Ultra-supercritical Technology Research Articles

Effect of different loading conditions on corrosion fatigue crack growth rate of a nickel-based alloy in supercritical water

Advanced ultra-supercritical (A-USC) technology improves the initial steam temperature to 650 °C and more. In such an extremely corrosive medium environment, metallic materials are susceptible to corrosion fatigue. In the present study, the aim is to evaluate the effect of maximum stress intensity factor (Kmax), stress ratio (R), waveform, frequency, and holding time (th) on the corrosion fatigue cracking behavior of C-HRA-2 (a candidate nickel-based alloy for A-USC units) in supercritical water (650 °C/25 MPa). The results show that with the increase of Kmax, the corrosion fatigue crack growth rate (CFCGR) increases and satisfies the exponential relationship. The decrease in R and frequency both cause the rise of CFCGR, which satisfies the logarithmic linear relationship. Sinusoidal and triangular wave loading have no significant effect on the CFCGR. Trapezoidal wave with th has a larger CFCGR while with the rise in th, the CFCGR increases. The crack propagation path is straight, perpendicular to the loading direction, and secondary cracks are also observed. Transgranular and intergranular mixed fractures occurred during continuous loading. The proportion of intergranular fracture increases significantly as holding time is applied. The corrosion fatigue crack growth of C-HRA-2 in supercritical water can be explained by dynamic embrittlement mechanism.

Low-carbon development pathways for provincial-level thermal power plants in China by mid-century

Phasing out thermal power plants is vital to combatting climate change. Less attention has been given to provincial-level thermal power plants, which are implementers of the policy of phasing out backward production capacity. To improve energy efficiency and reduce negative environmental impacts, this study proposes a bottom-up cost-optimal model to explore technology-oriented low-carbon development pathways for China's provincial-level thermal power plants. Taking 16 types of thermal power technologies into consideration, this study investigates the impacts of power demand, policy implementation, and technology maturity on energy consumption, pollutant emissions, and carbon emissions of power plants. The results show that an enhanced policy combined with a reduced thermal power demand would peak carbon emissions of the power industry at approximately 4.1 GtCO2 in 2023. Meanwhile, most of the inefficient coal-fired power technologies should be eliminated by 2030. Carbon capture and storage technology should be gradually promoted in Xinjiang, Inner Mongolia, Ningxia, and Jilin after 2025. Energy-saving upgrades on 600 MW and 1000 MW ultra-supercritical technologies should be emphatically carried out in Anhui, Guangdong, and Zhejiang. By 2050, all thermal power will come from ultra-supercritical and other advanced technologies.

The Experimental Evaluation of Energy Efficiency and Carbonic Emission Rates for All Stable Loads of Larger-Scale (+600 MW) Coal-Fired Power Generation Units in Vietnam

Performance guarantees and tests of thermal power plants are usually carried out at 100% rate output capacity. However, fossil-fired power plants have decreased full load hours, affecting energy efficiency, and are subjected to frequent load changes caused by variable renewable electricity and potential grid stability. Therefore, this study is conducted to calculate and draw the characteristic curves for all stable loads of coal-fired power units including the 60%, 75%, and 100% rate output. The study focuses on the corrected plant net heat rates—gross unit outputs, net standard coal consumption rates—throttle steam pressures, and corrected plant net efficiencies—carbonic emission rates. In addition, the experimental investigation for energy efficiency and carbonic emission of the latest larger-scale (+600 MW) coal-fired power generation units in Vietnam are also implemented using a performance guarantee calculation software called “PG_Cal” version 0.0, which is based on a mass and energy balance method by MATLAB programing language. From the results of this study, it is suggested that the performance guarantees and tests of new coal-fired units should be carried out at different stable loads, including minimum load. Vietnam should apply the ultra-supercritical technology for new units in order to increase their efficiency and decrease carbon dioxide emissions.

