Chemical Engineering Commons^™

Independent Effects Of Surface And Gas Temperature On Coal Fly Ash Deposition In Gas Turbines At Temperatures Up To 1400 C, Robert Laycock, Thomas H. Fletcher

Faculty Publications

Deposition of coal fly ash in gas turbines has been studied to support the concept of integrated gasification combined cycle (IGCC). Although particle filters are used in IGCC, small amounts of ash particles less than 5 microns in diameter enter the gas turbine. Previous deposition experiments in the literature have been conducted at temperatures up to about 1288 C. However, few tests have been conducted that reveal the independent effects of gas and surface temperature, and most have been conducted at gas temperatures lower than 1400 C. The independent effects of gas and surface temperature on particle deposition in a …

Size-Controlled Large-Diameter And Few-Walled Carbon Nanotube Catalysts For Oxygen Reduction, Xianliang Wang, Qing Li, Hengyu Pan, Ye Lin, Yujie Ke, Haiyang Sheng, Mark T. Swihart, Gang Wu

Faculty Publications

We demonstrate a new strategy for tuning the size of large-diameter and few-walled nitrogen-doped carbon nanotubes (N-CNTs) from 50 to 150 nm by varying the transition metal (TM = Fe, Co, Ni or Mn) used to catalyze graphitization of dicyandiamide. Fe yielded the largest tubes, followed by Co and Ni, while Mn produced a clot-like carbon morphology. We show that morphology is correlated with electrocatalytic activity for the oxygen reduction reaction (ORR). A clear trend of Fe > Co > Ni > Mn for the ORR catalytic activity was observed, in both alkaline media and more demanding acidic media. The Fe-derived N-CNTs exhibited …

Overview Of Estimation Methods For Industrial Dynamic Systems, John Hedengren, Ammon Eaton

Faculty Publications

Measurement technology is advancing in the oil and gas industry. Factors such as wireless transmitters, reduced cost of measurement technology, and increased regulations that require active monitoring tend to increase the number of available measurements. There is a clear opportunity to distill the recent flood of measurements into relevant and actionable information. Common methods to do this include a filtered bias update, implicit dynamic feedback, Kalman filtering, and moving horizon estimation. The purpose of these techniques is to validate measurements and align imperfect mathematical models to the actual process. Additionally, they can determine a best-estimate of the current state of …

Prediction And Validation Of External Cooling Loop Cryogenic Carbon Capture (Ccc-Ecl) For Full-Scale Coal-Fired Power Plant Retrofit, Mark J. Jensen, Christopher S. Russell, David Bergerson, Christopher D. Hoeger, David J. Frankman, Christopher S. Bence, Larry Lin Baxter

Faculty Publications

Bench-scale experiments and Aspen Plus (TM) simulations document full-scale, steady-state performance of the external cooling loop cryogenic carbon capture (CCC-ECL) process for a 550 MWe coal-fired power plant. The baseline CCC-ECL process achieves 90% CO2 capture, and has the potential to capture 99+ % of CO2, SO2, PM, NO2, Hg, and most other noxious species. The CCC-ECL process cools power plant flue gas to 175 K, at which point solid CO2 particles desublimate as the flue gas further cools to 154K. Desublimating flue gas cools in a staged column in direct contact with a cryogenic liquid and produces a CO2-lean …

High Temperature Proton Exchange Membranes With Enhanced Proton Conductivities At Low Humidity And High Temperature Based On Polymer Blends And Block Copolymers Of Poly(1,3-Cyclohexadiene) And Poly(Ethylene Glycol), Shawn Deng, Mohammad K. Hassan, Amol Nalawade, Kelly A. Perry, Karren L. More, Kenneth A. Mauritz, Marshall T. Mcdonnell, David J. Keffer, Jimmy W. Mays

