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An exhaust-gas purification installation for purifying exhaust gas from an internal combustion engine includes an exhaust-gas catalytic converter which is arranged in an exhaust pipe of the internal combustion engine and a catalytic fuel reformer for generating a hydrogen-containing reformer gas whi

An exhaust-gas purification installation for purifying exhaust gas from an internal combustion engine includes an exhaust-gas catalytic converter which is arranged in an exhaust pipe of the internal combustion engine and a catalytic fuel reformer for generating a hydrogen-containing reformer gas which can be fed to the exhaust pipe on an entry side of the exhaust-gas catalytic converter. It is possible for a hydrocarbon-containing fuel, which can be used to operate the internal combustion engine, to be fed to the fuel reformer in order to generate the reformer gas. An exhaust-gas heater can heat the exhaust-gas part-stream which is fed to the fuel reformer. In a method according to the invention, an exhaust-gas part-stream which is removed from the exhaust pipe is heated and fed to the fuel reformer.

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1. An exhaust-gas purification method for purifying an exhaust gas from an internal combustion engine using an exhaust-gas purification system having an exhaust pipe with an exhaust-gas catalytic converter arranged in it and a catalytic fuel reformer, comprising:feeding a fuel which is used to opera

1. An exhaust-gas purification method for purifying an exhaust gas from an internal combustion engine using an exhaust-gas purification system having an exhaust pipe with an exhaust-gas catalytic converter arranged in it and a catalytic fuel reformer, comprising:feeding a fuel which is used to operate the internal combustion engine to the fuel reformer in order to generate a hydrogen-containing reformer gas,removing an exhaust-gas part-stream from the exhaust pipe,transferring heat between the reformer gas and the exhaust-gas part-stream by way of a heat exchanger, andfeeding the exhaust-gas part-stream to the fuel reformer. 2. The exhaust-gas purification method according to claim 1, wherein the reformer gas generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when a temperature on the entry side of the exhaust-gas catalytic converter or in the exhaust-gas catalytic converter falls below a predeterminable limit value. 3. The exhaust-gas purification method according to claim 1, wherein the reformer gas which is generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when the exhaust gas from the internal combustion engine which is fed to the exhaust-gas catalytic converter has an excess of air. 4. The exhaust-gas purification method according to claim 3, wherein the reformer gas generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when a temperature on the entry side of the exhaust-gas catalytic converter or in the exhaust-gas catalytic converter falls below a predeterminable limit value. 5. The exhaust-gas purification method according to claim 1, wherein, in order to heat the exhaust-gas part-stream, the exhaust-gas part-stream is passed through a separate exhaust-gas heater. 6. The exhaust-gas purification method according to claim 5, wherein the reformer gas which is generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when the exhaust gas from the internal combustion engine which is fed to the exhaust-gas catalytic converter has an excess of air. 7. The exhaust-gas purification method according to claim 5, wherein the reformer gas generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when a temperature on the entry side of the exhaust-gas catalytic converter or in the exhaust-gas catalytic converter falls below a predeterminable limit value. 8. An exhaust-gas purification method for purifying an exhaust gas from an internal combustion engine using an exhaust-gas purification system having an exhaust pipe with an exhaust-gas catalytic converter arranged in it and a catalytic fuel reformer, comprising:feeding a fuel which is used to operate the internal combustion engine to the fuel reformer in order to generate a hydrogen-containing reformer gas,removing an exhaust-gas part-stream from the exhaust pipe,heating the exhaust-gas part-stream, andfeeding the heated exhaust-gas part-stream to the fuel reformer,wherein, in order to heat the exhaust-gas part-stream, the exhaust-gas part-stream is passed through at least one of an exhaust-gas heater and a high-temperature heat exchanger through which the reformer gas flows. 9. The exhaust-gas purification method according to claim 8, wherein the reformer gas which is generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when the exhaust gas from the internal combustion engine which is fed to the exhaust-gas catalytic converter has an excess of air. 10. The exhaust-gas purification method according to claim 8, wherein the reformer gas generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from tim e to time when a temperature on the entry side of the exhaust-gas catalytic converter or in the exhaust-gas catalytic converter falls below a predeterminable limit value. 