USE OF RELATIVE FUEL ECONOMY INDICATOR FOR OPTIMIZATION OF CHP CCGT PARAMETERS

The paper justifies a possibility of using an indicator of relative fuel economy in comparison with separate generation of electric power and heat in solving problems related to optimization of combined heat and power combined-cycle gas plants (CHP CCGT) in modern economic conditions. We established the relationship between the value of relative fuel economy in comparison with the separate generation of electric power and heat for CCGT with external (system) conditions, parameters, structure and mode of operation of the power plant, as well as the integral economic effect. It was found that for a given type of gas turbine (GT), the efficiency of the cycle, the specific generation of electricity at thermal consumption and the relative fuel economy in comparison with the separate generation of electric power and heat for CCGT is determined by the parameters of the utilization circuit. It was found, that the coefficient of heat use of fuel of CCGT, practically does not depend on the initial parameters of steam. It was found, that the cycle efficiency, the specific generation of electricity at thermal consumption and relative fuel economy in comparison with the separate generation of electric power and heat for CCGT have a pronounced maximum, achieved at the same value of the initial steam pressure. The initial steam pressure was optimized for a CCGT (based on GT13E2) with a steam circuit of the same pressure level using the indicator of relative fuel economy compared to separate generation of electric power and heat. For this type of CCGT thermal power station, the optimal initial pressure is 5.5-6 MPa, while for a CCGT electric power station (based on GT13E2), the optimal initial steam pressure is 3-3.5 MPa. It was found that external conditions, reflected by the type (efficiency) of the replaced electric power station, have significant impact on the relative fuel economy in comparison with separate generation of electric power and heat for CCGT. The relative fuel economy in comparison with separate generation of electric power and heat for CCGT thermal power station (based on GT13E2) compared to the CCGT electric power station (based on GT13E2) is 26-26.5%, and compared to the steam power plant (based on the C-300-240 serial unit), the relative fuel economy will increase to 37.9%.