Behaviour of synthetic nickel mattes under suspension smelting conditions

A single-particle laminar-flow technique was used to study the oxidation of four synthetic nickel mattes in three size fractions (<37, 62-88 and 125-177 μm). The reaction gas composition was varied from N₂ + 21 to N₂ + 75 vol% O₂ and the gas preheating temperatures ranged from 500 to 1100°C. The four mattes were synthesized so that Ni/Cu ratios of 1 and 10 were obtained with a high and a low iron content. Chemical analysis of the particles was used to determine the degree of oxidation of the materials, and optical and scanning electron microscopy was used to detect their morphology, internal composition and structure. The best sulphur removal from the synthetic nickel mattes was achieved under the most oxidizing conditions and with the finest size fraction. In addition, the reactivity of the mattes was clearly dependent on the particle size as well as on the chemical composition of the material. The matte with Ni/Cu = 1 and high iron content was found to be the most reactive and the matte with Ni/Cu = 10 and low iron content the least reactive; the coarse-fraction particles of the latter did not react at all under the conditions studied.