The objective of the study is to model and optimize the thermochemical conversion of granular biomass particles in a rotary drum reactor. For the numerical modeling of the heat- and mass transfer processes, as well as for the chemical conversion of the biomass the CFD (Computational Fluid Dynamics) code OpenFOAM on the supercomputer bwUniCluster at the Steinbuch Centre for Computing (KIT) will be applied. For this purpose, the master thesis will be carried out in a close collaboration with scientists from SCC, SimLab Energy.
The setup of the model starts with a mesh generation for the rotary drum tube as shown in the figures below. As a first simulation step, one of the existing Lagrangian particle tracking methods for the transport of the particles has to be applied. Then, the heat transfer from the hot wall to the bed and the gas will be included in the simulations. Finally, mass transfer between solid phase and gas phase during drying and conversion will also be taken into consideration.
Evaluation of the results:
The first results consider the degree of mechanical mixing of particles. Here, the residence time of particles of different sizes will be evaluated statistically as a function of the geometry, the degree of filling of the reactor, and its angle of inclination. The effects of different collision models for the particles will be assessed as well. Consequently, the heat transfer from the reactor wall will be included in the model and results regarding the temperature distribution of the particles as well as the overall energy balance in the reactor will be collected and evaluated. After the drying and the chemical conversion of the biomass is applied, the time evolution of these processes in single particles will be processed graphically together with the overall temperature distribution in the reactor. The obtained results will be evaluated in terms of possible energy optimizations of the reactor processes.
The simulation tool:
OpenFOAM, a C toolbox for development of customized numerical solvers has been chosen as the software package for this study since it has a great potential to solve continuum mechanics problems including CFD and particle tracking. The simulation model will be prepared and tested on the local cluster of the Institute (EBI-VBT) and the production runs will be carried out on the KIT supercomputer bwUniCluster. Results will be visualized with Paraview.
The scope of the work
- Literature review and introduction to OpenFOAM and relevant tutorials
- Generating computational grid with simple reactor geometry and boundary conditions
- Initial calculation of numerical domain filled with particles considering particle size distributions
- Statistics of the movement of particles in the geometry and visualization of results
- Parametrization and sensitivity analysis of the model based on of different degree of filling as well as geometrical conditions resulting in a graphical output
- Heat transfer to the bed of particles and to the freeboard gas
- Mass transfer calculations based on drying and devolatilization
- Documentation of the study as a written scientific work
- Presenting the result of the study