Study On Low-prussure Steam Temperature Dynamic Characteristies Of Ultra Supercritical Double-reheat Unit

The performance test of the No.3 unit in Taizhou power plant in November 2015 shows that ultra supercritical double-reheat units have better capacity than single reheat units on economic benefits and environmental benefits.Before the required new alloy materials of 700? degree ultra supercritical units make a breakthrough and get to large-scale production,ultra supercritical(USC)double-reheat technology can be an effective feasible to improve the thermal efficiency of the unit.Comparing with a conventional reheat unit,the boiler and the steam turbine structure of a double-reheat technology is more complex.Low-pressure steam temperature is a new controlled object and its control strategy is still in the exploratory stage.Relying on Laiwu 1000MW USC double-reheat unit of Huaneng Group,analysis on dynamic characteristics of low-pressure reheat steam temperature has been done in this paper:(1)By searching the relevant literature on the development of double-reheat technology,the characteristics and development status of the double-reheat technology are summarized.Before the required new alloy materials of 700? degree ultra supercritical units make a breakthrough,double-reheat ultra supercritical technology can be an effective feasible to improve the thermal efficiency of the unit.(2)Method for modeling the system of unit system is analyzed.The simulation support platform APROS is chosen as the modeling tool.The material of 1000MW ultra supercritical double-reheat unit is taken as reference to grasp its structure and to build its principle model.(3)Research project on dynamic characteristics of low-pressure steam temperature is made.The model having been built is communicated by OPC to Matlab to record related test data.Under 100%BMCR condition,wind flow?feedwater flow?coal flow?position of flue gas recirculation fan baffle and position of flue gas distribution baffle are chosen as disturbance factor.By Single variable disturbance test,comparing with conventional single-reheat unit,analysis and research on dynamic characteristics of low-pressure reheat steam temperature in 1000MW ultra supercritical double-reheat units are made.Low-pressure steam temperature is significantly affected by gas distribution baffle and flue gas recirculation rate,but its effect takes long time.Low-pressure reheat steam coolwater can effectively influence low reheat steam temperature in a short period of time,but will affect the units of the economy.So the gas distribution baffle and flue gas recirculation fan outlet baffle can be set as the main control means of steam temperature and the low spray water be set as auxiliary means of regulation.By analysis on dynamic characteristics of low-pressure reheat steam temperature in 1000MW ultra supercritical double-reheat unit,the research on the related control strategy is hope to be helpful.