US1924860A - Apparatus for bleaching pulp - Google Patents

Description

Aug. 29, 1933. H. JOHN ET AL APPARATUS FOR BLEACHING PULP 2 Sheets-Sheet 1 Original Filed May 20. 1931 I lfiueniors Hal/25 Jb/IJZ Cid/am alelkfiufie.

Aug. 29, 1933.

v APPARATUS FOR BLEACHINQ PULP Original Filed May 20 193i 2 Sheets-Sheet 2 H, JOHN ErAL P 1,924,860

Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE APPARATUS FOR BLEACHING PULP Original application May 20, 1931, Serial No.

538,650. Divided and this application December 22, 1931. Serial No. 582,568

13 Claims.

Our invention relates broadly to bleaching apparatus and may be used in connection with the bleaching of various types of materials, but has particular applicability in connection with the treatment of wood pulp, and especially sulphite pulp, in the manufacture of paper.

An object of our invention is to provide new and improved apparatus for the bleaching of fibrous material, especially adapted for use in connection with .the manufacture of sulphite pulp, which apparatus is simple in construction, inexpensive to fabricate, highly efficient in operation, rugged, and generally-satisfactory for the purposes in view.

A further object is to provide new and improved means for feeding pulp into a bleaching chamber, whereby the pulp; prior to admission to the chamber, will function as a gas seal therefor.

Another object is to provide improved means 2 for removing bleached pulp from the bleaching chamber, while permitting the bleaching operation to continue in the mass of pulp disposed therein, said mass functioning as a seal to prevent escape of any substantial portion of the bleaching agent through the pulp exit.

Various other objects and advantages will become readily apparent as the description proceeds.

This application is a division of our co-pending application Serial No. 538,650, filed May 20, 1931.

Referring now to the drawings forming part of this specification and illustrating a preferred embodiment of the improved apparatus:

Fig. 1 shows an elevation of a bleaching tank and tower;

Fig. 2 is an enlarged sectional view taken substantially on the line 2-2 of Figure 1;

Fig. 3 is a sectional view taken on the line 3--3 of Figure 2;

Fig. 4 is a sectional view taken on the line 44 of Figure 3;

Fig. 5 is a fragmentary vertical sectional view, on an enlarged scale, of the lower portion of the tank and parts co-operating therewith;

Fig. 6 is a sectional view taken substantially on the line 6-6 of Figure 1, and

Fig. 7 is a sectional view taken on the line 7-7 of Figure 5.

In carrying out our process, we start with unbleached chemical pulp suspended in water. While, as stated above, the process has particular applicability to sulphite pulp, it is not necessarily restricted thereto. The pulp is thickened to a consistency above 22 per cent (where consistencies are mentioned in this specification, it will be understood to be on a bone-dry basis), preferably about 25 per cent, although consistencies running considerably higher may be used. At the same time, the pulp is formed into a continuous porous web. This may be accomplished on 50 an Oliver filter or other suitable apparatus. The web is then shredded into relatively small pieces, preferably not over an inch in any dimension, and these pieces are then conveyed to the apparatus, shown in the drawings, as by means of a belt con- 5 veyer or the like.

Turning now to the drawings, the improved apparatus comprises a tower 10 which is mounted over a tank 12. The tower 10 is preferably square in cross section and may be formed of ceramic tile and may conveniently be built up in sections, as clearly shown in Figure 1. Arranged at various points along the tower 10 is a plurality of feed grates 15. Referring more particularly to Figures 2 to 4, inclusive, each of these grates 76 comprises a plurality of aligned stuffing boxes 16l6 extending on opposite sides of the tower and journaling parallel shafts 1'7. These shafts are retained by means of suitable thrust bearings (not shown) disposed in a housing 18 and carry- 80 ing intermeshing spur gears 19, arranged in a housing 20. One of the shafts 17 of each grate projects, as at 17, for connection to a source of power (not shown) with a variable speed device, whereby each grate may be rotated at any desired speed independently of the others for regulating the feed of pulp that may bedisposed thereon.

