DE102005035244A1 - Method and device for the production of wood-based panels - Google Patents

Abstract

The invention relates to a process for the production of wood-based panels from a mixture of fine, coarser and long particles containing lignocellulose and / or cellulose containing binder, such as shavings, fibers or long chips, consisting of one or more layers, which are brought into a final shape by pressing and be cured. The invention for the method consists in that during the falling of a particle stream from the scattering bunker or into the scattering head from nozzles water vapor with a temperature of 100-180 ° C., preferably 105-130 ° C., for setting the moisture and the temperature of the particles in the particle stream is injected. The device for carrying out the method is designed in such a way that in the spreading machine (1) between the dosing hopper (2) and the spreading head (3) and / or in the spreading head (3) on guide plates (7), steam strips (8) with steam nozzles (15 ) are attached over the entire width of the spreading head (3).

Description

The The invention relates to a process for the production of wood-based panels according to the generic term of claim 1 and and an associated apparatus for carrying out the Method according to claim 14.

The ideal humidity and heat setting of the to be pressed particles in the wood-based panel manufacturing employed the professional world for a long time. Especially a gentle warming up or until just below the process temperature without damaging the used particles or the applied adhesive was already addressed in many literature. In addition to high frequency radiation can also be used with hot air, Steam or an air-vapor mixture can be used around a scattered Pressgutmatte shortly before a press to a corresponding temperature to warm. This is usually always just before the floor or continuously working press preheated to activate the adhesive used. When heating with high-frequency radiation, it is necessary a homogeneous moisture distribution to reach, either because of heat or not heated enough partitions arise can, the disadvantageous in the case of this produced wood-based panel can affect. Also an injection of fluids in a press mat as preheating is not always considered optimal too rate. Especially with very specific layered scattered pressed material mats with multiple layers it is not desirable with a strong one fluid flow to charge for a shift and partial concentration of the scattered particles provides. Costly efforts are also being made to sprinkle a pressed material mat according to exactly defined specifications. Especially in oriented scattering as in OSB or OSL plate production is the Orientation of particles with high percentage guaranteed be. There it is counterproductive an oriented scattering with fluid flows out hot air or to apply steam mixtures. To the shifting work of the fluid flows To compensate is usually a passage of fluids being carried out in so-called pre-pressing before a main press, being already Pressure is exerted on a scattered Pressgutmatte. But still can there are shifts of the scattered material to be pressed. In production of wood-based panels with special top layers of very small Particles leads It even causes the small particles from the topcoat to be in the middle layer (with larger particles) transferred which can lead to non-application of particle preheating.

From the DE 44 34 876 C2 has become known a method and a plant for the continuous production of multi-ply wood panels, in which a pressed material mat is made of various layers of different chip mixtures with different spreaders. This pressed material mat is then pressed and cured in a continuously operating press. In a minor aspect of this method and the system it is mentioned that the temperatures of the material used are adjusted for individual layers in the scattering stations. The temperature increase should be done by means of superheated steam or wet steam. The standard humidity of the glued chips should be reduced below the usual level, which is set without preheating. A concrete embodiment of this method or a device for preheating the particles is not explained in detail in this literature.

In the newer DE 103 14 623 B3 a device and a method for the production of wood-based panels has been disclosed, are sprinkled with the wood chips to a single or multi-ply web and then pressed under pressure and temperature influence to a wood-based panel, wherein at least one roller is heated in the scattering device is executed. In addition to the question whether the heating of heated rolls ensures sufficient heat transfer to the particles, this method of particle preheating in a scattering station is not economical due to the disproportionate heating costs.

The Object of the present invention is a method for preheating Particles, especially fibers or chips, in a spreader to form a pressed material mat in the course of the production of wood-based panels to create, which makes it possible to avoid the disadvantages presented above and the mentioned possibility a temperature setting in the scattering stations with a minimum To allow effort. Furthermore, an apparatus for carrying out the method is to be created who is able to work economically.

The Task is according to the invention according to claim 1 solved by that while the falling of the particle stream from the scattering bin or in the scattering head from nozzles in the particle curtain water vapor at a temperature of 100 ° -180 ° C, preferably 105-130 ° C for setting the Moisture and the temperature of the particles is injected.

The solution for a device for carrying out the method according to claim 14 is that in the scattering machine between dosing bunker and scattering head and / or in the scattering head to Leit Metal strips are fitted with steam nozzles over the entire width of the spreading head.

further education and advantageous embodiments of the method and the device are in the subclaims specified.

