A method of controlling a catalytic exhaust system having a first catalytic unit located upstream of a second catalytic unit includes i) providing a relationship between the temperature of the first catalytic unit, an amount of NH3 stored in the second catalytic unit, and a corresponding limit value of the amount of NH3 permitted in the first catalytic unit; ii) measuring or estimating the amount of NH3 in the second catalytic unit; iii) measuring or estimating the temperature of the first catalytic unit; iv) using the relationship and measured/estimated parameters of steps ii and iii to provide the limit value for the amount of NH3 to be stored in the first catalytic unit; and v) using the parameter from iv in the control of the catalytic exhaust system.

An internal combustion engine (1), with an engine regulating device (3) and an exhaust gas aftertreatment device (16) with an SCR catalytic converter (4) for the reduction of at least one NO.sub.x component, and with a catalytic converter regulating device (6), wherein the engine regulating device (3) is prescribed a target value for an NO.sub.x mean value of the NO.sub.x component of the exhaust gases, which mean value results at an outlet point (7) of the exhaust gas aftertreatment device (16) in relation to a predefinable time period, and the engine regulating device (3) is configured at least in one operating mode to continuously calculate an NO.sub.x reference value for the catalytic converter regulating device (6) with consideration of No.sub.x components which have already been emitted and the predefined target value, which reference value is selected in such a way that the predefined target value results at the outlet point of the exhaust gas aftertreatment device (16) at the end of the predefinable time period when the calculated NO.sub.x reference value of the catalytic converter regulating device (6) is fed as NO.sub.x setpoint value to the regulating means.

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.

An exhaust gas aftertreatment system for an internal combustion engine includes an inlet conduit, a reductant decomposition chamber, a first selective catalytic reduction (SCR) catalyst member, a second SCR catalyst member, a mixing chamber, a particulate filter, a reductant delivery system, and a hydrocarbon delivery system. The inlet conduit is configured to receive exhaust gas from the internal combustion engine. The reductant decomposition chamber is fluidly coupled to the inlet conduit and configured to receive the exhaust gas from the inlet conduit. The first SCR catalyst member is fluidly coupled to the reductant decomposition chamber and configured to receive the exhaust gas from the reductant decomposition chamber. The second SCR catalyst member is fluidly coupled to the first SCR catalyst member and is configured to receive the exhaust gas from the first SCR catalyst member.

Known catalyst systems for the catalytic combustion of ammonia to form nitrogen oxides consist of a plurality of single- or multilayer catalyst gauzes warp-knitted, weft-knitted or woven from platinum-based noble metal wire, which, when arranged one behind the other in a fresh gas flow direction, form a front group of gauze layers and at least one downstream group of gauze layers arranged after the front group. To provide from this starting point a catalyst system for use in a medium-pressure plant for ammonia oxidation, with which a high service life and a high yield of the main product NO can be achieved, it is proposed that the front group comprises a gauze layer or a plurality of gauze layers made of a first, rhodium-rich noble metal wire, wherein the gauze layer or one of the gauze layers made of the rhodium-rich noble metal wire is a front gauze layer facing the fresh gas, and that the downstream group comprises gauze layers made of a second, rhodium-poor noble metal wire, wherein the rhodium content in the rhodium-rich noble metal wire is at least 7 wt. % and no more than 9 wt. % and is at least 1 percentage point higher than the rhodium content in the rhodium-poor noble metal wire

Various embodiments relate to a selective catalytic reduction system for treating exhaust gases of an internal combustion engine. The system includes an inlet section that receives exhaust gases from the engine. The system includes a tank storing diesel exhaust fluid (“DEF”), a pump, a valve, and an injector each in fluid communication with each other. The injector is coupled to the inlet exhaust pipe and configured to inject DEF into the exhaust gases flowing through the inlet exhaust pipe in a plurality of pulses. Each of the plurality of pulses injects a constant volume of DEF into the inlet exhaust pipe. The system further includes a controller configured to operate the pump and the valve such that a time interval between successive constant volume pulses of the plurality of pulses is varied based on a variable oxides of nitrogen content of the exhaust gases.

Systems and methods of the present invention related to an exhaust gas purification system comprising: (a) a first injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas; (b) a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalyst reduction (SCR) catalyst and an oxidation catalyst; (c) a second injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas, located downstream of the filter; and (d) a downstream catalyst comprising a selective catalytic reduction catalyst, located downstream of the second injector.

A system for treatment of an exhaust gas stream from an engine is provided, containing an upstream selective catalytic reduction (SCR) catalyst, which receives the exhaust gas stream without any intervening catalyst, a diesel oxidation catalyst (DOC) positioned downstream thereof; a catalyzed soot filter (CSF) downstream of the diesel oxidation catalyst; a second SCR catalyst positioned downstream of the catalyzed soot filter; and an ammonia oxidation (AMOx) catalyst. The application also describes use of such systems to reduce nitrogen oxides (NOx) and hydrocarbons (HC) in an exhaust gas stream.

Systems, apparatuses, and methods include predicting a sulfur exposure of one or more copper-zeolite catalysts deployed in an exhaust aftertreatment system; comparing the predicted sulfur exposure to a predefined sulfur exposure threshold; and responsive to the determination, heating the exhaust aftertreatment catalyst to a predefined heat treatment temperature for a predefined time period to desulfate the one or more copper-zeolite catalysts.

Disclosed is a method for selective catalytic reduction operating by desorbing ammonia from at least one storage cartridge in an exhaust line at the output of a motor vehicle engine, the cartridge being arranged in at least one bypass branch of a main line of the exhaust line. The exhaust gas flow rate in the bypass branch is controlled according to an estimated or measured temperature in the bypass branch and a desired amount of ammonia to be injected by desorption estimated in the exhaust line to provide a catalytic reduction of the nitrogen oxides present in the exhaust gas, a temperature of the cartridge being estimated according to the gas flow rate at the temperature estimated or measured during a given time interval and corresponding to an amount of desorbed ammonia equal to the desired amount of ammonia.