Search Results for ultra-supercritical steam power plants

A new 12%Cr steel, VM12, has been developed with the combined strength and oxidation resistance characteristics desired for high-temperature applications. The steel increases chromium content by around 0.2% to improve oxidation properties while alloying with other elements such as cobalt, tungsten, and boron to meet a range of requirements, including extending fatigue life. The steel is designed to have the same creep strength as T/P92 but with better oxidation resistance due to the higher chromium content. It has about a 0.2% increase in mechanical properties compared to T/P92 steel. Results are presented for tubes and pipes cast with a variety of surface conditions. In addition, detailed results are provided on the effects of alloying elements on creep and oxidation resistance.

Super 304H is a new generation of advanced austenitic stainless steels that is increasingly being used in superheater/ reheater (SH/RH) sections of thermal ultra-supercritical steam power plants due to its high creep strength combined with good oxidation resistance and microstructure stability. However, recent studies have shown significant microstructural changes and associated degradation in creep performance during long-term service exposure in this alloy. Microstructure evolution during service and its effect on the long-term creep performance has not been comprehensively assessed. In this work, variations in the microstructure of long-term service exposed Super 304H RH tubes (~99,600 hours at 596°C steam temperature) are documented. The results for the ex-service material are compared to well-documented laboratory studies to provide perspective on improved life management practices for this mainstay advanced stainless steel.

A study is being conducted on turbine materials for use in ultra-supercritical (USC) steam power plants, with the objective of ensuring no material-related impediments regarding maximum temperature capabilities and the ability to manufacture turbine components. A review of the state-of-the-art and material needs for bolting and casing applications in USC steam turbines was performed to define and prioritize requirements for the next-generation USC turbines. For bolting, several potentially viable nickel-base superalloys were identified for service at 760°C, with the major issues being final material selection and characterization. Factors limiting inner casing material capabilities include casting size/shape, ability to inspect for discontinuities, stress rupture strength, and weldability for fabrication and repairs. Given the need for precipitation-strengthened nickel-base alloys for the inner casing at 760°C, the material needs are two-fold: selection/fabrication-related and characterization. The paper provides background on turbine components and reviews the findings for bolting and casing materials.

The rapid development of Chinese economy (recently in the order of 10%/year) is requiring sustainable growth of power generation to meet its demand. In more than half century after the foundation of People's Republic of China, the Chinese power industry has reached a high level. Up to now, the total installed capacity of electricity and annual overall electricity generation have both jumped to the 2 nd position in the world, just next to United States. A historical review and forecast of China electricity demand to the year of 2010 and 2020 will be introduced. Chinese power plants as well as those worldwide are facing to increase thermal efficiency and to decrease the emission of CO 2 , SO X and NO X . According to the national resources of coal and electricity market requirements in the future 15 years power generation especially the ultra-super-critical (USC) power plants with the steam temperature up to 600°C or higher will get a rapid development. The first two series of 2×1000MW USC power units with the steam parameters 600°C, 26.25MPa have been put into service in November and December 2006 respectively. In recent years more than 30 USC power units will be installed in China. USC power plant development will adopt a variety of qualified high temperature materials for boiler and turbine manufacturing. Among those materials the modified 9- 12%Cr ferritic steels, Ni-Cr austenitic steels and a part of nickel-base superalloys have been paid special attention in Chinese materials market.

Advanced ultra-supercritical (USC) steam power plants promise higher efficiencies and lower emissions. The U.S. Department of Energy (DOE) aims to achieve 60% efficiency in coal-based power generation, requiring steam temperatures of up to 760°C. This study presents ongoing research on the oxidation behavior of candidate materials for advanced steam turbines, with a focus on estimating chromium evaporation rates from protective chromia scales. Due to the high velocities and pressures in advanced steam turbines, evaporation rates of CrO 2 (OH) 2 (g) are predicted to reach up to 5 × 10 −8 kg m −2 s −1 at 760°C and 34.5 MPa, corresponding to a solid chromium loss of approximately 0.077 mm per year.

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.

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.

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.