It has become more surprising Way out that it is necessary to warm the particles to a maximum 80 ° C is sufficient is, steam over inject the full width into the falling particle stream. The predominant Part of the vapor condenses on the particles of the falling down Particle stream and does not mix with the air, which is in the particle stream is located. Rather, the injected steam replaced the air between the falling particles. Because at one Mixing the steam with existing air would only change the air temperature and increases the relative humidity in a vapor-air mixture, which not to raise the temperature Particles leads. Important in this process is a sufficient vapor velocity to reach into the particle stream, so that the entire falling Particle stream is continuously supplied with steam. penetrates The steam completely blows the flow of particles on almost every one Particles of the vapor condenses and heats the particle with it. A uneven heating only a part of the particle flow do not take place here. A such unequal heating would to Example of plate curvatures and differences from upper to lower plate half lead to the pressure. According to the invention is through the use of nozzles such a high vapor velocity achieved that a particle flow penetrated by up to 30 cm thickness straight.

The The exit velocity of the steam from the nozzle is between 5 and 50 m / sec. The exit velocity becomes dependent on the thickness of the particle flow and the Bedüsungswinkels selected. Prefers become flat jet nozzles used a complete Steam curtain form, through which the particles across the full width fall. The advantage of the invention is in addition to the uniform heating of all Particle of a particle flow and the low loss of steam through the targeted introduction into a particle stream. In case of incomplete condensation, for example, in case of insufficient introduction of the vapor into the particle stream, can the remaining steam on the walls of the spreader and the baffles condense, causing it to water formation as well Condensate stains on the plates comes.

The jetting should be after the particles leave the spreading hopper or the dosing bunker done on the way to the scattering head. The nozzles and the pipe for steam supply the nozzles can in the baffles are integrated or even at a certain distance from 1-30 cm are mounted to the particle flow. The spray can also be from both sides alternately or simultaneously in the particle flow. These Allow arrangements a steam curtain is formed into which the particles enter and the steam losses described above do not occur.

Of the Steam jet should be at an angle of 20-160 °, preferably 90 ° on the Be directed particle flow. If too low an angle is selected, penetrates the steam is not complete the particle flow and the heating is uneven. The Steam quantity is selected according to the Preheating temperature in dependence set the passing of the steam bar mass flow. For example, for heating of a particle stream fibers of 40 t / h from 40 ° to 50 ° C, a vapor quantity of 320 kg / h at more complete Condensation of the injected Steam needed, ie 0.8 kg / h of steam per 1 t / h of particulate material. As a small part the steam is not condensed and mixed with the air about 380 kg / h on the particle flow by means of a steam strip. The the steam bar supplied Steam quantity per unit time can be determined by means of a proportional steam valve or a pressure reducing valve.

fluctuating Particle temperatures in the pressed material mat, mostly due to outside temperature differences are caused frequently the cause of burst wood-based panels after a press. The temperature The particles in the pressed material mat can be measured and used for control the amount of steam or to adjust the valve position of the steam valve be used. This will cause a constant particle temperature before a press getting the production security regarding Platzer of the plates after the press significantly increased and also a further optimization of the press program. By a for a particle temperature optimized pressing program can increase the pressing speed be increased at a constant particle temperature. It means that the press speed and the plant capacity not only by the increased particle temperature but also increased by more constant production conditions become.

In order to obtain a pronounced density profile with high cover layer densities and low middle layer density, the particles of the cover layers should preferably be raised to a temperature higher than 60 ° C., preferably 80 ° C., while the particles of the middle layer are heated to a maximum of 60 ° C. In some applications, a homogeneous density profile with a uniform density across the plate cross section is also desired. In this case, the middle layer at a much higher temperature and the top layer is not or on preheated to a maximum of 50 ° C. The glued particle moisture must be lowered with increasing temperature increase, since the moisture of the particles increases due to the condensation of the steam. Per 1 ° C temperature increase, the humidity must be reduced by 0.04-0.08%. By this measure, the usual control humidity before the press is not changed by the preheating. The steam supply pipe for the nozzles should be equipped with a condensate separator. The first time steam is introduced into the pipe, condensate forms, which could leak as water from the nozzles and cause condensation on the plates. The use of slightly superheated steam prevents wet steam from escaping from the nozzles, which would lead to water spots on the plates.

