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At least 1,315 records · Page 73

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

Thermal Modeling of a Novel Air-Cooled Temperature Swing Adsorption Compressor (AC-TSAC)

Contaminant removal technology, such as the Carbon Dioxide Removal Assembly (CDRA) on the International Space Station (ISS), is critical to Environmental Control and Life Support Systems (ECLSS), which enable humans to live and work in outer space. The CDRA includes an adsorbent bed, which absorbs CO 2 from the cabin air and releases it to a Sabatier reactor for water production when thermally cycled. An effective system would heat and cool the adsorbent quickly and uniformly to maximize the amount of CO 2 removed from the cabin and delivered to the Sabatier reactor. Air-Cooled Temperature Swing Adsorption Compressors (AC-TSAC) are promising for use downstream of the CDRA because they are a simple alternative to more mechanically-complex compressors, which are currently in use on the ISS. The current investigation addresses the thermal modeling of potential AC-TSAC designs. An initial thermal model was created and validated by comparing the model outputs to experimental data for the heating phase. Several design trades were conducted, including bed geometry (rectangular vs. cylindrical), bed structural material (i.e., the material that makes up the walls and shelves), and configuration of heat spreading elements within the bed. Also investigated is AC-TSAC performance sensitivity to the thermal conductivity of the adsorbent material and the heat pipes as well as the input power for heating. The results from these studies will inform the design of the next generation of the AC-TSAC, and the thermal modeling results will be further validated through testing.

Hannah S. Alpert↗

NASA NTRSDate not supplied

Thermal Modeling of a Compressor for CO2 Removal in the International Space Station

Contaminant removal technology, such as the Carbon Dioxide Removal Assembly (CDRA) on the International Space Station (ISS), is critical to Environmental Control and Life Support Systems (ECLSS), which enable humans to live and work in outer space. The CDRA includes an adsorbent bed, which absorbs CO2 from the cabin air and releases it to a Sabatier reactor for water production when thermally cycled. An effective system would heat and cool the adsorbent quickly and uniformly to maximize the amount of CO2 removed from the cabin and delivered to the Sabatier reactor. Air-Cooled Temperature Swing Adsorption Compressors (AC-TSAC) are promising for use downstream of the CDRA because they are a simple alternative to more mechanically-complex compressors, which are currently in use on the ISS. A thermal model of the AC-TSAC was created in COMSOL and validated by comparing the model outputs to experimental data for the heating phase of the cycle. Subsequently, several design trades and performance sensitivities were conducted, including bed geometry (rectangular vs. cylindrical), bed structural material (i.e., the material that makes up the walls and shelves), thermal conductivity of the adsorbent material and bed structural materials, and the input power for heating. The results from these studies will inform the design of the next generation of the AC-TSAC, and the thermal modeling results will be further validated through testing.

Hannah Alpert↗

NASA NTRSDate not supplied

Thermal Modeling of a Compressor for CO2 Removal in the International Space Station

Contaminant removal technology, such as the Carbon Dioxide Removal Assembly (CDRA) on the International Space Station (ISS), is critical to Environmental Control and Life Support Systems (ECLSS), which enable humans to live and work in outer space. The CDRA includes an adsorbent bed, which absorbs CO2 from the cabin air and releases it to a Sabatier reactor for water production when thermally cycled. An effective system would heat and cool the adsorbent quickly and uniformly to maximize the amount of CO2 removed from the cabin and delivered to the Sabatier reactor. Air-Cooled Temperature Swing Adsorption Compressors (AC-TSAC) are promising for use downstream of the CDRA because they are a simple alternative to more mechanically-complex compressors, which are currently in use on the ISS. A thermal model of the AC-TSAC was created in COMSOL and validated by comparing the model outputs to experimental data for the heating phase of the cycle. Subsequently, several design trades and performance sensitivities were conducted, including bed geometry (rectangular vs. cylindrical), bed structural material (i.e., the material that makes up the walls and shelves), thermal conductivity of the adsorbent material and bed structural materials, and the input power for heating. The results from these studies will inform the design of the next generation of the AC-TSAC, and the thermal modeling results will be further validated through testing.

