Classifying – separating – and assorting solids – Fluid suspension – Gaseous
Patent
1995-11-30
1998-03-10
Nguyen, Tuan
Classifying, separating, and assorting solids
Fluid suspension
Gaseous
209146, 209154, B07B 704
Patent
active
057251029
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method for separating heavy particles, such as latex particles, from a particulate material, such as wood fibres produced from rubber trees, which contains such heavy particles and which is transported by means of air from a first station, such as a container, to a second station, such as a plant for manufacturing fibreboards. The invention also relates to a device for carrying out the method.
In the manufacture of fibreboards, wood fibres are pneumatically transported, first from a drying plant to a collecting container and thence to a forming station. In the forming station, the fibres are placed as a mat on a wire, through which the transport air is sucked off. The fibre mat is thereafter pressed into fibreboards under given pressure and temperature conditions.
In the manufacture of fibreboards, it is essential that contaminants in the form of heavy particles be separated from the flow of material. In a method, known from PCT/SE91/00603 (SE 9003092-5), for separating large-size and hence heavy particles from the wood fibres when transported from the collecting container to the forming station, the wood fibres are introduced into a settling chamber as a downwardly-directed flow of material via a downwardly-facing settling chamber inlet, and is transported away from the settling cheer as an upwardly-directed flow of air-material via a settling chamber outlet disposed beside the inlet. Jets of compressed air, directed obliquely at the downwardly-directed flow of material, are blown into the settling chamber in order to decelerate the flow of material and to spread it in the transverse direction towards the outlet, the flow of transport air being blown into the settling chamber so as to encounter from below the decelerated and spread flow of material and, together with it, form the above-mentioned flow of air-material.
While this known method has proved to serve its purpose quite well for separating heavy particles in the form of glue lumps and fibre flocks from a particulate material in the form of glue-coated wood fibres, it yields an unsatisfactory result when separating heavy particles in the form of latex particles from a particulate material in the form of wood fibres produced from rubber trees.
One object of the present invention is to provide a method making it possible to efficiently separate also latex particles from wood fibres produced from rubber trees.
According to the invention, this object is achieved by a method which is of the type stated by way of introduction and which is characterised in that the particulate material in a substantially downwardly-directed flow is transported in known manner to a so-called Coanda sifter, in which the material is conducted over a downwardly-facing, convexly single-curved surface in order to impart to the particles a direction of motion which is dependent on the weight of the particles and in which the particles are guided into a so-called zigzag sifter disposed after the Coanda sifter and having a plurality of zigzag-shaped, substantially vertical walls which define between them channels extending upwards in zigzag fashion, the particles being guided into the channels of the zigzag sifter in the lower portions thereof and from the side substantially parallel to the walls, and that the particles are transported in known manner up through the zigzag-shaped channels by means of a flow of transport air which is so adjusted that the heavy particles are separated in the zigzag sifter.
Another object of the present invention is to provide a device for carrying out this method.
According to the invention, this object is achieved by means of a device which is characterised by a so-called Coanda sifter which is adapted in known manner to receive a substantially downwardly-directed flow of the particulate material and which has a downwardly-facing, convexly single-curved surface in order to impart To the particles a direction of motion dependent on the weight of the particles, and a so-calle
REFERENCES:
patent: 2674374 (1954-04-01), Elliott et al.
patent: 4416070 (1983-11-01), Vedenpa et al.
patent: 4712277 (1987-12-01), Gustavsson
patent: 4872972 (1989-10-01), Wakabayashi et al.
ABB Flakt AB
Nguyen Tuan
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