The treatment of laterites has been a research hotspot in extractive metallurgy over the past decades. Industrially, the pyrometallurgical treatment of laterites is mostly accomplished with a well-established method, namely, the rotary kiln–electric arc furnace (RKEF) process, which includes three main operations—calcination, prereduction, and smelting—followed by further refining for the removal of impurities from the raw ferro-nickel. As indicated in many studies of the RKEF process, the major downside of this method is its high energy consumption. Efforts have been made to lower this consumption. Furthermore, several new processes have been proposed. Among these, low-grade ferro-nickel production is regarded as the most widely and industrially used process after traditional RKEF operation. Although not widespread, other alternative processes of industrial scale have been generated since the start of the millennium. Recently, certain innovative processes have been tested either in the laboratory or at pilot-scale. In this paper, a literature review related to the smelting of laterites is made, and an emphasis on new processes and some examples of new developments in the RKEF process are presented.
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.
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