A reactor-scale CFD model of soot formation during high-temperature pyrolysis and gasification of biomass

• Published in: Fuel (Guildford) Vol. 303; p. 121240
• Main Authors: Chen, Tao, Li, Tian, Sjöblom, Jonas, Ström, Henrik
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2021; Elsevier BV
• Subjects: Air pollution; Air temperature; Algorithms; Biomass; Biomass gasification; Cellulose; Computational fluid dynamics; Computational fluid dynamics modeling; Computer applications; Contamination; current; Dust; Eulerian-Lagrangian; Fluid dynamics; Gasification; Hemicellulose; High temperature; High-temperature gasification; High-temperature pyrolysis; Hydrodynamics; Lignin; Mass transfer; Mathematical models; Multiphase flow; Operating temperature; Optimization; Pyrolysis; Pyrolysis and gasification; Reactors; Soot; Soot formation; Soot formations; Soot generations; Tar; Tube furnaces; Two-equation model; Biomass gasification; Soot formation; Eulerian-Lagrangian; Two-equation model
• ISSN: 0016-2361; 1873-7153; 1873-7153
• DOI: 10.1016/j.fuel.2021.121240

•Reactor-scale soot modeling for biomass high-temperature gasification is established.•Simplified tar model is developed for cellulose, hemicellulose and lignin, respectively.•The difference of soot yield from the basic biomass components is well captured.•Tar reforming plays an important role in controlling soot generation during steam gasification.•The impact of surface growth through HACA mechanism on soot yield is relatively small. Soot generation is an important problem in high-temperature biomass gasification, which results in both air pollution and the contamination of gasification equipment. Due to the complex nature of biomass materials and the soot formation process, it is still a challenge to fully understand and describe the mechanisms of tar evolution and soot generation at the reactor scale. This knowledge gap thus motivates the development of a comprehensive computational fluid dynamics (CFD) soot formation algorithm for biomass gasification, where the soot precursor is modeled using a component-based pyrolysis framework to distinguish cellulose, hemicellulose and lignin. The model is first validated with pyrolysis experiments from different research groups, after which the soot generation during biomass steam gasification in a drop-tube furnace is studied under different operating temperatures (900–1200 °C) and steam/biomass ratios. Compared with the predictions based on a detailed tar conversion model, the current algorithm captures the soot generation more reasonably although a simplified tar model is used. Besides, the influence of biomass lignin content and the impact of tar and soot consumptions on the soot yield is quantitatively studied. Moreover, the impact of surface growth on soot formation is also discussed. The current work demonstrates the feasibility of the coupled multiphase flow algorithm in the prediction of soot formation during biomass gasification with strong heat/mass transfer effects. In conclusion, the model is thus a useful tool for the analysis and optimization of industrial-scaled biomass gasification.