Hydrodynamics, mass transfer and gas scrubbing in a co-current droplet column operating at high gas velocities

The main objective of this work was to propose a new process for household fume incineration treatment: the droplet column. A feature of this upward gas-liquid reactor which makes it original, is to use high superficial gas velocities (13 ms(-1)) which allow acid gas scrubbing at low energy costs. Tests were conducted to characterize the hydrodynamics, mass transfer performances, and acid gas scrubbing under various conditions of superficial gas velocity (from 10.0 to 12.0 ms(-1)) and superficial liquid velocity (from 9.4. 10(-3) to 18.9. 10(-3) in s(-1)). The following parameters characterized the hydrodynamics: pressure drops, liquid hold-ups, and liquid residence time distribution were identified and investigated with respect to flow conditions. To characterize mass transfer in the droplet Column, three parameters were determined: the gas-liquid interfacial area (a), the liquid-phase volumetric mass transfer coefficient (k(L)a) and the gas-phase volumetric mass transfer coefficient (k(G)a). Gas absorption with chemical reaction methods were applied to evaluate a and k(G)a, while a physical absorption method was used to estimate k(L)a. The influence of the gas and liquid velocities on a, k(L)a, and k(G)a were investigated. Furthermore, tests were conducted to examine the utility of the droplet column for the acid gas scrubbing, of gases like hydrogen chloride (HCl) and sulfur dioxide (SO2). This is a process of high efficiency and the amount of pollutants in the cleaned air is always much lower than the regulatory European standards imposed on household waste incinerators.