas from the test station  32   a ,  36   a ,  38   a ,  38   a ′, the further test station  32   a ,  36   a ,  38   a ,  38   a ′ and the additional test stations  32   a ,  36   a ,  38   a ,  38   a ′ (see  FIG.  2   ). The exhaust gas line  52   a  is partly disposed in at least one stack layer  22   a  of the seven stack layers  22   a  different from the test layer  34   a . The exhaust gas line  52   a  is partly disposed in the mixing layer  30   a.    
     The exhaust gas line  52   a  is partly disposed in the at least one hydration layer  26   a . The exhaust gas line  52   a  extends through the mixing layer  30   a , in particular along the stacking direction  48   a . The exhaust gas line  52   a  extends through the at least one hydration layer  26   a , in particular along the stacking direction  48   a . The exhaust gas line  52   a  is disposed spaced apart from the at least one test layer  34   a . The exhaust gas line  52   a  is disposed in the mixing layer  30   a  spaced apart from the mixing chamber  28   a.    
     The exhaust gas line  52   a  is disposed in the hydration layer  26   a  spaced apart from the reaction chamber  42   a . The exhaust gas line  52   a  is configured to discharge exhaust gas from the test station  32   a ,  36   a ,  38   a ,  38   a ′, from the further test station  32   a ,  36   a ,  38   a ,  38   a ′ and from the additional test stations  32   a ,  36   a ,  38   a ,  38   a ′. The test station  32   a    36   a ,  38   a ,  38   a ′, the further test station  32   a ,  36   a ,  38   a ,  38   a ′ and the additional test stations  32   a ,  36   a ,  38   a ,  38   a ′ are disposed equidistantly from the mixing chamber  28   a  in relation to a gas path from the mixing chamber  28   a  to the respective test stations  32   a ,  36   a ,  38   a ,  38 ′ a.    
     All of the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  are disposed equidistantly from the mixing chamber  28   a  in relation to a gas path from the mixing chamber  28   a  to the respective test stations  32   a ,  36   a ,  38   a ,  38 ′ a . All of the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  are disposed symmetrically to one another on the test layer  34   a  around a gas outlet  54   a  from the mixing chamber  28   a . The mixing chamber preferably  28   a  comprises the gas outlet  54   a . The gas outlet  54   a  is preferably disposed centrally on an outer side of the mixing chamber  28   a  which faces toward the test layer  34   a . A gas path from the mixing chamber  28   a , in particular from the gas outlet  54   a  of the mixing chamber  28   a , to each test station  32   a ,  36   a ,  38   a ,  38 ′ a  is configured to be the same length. The gas path from the mixing chamber  28   a , in particular from the gas outlet  54   a  of the mixing chamber  28   a , to each test station  32   a ,  36   a ,  38   a ,  38 ′ a  is configured to have the same shape (see  FIG.  4   ). 
     The gas control unit  12   a  comprises at least one further stack layer  22   a , in particular a feed gas distribution layer  56   a  (see  FIG.  4   ). The feed gas distribution layer  56   a  is disposed between the mixing layer  30   a  and the test layer  34   a . The feed gas distribution layer  56   a  delimits a feed gas line  58   a . The feed gas line  58   a  connects the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  equidistantly in relation to a gas path to the at least one mixing chamber  28   a.    
     The feed gas distribution layer  56   a  is disposed directly adjacent to the mixing layer  30   a . The feed gas distribution layer  56   a  is disposed spaced apart from the test layer  34   a  by at least one stack layer  22   a , in particular an exhaust gas collector layer  66   a . The gas outlet  54   a  of the mixing chamber  28   a  is connected in a gas-conductive manner to the feed gas distribution layer  56   a , in particular to the feed gas line  58   a . The feed gas line  58   a  is configured such that it is limited to a symmetrical shape around a central feed gas connector recess  60   a  for uniformly connecting the test stations  32   a ,  36   a ,  38   a ,  38   a ′ to the mixing chamber  28   a  with respect to the gas path from the mixing chamber  28   a  to the test stations  32   a ,  36   a ,  38   a ,  38   a ′. The feed gas line  58   a  is configured such that it is limited to an X-shape in the feed gas distribution layer  56   a  (see plan view along the stacking direction  48   a  in  FIG.  4   ). The feed gas line  58   a  is connected to the mixing chamber  28   a  at the feed gas connector recess  60   a , in particular by a straight gas line  62   a  which extends in the stacking direction  48   a . The feed gas line  58   a  is connected at ends which are spaced apart from the feed gas connector recess  60   a  to a respective test station  32   a ,  36   a ,  38   a ,  38 ′ a , in particular by a straight gas line  64   a  which extends in the stacking direction  48   a . The feed gas line  58   a  is configured in the feed gas distribution layer  56   a  without limitation in a stacking direction  48   a . The feed gas line  58   a  is configured in the feed gas distribution layer  56   a  with a limitation of at least 95% in a stacking direction  48   a.    
     The gas control unit  12   a  comprises a further stack layer  22   a , in particular the exhaust gas collector layer  66   a . The exhaust gas collector layer  66   a  is disposed between the mixing layer  30   a  and the test layer  34   a . The exhaust gas collector layer  66   a  delimits an exhaust gas section line  68   a . The exhaust gas section line  68   a  connects the test stations  32   a ,  36   a ,  38   a ,  38   a ′ equidistantly at least in relation to a gas path to the exhaust gas line  52   a.    
