US2727439A - Apparatus for treating pulp - Google Patents

Description

1955 P. s. BOLTON ET AL 2,727,439

APPARATUS FOR TREATING PULP Filed May 5, 1953 3 Sheets-Sheet 1 FIG. I

INVENTORS FH/L/P EZEUL 'rUN fAL/L W Han s 550 ATIZZFNEY Dec. 20, 1955 P. s. BOLTON ETAL APPARATUS FOR TREATING PULP 3 Sheets-Sheet 2 Filed May 5, 1953 FIG. 2

INVENTORE FH/L /F 5501, 727M 54M, W HUR'EYEEEH ATTUHNE'Y Dec. 20, 1955 P. s. BOLTON ETAL 2,727,439

APPARATUS FOR TREATING PULP Filed May 5, 1953 3 Sheets-Sheet 3 F IG.4 33 5 A i 1 a l 'iaei a2 L Ii V WET H j 111 ML v ||1 xm HmLHIII aa I 24 a1 United States Patent APPARATUS FOR TREATING PULP Philip S. Bolton, West Newton, Mass, and Paul W. Horeyseclr, Norwich, Conn., assignors to Robert Gair Company, Inc., New York, N. Y., a corporation of Delaware Application May 5, 1953, Serial No. 353,036

6 Claims. (Cl. 9220) This invention relates to the preparation of pulp from waste paper, and more particularly to apparatus for defibering the paper without disintegrating or breaking up undesired extraneous or foreign material.

This application is a combined division and continuation-in-part of our application Serial No. 38,386, filed July 13, 1948, now abandoned.

In the manufacture of paper board from waste paper, and particularly from the so-called mixed paper grades of waste paper, the dry waste paper is usually fed continuously into a beater tub or vat together with water, and a slurry of partially defibered paper passes out of the tub or vat continuously through a perforated plate. This slurry ordinarily contains about three parts by weight of dry paper suspended in 97 parts of water, and is known as a pulp or stock of 3% density.

This pulp is then diluted, usually to a density of around A2%, and passed through some form of settling apparatus so that heavy extraneous materials, such as sand, metal, etc., can settle out by gravity. The pulp is then usually filtered or thickened again to a suitable pumping density, such as 3% and subjected to refining in Iordans or similar equipment before going to the paper machine. The stock, however, contains about 1 to 2% (on a dry basis) of lightweight foreign material such as cellophane, fruit peelings, rubber, match sticks, wood shavings, etc. most of which is non-fibrous and is deleterious if incorporated in the final paper board product.

If this foreign material is in the stock which goes to the refiners, it is ground up and forms weak spots and dirt specks in the final sheet.

Efiorts have been made to remove this light weight foreign material by various screening devices before the stock is refined. A screen which is fine enough to remove the foreign material, however, also separates with it anywhere from about 5 to 20% of the good fiber because of the paper in the stock which is not properly defibered at this stage.

One object of our invention is to provide improved apparatus for defibering either the entire mass of the original pulp or slurry before or after the heavy foreign material is settled out, or the undefibered paper and light foreign material rejected in screening without disintegrating this light foreign material, and thus permit separation of substantially all of the fibrous material from the undesired or non-fibrous foreign material.

A further object of our invention is the provision of apparatus suitable for accomplishing such defibering without using uneconomical amounts of power.

In the drawings,

Figure 1 is a plan view of one form of apparatus constructed in accordance with our invention.

Figure 2 is a transverse sectional view through the apparatus taken approximately on the line 22 of Figure 1.

Figure 3 is a transverse sectional view through a modified form of apparatus constructed in accordance with our invention and suitable for carrying out continuously the defibering of waste paper of the character indicated.

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Figure 4 is a central vertical sectional view of another modified form of apparatus constructed in accordance with our invention and suitable for carrying out continuously the defibering of waste paper.

Figure 5 is a transverse sectional view taken approximately on the line 5--5 of Figure 4.

We have found that efiicient and satisfactory defibering of the paper or fibrous material in a waste paper stock can be accomplished economically without breaking up the light non-fibrous materials by suitable agitation of the stock or pulp at a high density. By high density is meant a density of the order of 6 to 14% fiber. Up to 6% density, a paper pulp acts as a fluid, will flow by gravity and can readily be pumped using a centrifugal pump. As the density of the pulp is increased from 6 to 14% the slurry becomes more and more of a semi-solid that will not flow by gravity, and at densities above 14%, it very closely approaches a soft solid mass. We prefer to carry out our defibering treatment with a pulp of about 10 to 14% density and the best results have been obtained using a pulp of around 12% density, i. e. a pulp containing by weight about 12 parts of fiber and 88 parts of water.

