Mass Transfer Studies on Ternary Systems in a Bench-scale Liquid-Liquid Extraction (LLX) Column and a Comparison with Simulations

Ashok Khanna,Debjit Sanpui,Manish K. Singh 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.2

Mass transfer studies in a laboratory scale extraction column have been conducted for Toluene-Acetone-Water and MIBK-Acetic Acid-Water systems. From these experiments stage-wise solute (Acetone or Acetic-Acid)composition profiles have been obtained for both dispersed and continuous phase. These composition profiles havebeen compared with those obtained from ASPENPLUS, CHEMSEP and LLXSIM simulators. For liquid-liquid equilib-rium calculations all these simulators use UNIFAC and UNIQUAC model. The binary interaction parameters for theUNIFAC are inbuilt in ASPENPLUS and CHEMSEP. UNIQUAC binary parameters were borowed from DECHEMA.Eror square analysis indicates that simulations based on non-equilibrium option of LLXSIM match closely withexperimental results. Temperature profiles and hydrodynamic features characterized by number of drops and staticholdup on the stages have been compared between the LLXSIM simulated and the experimental results and these matchwel. However simulations on ASPENPLUS give sum of relative error-squares for all the experimental runs at least tentimes higher, in spite of tuning the average stage efficiency.

Selection of Mass Transfer Correlations for Rate Based Liquid-Liquid Extraction Model

Sanpui, Debjit,Khanna, Ashok 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4

A rate-based model for mass transfer in liquid-liquid extraction (LLX) has been developed using three distinct stages of drop formation, drop fall or rise and drop coalescence. Binary diffusivities in infinite dilution as well as for concentrated multicomponent mixtures were used to estimate the Maxwell-Stefan binary mass transfer coefficients for both the phases. The mass transfer resistances associated with these coefficients have been categorized in four configurations. Because of the very large number of computations associated with repeated calculations of mass transfer coefficients, a local model has been incorporated. A comparative study between rate-based and non-equilibrium simulator and our bench scale experiments (LLX of toluene-acetone-water system) has been done. The stage-wise composition profiles of acetone in water and toluene phase of the experimental and simulation runs have been compared by using the relative error square analysis. Based on this analysis, best mass transfer combination and mass transfer resistance model has been selected.

Process Systems Engineering, Process Safety, Transport Phenomena : Selection of Mass Transfer Correlations for Rate Based Liquid-Liquid Extraction Model

( Debjit Sanpui ),( Ashok Khanna ) 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4

A rate-based model for mass transfer in liquid-liquid extraction (LLX) has been developed using three distinct stages of drop formation, drop fall or rise and drop coalescence. Binary diffusivities in infinite dilution as well as for concentrated multicomponent mixtures were used to estimate the Maxwell-Stefan binary mass transfer coefficients for both the phases. The mass transfer resistances associated with these coefficients have been categorized in four configurations. Because of the very large number of computations associated with repeated calculations of mass transfer coefficients, a local model has been incorporated. A comparative study between rate-based and non-equilibrium simulator and our bench scale experiments (LLX of toluene-acetone-water system) has been done. The stage-wise composition profiles of acetone in water and toluene phase of the experimental and simulation runs have been compared by using the relative error square analysis. Based on this analysis, best mass transfer combination and mass transfer resistance model has been selected.

Experimental analysis and development of correlations for gas holdup in high pressure slurry co-current bubble columns

Shyam Kumar,Ashok Khanna 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.11

The effect of liquid and gas velocities, solid concentrations, and operating pressure has been studied ex-perimentally in a 15 cm diameter air-water-glass beads bubble column. The superficial gas and liquid velocities variedfrom 1.0 to 40.00 cm/s and 0 to 16.04 cm/s, respectively, while the solid loading varied from 1 to 9%. The gas holdupin the column was reduced sharply as we switched from batch to co-current mode of operation. At low gas velocity,the effect of liquid velocity was insignificant; while at high gas velocity, increasing liquid velocity decreased the gasholdup. Drift flux approach was applied to quantify the combined effect of liquid and gas velocities over gas holdup. For co-current three phase flows, the gas holdup decreased with increase in solid loading for all pressures. But for batchoperations, when solid loading was 5% or more, settling started leading to higher gas holdup. Increasing pressure fromatmospheric conditions increased the gas holdup significantly, flattening asymptotically.

Closure Equations in the Estimation of Binary Interaction Parameters

Ahmad, Syed Akhlaq,Khanna, Ashok 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4

Binary interaction parameters used in the UNIQUAC activity coefficient model are found to be dependent on each other and related by a linear relation termed as the closure equation. For a ternary system, six binary interaction parameters are related by one closure equation. Similarly for quaternary systems, three independent closure equations are obtained for the twelve binary interaction parameters and for quinary systems there are six closure equations for twenty parameters. Each closure equation consists of six parameters. The binary interaction parameters that do not satisfy the closure equations may lead to a less accurate prediction of liquid-liquid equilibria. In this work the binary interaction parameters have been estimated with and without closure equations for few ternary and quaternary systems. Parameters that satisfy the closure equations exhibit better root mean square deviation than those that do not satisfy the closure equations in most of the cases. A similar behavior is observed for NRTL modl also.

