Flotation Time Research Articles

Fluorine in Coal: The Modes of Occurrence and its Removability by Froth Flotation

ABSTRACTFluorine is one of the trace elements in coal that is harmful to the ecological environment and human’s health. Flotation, a method of fine-coal processing, may be useful in reducing the fluorine content in coal before coal combustion. For this purpose, a coal sample with high fluorine content (357 μg/g) was selected for the present work. The modes of occurrence of fluorine were examined by sequential chemical extraction, screening tests, and float-and-sink tests; the removability of fluorine in coal was investigated by bench-scale flotation tests. Results indicated that fluorine tends to enrich in large-density fractions and fine-size fractions; fluorine mainly occurred in residual-associated form and carbonate- and Fe/Mn-associated form. Flotation can play an important role in the removal of fluorine from coal. In this study, the optimal amount of flotation reagents was determined by statically designed experiments. Under the optimum condition of 100 g/t diesel oil, 150 g/t 2-octanol, and 200 g/t sodium hexametaphosphate and a 5-minute flotation time provided a 56.81% yield of clean coal. The relative fluorine removal rate was 57.84%, and a total of 76.05% of the total fluorine was removed.

Evaluation and Optimization of Effective Parameters on Zinc Sulfate Flotation by the Taguchi Method

In this research, optimization of effective parameters on zinc flotation of zinc sulfate obtained from the zinc sulfate process is investigated by the Taguchi method. Experiments were evaluated with regard to seven factors in two levels by a Taguchi L8 orthogonal array. The optimum conditions proposed by the model for zinc sulfate flotation tests are as follows: amount of collector and frother 100 g/t, flotation time of 30 min, pH = 9, S/L = 30/70, rotor speed = 1250 rpm and preparation time = 100 min. Under these conditions the zinc grade in the flotation product was 41.5 %, which is little different to the actual amount of 42 % from the flotation tests.

Ultrasound Assisted Ash and Sulphur Removal from Bitumen Using Column Flotation Technique: Experimental, RSM and ANN Methods in Modelling and Optimization of Process

To remove ash and pyritic sulphur from bitumen an experimental study was performed to investigate the use of low frequency ultrasound wave in column flotation. For this purpose, a column flotation rig was equipped with a low frequency 24 kHz ultrasound transducer. The bitumen samples had sulphur content of 9.6 % (6.81 % in the pyritic sulphur form) and 26.4 % ash. All the experiments were carried out under pulp containing 5 % of solid, particle size of 100mesh and aeration rate of 4L/min using pine oil and kerosene as frother and collector agents, respectively. The effects of four parameters including the amounts of collector and frother agents, ultrasound power and ultrasound times were investigated. The optimum conditions for column flotation process with assisted ultrasound were; 1.5 kg/tbitumen of collector, 0.4 ppm of frother, ultrasound power equal to 300 W and ultrasound time of 3 min under flotation time of 5 min. In these conditions, 87.72 % of pyritic sulphur (i.e., 68.03 % of total sulphur) and 83.29 % of ash were removed. Accordingly, the enhancement of column flotation yield with ultrasound mode was approximately 11.9 and 10.3 % more than without ultrasound for ash and pyritic sulphur removal, respectively. The effect of process factors including amounts of collector and frother agents, ultrasound power and ultrasound time on ash and pyritic sulphur removal was investigated by central composite design (CCD) of RSM and multilayer feed forward back propagation neural network with the topology of 4-6-1.

Recovery Slime Waste from Feldspar Flotation Plant at Attanee International Co. Ltd., Tak Province, Thailand

