DE102006019406A1 - Selective oxidation-reactor for purification of carbon monoxide from gas mixture, comprises first- and second tube guiding cooling agent, third tube arranged between first and second tubes, fourth tube and holding device locking four tubes - Google Patents

Abstract

The selective oxidation-reactor for the purification of carbon monoxide from gas mixture, comprises first- and second tube guiding a cooling agent, a third tube arranged between the first and the second tubes, a fourth tube and a holding device locking the four tubes. The four tubes are coaxially arranged with different radii and are fluidically connected. A temperature measuring point (150) is arranged in the reactor. The holding device has a reactor head and reactor base. The catalyst is a catalyst bed (122). The first tube is an external tube and the second tube is an internal middle tube. The selective oxidation-reactor for the purification of carbon monoxide from gas mixture, comprises first- and second tube guiding a cooling agent, a third tube arranged between the first and the second tubes, a fourth tube and a holding device locking the four tubes. The four tubes are coaxially arranged with different radii and are fluidically connected. A temperature measuring point (150) is arranged in the reactor. The holding device has a reactor head and reactor base. The catalyst is a catalyst bed (122). The first tube is an external tube, the second tube is an internal middle tube, the third tube is an exterior middle tube and the fourth tube is an internal tube of four coaxially arranged tubes. A first supplying line, which supplies gas mixture to the reactor and a second supplying line, which supplies oxygen-containing gas to the reactor are fluidically connected and are arranged to each other in reverse flow direction. The cooling agent is the cooling water of a fuel cell. The third tube comprises a catalyst and is enforceable from the flow of the gas mixture. The reactor head consists of devices for the intake of the supply lines and/or devices for the access of the temperature measuring point and/or devices for the distribution of the gas mixture and/or the cooling agent and/or devices for supplying catalyst into the reactor and/or devices for the distribution of the gas mixture. Independent claims are included for: (1) a reformer-fuel cell system; and (2) a method for the purification of carbon monoxide from gas mixture.

Description

object the invention is a selective oxidation reactor for carbon monoxide purification, a reformer fuel cell system with such a selective Oxidation reactor and a method for fine carbon monoxide purification by means of a such selective oxidation reactor.

It is known that by steam reforming hydrocarbons, especially methane as the main constituent of natural gas, a hydrogen-containing product gas can be produced. The steam reforming essentially follows the two independent reaction equations CH ₄ + H ₂ O⇔CO + 3H ₂ Δh ₀ = 206kJ / mol and CH ₄ + 2H ₂ O ⇔ CO ₂ + 4H ₂ Δh ₀ = 165 kJ / mol under heat supply to a catalyst. Such a hydrogen mixture produced in the steam reforming is essentially composed, for example, as follows:
7% CO ₂ , 9% CO, 1% CH ₄ , 27% H ₂ O and 56% H ₂ . Such a gas mixture is unsuitable for use in PEM fuel cells, since the existing carbon monoxide attacks the catalysts of the fuel cell and significantly reduces the speed of the oxidation necessary for the production of electricity. For this reason, it is necessary to purify the gas mixture before use in such a way that the carbon monoxide content is reduced to a few percent in downstream high-temperature fuel cells, and to 10-100 ppm in downstream low-temperature fuel cells. This usually takes place in two successive reaction stages, the first having a so-called shift converter and the second stage having a gas fine purification by means of selective oxidation or selective methanation. In the shift converter stage, the conversion proceeds according to the exothermic homogeneous water-gas reaction CO + H ₂ O⇔CO ₂ + H ₂ Δh ₀ = -41kJ / mol

The shift converter stage generally has two different temperature levels, namely the high-temperature shift (HT shift), for example, on an Fe-Cr catalyst at temperatures between 300-500 ° C. and the low-temperature shift (NT shift). for example, on a Cu-Zn catalyst at temperatures of 200-300 ° C. After such a shift conversion, the gas mixture contains a carbon monoxide content of about 0.5 to 1%. In order to further reduce this carbon monoxide content, which is still too high especially for low-temperature fuel cells, the abovementioned gas-fine purification stage is connected downstream. In this case, the carbon monoxide present in the gas mixture reacts with the addition of oxygen and in the presence of a suitable catalyst to carbon dioxide, according to the reaction CO + ½O ₂ ⇔ CO ₂ Δh ₀ = -283.6 kJ / mol

This reaction should proceed as far as possible selectively, ie with as much as possible suppressed hydrogen oxidation H ₂ + ½ O ₂ ⇔ H ₂ O .DELTA.h ₀ = -243.5 kJ / mol

