Influence of Particles and Electrolyte on Gas Hold-Up and Mass Transfer in a Slurry Bubble Column

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Keshav C Ruthiya ◽  
John van der Schaaf ◽  
Ben F.M. Kuster ◽  
Jaap C Schouten
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Bubble Column ◽  
Bubble Diameter ◽  
Interfacial Area ◽  
Large Bubble ◽  
Volumetric Mass Transfer Coefficient ◽  
Gas Velocity ◽  
Slurry Concentration

In this paper, the influence of carbon and silica particle slurry concentration up to 20 g/l (4 vol%) on regime transition, gas hold-up, and volumetric mass transfer coefficient is studied in a 2-dimensional slurry bubble column. From high speed video image analysis, the average large bubble diameter, the frequency of occurrence of large bubbles, the gas-liquid interfacial area, and the large bubble hold-up are obtained. The liquid side mass transfer coefficient is calculated from the volumetric mass transfer coefficient and the gas-liquid interfacial area. The lyophilic silica particles are rendered lyophobic by a methylation process to study the influence of particle wettability. The influence of organic electrolyte (sodium gluconate) and the combination of electrolyte and particles is also studied. It is found that lyophilic silica, lyophobic silica, and lyophobic carbon particles at concentrations larger than 2 g/l (0.4 vol%) decrease the gas hold-up and shift the regime transition point (where the first large bubbles appear) to a lower gas velocity. The volumetric mass transfer coefficient increases with gas velocity, increases with electrolyte concentration, decreases with slurry concentration, and is higher for lyophobic particles. The liquid side mass transfer coefficient increases with gas velocity, bubble diameter, and is higher for lyophobic particles. A correlation for the mass transfer coefficient based on dimensionless numbers is proposed for the heterogeneous regime.

Enhancement of Gas Physical Absorption in Gas-Liquid-Liquid System

2011 ◽  
Vol 201-203 ◽  
pp. 2870-2874
Author(s):  
Wen Xiu Li ◽  
Guang Rong Xu ◽  
Zhi Gang Zhang ◽  
Zhi Ling Ji
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Organic Phase ◽  
Amplification Factor ◽  
Bubble Diameter ◽  
Interfacial Area ◽  
Volumetric Mass Transfer Coefficient ◽  
Absorption Increase ◽  
Physical Absorption

The enhancement of physical absorption of CO2 in the presence of second liquid phase (dispersed organic phase) was investigated due to many important industrial applications. Gas-liquid interfacial area, volumetric mass transfer coefficient and amplification factor were calculated and discussed using penetration model. The experimental results indicated that addition of the dispersed organic phase to water leads to the increase of volumetric mass transfer coefficient by 46%, 34%, 20% for heptanol, toluene and heptane respectively. The performed in this paper shows that addition of the dispersed organic phase to water increases gas-liquid interfacial area and reduces bubble diameter. These two effects play an essential role in the rate of carbon dioxide absorption increase. The effect of enhancement could be quantified by an amplification factor.

scholarly journals Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

2021 ◽  
pp. 34-34
Author(s):  
Predrag Kojic ◽  
Jovana Kojic ◽  
Milada Pezo ◽  
Jelena Krulj ◽  
Lato Pezo ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Airlift Reactor ◽  
Volumetric Mass Transfer Coefficient ◽  
Cfd Model ◽  
Gas Velocity ◽  
Liquid Mass ◽  
External Loop ◽  
Liquid Mass Transfer

The objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift reactor (ELAR). The ELAR was operated in three cases: different inlet velocities of fluids, different alcohols solutions (water, 0.5% methanol, 0.5% ethanol, 0.5% propanol and 0.5% butanol) and different concentration of methanol in solutions (0%, 0.5%, 1%, 2% and 5%). The influence of superficial gas velocity and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAR was studied. Experimentally, the gas hold-up, liquid velocities and volumetric mass transfer coefficient values in the riser and the downcomer were obtained from the literature source. A computational fluid dynamics (CFD) model was developed, based on two-phase flow, investigating different liquids regarding surface tension, assuming the ideal gas flow, applying the finite volume method and Eulerian-Eulerian model. The volumetric mass transfer coefficient was determined using CFD model, as well as artificial neural network model. The effects of liquid parameters and gas velocity on the characteristics of the gas-liquid mass transfer were simulated. These models were compared with appropriate experimental results. CFD model successfully succeed to simulate the influence of different alcohols regarding the number of C-atoms on hydrodynamics and mass transfer.

scholarly journals Determination of the ozone volumetric mass transfer coefficient in bubble column with two-fluid nozzle gas distributor

2015 ◽  
Vol 69 (5) ◽  
pp. 553-559 ◽  
Author(s):  
Milica Djekovic-Sevic ◽  
Nevenka Boskovic-Vragolovic ◽  
Ljiljana Takic ◽  
Radmila Garic-Grulovic ◽  
Srdjan Pejanovic
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Bubble Column ◽  
Operating Conditions ◽  
Volumetric Mass Transfer Coefficient ◽  
Gas Distributor ◽  
Liquid Mass Transfer ◽  
Two Fluid

