DE102018005205A1 - Classifier and method for classifying - Google Patents

Abstract

The invention relates to a classifier for separating coarse particles (15a) and / or fine particles (15b) from a particle stream (15) in the course of the production of wood-based panels, in particular fiber or chipboard, with a classifier housing (2) which has at least one material inlet ( 6) and has at least one supply air inlet (7), at least a portion of the material supplied through the material inlet (6) being able to be subjected to an air flow (21) supplied through the supply air inlet (8), the classifier housing (1) having at least one Has outlet opening (9, 10, 11) and a guide device (14, 14a, 14) for the coarse particles (15a) and / or fine particles (15b) to be separated out. In order to avoid caking on the housing wall of the classifier, it is provided that at least part of the classifier housing (2) and / or the guide device (14, 14a, 14) are rotatably mounted.

Description

The invention relates to a classifier for separating coarse particles and / or fine particles from a particle stream in the course of the production of wood-based panels, in particular fibreboard or chipboard, with a classifier housing which has at least one material inlet and at least one supply air inlet, at least part of which is provided by the Material inlet supplied material can be acted upon for screening with an air flow supplied through the inlet air inlet, the classifier housing having at least one outlet opening and a guide device for the coarse particles and / or fine particles to be separated out.

The invention further relates to a method for classifying a particle stream in the course of the production of wood-based panels with said classifier.

Such a classifier is used to purify particle streams in the wood-based panel industry and in particular to remove undesired components from the particle stream. For example, metal parts, coarse fibers, rust pieces, glue particles or lumps of glue or silicates are to be removed from a stream of fibers or chips in order to protect downstream plants or plant parts, in particular the steel belts of continuously working wood-based material presses, from damage or abrasion. Such a classifier is, for example, from the DE102016117383 A1 known. The classifier described there is particularly preferably used in the course of the production of wood fiber boards for the separation of coarse particles from the fiber stream and consequently from the (glued) wood fibers (for example rubberwood fibers). Fiberboard means, for example, MDF boards (medium density fiber). In the course of the production of the fibers for wood fiber boards, the wood is first defibrated (in a refiner) and wet glued (for example in a blowline) and then dried. The classifier is preferably arranged downstream of these system components and particularly preferably the dryer of such a system.

The classifier works as an air classifier in that the material to be classed is introduced into the classifier housing via the material inlet and an air flow is applied to the side, which is blown into the classifier housing via the supply air inlets. The fibers are captured by the air flow or the air flows and discharged with the air flow via the (upper) exhaust air outlet and an exhaust air line connected to it. Coarse particles with greater weight are not caught by the air flow and fall down into the area of the coarse material outlet, which can be provided with a lock, so that the (undesired) coarse particles are removed.

However, it would also be desirable if a classifier could also sort out fine dusts, which can be found, for example, in and on fibers and chips of annual plants, in addition to the coarse material. Such a device is then used, for example, to separate and / or obtain silicates from vegetable material. This should z. B. avoid the problems caused by silicates in plate production. Alternatively or in addition, a new and economical way of producing or extracting silicates could be specified.

Such a sifter is in the application unpublished at the time of registration DE102017120033.9 described.

Incidentally, is from the EP 1 900 445 B1 a classifier for separating coarse and fine material in the production of wood fiber boards is known, in which a plurality of inlet openings arranged one above the other are provided for the classifying air. These inlet openings for the sifting air are arranged in a stepwise manner offset to improve the cross-flow sifting in the conveying direction of the material, that is to say in the sifting air flow direction towards the discharge opening. Three inlet openings arranged one above the other should preferably be provided for the classifying air.

In the prior art mentioned, it is known that the air flow does not flow through all areas of the classifier housing. This results in material “caking” and clumping of fibers or chips, particularly in the corners of the housing, which in turn can lead to undesirable swirling of the currents.

Starting from the known prior art, the invention has for its object to provide a classifier of the type described above, which is characterized by a high level of efficiency for both coarse and fine particles with a simple structure and thereby avoids caking on the housing wall of the classifier.

To achieve this object, the invention teaches in a classifier of the type described at the outset that at least part of the classifier housing and / or the guide device are rotatably mounted.

