DE9002743U1 - Device for generating heat by flameless combustion of a fuel in a gas stream - Google Patents

Description

GW io:G S5J.1..DE : ::

Emitec Company for Emissions Technology mbH D-5204 Lohmar 1

for the generation of heat by flameless combustion of a fuel in a gas stream".

The invention relates to a device for generating heat by flameless combustion of a fuel in an oxygen-containing gas stream, wherein the heat generated during combustion is to be captured in a core through which the gas stream can flow.

Corresponding devices for the following applications, namely for heating heat transfer fluids such as water or air in heating systems for motor vehicles, large halls or the like, as well as for heating honeycomb bodies in exhaust systems of motor vehicles which are provided with catalytically active coatings for converting exhaust pollutants into harmless agents.

Heating devices for motor vehicles, including in particular auxiliary and auxiliary heaters, are known in a wide variety of forms, as can be seen, for example, from EP-A-O 287 923 and DE-A-37 187. Such heating devices generally have arrangements for generating heat by burning a fluid fuel and are also provided with heat exchangers in which the heat generated during combustion is transferred to a heat transfer fluid such as air or water. EP-A-O 287 923 proposes that the exhaust gases produced during conventional combustion be passed through a catalytically active matrix for the purpose of cleaning before being released into the open air. DE-A-37 16 187 proposes that the fuel be at least partially stored in a

01 01

to burn in a catalytically induced, flameless reaction; for this purpose, the fuel is mixed with an air stream and the mixture is passed through a catalytically active matrix.

Behind the catalytically active matrix there is a heat exchanger in which the heat generated during combustion is transferred to a heat transfer fluid ^, whereupon the gas stream leaves the device.

DE-A-38 35 983 relates to the heating of a honeycomb body for treating the exhaust gases in a motor vehicle, whereby this is exposed to a hot gas stream. The gas stream is heated by catalytic combustion of a fuel that is mixed with this gas stream before it flows through the exhaust catalyst or another catalytically active element. It is also proposed to guide the gas stream behind the exhaust catalyst through a heat exchanger in which the heat remaining in the gas stream can be transferred to another heat carrier for heating the motor vehicle interior and/or the motor vehicle cooling water.

In order for a catalytically active element to develop its catalytic effect, its temperature must exceed a certain limit temperature, the so-called "light-off temperature". The noble metals usually used as catalysts, such as platinum, rhodium or palladium, as well as known catalytically active compounds, have light-off temperatures of around 200 °C or more. Accordingly, it is necessary to preheat a catalytically active element. In the combustion plants presented, this requires preheating devices that allow the catalytically active elements to be heated to sufficiently high temperatures. Such preheating devices can, for example, be electrical heating devices of any type; corresponding proposals can be found in DE-A-22 51 631. In DE-PS 5 63 757 it is also proposed to directly electrically heat a metallic carrier body with catalytic material applied to it.

01 02

heat.

Furthermore, a large number of carrier bodies are known which are provided with coatings made of catalytically active materials and are excellently suited as catalytically active elements? See, for example, the documents EP-B-O 049 489, EP-B-O 121 174, EP-B-O 121 175, EP-A-3 245 737 and EP-A-O 245 738.

All proposals of the state of the art for flameless

Combustion of a fuel in a catalytically active element has a substantial defect: When it reaches the catalytically active element, the gas stream usually has a relatively low temperature, namely essentially the temperature of the environment of the device from which it is taken. was. Therefore, a considerable part of the combustion heat generated in the catalytically active element must be used to heat the cold gas stream to a sufficiently high temperature before the combustion reaction can even begin. However, this means that the reaction in the catalytically active element active element becomes unstable as soon as the air mass flow rate of the gas flow exceeds a certain threshold. In particular, there is a risk that the catalyst in its inflow area, i.e. in the area that is first touched by the gas flow, will be cooled to such an extent that the catalytic reaction to A certain "dead zone" can therefore arise, which, depending on the mass flow rate and temperature of the gas flow, spreads over the entire catalytically active element, so that the reaction fails completely. In summary, it can be said that previously known methods for flameless combustion of a fuel in a gas stream are only suitable for generating heat within a limited, particularly highly restricted, power range.

