US1258568A - Process and apparatus for treating paper-pulp. - Google Patents

Description

G. C. HOWARD.

PROCESS AND APPARATUS FOR TREATING PAPER PULP.

APPLICATION FILED MAY 29. ms.

1 ,258,568. Patented Mar. 5, 1918.

WITNESSES: z 6 nvmvron K W 2/ 'f 27" ATTORNEY GUY c'. HOWARD, or TACOMA, WASHINGTON.

PROCESS AND APPARATUS FOR TREATING PAPER-PULP.

Specification of Letters Patent.

Patented Mar. 5, 1918.

Application filed May 29, 1916. Serial No. 100,460.

To all whom it may concern:

Be it known that I, GUY C. HOWARD, a

citizen of the United States, residin at Tacoma, in the county of Pierce and tate of "Washington, have invented certain new and useful Improvements in Processes and Apparatus for Treating Paper-Pulp, of which the following is a specification.

This invention relates to improvements in methods and apparatus for treating the fibers of wood pulp for use in making paper, and particularly to improvements in the operation known as heating the pulp wherein the fiber bundles are brushed, drawn out, and hydrated to improve their quality in paper making;

The beating of pulp as commonly practised in paper mills is effected in the socalled' Hollander or beating engine, and consists in causing the pulp to pass between a rapidly revolving roll and a stationary bed plate and wherein the fibers undergo a brushing out or drawing out, and hydration. Such brushing or drawing out action is mechanical, and consists in a crushing and brushing of the fibers and, to a certain extent, flattening them.

Hydrating the pulp is a term signifying that the pulp has acquired a soft, greasy or slippery feeling and is supposedly due to the absorption of water by the cellulose fibers.

Whether this absorption actually takes place to the extent supposed and whether it is a mechanical or a semi-chemical absorption of water by the cellulose fibers, is not definitely known. The chemical nature of cellulose would indicate more or less absorption of water by the fiber and result in its so-callcd hydration. At the same time, long continued soaking of the fiber in water does not effect the pronounced greasy feel to pulp that results from the beating treatment. The

, repeated passage of pulp through a centrifugal pump is reported as increasing the hydration. The violent mechanical pounding impact and agitation produced on the pulp by the beater rolls is a factor tending to increase the absorption of water by the cellulose fiber.

It is found in practical experiments with the present invention that the slippery, soft, greasy feeling to pulp beaten between the rolls of my said invent1on,is due more to the shape of the individual fibers after beating rather than to the actual hydration of the cellulose. The natural fiber from wood and other paper pulp materials is roughly cylindrical in cross section and many times its diameter in length. It is hollow and with closed ends to the fibers. In dry wood, this void inside the fiber is partially or wholly occupied by air. In wet wood, or in pulp, this space is more or less filled with water.

In the presently described treatment, these fibers are, to an extent, flattened out into what may be described as ribbon-shaped fibers rather than cylindrical, and the void inside the fiber eliminated by contact of the opposite fiber wall.

The flattening of pulp fibers in accordance with my invention and thereby giving them a somewhat ribbon shape instead of their natural cylindrical shape in cross section, would produce the slippery, greasy feeling which characterizes long-beaten pulp. 1

The hydration of the cellulose which gives it a rather more gelatinous structure, is also a factor in giving certain propertles to beaten pulp, but by experiment it is found that the resulting sha e of the beaten fiber is the most important actor, and that to effeet a maximum flattening of the fibers wlth a minimum of actual hydration of the cellulose, improves the paper making quality of the pulp. In this connection, it 1s noted that graphite owes its lubricating properties principally to the thin flake-like shape of its individual particles. Tale is characterized by a cleavage into plates and has a greasy feeling. Kaolin also occurs somewhat in scale-like crystals and is slippery to the touch, especially when: moist.

A fiber that is fiat and ribbon-like, is a better paper-making fiber than when cylindrical in shape as it forms a stronger and better sheet on the paper machine wire due to both its carrying the free water longer on the wire and the fact that fibers of this shape will mat and interlock more readily by the shake of the wire. it retains the filler and mineral color better and gives a more uniform surface to the sheet. lit is also more compact both as regards thickness of the sheet for a given weight and as regards flatness and compactness of surface which is a factor affecting the amount of sizing agent required. It makes a sheet that is easier to dry because in pulp as ordinarily beaten and treated in the Jordan engine, more or less free water is carried in the internal void space of the fibers and must be evaporated on the driers. Flattening the fibers would eliminate these voids and hence their tendency to carry free water through to the driers.

