Flotation Machine Research Articles

Editorial for Special Issue “Hydrodynamics and Gas Dispersion in Flotation”

Gas dispersion, the breakage of a mass of gas into a population of small bubbles, is one of the most important subprocesses occurring in flotation machines [...]

Oily wastewater treatment and reuse technology in low permeability oilfield

This paper takes Ordos Huaqing ultra-low permeability oilfield as the research object, analyzes the composition of the produced oily wastewater, and uses the treatment process of multiphase air flotation to shell filtration to quartz sand filtration to multi-effect evaporation to reuse the oily wastewater in the oilfield, analyzes the index changes of the purified oily wastewater. The results show that it has high oil content, salinity, sulfide, SS, sulfide and iron and manganese content. Through experimental combination and analysis of effluent quality, it is concluded that the process of multiphase air flotation→shell filtration→sand filtration→low temperature multi-effect evaporation is better, The average salinity of sewage in Huaqing oilfield used in the experiment is 2757 mg/L. and the dosage of polyaluminum chloride is 230 mg/L, polyacrylamide is 6 mg/L, the dissolved gas pressure of multiphase air flotation machine is 0.5 MPa, the reflux ratio of multiphase air flotation machine is 0.3, the dosage of defoamer is 5 mg/L, and the pH value is set at 5.5. The best treatment process of oilfield sewage and the best concentration of polyaluminum chloride and polyacrylamide are obtained. The research results provide theoretical data support for improving the treatment and reuse of oily wastewater in low permeability oilfield.

Hydrodynamics of fluidized bed flotation column with a homogeneous binary mixture of steel balls

The hydrodynamics of flotation machines can significantly impact the flotation performance of fine minerals, however, those of fluidized bed flotation columns with binary particles remain poorly understood. This paper investigated the hydrodynamics of fluidized bed flotation columns such as bed pressure drop, minimum fluidization velocity, bed expansion ratio, and gas holdup. The effect of liquid velocity, gas velocity, and particle size on hydrodynamics was discussed. The hydrodynamics of fluidized beds with binary particles was compared with that of unitary particles. Results showed that the hydrodynamics of the fluidized bed with binary particles lay between the fluidized bed with large and small particles as influenced by the combination of large and small particles. A fluidized bed flotation column with binary particles demonstrates great potential in changing hydrodynamics.

Improving the technology of extracting coal concentrate from fly ash from thermal power plants

Purpose. Study on the possibility of extracting coal underfire particles from the ash of the thermal power station by flotation. Intensification of the enrichment process of coal particles, development of a mathematical model for forecasting indicators of the ash function. Methodology. The method of fractional flotation was used to study the kinetics of the process of extraction of the valuable component. The technique of the planned experiment was applied, including the central composite rotatable plan of the second order for four factors affecting the ash content of the coal concentrate. Findings. According to fractional analysis, the concentration limit of coal particles was determined. During the flotation of fly ash, the best results were obtained on the EFM ejector type flotation machine, the yield of the foam product was 18.6 % with an ash content of 25.1 %, compared to the MFU mechanical type flotation machine, where the ash content of the foam product was 36.5 % with an average yield of 21.1 %. The optimal consumption of reagents at the level of no more than 3,500 g/t of the collector and foaming agent up to 250 g/t was determined experimentally, and the required flotation time was determined. Calculations were performed to determine regression coefficients and the degree of influence of factors on the flotation process. A mathematical model of the flotation process of TPP ash removal was determined, which characterizes the influence of the main factors. The graphs of the significance of the factors and the three-dimensional surface of the calculated response function were drawn up. Originality. The degree of influence of factors such as pulp pressure in the feed pipeline, collector consumption, foaming agent consumption, and flotation time on the process of beneficiation of TPP ash on the EFM ejector type flotation machine was determined. Practical value. The complex model makes it possible to predict the final indicators of the response function, namely the ash content of the secondary coal concentrate. The results will make it possible to improve the parameters of technological processes for the enrichment of TPP ashes.

