CN1799799B - Method and device for introducing steam into a material mat or into the covering thereof - Google Patents

Abstract

The invention relates to a method and a device for steaming mats or their coverings during the production of wood material boards, such as chipboards, fibre boards, synthetic material boards or chipboards, consisting of mixtures of binder-free lignocellulose and/or cellulose particles, such as wood shavings, fibres or chips, wherein the mat is pressed and hardened using pressure and heat after being fed into a single-or multi-layer press or a continuously operating press. The invention consists in that the steaming of the material mat by the steaming section is started at the center (I-I) of the material mat and then the wedge-shaped steaming is expanded towards the longitudinal edges (II-II; III-III) of the material mat during continuous production or the steaming of the material mat by the steaming section and the pressure chamber non-operation rows (a, c, e) and operation rows (b, d, f) for the steaming of the material mat are alternately carried out in the working direction by the steaming section .

Description

Method and apparatus for introducing steam into a mat or its covering

technical field

The invention relates to a method for introducing steam into a material consisting of a mixture of lignocellulosic and/or cellulose particles such as shavings, fibres, synthetic material or wood chips with or without binders in the manufacture of particleboard In a mat or in a covering layer of a mat, the invention also relates to a device for carrying out the method.

Background technique

"Matte" in the application refers to a mixture sprinkled on the molding belt, consisting of lignocellulosic and/or cellulose particles such as shavings, fibers or wood chips with or without binders, which can be Spread in multiple locations or layers and in different orientations. Such mats are mostly used in the continuous production of particleboard (MDF) or wood particle board (OSB), but can also be used in discontinuous processes. These mats are mostly pressed and hardened in a continuous process using a continuously working twin-belt extruder. The subject of the present application is the introduction of steam into the mat during the pre-compression preceding the continuous main extrusion or during the main extrusion itself or in each case only into the respective cover layer of the mat due to method limitations. In addition to introducing steam into and out of the mat, the steam treatment of mats of different widths is also a problem to be solved.

WO 1998 041 372 A1 and DE 101 61 341 A1 describe a method for the steam treatment of covering layers on mats of different widths. In this respect, in the case of a width adjustment of the mat during the steam treatment, the region of the steam plate without the mat underneath is disconnected. In addition, a steam treatment that breaks off the raw edges to a certain extent (about 5% of the width of the mat) in the direction of the center of the mat is also introduced to reduce the steam loss on the edges. The device is constructed in such a way that the steam channel is arranged perpendicular to the feeding direction, and the steam is ejected from the channel in the direction of the pad. The steam channel is closed at the edge of the mat by a cylinder feeding in the edge region. The steaming width inside the channel is therefore adjusted accordingly to the width of the mat and the steam loss at the edges, wherein in principle almost the entire width of the mat is steamed through the channel. WO 1998 041 372 A1 also describes that the length of the steam treatment zone (as seen from the feed direction) is adjusted according to the density profile. The length of the steam treatment zone is controlled by switching on individual channels. DE 101 61 341 A1 describes a device which can carry out the steam treatment according to the above method, but in which the width adjustment and the edge breaking are achieved by turning the correspondingly passing cylinders.

DE 44 47 847 A1 describes a device for purportedly steaming the coating. In the described device, the narrow side of the mat is sealed by means of telescopic plates, thereby avoiding steam ejection losses. Boxes distributed across the width of the mat perpendicular to the feed direction are used for the introduction of steam.

It has been shown that the methods and devices described above have the disadvantage that the covering layer cannot be steamed uniformly over the entire width of the mat. The uneven heating of the mat by the steam also results in the center of the mat being less heated across its width than the edge regions. The density profile on the vertical plate cross-section differs at the edges and also differs from the center of the plate. The 30% of the area from the edge to the center of the mat has a wider cover (area of higher density) and a greater density maximum when the cover is steamed than in the same area from the center. In addition, the center of the mat in the rear extrusion area heats up more slowly than the edges of the mat, so that only lower extrusion speeds can be achieved. This slow rise in temperature is a sign of insufficient steam being introduced into the center.

DE 39 14 106 A1 describes a method for the complete circulation or complete heating of a mat by means of steam, in which steam is introduced from one side and a vacuum is applied on the opposite side or steam is introduced simultaneously from both sides. In this respect, the steam treatment is carried out over the entire width of the mat by means of a steam box. However, it has been shown that the simultaneous introduction of steam from above and below does not result in uniform heating of the mat over its entire width and depth, and therefore only insufficiently increases the extrusion speed.

