Effect of Temperature on the Stability of Froth Formed in the Recycle Process Water of Oil Sands Extraction

The formation of a stable froth on the top of separation vessels plays an important role in bitumen flotation during bitumen recovery from oil sands. The effect of temperature on the stability of froth using recycle process water employed in bitumen extraction was investigated using a water column. The froth became less stable with increasing solution temperature. Once the solution temperature increased above 50°C, irreversible precipitation of the surfactants present in the recycle process water was observed, resulting in a less stable froth.     

Removal of motor oil by continuous multistage froth flotation: Effect of operational parameters

A continuous multistage froth flotation column was employed to remove motor oil from water at a low concentration (500 mg/L) using an extended surfactant – branched alcohol propoxylate sulphate sodium salt (C_14-15–8PO–SO₄–Na) – as a frother. The highest separation efficiency (97% motor oil removal with the enrichment ratio of 16 for motor oil) was obtained at a foam height of 60 cm, an air flow rate of 40 L/min, a feed flow rate of 60 mL/min, a surfactant concentration of 0.3% (w/v), and an NaCl concentration of 1.5% (w/v). The process performance increased with increasing tray number but beyond 4 trays, the system could only offer lower concentrations of motor oil and surfactant in the effluent.     

Optimization of some parameters in column flotation and a comparison of conventional cell and column cell in terms of flotation performance

In this study, a comparative evaluation was made between column and mechanical flotation cells for fine coal cleaning. In addition, the optimum values of operating parameters were examined, which are important to achieve a desired separation performance in column flotation, such as the frother concentration, the collector dosage, the froth thickness, the wash water rate, the air rate and the feeding rate. The coal sample was collected from a classifying cyclone overflow stream consisting of nominally −130 μm material. Ash, volatile mater, fixed carbon and total sulfur contents of the sample were found to be 47.50%, 20.80%, 31.70% and 0.75%, respectively. Comparison of the column and mechanical flotation results indicated that column flotation was considerably more efficient than mechanical flotation for fine coal cleaning. High froth thickness and wash water addition during column flotation made it possible to obtain cleaner coals. The column flotation produced a 15.60% product ash with a 50.92% clean coal yield and 81.85% combustible recovery.     

Diesel Oil Removal by Froth Flotation Under Low Interfacial Tension Conditions II: Continuous Mode of Operation

Abstract

The objective of this study was to investigate the relationship between interfacial tension (IFT) and foam characteristics and the efficiency of diesel oil removal from water in a continuous froth flotation column. The effects of operational parameters, including surfactant concentration, salinity, oil-to-water ratio, foam height, air flow rate, and hydraulic retention time (HRT) on the oil removal were investigated in the continuous mode of a froth flotation operation and compared to batch operation results. Unlike the batch system, for the continuous system used in the present study, having only branched alcohol propoxylate sulfate sodium salt surfactant (C_14–15(PO)₅SO₄Na) and NaCl present in the solution yielded such poor foam characteristics that a stable froth which overflowed the flotation column could not be produced, so the addition of sodium dodecyl sulfate (SDS) as a froth promoter was used to improve the foam stability. Unlike the batch froth flotation system with only C_14–15(PO)₅SO₄Na, the continuous froth flotation with the mixture of C_14–15(PO)₅SO₄Na and SDS, it was not possible to find a SDS and a NaCl concentration at which both ultralow IFT and good foaming were both achieved. Foam formation, stability, and production rate were found to be crucial parameters to the froth flotation efficiency. The continuous froth flotation system offers a high diesel oil removal of 96% in the single stage unit. Demonstration of efficient operation in the continuous mode in this work is important to the practical application of froth flotation in large scale processing.     

