In this work, the tests on the oxidative roasting process of zinc sulphide and zinc sulphide concentrate were carried. When zinc sulphide ores are used in the proces of obtaining the metalic zinc, then oxidative roasting operation is always a preliminary stage of the basic zinc production process. Both by the hydrometallurgical and by the pyrometallurgical method

Siwiec, G.

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374  METALURGIJA 61 (2022) 2, 374-376 G. SIWIECRESEARCH OF ZINC CONCENTRATE OXIDATIVE ROASTING PROCESSReceived – Primljeno: 2021-08-01Accepted – Prihvaćeno: 2021-10-20Preliminary Note – Prethodno priopćenjeG. Siwiec: grzegorz.siwiec@polsl.pl - Silesian University of Technol-ogy, Faculty of Materials Science, Katowice, PolandIn this work, the tests on the oxidative roasting process of zinc sulphide and zinc sulphide concentrate were carried. When zinc sulphide ores are used in the proces of obtaining the metalic zinc, then oxidative roasting operation is always a preliminary stage of the basic zinc production process. Both by the hydrometallurgical and by the pyro-metallurgical method.Keywords: zinc, zinc sulfide, zinc concentrate, oxidative roasting, thermogravimetric analysis (TG)INTRODUCTIONZinc, next to iron, aluminum and copper, is in the top four in terms of production volume among metals in the world. Currently, zinc, from primary sources, is obtained by two methods. The first method is a pyro-metallurgical process in which zinc oxide is reduced in a shaft furnace. The second method that is leading in the world is the hydrometallurgical proces, the final stage of which is electrolysis. In both technologies, when sulphide ores are used, the basic process of zinc production is preceded by the oxidative roasting of zinc sulphide concentrates, which were produced as a result of enrichment of zinc-bearing ores, most often by flotation [1, 2].The zinc sulphide concentrate consists mainly of ZnS. During roasting, the following reactions may occur: ZnS + 1,5O2 → ZnO + SO2 (1) SO2 + 0,5O2 → SO3 (2) ZnO + SO3 → ZnSO4 (3) ZnS + 2O2 → ZnSO4 (4) 3ZnSO4 + ZnS → 4ZnO + 4SO2 (5)On the other hand, the main components of the gangue, i.e. magnesium carbonate and calcium carbon-ate, undergo a process of thermal decomposition during roasting according to the reaction: MgCO3 → MgO + CO2 (6) CaCO3 → CaO + CO2  (7)As part of the presented work, research was carried out on the oxidative roasting process of zinc sulphide and zinc sulphide concentrate.ISSN 0543-5846METABK 61(2) 374-376 (2022)UDC / UDK 546.47:546.47.661.249:66.082:536.5.001.411METHODOLOGYThe research material used was zinc sulphide with a purity of 99 % and an industrial sulphide zinc concen-trate containing:• 53,3 % Zn in the form of ZnS,• 2 % of Pb in the form of PbS,• 6,6 % Fe in the form of FeO and Fe2O3,• 0,4 % Cd in the form of CdS,• 2,1 % Al2O3,• MgCO3 and CaCO3 – ballance.In the first stage, thermogravimetric tests (TG) were carried out, allowing to determine the influence of tem-perature on changes in the mass of the analyzed sample [3, 4]. In this stage of research, a Netzach, the STA 449 F3 Jupiter thermal analyzer, was used. The view of the device is shown in Figure 1. The heating program adopted in the first stage of the research included the gradual heating of samples (with a mass of 250 mg) at a rate of 20 oC / min to selected temperature values (700, 800, 900, and 1000 oC). At each of the given tempera-tures, the sample was isothermally heated for 30 min-utes and then heated to the next assumed temperature value. The research was conducted in an oxidizing at-mosphere.The second stage of the research was carried out in a horizontal resistance tubular furnace for samples weigh-Figure 1 Thermal analyzer375 G. SIWIEC: RESEARCH OF ZINC CONCENTRATE OXIDATIVE ROASTING PROCESSMETALURGIJA 61 (2022) 2, 374-376ing of 1 g. The experiments were conducted in an oxi-dizing atmosphere at temperatures of 700 oC, 800 oC and 900 oC (the temperatures were selected based on the results from the first stage). The duration of the process for each of the temperatures was 5, 10, 15, 20, 25 and 30 minutes.RESEARCH RESULTSFigures 2 and 3 show the results of thermogravimet-ric tests with the use of ZnS and industrial zinc sulphide concentrate.The test results obtained in the second stage of the tests with the use of a horizontal tube furnace for zinc sulphide and zinc concentrate are presented in Fig-ures 4-6.SUMMARYBy analyzing the obtained thermogravimetric curve for the ZnS sample, it was found that the oxidative Figure 2 TG curve for ZnSFigure 6  Weight loss of ZnS samples and zinc sulphide concentrate after 30 minutes of roasting in a horizontal tube furnaceFigure 3 TG curve for zinc sulphide concentrateFigure 4  Changes in sample weight during the roasting of zinc sulphide in a horizontal tube furnaceFigure 5  Changes in sample weight during the roasting of sulphide zinc concentrate in a horizontal tube furnaceroasting process of zinc sulphide was characterized by a quick and one-stage loss of sample mass, and its mass stabilization was achieved after exceeding the tempera-ture of 700 oC. For the concentrate sample, the roasting process was gradual and much slower than in the case of pure ZnS. This phenomenon is mainly related to the complex chemical composition of the concentrate (e.g. the content of calcium carbonate) and the fact that it contains less zinc sulphide.In the oxidative roasting of zinc sulphide in a hori-zontal tube furnace, the time course of the process was similar at all temperatures. The same can be said about the course of the oxidative roasting process of zinc con-376  METALURGIJA 61 (2022) 2, 374-376 G. SIWIEC: RESEARCH OF ZINC CONCENTRATE OXIDATIVE ROASTING PROCESScentrate. The highest weight loss of samples in the pro-cesses carried out in this furnace was recorded at the temperature of 900 oC. Moreover, the mass losses of samples at 800 oC are lower than at 700 oC and 900 oC, which may indicate that under these conditions one of the reaction products, apart from ZnO, may be ZnSO4.AcknowledgmentsArticle published from the BK-230/RM0/2021 (11/020/BK_21/0080) resourcesREFERENCES[1] Kaartinen J., Hätönen J., Hyötyniemi H., Miettunen J.: Machine-vision-based control of zinc flotation-A case study, Control Engineering Practice 14 (2006), 12, 1455-1466[2] Ejtemaei M., Gharabaghib M., Irannajad M.: A review of zinc oxide mineral beneficiation using flotation method, Advances in Colloid and Interface Science 206 (2014), 68-78[3] Matuła T., Siwiec G.: Reduction of lead oxide by fine-gra-ined carbonaceous materials, Arch. Metall. Mater. 64 (2019), 2, 647-652[4] Jabłońska M., Maciąg T., Nowak M., Rzychoń T., Czerny M. Kowalczyk K.: Thermal and structural analysis of high--tin bronze of chemical composition corresponding to the composition of the singing bowl, J. Therm. Anal. Calori-metry 137 (2019), 3, 735-741Note: Nowak P. is responsible for English language, Katowice, Poland

Research of zinc concentrate oxidative roasting process

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