"Silo for RPET" Project

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R&D Project

Silo for RPET with negative sloped walls conical body and bottom scraper-shaker.

Objectives and technical and scientific advances

The Silo for RPET project is part of the investigation and experimental development of technology and industrial processes aiming to obtain technical improvements in methods and equipment for handling and processing bulk solid materials. In this context, it involved the study, design and development of prototypes for new granulates processing equipment.

The industrial use of Polyethylene terephthalate (PET) thermoplastic polymers had an accelerated growth in the last quarter of the 20th century, leveraged on the certification of its safe exploitation in the food and beverage sector, aiming at the manufacture of bottles, containers and, in a comprehensive way, packaging for various purposes. As a result of this growth in the use of this type of material, concerns have arisen about its environmental impact and the need for recycling.

During the time, occasionally very long, that these by-products pass inside the storage silos, usually located outdoors and, therefore, exposed to important thermal variations, RPET particles are subjected to the compression effect of several cubic meters of superimposed material, experiencing phenomena of “physical deformation and bonding”. In practice, these phenomena translate into the formation of material domes that inhibit the complete unloading of the storage silo.

METALOGONDE studied this reality in detail, analyzed the characteristics of crushed PET flakes and categorized the technologies used in the storage process as well as the main risks and incidents that tend to occur. Variables such as scale size, weight and thickness, storage volumes and compression pressures, range of thermal variation inside the silo, humidity conditions and the effect of industrial and organic contaminants were considered.

This work led to the formulation of the research hypothesis supported by the premise that it is possible to act on structure and geometry of storage silos, in order to minimize and, ideally, eliminate the formation of “domes”.

Although the focus of this project was the storage of laminated RPET, the conclusions suggest that the investigated hypotheses, the generated knowledge and the technology developed are possible to spread across other industrial applications that require storage processes of solid bulks inside silos, namely in the food, beverage and pharmaceutical industries.

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