DRI Technology

Therefore, the process has both low energy consumption and low environmental impact, making it an environment-friendly process. The direct reduction of the oxide is carried out on a continuous basis. The iron oxide, fed to the top of the shaft furnace, flows downward under gravity and is discharged from the bottom in the form of direct reduced iron. The shaft furnace has two main gas circuits. In the upper circuit, iron oxide is preheated and reduced by counter flowing reducing gas, consisting of predominantly hydrogen and carbon monoxide. The lower circuit introduces a mixture of reducing gas and natural gas for the purpose of carburizing the direct reduced iron. The reducing gas is generated in the reformer by catalytically reforming a mixture of fresh natural gas and recycled top gas from the shaft furnace. The reformer is a refractory lined furnace containing alloy tubes filled with a nickel-based catalyst. The feed gas mixture flows upward through the catalyst bed where it is heated and reformed. The reducing gas leaves the reformer at near equilibrium conditions, containing 90 to 92 per cent hydrogen and carbon monoxide. The gas is then directly conveyed to the shaft furnace. The thermal efficiency of the reformer is greatly enhanced by the heat recuperator. This unit consists of two shell and tube type heat exchangers in the flue gas duct coming from the reformer. The heat exchangers recover the sensible heat from the reformer flue gas to preheat combustion air (used in the reformer burners) to 640 °C and to preheat the process gas (mixture of top gas and natural gas fed to the reformer tubes) to 540 °C.