Multi-stage body with a multitude of flow channels, production and use

Description

TECHNICAL FIELD

[0001] The invention relates to a multi-stage body according to the patent claim STATE OF THE ART

[0002] The development of catalytic converters and particulate filters has given rise to a series of geometric channel structures, which are primarily manufactured using extrusion processes and feature a monolithic structure. These mostly ceramic bodies have a channel shape along their length and promote laminar flow, which adversely affects the wall contact of the exhaust streams to be cleaned. In contrast, catalyst supports wound from ceramic or metal foil, which may have punched and bent wall segments, but overall have a monolithic structure and, above all, offer only a small wall surface for accommodating the catalyst substance.Monolithic bodies that are mechanically connected to one another via the catalyst or filter housing are also known, for example in combination bodies with different catalysts, which are held more or less stably in their position by the packing pressure in the catalyst or filter housing, usually via a thermally swelling insulation layer.

[0003] While these systems usually have a binder layer that absorbs the catalyst using a wash-coat process, the direct coating of the ceramic monolithic channels with catalyst is also known and state of the art. The coating itself is not the subject of this discussion and can be found in published prior art.

[0004] DE 198 30 342 C1, DE 39 04 550 A1 and JP S49 1548 U disclose bodies with a plurality of flow channels. OBJECT OF THE INVENTION

[0005] The object of the invention is to develop a new generation of catalyst supports and filters with optimized flow behavior of the media passed through the support compared to the prior art, additionally optimized in the flow medium back pressure and in the flow medium temperature, if possible executable in ceramic as well as in metal, glass, plastic or in composites, in each case suitable for direct coating with catalyst and / or by means of an intermediate layer in the form of a so-called wash-coat.

[0006] This object is achieved by a multi-stage body for catalysts having the features of patent claim 1.

[0007] According to the invention, the solution for optimising the wall contacts of the media volume flow in catalysts and filters, especially in applications in hot gas operation such as combustion engine exhaust gases, is that it cannot only be a singular structural optimisation in the form of wall thickness deviations, geometric channel shapes such as square, rectangular, round or hexagonal, but that a multifunctional structural optimisation is required, which takes into account the aspects of turbulence in the flow within a media flow channel, the associated prevention of laminar paths and flow blockages, the associated pressure differences between the inlet and outlet of the media volume flow from the body, also referred to as pressure loss, the maximisation of the wall contact rate of the media volume flow and the differences in volume flow, media velocity and differential temperatures across the carrier cross-section,considered and solved constructively.,

[0008] With the development of generative manufacturing methods, new degrees of design freedom have emerged, leading to new optimizations of channel geometries through stereolithography, filament printing, powder bed printing, and selective laser sintering and melting processes for prototypes and small batches, as well as 3-dimensional screen printing for series production.

[0009] A cumulative analysis of individual flow channels within a catalyst carrier has shown that, with conventional monolithic structures, turbulent regions can only occur in the initial entry phase of the exhaust gas flow, but these only extend a few millimeters into the channel depth. Following this, the flow is largely laminar until the exhaust gas flow exits, with slight disturbances only occurring in the immediate vicinity of the flow at the channel wall. If the wall is aerodynamically rough, so-called flow blockages occur, particularly at elevated temperatures. As a result, large channel openings must be selected, resulting in significantly reduced channel wall surface areas. Furthermore, once the exhaust gas flow has entered a channel, it can no longer change.This is particularly disadvantageous if the exhaust gas volume flow is not evenly distributed before entering the body, as this can lead to an underload of the channel if the volume flow rate is low, and thus the catalytic effectiveness can only be partially utilized, and in the other case if the volume flow rate is high, the channel can be overloaded, and thus there is a risk of uncleaned exhaust gases escaping and possibly even flow blockages, which means that the catalytic effectiveness of this channel is close to zero.

