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supercritical pressures
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Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 930-938, October 21–24, 2019,
... Abstract Direct-fired supercritical CO 2 (sCO 2 ) cycles are expected to result in sCO 2 with higher impurity levels compared to indirect-fired cycles. Prior work at ambient pressure showed minimal effects of O 2 and H 2 O additions, however, a new experimental rig has been built to have...
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Direct-fired supercritical CO 2 (sCO 2 ) cycles are expected to result in sCO 2 with higher impurity levels compared to indirect-fired cycles. Prior work at ambient pressure showed minimal effects of O 2 and H 2 O additions, however, a new experimental rig has been built to have flowing controlled impurity levels at supercritical pressures at ≤800°C. Based on industry input, the first experiment was conducted at 750°C/300 bar in CO 2 +1%O 2 -0.25%H 2 O using 500-h cycles for up to 5,000 h. Compared to research grade sCO 2 , the results indicate faster reaction rates for Fe-based alloys like 310HN and smaller increases for Ni-based alloys like alloys 617B and 282. It is difficult to quantify the 310HN rate increase because of scale spallation. Characterization of the 5,000 h specimens indicated a thicker reaction product formed, which has not been observed in previous impurity studies at ambient pressure. These results suggest that more studies of impurity effects are needed at supercritical pressures including steels at lower temperatures.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 844-854, October 11–14, 2016,
..., ppm levels of O2, H2O, etc.) [11-19]. A few studies have begun to look at the effect of impurities in CO2 at high temperature and pressure [20-22]. However, there are few experimental facilities 844 where impurities of 1-10%H2O and 1-3%O2 can be controlled and monitored at supercritical pressures...
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In both direct- and indirect-fired supercritical CO 2 (sCO 2 ) cycles, there is considerable interest in increasing the size and efficiency of such systems, perhaps by increasing the peak temperature to >700°C. However, relatively little experimental data are available under these conditions with pressures of 200-300 bar. Furthermore, impurities such as O 2 and H 2 O in the CO 2 may greatly alter the compatibility of structural alloys in these environments. While an experimental rig is being constructed that can measure and control the impurity levels in sCO 2 at 200-300 bar, initial 1 bar experiments at 700°-800°C for 500 h have been conducted in high-purity and industrial grade CO 2 , CO 2 +0.15O 2 and CO 2 +10%H 2 O and compared to exposures in dry air and 200 bar sCO 2 . These results, focusing on Fe- and Ni-base structural alloys and commercial chromia- and alumina-forming alloys, indicate that modifications in the environment did not strongly affect the reaction products at 700°-800°C.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 1183-1194, October 15–18, 2024,
... Abstract Supercritical carbon dioxide cooling during machining has been identified as an effective measure to mitigate the risk of stress corrosion cracking in materials utilized in the primary circuit of light water reactors, particularly in pressure vessel structural steels. This study aims...
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Supercritical carbon dioxide cooling during machining has been identified as an effective measure to mitigate the risk of stress corrosion cracking in materials utilized in the primary circuit of light water reactors, particularly in pressure vessel structural steels. This study aims to compare two different cooling methods, the novel supercritical carbon dioxide and conventional high pressure soluble oil, employed during both milling and turning processes for SA508 Grade 3 Class 2 and AISI 316L steels. As the surface conditions of materials are critical to fatigue properties, such as crack initiation and endurance life, the fatigue performance of both cooling methods for each process were then evaluated and the impact on properties determined. To compare the potential benefits of supercritical carbon dioxide cooling against conventional soluble oil cooled machining, fatigue specimens were machined using industry relevant CNC machine tools. Surface finish and machining methods were standardized to produce two different specimen types, possessing dog- bone (milled) and cylindrical (turned) geometries. Force-controlled constant amplitude axial fatigue testing at various stress amplitudes was undertaken on both specimen types in an air environment and at room temperature using a stress ratio of 0.1. The fatigue performance of the supercritical carbon dioxide cooled specimens revealed substantially greater endurance lives for both SA508 and 316L materials, when compared with specimens machined using high pressure soluble oil cooling.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 86-97, October 22–25, 2013,
... the fluid moves up twice through the same elevation, then a third pass continues up to the roof [6]. Exit fluid temperature reaches about 385C (725F). Enclosure circulation requires increasing pressure to 24.1 MPa (3500 psi) supercritical operation (called constant pressure) after the convection pass outlet...
