In-Depth Exergy Analysis of the Thermochemical Conversion of Flax Straw via Pyrolysis

Pyrolysis is a promising thermochemical conversion process for transforming biomass waste into valuable products like bio-oil, syngas, and biochar. Understanding the thermodynamic efficiency of this process is important for optimizing its design and operation conditions. This study presents a novel approach for analyzing lignocellulosic biomass pyrolysis, including flax straw, by using conventional and advanced exergy techniques at different operating temperatures. Using Aspen Plus software, the pyrolysis process was accurately simulated, and system inefficiencies and possible areas for improvement were identified by performing both conventional and advanced exergy analysis. This study addresses the requirements to maximize the yield of valuable products, such as biochar, bio-oil, and biogas, while minimizing exergy losses. The pyrolysis reactor, cyclone, and flash were the main sources of exergy destruction, accounting for 32.2%, 31.8%, and 18.7% of the total exergy destruction, respectively. An advanced exergy analysis revealed that endogenous exergy, which is attributable to internal system irreversibilities, was the primary contributor to exergy destruction within the flax straw pyrolysis process. Notably, 35.6% of the total exergy loss can be potentially mitigated. The findings further suggest that temperature optimization has the potential to significantly reduce exergy destruction by 31.7% via enhancing reaction kinetics and overall conversion efficiency.