Conventional and Advanced Exergoeconomic Analysis in a Nitric Acid Production Plant

An advanced exergoeconomic analysis (AEA) allows determining the part of Exergy Destruction and total investment costs that can be avoided. The results of the advanced analysis show the economic costs to be reduced and improvements that can be achieved for the system in terms of the overall efficiency. A Nitric Acid Production Plant of 350 tons/day was taken as case of study to implement a conventional and advanced exergoeconomic analysis. In this work, the investment costs and exergy destruction of the components of the system were divided into 2 groups such as endogenous/exogenous and avoidable/unavoidable parts to obtain accurate information about the performance of the plant. Conventional exergoeconomic analysis showed that 58.5% of the total cost of the exergy destruction is caused by the catalytic converter with a cost rate of 687.84 $/h. The highest values of the exergoeconomic factor were for Tail Gas Desuperheater (99.01%), Condenser (96.35%) and Tail Gas Heater (87%). The costs of the production process can be improved by reducing the total investment of these three components. The lowest value of exergoeconomic factor was calculated for the Catalytic Converter (15.25%) which implies that thermodynamic efficiency of this equipment must be enhanced. Based on AEA results, most exergy destruction of the Catalytic Converter is avoidable and exogenous. The destruction cost of the avoidable exergy for this component was 54.4 $ / h, which means that more than 50% of the total cost of the exergy destruction of the Catalytic Converter can be minimized to improve the performance of other equipment of the plant. Most exergy destruction costs for Tail Gas Heater, Absorption Tower and Air Heater, are unavoidable and endogenous and they cannot be reduced by improving the performance of these equipments. In addition, the cost of the exergy destruction of the Tail Gas Desuperheater is largely unavoidable (66.9 $ / h). In particular, 85%, 88% and 83% of the investment cost of the Tail Gas Desuperheater, the Absorption Tower and the Catalytic Converter, respectively, are exogenous; that is, it is only affected by the structure of the plant and the operation of the other components, but not by its internal thermodynamic inefficiencies.