The purpose of this research is to recover slime waste from feldspar flotation plant at Attanee International Co. Ltd., Tak province. Slime waste with particle size less than 230 mesh, is found about 20% of the total ore feed. Since 1985, company has been producing slime waste approximately 200,000 tons, causing a huge pile of stock and obstructing the operation area. The mineral compositions of slime waste by X-Ray Diffraction (XRD) showed that it consisted of albite, orthoclase, quartz, and ferrous impurity minerals such as muscovite, biotite, mica, and garnet. The elemental analysis by X-Ray Fluorescent (XRF) showed that the percentage of grade contained 72.53% SiO 2 , 15.70% Al 2 O 3 , 1.56% Fe 2 O 3 , 0.16% TiO 2 , 0.40% CaO, 0.07% MgO, 4.87% K 2 O and 4.38% Na 2 O. After that, this slime waste was sent to the processes of dirt washing, classifying, attrition scrubbing, separating the ferrous impurity minerals, and preparing for flotation by washing drum, trommel, attrition scrubber, cone classifier, permanent drum magnetic separator, wet high intensity magnetic separator, and hydrocyclone. At this stage, the slime mainly consisted of albite, orthoclase, and quartz with 74.43% SiO 2 , 15.15% Al 2 O 3 , 0.12% Fe 2 O 3 , 0.04% TiO 2 , 0.43% CaO, 0.01% MgO, 4.73% K 2 O and 4.75% Na 2 O at a yield 35%. Study on fine feldspar flotation, which is for removing quartz from feldspar, showed that the optimum condition of 20% solids must be adjusted to pH 2 by hydrofluoric acid (HF), using A-TD as a collector at 1,400 grams per ton feed, conditioning time and flotation time of 5 minutes each. The results of the study showed that the recovery of feldspar attained 69.7% with 67.82% SiO2, 18.54% Al 2 O 3 , 0.14% Fe 2 O 3 , 0.03% TiO 2 , 0.52% CaO, 0.006% MgO, 6.88% K 2 O and 6.07% Na 2 O, which meet ceramic industry’s specifications.

Kinetic approach to the study of froth flotation applied to a lepidolite ore

The number of published studies related to the optimization of lithium extraction from low-grade ores has increased as the demand for lithium has grown. However, no study related to the kinetics of the concentration stage of lithium-containing minerals by froth flotation has yet been reported. To establish a factorial design of batch flotation experiments, we conducted a set of kinetic tests to determine the most selective alternative collector, define a range of pulp pH values, and estimate a near-optimum flotation time. Both collectors (Aeromine 3000C and Armeen 12D) provided the required flotation selectivity, although this selectivity was lost in the case of pulp pH values outside the range between 2 and 4. Cumulative mineral recovery curves were used to adjust a classical kinetic model that was modified with a non-negative parameter representing a delay time. The computation of the near-optimum flotation time as the maximizer of a separation efficiency (SE) function must be performed with caution. We instead propose to define the near-optimum flotation time as the time interval required to achieve 95%–99% of the maximum value of the SE function.

Study on the Flotation Behavior of Fine Coal in the Cyclonic-Separation Process

ABSTRACTFine-mineral separation has been a difficult problem in the mineral-processing field. A new cyclonic-flotation system was designed to solve the fine-mineral-recovery problem. Its design and operation are different from those of other cyclonic-flotation columns. In this study for the new cyclonic column, optimal reagent dosages, solid concentration, and aeration rate were determined. Many factors influence the operation of column flotation; however, in this study, mainly the effect of the circulation rate on the flotation behavior of the wide and narrow particle-size ranges of coal was investigated. The chosen circulation rates were 0.895, 1.044, 1.210, 1.369, 1.461, 1.578, 1.653, and 1.752 m/s. The wide particle size refers to a value of less than 0.5 mm. The narrow particle-size ranges refer to values from −250 to +75 μm, −75 to +45 μm, −45 μm, and +250 μm. The results showed that the combustible recovery of the narrow-size particles increased first and then decreased with the increasing circulation rate. The combustible recovery order of the narrow-size ranges in the same flotation time was as follows: −250 to +75 μm > −75 to +45 μm > −45 μm > +250 μm.

Separation of plastics: The importance of kinetics knowledge in the evaluation of froth flotation

Froth flotation is a promising technique to separate polymers of similar density. The present paper shows the need for performing kinetic tests to evaluate and optimize the process. In the experimental study, batch flotation tests were performed on samples of ABS and PS. The floated product was collected at increasing flotation time. Two variables were selected for modification: the concentration of the depressor (tannic acid) and airflow rate. The former is associated with the chemistry of the process and the latter with the transport of particles. It was shown that, like mineral flotation, plastics flotation can be adequately assumed as a first order rate process. The results of the kinetic tests showed that the kinetic parameters change with the operating conditions. When the depressing action is weak and the airflow rate is low, the kinetic is fast. Otherwise, the kinetic is slow and a variable percentage of the plastics never floats. Concomitantly, the time at which the maximum difference in the recovery of the plastics in the floated product is attained changes with the operating conditions. The prediction of flotation results, process evaluation and comparisons should be done considering the process kinetics.