Froth flotation as primary treatment of flowback water: Removal of total organic carbon and prediction of kinetics

Petroleum and exploration industries employ a hydrofracking process where a large volume of water (fracturing fluid) is injected and a fraction (known as flowback water) is returned to the surface. Froth flotation is a typical process employed for the primary treatment of water. In the present work, froth flotation has been used as a pretreatment method for real flowback water sourced from the petroleum and shale gas exploration industry. In the present work, a first-principle based convective mass transfer model has been developed to describe the froth flotation performance. The resultant equation was solved analytically and compared with the numerical solution, and a parametric sensitivity analysis of the process performance was also undertaken. In addition, a correlation to estimate the flotation rate constant was proposed, thereby circumventing the need to obtain a large number of cumbersome parameters experimentally. Overall, this study proposes froth flotation as an efficient primary treatment method towards the separation of dispersed oil droplets from the flowback water and the corresponding prediction of kinetics using a first-principle based transport model.     

泡沫浮选耦合膜过滤回收有机废水中纳米TiO2光催化剂的工艺

本研究的目的是开发一种新型的泡沫浮选耦合超滤技术的方法,以实现从有机废液体系中经济、高效地回收纳米TiO₂光催化剂。首先,对超滤膜分离有机废液中纳米TiO₂光催化剂的使用效率,包括透过通量和截留率进行评价。随后,为了减少超滤操作进料液中纳米TiO₂光催化剂的浓度,在泡沫浮选阶段确定以阳离子表面活性剂——十六烷基三甲基溴化铵（CTAB）作为捕获剂,研究了CTAB浓度、气体体积流速、分布器孔径对泡沫浮选回收纳米TiO₂光催化剂富集效率的影响。最后,确定泡沫浮选耦合超滤耦合回收纳米TiO₂光催化剂的工艺条件。试验结果表明,采用耦合工艺,在pH 7.0、CTAB浓度0.20g/L、气体体积流速15mL/min以及分布器孔径180μm的条件下,纳米TiO₂光催化剂富集比和回收率分别为22.52和99%,同时膜的使用寿命较非耦合操作提高了133％。     

On Fiber Rejection Loss in Flotation Deinking

Reducing fiber rejection loss in flotation deinking is very important to conserve natural resources and reduce the cost of secondary fibers in paper recycling. This study examined two aspects of the problem, fiber consistency in the rejection stream and rate of froth (or wet stream) rejection. Flotation experiments were conducted using both nylon and wood fibers in column and commercial bench‐scale flotation deinking cells. It was found that increased froth stability resulted in a lower fiber consistency in the wet reject stream. However, it also increased rejection rate of the wet stream. As a result, the total fiber rejection loss was increased with the increase of froth stability. The results obtained suggest that controlling froth stability through reducing frother application and froth rejection are effective ways to reduce fiber yield loss in flotation deinking. This study also experimentally measured water and fiber drainage in fiber suspended froth to explain the effect of froth stability on fiber consistency in the reject stream using froth drainage dynamics.     

泉店选煤厂浮选系统改造

通过分析泉店选煤厂原浮选系统工艺流程,提出了选煤厂主要存在浮选尾煤灰分低,浮选药耗高,浮选系统处理能力偏低,浮选床效率低,浮选精矿池泡沫量大等问题。针对选煤厂存在的问题,提出2种改造方案,并最终确定采用新建浮选车间并安装2台浮选机替换原有浮选床的改造方案。改造完成后,泉店选煤厂浮选尾煤灰分、精煤产率和可燃体回收率分别提高了55.61%,43.86%和44.51%,精煤灰分降低了0.29%,药剂用量减少了0.22 kg/t;浮选精矿池泡沫量明显降低,加压过滤机上料情况明显好转,处理量增大,且减少了1台空压机的使用;选煤厂每年增加精煤收益,节省电费和药剂费用总计12770.74万元。     

Assessment of Bitumen Re c overy from the Athabasca Oil Sands Using a Laboratory Denver Flotation Cell

A methodology was developed in this study to evaluate the effect of operating parameters on the processability of oil sands using small‐scale laboratory experimental devices. By subtracting bitumen recovered to the froth by entrainment with water, the concept of “true flotation recovery” is proposed to describe bitumen recovery resulting from bitumenbubble attachment. The experimental results indicated that “true flotation recovery” is a more sensitive and meaningful marker than overall bitumen recovery to evaluate the processability of oil sands using small‐scale laboratory test units.     