Both Reactions are exothermic, i. warmth leaving, where - um an approximate isothermal and stationary reaction to ensure - a steady heat output must take place. This is effected by means of a cooling device.

by virtue of the selectivity provided by the catalysts used, which is the relationship between the targeted carbon monoxide oxidation conversion and the to suppress Hydrogen oxidation turnover sets can - if the carbon monoxide content in the gas mixture is known - the Amount of the oxygen to be supplied to the gas mixture due to the stoichiometric conditions be calculated. It must have a good mixing of the gas mixture and the one to be supplied Oxygen, as otherwise due to the low partial pressures of Carbon monoxide and oxygen are locally different due to inhomogeneities concentration ratios form.

The US 5,843,195 discloses a fuel reformer consisting of a reformer unit and an oxidation unit. The catalyst is made of a special Pl-Ru alloy which oxidizes the carbon monoxide produced in the reformer unit to carbon dioxide.

The US 5,712,052 discloses a fuel cell generator having a reformer and a shift reaction unit. In a downstream oxidation unit, carbon monoxide reacts with oxygen to form carbon dioxide, with a carbon monoxide sensor disposed in the fuel cell to regulate the oxygen supply depending on the carbon monoxide concentration.

in the Prior art systems for carbon monoxide purification can not so compact due to their size or complexity be that they can be manufactured with few components.

Of the Invention is therefore based on the object to a solution create, which allows one to provide a compact carbon monoxide purification stage.

The The object of the invention is achieved by providing a selective Oxidation reactor for carbon monoxide fine purification, its use in reformer fuel cell systems and by a method for fine carbon monoxide purification by means of the selective according to the invention Oxidation reactor solved.

The The present invention therefore relates to a selective oxidation reactor for the fine carbon monoxide purification of a gas mixture, comprising at least three substantially coaxially arranged tubes with different Radii and a holding the at least three tubes holding device, where a is a coolant leader first of the at least three tubes with at least one of the coolant premier second of the at least three tubes in fluid-carrying line connection is and a catalyst having and from the gas mixture flowed through third of the at least three tubes is arranged.

Of the selective according to the invention Oxidation reactor for fine carbon monoxide purification of a gas mixture has a by the particular arrangement of coolant leading and the catalyst having pipes, due to their different Radii and their essentially coaxial arrangement between the Tubes define annular gap volumes, a compact design. To one as possible clear and thereby concise and readable representation of the invention to enable becomes following shortening Spelling introduced: "in" or "out" one or "through" a pipe which is not the inner tube is meant "in" or "out of" or "through" that of this tube and from that to the nearest inner tube formed annular gap volume. The from this design resulting low complexity allows a low cost production. The device according to the invention is preferably suitable as a compact carbon monoxide fine cleaning stage for fine carbon monoxide purification in mobile fuel cell power plants, but also for all other hydrogen generators are used. It fulfills the inventive device the high demands made on mobile power generators in terms of low system complexity, low production costs and simple production are made.

The The invention also relates to a reformer fuel cell system comprising a reformer for converting a hydrocarbon-containing energy carrier, a the reformer downstream gas mixture cleaner and a gas mixture cleaner Downstream fuel cell for power generation, the Gas mixture cleaner at least one selective oxidation reactor according to the invention having. Such a system may, due to the advantages of the selective Oxidation reactor be made compact and efficient.

moreover The invention also relates to a process for fine carbon monoxide purification a gas mixture, wherein the gas mixture by means of a selective according to the invention Oxidation reactor is purified by carbon monoxide. Such a procedure allows an efficient and cost effective Carbon monoxide fine cleaning.

In a preferred embodiment For example, the selective oxidation reactor comprises three tubes, the first one Tube an outer tube, the second tube is an inner tube and the third tube is a middle one Tube of three coaxial tubes is. This will be a from the outside and inside caused cooling ensures the catalyst having the tube.

In another embodiment For example, the selective oxidation reactor comprises four tubes, one of which coolant leading first the four tubes with a coolant leading second of the four tubes in fluid-carrying Line connection is and between the first and the second the four tubes have the catalyst and the current from the current arranged third of the four tubes of the gas mixture is and the third with a fourth of the four tubes in fluid leading Line connection is. A four tube arrangement allows one other flow of the gas mixture through the selective oxidation reactor.

Prefers is the first tube an outer tube, the second pipe is an inner middle pipe, the third pipe an outer middle pipe Pipe and the fourth pipe an inner pipe of four arranged coaxially Pipes. In this case, an advantageous temperature of both the Catalyst comprising pipe as well as the gas mixture stream achieved.

