Laboratory study of surface paste disposal for sulfidic tailings: Physical model testing

Surface paste disposal (SPD) of tailings is a recent technique for the management of mine tailings. It consists in dewatering (by thickening and filtering) the tailings before deposition to obtain a self-supporting and homogenous tailings stack. Paste tailings could become an advantageous alternative to conventional impoundments used for slurry tailings. However there are only few detailed studies on the environmental behavior of this approach. In this investigation, a sulfidic paste tailings was deposited in a laboratory-scale physical model (area of 2 m × 0.5 m) in nine layers. A proportion of 2 wt.% of binder was added in the two bottom layers; based on a previous study, this configuration should improve the environmental behavior. The paste tailings in the model have been wetted every 4 weeks with 40 L of water. The volumetric water content of the paste was monitored in each layer during the wetting and the drying phases. Two samples were cored in the tailings after 14 wetting/drying cycles to collect paste specimens. The study focuses on the geochemical analyses of the leachate collected during the experiment, the evolution of the water retention in both cemented and uncemented paste layers, and the characterization of the paste samples. Results show that the pH of the leachate remained circum-neutral during the experiment, although some preferential oxidation pathways were observed in the paste samples. The measurements also show that the evolution of the water content during the drying phases was different for cemented and uncemented layers. The desiccations cracks at the surface of the paste stack reopen at the same place after each wetting, but the crack intensity factor (CIF) decreased from 1.48 to approximately 0.2 during the 6th first wetting/drying cycles.     

Saturated hydraulic conductivity of cemented paste backfill

The key design parameters of cemented paste backfill (CPB, a mix of tailings, water and binder) are strongly influenced by its saturated hydraulic conductivity (permeability). However, our understanding of the permeability of CPBs, as well as factors that affect it and its evolution with time, is limited. Hence, a laboratory investigation is conducted to study the hydraulic conductivity of CPBs and develop a model for predicting its evolution with time. The results show that the hydraulic conductivity of CPB is time-dependent. As the curing time increases, the hydraulic conductivity decreases. The permeability is also affected by the mix components. The permeability decreases as the binder content increases or the w/c ratio decreases. Medium tailings with 45% fine particles confer lower hydraulic conductivity to the CPB. The sulphate can have two opposite effects on the permeability of CPBs, contributing to an increase or decrease. However, the magnitude of the influence of the mix components depends on the curing time and is generally more pronounced at early ages (7 days). Moreover, this study demonstrates that the hydraulic conductivity decreases with curing temperature and time for the studied CPBs. However, the effect of curing temperature on the hydraulic conductivity of CPBs is more significant in early age samples (up to 7 days) and depends on the binder type. Furthermore, the mechanical damage can significantly increase the hydraulic conductivity. Finally, the authors propose a simple function for the prediction of the evolution of the hydraulic conductivity of CPB with time. The validation results show that the developed model is able to predict the time-dependent change of the hydraulic conductivity with good accuracy.     

Stability analysis of a copper tailings dam via laboratory model tests: A Chinese case study

The upstream method is a popular method for raising tailings dams. Currently in China there are more than 12,000 tailings impoundments and almost 95% of them use the upstream method for the construction of the dam. Statistical data has shown that the tailings impoundment is one of the main sources of risk in the mining industry. Failures of tailings impoundments have resulted in the loss of many lives, considerable property damage, and irreversible pollution in downstream areas. Therefore, the safety of tailings management facilities has been of increasing concern to governments and local communities. The management of a conventional tailings storage facility requires the maintenance of a high level of structural stability. Therefore, according to the relevant mine Acts, the mine operators are required to conduct stability analyses for all types of tailings facilities, whether they are new, active, or decommissioned. For the stability analysis of tailings dams, the accurate profile of the tailings dam is very important. The profiles are easily obtained for both active and decommissioned tailings facilities because their data can be collected through field investigations. However, collecting basic data from newly constructed tailings facilities is difficult. In this paper, a laboratory physical model test has been performed. The construction process for new tailings impoundment has been physically simulated in the laboratory, where the tailings particle composition and distribution below a beach, the change of phreatic surface of the dam, and the engineering properties of the tailings of the dam profiles have been measured. A new tailings facility, Yangtianqin tailings impoundment, owned by Tongchang copper mine of Yuxi Mine Co., was used as a case study to illustrate the physical modeling of the tailings dam. In the model test, the geometrical model of pond area was constructed according to the scale factor, λ_L, of 1:200 (model:prototype), and the tailings discharge system was also established, the tailings slurry then being discharged based on the design data. Finally, on the basis of the model test results on profiles, the stability analysis of the tailings dam at different heights was conducted under different conditions. The model test results and stability analysis show that the height of the tailings dam should be less than that originally planned. The original design of Yangtianqing tailings impoundment should therefore be revised for the safety of the tailings impoundment.     

