FUZZY-BASED MODELING AND CONTROL OF AN INDUSTRIAL FLOTATION COLUMN

In the mineral production industry, separation of valuable from gangue minerals is generally carried out using the flotation process. Mineral recovery into the concentrate and the grade of the concentrate are the main metallurgical parameters of the flotation process. In the present investigation, a fuzzy model was developed to simulate the relationship between the process conditions (i.e., gas velocity, slurry solids %, frother dosage, and frother type) and the metallurgical performance of an industrial flotation column in a copper concentrator in Iran. Afterwards, an intelligent model–based control system was designed to control the process performance at the desired level using fuzzy logic rules. Simulation results show that the developed controller is capable of maintaining the process performance at its target level within a reasonable time.     

Modeling the Relationship between Froth Bubble Size and Flotation Performance Using Image Analysis and Neural Networks

Machine vision technology now offers a viable means of monitoring and control of froth flotation systems. In this study the relationship between process conditions and the surface bubble size as well as the process performance in the batch flotation of a copper sulfide ore is discussed and modeled by neural networks. Flotation experiments are conducted at a wide range of process conditions (i.e., gas flow rate, slurry solids %, frother/collector dosage, and pH) and the froth mean bubble size along with the metallurgical parameters are determined for each run. An adaptive marker based watershed algorithm is successfully developed for segmentation of the froth images and measurement of the bubble size at different conditions. The results show that there is a strong correlation between process conditions and the froth mean bubble size, which is of great importance for control purposes. Even though the metallurgical parameters can be estimated from the froth mean bubble size alone, other froth features (i.e., froth velocity, color, and stability) are required to be measured in order to achieve more accurate predictions of the process performance.     

典型氧化铜铅锌矿物浮选的表面硫化研究进展

近年来随着硫化矿石资源的枯竭,氧化矿石资源的开发利用越来越受到关注。工业上普遍使用硫化浮选来回收氧化铜铅锌矿物资源,硫化是该工艺的关键环节。本文简述了5种典型的氧化矿物,分析了硫化的作用,重点综述了氧化矿物表面硫化机理及其影响因素的研究进展。指出氧化矿物的硫化过程包括化学吸附和化学反应两个阶段,硫离子在矿物表面吸附后,与氧化矿物反应生成金属硫化物层进而活化浮选;矿浆pH与温度、硫化时间、硫化剂用量及其添加方式、金属离子和矿物自身特征等多种因素能显著影响氧化矿物的硫化反应,且各因素之间可能存在交互影响;通过添加某些药剂可以强化氧化矿物的表面硫化,能提高硫化反应的速率与程度,或增大硫化产物的机械强度。分析认为目前表面硫化的一些影响因素及强化硫化的机制仍不清楚,应通过多学科交叉、原位表征技术和计算机模拟等手段加强研究,从而更好地指导生产;同时利用3种手段也是浮选研究的发展方向和必然要求。     

State evaluation of copper flotation process based on transfer learning and a layered and blocked framework

State evaluation is vital to ensure the process operating optimality for copper flotation processes. Specifically, the froth image is the comprehensive embodiment of raw ore properties and process operations, which is one of the key factors to realize condition recognition and state evaluation. Firstly, a feature mosaic technique-based neural network framework is proposed. The input image features are extracted from the different network structures, which can achieve higher precision in condition recognition and state evaluation than a single neural network framework. Then, an improved deep convolutional generative adversarial networks (DCGAN) model based on feature matching and maximize mean discrepancy (MMD) distance is investigated so that the froth images with high similarity, integrity, and balance to the original images can be generated. Therefore, the problem of small image sets and the lack of labelled images for some sub-processes can be solved. Finally, a layered and blocked state evaluation model is constructed based on the improved DCGAN model and transfer learning (TL) so that the state evaluation of the copper flotation process with multiple sub-processes, long process, and small image sets of some sub-processes is solved. The effectiveness of the proposed method is verified through a series of data experiments on a copper flotation industrial process.     

