Flotation Stage Research Articles

Design and Comparison of Fractional-Order Controllers in Flotation Cell Banks and Flotation Columns Used in Copper Extraction Processes

This work explores efficiency improvements in the copper flotation stage, a complex nonlinear, multivariable process subject to numerous perturbations. The primary objective is to design a fractional-order PID (FOPID) control strategy and a fractional-order model reference adaptive control (FOMRAC) system. The parameters for these controllers are optimized using the particle swarm optimization (PSO) algorithm with an objective function tailored to the control goals. This study employs models of both a bank series of five flotation cells and a flotation column. Their performance results are compared against traditional controllers, such as an integer-order PID and MRAC. The findings reveal that fractional-order controllers offer notable advantages over their integer-order counterparts, showing improved performance metrics with minimal changes to the existing control framework. This research highlights the effectiveness of fractional control in enhancing flotation processes and introduces a novel application of fractional control techniques in this area.

Preparation of high-purity magnetite from iron ore concentrate

In pursuit of environmental protection and green, low-carbon economic development, China has proposed the dual-carbon strategies of carbon peak and carbon neutrality. To achieve the dual-carbon goals, traditional steel metallurgical production processes are gradually shifting towards green and low-carbon hydrogen metallurgical processes. However, hydrogen metallurgical processes have strict requirements for raw materials and typically require the utilization of high-grade iron concentrates. The scarcity of high-grade iron ore in China severely constrains the development of hydrogen metallurgical processes. Therefore, this study proposes the utilization of ordinary magnetite concentrate to produce high-grade magnetite. Comprehensive analytical methods, including chemical analysis, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) analysis, laser particle size testing, optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and mineral liberation analysis, were employed to elucidate the mineralogical characteristics of the iron concentrate. The analysis revealed that the iron concentrate had a total iron (TFe) grade of 65.56 %, with SiO2 and Al2O3 contents of 8.28 % and 0.38 %, respectively. Subsequently, a combined beneficiation process involving magnetic separation, flotation, and chemical leaching was conducted. Experimental results showed that a single magnetic separation obtained an iron concentrate grade of 67.52 % with an overall recovery of 86.18 %. Following magnetic separation, flotation was conducted to increase the concentrate grade. With one roughing and four cleaning flotation stages, a concentrate grade of 72.19 % and a 36.36 % overall recovery were achieved. A subsequent leaching operation after flotation yielded high-purity magnetite with a Fe grade of 72.30 % and an overall recovery of 35.68 %. The high-purity magnetite was confirmed to have a purity of up to 99.9 % based on chemical titration, XRD analysis, magnetic susceptibility measurement, and SEM analysis. Furthermore, detailed kinetics studies on leaching were conducted to elucidate the reaction mechanism, revealing an apparent activation energy of 25.70 kJ/mol. The successful implementation of this process will provide a benchmark for producing similar high-purity magnetite concentrates and contribute to China’s dual-carbon goals.

Recovery of Apatite from Magnetic Concentration Tailings by Flotation

Iron concentration tailings contain many valuable minerals, including apatite, which is not currently being recovered despite its use to make fertilizers and chemicals. This article proposes a flotation circuit to recover apatite from tailings generated by mining in Chile, based on laboratory tests and using the “Split Factor” method. The iron tailings were characterized by granulometry, chemical and mineralogical analyses, zeta potential, and contact angle. The effect of the collector, frother, and dispersant dose, along with the number of flotation stages, on both the grade and recovery of P2O5 were studied. The results indicate that it is possible to produce concentrates with a P2O5 grade of 29.1% and 89.6% recovery in a flotation circuit that includes the rougher–scavenger–cleaner stages. To obtain these results, it is only necessary to condition the iron tailings with 400 gt−1 of Atrac-2600, 400 gt−1 of sodium silicate, 10 min of conditioning time, pH adjustment to 10, and a time for the rougher, cleaner, and scavenger stages set at 10, 7.6, and 6.8 min, respectively. A chemical interaction is suggested, where the collector is specifically adsorbed onto the apatite surface.

