DE4420753A1 - Methanol reformation - Google Patents

Abstract

An assembly reconstitutes methanol using steam in a converter having a number of catalyst-filled tubes surrounded by a heating medium. The novelty is that each reaction tube (3) is surrounded by a second concentric outer tube (5) to form a passage (4) through which the heating medium flows. Further that the housing inner chamber (18) is also filled with catalytic material (17) in the space between the second outer pipe (5) and outer casing (2). After the reformed gas has flowed through the reaction pipes (3), it passes to the housing inner chamber (18) by means of a return tube (13). The reformed gas leaves the casing (2) by an outlet (14).

Description

The invention relates to a device for steam reforming tion of methanol according to the preamble of claim 1.

From JP-OS 59-184705 is a device for methanol reforming known in which a methanol / water mixture in Reaction tubes filled with catalyst material and in are arranged in a housing, is converted. The for the The heat energy required for reforming is supplied to the reform gas Heat transfer medium that passes through the area between the reaction pipes and the housing is fed.

This arrangement has the disadvantage that the construction required Space is relatively large and that the heat transfer from the heat transfer medium medium on the reform gas is insufficient.

The object of the invention is to provide a device for Steam reforming of methanol to create the Reforming of methanol while minimizing the required space can be carried out as efficiently as possible can.

The object is achieved by the characterizing Features of claim 1 solved.

The arrangement according to the invention has the advantage that for the heat transfer medium in comparison to conventional tube bundles reactors require little space. While conventional pipe bundle reactors of the heat transfer media the entire room between the pipes and the common housing  in the proposed arrangement this space also for the Catalyst and the reaction used. The heat transfer medium is guided here in the annular gap of the concentric tubes. Here is a good heat transfer to the inner and outer tube achieved, which by lead structures or introduction of Grooves, as usual with safety double pipes, further ver can be improved. By arranging lead structures in the reaction tubes can also have a good heat transfer from the pipe wall on the reform gas can be guaranteed. Soon is the share of the catalyst volume in the total volume very large. As a result, the active catalyst area is referred to increases the space required. Overall, this can be an extreme compact device for reforming can be provided.

Further advantages and configurations result from the subclaims Chen and the description. The invention is as follows described in more detail with reference to a drawing, wherein

Fig. 1 is a schematic representation of a device according to the invention for the steam reforming,

Fig. 2 shows a section perpendicular to the reaction tubes through the device of Fig. 1 and

Fig. 3 shows a further embodiment.

The total indicated in FIGS. 1 and 2, with 1 tubular reactor comprises a housing 2 are arranged in a plurality of parallel reaction tubes 3 ver current. The reaction tubes 3 are each surrounded by a concentrically arranged outer tube 5 to form heat transfer channels 4 . The housing 2 has a housing cover 6 and a housing base 7 , wherein the housing cover 6 and the housing base 7 are connected via flange connections 8 , 9 at opposite ends to the housing 2 . On the housing cover 6 for the methanol / water vapor mixture and for the heat transfer medium each have an inlet line 10 , 11 is arranged. The reformed gas and the heat transfer medium are distributed to the individual reaction tubes 3 via channels (not shown) in the housing cover 6 . On the housing base 7 , the heat transfer medium and the reforming gas are collected via channels, also not shown, and discharged from the housing 2 . While the heat transfer medium is discharged directly via an outlet line 12 , the reformed gas is fed again to the tube reactor 1 via a return line 13 . For this purpose, the return line 13 opens into a side wall of the housing 2 . An outlet line 14 is also provided on the opposite side wall of the housing 2 , via which the reformed gas is discharged again from the housing 2 .

The internal structure of the tubular reactor 1 is explained in more detail below with reference to FIG. 2. Inserts 15 made of aluminum, which have a star-shaped cross section, are provided in the reaction tubes 3 . These improve the heat transfer from the heat transfer medium through the pipe wall to the reformed gas. The heat transfer medium, for example hot oil, flows into the heat carrier channels 4 formed between the reaction tube 3 and the outer tube 5 . Structures for improving the flow properties are provided in the heat transfer channels 4 . For this purpose, depressions 16 , which run essentially in the flow direction, are arranged on the inner surfaces of the outer tubes 5 . However, it is also possible to insert special internals into the gap between the outer tube 5 and the reaction tube 3 .

To reform the methanol, both the reaction tubes 3 and the housing interior 18 in the area outside the outer tubes 5 are filled with a suitable catalyst bed 17 . The bulk material in the reaction tubes 3 preferably has a grain diameter of <2 mm, the inside diameter of the reaction tubes 3 itself preferably being chosen to be <30 mm. A catalyst 17 with a different sieve fraction, for example with a coarser grain size, can be used in the housing interior 18 .

