EP2041023A1

EP2041023A1 - Reformer, and method for reacting fuel and oxidant to gaseous reformate

Info

Publication number: EP2041023A1
Application number: EP07764358A
Authority: EP
Inventors: Stefan Kah
Original assignee: Enerday GmbH
Current assignee: Enerday GmbH
Priority date: 2006-07-17
Filing date: 2007-06-12
Publication date: 2009-04-01
Also published as: DE102006032956A1; BRPI0714340A2; AU2007276585A1; CN101573289A; CA2657534A1; JP2009543753A; EA200970037A1; KR20090020690A; WO2008009250A1; US20100189639A1; DE102006032956B4

Abstract

The invention relates to a reformer for reacting fuel and oxidant to gaseous reformate. Said reformer comprises an oxidation zone (10), an evaporation zone (16), and a catalytic H2 production zone (20). A gaseous mixture of fuel and oxidant can be fed to the oxidation zone (10) for oxidation purposes, a process during which oxidant-containing exhaust gas is produced; fuel and an evaporator gas can be fed to the evaporation zone (16) so as to produce a fuel-containing evaporator gas mixture; and an ignitable reforming gas mixture containing evaporated fuel and oxidant-containing exhaust gas can be fed to the catalytic H2 production zone (20) so as to produce the gaseous reformate. In order to reduce the risk of spontaneous ignition in the evaporator zone (16), mixing and feeding means (28) to which oxidant-containing exhaust gas can be fed from the oxidation zone (10) and fuel-containing evaporator gas mixture can be fed from the evaporation zone (16) are disposed upstream of an inlet of the catalytic H2 production zone (20) so as to produce the reforming gas mixture and feed said reforming gas mixture into the catalytic H2 production zone (20). Recirculation means (26) are provided for recirculating reformate produced in the catalytic H2 production zone (20) into the evaporation zone (16) as evaporator gas. The inventive design prevents an ignitable gas mixture from forming in the evaporator zone (16). The invention further relates to a corresponding method for reacting fuel and oxidant to gaseous reformate.

Description

REFORMERS AND METHOD FOR THE IMPLEMENTATION OF FUEL AND OXIDIZING AGENT

GASIFIC REFORMAT

The invention relates to reformers for converting fuel and oxidant into gaseous reformate, comprising an oxidation zone, an evaporation zone and a zone for catalytic H ₂ generation, wherein the oxidation zone comprises a gaseous mixture of fuel and oxidant.

The evaporation zone fuel and an evaporator gas for producing a fuel-containing evaporator gas mixture can be fed and wherein the zone for the catalytic H ₂ generation an ignitable,

15 vaporized fuel and oxidant-containing exhaust gas containing reforming gas mixture to produce the gaseous reformate can be fed.

The invention further relates to a process for converting fuel and oxidant to gaseous reformate wherein, in an oxidation zone, a fuel mixed with a gaseous oxidant is oxidized to produce an oxidation-containing exhaust gas, wherein in an evaporation zone, fuel with a vaporizing gas is added a fuel-containing evaporator gas mixture is evaporated and wherein in a zone for the catalytic H ₂ generation a vaporized fuel and oxidant-containing exhaust gas containing reforming gas mixture is reformed to produce the gaseous reformate. 30

Generic reformer and generic method, as they are known from DE 103 59 205 Al, have numerous applications, in particular they serve a Fuel cell to supply a hydrogen-rich gas mixture from which then based on electrochemical processes electrical energy can be generated. Such fuel cells are used, for example, in the automotive sector as additional energy sources, so-called APUs ("Auxiliary Power Units").

The known method represents an essentially three-stage process. In a first stage, an oxidation zone is fed with hydrocarbon-containing fuel, eg diesel, and oxidized in an exothermic reaction, ie burned. This produces a typically 800 to 1000 ⁰ hot exhaust gas, which still contains 0 xidationsmittel, that is typically oxygen at a sufficient initial oxygen concentration of the combustion air.

