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Extraction of Lead and Zinc from a Rotary Kiln Oxidizing Roasting Cinder

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Extraction of Lead and Zinc from a Rotary Kiln Oxidizing Roasting Cinder metals Article Extraction of Lead and Zinc from a Rotary Kiln Oxidizing Roasting Cinder Junhui Xiao 1,2,3,* , Kai Zou 1,3, Wei Ding 1,3, Yang Peng 1,3 and Tao Chen 1,3 1 Sichuan Engineering Lab of Non-Metallic Mineral Powder Modification and High-Value Utilization, Southwest University of Science and Technology, Mianyang 621010, China; [email protected] (K.Z.); [email protected] (W.D.); [email protected] (Y.P.); [email protected] (T.C.) 2 Key Laboratory of Sichuan Province for Comprehensive Utilization of Vanadium and Titanium Resources, Panzhihua University, Panzhihua 61700, China 3 Key Laboratory of Ministry of Education for Solid Waste Treatment and Resource Recycle, Southwest University of Science and Technology, Mianyang 621010, China * Correspondence: [email protected] or [email protected]; Tel.: +86-139-9019-0544 Received: 28 February 2020; Accepted: 1 April 2020; Published: 2 April 2020 Abstract: In this study, sulfuric acid leaching and gravity shaking-table separation by shaking a table are used to extract lead and zinc from a Pb-Zn oxidizing roasting cinder. The oxidizing roasting cinder—containing 16.9% Pb, 30.5% Zn, 10.3% Fe and 25.1% S—was obtained from a Pb-Zn sulfide ore in the Hanyuan area of China by a flotation-rotary kiln oxidizing roasting process. Anglesite and lead oxide were the main Pb-bearing minerals, while zinc sulfate, zinc oxide and zinc ferrite were the main Zn-bearing minerals. The results show that a part of lead contained in lead oxide is transformed to anglesite, and a 3PbO PbSO H O-dominated new lead mineral phase after acid leaching. A zinc · 4· 2 leaching efficiency of 96.7% was obtained under the leaching conditions used: a leaching temperature of 55 ◦C; a leaching time of 90 min; a sulfuric acid dosage of 20%; a sulfurous acid dosage of 4%; a cinder particle size of <0.3 mm; and a solid-liquid ratio of R = 1:4. After the gravity shaking-table separation, a lead concentrate with 50.2% Pb, 2.33% Zn and lead recovery of 86.0% was produced. The main chemical compounds in leaching residue are anglesite, 3PbO PbSO H O, SiO and ZnFe O , · 4· 2 2 2 4 while the main chemical compounds in lead concentrate are anglesite, 3PbO PbSO H O and SiO . · 4· 2 2 Keywords: lead; zinc; oxidizing roasting cinder; acid leaching; gravity separation 1. Introduction Lead and zinc mineral resources in China are abundant and widely distributed, but relatively concentrated. According to the statistical data of the United States geological survey, the world’s confirmed reserves of lead were 89 million tons in 2013, of which China’s reserves were 14 million tons, accounting for 15.7% of the total. The global reserves of zinc were 250 million tons, of which China’s reserves were 43 million tons, accounting for 17.2% of the total. Chinese reserves of both metals are ranked second in the world. The mineral resources report of the Ministry of Land and Resources shows that the confirmed reserves of lead and zinc were 73.849 million tons and 144.861 million tons in China, respectively. According to the degree of ore oxidation, lead-zinc ore can be divided into sulfide ore (lead or zinc oxidation < 10%), mixed ore (lead or zinc oxidation 10–30%) and oxidized ore (lead or zinc oxidation > 30%). The degree of ore oxidation is closely related to the selection of the separation method and technological process used for metal recovery. Sulfide ore accounts for the majority of lead-zinc ore in China, as well as worldwide. According to the differences in mineral floatability and floating speed, the process for lead-zinc ore can be divided into three categories: selective flotation; bulk flotation; and combined flow. On this basis, according to specific ore properties, many technological processes have Metals 2020, 10, 465; doi:10.3390/met10040465 www.mdpi.com/journal/metals MetalsMetals2020 2020, 10,, 46510, x FOR PEER REVIEW 2 of 214 of 14 in mineral floatability and floating speed, the process for lead-zinc ore can be divided into three beencategories: derived, suchselective as the flotation; direct bulk selective flotation; flotation and combined process, partial flow. On selective this basis, flotation according process, to specific floatable flotationore properties, process, many asynchronous technological flotation processes process, have partialbeen derived, bulk flotation such as the process, direct selective fully bulk flotation flotation process,process, branch partial series selective flotation flotation process, process, gravity floatabl separation-floatatione flotation process, asynch processronous and flotation floatation-gravity process, separationpartial bulk process, flotation etc. process, Sometimes fully a bulk combined flotation process process, of branch beneficiation series fl andotation metallurgy process, gravity is used to processseparation-floatation extremely refractory process bulk and lead-zinc floatation-gravity