RU2064053C1 - Catalytic unit for cleaning waste gases and method of its manufacture - Google Patents

Abstract

FIELD: cleaning waste gases. SUBSTANCE: catalytic unit has gas-permeable roll formed by layers being wound whose surfaces are coated with catalyst applied on metal oxide; one layer is made of corrugated steel band and other layer is made in form of stack of wires and is located in way of winding for intersection with corrugations of adjacent layer; at point of intersection, layers are pressed one in other. Method of manufacture of catalytic unit consists in corrugation of steel band on rolls, passing of layers through guide at simultaneous winding of layers in roll accompanied by heating of both layers by passing the electric current. Then oxide layer is formed on surfaces of roll and catalyst is applied to it; one layer is formed by stack of wires; both layers are subjected to forced tension. Electric current is supplied to guides. Winding of roll is effect by means of additional roller which is kept in pressed state. Electric current may be also supplied to guide of layer and to additional roller. Guide of layer formed by stack of wires is reciprocated in direction perpendicular to direction of winding. In this case, deformed areas are located in passage in different sections. EFFECT: saving of catalyst; increased yield of product. 6 cl, 7 dwg

Description

 The present invention relates to the field of mechanical engineering, namely, devices that reduce the content of harmful substances in the exhaust gases of automobiles.

A device for cleaning exhaust gases is known, the honeycomb structure of which is formed of flat and corrugated tapes rolled up into a spiral roll so that numerous through channels are formed [1]
The manufacturing method described in the patent provides for the welding of flat and corrugated tapes between each other at the points of the oscillating laser gun before forming a roll, and its activation after the formation of the roll. Such a catalytic unit has a low cleaning efficiency due to the establishment of a laminar gas flow and the formation along the walls of the channels of the hydrodynamic boundary layer, limiting the transfer of mass of gases to the catalyst after the disappearance of the turbulization effect at the entrance to the channels.

 The disadvantage of the manufacturing method is the low strength of the honeycomb structure due to the fact that the weld points are quite rare and during winding into a spiral roll, the adjacent welded (double) layers are not fastened together, which does not exclude their displacement relative to each other due to the pulsation of the gas flow acting per roll together with high temperature and vibration. The displacement of the layers is accompanied by a violation of the catalytic layer and the shedding of the catalyst, which leads to a decrease in the cleaning efficiency.

The closest in technical essence to the proposed version of the block is a catalytic block, consisting only of corrugated steel tape, the corrugations of which are made at an angle to the edge of the tape. This tape is wound in a spiral roll so that the ridges and troughs of the corrugations of adjacent layers intersect each other, resulting in intersecting gas channels, and at the intersections of the ridges and troughs of adjacent layers are pressed one into the other [2]
This application describes a method for manufacturing a catalytic unit, including corrugating a steel strip, winding a coil with simultaneous heating of the tape between two electrodes, which ensures that the crests and troughs of the corrugations of the adjacent layers are pressed in at their intersections, the formation of the oxide layer on the tape surfaces and the deposition of catalyst on it.

 Such a catalytic unit has high strength, its layers are reliably fixed from displacement relative to each other. Due to the turbulent nature of the gas flow throughout the block, it has an increased degree of purification. It should also be noted its manufacturability for blocks with a diameter of up to 140 mm (for cars).

A disadvantage of the known technical solution is that the method does not allow with a high degree of quality stability to produce blocks with a diameter of more than 150 mm, used for cleaning exhaust gases of cars with an engine capacity of more than 3 liters. This is due to the fact that with an increase in the diameter of the block, the moment of a pair of friction forces arising between the forming roll and roller electrodes, the preload force of which reaches 30 kg, increases the force acting on the winding mandrel and the central turns of the corrugated tape. As a result, the mandrel begins to experience large torsional deformations, and the corrugations of the tape, starting from the central turns, are straightened and wound one on top of the other. The cellular structure is deformed and the block loses strength. In this case, the yield of products in production is about 20
The aim of the invention is to increase the yield of products with a large section of the block.