Catalytic steam reforming is a mixture from methanol and water vapor with the supply of heat to one suitable catalyst converted to hydrogen, being the same Carbon dioxide is generated early:

CH₃OH + H₂O → 3 H₂ + CO₂

This reaction can be divided into the strongly endothermic Pyrolysis:

CH₃OH → 2 H₂ + CO

and into the weakly exothermic shift reaction:

CO + H₂O → CO₂ + H₂

In mobile applications, such as water vapor reform for fuel cells in motor vehicles, it is important that the required yield of hydrogen gas possible as little space and weight as possible can. Since the reaction only takes place with the addition of heat, it is However, the yield depends on the heat input. Therefore, the Reactor be designed so that an optimal heat transfer from a provided heat transfer medium on the reform gas and on the catalyst material is guaranteed. For this purpose, in generally a variety of elaborately designed heating channels needed so that the proportion of the filled with catalyst Volume of the total volume reduced. Since the yield, however also depends on the active catalyst area, this means at the same time again a reduction in the yield. So is it is crucial to reform the methanol with regard to this optimize both factors.

With the aid of the arrangement described, the reforming of the methanol / water vapor mixture can be carried out in a two-stage process. The first stage, which is carried out in the reaction tubes 3 , is optimized with regard to the heat transfer between the heat transfer medium and the catalyst material 17 or the gas to be reformed. Here, the conversion of the methanol is carried out at a temperature of 250 ° to 350 ° Celsius, the degree of conversion in this first stage preferably being less than 90%.

The conversion of methanol is then completed in the interior 18 of the housing. This second stage is heated less and therefore runs at slightly lower temperatures. Since the CO shift reaction takes place preferentially, so that the CO content in the reform gas is reduced. In the two stages, different catalysts 17 optimized for the respective process can be used. The entire reaction is operated under pressure, preferably 1-15 bar.

The advantage of this arrangement is that of conventional ones Shell and tube reactors have particularly little space for the heat transfer medium medium, as well as the high proportion of the catalyst volume in the total volume. This allows a good degree of implementation with reduced Space requirements can be realized.

In addition to the embodiment shown here with a rectangular Ge housing 2 , cylindrical or other housing shapes can be ended ver. The arrangement of the reaction tubes 3 within the housing 2 should not be limited to the embodiment shown with two staggered rows, but also include other orders. If the housing cover and housing base are designed accordingly, the flow guidance in the reactor and the supply and discharge of the media can be designed differently. For example, all media can be supplied and removed via the housing cover. It is also possible to redirect the reactant flow inside the reactor after flowing through the inner tubes and then return it in countercurrent through the catalyst-filled tube outer space. Finally, the reaction tubes 3 can also have other cross-sectional shapes in addition to the circular cross-section shown.

Such an exemplary embodiment is shown in FIG. 3, the same parts being identified with the same reference numbers as in FIGS . 1-2. In contrast to the first embodiment, for example, the reaction tubes 3 open directly into the housing interior 18 . This eliminates the need for an external return line. In addition, the outlet line 14 is not arranged on one of the side walls of the housing 2 , but is integrated in the housing cover 6 . This results in a gas flow in the housing interior 18 , which is essentially parallel to the reaction tubes 3 , but in the opposite direction. The heat transfer medium can still be removed via the outlet line 12 .

Claims (7)

1. Device for the catalytic steam reforming of methanol with a plurality of reaction tubes arranged in a housing and flowed through by the water vapor / methanol mixture, which are filled with catalyst material and flowed around by a heat transfer medium, characterized in that the reaction tubes ( 3 ) for forming heat transfer channels ( 4 ) are each surrounded by a concentric outer tube ( 5 ) that the housing interior ( 18 ) in the area outside the outer tubes ( 5 ) is also filled with catalyst material ( 17 ) that the reformed gas after flowing through the reaction tubes ( 3 ) via a Recirculation ( 13 ) is passed into the housing interior ( 18 ) and that an outlet line ( 14 ) is provided on the housing ( 2 ) for removing the reformed gas. 2. Device according to claim 1, characterized in that in the heat transfer channels ( 4 ) structures ( 16 ) are provided for guiding the heat transfer medium. 3. Devices according to claim 1, characterized in that inserts ( 15 ) made of a thermally conductive material are arranged in the reaction tubes ( 3 ). 4. The device according to claim 3, characterized in that the inserts ( 15 ) have a substantially star-shaped cross section. 5. Apparatus according to claim 1, characterized in that a common return line ( 13 ) is provided for all reaction tubes ( 3 ), the return line ( 13 ) or as outlet line ( 14 ) on opposite, substantially parallel to the longitudinal axes of the reaction tubes ( 3 ) open or open running sides of the housing ( 2 ). 6. The device according to claim 1, characterized in that the reaction tubes ( 3 ) for recycling the reformed gas open directly into the housing interior ( 18 ). 7. The device according to claim 6, characterized in that the outlet line ( 14 ) on the outflow side of the reaction tubes ( 3 ) opposite side of the housing ( 2 ) is arranged.