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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 OSTI2023

Mainstream nitrogen removal from low temperature and low ammonium strength municipal wastewater using hydrogel-encapsulated comammox and anammox

Application of partial nitritation (PN)-anammox to mainstream wastewater treatment faces challenges in low water temperature and low ammonium strength. In this study, a continuous flow PN-anammox reactor with hydrogel-encapsulated comammox and anammox was designed and operated for nitrogen removal from mainstream wastewater with low temperature. Long-term operation with synthetic and real wastewater as the feed demonstrated nearly complete ammonium and total inorganic nitrogen (TIN) removal by the reactor at temperatures as low as 10 °C. A significantly decreased nitrogen removal performance and biomass activity was observed in the reactor at 4 °C before a selective heating strategy was employed. A novel heating technology using radiation to heat carbon black co-encapsulated in the hydrogel matrix with biomass was used to selectively heat biomass but not water in the treatment system. This selective heating technology enabled nearly complete ammonium removal and 89.4 ± 4.3 % TIN removal at influent temperature of 4 °C and reactor temperature 5 °C. Activity tests suggested selective heating brought the biomass activity at influent temperatures of 4 °C and reactor temperature 5 °C to a level comparable to that at 10 °C. Comammox and anammox were consistently present in the system and spatially organized in the hydrogel beads as revealed by qPCR and fluorescence in-situ hybridization (FISH). The abundance of comammox largely decreased by 3 orders of magnitude during the operation at 4 °C, and rapidly recovered after the application of selective heating. The anammox-comammox technology tested in this study essentially enabled mainstream shortcut nitrogen removal, and the selective heating ensured good performance of the technology at temperature as low as 5 °C.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Atmospheric methane removal: a research agenda

Atmospheric methane removal (e.g. in situ methane oxidation to carbon dioxide) may be needed to offset continued methane release and limit the global warming contribution of this potent greenhouse gas. Because mitigating most anthropogenic emissions of methane is uncertain this century, and sudden methane releases from the Arctic or elsewhere cannot be excluded, technologies for methane removal or oxidation may be required. Carbon dioxide removal has an increasingly well-established research agenda and technological foundation. No similar framework exists for methane removal. We believe that a research agenda for negative methane emissions—‘removal' or atmospheric methane oxidation—is needed. We outline some considerations for such an agenda here, including a proposed Methane Removal Model Intercomparison Project (MR-MIP). This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Green synthesis of sulfur‐doped g‐C 3 N 4 nanosheets for enhanced removal of oxytetracycline under visible‐light irradiation and reduction of its N ‐nitrosodimethylamine formation potential

Abstract BACKGROUND In this study, sulfur‐doped g‐C 3 N 4 (SCN) nanosheets were synthesized using thiourea as a precursor, and then used to catalyze the degradation of oxytetracycline (OTC) under visible‐light irradiation. OTC was chosen as target contaminant because of it being an important precursor of N ‐nitrosodimethylamine (NDMA). RESULTS The removal of OTC was influenced by its initial concentration, initial pH, SCN dosage and water matrices. OTC (≤10 mg L −1 ) was almost completely removed in 40 min under the conditions of an initial pH of 7.0 and a SCN dose of 1.0 g L −1 , and its degradation was well described by the pseudo‐first‐order kinetics model. Water matrices would also influence the degradation of OTC in the system. Electron paramagnetic resonance analysis and trapping experiments confirmed that the function of the radicals for OTC removal followed the order of • O 2 − > • OH > h + . Eight transformation products were determined during the degradation of OTC, it being removed through four pathways: methyl oxidization, demethylation, decarbonylation and secondary alcohol oxidation. SCN was stable in the system, as the removal efficiency of OTC was not significantly reduced even after three recycles. In addition, 55.5% of NDMA formation potential of OTC was reduced after SCN catalytic oxidation. CONCLUSIONS The results imply that the visible‐light‐driven SCN catalytic oxidation is an effective technology not only for the removal of OTC but also for the reduction of NDMA formation potential. © 2021 Society of Chemical Industry

Dou, Yicheng↗
DOE OSTI2022

Removal of As(V) from wastewaters using magnetic iron oxides formed by zero-valent iron electrocoagulation

