TECHNICAL FIELD
[0001] The present invention relates generally to a defibrator used in the manufacture of
pulp from lignocellulosic material, such as wood chips, and more particularly to a
blow valve through which fibrous pulp leaves a defibrator housing, and even more particularly
to a specific mounting arrangement for such a blow valve between a discharge pipe
and a specially arranged mounting pipe connected to the defibrator housing.
BACKGROUND
[0002] A defibrator is a refining apparatus in which lignocellulosic materials, e.g., wood
chips, saw dust and other fibrous materials from wood or plant, are ground between
two refining elements in an environment of steam. A typical defibrator for processing
fibrous materials is a disc-type refiner, wherein two refiner plates - which also
are referred to as refiner discs - are positioned opposite to each and wherein at
least one refiner plate rotates with respect to the other refiner plate. The lignocellulosic
material to be refined is fed into a central inlet in at least one of the two refiner
plates, and moves therefrom into a refining gap arranged between the two refiner plates.
As at least one of the refiner plates rotates, centrifugal forces created by the relative
rotation between the two refiner plates move the lignocellulosic material outwards
and towards the periphery of the refiner plates. The opposing refiner plates have
surfaces that include bars and grooves, and the lignocellulosic material is - in the
refining gap provided between crossing bars of the opposing refiner plates - separated
into fibers by forces created by the crossing bars as the refiner plates rotate in
relation to each other. Another type of defibrator is a drum-type refiner, in which
a refining gap is formed between an outer cylindrical drum and a rotor that rotates
inside the outer cylindrical drum.
[0003] In the thermo-mechanical refining process referred to above, a considerable amount
of energy is required to create and maintain the rotational movement that separates
the lignocellulosic material into fibers, and a large part of this mechanical energy
is converted into heat, whereby steam is generated in a defibrator housing in which
the defibrator with its refining elements is arranged. The pulp created by the defibrator
is fed out from the defibrator housing through a discharge pipe, and because of the
pressurized atmosphere prevailing inside the defibrator housing, a blow valve - also
referred to as a discharge valve - is arranged at the defibrator housing and is connected
to the discharge pipe, and the pulp is fed through this blow valve before being fed
into the discharge pipe for further transport and processing. An arrangement of this
type is, e.g., disclosed in the
U.S. Patent No. 4,163,525. Further,
U.S. Patent No. 3,765,611 discloses a refiner, in which a tubular adapter means is arranged between a refiner
housing and a blow valve. No information is given about the dimensions of the adapter
means.
[0004] As indicated above, the energy consumption in a defibrator is high, and there are
always ongoing efforts to reduce this energy consumption and thereby the operating
costs of a defibrator. This can, for example, involve more efficient use of the steam
generated in the refining process. Another technical challenge is a substantial wear
of components in a defibrator, which reduces the operating life-time of these components
and leads to high operating costs. Examples of such wear-subjected components are
the refining elements, e.g. refiner plates, and also the blow valve, which is arranged
at the defibrator housing and through which pulp is fed out into a discharge pipe.
An object of the present invention is therefore to reduce the energy consumption in
a system comprising a defibrator. Another object is to increase the operational life
time for a blow valve arranged at a defibrator housing by reducing the wear of this
blow valve.
SUMMARY OF THE INVENTION
[0005] The above-mentioned objects are achieved with a pulp refining system comprising a
defibrator, a defibrator housing and a blow valve according to the independent claim.
Preferred embodiments are set forth in the dependent claims.
[0006] The invention relates to a pulp refining system comprising a defibrator arranged
in a defibrator housing, which has a portion from which pulp is fed out to a discharge
pipe. The pulp refining system comprises further a blow valve, which - according to
the invention - is mounted before (as seen in the pulp transport direction) the discharge
pipe and is connected to the defibrator housing by a mounting pipe having a length,
which is at least about 0.2 meter, and more preferably at least about 0.5 m, and even
more preferably about 0.7-1.5 m. In one embodiment of the invention, the mounting
pipe has the same diameter at its inlet, which is connected to the defibrator housing,
as at its outlet, which is connected to the inlet of the blow valve. This diameter
is further preferably the same as the diameter of a flow channel through the blow
valve when the blow valve is in a fully open position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention will be further explained hereinafter by means of non-limiting
examples and with reference to the appended drawings, wherein:
Fig. 1 is a schematic illustration of a pulp refining system according to the present
invention.
