An exhaust gas purification system for an internal combustion engine includes a dual passage portion having a first passage and a second passage which are connected in parallel to each other. In the first passage, a first catalyst constructed of lean NOx catalyst is located and further a second catalyst constructed of oxidizing catalyst or three-way catalyst is located downstream of the first catalyst. In the second passage, a third catalyst constructed of oxidizing or three-way catalyst is located. A flow switching valve is provided so as to switch the flow of exhaust gas between the first passage and the second passage. The flow switching valve is switched so that exhaust gas flows through the third catalyst when the engine is being warmed-up and flows through the first catalyst and the second catalyst after the engine has been warmed-up.

Exhaust gas purification system for an internal combustion engine

Hydrogen gas from a hydrogen generator which creates hydrogen gas by the electrolysis of water or water vapor is supplied at the entrance to a catalyzer provided in an exhaust line. The catalyzer performs a catalytic reaction between hydrogen gas and nitrogen oxides to achieve decomposition into nitrogen gas and water vapor in the exhaust from an internal combustion engine. The nitrogen oxides are directly reduced with said hydrogen gas in a low temperature atmosphere not higher than 350° C. to achieve efficient reduction in the nitrogen oxides. The improved method and apparatus provide a catalytic system with which the nitrogen oxides in the exhaust from a lean burnt engine or a diesel engine can be effectively reduced irrespective of the concentration of oxygen gas in the exhaust without impairing the good fuel economy of those engines.

Method and apparatus for reducing nitrogen oxides from internal combustion engine

An apparatus for treating an exhaust gas stream from cold startup through continuous operating conditions of an internal combustion engine includes an oxidizing catalyst bed disposed in an exhaust pipe and a reducing catalyst bed disposed in the exhaust pipe downstream from the oxidizing catalyst bed. The oxidizing catalyst bed has one or more oxidizing catalysts and the reducing catalyst bed has one or more reducing catalysts. A method is provided for treating an exhaust gas stream both during cold start and during continuous operating conditions of an internal combustion engine by passing the stream through an oxidizing catalyst bed having one or more oxidizing catalysts at a light off temperature; a reducing catalyst bed having one or more reducing catalysts and providing hydrogen into the reducing catalyst bed to condition the reducing catalyst; and introducing hydrogen into the internal combustion engine during cold startup.

Catalytic reduction of emissions from internal combustion engines

A process and system for low NOx cogeneration to produce electricity and useful heat. Fuel and oxygen are provided to an internal combustion engine (10) connected to drive an electric generator (9), thereby generate electricity. An exhaust stream is recovered from the engine. Fuel is added to the exhaust stream to create a fuel-rich mixture. The fuel enriched stream is provided to an afterburner (18) to provide a heated oxygen-depleted stream. The oxygen-depleted stream is cooled in a first heat exchanger (22). Conversion oxygen is admixed with the cooled stream which is then passed over a catalyst bed (25) under overall reducing conditions. The stream from the reducing catalyst bed is cooled and air is added to produce a further cooled stream and the further cooled stream is passed over an oxidizing catalyst bed (26) to oxidize remaining combustibles.

Low NOx cogeneration process and system

A reductant injection control strategy for controlling an amount of nitrogen oxide reducing agent injected upstream of a first and second serially placed nitrogen oxide catalyst, calculates the reductant injection For the first catalyst and second catalyst. The reductant injection for the first catalyst is based on engine operating conditions. The reductant injection for the second catalyst is based on the reductant injection for the first catalyst and a conversion efficiency of the first catalyst.

Emission control system

A method of and a system for cleaning exhaust gases from engines of motor vehicles, wherein the exhaust gases are passed through reducing and oxidizing catalysts so that nitrogen oxides are reducing in the reducing catalyst and carbon monoxide and hydrocarbons are oxidized in the oxidizing catalyst. The engines are so arranged as to be operable on a relatively thin mixture which is preferably proportioned to provide an excess-air ratio of about 1.0 to 1.15 so that substantially no carbon monoxide and hydrogen are present in the exhaust gases emitted from the engine. A reducing agent such as hydrocarbons is admixed to the exhaust gases entering the reducing catalyst for removing an excess of oxides and reducing the nitrogen oxides in the exhaust gases while secondary air is supplied to the exhaust gases entering the oxidizing catalyst for assisting in the oxidization of the carbon monoxide and hydrocarbons remaining in the exhaust gases passed through the oxidizing catalyst.

Tadashi Nagai

Papers

Apparatus for supplying fuel to a dual-catalyst exhaust treatment system

Verfahren zum reinigen der abgase des motors eines kraftfahrzeugs