Challenges in developing polymer flocculants to improve bitumen quality in non-aqueous extraction processes: an experimental study

Dixon, Daniel V.; Stoyanov, Stanislav R.; Xu, Yuming; Zeng, Hongbo; Soares, João B. P.

doi:10.1007/s12182-019-00414-z

Cited by 16 publications

(8 citation statements)

References 48 publications

(70 reference statements)

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“…The main focuses of research are placed on development and synthesis of novel polymers for oil sands treatment (including thermal sensitive polymers, inorganic–organic hybrid polymers, etc. ), − in order to reduce flocculant dosages, enhance sediment consolidation, and convert the tailings to soils for reclamation. Anionic polyacrylamide (APAM) is the most widely used for enhancing solid–liquid separation, because of their low cost, satisfactory performance of high molecular weights, and less environmental issues than conventional cationic polymers.…”

Section: Introductionmentioning

confidence: 99%

Synergy between Dual Polymers and Sand-to-Fines Ratio for Enhanced Flocculation of Oil Sand Mature Fine Tailings

Zhou¹,

Li²,

Zhang

2021

Energy Fuels

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The current challenges in dewatering oil sand mature fine tailings (MFTs) by flocculation using a single flocculant include the requirement of very high doses and high cost, inefficient flocculation, and low content of solids in sediment. The obtained flocculated sediment with less than <40 wt % solids is difficult in further consolidation and dewatering for the final disposal. In this work, we examined a new approach for dewatering by dual polymer flocculation in combination with varying sand-to-fines ratios (SFRs) in MFTs. The dual polymers were an anionic polyacrylamide (APAM), and a nanosized cationic hybrid polymer (NHP). Our results confirmed that using single polymers alone was unable to achieve satisfactory flocculation. The solids content in the sediment was <30%, even with increasing flocculant dosages up to 2000 ppm for APAM, and 5000−8000 ppm for NHP, respectively. Although better flocculation was obtained by dual polymers, with reduced total flocculant dosages, the improvement was also limited, in terms of the final sediment solids content (<44%). However, much improved flocculation performance was obtained by increasing the SFR value of the MFT (from 0.1 to 1.5), with significantly reduced total polymer dosages at only 650 ppm. Using different combinations of SFR values and dual polymer dosages, the sediment solids could reach 56 wt % after 24 h of natural settling. It was found that the dual polymer system was less sensitive to the changes in polymer dosages, and that no "overdosing" phenomenon was observed for the tested dual polymers. To rationalize the synergy from dual polymers and SFR, we propose that loose and extended flocs formed by the large anionic polymer and suspended fines were consolidated by the small and cationic polymer through strong electrostatic attraction with fines and the large anionic polymer. Coarse sands were "cores" to carry and condense the loosely structured flocs of fine solids, and they exclude the entrapped water inside the flocs. Our work demonstrates that combining dual polymers and suitable SFRs may be an effective strategy to produce sediment with high solids contents, reduce the required flocculant dose, eliminate overdosing issues, and achieve fast settling rates.

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Section: Introductionmentioning

confidence: 99%

Synergy between Dual Polymers and Sand-to-Fines Ratio for Enhanced Flocculation of Oil Sand Mature Fine Tailings

Zhou¹,

Li²,

Zhang

2021

Energy Fuels

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“…Liquid drops/air bubbles dispersed in another immiscible liquid are ubiquitous in industrial productions including food, pharmacy, cosmetics, and petroleum energy. − Such multiphase systems are, for the most part, noted as emulsions or foams typically consisting of two phases. , A wealth of research works regarding both the static and dynamic interactions between homodispersed monomers have been carried out to provide insight into the stabilization mechanism of emulsions and foams. − The more complicated heterointeraction between drops and bubbles dispersed in liquid has also attracted attention due to its practical significance in applications such as air flotation and surface wetting. − One of the complexities of drop–bubble systems is that the interaction appears to be material specific . For instance, oil drops and bubbles dispersed in aqueous solutions tend to readily flocculate, while water drops and bubbles dispersed in nonpolar liquids intensely repel each other (see Results and Discussion section).…”

