US1683782A - Method and apparatus for washing pulp - Google Patents

Description

Sept. 11, 192a 1,683,782

C. A. JOHNSON METHOD AND APPARATUS FOR WASHING PULP Filed April 10, 1924 5 Sheets-Sheet 1 J p1 U h I J @2065 j q maacmd'a Sept. 11, 1928, 1 1,683,782

C. A. JOHNSON IETHOD AND APPARATUS FOR WASHING PULP Filed April 10, 1924 5 Sheets-Sheet 2 Sept. 11, 1928 1,683,782

C. A. JOHNSON METHOD AND APPARATUS FOR WASHING PULP Filed April 10, 1924 5 Sheets-Sheet 3 Sept. 11, 1928 1,683,782

C. A. JOHNSON METHOD AND APPARATUS FOR WASHING PULP Filed April 10, 1924 5 Sheets-Sheet 4 Sep '11, 1928.

c. A. JOHNSON METHOD AND APPARATUS FOR WASHING PULP 5 Sheets-Shee t 5 Filed April 10, 1924 Patented Sept. 11, 19 28. 7

UNITED STATES 1,683,782 PATENT OFFICE CEARIES A. JOHNS ON, OF LA TUQUE, QUEBEC, CANADA, ASSIGNOR TO BROWN COM- ]?ANY, OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE.

METHOD AND AIPARATUS FOR WASHING PULP.

I Application filed April 10, 1324. Serial No. 705,546.

This invention relates to a method and apparatus "for" washing pulp and 1s of the general type disclosed in Patent No. 1,421,

I more efficiently effect the washing.

In the construction of the patent hereinbefore mentioned the washing takes place in a series of effects in which the, pulp is received from a preceding effect, or in the case of the first effect, from the digester, and is thoroughly agitated with wash liquor passing through the effects serially in the opposite direction to the progress of the pulp. It is then screened or filtered out and the wash liquor pressed therefrom and the pulp passed to the next effect for a simi lar treatment. The wash liquor for each effect is taken from and returned to a tank beneath that effect and overflows from one tank to the tank of the next preceding effect, that is, toward the initial pulp treating effect.

It will be evident that in this construction the liquor strained from the pulp in each effect is more concentrated than in the tank; below from which it is taken and to which it returns, thus increasing the concentration of the liquor as supplied to that effect. It is also evident that the less concentrated the liquor supplied to each washing stage, the more effective it is in removing soluble constituents from the batch of pulp.

In the construction of this invention, therefore, that proportion of the liquor which passes from each to a preceding effect is taken directly from the cylinder tub or straining tank instead of from the supply tank of that effect. This results in less concentration of the washing liquor in the supply tank since that portion removed in the generalprogress of the wash liquor toward the first effect to which the pulp is initially supplied, is the most highly concentrated portion. At the same time, however, it causes the wash liquor in the supply tank of the next preceding effect to be more highly concentrated than before, this, of course, offsetting to some extent the advantages resulting from removing the most highly concentrated portion thereof for the next previous effect. The netresult, however, isv quite advantageous.

Approximately 10% of the wash liquor, is usually taken from one of the weak.

effects ofthe apparatus, that is, one near the final washing of the pulp, and used as make-up liquor for a succeeding run of pulp. The remainder is passed through the apparatus and is removed in highly concentrated condition to the evaporator for reclamation of the chemicals therein. The quantity of wash water added to the last effect is determined by the relative imporsmall amount of liquor will be used. In-

practice the two requirements are balanced against each other. With the apparatus of the present invention the number of effects may be reduced from that used with the apparatus of the patent hereinbefore mentioned without a corresponding decrease in the effectiveness of the washing, or with the same number of effects the washing is correspondingly more thorough.

Other improvements have also been made, such as for example, in the construction of the screening molds so that they are more effective for their intended purpose."

For a more complete understanding of this invention, together with other advantageous details and combinations of parts, reference may be had to the accompanying drawings in which Figure 1 is a diagrammatic view showing the baths of pulp and wash liquor with the lignin and chemicals progressively removed thereby from the pulp and illustrating the paths taken thereby through the apparatus.

Figure 2 is a view partly in side elevation and partly in longitudinal section of the apparatus- Figure 3 is' a top plan thereof.

Figure 4 is a perspective of a portion of the apparatus.

Figure 5 is a lateral section on line 5- of Figure 2.

a Figure 6 is a fragmentarysection to a larger scale at one end of a filter cylinder.

