초록 ▼

Urea is pyrolyzed in a chamber designed to facilitate gasification of the urea by pyrolysis with conversion of urea to ammonia and isocyanic acid (HNCO) with water vapor and carbon dioxide. The product gases are introduced into exhaust gases from a lean-burn engine, preferably upstream of a turbocha

Urea is pyrolyzed in a chamber designed to facilitate gasification of the urea by pyrolysis with conversion of urea to ammonia and isocyanic acid (HNCO) with water vapor and carbon dioxide. The product gases are introduced into exhaust gases from a lean-burn engine, preferably upstream of a turbocharger. The exhaust gases are then contacted with an SCR catalyst.

대표청구항 ▼

[ We claim:] [1.] A method for reducing the emissions of NO.sub.x from a lean-burn engine having associated therewith an exhaust system having an exhaust passage leading to an SCR reactor effective for selective catalytic NO.sub.x reduction, comprising:feeding an aqueous urea solution from a storage

[ We claim:] [1.] A method for reducing the emissions of NO.sub.x from a lean-burn engine having associated therewith an exhaust system having an exhaust passage leading to an SCR reactor effective for selective catalytic NO.sub.x reduction, comprising:feeding an aqueous urea solution from a storage vessel through a line to an injector;returning urea solution from the injector to the storage vessel, the rates of feed and return being sufficient to supply urea as needed to the exhaust gases for NO.sub.x reduction and maintain the temperature of the urea solution sufficiently low that it is not permitted sufficient time at elevated temperature to hydrolyze the urea to such an extent that solids precipitate;spraying an aqueous solution of urea from the injector into a pyrolysis chamber having openings therein to permit discharge of gases generated by pyrolysis of the urea and vaporization of water;maintaining the solution within the pyrolysis chamber for a time sufficient to evaporate water from the solution and pyrolyze the urea;introducing gaseous products discharged from the pyrolysis chamber into exhaust gases from the lean-burn engine; andcontacting the exhaust gases containing the gaseous products discharged from the pyrolysis chamber with an SCR reactor at an exhaust gas temperature effective for selective catalytic reduction.