FI70436C - FOERFARANDE FOER MATNING AV FLIS I EN RAFFINOER - Google Patents

Description

70436

METHOD OF INPUTING CHIPS INTO THE MILL - FÖRFARANDE FÖR MATNING AV FLIS I EN RAFFINÖR

The present invention relates to a method for feeding wood raw material to a refiner, in which method wood is fed from a warehouse, a preheating vessel or a similar storage location to a shredding device such as a grinder.

The share of mechanical pulps as a raw material for papermaking is significant. Their competitiveness relies mainly on hot milling, which is made from wood chips, i.e. chips, by grinding continuously between two grinding plates. An elevated temperature is used in the manufacture of the hot mill to allow the lignin to soften and the fibers to separate without breaking.

In principle, the hot milling method has been known for a long time. As technology advances, more attention has been paid to the size of refiners and their energy consumption than before. Efforts have been made to utilize the steam generated in the process in various ways as a donor of thermal energy and for the transfer of pre-ground pulp in pipelines. This type of technique has been presented e.g. in the applicant's own Finnish patents 51717 and 62149.

On the other hand, the refiners themselves have also been improved, today there are, for example, two-phase refiners which allow the grinding of chips in two stages to be carried out in the same refiner, without complicated transfer and feed equipment between the two refiners.

However, in the presently known hot-mill grinders, the feeding of the chips themselves to the grinder is still arranged in a relatively complicated and uneconomical manner. Usually the chips are fed in such a way that the chips are conveyed by compressed air and / or mechanically conveyed to a preheater, from which the chips are fed to a refiner by a tray feeder or the like. In addition to the relative complexity of the known chip feed methods, they have other disadvantages, such as the leakage due to the multi-stage unpressurized feed arrangement and the high air content of the chips, as well as the low or uneconomical chip preheating for the same reasons.

The object of the present invention is to provide a method by means of which the feeding of chips to the refiner can be simplified and made more efficient and more economical. To achieve this, the method according to the invention is mainly characterized in that at least a part of the steam coming from the refiner and the wood generated during grinding is passed to a dosing or feeding device of one or some refiners for conveying the unground chips to the refiner.

Since the chip transfer and transport medium thus forms a closed circuit, the hardware solutions are considerably simplified. In addition, a low air content of the medium is achieved without further measures. Chips can be fed to several grinders from the same feed point (preheating vessel).

A preferred embodiment of the method according to the invention is characterized in that the pressure of the steam generated during grinding is increased by a blower, by means of which a sufficient pressure is generated in the steam for feeding unground wood chips. The recirculation system may include the return of wood parts recovered in the separator to a wood preheating vessel.

Another preferred embodiment of the method according to the invention is further characterized in that the steam coming from the refiner is passed to a chip preheating vessel to preheat the chips. In this way, the simplest supply arrangement is obtained, in which the preheating vessel either itself is large enough to form a '- "' 3 * ..... * '* · * ......

70436 chip, or the intermediate container is a separate container outside the invention.

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 chip feed arrangement according to a known method,

Fig. 2 shows an embodiment of the method according to the invention,

Fig. 3 shows another embodiment of the method according to the invention.

Thus, Figure 1 shows a commonly used refiner feed method. In it, the chips are blown by a fan 8 from an intermediate tank 1 through a surge tank 2 to a distribution screw 3. From the distribution screw 3 the chips are possibly fed to several 10 pressures towards the surge tank 2, which allows the chips to move in the pipe. Equalization tank 2 air pressure will be discharged in accordance with the arrow on the chips falling down jakoruuvistolle. The wood chips are then fed at normal pressure by means of mechanical feeders, in which case the deaeration is left to the tray feeders 4 and 6.

The solution according to the invention shown in Fig. 2 for blowing chips from the intermediate storage 11 takes place by blowing the return steam generated in the first grinding step, for which the necessary kinetic energy is generated by the blower 13. Chips are fed from

:. ..- ....:.. wherein the wood chips that accompanied the steam are separated and returned to the intermediate storage 11 by the pipe 19, the excess steam is discharged by the valve 20, and the rotatable steam is fed through the fan 21 to the shut-off feeder 14 of the intermediate storage.

In another embodiment of the invention shown in Fig. 3, the preheating tank is separated into its own unit 22, to which chips are fed from an intermediate storage or similar tray feeder 23. The separator device according to Fig. 1 is not necessary with its pressure tending out of the vessel along the tube 25. This provides a remarkably simple feeding arrangement.

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.

11

Claims (4)

5. 70436 A method for feeding wood raw material to a refiner, the method comprising feeding wood from a warehouse, preheating vessel or similar storage location (1,11,22) to a shredding device such as a grinder (7), characterized in that at least part of the wood material from the refiner (7) the steam generated during grinding is passed to the dosing or feeding device (14, 24) of one or more refiners (7) for conveying the unground chips to the refiner (7) by means of steam. Method according to Claim 1, characterized in that the pressure of the steam generated during grinding is increased by means of a fan (13), by means of which a sufficient pressure is generated in the steam for feeding unground wood chips. Method according to Claim 1 or 2, characterized in that the steam coming from the refiner (7) is passed to a separator device (18), in which the pieces accompanying the steam are returned to the preheating vessel (12). Method according to Claim 1 or 2, characterized in that the steam from the refiner (7) is passed to a chip preheating vessel (22) for preheating the chips.