Experimental investigation of gas-liquid mass transfer of ozone in water, in bubble column with two-fluid nozzle gas distributor (BKDM), under different operating conditions, are presented in this work. The main objective was to determine the ozone volumetric mass transfer coefficient, kL a, in calm uniform section of the column, under different values of gas and liquid flow rates. Obtained values of these coefficients were compared with the values in countercurrent bubble column. The critical liquid flowrate, when gas hold up reaches its maximum, was experimentally determined. It was shown that the maximum value of the ozone volumetric mass transfer coefficient is obtained just when liquid flowrate is at its critical value.

scholarly journals Study on Mass Transfer Characteristics of Hydrate-based Gas Absorber

2021 ◽  
Vol 333 ◽  
pp. 04002
Author(s):  
Shun Takano ◽  
Ryosuke Ezure ◽  
Yusuke Takahashi ◽  
Hiroyuki Komatsu ◽  
Kazuaki Yamagiwa ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Gas Separation ◽  
Bubble Column ◽  
Hydrate Formation ◽  
Continuous Operation ◽  
Gas Absorption ◽  
Volumetric Mass Transfer Coefficient ◽  
Type Apparatus

Hydrated-based gas separation is a method capable of selectively separating and recovering greenhouse gases. Although a conventional hydrate-based gas separation apparatus is a batch or a semi-batch system, continuous operation is preferable to increase the throughput of gas without changing the apparatus volume. Recently, we proposed a flow type apparatus to allow continuous operation of hydrate formation (absorption) and subsequent decomposition (desorption). The aim of this study is to investigate the mass transfer characteristics of the continuous apparatus using the HFC134a-N2 mixed gas system. The volumetric mass transfer coefficient was calculated especially during a steady state of gas absorption. Besides, we compared mass transfer performance between the hydrate-based gas absorber and a conventional bubble column. Sodium dodecyl sulfate was used as a hydrate dispersant. In the flow type apparatus, the gas-liquid contact was good and the hydrate slurry state was observed during hydrate formation. In the surfactant solution, the volumetric mass transfer coefficient increased in comparison with that in water. The volumetric mass transfer coefficient with hydrate was higher than that of the bubble column. These results suggest that hydrate formation improves gas absorption performance.

Effect of Vibrating Sparger on Mass Transfer, Gas Holdup, and Bubble Size in a Bubble Column Reactor

2013 ◽  
Vol 11 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Laleh Hadavand ◽  
Ali Fadavi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Vibration Frequency ◽  
Bubble Size ◽  
Bubble Column ◽  
Gas Holdup ◽  
Bubble Column Reactor ◽  
Gas Velocity ◽  
Superficial Gas Velocity

Abstract Bubble size has a key role in gas holdup and mass transfer in bubble column reactors. In order to have small and uniform bubbles, a new structure was designed; the reactor operates in two modes, with vibrating sparger and conventional bubble column in which sparger is fixed. In vibrating mode, the sparger vibrates gently during gas entering. The vibrating sparger performs like a paddle, resulting in a forced recirculation of gas–liquid inside the reactor; moreover, the bubble detachment is accelerated. The superficial gas velocity was between 0.003 and 0.013 ms− 1, and the vibration frequency was changed between 0 and 10.3 Hz. The bubble size was measured at three various positions of the reactor height by photographic method and using MATLAB 7.0.1 software. The mass transfer coefficient was determined by means of the dynamic gassing-out method. The results show that the bubbles were bigger in vibrating mode than those working without vibration. The bubble size decreases with increase in height from sparger. Gas holdup increased with increase in superficial gas velocity and vibration frequency. The effect of vibration increased the gas holdup with an average of 70% for all superficial gas velocities. Volumetric mass transfer coefficient was almost stable as vibration frequency increased.

Experimental and Computational Studies of Aerated Stirred Tank with Dual Impeller

2020 ◽  
Vol 18 (3) ◽  
Author(s):  
Shivanand M. Teli ◽  
Viraj S. Pawar ◽  
Channamallikarjun Mathpati
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Large Scale ◽  
Interfacial Area ◽  
Gas Velocity ◽  
Stirred Tanks ◽  
Mixing Performance ◽  
Liquid Systems ◽  
Superficial Gas Velocity

AbstractStirred tanks are commonly used in chemical and allied industries for reaction and separation. In order to improve the mixing performance, large scale reactors are often equipped with multiple impellers. In the case of gas-liquid systems, the gas hold-up, mass transfer coefficient, and interfacial area strongly depend on the size and type of impellers, clearance between impellers and superficial gas velocity. In the present work, the effect of the impeller speed, superficial gas velocity, and top impeller position has been investigated on gas hold-up, interfacial area, and mass transfer coefficient. Computational fluid dynamics have been carried out for the multiphase multi-impeller system and the model predictions have been compared with the experimental data.

Sign in / Sign up

Export Citation Format

Share Document