Directed Fluidized Bed in Drying Machines: Main Stages of Optimization Calculation

Abstract

The article deals with the study of main hydrodynamic characteristics of the directed fluidized bed in gravitation shelf dryers. The algorithm to calculate hydrodynamic characteristics of the directed fluidized bed in the dryer’s workspace is described. Every block of algorithm has theoretical model of calculation. Principles of disperse phase motion in various areas in the gravitation shelf dryer are established. The software realization of author’s mathematic model to calculate disperse phase motion trajectory in free and constrained regime, disperse phase residence time in the dryers’s workspace, polydisperse systems classification is proposed in the study. Calculations of disperse phase motion hydrodynamic characteristics using the software product ANSYS CFX, based on the author’s mathematic model, are presented in the article. The software product enables to automatize calculation simultaneously by several optimization criteria and to visualize calculation results in the form of 3D images. The data on the construction of a computational model and computational grid for modeling the gas flow motion is presented. The results of determining the gas flow velocities field in the workspace of a gravitational shelf dryer distinguishing the specific zones of the drying agent’s motion are demonstrated. High and low-intensity places of gas flow are established in the dryer.The residence time of particles in the dryer is calculated depending on the technological and design parameters of the drying process, in particular, the constraint degree of the particle flow. The influence degree of the dryer’s features and its operating mode on the expected “hydrodynamic” residence time of the material in the device is established. The obtained value of the “hydrodynamic” residence time of the material in the device is compared with the drying time to find the optimal design of the dryer.