Faculty Publications

Hot (at 120 °C) and dry (20% relative humidity) operating conditions benefit fuel cell designs based on proton exchange membranes (PEMs) and hydrogen due to simplified system design and increasing tolerance to fuel impurities. Presented are preparation, partial characterization, and multi-scale modeling of such PEMs based on cross-linked, sulfonated poly(1,3-cyclohexadiene) (xsPCHD) blends and block copolymers with poly(ethylene glycol) (PEG). These low cost materials have proton conductivities 18 times that of current industry standard Nafion at hot, dry operating conditions. Among the membranes studied, the blend xsPCHD-PEG PEM displayed the highest proton conductivity, which exhibits a morphology with higher connectivity of …

Application Of A Coated Film Catalyst Layer Model To A High Temperature Polymer Electrolyte Membrane Fuel Cell With Low Catalyst Loading Produced By Reactive Spray Deposition Technology, Timothy D. Myles, Siwon Kim, Radenka Maric, William E. Mustain

Faculty Publications

In this study, a semi-empirical model is presented that correlates to previously obtained experimental overpotential data for a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The goal is to reinforce the understanding of the performance of the cell from a modeling perspective. The HT-PEMFC membrane electrode assemblies (MEAs) were constructed utilizing an 85 wt. % phosphoric acid doped Advent TPS® membranes for the electrolyte and gas diffusion electrodes (GDEs) manufactured by Reactive Spray Deposition Technology (RSDT). MEAs with varying ratios of PTFE binder to carbon support material (I/C ratio) were manufactured and their performance at various operating temperatures was …

Ash Formation And Deposition During Oxy-Coal Combustion In A 100 Kw Laboratory Combustor With Various Flue Gas Recycle Options, Zhonghua Zhan, Andrew R. Fry, Danxi Yu, Minghou Xu, Jost O.L. Wendt

Faculty Publications

Fouling and slagging processes are important in oxy-coal combustion processes because they greatly influence heat transfer and boiler performance. Ash partitioning processes are precursors to deposition processes and so in order to predict the latter one must have a good understanding of the former. This work involves a 100 kW rated down-fired oxy-fuel combustor outfitted with sophisticated ash aerosol and ash deposit sampling equipment. The work differs from that previously published, in that here we focus on the effects of changes in the composition and amounts of actual recycled flue gas (RFG) streams used in oxy-coal combustion, not using once …

Hybrid Dynamic Optimization Methods For Systems Biology With Efficient Sensitivities, Nicholas Lewis, John Hedengren, Eric Haseltine

Faculty Publications

In recent years, model optimization in the field of computational biology has become a prominent area for development of pharmaceutical drugs. The increased amount of experimental data leads to the increase in complexity of proposed models. With increased complexity comes a necessity for computational algorithms that are able to handle the large datasets that are used to fit model parameters. In this study the ability of simultaneous, hybrid simultaneous, and sequential algorithms are tested on two models representative of computational systems biology. The first case models the cells affected by a virus in a population and serves as a benchmark …

Morphology Of Nanoporous Carbon-Binder Domains In Li-Ion Batteries—A Fib-Sem Study, Severin Vierrath, Lukas Zielke, Riko Moroni, Andrew Mordon, Dean R. Wheeler, Roland Zengerle, Simon Thiele

Faculty Publications

FIB-SEM tomography is used to reconstruct the carbon-binder domain (CBD) of a LiCoO2 battery cathode (3.9 × 5 × 2.3 μm3) with contrast enhancement by ZnO infiltration via atomic layer deposition. We calculate the porosity inside the CBD (57.6%), the cluster-size distribution with a peak at 54 nm, and the pore-size distribution with a peak at 64 nm. The tortuosities of the pore space (1.6–2.0) and the CBD (2.3–3.5) show a mild anisotropy, which is attributed to the fabrication process. A comparison to a modeled homogenous CBD reveals that clustering in the CBD decreases its electronic conductivity while increasing …

An Improved Statistical Analysis For Predicting The Critical Temperature And Critical Density With Gibbs Ensemble Monte Carlo Simulation, Richard A. Messerly, Richard L. Rowley, Thomas A. Knotts Iv, W Vincent Wilding

