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.     

Effect of Operating Temperature on Water‐Based Oil Sands Processing

Operating temperature is one of the most important controlling parameters in oil sands processing. Considering the massive energy consumption and green house gas emission, lowering the processing temperature is highly desirable. To achieve such an ambitious goal requires a comprehensive understanding on the role of temperature in oil sands processing. This paper provides an overview of major findings from existing studies related to oil sands processing temperature. The relation between temperature and bitumen recovery is discussed. The effect of temperature on the physiochemical properties of oil sand components, such as bitumen viscosity, bitumen surface tension and surface potentials of bitumen and solids, is analyzed. The interactions between bitumen and solids and between bitumen and gas bubbles as a function of temperature are recounted. Also discussed is the role of chemical additives in oil sand processing. It has been found that temperature affects nearly all properties of oil sands among which bitumen viscosity and bitumen‐solids adhesion impose a prominent impact on bitumen recovery. The use of selected chemical additives can reduce bitumen viscosity and/or the bitumen‐solids adhesion, and thus provide a possible way to process oil sands at a low temperature while maintaining a high bitumen recovery.     

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.     

水基提取技术用于油砂分离的研究进展

油砂作为一种重要的非常规油气资源,其分离技术的研究近些年来引起了国内科研工作人员的重视。介绍了目前世界上最重要的油砂分离技术--水基提取技术的基本原理及影响油砂分离的重要影响因素,阐述了油砂结构、特性与水基提取分离的重要关系及分离条件对沥青回收率的重要影响作用,同时探讨了原子力显微镜用于油砂水基分离过程中相关微观机理研究的重要应用,最后对水基提取技术用于油砂工业生产的流程进行了简单介绍。     

Effect of molecular weight and charge density on the performance of polyacrylamide in low‐grade oil sand ore processing

The effect of charge density and molecular weight (MW) of partially hydrolyzed polyacrylamide (HPAM) polymers on their performance in processing low‐grade oil sand ores was investigated. Bitumen extraction and tailings settling tests were carried out and an atomic force microscope (AFM) was used to directly measure the bitumen‐solid and solid‐solid interaction forces. It was found that HPAM polymers with a low MW acted as dispersants in the bitumen extraction process, resulting in low bitumen recovery and slow tailings settling but improved froth quality. In contrast, the use of HPAM polymers with a high MW improved both bitumen recovery and tailings settling but deteriorated froth quality. To achieve high bitumen recovery and fast tailings settling, a HPAM polymer must have a low to medium charge density (～30%) and a high MW (17.5 million Daltons). A stronger clay‐bitumen adhesion force normally resulted in a lower bitumen recovery. Fast tailings settling was achieved in the presence of a strong solid‐solid adhesion force.     

Effect of clays and calcium ions on bitumen extraction from athabasca oil sands using flotation

A novel approach, based on the doping of rich estuarine oil sands with calcium and/or clays, was developed to study bitumen extraction. The batch flotation tests showed that the addition of either calcium ions up to 40 p.p.m., or kaolinite, illite and montmorillonite clays at 1 wt% of oil sands processed had marginal effect on bitumen recovery from the estuarine ores. A sharp reduction in bitumen recovery was observed only when calcium ions greater than 30 p.p.m. and 1 wt% montmorillonite clays were added together. While bitumen recovery correlated well with changes in water/air/bitumen contact angle, no correlation was found between bitumen recovery and measured zeta potential of clays or surface tension of the supernatants from the flotation slurry. The wettability of bitumen was identified as a key element in determining bitumen recovery. The aqueous solution analysis for calcium ions showed that most of the added calcium ions disappeared from the solution when montmorillonite clays were present. The addition of illite or kaolinite clays changed the calcium ion concentration in the slurry only marginally. Stronger adsorption of calcium ions on montmorillonite than on either kaolinite or illite is considered to be responsible for the increased bitumen wettability, and hence reduced bitumen recovery.     