Accordingly, the invention is based on the object of generating heat by flameless combustion of a fuel

01 03

substance in a gas stream so that the combustion reaction is stable and has a sufficiently large control range for the heat output for practical application.

This object is achieved according to the invention by a device for generating heat by flameless combustion of a fuel in a gas stream containing oxygen, wherein:

a) the gas stream flows through at least one heating device, along at least one feed device for the fuel and along at least one first catalytically active element;

b) the gas stream is guided at least partially in a loop and flows through a first conveying device and along the first catalytically active element;

c) a gas containing oxygen can be fed into the loop and a part of the gas flow can be fed out of the loop.

An essential element of the invention is the at least partial guidance of the gas flow in a loop which contains the catalytically active element and also a conveying device for maintaining the gas flow in the loop. In the loop, at least a portion of the gas flow flowing out of the catalytically active element is fed back to the inflow side of the catalytically active element. If the temperature of the outflowing gas flow is relatively high due to the combustion, the gas flow portion guided in the loop results in an increase in the temperature of the gas flow flowing towards the catalytically active element. This prevents the area of the catalytically active element flowing towards the gas flow from cooling down too much and the formation of dead zones is excluded. In addition, by appropriately selecting the recirculated portion, a substantially uniform utilization of the catalytically active element over its entire extent can be achieved. The portion of the combustion heat which is used to heat up the fuel-containing

01 04

The result is a considerable increase in the control range for the heat output generated, without having to accept any significant reduction in thermal efficiency.

Compared to the possibilities of the prior art, according to the invention, the operating conditions of the combustion can be determined for the first time without taking into account the heat transport in the catalytically active element. The mass flow rate of a gas flow at ambient temperature that flows towards the catalytically active element must remain below a critical value that is determined by the amount of heat transport to the upstream side of the catalytically active element. With sufficiently high preheating of the gas flow flowing towards the catalytically active element, as is possible according to the invention, this limit is shifted to higher flow rates, possibly to values beyond practical applicability. This enables an operating mode in which the fuel-oxygen ratio in the gas flow is kept at a constant value regardless of the required heat output and the heat output is regulated only by the mass flow rate of the gas flow. The temperature of the gas stream as it flows towards the catalytically active element remains at a sufficiently high value due to the recirculation through the loop, so that the combustion reaction can be kept completely stable.

A favorable development of the invention is characterized in that the majority of the gas flow, for example to a compartment of about 70 SS to about 90%, is guided in the loop. This essentially creates a gas circulating flow into which fuel and air (or other oxygen-containing gas) can be fed as required and from which gas can be fed out as required, e.g. to limit the pressure. This means that the advantages of heat storage in the gas flow,

01 05

in particular to maintain a sufficiently high operating temperature of the catalytically active element; to avoid excessive thermal stress, the temperature of the gas flow can be limited by heat extraction in the loop, in particular kept at a temperature in the range of the start-up temperature of the catalytically active element. When the system according to the invention has reached its operating temperature, heat generation to maintain this operating temperature is only necessary to the extent that the removal of heat must be compensated.

The combustion is advantageously started in such a way that, before the catalytic reaction begins, the gas flow in the loop is heated by a heating device, which is preferably electrically operated, until its temperature reaches the light-off temperature of the catalytically active element or until the catalytically active element is sufficiently heated. Further measures to initiate the combustion, such as special pilot burners or electric spark plugs, are not required.

When starting the combustion, the feeding of oxygen-containing gas into the circulating gas stream can advantageously be omitted once a gas stream with sufficient oxygen content has been built up. Also, no continuous addition of fuel is required before the combustion begins; it is completely sufficient to add a small amount of fuel to the gas stream once, since a specific mixture ratio of fuel and oxygen is not important for catalytic combustion. The oxygen-containing gas stream mixed with fuel is only heated up by the heating device until the catalytically active element is activated by heat transfer and/or

01 06

direct preheating has reached a temperature at which the &Aacgr; catalyst is activated. The start of combustion j is therefore completely safe in every phase, since high concentrations of fuel, with the associated danger of misfires can be avoided.

