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    DETERMINATION OF AVOIDABLE & UNAVIODABLE EXERGY DESTRUCTIONS OF FURNACE-AIR PREHEATER COUPLED SYSTEM IN A PETROCHEMICAL PLANT
    (Yildiz Technical Univ, 2016) Sert, Selay; Balkan, Firuz
    This study was performed with the intention of giving a deeper insight about the thermodynamic effectiveness of a thermal system. In this study, a fired heater (or furnace) existing in a petrochemical plant located in Aliaga, Izmir, Turkey were investigated from both first and second law point of view to identify the true magnitude of thermodynamic inefficiencies and reveal the true potential improvements for the system components. Hence, apart from the classical energy analysis, both conventional and advanced exergy analysis were applied to the system. The major source of inefficiencies within the system was enlightened by determining the exergy destructions and recommendation for possible modifications for improving thermodynamic efficiencies were stated. For each system component, amount of exergy destructions were determined and exergy efficiencies were calculated as 40.9% and 39.3% for fired heater (FH) and air preheater(APH), respectively in conventional exergy analysis. Besides, applying the advanced exergy analysis method it was seen that exergy efficiencies can be increased up to 52.4% and 85.8%, respectively.
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    Enhancement of thermal efficiency of a natural gas furnace in a petrochemical plant
    (Ege Üniversitesi, Fen Bilimleri Enstitüsü, 2016) Sert, Selay; Balkan, Firuz
    This study consists two parts. In the first part, it was aimed to improve the thermal efficiency of an aromatic hydrocarbon furnace placed in a petrochemical plant located in Aliağa, İzmir. Exit temperature of the flue (stack) gas is being descreased to 259 °C by an air preheater (APH) existing in the plant. To increase the system effciency this temperature should be further decreased. For this purpose, two processes were investigated. 1) Increasing heat transfer area of existing APH, 2) placing a waste heat boiler after APH and it was seen that first method was not economically appropriate, since the remarkable fuel saving can only be achieved in very high area increase. In the second process, producing medium-low pressure steam, requires less heat transfer area in comparison with the first process and thermal efficiency of the combined system attains higher values with lower costs. In the second part of the study, the system was investigated from the second law of thermodynamics point of view. Conventional exergy efficiency of the furnace was calculated as 41.4%. By appling advanced exergy analysis, exergy efficiency of the unit can be increased up to 52.4% with suitable modifications. Conventional exergy efficiency of the air preheater was found as 37.0% and it was concluded that by improving working conditions and determining avoidable irreversibilities, the exergy efficiency of APH can be increased up to 83.5%. Likewise, for WHB, it was seen that conventional exergy efficieny was 45.7% and advanced exergy efficiency was 62.8%.