The rotation of the housing wall or guide device largely prevents the accumulation of fibers or chips. Since the major part of the inner wall of the classifier housing itself rotates or is at least swept by a rotating guide device, caking cannot occur.

The source material, i.e. the particle flow, is blown into the rotationally symmetrical classifier with air support and, depending on the weight or size of the particles, lies more or less far away from the point of injection due to gravity on the inner wall or becomes a fine particle from the air flow through the classifier housing carried through and removed at the other end. Depending on how far the particles are and whether they are carried in the area of the guide device, the guide device is then able to guide them to the desired removal point.

In order to avoid dynamic imbalance, it is advantageous if the largest part of the classifier housing is essentially rotationally symmetrical. Here primarily tubular housings with a round cross section come into consideration, which are supported at their ends and are driven, for example, from one side. Due to the missing "corners", caking storage can be almost completely avoided.

The guide device is preferably helical.

When this guide device rotates, the material carried by the air flow into the area of the guide device is automatically transported to one of the outlet openings. This happens largely automatically, without having to consider complicated turbulence, as is the case with conventional classifiers.

The guide device particularly preferably consists of a left-handed and a right-handed helical area.

This allows particles to be transported in two different directions to two different outlet openings. If, for example, the heavier particles were deposited on the inner wall in the front area of the classifier due to gravity in the air flow direction, they would be able to be transported back to a first outlet opening by a guide device with a left-hand slope. In contrast, lighter particles that have deposited in the area of the right-hand slope of the guide device are transported further forward to a second outlet opening.

It is advantageously ensured that the guide device is arranged rotatably together with the rotationally symmetrical part of the classifier housing.

The classifier housing and the guiding device thus become quasi one-piece. Complicated storage between the classifier housing and the control device is avoided.

It is particularly expedient for the guide device to consist of a helical strip attached to the inner wall of the housing.

Such a helical bar can be identical in outer diameter to the inner diameter of the classifier housing. This enables the guide device to be attached in a simple manner by welding, gluing or screwing. The classifier housing then no longer requires any maintenance.

The classifier housing preferably comprises a conical tube as a rotationally symmetrical part.

The pressure profile in the classifier can be set by the cross section then opening or closing in the air flow direction. To do this, the angle of the cone is determined in advance by a flow calculation.

It is advantageous if the rotatable, rotationally symmetrical classifier housing part is mounted in such a way that it extends into a fixed inlet and / or outlet casing.

These bezels then usually form part of the classifier housing in the air inlet and outlet area. They include the fixed end walls of the rotating housing part, against which they are preferably sealed. This offers the possibility of arranging the inlet air inlet and outlet as well as inlet and outlet openings for the material flows in a simple manner. The inlet and outlet openings can also be provided with known cellular wheel locks with relatively little effort because of the fixed lines. As a result, or pressure spaces can be limited and material can also be metered. In addition, bursting devices can be integrated in the fixed surrounds with slight structural measures, so that excellent prevention against an explosion risk of fine wood dust can also be integrated, because the bursting discs can, for example, act in an outside area that is not frequented by personnel.

It is preferably provided that dust can be removed via an exhaust air outlet.

This exhaust air outlet is usually located at the end of the classifier housing opposite the air inlet and can also be installed in an outlet casing. With the help of this exhaust air outlet, not only wood dust but also, for example, the silicates can be separated excellently. An exhaust air duct is usually connected to this air outlet. This exhaust air line has, for example, a material switch in known technology. Due to occurring Centrifugal forces in this area are divided into a particle / air mixture on the one hand and air on the other, so that a certain amount of air can be separated from the amount of fibers. The entire system thus works more energy-efficiently, since a lower volume of air is transported on. The separated amount of air is then fed back to the classifier, for example via a fan, and possibly previously mixed with fresh air.

Overall, the design of the classifier according to the invention inside the housing offers a very uniform flow pattern of the particles of different mass or size, as is not known in conventional classifiers.

The invention is explained in more detail below with reference to drawings showing two exemplary embodiments.
The 1 shows a classifier according to the invention in a simplified schematic representation with a material inlet in the inlet air inlet, and 2 shows a comparable sifter according to the invention in a simplified schematic representation with a material inlet via opening rollers in the inlet casing.

