MASS-TRANSFER CHARACTERISTICS OF GASES IN N-HEXANE AT ELEVATED PRESSURES AND TEMPERATURES IN AGITATED REACTORS

The solubilities C*, mass transfer coefficients k(L)a, and volumetric mixing power input P*/V(L) were measured for H2, N2 and CH4 in n-hexane at various pressures (1-50 bar), temperatures (328-378 K), and mixing speeds (800-1200 rpm) in a four-liter gas-inducing type of agitated autoclave. The C* values were calculated using the Peng-Robinson equation of state. The K(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* values were obtained using a torquemeter. All operating variables, including the decline of system pressure as a function of time, were recorded using an on-line computer and data acquisition system. Analysis of the data showed that C* for the three gases increased with gas partial pressure. C* values for partial pressure. C* values for H2 and N2 increased whereas those for CH4 decreased with temperature. In the ranges of operating conditions used, the C* values followed the order (C*)CH4 > (C*)N2 > (C*)H2 The experimental C* values were modeled using quadratic relationships. k(L)a values for all the gas-liquid systems increased with mixing speed. k(L)a values for H2 decreased whereas those for N2 and CH4 increased with pressure. No particular trend for the effect of temperature on k(L)a was observed. In the ranges of operating conditions used, k(L)a values followed the order (k(L)a)CH4 < (k(L)a)N2 < (l(L)a)H2 k(L)a values were found to increase with P*/V(L) at constant pressure and temperature. An empirical correlation to predict k(L)a for H2, N2, and CH4 in n-hexane as a function of dimensionless numbers was proposed.