DE10057418A1 - Reactor unit used for steam reforming a gas mixture stream containing hydrocarbons in fuel cells has sheet layers with heating fluid channels and gas mixture channels arranged to form a specified angle - Google Patents

Abstract

Reactor unit has sheet layers (2) partially forming a honeycomb structure (3) through which a fluid can flow. The layers having heating fluid channels (4) arranged parallel to the heating fluid direction (5) and gas mixture channels (6) arranged parallel to the gas mixture direction (7). The heating fluid channels and the gas mixture channels form an angle of 45-135, especially 90 deg . Preferred Features: The sheet layers are structured so that the gas mixture channels are arranged with the heating fluid channels between two sheet layers. The sheet layers forming the gas mixture channels have a catalytically active coating. The reactor unit further comprises an electrical heater.

Description

The invention relates to a reactor unit for steam reforming a hydrocarbon-containing gas mixture stream according to the preamble of Claim 1. Such a reactor unit and such a reactor unit Comprehensive reformer system are particularly suitable for the production of one hydrogen-rich gas stream, in particular for the purpose of operating a mobile fuel cell, which is used for example in motor vehicles.

The technology of the fuel cell is based on the reversal of the Water electrolysis. During electrolysis, the gases flow Hydrogen and oxygen provided from water, so turns at Fuel cell this reaction around. So the fuel is for one Fuel cell hydrogen, i. H. Hydrogen can be considered the real fuel be considered for the electrochemical implementation in fuel cells. The problem is less in the use of hydrogen than rather in its production. Especially for use in mobile applications The question arises whether the hydrogen is carried in the vehicle and is used, or whether it is used indirectly in so-called hydrogen carriers such as methanol, gasoline, etc. is saved and only then in Vehicle itself is converted to hydrogen. As for the operation of Fuel cells required hydrogen, there is still no infrastructure and the storage of hydrogen with today's options is still very much is complex, the question of the supply of vehicles with fuel from elementary meaning. For this reason, the  Development of hydrogen-producing auxiliary units in the vehicle (Reformer) pushed hard.

The term reforming describes a series of processes for production hydrogen-rich gases, so-called reformates. The use of Catalysts in the reformer enable acceleration and acceleration better control of processes. The most important processes for Generation of hydrogen briefly explained.

In the partial oxidation, oxygen or air is added as the oxidizing agent to the vaporized hydrocarbon. This creates a highly exothermic oxidation reaction that produces excess heat. Since the heat of reaction is generated inside the reactor, good start and load change times can in principle be achieved. However, the hydrogen content of the resulting cracked gas is low (approx. 50% H ₂ ) and the CO content is high (approx. 3 to 4% CO).

One of the possibilities for reforming hydrocarbons is Steam reforming is the most common process. It works Water vapor due to its oxygen content on the one hand as an oxidizing agent to separate and carry the hydrogen contained in the fuel from the carbon on the other hand, contribute to hydrogen production. Hence arise for pure Steam reforming processes even at low temperatures highest hydrogen yields of all reform processes.

Steam reforming reactions are highly endothermic and therefore require external ones Heat sources. The resulting challenge is, despite the necessary heat transfer processes and the associated Time constants the start and load change times of the reformer as low as to keep possible.  

A compact steam reformer is known, for example, from US Pat. No. 5,733,347 known. The plate-shaped steam reformer has one Reformer area in which a hydrocarbon-containing gas stream with the help is reformed by water vapor. The reform area is also from surrounded by plate-shaped heating elements. The reformer area is further divided into two marginal areas and a central area, which too reforming gas mixture first the edge areas near the heating elements flows through, and then led in countercurrent through the central area becomes. The individual plate-like elements of the steam reformer are smooth and structured sheets that are at least partially catalytic coated and flowable for a gas stream. The flow direction the gas flows in the adjacent plate-shaped segments is always opposite, with some means for redirecting the flow direction are needed. The plate-like segments also have a certain width on, so that heat transfer essentially only between the Part gas flows can be exchanged, which near the wall of the Stream segments. This can lead to an inhomogeneous temperature distribution and thus also lead to different levels of reform.