Each of the shafts 1'7 has fixed thereon, within the tower, a feed-control member 21 forming part of the grate 15. These members, as best seen in Figure 4, are peculiarly formed, whereby the pulp may be fed therebetween, while, at the same time, jamming of the grates, due to packing of pulp between the feed members, is avoided. It 9 will be seen that eachmember 21 is in cross section roughly in the shape of an equilateral triangle with the vertices rounded to form convex edges 22 and with the sides curved to form concave faces. 23. The shafts 17 are, of course, rotated in opposite directions by means of their respective gears and the feed members 21 are arranged in identically the same position relative to the tower 10, as clearly shown in Figure 4, so that an edge 22 of each member will arrive in a horizontal plane simultaneously and thus will be disposed opposite a concave face 23 of an adjacent feed member.

. The tank 12 with which the tower 10 communicates may be built of-hollow tile 13 and lined a tubular shaft 46.

grates from the bottom, while the conduit 30' admits gas into the upper portion of the dome 2'7. A pile 31 of pulp is maintained on the grates.

Turning now to Figure 5, it will be seen that the tank 12 is supported in suitable masonry 32 which may be part of a floor, which masonry may be reinforced by suitable structural metal elements-(not shown). The tank is provided with a slightly concave circular floor 33, preferably formed of tile similar to the side walls 14 and leading to a central well 35. (Figure 6.) This well is provided by means of a tubular member 36 flanged at its upper end, as indicated at 3Tjwfiich flange forms a portion of the floor of the tank.

Adjacent the upper portion of the tubular member 36 is formed a spider 38 which supports a substantially vertical bearing 39. The tubular member 36 communicates with an elbow 40 provided at its lower portion with a vertical bearing 41 aligned with the bearing 39 and on its side with a pair of substantially horizontal parallel bearings 42, only one of which is seen in the drawings. A water pipe 43 communicates with the elbow 40.

' Arranged in the bottom of the tank is a hollow agitating member 45. As best seen in Figures 5 and 6, this member has two blades or arms curved so as to be substantially S-shaped and thus provide a pair of pockets on the sides thereof in its direction of rotation. It will also be observed that the lower contour of this member conforms substantially to the concave formation of the bottom wall 33 of the tank. The agitator is provided with a collar 45 whereby it is secured to The hollow arms of the agitator 45 terminate in laterally extending nozzles 4'7 which point'in the direction of rotation of the arms., As clearly shown in Figure 5, the hollow shaft 46 communicates with the agitator arms by means of suitable ducts in the shaft and in'the collar 45', these ducts being represented generally by the numeral 49. The shaft 46 is journaled in the bearings 39 and 41 and the lower portion thereof extends through a suitable stuff- "ing box 50 with which communicates a water pipe 51. The shaft is provided with ducts 52 whereby fiuid may pass into the bore of the shaft. The shaft is connected through a suitable coupling 54 and reducing mechanism '55 to a motor 56 or other suitable source of power.

The elbow 40 is connected to a pipe section 60 which in turn is connected to an elbow 62. The pipe section 60 may conveniently have a drain plug 63 at the bottom thereof. Projecting horizontally from the elbow 62 is a pair of stuffing boxes 61, each having a packing ring 64 and gland 65.

J ournaled in each of the bearings 42 is a shaft 67 carrying a plurality of paddles or propeller blades 68 of any suitable design for moving the material through the pipe 60 and parts communicating. therewith. The parallel shafts 6'7 are also journaled through the packing rings 64 and glands and through bearings '70. These bearings may be formed integrally with a disk '71 which may be secured to the stuffing box as by means of bolts or the like. One of the shafts 67 has secured thereto outside of the bearing '70 a pulley '72 over which is trained a chain '73 connected to any suitable source of power, such as a motor '74, or the like, whereby motion may be transmitted to the shaft 6'7 and to the propellers 68. Motion is transmitted from one of the shafts 67 to the other through a gear '75.

The elbow 62 is connected to a pipe section '76 which may be anchored in the concrete 32 and re tained by means of grout '77 or the like. The section 36 may be similarly secured, as by means of grout '77.

The pipe section '76 communicates with a weir box '79, from .which the flow may be controlled by means of an adjustable dam.

