Dust deflagrations are rather fast processes. They are often modelled by pyrolysis approaches neglecting inner particle transport limitations. In the developed models, Lycopodium was chosen to investigate the inner particle effects in dust deflagrations. The first step is the modelling of the dust deflagration by using a flame speed approach. Consequently the dust characterisation was done by experiments in a 20 litre SIWEK vessel. After the model evaluation of the flame front position and temperature, Lagrangian tracer particles were placed in front of the flame. The flame front is passing these particles, which are used for metering data, such as composition and temperature of the gas to calculate heat transfer coefficient and the mass transfer coefficient of each species. The results of the tracer particles are used as boundary conditions of 3D-, 1D- and 0D- single particle models. The single particle model considers a gaseous phase in the pores and a non-mobile phase for the solid and liquid substances by using an Eulerean approach. In addition, the gaseous phase includes heat and mass transport by convection and diffusion/conduction in the pores. The non-mobile phase considers only heat conduction. To model the pyrolysis, tar and char heterogeneous reactions are included, as well as a set of homogenous reactions. During the combustion, the Lycopodium particles heat up. After reaching higher equilibrium vapour pressures, the oil content of the particle starts to evaporate below the boiling point. After the last oil content is evaporated the temperature of the particle starts to rise fast and pyrolysis begins. Due to the short pyrolysis reaction period, most of the lignin structure is conserved. These results are also shown by microscope pictures of Lycopodium particles after a dust deflagration. During the whole process, temperature differences between the surface and the core of the particle were determined.
|Translated title of the contribution||Numerical investigation on inner particle effects in Lycopodium/Air dust deflagrations|
|Publication status||Published - 2015|
Bibliographical noteembargoed until null
- Dust deflagrations
- single particle model