Characterization of organic‐coated solids isolated from different oil sands

Solids isolated from weathered oil sands ores and those having low‐ and high‐fine solids content were studied. The organic matter (OM) adsorbed on the solids was found insoluble in most common solvents, contributing significantly to the change of solid surface properties. The surface properties of these solids were found to affect the entire process cycle of obtaining synthetic crude oil from surface‐mined oil sands using a water‐based extraction process, and managing the existing tailings ponds. In this study, the low‐fine solids ore possessed the lowest amount of organic‐coated solids and highest bitumen recovery. Siderite and pyrite, which tend to concentrate in the hydrocarbon phase were observed in the isolated solids from the weathered and high‐fine ores but were absent in the low‐fine ores. In all the ores studied, the solids from the bitumen froth possess less quartz, and more carbonates compared with solids from the tailings. Elemental analysis by energy dispersive X‐ray spectroscopy (EDX) and elemental analyser revealed the presence of more transition metals (iron and titanium), and carbon in the solids obtained from the bitumen froth when compared with those from the tailings. Infrared (IR) spectroscopy study substantiated the results obtained by X‐ray diffraction and elemental analysis. IR spectra showed a likely association between OM and carbonates in the organic‐coated solids isolated from bitumen froth. More organic‐coated solids were found in weathered oil sands than in other types of ores and observed to reduce bitumen recovery from oil sands.     

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.

     

Solvent screening for non‐aqueous extraction of Alberta oil sands

Non‐aqueous extraction of bitumen from oil sands has the potential to reduce fresh water demand of the extraction process and eliminate tailings ponds. In this study, different light hydrocarbon solvents, including aromatics, cycloalkanes, biologically derived solvents and mixtures of solvents were compared for extraction of bitumen from Alberta oil sands at room temperature and ambient pressure. The solvents are compared based on bitumen recovery, the amount of residual solvent in the extracted oil sands tailings and the content of fine solids in the extracted bitumen. The extraction experiments were carried out in a multistage process with agitation in rotary mixers and vibration sieving. The oil sands tailings were dried under ambient conditions, and their residual solvent contents were measured by a purge and trap system followed by gas chromatography. The elemental compositions of the extraction tailings were measured to calculate bitumen recovery. Supernatants from the extraction tests were centrifuged to separate and measure the contents of fine solid particles. Except for limonene and isoprene, the tested solvents showed good bitumen recoveries of around 95%. The solvent drying rates and residual solvent contents in the extracted oil sands tailings correlated to solvent vapour pressure. The contents of fine solids in the extracted bitumen (supernatant) were below 2.9% for all solvents except n‐heptane‐rich ones. Based on these findings, cyclohexane is the best candidate solvent for bitumen extraction, with 94.4% bitumen recovery, 5 mg of residual solvent per kilogram of extraction tailings and 1.4 wt% fine solids in the recovered bitumen. © 2012 Canadian Society for Chemical Engineering     

Characterization of Athabasca oil sands froth treatment tailings for heavy mineral recovery

Titanium (Ti) and zirconium (Zr) minerals (heavy minerals) in the Athabasca oil sands are concentrated in the bitumen froth treatment tailings during the hot water bitumen extraction operations. Recovery processes for these minerals have been explored since the 1970s, yet there is still no established process flowsheet to economically recover these minerals. We recently carried out a research project based on the knowledge of these previous studies. The objective of the project was to study the effect of residual bitumen removal methods from the froth treatment tailings on the separation characteristics of the heavy minerals contained in the tailings. The work reported in this paper is part of the project and it concerns the characterization of the froth treatment tailings. It was found that, rather than burning it off, the residual bitumen in the froth treatment tailings is worth recovering. Separation properties of the heavy minerals contained in the froth treatment tailings were studied by chemical assays, particle size-assay analysis, magnetic susceptibility measurements, gravity and magnetic separation, mineralogical analysis and scanning electron microscope (SEM) analysis coupled with energy dispersive x-ray (EDX) analysis.     

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.     

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.     

