The Analysis And Research On The Safe And Economic Operation Of 660MW Ultra-supercritical Steam Turbine

Nowadays the units of new-built coal-fired power station are now developing in the direction of super-high parameters,big capacity and high efficiency with capacity greater than 600 MW,Which mainly consisting of super-critical or ultra-supercritical units.The Ultra supercritical steam turbines are different from other type of units in structure,particularly the units which are produced by Shanghai Steam Turbine Company using SIEMENS Technology.High capacity thermal power generation unit take charge of load regulation is becoming the norm because of the changes of power supply structure of the whole country.Pursuing the maximum economic benefits under Automatic Generation Control(AGC)constraints for power station has been one of the main research topics.Thermodynamic system,structure and equipment of the Ultra-supercritical unit will become the study target by using thermal test,theoretical analysis in this article.What the text research mainly provide some reasonable methods and suggestions on equipment Online monitoring,safety issues and Economical operation for similar type units.Firstly,modeling the regenerative heaters and the steam power plant condenser under off-desing conditions based on dimensionless method.The traditional models of regenerative heaters which in off-desing conditions is very complicated due to the phase-change problem in the heaters need to be taken into account in while modeling.A dimensionless method is built up for regenerative heater according to actual measurements to reflect its operation status in off-desing conditions which is then applied to the first low-pressure heater of a 660MW ultra-supercritical steam turbine unit in this paper.Results show that the deviation of calculation results of the model and actual data are very small.The model of the method is simple and credible and can be used as tools for practical troubleshooting in power plant.In the classical approach,the effectiveness of a steam power plant condenser can be given as a function of an overall heat transfer coefficient,heat transfer surface area,cooling water mass flow rate,and the specific heat of water.The calculation of the overall heat transfer coefficient requires additional equations to determine the overall heat transfer coefficient from steam and water as well as similarity numbers,which raises further difficulties in developing a model.A dimensionless method is built up for power plant condenser according to actual measurements to reflect its operation status in off-desing conditions.The method is justified to provide a single equation for the steam power plant condenser effectiveness in off-design conditions as a function of three independent parameters,such as cooling water temperature at the inlet,cooling water mass flow rate,and steam temperature,along with corresponding reference parameters,which is then applied to the condenser of a ultra-supercritical steam turbine unit in this paper.Results show that the deviation of calculation results of the model and actual data are very small.The model of the method is simple and credible and can be used as tools for practical troubleshooting in power plant.Secondly,the power plant safety systems problem has to be taken into account from the low pressure vacuum protection for the ultra-supercritical unit.Condenser vacuum is an important safety index in steam turbine generator unit,as well as economic index.The decreasing of vacuum may lead to serious problems such as distortion of low pressure and vibration problem.However,little research has been done in this area and problems such as small flow rate in the LP last stage because of vacuum declining.Many maintenance workers overlook the incident handling of vacuum declining and logical protection in power station,especially the small flow rate in the large-scale of generating units with long blade stage.This article focused on condenser vacuum protection settings and the handling methods of vacuum declining and provide some reasonable suggestions.Finally,the electric power market of our country has been entering the stage of oversupply.The average annual load of power unit and annual utilization hours of installed capacity decreased year by year.For these reasons and more,numerous great capacity units have to take charge of load regulation at present.Research on the steady pressure throttle preparing stream mode Operation-control Strategy started relatively late and still in an exploratory stage in China.How to provide the maximum economic benefits under AGC constraints via a reasonable control strategy is a hard problem for a power station.The field thermal test for a certain unit was carried out to explore the modes of optimal distributing steam and get the operational characteristics of this unit.Next model the steam turbine system and regenerative system for this unit according to the design information and the thermal test data.Then,calculating a number of Off-design conditions to enrich data sources.Making an attempt to rationalize a reasonable operation-control strategy both juggling peak modulation and energy Conservation at last.