Energetic and Environmental Analysis of Partial Repowering of a Coal Fired Power Plant Through Upstream GT Integration and Employing Waste Heated Feed Water Heaters
This paper presents a theoretical study of partial repowering scheme for an existing 210MW coal fired power plant and reports predicted performance improvement obtainable from the repowering by using Cycle Tempo software. In this method old boiler is used as it is, only modifying its air heater and forced flow sections. Out of four operating coal mills, one mill is considered to be taken out. A new natural gas fired gas turbine (GT) block is considered to be integrated with the existing plant whose exhaust is fed to the existing boiler. The GT size is selected such that its exhaust provide heat input equivalent to the replaced coal mill. The burners associated with that coal mill are assumed to be modified to handle hot exhaust gas from the GT block. It is noticed that a substantial amount of energy is available in the flue gas, coming out from the boiler, after the air preheater which can partially meet the heat loads of feed water heaters. This helps in saving of intermediate pressure (IP) and low pressure (LP) bleed steam and consequent increase in the output of the steam cycle. The partial repowering results in nearly 40% increase in capacity of the plant (from 210MW to 284MW). It also results in substantial increase in overall efficiency of the repowered plant by 28%, and consequent decrease in plant heat rate by 22%. The specific CO2 emission of the plant decreases about 31% after repowering.