Hydrodynamics and mass transfer in high-pressure trickle-bed reactors

The effect of pressure on the hydrodynamics and the gas-liquid mass transfer characteristics in cocurrent downward trickle-bed reactors was studied. Experimental data were obtained by testing more than 40 various gas-liquid-solid systems at 0.1-8.1 MPa. Based on high-pressure transition data, a modified Charpentier flow chart was proposed to determine the influence of pressure on the transition between trickle- and pulse-flow regimes. Consideration of two-phase systems exhibiting nonfoaming behavior showed that the two-phase pressure drop is described well by the modified Lockhart-Martinelli dimensionless ratio. At very low reduced gas velocities, it was demonstrated that both the gas-liquid interface area and the volumetric liquid-side mass-transfer coefficients are independent of pressure. At high reduced gas velocities, an increase in the above-mentioned mass-transfer parameters with pressure can be explained by the influence of the gas inertia on the formation of small gas bubbles within the trickling liquid films.