Primary Zinc Production Research Articles

Carbon footprint of the hot-dip galvanisation process using a life cycle assessment approach

This work presents the carbon footprint (CF) of two hot-dip galvanisation (HDG) installations located in Spain with differences in the galvanising capacity and in the manufacturing process. The study determines the influence of the direct emissions (scope 1), emissions from electricity production (scope 2), and indirect emissions from upstream and downstream processes (scope 3). The results showed that steel and primary zinc production were the principal contributors to the CF. So, efforts should be focused on reducing the impact of the raw material production included in scope 3. Furthermore, two sensitivity analyses are presented: i) the production of one kg of two types of zinc products, special high-grade and redistilled zinc; ii) the use of two coatings: zinc for galvanisation and paint for pre-printed steel. The environmental impacts in SHG zinc were higher than in redistilled zinc, for all the impact categories due to the great influence of heavy metals emission. The results for zinc and paint protections showed that under the same level of corrosion, a greater thickness of paint is needed to protect steel pieces, compared to zinc coating. This sustainability assessment of the HDG industry recommends the sought of technology alternatives aimed at resource efficiency, such as zinc recovery from spent pickling baths, that could provide the desirable reduction of the environmental impacts associated to primary resource usage and waste treatment.

Thermodynamic Considerations for a Pyrometallurgical Extraction of Indium and Silver from a Jarosite Residue

Indium and silver are technologically important, critical metals, and in the majority of cases, they are extracted as a by-product of another carrier metal. The importance of indium has seen recent growth, and for technological reasons, these metals can be found in industrial residues from primary zinc production, such as the iron precipitate—jarosite. To secure the supply of such metals in Europe, and with the idea of a circular economy and the sustainable use of raw materials, the recycling of such industrial residues is coming into focus. Due to the low value of jarosite, the focus must lie simultaneously on the recovery of valuable metals and the production of high-quality products in order to pursue an economical process. The objective of this article is to give the fundamentals for the development of a successful process to extract the minor elements from roasted jarosite. As such, we use thermodynamic calculations to show the behavior of indium and silver, leading to a recommendation for the required conditions for a successful extraction process. In summary, the formation of chlorine compounds shows high potential to meet the challenge of simultaneously recovering these metals together with zinc at the lowest possible energy input.

Global strategic level supply planning of materials critical to clean energy technologies – A case study on indium

Many clean energy technologies depend on some rare materials, and significant concerns about the sufficient supply of these materials have been raised recently. Most of the rare materials are so called by-product materials, and thus their supplies heavily rely on the demand of base metals. This study develops a generic mixed integer linear programming to investigate global strategic level capacity and production planning for both base and by-product materials. Other decisions relevant to capacity expansions and productions are also considered. The model is demonstrated using indium as a case study. Indium is a key material needed by two emerging clean energy applications, copper indium gallium selenide photovoltaics and light-emitting diode lighting. Supply of indium exclusively depends on primary zinc production, and concerns have been raised on whether there will be sufficient supply to support widespread applications of these two technologies. Capacity expansions of indium refinery facilities can be the first solution to overcome its supply risk. All the decisions included in the model are numerically analyzed. Sensitivity of all the parameters to the total cost are also studied. Indium content in the ore, inflation rates, and discount rates are found to have significant impact on the total cost.

A global life cycle assessment for primary zinc production

The purpose of this study was to update the average environmental impacts of global primary zinc production using a life cycle assessment (LCA) approach. This study represents the latest contribution from zinc producers, which historically established the first life cycle inventory for primary zinc production in 1998 (Western Europe) and the first global LCA-based cradle-to-gate study for zinc concentrate and special high-grade zinc (SHG; 99.99 %) in 2009. Improvements from the previous studies were realized through expanded geographical scope and range of production technologies. The product system under study (SHG zinc) was characterized by collecting primary data for the relevant production processes, including zinc ore mining and concentration, transportation of the zinc concentrate, and zinc concentrate smelting. This data was modeled in GaBi 6 and complemented with background data from the GaBi 2013 databases to create the cradle-to-gate LCA model. Allocation was used to distribute the inputs and outputs among the various co-products produced during the production process, with mass of metal content being the preferred allocation approach, when applicable. In total, this global study includes primary data from 24 mines and 18 smelters, which cover 4.7 × 106 MT of zinc concentrate and 3.4 × 106 MT of SHG zinc, representing 36 and 27 % of global production, respectively. While the LCA model generated a full life cycle inventory, selected impact categories and indicators are reported in this article (global warming potential, acidification potential, eutrophication potential, photochemical ozone creation potential, ozone creation potential, and primary energy demand). The results show that SHG zinc has a primary energy demand of 37,500 MJ/t and a climate change impact of 2600 kg CO2-eq./t. Across all impact categories and indicators reported here, around 65 % of the burden are associated with smelting, 30 % with mining and concentration, and 5 % with transportation of the concentrate. Sensitivity analyses were carried out for the allocation method (total mass versus mass of metal content) and transportation of zinc concentrate. This study generated updated LCA information for the global production of SHG zinc, in line with the metal industry’s current harmonization efforts. Through the provision of unit process information for zinc concentrate and SHG zinc production, greater transparency is achieved. Technological and temporal representativeness was deemed to be high. Geographical representativeness, however, was found to be moderate to low. Future studies should focus on increasing company participation from underrepresented regions.