Electrocoagulation of zero-valent iron has been widely applied to the removal of dissolved arsenic, but the solid-liquid separation of arsenic-containing precipitates remains technically challenging. In this work, zero-valent iron was electrochemically oxidized to magnetic iron oxides for the removal of As(V) from simulated and actual mining wastewaters. The results indicated that lepidocrocite was formed when zero-valent iron was oxidized by dissolved oxygen, but ferrihydrite and green rust were first formed and then transformed to magnetic iron oxides (mainly magnetite and maghemite) in the electrochemical oxidation from 0 to 0.9 V (vs. SCE), which facilitates the adsorption of As(V) and subsequent solid-liquid separation under a magnetic field. In simulated As(V)-containing solution with initial pH 7.0, zero-valent iron was electrochemically oxidized to magnetite and maghemite at 0.6 V (vs. SCE) for 2 h. The As(V) concentration first decreased from 5127.5 to 26.8 μg L -1 with a removal ratio of 99.5%. In actual mining wastewaters, zero-valent iron was electrochemically oxidized to maghemite at 0.6 V (vs. SCE) for 24 h, and the As(V) concentration decreased from 5486.4 to 3.6 μg L -1 with a removal ratio of 99.9%. The removal ratio of As(V) increased slightly with increasing potential, and increased first and then decreased with increasing initial pH. Compared with that of SO 4 2- and NO 3 - , the presence of Cl - significantly enhanced the removal of As(V). This work provides a highly efficient, facile and low-cost technique for the treatment of arsenic-containing wastewaters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Mechanistic insights into sulfate and phosphate-mediated hexavalent chromium removal by tea polyphenols wrapped nano-zero-valent iron

Nano zero-valent iron via green synthesis (g-nZVI) has great potential in removing toxic hexavalent Cr(VI) from industrial wastewater. Sulfate and phosphate in wastewater can influence Cr(VI) removal by g-nZVI. Here, in this study, the Cr(VI) removal kinetics by different g-nZVI materials were investigated with the existence of sulfate and/or phosphate, and the corresponding mechanisms were first revealed using multiple characterizations, including X-ray absorption near-edge spectra (XANES) and X-ray photoelectron spectroscopy (XPS). The results showed that Cr(OH) 3 was the dominant species initially formed on the surface of g-nZVI particles before transforming to Cr 2 O 3 during the reaction of g-nZVI with Cr(VI). Sulfate in wastewater can promote the reduction from Cr(VI) to Cr(OH) 3 by g-nZVI, because sulfate triggers the release of Fe(II) and tea polyphenols (from tea extracts) from the g-nZVI surface due to the corrosion of Fe 0 core, which is in line with an obvious increase in pseudo-second-order rate constant (k 2 ) and subtle change in Cr(VI) removal capacity (q e ). However, phosphate impedes the g-nZVI corrosion and inhibits q e because of the inner-sphere complexation of phosphate onto g-nZVI decreasing the released Fe(II) for Cr 2 O 3 production. When sulfate and phosphate coexisted in contaminated water, the inhibition effect of phosphate in Cr(VI) removal by g-nZVI was stronger than the promotion of sulfate. Accordingly, q e value of g-nZVI declined from 93.4 mg g –1 to 77.5 mg g –1 , while k 2 remained constant as the molar ratio of phosphate/sulfate increased from 0.1 to 10 in water. This study provides new insights into applying g-nZVI in efficient Cr(VI) removal from contaminated water with enrichment of sulphates and phosphates.

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

Mechanisms of phosphate removal by Micron-Scale Zero-Valent iron

Extensive studies have been carried out on phosphate removal by zero valent iron (ZVI). Different mechanisms of phosphate removal by ZVI such as phosphate adsorption and precipitation of ferric phosphate and vivianite (Fe 3 (PO 4 ) 2 ·8H 2 O) have been reported. In this study, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray powder diffraction (XRD), and X-ray absorption near edge spectroscopy (XANES) were used to elucidate the mechanisms of phosphate removal by micron-scale zero-valent (mZVI). Time-series ATR-FTIR analysis revealed that phosphate was removed by ZVI in two steps: a) adsorption of phosphate in the first 3 days, and b) slow conversion of the adsorbed phosphate into the precipitated form in 6 days. XRD and XANES analysis determined that iron oxides, ferric ion, and ZVI with oxide layer inhibited the formation of vivianite, resulting in the formation of phosphate precipitates, such as H 2 Fe(II)P 2 O 7 . The results suggested that phosphate is removed by ZVI mainly through precipitation under aerobic conditions. In conclusion, the knowledge gained in this study improves the fundamental understanding of the phosphate removal processes via ZVI.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Rapid photooxidation and removal of As(III) from drinking water using Fe-Mn composite oxide

