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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Uncertainty Quantification Analysis of Both Experimental and CFD Simulation Data of a Bench-scale Fluidized Bed Gasifier

Adequate assessment of the uncertainties in modeling and simulation is becoming an integral part of the simulation based engineering design. The goal of this study is to demonstrate the application of non-intrusive Bayesian uncertainty quantification (UQ) methodology in multiphase (gas-solid) flows with experimental and simulation data, as part of our research efforts to determine the most suited approach for UQ of a bench scale fluidized bed gasifier. UQ analysis was first performed on the available experimental data. Global sensitivity analysis performed as part of the UQ analysis shows that among the three operating factors, steam to oxygen ratio has the most influence on syngas composition in the bench-scale gasifier experiments. An analysis for forward propagation of uncertainties was performed and results show that an increase in steam to oxygen ratio leads to an increase in H2 mole fraction and a decrease in CO mole fraction. These findings are in agreement with the ANOVA analysis performed in the reference experimental study. Another contribution in addition to the UQ analysis is the optimization-based approach to guide to identify next best set of additional experimental samples, should the possibility arise for additional experiments. Hence, the surrogate models constructed as part of the UQ analysis is employed to improve the information gain and make incremental recommendation, should the possibility to add more experiments arise. In the second step, series of simulations were carried out with the open-source computational fluid dynamics software MFiX to reproduce the experimental conditions, where three operating factors, i.e., coal flow rate, coal particle diameter, and steam-to-oxygen ratio, were systematically varied to understand their effect on the syngas composition. Bayesian UQ analysis was performed on the numerical results. As part of Bayesian UQ analysis, a global sensitivity analysis was performed based on the simulation results, which shows that the predicted syngas composition is strongly affected not only by the steam-to-oxygen ratio (which was observed in experiments as well) but also by variation in the coal flow rate and particle diameter (which was not observed in experiments). The carbon monoxide mole fraction is underpredicted at lower steam-to-oxygen ratios and overpredicted at higher steam-to-oxygen ratios. The opposite trend is observed for the carbon dioxide mole fraction. These discrepancies are attributed to either excessive segregation of the phases that leads to the fuel-rich or -lean regions or alternatively the selection of reaction models, where different reaction models and kinetics can lead to different syngas compositions throughout the gasifier. To improve quality of numerical models used, the effect that uncertainties in reaction models for gasification, char oxidation, carbon monoxide oxidation, and water gas shift will have on the syngas composition at different grid resolution, along with bed temperature were investigated. The global sensitivity analysis showed that among various reaction models employed for water gas shift, gasification, char oxidation, the choice of reaction model for water gas shift has the greatest influence on syngas composition, with gasification reaction model being second. Syngas composition also shows a small sensitivity to temperature of the bed. The hydrodynamic behavior of the bed did not change beyond grid spacing of 18 times the particle diameter. However, the syngas concentration continued to be affected by the grid resolution as low as 9 times the particle diameter. This is due to a better resolution of the phasic interface between the gases and solid that leads to stronger heterogeneous reactions. This report is a compilation of three manuscripts published in peer-reviewed journals for the series of studies mentioned above.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2026

Two-Way Coupled CFD/DEM Simulation of Electromagnetic Heating in a Fluidized Bed Reactor

A set of tools has been developed to couple a multiphase reacting computational fluid dynamics solver (MFIX) with two computational electromagnetic solvers (COMSOL and Elmer). In contrast to several recent investigations, which calculate a single static EM field prior to the CFD calculation, in the present work the electromagnetic field is periodically updated during the simulation. This enables the EM field and associated EM heating predictions to reflect the effects of evolving material properties (temperature, composition, size etc.) and the evolving distribution of material in the system. The present work uses effective medium theory (EMT) for the electromagnetic field calculations since the goal is to apply the tool for industrial scale reacting systems. Predictions using MFIX/COMSOL and MFIX/Elmer are compared to in bed thermocouple measurements from a fluidized bed experiment and recent simulation predictions and recent experiments performed at NETL. The NETL experiments also include packed bed operating conditions. Coupled MFIX/COMSOL simulations at these conditions are compared with similar simulations using only COMSOL to measure errors due to the solver coupling approach.

