Simulation of pore scale fluid flow of granular ore media in heap leaching based on realistic model

Two-dimensional images of the granular ore media with different grain sizes were obtained from the X-ray computed tomography.Combined with the digital image processing and finite element techniques,the original grayscale images were transformed into the finite element models directly.By using these models,the simulations of pore scale fluid flow among particles were conducted with the COMSOL Multiphysics,and the distribution characteristics of fluid flow velocity and pressure were analyzed.The simulation results show that there exist obvious preferential flow and leaching blind zone in each granular medium.The flow velocity at pore throat is larger than that of pore body and the largest velocity reaches 0.22 m/s.The velocity decreases gradually from the center of pore throat and body to the surface of particles.The flow paths of granular media with larger grain size distribute equally,while the fluid flow velocities in most of areas of granular media with smaller grain size are lower,and some of them approach to zero,so the permeability is very low.There exist some pore clusters with different pressures,which is the basic reason for the uneven flow velocity distribution.

Simulation of coupled flowing-reaction-deformation with mass transfer in heap leaching processes

Governing equations for a fully coupled flowing-reaction-deformation behavior with mass transfer in heap leaching are developed. The model equations are solved using an explicit finite difference method under the conditions of invariable application rate and constant hydraulic head. The distribution of the degree of the saturation, as well as the distributions of the concentration of the reagent and the solute is given. A cubic relationship between the mineral recovery and the leaching duration is obtained based on the numerical results. The relationship can be used to predict the recovery percentage of the valuable metal.

Dynamic experiment and numerical simulation of solute transmission in heap leaching processing

Solute transmission in saturated ore heap was studied numerically and experimentally. The convection-diffusion equation (CDE) used to describe the mass transportation in porous media was solved by characteristic difference method to give the distribution of the concentration of ferrous ion in the ore column. To calibrate the computational model, a column test was performed using infiltration of sulfide ferrous solution (the initial concentration is c0=0.04 mol/L) on a 100 cm high column composed of ore particles smaller than 10 mm for 2.5 h. The numerical analysis shows that the results obtained from numerical modeling under the same operating conditions as used for column test are in good agreement with those from experimental procedure on the whole trend, which indicates that the model, the numerical method, and the parameters chosen can reflect the rule of ferrous ion transmission in ore heap.

Pretreatment of copper-bearing refractory gold ores by bio-heap leaching

The refractory gold ores associated with rich copper and trapped in pyrite and quartz were studied. With conventional technique （all-sliming cyanidation）, the gold recovery rate is only 51.78%. To eliminate the negative effects of copper and pyrite on cyanidation and increase the gold recovery rate, the investigation on bio-heap leaching pretreatment was made, by which Cu would be dissolved and gold would be liberated from pyrite. The experiment adopted mixed bacteria, mainly ThiobaciUus ferrooxidan （named T.fl ）, as the bacterial catalyst for bio-preconditioning and was carried out in a PVC column with a diameter of 20 cm and a height of 1.3 m loaded with gold ores. The temperature was controlled between 28 and 30℃, the pH value was kept between 2.0-2.5, and the flux of sprinkling bacterial liquid was maintained 0.80 L/h. After 45-day＇s bio-oxidization, among the samples sizing from 0 to 5 mm, the oxidation rates of Cu, Fe and S were respectively 44.62%, 28.16% and 25.46%, and the gold recovery rate by cyaniding increased to 80.35%. The bio-heap leaching pretreatment can therefore effectively dissolve Cu and liberate gold from pyrite and lead to the increase of gold extraction.

Evolvement of permeability of ore granular media during heap leaching based on image analysis

The column leaching experiment of ore granular media was carried out with the home-made multi-functional experimental apparatus and the pore structure of ore granular media was scanned by the X-ray computed tomography machine before and after leaching.The porosities of each section before and after leaching were calculated based on CT images processing,and the permeability of each zone before and after leaching were also calculated with Carman-Kozeny equation.The permeability evolvement law was disclosed.The results indicate that before leaching the permeability of the ore granular media in different height has not much difference and the value ranges from 5.70×10-4mm 2to 1.11×10 -3mm 2,where the lowest one locates in the bottom zone.After leaching the permeability distributes inhomogeneously along the height of the column and the value ranges from 3.44×10 -4 mm 2 to 2.25×10 -2 mm 2 ,where the lowest one is in the same place.Except for the bottom zone,the permeability of other zones increases after leaching,especially the top zone.Through comparison of the permeability at bottom zone before and after leaching,the whole permeability after leaching decreases by 39.65%that coincides with the measured experimental data.

