Roughing and cleaning flotation behaviour and the realistic simulation of complete plant performance

Data are presented which illustrate a range of flotation behaviour observed for roughing and cleaning operations in industrial plants. Differences are observed in the size by size recoveries in cleaner flotation from those measured in the roughers.The implications of these differences to flotation modelling are discussed, and the importance of conducting confirmatory laboratory batch flotation tests is emphasized.Batch flotation tests have indicated that for certain minerals the flotation characteristics in the cleaner tests are substantially different from those in rougher tests conducted under the same conditions of pulp level, impeller speed, aeration rate and froth removal. The differences are most pronounced for the coarse particles.Computer simulations of a rougher-cleaner circuit have been done to illustrate the effects of these differences on predicted circuit performance. The differences are significant and arise mainly from differences in the behaviour of coarse particles.     

Flotation and depression control of arsenopyrite through pH and pulp redox potential using xanthate as the collector

The role of pH and pulp redox potential (E_H) to control the flotation and depression of arsenopyrite has been investigated through studies on microflotation of arsenopyrite crystals and batch flotation of an arsenopyritic ore using isopropyl xanthate as collector. The transition between flotation and depression of arsenopyrite is established by the reversible potential of the xanthate/dixanthogen couple. Adsorption of arsenate ions on ferric hydroxide has been studied through electrokinetics to delineate mechanisms involved in the depression of arsenopyrite using oxidants. Chemical binding between arsenate species and ferric hydroxide sites on arsenopyrite is suggested as the mechanism responsible for depression of arsenopyrite. E_H conditions are given for the flotation and depression of arsenopyite at various pH values for the arsenopyritic ore.     

Beneficiation of sillimanite by column flotation—a pilot scale study

A fully automated semi-commercial flotation column incorporating state of the art instruments was designed to study the amenability of flotation column for the beneficiation of different minerals. In the present study, beneficiation of sillimanite was investigated by installing the flotation column in the flotation circuit of Orissa Sands Complex, Indian Rare Earths Limited, Chatrapur, Orissa. The effect of process parameters on sillimanite grade and recovery was investigated. At optimum conditions, the flotation column was operated continuously with a feed rate of one ton per hour and demonstrated the efficiency of the technology for the beneficiation of sillimanite. The results show that a concentrate assaying 96% sillimanite at 90% recovery can be obtained in a single column flotation stage.     

The effect of dextrin on surface properties and the flotation of molybdenite

The effect of dextrin on molybdenite surface properties has been investigated experimentally through measurements of zeta potentials, adsorption densities, contact angles, Hallimond tube flotation and oil flotation response. These studies indicate that the adsorption of dextrin on molybdenite occurs through physical interaction with the surface, possibly due to hydrophobic bonding. The hydrophobic bonding mechanism is in accord with the magnitude of the adsorption free energy, which was estimated to be—5.4 kcal per mole of dextrin monomers. Dextrin was found to be a very effective depressant for the air flotation of molybdenite in the absence of a collector, whereas it does not effectively depress molybdenite in an oil flotation process using iso-octane. This has been discussed qualitatively from the contributions of electrical double layer repulsion, van der Waals' attraction, and hydration effects.     

新型捕收剂RA-92在低品位碳酸锰矿选矿中的应用

微细粒低品位锰矿由于颗粒间的非选择性聚集、浮选药剂用量大、浮选效率低等技术难题而致使其利用困难,造成大量浪费。在品位低于13%的锰矿浮选技术研究中,捕收剂最受关注,前人已研究了多种类型的捕收剂,所得精矿品位在16.9%~18.3%之间,回收率为56%~97%,回收率比较理想,但精矿品位总体不高。本文将新型捕收剂RA-92应用于湖南凤凰-花垣地区低品位碳酸锰矿(锰品位为10.7%)的选矿工艺中,实验研究了磨矿细度、pH值、抑制剂和捕收剂用量对浮选效果的影响,在最佳工艺条件下,精矿品位由原矿的10.7%提升至17.4%,回收率达到80.2%。研究表明RA-92对碳酸锰矿具有良好的捕收性能,浮选工艺相对简单且捕收剂用量少,浮选成本较低,可为此种捕获剂在微细粒低品位碳酸盐锰矿选矿中的应用得到推广。     

The optimisation of flotation networks

The generalised optimisation of a flotation network is studied by means of using variable connections (structural parameters) and variable enhancement factors which are used instead of a flotation model to describe the separation process. The enhancement factors are functions of variables affecting the flotation process. These functional relationship may be derived by means of using a flotation model. Bounds are placed on the enhancement factors by means of either using a flotation model or by inspection of existing pilot or commercial plant data. These bounds, together with external, system and mass balance constraints and an appropriate objective function, define the general optimisation problem for a flotation network.The optimisation problem above may be solved by non-linear programming methods, however, it is easily transformable into a Linear Programme which is easy to solve. The procedure has been applied to a flotation circuit comprising three banks of cells for which an optimal set of connections and enhancement factors has been computed for varying constraints.A simulation procedure based on a gamma flotation model has been applied to one of the optimal circuits so as to compute the flotation variables.     

