US1891957A - Device for distributing wood chips in pulp digesters - Google Patents

Description

Dec. 27, 1 932. B. F. SMITH DEVICE FOR DISTRIBUTING WOOD CHIPS IN PULP DIGESTERS Filed Dec. 5. 1931 Patented Dec. 27, 1932 UNITED STATES PATENT OFFICE BERNARD F. SMITH, OF AIPLETON, WISCONSIN, ASSIGNOR T0 PAPER PATENTS COI- IANY, OF NEENAH, WISCONSIN, A CORPORATION OF WISCONSIN DEVICE FOR DISTRIBUTING WOOD CIIPS PULP DIGESTERS Application led December This invent-ion relates to the general art of paper making, and has reference more particularly to an improved mechanism for distributing wood chips in pulp digesters.

The general object of the invention is to provide an apparatus whereby the chips may be so distributed in the digester as to effect, in the first place, more uniform cooking conditions through a more uniform temperature dist-ribution within the digester, thereby improving the yield and quality of the pulp;

and, in the second place, to secure a larger charge of chips being introduced into the digester than is possible by the procedure heretofore practiced by reason of a closer piling of the chips, thus considerably increasing the capacity of the cooking equipment.

In the present customary method of filling digesters with chips, a spout is placed over the top nozzle of the, digester, and the sliding gate in the chip bin bottom immediately above the spout is opened. The chips fall bv gravity through the spout and into the digester. As is the case with all materials in small pieces, a cone-shaped pile is formed in the dig-ester. the entering chips dropping on the apex and sliding down to a position of rest somewhere along the sides of the pile. The chips. having a slab-like form or shape, tend to take a position of most stable equilibrium. which means that they will rest on one of the faces having the greatest surface area, rather than on one of the edges. They slide down the cone in this position, with the result that a charge of chips is formed in the digester having a stratification corresponding to the angle of repose of th'e material. Not infrequently a stream of chips dropping from the bin enters the top of the digester eccentrically, and this leads to a stratification apex line somewhat eccentric to the vertical center line of the digester. However. the angularity of the stratification still exists.

Considering now the effect of this peculiar stratification upon the cooking process, after the digester is filled with chips and cooking liquor is introduced, the vessel is usually iilled to the top with the re-agcnt and sealed by a top nozzle cover or cap, whereupon the heating ot the contents is begun. Two methods of 5, 1931. Serial No.l 579,226.

at regular intervals in one horizontal plane of the surface of the bottom cone. The steam is quickly condensed to water by the cooking liquor and gives up its latent heat, as well as a portion of its sensible heat, to the latter. This warm liquor rises by convection through the digester contents, displacing colder liquor above, which falls t0 the bottom of the digester, is heated and, in turn, rises. Thus a convection current of circulation develops in the liquor portion of the digester contents. As the contents warm up the vapor pressure of the liquid, and also gas pressure of the dissolved sulphur dioxide in case of sulphite cooking liquor, causes a development of pressure in the digester. Further, the condensed steam increases the liquid content of the digester, causing it to lill up and develop a hydrostatie pressure, which is usually allowed to reach a predetermined maximum and is then maintained at this point by relief of excess water vapor, sulphur dioxide gas ahd liquor through suitable outlets in the top nozzle. The relief of sulphur dioxide gas, in the sulphite process particularly, aids also in maintaining a circulation of the liquid content. The gas is released in the form of bubbles, and these rise through the digester, causiplg upward motion of the liquid surrounding t em.

Now, the liquid must naturally flow in channels formed by the interstices between the chips. And if the chips have an angular stratiiication, such. as results from the usual method of filling, the channels or interstices must be somewhat continuous in the direction of the angular alignment or stratification. Since these channels lead upward and away from the walls of the digester to its axis, the liquid stream in rising tends toward the axis or center of the digester, and in descending it follows the outside walls of the vessel because of the cooling eiiect resulting from radiation of heat from these walls. Hence, the

tion, itfh'asan 'adverse effect n'ponfthe pulp.

