A commercial NiO (green nickel oxide, 86 wt% Ni) powder was reduced using a batch-type fluidized-bed reactor in a temperature range of 500 to
and in a residence time range of 5 to 90 min. The reduction rate increased with increases in temperature; however, agglomeration and sintering (sticking) of Ni particles noticeably took place at high temperatures above
. An increasing tendency toward sticking was also observed at long residence times. In order to reduce the oxygen content in the powder to a level below 1% without any sticking problems, which can lead to defluidization, proper temperature and residence time for a stable fluidized-bed operation should be established. In this study, these values were found to be
and 60 min, respectively. Another important condition is the specific gas consumption rate, i.e. the volume amount (
) of hydrogen gas used to reduce 1 ton of Green NiO ore. The optimum gas consumption rate was found to be
-NiO for the complete reduction. The Avrami model was applied to this study; experimental data are most closely fitted with an exponent (m) of
and with an overall rate constant (k) in the range of 0.35~0.45, depending on the temperature.