Spatially resolved exergy analysis and irreversibility mapping of corn-cob biomass gasification in a concentric-tube allothermal reactor

Abstract

In this work, a one‑dimensional local exergy analysis is carried out for corn‑cob gasification in a concentric‑tube reactor. The domain is discretized into differential control volumes and closed with exergy balances for the biomass feed, gasifying agent, and heat supplied from the inner combustion zone; outlet streams include syngas, tar, and unconverted char. Physical and chemical exergies are evaluated for all streams, and the physical exergy of volatiles is approximated from water‑vapor properties. A complementary CFD model provides gas composition and temperature fields used for comparison and interpretation. The resulting irreversibility map exhibits two pronounced peaks—near the combustion region and at the devolatilization front—coincident with intense thermal conversion. The total destroyed exergy is 102.8 kW (9.91 % deviation from a reference configuration), while the exergy efficiency is 66.14 % (≈3 % deviation); the cold‑gas efficiency is 31.86 %. These results validate the modeling framework and show that local exergy mapping pinpoints design targets (e.g., heat‑transfer coupling and devolatilization control) to improve reactor performance and syngas quality in biomass gasification.