Device for post-treatment of exhaust gases of a lean burning internal combustion engine

An assembly for treating the exhaust gases of an internal combustion engine, comprising:

• an exhaust line having an upstream side and a downstream side, and a catalytic converter disposed proximate the downstream side of said exhaust line;
• a static mixer disposed proximate the upstream side of said exhaust line between said engine and said converter, in the path of exhaust gases flowable therethrough;
• means disposed upstream of said static mixer for injecting a spray of a reducing agent into a segment of flow of said exhaust gases passing through said static mixer;
• and
• an intermediate conduit between said static mixer and said converter, wherein said intermediate conduit includes an inner pipe, an outer pipe surrounding the inner pipe, and an air gap between the inner pipe and the outer pipe along an axial direction of the intermediate conduit, wherein an end of the upstream side of said exhaust line is configured to be positively inserted into the inner pipe of the intermediate conduit, wherein the inner pipe has a constant diameter along the axial direction of the intermediate conduit, wherein a length of the air gap of the intermediate conduit along the axial direction is greater than the diameter of the inner pipe.