JP2004002184A - Method for preventing flashback of gaseous mixture flowing into reaction chamber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing flashback of a gaseous mixture flowing into a reaction chamber. <P>SOLUTION: The method for preventing flashback of a gaseous mixture flowing into a reaction chamber features that the cross-sectional area of the through flow is varied in the region between the entrance opening and the reaction space according to the volume of the flowing gaseous mixture in such a manner that the velocity v of the gaseous mixture is controlled to be higher than the burning rate vbr of the gaseous mixture in at least most of the volume generated (load L). The present invention also relates to a reactor equipped with the entrance opening for the gaseous mixture, a distribution zone for the gaseous mixture equipped with a device which varies the cross-sectional area of the through flow, and the reaction chamber so as to carry out the above method. The present invention can be applied for e.g. a self-heating reactor which supplies a hydrogen-containing gas to a fuel cell APU. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for preventing flashback of an air-fuel mixture flowing into a reaction chamber where the cross-sectional area that flows through changes in the region between the inlet opening and the reaction chamber. Furthermore, the invention relates to a reactor for carrying out the above-described method and to its use with the reactor.
[0002]
[Prior art]
From the general prior art, reactors comprising an extract mixture which is converted in a reaction chamber are known. In the case of what are generally referred to as autothermal reactors with a catalyst in the reaction chamber, the conversion of the extract is carried out so that exothermic and endothermic reactions occur in the reaction chamber. After starting and / or if the extract is properly adjusted, no further supply of heat energy is required. Autothermal reforming of an extract mixture consisting of air, steam and hydrocarbon-containing compounds, such as gasoline, is an example of such a reaction.
[0003]
[Patent Document 1]
German Patent Invention No. 195 26 886 C1 Specification
[0004]
[Patent Document 2]
German Patent Application Publication No. 100 02 025 A1
[0005]
[Problems to be solved by the invention]
Extracts that flow into the reactor through the inlet opening are usually allowed to mix the extracts thoroughly with each other and, if appropriate, evaporate them simultaneously before passing through the actual reaction chamber. Correspondingly, a zone is first passed through which they are converted there. In such a reactor, a combustible mixture is already present in this mixture distribution zone. If there is a flashback from the reaction chamber into the mixture distribution zone, i.e. if spontaneous ignition occurs in this region, the mixture located there is at least partially converted. As a result, the thermal energy is an area that does not require that thermal energy and, under certain conditions, has an adverse effect in the form of thermal overload on the mixture distribution zone itself and on its immediate periphery. Released. However, a generally more critical drawback is that the heat energy released in the gas mixture distribution zone is lost in the region of the reaction chamber. The conversion of the air-fuel mixture in the reaction chamber and / or the composition and temperature of the air-fuel mixture flowing out of the reaction chamber are thus weakened and do not occur at all in the worst case.
[0006]
Patent Document 1 does so on condition that a hydrogen-containing formate with minimal carbon monoxide content should be obtained as long as it is in all operating and loading conditions that occur in the reforming of methanol. Is proposed, whereby the total length and / or effective inlet cross-section of the input end reaction chamber section temperature controlled to a high methanol conversion rate is temperature controlled to a high methanol conversion rate. It can be set according to the throughput of the mixture to be formed so that the gas mixture reformed in the reaction chamber section occurs with a substantially constant residence time. As a result, the reforming of methanol can also be carried out so that a highly variable throughput gas mixture is always reformed at a high methanol conversion rate and also with an undesirably low carbon monoxide formation.
[0007]
In view of the objective of improving the dynamic response behavior of the reaction in the reaction chamber with the catalyst, US Pat. The method of receiving is also disclosed. A piston located in the reactor or in the duct to the reactor is pressed against the spring, here by the medium and by the pressure in the medium, opening up some of the effective cross section.
[0008]
According to the description of the above-mentioned patent document 2 by the above-mentioned two methods or corresponding devices, the conversion of methanol, i.e. the medium, which is generally reformed oil (gasoline), is a cost of control, regulation and input to the actuator system. Affected by some.