Proceeding from this, it is an object of the present invention to Reactor unit for steam reforming a hydrocarbon-containing one To specify gas mixture flow, which is simple and an improved Heat transfer from the heating medium to the gas mixture stream to be reformed allowed. This object is achieved by a reactor unit according to the Features of claim 1. Advantageous further developments are the subject of dependent claims.

The reactor unit for steam reforming a hydrocarbon-containing gas mixture stream has sheet metal layers, which at least partially form a honeycomb structure through which a fluid can flow. The Sheet metal layers have heating fluid channels parallel to a heating fluid flow direction  and gas mixture channels parallel to a gas mixture flow direction. The Reactor unit according to the invention is characterized in that the Heating fluid channels and the gas mixture channels enclose an angle that is preferably between 45 ° and 135 °, in particular about 90 °.

Steam reforming preferably runs at temperatures from 400 ° to 700 ° C. This has the consequence that that flowing into the reactor unit Gas mixture is heated to this temperature as quickly as possible then also an effective hydrogen yield in the reactor unit to be able to achieve. Since the gas mixture is in operation with a specifiable Flow rate flowing through the reactor unit has a slower rate Heating of the gas mixture stream with a view to a predefinable one Hydrogen yield an axially longer formation of the gas mixture channels Episode. The reactor unit according to the invention ensures that the Heating fluids at an angle of 45 ° to 135 ° across Gas mixture flow direction, with already in the inlet area of the Gas mixture flow into the reactor unit has a very large temperature difference of the heating fluid in relation to the gas mixture flow is pronounced. While at a heat exchange in the counterflow principle the highest temperatures of the Gas mixture flow on the outlet side is determined at the embodiment according to the invention a higher temperature just in Entry area reached. The axial length of the gas mixture channels can thereby can be reduced, which also makes the reactor unit particularly compact can be. In addition, a crossed arrangement of heating fluid channels facilitates and gas mixture channels the supply of the heating fluid and the Gas mixture, since the corresponding connections are clearly different can be arranged at a distance.

It is particularly advantageous that the sheet metal layers are layered, wherein especially the sheet metal layers with the gas mixture channels between two Sheet metal layers with heating fluid channels are arranged. This means that the  Sheet layers with the heating fluid channels between two sheet layers Heating fluid channels is arranged, these essentially as far from each other are spaced like the structural height of the honeycomb structure of the sheet metal layer with the Gas mixture channels. This ensures that everyone Gas mixture channel arranged adjacent to a sheet metal layer with heating fluid channels is. The structure height of the honeycomb structure is preferably less than 5 mm. A such a reactor unit ensures a particularly good one Heat exchange between the heating fluid and the gas mixture flow.

According to a further embodiment, the reactor unit has sheet metal layers alternately smooth and corrugated sheets. One with smooth and wavy Reactor unit designed in sheet metal is particularly easy to manufacture, very much temperature resistant and allows a very flexible shaping of the Reactor unit.

According to a further embodiment, at least the sheet metal layers which have the Form gas mixture channels, a catalytically active coating. Preferably all sheet metal layers have a catalytically active coating. For one effective hydrogen generation by means of steam reforming lower temperatures (approx. 400 ° C) are particularly catalytically active Coatings used, the copper oxides, zinc oxides, or nickel oxides Include precious metals.

According to yet another embodiment, at least the sheet metal layers have which form the gas mixture channels, surveys for swirling the Gas mixture flow, which is at least partially in the gas mixture channels hineinerstrecken. The elevations form a inside the gas mixture channels Kind of flow edge, whereby the gas mixture flowing past is swirled. In this way, for example, the heat exchange within the Gas mixture flow improved and thus faster for steam reforming required temperature reached.  

According to yet another embodiment, the sheet metal layers are with sheets executed, wherein the sheets have openings for the gas mixture flow are at least partially flowable. The communicating so formed Gas mixture channels or heating fluid channels ensure one Mixing of the gas stream or fluid. While at one such configuration of the heating fluid channels a more effective use of the Provided thermal energy is in the foreground, has such Design of the sheets with openings in the gas mixture channels also one positive impact in terms of concentration differences from yet to reforming hydrocarbons in the gas mixture stream. This will make one higher hydrogen yield ensured.

