A two-stage reduction process for the production of high-purity ultrafine Ni particles in a micro-fluidized bed reactor

A novel two-stage reduction process for synthesis of ultrafine nickel powder with a high purity and low density in a fluidized bed reactor has been developed in this work.The raw ultrafine NiO particles are first pre-reduced using hydrogen at lower temperatures(340-400 ℃),followed by further reduction at higher temperatures(500-600 ℃).The self-agglomeration of Ni particles formed during low-temperature reduction decreases the sintering activity of the newly formed ultrafine Ni particles,leading to good fluidization quality,even for the subsequent high-temperature reduction process.The agglomerated Ni particles have a high Ni content(above 99wt%),a low density(0.78 g/cm~3) and a uniform particle size(approximately 100μm).A concept design for a novel two-stage fluidized bed reactor process used to produce high-purity Ni powder was also proposed.This approach may be extended to the synthesis of other ultrafine/nanosized metals or metal oxides through a fluidization method.