Palladium stripping rates in PGM refining

This study investigates the stripping (back-extraction) of palladium from the perspective of mixer–settler hydrodynamics. A hydroxyoxime extractant and hydrochloric acid medium are used. Firstly, the palladium stripping rate (chemistry) is determined using a vigorously stirred laboratory unit cell. This increases with operating temperature and stripping acid concentration. At optimal chemical conditions (25 °C, 6 N HCl), the stripping rate is sufficiently fast for equilibrium to be reached within 5–10 minutes. Secondly, the palladium stripping rate (hydrodynamics) is determined using a pilot-scale mixer–settler. The mixer–settler is operated with a 4-bladed radial disc and a 6-bladed Rushton turbine impeller, over a range of impeller speeds corresponding to power intensities of 2 to 5 kW/m³. The palladium stripping rate increases with increasing impeller speed for both the radial disc and Rushton turbine impellers. The overall mass transfer coefficient also increases with increasing power intensity, up to power intensities 100% higher than those used in typical plant stripping mixer vessels. When benchmarked against the power intensity, not much difference between the two impellers is noted. The study concludes that the stripping of palladium by solvent extraction as used in the PGM industry can be improved by operating at higher power intensities.     

Cold Model Study on Mg Desulfurization of Hot Metal Under Mechanical Stirring

The new method of in-situ desulfurization with mechanical stirring of new type impellers was introduced,in which the bubble′s dispersion and disintegration of magnesium vapor were the key to boosting the desulfurization efficiency and increasing the utilization rate of magnesium.Effects of different new type of impellers on bubble dispersion and disintegration were studied through bubble image analysis,gas-liquid mass transfer,and power consumption levels of different impeller structures.The results showed that the sloped swept-back blade impeller-2produces optimal bubble′s dispersion and disintegration,as well as higher volumetric mass transfer coefficient and CO2gas utilization while consuming the least power.Numerical simulation result with Fluent software also showed that the sloped swept-back blade impeller-2has higher turbulent kinetic energy and better velocity distribution than the other two impellers.     

BROGIM®: A new three-phase mixing system testwork and scale-up

BROGIM® is a mixing concept for bioleach tanks that provides high oxygen transfer performances, by means of an air dispersing flat blade turbine at the bottom, and mixing, with low power-consuming propellers at the upper part of the rotating shaft. Oxygen transfer performances of this system have been firstly determined in a small-scale testwork in an 850-l tank. A pilot-scale study in a 65-m³ tank enabled to define rules for the scaling-up procedure. The paper describes the philosophy for the scale-up of the mixing system installed in industrial tanks of up to 1250 m³ operating volume.At industrial scale, it has been shown that the BROGIM® system exhibits little power differences between gassed and ungassed conditions, for air flowrates up to 24,000 Nm³ h^− 1 comparatively to what was found at smaller scales. The agitator is able to run with or without air with no need for oversizing the power of the electrical driving motor.A procedure for oxygen transfer coefficient (k_la) determination in real conditions has been tested. It is essentially based on gas balance measurement for establishing the oxygen uptake rate and dissolved oxygen measurement at different levels in the tank.     

桨叶形状对KR法脱硫混合行为影响的数值模拟

为了改善KR搅拌法脱硫剂浪费严重的问题，开发3种新型搅拌桨改善铁水和脱硫剂的混合效果。应用CFD技术，以速度场、湍动耗散率和混匀时间为特征，描述液面的卷入能力和内部混合能力。通过对比3种桨形与传统桨形（A桨）的铁水流动结构，分析结构参数和操作参数之间的影响规律。研究结果表明，方形桨（B桨）卷入脱硫剂的能力和改善混合效果强于其他3种桨形，随转速从60r/min增加到80r/min，柱状回转区体积减小60%，死区体积减小67%，混匀时间缩短52%；D桨的下倾角和径向斜边改善了搅拌桨下方死区混合效果，随转速从60r/min增加到80r/min，死区体积减小51%，混匀时间缩短48%；C桨的卷入能力和混合效果介于D桨和B桨之间；A桨效果最差。     