The reason that the above method of steaming is not uniform across the entire width and depth of the pad is that the air within the pad which presents flow resistance to incoming steam does not escape uniformly during steaming. In the center of the mat there is therefore a very high counterpressure against the incoming steam, which pressure is not so pronounced at the edges, since here the open narrow sides of the mat are open and air can escape. Therefore, the steam passes through the edge at the same pressure to a greater cross-sectional depth than the center of the pad. That is to say, it turned out that this method of steam treatment or cover steam treatment with the described apparatus was not satisfactory.

A further disadvantage is that the steam used and sprayed into the mat condenses in the steam chamber above the mat and causes water to collect there. The condensed water can drip onto the mat and form water spots first on the extruded product and thus on the finished wood material board itself. Such wood material panels are rejects and must be rejected upon visual inspection. However, since small water stains can be completely missed during a visual inspection of wooden material panels that are several square meters in size, this can lead to defective products being delivered to the customer and a corresponding damage to the image of the manufacturer.

Contents of the invention

The object of the present invention is to further develop the method of steam treatment of the covering layer, so that the homogeneous density section can increase the extrusion speed over the entire plate width and the method of simultaneous steam introduction from above and below for heating the entire mat cross section This is improved so that the entire pad or cover can be heated evenly, both in width and thickness.

This object of the present invention is based on a method for the production of wood chips, fibers or wood chips, such as particle boards, fiberboards, synthetic material boards, composed of a mixture of lignocellulosic and/or cellulose particles with or without binders. Or a method for steaming a mat or its covering layer when boards of wooden material such as particle boards is realized, wherein after feeding the mat into a single- or multi-layer press or a continuously operating press Pressed and hardened under pressure and heat, the mat is passed through a steaming section where the steaming starts first in the center of the mat and then wedge-shaped (keilformig) steaming towards the longitudinal edges of the mat during continuous production expand.

With this solution, the air is released before the steam continues into the depth direction of the mat, and the air can escape only and eventually through the narrow face of the mat without great flow resistance in the direction of the narrow face of the mat.

The advantage here is that the steaming surface is divided into different steaming fields, wherein a plurality of fields can be present in a "checkerboard" manner, both in the transverse direction and in the longitudinal direction. With these fields individually or in groups variable and adjustable, different steam treatments can be used to control the entire pad depth or just the cover layer. Particularly advantageous in this respect is wedge-shaped steaming or also alternating steaming. Furthermore, when all pressure chambers are switched on, the steam pressure in the individual chambers can be adjusted differently (steam pressure in the center of the mat is higher than in the peripheral chambers). By means of these measures, the covering layer can be heated both uniformly and sufficiently over the width. It is also possible in a targeted manner to enter more steam in the center of the mat (as seen by the width) than at other points (deeper condensation front towards the center of the mat), wherein the known low transverse stresses in the center of the plate can be solved here.

Description of drawings

Further advantageous measures and configurations of the subject matter of the invention are described below with reference to the drawings. in:

Figure 1 shows the possible introduction of the pressed product mat through the steam chamber in a top view in the working direction;

Figure 2 shows the wedge-shaped introduction of steam through the pressure chamber according to Figure 1 (hatched surface); and

Figure 3 shows the alternate introduction of steam only through the pressure chambers in rows b, d and f according to Figure 1; and

FIG. 4 shows a schematic side view of a pressure chamber with a heating device.

Detailed ways

FIG. 1 shows a plan view of a field of pressure chambers arranged above a mat of pressed material in the working direction (AR) of an extrusion manufacturing plant without steam treatment. The arrow in the working direction indicates the inlet side of the steam treatment section (G). In this case, the pressed material mat can be additionally compacted in the working direction when using this method, for example during pre-pressing or main pressing. According to FIG. 2, the wedge-shaped steam treatment is now switched on in the working direction, which causes the air to be gradually evacuated from the center I-I of the mat to the sides II-II and III-III of the mat and replaced by steam. Depending on the pressure exerted in the pressure chamber, it can be completely filled with air being expelled, or a pure blanket steam treatment with the corresponding blanket preheated.

