Completed Research
Mass transfer characteristics of gases in aqueous and organic liquids at elevated pressures and temperatures in agitated reactors
Min-Yan Chang, PhD, 1991
(Abstract: UMI Dissertation Publishing)
The gas solubilities (C*), volumetric liquid-side mass transfer coefficients (kLa) and net volumetric mixing power input (P*/VL) were measured for hydrogen (H2), nitrogen (N2), carbon monoxide (CO) and methane (CH4) in water, n-hexane, n-decane, n-tetradecane and cyclohexane liquids at various pressures (1-60 bar), temperatures (328–528 K), mixing speeds (0–26.7 Hz) and liquid volume (2.0 – 3.0 x 10-3 m3) in a four-liter, gas-inducing type, mechanically agitated autoclave. Solid particles, Illinois #6 and Upper Freeport coals at 200 mesh x 0 and 28 mesh x 0, were also used with 0-15 wt.% concentration. The C* values were calculated using a modified Peng-Robinson equation of state. The kLa data were determined using the transient physical gas-absorption technique, and a rigorous calculation method considering the change of the liquid phase volume was introduced. The P*/VL values were obtained using a torque-meter. All the operating variables including the decline of the system pressure as a function of time were recorded using an on-line computer and real-time data acquisition system. Analysis of the data showed that C* for all gases increased with gas partial pressure. C* values for H2, N2 and CO increased whereas those for CH4 decreased with temperature. In the ranges of the operating conditions used, the C* values followed the order: C*CH4 > C*CO > CN2 > CH2. The experimental C* values were modeled using quadratic relationships. kLa values for all gas/liquid systems increased with mixing speed. In general, kLa values for H2 decreased whereas those for N2, CO and CH4 increased with gas partial pressure. No particular trend for the effect of temperature on kLa was observed. In the ranges of operating conditions used, kLa values generally followed the orders: kLa CH4 < kLa CO < kLa N2 < kLa H2 in all five liquids used and kLa in water > kLain n-hexane > kLain cyclohexane > kLain n-decane > kLain n-tetradecane for H2, N2 and CH4 gases but kLain n-tetradecane > kLain n-decane > kLain cyclohexane > kLain n-hexane for CO gas. kLa values decreased with solid particle concentration in the liquid. No significant difference in kLa values, however, was observed for both coals at 28 mesh x 0 and 200 mesh x 0 particle sizes. kLa values were found to increase with P*/VL at constant pressure and temperature. Empirical correlations to predict kLa values for H2, N2, CO and CH4 in organic and inorganic liquids/slurries as functions of dimensionless numbers were proposed.