US2545917A - Drainage device for drum driers - Google Patents

Description

March 20, 1951 J. c. cowu-z DRAINAGE DEVICE FOR DRUM DRIERS Filed July 19, 1948 2 Sheets-Sheet 1 INVENTOR Jfl/VfS 6.601405,

ATTORNEY S R E I R D Em m wF w I w J D E G A N I m D March 20, 1951 2 Sheets-Sheet 1 Filed July 19, 1948 INVENTOR ATTORNEY Patented Mar. 20, 1951 DRAINAGE DEVICE FOR DRUM DRIER/S James. C. Cowie Liverpool, Nova Scotia, Canada, assignor to Mersey Paper Company, Limited, a corporation of .Nova Scotia, Canada 1 Application July 19, 1948, 'Serial'No. 39,422

. In Canada July 15, 1948 .14 Claims.

1 iinventionris directed to improvements in rotatable drum .driers. The improvements are particularly directed to the :removal of water which :forms as a condensate in steam-heated driers :and the :removal of surplus water in'the type of apparatus .known :as' sweat :driers.

1The1efiicient removal of water which collects in such rotatable cylindrical driers has been .a problem that has faced designers and operators or driers of this type for many :years. In steamheated drier-s the steam, on cooling, condenses to water vapour whichcollects at the lowest point on the vcircumference f the drum. .In the sweat type of drier, cold water is forced against the inner peripheral walls of the cylinder and the surplus drains to the lowest pointiof the'cylinder and must be removed. Unless .such water is removed continuously, erratic operation of the equipment occurs coupled with excessive consumption of power.

The insulating efiect of a film of water which is usually'created by the action'of centrifugal force on the inside-of the walls of the drier decreases the transference of heat through the drier walls withconsequent lowering'of the thermal tefiiciency of theequipment.

Rotatable driersof this type usuallyconsist-of ahollow cylinderof greater length than the diameter. The drier is customarily arranged to rotate aboutzan axis which is coincident'with the major axis of the cylinder. ,Mechanical means customarily actuated by electric motors provides rotation-to the drum. Where it is desired to use the equipment for the purpose of drying, heat'is supplied to the interiorof the cylinder and the material to be dried which is usually in the form of 'a;pulp=or thin film is passed over the external periphery-of thesoylinder. In some :cases equipmer t-of thisnature is used with the flow of heat reversed, that is, a cold:medium :is forced against the internalperipheral walls in order thatthe material {73117319111011 the outside 'of the drum may be "chilled. Drum driers of this .latter type are .used xinJ-manyindustries but have a particular application in the manufacture -of paper. When to remove the ".water -which zcollects :in a pool at the-dearest :pointpntthezcircnmference10f the. shell has been common for many years. isiphonshave noltbeen'generallyrsuccessful asit has been'f-ound that the water does not collect in sufficient-volume or :under :suitable conditions to enable :the siphon to remove the water "in-a continuous stream. It-is well mecognized that eunlesstheflow of liquid is continuous through a siphon that theLdeviceawill ndt;function .efiiciently.

The centrifugal force created the "rotation of "the :drier tends :to draw the condensate water up the inner wall of thedrumpin the'direction'of rotation. Untilthe angular 'velocity :of thexdrum reaches .a critical -;value i the vmass :of water will not :form a continuous film :.b.ut will slip and =return to the lowest ;point on the circumference. When :the angular velocity increases andpasses a specific critical figure which depends upon several variables'iin'cluding the size of the :cylinder, the:.mass of water will nolonger slip but :will form :a continuous ifilm. The formation of this continuous film :provides distinct advantages in the operation of a drum drier. :The changefrom amoving mass of water toa continuous film, materially reduces the consumption :of :power :by avoiding :the necessity of raising periodically'the mass .of water. vAttempts have been made 'to produce a continuous 'film at lower angular-velocities of the drier by mechanical attachments within the drum :in :order to reduce "the power load.

