FI70435C - FOER FARING FOR ORDERING PULVERISER AV TRAEFLIS - Google Patents

Description

70435

METHOD AND APPARATUS FOR GRINDING WOOD CHIPS - FÖRFARANDE OCH ANORDNING FOR PULVERISERING AV TRÄFLIS

The present invention relates to a method and apparatus for grinding wood chips, in which method the wood chips are ground in two steps so that the chips are introduced into a first grinding slot consisting of a non-rotating grinding surface transverse to the grinding axis and a counter-rotating blade disc arranged opposite the surface. then the once milled mill is passed to another milling slot connected to the same shaft of the machine for re-milling.

In the further processing and processing of wood chips, mechanical fiberization is increasingly used in the refiner in either unpressurized or pressurized conditions. In such an operation, due to the nature of the grinding, steam is necessarily formed as the medium. In the process, steam is formed from the water contained in the chips as well as additional water which is fed into the blade slot to obtain the desired consistency.

A typical such mass grinder is the so-called a disc mill, i.e. a disc mill in which the chipped wood material is first formed into small sticks and finally into fibers between the rotating discs or between the blades between the rotating disc and the stator.

In the known devices, no special attention has been paid to the separation of steam from the ground wood chips, but steam has been allowed to escape through feed openings or the like. In particular, in some two-stage grinders, the steam is allowed to pass with the mass to be ground directly to the next grinding stage. In such cases, the grinders are subjected to additional stresses due to overpressure, and the controllability of the grinding process is poor because the transfer of the powder from one grinding stage to another is essentially uncontrolled and it is not possible to check the quality of the intermediate.

It is an object of the present invention to obviate the above-mentioned disadvantages and to provide a two-stage grinding of wood chips in one grinder so that the resulting vapor pressure is used to pump the powder from one grinding stage to another. In order to achieve this effect, the method according to the invention is characterized in that a substantial part of the steam generated in the first grinding stage is separated by a steam separator such as a cyclone, through which the once ground pulp is recycled before being passed to the second grinding stage.

An apparatus for carrying out the method according to the invention, comprising two non-rotating grinding surfaces transverse to the axis of the refiner, and opposing grinding surfaces arranged against these grinding surfaces on one or more axis rotating blade discs so as to form two grinding slots connected to the same axis of the apparatus. in the second refining slot the once ground pulp is transferable to the second slot for re-grinding, is characterized in that the device has a steam separator such as a cyclone through which the once ground pulp can be fed before it is passed to the second grinding step.

Another preferred embodiment of the device according to the invention is characterized in that the steam separator consists of a device based on centrifugal separation.

The invention will now be described in more detail by way of example with reference to the accompanying drawing, in which

Fig. 1 shows a device according to the invention with one blade disc and seen from the side, 70435

Fig. 2 shows a device according to the invention with two blade discs and a side view.

In Figure 1 the chips are fed according to the arrow C kuljetinruu-2 for the opening of the screw 3. The two centrifugal field occupies the first jauhinrakoon chips 4, which consists of a blade disc 5 and 6 attached to the refining surface of the device body 1 attached to the antibodies seven steel.

The steam generated during grinding passes as a vapor fiber mixture G to a cyclone 8 acting as a vapor separator, from which the mill falls onto a screw 9 which is coaxial but opposite to the screw 2. The screw 9, in turn, introduces the grinder G into the second refining slot 10, which has a structure corresponding to the first refining slot 4. The second goal in the refining gap with the steam exits the pre-milled fibers F out of the device in accordance with the arrow. Adjustment of the knife gap, or the refiner load is adjusted until the blades 7 moving e.g. hydraulically as shown by arrow 11.

The operation of the device according to Figure 2 is similar. The chips C are fed from the opening 22. The interior of the refiner body 12 is divided in two by a partition 13. The chips C fall onto a screw 14 which conveys it to the refiner slot 15 and uses its centrifugal force to force the chips into the slot for grinding. The refining slot 15 is now formed by a refining surface 6 placed on a rotating refining disc 17 with a shaft 16 and a refining blade 7 attached to the device body 12. After the first refining step, the steam-fiber mixture G for another grind. The second goal in the refining gap with the steam exits the pre-milled fibers F out of the device in accordance with the arrow. The adjustment of the blade gap, i.e. the adjustment of the load of the refiner, also takes place here by moving the counterblade 7 e.g.

4 70435 hydraulically accordance with the arrow 21.

It will be clear to a person skilled in the art that the various embodiments of the invention are not limited only to the example given above, but may vary within the scope of the claims set out below.

Tue

Claims (3)

70435 A method for grinding wood chips, the method comprising grinding wood chips in two steps so that the wood chips (C) are fed into a first refining slot (4, 15) consisting of a non-rotating refining surface (7) transverse to the refining axis and a rotating blade disc placed against this surface. (5,17), after which once ground the chips (G) are passed to another grinding slot (10,20) connected to the same axis of the device for re-grinding, characterized in that a substantial part of the steam generated in the first grinding step is separated by a steam separator such as a cyclone (8), through which the once ground mill (G) is recycled before it is passed to the second grinding stage. Apparatus for grinding wood chips according to claim 1, having two non-rotatable grinding surfaces (7) transverse to the grinding shaft (16) and opposite grinding surfaces (5,17) arranged opposite one of the grinding surfaces and arranged on one or more rotating blade discs (5, 17). 6) so as to form two refiner slots (4,10 and 15,20) connected to the same shaft (16) of the device, and in which the once ground mill (G) in the second refiner slot (4,15) is displaceable into the second slot ( 10,20) for re-grinding, characterized in that the device has a steam separator such as a cyclone (8), through which the once-milled mill (G) can be fed before it is passed to the second grinding stage. Device according to Claim 2, characterized in that the steam separator (8) consists of a device based on centrifugal separation.