The effect of particle size and some operating parameters in the separation tank and the downcomer on the Jameson cell recovery

The aim of this work is to investigate the effect of some operating variables and particle size on the Jameson cell performance. This is done by investigating the effect of varying different parameters such as concentrate flow rate and immersion depth of the downcomer for separation tank recovery, while jet length, jet velocity and holdup within the downcomer are used for downcomer recovery. It was found that altering these parameters play a significant role in recovery of different sized particles. An increase in concentrate flow rate and a decrease in immersion depth result in much more improving effect on recovery as particle size increases. An increase in jet length, jet velocity and holdup results in the recovery improvement for fine particles and loss of recovery for medium/coarse particles.     

射流浮选柱内纵向气泡均匀性的试验研究

在实验室射流浮选柱上进行了纵向气泡分布规律影响因素的试验.利用自制充气量测试仪测定浮选槽内不同深度的充气量,以样本均值和样本变异系数为指标,研究了射流器给料压力、喉管直径、喷嘴直径对浮选槽内充气量及纵向气泡分布均匀性的影响.结果表明：在试验范围内,压力越高,喉管越细,浮选槽内充气量越大,纵向气泡均匀性越好;当压力一定时,大喷嘴气泡均匀性明显好于小喷嘴.通过流体力学初步分析,解释了基本试验现象.     

工业浮选柱的气含率测定及其影响因素研究

气含率是影响浮选柱分选效果的重要参数之一。采用压差法测定浮选柱内部的气含率,并基于直接数字控制(DDC)技术和MCGS组态软件,设计开发了适合于工业浮选柱的气含率测试系统。通过对循环压力、充气量和起泡剂用量3个因素进行试验,研究了它们对工业浮选柱气含率的影响。结果表明:循环压力、充气量和起泡剂用量对气含率影响显著;在一定范围内气含率随着循环压力、充气量和起泡剂用量增大而增大,当增大到一定程度时气含率增大的幅度逐渐减小。     

Study of gas holdup and pressure characteristics in a column flotation cell using coal

Present work has been carried out to observe the effect of process variables (gas flow rate, feed flow rate, solid concentration and frother concentration) on gas holdup and pressure characteristics in flotation column using coal. Gas holdup has been estimated using phase separation method while piezometers have been used to obtain column’s axial pressure profile. It was observed that gas holdup in collection zone was affected by both air as well as feed flow rates. Up to 6% change in gas holdup may occur when the feed flow rate changes from 1–2 cm/s. It was also observed that addition of coal decreased the gas holdup while addition of methyl isobutyl carbinol (MIBC) had opposite effect. Almost linear variation in columns axial pressure characteristics has been observed with gas flow rate. An empirical relationship between gas holdup in the flotation column with column’s axial pressure difference was developed.     

新型柱浮选泡沫自吸输送装置内流特性的数值模拟

采用Fluent软件对叶轮直径450 mm、高度142 mm的吸浆器进行了气液两相数值模拟,研究了气泡直径、叶轮转速和含气率对吸浆器内流特性的影响。结果表明：气泡直径和含气率是影响吸浆器吸浆能力的关键因素,当含气率达45%时,叶片吸力面附近气相回流现象基本消失,但含气率越高,吸浆器的吸浆能力越低;气泡直径越大,叶轮中心区域和叶片吸力面区域含气率越高,聚集在叶轮中心区的气团越大,吸浆器的吸浆能力越低;叶轮转速越高,叶轮内气液分离现象越明显。     

浮选柱气含率及其影响因素对煤泥分选的研究

利用压差法检测浮选柱气含率,通过正交设计和煤泥浮选实验,研究循环压力、进气量和起泡剂浓度对气含率的影响以及气含率对煤泥浮选效果的影响.结果表明,起泡剂浓度对气含率的影响最大,进气量次之,循环压力最小.在一定范围内,随着气含率的增大,精煤产率增大,精煤的灰分也随之增大,精煤质量下降.当气含率为24.17%时,精煤产率为87.35%,精煤灰分为10.02%.随着循环压力增大,精煤产率增大,但精煤灰分有所下降.分析指出气含率大小可作为调节浮选柱矿物分选指标的一个参考标准.     

200m~3充气机械搅拌式浮选机动力学研究

对目前国内单槽容积最大的浮选机——200m~3充气机械搅拌式浮选机进行了动力学研究,主要测量和分析了浮选机在4种叶轮转速、6个充气量水平下的充气量、空气分散度、转速、功率、空气保有量,气泡直径等参数,结果表明,当主轴转速为109r/min,200m~3充气机械搅拌式浮选机动力学测试效果最佳,浮选机性能优良。     

KYF型浮选机气泡特征参数分析与探讨—KYF浮选机流场测试与仿真研究(五)

