Mixing of powders under periodic shear stress: effect of initial filling level

Powder Mixing continues being of great importance in the field of particle technology because of the challenge to get homogeneous mixtures at a large scale. However, it is still moderately understood because of the complexity of designing 3D experiments that consider all the factors affecting the powder flow and powder mixing, hindering the acquisition of enough data that would provide a basic conception of powder behavior. This study involves a simple granular material mixing system of low friction that has five walls, where two of them are high friction moving walls following a cyclic function, and the others are non-friction static walls. The purpose was to create a complete set of 3D experiments of powder distribution to have a better insight into the inside mixing behavior as a function of the initial powder filling level. Experiments at different filling heights were run, obtaining the best mixing at the highest filling level. It was obtained a non-mixing zone with a triangle shape highly affected by the column particle weight. The increase of the vertical component of the resultant force produced by the acrylic motion walls causes a high momentum transfer in the x, y and z directions resulting in a decrease in the no-mixing zone. It was found an asymptotic behavior of the triangle height as a function of the initial filling height of the powders which indicates that values above a limited initial filling level will not have a significant effect on the triangle. A filling height increment of 100 % from 3.81 to 7.62 cm causes an increase in the mixing of 4.44 %. DEM simulations for mixing in the low-shear equipment were run to compare the experimental wor

Devolatilization of African Palm (Elaeis guineensis) Husk studied by TG-MS

Using simultaneous thermogravimetrical analysis coupled with mass spectroscopy, the pyrolysis of African palm husk, using several heat rates and programs was performed. Seven relations of mass/charge were followed of the evolved gas of the pyrolysis process, fitting the kinetics and the mass spectroscopy signals to the distributed activation energy model (DAEM) with different numbers of pseudo-components. Fitting with four pseudo-components proved to be the best for modeling the thermal degradation process. Kinetic parameters were not affected by the heating rate or program employed, which agrees with other reports for similar biomass. Methane, methanol formaldehyde, furfural were successfully fitted to the DAEM model, nevertheless CO2 and NO2 were not able to be represented by this model due to its production in secondary reactions in gaseous phase.Se estudió la pirólisis del cuesco de palma africana utilizando diferentes programas de calentamiento, recurriendo al uso de la técnica simultánea de análisis termogravimétrico acoplado a espectrometría de masas. En los gases de evolución, se siguieron las intensidades de señal de espectrometría de masas de siete relaciones m/z. La cinética de pirólisis de este residuo del procesamiento de aceite de palma se ajustó al modelo de distribución de energías de activación con diferentes números de pseudo-componentes. Los resultados del ajuste mostraron que son necesarios al menos cuatro pseudo-componentes para modelar satisfactoriamente los perfiles termogravimétricos de la pirólisis del cuesco de palma. Se encontró que la velocidad de calentamiento no afecta significativamente los parámetros del modelo cinético, los cuales se encuentran en concordancia con los reportados en la literatura para biomasas similares. Los perfiles de las curvas de intensidad de señal para las relaciones m/z seleccionadas se modelaron utilizando los parámetros cinéticos obtenidos del ajuste de los datos termogravimétricos, lográndose resultados satisfactorios para las relaciones m/z correspondientes a fragmentos de moléculas como metano, metanol, formaldehído y furfural. La falta de ajuste de las intensidades de señal correspondientes a CO2 y NO2 se atribuyó a que la formación de estos compuestos es consecuencia no sólo de la descomposición de la biomasa, sino también a su aparición resultado de reacciones secundarias en fase gaseosa