淋滤浸出过程的流体力学和传质

本文总结了淋滤过程的流体力学行为的初步研究结果。根据矿石堆粒层中溶液的存在形态及多孔介质扩散过程的基本概念提出的淋滤过程传质模型—孔隙扩散控制的“双膜传递过程”，已被试验结果所证实。     

Use of mesh adaptivity in simulation of flow in packed beds – A case study

Computational modelling of transport phenomena in packed beds is of interest in a wide range of engineering applications. We simulate flow in packed beds with similar conditions to heap leaching processes. The governing equations are the conservation of mass and Darcy’s law. The primary variables are pressure and saturation. To discretize the governing equation, a control volume finite element method is used. The numerical scheme is implemented in Fluidity, a general purpose flow simulator that is equipped with anisotropic mesh adaptivity techniques to control local solution errors and increase computational accuracy. We demonstrate the application of the developed method to solve for incompressible flow of air and liquid within packed beds of mono-dispersed non-porous particles and compare our results with experimental measurements by Ilankoon and Neethling (2012). To study the effect of heterogeneity on flow regime in packed beds, an experiment is conducted on a packed bed consisting of two regions with different particle sizes. The non-uniform packed bed is also simulated numerically and our comparison shows very good agreement. Mesh adaptivity resolves saturation fronts in two regions of the column with high-resolution meshes and reduces the discretization error. This study serves as a validation for our numerical approach for prediction of hydrodynamics of heap leaching processes at large scales.     

Liquid spread mechanisms in packed beds and heaps. The separation of length and time scales due to particle porosity

The distribution of liquid within a heap is a key factor in the system performance as it has a strong effect on the transport of both reagents and leached species and thus the leaching rate. How liquid spreads from drippers and the subsequent development of flow paths and any associated channelling is thus important. In this paper a pseudo 2-D column was used to investigate the horizontal spread of liquid in the vicinity of dripper in columns packed with both narrowly sized particles and more realistic particle size distributions. Both systems had distinct separation of the time scales at which different saturation features developed. There was an initial rapid formation of flow paths in the inter-particle spaces with only local wetting of the intra-particle spaces, though this was associated with little spread. Over a much longer time period there was extensive horizontal spread of the liquid within the ore particles, though this was associated with virtually no vertical flow. The externally held liquid (liquid content between the particles) showed strong channelling behaviour, especially in the realistically sized particles, despite the care that was taken to ensure uniform packing. This effect can be reduced by changing initial bed conditions and employing dense drip emitter locations, but it cannot be completely eliminated as particle level heterogeneities in heap leaching systems affect external flow paths creation. Hysteresis in the amount of liquid spread was also demonstrated, with the total spread depending not only on the current flow rate, but also on the flow history.     

Computer simulation of fluid motion in a porous bed using a volume of fluid method: Application in heap leaching

Heap leaching is a process extensively used by the mining industry to recover metals from low-grade ores and large quantities of submarginal material resources. Understanding flow through a packed particle bed is important to enhance the performance of heap leaching with respect to design and operating considerations. Complex fluid behavior in porous media, such as film flow, fragmentation, coalescence of droplets, and rivulet flow with or without meandering, has been widely observed in laboratory experiments. In this study, to provide detailed information of momentum and mass transfer phenomena in a granular bed direct numerical simulations (DNS) were performed. In this case the liquid–gas flow through a granular bed was considered comprised of monosized, spherical, solid particles arranged randomly in a cylindrical container. The volume of fluid (VOF) method was used to compute velocity field as well as liquid volume fraction distributions in the container. The results obtained suggest that the liquid phase distribution in the bed is mainly controlled by surface tension and particle induced turbulence appears to have insignificant effects. These results allow us to obtain a better understanding of the fundamental physics governing unsaturated fluid flow. This finding seems to have a significant impact in the design of efficient multi-phase reactors for heap leaching and bioleaching processes.     

