Comparison of classic combined power plant and combined power plant with water injection

Temperatura dimnih plinova na ulazu u plinsku turbinu u praksi se smanjuje dovođenjem više zraka nego što je potrebno za potpuno izgaranje goriva. Osim navedene metode, temperatura dimnih plinova može se smanjiti i ubrizgavanjem vode. U radu je izrađen model klasičnog kombiniranog postrojenja te model kombiniranog postrojenja s ubrizgavanjem vode korištenjem EBSILON® Professional programskog paketa. U radu se uspoređuju maksimalne termodinamičke iskoristivosti oba postrojenja. Kako bi se postigla maksimalna termodinamička iskoristivost oba kombinirana postrojenja koristi se optimalni raspored izmjenjivačkih površina unutar generatora pare na otpadnu toplinu. Osim toga, tlakovi na izlazu iz kompresora te tlakovi vode unutar generatora pare na otpadnu toplinu podvrgnuti su optimizaciji s funkcijom cilja maksimalne termodinamičke iskoristivosti cijelog postrojenja. Dobivena termodinamiĉka iskoristivost kombiniranog postrojenja s ubrizgavanjem vode znatno je niža od one kod klasičnog kombiniranog postrojenja. Dobrim dijelom razlog je nemogućnost iskorištavanja topline predane ubrizganoj vodi zbog pinch točaka unutar generatora pare na otpadnu toplinu.The flue gas temperature at the entrance to the gas turbine in practice is reduced by bringing more air than it is required for complete fuel combustion. In addition to the above mentioned method, the flue gas temperature can be reduced by injecting water. In this paper, a model of a classic combined power plant and a model of a combined power plant with water injection has been developed using the EBSILON® Professional software package. This paper compares the maximum thermodynamic efficiency of both plants. In order to achieve the maximum thermodynamic efficiency of both combined plants, the optimal arrangement of the exchange surfaces within the heat recovery steam generator is used for the waste heat. In addition, pressure outlets from the compressor and pressures levels inside the heat recovery steam generator were subjected to optimization algorithm with the function of maximizing the thermodynamic efficiency of the entire plant. The calculated thermodynamic efficiency of the combined power plant with water injection is considerably lower than that of a classical combined power plant. The reason is the inability to use the heat delivered to the injected water due to the pinch of points within the steam generator to the waste heat