[0009]
In particular, the problems described at the beginning of the flashback that plays the role of an autothermal process are not recognized in the two above-mentioned documents.
[0010]
The object of the present invention is to provide a method for avoiding flashback of the air-fuel mixture flowing into the reaction chamber, and in particular to provide a reactor used to carry out the method.
[0011]
[Means for Solving the Problems]
According to the present invention, the object is to reduce the cross-sectional area through which the flow rate of the air-fuel mixture becomes larger than the combustion speed of the air-fuel mixture in at least the majority of the generated volume of the air-fuel mixture. This is achieved by varying the region in the region between the inlet opening and the reaction chamber.
[0012]
Since the flashback occurs only when the combustion velocity vbr of the air-fuel mixture is larger than the flow velocity v that flows into the element that has already reacted or burned, the flow velocity in the mixture distribution zone is sufficiently high. You can avoid flashback.
[0013]
Adaptation to the required load conditions is usually carried out in such a reactor which is carried out by changing the volume flow of the incoming mixture. It can be seen that if the cross-sectional area to be flowed through is configured such that the maximum flow velocity vmax occurs at full load, the combustion velocity vbr will typically be on the order of 30% to 50% of the maximum velocity, This is because wastefully high pressure losses will occur at higher load ranges, which is important for operation as a result of “excessively” small cross-sectional areas. However, this only uses 50% to 70% of the expected load spread, and the remaining 30% to 50% is used for the reactor because there is a risk of flashback, which is the drawback described at the beginning. It also means that.
[0014]
Using the method according to the invention, a flow velocity v higher than the combustion velocity vbr in each case is obtained by changing the cross-sectional area through which the region upstream of the reaction chamber having a predefined flow rate according to the law of continuity. Setting is particularly advantageous. In this way, it is possible to use most of the load spread than before. It is also possible to ensure that flashback does not occur over the entire range of the load spread of the reactor used in this way. The release of thermal energy can occur exactly where it is desired, particularly within the reaction chamber itself. Thus, the reaction chamber can be used under ideal operating conditions so that the desired composition and desired temperature level can be achieved reproducibly at the output of the reaction chamber.
[0015]
In addition to these problems described at the outset regarding the release of thermal energy in the undesired areas as a result of flashback, the formation of unwanted by-products also occurs due to flashback during the conversion of the extract. In the case of these by-products, ie, extracts containing carbon, soot will accumulate and adversely affect the manner of operation of the reactor. They accumulate in, for example, catalysts, sensors, mechanically moved moving parts, etc. and impair their function. However, by preventing flashback, this formation of by-products and the associated adverse consequences can also be avoided.
[0016]
According to one very advantageous development according to the invention, in the case of a cold start of a reactor having at least a reaction chamber, the cross-sectional area that flows through increases from the center of the flow as the volume of the incoming mixture increases. .
[0017]
Since the cross section opens from the center of the flow, the central flow flowing into the reaction chamber is achieved even if it is a small volume flow. The heat generated in the center of the reaction chamber is distributed to the surrounding region of the reaction chamber, particularly when the reaction chamber is configured with, for example, a catalyst disposed on the carrier material and the heat in the carrier material dissipates heat by heat conduction. The This refinement of the invention makes it possible, on the one hand, to operate continuously in the case of a sudden increase in load, and on the other hand to improve the cold start behavior, in particular to make a quick transition in the “normal” operating phase. The reduction in the time required for cold start is that the heat dissipated to the outside by heat conduction heats the surrounding area of the reaction chamber, so that at least all of the load range is less or less than full load, with no or at least little heat. It is achieved in that it is not lost.
[0018]
If the reactor is instead in a steady state operating phase without high dynamic demands and / or in an operating phase where heat loss is tolerated without significantly adversely affecting the quality of the product produced, According to one highly preferred refinement, it is also possible to vary the cross-sectional area through which, in the long run, all of the reactor region is in contact with the incoming mixture at least approximately the same time. It is.
