Analysis of accretions from the settler of a nickel flash smelting furnace

Abstract

Accretions from beneath the reaction shaft and the settler of a nickel flash smelting furnace were subjected to chemical, optical microscope and scanning electron microscope analysis. Accretions are deposited materials which build-up on the reaction shaft, uptake shaft throat and walls of flash furnace. The accretions consisted mainly of (Ni, Fe)₂SiO₄, and olivine 2(Mg, Fe)O.SiO₂. Dust collected from the Kalgoorlie Nickel Flash Furnace was investigated by optical and scanning electron microscope and contained (Ni, Fe)₂SiO₄, spinel and olivine with a low iron content. The mechanism of accretion formation was studied by heating dust from the Kalgoorlie flash furnace over the temperature range 1523 to 1723 K at known oxygen pressures which were controlled by CO/CO₂ gas mixtures. The results showed that temperature and oxygen pressure have an effect on the composition of the Fe₃O₄ spinel and orthosilicate, especially the iron, nickel and silica contents. The composition of these accretions consisted of small grains of Fe₃O₄ spinel and a solid solution series of (Ni, Mg)₂SiO₄ Comparison of the laboratory accretion, furnace dust and accretion samples indicated that the furnace accretion was probably formed by the dust sticking to the wall of the flash furnace. The original accretion should be a Fe₃O₄ spinel and olivine. During formation, the Fe₃O₄ spinel was probably altered to be (Ni, Fe)₂SiO₄ because of the addition of nickel oxide, and the reaction with SiO₂ in olivine.