Design And Application Of Reheat Steam Temperature Control System For Ultra-supercritical Secondary Reheat Unit

As the current environmental problems faced by coal-fired power plants are becoming more and more serious,how to use advanced technology to reduce the emission of pollutants from thermal power units and improve the efficiency of the units is the most important problem that China needs to solve in developing coal-fired units.Internationally,ultra-700°C technology and secondary reheating technology are currently the two main research directions.However,since materials that can withstand high temperatures above 700°C are still in the research and development period,secondary reheating technology has become the current development of thermal power units in China.Important breakthrough technology.This paper summarizes and analyzes the design methods of steam temperature control of secondary reheating units at home and abroad.Based on the layout characteristics of the heating surface of the tower type DC furnace in Da Tang Dong Ying Thermal Power Plant,a set of reheat temperature control for an ultra-supercritical secondary reheating unit is designed.Strategy.According to the designed control strategy,the reheat steam temperature control adopts the flue gas baffle control to coordinate the burner swing angle control,and the micro water spray temperature reduction control is used as an auxiliary adjustment method,and finally the accident water spray temperature reduction is used as a part of over temperature protection.The system control method of the defense line.The burner swing angle swing control is automatically adjusted by reducing the reheat steam temperature deviation;where the flue gas baffle passes once,the corresponding deviation of the second reheat steam temperature and its set value,and the deviation of their respective corresponding differences Close to zero,to ensure the stability of the reheated steam temperature under normal operating conditions.If the temperature of the reheated steam still shows an upward trend,select a small amount of water spray or a crisis water spray according to the rising degree to ensure the safe operation of the unit.Unit 1 of Dong Ying 2 × 1000 MW ultra-supercritical unit,which is based on in this paper,will enter the site for commissioning in September 2019.The control system was completed on the DCS of HollySys,and the control effect of the reheat steam temperature control strategy was verified by load lifting test during debugging.With the issuing of lifting and lifting load instruction,the coordinated control system will make the total coal quantity and water supply rapidly change in a positive direction with the load under the action of BIR,causing the reheat steam temperature to fluctuate violently.At this point,through the reheat steam temperature control system designed in this paper,the fluctuating reheat steam temperature is stabilized at the preset value,and the reheat steam temperature is controlled.The research and analysis of the reheat steam temperature control system of the secondary reheat unit can provide some reference for the practical application of the reheat steam temperature control of the ultra-supercritical secondary reheat unit.