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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

High-temperature oxidation of advanced FeCrNi alloy in steam environments

Alloys of iron-chromium-nickel are being explored as alternative cladding materials to improve safety margins under severe accident conditions. Here, our research focuses on non-destructively investigating the oxidation behavior of the FeCrNi alloy “Alloy 33” using synchrotron-based methods. The evolution and structure of oxide layer formed in steam environments were characterized using X-ray diffraction, hard X-ray photoelectron spectroscopy, X-ray fluorescence methods and scanning electron microscopy. In conclusion, our results demonstrate that a compact and continuous oxide scale was formed consisting of two layers, chromium oxide and spinel phase (FeCr 2 O 4 ) oxides, wherein the concentration of the FeCr 2 O 4 phase decreased from the surface to the bulk-oxide interface.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evidence of redox cycling as a sub-mechanism in hydrogen production during ethanol steam reforming over La 0.7 Sr 0.3 MnO 3-x perovskite oxide catalysts

Ethanol steam reforming (ESR) is of societal interest. Here, in this work, experiments were conducted to ascertain if some of the H 2 is produced by a redox cycle involving H 2 O filling oxygen vacancies over reducible oxide catalysts. Redox cycling experiments were performed over La 0.7 Sr 0.3 MnO 3-x (100) in ultra-high vacuum. It was found that H 2 was produced from redox cycling with alternating ethanol and water exposures over La 0.7 Sr 0.3 MnO 3-x (100), with both half-cycles occurring at temperatures ≤800 K. In the first half-cycle, ethanol ‘directly’ reduced the surface to create oxygen vacancies (not by a CO intermediate), and in the second half-cycle water filled oxygen vacancies to make H 2 . The H 2 production during the water exposure has a half-cycle turnover frequency of >3.2 × 10 -2 molecules site -1 s -1 in the temperature range of 700–800 K, which is fast enough to be part of the ESR full catalytic cycle. Flowing both reactant gases together, ethanol and water, over La 0.7 Sr 0.3 MnO 3-x (100) and La 0.7 Sr 0.3 MnO 3-x powders significantly increases hydrogen production compared to pure ethanol. The results suggest that steady state ESR includes a sub-mechanism of ethanol ‘directly’ reducing the surface to create oxygen vacancy, and water filling oxygen vacancy to make some of the H 2 by a Mars van Krevelen type mechanism.

08 HYDROGEN↗
DOE OSTI2018

Incorporating anaerobic co-digestion of steam exploded or ammonia fiber expansion pretreated sugarcane residues with manure into a sugarcane-based bioenergy-livestock nexus

The co-digestion of pretreated sugarcane lignocelluloses with dairy cow manure (DCM) as a bioenergy production and waste management strategy, for intensive livestock farms located in sugarcane regions, was investigated. Ammonia fiber expansion (AFEX) increased the nitrogen content and accelerated the biodegradability of sugarcane bagasse (SCB) and cane leaf matter (CLM) through the cleavage of lignin carbohydrate crosslinks, resulting in the highest specific methane yields (292–299 L CH4/kg VSadded), biogas methane content (57–59% v/v) and biodegradation rates, with or without co-digestion with DCM. To obtain comparable methane yields, untreated and steam exploded (StEx) SCB and CLM had to be co-digested with DCM, at mass ratios providing initial C/N ratios in the range of 18 to 35. Co-digestion with DCM improved the nutrient content of the solid digestates, providing digestates that could be used as biofertilizer to replace CLM that is removed from sugarcane fields during green harvesting.

09 BIOMASS FUELS↗
DOE OSTI2023

Isotope effect in formaldehyde steam reforming on Pt/m-ZrO 2 : Insight into chemical promotion by alkalis

Infrared spectroscopy, temperature programmed reaction mass spectrometry (TP-reaction/MS), and catalyst testing were used to investigate alkali promotion of dehydrogenation selectivity during formaldehyde steam reforming (FSR) on Pt/m-ZrO 2 . In a preferred pathway, formaldehyde reacts with water forming hydrogen and formate, followed by forward formate decomposition to CO 2 and H 2 . Alkali-doping of 2 wt% Pt/m-ZrO 2 increases catalyst basicity, which weakens the formate C-H bond promoting formate dehydrogenation / decarboxylation. Promotion by alkali in FSR was observed through a formate nu(CH) band shift to lower wavenumbers in infrared spectroscopy, and through a decrease in the normal isotope effect in switching from H-to D-labeled formalde-hyde in TP-reaction/MS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Research goals for minimizing the cost of CO 2 capture when using steam methane reforming for hydrogen production