     The exhaust gas collector layer  66   a  is disposed between the mixing layer  30   a  and the test layer  34   a . The exhaust gas collector layer  66   a  is disposed directly adjacent to the test layer  34   a . The exhaust gas collector layer  66   a  is disposed spaced apart from the mixing layer  30   a  by at least one stack layer  22   a , in particular the at least one feed gas distribution layer  56   a . The exhaust gas line  52   a  is connected in a gas-conductive manner to the exhaust gas section line  68   a . The exhaust gas section line  68   a  is configured to a shape around a central exhaust gas connector recess  70   a  for uniformly connecting the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  to the exhaust gas line  52   a  with respect to the gas path from the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  to the exhaust gas line  52   a  (see plan view along the stacking direction  48   a  in  FIG.  3   ). The exhaust gas section line  68   a  is connected to the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  at exhaust gas recesses  71   a  which are spaced apart from the exhaust gas connector recess  70   a , in particular by a straight gas line  72   a.    
     The test system  10   a  comprises an air mixture line  74   a  (see  FIG.  1   ). The air mixture line  74   a  is configured for supplying the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  with an air mixture. The air mixture line  74   a  comprises a common rail unit  76   a . The common rail unit  76   a  is configured for uniformly supplying the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  with the air mixture. The air mixture line  74   a  is disposed entirely outside the gas control unit  12   a . The air mixture is configured as a mixture of at least nitrogen and at least oxygen. The common rail unit  76   a  is connected to the individual test stations  32   a ,  36   a ,  38   a ,  38 ′ a  by four gas lines  78   a.    
     The gas control unit  12   a  comprises a base layer  80   a  for connecting a metallic furnace bottom  84   a  to the gas control unit  12   a . The gas control unit  12   a  comprises a cover layer  82   a  for covering and for keeping the test stations  32   a ,  36   a ,  38   a ,  38 ′ a  at a defined temperature during a test operation. 
     The exhaust gas line  52   a  extends through the mixing layer  30   a , through the hydration layer  26   a , through the base layer  80   a , through the feed gas distribution layer  56   a , partly through the exhaust gas collector layer  66   a , always in the stacking direction  48   a.    
       FIG.  2    in particular shows the gas control unit  12   a  in a partially transparent illustration with only one of the test stations  32   a ,  36   a ,  38 ′ a ,  38 ′ a  for the sake of clarity.  FIG.  3    in particular shows the exhaust gas collector layer  66   a  in a view along the stacking direction  48   a .  FIG.  4    in particular shows the feed gas distribution layer  56   a  in a view along the stacking direction  48   a . The feed gas distribution layer  56   a  and the exhaust gas collector layer  66   a  are in particular connected to the next stack layer  22   a  at an open side of the exhaust gas section line  68   a  and the feed gas line  58   a  by 5 mm thick gold strips  88   a  to form a gas-tight sealing region  86   a  defined within by the gold strips  88   a .  FIGS.  3  and  4    are schematic and not uniformly dimensioned and serve only to provide better understanding.  FIG.  5    in particular shows the test layer  34   a  in a view along the stacking direction  48   a  with all four test stations  32   a ,  36   a ,  38   a ,  38 ′ a  in an example of an arrangement.  FIG.  6    in particular shows the common rail unit  76   a  in a view along the stacking direction  48   a . The common rail unit  76   a  delimits an outer gas flow ring  90   a  for creating the uniform air mixture. 
       FIG.  7    shows a further design example of the invention. The following descriptions and the drawings are limited substantially to the differences between the design examples, wherein, with respect to identically named components, in particular with respect to components having identical reference signs, reference can in principle also be made to the drawings and/or the description of the other design examples, in particular of  FIGS.  1  to  6   . To distinguish between the design examples, the letter a has been placed after the reference signs of the design example in  FIGS.  1  to  6   . In the design example of  FIG.  7   , the letter a has been replaced by the letter b. 
       FIG.  7    shows an alternative test system  10   b . The test system  10   b  comprises a gas control unit  12   b . The gas control unit  12   b  comprises a stack layer  22   b , in particular a gas distribution layer  92   b . The gas distribution layer  92   b  is configured as a one-piece variant of the exhaust gas collector layer  66   a  with the feed gas distribution layer  56   a  of the previous design example. 
     The gas distribution layer  92   b  is disposed between a mixing layer  30   b  and a test layer  34   b . The gas distribution layer  92   b  delimits a feed gas line  58   b . The feed gas line  58   b  connects four test stations  32   b ,  36   b ,  38   b ,  38   b ′ equidistantly at least in relation to a gas path to a mixing chamber  28   b . The gas distribution layer  92   b  delimits an exhaust gas section line  68   b.    
     The exhaust gas section line  68   b  connects the four test stations  32   b ,  36   b ,  38   b ,  38   b ′ to the exhaust gas line  52   b  equidistantly with respect to an effective gas path, in particular a combination of the length of the gas path and the geometry of the gas path, from the test stations  32   b ,  36   b ,  38   b ,  38   b ′ to the exhaust gas line  52   b.    
     The feed gas line  58   b  is delimited by the gas distribution layer  92   b  at the same level as the exhaust gas section line  68   b , in particular with respect to the stacking direction  48   b . The feed gas line  58   b  and the exhaust gas line  52   b  are disposed spaced apart from one another by at least 5 mm of material of the gas distribution layer  92   b.    
     The exhaust gas section line  68   b  is configured to a symmetrical shape about a central exhaust gas connector recess  70   b  for uniformly connecting the test stations  32   b ,  36   b ,  38   b ,  38   b ′ to an exhaust gas line  52   b  with respect to an effective gas path, in particular a combination of the length of the gas path and the geometry of the gas path, from the test stations  32   b ,  36   b ,  38   b ,  38   b ′ to the exhaust gas line  52   b .  FIG.  7    in particular shows the gas distribution layer  92   b  in a plan view along the stacking direction  48   b.