A particularly advantageous possibility for operating the device according to the invention is characterized in that the feed of fuel into the gas stream is always as low as possible is maintained so that the resulting fuel-gas mixture is not self-igniting, and in particular not explosive. As already explained, the temperature of the gas stream when flowing towards the catalytically active element can be largely independent of its Flow velocity, and thus the mass flow rate, can be kept sufficiently high. Accordingly, the mass flow rate of the gas flow can be adapted essentially freely to the amount of fuel supplied, which determines the thermal output; in particular, the mixing ratio of Fuel and oxygen in the gas stream are kept constant, preferably constantly lean. This enables practically completely safe operation.

The injection of fresh, oxygen-containing gas into the Loop is advantageously limited in such a way that the

Temperature of the gas flow when it reaches the catalytically active element does not fall below its start-up temperature. This possibility is always open within the scope of the invention? its advantages naturally arise primarily when if combustion is carried out with a constantly lean fuel-air mixture.

The discharge of gas from the gas flow guided in the loop is, without prejudice to further configurations, advantageously controlled in such a way that a discharge occurs when the gas pressure in the loop

COO01 07

exceeds a certain limit value. Combustion with a high excess of oxygen makes it possible to recirculate the gas flow several times without losing the good properties of the invention, including the pronounced lack of pollutants in flameless combustion. The only thing that is associated with the heating of the gas flow is an increase in the internal pressure, which must be counteracted by releasing gas. Release can be carried out by means of suitable _valves, in particular by means of automatic overpressure safety valves. Under certain circumstances, pressure control can also be achieved by purely fluid-technical measures, for example by designing the gas outlet serving for discharge as a branch line with a sufficiently small hydraulic cross-section.

A particular field of application of the invention is the generation of thermal energy for heating purposes; in particular, it relates to portable and mobile heating systems, such as heating fans for warehouses or the like, and heating systems for motor vehicles. Accordingly a device according to the invention is designed for the generation of heat energy with a maximum thermal output of about 10 kilowatts, in particular up to about 7 kilowatts, preferably in the range of 4 kilowatts.

The invention finds advantageous applications primarily for introducing the heat generated in the gas stream into a component that can be flowed around and/or through, namely one or more heat exchangers and/or one or several exhaust catalysts.

The invention relates to a device for introducing heat generated by flameless combustion of a fuel in a gas stream into a component which is surrounded by and/or flows through the gas stream, containing:

01 08

a) a gas guidance system for guiding the gas flow, with at least one loop, a delivery device for delivering the fuel, a gas inlet, a gas outlet and the component;

b) arranged in the loop are a first conveying device for maintaining the gas flow in the loop, a heating device and a first catalytically active element.

A device with these features is ideally suited for use as a portable or mobile heating system, for example as a stationary additional heating system for a motor vehicle or as a portable heating system for heating large halls. It is also possible to use inexpensive materials for the construction due to the flameless combustion and relatively low operating temperatures, although losses in terms of service life and durability must be accepted.

The arrangement of the feed device for the fuel is relatively uncritical; it can be arranged in the gas inlet so that fuel can only be fed into the gas flow together with a certain amount of fresh gas. This at least prevents a lack of oxygen from occurring in the gas flow guided in the loop, which would consequently lead to the production of pollutants such as carbon monoxide during combustion. However, it can also be useful to arrange the feed device so that fuel is injected directly into the loop. In this way, the gas flow can be guided in the loop for at least a while without the addition of fresh gas, which is particularly interesting with low heat outputs in terms of avoiding heat leaks. It is of course then necessary to prevent the occurrence of a lack of oxygen by means of suitable monitoring measures.

For the arrangement of the component into which the combustion heat

01 09

K 1 is to be introduced, there are also several possibilities: This component can be part of the loop and be included in the M already mentioned system for controlling the temperatures in the ■2 gas stream. The component removes heat from the 5 gas stream in any case; if it is located in the loop $, it can be dimensioned so that the temperature of the gas stream, when the component &eeacgr;*.::, .h has flowed, is at a temperature level in the range of the light-off temperature of the Kj.I lytically active element; the operation of the combustion with practically complete recirculation of the gas stream in the loop, with all the resulting advantages, can be realized in this way. The insertion of the component in the loop is by no means compulsory; with appropriate design of the other components of the loop, the component can also be arranged in the gas outlet, whereby the advantages of stabilizing the flameless combustion by partial recirculation of the gas stream are still retained. Moreover, it is very conceivable and also advantageous to arrange both a component in the loop and a component in the gas outlet; in certain applications this can result in additional advantages.

