US2765588A

US2765588A - Device for uniform distribution of material over a horizontal cross-sectional area of a vertically extending zone

Info

Publication number: US2765588A
Application number: US315798A
Authority: US
Inventors: Puhr-Westerheide Jurgen
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1952-10-20
Filing date: 1952-10-20
Publication date: 1956-10-09
Anticipated expiration: 1973-10-09

Description

Oct. 9, 1956 J- PUHR-WESTERHEIDE 2,765,588 DEVICE FOR UNIFORM DISTRIBUTION OF MATERIAL OVER A HORIZONTAL CROSS-SECTIONAL AREA Filed Oct. 20, 1952 OF A VERTICALLY EXTENDING ZONE 2 Sheets-Sheet 1 INVENTOR Jurgen Puhr-Wrzfarheide ATTORNEY 1956 J. PUHR-WESTERHEIDE 2,765,588

DEVICE FOR UNIFORM DISTRIBUTION OF MATERIAL OVER A HORIZONTAL CROSS-SECTIONAL AREA OF A VERTICALLY EXTENDING ZONE Filed Oct. 20, 1952 2 Sheets-Sheet 2 INVENTOR dzzrgen abr- Wser/zeia/e ATTORNEY DEVICE FOR UNIFORM DISTRIBUTION OF MA- TERIAL OVER A HORIZONTAL CROSS-SEC- IOfiligAL AREA OF A VERTICALLY EXTENDING Jurgen Puhr-Westerheide, Oberhausen, Germany, as-

signor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application October 20, 1952, Serial No. 3155798 Claims. (Cl. 519) T his invention relates to apparatus for distributing material substantially uniformly over a horizontal crosssectional area of a vertically extending zone and, more particularly, to a centrifugal spreader of uniform effective radius operated by driving means effective to periodically vary the angular velocity of the spreader.

While not limited thereto, the invention is particularly adapted to arrangements for cleaning the gas contacted surfaces of tubular heat exchangers. In such exchangers, heat transfer may be effected by heat transfer from relatively hot combustion gases to metal tubes carrying rela tively cooler liquids or vapors. Depending upon the characteristics of the fuel burned to produce the hot gases and upon the efliciency of combustion, the hot gases flowing over the tubes will carry a greater or less amount of fly ash and other solids in suspension, and a proportion of these solids are deposited upon the gas contacted tube surfaces.

The thus deposited solids reduce the efiiciency of heat transfer from the gases to the tubes, and the deposits, if not removed, may build up to an extent sufficient to bridge inter-tube spaces and at least partially block the gas passes. Accordingly, it is desirable to remove the deposited solids either at regular intervals or whenever the deposits have built up to a predetermined extent.

Soot blowing is effective in dislodging the finer deposited solids which have not adhered to the tube surface, but is not effective to remove solidified slag from the surfaces. Various arrangements have been proposed for dislodging the adhering solids, and one effective method is to discharge relatively hard pellets, metal balls, or gravel over the gas contacted tube surfaces. The pellets may be forcibly discharged from nozzles against the tube surfaces or may be distributed above the tube surfaces to fall by gravity thereover.

in the latter case, the pellets are discharged from a centrifugal distributor rotatable about an upwardly extending axis located substantially centrally of a horizontal cross-sectional area over which the pellets are distributed to fall through a substantially vertically extending zone in which the tubular heat exchanger is arranged. In order to secure substantially uniform distribution of the pellets over the horizontal area, the distributor is preferably formed with an involute periphery so that varying redial discharge velocities are imparted to the pellets for uniform distribution thereof over the horizontal area. The pellets may be fed to the distributor through a feed conduit coaxial with the axis of rotation.

Whiie the involute distributor is effective in obtaining substantially uniform distribution of the pellets over the horizontal cross-sectional area, it is subject to mechanical difficulties because of its non-circular form. Due to the unequal radial location of points on its periphery, the involute distributor is not in dynamic balance, thus introducing undesirable stresses on its mounting and driving arrangement. This lack of dynamic balance can be corrected by the use of equalizing or balancing weights attached to the distributor. However, determination of tates atent the mass of these weights and their relative position necessitates a time consuming balancing operation in volving the testing of every involute distributor before the latter is placed in operation.

In accordance with the present invention, a uniform distribution of the pellets over the horizontal crossectional area is effected without the necessity for such dynamic balancing by utilizing a distributor having a circular periphery concentric with its axis of rotation, and driving this distributor at periodically varying angulaf velocities. The driving arrangement is so designed that the time period of operation at any angular velocity is proportional to the value of the angular velocity, thus taking into account the greater area to be covered at larger radii of distribution. At the very low angular velocities the pellets have a very low or substantially zero radial velocity and follow over the central core of the distribution area. With increasing angular velocities, the pellets are given increasing radial velocities so that they are distributed over circular strip areas of increasing radii. With each increase in distribution radii, the area to be covered increases as an exponent of the radius of distribution. Hence, the number of balls distributed must be increased with increasing radii of distribution to achieve uniform distribution per unit of area.

