Page 157 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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and to reduction of the gas and liquid velocities at the loading and flooding
points. The reduction of the packing element dimensions leads also to
increasing of the pressure drop. That is why the selection of the dimensions of
the packing elements can be made only through an optimization procedure,
taking into account not only the process type and the concentrations of the
flows, but also the loading of the apparatus.

Fig 1. Principle comparison of different packings in coordinates NTUQ as a function of
H

The possibility to increase the efficiency of the packing by applying the
results of the mass transfer theory was proved by us experimentally in 1969 [8,
9] using ceramic 25 mm Rasehig rings whit a height equal to their diameter and
also rings with smaller height of the element. The ratio of the height to the
diameter varied from 0.43 to 1. The results showed [8] that the volumetric
liquid-side controlled mass transfer coefficient in case of shorter elements was
up to 45% higher. In case of gas-side controlled process, the increasing was up
to 35%. It must be mentioned also that the reduction of the height of the
elements leads not only to increasing of the mass transfer rate but also to
reduction of the pressure drop, the value of which can be reduced up to 20%.