الملخص الإنجليزي
The move towards processes in small and microdevices has been increased
recently due to the enhanced heat and mass transfer rate of these devices. One
particular area of application is liquid-liquid extraction. Hence, the key goal of this
study is to miniaturize the implementation of extractive desulfurization of diesel by
adopting microchannel technology to overcome the mass transfer limitation of
conventional liquid-liquid extraction. The efficiency of the solvent extraction as a
result of two-phase flow in an intensified channel highly depends on the flow patterns.
In this work, the hydrodynamics of conventional polyethylene glycol 200 (PEG200)
and simulated diesel have been investigated intensively by varying several parameters
such as junction shape and diameter, channel diameter, and channel saturation at
different mixture velocities and solvent volume fraction. To study the effect of solvent
properties, experiments were carried out by complexing the polyethylene glycol into a
deep eutectic solvent (DES) form by adding a specific amount of tetra butyl
ammonium bromide (TBAB) to the PEG200. The main observed patterns were the
drop, plug, various states of annular flow, and irregular flow. Those patterns were
highly influenced by the channel diameter. Using DES as a liquid solvent resulted in
the development of a different form of plug flow known as plug dispersed flow. The
measured pressure drop was found to rise with increasing solvent velocity, solvent
viscosity, and decreasing channel diameter. The dimensionless analysis showed a
reasonable agreement with the experimental work. A new friction factor correlation
was generated based on the homogenous pressure drop model using our experimental
results. This resulted in improved predictions of the measured pressure drop. The
computational fluid dynamics (CFD) was employed using the Volume of Fluid (VOF)
model and results were validated with the experimental data. Both experimental and
numerical results revealed two-phase flow patterns.
The second part involved the utilization of the optimized experimental setup for
the extraction of thiophene (Thio) and dibenzothiophene (DBT) from liquid fuel using
both solvents. The central composite design (CCD) was employed to visualize the
main and interaction effect of different operation factors including channel diameter,
channel length, mixing velocity, and volume fraction on the extraction of sulfur
compounds. It was found that extraction efficiency fluctuates with respect to mixture
velocity. Moreover, the extent of extraction increased with increasing channel length
and decreasing channel diameter. Channel cross-sectional area had almost no effect on
the EDS efficiency. Finally, a scale-up design based on the numbering-up technique
was implemented to check the possibility of implementing the model for high
throughput. The proposed scale-up design enhances the mass transfer and the
equilibrium was reached in a shorter micro-extractor. Deep removal of sulfur containing components from simulated diesel was achieved in four extraction stages.
The percentage of DBT extraction using PEG200 and DES was 98.38 % and 98.66 %
respectively. While the deep removal of sulfuric components from real diesel was
achieved in six stages. This work gives a clear understanding about the behavior of
different solvents to the removal of sulfuric achieve efficient sulfur reduction from
liquid fuel in a small scale. It also opens the door for efficient scale-out of
microchannels.
