Hydrometallurgical processing of Platreef flotation concentrate

Platinum producers are evaluating hydrometallurgical process routes to extract platinum group metals (PGM) and base metals (BM) from flotation concentrate that are alternative to conventional pyrometallurgical matte smelting treatment of flotation concentrates. This approach would attract several potential benefits to the cost-effective processing of lower-grade and high-chromium concentrates. Ivanhoe Nickel and Platinum Ltd. wished to investigate this option on samples arising from their Platreef project in the northern limb of the Bushveld Complex in South Africa, from concentrate containing 1.5 g/t Pt, 2.5 g/t Pd and 0.5 g/t Au, as well as 1.5% Ni and 1.2% Cu. Other PGMs assayed rather low grades in the concentrate (Rh 128 ppb; Ru 153 ppb; Os 18 ppb; Ir 31 ppb) so the focus was on Pt, Pd and Au in this study. Some twenty-two hydrometallurgical process flowsheet variants were considered for evaluation in a testwork programme combining several conventional and proprietary unit process technologies.The testwork outcomes suggested that a hydrometallurgical flowsheet alternative to smelting (the patented Kell Process) is potentially a practical, environmentally benign and energy-efficient approach for treating low-grade Platreef concentrate with relatively low risk. This process broadly comprises selective leaching of base metals by pressure oxidation, followed by leaching of PGMs after a roasting pretreatment step shown to render PGMs and particularly Pt amenable to leaching. The process embodies separation of the value metals (PGM and base metals) into separate chloride and sulfate solution streams, respectively, and impurity elements (Fe, Al and gangue) into a tailings product. Key elemental deportments from the un-optimized process were Ni 96%, Co 94%, Cu 94%, Pt 96%, Pd 94% and Au 87%.Preliminary work indicated that further improvements in value metal recoveries, impurity separations and reagent consumptions may be gained from further optimization of the individual unit processes. Moreover, the recycle of key reagents uses existing proven technologies, rendering the process more economically and environmentally favourable. Initial assessment suggests that the Kell Process should offer both economic and environmental benefits over conventional pyrometallurgical matte smelting treatment of Platreef flotation concentrate.     

The pros and cons of reductive matte smelting for PGMs

Platinum group metals (PGMs) are traditionally smelted in electric furnaces where the valuable metals are collected in a base-metal sulphide matte. An alternative to this process is the ConRoast process that uses reductive alloy smelting in a DC arc furnace to collect the valuable metals in an iron-rich alloy. Reductive smelting of feed materials containing PGMs, using carbon as a reducing agent, can be used to obtain high PGM and base-metal recoveries and to ensure the solubility of chromium in slags.Based on work carried out in Mintek’s 3 MW DC arc furnace at throughputs of over 1000 tons per month, it was found that PGMs could be collected effectively, and that the chromium problem could be managed. However, if matte is present in the furnace, there remains a significant risk of furnace failure. Furthermore, the PGM ‘lockup’ (inventory inside the furnace) in a process that used reductive matte smelting of UG2 concentrates was much greater than that of reductive alloy smelting. Further differences exist in the better working environment and lower emissions of SO₂ in the case of the ConRoast process.     

Determination of the relative leaching kinetics of Cu, Rh, Ru and Ir during the sulphuric acid pressure leaching of leach residue derived from Ni-Cu converter matte enriched in platinum group metals

Hydrometallurgical process routes are typically used for separation of platinum group metals (PGMs) from base metals in Ni-Cu converter matte. Nickel dissolution is primarily achieved in the first stage leach (high pressure or atmospheric leaching, or a combination of the two), which is followed by second stage high pressure sulphuric acid/oxygen leaching to dissolve copper and the remaining nickel. PGMs are recovered from the leaching residue, and their dissolution must hence be limited. The leaching of base metals in the first stage has been characterised, but there is a limited understanding of the behaviour of metals, and more specifically PGMs, in the second stage pressure leach. This research presents the results of laboratory work performed to investigate the kinetics of leaching in the second stage pressure leach. The influence of key operating parameters such as the temperature, pressure, and initial acid concentration on PGM dissolution was investigated.     