[0010] These deficiencies were addressed by the invention of a completely new design of the catalyst or filter body. After coating each individual channel and the body with a catalytic substance, this improves the parameters of turbulent exhaust gas flow rate, increased wall contact of the exhaust gas flow rate, homogenization of the flow rate across the body cross-section, homogenization of the temperature profile across the body cross-section, minimization of the risk of flow blockage, reduction of the risk of regional overheating, and ultimately enables a reduction in body dimensions through increased efficiency. This innovative design offers the possibility of modifying the external component geometry, since the lower exhaust backpressure with a reduced body cross-section allows the length to be increased without any loss of power.This allows the residence time of the exhaust gas volume flow in the catalytically active body component to be significantly extended without reducing the volume flow or increasing the backpressure. The new design enables a wide variety of individual channel geometries, including squares, rectangles, hexagons, ellipses, and circles, as well as the use of dense materials, porous materials, ceramics, metals, glasses, plastics, and composites, while freely designing the external geometry of the body. It also allows the combination of changing channel geometries in the transverse direction (the X and Y axes), as well as in the longitudinal direction (the Z axis). A new design feature is that the body segments are functionally short in the Z direction to prevent the formation of laminar flows. DESCRIPTION OF THE INVENTION

[0011] Further advantages of the invention will become apparent from the dependent claims and from the following description, in which the invention is explained in more detail with reference to an embodiment illustrated in the schematic drawings. It shows: Fig. 1 shows two filter bodies arranged one above the other, Fig. 2 shows four filter bodies in top view, which are arranged offset from one another, Fig. 3 shows a plan view of two three-part flow channels, and Fig. 4 shows the material selection for possible areas of application.

[0012] In the figures, the same reference symbols have been used for the same elements and initial explanations apply to all figures unless expressly stated otherwise.

[0013] The following table shows the most important parameters of the new body compared to the state of the art: function in the longitudinal direction of the channel in the transverse direction of the channel in body transverse axis in body longitudinal axis Flow type turbulent turbulent turbulent turbulent Reactor surface high high high high catalytic activity high high high high Flow directions X,YZ X,YZ XY Z Volume flow in the duct different different . / . . / . Volume flow in the body . / . . / . distributed distributed pressure loss small amount . / . . / . small amount Temperature distribution homogen homogen homogen homogen Pressure shock sensitivity small amount small amount small amount small amount Risk of overheating small amount small amount small amount small amount Risk of hypothermia small amount small amount small amount small amount Flow blockages small amount small amount small amount small amount mechanical strength high high high high

[0014] The invention is also based on the finding that the volume flow entering a conventional channel has turbulences of only a few mm in the Z-direction, which are large enough to cause intimate wall contact and mixing behind the inlet phase and already after this short distance in the Z-axis direction assumes a more laminar character and the possible catalytic effectiveness decreases continuously due to the increasing laminar flow shape over the longitudinal axis.

[0015] The catalyst, filter body or reactor body 8 and 9 in Figure 1has surfaces which lead to turbulence in the flow direction, which acts as baffles 1 on the volume flow inlet side and as flow separation edges 2 on the volume flow outlet side. The baffles 1 and baffle edges 2 are arranged such that they do not occupy more than 75 percent of the cross-section of the individual flow channel. Preferably, but not exclusively, in the case of more or less rectangular, square, or hexagonal-shaped individual flow channels or individual ducts, and also possible in the case of round, elliptical, or freely formed individual duct geometries, it has been shown that the baffles 1 and separation edges 2 are arranged such that fluidic sub-channels 3, 4, and 5 are formed in the individual duct.

[0016] In the simplest design, an offset of two filter bodies 8 and 9 in Figure 2This means that an individual channel in the flow direction already forms baffles 1 and separation edges 2 after a section Z1. This results in the catalyst filter or reactor body 20 changing its structure at least once in the volume flow direction, in that the structural change is caused in the simplest case by an offset of the channel structures in the flow direction. Using the example of the rectangular individual channel, from which the invention for channel shapes other than rectangular channel cross-sections arises, the offset is caused by a displacement of the channel planes by each, but not exclusively, half a channel width in the X-direction and in the Y-direction. Figure 2 The offset is formed with the four filter bodies 8, 9, 10 and 11.

[0017] This arrangement in the simplest case means that the channel levels, relative to the individual channel, are connected to each other with at least four point surfaces in order to ensure the mechanical body strength and the thermal conductivity across the channel levels.