It has been found that it is particularly advantageous for the preheating of the covering to be treated with field-on steam of the following widths;

At the beginning of the preheat (approximately 20% of the steamed length), 20% of the pad width g steamed on the pad center I-I as seen by the width, then 40% (again 20% of the steamed length), then 80% (again 20% of the steam treatment length), and finally the total pad width g. Utilizing this width adjustment of the steam pressure through the length of the steam treatment zone G, the mat has a uniformly heated cover layer after passing through the preheating device, for example through each 15% of the upper and lower material of the entire mat center g; The remaining 35% (each cover layer side) was not heated. Thus 70% of the cushion core is free of steam. The panels produced by means of this method have a uniform vertical density profile both on the edges and in the center I-I of the mat. The plate properties like flexural strength which correlate with the density profile are exactly the same on the edges II-II and III-III as in the center of the mat I-I. The extrusion speed can be significantly increased compared to the above method, because the hot extrusion on the center I-I of the mat heats the intermediate layer to a viscous temperature of about 100° C. at the same point in time as the edges II-II and III-III of the mat. Mixture hardening temperature.

The air discharge and thus also the uniform steam treatment can also be supported by setting the steam pressure higher at the mat center I-I than at the mat edges II-II and III-III. In addition, different steam pressures can also be adjusted via the steam treatment section G of the steam treatment. For cover steaming in the rear region of steaming section G (approximately starting from d or e), it is better to work with lower steam pressure on the pad center I-I, so that the penetration depth of the steam front does not exceed the depth of the material. Pad edges II and III.

In order to provide high steam quantities over short steaming lengths either in the case of thick mats at high extrusion speeds or in the case of large steaming depths required, high steam pressures must be applied to the mat. This results in side venting of the product despite the fact that the steam plates are on both sides of the mat. In order to avoid this problem at the edge regions II-II and III-III of the mat, the steam pressure is set lower over the entire steam treatment section G than in the center I-I of the mat. Side venting of wood products such as shavings or fibers can thus be avoided. This adjustment can likewise be adapted experimentally again in the rear steaming section G with the device according to the invention, if the escaping gas finds its way out via the edge of the mat and the increased flow velocity no longer causes degassing.

The possibility exists, of course, that under special production conditions (in particular different pad thicknesses), the pad center I-I, seen from the pad width g, has lower transverse stresses than the edges II-II or III-III. In this case the heating of the center I-I of the mat takes place more slowly than the edges II-II and III-III. For a given mat thickness, therefore, the steam treatment of the cover layer must be carried out in such a way that more steam, ie humidity and heat, is delivered to the center of the mat. The heating depth of the mat through the cross-section is therefore substantially higher at the center I-I of the mat than at the edges as seen through the mat width g. For example 15% of the material depth is heated at the edges and 20% at the center. Using this method it is possible to produce plates with almost identical transverse stress and density profiles at high extrusion speeds. In order to convert this possibility, the steaming is carried out wedge-shaped such that 20% of the pad width on the pad center I-I passes not 20% of the steaming section G of the steaming, but 40% of the steaming section G. Alternatively, however, the introduction as in the above example can be used, but in which a higher steam pressure is used in the center I-I of the mat than at the edges II-II and III-III.

For steaming mats of different mat widths, it is possible to disconnect the external steaming field on edges II-II and III-III where there is no material underneath the narrow mats to avoid unnecessary steam consumption.

Weight fluctuations caused by diffusion inaccuracies lead to locally higher mat densities, which are present over longer production times in a certain width region of the mat, for example in the center 20% of the width of the mat. This higher weight per unit area portion of the mat is identifiable in the unit area measurement prior to steam treatment. In areas of higher weight per unit area the steam pressure must be adjusted slightly higher to achieve the same steaming depth or longer sections must be steamed as seen in the conveying direction.

Likewise, if steam is introduced from both sides and air is trapped in the center of the mat over the entire width of the mat, complete heating cannot be achieved until the mat is fully ventilated in the center of the center layer. Wedge steaming as described above or using higher steam pressures over the entire length of the steaming can also solve this problem, thereby eliminating the interfering area of air entrainment and ensuring full width and thickness of the mat during full flow through of the mat. Even heating.