Investigating Factors Affecting on the Efficiency of Dynamic Mixers

Mixers are widely used in chemical and hydrometallurgical processes. For instance, one of the greatest challenges in the field of hydrometallurgy process is agitation made by impeller inside mixers. Solvent extraction is a process for separating components in solution by their distribution between two immiscible liquids. Dynamic mixers are qualified as efficient vessels for mixing in processes accompanied by mass, momentum and heat transfer and chemical reaction. One of the advantages of this type of receptacles is their high productivity. In this study, recent conceptual and technological innovations in various dynamic mixers are reviewed. For this purpose, geometrical, operational, and physical effective parameters in the most important research are investigated. In addition, optimal parameters, drop size measurement, and distribution are discussed. Current industrial applications and efficiency are discussed from a process perspective, focusing on mixing. Considering the development of flow equipment in various flow regimes, advances in this field will play a crucial role in scientific and industrial communities. For design and optimization of the dynamic mixers, some models are used. The model structure is selected based on its good compromise between accuracy and complexity. Validation of the computational fluid dynamics models with experimental data by using progressive methods resulted in realistic simulations. In recent researches, there has been an increasing interest in the development of alternative designs for improvements of key elements, such as geometry of baffles, mixer vessels, impellers, operational parameters of mixers and impellers, etc.     

Pressure leaching of a sulphide copper concentrate with simultaneous regeneration of the leaching agent

An experimental study is presented of leaching of a sulphide copper concentrate with aqueous ferric sulphate under oxygen pressure. The effects of oxygen pressure, sulphuric acid concentration and ferrous iron additions on the copper leaching rate have been determined. Partial pressure of oxygen has been found to govern the rate of copper leaching while the concentration of sulphuric acid only slightly influences this rate. Oxygen enhances the leaching rate mainly by oxidizing ferrous iron to ferric iron — the major leaching agent — and not by direct action on the minerals.Leaching of a sulphide copper concentrate under oxygen pressure with aqueous ferric sulphate leads to a three-fold reduction of both the necessary leaching time and ferric sulphate concentration in the leaching solution over those for conventional leaching with concentrated aqueous ferric sulphate.     

铜渣浸出中镍的浸出行为研究

研究了高冰镍选择性氧化浸出产生的铜湘在常压氧气浸出过程中镍的溶解行为,考查了硫酸浓度、氯化物浓度、氧气流量及温度等参数对其的影响。     

镍精矿加压酸浸新工艺研究

研究了金川镍精矿加压一步全浸镍、钴、铜新工艺,浸出液中和除铜后萃取分离镍钴,镍、钴、铜的浸出率可分别达到99.5%、98%和98%以上。该工艺与硫酸选择性浸出相比具有金属浸出率高、分离彻底、易分别回收等优点。     

Resistance Characteristics of Surface Aerators

The resistance characteristics in terms of power consumption, interpreted in terms of Power number (P0), of unbaffled surface aeration systems consisting of flat bladed impellers, were studied in two shapes of surface aerations tanks: square and circular. Experiments were conducted in three different sizes in each of the geometrically similar unbaffled square and circular surface aerators. Results have shown that the P0 cannot be simulated singularly either with Reynolds number R or with Froude number as there are scale effects; hence there appears to be a need for incorporating the effects of both R and F. It is found that P0 is uniquely related to a parameter X ( = F4/3R1/3), which is defined as a parameter governing the theoretical power per unit volume for both shapes of aeration tanks; however, such relationships are different for both shapes of aerators. Interestingly P0 values are always higher in square surface aerators than in circular surface aerators, which suggests that the circular surface aerators require less power input than the square surface aerators. The usefulness of such correlations was demonstrated in estimating the power requirement while achieving a required oxygen transfer coefficient in surface aerators.     

