A segmented, heated urea mixer and an exhaust system to control NOx emission from combustion engines comprising a plurality of elements, at least one element independently heatable by an external power source to a temperature above a temperature of another element. A method of using the exhaust gas mixer and an exhaust gas mixer system further comprising a controller is also disclosed.

Described are exhaust gas treatment systems for treatment of a gasoline engine exhaust gas stream. The exhaust gas treatment systems comprise an ammonia generating catalyst and an ammonia selective catalytic reduction (SCR) catalyst downstream of the ammonia generating catalyst. The ammonia generating catalyst comprises a NO.sub.x storage component, a refractory metal oxide support, a platinum component, and a palladium component. The ammonia generating catalyst is substantially free of ceria. The platinum and palladium components are present in a platinum to palladium ratio of greater than about 1 to 1.

A reductant injecting device includes: a honeycomb structure comprising: a pillar shaped honeycomb structure portion having a partition wall that defines a plurality of cells each extending from a fluid inflow end face to a fluid outflow end face; and at least one pair of electrode portions arranged on a side surface of the honeycomb structure portion; an inner cylinder being configured to house the honeycomb structure; a urea sprayer arranged at one end of the inner cylinder; and an outer cylinder arranged on an outer peripheral side of the inner cylinder, the outer cylinder being spaced apart from the inner cylinder. A flow path through which the carrier gas passes is formed between the inner cylinder and the outer cylinder.

A driver inducement method and a driver inducement system for a vehicle that induce a driver to replenish a urea considering a urea level in a urea tank and an actual vehicle speed are disclosed. The driver inducement method may include: calculating a first residual travel distance according to a urea level and an average urea consumption if an engine is started; calculating a final residual travel distance based on the first residual travel distance according to the urea level and the average urea consumption and a second residual travel distance according to the urea level and a vehicle speed, if the first residual travel distance according to the urea level and the average urea consumption is smaller than a threshold distance; and limiting an engine output according to the final residual travel distance.

The present invention relates to a method for generating ammonia from an ammonia precursor substance and to the use thereof for reducing nitrogen oxides in exhaust from industrial facilities, from combustion engines, from gas engines, from diesel engines or from petrol engines.

This catalyst system simultaneously removes ammonia and enhances net NOx conversion by placing an NH.sub.3-SCR catalyst formulation downstream of a lean NOx trap. By doing so, the NH.sub.3-SCR catalyst adsorbs the ammonia from the upstream lean NOx trap generated during the rich pulses. The stored ammonia then reacts with the NOx emitted from the upstream lean NOx trap-enhancing the net NOx conversion rate significantly, while depleting the stored ammonia. By combining the lean NOx trap with the NH.sub.3-SCR catalyst, the system allows for the reduction or elimination of NH.sub.3 and NOx slip, reduction in NOx spikes and thus an improved net NOx conversion during lean and rich operation.

A method for operating an exhaust gas purification system of an internal combustion engine, which can be operated in a lean operating mode and in a rich operating mode, is disclosed. The exhaust gas purification system has, arranged one after the other in the direction of flow of the exhaust gas, an ammonia-forming catalyst, a first exhaust gas sensor, an ammonia-SCR catalyst, a nitrogen oxide storage catalyst and a second exhaust gas sensor. Exhaust gas sensors emit a first signal correlating with the nitrogen oxide content of the exhaust gas and a second signal correlating with the lambda value of the exhaust gas. In diagnostic operation, the ammonia storage capacity of the ammonia-SCR catalyst and the oxygen and optionally the nitrogen oxide storage capacity of the nitrogen oxide storage catalyst can be determined by analyzing the signals of the first and second exhaust gas sensors.

A system and method for utilizing fuel as an on-board reductant for selective catalytic reduction of NOx is provided and includes a controller for controlling an engine to produce a lean first exhaust stream and a rich second exhaust stream that are received in respective first and second passageways of a dual path aftertreatment system. The rich second exhaust stream reacts with NOx stored in a NOx storage and reduction catalyst of the second passageway to regenerate this catalyst and generate ammonia. The first exhaust stream and the second exhaust stream having the generated ammonia are combined in a downstream common passageway to form a combined lean exhaust gas stream where the ammonia carried therein is stored or used by an SCR catalyst of the common passageway for NOx reduction. The engine is subsequently controlled to produce a rich first exhaust stream and a lean second exhaust stream.

The invention provides an emission control system for treatment of an exhaust gas stream of an engine, including an engine producing an exhaust gas stream; an SCR catalyst unit downstream from the engine and in fluid communication with the exhaust gas stream; and an ammonia generation system comprising a reservoir containing ammonium hydroxide and an ammonia injector, wherein the reservoir is in fluid communication with the ammonia injector and the ammonia injector is in fluid communication with the exhaust gas stream upstream of the SCR catalyst unit. A method of treating an exhaust gas stream of an engine is also provided, including the steps of heating ammonium hydroxide to produce gaseous ammonia and transferring the gaseous ammonia through an ammonia injector into the exhaust gas stream such that the gaseous ammonia disperses within the exhaust gas stream upstream of a SCR catalyst unit.

A method for monitoring a gas sensor (14) which comprises two electrochemical measuring cells (20, 30) and which is arranged in an exhaust tract (10) of an internal combustion engine (11), wherein the sensor elements (20, 30) exhibit a substantially identical sensitivity towards a first gas component and a different sensitivity towards a second gas component and are insensitive towards further gas components. In an operating state in which an exhaust gas stream at the gas sensor (14) contains less of the second gas component than of the first gas component a concentration of the first gas component is calculated from each of the sensor signals from the sensor elements (20, 30) and a defect in a sensor element (20, 30) is deduced from the concentrations of the first gas component.