Method for improving coating of honeycomb body with catalyst activity coating agent

Abstract

The invention relates to a method for producing an apparatus for aftertreatment of exhaust gases and for coating a honeycomb body (1) arranged in said apparatus with a catalytically active surface coating agent, the honeycomb body (1) being formed from at least partially structured metal sheets which are stacked on top of one another and rolled up so that the honeycomb body defines a number of flow channels through which a flow can pass along a main flow direction, the honeycomb body being accommodated in an inner shell (2) and permanently connected to said inner shell (2), which is arranged in an outer shell (6) acting as a housing and permanently connected to said outer shell (6), and prior to the application of the catalytically active coating agent into the flow channels formed by the honeycomb body (1), one or more voids (7) formed between the outer shell (6) and components arranged in said outer shell (6) are filled with a filler (8).

Description

Technical Field

[0001] The present invention relates to a method of manufacturing an apparatus for post-treating exhaust gas and coating a honeycomb body provided in the apparatus with a catalytically active surface coating agent, wherein the honeycomb body is formed from a plurality of at least partially structured metal sheets, these sheets are stacked and wound on top of each other, whereby the honeycomb body forms a plurality of flow channels through which flow is possible along the main flow direction, the honeycomb body is accommodated in an inner shell and permanently joined to this inner shell, and the inner shell is arranged in and permanently joined to an outer shell serving as a housing.

Background Art

[0002] A honeycomb body for a catalyst for post-treating the exhaust gas of an internal combustion engine has a plurality of flow channels through which flow is possible along the main flow direction. The honeycomb body, especially a honeycomb body made of metal, is formed by a large number of smooth and / or at least partially structured metal sheets, which are stacked and wound on top of each other to form the final honeycomb body. The substrate formed from the metal sheets is inserted into a housing for stabilization and protection against mechanical external factors and is permanently joined to this housing.

[0003] In the simplest case, the housing is formed by a tube configured to accommodate the substrate inside. Another function of the housing is to ensure the flow through the honeycomb body and in particular to avoid the flow of exhaust gas outside the honeycomb body.

[0004] The fixing of the substrate in the housing must occur continuously on the one hand, and at the same time the housing is required to be configured as lightweight and thus thin-walled as possible. Some embodiments of the catalyst have an inner shell that directly accommodates the substrate. In this case, this inner shell is supported by the housing or the outer shell via a suitable support.

[0005] Devices in the prior art have the disadvantage that, in particular, voids occur between the individual elements of the catalyst, for example between the inner shell and the outer shell. These voids can be blocked by the catalytically active material, the so-called washcoat, during the coating of the substrate with the washcoat. Due to mechanical vibrations and thermal effects during operation, the material fixed in the voids can separate, which can cause damage and / or catalytic inactivity of components arranged downstream for exhaust gas aftertreatment.

[0006] Furthermore, the washcoat supplied into the gaps does not participate in the catalytic reaction in the honeycomb body and thus has the disadvantage of not functioning. Therefore, the amount of washcoat actually required to coat the honeycomb body is inherently small. If the washcoat contains expensive noble metals, the unnecessary large consumption is particularly disadvantageous. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0007] Accordingly, an object of the present invention is to provide a method that enables the honeycomb body in the housing to be coated as accurately as possible with the minimum necessary amount of washcoat, and in particular to avoid supplying the washcoat to areas that do not participate in the catalytic reaction. MEANS FOR SOLVING THE PROBLEM

[0008] The problem regarding the method is solved by a method having the features of claim 1.

[0009] One embodiment of the present invention is a method for manufacturing an apparatus for post-treating exhaust gas and coating a honeycomb body provided in the apparatus with a catalytically active surface coating agent, wherein the honeycomb body is formed from a plurality of at least partially structured metal sheets, these sheets being stacked and wound on top of each other, whereby the honeycomb body forms a plurality of flow channels that can be flowed through along the main flow direction, the honeycomb body is accommodated in an inner shell and is permanently joined to this inner shell, the inner shell is arranged in an outer shell that serves as a housing and is permanently joined to this outer shell, and prior to the supply of the catalytically active coating agent into the flow channels formed by the honeycomb body, one or more voids formed between the outer shell and the components arranged in this outer shell are filled up with a filler.

