Dynamic Measurement of Carbon Dioxide Volumetric Mass Transfer Coefficient in a Well-Mixed Reactor Using a pH Probe: Analysis of the Salt and Supersaturation Effects

Abstract

This paper presents a new method for the evaluation of volumetric mass transfer coefficients (kLa) using a pH probe response recorded during the absorption of carbon dioxide in a well-mixed reactor. For this method of evaluation, it is not necessary to know the reaction equilibrium constant, the experiment start time, or the initial and final steady-state pH probe readings. The experimental procedure is based on Hill's recent publication (Ind. Eng. Chem. Res. 2006, 45, 5796). Hill reported a decrease in kLa following the addition of salt during carbon dioxide absorption in a well-mixed reactor and explained it as the result of ionic charge effects reducing the ability of carbon dioxide molecules to diffuse away from the surface. Generally, oxygen absorption from air is preferred because the solubility of oxygen is low and, thus, so will be the gas-phase depletion. In such experiments, the mass transfer coefficients are less affected by gas-phase residence time distribution and by bubble-size distribution....