Effect of microwave pre-treatment on ultramafic nickel ore slurry rheology

Low-grade ultramafic nickel ores, while representing a large potential nickel resource, are difficult to process due to their high serpentine content. Serpentine is anisotropic and the mineral particles tend to be non-spherical, resulting in challenging slurry rheology. In general, suspensions of serpentine minerals have high viscosity and yield stress, which can be detrimental in comminution and flotation operations. It is proposed that ultramafic nickel ores be treated with microwave radiation prior to grinding in order to reduce slurry viscosity and yield stress. The rheology of two different ultramafic nickel ores, before and after microwave pre-treatment, was characterized in this work. Serpentine minerals were found to dominate the rheology of the untreated ultramafic nickel ores, with the ore containing minor chrysotile exhibiting higher viscosity and yield stress than the ore containing strictly lizardite serpentine. Microwave pre-treatment was found to greatly reduce the shear viscosity (average 80% reduction at 200 s⁻¹) and direct yield stress (peak yield stress reduced by 92–93%) of ultramafic nickel ore slurries. The reduction in slurry viscosity and yield stress of the ore slurries as a result of microwave pre-treatment was attributed to the conversion of serpentine to olivine.     

Mineral carbon storage in pre-treated ultramafic ores

Mineral carbon sequestration (MCS) is a type of carbon storage based on natural rock weathering processes where CO₂, dissolved in rainwater, reacts with alkaline minerals to form solid carbonates. Although MCS has advantages over other carbon storage techniques, an economic MCS process has not yet been developed. Two approaches were taken in this work to attempt to reduce the cost of MCS. The first approach was to use a waste material, serpentine waste from ultramafic nickel ore processing, as a feedstock. The second approach was to develop pre-treatments to increase the carbon storage capacity of the feedstock. Two pre-treatments were investigated in this work, including microwave pre-treatment and leaching with ligands at neutral to alkaline pH. The carbon uptake of ultramafic ores was found to increase with increasing microwave pre-treatment after a threshold heating time of 4 min was surpassed. A maximum carbon uptake of 18.3 g CO₂/100 g ore (corresponding to a carbonate conversion of 36.6%) was observed for microwave pre-treated ore. The increase in carbon uptake was attributed primarily to the conversion of serpentine to olivine in ultramafic ores that occurs as result of microwave pre-treatment. The effect of five different ligands (catechol, citrate, EDTA, oxalate and tiron) on the carbon uptake of ultramafic ores was investigated. Of the ligands tested, only catechol and tiron were found to both improve the leaching of magnesium from the ores and the quantity of CO₂ stored. A maximum carbon uptake of 9.7 g/100 g ore (corresponding to a carbonate conversion of 19.3%) was observed for ultramafic ore pre-leached and carbonated in tiron solution at pH 10. This is the first time ligands have been reported to improve the carbon uptake of mineral carbon sequestration feedstock. Although process optimization work was not conducted, both microwave pre-treatment and leaching with ligands at neutral to alkaline pH show promise as ways to lower the cost of MCS.     

Some factors that affect beneficiation of sulphide nickel–copper ores

Sulphide Ni–Cu deposits occur typically in mafic and ultramafic igneous rocks and intrusions. The occurrence of minerals affects the separation efficiency of the sulphides. Coarse grained ores are often relatively easy to process, but some ores have altered in metamorphosis. Disseminated secondary minerals often require fine grinding for mineral liberation. Fine serpentine, however, causes problems in flotation processes, for example, by increasing the viscosity of the pulp. The floatability of minerals also depends on process variables. Process iron is usually in galvanic contact with particles and has an effect on the surface reactions of sulphides. Oxidation and dissolved ions in process water are also essential factors in the flotation processes.     

Ligand-promoted dissolution of serpentine in ultramafic nickel ores

The ligands catechol, citrate, EDTA, oxalate and tiron were investigated for their ability to improve the dissolution of serpentine in ultramafic nickel ores at neutral to alkaline pH to enhance mineral carbon sequestration. It is desirable to leach magnesium from serpentine in ores at neutral to alkaline pH so that leaching and carbonation can be conducted at the same pH value, and ultimately so that the reagent requirements of mineral carbon sequestration can be reduced. Both solution modeling and experimental work were conducted. The solution modeling revealed that each of the ligands studied is able to enhance the solubility of magnesium at the desired pH, with the order of effectiveness being EDTA > tiron > citrate > catechol > oxalate. Experimentally it was shown that the ligands studied could improve both the total amount and rate of magnesium leaching from ultramafic nickel ores. The order of ligand effectiveness based on the experimental work for the Pipe ore was EDTA ⩾ tiron > catechol > oxalate ⩾ citrate. For the OK ore, the order was tiron > EDTA = catechol > oxalate > citrate. Overall, the ligands studied in this work, particularly EDTA, tiron, and catechol, appear promising for enhancing the dissolution of serpentine in ultramafic nickel ores at neutral to alkaline pH.     