A further development of the device according to the invention, which can be added to other developments, is characterized in that the first catalytically active element that causes the flameless combustion is a component of the heating device. The device therefore has a first catalytically active element that can be heated essentially directly and immediately. When this device is put into operation, which is carried out in the manner described by preheating the gas flow using the heating device, the first catalytically active element is heated directly and can therefore reach its starting temperature particularly quickly. If this is the case, the flameless combustion begins and provides additional energy for heating the gas flow and the other components of the

01 10

Device. The amount of heat energy required to start combustion from outside the device can thus be considerably reduced, which is particularly important with regard to possible applications in

5 motor vehicles is interesting.

The heating device itself is advantageously formed with a heating conductor arrangement that can be supplied with an electric current. Electric heating is a simple and clean option and is therefore superior to other heating devices, such as conventional burners.

The feeding of gas into the device does not usually occur automatically; a means of conveying fresh gas must be provided. This conveying means can be provided by a suitably designed first conveying device in the loop; otherwise a second conveying device for supplying fresh gas to the loop can be arranged in the gas inlet.

It is also advantageous to provide sensors for monitoring operation in the device according to the invention. Lambda sensors for determining the composition of the circulating gas flow and also thermocouples for monitoring the operating temperatures are particularly suitable and useful for this purpose.

A key area of application of the invention is the heating of catalytically active elements, in particular the heating of exhaust catalysts in the exhaust system of a motor vehicle before the combustion engine is started. The electrical heating of exhaust catalysts with metallic carrier bodies is known, but this is only useful for special carrier bodies that are optimized in terms of their electrical resistance. In order to achieve meaningful preheating, the carrier body must be subjected to powers of 1 kW and above; the provision

t * e &iacgr; * * * &idigr; » t - ? e &iacgr;

However, such performance is only possible to a very limited extent with the electrical system of a motor vehicle. In addition, the electrical resistance of a metallic carrier body of conventional design is only a few hundredths of an ohm, depending on its size, which is not ideal for electrical heating in view of the loss resistance in the supply lines. The invention now allows an exhaust gas catalyst to be heated with the heat from a clean and safe combustion reaction, whereby heating outputs of up to several kilowatts are easily possible. Any electrical heating only affects the first catalytic element, which triggers the heat-producing combustion reaction. However, this first catalytic element is usually smaller than the exhaust gas catalyst, so that the problem of low electrical resistance arises to a much lesser extent, if at all. In addition, the first catalytic element is not subjected to the thermal and mechanical stresses of the exhaust gas catalyst, which is exposed to a pulsating exhaust gas flow; Accordingly, it does not need to be trimmed to the highest load capacity and thus offers a wealth of design options for increasing the electrical resistance.

A further area of application of the invention is the provision of heat for heating purposes, in particular for heating motor vehicles, wherein in the device according to the invention at least one component used to absorb heat is a heat exchanger. The heat exchanger has both a channel system for guiding the gas flow and a channel system for guiding a heat transfer fluid, in particular air or water. When the device is in operation, the heat transfer fluid is transported through the heat exchanger by an external or internal conveying device, where it heats up and then serves the desired heating purpose.

, Both air and water can be used as heat transfer fluid. Especially in the case of vehicle heating, the device can be integrated into the cooling liquid system, whereby if.i the latter case simultaneously with the heating of the

c Preheating of the combustion engine is possible in the interior before start-up.

Without prejudice to further embodiments, a particularly advantageous development of the device according to the invention

,j-, with heat exchanger characterized in that the heat exchanger carries the first catalytically active element that triggers the combustion reaction, for example in such a way that the piping system of the heat exchanger that carries the gas flow has walls that carry catalytically active layers on which

,ε the gas flow passes by (the possibility of the presence of another first catalytically active element should not be excluded). A suitably improved device has a very short transfer path for the combustion heat; the heat transfer takes place in such a way with

2Q high efficiency and particularly low losses, and a particularly compact design for the device can be achieved.