硫化铜精矿氧压浸出回收电积铜的工艺研究

介绍了几种硫化铜精矿的加压湿法炼铜技术,对于氧化铜矿少的地区,由于一段氧压浸出终酸较高,后续工序的降酸过程复杂,渣带走铜损失大,该工艺有一定局限。两段逆流氧压浸出虽然较好的解决了降酸的问题,但是两段氧压浸出需要采用两个高压釜,设备投资较高,操作更复杂。硫化铜精矿控温氧压平行浸出回收电积铜的工艺在高压釜中段部位增加一个进料口,两个进料口分别加入磨细的精矿矿浆,通过控制前后段不同的浸出温度,同时实现了浸铜和除铁降酸的目的,节省了设备投资。     

氨法浸出电镀废渣中镍铜的工艺

实验采用NH3-NH4+-H2O体系浸出电镀废渣中镍和铜,通过正交试验研究了总氨浓度、氨铵比、液固比、温度、浸出时间对浸出率的影响.结果表明,在总氨浓度为6 mol/L、氨铵比为1∶1、液固比为8∶1、浸出温度80℃、浸出时间3h的最优条件下,镍的浸出率可达到82％,铜的浸出率可达到95％.     

某铜金精矿加压氧化-氰化浸出试验研究

本文对某铜金精矿进行了高温加压氧化—氰化工艺试验研究,探讨了浸出时间、浸出温度、氧分压和初始NaCl浓度等工艺参数对铜浸出率的影响以及后续氰化条件对金银浸出率的影响。结果表明,在综合条件下,即粒度-325目占90%、初始NaCl浓度40 g/L、浸出温度180 ℃、氧分压0.6 MPa、液固比5∶1、浸出时间2.5 h以及搅拌速度750 rpm,在氰化条件：振荡氰化、液固比2∶1、NaCN加入量10 kg/t浸铜渣和氰化时间24 h,金、银、铜的浸出率分别为98.3%、94.7%和99.7%。该铜金精矿采用加压酸浸—氰化提取金银铜工艺具有对3种有价金属回收率高、氧化速度快、对矿石中杂质不敏感及对环境污染小等优点,具有较好的工业化前景。     

Ferrous iron oxidation and uranium extraction by Thiobacillus ferrooxidans

The microbiological oxidation of ferrous iron in batch and continuous systems has been investigated in relation to uranium extraction from a low-grade ore by Thiobacillus ferrooxidans. The influence of the parameters, agitation, and aeration on oxygen saturation concentration, rate of oxygen mass transfer, and rate of ferrous iron oxidation was demonstrated. The kinetic values, Vmax and K were determined using an adapted Monod equation for different dilution rates and initial concentrations of ferrous iron. The power requirements for initial leaching conditions were also calculated. Uranium extraction as high as 68% has been realized during nine days of treatment. Regrinding the leach residue and its subsequent leaching yielded 87% uranium solubilization.     

刚柔组合桨搅拌强化锰矿浸出数值模拟

通过CFD软件对以SO₂气体为还原剂的锰矿浸出过程进行数值模拟,对比刚性单桨、刚性双桨及刚柔组合桨对于气-固-液三相混合强化作用。通过对固相及气相浓度云图分析,比较三种不同结构配置的搅拌反应器对固体颗粒悬浮和气体分散的作用大小,并对搅拌反应器内宏观、介观及其微观混合性能通过轴向和纵向的速度、湍动能及湍动能耗散率进行对比分析。结果表明：刚柔组合桨流场内并未出现颗粒团聚、气体分散不均等现象,并在流场上部对于颗粒悬浮及气体分散作用明显要强于单轴单桨及单轴双桨;刚柔组合桨的宏观、介观及其微观混合性能的表现均优于单轴单桨及单轴双桨。     

Mechanisms and kinetics underlying the oxidation of magnetite in the induration of iron ore pellets

The chemical and transport phenomena that may participate in controlling the oxidation rate of magnetite pellets were examined. Reaction rates were measured under a varying range of conditions including temperature, oxygen partial pressure, and porosity of the pellet. Models based on the initial as well as developing reaction rates were used to explain the experimental findings. In contrast with many experimentally-made agglomerates, all pellet samples were made with a uniform internal structure. Such a condition was a prerequisite to obtaining a meaningful correlation of the experimental data with the theoretical base. A study of the initial reaction rates revealed that two mechanisms were operative in the first stages of pellet oxidation. Up to about 420°C a surface type of chemical reaction was the controlling step, while above 420°C mass transfer through the gaseous boundary layer was the controlling step and dominated the reaction rate. As the reaction developed within the pellet, mass transfer through the gaseous boundary layer as well as that through the product layer became the controlling steps. These mechanisms were studied in the temperature range of from 1000° to 1200°C and the role played by each was found to be a function of the amount of oxidation which had taken place. Formerly with the International Nickel Company, Formerly with the International Nickel Company,     

