Study of High Temperature&High Pressure Tube Used for Ultra Supercritical Unit
|School||North China Electric Power University|
|Keywords||Ultra Supercritical Unit High-Temperature Resistant Materials P92 Four-Main Pipelines Piping Specifications|
The relationship between thermodynamic parameters and thermal efficiency of ultra supercritical units was analyzed in this paper. Temperature and pressure were discussed to describe the development of ultra-supercritical units, and further technic comparation was made based on these two parameters. Combined with China’s ultra supercritical units development, Shanghai Turbine (26.25MPa/600℃/600℃) was chosen as the study object in this paper.The regulations for design parameters of "Code for the thermal power plant steam/water pipe" and "ASME B31.1" were compared, and relative technical and economic comparations were mades "Tube rules" was recommended to determine the design parameters of the Four-Main pipelines.The development of high-temperature pipe material, pearlite heat resistance low alloy steel and ferrite/martensite were introduced. P91, P92, E911and PI22, four high-temperature pipe materials were put forward to be applied in ultra supercritical units.Based on the analysis of the Four-Main pipelines’ material selection principles, the material object, and emphatically the technic and economic comparation of main steam pipe’s and hot reheat pipe’s materials were determined as follows.1) P92steel was recommended to be adopted as the material of main steam pipe and hot reheat steam pipe;2) low alloy steel A691Crl-1/4CL22was recommended to be adopted as the material of cool reheat steam pipe;3)15NiCuMoNb5-6-4was recommended to be adopted as the material of high-pressure water supply pipe. Furthermore, the technic reliability of P92steel was analyzed and compared based on welding problems, operational stability, high temperature steam oxidation&corrosion resistance and welding requirements of different materials with turbine interface.In addition, pipe diameter and wall thickness calculation method were introduced and the parameters and relevant principles calculating piping specifications were determined. The economic influences of pressure drop of the main steam piping and reheat steam piping system (including cool reheat steam pipe, boiler reheater reheat steam and hot reheat steam pipe) on the unit operation were investigated, and the main factors (pipe inner diameter, pipeline frictional resistance, and pipeline1℃al resistance, etc) affecting piping pressure drop were analyzed. Through the economic&technic comparisions of increasing initial pipeline investment and thermal efficiency, Four-Main pipelines’ pipe specification was determined in this study.