Fluid dynamic bubble phase study of an urea fluidized-bed by CFD

M. ZAMBON; C. MORA BASAURE; V. MUÑOZ; D. ASENSIO; V. BUCALÁ; G. MAZZA

Lyon

Congreso; XIVème Congrès de la Société Française de Génie des Procédés (SFGP2013); 2013

SFGP

Granulate urea is one of the most often used nitrogen-based fertilizers. The granulator forms the heart of the urea granulation circuit and fluidized bed units provide an appropriate operation that allows a good control of the production process. This contribution is an important stage to make possible the entire CFD simulation of a granulation fluidized bed from molten urea atomization. This work concerns a hydrodynamic study of an air-urea fluidized bed for uniform particle size, including minimum fluidization velocity, pressure drop and bed expansion evaluation, in order to achieve a thorough understanding of the bed behavior.Based on the essential role of the bubbles in the definition fluid dynamic pattern of the fluidized bed, a detailed study of bubbles formation and movement, shape and rise velocity is carried out here in the framework of the ANSyS Fluent 13CFD software.Specific experiments were conducted in a conical pilot-scale fluidized bed with the aim of validating CFD simulations. Both, experimental measurements and simulations were carried out for a bed of spherical particles of 2.6 mm of diameter. The gas used as fluidizing agent was air at atmospheric conditions.A multifluid Eulerian approach for granular flow, was adopted from ANSyS Fluent menu in CFD simulations. CFD simulations were carried out on 2D and 3D but 3D was adopted particularly to observe the behavior of the rising bubbles and its interaction with their neighbors.Predictions of the principal macroscopic bed properties, pressure drop, bed expansion and minimum fluidization velocity values show an excellent agreement with corresponding experimental measurements.This study provides significant evidence of the convenience of using 2D simulations, which strongly reduces the computation time almost without affecting the accuracy of calculations. Results of predicted bubble diameter, sphericity and rise velocity are compared with corresponding values obtained from correlations reported in the literature. A good agreement was observed in comparisons.