The question is how this can best be accomplished when dealing with individual fibers as minute and numerous as encountered in making a sheet of paper. The common beater with revolving roll and stationary bed plate elfects this flattening action to some extent when the roll is down hard and on such fibers as actually pass between the knife edge on the roll and the bed plate.

The long treatment required to thoroughly beat pulp is evidently due to the long time necessary to assure the major portion of the individual fibers actually having passed between the knife edge and the bed plate when account is taken of the fact that some of the fibers are carried past the bed plate by the pockets in the roll.

Furthermore, if a flattening efiect is desired, the rubbing of the knife edge pastthe stationarybed plate is not thought to be the proper mechanical action to accomplish this although it probably does it to a slight extent. By experiment it is shown that the best flattening efi'ect will be accomplished by a passing of fibers lengthwise between two solid rolls. If the fibers were placed side by side and caused'to pass lengthwise in a sin gle fiber thickness between two pressure rolls, the individual fibers would be fiattened out into ribbon shapes and the internal void in each fiber would be eliminated by contact of opposite walls of the fiber.

If quickly passed through the rolls, this flattening would probably be accompanied by a bursting of the fiber wall at some point to allow the escape of water contained in the internal void.

The quality of softness and texture of fiber is regulated by the cooking process by which the pulp is made. l/Vith properly cooked stock, the most efiicient beater would be a machine which gives the maximum fiattening and bursting of the individual fibers with the minimum of actual hydration of the cellulose. Such a beater may properly be called a machine to ,super-calender the individual fibers before they are made into the sheet of paper.

intense The machine covered by this invention has for one of its objects the accomplishment of this efiect on the pulp. The ordinary beater generally works on pulp of relatively thick consistency and works to the best advantage on such stock. The machine of my invention is designed for either treating the stock in dilute consistency such as it exists between the paper machine screens and the lFourdrinier wire, or as it comes from the pulp mill screens before being deckered.

A further object of the invention is to separate the pulp fibers passing through the rolls from a large percentage of the water with which it is conveyed to the point where the rolls effect their action, and thereby adapted for use as a decker or pulp thickener.

The machine made in accordance with my invention, however, will act upon the stock in a thick consistency such as deckered stock similar to that furnished to the ordinary beater.

The invention consists in the method of treating paper stock, as heretofore outlined,

I roll of contact.

Tn the drawings, Figure 1 is a plan view of apparatus utilized with an embodiment of my invention. Fig. 2 is a transverse sectional view of the same taken on line 22 of Fig. 1. Fig. 3 is a fragmentary detail view in horizontal section showing the mannor of mounting the bearings of the crushing rolls.

Referring to said views, the reference nu meral 1 indicates a vat of semi-circular form in cross-section having vertical end walls 2 and 3 in which cylindrical rolls 5 and 6 are rotatably mounted, and arranged symmetrically with respect to the interior configuration of the vat. An inlet for-the admission of a mixture of pulp and water is Provided at 7 upon one side of said vat and upon the opposite side an outlet 8 arranged below the level of the inlet is pro vided with means to adjust the-level of said outlet whereby the flow of pulp stock through the vat may be more efliciently controlled.

Such means illustrated herewith consists of vertically arranged guideways 10 formed or provided upon the side walls 2 and 3 of the vat, and one or more strips 11 of suitable widthsadapted to have their opposite ends engage within said guideways and form a weir or gate over which the stock must flow and the relative heights of the inlet and outlet adjusted.

12 indicates a launder or trough through which the pulp stock is conveyed to the vat and 13 a similar device to catch the overflow and convey the same to its desired destination.

Said rolls 5 and 6 are each provided with axially disposed spindles 21 which are mounted for rotation in journal- boxes 15 and 16, respectively, secured to the end walls 2 and J. The axes of said rolls are in parallel and'preferably arranged in horizontal relation, although their arrangement in an inclined plane whereby the direction of the current passing between the rolls would be either substantially vertically upward or upwardly inclined even to approaching. the horizontal, may have some merit and is contemplated in the scope of the invention.