Mechanochemical sulfidization of a mixed oxide-sulphide copper ore by co-grinding with sulfur and its effect on the flotation efficiency

Mechanochemical sulfidization of a mixed sulfide/oxide copper ore by co-grinding with sulfur and additives including Mg(NO₃)₂ and Fe(NO₃)₃ salts and iron, aluminum and magnesium powders was investigated for the first time. Also, the influence of sulfidization during the wet-milling process was examined on the separation efficiency and recovery of copper in detail. The results demonstrated that co-grinding with sulfur solely had the best flotation performance at the value of 0.5 wt.% and it was attributed to the possible existence of S-O bonding on copper oxides surfaces. In addition, adding magnesium nitrate salt, magnesium powder, iron nitrate salt and aluminum powder as additive associated with 0.5 wt% sulfur into ball milling caused the flotation improvement at the amounts of 0.2 wt%, 0.2 wt%, 0.5 wt% and 0.5 wt%, respectively. Also, the effect of grinding time and sulfidization pH with 0.5 wt% sulfur solely was determined and pHs of 7.5 to 8.5 gave the best results. The highest recovery (75.76%) and separation efficiency (63.44%) were achieved at pH of 7.5 and 8.5, respectively.     

Some aspects of the electrochemistry of the flotation of pyrrhotite

The iron sulfide mineral, pyrrhotite (Fe_(1–x)S), has long been known to be more difficult to recover by flotation from alkaline slurries than many other base metal sulfide minerals. This paper summarizes the results of an electrochemical study of the surface reactions that occur during the flotation of nickeliferous pyrrhotite in the recovery of nickel and the platinum group metals. Mixed potential measurements conducted with natural pyrrhotite electrodes in various stages of an operating flotation plant showed that the mineral potential is positive to the equilibrium potential of the xanthate/dixanthogen couple. Similar results were obtained during batch flotation experiments and in synthetic solutions in the laboratory. Cyclic voltammetric and potentiostatic current/time transient experiments were used to investigate the oxidation of pyrrhotite under various conditions. In addition, the reduction of oxygen, the reaction of copper ions and the oxidation of xanthate ions at the mineral surface were investigated. The formation of dixanthogen on pyrrhotite surfaces is thermodynamically favourable in plant flotation slurries. However the interaction with xanthate at pH values above 7 is inhibited by a surface species formed during the conditioning prior to xanthate addition. In acidic solutions copper ions react readily with pyrrhotite to form a species, possibly CuS that can be oxidized at potentials above 0.4 V. At pH 9 this species does not form and there is no electrochemical reaction between pyrrhotite and copper ions. The beneficial effects of copper ions to flotation performance appear to be related to an enhancement of the oxidation of xanthate.     

Cu2+对磁化蒸馏水改善辉钼矿浮选效果的影响

通过单矿物浮选实验、Zeta电位测试及X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和能谱(EDS)分析，研究了Cu2+对磁化蒸馏水改善辉钼矿浮选效果的影响。结果表明，用磁化蒸馏水浮选时，在煤油用量160 mg/L及2＃油用量80 mg/L的条件下，Cu2+浓度为320 mg/L时辉钼矿回收率可达83.06%，比Cu2+浓度为0时的回收率增加了3.14个百分点，Cu2+对磁化蒸馏水改善辉钼矿浮选效果的影响较小。Cu2+和Cu(OH)+吸附在辉钼矿表面使其Zeta电位正向增大，有利于煤油在辉钼矿表面的吸附。辉钼矿表面上吸附的Cu2+和Cu(OH)+与溶液中的MoO42?反应生成CuMoO4沉淀并覆盖在辉钼矿断裂面上，抑制了辉钼矿断裂面中钼元素和硫元素的氧化反应及氧化钼溶解，最终对磁化蒸馏水改善辉钼矿浮选效果有积极影响。     

