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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Applications of tribology to determine attrition by wear of particulate solids in CFB systems

In recent years, much attention has been focused on the development of novel technologies for carbon capture and chemicals production that utilize a circulating fluidized bed (CFB) configuration; examples include chemical looping combustion and circulation of temperature swing adsorbents in a CFB configuration for CO 2 capture. A major uncertainty in determining the economic feasibility of these technologies is the required solids makeup rate, which, among other factors, is due to impact and wear attrition at various locations, including standpipes, cyclones, and the gas jets in fluid beds. While correlations have been developed that estimate the attrition rates at these areas, these correlations are dependent on constants that are uncertain without extensive experiment in the corresponding unit operation. Thus, it is difficult to determine the attrition rate a priori without performing extensive experiments on the materials or scaling up entirely. In this work, the authors outline a methodology for predictive attrition based on fundamental material properties from fields of tribology—specifically, the study of wear—to the knowledge of forces and sliding distances determined from hydrodynamic models to develop basic attrition models for novel CFB systems. The equations are derived for the standpipe and cyclone, which are common components found in CFBs, and the cyclone equation is compared to experimental data of attrition in the literature. The cyclone equation derived in this work results in an abrasion rate based on (1) material properties such as particle density and hardness, (2) inlet velocity, and (3) cyclone geometry. According to this equation, increasing the diameter of the cyclone and the solids inlet velocity tends to increase the rate of abrasion of the catalyst, while decreasing the hardness increases the abrasion rate. The functionality of the increasing attrition rate with velocity increase implies that increasing the efficiency of the cyclone may also increase the attrition rate via abrasion. With modifications to the severity coefficient term to include the solids loading, the cyclone equation derived in this work fits data from Reppenhagen and Werther with a coefficient of determination (R2) of 92%.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Application of MP-PIC on Dual Interconnected Chemical Looping Cold Flow System: Validation Process with Hydrodynamic Experiments

Chemical looping with oxygen uncoupling (CLOU) is a promising carbon capture technologies, that utilizes a dual fluidized bed interconnected by loopseals to selectively separate oxygen from ambient air. This study validated Barracuda-VR® hydrodynamic simulations of dual circulating fluidized bed. The experiments were run on a scaled-down cold-flow unit of a 100 kW dual reactor to find the quantities of interest: circulation rate, bed mass location distribution, and pressure profile. The numerical parameters of time step and grid resolution were studied to find the numeric uncertainty for the quantities of interest. The scenario parameters of flowrates, particle densities, and particle voidage were studied. The uncertainty from the model parameters of tangent-to-wall, drag multiplier, and stress model were studied. Simulation and experimental results matched over some of the parameters studied. These can be used to scale the system back to the 100 kW dual reactor and to a larger system.

Hamilton, Matthew A↗
DOE OSTI2017

Kinetic theory-based numerical modeling and analysis of bi-disperse segregated mixture fluidized bed

We discuss a series of continuum Euler-Euler simulations of an initially mixed bi-disperse fluidized bed which segregates under certain operating conditions. The simulations use the multi-phase kinetic theory-based description of the momentum and energy exchanges between the phases by Simonin’s Group [see e.g. Gourdel, Simonin and Brunier (1999). Proceedings of 6th International Conference on Circulating Fluidized Beds, Germany, pp. 205-210]. The discussion and analysis of the results focus on the fluid-particle momentum exchange (i.e. drag). Simulations using mono- and poly-disperse fluid-particle drag correlations are analyzed for the Geldart D-type size bi-disperse gas-solid experiments performed by Goldschmidt et al. [Powder Tech., pp. 135-159 (2003)]. The poly-disperse gas-particle drag correlations account for the local particle size distribution by using an effective mixture diameter when calculating the Reynolds number and then correcting the resulting force coefficient. Simulation results show very good predictions of the segregation index for bidisperse beds with the mono-disperse drag correlations contrary to the poly-disperse drag correlations for which the segregation rate is systematically under-predicted. The statistical analysis of the results shows a clear separation in the distribution of the gas-particle mean relaxation times of the small and large particles with simulations using the mono-disperse drag. In contrast, the poly-disperse drag simulations have a significant overlap and also a smaller difference in the mean particle relaxation times. This results in the small and large particles in the bed to respond to the gas similarly without enough relative time lag. The results suggest that the difference in the particle response time induce flow dynamics favorable to a force imbalance which results in the segregation.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Method to estimate uncertainty associated with parcel size in coarse discrete particle simulation

