Modification of the Cooling System the Gas Turbines of Garri-2 Power Station

Abstract

The cooling system of gas turbines is regarded as an important and basic system that affects the efficiency of the gas turbines units. The gas turbine units 5, 6 and 7 at Garri-2 Power Station are examples of the gas turbine units that are greatly affected by the cooling system. Since their installation in 2001, these units suffered from low efficiency of the system used (fin-fan air cooler), as it depends on the ambient temperature in the process of heat exchange. This leads to the rise of the temperature of the lube oil, used in bearings lubrication, during the period from March to September. The temperature of the lube oil may reach 79°C during this period which causes a drop in the efficiency and automatic stop of the gas turbine unit. The objective of this research is to investigate the feasibility of improving the efficiency of the cooling system in gas turbine units 5, 6 and 7 by utilization of the surplus cooling capacity of the station cooling towers. To meet the objective of this research, calculations were carried out to determine the surplus cooling capacity. The calculations showed that there was a surplus cooling that could be used in cooling gas turbine units. The necessary calculations were made to select a heat exchanger to be used in cooling gas turbine units. Also an economic study was conducted to determine the feasibility of this modification. The study showed that the cooling system of the gas turbine units would become more efficient by incorporating a heat exchanger in the system to utilize the surplus cooling capacity of the cooling towers. The cost this modification in could be recovered in not more than 17 months with an annual saving to equivalent 285845.76 SDG.