Cyclonic Microbubble Flotation Column Research Articles

Study on inhibition mechanisms of detachment of coal particles from oily bubbles in flotation column

The cyclonic microbubble flotation column is an efficient separation equipment in the beneficiation process of metallic and non-metallic minerals. However, the higher detachment rate of coarse particles in the pulp, pulp-froth interfacial zone, and froth zone is an issue that needs to be addressed urgently in column flotation. Compared with traditional air-water bubbles, oily bubbles have higher hydrophobicity, which is beneficial for strengthening the bubble-particle attachment and inhibiting the bubble-particle detachment. Therefore, oily bubbles were introduced into the cyclonic microbubble flotation column to reduce the particle detachment rate. Firstly, an improved cyclonic microbubble flotation column was set up, and traditional air-water bubbles were placed by oily bubbles through the combined use of an atomizer and a bubble generator during experiments. Subsequently, we investigated the feasibility of using oily bubbles as a flotation carrier to regulate the particle detachment rate, improve the particle recovery, and explore the mechanism behind this. Column flotation results showed that recovery rates generated from experiments with oily bubbles are higher than those with air-water bubbles under different operation conditions, and the particle detachment rate in the interfacial region was significantly reduced with the use of oily bubbles. Recoveries and flotation rate constants generated from collection zones for each particle size range indicated that the use of oily bubbles can increase the upper limit of flotation particle size compared with the use of air-water bubbles. Calculated detachment rates showed that the use of oily bubbles can effectively reduce the detachment probability of particles with different sizes in the collection zone. Combined with the observation of ultrasonic-assisted oscillation, it is proved that the oil coating film on the oily bubble significantly improves the resistance of oily bubbles to turbulent disturbance. In addition, the increase in hydrophobic force between oily bubbles and particles and the growth of the three-phase contact periphery are beneficial to reducing the particle detachment probability due to turbulent disturbance in the collection zone. Results from bubble coalescence experiments showed that the existence of oily bubbles significantly reduced bubble coalescence time and increased the damping coefficient. Compared with air-water bubbles, oily bubbles have a stronger damping effect on the oscillation caused by bubble coalescence, inhibiting the violent bubble surface deformation and the induced particle detachment during bubble coalescence. Therefore, the introduction of oily bubbles is a promising idea to reduce the detachment probability of coarse particles and increase the upper limit of particle size in column flotation.

Effects of a cyclonic microbubble flotation column operating parameters on coal process responses

ABSTRACT Processing fine and ultrafine coal particles from primary resources is essential for sustainable development. As one of the most recently developed enrichment equipment, cyclonic microbubble flotation columns (FCMC) showed high efficiency in upgrading various fine minerals. However, understanding the effect of FCMC operating variables on coal upgrading process responses remains a black box and needs fundamental assessments. To fill the gap, this study examined the influence of circulating pump pressure and froth height on the recovery of different coal particle size ranges to assess and explore fundamental FCMC performance. The experimental results established that increased froth height would simultaneously reduce the collection and froth recovery. Coarse particles in the high froth height were detached due to bubble coalescence or rupture, while the liquid drainage reduced fine particle pollution of froth products. Increasing circulating pump pressure would increase the collection zone’s turbulence, lead to coarse particle detachment, and reduce collection recovery. Meanwhile, increasing circulating pump pressure could promote froth stability and decrease froth detachment in the froth zone. The calculated first-order rate constant (k c) confirmed that the flotation rate constants of coarse (−0.5 + 0.25 mm) and fine (−0.074 mm) particles were low, while the intermediate particles (−0.125 + 0.074 mm) had faster flotation kinetics.

Exploring the Relationships between Gas Dispersion Parameters and Differential Pressure Fluctuations in a Column Flotation.

Flotation separation, which is the most important mineral beneficiation technique, is dependent on gas dispersion (hydrodynamic conditions). Thus, many investigations have focused on the precise determination of hydrodynamic conditions such as Reynolds number of the bubbles, bubble velocity, and bubble diameter. However, few studies have examined their relationships with pressure fluctuations in a column flotation. This study introduced the differential pressure fluctuations as an actual variable that could be considered to determine the collection zone’s hydrodynamic conditions in a cyclonic microbubble flotation column. In general, the outcomes indicated that superficial gas velocity had the most substantial relationship with the differential pressure fluctuations among other flotation factors (such as pump speed, superficial gas velocity, superficial water velocity, and frother dosage). Furthermore, a high coefficient of determination (R2 > 0.77) for the equation generated to assess the relationships demonstrated that differential pressure fluctuations could be used as a promising tool to determine the hydrodynamic parameters’ characteristics in the flotation columns.