Hannah Alpert↗

NASA NTRS2026

Recirculating and Sub-Atmospheric Rapid Cycle Amine Swing Bed Testing at Various Metabolic Profiles, Temperatures, and Half-Cycle Times

Sixty years since the first spacewalk, NASA’s Extravehicular Mobility Unit (xEMU) exploration space suit has undergone numerous design improvements and iterations. As commercial manufacturers develop next-generation systems to support increasingly complex missions, including Moon-to-Mars architecture prototyping and the design of the Martian Portable Life Support System (PLSS), material selection and individual subunit testing under realistic metabolic and pressure conditions are paramount. To determine whether a reusable carbon dioxide (CO 2 ) scrubber design and adsorbent can be utilized in new suit configurations, an all-encompassing test rig is required to compare existing and newly developed technologies. The test rig must be capable of sub-atmospheric testing, calibrated humid CO 2 dosing, and facilitation of the evaluation of sorbents across a wide range of operational requirements. Recently, XploSafe has developed an Extravehicular Mobility Unit (xEMU) testing rig specifically designed to explore CO 2 and humidity control materials for spacesuits. This closed-loop recirculating swing bed (Rapid Cycle Amine Test Rig) was utilized to compare adsorbent utility across a wide range of xEMU operating conditions. Following successful testing with Xplo-SA9T over multiple simulated eight-hour Extravehicular Activity (EVA) tests, improvements to the test stand were considered. Regeneration vacuum supply within the test rig was updated to more closely resemble space vacuum, theoretically increasing half-cycle timing. An improved water vapor delivery system was incorporated to dose a wider calibrated range of humidity over both short and long-duration EVAs. A range of metabolic profiles between 800 and 3000 BTU/h were tested, and the corresponding average CO 2 steady-states were compared. The effect of dosing temperature at the adsorbent bed inlet between 10 and 40 ̊C and the corresponding CO 2 removal efficiency was also evaluated.

John R Tidwell↗

DOE OSTI2014

Metal-organic frameworks for Xe/Kr separation

Metal-organic framework (MOF) materials are provided and are selectively adsorbent to xenon (Xe) over another noble gas such as krypton (Kr) and/or argon (Ar) as a result of having framework voids (pores) sized to this end. MOF materials having pores that are capable of accommodating a Xe atom but have a small enough pore size to receive no more than one Xe atom are desired to preferentially adsorb Xe over Kr in a multi-component (Xe--Kr mixture) adsorption method. The MOF material has 20% or more, preferably 40% or more, of the total pore volume in a pore size range of 0.45-0.75 nm which can selectively adsorb Xe over Kr in a multi-component Xe--Kr mixture over a pressure range of 0.01 to 1.0 MPa.

36 MATERIALS SCIENCE↗

DOE OSTI2016

High and rapid hydrogen release from thermolysis of ammonia borane near PEM fuel cell operating temperature

A system for generating and purifying hydrogen. To generate hydrogen, the system includes inlets configured to receive a hydrogen carrier and an inert insulator, a mixing chamber configured to combine the hydrogen carrier and the inert insulator, a heat exchanger configured to apply heat to the mixture of hydrogen carrier and the inert insulator, wherein the applied heat results in the generation of hydrogen from the hydrogen carrier, and an outlet configured to release the generated hydrogen. To purify hydrogen, the system includes a primary inlet to receive a starting material and an ammonia filtration subassembly, which may include an absorption column configured to absorb the ammonia into water for providing purified hydrogen at a first purity level. The ammonia filtration subassembly may also include an adsorbent member configured to adsorb ammonia from the starting material into an adsorbent for providing purified hydrogen at a second purity level.

08 HYDROGEN↗

DOE OSTI2017

Metal-organic frameworks for adsorption and separation of noble gases

A method including exposing a gas mixture comprising a noble gas to a metal organic framework (MOF), including an organic electron donor and an adsorbent bed operable to adsorb a noble gas from a mixture of gases, the adsorbent bed including a metal organic framework (MOF) including an organic electron donor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Hydrogen purification systems for PEM fuel cells

08 HYDROGEN↗

DOE OSTI2019

ATOMISTIC CHARACTERIZATION OF METAL-ORGANIC FRAMEWORKS FOR SUB-AMBIENT PRESSURE SWING ADSORPTION OF POST-COMBUSTION CO2 CAPTURE AND SEPARATION

