Carbon capture test unit design and development using amine-based solid sorbent
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Breault, Ronald W.↗
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Design, Development, and Operation of an Integrated Fluidized Carbon Capture Unit Using Polyethylenimine Sorbents
In this paper, we present the design, development, and operation of a reactor system for CO 2 capture. Modifications were implemented to address differences in sorbent from 180 μm Geldart group B to 115 μm Geldart group A material; operational issues were discovered during experimental trials. The major obstacle in system operation was the ability to maintain a constant circulation of a solid sorbent stemming from this change in sorbent material. The system consisted of four fluid beds, through which a polyamine impregnated sorbent was circulated and adsorption, preheat, regeneration, and cooling processes occurred. Pressure transducers, thermocouples, gas flow meters, and gas composition instrumentation were used to characterize thermal, hydrodynamic, and gas adsorption performance in this integrated unit. A series of shakedown tests were performed and the configuration altered to meet the needs of the sorbent performance and achieve desired target capture efficiencies. Methods were identified, tested, and applied to continuously monitor critical operating parameters including solids circulation rate, adsorbed and desorbed CO 2 , solids inventories, and pressures. The working capacity and CO 2 capture efficiency were used to assess sorbent performance while CO 2 closure was used to define data quality and approach to steady-state. Testing demonstrated >90% capture efficiencies and identified the regenerator to be the process step limiting throughput. Sorbent performance was found to be related to the reactant stoichiometry. Finally, a stochastic model with an exponential dependence on the relative CO 2 /amine concentration was used to describe 90% of the variance in the data.
01 COAL, LIGNITE, AND PEAT↗
Energy localization efficiency in 1,3,5-trinitro-2,4,6-triaminobenzene pore collapse mechanisms
Atomistic and continuum scale modeling efforts have shown that the shock-induced collapse of porosity can occur via a wide range of mechanisms dependent on pore morphology, the shockwave pressure, and material properties. The mechanisms that occur under weaker shocks tend to be more efficient at localizing thermal energy but do not result in high, absolute temperatures or spatially large localizations compared to mechanisms found under strong shock conditions. However, the energetic material 1,3,5-trinitro-2,4,6-triaminobenzene (TATB) undergoes a wide range of collapse mechanisms that are not typical of similar materials, leaving the collapse mechanisms and the resultant energy localization from the collapse, i.e., hotspots, relatively uncharacterized. Therefore, we present the pore collapse simulations of cylindrical pores in TATB for a wide range of pore sizes and shock strengths that trigger viscoplastic collapses that occur almost entirely perpendicular to the shock direction for weak shocks and hydrodynamic-like collapses for strong shocks that do not break the strong hydrogen bonds of the TATB basal planes. The resulting hotspot temperature fields from these mechanisms follow trends that differ considerably from other energetic materials; hence, we compare them under normalized temperature values to assess the relative efficiency of each mechanism to localize energy. The local intra-molecular strain energy of the hotspots is also assessed to better understand the physical mechanisms behind the phenomena that lead to a latent potential energy.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Efficient small-scale dynamo in the solar convection zone
We investigate small-scale dynamo action in the solar convection zone through a series of high-resolution MHD simulations in a local Cartesian domain with 1 R{sub ⊙} (solar radius) of horizontal extent and a radial extent from 0.715 to 0.96 R{sub ⊙}. The dependence of the solution on resolution and diffusivity is studied. For a grid spacing of less than 350 km, the rms magnetic field strength near the base of the convection zone reaches 95% of the equipartition field strength (i.e., magnetic and kinetic energy are comparable). For these solutions the Lorentz force feedback on the convection velocity is found to be significant. The velocity near the base of the convection zone is reduced to 50% of the hydrodynamic one. In spite of the significant decrease of the convection velocity, the reduction in the enthalpy flux is relatively small, since the magnetic field also suppresses the horizontal mixing of the entropy between up- and downflow regions. This effect increases the amplitude of the entropy perturbation and makes convective energy transport more efficient. We discuss potential implications of these results for solar global convection and dynamo simulations.
