Optimization of ferronickel production from Sivrihisar nickel laterite ore

Thesis Type: Doctorate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Department of Metallurgical and Materials Engineering, Turkey

Approval Date: 2014




In this study, pyrometallurgical treatment of limonitic laterite ore from Sivrihisar region was investigated. The run-of-mine (ROM) ore contained 1.26 wt.% Ni but was initially upgraded to 1.405 wt.% Ni by screening out the +50 mm particles. Finer than 50 mm ore was crushed to -1 mm and used in the experiments. Then, the ore was calcined at different temperatures. The optimum calcination conditions were determined as 700°C and 40 min. which resulted in 10% weight loss. At the next (prereduction) stage, the calcined ore was reduced at 700-1100°C by the addition of 5.74, 8.61 and 11.48 wt.% coal under argon atmosphere. It was found that the metallization of iron was limited until 900°C but increased rapidly at higher temperatures. The metallization of nickel and cobalt initiated at much lower temperatures and increased with temperature. The results also showed that increased coal additions did not affect the iron metallization up to 900°C. At 1000°C the metallization of Fe became slightly better, but its effect was more pronounced at 1100°C. The increased coal addition increased the nickel reduction at all temperatures, while it had no effect on the metallization of cobalt. The usage of 70%N2-20%CO2-10%CO gas mixture as reducing atmosphere substantially improved the reduction process below 1000°C. Finally, the reduced ore was smelted to produce ferronickel. No coal was added at the smelting stage and the reduction reactions were completed by the unreacted coal from the previous prereduction stage. Conditions were adjusted to produce a ferronickel containing ~15% Ni. The physical and the chemical losses of nickel in the slag were directly proportional to the ferronickel grade. Colemanite was added to the charge to decrease the physical losses in the slag and to increase nickel recovery but no positive effect was observed.