JPS6348720Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the field of thermomechanical pulping in which wood chips are steam treated and then pressed before being fed to a refiner. A particular improvement of the present invention is that the steam-treated and pressed wood chips are accommodated in bulk and the chips are shredded on the way to the inlet of the refiner, thereby providing a more uniform flow to the refiner process. It is in the transfer process that makes up the supply.

PRIOR TECHNOLOGIES AND THE PROBLEMS TO BE SOLVED Until recently, the two most common pulping methods were mechanical pulping operations, in which the wood chips were mechanically ground, usually with a rotating grindstone, and sulfate or sulfite processing. It was a chemical treatment method in which wood chips were treated in a tank. Mechanical methods are less expensive, but produce fibers that are shorter than optimal for use in various types of paper making. On the other hand, chemical methods require the use of large equipment such as expensive high pressure tanks and the like. The initial cost of equipment and operating costs for chemical processes are not always justified.

In recent years, a new technology known as thermomechanical pulping and refining has gained commercial acceptance. In a typical thermomechanical pulping operation,
Wood chips are fed from the chip storage tank to the chip cleaning device and then by screw feed to the rotary feed valve. A rotary feed valve feeds the chips into a steam line operating at superatmospheric pressure. Material is introduced into one end of the tube and transferred to the outlet end by a screw conveyor. As the material is transported through the tubes, the wood chips come into contact with steam from a number of steam injection tubes maintaining a uniform steam pressure across the tubes.

After being treated in a steam pipe that raises the temperature of the material to above the softening temperature of the lignin, the material passes through a first stage pressurized refiner connected to a blow-off valve. The steam and pulp mixture then passes through a cyclone separator, and a conveyor system supplies the pulp freed from the steam of the separator to a pressureless second stage refiner. The pulp produced in the second stage refiner is then sent to a stock storage tank and undergoes further steps common to any process to formulate a fiber suspension suitable for use in a headbox.

U.S. Pat. No. 3,921,918 discloses that the fiber material is infiltrated with steam in a preheater, and then in a disk-cliff ironer under conditions of producing steam while returning at least a portion of the generated steam to the preheater. A mechanical refining method is described that consists of refining a steam treated material.

US Pat. No. 3,661,328 describes a pulp refining device using a multi-stage disc refining method. In the first stage, refining is performed in a pressurized state at an appropriately elevated temperature. Next, a disk refining process is performed under atmospheric pressure. However, it is said that such a multi-stage refining method reduces the volume of fibers in the furnish.

“Tappi” Vol. 45, April 1962, p. 257, “Mechanical Pulp from Material Chips”
(Mechanical Pulp From Chips).

US Pat. No. 2,935,931 and US Pat. No. 2,975,096 describe high-pressure fiber disintegration using a screw conveyor.

In a typical commercially available thermomechanical pulping process, a screw conveyor feeds the compressed and soak-softened chips to a first stage refiner. However, in this case, the supply to the refiner becomes uneven, causing various difficulties. This is because the pressed material tends to form clumps of varying size. As the crushed chips are pushed out along the horizontal introduction pipe, the chips will intermittently fall from the end of the horizontal introduction pipe. This horizontal inlet pipe is connected to a vertical steam separation chamber. This falling into clumps of different sizes causes large variations in the rate at which chips reach the refiner, resulting in substantial variations in the load on the refiner. This results in non-uniform pulp quality. Such operation is therefore unsatisfactory.

Means for Solving the Problems The present invention has been made in an attempt to solve the above-mentioned disadvantage of forming compressed chip lumps of various sizes. That is, the present invention includes a first screw conveyor device that receives wood chips treated with steam and compresses the wood chips to reduce their moisture content while conveying the wood chips; arranged coaxially and in series at the end thereof and having a feed rate faster than the feed rate of the first screw conveyor device, receiving the crushed wood chip mass from the first screw conveyor device and compressing the crushed wood chips; a second screw conveyor device for shredding the wood chip mass into relatively small chip chunks; and a refiner for receiving the small chip chunks produced by the shredding action of the second screw conveyor device. A steam-treated wood chip pressing device comprising:

According to the invention, wood chips are brought into contact with a gaseous vapor at a constant temperature and for a time sufficient to bring the temperature of the chips close to that of the gaseous vapor, so that the steam-treated chips are mechanically heated. While being transported, it is compressed to reduce the moisture content and produce a compressed wet mass. The compressed mass is then shredded by further transport at a higher speed than the initial transport, after which the shredded mass to fairly uniform dimensions is introduced into the inlet of the refiner.

During the initial transfer, the chips are crushed with a crushing ratio of at least 2.5 to 1. The contact with the gaseous vapor is carried out under atmospheric pressure and the initial pressing of the steam-treated chips is carried out to a moisture content of at least 30%.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of the invention is made in conjunction with the accompanying drawings that illustrate various embodiments.

Referring to FIG. 1, numeral 10 generally indicates a chip storage tank open to the atmosphere, into which extends a manifold 11 carrying a plurality of steam injection tubes 12. Steam at substantially atmospheric pressure is passed from conduit 13 to manifold 11 under the control of gate valve 14 . Other steam sources can be used if needed or desired.

The residence time of wood chips in the chip storage tank during steaming is typically on the order of 1 to 5 minutes, or long enough to bring the chips at least close to the steam temperature (212°C, 100°C). It's time. After steaming under atmospheric conditions, the chips are sent to a plug screw feeder or first screw conveyor device 15 driven by a motor 16'. In the first screw conveyor system 15, the atmospheric pressure in the chip storage tank 10 is isolated from the superatmospheric pressure in the first stage refiner 16. 1st
The screw conveyor system 15 feeds the chips via a vertical steam separation pipe 17 to the inlet conveyor 18 of the first stage refiner 16.

In the first screw conveyor device 15, the steamed chips are subjected to substantial squeezing. As a result, the water content can be reduced by only about 50% with conventional plug feeders.
It is reduced to around 30% or preferably 25%. This means that the device has a compression ratio of at least 2.5:1 or preferably 2.7:1 compared to the usual 1.9:1.
The high compression ratio achieved to a certain extent breaks up the bonds between the fibers of the chips more strongly than usual, allowing the first stage of refining to be carried out with less power.

Under normal operating conditions in the first screw conveyor system 15, crushed and soak-softened chips are delivered to the first stage refiner. However, as it is, the difficulty of uneven supply arises as the pressed material tends to be lumps of various sizes. When the crushed chips are forced into the vertical steam separation tube 17, the chips tend to fall into the inlet of the first stage refiner at irregular intervals, which causes large variations in the rate at which chips reach the refiner. will occur. As a result, considerable variations in the load on the refiner occur. This results in pulp quality that is not as uniform as desired.

To compensate for this irregular supply, in the present invention, before the wood chips enter the vertical steam separation pipe 17,
The wood chips are further crushed. To accomplish this, a device of the type shown in FIGS. 2 and 3 is used. The end of the first screw conveyor device 15 has a hollow truncated brine section 15a and an annular flange 1.
It ends in 5b. The annular flange 15b is connected to a flange 20a of a hollow frusto-conical joint 20 by bolts 19. The frusto-conical joint is provided with a flange 20b, which flange has an annular flange 22a which joins flange 20b at one end.
It is attached with a joint part 22 of uniform diameter and bolts 21. The annular flange 22b on the opposite side of the coupling portion 22 is attached to the annular flange 17a of the vertical steam separation pipe 17.

The first screw conveyor device 15 has a first
Shaft 23 with a second screw conveyor device 24 for moving the steamed chips to the stage refiner.
There is.

A suitable recessed space is provided at the end of the shaft 23 to accommodate a sleeve-type bearing 25. The bearing accommodates a small-diameter end 26a of a main shaft provided in a hollow threaded shaft 26. The other end of the hollow screw shaft 26 is rotatably supported within a bearing 29 and is attached at a weld 27 to a drive shaft 28 driven by a motor 30 via a speed reducer 31 .

As shown in FIGS. 2 and 3, the hollow shaft 26 has a screw blade 3 with a gradually increasing radius.
It carries 2. In one preferred configuration of the invention, the pitch of the screw vanes 32 is greater than the pitch of the screw vanes 24 of the first screw conveyor system. As a result, when the shaft 23 and the screw shaft 26 rotate at the same speed, the screw vane 32 acts to pull the compressed material supplied by the screw vane 24 at a faster rate than the rate at which the material is supplied. This action breaks up the steam-treated material chips into tiny pieces. The fine particles fall uniformly into the vertical steam separation pipe 17 due to gravity, and
Inlet conveyor 1 feeding the stage refiner 16
It ends at 8.

