[0001] The present invention relates to a procedure for the refining of a pulp mixture
or equivalent in a refiner comprising oppositely placed refiner blades, of which the
rotor blade rotates and the stator blade is stationary, a pulp refining zone being
formed between the blades.
[0002] As is well known, the motion of the rotor blade relative to the stator blade gives
rise to a strong turbulence of the pulp mixture in the grooves of the blades. During
the refining process, the pulp flows in the refiner in various directions. At the
infeed end of the refining zone, the pulp flows towards the delivery side in the grooves
of both blades. In the refining zone, in addition to the flow towards the delivery
side, the pulp also flows transversely from the rotor blade to the stator blade and
vice versa, and in the grooves of the stator blade the pulp also flows back towards
the infeed side.
[0003] As the pulp mixture fed into the refiner is inhomogeneous, containing different fibre
fractions, it is essential for the achievement of good refining results that it should
be possible to refine those fractions which need refining and to avoid overrefining
fractions already refined as well as to avoid superfluous and damaging refining of
fractions which need no refining at all. The object of the invention is to create
a procedure that achieves this aim. The procedure of the invention is characterized
in that, by making use of the forces generated by the rotation of the rotor blade,
the pulp mixture is separated into fractions or part of the pulp mixture is directed
away from the area of the refiner blades for fractionation.
[0004] A preferred embodiment of the invention is characterized in that at least one of
the fractions obtained is returned to the same refiner.
[0005] Another preferred embodiment of the invention is characterized in that at least
one of the fractions obtained is returned to a separate refiner designed for this
fraction.
[0006] Yet another preferred embodiment of the invention is characterized in that the fraction
to be returned is returned to the infeed side of the refiner.
[0007] An advantage provided by the procedure of the invention is that it makes it possible
to refine those fractions which need refining and to avoid overrefining fractions
already refined.
[0008] In the following, the invention is described in detail by the aid of examples of
preferred embodiments by referring to the attached drawings, in which
Fig. 1 illustrates the priniciple of the turbulence occurring in the grooves of the
refiner blades at two different stages.
Fig. 2 illustrates the principle of pulp flow within the refiner.
Fig. 3 illustrates the principle of fractionation by the procedure of the invention.
[0009] Fig. 1 illustrates the turbulent flow occurring in the grooves 5, 4 between the rotor
blade 1 and the stator blade 2. The rotor blade rotates in the direction indicated
by arrow 3. In the first picture the grooves of the rotor blade are directly opposite
to those of the stator blade. In the second picture, the rotor blade 1 has turned
a little to the right.
[0010] Fig. 2 illustrates the internal pulp flow within the refiner. During refining, the
pulp flows in several directions. At the entry end of the refining zone, the pulp
flows in the grooves 4, 5 of both the stator 2 and the rotor 1 blades towards the
delivery side 6. In the refining zone, besides flowing towards the delivery side 6,
the pulp also flows transversely from the rotor blade 1 to the stator blade 2 and
from the stator blade back to the rotor blade, and in the grooves 4 of the stator
blade 2 the pulp also flows back towards the infeed side 7. The different directions
of flow are indicated with arrows in fig. 2.
[0011] Fig. 3 illustrates the principle on which the refiner is utilized for separating
pulp into fractions. The direction of rotation of the rotor blade 1 is again indicated
by arrow 3. The procedure of the invention makes use of the motion of the rotor blade
1 (circumferential speed approx. 15-40 m/s) to achieve fractionation at points 8 and
10, where the pulp mixture is separated into corresponding fractions 8a, 8b, 8c and
10a, 10b, 10c. It is also possible to direct part of the pulp mixture out of the refiner
at point 9 for external fractionation, resulting in fractions 9a, 9b, 9c. At least
one of the fractions obtained is returned either to the same refiner or to a different
refiner designed for the refining of this particular fraction. This fraction can be
returned either to the infeed side 7, to the area of the refining zone or to the return
flow taking place from the delivery side 6 to the stator blade 2.
[0012] The invention is in no way restricted by the manner in which the forces generated
by the rotary motion of the rotor blade are utilized for fractionation. Among the
possible alternatives are e.g. the use of top separators in conjunction with the refiner
blades, a hole or holes made through the blades, various screens etc.
[0013] It is obvious to a person skilled in the art that of the invention is not restricted
to the examples of its embodiments described above, but that it may instead be varied
within the scope of the following claims.
1. Procedure for the refining of a pulp mixture or equivalent in a refiner comprising
oppositely placed refiner blades (1, 2), of which the rotor blade (1) rotates and
the stator blade (2) is stationary, a pulp refining zone being formed between the
blades, characterized in that, by making use of the forces generated by the rotation of the rotor blade
(1), the pulp mixture is separated into fractions or part of the pulp mixture is directed
away from the area of the refiner blades for fractionation.
2. Procedure according to claim 1, characterized in that at least one of the fractions obtained (8a-c, 9a-c, 10a-c) is returned to
the same refiner.
3. Procedure according to claim 1, characterized in that at least one of the fractions obtained (8a-c, 9a-c, 10a-c) is returned to
a separate refiner designed for this fraction.
4. Procedure according to claim 2 or 3, characterized in that the fraction to be returned (8a-c, 9a-c, 10a-c) is returned to the infeed
side of the refiner.
5. Procedure according to claim 2 or 3, characterized in that the fraction to be returned (8a-c, 9a-c, 10a-c) is returned to the area of
the refining zone of the refiner.
6. Procedure according to claim 2 or 3, characterized in that the fraction to be returned (8a-c, 9a-c, 10a-c) is returned to the return
flow taking place from the delivery side (6) of the refiner to the stator blade (2).