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Full-Text Articles in Engineering
Utility Of An Empirical Method Of Modeling Combined Zero Gap/Attached Electrode Membrane Chlor-Alkali Cells, Clifford W. Walton, Ralph E. White
Utility Of An Empirical Method Of Modeling Combined Zero Gap/Attached Electrode Membrane Chlor-Alkali Cells, Clifford W. Walton, Ralph E. White
Faculty Publications
An extensive survey of the Docktor-Ingenieur Dissertationen of Jakob Jörissen and Klaus-R. Menschig, both originally from the Universität Dortmund, is presented in regard to the empirical modeling of membrane chlor-alkali cells and how it can be applied to a combined zero gap/attached porous electrode layer membrane cell. Particular emphasis isplaced on Menschig's work on zero gap (ZG) and attached porous electrode layer (APEL) membrane chlor-alkali cells, the first such research to appear in the open literature. Menschig developed various computer programs to characterize these ZG and APEL membrane chlor-alkali cells. He characterized these cells by using the following parameters: the …
Parallel-Plate Electrochemical Reactor Model: A Method For Determining The Time-Dependent Behavior And The Effects Of Axial Diffusion And Axial Migration, T. V. Nguyen, C. W. Walton, Ralph E. White, J. Van Zee
Parallel-Plate Electrochemical Reactor Model: A Method For Determining The Time-Dependent Behavior And The Effects Of Axial Diffusion And Axial Migration, T. V. Nguyen, C. W. Walton, Ralph E. White, J. Van Zee
Faculty Publications
A method is presented for determining the effects of time dependence, axial diffusion, and axial migration in aparallel-plate electrochemical reactor (PPER). The method consists of formulating the governing equations and applying a numerical integration technique to solve a set of time-dependent, nonlinear, coupled, multidimensional equations. This formulation reveals that the steady-state performance of the PPER depends on the cell potential and three dimensionless groups. Predictions of the concentration, potential, and local current distributions in a PPER are presented for the electrowinning of copper from an aqueous, hydrochloric acid solution. These predictions show that axial diffusion and axial migration are significant …
Predicting Shunt Currents In Stacks Of Bipolar Plate Cells, Ralph E. White, C. W. Walton, H. S. Burney, R. N. Beaver
Predicting Shunt Currents In Stacks Of Bipolar Plate Cells, Ralph E. White, C. W. Walton, H. S. Burney, R. N. Beaver
Faculty Publications
A method is presented for predicting shunt currents in stacks of undivided and divided bipolar plate cells. The method is an efficient way of solving the coupled sets of algebraic equations that arise from using circuit analog models to represent the current paths in stacks of undivided or divided bipolar plate cells. These algebraic equations can be eitherlinear or nonlinear depending upon the current-potential relationships used in the model (i.e., nonlinear circuit elements can be included). The method is used to show the importance of including nonsymmetrical resistances and nonlinear circuit elements in the models. Also, the method …
A Mathematical Model Of A Zn/Br2 Cell On Charge, M J. Mader, Ralph E. White
A Mathematical Model Of A Zn/Br2 Cell On Charge, M J. Mader, Ralph E. White
Faculty Publications
A mathematical model of a parallel plate electrochemical cell with a separator and a homogeneous bulk reaction is presented. The model is based on the Zn/Br2 redox couple and can be used as an aid for the design of an efficient rechargeable storage battery. It is shown that four independent variables exist for the system at a fixed temperature: the effective separator thickness, the residence time, the channel width, and the potential driving force. Performance criteria of interest for the Zn/Br2 battery are defined. Predictions of performance during the charging process are presented. It is shown that the …
Simple Models For Diaphragm-Type Chlorine/Caustic Cells I. Dynamic Behavior, John Van Zee, Ralph E. White, A T. Watson
Simple Models For Diaphragm-Type Chlorine/Caustic Cells I. Dynamic Behavior, John Van Zee, Ralph E. White, A T. Watson
Faculty Publications
A simple model of the dynamic behavior of a diaphragm-type chlorine/caustic cell is presented. The model is based upon measurable diaphragm properties and the mass transfer of hydroxyl ion through the diaphragm. The anolyte is modeled simply as a region in which the OH– ion concentration is fixed, the diaphragm is modeled as a plug-flow reactor with an electrochemical reaction occurring at the catholyte/diaphragm interface where the cathode is placed, and the catholyte is modeled as a completely stirred flow reactor. Analytical integration of the governing equations for thesemodels yields two mathematical expressions: one for the concentration distribution of …
