US2844887A - Dryer - Google Patents

Description

July 29, 1958A L.' HoRNBosTEL DRYER Filed Feb. 8, 1957 [nz/E17 fr" Lovb HofPA/BosrEL M yz/g5.

...... l lllll Unite DRYER Lloyd Hornbostel, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis., a corporation of Wisconsin The instant invention relates to a dryer drum for a paper machine, and more particularly, to an improved dryer drum structure and an improved method of heating the dryer drum.

As conventionally employed in the art, dryer drums for paper machine drying sections generally consist of a cylindrical shell, spaced heads extending radially across the shell to close the open ends thereof and carrying means for journaling the shell for rotation, and means for introducing a heat exchange uid into the interior of the shell. The Yankee dryer drum has generally the same structural arrangement, as now used in the art, except that the Yankee dryer drum is ordinarily of substantially greater size than the dryer drums in the conventional dryer section of a paper machine. Nevertheless, in each case these dryer drums (whether the large Yankee dryer drum or the smaller conventional drum) have certain operating limitations. for the shell define a minimum thickness therefor; and the greater the thickness of the shell the slower the heat transfer therethrough. Also, the higher the steam pressure within the shell, the greater the'thickness required therefor. In view of this, there are definite limitations in shell size and usable steam pressure for any given shell, so that the maximum capacity of the shell for drying purposes is also limited.

As will be appreciated, a given shell structure can withstand only a certain maximum steam pressure therein and this maximum steam pressure which may be maintained within the shell determines the maximum amount of heat which can be supplied to the shell and thus the maximum amount of drying which can be effected by passing a paper web over the shell. For years these limitations have been recognized and the industry has continued to use the conventional dryer drum structure.

In contrast, the instant invention is based upon the discovery that the usual heat exchange fluid, namely, steam may be confined in small pipes or conduits within the shell; and this steam (or any other heat exchange fluid such as hot oil) may thus be forced into the shell at pressure substantially greater than the pressure which the shell itself could ordinarily stand. Heat transfer from the heat exchange iiuid within the small pipes or conduits is effected, according to the present invention, by the use of'a relatively non-volatile liquid (which does not build up a pressure comparable to the heat exchange fluid at the temperatures involved) and the fluid is maintained in uniform contact with the inner periphery of the shell by centrifugal force during rotation of the shell. f

The small pipes or conduits carrying the heat exchange fluid are rotatably mounted adjacent the inner periphery of the shell for rotation relative to the shell rotation so as to be continuously immersed in the non-volatile liquid which flows freely within the shell and to continuously agitate said liquid.

It is, therefore, an important object of the instant invention to provide an improved dryer drum structure.

The strength requirements rates Patent It is another object of the instant invention to provide an improved method of heating a dryer drum.

Still another object of the instant invention is to provide an improved dryer drum comprising a rotatably mounted cylindrical shell, a head closing each end of the shell, and a steam conduit within the shell adjacent the shell interior mounted for rotation relative to said shell.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part hereof.

On the drawings:

Figure 1 is a view with parts shown in full view and in 4 sectional elevation taken substantially along the longitudinal axis of rotation of a dryer drum of the present invention;

Figure 2 is a sectional elevational View taken substantially along the line II-Il of Figure 1; and

Figure 3 is an enlarged detail view of the condensate drainage header employed in the practice of the instant invention.

As shown on the drawings:

The reference numeral 10 indicates generally a dryer drum of the present invention including a cylindricalv shell 11 having open ends closed by annular heads 12 and 12a bolted thereto and extending radially thereacross. Each of the annular heads 12 and 12a, respectively, has bolted thereto about its inner periphery an annular journal ring 13, 13a. Journals 15 and 15a are secured, respectively, to the journal rings 13, 13a by a suitable means such as screws (not shown); and the journals 15, 15a are rotatably carried in bearings shown diagrammatically at 16 and 16a. The bearings 16, 16a thus corotatably mount the journals 15 and 15a, the journal rings 13 and 13a, the shell heads 12 and 12a and the shell 11.

The direction and speed of rotation of the shell 11 is controlled by a gear 17 corotatably mounted on the journal 15 anddriven by a drive gear 18 (shown only partially) connected to a suitable source of power in the usual manner of driving dryer rolls.

