US2342225A - Paper pulp preparation - Google Patents

Description

1765- 1944- A. P. SCHNYDER PAPER PULP PREPARATION Filed Dec. 30, 1941 3 Sheets-Sheet l From 049 /9" iii! mvlm'on 401/005 1? 50mm? BY MHW ATTORNEYS Feb. 22, 1944. A. P. SCHNYDER 2,342,225

PAPER PULP PREPARATION Filed Dec. 30, 1941 3 Sheets-Sheet 2 l NV E NTOR Aux/U115 P. ScH/vrDm Feb. 22, 1944. A. P. SCHNYDER 2,342,225

PAPER PULP PREPARATION Filed Dec. so, 1941 :5 Sheets-Sheet 5 d INVENTOR 5 Aux/mus Sal/W051? Patented Feb. 22, 1944 UNITED STATES PATENT OFFICE 2.342.225 rarna PULP PREPARATION Auxillus P. Sclmyder, Teaneck, N. 1. Application December 30, 1941, Serial No. 5243848 18 Claims. (01. 92-7) This invention relates to paper-pulp preparation and has for an object the provision of improvements in this art.

In the preparation of pulp by the soda or sulphate processes, there is a stage in which a batch of material is treated in a closed cooker or 'digester at super-boiling temperature and pressure and the cook then discharged into a blow tank to release or flash oil the steam. These blow tanks are of large capacity, usually accommodating several cooks, and are employedalso for storing the stock. Since the blown stock is so thick that it cannot be readily pumped it is diluted, as with liquor, before it is removed from the blow the stock withdrawn at the bottom of the tank One usual form of blow tank is conical at the top and bottom, being largest near the midheight in the region between the adjacent bases of the cones. It has been the common practice to terminate the blow pipe tangentially in the upp r part of the blow tank in a vertically elongated opening to cause the stock to form a flattened spiral band around the interior wall of the tank reaching down to the level at which the stock stands in the tank. When the entering stock fell into the stored material it caused splashing, which entrained a certain amount of fibers with the escaping or flash steam which left at the top of the tank. This trouble was aggravated by the practice of placing the opening of the blow pipe at some distance below the top of the tank to provide a steam spacewhere the fibers might have some opportunity of settling out. Consequently, it often happened that the very opposite of the desired effect was obtained; that is, the entrainment of fibers in the flash steam was increased rather than reduced.

It has also been the common practice to place a vertical-shaft paddle agitator in the bottom cone of the tank with sets of paddle blades at different levels. The dilute liquor was introduced through several ports in the side of the conical bottom at the zone of the paddle agitator and the dilute stock was withdrawn at or near the bottom of the done. There were a number of objections to this arrangement. For one thing. it

was difllcult to maintain a tight Joint at the and created a hazard to subsequent operations and equipment.

The present invention overcomes these former difliculties and improves the separation of iibers from the flash steam; simplifles and improves the mixing of liquor with the thick stock; insures proper mixing and consistency of the dilute stock; provides thorough separation and convenient removal of tramp iron and other heavy harmful foreign material; avoids clogging of the discharge pump and piping: provides separate and large storage space for both thick and dilute paper stock; and furnishes other advantages which will be apparent from the disclosure hereinbelow of an exemplary embodiment of the invention. In the drawings which illustrate this embodiment:

Fig. 1 is a central vertical section through a blow tank and associated parts embodying the present invention;

Fi 2 is an enlarged section through the blow pipe terminal in the top portion of the tank;

Fig. 3 is a generally horizontal sectiontaken on the line 3-3 of Fig. 2;

Fig. 4 is an enlarged horizontal section taken on the line 1-4 of Fig. 1;

Fi 5 is an enlarged vertical section taken on the line 5-5 of Fig. 4; and

Fig. 6 is a vertical section taken on the line 6-8 of Fig. 4.

Referring to the drawings, wherein like reference characters designate the same parts throughout, there is provided a large tank It which is cylindrical from the base ll upward for most of its height and terminates in a conical portion II at the top. Since th cylindrical base false-bottom will be suitably flattened on the sides at the open bottom end as at I! to correspond. The upper edge 18 of the false-bottom closely fits within the cylindrical portion of the tank In but need not be secured thereto. When left inattached, free expansion and contraction move-- ments are accommodated.

