Bitumen Recovery with Oily Air Bubbles

Air‐kerosene bubbles were used in a novel laboratory scale pipeline loop to assess the extraction performance of poor processing oil sand ores. The addition of kerosene to air, whereby producing oily bubbles, substantially enhanced bitumen recovery from poor processing oil sand ores. The oily bubbles were added in a pipeline loop during bitumen liberation from the sand grains. The bitumen recovery from poor processing ores with the addition of the oily bubbles to the conditioning slurry becomes comparable to that of good processing ores. The present findings can be of substantial benefit to the oil sands industry.     

脱油沥青喷雾造粒过程影响因素分析

利用重油梯级分离耦合萃余残渣喷雾造粒的方法将脱油沥青制成沥青粉,为脱油沥青提供了良好的应用前景.在连续溶剂脱沥青装置上考察了影响脱油沥青造粒的主要因素,原料为加拿大油砂沥青、委内瑞拉常压及减压渣油、中东减压渣油,溶剂为正丁烷、正戊烷、正己烷及其混合溶剂,萃取塔底温度分别为130、146、160℃,而副溶剂温度为130℃...     

Understanding Water‐Based Bitumen Extraction from Athabasca Oil Sands

The current state of knowledge on the fundamentals of bitumen recovery from Athabasca oil sands using water‐based extraction methods is reviewed. Instead of investigating bitumen extraction as a black box, the bitumen extraction process has been discussed and analyzed as individual steps: Oil sand lump size reduction, bitumen liberation, aeration, flotation and interactions among the different components that make up an oil sand slurry. With the development and adoption of advanced analytical instrumentations, our understanding of bitumen extraction at each individual step has been extended from the macroscopic scale down to the molecular level. How to improve bitumen recovery and bitumen froth quality from poor processing ores is still a future challenge in oil sands processing.     

油砂沥青分离技术研究进展

油砂作为一种储量丰富的非常规石油资源,越来越受到世界各国的广泛关注。对于油砂的加工利用,其前提就是油砂沥青的分离,因此对其技术的研究十分必要。本文首先介绍了油砂的组成及分类,然后着重对几种主要油砂分离技术（热水洗法、有机溶剂萃取法、超临界流体萃取法、超声波辅助萃取法、离子液体萃取法和热解干馏法）的优缺点进行了汇总,并详细分析了它们各自的分离流程。其中,热水洗法、有机溶剂萃取法和热解干馏法是目前研究相对成熟的3种方法,而其他方法虽然分离效果相对高,但是对工艺条件和设备的要求较高,导致较高的投资和运行成本,因此还需要对这些油砂沥青分离工艺进行更加深入的研究,以满足工业化应用的要求。最后,对油砂沥青分离技术的发展前景进行了展望。     

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands: I. Flotation chemistry of water‐based oil sand extraction

The role of surface hydrophobicity in water‐based oil sand extraction is examined from the perspective of mineral flotation separation. Although anionic carboxylates (sulphonates) released from bitumen are helpful for charging bitumen and liberating bitumen from sand grains, their presence in oil sand slurries tends to make bitumen and bubbles less hydrophobic. In addition, solid hydrophobization under oil sand extraction conditions can occur through different mechanisms of carboxylate adsorption. It is the hydrophobized fine solids that present challenges for achieving a high bitumen recovery with a good froth quality, due to their competition with bitumen for attachment to bubbles. While chemisorption of carboxylates contributes to hydrophobization of heavy minerals present in oil sands, carboxylate adsorption activated by hydrolyzed metal cations alters silica and clays from hydrophilic to hydrophobic. Different adsorption mechanisms of calcium on silica, clays, and other minerals are analyzed to explain why fine solids of varying mineralogy in combination with calcium affect bitumen extraction differently. Metal ions that activate solid hydrophobization under oil sand extraction conditions are identified from dynamic attachment of solids from mature fine tailings (MFT) to bitumen. To mitigate the effect of fines on oil sand extraction, selective flocculation of fine solids is recognized as especially feasible for bitumen flotation recovery from oil sand middling streams. Future research in reducing or eliminating caustic addition, understanding the role of inorganic anions, and searching for feasible techniques for treating MFT based on different mineralogy and surface properties, are briefly discussed.

