Modelling the Effect of Solution Composition and Temperature on the Conductivity of Zinc Electrowinning Electrolytes

Zinc electrowinning is an energy-intensive step of hydrometallurgical zinc production in which ohmic drop contributes the second highest overpotential in the process. As the ohmic drop is a result of electrolyte conductivity, three conductivity models (Aalto-I, Aalto-II and Aalto-III) were formulated in this study based on the synthetic industrial electrolyte conditions of Zn (50–70 g/dm3), H2SO4 (150–200 g/dm3), Mn (0–8 g/dm3), Mg (0–4 g/dm3), and temperature, T (30–40 °C). These studies indicate that electrolyte conductivity increases with temperature and H2SO4 concentration, whereas metal ions have negative effects on conductivity. In addition, the interaction effects of temperature and the concentrations of metal ions on solution conductivity were tested by comparing the performance of the linear model (Aalto-I) and interrelated models (Aalto-II and Aalto-III) to determine their significance in the electrowinning process. Statistical analysis shows that Aalto-I has the highest accuracy of all the models developed and investigated in this study. From the industrial validation, Aalto-I also demonstrates a high level of correlation in comparison to the other models presented in this study. Further comparison of model Aalto-I with the existing published models from previous studies shows that model Aalto-I substantially improves the accuracy of the zinc conductivity empirical model.

Processing and Characterization of Self-Reducing Briquettes Made of Jarosite and Blast Furnace Sludges

Jarosite sludge coming from the hydrometallurgical zinc production route is a hazardous material, which is currently neutralized and landfilled by the so-called Jarofix® process. The present study aims to assess the mechanical and metallurgical properties of briquettes made of jarosite powder with blast furnace sludges, acting as a reductant material, to recover the iron oxide in the form of pig iron and produce an inert slag, increasing the recovery of materials considered as wastes nowadays. Starch was used as a binder (0, 5, 10 wt%), and two different briquetting pressure levels were used (20 and 40 MPa). The results show that briquetting without a binder is not desirable, as the agglomerating forces provided by pressure only are not sufficient, as the briquettes are very fragile and not handy. The binder addition increased noticeably the briquettes resistance, however, only little distinction between the 5 and 10 wt% levels were seen. The briquetting pressure, on the other hand, showed a bigger role on the cold mechanical properties of the bound briquettes. The briquettes pressed at 40 MPa reached an average compressive strength higher than 12 MPa and good abrasion and drop resistance were seen, also showing that their production with starch as a binder is feasible. A special remark is done regarding the roasting treatment of the jarosite powder before the briquetting process, as an undesirable compound (thenardite) was formed within some briquettes due to a non-uniform heating of the powder, which hindered the briquettes mechanical properties. Metallurgical properties open the possibility to use such briquettes for iron production in cupola furnaces. Graphical Abstract

Purification of Zinc Oxide from Chlorides Using Microwave Radiation

Waelz oxide is a secondary zinc raw material and a product of Electric Arc Furnaces (EAF) dust, copper smelters dust and zinc production residues. The use of Waelz oxide in the traditional RLE (Roasting-Leaching-Electrowinning) zinc production scheme requires the removal of halogens (fluorides and chlorides). Waelz oxide is mainly composed of zinc oxide, also contains zinc chloride. Zinc chloride is removed into the gas phase at heating. Microwave heating is one of the promising methods. Test experiments of microwave heating of a ZnO-ZnCl2 mixture were carried out. It was shown that zinc chloride absorbs microwave radiation; zinc oxide does not absorb microwave radiation. The degree of zinc chloride removal from ZnO-ZnCl2 mixture was 100%.

