SEARCH · Engineering Papers

Results for “STEAM”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Evaluation of Steam Cycle Upgrades to Improve the Competitiveness of U.S. Coal Power Plants (Final Scientific / Technical Report)

Increasing the competitiveness of the existing pulverized-coal utility fleet in the United States may be achieved by decreasing heat rate, via increases in steam cycle efficiency through upgraded steam temperatures and use of latest technology available in steam turbine and blading design. The average net plant efficiency of the US coal-fired fleet is approximately 33% (HHV). Plant efficiency increases to approximately 41.4% (HHV) at 1,350°F (732°C) steam temperature. However, achieving these Advanced Ultra-Super Critical (AUSC) steam conditions requires the use of advanced high-temperature materials. While there has been a significant amount of DOE-funded materials R&D, most of the related design work has focused on new (greenfield) units, rather than on opportunities to retrofit this advanced technology to the existing utility fleet. If technology, based upon the advanced materials required for AUSC steam conditions, may be applied to the existing fleet, using an economically viable retrofit, a higher capacity factor can be expected as a result of the increased plant competitiveness. The Electric Power Research Institute (EPRI) was awarded a project by the US Department of Energy to examine the technical and economic feasibility of a series of steam cycle upgrades to the two most prevalent types of U.S. coal power plants: 2,400 psig (16.6 MPa) subcritical and 3,500 psig (24.1 MPa) supercritical pulverized coal units. The nine upgrade options that were originally being considered included increasing the main and reheat steam temperatures from 1,000°F (538°C) to 1,100°, 1,200°, and 1,350°F (593°C, 649°C, and 732°C) while holding the steam pressures constant at their original design values, and cases where just the main steam or reheat steam temperatures were increased. The objective was to minimize the modifications required to the existing power plant while still providing a significant improvement in heat rate. The upgrade options assumed that the boiler enclosure envelope remained unchanged from each base case, and that all applicable OEM design guidelines for normal commercial units were imposed. For the highest temperature supercritical case, an option of using a low-pressure molten salt loop to transfer heat from the furnace to the steam was examined. The first major task of the work scope was designed to examine the technical feasibility of various upgrade options, while the subsequent work determined economic viability of the technically feasible upgrade options. Prior to evaluating the effect of these increased temperatures, a “base case” model of a subcritical and supercritical PC boiler was created, which was used for comparative purposes. Upgrade options were evaluated at full-load, part-load and dynamic transient conditions. Once the technical feasibility of each upgrade option was evaluated, the economic value of the heat rate improvement of each feasible option was determined by detailed modeling of unit dispatch in several regional power markets. The dispatch model was used to estimate the amount of revenue from power sales the upgraded unit would receive in comparison to a non-upgraded version of the same power plant. As a parallel task to the dispatch analysis, the capital cost of implementing the upgrades was estimated. The capital cost estimates were then compared to the increased revenue estimated by the dispatch modeling to determine the economic attractiveness of each upgrade option. Several upgrade options were determined to be technically feasible. The net present value (NPV) of the costs for steam cycle upgrades considered in this study ranged from approximately $\$$111 to $\$$130 million. The economic modeling results show that the unit dispatch changes resulting from steam cycle upgrades are relatively small, due largely to heat rate (and operating cost) changes being relatively small. Additionally, the cost of each upgrade exceeds the net revenue increases associated with the upgrade case. Note that the breakeven values are higher for subcritical retrofits, but the capital costs for the subcritical upgrades are also slightly higher. In typical new pulverized coal plants, fuel accounts for approximately 25% of the cost of electricity (COE), while capital costs represent around 50% of the COE. Therefore, in order to improve the heat rate by 4% one can only afford to increase the capital cost by 2%, at the same cost of electricity. The conclusion of this study is that without a cost for emitting CO 2 , it will be difficult to pay for significant efficiency improvements on plants firing low cost coals.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2021