     

Effect of ore quality on non-aqueous oil sand extraction performance

Current commercial aqueous based extraction processes are energy and greenhouse gas (GHG) intensive and require large tailings ponds. Non-aqueous extraction (NAE) of bitumen from mineable oil sands is an alternative that eliminates tailings ponds with potentially lower energy requirements and GHG emissions. The economics of the NAE process depend partly on the impact of ore quality on bitumen recovery and product quality (low water and solids content). It has been claimed that NAE performance is insensitive to the quality (bitumen content) of the oil sand ores. However, the available data are ambiguous because different extraction methods and solvents were used in different studies and, in many cases, a limited range of ore qualities was examined. In this study, bitumen was extracted from eight ores of different quality with cyclohexane using a multistage method equivalent to a countercurrent process with a solvent/ore ratio of 0.67 w/w. The bitumen recovery and the water and solids content of the product bitumen were determined for each ore. It was found that bitumen recovery correlated negatively to clay content of the ore. The loss of recovery was attributed to bitumen adsorption on clays. The product quality was insensitive to the ore quality and instead depended on the density of the fluid medium, as expected with a centrifuge-based separation method. The recovery and product quality from the NAE method were similar to those from aqueous extractions.     

Water‐Based Bitumen Recovery from Diluent‐Conditioned Oil Sands

Important process development aspects leading to more efficient bitumen recovery from diluent‐conditioned oil sands by water‐based methods are discussed. Bitumen viscosity of 0.5–2 Pa·s is required at the processing temperature and can be reduced to this level by bitumen dilution with an organic solvent. Oil sand porosity, however, poses a restriction on the amount of diluent that can be accepted by the oil sand. Also oil sand‐diluent conditioning time is an important process parameter and can vary from a few minutes for oil sands with low‐viscosity bitumen to several hours if viscosity of the bitumen is high. Additionally, the bitumen separation efficiency during digestion and flotation can be enhanced by reducing the bitumen/water interfacial tension through addition, for example, of tripolyphosphate to the aqueous phase.     

有机溶剂萃取加拿大油砂应用研究

介绍了溶剂作为萃取剂分离油砂的技术,溶剂萃取油砂过程包含两个阶段:沥青相向溶剂的溶解过程和沥青、溶剂与砂粒的分离过程。考察了单一溶剂甲苯、丙酮、乙酸乙酯和甲苯/正庚烷、丙酮/正庚烷、乙酸乙酯/正庚烷组成的复合溶剂体系在相同条件下对油砂沥青的萃取率,在此基础上进一步对比了不同溶剂体系对沥青四组分饱和分、芳香分、胶质和沥青质的萃取效果,同时考察了不同浓度的沥青-溶剂溶液的表面张力,结果表明在油砂萃取过程中沥青-溶剂体系的表面张力主要取决于所选溶剂的种类,而沥青的浓度对溶液表面张力的影响不大。混合溶剂体系甲苯/正庚烷、丙酮/正庚烷、乙酸乙酯/正庚烷相比纯溶剂萃取率较高,其沥青溶液表面张力较低,是良好的分离油砂溶剂体系。     

Interaction between Bitumen and Fines in Oil Sands Extraction System: Implication to Bitumen Recovery

Colloidal interactions between bitumen and fines, extracted directly from oil sand ores, were investigated with zeta potential distribution measurement and surface force measurement using an atomic force microscope (AFM). Fines from good processing ores exhibit a negligible attachment to bitumen surfaces, due to hydrophilic nature of the fines. Fines from poor processing ores exhibit a stronger attachment to bitumen surfaces by an attractive hydrophobic force between bitumen and fines, due to hydrophobic nature of the fines and the presence of high concentration divalent cations in the processing water.     

溶剂抽提法分离印尼油砂的实验研究

利用溶剂抽提法对印尼油砂进行萃取分离实验,综合考察了剂砂比、抽提温度、抽提时间、抽提次数等操作条件对油砂沥青提取的影响,确定较佳的油砂分离条件。结果表明,印尼油砂更适合采用溶剂抽提法分离,从油砂沥青提取率、操作成本和环保多角度考虑,在超声波的作用下,剂砂比为2．5,抽提温度40℃,抽提时间30min,抽提3次的条件下,油砂沥青的提取率较高,达到20．31％。     

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.     

