Assessment of Water Sources and Mixing of Groundwater in a Coastal Mine: The Sanshandao Gold Mine,China

Water inrush is a potential disaster in the Sanshandao Gold Mine, which is located on the coast of the BoHai Sea. A conceptual model based on the water chemistry and hydrogeological setting was established to identify potential water sources. Then, a mixing pattern was developed based on the δ¹⁸O and Cl^? values. Finally, a linear mixing model was used to estimate the mixing ratios of water sources at each site. Four sources were identified: freshwater: (F), quaternary water (Q), seawater (S), and brine (B), and four mixing patterns were developed: B-F-Q, F-Q-S, B-Q-S, and B-S. The mixing ratios showed that brine was the main water type when mining began. However, seawater (mean?=?48.3%) and quaternary water (mean?=?36.04%) came to dominate the groundwater composition over a short period of time. The field investigations and hydrochemical analysis indicated that the main flow paths of these waters were along NW-oriented fractures and the F3 fault. Freshwater mainly recharged the shallow fractures (above ?285 m) and represented a small proportion of the groundwater (mean?=?11.2%). The main freshwater flow paths were bare rock fractures in the mountains.     

Modelling of residence time distribution of liquid and solid in mechanical flotation cells

This paper presents the results of modelling the residence time distribution (RTD) in mechanical flotation cells, measured in several plants, using the radioactive tracer technique. Results include mechanical cells of 100–300 m³ operated with effective residence times from 2 to 7 min. Data were obtained in forced air and self-aerated cells for liquid and non-floatable solids (per size classes). Different RTD model structures including perfect mixing, Large and Small Tanks in Series (LSTS) and by-pass flow plus perfect mixing were evaluated and compared for single cells. The actual mixing regimes were related to the effective residence times and cell designs based on the model fitting. By-pass flow percentages were typically lower than 10%, therefore the perfect mixing model plus a dead time was a suitable model structure in most cases.On the other hand, the arrangement of cells in series was in most cases effective in reducing the bypass flow observed in single cells. In addition, the N mixed tanks-in-series model was used to represent the mixing regime along flotation banks, which were operated with mean residence times in the range of 18–53 min. Results showed that the N equivalent tanks-in-series values were closer to the actual values in most cases. In some applications, slight by-pass propagation was observed because of circuit layout, problems with the level control system, solid settling and/or high flowrates.     

渣罐底吹搅拌混合特性的模型研究

渣罐内添加剂的混匀行为对含钛高炉渣中钙钛矿的析出和长大存在重要影响。本文在底吹渣罐水模型的基础上,测定了粘度、气体流量对熔池底吹搅拌混匀时间的影响。结果表明,粘度相同时,随底吹气体搅拌能密度增大,溶液混匀时间缩短;搅拌能密度相同时,随溶液的粘度增大,溶液的混匀时间变长。回归出了水模型溶液的混匀时间与搅拌功率密度和粘度的关系方程式,并在此基础上计算出了25 t熔渣的混匀时间表达式。     

The effect of distributor configuration on the hydrodynamics of the teetered bed separator

The teetered bed separator (TBS) is a gravity concentration device which operates on the principle of hindered settling. The hydrodynamics of the separator and fundamental particle interactions in the teeter bed were investigated for a two phase liquid–solid system with the coal particles of a wide size and density distribution considered as multiple solid phases. Seven distributor plates of varying aperture size and geometric arrangement were considered. The flow behaviour was predicted using the Multiphase Eulerian and Mixture Model in the commercial CFD package, Fluent 6.1. The simulations gave an indication of the dead zones, turbulent regions, wall effects and the specific flow pattern due to each plate. The model may be used to predict the most appropriate distributor configuration for the separation process based on the flow patterns and particle interactions in the unit. A laboratory scale TBS was constructed to investigate the separations achievable using the simulated designs. Coal particles sized between 2 and 0.038 mm with a specific gravity (SG) range of 1.2–2.0 were used as the material to separate. Partition curves were plotted for the separations carried out under modeled conditions and the Ecart probable (E_p) and cut point density (D₅₀) obtained. The simulations and experimental testwork indicated that Plate 3 may be the most appropriate distributor configuration for the investigated conditions due to the even velocity profile with minimum flow disturbances experienced in the coal separation process.     