环流浮选塔用于含油污水处理的实验研究

以空气/含柴油污水为模拟介质体系,在环流浮选塔(外筒体内径100 mm,高932 mm;导流筒内径59 mm,高780 mm)上考察了操作气速、液相流量及浮选塔上部空间填料设置对油-水分离效率的影响. 结果表明,分离效率随操作气速增大先增后降,随液体流量增大而降低;与传统空筒式浮选塔相比,环流浮选塔的分离效率比常规空筒式浮选塔有显著提高. 实验确定的最佳操作气速为0.015~0.02 m/s,最佳液相流量为20 L/h,在环流浮选塔上部设置填料的情况下,油-水分离效率最高可达57.3%. 基于实验数据建立了涉及气泡特性、液相物性、气液相流量及油滴返混影响因素在内的分离效率的经验模型,与实验值吻合较好.     

一种新型浮选柱的数值模拟及性能研究

自主研制了一种新型多级规整填料浮选柱,应用计算流体力学软件FLUENT6.3.26进行数值模拟计算,对其内部的气液两相流动进行了考察,采用了欧拉-欧拉多相流模型,对气相的模拟采用单一气泡尺寸,液相湍流采用了标准k-ε模型,两相之间的动量传输仅考虑曳力作用。通过模拟,获得了不同实验条件下浮选柱内部的气液速度场分布、气含率分布等,对部分模拟结果进行了定量比较。结果表明随着气相流量的增大,浮选柱内部气含率增大,液体循环速度增大,从而气液之间混合更加充分,这对于提高浮选柱的分选效率和设备的放大有重要意义。在唐山钱家营开滦煤矿选煤厂进行了以其煤浆为原料的浮选性能的测试,在气体1.25 m³/h,进料0.05 L/h条件下20 min停留时间获得了精煤灰分10.28%,尾煤灰分43.39%,精煤产率52.53%的指标,与该厂浮选精煤灰分10.58%相接近。     

Improvement of the Flotation Selectivity in a Mechanical Flotation Cell by Ultrasound

In this study, the effect of ultrasound on froth and pulp phases has been investigated in the flotation of two different ore samples, namely barite and chalcopyrite. In order to determine the overall flotation rate constants at various froth depths, incremental recoveries obtained from the flotation tests with and without ultrasound were fitted to a first-order rate equation. Thus, the recoveries of froth and pulp phases were calculated.

The use of ultrasound speeded up the bubble coalescence and therefore reduced the froth phase recovery in the ultrasonic flotation of both barite and chalcopyrite. In addition, the results indicate that there is a considerable effect of ultrasound on the pulp phase recovery in the chalcopyrite flotation whereas no significant differences in the separation performance were obtained from the ultrasonic flotation of barite with and without ultrasound. The results also indicate that a pronounced selectivity effect was obtained from the ultrasonic flotation of both barite and chalcopyrite. The use of ultrasound in the froth remarkably improves the quality of the chalcopyrite concentrate, especially at the shallow froths. Therefore, either effective pulp volume can be increased without sacrificing the separation selectivity or the pulp density can be decreased to obtain better product quality at shallow froths in the ultrasonic flotation of chalcopyrite.     