In the operation of the device just described in accordance with our preferred process, the pulp which has been thickened and shredded, as above described, is delivered to the top of the tower 10 and dumped therein. Its passage through the tower is controlled by means of the rotating feed grates 15. These grates serve to control the flow of pulp into the tank 12, which may be referred to as the reaction chamber,

and are so operated as to maintain a pile of pulp on top of each one, which acts as a gas seal, the piles, however, being so adjusted that there will be space between each pile and the grate above it (see Figure 1).

It might be mentioned at this point that various other constructions may be provided for feeding material to the reaction chamber 12 which would also serve as a gas seal therefor, in lieu of the tower described and illustrated. Thus, we might feed the pulp into the chamber by shoving it by means of a suitable propeller through a tube, this tube being either horizontal or slightly inclined upwardly toward the point of discharge, which would be at or adjacent to the top of the reaction chamber. A screw conveyor, plunger, or other suitable means might be used to propel the stock in the tube, which would be moved in such a manner as always to have therein a mass of unbleached pulp through which any escaping gas would have to pass, whereby the gas would be effectively prevented from escaping.

The bleaching gas, preferably chlorine, is introduced at all events through he conduit 30, whereby it is permitted to flow over the pulp lying in the tank. As shown, the gas may also be introduced through the conduit 30 above one or more of the feed grates. The falling of the shredded pulp through the gas afiords intimate mixing therewith. The amount of gas introduced is'proportioned to the degree of bleaching desired, generally between 50 and per cent of complete bleaching. As our preferred process is carried out, we preferably accomplish about 65 per cent bleaching at this stage.

The pulp is allowed to accumulate in the tank in a pile deep enoughto reach economically practical exhaustion of the gas at the bottom of the pile. The arms 45 are continuously rotated during the conduct of the bleaching operation and water sprayed out of the nozzles 4'7. It will be seen that water is thus only injected into the 4 preferably added to the water injected into the tank through the rotating arms to neutralize enough of the acid liberated during the gassing treatment so that the stock will not be too corrosive to the subsequent equipment. At the same time, the lime accelerates the exhaustion of any remaining traces of chlorine in the stock, thus,

preventing discomfort to the personneland corrosion of equipment when the stock is removed from the tank.

'The height of the water level in the bottom of the tank is controlled by the dam in the weir compared with what that concentration would be if the stock were diluted immediately with water.

Another function of the pile of stock is to act practically as a seal to prevent access of the chlorine in the top of the tank to the water in the bottom and thus avoid dissolving too much chlorine in the water. The combined effect of these two functions is that the chlorine mixed with the pulp is practically exhausted before the stock is mixed with the water. If, on the other hand, much chlorine were mixed into the water at the outlet, either the time necessary for exhausting, if alkali were not added, would be excessively long, or the economy of chemicals would suffer from undesirable side reactions on dissolve chines, if desired.

substances in the water.

The tank is discharged through the well 35, which, as stated above, serves as a water seal, the stock being moved from the sides toward the well 35 by means of the rotating arms 45, water being projected ahead of the arms from the spouts 4'7. Thus, the consistency of the pulp is lowered by admixture with water so that, due to the action of the rotating arms and the pressure of the pile of pulp, the mixture will flow out of the tank at the rate necessary to maintain the top of the pile at the desired height. The consistency of the pulp is further lowered by admix ture' with water from the pipe 43 to from 1.5 to 2 per cent, in which condition the mixture flows very much like water. The material passes down the well through the pipe section 36, elbow 40, pipe 60, elbow 62, and pipe 76 into the box 79, the paddles 68 serving to propel and also to mix the material to a smooth consistency.

The material flows over the dam in the weir' box 79 and thence flows through a down-spout 81 into a storage tank (not shown) below. By adjusting the level of the dam, the water levelin the reaction tank may be controlled, as stated above.

From the storage tank, which is used mainly to eliminate the fluctuations in the discharge from the reaction tank, the stock is pumped to a thickener, which again may be an Oliver filter, where the stock is reduced again to a consistency of between 20 and 25 per cent. It is evident that the dilution of the stock after the gassing, followed by the thickening, constitutes a dilution washing. This may be increased by a displacement wash on the thickener, or by additional washing ma- Pulp prepared as above described is not at all white and requires further bleaching for most purposes. Such further bleaching may be effected as described in our co-pending parent application referred to above, or otherwise.

