Green and efficient mineral phase transformation of saprolitic nickel laterite ore through fluidized pre-heating and hydrogen-based pre-reduction processes

Abstract

Nickel laterite ore is an important nickel-bearing mineral. Research on pre-heating and hydrogen pre-reduction in the pyrometallurgical process of nickel laterite ore is very limited, especially when using fluidized bed roasting. This study systematically explores the mechanisms of fluidized bed pre-heating treatment and hydrogen pre-reduction in the roasting process of saprolitic nickel laterite ore. According to single-factor experiment results, the appropriate pre-heating and pre-reduction conditions were a pre-heating temperature of 700 °C, a pre-heating time of 30 min, a pre-reduction temperature of 700 °C, a pre-reduction time of 30 min, and a hydrogen concentration of 80%. Then, the nickel metallization rate and iron metallization rate reached 90.56% and 41.31%, respectively. Various analytical and testing methods were employed to study the changes in phase composition, magnetism, surface element valence states, and microstructure of nickel laterite ore during fluidized pre-heating and pre-reduction. The study shows that hydrogen can achieve nickel reduction at relatively low temperatures. It was also found that pre-heating treatment of nickel laterite ore is beneficial. Pre-heating opens up the mineral structures of serpentine and limonite, allowing the reducing gas and nickel to interact quickly during the reduction process, enhancing the pre-reduction process.

Keywords

nickel laterite ore / fluidization / hydrogen pre-reduction / phase transformation / microstructure

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