Fig. 2 is a schematic illustration of a blow valve, a discharge pipe and a mounting
pipe arranged in the pulp refining system illustrated in Fig. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0008] Fig. 1 illustrates schematically a refining system 1, which comprises a defibrator
2 with a first refining element 3 and a second refining element 4. In this example,
the first refining element 3 is a stationary refining disc 3, while the second refining
element 4 is a rotating refining disc 4. However, the type of refining elements is
not crucial for the present invention, and the refining elements could, for example,
instead of refining discs be a rotor that rotates within an outer drum. The defibrator
2 is arranged within a defibrator housing 5, which, because of the steam generated
by the mechanical forces created when the lignocellulosic material is ground between
the first refining element 3 and the second refining element 4, contains a pressurized
atmosphere. Pulp, which has been ground between the two refining elements 3, 4, leaves
the defibrator housing 5 at a house portion 6, and enters into a mounting pipe 7,
whose inlet 8 is connected to the defibrator housing 5 and whose outlet 9 is connected
to an inlet 10 of a blow valve 11, whose outlet 12 is connected to an inlet 13 of
a discharge pipe 14.
[0009] The provision of a mounting pipe, such as mounting pipe 7, is a novel arrangement
according to the invention, because the standard practice in the field is to arrange
a blow valve, such as blow valve 11, in direct connection with a defibrator housing,
such as defibrator housing 5. However, by providing the mounting pipe 7, which has
non-negligible length, surprisingly positive effects have been achieved both regarding
the energy consumption of the defibrator 2 and also regarding the wear of the blow
valve 11. Without wishing to be bound be theory, it is believed that the provision
of the mounting pipe 7 before the blow valve 11 creates a laminar pulp flow through
the blow valve 11, i.e. the pulp flow at the exit from the defibrator housing 5, i.e.
at the inlet 8 of the mounting pipe 7, is presumably highly turbulent, and by providing
the mounting pipe 7, which has a non-negligible length, the pulp flow is "settling
down" and a laminar flow is established at the outlet 9 of the mounting pipe 7. And
it is further believed that this laminar pulp flow is less aggressive and exposes
the inner surfaces of the blow valve 11 to less wear. The reduction of energy consumption
in the defibrator 2 is more difficult to understand, but it could be that when a turbulent
pulp flow encounters a blow valve - as is the case when a blow valve is mounted directly
at a defibrator housing - shock waves are created which are transferred back through
the pulp to the rotating refining element and counteract its movement, something which,
in turn, requires energy to overcome. Thus, by creating a laminar pulp flow through
a blow valve, these repercussioning shock waves are eliminated, which has a positive
effect on the energy consumption.
[0010] To achieve a laminar pulp flow through the blow valve 11, the mounting pipe 7 has
been given a length of at least about 0.2 m, and more preferably a length of at least
about 0.5 m, and even more preferably of at least about 0.7 m. In Fig. 1, the length
of the mounting pipe 7 is indicated by an "L". The maximal length of a mounting pipe,
such as mounting pipe 7, is not so crucial for practicing the present invention. However,
if for some reasons the blow valve 11 is closed, pulp will plug and block the mounting
pipe 7 and it may take a considerable time to remove this pulp and put the refining
system 1 back into operation again. Furthermore, it is the steam pressure generated
in the defibrator 2 that drives the refining system 1, i.e. the steam pressure forces
the pulp forward and through the mounting pipe 7, the blow valve 11 and the discharge
pipe 14 and also through further components and pipes which are not seen in the figures;
and more specifically, it is the pressure drop over a pipe or component section, such
as over mounting pipe 7, that creates a pulp flow through the section in question.
Hence, a blow valve, such as blow valve 11, cannot be positioned so far from a pressure
generating defibrator so that the pressure has dropped to zero or essentially zero.