quality and yield. It leads to non-uniformityin the product, inasmuch as part of the wood is :eipofs'ed 'thCQCQOking-reagent at a higher temperatreforatmuch longer time than other parts l. Naturally, the cooking process is not cmplteduntil all the wood has been converted into,.pulp,1and by the time the contents of the colder zones are completelyconverted, the contents' of the warmer central zones .will be considerablyv overcooked, resulting-in" 'a Hveryi' appreciable yield and v strength losszwhich,1`coursfe,is undesirable. lAmore modern system ofhfvcooking involves' the'forced'circulation' of hot -cooking liquor through ltherdige'ster,v accomplished by withdrawingthe liquor from the top or bottom of the ldi'gester, passing yit through a pump, and

vforcing itfback intoj-th e-dige'ster at the bottom or top", as fthe case maybe. This modificationis less -Vproductivejof zones of unequal temperatures in thejfdigester,"bu`t its eiiiciency in thisffres'p'ectl is not complte. The angular stratification-of the chips causes most of the liquor, tio' `flow vrthrough the central zone of thefdig's't'erifithe'liquorisforced in at the bottom gbi: along the walls ifideli'vered at the l. Atopi and this leadsfto somewhat inactive zones in' thediges'ter' contents which are not pulped as rapidly asv body: 'of the contents. The'Qpresentfinvention aims to eliminate theundesirable c :ditionsliiithe digester outabove, and'fnploys, as themain feature "of .the invention, ya novel device in the nature of "aufv eccentric cone; rotatably. suspended in the' digester'slightly below the charging nozzle of the latterandr'ldisposediin the path of Fl the [falling stream of cfhfipsn,I for creating a substantially horizontal1strati`fication of the chips 'inthe fdigester'andacloser packing of the same,l bywhic'hV ai morel uniform cooking andacnsiderable increase thepulp ob- ,tained feach' charger are secured.

.The-A invention, its 'mdeof operation, and

the benefits, and y advantages inherent therein will `lall ,be Yunderstoodfand appreciated'byf:personsfvfamiliar with this branch of ,the'fpap'er making/art fromv the following detailed description, `taken in, connection with the accompanying drawing', wherein I have illustratedpnepractical and simple form in which` .invention maybe embodied, and VHWShCh-l-il i `I Vig..flfiska.. view in i vertical axallsectionofa pulp digester and its chip-distributing mechanism, illustrating the substz uitiallyl lhorizontal stratification of the charge obtained by the use of the present distributor.

Fig. 2 is a vertical section on an enlarged scale through the upper portion of the digester and its nozzle, showing the improved device for distributing the inflowing stream and effecting the horizontal stratification of thechargey 1.1..' i

Fig. 3 is a further enlarged axial section of the anti-friction bearing member for the shaft of thecone(distributor. -v

Fig. 4 is a top plan View of the ,cone distributor, in section through its shaft on the line 4-4 of'Fig. 2.

Figr 5 is an enlarged side elevation of the cone distributor and its shaft, partly broken out and in section, showing a countersunlr bushing through which the cone is keyed to its shaft.

Referring to the 4drawing-10 designates a vdigester of the usual form having a conical bottom portion 11 and a charging nozzlev 12;

and at 13 is indicated in Fig. 1 a pipe for steam or hot cooking liquor entering the lower end of the di gester.

14 designates a sleeve of-a size to have an easy sliding fit in the charging nozzle 12 and formed on its upper end with an annular flange 15 resting on the upper end of the nozzle. To the lower end of the inner wall of the sleeve 14 are attached, as by soldering, welding, or otherwise, equally spaced pairs of angle-attaching strips 16, between the in- I wardly projecting limbs of which are riveted or otherwise secured the outer ends of a plurality of downwardly and inwardly inclined flat spider arms17 secured at their inner ends to a vertical bearing casing 18. In the upper and lower ends of the casing 18 are anti-friction bearings 19 and 20 of the ball type that are locked in place by upper and lower lock nuts 21 and 22. These lock i nuts engage threaded portions 23 and 24 of a vshaft section 25, which latter is formed with upper and lower annular shoulders 26 and 27 against which the inner rings of the bearings 19 and 20 are pressed by thelock nuts 21 and 22. These spaced anti-friction bearings afford a rigid and nearly frictionless lateral support for the rapidly rotating shaft 25; the Y.construction,permitting the filling ofthe space Within the bearing casing 18 with a suitable lubricant (not shown) and the escape of the lubricant Abeing guard-y ed against by upper and lower glands 28 and 29 attached to the ends ofthe casing 18 by` screws 30. and internally grooved to receive packing rings 31.