Simple Models For Diaphragm-Type Chlorine/Caustic Cells Ii. Effect Of Acidic Anolyte On Steady-State Caustic Yield, John Van Zee, Ralph E. White
Simple Models For Diaphragm-Type Chlorine/Caustic Cells Ii. Effect Of Acidic Anolyte On Steady-State Caustic Yield, John Van Zee, Ralph E. White
Faculty Publications
A simple steady-state model of a diaphragm-type chlorine/caustic cell in which the diaphragm is divided into two regions by a homogeneous acid-base reaction is presented. The location of the reaction affects significantly the caustic yield and effluent concentration. The model is used to predict the location of this reaction as a function of the operating variables, the physical constants, and three measurable properties of the diaphragm. These measurable properties are the MacMullin number or resistivity ratio of electrolyte-filled diaphragm relative to the electrolyte, the Darcy's law diaphragmpermeability, and the diaphragm thickness. The model is used to predict a maximum in …
Parallel Plate Electrochemical Reactor Model: Material Balance Closure And A Simplification, M J. Mader, C W. Walton, Ralph E. White
Parallel Plate Electrochemical Reactor Model: Material Balance Closure And A Simplification, M J. Mader, C W. Walton, Ralph E. White
Faculty Publications
A material balance closure calculation is presented to test the consistency of a previously published model of a parallelplate electrochemical reactor. New expressions are used in this procedure to calculate the average concentration of species i and the average current density for reaction j from the predicted concentration and potential distributions. Also, the previously presented model equations are simplified by assuming that the axial concentration gradient for species i can be approximated by a step change from the known feed concentration to the unknown outlet concentration. This one-step model provides a qualitative evaluation of cell performance and adds insight into …
A Mathematical Model For A Parallel Plate Electrochemical Reactor, Cstr, And Associated Recirculation System, T V. Nguyen, C W. Walton, Ralph E. White
A Mathematical Model For A Parallel Plate Electrochemical Reactor, Cstr, And Associated Recirculation System, T V. Nguyen, C W. Walton, Ralph E. White
Faculty Publications
A mathematical model is presented for a system comprised of a parallel plate electrochemical reactor (PPER) and a continuous, stirred-tank reactor (CSTR) under both total and partial recycle. The model is used to predict the time dependent behavior of the electrowinning of copper from an aqueous, hydrochloric acid solution. The model includes many important aspects of a PPER/CSTR system which have been neglected previously. These aspects are the kinetics of electrode reactions, the electroneutrality condition, three mass transfer processes for ionic species in the electrolyte (diffusion, ionic migration, and convection) and the electrode gap in the PPER, and the inclusion …
Using Parameter Estimation Techniques With A Simple Model Of A Diaphragm-Type Electrolyzer To Predict The Electrical Energy Cost For Naoh Production, John Van Zee, Ralph E. White
Using Parameter Estimation Techniques With A Simple Model Of A Diaphragm-Type Electrolyzer To Predict The Electrical Energy Cost For Naoh Production, John Van Zee, Ralph E. White
Faculty Publications
Predictions of the electrical energy cost for NaOH production are determined as a function of the independent operating variables and diaphragm characterizing properties. The predictions are based on data from a statistically designed experiment, a simple model of a diaphragm-type electrolyzer, a simple model of the cell voltage losses, and parameter estimation techniques. The data were obtained over a sufficiently large range of operating conditions so that the resulting design equation may be industrially useful. The simple model of the diaphragm is based on the mass transport of the hydroxyl ion, a linear potential gradient, and is presented in terms …
Extension Of Darby's Model Of A Hydrophylic Gas Fed Porous Electrode, Ralph E. White, M. A. Nicholson, L. G. Kleine, J. Van Zee, R. Darby
Extension Of Darby's Model Of A Hydrophylic Gas Fed Porous Electrode, Ralph E. White, M. A. Nicholson, L. G. Kleine, J. Van Zee, R. Darby
Faculty Publications
A model presented previously by one of the authors (1,2) is reviewed and extended. Aspects of this model which were not previously available in the open literature are considered, and the model is extended to include previously neglected terms in the governing differential equations, fractional reaction orders in the current density-overpotential expression, and mass-transfer coefficients to account for mass-transfer resistance of the reactants to the faces of the porous electrode. The model is used to predict quantities of interest for oxygen reduction in an acidic aqueous solution in a porous carbon electrode.