浮选机内气泡特征参数和流动规律的研究一直是浮选机研究的重点和难点。本文利用电导探针法和CFD数值方法研究了浮选机内气泡特征参数及其分布特性。通过电导探针法获取了浮选机内气泡直径、速度和气含率等气泡特征参数。利用CFD数值方法揭示了浮选机内气含率的分布特征,预测结果同试验观察一致。并进一步研究了浮选机关键运转参数对气含率分布的影响规律。试验结果表明,CFD预测的气含率同试验测试结果吻合。     

高硫高砷金精矿三相流化床流动特征模拟

常温常压条件下基于欧拉模型, 利用Fluent软件对高1.6 m、内径0.09 m的高硫高砷金精矿三相流化床流动特征进行了数值模拟。模拟过程以空气为气相且为连续相, 液态水为液相, 密度为3.2 g/cm3、粒径为0.5 mm的高硫高砷金精颗粒为固相。模拟结果显示, 流场的压力从计算域的入口到出口逐渐降低,速度场的变化对气液固局部相含率的分布影响显著; 在径向上, 气含率(ε_g)从计算域中心往边壁降低, 在轴向上也逐渐降低; 固含率(ε_s)从计算域的入口到出口逐渐减小, 从计算域中心向边壁ε_s增加。模拟结果与实验结果一致, 可为合理设置气流速度以及金矿投放量提供依据。     

GAS holdup and RTD measurement in an industrial flotation cell

In this work, the measurement of the axial gas holdup profile and gas residence time distribution (RTD), in a 130 m³ self-aerated flotation cell, is presented. For this purpose, a radioactive tracer gas was activated in the Nuclear Reactor of the Chilean Commission of Nuclear Energy.The gas tracer, Freon 13B1, was injected as an impulse signal at the gas (air) inlet point, located at the top of the cell, from which the gas tracer circulates first through the rotor, where the bubble dispersion occurs, and then the gas becomes well distributed over the whole cross-sectional area before leaving the cell.The axial gas holdup profile was estimated from the transient gas concentration measurement at different depths inside the cell. From these experiments it was found that the air entering the cell was preferentially distributed in the upper half of the cell, while the gas entrainment into tailings was negligible. The mean gas holdup was 8.8%, and consequently the effective pulp volume of collection zone was 91.2%.The gas concentration on top of froth was recorded for RTD measurement of the gas leaving the cell. It was found that the mean gas residence time was around 42 s and the mixing condition for gas and pulp was similar.     

高压气幕风速的试验研究

高压气幕风速是影响高压气幕隔尘能力的重要因素。通过试验,确定了高压气幕风速与高压气幕的喷孔直径d、喷孔出口风速v0及喷射距离s的关系,建立了高压气幕风速的衰减模型。根据高压气幕风速的衰减模型制作的高压气幕,在现场应用,隔尘率达41%。高压气幕是煤矿综掘工作面综合防尘的有效措施之一。     

Air core formation in the hydrocyclone

Air core formation has been investigated in hydrocyclones operated with clear water and a lucid suspension of glass balls. Hydrocyclones form a central air core which extends over the complete hydrocyclone length. Air is sucked in the core at the underflow discharge. The air core diameter can be determined balancing the positive pressure gradient and the centrifugal force in the rotational flow field. In dense flow separation (high feed solids content) the air core in the conical part of the hydrocyclone is suppressed. The hydrocyclone operates as it is air sealed because the solids are discharged trough the underflow as a rope. Then, air can be introduced to the hydrocyclone only on the feed side. In practice, feed suspension always contains more or less dissolved or dispersed air. Observations in a transparent hydrocyclone show that dissolved gas is released due to the pressure drop inside the hydrocyclone. The generated micro bubbles grow by coalescence and move in the centrifugal field toward the centre, where an air core is formed.     

JJF-130m^3机械搅拌式浮选机动力学研究

对三种转速叶轮、四种浸没深度进行了分析,叶轮线速度为6.6m/s即主轴转速105r/min、浸没深度510mm时,JJF-130m~3机械搅拌式浮选机动力学测试效果最佳。在最佳转速和最佳浸没深度条件下进行了浮选动力学研究,主要测量了吸气量、空气分散度、转速、功率、空气保有量等有关参数,并分析了吸气量与空气分散度、功率、空气保有量的关系,通过分析可以看出JJF-130m~3浮选机性能优良。     

基于CFD的气液两相射流引射器设计模拟研究

文章采用Fluent模拟软件对气液两相引射器的最优尺寸进行了数值模拟研究,并分析了引射压力和出口背压对引射器工况的影响。研究结果表明:引射器内射流喷嘴直径受流场发育情况、压力特性曲线和气相体积浓度等因素的影响和制约,综合考虑这四种因素,确定了喷嘴直径范围为16~20mm;当引射压力一定时,随着出口背压的增大,气相流量、气相浓度和出口流速均逐渐减小;当出口背压一定时,射流气相浓度随引射压力的增大呈逐渐上升趋势。     

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.     