拉么锌矿尾矿处理方案研究

拉么锌矿选矿厂尾矿采用低浓度排放方式,面临能耗较高、外排废水量大、重金属离子超标、枯水期选厂生产用水紧张等问题,详细分析了拉么锌矿选矿厂尾矿处理现状。通过尾矿性质分析,得出尾矿成分、含量及尾矿以中细粒为主;借助尾矿沉降试验,测出尾矿浆达到良好沉降效果时絮凝剂的添加量;研究出了膏体制备的工艺流程及浓缩指标。同时对高浓度尾矿料浆进行塌落度试验及环管输送试验,对尾矿浆输送浓度、体积和速度进行测算,最终得出了合理的输送方案。制定了一套适合拉么锌矿选矿厂尾矿处理的方案,即尾矿料浆浓度为70%的膏体尾矿运排方案。该方案具有使生产用水循环利用,尾矿入库干堆排放、外排废水量少等优点,解决了当前拉么锌矿选矿厂尾矿处理面临的问题。     

灵寿碎云母尾矿综合利用试验研究

本文以灵寿碎云母矿风选的尾矿为研究对象，通过多种条件试验和流程的对比试验，从中分选出产率约26％的云母、15％的长石、40％的石英和5％的钛赤铁矿等四种合格精矿产品，尾矿利用率在85％以上．从而实现了二次资源的综合利用，社会效益、经济效益十分显著。     

利用金矿尾矿制作建筑材料蒸压砖的工艺研究

随着矿产资源的不断开发,大量的尾矿被长期堆积,既浪费资源,又带来严重的环境问题。为此,作者对应用金矿尾矿制作蒸压砖的可行性进行了试验研究。结果表明,制得蒸压砖的密度为1900~2000kg/m3,抗压强度达到国家标准规定的MU15级砖的要求,实现了尾矿的资源化。     

Impact of recycling cyanide and its reaction products on upstream unit operations

A typical operations outcome to dealing with the environmental and economic issues associated with cyanide in gold plant tailings streams involves the recycle of cyanide and its associated reaction products. This recycle stream may take the form of return dam water or tailings thickener overflow to the mill, or a cyanide recovery stream to the leach from a SART (sulphidization–acidification–recycling–thickening) or AVR (acidification–volatilization–reneutralization) circuit. The chemical composition and cyanide speciation of these solutions may be relatively complex, containing various metal cyanide species, thiocyanate, cyanate and other breakdown products.Several of these species are reported to have a deleterious effect on upstream unit operations. For example, while cyanide is in common use as a depressant for pyrite in mineral flotation, ferrocyanide and thiocyanate ions have also been shown to exhibit a depressant action in some cases. Primary flotation recovery of gold can thus be compromised and may be responsible for significant lost revenue, particularly from high-grade refractory gold operations. Bioleaching plants tend to separate cyanide circuits to an independent water balance to ensure that no cyanide or thiocyanate returns to inflict dire consequences on the bacterial population. Tolerable levels of these ions are exceedingly low, creating a risk factor and constraining water balance flexibility. Milling-in-cyanide has been periodically mooted as a beneficial circuit modification, particularly in operations that have tailings thickening, SART or dolomitic ore from which significant levels of free and complexed cyanides and thiocyanates are present. Potential consequences include unwanted side reactions with freshly activated mineral surfaces within mills operating at elevated temperatures and significant cyanide losses under these conditions.The evidence for the effects of recycled cyanides and associated species on upstream gold processing circuits have to date not been assessed in a systematic fashion. This paper presents a review of the available literature and analysis of associated data in these areas. Common arguments from operators justifying certain process plant configurations, modifications and operating setpoints around recycle streams are examined. Impacts of cyanide recycle on milling, flotation and bioleaching are quantified in the context of exemplary case studies. The various literature and case study flowsheets provide a useful analysis of the application of recycle streams to operating plant flowsheets, often requiring creative or inelegant solutions. In the current work, plant operating data is analyzed to quantify some of these effects; moreover, a simulation model has been developed to further quantify and explain some of these effects and provide insight into the decision-making process for plant designers and operators alike. Recycles without water treatment or other means may raise thiocyanate and cyanide levels above site-specific tolerances for operability.     