Theory of Spherical Agglomeration. II. Layering/Crushing Process in a Rotating Conical Drum

Abstract

A theoretical study is made of the so-called layering/crushing agglomeration process in a rotating conical drum under steady-state continuous flow conditions. A particular application is the separation of bitumen from the solid particles in oil sands, where the nonwetting liquid is a bitumen-solvent mixture and the wetting liquid is water. It may be assumed that the water is completely imbibed by the agglomerating granules (particles), so that the system consists of granules suspended in the nonwetting liquid. In the layering/crushing process, the granules are divided into two nonoverlapping size distributions, the small crushed granules and the large granules on which the layering takes place. The agglomeration process therefore becomes a complicated example of three-phase flow. The three phases are the continuous nonwetting liquid and the two granular phases. The steady-state mass balance equations for the two groups of granules in the rotating conical drum can be integrated approximately. The mean velocity of the layered (large) granules parallel to the axis of the cone is directed from apex to     

Capillary Curves for Ex‐situ Washing of Oil‐Coated Particles

The oil removal efficiency for the ex situ extraction of bitumen from oil sands, or ex situ washing of oil‐contaminated sand and related processes is determined by the balance of forces at the oil/water and solid/fluid interfaces. The objective of this work is to estimate the balance of forces at the interface using dimensionless numbers, and their use in evaluating and engineering ex situ soil washing processes. To this end, bitumen was removed from bitumen‐coated sand particles using a two‐step process. In the first step, the particles were mixed with a suitable solvent (toluene) used, primarily, to reduce the viscosity of bitumen. The particles were then mixed with water or an aqueous surfactant solution capable of producing low interfacial tensions with the solvent‐bitumen mixture. The fraction of oil retained after washing was evaluated as a function of interfacial tension, solvent/bitumen ratio, mixing time, mixing velocity, and particle size. These ex situ washing conditions were normalized using dimensionless film and particle‐based Weber and Capillary numbers. The fraction of oil retained by the particles was plotted against these dimensionless numbers to generate capillary curves similar to those used in enhanced oil recovery. These curves reveal the existence of a critical film‐based Weber number and a particle‐based Capillary number that can be used in the design or evaluation of soil washing processes. The film‐based Weber number also explained literature data that associates interfacial tension with the removal of oil from oil‐based drill cuttings, as well as field observations on the role that particle size plays on the removal of oil in soil washing operations.     

Bitumen—sand interaction in oil sand processing

Bitumen—sand interaction was studied as a function of pH, particle size, temperature and solvent addition to bitumen. Sand particles can be easily detached from the bitumen surface at pH> 6. At pH < 6, strong attachment between bitumen and sand is observed. The bitumen—sand interaction is also particle-size dependent: the finer the particles, the stronger the attachment. The detachment of coarse particles from bitumen can be achieved by increasing the alkalinity of the solution, but not for fine particles, indicating that the particle size is one of the critical factors affecting liberation of bitumen from sand. Increasing temperature has two effects: it is not only reduces the viscosity to facilitate bitumen liberation, but also increases the electrostatic repulsion between sand and bitumen. This is confirmed by the DLVO theory and is in agreement with the batch extraction results on real oil sands.     

离子液体促进溶剂萃取油砂沥青

传统水洗法和溶剂萃取法萃取油砂沥青时,存在沥青中含有沙土和残沙中含有油等缺点。为解决上述缺点,本文采用不同比例的乙酸甲酯/正庚烷复合溶剂萃取油砂沥青,研究了离子液体（1-丁基-3-甲基咪唑四氟硼酸盐,[Emim]BF4）对该溶剂萃取体系的萃取率和分离洁净程度的影响。采用红外光谱仪和扫描电镜对萃取后的残沙和沥青的洁净程度进行了定性分析,并结合元素分析仪和电感耦合等离子体发射光谱仪获得萃取后残沙和沥青的洁净程度的定量结果。实验结果表明：当复合溶剂体积比为2∶3时,[Emim]BF4促使沥青回收率达到最大值94.20%,比单纯复合溶剂萃取体系的最大萃取率高7.92%;通过上述测试方法的定性和定量分析,证明了[Emim]BF4能有效解决沥青夹带沙土和残沙中含油的问题。     

