Reduction of Nickel Oxide Powder and Pellet by Hydrogen

Reduction of nickel oxide (NiO) powder and pellet by hydrogen was studied in a thermogravimetric apparatus. The variables studied were temperature (573, 673, 773, 873, 973 K) and hydrogen flow rate (100, 150, 200 cc min(-1)). With NiO powder 70-80 % reduction and with NiO pellets about 95 % reduction were achieved. With both NiO powder and pellets, the rate of reduction increased with increasing temperature and hydrogen flow rate and the linear nature of the fractional reduction versus time (F vs. t) plot, for the most part of the reduction at all temperatures, supported a rate control by gas film diffusion. The activation energies for the reduction of NiO powder and NiO pellet were found to be 20.14 and 19.21 kJ mol(-1), respectively. The SEM images showed that the grain size of nickel (Ni) produced was 1-2 mu, and the XRD analysis established the presence of Ni (and the absence of NiO) in the reduced sample.