Showing papers on "Packed bed published in 2018"

Automated measurements of gas‐liquid mass transfer in micropacked bed reactors

Abstract: Gas-liquid mass transfer in micro-packed bed reactors is characterized with an automated platform integrated with in-line Fourier transform infrared spectroscopy. This setup enables screening of a multidimensional parameter space underlying absorption and with chemical reaction. Volumetric gas-liquid mass transfer coefficients (kLa) are determined for the model reaction of CO2 absorption in a methyl diethanolamine/water solution. Parametric studies are conducted varying gas and liquid superficial velocities, packed bed dimensions and packing particle sizes. The results show that kLa values are in the range of 0.24∼0.64 s−1, which is about one-to-two orders of magnitude larger than those of conventional trickle beds. An empirical correlation predicts kLa in micro-packed bed reactors in good agreement with experimental data. This article is protected by copyright. All rights reserved.

Computational fluid dynamics modeling of viscous liquid flow characteristics and end effect in rotating packed bed

Abstract: 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.

CO 2 capture by amine-based aqueous solution containing atorvastatin functionalized mesocellular silica foam in a counter-current rotating packed bed: Central composite design modeling

Abstract: Novel mesocellular silica foam functionalized with atorvastatin (MCF-AT) was synthesized and applied to overcome the mass transfer limitation in carbon dioxide absorption by rotating packed bed (RPB). The MCF-AT with high order pore distribution and regular rod morphology material was dispersed in monoethanolamine (MEA) by ultrasonic dispersion method without any surfactant addition. Structural and chemical properties of MCF-AT were characterized by low angle XRD, FE-SEM, FTIR, BET and BJH analysis. The effect of operational parameters such as the gas and solution flow rate, MCF-AT dosage and rotational speed have been investigated and optimized by central composite design (CCD) combined with desirability function (DF) method. The maximum achieved carbon dioxide absorption percentage was 99.46% at condition which set at 15 L min−1 gas flow rate, 0.2 L min−1 solution flow rate, 0.15 g MCF-AT and 800 rpm rotational speed. Results indicated that using MEA solution in absence of MCF-AT has ability to 76.96% CO2 capture percentage which significantly improved following addition of MCF-AT to MEA solution due to the availability of appropriate pores and reactive functional groups which have more tendency for trapping and/or binding CO2.

Chemical looping Steam reforming of Acetic Acid in a Packed Bed Reactor

Abstract: Chemical looping steam reforming of acetic acid (CLSR-HAc) was carried out in a packed bed reactor at 650 °C and 1 atm using two nickel-based catalysts (‘A’ with alumina support and ‘B’ with calcium aluminate support) to study the effect of the temperature of oxidation (TOX) on the efficiency of the process and the materials properties of the catalysts upon cycling. CLSR-HAc could not be sustained with steady outputs with TOX of 600 °C for catalyst A, but it was conducted successfully at temperatures up to 800 °C, whereas with B it could be operated reaching close to equilibrium conditions over five cycles with TOX of 600 °C. CLSR-HAc can run efficiently for further cycles at the right operating conditions (S/C of 3, WHSV of 2.5 h−1, TOX 800 °C, TSR 650 °C) even in the presence of the side reactions of acetic acid decomposition and coking. The yield of hydrogen produced had a minimum efficiency of 89% compared to equilibrium values, and the acetic acid conversion was in excess of 95% across 10 chemical looping steam reforming cycles. High purity hydrogen (>90% compared to equilibrium values) was also produced in this study. Chemigrams obtained from TGA-FTIR analysis indicates that two forms of carbon were formed on the catalyst during CLSR-HAc; TEM images and diffraction patterns indicate that poly graphitic carbon and amorphous carbon were formed while SEM images of the oxidised catalyst showed that the carbon was eliminated during the oxidation step of CLSR. A full carbon elemental balance of the process confers that majority of the carbon share (ca 90%) was utilised for efficient steam reforming of acetic acid with ca 10% of the carbon input deposited during the reduction step and subsequently burned during oxidation over the CLSR cycles.

Mass Transfer Parameters for Packings: Effect of Viscosity

Abstract: The effect of liquid viscosity (μL) on the effective mass transfer area (ae) and liquid film mass transfer coefficient (kL) of packing must be known to determine packing height. Most existing correlations are based on water and are not applicable to viscous systems. In this work, ae, kL, and gas film mass transfer coefficient (kG) were measured in a 0.43 m ID packed column with 0.5–3 m of packing. Liquid viscosity was varied from 0.8 to 70 mPa·s by adding glycerol to water. Liquid viscosity has an insignificant effect on ae over the range of μL investigated. The total dependence of kL on μL is −0.75, of which −0.35 is indirect influence through diffusivity, and −0.4 is direct influence through liquid turbulence. Universal mass transfer models for packing were developed as functions of packing geometry, operating condition, and fluid property.