Coarse grained particle methods significantly reduce the computation cost of large‐scale fluidized bed simulation by lumping many real particles into a computation parcel. This research provides a method to estimate the errors associated with parcel size in large‐scale fluidized bed simulations. This uncertainty is first quantified in small scale domains by comparing results of discrete particle method with that employing coarse parcels of different sizes. Then, this uncertainty is correlated with parcel size and simulation domains consisting of a simple homogeneous cooling system and more complex bubbling and circulating fluidized beds. These correlations allow us to accurately estimate the uncertainty in large‐scale fluidized beds based solely on data obtained in smaller systems. The ability to estimate model‐related uncertainty in larger systems makes this method relevant for industrial applications. © 2018 American Institute of Chemical Engineers AIChE J , 64: 2340–2350, 2018

Lu, Liqiang↗
DOE OSTI2018

Experience with Chemical Looping Combustion of Coal in a 200 kW Dual Fluidized Bed Reactor

The University of Utah recently commissioned a dual fluidized bed process development unit (PDU) for investigating chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) of coal. The reactors and supporting systems were sized to support at least 200 kW of coal input based on available reaction rate data. Both the air reactor and fuel reactor are circulating fluidized beds and bed material passes between the reactors via loop seals. The reactors are refractory-lined rather than electrically heated, so the system must be preheated with natural gas before chemical looping combustion can begin. Air and steam are preheated through a combination of electric heating and natural gas burners and reactor product gas flows through heat exchangers and bag houses to cool and clean the gas of particulate. As is typical with pilot-scale systems, several operational challenges were encountered as the system was brought online and operation progressed from heatup and initial testing with gaseous fuels towards full CLOU processing of coal. The system hardware and operational procedures have undergone several modifications, but the PDU can now reliably be preheated to the operating temperature and coal can be fed at the target feed rate. This paper presents the PDU, describes the procedures for evaluating carbon conversion, CO2 capture and CO2 purity, and presents initial results from chemical looping combustion of coal with non-CLOU and CLOU carriers. General experience of operating the plant and notable challenges and solutions are also presented.

Whitty, Kevin J.↗
DOE OSTI2016

Uncertainty quantification tools for multiphase gas-solid flow simulations using MFIX

Computational fluid dynamics (CFD) has been widely studied and used in the scientific community and in the industry. Various models were proposed to solve problems in different areas. However, all models deviate from reality. Uncertainty quantification (UQ) process evaluates the overall uncertainties associated with the prediction of quantities of interest. In particular it studies the propagation of input uncertainties to the outputs of the models so that confidence intervals can be provided for the simulation results. In the present work, a non-intrusive quadrature-based uncertainty quantification (QBUQ) approach is proposed. The probability distribution function (PDF) of the system response can be then reconstructed using extended quadrature method of moments (EQMOM) and extended conditional quadrature method of moments (ECQMOM). The report first explains the theory of QBUQ approach, including methods to generate samples for problems with single or multiple uncertain input parameters, low order statistics, and required number of samples. Then methods for univariate PDF reconstruction (EQMOM) and multivariate PDF reconstruction (ECQMOM) are explained. The implementation of QBUQ approach into the open-source CFD code MFIX is discussed next. At last, QBUQ approach is demonstrated in several applications. The method is first applied to two examples: a developing flow in a channel with uncertain viscosity, and an oblique shock problem with uncertain upstream Mach number. The error in the prediction of the moment response is studied as a function of the number of samples, and the accuracy of the moments required to reconstruct the PDF of the system response is discussed. The QBUQ approach is then demonstrated by considering a bubbling fluidized bed as example application. The mean particle size is assumed to be the uncertain input parameter. The system is simulated with a standard two-fluid model with kinetic theory closures for the particulate phase implemented into MFIX. The effect of uncertainty on the disperse-phase volume fraction, on the phase velocities and on the pressure drop inside the fluidized bed are examined, and the reconstructed PDFs are provided for the three quantities studied. Then the approach is applied to a bubbling fluidized bed with two uncertain parameters, particle-particle and particle-wall restitution coefficients. Contour plots of the mean and standard deviation of solid volume fraction, solid phase velocities and gas pressure are provided. The PDFs of the response are reconstructed using EQMOM with appropriate kernel density functions. The simulation results are compared to experimental data provided by the 2013 NETL small-scale challenge problem. Lastly, the proposed procedure is demonstrated by considering a riser of a circulating fluidized bed as an example application. The mean particle size is considered to be the uncertain input parameter. Contour plots of the mean and standard deviation of solid volume fraction, solid phase velocities, and granular temperature are provided. Mean values and confidence intervals of the quantities of interest are compared to the experiment results. The univariate and bivariate PDF reconstructions of the system response are performed using EQMOM and ECQMOM.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Moving Bed Chemical Looping Combustion Fuel Reactor Modeling and Sensitivity Analysis

