Flamelet/progress variable modeling of partial oxidation systems: From laboratory flames to pilot-scale reactors

Abstract

Partial oxidation (POX) reactors are characterized by different reaction regimes: the near burner zone is mainly governed by the mixing of the initially non-premixed reactants and by the fast oxidation zone, while the post-flame zone is mainly governed by the slow reforming reactions under almost fully premixed conditions. Advanced turbulence–chemistry interaction models are required to describe different regimes in POX reactors. This work investigates the use of the flamelet/progress variable (FPV) approach in laminar and turbulent POX reactors. The FPV approach allows different times and length scales to be captured, using a progress variable to describe the advancement of the reactions in reacting mixtures. The solution of the chemical reactions is generally separated from the solution of the flow and mixing by pre-calculating solutions of one-dimensional canonical flames. The solution of the chemistry is stored in look-up tables and linked to the solution of the flow using the mixture fraction and the progress variable scalars. In this work, different methods for generating the flamelet look-up tables are analyzed for a laboratory reference laminar POX flame. The results are compared to the direct numerical simulation with the goal of identifying the most suitable flame structure for tabulation in POX systems. These results are then used to build a FPV table. Finally, a pilot-scale high-pressure POX reactor was investigated and the numerical results are validated using the measured composition of the syngas at the exit of the reactor.