ores or lead-zinc separation oxide process, ores etc. [1–3 Sometimes]. a combined processThere areof beneficiation a large amount and metallurgy of Cu-Pb-Zn is used polymetallic to process sulfide extremely ores refractory in the Hanyuan bulk lead-zinc area of ores China, or of whichlead-zinc the main oxide metal-containing ores [1–3]. minerals are chalcopyrite, galena, sphalerite, marmatite and pyrite. The mainThere gangue are a mineralslarge amount are dolomite,of Cu-Pb-Zn calcite, polymetallic quartz, sulfide feldspar, ores mica,in the chlorite,Hanyuan montmorillonite,area of China, etc.of Assemblages which the main of galena, metal-containing sphalerite andminerals marmatite are chalcopyrite, (Fe-sphalerite) galena, are sphalerite, currently producedmarmatite asand solid pyrite. The main gangue minerals are dolomite, calcite, quartz, feldspar, mica, chlorite, solutions with a fine grain size, and occur in these ores. Copper concentrate with more than 20% Cu, montmorillonite, etc. Assemblages of galena, sphalerite and marmatite (Fe-sphalerite) are currently lead concentrate with more than 62% Pb and mixed Pb-Zn sulfide concentrate with about 40% Pb + produced as solid solutions with a fine grain size, and occur in these ores. Copper concentrate with Zn weremore obtainedthan 20% byCu, floatation lead concentrate in the localwith dressingmore than plant. 62% Pb The and elements mixed Pb-Zn associated sulfide with concentrate the sulfide mineralswith about are sulfur, 40% silver,Pb+Zn cadmium,were obtained gallium, by floatati indium,on arsenic in the andlocal antimony. dressing plant. The separation The elements of lead andassociated zinc from with the lead-zinc the sulfide sulfide minerals ore isare di ffisulfur,cult usingsilver, just cadmium, flotation, gallium, due to theindium, close arsenic association and of leadantimony. with zinc. The With separation the development of lead and of zinc the market,from the thelead-zinc price ofsulfide lead-zinc ore is mixed difficult concentrate using just has tendedflotation, to decrease, due to the while close a association large number of lead of with these zinc. concentrates With the development are unsalable, of the neither market, of the which price are conduciveof lead-zinc to the mixed improvement concentrate of economichas tended benefits. to decrease, Therefore, while a it large is crucial number that of the these effective concentrates separation of leadare unsalable, and zinc mixedneither lead-zinc of which are concentrate conducive is to studied the improvement [4–9]. of economic benefits. Therefore, it isAt crucial present, that sulfatingthe effective roasting-leaching separation of lead and and high-pressure zinc mixed lead-zinc acid leaching-extraction concentrate is studied separation [4–9]. are the mainAt metallurgical present, sulfating methods roasting-leaching to process Pb-Znand high-pressure bulk concentrate. acid leaching-extraction Zinc sulfate is separation obtained byare the leachingthe main and metallurgical formation of methods crystal line to process products, Pb-Zn while bulk the concentrate. lead sulfate Zinc remains sulfate in is the obtained leaching by residue. the Theleaching high-pressure and formation acid leaching of crystal process line products, is used while to dissolve the lead sulfate lead and remains zinc in into thePb leaching2+and residue. Zn2+ ions, The high-pressure acid leaching process is used to dissolve lead and zinc into Pb2+and Zn2+ ions, respectively. Then, lead and zinc are further extracted by electrodeposition and other processes to respectively. Then, lead and zinc are further extracted by electrodeposition and other processes to achieve effective separation [10–16]. In the local mining enterprises, lead-zinc bulk concentrate is achieve effective separation [10–16]. In the local mining enterprises, lead-zinc bulk concentrate is treatedtreated in a in rotary a rotary kiln, kiln, and and the the schematic schematic diagram diagram isis shownshown in in Figure Figure 1.1. E Sensor D Sensor C Sensor B Sensor A Sensor Feeding Combustion chamber hole Φ3.6 m Discharge hole 2 m 4.0 m 5.5 m 6.0 m 2.5 m FigureFigure 1. 1.Schematic Schematic diagramdiagram of rotary kiln kiln in in the the local local factory. factory. TheThe roasting roasting temperature temperature and and roasting roasting atmosphereatmosphere are are the the two two key key factors, factors, and and are are the the most most difficult to control in the oxidizing roasting process of mixed lead-zinc concentrate. The amount of difficult to control in the oxidizing roasting process of mixed lead-zinc concentrate. The amount of air air in and out of the blower is used to control the roasting atmosphere. If the oxygen content is in and out of the blower is used to control the roasting atmosphere. If the oxygen content is sufficient, sufficient, the roasting products are mainly sulfates. If the oxygen content is insufficient, the roasting the roasting products are mainly sulfates. If the oxygen content is insufficient, the roasting products products are mainly oxides.
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