Special Issue; Products for Industrial Machinery - NTN

Honing Sludge and Electro Furnace Dust Briquetter
Product
Slag
Exhaust
Electric arc furnace
Dust
Scrap
Briquette
150120H
Filter
Dust
Carbon
Water
Pelletizer
Pellets
Iron
content
Dezincification
system
Commissioning to
outside disposal agents
Zinc bullion
Fig. 11 Recycling of EAF (electric arc furnace) dust
NTN EAF dust briquetter
carbon, which functions as a reducing agent and fuel,
and the mixture is formed into pellets. The resultant
pellets are not suitable for direct loading into an
electric arc furnace due to their low mechanical
strength and difficulty in handling. Therefore, the
pellets are formed into briquettes with the authors’
newly developed briquetter, and then the briquette is
loaded into the electric arc furnace. Since EAF dust is
repeatedly recycled, the concentration of zinc, which
has a relatively low boiling point, in the EAF dust will
increase and pose a problem in operating the electric
arc furnace. Therefore, when the zinc concentration
reaches a specific upper limit, the iron content is
separated from the zinc content. The iron content is
reloaded into the furnace while the zinc content is
recycled as a valuable material.
Thanks to this recycling scheme, the disposal of
EAF dust by landfill, no longer necessary. The number
of zinc removal cycles can be decreased, thereby
dramatically reducing the costs associated with
industrial waste disposal.
3.2 Overview of the authors’ briquetter
1) Formation principle
The principle of this briquette formation method is
schematically illustrated in Fig. 12. The pellets are
loaded into the die, and then the upper and lower
punches apply force to the pellets in the die to convert
the pellets into a briquette.
Upper punch
Pellets
Lower punch
Die
Fig. 12 Moulding method
2) Effects of various factors on the strength of
briquettes
The authors investigated the effects of factors
associated with materials and formation conditions on
the mechanical strength of the briquettes obtained.
The results of these investigations are shown in Figs.
13 through 16. The mechanical strength of the
briquettes was translated into indexes by dropping
each briquette from 1 meter above to a 5-cm thick
layer of raw material powder and then counting the
number of fractured pieces resulting. The greater the
index is, the greater the mechanical strength of the
briquette. By appropriately selecting the water and
carbon content in the pellets and the formation
-77-