For at least these reasons, the length of the mounting pipe 7 should not be longer
than necessary, and a suitable maximal length is about 1.5 m, i.e. 0.2 m ≤ L ≤ 1.5
m. The mounting pipe 7, the blow valve 11 and the discharge pipe 14 are schematically
illustrated in Fig. 2. The mounting pipe 7 has preferably a circular inner cross-section
with an inner diameter d
1, which preferably is constant, i.e. the diameter d
1 is the same at the inlet 8 of the mounting pipe 7 as at the outlet 9 of the mounting
pipe 7. Further, the blow valve 11 comprises a valve housing 15, which, inter alia,
encloses a flow channel 16, through which the pulp is intended to flow. The cross-sectional
area of the flow channel 16 can be regulated by a valve member 17, which can be introduced
into the flow channel 16 to thereby reduce the size of the cross-sectional area of
the flow channel 16, but according to the present invention, the cross-section of
the flow channel 16 of the blow valve 11 is preferably equal to the cross-section
of the mounting pipe 7. The latter is typically but not necessarily the case when
the blow valve 11 is in its fully open position, i.e. when the valve member 17 has
been retracted out of the flow channel 16 and does not restrict the pulp flow through
the blow valve 11. The flow channel 16 has a preferably a circular cross-section with
a diameter d
2, which is preferably equal, or at least approximately equal, to the diameter d
1 of the mounting pipe 7, which then preferably also has a circular cross-section with
d
1 ≅ d
2. If for some reasons, other cross-sectional shapes than circular are chosen for a
mounting pipe and a flow channel through a blow valve, these cross-sectional shapes
should be essentially equal for the mounting pipe and the flow channel, and the cross-sectional
areas should also be essentially equal. By this arrangement, when the cross-section
of the flow channel 16 through the blow valve 11 is equal, both in shape and size,
to the inner cross-section of the mounting pipe 7, a laminar pulp flow is ensured
through the blow valve 11, which, in turn, reduces wear on the blow valve 11. Also,
the risk of micro-scale shock waves, which travel back through the pulp and counteract
the rotational movement of the rotating refiner element 4, is reduced, which has a
positive effect on the energy consumption of the refiner system 1.
[0011] Although the present invention has been described with reference to specific embodiments,
also shown in the appended drawings, it will be apparent to those skilled in the art
that many variations and modifications can be done within the scope of the claims
below. It should in particular be noted that in the embodiment shown in Fig. 1 and
Fig. 2, the mounting pipe 7 has been shown as a separate component. It is, however,
within the scope of the invention that a mounting pipe is created as a prolonged inlet
portion of a blow valve, i.e. the inlet portion is integrated with the blow valve.
A mounting pipe according to the invention is therefore in this case configured as
a mounting portion of a blow valve. A combination of a separate mounting pipe and
a mounting portion of a blow valve is also within the scope of the invention. In any
case, a length of a mounting pipe, such as the length L in Fig. 1, or a length of
a mounting pipe which is configured as a mounting portion of a blow valve, or a length
of a combination of a mounting pipe and a mounting portion, should always be measured
from a defibrator housing to a first or closest side - as seen in the pulp transport
direction - of a valve member arranged in a blow valve, which is connected to a discharge
pipe.
1. A pulp refining system (1) for mechanically refining of lignocellulosic material,
comprising:
a defibrator (2),
a defibrator housing (5), in which the defibrator (2) is arranged,
a blow valve (11) comprising a valve member (17) and having an inlet (10) and an outlet
(12) and being adapted for regulating a flow of pulp therethrough, and
a discharge pipe (14) having an inlet (13) which is connected to the outlet (12) of
the blow valve (11), and
a mounting pipe (7) having an inlet (8), which is connected to the defibrator housing
(5), being arranged between the defibrator housing (5) and the blow valve (11),
characterized in that said mounting pipe (7) has a length (L) of at least about 0.2 meter, wherein the
length of the mounting pipe (7) is measured from the defibrator housing (5) to a closest
side of said valve member (17) arranged in the blow valve (11).
2. The pulp refining system (1) according to claim 1, characterized in that the length (L) of the mounting pipe (7) is at least about 0.5 meter.
3. The pulp refining system (1) according to claim 1, characterized in that the length (L) of the mounting pipe is such that 0.2 m ≤ L ≤ 1.5 m.
4. The pulp refining system (1) according to any preceding claim, characterized in that the mounting pipe (7) is provided as a separate component.
5. The pulp refining system (1) according to anyone of the claims 1-3, characterized in that the mounting pipe is configured as an inlet portion of the blow valve.
6. The pulp refining system (1) according to anyone of the claims 1-3, characterized in that the mounting pipe is configured as a combination of a separate component and an inlet
portion of the blow valve.
7. The pulp refining system (1) according to anyone of the preceding claims, characterized in that the mounting pipe (7) has a cross-section, which is essentially equal, both in shape
and size, to the cross-section of an interior flow channel (16) in the blow valve
(11).
