A direct smelting plant for producing molten metal from a metalliferous feed material using a molten bath based direct smelting process is disclosed. The plant includes a gas delivery duct assembly extending from a gas supply location away from the vessel to deliver oxygen-containing gas to gas injection lances extending into a direct smelting vessel. The gas delivery duct assembly includes a single gas delivery main connected to the gas injection lances to supply oxygen-containing gas to the gas injection lances. The gas delivery main is located at a height above a lower half of the vessel.