The interior space abov the false-bottom is employed for the reception of thick stock, however, reserving the space generally enclosed by the conical top portion l2 for a steam chest l9.

The thick paper stock from the digester is introduced by way of a blow pipe 20 provided with a spreader head 2| at the center of the tank.

The end of the pipe and the shape of the spreader head 2| are shown in Figs. 2 and 3. Here it may be seen that a core 22 fans out the pipe opening into a thin annular space23 which delivers the stock as a thin umbrella-shaped sheet 24. The outer edge of the sheet may extend to the side walls of the tank or may splash into the bath of stock, depending on the diameter of the tank, the force of the blow, the height of I the surface of the bath and the area of the annular opening 23. The spacers 25 which support the core 22 may be narrow or may be placed well up in the outlet opening but may be placed near the outer end and have a V-shape, as shown. In the first case the umbrella-shaped sheet will be substantially continuous, and in the second case it will be continuous except for the narrow sectors where the supports divide it. In either case the flash steam, which mightentrain fibers after the splash, is caused to pass through the sheet of entering material and thus receive a scrubbing treatment to cause it to release the fibers.

The-tank is sufliciently large,to hold several cooks and may be used for storage as well as mixing. The several levels a, b and 0 indicated in Fig. 1 represent, for example, one, two and three cooks or batches, respectively.

The steam has an excellent opportunity to flash from the umbrella-shaped sheet of discharging material because of the central location and extremely large area exposed. This flash steam swirls upward and is caused to sharply reverse its direction of flow several times by baflie means before it escapes by way of the steam outlet pipe at the top of the tank. The baflie means or trap as here shown comprises a cup 3! having its upper annular edge well above the lower end of the pipe 30. The steam is thereby caused to sharply reverse its direction of flow twice, once at the upper edge of the cup and once at the lower edge of the pipe. The moisture and fibers entrained with the steam are collected in the cup and flow back by a drain pipe 32 into the material in the blow pipe 20. The drain pipe opens along the direction of flowin the blow pipe to utilize the injector ,principle in entrainingthe material from the cup and in avoiding flow of material from the blow pipe into the cup. The cup is conveniently connected with the pipe 20 by members 3 la' and the assembly is supported from'the tank by thin members 3) so as to leave the upper edge practically unobstructed.

The stock is diluted in the bottom of the tank and the dilute stock is carried in the outer space .33 between the cylindrical tank l0 and the false- .bottom l5. This space is of suflicient capacity to provide for continuous withdrawal andwash- 'ing operations while batches are periodically charged. It also provides storage space for returning the contents of a washer in an emergency, whereas previously a separate tank was required. Dilution is accomplished by a paddle mixer 34 and a propeller 35 secured on a horizontal agitator shaft 38 driven by an agitator motor Ml The paddle mixer 34 is disposed below the open end of the false-bottom l5 and the propeller 35 is placed in an opening in a side wall of the inner base l6 formed by a shroud ring 38 set into the wall. The spider of the shroud ring carries a bearing 39 for the inner end of the shaft l6. Another bearing for the shaft is carried by a fluid tight partition 40 set in the opposite side wall of the base [6.

The motor MI is preferably set into an alcove 43 within the tank It! formed by side walls 44, an inclined end wall 45 extended upward from the base l6, and a cover 46.

Diluting liquor is introduced into the interior space near the bottom but above the paddle mixer 34 by way of one or more ports supplied .by a valved liquor pipe 41. The thick stock and diluting liquor are drawn down by the inwardly inclined blades 48 of the paddle mixer 34 and then forced outwardly through the wall by the propeller 35. The blades 48 are set in a central shroud ring 49 and cut the heavy material down without allowing arching on any supports. The blades on the sides and bottom operate fairly closely to axially aligned or cylindrical side walls 50a. 50b, 50c, 56d and 50a. The walls 501) and 50d are approached by outwardly and downwardly inclined walls 5!!) and v5ld from spaced bottom circulation inlets 55a and 55b, and the walls 50b, 50c and 50d emerge into upwardly and inwardly inclined walls 521), 52c and 52d leading to the opening of propeller ring 38.