Preferably are a reactor supplying the gas mixture feeding first and a reactor supplying an oxygen-containing gas to the second supply line, which preferably in countercurrent to each other, in fluid-carrying Line connection. By such an arrangement of the leads is a particularly efficient mixing of the gas mixture and reaches the oxygen gas.

Prefers is one the coolant in the selective oxidation reactor incoming supply line, preferably in countercurrent to the flow of the gas mixture arranged. By the arrangement of the coolant supply line in the countercurrent to the flow of the gas mixture is a particularly efficient cooling and achieved a particularly efficient removal of excess heat.

In a preferred embodiment, at least one temperature measuring point is angeord net in the selective oxidation reactor. The arrangement of at least one, preferably a plurality of the temperature measuring points of the temperature of the catalyst allows a check on the basis of the erlang th temperature measurement results and optionally caused by a control change in temperature by means of correction and / or cooling and / or change of the oxygen gas and / or other conceivable modifications of the coolant.

In a further embodiment the holding device has two end face elements, preferably a reactor head and a reactor bottom. The arrangement of End face elements allows for a stable lock in the selective oxidation reactor arranged pipes and allows In addition, a compact installation of the corresponding supply lines / leads and continues to provide - if necessary - a degree the corresponding arranged in the selective oxidation reactor Tube.

Prefers the reactor head has devices for receiving the supply lines and / or devices for access to the at least one temperature measuring point and / or devices for distributing the gas mixture and / or the coolant and / or Devices for introducing catalyst into the reactor. One so equipped, preferably from a one-piece multifunction reactor head allows a compact installation of the necessary supply / discharge lines, allows, if necessary access to the attached in or near the catalyst Temperature measuring points, enabled by Distributor distribution the distribution of, for example, one centrally arranged gas mixture feed gas mixture on several areas of the catalyst having the pipe allowed optionally a distribution and / or line of cooling water and has openings on, by means of which the catalyst is introduced into the reactor can.

In a further preferred embodiment the catalyst is a catalyst bed. Such a catalyst bed has a large reaction surface and is also unproblematic in the catalyst having Tube can be inserted.

Finally is the coolant of the selective oxidation reactor the cooling water a fuel cell. By using the fuel cell cooling water as a coolant in the selective oxidation reactor finds an optimal use of heat generated in the selective oxidation reactor instead. By use the excess heat in for example heating circuits is by constructive adjustment of the temperature level and the volume flow of cooling water usually no further temperature or flow control of the cooling water necessary.

The the aforementioned and the claimed and in the embodiments described to be used according to the invention Components are subject in size, shape, Design, material selection and technical conception no special Exceptions, so that those known in the field of application Selection criteria unrestricted Application can be found.

Further Details, features and advantages of the subject matter of the invention emerge from the dependent claims as well as from the following description of the associated drawing, in the - exemplary - a preferred Embodiment of Invention is shown. In the drawing shows:

1 a selective oxidation reactor according to the invention in longitudinal section with three coaxially arranged tubes;

2 a selective oxidation reactor according to the invention in longitudinal section with four coaxially arranged tubes;

In the embodiment according to 1 indicates the selective oxidation reactor 100 for carbon monoxide fine cleaning of a gas mixture on a coaxial arrangement of tubes, said in accordance with 1 illustrated embodiment selected tube assembly 200 also an outer, first tube 201 , a middle, second tube 202 and an inner, third tube 203 includes. The tubes, which need not necessarily be cylindrical, but can also be configured oval or polygonal, may be different in pairs or the same length, but have different radii. Due to the different radii of the tubes, the annular gap volume V of the reactor 100 Are defined. The coaxial position of the pipes 201 . 202 . 203 to each other by means of the end face arranged reactor head 300 or of the reactor bottom 310 locked. The preferred coaxial arrangement need not be strictly met. Through the reactor bottom having a central opening 310 is by means of a cooling water supply 140 an example of a fuel cell (not shown) coming cooling water for cooling the selective oxidation reactor 100 Reactor bottom side in the inner, third tube 203 initiated. The introduced cooling water flows through the inner, third tube 203 up to its reactor head end, wherein the cooling water the pipe surface and by means of heat conduction in the middle, the second tube 202 arranged catalyst cools. At the reactor head end of the inner, third tube 203 the cooling water by means of an inner, third tube 203 and the outer, first tube 201 connecting line connection passing through a channel, a hole in the reactor head 300 and / or can be realized by another line connection, in the outer, first tube 201 forwarded. During the passage of the äu ßeren, first pipe 201 the cooling water cools the tube surface of the middle, second tube 202 and by heat conduction in the middle, second tube 202 arranged catalyst before it by means of a cooling water drainage 142 is returned from the reactor into, for example, the fuel cell cooling circuit. Optionally, a parallel cooling is conceivable. In such a parallel cooling, the cooling water in the DC direction through the inner, third tube 203 and through the outer, first tube 201 guided.