基于AHP的某氧化铜矿选矿流程决策

针对四川某难选氧化铜矿,在进行初步研究基础上拟定了五种不同浮选流程.浮选流程的选择需要综合考虑回收率、品位和产率三个指标,这些因素的重要性难以精确区分界定.在此背景下,将层次分析法(AHP)用于选矿指标评价,得到可量化的评价指标,以此来确定最佳浮选流程.采用层次分析法分别建立精矿和尾矿的层次分析模型,定性定量的确定回收率、品位和产率的权重进行分析,最后综合总目标排序进行分析评价.研究结果表明,精矿模型和尾矿模型在优先考虑回收率或者品位的情况下,均选择流程五为最佳浮选工艺流程,与结合经验判断结果一致,验证了层次分析法用于选矿流程决策的可行性,增强了决策的准确性.     

Complexes Formed by Quaternary Ammonium Salts with Xanthates,and Synergistic Effects in Adsorption of Xanthate Ions on Reduced Copper Powders

Abstract

Precipitates formed in equimolar solutions of long chain xanthates and alkyl trimethyl ammonium bromides (C _n TAB) have been analyzed by chemical, X-ray diffraction, and infrared spectroscopic methods and were found to consist of a 1:1 complex of long-chain anions and cations. It is inferred that analogous ion-pair complexes, but in a solubilized form, exist in mixed solutions of shorter chain compounds, e.g., potassium ethyl xanthate (KEtX) and C₁₂TAB. Tests showed that a reduced copper surface adsorbs xanthate ions from such mixed solutions under anaerobic conditions when no adsorption of uncomplexed xanthate ion is possible. In the temperature range 4 to 20°C, an Arrhenius activation energy of 22.6 kcal/mole was evaluated for adsorption from equimolar solutions KEtX and C₁₂TAB. Characteristic changes in the behavior of xanthate due to its complexing with C _n TAB may have important applications in separation of solids by flotation, particularly under oxygen-deficient or reducing conditions, i.e., when normally flotation with xanthate ions is impossible, owing to their inability to adsorb under anaerobic condition.     

响应曲面法优化氧化铜渣浮选提铜工艺

江西某炼铜炉渣含铜量高,具有较高的经济价值。由于该铜渣中铜矿物以氧化矿为主,且硫化矿表面被氧化,直接浮选铜回收率低、经济效益差。通过添加活化剂,活化氧化铜矿物,并利用响应曲面中心复合设计原理对浮选工艺条件进行优化,研究氧化钙、硫化钠、Z-200对浮选效果的响应。结果表明,Z-200用量是影响精矿品位和回收率的主要因素,且各响应因素间存在交互效应,在CaO用量为25 g/t,Na₂S用量为500 g/t,Z-200用量为100 g/t的最优条件下,闭路试验获得精矿平均品位12%,精矿铜回收率为86.57%,采用该浮选优化工艺能获得较好的回收效果。     

Implication of the microstructure of binary Cu/ZnO catalysts for their catalytic activity in methanol synthesis

Binary Cu/ZnO catalysts with varying molar ratios (90/10 through 10/90) were studied under methanol synthesis conditions at 493 K and at atmospheric pressure. The methanol synthesis activity of the catalysts was correlated to their specific Cu surface area (N₂O reactive frontal chromatography, N₂O RFC) after reduction in 2 vol% H₂ at 513 K. Activity data were supplemented with a detailed analysis of the microstructure, i.e., crystallite size and strain of the reduced Cu and the ZnO phases after reduction using X-ray diffraction line profile analysis. The estimated copper surface area based on a spherical shape of the copper crystallites is in good agreement with data determined by N₂O RFC. A positive correlation of the turnover frequency for methanol production with the observed microstrain of copper in the Cu/ZnO system was found. The results indicate a mutual structural interaction of both components (copper and zinc oxide) in the sense that strained copper particles are stabilized by the unstrained state of the zinc oxide microcrystallites. The observed structural deformation of ZnO in samples with higher Cu loading can originate, for instance, from epitaxial bonding of the oxide lattice to the copper metal, insufficient reduction or residual carbonate due to incomplete thermal decomposition during reduction. Additional EXAFS measurements at the Cu K and the Zn K edge show that about 5% ZnO are dissolved in the CuO matrix of the calcined precursors. Furthermore, it is shown that the microstructural changes (e.g., size and strain) of copper can be traced back to the phase composition of the corresponding hydroxycarbonate precursors.     