 This goal is achieved by the fact that in the known catalytic unit containing a gas-permeable roll formed by wound layers, the surfaces of which are coated with a catalyst deposited on a metal oxide, one of the layers in the block is made of corrugated steel tape, and the second layer is located in the winding direction with the possibility of intersection with corrugations of the adjacent layer and at the intersections, the layers are pressed one into the other, the second layer is made in the form of a set of wires.

 A method of manufacturing the inventive device differs from the known method in that in addition to corrugating the steel strip on the rolls, passing layers through the guides, simultaneously winding the layers by passing an electric current, forming an oxide layer and applying a catalyst, one of the layers is formed from a set of wires and both layers are tensioned with effort.

 In order to create a roll having an equal or different density structure of the channels, namely, to obtain a rational, in terms of gas dynamics, structure, the degree of deformation in the process of winding is varied by the speed of winding, the magnitude of the current and the tension force of the tape and wires. Thus, a change in the winding speed depending on the number of winded turns leads to an increase or decrease in the time of heating of the corrugations in the places of their contact with the wires, a change in the current value leads to a change in the degree of heating of the wires, a change in the tension force leads to a change in the amount of indentation of the wires into the corrugations.

In accordance with one of the proposed options, an electric current is supplied to the guides in contact with the tape and wires. In this case, an electrical circuit is formed: wire guide wire roll
corrugated tape tape guide. To create additional deformation forces of the corrugations, the winding is produced using an additional roller, which is supported in a compressed state with a roll. The preload force during the winding process is kept constant or changed depending on the number of wound turns.

 In accordance with another embodiment of the manufacturing method, an electric current is supplied to the guide layer formed by a set of wires, and to an additional roller, which is in a pre-tensioned state with the forming roll with a force providing for the deformation of the corrugations. In this case, the roller captures the entire length of the roll, as a result of which all points of intersection of the wires with the crests of the corrugations are deformed. The preload force during the winding process is kept constant or varies depending on the number of winded turns. Formed in this case, the electrical circuit includes a guide wire wire roll roller electrode.

 To increase the channel cross section and reduce hydraulic resistance, the guide of the layer formed by a set of wires is moved back and forth in the direction perpendicular to the winding direction. In this case, the deformed places are located along the channel in different sections.

 Figure 1 shows a catalytic unit, its gas permeable structure; in FIG. 2.3 options for possible deformation of the corrugations and the placement of wires; in FIG. 4,5,6,7 diagrams illustrating the proposed options for a method of manufacturing a gas-permeable roll.

 The catalytic unit 1 contains one corrugated metal strip 2 of X23U5 steel and several wires 3 of an alloy with high electrical resistance, for example X20H80 or X23U5. The tape and wire originate in the center of the block and turn by turn, overlapping each other, wound into a gas-permeable spiral roll of a round or oval shape. The wires 3 are located in the direction of winding across the crests of the corrugations 4 of the tape 2 and, in order to strengthen the roll, and also to exclude the possibility of displacement of the spiral turns of the tape and wires relative to each other, the wires are pressed into the corrugations adjacent to them by an amount of h. This value is 0.1-0.5 of the diameter of the wires d = 0.5 mm and, depending on the specific application conditions, it is the same in the whole volume of the roll or different from the center to its outer surface, i.e. the roll has equal or different density structure. In most cases, for rational organization of the gas flow, the roll should have a density decreasing from the center to the outer surface. At h = 0.5d, adjacent turns of the tape overlap each other, contacting in some places with each other by crests of corrugations, thus forming numerous through channels. At h <0.5d, the corrugated turns of the tape do not contact each other and a gap is formed between their ridges in the form of a single spiral slit of height S. In this case, the roll has one spiral through channel, the surfaces of which are formed by a corrugated tape.

 In addition to fastening, wires play the role of flow turbulators and are located along the length of the channel at a certain distance from each other t≅25 mm, namely 10 mm. This distance is determined from the gas flow conditions, the required strength of the roll and directly affects the cleaning efficiency.

 In a roll, the spiral turns of each individual wire are located in one plane perpendicular to the longitudinal axis of the roll, or pass along a helical line, the direction of which after each turn or several turns is reversed (from right to left and vice versa).

