Catalysis and Reaction Engineering Commons^™

A Fully Coupled Fluid-Particle Flow Solver Using Quadrature-Based Moment Method With High-Order Realizable Schemes On Unstructured Grids, Varun Vikas, Z. J. Wang, Alberto Passalacqua, Rodney O. Fox

Rodney O. Fox

Kinetic Equations containing terms for spatial transport, gravity, fluid drag and particle-particle collisions can be used to model dilute gas-particle flows. However, the enormity of independent variables makes direct numerical simulation of these equations almost impossible for practical problems. A viable alternative is to reformulate the problem in terms of moments of the velocity distribution function. A quadrature method of moments (QMOM) was derived by Desjardins et al. [1] for approximating solutions to the kinetic equation for arbitrary Knudsen number. Fox [2, 13] derived a third-order QMOMfor dilute particle flows, including the effect of the fluid drag on the particles ...

Numerical Simulation Of Turbulent Gas-Particle Flow In A Riser Using A Quadrature-Based Moment Method, Alberto Passalacqua, Rodney O. Fox

Rodney O. Fox

Gas-particle flows are used in many industrial applications in the energy, oil and gas fields, such as coal gasification, production of light hydrocarbons by fluid catalytic cracking, catalytic combustion and different treatments aiming to reduce or eliminate pollutants. The particle phase of a gas-particle flow is described by analogy to a granular gas, by finding an approximate solution of the kinetic equation in the velocity-based number density function. In the recent past, many studies have been published on the mathematical modeling of gas-particle flows using hydrodynamic models (e.g. Enwald et al. 1996), where Navier-Stokes-type equations are solved to describe ...

Numerical Simulations Of Turbulent Bluff-Body Flames Using Multi-Environment Presumed Pdf Method With Realistic Chemistry, Qing Tang, Wei Zhao, Micahel Bockelie, Rodney O. Fox

Rodney O. Fox

A Computational Fluid Dynamics (CFD) tool for performing turbulent combustion simulations that require finite rate chemistry is developed and tested by modeling a series of bluff-body stabilized flames that exhibit different levels of finite-rate chemistry effects ranging from near equilibrium to near global extinction. The new modeling tool is based on the multi-environment probability density function (MEPDF) methodology and combines the following: the direct quadrature method of moments (DQMOM); the interaction-by-exchange-with-the-mean (IEM) mixing model; and realistic combustion chemistry. A pseudo time splitting scheme is adopted to solve the MEPDF equations; the reaction source terms are computed with a highly efficient ...

Modeling Fluidization In Biomass Gasification Processes, Emmanuela Gavi, Theodore J. Heindel, Rodney O. Fox

Rodney O. Fox

Extensive validation of computational fluid dynamics (CFD) models is required when modeling biomass fluidization, because several required model inputs are not know or not easily measured experimentally for biomass. In the present work, CFD fluidization modeling of a biomass bed is validated by comparison with X-ray computed tomography experimental data. A parametric study was carried out by employing ground walnut shell or ground corncob as model biomass bed materials, and fluidization was performed at a gas velocity twice the minimum fluidization velocity. An important result is the use of an "effective density" for biomass in the CFD model, the use ...

Turbulent Combustion Of Polydisperse Evaporating Sprays With Droplet Crossing: Eulerian Modeling And Validation In The Infinite Knudsen Limit, S. De Chaisemartin, L. Freret, D. Kah, F. Laurent, Rodney O. Fox, J. Reveillon, M. Massot

Rodney O. Fox

The accurate simulation of the dynamics of polydisperse evaporating sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. The difficulties encountered by the usual Lagrangian approaches make the use of Eulerian models attractive, aiming at a lower cost and an easier coupling with the carrier gaseous phase. Among these models, the multi-fluid model allows for a detailed description of the polydispersity and size-velocity correlations for droplets of various sizes. The purpose of the present study is twofold. First, we extend the multi-fluid model in ...

Conditional-Moment Closure With Differential Diffusion For Soot Evolution In Fire, J. C. Hewson, A. J. Ricks, S. R. Tieszen, A R. Kerstein, Rodney O. Fox

Rodney O. Fox

The conditional-moment closure (CMC) equation for the evolution of a large Lewis number scalar, soot, is derived starting from the joint probability density function (pdf) equation for the gas-phase mixture fraction, ξ g , and the soot mass fraction, Y s . Unlike previous approaches starting with the joint pdf, the residual terms that result from the typical closure models were retained. A new formulation of the one-dimensional turbulence (ODT) model suitable for spatially evolving flows with buoyant acceleration and radiative transport in participating media was employed to carry out simulations of a prototypical ethene fire. The resulting ODT evolution of ξ ...

Consistent Hybrid Les-Fdf Formulation For The Simulation Of Turbulent Combustion, Venkatramanan Raman, H. Pitsch, Rodney O. Fox

Rodney O. Fox

The numerical simulation of turbulent reactive flows is a complex and challenging problem with widespread practical use. Recent breakthroughs in algorithmic techniques and the drastic increase in computing power have provided us with the tools to understand the complex interaction between turbulence and chemical reactions. In the past decade, the use of the large-eddy simulation (LES) technique has made it possible to make accurate predictions of turbulent flows even for complex configurations.