The influence of frother types and concentrations on fine particles’ entrainment using column flotation

Entrainment which is the characteristic feature of fine particles is closely related to water recovery. It is based on the changes depending on the establishment of linear relationship between water recovery and solid recovery. This paper deals with the investigation of the effect of frother types and concentrations on fine particles’ entrainment using column flotation. Entrainment of fine particle using a mixture of artificial ore (celestite:calcite; 1:1) was investigated in column flotation. In a two-phase system (water/air), the variation of bubble diameters and gas hold-up with a superficial air rates using different frother types and concentrations were tested. The results showed that the frother types and concentrations had significant effect on the grade and recovery, superficial air rate, gas hold-up and fine gangue entrainment. Entrainment factors for frother types and concentrations were compared in flotation column. Kirjaveinen^[11] model was used for describing the specific entrained factor (P_i) of hydrophilic particles. It has been found that Kirjaveinen model supports the results of this study.     

Flow characterization of a flotation column

The flow characteristics of a froth flotation column have been experimentally studied using air and aqueous surfactant solutions without the presence of solids. The hold-up behaviours of the bubbly and the froth zones of the column were linked together using the drift-flux model. The ratio of the gas drift-flux, j_gf, to the bubble terminal velocity, V, for both the bubbly and the froth zones was found to be well correlated by the Richardson–Zaki equation:      

Diesel Oil Removal by Froth Flotation Under Low Interfacial Tension Conditions I: Foam Characteristics,and Equilibration Time

Abstract

Froth flotation is a surfactant‐based separation process which is suitable for treating dilute wastewaters. To achieve high performance for the froth flotation operation, the combination of an ultra‐low interfacial tension (IFT) between excess oil and excess water phases, high foam production rates, and high stability of the foam produced, must be attained. To obtain the ultra‐low interfacial tensions, a Winsor Type III or middle phase microemulsion has to be formed. In this study, branched alcohol propoxylate sulfate sodium salt with 14–15 carbon number and 4 PO groups (Alfoterra 145–4PO) was used to form microemulsions with diesel oil. From the results of this work, an increase in surfactant concentration decreased the IFT, and increased foam stability. To obtain the minimum IFT in the region of a Winsor Type III microemulsion, the addition of 5 wt.% NaCl was needed. However, this optimum salinity does not result in effective froth flotation due to poor foam characteristics. The results indicate that both the IFT and the foam characteristics should be optimized to achieve high efficiency of oil removal in a froth flotation operation. Unlike the previously‐studied ethylbenzene system, agitation of the solution before introduction into the flotation column yielded the lowest diesel oil removal efficiency because of the poor foam characteristics compared to either unagitated systems or systems allowed to equilibrate for one month.     

Effects of residual concentration of collector CTAC on flotation behavior of illite

ABSTRACT

In present study, illite flotation behavior with Cetyl Trimethyl Ammonium Chloride (CTAC) as the collector has been studied to investigate the effects of its residual concentration on froth stability and flotation. Results showed that, with increasing conditioning time, the residual concentration (frother concentration) and froth height decreased simultaneously, while the adsorbed amount (particle hydrophobicity) increased. Increasing CTAC conditioning time decreased the residual concentration in solutions, resulting in poor froth stability and flotation recovery at high pH; the adsorption rate of CTAC on illite surface was relatively high at higher pH due to strong electrostatic mechanism, making CTAC residual concentration decrease.     

The influence of solvent and demulsifier additions on nascent froth formation during flotation recovery of Bitumen from Athabasca oil sands

In the commercial slurry conditioning and flotation process applied to Athabasca oil sands the primary bituminous froth can contain significant amounts of emulsified water and suspended solids. Previous work [Fuel Process. Technol. 56 (1998) 243] has shown that a small chemical addition during the nascent froth process can yield froth of higher quality, without sacrificing bitumen recovery or increasing tight emulsion-forming tendency. In the present work we have investigated the addition of demulsifiers, mostly water-in-oil (W/O) emulsion breaking agents, in an attempt to encourage water droplet coalescence and separation from nascent froth. It was found that certain combinations of high HLB surfactants and solvents can be added in small amounts during the nascent froth process to cause significant reductions in froth water content without sacrificing bitumen recovery. The existence of an optimum surfactant concentration for such beneficial additives correlates with a minimum in interfacial tension and is consistent with conventional oilfield demulsifier experience. The application of our results could lead to a substantial increase in the throughput capacity of froth handling and treatment plants.     