As already mentioned, in the device according to the invention, heat-absorbing components can be arranged both in the gas supply system forming the loop and in the gas outlet. A corresponding, particularly interesting development results from the arrangement of a heat exchanger in the loop and in the gas outlet, whereby the channel systems of the heat exchangers carrying the heat transfer fluid preferably communicate with _one another, in particular are connected in series. Such a device delivers a relatively strongly cooled exhaust gas from the gas outlet and is therefore particularly suitable for use in heat-sensitive _environments or environments that need to be protected against excessive heat, for example vehicle interiors.

14 ... .

The invention is further explained using the embodiments shown schematically in the drawing, where the figures of the drawing show devices for generating heat through flameless combustion of a fuel in a gas flow guided in a loop and introducing this heat into a component. In detail:

Figure 1 shows a device for heating an exhaust gas catalyst in a motor vehicle;
Finur 7 pine Vorr 1 rhtiinn to remove the heat of the combustion

" Zf ' üi* ** s

generated heat by means of a heat exchanger; Figure 3 shows a device of the type shown in Figure 2, which is particularly suitable, for example, as an auxiliary or auxiliary heater in a motor vehicle.

To explain the details essential to the invention, reference is first made to all three figures of the drawing at the same time; it is noted that the reference numerals 101 to 117 refer to Figure 1, the reference numerals 201 to 209 to Figure 2 and the reference numerals 301 to 319 to Figure 3. In any case, the device according to the invention has a gas guide system 102, 202, 302 which consists of pipes or the like and serves to guide the gas flow, the gas guide system 102, 202, 302 having at least one loop 103, 203, 303 in which the gas flow is guided in a circle. Fresh gas with an oxygen content, in particular air, can be fed to the gas flow circulating in the loop 103, 203, 303 ^through a gas inlet 104, 204, 304. A certain proportion of the circulating gas flow can be fed out through a gas outlet 105, 205, 305. While the feeding out of gas can be essentially passive, for example by the gas outlet 105, 205, 305 being designed as an elongated pipe with a hydraulic cross section that is significantly smaller than the average hydraulic cross section of the loop 103, 203, 303.

Oh oh

hf »+ ti

Pipe system, the gas must be fed in actively, via suitable conveying means. The circulation of the gas flow in the loop 103, 203, 303 is effected by a first conveying device 106, 206, 306, in particular a blower, which is arranged in the part of the gas supply system 102, 20?, 302 forming the loop 103, 203, 303. To feed fuel into the gas flow, the loop 103, 203, 303 contains a corresponding feed device 107, 207, 307, namely a nozzle or nozzle arrangement with a suitable fuel supply system. According to the invention, the combustion of the fuel takes place in a flameless, catalytically effected manner. For this purpose, the loop 103, 203, 303 has a catalytically active element 109, 209, 309, in particular a honeycomb body through which the gas flow can flow and which has a large number of channels which have a coating of a catalytic material (platinum, rhodium or the like) on their walls facing the gas flow. As is known, combustion in the catalytically active element 109, 209, 309 only begins when the temperature of the gas flow passing the catalytic material exceeds the light-off temperature of the catalyst. Accordingly, a heating device 108, 208, 308 is provided in the loop 103, 203, 303. This heating device 108, 208, 308 can be a heating conductor arrangement to which an electric current can be applied, but it can also be designed as a normal burner or as a heat exchanger depending on the application. Finally, each device shown has at least one component 101, 201, 301, 318 into which the heat generated during the flameless combustion in the circulating gas flow is to be introduced.

Examples of applications are explained in more detail below in the individual descriptions of the figures in the drawing.

Figure 1 shows a schematic representation of the application of the invention in the context of a device for heating an exhaust gas catalyst in the exhaust system of a motor vehicle; the exhaust gas catalyst represents the component 101, which