The floor of the tank base ll slopes from the sides and center toward a trough and this slopes toward the right side under the alcove 43. On one side of thealcove and within the outer chamber 33 there is located a sump 56. Within the base below the floor under the alcove there are provided a plurality of transverse ducts 51 and 58 connecting at the interior floor level the interior spaces on either side of the alcove.

A valve controlled discharge pipe Bil, prefer ably entering the sump somewhat above the bottom, serves to remove the dilute stock from the tank. The fluid is moved by a pump 6! driven by a motor M2.

The main circulation which prevails when the mixer and propeller are operating is in the direction indicated by the arrows in Fig. 4. This is largely horizontal. In addition, however, there is provided a secondary circulation of smaller proportions in a vertical direction as indicated in Fig. 1. Here the dilute stock moves downward through the inclined tubes 63 set in the false-bottom IE to the interior space and serves to assist the downward movement of the thick stock. This is like a lubricating action, the

' tion, will stand in the outer space, because it is too thick to flow down easily through the restricted bottom opening of the inner space.

Sincethetop oitheouterspaceflisclosed and the level varies from time to time, a pressure pocket is likely to develop so, to guard against this, the space is connected with the steam chest I! by a by-pass pipe Cl.

At the start of operations before the initial blow is made, the bottom of the tank is supplied with hot liquor or water to iully submerge the mixing blades and thus protect them from destructive impact oi the falling stock. The agitator can be started either before or during the blow. As soon as the proper consistency is reached, as determined by the load reading of the agitator motor, by other gauges, or by experience, the pump motor is started to bleed of! the required amount of dilute stock to maintain the desired consistency.

The internal circulation is as indicated, and this in connection with the large generally fiat floor and ample sump, permits pieces of tramp iron or other heavy stray objects tosettle out where they are not withdrawn into the discharge pump. Suitable clean-out openings are provided but it is not believed to be necessary to show them.'

Also, there may be provided a control panel with a level indicator for the :outer or dilute stock space It, a wattmeter or ammeter in the agitator motor circuit and control push buttons for the agitator and pump motors. This panel-may be placed at a remote location as. for example, at the first washer for the discharged dilute stock or any other suitable location. The liquid for dilution may be derived from the washer, and the valve controlling the liquor pipe l'l may also be located at the washer. Ii. desired, a float in the dilute stock chamber may be employed to control the liquor pipe valve and by this the concentration of the dilute stock.

Certain conditions in tank levels may at times require stoppage of the agitator for a limited time,'to prevent undue lowering in the outer space for example, to re-establish operating flexibility.

It is thus seen that the invention provides a blow tank construction oi an improved type, which will give pronounced benefits in several phases of operation, which will be economical to build and maintain, and which will produce improved stock and avoid waste. It conserves heat and power and also avoids the necessity for separating and returning fibers from steam condensed outside the blow tank.

While one embodiment of the invention has been specifically illustrated and described, it is to be understood that the invention may have various embodiments within the limits of the prior art and the scope of the subioined claims. It is also to be understood that while the invention has been disclosed in connection with pulp preparation, it may have broader applications.

I claim:

l. A blow tank installation adapted for making pulp, comprising in combination, a tank providing storage space for thick pulp stock in the lower portion and a flash steam space in the upper portion, a blow pipe entering the steam space, a flash steam outlet in the top of the tank, a fiber and moisture trap in said outlet, a drain at the bottom of said trap entering the blow pipe in the direction of flow therein for returning the separated moisture and steam thereto on the injector principle, and a spreader head on the end or the blow pipe near the center 01' the tank i'or discharging the hot stock in an umbrella-shaped sheet through which the under-flash steam passes for a scrubbing action in travelling to the trap 3. A blow tank installation adapted for making pulp, comprising in combination, a tank providing storage space for thick pulp stock in the lower'portion and a flash steam space in the upper portion, a blow pipe for discharging hot stock into the steam space, a flash steam outlet in the top of the tank, a restricted outlet for stock in the bottom or the storage space, a chamber for dilute stock below said outlet, means for supplying diluting liquid to the thick stock in said bottom outlet, and impeller means in said dilute stock chamber for mixing the thick stock and iiquid'in and below said bottom outlet and pro-- ducing are-circulating flow of the diluted stock in said dilute stock-chamber across and below said bottom outlet.