By during the passage of the selective oxidation reactor 100 takes place heat transfer to the cooling water, this is heated and can be used to heat a heating circuit, whereby an efficient use of process heat is ensured. At a suitable constructive temperature level is thus a permanent cooling of the selective oxidation reactor 100 and the fuel cell with an optimally designed cooling water circuit without further Kühlwasserdosier- or - control effort possible. An optional regulation of the cooling water acting in addition, based on process parameters to be determined, can be integrated and will be described below.

The middle, second tube 202 encloses an annular gap volume whose inner and outer sides by that in the inner, third 203 and outer, first tube 201 cooled cooling water is cooled, and that is a catalyst in the form of a pellet consisting of catalyst bed 122 receives. The gas mixture to be purified is through a central on the reactor head 300 arranged gas mixture feed line 110 to one also at the reactor head 300 arranged distributor device 130 forwarded. The distributor device 130 consists essentially of any number, for example four, of the central gas mixture supply line 110 obliquely extending in the direction of the reactor interior holes in the reactor head 300 , such dimensions and positions within the reactor head 300 have that the gas mixture at, for example, four points as homogeneous as possible and symmetrical in the reactor head side substantially open end of the middle, second tube 202 is initiated. At the same time by means of an oxygen gas supply line 104 within and / or outside and / or at least near the gas mixture feed line 110 is arranged, fed oxygen-containing gas. Oxygen gas supply 104 and gas mixture feed line 110 are preferably in countercurrent to each other in line connection, ie in any but a mixture permitting contact, with an efficient mixing of the gas mixture and the oxygen gas is ensured. In order to optimize the mixing, a static mixer (not shown) in the form of a turbulence generating device, such as a grid or the like, can also be arranged. The gas mixture-oxygen gas mixture now passes through the distributor device 130 in the catalyst bed 122 containing middle, second raw _r 202 , The cooling of the selective oxidation reactor 100 is set such that a predetermined by the corresponding catalyst temperature window, for example, between 90 and 170 ° C, is retained, so that the most efficient carbon monoxide oxidation takes place at the same time as possible suppressed hydrogen oxidation in the catalyst bed. The purified by oxidation of carbon monoxide to carbon dioxide gas mixture passes at the reactor bottom side end of the middle tube 202 through a gas-permeable, but for the catalyst bed 122 impermeable device, such as a net, a membrane or a screen or the like, in the gas mixture discharge 112 , The now low-carbon and hydrogen-rich gas can be made to closing, for example, a fuel cell available.

In order to determine the process temperature and to correct if necessary, in the catalyst bed several temperature measuring points 150 , which are formed for example by means of thermocouples or PT-100 resistance elements, for example in the upper, middle and lower regions of the reaction space 120 arranged. The measurement information provided by the temperature measurement sites, such as voltages detected by the thermocouples, is processed in an optional control device (not shown) to monitor the temperature and to control the temperature by means of a change in coolant flow rate or coolant temperature or similar control mechanisms. For this purpose, the reactor head 300 one or more holes allowing the passage of one or more thermocouples. The reactor head 300 further points in particular in the central gas mixture supply line 110 a sieve or similar device, so that the fluidized by the flow of the introduced gas mixture-oxygen gas mixture catalyst bed 122 did not get into the supply lines. In addition, the screen provides a protection that prevents tilting of the reactor parts of the reactor bed 122 out or in the openings of the reactor head 300 fall.

Furthermore, in order to measure the carbon monoxide content of the gas mixture to be purified and, correspondingly, regulate the oxygen gas supply according to the stoichiometric ratios prescribed by the reaction equations, carbon monoxide sensors may optionally be present in or upstream of the gas mixture feed line 110 and / or after or in the gas mixture discharge 112 to be ordered. Using egg ner such device, it is possible to determine the carbon monoxide content before and after the cleaning and so in the catalyst bed 122 to optimize ongoing reactions using the process parameters (such as oxygen concentration, temperature, pressure, etc.).

