Study on the Refining Conditions of Nickel Pig Iron for High Purity Nickel Matte Production

Nickel has been known to be the most important metallic resource, which has been used in various products, such as multi-layer ceramic capacitors, Li-ion batteries, heat-resistance super alloys. Those Ni resources have various types such as metallic nickel, ferronickel alloy, nickel matte, and nickel sulfate depending on the situation. In a production route of high purity nickel matte from ferronickel, which had been implemented many decades ago, a large amount of by-product, as well as relatively high operational cost, have been recently drawing attention. To resolve arisen problems, nickel pig iron can be suggested as a low-cost raw material. The possibility of upgrading nickel pig iron by removal of Fe and enrichment of Ni was investigated by lab-scale oxidation experiments. It was found that major impurities like C and Si should be removed before Fe oxidation initiates. And decarburization and desiliconization of nickel pig iron were enhanced by oxygen injection, compared with other blowing manners. The slag conditions for effective Fe oxidation were discussed using thermodynamic calculation and oxygen blowing tests. Conclusively, the continuous addition of CaO during oxygen blowing enables the formation of liquid slag and further Fe oxidation. In the case of Fe2O3-SiO2 based slag, liquid slag seems to be limited by MgO dissolution from refractory