Machine for washing fibrous suspensions

Abstract

A machine for washing fibrous suspensions has a pair of cylindrical drums; and a flexible belt with through holes carried by the drums. A conveyor carries the suspension to a contact line between the flexible belt and the first drum. A drive rotates at least one of the drums; and a collection received and pollutant agents; and another collection recess of the cellulose fibres. The conveyer has a head box below the flexible belt and upstream the first drum. The head box has a conveying conduit and) an outlet mouth transversally disposed with respect to the flexible belt. A flow conveyor, disposed between the head box and the first drum, has a laminar body with an inlet edge, downstream the outlet mouth, and an outlet edge, immediately upstream the contact line of the flexible belt with the first drum.

Description

BACKGROUND OF THE INVENTION [0001] The present invention is about a machine for washing the cellulose fibre which is used in paper manufacture. [0002] It is known that, in paper manufacturing processes, different stocks of cellulose fibre are used, whose characteristics should be carefully selected since they are determinant for defining the quality of the manufactured paper. [0003] In particular, the cellulose fibre has to be separated from the pollutant particles present therein, which are particularly relevant when the feedstock is for instance waste paper. [0004] Such separation is obtained with the aid of particular machines for washing fibrous suspensions which, although in their different specific embodiments, all substantially consist of a pair of drums, of which at least a driven one, around which a flexible belt provided with through holes is wound as a loop ring. [0005] The pair of drums comprises a grooved drum, provided with a plurality of mutually parallel circumferent...

AI Technical Summary

Benefits of technology

"The invention is a machine for washing cellulose fibers that reduces the amount of short fibers and impurities that are eliminated during the washing process. It also allows for the modification of the speed and thickness of the fluid film of cellulose fibers, while reducing the amount of water that needs to be purified. The machine includes a frame, cylindrical drums, a flexible belt, conveying means, driving means, and collecting means. A conveyor is used to gradually accelerate the fibrous suspension and prevent turbulent movement, which can lead to the loss of short fibers. The suspension is conveyed between the drum and the belt without mutual grazing, and the speed of the belt is matched to the speed of the drum."

Problems solved by technology

A first inconvenience is due to the fact that, in the zone upstream the winding point of the belt around the drum, even many of the shortest cellulose fibres pass through the holes of the flexible belt together with the fluid and the impurities contained in the suspension, thus being dispersed.

Such inconvenience occurs because of the difference between the speed of the suspension conveyed through the head box outlet mouth and the speed of the belt.

It is evident that such loss of fibre involves a loss of feedstock, with a consequent costs increase.

Another acknowledged inconvenience is due to the fact that, always because of the turbulent movement to which the fibrous suspension penetrating between the flexible belt and the drum is submitted, the shortest cellulose fibres tend to pass through the belt holes even in the zone immediately downstream the contact line between the belt and the drum, with further losses of feedstock.

A further inconvenience is due to the fact that, in the machines of known type, it is not possible to modify the characteristics of speed and thickness of the fluid flow outgoing from the head box, unless the pressure above the head box, and thus the throughput, is changed.

Not the least inconvenience is also due to the fact that the washing machines of known type produce a considerable quantity of water polluted by the impurities extracted by the washed suspension, which have to be properly treated in depurators before being eventually reused in the productive cycle.

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