Negative Impact of High Stirring Speed in Laboratory-Scale Three-Phase Hydrogenations

Date

2014-11-19

Author

Ayrancı Tansık, İnci
Shen, Jing
Semagina, Natalia

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

159
views

0
downloads

An increase in stirring speed is generally considered to be an a priori means of reducing external mass-transfer limitations in fast three-phase hydrogenations that are performed in a stirred tank. We provide experimental evidence for a 300-mL stirred reactor that, above a certain impeller speed, the efficiency of gas-liquid mass-transfer decreases, resulting in the decreased reaction rate. The phenomenon is attributed to the high degree of gas recirculation with large cavities behind the blades. The recirculation may decrease hydrogen concentration in the remainder of the tank, thus decreasing the concentration gradient that controls mass transfer. The model reaction in this work was 2-methyl-3-butyn-2-ol semihydrogenation with Lindlar catalyst Pd-Pb/CaCO3. The test impellers were a Rushton turbine, a down-pumping pitched blade turbine, and up-pumping A340 impellers. The kinetic experiments were combined with the measurement of volumetric gas-liquid mass-transfer coefficient, flow pattern analysis and impeller power demand calculations. Although the study does not include kinetic analysis, it provides guidance to the three-phase reaction system analysis that the highest stirring speed may enhance mass-transfer limitations and should not be used without caution.

Subject Keywords

Mass-transfer, Reactors, Turbıne

URI

https://hdl.handle.net/11511/41632

Journal

INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH

DOI

https://doi.org/10.1021/ie5017927

Collections

Department of Chemical Engineering, Article

Suggestions

OpenMETU
Core

Acoustic radiation from a fluid-filled, subsurface vascular tube with internal turbulent flow due to a constriction Yazıcıoğlu, Yiğit; Spohnholtz, Todd; Martin, Bryn; Loth, Francis; Bassiouny, Hisham S. (Acoustical Society of America (ASA), 2005-08-01) The vibration of a thin-walled cylindrical, compliant viscoelastic tube with internal turbulent flow due to an axisymmetric constriction is studied theoretically and experimentally. Vibration of the tube is considered with internal fluid coupling only, and with coupling to internal-flowing fluid and external stagnant fluid or external tissue-like viscoelastic material. The theoretical analysis includes the adaptation of a model for turbulence in the internal fluid and its vibratory excitation of and interac...
Numerical Simulation of Reciprocating Flow Forced Convection in Two-Dimensional Channels Sert, Cüneyt (ASME International, 2003-5-20) <jats:p>Numerical simulations of laminar, forced convection heat transfer for reciprocating, two-dimensional channel flows are performed as a function of the penetration length, Womersley (α) and Prandtl (Pr) numbers. The numerical algorithm is based on a spectral element formulation, which enables high-order spatial resolution with exponential decay of discretization errors, and second-order time-accuracy. Uniform heat flux and constant temperature boundary conditions are imposed on certain regions of the ...
Mathematical expression of the temperature profile and experimental determination of compression heating of ethylene glycol during high hydrostatic pressure processing Buzrul, S.; Alpas, Hami; Largeteau, A.; Demazeau, G. (Informa UK Limited, 2007-03-01) In this study, we aimed to describe the temperature profile in the pressure vessel and the compression heating during high hydrostatic pressure (HHP) processing. Regression coefficients (R-2), root mean square error (RMSE) values and residual plots suggested that fourth-order polynomial function produced reasonable fits to define the temperature profile for all the pressures studied (300-600 MPa). If all the coefficients of this empirical model are determined, initial and final temperatures, a value close t...
Prediction of ducted diaphragm noise using a stochastic approach with adapted temporal filters Karban, Ugur; Schram, Christophe; Sovardi, Carlo; Polifke, Wolfgang (SAGE Publications, 2019-01-01) The noise production by ducted single- and double-diaphragm configurations is simulated using a stochastic noise generation and radiation numerical method. The importance of modeling correctly the anisotropy and temporal de-correlation is discussed, based on numerical results obtained by large eddy simulation. A new temporal filter is proposed, designed to provide the targeted spectral decay of energy in an Eulerian reference frame. An anisotropy correction is implemented using a non-linear model. The acous...
Evaluation of fluctuating pressures measured with connection tubes Aydın, İsmail (1998-01-01) The dynamic characteristics of fluctuating pressure measuring systems composed of connection tubing and pressure transducers were analyzed. A method of correction for the effects of resonance and viscous damping on the measured pressure fluctuations was proposed. A mathematical model of the measuring system was formed combining the governing equations of the unsteady flow in the rigid connection tubing and the corresponding volumetric deformation in the transducer. Numerical solution of the governing equati...

Citation Formats

İ. Ayrancı Tansık, J. Shen, and N. Semagina, “Negative Impact of High Stirring Speed in Laboratory-Scale Three-Phase Hydrogenations,” INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, pp. 18091–18094, 2014, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/41632.