The perimeters of the rolls are in close proximity, which point of closest proximity may be termed herein, for convenience, the pinch. The clearance at the pinch is only such as to avoid as much as practicable, actual contact between the rolls although to get the desired flattening effect on fibers, it is essential that the rolls operate with a clearance between the rolls of less extent than the thickness of the individual fibers.

The spindles 21 of the roll 5 are mounted in apertured bearing-blocks 17 within the journal boxes 15 and a suitable hard rubber or other cushioning device 18 may be inserted therein to lessen the vibration developing from the relatively rapid rotation of the roll.

Thespindles 21 of the roll 6 are similarly mounted in bearing-blocks 20 which are slidably secured in journal-boxes 16. A setscrew or equivalent 23 threaded through the journal boxes 16 upon the side adjacent the roll 5 and engaging the block 20 to limit the movement of the roll 6 toward the companion roll 5.

A spring 25 engages each of the blocks 20 upon their opposite side, whose tension is regulated by means of set-screws 26.

It is essential that said rolls be driven at a relatively high speed, that is to say, about five hundred revolutions per minute in order to develop a sufficient surface film friction with a relatively smooth surfaced roll and to obtain the desired capacity and output.

Preferably the rolls are independently driven as by power belts 27 and 28 engaging pulleys 30 and '31, respectively mounted upon the spindles of the rolls 5 and 6.

For super-calendering or for the flattening effect upon the fibers, the rolls should be driven at practically the same speed. A differential surface speed will effect a brushing or drawing out action upon the fibers at the line of contact, and when this is desired, the desired relative speeds may readily be given by reason of the independent driving devices provided.

Where this differential motion is desirable is in treating relatively coarse material in which the fibers exist in small bundles, as in ground wood screenings and, to a certain extent, in regular ground wood pulp, also in some cases in raw cooked sulfite. Such materials would generally be treated in relatively thick consistency and with a minute abrasive surface to the rolls.

One or both of said rolls are provided passage of a certain amount of water between the rolls to maintain proper consistency of pulp after passing and to assist in.

the approach of fiber to the pinch.

The grooves are relatively narrow and deep to give suitable cross section area and still not materially reduce the lineof actual roll contact.

F or a strictly flattening effect on the fibers, and where the surface velocity of the rolls is practically the same, a smooth polished surface on the roll will best serve the purpose. As above stated, where a brushing out of the fibers is desired, and where a differential surface velocity exists between rolls, a slightly rough or abrasive surface to the rolls is advisable. It is not necessary or desirable that this surface be rough to the extent of sand-stone or an emery wheel. What is desired is a minutely rough surface commensurate with fiber dimensions and for the purpose of simply preventing a slippage between the fiber and the surface of the rolls. For example, gray cast iron through the wearing away of its minute graphite particles under the action of pulp and water, should maintain under service sufficiently rough surface for the purpose. The amount of this graphite constituent of the iron would not be apparent on the pulp.

For smooth rolls, various materials suggest themselves as available, such as steel, bronze and hard rubber, and under some conditions the two rolls may be formed of different materials with desirable results; for example, one of hard rubber and the other of steel or bronze.

Doctors 35 and 36 are slidably' mounted in guideways 37 in the end walls of the vat and engage with the upper surface of the rolls 5 and 6 respectively, whereby the course of the pulp travel through the vat and relative to the rolls, may be controlled. The ends of the rolls make a close running fit with the ends of the vvat. The arrangement and disposition of the rolls in the vat, and the disposition of the doctors 35 and 36 relative to the rolls, result in certain zones or areas bein formed within the vat that may be descri ed as follows Zone Awherein the pulp stock is received and flows through channel B owing to the relatively high hydraulic head usually maintained in this zone, and to the filmfriction generated by the rapid revolution in the direction indicated by the arrow, of the roll 5.

The course of the pulp material and water carries it next into zone C where the forces of therapidly revolving rolls 5 and 6 act upon the pulp and set up a variety of cross currents and eddies whlch effecta barrier against the further free progress of the pulp through the vat, the larger part of the pulp material being drawn between the rolls and entering the zone D where, in the absence of the doctor 36, such material can flow directly out of the outlet 8.

