Numerical simulation of lignin gasification: The role of gasifying agents in entrained-flow reactors

Abstract

Biomass gasification using an Entrained-Flow Reactor (EFR) is an effective strategy for sustainable energy production and climate change mitigation. However, optimizing gasification efficiency and syngas quality requires a thorough understanding of the influence of gasifying agents. This study investigates the effects of different gasifying agents—air, CO₂, steam, and CO₂-steam mixtures—on lignin gasification in an EFR. Utilizing a validated Eulerian-Lagrangian Computational Particle Fluid Dynamics (CPFD) model, we examine how these agents impact biomass conversion to syngas, focusing on key parameters like hydrogen to carbon monoxide ratio, and the lower heating value (LHV) of syngas. Our findings reveal that air, due to nitrogen dilution, results in suboptimal lignin-to-syngas conversion, yielding lower energy content and hydrogen production. In contrast, steam enhances conversion efficiency, significantly increasing hydrogen output and LHV. CO₂ as a gasifying agent boosts carbon monoxide levels through interactions with solid carbon, leading to a higher energy content in the syngas. The CO₂-steam mixture is particularly effective, producing syngas with a high hydrogen concentration, primarily due to the water–gas shift reaction and steam’s reaction with the lignin carbon. This research addresses the limitations of existing studies by providing detailed, quantitative insights into the impact of gasifying agents on lignin gasification in an EFR. By adjusting the CO₂-to-steam ratio, operators can precisely control the composition of syngas for targeted applications such as Fischer-Tropsch synthesis, methanol production, and fermentation. The study highlights the potential of advanced simulation techniques to optimize biomass gasification processes, offering significant improvements in efficiency and energy yield over current methods.