This study proposes a systematic framework for exergy analysis of chemical processes implemented directly in UniSim Design and demonstrates its application to sulfuric acid production via the double contact process. Thermal, mechanical, and chemical exergies are evaluated within the simulator, enabling an integrated assessment of unit- and plant-level irreversibilities. Results indicate that the sulfur-burning furnace and major heat exchangers account for more than 70% of total exergy destruction. Increasing steam pressure from 42 to 60 bar reduces lost work by 2381 kW (1.33%) and increases potential power generation by 16%, whereas optimization of selected heat-exchanger outlet temperatures yields only marginal improvements. Process rearrangement of the furnace and heat recovery section confirms that the associated irreversibilities are unavoidable and endogenous. The overall plant exergy efficiency is 21.02%, increasing to 48.25% when product stream exergy is included. Grassmann diagrams are used to visualize exergy flows and losses. The results demonstrate UniSim Design as a robust and transparent platform for applied exergy analysis of industrial processes.
Ferreira et al. (Fri,) studied this question.