4. A blow tank installation adapted for making pulp, comprising in combination, a tank for receiving thick stock, a false-bottom in said tank forming a support for storing thick stock in an upper chamber with a funnel-shaped outlet downward and forming with said tank a compartment below and around said outlet for storing dilute stock, means for supplying diluting liquid to the thick stock near said outlet, and means for mixing stock at said outlet and circulating the dilute stock in said compartment within and across the end of said outlet.

5. A mixing and storage installation adapted for making pulp, comprising in combination, a tank, means dividing the space in the bottom of the tank to form a first compartment for receiving and storing thick stock and a second compartment for receiving and storing dilute stock, the first compartment having an opening in the bottom into the second compartment, and means for circulating and re-circulating dilute stock in the second compartment across said outlet to draw down and mix in the heavy stock, said circulating means comprising a transverse enclosed passageway opening at both ends into said second compartment, and means for circulating stock through said passageway.

6. A mixing and storage installation adapted for making pulp, comprising in combination, a tank, means dividing the space in the bottom of the tank to form a first compartment for receiving and storing thick stock and a second compartment for receiving and storing dilute stock, the first compartment having an opening in the bottom into the second compartment, and means for circulating dilute stock in the second compartment across said outlet to draw down and mix in the heavy stock, said circulating means comprising a propeller on a horizontal shaft beneath the outlet moving material horizontally across and beneath the lower end of the outlet.

7. A mixing and storage installation adapted for making pulp, comprising in combination, a tank, means dividing the space in the bottom 01 the tank to form a first compartment for receiving and storing thick stock and a second compartment for receiving and storing dilute stock,

the first'compartment having an opening in the bottom into the second compartment, and means for circulating dilute stockin the second compartment in and across said outlet to draw down and mix in the heavy stock, said circulating means comprising a centripetal impeller at said outlet mounted on a horizontal shaft for agitating material in said outlet and a propeller on said shaft for moving the fluid along the axis of the shaft across and beneath said outlet.

8. A mixing and storage installation for pulp stock and the like comprising in combination, a a

tank, means dividing the space in the bottom of r the tank to form a first compartment for thick stock, a second compartment for dilute stock, and a mixing compartment below the first compart- .ment connected therewith by a restricted outlet opening and connected with the second compartment by restricted side openings at opposite sides, a horizontal agitator shaft passing beneath said outlet opening and into one of said side openings, and a propeller on said shaft in the side opening for circulating fluid stock through said mixing compartment and in said second compartment anddiluting and drawing down thick stock.

9. A mixing and storage installation for pulp stock and the like comprising in combination, a

mixing compartment and in said second compartment and diluting and drawing down thick stock, and a centripetal mixer on said shaft disposed partly in said outlet opening.

10. A mixing and storage installation for pulp stock and the like comprising in combination, a tank which is cylindrical at its lower portion resting upon a fioor. a conical false-bottom in said tank provided with an outlet at the bottom above the floor, an enclosure fitting about the lower end of the false-bottom to form a mixing chamber, the space inside and above said false-bottom forming a first compartment for thick stock and the space between the lower portion of said tank and said false-bottom and enclosure forming a second compartment for dilute stock, means for diluting thick stock and drawing it down into said mixing compartment through said outlet and circulating it through an opening in said enclosure into said second compartment, and means for withdrawing dilute stock from said second compartment.