The hot, oxygen-containing exhaust gas is then introduced into an evaporation zone, in which further fuel is added. In the typical use of liquid fuel, this evaporates due to the high temperature, forming an ignitable fuel / exhaust gas mixture. This is then reacted in a zone for catalytic H ₂ generation, typically using a partial oxidation catalyst, to a hydrogen-containing gas, the synthesis gas or reformate. This process is known as CPOX (catalytic partial oxidation). The reformate is subsequently fed to a fuel cell, where it is used together with oxygen to form water according to known principles for generating electrical energy.

A disadvantage of the known method is that in the evaporation zone an ignitable mixture is formed, which carries the risk of spontaneous auto-ignition, resulting in soot deposits in the downstream catalyst and the Need to interrupt the process. The spontaneous auto-ignition is currently counteracted with a very precise control of the ratio of burned and vaporized fuel, which leads to a significant limitation of the parameter range in which the reformer can work stably.

The invention has for its object to provide a reformer and a method for converting fuel and Oxidati- onsmittel to Refortnat available, in which the problems mentioned are at least partially overcome and in particular the variation of the operating parameters, the stable Allow operation, is extended.

This object is achieved with the features of the independent claims.

Advantageous embodiments of the invention are indicated in the dependent claims.

The invention is based on the generic reformer in that for generating the reforming gas mixture and for feeding it into the catalytic H ₂ generation zone upstream of an inlet of the catalytic H ₂ generation zone, mixing and feed means are arranged, on the one hand oxidant-containing offgas from the oxidation zone and, on the other hand, fuel-containing evaporator gas mixture can be supplied from the evaporation zone, with recirculation means being provided for returning the reformate produced in the zone for the catalytic production of H ₂ as evaporator gas into the evaporation zone. The invention is based on the generic method characterized in that mixed to produce the reformation gas mixture oxidant-containing exhaust gas with a fuel-containing evaporator gas mixture and see in the zone for the catalytic H ₂ production is fed, wherein in the zone for the catalytic H ₂ production produced reformate as an evaporator Gas is returned to the evaporation zone.

The effects and advantages of the reformer and the method according to the invention will be discussed together below.

In contrast to the prior art, it is provided in the context of the invention that the hot exhaust gas from the oxidation zone is not used as evaporator gas in the evaporation zone, but rather that reformate generated in the reforming zone is recycled as evaporator gas into the evaporation zone, where it Fuel, which is evaporated due to the high reformate temperature, enriched.

The hydrogen-containing reformate together with the vaporized fuel does not form an ignitable mixture due to the absence of an oxidizing agent, so that there is no risk of spontaneous autoignition in the evaporation zone. An ignitable mixture is first produced by downstream mixing and feed means, in which an ignitable reforming gas mixture is formed by mixing the fuel-enriched reformate from the evaporation zone and the oxidant-containing offgas from the oxidation zone and fed into the zone for catalytic H ₂ production.

Another advantage of the invention is that the hydrogen contained in the reformate used as evaporator gas the - S -

Soot formation during the evaporation of the enrichment fuel is reduced. The fuel evaporation is typically carrier gas controlled, so that even low evaporator temperatures - well below the boiling point of the components contained in the fuel - sufficient to evaporate the fuel. This temperature reduction also leads to a gentle low-carbon fuel evaporation.

Conveniently, the mixing and feeding means are designed as injector nozzle. On the one hand, this has the advantage that no large-volume, ignitable mixture-containing area is formed which could harbor the risk of spontaneous autoignition. Rather, feeding the ignitable mixture into the zone for catalytic H ₂ production at high speed ensures that flashback is ruled out.

Advantageously, the injector nozzle is exhaust gas driven, i. The kinetic energy of the oxidant-containing exhaust gas from the oxidation zone is used as the energy source for the mixing and feeding of the ignitable reforming gas mixture. By correct adjustment of the mechanical nozzle properties, the optimal mixing ratio of oxidizing exhaust gas and enriched evaporator gas can be permanently adjusted without a constant, active control of the components would be required. For example, the injector nozzle can operate on the principle of the Venturi nozzle.

