PbZn 2020: The 9th International Symposium on Lead and Zinc Processing: Zinc Hydrometallurgy
Sponsored by: The Mining and Materails Processing Institute of Japan, Nonferrous Metals Society of China, GDMB: The Society for Mining, Metallurgy Resourcce and Environmental Technology, Metallurgy & Materials Society of the Canadian Institute of Mining, Metallurgy & Petroleum, TMS Extraction and Processing Division, TMS: Hydrometallurgy and Electrometallurgy Committee, TMS: Process Technology and Modeling Committee, TMS: Pyrometallurgy Committee, TMS: Recycling and Environmental Technologies Committee
Program Organizers: Andreas Siegmund, LanMetCon LLC; Shafiq Alam, University of Saskatchewan; Joseph Grogan, Gopher Resource; Ulrich Kerney, Recylex; Cheng Liu, China Enfi Engineering Corporation; Etsuro Shibata, Tohoku University
Tuesday 3:40 PM
February 25, 2020
Room: 15A
Location: San Diego Convention Ctr
Session Chair: Etsuro Shibata, Tohoku University
3:40 PM
Development of the New Zinc-separation Process for the Blast Furnace Dust: Mariko Shinoda1; Toyoshi Yamaguchi1; Ryota Murai1; Goro Okuyama1; Ikuhiro Sumi2; 1JFE Steel Corporation; 2JFE Holdings, Inc.
Blast furnace dust has been recycled as iron source in sintering process. However, dust-recycling rate is limited due to the zinc in dust. Thus, it is necessary to remove zinc from dust. In this study, laboratory-scale experiments were conducted and we propose new hydrometallurgical process. This process is composed of acid leaching, leachate-purification and zinc-recovery. By acid leaching, 68 wt% of zinc was selectively leached under the pH value of 2.0, while only 6.4 wt% of iron was leached. Leachate-purification is the key process. The iron leached by acid leaching was completely separated from leachate under the pH value of 5.0, added with hydrogen peroxide. Zinc was finally recovered as zinc hydroxide at alkali condition such as the pH value of 9.0. Zinc concentration in the sludge was concentrated to 42.6 wt%. Thus, dust can be potentially used as zinc source as well as iron source.
4:00 PM
Outotec Gypsum Removal Circuit and Outotec Cooling Tower Performance in Neutral Solution Cooling: Tuomas Hirsi1; Björn Saxen1; 1Outotec
In a gypsum removal process a solution which is saturated with calcium is cooled to lower temperature with solution cooling towers to remove gypsum (CaSO₄·2H₂O) before next process step. In zinc refineries gypsum removal is part of the solution purification step before electrowinning. Gypsum removal after leaching is important to control the maintenance load of the downstream equipment. Outotec gypsum removal plant has been started in 2018 as a part of the zinc direct leaching plant in Torreon, Mexico. The plant utilizes Outotec cooling towers for solution cooling and Outotec high rate thickener for solid particle separation from the solution flow. First operation results are showing efficient gypsum removal from the solution flow.In this paper we present the Outotec gypsum removal process, show results from operation and discuss the importance of efficient operation and low emissions from the solution cooling.
4:20 PM
Refining of Zinc Chloride by the Combination of Cementation Reaction and Vaccuum Distillation: Gen Kamimura1; Hiroyuki Matsuura1; 1University of Tokyo
In order to develop an efficient recycling process of zinc from electric arc furnace (EAF) dust, several refining methods of crude zinc chloride, which can be produced through selective chlorination and evaporation process of EAF dust, were investigated. In the experiments with cementation reaction using metallic zinc at 723 K, the removal of cadmium from 40mol%ZnCl2-KCl-NaCl melt was focused on, which standard electrode potential is close to that of zinc. Cadmium chloride was effectively removed from molten salt when KCl was added to ZnCl2 rather than NaCl. With two steps of cementation reaction, cadmium was removed to about 10 massppm with adding fewer metallic zinc. In the experiments with vacuum distillation at 800 K, the separation of ZnCl2 from impurities with lower vapor pressures was investigated using a laboratory-scale electric furnace with wide temperature distribution.
