Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Patent
1997-12-29
1999-04-20
Denion, Thomas E.
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
60290, 60289, 60301, 60303, 60307, F01N 300
Patent
active
058947280
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an exhaust emission control device for a diesel engine which eliminates NOx by reducing it to N.sub.2, H.sub.2 O, CO.sub.2, etc.
BACKGROUND ART
Conventionally, a method has been known in which the hydrocarbons in the exhaust gas are compulsorily enriched, and are brought into contact with a transition metal carrying metallo-silicate catalyst, such as a copper/zeolite catalyst, or a transition metal carrying oxide catalyst, such as a copper/alumina catalyst, to reduce and eliminate NO.sub.x in the exhaust gas. In the conventional methods, ethylene, propylene, or diesel fuel, such as kerosene and light oil, is used as the reducing agent hydrocarbon. However, in order to eliminate NO.sub.x, a large amount of the reducing agent is necessary. As a concrete example, under practical conditions of diesel exhaust gas, in order to reduce and eliminate NO.sub.x, a hydrocarbon weight of two and half times to four times as much as that of the NO.sub.x, is necessary.
Contrary to the above, in Japanese Patent Application Laid-open No. 6-327974, it is described that the required amount of reducing agent can be substantially reduced by using an alcohol (especially ethanol) as the reducing agent. However, ethanol and propanol are more expensive as compared to ethylene and diesel fuel; and moreover it is necessary to separately prepare an additional substance as the reducing agent, so that the above art cannot be regarded as practical.
In Japanese Patent Application Laid-open No. 5-133218, it is proposed that fuel be reformed to a plurality of substances, including an alcohol which can be used as the reducing agent. However, since the reducing agent which is obtained after reforming is a kind which does not aim at an oxygen-containing compound such as, especially, an alcohol, there are disadvantages in that: and so that the performance of the reforming catalyst is easily lowered.
SUMMARY OF THE INVENTION
The present invention is made to eliminate the disadvantages of the conventional art described above, and its object is to provide an exhaust emission control device for a diesel engine which is small and simple, and which efficiently reduces NO.sub.x in the exhaust gas to N.sub.2, H.sub.2 O, and CO.sub.2, to eliminate the same.
An exhaust emission control device for a diesel engine related to the present invention is an exhaust emission control device for a diesel engine including a reforming catalyst, for reforming diesel fuel, such as kerosene or the like, to reducing hydrocarbons; and for supplying the reducing hydrocarbons into an exhaust pipe; and a NO.sub.x catalyst, which is disposed in the exhaust pipe at a position downstream from the supplying position, and which reduces and controls NO.sub.x in the exhaust gas from the diesel engine, and is characterized by the reforming catalyst being a reforming catalyst which reforms either a mixture of diesel fuel and water, or a mixture of diesel fuel, water, and air, to at least one oxygen-containing compound, and supplies the oxygen-containing compound into the exhaust pipe. It is desirable that the oxygen-containing compound is an alcohol with two or more carbon atoms per molecule.
Further it is desirable that the exhaust emission control device includes: flow control means, for respectively controlling the flow of the diesel fuel, the water, and the air, and for supplying the diesel fuel, the water, and the air to the reforming catalyst; inlet temperature detecting means, for detecting the inlet temperature of the NO.sub.x catalyst; and a controller, for receiving a temperature signal from the inlet temperature detecting means and for outputting supply flow signals respectively to the flow control means. The exhaust emission control device can include a reducing agent adding nozzle, disposed in the exhaust pipe at a position upstream from the NO.sub.x catalyst; as well as a fuel tank; a water tank; and an air source, which are designed to be supply sources of the diesel fuel, the water, and the air, respectively. Th
REFERENCES:
patent: 4059415 (1977-11-01), Kosaka et al.
patent: 4958490 (1990-09-01), Harjunpaa 60274
Denion Thomas E.
Komatsu Ltd.
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