Thermo-environmental and economic analyses of an integrated heat recovery steam-injected gas turbine
Abstract One of the methods of gas turbine performance improvement is steam injection into combustion chamber. Moreover, heat recovery is introduced as another method for enhancing energy and exergy efficiencies. In this paper, these two methods were combined in a system of Integrated Heat Recovery Steam Injected Gas Turbine (IHRSI) equipped with an anti-surge system. A heat exchanger was used for waste heat recovery of the gas turbine exhaust and steam production. In these conditions, due to the energy balance in the HRSG, there was a relation between steam temperature and steam mass flow rate. One problem in IHRSI is determining optimum steam temperature. The increment of temperature decreases the steam mass flow rate and consequently has opposite effects on the various parameters. Therefore, in the present study, a comprehensive model based on the energy, exergy, environmental and economic analyses (4E) was presented. Eventually, the developed model introduced the optimum conditions of injected steam into combustion chamber. The optimum steam temperature of 318.5 °C was found in the case of 38 °C ambient temperature and 10% relative humidity. IHRSI at the optimum steam temperature increased net power output and thermal efficiency by 56 MW and 4.6% and reduced the cost of power generation by 25.5%.