Flow Field Characteristics and Flotation Efficacy in a Pulse Jet Flotation Machine: A Comprehensive Investigation

The design and optimization of flotation machines hold significant importance in enhancing the industrial-grade coal beneficiation process. In this research, the flow field characteristics and flotation performance of a novel pulse jet flotation machine (PJFM) were investigated. The results showed that a PJFM equipped with an innovative pulse cavity can improve the mineralization efficiency of coal due to the coupling of multiple jet shapes. The aeration performance of this PJFM also exceeds the usual desired targets of coal flotation machines, which are characterized by an aeration uniformity coefficient higher than 70% and dominant bubbles of 100~200 μm and 200~300 μm, including a small amount of −100 μm bubbles. The cavitation of the pulse jet achieved the modification of the coal particle surface, and subsequently, the electric potential of the coal largely decreased in absolute value, and the floatability of the coal significantly improved. The concentrate yield of step release flotation increased by 12.42%, while the ash content was only 0.45% higher. Furthermore, in the early stage of flotation, the flotation rate of 0~0.074 mm coal slurry is the fastest and is preferentially floated; in the later stage, the flotation of 0.25–0.5 mm particles dominates. The PJFM demonstrates enhanced particle size selectivity and superior performance in selective flotation.

Upgrading of talc-bearing copper-nickel sulfide ore by froth flotation using sodium phytate as depressant

Copper-nickel sulfide ores, as important sources of copper and nickel metals, always have large amount of clay-type gangue minerals like talc. In this work, selective flotation of copper-nickel sulfide ore was achieved by using a selective depressant of sodium phytate. Microscale flotation results show that sodium phytate can selectively and effectively depress talc flotation, but has a minor effect on the floatability of chalcopyrite and pentlandite. In batch-scale flotation tests of feed ore, containing 0.35% Cu, 0.68% Ni and 24.57% MgO, potassium butyl xanthate was employed as the collector in rougher (200 g/t), scavenger-1 (100 g/t), scavenger-2 (50 g/t) and scavenger-3 (25 g/t), and sodium phytate depressant was used in rougher (300 g/t) and cleaner-1 (100 g/t) stages of closed-circuit flotation to obtain a concentrate containing 2.66% Cu (79.7% recovery), 5.38% Ni (83.01% recovery), and only 6.39% MgO. The contact angle analysis showed that sodium phytate significantly improved the hydrophilicity of talc, but it only slightly increased the hydrophilicity of chalcopyrite and nickelpyrite. The FTIR and XPS tests showed that chemisorption of sodium phytate occurred on talc surface by the interaction between P-O/PO and Mg active sites. This work indicates that sodium phytate has strong potential as an inhibitor for the selective separation of talc from copper-nickel sulfide ores.

Challenges in flotation scale-up: The impact of flotation kinetics and froth transport

At present, data from industrial flotation operations is still limited and more tests and in-depth studies are required to improve the experimental procedures, measurement devices and analysis, to validate and interpret scale-up factors from batch to plant flotation operations.The new methodologies have contributed to improve predictions of flotation metallurgical performance using more refined scale-up methods, for example, analyzing the scale-up factor by size and liberation classes. These will allow for selecting the best equipment for each mineral and flotation stage (rougher, cleaner and scavenger).In this work, the effect of the pulp zone hydrodynamics affecting the collection residence time and flotation kinetics, and the froth transport, on the overall scale-up factors (typically around 1.8–2.3) was evaluated per particle size classes in the range of 22.5 to 300 µm. Two effects were found that partially explain the scale-up factor in the pulp zone, such as the pulp mixing regime (4–16%) depending on the cells number, and the solids segregation (2–7%) that decreases the residence time of larger particles. However, the most important contribution was the froth transport characteristics that determines the froth recovery which accounted for 48–58% of the scale-up factor, also increasing with particle size. In addition, it was found that the remaining percentage of the overall scale-up factor, around 31%, includes the uncertainty in the collection residence time estimation, which is lower than the effective pulp residence time, and the larger residence time of bubbles in industrial cells. Both effects hinder the identification of the actual flotation rate in the pulp zone.