1. Zellstoffmahlsystem (1) zum mechanischen Mahlen von Lignocellulosematerial, umfassend:
einen Zerfaserer (2),
ein Zerfaserergehäuse (5), in dem der Zerfaserer (2) angeordnet ist,
ein Blasventil (11), das ein Ventilelement (17) umfasst und einen Einlass (10) und
einen Auslass (12) aufweist und zum Regulieren eines Flusses von Zellstoff dort hindurch
angepasst ist, und
ein Auslassrohr (14) mit einem Einlass (13), der mit dem Auslass (12) des Blasventils
(11) verbunden ist, und
wobei zwischen dem Zerfaserergehäuse (5) und dem Blasventil (11) ein Montagerohr (7)
mit einem Einlass (8) angeordnet ist, der mit dem Zerfaserergehäuse (5) verbunden
ist,
dadurch gekennzeichnet, dass das Montagerohr (7) eine Länge (L) von mindestens etwa 0,2 Meter aufweist, wobei
die Länge des Montagerohrs (7) von dem Zerfaserergehäuse (5) zu einer nächsten Seite
des Ventilelements (17), das in dem Blasventil (11) angeordnet ist, gemessen wird.
2. Zellstoffmahlsystem (1) nach Anspruch 1, dadurch gekennzeichnet, dass die Länge (L) des Montagerohrs (7) mindestens etwa 0,5 Meter beträgt.
3. Zellstoffmahlsystem (1) nach Anspruch 1, dadurch gekennzeichnet, dass die Länge (L) des Montagerohrs derart ist, dass 0,2 m ≤ L ≤ 1,5 m.
4. Zellstoffmahlsystem (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Montagerohr (7) als separates Bauteil vorgesehen ist.
5. Zellstoffmahlsystem (1) nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das Montagerohr als ein Einlassabschnitt des Blasventils konfiguriert ist.
6. Zellstoffmahlsystem (1) nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das Montagerohr als eine Kombination aus einer separaten Komponente und einem Einlassabschnitt
des Blasventils konfiguriert ist.
7. Zellstoffmahlsystem (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Montagerohr (7) einen Querschnitt aufweist, der sowohl in Form als auch Größe
im Wesentlichen gleich dem Querschnitt eines inneren Strömungskanals (16) in dem Blasventil
(11) ist.
1. Système de raffinage de pâte (1) pour le raffinage mécanique d'un matériau lignocellulosique,
comprenant :
un défibreur (2),
un logement de défibreur (5), dans lequel le défibreur (2) est agencé,
une vanne de soufflage (11) comprenant un élément de vanne (17) et ayant une entrée
(10) et une sortie (12) et étant conçue pour réguler un écoulement de pâte à travers
celle-ci, et
un tuyau de décharge (14) ayant une entrée (13) qui est reliée à la sortie (12) de
la vanne de soufflage (11), et
un tuyau de montage (7) ayant une entrée (8), qui est reliée au logement de défibreur
(5), étant agencé entre le logement de défibreur (5) et la vanne de soufflage (11),
caractérisé en ce que ledit tuyau de montage (7) a une longueur (L) d'au moins environ 0,2 mètre, dans
lequel la longueur du tuyau de montage (7) est mesurée à partir du logement de défibreur
(5) jusqu'à un côté le plus proche dudit élément de vanne (17) agencé dans la vanne
de soufflage (11).
2. Système de raffinage de pâte (1) selon la revendication 1, caractérisé en ce que la longueur (L) du tuyau de montage (7) est d'au moins environ 0,5 mètre.
3. Système de raffinage de pâte (1) selon la revendication 1, caractérisé en ce que la longueur (L) du tuyau de montage est telle que 0,2 m ≤ L ≤ 1,5 m.
4. Système de raffinage de pâte (1) selon une quelconque revendication précédente, caractérisé en ce que le tuyau de montage (7) est fourni en tant que composant indépendant.
5. Système de raffinage de pâte (1) selon l'une quelconque des revendications 1 à 3,
caractérisé en ce que le tuyau de montage est configuré en tant que partie d'entrée de la vanne de soufflage.
6. Système de raffinage de pâte (1) selon l'une quelconque des revendications 1 à 3,
caractérisé en ce que le tuyau de montage est configuré en tant que combinaison d'un composant indépendant
et d'une partie d'entrée de la vanne de soufflage.
7. Système de raffinage de pâte (1) selon l'une quelconque des revendications précédentes,
caractérisé en ce que le tuyau de montage (7) a une section transversale, qui est sensiblement égale, à
la fois en forme et en taille, à la section transversale d'un canal d'écoulement intérieur
(16) dans la vanne de soufflage (11).