Solar Steam on Demand

INTRODUCTION: This Report summarizes the research and development project performed by Sunvapor and the subrecipient National Renewable Energy Laboratory (NREL) during the period of 10/01/2018-9/30/2021. The work was aimed at the economic integration of solar steam with an industrial process, and in particular, the advantages that a novel type of thermal energy storage and collector design could bring to the system. The completed work includes experimental research on the storage material, design of the collector, engineering of a complete solar steam plant, and economic analysis. The plant was, in the end, not constructed, due to COVID-19 impacts to the project host. PURPOSE: The purpose of the project was to test the hypothesis that a levelized cost of heat (LCOH) of 2¢/kWh delivered to a steam-consuming process, including energy discharged from storage, could be feasibly achieved. PROJECT OBJECTIVES: For Budget Period 1 our objectives were to engineer a prototype industrial solar steam generation system, and design and test a Latent Heat Energy Storage (LHES) lab-scale system. For Budget Period 2 our objectives were to construct and test the solar steam prototype plant, and to build and factory-test a full LHES module. For Budget Period 3 our objective was to integrate the storage module with the solar steam generator, show successful long duration energy tests of the combined system, and use the results to project the LCOH of delivered steam to a second-generation plant. PROJECT OUTCOMES: Various phase change materials (PCMs) for the LHES were tested for compatibility with industrial steam uses as measured by phase change temperature, stability of latent heat of fusion, and their corrosive effects on steel (the heat exchanger material). Two of these materials (sodium formate and sodium/ potassium) showed potential to meet the technical criteria. The estimated cost of a complete LHES module with these materials did not meet economic targets. The developmental collector design builds from previous work to exploit the potential cost advantages of a spaceframe of lumber construction. Design improvements were achieved in assembly efficiency and structural performance. A complete engineering package was completed for the solar steam system without storage that included the developmental as well as commercial arrays. The plant was permitted for construction. The storage CAPEX for a reference plant was estimate to be greater than $\$ 57$/kWh. The LCOH of the system without storage and with developmental collectors of lumber construction was projected to be 2¢/kWh, assuming a FCR of 8.2% over thirty years. PROJECT MILESTONES: The Milestones fully achieved in the first Budget Period includes obtaining a Letter of Intent from an industrial steam-consuming project host, issuance of a construction permit, and corrosion resistance. The Milestone that was partly achieved was the degradation in the latent heat of fusion. Milestones associated with Budget Periods 2 and 3, related to the construction and operation of the plant were not achieved as a result of the host shutting down the plant due to COVID-19 impacts. CONCLUSIONS: Sunvapor was able to secure an agreement with a host to build a fully engineered and permitted solar steam plant that met the host’s economic goals. As a basis for comparison, the solar field design was comprised of eight commercial collector arrays and one developmental Green Parabolic Trough Collector (GPTC) array. The projected LCOH with a solar field entirely populated with a second generation GPTC met the goal of 2¢/kWh. The experimental program concerning the PCM indicated the feasibility of meeting their technical requirements for industrial steam uses. The cost of the complete LHES exceeded its $\$ 14$/kWh target, and therefore the inclusion of LHES could not be economically justified. Due to COVID-19 impacts on the host, the solar steam plant was not constructed.

14 SOLAR ENERGY↗

DOE OSTI2012

An Energy Signature Scheme for Steam Trap Assessment and Flow Rate Estimation Using Pipe-Induced Acoustic Measurements

The US Congress has passed legislation dictating that all government agencies establish a plan and process for improving energy efficiencies at their sites. In response to this legislation, Oak Ridge National Laboratory (ORNL) has recently conducted a pilot study to explore the deployment of a wireless sensor system for a real-time measurement-based energy efficiency optimization framework within the steam distribution system within the ORNL campus. We make assessments on the real-time status of the distribution system by observing the state measurements of acoustic sensors mounted on the steam pipes/traps/valves. In this paper, we describe a spectral-based energy signature scheme that interprets acoustic vibration sensor data to estimate steam flow rates and assess steam traps health status. Experimental results show that the energy signature scheme has the potential to identify different steam trap health status and it has sufficient sensitivity to estimate steam flow rate. Moreover, results indicate a nearly quadratic relationship over the test region between the overall energy signature factor and flow rate in the pipe. The analysis based on estimated steam flow and steam trap status helps generate alerts that enable operators and maintenance personnel to take remedial action. The goal is to achieve significant energy-saving in steam lines by monitoring and acting on leaking steam pipes/traps/valves.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2019

Methane and Ethane Steam Reforming over MgAl2O4-Supported Rh and Ir Catalysts: Catalytic Implications for Natural Gas Reforming Application

