Column Flotation Technologies Research Articles

Improving recovery of iron using column flotation of iron ore slimes

In general, the industrial flowsheets for the beneficiation of itabirite iron ores from the Quadrilátero Ferrífero (Minas Gerais state) in Brazil involves grinding, desliming, magnetic separation and cationic reverse flotation using both mechanical and columns flotation cells. At Brazilian plants, it is estimated that Fe losses generated at the slimes stage range between 8% reaching values higher than 20%. Slimes generated at hydrocyclone containing particle sizes of approximately 99% < 45 μm, 25% > 10 μm, 45% < 5 μm and 15% < 1 μm, 3% of solids by weight and between 35% and 45% of Fe grade. This work aims at evaluating the technical feasibility of concentration of two slimes samples from two different plants in operation at the Quadrilátero Ferrífero using the column flotation technology without prior desliming. Despite the similarity in terms of mineralogy, grade and particle size distribution, the flotation results indicate a very distinct behavior considering similar process conditions, including variables such as collector type and dosage, depressant dosage, pH and circuit configuration. A final concentrate containing an Fe grade higher than 60%, 4% SiO2 and 3.1% Al2O3 with an Fe recovery up to 75% in rougher column flotation can be obtained from Sample 1 with 45.2% Fe, 28.6% SiO2 and 3.1% Al2O3, when a collector type amide-amine (Flotinor 5530) was used in substitution of a conventional amine collector. On the other hand, it was not possible to obtain a final concentrate containing an Fe grade higher than 55% from Sample 2 with 39.6% Fe, 33.4% SiO2 and 5.1% Al2O3, using both types of collector (amide-amine and amine) even when applying different types of column flotation circuits (rougher or rougher/cleaner). Based on literature review and the results obtained in this study, it can be observed the non-existence of a standard solution for an efficient slimes processing in the iron ore industry. Considering flotation as the most suitable technology for the treatment of such type of material, future research should focus on a deep fundamental study of the collector-depressant mechanism interaction with the iron-bearing and gangue minerals, especially in those ores with a high amount of alumina-containing minerals. Considerations about the effect of bubble generator device to flotation columns and its impact on the metallurgical performance are also discuss regarding to application at industrial scale to slimes concentration.

Improved Flotation Recovery and Selectivity of an Ultra-Fine Brazilian Phosphate Ore Using Eriez’ Column Flotation Technology

Eriez Flotation Division recently completed column flotation testing of two igneous phosphate ore samples from the Tres Estradas deposit as part of Aguia Resources’ bankable feasibility study for the greenfield project. Due to fine dissemination of the phosphate and associated grinding requirements, column flotation was selected for the metallurgical test program to address the inherent limitations of fine particle flotation using conventional mechanical flotation cells. Eriez’ column flotation cells with Cavitation-Tube spargers are a commercially-mature and efficient technology for flotation of fine particles that may otherwise not be feasible using conventional flotation machines. Accordingly, continuous column flotation pilot tests were conducted by Eriez on two ultra-fine (212x0 µm) samples of Tres Estradas carbonatite ore (fresh and oxidized) to determine flotation responses and develop an industrial circuit design. Using Eriez’ automated multi-stage column flotation circuit, the fresh carbonatite ore was upgraded from 3.6-4.1% P2O5 to 30-32% P2O5 at a P2O5 recovery of 71-80% using a rougher-scavenger-cleaner-cleaner circuit configuration. Similarly, the oxidized (saprolite) carbonatite ore was upgraded from 10.0-11.5% P2O5 to 32-33% P2O5 at a P2O5 recovery of 85-90% using a rougher-cleaner column circuit configuration. The benefits of Eriez’ column flotation technology realized from this test work include a higher degree of selectivity, increased recovery, and reduced collector dosage as compared to bench-scale mechanical flotation. Specifically, the recovery of fresh carbonatite and oxidized (saprolite) carbonatite ore by column floatation increased 2-3% and 5% respectively, while collector dosage was reduced by 20-40% and the required number of cleaning stages to achieve the target concentrate grade was reduced.

