Environmental Engineering Reference
In-Depth Information
Fig. 13.4
Generalized
materials flow for EAF dust
treatment
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been designated as a harmful industrial waste in Japan because it contains small
amounts of heavy metals such as lead and also a very small amount of dioxins.
Although numerous treatment processes have been proposed, only three have been
employed commercially in Japan. We now discuss recycling of Zn from EAF dust
recycling in more detail.
13.3
EAF Dust Recycling
Steel production from electric arc furnaces has been increasing and this trend is
likely to continue. As a result, increasing quantities of EAF flue dust containing
high zinc content will have to be treated and more zinc will become available for re-
cycling. A schematic material flow for zinc-coated steel scrap is shown in Fig.
13.4
.
When steel is being produced from scrap, the zinc remaining on the feedstock is
volatilized and captured in the flue dust which is filtered out from the furnace gases.
A substantial quantity of this dust is upgraded and then used as feedstock for the
production of primary zinc. This treatment is not economic however, and most EAF
dust has historically been landfilled. However, as the dust has become listed as a
hazardous waste and has to be disposed of in more highly regulated sites, the attrac-
tion has grown for technical improvements towards highly efficient recycling. In-
dustry is aware of the potential for further recovery of zinc from EAF dusts, and the
amount of these materials that are treated to recover the zinc content is increasing.
Today's EAF dust treatment processes are summarized in Fig.
13.5
which in-
cludes both commercial operation processes and pilot plant operation processes (but
excludes processes still at the laboratory scale). Pyrometallurgical processes such as
the Waelz kiln process have been commonly used to recover crude ZnO from EAF