Instantaneous Particle Acceleration Model For Gas-Solid Suspensions At Moderate Reynolds Numbers, Sudheer Tenneti, Rodney O. Fox, Shankar Subramaniam

Rodney O. Fox

Gas-solid flows are encountered in many industrial applications such as fluidized beds and coal gasification. The design and scale-up of such industrial devices required a better understanding of the characteristics of gas-solid suspensions. Device-scale computational fluid dynamics (CFD) simulations that solve for average quantities such as solid volume fraction and phasic mean velocity fields are being extensively used in the industrial design process. The capability of the simulations to accurately predict the characteristics of gas-solid flow depends upon the accuracy of the models for unclosed terms that appear in the equations for mass, momentum and energy conservation. Hrenya and Sinclair ...

A Quadrature-Based Moment Closure For The Williams Spray Equation, O. Desjardins, Rodney O. Fox, P. Villedieu

Rodney O. Fox

Sprays and other dispersed-phase systems can be described by a kinetic equation containing terms for spatial transport, acceleration, and particle processes (such as evaporation or collisions). In principle, the kinetic description is valid from the dilute (non-collisional) to the dense limit. However, its numerical solution in multi-dimensional systems is intractable due to the large number of independent variables. As an alternative, Lagrangian methods "discretize" the density function into "parcels" that are simulated using Monte-Carlo methods. While quite accurate, as in any statistical approach, Lagrangian methods require a relatively large number of parcels to control statistical noise, and thus are computationally ...

Numerical Description Of Dilute Particle-Laden Flows By A Quadrature-Based Moment Method, N. Le Lostec, Rodney O. Fox, O. Simonin, P. Villedieu

Rodney O. Fox

The numerical simulation of gas-particle flows is divided into two families of methods. In Euler-Lagrange methods individual particle trajectories are computed, whereas in Euler-Euler methods particles are characterized by statistical descriptors. Lagrangian methods are very precise but their computational cost increases with instationarity and particle volume fraction. In Eulerian methods (also called moment methods) the particle-phase computational cost is comparable to that of the fluid phase but requires strong simplificaions. Existing Eulerian models consider unimodal or close-to-equilibrium particle velocity distributions and then fail when the actual distribution is far from equilibrium. Quadrature-based Eulerian methods introduce a new reconstruction of the ...

Development Of High-Order Realizable Finite-Volume Schemes For Quadrature-Based Moment Method, Varun Vikas, Z. J. Wang, Alberto Passalacqua, Rodney O. Fox

Rodney O. Fox

Kinetic equations containing terms for spatial transport, gravity, fluid drag and particle-particle collisions can be used to model dilute gas-particle flows. However, the enormity of independent variables makes direct numerical simulation of these equations almost impossible for practical problems. A viable alternative is to reformulate the problem in terms of moments of velocity distribution. Recently, a quadrature-based moment method was derived by Fox for approximating solutions to kinetic equation for arbitrary Knudsen number. Fox also described 1st- and 2nd-order finite-volume schemes for solving the equations. The success of the new method is based on a moment-inversion algorithm that is used ...

Differential Surface Stress Sensor For Detection Of Chemical And Biological Species, K. Kang, Marit Nilsen-Hamilton, Pranav Shrotriya

Pranav Shrotriya

We report a sensor consisting of two micromachined cantilevers (a sensing/reference pair) that is suitable for detection of chemical and biological species. The sensing strategy involves coating the sensing cantilever with receptors that have high affinities for the analyte. The presence of analyte is detected by determining the differential surface stress associated with its adsorption/absorption to the sensing cantilever. An interferometric technique is utilized to measure the differential bending of the sensing cantilever with respect to reference. Surface stress associated with hybridization of single stranded DNA is measured to demonstrate the unique advantages of the sensor.

Acetone Production, Ali Ibrahim Neamah

The Hilltop Review

Iraq struggles with a lack of acetone production. This overall deficiency impacts the economy of countries like Iraq. Inasmuch, acetone is a vital chemical component for many items imported into this country such as nail polish remover. Therefore, a process of acetone production is proposed in this study.

The ideal process of producing acetone with 90.0% isopropyl alcohol (IPA) decomposition method is proposed within this study. The feed of the process is 100000 ton/ day. This amount of feed is suggested due to the demographic need of acetone for the Iraqi population as well as the surrounding Middle Eastern ...

The Dry Reforming Of Methane To Syngas And Subsequent Products, Sean Kasprisin 4347974, Timothy Poppert, Nykyta Vovk, Alexander Fox, Hussain Alsukairi

Honors Theses AY 16/17

Dry Reforming of Methane to Syngas other Subsequent Products

Hussain Alsukairi, Alexander Fox, Sean Kasprisin, Tim Poppert, Nykta Vovk

Chemical Engineering

University of Wyoming

Senior Design

Synthesis Gas, or syngas (a combination of Hydrogen and Carbon Monoxide) can be used in a plethora of different chemical processes and processing plants. Utilizing Steam reforming of methane has been the accepted method to create syngas and it utilized on an industrial scale. Steam reforming of methane results in the formation of Carbon Dioxide (a greenhouse gas) that has to be dealt with so the impact on the environment can be minimized. Dry-reforming ...