Solar concentrators employed in conjunction with highly efficient micro- and meso-channel reactors offer the potential for cost-effective upgrading of the energy content of natural gas, providing a near-term path towards a future solar-fuel economy with reduced carbon dioxide emissions. To fully exploit the heat and mass transfer advantages offered by micro- and meso-channel reactors, highly active and stable natural gas steam reforming catalysts are required. In this paper, we report the catalytic performance of MgAl2O4-supported Rh (5 wt.%), Ir (5 wt.%), and Ni (15 wt.%) catalysts used for steam reforming of natural gas. Both Rh- and Ir-based catalysts are known to be more active and durable than conventional Ni-based formulations, and recently Ir has been reported to be more active than Rh for methane steam reforming on a turnover basis. Thus, the effectiveness of all three metals to perform natural gas steam reforming was evaluated in this study. Here, the Rh- and Ir-supported catalysts both exhibited higher activity than Ni for steam methane reforming. However, using simulated natural gas feedstock (94.5% methane, 4.0% ethane, 1.0% propane, and 0.5% butane), the Ir catalyst was the least active (on a turnover basis) for steam reforming of higher hydrocarbons (C2+) contained in the feedstock when operated at <750 °C. To further investigate the role of higher hydrocarbons, we used an ethane feed and found that hydrogenolysis precedes the steam reforming reaction and that C–C bond scission over Ir is kinetically slow compared to Rh. Catalyst durability studies revealed the Rh catalyst to be stable under steam methane reforming conditions, as evidenced by two 100-hour duration experiments performed at 850 and 900 °C (steam to carbon [S/C] molar feed ratio = 2.0 mol). However, with the natural gas simulant feed, the Rh catalyst exhibited catalyst deactivation, which we attribute to coking deposits derived from higher hydrocarbons contained in the feedstock. Increasing the S/C molar feed ratio from 1.5 to 2.0 reduced the deactivation rate and stable catalytic performance was demonstrated for 120 h when operated at 850 °C. However, catalytic deactivation was observed when operating at 900 °C. While improvements in steam reforming performance can be achieved through choice of catalyst composition, this study also highlights the importance of considering the effect of higher hydrocarbons contained in natural gas, operating conditions (e.g., temperature, S/C feed ratio), and their effect on catalyst stability. The results of this study conclude that a Rh-supported catalyst was developed that enables very high activities and excellent catalytic stability for both the steam reforming of methane and other higher hydrocarbons contained in natural gas, and under conditions of operation that are amendable to solar thermochemical operations.

03 NATURAL GAS↗

DOE OSTI2013

Incorporating Supercritical Steam Turbines into Molten-Salt Power Tower Plants: Feasibility and Performance

Sandia National Laboratories and Siemens Energy, Inc., examined 14 different subcritical and supercritical steam cycles to determine if it is feasible to configure a molten-salt supercritical steam plant that has a capacity in the range of 150 to 200 MWe. The effects of main steam pressure and temperature, final feedwater temperature, and hot salt and cold salt return temperatures were determined on gross and half-net efficiencies. The main steam pressures ranged from 120 bar-a (subcritical) to 260 bar-a (supercritical). Hot salt temperatures of 566 and 600°C were evaluated, which resulted in main steam temperatures of 553 and 580°C, respectively. Also, the effects of final feedwater temperature (between 260 and 320°C) were evaluated, which impacted the cold salt return temperature. The annual energy production and levelized cost of energy (LCOE) were calculated using the System Advisory Model on 165 MWe subcritical plants (baseline and advanced) and the most promising supercritical plants. It was concluded that the supercritical steam plants produced more annual energy than the baseline subcritical steam plant for the same-size heliostat field, receiver, and thermal storage system. Two supercritical steam plants had the highest annual performance and had nearly the same LCOE. Both operated at 230 bar-a main steam pressure. One was designed for a hot salt temperature of 600°C and the other 565°C. The LCOEs for these plants were about 10% lower than the baseline subcritical plant operating at 120 bar-a main steam pressure and a hot salt temperature of 565°C. Based on the results of this study, it appears economically and technically feasible to incorporate supercritical steam turbines in molten-salt power tower plants.

