The invention relates to a method of producing flat chips out of wood, also designated as “OS chips” (“oriented strand”).
Structurally-oriented wood materials involve special lignocellulose-containing boards or molded articles that have oriented mechanical and hygric properties. Included among these wood material are LSL, PSL, and especially OSB. OSB is the structurally-oriented wood material of greatest economic significance. Due to the shape and size of the strands, the corresponding wood materials provide strong mechanical properties. As a result, they can be applied in particular as construction components in the construction industry.
U.S. Pat. No. 2,874,909A discloses a method for generating chips for fabricating boards and comprising the following method steps: an intermediate product is generated from fresh wood or recycled wood; the intermediate product is essentially bar-shaped; the intermediate product is fed to a chipper comprising a plurality of knives that are disposed on a knife ring, the blades of which run at least approximately parallel to the ring axis and which enclose a working space; the intermediate product is caused to revolve about the axis of the knife ring and thereby aligned such that it is oriented essentially parallel to the ring axis and is pressed against the blades of the knives by centrifugal force; the intermediate product measures several centimeters in length.
DE 11 71 143 B illustrates and describes the effect of heat, moisture, and pressure during the production of chips for the purpose of improving their quality.
A successful method for producing OS chips is described in EP 1 335 818 B1. Here the shape of the intermediate product is defined more precisely.
The method is capable of being improved, however. This mainly relates to the quality of the individual flat chip. The flat chip should if possible be of even higher quality in terms of its shape and its surface. In addition, the chipping process should produce the maximum in terms of high-quality flat chips but the minimum in terms of the fraction of fine material. Finally, the energy requirement should be minimized.
The fundamental problem to be solved by the invention is to provide a method by which a strand material composed of small-piece-type wood components (intermediate products such as Maxichips and flat chips) can be produced, which contains large fractions of distinctly laminar strands and small fractions of fine material. In addition, the energy for chipping should be minimized.
This problem is solved by the features of claim 1.
The fundamental ideas of the invention relate to the shape of the intermediate product and to providing an additional treatment step: Specifically, the intermediate product undergoes an intermediate treatment comprising the action of heat and moisture before it is further treated mechanically.
The referenced treatment with moisture and heat is applied to the intermediate product (Maxichip) after shredding. The treatment can be combined with the application of hyperbaric pressure.
Any heat sources can be used to effect the treatment with heat, such as, for example, microwave or infrared devices. A hot-water treatment or steam treatment can also be considered.
The entire method can be implemented batchwise or continuously. In the continuous process, use of worm conveyors is conceivable. This worm conveyor can be charged with a woodchip-water mixture. Pressure can be generated by a shut-off valve opening a restricted discharge slit at the end of the feed screw, thereby building up pressure within the feed screw. A steam treatment can also take place within the feed screw. Low pressure or excess pressure can also be applied.
The results are amazing. Specifically, the process according to the invention has the following advantages:
The following discussion describes the invention in more detail based on the drawing. In the drawing specifically:
The block diagram of
The material to be processed is first stored in station 100. In terms of this example, these can be used wood pallets. Obviously, all possible other lignocelluose-containing materials can be considered, as was mentioned above.
Rough pre-shredding occurs in station 101—for example, in a shredder.
Shredding occurs in station 102. The intermediate product is generated here. This is at least approximately bar-shaped.
A treatment with moisture and heat occurs in station 103. Treatment can consist of immersion in hot water. The water is at a temperature of more than 50° C.—for example, 60, 70, 80, 90, 100° C. The residence time ranges between 3 and 30 minutes. Even longer time periods can be considered—for example, one hour, two hours, etc.
Scalding with superheated steam can also be considered in place of immersion in hot water.
The wet-hot treatment can also take place under hyperbaric pressure or subatmospheric pressure, thus in a closed vessel. Here the intermediate product—and thus the wood chips—are completely penetrated by moisture. A certain level of plastification takes place, in some cases a solubilization of the lignin.
The intermediate product is pre-screened at station 104.
Chipping takes place at station 105. The result is OS chips having a chip thickness ranging between 0.2 and 0.8 mm, at best 0.2 to 0.6 mm.
After chipping, post-screening takes place at station 106.
This is followed by subsequent processing into OS board at station 107.
As seen in
The intermediate product 20 is fed into shaft-like inlet 6—see arrow. It then moves into the interior space surrounded by rotor 1. Here, intermediate product 20 comes to be oriented—either automatically or by an appropriate orientation device—such that it runs predominantly parallel to the longitudinal axis of rotor shaft 2, and thus more or less parallel to knives 4. The intermediate product is of considerable size, in particular, of considerable length when compared with wood pieces of this type that have previously been fed to knife-ring chippers.
Each knife assembly is constructed as follows: A support block 10 supports a cutting knife 11 that is affixed to support block 10 by a clamping plate 12 and a screw 13.
Each support block 10 has a wear surface 10.1. The critical aspect is that this wear surface 10.1 facing the machine axis is approximately flat and thus not concentric as in the prior art.
Here wear surface 10.1 is composed, as in
In the embodiment of
Number | Date | Country | Kind |
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10 2007 003 698.3 | Jan 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/000563 | 1/25/2008 | WO | 00 | 1/8/2010 |