Removal of Phosphorus, Sulphur, and Arsenic from Ferronickel and Nickel Alloys

In the petroleum industry catalysts are often used to accelerate the reaction rate and remove the hazardous sulphur and arsenic from crude oil. A large quantity of spent catalyst material is generated every year and this represents a relatively cheap source of nickel supply. In order to use this nickel for the production of stainless steel or nickel alloys, the phosphorus, sulphur and arsenic in the material must be removed. The aim of this project is to remove these impurities from the nickel-based alloy produced from recovery of spent catalyst without incurring a significant loss of other valuable elements. Slag refining of nickel alloy was carried out in a 10 kw induction furnace. The effects of an oxidizing slag, a weak reducing slag and a strong reducing slag were examined. It was found that a strong reducing slag containing 70wt% CaC2 and 30wt% CaF2 was most suitable for the simultaneous removal of phosphorus, sulphur and arsenic without incurring a significant loss of valuable metal elements. With this slag, more than 70wt% sulphur, 67wt% arsenic, and about 30wt% phosphorus were removed.