DEM simulation of the flow of grinding media in IsaMill

IsaMill is a high speed stirred mill for high efficiency grinding of mineral ores and concentrates. A numerical model based on the discrete element method (DEM) was developed to study flow of grinding media in IsaMill. The DEM model was first verified by comparing the simulated results of the flow patter, mixing pattern and power draw from those measured from a 1:1 scale lab mill. Then the flow properties were analysed in terms of flow pattern, flow velocity, force field and power draw. The effects of parameters relating to particle material (i.e., sliding friction coefficient and damping coefficient) and operational conditions (i.e., rotation speed and solid loading) were investigated. While the damping coefficient showed a negligible effect for the range considered, other three parameters had strong effects on the flow properties. Increasing the sliding friction caused the flow velocity and compressive force to have minimum values due to the competitive mechanisms for energy transfer and dissipation, but increased the power draw. The increase in the rotation speed and solid loading also increased the flow velocity, compressive force and power draw of mill. The particle scale information obtained would be useful to understand the fundamentals governing the flow of grinding media in IsaMill.     

Characterization of large size flotation cells

Design and operating conditions of large size mechanical flotation cells were evaluated by comparing it with the actual operating conditions in a plant. The objective was to determine the time scale-up factor, typically based on empirical rules. Experiments were conducted on the rougher flotation circuit at Minera Escondida Ltd. The circuit consisted of self-aerated mechanical cells of 160 m³, arranged in six parallel banks with nine cells each.The rougher circuit flotation kinetics was evaluated from direct sampling and local mass balances around each cell of the bank. Adjusted overall mass balances were also developed. This information was used to fit different kinetic flotation models, and it was found that the rectangular distribution function was the most appropriate to describe the distributed rate constant for industrial operation. Then, a rougher flotation simulator was developed to describe the actual operation in terms of the operating variables (mass flow rate, solid percentage, feed grade) and the actual volumetric flow rate entering to each cell. In this study feed pulp samples were taken in parallel from the rougher circuit and were simultaneously floated in laboratory. The kinetic behavior was then modeled at a laboratory batch scale in order to determine the time scale-up factor between laboratory batch flotation data and industrial size flotation. The time scale-up factor observed for large sized cells, 160 m³, was found reasonably similar to those previously determined for self-aerated mechanical cells, but of lower size, operating at similar recoveries. In addition, the relative effect of mixing, between laboratory batch and an industrial flotation bank was quantified by the ϕ parameter, separating the impact that kinetic and mixing changes have on the time scale-up factor.In general, the rougher flotation operation was found to reach the predicted metallurgical target, and that the optimal separability criterion was also respected.The diagnostic generates information about the internal state of the process and helps to identify potential improvements for design, operation and control of the circuit.     

Mixing characteristics of industrial columns in rougher circuit

The rougher circuit at Miduk Copper Concentrator, Iran, includes five Microcel™ flotation columns in parallel, each 12 m in height and 4 m in diameter. The main objective of this communication was to describe the mixing conditions of rougher columns using residence time distribution (RTD) data. A liquid radioactive tracer was employed to trace the material reported to tailing and concentrate. External scintillation detectors were used to record the tracer intensity without disturbing the flow pattern. Data analysis showed that large and small tank-in-series and N perfect mixers in series were the best models to present the flow pattern of liquid transferred to tailing and concentrate, respectively. Solids mean residence time from a theoretical model for counter-current columns was estimated. A 1.4:1 ratio between the residence time of liquids and solids was achieved. In order to complete the diagnosis, solid content and grade profiles along the collection and froth zone of one of the columns were also measured. The results of the present study showed that despite the presence of vertical baffles, the mixing conditions of industrial rougher columns were close to well mixed ones. The possible causes for mixing in industrial columns were described. As expected by increasing gas flow rate, the mean residence times of liquid transferred to both tailing and concentrate streams reduced and the mixing degree increased.     