Development and Qualification of Materials for Indian Advanced Ultra-Supercritical Coal-Fired Power Plant

Abstract India has embarked on an ambitious program of setting up efficient advanced ultra-supercritical (AUSC) technology with steam temperature and pressure of 993 K and 31 MPa, respectively. This article deals with the testing and qualification of indigenously produced materials for the Indian AUSC mission project, the research and development phase of which is currently in the advanced stage of completion. As part of this, exhaustive database pertaining to various mechanical properties including creep, low cycle fatigue (LCF), creep-fatigue interaction (CFI), high cycle fatigue (HCF), fracture toughness, and crack growth has been generated covering important candidate materials such as alloy 617M tubes and forgings, 304HCu stainless steel tubes, and alloy 625 castings. Tubes of both alloy 617M and 304HCu stainless steels are to be used in the boilers, whereas alloy 617M forgings would be used as turbine rotor and alloy 625 castings as turbine casings. The data have been subsequently used to establish design curves identifying safe regimes of operation with respect to creep, LCF, HCF, CFI, and fatigue and creep crack growths. The properties were seen to be comparable with those derived from internationally developed equivalent grades. The bimetallic weld joints between alloy 617M and 10Cr steels were also evaluated to derive the appropriate strength reduction factors under creep and cyclic loadings. Additionally, the influence of thermal aging at service temperature on the microstructural evolution and mechanical properties was investigated based on tensile and fracture properties to account for the service exposure induced degradation and associated embrittlement.

Research and Application of Double-Reheat Boiler in China

The ultra-supercritical (USC) double-reheat technology is an immediate area of research focus in China, since the thermal efficiency of USC double-reheat unit is higher than the USC single-reheat unit. The parameters and capacity of USC double-reheat unit in China have made major breakthroughs, and the thermal efficiency of the units are as high as 47–48%, which is the highest in the world. USC double-reheat boiler is one of the most important devices for USC double-reheat unit, and the design concept and precision have a vital effect on the operation of boiler and power station. The most difficult and important factors in the design of double-reheat boiler are the layout of heating surface and the steam temperature regulation method. Therefore, this work summarizes the arrangement of heating surface and temperature regulation method of existing double-reheat boiler in China. It is hoped that the work will set a benchmark for the development of double-reheat boiler and the future 700 °C power generation unit in the world.

Effects of coal compositions on the environment and economic feasibility of coal generation technologies

Coal has strategic importance for the global generation of electricity. However, the environmental impacts of its intense use are a concern, especially about greenhouse gases emissions. High Efficiency and Low Emissions coal-fired power plants are part of the approach known as Clean Coal Technologies, including supercritical (SC) and ultra-supercritical (USC) plants, since they allow cleaner and more efficient coal usage. This study analyzes how the usage of different coal compositions impacts the economic and environmental feasibility of operating units with higher efficiency when compared to conventional subcritical power plants. The analysis identified that the application of supercritical and ultra-supercritical technologies provided significant savings in fuel consumption, and consequently in CO2 emissions. The economic feasibility analysis identified that the annual savings change significantly among the analyzed coal compositions, in such manner that it determines whether the supercritical and ultra-supercritical technological alternatives can be economically viable in the long term or not. In general, these technologies are viable both as an alternative to mitigate CO2 emissions and to obtain better profitability through energy generation.

Experiment of adding molybdenum to AISI 310 to increase tensile strength

Supercritical coal power plants began in 1983 with 24.1 MPa moisture parameters and 538°C / 538°C temperature (superheated and reheated steam). Ultra supercritical technology began in 1993 with 24.1 MPa and 538°C / 593°C. Starting in 2000, an ultra-high temperature supercritical power plant was built at 25MPa and 600°C / 620°C in Tachibana and Isogo Powerplants. From this phenomenon, together coal at the power plant, there is often damage to the turbine blade because the material from the turbine blade is not able to withstand temperatures> 760°C. So the words between these can be analyzed by adding molybdenum on AISI 310 raw material in order to find a new material that is resistant to temperature > 760°C. Stainless steel is a steel that has an important role in the industry. One type of stainless steel is austenitic stainless steel. In general, stainless steels containing Ni, Cr and no other blends. The strength and tenacity of the austenitic stainless steel can be increased by alloying and thermo mechanical treatment (TMT). In the integration process, a structure can be carried out which can be improved by the mechanical properties of the material. To find out the austenitic stainless steel needs to be developed to increase resistance to the corrosive environment, and also its mechanical properties. This development can be done by combining AISI 310 with Molybdenum

Costs of avoided carbon emission from thermal and renewable sources of power in India and policy implications

India is the third-largest carbon emitter after the USA and China due to its over-reliance on low-efficiency coal-fired power plants. To reduce carbon emission, India has set up an ambitious target to harness power from renewable energy resources. To examine whether solar and wind are the least cost options to reduce carbon emission, the study estimates the cost of avoided carbon emission from thermal and renewable power generation in India. The study first estimates the Levelized Cost of Electricity Generation (LCOE). These LCOE estimates are then extended to calculate the avoided cost of carbon emission (CAC) from coal-based super and ultra-supercritical technologies along with solar, wind, and combined cycle gas-based power with respect to the subcritical power plant. The study also conducts sensitivity analysis and scenario building exercises. It establishes that super and ultra-supercritical power plants and not the solar or wind are the least-cost options for India to reduce its carbon emission. The study concludes with a set of important policy prescriptions.

