DE1289537B - Process for cleaning exhaust gases from internal combustion engines by catalytic oxidation - Google Patents

Description

1 2

Due to the increasing importance of bedding is led by different activities,

and widespread application of the invention according to the invention the secondary air when reaching a

internal combustion engines, especially in motor vehicles due to the thermal instability of the catalytic converter used

testify, the steadily increasing urgency of the accelerator moves to the limited temperature of the first, more active one

inclination of the with the during the combustion 5 catalyst bed before the second catalyst bed

Process through the exhaust gases mixed with the exhaust gases or in the second catalytic converter

ambient atmosphere is introduced more and more into the foreground.

and makes improvements to the previously known. In this way, it is possible to

Cleaning process that meets today's requirements- certain temperature of one or the other

struggled as a result of the increase in combustion power - the catalyst bed - as soon as the temperatures continued

machines no longer meet the requirements. increase - eventually the greater amount of

The task is to divert the when operating secondary air from the first bed and directly Combustion engines, in particular to allow power to flow into the second catalyst bed. The vehicles, escaping harmful combustion process can be controlled by a controllable valve system products, which in particular carbon monoxide and 15 run continuously, in which, depending on the occurrence of hydrocarbons contained in considerable quantities, the temperature a lesser or greater amount A large amount of secondary air flows through the catalytic converter system before it escapes into the atmosphere going to render harmless. This happens after or bypasses it completely. But it is also possible known method by post-combustion to supply secondary air in excess and to this by using the exhaust gases to achieve a cooling effect through appropriate contact 20, whereby one is beds are directed into which one or more of an automatic or semi-automatic control Contacts containing catalysts, e.g. B. can serve in grainy by shut-off elements. Form, are arranged, wherein the exhaust gas flow to- Such a catalyst system is allowed by means Additional air is supplied and the resulting mixture is regulated by means of a catalyst for the secondary air supply Oxidation over catalysts in a relatively high activity, which is subjected to a number of containers around which the first bed is susceptible to a temperature of 1000 ° C borrowed combustible materials in the exhaust gas stream of a normally running engine destroying electricity. With such a system, in developing, temperatures between 300 and which z. B. to maintain two catalyst beds or chambers 700 ° C in the first catalyst bed, are used, it is advantageous to refer to the catalyst system described above in the first bed 30 an active catalyst and in the second bed an on the normally running engine for protection having less active ones. This guarantees against malfunctions due to excessively high temperatures to ensure the "cold start period" of starting the half of the first catalyst bed. It The vehicle undergoes rapid catalytic oxidation and engine conditions occur in which rapid heating of the second bed due to air and partially or unburned fuel mixture the exothermic reaction in the first bed. That cause excessively high exhaust gas temperatures However, the first bed is inevitably not big enough. B. Long running with pulled starum to carry out a complete oxidation. To flap or misfire one or more Completion of the oxidation therefore leaves the cylinder, so that the catalyst is switched off so far as possible on the warmed up second bed. So- 40 systems or a diversion of the combustion gases As far as the second bed is also active, one is required. It is therefore also a regulator Oxidation to be desired, since with a tion of the exhaust gas flow by means of known ones highly active catalyst temperatures are created using temperature-controlled shut-off elements, high enough to damage excessively hot gases from either the first or digen. 45 derive from both catalyst beds.

The invention was therefore based on the task of- Furthermore, in the catalyst system, to create a catalyst system which, in addition to the catalyst beds, has a muffler on the one hand, the content of flammable components, or sound absorbers, so that - if such as B. carbon monoxide and hydrocarbons, exhaust gases bypass the catalyst bed completely in the exhaust 50 of the motor vehicle and the damping effect of the catalyst beds the exhaust gases under reliable functioning of the catalytic converter no longer exists - an excessive noise lyser system significantly reduce the ability to develop is avoided. A suitable execution is and which, on the other hand, has a long service life, for example. B. in it, the gases at the Kataly possessed, so that it bypasses the requirements in particular satorsystem, so that they are in the room when used in motor vehicles is sufficient. 55 between the catalyst bed and the housing wall gelan-Unter »Reliable function« is to be contrasted here, whereby within this space there are one or more, that by suitable means or arrangement rere layers of damping materials underneath System of the disturbing influence of an excessive are brought, which expediently the Kata temperature development within the catalyst bed - in the case of several layers, e.g. B. in shape systems is avoided. 60 nested hollow cylinders - surrounded. Ge

The object on which the invention is based can optionally be applied to the other, which is the catalyst

is achieved by the fact that when cleaning the ab- sator bed facing away from the gas flow in the

gases through catalytic oxidation of which part or area of the housing wall is still another from catalytic

unburned constituents provided by the exhaust gases through lysatormaterial of existing hollow cylinders

be a catalyst system arranged in the exhaust. This arrangement ensures that the

are directed, the exhaust gas flow together with the exhaust gas flow diverted by an or

Secondary air required for oxidation is passed through several layers of sound-absorbing material,

at least two separate catalytic converters, with the exhaust gas flow on one side being the

outer surfaces of the catalyst bed and on its other side the housing wall or there provided second catalyst layer touches. In this way, on the one hand, noise attenuation is achieved and on the other hand a certain afterburning due to contact with the periphery of the catalyst system maintained without excessive heating of the catalyst material.

The method according to the invention is explained in more detail with reference to the drawing. It shows

F i g. 1 a cleaning system for exhaust gases from internal combustion engines in longitudinal section,

Fig. 2 shows a cleaning system for exhaust gases from Motor vehicle engines in longitudinal section,

3 shows a cleaning system in cross section along the line AA in FIG. 2.

