Exhaust gas purification unit with reducing agent supply
AssigneeDaimlerChrysler AG
InventorsFrank Duvinage, Christian Goerigk, Arno Nolte, Markus Paule, Henning Sander
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Abstract
An exhaust gas purification unit for purifying the exhaust gas from an internal combustion engine which is preferably operated in lean burn mode, in particular a diesel engine used in motor vehicles, has a particulate filter and a SCR catalytic converter arranged in the exhaust pipe in succession in the direction of flow, and a reducing agent supply. Ammonia can be added to the exhaust gas from the internal combustion engine on the entry side of the SCR catalytic converter by the reducing agent supply. A hydrogen-generating unit enriches the exhaust gas from the internal combustion engine with generated hydrogen.
Claims17
An exhaust gas purification unit for purifying exhaust gas from an internal combustion engine operatable in lean burn mode comprising an exhaust pipe, in which a particulate filter and an SCR catalytic converter are operatively arranged in succession in a flow direction, and a reducing agent supply configured to supply ammonia to be added to the exhaust gas of the internal combustion engine on an entry side of the SCR catalytic converter, wherein a hydrogen generating unit is operatively arranged for enriching the exhaust gas from the internal combustion engine with generated hydrogen on demand in a first range of exhaust gas temperatures such that the SCR catalytic converter is able to reduce NOx under oxidizing conditions with the ammonia constituting a reducing agent in a second range of exhaust gas temperatures higher than the first range.
A method for purifying exhaust gas from an internal combustion engine, having an exhaust gas system comprising a particulate filter and an SCR catalytic converter downstream of the particulate filter, the method comprising
- supplying ammonia to the exhaust gas on an entry side of the SCR catalytic converter, and
- supplying hydrogen on demand for selectively enriching the exhaust gas immediately upstream of the SCR converter in a first range of exhaust gas temperatures such that the SCR catalytic converter is able to reduce NOx under oxidizing conditions with the ammonia constituting a reducing agent for NOx in a second range of temperatures higher than the first range.
Dependencies are inferred from the claim text.