METHOD OF TREATING LIGNO-CELLULOSE CONTAINING MATERIAL

METHODE DE TRAITEMENT D'UNE MATIERE LIGNOCELLULOSIQUE

English Abstract

Abstract of the Disclosure
An improved method for treating ligno-cellulose containing
material is disclosed which comprises disintegrating the material in a
refiner to obtain a mechanical pulp having a high concentration and a low
coarse material content, passing the thus formed pulp to storage chests
located at a wet-lap forming machine for storage, removing the stored pulp
and cleaning it by diluting and screening to reduce the coarse material
content and to obtain a pulp concentration suitable for further processing
in the wet part of a wet-lap forming machine, and passing the cleaned pulp
to the wet-lap forming machine for further processing.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for treating a ligno-cellulose containing material comp-
rising the steps of finely disintegrating said ligno-cellulose containing
material in a refiner to obtain a mechanical pulp having a high concentration
and a low coarse material content, passing the thus formed pulp to at least
one storage chest for storing until further processing is desired, "without
any prior screening and cleaning or dilution to a concentration suitable for
screening and cleaning", removing said pulp from storage, cleaning said
pulp by first diluting it with a liquid to a concentration suitable for
screening and then screening said diluted pulp to reduce its coarse material
content, and passing the thus cleaned pulp to the wet part of a wet-lap forming
machine, without any prior thickening and further storage.
2. The method of claim 1 wherein said pulp is subjected to further
processing in said wet-lap forming machine and at least part of said liquid
utilized to dilute said pulp prior to screening is supplied from the circula-
tion system at said wet part of said wet-lap forming machines.
3. The method of claim 2 wherein the back-water from said wet part
of said wet-lap forming machine is utilized to dilute said pulp prior to
screening.
4. The method of claim 1 wherein steam is produced in the refiner
during disintegration of the ligno-cellulose containing material, and said
steam is removed during said disintegration to avoid dilution of said pulp
whereby the concentration of the pulp formed in the refiner is maintained at
as high a level as possible.
5. The method of claim 1 wherein the mechanical pulp obtained from the
refiner has a concentration of 15%-40%, and a coarse material content of
0.3%-1.5% Sommerville.
6. The method of claim 5 wherein the concentration of said mechanical
pulp is 25%-35%.

7. The method of claim 5 wherein said level of coarse material is
0,4%-0.8% Sommerville.
8. The method of claim 1 wherein said pulp is diluted to a concentra-
tion of 0%-1% prior to screening.
9. The method of claim 1 further including the step of diluting the
pulp obtained from the refiner to a concentration of 3%-20% prior to passing
said pulp to said at least one storage chest.

Description

lOSSZ9~
The present invention relates to a method of treating ligno-
cellulose containing materials and the like.
During the manufacture of mechanical pulp, wood, or other ligno-
cellulose containing material, the material is normally disintegrated in
grinders or refiners. The resuling mechanical pulp normally contains
substantial amounts of coarse material, such as shives and splinters. There-
fore, it is necessary to clean the pulp to remove the coarse material so
that the pulp can then be transported to a series of storage chests where it
can be stored for further processing. The cleaning process requires diluting
the pulp to a concentration so that screening can be effected, and then
screening the diluted pulp in one or more steps. The stored pulp can, when
desired, be further processed in a paper making machine, or other wet-lap
forming apparatus.
In order to keep the dimensions of the storage chests in which the
cleaned pulp is stored within reasonable limits, the cleaned pulp must first
be thickened. Thus, it is necessary to utilize water extractors which take
up a good deal of space and give rise to substantial water circulation within
the plant. Further, the heat losses during each processing are very great.
It is an object of the present invention to provide a method for
the treatment of ligno-cellulose containing material which is to be stored
for further processing, which permits maintaining the dimensions of the stor-
age chests within reasonable limits but eliminates the necessity of cleaning
and thereafter thickening the pulp prior to storage, and the problems conse-
quent thereto.
According to the present invention, a process is provided for the
treatmen~ of ligno-cellulose containing material which comprises finely dis-
integrating the material in a refiner to obtain a pulp of high concentration
and which contains very small amounts of coarse material, and then transport-
ing the thus formed pulp, without any preceding separation of coarse material,
o