It is particularly advantageous that the sheets have a thickness of less than 0.08 mm have, preferably less than 0.04 mm, in particular less than 0.02 mm. On in this way, the sheet metal layers of the reactor unit are very small surface-specific heat capacity, which means that it can also be used immediately after a cold start Such a reactor unit has a very good heat transfer from the heating fluid the gas mixture flow is guaranteed.

According to a further embodiment, the reactor unit has additional ones Heating means, especially an electric heater. Especially in connection with Mobile reformer plants, it is important that the steam reforming very elemental hydrogen produced quickly after the start. Since the Water vapor reactions, however, are endothermic, the beginning of Hydrogen production is therefore temperature-dependent, the heat required are available immediately after the start of the reformer system. It is it is particularly advantageous to use additional heating means such as a to provide electrical heating. The necessary voltage source (e.g. Battery) can also be carried in mobile reformer systems, for example become. This ensures that the reformer unit is already heated,  before the heating fluid has a corresponding temperature and then preferably only compliance with the required temperature of the Gas mixture flow causes.

According to yet another embodiment, the reactor unit has one Unit cross-sectional area, at least the number of Gas mixture channels per unit cross-sectional area in gas mixture flow direction increases. It is particularly advantageous that the reactor unit in Gas mixture flow direction has several zones, at least the Channel density of the zone last arranged in the gas mixture flow direction is greater than 1000 cpsi ("cells per square inch"), preferably 1400 cpsi. A higher number of gas mixture channels in the gas mixture flow direction advantageous because, in particular, in the area of the reactor unit in which the Steam reforming suitable temperatures are present, due to the increased Number of channels (or channel walls) a significantly increased surface is provided, for example, to an improved catalytic Implementation of the hydrocarbons leads.

According to yet another embodiment, the reactor unit in Gas mixture flow direction several zones, the one in gas mixture Flow direction of the first arranged zone has a smaller surface area has specific heat capacity than in the downstream zone or the zones located downstream. This means that the inflowing gas mixture flow and / or heating fluid flow due to the low surface specific heat capacity in the first zone only a very low one Amount of heat is withdrawn. This also leads to faster Heating of the gas mixture stream.

According to a further aspect of the invention, a reformer system for Reforming a hydrocarbon gas mixture for a Fuel cell, in particular in a motor vehicle, proposed the one  Device for the partial oxidation of a hydrocarbon Gas mixture flow and an exhaust gas cleaning system includes. The Reformer system is characterized in that it is an inventive Has reactor unit. It is particularly advantageous that the reactor unit the device for the partial oxidation of the hydrocarbon-containing Gas mixture flow is connected directly downstream in the gas mixture flow direction. This has the advantage that the gas mixture flow already through the partial Oxidation is heated and thus the gas mixture stream as it enters the reformer unit is almost a suitable one for steam reforming Temperature. In this way, a reformer system is created that also the high requirements regarding cold start and load change behavior for operating a fuel cell in a motor vehicle.

Further advantages and particularly preferred configurations of the reactor unit according to the invention are described below with reference to the drawings explained in more detail, the invention not being shown Embodiments is limited. Show it:

Fig. 1 schematically and in perspective an embodiment of the honeycomb structure of the reactor unit of the invention,

Fig. 2 is a block diagram of a reformer unit with the fuel cell,

Fig. 3 is a detail view of an embodiment of a sheet metal layer,

Fig. 4 is a detail view of another embodiment of a sheet metal layer,

Fig. 5 shows schematically a reactor unit with an electric heater and

Fig. 6 shows schematically a further embodiment of the reactor unit.

