Yankee dryer cylinder operating without steam

Abstract

A Yankee dryer cylinder comprising a fixed hollow shaft provided with an inlet mouth through which a flow of hot air is fed into the cavity, and an outlet mouth through which the flow of hot air exits the dryer cylinder. The Yankee dryer cylinder provides, furthermore, a cylindrical shell having an internal surface and rotatably mounted about the fixed hollow shaft. Into the cavity a partition wall is provided which divides the fixed hollow shaft in a feeding portion and in a discharging portion.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the field of machines for producing paper and similar products and, in particular, relates to an improved structure of dryer cylinder, also known as Yankee dryer cylinder, or simply Yankee cylinder.STATE OF THE ART[0002]As known, the plants for producing paper provide the use of a headbox for distributing a mixture of cellulosic fibres and water on a forming fabric, and, in some cases, additives of different kinds. In this way, a determined amount of water is drained and, then, the dry content of the mixture layer arranged on the forming fabric is increased.[0003]The content of water is, then, reduced, through a sequence of passages among many fabrics and / or felts of the mixture layer, up to reach a consistency such that allows to pass through a drying section. This usually comprises at least a dryer cylinder, also called “Yankee dryer cylinder”, or simply “Yankee cylinder” and a drying hood that is fed with hot air. In pa...

AI Technical Summary

Benefits of technology

The present invention provides a novel Yankee dryer cylinder that addresses commonly faced issues of prior art cylinders. The new cylinder achieves uniform heat distribution and produces high quality finished products while reducing running costs. Additionally, the new cylinder has a simplified construction and is less expensive than prior art cylinders. A suction device is also provided to assist in the flow of hot gas from the dryer cylinder.

Problems solved by technology

Firstly, the great amount of steam that are necessary in these types of machines involves high running costs. Furthermore, it is necessary to use specific apparatuses both for producing steam and for transporting the steam same to the Yankee cylinder.

However, the solution described in EP0708301A1 does not appear to be particularly advantageous.

This considerably decreases the surface available for the heat exchange, thus reducing the efficiency of the machine.

Furthermore, the solution described in EP0708301A1, in particular, owing to the presence of the burners and the ducts, does not seem to be able to uniformly distribute the heat produced on the shell surface.

This thing negatively affects the quality of the final product.

A further drawback of the solution described in EP0708301 is that the internal volume of the cylinder can become saturated with inflammable gases and, therefore, the flame, which is produced by the internal burners, can cause explosions and, therefore, exposing the workers to risks, besides compromising the efficacy of the plant.

However, also this construction solution is complex and is not able to guarantee a uniform heat distribution at the internal surface of the shell.

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