As mentioned, the invention leads inter alia to the advantage that the evaporation of the enrichment fuel in the evaporation zone can be carried out at comparatively low temperatures. On the other hand, the reformate produced in the catalytic H ₂ generation zone typically has one very high temperature. In an advantageous development of the invention, it is therefore provided that heat is withdrawn from the recycled reformate during the recirculation. This can be realized, for example, by virtue of the fact that the return means have heat exchanger means for cooling the recirculated reformate. Preferably, the heat exchanger means are switched on and off as needed. The heat recovered in this way can be used, for example, for preheating a process air in a downstream fuel line system. Also, a use for preheating of fuel, as a heat source in the zone for the catalytic H ₂ generation, in an afterburner or in other components of the system is conceivable.

To the inventively provided recirculation of reformate in the evaporation zone, the reformate generated in the zone for the catalytic H ₂ production can be branched off in the region of the zone for the catalytic H ₂ production directly, ie the return means set in the region of the zone for the catalytic H ₂ - Generation. For this purpose, a gas sampling probe can be used in the zone for catalytic H ₂ production, which ensures a high recirculation rate of the gas stream to be recirculated. On the other hand, it is also possible to have the recirculating agent in one of the zone for catalytic H ₂ generation downstream range set. This can be done immediately behind the zone for the catalytic production of H ₂ or else behind one of the zone for catalytic H ₂ generation downstream fuel cell. Due to the electrochemical oxidation in the fuel cell, the oxygen content and thus the ratio 0 / C in the recirculated gas stream and thus also in the catalyst, which significantly influences the formation of soot. From a thermodynamic point of view, soot formation decreases with increasing O / C ratio, so that in this respect the return According to the fuel cell leadership may be advantageous over that after the reformer, if kinetic effects play a minor role in the formation of soot.

Typically, the hydrogen supplied to a fuel cell is not completely reacted with oxygen to form water. The exhaust gas of the fuel cell anode therefore usually still contains a usable concentration of hydrogen.

In a particular embodiment of the invention is therefore intended to recycle this anode exhaust gas as the evaporator gas in the evaporation zone. Of course, combinations of the aforementioned feedback options can be realized.

In a particularly favorable development of the invention, it is provided that the evaporator gas mixture is cleaned of contaminants before it is mixed with the oxidant-containing exhaust gas. For this purpose, preference is given between the mixing and feeding means, i. in particular the injector nozzle, and the evaporation zone gas cleaning agent for removing the contaminants from the evaporator gas mixture provided. This may be a basically known catalyst protection device containing catalyst poisons contained in the evaporator gas, e.g. Absorbs metals and soot precursors and can make harmless partially by reaction with the hydrogen contained in the reformate.

As explained, the present invention relates to a reformer and a method for producing a Re- formats. It should be noted, however, that the present invention also has advantages in an operating mode of the reformer does not directly produce a reformate. In this mode, here referred to as regeneration mode, the fuel enrichment in the evaporation zone is switched off. Thus, no reformate is formed in the zone for catalytic H ₂ production. Rather, combustion exhaust gas from the oxidation zone flows through the zone for catalytic H ₂ production. In the regeneration mode, this gas is fed via the recirculation means to the evaporation zone and mixed with "fresh" combustion gas via the mixing and feed means and introduced again into the zone for the catalytic production of H ₂ . By means of this exhaust gas recirculation, soot deposits, which may have formed in the evaporation zone and / or a gas purification unit connected downstream of the evaporation zone, may be burned and the corresponding elements thereby regenerated.

The invention will now be described by way of example with reference to the accompanying drawings with reference to preferred embodiments. Show it:

Figure 1 is a schematic representation of the structure of a reformer according to the prior art;

Figure 2 is a schematic representation of the construction of a reformer according to the invention with several optional additional elements; and

Figure 3 is a schematic representation of the structure of an alternative embodiment of the reformer according to the invention.

