Conventional and Advanced Exergetic and Exergoeconomic Analysis Applied to an Air Preheater System for Fired Heater (Case Study: Tehran Oil Refinery Company)

The present paper evaluates the plan of combustion air pre-heater installation on the fired heater from thermodynamics and thermos-economics point of view. As a real case study, one of the fired heaters (H_101) of Distillation unit in Tehran Oil Refinery, Iran, is intended. With applying an air pre-heater in this study, flue gases temperature falls down from 430 ºC to 200 ºC and combustion air temperature grows up from 25ºC to 350 ºC. By examining the energy and exergy analyses before and after the installation of air pre-heater, the increase in thermal efficiency by 20% and exergy efficiency by 37% and accordingly decreasing fuel consumption by 20% is observed. It is also indicated that the most exergy destruction is accrued in the fired heater (57.24%). In this study for the first time, based on advanced exergy analyses and concepts of endogenous/exogenous and avoidable/unavoidable parts, exergy destruction, exergy destruction cost rates and capital investment of combustion air preheater system are found which results show the endogenous and unavoidable parts in overall system are dominant. Also, the effect of flue gases temperature (T5) on the system performance is investigated through sensitivity analyses. It is seen that with rising T5, thermal efficiency and exergy efficiency in real, theory and unavoidable conditions decrease. The results demonstrate the majority parts of exergy destruction in fired heater and air preheater is endogenous, unavoidable and unavoidable endogenous. Considering the cost of air preheater and related equipment and operating and maintenance costs annually, the payback period is estimated to be less than 2 years. In this research, the EES and Excel were applied to calculate the amount.