Energy Saving and Emission Reduction Potential Evaluation of a Coal Mine Based on Fuzzy Hierarchical Analysis

Due to the non-renewability of coal resources and the effect of excessive resource loss on the economic development of enterprises forming a constraint, breakthroughs in high energy consumption to achieve energy saving and emission reduction in coal mines represent an important way to promote the development of coal enterprises. This paper takes the energy-saving work of the Wuyang coal mine, which is very representative of China’s Shanxi Province, as an example, and uses hierarchical analysis to establish an assessment system for energy conservation and emission reduction in coal mines. We adopted on-site research, expert scoring, and project guidance to divide the factors affecting energy conservation and emission reduction in the Wuyang coal mine into 24 categories, and we then used fuzzy mathematical calculations to assess potential, which is of better practicability. The study shows that the grade of energy saving and emission reduction in the Wuyang coal mine is of a medium level, and the potential of energy saving and emission reduction is large. The main influencing factors are improving the recovery rate of refined coal, renovating pressurized filters, eliminating high-energy-consuming equipment, optimizing the parking process, replacing the flotation machine, and ensuring the intelligent management of power metering. According to the relevant factors derived from the energy-saving and emission reduction work at the Wuyang coal mine for implementing the relevant measures, we provide a reference for the work of energy saving and emission reduction in mines in order to promote the sustainable development of the coal mining industry.

Investigating the Amenability of a PGM-Bearing Ore to Coarse Particle Flotation

Coarse particle flotation (CPF) is one of the strategies employed to reduce energy consumption in mineral-processing circuits. HydrofloatTM (HF) technology has been successfully applied in the coarse flotation of industrial minerals and sulphide middlings. However, this technology has not yet been applied in platinum group minerals (PGMs)’ flotation. In this paper, the amenability of platinum group minerals to CPF was investigated. Extensive flotation testwork was conducted to optimise the hydrodynamic parameters, i.e., bed level, air and water flow rates, in the flotation of coarse PGM feed using Hydrofloat. Mineralogical analysis of the feed and selected flotation products was conducted to understand the reasons for the recovery and loss of the valuable minerals. The results showed that the HF separator could upgrade the PGM ore with particles as coarse as +106 − 300 µm. For the optimised test, a reasonable Pt, Pd and Au recovery of 84% was achieved at a grade of 10 g/t and 16.5% mass pull, despite the platinum group minerals being poorly liberated (4.5 vol% fully liberated). The results demonstrated that HF achieved high recovery efficiencies across the 150–300 microns size fraction. The HF was therefore able to substantially increase the upper particle size that can be successfully treated by flotation in PGM operations. It was found that an increase in bed height, water rate and air flow rate resulted in an increase in recovery to a maximum. A further increase in the hydrodynamic parameters resulted in a decline in recovery. Hydrofloat outperformed the conventional Denver flotation machine across the following size fractions: +106 − 150 µm, +150 − 212 µm, +212 − 250 µm and +250 − 300 µm. The practical implications of the findings on the modification of existing circuits and the design of novel flowsheets for the processing of PGM ores with less water and energy consumption are discussed.

Engineering Fundamentals of Flotation Technology for Cleaning Wash Water Generated During Waste Treatment

The process of washing plastic wastes, namely polyethylene film and subsequent treatment of washing water by flotation is considered . The technological scheme for wastewater treatment forming after washing plastic wastes was proposed. The effectiveness of the proposed scheme was tested in the laboratory. A four-chamber mechanical flotation machine for washing plastic waste has been developed, as well as a column flotation tank for post-treatment of greasy wastewater for use in industrial practice.

