Variation of the Interfacial Area during Co2 Absorption into Alkanolamines Aqueous Solutions in a Bubble Column Reactor

INTRODUCTION Bubble columns are widely used in industrial gas-liquid operations (e.g. gas-liquid reactions, fermentations) in chemical and biochemical processes industries, due to their simple construction, low operating cost and high-energy efficiency. In all these processes, gas hold-up and bubble size are important design parameters since they define the gasliquid interfacial area available for mass transfer. In turn, bubble size distribution and gas hold-up in gas-liquid dispersions depend largely on column geometry, type of gas sparger, operating conditions and physico-chemical properties of the two phases [1]. On the other hand, if the absorption process is accompanied by a fast chemical reaction, the effect of time on the interfacial area should too be analysed. Dispersion of the gas into the column is a critical in determining the performance of gas-liquid systems. Small bubbles and a uniform distribution over the cross section of the equipment are desirable to maximize the interfacial area and improve transport phenomena [2]. The formation of bubbles at orifices submerged in a liquid has been the subject of many theorical and experimental works [3,4,5]. In the publications cited above, the main focus of research was on the bubble formation at a single orifice. However, other authors [6] have studied, experimentally, the influence of the distance on the bubble diameter, measuring bubbles at 25 and 45 cm from the sparger in a column 70 cm high. Despite considerable study of bubble column performance many basic questions concerning the effect of important operational parameters remain unanswered. For instance, although bubble column characteristics have been studied extensively over the last few decades, there is still a fair amount of uncertainty regarding the prevailing mechanisms of bubble formation. Break-up and coalescence of fluid objects play a crucial roles in a broad spectrum of multiphase flow processes such as the evolution of the bubble size distribution in stirred tanks and bubble columns [7]. Consequently, bubble size distribution in a vessel is not constant, but rather, may change due to bubble-bubble interactions leading to breakage or coalescence. In this work we have studied the absorption process of carbon dioxide into aqueous solutions of different alkanolamines, and we have measured the interfacial area and the gas SYMPOSIUM SERIES NO. 152 # 2006 IChemE