(29a) On Modeling of Gas-Phase Mass-Transfer in Structured Packings

This contribution summarizes results of gas phase mass-transfer characteristics measurement for several metal Mellapak structured packings under absorption conditions. These characteristics, volumetric mass-transfer coefficient (k_Ga) and effective mass-transfer area (a) has been measured using standard absorption systems of SO₂ chemisorption into the NaOH aqueous solution (k_Ga measurement) and CO₂ chemisorption into the NaOH aqueous solution (effective area measurement). Measurements were performed under atmospheric pressure in the column, which packed bed consisted of four elements of packing with diameter of 0,29m and total height of 0,84m.

Volumetric mass-transfer coefficient, k_Ga, and effective mass-transfer area, a, have been measured for all packings under various flow rates of the liquid phase and of the gas-phase. The flows have been chosen to cover whole spectra of conditions up to flooding. Combination of results enables evaluation of dependencies of mass-transfer coefficient k_G on phase-flows.

Three models for mass-transfer in structured packings (model of Billet and Schultes, DELFT model and SRP model) have been used for calculating gas-phase mass-transfer characteristics under the conditions for which the experiments were carried out. None of the models fully succeed in prediction of k_G, k_Ga and a absolute values and their dependence on the gas-phase velocity.     

Three of the studied packings, Mellapak M250Y, M350Y and M500Y, differ in the value of the geometrical area but are otherwise geometrically similar. There should therefore exist common dimensionless correlation interlinking hydrodynamic, transport and geometrical parameters of the system. Parameters of this correlation should be in agreement with basic hydrodynamic and transport imaginations behind the process. Verification of these basic imaginations used for modeling of gas-phase mass-transport in structured packings is presented on the basis of experimental results and development of such common correlation.