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Gas flotation is an efficient technique used in the petroleum industry to remove oil contamination from produced water. This method is based on attaching air bubbles to oil droplets to make oil droplets rise faster. We investigated the role of water salinity in the efficiency of the process, using a model flotation column. We show that flotation efficiency increases with water salinity, highlighting the importance of the electrostatic repulsion between oil drops and air bubbles. We also studied the attachment between drops and bubbles, monitoring the temporal evolution of the thin films between them. Stable attachment requires that the water films formed between oil drops and air bubbles break and the oil spreads at the bubble surface. Increasing the salinity of the solution decreases the repulsion between the oil drops and the air bubbles, which in turn decreases the water film stability. The films rupture more readily, improving the drop–bubble attachment and thus the flotation efficiency. The differences in water salinity can therefore lead to important changes in the flotation efficiency.

Water soluble polymers such as polyacrylamide are used in polymer flooding, which is an advanced technique of Enhanced Oil Recovery (EOR). It aims at improving crude oil displacement in reservoir by pushing it with a viscous injected fluid. Polymer flood is challenged by mechanical degradation of long macromolecules during intense flows. Many studies reported that above a critical extensional rate \hbox{$\varepsilon^{\mathrm{\cdot }}_{\mathrm{c}}$}, polymer chains can break and lose their rheological properties. The molecular weight (M) dependence of \hbox{$\varepsilon^{\mathrm{\cdot }}_{\mathrm{c}}$}for dilute solutions in laminar flows was shown to follow a power law: \hbox{$\varepsilon^{\mathrm{\cdot }}_{\mathrm{c}}$}≈ Mw–k. An experimental study has been performed to investigate the onset of mechanical degradation in both laminar and turbulent flows and for both dilute and semi dilute polyethylene oxide aqueous solutions. It reveals that the exponent k strongly depends on the concentration and flow regimes and also on solvent quality. Results show that mechanical degradation mainly affects long chains, that it is favoured at high concentrations, under poor solvent conditions. They also evidence that the extensional viscosity at low strain rates decreases to the same extent as shear viscosities due to mechanical degradation. However, the decrease of the extensional viscous properties at high strain rates is much more pronounced.

Heavy crude oils cannot be transported by pipeline without a prior reduction of their viscosity. This is commonly obtained by blending the oil with light hydrocarbons. In that case, the resulting viscosity of the mixture depends only on the dilution rate, on the respective viscosities and densities of the oil, and of the diluent. The addition of a polar solvent to a solution of asphaltenes in toluene acts on the colloidal structure of the asphaltenes. The relative viscosity of the solution decreases. Small-angle X-ray scattering (SAXS) measurements show that the radius of gyration of the aggregates of asphaltenes decreases too. In the same way, by mixing hydrocarbons and solvents owning polar functional groups in their molecule, it is shown that the efficiency of the dilution of heavy crude oils is enhanced. Hansen's theory can be used to screen the solvent efficiency. At constant dilution rate, the higher the polarity parameter or the hydrogen bonding parameter of the solvent, the greater the relative viscosity reduction of the diluted crude oil. Nevertheless, solvent owning high hydrogen bonding are generally more viscous than hydrocarbons. The influence of their interactions with the asphaltenes is hidden when the results are expressed in absolute viscosity. Only polar solvents giving few hydrogen bonding give a significant reduction of the viscosity of the diluted crude oil.

Because of very large reserves mainly located in Venezuela and Canada, heavy crude oils represent a significant energy supply. This article gives an overview of the geographical distribution of their resources and lists the recent projects of production. These projects have to face technological challenges in all phases of operation: reservoir, transportation and refining. The paper focuses on transportation, describing the different methods (heating, dilution, oil-in-water emulsion, upgrading and core annular flow). In order to improve them or develop new ones, a structural and rheological study was undertaken to appraise the origin of the high viscosity and counteract its effect.

Many advances have been made in the field of emulsions in recent years. Emulsion behavior is largely controlled by the properties of the adsorbed layers that stabilize the oil-water surfaces. The knowledge of surface tension alone is not sufficient to understand emulsion properties, and surface rheology plays an important role in a variety of dynamic processes. The complexity of petroleum emulsions comes from the oil composition in terms of surface-active molecules contained in the crude, such as low molecular weight fatty acids, naphthenic acids and asphaltenes. These molecules can interact and reorganize at oil/water interfaces. The pronounced nonlinear behavior of surface rheology for asphaltene layers might explain differences in behavior between surfactant and asphaltene emulsions. These effects are very important in the case of heavy oils because this type of crude contains a large amount of asphaltene and surface-active compounds. This article reviews different petroleum emulsion properties and the transport of high viscosity hydrocarbon as a crude oil in water emulsion.

A way for the recovery of plastic waste is the reprocessing. As they cannot be easily separated, the reprocessing of polyolefins appears as a special case of the processing of polymer blends. In order to understand the basic phenomena involved in these systems, binary and ternary blends are prepared from a high density polyethylene, a linear low density polyethylene, and a random ethylene-propylene copolymer. In a first step, the interactions between the different polyolefins are characterized in laboratory experiments (differential scanning calorimetry, optical microscopy, small-angle light scattering, wide-angle X-ray diffraction, mechanical properties). Then, it is shown that the original poor mechanical properties of the blends can be largely improved by optimizing the processing conditions. Finally, an extrapolation of these results to real plastic waste is presented.

Abstract: Frost is one of the main climatic stresses which has to be overcome by a winter pea crop. Some forage lines show a delayed floral initiation, which helps them to escape the main winter freezing periods, as a higher susceptibility to frost is observed after floral initiation commences. Frost tolerant forage peas have been used in all winter pea breeding programs in France and our main purpose was to evaluate to what extent those lines and the current winter varieties are variable for the date of floral initiation in field conditions. A field experiment was carried out during two years at the INRA experimental station of Mons (northern France). Different genotypes (9 in 1995–1996 and 12 in 1996–1997) were sown at approximately monthly intervals between September and June to provide a range of photothermal conditions. The date of floral initiation was determined by destructive sampling. We observed variability for the date of floral initiation among the different genotypes and sowing dates. Our data particularly highlighted the different reactions to photoperiod. Three varieties had no detectable reaction. Six varieties exhibited a quantitative response, with varied intensities. Lastly, the three forage varieties showed a qualitative, high response to photoperiod, which indicated the presence of the Hr allele, already described in Pisum.