Influence of hexylamine on kinetics of flotation and bubble attachment to the quartz surface

ABSTRACTIn this work flotation and single bubble tests were conducted with high purity quartz in water and hexylamine solutions at different pHs. It was found that flotation kinetics and time of the three-phase contact (TPC) formation (tTPC) at the quartz surface by the colliding bubble were affected by the hexylamine concentration and the solution pH. The TPC of the quartz/air bubble/hexylamine system was formed within the pH range 4–12. A strong relationship between the tTPC and flotation kinetics expressed as an inverse of the first-order rate constant (1/k) was obtained. The tTPC and 1/k values were the shortest within similar pH range.

Aqueous two-phase flotation for primary recovery of bacteriocin-like inhibitory substance (BLIS) from Pediococcus acidilactici Kp10.

An aqueous two-phase flotation (ATPF) system based on polyethylene glycol (PEG) and sodium citrate (NaNO3C6H5O7·2H2O) was considered for primary recovery of bacteriocin-like inhibitory substance (BLIS) from Pediococcus acidilactici Kp10. The effects of ATPF parameters namely phase composition, tie-line length (TLL), volume ratio between the two phases (VR), amount of crude load (CL), pH, nitrogen gas flow rate (FR) and flotation time (FT) on the performance of recovery were evaluated. BLIS was mainly concentrated into the upper PEG-rich phase in all systems tested so far. The optimum conditions for BLIS purification, which composed of PEG 8000/sodium citrate, were: TLL of 42.6, VR of 0.4, CL of 22% (w/w), pH 7, average FT of 30min and FR of 20mL/min. BLIS was partially purified up to 5.9-fold with a separation efficiency of 99% under this optimal conditions. A maximum yield of BLIS activity of about 70.3% was recovered in the PEG phase. The BLIS from the top phase was successfully recovered with a single band in SDS-gel with molecular weight of about 10-15kDa. ATPF was found to be an effective technique for the recovery of BLIS from the fermentation broth of P. acidilactici Kp10.

Ammonia modification for flotation separation of polycarbonate and polystyrene waste plastics

A promising method, ammonia modification, was developed for flotation separation of polycarbonate (PC) and polystyrene (PS) waste plastics. Ammonia modification has little effect on flotation behavior of PS, while it changes significantly that of PC. The PC recovery in the floated product drops from 100% to 3.17% when modification time is 13min and then rises to 100% after longer modification. The mechanism of ammonia modification was studied by contact angle, and Fourier transform infrared (FT–IR) and X–ray photoelectron spectroscopy (XPS) measurements. Contact angle of PC indicates the decline of PC recovery in the floated product is ascribed to an increase in surface wettability. FT–IR and XPS spectra suggest that ammonia modification causes chemical reactions occurred on PC surface. Flotation behavior of ammonia-modified PC and PS was investigated with respect to flotation time, frother concentration and particle sizes. Flotation separation of PC and PS waste plastics was conducted based on the flotation behavior of single plastic. PC and PS mixtures with different particle sizes are separated efficiently, implying that the technology possesses superior applicability to particle sizes of plastics. The purity of PS and PC is up to 99.53% and 98.21%, respectively, and the recovery of PS and PC is larger than 92.06%. A reliable, cheap and effective process is proposed for separation of PC and PS waste plastics.

Study on neutral chemical deinking of laser printed papers

A neutral deinking agent was applied for the deinking of laser printed papers under neutral or near neutral conditions of pH. The results showed that a deinking efficiency of 93% could be achieved with a laboratory made neutral deinking agent under optimum conditions. This neutral deinking agent, tagged as GWT, consists of anionic and nonionic surfactant, inorganic salt, etc. Optimum conditions were: GWT dosage of 2% (for dry recovered paper); pulping concentration of 10%~20%; pulping temperature of 60°C; pulping time of 25 min; conditioning time of 20 min; flotation concentration of 0.8%; and flotation time of 10 min. The neutral deinking technology is beneficial for the reuse of recovered paper due to its lower wastewater chemical oxygen demand (COD) and other chemical loads, thus resulting in lower treatment cost and environmental pollution compared with the regular alkali deinking process.

Physicochemical Characterization and Kinetic Study of Flotation Process Applied to the Treatment of Produced Water

Produced water (PW) discharged into the Mediterranean basin is a mixture of organic and inorganic materials of high toxicity and risk to the marine environment. This PW had a high water mineralization and significant amounts of suspended matter (SM). The detected levels of heavy metals, especially Ag+, Ba2+ and Pb2+ cations, were not negligible. The values of chemical oxygen demand (COD 735 mg/L) and total organic carbon (TOC 93.83 mg/L), which were very high, confirmed the presence of large concentrations of polycyclic aromatic hydrocarbons (PAHs) which were identified by infrared analysis. The total concentration of polycyclic aromatic hydrocarbons (PAHtot) in the PW sample was about 3.243 g/L. This can be treated by flotation in a very acidic medium at pH=2, in the presence of a neutral collector (Tween 80) at 0.5%, with an optimum cleaning efficiency of 93.67%, without necessarily generating the production of polluted sludge, in about 20 min, optimum time of flotation found. A study of flotation kinetics based on PAHtot recovery was carried out. It showed that the process followed Higuchi model. At the end of the treatment, all effluents were corrected from the acidic pH to the neutral pH, before to be discharged into the sea.

