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Show As shown in the process flow diagram, shaft power or electricity is generated via a gas turbine using air as the working fluid in a closed cycle. Air is compressed to a pressure of approximately 10 atmospheres without interstage cooling thereby providing an outlet temperature of approximately 800°F. This compressed air, further heated to 1,800°F in the recuperator, then drives the turbine generating approximately 300 KW electricity. The turbine exhaust is cooled and fed back to the compressor. It may be noted that an open cycle could also be used where the heat from the turbine exhaust is recovered via steam generation or preheating of natural gas, oxygen or cullet. Also, if a closed cycle is used, some working fluid other than air having superior thermodynamic properties could be utilized. Fired Gas Turbine Figure 6 depicts the process where substantially higher amount of power is generated by the incorporation of post combustion into the gas turbine cycle described above. The glass melter flue gas exchanges heat in the recuperator with the air/steam in the gas turbine cycle. In the process it is cooled from approximately 2,200°F to 750°F. Heat from the flue gas is further recovered downstream of the recuperator through cullet and oxygen preheating. The shaft power/electricity generating cycle in this case is a gas turbine cycle utilizing both indirect heat exchange as well as direct firing and heat recovery from the turbine exhaust. Air is compressed to the same pressure of 10 atmospheres as in the previous case, blended with the steam generated from the turbine exhaust, and then fed to the recuperator for indirect heat exchange. The air/steam mixture picks up approximately 5 MMBtu/hour as it is heated to close to 1000°F. This mixture is further heated in a combustor with direct natural gas firing. Air, steam and the products of combustion are fed at 1,800°F to a gas turbine to generate 1,600 KW electricity. The turbine exhaust at 1,040°F contains more available heat than the melter flue gas. This heat is recovered through natural gas preheating and the generation of steam for the cycle. The better utilization of the heat from the turbine exhaust make this process more energy efficient than the small gas turbine case. PROCESS EQUIPMENT Recuperator The recuperator is the key equipment component in both of these process schemes, especially in the small turbine case where a recuperator air outlet temperature as high as 1,800°F is desired. The recuperator will be designed as a cage type recuperator with the gas turbine air at high pressure flowing inside the tubes and the glass melter flue gas at low pressure flowing outside in the shell. The most important issue in the design of the recuperator is the material of construction of the tubes. Materials used for fabricating - 7 - |