An analysis of the dynamic characteristics of flotation circuits by time-series analysis

Time-series analysis techniques are used to investigate the dynamic characteristics of the flotation circuits on the Renison tin concentrator in Tasmania. Routine plant-operating data provide information on the variability of feed streams, the disturbances resulting from normal manual operation, the suitability of certain locations for sitting instruments, and some simple time delays in the circuit. It is also shown how plant upsets and abnormal conditions caused by large perturbations to the operation can prove useful in such studies. Finally, a dynamic experiment is described which shows that disturbances higher in frequency than those in the feed are induced in the roughing and scavenging operations, but that these are filtered out again in the cleaner circuit. The uses and limitations of these techniques are discussed.     

Oxidation-Reduction effects in the flotation of chalcocite and cuprite

A laboratory study of the batch flotation of chalcocite from chalcocite-quartz mixtures and of cuprite from cuprite-quartz mixtures with potassium ethyl xanthate as collector has shown that the oxidation-reduction state of the flotation pulp can have a pronounced influence on mineral floatabilities. At pH 11 chalcocite floated over a relatively narrow Eh range of about 300 mV; pH had no influence on the potential of the lower flotation boundary in reducing conditions but had a significant effect on the potential of the upper boundary in oxidizing conditions. Below this upper limit, the floatability was reversible with respect to Eh. Provided the Eh was in correct region chalcocite could be floated in the absence of measurable concentrations of dissolved oxygen.Cuprite displayed a high level of floatability with ethyl xanthate for which, by contrast with chalcocite, no flotation limit in reducing conditions was found; over a small range of potentials close to zero, its behaviour was strongly pH dependent.An attempt to account for the floatabilities of chalcocite and cuprite in terms of the formation of cuprous ethyl xanthate on their surfaces did not lead to correlations with the observed behaviour in reducing conditions but provided a rough correlation with the upper flotation potential limit. It is believed that more detailed and properly controlled comparative flotation studies of the chalcocite-xanthate and cuprite-xanthate systems could help to resolve some of the uncertainties associated with the effects of Eh, pH and oxygen concentration in sulphide mineral flotation.     

Effects of an ultrasonic field on the flotation selectivity of barite from a barite-fluorite-quartz ore

The influence of an ultrasonic field frequency of 22 kHz and intensity of 0.5 W/cm² has been examined on the flotation of barite, fluorite and quartz as well as on their ability to adsorb dodecyl- and cetylsulphates. The tests affected the flotation of pure minerals in a Hallimond tube as well as the flotation of a natural barite-fluorite ore. It has been found that ultrasonic pretreatment of minerals causes an increase in the flotation rate of barite and a decrease in the flotation rate of fluorite. Ultrasonic pretreatment of the natural barite-fluorite ore before its flotation is the most advantageous. In this case it is possible to obtain concentrates of barite composed of a low amount of CaF₂. This may be explained by the different effects of ultrasonic vibrations on barite and fluorite which cause some improvement of the selectivity of their flotation separation.For a full explanation of these results the effects of ultrasonic pretreatment of the minerals on their adsorption properties and surface topography have been investigated, as well as the direct influence of ultrasound on the adsorption process.     

Optimisation of operating variables of fine coal flotation using a combination of modified flotation parameters and statistical techniques

Optimisation of flotation parameters using rate models is not a new concept. The kinetic model based on time recovery data, which uses the extra dimension of rate, has been in vogue since time immemorial for scaling up of lab data. Often, interpretation on the performance of a flotation circuit, based only on R_∞ (the ultimate recovery) and k_s (the first-order rate constant of the component) may lead to wrong conclusions. In such cases, a modified flotation rate constant k_mod defined as the product of R_∞ and k_s, i.e., k_mod=R_∞k_s and selectivity index (SI), defined as the ratio of the modified rate constant of valuables to the modified rate constant of gangue, can be used. An attempt has been made in this paper to optimize the batch laboratory froth flotation parameters of fine coal using the above two concepts, i.e., k_mod and SI and statistical techniques.A flotation bank containing four Outukumpu cells was optimized using the results obtained from the lab study. The airflow number and the froth number were used as a basis for scale up. To gauge the performance of the froth flotation circuit, an efficiency parameter called the coefficient of separation or the CS was used. The yield from the flotation circuit improved, the froth ash reduced and the rejects ash went up.     