Local and global assessment of flotation kinetics

Most flotation data can be approximated with the first order kinetic equation. However, this equation frequently provides two, not one, parameters, that is the first order flotation rate constant k and maximum flotation recovery R max . Currently, the most often way of evaluation of a set of flotation data is by using efficiency e t o = k ·R max , being the slope of flotation kinetic curve at zero flotation time (t =0). This parameter has a local character and is useful only in very limited cases. It was proposed in this work to use a global flotation kinetic efficiency (e ) which can characterize the whole set of kinetic curves. For the considered in this work flotation data, a simple relation R max = e ·k was used. For other sets of flotation data, the global flotation kinetics efficiency very likely will be represented by another equation with the one-adjustable parameter.

Simultaneous aqueous two-phase flotation of sodium chlorophyllin and removal of sugars from saponified solution of bamboo leaves

An ethanol–tripotassium phosphate aqueous two-phase flotation (ATPF) system was first time studied for the separation of sodium chlorophyllin and sugars. The single factors influencing the recovery of sodium chlorophyllin in the top phase and removal of sugars in the bottom phase were investigated and optimized by response surface methodology (RSM). The maximum recovery percentage (88.28%) of sodium chlorophyllin were obtained at 0.55g/mL of tripotassium phosphate, 25mL/min of nitrogen flow rate, 26min of flotation time and 5mL of ethanol, meanwhile, the removal percentage of sugars reached 95.84%. Compared with aqueous two-phase extraction (ATPE), ATPF showed advantages of low consumption of organic solvent, high enrichment factors, and high separation effect. Sodium chlorophyllin were demonstrated theoretically and experimentally to have surfactivity. Finally, the scale-up experiments were conducted to further prepare sodium copper chlorophyllin, and the absorbance ratio (A406.00nm/A631.00nm) was 3.49. This method may blaze the trail for mass production of sodium copper chlorophyllin in industry.

Mechanism and Kinetics of Separation of Oil From Oil-in-Water Emulsion by Air Flotation

The authors investigate the application of air flotation for the removal of oil from oil-in-water emulsion using a flotation column of diameter 3.5 cm and height 106 cm. Several parameters affecting the separation efficiency such as effect of adding sodium chloride, effect of flotation time, and effect of air flow rate were investigated. The experimental data were also analyzed in terms of first-order kinetic rate model. Using this model flotation constant k and correlation coefficient r were determined. An equation relating flotation rate constant and the concentration of sodium chloride was developed. The maximum oil removal efficiency at optimized operating condition was found to be around 98.23%.

Seed dispersal capacity and post-dispersal fate of the invasive Spartina alterniflora in saltmarshes of the Yangtze Estuary

Spartina alterniflora is one of the most serious invasive species in the coastal saltmarshes of China. Seeds are generally considered to be the main method for this species to colonise new habitat, but little is known quantitatively about the seed dispersal capacity and post-dispersal fate (i.e., germination and survival time). We measured the duration of seed flotation, seed persistence and seed germination of S. alterniflora in three intertidal zones [low intertidal zone (LIT), middle intertidal zone (MIT) and high intertidal zone (HIT)] in the Yangtze Estuary on the eastern coast of China. The results showed that (1) the flotation time of S. alterniflora seeds ranged from 3 to 13 days, and the values were higher in HIT and MIT than in LIT; (2) the period of seed germination was from February to June, mainly in March and April, and seed source affected seed germination as the values for seeds from HIT and MIT were much higher than those from LIT, while burial sites had no effect on germination percentages, and (3) the seed persistence was less than a year regardless of seed source, which was characterised by a transient seed bank, with values being higher in HIT and MIT than in LIT. Our results suggested that low marsh plants were far less able to produce successful seeds, or conversely, that the mid-marsh location had plants with the greatest seed production and seed mass, and the high- and mid-marsh plants had good seed floatation ability, germination and survival. Thus, plants in the mid-and high-marsh may contribute disproportionally to an invasion.

