Technical field

[001 ] Invention relates to a catalyst element according to preamble of claim 1 .

[002] Invention relates also to a catalyzer assembly using a catalyst element and a method of manufacturing a catalyst element.

Background art

[003] Exhaust gas emission requirements of internal combustion piston engines become more and more stringent. In order to cope with such requirements there are various techniques available by means of which the gaseous emissions may be controlled when the engine is running. On the other hand, it is not desirable that the overall performance of the engine will suffer resulted from actions aiming to reduce the emissions.

[004] Especially catalysts are commonly used to speed up reactions of certain substances contained by the exhaust gases of internal combustion piston engines. Such substances are for example nitrogen oxides, hydrocarbons such as methane, carbon oxides etc.

[005] When utilizing a catalytic emission reduction system in connection with internal combustion piston engines there are several issues to consider. Firstly, the location of the system in the exhaust gas stream more or less defines the available temperature range in which the catalyst is to operate. Secondly, a risk of fouling and clogging is always an issue to consider, particularly in connection with engines operating with e.g. heavy fuel oil, although soot formation may take place with gas operated engines, too. Thirdly, the space requirements set of a catalytic emission reduction system are typically considerable. The general aim is to spend as little space as possible. A catalyzer in a large combustion engine comprises typically several catalyst elements which are arranged side by side filling the cross sectional area. In this kind of construction gaps between the elements needs to be sealed in appropriate manner. Typical solutions are for example fiber tape or steel plate profile blocking the gap. Both of these have drawbacks. Fiber tape or fabric needs compression to be fixed reliably and there is a risk of loose fibers blocking element interface on next catalyst layer in the flow direction of gas. Steel profile needs to be welded in order to be fixed reliably, but still there is a risk of loose parts.

[006] It is an object of the invention to provide a catalyst element by means of which a catalyzer assembly may be formed in straightforward manner. [007] It is also an object of the invention to provide a method of manufacturing a catalyst element.

Disclosure of the Invention

[008] Objects of the invention are substantially met by a catalyst element to be used in a catalyzer assembly as emission control device for gas, comprising a body to which a catalyst core is assembled, and which element comprises gas tight side walls and two opposite ends bordered by edges of the side wall, via which ends gas may be arranged to flow into and out from the catalyst core. It is characteristic to the invention that at the end of the catalyst element the body comprises an outward extension of its side wall edge folded from the plane of the side wall.

[009] By means of the outward extension the gap between two elements is closed when assembled in a catalyzer assembly.

[0010] According to an embodiment of the invention the body comprises an ex- tension at each side wall edge arranged substantially perpendicular to the side wall.

[001 1 ] According to an embodiment of the invention a number of successive extensions are extending inwards and a number of successive extensions are extending outwards. Advantageously the number is half of the number of sides of the element. This way the outward extensions are positioned on inward extensions of adjacent elements and the gap between two elements is efficiently closed when assembled in a catalyzer assembly.

[0012] In this context the terms inward and outward mean direction in respect to the plane of the side wall and the space embraced by planes of the side walls.

[0013] According to an embodiment of the invention the inward extensions and the outward extensions are formed so that adjacent elements may be locked with each other by the extensions when assembled side by side. When forming a catalyzer assembly an outwards extension of a first element lays on an edge of a sec- ond adjacent element, on which edge an inward extension of the second element is arranged so that the outward extension will be located on the inward extension.

[0014] According to an embodiment of the invention he body is formed of a gas impermeable sheet material.

[0015] According to an embodiment of the invention the extensions covers a gap between two adjacent elements on at least two directions when assembled side by side.

[0016] Objects of the invention are also met by catalyzer assembly for treating exhaust gas of an internal combustion engine, comprising a number of catalyst elements according to anyone of the claims 1 -7 arranged their side walls against each other so that the outward extensions of a first element are arranged on inward extension of other elements.

[0017] According to an embodiment of the invention the body is of square cross section and the outward extensions of a first element are arranged on inward extension of two other second elements. [0018] According to an embodiment of the invention the two adjacent catalyst elements are interlocked with each other by the outward extension and the inward extension of the side wall.

[0019] By interlocking it is meant locking of the articles with each other by the effect of the shapes or forms of the articles when brought together in appropriate manner. Thus, the extensions are provided with mating forms which, when brought together, prevent the movement of the elements at least in one direction.

[0020] When the element comprises extensions at two adjacent side walls they are orientated differently and so, they prevent movement at different directions. [0021 ] A catalyst element according to the invention may be manufactured in various manners, but considering the practical size of the element it is advantageous that the method of manufacturing a catalyst element comprising a steps of arranging a sheet of impermeable material of an elongated rectangular form, defining cross-wise folding positions, corresponding to a width of a side of a catalyst core to be used in the element, defining length-wise folding position corresponding to a length of the catalyst core to be used in the element, arranging a cut to the position of each cross-wise folding position extending from the edge of the sheet to the length-wise folding position, folding the sheet at the cross-wise folding positions and arrange the sheet to enclose the catalyst core, and folding the sheet at the length-wise folding positions so that extensions are formed of which a number of successive extension are extending inwards and a number of successive extension are extending outwards.

[0022] The other additional characteristic features of the invention will become apparent from the appended claims and the following description of the embodiments of figures.

Brief Description of Drawings

[0023] In the following, the invention will be described with reference to the ac- companying exemplary, schematic drawings, in which

- Figure 1 illustrates a section of a catalyzer assembly according to an embodiment of the invention,

- Figure 2 illustrates a top projection of a catalyzer assembly according to an embodiment of the invention,

- Figure 3 illustrates steps of manufacturing a catalyst element according to an embodiment of the invention, - Figure 4 illustrates a detail of the coupling between to two adjacent catalyst elements according to an embodiment of the invention,

- Figure 5 illustrates a top projection of a catalyzer assembly according to another embodiment of the invention, and

- Figure 6 illustrates a step of manufacturing a catalyst element according to another embodiment of the invention.