Effect of sulfur on the mineral phases of laterite ores at high temperature reduction

Recovery of nickel and cobalt from nickel laterites processed according to the Caron process is hampered by reduction of iron in limonite ores and formation of fosterite in saprolite ores. The Caron process involves the reduction of the ores at temperatures between 700 and 800 °C followed by ammoniacal leaching. The presence of sulfur has been found to markedly improve the Ni and Co recoveries from laterite ores. In this study, limonite and saprolite laterite ores were reduced in the presence of an activator, in the form of elemental sulfur. The mineral phases resulting from the reduction, both in the presence and absence of sulfur were related to recoveries and selectivity obtained from laboratory reduction and leaching tests. The mineral phases were examined using X-ray diffraction with a synchrotron radiation source. The role of sulfur and the history of reduction in effecting the increase in recovery and selectivity of nickel and cobalt was investigated in this study.     

Development of a model for serpentine quantification in nickel laterite minerals by infrared spectroscopy

An investigation into the possibility of using infrared techniques to quantify serpentine in nickel laterite ores was carried out. Results obtained from this preliminary study confirmed that high confidence in serpentine content prediction is possible obtaining RMSEP and R² values of 1.76 and 0.97 respectively.One hundred and forty mineral mixtures simulating limonite, transition and saprolite horizons of a Western Australian nickel laterite deposit were prepared. Diffuse reflectance infrared Fourier transform spectroscopy spectra obtained from these mixtures were used as a training set to prepare a quantitative model for serpentine content using Partial least squares multivariate analysis.The model in turn was validated by predicting the serpentine content of 20 synthetic mixtures with confidence. The model was applied to 10 natural ores from various deposits, diversity between the synthetic and natural ore assemblages meant the analysis was qualitative. Model development using real ore samples would be required to enable incorporation of the intrinsic properties of the natural serpentine and the ore mineralogy in general.     

印尼某低品位红土镍矿的热解性能

为提高红土镍矿火法冶炼工艺技术指标,对印尼某低品位红土镍矿进行了热解性能分析。结果表明：该红土镍矿属于典型的低品位过渡层红土镍矿,主要组成矿物为利蛇纹石、针铁矿、石英、铁蛇纹石、叶蛇纹石和高岭石,镍主要赋存于蛇纹石、橄榄石等硅酸盐类矿物中,部分以氧化镍形式赋存于针铁矿中。红土镍矿热解分析结果表明：在86 ℃时有1次失重过程,形成1个吸热峰,有H2O溢出,对应自由水的脱除;在268 ℃时有1次失重过程,形成1个吸热峰,有H₂O溢出,对应针铁矿的脱羟基过程;在589 ℃时发生失重,形成1个吸热峰,有H₂O溢出,对应高岭石、利蛇纹石的脱羟基反应;在816 ℃时有1个放热峰,而红土镍矿质量没有变化,对应利蛇纹石热解产生无定型的硅酸盐重结晶后产生镁橄榄石（Mg₂SiO₄）及顽火辉石（MgSiO₃）的过程;在1 126 ℃时有1次失重过程,有CO₂溢出,由白云石分解产生。试验结果对红土镍矿火法工艺的改进有指导作用。     

金川铜镍矿床中典型单矿物的提取

为研究金川铜镍矿代表性单矿物在浮选过程中的行为,认识、掌握和控制浮选过程,分离提取镍黄铁矿、磁黄铁矿、蛇纹石等代表性单矿物。利用双盘带式磁选机、筒式电动磁选机、QXC－1多用磁选仪,进行反复选别、分离,从二矿区富矿中制备了纯度分别为95.61%,95.46%的镍黄铁矿和磁黄铁矿。用磁选和重选联合流程,从金川贫矿中制备以橄榄石（占40％）、蛇纹石（占35％）为主的脉石矿物,橄榄石按化学组成为镁橄榄石,蛇纹石实际上包括了胶蛇纹石、叶蛇纹石和纤维蛇纹石诸变种。     

微波-化学溶液联合作用下矿石的劣化机理研究

为了提高微波辅助磨矿的适用性,以红透山铜矿和思山岭铁矿为研究对象,分别采用微波、盐酸溶液、草酸溶液及其组合的方式对矿石进行预处理.对比了7种预处理方式下矿石的升温特征、表面形态、磨矿效果,并通过介电常数、波速、微观照片揭示矿石的劣化机理.试验结果表明:铜矿和铁矿浸酸后介电常数减小,导致微波作用下升温速率降低,温度分布更...     

