DE2158276A1 - Method and device for treating wood chips with electrons - Google Patents

Description

Patent attorneys Dipl.-Ing. F. Weickmann, 2158276

Dipl.-Ing. H. Weickmann, D1PL.-PHYS. Dr. K. Fincke Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber

g MUNICH 86, POST BOX 860 820

MÖHLSTRASSE 22, NUMBER 48 39 21/22

<983921/22>

RADIATION DEVELOPMENT CO., Ltd.
3454 E. Broadway, Vancouver 12,
British Columbia, Canada.

Method and device for treating wood chips with

Electrons

In a common method of making paper stock from wood, the wood is cut into elongated chips that are approximately 19 mm wide and 3.2 mm thick (0.75 "and 1/8", respectively). A cloth mill can cut the wood on the spot; often, however, shavings are purchased that are in other places, for example in sawmills, from broken pieces and other waste that accumulates in the sawmill. In general, it is not possible to process the chips immediately after their production or their arrival; at most pulp mills there are therefore large stocks

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pile of shavings. The chips experience during storage usually some form of damage. Sometimes they are attacked by fungi that have a discoloration of the shavings and thus also of the stuff and the products made from them. Or it comes to other cellular disorders that affect the yield of stuff and therefore paper or other products made from the chips reduce. Depending on the length of storage, this can result in a weight loss of between five and twenty Percent lead.

Efforts have already been made to find methods of sterilizing the chips, such as the bacteria and to kill fungi that spoil the chips. So far, however, there is no economically justifiable and System useful in practice for treating the chips.

The invention is based on the object of such a treatment method and to provide an apparatus for practicing the method. To solve this problem are according to of the invention, the wood chips pneumatically by a reciprocating electron beam in a direction parallel to the The axis of reciprocation is transported in such a way that practically all surfaces of the chips are exposed to the electrons be in order in this way an irradiation and thus a sterilization of all surfaces and those under the To effect surface-lying parts. With such a procedure, the sterilization can take place while the Chips in a conventional manner from the chip-producing device or from the point of their arrival to the supply to be promoted.

It was also found that the shavings were bombarded with

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Electrons in addition to the extension of the storage time and an extensive reduction in the spoilage of chips bacteria, fungi and similar microorganisms still have the advantage when carried out at certain levels brings that the processing time, namely the cooking time, the number of chips is significantly reduced and from a certain amount of chips a greater yield of stuff with better ones physical properties is achieved.

For a better understanding of the invention, a device

to carry out the method according to the invention based on the ä

accompanying drawings explained in more detail. Show it:

Pig. 1 is a side view of a Vorri according to the invention attention j

Fig. 2 is a sectional view along the line 2-2 of Fig. 1} FIG. 3 is a sectional view along line 3-3 of FIG. 1.

In the drawings there is shown a conduit 10 which forms part of a pneumatic system through which wood chips are transported. Usually have such Pipelines have a circular cross-section with an average diameter between 15 cm and 60 cm and the wood chips are usually in a stream of air at one speed transported at about 1800 meters per minute (6000 feet per minute). In such conveyor systems, the Wood chips are evenly distributed in the conveying air flow and are not stored in layers, such as on conveyor belts or similar. According to the invention, a conveyor system is provided with a line piece 12, the one has a substantially trapezoidal cross-section, the cross-sectional area of which, however, is approximately the same as that of the pipe

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line 10 is. At both ends of the line piece 12 a transition part 14 is attached to the connection to the pipeline 10 produces. As an approximate reference point, the line section 12 expediently has a length of approximately 6 feet (183 cm).

Furthermore, a device is provided in order to expose the wood chips in the line piece 12 to high-energy electrons. A source of high-energy electrons 18 belongs to this device. The electron source 18 generates a narrow beam of fast electrons, the energy of which is on the order of a few hundred thousand volts got to. The electron source can be a Van de Graff generator or some other suitable type. The one from the generator generated electron beam is thrown down into a scanner 20, which is provided with means to the beam to swing back and forth on a linear path, the axis of which coincides with the axis of the line section 12 permit. The frequency of the electron beam is preferably a few hundred thousand periods per second. To the As usual, magnetic or electrostatic means can be used to deflect the beam are known to the person skilled in the art. The scanner 2o includes an evacuated chamber supported by vertical parallel side walls 24, 26 and sloping end walls 28, 30 is included. The bottom 32 of the scanner is preferably made of titanium or some other material that offers little resistance to the passage of electrons, but which passes through the Withstands temperature effects caused by electron bombardment. Likewise, the ceiling 34 of the line piece 12 is off Titanium or another material easily penetrable by electrons. The space between the floor 32 of the chamber and the ceiling 34 of the line piece is evacuated to the

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electrons passing through have the smallest possible resistance to oppose and also to provide additional protection for the evacuated chamber of the scanner 2o. An alarm or shutdown device (not shown) can also be provided to prevent any To indicate rupture in the ceiling 34, which appears due to a loss of vacuum in the space 36, and around to prevent the floor 32 from being damaged and the space 36 from being contaminated if the vacuum is lost.

