FI116237B - A catalyst for the treatment of gases and a process for its preparation and operation - Google Patents

Description

116237

A catalyst for the treatment of gases and a process for its preparation and operation

The invention relates to a catalyst for the treatment of gases. The invention also relates to a process for making such a catalyst and controlling its operation.

Technology background

For the treatment of gases, such as exhaust gases, cell-mounted catalysts are commonly used in gas pipelines. The cell has channels through which gas is passed. The ducts of the cell generally have catalytically active substances on their surface which can be used to transform the substances contained in the gas into a less harmful form. The cell can be connected to the catalyst and the cell can be internally reinforced with eg connecting pins and connecting plates. Connecting nails and plates are particularly used in metallic structures coated with catalysts prior to assembly of the catalyst co-15. Welding or soldering may also be used to connect the catalyst components.

The exhaust gas treatment catalyst is usually installed in a ·· ... exhaust pipe as close to the engine as possible to ensure efficient operation and to • • • • • • • • • • • • • • When heated, the catalyst must reach a certain Ignition Temperature 'before it can operate. On the other hand, the catalytic converter installed near the engine is subjected to very high loads as the fuel is burned at the highest possible temperature to improve efficiency - ':' 1 and reduce emissions.!! mode. Thus, the temperature of the catalytic converter cell with gasoline-powered engines 25 rises easily above 1000 ° C. However, the mechanical and thermal resistance of the catalyst is * significantly improved if it can be used, for example, at 1000 ° C; * ··. 800-900 ° C.

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Even at high temperatures, the operating conditions of the catalyst may be impaired. In this case, it will no longer function properly, eg at high engine speeds. The catalyst should therefore be warmed up, for example, when starting the engine; 1: and, as the exhaust temperature rises, it should be cooled.

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The reduction of nitrogen oxides with hydrocarbons under mild conditions occurs at a relatively narrow temperature range. For the Pt catalyst this range is 200-300 ° C and for the metal 2 116237 oxide catalyst is 300-600 ° C. Similarly, NOx adsorption catalysts (NOx trap) typically operate in the temperature range of 150-550 ° C and are thermally destroyed when the temperature rises above 700-800 ° C. In these applications, it is necessary to both prevent excessive temperatures and to keep the temperature at a suitable operating temperature. The reducing agent required for the reduction of nitrogen oxides, such as fuel or a special reducing agent, is fed by a separate injection into the exhaust gases into the exhaust manifold or by subsequent enrichment in the engine.

In particular, various heat transfer solutions have been proposed for use with Pt catalysts. Often a separate heat exchanger is used to cool the exhaust gases. However, a separate heat exchanger substantially increases the thermal mass and causes pressure losses in the exhaust system. If the car heat transfer medium is used in the heat transfer of the catalyst, both the heat transfer of the catalyst and the cooling system of the car will be damaged in the event of malfunctions and corrosion, and the engine may also be damaged. However, when the engine is started, the heat exchanger must often be bypassed to prevent it from cooling the exhaust gases. This results in technically complex solutions and the equipment is often also susceptible to malfunctions, eg valves.

The temperature of the catalyst can also be adjusted. There is known (DE 34 37 477) a method of heat transfer of a catalyst cell, in which the exhaust gas ducts of the cell are cooled by means of crosswise heat transfer ducts. A catalyst (US 5 987 885) has also been developed in which exhaust gas flows in catalyst tubes which are cooled by heat transfer air blown around them. In both of these processes, catalyst control is accomplished through relatively complex stand - alone techniques. under construction.

* '25 General Description of the Invention

A catalytic converter for gas treatment has now been invented, in which the connection of the components and the control of the catalyst are carried out in a very simple technical manner. Now, * · · 'ί -V is also an invented method for making and using such a catalyst.

: V; To achieve this object, the invention is characterized by the features set forth in the independent claims. Other claims disclose some preferred embodiments of the invention.