Determination of clay content in Canadian oil sands using x-ray florescence spectroscopy for diagnosis of ore processability

In this study, a simple and robust method based on the use of x-ray fluorescence (XRF) spectroscopy to measure potassium content as an indicator of illite in oil sands was proposed and tested. The XRF results of illite determination were compared with those determined using the conventional methylene blue titration (MBT) method. To test the suitability of the XRF method for determining illite content in various streams of oil sands processing as a diagnosis tool, a toluene-diluted-bitumen solution was used to contaminate solid surfaces prior to their analysis by the XRF and MBT methods. In order to remove the organic matter from the bitumen-contaminated solids for evaluating the XRF and MBT method, toluene washing and low temperature ashing were applied to the bitumen-contaminated solids prior to their analysis. The robustness of the XRF analysis in comparison with the MBT method was further confirmed by analyzing the solids extracted from bitumen froth and tailings stream. The results show that the XRF method was more tolerant to surface contamination and therefore more reliable in determining illite content in oil sands and relevant processing streams. It was also found that the potassium contents measured by the XRF method on solids from 10 ores show a strong correlation with the corresponding fines contents of these ores, indicating that the XRF method can potentially be used to determine the fines content of oil sands and related processing streams.     

Effect of Illite Clay and Divalent Cations on Bitumen Recovery

The adverse effect of illite clay on bitumen recovery was found to be related to its acidity. The addition of calcium or magnesium ions to the flotation deionized water had a marginal effect on bitumen recovery when measured using a Denver flotation cell. However, the co‐addition of illite clay and divalent cations caused a significant reduction in bitumen recovery. The effect was found to be compounded at a lower process temperature and low pH values. Zeta potential distributions of illite suspensions and bitumen emulsions were measured individually and as a mixture to investigate the effect of divalent cations on the interaction between bitumen and illite clay. The presence of 1 mM calcium or magnesium ions in deionized water had a significant effect on the interactions between bitumen and illite clay. Slime coating of illite onto bitumen was not observed in zeta potential distribution measurements performed in alkaline tailings water.     

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.     

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.     

Identification of clay minerals in coal and wastes from main coal washery, Zonguldak, Turkey

Identification of clay minerals present in coal and washery wastes is important in cleaning fine coal by froth flotation and in flocculation and dewatering. Therefore samples of wastes from jigs and the flotation cell at the Zonguldak main coal washery were collected and analyzed petrographically for their mineral matter content and by X-ray diffraction for their clay content. The “loss on ignition” method was carried out to determine their organic carbon and carbonates. The waste samples contain 48–68% clay minerals in addition to silicates, carbonates, sulfides and coal. Three clay minerals were identified, namely illite, kaolinite and chlorite. Illite seemed to be the dominant clay mineral in washery wastes. Loss on ignition indicated high percentages of organic matter in the fine jig tailings (21%) and flotation tailings (33%). 3%–6.5% of carbonates have also been found.     

Development of a vision‐based online soft sensor for oil sands flotation using support vector regression and its application in the dynamic monitoring of bitumen extraction

Extraction from oil sands is a crucial step in the industrial recovery of bitumen. It is challenging to obtain online measurements of process outputs such as bitumen grade and recovery. Online measurements are a prerequisite for innovating better process control solutions for process efficiency and cost reduction. We have developed a soft sensor to provide online measurements of bitumen grade and recovery in a flotation‐based oil sand extraction process. Continuous froth images were captured using a VisioFroth camera system on a batch flotation unit. A support vector regression (SVR) model with a Gaussian kernel was constructed to develop a soft sensor for bitumen grade and recovery using froth image features as the inputs. The model was trained and validated for batch flotation of different grades of oil sands ore at industry‐relevant process conditions. A Dean‐Stark analyzer was used to obtain offline grade and recovery measurements that were used to calibrate the soft sensor. Mean squared errors (MSE) of 62 and 74 were achieved for grade (%) and recovery (%), respectively, and this was obtained using 5‐fold cross validation. The developed soft sensor model has been applied successfully in the real‐time dynamic monitoring of flotation grade and recovery for different grades of ore and operating conditions.