We have found that it is advantageous to subject the entire slurry or pulp mass, either before or after settling out the heavy foreign matter, to the high density defibering treatment of our invention before screening, and that such treatment not only permits good separation of the fibrous material from the unbroken non-fibrous foreign materials by a conventional method of screening, but also produces a substantial increase in strength of the paper made from this stock.

The stock may, however, be screened first and the 520% material rejected by the screen, which includes both the undefibered paper and the non-fibrous foreign materials, subjected by itself to our high density defibering treatment. While the latter procedure involves the treatment of a smaller amount of material, the material after treatment has to be subjected to a second screening operation to separate the foreign matter, and we have found that this procedure does not result in as high a strength in the finished sheet as is obtained by the high density defibering of the entire stock.

The material to be subjected to defibering can be thickened in any conventional manner to the proper density, as will be understood by those skilled in the art, and is then preferably subjected in the thickened or high density state to an agitation which produces fiber on fiber friction to obtain as little cutting of the fibers themselves and as little disintegration of the non-fibrous portion as possible. In order to obtain this result, the agitating apparatus is preferably constructed to operate with fairly large metal to metal clearances. The speed of agitation may be relatively slow because of the high density of the material treated, and can be varied depending upon the particular construction of the apparatus and the particular density of the stock that is treated.

One form of apparatus that is suitable is shown in the drawings in Figs. 1 and 2, in which numeral 10 indicates a vat or tank of generally rectangular shape, preferably having a rounded bottom portion 11, and provided at its ends with suitable bearings 12 and 13 to support the agitator shaft 14. The agitator shaft 14 may be rotated by any suitable means, such as the pulley 15, driven from any suitable source of power (not shown). Welded or otherwise securely anchored to the shaft 14 are a plurality of rods 16. These rods are mounted in staggered relationship on the shaft and are preferably curved in the direction of the rotation of the shaft, as shown by the arrow in Fig. 2. This arrangement makes the rods self-cleaning so that they will not pick up long strings .or rags which frequently are present in the pulp before the foreign matter is separated. The rods are also inclined, some in one direction and some in the opposite direction, axially of the shaft, as seen in Fig. 1. This arrangement is desirable because of the high density of the pulp being treated and prevents the agitating rods from channeling the pulp and thus not properly performing their agitating function. By inclining the rods in one direction or another, the pulp may be made to move back and forth axially of the shaft as it is agitated, so that a fresh area of pulp is constantly being moved in front of each rod as the rod comes around.

In the operation of the batch apparatus shown in Figs. 1 and 2, the high density pulp mass containing the light weight foreign material is placed in the tank or tub 10, and the agitator shaft 14 is rotated at a sufficient speed and for a sufiicient time to produce by fiber on fiber friction the necessary defibering of the stock. For example, with a stock having a 12% density, the shaft may be rotated at 115 R. P. M. for from about 6 to 10 minutes. After such a treatment, the stock is diluted with water to a density less than about 1% and passed over a conventional screen having 4; perforations. The material then rejected by the screen will be almost completely foreign material, and this non-fibrous material will not be disintegrated or broken up so that it is likely to pass through the screen.

It will be understood that higher or lower rates and different times of agitation may be employed depending upon the particular construction of the apparatus and the nature and density of the stock treated.

The apparatus shown in Figs. 1 and 2 may also be designed for continuous operation by simply making the vat or tank 19 long enough so that stock introduced at one end is given the right amount of agitation while it is moving to the other end. The agitator rods may be arranged in helical fashion around the agitator shaft and inclined so as to move the stock gradually from one end to the other While producing the requisite agitation Without channeling.

Another form of apparatus is shown in transverse cross section in Fig. 3, and is similar to that described above, except that it is provided with multiple agitators. In this form, the tank is may be provided with any suitable number such as three parallel sections, each having a rounded bottom as shown at 19, 2d and 21. in these sections, parallel agitator shafts .22, 23, and 24 may be mounted for rotation and provided with suitably curved agitator rods 25; We prefer to arrange these shafts and rods so that the central shaft 23 is rotated in the opposite direction from the shafts 22 and 2 In such an apparatus, which may be generally rectangular in plan, the high density stock may be fed in at one corner continuously and the defibered stock withdrawn continuously through the pipe 26 located diagonally opposite the inlet. The rods 25 may be appropriately curved to avoid picking up strings or rags, and may be arranged around the shaft and inclined axially thereof so as to cause a gradual movement of the stock from the inlet to the discharge portion of the machine While the stock is being agitated.

