CRESWUP · Creep resistant steels and welds for ultra supercritical power plants

Creep resistant steels and welds for ultra supercritical power plants

The primary method of generating electricity worldwide is by fossil-fuel fired power plants, which have high CO2 emissions. In developing countries like India, fossil-fired power plants based on domestic coal reserves will remain a main source of electricity for many years to come. An immediate goal is to generate power from fossil-fired stations that are more efficient and therefore less polluting. Conventional coal fired power plants operate at steam temperatures between 538 and 566C and at a sub-critical pressure below 240 bars. Such power stations have high CO2 emissions due to low thermal efficiency (35-40%). To reduce emissions, new power stations need to operate at higher temperatures and pressures, which will improve the thermal efficiency. However, this leads to intensified loads on the materials in the hottest components of the steam cycle (boiler, steam lines and steam turbine), and new construction materials with improved resistance against creep, corrosion and thermal fatigue are needed for these components. State-of-the-art coal fired power plants operate at 600-620C and ultra-supercritical pressure of 300 bar, leading to thermal efficiencies of 43-47%, corresponding to 10-20% less specific emissions of CO2 compared with conventional plants. Construction materials for the most critical hot components in these USC plants are creep strength enhanced martensitic 9%Cr steels, such as Grade 91 and 92. Current R&D of materials for enhanced efficiency of coal fired power plants follow two directions. 1) the development of improved martensitic steels, which could enable USC plants with steam parameters up to 650C and 325 bar, and efficiencies of 48-50%. 2) Advanced Ultra Supercritical (A-USC) power plants operating at 700C and 350 bar pressure with more than 50 % efficiency. Nickel base alloys are the chosen construction materials for the hottest components in A-USC plants. However, the cost of these materials are 5-10 times higher than the cost of steels, and a number of technical issues related to the long-term performance of base materials and welded joints have been identified. Research in the present project focused on the characterization of microstructure and properties of new martensitic 11–12% Cr steels and welded joints currently under development . Improved understanding of relations between microstructure and properties of 11-12% Cr steels will improve the chances of a successful materials development of such steels, which could enable the construction of USC power plants with steam parameters of 325 bar and 650C. Furthermore, such steels would cut back the necessary amount of expensive Nickel base alloys in the more efficient A-USC power plants, and increase the overall economy of such plants. A final objective of the project was to establish contacts between research communities in Europe (Technical University of Denmark (DTU)) and India (Indira Ghandi Centre for Atomic Research (IGCAR)), working on materials development for USC power plants in order to further the research in both areas.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз