Relationship between reaction and diffusion during ultrafineNiOreduction toward agglomeration fluidization

The relationship between reaction and diffusion during ultrafine NiO reduction by H(2)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.

Automated summary

The study found that the reduction reaction in unreduced NiO powders follows the nucleation model. By incorporating grain-boundary diffusion and reaction, a modified force balance model was proposed to predict the agglomeration behavior of ultrafine Ni during the reduction of NiO in a fluidized bed reactor. Based on this model, it was discovered that decoupling grain growth from reduction is crucial for achieving full conversion while retaining nanosized grain sizes.