Fe-Mn composite oxide (FMO) is widely applied to the oxidation and removal of As(III) from water. However, As(III) can directly reduce manganese oxides, decreasing the oxidation capacity or reusability and thereby greatly limiting the applicability of FMO. Here, the oxidation capacity and reusability of FMO for As(III) were efficiently improved by light radiation, and the effect of typical coexisting ions (SO 4 2– and Ca 2+ ) on the removal of As(III) was also studied. O 2 •– produced from excited manganese oxide and ligand-to-metal charge transfer in iron oxide-As(III) complex enhanced As(III) oxidation and removal under light radiation. At an initial As(III) concentration of 1000 μg L –1 , the total As concentration was respectively decreased to 11.5, 1.5 and 4.4 μg L –1 under darkness, UV light and sunlight at 180 min, and could be reduced to below the guideline limitation of drinking water (10 μg L –1 ) within 40 and 60 min under UV light and sunlight, respectively. SO 4 2– exhibited negligible effect on As removal efficiency because FMO had obviously lower adsorption capacity and selectivity for SO 4 2– than for As(V). The adsorption of coexisting Ca 2+ on manganese oxide decreased the negative charge on the FMO surface, thereby improving As(III) adsorption and oxidation. FMO exhibited excellent reusability, and a total As removal efficiency of 99.1% was still maintained after five cycles of an adsorption-desorption process under UV light. Finally, this work elucidates the photochemical oxidation and removal mechanism of FMO for As(III), and proposes a low-cost and efficient method for the detoxification of As(III)-contaminated drinking water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Rapid and Efficient Arsenic Removal by Iron Electrocoagulation Enabled with in Situ Generation of Hydrogen Peroxide

Millions of people are exposed to toxic levels of dissolved arsenic in groundwater used for drinking. Iron electrocoagulation (FeEC) has been demonstrated as an effective technology to remove arsenic at an affordable price. However, FeEC requires long operating times (~hours) to remove dissolved arsenic due to inherent kinetics limitations. Air cathode Assisted Iron Electrocoagulation (ACAIE) overcomes this limitation by cathodically generating H 2 O 2 in situ. In ACAIE operation, rapid oxidation of Fe(II) and complete oxidation and removal of As(III) are achieved. Here, we compare FeEC and ACAIE for removing As(III) from an initial concentration of 1464 μg/L, aiming for a final concentration of less than 4 μg/L. We demonstrate that at short electrolysis times (0.5 min), i.e., high charge dosage rates (1200 C/L/min), ACAIE consistently outperformed FeEC in bringing arsenic levels to less than WHO-MCL of 10 μg/L. Using XRD and XAS data, we conclusively show that poor arsenic removal in FeEC arises from incomplete As(III) oxidation, ineffective Fe(II) oxidation and the formation of Fe(II–III) (hydr)oxides at short electrolysis times (<20 min). Finally, we report successful ACAIE performance (retention time 19 s) in removing dissolved arsenic from contaminated groundwater in rural California.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Electroprecipitation Mechanism Enabling Silica and Hardness Removal through Aluminum-Based Electrocoagulation

We evaluate the effectiveness of an aluminum-based electrocoagulation pretreatment system to remove dissolved silica and hardness. Silica and hardness limit water recovery during membrane-based desalination applications when silica and hardness exceed the solubility limit and generate scale on the membrane surface. We show that simultaneous removal of nearly all silica (95 ± 4%) and a significant amount of hardness (40–60%) occurs with a hydraulic residence time of 2 h and a charge loading between 0 and 1200 C/L. Increasing the residence time maximized the hardness removal (58 ± 8%) via the formation of larger flocs, which allowed for more constituent removal by gravity settling. We highlight the trade-offs between improved energy efficiency at lower charge loadings and an improved removal rate at a higher charge loading. We further compare the percentage of silica and hardness removed in multicomponent solutions and compare this to single component feed solution. We discuss the implications that operational considerations have in terms of cost and treatment capacity. Finally, a cost–benefit analysis comparing chemical coagulation with electrocoagulation indicates that electrocoagulation could be half the cost of chemical coagulation and could produce more stable effluent pH and conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Large CO 2 removal potential of woody debris preservation in managed forests