32 designates the main operating elementA I of the chip distributor, this, in the embodiment of the inventionherein shown, taking the form of an eccentric truncated cone. This cone member may be made of wood, metal or any other materialwell adapted to withstand the wear of contact with the falling stream of chips impinging thereon and dellected thereby. As shown in Figs. 2 and 5, the lower portion of the shaft 25 extends some distance below the bearing 18, and the cone 32 is formed with an eccentric axial bore 33 that is fitted ont-o the lower end portion of the shaft 25 from below the latter. The cone 32 may, of course, be fixed on the shaft to rotate with the latter by any suitable or desired means, but in Fig. 5 I have illustrated an attaching means well adapted to maintain the cone in rigid relation to the shaft under the considerable unbalance of the cone caused by its eccentric mounting when in very rapid rotation. The lower end of the axial bore 33 is formed with a stepped countersink comprising a wide shallow portion 34 and a narrower deeper portion35. Fitted within this countersink 1s a bushing comprising a body portion 36 filling the deeper countersink 35, and a head or Bange portion 37 filling the shallow colintersink 34. The bushing is locked on the shaft by an ordinary key 38 engaging registering keyways in the shaft and bushing and the bushing is locked to the cone by screws 39 passed through the ange 37 and into the body of the cone. The lower end ofthe shaft 25 is preferably tapered, as shown, and the bore of the bushing is correspondingly tapered to insure a tight fit and prevent any looseness or wobbling of the cone on the shaft due to wear. The lower end of the shaft is threaded to receive a nut 40, by which, and the usual cotter piny 41, the cone and its bushing are securely locked on the shaft.

The cone and its shaft may be driven by any suitable drive extending through the charging nozzle. but I have herein illustrated the use of a fiexible drive shaft 42 extending axially through the sleeve 14 and suitably coupled to the upper end of the shaft 21 as by means of a knurled nut 43 secured to the lower end of the fiexible `drive shaft 42. I may here state that after the digester has been filled with chips and before the contents are subjected to the digesting operation, it is, of course, necessary to remove from the charging nozzle 12 the chip distributor and its supporting means. By providing a ilexible drive shaft 42, the entire assembly can manifestly be withdrawn from the charging nozzle by simply lifting out supporting sleeve 14. In actual practice, the flexible `shaft 42 is suspended from an overhead trolley carrying a motor and a drive from the motor to the shaft 42; but as these features form no part of the present invention, I have not deemed it necessary to illustrate the same herein.

When loading the digester, the chips are directed into the upper end of the charging nozzle 12 through a suitable guide chute or hopper; and the descending stream of chips hereinabove set forth, are

imiun, which is sufliciently inclined to direct the chips outwardly to the circumference of the digester; so that, so far as the downward sliding of the chips is concerned, the chi s are deiected at widely varying angle's to e `axis of the digester, In addition to this sliding action of the chi s, the cbne also tends, by its rapid rotation, to throw the chips olf tangentially. The combined result of this sliding action at varying angles and tangential iinpellin action is to scatter the chips with substantial uniformity throughout the entire cross section of the digester, so that the body of chips builds up in the di gester with the substantially horizontal stratification indicated in the beneficial results of the invention, as

secured.

I claim:

1. The combination with a pulp digester, of mechanism for distributing chips therein, comprising a conical member formed with a downwardly and outwardly tapered chi -de fleeting surface presenting varying ang es of inclination to its axis, means for rotatably mounting said conical member below the charging nozzle of the digester in the path of 'the stream of chips, and means for rotating said conical member.

2. The combination with a pulp di ester, of mechanism for distributing chips t erein to create a substantially horizontal stratification of the chips in said digester, comprising a conical member of round cross-section formed with a chip-defiecting surface resenting progressively increasing angles o clination to its axis from a minimum to a maximum, means for rotatably mounting said conical member below the charging nozzle of the digester with its axis the airis of said nozzle, and means for rotating said conical member.

3. The combination with a pulp digester, of mechanism for distributing chips therein, comprising a truncated eccentric cone, means for rotatably mounting said cone below the chargin nozzle of the digester in the path of the fa ling stream of chips, and means rotating said cone.

4. The combination with a pul digester, of removable mechanism for distrihuting chips therein, comprising a sleeve slidingly fitting within the charging nozzle of the digester and formed lwith a flange on its up r end resting on said nozzle, a vertical aring member supported by said sleeve, a vertical shaft journaled in and extending below said bearing membei',`a truncated eccentric in line with Fig. 1, whereby mounted on the lower end of said shaft, and a drive shaft coupled to the upper end of said first-named shaft.

5. The combination with a pulp digester, of removable mechanism for distributing chips therein, comprising a sleeve slidingly fitting within the charging nozzle of the digester and formed with a flange on its upper end resting on said nozzle, a. vertical bearing member having arms attached to said sleeve, a vertical shaft journaled n and extending below said bearing member, a truncated eccentric cone formed with an axial bore mounted on the lower end of said shaft, said bore having a countersink at its lower end, a flanged bushing lling said countersink and keyed to said shaft, means for attaching the flange of said bushing to said coneJ and a drive shaft coupled to the upper end of said first-named shaft.

BERXARD F. SMITH.

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