     

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.     

Recovery,characterization and conceptual modelling of Non-Bituminous organic materials from oil sands

The hot water process has recovered approximately 90% of the bitumen in oil sands, but the remaining 10% of bitumen and naphtha has been lost to the tailings pond. Recovery of bitumen and non-bituminous combustibles (NBC) from centrifuge, scroll and final tailings has been considered. The effects of four sequestering agents, and of chemical additives such as CaCl₂ and FeCl₃ on the flotation behavior of bitumen, NBC and minerals in these tailings have been investigated. A simple method of isolating NBC materials has been developed. The flotation of both bitumen and NBC was enhanced by phosphate treatment and depressed by EDTA. NBC was characterized by its physical properties, energy content, functionality and chemical analysis. A conceptual model explains the interactions between the bitumen, minerals and NBC fractions present in tailings slurries.     

Characterization of four petrologic end members from Alberta oil sands and comparison between different mines and sampling times

The current research was performed on four petrologic end members samples from Syncrude's North Mine collected in 2012 (NM12), i.e. marine clay (MC), marine sand (MS), estuarine clay (EC), and estuarine sand (ES). The mineralogical compositions of the four petrological end members were determined using X‐ray diffraction (XRD), quantitative XRD (QXRD), elemental analysis, and particle size distribution (PSD) measurements. Bulk samples from the four petrologic end members, after bitumen removal, were mainly composed of clay minerals (kaolinite, illite, chlorite, and mixed‐layer expandable clays) and non‐clay minerals such as quartz, carbonates, feldspars, and traces of TiO₂ minerals, gypsum, and pyrite. Bulk samples of the clay end members were composed of significantly higher amounts of clay minerals and lower amounts of quartz compared with the bulk samples of the sand end members. XRD analysis of oriented preparations (air dried‐54 % RH and ethylene glycolated) of the < 0.2 μm fractions of the four end members showed that interstratified illite‐smectite of high (～30 %) and low (～10 %) expandability were observed only in clay‐rich end members, i.e. NM12‐EC and MC, respectively. Kaolinite‐smectite was only found in the < 0.2 μm fraction of the NM12‐MC with an expandability between 5 and 10 %. Interstratification of illite‐smectite was observed in the < 0.2 μm fraction of NM09‐MC and EC samples but the expandability was only 10 % for both fractions. However, kaolinite‐smectite was not found in the same fraction for NM09‐MC and EC. ES and EC had the highest and lowest bitumen contents, respectively, for the NM12, NM09, and AM10 samples.     

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。     

Fines/Water Interactions and Consequences of the Presence of Degraded Illite on Oil Sands Extractability

The chemical composition of the aqueous phase in oil sand slurries influences bitumen recovery from oil sands, especially those containing greater than 10% fines. The composition is controlled by a combination of mixing and dilution, ion exchange with clay surfaces and precipitation of divalent ions as carbonate minerals. Elevated levels of soluble potassium in the oil sand, which appear to be a marker for degraded illite or smectitic clays, are associated with depressed bitumen recovery. These clays have a swelling character and can contribute divalent ions to the slurry by ion exchange between the clay mineral surfaces and the process water.     

Wettability of fine solids extracted from bitumen froth

Production of synthetic crude oil from oil sands deposits in northern Alberta involves open pit mining, mixing the mined ore with water, extraction of aerated bitumen from the slurry, removal of water and solids from the froth formed, and upgrading heavy bitumen to liquid hydrocarbons. The success of the froth treatment operation, aimed at removal of fine solids and water from the bituminous froth, depends on the control of wettability of fine solids by the aqueous phase. Fine solids were extracted from bitumen froth by heptane. The partition of the extracted solids in aqueous, organic, and interphases was measured, and the wettability of the solids by water in various diluents was evaluated from contact angle measurements. The effect of diluent composition, sample drying, and surface washing on the wettability and fine particle partition was examined. The partition of fine particles correlated well with their wettabilities, and the results were found to be useful for interpreting the observations from froth treatment practice.     

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.     

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.