Each of the journals 15 and 15a is provided with an axially extending bore 19 and 19a, respectively. The bore 19 of the journal 15 receives a concentric conduit 20 which is a heat exchange fluid or steam (and condensate) drainage line. The drainage line 20 is rotatably mounted in the bore 19 and the line 20 is mounted for rotation on bearings 21 carried by a fixed sleeve 22 that is positioned as an axial extension of the journal 15. The sleeve 22 has an inward annular projection 23 carrying sealing strips 24 (formed in an annulus) to receive and position the rotatable condensate line 20 and to seal of the outer extremity of the bore 19 of the yjournal 15. An annular packing strip 25 is also carried by the fixed sleeve 22 mounted at contiguous faces between the sleeve 22 and the journal 15 as a seal permitting relative rotation thereof.

The drainage line 20 extends outwardly beyond the xed sleeve 22 to a fixed union 26 which receives the relatively rotatable drainage line 20 and receives condensate therefrom and disposes of the condensate through a drain line 27 equipped with a valve 27. The drain line 20 is also equipped with a corotatable gear 28 connected to a drive gear 29 (shown only partially), so that the drain line 20 may be rotated relative to the gear driven journal 15 both in speed and direction of rotation.

On the right-hand side of Figure l the mounting shown is generally the same as that shown in the left-hand side, except that the driven gears 17 and 23 are not required and steam is fed into the system from the right-hand side rather than condensate being drained out of the system (as on the left-hand side). Accordingly, elements having the same function as those already described on the left-hand side of Figure l are given the same reference numeral followed by the letter a. It will thus be seen that a fixed sleeve 22a mounts bearings 21a which rotatably receive a steam inlet line 20a. The steam enters the steam inlet line a through a source line 27'a with a control valve 27a therein and a fixed union 26a` The annular bore 19a of the journal 15a receives the steam inlet line 20a.

As those skilled in the art will readily appreciate, the instant invention does not require that the steam or heat exchange iluid be fed into one end of' the shell 11 and taken out from the other end' (as here shown), even though this is the most convenient and advantageous arrangement. It will be appreciated that the steam inlet and condensate drainage lines may be concentric, as shown inrLloyd` Hornbostel U. S. Patent 2,651,ll4,`and thus both lead through the same head in the shell`- 11. In such case, it would be preferable to extend either the steam inlet or the condensate drain line the full. axialv length of the shell 11 so as to simulate the arrangement here shown.

As best shown in Figure 2, the steam inlet line 20a leads into the shell 11 through one of' the heads 12'1zrand` a plurality of radial steam pipes 33 through 44 extend from the steam inlet 20a at the axis of the shell I1 to anY annular steam header 45 adjacent the en d of the shell 11 whereat the head 12a is located. T he radial pipes 33 through 44 are connected to the steam inlet 20a and the annular steam header 45 so as to provide uid communication therebetween. In this respect, it should` be4 noted that it is generally preferable to have the conduit system within the shell 11 formed as an integral part and this may require a change n the con-A ventional dryer drum structure in that one of the heads 12or 12a may be aixed thereto so that it may be more readily removed for maintenance purposes.

A plurality of heat exchange conduits or heat exchange iluid conduits 46 through 57 are mounted adjacent4 (but closely spaced from). the inner periphery ofthe shell 11 longitudinally thereof and in communication with the annular steam header 45 to receive steam therefrom. The conduits 46-57 are peripherally spaced andi. they extend along substantially the entire length of the shell 11 from closely adjacent one head 12a to closely adjacent the opposite head 12. The conduits 46-57.V are secured, to the annular steamheader 45 to form a sturdy structure; and the conduits extend from the steam header 45 to an annular condensate header 58 which is also secured securely to the conduits 46-57. Spent steam, condensate or other heat exchange uid is thus passed from the conduits 46757 into the drainage header 58 which is positioned closely adjacent to the head 12 and the inner periphery of the shell 11.