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Increasing the efficiency of the Rankine regenerative-reheat steam cycle to improve the economics of electric power generation and to achieve lower cost of electricity has been a long sought after goal. Advanced ultra-supercritical (A-USC) development for materials to reach 760C (1400F) is a goal of the U.S. Program on Materials Technology for Ultrasupercritical Coal-Fired Boilers sponsored by the United States (U.S.) Department of Energy and the Ohio Coal Development Office (OCDO). As part of the development of advanced ultra-supercritical power plants in this program and internally funded programs, a succession of design studies have been undertaken to determine the scope and quantity of materials required to meet 700 to 760C (1292 to 1400F) performance levels. At the beginning of the program in 2002, the current design convention was to use a “two pass” steam generator with a pendant and horizontal tube bank arrangement as the starting point for the economic analysis of the technology. The efficiency improvement achieved with 700C (1292F) plus operation over a 600C (1112F) power plant results in about a 12% reduction in fuel consumption and carbon dioxide emissions. The reduced flue gas weight per MW generated reduces clean up costs for the lower sulfur dioxide, nitrogen oxides and particulate emissions. The operation and start up of the 700C (1292F) plant will be similar in control methods and techniques to a 600C (1112F) plant. Due to arrangement features, the steam temperature control range and the once through minimum circulation flow will be slightly different. The expense of nickel alloy components will be a strong economic incentive for changes in how the steam generator is configured and arranged in the plant relative to the steam turbine. To offer a view into the new plant concepts this paper will discuss what would stay the same and what needs to change when moving up from a 600C (1112F) current state-of-the-art design to a plant design with a 700C (1292F) steam generator and turbine layout.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 885-896, October 15–18, 2024,
... Diego, CA. 894 [12] Pint B. A., Brese, R. G., High-Temperature Materials, in Fundamentals and Applications of Supercritical Carbon Dioxide Based Power Cycles, K. Brun and P. Friedman, eds., Elsevier, London, (2017), pp.67-104. [13] Pint, B. A., Brese, R. G., Keiser, J. R., Effect of Pressure...
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Supercritical CO 2 (sCO 2 ) is of interest as a working fluid for several concepts including the direct- fired Allam cycle as a low-emission fossil energy power cycle. Over the past 10 years, laboratory exposures at 300 bar sCO 2 have found reasonably good compatibility for Ni-based alloys at <800°C, including an assessment of the sCO 2 impact on room temperature mechanical properties after 750°C exposures. However, initial screening tests at 1 and 20 bar CO 2 at 900°-1100°C showed poor compatibility for Ni-based alloys. In an open cycle, the introduction of 1%O 2 and 0.1- 0.25%H 2 O impurities at 300 bar increased the reaction rates ≥2X at 750°C. At lower temperatures, steels are susceptible to C ingress and embrittlement. Creep-strength enhanced ferritic steels may be limited to <550°C and conventional stainless steels to <600°C. Two strategies to increase those temperatures are higher Ni and Cr alloying additions and Al- or Cr-rich coatings. Alloy 709 (Fe- 20Cr-25Ni) shows some promising results at 650°C in sCO 2 but reaction rates were accelerated with the addition of O 2 and H 2 O impurities. Pack aluminized and chromized Gr.91 (Fe-9Cr-1Mo) and type 316H stainless steel show some promise at 600°-650°C but further coating optimization is needed.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 602-622, October 25–28, 2004,
... Abstract Current state-of-the-art coal-fired supercritical steam power plants operate with high-pressure turbine inlet steam temperatures close to 600°C. The best of the recently developed and commercialized advanced 9-12Cr martensitic-ferritic steels may allow prolonged use at temperatures...