Effect of ore size and heap porosity on capillary process inside leaching heap

The capillary process coexists with gravity flow within leaching heap due to the dual-porosity structure. Capillary rise is responsible for the mineral dissolution in fine particle zones and interior coarse rock. The effect of particle size and heap porosity on the capillary process was investigated through a series of column tests. Macropore of the ore heap was identified, and its capillary rise theory analysis was put forward. Two groups of ore particles, mono-size and non-uniform, were selected for the capillary rise test. The result shows that particle size has an inverse effect on the capillary ultimate height, and smaller particles exhibit higher capillary rise. Meanwhile, the poorly graded group exhibits small rise height and velocity, while the capillary rise in the well-graded particles is much greater. The relationship between porosity and fitting parameters of capillary rise was obtained. Low porosity and high surface tension lead to higher capillary height of the fine gradation. Moisture content increases with the capillary rise level going up, the relationship between capillary height and moisture content was obtained.

Analysis of coupled flow-reaction with heat transfer in heap bioleaching processes

A mathematical model for heap bioleaching is developed to analyze heat transfer, oxygen flow, target ion distribution and oxidation leaching rate in the heap. The model equations are solved with Comsol Multiphysics software. Numerical simulation results show the following facts： Concentration of oxygen is relatively high along the boundary of the slope, and low in the center part where leaching rate is slow. Temper- ature is relatively low along the slope and reaches the highest along the bottom region near the slope, with difference being more than 6℃. Concentration of target mental ions is the highest in the bottom region near the slope. Oxidation leaching rate is relatively large in the bottom and slope part with a fast reaction rate, and small in the other part with low oxygen concentration.

Research progress in enhanced bioleaching of copper sulfides under the intervention of microbial communities

Compared with the traditional pyrometallurgical process, copper bioleaching has distinctive advantages of high efficiency and lower cost, enabling efficiently extracts of valuable metal resources from copper sulfides. Moreover, during long-term industrial applications of bioleaching, many regulatory enhancements and technological methods are used to accelerate the interfacial reactions. With advances in microbial genetic and sequencing technologies, bacterial communities and their mechanisms in bioleaching systems have been revealed gradually. The bacterial proliferation and dissolution of sulfide ores by a bacterial community depends on the pH, temperature, oxygen, reaction product regulation, additives, and passivation substances, among other factors. The internal relationship among the influencing factors and the succession of microorganism diversity are discussed and reviewed in this paper. This paper is intended to provide a good reference for studies related to enhanced bioleaching.

Lime Assisted Cyanide Leaching of Refractory Gold Ores from Ajialongwa Mine

Heap leaching is a promising, less costly, alternative technology for processing low grade gold ores compared with traditional, energy intensive processes (e.g. autoclave/tank leaching). This research investigated the effectiveness of lime for enhancing gold leaching rates of gold ores from ajialongwa gold mine in china. Column and heaping experiments were performed using cyanide leaching solutions at pH=10, with and without lime (CaO). The presence of lime greatly increased gold leaching rates. Column leaching experiments showed without the addition of lime, there was 35.2% of gold leached. The addition of lime resulted in the release of 50.56% gold. Lime assisted cyanide of refractory gold was proved by heap leaching experiments.

基于形态学开运算的浸矿体系孔隙结构及其演化特征

立足堆浸体系的偏析分层复杂结构,结合X-ray CT无损探测、形态学开运算处理、MATLAB和OsiriX可视化软件等手段,引入颗粒间孔隙的当量孔隙尺寸、面积、数量等关键表征参量,如从二维量化和三维可视化层面揭示浸矿体系中颗粒间孔隙结构特征及其演化规律.研究发现,细颗粒夹层呈“包裹体”状且均位于粗矿石颗粒的内部,分析认为其是造成堆浸体系颗粒偏析和分层的重要致因;浸矿作用下微细颗粒迁移导致矿堆内部发生沉积压实作用,由197 mm降至180 mm以下;浸矿21 d后,矿堆上部孔隙呈增大趋势,下部孔隙率呈减小趋势,此外,纵向当量孔隙的直径由2.81 mm减小至2.18 mm,其变化趋势和程度要显著大于横向颗粒间孔隙的当量直径;对比浸矿0 d和21 d的柱浸体系三维颗粒间孔隙结构,证实了细颗粒夹层所处区域的粘结聚集以及细颗粒夹层周边区域形成溶液绕流、溶液优势流动路径.