79 ASTRONOMY AND ASTROPHYSICS↗
Spatially adaptive stochastic methods for fluid–structure interactions subject to thermal fluctuations in domains with complex geometries
We develop stochastic mixed finite element methods for spatially adaptive simulations of fluid–structure interactions when subject to thermal fluctuations. To account for thermal fluctuations, we introduce a discrete fluctuation–dissipation balance condition to develop compatible stochastic driving fields for our discretization. We perform analysis that shows our condition is sufficient to ensure results consistent with statistical mechanics. We show the Gibbs–Boltzmann distribution is invariant under the stochastic dynamics of the semi-discretization. To generate efficiently the required stochastic driving fields, we develop a Gibbs sampler based on iterative methods and multigrid to generate fields with O(N) computational complexity. Our stochastic methods provide an alternative to uniform discretizations on periodic domains that rely on Fast Fourier Transforms. To demonstrate in practice our stochastic computational methods, we investigate within channel geometries having internal obstacles and no-slip walls how the mobility/diffusivity of particles depends on location. Our methods extend the applicability of fluctuating hydrodynamic approaches by allowing for spatially adaptive resolution of the mechanics and for domains that have complex geometries relevant in many applications.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
(U) Endpoint Energy and Scintillator Geometry Effects on the Swank Factor, Quantum Efficiency, and DQE(0) for High-Energy Radiography
High-energy radiography is used to image imploding materials to better understand weapon design and performance. The Enhanced Capabilities for Subcritical Experiments (ECSE) is a new facility proposal that aims to collect radiographic images of nuclear material. As part of the facility design, we aim to optimize data quality and radiographic performance by investigating different detector designs. We addressed design decisions by simulating different scintillator designs using M CNP6 and calculated the quantum efficiency, Swank factor, and detective quantum efficiency at zero-frequency (DQE(O)). First, we investigated the effects of the x-ray endpoint energy on the detector response. We generated three x-ray spectra with endpoint energies of 20 MeV, 22 MeV, and 24 MeV. The three raw spectra were filtered using the Dual-Axis Radiographic Hydrodynamic Test facility (DARHT) line-of-sight materials along with 1) flat field filtration using 7 cm tungsten alloy in the bullnose and 2) an FTO with 4 plates. The scatter-to-direct radiation ratio was much larger for FTO with 4 plates (50-60%) compared to the flat field with 7 cm of bullnose material (8%). We used these filtered spectra to calculate the detector response for the original DARHT segmented scintillator design. We found that the endpoint energy and filtration had a negligible effect on the detector response. The quantum efficiency was 0.63, the Swank factor was 0.84, and the DQE(O) was 0.53 for all six spectra.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Advanced Validation Risk-Informed Approach for the Flooding Tool Based Upon Smooth Particle Hydrodynamics: Validation and Development Status of NEUTRINO
Risk-Informed validation is to focus advanced validation on high-priority and critical elements of the RISMC methods and tools that can best be addressed by this targeted approach to validation. Initial validation focus will be on the RISMC flooding analysis computer software based upon Smoothed Particle Hydrodynamics (SPH), NEUTRINO. The NEUTRINO code is a SPH-based CFD software adopted as one of the RISMC modeling tools for external hazards analysis. This document discusses the validation and development activities of NEUTRINO, especially in relation to its simulation capability for flooding hazards analysis. In order to draw meaningful conclusions from the discussion, we first analyzed the potential risks to nuclear power plants in flooding scenarios (e.g., hazard modes, industry/regulatory concerns, etc.). Then, an initial high-level PIRT was proposed to define the key phenomena relevant to the analysis of flooding hazards. Finally, based on the framework of this PIRT analysis, the validation and development efforts that have been conducted to date for NEUTRINO were discussed. This analysis helped to determine the sufficiency, efficiency, and adequacy of the current code development and validation efforts for NEUTRINO.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
The influence of dense gas rings on the dynamics of a stellar disk in the galactic center
The Galactic center hosts several hundred early-type stars, about 20% of which lie in the so-called clockwise disk, while the remaining 80% do not belong to any disks. The circumnuclear ring (CNR), a ring of molecular gas that orbits the supermassive black hole (SMBH) with a radius of ∼1.5 pc, has been claimed to induce precession and Kozai–Lidov oscillations onto the orbits of stars in the innermost parsec. We investigate the perturbations exerted by a gas ring on a nearly Keplerian stellar disk orbiting an SMBH by means of combined direct N-body and smoothed particle hydrodynamics simulations. We simulate the formation of gas rings through the infall and disruption of a molecular gas cloud, adopting different inclinations between the infalling gas cloud and the stellar disk. We find that a CNR-like ring is not efficient in affecting the stellar disk on a timescale of 3 Myr. In contrast, a gas ring in the innermost 0.5 pc induces precession of the longitude of the ascending node Ω, which significantly affects the stellar disk inclination. Furthermore, the combined effect of two-body relaxation and Ω-precession drives the stellar disk dismembering, displacing the stars from the disk. The impact of precession on the star orbits is stronger when the stellar disk and the inner gas ring are nearly coplanar. We speculate that the warm gas in the inner cavity might have played a major role in the evolution of the clockwise disk.
