Retrofit and upgrading for life extension and low maintenance

In the mid 1950's, Foster Wheeler designed and constructed 4 natural circulation, balanced draft, pulverized coal-fired steam generators for the TVA at their Johnsonville Steam Plant in Tennessee. Each of these generators delivered 1,100,000 pounds of steam per hour at 2035 pounds per square inch gauge and 1053F at the superheater outlet. The reheater produced superheated steam at 1003F. Each steam generator served a turbine generator capable of producing 150,000 kilowatts of electric energy. These units were placed into initial operation between October 1958 and July 1959. Flue gases resulting from combustion in the 16 intervane-type pulverized coal burners released heat for absorption by the water cooled front wall and rear wall tube surfaces as well as the combined radiant superheat and water cooled sidewalls and superheater division wall surfaces. As the gases left the furnace, heat was absorbed in the convection superheater loops and the outlet legs of the convection reheater. The units have been upgraded and retrofitted as described in this article for higher peak efficiency to meet ever increasing energy demands and for better pollution control to meet changing EPA standards.