Faculty Publications

A rigorous statistical analysis is presented for Gibbs ensemble Monte Carlo simulations. This analysis reduces the uncertainty in the critical point estimate when compared with traditional methods found in the literature. Two different improvements are recommended due to the following results. First, the traditional propagation of error approach for estimating the standard deviations used in regression improperly weighs the terms in the objective function due to the inherent interdependence of the vapor and liquid densities. For this reason, an error model is developed to predict the standard deviations. Second, and most importantly, a rigorous algorithm for nonlinear regression is compared …

A Numerical Comparison Of Precipitating Turbulent Flows Between Large-Eddy Simulation And One-Dimensional Turbulence, Alex W. Abboud, Ben B. Schroeder, Tony Saad, Sean T. Smith, Derek D. Harris, David O. Lignell

Faculty Publications

This study presents the results of computational fluid dynamics simulations of a multiphase, reacting, turbulent mixing layer in an idealized geometry. The purpose is to compare large-eddy simulation (LES) to one-dimensional turbulence (ODT) and examine the trends of the flow under differing mixing conditions. Aqueous streams are mixed together to precipitate polymorphs of calcium carbonate. The polymorphs of calcium carbonate are tracked numerically using population balance equations (PBE). Each PBE contains all of the relevant physical models to track the particle evolution including nucleation, growth, and aggregation. A simple subgrid mixing model that is convenient for use with PBEs was …

Communication: Antibody Stability And Behavior On Surfaces, Derek B. Bush, Thomas A. Knotts Iv

Faculty Publications

Antibody microarrays have the potential to revolutionize molecular detection in scientific, medical, and other biosensor applications, but their current use is limited because of poor reliability. It is hypothesized that one reason for their poor performance results from strong antibody-surface interactions that destabilize the antibody structure and create steric interference for antigen recognition. Using a recently developed coarse-grain protein-surface model that has been parameterized against experimental data, antibody-surface interactions for two antibody orientations on two types of surfaces have been investigated. The results show that regardless of attachment geometry, antibodies tend to collapse onto hydrophobic surfaces and exhibit lower overall …

Hydrocarbon-Based Fuel Cell Membranes: Sulfonated Crosslinked Poly(1,3-Cyclohexadiene) Membranes For High Temperature Polymer Electrolyte Fuel Cells, Suxiang Deng, Mohammad K. Hassan, Kenneth A. Mauritz, Jimmy W. Mays

Faculty Publications

High temperature fuel cell membranes based on poly(1,3-cyclohexadiene) were prepared by a Polymerization-Crosslinking-Sulfonation (PCS) approach, and a broad range of membrane compositions were achieved using various sulfonating reagents and reaction conditions. Membranes were characterized for their proton conductivity and thermal degradation behavior. Some of the membranes showed up to a 68% increase in proton conductivity as compared to Nafion under the same conditions (100% relative humidity and 120 °C). Thermogravimetric analysis revealed that these membranes are thermally stable up to 200 °C. High proton conductivity and thermal stability, combined with much lower cost as compared to Nafion®, make these materials …

Optimum 3d Matrix Stiffness For Maintenance Of Cancer Stem Cells Is Dependent On Tissue Origin Of Cancer Cells, Esmaiel Jabbari, Samaneh K. Sarvestani, Leily Daneshian, Seyedsina Moeinzadeh

Faculty Publications

Introduction

The growth and expression of cancer stem cells (CSCs) depend on many factors in the tumor microenvironment. The objective of this work was to investigate the effect of cancer cells’ tissue origin on the optimum matrix stiffness for CSC growth and marker expression in a model polyethylene glycol diacrylate (PEGDA) hydrogel without the interference of other factors in the microenvironment.