[0018] Surprisingly, it has been found that with sufficiently shallow plane depths, sustained turbulent flow can be generated without a significant increase in volume flow backpressure. Various tests and simulations have shown that the effectiveness of generating turbulent flow using baffles and separation edges, especially for channel cross-sections below 5 mm, does not extend significantly deeper in the Z direction than four times the channel diameter. A structural change occurs at every 2.5 times the channel diameter. The structural change occurs at least once within a body, but at most below X times the channel diameter.Preferably, but not exclusively, it has been shown for the exemplary rectangular channel with a clear channel width of 1.5 mm that a structural change between 2.5 mm and 7.5 mm, preferably every 5 mm, has the highest turbulence generating and maintaining factor.

[0019] During the considerations, it was found that the resulting volume flow division during the transition of the exhaust gas volume flow from one structural level to the next structural level has a beneficial effect on the catalytic effect due to the resulting cross flow. Further considerations have led to the conclusion that it is advantageous to design the turbulence-generating baffles 1 in such a way that the individual channel is divided into several sub-channels 12 and 13 (see Figure 3), which are directly connected to each other in the Z-axis direction. In the non-exclusive example of the rectangular channel cross-section cited, a three-way division of the flow channel into sub-channels 12 and 13 was achieved by means of two smaller baffles 1, which extend into the flow channel approximately the same thickness as the wall, and one baffle 1, which extends into the flow channel approximately half plus half the wall thickness. This exemplary division generated several effects that had a positive impact on the catalytic efficiency and flow: Increasing the wall area available for reactions per flow channel in the Z-axis direction by means of impact surfaces and separation edge surfaces. Increasing the wall area available for reactions per flow channel segment in the X,Y-axis direction by means of impact surfaces and separation edge surfaces. Increasing the wall area available for reactions per flow channel level in the X,Y-axis direction by means of channel outer wall surfaces not covered with connection point surfaces. Increasing the number of connection surfaces between the structural levels from the exemplary four to the exemplary eight connections with resulting improvement in structural stability.

[0020] Other shapes, dimensions, arrangements and number of sub-channels 12 and 13 are also possible.

[0021] Considering the exemplary example, with a clear channel width of 1.5 mm, a channel wall thickness of 0.25 mm, two impact surface sizes of 0.25 mm * 0.15 mm and a third impact surface size of 0.25 mm * 0.875 mm and an element depth of 5 mm, compared to a monolithic flow channel with a clear channel width of 1.5 mm, the following results: Conventional: Reaction area 30 mm 2< New example: Inner wall area 32.75 mm 2< + Impact surface + Breakaway edge area 3.25 mm 2< Total reaction area 36 mm 2<

[0022] This simple channel design already allows an increase in the reaction area of ​​more than 20%, which can be further increased or reduced by design.

[0023] In the example presented, the design with a 1.5 mm clear channel width represents a conventional 1.2 mm clear channel within the available reaction area. With the increased clear width compared to the conventional monolithic state-of-the-art design, the flow cross-section is not restricted by the additively integrated baffles 1 and separation edges. Thus, the segmentation of the flow channels in the Z-axis direction, in particular, prevents the development of laminar flows and simultaneously prevents the formation of flow blockages, without leading to a significant increase in the volumetric flow backpressure.

[0024] The inventive idea of ​​generating turbulence takes into account the fact that, especially with limited external dimensions, such as in a catalytic converter, a maximum of volume flow wall contact with continuous mixing of the flow in all directions.

[0025] For turbulent flow to generate a high wall contact rate of the exhaust gas volume flow, wall filtration, chemical treatment, for example as a chromatography body for technical or medical applications, at least four effects are available: One effect that generates turbulence is the impact of the exhaust gas flow onto the surfaces known as baffles that extend into the individual flow channels. Here, the flow splits, changing the flow direction in the X and Y axes while maintaining the main flow direction in the Z axis. Another effect that generates turbulence is the exit of the exhaust gas flow from the lower edges of the baffles. This creates flow turbulence in the X and Y axes while maintaining the main flow direction in the Z axis.A further effect on turbulence generation is the impact of the volume flow upon entering a duct segment on the duct wall not occupied by pre-ducts, forming a baffle with the volume flow being distributed into four adjacent individual ducts. The volume flow exits the individual duct when the duct wall is not occupied by subsequent ducts, forming a separation edge with the volume flow being distributed into four adjacent individual ducts. A further effect is the volume flow behavior within a segment of an individual duct. As in the example according to [source]. Figure 3As outlined, the individual channel consists of two short impact surfaces and one impact surface extending across the center of the channel. This creates a triple U-shaped inner channel structure, each opening towards each other. While in the two resulting smaller U-shaped channel segments 13, a volume flow oriented towards the U-bottom arises, favored by the open U-shaped side to channel section 12 with a reducing flow velocity, in channel segment 12 an increased flow velocity with wall development towards the U-bottom of segment 12 arises, which is also forced into a flow development by the flow roller from the two smaller channel segments. This circulation caused by wall friction is significantly intensified by the turbulence of the impact surfaces and separation edges.However, before a laminar flow can be established, the channel level changes with additional baffles through the outer walls of the channels of the following level, so that an intimate mixing of the entire volume flow within the individual channel takes place.

