Minimum Energy Dissipation under Cocurrent Flow in Packed Beds

Functional analysis of mass balances on gas and liquid, and pressure drop equations describing the cocurrent flow in packed beds has yielded two criteria. Positive values of these criteria has been shown sufficient to achieve energy savings by synchronized periodic pulsations of inlet gas and liquid velocities or by liquid velocity only compared to the situation under the same mean steady inlet phase velocities. This, however, is not the case of pulsation by gas inlet velocity alone. The developed criteria have been evaluated from data obtained by experimental measurement of liquid holdup and gas pressure drop in a column 0.05 m in diameter packed to 1 m by 0.003 m glass spheres using water/air and toluene/air system. Our experiments showed these criteria to be fulfilled in the whole domain of gas and liquid velocities tested. Evaluation of the energy savings under pulsations relative to the steady state operation showed that the savings for water/air system may reach up to 4% with the maximum in region of high and intermediate liquid velocities and low gas velocities. For the toluene/air system the savings are somewhat lower and occur in the same velocity domain.