Section: Introductionmentioning

confidence: 99%

Atomic Force Microscopy Study of Non-DLVO Interactions between Drops and Bubbles

Wang

Xiao

et al. 2021

Langmuir

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The heterointeraction between liquid drops and air bubbles dispersed in another immiscible liquid is studied with the application of the atomic force microscopy (AFM) probe techniques. The tetradecane drops and air bubbles readily coalescence to form a lens-like structure in 100 mM sodium chloride aqueous solution, demonstrating strong hydrophobic (HB) attraction. The interaction range and strength of this hydrophobic attraction between oil drops and air bubbles is investigated by fine control of electrical double layer thicknesses related to specific electrolyte concentrations, and a midrange term in combination with a short-range term is found to present a proper characterization of this hydrophobic attraction. A further step is taken by introducing a triblock copolymer (Pluronic F68) into the aqueous solution, with results indicating that a relatively long-range steric hindrance (SH) furnished by a polymer “brush” surmounts the hydrophobic attraction. Finally, the interaction between a water drop and an air bubble in tetradecane is also measured as a comparison. The repelling action between a hydrophobic body (air bubble) and water drop indicates a strong repulsion. The present results show an interesting understanding of hydrophobic interactions between drops and bubbles, which is of potential application in controlling dispersion stability.

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“…Most of these studies highlighted the advantages of hydrophobic modifications of PAM-based flocculants and discussed how they improved dewatering. However, most polymers used acrylamide as a comonomer, which is known to retain large amounts of water via hydrogen bonding. − To overcome the above challenges, recent studies have focused on developing flocculants using polyolefins (e.g., polyethylene) or EPDM (ethylene-propylene-diene monomer) terpolymer as hydrophobic backbones. − The rationale of moving to insoluble, hydrophobic backbones is to enhance the dewaterability of the flocculated MFT and densification of the flocculated sludge. The EPDM is a suitable candidate due to its low cost, ease of control over chain length, and high shear resistance .…”

Section: Introductionmentioning

confidence: 99%

Flocculation Efficiency and Spatial Distribution of Water in Oil Sands Tailings Flocculated with a Partially Hydrophobic Graft Copolymer

Kalyanaraman

Najafabadi

Soares

et al. 2021

ACS Appl. Mater. Interfaces

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This work investigates the effect of partially hydrophobic grafted polymers on flocculation and dewatering of oil sands mature fine tailings. Here, we combine confocal microscopy and rheology to investigate how the graft density of ethylene-propylene-diene grafted with hydrolyzed poly(methyl acrylate) (EPDM-g-HPMA) affects its dispersion in water and flocculation efficiency in terms of sediment solids content and long-term dewatering of oil sands tailings. Increasing the graft density from 30 to 50% makes the flocculant easier to disperse, increases the rate of initial dewatering, and also enhances the viscoelastic response of the flocculated sediments. Conversely, the long-term rheological properties of the flocculated sediments were similar for all flocculants. Tri-dimensional microscopic details of the spatial distribution of water within the flocculated sludge provide novel insights into the performance of the flocculants. Increasing the graft density in EPDM-g-HPMA traps more water within the individual flocs and, consequently, decreases the post-flocculation dewatering rate. Our systematic approach confirms the importance of the spatial distribution of water in the flocculated sediment, which depends on how the flocculant is dispersed and how it retains water in the flocs.

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Challenges in developing polymer flocculants to improve bitumen quality in non-aqueous extraction processes: an experimental study

Cited by 16 publications

References 48 publications

Synergy between Dual Polymers and Sand-to-Fines Ratio for Enhanced Flocculation of Oil Sand Mature Fine Tailings

Synergy between Dual Polymers and Sand-to-Fines Ratio for Enhanced Flocculation of Oil Sand Mature Fine Tailings

Atomic Force Microscopy Study of Non-DLVO Interactions between Drops and Bubbles

Flocculation Efficiency and Spatial Distribution of Water in Oil Sands Tailings Flocculated with a Partially Hydrophobic Graft Copolymer

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