Froth stability and entrainment evaluation of a novel frother for KCl/NaCl flotation

The rate of KCl recovery by froth flotation using low-grade carnallite is 70%–85%. Herein, a novel frother, dipropylene glycol butyl ether (DPNB), was prepared to increase the flotation efficiency of KCl recovery systems. DPNB could be applied at only half the dosage of the conventional frother methyl isobutyl carbinol (MIBC) and achieve a KCl recovery rate of 94.8%–98.6% with a high KCl grade (63.2%–66.5%). To date, these results are the best reported for pneumatic flotation. DPNB had a 10% higher maximum dynamic stability factor compared with MIBC; moreover, the apparent entrainment velocity of DPNB was half that of MIBC. The molecular structure of DPNB had hydroxyl and ether groups, which promoted interactions with water, thereby contributing to its excellent froth stability. DPNB is environment friendly owing to its low volatility and, thus, a promising frother for the green and highly efficient flotation of KCl/NaCl.     

An investigation of the recovery of cryolite from alumina-electrolyte froth by flotation

In the industrial production of aluminium by the electrolysis of alumina, electrolyte froth, which is a mixture of carbon and cryolite is obtained at a rate of 50 kg of froth per ton of aluminium produced. Cryolite can be recovered from this mixture by flotation. In this study, the effects of the following parameters on flotation were experimentally investigated: particle size, type, combination, dosage and ratio of reagents, and conditioning time. It is found that it is possible to decrease the carbon content of cryolite below 1% by suitably choosing the operating parameters. Electrolyte froth must be ground to —100 mesh size for the liberation of carbon particles captured in the cryolite matrix. Any combination of two of the reagents, kerosene, fuel oil, creosote and terebenthene yield good results if used together with pine oil. Pine oil is found to be a more effective frother compared to Pril, a commercial detergent. Satisfactory separations are obtained when a kerosene-fuel oil mixture (50:50, v/v) is used as the collector with a dosage of 3.7 kg per ton of feed together with pine oil, the frother, with a dosage of 0.095 kg per ton of feed.     

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands—II. Flotation hydrodynamics of water-based oil sand extraction

Bitumen flotation hydrodynamics in water-based oil sand extraction is critically reviewed by comparing aeration of oil sand slurries with mineral flotation. The role of the two-stage particle-bubble attachment model in flotation is emphasized as a means to accelerate bitumen flotation recovery. It involves the generation of micro/nanobubbles and their frosting on hydrophobic bitumen droplets, followed by their attachment to a flotation-size bubble via its coalescence with the nanobubbles frosted on the bitumen. Nanobubble generation by hydrodynamic cavitation demonstrates that the size of nanobubbles can be reduced, and the number of nanobubbles increased by fast liquid flow, intensified agitation, high dissolved gas content and surfactant concentration. The mechanism of pre-existing gas nuclei in enhancing nanobubble generation by cavitation is utilized to produce a large volume of stabilized nanobubbles for practical flotation, by continuously recirculating the stream through a gas saturation tank or a cavitation tube. The aeration of oil sand slurries in hydrotransport pipelines is analyzed based on its similarity to dissolved air flotation. Bitumen extraction recovery increased significantly with the presence of nanobubbles in the system. The role of improved flotation hydrodynamics in bitumen recovery is briefly discussed in terms of the Suncor operation using flotation columns to process oil sand middling streams. Future research should be directed at understanding bitumen flotation kinetics, optimizing size ranges of nanobubbles for maximized flotation recovery, minimizing wearing of cavitation tubes in industrial operations, and intensifying the role of in-situ nanobubble nucleation on hydrophobic particles/bitumen droplets in flotation, especially for bitumen extraction from underperforming oil sands.