Impact of Biomass Particle Morphology on Pyrolysis and Gasification Processes: Insights from TGA and Reaction Kinetics

Abstract

This study investigates the influence of biomass particle size and shape on pyrolysis and gasification of pine wood in a laboratory-scale fixed-bed reactor. Biomass particles have been categorized into fine, medium, coarse, and large size ranges and shaped into spherical, cylindrical, flaky, and irregular geometries. Pyrolysis has been conducted at temperatures up to 800°C under nitrogen, while gasification has been performed at 800–1200°C in a CO₂-steam mixture. Thermo-Gravimetric Analysis (TGA) has been employed to monitor weight loss and heat flow. The findings have revealed that smaller, spherical particles significantly enhance decomposition rates, achieving higher gasification efficiencies at lower temperatures. These particles have produced hydrogen-rich syngas with an H₂/CO ratio of 1.1, while larger, irregular particles have favored carbon monoxide generation. Emission analysis has demonstrated that fine particles have reduced NOx, SO₂, and CO₂ emissions by up to 85%, 80%, and 70%, respectively. Kinetic analysis has shown that smaller particles require lower activation energy (31.23 kJ mol−¹) compared to larger particles (39.52 kJ mol−¹). This study emphasizes the critical influence of biomass particle size and geometry in optimizing reactor design, improving conversion efficiency, and minimizing environmental impacts. Unlike prior studies that vary particle size alone, this work simultaneously resolves the combined effects of particle size (four classes) and shape (four geometries) using TGA quantification, thereby filling a critical gap in the literature on size- and shape-resolved biomass conversion kinetics. These findings directly inform feedstock preparation protocols for optimizing fixed-bed reactor performance in bioenergy applications.