An apparatus for injecting particulate and/or gaseous material into a metallurgical vessel for use in a metallurgical process includes a duct to inject the material. The duct includes a duct wall of concentric annular passages for inflow of cooling water from a rear end to a forward end of the duct along a first of the annular passages and for outflow of cooling water from the forward end to the rear end of the duct wall along a second of the annular passages. The concentric annular passages are provided by concentric sleeves that consist of an inner sleeve, an outer sleeve, and an intermediate sleeve. The apparatus also includes a duct tip at a forward end of the duct joining at least the inner and outer sleeves so as to provide a water flow connection between the first and second water flow passages.