A plurality of radial condensateV or drainage pipesextend from the drainage line 20 radially outwardly and into the annular drainage header 58; and theonly radial pipes 59 and 60 that can be seen in Figure l are so designated, but it will be appreciated that it is preferable to employ radial drainage-pipes in an arrangement substantially the same as that shown for the radial steam pipes 33-44. Actually, the view of the drainage header 58 comparable to the, view of Figure 2 for the steam header 45 would be substantially identical thereto, except that the condensate header 58 is larger than the steam header 45 and extends radially outwardly a slightly greater distance for reasons which will be explained in the next paragraph.

Referring now to: Figure 3, it` will be seen that the steam conduit 52v feeds generally into the center of the drainage header 58, but the steam conduit 52 is somewhat smaller in size so that the drainage header 58 extends outwardly beyond the steam conduit 52. The radial drainage pipe 60, however, extends into the drainage header 58 radially beyond the steam conduit 52 to closely adjacent the radially outward portion of the drainage header 58. ln this way condensate which may be formed in the steam conduit 52 and has own into the drain header 58 will be thrown by the centrifugal force of the rotating shell 11 against the radially outward portion of the drainage header 58 so as to maintain a condensate level L thereat and the radial condensate pipe 60 extends beneath this level L (which is radially outward from the steam conduit 52) so that the condensate will be continuously removed through the radial condensate pipe 60 and from there into the axial aligned drainage line 20.

It will bel readily appreciated that the relatively small diameters (i. e. up to 20% of the shell diameter) of the steam conduits 46-57 will permit the use therein of steam of much higher pressure than could be used in the form of steam within the shell 11. The conduits 46-57. are preferably parallel units positioned closely to the shell 11 as here shown; but they may also be arranged as helical coils, etc., the main purpose being to supply heat as close to the shell as possible and also to elect agitation by relative rotation with the shell, which will' be explained'. By the use of the instant arrangement, greater heat input ismade possible. In order to transfer thisheat from the conduits 46-57 to the shell' 11 a liquid is maintained' in` the shell 11. The liquid A is held uniformly' against the entire periphery of the shell 11 by centrifugal force so as to continuously maintain a level around the inner periphery of the shell. Preferably the leveli La, is just suicient to submerge the conduits 46-57, since a minimum weight of liquid A is desired;

`Referring again to Figure 1, it will be noted that the liquid A is fed from` a suitable source (not shown) through a valvev 61 and an inlet line 62 carried by the fixed sleeve 22 and extending into the shell through the bore '19 of the journal 15. The liquid A is removed from the shell' I1 through a control valve 63 mounted in a drainage line 64 which extends through the tixed sleeve 2221 through the bore 19a of the journal 15 and' then radially outwardly along the wall 12a to closely adjacent' the shell311 (beneath the level La). A pump 65 may be used to evacuate the liquid A or remove the same from the interior ofA the yshell at a desired rate. Actually, in operation it may not be necessary to continuously add and Withdraw the liquid A; and this is an advantage ofthe instant.l invention because the heat is provided through the steam in the steam conduit system.

The liqu'id A employed is a heat conductor, of course, so that heat may be conductedI readily therethrough. to the shell 11 andi it is also a substantially non-volatile liq- 'uid so that excessive vapor pressure cannot build up Within the drum 11'. A number of relatively non-volatile oils may be used. Relatively non-volatile heat exchange liquids (such as Dowtherm) may also be used; Low

meltingmetals (such as Roses metal) may also be used.

The main requirement is that the liquid A is, infact, a` relatively iluid liquid at the operating temperature soy that it can be maintained against the inner periphery` of theshell 11'in a substantially uniform manner by the centrifugal force generated through conventional rotation of Ithel shell 111 The liquid'A will, of course, be in constant movement against theinner periphery of the shell; but' it'has-been foundthatit is particularlyimportant to effect deliberate agitation of the liquid A. This is accomplished 'by mountingA the steam conduit system for relative rotation with respect' toV the shell 11. Aswill be noted, the lines.; 20- and` 20awhich carry the steam conduit system conotatahly aref mounted for rotation on the bearings 21,-

21a and: driveV means inl the form of the gear system 28, 29,* permit rotation of the conduit assembly at different speeds anddifferent directions` from the speed and direction of rotation for the shell 11. This creates turbulence in the; liquid A; which.: affords heat transfer` through convectiontnather. than-,simply conduction. As shown in'Figure 2, the steam conduit system, indicated generally by the reference numeral S, is rotated in one direction while the shell is rotated in the opposite direction, as indicated -by the arrows. This results in the creation of great turbulence in the liquid A.