Photoactive Properties Of Nanostructured Titania Modified Polyurethanes, Chao Chen

Electronic Thesis and Dissertation Repository

In order to enhance both the photoactivity and physical/mechanical properties of titania/polyurethane (PU) nanocomposites, in-situ polymerization and film casting were investigated. Both self-degrading PU foams and self-cleaning PU coatings were prepared. Functional monomers were prepared usingDMPA (2,2-dimethylolpropionic acid) functionalized anatse TiO₂ and P25 for integration into polyurethane foam with a "grafting-from" synthetic method. This technique was found to successfully reduce the agglomeration effect of titania nanoparticles inside the foams. In addition, the photodegradation rate was enhanced by > 120% over unmodified foam at an optimized loading of 3wt% DMPA functionalized anatase TiO₂. The presence of DMPA ...

Synthesis, Characterization, And Properties Of Graphene-Based Hybrids With Cobalt Oxides For Electrochemical Energy Storage And Electrocatalytic Glucose Sensing, Sara C. Botero Carrizosa

Masters Theses & Specialist Projects

A library of graphene-based hybrid materials was synthesized as novel hybrid electrochemical electrodes for electrochemical energy conversion and storage devices and electrocatalytical sensing namely enzymeless glucose sensing. The materials used were supercapacitive graphene-family nanomaterials (multilayer graphene-MLG; graphene oxide-GO, chemically reduced GO-rGO and electrochemical reduced GOErGO) and pseudocapacitive nanostructured transition metal oxides including cobalt oxide polymorphs (CoO and Co3O4) and cobalt nanoparticles (CoNP). These were combined through physisorption, electrodeposition, and hydrothermal syntheses approaches. This project was carried out to enhance electrochemical performance and to develop electrocatalytic platforms by tailoring structural properties and desired interfaces. Particularly, electrodeposition and hydrothermal synthesis facilitate chemically-bridged ...

Characterization Of Iron Phthalocyanine As The Cathode Active Material For Lithium-Ion Batteries, Sarwan S. Sandhu, Joseph P. Fellner

Sarwan S. Sandhu

The developed thermodynamic functions for the determination of Gibbs free energy, enthalpy, and entropy of formation of solid lithium-iron phthalocyanine (LixFePc) from solid lithium and iron phthalocyanine as a function of x, defined as g-moles of the intercalated lithium per g-mole of iron phthalocyanine, at a fixed set of temperature and pressure conditions are presented. In addition, a proposed expression for the evaluation of lithium diffusion coefficient in solid iron phthalocyanine as a function of both x and temperature, and the experimental results from the ongoing research/development work on the lithium/iron phthalocyanine cells are included.

Tunable Nanocomposite Membranes For Water Remediation And Separations, Sebastián Hernández Sierra

Theses and Dissertations--Chemical and Materials Engineering

Nano-structured material fabrication using functionalized membranes with polyelectrolytes is a promising research field for water pollution, catalytic and mining applications. These responsive polymers react to external stimuli like temperature, pH, radiation, ionic strength or chemical composition. Such nanomaterials provide novel hybrid properties and can also be self-supported in addition to the membranes.

Polyelectrolytes (as hydrogels) have pH responsiveness. The hydrogel moieties gain or lose protons based on the pH, displaying swelling properties. These responsive materials can be exploited to synthesize metal nanoparticles in situ using their functional groups, or to immobilize other polyelectrolytes and biomolecules. Due to their properties, these ...

Platinum-Rhodium Alloy Electrocatalyst Activities In The Methanol Oxidation Reaction, William R. Sandorf

Honors Research Projects

This study evaluates the electrochemical activity of several compositions of platinum-rhodium alloys on carbon support to identify potential replacements for the expensive platinum electrocatalysts currently used in direct methanol fuel cells (DMFCs). The electrochemical active surface areas (ECSAs) of each sample were determined using cyclic voltammetry (CV) in a 0.5 M H₂SO₄ solution to normalize CV currents generated in the methanol oxidation reaction (MOR). The activity of five compositions was tested; Pt₃Rh, Pt₂Rh, PtRh, Pt₂Rh, and Pt₃Rh. 100 mg of each catalyst was synthesized at 10% by weight ...

Enzyme-Catalyzed Reactions Using Enzymes Immobilized On Non-Spherical Particles, Alexander D. Redfearn

Honors Theses and Capstones

Modern and industrial chemical reactions often utilize enzyme-catalyzed reactions to increase product yields. Given the high cost of enzymes it is desirable to preserve the activity of the enzymes and reuse them several times. In this study, I explored the possibility of immobilizing enzymes on custom-made non-spherical SU-8 microparticles to conduct enzyme-catalyzed reactions in flow reactors. The decomposition of hydrogen peroxide using bovine liver catalase was studied due to its well-understood enzyme kinetics. Soft lithography techniques were used to synthesize prismatic SU-8 microparticles. I will discuss the progress that has been made in immobilizing the enzyme on the particle surface ...