Fine and ultrafine flotation with the Concorde CellTM – A journey

The Concorde Cell is a high-intensity pneumatic flotation cell dedicated to fines and ultrafines. Its development by Professor Graeme Jameson and later on by Metso was driven by two considerations: a reduction in bubble size and an increase in the shear rate and energy dissipation rate increases the particle–bubble collision and attachment efficiencies of fine particles. The Concorde Cell is a technology which produces fine air bubbles with high carrying capacity, thereby allowing increased capacity per unit; smaller footprint and a greater recovery of valuable fine particles which can be lost in other flotation cells. In addition, with a smaller number of flotation stages or less recycle required to achieve the desired recoveries, operational expenditures like power, water and reagents can be reduced.In this article, the potential of the Concorde Cell is explored through six cases, from base metals to metallurgical coal. Its main operating parameters, Air-to-Pulp Ratio, froth washing, froth depth and tailings recycle ratio, are investigated and show that the metallurgical performance of the Concorde Cell follows expectations based on the literature. Amongst others, higher APR leads to higher mass pulls and higher recoveries but lower grades, deeper froth depth increases selectivity… But the data also demonstrate the typical complexity of flotation, whereby the negative impact of increased APR can be compensated with froth washing to maintain high grades at high recoveries for example.About ten industrial scale flotation projects worldwide are deploying the Concorde CellTM. The examples of a metallurgical coal washing plant in Australia and of a copper plant in Zambia prove the capacity of the Concorde Cell to better recover the fines and ultrafines while providing high selectivity. In the two case studies, the Concorde Cell outperformed the previous technology specifically on the finest fractions of the processed streams.

Enhancing nickel grade and recovery with counter-current washing of the concentrated bubbly-zone of a single stage REFLUX™ Flotation Cell

The recovery and concentration of the nickel sulphide mineral, pentlandite, present several challenges due to its relatively slow flotation, leading to excessive hydrophilic gangue minerals in the concentrate. The REFLUX™ Flotation Cell (RFC™) offers the potential for a significant hydrodynamic advantage over conventional flotation. Much of this advantage is due to the replacement of the pulp and froth phases with a concentrated bubbly zone, which in turn supports more intense counter-current washing by permitting a powerful and effective positive bias flux. Thus, the aim of this study was to investigate the nickel recovery and silica rejection in the RFC™, by applying a wide range of positive bias fluxes. The focus was on a single stage of separation in the RFC™ using a feed flux of 0.63 cm/s at a feed nickel grade of 2.1%. At the lowest bias flux of 0.1 cm/s, a nickel grade of 7.5% was obtained at a single stage recovery of 70.2%. By increasing the bias flux to 0.42 cm/s, the grade increased to 9.7% but the recovery fell to 64.9%. With an extreme bias flux of 1.04 cm/s, the grade reached 12.3%, while the recovery fell to 54.7%. The selectivity, given by the nickel recovery relative to the silica recovery, was estimated to be 121 at the highest bias flux, declining sharply with a reduction in the bias flux. The performance ratio proposed by Parkes et al (2022) was quantified by comparing the RFC™ performance with the batch kinetic results from a mechanical cell, the product grade being ∼7%. The performance ratio was based on the experiment at the lowest bias flux used in the RFC™, and found to be at least 6, meaning the RFC™ footprint would be reduced by a factor of ∼6 for a similar product grade. Based on the higher product grades achieved in the RFC™ using the higher positive bias fluxes, the performance ratio would likely exceed 10-fold given the need for the mechanical cell concentrate to undergo at least one further stage of flotation.

