Gas separation – With nonliquid cleaning means for separating media – With heating or cooling means
Patent
1997-11-17
2000-01-11
Simmons, David A.
Gas separation
With nonliquid cleaning means for separating media
With heating or cooling means
55482, 55DIG10, 55DIG30, 60303, 60311, B01D 2954, B01D 2962, B01D 3518
Patent
active
060131187
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a particulate trap for trapping and removing particulates such as carbon contained in diesel engine exhaust gas.
BACKGROUND ART
Emissions from automobiles are a major cause of air pollution. It is therefore of extreme importance to develop a technique for removing noxious components in automobile emissions.
It is particularly important and urgently required to develop a technique for removing particulates contained in diesel engine emissions, which are mainly NOx and carbon.
To remove such noxious components in exhaust gas, it has been proposed to provide a particulate trap in an exhaust gas line to trap and remove any noxious components. Other conventional exhaust gas purifying means include various improvements in the engine itself such as exhaust gas recirculation (EGR) systems and improved fuel injection systems. But none of them are decisive solutions.
As of today, it is considered more promising to treat exhaust gas with a trap. Rigorous efforts are now being made to improve such traps.
A particulate trap comprises a case mounted in an exhaust gas line, and a filter element housed in the case. Exposed to high-temperature exhaust gas, the filter element has to be highly heat-resistant. Also, in order to efficiently trap particulates, the filter element should have as large a trapping area as possible. It is also necessary to prevent leakage of exhaust gas through its mounting portion.
Moreover, the filter element has to be vibration-resistant enough not to be damaged or broken due to vehicle vibration, simple in structure so as to be manufactured at low cost. It is also required that the energy cost for regeneration of the filter element, i.e. for burning particulates trapped be as low as possible.
In order to meet all these requirements, various factors have to be taken into consideration, including the material and shape of the filter element, end sealing structure, and the structure for securing the filter element to the case.
Such particulate traps are disclosed e.g. in unexamined Japanese patent publications 6-146856, 6-264715, 5-222920, and 6-257422.
Particulates trapped have to be periodically removed for regeneration of the filter. Unexamined Japanese patent publications 5-22290, 6-146856, 6-264722 propose to burn particulates with an electric heater. These traps have a plurality of filters arranged in parallel. Some of these traps (such as one disclosed in unexamined Japanese patent publication 6-101449) have an exhaust gas purifier for regenerating the filter by burning while the engine is running without extremely reducing the heat efficiency of the heater (by controlling the flow rate of exhaust gas by means of valves) and while supplying enough oxygen for complete combustion of soot (particulates).
But in the case of a trap of the type that controls the amount of emissions, a delicate touch is required for such control. Also, a device for controlling the amount of emissions has to be resistant to heat from exhaust gas. Naturally, the entire trap tends to be complicated in structure and costly.
There is also known a relatively simple exhaust gas purifier of a type in which particulates are burned for regeneration of the filter while the engine is at a stop. Some of the devices of this type resort to an external air source or an electric fan for supplying oxygen necessary to burn particulates trapped during the regeneration step. More recent devices have a filter case having a shape that makes it possible to supply oxygen by natural convection, thereby eliminating the need for an external or auxiliary device for supplying oxygen.
Any of the particulate traps disclosed in the above-listed publications uses cylindrical filters. The trap disclosed in the publication 6-146856 has insulating members provided at either end of the cylindrical filters with one of the insulators sandwiched between the cylindrical filters and the case and the other pressed against the filter end by a screw-tightened presser to fix the filters and seal the filter en
REFERENCES:
patent: 5709722 (1998-01-01), Nagai et al.
Matsunuma Kenji
Nakajima Naruhito
Hopkins Robert A.
Simmons David A.
Sumitomo Electric Industries Ltd.
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