Turbulence Models for Single Phase Flow Simulation of Cyclonic Flotation Columns

Cyclonic fields are important for cyclonic static microbubble flotation columns (FCSMCs), one of the most important developments in column flotation technology, particularly for separation of fine particles, where the internal flow field has enormous influence on flotation performance. PIV (particle image velocimetry) and CFD (computational fluid dynamics) are the most effective methods to study flow fields. However, data is insufficient for FCSMC flow fields and similar cyclonic equipment, with turbulence model simulations producing different views to measured data. This paper employs an endoscope and PIV to measure axial and cross sections for single-phase swirling flow fields in FCSMCs. We then compare various turbulence model simulations (Reynolds stress model (RSM), standard k-ε, realizable k-ε, and RNG (renormalization group) k-ε) to the measured data. The RSM (Reynolds stress model) predicts cyclonic flow field best in flotation columns with 16.22% average relative velocity deviation. Although the realizable k-ε model has less than 30% relative deviation in radial and tangential directions, axial deviations reach 78.11%. Standard k-ε and RNG k-ε models exhibited approximately 40% and 30% radial and tangential deviation, respectively, and cannot be used even for trend predictions for axial velocity. k-ε models are based on isotropic assumptions with semi-empirical formulas summarized from experiments, whereas RSM fundamentally considers laminar flow and Reynolds stress, and hence is more suitable for anisotropic performance. This study will contribute to flotation column and other cyclonic flow field equipment research.

Bubble-Distribution Measurement in a Flotation Column

ABSTRACTWith improvement in mineral processing, column flotation technology has undergone enormous changes, and various flotation columns have emerged in large numbers. In this study, three types of laboratory-scale flotation columns, including countercurrent, cyclone, and jet flow, were designed, and their bubble sizes were measured by using an image-analysis technique. The effect of circulating rates on bubble distribution was discussed. The bubble sizes decreased as the circulating rate increased. The bubble diameters in the countercurrent and jet flow mineralization environments were the maximum and minimum, respectively, when the circulating rate was the same.

Evaluation of Flotation Collectors in Developing Zero Waste Technology for Processing Iron Ore Tailings

Reverse cationic column flotation technology is gaining traction in iron ore processing industry for recovering iron values from iron ore slimes/tailings. Development and selection of appropriate collector suitable to the material to be processed plays vital role in the development of the process/technology. Three cationic collectors which are vegetable oil based, biodegradable and environmental friendly were tested for their efficacy in reducing alumina and silica and improve iron content in the tailings of an operating iron ore washing plant. Selectivity index as defined by Douglas was used as response parameter to measure the efficiency of separation while comparing the performance of these collectors during flotation tests. Sokem 522C proved to be better in comparison to Sokem 701 and Sokem 702 with the highest selectivity index of 20.87. The concentrate generated analyzed 63.30% Fe, 2.20% SiO2 and 2.52% Al2O3 with 69.00% weight recovery and 79.21% Fe recovery from the tailings containing 55.14% Fe, 17.34% SiO2 and 4.04% Al2O3. The concentrate generated is suitable for pellet making due to its attractive granulometry and acceptable levels of alumina content (≤ 2.50%) in it. The tailings generated in this process could be utilised for cement manufacturing and tiles or pavement blocks making.The process developed is ‘zero waste’ while mitigating the environmental issues related to managing tailings in iron ore processing plants.

Effect of cone angles on single-phase flow of a laboratory cyclonic-static micro-bubble flotation column: PIV measurement and CFD simulations

Combination of cyclonic flotation and conventional column flotation is a novel column flotation technology. A cyclonic-static micro bubble flotation column (FCSMC) using this technology significantly improves recovery rate during flotation. However, the mechanism of cyclonic separation still remains black box. This paper presents CFD simulations on single-phase to find how different the reversal cone, a key part in cyclonic flotation unit in FCSMC, can affect the fluid flow, then corresponding mineral processing efficiency. PIV measurement is established for simulations validation. RSM-S turbulent model is used to obtain hydrodynamic characteristics in FCSMC. 38-, 48-, 58-, 68-degree cone angle cases are explored. Results show that three kinds of vortexes exist in a laboratory FCSMC: spiraling-up quasi-free vortex near wall, spiraling-up quasi-forced vortex near column axis and spiraling-down quasi-forced vortex between wall and axis of column. The vortexes are greatly affected by the angle of the reversal cone. In the column flotation unit, diameter and flux of quasi-forced vortex spiraling down increase while quasi-forced vortex spiraling up decreases with the angle increasing from 38° to 68°. Smaller angle generates larger overflow in cyclonic flotation unit. Both tangential velocity and centrifugal intensity in cyclonic flotation unit decrease. Disordered fluid flow in cyclonic flotation unit is generated under too small cone angle, like 38°. Besides, under too large cone angle, like 68°, centrifugal intensity in column flotation unit increases and quasi-forced vortex spiraling up flux in cyclonic flotation unit decreases or disappears. So the separation environment is deteriorated. Among the four degrees, optimal fluid flow of the laboratory cyclonic-static micro bubble flotation column can be maintained under an angle of 48°.