Froude Scaling 기법을 적용한 헬기 비상부주 장비 해수면 안정성 입증 시험

해상 운용 헬리콥터는 비상부주를 적용하여 탑승자의 안전한 탈출을 위해 일정시간 이상 안정된 상태를 유지할 수 있어야 한다. 규정에서도 헬기가 해상에 착륙 후 승객이 탈출할 수 있는 충분한 부양시간을 요구하고 있다. 이를 위해 국내개발 헬기의 비상부주 장비는 해수면에서의 안정성 입증을 위해 "Froude Scaling" 기법을 적용하여 수조시험을 수행하였다. 시험 형상 및 조건은 헬기 하중조건과 요구되는 규격을 고려하여 설정하였다. 시험결과 요구 조건인 해상 상태 코드4와 손상조건 해상 상태 코드2에서 안전성이 있음을 확인하였다. A marine helicopter should remain sufficiently upright to permit safe evacuation of all personnel with a flotation system. And the rule requires that after ditching in water, the adequate flotation time will allow the occupants to leave the rotorcraft. To this end, stability test of the emergency flotation system for Korean marine helicopter was performed by using "Froude scaling method" in water tank. Test configuration and conditions were determined in consideration of the helicopter loading condition and related specifications. Test results meet the stability requirements at sea state code 4 and sea state code 2 with puncture conditions.

Flotation experimental research of calcareous–siliceous phosphorite

Based on the analysis of occurrence states and properties of a calcareous–siliceous phosphorite, the effects of GZ1 collector dosage, regulator dosage, pulp density and particles size distribution of sample on concentrate indexes were investigated by reverse flotation technology. The rare earth oxidize (REO) grade and recovery of concentrate were also analyzed in the work. Two-stage reverse flotation technology was applied for the beneficiation of a calcareous–siliceous phosphorite. Under the integrated optimal single factor conditions of GZ1 collector 0.9kg/t, phosphate regulator 14kg/t and pulp density 35wt.%, mass fraction of particles size of −74μm of 85wt.%, flotation time of 11min and flotation pH of 5.5, the P2O5 grade increases from 14.64wt.% in raw ore to 26.82wt.% in the concentrate, and the recovery is 72.09wt.%, while REO grade increases from 0.08wt.% in the raw ore to 0.175wt.% in the concentrate, and the recovery is 86.08wt.%.

Entrainment in froth flotation: The degree of entrainment and its contributing factors

In froth flotation, the degree of entrainment affects the concentrate grade and it is often assumed to be only a function of particle size in models. Literature suggests that other variables might also have a significant impact on the degree of entrainment. In this study, a factorial batch flotation experiment using a mixture of liberated chalcopyrite and two liberated gangue minerals, quartz and hematite, was performed to investigate the effects of these other variables (including impeller speed, gas flow rate, froth height and the specific gravity of gangue mineral) on the degree of entrainment. Results show that the degree of entrainment varied significantly as the flotation test conditions changed. Particle density and the interaction between gas flow rate and froth height had a statistically significant effect on the average degree of entrainment measured for the entire test. The degree of entrainment also significantly changed with flotation time throughout each experiment. It is hypothesised that these effects are a consequence of the degree of entrainment being affected by the weight of particles (not just their size) because of its effect on particle settling as well as the froth structure which provides varying resistance to particle drainage. It is concluded that models for the degree of entrainment that incorporate only particle size are not sufficient to predict gangue recovery and concentrate grade in an industrial application.

The interaction of pH modifiers with kaolinite in copper–gold flotation

The objective of this study was to assess the effect of lime and soda ash as pH modifiers on the flotation of a copper–gold ore mixed with kaolinite at different concentrations. For the flotation experiments air flow rate, impeller speed, flotation time and other flotation reagents were kept constant, and the flotation outcomes were explained by the rheology behavior of the slurries and the type of particle aggregates formed with the addition of either lime or soda ash. Rheology measurements showed that lime increased apparent viscosities more than soda ash, but in Cryo-SEM images it was observed that the kaolinite aggregates in the slurry were similar in structure for both lime and soda ash additions. These two findings suggest that Ca2+ ions released from lime led to the formation of stronger aggregates that were more easily entrained as indicated by the changes in mass recovered to concentrate during flotation experiments. As a result, more dilution of the flotation concentrate grade occurred when adjusting pH with lime. A decrease in concentrate grade was the main negative effect in the flotation of the copper–gold ore mixed with kaolinite with the overall flotation recovery not affected.