Carbon dioxide absorption studies using amine-functionalized ionic liquids

Yamini Sudha Sistla,Ashok Khanna 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

Several amine-functionalized cation ILs were successfully synthesized, characterized and tested for CO2 absorption studies. Non-functionalized ILs were studied for comparison purpose. The primary amine-ILs have shown higher CO2 solubilities both on molar basis (mol of CO2/mol of IL) and on volume basis (g of CO2/L of IL), compared to non-functionalized and tertiary-amine ILs. Besides amine-functionalization of the cation, anion of the IL has strong influence on CO2 solubility due to its contribution by physical absorption. As a result, the [TF2N]-anion amine-ILs have higher CO2 solubility than [BF4]-anion amine-ILs. Among non-amine functionalized ILs, [P(14)666][TF2N] has the highest CO2 solubility.

Separation Technology, Thermodynamics : Closure Equations in the Estimation of Binary Interaction Parameters

( Syed Akhlaq Ahmad ),( Ashok Khanna ) 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4

Binary interaction parameters used in the UNIQUAC activity coefficient model are found to be dependent on each other and related by a linear relation termed as the closure equation. For a ternary system, six binary interaction parameters are related by one closure equation. Similarly for quaternary systems, three independent closure equations are obtained for the twelve binary interaction parameters and for quinary systems there are six closure equations for twenty parameters. Each closure equation consists of six parameters. The binary interaction parameters that do not satisfy the closure equations may lead to a less accurate prediction of liquid-liquid equilibria. In this work the binary interaction parameters have been estimated with and without closure equations for few ternary and quaternary systems. Parameters that satisfy the closure equations exhibit better root mean square deviation than those that do not satisfy the closure equations in most of the cases. A similar behavior is observed for NRTL modl also.

Mass Transfer Studies on Ternary Systems in a Bench-scale Liquid-Liquid Extraction (LLX) Column and a Comparison with Simulations

Sanpui, Debjit,Singh, Manish K.,Khanna, Ashok 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.2

Mass transfer studies in a laboratory scale extraction column have been conducted for Toluene-Acetone-Water and MIBK-Acetic Acid-Water systems. From these experiments stage-wise solute(Acetone or Acetic-Acid)composition profiles have been obtained for both dispersed and continuous phase. These composition profiles have been compared with those obtained from ASPENLUS, CHEMSEP and LLXSIM simulators. For liquid0liquid equilibrium caculations all these simulators use UNIFAC and UNIQUAC model. The binary interaction parameters for the UNIFAC are inbulit in ASPENPLUS and CHEMSEP, UNIQUAC binary parameters were borrowed from DECHEMA. Error square analysis indicates that simulations based on non-equilibrium option of LLXSIM match closely with experimental results. Temperature profiles and hydrodynamic features characterized by number of drops and static holdup on the stages have been compared between the LLXSIM simulated and the experimental results and these match well. However simulations in ASPENPLUS give sum of relative error-squares for all experimental runs at least len times higher, in spite of tuning the average stage efficiency.

Quantitative histology-based classification system for assessment of the intestinal mucosal histological changes in patients with celiac disease

Prasenjit Das,Gaurav PS Gahlot,Alka Singh,Vandana Baloda,Ramakant Rawat,Anil K Verma,Gaurav Khanna,Maitrayee Roy,Archana George,Ashok Singh,Aasma Nalwa,Prashant Ramteke,Rajni Yadav,Vineet Ahuja,Vishnu 대한장연구학회 2019 Intestinal Research Vol.17 No.3

Background/Aims: The existing histological classifications for the interpretation of small intestinal biopsies are based on qualitative parameters with high intraobserver and interobserver variations. We have developed and propose a quantitative histological classification system for the assessment of intestinal mucosal biopsies. Methods: We performed a computer-assisted quantitative histological assessment of digital images of duodenal biopsies from 137 controls and 124 patients with celiac disease (CeD) (derivation cohort). From the receiver-operating curve analysis, followed by multivariate and logistic regression analyses, we identified parameters for differentiating control biopsies from those of the patients with CeD. We repeated the quantitative histological analysis in a validation cohort (105 controls and 120 patients with CeD). On the basis of the results, we propose a quantitative histological classification system. The new classification was compared with the existing histological classifications for interobserver and intraobserver agreements by a group of qualified pathologists. Results: Among the histological parameters, intraepithelial lymphocyte count of ≥25/100 epithelial cells, adjusted villous height fold change of ≤0.7, and crypt depth-to-villous height ratio of ≥0.5 showed good discriminative power between the mucosal biopsies from the patients with CeD and those from the controls, with 90.3% sensitivity, 93.5% specificity, and 96.2% area under the curve. Among the existing histological classifications, our quantitative histological classification showed the highest intraobserver (69.7%–85.03%) and interobserver (24.6%–71.5%) agreements. Conclusions: Quantitative assessment increases the reliability of the histological assessment of mucosal biopsies in patients with CeD. Such a classification system may be used for clinical trials in patients with CeD.