The shape development of spherical and non-spherical char particles in the flame zone of an entrained-flow gasifier – A numerical study. (March 2020)

• Record Type: Journal Article
• Authors: Nguyen, Cong Bang; Scherer, Johannes; Guo, Qinghua; Kriebitzsch, Sebastian; Richter, Andreas
• Is Part Of: International journal of heat and mass transfer. Volume 149(2020)
• Publication Date: 2020-03
• Subjects: Gasification -- Combustion -- Char conversion -- Particle-Resolved CFD -- Particle shape development -- Non-spherical particles; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2019.119220
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Detailed modeling of particle shape development based on CFD. Focus on the flame zone of an industrial entrained-flow gasifier. Impact of several particle shapes on carbon consumption rate is shown. Shape development significantly affects drag and therefore particle trajectories. Assumption of spherical particles in entrained-flow models are not general valid. Graphical abstract: Abstract: The shape of a particle affects its trajectory in an entrained-flow gasifier significantly. For that reason, the present work studies how the particle shape is changed during the conversion process. Several non-spherical particles are considered. The focus is on the conversion process in the flame zone, since that is where the highest gradients in temperature and concentration occur across the particle. A particle-resolved transient CFD model was applied together with a mesh motion algorithm, enabling a detailed analysis of the complex interphase phenomena between the flow field and the reactive particle. It is shown that the particle morphology changes significantly during the conversion process. The final shape depends on the initial particle shape and the reaction rate distribution across the particle, which is a function of the particle Reynolds number. Only in exceptional cases is the remaining particle spherical after leaving the flame zone. This fact must be taken into account if drag coefficients and Nusselt and Sherwood number correlations are applied in a CFD-based reactor model.