US3217795A - Rotary drum dryer - Google Patents

Description

' Nov. 16, 1965 A. J. CIRRITO ROTARY DRUM DRYER 4 Sheets-Sheet 1 Filed March 24, 1961 Nov. 16, 1965 A. J. CIRRITO ROTARY DRUM DRYER 4 Sheets-Sheet 2 Filed March 24, 1961 Jm/m .vfl m I'm- 9% 4 Q a Nov; 16, 1965 A. J. CIRRITO ROTARY DRUM DRYER 4 Sheets-Sheet 3 Filed March 24, 1961 The present invention relates to improvement in a rotatable dryer, and more particularly, to dryers of the general type comprising a large drum providing an extensive cylindrical heating surface and means for heating said surface.

The demand for dryers of large diameter which will operate at increasing peripheral rates poses serious problems to provide a drum which will have the requisite strength and at the same time heat disseminating characteristics which will provide for efficient operation of the dryer at substantially increased peripheral speeds.

In carrying out the invention, applicant provides a novel and improved drum which is of the required strength to prevent sagging along its length, and is well adapted to contain a heating fluid such as steam at any desired pressure, and which, at the same time, will have substantially improved heat disseminating characteristics to insure an evenly distributed, constant temperature heat dissemination to the drying surface of the drum.

Further in accordance with the invention, the illustrated drum is constructed and arranged to be shipped and to be assembled in the field from a plurality of sections which are fitted together in a manner to provide an unbroken, uniform peripheral surface well adapted for the even dissemination of heat.

A feature of the invention consists specifically in the construction and assembly of the rim of the drum from a plurality of transverse sections, each of which is cored to form ducts within the rim extending parallel to the axis of the drum and spaced at intervals around the circumference of the drum. This construction is particularly adapted to provide a cylindrical rim for the drum which combines the required strength and, at the same time, the desired heat disseminating qualities of an efficient dryer.

Further in accordance with the invention, the individual sections of the drum and, more particularly, the rim portions thereof, are provided with end surfaces of which the outer edges and adjoining faces extending inwardly of said edges lie in a plane normal to the axis of the drum and are closely fitted to one another, so that the transfer of heat radially outwardly from the ducts to the surface of the drum will take paths parallel to the said end surfaces to insure a uniform distribution of heat across the joined ends of the drum sections.

To make the shell surface more resistant to wear or to develop surface characteristics particularly applicable to specific materials which are to be dried or otherwise processed such as applying a machine glaze to paper or drying a coating which requires a cast surface, it will be necessary to coat or plate the drum surface after assembly with chrome, ceramic or other pertinent material.

In those cases where the base metal of the shell is adequate surfacewise and it is desired to preserve an unbroken metallurgical surface across the section joints, it is only necessary to machine a small kerf symmetrically oriented at the joint for about a Ms" seal weld around the rim which will be machined, ground and polished to blend in with the entire shell surface in the final grinding operation after assembly.

In the preferred form of the invention shown, the ducts, which are in line with one another from section to section, are provided with liners in the form of copper rates atent pipes which extend from one end of the drum to the other within said ducts and which are expanded under pressure against the walls of said ducts into an intimate contact with the walls of said ducts. In this manner, full advantage is taken of the very high thermal conductivity of the copper piping to insure a maximum transfer of heat from the heating fluid, which may be steam, through the copper into the surrounding material of the rim, and thence radially to the external periphery of the drum.

It will be understood that liners of material other than copper having preferably a high thermal conductivity may be used. It will be understood also that the use of such liner is of advantage to prevent the possibility of escaping steam at the joints of said sections.

The liners constructed of copper or other material having a high conductivity characteristic have been found to be of particular advantage in that they substantially improve the circulation and dissemination of heat during the continued operation of the drum. It has been found, for example, that in drum structures which do not have tubes, or which have tubes of a conductivity comparable to that of the main shell, the condensate orientation in the tubes due to continuity and centrifugal force develops a resistance to heat flow from the steam to the dryer surface which is non-uniform in the axial direction. The condensate resistance thus manifested also makes it difficult to predict or achieve heat transfer uniformity circumferentially. Variations in the depth or thickness of the condensate stream is very substantially offset by the use of liner tubes of high thermal conductivity, which in the case of copper is in the order of 500 times that of water, so that the heat flow is around the condensate rather than through it. It will be understood that liners may be provided which are formed by coating or cladding the internal surfaces of said ducts with copper or other material having a high thermal conductivity.

