•Grids were established based on the reconstructed information from CT scan.•RSM/Euler and LES/VOF model were applied for the simulations.•Droplet and film flow were predicted to develop inside ...packing’s microchannels.•Liquid microflow will help to optimize the packing structure.
The liquid holdup and microflow in a rotating packed bed (RPB) reactor with nickel foam packing were studied by computational fluid dynamics. We used X-ray computed micro-tomography (CT) to obtain the structural information characterizing the packing. The geometry and grids were established based on the space-resolved reconstructed information from the CT scans. The Reynolds stress model with Eulerian approach and the large eddy simulation with volume-of-fluid approach were implemented. Simulation results show that once the liquid was jetted into the packing zone, it would be quickly split and synchronized with the packing rotation. Two liquid flow patterns of droplet and film flow were predicted to develop inside the microchannels of the packing zone as these were experimentally observed and confirmed by a high-speed camera. The present investigation of liquid microflow will help to optimize the packing structure and to develop befitting mass transfer models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Catalytic hydrogenation of maleic anhydride (MA) into succinic anhydride (SA) is one of the most important transformations in synthetic organic chemistry. Herein, we firstly synthesized ...well‐dispersed nickel particles confined by mixed metal oxides (Ni/MMO) derived from in situ transformation of Ni‐Al hydrotalcite in a rotating packed bed (RPB) to catalyze this process. A series of Ni/MMO catalysts (63 wt%–89 wt% Ni) were effectively fabricated and the structure–activity relationship was established. Results showed that a Ni/MMO catalyst (82 wt% Ni) with substantial surface defect sites and the highest Ni surface area among the prepared Ni/MMO catalysts, demonstrates the highest activity with ~100% MA conversion and ~100% selectivity to SA under 25°C within 77 min. This is, to our knowledge, the highest conversion and selectivity under room temperature to date. Moreover, the Ni/MMO catalyst prepared by RPB has higher specific surface area and Ni surface area, therefore possessing a higher hydrogenation rate compared to that by stirred tank reactor (1.69 vs. 1.36, 10−3·molMA/gcat/min). These results will provide an attractive option of the catalysts for MA hydrogenation, and a novel strategy for synthesizing nickel catalyst derived from Ni‐Al hydrotalcite.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In this work, the kinetics study on the reaction between CO2 and tertiary amine catalyzed by zinc(II)‐1,4,8,11‐tetraazacyclotetradecane complexes (CM) and zinc(II)‐1,4,7,10‐tetraazacyclododecane ...complexes (CN) was carried out in a stopped‐flow device. The effects of the catalyst concentration, type of tertiary amines, and temperature on the reaction rate (ν) and catalytic activity (φ) were studied. It was found that the catalyst concentration, tertiary amine with higher pKa, and temperature had positive effects on ν. ν in N‐methyl diethanolamine solution with 10.0 mol m−3 CM and CN were 16.62 and 26.05 folds than the uncatalyzed ν at 298 K, respectively. φ increased with increasing catalyst concentration, decreasing temperature and tertiary amine's pKa. In addition, the kinetics behavior of tertiary amine‐CM/CN‐CO2 systems conformed to the Michaelis–Menten model. The activation energies in catalytic systems were 4%–15% lower than that in the non‐catalytic systems.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The isobutane/butene alkylation process catalyzed by an acid solution is widely used to obtain high octane number gasoline components. However, limited by the mass transfer and mixing of the acid ...solution and the hydrocarbon liquid–liquid system, the product performance needs to be improved. Here, the alkylation reaction was strengthened by combining the chemical regulation of the reactant system and process intensification. Three homologs of sulphates and two hydrophilic surfactants were used as additives to regulate the properties of the acid solution, and the effect of different additives on isobutane/butene alkylation was investigated in a rotating packed bed. The Hammett acidity and solubility of isobutane in acid solutions with different additives were measured, and their synergistic effects on alkylation performance were explored. Under relatively mild conditions (the reaction at 8°C and an isobutane/butene ratio of 30:1), an excellent alkylate with a research octane number of approximately 99 was obtained, showing good industrial application prospects.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•A novel distributor obtains better liquid distribution without pump pressure.•A CFD simulation was accurately validated by high-speed camera imaging.•The flow behavior of liquid jet ...impacting on the liquid distributor was studied.•The impacting angle between the liquid and the wire mesh packing was obtained.
Rotating packed beds (RPBs) have been widely applied in multiphase systems. When handling some extreme operating condition systems, finding a suitable pump to provide pressure to force the feeding liquid to be evenly distributed by the distributor of the RPB is very costly. In this work, we designed new liquid distributors by using the kinetic energy of the rotating shaft as driving force to obtain uniform distribution. The performance of the liquid distribution has been investigated in terms of liquid flow behavior, liquid velocity, and impacting angle (α). Compared with bar and cantboard distributors, the radlamelle liquid distributor had the best distribution performance. By further optimization of the radlamelle structure, the left-hand wheel had better dispersion performance with α varying from 24.3 to 79.1°. This new liquid distributor without pump pressure expands the applications of the RPB in ultra-low or high temperature and high pressure operating conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To understand the mechanism of droplet dispersion, the behaviors of a droplet impacting on a single-layer wire mesh were investigated by computational fluid dynamics simulations with a detailed 3D ...geometry of real woven wire meshes. After validating the simulation data, the effects of different operating conditions on the liquid dispersion were systematically studied. The results showed that the cone angle of dispersion of the hydrophobic wire mesh increased by 37–103%, compared with the hydrophilic wire mesh. A more accurate dispersion angle can be obtained by the 3D simulation, compared to the previous high-speed imaging experiments with 2D photographs. The ratio of dissipated energy of the droplet impacting on the hydrophobic wire mesh was 29% lower than that on the hydrophilic wire mesh, allowing us to reveal the dispersion intensification mechanism of droplet breakage. This study provides insights into the droplet impaction and dispersion on the wire mesh packing, which can guide reactor design and optimization.