Exergy Analysis of Coal-Fired Power Plants in Ultra Supercritical Technology versus Integrated Gasification Combined Cycle

Exergy Analysis of Coal-Fired Power Plants in Ultra Supercritical Technology versus Integrated Gasification Combined Cycle

Development Trend and Strategic Countermeasures of Clean Coal Technology in China Toward 2035

China’s energy structure has long been dominated by coal. To achieve clean, high-efficiency utilization of coal in the country, it’s urgent to develop clean coal technologies (CCTs). After defining the concept of CCT, this paper identifies the advanced characteristics of CCT and predicts key cutting-edge technologies for 2035. By reviewing the development of major cutting-edge technologies in China and abroad, we give the strategic goal and path of China’s CCT development and corresponding policy suggestion. China has achieved a global leading position in technology research and development, equipment manufacturing, and demonstration project of advanced power generation technologies such as 700 ℃ ultra-supercritical technology, integrated gasification combined cycle/integrated gasification fuel cell combined cycle (IGCC/IGFC), and other technologies in coal deep processing industry. It has international competitiveness and advantages of research and development. However, there are still many problems in terms of independent innovation capability, scientific research mechanism and talent cultivation, and balanced development between regions and enterprises. It is necessary to plan for the long-term development of coal energy, deploy the development of modern coal chemical industry scientifically, actively deploy disruptive technology research and development and its engineering demonstration, and comprehensively improve CCT research and development and its industrial environment.

Composition Optimum Design and Strengthening and Toughening Mechanisms of New Alumina-Forming Austenitic Heat-Resistant Steels

In order to promote the development of ultra-supercritical technology, the optimum composition design of three new alumina-forming austenitic heat-resistant steels, based on Fe–22Cr–25Ni (wt. %), with low cost and excellent performance, and used for 700 °C ultra-supercritical unit was carried out using Thermo-Calc software. A comparison of the mechanical properties presented that with increasing Al content, the plasticity of the system was further improved. Based on the composition system, a systematic investigation regarding the structure stability, thermodynamic properties, and mechanical properties of these new steels was carried out to reveal possible strengthening and toughening mechanisms by employing the first-principles method. Calculation results showed that when Al existed in the Fe–Cr–Ni alloy system as a solid solution, the new structures were stable, especially under high temperature. The solution of Al and Al + Si could increase the value of B/G, namely improving the plasticity of the system, particularly in case of alloying with Al + Si. The inclusion of Si in the Fe–Cr–Ni–Al system was conducive to further improving the plasticity without affecting the strength, which provided references for the subsequent optimum composition design and performance regulation of alumina-forming austenitic heat-resistant steels.

Life cycle assessment of transformation from a sub-critical power plant into a polygeneration plant

Coal-fired power plants retirement is a worldwide problem due to the universal desire to control temperature increase less than 2 °C. Chinese government has also made clear plans to develop renewable electricity gradually in place of coal-fired electricity. The first to be affected are the small power units, which suffer from decreased operation hours and environmental protection problems simultaneously. The two possible fates of these small power plants are to be decommissioned or to be retrofitted into more advanced energy systems. Recently, we transformed a sub-critical power plant into a polygeneration plant using the dual fluidized bed pyrolysis technology and proposed two transformation methods, including the partial and complete transformation. A life cycle assessment (LCA) of the three scenarios, including two transformation scenarios and the original power plant scenario, is also performed to assess the transformation effect. The life cycle results are also compared with that of the ultra-supercritical (USC) unit and the integrated coal gasification combined cycle (IGCC) unit. As a result, 3600 MJ of energy output is adopted as the function unit. The LCA analysis indicates that the complete transformation for polygeneration is the best of all the five scenarios in view of almost all impact categories (CML 2001) and energy utilization performance. Compared with the original sub-critical power plant, the complete transformation can reduce greenhouse gas emissions by 36.5 percent. Besides, the complete transformation can also reduce acidification potential by up to 50.1 percent relative to IGCC. Moreover, the net energy efficiency of the complete transformation scenario is 3.65 percent higher than that of USC technology. Therefore, the current study may demonstrate the feasibility of transformation from the existing power plants to the polygeneration plants to achieve the goal of cleaner production, which may also provide a new idea for the upgrading of small power plants.