Separation performance of mechanical flotation cell and cyclonic microbubble flotation column: in terms of the beneficiation of high-ash coal fines

ABSTRACT Separation performance of mechanical flotation cell and cyclonic microbubble flotation column (FCMC) was compared in terms of the beneficiation of high-ash coal fines that has the characteristics of the content of <0.045 mm accounting for more than 50% of the flotation feed and the ash content of <0.045 mm being more than 50%. The optimal experimental results of the mechanical flotation were determined as the flotation perfection index η of 47.37%, the clean coal yield of 39.19% and the clean coal ash content of 10.78% at the feed pulp concentration of 40 g/L through twice explorative flotation experiments and the orthogonal experiment. It was found that the ash content of the clean coal had a strong dependence on the feed concentration. In contrast, the yield of the concentrate of the column flotation was increased to 43.26% with the lower ash content of 9.47% and the higher η of 54.51% even at higher feed concentration of 60 g/L. The remarkable separation efficient of the FCMC flotation column for the difficult-to-float coal slime that has the characteristics of high content of fine particles with high ash was attributed to the presence of the centrifugal force field, more microbubbles generated by hydrodynamic cavitation, the form of countercurrent mineralization, and thicker froth layer.

Comparison of mechanical flotation cell and cyclonic microbubble flotation column in terms of separation performance for fine graphite

Comparison of mechanical flotation cell and cyclonic microbubble flotation column in terms of separation performance for fine graphite

Design and Experimental Study of a Modified Cyclonic Microbubble Flotation Column System

ABSTRACTThe cyclonic–static microbubble flotation column (FCSMC) has been proven to be a promising technique for recovering fine-grained minerals. However, low recovery of coarse coal particles by the FCSMC has been reported due to utilization of a single mineralization step. In the present study, a novel modified flotation unit has been added to the conventional FCSMC to improve the recovery of coarse coal particles. The design aspects and operating procedures of the proposed modified cyclonic microbubble flotation column (MCMFC) were studied and the results were compared with the conventional FCSMC. Some data on the applications of MCMFC in industrial floatation processes have also been discussed. The results showed that MCMFC provided higher recovery of coarse coal particles compared to those by FCSMC. Specifically, for −500 + 250 μm coarse particles, the yield by MCMFC was 22.29% higher than that by FCSMC. Both concentrate yield and concentrate ash were found to be significantly affected by the inclusion of the modified flotation unit.

Application of cyclonic microbubble flotation column in Xiezhuang coal preparation plant: From laboratory to industrial scale

ABSTRACTThe application of cyclonic microbubble flotation column (FCMC) from laboratory to industrial scale was investigated in this study. The FCMC was found to be superior to the standard self-aeration flotation cell for separating the fine coal (below 0.5 mm in size) as sampled from the Xiezhuang coal preparation plant (CPP), and tested under laboratory conditions. Compared with the flotation cell, the ash content of clean coal obtained by the FCMC was reduced by 1.34 percentage points, whereas the clean coal yield and the flotation efficiency index was increased by 2.90 and 6.64 percentage points, respectively. Under these industrial conditions, compared with the IF-45W flotation cell, the clean coal ash content obtained by the industrial FCMC-5000 (the column diameter was 5000 mm) was also reduced by 2.70 percentage points, whereas the clean coal yield and flotation efficiency index increased by 15.10 and 18.99 percentage points, respectively. Furthermore, annual profits of the Xiezhuang CPP increased by 46.773 million RMB by replacing the IF-4.5W flotation cell with the FCMC-5000. The results showed that the FCMC was an efficient coal flotation unit, and its application in separating fine coal has the potential to create significant profits for the enterprise.