The catalyst according to the invention has a hollow coupling means for connecting the cell to which substances can be introduced for adjusting the said catalyst or any other catalyst connected to the gas pipeline. The material introduced into the hollow fitting means may be 3 116237 mm. a heat transfer agent, or any other material that affects the function or properties of the catalyst, such as a reducing agent, an oxidizing agent, or a catalyst. The action of the agent may be directed to the catalyst to which the agent is introduced or, for example, to another catalyst behind the catalyst. The conducting of the substance can influence e.g. catalyst and improve its mechanical and thermal resistance.

There may be one or more hollow coupling means in the same catalyst. The hollow coupling means may be mounted through the cell or may also be partially in the gas channel of the catalyst, preferably in front of the cell. One or more catalysts 10 according to the invention may be present in the same gas pipeline.

According to one object of the invention, a heat transfer medium may be introduced into the hollow coupling means for adjusting the catalyst. The heat transfer medium may be a gas such as air or exhaust gas, a liquid or a salt. The hollow connecting means can be used for heat transfer for both cooling and heating. The carbon-15 and hollow mounting structures of the catalyst act as a heat exchanger mounted in a gas stream.

For example, exhaust gas may be introduced into the hollow coupling means before or after exhaust gas flows through the catalyst cell. In this way, a very uniform temperature is obtained in the cell. Some of the hollow coupling means may be used to cool the cell 20 and some may be used for heating, whereby the heat-Yi state of the catalyst can be adjusted with great flexibility already by means of the exhaust gas. With the catalyst of the invention, the entire gas pipeline can be used as a heat exchanger and the catalyst can be either heated or cooled as appropriate.

·: ··· The use of hollow coupling devices has the essential advantage of not requiring, for example, separate external heat transfer equipment in the catalyst. In addition, the thermal mass of the catalyst does not increase significantly compared to e.g. female nail attached to the cell. Thus, the heat transfer in the YY catalyst of the invention is technically very simple. Also, the use of coupling means as heat transfer devices does not substantially increase the gas flow resistances, whereby the pressure loss of the catalyst remains low.

Y The temperature of the exterior surface of the catalyst, which is adjustable by the heat transfer medium, may also be kept at desired values, whereby the amount of insulation and shielding plates may be reduced.

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It is an object of the invention that the hollow coupling means are substantially opposed to the direction of flow of the gas to be treated in the catalyst. The heat transfer between the hollow coupling means and the gas is then effective because a particularly good heat transfer is formed between the outer surface of the hollow coupling means and the gas against which it is filed.

In the catalyst of the invention, the hollow connecting means are hollow screws having helical teeth. These have, for example, a multiple heat transfer surface area compared to, e.g., cavity nails, and are simple to install because the screws can be easily threaded through the cell. The screw helical teeth serve as effective heat transfer pads. The foils in the cell are effectively attached between the helical teeth of the screws, and the mobility of the foils is clearly less, especially when using stress, than when using smooth nails, for example. The gas can also efficiently pass the hollow screw in the cell so that it does not cause a great loss of pressure. When using a smooth nail, the gas flow is easily blocked and the heat transfer is also reduced.

15 The height, density and pitch of the tooth can influence the heat transfer efficiency and the mechanical resistance of the cell. The toothing of the hollow screws may be different at different points of the screw and some teeth may also be missing. The serration of the hollow screws can be selected to fit the distance between the foils. In the case of sparse toothing, the height of the toothing may be high, whereby most of the screws cover the radial direction. Few teeth also do not damage the honeycomb structure. With denser teeth -: 'i'; The la cell can be effectively supported while increasing the heat transfer surface.

At both ends of the screw there may be a nut, * ··· * on the outside and / or inside of the housing, which can be used to tighten, for example, a thin-shell circular, oval or race track 25 cell into a tight structure. The shell may even collapse slightly when tensioned, which mechanically supports the structure.

: The coupling means may also be only partially hollow in the axial direction, whereby the heat transfer '! Λ * material does not flow through the coupling means, but as if it were flushing the cavity from one side or both sides.