[0010] A basic method for manufacturing an apparatus with a honeycomb body in an inner shell that is permanently accommodated in an outer shell is known based on the prior art. The substrate is formed by stacking at least partially structured metal sheets on top of each other and then winding the laminate thus formed around one or more mandrels. After the substrate of the honeycomb body is inserted into the inner shell, it is joined to the inner shell, for example, by a brazing process.

[0011] The inner shell is preferably configured to be extremely thin and substantially serves to stabilize the substrate, thereby preventing the substrate from unfolding or spreading out in a fan shape.

[0012] Thereafter, the honeycomb body is inserted into a housing formed by the outer shell, which serves as a closure for the environment, and is permanently joined to this housing, for example, by brazing. The outer shell is significantly thicker than the inner shell, guides the flow of exhaust gas, mechanically protects the honeycomb body, and serves to attach it to other components for exhaust gas post-treatment.

[0013] In particular, between the inner shell and the outer shell, gaps are formed based on errors or simply based on the geometry of the individual components. Usually, a gap extending over the entire circumference in the circumferential direction occurs between the inner shell and the outer shell. In this case, the void extends regularly in the axial direction only along a partial section near where the inner shell and the outer shell are in contact. Such voids form a hollow chamber that allows access from the exhaust gas flow section, which is a volume enclosed within the outer shell.

[0014] To coat the substrate, the coating material is, for example, pushed through the flow path of the substrate by positive pressure or sucked through the flow path of the substrate by negative pressure. Thereby, the surface of the flow path is coated, and thus a catalytically active surface where a chemical reaction with the exhaust gas occurs is provided. The supply of the coating material also causes the supply of the coating material to the structure outside the substrate, and in particular, the coating material penetrates into the formed voids and stays there. As a result, on the one hand, the amount of the coating material remaining in the device increases significantly, and furthermore, the coating material separates from the voids during operation. Thereby, the coating material is entrained in the exhaust gas flow and may damage the components for exhaust gas aftertreatment arranged downstream in the flow direction. In particular, when a catalytically active material comes into contact with another catalytically active material in another honeycomb body, so-called poisoning occurs. In this case, a chemical reaction occurs that completely or at least partially destroys the catalyst arranged downstream. Therefore, it is urgently necessary to avoid the deposition of the catalytically active coating material in areas where it is not provided for coating.

[0015] To prevent the penetration of the coating material into the voids, the voids are filled with a filler prior to the supply of the coating material. This filler may be supplied into the gap, for example, by an injection needle.

[0016] The filler is not pushed back by the supply of the coating material and is cured to such an extent that it does not flow out of the voids naturally or is not sucked out of the voids.

[0017] The filler may preferably be supplied into the voids through an opening from the outside of the outer shell. Alternatively, the filler may be supplied directly into the voids from the open cross-section of the outer shell.

[0018] It is particularly advantageous if the filler is a gel-like organic material. The gel-like organic material is advantageous in ensuring that the entire void can be quickly and easily filled by directly injecting the filler into the voids. The filler preferably has material properties that enable injection into the voids. Furthermore, since the filler is formed to achieve sufficient strength inside the voids, the filler cannot be easily sucked out of or extruded from the voids.

[0019] It is also advantageous to supply the filler into the gaps and then subject the device to subsequent heat treatment, such as drying or calcination. This is advantageous because drying or calcination achieves a distinct temperature increase in the device, and since the filler preferably has limited thermal stability, it is no longer stable or completely dissolves after a certain temperature action.

[0020] A preferred embodiment is characterized by removing the filler from the voids after the supply of the catalytically active coating agent. This is advantageous for removing the filler before the start of operation of the device. Otherwise, during operation, the filler may separate from the voids under mechanical loads and thermal interactions. And the flow path may become clogged or the components in the exhaust gas system may be damaged.

[0021] It is also suitable to remove the filler from the voids by a thermal process. This is advantageous because the honeycomb body or the entire device usually passes through a plurality of process steps, and in these process steps, a significantly elevated temperature acts on the honeycomb body or the entire device. Therefore, without providing an additional working step, it can be ensured that the filler is heated above the critical temperature for this filler, thereby dissolving the filler.

