DE4316131A1 - Plate catalyst - Google Patents

Abstract

To increase the catalytic activity of plate catalysts, the invention provides that a plate catalyst which comprises a plurality of plates (2, 4) arranged in a cell box and coated with a catalytically active composition is provided with means (6, 14, 16, 20, 22) which deflect the fluid medium from a main flow direction (12) at least partially within the same reaction compartment (24, 26) and at least partially into adjacent reaction compartments (24, 26), a reaction compartment (24, 26) being delimited between each two directly adjacent plates (2, 4) and the cell box which is permeable to the fluid medium on an inlet and outlet side. Because of the vortexing now achieved of the fluid medium, the contribution induced by the flow guidance to catalytic activity of the plate catalyst increases. The invention can be used in principle in all plate catalysts through which flows a liquid or gaseous fluid medium. <IMAGE>

Description

The invention relates to a plate catalyst, the multiple in one Hal arranged and coated a catalytically active mass Covers plates.

Such plate catalysts are used, among other things, to reduce in one Nitrogen oxides contained in the gas mixture are used. Here, the nitrogen oxides together with a reducing agent previously introduced into the gas mixture, mostly ammonia NH₃, by the process of selective catalytic reduction (SCR) by contacting the catalytically active mass with water and Nitrogen implemented. The catalytically active mass with which the plates on both sides are usually comprised of titanium dioxide and one or more of the additives sets of tungsten trioxide, molybdenum trioxide and vanadium pentoxide. Examples of Kataly Sators of this type can be found, for example, in DE-PS 24 58 888.

A plate catalyst comprises as a mounting device for those with the catalytic active mass coated plates usually a so-called element box in which the catalyst plates evenly spaced and oriented parallel to each other are used. The element box usually has the shape of a cuboid on the end faces are open, which are the upstream and downstream sides for a flow medium, e.g. B. are the above gas mixture. The levels of the catalyst plates are oriented perpendicular to the planes of the end faces. A mainstream device for the gas mixture is oriented parallel to the edges of the element box, connect the opposite ends together.

Several of these element boxes equipped with catalytically active plates are in combined into one module and several modules form a level of plates catalysts. For example, there is a so-called DeNOx system for the people tion of nitrogen oxides in the flue gas of an incineration plant usually 3-5 levels sol plate catalysts.

In order to space the plates in an element box, the plates usually have embossed beads that run parallel to the main flow direction and the  Space between two immediately adjacent slabs into several subspaces divide. These subspaces are essentially laminar from the stream medium flows through, so that as the flow path progresses of the plate catalyst in the subspaces for catalytic conversion, for example, nitrogen oxides with ammonia, increasingly less advantageous increasing flow profile and an inhomogeneous gas distribution due to poor mixing of the components of the gas mixture results.

To improve this turbulence, static mixers are already known arranged in the flow direction of the gas mixture upstream of a plate catalyst are and disadvantageously a not insignificant distance in the wake area of the mixer for swirling the components of the flow medium claim (see DE-OS 41 23 161). Also, catalysts with a high one Known swirling cross-channel structure of the gas channels (subspaces). However, these catalysts cause a relatively high pressure drop in one Line for the flow medium and clog when heavily dusty and particulate which gas mixtures relatively quickly.

In addition, Kata are already from the German utility model G 89 01 773.0 known analyzer plates with openings, on each of which there are two tabs, which are bent away from the relevant catalyst plate in opposite directions. The La are shaped and dimensioned so that they are adjacent as spacers beard catalyst plates. The bending edges on which these tabs from the relevant catalyst plate are bent away, are parallel to the main flow direction in order to obstruct the flow as little as possible.

The invention is therefore based on the object of fitting a plate catalytic converter ben, where the catalytically active surface is particularly even and intense for catalytic conversion, such as. B. from stick contained in a flue gas oxides, is used. It is desirable if the pressure drop is as possible is low and clogging of the catalyst can be avoided as far as possible.

This object is achieved in that the plates means comprise the flow medium from a main flow direction at least partially within the same reaction space and at least partially in cont distract beard reaction spaces, with a reaction space between two immit  telbar adjacent plates and that on an upstream and downstream side for the Flow medium permeable mounting device is limited.