, ···. The hollow coupling means may have different directions relative to one another. The location of the hollow coupling means may be selected such that, for example, the heat transfer can be centralized, e.g. to the front or center of the catalyst cell, whereby the heat transfer may be directed to the most intense reaction zone. Connecting means can be installed e.g.

so that they are crossed with each other. The coupling means of the cell having a circular cross-section 5116237 can be mounted at an oblique angle with respect to one another, thereby forming the fan-like heat transfer apparatus in which the heat transfer is most effective in the center of the cell.

The catalyst cell of the invention may have an open-coated catalyst-5 structure consisting of a smooth and shirred foil pair. In this case, nail penetration is typically required to reinforce the cell, which is secured by welding to the shell around the cell.

Highly efficient heat transfer in the catalyst of the invention is achieved by the use of a foil ribbon wrapped obliquely in the cell with respect to the direction of gas flow, which is folded over the cell at appropriate intervals. In an oblique folded structure, the material transfer, and hence the heat transfer, is remarkably efficient also in the radial direction compared to straight cellular structures. Thus, a duct network is formed in the cell, in which the material and heat transfer are efficient, but whose structures do not have to be welded or soldered by assembling small pieces.

15 The foil tape can be coated as a straight foil before the cell assembly and even before the foil is shirred. By using open plating and hollow jointing means, very thin foil tape (e.g., 30-80 µm) and small channel sizes (e.g., 10-300 holes per cm 2) can be used. Hollow connection means can also be used in soldered or welded cells to improve heat transfer and strength.

* · * * The catalyst is particularly effective when it has two slanted cells in a row: shirred foil with foils at 90 ° to each other and also at 90 ° to the cells . This results in a 3 D blend where the catalyst is as efficient as possible and its heat transfer is also optimal. In addition, the hollow coupling means may be located axially at different locations within the cell so that the gas collides with the hollow coupling means as efficiently as possible.

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'·· * The height and width of two cells mounted in series may be substantially different, e.g., the width of one cell may be 2-10 x the width of another cell, whereby joining two 30 cells together in addition to the ducts in the space causes effective •. mixing zone. The direction of installation of the mixing foils may be parallel or shorter.

An open coated foil strip is manufactured, for example, by spraying the strip on both sides with a coating material before assembling the cell. On the other hand, the finished honeycomb structure 6 116237 can be coated, for example, by immersing it in a slurry containing catalysts.

The catalyst control agent can be directed to the hollow coupling means via a separate transfer means. The transfer means may be, for example, a pipe, piping or nozzle mounted at the end of the hollow connection means 5. The conveying means may also be part of the catalyst housing and cell through which the catalyst control agent is introduced into the hollow coupling means.

The transfer means may be, for example, a recess in the catalyst casing, which may be provided with separate air guide plates. The outside air is then directed through the slots of the shell 10 into and out of the hollow connecting means. In this case, the catalyst is technically simple and very cool, since, for example, heat transfer air can be passed directly through the catalyst casing. The air baffles of the recesses may be shaped so that as the vehicle speed increases, the amount of air directed to the hollow coupling means increases. Thus, the cooling of the catalyst is enhanced as the engine speed rises and the temperature of the gases increases.

When adjusting the temperature of the catalyst, for example, the heat transfer fluid may be directed through the transfer means to the hollow coupling means either by a separate fluid circulation or may be derived, for example, from the vehicle heat transfer system. The salt used in the heat transfer of the catalyst cell can be fed from its own separate heat transfer system. Molten salt recycling equipment can also be connected to this.

; For example, air can be directed to the hollow coupling means by means of a barrier pressure from the front end of the vehicle due to the drift. The air then flows through the transfer means to the hollow catalyst coupling means.

The heat transfer medium may be further led from the hollow connection means to the outside air of the transfer means, or the heat transfer medium may be recycled, e.g., through a separate heat exchanger, to the hollow connection means. Transferred to the heat transfer medium: The heat can also be utilized in other functions of the car. The separate heat exchanger may also be substantially within the hollow connection means. There may also be a heating resistor or other heat source within the hollow connection means.

