Microwave pretreatment of a double refractory gold ore

Double refractory gold ores, such as Barrick’s Goldstrike ore, contain both pyrite and carbonaceous matter and the latter results in the loss of gold from solution during cyanide leaching. One possible remedy is to roast the ore and thus oxidize the pyrite and remove the organic carbon. In this research, microwave roasting of a double refractory gold ore was investigated as an alternative method and the results were compared to those obtained by conventional roasting.The compositional changes of the ore during roasting were determined by thermogravimetric analysis (TGA). Also, both the real and the imaginary permittivities, which determine the amount of energy absorbed by the ore and the heating rate of the ore respectively, were evaluated. In addition, the microwave heating behaviour was studied. Conventional and both direct and indirect microwave roasting tests were performed and in all the cases, the pyrite was readily converted into hematite. Direct microwave roasting could not remove the organic carbon. Indirect microwave roasting was conducted using magnetite as a susceptor and preg-robbing was eliminated when about 94% of the organic carbon was removed. For both conventional and indirect microwave roasting, gold recoveries of over about 98% were achieved after cyanide leaching. For microwave roasting, both the total carbon removal rates and the heating rates were higher and the specific energy consumptions were lower than the corresponding values for conventional roasting.     

赤铁矿微波还原焙烧-弱磁选工艺研究

以活性炭为还原剂, 氩气为保护气, 采用微波还原焙烧的方法, 将3种低品位赤铁矿还原为磁铁矿, 并研究了微波还原焙烧温度、碳含量、保温时间及微波输出功率对其磁选指标的影响规律。结果发现: 相同质量3种赤铁矿进行微波还原焙烧, 随配碳量的增加, 其升温速率加快, 且3种赤铁矿具有相似的微波还原焙烧规律, 即: 在570～650 ℃、理论配碳量、微波输出电压220 V及保温10 min的条件下, 其还原产物弱磁选后的品位和回收率均达到最佳, 且磁铁精矿经细磨-二次磁选后, 铁品位均能提高到60％以上。该研究对开发低品位赤铁矿的选冶技术新流程有重要的指导意义。     

碳质金矿预处理技术研究进展

碳质金矿选别前的预处理是提高金精矿回收率的一种有效方法。随着难处理碳质金矿所占比例越来越多,采用焙烧法、氧化法、覆盖抑制法及竞争吸附法等单一预处理法的效果难以获得较高的金浸出率,可以采用浮选-焙烧氧化、微生物二次氧化及微生物-化学氧化等多段预处理工艺,增加金回收率的同时降低处理成本。介绍了碳劫金机理及近年来碳质金矿预处理技术的研究进展,分析了现有预处理方法的优缺点及应用情况,并展望了未来的发展方向。      

微波加热还原含碳红土矿的研究

研究了含碳红土矿在微波场中的加热还原焙烧,考察了不同含碳量情况下微波加热焙烧过程中的样品温度和产物的物相组成,以及浮氏体、磁铁矿和赤铁矿等不同价态的铁氧化物在微波场中的加热性能.结果表明,微波加热红土矿是一个热稳定过程,未出现热失控现象.红土矿的还原程度可通过调整加入碳粉的比例和微波加热时间来控制.还原焙烧过程中,碳粉加入量影响产物的物相组成,进而影响焙烧过程的温度.     

铁氧化物包裹类金矿提金的研究现状

部分难处理金矿中存在铁氧化物对金包裹的现象而阻碍提金过程,通过破坏铁氧化物结构可使金暴露而提高金浸出率。铁氧化物包裹金主要来自难处理金矿的氧化焙砂。目前针对此类金矿提金的工艺研究较少,主要包括酸溶法、还原法、氯化焙烧法、炼铁—电解法等。酸溶法工艺简单,效果较差;还原法工艺复杂,可获得较好的浸金效果;氯化焙烧法适应性强,综合利用效果好,但设备投资及维护费用高;炼铁一电解法可在富集金的同时生产纯铁,节约能耗,对矿石要求稍高。     

某褐铁矿微波磁化焙烧-弱磁选试验

以河南义马褐煤为还原剂,对印尼某褐铁矿进行微波磁化焙烧-弱磁选试验,主要考察了焙烧时间、焙烧矿磨矿细度及磁场强度对精矿指标的影响。试验结果表明：在还原剂配加量为5.4%、微波功率为1 kW的固定条件下,当焙烧时间为45 min（终点温度840 ℃）、焙烧矿磨矿细度为-200目占97.17%（-325目占82.03%,-400目占64.15%）、磁场强度为150 kA/m时,可获得铁品位为57.28%、铁回收率为83.95%的铁精矿。试验中发现,微波焙烧产品可以很容易就被磨得很细。     

王家滩菱铁矿焙烧选矿试验研究

菱铁矿为复杂难选矿种之一,采用常规选矿方法难以得到较高铁品位的铁精矿.针对昆钢王家滩菱铁矿资源,进行了焙烧和闪速焙烧试验研究.试验结果表明,常规的焙烧导致弱磁选精矿硫含量超标,而采用闪速焙烧可达到降硫目的,铁精矿硫含量低于0.20%,同时可获得比常规焙烧高4.72个百分点的回收率.     

