Selective reduction of nickel from lateritic ore using Na2SO4 in an NH3 atmosphere

Abstract

All sectors, including the ferronickel industry, are being encouraged by governments and campaigners to reduce CO2 emissions due to their effect on the global climate. Compared to using reductants that contain carbon, free-carbon reductants are an alternative solution in decarbonizing the ferronickel industry, known as a CO2-intensive industry. This study uses NH3, one of the H2 carriers, for the selective reduction process of nickel laterite ore, with Na2SO4 serving as a selectivity additive. This study aims to investigate the selective reduction process of nickel laterite ore using Na2SO4 in an NH3 atmosphere. A Na2SO4 variation of 0–20 % by mass was used to study this. For all Na2SO4 addition variations, a fixed temperature and duration of 900 °C and 4 hours were used respectively. Based on X-ray diffractometer analysis, all variations of the Na2SO4 mixture (0–20 %) can form metallic phases. The more Na2SO4 is used, the reduction reaction extent increases and then decreases. Using a 900 °C, 4 hours, and 15 % Na2SO4 additive mixture can achieve the highest reduction reaction extent of 81.6 ± 1.17 %. Morphologically, using 10 % Na2SO4 or higher has been able to separate nickel- and iron-rich areas from impurities. Smelting experiments at 1600 °C also proved that ferronickel metal had formed. This early indication suggests that an NH3 atmosphere can also facilitate the selective reduction of lateritic ores.

Keywords

• Limonitic nickel
• Ferronickel
• Ammonia utilization
• CO2 reduction
• Sustainable process