CFD↗
DOE OSTI2021

Saturation Carrying Capacity for Group A Particles in a Circulating Fluidized Bed

Empirical models continue to play a significant role in the design process of multiphase chemical reactors, particularly riser reactors in circulating fluidized bed (CFB) processes. It is imperative that accurate, industrial relevant correlations are developed to aid these design efforts. Using poor correlations could result in startup issues and significant redesign work. In this work, a new correlation is proposed to predict the saturation carrying capacity of Geldart Group A particles. This new correlation improves upon the currently available correlations for these materials and covers a broad range of Geldart Group A particles (particle diameters from 52 to 70 µm, and Archimedes numbers ranging from 5 to 20), superficial gas velocities (1 to 4 m/s), and riser diameters (0.066 to 0.3048 m). The new correlation has an Absolute Average Percent Deviation of only 17.6%, making it the most accurate correlation for Geldart Group A particles in the current literature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

R&D with NREL's 2'' Fluidized Bed Reactor (2FBR) Systems; R&D with the NREL Research Gasifier (NRG)

The Thermal and Catalytic Process Development Unit at NREL has state-of-the-art equipment for thermochemical process development and testing, ranging from catalyst and feedstock characterizations to bench-scale reactors to pilot plants. Within this facility is the 2 Inch Fluidized Bed Reactor, a versatile lab-scale thermal processing and catalytic upgrading system to evaluate the conversion of renewable and waste feedstocks into fuels and chemicals. In addition, the NREL Research Gasifier is a lab-scale gasification system, perfectly suited to study the conversion of biomass and waste streams to purified syngas. This fact sheet summarizes the capabilities of both systems.

09 BIOMASS FUELS↗
DOE OSTI2026

Two-Way Coupled CFD/DEM Simulation of Electromagnetic Heating in a Fluidized Bed Reactor - Extended Abstract

A set of tools has been developed to couple a multiphase reacting computational fluid dynamics solver (MFIX) with two computational electromagnetic solvers (COMSOL and Elmer). In contrast to several recent investigations, which calculate a single static EM field prior to the CFD calculation, in the present work the electromagnetic field is periodically updated during the simulation. This enables the EM field and associated EM heating predictions to reflect the effects of evolving material properties (temperature, composition, size etc.) and the evolving distribution of material in the system. The present work uses effective medium theory (EMT) for the electromagnetic field calculations since the goal is to apply the tool for industrial scale reacting systems. Predictions using MFIX/COMSOL and MFIX/Elmer are compared to in bed thermocouple measurements from a fluidized bed experiment and recent simulation predictions and recent experiments performed at NETL. The NETL experiments also include packed bed operating conditions. Coupled MFIX/COMSOL simulations at these conditions are compared with similar simulations using only COMSOL to measure errors due to the solver coupling approach.

CFD↗
DOE OSTI2018

Numerical and experimental comparison of tracer particle and averaging techniques for particle velocities in a fluidized bed

Particle tracking methods using emitted radiation show potential for following motion in opaque systems such as granular materials. Leading examples are Positron Emission Particle Tracking (PEPT) and Radioactive Particle Tracking (RPT). The application of such techniques sometimes requires the use of tracer particles which differ in size, density and/or shape from the particles of interest. This study investigates the extent to which such differences affect the result of the study by using the open source MFIX-DEM software to model particle motion in the travelling fluidized bed experiments. The results are compared with previously reported experimental studies using both PEPT and RPT. Consistent numerical results were obtained for both PEPT and RPT tracer particles. In determining averaged velocities using such techniques, there is a choice to be made between averaging velocities of particles crossing a virtual plane over a period of time (the “face-average” approach) or those passing through a defined volume over time (the “volume-average” approach). The differences between results obtained with these two methods are shown to be significant in this case, for both computation and experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Catalytic fast pyrolysis of bamboo sawdust via a two-step bench scale bubbling fluidized bed/fixed bed reactor: Study on synergistic effect of alkali metal oxides and HZSM-5

Catalytic fast pyrolysis of bamboo sawdust was conducted by a tandem bubbling fluidized bed/fixed bed reactor. Effect of pyrolysis and catalyst temperatures on product yield was studied. In addition, synergistic effect of HZSM-5 and base catalysts (including CaO, MgO, and SrO) for the promotion of aromatic hydrocarbons was revealed. Experimental results illustrated that both pyrolytic and catalytic reactor temperatures played pivotal roles in the yield of bio-oil, and the optimal pyrolysis and catalytic reactor temperatures were 550 °C and 500 °C, respectively. Ex-situ catalytic trial decreased the yield of bio-oil compared to in-situ run, while it facilitated the formation of phenol and alkylphenols. Mixed catalytic upgrading modes exhibited more significant aromatization and deoxygenation activities than sequential ones. In particular, ex-situ run using CaO mixed with HZSM-5 increased the concentration of aromatic hydrocarbons to 31.34%, which was ~11.48% higher than that derived from CaO and HZSM-5 sequentially processed mode. The dominated products in alkylphenols were cresol isomers and ethylphenols, and compared to sequential cases, mixed catalytic upgrading trials promoted the relative selectivity of phenol. Synergistic effect of base catalysts and HZSM-5 contributed to the production of monocyclic aromatic hydrocarbons, and CaO mixed with HZSM-5 mode showed the most prominent synergistic effect for the enhanced relative selectivity to xylenes and toluene.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Catalytic fast co-pyrolysis of bamboo sawdust and waste tire using a tandem reactor with cascade bubbling fluidized bed and fixed bed system