Interactions between sulphides and manganese dioxide in thiosulphate leaching of gold ores

The interactions between manganese dioxide and pyrite or chalcopyrite were investigated in both the ammoniacal and ammoniacal thiosulphate leaching systems. Pyrite and chalcopyrite dissolved at enhanced rates in the presence of manganese dioxide in both ammoniacal and ammoniacal thiosulphate solutions. The interactions between manganese dioxide and sulphides were also applied in the thiosulphate leaching of gold from a pyrite concentrate and a sulphide ore. The addition of a small amount of manganese dioxide in the thiosulphate leaching of the sulphide bearing gold ores improved both the kinetics and the overall gold extractions without much impact on thiosulphate consumption.A pre-treatment process with copper ammoniacal solutions enhanced gold extractions from the sulphide bearing ores and reduced thiosulphate consumption to a large extent. The sulphides partially degraded in the pre-treatment process likely exposing gold to leach solutions. SEM images of the surface corrosion of pyrite and chalcopyrite in contact with manganese dioxide showed that the pre-treatment with manganese dioxide enhanced the degradation of the sulphide matrices, thus achieved a better gold leaching from the sulphide bearing ores.     

新疆难处理金精矿焙烧预氧化—氰化提金工艺试验研究

对新疆某难处理金精矿进行工艺矿物学研究和焙烧预氧化—氰化提金工艺研究。试验结果表明,通过对该金精矿进行焙烧预氧化处理后,氰化金的回收率达91.42%,比常规氰化回收率提高了50.60%。这对于该类型金矿资源的充分利用有着重要意义。     

酒钢-1mm镜铁矿粉矿微波磁化焙烧—弱磁选试验

鉴于酒钢-1 mm镜铁矿粉矿采用常规选矿方法难以获得好的分选指标,进行常规磁化焙烧—弱磁选又需解决球团问题,以哈密烟煤为还原剂,对该粉矿开展了微波磁化焙烧—弱磁选研究,考察了煤粉用量、微波功率、焙烧温度、焙烧时间、焙烧产品磨矿细度和弱磁选磁场强度对所获铁精矿指标的影响。试验结果表明,在煤粉与矿石的质量比为5%、微波功率为1 k W、焙烧温度为550℃条件下将该粉矿微波磁化焙烧15 min,然后将焙烧矿磨细至-0.074 mm占85.65%,在92.16 k A/m磁场强度下进行1次磁选管选别,可获得铁精矿铁品位为55.10%、铁回收率为86.65%的较好指标,从而为该-1 mm镜铁矿粉矿中铁矿物的高效回收提供了一种新思路。     

微波焙烧在难选铁矿中的应用前景

由于微波加热具有加热速度快、反应灵敏、加热均匀、热效率高等优点,近几年在化学、化工和矿业方面的应用正逐渐开展。随着我国对铁矿石资源的需求越来越大,微博能在矿冶领域中潜在的重大作用越来越引起人们的高度重视。结合当前微波应用现状,阐述了微波焙烧在难选铁矿中的研究,重点介绍了微波在赤（褐）铁矿中研究现状,并指出微波在难选铁矿中的发展前景及研究趋势,同时对微波应用的前景进行展望。通过批量生产和技术提升大幅度降低工业用微波源的生产成本,从而降低微波高温设备的制造成本,微波高温设备将取代传统高温设备的市场,逐渐成为主流。      

难处理金矿的球团包衣焙烧预氧化法研究

本文讨论了一种用于含硫砷碳难浸金矿的全新预处理方法—球团包衣焙烧氧化法。该过程的最大特点是在精矿和粘接剂形成的球团外侧覆盖一层由硫砷固定剂组成的包衣层。球团焙烧氧化产生的二氧化硫和三氧化二砷气体以硫酸钙和砷酸钙的形式被固定在包衣层中 ,没有二氧化硫和三氧化二砷扩散到大气 ,不需要烟气净化设施 ,不会产生环境污染。总结了反应的热力学数据。试验所得指标为 :硫固定率大于 99.98% ,砷固定率大于 99.99% ,焙砂产率 74 % (相对精矿 ) ,去衣金损失率 0 .6 3% ,焙砂金浸出率 91.71%～ 92 .84 % ,优于普通焙烧氧化法的 78.6 3%。     