 The roll is made of tape with a thickness of 0.05 mm and a width of 90 mm. The corrugations are made in the form of triangles, trapezoids or a sinusoid 1.2 mm high. The corrugations of the corrugations with respect to the edge of the tape are at right angles.

 The roll contains 9 spiral wound wires.

The block is coated with a noble metal catalyst Pt and Rh
The catalyst is supported on alumina, which in turn is attached to the surface of the oxidized tape.

 During operation, the exhaust gases flow through the end surface of the unit into the channels. Passing through them and actively mixing, the gases come into contact with the catalytic layer, after which, purified from harmful components, they exit at the other end of the block.

 The method is as follows.

 Smooth steel tape 5 from the feed coil 6 is passed through the corrugation rolls 7, forming corrugations on the tape, the ridges of which are located at a right angle to the edge of the tape. Next, the corrugating tape passes along the guide roller 6 and is wound around the axis O in a spiral roll 9, and at the same time the wires 3 made of alloy with high electrical resistance are wound from the feeding coils 10 and passing along the guide roller 11. On the rollers 8.11 supply voltage U. The current passing through the wires and the corrugated tape provides heating of the wires, which in turn are heated at the points of contact of the corrugation. The tension force of the wires and tape ensures the deformation of the corrugations in these places.

 During the winding process, the degree of deformation of the corrugations varies with the winding speed, a change in the rotation speed n (10-60 rpm), the current and voltage U (5-24 V), as well as the tension force of the tape and wires, i.e. these parameters are kept constant throughout the entire winding cycle, or some of them, individually or jointly, vary depending on the number of winded turns. Winding can be done using roller 1 from a material with low thermal conductivity, which creates an additional deformation force P (5-15 kg), which is maintained constant or changed during winding.

 The voltage can be applied to the roller 11 and the roller electrode 13 (see Fig. 6). In this case, the roller electrode is used not only to supply electricity, but also to provide a deformation force P, which is also kept constant or changed during the winding process.

 The method provides an option for manufacturing a roll, in which the deformed places are located along the channel in different sections. To do this, an axial reciprocating movement of the guide roller 11 is performed in the direction perpendicular to the winding direction, as shown in FIG. 7.

 The rollers 8.11 and the roller electrode 13 are made of copper. The width of the roller electrode is 2-5 mm greater than the width of the tape.

 Roller 12 (see figure 5) is made of textolite. The alumina carrier is baked to steel. The catalyst was deposited by impregnating the support with Pt and Rh salts, followed by their reduction.

 Using the present invention will allow the manufacture of catalytic blocks of large cross section without significant loads on the winding mandrel and the central turns of the layers. In the production of blocks with a diameter of more than 150 mm, the yield of the product, compared with the prototype, increases from 20% to 98% YYY2 YYY4 YYY6

Claims (6)

 1. The catalytic unit of the exhaust gas catalyst containing a gas-permeable roll formed by wound layers, the surfaces of which are coated with a catalyst deposited on a metal oxide, one of the layers is made of corrugated steel tape and the other layer is located in the winding direction so that it can intersect the adjacent layer with corrugations moreover, the layers at the intersections are pressed one into the other, characterized in that, in order to save catalyst, another layer is made in the form of a set of wires.  2. A method of manufacturing a catalytic unit by corrugating a steel strip on rolls, passing layers through rails, simultaneously winding layers into a roll with heating both layers by passing an electric current, forming an oxide layer on the surface of the tape and applying a catalyst to it, characterized in that, In order to increase the yield of products with a large cross section of the block, one of the layers is formed from a set of wires and both layers are subjected to tension with effort.  3. The method according to p. 2, characterized in that the electric current is supplied to the guides.  4. The method according to PP. 2 and 3, characterized in that the winding of the roll is carried out using an additional roller, which is supported in a pre-tensioned state with the roll.  5. The method according to PP. 2 and 4, characterized in that the electric current is supplied to the guide layer formed by a set of wires, and to an additional roller.  6. The method according to PP. 2-5, characterized in that the guide layer formed by a set of wires is moved back and forth in a direction perpendicular to the direction of winding.

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