Method and apparatus for recovering fibers from white water of paper mill
AssigneeMetso Paper, Inc.
InventorsVesa Juutinen, Timo Pekkarinen
Life of this patent
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Abstract
In a papermaking process, filtering of white water containing fiber material is performed by feeding the white water to a filter on a surface of which a layer of auxiliary pulp has been formed, such that the white water is filtered through the layer of auxiliary pulp and fiber material in the white water remains in the layer of auxiliary pulp. The mixture of auxiliary pulp and fiber material is removed from the filter and is fed to a fractionating screen. The screen separates the mixture into a short-fibered pulp fraction that can be returned to the papermaking process, and a long-fibered pulp fraction that is returned to the filter where it is used as auxiliary pulp to form a layer on the filter surface.
Claims16
A method for recovering fiber material from white water that is separated from papermaking pulp used in a papermaking process, the method comprising:
- feeding the white water containing the fiber material to a filter, and feeding auxiliary pulp to the filter such that the auxiliary pulp forms a layer on a surface of the filter and the white water flows through the layer such that the fiber material remains in the layer formed by the auxiliary pulp so as to form a mixture of auxiliary pulp and fiber material on the surface of the filter;
- removing the mixture of auxiliary pulp and fiber material from the surface of the filter;
- feeding the removed mixture directly from the filter to a fractionation unit which fractionates the mixture of auxiliary pulp and fiber material into a short-fibered pulp fraction and a long-fibered pulp fraction;
- and
- returning the short-fibered pulp fraction to the papermaking process and returning the long-fibered pulp fraction as auxiliary pulp to the filter.
An apparatus for recovering fiber material from white water that is separated from papermaking pulp used in a papermaking process, the apparatus comprising:
- a filter having a filtering surface;
- means for feeding separate auxiliary pulp to the filter to form a layer of the auxiliary pulp on the filtering surface;
- means for feeding the white water to the filter such that the white water is filtered through the layer of auxiliary pulp on the filtering surface and the fiber material in the white water remains in the layer of auxiliary pulp to form a mixture of auxiliary pulp and fiber material on the filtering surface;
- means for removing the mixture of auxiliary pulp and fiber material from the filtering surface;
- a screen connected to the filter so as to receive the removed mixture of auxiliary pulp and fiber material directly from the filter, the screen operable for fractionating the mixture of auxiliary pulp and fiber material into a short-fibered pulp fraction and a long-fibered pulp fraction, such that substantially all of the fibers in the short-fibered pulp fraction are of a length less than or equal to a maximum length of fibers of the papermaking pulp, whereby the short-fibered pulp fraction can be returned to the papermaking process;
- and
- means for returning the long-fibered pulp fraction to the filter as auxiliary pulp to form a layer on the filter surface.
An apparatus for recovering fiber material from white water that is separated from papermaking pulp used in a papermaking process, the apparatus comprising:
- a gap filter comprising a pair of opposed wires traveling in a downstream direction and arranged such that a gap is formed between the wires, the gap converging in the downstream direction;
- means for feeding separate auxiliary pulp to the filter to form a layer of the auxiliary pulp on each of the wires;
- means for feeding the white water to the filter such that the white water is filtered through the layer of auxiliary pulp on the wires and the fiber material in the white water remains in the layer of auxiliary pulp to form a mixture of auxiliary pulp and fiber material;
- means for removing the mixture of auxiliary pulp and fiber material from the wires;
- a screen for fractionating the mixture of auxiliary pulp and fiber material into a short-fibered pulp fraction and a long-fibered pulp fraction, such that substantially all of the fibers in the short-fibered pulp fraction are of a length less than or equal to a maximum length of fibers of the papermaking pulp, whereby the short-fibered pulp fraction can be returned to the papermaking process;
- and
- means for returning the long-fibered pulp fraction to the filter as auxiliary pulp to form a layer on the wires.
Dependencies are inferred from the claim text.