Being able to assess
the solubility properties of asphaltenes is
essential for oilfield asphaltene risk assessment. The solubility
distribution of PetroPhase 2017 asphaltenes was characterized using
the asphaltene solubility class index (ASCI), which a simple methodology
based on precipitation onset determination in different heptols. This
ASCI method was also used to measure the polydispersity in terms of
solubility for PetroPhase 2017 asphaltenes that were fractionated
from the native crude oil with precipitants of different qualities.
Similar to other crude oils, asphaltenes from PetroPhase 2017 have
a high level of polydispersity, ranging from fractions “insoluble
in toluene” to “soluble in heptane”, which may
seem contradictory with the usual definition of asphaltenes. The modification
of the precipitant/crude oil ratio, with heptane as the precipitant,
also highlighted the presence of co-precipitated materials that did
not affect the solubility class of asphaltenes. From our experience
over the last 15 years, using ASCI or another equivalent tool, would
greatly improve the comparison between different studies on asphaltene,
similar to the well-known wax appearance temperature, which is measured
and reported in the vast majority of studies on paraffins.
A semibatch bitumen emulsification process to generate droplet size in the submicrometer range was developed in a coaxial mixer using a high-internal-phase ratio (HIPR) step followed by dilution to the final concentration of the dispersed phase. An HIPR emulsion is characterized by nonspherical droplets shape separated by thin films due to low ratio between the continuous-and dispersed-phase concentrations. The same mixing system was used to prepare the HIPR intermediate and the eventual emulsion, based on a pitched blade turbine on the high-speed shaft and two different types of close-clearance impellers on the low-speed shaft. It was found that the most critical process stage to achieve the mean droplet size was the preparation of the HIPR emulsion. The dispersed-phase and surfactant concentrations, the close-clearance impeller rotational speed, and agitation time were identified as key process parameters to control the droplet size. These parameters were combined to provide a prediction model of the average droplet size with two dimensionless parameters, namely, the initial surfactant concentration in the continuous phase and the bitumen weighted deformation.
Highly concentrated bitumen-in-water emulsions were produced with static mixers in continuous mode. The effect of the following process parameters on the average droplet size was studied: emulsion flowrate, static mixers configuration, and surfactant concentration as well as bitumen hardness, concentration, and temperature. Several static mixer configurations were investigated consisting of combinations of SMX (Sulzer Chemtech Ltd.) and helical elements with empty sections. The drop size results revealed that the mean droplet size could be scaled with the energy or the power draw depending on the static mixer configuration. Moreover, it was shown that the energy draw could capture the effect of emulsion flowrate and bitumen concentration on the mean droplet size, whereas the power draw (or the specific power) captured the effect of the emulsion flowrate and bitumen temperature. It was also demonstrated that the specific energy, or pressure drop, was minimized when SMX mixers were inserted after helical mixers.
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