Research On System Design And Thermal Economy Of700℃Ultra Supercritical Coal-fired Power Plant

At present, high-parameter and large-capacity coal-fired power plant is becoming themain kind of thermal power plant in China. Though related technologies have beenimproved greatly, there is still a big gap compared with foreign advanced level.It helps to find out the size and spatial distribution of energy-saving potential by analyzingthe energy consumption and distribution of the large-scale coal-fired power plant whenoperating under variable conditions. And that can also provide data supportfor reducing energy consumption and realizing energy conservation. This paper has donesome research on energy consumption and distribution of700℃advancedultra-supercritical power plant according to conventional super-critical power plant withcapacity of600MW, and the model was validated by the conventional super-critical powerplant. The paper has done some work in the following aspects:In this paper, the thermal economic indicators of a conventional super-critical powerplant have been calculated by heat quantity method. Meanwhile, main operation parametersof different working conditions including the heaters-removal condition are simulated byvariable-condition model. The results show that, economic impact of every parameter ofthe power plant varies with the load. Impact on thermal economic of low-pressure heaterchanges with the load, the fifth heater has highest impact on thermal economic. And impacton thermal economic of high-pressure heaters does not change obviously with the load.In this paper, exergy-loss distribution has been researched by use of exergy analysismethod of a conventional super-critical power plant. The results show that boiler unit hasgreatest exergy loss, and other units have lower energy loss comparatively. And exergy lossand exergy efficiency of boiler unit will reduce with the load decrease, but exergy loss andexergy efficiency of other units don’t have evident change. And exergy indicators of everyturbine and every heater change with the load. In this paper, two thermodynamic systems of700℃advanced ultra-supercriticalpower plant base on MC(master cycle) system and conventional system with capacity of1000MW have been designed according to one conventional supercritical power plant andthermodynamic method. Economic indicators have been calculated of these two systembased on heat quantity method. The results show that700℃advanced ultra-supercriticalpower plant based on conventional system has better thermal economy than a conventionalsupercritical power plant, and700℃advanced ultra-supercritical power plant based on MCsystem has best thermal economy.In this paper, off-design conditions of700℃advanced ultra-supercritical power plantbased on conventional system were simulated by the variable-condition model. The resultsshow that in this system main steam temperature has less compact on thermal economiccompared with conventional supercritical power plant, and reheat temperature has highercompact on thermal economic compared with conventional supercritical power plant; andfirst reheat temperature has higher compact than second reheat temperature. Meanwhilemain steam pressure has similar compact on thermal economic in these two kinds of powerplant. And there is lower impact of heater removal in700℃power plant based onconventional system compared with conventional power plant.In this paper, exergy-loss distribution has been researched by use of exergy analysis of700power plant base on conventional system and MC system. The results show that, boilerunit has greatest exergy loss, and other units have lower energy loss comparatively which issimilar with that in conventional power plant.700℃power plant based on MC system hashighest exergy efficiency and greatest thermal economic, because of thermal economicincrease of IP1and the third to sixth heaters.We can find some rules of energy consumption distribution both in conventionalpower plant and700℃power plant, and we find the reason of why thermal economic of700℃power plant base on MC system is increased, all of these have guiding significancefor the development of China ’s large coal-fired power plant.