Pacheco, James Edward↗

DOE OSTI2024

Effective direct steam regeneration of bis-iminoguanidine solid sorbent used for carbon dioxide capture

A cost-effective, energy-efficient sorbent regeneration process for phase-changing guanidines used for CO 2 capture was developed based on direct-steam stripping. This approach enhances the regeneration rate, simplifies the overall CO 2 capture process, and reduces the energy cost compared to conventional conductive thermal regeneration. A direct-steam sorbent regeneration reactor was developed, demonstrating that aqueous bis(iminoguanidines) (BIG) sorbents, e.g., methylglyoxal-bis(iminoguanidine) (MGBIG) and glyoxal-bis(iminoguanidine) (GBIG), could be efficiently regenerated with up to ~ 99 % CO 2 recovery through direct-steam stripping. Using low-temperature steam at 100 °C, a 4.5 times faster regeneration rate for GBIG carbonate sorbent (e.g., 30 min for 10 g) was demonstrated compared to conductive-heating (e.g., 135 min for 10 g) at 130 °C. Additionally, fully regenerated MGBIG converts into an aqueous MGBIG solution when the steam condenses onto the sorbent surface. Condensed steam with the guanidine can be easily recycled as an aqueous solution into the gas–liquid contactor to achieve a continuous-flow CO 2 -capture process. Molecular dynamics simulation was employed to provide a better understanding of the process. Higher heat transfer rates from steam to guanidine carbonate, compared to air heating, were attributed to the vibration resonance of water molecules within MGBIG with that of vapor molecules and the effective transfer of kinetic energy from vapor to solid. Technoeconomic analysis demonstrated that direct-steam stripping significantly decreases the CO 2 capture cost by 50 % compared to traditional conductive heating methods. Further, enhanced mass transfer facilitated by low-temperature steam and subsequent condensation effectively heats up the H 2 O-containing BIG-carbonate crystals, facilitating the desorption of CO 2 from the solid crystals, thereby leading to fast, effective, and energy-efficient sorbent regeneration.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Influences of air calcination and steam activation on microstructure and photocatalytic activity of continuous TiO{sub 2} fibers

Graphical abstract: Display Omitted Highlights: ► Effects of air calcination and steam activation on TiO{sub 2} fibers were studied. ► The photocatalytic activity was evaluated by degradation of formaldehyde. ► Steam activation promoted the anatase–rutile phase transformation. ► Steam activation decreased grain size and increased special surface area. ► Steam activation improved photocatalytic activity of TiO{sub 2} fibers. -- Abstract: Effects of air calcination and steam activation, on phase transformation, microstructure and photocatalytic activity of continuous TiO{sub 2} fibers prepared by sol–gel method were studied. The fibers were characterized by XRD, SEM, and N{sub 2} adsorption–desorption. The photocatalytic activity was evaluated by photocatalytic degradation of formaldehyde. Results showed that 100% rutile fibers heat-treated in air and steam were obtained at 800 °C and 600 °C, respectively. The anatase grain sizes and special surface areas of the fibers heat-treated at 500 °C in air and steam were 31.6 nm, 22.7 nm, 26.7 m{sup 2}/g and 32.3 m{sup 2}/g, respectively. The degradation rates of formaldehyde over the fibers heat-treated at 500 °C in air and steam were 92.3% and 98.6% after 14 h under UV irradiation, respectively. Compared with the air calcination, the steam activation promoted the anatase–rutile phase transformation, reduced the grain size, increased the special surface area, and improved photocatalytic activity of continuous TiO{sub 2} fibers.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Evaluation of steam supply performance: Steamer vs. bubbler

Water/steam electrolysis is a key enabling technology for clean, low-carbon and sustainable production of hydrogen and will play a crucial role in future hydrogen economy. For high temperature solid oxide electrolytic cells, steam is the chemical feedstock. A stable and accurate supply of steam to solid oxide electrolytic cells is of vital importance to smooth production of hydrogen. In this study, we compare steam supply performance of two commonly used steam generators: steamer and bubbler. Our results show that bubbler with proper volume and fritted inlet gas tubing can provide more stable and accurate steam supply than steamer for laboratory use. We also provide the explanation for the unstable steam supply observed in steamer. Overall, we conclude that bubbler is generally a better choice for small-scale laboratory use (e.g., ≤50%H 2 O, ≤100 sccm carrier gas flow) to produce stable and accurate steam and steamer might be a better choice for higher steam contents and flow rates (e.g., >60% H 2 O and >200) encountered in large-scale testing and/or aggressive high steam conditions.

