Conversion of fuel particles in a fluidized bed is also a particle changing process like granulation or coating. Thus we want to transfer our methods and perceptions from NaWiTec to the modeling of these high temperature processes. The aim is to develop a model based controller to optimize the energy yield of the biomass, and to respond fast in case of critical process states.

The basis of the required model is a population balance, where single particle kinetics (drying, devolatilization, attrition, etc.), continuum models of heat and mass transfer and the reaction network for biomass conversion are used. The population balance model (PBM) works with the change of certain particle properties in dependency on the property itself. For conversion processes particle mass and particle size were chosen to be considered in the Population Balance Equation.

To build up this aspired complex model, which should be applicable for all thermo-chemical conversion processes (combustion, gasification), it is necessary to take a closer look on the mentioned micro kinetics, what is happening in the current stage of the project. First we focused on the sub-processes of drying and devolatilization by using thermal gravimetric analysis. Now, we work on the particle size dependent shrinking behavior caused by these sub-processes. All effects should be taken into account like this. In the end we need to couple the dynamic population balance model and the existing hydrodynamic model of the gas phase.

Since the construction of the pilot plant has come to an end with the installation of the gas and particle measurement systems a high number of experiments first help to get to know the plant and process parameters under certain conditions and later to validate the modeling approach by comparing experimental data with simulation results.The very sensitive and high quality online measurement systems are able to detect the particle size distribution and the exact composition of the gas phase in the reactor aiming a dynamic monitoring of the process concerning energy yield and hazardous substances.

The higher security and the more efficient processes will help to establish thermo chemical conversion processes of biomass as one of the new energy generating systems we need in the future.







The work is funded by the German Federal Ministry of Science and Education (BMBF) as part of the InnoProfile project NaWiTec.