赞比亚某铜钴硫化矿浮选工艺研究

赞比亚某铜钴硫化矿含铜1.25%、钴0.088%。针对该矿石的工艺矿物学特征,进行了不同药剂种类及用量的条件试验,确定了铜钴混合浮选-铜钴分离的工艺流程。闭路试验获得了含铜31.52%、铜回收率为92.32%、含钴0.232%的铜精矿和含钴2.12%、钴回收率67.56%、含铜1.48%的钴精矿的较好指标。     

富钴铜冶炼渣提钴工艺的研究现状及展望

结合钴资源及钴市场近况,指出了从富钴铜冶炼渣中提钴的必要性及急切性。在传统的铜冶炼渣处理工艺已难以满足综合回收铜、钴等有价金属的情况下,近年来对从富钴铜冶炼渣中综合提取钴工艺方法的研究集中在优化还原硫化熔炼工艺和铜钴冰铜中铜、钴分离工艺组合上。研究表明：通过优化还原硫化熔炼的生产条件,可以得到较好的铜、钴回收率;而采用湿法工艺综合回收铜、钴存在工艺流程长,对设备要求苛刻等不足;采用磁选工艺分离铜、钴,因其能无缝衔接现有铜火法冶炼工艺且投资生产成本低而备受关注,后续有待进一步研究,找出最经济、环保的工艺参数。     

从铜钴合金及含钴废料中提取钴的研究现状与展望

分析了钴资源与钴市场现状,提出了综合处理铜钴合金及含钴废料的必要性,介绍了从铜钴合金和含钴废料中浸出铜、钴及回收钴的方法,指出传统的火法工艺不能处理铜含量高的物料,而采用一般的酸法工艺,钴浸出率不高(只能达到95%左右);利用液膜法和微生物浸出法,钴的浸出率最高只能达到96%,而如果采用氧化剂加低酸(酸浓度小于2 mol/L)浸出,则可大大提高浸出速度和浸出率.     

从铜钴合金及含钻废料中提取钴的研究现状与展望

分析了钴资源与钴市场现状,提出了综合处理铜钴合金及含钴废料的必要性,介绍了从铜钴合金和含钴废料中浸出铜、钴及回收钴的方法,指出传统的火法工艺不能处理铜含量高的物料,而采用一般的酸法工艺,钴浸出率不高（只能达到95％左右）;利用液膜法和微生物浸出法,钴的浸出率最高只能达到96％,而如果采用氧化剂加低酸（酸浓度小于2mol／L）浸出,则可大大提高浸出速度和浸出率。     

从钴硫精矿中回收钴的工艺探索试验研究

对钴硫精矿进行硫酸化焙烧-焙砂水浸钴铜-浸出液碳酸钠中和沉钴-钴铜渣浸出/萃取分离回收钴铜-焙砂浸出渣还原焙烧制铁精矿球团的处理工艺是可行的,可以综合回收其中的钴、铜、硫、铁;全流程钴的回收率大于80%。     

某海外湿法炼铜厂湿法炼铜工艺中钴金属的回收利用

目前很多中国企业在海外开采铜矿生产阴极铜,但是很多铜矿中伴生的钴金属并未得到很好的回收与利用,而是随着尾矿进去尾矿库堆存,造成了资源的浪费。结合某海外湿法炼铜厂工程实际案例,利用湿法炼铜工艺产生的低铜萃余液回收钴有价金属。低铜萃余液中含有铁、铜、锰等杂质离子以及钴有价金属,需先去除铁、铜、锰等杂质再回收钴金属。本案例采取除铁、除铜、沉钴、除镁、干燥的工艺流程,在低铜萃余液中依次加入石灰乳浆液除铁,加石灰乳浆液除铜,加氧化镁沉钴,加石灰乳浆液除镁,进闪蒸干燥等工序生产粗制氢氧化钴。     

高铜钴硫酸锌溶液锌粉高温净化除钴工艺研究

针对国内某冶炼厂高铜钴硫酸锌溶液净化除钴过程中存在高含量铜、钴离子造成在高温置换过程中钴返溶明显,造成锌粉用量大的问题,研究了锌粉加入方式、铜离子含量、温度、时间、锌粉用量等条件对高铜钴硫酸锌溶液一段高温净化除钴效果的影响,得出在较佳条件下,锌粉用量为钴含量75倍时净化后液中的Co可除至0.38mg/L,满足净化除钴要...     