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* ·; · “30 According to one object of the invention, the active ingredient of the catalyst ·: ·: can be introduced into the gases to be treated, e.g., inside the catalyst or in the gas pipeline. For some of the hollow coupling means, for example, a heat transfer medium, such as air, may be introduced, for example, outside the catalyst, and for some of the hollow coupling means, the material may be introduced, e.g.

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When introducing cooling air, for example, into the exhaust gases, it is possible to utilize the vacuum created by the exhaust gas flow. Hereby, the hollow coupling means and the cooling air transfer means are arranged such that the exhaust gases do not flow into the hollow coupling means, but the exhaust flow causes a vacuum which absorbs 5 cooling air along the transfer means into the hollow coupling means. In some cases, this arrangement may replace the use of a blower or a vacuum cleaner. The direction of exhaust gas flow can be ensured for sudden pressure fluctuations by installing a non-return valve in the transfer means or the hollow connection means, which prevents the flow of exhaust gas into the transfer means.

10 The cooling air supplied to the exhaust fumes increases the amount of air needed for combustion, which is useful when the exhaust gas mixture ratio is rich. If cooling, for example, of an? Adsorption catalyst followed by an oxidation or 3-act catalyst, it is preferable to introduce cooling air into the exhaust, whereby carbon monoxide, hydrogen, hydrocarbons, hydrogen sulfide and ammonia are effectively removed from the exhaust gas. The additional air introduced between the catalysts makes the mixture lean, whereby the emissions from the rich catalyst in the front catalyst can be eliminated in the rear catalyst. The catalyst of the invention may also be provided behind a standard NOx adsorption catalyst or a SCR catalyst in which nitrogen oxides are reduced with ammonia or derivatives thereof.

The catalyst of the invention may also be provided behind an uncoated or catalytically coated particle separator, such as a particulate trap. air and other catalyst or particulate trap agents, such as strong oxidants, can be used to enhance the combustion of soot. Additional air can be used to increase the formation of nitrogen dioxide, which promotes the combustion of soot.

Through the hollow coupling structure, not only air but also other active ingredients in the catalyst can be introduced into the gas to be treated. Such materials include, for example, NOx reducing agents such as ammonia, urea and hydrocarbons. Among the gases, i: can also be controlled, for example, liquids, such as reducing agents, which, while evaporating inside the cell, also cool it.

According to an object of the invention, the agent affecting the operation of the catalyst may be introduced into a hollow coupling means from one of the shells of the catalyst or gas pipeline. For example, when regulating the temperature of the catalyst, i >> introduced into the jacket space. the temperature of the heat transfer medium can be adjusted to either colder or hotter temperatures. The diaper space may, for example, be like the diaper space between the catalyst shell and the cell support structure, the diaper space between the catalyst support structure and the catalyst shell, or the diaphragm space of the front cone or tube in front of the cell.

According to one object of the invention, the material flow can be adjusted, if necessary, by means of a control device, such as a valve 5, connected to the transfer means or the hollow connection means. The position of the regulator can, in turn, be adjusted by means of a measuring sensor mounted in, for example, the gas pipeline, the catalytic converter, or the piping of the substance used to adjust the catalyst. The gauge can be used to measure, for example, temperature, pressure or the concentration of a particular compound such as nitrogen oxides, ammonia, carbon monoxide, hydrogen sulfide, hydrogen or hydrocarbons in the gas. The actuator can be completely closed, for example, when the engine 10 is started and, when the exhaust gas temperature rises, the actuator is adjusted so that the temperature of the cell is optimal for its operation and mechanical and thermal resistance. Since the regulator is in this case separated from the exhaust gas and only air, for example, flows through it, its operating conditions are good.

15 The flow of the heat transfer medium can be controlled by other control devices, such as a pump, fan or vacuum, in addition to the valves. Such a technique can be used, for example, when the vehicle is moving at low speed or suddenly stopped at high speed, whereby, for example, the airflow caused by the drifting force is not efficient enough to cool the catalyst alone. Also in stationary engines 20, the catalyst may be cooled by means of a separate pump or fan, or heat transfer means of a machine engine may be used to direct the heat transfer medium.