After exiting the scanner 20, the electron beam due to the repulsion between the electrons and de ?? Diffusing effect broadened by colliding with air molecules to form a diverging beam. the trapezoidal shape of the line piece 12 is chosen so that its side walls 38, 40 approximately with the actual Side edges of the electron beam collapse so that a fairly uniform coverage over the entire width of the line section 12 is obtained. While the wood chips pass the line piece 12, they fall constantly due to the Magnus effect on the flat chip surfaces messed up and change their height when passing through the line section. On a path of 183 cm (6 feet) in length the wood chip usually rotates six times with a change in height when it is transported in an air stream at a speed of about 183,000 cm per minute. at Due to the high oscillation frequency of the electron beam, a chip becomes evident as it travels through the line piece 12 hit by the electron beam so that all surfaces of the chip are exposed to electron bombardment are. The radiation intensity is controlled in such a way that fluctuations in speed and behavior the chips these on all surfaces of a radiation between

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0.2 and 0.5 megarads are exposed.

In order to achieve the required dose on all surfaces of a chip without tearing the pneumatic conveying properties of a system or having to reduce the speed of the conveying air * the chips must be conveyed by the beam along its scanning axis. Conversely, if the irradiation occurs in such a way that they send the chips by a beam on a plane perpendicular to Äbtastachse web lost to twc the required dosage a line section of the smaller depth provide that constantly difficulties would be expected due to a blockage of the line and the conveying speed as well as the pneumatic conveying properties of the system would be disturbed, so that it would be impossible to check the completeness of the irradiation of the wood chips.

The line section 12 is expediently surrounded by a housing 44 surrounded, which forms a chamber 46 through which water or another coolant circulates, so that the line piece 12 is not heated too much by the electron bombardment will.

Due to the fact that as a result of the scattering and tumbling motion of the wood chips on their way through the line section 12 all surfaces of the chips sound of radiation are hit, Ae electron source 18 can be of much lower intensity than if one were to try treat the chips by a resolution from only one sixth, such as by moving them on a conveyor belt or the like. In the latter case it would have to

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the intensity of the electron source must be so great that the Electrons could penetrate the stacked chips.

It has been found that treating the chips by electron bombardment increases the durability of the chips significantly increased during storage or, in other words, the deterioration of the chips in the course of a given period Time span significantly reduced.

Perhaps more significant is the observation that the Irradiation τοη wood chips obtained from these chips Stuff improved in both quality and yield. For example, it has been found that the degree of grinding of the stuff is significantly increased * but the strength is preserved remains or is even improved. It has also been found that the lignin content of the stuff can be higher. Through this the time required to produce the pulp is reduced and, of course, the proportion of Lignin that needs to be eliminated while maintaining strength and the yield of stuff from a given Amount of wood chips is growing.

In the exemplary embodiment described, modifications with regard to the arrangement and in details are within the scope of the invention possible.

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Claims (8)

2158--76 Expectations , \ y A method for treating wood chips with electrons, characterized in that an electron beam is generated that this electron beam is moved back and forth at a high frequency along a linear path, and that wood chips pneumatically on a path which coincides with the path of the electron beam are moved forward, whereby the surfaces of the wood chips are exposed to the bombardment by the electrons, while the wood chips tumble and rotate as they traverse the electron beam path. 2. The method according to claim 1, characterized in that the frequency of the electron beam is at least some Hundreds of periods per second. 3 · Device for performing the method according to claim 1 or 2, characterized by a electron beam source (18) which generates a beam of high-energy electrons, by deflection means such that they oscillate the electron beam back and forth in a linear path leaves, and by a pneumatic conveyor system (10, 12) for transporting the wood chips, which is a line piece (12), whose axis coincides with the linear electron path and in which the wood chips are exposed to the electron beam when passing through 209824/0682 4. Apparatus according to claim 3> characterized in that the line piece (12) has side walls (38, 40), which roughly coincide with the side edges of the electron beam. 5. Apparatus according to claim 3 or 4ι characterized in that that the line piece (12) is trapezoidal in cross section. 6. Apparatus according to claim 5 »characterized in that the line piece (12) on its length one has a constant cross-section and that the pneumatic system has a pipe (10) whose cross-sectional area is about the same size as the cross-sectional area of the line piece with the inlet end of the Pipeline is connected. 7. Device according to one of claims 3 to 6, characterized in that the line piece (12) is about 133 cm is long and the deflection device deflects the electron beam in such a way that it extends the entire length of the line section over. 8. Device according to one of the preceding claims 3 to 7 »characterized in that the deflection of the Electron beam, a scanner (20) is provided which forms an evacuated chamber, at one end of which the Electron source (18) is arranged such that it sends a beam of high-energy electrons to the opposite End (32) of the chamber throws, and in the deflection elements are provided that the electron beam this opposite end on a linear path 20982 / ι / 0682 Let it swing back and forth, with an electron window being arranged at this end, which is the exit the electrons from the scanner allows that further next to this end of the scanner, the line piece (12) is arranged such that its axis with the axis of the path coincides, the cover (54) of the line piece close to the scanner being an electron lens which allows the electron beam to enter the line piece. 209824/0682