[0026] The above effects do not only occur with rectangular individual channels as in the example shown, but can also be applied to other geometric configurations of the channel shape.

[0027] Favored by the turbulent flow in all individual channels and channel segments, the entire volume flow is distributed at the transition to the next level, especially in the X and Y axis directions of the body.

[0028] This results in further positive effects even with uneven distribution of the volume flow when entering the body: The exhaust gas volume flow is distributed within the body at the transition from one structural level to the next structural level, with the distribution being divided into stages from the flow component from channel 1 of the first level into channels 1, 2, 3 and 4 of the second level. After being distributed in the second level, the distributed volume flow from channel 1 is further distributed in the third level to channels 1, 2, 3, 4, 5, 6, 7, 8 and 9. At the same time, the resulting volume flow components from the adjacent cells of the first level also enter the next channel level. The channel openness created by the levels and the offset of the channels to one another results in volume flow equalization across the body cross sections. Shortly after the volume flow enters, the entire body cross section can be used for homogeneous volume flow processing with uniform pressure and volume ratios at the same average flow velocity.A pressure increase in an individual channel can no longer lead to a cleaning loss because the proportional volume flow can be diverted to the subsequent neighboring channels. The pressure loss across the body cross-section is thus evenly distributed and conventionally disadvantaged body regions, especially the body edge areas and the center of the body, can no longer be overloaded or underloaded. As a result, the achievable efficiency in the multi-stage body 20 increases. With the volume flow division shown, the temperature is also homogenized between the channel levels in the body cross-section in two ways across the body cross-section. One homogenization part is the supply of energy via the volume flow distribution through the flow distribution across the body cross-section, the second homogenization part is the distribution of the reaction heat generated by reactions on the channel walls.By equalizing the temperature profile across the body's cross-section, a deficit in the peripheral areas and an excess in the center of the body can be largely compensated, so that hypothermia or overheating can no longer occur to the extent that is inevitable with the current state of the art.

[0029] Depending on the application requirements, not only the number of impact surfaces and separation edges but also their size and shape can be individually adapted and can also be designed differently within a single channel of a body plane and / or between the body planes. In terms of construction, a rectangular channel shape and an offset of half a channel width in the X and Y axis directions is the most sensible, especially when used as a catalyst carrier. A smaller or larger offset is also possible, which can be advantageous in certain applications, or a rotation with or without offset is technically advantageous. The adjustment of the impact surfaces and separation edges and the support point surfaces of the plane connections must be adapted in terms of their position, shape and number to the plane structure.This is made possible, in particular but not exclusively, by the production of the body using generative manufacturing processes, especially three-dimensional screen printing, followed by three-dimensional powder bed printing, selective laser sintering and laser melting, filament printing, and other processes less suitable for series production. While manual assembly of plane discs using traditional joining techniques such as gluing, decorating, screwing, clamping, soldering, or diffusion bonding is feasible to a limited extent for model creation without technical requirements for precision and durability, it is economically and technically unsuitable for single-unit or series production.

[0030] In Figure 4The materiality of the body is presented for the selection of possible areas of application and evaluated using three characteristics for the new body. XXX stands for unlimited, XXO for mostly, X00 for less suitable, and 000 for unsuitable. It goes without saying that the list of possible applications and suitability contains only an exemplary selection. This is illustrated by the example of implants which have a direct coating, for example, antibiotics or cytostatics, or the wash-coat in the form of collagen is suitable for displaying vital cells as a catalyst for growth integration in the organism. The multifunctionality of the chromatography field is also cited here.It is also understood that the filter mentioned is less suitable for wall penetration filtration, but rather for surface filtration, unless the body geometry according to the invention is followed by or preceded by an area with alternately closed channels.

