Study On Steam Temperature Control Strategy Of Ultra-supercritical Double Reheat Units

Out of the ultra-supercritical double reheat unit has good economic andenvironmental benefits, it will be a trend of high parameter and large capacity thermalpower unit to develop ultra-supercritical double reheat unit on the basis of the existingmaterials technology and thermal control level. Due to the complexity and particularityof double reheat unit’s boiler construction, the problem demanding prompt solution ishow to realize the effective control of main steam temperature and two reheat steamtemperature.In this paper, based on the analysis of the existing foreign double reheat steamtemperature control method, for layout characteristics of heating surface and designparameters of double reheat tower boiler, a steam temperature control strategy was putforward to applied to ultra-supercritical double reheat units. The main steam temperatureis controlled by combustion of fuel-water ratio and spray desuperheater; The two reheatsteam temperatures are mainly regulated by the inclination of the burner and gas baffle,and spray desuperheating functions as fine adjustment. Taking into account the impact onmain steam temperature of the inclination of the burner, the angle changes of the burneris added into the spray desuperheating control loop. For the control of reheat steamtemperature, the deviation adjustment is used in this strategy. The inclination of theburner is regulated by the bigger deviation between the two reheat steam temperatures.The gas baffle is regulated by the deviation of the two deviation of the two reheat steamtemperatures, so as to keep the two deviations the same. The coordinated action of theburner and the gas baffle can keep the two reheat steam temperatures stable, also, thecontrol strategy makes the inclination of the burner and the gas baffle match each otherwhen regulating the reheat steam temperature.In this paper, the design and the configuration of the steam temperature controlstrategy are completed on Guodian Zhishen DCS. The experiments are taken on thesimulator of ultra-supercritical double reheat unit in the end, and the results show that thecontrol strategy is able to achieve the effective control of main steam temperature andtwo reheat steam temperatures.Through the research and analysis of the temperature control of ultra-supercriticaldouble reheat units, this paper can provides some reference to the practical application oftemperature control strategy, and it also has great significance in promoting and applyingdouble reheat thermal power plant in China.