Chemical looping combustion (CLC) is a novel, coal-based power generation technology that has currently achieved only small-scale, non-integrated development status, with the fuel reactor being the key developmental component in the CLC process. Both circulating fluidized bed (CFB) and moving bed fuel reactors have been the subjects of ongoing development campaigns. The objective of the effort described in this report is to characterize a moving bed fuel reactor by applying more detailed, reaction kinetics-based models that represent the nature of this reactor with a more fundamental foundation than has previously been reported by developers. This report describes the modeling basis, and a “base” fuel reactor’s design and performance characteristics resulting from the model. A major focus of the evaluation has been placed on studies of the sensitivity of the base moving bed fuel reactor performance, design, and CLC power plant cost implications to the key parameters.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2015

Development of a Two-fluid Drag Law for Clustered Particles using Direct Numerical Simulation and Validation through Experiments

This study presents a new drag model, based on the cohesive inter-particle forces, implemented in the MFIX code. This new drag model combines an existing standard model in MFIX with a particle-based drag model based on a switching principle. Switches between the models in the computational domain occur where strong particle-to-particle cohesion potential is detected. Three versions of the new model were obtained by using one standard drag model in each version. Later, performance of each version was compared against available experimental data for a fluidized bed, published in the literature and used extensively by other researchers for validation purposes. In our analysis of the results, we first observed that standard models used in this research were incapable of producing closely matching results. Then, we showed for a simple case that a threshold is needed to be set on the solid volume fraction. This modification was applied to avoid non-physical results for the clustering predictions, when governing equation of the solid granular temperate was solved. Later, we used our hybrid technique and observed the capability of our approach in improving the numerical results significantly; however, improvement of the results depended on the threshold of the cohesive index, which was used in the switching procedure. Our results showed that small values of the threshold for the cohesive index could result in significant reduction of the computational error for all the versions of the proposed drag model. In addition, we redesigned an existing circulating fluidized bed (CFB) test facility in order to create validation cases for clustering regime of Geldart A type particles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Validation and application of a multiphase CFD model for hydrodynamics, temperature field and RTD simulation in a pilot-scale biomass pyrolysis vapor phase upgrading reactor

Accurate prediction of transport phenomena is critical for VPU reactor design, optimization, and scale-up. The current study focused on the validation and application of a multiphase CFD model within an open-source code MFiX for hydrodynamics, temperature field, and residence time distribution (RTD) simulation in a non-reacting circulating fluidized bed riser for biomass pyrolysis vapor phase upgrading (VPU). First, an Eulerian-Eulerian approach three-dimensional CFD model was employed to simulate the pilot-scale VPU riser on the supercomputer Joule. Excellent quantitative agreement between experimental and simulated results was achieved for pressure drops and temperature field in a range of operating conditions. Then the validated multiphase CFD model was applied to predict gas and solid residence time distributions (RTDs) since prediction and analysis of RTD is an important tool to study the complex multiphase flow behavior and mixing inside chemical reactors. The predictions show that solid mean residence time is 3.5 times the gas residence time; the solid RTD is more sensitive to the process gas flow rate than the solids circulation rate.

09 BIOMASS FUELS↗
NASA NTRS2013

Electrical Capacitance Volume Tomography for the Packed Bed Reactor ISS Flight Experiment