79 ASTRONOMY AND ASTROPHYSICS↗
Investigations of non-linear polymers as high performance lubricant additives
Off-the-shelf available engine oils contain an assortment of additives that increase the performance of base oils and maximize the overall efficiency of the machine. With ever increasing requirements for fuel efficiency, the demand for novel materials that outperform older generations is also on the rise. One approach towards increasing overall efficiency is to reduce internal friction and wear in an engine. From an additive approach, this is typically achieved by altering the bulk oil’s viscosity at high temperatures via polymers. In general, the hydrodynamic volume of polymers increase (expand) at elevated temperatures and decrease (contract/deflate) with declining temperatures and this effect is enhanced be carefully designing specific structures and architectures. The natural thinning tendency of base oil with increasing temperatures is in part mitigated by the expansion of the macromolecules added, and the overall effect is decreasing the viscosity losses at high temperatures. Traditional polymer architectures vary from linear to dendritic, where linear polymers of the same chemical composition and molecular weight to its dendritic counterpart will undergo a more significant free volume change in solution with regards to temperature changes. This advantage has been exploited in the literature towards the production of viscosity modifiers. However, one major disadvantage of linear polymers is degradation due to mechanical shear forces and high temperatures causing a shorter additive lifetime. Dendrimers on the other hand are known to demonstrate superior robustness to shear degradation when compared to their respective linear counterparts. An additional advantage of the dendritic architecture is the ability to tailor the peripheral end-groups towards influencing polymer-solvent and/or polymer-surface interactions. Comb-burst hyperbranched polymers are a hybrid of the aforementioned architectures and provide several compromises between the traditional structures including the tailoring of peripheral functional groups, conformational flexibility via lipophilic long chain linkers, and a readily available synthesis amenable to scale-up. In the following communication, the synthesis of an aryl comb-burst hyperbranched polymer will be described. Some of the challenges we had to overcome are being highlighted, such as efforts towards increasing lipophilicity of the molecule via changes in saturated carbon content, controlling polymerization conditions to control average molecular weight and degree of branching. In addition, trends in viscosity modification of the bulk oil and wear/friction studies will be discussed.
Robinson, Joshua W.↗
Three-dimensional simulations of the non-thermal broadband emission from young supernova remnants including efficient particle acceleration
Supernova remnants are believed to be major contributors to Galactic cosmic rays. In this paper, we explore how the non-thermal emission from young remnants can be used to probe the production of energetic particles at the shock (both protons and electrons). Our model couples hydrodynamic simulations of a supernova remnant with a kinetic treatment of particle acceleration. We include two important back-reaction loops upstream of the shock: energetic particles can (1) modify the flow structure and (2) amplify the magnetic field. As the latter process is not fully understood, we use different limit cases that encompass a wide range of possibilities. We follow the history of the shock dynamics and of the particle transport downstream of the shock, which allows us to compute the non-thermal emission from the remnant at any given age. We do this in three dimensions, in order to generate projected maps that can be compared with observations. We observe that completely different recipes for the magnetic field can lead to similar modifications of the shock structure, although to very different configurations of the field and particles. We show how this affects the emission patterns in different energy bands, from radio to X-rays and γ-rays. High magnetic fields (>100 μG) directly impact the synchrotron emission from electrons, by restricting their emission to thin rims, and indirectly impact the inverse Compton emission from electrons and also the pion decay emission from protons, mostly by shifting their cut-off energies to respectively lower and higher energies.