A zone E is formed beyond the roll 6 which is principally white water from which the pulp has been largely extracted. The rotation of the roll 6 in the direction indicated by the arrow, resists the free movement of the water through the constricted passage F.

The rolls 5 and 6 being rapidly rotated in the directions indicated by the respective arrows in Fig. 2, cause an upward movement or current of water and pulp through their points of closest roximity or pinch. On even a highly polishedroll running at the speed specified, there is a very thin friction zone at the surface which will carry pulp and water up to the pinch. Even though this zone be very thin the surface velocity of the roll, together with its length, is ample to assure all the water and pulp in even dilute stock being carried'to the pinch.

Water will be squeezed out of the pulp at the inch and the downward velocity energy of t is will maintain a distinct swirl of pulp and water in the bottom of the vat. This swirl is eflected intending to bring all fibers into this thin friction zone on the surface of the rolls and thereby assist in their being caught at the pinch of the rolls. This swirl will maintain a natural bafiie to the pulp which will increase the tendency for it to be caught between the rolls before it can escape under the rolls 6 and thence out of the vat. The ooves32 in one or both rolls will effect a s ight upward current, pulling the fibers into the pinch zone.

The speed at which the rolls can be run, together with the permissible and practical length of such rolls, give a large capacity to a machine of this design even with a small clearance between rolls necessary to efle t a flattening of the individual fibers.

n consideration of the design and effect v narrates of this machine, it is noted that water is squeezed out of the pulp at the pinch of the rolls, and consequently there is a tendency for pulp of thick consistency to accumulate after passing the pinch, excepting as this consistency is modified by the water and some pulp which is allowed to pass through the grooves on the face of one or both rolls; that is to say, these high speed rolls eifect, to a certain extent, a separation of water from pulp. I

To make this action effective as a decker or pulp thickener, the contact doctor 36, is placed on top of the roll 6 to prevent. the flow of the pulp through the discharge outlet 8 and provision is made to remove the accumulated thickened pulp laterally at the ends of the roll above the pinch.

Such means consists in an opening 38 in one end wall of the vat, which is provided with a sliding gate 39, said opening leading into a trough or launder 40. Some water, of course, will pass through the pinch of the rolls and the groovesare designed in size to allow sufficient water through to give proper consistency to the deckered stock.

A machine of this kind will have large capacity as a decker and be simple in operation and up-keep. It eliminates the necessity for any cylinder wires. A vat with a single pair of rolls should remove a large proportion of the pulp.

It is obvious that a vat could be constructed with two or more pairs of rolls if desired, although a vat with a single pair of rolls as illustrated would remove a sulficient percentage of ground Wood pulp to allow of on the grinders.

From chemical pulp, the white water,

from one set of rolls would be combined with other white waters and finally cleaned ractical use of white water againf in either another roll vat or in suitable save-all.

What I claim as my invention, is-

1. The process of treating paper pulp, consisting in introducing pulp and water upon one side of a vat, causing said pulp and water to impinge upon the lower side of a pair of rapidly revolving rolls whereby the surface friction of said rolls will draw the pulp between the rolls and deliver the same thereabove, uniting the pulp and water in the vat at the side opposite to said inlet, and discharging the pulp and water from said vat at different points.

2. The process of treating paper pulp,

consisting in introducing pulp and water within a vat, causing said material to flow within the influence of a pair of rapidly revolving rolls whereby the surface friction of said rolls will draw a portion of said pulp and a reduced amount of water between the rolls to cause the same to rise and float upon the remainder, and discharging said with drawn pulp and water and the remainder of the water and pulp by separate outlets.

3. In apparatus of the class described, ai vat, a pair of cylindrical crushing rolls ro-.

tatably mounted in said vat and arranged to have their peripheral surfaces spaced apart, means to maintain a continuous fiow of pul and water within said vat at adjusted heights whereby said rolls are submerged and means to prevent the flow of the heavier pulp material beyond the roll.

4. In apparatus of the class described, a vat adapted to contain wood-pulp and Water, a dpair of cooperating rolls rotatably mount e in said vat, means to rotate said rolls in opposite directions whereby their surfaces at their closest proximity travel in upward directions, said rolls being spaced apart to admit of the passage of pulp therebetween and means to prevent the flow of the heavier pulp material beyond the rolls.