我国镍冶金的发展与工艺技术进步

我国的镍冶金生产近３０年来取得了巨大的发展，工艺技术的进步尤为突出。本文重点论述了我国镍冶金现有的电炉、闪速炉熔炼低冰镍－转炉吹炼高冰镍－铜镍磨浮分离－硫化镍阳极电解；高冰镍两段逆流硫酸选择性浸出－黑镍沉钴－电积；二次镍精矿制粒－沸腾焙烧生产氧化镍等工艺流程。同时，介绍了我国自行研究开发的高冰镍氯化精炼；焙烧－氨浸－氢还原；镍精矿微波脱硫－热等离子体熔炼高冰镍；大洋多金属结核常压氨浸和硫酸选择性浸出回收镍等有价金属的新工艺新技术。     

Biological treatment of precious metal refinery wastewater: A review

The refining of platinum group metals (PGMs) generates large volumes of wastewater which is highly contaminated by organic solvents and contains trace amounts of heavy metals. Treatment to reduce chemical oxygen demand and metal concentration to levels allowing reuse in refinery processes can help to alleviate the demand for clean water in arid/semi arid mining regions of the world. Traditional physicochemical treatment options have been favoured in the past for treatment of PGM wastewater but biological treatment is becoming increasingly popular. This review examines the need for treatment of PGM wastewater and various physicochemical technologies that are available for treatment of organic solvents and heavy metals. It also introduces various activated sludge technologies that have been shown to remove 99% of certain solvents, while biosorption has been demonstrated to be very effective in removal of heavy metals. A combination of biological treatment and biosorption can be a viable technology for the treatment of complex and potentially toxic wastewaters. Improved treated wastewater quality can allow for reuse in refinery processes which could lead to significant cost reduction and prove to be environmentally beneficial.     

Investigating the effect of slag bath conditions on the existence of multiphase emulsion zones in PGM smelting furnaces using computation fluid dynamics

The presence of chrome in electric arc furnaces smelting platinum group metals (PGM’s) has a number of potentially negative consequences. In cases where the slag chrome content is above the saturation limit the existence of near-stagnant conditions near the slag/matte interface increases the risk of chromite spinels settling and consolidating into a “mushy layer”, a three-phase suspension of slag, chromite and matte. The hold-up of matte above the elevation of the slag/matte interface can lead to the attack of freeze linings and copper cooling elements potentially causing failures of the furnace lining and significant downtimes as well as major safety risks. This paper investigates the relationship between typical furnace operating parameters and the behavior of the slag bath with respect to the formation of the “mushy” layer at the slag/matte interface using computational fluid dynamics (CFD). The extent of the potential “mushy” layer is seen to increase with decreasing electrode immersion and furnace power. Electrode immersion is, however, a considerably stronger driver is this regard. The CFD modelling results have aided in selecting appropriate furnace electrode immersion/power combinations intended to minimize “mushy” layer formation.     

从铅冰铜中高效选择性提取铜的工艺研究

采用高温高压纯氧氧化法选择性提取铅冰铜中铜, 研究了硫酸用量、浸出温度、反应时间、液固比、氧气压力、搅拌速度以及分散剂木质素用量对铜浸出率的影响及对浸出液中铁含量的影响。铅冰铜经氧压浸出后进行液固分离, 铅冰铜中的铜进入液相中, 绝大部分铁以赤铁矿的形式与铅、银、金等有价金属一起进入渣相中; 浸出后的硫酸铜溶液经调酸后直接进行旋流电解可得到合格的阴极铜产品, 浸出渣返回铅冶炼系统综合回收铅、银、金等有价元素。高温氧压浸出铅冰铜, 铜浸出率可达93.5%, 阴极铜产品质量达到99.975%, 有效实现了铅冰铜中铜的选择性提取。     

关于阜康铜渣冶炼工艺的研究和选择

我国独立开发的镍精炼新工艺已在新疆实际应用。经阜康冶炼厂选择性浸出提取后,金属化高冰镍原料中大量铜及贵金属进入了铜渣。在完成了阜康铜渣吹炼粗铜的试验研究任务之后,北京矿冶研究总院又制订了铜渣"焙烧—浸出—电解"方案,并进行了验证试验。证实了该工艺具有铜回收率高、浸出液较为纯净可直接电解、镍能综合回收、浸出渣率低和贵金属富集比高等特点。结合公司和阜康实际,最终推荐了焙烧、浸出方案。该方案已被新疆有关部门采纳,于1999年建成了国内能力最大的采用溶液电积工艺生产电解铜的车间(5000t电解铜/a),投产后经济效益显著。     

The environmental costs of platinum–PGM mining and sustainability: Is the glass half-full or half-empty?