[0019]
The loading of the reactor is therefore compensated over a long time average, especially if the reactor has a catalyst, for example, so that the aging process is evenly distributed throughout the reactor. Therefore, the useful life of the reactor can be extended.
[0020]
A reactor for carrying out the process according to the invention comprises, in order in the direction of flow, an extract inlet opening, a mixture distribution zone, and a reaction zone, the device for varying the cross-sectional area being flowed through, Deployed within the gas distribution zone.
[0021]
The process according to the invention can be ideally carried out in such a reactor embodiment. Here, how the devices that change the cross-sectional area are implemented as long as they can reliably achieve the essential functions under prevailing conditions in the mixture distribution zone, e.g. high temperatures, aggressive extracts, etc. It becomes practically important. These devices are implemented as continuously active devices, for example, in a manner such as iris diaphragm, as is known in optics.
[0022]
As an alternative, the device for changing the cross-sectional area in the mixture distribution zone, according to one highly preferred element of the reactor, divides the mixture distribution zone into a plurality of segments, at least a few of them. The inflow opening is at least partly closed.
[0023]
This design, which can be implemented very robustly, makes it possible to operate a device with a high degree of fault tolerance even under unfavorable conditions, for example with regard to temperature and medium aggression. In addition, the selective influence of the flow achieved in the gas distribution zone by corresponding built-in elements, diffusers etc. is, in the first place, fully maintained or achieved even at relatively low volume flows. Is done. If necessary, the effects described above can be adapted to each predefined volume flow by improving the segment shape for the volume flow. The inflow is therefore appropriately optimized not only with respect to the flow rate but also with respect to the formation of the flow. In particular, it is possible here to avoid dead zones where there is no sufficiently high flow velocity in the flow. As a result, on the one hand, undesired conversion of the extract and, on the other hand, the deposition of by-products formed can be avoided particularly conveniently in these dead zones.
[0024]
One particularly advantageous use of the process according to the invention and of the reactor described above is to generate at least oxygen, water, in particular to generate a hydrogen-containing gas for operating a fuel cell, in particular an auxiliary power unit fuel cell. Autothermal reforming of steam and extracted mixtures containing hydrocarbon-containing compounds, preferably gasoline or diesel.
[0025]
When used in this manner in a gas generation system for a fuel cell, the above advantages are particularly advantageous with respect to the maximum possible load spread and a robust and reliable operating design. When the fuel cell is used in a mobile system, such as an automobile, the advantages already described are particularly advantageous with respect to the basic requirements arising from the automobile components with respect to robustness, complexity, weight and dynamic way of operation.
[0026]
In the case of a cold start of a reactor having at least a reaction chamber, the cross-sectional area that flows through increases from the center of the flow as the volume of the incoming mixture increases. Because it occurs very often, the improvement in cold start behavior leads to a definitive improvement in the overall system, so such a system can be used very conveniently in this particular case application.
[0027]
Other advantageous refinements of the invention emerge from the other dependent claims and from the exemplary embodiments exemplified below with reference to the drawings.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a reactor 1 which is now adapted to operate as an autothermal reformer, and is only for illustrating the present invention with this example, and the specific application of the autothermal reformer. The case is not limited.
[0029]
According to its embodiment as an autothermal reformer for generating a hydrogen-containing gas, the reactor 1 contains on the carrier structure 3 a catalytic reaction active material, hereinafter referred to as catalyst carrier 3. The reaction chamber 2 is provided. Extract A entering the reactor 1, such as air, hydrogen and gasoline or diesel, passes through the inlet opening 4 to the mixture distribution zone 5 where the extract A is thoroughly mixed, if necessary, Still, components that are likely to remain liquid are vaporized and, if appropriate, overheated. Furthermore, the extracts A are distributed by the gas mixture distribution zone 5, for example by one or more diffusers, so that they flow into the reaction chamber as uniformly and homogeneously as possible.
