Inducing swirl in a gas flow. An apparatus for injecting gas into a metallurgical vessel supporting a metallurgical process is disclosed. The apparatus comprises a gas flow duct, an elongate central structure extending within the gas flow duct, and a plurality of flow directing swirl vanes disposed about the central tubular structure adjacent the forward end of the duct. The flow directing vanes are formed with internal water flow passages for flow of cooling water internally along each vane and the elongate central structure is formed with a cooling water supply passage for supply of coolingwater to the internal water flow passages in the vanes and a water return passage for outflow of cooling water which has passed through the internal water flow passages in the vanes.