The growing popularity of platinum group metals (or PGMs, including platinum and palladium) for a wide range of applications leads to some interesting issues for mining and sustainability. The uses of PGMs includes catalytic converters for air pollution control in vehicles, growing jewellery use, catalysts for various purposes (especially petroleum and chemicals processing), hydrogen fuel cells, and many others. Given the growing importance of most of these PGM uses in more sustainable technologies or in making industrial processes more efficient, it is critical to understand the complex sustainability issues which surround PGMs. At present, South Africa is the dominant PGMs producer and holds ～88% of estimated global resources, with additional production and resources in Russia, Zimbabwe, Canada and the United States. Given the concentrated location of PGM resources, what are the likely trends in PGM mining with respect to environmental sustainability? That is, what are the costs in terms of energy, pollution, greenhouse gas emissions, water, land use impacts, social impacts, economic aspects associated with this globally important industry? This paper compiles and analyses a range of data on PGM mining. It synthesizes a unique combination of data which relates typical production aspects such as ore grade and scale with sustainability aspects such as greenhouse, energy and water costs. The findings are critical in understanding the debate about the increasing environmental and social costs of some materials and technologies which are considered crucial for sustainable technologies based on PGMs. Overall, the paper represents a valuable insight into the environmental and resource sustainability of the PGM sector.     

Dissolution of platinum in catalyst materials using hydrochloric acid: A new method based on the use of complex oxides

Platinum group metals (PGMs) are used widely in various applications, including as environmental catalysts. Since PGMs are rare and expensive, they are recycled after being recovered. Currently, PGMs are recovered, after a pyrometallurgical step that upgrades the concentration, by dissolving in strong acids containing toxic oxidizing agents like aqua regia. To avoid the use of such toxic agents, we have proposed a new route to dissolve PGMs in hydrochloric acid (HCl) using complex oxides. In the present study, we used this new process to dissolve Pt in supported metal catalysts. Complex oxides of Pt were prepared by calcining mixtures of Pt/Al₂O₃ and alkali metal salts at 600–800 °C in air. These were then dissolved in 12 M HCl. The results showed that the Pt in the calcined samples dissolved readily in HCl and that the Pt solubility was nearly 100% under the appropriate preparation and dissolution conditions. We also confirmed that the new process is suitable for leaching PGMs from spent automotive catalysts.     

Recovery by hydrometallurgical extraction of the platinum-group metals from car catalytic converters

The car industry is one of the technological applications which more platinum-group metals (PGM) employs. Therefore, the recovery of the PGMs from the car catalytic converters could be an important source to obtain these precious metals, with economic and environmental consequences.In this work, the car catalytic converters were characterized through different techniques as X-ray diffraction, scanning electron microscopy and inductively coupled plasma.In order to suggest an environmentally friendly method for the recovery of PGMs, some conditions such as the reagents concentration and composition, energy optimization, pre-treatment in hydrogen atmosphere and a thermal pre-treatment were studied.In addition, a new alternative to recover at least the 95% of the PGMs present in the car catalytic converters by the application of lees aggressive, corrosive or expensive reagents and conditions is proposed.     

红土镍矿冶金工艺现状及前景分析

本文简要介绍了镍资源的性质特点及现状,分析了红土镍矿回转窑-电炉还原熔炼、还原焙烧－磁选、还原硫化熔炼３种火法工艺以及常压酸浸、高压酸浸等湿法工艺的优势与短板,并指出生物浸出在红土镍矿处理中的应用,探讨了未来红土镍矿冶金工艺的改进发展,指出红土镍矿湿法冶金将在今后扮演重要地位。     

氯化焙烧回收河南某黄金冶炼渣中的有价金属

黄金冶炼渣中含有大量的Au、Ag、Cu、Pb、Zn等有价金属,对其进行回收利用不仅可以减轻由尾渣堆存造成的环境污染,还能创造经济效益。为给河南某黄金冶炼渣中有价金属的回收利用提供依据,对该渣进行了高温氯化焙烧工艺优化试验。结果表明：冶炼渣在CaCl2加入量为7%、焙烧温度为1 100 ℃、焙烧时间为60 min条件下进行氯化焙烧,可以获得Au、Ag、Cu、Pb、Zn挥发率分别为96.01%、81.69%、86.57%、99.67%、99.07%的指标,实现了有价金属的综合回收。     

水淬焙烧渣中金铂钯的氯化浸出

为了回收水淬焙烧渣中的贵金属,本文提出了氯酸钠溶液、硫酸和氯化钠混合溶液从冰铜水淬渣中浸出金、铂、钯的方法,并对不同的影响因素进行了优化。 系统研究了固液比、硫酸浓度、氯化钠浓度、氯酸钠浓度、温度、粒度和浸出时间等主要参数, 结果表明铂浸出的动力学限制条件为,浸出液中氯离子浓度,而金钯动力学浸出限制条件为浸出液的氧化性。在氯酸钠自身歧化反应限制下,无法兼顾较高的氧化性以及较高的氯酸钠浓度,所以利用氯酸钠一次性浸出金铂钯难度较大。酸钠溶液,硫酸,氯化钠混合浸出冰铜水淬渣中金铂钯的优化的工艺参数为硫酸浓度为0.5M,氯化钠浓度为10%,在初始ORP值为1062(mv),在上述条件下金铂钯的浸出率分别为100%,78.56%,100%。     