[0030]
The reaction chamber 2 with the catalyst carrier 3 comprises an exothermic reaction zone 6 in which the extract coming from the mixture distribution zone 5 first flows through it, and its exothermic reaction zone 6 along the flow direction. Can be divided into two different zones with one endothermic reaction zone 7 following. Furthermore, the gas mixture distribution zone 5 has in principle the device shown here in dotted lines, which will be described in detail later.
[0031]
Referring to FIG. 1, a number of temperature distributions T are additionally plotted against the total length x of the reactor 1. The constant temperature distribution Tmin (T minimum in the figure) indicates the temperature that the reformed oil obtained from the extract A must at least hold when leaving the reaction chamber 2. This temperature Tmin is determined by the following components, such as a gas purification device, a shift stage, and the like. Ideally, the temperature distribution T1 reaches this temperature Tmin at the outlet of the reaction chamber 2 at the best possible level of efficiency and hence at the lowest possible inlet temperature Ti. In the case of a temperature distribution T1 that results in an inlet temperature Ti, the extract A releases the thermal energy Q1 contained therein during the reaction in the exothermic reaction zone 6. Next, the volume flow for cooling the region of the endothermic reaction zone 7 reaches a temperature T1a that is higher than or equal to the temperature Tmin at the output of the endothermic reaction zone 7, that is, the reaction chamber 2.
[0032]
However, since the combustible mixture of the extract A already exists in the mixture distribution zone 5, as already explained at the beginning, the flashback initiated by the high-temperature catalyst carrier 3 is conducted from the reaction chamber 2 to the heat chamber 2. In combination with the release of energy, it can take place in the region of the gas mixture distribution zone 5 resulting in at least partial conversion of the extract A. The temperature distribution T2 therefore typically occurs.
[0033]
The temperature distribution T2 starts at the same inlet temperature Ti. However, the release of the amount of heat energy Q2 contained in the extract A and corresponding in absolute value to Q1 has therefore already occurred in the region of the mixture distribution zone 5. However, as a result of this early release of energy Q2, the energy Q2 is not present in the region of the reaction chamber 2. The outlet temperature T2a resulting from the volume flow coming out of the reaction chamber 2 is therefore lower than the essential temperature Tmin. In addition to this, there is generally also a reduction in the conversion of the extract A used, so that there is a further increase in costs for producing reformate in the next component.
[0034]
Nevertheless, in order for a sufficiently high outlet temperature to still be achieved, the temperature distribution T2 is shifted upwards towards higher temperatures. However, the resulting temperature distribution T3 requires a higher inlet temperature Ti ′, thus reducing the efficiency of the reactor 1.
[0035]
FIG. 2 is a chart illustrating the dependency between the flow velocity v in the inflow region of the reaction chamber 2 and the load L representing the essential conversion of the reacting material or the volume of extract A. Both the flow rate v and the load L are normalized to the values that occur at the maximum flow rate vmax and the full load Lmax, respectively, and are displayed as a percentage.
[0036]
As a result of flashback or, under certain circumstances, as a result of spontaneous ignition of the extract A, the undesired energy release described above is that the flow rate v of the extract A is greater than the combustion rate vbr as described at the outset. Also happens only when it is small. In the chart of FIG. 2, the combustion rate vbr is therefore set to 40% of the maximum flow rate vmax. The relationship between the flow velocity v and the load L is given by the dotted curve 9. From the point of intersection 10 with the constant value vbr, the operating mode of the reactor 1 optimized for efficiency and reliable can be read as possible only with a load spread between 40% and 100% of the full load Lmax.
