Patent ID: 12240142

SPECIFIC DESCRIPTION OF THE INVENTION

InFIG.1a system is shown with the glue-coated plant particles, for example glue-coated fibers from annual plants, for example made of straw and particularly preferably rice straw and pressed into boards.

After for example precomminution in a straw chopper1, straw that is provided as a starting material M is comminuted in a first comminuter2, a hammer mill2in this embodiment. The material produced in this first comminuter2is fed to a first classifier3forming a first classifying stage for separating silicate particles from the straw particles. This first classifier3, which will be discussed in greater detail below, is shown in an enlarged view inFIGS.2to5.

In such a classifier3, which is an air classifier, the straw particles are introduced into the classifier housing5via an upper material inlet4and an air stream (supply air Z) is injected into the classifier housing. For this purpose, the classifier3has a front, upper air inlet6and a rear, upper air outlet7. A particle trap8is provided for the straw particles P that are freed of silicate S is provided beneath the air outlet7. A coarse-material trap9for receiving foreign bodies, for example stones or similar coarse material G, is upstream from the particle trap8in the direction of flow. In this classifier, the silicate particles S are entrained by the air stream due to their very small and uniform size and discharged via the air outlet7, while the plant particles that are intended for further processing, for example straw particles P, drop into the particle trap8and are discharged thence. In principle, it is possible to feed the straw particles that are freed of silicate to a glue coater and then to press the glue-coated particles into a board after forming a loose-particle mat in a press. In this embodiment shown, however, the straw particles that are freed of silicate in the first classifying stage are optionally fed to a second comminuter10in an additional step after being temporarily stored in a bunker13. In this embodiment, this second comminuter is a fiberizing device in which straw fibers are produced from the straw particles for making fiberboard. This fiberizing device10can, in an inherently known manner, have a digester11(merely suggested) in which the particles are softened for example with high-pressure steam. This is followed in an inherently known manner by a refiner12, in which the softened particles are ground into fibers. In the embodiment shown, the fibers ground in this manner do not, after appropriate drying, travel directly into a glue coater via a blow line, for example (not shown); instead, further separation of silicate particles from the straw particles or the straw fibers now produced is performed before glue-coating.

It is always possible to divide the particle stream into multiple parallel substreams and thus to work with multiple parallel classifiers. In the figures, only one classifier is shown as an example. The second classifier14, which is merely suggested inFIG.1, is again an air classifier. It is basically constructed in the same manner and functions in the same manner as the first classifier3that was already described, it being optionally possible to dispense with the coarse-material trap or stone trap in the vicinity of the second classifier. In any case, silicate particles S are again discharged and disposed of via an air outlet7in this second classifying stage or used for other processes. The straw fibers P that are freed of silicate S are in turn discharged via the particle trap8and, optionally after temporary storage in a bunker20, fed to a glue coater15. Even though only one glue coater15is shown as an example in the drawing, multiple glue coaters can be provided for parallel operation here as well. In this embodiment, this glue coater15is a mixer that, in terms of its construction and functionality, corresponds to the mixer described in DE 10 2009 057 916. In this glue mixer, the straw fibers are glue-coated with an isocyanate or other glue.

The glue-coated straw fibers produced in this manner and freed of silicate are now usable for making fiberboard. For that purpose, they are fed to a spreader22via a fiber classifier21, for example, in which lumps of glue or the like are separated. Using this spreader22, the glue-coated straw fibers are strewed on a conveyor belt, for example, to form a loose-particle mat and, from there, optionally after another pretreatment in a prepress, for example, the mat travels to a hot press25where the loose-particle mat of glue-coated straw fibers is pressed into a fiberboard. The press25can be a continuously operating press25, here a dual-belt press.

According to the invention, the classifier3or14is of particular importance for the separation of silicate particles from the particle stream of the straw particles or straw fibers. The classifier is shown inFIGS.2and5.

The classifier3or14is an air classifier. In this embodiment, it has a box-shaped housing5with the material inlet4, the air inlet6, the air outlet7, as well as the particle trap8and the coarse-material trap9. An upper chute16holding crushing rollers17is connected to the material inlet4. Moreover, feed screws18are shown that feed the material to the material inlet4. The material inlet4extends substantially over the entire width of the classifier housing5and is integrated into the upper wall or ceiling of the classifier housing in this embodiment shown, so that the material falls into the classifier housing from above. The air inlet6is integrated into the upper region of the front wall of the classifier housing. This air inlet6can also extend over the entire width of the classifier housing5. The air outlet7, which also extends over the entire width of the classifier housing, is on the rear wall of the classifier housing and then merges into at least one outlet line27with a reduced diameter, the stripped-out silicate particles S being discharged with the air stream via this line or lines27. In this embodiment, output augers29are provided in the lower particle trap8with which the straw particles P that are freed of silicate are discharged and fed to discharge lines.FIG.5shows the flow conditions in the classifier. It can be seen that, due to their small dimensions, the silicate particles S are discharged as an aerosol with the air stream via the upper air outlet7, while the straw particles P fall down due to gravity and into the particle trap8. Coarse material G, such as stones, for example, falls immediately after entering the housing5into the coarse-material trap9, which is also referred to as a “stone trap.”

The flow within the classifier is achieved in this embodiment by a suction device, meaning that exhaust fans are connected to the air outlet, with the effect that the supply air Z is supplied passively via the air inlet6. In this embodiment that is shown, fresh air is supplied in the first classifying stage, while the classifying air is conducted in a circuit (not shown) in the second classifying stage, so that the moisture level can be kept constant at this stage of the process after fiberization.

Moreover, it can be seen inFIGS.2to4that the classifier housing in the illustrated embodiment is produced in a very simple manner from multiple ISO freight containers, specifically from three standard containers28that are arranged one above the other, each with a length of 40 ft. Such a construction has the great advantage that the individual parts can be easily transported.

The air inlet6can be formed very simply by open container doors. A screen or the like can be integrated into the inlet in order to prevent the entry of foreign bodies. In addition, a rain cover26can be arranged above the inlet6.