Figure 7 is a similar view of an intermediate spider.

Figure 8 is an elevational detail to a lar'er scale.

igure 9 is a detail section on line 9-9 of Figure 8.

In general the apparatus comprises a series of effects, each consisting of a supply tank as 1 above which is a wash tank 3 and a strainer tank 4. Within each wash tank are positioned the agitators 5 by which the pulp and wash li uor are thoroughly mixed and washed and t e soluble constituents carried by the pulp removed as much as possible by the wash liquor. The end wall 6 of each wash tank, adjacent to the straining tank is lower than the other walls so that the mixture of pulp and wash liquor flows therefrom into the straining tank. Within the straining tank is positioned a straining cylinder 7 upon the outer face of which the pulp is picked up as on the cylmder mold of a paper machine, and the wash hquor is ressed therefrom by means of a couch roll riding on its upper face. The pulp adhering to the cylinder after this expressing operation is removed from the cylinder by means of a scraper 9 from whic it drops into the wash tank of a succeeding effect, this action being repeated in each efi'ect until the pulp is removed from the final effect in its washed condition, in each successive efi'ect more and more of the lignin and chemicals being removed by the wash liquor in which this material becomes more and more concentrated. This is indicated diagram matically in Figure 1, the fibrous stock being indicated by crosses and the lignin and chemicals by circles. The stock with the lignin and chemicals enters at the left hand end of the apparatus, as indicated in Figure 1, being mixed with suflicient of the concentrated efiluent wash liquor to render the pulp of proper consistency to be flowed to the first wash tank.

The first wash tank is indicated at A. The mixture of stock with its chemical and and lignin content then passes to the first straining cylinder 7 where the liquor is expressed thereform and the pulp then passes to the agitating and washing tank of the B eflect. Here it is mingled with wash liquor which has already been passed through the succeeding effects, as will later be described, in this effect some of the chemicals and lignin being taken therefrom as has been indicated by a smaller number of circles on the arrow at this point showing the rogress of the material. It then passes to the straining cylinder 7 of the B efiect where the liquor is expressed therefrom, this liquor flowing out from the ends of the cylinder and a portion passing into the supply tank 1 of the B efliect. From this tank the liquor is sup lied to the wash tank '3 of the same effect y means of the pump 15. A certain amount of the wash liquor draining from the cylinder 7 is, however, passed to the tank 1 of the A effect through the pipe 16.' From this tank the wash liquor may be withdrawn through the pipe 17 in a highly concentrated condition, this being shown in Figure 1 by a large number of circles on the arrow in this pipe. A still more highly concentrated liquor, however, is removed from the first straining tank 7 which may be taken off directly through the ipe 18, or returned to the tank 1 of the A e eet to mingle with the liquor removed through the pipe 17. From the B effect the pulp passes to the C effect where the same action takes place of washing the pulp with wash liquor and straining out the wash liquor, and so through the entire series of effects. In the last two effects, as H and J, a comparatively pure wash li uor (clear water) is sup hed through the pipes 20 and 21, this as s own being supplied to the straining cylinder tanks.

From each of these wash tanks the liquor passes through its straining cylinder, a part being carried to the corres onding supply tank 1 from which the wasli liquor for the washing tank of the same effect is derived, and a part passing to the tank 1 of the next preceding effect in the direction of move ment of the pulp. The vsame sequence of operations takes place in intermediate effects, the wash liquor being taken for each of these effects from the straining cylinder of the subsequent eifect in the direction of progress of the pulp while some of the wash liquor is returned to the supply tank from which it came in order to provide a circulation for the wash liquor through the pulp at a faster rate than the progress of the wash liquor from the last to the first effect. After passing through the straining tank of the last eifect J the 111 is removed comparatively free from hgmn and chemicals and is removed from the apparatus.