电炉还原熔炼氧化钴矿的生产实践

介绍了刚果（金）钴铜冶炼厂电炉还原熔炼处理钴铜氧化矿工艺的设计特点及生产实践。     

云南永平县水泄-厂街铜钴矿铜钴的赋存状态与选矿工艺学

云南永平县水泄-厂街铜钴矿是云南一典型的铜钴硫化矿床。通过岩矿鉴定和选矿试验查定了铜钴的赋存状态,矿床铜矿物呈独立矿物存在,钴矿物未见独立矿物存在。铜矿物和含钴矿物之间结构具复杂多样性,给选矿工艺带来较大困难。矿石选矿工艺学研究对工业选矿有指导意义。     

刚果(金)绿纱矿浮选铜钴精矿还原熔炼工艺研究

以刚果(金)绿纱矿浮选后的铜钴精矿为原料,采用还原熔炼工艺生产铜钴合金,考察了还原熔炼条件对铜钴回收率的影响。实验得出的最佳工艺条件为:CaO加入量25%、熔炼温度1 500℃、焦粉加入量6.5%、熔炼时间45 min,该条件下,铜的回收率大于98%,钴的回收率大于95%。     

刚果（金）氧化铜钴矿冶炼工艺综述

对刚果（金）加丹加省几家有代表性的氧化铜钴矿冶炼企业通常采用的火法和湿法工艺进行介绍和评述。其中该国国有企业生产电铜和电钴等最终产品,而该国中资企业一般生产中间产品或半成品。由于该国氧化铜钴矿冶炼化学试剂和原辅材料缺乏,进口相关试剂、材料提高了企业生产成本。     

Failure Resistance of Historic Stone Bridge Structure of Charles Bridge. II: Susceptibility to Floods

The paper is a follow-up to the first part devoted to an analogical problem investigated with a view to the degradation of the stone structure due to the effects of nonstress load, and it deals with the probability problem of the bridge structure collapse under the effect of an extreme flood wave. The paper presents the results of the numerical analysis of the response of the historic stone bridge structure of Charles Bridge of the 14th century to the flood wave effect simulated by angular rotation, subsidence, and shifting in the footing bottom of a bridge pier. Special focus is on the effect of interventions into the stone bridge structure dating back to the last major overhaul of 1967–1975, particularly, on the effect of the reinforced concrete slab (tie plate) connecting the opposite bridge breast walls increasing the rigidity of the breast walls and their structurally efficient connection to the vaults of the bridge arches. The numerical analyses performed point out the prevailing negative effects of the implemented interventions in terms of structural rigidity of the stone bridge structure exposed to the effect of a flood wave.     

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.     

New Orleans Levee System Performance during Hurricane Katrina: London Avenue and Orleans Canal South

Hurricane Katrina was one of the worst natural disasters in U.S. history. The effects of the hurricane were particularly devastating in the city of New Orleans. Most of the damage was due to the failure of the levee system that surrounds the city to protect it from flooding. This paper presents the results of centrifuge models conducted at Rensselaer Polytechnic Institute and the U.S. Army Corps of Engineers simulating the behavior of the levees at London Avenue North and South that failed during Hurricane Katrina. Those levees failed without being overtopped by the storm surge. Also included are the results of a centrifuge model of one levee section at Orleans Canal South, which did not fail during the hurricane. The key factor of the failure mechanism of the London Avenue levees was the formation of a gap between the flooded side of the levee and the sheetpile. This gap triggered a reduction of the strength at the foundation of the protected side of the levee. The results are fully consistent with field observations.     

Reliability-Based Optimal Design of Truss Structures Using Particle Swarm Optimization

In this work, the particle swarm optimization method is employed for the reliability-based optimal design of statically determinate truss structures. Particle swarm optimization is inspired by the social behavior of flocks (swarms) of birds and insects (particles). Every particle’s position represents a specific design. The algorithm searches the design space by adjusting the trajectories of the particles that comprise the swarm. These particles are attracted toward the positions of both their personal best solution and the best solution of the swarm in a stochastic manner. In typical structural optimization problems, safety is dealt with in a yes/no manner fulfilling the set of requirements imposed by codes of practice. Considering uncertainty for the problem parameters offers a measure to quantify safety. This measure provides a rational basis for the estimation of the reliability of the components and of the entire system. Incorporating the reliability into the structural optimization framework one can seek a reliability-based optimal design. For the problems examined herein, the reliability indexes of the structural elements are obtained from analytical expressions. The structure is subsequently analyzed as a series system of correlated elements and the Ditlevsen bounds are used for the calculation of its reliability index. The uncertain-random parameters considered in this work are the load, the yield-critical stress; and the cross sections of the elements. The considered design variables of the optimization problem are the cross-sectional areas of the groups, which control the size of the truss, and the heights and lengths that control the shape of the truss. The results of the optimization are presented for a 25-bar truss and a 30-bar arch and the robustness of the optimization scheme is discussed.     

