Optimization Of Start-up Process In Steam Turbine

With the structural adjustjment of grid, it has been improving for the requirements of units to respond to load changes. Thus, it is very vital for the key equipments of units to start as quickly as possible. In recent years, the research work about the quick start-up of steam turbine has been extensively conducted. Due to the characteristics of high efficiency, environmental protection and so on, gas-steam combined cycle unit, supercritical and ultra-supercritical unit are worldwidely extended.The starting time of steam turbine in gas-steam combined cycle unit is relatively long, which may cause the combine cycle unit not responding in time to the needs of peak and valley loads in the power network; for supercritical and ultra-supercritical units, because of there is no drum as conventional power plant, the steam turbine should start faster than that of convetional power plant to match the start-up speed of boiler. Therefore, the optimization of start-up process in steam turbine was studied, combining the methods of numerical experiments and field tests, the study on the starting process of steam turbine was conducted. A two-dimensional axisymmetric finite-element model of steam turbine rotor was established, and the nonlinear boundary conditions were determined, especially the impacts of warm-up operations on rotor stress were described in detail.Based on the numerical experimental results and considering the structure and operation characteristics of pilot unit, the optimized start-up processes were made. In the optimization of start-up process in combined cycle steam turbine of a300MW power plant, results show that for warm start-up, the maximum stress of steam turbine rotor decreases11MPa, the starting time shortens36min and the low cycle fatigue life consumption reduces0.0008%, respectively, while for cold start-up, the maximum stress decreases261MPa, the starting time shortens32min and the low cycle fatigue life consumption reduces0.0197%. The results of the numerical experiments of a660MW surpercritical unit show that for cold start-up, the the low cycle fatigue life consumption increases0.00452%, the maximum stress of steam turbine rotor increases53MPa, while the starting time shortens229min, that means great potential for optimization.