Indian Journal of Science and Technology

Abstract

Background: Exergy analysis has been recognized as a feasible approach to evaluate and improve industrial processes by identifying major irreversibilities in a system. Objectives: This work attempts to apply exergy analysis to a third-generation biodiesel production from Chlorella vulgaris microalgae. Methods/Analysis: Commercial industrial process simulation software was used to simulate this process. The specific exergy of many substances were found in literature and the others were calculated using Szargut, Morris & Steward’s equation. A global exergy balance around the system was carried out in order to determine total irreversibilities. The contribution of unit operations and equipment to total irreversibilities was also considered. In addition, exergy efficiency and exergy emission were calculated for each stage (pretreatment, reaction, separation, biodiesel purification, and glycerol treatment). Findings: The global exergy efficiency was calculated in 86% similar to the results reported in other researches. The equipment that contributes the most to total irreversibility was the separation column used to remove alcohol with 487.55 kJ/kg BD. In addition, the highest irreversibilities (5.22 MJ/kg BD) and exergy emission (2.71 MJ/ kg BD) per stage were reached during biodiesel purification. Novelty/Improvement: The application of exergy analysis allowed to identify potential improvements in this case of study, mainly in biodiesel purification stage and process modifications are suggested to reduce total irreversibilities as reutilizing methanol and glycerol streams.

Keywords: Biodiesel, Exergy Analysis, Microalgae, Process Simulation, CAPE