Cadmium Flows Caused by the Worldwide Production of Primary Zinc Metal

SummaryMaterial flows of the economic cycle can contain toxic substances, which enter the economy as impurities in raw materials or are intentionally added as minor or even main constituents during the manufacture of industrial or consumer goods. Cadmium, predominantly associated with zinc minerals, is a by‐product of the primary zinc production. Cadmium is generated when zinc is extracted from zinc ores and concentrates, an intermediate product resulting from flotation processing after the zinc ore has been mined and milled. Information on the amount of cadmium generated from zinc extraction is rarely published. In this article, we assess generation and fate of cadmium accumulating worldwide in the production of primary zinc from ores and concentrates. Model calculations for the beginning of the 21st century show that annually about 30,000 tonnes of cadmium were generated, but only approximately 16,000 tonnes were converted to primary cadmium metal, key material for the production of other cadmium compounds (e.g., cadmium oxide), and cadmium‐containing goods (e.g., nickel−cadmium batteries). Hence, about 14,000 tonnes of cadmium must have been transferred somewhere else. The fate of about 5,500 tonnes can be plausibly explained, but it is difficult to determine what happens to the rest.

Determination of PCDDs, PCDFs, PCBs and HCB emissions from the metallurgical sector in Poland

The aim of the project was to measure the actual emissions of PCDD/F, PCBs and HCB from 20 selected metallurgical installations in Poland, in order to update the national inventory of dioxin emission from metallurgical industry for developing a strategy for dioxins and furans emission abatement from the subject facilities (UNEP 2005). Sampling methodology used in this work was developed at the Cracow University of Technology because of the complexity of simultaneous sampling and determining PCDFs, PCDDs, PCB and HCB. For the determination a GC-MS/MS system was used. Results from the work indicate that the highest dioxins and PCB concentrations were recorded for iron ore sintering plants at 1.10-1.32 ng total1 TEQ/Nm3 followed by aluminium scrap melting at 0.03-0.66 ng total TEQ/Nm3. The highest HCB concentrations at 613-1491 ng/Nm3 were also recorded fo iron ore sintering plants, whereas at aluminium plants the HCB concentrations were in the range of only 10.1-22.7 ng/Nm3. The above investigations indicate that secondary aluminium production is the most significant dioxins source, if calculated as emission factor values. However, iron ore sintering plants are operating at much higher production capacity, causing this process to become the major source of dioxins, PCB and HCB pollution to the atmosphere in Poland. Based on the performed tests and the environmental reviews of selected plants several recommendations were formulated for the reduction of generation or of emission of these pollutants from iron ore sintering plants, electric arc furnace steel production processes, hot-blast furnace operations, secondary aluminium smelting and primary zinc production from zinc cathodes.

INNOVATIVE HYDROMETALLURGICAL PROCESSES FOR THE PRIMARY PROCESSING OF ZINC

The zinc industry has been in the forefront of hydrometallurgical developments for almost a century. The development of pressure leaching in the 1980s and the development of atmospheric direct leaching in the 1990s for treating zinc-sulphide concentrates have resulted in a number of zinc-refinery expansions without an increase in roasting capacity. Likewise, solvent extraction techniques are now used for the hydrometallurgical treatment of zinc-oxide ores on an industrial scale. The treatment of poor and complex zinc-sulphide resources has been extensively studied using processes as diverse as pyrolusite leaching and heap bioleaching. Finally, the precipitation of relatively pure zinc oxide at the mine site, a process that has been proven to be technically feasible very recently, may significantly change the paradigm of primary zinc production.

Kinetics of zinc ferrite leaching in caustic media in the deceleratory period

In this research, the role of zinc ferrite in the hydrometallurgical recovery of zinc in both primary zinc production and zinc-containing waste treatment processes is discussed. In the present work, experiments were performed on the caustic leaching of pure zinc ferrite. The effects of leaching time, caustic concentration and temperature were investigated in the deceleratory period. Atomic Absorption Spectroscopy (AAS) and X-Ray Diffraction (XRD) analyses were employed to analyze both the leach solutions and the residues. It was found that the percentage of decomposed zinc ferrite increased linearly with increasing leaching time. Although the decomposition rate increased with the caustic concentration, it was limited by the high viscosity of the concentrated leach solutions. The maximum percentage of decomposed zinc ferrite was only about 9% under the experimental conditions. Based on the experimental results, it was postulated that the dissolution rate of zinc ferrite in the deceleratory period, was controlled by the diffusion of zinc ions in the imperfect zinc ferrite lattice. The dissolution reaction could be represented as follows: ZnFe 2O 4+2[OH −]=ZnO 2 2−+Fe 2O 3+H 2O