[0037]
In order to reduce the flashback problem and to allow the use of the greater part of the load spread with optimized efficiency, i.e. having a temperature profile similar to T1, the device 8 is able to mix the reactor 1 Provided in the air distribution zone 5. Since these devices 8 are used to change the cross-sectional area through which the region of the mixture distribution zone 5 flows according to the volume flow of the inflowing extract A, the variable flow velocity v can be set according to a continuous law. . As a result, the flow velocity v in that region before the entrance to the reaction chamber 2, here in particular the region between the inlet opening 4 and the reaction chamber 2, is greater than the combustion velocity vbr over the maximum possible region where the flow velocity v is spread of the load. Or is set according to the volumetric flow of extract A, which ideally results from a predefined value for adjusting extract A. Here, all or some of the predefined values showing the conversion characteristics as much as possible are used for metering, for example fuel metering. The adaptation of the flow rate v here is usually provided with an enlargement of the channel cross-sectional area to distribute the extract A over the entire cross section of the reaction chamber 2 at least at full load, so that the mixture distribution zone 5 in this very area is very important. The problems with flashback are therefore essentially concentrated in this region upstream of the reaction chamber 2.
[0038]
FIG. 3 is a cross-sectional view of half of the rotationally symmetric structure of the reactor 1 and shows a possible improvement of the device 8 in the region of the gas mixture distribution zone 5 of the reactor 1. The device 8 is here constituted by a plurality of annular walls that divide the mixture distribution zone 5 into segments 11. These segments 11 forming the annular duct 111 here are closed by an annular cover element 13 corresponding to the inlet cross-sectional area 12 of said segment 11. The cross-sectional area that flows through in the gas distribution zone 5 is thus released or closed in a number of stages. Of course, at least two such segments 11 are necessary to ensure the desired method of operation. The maximum number is determined not only by the load spread, but also by the structural space and the cross-sectional area where there is a flow through the mixture distribution zone 5.
[0039]
For this application of the exemplary embodiment, five annular ducts 111 and their corresponding four annular cover elements 13 are selected. Assuming that the load L is increased and the individual annular ducts 111 are continuously opened, the resulting curve of the flow velocity v is illustrated by the dashed-dotted curve 14 in FIG. After reaching approximately 8% of the full load Lmax, all of the flow velocity v is above the combustion rate vbr. The area of load spread used under nearly ideal operating conditions is therefore between 8% and 100%. This represents a significant improvement to the design described by curve 9.
[0040]
The design of the device 8 in FIG. 3 shows here that the distribution of the incoming mixture of the extract A can be reached in the mixture distribution zone 5. For this purpose, for the reasons described above, the cross-sectional area that flows through is expanded in the direction of the catalyst carrier 3 by the use of the flow distributor 15 like a diffuser. The structure of the segments 11 is selected such that each of the inlet cross-sectional areas 12 has a specific area of the effective cross-section that is the sum of the inlet cross-sectional areas 12 and thus flows through. Each segment 11 also has an outlet cross-sectional area 16 whose inlet cross-sectional area 12 has the same proportion of outlet cross-sectional areas 16 as the total of inlet cross-sectional areas 12. The cross-sectional area through which the flow through, i.e. the fluid effect produced by the diffuser, is therefore transmitted to each segment 11, so that a comparable flow onto the catalyst carrier 3 is the volume flow of extract A or is it closed? Or it is always achieved regardless of the number of open segments 11.
[0041]
According to the exemplary embodiment proposed herein, the annular cover elements 13 are arranged fixedly on one another on a common carrier 17. In this design, which is very rugged and also has a high fault tolerance even under the expected aggressive conditions in the mixture distribution zone 5, the annular cover elements 13 are moved together and are predefined by the arrangement. In the process, the individual annular ducts 111 are continuously opened during the process or are arranged on the carrier 17 in such a way that the cross-sectional area through which they flow is continuously enlarged in the direction of the individual ducts 111. Instead of the movement of the full covering element 13 which is also theoretically possible, the common carrier 17 has a very robust design, in each case individually and independently of each other. The carrier 17 itself is moved in the direction of the main stream of the extract A. This is more preferred with respect to contamination of the sliding surface compared to lateral movement with respect to the flow. Furthermore, the movable parts that are to be moved relative to each other are not pressed against each other by fluid pressure, which increases the friction and therefore also increases the force required to actuate. The driver of the carrier 17 moves very slightly towards the outside of the reactor 1 if the carrier 17 is configured to have a corresponding length or if there is a suitable transmission element, for example a push-pull rod. Is done. The situation is comparable to guides and seals. The design is therefore carried out independently of the conditions relating to the temperature and aggressiveness of the extract A that reaches the region of the inlet opening 4 and the region of the mixture distribution zone 5, so that not only sealing and induction but also control Adjustments and / or adjustments are also performed with a high degree of reliability and easily and cost-effectively.
