Double-Slit Model for Partially Wetted Trickle Flow Hydrodynamics

A Double-Slit Model Developed Can Predict the Frictional Two-Phase Pressure Drop, External Liquid Holdup, Pellet-Scale External Wetting Efficiency, and Gas - Liquid Interfacial Area in Cocurrent Downflow Trickle-Bed Reactors Operated under Partially Wetted Conditions in the Trickle Flow Regime. the Model, an Extension of the Holub Et Al. (1992, 1993) Mechanistic Pore-Scale Phenomenological Approach, Was Designed to Mimic the Actual Bed Void by Two Inclined and Interconnected Slits: Wet and Dry Slit. the External Wetting Efficiency is Linked to Both the Pressure Drop and External Liquid Holdup. the Model Also Predicts Gas - Liquid Interfacial Areas in Partially Wetted Conditions. an Extensive Trickle-Flow Regime Database Including over 1,200 Measurements of Two-Phase Pressure Drop, Liquid Holdup, Gas - Liquid Interfacial Area and Wetting Efficiency, Published in 1974-1998 on the Partial-Wetted Conditions, Was Used to Validate the Modeling Approach. Two New Improved Slip-Factor Functions Were Also Developed using Dimensional Analysis and Artificial Neural Networks. High-Pressure and -Temperature Wetting Efficiency, Liquid Holdup, Pressure Drop, and Gas - Liquid Interfacial Area Data from the Literature on the Trickle-Flow Regime using Conventional Monosized Beds and Catalyst Bed-Dilution Conditions Were Successfully Forecasted by the Model

Discriminating Trickle-Flow Hydrodynamic Models: Some Recommendations

The Forecasting Ability of Five One-Dimensional (1-D) Two-Fluid Phenomenological Models for Liquid Holdup and Two-Phase Pressure Drop in Trickle-Flow Reactors Was Evaluated using the Most Comprehensive Trickle-Flow Regime Database. All of These Models, Namely, the Permeability Model, the Slit Model, the Extended Slit Model, the 1-D CFD Model, and the Double-Slit Model Can Be Used to Predict Liquid Holdup. among Them, the Permeability and the Slit Models, Because of a Much Simpler Structure, Are Recommended. the Extended Slit Model based on Iliuta Et Al. (Ind. Eng. Chem. Res. 1998, 37, 4542) Shear and Slip Constitutive Relationships Can Be Employed for Two-Phase Pressure Drop Predictions. When the Knowledge of Wetting Efficiency Becomes Essential at Very Low Liquid Flow Rates, the Double-Slit Model is Recommended

A comparative study of biodegradation of vinyl acetate by environmental strains

Four Gram-negative strains, E3_2001, EC1_2004, EC3_3502 and EC2_3502, previously isolated from soil samples, were subjected to comparative studies in order to select the best vinyl acetate degrader for waste gas treatment. Comparison of biochemical and physiological tests as well as the results of fatty acids analyses were comparable with the results of 16S rRNA gene sequence analyses. The isolated strains were identified as Pseudomonas putida EC3_2001, Pseudomonas putida EC1_2004, Achromobacter xylosoxidans EC3_3502 and Agrobacterium sp. EC2_3502 strains. Two additional strains, Pseudomonas fluorescens PCM 2123 and Stenotrophomonas malthophilia KB2, were used as controls. All described strains were able to use vinyl acetate as the only source of carbon and energy under aerobic as well as oxygen deficiency conditions. Esterase, alcohol dehydrogenase and aldehyde dehydrogenase were involved in vinyl acetate decomposition under aerobic conditions. Shorter degradation times of vinyl acetate were associated with accumulation of acetic acid, acetaldehyde and ethanol as intermediates in the culture fluids of EC3_2001 and KB2 strains. Complete aerobic degradation of vinyl acetate combined with a low increase in biomass was observed for EC3_2001 and EC1_2004 strains. In conclusion, P. putida EC1_2004 is proposed as the best vinyl acetate degrader for future waste gas treatment in trickle-bed bioreactors

Removal of gaseous toluene using immobilized Candida tropicalis in a fluidized bed bioreactor

A pure yeast strain Candida tropicalis was immobilized on the matrix of powdered activated carbon, sodium alginate, and polyethylene glycol (PSP beads). The immobilized beads were used as fluidized material in a bioreactor to remove toluene from gaseous stream. Applied toluene loadings were 15.4 and 29.8 g/m3 h in Step 1 and Step 2, respectively, and toluene removal was found above 95% during the entire operation. A continuous pH decline was observed and pH of the suspension was just above 6 in Step 2 but no adverse effects on treatment efficiency were observed. The CO2 yield values were found to be 0.57 and 0.62 g-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_{{{\text{CO}}_{2} }} /{\text{g-}}C_{\text{toluene}}$$\end{document} in Step 1 and Step 2, respectively. These values indicate that a major portion of toluene-carbon was channeled to yeast respiration even at higher toluene loading. In conclusion, immobilized C. tropicalis can be used as a fluidized material for enhanced degradation of gaseous toluene

Gas-liquid mass transfer in trickle-bed reactors: Gas-side mass transfer

New data of gas-liquid mass transfer for cocurrent downflow through packed beds of non-porous particles are presented. Mass transfer parameters for air/carbon dioxide/water and air/carbon dioxide/sodium hydroxide systems were evaluated by least squares fit of the calculated CO2 concentration profiles in the gas phase to the experimental values. The dependence of k(G)a on gas and liquid flow rates is caused by the dependence of gas-liquid interfacial area, not by the gas-side mass transfer coefficient k(G). In the case of the absorption of dilute carbon dioxide the gas-side resistance is considerably smaller than the liquid-side resistance. In the pulse flow regime, gas-liquid interfacial area calculated from k(L)a and k(L) values obtained by physical, respectively, chemical absorption are lower than the gas-liquid interfacial area evaluated from the measurements under reaction conditions

Effect of electrostatic interactions on the vapor-liquid equilibrium representation in mixed solvent electrolyte systems

This work considers the calculation of the effect of the electrolyte on the vapor-liquid equilibrium (VLE) of mixed solvent systems at different salt concentrations and at atmospheric pressure in order to evidence the influence of the electrostatic term on the VLE representation. Two modified UNIQUAC models (Sander et al., 1986 and Macedo et al., 1990), which take into account the long-range electrostatic interactions using different types of the Debye-Huckel term, are used. The calculations are based on the complete experimental data (VLE and salt solubility). The long-range term, although important in the representation of electrostatic interaction forces, is shown to have rather little effect on the representation of the solvents, practically nonsignificant at low salt concentrations

Salt effect of LiCl on vapor-liquid equilibrium of the acetone-methanol system

The effect of lithium chloride (LiCl) at salt mole fractions from 0.005 to 0.15 and at saturation on vapor-liquid equilibrium (VLE) of the binary acetone-methanol system has been experimentally investigated at 101.32 kPa using a modified Othmer equilibrium still, in order to elucidate the behavior of this mixture whose existing data are rather contradictory. The salting-out effect of the salt on the VLE of the mixed solvent was explained by the preferential solvation theory. The experimental data were correlated by the electrolytic NRTL model of Mock et al. (1986). The mean absolute deviations of the correlation for gamma and T are 0.018 and 0.74 K, respectively. (C) 1998 Elsevier Science B.V. All rights reserved