A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer
A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer
Faculty Publications
A mathematical model is presented for the Br2/Br– electrode reaction at a rotating disk electrode. The model includes current density-overpotential expressions for the electrode reaction according to either the Volmer-Heyrovsky (V-H) or the Volmer-Tafel (V-T) mechanism and the transport equations including the effect of ionic migration. The model is used to predict current-overpotential curves for various cases of interest. Qualitative comparison of the model predictions to literature data shows that either the V-H or the V-T mechanism, with V controlling, may be acceptable for the Br2/Br– reaction.
Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby
Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby
Faculty Publications
It is often desirable to be able to predict the total current density at an electrode when multiple electrochemical reactions occur there under potentiostatic control. It is also sometimes desirable to include the effect of ionic migration within the diffusion layer upon the predicted total (1) and partial current densities (2). A procedure for doing this can be illustrated by considering the rotating disk electrode (RDE) system and the associated potential distribution near the RDE as shown in Fig. 1 and 2.
An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White
An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White
Faculty Publications
An experimental analysis of the Br2/Br– redox reaction in a porous back fed ruthenium-coated titanium electrode is described. A mathematical model of the steady-state process is presented. Nonlinear regression of the model against the experimental data gives physically meaningful parameter estimates; these parameters and the model provide a design equation for the porous electrode current as a function of specific surface area, bulk Br2 concentration, average total overpotential, and the Reynolds number. The design equation shows that the back fed electrode could reduce the loss of Br2 across the separator and the ohmic loss in …
Potential-Selective Deposition Of Copper From Chloride Solutions Containing Iron, Ralph E. White, James A. Trainham, John Newman, Thomas W. Chapman
Potential-Selective Deposition Of Copper From Chloride Solutions Containing Iron, Ralph E. White, James A. Trainham, John Newman, Thomas W. Chapman
Faculty Publications
The hydrometallurgy of copper may involve leaching of the metal from its ore with an aqueous solution containing cupric and ferric chloride. The subsequent deposition of copper from such a process stream is modeled here in an idealized electrochemical cell with a rotating-disk electrode. The potential distribution and concentration profiles within the diffusion layer are predicted for given potential differences between the electrode and the solution. The cuprous ion, which is formed by the reduction of the complexed cupric ion at the electrode, is stabilized in the chloride solution and can react either at the electrode or with ferric species …
Electrochemical Reduction Of Molybdate In The Presence Of Zinc Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, R. Cvetkovic, Branko N. Popov, H. A. Laitinen
Electrochemical Reduction Of Molybdate In The Presence Of Zinc Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, R. Cvetkovic, Branko N. Popov, H. A. Laitinen
Faculty Publications
Two chronopotentiometric waves were observed for the electrochemical reduction of molybdate in the presence of zinc chloride, with quarter-wave potentials of –1.5V and –1.75V vs. the Pt(II)/Pt reference electrode, respectively. It was observed that an increase in the molybdate concentration causes a decrease of the first transition time indicating a chemical reaction between ZnCl2 (which is reduced at –1.5V) and Li2MoO4 in the melt forming ZnMoO4 which is sparingly dissociated in LiCl-KCl eutectic. The equilibrium constant for the observed reaction was calculated. X-ray powder diffraction patterns of the reduction product of ZnMoO4 have been …
Electrochemical Reduction Of Molybdenum(Vi) Compounds In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen
Electrochemical Reduction Of Molybdenum(Vi) Compounds In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen
Faculty Publications
Molybdenum (VI) oxide reacts with molten LiCl-KCl eutectic at 450° to form MoO2CI2, which probably is present as an anion MoO2Cl4=, and pyromolybdate, Mo2O7=. Both of these species are electrochemically reduced to MoO2, which can be reoxidized to MoO2Cl2 by current reversal. A second reduction step, observed whether MoO3 or Mo2O72− is added to the melt, can be attributed to the reduction of MoO4−−, formed as a secondary reaction product in the first …
Electrochemical Reduction Of Chromate In The Presence Of Nickel Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen
Electrochemical Reduction Of Chromate In The Presence Of Nickel Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen
Faculty Publications
Chronopotentiometry of chromate in the presence of NiCl2 in molten LiCl-KCl eutectic reveals a diffusion controlled, three electron reduction step. In the presence of excess NiCl2, chromate is reduced at −0.35V vs. Pt(II)/Pt reference electrode and the electroactive species responsible for the chrono-potentiometric wave is estimated to have a diffusion coefficient of 1.06 · 10−5 cm2 sec−1 at 450°C. The stoichiometry of the reduction product depends mainly on the temperature at which the deposit is formed. At 500°C the deposit approaches the composition LiNi2CrO4. X-ray powder diffraction shows the deposit …