Detailed Description of Drawings

[0024] Figure 1 depicts a section of a catalyzer assembly 10 for treating exhaust gas of an internal combustion engine. The catalyzer assembly 10 comprises a number of catalyst elements 12 which are arranged their side walls 14 against each other forming a suitably unit to cover the cross sectional area of a gas flow channel of an enclosure in which they are arranged. The catalyst element comprises a catalyst core 16.

[0025] The catalyst elements 12 are separate units and they are installed side by side. A gap between the walls of the elements is sealed so that the gas is flowing through the catalyst core and not between the elements, at least to practical extent. In figure 2 there is shown a top projection of a catalyzer assembly 30 in which the cores of the catalyst is not present for clarity reasons. The catalyst element 12 comprises a body 18 which is manufactured of gas impermeable sheet like material such as metal plate. The body is formed by folding a properly cut piece of the plate as will be explained later. The catalyst element has two opposite ends 23 bordered by the edges 20 of the side wall, which is more clearly illustrated in figure 1 . As is clear from above the side walls are gas tight and the body forms a space for the catalyst core which is open at its ends. The catalyst core is placed into the body so that if flow channels are opening at the open ends of the body.

[0026] In the sheet material of the body there are arranged extensions 22 at the end of the body which have been folded to extend outwardly from the space of body 18 forming an outward extension of its side wall. The extension may be arranged generally perpendicular to plane of the wall 14 but it may be formed to have other than flat form. In this embodiment the body comprises four side walls 14 arranged perpendicularly to each other, thus the cross section is a square.

[0027] In the square body outward extensions 22 have been arranged to two of the adjacent side walls 14. This way the extension may be said to be successive. In two other side walls there are also extension 24 arranged but they have been folded to extend inwardly into the space of the body 18. Also the inward extensions may be arranged generally perpendicularly orientated in respect to plane of the wall 14. The inward extension may be formed to have other than flat form, even if not shown in the figures. The inward extensions serve for preventing the longitudinal movement of the catalyst core in the space inside the walls, on one hand.

[0028] A catalyzer assembly 30 comprises a number of catalyst elements 12 ar- ranged their side walls against each other so that the outward extensions 22 of a first element 12.1 are arranged on inward extension 24 of a second element. More particularly, when the body is square the outward extensions 22 of a first element are arranged on inward extension 24 of two other second elements. [0029] In figure 3 there is shown the main steps of manufacturing a catalyst element. In part 3a there is shown a piece sheet 50 of impermeable material of an elongated rectangular form, into which a number of cross-wise folding positions 52 are defined. In case the core to be used has rectangular cross section the body will need three folding positions to form the corners. The distance between the folding positions corresponds to a width of a side of a catalyst core to be used in the element. Additionally, a length-wise folding position 54 is defined, which corresponds to a length of the catalyst core to be used in the element. The length means the dimension in the gas flow direction in the core. Next a cut 56 is arranged to the position of each cross-wise folding position 52. This is shown in part 3b of figure 3. The cut is extending from the edge of the sheet to the length-wise folding position 54. The form of the cut is ruled e.g. by the fact if the extension thus formed will be an inward or outward extension. The sheet 50 is folded at the crosswise folding positions so and the catalyst core is arranged to be enclosed by the sheet as is shown in the part 3c. Additionally the sheet is folded at the length-wise folding position of each side wall so that extensions are formed of which a number of successive extension are extending inwards 24 and a number of successive extension are extending outwards 22.

[0030] In figure 4 there is shown a detail of the coupling between to two adjacent catalyst elements 12.1 , 12.2 being arranged their walls 14 against each other. As can be seen in the figure the two adjacent catalyst elements, the first catalyst element 12.1 and the second catalyst element 12.2, are interlocked with each other by the outward extension 22 and the inward extension 24 of the side wall 14. The outward extension 22 at least partly embraces the inward extension 24 and this way prevents the first element 12.1 moving away, sideways in the figure, from the second element 12.2. The outward extension may be also curved back under the inward extension, as is depicted by dashed lined, so that longitudinal, upwards in the figure, mutual movement is restricted. [0031 ] The extensions are here generally U-shaped so that the outward extension 22 substantially encloses and covers the inwards extension 24.

[0032] In figure 5 there is shown a top projection of a catalyzer assembly 30 of hexagonal cross section. In other respect it corresponds to the square one shown in the other figures. A hexagonal catalyst element is manufactured so that a piece sheet 50 of impermeable material of an elongated rectangular form is arranged, into which a number of cross-wise folding positions 52 are defined. In case the core to be used has hexagonal cross section the body will need five folding positions to form the corners. The distance between the folding positions corresponds to a width of a side of a catalyst core to be used in the element. Additionally, a length-wise folding position 54 is defined, which corresponds to a length of the catalyst core to be used in the element. The length means the dimension in the gas flow direction in the core. Next a cut 56 is arranged to the position of each cross-wise folding position 52. This stage is shown in the figure 7. The cut is ex- tending from the edge of the sheet to the length-wise folding position 54. The form of the cut is ruled e.g. by the fact if the extension thus formed will be an inward or outward extension. The sheet 50 is folded at the cross-wise folding positions so and the catalyst core is arranged to be enclosed in the similar manner as is shown in the part 3c. Additionally the sheet is folded at the length-wise folding position of each side wall so that extensions are formed of which a number of successive ex- tension are extending inwards 24 and a number of successive extension are extending outwards 22.

[0033] While the invention has been described herein by way of examples in con- nection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the invention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such a combination is technically feasible.