Induction and Coverage Times for Crude Oil Droplets Spreading on Air Bubbles

The interactions between crude oil droplets and air bubbles were studied by the droplet–bubble micromanipulator technique. Eight crude oils were investigated, and some aspects of the involved mechanisms were discussed. The induction time was measured for air bubbles approaching crude oil droplets in different aqueous phases. Distinct differences were observed in the presence and absence of salts, which showed the importance of long-ranged electrostatic repulsive forces on thin-film stability. The results also suggested that adsorption of dissolved hydrocarbons at air bubble surfaces may increase the potential energy barrier in the thin liquid film. Furthermore, the time needed for crude oil droplets to spread over the air bubble surfaces (referred to as coverage time) was determined for the crude oils. The results showed that the spreading velocity decreased with increasing viscosity of the crude oil. The detailed understanding of this type of interaction is considered to be a precursor for improving the oil removal efficiency during the flotation process

Correlations between Crude Oil Composition and Produced Water Quality: A Multivariate Analysis Approach

A matrix of 18 synthetic produced water samples was analyzed by partial least-squares (PLS) regression modeling. This has been done to investigate the correlation between crude oil properties and water solubility and affinity of the dissolved hydrocarbons for air/water interface which is referred to as produced water quality. The synthetic produced water samples were prepared with nine crude oils and two aqueous phases in the presence and absence of divalent cations (Ca²⁺, Mg²⁺). The total organic carbon content and dynamic surface tension was determined for the samples. The findings of the PLS modeling are summarized as follows: produced water quality was not correlated to the amount (wt %) of aromatics, resins, and asphaltenes in the crude oils but with the amount (wt %) of heteroatoms present in the different fractions. The water solubility and affinity for air/water interfaces of the crude oil hydrocarbons was promoted by oxygen-containing compounds and reduced by nitrogen- and sulfur-containing compounds. Heteroatom-containing molecules of similar class originating from aromatic, resin, and asphaltene fractions of crude oils contributed to different degrees of water solubility and affinity for adsorption at air–water interfaces. This can be related to the differences in the molecular structures of the compounds. Furthermore, the presence of divalent cations showed more influence on the quality of produced water samples of crude oils with high total acid number and nitrogen content

Enhanced sedimentation and coalescence of petroleum crude oil emulsions by the new generation of environmentally friendly yellow chemicals

This study compares by means of new and advanced destabilization protocols the efficiency of new chemistry environmentally friendly (yellow) demulsifiers with already commercially available red demulsifiers in destabilizing two types of water-in-oil (w/o) emulsions: petroleum crude oil emulsions and model dense packed layers (DPLs). Oil?water separation profiles were measured by low-field nuclear magnetic resonance (NMR), which allows monitoring the water content as well as the mean droplet size in the emulsion as function of the sample height and the time. Separation profiles measured by NMR depicted an increase of the free water release kinetics as the concentration of demulsifier as well as the sedimentation rate increased. The water resolution was not substantially improved by increasing the concentration further while the water quality was worse, most likely due to adsolubilization. There was no observation of DPL formation in these crude oil emulsions. Four different demulsifiers were tested on a model DPL and compared with normal crude oil emulsions. One chemical showed higher efficiency in destabilizing DPL than destabilizing crude oil emulsion. The interfacial rheological properties for one of the systems showed a slight increase in the elastic modulus (E?), as the concentration of demulsifier increased. The increment of the elastic modulus is not totally understood. The most central parameters were represented by principal component analysis (PCA). PCA did not contribute in a better characterization of the chemicals. The new-generation yellow demulsifiers did not reproduce the efficiency of commercially available, less environmentally friendly, (red) demulsifiers

Composition and Dynamic Adsorption of Crude Oil Components Dissolved in Synthetic Produced Water at Different pH Values

The effect of pH on the extent and type of dissolved components in synthetic produced water samples prepared from seven crude oils was investigated. More nitrogen containing compounds, probably due to improved water solubility of pyridinic nitrogen functionalities, were seen at the low pH. The affinity of the water-soluble compounds for air–water interfaces was in most cases higher at higher pH. This was due to increased oxygen content in the water-soluble species, probably associated with carboxylic acid functionalities. Differences in the affinity of water-soluble crude oil components to gas bubbles are anticipated to influence the oil removal efficiency by gas flotation. The dynamic interfacial adsorption was followed by a maximum bubble pressure tensiometer, while the dissolved species were characterized by total organic carbon measurements, total nitrogen measurements, FT-IR spectroscopy, and UV/vis spectroscopy