Comparative analysis of the main occupations working conditions in the copper production by pyrometallurgical and hydrometallurgical methods in Russia

Introduction. The primary materials for copper production are sulfide copper-nickel and oxidized ores with a copper percentage of 1.5-4%, traditionally processed by the pyrometallurgical method. For processing depleted copper-containing raw materials (less than 1%), the pyrometallurgical approach is not commonly suitable. The introduced hydrometallurgical way differs by including in one production process, combined underground leaching of ore, extraction of copper from solution, and the following electrolysis. At the same time, insufficient attention is paid to the hydrometallurgical method of processing depleted copper raw materials from a hygienic standpoint in our country. Materials and methods. Based on the results of our research carried out at copper-smelting plants using pyro- and hydrometallurgical methods of processing raw materials, a comparative analysis was carried out for such indicators as the pollutants content in the workplaces’ air at different stages of production, predicted values of occupational cancer risks, toxicity indicators, and the health and essential physiological functions of workers. Results. Working under increased heat intensity in hot shops, exposure to sulfur-containing gases and industrial aerosols leads to significant changes in hemodynamics and thermoregulation stress in workers. In the hydrometallurgical production of copper, the only occupational hazard exceeding hygienic standards is sulfuric acid vapours, and changes in physiological parameters and thermoregulation are insignificant. The predicted values of occupational cancer risk for hydrometallurgical machines operators exceed the acceptable level after 9-10 years of working experience. For smelters, an unacceptable level of risk is achieved with up to 5 years of working experience. Conclusion. For the first time in the country, a hygienic assessment of the hydrometallurgical method of processing depleted copper raw materials was proved to be the only appropriate method of improving working conditions in copper production.

CFD Modeling of Multiphase Flow in an SKS Furnace with New Tuyere Arrangements

There has been a great deal of focus on the optimization of tuyere arrangements in SKS bottom blown copper smelting furnaces since the last decade, as the improved furnace operation efficiency of SKS technology has potential that cannot be ignored. New –x + 0 + x deg tuyere arrangements with 14 tuyeres are proposed in this research paper. Using a previously verified numerical model, CFD tests on the velocity distribution and wall shear stress for scaled-down SKS furnace models were conducted, with a constant total volumetric gas flow rate, and different operating parameters and furnace cross-section geometries. The results indicate that, at a relatively low gas injection speed compared with the previously optimized tuyere arrangement, although the –x +0 +x deg tuyere arrangements are unable to supply enhanced agitation in the typical round furnaces, they achieve better performance in elliptical furnaces. At a comparatively higher gas injection speed, the – x + 0 + x deg tuyere arrangements can improve the agitation performance in a round furnace while maintaining an acceptable wall shear stress on the bottom and side wall. The agitation enhancement with the − x +0 +x deg tuyere arrangements can essentially be attributed to stronger interactions between bubble plumes and furnace side walls. To further exploit the advantages of the new tuyere arrangements, an optimized tuyere angle was confirmed by a full-scale furnace model simulation.

The smelting of copper in the third millennium cal BC Trentino, north-eastern Italy

This paper presents observations and analyses on seven slag pieces from two third-millennium cal BC (Late Copper Age/Early Bronze Age) rock shelters in the Trentino, north-eastern Italy: La Vela di Valbusa and the Riparo di Monte Terlago. We review previous work on contemporary slags from the region and show that the smelting did not follow the well-known ‘Timna’, ‘Eibner’ or so-called ‘Chalcolithic’ copper smelting processes. We show that ethnographic accounts of copper smelting in the Himalayas (Sikkim and Nepal) illuminate the smelting process, in particular the lack of preliminary roasting or ore beneficiation by washing, the use of slags as fluxes for the first smelt (matte smelting) and the use of wooden (?) implements to lift the hot slags from the furnace during the smelt. The rock inclusions in the slag are consistent with an ore origin from mines at Calceranica or Vetriolo, as previously reported in the literature.

Effect of Fe/SiO2 Ratio and Fe2O3 on the Viscosity and Slag Structure of Copper-Smelting Slags

Secondary copper smelting is an effective means of treating waste resources. During the smelting process, the viscous behavior of the smelting slags is essential for smooth operation. Therefore, the effects of Fe/SiO2 ratio and Fe2O3 contents on the viscous behavior of the FeO−Fe2O3−SiO2−8 wt%CaO−3 wt%MgO−3 wt%Al2O3 slag system were investigated. The slag viscosity and activation energy for viscous flow decrease with increasing Fe/SiO2 from 0.8 to 1.2, and increase as the Fe2O3 content increases from 4 wt% to 16 wt% at Fe/SiO2 ratio of 1.2. However, under the conditions of Fe/SiO2 of 0.8 and 1.0, the viscosity and activation energy for viscous flow show a minimum value at Fe2O3 content of 12 wt%. Fe2O3 exhibits amphoteric properties. In addition, the increase in Fe2O3 content raises the breaking temperature of the slag, while the Fe/SiO2 ratio has the opposite effect. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy show that increases in Fe/SiO2 ratio lead to simplification of the silicate network structure, while increases in Fe2O3 content improves the formability of the network. This study provides theoretical support for the related research and application of secondary copper smelting.

Chemical Composition and Source Apportionment of PM2.5 in A Border City in Southwest China

This paper studied the chemical characteristics and seasonal changes of PM2.5 in plateau cities on the southwest border of China. Urban air was sampled in Baoshan City during the rainy and dry seasons. Finally, 174 PM2.5 filters were collected (including 87 quartz and 87 Teflon samples for PM2.5). The mass concentrations, water-soluble inorganic ions, organic and inorganic carbon concentrations, and inorganic elements constituting PM2.5 were determined. Positive definite matrix factorization was used to identify potential sources of PM2.5, and the backward trajectory model was used to calculate the contribution of the long-distance transmission of air particles to the Baoshan area. It was found that in the wet season, most of the air masses come from the Indian Ocean and Myanmar. In the dry season, the air mass mainly comes from the China and Myanmar border area. The average concentration of PM2.5 in the wet and dry seasons was 23.17 ± 12.23 μg/m3. The daily mean value of OC/EC indicated that the measured SOC content was generated by the photochemical processes active during the sampling days. However, elements from anthropogenic sources (Na, Mg, Al, Si, P, K, Ca, Ti, Fe, Cu, Zn, Sb, Ba, and Pb) accounted for 99.51% and 99.40% of the total inorganic elements in the wet season and dry season, respectively. Finally, source apportionment showed that SIA, dust, industry, biomass burning, motor vehicle emissions, and copper smelting emissions constituted the major contributions of PM2.5 in Baoshan. Using combined data from three measurement sites provides a focus on the common sources affecting all locations.