9. Gas

9.1 Gas evolution in the blast furnace

The gas produced at the tuyeres at flame temperature (2,000-2,300°C) is continuously cooled down to throat temperature (100-150°C) as it rises, due to counter-current thermal and chemical exchanges with the charge. On average, the average residence time of the gas in the charge is of the order of 8 to 12 s, which, for a blast furnace with a useful height of 25 m (distance between tuyere and throat), corresponds to a velocity of the order of 2 to 4 m/s. Depending on loading conditions, the residence time of the gas at the center of the blast furnace may be lower, in the order of 4 to 5 s.