Investigation of the Mixing on Grate Firing Systems

Project Number 294

The aim of the present investigation is the experimental and numerical study of the mixing and transport processes of granular media on different types of grate firing systems in order to understand the mechanisms involved as well as the influence of material and system parameters.

Because of the distributed arising of biogenous granular fuel the most municipal solid waste (MSW) incinerators are rather small and decentralized facilities, which are mostly constructed, maintained and operated by small and medium-sized enterprises (SME). Therefore, especially SME's will benefit from the results of the project.

Through the possibility to provide quantitative predictions about the dependency of the mixing rates, porosity, effective mass and material diffusion on geometrical and operation conditions of MSW Incinerators, the possibility to optimize MSW Incinerators operation is enhanced. A further aim is to provide a validated tool, which can help to avoid a time-consuming and cost-intensive empirical approach.

To realize the above stated aims the Discrete Element Method (DEM) is used as a tool to model granular systems. The method tracks every single particle in a system of a granular media. Hence, DEM is able to determine detailed information about position as well as translational and rotational velocity of each single particle. Such a parallel three-dimensional DEM code for a large number of particles and industrial scale systems was developed at the LEAT within the last years.

The project is funded by the German Federal Ministry of Economics via the Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF, funding no. 15061 N). It is carried out from December 2006 to September 2009 at the Bochum University (LEAT). A working group of the Working Panels "Biomass" and "Thermal Waste Utilisation" technically supports the investigations.