US2730888A - Apparatus for treating pulp with liquid - Google Patents

Description

Jan. 17, 1956 Filed Dec. 31, 1952 G. A. SEELY ETAL APPARATUS FOR TREATING PULP WITH LIQUID 2 Sheets-$heet 1 GEORGE A.SEELY WALTER E. SEGL ERNEST 8. WILSON INVENTORS Jan. 17, 1956 s. A. SEELY ETI'AL APPARATUS FOR TREATING PULP WITH LIQUID 2 Sheets-Sheet 2 Filed Dec. 51. 1952 FIG 3 FIG. 4

GEORGE A. SEELY WALTER E. SEGL ERNEST 8. WILSON INVENTOR.

AGENT.

United States Patent APPARATUS FOR TREATKNG PULP WIT H LIQUID George A. Seely, Hopewell, Va., and Walter E. Segl and Ernest S. Wilson, Wilmington, DeL, assignors to Her.- cules Powder Company, Wilmington, Del a corporw tion of Delaware Application December 31, 1952, Serial No. 329,074

Claims. (Cl. 68-181) This invention relates to an improved pulp treatment apparatus. In a specific aspect, this invention relates to an improved high density tower for the continuous treat me 4r P lp- In the bleaching of pulp, it has sometimes been found desirable to employ in the process a high density bleach tower wherein pulp to be bleached is continuously fed to the top of the tower and bleached pulp is continuously removed from the base of the tower. The bleached pulp is washed with water and the washed pulp is then ready for further treatment. The pulp entering the top of the tower is usually hot and wetted with bleach solution. The pulp contains sufficient bleach solution for the bleaching reaction, but there is susbtantially no free bleach solution present in the entering feed stock. As the mass of pulp passes downwardly through the bleach tower, the compressive force of the pulp in the upper portion of the bleach tower tends to form a hard, compact mass in alower portion of the tower. It is thus apparent that the removal of the bleached pulp from the base of the bleach tower can be a difficult operation.

One of the prior art methods of removing bleached pulp from the base of the tower involved the use of a revolving scraper to keep the bleached pulp flowing through a discharge opening in the bottom of the tower. Since the pulp is in a hard, compact mass in the bottom of the tower, the difiiculty of employing such an apparatus is quite apparent. Another prior art method involved the insertion of a pylon in the bottom of the tower and a water spray was employed to slurry and to regulate the removal of the bleached pulp. This method contemplatedthat the stock would bridge from the pylon to the tower wall and that the downward passage of the stock could then be regulated by the water spray. However, the stool: frequently would not bridge and withdrawal of the bleached pulp was quite difiicult and uncontrollable.

It is an object of this invention to provide a novel and improved bleach tower.

It is another object of this invention to provide a novel and improved tower for the bleaching of pulp wherein the construction of the tower permits uniform and controllable removal of the bleached pulp in a liquid slurry.

Further andadditional objects of this invention will be apparent from the detailed disclosure and the accompanying drawing. a

The apparatus of this invention comprises an elongated, vertically disposed chamber or tower for bleaching pulp containing a cellulosic material, such as cotton lin ters or wood pulp. The bottom portion of the tower is provided with a bulged or protuberant section, and dis posed within this protubcrant section are a solid, circular bathe either horizontally disposed or sloping downwardly from the center of the chamber to the wall of the chamber, and means for moving or forcing bleached pulp toward the wall of the chamber.

Fig. 1 is an elevational view of the improved bleaching tower.

2,730,888 Patented Jan. 17, 1956 Fig. 2 is a plan view through section 2--2 of the improved bleaching tower.

Figs. 3 and 4 are alternative elevational views of the improved bleaching tower.

Referring now to the accompanying drawings, Figs. 1, 3 and 4 are elevational views of the improved bleaching tower of this invention. Bleaching tower or column 10 is an elongated cylindrically shaped chamber containing bleaching zone 10a and a slurrying zone 10b. In most instances, the bleaching zone which is in the upper portion of the column comprises the major portion, for example, about or more of the entire volume of the column. However, it will be understood that the volumetric proportions of the bleaching Zone and slurrying zone are variable and depend upon such factors as the material being processed, treatment time, and the like. The bleaching zone and slurrying zone of column 10 are separated by a bulged or protuberant section 12 of the bleach tower. A desirable design for this bulged section of the column is an enlarged cylindrical section superimposed upon and in direct communication with an inverted truncated cone. The inverted truncated cone tapers downwardly and inwardly toward the lower portion of the column or the slurrying zone, and the enlarged cylindrical section is larger in diameter than the diameter of the bleaching zone of the column. A solid circular battle or umbrella 14 is disposed in the cylindrical portion of bulged section 12. Baflle 14 preferably slopes downwardly from the center of the column toward the outer wall of the bulged section, but, if desired, a horizontally disposed baffle can be used. The lower or outer extremity of battle 14 is in the bulged section of the column. Thus, the radius of baflle 14 is greater than the radius of the bleaching zone of column 10 and baffle 14 forms an annular space with the outer wall of the cylindrical portion of bulged section 12. Also, disposed within bulged section 12-and above baffle 14 are transport jets l6 and slice arms 18 which provide a means for disintegrating any remaining piers or pillars of pulp that tend to form in the bleaching section of column 10. The action of jets 16 andslice arms 18 forces or moves the pulp around baffle M and into the slurrying section of column 10. Jets 16 and slice arms 18 are attached to and supported by revolving nozzle block 34 which is disposed above pylon 20. Supporting ribs 36 attached to baflle 14 and pylon 20 provide the necessary support for baffle 14. Pylon 20 forms a casing through which Water or other fluid is forced for passage through jets 16. Jets 16 and slice arms 18 are revolved by power shaft 22 which is at: tached to a source of power not shown. Zone 1% is provided with agitating means 38 to maintain the slurry consistency in zone 1013.