This paper presents a techno-economic assessment of adding state-of-the-art solvent-based CO 2 capture technologies to greenfield steam methane reforming (SMR)-based H 2 production plants and quantifies the impacts of improvements in CO 2 capture technology. Current conventional capture technologies are reviewed, and future technologies in intermediate and long-term scenarios are analyzed. The results show that adding significantly more efficient solvent-based capture technologies leads to an equivalent rate of natural gas consumption as that of a conventional SMR plant without capture, despite capturing most of the CO 2 and producing the same amount of H 2 . Overall, improvements in reboiler duty and reductions in capital costs can significantly reduce the cost of H 2 production and cost of capture. Particularly, the reboiler duty of pre-combustion capture and the capital cost of post-combustion capture have the greatest impact. Based on the results, research goals are suggested. Solvent development is recommended—particularly pre-combustion solvents—for reducing the reboiler duties, and process schemes to reduce the capital costs. Costlier but more efficient solvents can be considered. A sensitivity analysis using natural gas price shows that technological improvements can reduce the impacts of high natural gas prices. The degree of economic feasibility of CO 2 capture increases with improvements to the capture technology.

08 HYDROGEN↗
DOE OSTI2022

Coupling AFEX and steam-exploded sugarcane residue pellets with a room temperature CIIII-activation step lowered enzyme dosage requirements for sugar conversion

In this study, the potential integration of steam explosion (StEx) and ammonia fiber expansion (AFEX) with existing sugar/ethanol mills to form decentralized pre-processing depots was explored. Both StEx and AFEX pretreatment facilitated the production of sugarcane bagasse (SCB) and cane leaf matter (CLM) pellets with significantly higher bulk density, mechanical durability, and hydrophobicity relative to their untreated biomass pellet controls. However, ethanol production from standalone StEx and AFEX-treated SCB and CLM pellets required enzyme dosages greater than 21 mg/g glucan to achieve enzymatic hydrolysis sugar yields of 75% and ethanol titres greater than 40 g.L -1 . Coupling AFEX-treated SCB or CLM pellets with a room temperature CIII I -activation step using liquid ammonia lowered enzyme dosage requirements by more than 50% without affecting ethanol titers and production yields (greater than300 L per Mg residual dry matter raw dry biomass (RDM)). In contrast, treating StEx-treated pellets with CIIII-activation using liquid ammonia did not result in similar enzyme dosage reductions, due to pseudo-lignin formation, leading to enzyme deactivation and/or lignin blockage that retarded enzymatic hydrolysis at low enzyme dosages. A gross energy conversion assessment revealed that low enzyme dosage (3-4 mg enzyme/g RDM) ethanol and electricity co-production from AFEX and CIII I -activated SCB and CLM can recover up to 73% of the energy in the untreated biomass, compared to 54% recovered by StEx and CIII I -activation. The results from this work suggest that StEx or AFEX based pre-processing depots can produce dense and mechanically durable biomass pellets. The AFEX-treated pellets can be easily upgraded using a room temperature CIII I -activation step at the biorefinery to significantly reduce bioconversion enzymes.

42 ENGINEERING↗
DOE OSTI2017

A physics-based model for industrial steam-methane reformer optimization with non-uniform temperature field

In an industrial hydrogen production facility, steam-methane reforming reactions take place inside hundreds of catalyst-filled tubes placed in a large scale, high temperature furnace. Process efficiency depends strongly on the wall temperature distribution of the ensemble of reformer tubes; a narrower distribution has a process intensification effect, by providing similar processing experience to every feedstock molecule. Such process intensification efforts require a furnace model that can predict the temperature distribution as a function of operating conditions. Currently available furnace modeling solutions are either computationally intensive, making them unsuitable for (online) optimization calculations, or empirical, having limited accuracy when wide changes in operating conditions are required. Here in this work, a physics-based furnace model is presented that overcomes these limitations. Empirical perturbations in a Hottel zone radiation model are proposed to capture the spatially non-symmetrical temperature distribution. The low computational time makes the model suitable for operational intensification based on reduction of temperature distribution non-uniformity.