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Current state-of-the-art coal-fired supercritical steam power plants operate with high-pressure turbine inlet steam temperatures close to 600°C. The best of the recently developed and commercialized advanced 9-12Cr martensitic-ferritic steels may allow prolonged use at temperatures to about 620°C, but such steels are probably close to their inherent upper temperature limit. Further increase in the temperature capability of advanced steam turbines will certainly require the use of Ni-based superalloys and system redesign, as seen in the European programs that are pioneering advanced power plants capable of operating with 700°C steam. The U.S. Department of Energy (DOE) has recently undertaken a concerted effort to qualify ultra-supercritical boiler tubing and piping alloys for 720/760°C steam for increased efficiency and reduced emissions. It is, therefore, necessary to develop the corresponding USC steam turbine, also capable of reliable operation at such conditions. This paper summarizes a preliminary assessment made by the Oak Ridge National Laboratory (ORNL) and the National Energy Technology Laboratory (NETL) of materials needed for ultra-supercritical (USC) steam turbines, balancing both technical and business considerations. These efforts have addressed an expanded portfolio of alloys, that includes austenitic stainless steels and alloys, in addition to various Ni-based superalloys for critical turbine components. Preliminary input from utilities indicates that cost-effective improvements in performance and efficiency that do not sacrifice durability and reliability are prime considerations for any advanced steam turbine technology.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 451-462, October 25–28, 2004,
... alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections. Initial results of this research are presented. coal generation coal power plants steam temperature steam turbines ultra supercritical steamside oxidation httpsdoi.org/10.31399...
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Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions, which are goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives. Most current coal power plants in the U.S. operate at a maximum steam temperature of 538°C. However, new supercritical plants worldwide are being brought into service with steam temperatures of up to 620°C. Current Advanced Power Systems goals include coal generation at 60% efficiency, which require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections. Initial results of this research are presented.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 924-930, October 11–14, 2016,
... out in a supercritical water (SCW) autoclave at 700°C/250 bar with 150 ppb dissolved oxygen in the inlet flow and a pH of 7 (measured at room temperature in the low pressure part of the recirculation loop). The test duration was up to 1000 h. The autoclave is connected to a recirculation water loop...
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High efficiency in power generation is not only desirable because of economical reasons but also for enhanced environmental performance meaning reduced quantity of forming ash and emissions. In modern medium to large size plants, improvements require supercritical steam values. Furthermore, in future there will be an increasing share of renewables, such as wind and solar power, which will enhance the fluctuation of supply with the consequence that other power sources will have to compensate by operating in a more demanding cyclic or ramping mode. The next generation plant will need to operate at higher temperatures and pressure cycles coupled with demanding hot corrosion and oxidation environments. Such an operation will significantly influence the performance of materials used for boilers and heat exchanger components by accelerating oxidation rates and lowering mechanical properties like creep resistance. The paper discusses the oxidation behaviour of San25, 800H and alloy 263 in supercritical water at temperatures 650 and 700 °C at 250 bar, and compares the changes of mechanical properties of materials at these temperatures.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 254-264, October 22–25, 2013,
... Abstract Significant development is being carried out worldwide for establishing advanced ultra supercritical power plant technology which aims enhancement of plant efficiency and reduction of emissions, through increased inlet steam temperature of 750°C and pressure of 350 bar. Nickel base...