The device is constructed in such a way that the steam treatment surface is divided into different steam treatment fields, wherein both the transverse (v, w, x, y, z) and longitudinal (a, b, c, d, e, f) Any number of fields can be distributed for a checkerboard appearance. By individually or in groups variable disconnection and modulating control of the steam pressure or steam volume of these fields, it is possible to control different steam treatment zones in terms of steam treatment pressure or the steam treatment volume transversely through the mat.

Of course, it is obvious that the steam treatment field can also be provided in a slightly smaller scale and applied according to the prior art. With a corresponding reduction of the individual steam treatment fields, it is therefore conceivable to carry out a curved steam treatment across the width of the mat to a large number of steam treatment fields in the transverse direction and in the longitudinal direction.

FIG. 4 shows a schematic side view, from which it can be clearly seen that the mat 2 on the conveyor belt 1 leads in the working direction from above and below through the arrangement of the pressure chambers 3 . The conveyor belt 1 is usually designed as a screen belt and can thus pass through the steam. This device is generally used in the pre-compaction and pre-compaction with different parameters adjusted before the continuous operation of the twin-belt extruder. A heating device 4 above the pad 2 is arranged in the pressure chamber 3 . This prevents possible condensation in the pressure chamber 3 itself and thus water dripping onto the mat 2 . Depending on the intensity of the steam flow, the heating of the pressure chamber 3 can also be expediently carried out below, so that the steam flow does not carry condensate and thus reaches the mat 2 from below. In addition, when using a sieve belt, the conveyor belt 1 has a heating device 5 in the working direction AR of the mat 2 before the steam treatment fields a, b, c, d, e, f, in order to bring the conveyor belt 1 to a level almost equal to or higher than that used for The temperature at which the preheated fluid condenses.

It is self-evident for professionals that the heating of the pressure chamber or the conveyor belt must be switched off with steam before the pressure chamber is used.

reference symbol

I-I, II-II, III-III The longitudinal line segment of the pad in the working direction

a, b, c, d, e, f The setting of the pressure chamber in the working direction

g Pad Width

G steam treatment section in working direction

1 conveyor belt

2 Pads

3 Pressure chamber

4 Heating device

5 Heating device

Claims (29)

1. one kind is used for making by wood shavings, fiber or wood chip be this to add or not to add the picture particieboard that a mixture of the lignocellulosic of adhesive and/or cellulose grain is formed, fiberboard, during this composite wood boards of synthetic material plate or sawdust-board one backing strap or its cover layer are carried out steam treatment process, wherein, behind the forcing press of this backing strap being sent into an individual layer or multi-daylight press or a continuous operation, under the situation of working pressure and heat, suppress and harden, it is characterized in that, the steam treatment of this backing strap by a steam treatment section (G) be at first in backing strap center (I-I) beginning, then at the steam treatment of the production period wedge shape continuously longitudinal edge (II-II to this backing strap; III-III) expansion.

2. by the described method of claim 1, it is characterized in that, 20% backing strap width (g) carries out steam treatment during beginning on 20% steam treatment section (G), 40% backing strap width (g) upward carries out steam treatment to backing strap width (g) in 20% steam treated section (G) subsequently, 80% backing strap width (g) carries out steam treatment by 20% steam treatment section (G) then, and last all backing strap width (g) carry out steam treatment by the residue section of steam treatment section (G).

3. by claim 1 or 2 described methods, it is characterized in that handle for the wedge shape steam treatment and the indirect steam of backing strap center (I-I), the backing strap width (g) with 20% is by the steam treatment section (G) of equipment for steam treatment 40%.

4. by claim 1 or 2 described methods, it is characterized in that, handle, use the steam pressure that is higher than edge (II-II and III-III) here for the wedge shape steam treatment and the indirect steam of backing strap center (I-I).

5. by the described method of claim 1, it is characterized in that, the steam treatment that backing strap makes progress at producer by the steam treatment section (G) predesignated from backing strap center (I-I) to longitudinal edge (II-II; III-III) apply the steam pressure that successively decreases.

6. by the described method of claim 1, it is characterized in that, when the pure wedge shape cover layer steam treatment of backing strap, therefore reduce steam pressure on the operative orientation of backing strap center (I-I) in the Background Region of steam treatment section (G), the degree of depth that enters backing strap thickness from the front at backing strap center (I-I) steam is no more than backing strap edge (II-II; III-III).

7. by aforementioned claim 1 or 2 described methods, it is characterized in that, the balancing gate pit that is not used in steam treatment is used to discharge air active or passive lead diffusing.