Further advantageous measures and embodiments of the subject matter of the invention will become apparent from the dependent claims and the following description of the drawing.

It demonstrate:

1 Schematic side view of a spreader according to the invention with arrangement of the steam strip on the baffles in the scattering head area,

2 Enlarged view 1 with arrangement of steam strips in the falling area of the particles between dosing bunker and scattering head with several variants and

3 Section view after 1 with view of steam strips and steam nozzles.

According to the drawings, there is a spreader 1 from a dosing bunker 2 with scattered head arranged underneath 3 , Usually, the particle flow 6 across the width of the spreading head 3 in the dosing bunker 2 depending on the requirement of the wood-based panel to be produced by means of the discharge belt 13 and the discharge rollers 12 discharged and conveyed into the spreading head. The particle flow hits 6 in a first embodiment of the invention to an adjustable guide flap 4 that the particle flow 6 specifically on dividing rollers 5 directs the particle flow 6 in the scattering head 3 to distribute. After any further division by further rolls of the divided particle flow 6 finally via baffles 7 on the orientation rollers 9 guided. The orientation rollers 9 Depending on the requirements, the particles are oriented or not oriented to the forming belt 10 and thus form the pressed material mat 11 or with several sequentially arranged spreading machines 1 also only one layer of a pressed material mat 11 , The pressed material mat 11 is then pressed as fast as possible in a press (not shown). This can be depending on the equipment a floor or continuously operating press for the production of wood-based panels.

For temperature control of the particle flow 6 are in the baffles 7 steam strips 8th arranged the steam in the passing particle stream 6 inject. It is not essential for the purposes of the invention, whether the steam strips 8th in the upper or lower part of the baffles 7 are arranged. To avoid stray errors, it is common for the baffles 7 To construct so that caking or accumulation of particles, especially on the back, be avoided. It is up to the reading designer, like the steam rails 8th To arrange or encapsulate to ensure a smooth dispersion. In a second embodiment according to 2 , which can also occur in combination with the first, can be found the steam strips 8th directly above the dividing rollers 5 , or below the dosing bunker 2 , The bulk of the particle flow must be 6 not necessarily from a dosing bunker 2 but can also be done directly from a blow-line or other delivery variants for particles. In this variant, the one from the dosing bunker 2 exiting particle flow 6 at the moment by means of the steam bar 8th steamed when he hit the baffle 4 meets. But it is also possible a spraying below the guide flap 4 provide and / or the spraying at an angle of 20 ° (shown) to 160 ° (not shown) to perform falling / sliding particle flow. The spraying takes place over the entire width of the particle stream 6 instead of and can also be from two sides, but parallel to the transport direction of the forming belt 10 , take place to avoid stray errors. When spraying with steam, this has a temperature of 100 ° to 180 ° C, preferably from 105 to 130 ° C. In this case, a control of the supplied amount of steam depending on the desired temperature of 40 ° -80 ° C and the particle throughput can be performed with the Pressgutmatte 11 should leave the spreader and optimally pressed immediately afterwards. When using 0.8 to 1.5 kg / h steam per ton / hour of passing particles, this leads to a temperature increase of one degree Celsius. The spraying can be carried out at a speed of 5 to 50m / s.

When using multiple spreaders 1 a multilayer pressed material mat is created 11 which can be pressed into a multi-layer wood-based panel. As a rule, different particles are present in the different spreading machines 1 for use. Depending on the use of the particles for middle or outer layers of a Multilayer press mat must therefore also be set to different parameters in the spreaders, especially in order to obtain a pronounced density profile over the thickness of the wood-based panel. To generate a density profile with high cover layer densities and low mid-layer density, the particle flows must 6 the cover layers to 70 ° -80 ° C and the particle flows 6 the middle layers are preheated to 50 ° -60 ° C. To produce a uniform density profile across the thickness of the wood-based panel, the particle flows 6 the cover layers to 50 ° C and the particle flows 6 the middle layers are preheated to 70 ° -80 ° C.

With different design of steam strips 8th can the steam nozzles 15 be designed as flat jet nozzles, be arranged close to each other and in several rows. It is possible the rows of steam nozzles 15 at different angles to the particle flow 6 to increase the efficiency of the steam injection. It is of course possible the steam bar 8th form as a tube or as a square, with the steam bar 8th always means for condensate removal 14 should have or a condensate bag is attached. The optimal arrangement of steam strips 8th to the particle flow is 1 to 20 cm away, with the steam strip 8th Of course, it can also be designed to be pivotable.

