Diffusion in nickel oxide pellets–effects of sintering and reduction

✍ Scribed by K. K. Kim; J. M. Smith

• Publisher: American Institute of Chemical Engineers
• Year: 1974
• Tongue: English
• Weight: 912 KB
• Volume: 20
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690200407

✦ Synopsis

Abstract

Diffusion rates were measured at 25°C and 1 atm by a steady state method in pellets of nonporous nickel oxide particles in order to determine the effects of sintering and chemical reduction. Sintering led to a striking decrease in diffusion flux; tortuosities above 100 were found for highly sintered (porosity 0.03) pellets. Reduction caused a sharp increase in diffusion rate when the original pellet was highly sintered. For an originally unsintered pellet the diffusion rate decreased with extent of reduction.

These phenomena were explained quantitatively by using: (1) the random pore model to predict tortuosity factors for an unsintered, unreduced pellet, and (2) the extent of pore interconnections and the fractional reduction to treat the effects of sintering and reduction. In this way an approximate, predictive equation was derived which contained no arbitrary parameters and which required for application only data on porosity and extent of chemical reduction.