".There is, however, a serious disadvantage to be considered in connection with the formation of the continuous film of water inside the drum. Although the power consumption is materially lessened when thefilm is formed-the consumption of steam is .not decreased, but tends totincrease. This increasein steam consumption is'due to the insulating effect'of the water film to the transfer of heat from the interiorto the exterior of the shell. ,It is a further object of this invention to provide means for the removal of condensate water from drum driers in such a manner that the-consumption of heat units is decreased along with decreased power consumption.

It.-is an additional object not this invention to provide a- -rotatable drum drier :in which the film of. moisture on the internal walls .is of such small magnitude that it presents little or no'insulating effect .to Y the passage of .heat either :from the ,interior outwards .or ;from the outside to the .interior of the drum.

.The above objects and other desirable objects are accomplished by the novel means constituting :thisinvention. .In this :inventioma conventionalisiphonzis usedforthe actual removal of the water and in addition a stationary blade or scraper is suspended within the interior and ap-- proximately parallel to the longitudinal axis of the drier. The scraping edge of the blade is closely fitted to, but does not actually contact the internal peripheral wall of the drier. This blade improves the drainage of the water from the drum in two ways, first, it prevents the formation of a film of water and the gathering of excessive amounts of water in one place; and secondly, the blade directs the water collected, in an efficient manner, to the siphon device whereby the latter device may work efiiciently.

In the accompanying drawings the invention will be more fully described along with the fol lowing detailed description with reference to preferred embodiments of the actual invention.

Figure 1 represents a side elevation of the drum in section when used as a heat type drier.

Figure 2 is an end elevation in section along the line AA of Figure 1.

Figure 3 is a plan view in section of the drier of Figure 1.

Figure 4 is a side elevation in section of another embodiment of the invention.

Figure 5 is an end elevation on the line BB of Figure 4.

Figure 6 is a plan view in section of the embodiment of the invention shown in Figure 4.

As the invention pertains to drainage devices for use in association with rotary drum driers the actual construction of the drier itself will not be described in detail herewith except for those portions which are pertinent for a proper understanding of the invention.

In Figure 1 the drier is shown generally by the numeral I3 and consists of a cylindrical shell I I which has a hollow interior i 2. Closure means I3 serve to close the ends of the cylinder and to provide, in addition, bearing surfaces for the drier when it rotates about a longitudinal axis on shafts I l. Driers of this type are usually mounted on trunnions, not shown in the accompanying drawings, and are rotated by conventional means well known to those skilled in the art. Accordingly the description of the invention will not be encumbered by the inclusion of these well known details.

Extending through the centrally disposed longitudinal supporting shafts I4 is a stationary pipe I5 which runs the full length of the drier. The pipe I 5 normally carries steam to supply heat to the internal walls of the drier. Suitable holes I5 are provided throughout the length of the pipe I5 to permit steam to escape into the interior of the drier shell. Also running axially through the shaft I4 is a pipe I6 which extends radially within the drier and terminates in the siphon IT which functions to drain water from the shell. The opening in the siphon is in close proximity to the inner periphery of the drum. This siphon operates in a similar manner to other siphons used in analogous arts to drain water from one level to another.

Suspended from the steam pipe It by hangers or support arms I8 is a longitudinal scraper blade I9 which does not move in relation to the drum. The longitudinal axis of the scraper blade i9 coincides with the longitudinal or major axis of the drier shell at one end of the shell but diverges towards the other end of the shell by a horizontal angle in the neighbourhood of 3 degrees. This divergence of the scraper blade is clearly shown in Figure 3 of the drawings. The siphon I1 is disposed at one end of the drier a d arranged in a vertical plane which extends through the geometric centre of the drum.

The scraper blade I 9 and the siphon I! are arranged to be stationary when the drier shell rotates. The siphon I I is usually disposed immediately in front of the scraper blade at one end of the drier shell. The two elements are arranged in such a manner that the siphon pipe is on the leading side of the blade. The leading edge of the scraper is that edge which faces counter to the direction of rotation of the drum.