Catalytic fast co-pyrolysis (co-CFP) of bamboo sawdust and waste tire over HZSM-5 and MgO was conducted using a tandem pyrolysis and upgrading system which consists of a bubbling fluidized bed and a fixed bed reactor. HZSM-5 mixed and sequential with MgO modes were studied to explore the additive effect for the promotion of aromatic hydrocarbons. Experimental results indicated that co-CFP of bamboo sawdust with waste tire over pure HZSM-5 increased the yields of pyrolysis oil and char, while the gas yield decreased with the increasing of waste tire percentage in the feedstock blends. The product distribution of pyrolysis oil obtained from co-CFP of bamboo sawdust and waste tire over pure HZSM-5 was dominated by aromatic hydrocarbons, and the relative concentration increased from 26.71 to 71.50% as the waste tire percentage elevated from 0 to 60 wt%. Co-CFP of bamboo sawdust and waste tire using HZSM-5 mixed with MgO mode produced a higher yield of pyrolysis oil than the sequential mode when HZSM-5/MgO mass ratio was raised from 1:4 to 1:1. However, the sequential mode was proved to be more effective in the promotion of aromatic hydrocarbons than the mixed mode at a higher HZSM-5 proportion. A positive additive effect for alkylbenzenes was found when the sequential mode was used at varying HZSM-5/MgO mass ratios. Regarding the olefins, C10 olefins were main products, and limonene selectivity increased at first and then decreased with the highest selectivity of 38.87% occurring at HZSM-5/MgO of 2:3 in the mixed mode case. In conclusion, the additive effect of HZSM-5 and MgO indicated that both the mixed and sequential modes inhibited the formation of polycyclic aromatic hydrocarbons with the most significant additive effect obtained at HZSM-5/MgO mass ratio of 1:1 using the mixed mode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Investigation of methane and ethane pyrolysis with highly active and durable iron-alumina catalyst to produce hydrogen and valuable nano carbons: Continuous fluidized bed tests and reaction rate analysis

The goal of this research work was to evaluate a novel iron-alumina catalyst for methane and ethane pyrolysis with high conversion rates to H 2 with a long life time to address two major issues reported with previous catalysts. Fluidized bed tests demonstrated continuous hydrogen production while collecting carbon containing fines. During the 230 h fluid bed test the methane conversion rate to hydrogen at 700 °C remained above 80% for 160 h while creating valuable nano carbons. Similarly high catalyst lifetimes with high methane conversions have not been reported before. Ethane was more active than methane for pyrolysis with 100% conversion to H 2 . Transmission electron microscopy and Raman analysis of the carbon showed single and multiwall nanotubes and conglomerate nano-fibers. Ethane did not impact the allotrope of carbon formed. TGA was used to create a data array that was used for kinetic analysis and reaction model parametric regressions. Ethane had a higher rate of pyrolysis that was 2.3–2.8 times that of methane. Ethane pyrolysis was found to be more sensitive to temperature with a higher activation energy of 62 kJ/mol as compared to methane at 43 kJ/mol. The frequency factor, A i , was significantly higher for ethane at 0.73 [[kmol/m 3 -sec]/[N/m2] n ] compared to 0.03 for methane on the same basis. Both gases had a functional partial pressure order dependence of ~0.6 based on the regression analysis.

08 HYDROGEN↗
DOE OSTI2024

Characterization of fluidized bed chemical vapor deposition ZrC coatings on PyC/YSZ kernels deposited under differing conditions

In this study, coated fuel particle architectures with ZrC coatings are candidate fuels for advanced power reactors and space nuclear propulsion (SNP) concepts. Owing to its relevance to SNP, the composition, microstructure, and mechanical properties of eight ZrC coatings prepared by fluidized bed chemical vapor deposition were evaluated. Evaluation by SEM and EBSD showed that all grains were columnar. Across the various examined samples, minor axis diameters varied between 0.3 and 1.1 μm, and major axis diameters varied between 0.4 and 2.3 μm. Major and minor diameters increased with thickness particularly at higher deposition temperatures in which the major grain axis (from an ellipse fit to the grain shape) increased by 2.5 μm over the entire coating. Coatings with higher reactive gas flows and Zr/C concentrations closer to 1 were observed to contain nanocrystalline graphite deposits. Reactive gas flow doubling led to increases in coating thickness from around 10–15 μm to around 22–27 μm.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Multiphase flow simulations of a moving fluidized bed regenerator in a carbon capture unit