[0042]
The opening and closing of the individual segments 11 is performed by the arrangement of an annular cover element 13 in which the segments 11 that are close to each other are continuously opened or closed. This means that in each case a region with a new inflow in the region of the catalyst carrier 3 or a region where the inflow no longer exists is immediately adjacent to each other. They therefore interact with each other and the heat energy can be exchanged very easily, so that the operation of the reactor 1 is more uniform and therefore an improvement with respect to the desired conversion.
[0043]
In particular, in the case of a cold start of the reactor 1, this is very important if there is initially an inflow onto the catalyst carrier 3 in the centrally located region 18 through the continuous opening of the individual segments 11 from the inside to the outside. Conveniently used. As a result of heat conduction occurring in all directions in the catalyst carrier 3, heat is initially transferred from the first used central region 18 to the entire surrounding region. If the inflow to the surrounding area is released through the increased volume flow of extract A by opening the adjacent segment 11, this area is already preheated so that the catalytically active material is moved very quickly. The temperature has been reached, or perhaps it has already been reached. The conversion of extract A starts very quickly and the time required to cold start reactor 1 is reduced. In addition, under all conditions of partial load, heat transfer out of the region of the reaction chamber 2 that always constitutes heat loss to the surroundings is avoided or at least considerably reduced, so that the reactor 1 It also increases because of efficiency.
[0044]
FIG. 4 illustrates an alternative embodiment of the device 8. Again, the mixture distribution zone 5 is divided into individual segments 11. These are implemented as concentric annular ducts 111 around a central duct 112 arranged in the central region. In the region of the inlet opening 4, the segment 11 whose cross-section in FIG. The The requirements described above and the preferred refinements apply here in the same way, except for those of the annular cover element 13. The reference symbols for FIG. 4 and the following figures of the exemplary embodiment are used in the same way as those of FIG. 3 when there are comparable methods of operation of the components and / or cross-sections.
[0045]
Instead of the annular cover element 13, the device 8 according to the modification according to FIG. 4 has a sheath 19 and a needle 20. These, which are cross-sectional views about the line VV of FIG. 4 shown in the cross-sectional view above, are shown in FIG. The functional principle described above for the device remains unchanged here. However, as a result of the construction with the sheath 19 and the needle 20, each individual segment 11 or its inlet cross-sectional area 12 is optional, open or closed. Needle 20 and sheath 19 are moved in the direction of flow of extract A for this purpose. The drive is also very easily moved here towards the outside of the reactor 1 if the needle 20 and / or the sheath 19 are considered to be corresponding lengths. The situation is comparable to guides and seals. The design is therefore also carried out here independently of the conditions relating to the temperature and aggressiveness of the extract A that reaches the region of the inlet opening 4 and the region of the mixture distribution zone 5.
[0046]
In order to ensure the exchange of the extract A over the entire range of the inlet opening 4 and thus provide the possibility to open and close the segments 11 in the desired order, the needle 20 and the furthest from the needle At least the sheath 19 arranged between the sheaths arranged remotely should have an opening 21. It can be implemented as drilled holes, windows, etc., and under certain circumstances these openings 21 which also constitute the maximum possible area of the sheath 19 allow the extract A over the entire cross-sectional area of the inlet opening 4. It is possible to ensure replacement. If the needle 20 is guided backwards from the structure, it is appropriate, as illustrated, under certain circumstances, ie it is necessary here, and the outermost part of the sheath 19 also has an opening 21. In this case, for example, it can be used in a volume flow to the inlet opening 4 that is perpendicular to the needle 20.