高岭土尾矿高效开发利用的新进展

高岭土尾矿是高岭土矿选矿过程中产生的固体废弃物,随着排放量越来越大,所产生的问题也日趋严重。阐述了我国高岭土尾矿的现状、特点及高岭土尾矿高效利用的重要性,高岭土尾矿中有价成分回收再利用的研究进展以及高岭土尾矿在建筑材料、陶瓷玻璃制品、无机高分子絮凝剂等矿物材料中的应用情况。阐述了二次资源的高效开发利用与经济发展问题、环境问题密切相关,并且具有综合的社会效益、经济效益和生态环境效益。从资源有效利用和提升资源利用价值的角度,指出了未来高岭土尾矿的高效开发利用与技术开发的发展方向,而未来走尾矿产业化道路已经成为实现我国矿产资源可持续发展的必然选择。     

某烧绿石尾矿选铌试验研究

国外某地含有丰富的烧绿石资源,属碱性碳酸盐矿体,原矿Nb2O5含量大于1%,在经历长流程胺法烧绿石浮选之后,尾矿含Nb2O5较高,铌资源未能得到综合回收,该烧绿石尾矿仍具有较高的回收价值。由于该尾矿长期在尾矿库堆存,药剂污染严重、含泥量较大,本工艺预先采用“磨矿擦洗-脱泥”的工艺改善其浮选性质,然后通过“磁选-脱钙”的工艺进行杂质矿物抛废,最终采用螯合类组合捕收剂实现烧绿石的选择性高效捕收。在原料Nb2O5品位0.71%的条件下,获得了Nb2O5品位55.07%、回收率38.23%的烧绿石精矿,尾矿中烧绿石资源得到回收。     

Wear performance and cost effectiveness––a criterion for the selection of grinding media for wet milling in mineral processing operations

Experiments to evaluate the milling performance, hence the relative cost effectiveness index of selected grinding media were conducted in a laboratory scale ball mill. The five types of grinding mill balls studied were eutectoid steel, low alloy steel, medium chromium cast iron, cast semi-steel and unalloyed white cast iron. The results obtained show that the heat-treated medium chromium cast iron ball possess a superior combination microstructure, wear resistance, and despite its high price per tonne, cost effectiveness.     

Reinforced terraced fields method for fine tailings disposal

New mining technologies can exploit low-grade ores but they produce high volumes of waste, such as tailings. Further, current mineral processing techniques produce more and more fine tailings. How to dispose of these tailings is a key issue in the sustainable operation of a mine. A traditional method is to construct a settling or tailings pond for storage. Such a method requires sufficient coarse particles to raise a dam or embankment. However, the fine tailings contain little coarse particles and have poor mechanical properties. The stability of a tailings dam thus becomes a major issue if the traditional method is used. According to statistical data, all fine tailings dams or ponds in China have failed or have failure potential. Therefore, fine tailings disposal is a challenge to mine operators and new disposal methods should be explored for the stability improvement of tailings dams. In this paper, an innovative method of reinforced terraced fields is presented to satisfy the specific requirement of fine tailings disposal. By using an actual mine, this paper reports in detail the design concept and procedures for this method. Its feasibility is evaluated and its fundamental are analyzed.     

