Estudo da fluidodinâmica de leito vibro-fluidizado horizontal

Abstract

Applications of the mechanical vibration with the intention of to facilitate the fluidization and to increase the transfers of heat, mass and amount of movement are processes commonly used in the agribusinesses, as for instance, in the granulation, covering and, above all the drying, where ponders the largest number of applications. Other advantages of the use of the vibration on the beds conventional fluidized are: the control easiest of the time of residence of the particles for the manipulation of the vibration parameters; decrease of the amount of air for the fluidization; reduction of the dimensions of the equipments; more uniform and efficient drying of materials agglomerates; elimination of the areas died inside from the equipment. The present work studied the fluid dynamic behavior of horizontal vibratefluidized bed building for this the characteristic curves of pressure drop and standard deviation of the pressure drop in relation to velocity of the air of the bed in different vibration conditions. The influence of parameters was evaluated as frequency and width vibration and the material load in the bed. The equipment used in the work was a horizontal vibrate-fluidized bed of steel carbon formed by a rectangular section of 0,9 meter of length, 0,34 meter of width and 0,77 meter of height. The bed is sustained by a system of four springs connected to support of 0,74 meter of height. The particle used in the study were glass spheres with medium diameter of 3,89x10-4 meter and density of 2,5 g/cm3 meeting in the group B of GELDART (1973). For the monitoring of the values of superficial velocity of the gas and pressure drop in the bed, an termanemometer and two transductions of differential pressure were used coupled the a plate of acquisition of data. The data were processed and analyzed in a microcomputer with the aid of the software LabVIEW. In agreement of preliminary tests was possible to define the vibration conditions in which the bed presented larger stability using like this an interval from 13 to 16 Hz for the vibration frequency and limits from 0,167 to 0,733 width millimeters. To evaluate the influence of the chosen operational parameters the technique of central planning it was used with four replicas in the center, generating 18 experiments. For the statistical analysis of the data, it could be observed that the mass presented larger significance, following by the width and that the frequency didn't present a significant effect in the pressure drop. A visual interpretation of the results through the surfaces of answer of the planning presented effects not only of the isolated variables, but also their interactions. An influence could be observed strongly lineal of the mass in the pressure drop of the bed for all of the width levels, finding higher level for intermediate values of width. Already for the width it was noticed a quadratic function regarding pressure generating minimum values of pressure when used maximum values of width. In a similar way, it is noticed by the answer surface that, for the lowest level of vibration frequency they were the largest values of velocity being more accentuated for intermediate levels of width. The effect mass was verified in the several frequency levels, where the increment carted in an increase in the answer of the velocity along the answer surface. For the minimum vibrate-fluidization velocity found the higher values for the same in the condition of larger mass and intermediate values of width.