01 02

by flameless combustion of the fuel in the circulating gas flow and to be heated by this heat. The gas guide system 102 is formed from an exhaust pipe section 113 in which the exhaust gas catalyst 101 is arranged, whereby, viewed in the direction of the exhaust gas flow, the exhaust pipe section 113 has an inlet 114, 113 in front of and behind the exhaust gas catalyst 101. The inlets 114, 115 are connected to one another via a bypass line, so that the loop 102 is formed. from the area between junctions 114 and 115 Exhaust pipe section 113 and the bypass line. This can be closed at both inlets 114, 115 by means of flaps 116, 117, which is important in terms of the performance of the device when exposed to exhaust gas to protect the bypass line. In principle, the flaps 116, 117 are not necessary; they serve less to ensure the proper functioning of the device according to the invention, but rather to protect the devices located in the bypass line. A lambda probe 111 and a thermocouple 112 are integrated into the gas supply system 102. As a rule, a lambda probe 111 is assigned to the exhaust gas catalyst 101 anyway, and it is recommended that this be used when operating the device according to the invention for controlling flameless combustion. The

Thermocouple 112 can be used when the

Exhaust gas catalyst 101 with exhaust gas serves as a function control for the exhaust gas catalyst 101; within the scope of the invention it is helpful for determining the temperature of the exhaust gas catalyst 101 to be heated. In which the inlets 114, 115 are connected to one another As already mentioned, the first conveying device 106, the feed device 107, the heating device 108 and the first catalytically active element 109 are accommodated in the bypass line connecting the two bypass lines; in addition, the gas inlet 104 opens into the bypass line. The gas outlet 105 is in the illustrated For example, the exhaust pipe leading to the outside is directly connected. In the gas inlet 104, a second

01 03

Conveying device 110 for supplying fresh air. In addition, in a favorable embodiment of the invention, the heating device 108 is combined with the first catalytically active element 109; this can be achieved in concrete terms, for example, by using a metallic honeycomb body as a carrier for the catalytically active layer, through which an electric current can flow and thus be heated. This is a particularly good choice, since it ensures that the catalytic reaction begins after a short start-up time of the device according to the invention; heating the first catalytically active element 109 also has the advantage that the catalytic reaction can be stabilized as long as the temperature of the circulating gas flow is not below the required starting temperature. In the example shown, the feed device 107 for the fuel is located in the bypass line between the gas inlet 104 and the heating device 108. The positioning of the feed device 107 in the loop 103 is relatively uncritical; in the present example, it should of course be avoided to provide the feed device directly in the exhaust pipe section 113. Means for conveying the fuel are not shown in Figure 1, since their use is familiar to those skilled in the art.

Figure 2 shows a device in which the component 201 to be subjected to the heat generated during combustion is a heat exchanger for heating a heat transfer fluid such as air or water, for example for use in a heating system, in particular a portable or mobile heating system in the form of a parking heater or additional heater for a motor vehicle. As a special feature in Figure 2, the feed device 207 for the fuel is not contained directly in the loop 203, but in the gas inlet 204. In this case, fuel can only be fed to the gas flow circulating in the loop 203 together with fresh air (for which a feed device (not shown) is required);

01 04

This has the advantage that the occurrence of an oxygen deficiency in the circulating gas flow is excluded, which would otherwise only be possible by carefully monitoring the combustion process. The gas outlet 205 is shown as a relatively long line with a small hydraulic cross-section. The length of the line prevents the gas flow from being whirled out into the open in an uncontrolled manner through the gas outlet; however, a pressure increase in the loop 203 is reliably excluded because there are no closing devices in the gas outlet 205. It goes without saying that, within the framework of corresponding requirements, the provision of closing devices such as valves or the like in the gas outlet 205 is possible.

Figure 3 shows a further embodiment of the device according to the invention for transferring the heat generated during the combustion process to a heat transfer fluid, whereby the transfer in the present case takes place in two heat exchangers 301, 318 connected in series. A first heat exchanger 301 is arranged directly in the loop 303 and a second heat exchanger 318 is located in the gas outlet 305. The most important function of the second heat exchanger 318 is to cool the exhaust gas discharged through the gas outlet 305, which can be useful, for example, in the context of a motor vehicle auxiliary heater that is to be arranged in the interior of a motor vehicle. As a special feature, the first heat exchanger 301 develops a certain catalytic effect, for example in that the channels of the heat exchanger 301 through which the gas flow can flow have a catalytically effective coating on their walls. Under certain circumstances, the first heat exchanger 301 can completely take over the function of the first catalytically active element 309, which is advantageous with regard to a design of the device that is as compact as possible.