In the figures there is a sifter for the separation of coarse particles 15a from a particle stream, in particular fiber or chip stream, represented in the course of the production of wood-based panels, in particular wood-fiber boards. Such a classifier is preferably integrated in a plant for the production of wood-based panels, in particular in order to remove undesired constituents (eg metal parts, lumps of adhesive, coarse fibers, rust pieces or the like) from a material flow (eg from glued fibers), in particular to connect downstream plants or Protect system parts (e.g. steel belts of a continuously working wood-based panel press) from damage. At the same time, each of the classifiers shown in the figures is also used to collect fine particles 15b , for example silicates, to filter out of a material flow. This is done by removing the dust particles with the exhaust air through the exhaust air outlet 8th be dissipated.

The sifter 1 has a classifier housing in both figures 2 on which is a rotationally symmetrical middle part 3 and an entrance bezel 4 as well as an exit bezel 5 having. The name entrance bezel 4 and home facing 5 refers to the main flow direction of the incoming air 21 ,

It is identical in both versions that a particle stream to be viewed 20 with the help of the supply air 21 moving into the classifier housing at high speed 2 enters from the entrance bezel 4 through the rotationally symmetrical middle section 3 partly up to the initial edging 5 will be carried.
Depending on the weight or size, the heavier particles fall out of the air flow sooner or later due to gravity and settle in the lower area on the housing wall. The coarse material falls 15a , for example stones or lumps, already within the entrance frame 4 into the coarse material outlet located there in the lower area 9 or is there via a guidance device 14 directed. In contrast, the good material 15c to the good material outlet 10 worn or guided. The fine dust 15b is in the exemplary embodiments through the exhaust air outlet 8th . 11 discharged, but could also have a separate fine dust outlet if the exhaust air and fine dust are separated again.

The particle flows indicated by arrows 15 . 15a . 15b . 15c should clarify which way coarse material 15a , Particulate matter 15b and good material 15c to take.

In the same way, arrows indicate the material supply to be viewed 20 who have favourited Supply Air 21 and the exhaust air 22 shown.

In the rotationally symmetrical part 3 of the classifier housing 2 is a guidance system 14 provided the at least one helical, helical strip 19 comprises, the outer diameter of the inner diameter of the rotationally symmetrical part 3 is adjusted.

If this guide 14 rotates, particles that are on the inner wall of the rotationally symmetrical part 3 have deposited, because they have dropped out of the air flow due to the gravitational forces, shifted in a direction parallel to the longitudinal axis of the rotationally symmetrical part. The direction in or against the air flow direction is determined by whether the bar 19 the control facility 14 represents a left-handed or right-handed screw thread and whether it rotates clockwise or counterclockwise. Incidentally, the guide device could rotate together independently of the rotationally symmetrical part or connected to it. In both exemplary embodiments, two guide devices are provided, one guide device with a left-handed screw thread 14a and a guide device with a right-handed screw thread 14b that as a kind of threaded ledge 19 on the inner wall of the rotationally symmetrical part 3 is welded on. This offers the advantage that the precipitated particles, which have precipitated in the area in the front in the air flow direction because they are particularly heavy and would possibly have an adverse effect on subsequent processes, are returned to the coarse material outlet 9 can transport and dispose of. In contrast, particles in the range of Guide device with right-handed screw thread 14b fail and are suitable for the production of wood-based panels, to the outlet for good material 10 transported. The rotationally symmetrical part 3 in camps 12 stored and via at least one drive 13 set in rotation.

In the case in which the pressure in the rotationally symmetrical part is to be influenced in the longitudinal direction, the rotationally symmetrical part can also deviate from the tubular shape with the same round cross-section and taper, for example. Flow calculations can precede the shape design. For the sake of simplicity, the rotationally symmetrical part is 3 shown cylindrical in the figures.

Particles that do not fail at all, for example fine dust, are removed with the exhaust air through the exhaust air outlet 8th discharged. This includes, for example, fine dust made of silicates when sifting straw fibers, which can be used later.

The two embodiments according to 1 and 2 differ only in the location of the material inlet. In 2 the particle flow to be sifted is fed to the air duct leading to the supply air 7 leads. The material is already accelerated in the air line and blown into the classifier housing.

