(142bl) The Microdroplet Generation in Supercritical CO2 by a High Pressure Microfluidic Device

The microdroplet generation in supercritical CO₂ by a high pressure microfluidic
device *

Kang Qin¹, Kai Wang²,
Tao Wang³, Guangsheng Luo

The State Key Laboratory
of Chemical Engineering, Department of Chemical Engineering, Tsinghua
University, Beijing 100084, China

The biphasic
system constituted with supercritical carbon dioxide (ScCO₂) and another liquid phase, has some
unique characters in the chemical reaction and separation processes, as well as
its strong ability to couple reaction and separation in one integrated process.
To increase the mass transfer rate between the ScCO₂ phase and the liquid
phase, the microdispersion processes of several ScCO₂/liquid systems
are investigated in this study with a high pressure T-junction microfluidic
device.  The visible microfluidic device with an online high-speed camera
imaging system can withstand a pressure of 25MPa and the generations of water
and ionic liquid droplets in ScCO₂ are experimentally studied.  The
effects of pressure, temperature and dispersion method on the two-phase flow
pattern and the dispersion size of droplets are discussed and a model equation
is established for the microdispersion process in ScCO₂/liquid
systems. Comparisons between droplet generation processes in ScCO₂, liquid
CO₂ and gaseous CO₂ are also made for understanding the characters
of microdispersed ScCO₂/liquid systems. The differences of
microdispersion of unsaturated and saturated liquid with CO₂ were
observed. 

Key words: supercritical carbon dioxide; biphasic
system; droplet generation; microfluidic; T-junction
microchannel