The heating device 308 is advantageously operated with an electric current. The gas inlet 304 has

01 05

= SSSS i

a second delivery device 310 required to deliver fresh gas has an inlet valve 319 which serves for the fine regulation of the amount of fresh gas delivered to the loop 303. The arrangement shown is representative of a large number of possible designs.

000 01

Claims (21)

Protection claims 1. Device for introducing heat generated by flameless combustion of a fuel in a gas stream into a component (101; 201; 301; 318) around which the gas stream can flow and/or through, containing: a) a gas guiding system (102; 202; 302) for guiding the gas flow, with at least one loop (103? 203; 303), a feed device (107; 207; 307) for feeding the li-v r* j & a _j r> &igr; i_f*k i &lgr; r\ t. . / . . -» r\ &igr;» \ *■.£_.».« r> -. ...«. &igr; _ &eegr; JU DiKIIIIbLUI I Kb, t? JJIt? Ill Ua^CJ-MXCIkJ VJ-UHJ ^UHJ SKJH J CXIICIH UQSaUSiau (105; 205; 305) and the component (101, 201; 301; 318); b) arranged in the loop (103; 203; 303) are a first conveying device (106; 206; 306) for maintaining the gas flow in the loop (103; 203; 303), a heating device (108; 208; 308) and a first catalytically active element (109; 209; 309). 2. Device according to claim 1, wherein the component (101; 201; 301) is arranged in the loop (103; 203; 303). 3. Device according to claim 1 or 2, wherein the component (318) is arranged in the gas outlet (105; 205; 305). 4. Device according to one of the preceding claims, wherein the first catalytically active element (109; 209; 309) is part of the heating device (108; 208; 308). 5. Device according to one of the preceding claims, wherein the heating device (108; 208; 308) comprises a heating conductor arrangement to which an electric current can be applied. 6. Device according to one of the preceding claims, wherein the gas inlet (104; 204; 304) contains a second conveying device (110) for supplying gas into the gas stream. 7. Device according to one of the preceding claims, wherein 02 01 _o - t φ - * ' t at least one lambda probe (111) is arranged in the loop (103; 203; 303). 8. Device according to one of the preceding claims, wherein at least one thermocouple (112) is arranged in the loop (103; 203; 303). 9. Device according to one of the preceding claims, wherein the component (101; 201; 301; 318) comprises a second catalytically _ la.·. i-i J- Mnl \ J — i. aMivca C-LCIIICUl \±*j±j xsu 10. Device according to claim 9, wherein the gas guide system (102; 202; 302) is partially part of an exhaust system for a motor vehicle and the second catalytically active element (101) is an exhaust gas catalyst in the exhaust system. 11. Device according to claim 10, wherein the exhaust gas catalyst is located in an exhaust pipe section (113) which has on both sides of the exhaust gas catalyst inlets (114; 115) which are connected to one another via a bypass line, and wherein the loop (103; 203; 303) is formed by the exhaust gas pipe section (113) and the bypass line. 12. Device according to claim 11, wherein at least one of the Inlets (114; 111.) can be closed by a controllable flap (116; 117) or the like. 13. Device according to one of claims 1 to 8, wherein the component (101; 201; 301; 318) is a heat exchanger (301; 318) with at least one hot channel through which the gas flow can flow and at least one cold channel through which a heat transfer fluid can flow. 14. Device according to claim 13, wherein the heat transfer fluid is a gas, in particular air. 02 02 15. Device according to claim IA, wherein the cold channel is part of an air heating system, in particular an air heating system in a motor vehicle. 16. Device according to claim 13, wherein the heat transfer fluid is a liquid, in particular water. 17. Device according to claim 16, wherein the cold channel is part of a cooling fluid system in a motor vehicle. 18. Device according to one of claims 13 to 17, wherein the heat exchanger (301; 318) carries the first catalytically active element (109; 209; 309). 19. Device according to claim 18, wherein the hot runner has a wall facing the gas flow, on which a catalytically active layer is applied. 20. Device according to one of claims 13 to 19, wherein a first heat exchanger (301) is mounted in the loop (103; 203; 303) and a second heat exchanger (318) is mounted in the gas outlet (105; 205; 305). 21. Device according to claim 20, wherein the cold channel of the first heat exchanger (301) communicates with the cold channel of the second heat exchanger (318). 02 03