Comparative study of conventional cell and cyclonic microbubble flotation column for upgrading a difficult-to-float Chinese coking coal using statistical evaluation

ABSTRACTInvestigations were executed to upgrade a difficult-to-float coking slime (38.40°Contact angle and 40.14% ash content) by conventional flotation cell and cyclonic microbubble flotation column technologies. Firstly, flotation performance of conventional cell considering interactions of collector dosage, pulp density, and frother dosage was estimated by statistical evaluation. The conventional cell results indicated that clean coal with 11.89% ash content was obtained at 53.94% yield and 79.40% combustible recovery. Secondly, the effects of controlling factors (froth depth and circulating pulp pressure) on the flotation performance of cyclonic microbubble flotation column technology (FCMC) were investigated according to the earlier conventional cell studies. The combustible recovery of the clean coal could be further increased to 90.54% at 62.78% yield and 11.67% ash content by using the FCMC. Finally, the flotation performance in the conventional flotation cell and FCMC was compared with that of the release analysis data. It was concluded that, in general, the performance of the conventional flotation cell was poorer, while the flotation performance of the FCMC was better than that of the release analysis data. Therefore, this difficult-to-float coking coal can be concentrated to a qualified product with minimal usage of reagent and low cost by using the cyclonic microbubble flotation column technology.

Kinetic modeling and optimization of flotation process in a cyclonic microbubble flotation column using composite central design methodology

In this work, a composite central design with five levels and four variables was employed to model and optimize the batch flotation kinetic process in a cyclonic microbubble flotation column (FCMC). 30 sets of batch flotation rate tests were executed at different conditions of pulp concentration (X1), frother dosage (X2), flow rate of circulation pulp (X3) and froth depth (X4). It was observed the maximum flotation time (tmax) obtained in tests fluctuated wildly under different conditions. Statistical analysis based on the model fit and stability was performed to discriminate six kinetic models. The response surface methodology was used for the identification and development of significant relationship between process variables. Statistical analysis indicated that the modified Kelsall model was the optimal kinetic model for characterizing the flotation process. Analysis of variance results revealed that the effect of X1 was significant for all process responses. X4 was found as a significant independent factor for the two response variables of tmax and the ultimate combustible recovery (ε∞) of the optimal kinetic model. X3 had a significant influence on the parameter of the optimal kinetic model (the fraction of flotation components with the slow rate constant). Furthermore, the maximum flotation time and ε∞ were significantly influenced by the interaction between X1 and X4. Based on the result of optimization it was found that the desired ultimate combustible recovery with an appropriate flotation time was obtained from the flotation process with a given range of experimental variables (X1: from the intermediate levels to the higher levels; X2: the intermediate level; X3: 220g/t and X4: 25.00mm). There was an acceptable relationship between predicted and actual values with one of the optimal conditions (Adj. R2=0.9971). The response surface methodology was effective for predicting and optimizing the batch flotation process of FCMC.

A Design of an Inclined Froth Zone in Column Flotation Device to Reduce Ash Content in Clean Coal

A modified column flotation was designed based on the cyclonic microbubble flotation column (FCMC). In the modified flotation column, the froth zone was designed with an inclined arrangement to enhance the gravity settling of coarse middling particles, which were collected as a third product. The modified flotation column was referred as S-FCMC. In this study, the effects of process parameters (collector dosage, frother dosage, superficial gas velocity, and froth layer height) on the performance of the S-FCMC were investigated. For comparison purposes, tests were also conducted using the standard FCMC. The results showed that clean coal obtained using the S-FCMC had lower ash content than that obtained with the FCMC. Under the optimized operating conditions, the decrease in clean coal ash content and clean coal yield was 1.29% and 3.93%, respectively. The increase in tailings ash content and flotation efficiency index was 6.77% and 1.57%, respectively. About 64.55% of the settled (third) product in the inclined zone consisted of −0.045 mm sized particles and the ash content of this size fraction was 58.04%.

Research on Pressure Drop Performance of the Packing-Flotation Column

Abstract A packing-flotation column was proposed to optimize the flotation environment A research system was established using a 100 mm diameter cyclonic micro-bubble flotation column to study fluid properties. Dry-plate and wet-plate pressure drops were studied and the corresponding pressure drop equations developed. The results show that the dry-plate pressure drop of the packing cyclonic micro-bubble flotation column is 10-15 times less than that of the chemical tower, which is principally shown in its relatively small resistance coefficient, ξ ≈ 0.0207. The wet-plate pressure drop is 2-3 times higher than that of the chemical tower, which is largely caused by the separation materials and characteristics of the equipment. With flotation, the greater the pressure drop, the better the flotation environment.