The hollow coupling means according to the invention can be used in various catalysts. Catalyst cells may be, for example, open-stacked or rolled, soldered or welded. The shape of the cell may be, for example, folded over, superimposed: V, spirally wound into S or J. Also, the material of the cell and the catalyst of the cell channels may vary. Preferably, the material of the cell is a thin metal foil. The good heat transfer of the metal cell will equalize the temperatures at the front of the cell, even if the hollow connecting means is in the center of the cell.

Although the heat transfer surface area of the catalyst according to the invention is generally: "markedly smaller than that of the massive solid heat exchangers themselves, the relatively small heat transfer fluid flow, especially when. . when the temperature of the gas being treated is high. The heat transfer depends, for example, on the temperature difference between the exhaust gas and the heat transfer medium, the heat transfer area and the flow rates. For example, the heat capacities of air and exhaust gas are substantially equal to 9116237, whereby a small drop in temperature, e.g. 50-100 ° C, is already achieved with a relatively small amount of air when the air temperature rises 100-500 ° C in hollow connecting means.

The catalyst of the invention can be used, for example, to purify the exhaust gases of all engines where catalyst control is a problem.

It is suitable for use in, for example, 3-point applications, as well as in the treatment of exhaust gases from 2-stroke light engines, diesel engines, light gasoline engines (eg GDI engines) and natural gas engines or biogas engines. The same structure can also be used in processes or syntheses where similar catalyst structures can be used and the catalyst needs to be adjusted. By means of the structure according to the invention it is possible, for example, to adjust the temperature of the catalyst, for example, or to add substances necessary for improving the purification process.

Specific Description of the Invention Some embodiments of the invention will now be described in detail with reference to the accompanying drawings.

Figure 1 shows a catalyst in which a slanted cell is connected to the shell of a circular catalyst by cavity screws.

* · *: Fig. 2 shows a catalyst in which a straight cell is connected to the casing of a circular catheter: ν '20 by means of hollow screws.

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Fig. 3 shows a catalyst mounted in a gas pipeline having hollow screws in different directions.

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1, a skewed cell 2 is connected to the housing 3 of the catalyst 1 by means of cavity screws 4. A heat transfer medium 5 has been introduced into the cavity screws 4; The threaded teeth 7 of the screws 4 serve as an efficient heat transfer surface and at the same time

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. ·, Also effective in securing the foils of the cell 3 9.

: ** [: In Figure 2, a direct cell 6 is connected to the shell 3 of the catalyst 2 by means of the cavity screws 4. A heat transfer medium 5 has been introduced into the cavity screws 4. The threaded teeth 7 of the cavity screws 4 * * * 'act as an effective heat transfer surface and at the same time also effectively seal the foils 8 of the cell 3.

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In Figure 3, a catalyst 61 is mounted in the exhaust piping 68-68 ', the cell 62 of which is connected to the housing 63 by means of the hollow screws 64, 64'. The hollow screws 64 and 64 'are perpendicular to one another. The cell 62 also has a cavity nail 64 "inside it to support the cell and increase the heat transfer surface. Gas 67 flows through catalyst 61 from tube 68 to tube 68 '. Air may be introduced into cavity tubes 64 and raw gas 64 may be introduced into the cavity tubes 64'. the head as air, which then cools the front of the catalyst and warms it at the rear.

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Claims (19)