提高我国铀矿堆浸经济效益的主要途径和适用技术(待续)

结合我国铀矿堆浸实际,在重视堆浸可行性研究、采用强化堆浸技术、改进堆浸装备水平、严格工艺条件及拓宽堆浸的应用范围等方面提出一些有效途径及适用技术,包括采用抖酸熟化－高铁淋滤浸出、细菌堆浸、制粒堆浸、逆流堆浸,选用优质底垫层材料,研制大型机械化筑卸堆方法和设备,推广滴灌式布液,优化堆浸工艺参数,以及开发与堆浸相配套的回收设备等,以提高浸出率、缩短堆浸周期,获得更大的经济效益。     

提高我国铀矿堆浸经济效益的主要途径和适用技术（续完）

结合我国铀矿堆浸实际,在重视堆浸可行性研究、采用强化堆浸技术、改进霍浸装备水平、严格工艺条件及拓宽堆浸的应用范围等方面提出一些有效途径及适用技术,包括采用拌酸熟化高铁淋滤浸出、细菌堆浸、制粒堆浸、逆流堆浸,选用优质底垫层材料,研制大型机械化筑堆方法和设备,推广滴灌式布液,优化堆浸工艺参数,以及开发堆浸相配套的回收设备等,以提高浸出率、缩短堆浸周期,获得更大的经济效益。     

某铀矿井下采空区筑堆浸出试验研究

本文介绍了井下采空区筑堆浸出试验研究的主要成果,该研究是为了解决某铀矿原采用的留矿淋浸法所存在的矿石块度难以控制、浸出效果差的问题而开展的有针对性的试验研究。根据某铀矿井下高柱浸出条件试验成果,确定采空区筑堆浸出试验矿样粒度为-18mm。采空区筑堆方式采用多点分次进料自然筑堆方式,确保筑堆粒度均匀,矿堆面平整。布液采用矿堆上部微灌喷淋+上盘布液孔局部滴淋的综合方式,减少了矿堆淋浸死角。试验采场矿堆高度18m,筑堆品位0.027 6%,经过184d的布液淋浸,液计浸出率达到95.00%,渣计浸出率达到88.77%,取得了较好的浸出效果。该技术可应用于该铀矿床实现井下采场堆浸,并可推广应用于其他赣南花岗岩型低品位铀矿床的矿床开发生产中。     

堆浸浸出速率的灰色预测

针对堆浸浸出过程的复杂性和不确定性,采用灰色系统理论对堆浸浸出速率的灰色预测进行了研究。根据堆浸的浸出动力学特点,结合实例,建立了堆浸浸出速率的等维灰数递补GM(1,1)模型。预测结果表明:采用该模型进行预测,预测方法合理,预测精度可靠,其最大相对误差仅为2 5%。     

基于数值示踪试验的浮选柱停留时间分布模型分析

浮选柱是实现泡沫浮选的核心技术装备。由于对细粒矿物优异的分选性能和较低的能耗,使得浮选柱得到了广泛应用。因此,研究揭示浮选柱内流动特性具有重要意义。轴向扩散模型和多槽串联模型是常用的反应器理论分析模型。本文应用轴向扩散模型和多槽串联模型分析了浮选柱流动特性,特别是物料的停留时间分布。采用计算流体力学方法研究了实验室浮选柱内示踪物的浓度变化。基于数值示踪试验,确定了轴向扩散模型和多槽串联模型的特征参数Pe和N。应用轴向扩散模型和多槽串联模型理论预测的浮选柱停留时间分布同试验结果吻合。     

细菌氧化再生液逆流淋浸铀矿的实践

七五三铀矿属于高硅酸盐型原生矿，铀品位为０．３６％一０．４４２％，四价铀占８５％。为降低工程投资和操作费用，进行了４段逆流淋浸的扩大试验，平均淋浸５０ｄ，每吨矿用酸量为３８ｋｇ，浸出率大于９５％。采用逆流淋浸方式，控制菌浸液中有害物质的极限浓度，并用同步再生法能有效地氧化菌浸液。２５ｔ吨矿石的单堆淋浸对照试验，也获得浸出率大于９５％的结果，并可节省用酸量３０％，省去软锰矿（含ＭｎＯ２４０％）２．０％。采用该方法处理七五三铀矿，技术上可行，经济上合算，提供了一种淋浸铀矿的新方法。     

河南某低品位金矿堆浸试验研究

河南某金矿为低品位高泥质氧化金矿,金含量0.98 g/t,实验室采用柱浸工艺模拟现场堆浸进行试验研究,通过对矿石粒度、氧化钙用量、喷淋液氰化钠浓度、浸出时间等工艺参数进行优化,确定了最佳条件,并获得了较好的选别指标,金浸出率89.23%,浸渣金品位0.11 g/t。如原矿含泥较高,则可进行分级处理,分级后粗级别采用堆浸工艺,细级别则采用搅拌浸出工艺。试验所采用的工艺为处理同类型金矿提供了强有力的技术支撑。     