Developing cost-effective and less energy-intensive carbon capture processes for dilute CO2 sources is of high interest. Adsorption-based CO2 capture such as pressure swing adsorption (PSA) is one promising approach to this challenge. PSA and other cyclic adsorption processes are materials-enabled separations that use porous adsorbents, including metal-organic frameworks (MOFs). This thesis examines post-combustion carbon capture in sub-ambient PSA, a potential route to an effective adsorption process, using MOF materials via molecular modeling. We first estimated the reproducibility of CO2 adsorption isotherm measurements in MOFs via literature meta-analysis. This chapter provides a comprehensive summary of the state of knowledge regarding CO2 adsorption in MOFs and its implications for molecular modeling of adsorption in MOFs. We then examined the upper bounds on CO2 swing capacity in sub-ambient PSA by Grand Canonical Monte Carlo (GCMC) simulation of an extensive collection of MOFs. A wide variety of MOFs was found to have swing capacity exceeding 10 mol/kg at sub-ambient temperatures provided that MOFs are appropriately selected based on their physical properties. We also assessed the capability of simple proxies for adsorbent performance and approximate models of cyclic adsorption to predict the outcomes of detailed process models of adsorption-based CO2 capture processes. To this end, we discuss the correlations between predictions from the simpler models and detailed process models. As a separate contribution, molecular modeling of chemical warfare agents (CWAs) adsorption in MOFs was analyzed. Molecular models of adsorption of CO2, CWAs or other molecules typically employ a rigid framework approximation for computational convenience. All real frameworks including MOFs, however, have intrinsic flexibility due to thermal vibrations. We examine the implications of this simple observation for quantitative predictions of the properties of adsorbed CWAs.

Park, Jongwoo↗

DOE OSTI2021

Clean and High-Efficiency Natural Gas Furnace with Advanced Acidic Gas Trap Technology

Ccurrent natural gas condensing furnaces generate substantial acidic condensate and SOx/NOx/CO/HC/methane emissions, causing long-term environment issues related to air, water and soil. Acidic condensate occurs when flue gases within the furnaces cool down below the dew points of acidic gases, which upon condensation, combine with water vapor to produce acidic solutions. The acidic condensate causes serious corrosion and fouling problems in natural gas condensing furnaces. This paper presents a novel solution to use an advanced adsorption technology based on monolithic acidic gas trap (AGT) adsorbers for SOx trapping, NOx redox, and formic acid/CO/HC/methane oxidation, enabling a new natural gas furnace with utra-clean flue gas and neutral condensate. When the AGT adsorber is appropriately integrated with natural gas furnaces, the acidic gases of SOx, NOx and formic gas/CO/HC will be continuously adsorbed, redoxed or oxidized, respectively, from the flue gas during a regular heating season, except for occasional regeneration activities for SOx trapping. In the paper, we present results from a prototype furnace employing the novel AGT component, which enables a pH of the condensate =7, NOx emissions of 1-2 nanograms/joule and an annual fuel utilization efficiency (AFUE) of 96%, providing a cost-effective technology for condensing furnaces that is eco-friendly to the environment.

Gao, Zhiming↗

DOE OSTI2022

Desulfurization and sulfur tolerant hydrogenation processes of hydrocarbon feedstocks

The present invention relates to the use of adsorbents comprising zinc oxide nanowires decorated with catalytically active metal particles for the removal of sulfur from hydrocarbon feedstocks, including the desulfurization of diesel fuels and the deep desulfurization of natural gas, and to the use of decorated zinc oxide nanowire adsorbents for the hydrogenation of naphthalene selectively to tetralin in the presence of sulfur compounds. The adsorbent comprises nickel metal particles or nickel-zinc alloy particles deposited on zinc oxide nanowires.

Sunkara, Mahendra↗

DOE OSTI2023

Process for purifying hydrogen gas for use in fuel cells

The invention generally relates to a process for purifying a hydrogen gas for use in a fuel cell. The process involves taking a hydrogen feed stream from a high-pressure tank and passing it through a purifier comprising an adsorbent to provide a purified hydrogen stream which is sent to a fuel cell. A particular adsorbent which can be used is a metal-organic framework composition. The adsorbent can be housed in a device such as a canister or cartridge having an inlet and outlet port.