11. A mixing and storage installation for pulp' stock and the like comprising in combination, an

' outer tank and an interior partition forming a first compartment for thick stock and a' second compartment for dilute stock with a transfer outlet therebetween, means for diluting thick stock in said outlet for transferring it from the first compartment to the second compartment, impeller means for circulating and recirculating dilute stock through the outlet from the first compartment and drawing down stock from the first compartment and means for withdrawing dilute stock from the second compartment.

12. A mixing and storage installation for pulp stock and the like comprising in combination, an outer tank and an interior partition forming a first compartment, for thick stock and a second compartment for dilute stock, means for diluting thick stock and transferring it from the first compartment to the second compartment, means for withdrawing dilute stock from the second compartment, and a by pass from the confined space above the dilute stock in the second compartment to the confined space above the thick stock in the first compartment.

13. A mixing and storage installation for pulp stock and the like comprising in combination, an outer tank and an interior partition forming a first compartment for thick stock and a second compartment for dilute stock, means for diluting thick stock and transferring it from the first compartment to the second compartment, means for Withdrawing dilute stock from the second compartment. and means for circulating some of the dilute stock back into the first compartment above the bottom outlet thereof for assisting the movement of thick stock downward toward said outlet.

14. A mixing and storage installation for pulp stock and the like comprising in combination, an outer tank and an interior partition forming a first compartment for thick stock and a second compartment for dilute stock, means for diluting thick stock and transferring it from the first compartment to thesecond compartment said diluting means including a. pipe for introducing diluting liquid from outside into said first compartment near the bottom outlet thereof and means for circulating some of the .dilute stock back into the first compartment above the bottom outlet thereof for assisting the movement of thick stock downward toward said outlet, and means for withdrawing dilute stock from the second compartment.

15. A mixing and storage installation for pulp stock and the like comprising in combination, an outer tank and an interior partition forming a first compartment for thick stock and a second compartment for dilute stock, means for diluting thick stock and transferring it from the first compartment to the second compartment, said diluting means including a pipe for introducing diluting liquid from outside into said first compartment near the bottom outlet thereof and an opening through said partition above the bottom outlet thereof for circulating some of the dilute stock back into the first compartment for assisting the movement of the thick stock downward toward said outlet and means for withdrawing dilute stock from the second compartment.

16. The method of treating pulp stock which comprises, maintaining a supply of thick stock in a chamber having a bottom outlet opening, maintaining a supply of dilute stock in a chamber about and below the outlet opening to a height to submerge theopening and stand above it on the outside, and circulating and re-circulating the dilute stock past said outlet opening to dilute the thick stock and draw it out.

17. The method of treating pulp stock which comprises, maintaining a supply of' thick stock in a chamber having a bottom outlet opening,

ing from said thick stock chamber and. also in a ing,mixingthe dilutestockwiththe thinstoclr and the diluting liquid in said outlet opening, and drawing oi! the dilute stock at a point away from said outlet opening.

18. The method of treating pulp stock which comprises, introducing thick hot stock into a thick stock storage chamber connected at the top with a steam condenser which tends to maintain a vacuum in the chamber and cause a rapid elimination of flash steam, spreading the hot stock in an umbrella-shaped sheet toward the outer walls of the chamber to trap under-flash steam above the bath and cause it to pass through the sheet with. a scrubbing action to remove tibers,.passing the escaping steam through a trap in the chamber to remove moisture and entrained fibers, passing the trapped moisture and fibers back into the incoming hot stock, providing a body oi diluting liquid in a mixing chamber below and about a bottom outlet open- 20 flat-bottomed dilute stock chamber connected laterally with the mixing chamber at spaced points, circulating the diluting liquid through the mixing chamber past and in the outlet opening to dilute and draw down thick stock and to circulate dilute stock over the flat bottom of the dilute stock chamber, introducing diluting liquid as needed in said outlet opening, re-circulating some of said diluted stock from the dilute stock chamber back into the thick stock chamber along the sides near the outlet opening to assist the stock in moving down, venting the top of the dilute stock chamber into the top of the thick stock chamber, withdrawing dilute stock from the dilute stock chamber, and periodically removing separated heavy refuse from the flat bottom of the dilute stock chamber.

AUXILIUS P, SCHNYDER.

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