Methods

Human MCF7 and MDA-MB-231 breast carcinoma, HCT116 colorectal and AGS gastric carcinoma, and U2OS osteosarcoma cells were used. The cells were encapsulated in PEGDA gels with compressive moduli in the 2-70 kPa range and optimized cell seeding density …

Plant-Level Dynamic Optimization Of Cryogenic Carbon Capture With Conventional And Renewable Power Sources, Seyed M. Safdarnejad, John Hedengren, Larry Lin Baxter

Faculty Publications

Increasing competitiveness of renewable power sources due to tightening restrictions on CO₂ emission from fossil fuel combustion is expected to cause a shift in power generation systems of the future. This investigation considers the impact of the Cryogenic Carbon Capture™ (CCC) process on transitional power generation. The CCC process consumes less energy than chemical and physical absorption processes and has an energy storage capability that shifts the parasitic loss of the CCC process away from peak hours. The CCC process responds rapidly to the variation of electricity demand and has a time constant that is consistent with the intermittent …

Investigating The Impact Of Cryogenic Carbon Capture On Power Plant Performance, Seyed M. Safdarnejad, L. Kennington, Larry Lin Baxter, John Hedengren

Faculty Publications

Cryogenic Carbon Capture (CCC) is a CO2 mitigation process that can be integrated into existing baseline and load following fossil-fueled power plants. This process consumes less energy than conventional chemical absorption and includes energy storage capability. The CCC process has a fast response time to load changes to allow higher utilization of intermittent renewable power sources to be used at a grid-scale level in the power sector. The impact of the CCC process on the performance and operating profit of a single fossil-fueled power generation unit is studied in this paper. The proposed system (power production from wind, coal, and …

Advances In Catalyst Deactivation And Regeneration, Calvin H. Bartholomew, Morris D. Argyle

Faculty Publications

Catalyst deactivation, the loss over time of catalytic activity and/or selectivity, is a problem of great and continuing concern in the practice of industrial catalytic processes. Costs to industry for catalyst replacement and process shutdown total tens of billions of dollars per year. While catalyst deactivation is inevitable for most processes, some of its immediate, drastic consequences may be avoided, postponed, or even reversed through regeneration.

Morphology And Magnetic Properties Of Sulfonated Poly[Styrene-(Ethylene/Butylene)-Styrene]/Iron Oxide Composites, Sateesh K. Peddini, Huy N. Pham, Leonard Spinu, James L. Weston, David E. Nikles, Kenneth A. Mauritz

Faculty Publications

α-Fe₂O₃ structures were initiated in the sulfonated polystyrene block domains of poly[styrene–(ethylene/butylene)–styrene] (SEBS) block copolymers via a domain-targeted in-situ chemical precipitation method. The crystal structure of these particles was determined using wide-angle X-ray diffraction and selected area electron diffraction using a transmission electron microscope (TEM). TEM revealed that for less sulfonated SEBS (10 mole%), nanoparticles were aggregated with aggregate size range of 100–150 nm whereas for high sulfonation (16 and 20 mole% sSEBS) there were needle-like structures with length and width of 200–250 nm and 50 nm, respectively. Dynamic mechanical analyses suggest that initial iron oxide nanoparticle …

Post-Installed Fiber Optic Pressure Sensors On Subsea Production Risers For Severe Slugging Control, Ammon Eaton, Seyed M. Safdarnejad, John Hedengren, Kristi Moffat, Casey Hubbell, David Brower, Alexis Brower

Faculty Publications

Fiber optic sensors have gained increasing use in monitoring offshore structures. The sensors have successfully monitored flowlines, umbilicals, wells, Tension Leg Platform (TLP) tendons, production and drilling risers, and mooring lines. Fiber optic sensors are capable of monitoring strain, temperature, pressure, and vibration. While the success of fiber optic monitoring has been clearly demonstrated, the sensors are now under consideration for automation applications. This paper details the plausibility of using pressure measurements from post-installed fiber Bragg grating (FBG) sensors with Model Predictive Control (MPC) to suppress severe slugging in subsea risers. Prior control schemes demonstrate that slugging is mitigated using …