甘肃某金矿石选矿试验研究

根据矿石性质进行了选矿试验研究。其中,全泥搅拌氰化浸出金浸出率为94.01%;对-15mm和-25mm矿样进行柱浸,金浸出率分别为87.18%和84.28%。试验结果表明,该矿石适合就地浸出生产。     

碱法堆浸提铀新工艺的研究

研究了一种从碱性矿石中堆浸提铀的新工艺, 即加溶浸剂(Na₂CO₃ 、NaHCO₃)加热强化浸出工艺。该工艺的流程为:原矿※破碎※焙烧※预处理※加热※浸取与洗涤※铀的浓缩与纯化。使用该工艺可以使铀的浸出率达到82%以上(常规堆浸51%), 而且, 浸出时间只有8 d(常规堆浸36 d), 液固比(L/S)只有0.8(常规堆浸2.7), 使浸出液的铀金属质量浓度成倍地增加, 这非常有利于铀的浓缩与纯化。     

赣州铀矿草桃背矿石细菌堆浸试验研究

介绍了草桃背铀矿细菌堆浸试验的结果,与常规堆浸相比,细菌堆周期缩短约50％,浸出率提高10％,酸耗相应降低。该结果为草桃背矿石堆浸提出了一种可选择的技术改造方案。     

新疆某铀矿石浸出试验

为了给新疆某铀矿采用地面堆浸和井下原地爆破堆浸的采矿新方法恢复生产提供依据，对该矿矿石进行了试验室搅拌浸出和柱浸试验。试验结果表明，该矿矿石氧化剂耗量少、浸出时间短、酸耗较低，属易浸矿石。矿石粒度对浸出率影响较大，当粒度从-5mm增加到-20mm时，矿石的柱浸渣计浸出率从88.7％下降到75．2％。氧化剂可提高浸出液铀浓度，但提高幅度不大。     

某低品位金矿石综合回收金的研究与实践

针对某低品位金矿石的物质组成和矿石的结构、构造及金的赋存状态,决定用堆浸的方法来处理该低品位矿石。通过柱浸进行了不同粒度的渗透性、CN-浓度及浸出时间对浸出率的影响等条件试验,确立了较佳堆浸的工艺条件,并在此基础上成功地进行了大规模的堆浸,堆浸结果为该金矿带来了较好的经济效益和社会效益。     

混合硫化矿在硫酸铁体系下的浸出动力学研究

在硫酸铁酸性介质体系下,为揭示次生硫化铜矿堆浸过程中铜蓝与黄铁矿的浸出过程,利用纯矿物进行浸出模拟试验。纯矿物电位控制试验结果的化学动力学分析表明:铜蓝与黄铁矿浸出速率受表面化学反应控制,500mV(vs.Ag/AgCl)浸出条件下,黄铁矿浸出速率的提升量比铜蓝高出1倍,黄铁矿对电位表现出更强的相关性。结合低品位次生硫化铜矿生物浸出生产实际,进行了实际矿石柱浸验证试验,电位调控能使铁浸出率最高降低2个百分点,控制电位浸出的方式为次生硫化铜矿生物堆浸的过程控制提供了参考。     

堆浸工艺中溶浸剂的作用机理与流动特性

分析了溶浸剂的作用机理,认为堆浸浸出过程是一个多相反应动力学过程,浸出速度与溶解化学反应速度、反应物和生成物的扩散速度等因素有关。根据多相反应扩散动力学理论,给出了化学溶浸剂溶浸开采金属的定量描述。在假定裂隙岩体为拟连续介质,流体在整个岩体中的流动规律服从Darcy定律的条件下,导出了溶浸剂在多孔介质中流动的孔-裂隙二重非稳定渗流数学模型。     

某低品位铀矿石的浸出性能研究

采用搅拌浸出和柱浸2种方式对江西某矿低品位铀矿石进行浸出性能的试验验研究。搅拌浸出结果表明,该矿石属易浸出矿石,在硫酸质量浓度为10g/L、搅拌浸出12h时,铀的浸出率高于85%,且加氧化剂对浸出改善较小。柱浸试验结果表明,-5mm为堆浸工艺的最佳筑堆粒度,此时,铀的浸出率为85.7%,酸耗为4.6%(与矿石质量比),且矿堆透水性能良好,为33L/(m2.h)。试验获得的浸出参数,可作为堆浸工业性试验设计和生产中调整浸出参数的依据。