System and method for treatment of an exhaust stream and control system therefor

A method for treatment of an exhaust stream resulting from a combustion in a combustion engine, the method comprising:

• catching soot and ash created by the combustion by utilization of a particulate filter;
• controlling a supply of an additive into the exhaust stream by utilization of a dosing arrangement arranged downstream of the particulate filter;
• reduction of nitrogen oxides NOx in the exhaust stream by utilization of the supplied additive and a reduction catalyst arrangement arranged downstream of the dosing arrangement, the reduction comprising a first reduction of nitrogen oxides NOx primarily in a first temperature interval T1 by a first selective catalytic reduction catalyst, and a second reduction of nitrogen oxides NOx primarily in a second temperature interval T2 by a second selective catalytic reduction catalyst arranged downstream of the first selective catalytic reduction catalyst, wherein the first temperature interval T1 is at least partly higher than the second temperature interval T2;
• and
• interaction of the first selective catalytic reduction catalyst and particles in the exhaust stream being created by one or more of the supply of the additive into the exhaust stream and a transformation of the additive when flowing through the exhaust treatment system, the interaction being caused by an opening degree of the first selective catalytic reduction catalyst arranged such that:
• the particles are at least partly captured and removed by the first selective catalytic reduction catalyst;
• and
• accumulation of soot and ash created by the combustion, which would affect the interaction of the first selective catalytic reduction catalyst and the particles, is at least partly avoided.

A computer program product stored on a non-transitory computer-readable medium, said computer program product for treatment of an exhaust stream resulting from a combustion in a combustion engine, wherein said computer program product comprising computer instructions to cause one or more computer processors to perform the following operations:

• controlling a supply of an additive into the exhaust stream by utilization of a dosing arrangement arranged downstream of a particulate filter configured to catch soot and ash created by the combustion;
• reduction of nitrogen oxides NOx in the exhaust stream by utilization of the supplied additive and a reduction catalyst arrangement arranged downstream of the dosing arrangement, the reduction comprising a first reduction of nitrogen oxides NOx primarily in a first temperature interval T1 by a first selective catalytic reduction catalyst, and a second reduction of nitrogen oxides NOx primarily in a second temperature interval T2 by a second selective catalytic reduction catalyst arranged downstream of the first selective catalytic reduction catalyst, wherein the first temperature interval T1 is at least partly higher than the second temperature interval T2;
• and
• interaction of the first selective catalytic reduction catalyst and particles in the exhaust stream being created by one or more of the supply of the additive into the exhaust stream and a transformation of the additive when flowing through the exhaust treatment system, the interaction being caused by an opening degree of the first selective catalytic reduction catalyst arranged such that:
• the particles are at least partly captured and removed by the first selective catalytic reduction catalyst;
• and
• accumulation of soot and ash created by the combustion, which would affect the interaction of the first selective catalytic reduction catalyst and the particles, is at least partly avoided.

A control system arranged for controlling an exhaust treatment system for treatment of an exhaust stream resulting from a combustion in a combustion engine, the treatment comprising:

• catching soot and ash created by the combustion by utilization of a particulate filter;
• controlling a supply of an additive into the exhaust stream by utilization of a dosing arrangement arranged downstream of the particulate filter;
• reduction of nitrogen oxides NOx in the exhaust stream by utilization of the supplied additive and a reduction catalyst arrangement arranged downstream of the dosing arrangement, the reduction comprising a first reduction of nitrogen oxides NOx primarily in a first temperature interval T1 by a first selective catalytic reduction catalyst, and a second reduction of nitrogen oxides NOx primarily in a second temperature interval T2 by a second selective catalytic reduction catalyst arranged downstream of the first selective catalytic reduction catalyst, wherein the first temperature interval T1 is at least partly higher than the second temperature interval T2;
• and
• interaction of the first selective catalytic reduction catalyst and particles in the exhaust stream being created by one or more of the supply of the additive into the exhaust stream and a transformation of the additive when flowing through the exhaust treatment system, the interaction being caused by an opening degree of the first selective catalytic reduction catalyst arranged such that:
• the particles are at least partly captured and removed by the first selective catalytic reduction catalyst;
• and
• accumulation of soot and ash created by the combustion, which would affect the interaction of the first selective catalytic reduction catalyst and the particles, is at least partly avoided.