A methodology for the optimization of wet granulation in a model planetary mixer

This paper investigates a methodology for the optimization of wet granulation processes in planetary mixers. A model formulation was granulated in a planetary mixer (two different bowl sizes). The wet masses were characterized by their bulk density and consistency (as measured by mixer torque rheometry), and the feasibility of scale-up from one mixer bowl to the other was studied using a dimensionless numbers approach for the estimation of the power consumption at the granulation end point. Both bowls gave the same dimensionless power relationships (a relationship between the power number, Reynolds number, Froude number, and bowl fill ratio), which could therefore be used for calculating the power consumption level when the wet mass achieves its target values of density and consistency, i.e., the point at which granulation should be stopped. It was also shown that batches granulated in different conditions (batch size, blade speed) in two planetary mixers, but presenting similar wet mass characteristics (bulk density and consistency) led to dry granules of similar properties: granule size distribution, density, friability, and flow. This work suggests that it is possible to characterize the wet mass by only two parameters which describe the quality of the downstream granules. The scale-up procedure based on the use of dimensionless numbers was found to be applicable to planetary mixers, provided they give one common dimensionless power relationship.     

含铜金精矿沸腾焙烧浸出扩大试验

对焙烧料进行了水一酸浸出铜的试验研究，得到的铜浸出率在８０％以上。对浸出铜渣进行了氰化浸出金的研究，金的氰化浸出率达到了９７％。用０．１８ｍ＾２沸腾炉及１ｍ＾３浸出槽，进行了焙烧及浸出扩大试验，验证了小试结果，得出了可供工业设计的可靠参数与指标。     

某浮选铜精矿中铜、金浸出试验研究

在氯盐酸性体系中,对某浮选铜精矿进行了加压氧化浸铜的试验研究,探讨了温度、氧气分压、硫酸用量、氯化钠用量等对铜精矿中铜、铁浸出的影响。试验结果表明：在氧化温度110℃、氧分压0．45MPa、矿样粒度-0．043mm占85％、硫酸用量90g／L、氯化钠用量30g／L、液固比5／1、浸出时间2、5h、搅拌速度750r／min初始条件下,获得铜浸出率为92．18％。铜浸出渣经摇床重选脱硫,脱硫渣氰化浸金。当浮选精矿铜浸出率达到90％上时,对应渣中金的氰化浸出率都在96％以上。     

Leaching kinetics of copper from natural chalcocite in alkaline Na4EDTA solutions

The leaching behavior of copper from natural chalcocite (Cu₂S) particles in alkaline Na₄EDTA solutions containing oxygen was examined at atmospheric pressure. The EDTA leaching process took place with consecutive reactions, where the solid product of the first reaction, covellite (CuS), became the reactant for the second. The copper leached into the alkaline solutions was immediately consumed by the chelation of copper (II) with EDTA, and the mineral sulfur was completely oxidized to sulfate ion. The experimental data for the leaching rate of copper were analyzed with a familiar shrinking-particle model for reaction control. The conversion rate of chalcocite to covellite was found to be about 10 times as high as the dissolution rate of covellite. The time required for complete dissolution of covellite was directly proportional to the initial particle size and was inversely proportional to the square root of the product of the hydroxide ion concentration and the oxygen partial pressure, but it was independent of the Na4EDTA concentration in the presence of excess Na₄EDTA. The observed effects of the relevant operating variables on the dissolution rate were consistent with a kinetic model for electrochemical reaction control. The kinetic model was developed by applying the Butler-Volmer equation to the electrochemical process, in which the anodic reaction involves the oxidation of covellite to copper (II) ion and sulfate ion and the cathodic reaction involves the reduction of oxygen in alkaline solution. The rate equation allowed us to predict the time required for the complete leaching of copper from chalcocite in the alkaline Na4EDTA solutions.     

A kinetic model for the acid-oxygen pressure leaching of Ni–Cu matte

A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni₃S₂. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O₂ flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O₂ flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase.