Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1991-10-21
1993-01-19
Kummert, Lynn M.
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
422171, 422174, 422180, 422186, 55DIG30, 60275, 60300, 60320, 423212, F01N 320
Patent
active
051805596
DESCRIPTION:
BRIEF SUMMARY
The invention relates to reducing emission of toxic gases when cold starting, an engine and during engine warm-up.
DESCRIPTION OF THE PRIOR ART
In order to reduce unburnt hydrocarbons, carbon monoxide and oxides of nitrogen in exhaust gases, it is known to include in the exhaust system a catalytic converter. Such catalytic converters comprise a honeycomb matrix, usually ceramic, defining a large surface area over which the exhaust gases pass and a catalyst, often comprising fine particles of a noble metal such as platinum and sometimes a base metal such as cerium oxide, supported in a porous wash coat, for example of alumina, which is applied to the surface of the matrix.
Many countries now have laws governing permissible limits of gas emissions and these are measured over a standardised drive cycle which starts from a cold engine. In tests, it has been found that nearly a third of all the measured emissions during the drive cycle occur in the first hundred seconds from start. In part, this is caused by the fact that the toxic gas content of the exhaust gases on leaving the combustion chamber is higher when the engine is cold than after the engine has warmed up. The other reason is that the efficiency of the conversion depends upon the operating temperature of the catalyst and while the catalytic converter operates satisfactorily at normal engine running temperatures, during cold-start and warm-up, before the catalyst reaches a so-called light-off temperature, the converter is almost ineffective.
Both these causes of toxic gas emission during warm-up are known and proposals have been made in the past to reduce engine warm-up time and catalyst light-off time. The present invention addresses only the second of these two known problems. Hitherto, attempts to heat the catalyst have relied on heating elements designed to heat up both the matrix and the catalytic coating. Such proposals can be found in GB-1,349,426 and GB-1,492,737. However, the matrix has a large thermal capacity and poor thermal conductivity and the combined effect of these two properties is that heating of the converter in this manner is not very rapid nor effective. For this reason, many prior art proposals have required pre-heating of the catalytic converter but this is not a satisfactory solution because a driver cannot be expected to wait several minutes for the catalyst to reach its light off temperature before starting the engine.
SUMMARY OF THE INVENTION
The present invention, in its broadest aspect, provides a method of reducing the light off time of a catalytic converter which comprises exposing the matrix of the converter to an alternating magnetic field or to electromagnetic radiation having such a frequency that the wash coat and the particles of catalyst supported by the matrix are heated to the light-off temperature without a corresponding increase in the temperature of the entire matrix.
According to a second aspect of the invention, there is provided an exhaust system incorporating a catalytic converter and a microwave source or an induction heater connected to the converter for heating the converter before or during cold starting in order to reduce the light-off time of the catalyst.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic elevational view of a catalytic converter assembly in accordance with this invention.
DETAILED DESCRIPTION AND BEST MODE
The use of microwave and R.F. energy as a source of heat has been proposed in other, but not analogous, applications. Outside the field of motor vehicles, it has been suggested in GB-663,914 to use microwave energy to speed up endothermic reactions, whether or not they involve the use of a catalyst. In this case, a purposely designed reaction chamber is used and energy is supplied continuously to enable the reaction to take place. The dielectric properties of the materials in the reaction chamber are selected to achieve the desired heating effect on exposure to radiation.
The present invention differs from this prior art proposal in all these respects. In pa
REFERENCES:
patent: 4945721 (1990-08-01), Cornwell et al.
Ford Motor Company
Kummert Lynn M.
Malleck Joseph W.
May Roger L.
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