A method of roasting carbonate iron ore in a shaft furnace. The ore sinks continuously down the furnace while a current of hot air or flue gas, with a low carbon dioxide content, is passed through the body of the ore and a current of cold air is passed upward through the lower part of the shaft, this part acting as a cooling chamber for the ore and as a preheating flue for the air, which rapidly oxidizes the ferrous oxide in the upper regions of the furnace. The quantity and temperature of the hot gases and cold air are carefully regulated, so as to keep the carbon dioxide content of the flue gas at a minimum and thereby ensure thorough roasting of the ore at the lowest possible temperature. A furnace roasting 181 to 408 t/d requires about 176,400 to 220,500 kg.cal/t (736 to 923 kg.kJ/t), giving a heat efficiency of 73%. Osborne
Source: Dictionary of Mining, Mineral, and Related Terms
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