堆浸体系内微细颗粒在孔隙内迁移和附着规律

在堆浸过程中,堆浸体系内游离的颗粒会随着溶液的流动而移动,从而对浸出的速度和效率产生影响.对于粒径较小的微细颗粒,虽然难以对矿石颗粒间孔隙产生堵塞,但其在孔隙壁表面的大量附着也会影响溶液对矿石的内渗从而降低浸出效率.本文基于真实的孔隙结构使用Fluent软件开展仿真模拟实验,从粒径、颗粒密度和流体流速三个方面探究它们对微细颗粒在孔隙内迁移和附着行为的影响.模拟结果表明,当颗粒粒径为1×10^(-6) m时几乎没有颗粒会沉积附着在孔隙内.而随着粒径的增大,在1×10^(-6)~1×10^(-4) m的粒径范围内,附着在孔隙壁表面的颗粒数量会呈现先增多后减少的趋势,且对于不同密度的颗粒,其附着数量在峰值处的占比均超过了90%.观察发现颗粒的主要附着部位为弯孔隙的外壁以及流速较小、坡度较缓的小孔隙内.分析认为粒径和密度越大的颗粒,其重力和惯性对其运动轨迹的影响越大,而流体对其轨迹运动的影响越小,在迁移过程中更容易靠近孔隙壁从而导致颗粒附着.且大粒径、大密度的颗粒主要在大孔隙内迁移,轨迹较为集中.而小粒径、低密度的颗粒,在高流速流体内迁移时,其水平运动幅度更大,迁移轨迹分布更加分散,更容易进入小孔隙内迁移.

低品位复杂钼矿拌酸熟化堆浸工艺研究

针对沽源460低品位复杂钼矿中钼矿物以微细脉状形式被褐铁矿所包裹,矿石细碎后泥化现象严重的问题,研究了以拌入高酸加温熟化破解铀、钼矿物的包裹体,并对处于硫化态的钼矿物进行氧化,进而实现难处理铀钼矿的高效浸出,再通过加入耐酸耐高温的天然粘合剂凹凸棒,解决了熟化后的矿石物料在筑堆浸出过程中遇水易泥化而导致渗透性差的问题。确定的最佳熟化条件为:矿石粒度-2.5 mm,熟化酸用量10%,黏合剂凹凸棒拌入量8%,熟化温度90℃,熟化时间24 h,铀渣计浸出率63.4%,钼渣计浸出率75.0%。

低品位氧化铜钴矿堆浸试验研究

对刚果(金)某低品位氧化铜钴矿资源进行了堆浸试验研究,考察了喷淋强度、喷淋酸度和矿石粒度对铜钴浸出率的影响。结果表明,喷淋酸度和喷淋强度对铜钴浸出速度和累计浸出率影响显著,而矿石粒度对浸出过程影响不大。确定了低品位氧化铜钴矿适宜的堆浸条件为:喷淋酸度20 g/L,喷淋强度15 L/(m^(2)·h),矿石粒度-40 mm。在此条件下,堆浸100 d,铜和钴累计浸出率分别可达90.89%和82.27%。

某低品位氧化铜矿堆浸液萃取铜的试验研究

采用不同品牌的3种萃取剂从某低品位氧化铜矿堆浸液中萃取铜,考察25℃时3种萃取剂的萃取-反萃反应等温平衡相过程及相应的分相速率,绘制萃取和反萃工艺过程的McCabeThiele等温平衡线,根据实验数据计算了3种萃取剂对应的萃取率、反萃率、铜和铁排斥比及净铜迁移量。结果表明,萃取剂A的萃取率为99.3%,反萃率为97%,铜和铁排斥比为816,净铜迁移量为2.68 g/L,是最适合萃取该氧化铜矿堆浸液的萃取剂。

硫酸盐型盐湖卤水盐田钾矿浮选尾矿堆浸溶钾工艺研究

以罗布泊盐湖卤水含硫酸盐矿浮选尾矿为原料,高钠低钾卤水为浸取液,采用原位堆浸方法浸取硫酸钾浮选尾矿中K^(+)、Mg^(2+)、SO_(4)^(2-)等有价元素,实现罗布泊盐湖卤水盐田含硫酸盐矿浮选尾矿中K^(+)、Mg^(2+)、SO_(4)^(2-)等有价元素的综合回收利用。试验数据表明:经过堆浸工艺,实现了浮选尾矿中K^(+)的回收;尾矿中K^(+)含量从3.84%降至0.83%;K^(+)收率≥77%,Mg^(2+)收率≥79%,SO_(4)^(2-)收率≥73%,浸取液K^(+)含量达到1.42%。