The effects of chrysotile mineralogical properties on the rheology of chrysotile suspensions

Chrysotile (serpentine) is a phyllosilicate mineral that occurs as a major gangue mineral in many ores (e.g. Mt. Keith nickel sulphide ore, Western Australia). It is believed that the distinctive morphology and electrical surface charge of chrysotile particles are central to the problematic rheological behaviour and low solids throughput typically experienced in the processing of such ores. This study investigates the effects of both these factors on the rheology of chrysotile suspensions.Chrysotile particles were found to carry a net positive charge over the range pH 2-11, with an apparent point of zero charge at pH 8.23. This is a direct result of the convoluted mineral structure of chrysotile fibres, which comprise a positively charged brucite outer layer. The disparity in the point of zero charge and range of maximum yield stress for chrysotile is consistent with the anisotropic nature of chrysotile particles. The long, thin fibres are easily entangled to form suspensions with much higher plastic viscosities and Bingham yield stresses than non-fibrous particles.Although chrysotile shape and surface charge are fundamental to the rheology of chrysotile suspensions, it was found that shape plays a more significant role.     

蛇纹石有价成分的提取与富集

蛇纹石作为一种重要的非金属矿物,广泛用于多种工业领域。本文介绍了蛇纹石的基本性质和结构,综述了国内外蛇纹石有价成分提取和富集的研究现状,主要介绍了氧化镁、氢氧化镁等镁系列产品、硅系列产品以及重金属镍和贵金属钯提取工艺。系统介绍了镍的提取技术,如还原焙烧—磁选法、还原焙烧—氨浸法、常压酸浸法和加压酸浸法等。提出了开发综合利用蛇纹石的重要意义及相关研究方向。     

Confined particle bed breakage of microwave treated and untreated ores

The effect of microwave treatment on the processing of mineral ores was investigated through simulations of microwave heating, thermal damage and confined particle bed breakage test on bonded-particle models. The simulations were undertaken on two-phase mineral ore consisting of a microwave-absorbing mineral in a non-absorbing matrix. The microwave heating was simulated by dissipating a volumetric heat source in the absorbent phase. The progeny size distribution and degree of liberation for the untreated and microwave treated ores after breakage tests were determined by undertaking image analysis of the model outputs. It was shown that microwave treatment at high power density considerably changed the progeny size distribution and enhanced the degree of liberation in confined particle bed breakage tests. It was also found that crushing velocity has a significant effect on both progeny size distribution and liberation, particularly for the ore treated at high power density.     

某高镁铜镍矿石浮选试验

某高镁铜镍矿石含镍0.76%、铜0.16%、氧化镁25.12%,铜矿物主要为黄铜矿,镍矿物主要为镍黄铁矿,脉石矿物主要有透闪石、滑石、蛇纹石,橄榄石、透辉石及绿泥石等少量,有害杂质组分滑石、蛇纹石及绿泥石等的含量高达42%。矿石中铜、镍的氧化率均较低,原生硫化铜占总铜的87.50%,硫化镍占总镍的98.68%。为获得低镁铜镍混合精矿,进行了选矿试验。结果表明,矿石在磨矿细度为-0.074 mm占70%的情况下,采用2粗2扫2精,精选1尾矿连续2次精扫选,精选2尾矿与精扫选1精矿合并返回,其他中矿顺序返回流程处理,可获得铜品位为2.28%、镍品位为11.81%、铜回收率为70.37%、镍回收率为76.20%、氧化镁含量仅为4.38%的铜镍混合精矿,产品达到一级品质量标准(镍品位大于10%,氧化镁含量小于6%);抑镁效果取得成功的关键在于在精选段添加了北京矿冶研究总院研制的含镁脉石矿物的高效抑制剂——改性CMC(总添加量为480 g/t)。试验流程具有稳定、低药耗、高效等优点,适合该矿石的处理。     

金川三矿区低品位铜镍矿石工艺矿物学研究

通过工艺矿物学研究,查明了金川三矿区低品位铜镍矿石的矿物组成、铜镍的赋存形式及主要有用矿物的嵌布特性。研究结果表明：矿石中的铜、镍主要以镍黄铁矿、紫硫镍铁矿、黄铜矿、墨铜矿形式存在,但其他硫化矿物及脉石矿物与它们嵌布关系密切而复杂;矿石蛇纹石蚀变严重,易于泥化。这些将给铜、镍的分选带来不利影响。     