08 HYDROGEN↗

DOE OSTI2022

Materials for Advanced Ultra-Supercritical (A-USC) Steam Turbines --- A-USC Component Demonstration

The U.S. Advanced Ultra-Supercritical (A-USC) Consortium was formed in 2001 as a government/industry program, sponsored by the U.S. Department of Energy (DOE) and the Ohio Coal Development Office (OCDO) and cost shared by industrial and not-for-profit partners. The purpose of the consortium was to advance the state of the art for power generation by evaluating and developing materials that allow the use of advanced steam cycles in coal-based power plants. These advanced cycles, with steam temperatures up to 1400°F (760°C), can increase the efficiency of coal-fired boilers from an average of 35% (current U.S. fleet) to more than 45% higher heating value (HHV) (>49% lower heating value [LHV]). The increase in a plant’s efficiency is limited unless new materials able to withstand these higher operating temperatures and pressures are identified and approved for use. The A-USC Consortium identified these needed materials during earlier phases of the program. It developed the welding and joining techniques along with manufacturing processes for casting and wrought products made from these new high-nickel alloys. It subjected these materials to extensive laboratory and steam loop testing. It then obtained ASME code approval for their use in U.S. boiler systems. The program’s successes leave this last remaining activity (ComTest Phase 2) that the U.S. utility industry has recommended to be accomplished prior to commercialization. The focus of the activity is the evaluation and demonstration of commercial readiness for “full scale” components to be made from these nickel-based alloy materials and provided by a U.S. domestic supply chain that is new to working with these alloys. According to studies completed by the Electric Power Research Institute (EPRI), the cost of an A-USC plant is approximately 20% higher than a non-A-USC plant because of its use of nickel-based alloys needed for the high temperature operating conditions. However, CO 2 reductions of approximately 30% from the current fleet average provide a strong incentive for its consideration. The actual costs and perceived value for CO 2 abatement will determine whether new or retrofitted plants are undertaken, although decisions to build A-USC plants in India would indicate its economic feasibility while also being part of a global carbon emissions strategy. The work by the A-USC Consortium, prior to the start of the ComTest project, has included lab scale and pilot scale materials testing, both in air and oxy-combustion. This testing has included air-cooled and steam-cooled “loops” that were installed into existing operating utility boilers to gain exposure of these materials to realistic conditions of high temperature and corrosion caused by the constituents in the coal ash. The A-USC Consortium also gained ASME Code approval of the Inconel 740 material, has cast and extruded the largest high nickel precipitation hardened alloys, and developed unique welding techniques to avoid problems identified by the competing European program. However, as valuable as these material test loops and accomplishments have been for obtaining information, their scale is below that required to minimize the risk associated for a U.S. utility to build a multibillion-dollar A-USC power plant. To reduce the final identified risk barrier to full-scale commercialization of these advanced materials and systems, the A-USC Consortium (guided by a utility industry advisory committee) has identified the key areas of the technology they desire to see as being capable of full-scale manufacturing and/or fabrication from an identified, capable U.S. domestic supplier base. A significant amount of work was accomplished during Phase 1 to identity the components, as well as the component size, that would be manufactured from advanced alloys such as Inconel 740H or Haynes 282 alloys. Pathways to supply these components for ComTest have been identified, as well as any further development that would be required. The Phase 2 effort used Phase 1 findings for designing these key full-scale components for A-USC boilers and turbines to include large castings; extrusions, forgings, fabrication of water walls and steam loops with headers from advanced materials, raw material (such as pipe extrusion billets) are at the commercial readiness level to permit advancement to a demonstration project. The Phase 2 work scope was addressed by a diverse team, including government, industry, and not-for-profit partners. The work scope under Phase 2 addressed fabrication of components identified as being outside of the proven capabilities of the existing supply chain, including the following: Steam turbine rotor forging and Haynes 282 nozzle carrier casting Superheater and reheater header and tube assemblies Large-diameter pipe extrusions and forgings Test valve articles to support ASME Code approval. In addition, key fabrication steps were completed, including boiler weld overlays and simulated field repairs. Throughout, extensive inspection and quality assurance testing of the components were performed. The team worked to advance ASME Code approval for key components and processes. Although much of the focus of ComTest Phase 2 was the high-temperature nickel-based alloy materials, a broader range of materials were incorporated, which would be representative of the materials used in full-scale A-USC power plant applications and have cross-cutting applicability on other high-temperature power generation options, such as advanced nuclear, supercritical CO 2 cycles, and central solar receivers. This report that has been submitted is organized in the following manner: Section 1 contains an Executive Summary. Section 2 discusses the ComTest project background and organization. Section 3 discusses project management and reporting. Section 4 discusses the procurement of nickel-based alloy and other A-USC materials and components. Section 5 discusses the fabrication of procurement of nickel-based alloy and other A-USC materials and components. Section 6 discusses the fabrication of cast nickel-based A-USC steam turbine components. Section 7 discusses the fabrication of forged nickel-based A-USC steam turbine piping and steam pipe components. Section 8 discusses the qualification of pressure relieve valves (PRVs) for A-USC power plants. Section 9 discusses proposed plans for future evaluation of A-USC components. Section 10 contains the summary and conclusion.