某金矿提金工艺改造及生产实践

针对贵州某微细粒浸染型含泥氧化金矿堆浸过程中金浸出速率慢和金浸出率低的问题,对现场生产工艺进行了优化。在矿石工艺矿物学研究和堆浸提金条件试验基础上,结合现场生产实际,诊断出制约堆浸过程提金困难的主要原因是矿石中金矿物大多以微细粒形式存在、矿物单体解离度差、易泥化矿物含量高、矿堆渗透性较差、浸液pH和氰化物质量分数较低、喷淋强度较大等。针对生产过程中存在的问题,采取相应优化措施,经现场改造后,金浸出率由35%提高至57%,达到预期优化效果,为企业带来显著经济效益。

Three-dimensional simulation of pore scale fluid flow in granular ore media with realistic geometry

The images of granular ore media were captured by X-ray CT scanner. Combined with digital image processing and finite element techniques, the three-dimensional geometrical model, which represents the realistic pore structure of the media, was constructed. With this model, three dimensional pore scale fluid flow among particles was simulated. Then the distributions of fluid flow velocity and pressure were analyzed and the hydraulic conductivity was calculated. The simulation results indicate the fluid flow behaviors are mainly dominated by the volume and topological structure of pore space. There exist obvious preferential flow and leaching blind zones simultaneously in the medium. The highest velocities generally occur in those narrow pores with high pressure drops. The hydraulic conductivity obtained by simulation is the same order of magnitude as the laboratory test result, which denotes the validity of the model. The pore-scale and macro-scale are combined and the established geometrical model can be used for the simulations of other phenomena during heap leaching process.

滤材沉积法回收贫液中载金粉炭试验研究

内蒙古某金矿每年随贫液上浸堆的固体量约73 t,其中粉炭量约40 t,吨炭载金量约373 g,金随粉炭流失的同时,堆上浸出的金还被粉炭截留,采用管道中布置滤袋效果不理想。试验采用滤材沉积方式捕收贫液中粉炭,即将滤材折叠形成一定构型,放入贫液池使粉炭自然沉积。针对粉炭和贫液性质选择3种滤材,并进行表面粗糙度测试,通过试验对比粉炭在不同滤材的沉积效果,发现沉积能力与滤材表面粗糙度呈正相关;通过沉积动力学试验,探明沉积率随时间先增后降,且沉积能力受滤材孔径影响,孔径为粉炭粒径D80的1.5倍时最佳;采用高压气水联合脱附沉积粉炭。结果表明:20μm聚丙烯无纺滤材沉积16 h效果最佳,单位面积沉积量为79.31 g/m2,贫液流经沉积单元所含粉炭量40%可被捕收,脱附率达88.7%,综合回收率达35.5%,且脱附后滤材有较好的二次使用性。研究结果对采用活性炭作为吸附剂的堆浸工艺均有一定的借鉴意义。

酸法制粒堆浸中黏结剂的研究现状与展望

为了将酸法制粒技术应用在矿物堆浸中,根据矿物酸法制粒中黏结剂的不同性质,探讨了多种黏结剂在酸法制粒过程中的适用条件,并列举了4种简便且有效的黏结剂添加效果检测方法,用于评估黏结剂的制粒效果。未来,符合制粒要求、成本低且具有良好粘结性能的新型黏结剂的研发,是黏结剂研究的重点方向,亦是酸法制粒技术能否大规模应用于工业化生产的关键。

中国铀矿采冶技术发展与展望

对中国铀矿采冶工业的发展作了全面的回顾,重点介绍了中国铀矿地浸、堆浸、原地爆破浸出技术的研究进展与应用水平;在对中国铀矿采冶形势和存在的问题分析的基础上,结合矿床资源的特点,指出了中国铀矿采冶技术发展的方向。21世纪中国铀矿冶工业面临新的发展机遇和挑战,只有开发新的采、选、冶技术,提高铀资源的利用水平,减少铀矿采冶对环境的影响,才能实现铀矿冶的可持续发展和经济与环境的协调发展。