Evaluating the Thermal Efficiency of a Shaft Furnace for Roasting Siderite Ore

The roasting of siderite ores in shaft furnaces is characterized by significant nonuniformity of the temperature and velocity fields at all levels of the charge. Heat exchange takes place at a low rate in the preheating zone, leading to the formation of flue gases with a temperature of about 230°C and displacement of most of these gases toward the area where they are sucked out of the furnace. The temperature of the heat carrier is highest when it leaves the firebox. In the cooling zones, the best conditions for reducing the temperature of the materials are created in the peripheral region farthest from the area where the heat carrier is delivered. The thermal processing of siderites is no more than 78% completed in the preheating zone and consolidation of individual lumps of the core is limited to the stage in which products from decomposition of the carbonates are oxidized. Part of these processes are completed in the cooling stage. Solid phase sintering and melting of the materials are limited to the cooling zones and proceed to no more than take place more than 1–3% completion. The yield of roasted siderite is no greater than 47.67%. Roasting of the siderite occurs with the evolution of a small amount of heat from the oxidation of oxides of iron and manganese. Thermal efficiency is no higher than 35% in cooling zone 1 and 84.42% in cooling zone 2.