The invention pertains to a spray/gas mixer, comprising: a main body having a circumferential wall with a first longitudinal axis (A) and extending from a first end to a second end, the first end defining an inlet opening, the second end defining an outlet opening; a divider baffle inside the interior; a swirl duct within the interior along a second longitudinal axis (B), having one end adjacent to the wall and a second end extending to the divider baffle; an injector orifice at the first end of the swirl duct; a swirl promoting means; and a restrictor arrangement. The swirl promoting means is arranged between the divider baffle and the restrictor arrangement, such that gas passing through the swirl promoting means is swirled around the first longitudinal axis (A) before passing through the restrictor. The restrictor arrangement is disposed between the swirl promoting means and the second end, forcing gas reaching it from an upstream side away from a peripheral region of the interior towards a center axis of the main body.