Reliability-Based Design for External Stability of Mechanically Stabilized Earth Walls

A two-phase approach was used to develop a reliability-based design (RBD) method for external stability of mechanically stabilized earth (MSE) walls. In the first phase, a parametric study was conducted using Monte Carlo simulation to identify parameters that affect the probability of external failure of MSE walls. Three modes of failure were considered: sliding, overturning, and bearing capacity. External stability was assessed by treating the reinforced soil as a rigid mass using the same procedures employed for conventional gravity-type wall systems. Results from the parametric study indicate that the mean and coefficient of variation of the backfill friction angle are significant for sliding, the mean and coefficient of variation of the friction angle of the backfill and coefficient of variation of the unit weight of the backfill are significant for overturning, and the mean and coefficient of variation of the friction angle of the foundation soil and the mean of the backfill friction angle are significant for bearing capacity. In the second phase, a series of additional simulations was conducted where the significant parameters identified in the parametric study were varied over a broad range. Results of these simulations were used to develop a set of RBD charts for external stability of MSE walls. A comparison indicates that similar reinforcement lengths are obtained using RBD and conventional methods and that the inherent probability of external failure in conventional deterministic design is ? 0.001. This probability of external failure is similar to inherent probability of failure reported by other investigators for similar geotechnical structures.     

Artificial Ground Freezing of Fully Saturated Soil: Viscoelastic Behavior

The transport and mechanical properties of saturated soil drastically change when temperatures drop below the freezing temperature of water. During artificial ground freezing, this change of properties is exploited in order to minimize deformations during construction work and for groundwater control. Whereas for the latter only the size of the frozen-soil body is relevant, which is obtained by solving the thermal problem, the design of the ground-freezing work for support purposes requires information about the mechanical behavior of frozen soil. In addition to the quantification of the improvement of mechanical properties during freezing, information about the dilation associated with the 9% volume increase of water during freezing is required in order to assess the risk of damage to surface infrastructure caused by frost heave. In this paper, a micromechanics-based model for the prediction of both the aforementioned phase-change dilation and the elastic and viscous properties of freezing saturated soil is presented. Hereby, the macroscopic material behavior is related to the behavior of the different constituents such as soil particles, water, and ice. Combined with the solution of the thermal problem, the proposed model provides the basis for predictions of the performance of support structures composed of frozen soil.     

Influence of Precipitates on Hydraulic Performance of Permeable Reactive Barrier Filters

A study was conducted to elaborate a predictive model that deals with the hydraulic conductivity reduction of permeable reactive barriers (PRBs) used for the in situ treatment of contaminated groundwater. As PRBs are composed of reactive and permeable filters through which the contaminated groundwater flows, their longevity has to be studied from both hydraulic and chemical points of view. Therefore, one-dimensional (1D) column filtration experiments were performed at a pilot scale, and an integrated model based on the solution of the advection-reaction-dispersion (ARD) mass balance equation was developed to study the space and time evolution of the hydraulic conductivity. This model uses the well-known Kozeny-Carman relation, which considers that permeability depends on the porosity and specific surface of the porous media. The ARD equation is solved by using the PHREEQC software with numerous capacities on the chemical point of view. Thanks to specific assumptions on the geometry of the precipitations, by using the floating-spheres model and the introduction of the “balanced time principle,” the evolution of the profiles of conductivity are computed and compared with those deducted from differential pressure measurements in the laboratory. Results of numerical simulations conducted with the model show that the largest porosity reductions occur on a 10-cm-thick layer at the entrance of the PRB as a result of precipitation of calcite minerals (prefilter).     

Pseudostatic Coefficient for Use in Simplified Seismic Slope Stability Evaluation

Pseudostatic slope stability procedures are commonly used in engineering practice. However, the selection of the seismic coefficient employed in the analysis is often based on precedence without due consideration of the amount of seismic displacement that constitutes satisfactory performance for each particular project and without incorporating the vastly different seismic exposure for sites around the world. In this Note, a rational basis for selecting the seismic coefficient is presented. The proposed procedure requires that the engineer establishes the project-specific allowable level of seismic displacement. The seismic response characteristics of the slope are represented by the fundamental period of the potential sliding mass, and the site-dependent seismic demand is characterized by the 5% damped elastic design spectral acceleration at the degraded period of the potential sliding mass. The level of uncertainty in the estimates of the seismic demand and displacement can be handled through the use of different percentile estimates of these values. With the proposed equations, the engineer can properly incorporate the amount of seismic displacement judged to be allowable and the seismic hazard at the site in the selection of the seismic coefficient.