Entrained flow gasification. Part 3: Insight into the injector near-field by Large Eddy Simulation with detailed chemistry

Entrained flow gasification is a promising process for the conversion of low-grade feedstock, e.g. highly viscous slurries and suspensions with a significant content of solid particles, to high quality fuels. A major scientific challenge is the prediction of the physical and chemical phenomena occurring in such high-temperature and high-pressure multiphase flow systems. In this context, this article is the sequel to “Entrained flow gasification. Part 1: Gasification of glycol in an atmospheric-pressure experimental rig ” [1] and “Entrained flow gasification. Part 2: Mathematical modeling of the gasifier using RANS method ” [2]. The same strategy as in the first two parts was followed. In order to reduce complexity, this study focused on a two-phase (gas and liquid) flow system with a model fuel (mono-ethylene glycol) under the simplified conditions provided by the atmospheric lab-scale gasifier REGA. Using the experimental data set provided in Part 1 of the coordinated papers for validation purposes, the main focus of this study was on the detailed understanding of the near injector region of the entrained flow gasifier REGA. The unsteady flow and the chemical conversion in the gasifier were investigated by means of Large Eddy Simulations with a detailed chemistry solver including 44 individual species and a direct calculation of 329 chemical reactions. The dispersed phase was solved by Lagrangian Particle Tracking. Downstream comparisons with experimental data showed a reasonable agreement concerning temperature and species profiles. The analysis of the injector near-field revealed that the high temperature reaction zone close to the injector could not be explained by a direct reaction of the fuel with the oxidizer. Instead, carbon monoxide and hydrogen mainly formed on the axis were transported upstream by the recirculation zone. The reaction of CO and H2 with the oxygen stabilized the flame. The heat release from this reactions supported the vaporization and decomposition of fuel as well as the downstream gasification reactions.