Влияние сульфата железа, сернистого натрия и их смеси на флотацию сфалерита в щелочной среде

Introduction. The quality of the enrichment process is affected by many factors, ranging from the characteristics of the raw materials supplied to the enrichment plant to the enrichment technology and the agents used. Strict process control is required at all stages from mining to concentrate extraction. Copper-zinc ores of Russian deposits are difficult for enrichment due to high mass fraction of pyrite in ore and fine irregular intergrowth of sulfide minerals between themselves and with rock minerals. The practice of enrichment of copper-zinc ores has established that it is impossible to obtain high-quality zinc and pyrite concentrates without adding sphalerite flotation modifier agents to various flotation operations. To improve the flotation activity of sphalerite, copper sulphate is used as an activation additive in the enrichment process chain. Purpose of work. To study the effect of sulfhydryl collectors on flotation of sulfide minerals, and development of innovative technologies of flotation of copper-zinc and polymetallic ores considering the acidity of the environment. Materials and methods. In the experimental part of the work, several methods of materials and agents preparing were used, a variety of equipment was used, as well as methods of analysis and processing of results. The material composition and grain size distribution of sphalerite was studied using the MLA System Quanta. X-ray phase analysis of sphalerite was carried out at the University of science and technology "MISIS" in Research Laboratory of ultra-hard materials on Rigaku Geigerflex device using monochromatized CuKα-radiation. Thermographic studies were carried out using a Q -1500D derivatograph. The following flotation agents were used in the work: collector - butyl potassium xanthate, foam agent MIBC, medium regulator - lime, modifiers - iron sulfate, sodium sulphide and mixture of iron sulfate and sodium sulphide. Flotation experiments were carried out on the laboratory flotation machine FL-189 G. Results. The kinetics of sphalerite flotation is characterized not by a single value of the flotation kinetics constant for all flotation mineral grains, but by a set of such values corresponding to quite certain fractions of sphalerite extracted in the foams product. It has been found that in the initial period of flotation the mineral grains with a high value of the flotation velocity constant are flotated, and in the final period of flotation the grains of the same mineral with a low value of the same flotation velocity constant are flotated. Discussion. The introduction of iron (II) sulphate into the mineral slurry leads to a redistribution of the flocculated mineral between medium and lightly flocculated fractions. This indicates that iron (II) sulphate acts as an activator for sphalerite flotation. At a low flow rate of this agent, the proportion of medium flotable fractions increases and the proportion of easily and hardly flotable fractions decreases. With increase in the agent consumption up to 400 g/t and more, the opposite picture is observed - the proportion of medium flotable fraction decreases and the proportion of easily flotable fraction increases in flocculated sphalerite. The replacement of iron (II) sulphate by sodium sulphate has the opposite effect on the flotation spectrum of sphalerite. The introduction of a mineral suspension of a solution of sodium sulfide and iron (II) sulfate into the liquid phase at a consumption of 200 g/t of each agent leads to a decrease in the proportion of easily and especially medium floatable fractions of the mineral and an increase in the proportion of difficultly floatable fractions. Conclusions: 1. An increase in the pH of pulp liquid phase leads to a decrease in the extraction of zinc concentrate in the foam product during flotation with butyl xanthate. 2. The introduction of a solution of sodium sulfide with ferrous sulfate reduces the floatability of the mineral, which is reflected in a decrease in the extraction of zinc concentrate. 3. Sodium sulfide and iron sulphate, while simultaneously dosing them into the flotation pulp, act as depressants in the sphalerite flotation process. 4. Sodium sulfide depresses sphalerite at all studied pH concentrations. Resume. The results of the research can be useful in improving the methods for processing sulfide ores (lead-zinc and copper-zinc) which are included in the group of polymetallic ores. The developed methods of flotation processing make it possible to improve the quality of enrichment and increase the extraction of a valuable component.

Studi Pengaruh Titik Penambahan Sodium Isobutyl Xanthate (SIBX) dan Kecepatan Impeller pada Performa Flotasi Mineral Tembaga

