Математичне моделювання процесів зневоднення та гранулювання у псевдозрідженому шарі

Abstract

Approaches to the mathematical modeling of dehydration and granulation in a fluidised bed. Classification by type models interfacial interaction. Proanalizovno basic approaches to building mathematical models of processes of dehydration and granulation in a fluidised bed, basic assumptions and characteristics determine basic technological parameters proposed by different authors.The most complete mathematical model can be characterized by the number of phases. The term mean area containing solid or gas. They may differ in Volumetric particles of solid appearance, and for hydrodynamic characteristics. The first approaches to mathematical modeling apparatus for dewatering and granulation in fluidized bed based on a single-phase models, ignoring the segregation of gas and solid particles from the presence of cavities. So were trying to predict the performance of the device fluidized-bed exclusively for residence time distribution, ie axial mixing gases. This attempt was unsuccessful because the transformation described in the fluidized bed is worse than in the case of ideal mixing. Performance fluidized-bed unit is determined by the contact between the gas and solid particles, given the presence of bubbles. It is essential taking into account the characteristics of hydrodynamics.According to the research made the following generalization.Model Orcutt: This model allows piston flow regime in both phases, gives good results distribution profiles of concentration by taking into account interphase mass transfer. Needs to refine the specific experimental data.Model Partridge-Rowe: Neglect of a two-phase theory caused a serious problem for this model. Estimated bubble phase region exceeds the total area of the layer. Attempts to adjust gas flows in phases not overcome this problem completely.Model Kato-Wen: This model provides a satisfactory concentration distribution profile in phase bubbles, but it can not predict the concentration of the emulsion phase and can not predict the drop in concentration at the surface layer.Model Kunii-Levenspiel: The best match was found using this model. With this model correctly predicted concentration in dense phase, due to the low speed interphase mass transfer. It was established that the total mass transfer model Kunii-Levenspiel limited resistance between the cloud and the emulsion and the model is simplified to two phases, phase aligning bubbles and clouds.