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IJS, KILJ, NUK, PNG, UL, UM
•Designed packing rings were accurately manufactured by three-dimensional printing.•Liquid flow in a multiliquid-inlet rotating packed bed reactor were investigated.•Liquid holdup in different ...packing rings was simulated.•A combined method for liquid flow behavior was proposed.
The multiliquid-inlet rotating packed bed (MLI-RPB) reactor has been proved to have excellent gas-liquid mass-transfer performance. However, studies of liquid flow behavior, the fundamentals to understand the mass-transfer process, in packing rings of the MLI-RPB reactor are scarce. In this work, the designed packing rings were accurately manufactured via three-dimensional (3D) printing technology. The liquid flow behavior in different zones of the MLI-RPB reactor were comprehensively investigated via the high-speed photography method. Except for liquid droplet and liquid film, a new type of liquid bridge was observed in the packing rings. Quantitative analyses have been discussed, such as the average diameter of droplet out of packing rings ranging from 0.2 to 0.9 mm and the value of droplet size distribution width m ranging from 5 to 9. In addition, computational fluid dynamics (CFD) simulation of liquid flow in the MLI-RPB reactor was conducted based on the no-simplified geometry model. Liquid velocity magnitude along radial direction in the MLI-RPB reactor and the liquid holdup in different packing rings was calculated. Combining three technologies of 3D printing, high-speed photography, and CFD simulation can provide an efficient pathway for packing design and hydrodynamics research of not only the MLI-RPB reactor, but also other RPB reactors with wire mesh packing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Because of significant influence on momentum, mass, and heat transfer processes, the energy dissipation rate (ε) serves as the basis for new mixers or reactors. However, there is no research of ε ...when a high-gravity (HiGee) device is used as a microbubble generator. In this work, a HiGee microbubble generator (HMG) was first proposed and a mathematical model of ε of HMG was established for the first time. Results showed that the ε increased from 0 to 320 W/kg when the rotational speed increased from 0 to 1400 r/min. The deviations of ε between the experimental results and calculated results using the model were within ±15%. Compared to other microbubble generators, the HMG can easily realize controllable ε by the rotational speed, which shows that HMG is a promising and efficient microbubble generator for the enhancement of gas–liquid mass transfer.
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IJS, KILJ, NUK, PNG, UL, UM
As an important intermediate, nitrosyl sulfuric acid (NSA) is widely used in diazotization in the fine chemical industry. However, the conventional gaseous SO2 method in the Venturi tubular reactor ...has low reaction efficiency and high energy consumption due to insufficient gas–liquid contact. In this work, a rotating packed bed (RPB) reactor was first applied for the synthesis of NSA, in which a liquid SO2 and HNO3 reaction occurred. Effects of the rotational speed, reaction temperature, mole ratio of SO2/HNO3, and flow rate of SO2 on the product quality and NSA yield were investigated. Results indicated that the NSA yield increased by 9.5% with the rotational speed from 100 r/min to 500 r/min. Compared with the conventional Venturi reactor with gas–liquid reaction, the RPB reactor with a liquid–liquid reaction could reduce the volume of the reactor by 1 order of magnitude, quantity of equipment by 69%, steam consumption by 100%, and electricity consumption by 43%
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IJS, KILJ, NUK, PNG, UL, UM
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A CFD model was developed to reveal liquid, especially viscous liquid, flow characteristics in RPB, and an novel way was proposed to quantify the thickness of end effect zone.
•A CFD ...model was built to reveal viscous liquid flow characteristics in RPB.•The CFD results agreed well with by published experimental data.•Effects of operation conditions on viscous liquid flow pattern were analyzed.•An effective approach to specify the liquid-side end effect in RPB was proposed.•The viscosity has great influence on the end effect zone of RPB.
Processing viscous fluid system in industrial applications is one of the challenges in process intensification. In this work, a two-dimensional CFD model was developed to reveal viscous liquid flow characteristics in the injection zone, inner cavity, packing zone and outer cavity of rotating packed bed (RPB). The CFD results agreed well with the published experimental data. The transition of the liquid flow pattern in RPB was discussed with operating conditions. The liquid viscosity showed no significant influence on the liquid holdup and the average diameter of droplets in RPB. In addition, the liquid holdup and droplet diameter decreased as rotational speed increased, and increased as liquid flow rate increased. Based on the simulated results of residence time distribution along radial direction, the end effect zone of RPB was specified, and a novel way was proposed to quantify the thickness of end effect zone. Results showed that the viscosity had great influence on the end effect zone, which had guiding significance for practical operations and configuration optimization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