By arranging the scraper blade with the longi tudinal axis diverging from the longitudinal axis of the drier shell, as described above, water scraped from the internal peripheral walls of the shell is led towards the collecting point The materials used in constructing the drum drier, and the features of the drainage system constituting the invention, have not been enumerated in this description as they will obviously depend upon the decision of the designer for each particular application and in addition, because the proper functioning of the invention is not attributed to any particular material of construction other than materials which would obviously be unsuitable for this type of apparatus.

In operation, the drier is heated by means of steam entering through pipe I5 into the interior of the drier and the drier rotated at the speed which has been found most suitable for the particular drying operation. The material to be dried is then flowed upon the exterior of the drum I 0 which may be covered with felt or other foraminous material as is well known to those skilled in the art. Condensate water from the cooling of the steam collects upon the internal walls of the shell and tends to flow to the lowest point on the periphery of the drum. The scraper blade and siphon pipe are arranged at the lowest point on the circumference of the shell which is the point where there will normally be the greatest volume of water. The elements constituting this invention are as previously described. arranged in such a manner that water carried by the rotating shell will be exposed to the col-' lecting and removing action of the blade and siphon. The water collected by the action of the blade I9 flows along the length of the blade and is removed from the shell by the siphon pipe I'l- In previous devices designed to drain water from the interior of the shell and incorporating a siphon, it was found that there was undue tur-'- bulence in the water which caused erratic operation of the siphon. The present invention directs the water to the mouth of the siphon and provides a pool of water with much less turbulence than is normally experienced.

In the other embodiments of the invention shown in Figures 4, 5 and 6 the drier is adapted to be used as a sweat drier which has a particular application in the paper industry. The drier itself is constructed in a similar manner to that described above and the pipe I5 is now used as a means rev supplying cold water which passes out of-jets l5 and. is forced against the internal walls of thev drier. In this type of drier; it will besobvious, that large quantities of water must housed in, order toadequately cool the walls of the drier. The adequate removal of these large quantities. of water which accumulate within the drier is one of the problems which is solved. by the use of this invention. A, specific embodiment of the invention applied to a sweat drier is illustrated in. Figures 4,5 and 6'.

In, this particular embodiment two siphons H are .used which are located near the ends of the drum. The scraper blade l9 which in'this embodiment of the invention consists of two segments which are mounted in such a manner that they diverge from a position close to the siphons 11 towards the centre in an arcuate manner as clearly shown in Figure 5. The amount of divergence of each section of the blade is approximately 3 degrees. Other than the specific differences immediately pointed out the scraper blade is constructed in the manner similar to that used in the first described embodiment and functions in a similar manner to scrape or break the film of water formed by centrifugal force on the in.- ternal peripheral walls and to lead the water to the siphon pipes i1.

Tests have been conducted on full-sized driers and have shown that the invention operates to adequately remove condensate water from the interior of the driers of the type described. It has been found that the film of water formed on the interior walls of the shell by the action of centrifugal force is broken up by the action of the scraper blade to such a degree that there is only a perceptible wetness on the walls of the shell after any particular section of the wall has passed the blade. As mentioned above, the blade is positioned in such a manner that turbulence in the collected water is minimized and consequently the siphon operates in a much more continuous manner than siphons in previously known driers. It should be stated here that the action of the siphon in removing water is assisted in the steam-heated drier by the differential pressure created by the pressure of steam within the shell and in the sweat type of drier by air forced into the interior of the shell.

In tests conducted on a drier that normally had a water load of about 100 lbs. it was found that this water load was practically eliminated when the drier was equipped with the present invention.

