An Eulerian-Lagrangian method for wet biomass carbonization in rotary kiln reactors

This study presents numerical simulations of rotary kiln reactors for wet biomass carbonization. For this, a numerical tool has been developed resolving the carbonization process in time and space. Biomass particles are represented by Lagrangian particles that collide and form a moving bed. The gas phase is treated as an Eulerian phase. Both phases are fully coupled with the exchange of momentum, energy, and mass of chemical species. The tool is implemented in the open-source OpenFOAM (R) framework and additional submodels for devolatilization, drying and radiation have been developed for the conditions relevant during the carbonization process. In this way, models for the complex physical processes are combined in a single simulation tool. A rotary kiln reactor of laboratory-scale is used to validate the numerical tool and to perform parameter studies to determine biomass conversion in dependence on the wall temperatures. The results also give insight into the sensitivity of biomass to carbon conversion with respect to the biomass moisture content and mass flow rate. The validated tool is used to perform simulations of an industrial-scale rotary kiln reactor, which are carried out on a supercomputer on up to 1120 CPU cores. The simulations demonstrate the effect of different wall temperatures on the optimal conversion of biomass to char and help to choose the optimal wall temperatures depending on the biomass properties.

Automated summary

This study presents numerical simulations of rotary kiln reactors for wet biomass carbonization, utilizing a developed numerical tool to model complex physical processes. By validating the tool on laboratory-scale reactors and conducting simulations on an industrial-scale reactor, the study provides insights into optimizing wall temperatures for biomass conversion to char.