SE1650825A1

SE1650825A1 - Defibrator with separated blow valve

Info

Publication number: SE1650825A1
Application number: SE1650825A
Authority: SE
Inventors: Wallin Per; Ahlgren Rjan; Nyberg Per; Eriksson Per; GRANNAS Mattias
Original assignee: Valmet Oy
Priority date: 2016-06-13
Filing date: 2016-06-13
Publication date: 2017-10-10
Also published as: EP3469139A1; BR112018068968A2; CN109154140A; EP3469139A4; US20190309471A1; EP3469139B1; CN109154140B; WO2017217909A1; SE539556C2

Abstract

ABSTRACT The invention relates to a pulp ref1ning system for niechanically ref1ning of lignocellulosicmaterial, coniprising a def1brator, a def1brator housing, in which the def1brator is arranged,a blow valve having an inlet and an Outlet and being adapted for regulating a ﬂow of pulptherethrough, and a discharge pipe having an inlet, which is connected to the outlet (12) ofthe blow valve, wherein a n1ounting pipe having an inlet, which is connected to thedef1brator housing, is arranged between the def1brator housing and the blow valve, said n1ounting pipe having a length of at least about 0.2 meter. Fig l for publication.

Description

DEFIBRATOR WITH SEPARATED BLOW VALVE TECHNICAL FIELD The present invention relates generally to a def1brator used in the manufacture of pulpfrom lignocellulosic material, such as wood chips, and more particularly to a blow valvethrough which fibrous pulp leaves a defibrator housing, and even more particularly to aspecific mounting arrangement for such a blow valve between a discharge pipe and a specially arranged mounting pipe connected to the def1brator housing.

BACKGROUND A def1brator is a refming apparatus in which lignocellulosic materials, e.g., wood chips,saw dust and other f1brous materials from wood or plant, are ground between two refmingelements in an environment of steam. A typical def1brator for processing f1brous materialsis a disc-type refiner, wherein two ref1ner plates - which also are referred to as ref1nerdiscs - are positioned opposite to each and wherein at least one refiner plate rotates withrespect to the other ref1ner plate. The lignocellulosic material to be ref1ned is fed into acentral inlet in at least one of the two ref1ner plates, and moves therefrom into a refminggap arranged between the two ref1ner plates. As at least one of the ref1ner plates rotates,centrifugal forces created by the relative rotation between the two ref1ner plates move thelignocellulosic material outwards and towards the periphery of the ref1ner plates. Theopposing ref1ner plates have surfaces that include bars and grooves, and the lignocellulosicmaterial is - in the refming gap provided between crossing bars of the opposing ref1nerplates - separated into f1bers by forces created by the crossing bars as the refiner platesrotate in relation to each other. Another type of def1brator is a drum-type ref1ner, in whicha refming gap is formed between an outer cylindrical drum and a rotor that rotates inside the outer cylindrical drum.

In the therrno-mechanical refming process referred to above, a considerable amount ofenergy is required to create and maintain the rotational movement that separates thelignocellulosic material into fibers, and a large part of this mechanical energy is converted into heat, whereby steam is generated in a def1brator housing in which the def1brator with its refining elements is arranged. The pulp created by the deﬁbrator is fed out from thedefibrator housing through a discharge pipe, and because of the pressurized atmosphereprevailing inside the defibrator housing, a blow valve - also referred to as a dischargevalve - is arranged at the defibrator housing and is connected to the discharge pipe, and thepulp is fed through this blow valve before being fed into the discharge pipe for furthertransport and processing. An arrangement of this type is, for example, disclosed in the U.S.

Patent No. 4,l63,525 to Reinhall.