[0031] The multi-level body, preferably designed as a catalyst support, can be manufactured from a variety of materials. Ceramics, metal, glass, and plastic, in either porous or dense form, are particularly suitable for technical applications. Plastics and organic materials, on the other hand, are more suited to use in the medical device and implant sectors for the new body. The inventive design also makes it possible to change the material for each body level if this is not already done during the production of the levels. It has been shown that, especially for use as a catalyst support, the channel shape is ideally suited to absorbing the catalytically active substance and making it sustainably available for the catalytic reaction. Both direct coating and coating using an intermediate carrier layer, the wash-coat, are suitable coating methods here.The same applies to chemical reactors and its use as a chromatography body, where the new body enables defined reaction and flow control. Defined and complete conversion reactions with identical time, volume, pressure, and temperature are particularly important for so-called biochromatography, the blood processing and purification process. The new body enables reproducible reactions without relying on statistical body distributions, as is the case with bulk chromatography bodies. The body's shape also makes it possible to recycle the body multiple times, or to clean and dispose of it separately after use.

[0032] As an example of the various application areas and dimensions, an example of a body for use as a catalyst support is shown below. A material template consisting of a mixture of cordierite and silicon carbide powder, mixed with an additive combination to form a screen printing mass, is processed using three-dimensional screen printing. The layout of the first forming tool, the printing screen, includes a series of catalyst support arrangements with the constructed first plane of the support and its outer shape, the inner support structure containing the catalyst support channels.After printing the first support level at a height of 5.0 mm selected here, the second forming tool is printed with the channel geometry offset by ½ the channel width in the X and Y axes and rotated by 90°, whereby the outer geometry of the bodies in this printing level is congruent with that of the first printing level, also up to a height of 5.0 mm. The resulting 10 mm print height is followed by the third forming tool, the fourth forming tool, and so on, until the entire body height is reached. The printed body is then separated and fired in a thermal sintering process until the desired strength is achieved. This also involves the release of the printing additives. In the present example, the fired catalyst support, which here is made of a porous material, is impregnated with a solution of rare earths, the composition of which has a catalytic effect, using vacuum assistance.After the excess catalyst has been removed, it is bonded to the composite composition of the carrier material made of cordierite and silicon carbide in a further thermal firing process.

[0033] In the geometric design of the example, the catalyst carrier has an outer diameter of 100 mm. The outer wall of the carrier is reinforced with a wall thickness of 0.5 mm compared to the wall thicknesses of the channel structures. In the example shown, the channel structures consist of quadrilaterals with an outer wall thickness of 0.25 mm and a clear channel width of 1.5 mm. While a baffle element / separation edge element with a width of 0.25 mm and a depth extending into the channel of 0.15 mm is arranged centrally on one and the opposite channel side walls, there is a baffle element / separation edge element with a width of 0.25 mm and a depth extending beyond the channel center of 0.875 mm on one of the remaining channel walls.The channels in the next plane of the body then sit with their side walls on the centers of the side walls of the preceding channel and the center of the long impact surface element, and are firmly bonded to them by the subsequent sintering process. In addition to the impact surfaces 1 and separation edges 2, the individual channels thus formed have an internal channel structure with two small U-shaped and one wider U-shaped sub-channel opposite each other, with the U-shaped openings of the sub-channels abutting against each other.

[0034] In one variant, the baffle elements and the separation edge elements are designed slightly wider than the subsequent channel wall thickness, creating additional offset planes in the overlapping areas that increase turbulence. This design is more suitable for slow-flowing gas streams, as the time factor for gas passage through the body in the Z-axis direction is usually desired.

[0035] The example given can now be easily applied by the expert to other applications, materials, external geometries, channel shapes, internal channel shapes, baffle surface shapes / tear-off edge shapes and their number and dimensions, as well as to different body element heights, as well as the shape and application of a possible catalytic or reactive coating in the direct coating and / or wash-coat process.

