Abstract

The gas solubilities ($C\sp\*$), volumetric liquid-side mass transfer coefficients (k$\sb{L}$a) and net volumetric mixing power input $(P\sp\*/V\sb{L}$) were measured for hydrogen (H$\sb2$), nitrogen (N$\sb2$), carbon monoxide (CO) and methane (CH$\sb4$) 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 $\times$ 10$\sp{-3}$ m$\sp3$) 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 $C\sp\*$ values were calculated using a modified Peng-Robinson equation of state. The k$\sb{L}$a 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 $P\sp\*/V\sb{L}$ 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 $C\sp{\*}$ for all gases increased with gas partial pressure. $C\sp{\*}$ values for H$\sb2$, N$\sb2$ and CO increased whereas those for CH$\sb4$ decreased with temperature. In the ranges of the operating conditions used, the $C\sp{\*}$ values followed the order: ($C\sp{\*}$)$\sb{\rm CH{\sb4}} >$ ($C\sp{\*}$)$\sb{\rm CO} >$ ($C\sp{\*}$)$\sb{\rm N{\sb2}} >$ ($C\sp{\*}$)$\sb{\rm H{\sb2}}$. The experimental $C\sp{\*}$ values were modeled using quadratic relationships.

$k\sb{L}a$ values for all gas/liquid systems increased with mixing speed. In general, $k\sb{L}a$ values for H$\sb2$ decreased whereas those for N$\sb2$, CO and CH$\sb4$ increased with gas partial pressure. No particular trend for the effect of temperature on $k\sb{L}a$ was observed. In the ranges of operating conditions used, $k\sb{L}a$ values generally followed the orders: ($k\sb{L}a)\sb{\rm CH\sb4}<(k\sb{L}a)\sb{\rm CO}<(k\sb{L}a)\sb{\rm N\sb2}<(k\sb{L}a)\sb{\rm H\sb2}$ in all five liquids used and ($k\sb{L}a)\sb{\rm in\ water}>(k\sb{L}a)\sb{\rm in\ n-hexane}>(k\sb{L}a)\sb{\rm in\ cyclohexane}>(k\sb{L}a)\sb{\rm in\ n-decane}>(k\sb{L}a)\sb{\rm in\ n-tetradecane}$ for H$\sb2$, N$\sb2$ and CH$\sb4$ gases but ($k\sb{L}a)\sb{\rm in\ n-tetradecane}>(k\sb{L}a)\sb{\rm in\ n-decane}>(k\sb{L}a)\sb{\rm in\ cyclohexane}>(k\sb{L}a)\sb{\rm in\ n-hexane}$ for CO gas. $k\sb{L}a$ values decreased with solid particle concentration in the liquid. No significant difference in $k\sb{L}a$ values, however, was observed for both coals at 28 mesh x 0 and 200 mesh x 0 particle sizes. $k\sb{L}a$ values were found to increase with $P\sp{\*}/V\sb{L}$ at constant pressure and temperature. Empirical correlations to predict $k\sb{L}a$ values for H$\sb2$, N$\sb2$, CO and CH$\sb4$ in organic and inorganic liquids/slurries as functions of dimensionless numbers were proposed.