Frother-related research at McGill University

Over the past ten years the Mineral Processing group at McGill University has developed techniques to determine gas dispersion properties (gas superficial velocity, gas holdup, bubble size and bubble surface area flux) in flotation machines. This work is finding application in metallurgical diagnostics and cell characterization. The picture, however, will remain incomplete until the impact of chemistry on bubble production, and hence on gas dispersion, is understood. This has prompted investigations into frothers.There are two areas addressed in this communication: frother analysis and frother characterization.Coincident with the centenary, for 100 years there was no convenient frother analysis procedure. A colorimetric technique originally developed for alcohols had been applied to MIBC (Parkhomovski, V.L., Petrunyak, D.G., Paas, L., 1976. Determination of methylisobutylcarbinol in waste waters of concentration plants. Obogashchenie Rud 21 (2), 44–45). Using this as a starting point, the technique was successfully extended to a wide range of commercial frothers and shown to be robust against most common ‘contaminants’. The technique is readily used on-site and some observations from plant surveys are described.Characterization of frothers has taken two routes, determining water carrying rate and investigating properties of thin bubble films.Second only to transporting particles the recovery of water by bubbles has the most influence on metallurgy. The question posed was whether this ‘water carrying’ property could be related to frother type. In a specially designed column the volume rate of water to the overflow per unit cross-sectional area (‘carrying rate’, J_wo) and gas holdup (ε_g) at controlled froth depths were measured. The J_wo–ε_g relationship proved approximately linear and dependent on frother type, with four frother ‘families’ being identified.Bubble thin films have been studied for soaps and the techniques were adapted for frothers. From infrared analysis it became apparent that the frother molecule, while itself not seen, had an impact on organizing water molecules, apparently forming a film of bound water on the bubble surface. Exploiting the interference pattern generated in UV/Vis the film thickness (d) was determined; for MIBC d was less than 160 nm while for DF250 d was ∼600 nm. Taking a representative frother from the four families identified above, the water carrying rate at a given gas holdup increased with film thickness.Possible implications of the findings on the role of frother in bubble production are explored.     

Numerical analysis of hydrocyclones with different vortex finder configurations

This paper presents a numerical study of the multiphase flow and performance of hydrocyclone by means of two-fluid model, with special reference to the effects of diameter, length and shape of vortex finder at a wide range of feed solids concentrations. The considered shapes include the conventional cylindrical style and the new conical and inverse conical styles. The simulation results are analysed with respect to cyclone flow and performance in term of cut size d₅₀, water split, Ecart probable E_p and inlet pressure drop. It is shown that when vortex finder diameter or shape varies, a compromised optimum performance can be identified, resulting in relatively small inlet pressure drop, E_p, and water split. Both d₅₀ and E_p are more sensitive to feed solids concentration than inlet pressure drop and water split. Overall, the effect of vortex finder length on the separation efficiency of particles is much less significant than diameter and shape, which shows opposite trends at low and high feed solids concentrations. All these results can be well explained using the predicted tangential and axial velocities and solid volume fraction.     

Analysis of stirred mill performance using DEM simulation: Part 1– Media motion, energy consumption and collisional environment

Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot scale tower mills and pin mills are carried out in order to investigate the relative performance of these stirred mills. Media flow patterns and energy absorption rates and distributions are analysed here. In the second part of this paper, coherent flow structures, equipment wear and mixing and transport efficiency are analysed.     

