Arrangement for exhaust-gas aftertreatment system for an internal combustion engine and method for operating the exhaust-gas aftertreatment system arrangement

#This application claims priority to German Patent Application No. 102013212801.0, filed Jul. 1, 2013, the entire contents of which are hereby incorporated by reference for all purposes.

#The present disclosure relates to an arrangement for an exhaust-gas aftertreatment system for an internal combustion engine and a method for operating the arrangement.

#Internal combustion engines may generate considerable amounts of nitrogen oxides (NOx) during operation. In the case of diesel and gasoline lean-burn engines used in motor vehicles, the amounts of nitrogen oxide in the exhaust gas are generally higher than the admissible limit values, such that exhaust-gas aftertreatment is desired in order to reduce the NOx emissions. In one prior art method, an SCR (Selective Catalytic Reduction) catalytic converter is used for reducing the NOx emissions. For the conversion of the nitrogen oxides by an SCR catalytic converter into non-hazardous substances, a supply of ammonia (NH3) may be needed, for example by way of an injection of a urea solution into the exhaust-gas stream. In another widely used method, use is made of a NOx storage catalytic converter (Lean NOx Trap, LNT) which absorbs and stores the nitrogen oxides contained in the exhaust gas of the internal combustion engine. A regeneration of the NOx storage catalytic converter must be performed from time to time, for which purpose it is necessary for an excess of fuel to be generated in the exhaust gas that is conducted through the NOx storage catalytic converter, which entails an additional consumption of fuel. Thus, both for the operation of an SCR catalytic converter and also of a NOx storage catalytic converter, additional costs are incurred owing to the needed provision of ammonia and of additional fuel.

#FIG. 1 shows an exemplary embodiment of an arrangement according to the invention for exhaust-gas aftertreatment for an internal combustion engine;

#FIG. 2 shows a method for operating an exhaust-gas aftertreatment system arrangement; and

#FIG. 3 shows another method for operation of an exhaust-gas aftertreatment system.

#US 2006/0168948 A1 discloses a sequence of two NOx storage catalytic converters, wherein the first NOx storage catalytic converter is an aluminum oxide-based NOx storage catalytic converter and the second is a conventional NOx storage catalytic converter. During a desulfurization of the first NOx storage catalytic converter, the exhaust-gas stream is conducted past the second NOx storage catalytic converter through a bypass branch such that no sulfur passes to said second NOx storage catalytic converter either during normal operation or during the desulfurization of the first NOx storage catalytic converter.

#In DE 196 26 837 A1, a NOx storage catalytic converter of an exhaust system of a diesel internal combustion engine is regenerated in targeted fashion under operating conditions in which there is a low NOx content in the exhaust-gas stream. In this case, the exhaust-gas stream is conducted predominantly past the NOx storage catalytic converter, and the NOx storage catalytic converter is regenerated by an injection of fuel. An oxidation catalytic converter is arranged in the downstream, re-merged part of the exhaust system. In US 2006/0213187 A1, the exhaust-gas stream is conducted successively through an oxidation catalytic converter, a particle filter, a NOx adsorber, and an SCR catalytic converter, wherein the NOx adsorber can be bypassed via a bypass line during a regeneration phase.

#In the known exhaust-gas aftertreatment arrangements and methods for the reduction of NOx emissions in the applications described above, considerable additional operating costs are incurred owing to the needed provision of ammonia and additional fuel. Furthermore, whether a regeneration of the NOx storage catalytic converter is possible is dependent on the operating conditions of the internal combustion engine, in particular on the current engine speed and the current load.