11. The exhaust-gas purification method according to claim 8, wherein the exhaust-gas heater is electrically heated at least from time to time. 12. The exhaust-gas purification method according to claim 11, wherein the reformer gas which is generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when the exhaust gas from the internal combustion engine which is fed to the exhaust-gas catalytic converter has an excess of air. 13. The exhaust-gas purification method according to claim 11, wherein the reformer gas generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when a temperature on the entry side of the exhaust-gas catalytic converter or in the exhaust-gas catalytic converter falls below a predeterminable limit value. 14. The exhaust-gas purification method according to claim 11, wherein, when the fuel reformer is being started up, the exhaust-gas part-stream is passed through the electrically heated exhaust-gas heater and is heated in the process, and when the fuel reformer is operating normally, the exhaust-gas part-stream is passed through the high-temperature heat exchanger and is heated in the process. 15. The exhaust-gas purification method according to claim 14, wherein the reformer gas which is generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when the exhaust gas from the internal combustion engine which is fed to the exhaust-gas catalytic converter has an excess of air. 16. The exhaust-gas purification method according to claim 14, wherein the reformer gas generated by the reformer is fed to the exhaust gas upstream of the exhaust-gas catalytic converter at least from time to time when a temperature on the entry side of the exhaust-gas catalytic converter or in the exhaust-gas catalytic converter falls below a predeterminable limit value. 17. An exhaust-gas purification installation for purifying an exhaust gas from an internal combustion engine, comprising:an exhaust-gas catalytic converter which is arranged in an exhaust pipe of the internal combustion engine,a catalytic fuel reformer adapted to generate a hydrogen-containing reformer gas which can be fed to the exhaust pipe on an entry side of the exhaust-gas catalytic converter, feeding of a hydrocarbon-containing fuel, which can be used to operate the internal combustion engine, to the fuel reformer being possible in order to generate the reformer gas,an exhaust-gas heater provided so as to heat an exhaust-gas part-stream which is fed to the fuel reformer, anda heat exchanger adapted to transfer heat between the reformer gas which emerges from the fuel reformer and the exhaust-gas part-stream which is fed to the fuel reformer. 18. The exhaust-gas purification installation according to claim 17, wherein the exhaust-gas catalytic converter is a denox catalytic converter. 19. The exhaust-gas purification installation according to claim 17, wherein the exhaust-gas catalytic converter is an oxidation catalytic converter. 20. The exhaust-gas purification installation according to claim 19, and further comprising a denox catalytic converter arranged in the exhaust pipe downstream of the oxidation catalytic converter, wherein the reformer gas can be fed to the entry side of the oxidation catalytic converter and to an entry side of the denox catalytic converter. 21. The exhaust-gas purification installation according to claim 17, wherein the exhaust-gas heater is electrically heatable. 22. The exhaust-gas purification installation according to claim 21, wherein the exhaust-gas heater is of cylindrical configuration and, in its interior, has a coiled passage, which runs substantially in the axial direction, for guiding the exhaust-gas part-stream. 23. The exhaust-gas purification installation according to claim 21, wherein the exhaust-gas catalytic converter is a denox catalytic converter. 24. The exhaust-gas purification installation according to claim 21, wherein the exhaust-gas catalytic converter is an oxidation catalytic converter. 25. The exhaust-gas purification installation according to claim 24, and further comprising a denox catalytic converter arranged in the exhaust pipe downstream of the oxidation catalytic converter, wherein the reformer gas can be fed to the entry side of the oxidation catalytic converter and to an entry side of the denox catalytic converter. 26. The exhaust-gas purification installation according to claim 17, wherein the exhaust-gas heater is of cylindrical configuration and, in its interior, has a coiled passage, which runs substantially in the axial direction, for guiding the exhaust-gas part-stream. 27. The exhaust-gas purification installation according to claim 26, wherein the exhaust-gas catalytic converter is a denox catalytic converter. 28. The exhaust-gas purification installation according to claim 26, wherein the exhaust-gas catalytic converter is an oxidation catalytic converter. 