Improving flotation energy efficiency by optimizing cell hydrodynamics

Flotation is not a particularly energy intensive process. Therefore, flotation optimization has traditionally been focused on grade and recovery performance improvements. However, with the growing need for energy efficiency and the dramatic increase in flotation cell size in recent years it is worth considering how well energy is utilised within flotation cells. In conventional flotation cells a certain amount of energy is required to meet the basic requirements for flotation (air dispersion, solids suspension and particle-bubble collision). This paper investigates how that energy is dissipated in the flotation cell to determine the most efficient use of the imparted energy. The distribution of turbulence and its effect on flotation kinetics are investigated in a mechanical 3 m³ flotation cell for a range of hydrodynamic conditions. The effect of the different conditions are evaluated considering the Power Number (N_P); a dimensionless number that is a useful hydrodynamic indicator as it represents the ratio of energy added to the flotation cell dissipated as shear to that used to generate bulk flow. Results show that flotation rate in the collection zone and the fraction of the cell with higher turbulence increases as more of the power drawn by the impeller is dissipated as shear in the impeller-stator region (higher Power Number). This should promote higher collision rates and more efficient use of the energy imparted in the flotation cell.     

高气泡表面积通量浮选柱浮选硫化铜矿的研究

高气泡表面积通量浮选柱可以在较高表观充气速率情况下,有效地提高气泡表面积通量,避免因气泡携带能力不足导致的回收率损失。高气泡表面积通量浮选柱和机械搅拌浮选机浮选浸染型矽卡岩铜矿石的对比试验表明。采用铜硫混合浮选再铜硫分离流程或优先浮铜流程,高气泡表面积通量浮选柱在减少精选作业次数的情况下,浮选指标明显优于机械搅拌浮选机,提高的幅度与流程有关。     

An evaluation of the role of particle size in the flotation of coal using different cell technologies

A large variety of new flotation cells has been introduced in the last few years, probably as a result of the successful introduction of column flotation in the minerals processing industry. In common with the column cell, a number of these new cells employ an essentially quiescent separation zone. However, a number of novel cell designs have been introduced that use agitation mechanisms similar to those employed on conventional flotation cells. The aim of this investigation was to evaluate flotation behaviour in both an agitated and non-agitated environment, particularly with respect to particle size. A hybrid ‘agitated’ column cell was designed for the investigation, and the operation of this unit was compared to that of a column cell, and to a batch flotation cell, on a laboratory scale. The testwork was conducted on coal fines, as problems with the flotation of coarse coal particles in a column cell had previously been identified. It was demonstrated that the addition of an agitated stage to a column cell can significantly improve the coarse particle recovery in comparison to the conventional column cell, while maintaining good selectivity in the fine sizes.     

柱浮选充填及工业应用

充填是提高浮选柱分选效率和降低浮选柱高度的最有效途径之一。指出了填料充填与筛板充填两种充填方式的区别及填料充填浮选柱在工业应用中的缺陷,分析了两种充填方式对浮选环境的改变以及对浮选结果的影响。以筛板充填为基础,对旋流-静态微泡浮选柱浮选段进行优化充填,提出了筛板充填和蜂窝管充填的高效混合充填模式。该充填模式的特点是利用蜂窝管降低涡流,减小射流气泡的径向分散;利用筛板继续分割破碎气泡,延长气泡路径,稳定泡沫层。把混合充填模式应用到旋流-静态微泡浮选柱选矿工业试验中,柱体底部大尺度涡旋得到抑制,气泡径向弥散均匀,矿浆停留时间延长,显著改善分选过程和指标。     

SF型自吸式浮选机的研制与推广应用

北京矿冶研究总院研制成功的SF型浮选机,是一种自吸式机械搅拌浮选机．该机的主要特点是吸气量大、单容功耗低、搅拌力强、分选效率高．自1987年SF－4型浮选机经部级鉴定以来,已有13种规格约5000余台应用于工业生产,取得了良好的经济效益和社会效益．本文论述了SF型自吸式浮选机的结构、特点及推广应用情况。     