Conical filtering centrifuge for separation of solvent-diluted bitumen from oil sand mineral particles

The development of a continuous process for the separation of solvent-diluted bitumen from mineral particles is an important step for the development of solvent-based extraction technology of bitumen from mined oil sands. In this work, a custom-made conical filtering centrifuge is used to separate toluene-diluted bitumen from oil sand mineral particles. Compositions of wet granular samples are analyzed before and after centrifugation for three different oil sand ores. Results suggest that conical filtering centrifuges could be used for continuous separation of solvent-diluted bitumen from oil sand ores with relatively coarse particles.     

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.     

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.     

不同有机溶剂对新疆油砂沥青的组成性质影响

油砂作为一种非常规石油资源,越来越受到人们的重视。油砂沥青的含量和性质对其开发有着重要的影响。有机溶剂抽提可以测定油砂沥青的含量。本文研究了3种溶剂对新疆油砂的抽提能力,并对不同溶剂抽提得到的新疆油砂沥青进行了性质分析。结果表明,新疆油砂含油率（甲苯测）为11.75%,属于中品位油砂矿;甲苯、氯仿和石油醚3种不同溶剂对新疆油砂沥青进行抽提,发现3种溶剂抽提能力的大小关系为氯仿＞甲苯＞石油醚;抽提过程中,氯仿表现出对胶质和沥青质较强的萃取能力,而石油醚对沥青质的萃取能力几乎为0,采用氯仿可以更准确地测定油砂沥青的含量。氯仿抽提得到新疆油砂沥青及其组分的杂原子含量和分子量高于甲苯和石油醚抽提的。由红外谱图发现,氯仿抽提得到的油砂沥青的含氧、含硫官能团的吸收峰强度大于甲苯和石油醚抽提的,表明氯仿对油砂沥青中极性物质的抽提能力更强。     

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.

     

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。     

Wettability alteration of solid surface to enhance the bitumen liberation and the water-based processability of weathered oil sands

Weathering often induces bituminous materials adsorbing on the sand grains and leads to poor processability of the oil sands. Chemical and microbial pre-treatment of the prepared weathered ore model and a weathered oil sand ore were carried out to improve the solids surface wettability so as to facilitate the bitumen liberation and recovery. It was found that although all the cetyl trimethylammonium bromide (CTAB), sodium dodecylbenzene sulphonate (SDBS), and microbial culture medium could greatly decrease the surface tension of the solution, the CTAB treatment failed to improve the bitumen liberation, while the SDBS and microbial treatment significantly accelerated the bitumen liberation from the silicon substrates. The wettability analysis showed that the improved bitumen liberation could be attributed to the alteration of the solids surface wettability from hydrophobic to hydrophilic by the SDBS and microbial treatment. Inconsistent with the findings of the bitumen liberation, floatation tests of a weathered ore showed that the CTAB pre-treatment only gave a low bitumen recovery of 33%, while the SDBS and microbial pre-treatment improved the processability of the ore. In particular, the microbial treatment was more effective at removing the adsorbed organics from the solids and improved the surface hydrophilicity, resulting in a much better bitumen recovery of 95%. This work provides a way to improve the processability of the weathered ore by altering the solids surface wettability.     

油砂沥青超声波减粘工艺研究

油砂沥青粘度较大,自然状态下不易流动,严重影响了管道输送及加工,针对目前油砂沥青研究中存在的问题,采用超声波进行了减粘的实验研究。实验综合考察了超声波作用时间、温度、超声波频率、超声波功率等因素对减粘效果的影响。实验结果表明,在适当的超声作用时间(20 min)、适宜的温度(30℃)、适宜的超声波频率(20 kHz)和超声波功率(250 W)的条件下,油砂沥青的减粘率可达80%以上。经超声波处理后的油砂沥青粘度略有恢复,但仍远低于处理前的粘度,超声波减粘效果良好。     