Sulphidizing reactions in the flotation of oxidized copper minerals,II. Role of the adsorption and oxidation of sodium sulphide in the flotation of chrysocolla and malachite

The rate of consumption of sulphide in the sulphidizing reactions of malachite and chrysocolla has been measured. The oxidation of sulphide ions at the surface of sulphidized chrysocolla was shown to take place. The influence of thiosulphate anions on the xanthate flotation of sulphidized malachite and chrysocolla was investigated and it was shown to depress the flotation of chrysocolla strongly.The result suggest, that the presence of thiosulphate as a product of simultaneous oxidation can be one of the reasons for the more difficult flotation of sulphidized chrysocolla.     

An appreciation of galena concentration using a steady-state flotation model

A general-purpose computer program has been developed for the steady-state modelling of flotation plants. It permits simulation of flotation banks, made up of any number of cells, interconnected if necessary through a regrind unit. Specification of the fresh feed material in terms of the relative amounts and flotation-rate behaviour of its flotable components is necessary so that the program can then calculate the concentration of these components in all the plant streams.The use of the program for plant investigation is demonstrated using data for a lead concentration plant. The model was fitted to steady-state plant data and then tested by comparing the predictions of the model with actual plant measurements at a second feed condition. Full circuit simulation results are also presented to show how steady-state modelling can be used to give information on the likely response of the plant to other changes in feed material and the benefits which might result from rearrangements of the circuit.     

Adsorption and flotation behavior of manganese dioxide in the presence of octyl hydroxamate

The adsorption of octyl hydroxamate on electrolytic manganese dioxide was investigated through adsorption studies, electrophoretic mobility measurements, infrared spectroscopy and Hallimond tube flotation. The adsorption measurements at room temperature and flotation studies show that a peak in adsorption density and flotation response occurs around pH 9. IR spectra indicate the presence of basic manganous hydroxamate complex at the surface. The electrophoretic mobility studies suggest that hydroxamate adsorbs specifically at the manganese dioxide/water interface. Adsorption measurements at an elevated temperature show that adsorption density increases with increasing temperature. It is postulated that the reactive species in adsorption could be the hydroxamic acid species.     

Influence of adsorbed polysaccharides and polyacrylamides on talc flotation

The adsorption and action of various polymers on talc has been investigated. Two families of polymers (starch-based polysaccharides and synthetic polyacrylamides) with specific molecular weights and functional group chemistry were studied. Adsorption isotherms, acoustophoresis, and contact angle studies enabled polymer adsorption behaviour, adsorbed layer thickness, and the hydrophilicity of the polymer-treated talc surface to be determined. Flotation testing on the treated talc revealed a hierarchy of effectiveness within the group of polymers studied. The observed trends in flotation performance are discussed with reference to the measured polymer layer properties. A 3D correlation plot of adsorbed layer thickness and contact angle against flotation recovery indicates that it may be feasible to predict an order of effectiveness for polymeric depressants based solely on measurements of the adsorbed layer properties, without recourse to flotation testing. This approach would be desirable when screening large numbers of potential depressants.     

A review of spectroscopic techniques applied to the study of interactions between minerals and reagents in flotation systems

This review article discusses the existing and potential applications of a variety of spectroscopic techniques to determine the interactions between minerals and reagents in flotation systems. To date it is found that infrared spectroscopy is the most successful and the relevant data in the literature is critically evaluated. X-ray photo-electron spectroscopy has also been successfully applied to study mineral—reagent interactions. The potential applications of other spectroscopic techniques (Raman, photo-acoustic, nuclear- and electron-spin resonance, Auger electron, secondary-ion mass spectroscopy, etc.) are also discussed in the above context. The low-surface areas of minerals in flotation systems are a major limitation to the use of some spectroscopic techniques in studying the mineral surface. The suite of reagents used in flotation systems often imposes an additional complicating feature in obtaining relevant spectroscopic data about mineral surfaces. Nevertheless, spectroscopic studies used in the above manner, will continue to give a better understanding of the flotation process.     

