Estudo experimental e numérico do efeito de variáveis operacionais e de projeto sobre a dinâmica de partículas em tambores rotatórios com suspensores

Abstract

Flighted rotary dryers are commonly used due to their high processing capacity and application versatility. The performance of flighted rotary dryers depends on the distribution of the particles in the cross-section of the drum. The flight shape controls the cascade pattern of particles in the active region, where the fluid-particle contact is more effective. The design of these flights is a complex task and studies are necessary to gain an in-depth understanding of the particle dynamics. Thus, the present study investigated how the characteristics of the flight and its positioning on the cylindrical shell affect the behavior of particles in a rotating drum with twelve equally spaced flights. Initially, a stainless steel drum was used in order to evaluate, by DEM simulations, the effect of the shape and size of the flight on the distribution of solids in the active region. It was observed that three-segment flights increase amount of solids in the active region and they are capable of carrying the particles up to elevated angular positions. Thus, the three-segment flight was used to investigate the effect of angles between segments (α1, α2, α3) on the granular dynamics. An optimization study was performed for determining the best combination of angles (OPDES). Then, a rotary drum was made of ABS (acrylonitrile butadiene styrene) copolymer using the combination of angle OPDES. The ABS drum was composed of a set of rings (identified by sections), allowing it to vary its length (L) and intersperse the flights along the cylindrical shell. For the drum with 50 mm of length, equivalent to two sections (A to B), it was observed that interspersed flights with the separation distance of 15° improved the distribution of solids in the active region. For the ABS drum with 150 mm of length, equivalent to six sections (A to F), it was possible to evaluate the arrangement of flights in the spiral form. This arrangement provided a better performance in the distribution of particles over the active region when section D (75 mm ≤ L ≤ 100mm) operated at design loading condition. The flights in the spiral form promoted an increase of more than 50% in the area of active region occupied by solids and a reduction of up to 54.1% in the dispersion heterogeneity of the particle curtain, enhancing the use of the area available for drying.