Exergoenvironmental analysis of a ultra-supercritical coal-fired power plant

This paper presents an exergoenvironmental analysis for a coal-fired ultra-supercritical technology. The study was carried out for a generating unit of 800 MWe of power, which uses bituminous coal as fuel. The environmental impact rates associated with: the destruction of exergy, to the life cycle of the components, to pollutants formation, besides the indicator of relative difference and the exergoenvironmental factor for each of the components of the system are evaluated. It was identified that the flow of cooling water and exhaust gas has a significant environmental impact rate (349.39 mPts/s and 702.26 mPts/s, respectively), which represents an impact rate per kWh of generated electricity of 1.57 and 3.16 mPts/kWh, respectively. The impact rate for the electricity generated by the ultra-supercritical system is 40.78 mPts/kWh. The environmental impact rate associated with the component (production, operation and maintenance, and disposal) is not significant in the analysis of this system. The environmental impact rate related to the destruction of exergy is representative in system (35.36%), together with the formation of pollutants which is the main source of environmental impact of system (64.55%) due to the large contribution of emissions provided by the combustion of coal. The system with ultra-supercritical technology presents itself as an alternative to less efficient coal generation systems, such as subcritical and even supercritical, but it promotes a high environmental impact rate when compared to other generation systems. The incorporation of exhaust gas treatment equipment, such as to particulate removal, gas desulphurisation, and removal of nitrogen oxides, can significantly reduce the environmental impact of the system.

The inclusion of short-transverse displacements in the eigenstrain reconstruction of residual stress and distortion in in740h weldments

The purpose of the present study is to predict the residual stress and distortion of Inconel Alloy 740H componentns during the fabrication of welded components used for advanced ultra-supercritical technology by means of solving the inverse eigenstrain problem. The proposed model determines the distribution of two components of eigenstrain using two-dimensional displacement data obtained from high precision coordinate measurements. Input for the model is provided by the geometric characterisation of electric discharge machining (EDM) sectioned weld bead on plate sample, namely, the out-of-plane distortion of a transverse thin section across the weld line. The deplanation of the original sample is used for cross-validation using the contour method approach, modified recently by the present authors on the basis eigenstrain-based analysis. After determination of the distribution of eigenstrain components, residual stress and displacement calculations are performed in the whole body of as-welded and heat-treated plate models. Results are first verified using experimentally determined residual stress, displacement and distortion on the sectioned surfaces. In addition, 12 mm slices are cut from both model geometries and calculations are repeated using previously determined eigenstrain distributions. Measured distortions on the surface of bar models allowed a fourth term for verification of the eigenstrain distribution.

Diffusion of China’s coal-fired power generation technologies: historical evolution and development trends

With increasing environmental pressure and the promotion of structural reforms on the supply side, a trend of transformation and upgrading is inevitable in coal-fired power generation. This study aims to analyze the historical evolution and predict the development trends of subcritical (Sub-C), supercritical (SC) and ultra-supercritical (USC) coal-fired power generation technologies in China. Employing the hierarchical clustering method, we divided 29 Chinese Provinces into four clusters based on their resource endowment, economic development level, technological development and power supply structure. Then, with the Bass model, we analyzed the national- and provincial-level diffusion processes of these three technologies. The results show that currently, at the national level, Sub-C coal-fired power generation technology is in the mature stage, SC technology is in the late growth period, and USC technology is in the rapid growth phase. Further, the diffusion of these three technologies has different characteristics in different clusters of provinces, and it is being transferred from economically developed eastern provinces to economically underdeveloped central and western provinces where coal resources are relatively rich. This research is helpful to the government in making policies to optimize the technical and regional structures of coal-fired power generation.

Development of heat-resistant Fe-based alloys for A-USC steam boiler using ultra-high purity (UHP) technology

The design of ultra-high purity (UHP) Fe-based alloys for advanced ultra-supercritical (A-USC) technology is suggested in this work. The creep testing at 700 °C and a stress level of 150 MPa have been performed in air. The addition of small amount of reactive-elements, W, Nb, Zr and Sc, has been undertaken into model alloys with the intention to promote the precipitation strengthening. Optimizing the chemical composition coupled by pre-straining enabled improving the creep resistance; hence a creep-rupture life of 750 h was reached. The oxidation resistance in supercritical water is remarkably enhanced by small addition of Sc.

