Device and method for generating a mixture of reducing agent and air

A device for generating a mixture of reducing agent and air for catalytically removing nitrogen from exhaust gases of internal combustion engines, having a mixing space (16) into which reducing agent can be introduced via a reducing agent delivery conduit (64, 164) and air can be introduced via an air delivery conduit (61, 165), characterized in that means (20, 21, 22, 23, 24, 60, 61, 165) for pressurizing the air are provided, so that the air that acts on the reducing agent is carried with a supercritical pressure difference through the air delivery conduit, and the air quantity flowing into the mixing chamber can be kept constant in certain pressure regions, independently of a pressure prevailing in the mixing space, and the mixing space is embodied as a space separate from the arrangement carrying the exhaust gases, and the mixture of reducing agent and air can be transported from the mixing chamber to a catalytic converter (30) via a line (25) communicating with the mixing space, and the reducing agent delivery conduit (64, 164) is embodied as a nozzle (63) disposed in a mixing chamber housing bore (62), and the air delivery conduit is embodied as an annular gap (61), concentrically surrounding the nozzle (63), between the nozzle and the wall (62a) of the mixing chamber housing bore (62), and an end portion (61a) of the annular gap (61), which portion discharges into the mixing space (16), is embodied as widening in the flow direction of the air.