Direct leach approaches to Platinum Group Metal (PGM) ores and concentrates: A review

Platinum Group Metals (PGMs), often with associated gold, have very few occurrences where they are present in an ore deposit at economically extractable levels. They are classified as both precious and critical metals due to their scarcity and their wide industrial use. With deteriorating socio-political environments in most primary PGM producing countries, PGM deposits that are smaller but in less risky jurisdictions have to be evaluated. However, the lower PGM grades, increased mineralogical complexity of the ores, capital intensity and strict environmental regulations in other international jurisdictions, limit the implementation of conventional metallurgical processing options, particularly smelter-based operations. The conventional smelter-based process options are justifiable for high grade, low chromite, large resource and long life-of-mine operations.In the present paper, we review some of the most recent literature on the predominantly hydrometallurgical approaches to PGM extraction. A number of metallurgical processes that generate either a PGM rich leachate or a residue containing metal values, and the various methods in use for their recoveries from pregnant rich solutions are reviewed. Sixteen process flowsheet variants combining conventional and proprietary unit process technologies are provided, and their process chemistries and key technical operating parameters are compared. Where appropriate, the key thermodynamic and kinetic factors are given and compared.     

Thermodynamic modelling of the multiphase pyrometallurgical processing of electric arc furnace dust

Electric arc furnace (EAF) dust is produced when automobile scrap is remelted in an electric arc furnace and about 10–20 kilograms are generated per ton of steel. The major elements present in the dust are usually zinc, iron and calcium with smaller amounts of numerous other elements such as lead, copper and nickel. Typically, in the pyrometallurgical EAF dust treatment processes, the lead and zinc are separated as a crude zinc oxide while the iron is generally not worth recovering. Copper and nickel are usually not recovered as they report either to the oxide residue or to any metallic iron that is produced. In the present research, the recovery of the non-ferrous metals in a multiphase system consisting of gas, slag, matte, metal and solid carbon phases was investigated. The equilibrium compositions of the various phases, resulting from the smelting of the dust, were calculated using the SOLGASMIX module of Outokumpu HSC Chemistry. The effects of the following operating variables were investigated; carbon additions, sulphur additions, nitrogen and oxygen additions, temperature and dust composition. The thermodynamic modelling results show that the majority of the non-ferrous metals can be recovered, with the zinc and lead concentrating in the gas phase and the nickel and copper concentrating in the matte phase.     

奴拉赛古铜矿冶炼技术研究

新疆奴拉赛古铜矿采炼硫化矿石,使用“硫化矿-冰铜-铜”工艺。还原熔炼中添加砷矿物,最终产品是砷铜。该遗址相当于东周时期。硫化矿添加砷矿物冶炼砷铜的技术,对揭示当地青铜时代的冶金技术,探讨砷铜和硫化矿冶炼技术的源流有重要意义。     

还原挥发富集火法炼铅锑渣中铟及其他有价金属的热力学分析

根据火法炼铅锑弃渣的特点,对回转窑火法还原挥发富集该渣中的铟及其他有价金属进行热力学分析.计算出的渣中相关化合物最低还原温度及蒸气压与温度的关系表明了工艺的可行性,结果可为实际生产提供指导.     

硫化镍加压浸出研究进展与应用

硫化镍是镍冶炼的重要原料,加压浸出技术在硫化镍冶炼中占有重要地位。本文对硫化镍加压浸出研究及应用进行了简单的介绍。根据反应体系的不同,镍加压浸出分为酸性加压浸出和氨性加压浸出两大类,工业生产中氨性加压浸出应用较少,以酸性加压浸出为主。硫化镍加压浸出处理原料灵活多样,主要包括硫化镍精矿、镍锍、镍钴硫化物等。另外,其在镍冶炼渣、低品位复杂物料处理方面也有一定的研究应用。加压浸出工艺灵活,综合回收率高,可同时生产镍、钴、铜、铂族金属等多种产品,主产品即可为硫酸镍,也可为电镍或镍粉,产品质量高,环境污染小,具有一定的市场竞争力。     

电镀泥热处理可浸性研究

按照环保的标准和要求，柏林工业大学冶金研究所对不同种类、成分的电镀泥进行了试验室研究，对含金属的废电镀泥进行直接和经火法预处理后的浸取溶出。研究采用包括回转窑、电弧炉及闪速熔炼等火法处理工艺，进而对溶出液的金属含量与饮用水中允许金属含量及弃渣堆存的要求进行比较。