Application of radiotracers as tools to determine feed flowrate imbalances and particle size segregation in industrial flotation circuits

This publication presents the application of radiotracers in the characterization of industrial flotation circuits. Two examples are showcased: the detection of feed flow rate imbalances and the characterization of particle size segregation in automatic mineral-cutting machines. The feed pulp distribution was determined from the mean residence times. Particle size segregation was measured by sampling the cutting machines (≅ 25 grams samples) using coarse, intermediate, and fine-sized radiotracer particles. Radiotracers were injected into the feed streams and measured at various points of the circuit using nuclear instruments, allowing for non-invasive and real time detection. Results show that in the rougher flotation stage, the feed flow is distributed almost evenly in lines 2 and 3 (approximately 38% of the flow goes to each line) and to a lesser extent towards line 4 (approximately 24%). In lines 1 and 2 of the scavenger stage, a higher percentage of the flow goes towards line 1 (approximately 59%) and a lower percentage towards line 2 (41%). Line 6 of the rougher flotation is the fastest of the circuit (shortest residence time). In addition, the inlet mineral-cutting machine of the rougher stage segregates particles with a bias for fine sizes (11.4 % more fine-sized particles than coarse ones). This work is an example of how radiotracer technology can be applied to improve metal production and processes. Radiotracers provide reliable information to be used in combination with other metallurgical data to properly assess flotation circuits.

Filtration of fine mineral particles assisted by nanobubbles

This study investigates the effect of nanobubbles (NBs) on the filtration rate of quartz and iron ore tailings (fine and coarse samples) using a bench-scale press filter operating at 8 bar. The NBs dispersion was generated through hydrodynamic cavitation in a needle valve after 25 min of air saturation in water at constant pressure (Psat = 2.5 bar). To assess the influence of particle size and hydrophobicity (amine conditioning) on the filtration rate, quartz samples with varying particle size distributions were employed. Subsequently, fine (Dm = 7 µm) and coarse (Dm = 90 µm) tailings were examined as a case study. These tailings were collected from the desliming hydrocyclone (prior to the flotation stage) and the floated product (silica and silicate particles) from the reverse cationic flotation of a Brazilian iron ore mill. Filtration tests were conducted with the quartz samples after treatment with 180 g t−1 of dodecyl-ether-amine at pH 7.5. The results revealed that NBs significantly improved the filtration rate (approximately 20%) for fine (Dm = 7 µm) and medium-sized quartz samples (Dm = 129 µm). Conversely, no substantial effect was observed with the coarse material (Dm = 307 µm), due to its higher porosity. The enhanced filtration rate was validated with fine iron tailings, where NB conditioning reduced the filtration time by about 30%. Similar to the results with quartz, this positive effect diminished when fines were mixed with coarse tailings because of the enhanced porosity of the resulting cake. The underlying operating mechanism seems to be the enhancement of mineral particle hydrophobicity induced by the NBs. In addition, theses bubbles reduce the capillary forces responsible for retaining liquid within the cake's porous section, allowing a more rapid flow of the filtrate. This technique appears to hold substantial potential for tailings management in the iron mineral industry, and extended trials at a pilot scale will be scheduled.

Awaruite, a New Large Nickel Resource: Flotation under Weakly Acidic Conditions

To support the transformation to clean low carbon technologies, there is a demand for critical metals such as nickel. Awaruite is a less common nickel-bearing mineral with unique properties and responses to mineral separation. This paper presents the findings of a flotation study to recover awaruite from the Baptiste ultramafic deposit, located in central British Columbia, Canada. Nickel recoveries of up to 65% at the rougher stage were obtained with xanthate as a collector at a pH level of 4.5. Awaruite flotation was shown to be highly dependent on the slurry pH. At weakly acidic conditions, the awaruite surface is activated through the dissolution of the passivation layer formed during grinding in alkaline conditions. Desliming was shown to reduce the acid consumption required to maintain the pH, probably by removing the highly reactive serpentine slimes generated during grinding. Rougher, followed by cleaner stages of flotation, showed that a high-grade concentrate can be produced with up to 45% nickel, 1.3% cobalt, 0.7% copper and negligible concentrations of penalty elements, such as arsenic, lead, and selenium, among others. A nickel flotation concentrate from an awaruite deposit is a promising feedstock for not only stainless-steel production but also for clean energy technologies.