In this way it is achieved that the flow medium within each Reaction space is swirled in the trailing area of the agent. Because of the partial Deflection of the flow medium into adjacent reaction spaces becomes a ver vortexing of the components of the flow medium and a mass exchange between The adjacent reaction spaces reached the total catalyst volume detected. In this way, those contained in the flow medium Components, for example nitrogen oxides and ammonia, work particularly well together who mixes and are particularly often due to their swirling to the waiter area of the catalyst plates. Because the flow medium from these with each only to a small extent from the main flow direction is steered, there is a relatively low pressure drop. Furthermore arise only very limited areas in which dusts are contained in the flow medium and / or can deposit particles. This leaves the risk of constipation of the catalyst very low.

In a structurally simple design, the above can do that Flow medium deflecting means deflecting elements, which consist of a plat protrude from the plane and the openings for the flow medium assigned in the plates. So, for example, means in the panels Breakthroughs are punched. The deflection elements can also be on the plate be solid molded bodies that swirl and / or deflect the flow medium.

In a direct further development of this embodiment, the deflection elements are from the Plate level bent out at a bending edge, the bending edge with the Main flow direction includes an angle α that is greater than 0 ° and smaller than 180 °, and which is preferably between 20 and 160 °. That way he the openings are directly through the plate level made deflection elements, which are now oriented to the main flow direction, that local pressure in a leading and trailing area of these deflection elements differences in the flow medium are generated. These pressure differences both cause a swirling of the flow medium in the same reac tion space as well as a mixing of the flow medium with parts of the flow medium from neighboring reaction spaces through the passage openings through it.  

Because the deflection elements by an angle of inclination β, which is preferably between 10 and 60 ° carries, are inclined, baffle surfaces are countered to the flow medium with a high degree of turbulence due to their inclination and at the same time cause only a relatively low pressure drop.

To the flow medium particularly well and at least partially from a re initiate action space in neighboring reaction spaces, it is advantageous if the Deflection elements of the main flow direction are inclined, then the passage openings in the flow direction of the flow medium directly are arranged in front of the deflection elements. Likewise, the deflection elements however, also be inclined in the main flow direction, in which case the Passages preferably in the flow direction of the flow medium are arranged behind the deflection elements.

To keep the catalytic activity of the plate catalyst as uniform as possible to be able to use the entire catalytically active surface and that from the Plate catalyst exiting volume flow per cross-sectional area the entire cross-sectional area of the flow channel as evenly as possible ask, it is advantageous if the deflecting elements of a plate according to different Project sides out of the board level. As a result, the flow meter dium deflected in equal parts on different sides of the plates.

A simple construction of the plate catalyst results if the plates are by means of the deflection elements are spaced. This way it can be great catalytic active surfaces based on the total volume of the plate catalyst simple stacking of the catalyst plates in the holder, preferably in an element box.

It is advantageous if the length and width of the deflection elements are small against the The length and width of the panels are. Because of this dimensioning of the deflection elements is a good local swirling of the flow medium in the wake offers each deflection element as well as the formation of a flow system, that extends over the entire catalyst volume, adjustable.

All of the above measures contribute significantly to improvement and improvement Exercise of the flow induced contribution to catalytic activity  plate catalyst. Further advantageous embodiments of the invention can be found in the other subclaims.

Embodiments of the invention are explained in more detail with reference to 4 figures. Show it:

Figure 1 is a partially broken plan view of two stacked Ka talysatorplatten.

FIG. 2 shows a section along the line II-II in FIG. 1 through a stack of several plate pairs according to FIG. 1;

. Fig. 3 is a section along the line III-III in Figure 1 by a stack of a plurality of pairs of plates according to FIG. 1; and

Fig. 4 is an enlargement of the dashed in Fig. 1 circular section IV.

In FIGS. 1-4, like parts have like reference numerals.

Fig. 1 shows in a partially broken view of two stacked catalyst plates 2, 4 in the plan view. The rectangular catalyst plates 2, 4 are coated on both sides with a catalytically active material, but for reasons of clarity in Figs. 1-4 not is shown. The rectangular catalyst plates 2 , 4 comprise deflection elements 6 , which are arranged in the manner of a matrix in n rows and m columns with n = 4 and m = 8. The deflection elements 6 are arranged in such a way that in a selected row the deflection elements are only occupied in places with an even column index m and in the rows directly adjacent thereto, only places with an odd column index m are occupied. The catalyst plates 2 , 4 are arranged in a stacked manner according to a diagram ababa, etc., the type b resulting from turning the type a (one of the two catalyst plates 2 , 4 ) around a symmetry axis 8 shown in FIG. 1, which is technically with a relatively little effort is feasible.