To accelerate the commercialization and deployment of carbon capture technologies, computational fluid dynamics (CFD)-based tools may be used to model and analyze the performance of carbon capture devices. This work presents multiphase CFD-based flow simulations for the regeneration device responsible for extracting CO 2 from CO 2 -loaded sorbent particles before the particles are recycled. The use of solid particle sorbents in this design is a departure from previously reported systems, where aqueous sorbents are employed. Another new feature is the inclusion of a series of perforated plates along the regenerator height. The influence of these plates on sorbent distribution is examined for varying sorbent holdup, fluidizing gas velocity, and particle size. The residence time distribution of sorbents is also measured to classify the low regime as plug flow or well-mixed flow. The purpose of this work is to better understand the sorbent flow characteristics before reaction kinetics of CO 2 desorption can be implemented.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2017

Flash Pyrolysis of Oleaginous Biomass in a Fluidized-Bed Reactor

In this study, flash pyrolysis was performed using milled soybean as a model substrate to assess the production of liquid fuels from oleaginous biomass feedstocks. A laboratory-scale fluidized-bed flash pyrolysis reactor that allowed rapid heat transfer to the biomass along with short vapor residence time was designed and constructed. Pyrolysis was performed between 250 and 610 °C with a vapor residence time between 0.2 and 0.3 s. At 550 °C or higher, nearly 70% of the initial feed mass as well as feed carbon was recovered in bio-oil. In addition, 90% of the feedstock lipids were recovered in the bio-oil at these pyrolysis conditions. The high liquid products yields were attributed to (1) the low secondary degradation of bio-oils due to the short vapor residence time and (2) the high recovery of liquids in a novel dry ice packed-bed condenser that provided a high surface area for condensation/aggregation of dilute bio-oil vapors/aerosols that were entrained in the carrier gas. The bio-oil from this study had higher C and H content, higher calorific value, and lower oxygen and water content than bio-oil from wood. Finally, these results show that high-quality bio-oil at high yield can be obtained from flash pyrolysis of oleaginous feedstock.

09 BIOMASS FUELS↗
DOE OSTI2018

Integrated Particle- and Reactor-Scale Simulation of Pine Pyrolysis in a Fluidized Bed

We report results from a multiscale computational modeling study of biomass fast pyrolysis in an experimental laboratory reactor that combined the hydrodynamics predicted by a two-fluid model (TFM) with predictions from a finite element model (FEM) of heat and mass transfer and chemical reactions within biomass particles. The experimental pyrolyzer consisted of a 2-inch (5.1 cm)-diameter bubbling fluidized bed reactor (FBR) fed with milled pine pellets. The predicted FBR hydrodynamics included estimates of the residence times that the gas and biomass particles spend in the reactor before they exit. A single-particle FEM model was constructed based on geometry and heat transfer properties determined from optical and X-ray Computed Tomography (XCT) measurements of wood and char particles collected from the experimental FBR, along with previously proposed pyrolysis reaction kinetics. Taken together, the combined TFM and FEM simulation results predicted net bio-oil yields at the reactor exit that agree well with experimental observations, without any arbitrary fitting parameters. The combined computational models also provided practical information about the most important reactor and feedstock parameters.

09 BIOMASS FUELS↗
DOE OSTI2019

Examining and Modeling Oxygen Uncoupling Kinetics of Cu-Based Oxygen Carriers for Chemical Looping with Oxygen Uncoupling (CLOU) in a Drop Tube Fluidized Bed Reactor

Chemical looping combustion with oxygen uncoupling (CLOU) is a promising carbon capture and storage (CCS) technology for conversion of gaseous and solid hydrocarbon fuels where the release of gaseous O 2 from an oxygen carrier is favored at high temperature and low O 2 partial pressure. One promising CLOU material is the copper oxide redox system (CuO–Cu 2 O). The primary objective of this study was to examine the use of a drop tube fluidized bed reactor (DT-FBR) for evaluating the kinetics of oxygen uncoupling with Cu-based oxygen carriers. Appropriate rate expressions from redox experiments are needed to model and scale up CLOU systems. Additionally, the determined oxygen uncoupling kinetic parameters were validated using a computational fluid dynamic model. Two oxygen carriers consisting of 20 wt % CuO/Al 2 O 3 and 9 wt % CuO/Al 2 O 3 were prepared by physical mixing. A third oxygen carrier sample was prepared at 9 wt % CuO/Al 2 O 3 by incipient wetness impregnation. The reaction rates of the copper oxide redox system are strongly dependent on thermodynamic effects of the oxygen partial pressure relative to the equilibrium oxygen partial pressure. The results presented in this paper offer an alternative and simplified kinetic analysis compared to that traditionally presented in the literature for the thermal reduction of copper oxide or other CLOU oxygen carriers. The reactor system used in this study allows for operating parameters to be adjusted, minimizing thermodynamic and mass transfer limitations, which eliminates the need for more complex kinetic/thermodynamic reaction models. The reaction kinetics measured in this study is compared based on the preparation method and the CuO weight percent loading. These results may aid in the development of CLOU technologies during reactor design and process modeling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