Limiting climate warming to 1.5 °C requires reductions in greenhouse gas emissions and CO 2 removal. While various CO 2 removal strategies have been explored to achieve global net-zero greenhouse gas emissions and account for legacy emissions, additional exploration is warranted to examine more durable, scalable and sustainable approaches to achieve climate targets. Here, in this study, we show that preserving woody debris in managed forests can remove gigatonnes of CO 2 from the atmosphere sustainably based on a carbon cycle analysis using three Earth system models. Woody debris is produced from logging, sawmill wastes and abandoned woody products, and can be preserved in deep soil to lengthen its residence time (a measure of durability) by thousands of years. Preserving annual woody debris production in managed forests has the capacity to remove 769–937 GtCO 2 from the atmosphere cumulatively (10.1–12.4 GtCO 2 yr −1 on average) from 2025 to 2100, if its residence time is lengthened for 100–2,000 years and after 5% CO 2 removal is discounted to account for CO 2 emission due to machine operation for wood debris preservation. This translates to a reduction in global temperatures of 0.35–0.42 °C. Given the large potential, relatively low cost and long durability, future efforts should be focused on establishing large-scale demonstration projects for this technology in a variety of contexts, with rigorous monitoring of CO 2 removal, its co-benefits and side-effects.

Luo, Yiqi [Cornell Univ., Ithaca, NY (United State↗
DOE OSTI2024

Uncertainty in determining carbon dioxide removal potential of biochar

A quantitative and systematic assessment of uncertainty in life-cycle assessment is critical to informing sustainable development of carbon dioxide removal (CDR) technologies. Biochar is the most commonly sold form of CDR to date and it can be used in applications ranging from concrete to agricultural soil amendments. Previous analyses of biochar rely on modeled or estimated life-cycle data and suggest a cradle-to-gate range of 0.20–1.3 kg CO 2 net removal per kg of biomass feedstock, with the range reported driven by differences in energy consumption, pyrolysis temperature, and feedstock sourcing. Herein, we quantify the distribution of CDR possible for biochar production with a compositional life-cycle inventory model paired with scenario-aware Monte Carlo simulation in a 'best practice' (incorporating lower transportation distances, high pyrolysis temperatures, high energy efficiency, recapture of energy for drying and pyrolysis energy requirements, and co-generation of heat and electricity) and 'poor practice' (higher transportation distances, lower pyrolysis temperatures, low energy efficiency, natural gas for energy requirements, and no energy recovery) scenarios. In the best-practice scenario, cradle-to-gate CDR (which is representative of the upper limit of removal across the entire life cycle) is highly certain, with a median removal of 1.4 kg of CO 2 e/kg biomass and results in net removal across the entire distribution. In contrast, the poor-practice scenario results in median net emissions of 0.090 kg CO 2 e/kg biomass. Whether this scenario emits (66% likelihood) or removes (34% likelihood) carbon dioxide is highly uncertain. The emission intensity of energy inputs to the pyrolysis process and whether the bio-oil co-product is used as a chemical feedstock or combusted are critical factors impacting the net carbon dioxide emissions of biochar production, together responsible for 98% of the difference between the best- and poor-practice scenarios.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Mirror nucleon removal reactions in p-shell nuclei

Nucleon removal reactions have been shown to be an effective tool for studying the single particle structure of nuclei. This work continues efforts to experimentally probe and benchmark the reaction and structure models used to calculate the removal reaction cross sections when using microscopic nuclear structure inputs. Here, three different single nucleon removal reactions were performed, from p -shell nuclei with masses A = 7, 9, and 10. The residual nuclei from the reactions were detected in coincidence with γ rays to determine partial cross sections to individual final states. The eikonal direct-reaction model is combined with overlap functions and residual nucleus densities from microscopic, variational Monte Carlo calculations to provide consistent nuclear structure input to the partial cross section calculations. Comparisons of measured and calculated cross sections, including for mirror reactions, are presented. The analysis of the partial cross sections leading to the ground states shows a similar behavior to the one observed from analyses of inclusive cross sections using shell model nuclear structure input: the theoretical description of the removal process is in better agreement with the data when removing weakly bound nucleons, than when removing well-bound ones. The two mirror reaction pairs presented here show consistent results between the respective members of the pairs. The results obtained for the population of the excited states, however, show a systematically different trend that appears connected to the structure part of the calculation. Additional cases are needed to better understand the respective roles of structure and dynamical effects in the deviations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Proton removal from Br 73 , 75 to Se 72 , 74 at intermediate energies