Following the successful completion of a 14-year effort to develop and test materials which 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 started on a project to build an A-USC component test facility, (A-USC ComTest). Among the goals of the facility are to validate that components made from the advanced alloys can perform under A-USC conditions, to accelerate the development of a U.S.-based supply chain for the full complement of A-USC components, and to decrease the uncertainty for cost estimates of future commercial-scale A-USC power plants. The A-USC ComTest facility will include a gas fired superheater, thick-walled cycling header, steam piping, steam turbine (11 MW nominal size) and valves. Current plans call for the components to be subjected to A-USC operating conditions for at least 8,000 hours by September 2020. The U.S. consortium, principally funded by the U.S. Department of Energy and the Ohio Coal Development Office with co-funding from Babcock & Wilcox, General Electric and the Electric Power Research Institute, is currently working on the Front-End Engineering Design phase of the A-USC ComTest project. This paper will outline the motivation for the project, explain the project’s structure and schedule, and provide details on the design of the facility.

A recent engineering design study conducted by the Electric Power Research Institute (EPRI) has compared the cost and performance of an advanced ultra-supercritical (A-USC) pulverized coal (PC) power plant with main steam temperature of 700°C to that of conventional coal-fired power plant designs: sub-critical, supercritical, and current USC PC plants with main steam temperatures of 541°, 582°, and 605°C, respectively. The study revealed that for a US location in the absence of any cost being imposed for CO 2 emissions the A-USC design was a slightly more expensive choice for electricity production. However, when the marginal cost of the A-USC design is compared to the reduction in CO 2 emissions, it was shown that the cost of the avoided CO 2 emissions was less than $25 per metric ton of CO 2 . This is significantly lower than any technology currently being considered for CO 2 capture and storage (CCS). Additionally by lowering CO 2 /MWh, the A-USC plant also lowers the cost of CCS once integrated with the power plant. It is therefore concluded that A-USC technology should be considered as one of the primary options for minimizing the cost of reducing CO 2 emissions from future coal power plants.

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.

In the later half of the last century great progress in alloy development for power applications was seen to improve thermal efficiency with increasing steam temperature. Meanwhile, many material-related troubles have been experienced due to rising temperature and uncertainty in the properties of fabricated metal. For further improvement in the thermal efficiency of fossil-fired power plants with ultra supercritical steam parameter conditions aiming at temperatures above 700°C, alloy development concepts and material issues with increasing steam temperature must be reviewed and discussed. In this paper new findings in the areas of alloy developments, creep failure in base metal and weldments, thermal fatigue failure and steam oxidation/hot corrosion are presented and discussed, as well as the economical aspect of material development, which is essential to realize unprecedented ultra supercritical steam conditions.

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.

As the demand for worldwide electricity generation grows, pulverized coal steam generator technology is expected to be a key element in meeting the needs of the utility power generation market. The reduction of greenhouse gas emissions, especially CO 2 emissions, is vital to the continued success of coal-fired power generation in a marketplace that is expected to demand near-zero emissions in the near future. Oxycombustion is a technology option that uses pure oxygen, and recycled flue gas, to fire the coal. As a result, this system eliminates the introduction of nitrogen, which enters the combustion process in the air, and produces a highly-concentrated stream of CO 2 that can readily be captured and sequestered at a lower cost than competing post-combustion capture technologies. Oxycombustion can be applied to a variety of coal-fired technologies, including supercritical and ultra-supercritical pulverized coal boilers. The incorporation of oxycombustion technology in these systems raises some new technical challenges, especially in the area of advanced boiler materials. Local microclimates generated near and at the metal interface will influence and ultimately govern corrosion. In addition, the fireside corrosion rates of the boiler tube materials may be increased under high concentration oxygen firing, due to hotter burning coal particles and higher concentrations of SO 2 , H 2 S, HCl and ash alkali, etc. There is also potential to experience new fouling characteristics in the superheater and heat recovery sections of the steam generator. The continuous recirculation of the flue gases in the boiler, may lead to increasing concentrations of deleterious elements such as sulfur, chlorine, and moisture. This paper identifies the materials considerations of oxycombustion supercritical and ultrasupercritical pulverized coal plants that must be addressed for an oxycombustion power plant design.

India's current installed power generating capacity is about 225,000 MW, of which about 59% is coal based. It is projected that India would require an installed capacity of over 800,000 MW by 2032. Coal is likely to remain the predominant source of energy in India till the middle of the century. India is also committed to reducing the CO 2 emission intensity of its economy and has drawn up a National Action Plan for Climate Change, which, inter alia, lays emphasis on the deployment of clean coal technologies. With this backdrop, a National Mission for the Development of Advanced Ultra Supercritical Technology has been initiated. The Mission objectives include development of advanced high temperature materials, manufacturing technologies and design of equipment. A corrosion test loop in an existing plant is also proposed. Based on the technology developed, an 800 MW Demonstration A-USC plant will be established. Steam parameters of 310 kg/cm 2 , 710 °C / 720 °C have been selected. Work on selection of materials, manufacture of tubes, welding trials and design of components has been initiated. The paper gives details of India's A-USC program and the progress achieved.

