Numerical modeling of carbon dioxide chemisorption in sodium hydroxide solution in a micro-structured bubble column

Gas-liquid flows with solid catalyst particles are encountered in many applications in the chemical, petrochemical, and pharmaceutical industries. Most commonly, two reactor types, slurry bubble column (SBC) and trickle bed (TB) reactors are applied for large scale in the industry. Both of these types of reactors have some disadvantages limiting their efficiencies. To overcome the aforementioned disadvantages, a novel reactor type, micro-structured bubble column (MSBC), is proposed in Jain et al. (2013). In the MSBC, micro-structuring of the catalyst carrier is realized by introducing a static mesh of thin wires coated with catalyst inside the column. Wires also serve the purpose of cutting the bubbles, which in turn results in high interfacial area and enhanced interface dynamics. Moreover, the static catalytic mesh ensures lower cost by avoiding filtration of catalyst particles. In this paper, the MSBC is numerically studied using the hybrid volume of fluid - discrete bubble model (VOF-DBM) presented in Jain et al. (2014). The VOF-DBM is extended with a description of wire-meshes and the bubble cutting algorithm as introduced in Jain et al. (2013). Furthermore, a model for mass transfer with chemical reaction as developed by Darmana et al. (2007) is included in the model to study the impact of the wire-mesh and bubble cutting on the chemical reaction rate. In this work, first the model implementation and results are verified for a wide spectrum of parameters from the data available from previous studies, analytical results and experimental findings. Subsequently the model is applied to carry out a parameter study on the chemisorption of CO₂ in a NaOH solution, employing different mesh configurations. Since the reaction chosen here is very fast, mass transfer is the limiting step. It is found that the mass transfer can be considerably increased by stacking multiple meshes in the column.