Title page for ETD etd-02082005-144412 ( Browse

Type of Document

Master's Thesis

Author

Soriano, Jean-philippe

URN

etd-02082005-144412

Title

Mass Transfer Characteristics in an Agitated Slurry Reactor Operating Under Fischer-Tropsch Conditions

Degree

Master of Science in Chemical Engineering

Program

Chemical Engineering

School

School of Engineering

Advisory Committee

Advisor Name	Title
Badie I. Morsi	Committee Chair
Patrick Smolinski	Committee Member
Rachid Oukaci	Committee Member
Robert Enick	Committee Member

Keywords

stirred reactor
mass transfer
central composite statistical design
Fischer-Tropsch
solubility
gas-inducing reactor

Date of Defense

2005-02-11

Availability

unrestricted

Abstract

In this study, the equilibrium solubility, C*, and the volumetric mass transfer coefficient, kLa, were measured for 4 different gases (He, CO, N2 and H2) in two different liquids (Poly-Alpha-Olefins, PAO-8 and C70 Sasol Wax) in a 1-liter agitated reactor operating in a Gas Inducing mode under the typical conditions of Fischer-Tropsch synthesis. The effect of operating variables, including pressure (0.7 – 3.5 MPa), temperature (423 – 523 K), mixing speed (13.3 – 20 Hz), and alumina powder (used as a support for cobalt catalyst) concentration (0 - 50 wt.%) on kLa and C* values were statistically investigated using the Central Composite Statistical design and analysis technique. The data were measured within wide ranges of operating condition covering the industrial range of this Fischer-Tropsch synthesis. The transient physical gas absorption technique was used to determine kLa under the operating conditions used.

The C* values for the four gases in the two liquids used appeared to increase linearly with increasing pressure at constant temperature, i.e., obey Henry’s Law over the pressure ranges studied. The C* values were found to decrease and then increase with increasing temperature and the effect of temperature on C* was described by an Arrhenius-type equation, where the apparent activation energy of absorption was a function of temperature. The solubility values for the four gases in the two liquids used followed the trend: C*CO>C*N2>C*H2>C*He and the values in Sasol wax were slightly higher than obtained those in PAO-8.
The kLa values for the four gases in the two liquids were found to increase with increasing pressure, temperature and mixing speed. The kLa values, however, slightly decreased (20%) at solid concentrations less than 30 wt% and then dramatically decreased (80%) with increasing solid concentrations from 30 to 50 wt%. Under similar operating conditions, kLa values for the four gases were found to be higher in Sasol wax than in PAO-8. This behavior was related to the greater gas-liquid interfacial area created in the Sasol wax due to its lower surface tension and foamability when compared with those of the PAO-8.
Statistical correlations were developed to predict the kLa values for the four gases in the two liquids with a regression coefficient (R2) greater than 97%. Also, an empirical correlation using dimensionless numbers was proposed to predict kLa values in gas induction slurry agitated reactors with a regression coefficient (R2) greater than 94%.

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