ANALYSIS AND PROSPECTIVE UTILIZATION OF TECHNOGENIC SLAG WASTE FROM A LEAD PLANT

The article presents the analysis and results of the study of technogenic slag waste of lead-zinc production. Slags of lead-zinc production contain a large number of toxic compounds: lead, zinc, osmium, cadmium, which are dangerous sources of environmental pollution. Due to the open storage of slags, it was found that the maximum permissible concentrations of lead were exceeded. Utilization of man-made slag waste is of great importance for reducing the negative impact on the safety of life and improving the environmental situation in the region. At the same time, slags are valuable raw materials containing compounds of non-ferrous and rare-earth metals. The article shows the results of laboratory studies of slags to determine the qualitative and quantitative composition of valuable components in the waste of lead production and the possibility of their further processing and disposal. Studies of the material of the heavy slag fraction were carried out on an electron probe microanalyzer of the JEOL IXA-8230 Electron Probe microanalyzer brand. X-ray diffractometric analysis of the average slag sample was performed on a DRON-4 diffractometer with Cu radiation, graphite monochromator. Samples were selected heavy fraction and manufactured artificial polished sections (briquettes). The sections were studied under the microscope of the brand LEICA DM 2500P and immersion in liquids. According to the results of research, it was found that lead slags contain a sufficiently high amount of non-ferrous metal compounds: lead oxide up to 0.7 % and zinc oxide up to 8.5 % of the weight amount of slag, which makes the process of recycling toxic waste from lead production technically and economically feasible.

Fifty years of metallurgical production of zinc and cadmium in Serbia

Serbia has plenty of rich sites and active excavation mines of polymetallic ores of lead and zinc and centuries-old practice of their exploitation. In Serbia, the metallurgical processing of zinc concentrate started in 1955 at Zorka company in Šabac, while in the town of Kosovska Mitrovica, it began in 1967 at the Trepča combine. Several factors, including the fall o Yugoslaviam general societal circumstances and ownership transition, lead to a significant decline in production since 1992. It developed to the final halt of zinc's metallurgical production in 1999 at Trepča and in 2002 at Zorka. During the work-life o both production sites, since they opened till they closed, there were several reconstructions and capacity expansions, and all the while, the normalization and renewal of zinc production in Serbia hasn't been realized till 2021.

PROCEDURE FOR DETERMINING HYDRAULIC JET BARBOTTER RESISTANCE FOR COLLECTING FINE DUST

В СКГМИ (ГТУ) разработана конструкция струйного барботера, в основу которого положена запатентованная конструкция основного узла аппарата -распределительной тарелки, позволяющей реализовать в барботере пенный режим. Данный пылеуловитель позволяет улавливать мелкие частицы пыли ( < 1 мкм), включая наночастицы, не улавливаемые в рукавных фильтрах. В статье приведена методика расчета гидравлического сопротивления барботера, необходимая для использования при выборе вентилятора для процесса пылеулавливания в барботере. Гидравлическое сопротивление барботера определяется как сумма составляющих: статического давления слоя жидкости, капиллярного перепада в зоне образования пузырьков и сопротивлений деталей распределительной тарелки. Разработанная методика была использована при проектировании технологической линии очистки газов от пылевидных возгонов вельц-печей цинкового производства, содержащих наночастицы. North Caucasian Institute of Mining and Metallurgy (State Technological University) has developed a design of a jet bubbler which is based on the patented design of the device main unit - a distribution plate, which allows to implement a foam mode in the bubbler. This dust collector allows you to capture small dust particles (< 1 microns), including nanoparticles, that are not captured in bag filters. The article presents a method for calculating the hydraulic resistance of the bubbler, which is required for use, when selecting a fan for the process of dust collection in the bubbler. The hydraulic resistance of the bubbler is defined as the sum of the components: the static pressure of the liquid layer, the capillary drop in the zone of bubbles formation and the resistances of distribution plate parts. The developed method was used in the design of a process line for cleaning gases from pulverized ascents of waelz kiln of zinc production containing nanoparticles.

PROCESSING OF SLAGS OF COPPER MANUFACTURING WITH THE USE OF IDEAL MIXING EQUIPMENT

The article discusses the issues of processing slag of copper production using devices that model ideal mixing. It has been shown that the use of this type of apparatus increases the efficiency of physical and chemical processes and significantly reduces the copper content in dump slags. It has been found that the process of reduction of ferric iron oxide by the clinker in the initial period takes place in the kinetic mode. After reducing the concentration of magnetite (3-5%) in the slag, the process of reducing it passes into the diffusion region, that is, restoring the excess content of ferric iron in iron silicate melts takes a short period of time during which the process can be carried out, without significantly delaying the operation time of the main industrial equipment. The optimal slag magnetite reducing agent is determined to be zinc production waste