Morris, William↗

DOE OSTI2015

Evaluation of a low cost humate solution as an in situ amendment to enhance attenuation of uranium in an acidic plume - 15445

A single well injection test was conducted in the acidic portion of a groundwater contamination plume beneath the F-Area Seepage Basins on the U.S. Department of Energy's Savannah River Site to evaluate humate as a viable amendment to enhance attenuation of uranium and other radionuclides. Humate is typically used as an inexpensive organic fertilizer. A solution of humate was injected into a monitoring well in the heart of the F-Area Seepage Basins plume. The geochemical conceptual model suggests humate adsorbs to mineral surfaces creating a subsurface treatment zone in which uranium adsorption is enhanced. Following humate injection, groundwater was sampled from the injection well at regular intervals to determine the composition of groundwater and to evaluate the sorption of contaminants within the treatment zone. Attenuation of uranium, radioiodine and Strontium-90 was determined by comparing concentrations to analytes unaffected by the humate, specifically tritium, nitrate, and specific conductance. The post-injection monitoring data showed enhanced uranium attenuation in the treatment zone as uranium concentrations rebounded to only 68% of the pre-test concentrations. Radioiodine attenuation was complicated by changing speciation during the test. When pH was elevated by the humate injection, iodate dominated and enhanced attenuation was observed. As pH decreased, iodide dominated and enhanced attenuation decreased. Humate did not significantly attenuate Strontium-90. Results of the humate injection test demonstrate that humate strongly adsorbs to the aquifer sediments at acidic pH. Humate desorption curves suggest that a substantial fraction of humate will remain adsorbed to the sediments for long-periods of time. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Development of Treatment Process for Radioactive Wastewater Generated from Molybdenum-99 Study - 16415

Molybdenum-99 (Mo-99) high acidic waste solution was securely stored at INER for numerous years. Until 2004, the procedures of waste solution draw-out and pressure-release were accompanied, along with construction of treatment facilities. In 2009, after simulated solution and small volume Mo-99 waste solution tests, the treatment procedure was determined. Then batch-scale treatment facilities were set up. The waste solution was preserved using the instrument, along with modification of some facilities simultaneously. Ultimately all of 12 tanks of Mo-99 inorganic waste solution stored in Building 014 were finished on July, 2012. And residential 5 tanks of those solution served in Building 015B were also completed on September, 2014. A practicable process has been developed for treating radioactive waste generated from Mo-99 study, and it can effectively remove radionuclides from a nitric acid solution. At first, after the waste was sucked from the bucket, the pH value was adjusted to about 10.0 through acid-alkali neutralization. Then, an adsorbent of natural zeolite powder was added to adsorb nuclides, and two adsorption columns filled with Cs-treat and Sr-treat adsorbents were used for removing nuclear species of Cs-137 and Sr-90. In this step, the nuclear species of Cs-137 and Sr-90 contained in the liquid waste are significantly reduced to a degree for manual operation allowable. Then, nitrate ion and mercury ion were removed through another procedure. As a result, the operations were safer and more efficient than other conventional methods. Additionally, the hazard of accidental leakage caused by corrosion of the bucket after long period of storage can be effectively prevented and potential pollution threats are also eliminated. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

Adsorptive Removal of Cs-137 and Sr-90 from Water in the Spent Fuel Pool of Taiwan Research Reactor - 18169

The cleanup of spent fuel pool in Taiwan Research Reactor (TRR) is a significant milestone in the decommissioning project of TRR. Due to the water was polluted by the ruptured spent nuclear fuel rods, the fission products and actinides were required to be removed from the water prior to transporting the water to the radioactive liquid wastes treatment plant. A granular aluminosilicate adsorbent (namely GWC) was loaded into a special designed water submersion adsorber to remove radionuclides from water in consideration of the subsequent retrieving after used. The unit is able to be placed underwater without heavy shield shroud, and easily to be assembled and disassembled. More than 95% of β-emitters had been removed from the 980 m{sup 3} of contaminated water in the SFP and generated about 1.5 m{sup 3} of spent GWC which adsorbed with 4*10{sup 12} Bq of radionuclides. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Conventional and Next Generation Treatment Technologies for PFAS - 20067

