Environmental Engineering Reference
In-Depth Information
Table 13.1
Comparison of pyrometallurgical processes for EAF dust treatment in Japan
Process
Furnace
operation
Energy
Product
Raw material
flexibility
De-lead
process
Waelz
Large/complex Coke, car-
bon, oil
Crude ZnO
sinters
Low
Chlorinated
roasting
Rotary Hearth Large/complex Coal, natural
gas
ZnO, iron
Low
-
MF
Small/simple
Coke, oil
Crude ZnO, slag High
-
St. Joseph
Large/complex Electricity
ZnO, sinters
Low
Chlorinated
roasting
DSM
Small/simple
Coal
Crude ZnO
Low
-
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Fig. 13.6
Schematic illustration of Rotary Hearth Furnace process
The Mitsui Furnace (MF) originally developed by Mitsui Mining & Metals, Ltd.
is a unique short blast furnace type as shown in Fig.
13.7
. Briquettes of EAF dust
and cokes are put into the furnace from the top, and hot air is blown from a tuyere
as used in a blast furnace, and ZnO and ZnFe
2
O
4
are reduced to zinc gas by cokes in
the furnace. This process produces crude ZnO and molten slag. Making molten slag
has merit because it is easy to use for construction minerals; however iron cannot
be recycled.
One technical problem of EAF dust is that the pyrometallurgical processes are
not the final stage required to supply metallic zinc but only the middle stage, since
they produce only crude ZnO. One more step such as the ISF (Imperial Smelting
Furnace) process is necessary to refine the crude ZnO into zinc.