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.

One of the pathways for achieving the goal of utilizing the available large quantities of indigenous coal, at the same time reducing emissions, is by increasing the efficiency of power plants by utilizing much higher steam conditions. The US Ultra-Supercritical Steam (USC) Project funded by US Department of Energy (DOE) and the Ohio Coal Development Office (OCDO) promises to increase the efficiency of pulverized coal-fired power plants by as much as nine percentage points, with an associated reduction of CO 2 emissions by about 22% compared to current subcritical steam power plants, by increasing the operating temperature and pressure to 760°C (1400°F) and 35 MPa (5000 psi), respectively. Preliminary analysis has shown such a plant to be economically viable. The current project primarily focuses on developing the materials technology needed to achieve these conditions in the boiler. The scope of the materials evaluation includes mechanical properties, steam-side oxidation and fireside corrosion studies, weldability and fabricability evaluations, and review of applicable design codes and standards. These evaluations are nearly completed, and have provided the confidence that currently-available materials can meet the challenge. While this paper deals with boiler materials, parallel work on turbine materials is also in progress. These results are not presented here in the interest of brevity.

Reducing emissions and increasing economic competitiveness require more efficient steam power plants that utilize fossil fuels. One of the major challenges in designing these plants is the availability of materials that can stand the supercritical and ultra-supercritical steam conditions at a competitive cost. There are several programs around the world developing new ferritic and austenitic steels for superheater and reheater tubes exposed to the advanced steam conditions. The new steels must possess properties better than current steels in terms of creep strength, steamside oxidation resistance, fireside corrosion resistance, and thermal fatigue resistance. This paper introduces a series of experimental 9%Cr steels containing Cu, Co, and Ti. Stability of the phases in the new steels is discussed and compared to the phases in the commercially available materials. The steels were tested under both the dry and moist conditions at 650°C for their cyclical oxidation resistance. Results of oxidation tests are presented. Under the moist conditions, the experimental steels exhibited significantly less mass gain compared to the commercial P91 steel. Microstructural characterization of the scale revealed different oxide compositions.

SUPER304H (18Cr-9Ni-3Cu-Nb-N, ASME CC2328) and TP347HFG (18Cr-12Ni-Nb, ASME SA213) are advanced fine-grained microstructure steel tubes developed for high strength and superior steam oxidation resistance. Their exceptional performance is demonstrated by the longest creep rupture tests, with SUPER304H tested at 600°C for 85,426 hours and TP347HFG at 700°C for 55,858 hours, both maintaining stable strength and microstructure with minimal σ phase formation and absence of other brittle phases compared to conventional austenitic stainless steels. HR3C (25Cr-20Ni-Nb-N, ASME CC2115) was specifically developed for high-strength, high-corrosion-resistant steel tubes used in severe corrosion environments of ultra-supercritical (USC) boilers operating at steam temperatures around 600°C. The longest creep test for HR3C, conducted at 700°C and 69 MPa for 88,362 hours, confirmed its high and stable creep strengths and microstructural integrity across the 600-800°C temperature range. These innovative steel tubes have been successfully installed in the Eddystone No. 3 USC power plant as superheater and reheater tubes since 1991, with subsequent microstructural investigations after long-term service exposure revealing their remarkable performance. The paper provides an up-to-date analysis of the long-term creep rupture properties and microstructural changes of these steels following extended creep rupture and aging processes, highlighting their successful application as standard materials for superheater and reheater tubes in newly constructed ultra-supercritical boilers worldwide.

This paper examines the ongoing significance of pulverized coal-fired steam plants in global power generation, focusing on technological advancements and strategies for improving efficiency and reducing CO 2 emissions. It traces the development of Ultra-Supercritical (USC) plants with steam temperatures around 600°C and explores immediate opportunities for further efficiency enhancements, including the innovative Master Cycle. The potential for increasing steam temperatures to 650°C using new steels and to 700°C with nickel-based AD 700 technology is discussed. The paper outlines a comprehensive strategy for CO 2 emission reduction: maximizing plant efficiency, co-firing with CO 2 -neutral fuels, and integrating with district heating/cooling or industrial heat consumers. Carbon capture and storage techniques are presented as a final step in this multi-faceted approach to sustainable power generation.