There are other designs for column '10 which incorpoi-ate this invention and which are within the scope of the invention. For example, the lower portion of the column, which includes the bulged section and the slurryin zone, can be of substantially uniform diameter, as shown in Fig. 3. In that event the diameter of the entire lower portion of the column will be greater than the diameter of the bleaching zone of the column. desired, the diameter of the slurrying zone of the column can be smaller than the diameter of the bleaching Zone, as shown in Fig. 4. The important feature is theprovision of a zone between the bleaching and slurrying zones of greater diameter than the bleaching zone and housing baffle 14, jets 16 and arms 18. The optimum radius of arms 18 is substantially as great as the radius of the bleaching zone of column 10 in order to. insure com plete disintegration of any piers of bleached linters that are formed. The radius of arm 18 can be greater than the radius of the bleaching zone but the additional radial length of arm 18 is not essential.

In actual operation, pulp wetted with bleach liquid and heated to the desired temperature enters column 10 via entrance'opening 24. The bleaching of the pulp is carried out in bleaching zone 10:: of column 10, and the design of column 10 is such that the pulp and bleaching liquid are retained within bleaching zone 10a for a predetermined period of time. The length of the bleaching period is varied by changing the level of the top surface of the stock in tower 10, i. c., longer bleach periods areobtained by raising the stock level. As the pulp progresses downwardly through the column, the weight of the pulp being fed into the bleaching chamber brings free bleaching liquid to the surface of the pulp, thus efiiecting a redistribution of liquid and adequate bleaching action. Due to the compressive action resulting from the pulp being. fed into the bleach tower, the pulp tends to mold itself into a shape similar to the contours of the column. Consequently, withdrawal of the pulp from the pulp to be moved outward over the periphery of bafile 14 by the action of rotating jets 1.6, which slice and convey by hydraulic action the major portion of the pulp outward over the periphery of bafile 14. At times some segments of the pulp are not moved outwardly by the action of jets 16, and when this occurs the weight of the pulp in bleaching zone 10a is concentrated on one or more of these small segments. This concentration of pressure forms dense, hard piers which are substantially immune to subsequent jet action. Consequently, partial or complete stoppage of movement of stock down the tower results. Slice arms 18 follow jets 16, and they cut or slice the piers. and render the pulp of which they are composed susceptible to outward movement by the ensuing sweep of jets 16. Jets 16 are rotated by a variable speed drive, and by controlling the speed of rotation of the jets it is possible to control the rate of withdrawal of bleached pulp from tower 10. Also, uniform passage of bleached pulp from the bleaching zone to the slurrying zone of tower 10 can be effected without any formation of piers or pillars. Slurrying water is introduced to zone 10b via line 26 and bleached pulp slurried in water is removed from the column via line 28. The resulting slurry of bleached pulp in water is removed for any further treatment that is necessary, and in some instances, depending upon the nature and design of the equipment employed, it is desirable to recycle a small portion of the slurry to the column via line 30. For most effective operation, the recycled slurry enters the bulged section of column 12 immediately above baffle plate 14. Water for jets 16 enters the column via inlet 32. It will be understood that the water from jets 16 provides a minor portion of the slurrying liquid for use in zone 10b.

Fig. 2 is a plan view through section 2--2 of the im proved bleaching tower showing jets 16 and slice arms 18 and their location in bleaching column 10. Any number of jets and slice arms can'be employed to assist in the disintegration of piers of bleached pulp. It has been found, however, that two jets and two slice arms will effectively carry out the uniform movement of stock from zone 10a to zone 10b. It has also been found to be quite effective to employ the jets and slice arms in the same horizontal plane, although this design is not essential for the operation of the column; It is also desirable to place the slice arms at the mid-point between baffle plate 14 and the lower extremity of bleaching zone itla. in order to assist in the removal of the bleached pulp from the bulged section of the column, it is desirable that slice arms 18 curve backwardly and away from any pillars that are to be disintegrated by the slice arms.

Variations in the design of the bleach tower within the scope of this invention will be apparent to those'skilled in the art from the above disclosure. For example, in the above detailed description of the apparatus a column for bleaching pulp has been described. However, it will be understood that a column or tower within the scope ofthis invention can be used for other treating operations, such as an alkaline extraction treatment of bleached pulp. Also, the column has been described as being cylindrically shaped, but this preferred design is not essential to the operation of the column. For example, the design of the column can be such that a horizontal cross-section of the column is oval or square instead of circular as in a cylindrical column.