79 ASTRONOMY AND ASTROPHYSICS↗
Efficient multi-keV x-ray source generated by nanosecond laser pulse irradiated multi-layer thin foils target
A new target configuration is proposed to generate efficient multi-keV x-ray source using multiple thin foils as x-ray emitters. The target was constructed with several layers of thin foils, which were placed with a specific, optimized spacing. The thin foils are burned though one by one by a nanosecond-long laser pulse, which produced a very large, hot, underdense plasma. One-dimensional radiation hydrodynamic simulations show that the emission region and the multi-keV x-ray flux generated by multi-layer thin foil target are similar to that of the low-density gas or foam target, which is currently a bright multi-keV x-ray source generated by laser heating. Detailed analysis of a range of foil thicknesses showed that a layer-thickness of 0.1 μm is thin enough to generate an efficient multi-keV x-ray source. Additionally, this type of target can be easily manufactured, compared with the complex techniques for fabrication of low-density foam targets. Our preliminary experimental results also verified that the size of multi-keV x-ray emission region could be enhanced significantly by using a multi-layer Ti thin foil target.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Anisotropic single-particle dissipative particle dynamics model
We have developed a new single-particle dissipative particle dynamics (DPD) model for anisotropic particles with different shapes, e.g., prolate or oblate spheroids. In particular, the conservative and dissipative interactions between anisotropic single DPD particles are formulated using a linear mapping from the isotropic model of spherical particles. The proper mapping operator is constructed between each interacting pair of particles at every time step. Correspondingly, the random forces are properly formulated to satisfy the fluctuation-dissipation theorem (FDT). Notably, the model exactly conserves both linear and angular momentum. We demonstrate the proposed model's accuracy and efficiency by applying it for modeling colloidal ellipsoids. Specifically, we show it efficiently captures the static properties of suspensions of colloidal ellipsoids. The isotropic-nematic transition in an ellipsoidal suspension is reproduced by increasing its volume fraction or the aspect ratio of ellipsoid particles. Moreover, the hydrodynamics and diffusion of a single colloidal ellipsoid (prolate or oblate with moderate aspect ratios) are accurately captured. The calculated drag force on the ellipsoid and its diffusion coefficients (both translational and rotational) agree quantitatively with the theoretical predictions in the Stokes limit.
Computer Science↗
Enhanced x-ray emissions from Au-Gd mixture targets ablated by a high-power nanosecond laser
As an important x-ray source, enhancement of x-ray emissions from laser-produced plasmas is imperative for various applications. High-Z Au-Gd mixture targets are proposed to enhance the laser to x-ray conversion efficiency compared to pure Au target. In the experiments, a 1 ns frequency-tripled (351 nm wavelength) laser light was used to obtain an intensity of 3×10{sup 14} W/cm{sup 2} on the targets. The x-ray spectra, total absolute x-ray emissions of all space, M-band fraction and backscattering from pure Au and Au-Gd mixture have been measured, respectively. It is shown that the absolute laser to x-ray conversion efficiency for the Au-Gd mixture containing 60% gold by atom is 47.7%, which has a 15% enhancement compared with that of the pure Au target. The experimental results are consistent with the radiation hydrodynamic simulations.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Investigation of Coal-biomass Catalytic Gasification using Experiments, Reaction Kinetics and Computational Fluid Dynamics
A collaborative effort involving experiments, kinetic modeling, and computational fluid dynamics (CFD) was used to understand co-gasification of coal-biomass mixtures. The overall goal of the work was to determine the key reactive properties for coal-biomass mixed fuels. Sub-bituminous coal was mixed with biomass feedstocks to determine the fluidization and gasification characteristics of hybrid poplar wood, switchgrass and corn stover. It was found that corn stover and poplar wood were the best feedstocks to use with coal. The novel approach of this project was the use of a red mud catalyst to improve gasification and lower gasification temperatures. An important results was the reduction of agglomeration of the biomass using the catalyst. An outcome of this work was the characterization of the chemical kinetics and reaction mechanisms of the co-gasification fuels, and the development of a set of models that can be integrated into other modeling environments. The multiphase flow code, MFIX, was used to simulate and predict the hydrodynamics and co-gasification, and results were validated with the experiments. The reaction kinetics modeling was used to develop a smaller set of reactions for tractable CFD calculations that represented the experiments. Finally, an efficient tool was developed, MCHARS, and coupled with MFIX to efficiently simulate the complex reaction kinetics.