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Significant development is being carried out worldwide for establishing advanced ultra supercritical power plant technology which aims enhancement of plant efficiency and reduction of emissions, through increased inlet steam temperature of 750°C and pressure of 350 bar. Nickel base superalloy, 50Ni-24Cr-20Co-0.6Mo-1Al-1.6Ti-2Nb alloy, is being considered as a promising material for superheater tubes and turbine rotors operating at ultra supercritical steam conditions. Thermal fluctuations impose low cycle fatigue loading in creep regime of this material and there is limited published fatigue and creep-fatigue characteristics data available. The scope of the present study includes behavior of the alloy under cyclic loading at operating temperature. Strain controlled low cycle fatigue tests, carried out within the strain range of 0.2%-1%, indicate substantial hardening at all temperatures. It becomes more evident with increasing strain amplitude which is attributed to the cumulative effects of increased dislocation density and immobilization of dislocation by γ′ precipitates. Deformation mechanism which influences fatigue life at 750°C as a function of strain rate is identified. Hold times up to 500 seconds are introduced at 750°C to evaluate the effect of creep fatigue interaction on fatigue crack growth, considered as one of the primary damage mode. The macroscopic performance is correlated with microscopic deformation characteristics.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 791-802, October 22–25, 2013,
... Abstract To improve the efficiency of fossil fuel power plants the operating temperatures and pressures need to be increased. However, at high temperatures the steam side oxidation resistance becomes a critical issue for the steels used especially at the final stages of superheaters...
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To improve the efficiency of fossil fuel power plants the operating temperatures and pressures need to be increased. However, at high temperatures the steam side oxidation resistance becomes a critical issue for the steels used especially at the final stages of superheaters and reheaters. Apart from the chemical composition of the material, surface condition is a major factor affecting the oxidation resistance in steam and supercritical water. In this paper, stainless boiler steels (UNS S34710, S31035, S31042, and S30942) are investigated for oxidation resistance in flowing supercritical water. Tests were conducted in an autoclave environment (250 bar, with 125 ppb dissolved oxygen and a pH of 7) at 625°C, 650°C and 675°C for up to 1000 h. Materials were tested with as-delivered, shot peened, milled or spark eroded and ground surface finish. The results show a strong influence of surface finish at the early stages of oxidation. Oxides formed on cold worked surfaces were more adherent and much thinner than on a spark eroded and ground surface. This effect was stronger than the influence of temperature or alloy composition within the tested ranges.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 552-558, October 25–28, 2004,
... Abstract Improving power plant efficiency through supercritical steam pressures and very high steam temperatures up to 700°C and beyond is an effective approach to reducing fuel consumption and CO2 emissions. However, these extreme steam temperatures necessitate the use of nickel-base alloys...
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Improving power plant efficiency through supercritical steam pressures and very high steam temperatures up to 700°C and beyond is an effective approach to reducing fuel consumption and CO2 emissions. However, these extreme steam temperatures necessitate the use of nickel-base alloys in the high-pressure/intermediate-pressure turbine sections requiring very large component sections that cannot be met by steels. Saarschmiede, involved in manufacturing large components for the power generation industry and research programs on advanced 9-12% chromium steels, has extensive experience producing nickel and cobalt-base alloy forgings for applications like aircraft engines, aerospace, land-based gas turbines, and offshore. This paper reports on the manufacturing and testing of large-section forgings made from candidate nickel-base alloys like 617 and 625 for high-pressure/intermediate-pressure turbine components in power stations operating at 700°C and higher steam temperatures.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 55-65, October 11–14, 2016,
... strength have led to increased use of thermo-mechanically processes stainless steels such as Super 304H and 347HFG, inner diameter (ID) shot peeing, and higher chromium alloys such as HR3C [2]. With respect to waterwall tubing, the concern is twofold. High supercritical pressures and the use of high heat...