新型细粒浮选柱的研究

有新的理论认为,“矿浆有适度紊动”比“矿浆静态”更有利于细粒的分选。基于此新理论,设计了一套新型细粒浮选柱的实验室装置系统,并进行室内小型浮选试验。试验结果表明,在同等试验条件下,无论是精矿品位还是回收率,新型细粒浮选柱都高于Jameson射流浮选柱和XFD机械搅拌浮选机。介绍了新型细粒浮选柱的结构和工作原理。     

新型细粒浮选柱的研究

基于Jameson浮选柱的下导管充气与矿化技术,作者设计了1套新型细粒浮选柱的实验室装置。试验结果表明,在同等试验条件下,无论是精矿品位还是回收率,新型细粒浮选柱都高于Jmneson射流浮选柱和XFD机械搅拌浮选机。     

浮选柱的过去、现在及将来

介绍了国内外浮选柱的发展概况和部分浮选柱的结构。我国浮选柱与国外浮选柱相比,性能不相上下,但因我国电力不足,无法保证矿山供电,浮选柱经常停车,频繁放矿,金属矿物大量流失,选矿厂宁可再度采用浮选机。文中指出了我国浮选柱复苏的条件。     

Effect of slurry rheology on gas dispersion in a pilot-scale mechanical flotation cell

This paper investigates the effect of slurry rheology on gas dispersion in a 100 l pilot-scale Batequip mechanical flotation cell. The study is conducted using Kaolin, Bindura nickel and Platreef slurries. All three ores display typical non-Newtonian rheological behaviour. The slurry yield stress and viscosity increase exponentially with solids concentration. Bubble size and gas hold-up vary from 0.60 to 1.10 mm and 2% to 15%, respectively. At low/moderate solids concentrations, bubble size and gas holdup display characteristic trends, as noted in numerous literature studies. At high solids concentrations, both bubble size and gas holdup decrease significantly, which is an unexpected finding. This is attributed to the formation of a ‘cavern’ of slurry around the impeller, due to the very high slurry yield stresses. This ‘cavern’ results in the generation of small bubbles in the impeller zone, but poor dispersion of these bubbles throughout the cell, resulting in low gas hold-ups.     

Recovery of phosphate ores in the modified three-product column (3PC) flotation cell

This work details the results obtained for the rougher flotation of phosphates in a modified flotation cell known as a three-product column (3PC), at both the laboratory and pilot plant scales. Results were compared to a conventional column cell-CCC. The 3PC cell separates the drained (rejected) particles from the froth zone (third product) and uses a secondary wash water system between the feed and the froth zone (II). Bench-scale studies measured the effect of the two water surface rates on mass and metallurgical recoveries and concentrate grades (P₂O₅, Fe₂O₃, and SiO₂) in all the flows. At pilot scale, the influence of wash water (J_W2) and column design on the flotation separation parameters was studied. Results showed that, compared with the conventional column cell (CCC), the 3PC yielded, in all cases, clean high-grade concentrates, with a minor concentration of impurities (Fe₂O₃ and SiO₂). Concentrate recoveries ranged from 40% to 70% for apatite and were lower when compared to CCC, but it is believed that the third product could be recycled to the fee. This drop-back product operating with J_W2 = 0.0 cm s⁻¹ might yield 5–10% extra in apatite recoveries and enhancing this J_W2 values, the apatite recovery decreased by 0.5–3% but rejection of impurities was very high. Results appear to show that the 3PC may be used as a rougher-flash or Cleaner unit with an optional recycle of the third product into the rougher or simply discarding it. Data on the influence of some cell design and gas dispersion parameters on process efficiency are reported, and the potential practical applications for this type of cell are envisaged.     

