Papers by Keyword: Ultra Supercritical

Abstract: In order to solve the problem of high temperature corrosion to water wall of opposed wall fired ultra supercritical boiler, comprehensive study is carried out by combining theoretical analysis and experimental research, obtaining the variation of flue gas composition before and after introduction of near wall wind and effect of primary air velocity, central air opening, swirl intensity of outer secondary air and inner secondary air opening on composition of flue gas in near wall region. The results show that 1) the introduction of near wall wind significantly improves reducing atmosphere in near wall region; 2) among the four parameters listed above, swirl intensity of outer secondary air and inner secondary air opening have greater influence on composition of near wall flue gas; 3) under the comprehensive effect of swirl intensity of outer secondary air and inner secondary air opening, the volume fraction of CO in near wall flue gas can be controlled below 1500ppm, which effectively disturbs the condition for high temperature corrosion.

Abstract: The rotor of ultra supercritical steam turbine runs in bad condition with high parameters of steam. The large heat stress of rotor may appear when the operating conditions of turbine unit is changed, for example, adjusting load to meet the requirements of peak and valley of grid, especially, improper operation causing serious damage to rotor. According to theory of thermal stress analysis, first, the steam parameters and their heat transfer coefficients of all cascades of 1000MW ultra supercritical steam turbine is calculated. Then the temperature field and stress field of the high-pressure rotor in the process of cold startup calculated by the finite element software are analyzed and discussed. The results are important to the startup and changing conditions of 1000MW ultra supercritical steam turbine unit.

Abstract: The automatic plant startup and shutdown control system (APS) of ultra supercritical unit was studied and analyzed in this paper. According to the difficulties and features of APS design, complete architecture structure and hierarchical control method of APS system were proposed. The interface software between APS and modulation control system (MCS) was developed. The whole process control strategies of feed water system, fuel system, air-flue gas system, bypass system and deaerator water level system were optimized. These strategies realized the whole process control of fuel, feed water and induced & draft fan. The special control strategies of main steam temperature, boiler dry-wet state transition and hot cleaning were also proposed in this paper. It first realized the automatic startup and shutdown of ultra supercritical unit in China.

Abstract: Power plant’s NO.3 boiler in Suizhong is 1000MW ultra supercritical concurrent boiler. As a result of the increase in the price of coal at present, loss incurred in most of the power plants, the most effective medium to realize profit is burning lignite. This paper analyzed its economic indicators, and summarized its survey.

Abstract: The key technology of supercritical boiler is water wall, this paper is mainly analyzed the dangerous working conditions of supercritical boiler water wall. On the one hand, from working substance’s point of view, we adopt traditional pressure drop method to judge the heat transfer deterioration position under sub-critical pressure; on the other hand, we use temperature test point combining calculation formula of wall temperature to judge the heat transfer deterioration position under supercritical pressure, and combining improved zoned thermal calculation method to get wall surface thermal load distribution map. Through an instance calculation, when boiler unit under 40% of full load, the maximum thermal load is near 20 meters of furnace height and when it under 100% full loads, the maximum thermal load is near 30 meters of furnace height. So we can control all kinds of heat transfer deterioration position through changing hydrodynamic condition and ward off the highest thermal load area, which is significant to operation.

Abstract: The U.S. Department of Energy (DOE) Office of Fossil Energy is intensely promoting research and development of materials for advanced steam cycle systems and for oxy-fuel combustion systems. At Argonne National Laboratory, we have conducted studies to evaluate the corrosion performance of candidate structural alloys in coal-ash and in steam environments, in support of advanced steam cycle systems. The laboratory tests simulate the combustion atmosphere of advanced steam-cycle systems and three deposit chemistries that included ash constituents, alkali sulfates, and NaCl. Corrosion rate data will be presented for several Fe- and Ni-base alloys along with the mechanistic understanding of the corrosion processes. In the study on materials for oxy-fuel applications, we have evaluated the corrosion performance of the materials in CO2, steam, and in steam-CO2 mixtures. Materials selected for the study include intermediate-chromium ferritic steels, Fe-Cr-Ni heat-resistant alloys, and nickel-based superalloys. Information will be presented for materials exposed at temperatures between 650 and 950°C for times up to 10,000 h. In the ongoing experiments, we have incorporated low levels of sulfur and chlorine compounds (in addition to CO2 and steam) in the exposure environment to establish the role of second/third reactant on the scaling, internal penetration, and long term performance of the structural alloys.

Abstract: The alloys required for fossil fuel power systems are transitioning from stainless steels that operate below 600oC to nickel-based alloys that can operate up to 760oC in advanced ultra-super critical steam turbines. This transition brings with it major metallurgical as well as economic challenges related to alloy design, melt processing, and fabrication of these large size components. The alloys, in general, must maintain creep resistance over 100,000 hours of service life while at the same time maintaining resistance to severe steam oxidation and general oxidation. A need exists for nickel-based alloys that are not only highly alloyed, but are also impervious to phase instabilities during initial processing and service. The potential exists for severe segregation when casting large ingots. This possibility must be dealt with during thermo-mechanical processing to obtain the wrought structures that can be inspected to design defect levels. This paper will detail these challenges as they have been addressed in smaller aerospace turbines and discuss strategies to overcome these problems. New computational modeling tools will play a critical role in engineering solutions for alloy design, solidification, forging, and heat treatment. Since any solution also needs to be economically viable, the paper also discusses processing cost issues in terms of the process yields and operational strategies. The use of powder metallurgy will also be reviewed as a cost effective alternative to alloys that have traditionally been cast-wrought processed.

Abstract: Power generation from coal using ultra supercritical steam results in improved fuel efficiency and decreased greenhouse gas emissions. Results of ongoing research into the oxidation of candidate nickel-base alloys for ultra supercritical steam turbines are presented. Exposure conditions range from moist air at atmospheric pressure (650°C to 800°C) to steam at 34.5 MPa (650°C to 760°C). Parabolic scale growth coupled with internal oxidation and reactive evaporation of chromia are the primary corrosion mechanisms.