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Early supercritical units such as American Electric Power (AEP) Philo U6, the world’s first supercritical power plant, and Eddystone U1 successfully operated at ultrasupercritical (USC) levels. However due to the unavailability of metals that could tolerate these extreme temperatures, operation at these levels could not be sustained and units were operated for many years at reduced steam (supercritical) conditions. Today, recently developed creep strength enhanced ferritic (CSEF) steels, advanced austenitic stainless steels, and nickel based alloys are used in the components of the steam generator, turbine and piping systems that are exposed to high temperature steam. These materials can perform under these prolonged high temperature operating conditions, rendering USC no longer a goal, but a practical design basis. This paper identifies the engineering challenges associated with designing, constructing and operating the first USC unit in the United States, AEP’s John W. Turk, Jr. Power Plant (AEP Turk), including fabrication and installation requirements of CSEF alloys, fabrication and operating requirements for stainless steels, and life management of high temperature components
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 347-355, October 11–14, 2016,
... Failure Analysis, Vol. 50, (2015), pp20-28. [6] Viswanathan, R., Coleman, K. C., Materials for Ultra-Supercritical Coal-Fired Power Plant Boilers, Pressure Vessels and Piping, Vol. 83, (2006), pp778 783. 355 Copyright © 2016 ASM International. All rights reserved. 2016 ASM International ...
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Up to now, the amount of supercritical boilers in China has ranked number one in the world. Many supercritical boilers have run for more than 100,000 hours. Creep becomes one of the main reasons for supercritical boiler tubes failure. In this article, the failure of superheater tubes in a supercritical boiler was analyzed, the microstructural evolution of austenitic stainless steel tubes were studied, a full investigation into the failure cause was carried out involving in visual examination, optical microscope, SEM, TEM and XRD. The results show, sigma phase precipitates in this austenitic steel with the extension of service time, sigma precipitates form at grain boundaries by continuous chain. Sigma precipitates are hard and brittle, weaken grain boundaries and cause microscopic damage, eventually lead to boiler tubes failure.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1215-1223, October 21–24, 2019,
... Abstract Both of high pressure main throttle valves and one governing valves were jammed during the cold start of steam turbine served for 8541 hours at 600 °C in an ultra supercritical power plant. Other potential failure mechanisms were ruled out through a process of elimination, such as low...
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Both of high pressure main throttle valves and one governing valves were jammed during the cold start of steam turbine served for 8541 hours at 600 °C in an ultra supercritical power plant. Other potential failure mechanisms were ruled out through a process of elimination, such as low oil pressure of digital electro-hydraulic control system, jam of orifice in the hydraulic servo-motor, and the severe bending of valve stem. The root cause was found to be oxide scales plugged in clearances between the valve disc and its bushing. These oxide scales are about 100~200 μm in thickness while the valve clearances are about 210~460 μm at room temperature. These oxide scales are mainly composed of Fe 3 O 4 and Fe 2 O 3 with other tiny phases. Both of valve disc and its bushing were treated with surface nitriding in order to improve its fatigue resistance, which unexpectedly reduces the steam oxidation resistance. On the other hand, significant fluctuation of valve inner wall temperature during operation accelerated the exfoliation of oxide scales, and the absence of full stroke test induced the gradual accumulation of scales in valve clearances. In light of the steam valve jam mechanism in the present case, treatments in aspects of operation and resistance to steam oxidation are recommended.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 460-469, October 21–24, 2019,
... Abstract Materials are the key to develop advanced ultra-supercritical (A-USC) steam generators. Operating at temperature up to 760°C and sustained pressure up to 4500 psi. Pressure vessel and piping materials may fail due to creep, oxidation, and erosion. Valves are particularly subjected...