Microwave carbothermic reduction roasting of a low grade nickeliferous silicate laterite ore

The known resources of nickel sulphide ores are quickly diminishing and in order to satisfy future nickel demands, nickel laterite deposits are being investigated as an alternative. Currently, expensive leaching and smelting processes are used to process the nickel laterite ores. The objective of the present research was to produce a high grade nickel concentrate via microwave carbothermic reduction roasting followed by magnetic separation. A thermodynamic model was developed for the roasting process in order to determine the optimum experimental conditions. The experimental variables investigated were: microwave energy and argon shrouding for the reduction tests and the magnetic field strength for the concentration stage. The behaviours of nickel and cobalt were studied in the reduction and magnetic separation processes. By optimizing the reducing and magnetic separation conditions, a high grade concentrate containing 9.2% nickel with a nickel recovery of 88.8% was achieved.     

Microwaves in extractive metallurgy: Part 1 – Review of fundamentals

Microwave radiation is a relatively new energy source, which has considerable potential for various applications in mineral processing and extractive metallurgy. However, the strengths of the interaction of the microwave radiation with the materials of interest are largely unknown. Additionally, in contrast to the aqueous solutions used in hydrometallurgy, the microwave interaction with the heterogeneous solids used in pyrometallurgical processes is difficult to model from fundamentals. Since the microwave heating characteristics of most of the materials cannot be predicted, research is being performed to determine the underlying factors which govern the microwave response of ores, concentrates, reducing agents and other feedstocks used in pyrometallurgical processes. In the present research, the techniques used to measure the microwave coupling characteristics are outlined and the application of these techniques to some relevant pyrometallurgical materials is reviewed.     

镍黄铁矿与蛇纹石浮选分离中有机抑制剂的机理研究进展

蛇纹石是一种富含镁的硅酸盐矿物,常与镍黄铁矿共伴生。在镍黄铁矿浮选过程中,蛇纹石的上浮会造成镍精矿中镁含量超标,从而影响镍黄铁矿的冶炼。介绍了蛇纹石的晶体结构和表面性质,剖析了蛇纹石难以抑制的原因,阐明了常用有机抑制剂羧甲基纤维素、淀粉类、壳聚糖、瓜尔胶及组合药剂对蛇纹石的抑制机理。      

澳大利亚布朗斯炭质页岩铜镍钴矿工艺矿物学研究

为了确定澳大利亚布朗斯地区炭质页岩铜钴镍矿资源合适的选矿工艺,对该地区有代表性矿样开展了工艺矿物学研究。结果表明:1矿石为典型的沉积型炭质页岩多金属矿,矿物组成复杂,主要金属矿物为黄铜矿、斑铜矿、硫钴镍矿等,矿石中钴、镍等有价元素以类质同象的形式或呈机械夹杂物分布于硫镍钴矿、黄铁矿及脉石矿物中,脉石矿物主要为炭质、白云母、多水高岭石等。2矿石中各矿物间共生关系复杂,普遍存在着交代结构和相互浸染构造,致使部分可浮性较好的炭质矿物易浮选进入硫化矿精矿中,同时部分微细粒硫钴镍矿被黄铜矿包裹,浮选时易进入铜精矿中。3矿石中黄铜矿和黄铁矿属中细粒嵌布范畴,硫镍钴矿属细粒—微粒嵌布范畴。根据矿石工艺矿物学特征,建议采用阶段磨矿—阶段选别的工艺依次回收铜、钴、镍、硫,尾矿可作为钾化肥。     

新疆某难选硫化铜镍矿选矿试验研究

根据新疆某硫化铜镍矿矿石的工艺矿物学特性,进行了详细的选矿试验研究,采用一粗一精两扫、中矿顺序返回的铜镍混合浮选流程,使用碳酸钠做pH调整剂,六偏磷酸钠做分散剂,羧甲基纤维素做抑制剂,混合黄药做捕收剂,处理该矿石,得到了混合精矿含镍10.89%、含铜4.27%,镍回收率81.61%、铜回收率85.03%的指标,氧化镁含量低于6.8%,产品质量符合冶炼要求。对六偏磷酸钠和羧甲基纤维素在硫化铜镍矿浮选中的作用机理进行了分析,结果表明六偏磷酸钠能分散蛇纹石与硫化矿物,降低蛇纹石对硫化矿物浮选的影响,而羧甲基纤维素能抑制含镁硅酸盐矿物的上浮,实现硫化矿物与含镁硅酸盐脉石的浮选分离。因此,在含有多种镁硅酸盐脉石矿物的硫化铜镍矿中同时使用六偏磷酸钠和羧甲基纤维素是该类矿石高效利用的关键。     

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.