Column versus Mechanical Flotation for Calcareous Phosphate Fines Upgrading

Froth flotation, either conventional or column, has been studied for phosphate upgrading. In this study, a reverse flotation scheme using either mechanical or column flotation was applied for the beneficiation of Al-Jalamid Saudi phosphate ores. It is classified as a sedimentary phosphate with calcite as main impurity (calcareous type). The effects of different operating parameters were evaluated for both conventional and column flotation. A mixture of oleic acid and kerosene is used as a collector, sulfuric acid as pH regulator and sodium sulfate as phosphate depressant. The results of this study revealed that both conventional and column flotation technology can be adopted for this type of ore. A high grade concentrate of 35% P2O5 can be achieved at a high recovery of 95%. Comparing the results of the both techniques indicates the superiority of column at fine sizes. However, the mechanical cells are more suitable at high solid liquid ratios because of good particle dispersion and good mixing in the mechanical cells.

Beneficiation of Saudi phosphate ores by column flotation technology

Phosphoric acid industry is expected to develop in Saudi Arabia in the near future. This is ascribed to the discovery of phosphate in AI-Jalamid area located in the northern region of Saudi Arabia, the availability of sulfur as a by-product from petrochemical industries and the construction of phosphate fertilizers required by the growing agricultural sector. The discovered Saudi phosphate ores are of sedimentary origin with calcite and dolomite as the main impurities. The beneficiation of this type of ores is a key factor for the successful production of phosphoric acid by the wet process. In the present work, a flotation column has been designed and applied in the beneficiation of Al-Jalamid Saudi phosphate ores of the calcareous type by reverse scheme. The significant parameters like superficial gas velocity, slurry feed rate, particle size of processed ore, wash water consumption and collector dosage of flotation process are investigated to achieve the best recovery and quality of the beneficiated ores.The results of this study revealed that column flotation technology is a promising tool for beneficiation of calcareous phosphate ores. A high purity ore of 35% P2O5 can be easily achieved at a high recovery value of 95% starting from a rock contains 25% P2O5, high calcite content (52.7% CaO) and CaO:P2O5 ratio equals 2.1.

Cyclonic flotation column of siliceous phosphate ore

The introduction of cyclonic circulation method is one of the most important developments in column flotation technology in the last years. In this study, effect of a cyclonic flotation column on the flotation performance of a siliceous phosphate ore was evaluated by the experiments on circulation pressures and circulation methods. The feed and flotation products were characterized by size fraction, X-ray diffraction and X-ray fluorescence. The results showed that both of the P2O5 grade and recovery of the concentrate increased with circulation pressure under the condition of cyclonic circulation. Under the optimal circulation pressure 0.24Mpa, Flotation comparison results at different circulation methods showed that the P2O5 recovery for cyclonic circulation reached 86.03%, which was increased by 4.9 percentage points comparing with that of direct flow circulation. The size analysis of the products demonstrated that cyclonic circulation method promoted the recovery of fine particles. Theoretical analysis results show that centrifugal force field can reinforce the mineralization of fine particles as well as decrease the lower limit for efficient flotation.

The Application and Development of Microbubble Column Flotation Technology in China

Since the early 1980s, great progress has been made in microbubble column flotation technology. As one of the important mineral processing methods, the application and development of this technology in China are summarized in this paper from four respects. Firstly, a patented cyclone- static microbubble separation method was proposed to overcome the notable problems mentioned in the previous flotation columns. Secondly, microbuble column flotation was introduced to separate the high ash as well hard-to-separate coal slime generated from dense medium processes. The characteristics of the microbubble column, and the flotation process for fine coal and the high ash coal separation was analyzed. Thirdly, the application of microbubble column flotation in China was detailed introduced, especially the characteristics of series microbubble column flotation equipment, and efficient column type coal slime separation crafts were discussed. The application of microbubble column flotation particularly in low ash content coal preparation, and discarded coal slime processing technology were presented. Finally, microbubble column flotation has been extended to non-coal mineral processing, such as magnetite concentrate upgrading (concentration iron and removing silicon), sulfide copper mine separation, white tungsten flotation, etc., the related research was briefly introduced in this paper as well.