1

spreader

2

Dosing hopper

3

spreading head

4

deflector

5

Aufteilwalzen

6

particle stream

7

baffle

8th

steam bar

9

orienting rolls

10

forming belt

11

press material mat

12

feedingout

13

discharge conveyor

14

condensate drain

15

steam nozzles

Claims (23)

Process for the production of wood-based panels from a mixture of binder-added fine, coarse and long lignocellulosic and / or cellulosic particles, such as shavings, fiber or long chips, consisting of one or more layers, wherein the layers of scattering stations are moving toward a moving continuous forming belt a Pressgutmatte be scattered, which is then brought under application of pressure and heat by pressing in a final shape and cured, characterized in that during the dropping of a particle stream from the scattering bin or in the scattering head of nozzles water vapor at a temperature of 100 ° -180 ° C, preferably 105-130 ° C for adjusting the humidity and the temperature of the particles is injected into the particle flow. Method according to claims 1 and 2, characterized by a control of the amount of steam supplied dependent on the desired preheat from 40-80 ° C as well as the Particle throughput performed becomes. Process according to claims 1 to 3, characterized that for one ton / hour of passing particles for a Celsius temperature increase 0.8 up to 1.5 kg / h of steam is used. Process according to claims 1 to 4, characterized that the glued moisture before evaporation per 1 ° C temperature increase to 0.04 to 0.08 (wood moisture) is lowered. Process according to claims 1 to 5, characterized that the steam is at an angle of 20-160 ° to the falling particle flow is injected. Process according to claims 1 to 6, characterized that the injection of steam at a speed of 5 to 50 m / s performed becomes. Process according to claims 1 to 7, characterized that the injection of steam into the particle stream between scatter bunker and before entering the scattering head over the full width of the particle stream he follows. Process according to claims 1 to 8, characterized that the spraying the particle flow in the region of the dividing rolls and / or the baffles done in the spreading head of a spreader. Process according to claims 1 to 9, characterized that the spraying from two sides of the particle flow. Process according to claims 1 to 10, characterized that the spraying in scattering head only parallel in direction or opposite direction the Formbandvorschubes is performed. Process according to claims 1 to 11, characterized in that, depending on the use of Particle for middle or outer layers of a Mehrschichtpressgutmatte different parameters are set in the spreading machines. Method according to claim 13, characterized in that that for producing a density profile with high cover layer densities and low middle layer density, the particle flows of the cover layers to 70 ° -80 ° C and the particle streams the middle layers are preheated to 50 ° -60 ° C. Method according to claim 13, characterized in that that to produce a uniform Density profile the particle flows the cover layers at 50 ° C and the particle streams the middle layers are preheated to 70 ° -80 ° C. Device for carrying out the method according to claim 1, characterized in that in the spreader ( 1 ) between dosing bunker ( 2 ) and scattering head ( 3 ) and / or in the scattering head ( 3 ) on baffles ( 7 ) Steam strips ( 8th ) with steam nozzles ( 15 ) over the entire width of the scattering head ( 3 ) are mounted. Apparatus according to claim 14, characterized in that the steam nozzles ( 15 ) are designed as flat jet nozzles. Device according to claims 14 or 15, characterized in that the steam strip ( 8th ) is designed as a tube or as a square. Device according to claims 14 to 16, characterized in that the steam strip ( 8th ) Means for condensate removal ( 14 ) and that a condensate bag is attached. Device according to claims 14 to 17, characterized in that the steam strip ( 8th ) Is located 1 to 20 cm away from the particle flow. Device according to claims 14 to 18, characterized in that the steam nozzles ( 15 ) across the width of the steam strip ( 8th ) are arranged with such a small distance that the steam forms a closed steam jet as seen across the width. Device according to claims 14 to 19, characterized in that for setting the Bedüsungswinkels the steam strip ( 8th ) is pivotally mounted. Device according to claims 14 to 20, characterized in that the steam nozzles ( 8th ) in several rows on the steam strip ( 8th ) are arranged. Apparatus according to claim 21, characterized in that the rows of steam nozzles ( 8th ) with different angles to the particle flow ( 6 ) are arranged. Device according to claims 14 to 22, characterized that for adjusting the amount of steam per unit time, a proportional steam valve or a pressure reducing valve is arranged.