High-Throughput Screening Using Fourier-Transform Infrared Imaging, Erdem Sasmaz, Kathleen Mingle, Jochen A. Lauterbach

Faculty Publications

Efficient parallel screening of combinatorial lib­ra ries is one of the most challenging aspects of the high­throughput (HT) heterogeneous catalysis workflow. Today, a number of methods have been used in HT catalyst studies, including various optical, mass­spectrometry, and gas­chromatography techniques. Of these, rapid­scanning Fourier­transform infrared (FTIR) imaging is one of the fastest and most versatile screening techniques. Here, the new design of the 16­channel HT reactor is presented and test results for its accuracy and reproducibility are shown. The performance of the system was evaluated through the oxidation of CO over commercial Pd/Al2O3 and cobalt oxide nanoparticles synthesized with different …

Enhancing Grain Boundary Ionic Conductivity In Mixed Ionic–Electronic Conductors, Ye Lin, Shumin Fang, Dong Su, Kyle S. Brinkman, Fanglin Chen

Faculty Publications

Mixed ionic–electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report the concept of targeted phase formation in a Ce0.8Gd0.2O2−δ–CoFe2O4 composite that serves to enhance the grain boundary ionic conductivity. Using transmission electron microscopy and spectroscopy approaches, we probe the grain boundary charge distribution and chemical environments altered by the phase reaction between the two constituents. The formation of an emergent phase successfully avoids segregation of the Gd dopant and depletion of oxygen vacancies …

Parameter Estimation For Towed Cable Systems Using Moving Horizon Estimation, Liang Sun, Jeremy Castagno, John Hedengren, Randall Beard

Faculty Publications

This paper presents a strategy for optimal estimation of parameters for towed cable systems using moving horizon estimation (MHE). The main contributions of the work include a novel formulation of MHE using a dead-band that explicitly rejects measurement noise, real-time implementation results, and the investigation of time-varying stochastic disturbances as well as unknown yet constant disturbances. Further analysis is conducted on the observability and sensitivity of key parameters to determine which parameters can be estimated by the proposed approach using real-time streaming data from experiments. In addition to the real-time results, an offline multiobjective optimization is conducted to reveal the …

Insights Into Ultrasonic Release From Eliposomes, Marjan Javadi, William G. Pitt

Faculty Publications

A novel nanosized liposomal carrier was prepared consisting of perfluorocarbon emulsion droplet(s) encapsulated inside a liposome, which is called an eLiposome. This 200-nm construct is useful for acoustically activated drug delivery because ultrasound causes the emulsion droplet to expand from liquid to gas, which expansion ruptures the eLiposome bilayer and releases the internal contents. This study focuses on the parameters that influence control of the release of calcein (a model drug), including ultrasound amplitude, insonation time, and perfluorocarbon vapor pressure as a function of temperature and composition. The results show that calcein release increases as the ultrasound amplitude or insonation …

Heterogeneous Catalyst Deactivation And Regeneration: A Review, Morris D. Argyle, Calvin H. Bartholomew

Faculty Publications

Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key features and considerations for each of these deactivation types is reviewed in detail with reference to the latest literature reports in these areas. Two case studies on the deactivation mechanisms of catalysts used for cobalt Fischer-Tropsch and selective catalytic reduction are considered to provide additional depth in the topics of …

The Effects Of Multiple Probes On The Hybridization Of Target Dna On Surfaces, Ryan C. Welling, Thomas A. Knotts Iv

Faculty Publications

DNA microarrays have disruptive potential in many fields including genetics and medicine, but the technology has yet to find widespread clinical use due to poor reliability. Microarrays work on the principle of hybridization and can only be as dependable as this process is reliable. As such, a significant amount of theoretical research has been done to understand hybridization on surfaces on the molecular level. Previous simulations of a target strand with a single, surface-tethered probe molecule have yielded valuable insights, but such is an ideal system and little is known about the effects of multiple probes—a situation that more closely …