The efficiency of indigenous and designed consortia in bioleaching stirred tank reactors

The efficiency of bioleaching is dependant on the establishment of an active microbial community. There is debate as to whether an indigenous microbial community is superior to one composed of microbial strains selected for specific physiological traits. The bioleaching efficiency of three microbial communities was studied: the indigenous community of a commercial bioleaching system (KCCL), a reconstituted consortium of the four major organisms which comprise KCCL that had been ‘un-adapted’ through a period of continuous maintenance in synthetic media (KCCR) and a specifically designed consortium of bioleaching organisms (KCCD). Acidithiobacillus caldus was unable to re-establish itself in the reconstituted, un-adapted consortium. However, the bioleaching rate of this consortium improved over time, and its overall performance was very similar to that of the indigenous community. This was despite the absence of an obligate sulfur-oxidising species, which resulted in the generation of substantially less acid. The performance of the designed consortium was poor, and the results implied that bioleaching consortia (mesophiles or moderate thermophiles) cannot be assembled ‘off-the-shelf’, at least not without a substantial period of adaptation.     

Development of testing procedure for ceramic disc filters

Small-scale laboratory tests for sizing and designing disc filters are typically performed by using leaf test equipment. Although the basic tests are fairly simple and quick, the accuracy and repeatability of the results may be poor due to various reasons. In addition to errors caused by variations in the structure of the equipment, also the skills and experience of the person performing the tests is of great importance. This paper introduces an experimental study carried out for defining the most important sources of errors in these kinds of laboratory tests and for estimating their influence on the final test results. The results obtained in this study were utilized for designing an improved version of the test equipment and also for creating a standard procedure for performing the tests. The results acquired with the small-scale laboratory tests were in good agreement with the performance results obtained from full-scale ceramic disc filters operating in industrial processes.     

Cemented products containing waste from mineral processing and bioleaching

The characteristics of cemented products ranging in initial consistency from ‘paste-like’ to ‘flowable’, relevant to paste backfill and backfill with controlled low strength materials (CLSM), respectively, were compared for mixes incorporating waste from pilot scale bioleaching of European refractory gold, copper and copper/nickel sulphide flotation concentrates. Compositional and structural properties were linked to mechanical strength, hydraulic conductivity and hydrolytic stability (leachability) in fabricated laboratory specimens containing sand, pulverised fuel ash, waste and Portland cement in the proportions 70, 15, 10 and 5, respectively, together with variable quantities of water. In some experiments, sand was replaced by flotation tailings.The results showed that mixtures containing 10% of waste with 15.0–37.5% water by mass gave cemented materials with unconfined compressive strength (UCS) in the range 0.4–3.0 MPa after 28 days of hardening, this range encompassing typical paste-fill and CLSM formulations. They also indicated formulations giving maximum UCS and retention of strength at higher water content in the presence of the (finer sized) waste. Hydraulic conductivity (10⁻⁷–10⁻⁹ m/s) was comparable to commercial CLSM. Chemical analysis indicated low levels of most toxic elements and correspondingly low diffusion leaching, thus reducing requirements for special lining or encapsulation procedures to avoid groundwater contamination. However, chromium leaching, for example, remained an issue, thus indicating a need for further development before regulatory acceptance and deployment in field applications can become feasible.The formulated materials are consistent in principle with a scheme of integrated waste management based on designed combinations of paste (for mine backfill), CLSM (for engineering foundation construction) and mineral bulk (for site landscape/soil restoration). In particular, they facilitate production of different materials for paste backfill and CLSM applications by judicious adjustment of water content.     

云南迪庆铜铅锌硫化矿浮选分离研究

这是一篇矿物加工工程领域的论文。随着选矿技术的不断发展和对矿产资源重视程度的提高,对于尾矿综合利用的研究越来越多。采用化学多元素分析、SEM等技术对某钒钛磁铁矿选铁尾矿中的铜矿物进行表征,研究表明其中主要有价元素为铜,且主要以硫化铜形式存在。在选矿工艺研究方面,以河北某钒钛磁铁矿尾矿为研究对象,选用丁基黄药、A8及MK305对选铁尾矿中的铜进行浮选回收实验,通过单一捕收剂实验、组合捕收剂实验、捕收剂用量实验以及2^#油用量实验,确定在A8：MK305用量比为1∶1,粗选捕收剂用量为45 g/t,2^#油为7.5 g/t时,获得较佳的浮选技术指标。闭路实验结果表明,选铁尾矿经过一次粗选、一次扫选后,得到的粗精矿经再次磨矿至-0.074 mm含量大于85%,添加生石灰12 kg/t,经过一次粗选、三次精选、两次扫选,可以得到品位18.94%的铜精矿,回收率为60.88%,实现了选铁尾矿中金属铜的回收利用。     