[0036] Another exemplary example shows an absorber body made of a silicon carbide mass with appropriate sintering, which is used in solar energy generation, here preferably in stationary solar tower power plants and mobile dish energy generators. In this special embodiment, the design of the impact surface elements and the separation edges in the first body level are larger than in the body for catalysts. For example, the impact surface elements are 0.3 mm wide and also 0.3 mm deep, with the third impact surface portion having a width of 0.25 mm and a depth of 1.25 mm. This dimensioning of the first body level is primarily suitable for absorbing solar energy and is calculated to be correspondingly thin with a level thickness of 3.5 mm, since vertical solar radiation can hardly penetrate deeper into the structure.The body planes following the first body plane serve to conduct heat from the first body plane and transfer the heat to the flow medium, which in the case of tower power plants is usually air. After the heated air exits the absorber, it is used for conventional energy generation using turbine technology or, in the case of excess supply, for feeding into heat storage systems.

Claims

1. Multi-stage body having a multiplicity of flow ducts, characterized in that the body has, in the individual flow duct in the flow direction, at least one turbulence-generating surface which forms a non-closed sub-duct and is connected to the duct wall and which, on flow entry, forms a baffle surface (1) and, on flow exit, forms a tear-off edge (2) for the flow, in that the body has a plurality of duct structures which are arranged in connection one after the other and form a stepped transition to one another in the flow direction, the baffle surface (1) and the tear-off edge (2) being arranged such that they occupy not more than 75 percent of the cross section of the individual flow duct, and in that the body is produced by generative production.

2. Multi-stage body according to claim 1, characterized in that a side wall element projects into each flow duct as baffle surface (1), which side wall element forms the baffle surface (1) on the flow entry side and the tear-off edge (2) on the exit side, and in that the baffle surfaces (1) and tear-off edges (2) serve to bring about a turbulent flow.

3. Multi-stage body according to claim 1 or 2, characterized in that the duct wall as catalyst support is coated with a catalytically active substance of the rare earths directly and / or via an intermediate support.

4. Multi-stage body according to claim 1 or 2, characterized in that the duct wall as catalyst support is coated with a catalytically active substance of the transition metals directly and / or via an intermediate support.

5. Multi-stage body according to claim 2, characterized in that the baffle surfaces (1) and tear-off edges (2) divide the individual flow duct into more than one sub-duct which are connected to one another and which each have an open side with respect to one another.

6. Multi-stage body according to claim 5, characterized in that the sub-ducts are formed in a flow duct have different levels of wall friction which serve to bring about rolling of the flow over the side walls in the flow direction.

7. Multi-stage body according to claim 6, characterized in that the baffle surfaces (1) and the tear-off edges (2) divide the flow duct into at least three sub-ducts which are open on one side and of which at least one sub-duct part has a larger throughflow area than the at least two remaining sub-flow ducts.

8. Multi-stage body according to one of claims 1 to 7, characterized in that the flow direction (Z) forming the body is divided into more than one plane, and in that each duct position of the following plane is arranged offset and / or rotated in the X direction and in the Y direction transversely to the flow direction with respect to the duct position of the preceding plane.

9. Multi-stage body according to claim 8, characterized in that, by offsetting the position of the following ducts with respect to the preceding ducts, additional baffle surfaces and tear-off edges are formed from those parts of the end sides of the duct side walls which are not occupied by side wall elements, with baffle surfaces or with tear-off edges of the adjacent body planes.

10. Multi-stage body according to claim 9, characterized in that the individual flow duct in one body plane merges into two different individual ducts of the following plane in order to divide the volume flow.

11. Multi-stage body according to claim 10, characterized in that the individual duct connections are arranged such that a pressure distribution, a temperature distribution and a volume flow distribution take place over the body planes.

12. Production of the body according to at least one of claims 1 to 11 by a method of generative production, in particular by a 3-dimensional screen printing and / or by a 3-dimensional powder bed printing and / or by a 3-dimensional laser sintering and / or a 3-dimensional laser melting and / or a filament printing.

13. Production of the body according to claim 12, characterized in that the body is produced from ceramic, glass, metal, plastic, organic substances or composites.

14. Use of the body according to at least one of claims 1 to 11 in the automotive sector as catalyst support or as filter or as combined body.

15. Use of the body according to at least one of claims 1 to 11 in the energy sector as absorber or heat exchanger.

16. Use of the body according to at least one of claims 1 to 11 in the chemical sector as chemical reactor or chromatographic body.

17. Body according to at least one of claims 1 to 11 for use as medical implant, as growth scaffold or as washer.