The elimination of the water load and the breaking up of the film formed on the internal peripheral walls by centrifugal force contributes materially to the efiiciency and economy of the operation of rotating drum driers. The elimination of the water load decreases the power necessary to rotate the drier and in addition removes the periodic surges which were imposed upon the driving mechanism of driers in use prior to this invention. Because the accumulation of large masses of water within the drier is prevented, it is no longer necessary to maintain steam pressure in a drier which is not operating in order to evacuate water through the siphon. A beneficial result of this procedure is to eliminate the burning of the felts on the exterior of the drier which had been a common experience in the past. The elimination of the normal film of water caused by centrifugal force obviously reduces the insulating effect previously experienced, and automatically increases the heat efficiency of the drier. A reduction in the amount ofheat' units that have to be supplied to the drier in order to achieve efficient drying is also experienced".- In this connection, it has been found that the tem perature at which the drier operatescan be materially reduced because of the greater heat transmission through theshell of the drier.

Consequently, it will be apparent that by the use of this invention the operation of driers of thetype described with particular application to the paper-making industry results in increased efficiency and more economical operation. In addition, because of the removal of the heavy starting load experienced with conventional equipment due to the mass of water within the drum, smaller driving equipment both of an electrical and mechanical nature could be used.

The invention has been described with particular reference to the use of driers in the paper industry but it is obvious that driers of the same type which are being used in other industries could be adapted to use the drainage system of this invention with beneficial results.

I claim:

1. In a drier, a hollow horizontal shaft, a rotating drum mounted to turn about said shaft, means to feed steam to the interior of said shaft, means for evacuating Water therefrom comprising a stationary siphon extending radially of the interior of the drum, the radial extremity of the siphon being in close proximity to the inner periphery of the drum substantially at the bottom thereof, and means for removing water from the internal drum wall and directing it to the radial extremity of the siphon comprising a stationary blade past which the drum rotates extending longitudinally and carried by said shaft in close proximity to the surface of the inner wall of the drum substantially at the bottom thereof, the blade being disposed at a horizontal angle of about three degrees to the major axis of the drum, the portion of the blade remote from the siphon being displaced angularly in the direction opposite the direction of rotation of the drum with respect to the portion of the blade adjacent the siphon, the radial extremity of the siphon being on the side of the blade towards which the drum rotates, and the vertical plane perpendicular to the drum axis through the radial extremity of the siphon intersecting the blade.

2. In a drier as claimed in claim 1, said blade being disposed at an angle of about twenty degrees from the vertical.

3. In a drier, a hollow horizontal shaft, a rotating drum mounted to turn about said shaft, means to feed steam to the interior of said shaft, means for evacuating water therefrom comprising stationary siphons extending radially of the interior of the drum, the radial extremities of the siphons being in close proximity to the inner periphery of the drum substantially at the bottom thereof and at opposite ends thereof, and means for removing water from the internal drum wall and directing it to the radial extremities of the siphons comprising stationary blade parts carried by said shaft past which the drum rotates extending longitudinally and in close proximity to the surface of the inner wall of the drum substantially at the bottom thereof, the blade parts being disposed at a horizontal angle of about three degrees to the major axis of the drum, the central portions of the blade parts remote from the siphons being displaced angularly in the direction opposite the direction of rotation of the drum with respect to the portions of the blade parts 7 adjacent the siphons, the radial extremities of the siphons being on the sides of the blade towards which the drum rotates, and the vertical planes perpendicular to the drum axis through the radial extremities of the siphons intersecting the blade parts.

4. In a drier as claimed in claim 3, said blade parts being disposed at an angle of about twenty degrees from the vertical.

- JAMES C. COWIE.

REFERENCES CITED .The following references are of record in the file of this patent:

Number 8 UNITED STATES PATENTS Name Date Hunting Jan. 22, 1901 Dodge Feb. 6, 1917 Kingsley Apr. 18, 1922 Gladin Feb. 12, 1924 Wyld Dec. 30,1924 Harrison May 15, 1928 Sandwell Mar. 7, 1939 FOREIGN PATENTS Country Date Number Great Britain 1914

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