金属矿山尾矿处理技术进展

介绍了国内外在尾矿高效浓缩、全尾矿充填采空区和膏体尾矿干式堆存方面的研究和应用进展;分析了这些尾矿处理新方法的特点;指出随着人们环保意识的增强,安全、高效和环境友好的尾矿处理方法将逐步取代传统的尾矿地表堆存方法。     

萤石资源现状及战略性价值分析

这是一篇矿物加工工程领域的论文。某稀土矿矿石中伴生萤石和锶钡矿物,由于该样品成分和嵌布关系复杂,矿物嵌布粒度细,且萤石和锶钡矿物浮选性质相近,常规药剂和工艺无法实现样品中伴生萤石和锶钡矿物的富集和分离,影响当地生态环境,造成国家矿产资源的重大浪费。针对该样品,开展浮选药剂优选和工艺优化,形成适于该稀土尾矿资源化利用的混合浮选-分离再提纯选矿工艺。研究结果表明,针对SrO品位为8%,CaF₂品位为16%的稀土尾矿,经混合浮选-再分离提纯工艺可以得到品位为90%的萤石精矿和锶钡混合精矿纯度90%的锶钡精矿,研究结果可以为同类型尾矿资源化利用提供借鉴。

     

煅烧含伊利石尾矿制备充填胶凝材料试验研究

尾砂的大量堆存不但占用土地,而且对周围环境造成严重影响。受可塑性差、活性低等因素制约,我国尾砂利用面临着着产品附加值低、利用率低等共性难题。基于此,本文利用高温煅烧(600-1000℃)提高含伊利石尾矿的活性,将其应用于充填胶凝材料的制备。通过试验得知,含伊利石尾矿的活性随着煅烧温度的升高而增强。将1000℃条件下活化的含伊利石尾矿制备的充填胶凝材料用于井下充填,当胶凝材料和尾砂质量比为1:6,料浆浓度为70%时,充填体3d和28d抗压强度分别为0.43 MPa和2.27 MPa。另一方面,与水泥基充填材料相比,利用含伊利石尾矿制备的充填胶凝材料可节省约11.87%的充填成本。据此,利用含伊利石尾矿制备充填胶凝材料,一方面开辟了尾矿大宗资源化利用的新途径,同时也有利于降低充填成本,切实推进我国绿色矿山建设。     

Technique to automate measurement of water overflow rate in frother characterization testing

A novel method for measuring water overflow rate from a laboratory column in the air-water system is presented. The method is based on accumulating overflow in a tube and measuring the rate of increase in pressure. The development is a further step towards automating frother testing.     

A process mineralogy approach to geometallurgical model refinement for the Namakwa Sands heavy minerals operations,west coast of South Africa

The original geometallurgical model for the Namakwa Sands deposit was modified to accommodate ore blends in addition to the various single ore types. A process mineralogy approach was followed in a structured and systematic manner to evaluate the integrity of the adjusted model, particularly for ilmenite and zircon, the minerals of highest intrinsic value. This study reproduced recovery relationships predicted by the geometallurgical model for each of the key process functions, and as a result the integrity of the geometallurgical model is validated. Overall, the recovery potential determined for ilmenite and zircon are well adjusted to model estimates. Poor mineral liberation, an anomalously high abundance of garnet and pyroxene and variation in particle chemistry are recognized as the key recovery penalties. The gangue content is the most significant constraint to ilmenite recovery, whereas zircon chemistry is the most important negative factor in the production of a premium quality zircon product. Results of this study contributed to the refinement of the current geometallurgical model and also identified opportunities to optimise mineral resource utilisation in the future.