01 COAL, LIGNITE, AND PEAT↗

NASA NTRS2009

Design Evolution and Verification of the A-3 Chemical Steam Generator

Following is an overview of the Chemical Steam Generator system selected to provide vacuum conditions for a new altitude test facility, the A-3 Test Stand at Stennis Space Center (SSC) in Bay St. Louis, MS. A-3 will serve as NASA s primary facility for altitude testing of the J-2X rocket engine, to be used as the primary propulsion device for the upper stages of the Ares launch vehicles. The Chemical Steam Generators (CSGs) will produce vacuum conditions in the test cell through the production and subsequent supersonic ejection of steam into a diffuser downstream of the J-2X engine nozzle exit. The Chemical Steam Generators chosen have a rich heritage of operation at rocket engine altitude test facilities since the days of the Apollo program and are still in use at NASA White Sands Test Facility (WSTF) in New Mexico. The generators at WSTF have been modified to a degree, but are still very close to the heritage design. The intent for the A-3 implementation is to maintain this heritage design as much as possible, making minimal updates only where necessary to substitute for obsolete parts and to increase reliability. Reliability improvements are especially desired because the proposed system will require 27 generators, which is nine times the largest system installed in the 1960s. Improvements were suggested by the original design firm, Reaction Motors, by NASA SSC and NASA WSTF engineers, and by the A-3 test stand design contractor, Jacobs Technology, Inc. (JTI). This paper describes the range of improvements made to the design to date, starting with the heritage generator and the minor modifications made over time at WSTF, to the modernized configuration which will be used at A-3. The paper will discuss NASA s investment in modifications to SSC s E-2 test facility fire a full-scale Chemical Steam Generator in advance of the larger steam system installation at A-3. Risk mitigation testing will be performed in early 2009 at this test facility to verify that the CSGs operate as expected. The generator which will undergo this testing is of the most recent A-3 configuration, and will be instrumented far in excess of what is normally required for operation. The extra data will allow for easier troubleshooting and more complete knowledge of expected generator performance. In addition, the early testing will give SSC personnel experience in operating the CSG systems, which will expedite the process of installation and activation at A-3. Each Chemical Steam Generator is supported by a complement of valves, instruments, and flow control devices, with the entire assembly called a "module." The generators will be installed in groups of three, historically called "units". A module is so called because of its modular ability to be replaced or serviced without disturbing the other two modules installed on the same unit. A module is pictured in Figure 1, shown with its generator secured by white bands in its shipping (vs. installed) configuration. The heritage system at WSTF is composed of a single unit (three generator modules), pictured in Figure 2 as it was installed in 1965. In contrast, A-3 will have nine units operating in parallel to achieve vacuum conditions appropriate for testing the J-2X engine. Each of the combustors operates in two modes and achieves the so-called "full-steam" mode after all three of its stages ignite. Ignition of the first stage is achieved by exciting a spark plug; the second stage and main stage are lit by the flame front of the previous stage. The main stage burns approximately 97% of the total propellant flow and uses the heat energy to vaporize water into superheated steam. While the main stage remains unlit, the combustor is in so-called "idle" mode. In the WSTF system, this idle mode is not optimized for water usage, and does not need to be, as the water is pumped from a large reservoir. The water supply at A-3 will be contained in tanks with finite volume, so water optimization is preferred for the modnized configuration. Multiple solutions for this issue have been proposed, with the leading concept being a change to the operational definition of "idle mode," with the generator running in a lower heat flux condition.

Kirchner, Casey K.↗

DOE OSTI2016

Apparatus and method for acoustic monitoring of steam quality and flow

An apparatus and method for noninvasively monitoring steam quality and flow and in pipes or conduits bearing flowing steam, are described. By measuring the acoustic vibrations generated in steam-carrying conduits by the flowing steam either by direct contact with the pipe or remotely thereto, converting the measured acoustic vibrations into a frequency spectrum characteristic of the natural resonance vibrations of the pipe, and monitoring the amplitude and/or the frequency of one or more chosen resonance frequencies, changes in the steam quality in the pipe are determined. The steam flow rate and the steam quality are inversely related, and changes in the steam flow rate are calculated from changes in the steam quality once suitable calibration curves are obtained.