The apparatus by which this sequence of operations is carried out is shown more in detail in Figures 2 to 9. As shown best in Figures 2, 3, 4 and 5 the straining cylinder tank is bridged by the straining cylinder 7 the ends of this cylinder opening into end tanks 30 and 31. These tanks 30 and 31 closed at their upper ends are in communication with each other through an equalizing channel 32 at the lower edge of the straining tank 4. From one face of the tank 30 beneath the level of the liquor therein extends a pipe 33 which passes horizontally through the upper ort10n of the supply tank and into a stan pipe 34. The upper end of this standpipe opens into the tank 31. This standpipe extends beneath the level of the pool of liquor in the supply tank and at its lower end is a conical valve normally urged upwardly into seating engagement with the standpipe end b means of a spring 36 surrounding a. rod 3 to the lower end of which the valve 35 is fixed, the tension of this spring being adjustable by rotation of a handle 38 at the upper end of the rod. By this means a column of liquor may be maintained within the standpipe and the end tanks 30 and 31 to the desired height. Communicating with the standpipe is a pipe 40 which extends through the supply tank 1 and through its side wall 1nto the supply tank of the next preceding effect as shown at 41-where it opens beneath the surface of the liquor therein. With1n 1ts own sup ly tank this pipe 40 1s prov ded with a) oat valve 42, the float 43 thereof being within the corresponding supply tank and acting to maintain the level in this tank to a predetermined position somewhat below the to of the wall 45 which separates this tank rom the preceding supply tank.

The pipe leads from the lower portion of each supply tank to the correspondingpump 15 bywhich the washmg liquor is pumped through a pipe 51 to the ag1tating tank of the same effect. A check valve 52 is positioned at the upper end of the pipe 51 where it enters the agltator tank and the extent to which this check valve may be open may be determined by a screw rod 53 bearing thereon and adjusted by means of a hand wheel 54 at its upper end above the closed upper end of the agitator tank. *This mechanism as described is similar tothat of the patent hereinbefore mentioned with the exception of the pipe 40 leading to the previous supply tank and the float valve carried thereby which are not present in the patent. I The partition wall 45 between the supply tanks. of adjacent effects may be formed as a weir in the manner, described in the patent so that the wash liquor may flow from tank to tank thereover, if forany reason the float valve should become inoperative and the level of the liquor in the corresponding supply tank be raised to a sufficient height. The strainer cylinders and couch rolls are partly enclosed by hoods (see Figure 4) hinged thereto at one edge, their central portions being open above these cylinders so that they may be accessible. At are shown valved vent pipes leading from the upper ends of the supply tanks by which foaming within these tanks may be relieved.

With the construction of the present invention it will be seen that the wash liquor for each supply: tank, in its normally operative condition, is taken from the straining cylinder of the succeeding effect where the wash liquor for that effect is the most high 1y concentrated. This tends to maintain the pool of wash liquor in the supply tank of that effect, particularly in the last few efbetween the straining cylinder and couch roll as shown being positioned within the tank 30. The ends of the straining cylinder 7 communicate with the interiors of the tanks 30 and 31 and may be packed in any suitable manncr, for example, as described in the patent hereinbefore mentioned. The cylinder itself, however, is preferably made as indicated in Figures 6 and 7. Referring to these figures, the straining cylinder com-- prises end castings or spiders as shown at 600 having rim portions 61 and hub portions 62 connected by spokes 63. The rim portions 61 extend into openings through the inside walls of the tanks 30 and 31 and adjacent the spokes 63 they are formed with portions of larger diameter as at 64, each having a laterally extending annular shoulder 65 to the outer face of which may be fixed a cylindrical sheet metal casing 66 punched out with openings from one-eighth to a quarter of an inch in diameter, this casing forming a foundation for a wire mesh surface material 67. Between the end castings 600 are positioned a series of spiders 70 shown in Figure 7, each spider having a hub 71, the hu s of the respective spiders being assembled in coaxial abutting relation. These spiders have spokes 72 supporting at their outer ends a rim 73. This rim has a series of spaced annular ribs 74 projecting therefrom, the ends of which form annular seats to receive the plate 67 and maintain it in true circular form against the pressure ex erted thereon by the couch roll, The ribs 7 4 of the several spiders are spaced substantially uniformly throughout the operative.

length of the cylinder. The ribs thus adequately support the plate 67 against the pressure of the rolls 8 and the pulp therebetween without requiring the large number of spiders which would be required should each spider have but one annular bearing member to support the plate 67.