[0047]
The manner of operation during the opening and / or closing of the individual segments 11 therefore does not require consideration of the mechanical specifications because of the design of the device 8, and in particular the requirements of the reactor 1, here in particular of the reaction chamber 2, ie the catalyst. It is freely adapted to these of the carrier 3. The use of the operating method described at the beginning for the optimization of cold start behavior, the optimization of the aging process, etc. is therefore possible very easily and flexibly.
[0048]
Furthermore, the design as described in FIGS. 4 and 5 makes it possible to avoid or at least reduce dead zones of the extract flow in the region of the mixture distribution zone 5. The formation of by-products, such as soot, during the autothermal reforming of gasoline or in particular diesel as described at the beginning is therefore ideally prevented. Thus, the surface of the catalytically active material is prevented from being coated with mechanism contamination, in particular soot. Therefore, not only the useful life of the reactor 1 and the quality of the reformed oil but also the operational reliability of the reactor 1 can be improved.
[0049]
FIG. 6 illustrates another alternative embodiment of the device 8. Again, the mixture distribution zone 5 is divided into individual segments 11. These segments 11 are formed by dividing walls which divide the mixture distribution zone 5, which here has a circular cross-sectional shape, into three line regions 113 in the shape of a quadrant. A segment 11 in the region of the inlet opening 4 whose cross section is illustrated once again in FIG. 6 at the junction between the inlet opening 4 and the mixture distribution zone 5 is also implemented here as a region opening in the direction of flow. The Each line region 113 in the region between the inlet opening 4 and the mixture distribution zone 5 has an inlet opening 22. The inlet cross-sectional areas 12 described above and these inlet openings 22 whose functions substantially correspond to each other are closed in order, so that the individual line regions 113 are opened and closed individually and independently of each other.
[0050]
Theoretically, any desired method for opening or closing is possible, but adopting the solution schematically illustrated in FIG. 7 where the inflow openings 22 are each closed and / or opened by needles 23. Is particularly desirable. Not only the operation of the needle 23 but also the operation method and the support device / guide are the same as those described above for the needle 20 and the sheath 19.
[0051]
All of the apparatus embodiments also cover the preferred possibilities in the reactor 1 described above and in particular generally discussed within the scope of FIG. Furthermore, all suitable combinations of individual features from the various exemplary embodiments are conceivable for forming other devices 8. These also implement the preferred method of operating and operating the reactor 1 as well, and are within the scope of the present invention.
[Brief description of the drawings]
1 shows a reactor operated as an autothermal reformer as well as an expected temperature distribution T over the entire length x of the reactor.
FIG. 2 is a diagram of a flow velocity v in a region flowing into a reaction chamber according to a load L.
FIG. 3 is a diagram showing an expected improvement of a reactor equipped with a device for changing a cross-sectional area to be flown through.
FIG. 4 is a diagram of an alternative modification of a reactor equipped with a device for changing the cross-sectional area through which it flows.
FIG. 5 is a cross-sectional view taken along line VV of the embodiment of FIG.
FIG. 6 is a diagram of another alternative modification of a reactor equipped with a device for changing the cross-sectional area through which it flows.
7 is a cross-sectional view taken along line VII-VII in the embodiment of FIG.