[0022] Furthermore, it is advantageous to fill the voids such that the open cross-section closer to the supply location for supplying the catalytically active coating agent is closed by the filler. This is particularly important to ensure that the coating material can never adhere within the voids. This is ensured by the closure of the open cross-section.

[0023] In a preferred configuration, the filler may be configured to expand after supply, and in some cases, a portion of the supplied filler amount bulges out of the voids, thereby ensuring that the coating material cannot enter the voids.

[0024] Advantageous improvements of the present invention are described in the dependent claims and the following description of the drawings.

[0025] Hereinafter, the present invention will be described in detail based on an embodiment with reference to the drawings.

Brief Description of the Drawings

[0026]

Figure 1

Embodiments for Carrying Out the Invention

[0027] Figure 1 shows a cross-sectional view of an apparatus for post-treatment of exhaust gas. In the center, a honeycomb body 1 formed from a metal substrate is disposed. This honeycomb body 1 is housed within an inner shell 2. This inner shell 2 positions the substrate, protects against spreading and unfolding into a fan shape, and at the same time protects the substrate against mechanical influences. Honeycomb bodies of this structural form are known in a wide variety of forms in the prior art.

[0028] In Figure 1, on the upstream side of the honeycomb body 1, a heating disk 3 coupled to the honeycomb body 1 via support pins 4 is disposed. This heating disk 3 is connected to a voltage source via the electrical feed-through 5 shown in the figure and can thus be energized. Thereby, a temperature rise is achieved.

[0029] The honeycomb body 1 is inserted into an outer shell 6 with its inner shell 2 and is continuously joined to this outer shell 6, for example, by brazing. A gap 7 is formed between the outer shell 6 and the inner shell 2. This gap 7 may be intentionally created based on the component geometry or may be formed based on errors between the components. Also, gaps are basically assumed between all components of the apparatus.

[0030] In the embodiment of Figure 1, since the gap 7 is filled with a filler 8, nothing can penetrate into the gap 7, especially from the side closer to the heating disk 3.

[0031] The wash coat that coats the substrate of the honeycomb body 1 is, for example, pushed into the honeycomb body by positive pressure and / or drawn through the honeycomb body by negative pressure. Also, the honeycomb body 1 may be flushed with the wash coat. In all of these processes, if the gap is not closed, the probability that the wash coat will penetrate into the gap 7 is extremely high.

[0032] The filler is accurately supplied into the gap 7, for example, by an injection needle, whereby the gap 7 can be filled up, especially the open cross-section can be filled up.

[0033] The embodiment of FIG. 1 does not have particularly limiting features and is used to clarify the idea of the present invention.

Explanation of Reference Numerals

[0034] 01 Honeycomb body 02 Inner shell 03 Heating disk 04 Support pin 05 Electrical feedthrough 06 Outer shell 07 Gap 08 Filler

Claims

1. A method of manufacturing a device for post-treating exhaust gas and coating a honeycomb body (1) provided in the device with a catalytically active surface coating agent, wherein the honeycomb body (1) is formed from a plurality of sheets of structured metal, at least partially, the sheets being stacked and wound on top of each other, whereby the honeycomb body forms a plurality of flow channels that are flowable along the main flow direction, the honeycomb body being housed within and continuously bonded to an inner shell (2), the inner shell (2) being disposed within and continuously bonded to an outer shell (6) acting as a housing, in the method, prior to the supply of the catalytically active coating agent into the flow channels formed by the honeycomb body (1), filling one or more voids (7) formed between the outer shell (6) and components disposed within the outer shell (6) with a filler (8).

2. The method according to claim 1, characterized in that the filler (8) is a gel-like organic material.

3. The method according to claim 1 or 2, characterized in that the filler (8) is supplied into the voids (7) and then the device is subjected to a subsequent heat treatment, such as drying or calcination.

4. The method according to claim 1, characterized in that the filler (8) is removed from the voids (7) after the supply of the catalytically active coating agent.

5. The method according to claim 1, characterized in that the filler (8) is removed from the voids (7) by a thermal process.

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