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The rim 7 3 is perforated at intervals as at 75 to permit the 'wash liquor passing through the perforation of the cylindrical plate and into the spaces between the ribs 74 to pass to the interior of the cylinder. At 76 are shown perforations through the spokes through which tie rods may be passed to hold the spiders and end castings in firm assembled position. Through the central hubs of the end castings and the s iders is positioned the shaft 78 b which t e cyliner is carried and rotate The couch roll 8is fixed to a shaft 80 which is journaled above the corresponding strainer cylinder so as to rest on the pulp picked up on its outer face. As shown in F1 gures 5, 8 and 9, it is supported so that any desired proportion of its weight may be caused to exert pressure on the pulp. For this purpose the shaft 80 is shown as journaled in bearings 81, each of these hearings being slidable be tween pedestal jaws 82 in the supporting frame 83. Above the bearing 81, a plate 84 is held in fixed position between the jaws 82, and resting on this plate is a coil spring 85 which surrounds an adjusting bolt 86. This bolt is threaded through a cap plate 87 resting on the upper end of the spring 85 and is also threaded through a flange 88 at the upper end of a vertical extension 89 of the bearing 81. This bolt 86 also passes loosely through a cap plate 90 bridging the jaws 82. By turning the bolt 86 the pressure exerted by the spring 85 tending to raise the cap bar 87 may be adjusted, and through the connection of this cap bar through the bolt 86 to the flange 88 this adjusts the pressure exerted to raise the bearing 81. In the position shown the bolt 86 is threaded down to its lowest position so that the spring 85 is under its greatest possible tension. A stop bolt 91 may be threaded through the lower portion of the frame 83 to limit the downward movement of the bearing 81.

It will be seen from this description that the pulp is washed in a plurality of separated batches, the wash water being repeatedly circulated through the batches and the pulp progressing from one to a succeeding batch. T he separation of the batches insures that the washin of each shall not be modified by the conditions of the pulp in an adjacent batch except in so far as this is effected by the wash water derived therefrom so that the washing conditions of each batch are always under close control.

Having thus described an embodiment of this invention it should be evident to those skilled in the art that various changes and modifications might be made therein without departing from its spirit or scope as defined by the appended claims.

I claim:

1. A process of washing fibrous material which comprises simultaneously a itating and washing aplurality of separated batches of said material in a plurality of separate baths, maintaining a supply pool for each bath, straining out the liquor from the fibrous material in each bath and passing the strained material to a succeeding bath, and passing liquor so strained out from such material to the pool for a preceding bath in terial to the pool for the next the direction of travel of the fibrous material.

2. A process of washing fibrous material which comprises simultaneously a itating and washing a plurality of separated batches of said material in a plurality of separate baths, maintaining a supply pool for each bath, straining out the liquor from the fibrous material in each bath and passing the strained material to a succeeding bath, and passing liquor so strained out from such mapreceding bath in thle direction of travel of the fibrous materfa 3. A process of washing fibrous material which comprises simultaneously agitating and washing a plurality of separated batches of said material, maintaining a supply 001 for each bath straining out the liquor f rom the fibrous material in each bath and passing the strained material to a succeeding bath and passing some of the liquor so strained out directly to the pool for the next preceding iath in the direction of travel of the fibrous material and the, remainder of the liquor to the pool for the same bath.

4. A process of washing fibrous material which consists in simultaneously agitating and washing a plurality of separated batches of said fibrous material in baths of washing liquor, successively feeding the said material from bath to bath and straining the wash liquor therefrom, collecting such strained liquor into separate pools, returning some of the liquor in said pools to the baths from which they came, and conducting some of such liquor as strained directly to the pool of the receding bath in the direction of travel 0 the fibrous material.

5. The process of washing fibrous material which consists in forming a succession of pools of washing liquor, circulatin the wash liquor from each pool through a ath, continuously feeding fibrous material through the successive separated baths, agitating and washing the batches of fibrous material in said baths, ex ressin from said fibrous material as it is eing ed from bath to bath a portion of the liquor mingled therewith, returnin a portion of said expressed liquor to the bath from which it came, conducting the remainder of said expressed liquor directly to a succeeding bath and thereby producin a progression of the wash liquor from but to bath in a direction opposite to the proression of the fibrous material, withdrawing t e concentrated liquor from the first bath, and supplying a relatively pure liquor to the last bath.

6. The process of washing fibrous material which consists in forming a series of separated pools and separated baths forwash liquor, the baths being at the higher elevation, continuously feeding the fibrous material from bath to bath, washing it in each Ian bath, and then expressing aportion of the liquor therefrom, continuously supplying liquor from each pool to its corresponding bath, maintaining a column of strained liquor for each bath, delivering a portion of the strained liquor to the pool from which it terial successively passes, means for strain-- ing out a portion of the washing liquor as the fibrous material passes from one to a succeeding mechanism, and means for re-,

turning a portion of said strained liquorto the correspond ng mechanism and a portion directly to the next previous mechanism in the direction of progress of said fibrous material.

