Chemisorption of CO₂ in a gas–liquid vortex reactor: An interphase mass transfer efficiency assessment

Abstract

To develop cost-effective CO 2 capture technology process intensification will play a vital role. In this work, the capabilities of a gas-liquid vortex reactor (GLVR) as novel process intensification equipment are evaluated by studying its interphase mass transfer parameters to build up the fundamentals for its future application to for example, CO 2 capture. The NaOH-CO 2 chemisorption system and Danckwerts' model are applied to obtain the effective interfacial area and liquid-side mass transfer coefficient. Results show that the gas-liquid contact in the GLVR is capable of both generating a large interfacial area in a small reactor volume and creating a region with high-energy dissipation to improve mass transfer. A comparison of the volumetric mass transfer coefficients with data reported in literature for conventional and intensified reactor types confirms a superior mass transfer efficiency and, most importantly, a favorable energetic efficiency of the GLVR.

Design and Optimization of Gas–Liquid Vortex Unit Using Computational Fluid Dynamics (CFD) Simulation

“…The momentum equation for phase q is expressed as ∂ ∂ t false( α q ρ q u⃗ q false) + ∇ · false( α q ρ q u q → u q → false) = − α q ∇ p + F → G − L − ∇ · τ 0em ̅ q + α q ρ q g where p represents pressure, g is the gravitational acceleration, α q ∇ p is the pressure gradient, and τ ̅ q is the viscous stress–strain tensor. As a consequence of the high-speed rotation of the gas–liquid layer and the strong interactions between phases in the GLVU, ,, the overall interphase forces F → G − L to be considered are drag, lift, and turbulent dispersion forces between the gas phase and the liquid phase. The drag force is often regarded as the most important interphase force. − …”

“…20,21 More recently, the interphase mass-transfer efficiency in a GLVU was evaluated by studying the chemisorption of CO 2 in a NaOH solvent. 4 that the effective specific interfacial area in the GLVU varied in the range of 860−2750 m 2 /m 3 while the range of the volumetric mass-transfer coefficient was 1−10 s −1 . These values confirm the high mass-transfer efficiency and mixing efficiency in a GLVU.…”

“…One of the main reasons for this is the limited mass-transfer efficiency. In other words, mass-transfer limitations hinder CO 2 capture performance and efficiency. , …”

“…In other words, mass-transfer limitations hinder CO 2 capture performance and efficiency. 4,5 Process intensification (PI) refers to the improvement of processes at the operational, functional, and phenomena levels in a unit. This can be achieved through the integration of unit operations, the integration of functions and phenomena, or by specifically enhancing the phenomena for a set of target operations.…”

“…In this reactor, a large and rapidly renewed interface area is generated, which was observed to significantly enhance the gas−liquid mass-transfer performance. 4,20,21 In the context of CO 2 capture, the large gas−liquid interface combined with a long contact time is essential to realize a high CO 2 absorption efficiency, especially when large liquid flows are processed in industrial processes. In some literature, 22−24 the low gas−liquid contact time due to large flows in intensified reactors was found to result in inadequate absorption of CO 2 and thus a lower CO 2 removal efficiency.…”