The deflection elements 6 are punched out of the catalyst plates 2 , 4 on three sides and bent out at a bending edge 10 (see FIG. 4) against a main flow direction 12 from a plate plane 18 (here the graphical representation plane). The deflected from the plates 2 , 4 Auslenkele elements 6 leave in the plates 2 , 4 through openings 7 (see FIGS. 2 and 3) for the flow medium. The main flow direction 12 and the direction of the bending edge 10 are at an angle α of approximately 90 ° to one another. This angle α of about 90 ° is not absolutely necessary, but it is sufficient in other embodiments also if the direction of the bending edge 10 has only a small component in the direction perpendicular to the main flow direction 12 .

The section shown in Fig. 2 along the line II-II in Fig. 1 by a stack arrangement of catalyst plates 2 , 4 emphasizes that directly in a row he adjacent deflection elements 14 , 16 in opposite directions from the plate plane 18 (see. In Fig. 2 and Fig. 3 dashed lines 18) are bent out.

Fig. 3 shows the same arrangement of the catalyst plates 2 , 4 , according to FIG. 2, only now along the section of the line III-III in Fig. 1. On a selected steering element 20 , an inclination angle β is shown, the exemplary embodiment for the selected Ausfüh is about 50 °. Since the catalyst plates 2 , 4 by means of the deflection elements 6 , 14 , 16 , 20 are spaced, it is inevitable that the distance between the plates 2 , 4 depends on the choice of the angle of inclination β. Tilt angles that can be implemented in practice are between 10 and 60 °. The plate spacing ranges from about 1 to 20 mm. It is taken into account that the area of the deflection elements 6 , 14 , 16 , 20 is small compared to the area of the plates 2 , 4 .

In Fig. 3 the effect of the Auslenk is clearly illustrated elements 22 to a flow medium at a selected articulating member 22. The flow medium flows along the main flow direction 12 into a reaction chamber 24 delimited by the catalyst plates 2 , 4 . Because the deflection element 22 bent out of the plate plane 18 by the angle of inclination β is directed in the opposite direction to the main flow direction 12 , at least part of the flow medium flows along an arrow 26 drawn through the passage opening 7 into a neighboring reaction space 28 . Another part of the flow medium, which remains in the reaction chamber 24 , is swirled at the edges of the deflection element 22 , as indicated by arrow 30 . This part is thus also, like the part of the flow medium introduced into the adjacent reaction chamber 26 , deflected from the main flow direction 12 . This repeated deflection of the flow medium from the main flow direction 12 according to the arrows 26 , 30 ensures that the components of the flow medium, for example nitrogen oxides contained in a flue gas of a combustion system and ammonia introduced into the flue gas, homogeneously over the entire reaction spaces 24 , 28 according to FIG. 1-3 constructed Plattenkataly crystallizer are mixed together. In this way, local differences in concentration of these two reactants, which are extensive over the entire catalyst volume, are also compensated for.

As a consequence, the swirling of the components of the flow medium leads to the individual components of the flow medium being brought up to the catalytically active surfaces of the catalyst plates 2 , 4 considerably more often. This has the result that the probability of a three-way impact between the reactants, here for example the nitrogen oxides and the ammonia, and the active centers of the catalyst is considerably increased compared to catalyst plates with only laminar flow and known from the prior art. The absorption of the nitrogen oxides and the ammonia on the catalytic material is particularly advantageous in that the nitrogen oxides are reacted together with the ammonia at the catalytically active centers of the catalytically active layer of the catalyst plates 2 , 4 to nitrogen and water.

Since the deflection elements 6 are small compared to the dimensions of the catalyst plates 2 , 4 , the pressure drop, which is inevitably caused by the deflection of the flow medium from the main flow direction 12 , remains within tolerable values. Also, the risk of a blockage of the reaction spaces 24 , 26 by a flue gas heavily laden with particles and dust, for example, must be excluded, since due to the good microscopic turbulence (see arrows 26 , 30 ) of the flow medium, no dead spaces in the reaction spaces 24 , 26 arise .

A plate catalyst configured in the manner shown achieves the same given conditions due to the flow deflection much higher Separation levels as plate catalysts, which are almost exclusively laminar be flocked. Conversely, this also means that given the separation rate the catalyst volume of a plate catalyst according to the invention considerably can be chosen to be smaller than the catalyst volume for one finally laminar-flow plate catalyst according to the prior art.