Comparing the effect of salts and frother (MIBC) on gas dispersion and froth properties

The Raglan concentrator (Xstrata Nickel) does not employ frother. It was considered this might be the result of the high salt content in the process water (ca. 30 000 ppm). Two-phase (solution–air) and three-phase (slurry–air) tests were undertaken in a laboratory column to quantify the effect of inorganic ions present in the water (a range of polyvalent ions). The measurements focused on gas dispersion (bubble size and gas holdup) and froth overflow rate. The results were compared to a typical frother (MIBC) system. The two-phase tests revealed reduced bubble size, increased gas holdup and limited froth formation in salt solutions. The gas holdup correlated with ionic strength. At an ionic strength ca. 0.4 (=0.4 M NaCl) the increase in gas holdup was comparable to ca.10 ppm MIBC. In three-phase tests on a sulphide ore, bubble size and froth overflow rate were again comparable between 0.4 M NaCl and 10 ppm MIBC. The observations help explain why the Raglan plant can operate without frother addition.     

基于Fluent的空气射流切削式反循环钻头参数优化

针对黄土地层,提出利用空气代替钻井液的反循环气体喷射技术。但现有技术对反循环气体喷射钻头切削土体的能力没有具体优化讨论。利用fluent软件,优化反循环喷射钻头结构参数,对不同底喷孔直径、底喷孔数量、底喷孔扩大段直径、底喷孔扩大段数量、喷射孔数量5个结构参数进行模拟分析。分析结果表明,在进风流量一定的情况下,增加底喷孔的数量或增大底喷孔的直径会削弱钻头的空气射流切削能力和反循环能力。底喷孔直径为3 mm,底喷孔个数为2个,底喷孔扩大段直径为8 mm,底喷孔扩大段长度为5 mm,内喷孔数量为5个时,反循环喷射钻头喷射能力和反循环能力最优。     

Industrial testing of a gas holdup sensor for flotation systems

The role of gas holdup in flotation has long been discussed but never demonstrated, arguably because a reliable measurement technique has not been available. Work was initiated to develop a gas holdup sensor for industrial operations based on the use of two so-called flow cells for measuring the conductivity of the pulp with and without air. These are the measurements required to estimate gas holdup using Maxwell’s equation that relates conductivity to concentration of a dispersed non-conducting phase (i.e., bubbles) in a continuous liquid phase (pulp in this case). After a series of prototypes a unit robust enough for industrial use that continuously measures and delivers signals easily integrated into a plant PLC system has been developed. This communication describes the working principle along with some construction details. The experience of plant tests, ranging from paper to mineral pulps, and mechanical cells to columns, is reviewed.     

Modelling of entrainment in industrial flotation cells: Water recovery and degree of entrainment

Entrainment in flotation can be considered as a two-step process, including the transfer of the suspended solids in the top of the pulp region just below the pulp–froth interface to the froth phase and the transfer of the entrained particles in the froth phase to the concentrate. Both steps have a strong classification characteristic. The degree of entrainment describes the classification effect of the drainage process in the froth phase. This paper briefly reviews two existing models of degree of entrainment. Experimental data were collected from an Outokumpu 3 m³ tank cell in the Xstrata Mt. Isa Mines copper concentrator. The data are fitted to the models and the effect of cell operating conditions including air rate and froth height on the degree of entrainment is examined on a size-by-size basis. It is found that there is a strong correlation between the entrainment and the water recovery, which is close to linear for the fines. The degree of entrainment decreases with increase in particle size. Within the normal range of cell operating conditions, few particles coarser than 50 μm are recovered by entrainment. In general, the degree of entrainment increases with increase in the air rate and decreases with increase in the froth height. Air rate and froth height strongly interact with each other and affect the entrainment process mainly via changes in the froth retention time, the froth structure and froth properties. As a result, other mechanisms such as entrapment may become important in recovering the coarse entrained particles.     

Dynamic characterization of column flotation process laboratory case study

The objective of metallurgical column control is to achieve the economic optimum combination of concentrate grade and mineral recovery for any given feed. Metal prices and the cost of consumables will dictate the metallurgical concentrate and mineral recovery targets. Furthermore, experience has shown that collection zone height, air holdup and bias water flow rate are key parameters (controlled variables) that affect metallurgical performance. The collection zone height is related, mainly, with the residence time of the particles inside the collection zone, air holdup is correlated to the available surface area of air bubbles and bias water flow rate is an indirect measure of the cleaning action of the froth zone. However, these variables cannot be directly manipulated. Instead, wash water, air and underflow flowrates are the directly manipulated variables [1]. Therefore, if dynamic relationships could be established between the three manipulated variables and the three controlled variables, column metallurgical control may be improved. This study was an attempt to model these relationships using a tool known as System Identification, that includes Transient Analysis.The study consists in experimental tests, transient response analysis and identification of black box type models with cross validation.The experimental work was performed in a pilot scale laboratory flotation column of 3.2 m high by 80 mm of diameter. This flotation column operates in a plant with all the required instrumentation installed. The study considers the operation of the two phase air-water system.