SE514351C2 - Method and apparatus for producing lignocellulosic discs - Google Patents

Abstract

In a method and an arrangement for continuously producing lignocellulose-containing boards, the material is disintegrated into particle and/or fibre form, glue-coated, dried, and formed into a mat (1). The mat is pressed into board form (3) in a continuous steam injection press (2) and the board then passed through an after-conditioning zone (4). A specific volume of air having a specific moisture content and temperature is drawn through the board (3) in the after-conditioning zone (4) by suction.

Description

l. 2 the dimensions of the disc change, so that the surface layer comes loose. In order to achieve a desired equalization between the different layers, it is common for the discs to be stored for a number of weeks.

Another known problem is that the discs, when they come out of the press, are not dimensionally stable. This is especially noticeable * in the fact that the discs shrink or swell during a process that can take one or a few days. This means that calibration grinding is usually not performed on the discs until after they have been stored in intermediate storage for a few days.

Another known problem is that the discs, when they come out of the hot press, are too hot to be stacked and stored. If the boards are stacked at too high a temperature, degradation of the adhesive joints can start and the boards weaken. This is usually remedied by allowing the discs to reside in a so-called cooling wheel. From the above it appears that it is conventionally used where the temperature drops by self-convection. press technology and disc production involve a number of costly handling steps and intermediate storage after the actual disc production. The object of the invention is therefore to stabilize a board in a continuous process with respect to moisture content, temperature and dimensional stability and thereby avoid expensive handling and storage. By obtaining dimensional stability, the boards can also be ground immediately after production to a final thickness. This object is achieved by the method and the device according to the invention obtaining the features stated in the claims.

The invention will now be described in more detail with reference to the accompanying drawing, which in a longitudinal section schematically shows a plant according to the invention.

The system shown in the drawing is based on the system shown in SE 504 638, which describes a continuous injection procedure. A mat 1 formed of lignocellulosic material is fed into a continuous steam injection press 2 and pressed there into discs 3. When these come out of the continuous steam injection press 2, they enter a post-conditioning zone 4. In this zone 4, as shown, In the example, two post-conditioning units 5 and 6 are provided. From the post-conditioning zone 4, the discs 4 can be transferred directly to a grinding machine 7 for grinding to a final thickness.

According to the invention, each post-conditioning unit 5, 6 has an air supply unit 8 with a suction fan 9 and a heater 10. A meadow or water supply device 11 can also be provided for humidifying the air. The air is sucked in at 12 in the two air supply units. As can be seen from the drawing, the air is supplied from above in the post-conditioning unit 5 and from below in the post-conditioning unit 6.

When the discs come out of the continuous steam injection press 2, they thus enter the post-conditioning zone 4, where air with a certain amount in relation to the disc production and a certain moisture content and temperature is sucked through the discs by means of negative pressure. In the first post-conditioning unit 5 the air is sucked in the downward direction through the disc and in the post-conditioning unit 6 the air is sucked in the opposite direction upwards through the disc. However, this double air flow in opposite directions is not necessary to achieve an effect, but in some cases it is possible to be satisfied with flow in only one direction and consequently with only one post-conditioning unit.

As an example, a disc with a density of 600 kg / Uf and a thickness of 16.6 mm is cooled from 100 to 60 ° C in 60 seconds with a negative pressure of 15 kPa. As another example, it can be mentioned that a disc with a density of 600 kg / m 3 and a thickness of 32 mm is cooled in a corresponding manner in 80 seconds.

What has also been found during disc production in a pilot plant is that discs with a thickness of 10 mm and a density of 650 kg / m fl have a stable thickness after passing the post-conditioning zone. manufactured according to this invention, a Measurements obtained one or more days after the production show that disks which have passed the post-conditioning zone retain their thickness, while disks which have not passed this zone can often shrink up to 1 mm within a day, in the same way as conventional produced discs.

Conventionally produced discs have an increased density in the surfaces, but because the steam injection press can also produce discs which do not have an increased density in the surfaces, the air flow and thus the conditioning and temperature reduction decreases faster than with conventional handling of discs.

Claims (5)

W U 20 25 30 35 - š) -i s14; 4ss fi PATENTKRAV A method of continuously producing lignocellulosic sheets, in which the material decomposes into particles and / or fibers, is glued and dried and formed into a mat (1), which in a continuous injection molding press (2) is pressed into a sheet (3), which then passes a post-conditioning zone (4), characterized in that air of a certain amount, moisture content and temperature is sucked through the disc in the post-conditioning zone (4), and that the disc (3) is ground directly after the post-conditioning zone (4) to final thickness. Method according to claim 1, characterized in that the air is sucked first in one direction through the disc (3) and then in the opposite direction. Method according to Claim 1 or 2, characterized in that the disc (3) in the injection press is given the same density in the surface layers as in the middle layer. Device for applying the method according to any one of claims 1 - 3 and comprising an injection press (2) and (4). The post-conditioning zone (4) comprises at least one post-conditioning unit, a post-conditioning zone characterized in that post-conditioning (5) with an air supply unit (8) for air flow through a continuous disc, and in that a grinding machine (7) is arranged after the post-conditioning zone (4) for grinding. of the disc (3) to final thickness. Device according to claim 4, characterized in that the post-conditioning zone (4) comprises two post-conditioning units (5 and 6), which are each provided with an air supply unit for flowing through said disc (3) in opposite directions.