As indicated above, the energy consumption in a defibrator is high, and there are alwaysongoing efforts to reduce this energy consumption and thereby the operating costs of adefibrator. This can, for example, involve more efficient use of the steam generated in therefining process. Another technical challenge is a substantial wear of components in adefibrator, which reduces the operating life-time of these components and leads to highoperating 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 andthrough which pulp is fed out into a discharge pipe. An object of the present invention istherefore to reduce the energy consumption in a system comprising a defibrator. Anotherobject 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 The above-mentioned objects are achieved with a pulp refining system comprising adefibrator, a defibrator housing and a blow valve according to the independent claim.

Preferred embodiments are set forth in the dependent claims.

The invention relates to a pulp refining system comprising a defibrator arranged in adefibrator housing, which has a portion from which pulp is fed out to a discharge pipe. Thepulp 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 isconnected to the defibrator housing by a mounting pipe having a length, which is at leastabout 0.2 meter, and more preferably at least about 0.5 m, and even more preferably about 0.7-l.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 connectedto 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 The present invention will be further explained hereinafter by means of non-limiting examples and with reference to the appended drawings, wherein: Fig. l 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. l.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. l illustrates schematically a refining system l, which comprises a defibrator 2 with afirst refining element 3 and a second refining element 4. In this example, the ﬁrst refiningelement 3 is a stationary refining disc 3, while the second refining element 4 is a rotatingrefining disc 4. However, the type of refining elements is not crucial for the presentinvention, and the refining elements could, for example, instead of refining discs be a rotorthat rotates within an outer drum. The defibrator 2 is arranged within a defibrator housing5, which, because of the steam generated by the mechanical forces created when thelignocellulosic material is ground between the first refining element 3 and the secondrefining element 4, contains a pressurized atmosphere. Pulp, which has been groundbetween the two reﬁning elements 3, 4, leaves the defibrator housing 5 at a house portion6, and enters into a mounting pipe 7, whose inlet 8 is connected to the defibrator housing 5and whose outlet 9 is connected to an inlet 10 of a blow valve ll, whose outlet 12 is connected to an inlet l3 of a discharge pipe l4.

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 ll, in direct connection with a defibrator housing, such asdef1brator housing 5. However, by providing the mounting pipe 7, which has non-negligible length, surprisingly positive effects have been achieved both regarding theenergy consumption of the def1brator 2 and also regarding the wear of the blow valve ll.Without wishing to be bound be theory, it is believed that the provision of the mountingpipe 7 before the blow valve ll creates a laminar pulp ﬂow through the blow valve ll, i.e.the pulp ﬂow at the exit from the def1brator housing 5, i.e. at the inlet 8 of the mountingpipe 7, is presumably highly turbulent, and by providing the mounting pipe 7, which has anon-negligible length, the pulp ﬂow is “settling down” and a laminar ﬂow is established atthe outlet 9 of the mounting pipe 7. And it is further believed that this laminar pulp ﬂow isless aggressive and exposes the inner surfaces of the blow valve ll to less wear. Thereduction of energy consumption in the def1brator 2 is more difficult to understand, but itcould be that when a turbulent pulp ﬂow encounters a blow valve - as is the case when ablow valve is mounted directly at a def1brator housing - shock waves are created which aretransferred back through the pulp to the rotating ref1ning element and counteract itsmovement, something which, in tum, requires energy to overcome. Thus, by creating alaminar pulp ﬂow through a blow valve, these repercussioning shock waves are eliminated, which has a positive effect on the energy consumption.