Various changes, modifications and improvements coming within the spirit of our invention will doubtless occur to those skilled in the art. Hence, we do not wish to be limited to the precise embodiments herein disclosed but wish to be limited solely by the scope of the appended claims, which are to be interpreted as broadly as the state of the art will permit.

We claim as our invention:

1. In apparatus of the class described, a reaction chamber having side walls and a bottom wall with an outlet in the central portion thereof, a

tubular shaft, a hollow scraper mounted on said shaft adjacent said bottom wall and communicating with said shaft, said scraper comprising a pair of oppositely curved arms arranged on opposite sides of said shaft, said arms having nozzles adjacent their extremities, said. nozzles extending in a direction for projecting fluid in the direction of travelpf said arms into said chamber,

--means for conducting liquid to said shaft, and

means for rotating said shaft.

.2. In combination with apparatus as defined in claim 1, means for introducing pulpy material into the upper-portion of said chamber and operating as a gas seal therefor. Q

3. In apparatus of the class described, a device for subjecting material to a gaseous bleaching agent, comprising a vertical tower, a plurality of grates arranged at spaced points longitudinally of said tower, means for rotating said grates so as to regulate the passage of pulpy material through said tower, and means for introducing a gaseous bleaching agent below certain of said grates.

4. In apparatus of the class described, a reaction chamber having side walls and a bottom wall having an outlet therein, means for introducing pulp and means for introducing a bleaching gas into said chamber, a scraper arranged above said bottom wall for moving material toward said outlet, means for diluting the pulp leaving said chamber, a discharge conduit for maintaining a liquid seal'a't said outlet, and means for controlling the liquid level in the lower portion of said chamber comprising an adjustable weir communicating with said discharge conduit.

5. In apparatus of the class described, a conduit, a pulp-feeding grate disposed transversely in said conduit, said grate comprising a plurality of parallel, rotatable feed members, said feed members each being approximately triangular in cross section and arranged in such angular positions relative to said conduit, whereby the edges thereof, when they arrive in the plane of the axes of said members, will lie opposite a face of an adjacent feed member, and means for rotating said feed members in opposite directions.

6. Apparatus as defined in claim 5 wherein said feed members have convex edges and concave faces and wherein said conduit is disposed vertically, whereby pulp may be fed by gravity and the feed controlled by means'of said grate.

7. In apparatus of the class described, a reac-' tion chamber having side walls and a concave bottom wall having an outlet in the central portion thereof, a tubular shaft extending through said outlet. a hollow scraper mounted on and communicating with said shaft, said scraper comprising a pair of curved arms arranged on opposite sides of said shaft in 8 formation and having 'nozzles' at the ends thereof for injecting streams claim '7, a .U-shaped conduit communicating" with said outlet,- means for injecting liquid into said conduit for increasing the fluidity of pulp' moved therethrough, means for propelling material through said conduit, and means comprising a weir box communicating with the discharge end of said conduit for controlling the liquid level in the lower portion of said chamber.

10. A combination as defined in claim 5, wherein said conduit consists of a vertically arranged tower.

11. In apparatus of the class described, a reaction chamber having side walls and a bottom wall with an outlet in the central portion thereof, the

interior of said chamber being substantially free to permit unobstructed passage of material therethrough, a hollow shaft extending upwardly through said outlet, a hollow scraper in the bottom of said chamber attached to and communieating with said shaft for conveying material toward said outlet, said scraper having a nozzle thereon for diluting pulp in the bottom of said chamber and washing .the same toward said outlet.

12. In apparatus of the class described, a reaction chamber having side walls and a bottom wall with an outlet in the central portion thereof, the interior of said chamber being substantially free to permit unobstructed passage of material therethrough, a hollow shaft extending upwardly through said outlet, a substantially S-shaped hollow scraper mounted on said shaft adjacent the bottom wall of said chamber for moving material toward said outlet, said scraper havingnozzles adjacent the ends thereof, means for rotating said shaft, and means for conveying liquid thereto. 13. In combination with a device as defined in claim 11, a U-shaped conduit communicating with said outlet, means for injecting liquid into said conduit for increasing the fluidity of pulp moved therethrough, and means for propelling material through said conduit.

HANS JOHN.

CLARENCE C. LE FEBVRE.-

HORACE DU B018.

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