Processing of oxidized nickel ores using sintering, roasting and leaching processes

Abstract

• The initial ore consists of α-iron oxide (74%) in a magnetically ordered phase. • After firing at 700 °C, iron oxide α-Fe2O3 (91%) prevails. • Optimum roasting temperature is 650 °C. • Crystalline hematite forms at temperatures above 700 °C. • Extraction of nickel into solution is 78.5%, cobalt −92.2%. The article is devoted to the results of research into the process of sintering, roasting and leaching of oxidized nickel ores, with selection of optimal parameters that include the addition of various reagents, varying the temperature, duration and roasting program, as well as creating the necessary atmosphere in the roasting furnace. It was revealed that only a small part of ferruginous minerals forms iron sulfate during sulfation with sulfuric acid, even at elevated temperatures. It is possible to reduce the loss of nickel binded with oxygen compounds of iron after the roasting at temperatures not exceeding 650 °C, while recrystallization of iron oxides occurs with the formation of α-Fe 2 O 3 , and the nickel is released, that can be leached. In general, the sintering and roasting process makes it possible to achieve a higher extraction of nickel and cobalt; it is shown that nickel, being a part of various ore minerals, is available for extraction at different stages of ore processing.