The effect of particle shape and hydrophobicity in flotation

The effect of particle shape on the flotation process has been investigated in laboratory experiments with monosized spherical ballotini and ground ballotini. The particles were treated by partial methylation with trimethylchlorosilane to achieve varying degrees of hydrophobicity. In flotation, the process of film thinning and liquid drainage is critical in the formation of stable bubble–particle attachments and this is affected by the particle shape and surface hydrophobicity. Flotation tests with different particle sizes were conducted in a modified batch Denver cell. Predictions from a computational fluid dynamic model of the flotation cell that incorporates fundamental aspects of bubble–particle attachment were compared with data from flotation tests. Contact angles of the particles were measured using a capillary rise technique to indicate surface hydrophobicity. Ground ballotini generally has higher flotation rates than spherical ballotini; the results are consistent with effects from faster film thinning and rupture at rough surfaces and are well correlated by the sphericity index.     

Flotation of calcareous Mussorie phosphate ore

Separation of Mussorie rock phosphate (P₂O₅ = 20%) from Uttar Pradesh, India, containing pyrite, calcite and other carbonaceous impurities by flotation has been successfully attempted to upgrade the phosphate values. Based on Hallimond cell flotation results of single and synthetic mineral mixtures of calcite and apatite using oleic acid and potassium phosphate, conditions were obtained for the separation of calcite from apatite which is considered to be the most difficult step in the beneficiation of calcareous phosphates. Further studies using 250 g of the mineral (?60 +150 and ?150 mesh fractions, deslimed) in laboratory size Fagergren subaeration machine employed a stagewise flotation viz. carbonaceous materials using terpineol, pyrite using potassium-ethyl xanthate and calcite using oleic acid respectively. Separation was, however, found to be unsatisfactory in the absence of a depressant.Among starch, hydrofluosilicic acid and dipotassium hydrogen phosphate, which were tried as depressants for apatite in the final flotation stage, dipotassium hydrogen phosphate proved to be superior to others. However, the tests with the above fractions did not yield the required grade. This was possibly due to insufficient liberation of the phosphate mineral from the ore body and different experimental conditions due to scale up operations. Experiments conducted using ?200 mesh deslimed fractions has yielded an acceptable grade of 27.6% P₂O₅ with a recovery of about 60%. The results have been explained in terms of the specific adsorption characteristics of phosphate ions on apatite and the liberation size of the mineral.     

The effect of hydrodynamic conditions on true flotation and entrainment in flotation of a complex sulphide ore

The separation efficiency and selectivity of flotation are directly proportional to recoveries of the mineral species in the feed due to true flotation and entrainment. In this study, effects of the hydrodynamic conditions on true flotation and entrainment were investigated by using a fractional factorial experimental design. A method previously described in the literature was applied to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore. In order to apply the method, the kinetic flotation tests were conducted under various hydrodynamic conditions defined by some physical variables. Some of these tests were conducted in the presence and absence of a collector to evaluate the self-induced floatability. The selectivity index of the mineral species for entrainment was seen to be suitable evaluation of the non-selectivity and efficiency of the entrainment. Furthermore, the results of the size-by-size analysis of the froth products indicated that the presence of the self-induced hydrophobic particles in the feed is as important as the presence of very fine particles for accurate estimation of true flotation and entrainment in flotation of a complex sulphide ore. In addition, the estimated results for entrainment in flotation of the complex sulphide ore can be misleading. Therefore, a new approach would be necessary to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore.     

A laboratory study of the influence of sodium sulphide and oxygen on the collectorless flotation of chalcopyrite

The flotability of chalcopyrite in the absence of conventional collectors and its dependence on the oxidation-reduction state of the system has been determined in batch flotation tests on high-grade mineral both alone and mixed with quartz. It has been concluded that chalcopyrite is not floatable in reducing conditions either in the presence or absence of sodium sulphide but becomes floatable when oxygen is made available. No evidence was found to suggest that chalcopyrite ground in the near absence of oxygen is highly floatable.     

The effect of thermal treatment on the flotation of chrysocolla

Flotation studies using a Hallimond tube have been carried out on purified samples of chrysocolla. The results confirm that by heating the sample to 550°C, flotation of the sulphidized sample with amyl xanthate is considerably improved. Flotation with sodium dodecyl sulphate is also considerably higher. The recovery with cationic collectors is not modified by the thermal treatment.Electrophoretic mobility measurements and flotation studies using benzene instead of air for the collection of the particles suggest that the increase in flotation after thermal treatment is a consequence of (1) an increase in the solubility of copper ions and their adsorption on to the surface of the particles, and (2) an increase of the intrinsic hydrophobicity of the particles due to condensation of some of the free silanol groups on their surface.