47 OTHER INSTRUMENTATION↗

DOE OSTI2019

Apparatus and method for acoustic monitoring of steam quality and flow

02 PETROLEUM↗

DOE OSTI2016

Experimental study on the guillotine break accident of the main steam line with Atlas

A main steam line break (MSLB) accident is defined as a pipe break in the main steam system of a nuclear power plant. The MSLB accident is characterized as cool-down event due to the increased steam flow rate, which causes excessive energy removal from the steam generators and eventually reactor coolant system. This results in a decrease in reactor coolant temperature. The cool-down causes an increase in core reactivity due to the negative moderator and Doppler reactivity coefficients. The thermalhydraulic integral effect test was performed to simulate a double-ended guillotine break accident of the main steam line of a pressurized water reactor. With an aim of simulating the MSLB accident as realistically as possible, a pertinent scaling approach was taken, especially focusing on a break flow. The main objectives of this test were not only to provide physical insight into the system response of a nuclear power plant during the MSLB accident but also to produce an integral effect test data to validate the safety analysis codes. In the present test, asymmetric thermal-hydraulic behavior was clearly observed between the loops. In the cold leg-1A and -1B where the affected steam generator is connected, the flow rates were higher and the fluid temperatures were lower than those in the cold leg-2A and -2B. This could be attributed to the excessive heat removal in the cold leg-1A and -1B through the affected steam generator. This integral effect test data will be used to evaluate the prediction capability of existing safety analysis codes. Furthermore, this data can be utilized to identify any code deficiency for a MSLB simulation, especially for DVI-adapted plants. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2018

The Role of Biomass Composition and Steam Treatment on Durability of Pellets

Steam treatment has been reported to improve the durability of wood pellet likely by changing the physical and chemical structures of wood particles, but published literature is inconclusive about which structure change is the major reason for enhanced durability. Here, in this paper, steam treatment was combined either with alkaline or with SO 2 to study. The solids obtained after steam treatments along with a control sample were dried and each was compacted into pellets. The pellets were then tested for durability. Steam treatment alone dominated improvements in durability. The pellet durability increased with the amount of xylose, but xylose performed better in the pellet from raw poplar than did in the pellet from treated poplar. Water-soluble components contributed a maximum 4% of the durability of poplar pellets. The addition of lignin and sugars to substrates after steam treatment did not improve durability significantly. The surface modification that took place as a result of size reduction during steam treatment was the major reason, contributing about 50% of the durability of the pellet from steam-treated poplar. The acidity of steam treatment slightly affected the relative contributions of these structure changes on the durability. Lastly, the new knowledge helps tailor the chemical and/or mechanical pretreatment involved in pelleting biomass to durable pellets.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2015

Steam explosion of oil palm residues for the production of durable pellets

Here we investigated the effect of steam explosion pretreatment on the physical and mechanical properties of the pellets made from empty fruit bunch (EFB) and palm kernel shell (PKS) and we compared to that of softwood Douglas fir (DF). We found that the high heating value of the empty fruit bunch was increased by 21% after steam explosion pretreatment. The pellet density of EFB and Douglas fir pellets did not change while the pellet density of PKS increased from 1.13 to 1.21 g/cm 3 after steam explosion. That may be attributed to the rapid volatilization of high mass fraction extractives during high pressure steaming and lead to the shrinkage of micropores of the PKS fibers. The maximum brealdng strength of steam exploded EFB and PKS were increased by 63% and 45%, respectively. The required compaction energy for the steam exploded EFB pellet is 44.50 J/g while that of the untreated EFB pellet is 30.15 J/g. Similar to Douglas fir, the required extrusion energy for the steam exploded EFB pellet was about 6 times than that of the untreated EFB pellet. The increased extrusion energy is mainly contributed by the increase in mono-saccharides by auto-hydrolysis during steam explosion pretreatment.