42 ENGINEERING↗
DOE OSTI2015

Integrated solar thermochemical reaction system for steam methane reforming

Solar-aided upgrade of the energy content of fossil fuels, such as natural gas, can provide a near-term transition path towards a future solar-fuel economy and reduce carbon dioxide emission from fossil fuel consumption. Both steam and dry reforming a methane-containing fuel stream have been studied with concentrated solar power as the energy input to drive the highly endothermic reactions but the concept has not been demonstrated at a commercial scale. Under a current project with the U.S. Department of Energy, PNNL is developing an integrated solar thermochemical reaction system that combines solar concentrators with micro- and meso-channel reactors and heat exchangers to accomplish more than 20% solar augment of methane higher heating value. The objective of our three-year project is to develop and prepare for commercialization such solar reforming system with a high enough efficiency to serve as the frontend of a conventional natural gas (or biogas) combined cycle power plant, producing power with a levelized cost of electricity less than 6¢/kWh, without subsidies, by the year 2020. In this paper, we present results from the first year of our project that demonstrated a solar-to-chemical energy conversion efficiency as high as 69% with a prototype reaction system.

03 NATURAL GAS↗
DOE OSTI2023

Steam explosion pretreatment coupling high-temperature short-time sterilization facilitating cellulose degradation and sporulation-regulatory gene expression in high-solid fermentation

Steam explosion coupling high-temperature short-time sterilization (SE-HTST) was exploited to modify cellulosic biomass medium properties and promote high-solid fermentation (HSF). Biomass characterization analysis showed that SE-HTST enlarged microstructural pores and cavities in solid media, providing more effective space for microbial growth. Meanwhile, SE-HTST helped to release glucose from the cellulose with 35.8 ± 4.5, 20.0 ± 2.3, and 12.3 ± 5.7 mg glucose/g dry medium at 24, 48, and 72 h of fermentation, which were 3.1, 2.3, and 1.5 times higher than that in medium from conventional thermal sterilization (CTS), respectively. SE-HTST increased the viable cell and spore number of Bacillus subtilis by 1.8 and 1.6 times at 72 h of fermentation compared to CTS. Moreover, the expressions of master transcriptional gene spo0A and the early sigma factors of sigF and sigE genes gradually increased in the SE-HTST medium, showing enhanced sporulation in HSF. Therefore, SE-HTST is an effective strategy for facilitating cellulose degradation, improving glucose nutrients in biomass medium, and promoting sporulation-regulatory gene expression during high-solid fermentation, which enhances the production of microbial ecological agents using B. subtilis significantly.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Characterization of steam impulse turbine for two-phase flow

The characterization of a steam impulse Terry turbine operating with single- and two-phase air–water ingestion has been performed; the air mass fraction ranged from 1.0 (single-phase air) down to 0.05. The two-phase characteristics were obtained over a range of turbine inlet pressures and turbine rotational speeds. Here, the torque produced and the mixture flow rate through the turbine were recorded. Based upon experimental air/water measurements, the turbine Affinity Laws have been modified to include the effects of two-phase flow.

42 ENGINEERING↗
DOE OSTI2022

Flow structures of the cross-flow over a five-layer helically coiled steam generator geometry

The helically-coiled heat exchanger (HCSG) offers advantages over straight tubes such as compactness in geometry, increased heat transfer coefficients, and capability to absorb thermal expansion. In this study, the time-resolved velocity field data of shell-side crossflow over a five-layer helically coiled steam generator geometry was obtained using Particle Image Velocimetry (PIV) between adjacent rods in four regions with up to 5000 frames per second (5 kHz) at approximately Re u = 3600. The slant rod bundle created different flow patterns in different regions. Proper Orthogonal Decomposition (POD) revealed high-energy-mode flow structures. Due to the confined flow channel geometry, the large flow structures were not advected resulting in no strong POD mode paring. Continuous Wavelet Transform (CWT) visualized the characteristics of flow fluctuation in time and frequency domain simultaneously, which ranged in Strouhal number, S u , between 0.03 and 1.17. In the wake regions of the rods, flows changed in both pattern and magnitude over time. Once a pattern formed, it continued for relatively shorter than straight tube arrays, before changing the pattern again. The histograms of the POD time coefficients presented this multimodal flow characteristics. The current study focuses more on whole flow field analyses in the selected regions rather than local point-wise analyses. Finally, this study revealed that various Strouhal numbers can exist in the helically coiled heat exchanger geometry, which was not observed in straight tube arrays. In particular, Strouhal numbers smaller than 0.1 do not seem to be caused by vortex shedding but seem to be the result of the combination of complex geometry and possible multimodal trends. Based on the current observation, further works would involve intensive instantaneous point-wise analyses on the interactions between important locations such as separation points, stagnation points, shear layers, etc.