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Materials are the key to develop advanced ultra-supercritical (A-USC) steam generators. Operating at temperature up to 760°C and sustained pressure up to 4500 psi. Pressure vessel and piping materials may fail due to creep, oxidation, and erosion. Valves are particularly subjected to loss of function and leakage due to impermeant of the sealing surfaces. New materials, less susceptible to the above damage modes are needed for A-USC technology. Two Ni-based superalloys have been identified as prime candidates for valves based materials. Hardfacing is applied to sealing surfaces to protect them from wear and to reduce friction. Stellite 6 (Cobalt-based alloy) is the benchmark hardfacing owing to its anti-galling properties. However, the latest results tend to indicate that it is not suitable for high pressure application above 700°C. An alternative hardfacing will be required for A-USC. New Ni- and Co- based alloys are being developed for applications where extreme wear is combined with high temperatures and corrosive media. Their chemistry accounts for the excellent dry-running properties of these alloys and makes them very suitable for use in adhesive (metal-to- metal) wear. These new alloys have better wear, erosion, and corrosion resistance than Stellite 6 in the temperature range 800°C ~ 1000°C. As such, they have the potential to operate in A-USC. Velan recently developed an instrumented high temperature tribometer in collaboration with Polytechnique Montreal to characterize new alloys including static and dynamic coefficients of friction up to 800°C. We present herein the methodology that has been devolved to explore the effects of elevated temperature on the tribological behavior of those advanced material systems, with the goal of capturing the basis for the specification, design, fabrication, operation, and maintenance of valves for A-USC steam power plants.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1268-1282, October 22–25, 2013,
... Abstract Alloy 718, widely used for its high-temperature performance in various applications, is being investigated for use in advanced power plants. Driven by the need for efficiency improvements, these plants demand higher temperatures and pressures, putting significant stress on critical...
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Alloy 718, widely used for its high-temperature performance in various applications, is being investigated for use in advanced power plants. Driven by the need for efficiency improvements, these plants demand higher temperatures and pressures, putting significant stress on critical components like boiler tubes and turbines. With existing steels and alloys struggling at such high temperatures, researchers are exploring alternatives. New generation plants target steam turbine inlet temperatures of 720°C and pressures of 350MPa, necessitating superalloys for high- and intermediate-pressure rotor sections. The Thermie Advanced project explored the potential of 718 for these applications. A trial rotor disk, forged using advanced processes, underwent a novel heat treatment to enhance microstructural stability and improve creep behavior. Ongoing creep tests exceeding 100,000 hours suggest a potential 50°C increase in the operational limit compared to standard 718. This 12-year research effort holds promise for utilizing 718 in forged components of advanced ultra-supercritical power plant steam turbines, potentially operating up to 700°C.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 647-654, October 21–24, 2019,
... up to 20 000 hours. The morphology of the oxide scale and the microstructure of the bulk material were investigated. In addition, the effect of surface finish and pressure on the steam oxidation were also studied. advanced ultra-supercritical fossil power plants austenitic stainless steel...
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Sanicro 25 material is approved for use in pressure vessels and boilers according ASME code case 2752, 2753 and VdTUV blatt 555. It shows higher creep rupture strength than any other austenitic stainless steels available today. It is a material for superheater and reheaters, enabling higher steam parameters of up to about 650 °C steam (ie about max 700 °C metal) without the need for expensive nickel based alloys. The aim of the present study is the investigation of the steam oxidation resistance of the Sanicro 25. The long term test was conducted in the temperature range 600 -750 °C up to 20 000 hours. The morphology of the oxide scale and the microstructure of the bulk material were investigated. In addition, the effect of surface finish and pressure on the steam oxidation were also studied.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 823-831, October 11–14, 2016,
... and ultrasonically degreased in ethanol. Exposure testing was carried out in a supercritical water (SCW) autoclave at 650°C/250 bar with 150 ppb dissolved oxygen in the inlet flow and a pH of 7 (measured at room temperature in the low pressure part of the recirculation loop). The test durations were 1200 h and 1800...
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For higher efficiency and competitive overall performance, it would be an advantage to be able to safely exceed the highest operational values, currently up to about 600-620°C/25-30 MPa in supercritical (SC) boiler plants. Under such operating conditions the oxidation resistance in SC water tends to limit the potential for further improvement of efficiency. The way to increase the oxidation resistance of traditional austenitic boiler tubes e.g. TP 347H is to do additional cold work on the boiler tube inner surface. In the current paper the effect of cold work on the oxidation resistance of TP347H and TP347HFG has been evaluated by shot peened samples with different parameters and subjecting those samples to supercritical oxidation exposure. The results show an improvement in the oxidation resistance of the alloys, especially in the large grained alloy TP347H. Also the uniformity of the deformation layer was seen to have an influence on the oxidation resistance, since the oxide nodules start to grow at locations with the thinnest or no deformation layer.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 1001-1009, October 11–14, 2016,
... Abstract The efficiency of power plants is depending on the steam temperature and/or the steam pressure. Efficiency increasing from 35% to 42-45% require increasing of the steam temperature over 600°C and the pressure over 26 MPa. According to the designer opinion it is not profitable to use...
