Abstract
The volumetric liquid–solid (L-S) mass transfer coefficient under gas–liquid (G-L) two-phase flow in a silicon-chip-based micropacked bed reactor (MPBR) was studied using the copper dissolution method and was related to the reactor hydrodynamic behavior. Using a high-speed camera and a robust computational image analysis method that selectively analyzed the bed voidage around the copper particles, the observed hydrodynamics were directly related to the L-S mass transfer rates in the MPBR. This hydrodynamic study revealed different pulsing structures inside the packed copper bed depending on the flow patterns established preceding the packed bed upon increasing gas velocity. A “liquid-dominated slug” flow regime was associated with an upstream slug flow feed. A “sparse slug” flow regime developed with an upstream slug-annular flow feed. At higher gas velocity, a “gas continuous with pulsing” regime developed with an annular flow feed, which had similar features to the pulsing flow in macroscale packed beds, but it was sensitive and easily destabilized by disturbances from upstream or downstream pressure fluctuations. The volumetric L-S mass transfer coefficient decreased with increasing gas velocity under the liquid-dominated slug flow regime and became rather less affected under the sparse slug flow regime. By resolving the transition from the liquid-dominated slug flow to the sparse slug flow and capturing the onset of the gas-continuous with pulsing regime, we gained new insights into the hydrodynamic effects of G-L flows on the L-S mass transfer rates in a MPBR.
Highlights
Microreactors are useful tools for chemical reaction and kinetic studies
Micropacked bed reactors (MPBRs) or microfixed bed reactors, which combine the benefits of microreactors and fixed-bed reactors, have been demonstrated to be promising tools for multiphase catalytic reaction systems in investigating catalyst performance,[3−6] reaction kinetics,[7] and chemical synthesis.[8−11] Enhanced mass transfer in micropacked bed reactor (MPBR) has been reported by many researchers
Hydrodynamic studies using a high-speed camera revealed that different pulsing structures developed inside the packed copper bed, as a result of the flow patterns established preceding the packed bed
Summary
Because of reduced length scales, they can offer advantages such as improved temperature control, accelerated heat and mass transfer, and enhanced mixing of reactants.[1,2] Micropacked bed reactors (MPBRs) or microfixed bed reactors, which combine the benefits of microreactors and fixed-bed reactors, have been demonstrated to be promising tools for multiphase catalytic reaction systems in investigating catalyst performance,[3−6] reaction kinetics,[7] and chemical synthesis.[8−11] Enhanced mass transfer in MPBRs has been reported by many researchers (refer to the review by Zhang et al.[12]).
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