42 ENGINEERING↗
DOE OSTI2021

Simulation of 12-bed vacuum pressure-swing adsorption for hydrogen separation from methanol-steam reforming off-gas

This study focuses on analysis of a 12-bed vacuum pressure-swing adsorption (VPSA) process capable of purifying hydrogen from a ternary mixture (H 2 /CO 2 /CO 75/24/1 mol%) derived from methanol-steam reforming. The process produces 9 kmol H 2 /h with less than 2 ppm and 0.2 ppm of CO2 and CO, respectively, to supply a polymer electrolyte membrane fuel cell. The process model is developed in Aspen Adsorption® using the “uni-bed” approach. A parametric study of H 2 purity and recovery with respect to adsorption pressure, adsorbent height, activated carbon:zeolite ratio, feed composition, and number of beds is performed. Results show 12-bed VPSA can meet the H 2 purity goals, with H 2 recovery as high as 75.75%. Adsorption occurs at 7 bar, the column height is 1.2 m, and the adsorbent ratio is 70%:30%. Furthermore, a 4-bed VPSA can achieve the same purity goals as the 12-bed process, but H 2 recovery decreases to 61.34%.

03 NATURAL GAS↗
DOE OSTI2022

DBD plasma-assisted ethanol steam reforming for green H 2 production: Process optimization through response surface methodology (RSM)

Herein this work investigates ethanol steam reforming (ESR) to produce hydrogen (H 2 ) in a dielectric barrier discharge (DBD) plasma reactor. A five-level, three-factor experiment design was performed using a response surface methodology (RSM) to evaluate the combined effects of the three process parameters, including discharge power, total flow rate, and ethanol-to-water (EtOH/H 2 O) molar ratio on the plasma-assisted ESR reaction. Quadratic regression models were employed in RSM to fit the experimental results and present the correlation between process parameters and targeted responses (EtOH conversion, H 2 yield, H 2 selectivity, and specific energy requirement (SER) for H 2 production). The results suggested that the EtOH/H 2 O molar ratio is considered to have the most significant effect on the EtOH conversion and H 2 , H 2 selectivity, while the total flow rate is the most significant parameter determining SER for H 2 production. Process optimization demonstrated the optimal process conditions, including a discharge power of 55.9 W, a total flow rate of 26.7 ml/min, and an EtOH/H 2 O molar ratio equal to 0.34. A validation test was performed and confirmed the feasibility of the optimization process.

08 HYDROGEN↗
DOE OSTI2014

Performance of the Fluidized Bed Steam Reforming Product Under Hydraulically Unsaturated Conditions

Currently, several candidates for secondary waste immobilization at the Hanford site in the State of Washington, USA are being considered. To demonstrate the durability of the product in the unsaturated Integrated Disposal Facility (IDF) at the site, a series of tests have been performed one of the candidate materials using the Pressurized Unsaturated Flow (PUF) system. The material that was tested was the Fluidized Bed Steam Reformer (FBSR) granular product and the granular product encapsulated in a geopolymer matrix. The FBSR product is composed primarily of an insoluble sodium aluminosilicate matrix with the dominant phases being feldspathoid minerals mostly nepheline, sodalite, and nosean. The PUF test method allows for the accelerated weathering of materials, including radioactive waste forms, under hydraulically unsaturated conditions, thus mimicking the open-flow and transport properties that most likely will be present at the IDF. The experiments show a trend of decreasing tracer release as a function of time for several of the elements released from the material including Na, Si, Al, and Cs. However, some of the elements, notably I and Re, show a steady release throughout the yearlong test. This result suggests that the release of these minerals from the sodalite cage occurs at a different rate compared with the dissolution of the predominant nepheline phase.