液态添加剂对CFB锅炉SNCR脱硝的影响

为提高SNCR脱硝技术在低温下的脱硝效率,选取乙醇、NaCl、Na OH三种液态物质作为添加剂,在小型机理脱硝实验台和中等规模脱硝实验台上开展了研究。研究结果表明,小型实验台上,650℃、添加剂加入比例0~0.6条件下,乙醇可将脱硝效率从5%提升到45%,微量的(20×10-6)NaCl可以提高800℃以上的脱硝效率。在中等规模脱硝实验台上,乙醇因具有最佳的混合条件不同温度下对脱硝的促进作用差异明显,NaCl,NaOH因床料含有Na对脱硝无明显促进作用。添加剂与还原剂混合条件、床料成分等会使添加剂在CFB锅炉实际使用过程中产生与机理实验相差较大的结果。     

The use of a factorial experimental design to study collector properties of N-allyl-O-alkyl thionocarbamate collector in the flotation of a copper ore

A three-factor, three-level, face centered cubic (FCC) experimental design was used to study the effect of important chemical variables—collector chain length, collector concentration and frother type—on the collector properties of the recently developed N-allyl-O-alkyl thionocarbamates (ATC) in copper flotation from a porphyry ore. The objectives of this study were to exploit the advantages of using experimental designs to evaluate multivariable effects and interactions, and to develop fundamental applications knowledge that is currently lacking for the ATC collectors.The effects of these process variables on copper recovery, copper concentrate grade, iron recovery, and particle size of the flotation concentrate were determined and the best process conditions were identified. The flotation efficiency of the ATC was compared with that of two better-known collectors, the O-alkyl-N-ethoxycarbonyl thionocarbamate (ECTC) and the N-alkyl-N-ethoxycarbonyl thiourea (ECTU).     

The importance of flocculant choice with consideration to mixing energy to achieve efficient solid/liquid separation

Separation efficiency reaches a maximum dependent upon the level of flocculant solution–substrate mixing for a fixed flocculant dose. At low levels of mixing poor separation is due to poor distribution of the flocculant molecules. At high levels of mixing floc attrition occurs which reduces the separation efficiency. On either side of this maximum conditions leading to similar sedimentation rates can be identified. At these similar sedimentation rates lower sediment volume and supernatant turbidity are obtained with flocs which have undergone a degree of breakage.The unique molecular architecture (UMA^®) type of flocculant was found to be superior to a standard flocculant at several levels of mixing. This superior performance was explained by relative ease of distribution of flocculant molecules in the suspension and by greater floc strength. However, differences in floc density did not explain performance differences.Evidence for the concept of “undermixing” is presented, which can explain poor solid–liquid separation performance which otherwise could appear to be explained by flocculant overdosing.     

Estimation of the actual bubble surface area flux in flotation

The bubble surface area flux, S_B, defined as the ration between the superficial gas rate J_G and the Sauter mean bubble diameter D₃₂, has been widely used to describe the gas phase dispersion efficiency in flotation machines, and from this predict flotation performance, notable mineral recovery to forecast plant economics.In this work, results of bubble size distribution (BSD) generated in a pilot column are analyzed. Using video and image analysis techniques, the impact of different sampling rates on the BSD was evaluated. Measurements were carried out for D₃₂ = 1–2 mm, J_G = 0.5–1.5 cm/s and two frother concentration, with a maximum sampling rate of 100 fps. In addition, the bubble rise velocity in the bubble swarm was measured, as a function of the individual bubble diameter, for different operational conditions.The identification of the BSD depends on the proper selection of the visual field and sampling rate for acquisition and processing of bubble images. Distortion in the estimation occurs because a larger holdup of small bubbles is observed, relative to the overall data set, due to their lower velocity.The actual BSD was obtained by correcting the observed population, considering the effect of bubble rise velocity. Thus, the actual bubble surface area flux, S_B, was calculated. The results were evaluated at a pilot scale (air–water system) as well as an industrial plant scale (air-pulp system).     