FEASIBILITY STUDY ON USE OF PREDISPERSED SOLVENT EXTRACTION/ FLOTATION TECHNIQUES FOR REMOVAL OF ORGANICS FROM WASTEWATERS

The objective of this study was to consider the feasibility of using a predispersed solvent (decane) extraction/flotation process, involving a very low solvent/feed ratio, to remove dissolved hazardous organics, e.g. ortho dichlorobenzene from wastewaters. Procedures have been established for formulating and characterizing these predispersed solvents (polyaphrons) produced and for evaluating performance in extraction/flotation studies. Extraction/flotation using selected ca. 15 micron diameter polyaphrons in conventional mixer/separator with typical short hold-up times were 5 to 10 times more effective in removing ortho dichlorobenzene from water (less than 1/500 solvent to feed ratio) than with identical tests using a similar quantity of straight solvent. Initial results look encouraging, but further process evaluation of various applications will be required to assess the potential for this new separations process.     

FEASIBILITY STUDY ON USE OF PREDISPERSED SOLVENT EXTRACTION/ FLOTATION TECHNIQUES FOR REMOVAL OF ORGANICS FROM WASTEWATERS

The objective of this study was to consider the feasibility of using a predispersed solvent (decane) extraction/flotation process, involving a very low solvent/feed ratio, to remove dissolved hazardous organics, e.g. ortho dichlorobenzene from wastewaters. Procedures have been established for formulating and characterizing these predispersed solvents (polyaphrons) produced and for evaluating performance in extraction/flotation studies. Extraction/flotation using selected ca. 15 micron diameter polyaphrons in conventional mixer/separator with typical short hold-up times were 5 to 10 times more effective in removing ortho dichlorobenzene from water (less than 1/500 solvent to feed ratio) than with identical tests using a similar quantity of straight solvent. Initial results look encouraging, but further process evaluation of various applications will be required to assess the potential for this new separations process.     

Removal of toxic metal ions from aqueous systems by biosorptive flotation

Biosorptive flotation was used as a combined operation for the simultaneous abstraction of nickel, copper and zinc ions from aqueous streams. Laboratory‐scale batch experiments, as well as pilot‐scale continuous experiments, have been conducted. Grape stalks, a by‐product of the winery industry, were used as sorbent material. The experimental procedure consisted of two consecutive stages: (i) biosorption, and (ii) flotation. The possibility of reusing biomass, after appropriate elution, was also examined. The main parameters examined were biomass concentration, particle size of sorbent, surfactant concentration, pH and flocculation. Flotation removals, following laboratory‐scale experiments, were found to be in the order of 100, 85 and 70% for copper, zinc and nickel, respectively. In pilot‐scale experiments, biomass sorption capacities were determined as 25 for copper, 81 for zinc and 7 µmol dm^?3 for nickel. The order of biomass affinity regarding the studied metals was Cu > Zn > Ni. Short retention time and high effectiveness suggest that biosorptive flotation is a promising treatment process for the removal of toxic metals from contaminated aqueous solutions. © 2002 Society of Chemical Industry     

Bioremoval of Metal Ion and Water Treatment in a Hybrid Unit

Abstract

Several biomass types, such as yeast (in the present Saccharomyces, a brewery waste), have been reported to remove heavy metals (i.e., zinc) from aqueous solution. The separation of metal-loaded biomass and hence, the production of a clean water stream using a hybrid flotation-microfiltration unit were investigated. The hybrid cell consisted of a microfiltration module submerged directly into a flotation cell. Air bubbling, constituting the transport medium during flotation, meanwhile has been used in order to limit the membranes fouling. The effects of air sparging, the solid particle content, and the type and concentration of flotation reagents on the performance of the hybrid process were the main examined parameters.     

