Hydrogen Reduction of NiO Particles in a Single-Stage Fluidized-Bed Reactor without Sticking

Title & Authors
Hydrogen Reduction of NiO Particles in a Single-Stage Fluidized-Bed Reactor without Sticking
Oh, Chang-Sup; Kim, Hang Goo; Kim, Yong Ha;

Abstract
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 $\small{600^{\circ}C}$ 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 $\small{600^{\circ}C}$. 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 $\small{550^{\circ}C}$ and 60 min, respectively. Another important condition is the specific gas consumption rate, i.e. the volume amount ($\small{Nm^3}$) of hydrogen gas used to reduce 1 ton of Green NiO ore. The optimum gas consumption rate was found to be $\small{5,000Nm^3/ton}$-NiO for the complete reduction. The Avrami model was applied to this study; experimental data are most closely fitted with an exponent (m) of $\small{0.6{\pm}0.01}$ and with an overall rate constant (k) in the range of 0.35~0.45, depending on the temperature.
Keywords
hydrogen reduction;NiO particles;fluidized bed;sticking;
Language
English
Cited by
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