Evaluation of the use of the SIBX addition point and energy consumption in a flotation machine is an optimization effort to increase recovery in a valuable mineral separation process. The purpose of this study was to maximize the use of reagents and energy consumption in flotation machines by looking for the effect of the SIBX addition point and impeller speed variations on copper recovery. In the experiments, the authors vary the impeller speed and the SIBX addition points. The impeller speed is varied into five different speeds. While the SIBX addition point into four different points. From the variation of the experiment, the test must be done within 20 flotation kinetics. Those tests were performed for 8 minutes and will generate 4 concentrates and tailings. From this information, a graph of the relationship between recovery and time is obtained, and it can be seen that the point of adding SIBX and impeller speed is to produce optimal recovery values. From the available tailings and feed, an analysis of particle size and distribution is also carried out to check the effectiveness of changing the impeller speed pattern to provide kinetic energy for particles of various sizes to collide with air bubbles and increase the probability of collection of valuable minerals, so that high recovery is obtained in various areas. particle size. Of all the speed variations used in the impeller, the best kinetic recovery comes from the addition of SBX in the 0 min, 2 min, and 4 min. While the worst comes from the addition in the 6 min. Copper kinetic recovery is only affected by the nature and amount of hydrophobic particles but is not affected by impeller speed. Copper recovery at each end of the experiment showed the same value which is an average of about 94%.

Разработка и настройка алгоритма программной идентификации отклонений в пенном слое калийной флотомашины

The article deals with the problems that arise in the practical application of the method of glare recognition of the parameters of the froth layer of a potash ore flotation machine. These include choosing the best statistical characteristic, filtering and averaging settings, checking the possibility of taking into account anti-glare, and the need for adaptive signal renormalization. Objective of the study is to develop an algorithm for identifying a flotation cell as an object of automatic control, which is possible only after solving these problems. Materials and methods of research. The study was carried out on the materials of an experimental survey of a potash flotation machine. During the shooting, a standard step signal was applied to the machine cell, which was expressed in a change in the composition of the amino-oil mixture, which caused a transient process. For different statistical characteristics (the number of bubbles, the number of red components in the frame, the average and median distances between the centers of the bubbles), various methods of filtering and averaging the data were tested. At the same time, the problem of identifying the gain and the time constant of the object was solved. The best characteristic and methods of its processing were chosen on the basis of the root-mean-square deviation of the calculated transient process from field data obtained by glare recognition of the foam layer surface. Results. Processing several frames in a row, taken at the same position of the foam, slightly improves the result, but significantly loads computing power. Blind filtering by ten points has practically no effect on the data processing time. To improve the identification, data renormalization was used, which consists in the adaptive selection of the zero and single signals in the conditions of noisy data. The localization method was used to determine the optimal delay from the point of view of the quadratic deviation before the start of the transient process. Conclusion. As a result, the best filtering and data averaging settings were obtained, providing the smallest identification error. The time constant of the cell turned out to be close to the results of previous authors, obtained, among other things, by visual observation of the flotation machine. Accounting for antiglare does not significantly affect the parameters of the object. An important conclusion is that one statistical characteristic describes well the beginning of the transient process, and the other describes its end. This must be taken into account when building a deviation signaling system.

Optimization of cell depth and concentration zone height in a countercurrent flotation machine

Due to the growing complexity of ore processing, equipment and technologies with higher separation efficiency are currently in demand. Flotation machines with a countercurrent flow of slurry and bubbles are increasingly being used. Yet still, certain issues related to optimizing flows in a flotation cell by adjusting the cell height and feed point depth remain insufficiently studied. Pilot tests of a countercurrent flotation machine with a jet-ejector aerator in rougher flotation at a facility of Phosphorit Industrial Group LLC have demonstrated an increase in separation efficiency after a chamber height adjustment from 3.5 to 5.0 m with a 1.5 m deeper feed point. The mass fraction of P2O5 in the froth product increased from 20–22 to 25–27 % with a decrease in froth yield from 32–35 to 21–24 %. The flotation tail grades correspond to those of the dump waste product (1.00 ± 0.39% P2O5 according to the data on 116 samples); the load of cleaner operations has also been normalized. An original sampler designed by B. S. Chertilin was used to test the mineral load of bubbles at different depth points in the cell. The results indicate the extreme nature of the load distribution with a monotonous increase in P2O5. This confirms the main role of the process of predominant shedding of waste rock particles from the bubbles in the concentration zone (above the feed point) with the higher separation efficiency achieved.

