Abstract:
Zincor, a zinc refinery in South Africa, uses oxygen enrichment of
up to 26% O2 in its fluidizing air to increase concentrate-throughput
in its fluidized bed roasters. The aim of the study is to determine
whether O2 enrichment can be reduced by introducing micropelletized
concentrate into the feed blend, while maintaining
concentrate throughput rates and calcine quality. A laboratory scale
fluidized roaster was used to determine the strength and oxidation
kinetics of suitable micro-pellets. The strength of the pellets was
determined by the extent of attrition during roasting. It was found
that micro-pelletization decreases the fines in the feed to the
roasters; the –500 μm fraction decreased from 87% to 10%. The
micro-pelletized particles do break down during roasting, which
increases the -500 μm fraction to 31%. The general morphologies of
the roasted particles are similar to those found by previous workers.
Micro-pelletized concentrate particles require more time than nonpelletized
concentrate particles to oxidize in the roasting step,
although this is less than the mean residence time of the Zincor
roasters. Roasting micro-pellets in O2-enriched fluidizing air
increased the reaction rate.