Although the heat exchange uid ordinarily preferred for use in the practice of the instant invention is steam because of its availability, it will 'be appreciated that other heat exchange fluids suc-l1 as heated oils, etc. may be employed in the practice of the instant invention.

\I\t w-ill thus be seen that the instant invention comprises a method of heating a dryer drum shell 111 which comprises holding a relatively non-volatile liquid A uni- -formly against the entire inside periphery of the shell 11 with centrifugal force, rotating a heat conductive solid `S (in the form of the entire system, or spec'iiically the conduits 46-57) in the liquid A, and heating the solid S with a fluid such as steam maintained separate and Iapart from the liquid A, or heat-ing the solid S by condensing a uid such as steam thereagainst to heat the same.

It will be understood that modifications and variations may be effected wit-hout departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

il. A dryer drum comprising a cylindrical shell, a head closing each end of the shell, rst means corot-ata'bly mounting said shell and said heads, a steam inlet line leading into the shell through one of said heads, a plurality of steam conduits mounted adjacent the inside Wall of said shell receiving steam from said inlet line, a steam exhaust drainage line leading from the shell through one of said heads receiving steam from said steam conduits, and second means corotatahly mounting said steam inlet line, conduits and drainage line for rot-ation relative to said heads and shell.

2. A dryer drum comprising a cylindrical shell, a head closing each end of the shell, first means corotatably mounting said shell and said heads, a steam inlet line leading into the -shell through one of said heads, an annular steam header adjacent one end of the shell, a plurality of radial steam pipes extending from the steam inlet line to said annular steam header adjacent one end of the shell, a plurality of steam conduits mounted adjacent the in- -side Wall o'f said shell receiving seam from said annular header, .a steam exhaust drainage line leading from the shell through one of said heads receiving steam from said steam conduits, and second means corotatably mounting said steam inlet line, conduits, radial pipes, annular header and drainage line for rotation relative to said heads and shell.

'3. A dryer drum comprising a cylindrical shell, a head closing each end of the shell, -lirst means corotatably mounting said shell and said heads, a steam inlet line leading into the shell through one of said heads, a plurality of steam conduits mounted adjacent the inside wall of said shell receiving steam from said inlet line, an annular steam exhaust header receiving one end of each of said steam conduits, a steam exhaust drainage line leading from the shell through one of said heads receiving steam from said steam exhaust header, Iand second means corotatably mounting said steam inlet line, conduits, steam exhaust header and drainage linefor rotation relative to said heads and shell.

4. A dryer drum comprising a cylindrical shell, a head closing each end of the shell, rst means corotatably mounting said shell and said heads, a steam inlet line leading into the shell through one of said heads, `an annular steam header adjacent one end of the shell, a plurality of radial steam pipes extending from the steam inlet line yto said annular steam header adjacent one end of the shell, a plurality of steam conduits mounted adjacent the inside wall of said shell receiving steam from said Iannular steam header, an annular steam exhaust header receiving one end of each of said steam conduits, a steam exhaust drainage line leading from the shell through one of said heads receiving steam from said steam exhaust header, and second means corotat-ably mounting said steam inlet line, conduits, radial pipes, Iannular headers and drainage line for rotation relative to said heads and shell.

5. A dryer drum comprising a cylindrical shell, a head closing each end of the shell, first means corotatably mounting said shell and said heads, a steam inlet line leading into the shell through one of said heads, a plurality of steam conduits mounted adjacent the inside wall of said shell receiving steam from said inlet line, a steam exhaust drain-age line leading from the shell through one of said heads receiving steam from said steam conduits, second means coroftatahly mounting said steam inlet line, conduits and drainage line for rotation relative to said heads and shell, `and heat exchange iluid inlet and drainage lines, separate and apart from said steam inlet and drainagelines, leading into the shell through at least one of said heads.

References Cited in the le of this patent UNITED STATES PATENTS

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