The classifier housing in 2 points at its top in the entrance bezel 4 a material inlet 6 on, for example, glued fibers are introduced, which are supplied, for example, by a dryer after gluing. In the area of the material inlet 6 or above or below the material inlet there can be opening elements, for example opening rollers 18 , be arranged, which are only hinted at in the figure. The fibers or chips pass through the material inlet 6 in the interior of the classifier housing 2 , The classifier housing points below the material inlet 6 in the wall of the entrance surround 4 an air intake 7 on. Of course, several inlet air inlets, possibly of different widths and sizes, can also be provided here.

Via the inlet air 7 the air is fed in and through the material inlet 6 entering fibers or chips are caught by the air flow and transported into the rotationally symmetrical part. Coarse particles, for example metal or rubber particles, are removed by the air flow as in the exemplary embodiment 1 not in the area of the exhaust air outlet 8th transported, but they fall down into the area of the coarse material outlet 9 and are there over a lock 16 removed.

The locks 16 are examples of the material inlet at 1 and at both figures at the coarse material outlet 9 and good material outlet 10 shown. First and foremost, they cause the pressure in the classifier housing 2 cannot change.

In the event that there is a dust explosion, are in the entrance and exit edging 4 . 5 Rupture discs 17 provided a blast of explosion in an area from the classifier housing 2 lets out who is not frequented by staff.

LIST OF REFERENCE NUMBERS

1

sifter

2

classifier

3

Rotationally symmetrical part

4

entrance Mount

5

output mount

6

material inlet

7

supply air inlet

8th

exhaust outlet

9

Coarse material outlet

10

Good material outlet

11

Fine dust / silicate outlet

12

camp

13

drive

14

guide

14a

Guide device with left-handed screw thread

14b

Guide device with right-handed screw thread

15

particle stream

15a

Arrow particle flow coarse

15b

Arrow particle flow fine dust

15c

Arrow particle stream good material

16

rotary

17

rupture disc

18

opening roller

19

strip

20

Arrow material feed

21

Arrow supply air

22

Arrow exhaust air

23

seal

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102016117383 A1 [0003]
• DE 102017120033 [0006]
• EP 1900445 B1 [0007]

Claims (11)

Sifter for separating coarse particles (15a) and / or fine particles (15b) from a particle stream (15) in the course of the production of wood-based panels, in particular fiber or chipboard, with a sifter housing (2) which has at least one material inlet (6) and at least has an air inlet (7), at least some of the material supplied through the material inlet (6) can be acted upon by an air flow (21) supplied through the air inlet (8), the air separator housing (1) having at least one outlet opening (9, 10, 11) and a guide device (14, 14a, 14) for the coarse particles (15a) and / or fine particles (15b) to be separated, characterized in that at least part of the classifier housing (2) and / or the guide device (14, 14a, 14) are rotatably mounted. Classifier according to Claim 1 , characterized in that part of the classifier housing (2) is essentially rotationally symmetrical. Classifier according to Claim 1 or 2 , characterized in that the guide device (14, 14a, 14b) is helical. Classifier according to one of the Claims 1 to 3 , characterized in that the guide device (14, 14a, 14b) consists of a left-handed and a right-handed helical area. Classifier according to one of the Claims 1 to 4 characterized in that the guide device (14, 14a, 14b) is arranged rotatably together with the rotationally symmetrical part (3) of the classifier housing (2). Classifier according to one of the Claims 1 to 5 , characterized in that the guide device (14, 14a, 14b) consists of a helical strip (19) attached to the inner wall of the housing. Classifier according to one of the Claims 1 to 6 characterized in that the classifier housing (2) comprises a conical tube of rotationally symmetrical part (3). Classifier according to one of the Claims 1 to 7 characterized in that the rotatable, rotationally symmetrical classifier housing part (3) is mounted such that it extends into a fixed inlet and / or outlet casing (4, 5). Classifier according to Claim 8 , characterized in that a seal (23) is provided between the rotationally symmetrical classifier housing part (3) and the inlet and / or outlet casing (4, 5). Sifter according to one of the preceding claims, characterized in that fine dust (15b) can be removed via an exhaust air outlet (8). Method for classifying a particle stream in the course of the production of wood-based panels with a classifier (1) according to one of the Claims 1 to 10 , characterized in that at least a part of the classifier housing (3) is rotationally symmetrical and rotates during the classifying process.

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