Further in accordance with the invention, it is proposed to provide headers at each end .of the drum, each having at least two circumferential conduits, one of which serves as an inlet conduit and the other as an exhaust conduit. Another embodiment consists of an alternating arrangement of the apertures extending lengthwise to the drum, so that steam is introduced at one end of the cylinder through the appropriate inlet conduit and is passed through alternate apertures to the associated exhaust conduit at the other end of the cylinder, and steam is similarly introduced to the opposite end of the cylinder through the inlet conduit at said opposite end of the drum and is passed in the reverse direction through the intermediate apertures to the exhaust conduit at the first mentioned end of the drum, thus further offsetting any tendency toward uneven heating which may result from the building up of a condensate gradient in the system.

In the drawings,

FIG. 1 is an isometric view of the drum in the form of a Yankee dryer for drying paper;

FIG. 2 is a longitudinal vertical sectional view through the drum of FIG. 1 taken on line 22;

FIG. 3 is a fragmentary end view partly in section of a portion of the :drum shown on FIG. 2 as indicated by line 3-3;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 3;

FIG. 5 is a view similar to FIG. 3, but taken at the other end of the drum as indicated by line 5-5;

FIG. 6 is a sectional view taken on line 66 of FIG. 5;

FIG. 7 is an end view of a modified drum;

FIG. 8 is an end view of the other end of the modified drum of FIG. 7;

FIG. 9 is a view taken on line 9-9 of FIG. 7;

FIG. is a similar view taken on line 101tl of FIG. 8;

FIG. 11 is an enlarged view taken on the arc ll1-11 of FIG. 7 indicating direction of flow in that embodiment;

FIGS. 12 and 13 are views similar to FIGS. 4 and 6 of this modified form of the invention;

FIG. 14 is an enlarged section of the juncture between two rim sections illustrating a modified form of seal therebetween; and

FIG. 15 is a similar section illustrating another modification in which a coating has been applied to the peripheral surface of the drum.

Generally speaking, the purpose of the invention is to provide a heat-exchange revolving drum in which the heating is accomplished by passing steam through a large number of longitudinally extending ducts located close to the surface of the drum rather than filling the entire interior of the drum with live steam with the consequent advantages of stronger construction and safety. Additionally, the arrangement permits the drum to be assembled from essentially identical sections into a drum of any desired longitudinal dimension. Steam or other heating fluid is admitted through a trunnion and the condensate is removed in the same Way.

Turning to the drawings, the assembled sectionalized drum is indicated generally by the numeral made up of circular sections 20a, 20b, etc. Each section comprises a circular rim. Spoke supports are shown joining the end rims to the trunnion. The rim is provided with a sideby-side series of longitudinal cored ducts 22 which are in registry when the sections are assembled. Steam is introduced through the conduit 24- through a trunnion 26. The steam passes from the central duct through pipes 28 into conduits 30 in the end spokes 32. Thence the steam is allowed to enter a circular conduit 34 which is located at one end of the drum assembly. The duct 34 communicates with the passages 22 so that steam can pass therethrough fro-m left to right as seen in FIG. 2. Condensate will collect in the similar channel 36 at the other end of the drum, and it is removed through siphons communicating through pipes 40 with the condensate line 42.

Preferably, the ducts 2 are lined with copper or some other highly heat-conductive material so that heat will be conducted most rapidly to the surface of the drum. This copper tubular lining is indicated by the numeral 44 in FIGS. 3-6. The communication between the conduit 30 and the annular channel 34 is provided by the short lengths of piping 46 visible at the top left of FIG. 2 and as shown in FIG. 3.

Thus, in the forms of the invention shown in FIGS. 1-6, it will be seen that the steam which is under high pressure is confined in relatively small tubes so that rupture would not mean an explosion. Secondly, the tubes are located near the surface of the drum so that the heat can transfer most readily to the heating surface thereof. Furthermore, the thickness of material between the ducts 22 and the surface of the drum is at a minimum because it is not necessary to confine a large volume of high-pressure steam inside the drum. Furthermore, due to the arrangement for withdrawal of condensate, the condensate does not form a layer between the heating medium and the outer shell which is the case in prior art dryers. This again improves heat-conductivity.