The development of an environmentally friendly leaching process of a high C,As and Sb bearing sulfide gold concentrate

An environmentally friendly leaching process, consisting of the pretreatment of alkaline pressure oxidation and thiosulfate leaching, has been developed to efficiently extract gold from a high carbon, arsenic and antimony bearing sulfide gold concentrate. The Au extraction from the concentrate by direct cyanidation was very low mainly due to the encapsulation of gold by associated minerals and the preg-robbing effect of graphite and organic carbon. The pretreatments of permanganate oxidation and oxidative roasting both could effectively liberate encapsulated gold and eliminate the preg-robbing effect on cyanidation. However, the reagent dosage of permanganate oxidation was high and the final oxidation solution contained substantial quantities of toxic ions. The flue gas of oxidative roasting also contained a lot of poisonous oxides, and the extremely drastic reaction environment of roasting led to the secondary encapsulation of gold by newly generated oxides. The pretreatment of alkaline pressure oxidation effectively liberated encapsulated gold with less than stoichiometric reagent dosage and simultaneously relieved the secondary encapsulation of gold, but could not completely remove graphite and organic carbon. Because carbonaceous matter had a weak affinity for gold thiosulfate complex, the Au extraction by thiosulfate leaching after the pressure oxidation achieved 86.1% whilst the thiosulfate consumption was 35.3 kg/t-concentrate. This process of alkaline pressure oxidation–thiosulfate leaching neither used toxic reagent nor released poisonous gas, and furthermore its effluents contained few toxic ions.     

The effect of non-sulphide gangue minerals on the flotation of sulphide minerals from Carlin-type gold ores

Flotation pre-concentration of sulphide and gold values from certain Carlin-type deposits characterised as double-refractory gold ores is quite challenging. Numerous studies conducted on these ores in many laboratories globally (including the present study) under a variety of chemical and physical conditions have merely confirmed low recovery (and poor concentrate grades) for sulphide minerals and gold, and poor separation between sulphide minerals and carbonaceous matter, even when the valuable minerals are adequately liberated. None of the traditional reasons based on liberation or the choice of chemical and physical conditions and separation strategies could provide satisfactory explanation for the observed poor separation.In this study, the focus was on the role of non-sulphide gangue (NSG) minerals. It was hypothesised that specific NSG minerals have a detrimental effect on flotation recovery of gold bearing minerals and their separation selectivity. In order to test this hypothesis and delineate the effect of the various gangue minerals, a new approach was taken. This involved first isolating the various mineral components of a double-refractory gold ore from one of the Carlin-type deposits using a gravity separation technique. Then flotation experiments were performed using a mixture design on various mixtures of these isolated components under controlled conditions. The results of these mixture experiments supported the hypothesis and demonstrated, for the first time for these types of ores, that even small amounts of NSG minerals, especially carbonaceous matter and clays, had a large adverse effect on the flotation of sulphides and selectivity of separation. While it is tempting to attribute the observed effects solely to slime coating, there is no basis to do so at this stage; it is more reasonable to propose that multiple contributions exist. The results of this study provide the much-needed context and direction for further fundamental studies and for developing processing strategies.     

高含碳金矿石浮选工艺流程试验研究

某高含碳金矿(碳品位6.68%),金共生有用矿物为黄铁矿、毒砂以及微量的石墨,一部分黄铁矿包裹在碳质物中。采用两次粗选、粗精矿1两次精选、粗精矿2四次精选、三次扫选的混合浮选工艺流程,获得金精矿(金精矿1+金精矿2)金品位42.18g/t、银品位46.70g/t,金回收率85.87%,银回收率62.86%的浮选指标,在回收金的同时综合回收了银。此工艺流程为含碳金矿选矿厂提供了一个易于工业化实施的工艺流程。     

