Characterization of the Precipitation Modes of Paraffin Wax in Water-in-Model-Oil Emulsions

Li, Yujiang; Li, Chuanxian; Sun, Guangyu; Chen, Xinya; Liu, Daiwei; Yang, Fei; Zhao, Yu-Guo

doi:10.1021/acs.energyfuels.0c02902

Cited by 13 publications

(3 citation statements)

References 55 publications

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“…According to previous studies, the viscosity, gel temperature, and yield stress , of waxy oil emulsion was increased in contrast with those of waxy oil. The added water cut changed the original structure of the waxy oil, where the precipitated wax crystals connected with water droplets through interfacial adsorption , and/or enveloped small water droplets to the inside of the wax crystal network, forming a wax crystal-water droplet aggregation that is shown in Figure . The liquid oil phase with the other components, such resin and asphaltene, was also entrapped at the inner space of the aggregation.…”

Section: Resultsmentioning

confidence: 99%

Experimental Study on the Effect of Wax Crystal-Water Droplet Aggregations on Wax Deposition of Water-in-Oil Emulsions

Wang

et al. 2023

Energy Fuels

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Wax deposition in waxy crude oil emulsions remains a flow assurance challenge in offshore production. Wax molecular diffusion driven by the positive temperature gradient from the liquid to the pipe wall has been widely studied and regarded as the primary wax deposition mechanism; however, a considerable wax deposit of emulsions at a zero-temperature difference was detected, in which condition molecular diffusion is not likely to occur, suggesting there were other mechanisms that contribute to wax deposition. In this work, the wax deposition mechanism of water-in-oil emulsions at a zero-temperature difference was explored by a cold finger apparatus regarding the role of wax crystals and water droplets on wax deposition. Through microscopy observation and component measurement of deposits, the wax deposition mechanism, namely, wax crystal-water droplet aggregation formation and adhesion behavior, was proposed. During wax deposition, wax crystals in the emulsion interacted with water droplets, organizing the basic structure of aggregation. The liquid oil phase was entrapped at the inner space of the aggregation and entrained by the wax crystal-water droplet structure to generate a wax deposit. The formation of wax crystal-water droplet aggregations depends on the experimental temperature, where a larger size of aggregations that formed at a lower temperature preferred to yield a thicker deposit under the same stirring speed, while for the same temperature operation conditions, the medium and low speed promoted the adhesion behavior of the aggregations to the cold finger resulting in an increase in deposits; however, the high stirring condition sloughed off the formed deposits, reducing the deposit mass. The findings denote that the presence of wax crystal-water droplet aggregations in emulsion should be considered when describing the wax deposition process at low temperatures.

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Section: Resultsmentioning

confidence: 99%

Experimental Study on the Effect of Wax Crystal-Water Droplet Aggregations on Wax Deposition of Water-in-Oil Emulsions

Wang

et al. 2023

Energy Fuels

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“…If the wax molecules cannot cocrystallize with the emulsifier, the wax molecules will not crystallize at the water droplet interface. Li et al showed that wax crystals not only precipitate in the oil phase but also precipitate and adsorb at the oil–water interface and force the interface to solidify, resulting in wrinkling of the interface as it shrinks and a more viscoelastic gelling structure of the emulsion. It has also been suggested in the literature that water droplets provide the necessary nucleation sites for the crystalline precipitation of wax molecules, thus making them precipitate more easily …”

Section: Wax: Structures and Thermodynamic And Phase Behaviorsmentioning

confidence: 99%

Advances in and Perspectives on Strategies for Improving the Flowability of Waxy Oils

Yao

Sun

et al. 2022

Energy Fuels

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The research on the flowability of waxy oil has spanned more than a century and is still attracting much attention. How to improve the flowability of waxy oil to ensure safe and efficient pipeline transportation and storage is of great practical importance for the industry. In this work, we have systematically reviewed the research advances in improving the flowability of waxy oil. First, the crystallization properties and phase behavior of waxes are described based on their chemical structure, thermodynamic properties, and solution phase properties, with emphasis on the solventized layer properties of wax crystals. Then, the mechanisms, process, and research progress in flow improvement of waxy oil are discussed from three major aspects: process improvement, equipment improvement, and chemical treatment, with emphasis on the summary of waxy oil pour point depressants in recent years. The remaining challenges and perspectives for future research on flow improvement of waxy oil are presented.

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“…This stability depends greatly on the interaction between water droplet fillers and fat/wax crystals dispersed in the continuous oil phase . These crystals either aggregate as a spatial network that physically encloses the water droplets, thereby preventing droplet collisions, , and/or are modified by an emulsifier as an interfacial attaching species to create a solid shell around individual water droplets, thereby hindering the contact, flocculation, and coalescence of droplets. − The stability of the emulsion is maintained by these two mechanisms . Moreover, there are two kinds of interfacial attachment.…”

Section: Introductionmentioning

confidence: 99%

Water Droplets Tailored as Wax Crystal Carriers to Mitigate Wax Deposition of Emulsion

Wang

et al. 2023

ACS Omega

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This study explores how the micro-distribution change of wax crystals from the continuous oil phase to the oil−water interface mitigates the macro wax deposition of an emulsion. Two types of interfacial actions between wax crystals and water droplets, interfacial adsorption and interfacial crystallization, which were induced by two different emulsifiers, sorbitan monooleate (Span 80) and sorbitan monostearate (Span 60), respectively, were detected by differential scanning calorimetry and microscopy observation. The wax interfacial crystallization promoted by Span 60 resulted in the wax being nucleated directly at the oil−water interface prior to the continuous oil phase, conferring the nascent wax crystals and water droplets to be combined as coupled particles. The utilization of the wax interfacial crystallization behavior to hinder wax deposition of an emulsion was further explored. When the coupled wax crystal−water droplet particles were formed during the wax deposition process, water droplets acted as wax crystal carriers, entraining these nascent wax crystals to disperse in the emulsion, which significantly reduced the amount of wax crystals available to form the network of the deposit. In addition, this change also led to the basic structural units in the wax deposit evolving from wax crystal clusters/networks to water droplet flocs. The study elucidates that through adjusting the dispersion of wax crystals from the oil phase to the oil−water interface, water droplets could act as a functional component to tailor the properties of the emulsion or resolve related flow and deposition problems in pipeline transportation.

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Characterization of the Precipitation Modes of Paraffin Wax in Water-in-Model-Oil Emulsions

Cited by 13 publications

References 55 publications

Experimental Study on the Effect of Wax Crystal-Water Droplet Aggregations on Wax Deposition of Water-in-Oil Emulsions

Experimental Study on the Effect of Wax Crystal-Water Droplet Aggregations on Wax Deposition of Water-in-Oil Emulsions

Advances in and Perspectives on Strategies for Improving the Flowability of Waxy Oils

Water Droplets Tailored as Wax Crystal Carriers to Mitigate Wax Deposition of Emulsion

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