Size-by-Liberation Characterisation of an Industrial Flotation Bank in Rougher and Cleaner–Scavenger Operation

The flotation process characterization is typically based on the mineral properties and related to the feed particle size. Laboratory testing allows for the evaluation of the batch flotation kinetics, while plant surveys are carried out for the plant evaluation, and sometimes the rougher flotation stage is also characterized by kinetics, considering either the full sampling of the circuit or the short-cut method. Comparisons of plant and batch results are useful for identifying the scale-up factors. The kinetic evaluation of cleaner stages is less common in plant surveys, and usually, only the overall cleaner and scavenger results are reported. This condition limits a more comprehensive understanding of these stages, which have significant differences from the rougher operation. In this study, the effect of main operating variables in cleaner and scavenger stages, such as finer particle size, higher mass recoveries, higher liberation, particles entrainment, froth recoveries, mineral grades, froth depth, gas rate, and others, was analysed by using an industrial simulation tool that was built from a wide industrial database. For this purpose, data from plant kinetic surveys was used to characterize the mineral feed entering the cleaner–scavenger stage, which allowed for calibrating the simulation tool and predicting the overall circuit performance. The metallurgical results of the cleaner–scavenger bank were compared with those when the bank was operating at a rougher stage (previous operation). The results allowed for evaluating the differences in metallurgical results of the cleaner–scavenger and rougher banks, mainly related to the differences in particle size and liberation as well as in the mass flowrate of collected particles, which affects bubble loading and consequently froth stability, that in turns impacts on froth recovery. The operating conditions and mineral characteristics of each stage also impacted the water recovery and gangue entrainment along the banks. The comparison of predicted recoveries and grades in rougher, cleaner, and scavenger stages showed a good agreement with plant data. These results validated the simulation tool, which is useful and flexible enough to characterize different stages, predict performance and explore new operating conditions.

INFLUENCES OF GRINDING CONDITIONS ON GALENITE-SPHALERITE FLOTATION KINETICS

Grinding is more than just crushing, it is also a process that causes a chemical reaction on the surface of the mineral. Water used in the grinding process significantly affects the galvanic interaction. 
 Different grinding conditions result in different pulp chemistries. This becomes especially important in sulfide flotation in terms of recovery and selectivity. There are limited studies examining the effects of dry and wet grinding prior to the flotation of sulfide minerals. This study compared the effects of wet and dry grinding on the flotation kinetics of complex Pb-Zn sulfide ore at P80 of 20 and 50 µm grind sizes. Results showed that dry grinding positively affected the sphalerite ore flotation compared to wet grinding in terms of recovery and grade in both galenite and sphalerite rougher flotation stages. Considering that the effect of dry grinding was due to the difference in pulp chemistry, the reasons were explored based on particle morphology, and pulp potentials. 
 The results showed that grinding the same ore under dry and wet conditions significantly affected the flotation performance. In light of the pulp potential measurements, it was determined that the reducing environment obtained in the wet grinding negatively affected the flotation performance, while the oxidizing environment formed during the dry grinding affected the flotation performance positively. This was attributed to the fact that galvanic interactions that occurred during wet grinding were significantly reduced during dry grinding. Hence, better galenite and sphalerite flotation was obtained following dry grinding.