High-efficiency separation of oil sands using ChCl-based deep eutectic solvents

Deep eutectic solvents (DESs) are a kind of potential lixiviant for extraction processing. Unlike conventional ionic liquids (ILs), DESs are relatively cheap and environmentally friendly. Herein, three different ChCl-based DESs, namely, choline chloride/urea, choline chloride/ethylene glycol, as well as choline chloride/propandioic acid, were synthesized and used to enhance bitumen recovery from oil sand by petroleum ether extraction. The results showed a multiphase system formed after mixing the components at ~25°C, consisting of sands and clays, a DES layer, and a petroleum ether layer containing the bitumen. These DESs were immiscible with bitumen or petroleum ether. Coupled with a density difference, a clear phase separation was presented between the bitumen–petroleum ether mixture and DES. The DES functioned as a separating agent, keeping the petroleum ether–bitumen mixture and spent sand apart from each other. The results showed that the bitumen recovery was increased by ~12% compared with that without the DESs. We deduced that the enhancement in the separation may result from the reduction of adhesion between bitumen and sand by the DESs. The ChCl-based DESs and petroleum ether could be readily recycled to reduce industrial costs. After 10 cycles, the bitumen recovery remained above 86%.     

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。     

Novel polymer aids for low‐grade oil sand ore processing

In the present study, a hybrid Al(OH)₃‐polyacrylamide (Al‐PAM) was synthesized and used in combination with a partially hydrolyzed polyacrylamide (HPAM) to process a low‐grade oil sand ore. It was found that Al‐PAM was capable to improve bitumen froth quality and tailings settling. But it led to deterioration in bitumen recovery due to the formation of large bitumen lumps during the bitumen extraction process. To resolve this problem, HPAM was added in combination with Al‐PAM as a dual system. The use of the dual system at a low dosage achieved a holistic improvement in bitumen recovery, froth quality, and tailings settling. To understand the role of Al‐PAM and the dual system in the bitumen extraction process, bitumen‐clay, bitumen‐bitumen, and clay‐sand interaction and adhesion forces were directly measured using an atomic force microscope (AFM). The measured forces indicate that bitumen recovery and tailings settling are controlled by the colloidal interaction and adhesion forces between the oil sand components.     

加拿大油砂沥青部分改质技术综述

介绍了加拿大油砂资源情况、主要性质、改质技术现状和原油外输能力,重点调研了有工业应用潜力的部分改质技术,包括工艺技术现状、核心流程、技术特点和存在问题等。从部分改质产品性质、改质深度、改质过程的碳排放强度、是否存在副产品等多种维度,分析油砂沥青部分改质技术的未来发展趋势。其中对油砂沥青进行缓和热裂解,或缓和热裂解结合沥青质脱除技术是油砂沥青部分改质的技术核心;目标是在满足加拿大管道要求的前提下,尽可能减少稀释剂用量、保证部分改质产品的稳定性,降低改质工艺过程的碳排放强度。     

Separation and Characterisation of Problematic Solids from Athabasca Oil Sands and Waste Unit Samples

Traditionally, Athabasca oil sands have been classified by bitumen and fines (<44 µm) contents. However, these markers do not always identify ores with poor processing characteristics. Consequently, there is a need to discover other characteristics to define problem ores. Here we describe a separation scheme for oil sands solids fractions based on their physical and surface properties. Clay material (<3 µm) and its ultra‐fine (<0.3 µm) component are of particular interest. Settling tests on ultra‐fine clay suspensions confirm that this fraction is the major cause of sludging during primary bitumen separation. Waste units, or barren oil sands, are shown to be a major source of this component.     

Investigation of Oil Sands Froth Treatment

Two oil sand froth treatment methods are investigated: 1) dilution with an aromatic solvent followed by centrifugation (AS Method); 2) dilution with a paraffinic solvent followed by gravity settling (PS Method). The effectiveness of the methods is assessed in terms of bitumen recovery and the water content in the recovered diluted bitumen. The optimum solventto‐bitumen ratios are identified considering process type, ore quality, temperature, and residence time.