Influence of hydrodynamic variables on scaling up of mechanical flotation cells

Flotation performance is influenced by many hydrodynamic variables, such as impeller speed, airflow rate, and cell geometry. These variables’ effects and interactions remain unsatisfactorily explored, especially concerning scaling-up procedures. As an innovative approach, this study considered factorial-designed experiments to explore the effects of hydrodynamic factors (impeller tip speed and superficial gas velocity) on scaling up the Outotec GTK LabCell™ mechanical flotation machine cells, common equipment used as a benchmark for many industrial pre-feasibility studies. Therefore, the influence of hydrodynamic variables and their interactions on flotation performance was evaluated in two cells (2 L and 7.5 L). The evaluation was based on the flotation rate constant “k” calculated by first- and second-order equations. Analysis of the particle size distribution indicated that the performance of the two cells was different, as shown by the finer concentrate for the 2-L cell compared to the 7.5-L cell. The outcomes demonstrated that symmetrical design in the geometry of mechanical flotation cells would lead to an accurate scaling up based on the metallurgical responses. Otherwise, the scaling procedure could only be accurate under some specific conditions. As a criterion, the results showed that using k, the scaling-up process between these two GTK LabCell™ mechanical flotation machine cells (2 L and 7.5 L) would be possible only under a specific superficial gas velocity (0.14 cm/s) apart from the impeller tip speed (R2 = 1). These results could potentially be key for the future design and development of mechanical flotation cells.

Effect of strong collectors and frothers on coarse particle flotation using the HydroFloat™ for a North American concentrator

ABSTRACT In conventional flotation, particles larger than 150 μm tend to float poorly, especially those with high specific gravity. The flotation equipment, HydroFloat™, has been implemented in the mining industry and has resulted in significant improvements in coarse particle recovery, particularly when used with strong collectors and frothers. A North American concentrator processing copper-molybdenum (Cu-Mo) ore has been having difficulties in recovering particles coarser than 150 μm. Presently, the concentrator uses sodium ethyl xanthate and X-133 frother (baseline). Previous tests conducted using stronger collectors and frothers showed that potassium amyl xanthate (PAX) and FrothPro 630 increased Cu recovery by 3% using a conventional laboratory flotation machine. In that testwork, chalcopyrite recovery for particles > 300 μm was low (~55%) under a range of testing conditions. Thus, the HydroFloat™ was tested using potassium ethyl xanthate and PAX in an attempt to increase Cu recovery for particles > 300 μm. Results showed that the recovery of chalcopyrite particles > 300 μm increased by more than 10%, depending on the test condition.

A scale-up approach for industrial flotation cells based on particle size and liberation data

The current scaleup approaches usually consider the overall metallurgical results, without including the efficiency of flotation machines at different particle size and liberation classes. This approach can limit the prediction of the industrial metallurgical performance, mainly when the mineral feed characteristics change significantly over time. This paper presents a scale-up approach, which allows for estimating scale-up factors per size and liberation class. The plant survey was developed in a copper concentrator in Chile. Plant kinetic testing on three rougher circuits of 130 and 300 m3 cells, in parallel with batch flotation tests using the same rougher feed samples, allowed the estimation of average scale up factors in the range of 1.8–2.2, which are in good agreement with the typical values observed in flotation scale up. All the samples included sieving, and chemical and mineralogical analysis. Scale up factors, batch-plant, showed a correlation with particle size classes, where the scale up factor increases (1.5–2.5), when particle size increases (20–150 µm), according to the data. This effect becomes stronger for particle sizes larger than 100 µm, reaching scale up values around 3–4. This means that the scale up factors are sensitive to the particle size distribution in the plant feed and must be considered.An alternative estimation of scale up factors in terms of the mineral liberation showed a similar trend with those of particle size classes, where the less liberated (mainly coarser sizes) minerals have the largest scale up factors, while decreasing for the highly liberated (mainly finer sizes) minerals.