CFD-PBM simulation of the column flotation unit of FCMC: Importance of gas–liquid interphase forces models

The cyclonic micro-bubble flotation column (FCMC) is an efficient flotation device for the separation of fine minerals, but its mechanisms are rarely studied using computational fluid dynamics (CFD). This paper reports the air–water two-phase computational fluid dynamics-population balance model (CFD-PBM) simulations for the column flotation unit of an FCMC. The shear stress transport (SST) k-ω model with curvature correction (CC) is used to simulate turbulence effects. Then, the interphase forces models considering bubble size distribution are selected according to the experimental data in a bubble column, which is in analogy to the column flotation unit of the FCMC. Finally, the optimal combination of interphase forces models (i.e., the Ishii–Zuber drag force model, the Hosokawa–Frank wall lubrication force model, and the Lopez de Bertodano turbulent dispersion force model) is applied to simulate an FCMC with a superficial gas velocity of 0.0144 m/s. The results show that the CFD-PBM simulation can achieve a relative error of 9.09% for gas volume fraction and −5.45% for bubble rising velocity, indicating the reliability of the selected combination of interphase forces models.     

制备条件对Cu/Al2O3 选择性催化还原NO的影响研究

考察了制备方法、活性组分负载量和焙烧温度对Cu/Al₂O₃ 选择性催化还原NO的影响。结果表明，采用溶胶-凝胶+浸渍法制备的Cu/Al₂O₃催化剂活性最好；负载Cu质量分数为15%时，催化剂的活性温域最宽，最大活性温度最低，催化活性最好；最佳焙烧温度为750 ℃。     

Simultaneous Removal of Algae and Their Secondary Algal Metabolites from Water by Hybrid System of DAF and PAC Adsorption

Abstract

The feasibility of a hybrid system consisting of powdered activated carbon (PAC) adsorption and dissolved air flotation (DAF) processes was examined for the simultaneous removal of algae (anabaena and mycrocystis) and their secondary algal metabolites (2‐methylisoboneol and geosmin). Before studying the hybrid system, adsorption equilibrium and kinetics of organics (2‐methylisoboneol and geosmin) produced from algae on three powdered activated carbons (wood‐based, coal‐based, coconut‐based) were studied. The flotation efficiency of algae and PAC in DAF process was evaluated with zeta potential measurements. Interestingly, we found that the agglomerate of bubble and PAC particle can be successfully floated by DAF. In addition, the simultaneous removal of algae and organics (i.e., secondary algal metabolites) dissolved in water can be achieved by using the hybrid system of adsorption/DAF processes.     

含铜磁黄铁矿的选矿研究

在对江西某含铜磁黄铁矿的选矿研究中采用了全浮和磁－浮两种工艺。全浮工艺获得硫精矿品位３５．５６％，收率９０．０８％，铜精矿品位１７．８５％、收率７２．８４％。磁－浮联合工艺获得硫精矿品位３４．２％、收率９４．５％，铜精矿品位１８．９８％、收率５６．１０％。全浮用药量较磁一浮工艺高，但耗水量小。全浮工艺的铜回收率较高。两种工艺均能获得较好的选矿指标。     

某铜矿选矿实验研究

为了开发某铜矿资源,对其进行了可行性实验研究.根据矿石物相分析结果,采用硫化铜与氧化铜混合浮选工艺,并选用新型高效浮选药剂,可获得铜精品位20.29%,收率70.68%的铜精矿.