Advanced subgrid model for the gasification of Athabasca asphaltene in entrained-flow reactors

Recently, heavy bituminous crudes have increasingly being coming into focus as feedstock for synthesis-gas production. One of the heaviest compounds of petroleum is asphaltenes, which are formed during the primary upgrading process of bitumen. One feasible option for asphaltene utilization is their gasification in an entrained-flow gasifier. In this view, modeling can be used as an initial step in the design and optimization of large-scale gasifiers. This work presents a new subgrid model for computational fluid dynamics (CFD) based modeling of the gasification of Athabasca asphaltene particles (median diameter of 207 μm) in an entrained-flow reactor. The model is based on a virtual homogeneous reaction zone (VHRZ) concept (originally developed by [1]). However, in the present formulation the model considers melting, pyrolysis, homogeneous reactions in the particle vicinity and heterogeneous reactions of the char, where the VHRZ thickness is calculated using boundary layer approximation. The model has been verified using preliminary experimental data obtained for Athabasca asphaltene gasified in a lab-scale drop tube furnace (DTF). Experiments have been conducted for two different oxygen ratios, where the experimental conditions are analyzed using CFD. Good agreement between submodel predictions and experiments has been demonstrated. Finally, the results of the subgrid model emphasize the relevance of the energy feedback from the particle vicinity to the particle surface. A sensitivity study of model parameters shows that the ambient temperature and the assumed particle density have a mayor impact on the overall particle conversion.