Continuous adaptation of a digital twin model for a pilot flotation plant

Model-based methods have a key role in achieving the technical, economical, and environmental performance improvements of the mineral processing systems. However, unmodeled process phenomena and disturbances leading to unreliable modeling results, may prevent the efficient online utilization of these methods at the operational level after the deployment of the model. This study demonstrates the feasibility of online adaptation of a dynamic, mechanistic process models in mineral beneficiation application at a pilot environment. At first, a digital twin of the grinding and flotation stages of a pilot-scale plant was developed. In the experimental campaign, a change from copper-zinc-pyrite ore to a mixture of pyrite-rich and non-sulfide gangue-rich material was carried out. Thus, during experiments, a notable change in the flotation performance was observed, which could not be replicated by a constant-parameter digital twin model. The proposed parameter adaptation framework, encompassing stochastic optimization in moving time windows, was found to be suitable for finding new optimal model parameters during the changing experimental conditions by using the elemental grades in different flotation stages. In addition, simulation studies are presented to highlight the challenges of digital twin parameter adaptation in mineral processing applications, where often only a sparse and disturbance influenced data from the key process variables are available. The adaptive digital twin allows applying the dynamic, mechanistic process models efficiently for predictive simulations in operational decisions leading to more sustainable and resource-efficient minerals processing.

Prospects of pulp aeration for the cleaner production of pyrrhotite-rich type copper sulfide ore: Mechanism and application

Mineral extraction is facing increasingly severe challenges in terms of environment protection and cost reduction. Abundant of lime and sulfuric acid were consumed in the traditional high alkaline process (HAP) to extract chalcopyrite and iron sulfides. In this study, pulp aeration process (PAP) was proved a low-cost and environment friendly method in the processing of a pyrrhotite-rich type copper sulfide ore. Flotation results confirmed that pulp aeration was able to selectively depress pyrrhotite and pyrite flotation under ML8 system, thus 3000 g/t lime was cancelled during copper flotation stage, and around 4000 g/t sulfuric acid was saved during the subsequent sulfur flotation stage due to the low initial pulp pH. In the novel PAP, the directly production cost decreased by 4.34 RMB/t, besides, approximately 3.6 kg carbon dioxide and other waste could be reduced indirectly. Mechanism research revealed that pulp aeration oxidized the surface of pyrrhotite and pyrite, which further depressed the subsequent ML8 adsorption. However, the adsorption of ML8 on chalcopyrite was stable enough and it was unaffected by pulp aeration. Overall, pulp aeration was an environment friendly and cost-effective method for the separation of high-pyrrhotite type copper sulfide ore, which possessed broad industrial application prospects.

Modelling of the flotation process by Central Composite Design for obtaining superior grade feldspar

Feldspar is usually found in conjunction with titanium and iron minerals. Feldspar should be separated from other minerals by generally magnetic separation or/and flotation with high grade. However, due to the similarities in the properties, feldspars are difficult to separate from gangue minerals by flotation. In this study, the degradability of iron was investigated by mica flotation, and Central Composite Design (CCD) was used to plan and analyze the results. During the study, the effect of solid ratio, pH, collector amount and airflow on the iron content and the yield of the obtained clean feldspar were modelled. Then, estimation of the optimum conditions and verification tests were performed. The iron content was reduced to 0.14% by mica flotation. However, this reduction amount was found to be insufficient. Finally, iron content was reduced to 0.05%. Considering that the maximum iron content of the superior grade feldspar is 0.1%, it can be said that two stage flotation is successful without different processes such as magnetic separation.

Study on surface physical and chemical mechanism of nanobubble enhanced flotation of fine graphite

It has been concluded in a recently published investigation that the nanobubble flotation process significantly reduces the number of fine flake graphite flotation stages and improves the flotation performance. The present study was conducted to explore the mechanisms of surface nanobubbles enhancing flake graphite flotation by investigating effects of nanobubbles on surface properties of graphite and interactions between particles and bubbles by use of contact angle analyzer, zeta potential analyzer, Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS). The study results show that nanobubbles can improve the surface properties of graphite and enhance the adsorption effect of collector, which increased the contact angle of the graphite surface by 11.93° compared with conventional flotation. Infrared spectroscopy and potential analysis showed that the nanobubbles could enhance the hydrophobic attraction and reduce the electrostatic repulsion between the collector and the graphite surface, which was beneficial to enhance the hydrophobic surface of the graphite and enhance the agglomeration of fine graphite particles. XPS analysis showed that the nanobubbles covered polar hydrophilic groups (such as CO, CO, COOH) on the graphite surface, which enhanced the adsorption of collector to improve the hydrophobicity of graphite surface.

