University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Chemical Engineering Science

  • Publisher: Elsevier
  • FAD Code: CHES
  • CODEN: CESCAC
  • ISSN: 0009-2509
  • Abbreviation: Chem. Eng. Sci.
  • DOI Prefix: 10.1016/j.ces,10.1016/S0009-2509
  • Language: English
  • Comments: Fulltext from 1951 V1

Citations 12

"Novel Flow Injection Synthesis Of Iron Oxide Nanoparticles With Narrow Size Distribution"
Chem. Eng. Sci. 2006 Volume 61, Issue 14 Pages 4625-4633
German Salazar-Alvarez, Mamoun Muhammed and Andrei A. Zagorodni

Abstract: A novel synthesis method based on a flow injection technique was developed and the synthesis of magnetite nanoparticles was performed to demonstrate the concept. The technique consisted of continuous or segmented mixing of reagents under laminar flow regime in a capillary reactor. Different schemes of the flow injection synthesis were evaluated and the continuous mode was found to be more advantageous for the synthesis of the iron oxide particles. The material was characterized by X-ray diffraction, thermal analysis, electron microscopy, and magnetic susceptometry. The obtained magnetite nanoparticles had a narrow size distribution in the range 2-7 nm. The influence of chemical parameters and conditions on properties of the material was investigated.

"Experimental Investigation Of Liquid-liquid Mixing In T-shaped Micro-mixers Using µ-LIF And µ-PIV"
Chem. Eng. Sci. 2005 Volume 61, Issue 9 Pages 2968-2976
Marko Hoffmann, Michael Schlüter and Norbert Räbiger

Abstract: Microreaction engineering enables new strategies in process intensification, e.g. reactions with high selectivity, through exploitation of the smallest scales. A basis for this is a precise analysis of local mass transfer and hydrodynamics in micro-mixers for different flow regimes. The micro-mixer we used for experimental investigations is a simple T-shaped micro-mixer with rectangular cross-sections and very smooth surfaces (reactive ion etching) to enable a good approximation by numerical models. Although the investigations were performed in the low Re range without turbulence, the T-shaped micro-mixer intentionally promotes the generation of vortex structures. The goal of this research work is to show that despite laminar flow conditions short diffusion lengths are achievable and to clarify the mechanisms and required conditions. For the determination of the mixing quality and the specific contact area between the species the concentration field is measured using the technique "micro Laser-induced fluorescence" (µ-LIF). For further understanding and verification of numerical models the velocity field is measured by "micro Particle Image Velocimetry" (µ-PIV).

"Evaporative Liquid Jets In Gas-liquid-solid Flow System"
Chem. Eng. Sci. 2001 Volume 56, Issue 21-22 Pages 5871-5891
L. -S. Fan, R. Lau, C. Zhu, K. Vuong, W. Warsito, X. Wang and G. Liu

Abstract: Some aspects of the fundamental characteristics of evaporative liquid jets in gas-liquid-solid flows are studied and some pertinent literature is reviewed. Specifically, two conditions for the solids concentration in the flow are considered, including the dilute phase condition as in pneumatic convey and the dense phase condition as in bubbling or turbulent fluidized beds. Comparisons of the fundamental behavior are made of the gas-solid flow with dispersed non-evaporative as well as with evaporative liquids.For dilute phase conditions, experiments and analyzes are conducted to examine the individual phase motion and boundaries of the evaporative region and the jet. Effects of the solids loading and heat capacity, system temperature, gas flow velocity and liquid injection angle on the jet behavior in gas and gas-solid flows are discussed. For dense phase conditions, experiments are conducted to examine the minimum fluidization velocity and solids distribution across the bed under various gases and liquid flow velocities. The electric capacitance tomography is developed for the first time for three-phase real time imaging of the dense gas-solid flow with evaporative liquid jets. The images reflect significantly varied bubbling phenomenon compared to those in gas-solid fluidized beds without evaporative liquid jets.

"Kinetic Studies Of Acid Inactivation Of α-amylase From Aspergillus-oryzae"
Chem. Eng. Sci. 1996 Volume 51, Issue 1 Pages 37-43
Morten Carlsen*, Jens Nielsen and John Villadsen

Abstract: The stability of α-amylase from Aspergillus oryzae has been studied at different pH. The enzyme is extremely stable at neutral pH (pH 5-8), whereas outside this pH-range a substantial loss of activity is observed. The acid-inactivation of α-amylase from A. oryzae was monitored online by a FIA-system. At low pH (pH<4.0) the inactivation follows first-order kinetics, and the rate constant is given by the empirical expression k = 1.19 x 10(7) (1.99)(h-1) illustrating that the inactivation process is highly dependent of the pH in the medium. At pH 6 the acid-inactivated enzyme regains part of its activity, and the reactivation process also follows first-order kinetics. The irreversible loss of activity is found not to result from a protease contamination of the protein samples. A proposed model, where irreversibly inactivated a-amylase is formed both directly from the active enzyme and via the reversibly inactivated enzyme, describes the experimental data very well.
α-Amylase Kinetic Process monitoring

"A Computational Technique For Simulating The Dynamic Response Of A Flow Injection Analysis System"
Chem. Eng. Sci. 1992 Volume 47, Issue 7 Pages 1591-1600
Steven H. Isaacs and Henrik Soeberg, Lars H. Christensen and John Villadsen