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to storage chests for storage pending further desired processing "without
any prior screening and cleaning or dilution to a concentration suitable for
screening and cleaning". The stored pulp can then be passed from the storage
chests directly to a cleaning operat-
-la-

1055Z91
ion wherein the pulp will first be diluted to a concentration suitable for
screening and then screened to remove the coarse material content of the pulp
and to provide the pulp with a final concentration suitable for further proces-
sing in the wet part of a paper making machine or other wet-lap forming
apparatus, without any prior thickening and further storage.
Although it was previously known that the use of refiners, or more
particularly disc refiners, enabled a pulp having a high concentration and
containing a very small amount of coarse material to be obtained, it was not
heretofore recogni~ed that such material could be passed to storage chests
without the necessity of prior separation of coarse material after the disin-
tegrating step. Thus, such recognition has enabled virtually a complete elim-
ination of the thickening operations which were necessary subsequent to the
cleaning step so that the pulp which was to be transported to the storage
chests, could be of a high enough concentration so that the dimensions of the
storage chests could be maintained within reasonable limits. Further, by
passing the pulp from the refiner to the storage chests and conducting the
cleaning operation subsequent to storage and prior to further processing in
the wet-lap forming machine, there is a reduction in the amount of water
circulation necessary in the plant and consequently in the amount of heat
losses. The dimensions of the storage chests are reduced and the necessity
for water extractors eliminated to the greatest extent possible.
A particular and at present preferred embodiment of the present
invention will now be described, by way of example only, with reference to
the accompanying drawing in which the Figure is a schematic representation
of the preferred process.
In accordance with the preferred embodiment of the present inven-
tion, the ligno-cellulose containing raw material 1 is finely disintegrated
to a high concentration of from 15%-40% and preferably from 25%-35%, in one or
more refiners 2. The pulp, which has a coarse material content of 0.31%-1.5%
and preferably 0.4%-0.8% Sommerville, is then passed to storage chests 3.
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10~;5291
The preferred pulp concentration for storage is from 3%-20% depending upon
the kind of storage container and discharge equipment used. Therefore, it
may be necessary to dilute the pulp obtained from the refiners to such a
concentration, However, in no event is the pulp diluted to such a low con-
centration as would be required for screening, such concentration normally
being below 1%. The thus formed pulp is, when further processing is desired,
removed from the storage chests and passed to a cleaning operation wherein it
is diluted and passed through screens and cleaners 4 whereby the pulp is
brought to a final concentration suitable for further processing in a wet-lap
forming machine. The pulp having such final concentration is passed directly
to the wet part 5 in a wet-lap forming machine. In this regard, other types
of pulps and chemicals can be admixed with the pulp, such other pulps and
chemicals being supplied from tanks 6.
As a result of the novel process of the present invention, it is
also possible that the conventional water circulation system 7 at the wet part
of the wet-lap forming machine can be extended to comprise the cleaning and
screening system as well. For example, the back-water from the wet part 5
can be utilized to effect the dilution of the pulp prior to the cleaning and
screening operations. The flow of such back-water can be controlled by the
valves 8 and 9. If desired, the ligno-cellulose containing material can be
pre-heated prior to the disintegrating step. Furthermore, any steam produced
in the refiners can be conducted away and utili~ed as steam heat or, after
concentration with water, as hot water. The steam drain 10 has the effect of
avoiding any unnecessary dilution of the pulp produced in the refiners which
serves to maintain the concentration of the pulp produced at the highest
possible level.
While the invention has been described with a certain degree of
particularity, it is to be understood that the present disclosure is made by
way of example only and that numerous variations as may become apparent to
those skilled in the art may be made without departing from the spirit and
scope of the invention as hereinafter claimed.
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