The construction of the drum from a series of similar transverse sections has substantial advantages in that a relatively thin cast ri-m may be employed which is cored and/or drilled to provide heat disseminating ducts which are placed in close proximity to the outer peripheral surface of the drum. The individual sections are restricted to a width, preferably under three feet, within which satisfactory coring or drilling of the casting can be carried out. The method here carried out of constructing a drum from a number of substantially identical transverse sections each having its own flanges and outer rim which is cored or drilled to form longitudinal ducts adapted to be aligned with the cored ducts of adjoining sections permits of substantial flexibility in length of drum, ease of assembly, and ensures maximum strength and durability. Furthermore, this permits shipment of the device broken down to the place where it is to be used. There the sections are assembled and the exterior surface ground to the necessary high polish. This is an important consideration because when the drum is used as a Yankee dryer it may be a very substantial diameter and there is a shipping problem unless the drum can be broken down into smaller parts.

FIG. 14 illustrates a modification of the invention in which a seal weld of the same material as the rims is formed between the peripheral edges of abutting rims. A small kerf which may be As in width is cut between the abutting end surfaces :at the peripheral edge thereof, a weld 47 is formed in the groove thus for-med, and the peripheral surface is ground to form a smooth unbroken surface of the same metal throughout.

FIG. 15 illustrates a further modification of the invention in which a coating 48, which may be of any desire-d material such as chrome, or a ceramic or other material suitable to the particular process being carried out, is applied to the peripheral surface of the drum.

In the embodiment of the invention shown in FIGS. 7 and 8 each of the several circular conduits is divided up into quadrants which are sealed off from one another (see FIGS. 7 and 8). The conduit 50 is thus separated into conduits 50a, 59b, 50c, and 50d, and conduit 52 is similarly separated int- o conduits 52a, 52b, 52c and 52d. Four separate steam lines 30a, 30b, 30c and 30d supply steam from the main inlet 24 to the respective quadrants 50a, 50b, 500 and 50d. At the opposite or right hand end of the drum, four steam lines designated at 54a, 54b, 54c and 54d supply steam to the segmental circular conduits 52a, 52b, 52c and 5201, respectively. Each quadrant of the circular conduit 50 is connected with alternate apertures 56 through which steam passes to the circular conduit 36 at the opposite or right hand end of the drum which in this embodiment of the invention is connected with exhaust line 42 by means of four outlet pipes 58 spaced one in each quadrant of the drum.

Each of the segmental circular conduits 52a, 52b, 52c and 52d at the right hand end of the drum is connected by means of the intermediate apertures 60 with the circular conduit 34 at the left hand end of the drum. Outlet pipes 62 spaced one in each of the four quadrants of the drum connect the conduit 34 with the exhaust line 42.

Steam introduced into the segmental conduits 50a, 50b, 50c and 50d can travel through alternate apertures 56 to the circular conduit 36 and outlet pipes 58 to exhaust. Steam introduced into segmental conduits 52a, 52b, 52c and 52d can travel in the opposite direction through intermediate apertures 60 to the circular conduit 34 and thence through outlet pipes 52 to exhaust. With the arrangement described and as shown in detail in FIGS. 11 to 13, a very even distribution of the heating medium is achieved and with a minimum tendency to build up a serious condensate resistance in the system.

Both embodiments show steam being introduced through the spokes. This is to insure the spokes heating up substantially as the remainder of the cylinder thereby minimizing thermal stresses due to differences in expansion due to heating. This means is well known to those versed in the art. Alternately, other supporting means may be considered between the trunnions and the rim such as disc ends with independent external piping for steam supply and condensate removal. The headers 34 and 36 may also be substituted for by external piping. In every case proper consideration must be given to the design to in sure minimal thermal stresses.

In all cases the rims discussed so far are cast. However, rolled and welded rims with welded-on flanges would serve as well. The weldments, like the casting, would to finally machined after stress relieving for accurate assembly.

