Characterising rag‐forming solids

Abstract

In oil sands froth treatment an undesirable intermediate layer often accumulates during the separation of water-oil emulsions. The layer referred to as 'rag' is a complex mixture of water, oil, solids and interfacially active components. The presence of a rag layer has a detrimental impact on separation of water and fine solids from diluted bitumen. The current study focuses on characterization of solids from a rag layer forming stream of a naphthenic froth treatment plant in an attempt to understand the mechanism of rag layer formation. Through detailed characterization of rag-forming and non-rag-forming solids, the mineralogy of solids and their contamination were shown to be critical to rag layer formation. The iron-based minerals such as siderite and pyrite were found to be enriched within the rag layer. Analysis of surface organic complexes confirms a high level of organic matter association with these solids through the binding of carboxylic acid group with iron on solids, resulting in a surface hydrophobicity susceptible for rag layer formation.

Understanding Mechanisms of Asphaltene Adsorption from Organic Solvent on Mica

“…[14][15][16][17][18][19][20] In oil production, the formation of a complex multiphase dispersion layer in the middle of oil-water separation vessel, known as rag layers, is frequently encountered. 21,22 The rag layers are extremely stable multiemulsions with the stabilizing species identified as surfactants, asphaltenes and inorganic fine particles. The inorganic fine particles are predominantly iron-containing solids that readily associate with organic compounds such as asphaltenes to form biwettable solids which preferentially stabilize w/o emulsions.…”

CHAPTER 11. Particle-Stabilized Emulsions in Heavy Oil Processing

“…62 In a recent study, focus was placed on characterizing solids from a rag layer sample taken from the secondary cyclone overflow of a naphthenic bitumen froth treatment plant. 8 The received rag layer was found to be fragile and easily destroyed by handling. However a thick rag layer as much as 40 vol% of the total sample could be reformed even after vigorous mechanical agitation and then left undisturbed at room temperature for 14 days.…”

“…Contamination of clays and heavy minerals by organic matter results in a patchy particle of hydrophilic and hydrophobic segments. 8 These particles can be considered Janus-like with two distinct surface properties. Binks and Fletcher 9 provided a theoretical assessment of the detachment energy of Janus particles from an oilwater interface to a bulk oil or water phase by considering a particle geometry as shown in Figure 11.3.…”

“…58 A recent study on an industrial sample revealed that rag layers are very stable complex oil-continuous emulsions of typically high solids content. 8 Rag layer formation is commonly encountered in oil sands processing and the extraction of bitumen where asphaltene precipitation coupled with the presence of biwettable fine solids prevents droplet coalescence and phase separation. Although low-quality oil sands contain a high fines fraction which is frequently shown to promote the formation of stable liquid-liquid interfaces, the role of fines in rag layer formation is less clear.…”

Molecular Interactions between a Biodegradable Demulsifier and Asphaltenes in an Organic Solvent

“…In particular, iron-bearing heavy minerals such as siderite and pyrite have been shown to preferentially partition in the rag layer due to strong binding between carboxylic acids of organic compounds native in crude oil and the heavy minerals. 39 Several recent studies highlighted chemical and structural differences between asphaltenes that strongly adsorb at the oil-water and oil-solid interfaces and those remaining in the bulk oil. 40,41,42 An extended SARA analysis 33 where asphaltenes are fractionated and characterized according to their adsorption affinity confirmed differences between adsorbed asphaltenes and whole asphaltenes.…”