Hydrogen reduction of nickel oxide in presence of dispersed second phase

Abstract

Effect of dispersed second phase on the reduction kinetics of solid-gas reaction, with particular reference to the reduction of nickel oxide by gaseous hydrogen has been investigated in the temperature range 250-660°C. Calcia stabilised zirconia (CSZ). Al,Oj, CaO. MgO. and ZrO, were used as dispersoids. The reduction kinetics was found to be strongly influenced only in ihe presence of CSZ as a dispersoid; the maximum increase in the rate of reduction was for the mixture containing 25 moleft CSZ. For the same concentration of CSZ the increase in the rate of reduction was proportional to the surface area of the dispersed phase. The results have been found to be consistent with interfacially controlled reaction. A model depicting the influence of CSZ has been proposed.