Metallurgical testing and CFD simulation of StackCell® SC-50 high-intensity flotation machine

An extensive field test was conducted by Rio Tinto and Eriez to evaluate the operability and metallurgical performance of a StackCell® SC-50 high-intensity flotation machine for recovery of copper and molybdenum from flotation tailings. The field test of the 15-m 3 StackCell flotation cell was conducted at Rio Tinto’s state-of-the-art tailings recovery demonstration plant located within Kennecott Utah Copper’s tailings facility. The metallurgical results demonstrate that the StackCell technology provides a unique solution for recovering metal values from tailings, with excellent selectivity and an order of magnitude increase in flotation kinetics compared to conventional mechanical flotation machines. The metallurgical advantages of the StackCell are particularly pronounced for treating fine tailings, with upgrade ratios >25 achieved at average copper and molybdenum recoveries of 20% and 28%, respectively, within approximately one minute of flotation residence time. Computational fluid dynamics (CFD) simulations were conducted to provide a fundamental explanation of the findings from metallurgical field measurements. The simulations show that maximum levels of turbulent dissipation rates in the StackCell contacting chamber are nearly 5 times that of rotor/stator mechanisms in conventional mechanical flotation machines. Furthermore, the high levels of turbulent dissipation rates in the contacting chamber are favorable for high collisions and attachments rates of fine particles with air bubbles.

Using Top-of-Froth Conductivity to Infer Water Overflow Rate in a Two-Phase Lab-Scale Flotation Column

The metallurgical performance of a flotation machine is largely defined by phenomena occurring in the froth zone. The water content in the froth affects recovery by influencing froth stability and mobility and, at the same time, reduces grade by mechanical entrainment of gangue particles in the overflow water. Efficient operation requires a compromise between the water carried by bubbles from the collection zone and that which overflows. It is believed that the most suitable operating strategy could be based on the measurement of froth water content, as a strong correlation with water overflow is anticipated. This work reports the testing results of an in situ electrical conductivity sensor continuously measuring the froth zone water content in a laboratory-scale flotation column. The test program included simultaneous measurement of froth conductivity and water overflow rates for changes in gas flow rate and frother concentration. The results show a stronger dependence of the measured top-of-froth water content on frother concentration than on the gas flow rate. A relatively linear trend was shown between top-of-froth water content and water overflow rate for a given air rate and frother.

A new approach to measure gas holdup in industrial flotation Machines. Part III: Industrial prototype design and assessment

• An industrial gas holdup sensor prototype was validated in a 250 m 3 flotation cell at Los Pelambres. • A weakly dependence of sensoŕs discharge coefficient to Reynolds number was observed. • Gas holdup predictions were largely insensitive to errors in the anticipated pulp kinematic viscosity. • Submersible sensor provided robust accurate gas holdup measurement over long periods of time. An industrial gas holdup sensor was designed, constructed, and its performance assessed on a 250 m 3 self-aerated Wemco cell at Los Pelambres concentrator. The submersible sensor comprised a ceramic-liner IP68 magnetic flowmeter assembled to a stainless steel gas exclusion cell, which resembles an inverted truncated cone. The gas exclusion cell was designed to avoid low-velocity sections where particles could settle. When the sensor device is vertically immersed in an aerated pulp a continuous downward flow of pulp without bubbles is induced through it. A remotely installed processing unit converts the flow velocity signal, provided by the magnetic meter, into a gas holdup signal, by applying Bernoullís equation to the induced flow. The ideal velocity in the Bernoullís equation is obtained by multiplying the measured velocity and the discharge coefficient. The discharge coefficient was found to be fairly constant over a wide range of Reynolds numbers. Gas holdup measurements were compared against those obtained by sampling a fixed volume of aerated pulp using the JK Tech Air Holdup Probe. These tests were conducted on different days over nine months to allow for the pulp properties to change. Gas holdup changes in the flotation machine were achieved by restricting the air intake to the cell by placing a stainless steel cap on top of the air suction pipe. Short and long-term testing demonstrated the sensoŕs capability to provide reliable and accurate continuous-time gas holdup measurements for industrial flotation machines.