K-FV50NS充气式浮选机的应用

介绍了普浮乐浮选机的工作原理及结构特点,并对普浮乐浮选机与传统机械搅拌式浮选机在工艺效果及经济效益等方面进行比较,证实了普浮乐充气式浮选机可作为机械搅拌式浮选机的重要补充或成为其替代产品.     

高气泡表面积通量充气器气泡特征参数试验研究

充气器生成气泡的特征参数是影响气泡表面积通量的关键因素。利用电导探针法和拍照测径法获取了充气器产生气泡的直径、速度及其分布特征。利用CCD高速相机获取了充气器的气泡分散特征。结合浮选柱的清水试验研究,分析了充气器喷嘴直径和充气压力两个关键参数对气泡特征参数影响。研究表明,KYZ浮选柱充气器能形成高气泡表面积通量的柱内分选环境。工业应用表明,KYZ浮选柱高气泡表面积通量充气器能够实现优异的分选性能。     

Effect of Jameson cell operating variables and design characteristics on quartz-dodecylamine flotation system

The Jameson cell is a relative newcomer to separation science and technology. Its mode of operation and mechanisms differ drastically from the other flotation machines. It has a number of unique parameters affecting flotation performance. An experimental investigation of Jameson cell operating variables and some design features was carried out within the quartz-dodecylamine flotation system. These parameters included jet length, bias, % solids, downcomer plunge length, and tank diameter studied for up to three different particle size groups (i.e., −250 + 106, −106 + 53 and −53 μm). The recovery of the medium and coarse size particles dropped by 10–15% as the free jet length increased, while that of fines was nearly independent of it. The bias factor negatively affected the recovery of all three size groups almost by same proportion. The effect of the downcomer plunging length on recovery was generally negative, but it was significant only for the coarsest size groups when the plunging length was beyond 50 cm. These negative effects on flotation recovery were mostly attributed to turbulence and its particle size dependent characteristics.     

浮选柱技术的应用现状及发展趋势

相比于传统浮选机,浮选柱具有结构简单、易于调控、浮选效率高等优势,更适于处理品位低、嵌布粒度细、矿物组成复杂的矿石资源,其研究和应用逐渐成为矿物加工领域关注的焦点。介绍了浮选柱的发展历程和分类,重点阐述了各种新型浮选柱CPT浮选柱、Jameson浮选柱、充填型浮选柱、旋流-静态微泡浮选柱、CCF浮选柱、KYZ浮选柱、CFC浮选柱在矿物浮选中的应用现状,通过与浮选机的浮选指标对比,在处理微细粒难选矿物时,浮选柱具有常规浮选机所不可比拟的分选效果;同时归纳了电解浮选技术、磁浮选技术、流态化浮选技术与柱浮选技术结合的代表性浮选设备—磁浮选柱、电解浮选柱、流态化浮选柱等的应用进展;最后,指出了浮选柱的未来研发方向应侧重于自动控制系统的完善、流体动力学数值模拟的研究以及与综合力场的结合等方面。     

Assessing the stirred mill design space

In the context of the mining industry, smaller grain size and other mineralogical characteristics have motivated the need to grind finer. In order to address this need, the interest in fine grinding technologies has grown over the last 20 years as is illustrated by a growing body of knowledge on stirred milling. Emphasis in recent years has been on the use of computationally intensive modeling and simulation methods such as the discrete element method (DEM) and computational fluid dynamics (CFDs). However, due to the computational requirements of these two methods, initiating a study that spans the stirred mill design space would take a lot of computational effort and time. Therefore the goal of this paper is to propose and apply a simplified stirred mill model that will then be used to assess configurations in the stirred mill design space.To this end, a stirred mill model was proposed based on the assumption that the main if not only mechanism of ore breakage is shear. As the basis of this model is the fluid mechanics definition of shear stress, the stirred mill power model became a function of viscosity, mill speed and a new parameter called shear volume. An initial validation using published data indicated the shear based power model correlated well with measured power.Establishing a morphological chart to delimit the stirred mill design space indicated that 24 design and operating conditions can be assess using the established shear volume measure. The results indicated for the mill configurations tested that a change in stirred mill liner design can potentially increase shear volume and power from 14% to 290% as compared to smooth chamber liners.     