What we claim and desire to protect by Letters Patent is:

1. Apparatus for treating pulp comprising, in combination, an elongated, vertically disposed treating chamber; and, disposed below said treating chamber and in direct communication therewith, a second chamber of greater cross-sectional area than said treating chamberand housing a solid baffle of greater cross-sectional area than said treating chamber and forming an annular space with the periphery of said second chamber; and means for moving treated pulp toward the periphery of said second chamber.

2. Apparatus for bleaching pulp comprising, in combination, an elongated, cylindrically shaped, vertically disposed bleaching chamber; a second cylindrical chamber of greater diameter than said bleaching chamber disposed below and in direct communication with said bleaching chamber; a solid, circular baffle of greater diameter than said bleaching chamber disposed in said second chamber and sloping downwardly from the center of said second chamber and forming an annular space with the periphery of said second chamber; means for spraying a liquid under pressure from the center of said second chamber toward the periphery thereof and disposed above said baflle; and an arm revolvable about the center of said second chamber and disposed above said 3. Apparatus for bleaching pulp comprising, in combination, an elongated vertically disposed chamber, said chamber including a high pulp density cylindrically shaped bleaching zone and a low pulp density cylindrically shaped slurrying zone, said bleaching zone and said slurrying zone being joined by a protuberant section of said chamber; a solid circular bathe of greater diameter than said bleaching zone disposed in said protuberant section and sloping downwardly from the center of said protuberant section and forming an annular space with the periphery thereof, the lower extremity of said balfie being in said protuberant section; means for rotatively jetting a liquid under pressure from the center of said protuberant section toward the periphery thereof and disposed above said baflle; and an arm revolvable about the center of said protuberant section and disposed above said baflle, the length of said arm being at least equivalent to the radius of said bleaching zone. 7

4. Apparatus for bleaching pulp comprising, in combination, an elongated, vertically disposed chamber, said chamber including a high pulp density cylindrically shaped bleaching zone and a low pulp density cylindrically shaped slurrying zone, said bleaching zone and said slurrying zone being joined by a protuberant section of said chamber, the upper portion of said protuberant section being cylindrically shaped and of greater diameter than said bleaching zone and the lower portion of said protuberant section being in the form of an inverted truncated cone in direct communication with said upper portion and tapering downwardly and inwardly toward.

said slurrying zone; a solid circular bafile of greater diameter than saidbleaching zone disposed in said protuberant section and sloping downwardly from the center of said protuberant section and forming an annular space with the periphery thereof, the lower extremity of said bafflle being in said protuberant section; means for rotatively jetting water under pressure from the center of said protuberant section toward the periphery thereof and disposed above said bafile; and an arm revolvable about the center of said protuberant section and disposed above said baffie, the length of said arm being equivalent to the radius of said bleaching zone.

5. Apparatus for bleaching pulp comprising, in combination, an elongated, vertically disposed chamber, said chamber including a high pulp density cylindrically shaped bleaching zone and a low pulp density cylindrically shaped slurrying zone, said bleaching zone and said slnrrying zone being joined by a protuberant section of said chamber, the upper portion of said protuberant section being cylindrically shaped and of greater diameter than said bleaching zone and the lower portion of said protuberant section being in the form of an inverted truncated cone in direct communication with said upper portion and tapering downwardly and inwardly toward said slurrying zone; a solid circular bafiie of greater diameter than said bleaching zone disposed in said protuberant section and sloping downwardly from the center of said protuberant section and forming an annular space with the periphery thereof, the lower extremity of said bafile being in said protuberant section; means for rotatively jetting water under pressure from the center of said protuberant section toward the periphery thereof and disposed above said baffle and revolving about the center of said protuberant section; and an arm revolvable in the same horizontal plane with said Water spraying means, the length of said arm being equivalent to the radius of said bleaching zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,968,994 Davies Aug. 7, 1934 2,513,344 McEwen July 4, 1950 FOREIGN PATENTS 904,673 France Mar. 12, 1945

Claims (1)

1. APPARATUS FOR TREATING PULP COMPRISING, IN COMBINATION, AN ELONGATED, VERTICALLY DISPOSED TREATING CHAMBER; AND DISPOSED BELOW SAID TREATING CHAMBER AND IN DIRECT COMMUNICATION THEREWITH, A SECOND CHAMBER OF GREATER CROSS-SECTIONAL AREA THAN SAID TREATING CHAMBER AND HOUSING A SOLID BAFFLE OF GREATER CROSS-SECTIONAL AREA THAN SAID TREATING CHAMBER AND FORMING AN ANNULAR SPACE WITH THE PERIPHERY OF SAID SECOND CHAMBER; AND MEANS FOR MOVING TREATED PULP TOWARD THE PERIPHERY OF SAID SECOND CHAMBER.

Images