Resource Efficiency Evaluation of Pyrometallurgical Solutions …
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However, if the zinc fuming rates of the DZS plant were lower than the reported
rates by Wood et al., the high zinc concentration in the smelting slag would cause
viscosity issues. Therefore, the zinc in the smelting slag would need to be reduced by
recirculating clean slag and feeding iron residues to the smelter. This would increase
the material circulating along the DZS, thus the resource consumption would be
larger, as Fig. 4a shows for the cases 2–6. Furthermore, the use of oxygen-enriched
air in DZS reduces the resource consumption as the quantity of nitrogen introduced
to the furnace decreases, as the “0 RLE–100 DZS (No O 2 Enr.)” shows.
If the zinc ferrites are treated in a fumer instead of leaching them in the hot
acid leach, the jarosite precipitation process is avoided. This case, represented in
the scenario 8, has a resource consumption that is comparable to treating 80% of
the concentrate in a DZS flowsheet. The reason for this high resource consumption
is that the zinc ferrites would be fumed together with the precipitated lead-silver
residue increasing the amount of material to fume. This action would also increase
the lead circulation load since the lead-silver residue to which lead reports, is not
produced.
The scenario 7 represents the pyrometallurgical treatment of the jarosite residue
produced during the RLE. This option would convert the jarosite residue into a slag
through two stages, jarosite smelting and reduction. Obviously, these extra stages
would require extra resource consumption; however, it is not as high as the other
options evaluated. The required energy and the reductant feed in this scenario would
be lower in comparison to the consumptions of the DZS or ferrites fuming since a
slag recirculation would not be required, i.e. the zinc content in the jarosite is low
enough to avoid problems associated to a high viscous slag.
Emissions and Their Associated Environmental Impact
The simulation of the system provides a good characterization of the emissions and
residues in terms of composition and flow rates. Therefore, by linking the results of
the simulation to a life cycle assessment (LCA) software, the environmental impact
of the system can be evaluated. It can be done through the dedicated LCA tool of HSC
Sim, which connects the simulation platform with GaBi [16]. This methodology has
been applied to evaluate the environmental impact of primary copper production,
e-waste recycling, and nickel pig iron using the HSC Sim process simulation tool
[11]. By using the same methodology, the environmental impact of the ten scenarios
defined has been obtained.
Within all the environmental impact indicators, the global warming potential
(GWP), measured in kg of CO 2 equivalent, will be discussed in this case. As depicted
in Fig. 5, the GWP shows a similar increasing trend that the resource consumption.
The CO 2 emissions associated with the RLE flowsheet, which are mainly generated when the electricity required for the zinc electrowinning is produced, remains
constant since the amount of zinc cathodes produced in all the studied scenarios is
the same (30 t/h). However, the CO 2 emissions increase with the use of the DZS
357
However, if the zinc fuming rates of the DZS plant were lower than the reported
rates by Wood et al., the high zinc concentration in the smelting slag would cause
viscosity issues. Therefore, the zinc in the smelting slag would need to be reduced by
recirculating clean slag and feeding iron residues to the smelter. This would increase
the material circulating along the DZS, thus the resource consumption would be
larger, as Fig. 4a shows for the cases 2–6. Furthermore, the use of oxygen-enriched
air in DZS reduces the resource consumption as the quantity of nitrogen introduced
to the furnace decreases, as the “0 RLE–100 DZS (No O 2 Enr.)” shows.
If the zinc ferrites are treated in a fumer instead of leaching them in the hot
acid leach, the jarosite precipitation process is avoided. This case, represented in
the scenario 8, has a resource consumption that is comparable to treating 80% of
the concentrate in a DZS flowsheet. The reason for this high resource consumption
is that the zinc ferrites would be fumed together with the precipitated lead-silver
residue increasing the amount of material to fume. This action would also increase
the lead circulation load since the lead-silver residue to which lead reports, is not
produced.
The scenario 7 represents the pyrometallurgical treatment of the jarosite residue
produced during the RLE. This option would convert the jarosite residue into a slag
through two stages, jarosite smelting and reduction. Obviously, these extra stages
would require extra resource consumption; however, it is not as high as the other
options evaluated. The required energy and the reductant feed in this scenario would
be lower in comparison to the consumptions of the DZS or ferrites fuming since a
slag recirculation would not be required, i.e. the zinc content in the jarosite is low
enough to avoid problems associated to a high viscous slag.
Emissions and Their Associated Environmental Impact
The simulation of the system provides a good characterization of the emissions and
residues in terms of composition and flow rates. Therefore, by linking the results of
the simulation to a life cycle assessment (LCA) software, the environmental impact
of the system can be evaluated. It can be done through the dedicated LCA tool of HSC
Sim, which connects the simulation platform with GaBi [16]. This methodology has
been applied to evaluate the environmental impact of primary copper production,
e-waste recycling, and nickel pig iron using the HSC Sim process simulation tool
[11]. By using the same methodology, the environmental impact of the ten scenarios
defined has been obtained.
Within all the environmental impact indicators, the global warming potential
(GWP), measured in kg of CO 2 equivalent, will be discussed in this case. As depicted
in Fig. 5, the GWP shows a similar increasing trend that the resource consumption.
The CO 2 emissions associated with the RLE flowsheet, which are mainly generated when the electricity required for the zinc electrowinning is produced, remains
constant since the amount of zinc cathodes produced in all the studied scenarios is
the same (30 t/h). However, the CO 2 emissions increase with the use of the DZS