Effect of geometric configuration on hydrodynamics, heat transfer and RTD in a pilot-scale biomass pyrolysis vapor-phase upgrading reactor

Abstract

The effect of geometric configurations on flow hydrodynamics, heat transfer, and residence time distribution (RTD) in a pilot-scale biomass pyrolysis vapor phase upgrading (VPU) reactor is comprehensively studied by numerical simulations. More specifically, three types of carrier gas structure, three types of particle feed structure, and five types of outlet structure are included in the present study. The results demonstrate that the effect of geometric configurations on heat transfer and RTD is much more pronounced than that on flow hydrodynamics such as the axial particle distribution, probably due to the low particle inventory. In this case, it is necessary to verify the difference of the temperature field in the grid independence analysis in addition to flow dynamics. Furthermore, we find that the carrier gas inlet and particle feed have an important influence on the particle distribution at the bottom of the reactor and thus affect the back-mixing behavior at both the bottom and outlet. As a consequence, such back-mixing flows further affect the temperature field and RTD substantially. Moreover, reducing the abrupt structure contributes to the catalyst particles well-distributed at the bottom of the reactor. This can reduce the mean residence time and variance, thereby decreasing the particle and gas temperature in the reactor. This work has a potential to provide a feasible guideline for biomass pyrolysis VPU reactor design and optimization.