Estudo de secagem e dimensionamento de secador de casulos do bicho-da-seda.

Abstract

The drying unit operation has relevant importance to the storage of biological products. The cocoon produced by the Bombix mori L. consists of 3 parts: the shell, the chrysalis and the booty and possesses an initial moisture content of 68-70% (w.b.), with the shell (which is formed for silk yarn) basically constituted of fibroin and sericin. The cocoon is a material of variable form and it is marketed with the objective to produce silk yarns, which are used on the manufacturing of high cost products. Due to its high moisture content and the low life cycle of chrysalis ( 4-5 days after crop of the cocoon ), the drying of the silkworm cocoon is a very important operation as they need to be stored with low moisture content (10-12% d.b.) in order to minimize its deterioration as well as to prevent the transformation of the chrysalis into a moth. If this process occurred, the cocoon owned break by an alkaline juice expelled by the moth. The purpose of the work is to study the silkworm cocoon drying and to present a project of a drier prototype of continuous operation and crossflow. Drying experiments were made in fixed bed and crossflows. Influences of the air temperature, the airflow and layer thickness during the silkworm cocoon drying Bombix mori L. were tested. The conclusion was that the drying kinetic depends strongly in the air temperature, it does not depend on the airflow and depends slightly on the cocoon layer thickness. Equations to describe the cocoon drying kinetic behavior in fixed bed were proposed and a high determination coefficient was obtained ( > 0,99 ). The project of a drier prototype of continuous operation and crossflow, the mathematical modeling and the hypotheses used to define its dimensions were presented. Comparing this to similar ones, it proved to be technically and economically viable.