Abstract: A computational technique is presented for obtaining the dynamic response to a gas diffusion module as part of a flow injection analysis (FIA) system. Based on orthogonal collocation, Laplace transformation, and Fourier series, the method provides a relatively quick way to account for dispersive effects occurring via longitudinal convection and lateral diffusion. Simulation examples, including a comparison with a dynamic signal obtained with an actual FIA system, are provided.
Computer Gas diffusion Laplace Simulation Fourier transform

"An Automated Glucose Isomerase Reactor System With Online Flow Injection Analyzers For Monitoring Of PH, Glucose And Fructose Concentrations"
Chem. Eng. Sci. 1990 Volume 45, Issue 4 Pages 1031-1042
Jens Gram and Michael de Bang, John Villadsen*

Abstract: The literature on glucose isomerization with immobilized glucose isomerase has been reviewed with respect to thermodynamics and kinetics of the reaction and the industrial process layout. A laboratory scale fixed-bed reactor for isomerization of glucose with immobilized glucose isomerase has been constructed. A system for sample withdrawal and three flow injection analyzers-measuring glucose, fructose and pH-has been developed, automated and used to monitor the process. The equipment is controlled by a personal computer with interface expansion boards. The isomerization process has been monitored in steady-state operation as well as in pH transients. Using a commercial immobilized glucose isomerase (Sweetzyme Q from NOVO Industri A/S), the isomerization process has been studied with respect to equilibrium conversion, composition of the feed syrup, film diffusion resistance, enzyme deactivation and buffering effect of the immobilized enzyme. The experience from computerization of the equipment and the use of flow injection analyzers is summed up and the potential of such analyzers for monitoring biotechnological processes is discussed.
pH Glucose Fructose pH Immobilized enzyme

"Tracer Curves And The Residence Time Distribution"
Chem. Eng. Sci. 1970 Volume 25, Issue 10 Pages 1611-1613
Octave Levenspiel, B. W. Lai and C. Y. Chatlynne

Abstract: For a pulse input, the shape of the output tracer curve depends on the way the tracer is distributed across the flowing fluid, and the way it is measured. The authors properly relate the different curves that may be obtained for flows with negligible cross diffusion, and show which one of these represents directly the residence time distribution of the flowing fluid.
Theory Diffusion

"The Interpretation Of Residence-time Experiments"
Chem. Eng. Sci. 1970 Volume 25, Issue 10 Pages 1605-1609
Octave Levenspiel and J. C. R. Turner

Abstract: The results of tracer experiments can depend on the methods of injection and measurement of the tracer when the fluid velocity is not uniform through the injection and measurement planes. Some simple examples show that incorrect residence-time distributions will be derived if this fact is not considered. For laminar flow in a tube, the results obtained will differ widely, depending on the techniques used.
Theory Injection technique Laminar flow

"Fluid Dispersion-generalization And Comparison Of Mathematical Models. 2. Comparison Of Models"
Chem. Eng. Sci. 1962 Volume 17, Issue 4 Pages 257-264
K. B. Bischoff and Octave Levenspiel

Abstract: The models for axial-dispersed plug flow and dispersed plug flow are interrelated and are also related to more general models which do not assume plug flow and constant values for the dispersion coefficients. These relations are considered with restrictions.
Theory Dispersion Plug flow

"Fluid Dispersion-generalization And Comparison Of Mathematical Models. 1. Generalization Of Models"
Chem. Eng. Sci. 1962 Volume 17, Issue 4 Pages 245-255
K. B. Bischoff and Octave Levenspiel

Abstract: Methods for handling mixing have been based on models that use diffusion equations with modified diffusion coefficients. These are called dispersion models. The relation between all models which have been used is summarized, and the associated measurement techniques are generalized. A quantitative evaluation of the error involved with a given model can be made.
Theory Diffusion Dispersion Diffusion coefficients Mixing

"Diffusion-type Model For The Longitudinal Mixing Of Fluids In Flow"
Chem. Eng. Sci. 1957 Volume 6, Issue 4-5 Pages 227-233
Octave Levenspiel and W. K. Smith

Abstract: Longitudinal mixing may be characterized by a coefficient analogous to the coefficient of molecular diffusion. The Peclet number can be used as a similarity criterion for longitudinal mixing. The skewness of concentration from the concentration peak must be carefully recognized in interpreting experimental data and examined in view of the pertinent Peclet no.
Diffusion Theory Mixing

"Holding Time Distributions Of The Gaussian Type"
Chem. Eng. Sci. 1956 Volume 5, Issue 6 Pages 258-270
A. Klinkenberg and F. Sjenitzer

Abstract: Holding-time distributions are of great importance in a considerable number of separation and conversion processes. In the majority of cases it is desired that the distribution be as narrow as possible and there are accordingly many examples where a peak signal at the entrance gives rise to a comparatively narrow band in the effluent, which has then Gaussian shape. Several mechanisms have been proposed to account for such a phenomenon. In the present study, these mechanisms are analyzed on a statistical basis in terms of their basic variables. It is also shown that various mechanisms may be combined by adding variances, diffusion coefficients or heights corresponding to a theoretical plate. It is obviously not possible to identify the mechanism by observing a single Gaussian elution curve. Neither is this possible by observing a series of such curves for systems or columns of different lengths, in all theories the width of the Gaussian curve increasing in proportion to the square root of the length of the system. In the experiments, variation of flow rate, particle size, and diffusion coefficients is necessary in order to reach conclusions regarding the mechanism or mechanisms responsible for the elution curve.
Theory Dispersion Diffusion coefficients