Exhaust Gas Purifier

Abstract

It is intend to provide at low cost an exhaust gas purifier capable of in an internal combustion engine or other combustion instrument mainly driven under excess air conditions, efficiently removing nitrogen oxides from exhaust gas. A nitrogen oxide adsorbent (4) is disposed in an exhaust passage, which the nitrogen oxide adsorbent (4) is composed of a lithium composite oxide of the general formula LiAxOy or LiAxPO4, containing as constituent elements lithium (Li) and at least one element (A) selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), vanadium (V), chromium (Cr), iron (Fe), titanium (Ti), scandium (Sc), and yttrium (Y). For example, the nitrogen oxide adsorbent (4) is composed of a lithium composite oxide, such as lithium manganate (LiMnO3), the lithium titanate (Li2TiO3) or lithium manganate phosphate (LiMnPO4).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional application of application Ser. No. 11 / 887,118, filed Sep. 25, 2007, which is a National Phase of International Application No. PCT / JP2006 / 304996, filed Mar. 13, 2006, which claims priority under 35 U.S.C. §119 to Japanese Patent Application No. JP 2005-093798, filed Mar. 29, 2005, and Japanese Patent Application No. JP 2005-093802, filed Mar. 29, 2005, the entire disclosures of which are herein expressly incorporated by reference.TECHNICAL FIELD[0002]The present invention relates to an apparatus for purifying exhaust gas of an internal combustion engine such as a diesel engine, a gas engine, a gasoline engine, and a gas turbine engine or a combustion device such as an incinerator and a boiler. More particularly, the present invention relates to an exhaust gas purifier suitably removes nitrogen oxide while being installed within an exhaust gas passage of the internal combustion engine or the like which is ...

AI Technical Summary

Benefits of technology

The invention provides an exhaust gas purifier that can efficiently remove nitrogen oxides from internal combustion engines or combustion instruments operated under excessive air condition. The purifier uses a nitrogen oxide adsorbent made of lithium composite oxide, which is a low-cost material that can be easily obtained. The purifier can be installed in the exhaust passage of the engine or instrument and does not require a large amount of sulfur in the fuel. The purifier can also be used in small gas engines or automobiles with a three-way catalyst. The purifier can efficiently detoxify nitrogen oxides and discharge them to the atmosphere at low cost. The purifier can also be used in industrial engines or combustion instruments operated under excessive air condition. The purifier can be easily maintained and does not require a high-level control of the engine or instrument. The purifier can also be supported by a porous support or a support made of aluminum oxide or anatase titanium oxide, which further improves the NOx adsorbing power. The purifier can also be burned at a high temperature to further improve its NOx adsorbing power.

Problems solved by technology

However, the apparatus itself is large and extremely expensive, and a maintenance cost of the reducing agent such as ammonia and urea is also increased.

Further, there is a high possibility that the unconsumed ammonia is discharged into atmosphere.

In the nitrogen oxide occluding type catalyst which is commercialized in the small gas engine and automobile gasoline engine, the purifier becomes expensive because the noble metal is always contained as the catalyst component, an operation range (such as temperature and SV value) where the reduction can completely be performed is restricted to a narrow range, and complicated lean and rich control (control of air and fuel supply amounts) is required on an engine side.

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