Abstract: A material injection nozzle for a spray drying system of the type wherein the material to be dried is introduced into the exhaust pipe of one or more pulse jet engines and borne upwardly through openings in the floor of a vertical drying chamber is disclosed. The nozzle includes a substantially cylindrical member that is coaxially mounted within the pulse jet engine exhaust pipe to extend from the exit opening thereof to a point below the termination of a material feedpipe that passes coaxially upward through the lower portion of the pulse jet engine exhaust pipe. In all cases, the nozzle is dimensioned and arranged to interact with the high temperature gaseous flow and acoustic field within the exhaust pipe to eliminate or greatly reduce adherence of material passing through the exhaust pipe which would otherwise accumulate as a burned, hardened substance and cause the pulse jet engines to malfunction and cease operating.