A method for exhaust gas aftertreatment in a gasoline engine and an exhaust gas aftertreatment system are provided. In the method, two catalytic converters arranged in the exhaust gas tract of the gasoline engine are operated in different states. A first three-way catalytic converter is operated in a slightly low-oxygen range, and a second three-way catalytic converter is operated in a slightly oxygen-rich range. Secondary air is furthermore blown into the exhaust gas tract between the two three-way catalytic converters. It is thereby possible to reduce the output of emissions of the gasoline engine to a great extent. An exhaust gas aftertreatment system is likewise explained.

An exhaust gas purification device is disclosed provided with a denitration catalyst for reducing and removing nitrogen oxides in exhaust gas using ammonia as a reducing agent in a gas flow passage through which the exhaust gas discharged from a boiler flows, and which injects ammonia into the exhaust gas flowing through the gas flow passage on an upstream side of the denitration catalyst, including multiple disturbing plate support members, and a disturbing plate. The multiple disturbing plate support members are fixedly provided on a downstream side of the denitration catalyst and arranged extending linearly in a flow path cross section to cross the gas flow passage. The disturbing plate includes an exhaust gas flow facing surface exposed on an upstream side and is fixed to the disturbing plate support members so that a position thereof in the flow path cross section can be changed.

The present disclosure relates to a device and a method for monitoring an SCR exhaust gas after-treatment device. The method involves monitoring of a ratio between reducing agent quantity and nitrogen oxide conversion, especially a ratio between ammonia quantity and nitrogen oxide conversion, of the SCR exhaust gas after-treatment device. The nitrogen oxide conversion is detected or determined with a cross sensitivity to ammonia. The method furthermore involves determining of an ammonia slip condition based on the monitored ratio between reducing agent quantity and nitrogen oxide conversion. The method may offer the benefit of being easily carried out and implemented in an easy manner.

An abnormality determination apparatus for an ammonia sensor is usable in an exhaust purification system including a catalyst, a supply apparatus, an ammonia sensor, an NO.sub.X sensor, and an oxygen sensor. During a continuation period within which ammonia supply to the catalyst continues after the supply apparatus stops supply of reductant, the abnormality determination apparatus calculates the ammonia concentration on a downstream side of the catalyst as a first concentration value, based on an output of the ammonia sensor and an output of the oxygen sensor. During the continuation period, the abnormality determination apparatus calculates the ammonia concentration on the downstream side of the catalyst as a second concentration value, based on an output of the NO.sub.X sensor and the output of the oxygen sensor. The abnormality determination apparatus determines presence or absence of abnormality in the ammonia sensor based on the first concentration value and the second concentration value.

A selective catalytic reduction system control system (10) and method of its use include an ammonia (“NH.sub.3”) slip sensor (13) located within an interior space (27) of an exhaust stack (15) of a selective catalytic reactor (31), toward an inlet end (25) of the stack (15); a housing (17) located within the interior space of the exhaust stack; the housing including face panels 19; a nitrogen oxides (“NOx”) sensor (11) contained within an interior space (29) defined by the face panels of the housing, at least two of the face panels (19.sub.I, 19.sub.O) containing an oxidation catalyst; and a dosing controller (59) in communication with the NH.sub.3 and NOx sensors, the dosing controller including a microprocessor with dosing logic embedded thereon. The housing with oxidation catalyst acts as a linear box, isolating the NOx sensor from NH.sub.3 slip, linearizing the NOx sensor signal.

A gas sensor system is equipped with a first gas detection unit, and a second gas detection unit. The first and second gas detection units include a gas introduction port for introducing a gas to be measured, a measurement chamber communicating with the gas introduction port, a conversion medium (NH.sub.3 oxidation catalyst) arranged between the gas introduction port and the measurement chamber, and which converts a portion of a first gas type into a second gas type, and a detection device that detects the second gas type. A ratio of diffusion resistances of the first gas detection unit and the second gas detection unit is greater than or equal to 0.71 and less than or equal to 1.4.

A first gas sensor having a first sensor element includes a first protective cover that protects the first sensor element, and a second gas sensor having a second sensor element includes a second protective cover that protects the second sensor element. The first protective cover is coated with an oxidation catalyst for one target component from among a plurality of target components, and the second protective cover is coated with an inert catalyst for the one target component.

Disclosed is a method for control of dosage of a reducing agent into an exhaust stream, which includes: determining at least one sensor signal S.sub.NOx from at least one nitrogen oxides NO.sub.x sensor arranged downstream of at least one of the one or more reduction catalysts as at least one sensor correction value S.sub.NOx_corr, respectively, if: 1) the engine rotates without fuel supply; 2) an exhaust mass flow M′.sub.exh is greater than an exhaust mass flow threshold M′.sub.exh_th; M′.sup.exh>M′.sub.exh_th; and 3) the sensor signal S.sub.NOx has had a value smaller than a sensor signal threshold S.sub.NOx_th; S.sub.NOx<S.sub.NOx_th; during at least a predetermined time period T.sub.con; determining at least one adjusted sensor signal S.sub.NOx_adj based on the at least one sensor signal S.sub.NOx and the at least one sensor correction value S.sub.NOx_corr, respectively; and controlling the dosage of the reducing agent based on the at least one adjusted sensor signal S.sub.NOx_adj.

The invention concerns a method for monitoring an SCR catalytic converter in an exhaust line of an internal combustion engine, into which a reducing agent solution for the reduction of nitrogen oxides is dosed, wherein the SCR catalytic converter is diagnosed as defective if a measured variable is below a corresponding threshold and wherein the diagnosis of the SCR catalytic converter occurs when enabling criteria are met, wherein the enabling criteria are selected depending on a BPU model and a WPA model such that when the SCR catalytic converter (3) conforms to the BPU model, ammonia slip occurs through this SCR catalytic converter (3), and when the SCR catalytic converter corresponds to the WPA model, no ammonia slip occurs through this SCR catalytic converter.

A method for controlling an SCR catalytic converter (20, 30), comprising detecting (200) concentration values (314, 324; 414, 424) in the exhaust gas downstream of the catalytic converter (20), wherein at least one concentration value for NH.sub.3 and one concentration value for NO.sub.x is detected; calculating (202) modeled concentration values (316, 322; 416, 422) for NH.sub.3 and NO.sub.x downstream of the catalytic converter on the basis of a catalytic converter model, wherein the model comprises an aging parameter (342, 442) which at least partially describes aging of the modeled catalytic converter; comparing (208) the detected concentration values with the modeled concentration values; and, in a manner dependent on the result of the comparison, changing the aging parameter (342, 442) of the model and/or changing a predefined dosing quantity for a reducing agent in the SCR catalytic converter.