The invention relates to a regeneration air system for an exhaust aftertreatment system of an internal combustion engine and to such an exhaust aftertreatment system. The regeneration air system comprises a regeneration air delivery element, a regeneration air duct, and a regeneration air valve. A sensor system is provided in the regeneration air duct with which a regeneration air mass flow {dot over (m)}.sub.SL can be determined exactly. The exhaust aftertreatment system comprises an exhaust system with an exhaust duct in which, in the direction of flow of an exhaust gas through the exhaust duct, a three-way catalytic converter is arranged underhood and a four-way catalytic converter is arranged downstream. A provision is made that an intake point for the regeneration air from the regeneration air system is formed on the exhaust duct downstream from the underhood three-way catalytic converter and upstream from the four-way catalytic converter.

A method (200) for ascertaining a catalytic converter state is proposed, wherein an exhaust-gas catalytic converter (130) is monitored on the basis of a catalytic converter model. Here, the catalytic converter model is adapted (250) in a manner dependent on measured values detected by means of one or more sensors (145, 147), wherein a frequency and/or a degree of the adaptation of the catalytic converter model is detected (260). The catalytic converter state is ascertained (270) as non-critical if the frequency and/or the degree of the adaptation do not exceed a predeterminable threshold value or is ascertained (270) as critical if the frequency and/or the degree of the adaptation exceed the predeterminable threshold value.

A fluid tank thaw system that includes a fluid tank that receives a first fluid. A heating element within the fluid tank that heats the first fluid. A magnetic stir system that stirs the first fluid within the fluid tank to increase a thaw rate of the first fluid. The magnetic stir system includes a magnetic stirrer within the fluid tank. The magnetic stirrer rotates within the fluid tank to agitate the first fluid. An electric coil changes polarity to rotate the magnetic stirrer.

An aftertreatment system comprises a reductant storage tank and a SCR system including a catalyst for reducing constituents of an exhaust gas. A reductant insertion assembly is fluidly coupled to the reductant storage tank and the SCR system. A controller is communicatively coupled to the reductant insertion assembly. The controller is configured to: determine an initial pressure of the reductant, determine a first pressure at which the reductant is to be delivered to the selective catalytic reduction system and adjust an operating parameter of the reductant insertion assembly. The adjustment of the operating parameter results in an at least selective delivery of the reductant at the first pressure to the SCR system.

Provided is a control device configured to be able to execute a forced regeneration process in an engine which includes a DOC and DPF disposed in an exhaust passage of the engine, and a temperature increase unit including an exhaust throttle valve, for increasing a temperature of each of the DOC and the DPF. The forced regeneration process includes a first temperature increase process of controlling the temperature increase unit such that the temperature of the DOC is increased to a first temperature, and a second temperature increase process of controlling the temperature increase unit such that the temperature of the DPF is increased to a second temperature which is higher than the first temperature after completion of the first temperature increase process. The control device includes a valve opening/closing operation execution part configured to cause the exhaust throttle valve to execute a valve opening/closing operation of increasing an opening degree of the exhaust throttle valve to be greater than a predetermined opening degree for a predetermined time, when the forced regeneration process is switched from the first temperature increase process to the second temperature increase process.

An engine exhaust aftertreatment device, comprising a first exhaust treatment unit and/or a second exhaust treatment unit; the first exhaust treatment unit comprises a first bypass pipeline (1) and a first connection pipe (4) provided between a DPF (2) and an SCR (3), one end of the first bypass pipeline (1) being in communication with a turbine front exhaust pipe (9), and the other end of the first bypass pipeline being in communication with the first connection pipe (4); the second exhaust treatment unit comprises a second bypass pipeline (19) and a second connection pipeline (20) provided between a DOC (13) and the DPF (2), one end of the second bypass pipeline (19) being in communication with the turbine front exhaust pipe (9), and the other end of the second bypass pipeline being in communication with the second connection pipeline (20); when it is detected that an engine (11) satisfies a starting condition of the first exhaust treatment unit, the first exhaust treatment unit starts; and when it is detected that the engine (11) satisfies a starting condition of the second exhaust treatment unit, the second exhaust treatment unit starts. Said device and method greatly improve the exhaust treatment efficiency and reduce the risk of exhaust excessive emission.

A method of treating exhaust gas in an exhaust passage using a selective catalytic reduction system is provided. The system comprises a hydrolysis catalyst in the passage upstream of a SCR catalyst, and a diesel exhaust fluid (DEF) dosing unit for injecting DEF onto the hydrolysis catalyst at a variable DEF dosing rate. The method comprises the steps of predicting an initial DEF dosing rate for converting all nitrogen oxide (NOx) contained in the exhaust gas, and estimating an amount of ammonia stored on the SCR catalyst. The method further comprises the steps of measuring a NOx conversion rate for the system, and adjusting the initial DEF dosing rate based upon the ammonia storage estimate and the measured NOx conversion rate to produce a first adjusted DEF dosing rate. An amount of ammonia-equivalent stored on the hydrolysis catalyst is then estimated, and the first adjusted DEF dosing rate is adjusted based upon the ammonia-equivalent storage estimate to produce a second adjusted DEF dosing rate. DEF is then injected at the second adjusted DEF dosing rate.

A method for controlling a return valve of an exhaust system and to an exhaust system with a control unit which is configured to carry out the method. The method is based on the object of avoiding an overpressure in the line system for urea solution as a result of a reduction in the injection rate. The method includes the steps of determining whether one or more of the following states are present during the operation of the exhaust system: a) an injection rate per unit of time of urea solution of the dosing valve is less than or equal to a predefined injection limit, b) a pressure measured by the pressure sensor in the line system overshoots a predefined first upper pressure limit (P2). The return valve is opened for a first predefined opening duration (Δt1) if states a) and b) are present and at least one of the states has already been present for at least a predefined period of time (Δta). The return valve is closed after the first predefined opening duration (Δt1) has elapsed.

A method for operating an internal combustion engine which has an exhaust-gas system in which a first exhaust-gas purification component and a second exhaust-gas purification component are arranged, and which has an opening-in point via which secondary air can be injected into the exhaust-gas system. The method is distinguished by the fact that an outlet concentration of the at least one exhaust-gas constituent prevailing at an outlet of the first exhaust-gas purification component is calculated by means of an outlet emissions model, and that an inlet concentration of the at least one exhaust-gas constituent prevailing at an inlet of the second exhaust-gas purification component is determined in a manner dependent on the calculated outlet concentration, and that the internal combustion engine is operated in a manner dependent on the thus determined inlet concentration of the at least one exhaust-gas constituent.

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.