Figure 1 shows a schematic representation of the structure of a reformer according to the prior art. In a burner - S -

10, which comprises the oxidation zone, is supplied via a first feed line 12 and air via a second supply line 14 liquid fuel, such as diesel. The burner 10 typically has a mixing zone (not separately shown) for forming an ignitable gas mixture from the combustion air and the fuel. This mixing zone is upstream of the actual oxidation zone. The resulting during combustion in the burner 10 exhaust gas, which also contains unreacted oxygen during combustion, is fed into an evaporator 16 and serves as the evaporator gas there. The evaporator 16 has a supply line 18 for further liquid fuel, with which the evaporator gas is enriched. Due to the high temperatures of the supplied via the supply line 18 liquid fuel is evaporated. The enriched gas, ie the mixture of the evaporator gas and vaporized fuel forms an ignitable Reformation gas mixture which is fed into the downstream zone 20 for the catalytic H ₂ production, which in particular comprises a CPOX catalyst. In the zone 20 for the catalytic production of H ₂ hydrogen-containing reformate is generated by catalytic means, which can be supplied to a downstream fuel cell 22. The exhaust gases of the fuel cell are suitably treated depending on the structure of the system, which is indicated in Fig. 1 as a derivative "to the system".

FIG. 2 shows a schematic representation of a reformer according to the invention. The same reference numerals as in FIG. 1 are used for corresponding elements. In the embodiment of FIG. 2, a gas extraction unit 24 is arranged upstream of the fuel cell. It should be noted that the schematic representation of Figure 2 does not necessarily show the objective, but essentially the functional elements. So can the gas extraction unit 24 may also be integrated into the zone 20 for the catalytic production of H ₂ . The function of the gas extraction unit 24 is to recycle a portion of the hydrogen-containing reformate generated in the zone 20 for the catalytic production of H ₂ via the return line 26 into the evaporator 16. As the evaporator gas in the evaporator 16 is thus not used in contrast to the prior art, the exhaust gas from the burner 10 but via the return line 26 recycled reformate.

The exhaust gas from the burner 10 and the enriched evaporator gas from the evaporator 16 are supplied together to an injector 28, which is preferably designed as a driven by the exhaust gas from the combustor 10 nozzle. In the injector 28, the two gas streams are mixed and the resultant ignitable mixture is fed into the zone 20 for the catalytic production of H ₂ .

In the embodiment shown in FIG. 2, an optional heat exchanger 30 is integrated into the return line 26. This is shown in dashed lines in Figure 2 to indicate its optional character. The heat exchanger 30 can preferably be switched on and off as required and in particular serves to cool the reformate recirculated via the return line 26. The heat exchanger

30 can be used as an active temperature control to keep the temperature in the evaporator 16 in an optimal range. Furthermore, the temperature in the evaporator can be adjusted by the heat exchanger so that the ignition temperature of the soot is achieved and the soot oxidation is targeted. Thus, the evaporator can be exempt from soot, ie regenerated. As a further option, in the embodiment of FIG. 2 a gas cleaning unit 32 is provided, which is arranged between the evaporator 16 and the injector 28. This gas cleaning unit 32 is used to remove so-called catalyst poisons from the gas stream or the conversion of harmful compounds (soot precursors) to harmless compounds. The conversion can be done for example by the recirculated hydrogen, z. B. by hydrogenation of acetylene, ethylene, polycyclic aromatic compounds.

FIG. 3 shows essentially the same structure as FIG. 2, with the same reference numbers again designating corresponding elements. In contrast to FIG. 2, however, FIG. 3 shows that the gas extraction unit 24 is functionally arranged behind the fuel cell 22. With this variant of the invention, anode exhaust gas of the fuel cell 22 can be recycled.

Of course, the embodiments shown in the figures and discussed in the specific description represent only illustrative embodiments of the invention. The skilled person is given a wide range of possible variations. In particular, it is conceivable to combine the embodiments of FIG. 2 and FIG. 3 in such a way that both reformate from zone 20 for the catalytic production of H ₂ and fuel cell exhaust gas from fuel cell 22 are supplied to evaporator IG as evaporator gas.