09 BIOMASS FUELS↗
Commission < 5 µm spatial resolution x-ray imager for High Resolution Turbulence experiments
This report presents the successful development, commissioning, and deployment of the Scintillation-Based X-ray Imager (SBXI) for the High-Resolution Turbulence (HRT) campaign at the National Ignition Facility (NIF). The SBXI system was designed to overcome the spatial resolution and efficiency limitations of conventional x-ray imaging detectors. Through careful system engineering, rigorous laboratory characterization, and experimental validation at NIF, the SBXI has demonstrated spatial resolution at the object plane of 5 μm (±0.5 μm) and a detective quantum efficiency (DQE) of 34% at 7.2 keV, both of which surpass the requirements set by the campaign, and meeting the L2 milestone. The system’s deployment enables high-fidelity imaging of fine-scale hydrodynamic instabilities, directly supporting advanced turbulence model validation and future high energy density physics research.
42 ENGINEERING↗
Simulations of the Stable Expansion of a Monoelement Three-Component Explosive-Emission Plasma
The results of numerical simulations of the stable expansion stage of a micro explosive plasma plume are presented. A three-liquid hydrodynamic model was used with corrections allowing its application to the consistent description of the transfer of particles in a monoelement plasma with ions with two different charges and of the electron transfer in a changing plasma–collector vacuum gap. The evolution of concentration profiles, the drift velocity, and electron and ion temperatures in plasma are analyzed depending on conditions of a collector. It is shown in the model that the velocity separation of ions with different charges occurs efficiently in the absence of an external electric field, whereas in a current-carrying plasma, the ions with different charges move with almost identical velocities.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Detailed energy distributions in laser-produced plasmas of solid gold and foam gold planar targets
Foam gold was proposed to increase the laser to x-ray conversion efficiency due to its important applications. To understand the mechanism of x-ray enhancement, the detailed energy distributions and plasma profiles for laser-irradiated solid gold and foam gold targets were studied comparatively by hydrodynamic simulations using the code Multi-1D. It is confirmed that the radiation heat wave is subsonic for the normal solid gold target, while supersonic for the foam gold target. The shock wave, which is behind the supersonic radiation heat wave for the foam gold target, generates a plasma temperature gradient with high temperature near the shock wave front to produce an additional net outward radiation for enhancement of the x-ray emission. Much larger inward plasma velocity is also driven by the shock wave as an initial plasma velocity for the laser deposition and electron thermal conduct zone, which decreases the expanding plasma kinetic energy loss and helps to increase the x-ray radiation.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
A Gaussian process based surrogate approach for the optimization of cylindrical targets
Simulating direct-drive inertial confinement experiments presents significant computational challenges, both due to the complexity of the codes required for such simulations and the substantial computational expense associated with target design studies. Machine learning models, and in particular, surrogate models, offer a solution by replacing simulation results with a simplified approximation. In this study, we apply surrogate modeling and optimization techniques that are well established in the existing literature to one-dimensional simulation data of a new cylindrical target design containing deuterium–tritium fuel. These models predict yields without the need for expensive simulations. We find that Bayesian optimization with Gaussian process surrogates enhances sampling efficiency in low-dimensional design spaces but becomes less efficient as dimensionality increases. Nonetheless, optimization routines within two-dimensional and five-dimensional design spaces can identify designs that maximize yield, while also aligning with established physical intuition. Optimization routines, which ignore constraints on hydrodynamic instability growth, are shown to lead to unstable designs in 2D, resulting in yield loss. However, routines that utilize 1D simulations and impose constraints on the in-flight aspect ratio converge on novel cylindrical target designs that are stable against hydrodynamic instability growth in 2D and achieve high yield.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