Apparatus to Measure Ethanol Extraction Rates During Supercritical CO2-Based Drying of Alcogels.
Abstract: An important
and time consuming portion of the manufacturing of aerogel insulation is the
supercritical carbon dioxide extraction step. An improved understanding of its kinetics
is likely to reduce the time and energy required to dry alcogels and thus make aerogel
insulation more economically feasible. A supercritical CO2 extraction apparatus was
designed, constructed, and character... read moreized. Then the rate of ethanol removal from a 220 mm
tall x 46.2 mm inner diameter x 5 mm thick annulus of alcogel as a function of time was
measured. Three independent techniques to track the mass fraction of ethanol in the
effluent were considered. First, an IR-based sensor was used to directly measure it.
Secondly, an equation of state for the CO2 + ethanol system to compute mass fraction of
ethanol as a function of temperature, pressure and density was utilized to extract mass
fraction from effluent densities measured by a Coriolis flowmeter. Lastly, the ethanol
in the effluent stream was condensed into a graduated cylinder mounted on a laboratory
scale. The apparatus allows for control of the thickness of the (annular geometry)
channel for carbon dioxide flow surrounding the alcogel in addition to pressure,
temperature, and mass flow rate of carbon dioxide. The experimental results highlight
the impact of carbon dioxide mass flow rate on ethanol removal rate and overall drying
time. The apparatus can be used to collect benchmark data for the extraction process and
those data may then be compared to predictions from various models of the extraction
process. Additionally, the rig was modified for density measurements of the CO2 +
ethanol binary system as a function of mixture composition, temperature, and pressure in
order to develop higher accuracy equations of state for the CO2 + ethanol
Thesis (M.S.)--Tufts University, 2011.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Marc Hodes.
Committee: Vincent Manno, and Mez Polad.
Keywords: Mechanical engineering, and Materials Science.read less