The mechanism of leaching of gold from refractory ores

Refractory gold ores commonly contain free gold, submicroscopic gold, base metal sulphides, pyrite, pyrrhorite, labile sulphides and carbonaceous material. The analysis of gold deportment with the diagnostic leaching technique has opened a research field to gain more insight into the fundamentals of the kinetic behaviour of gold dissolution from refractory ores. Hence, more detailed studies on the kinetics of the reactions that occur during leaching with cyanide are now possible.Previous research work has indicated that the dissolution rate of gold during cyanidation becomes depressed after a certain time with no further increase in the rate. However, a second noticeable increase in the gold dissolution rate has been observed after a leaching time of 5 to 12 hours during some of the cyanidations, following the destruction of a mineral with the diagnostic leaching technique. If such a second increase in dissolution rate does not occur, the re-leaching of the filtered solids with a fresh cyanide solution yields an additional gold extraction of 4 to 8 %.Various experimental results have indicated that a passivative film forms on the surface of some of the liberated gold. The selective destruction of the various minerals with oxidative acid leaches destroys and/or decomposes certain minerals which may form films on the gold surface by precipitation. The chemical composition of these films and precipitates depends on the mineralogy of the sample. These films may be oxides, sulphides, carbonates and cyanide complexes.The complexes can be destroyed, depending on the nature of the film, by interstage dilute acid and/or cyanide washes in an agitated vessel. The destruction of the films exposes the gold surface for cyanidation. Whereas most of the previous studies on the leaching of gold have focused on the whole ore, the emphasis in this study was on the leaching behaviour of gold from various ore constituents. This approach of studying the leaching behaviour of different gold bearing minerals has provided reasons why some ores leach better than others.     

难选弱磁性铁矿石闪速(流态化)磁化焙烧成套技术开发与应用研究

针对难选弱磁性菱铁矿、褐铁矿采用常规选矿方法不能有效分选的难题,进行了基础理论研究、成套技术与装置研发以及系统工程技术集成等,开发了高效处理难选弱磁性铁矿石的闪速磁化焙烧成套技术与装备,并在湖北黄梅建成了首个60万吨/年的产业化工程项目并稳定生产。原矿品位32.52%的菱(褐)铁混合矿,经闪速磁化焙烧处理后,工业生产可获得铁精矿品位57.52%、SiO₂含量4.76%、铁回收率90.24%的先进技术指标;原矿焙烧热耗31.22 kgce/t,产品铁精矿制造成本234.36元/吨,低于其它焙烧方法。该技术的推广应用前景十分广阔。     

某高硫含砷碳低品位难处理金矿选矿试验研究

某低品位金矿石原矿含金1.68 g/t，砷0.43%、碳0.40%、硫3.20%，金以显微或次显微形式浸染于毒砂、黄铁矿、褐铁矿中，具有载金矿物粒度细、砷和碳含量高等特点，是典型的低品位含砷碳极难处理 金矿石，严重影响金的浮选指标。为回收利用矿石中的金，分别进行了直接全泥氰化浸出、重选、浮选三种方案对比试验研究。结果表明，直接全泥氰化浸出率仅5%，重选金精矿回收率不足10%，浮选可获得金品位 15.04 g/t、回收率77.13%的金精矿。由于浮选金精矿含砷、碳、硫有害元素均较高，浮选尾矿含金0.42 g/t，损失较高，因此试验采用焙烧预处理以脱除金精矿和尾矿中的有害元素，然后焙砂氰化浸出回收金。最终 试验采用浮选—金精矿焙烧氰化浸出—尾矿焙烧氰化浸出联合工艺，得到金总回收率70.66%的较好指标，有效地回收了矿石中的金。     

Bonded-particle modelling of microwave-induced damage in ore particles

Microwave heating of mineral ores offers a mechanism to induce fractures around grain boundaries due to the different rates of microwave power dissipation and the differences in thermal expansion coefficient among various minerals in the ore particles. As a consequence, this has the potential to reduce the energy required in subsequent grinding and to enhance liberation of valuable minerals. In this paper, numerical simulation using a bonded-particle model was undertaken to provide a better understanding of the mechanism of microwave-induced micro-fracture and to predict the effect of microwave power delivery and ore texture on microwave treatment of ores. Computational simulations of microwave heating and thermal damage have been carried out on two-phase conceptual ores. It was shown that the extent of damage and the crack pattern in an ore sample for the same microwave energy input depend strongly on the applied power density and the microwave absorbent phase grain size. It is possible both to reduce the energy input and to localize the microwave-induced damage around the grain boundaries by operating at high power density. It was also shown that high power pulsed equipment would be more efficient than continuous wave equipment for treating fine-grained ores.     

降低含砷金精矿两段焙烧提金过程中氰化物用量的途径

针对某含砷难处理金精矿两段焙烧工业生产中焙砂氰化物单耗较高,达到8～10kg/t(焙砂)的实际情况,本文研究探索了焙砂氰化浸出工艺,通过调整生产工艺,氰化钠的单耗降低至4.0kg/t(焙砂),不但生产成本降低了,而且金的浸出率也相应提高到90%以上,为企业创造了良好的经济效益。本文对含砷难处理金精矿两段焙烧生产过程中降低氰化物消耗、降低渣金品位以及指导金精矿两段焙烧实际生产具有指导作用。