The invention having been described, what is claimed is:

1. In a rotatable dryer, the combination of a large rotary drying drum comprising a series of axially integrated transverse cylindrical sections each section comprising a rim having an external drying surface and provided with a series of ducts each parallel to the axis of said drum spaced about the circumference of the rim, and the ducts of adjoining sections being disposed in alignment to provide a series of ducts extending the full length of the drum, a liner pressed into intimate contact with the walls of each duct, each said liner extending continuously from one end of the drum to the other, a header at each end of the drum each having two circumferential channels, one inlet and one exhaust channel at oppostie ends of the drum being connected with the ends of alternate liners to form one steam circulating system, and one inlet and one exhaust channel at opposite ends of the drum being connected with the ends of intermediate liners to form a second steam circulating system, supply connections to each said inlet channel for supplying a heating medium to one said steam circulating system at one end of the drum and to said other steam circulating system at the other end of the drum.

2. In a rotatable dryer, the combination of a large rotary drying drum comprising a series of axially integrated transverse cylindrical sections each section comprising a rim having an external drying surface and a series of ducts each parallel to the axis of said drum spaced about the circumference of the rim, and the ducts of adjoining sections being disposed in alignment to provide a series of ducts extending the full length of the drum, a liner pressed into intimate contact with the walls of each duct, each said liner extending continuously from one end of the drum to the other, a header at each end of the drum having a circumferential exhaust channel, and in each header a series of segmental circumferential supply channels, selected liners being connected between said supply channels at one end of the drum and the exhaust channel at the other end of the drum and intervening liners being connected between said supply channels at the other end of the drum and the exhaust channel at the first mentioned end of the drum.

3. A rotatable dryer having, in combination a rotary drying drum comprising a series of cylindrical axially abutting rim sections, each said rim section having annular end interface contact surfaces axially integrating said r-im sections with each other, ducts extending longitudinally through each of said rim sections at circumferentially spaced intervals about the periphery thereof, the corresponding ducts of the several sections being in alignment with each other to form continuous passageways extending the length of the drum, one piece liner tubes within the ducts having an intimate heat transmitting contact with the walls thereof and extending the full length of said passageways, and heating medium supply and exhaust connections for passing a heating medium through said liner tubes comprising headers at each end of said drum connected with opposite ends of the respective liner tubes.

References Cited by the Examiner UNITED STATES PATENTS 543,051 7/1895 Phillips -a 88 544,782 8/1895 Bragg 16589 550,988 12/1895 Mandot 16589 695,041 3/1902 Fues 16589 1,675,274 6/1928 Miller 34-424 1,781,378 11/1930 Feeney 16590 1,899,256 2/1933 Brannen 16590 2,015,747 10/1935 Drake 165-9O 2,661,545 12/1953 Messinger 34-124 2,707,096 4/1955 Koopmans 165180 X 2,821,772 2/1958 Billetter 29157.3 2,932,091 4/1960 Day 34-124 2,974,404 3/1961 Humenik et al. 29-157.3

CHARLES SUKALO, Primary Examiner.

HERBERT L. MARTIN, PERCY L. PATRICK, FRED- ERICK L. MA'ITESON, ]R., Examiners.

Claims (1)

1. IN A ROTATABLE DRYER, THE COMBINATION OF A LARGER ROTARY DRYING DRUM COMPRISING A SERIES OF AXIALLY INTEGRATED TRANSVERSE CYLINDRICAL SECTIONS EACH SECTION COMPRISING A RIM HAVING AN EXTERNAL DRYING SURFACE AND PROVIDED WITH A SERIES OF DUCTS EACH PARALLEL TO THE AXIS OF SAID DRUM SPACED ABOUT THE CIRCUMFERENCE OF THE RIM, AND THE DUCTS OF ADJOINING SECTIONS BEING DISPOSED IN ALIGNMENT TO PROVIDE A SERIES OF DUCTS EXTENDING THE FULL LENGTH OF THE DRUM, A LINER PRESSED INTO INTIMATE CONTACT WITH THE WALLS OF EACH DUCT, EACH SAID LINER EXTENDING CONTINUOUSLY FROM ONE END OF THE DRUM TO THE OTHER, A HEADER AT EACH END OF THE DRUM EACH HAVING TWO CIRCUMFERENTIAL CHANNELS, ONE INLET AND ONE EXHAUST CHANNEL AT OPPOSITE ENDS OF THE DRUM BEING CONNECTED WITH THE ENDS OF ALTERNATE LINERS TO FORM ONE STEAM CIRCULATING SYSTEM, AND ONE

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