8. by claim 1 or 2 described methods, it is characterized in that single steam treatment field is opened wide or is connected on the vacuum to atmosphere.

9. by claim 1 or 2 described methods, it is characterized in that the marginal zone can disconnect formation separately.

10. by the described method of claim 1, it is characterized in that, the balancing gate pit is reached equal or be higher than the temperature of the fluid condensation temperature that is used for preheating.

11. by claim 1 or 2 described methods, it is characterized in that, when using steam, the temperature of balancing gate pit be transferred to and be higher than 100 ℃.

12. by aforementioned claim 1 or 2 described methods, it is characterized in that, when on backing strap and below the person of territory, using the sieve band, make these sieve bands with reach the temperature that equals or be higher than the fluid condensation temperature that is used for preheating equally before employed fluid contacts.

13. a method is used for making by wood shavings, fiber or wood chip be this to add or not to add the picture particieboard that a mixture of the lignocellulosic of adhesive and/or cellulose grain is formed, fiberboard, during this composite wood boards of synthetic material plate or sawdust-board one backing strap or its cover layer are carried out steam treatment process, wherein, behind the forcing press of backing strap being sent into an individual layer or multi-daylight press or a continuous operation, under the situation of working pressure and heat, suppress and harden, it is characterized in that row (a does not work for the steam treatment of this backing strap by a steam treatment section (G) and the balancing gate pit that is used for the backing strap steam treatment, c, e) and work row (b, d, f) alternately on operative orientation, undertaken by steam treatment section (G).

14., it is characterized in that handle for the wedge shape steam treatment and the indirect steam of backing strap center (I-I), the backing strap width (g) with 20% is by the steam treatment section (G) of equipment for steam treatment 40% by the described method of claim 13.

15., it is characterized in that by the described method of claim 13, handle for the wedge shape steam treatment and the indirect steam of backing strap center (I-I), use the steam pressure that is higher than edge (II-II and III-III) here.

16. by the described method of claim 13, it is characterized in that, the steam treatment that backing strap makes progress at producer by the steam treatment section (G) predesignated from backing strap center (I-I) to longitudinal edge (II-II; III-III) apply the steam pressure that successively decreases.

17. by the described method of aforementioned claim 13, it is characterized in that, the balancing gate pit that is not used in steam treatment is used to discharge air active or passive lead diffusing.

18., it is characterized in that single steam treatment field is opened wide or is connected on the vacuum to atmosphere by the described method of claim 13.

19., it is characterized in that the marginal zone can disconnect formation separately by the described method of claim 13.

20. by the described method of claim 13, it is characterized in that, the balancing gate pit reached equal or be higher than the temperature of the fluid condensation temperature that is used for preheating.

21. by the described method of claim 13, it is characterized in that, when using steam, the temperature of balancing gate pit be transferred to and be higher than 100 ℃.

22. by the described method of aforementioned claim 13, it is characterized in that, on backing strap and/or below during use sieve band, make these sieve bands with reach the temperature that equals or be higher than the fluid condensation temperature that is used for preheating equally before employed fluid contacts.

23. device that is used for steam treatment backing strap before extruding, it is characterized in that, continuous steam treatment surface is divided into different steam treatment fields, wherein, no matter be to go up still at laterally (v, w, x, y, z) to go up checkerboard type at vertically (a, b, c, d, e, f) and distribute a plurality of fields are set, and each steam treatment field both can also can control in groups in single control, and each or each group all can regulated formation on the quantity of steam or on steam pressure.

24., it is characterized in that one is provided with heater (4) in the balancing gate pit (3) of backing strap (2) steam treatment field (a, b, c, d, e, f) by the described device of claim 23.

25., it is characterized in that heater (4) is made up of radiator by the described device of claim 24.

26., it is characterized in that heater (4) is made up of the electrical heating pad by the described device of claim 25.

27. by the described device of claim 24, it is characterized in that, heater (4) be arranged on top in the balancing gate pit (3) and/or below.

28. by the described device of claim 23, it is characterized in that, a heater (5) of conveyer belt (1) be set on the operative orientation (AR) of the front backing strap (2) of steam treatment field (a, b, c, d, e, f).

29., it is characterized in that heater (5) is made up of roller, contact mat or convection current beam by the described device of claim 28.

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