It is also possible to drive the screw shaft 26 at a higher speed than the shaft 23. In this case, the screw blades 32 and 24 can have the same pitch. Further, the speed of the screw shaft 26 can be made higher than the rotational speed of the shaft 23, and the screw blades 32 can also have a pitch larger than that of the screw blades 24.
What is important is that the screw vanes 32 have a shredding action, breaking up the compressed mass fed by the first screw conveyor device 15 into relatively small pieces.

The first stage refiner 16 is approximately 20 to 80 psi (138
~552KPa) pressure. The refiner itself is preferably a horizontal single-disc cliff eyeer of the type sold by Beloit under the trade name Uni-Mount. Essentially, this type of refiner has a single dynamically balanced disc driven by a synchronous or induction motor. During operation of the refiner, steam is generated which can conveniently be used as a source of steam to the conduit 13 by providing a conduit 34 extending from the vertical steam separation pipe 17 to the gate valve 14. The refined material is discharged via conduit 40.

The embodiment of the invention shown in FIG. 4 can also be used satisfactorily. In this version of the invention, as shown in FIG. 4, a shaft 35 forms part of a first screw conveyor system and is provided with screw vanes 36 for forcing the squeezed mass to the right.
is listed. The second screw conveyor device has a screw shaft 35 in the same manner as shown in FIG.
A hollow shaft connected to the shaft is used. however,
The screw vanes 38 of the second screw conveyor device are oriented oppositely to the screw vanes 36, and the hollow shaft 37 is driven in the opposite direction to the screw shaft 35. As material is fed from screw vanes 36 to screw vanes 38, a shredding action also occurs.

In the apparatus for carrying out the invention, there are no other fixed obstacles that prevent the movement of the crushed chip mass. The end of the second screw conveyor device is supported at the end of the first screw conveyor device. The lateral loads on the second screw conveyor device are not large. And because the screw is of rigid construction and is cantilevered in the squeeze area with strong bearings, the second screw conveyor device can thus be supported at the end of the shaft of the screw.

When transferring the pressed and steamed material from the screw to the tube, it is important that there are no abrupt changes in the cross-sectional area through which the chip mass has to pass. As best shown in FIG. 3, the starting end of the screw vanes of the second screw conveyor system must have a substantially zero radial dimension at the point of transition with the first screw conveyor system. No. If the end of the shaft does not have the above configuration,
The leading end of the screw vane of the second screw conveyor system is required to shear a portion of the crushed chip mass. Otherwise, more power would be required to drive the second screw conveyor system and greater lateral loads would be placed on the chip mass.

It is clear that various modifications can be made to the embodiments described above without departing from the scope of the invention.

[Brief explanation of drawings]

Fig. 1 is a partial schematic diagram of the entire equipment for processing wood chips according to the present invention from the time the chips are steam-treated to the time they pass through the refiner. FIG. 3 is a cross-sectional view taken substantially along the - line in FIG. 2, and FIG. 4 is a conveyor rotating in the opposite direction. FIG. 3 is a schematic diagram showing a modification of the present invention; 10... Chip storage tank, 11... Manifold, 12
... steam injection pipe, 13 ... conduit, 14 ... portal valve, 15 ... plug screw feeder or first screw conveyor device, 15a ... hollow frustoconical section, 15b ... annular flange, 16... First stage refiner, 16'... Motor, 17... Vertical steam separation pipe, 17a... Annular flange, 18...
...Inlet conveyor, 19... Bolt, 20... Hollow frusto-conical joint, 20a, 20b... Flange, 21... Bolt, 22... Joint, 22a,
22b... annular flange, 23... shaft, 24...
Screw blade, 25...Bearing, 26...Screw shaft, 26a...Small diameter end, 27...Welded part, 28
... Drive shaft, 29 ... Bearing, 30 ... Motor, 3
1...Reducer, 32...Screw blade, 34...
... Conduit, 35 ... Screw shaft, 36, 38 ... Screw blade, 37 ... Hollow shaft, 40 ... Conduit.

Claims (1)

[Scope of utility model registration request] a first screw conveyor device for receiving the steam-treated wood chips and squeezing the wood chips to reduce their moisture content during transport; arranged in series coaxially with the first screw conveyor device and having a feed rate faster than the feed rate of the first screw conveyor device;
a second screw conveyor system that receives the compressed mass of wood chips from the first screw conveyor system and shreds the compressed mass of wood chips into relatively small chip masses; Apparatus for pressing steam-treated wood chips, comprising a refiner for receiving said small chunks of chips produced by the shredding action of a Yukon conveyor.