Operation State Evaluation And Performance Optimization Of Gas-steam Combined Cycle Unit

A steel company power plant gas-steam combined cycle unit,whose design output power was 150 MW and combined cycle efficiency was 45.5%,was the world's first single burning low calorific value of blast furnace gas,which is friendly to environment.Since the unit put into operation,the operation performance has been in a downward trend,the unit cycle efficiency can only be maintained at around 36%,and maximum output can only reach 120 MW or so.In this condition,study of performance evaluation and fault diagnosis of this unit has an important role in energy saving and emission reduction.This paper takes the unit mentioned above as study object,the calculation model of main components' performance and total performance of the unit are established,and the performance change trend of the unit from the commissioning of the unit to now are evaluated.By doing this,the paper points out that the main reason for the decline in unit performance is performance degradation of high-pressure evaporator in heat recovery steam generator,and proposes the corresponding improvement program which will provide references to performance optimization of the unit.The main research contents of this paper are as follows:Firstly,according to the structure and operation principle of the unit,the performance calculation model of the unit total performance and the main equipment of the unit is established,and the performance calculation table is compiled.The performance calculation model was verified by the data of the performance acceptance test,which proved the correctness of the calculation model.Secondly,collect and sort out the offline,steady-state operating data from 1998 to 2014,total performance of the unit and the performance of the main equipment of the unit is calculated by performance calculation table,the performance change curve of the main equipment were drawn,combined with relevant parameters of the unit were analyzed.It turns out that a substantial decline in unit performance problems mainly lies in the waste heat boiler of the high-pressure evaporator and low-pressure evaporator performance degradation.What's more,the paper analyzes the possible causes of performance degradation in conjunction with the unit maintenance data.Finally,in view of the present situation of the waste heat boiler performance,the optimization scheme for the installation of the flow guide plate is presented.By numerical calculation software,the flow statuses of the flue gas before and after the installation of the transition flue are simulated.It is found that the installation of guide plate in the transition flue duct can make the HRSG's inlet flue gas flow rate more uniform,and reduce the pressure loss of the flue gas in the transition flue duct,which proves the feasibility of the optimization scheme.