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The efficiency of power plants is depending on the steam temperature and/or the steam pressure. Efficiency increasing from 35% to 42-45% require increasing of the steam temperature over 600°C and the pressure over 26 MPa. According to the designer opinion it is not profitable to use classical low alloy creep resistant steels 16Mo3, 13CrMo4-5 or 10CrMo9-10 for membrane waterwall construction for these service condition. New modified low alloy creep resistance T23 and T24 (7CrMoVTiB10-10) steels were developed for membrane waterwalls. Welding of these steels with small thickness (around 6.3 mm) should be enabled without preheating and post weld heat treatment (PWHT) due to the lower carbon content below 0.1%. High creep rupture strength (CRS) values are achieved by Ti, N and B elements alloyed to T24 steel. The original expectation that the welding small thickness without preheating was early overcome and was wrong. According to the present experience the T24 steel is welded with preheating at 150-250°C depending on the wall thickness and welded joint toughness in order to achieve required hardness and impact toughness values. Opinions on the T24 welded joints post weld heat treatment (PWHT) requirements are still inconsistent. Especially the membrane waterwalls of the supercritical power plants are still produced without PWHT.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1476-1486, October 21–24, 2019,
... of challenges for the future of coal as a sustainable and viable fuel source. Since the cycle efficiency of a steam power plant is directly related to the steam temperature and pressure, advanced ultra-supercritical (A-USC) steam cycles have the potential to improve cycle efficiency, reduce fuel costs...
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Following the successful completion of a 15-year effort to develop and test materials that would allow advanced ultra-supercritical (A-USC) coal-fired power plants to be operated at steam temperatures up to 760°C, a United States-based consortium has been working on a project (AUSC ComTest) to help achieve technical readiness to allow the construction of a commercial scale A-USC demonstration power plant. Among the goals of the ComTest project are to validate that components made from the advanced alloys can be designed and fabricated to perform under A-USC conditions, to accelerate the development of a U.S.-based supply chain for key A-USC components, and to decrease the uncertainty for cost estimates of future commercial-scale A-USC power plants. This project is intended to bring A-USC technology to the commercial scale demonstration level of readiness by completing the manufacturing R&D of A-USC components by fabricating commercial scale nickel-based alloy components and sub-assemblies that would be needed in a coal fired power plant of approximately 800 megawatts (MWe) generation capacity operating at a steam temperature of 760°C (1400°F) and steam pressure of at least 238 bar (3500 psia).The A-USC ComTest project scope includes fabrication of full scale superheater / reheater components and subassemblies (including tubes and headers), furnace membrane walls, steam turbine forged rotor, steam turbine nozzle carrier casting, and high temperature steam transfer piping. Materials of construction include Inconel 740H and Haynes 282 alloys for the high temperature sections. The project team will also conduct testing and seek to obtain ASME Code Stamp approval for nickel-based alloy pressure relief valve designs that would be used in A-USC power plants up to approximately 800 MWe size. The U.S. consortium, principally funded by the U.S. Department of Energy and the Ohio Coal Development Office under a prime contract with the Energy Industries of Ohio, with co-funding from the power industry participants, General Electric, and the Electric Power Research Institute, has completed the detailed engineering phase of the A-USC ComTest project, and is currently engaged in the procurement and fabrication phase of the work. This paper will outline the motivation for the effort, summarize work completed to date, and detail future plans for the remainder of the A-USC ComTest project.
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