Hydrodynamika vícefázových reaktorů

Abstract

The multiphase flow reactors are widely used in the chemical and other process industry. Multiphase flow reactor with internal circulation loop called Pachuca was in focus of interest of my thesis. The Pachuca tank is a typical hydrometallurgical reactor for leaching of ore, other minerals, or metallurgical wastes. Study of hydrodynamic behavior of multiphase flow in reactor with a draft tube (with internal circulation loop) was the main topic of my PhD thesis. Design and construction of laboratory reactor with the draft tube was first aim of my work. The hydrodynamics parameters such as gas hold-up, density of dispersion, liquid circulation velocity and loss coefficient were determined from measured pressure differences. The inverse U-tube manometers were used for the measurement of the pressure differences. The geometry of equipment was characterized by the dimensionless ratio of diameter of the draft tube to the diameter of reactor (ddf /dc). This ratio had a primary influence to the hydrodynamics parameters. Increasing of liquid circulation velocity in the draft tube (riser) simultaneously with gas hold-up in annulus (downcomer) decreasing as a function of decreasing ratio ddf /dc was observed. Position of the draft tube was further parameter, which affected the hydrodynamics of multiphase flow. These positions were characterized by the dimensionless ratio of the draft tube upper end and the liquid level heights, and by the dimensionless ration of the draft tube lower end and the bottom of reactor. Patterns of the bubbles circulation regimes to the hydrodynamic in the laboratory reactor were observed besides of the quantitative parameters. Large number of geometry configurations can be varied and the measurement is time consuming. For these reasons, simple numerical model was suggested. The COMSOL Multiphysics software with bubbly flow model was used for CFD simulation. The results of experiments and results of CFD simulation were compared for three magnitudes of ratio ddf /dc. Agreement between the respective results proved that the numerical simulation is suitable tools for investigation of three-phase flow. Optimized design of three-phase flow reactor was suggested on the base of the results for the two-phase flow. Hysteresis of the pressure difference was found in three-phase flow reactor and then, critical gas volumetric flows for suspended solid particles have been determined for increasing and decreasing gas volumetric flow, respectively.