细粒矿物浮选技术和高效浮选柱研究进展

在分析细粒矿物浮选特性的基础上,综述了载体浮选、絮凝浮选、生物浮选、综合力场浮选等近年来应用广泛的新型细粒矿物浮选技术,并介绍了Jameson浮选柱、充填式浮选柱、旋流-静态微泡浮选柱这3种高效细粒矿物浮选柱,最后对细粒矿物浮选技术今后的研究方向进行了展望。     

浮选柱在国内金属矿选矿中的研究及应用

浮选柱凭着其结构简单、占地面积小、技术指标好等优点,在国外得到了广泛的应用,而目前国内主要用于煤的浮选,在金属行业中的应用较少。本文介绍了浮选柱在选别国内铜矿、铅锌矿、金矿、铁矿、镍矿、钼矿及其尾矿中的研究及取得的良好效果,指出了浮选柱在国内金属矿选矿中有着广阔的市场前景。     

A review of turbulence measurement techniques for flotation

Flotation is one of the most important primary separation processes in the minerals industry. As far as the mechanism of flotation is concerned, turbulence is one of the key parameters determining flotation performance because it affects three main processes: suspension of particles, air dispersion and particle-bubble collision, attachment and detachment. To study turbulence in industrial flotation cells, both numerical simulation and experimental measurement can be performed. Development of turbulence models and validation of Computational Fluid Dynamic (CFD) numerical simulation need experimental data obtained from turbulence measurement techniques that can be used in the three phase abrasive opaque environment present in a flotation cell. In this paper, the different techniques which have been used to characterise turbulence in the literature are reviewed in terms of their basic principles, system structure, range of application and limitations. Laser Doppler Anemometry (LDA), Particle Image Velocimetry (PIV), Constant Temperature Anemometer (CTA) and the Aeroprobe are all techniques that have been widely used to characterise the turbulence created in flotation machines operating with only fluid (or fluid and air). They cannot however be used when the concentration of solids is high as commonly occurs in a flotation machine. Techniques that have been identified that have the potential to be used to produce accurate measurements in three phase flows include Positron Emission Particle Tracking (PEPT), Piezoelectric Vibration Sensor (PVS) and Electrical Resistance Tomography (ERT). It is envisaged that applications of PEPT in three phase flotation cells will mostly be confined to studies at the laboratory scale. ERT has been tested in flotation cells filled with water and air but needs more development before it can be applied confidently in industrial scale flotation units. PVS, on the other hand, has been validated at laboratory scale and has been applied successfully for measuring turbulence in large scale operating flotation machines.     

Review of hydrodynamics and gas dispersion in flotation cells on South African platinum concentrators

Hydrodynamic and gas dispersion parameters, obtained from industrial flotation cells on South African Platinum concentrators, are reviewed in this paper. Hydrodynamic results show that power intensities are slightly higher than those typically observed in industrial flotation cells while impeller tip speeds and Froude numbers are within the range found in industrial cells. Gas dispersion results show that air flow rates, air flow numbers and air flow velocities vary significantly from cell to cell but are within the range typically found in industrial flotation cells. Gas dispersion results also show reasonably broad variations in bubble size, gas holdup and superficial gas velocity, although bubble surface area fluxes are shown to lie within a fairly narrow range of 50–70/s.     

FJC喷射式浮选机在城郊选煤厂的应用

 介绍了FJC型喷射式浮选机的结构、工作原理和技术特点;对FJC型喷射式浮选机与机械搅拌式浮选机的分选效果进行了比较;介绍了喷射式浮选机的优越性及使用过程中所总结出的几点经验;喷射式浮选机为全厂带来了很大的经济效益和环境效益。