Referring next to Figs. 4 and 5, we have illustrated therein another modification of the invention which, while similar in a number of respects to the form shown in Figs. 1 and 2, is adapted to carry out our defibering treatment continuously rather than in batches. This modification includes an upstanding tank or vat 28 that may be supported in any desired manner, and that consists of a right circular cylindrical side wall 29, a top wall 30 and a bottom wall 31. A vertical agitator shaft 32 extends upwardly through the center of the tank and is mounted for rotation in bearings 33 and 3 Asin the case of the first-described form of the invention, agitator shaft 32 may be rotated by any suitable means, such as a pulley 35, driven from a suitable source of power (not shown). Affixed to the shaft, by welding or otherwise, is a plurality of rods 36. These rods are also mounted in staggered relationship on the shaft, and are curved in the direction of rotation of the shaft as indicated by the arrows in Figs. 4 and 5, to the end that the rods are selfcleaning so that they do not pick up long strings or rags 5 which may be present in the pulp before the foreign matter is separated therefrom. The rods, as best shown in Fig. 4, are inclined upwardly with respect to the axis of the shaft.

The high density stock to be treated is introduced continuously into tank 28 by way of an inlet pipe 37 that communicates with the upper end of the tank, andthe defibered stock is withdrawn continuously through a discharge pipe 38 located at the bottom of the tank and remote from inlet pipe 37. The parts are so constructed and arranged as to perform their intended function in an entirely satisfactory and trouble-free manner. The rods, by virtue of their being curved and upwardly inclined with respect to the shaft, efiect adequate defibering of the fibrous content of the pulp without causing disintegration or breaking up of the non-fibrous constituents. Additionally, the arrangement of the rods prevents the pulp from passing prematurely downwardly through the tank and then outwardly by way of the discharge pipe.

The foregoing forms of our apparatus are described only by Way of example, and it will be apparent to those killed in the art that very manyother variations of such apparatus may be used.

A particular advantage of our invention is that because e onomical in the treatment of stock of lower densities. r example, if a stock or" 3% density containing 1200 lbs.

of fiber on a dry basis is to be heated, it is necessary to raise the temperature of 38,800 lbs. of water.

On the o. t. u. for each degree the temperature is raised. h ve mentioned the application of our high density iefihering process to the entire stock after settling out lOlElgll material which may be separated from the stock by onventional screening. Another, and possibly it best, procedure or flow sheet for the use of our in ten-tion to thicken and subject the stock to our high 1 ity defibering directly as it comes from the breaker For example, in such a procedure, the slurry ensity, subjected at this hi h density to the deiiher g agitation, then diluted to a suitable density such as .6%, passed successively through a settling trough and *"er a screen to remove heavy and light foreign material,

d then thickened to 3% density or thereabouts for reni g or other conventional treatment before going to GD c paper machine.

The terms and expressions which we have employed are used as terms of description and not of limitation, and WC have no intention. in the use of such terms and-expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize t various modifications are possible within the scope or the invention claimed.

l. Apparatus for defibering pulp which comprises a receptacle, a shaft mounted for rotation therein, and a plurality of rigid rod-like members fixed to said shaft in ed relationship, said members being curved in the ection of rotation of the shaft, inclined with respectto the axis of the shaft and having asubstantial clearance 75 with the walls of the receptacle.

:ssist in defibering waste paper and which are usually unm the breaker beater would be thickened to the desired 2. Apparatus in accordance with claim 1 wherein the rods are so arranged that the junctures thereof and the shaft lie along a generally helical path.

3. Apparatus for defibering pulp which comprises a receptacle, a shaft mounted for rotation therein, and a plurality of rigid rod-like members fixed to said shaft in staggered relationship, said members being curved in the direction of rotation of the shaft and having a substantial clearance with the walls of the receptacle, a number of the members being inclined in one direction with respect to the axis of the shaft and the remaining members being inclined in the opposite direction with respect to the axis of the shaft.

4. Apparatus in accordance with claim 3 wherein the rods are so arranged that the junctures thereof and the shaft lie along a generally helical path, said rods being so inclined as to effect gradual movement of the pulp from one end of the receptacle to the other.

5. Apparatus for defibering pulp which comprises a receptacle, a shaft mounted for rotation therein, and a plurality of rigid rod-like members fixed to said shaft in staggered relationship, said members being curved in the direction of rotation of the shaft, inclined in one direction with respect to the axis of the shaft and having a substantial clearance with the walls of the receptacle.

6. Apparatus in accordance with claim 5 wherein the receptacle comprises an upstanding right circular cylindrical side wall, the axis of rotation of the shaft is substantially vertical, and the members are inclined upwardly with respect to the axis of the shaft.

References Cited in the file of this patent UNITED STATES PATENTS 642,387 Tempied et a1 Jan. 30, 1900 856,859 Gentieu June 11, 1907 1,389,281 Winestock Aug. 30, 1921 1,696,639 Lewis Dec. 25, 1928 2,592,481 Spencer et al Apr. 8, 1952 FOREIGN PATENTS 111,037 Germany June 7, 1900 501,593 Belgium May 23, 1952

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