The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential to the realization of the invention both individually and in any combination. List of reference numbers:

10 burners 12 air supply

14 fuel supply line

16 evaporators

18 fuel supply line

20 zone for catalytic H ₂ production 22 fuel cell

24 gas sampling probe

26 return line

28 Inj ector

30 heat exchanger 32 gas cleaning unit

Claims

Claims 1. A reformer for converting fuel and oxidant to gaseous reformate comprising an oxidation zone (10), an evaporation zone (16) and a zone (20) for catalytic H ₂ production, the oxidation zone (10) being a gaseous reformate Mixture of fuel and oxidant for oxidation to produce oxidizing agent-containing exhaust gas can be supplied, wherein the evaporation zone (16) fuel and an evaporator gas for producing a fuel-containing evaporator gas mixture can be supplied and wherein the zone (20) for the catalytic H ₂ generation an ignitable, vaporized fuel and oxidant-containing

Exhaust-containing reformate gas mixture for supplying the gaseous reformate can be supplied, characterized in that for generating the reformate gas mixture and for feeding it into the zone (20) for the catalytic H ₂ - generation before an input of the zone (20) for the catalytic H ₂ generation mixed and feed means (28) are arranged, to which oxidant-containing exhaust gas from the oxidation zone (10) on the one hand and fuel-containing evaporator gas mixture from the evaporation zone (16) can be supplied, with recirculation means (26) for recycling in the zone (20) to the catalytic converter H ₂ generation produced reformate as evaporator gas in the evaporation zone (16) are provided.

2. Reformer according to claim 1, characterized in that the mixing and feeding means are designed as injector nozzle (28).

3. A reformer according to claim 2, characterized in that the injector nozzle (28) is driven by the supplied oxidative medium-containing exhaust gas.

4. Reformer according to one of the preceding claims, characterized in that the return means (26) have heat exchanger means (30) for cooling the recirculated reformate or for initiating the soot oxidation in the evaporator.

5. A reformer according to claim 4, characterized in that the heat exchanger means (30) are switched on and off as needed.

6. Reformer according to one of the preceding claims, characterized in that the return means (26) for the removal of reformate from the zone (20) for the catalytic H ₂ generation in the region of the zone (20) for the catalytic H ₂ - production begin.

7. Reformer according to one of claims 1 to 5, characterized in that the recirculation means (26) for the removal of reformate in one of the zone (20) for the catalytic H ₂ - generate generation downstream region.

8. A reformer according to claim 7, characterized in that the return means (26) for dissipating reformate to an anode exhaust gas line of the zone (20) for catalytic H ₂ generation downstream fuel cell (22) set.

9. Reformer according to one of the preceding claims, characterized in that between the mixing and feed means (28) and the evaporation zone (16) Gasreinigungs- are provided (32) for removing contaminants from the evaporator gas mixture.

10. A method for converting fuel and oxidant to gaseous reformate, wherein in an oxidation zone (10) a fuel mixed with a gaseous oxidant is oxidized to produce an oxidant-containing exhaust gas, wherein in an evaporation zone (16) Fuel is vaporized with an evaporator gas to a fuel-containing evaporator gas mixture and wherein in a zone (20) for the catalytic H ₂ generation a vaporized fuel and oxidant-containing exhaust gas containing reforming gas mixture is reformed to produce the gaseous reformate, characterized in that for generating the reforming gas mixture oxidant-containing exhaust gas mixed with fuel-containing Verdampfergas- mixture and is fed into the zone (20) for the catalytic H ₂ - generating, in the zone (20) for the catalytic H ₂ generation produced reformate as evaporator gas in the evaporation zone (16) is recycled.

11. The method according to claim 10, characterized in that the recirculated heat is withdrawn during the recycling heat.

12. The method according to any one of claims 10 or 11, characterized in that the evaporator gas mixture is cleaned of contaminants before mixing with the oxidant-containing exhaust gas.