Development and Application of Direct Numerical Simulations for Reactive Transport Processes at Single Bubbles

In reaction engineering one major concern is with reactor performance for competitive reaction networks in which the formation of desired product and by-product takes place depending on process conditions. Particularly for gas-liquid reaction systems, process design and analysis require detailed knowledge on the local interplay of two-phase fluid dynamics, interfacial species transport and chemical reactions to assess product yield and selectivity reliably. Direct Numerical Simulations play a significant role in understanding these coupled processes. This chapter focuses on numerical simulations of reactive mass transfer at bubbles using the Arbitrary Lagrangian-Eulerian interface tracking methodology. For a prototypical competitive consecutive reaction at freely rising and Taylor bubbles in a circular milli-channel, we study local mass transfer coefficients, reaction enhancement and local product selectivity for different reaction intensities, i.e. Damkohler numbers. Local data gained from comprehensive simulation campaigns provide insights into regions of enhanced mass transfer and high product selectivity in the bubble wake. For realistic Schmidt numbers the influence of the bubble Reynolds number is found to decrease.