Herein we report new experimental data for excited states of 72,74 Se obtained from proton removal from 73,75 Br secondary beams on a proton target. The experiments were performed with the Ursinus-NSCL Liquid Hydrogen Target and the combined GRETINA+S800 setup at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University. Within uncertainties, the inclusive cross sections for proton removal from 73,75 Br on a proton target are identical suggesting that the same single-particle orbitals contribute to the proton-removal reaction. In addition, details of the partial cross section fragmentation are discussed. The data might suggest that l = 1, 2, 3, and 4 angular momentum transfers are important to understand the population of excited states of 72,74 Se in proton removal. Available data for excited states of 74 Ge populated through the 75 As(d, 3 He) 74 Ge proton-removal reaction in normal kinematics suggest indeed that the fp and sd shell as well as the 1g 9/2 orbital contribute. A comparison to data available for odd-A nuclei supports that the bulk of the spectroscopic strengths could be found at lower energies in the even-even Se isotopes than in, for instance, the even-even Ge isotopes. In addition, the population of high-J states seems to indicate that multi-step processes contribute to proton-removal reactions at intermediate energies in these collective nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Options for the Removal of Cesium and Strontium from Acidic Uranyl Sulfate Solutions from Molybdenum-99 Production

A small laboratory-scale column process aimed at removing fission products from prototypical acidic sulfate solution wastes from a prototypical Mo-99 recovery process has been operated in a radioactive materials hood at Savannah River National Laboratory. This equipment has been operated with realistic concentrations of uranium (0.4 wt % 235 U), plutonium ( 239 Pu), neptunium ( 237 Np), non-radioactive surrogates of common fission products (including Cs and Sr) and two promising absorbents AMP-PAN and CST R91290-B. The goal of this work was to demonstrate the removal and concentration of high specific activity isotopes which are expected to dominate the classification of the low-level waste from the production of 99 Mo. Both AMP-PAN and CST R9120-B are attractive absorbents for the removal of 137 Cs from an acidic sulfate waste stream. They do not provide a solution for the removal of 90 Sr from the acidic solutions, but CST should be investigated at a higher pH. Limited removal of transuranic species and almost no removal of uranium was observed in this testing. This could be important due to the relatively large amount of uranium expected to be present in such waste streams. The capacity of these absorbents for 137 Cs will likely be dependent on the Cs concentration in the solutions processed but loading in the range of 0.2 to 5 mg Cs per gram of absorbent appears to be achievable.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Cesium Removal from Surrogate Pyroprocessing Salt by Electrodeposition

Active metals in used nuclear fuel dissolve into the salt during pyroprocessing and are not removed by electrorefining or drawdown operations. The buildup of 137 Cs over time increases the heat load and ionizing radiation level of the salt such that it must be replaced frequently, resulting in a significant amount of salt waste. An effective means of managing cesium in the molten salt electrolyte would increase the efficiency of pyroprocessing and decrease the volume of salt waste requiring disposal. A previous report summarized issues that must be addressed when developing a removal strategy and assessed the suitability of existing methods and remaining technological gaps to their application (Rose and Thomas 2023). Cesium is extremely stable in molten salt as a chloride—even more stable than the LiCl-KCl eutectic base salt used for pyroprocessing fuel—which makes removing cesium a challenge. However, sufficiently strong atomic interactions occur between active metal species and liquid metals that make the electrodeposition of active metal fission products into liquid metal electrodes energetically favorable. The feasibility of recovering cesium from LiCl-KCl pyroprocessing salt through electrodeposition into liquid metals is eing assessed by identifying potentially effective liquid metals and performing tests to determine the effectiveness of electrodepositing cesium from a LiCl/KCl salt into these liquid metals. Previous studies investigating the electrodeposition of Sr 2+ , and Ba 2+ into zinc, cadmium, bismuth, lead, tin and antimony have shown that alkali and alkaline earth metals can be electrodeposited at liquid metal cathodes (Kim et al., 2018). The removal of Ba 2+ and Sr 2+ was measured to be more efficient than the removal of monovalent cations due to the greater thermochemical driving force for alloying those elements with the liquid metal (Jang et al. 2022). Because the equilibrium potentials are dependent on the interactions of the active metal in the liquid metal, it is likely that the other alkali metals Li + , and K + , will deposit from LiCl/KCl salt with the Cs + . Therefore, application of this method to recover active metals from pyroprocessing salt will benefit from the use of a liquid metal and set of operating conditions that sufficiently increase the reduction potential of cesium to remove cesium from the waste salt with an acceptable amount of co-deposited lithium and potassium.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1984

