Contributions of Non-ferrous Smelters to Metal Resource …
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unique waste, which is generated from the melting treatment of incineration ash of
municipal solid wastes in Japan.
Zinc in EAF dust is concentrated and recovered in the crude zinc oxide. At the same
time, fluorine (F), which is considered to be derived from the flux in the EAF process,
is also mixed in the crude zinc oxide. As fluorine impedes the zinc electrowinning
process, a high-cost halogen removal treatment is required when charging crude zinc
oxide into a hydrometallurgical zinc smelter process. Therefore, the ISP method,
which is resistant to halogen impurities, is responsible for the treatment of secondary
raw materials of zinc [21]. Although this process is declining outside of China, one
smelter is still in operation in Japan. Thus, it is important to maintain the ISP smelter
as the central base for zinc recycling in Japan. However, secondary raw materials
containing low-boiling zinc tend to be accompanied by other low-boiling metals,
particularly mercury (Hg). In Japan, mercury is recovered and refined from various
mercury-containing wastes including smelting residues at the Itomuka plant [25],
but more efficient mercury recovery will be necessary through collaboration between
non-ferrous smelters and the Itomuka plant in future.
Conclusions
The following summarizes the topics that should be considered in the future for
the construction of a metal resource circulation system based on the non-ferrous
smelting industry in Japan. For copper smelters, physical separation techniques of
secondary raw materials such as E-scrap for the purpose of separating and removing
impurities are important as pretreatment. Furthermore, impurities such as solder,
mounted components and iron scrap mixed with precious metals should be treated
properly in lead smelters. In addition, for the treatment of flame-retardant plastics
generated in large quantities after the physical separation of secondary raw materials,
thermal recycling and halogen removal are conducted simultaneously using smelting
facilities. If possible, low-temperature volatilization technique for heavy metals by
halogenation should be also considered.
Combining copper and lead smelters is ideal for the treatment of various secondary
raw materials by exchange of intermediate by-products (smelting residues), as well
as the recovery of valuable metals. The secondary smelting industry such as lead
smelters is considered to occupy an important position as a social infrastructure
industry in the treatment of solid wastes containing heavy metals, particularly by
playing an important part in waste disposal. In addition, it is possible to concentrate
and recover environmental load elements such as Hg and As in the smelting processes.
However, their chemical stabilization and the construction of a system for their final
disposal are important issues to be considered by the entire non-ferrous smelting
industry across the globe.
289
unique waste, which is generated from the melting treatment of incineration ash of
municipal solid wastes in Japan.
Zinc in EAF dust is concentrated and recovered in the crude zinc oxide. At the same
time, fluorine (F), which is considered to be derived from the flux in the EAF process,
is also mixed in the crude zinc oxide. As fluorine impedes the zinc electrowinning
process, a high-cost halogen removal treatment is required when charging crude zinc
oxide into a hydrometallurgical zinc smelter process. Therefore, the ISP method,
which is resistant to halogen impurities, is responsible for the treatment of secondary
raw materials of zinc [21]. Although this process is declining outside of China, one
smelter is still in operation in Japan. Thus, it is important to maintain the ISP smelter
as the central base for zinc recycling in Japan. However, secondary raw materials
containing low-boiling zinc tend to be accompanied by other low-boiling metals,
particularly mercury (Hg). In Japan, mercury is recovered and refined from various
mercury-containing wastes including smelting residues at the Itomuka plant [25],
but more efficient mercury recovery will be necessary through collaboration between
non-ferrous smelters and the Itomuka plant in future.
Conclusions
The following summarizes the topics that should be considered in the future for
the construction of a metal resource circulation system based on the non-ferrous
smelting industry in Japan. For copper smelters, physical separation techniques of
secondary raw materials such as E-scrap for the purpose of separating and removing
impurities are important as pretreatment. Furthermore, impurities such as solder,
mounted components and iron scrap mixed with precious metals should be treated
properly in lead smelters. In addition, for the treatment of flame-retardant plastics
generated in large quantities after the physical separation of secondary raw materials,
thermal recycling and halogen removal are conducted simultaneously using smelting
facilities. If possible, low-temperature volatilization technique for heavy metals by
halogenation should be also considered.
Combining copper and lead smelters is ideal for the treatment of various secondary
raw materials by exchange of intermediate by-products (smelting residues), as well
as the recovery of valuable metals. The secondary smelting industry such as lead
smelters is considered to occupy an important position as a social infrastructure
industry in the treatment of solid wastes containing heavy metals, particularly by
playing an important part in waste disposal. In addition, it is possible to concentrate
and recover environmental load elements such as Hg and As in the smelting processes.
However, their chemical stabilization and the construction of a system for their final
disposal are important issues to be considered by the entire non-ferrous smelting
industry across the globe.