A New Era in Smelting Sustainability—Intensification …
67
Recent Improvements in the Ausmelt Process for Zinc
Fuming
The Ausmelt zinc fuming process as operated commercially to date has typically
been characterised by:
• Lance operation with relatively low oxygen enrichment (≤45 vol. %), with cooling
required for preservation of the lance tip provided by the injected process gases.
• Use of shrouded lances for efficient afterburning of volatilised compounds within
the furnace and consequently, improved heat recovery efficiency to the bath by
molten slag splash.
• Use of an intensively cooled, lower furnace construction, incorporating copper
cooling elements, due to high slag superheat and intensive splashing.
• Use of a membrane (WHB) upper furnace construction (where economic), due to
high freeboard temperatures and to capture waste heat from the process offgas for
steam generation.
• Feeding of slag in hot, liquid form, where possible, for maximum energy efficiency.
• Feeding of solid feeds in wet form for simplicity.
• Use of coal as a fuel and reducing agent.
Due to the inherent versatility of the Ausmelt process, fuming has been conducted
commercially using either batch or continuous modes, including:
• Batch fuming of liquid slag bath held within the Ausmelt furnace as a process
stage.
• Continuous 2 stage fuming, with solid and/or liquid feed to the first Ausmelt
fuming furnace followed by continuous liquid flow into the second Ausmelt fuming
furnace.
• Continuous single-stage fuming, with solid and/or liquid feed to the Ausmelt
fuming furnace.
Improvement 1: Optimising Fuming Process Stages
Given the range of fuming process modes available, selection of the optimum process
flow sheet for a particular project must consider not only the feed materials to be
treated (composition and throughput) but also constraints around capital investment,
target product quality, metals recovery and environmental impacts. For example,
continuous processing in either a single or multiple furnaces provides for more stable
operation with less variability in lance and offgas conditions. On the other hand, batch
fuming can offer savings in capital investment by performing multiple process stages
in a single vessel rather than needing separate furnaces for each process stage.
67
Recent Improvements in the Ausmelt Process for Zinc
Fuming
The Ausmelt zinc fuming process as operated commercially to date has typically
been characterised by:
• Lance operation with relatively low oxygen enrichment (≤45 vol. %), with cooling
required for preservation of the lance tip provided by the injected process gases.
• Use of shrouded lances for efficient afterburning of volatilised compounds within
the furnace and consequently, improved heat recovery efficiency to the bath by
molten slag splash.
• Use of an intensively cooled, lower furnace construction, incorporating copper
cooling elements, due to high slag superheat and intensive splashing.
• Use of a membrane (WHB) upper furnace construction (where economic), due to
high freeboard temperatures and to capture waste heat from the process offgas for
steam generation.
• Feeding of slag in hot, liquid form, where possible, for maximum energy efficiency.
• Feeding of solid feeds in wet form for simplicity.
• Use of coal as a fuel and reducing agent.
Due to the inherent versatility of the Ausmelt process, fuming has been conducted
commercially using either batch or continuous modes, including:
• Batch fuming of liquid slag bath held within the Ausmelt furnace as a process
stage.
• Continuous 2 stage fuming, with solid and/or liquid feed to the first Ausmelt
fuming furnace followed by continuous liquid flow into the second Ausmelt fuming
furnace.
• Continuous single-stage fuming, with solid and/or liquid feed to the Ausmelt
fuming furnace.
Improvement 1: Optimising Fuming Process Stages
Given the range of fuming process modes available, selection of the optimum process
flow sheet for a particular project must consider not only the feed materials to be
treated (composition and throughput) but also constraints around capital investment,
target product quality, metals recovery and environmental impacts. For example,
continuous processing in either a single or multiple furnaces provides for more stable
operation with less variability in lance and offgas conditions. On the other hand, batch
fuming can offer savings in capital investment by performing multiple process stages
in a single vessel rather than needing separate furnaces for each process stage.