09 BIOMASS FUELS↗

DOE OSTI2023

Experimental study on kinetic oxidation of graphite IG-110 by steam

Graphite is proposed for use in High-temperature Gas-cooled Reactors (HTGRs) as the fuel matrix, neutron moderator/reflector, and core structural material. One important property of nuclear grade graphite is their resistance to oxidation in high-temperature environment. Extensive investigation has been performed in the literature for graphite oxidation by air. However, available experimental data are still limited for graphite oxidation by steam under conditions comparable to a postulated steam ingress accident in HTGRs. In this study, the oxidation rate of graphite IG-110 by steam was measured at temperatures from 850 to 1100 °C with the steam partial pressure varying from 0.5 to 20.0 kPa and the hydrogen partial pressure varying from 0 to 2.0 kPa. Further analysis confirms the oxidation process in this present study is dominated by the chemical kinetics, which lends credit to the data for being used to develop numerical models. It was observed that the increase of the kinetic oxidation rate with the steam partial pressure tends to become less apparent if the steam partial pressure keeps increasing. In addition, it was found that the partitioning of hydrogen inhibits the graphite-steam reaction process even with the steam partial pressure up to 20.0 kPa. However, this inhibiting effect starts to become saturated when the hydrogen partial pressure exceeds 1.0 kPa. The oxidation rates were fitted to the conventional Langmuir-Hinshelwood (LH) and Boltzmann-enhanced Langmuir-Hinshelwood (BLH) models by a multivariable optimization algorithm. The BLH model exhibits a better accuracy than the LH model within the specified experimental conditions. The predicted oxidation rate using the BLH model shows a mean relative difference of about 24% with the maximum difference of about 55% when compared with our experimental data.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2018

3-D Unsteady Model for Be-Steam Reaction in Water-Cooled Ceramic Breeder Blanket

Here, the design of the water-cooled ceramic breeder (WCCB) blanket includes beryllium multiplier layers. At elevated temperature, beryllium reacts with steam in an exothermic reaction producing beryllium oxide and hydrogen. Such situation may occur in WCCB in the case of the rupture of one of the cooling pipes in the blanket module. This process occurs locally in a complex 3-D geometry of the blanket containing several different granular levels and a network of cooling pipes and structural supports. The process is also inherently unsteady since reaction rate depends on concentration of steam and pure beryllium which changes in time. In order to perform the detailed analysis of the process, the model of the reacting flowthrough porous media was developed and introduced into 3-D computational fluid dynamics code. In this model, granular beds are introduced as porous solids simplifying the model geometry and reducing typical mesh size to manageable amount of tens of millions of elements. A reaction rate between solid beryllium and steam is obtained from experimental results, and depends on temperature and concentration of the reactants. The differential equation for beryllium oxide fraction is introduced, allowing obtaining distributions of beryllium oxide in space and time. Multicomponent flow consisting of a homogenous mixture of steam and hydrogen is considered flowing through the porous solid with variable properties. Sink and source terms for steam and hydrogen fractions are determined by local beryllium oxide mass fraction source according to the molar ratios of beryllium steam reaction. The conjugated heat transfer approach is applied to calculate heat transfer in support structures as well as coolant flow, simultaneously with the porous medium steam flow in a blanket's granular beds. The model is validated using experimental data on beryllium steam reaction for granular bed samples.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2017

Steam Reforming of Acetic Acid over Co-Supported Catalysts: Coupling Ketonization for Greater Stability

We report on the markedly improved stability of a novel 2-bed catalytic system, as compared to a conventional 1-bed steam reforming catalyst, for the production of H2 from acetic acid. The 2-bed catalytic system comprises of i) a basic oxide ketonization catalyst for the conversion of acetic acid to acetone, and a ii) Co-based steam reforming catalyst, both catalytic beds placed in sequence within the same unit operation. Steam reforming catalysts are particularly prone to catalytic deactivation when steam reforming acetic acid, used here as a model compound for the aqueous fraction of bio-oil. Catalysts comprising MgAl2O4, ZnO, CeO2, and activated carbon (AC) both with and without Co-addition were evaluated for conversion of acetic acid and acetone, its ketonization product, in the presence of steam. It was found that over the bare oxide support only ketonization activity was observed and coke deposition was minimal. With addition of Co to the oxide support steam reforming activity was facilitated and coke deposition was significantly increased. Acetone steam reforming over the same Co-supported catalysts demonstrated more stable performance and with less coke deposition than with acetic acid feedstock. DFT analysis suggests that over Co surface CHxCOO species are more favorably formed from acetic acid versus acetone. These CHxCOO species are strongly bound to the Co catalyst surface and could explain the higher propensity for coke formation from acetic acid. Based on these findings, in order to enhance stability of the steam reforming catalyst a dual-bed (2-bed) catalyst system was implemented. Comparing the 2-bed and 1-bed (Co-supported catalyst only) systems under otherwise identical reaction conditions the 2-bed demonstrated significantly improved stability and coke deposition was decreased by a factor of 4.

Environmental Molecular Sciences Laboratory↗