Computer simulation application for substantiation of industrial wastewater treatment technology

The wastewater treatment of the mining industrial enterprises is implemented using mechanical, chemical, biological and physic-chemical methods. The mechanical treatment is used to prepare wastewater for biological, physicochemical and other methods of the deep treatment. In recent years, the field of the physicochemical treatment methods application has been expanding, and their share among other methods has increased. The Mining Institute of the Kola Science Centre of the RAS has been developed a technology of the industrial wastewater treatment based on the synergetic effect of the pollution concentrating in a multiphase medium with formed surface properties of the phases, tested at the mining enterprises of the Kola MMC (Lovozero GOK LLC and Kovdor GOK) and including coagulation, sorption and flotation in activated water dispersion of air. To substantially reduce the cost, duration and complexity of the process of the developing wastewater treatment methods at mining enterprises, an approach based on the use of the mathematical and computer simulation methods, the development of the virtual laboratory benches that fully reproduce the technological processes and devices used. The mathematical simulation of the fine particles coagulation and aggregation in the process of the industrial wastewater treatment from dissolved impurities was carried out. The simulation made it possible to reveal the kinetics of the adsorption process of the contaminants components by the surface of the formed iron hydroxide colloidal particles, which determines the size and lifetime of the floccules. A virtual laboratory stand was created to study the water treatment processes based on the ANSYS Fluent software. This stand simulates the operation of the Outotec radial thickener with a diameter of 30 meters, which made it possible to develop recommendations for the technological regimes optimization for the greater particle aggregation efficiency. The possibility of the application in the technology the column flotation machine – an analogue of the flotation machine of the Canadian Process Technologies Inc. CETCO, was considered.The authors appreciate participation of Junior Researcher A. S. Kitaeva A. S. in the work on the article’s material.

Gas Dispersion Characteristics in a Novel Jet-Stirring Coupling Flotation Device

A jet-stirring coupling flotation device (JSCFD) was proposed to analyze the distribution characteristics of gas holdup and bubble Sauter mean diameter (D32) in a gas–liquid system under various parameters. Results of studies suggested that the gas holdup increased with methyl isobutyl carbinol concentration, feeding pressure, and gas flow rate. The maximal gas holdup in the absence of the stirring impeller was ∼23.29% for the bubble size of 0.59 mm, which was considerably lower than the maximum gas holdup of 66.27% for the bubble size of 0.31 mm in the presence of the stirring impeller; the gas holdup was raised by ∼43% due to the bubbles torn by the stirring impeller to generate extensive smaller size bubbles and increase the content of small bubbles, and increasing the stirring impeller speed was conducive to reduce the bubble size and increase the gas holdup in JSCFD. Compared to traditional flotation machines, the size of bubbles generated by JSCFD was smaller, and the gas holdup distribution conforms to the following order: JSCFD > mechanical flotation machine > column flotation, which demonstrated that the JSCFD had a noticeable effect on increasing the gas holdup and reducing the bubble size.

A Method to Detect Abnormal Gas Dispersion Conditions in Flotation Machines

This short communication presents a methodology to detect abnormal gas dispersion conditions in flotation machines. These abnormal conditions are characterized by the significant presence of cap-shaped bubbles. The approach considers the use of a bubble size analyzer to measure gas dispersion at industrial scale. The detection of abnormal conditions is critical when estimating bubble size by automated software. Otherwise, the estimates are significantly biased, since irregular bubbles are typically removed from the analysis. From the recorded images and the respective black and white representation, the variability of the shadow percentage caused by the bubbles in the vision field, abruptly increases in the presence of cap-shaped bubbles. Experimental conditions with coefficients of variation lower than 60–70% in the shadow percentage represent spherical and spherical-ellipsoidal regimes. In the former, automated bubble sizing software has proved to be sufficiently effective in obtaining reliable results. In the latter, different segmentation techniques have been proposed to obtain satisfactory results. Abnormal conditions are detected under coefficients of variation greater than 80% in the shadow percentage. The presence of cap-shaped bubbles causes inefficiencies in the collection of hydrophobic minerals in the pulp zone as well as disturbances in the separation stage (froth zone). Therefore, the detection of these irregular bubbles is suitable to provide feedback to flotation processes, allowing gas dispersion to be driven towards normal operating conditions.