Analysis Of Energy Loss And Optimization On Variable Load Operation Of Large Steam Turbine In Thermal Power Plant

With the rapid development of the national economy and changes in domestic electricity consumption structure, China power grid load’s peak valley difference is becoming larger and larger. Many large steam turbine units also have to participate in the peak-load regulating work, and the time of regulating work is longer and longer, it makes steam turbine units are often in variable load operation condition. Because of steam turbine units’actual parameters deviating from the design parameters under variable load operation, unit’s thermal efficiency and safety will reduce significantly. On the premise of ensuring the safe operation of the unit, how to improve the unit’s thermal efficiency under variable load operation, is our urgently needed work to research. In the main influence factors of steam turbine unit’s thermal efficiency under variable load operation, only the operation modes of the unit can be changed by manual operations. Therefore, the research on various operation modes’ influence of power plant unit under variable load has very important significance.In the current situation, steam turbine unit often adopts constant pressure, sliding pressure or composite sliding pressure operation modes under variable load operation. Combining today’s large steam turbine’s operating reality in thermal power plant, this paper analyzed the characteristics of steam turbine’s different operation modes under variable load condition, researched the effect of different variable load operation mode on unit’s thermal efficiency and safety. At the same time, taking the 600 MW steam turbine of power plant in Hunan Province as an example, this paper compared the steam rate, heat rate, absolute electrical efficiency, temperature of governing stage and exhaust temperature of high pressure cylinder of steam turbine unit with constant pressure and sliding pressure operation modes under variable load operation by way of calculation and analysis. The research proves that steam turbine unit adopting composite sliding pressure operation mode, which is adopting constant pressure operation under high load and sliding pressure operation under partial load, not only can improve the thermal economy of unit and reduce the energy consumption, but also can ensure the running safety of equipment and improve the unit’s peak-load regulating performance.According to the characteristics of steam turbine in composite sliding pressure operation, this paper summarized a set of optimization method of steam turbine under variable load operation. With the aid of using governing stage characteristic parameter and considering the pressure loss of the turbine admission valves, this paper presented a universal method of obtaining composite sliding pressure curve of steam turbine. On the basis of obtaining steam turbine’s operation curve, we got the optimization test curve of composite sliding pressure operation by further test parameters optimization. Also taking the 600 MW steam turbine in power plant as an example,we obtained the composite sliding pressure operation curve of steam turbine by calculating, and verified the correctness by comparing the calculated curve with the operation curve of the manufacturer. Based on the curve parameters, we gained the optimization test curve of steam turbine in composite sliding pressure operation.Finally, using the LAB VIEW developing environment which is a good graphical editing language for engineering application, this paper compiled the optimization application software of steam turbine’s energy consumption under variable load operation, as an auxiliary tool to optimization calculation of steam turbine unit under variable load operation.