Fig. 1 shows a first embodiment of a honeycomb structure through which a fluid 3 shows schematically and in perspective, a reactor unit 1 of the invention. The honeycomb structure 3 of a reactor unit 1 according to the invention is formed with sheet-metal layers 2 , the sheet-metal layers 2 having heating fluid channels 4 parallel to a heating fluid flow direction 5 and gas mixture channels 6 parallel to a gas mixture flow direction 7 . The heating fluid channels 4 and the gas mixture channels 6 enclose an angle 8 which is approximately 90 °. The sheet metal layers 2 comprise smooth sheets 9 and corrugated sheets 10 . The sheets 9 and 10 delimit the channels 6 and 4 , the channels having a length 26 and a structural height 27 . The illustrated embodiment shows sheet metal layers 2 with gas mixture channels 6 , which are each arranged between two sheet metal layers 2 with heating fluid channels 4 . Each individual gas mixture passage 6 is disposed adjacent to a sheet-metal layer 2 with Heizfluidkanälen. 6

FIG. 2 shows a block diagram of a reformer system 19 with a fuel cell 20 connected downstream. A hydrocarbon-containing gas stream (C _m H _n ) and an oxygen-containing gas stream (O ₂ ) are first fed to a device 21 for partial oxidation. When these two gas streams are burned, a hydrogen-rich gas mixture stream is generated which is fed further downstream to a reactor unit 1 according to the invention. For this purpose, a heating fluid is supplied to the reactor unit 1 , which is designed here as heated water. The reactor unit 1 is connected downstream of an exhaust gas purification system 22 . Residual amounts of carbon monoxide in the gas mixture stream are eliminated in the exhaust gas purification system 22 . The particularly pure, hydrogen-rich gas mixture produced in this way is now fed to a fuel cell 20 which generates energy with the aid of the hydrogen made available. Such a reformer system is particularly suitable for installation in motor vehicles, since it is distinguished by a particularly good starting and load change behavior.

FIG. 3 shows a detailed view of a sheet metal layer 2 with gas mixture channels 6 through which a gas mixture can flow in a gas mixture flow direction 7 . The sheet metal layer 2 comprises a corrugated sheet 10 and a smooth sheet 9 . The corrugated sheet 10 is designed with elevations 12 which extend into at least part of the gas mixture channels 6 . The elevations 12 were embossed here in the corrugated sheet 10 , these protruding only on one side of the corrugated sheet 10 . In another embodiment, such as a two-sided embossing, the elevations 12 preferably extend into all gas mixture channels 6 . The elevations 12 run transversely to the gas mixture flow direction 7 in order to effect an effective swirling of the gas mixture flow. The elevations 12 preferably have a height that is less than 30%, in particular less than 10%, of the structure height 27 of the honeycomb structure 3 .

Fig. 4 shows another embodiment of a sheet-metal layer 2 of smooth and corrugated sheets 9 10th The sheets 9 and 10 have a thickness 14 , which is preferably less than 0.08 mm. The sheet metal layer 2 shown forms gas mixture channels 6 through which a gas mixture flows in a gas mixture flow direction 7 . The gas mixture channels 6 have a catalytically active coating 11 . The corrugated sheets 10 have elevations 12 and openings 13 in order to cause the gas mixture stream to flow through. In this embodiment, the elevations 12 extend into all gas mixture channels 6 of the sheet metal layer 2 . The elevations 12 in this embodiment are higher than in the embodiment shown in FIG. 3.

The sheet layers 2 with the Heizfluidkanälen 4 can also be as the sheet metal layers 2 shown in Fig. 3 and Fig. 4 carried out at a further embodiment.

Fig. 5 shows schematically and in perspective, a reactor unit 1 with an electrical heater 15. For reasons of clarity, the channels are not drawn to scale in relation to the size of the reactor unit 1 . As already explained, the reactor unit 1 preferably has a channel density of more than 1000 cpsi. The electrical heater 15 is connected via connections 16 to the sheet metal layers 2 in such a way that a current path 24 is formed in the interior of the reformer unit 1 . The current path 24 can be implemented, for example, with the aid of an insulating 23 coating of the smooth sheets 9 and corrugated sheets 10 through which current flows, or, for example, with a heating wire arranged in the interior of the reformer unit 1 . In order to arrange a current path 24 evenly distributed in the reactor unit, for example baffles 25 can be used, which serve for the current transmission to predetermined locations of the reactor unit 1 , the reactor unit 1 shown is also protected from the outside by insulation 23 , so that a fault current is avoided.

