Relationship between reaction and diffusion during ultrafine NiO reduction toward agglomeration fluidization

Abstract

The relationship between reaction and diffusion during ultrafine NiO reduction by H2 in a fluidized bed reactor were investigated. The result illuminates that the reduction reaction proceeding in the unreduced NiO powders is according to the nucleation model. A modified force balance model between cohesive and collision forces incorporating grain‐boundary diffusion and reaction is proposed to predict the agglomeration behavior of ultrafine Ni during the reduction of NiO in a fluidized bed. The modified force balance model shows more precise predictions than the model without consideration of grain‐boundary diffusion. Based on the model, it is found that the core of the two‐step reduction is to decouple grain growth from reduction for achieving full conversion while retaining nanosized grain sizes.