8. An apparatus for washing fibrous material which comprises a series of associated washing and screening tanks provided with agitators and screens, means for passing the fibrous material therethrough in one direction, means for returning some of the liquor strained from said screens to its associated washin tank, and means for conducting the remain er of said strained liquor to the next previous washing tank whereby the liquor progresses in the opposite direction to the fibrous material.

9. An apparatus for washing fibrous material comprising a series of storage tanks for containing pools of wash liquor, a series of washing tanks above said storage tanks, straining mechanism for each washing tank, means for passing the fibrous material through said washing tanks and straining mechanisms in succession, means for circulating wash liquor between each storage tank and the washing tank above, and means for conducting a portion of the wash liquor from each straining mechanism to the storage tank of the next preceding washing mechanism in the direction of travel of the fibrous material.

10. An apparatus for washing fibrous material comprising a series of storage tanks for containing wash liquor, a washing tank for each storage tank, means for passing the fibrous material through said washing tanks successively,.screening mechanism for each washing tank through which the fibrous material passes on its way to the next washing tank, a standpipe to receive the wash liquor from each screening mechanism, a valve for permitting escape of liquor from each standpipe into the storage tank from which it came and acting to maintain a predetermined head of liquor in said standpipe, and means for conducting liquor from said standpipe into the storage tank of the washing tank next preceding in the order of treatment of said fibrous material.

11. An apparatus for washing fibrous material comprising a series of storage tanks for containing wash liquor, a washing tank for each storage tank, means for passing-the fibrous material through said washing tanks successively, screening mechanism for each washing tank through which the fibrous material passes on its way to the next washing tank, a standpipe to receive the wash liquor from each screening mechanism, a valve for permitting escape of liquor from each standpipe into the storage tank from which it came and acting to maintain a predetermined head of liquor in said standpipe, means for conducting liquor from said standpipe into the storage tank of the wash ing tank next preceding in the order of treatment of said fibrous material, and means for automatically regulating the proportion of liquor passing from said standpipe to each of its communicating storage tanks to maintain the liquid in each of said storage tanks at predetermined levels.

12. An apparatus for washing fibrous material comprising a series of storage tanks for containing wash liquor, a washing tank for each storage tank, agitating means in each wash tank, a screening tank to which the fibrous material and liquor passes from each washing tank and from which the fibrous material passes. to a succeeeding washing tank, a standpipe to receive the liquor from each screening tank, a valve in each standpipe opening under a predetermined head of liquor therein and permitting escape of liquor into a storage tank, means for taking liquor from said storage tank to the corresponding washing tank, means for taking liquor from each standpipe and conducting it to the storage tank corresponding to the washing tank next previous in the treatment of the fibrous material, means for supplying comparatively pure liquor to the last washing tank, and means for removing the more highly concentrated liquor from the storage tank at the opposite end of the series.

13. An apparatus for washing fibrous material comprising a series of storage tanks for containing pools of wash liquor, a washing tank above each of said storage tanks, agitating mechanism in each washing tank, a straining tank for each washing tank for receiving fibrous material and wash liquor therefrom, mechanism in each straining tank for straining the liquor from the fibrous material and passing the fibrous material to a succeeding washing tank, means for conducting wash liquor from each storage tank'to its superposed washing tank, means for conducting washing liquor from each straining tank to the supply tank preceding that from which its wash liquor comes in the direction of progress of the fibrous material, means for conducting sufiicient wash liquor from each straining tank to the storage tank from which it came to maintain a predetermined level of liquor therein, means for supplying relatively (pure liquor to the last washing tank in the irection of progress of the fibrous material, and means for removing the relatively concentrated liqnor from the first washing tank.

14. A strainer cylinder comprising a series of coaxially arranged spiders each havin a plurality of peripheral ribs thereon,

said ribs being space substantially uniformly throughout the operative length of said cylinder, and foraminous sheet material forming a cylindrical surface supported by said ribs.

15. A strainer cylinder comprising a series of spiders arranged coaxially, each spider having a central hub, the hubs of each adjacent spider abutting and each spider having spokes and a circular rim carried by said spokes, each of said rims having spaced peripheral ribs and perforated between said ribs, and a cylindrical surfacing of forumnous material enclosing said rims and sup ported on said ribs.

'16. A strainer cylinder comprising a series of coaxially arranged spiders each having a plurality of peripheral ribs thereon, and foraminous sheet material forming a cylindrical surface directly supported on said ribs.

In testimony whereof I have atfixed my signature.

CHARLES A. JOHNSON.

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