Investigation of sidewall boundary layer removal effects on two different chord airfoil models in the Langley 0.3-meter Transonic Cryogenic Tunnel

An investigation was carried out on two CAST 10-2 airfoil models with chords of 3 in. and 6 in. To evaluate the extent of sidewall influence on airfoil tests at transonic Mach numbers. The tests were conducted in the Langley 0.3-m Transonic Cryogenic Tunnel two-dimensional test section equipped with an upstream sidewall boundary layer removal system which reduces the boundary layer displacement thickness to about 1 percent of model halfspan from an initial 2 percent without boundary layer removal. Test results have shown the changes in the location of the shock on the upper surface of the airfoil to be about the same for both models with and without sidewall boundary layer removal. Even though large differences were noted in the high lift characteristics of the two models, the sidewall boundary layer removal had little effect on the differences. These tests also served to validate the boundary layer removal technique and the associated Mach number correction required with upstream boundary layer removal.

Murthy, A. V.↗
NASA NTRS2004

Microlith Based Sorber for Removal of Environmental Contaminants

The development of energy efficient, lightweight sorption systems for removal of environmental contaminants in space flight applications is an area of continuing interest to NASA. The current CO2 removal system on the International Space Station employs two pellet bed canisters of 5A molecular sieve that alternate between regeneration and sorption. A separate disposable charcoal bed removes trace contaminants. An alternative technology has been demonstrated using a sorption bed consisting of metal meshes coated with a sorbent, trademarked and patented as Microlith by Precision Combustion, Inc. (PCI); thesemeshes have the potential for direct electrical heating for this application. This allows the bed to be regenerable via resistive heating and offers the potential for shorter regeneration times, reduced power requirement, and net energy savings vs. conventional systems. The capability of removing both CO2 and trace contaminants within the same bed has also been demonstrated. Thus, the need for a separate trace contaminant unit is eliminated resulting in an opportunity for significant weight savings. Unlike the charcoal bed, zeolites for trace contaminant removal are amenable to periodic regeneration. This paper describes the design and performance of a prototype sorber device for simultaneous CO2 and trace contarninant removal and its attendant weight and energy savings.

Roychoudhury, S.↗
NASA NTRS2005

Resistively-Heated Microlith-based Adsorber for Carbon Dioxide and Trace Contaminant Removal

An integrated sorber-based Trace Contaminant Control System (TCCS) and Carbon Dioxide Removal Assembly (CDRA) prototype was designed, fabricated and tested. It corresponds to a 7-person load. Performance over several adsorption/regeneration cycles was examined. Vacuum regenerations at effective time/temperature conditions, and estimated power requirements were experimentally verified for the combined CO2/trace contaminant removal prototype. The current paper details the design and performance of this prototype during initial testing at CO2 and trace contaminant concentrations in the existing CDRA, downstream of the drier. Additional long-term performance characterization is planned at NASA. Potential system design options permitting associated weight, volume savings and logistic benefits, especially as relevant for long-duration space flight, are reviewed. The technology consisted of a sorption bed with sorbent- coated metal meshes, trademarked and patented as Microlith by Precision Combustion, Inc. (PCI). By contrast the current CO2 removal system on the International Space Station employs pellet beds. Preliminary bench scale performance data (without direct resistive heating) for simultaneous CO2 and trace contaminant removal was reviewed in SAE 2004-01-2442. In the prototype, the meshes were directly electrically heated for rapid response and accurate temperature control. This allowed regeneration via resistive heating with the potential for shorter regeneration times, reduced power requirement, and net energy savings vs. conventional systems. A novel flow arrangement, for removing both CO2 and trace contaminants within the same bed, was demonstrated. Thus, the need for a separate trace contaminant unit was eliminated resulting in an opportunity for significant weight savings. Unlike the current disposable charcoal bed, zeolites for trace contaminant removal are amenable to periodic regeneration.

Roychoudhury, S.↗