One recognizes in FIG. 1 a housing 1 in which a catalyst bed system 2, preferably centrally is arranged. The catalyst bed system 2 consists of a first catalyst bed 21 with catalyst supports 212 of relatively high activity and a second catalyst bed 22 with catalyst supports 222 less activity. In the first catalyst bed 21 opens a - from an engine, not shown coming - exhaust gas supply line 3, which has a branch line 31 which extends outside of the Catalyst bed 21 opens into the space between the catalyst system 2 and the housing 1. Between the branch of the branch line 31 from the exhaust gas feed line 3 and its confluence In the catalyst bed 21 there is a regulatable and controllable valve 33, which with arranged in the branch line 31 further valve 32 z. B. via a control device 34 in FIG There is an effective connection. Is within the exhaust gas supply line 3 before or after the valve 33 a temperature sensor (thermocouple) 35 is arranged, which actuates the valves 32,33.

A secondary air feed 4, which is a branch line, opens into the exhaust gas feed line 3 41 to the second catalyst bed 22. A valve 43 is provided in this branch line 41, which is connected to another valve 42 arranged in the secondary air supply 4 a control device operated by a thermocouple 45 located in the first catalyst bed 21 44 is in operative connection. This valve 42 can, if necessary, have less of an overpass line 46 Be bridged diameter than the secondary air supply 4. Within the catalyst beds 21, 22 are the catalyst supports 212,222 of different activity. The arrows I, II and III show the route taken by the exhaust gas secondary air flow through the catalytic converter system.

The F i g. 2 leaves essentially the same elements as in FIG. 1 recognize. The catalyst beds 21, 22 are also arranged one behind the other in the housing 1, but in such a way that the housing 1 is divided lengthwise into an upper space 11 and a lower space 12. That Catalyst bed 21 contains the catalyst supports 212 with high activity and the catalyst bed 22 contains the Catalyst support 222 with lower activity. Both catalyst beds 21, 22 are surrounded by a partition 5, which still divides the lower space 12 into a front section 122 and an outflow section 121, which carries the exhaust gas outlet connection 13, divided, separated from each other. The partition 5 takes in its part located in the lower space 12, the valve 32 for diverting the exhaust gases from the catalyst bed system 2 (cf. also FIG. 1), which are opened and closed by the control device 34 can. The control device 34 also gets its impulse here from the thermocouple 35, which is arranged in the exhaust gas feed line 3. The valves are in the secondary air supply 4 42, 43 attached so that the valve 43 of the secondary air opens the way to the upper space 11 or and the valve 42 blocks the secondary air supply to the exhaust gas jet in the exhaust gas supply line 3 regulates. The air supply is adjusted via the control device 44 via the one in the catalyst bed 21 located thermocouple 45 controlled.

In Fig. 3 shows the housing 1 in cross section along the line AA, the same reference numerals from the previous figures also being applicable here. The valve 32 is in the open position

ao shows.

The cleaning process can (FIG. 2) take place in such a way that the hot exhaust gases enter the front section 122 of the lower space 12 and with the valve 42 open and valve 43 closed mixed with secondary air. The exhaust gas-air flow passes through the openings 211 into the catalyst bed 21, whereby the exhaust gases are further catalytically burned, then reach the upper one Space 11 through the opening 221 of the second catalyst bed 22, with not yet burned fractions are further burned again, and enter the environment via the outflow section 121 in the connector 13 mainly as carbon dioxide and water vapor.

When the temperature in the catalyst bed 21 rises above a predetermined value, it switches through the thermocouple 45 the valve 42 off and the valve 43 on, so that the secondary air over the Space 11 is passed through the catalyst bed 22 and exits through the nozzle 13 in the direction of arrow III. It is also in special cases, which depend on the size of the plant and the nature of the combustion gases direct, possible to amplify the secondary air by regulating the valve 42 so that a cooling effect in the catalyst bed 21 is achieved. In the event that the exhaust gases have too high a temperature have, through the thermocouple 35 arranged in the exhaust gas supply line 3, the Valve 32 is opened and the exhaust gases are ejected directly through the outlet port 13, whereby they are only limited Perimeter come into contact with the catalyst beds 21, 22.

By arranging hollow cylindrical or shell-shaped noise-dampening elements, which are not shown in the drawings for the sake of clarity, and which may optionally be limited by a layer of catalyst-containing material in the area of the housing wall 1, the noise effect of bypassing the catalyst beds 21, 22 when the engine is idling exhaust gas flow that is no longer attenuated can be attenuated by the noise-absorbing elements and at least partially further burned through the outer catalyst layer.
In the arrangement according to FIG. 1, it is expedient to prefer hollow-cylindrical noise-absorbing elements and in the arrangement according to FIG. 2 shell-shaped elements located in the lower space 12.

Claims (1)

Claim: Process for cleaning exhaust gases from internal combustion engines, especially from motor vehicles, by catalytic oxidation of their partially or unburned components by the Exhaust gases are passed through a catalyst bed system arranged in the exhaust, the exhaust gas flow together with the necessary for oxidation Secondary air through at least two separate catalyst beds of different Activity is directed, characterized in that the secondary air at Reaching a temperature limited by the thermal stability of the catalyst used of the first, more active catalyst bed is admixed with the exhaust gases before the second catalyst bed or is introduced into the second catalyst bed. 1 sheet of drawings