4:40 PM
Increasing Current Efficiency To 93% In Jumbo Cellhouse At Vedanta’s HZL Tank House: Pankaj Sharma1; Chandru Chendurpandian1; Ameet Wali1; Ravi Ravada1; Lokesh Gurjar1; 1Hindustan Zinc Limited
In early 2015, it became apparent that with changing concentrate feeds, the impurity load projected for Hindustan Zinc starting in 2017 and beyond would quadruple and overwhelm the current Leaching-Electrolysis process. A project was started, following Six Sigma Standards, to select both optimal process and to evaluate the current Leaching-Electrolysis process. Effect of process parameters at Leaching-Electrolysis for the electrodeposition of zinc has been carried out & implemented. Influence of current density on the deposition process was also investigated. The efficiency of zinc deposition was affected by the temperature of cells, Gypsum section pH, Acidity of electrolyte & neutral leaching pH etc. There are many elements which are detrimental to the current efficiency in the electrolysis of zinc sulphate. This paper describes the project methodology, the impact on the plant and potential optimization for HZL’s Leaching-Electrolysis process.
5:00 PM
Purification and Comprehensive Recovery Metal Values from Zinc Hydrometallurgical Solution: Yue Yang1; Shaole Song1; Honghu Tang1; Li Wang1; Wei Sun1; Yuehua Hu1; 1Central South University
The cost of removing impurities from zinc hydrometallurgy solution by zinc replacement is expensive. Moreover, valuable metals, such as copper and cobalt, are difficult to be recovered when they enter into the zinc slag in the zinc replacement. In this study, a novel process for purification and comprehensive recovery metal values from zinc hydrometallurgical solution has been developed. A slow-release precipitator has been designed. Copper in zinc leaching solution has been selectively separated by a slow release mineralization process based on differences in solubility of zinc and copper sulfide. Almost 100% copper can be removed and the copper grade of precipitate can reach about 20%. We also designed a precipitator with -CSS- group for selectively recovering cobalt from zinc leaching solution after copper removal. It indicated that cobalt removal efficiency is almost 100% with little zinc loss. The cobalt grade of precipitate can reach almost 14%. All above results shows that the developed approach can effectively remove copper and cobalt from zinc hydrometallurgy solution, significantly reduce zinc powder dosage and realize the comprehensive recovery of copper and cobalt, and thus improving the economic efficiency of zinc smelting.
5:20 PM
The Mass Transfer Characteristics of Ozone Oxidation of Rare Scatted Metal Impurities in Zinc Sulfate Solution: Zhang Lihua1; Luo Yaoyao1; Wang Tian1; Qu Hongtao2; Zhang Jiale1; Libo Zhang1; Luo Yongguang3; 1Key Laboratory of Unconventional Metallurgy/Kunming University of Science and Technology; 2Yunnan Chihong Zn & Ge Co., LTD; 3Key Laboratory of Unconventional Metallurgy/Kunming University of Science and Technology/Yunnan Chihong Zn & Ge Co., LTD
There are abundant strategic rare scattered metal resources in lead and zinc deposits in China, especially zinc resources in Yunnan province, which are associated with indium (In), selenium (Se) and tellurium (Te), etc. The rare scattered metal ions with low valence dissolved into zinc leaching solution, and are difficult to remove by conventional zinc powder replacement method. They were enriched in the ZnSO4 solution, which caused serious problem to zinc electrowinning process such as hydrogen generation, zinc re-dissolution, plate burning, and low current efficiency, etc. So, they needed to be deeply removed from ZnSO4 solution. This article used ozone, a powerful oxidizing agent, to oxide the trace rare scattered metal impurities with low valence into higher valence and then occurred hydrolysis precipitation into sludge. The mass transfer characteristics between ozone and impurities in ZnSO4 solution was investigated. Effects of reaction temperature, ozone flow rate, and residence time on overall volumetric mass transfer coefficient (kLa) were studied. Furthermore, correlations relating kLa to the experimental parameters were also reported, and a gas-liquid mass transfer model was developed.