A device to be installed in a pipeline, characterized by at least one static mixer and at least one pre-mixer arranged in a sleeve, wherein said at least one static mixer is characterized by: a body having a plurality of slots through the body, said slots having one or more sides that are angled with respect to an axis passing through a center of the body; a plurality of arms extending from an outer edge of the body towards a center of the body, wherein the plurality of slots comprising at least one concentric ring of slots.