In the 2 illustrated embodiment of a selective oxidation reactor 100 differs from the embodiment described above essentially in that the selective oxidation reactor 100 a pipe arrangement 200 from now four instead of three coaxial tubes 201 . 202 . 203 . 204 includes. The inner, fourth "mixing tube" 204 in which the gas mixture by means of a reactor bottom gas mixture feed line 110 and the oxygen gas by means of a reactor head side oxygen gas supply line 104 through the reactor bottom 310 or reactor head 300 into the selective oxidation reactor 100 initiated, allows efficient mixing. This mixing of the gas mixture and the oxygen-containing gas takes place in accordance with the embodiment 2 therefore not in the reactor head 300 or outside the reactor. In addition, an educt temperature control is made possible by such an arrangement, since the inner, fourth "mixing tube" 24 by means of the inside of an inner middle, third tube 203 tempered guided coolant. The further distribution of the gas mixture-oxygen gas mixture into the reaction space 120 is through the distributor device 130 performed as described above. Also all other devices (such as the catalyst bed 122 , Temperature measuring point 150 , Gas mixture derivation 112 , static mixer, etc.) are functional as in the embodiment according to 1 in or on the selective oxidation reactor 100 locatable. Control of the process by means of temperature or carbon monoxide measurement data may optionally be performed as described above.

100

selective Oxidation reactor

104

Oxygen gas supply

110

Gas mixture supply line

112

Gas mixture deriving

120

reaction chamber

122

catalyst bed

130

distribution device

140

Cooling water supply

142

Cooling water discharge

150

Temperature measuring point

200

pipe arrangement

201

first pipe

202

second pipe

203

third pipe

204

fourth pipe

300

reactor head

310

reactor bottom

V

Annular gap volume

Claims (13)

Selective oxidation reactor for fine carbon monoxide purification a reactor flowing through the reactor Gas mixture comprising at least three substantially coaxially arranged Tubes with different radii and one the at least three tubes arresting holding device, wherein a coolant leading first of the at least three tubes with at least one leading the coolant second of at least three pipes in fluid-carrying line connection and a catalyst having and from the gas mixture flowed through third of the at least three tubes is arranged. Selective oxidation reactor according to claim 1, characterized characterized in that the selective oxidation reactor comprises three tubes, the first pipe an outer pipe, the second tube is an inner tube and the third tube is a middle one Tube of three coaxial tubes is. Selective oxidation reactor according to claim 1, characterized characterized in that the selective oxidation reactor comprises four tubes, wherein a the coolant leader first of the four tubes with a coolant leading second of the four tubes in fluid carrying Line connection is and between the first and the second the four tubes have the catalyst and the current from the current arranged third of the four tubes of the gas mixture is and the third with a fourth of the four tubes in fluid leading Line connection is. Selective oxidation reactor according to claim 3, characterized in that the first tube is an outer tube, the second tube an inner middle pipe, the third pipe an outer middle pipe and the fourth pipe an inner pipe of four coaxially arranged pipes is. Selective oxidation reactor according to one of the preceding Claims, characterized in that a reactor supplying the gas mixture first Feed line and a reactor supplying an oxygen-containing gas second Feed line, which preferably in the opposite direction to each other are arranged in fluid leading Line connection stand. Selective oxidation reactor according to one of the preceding Claims, characterized in that the reactor is a coolant preferably in countercurrent to the flow of the gas mixture feeding supply line having. Selective oxidation reactor according to one of the preceding Claims, characterized in that in the selective oxidation reactor at least a temperature measuring point is arranged. Selective oxidation reactor according to one of the preceding Claims, characterized in that the holding device has two end face elements, preferably a reactor head and a reactor bottom. Selective oxidation reactor according to claim 8, characterized characterized in that the, preferably integrally designed reactor head Devices for receiving the leads and / or devices for Access to the at least one temperature measuring point and / or devices for distributing the gas mixture and / or the coolant and / or devices for catalyst introduction into the reactor and / or devices having the distribution of the gas mixture. Selective oxidation reactor according to one of the preceding Claims, characterized in that the catalyst is a catalyst bed. Selective oxidation reactor according to one of the preceding Claims, characterized in that the coolant is the cooling water a fuel cell is. Reformer fuel cell system comprising a Reformer for converting a hydrocarbon-containing energy carrier, a the reformer downstream gas mixture cleaner and a gas mixture cleaner Downstream fuel cell for power generation, wherein the gas mixture cleaner at least one selective oxidation reactor according to one of claims 1 to 11 having. Process for the carbon monoxide purification of a gas mixture, wherein the gas mixture by means of a selective oxidation reactor according to one of the claims 1 to 11 of carbon monoxide is purified.