Fixed packed bed reactors are compact, require minimum power and maintenance to operate, and are highly reliable. These features make this technology a highly desirable unit operation for long duration life support systems in space. NASA is developing an ISS experiment to address this technology with particular focus on water reclamation and air revitalization. Earlier research and development efforts funded by NASA have resulted in two hydrodynamic models which require validation with appropriate instrumentation in an extended microgravity environment. To validate these models, the instantaneous distribution of the gas and liquid phases must be measured.Electrical Capacitance Volume Tomography (ECVT) is a non-invasive imaging technology recently developed for multi-phase flow applications. It is based on distributing flexible capacitance plates on the peripheral of a flow column and collecting real-time measurements of inter-electrode capacitances. Capacitance measurements here are directly related to dielectric constant distribution, a physical property that is also related to material distribution in the imaging domain. Reconstruction algorithms are employed to map volume images of dielectric distribution in the imaging domain, which is in turn related to phase distribution. ECVT is suitable for imaging interacting materials of different dielectric constants, typical in multi-phase flow systems. ECVT is being used extensively for measuring flow variables in various gas-liquid and gas-solid flow systems. Recent application of ECVT include flows in risers and exit regions of circulating fluidized beds, gas-liquid and gas-solid bubble columns, trickle beds, and slurry bubble columns. ECVT is also used to validate flow models and CFD simulations. The technology is uniquely qualified for imaging phase concentrations in packed bed reactors for the ISS flight experiments as it exhibits favorable features of compact size, low profile sensors, high imaging speed, and flexibility to fit around columns of various shapes and sizes. ECVT is also safer than other commonly used imaging modalities as it operates in the range of low frequencies (1 MHz) and does not radiate radioactive energy. In this effort, ECVT is being used to image flow parameters in a packed bed reactor for an ISS flight experiment.

Tomography↗
DOE OSTI2017

Evaluation of fast pyrolysis feedstock conversion with a mixing paddle reactor

We have developed a pyrolysis reactor based on a unique auger-paddle configuration with heat transfer material (HTM) and proved to achieve high heating rates and fast pyrolysis. We tested ten different biomass types and obtained bio-oil yields ranging from approximately 40% for thermally treated wood, to approximately 57% for crop residues (corn stover) and 67% yield for woody feedstocks (tulip poplar). These results, as well as the solid char yields, are similar to those obtained for the same feedstock using a circulating fluidized bed. Tests conducted without HTM resulted in lower bio-oil yields (ranging from 8 to 18% decrease in yield) and higher char yields with similar changes in magnitude, which is indicative of slow pyrolysis. In addition, a comprehensive study and analysis of the material residence time and mixing characteristics of the novel auger-paddle system is presented. These results thus demonstrate that an auger-paddle configuration is capable of achieving the high heating rates required for fast pyrolysis.

09 BIOMASS FUELS↗
DOE OSTI2017

A solution algorithm for fluid–particle flows across all flow regimes

Many fluid–particle flows occurring in nature and in technological applications exhibit large variations in the local particle volume fraction. For example, in circulating fluidized beds there are regions where the particles are closepacked as well as very dilute regions where particle–particle collisions are rare. Thus, in order to simulate such fluid–particle systems, it is necessary to design a flow solver that can accurately treat all flow regimes occurring simultaneously in the same flow domain. In this work, a solution algorithm is proposed for this purpose. The algorithm is based on splitting the free-transport flux solver dynamically and locally in the flow. In close-packed to moderately dense regions, a hydrodynamic solver is employed, while in dilute to very dilute regions a kinetic-based finite-volume solver is used in conjunction with quadrature-based moment methods. To illustrate the accuracy and robustness of the proposed solution algorithm, it is implemented in OpenFOAM for particle velocity moments up to second order, and applied to simulate gravity-driven, gas–particle flows exhibiting cluster-induced turbulence. By varying the average particle volume fraction in the flow domain, it is demonstrated that the flow solver can handle seamlessly all flow regimes present in fluid–particle flows.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Particulate solid attrition in CFB systems – An assessment for emerging technologies

Over the years, circulating fluidized bed systems have been designed for chemical conversion and energy recovery due to the ability of allowing continuous processing. While many CFB technologies are well established, a number of emerging technologies in recent years are utilizing the CFB concept, such as chemical looping combustion, novel continuous temperature swing adsorption, and transport gasifiers. A major uncertainty in these new technologies is the effect that attrition of bed material has on the overall process economics and system operability. Furthermore this work presents a review of the study of attrition for CFB systems, including relevant material properties, basic modeling and prediction, as well as particle population balance techniques. Because some of these new processes use novel materials, this work focuses on applying fundamental material properties to the understanding of attrition.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

The Development of a Generalized Riser Flow Regime Map Based Upon Higher Moment and Chaotic Statistics Using Electrical Capacitance Volume Tomography (ECVT)