29. The exhaust-gas purification installation according to claim 28, and further comprising a denox catalytic converter arranged in the exhaust pipe downstream of the oxidation catalytic converter, wherein the reformer gas can be fed to the entry side of the oxidation catalytic converter and to an entry side of the denox catalytic converter. 30. An exhaust-gas purification installation for purifying an exhaust gas from an internal combustion engine, comprising:an exhaust-gas catalytic converter which is arranged in an exhaust pipe of the internal combustion engine,a catalytic fuel reformer adapted to generate a hydrogen-containing reformer gas which can be fed to the exhaust pipe on an entry side of the exhaust-gas catalytic converter, feeding of a hydrocarbon-containing fuel, which can be used to operate the internal combustion engine, to the fuel reformer being possible in order to generate the reformer gas,an exhaust-gas heater provided so as to heat an exhaust-gas part-stream which is fed to the fuel reformer, anda high-temperature heat exchanger adapted to transfer heat from the reformer gas which emerges from the fuel reformer to the exhaust-gas part-stream which is fed to the fuel reformer. 31. The exhaust-gas purification installation according to claim 30, wherein the exhaust-gas catalytic converter is a denox catalytic converter. 32. The exhaust-gas purification installation according to claim 30, wherein the exhaust-gas catalytic converter is an oxidation catalytic converter. 33. The exhaust-gas purification installation according to claim 32, and further comprising a denox catalytic converter arranged in the exhaust pipe downstream of the oxidation catalytic converter, wherein the reformer gas can be fed to the entry side of the oxidation catalytic converter and to an entry side of the denox catalytic converter. 34. The exhaust-gas purification installation according to claim 30, wherein the exhaust-gas part-stream can be fed to the fuel reformer via at least one of the exhaust-gas heater and the high-temperature heat exchanger as desired. 35. The exhaust-gas purification installation according to claim 34, wherein the exhaust-gas catalytic converter is a denox catalytic converter. 36. The exhaust-gas purification installation according to claim 34, wherein the exhaust-gas catalytic converter is an oxidation catalytic converter. 37. The exhaust-gas purification installation according to claim 36, and further comprising a denox catalytic converter arranged in the exhaust pipe downstream of the oxidation catalytic converter, wherein the reformer gas can be fed to the entry side of the oxidation catalytic converter and to an entry side of the denox catalytic converter. 38. An e xhaust-gas purification installation for purifying an exhaust gas from an internal combustion engine, comprising:an exhaust-gas catalytic converter which is arranged in an exhaust pipe of the internal combustion engine,a catalytic fuel reformer adapted to generate a hydrogen-containing reformer gas which can be fed to the exhaust pipe on an entry side of the exhaust-gas catalytic converter, feeding of a hydrocarbon-containing fuel, which can be used to operate the internal combustion engine, to the fuel reformer being possible in order to generate the reformer gas,an electrically heatable exhaust-gas heater provided so as to heat an exhaust-gas part-stream which is fed to the fuel reformer, anda high-temperature heat exchanger adapted to transfer heat from the reformer gas which emerges from the fuel reformer to the exhaust-gas part-stream which is fed to the fuel reformer. 39. The exhaust-gas purification installation according to claim 38, wherein the exhaust-gas part-stream can be fed to the fuel reformer via at least one of the exhaust-gas heater and the high-temperature heat exchanger as desired. 40. An exhaust-gas purification installation for purifying an exhaust gas from an internal combustion engine, comprising:an exhaust-gas catalytic converter which is arranged in an exhaust pipe of the internal combustion engine,a catalytic fuel reformer adapted to generate a hydrogen-containing reformer gas which can be fed to the exhaust pipe on an entry side of the exhaust-gas catalytic converter, feeding of a hydrocarbon-containing fuel, which can be used to operate the internal combustion engine, to the fuel reformer being possible in order to generate the reformer gas,an exhaust-gas heater provided so as to heat an exhaust-gas part-stream which is fed to the fuel reformer, the exhaust-gas heater being of cylindrical configuration and, in its interior, having a coiled passage, which runs substantially in the axial direction, for guiding the exhaust-gas part-stream, anda high-temperature heat exchanger adapted to transfer heat from the reformer gas which emerges from the fuel reformer to the exhaust-gas part-stream which is fed to the fuel reformer. 41. The exhaust-gas purification installation according to claim 40, wherein the exhaust-gas part-stream can be fed to the fuel reformer via at least one of the exhaust-gas heater and the high-temperature heat exchanger as desired.