To achieve a laminar pulp ﬂow through the blow valve ll, the mounting pipe 7 has beengiven 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. l, the length of the mounting pipe7 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 theblow valve ll is closed, pulp will plug and block the mounting pipe 7 and it may take aconsiderable time to remove this pulp and put the ref1ning system l back into operationagain. Furthermore, it is the steam pressure generated in the def1brator 2 that drives therefining system l, i.e. the steam pressure forces the pulp forward and through the mountingpipe 7, the blow valve ll and the discharge pipe l4 and also through further componentsand pipes which are not seen in the figures; and more specif1cally, it is the pressure dropover 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 ll, cannot be positioned so far from a pressure generating def1brator so that the pressure has dropped tozero or essentially zero. For at least these reasons, the length of the mounting pipe 7 shouldnot be longer than necessary, and a suitable maximal length is about 1.5 m, i.e.0.2 m S L S 1.5 m. The mounting pipe 7, the blow valve 11 and the discharge pipe 14 areschematically illustrated in Fig. 2. The mounting pipe 7 has preferably a circular innercross-section with an inner diameter d1, which preferably is constant, i.e. the diameter d1 isthe 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 ﬂowchannel 16, through which the pulp is intended to ﬂow. The cross-sectional area of theflow channel 16 can be regulated by a valve member 17, which can be introduced into theflow channel 16 to thereby reduce the size of the cross-sectional area of the flow channel16, but according to the present invention, the cross-section of the ﬂow channel 16 of theblow valve 11 is preferably equal to the cross-section of the mounting pipe 7. The latter istypically 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 notrestrict the pulp ﬂow through the blow valve 11. The ﬂow channel 16 has a preferably acircular cross-section with a diameter dg, which is preferably equal, or at leastapproximately equal, to the diameter d1 of the mounting pipe 7, which then preferably alsohas a circular cross-section with d1 2 dg. If for some reasons, other cross-sectional shapesthan 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 ﬂowchannel, and the cross-sectional areas should also be essentially equal. By thisarrangement, when the cross-section of the flow channel 16 through the blow valve 11 isequal, both in shape and size, to the inner cross-section of the mounting pipe 7, a laminarpulp ﬂow is ensured through the blow valve 11, which, in tum, reduces wear on the blowvalve 11. Also, the risk of micro-scale shock waves, which travel back through the pulpand counteract the rotational movement of the rotating ref1ner element 4, is reduced, which has a positive effect on the energy consumption of the ref1ner system 1.

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 modif1cations can be done within the scope of the invention as described in the specification and defined With reference to the claims below. It should inparticular be noted that in the embodiment shown in Fig. l and Fig. 2, the mounting pipe 7has been shown as a separate component. It is, however, within the scope of the inVentionthat a mounting pipe is created as a prolonged inlet portion of a blow valve, i.e. the inletportion is integrated with the blow Valve. A mounting pipe according to the inVention istherefore in this case conf1gured as a mounting portion of a blow Valve. A combination ofa separate mounting pipe and a mounting portion of a blow Valve is also within the scopeof the inVention. In any case, a length of a mounting pipe, such as the length L in Fig. l, ora length of a mounting pipe which is conf1gured as a mounting portion of a blow Valve, ora length of a combination of a mounting pipe and a mounting portion, should always bemeasured from a def1brator 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.

Claims

1. A pulp ref1ning system (1) for mechanically ref1ning of lignocellulosic material,comprising:a def1brator (2),a def1brator housing (5), in which the def1brator (2) is arranged,a blow valve (11) having an inlet (10) and an outlet (12) and being adapted forregulating a ﬂow of pulp therethrough, anda discharge pipe (14) having an inlet (13) which is connected to the outlet (12) ofthe blow valve (11),characterized in that a mounting pipe (7) having an inlet (8), which is connected to thedefibrator housing (5), is arranged between the deﬁbrator housing (5) and the blow valve (11), said mounting pipe (7) having a length (L) of at least about 0.2 meter.

2. The pulp ref1ning 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 S L S 1.5 m.

4. The pulp ref1ning system (1) according to any preceding claim, characterized in that the mounting pipe (7) is provided as a separate component.

5. The pulp ref1ning system (1) according to anyone of the claims 1-3, characterized in that the mounting pipe is conf1gured as an inlet portion of the blow valve.

6. The pulp ref1ning system (1) according to anyone of the claims 1-3, characterizedin that the mounting pipe is conf1gured 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 length of the mounting pipe is measured from the defibrator housing (5) to a closest side of a valve member (17) arranged in the blow valve.

8. The pulp reﬁning system (1) according to anyone of the preceding clain1s,characterized in that the niounting 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).