Dynamic analyses have been applied to the temporal signals from an Electro Capacitance Volume Tomography instrument located near mid-height on the riser of an industrial-scale cold-flow circulating fluidized bed to characterize gas-solids flow behavior in the riser. Twelve capacitance electrodes surround the cylindrical riser over a height of 1.3 m. The instrument used a neural network deconvolution algorithm to determine the spatially resolved solids fraction recorded at 52 Hz. Experiments were carried out over a range of gas and solids flows in the transport regime using a Geldart Group B bed material, high density polyethylene with mean particle size of 880 μm. The radial solids distribution was found to vary from one-time step to the next between profiles typical of laminar and turbulent flow. The duration of time spent in each of these flow profiles depended upon the operating regime – dilute, core-annular, or fast fluidized bed. The chaotic structure of the temporal data was characterized using the three conventional approaches: the first 4 moments from the distribution of signal in time, system memory parameters from the autocorrelation function and the Hurst exponent, and analysis of the correlationentropy and correlation dimension of the attractor. These signal analysis techniques were used to clearly distinguish differences between different transport operating regimes. Specifically, it was experimentally observed that a riser transitions from core annular flow profile to dilute and dense regimes via increasing the frequency of short term transients to either dilute or dense flow profiles, respectively. A regime map was generated based upon these dynamics using solids flux and gas velocity axes. Fast fluidized, core annular, and dilute each exhibited different degree of dynamic characteristics typical of fluid dominated or particle compromising behavior. It should be noted that the magnitude for the different statistics was in the same range regardless of the regime, it was the radial profile for the statistic that changed and subsequently identified that there was a change in the regime. Finally, a reduced regime map was developed consisting of plotting the gas velocity normalized by the upper transport velocity versus the solids flux normalized by the saturation carrying capacity. The use of this reduced plot allowed the data from widely different conditions to be plotted and compared on the same<p>graph. Note that in many instances, some of the statistics identified the operating point as being in one regime while others indicated that it was in another indicating a transition region between dilute or core annular regimes and between the core annular and fast fluidization regimes. This now provides a tool that can be used to optimize process performance, identify changes in operating states, or replicate process dynamics during process scaling or changing operating parameters. </p>

Breault, Ronald↗
DOE OSTI2023

Scaling CFB risers: Beyond the data using microstructure similarity

Scaling circulating fluidized bed risers has been a point of contention for nearly a century. There have been numerous attempts to define various methodologies. These have all fallen short of providing a robust approach, primarily due to a lack of maintaining microstructure dynamics – a key factor in maintaining interphase heat and mass transfer. Recent work by the author put forward an approach based upon preserving dynamic similarity at different scales by ensuring that the microstructure remained similar by maintaining statistical and chaotic parameters across the scale. That work relied on a dimensionless regime map in which the x-axis was defined by the ratio of the solids flux to the saturation carrying capacity. This latter property was only good within the range of the data, and it became evident that extrapolation beyond the limits of the data could induce unrealistic conditions. Therefore, literature was reviewed to develop a better correlation for the saturation carrying capacity. In doing so, a critical riser diameter concept was developed and applied to the correlations for both Geldart Group A and B materials. The critical diameter for Geldart Group A and B materials is 0.2 m and 0.3 m, respectively. Here the paper then gives three examples on how to use the scaling approach to maintain dynamic similarity across the scales.

02 PETROLEUM↗
DOE OSTI2017

Techno-economic Evaluation of Utility-Scale Power Plants Based on the Indirect sCO 2 Brayton Cycle - Report

This report presents the results of a techno-economic analysis (TEA) of a coal-fired utility scale power plant based on the indirect supercritical carbon dioxide (sCO 2 ) Brayton cycle using an oxy-fired circulating fluidized bed (CFB). A baseline plant configuration was examined as well as three variations to the sCO 2 power cycle examining the impact of reheat (Rht), main compressor intercooling (IC), and a combination of reheat and main compressor intercooling (RhtIC). Each plant configuration was assessed at two turbine inlet temperatures of 620 °C and 760 °C.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2017

Techno-economic Evaluation of Utility-Scale Power Plants Based on the Indirect sCO2 Brayton Cycle - Presentation

This presentation discusses the results of a techno-economic analysis (TEA) of a coal-fired utility scale power plant based on the indirect supercritical carbon dioxide (sCO2) Brayton cycle using an oxy-fired circulating fluidized bed (CFB). A baseline plant configuration was examined as well as three variations to the sCO2 power cycle examining the impact of reheat (Rht), main compressor intercooling (IC), and a combination of reheat and main compressor intercooling (RhtIC). Each plant configuration was assessed at two turbine inlet temperatures of 620 °C and 760 °C.

Brayton power cycle↗