侧吹炉自动捅风眼机器人在某冶炼厂的应用

捅风眼是富氧侧吹炉工艺过程的重要操作，目前侧吹炉捅打风眼仍主要依靠人工，并不能满足现在铜冶炼工艺高效、安全、智能、可靠的需求，侧吹炉自动捅风眼机器人的成功研发与应用，能够有效提高生产效率，降低工人劳动强度，符合当前建设智能功能的需求。     

Analysis of stirred mill performance using DEM simulation: Part 2 – Coherent flow structures, liner stress and wear, mixing and transport

Stirred Mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot scale tower mills and pin mills are carried out in order to investigate the relative performance of these stirred mills. In the first part of this paper, media flow patterns and energy absorption rates and distributions were analysed to provide a good understanding of the media flow and the collisional environment in these mills. In this second part we analyse steady state coherent flow structures, liner stress and wear by impact and abrasion. We also examine mixing and transport efficiency. Together these provide a comprehensive understanding of all the key processes operating in these mills and a clear understanding of the relative performance issues.     

基于CFD技术的选矿药剂生产用反应釜流场特性研究概述

选矿药剂生产常使用机械搅拌式反应釜,产品质量与药剂经过混合后的均质性直接相关,反应釜内部的流场特性对设备的混合效率以及产品的均质性具有重要影响。CFD技术是研究反应釜流场特性的一种有效技术手段,本文概述了CFD技术在该领域的应用现状以及选矿药剂行业常用的反应釜内部流场特性的相关研究成果,并介绍了常见的设备优化技术手段。     

The effect of temperature and culture history on the attachment of Metallosphaera hakonensis to mineral sulfides with application to heap bioleaching

Temperatures in excess of 60 °C are required for efficient bioleaching of chalcopyrite. Within heaps, colonisation of the mineral with thermophilic archaea is important in reaching and maintaining these high temperatures. The effect of temperature and culture history on the attachment of Metallosphaera hakonensis, an extreme thermophilic acidophile identified as a key player in heap bioleaching, to sulfide concentrates and low-grade ore was investigated in shake flasks and packed beds. Attachment studies were conducted at 25 °C, 45 °C and 65 °C. The results show a clear relationship between increasing temperature and attachment efficiency for both suspended and packed bed systems. Attachment at 25 °C was low. Increasing the temperature to 45 °C improved attachment efficiency by between 50% and 100% while a further increase to 65 °C improved attachment by an additional 20-50%. Cells cultured on elemental sulfur as energy source prior to contacting showed 1.3 times greater affinity for the mineral concentrate than those cultured on sulphide mineral concentrates or ferrous sulphate. In contrast to previous studies using mesophilic organisms the selective attachment of Metallosphaera to sulfide minerals, relative to gangue, was less pronounced. Attachment efficiency was lower in the packed bed system which more closely mimicked flow through a heap. The cell surface properties surface charge and hydrophobicity as well as metabolic activity were investigated to provide insight into the observed phenomena. The data suggest that retention of thermophiles within the heap could be enhanced by a secondary inoculation following elevation of the temperature above 40 °C by the mesophilic pioneer species.     

CK式搅拌槽流场数值模拟分析

采用Mixture模型、多重参考系（Multiple reference frame,MRF）对CK式搅拌槽内流场进行数值模拟,分析其内部流场特性。结果表明,CK式搅拌槽内部流场主要由一个主循环流与两个小循环流构成,搅拌槽内流体呈"W"形进行上下循环运动;其内部压力槽顶部与底部的压力最大然后逐渐向搅拌中心减小,这种压力分布有利于促进搅拌混合;提高搅拌转速,可加速搅拌槽内介质混合过程,缩短混合时间;该结构搅拌槽的临界悬浮转速为130.51 r/min,当转速达到190 r/min时桨叶运转100转时搅拌槽内固相基本达到均匀悬浮,表明该结构搅拌槽具有较高效率的搅拌效果。