Steam Gasification Rates Of Three Bituminous Coal Chars In An Entrained-Flow Reactor At Pressurized Conditions, Aaron D. Lewis, Troy M. Holland, Nathaniel R. Marchant, Emmett G. Fletcher, Danley J. Henley, Eric G. Fuller, Thomas H. Fletcher

Faculty Publications

Three bituminous coal chars (Illinois #6, Utah Skyline, and Pittsburgh #8) were gasified separately at total pressures of 10 and 15 atm in an entrained-flow reactor using gas temperatures up to 1830 K and particle residence times gasification, although select experiments were performed at conditions where significant mass release was due to gasification by both H2O and CO2. The measured coal data were fit to three char gasification models including a simple first-order global model, as well as the CCKN and CCK models that stem from the CBK model. The optimal kinetic parameters for each of the three models are …

Fuel Element Combustion Properties For Live Wildland Utah Shrubs, Thomas H. Fletcher, Chen Shen

Faculty Publications

Current field models for wildfire prediction are mostly based on dry or low-moisture fuel combustion research. To better study the live fuel combustion behavior, a laminar flow flat-flame burner was used to provide a convection heating source to ignite an individual live fuel sample. In this research project, four Utah species were studied: Gambel oak (Quercus gambelii), canyon maple (Acer grandidentatum), big sagebrush (Artemisia tridentata), and Utah juniper (Juniperus osteosperma). Leaf geometrical parameters measured included individual leaf total mass, thickness, leaf width, leaf length, and moisture content. Time-stamped images of combustion behavior along with time-dependent mass data were recorded via …

The Application And Accuracy Of Structure From Motion Computer Vision Models With Full-Scale Geotechnical Field Tests, L. Palmer, Kevin W. Franke, R. Abraham Martin, B. E. Sines, Kyle M. Rollins, John Hedengren

Faculty Publications

Structure from motion (SfM) computer vision is a relatively new technology that allows engineers to reconstruct a three-dimensional (3D) model of a given scene using twodimensional digital photographs captured from a single, moving camera. SfM computer vision provides an economic and user-friendly alternative to other 3D scene-capture and modeling tools such as light distance and ranging (LiDAR). Although the resolution and accuracy of laser-based modeling methods are generally superior to vision-based modeling methods, the economic advantages associated with the latter may make it a useful and practical alternative for many geotechnical engineering applications. Although other engineering disciplines have investigated the …

Modeling Light Gas And Tar Yields From Pyrolysis Of Green River Oil Shale Demineralized Kerogen Using The Chemical Percolation Devolatilization Model, Daniel Barfuss, Ronald J. Pugmire, Thomas H. Fletcher

Faculty Publications

Recent detailed chemical structure analyses of three demineralized kerogens from Green River oil shale samples were used to generate input parameters for the chemical percolation devolatilization (CPD) model. This model uses a lattice network to describe pyrolysis of solid hydrocarbons, such as coal and biomass. It was necessary to modify the formulation of the CPD model to account for the long aliphatic carbon chains found in oil shale, because gases formed from these long chains condense at room temperature and are counted as tar. It was initially assumed that 20% of the aliphatic material was released as light gas during …

Simulation Of The Swelling Of High-Volatile Bituminous Coal During Pyrolysis. Part 2: Influence Of The Maximum Particle Temperature, He Yang, Thomas H. Fletcher, Ming Dong

Faculty Publications

A model was established previously to predict the swelling ratio of high-volatile bituminous coal during pyrolysis based on the assumption that the structure of bubble distribution in the particle at the beginning of the plastic stage is a central bubble surrounded by many surrounding bubbles. The initial number and size of the bubbles when the particles become plastic are calculated by the pressure in the particle, and the chemical percolation devolatilization (CPD) model is used to describe pyrolysis. In this paper, to obtain accurate results at low pyrolysis temperatures, the previous model is improved and the following parts in the …