FIG. 6 shows a schematic illustration of a reactor unit 1 which has a unit cross-sectional area 17 and zones 18 arranged one behind the other in the gas mixture flow direction. The zone 18.3 arranged last in the gas mixture flow direction 7 preferably has a number of gas mixture channels 6 per unit cross-sectional area 17 of greater than 1000 cpsi.

LIST OF REFERENCE NUMBERS

1

reactor unit

2

sheet metal layer

3

honeycomb structure

4

heating fluid passage

5

Heizfluidströmungsrichtung

6

Gas mixing passage

7

Gas mixture flow direction

8th

angle

9

smooth sheet metal

10

corrugated sheet

11

coating

12

survey

13

opening

14

thickness

15

electric heating

16

Connection

17

Unit cross-sectional area

18

Zone

19

reforming plant

20

fuel cell

21

contraption

22

emission control system

23

insulation

24

current path

25

baffle

26

length

27

structure height

28

supply

Claims (10)

1. reactor unit ( 1 ) for steam reforming a hydrocarbon-containing gas mixture stream, which has sheet metal layers ( 2 ) which at least partially form a honeycomb structure ( 3 ) through which fluid can flow, the sheet metal layers ( 2 ) heating fluid channels ( 4 ) parallel to a heating fluid flow direction ( 5 ) and gas mixture channels ( 6 ) parallel to a gas mixture flow direction ( 7 ), characterized in that the heating fluid channels ( 4 ) and the gas mixture channels ( 6 ) enclose an angle ( 8 ) which is preferably between 45 ° and 135 °, in particular approximately 90 ° is. 2. Reactor unit ( 1 ) according to claim 1, characterized in that the sheet layers ( 2 ) are layered, in particular the sheet layers ( 2 ) with the gas mixture channels ( 6 ) are each arranged between two sheet layers ( 2 ) with heating fluid channels ( 4 ). 3. Reactor unit ( 1 ) according to claim 1 or 2, characterized in that the sheet layers ( 2 ) with alternating smooth ( 9 ) and corrugated sheets ( 10 ) are executed. 4. Reactor unit ( 1 ) according to one of claims 1 to 3, characterized in that at least the gas mixture channels ( 6 ) forming sheet metal layers ( 2 ) have a catalytically active coating ( 11 ), preferably all sheet metal layers ( 2 ) have a catalytically active coating ( 11 ) on. 5. Reactor unit ( 1 ) according to one of claims 1 to 4, characterized in that at least the gas mixture channels ( 6 ) forming sheet metal layers ( 2 ) have elevations ( 12 ) for swirling the gas mixture flow, which at least partially into the gas mixture channels ( 6 ) extend. 6. Reactor unit ( 1 ) according to one of claims 1 to 5, wherein the sheet layers ( 2 ) with sheets ( 9 , 10 ) are carried out, characterized in that the sheets ( 9 , 10 ) have openings ( 13 ) for the Gas mixture flow can be at least partially flowed through. 7. Reactor unit ( 1 ) according to one of claims 1 to 6, wherein the sheet layers ( 2 ) with sheets ( 9 , 10 ) are carried out, characterized in that the sheets ( 9 , 10 ) have a thickness ( 14 ) less than 0.08 mm, preferably less than 0.04 mm, in particular less than 0.02 mm. 8. Reactor unit ( 1 ) according to one of claims 1 to 7, characterized in that the reactor unit ( 1 ) has additional heating means ( 15 , 16 , 23 , 24 , 25 ), in particular an electric heater ( 16 ). 9. Reactor unit ( 1 ) according to one of claims 1 to 8, wherein the reactor unit ( 1 ) has a unit cross-sectional area ( 17 ), characterized in that at least the number of gas mixture channels ( 6 ) per unit cross-sectional area ( 17 ) increases in the gas mixture flow direction ( 7 ) , 10. Reactor unit ( 1 ) according to claim 9, wherein the reactor unit ( 1 ) in the gas mixture flow direction ( 7 ) has several zones ( 18 , 18.1 , 18.2 , 18.3 ), characterized in that at least the gas mixture channel density in the gas mixture flow direction ( 7 ) last arranged zone ( 18 ) is greater than 1000 cpsi, preferably greater than 1400 cpsi.