Development of Ultra-high Purity (UHP) Fe-Based Alloys with High Creep and Oxidation Resistance for A-USC Technology

The design of ultra-high purity (UHP) Fe-based model alloys for advanced ultra-supercritical (A-USC) technology is attempted in this work. Creep testing has been performed in air at 700 °C and a stress level of 150 MPa. Analysis of the fracture surface and cross section of the crept specimen was performed. To evaluate the oxidation resistance in A-USC conditions, oxidation testing was performed in supercritical water (SCW) at 700 °C and 25 MPa. Weight gain (WG) measurements and meticulous characterization of the oxide scale were carried out. Based on thermodynamics and density functional theory calculations, some reactive elements in the Fe-Cr-Ni system were designated to promote precipitation strengthening and to improve the hydrogen-accelerated oxidation resistance. The addition of a 2 wt pct Mo into Fe-22Cr-22Ni-0.6Nb wt pct-based matrix did not significantly improve the creep resistance. The addition of 0.26 wt pct Zr coupled with cold working was effective for improving creep properties. The Mo-modified model alloy showed almost the same WG value as SUS310, while the Zr-modified alloy showed a higher WG value. Meanwhile, a Cr-enriched continuous oxide layer was formed at the oxidation front of the Zr-modified alloy and SUS310S after exposure to SCW conditions.

Statistical modeling of an integrated boiler for coal fired thermal power plant.

The coal fired thermal power plants plays major role in the power production in the world as they are available in abundance. Many of the existing power plants are based on the subcritical technology which can produce power with the efficiency of around 33%. But the newer plants are built on either supercritical or ultra-supercritical technology whose efficiency can be up to 50%. Main objective of the work is to enhance the efficiency of the existing subcritical power plants to compensate for the increasing demand. For achieving the objective, the statistical modeling of the boiler units such as economizer, drum and the superheater are initially carried out. The effectiveness of the developed models is tested using analysis methods like R2 analysis and ANOVA (Analysis of Variance). The dependability of the process variable (temperature) on different manipulated variables is analyzed in the paper. Validations of the model are provided with their error analysis. Response surface methodology (RSM) supported by DOE (design of experiments) are implemented to optimize the operating parameters. Individual models along with the integrated model are used to study and design the predictive control of the coal-fired thermal power plant.

Dynamic analysis of the boiler drum of a coal-fired thermal power plant

The subcritical coal-fired boilers of thermal power plants consist of a combustion chamber, economizer unit, drum unit (drum, riser, and downcomer), superheater unit (primary superheater, secondary superheater, and final superheater), and reheater unit. The input and output of these units are highly interactive in nature. The efficiency of the subcritical plants is only around 33%. The efficiency needs to be increased to produce more power for the increasing demand, which can be achieved only by implementing supercritical technology or ultra-supercritical technology. However, the conversion of existing subcritical power plants to supercritical power plants is impossible due to the installation cost. So in order to increase the overall efficiency of the existing subcritical power plants, boilers of such units must be examined in order to find safer operational practices. This paper highlights the mathematical modeling of the economizer unit and drum unit of boiler, which can help in enhancing the performance of the boiler system of the power plant. Mass and energy balances for the integrating boiler units have been formulated using first principle laws. The developed model has then been validated with actual plant data obtained from a 210 MW coal-fired thermal power plant. The performance of the open loop responses of the model are analyzed and are included in the results and discussion of the paper. The model provides support for level, pressure, and temperature measurements and predictions. The effect of changes in the parameters of the boiler are studied and discussed in detail.

Developing a Green Path Power Expansion Plan in Indonesia by Applying a Multiobjective Optimization Modeling Technique

AbstractThis paper aims to apply a multiobjective optimization modeling technique to a power expansion problem evaluating two objectives functions: minimizing the power generating cost and minimizing CO2 emissions, between which there is a tradeoff. A convex curve is obtained representing the relationship between the generating cost (Rp/kWh) and CO2 emissions (ton). This represents a bad-luck curve where there is an increasing marginal cost to reduce 1 t of CO2 emissions. This is because most of the less-carbon-intensive power plants consume oil, which has the highest fuel cost. Instead of simply minimizing CO2 emissions, this paper argues that Indonesia needs to pursue technology to switch from steam coal subcritical technology to supercritical and ultra-supercritical technology to reduce CO2 emissions. It is further found that the generating cost will increase by less than 1.6% and yearly CO2 emissions can be reduced by about 6.9% by adopting supercritical technology. This implies that adopting ultra-su...