Limonitic nickel laterite from Sivrihisar reserve in Turkey was reduced at 700-1100uC by the addition of 5?74, 8?61 and 11?48 wt-% coal under an argon atmosphere. The run-of-mine ore and the reduced samples were studied using X-ray diffraction. The metallisation of Fe was found to be limited up to 900uC, but increased rapidly at higher temperatures. The metallisation of Ni and Co increased when the temperature was increased from 700 to 800uC, almost levelled off up to 900uC and then increased up to 1100uC. The results also showed that increased coal additions did not affect Fe metallisation up to 900uC. At 1000uC the metallisation of Fe became slightly better, but its effect was more pronounced at 1100uC. The increased coal addition affected the nickel reduction equally at all temperatures, while it had no effect on the metallisation of Co.
Use of colemanite in metal-slag systems aims primarily to decrease the viscosity of slag and, therefore, achieve better metal-slag separation. Enhanced metal-slag separation is helpful to decrease the number of suspended metal/alloy droplets in slag, i.e. the physical losses. In the literature, successful use of colemanite was reported both in steelmaking and copper matte smelting processes. Ferronickel smelting slags contain nickel in the range of 0.1-0.2% and correspondingly, metal-slag distribution ratio values of nickel are reported even above 200. On the contrary, nickel recoveries are hard to exceed 95%. This can be mostly attributed to the physical losses of nickel due to very high slag volume in ferronickel smelters; for 1 ton of ferronickel, 10-15 tonnes of slag are generated regardless of the type of the laterite, which contains significant quantity of gangue components. The authors thought that use of colemanite could be a solution to decrease physical losses. Therefore, the use of colemanite in ferronickel smelting was investigated in the present work. Laboratory-scale smelting experiments were conducted using calcined and prereduced laterites in a vertical tube furnace under different gas atmospheres. The amount of colemanite added was in the range of 0-2.5% of the total charge. The experiments were also performed using ferronickel and slag samples obtained from a ferronickel smelter.
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