[Explanation of symbols]
1 reactor
2 reaction chamber
3 Carrier structure
4 Entrance opening
5 Mixture distribution zone
6 Exothermic reaction zone
7 Endothermic reaction zone
8 Equipment
9 Dotted curve
10 intersection
11 segments
12 Inlet opening / inlet cross-sectional area
13 Ring cover element
14 Dashed curve
15 Flow distributor
16 Exit cross-sectional area
17 Carrier
18 areas
19 sheath
20 needle
21 opening
22 Inlet opening / inlet cross-sectional area
23 Needle
111 annular duct
112 circular center duct
113 line area

Claims (20)

A method for preventing flashback of an air-fuel mixture flowing into a reaction chamber in which a cross-sectional area that flows through changes in a region between an inlet opening and the reaction chamber,
The cross-sectional area through which the flow velocity (v) of the air-fuel mixture (A) is higher than the combustion rate (vbr) of the air-fuel mixture (extract A) in at least most of the generated volume of the inflow air-fuel mixture (extract A). The method is characterized in that it is varied according to the volume of the inflowing mixture (extract A). Method according to claim 1, characterized in that the cross-sectional area to be flowed through is formed by a closed or open area (segment 11) through which the cross-section flows. 3. A method according to claim 2, characterized in that when the cross-sectional area to be flown through increases, the regions (segments 11) arranged respectively close to the flow-through region (segments 11) open. 4. The region (segment 11) arranged in each case closes to a non-flow-through region (segment 11) when the cross-sectional area through which it flows is reduced, according to claim 2 or 3, Method. The cross-sectional area to be flowed through is controlled in accordance with a predetermined value for measuring at least a part of the components of the air-fuel mixture (extract A). The method described in 1. In the case of a cold start of the reactor (1) with at least the reaction chamber (2), the cross-sectional area that flows through increases from the center of the flow (region 18) as the volume of the incoming mixture (extract A) increases. A method according to any one of the preceding claims, characterized in that it is characterized. The closure or opening of the flow-through region (segment 11) is such that, over the longer term, the entire region of the reactor (1) is in contact with the incoming mixture (extract A) at least approximately the same time. The method according to claim 2, wherein the method is performed. 8. The mixture according to claim 1, comprising an inlet opening (4) for the mixture (extract A), a mixture distribution zone (5), and a reaction chamber (2) in the order of the flow direction. A reactor for carrying out the method of claim 1, wherein the device (8) for changing the cross-sectional area to be flowed through is arranged in the mixture distribution zone (5). The device (8) divides the mixture distribution zone (5) into a plurality of segments (11), and at least some inflow openings (12, 22) of the segments (11) are at least partially closed. Reactor according to claim 8, characterized in that it can. Reactor according to claim 9, characterized in that the segment (11) is implemented as an annular duct (111). Reactor according to claim 9, characterized in that at least part of the annular duct (111) is at least partially closed by an annular cover element (13). Reactor according to claim 11, characterized in that the annular cover element (13) is closed in the main direction of flow in the mixture distribution zone (5). Reactor according to claim 11 or 12, characterized in that the annular cover elements (13) are arranged fixedly to each other and closed together. Reactor according to claim 9, characterized in that at least part of the annular duct (111) is at least partly closed by a sheath (19). 15. Reaction according to any one of claims 9 to 14, characterized in that the annular duct (111) is arranged around a circular central duct (112) which is at least partly closed by the needle (20). vessel. Reactor according to claim 9, characterized in that at least part of the inlet opening (22) of the segment (11) is closed by a needle (23). Reactor according to any one of claims 9 to 16, characterized in that at least a part of the segments (11) have their cross-sectional area expanding in the direction of flow. Each inlet cross-sectional area (12, 22) of the segment (11) has a specific area that is the sum of the inlet cross-sectional areas (12, 22) of all segments (11), and each segment (11) 18.) The outlet cross-sectional area (16) having a total proportion of the outlet cross-sectional area (16) of)), the proportion of the segments (11) being at least approximately the same. The reactor according to any one of the above. Reactor according to any one of claims 8 to 18, characterized in that the reaction chamber (2) has a catalytically active material arranged on a carrier structure. A mixture (extract) comprising at least oxygen, water, in particular steam, and a hydrocarbon-containing compound, preferably diesel or gasoline, to generate a hydrogen-containing gas for operating the fuel cell, in particular the fuel cell of the auxiliary power unit Use of the process according to any one of claims 1 to 7, characterized in that it is used with a reactor according to claim 19 for the autothermal reforming of A).

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