Study of fines in bitumen extracted from oil sands by heat-centrifugation

The temperature dependence of, first, the yield of bitumen extracted from oil sands and, second, of the coextracted solid particles in the bitumen was studied. Centrifugal extractions were performed in an argon (inert) atmosphere at temperatures ranging from 30 °C to 150 °C. The co-extracted solid particles were investigated through digital image analysis, instrumental neutron activation analysis and ash yield. The yield of bitumen increases with extracting temperature and is also dependent on the grade and origin of the oil sand. The quantity of fines, e.g. clay minerals or fine sand particles is dependent on the grade and origin of the oil sand. The total amount of co-extracted solid particles is found to be independent of the extracting temperature.     

Understanding weathering of oil sands ores by atomic force microscopy

Effect of weathering on colloidal interactions between bitumen and oil sands solids was studied by atomic force microscopy (AFM). The change in bitumen chemistry due to weathering was found to have a negligible effect on the interactions of bitumen with solid particles. However, the increase in solid surface hydrophobicity due to ore weathering reversed the long‐range interaction forces between bitumen and solids from repulsive to attractive with a corresponding increase in adhesion force. The measured force profiles between bitumen and various solids can be well fitted with the extended DLVO theory by considering an additional attractive force. The attractive long‐range force and increased adhesion force make the separation of bitumen from solids more difficult and the attachment of fine solids on liberated bitumen easier, thereby leading to poor bitumen liberation and lower aeration efficiency. Such changes account for the observed poor processability of the weathered ores. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Behavior of tar sand bitumen with paraffinic solvents and its application to separations for athabasca tar sands

A study was made of the dissolution of tar sand bitumen using low-molecular-weight paraffinic solvents at essentially ambient temperatures. The experimental data were obtained using the spinning disc technique, liquid-fluidized beds, and direct particle-size analysis of the insolubles. The results are consistent with a mechanism where the paraffins leach the soluble oil from the bitumen and leave behind a porous network of insoluble asphaltenes. This phenomenon of oil diffusing through an asphaltene layer was modeled using Fick's law for unsteady-state diffusion. An understanding of the mechanism of bitumen extraction with paraffins and also the effect of fluid mechanics in the tar sand system have been applied to obtain a novel separation of deasphalted oil and asphaltenes from Athabasca tar sands. This new separation technique has the potential of simplifying downstream processing for the bitumen and also of avoiding environmental problems associated with the present tar sand extraction technology.     

Oil Sand Slurry Conditioning Tests in a 100 mm Pipeline Loop

Fresh oil sand slurries were prepared and tested in a 100 mm pipeline loop at 37°C to evaluate the effects of average flow velocity, slurry air content and air injection method (bulk or continuous) on slurry conditioning, i.e., the evolution of the in‐pipe processes that promote gravity separation of bitumen‐air aggregates from the remainder of the slurry. The potential separability of the bitumen in the slurry was evaluated using a slurry Conditioning Index (CI). When no air was injected into the slurry, the slurry CI was low (≤0.1), indicating very poor conditioning. An increase in flow velocity from 2 m/s to 4 m/s and injection of 5% air (by volume) dramatically improved the slurry CI, to ～ 0.6. The improved slurry conditioning observed at the higher velocity is explained by the increased force of fluid turbulence experienced by the particles and the greatly enhanced bitumen‐air contact.     

Effect of weathering on oil sands processability

Effect of weathering on oil sand processability was studied using a good processing ore, a laboratory weathered ore and a naturally weathered ore. The laboratory weathered ore was prepared by weathering the good processing ore in an oven under controlled conditions to study the nature of ore weathering. It was found that the bitumen recovery, bitumen flotation rate, and bitumen froth quality were greatly reduced due to ore weathering. It was also observed that the fresh bitumen coating on a silicon surface could recede and liberate from the silicon surface easily even in a warm water of 35°C. However, after weathering of the bitumen coating, its liberation became more difficult and effective liberation of bitumen from the silicon surface could only occur at higher temperature of 65°C. The current study further confirms that weathering enhanced adhesion of bitumen with solids, causing difficulties for bitumen liberation from sand grains and hence poor processability of weathered ores.