Durability testing↗
DOE OSTI2022

Structure characterization and steam oxidation performance of U 3 Si 2 with Zr alloying additions

Research and development of high uranium density fuels supports the on-going effort to enhance reactor technology, safety, performance, and economics. Among high uranium density fuels, U 3 Si 2 is a favored fuel candidate due to its higher uranium density and improved thermal conductivity when compared to traditional UO 2 . While U 3 Si 2 demonstrates an improved fuel economy, it suffers from rapid degradation when exposed to water at T > 300°C. In order for U 3 Si 2 to be implemented in water cooled reactors, the water reaction must be understood and mitigated. Reported here is the performance of Zr alloying additions to U 3 Si 2 exposed to high temperature steam oxidation environments. Here, the investigation shows that homogenization heat treatment contributes to a delayed onset of oxidation and an improved homogeneity throughout the arc-melt fabricated alloyed compositions. Of the pre- and post-annealed samples, the post-annealed 7 vol% Zr addition exhibited the highest onset temperature of oxidation. A preliminary computational investigation to complement the experimental analysis assesses the solubility of Zr in U 3 Si 2 and its incorporation in the crystal lattice.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Performance of Ni-Fe/gadolinium-doped CeO{sub2} anode supported tubular solid oxide fuel cells using steam reforming of methane

Iron nanoparticles (Fe{sub 2}O{sub 3}) were added to NiO/gadolinium-doped CeO{sub 2} (GDC) anode supported solid oxide fuel cell (SOFC) for the direct methane-water fuel operation. The cell was co-sintered at 1400 C, and the anode porosity is 31.8%. The main size corresponding to peak volume is around 1.5 {mu}m. When steam and methane directly fed to the cell, the power density is about 0.57 W cm{sup -2} at 650 C. It is the familiar performance for H{sub 2} operation (4 times of flow rate) with same fuel utilization. Compare with the testing temperature of 600 and 650 C, there is almost no carbon fiber deposition at 700 C with steam/methane (S/C) of 5. At the same time, fuel operation of high value of S/C (=3.3) resulted in fiber-like deposition and degradation of power performance based on loading test results.

03 NATURAL GAS↗
DOE OSTI2012

Demonstration of a Highly Efficient Solid Oxide Fuel Cell Power System Using Adiabatic Steam Reforming and Anode Gas Recirculation

Solid oxide fuel cells (SOFC) are currently being developed for a wide variety of applications because of their high efficiency at multiple power levels. Applications for SOFCs encompass a large range of power levels including 1-2 kW residential combined heat and power applications, 100-250 kW sized systems for distributed generation and grid extension, and MW-scale power plants utilizing coal. This paper reports on the development of a highly efficient, small-scale SOFC power system operating on methane. The system uses adiabatic steam reforming of methane and anode gas recirculation to achieve high net electrical efficiency. The anode exit gas is recirculated and all of the heat and water required for the endothermic reforming reaction are provided by the anode gas emerging from the SOFC stack. Although the single-pass fuel utilization is only about 55%, because of the anode gas recirculation the overall fuel utilization is up to 93%. The demonstrated system achieved gross power output of 1650 to 2150 watts with a maximum net LHV efficiency of 56.7% at 1720 watts. Overall system efficiency could be further improved to over 60% with use of properly sized blowers.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

Flow instabilities in helical-coil steam generators for small modular reactors: A review

Here, this study covers the research and discoveries in two-phase flow-boiling instabilities available in the literature—specifically for a helical-coil steam generator (HCSG), including experimental findings, theoretical research, computational models, and system code analyses—supporting research and development of representative small modular reactors (SMRs). Like other new and advanced reactor systems, water-cooled SMRs require experimental data from both integral and separate thermal-hydraulics test facilities for the verification and validation (V&V) of the computational models and computer codes in order to design and obtain regulatory approval. The complex dynamics of two-phase flow-boiling instabilities includes flow regimes physics phenomena, flow-channel geometries, heat-transfer behavior, and interactions among the solid–liquid-gas within the system boundary, all of which are pivotal for understanding the design and operational challenges of SMRs. This study focuses on identifying the relevant knowledge gaps on boiling instabilities—specifically for a HCSG—and provides insights about future research direction optimizing the transport of thermal energy, mass-flow rates, and boundary conditions that ensure the adequate heat-transfer performance, operational stability, and safety associated with SMR systems.

20 FOSSIL-FUELED POWER PLANTS↗