An improved air injector for use in feed preparation in the primary reformer of a HABER processor for ammonia synthesis. In the HABER process, process gas is introduced at relatively high velocity downwardly in a process reactor through a vertical conduit. Along the axis of the conduit is an air supply pipe with a fixture which produces a plurality of downwardly and radially outwardly directed pipes attached to a plenum on the bottom of the air pipe. In this invention the number of circumferentially spaced pipes is doubled over the prior art and they are spaced circumferentially into rows directed outwardly at about a 45.degree. angle so as to present, more or less, a continuous plurality of streams of air which block the annular space and force the downflowing process gas to be turbulently mixed with the air and to form a pressurized mass of process gas and air, which is then forced, by the gas pressure, to flow downwardly in, more or less, a uniform manner through a volume of catalyst.