Reverse column flotation of iron ore

The use of column flotation was considered for the “reverse flotation” of iron ore, where the gangue (quartz) was recovered in the froth product. This use of the froth for carrying the gangue mineral rather than carrying the valuable concentrate significantly changes the operational requirements of the column. The objective of this work was to determine which of several column flotation technologies would be most suitable for this type of flotation operation. Studies were carried out using both the Jameson column and the Deister column. Comparative results are presented that show the capabilities of both column types in this application relative to conventional Wemco flotation cells. Columns were demonstrated to have grade-recovery performance superior to what could be achieved with conventional cells. Two-stage flotation with the columns could produce a concentrate that was up to 70.2% Fe at 87.5% iron recovery, compared to 70.4% Fe at only 77.7% iron recovery for four stages of flotation in conventional cells. It was shown to be particularly important to operate the columns to recover a maximum of the quartz gangue into the froth. It was noted that there are often problems in scale-up of laboratory columns to plant scale, because the increase in height and the decrease in the ratio of height to diameter at the larger scale allows more axial mixing and bubble coalescence, both of which degrade the column performance. Horizontal baffling was shown to improve column performance by reducing axial mixing and breaking up large bubbles, and so the use of such baffles in the reverse flotation application was investigated.

Cleaning of Egyptian coal by using column flotation to minimize the environmental pollution : Abdel Khalek, M. A. Afinidad, 2002, 59, (497), 34–38

This work aims to decrease the sulfur content of the Egyptian coal by using column flotation technology to be suitable for various applications. In this study, the column flotation parameters as air flow-rate, wash water,frother dosage and feed rate with its solid percent were studied. A clean coal was obtained containing 1.01% total sulfur with a yield of 82%, from Maghara coal (Sinai-Egypt) which contains 3.3% total sulfur as raw coal.

Cyclo-microbubble Column Flotation of Fine Coal

Cyclo-microbubble flotation column (CMFC) is an advanced column flotation technology for fine coal cleaning developed by China University of Mining and Technology (CUMT). It combines cyclone separation with column flotation to enhance pyritic sulfur rejection and separation efficiency. A specially designed external bubble generator is employed to efficiently precipitate fine bubbles on particle surface. A set of screen plates inside the column produces nearly plug-flow condition, which is preferred for flotation process. The CMFC technology has been successfully employed to recover fine coal from discarded waste ponds and replace conventional mechanical cells. Typical commercial testing results are described and analyzed. The column is very effective in cleaning particles down to 45 μm. Laboratory- and pilot-scale testing of CMFC has also demonstrated that the CMFC process can produce a superclean coal product of 1.5∼1.6% ash content from a 9.8% ash feed.

Development of a carrying-capacity model for column froth flotation

The prediction of carrying capacity for a given flotation technology has been commonly achieved using a simplified expression based on a representative particle size and density of the floatable material. However, this expression was derived with several assumptions and limited data ranges that limits accuracy for all materials and conditions. A new expression has been derived which incorporates the effects of particle size distribution and aeration rate. To evaluate the accuracy of the new expression, laboratory, pilot and full-scale data obtained from treating various US coals using the Jameson Cell have been applied to the model. A statistical analysis reveals that the new model provides significant improvement in the carrying capacity prediction. Based on Jameson Cell data, aeration rates below 1.8 cm/s have a significant impact on the carrying capacity. Particle size distribution, which was not included in the earlier expression, was found to significantly affect the carrying capacity by approximately 35% from a narrow to broad size distribution. An analysis, using the mineral data applied to validate the earlier expression, has shown that the new model can be extended to all other column flotation technologies treating feed material other than coal.

Column flotation studies of Alabama oil shale

Eastern US oil shale contains approximately 10 to 12 gallons of oil per ton and 7 to 10% pyritic sulfur. Physical beneficiation of these low grade shales using froth flotation provides a high grade material that makes extraction of oil more economically attractive. The Alabama oil shale used in the present study contained 16.46% organic carbon and 14.5 gallons of oil per ton as determined by Fischer assay. Liberation size of the kerogen was estimated at 10 µm. ‘Ken-Flote’ column flotation technology provided a high grade concentrate containing as much as 60% organic carbon. However, carbon recovery was about 60%. Carbon recovery was improved to 75–85% while maintaining concentrate grades in excess of 40% carbon by providing longer retention time in the column, which facilitated effective bubble-particle collision and attachment.