Catalyst used in the treatment of gases, said catalyst having a cell (2) and which cell has been connected to any other part of the catalyst by means of a connector, characterized in that the connector is one or more hollow connectors (4). ) which has threaded teeth (7) attachment of the cell (1, 2): 20 foils (8, 9), and to which a hollow connector (4) can be directed substances for control of the catalyst. • » Catalyst according to claim 1, characterized in that the hollow connection means (4) are substantially directed towards the direction of flow of the exhaust gases. • »• · Catalyst according to claim 1 or 2, characterized in that two or more components are present. The various connectors (84, 84 ') are different in relation to each other. Catalyst according to any of the preceding claims, characterized in that one or more transmission means (86), such as a pipe, a pipe network, a channel, a nozzle, a part of the catalyst shell or the catalyst, is connected to the iv: hollow connector (84) a part • . of the cell, for transferring the substance used to control the catalyst to the catalyst or from the catalyst. * · * • 4 Catalyst according to any of the preceding claims, characterized in that the hollow connector (105) or the transfer device (107) is such that the substance used for controlling the catalyst can be guided from a hollow screw (4) to the gas treated inside the the catalyst or gas pipeline network. Catalyst according to any of the preceding claims, characterized in that the hollow connector (74) or the transfer device (79) has a regulating device 5 (78) for controlling the flow, such as a valve or pump, for controlling the flow of the substance. which is used to control the catalyst. Catalyst according to any of the preceding claims, characterized in that the gas pipeline network (68), the catalyst (71) or the raw material for the substance used for controlling the catalyst has a measuring detector (77), whereby a control device (77) provides the control device ( 78) for flow control is regulated. Process for the manufacture of a catalyst used in the treatment of gases, characterized in that the catalyst cell is connected to any other part of the catalyst by means of one or more hollow connectors (4) to which can be directed a substance used for controlling the catalyst, and that the hollow connector (4) has threaded teeth (7) for attaching the foils (8, 9) of the cell (2, 6). 9. A method for controlling the function of a catalyst used in the treatment of gases and having a cell (2) and a shell (3) connected to each other by means of a connector, characterized in that the catalyst cell is connected to any other part of the catalyst by means of one or more inhalable connectors, and that one or more inhalable applicators have been used: connectors (4) which have threaded teeth (7) for attaching the foils (8) of the cell (2, 6). · * 9), and substances for control of the catalyst are directed to the connector (4). t " ': Process according to claim 9, characterized in that the substance used for controlling the catalyst is a gas, such as air, exhaust or flue gas, a liquid or a gas which is gasified or a solid which is converted to a gas. liquid. in Method according to claims 9-10, characterized in that the substance used for controlling the catalyst is directed to the hollow connector at the catalyst by means of the air draft or the heat exchange system of the engine. • I A method according to claims 9-11, characterized in that the substance used for controlling the catalyst is guided to the hollow connector by means of. . the negative pressure caused by the flow of the gas to be treated into the hollow connector. 116237 Process according to claims 9-12, characterized in that the substance used for controlling the catalyst, such as a heat exchanger, is circulated via a separate treatment unit, such as a heat exchanger. Method according to claims 9-13, characterized in that the catalyst is controlled by a tool, such as a heat resistor or a heat exchanger, which tool is located in the hollow connector (4) or in a device connected to the hollow connector. Method according to claims 9-14, characterized in that the substance used for controlling the catalyst is controlled from the hollow connector (105) to the gas being treated, such as into the catalyst (101 ') or in the gas pipeline network. Process according to Claim 15, characterized in that the substance used for controlling the catalyst is treated with a catalyst or gas pipe network connected to another catalyst, cell or other device, such as an oxidation catalyst, a 3-function catalyst, a NOx adsorption catalyst. , an SCR catalyst or with a catalytically coated or uncoated particle separator. 17. A method according to claims 9-16, characterized in that the substance used for controlling the catalyst is directed to the hollow connectors from the casing space of the catalyst and / or gas pipeline network, as well as from the shell space of the catalyst and the cell catalyst structure, from the mantle space between the catalyst support structure and the catalyst shell or from the mantle space for the front cone or tube located in front of the cell. • · · * · » 18. A method according to claims 9-17, characterized in that the flow of the substance used for controlling the catalyst is controlled by a control device, such as a valve or pump. • · t 1 1 25 Method according to claim 18, characterized in that the control device is controlled; By means of a message from a measuring detector mounted in the gas pipeline network, in the catalytic converter and / or in the transmitting means or in the flow meter of the substance used for the control of the catalyst. • · • 1 I I • I I »1 * 1 (11 * 1 I ·» t t I »·