A further improvement of a plate catalyst of the invention shown in FIGS. 1-4 is obtained when the plates 2, 4 detect a direction to the main flow 12 inclined and projecting from a main plane of the plate 18 wave structure, in addition, the means in relation to the main plane of the plate 18 inclined surface elements Plates 2 , 4 are arranged. The structure then additionally contributes to the turbulence of the flow medium, as a result of which the conversion rate achievable per unit of catalyst area can be increased further compared to the exemplary embodiments shown in FIGS. 1-4.

Claims (16)

A plate catalyst comprising a plurality of plates ( 2 , 4 ) arranged in a holding device and coated with a catalytically active composition, in which the plates ( 2 , 4 ) comprise means ( 6 , 14 , 16 , 20 , 22 ) which comprise a flow medium from a main flow direction (12) at least partially within a reaction space (24, 26) and at least partially into adjacent reaction spaces (24, 28) from direct, wherein a reaction chamber (24, 28) between each two immediately benachbar th plates (2, 4 ) and which is limited on an upstream and downstream side for the flow medium permeable holding device. 2. Plate catalyst according to claim 1, characterized in that the flow medium deflecting means are deflection elements ( 6 , 14 , 16 , 20 , 22 ) which protrude from a plate plane ( 18 ) and which passages ( 7 ) for the flow medium in the plates ( 2 , 4 ) are assigned. 3. Plate catalyst according to claim 2, characterized in that the deflecting elements ( 6 , 14 , 16 , 20 , 22 ) from the plate plane ( 18 ) at a bending edge ( 10 ) are bent out, the bending edge ( 10 ) with the main flow direction ( 12 ) includes an angle α that is greater than 0 ° and less than 180 °. 4. Plate catalyst according to claim 3, characterized in that the angle α is preferably greater than 20 ° and less than 160 °. 5. Plate catalyst according to one of claims 2 to 4, characterized in that the deflecting elements ( 6 , 14 , 16 , 20 , 22 ) are inclined by an angle of inclination β against the plate plane ( 18 ). 6. Plate catalyst according to claim 5, characterized in that the angle of inclination β is between 10 and 60 °. 7. Plate catalyst according to one of claims 2 to 6, characterized in that the deflecting elements ( 6 , 14 , 16 , 20 , 22 ) of the main flow direction ( 12 ) are inclined. 8. Plate catalyst according to one of claims 2 to 6, characterized in that the deflection elements ( 6 , 14 , 16 , 20 , 22 ) in the main flow direction ( 12 ) are inclined. 9. Plate catalyst according to one of claims 2 to 8, characterized in that the deflection elements ( 6 , 14 , 16 , 20 , 22 ) of a plate ( 24 ) protrude on different sides from the plate plane ( 18 ). 10. Plate catalyst according to one of claims 2 to 9, characterized in that the plates ( 2 , 4 ) by means of the deflection elements ( 6 , 14 , 16 , 20 , 22 ) are spaced apart. 11. Plate catalyst according to claim 10, characterized in that the length and width of the deflection elements ( 6 , 14 , 16 , 20 , 22 ) are small compared to the length and width of the plates ( 2 , 4 ). 12. Plate catalyst according to one of claims 2 to 11, characterized in that the plates ( 2 , 4 ) have a rectangular base, and that the deflection elements ( 6 , 14 , 16 , 20 , 22 ) on each plate ( 2 , 4th ) are arranged in the manner of a matrix in n rows and m columns. 13. A catalytic converter according to claim 12, characterized in that the deflecting elements ( 6 , 14 , 16 , 20 , 22 ) in a selected row only in places with an odd column index in and in the rows immediately adjacent to the selected row only in places with even Column index m are arranged. 14. Plate catalyst according to claim 13, characterized in that the number m of columns is an even number, and that the plates ( 2 , 4 ) are alternately stacked on one another according to a scheme ababa, etc., with type b by turning type a around an axis of symmetry ( 8 ) parallel to the column direction results. 15. Plate catalyst according to claim 13 or 14, characterized in that in a row immediately adjacent deflection elements ( 14 , 16 ) protrude in opposite directions from the plate plane ( 18 ). 16. Plate catalyst according to one of claims 1 to 15, characterized in that the plates ( 2 , 4 ) to the main flow direction ( 12 ) inclined and from the plate plane ( 18 ) projecting undulating structure, and that the means ( 6 , 14th , 16 , 20 , 22 ) in the ge with respect to the plate plane ( 18 ) inclined surface elements of the plate ( 2 , 4 ) are arranged.