Polyethylene glycol regulated carnallite decomposition-crystallization: Experimental and theoretical analysis

Currently, the “crystallization-flotation” process is widely used for the industrial production of KCl. However, the significant aggregation of KCl and NaCl in the decomposition-crystallization stage of carnallite leads to inefficient separation of the two particles in the flotation stage, which restricts the production of high-grade KCl. In this study, environmentally friendly polyethylene glycol (PEG) was used to regulate the decomposition-crystallization of carnallite for the first time, and the high-grade KCl was successfully prepared by reducing the degree of crystal aggregation. The crystals were characterized by SEM-EDS, FT-IR, XRD and AFM, and it was found that PEG which average Mn 800 (PEG 800) could adsorb on the crystal surface and effectively disperse NaCl and KCl. It was also found that there are two mechanisms by which PEG 800 achieves dispersion. On the one hand, PEG 800 micelles contain polyoxyethylene chains with large steric repulsion, which can prevent the adhesion of particles. On the other hand, PEG 800 can weaken the electric potential on the surface of KCl and NaCl and reduce the electrostatic interaction force between the particles. Finally, the behavior of Na, K, and Cl before and after the addition was simulated by molecular dynamics, and molecular dynamics calculations showed that PEG 800 could weaken the effect of NaCl on KCl.

Effect of lithium ion on the separation of electrode materials in spent lithium ion batteries using froth flotation

There is an urgent need to develop a recycling process for spent Lithium-Ion Batteries (LIBs). Amongst the various recycling technologies proposed, froth flotation is considered a cost-effective candidate for the separation of graphite from the lithium metal oxides due to the hydrophobic nature of graphite. However, experimental studies have identified that soluble lithium has a significant impact on the separation efficiency.Two series of experiments were undertaken to understand the influence of lithium ions. The first used a semi-synthetic mixture of spent anode and pure cathode material based on lithium nickel manganese cobalt oxide (LiNi0.33Mn0.33Co0.33O2) or NMC-111 cathode material. The second used mixed samples of spent lithium ion batteries of the same composition. Both the separation efficiency and the flotation kinetics are reported. The soluble lithium concentration is shown to have a significant impact on both. However, if the spent battery material is washed to reduce the lithium ion concentration, the flotation efficiency and kinetics are similar with the graphite recovery exceeding 90% and the graphite grade exceeding 84% in a single flotation stage.

전산유체해석을 활용한 일체형 침전부상조 미세기포수 및 최종처리수 유공관의 설계인자 검증 연구

In this research, the feasibility of the design parameters for microbubble distribution and perforated drainpipes in the integrated sedimentation and dissolved air flotation (SeDAF) process for an advanced wastewater treatment plant was verified using computational fluid dynamics (CFD) analysis. The flow rates for the raw water and the microbubble distribution stage were 100 and 15㎥/d respectively. In the simulation, the raw water was first introduced into the mixing tank and then passed on to the coagulation, sedimentation, and flotation stages in sequence. The flow velocity for each stage increased at the narrowed cross-sectional points. It was observed that some of the coagulated water flowing into the inclined plate module in the sedimentation stage spilled out. As a result of the CFD analysis, the average flow rate for the four perforated distribution pipes was 0.014 kg/s. The standard deviation (SD) for the simulations of original and alternative model was 0.00050 and 0.00062, respectively, which indicated that the simulations were successful and reliable. The SD for the average flow rate for the four perforated pipes was 0.00706, 0.00779, 0.00833, and 0.00938, respectively. The aver age flow rates for each pipe were decreased by 0.0003, 0.0000, 0.0002, and 0.0002 kg/s, respectively compared to the original model. This simulation of characterization of microbubble distribution and perforated drainpipe demonstrated that the design parameters for the distribution pipes were set so that the microbubbles were distributed evenly and that the perforated drainpipes successfully withdrew the treated water within the integrated SeDAF process.