5. In ap aratus of the class described, a vat adapte to contain wood pulp and water, a pair of codperating rolls rotatably mounted in said vat, means to rotate said rolls in opposite directions whereby their surfaces at their closest proximity travel in upward directions, said rolls being spaced apart to admit of the passage of pulp therebetween, a circumferential groove formed upon the surface of one of said rolls for the passage of pul and water and means to prevent the fiolviv o the heavier pulp material beyond the ro s.

6. In apparatus of the class described, a vat having an inlet at one side thereof and an outlet at the opposite side of said vat, means to adjust the relative elevation of said inlet and outlet to control the flow of pulp and water through the vat, a pair of rolls rotatably mounted in the end walls of said vat, means to adjust the clearance between said rolls and means to prevent the flow of the heavier pulp material beyond the rolls.

7. In apparatus of the class described, a vat having an inlet at one side thereof and an outlet at'the opposite side of said vat, means to adjust the relative elevation of said inlet and outlet to control the flow of pulp and water through the vat, a pair of rolls rotatably mounted in the .end walls of said vat, means to adjust the clearance between said rolls, grooves formed upon the face of said rolls and means to prevent the flow of the heavier pulp material beyond the rolls.

8 In apparatus of the class described, a vat having vertical substantially semi-circular'end walls and bottom and side walls of semi-circular configuration in cross-section, said vat having an inlet upon one side and an outlet upon the other side, said outlet lbeing adjustable as to height, a pair of rolls having its bearings rotatably journaled in said end walls and arranged with their peripheral surfaces spaced from said bottom wall of said vat to afford restricted passages for the flow of liquid material toward said outlet and means to prevent the flow of the heavier pulp material beyond the rolls.

9. In apparatus of the class described, a vat adapted to contain wet pulp material, a. pair of cylindrical rolls rotatably mounted in said vat,'one of said rolls having grooves formed in its periphery affording a passage between said rolls for said pulp material, and means to prevent the flow of'the heavier pulp material beyond the rolls.

10. In apparatus of the class described, a vat, said vat having an inlet upon one side and an outlet at its opposite side, said outlet being at a lower elevation than said inlet, and a pair of rolls having their axially arranged spindles rotatably mounted in the end-walls of said vat,-the axes of said rolls being in a substantially horizontal plane and at right angles to the flow of liquid material through said vat, and a doctor associated with the roll adjacent said inlet whereby the course of said material toward said outlet is beneath said rolls.

11. In apparatus of the class described, a vat having an inlet and an outlet for a mixture of pulp and water upon opposite sides of said vat, a pair of rolls rotatably mounted in said vat having their axes arranged transversely to the course of said mixture toward said outlet, an outlet intermediate said inlet and said first named outlet whereby the material passed between said rolls may be discharged and means associated with each roll to cause the mixture entering the vat to travel beneath the first roll and be substantially prevented from passing beyond the second roll when fed upwardly therebetween.

12. In apparatus of the class described, a vat having an inlet at one side thereof for a mixture of pulp and water, and an outlet at the opposite side of said vat for the dis charge of water, a pair of rolls rotatably mounted in the ends of said'vat having their axes arranged transversely to the course of said water from said inlet to the outlet, said rolls bein adapted when rotated to remove the pulp rom the water, an outlet in the end wall of said vat arranged above and intermediate said rolls whereby the pulp may be discharged and means associated with each roll to cause the mixture enterin the vat to travel beneath the first roll and e substantially prevented from passing beyond the second roll when fed upwardly therebetween- 13. In apparatus of the class described, a vat having an inlet at one side thereof for a mixture of ulp and water, and an outlet at the oppos1te side of said vat for the discharge of water, a pair of rolls rotatably mounted in the ends of said vat having their Wall of said vat arranged above and intermediate said. rolls whereby the pulp may be discharged, and a doctor associated. with each of said rolls for directing the mixture entering the vat to travel beneath the first taaaaee roll, and be substantially prevented from 10 passing beyond the second roll when fed up wardly therebetweeno Signed at Tacoma, Washington, this 17th day of May, tale,

GWY U. HOWARD. Witnesses:

do A. finernn'r, C, R Boon.

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