An apparatus for injecting gas into a vessel is disclosed. The apparatus comprises a gas flow duct from which to discharge gas from the duct, an elongate central structure extending within the gas flow duct, and a plurality of flow directing vanes disposed about the central structure adjacent the forward end of the duct to impart swirl to a gas flow through the forward end of the duct. The apparatus also comprises cooling water flow passages in the vanes that have inlets at the forward ends of the vanes and outlets at the rear ends of the vanes.