In 2016, the United States Environmental Protection Agency (USEPA) established a Health Advisory Limit (HAL) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) (individually and the summation) of 70 nanograms per liter (ng/L) based on developing toxicological information. These two compounds are among several thousand per- and polyfluoroalkyl substances (PFAS). Due to a multitude of commercially beneficial physical and chemical properties, the availability of PFAS-relevant and practical water treatment technologies is limited. The use of conventional adsorbents, such as activated carbon (AC) and anion exchange (AIX) resins, have become a 'de facto' interim measure to immediately address drinking water above this criterion. However, these adsorbents can have marginal long-term efficiency and are relatively unproven against the diversity of polyfluorinated compounds. Additionally, geochemical and/or co-contaminant competition can significantly impede adsorption based PFAS removal. These challenges may be addressed using engineered filtration, such as reverse osmosis or nanofiltration (RO/NF); however, for larger flow systems RO/NF may have unacceptable reject ratios as high as 35% and the capital cost may preclude these technologies. Extending these technologies to natural waters, which have various degrees of geochemical and co-contaminant competition, often requires a treatment train, combining conventional adsorbents or engineered filtration with pretreatment and more innovative and emerging remediation solutions for PFAS. Conventional and Next Generation water treatment technologies for PFAS generally employ one of three mechanisms (adsorption, separation, or destruction). These mechanisms include many types of technologies for both municipal drinking water and extracted natural water applications. The previously mentioned AC, AIX, and RO/NF are commercially available technologies that are actively being deployed for PFAS treatment. Research and development around these technologies is focused on optimization, and ultimate destruction of PFAS is achieved through incineration. Next Generation water treatment technologies include PFAS-specific flocculants, foam fractionation, novel AIX resins, new engineered adsorptive media, electrochemical treatment, sonolysis, and photolysis, radiation, and plasma (forms of advanced reductive processes [ARP]). Research and development around these technologies is focused on proof of concept and assimilation to real world applications. As the PFAS-relevant destructive technologies (such as incineration, electrochemical treatment, sonolysis, and ARP) are energy intensive, the state of the practice for PFAS water treatment is to focus adsorption/separation based technologies on reducing and concentrating the volume of water requiring destructive treatment. This enables more flexibility with respect to circulation frequency, residence time, and more control over energy usage. Water treatment for PFAS presently requires multiple technologies (i.e. a treatment train) to protect human health in a cost-conscious manner. An investment in research and development to explore new technologies is part of a key initiative for efficient protection of human health. This presentation attempts to review PFAS-relevant water treatment technologies and provide perspective as to their status with respect to applicability and commercial relevance. (authors)

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

CO2 Capture Using Amines Bound to Silica

One of the main culprits of global warming is the increased amount of carbon dioxide, or CO2, in the atmosphere. NASA's global climate reports a 13% increase in atmospheric CO2 from 2000 to present. Adsorptive CO2 capture by nitrogen groups of amine-containing solvents is one of the most mature technologies deployed in petrochemical and natural gas processing plants to purify industrial gases. However, key challenges in widespread application include solvent induced reactor corrosion, amine degradation, and high regeneration energy for repeated cycling. An alternative approach is to immobilize amines on solid supports. Key performance metrics of solid amine-based CO2 adsorbents include the CO2 adsorption capacity and stability to degradation over hundreds of thousands of regeneration cycles. Our research aims to develop descriptors for CO2 capture capacity and stability against oxygen-induced degradation for amines bound to porous silica supports using experimental and computational techniques. We experimentally measure the change in CO2-uptake using solid amine adsorbents with varying chemical compositions and exposure to varying gas streams and use high-performance computers to simulate the nature and strength of CO2-adsorption and oxidative degradation reaction mechanisms. Insights from our work can facilitate the development of stable solid amine adsorbents for large-scale CO2 capture processes.

amines↗

DOE OSTI2018

Trends in the Catalytic Activity of Hydrogen Evolution during CO 2 Electroreduction on Transition Metals

During CO 2 electroreduction (CO 2 R), the hydrogen evolution reaction (HER) is a competing reaction. We present a combined experimental and theoretical investigation of the HER activity of transition metals under CO 2 R conditions. Experimental HER polarization curves were measured for six polycrystalline metal surfaces (Au, Ag, Cu, Ni, Pt, and Fe) in the presence of CO 2 gas. We found that the HER activity of the transition metals is significantly shifted, relative to the CO 2 -free case. Density functional theory (DFT) calculations suggest that this shift arises from adsorbate–adsorbate interactions between *CO and *H on intermediate and strong binding metals, which weakens the *H binding energy. Using a simple model for the effect of *CO on the *H binding energy, we construct an activity volcano for HER in the presence of CO 2 gas that is consistent with experimental trends. In conclusion, the significant changes in HER activity in the presence of CO 2 gas is an important consideration in catalyst design and could help develop catalysts that are more selective for CO 2 R than the HER.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