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.

An after treatment method for a lean-burn engine is disclosed. The after treatment method is configured to control an after treatment system sequentially equipped with an ammonia production catalyst module, a selective catalytic reduction (SCR) catalyst, and a CO clean-up catalyst (CUC) on an exhaust pipe through which an exhaust gas flows and which is connected to a lean-burn engine. In the after treatment method, a rich air/fuel ratio (AFR) is controlled in multiple phases in response to detecting that conversion to the rich AFR is desired.

An internal combustion engine, exhaust system, exhaust gas treatment device includes an housing (18) including a housing inlet (34) and a housing outlet (60). An exhaust gas treatment unit (28), in the housing, includes an inlet (32) following the housing inlet and an outlet (38). An SCR catalytic converter device (30), in the housing, includes an SCR catalytic converter device inlet (54) following the exhaust gas treatment unit outlet and an SCR catalytic converter device outlet (56). A reactant releasing device (52) releases reactant upstream of the SCR catalytic converter device inlet. An exhaust gas duct (42), formed in an exhaust gas pipe (44), leads in the housing from the exhaust gas treatment unit outlet to the SCR catalytic converter device inlet, whereby exhaust gas leaving the SCR catalytic converter device at the SCR catalytic converter device outlet flows around the exhaust gas pipe in at least some areas.

An after treatment method for a lean-burn engine is disclosed. The after treatment method is configured to control an after treatment system sequentially equipped with an ammonia production catalyst module, a selective catalytic reduction (SCR) catalyst, and a CO clean-up catalyst (CUC) on an exhaust pipe through which an exhaust gas flows and which is connected to a lean-burn engine. NH.sub.3 generation in the ammonia production catalyst module is changed according to a temperature and a temperature change rate of the SCR catalyst.

A method for regenerating an exhaust gas filter on which soot is deposited, including sequentially conducting: a step 1 of impregnating the filter with a liquid having 50% by mass or more of a component having a boiling point of 550 C. or less when an ambient temperature in the filter is at least 40 C. lower than the boiling point; a step 2 of raising the ambient temperature in the filter after the impregnation to a temperature equal to or higher than the boiling point of the component; and a step 3 of supplying an oxygen-containing gas at a temperature exceeding 550 C. to the filter to burn the soot.

An operating liquid tank for a motor vehicle, comprising a tank wall enclosing a tank volume that can be filled with an operating liquid, a filling arrangement designed for introducing operating liquid into the tank volume, and a removal arrangement designed for the removal of operating liquid from the tank volume, wherein the removal arrangement comprises a pump assembly with a pump and a pump drive, the pump assembly comprises at least two assembly components that are formed separately from one another and are or can be coupled magnetically to one another, and of which a first assembly component as drive component comprises at least one part of the pump drive and a second assembly component as conveying component comprises a conveying part of the pump that can be driven by the pump drive relative to a conveying component housing for movement, wherein the tank wall extends between the drive component and the conveying component and physically separates the conveying component located on the inner face of the tank wall from the drive component located on the outer face of the tank wall.

A method of treating exhaust gas from an internal combustion engine includes sensing a temperature of the exhaust gas with a temperature sensor, comparing the sensed temperature with a threshold temperature, injecting a first reductant into the exhaust gas at a first location if the sensed temperature is less than the threshold temperature, and injecting a second reductant having a different composition than the first reductant into the exhaust gas at a second location if the sensed temperature is greater than the threshold temperature.

A method for operating a gas engine having an adjoining exhaust line through which exhaust line exhaust gas of the engine flows includes: operating the gas engine in accordance with a Miller cycle, such that a closing point of at least one intake valve of the gas engine is in a crank angle range of from about 50 of crank angle before bottom dead center (BDC) to about 10 of crank angle before BDC; and lowering, by at least one selective catalytic reduction (SCR) catalyst element in the exhaust line, a level of nitrogen oxides (NOx) in the exhaust gas flowing through the SCR catalyst element using hydrocarbons (CyHz) as a reducing agent. At least some of the hydrocarbons (CyHz) flowing through the SCR catalyst element are constituents of the exhaust gas of the gas engine.

A reductant generator includes a housing defining a chamber, an inlet to direct engine exhaust gas into the chamber, a moveable member that receives driving input from an engine and which is configured to compress engine exhaust gases within the chamber, and a supply to provide a fluid into the chamber to be transformed into reductant. The generator also includes an outlet from which the reductant is directed into an exhaust system.

An engine includes: an NOx catalyst and an SCR catalyst in an exhaust passage; an excess air ratio change device that changes an excess air ratio of an exhaust gas; and a reducing agent supply device that supplies a reducing agent for SCR including a material for NH.sub.3 or NH.sub.3 to a portion between the NOx catalyst and the SCR catalyst in the exhaust passages. The engine controls the reducing agent supply device in such a manner that a quantity of the reducing agent for SCR to be supplied from the reducing agent supply device to the exhaust passage 40 becomes small when the excess air ratio of the exhaust gas during regeneration control to regenerate the NOx catalyst is small, as compared to when the excess air ratio of the exhaust gas during regeneration control to regenerate the NOx catalyst is large.