More particularly, the distributor comprises a conical element to which the pellets are fed through a pipe or conduit extending coaxially with the axis of rotation. The distributor is rotated by a constant speed prime mover, such as a constant speed electric motor, which drives the distributor through an infinitely variable or stepless speed changing transmission of the type having a control lever movable to vary the output speed of the transmission. This control lever is provided with a cam follower engaged by a rotatably mounted cam driven at a uniform and constant angular velocity by the constant speed motor. The cam is so designed that the transmission control lever is held in a given speed selector position for a time period proportional to the particular output speed of the transmission.

For an understanding of the invention principles, reference is made to the following decsription of a typical embodiment thereof as illustrated in the accompanying drawing. In the drawing:

Fig. 1 is a central, vertical sectional view through a pellet distribution apparatus embodying the invention;

Fig. 2 is a somewhat schematic elevation view of the driving mechanism for the pellet distributor; and

Fig. 3 is a plan view of one form of driving mechanism useful with the invention; and

Fig. 4 is a side elevation view of the driving mechanism shown in Fig. 3.

The distributor 10 of the invention is mounted, for rotation about a substantially vertical axis, immediately beneath the roof 11 of a substantially vertically extending zone, such as a vapor generator gas pass containing one or more tubular heat exchangers (not shown). For example, 11 may be the roof of the gas pass shown in Fig. 4 of my copending application Serial No. 315,304, filed October 17, 1952.

Distributor 10 is designed to distribute pellets, for example steel balls having a diameter of 3 mm., uniformly over a horizontal cross-sectional area of the vertically extending zone. These balls are delivered to distributor 10 through a pipe or conduit 12 extending coaxially With the axis of rotation of distributor 10.

Pipe 12 is mounted to rotate about its axis in anti-friction bearings 13 supported on a framework 14 mounted on the supporting elements 16 for roof 11. The pipe 12 extends through a jacketing pipe 17 mounted vertically through roof 11, and is guided in a bearing 18 secured in the lower end of a gear housing 15.

Within gear housing is disposed a bevel gear secured on pipe or conduit 12, to rotate therewith, by means of a conical clamping sleeve 21 and a threaded cap 22. Bevel gear 20 is rotated by a bevel pinion 25 meshing with the bevel gear and comprising the output gear of a drive mechanism generally indicated at and described more fully hereinafter. Drive mechanism 30 is suitable supported on the framework 14.

At its lower end, pipe 12 is provided with a downwardly converging frusto-conical pellet delivery nozzle 23. Telescoped onto the lower end of pipe 12, and welded thereto, is a tubular axle or mounting member 24 for distributor 10.

In the illustrated embodiment, distributor 10 comprises a shallow conical disk having radial ribs 26 connecting the disk to tubular member 24. At the apex of disk 10 is a distributing cone 27, and in the space between the base of cone 27 and the inner ends of ribs 26, disk 10 is formed with holes 28 of somewhat larger diameter than that of the pellets. These have the function of distributing the pellets to the zone immediately beneath the apex of disk 10 and substantially on the axis of rotation.

Alternatively, the distributor may comprise one or more radially extending tubes of equal radial length and extending either horizontally or at a small angle to the horizontal downwardly and outwardly.

The driving arrangement 30 for distributor 10 will be best understood by reference to Fig. 2. Output shaft 31 of a constant speed electric motor is connected by a coupling 32 to the input shaft 33 of an infinitely variable or stepless speed-change transmission 40. As schematically indicated at 34, input shaft 33 is connected to drive a rotatable cam 50 at a uniform substantially constant speed.

Transmission is provided with a speed selector and control lever pivotally mounted at 41 on the casing of transmission 40 and constantly biased to the low speed position by a spring 42 connected between one end of lever 45 of the transmission housing. The other end of lever 45 carries a cam follower 43 continuously biased against the cam periphery 51 by spring 42. As cam. is rotated, lever 45 is oscillated back and forth to periodically vary the speed of output pinion 25 of transmission 40, this pinion driving the bevel gear 20. Thus, the angular velocity of disk 10 is correspondingly periodically varied to vary the radial velocity component of the pellets distributed from the disk or distributor, so that these pellets are distributed over narrow circular strips of periodically varying radii to achieve uniform distribution over the selected horizontal cross-sectional area.

Referring more particularly to Figs. 3 and 4, the output worm 34a of transmission 40 drives a worm wheel 34b secured to a shaft carrying the cam 50 on its outer end. Cam 50 continuously engages the end of a rod 43 which is connected to the speed selecting lever 45, so that the speed selecting lever is continuously moved in accordance with the designed periphery 51 of cam 50. Thus, the speed of output bevel gear 25 is continuously varied.

An important feature of the invention is the design of cam 50. The periphery 51 of this cam is so designed that the time period during which lever 45 is held at any selected output speed of pinion 25 is proportional to the value of such output speed. Thereby, the period during which distributor 10 is maintained at any given angular velocity is dependent upon the value of the angular velocity. Accordingly, with increasing areas to be covered at increasing radial velocity components of the pellets, the time period is such that the distribution of pellets per unit of area is substantially constant.

The invention distributor and its associated driving arrangement thus achieve a uniform distribution of the pellets over a given horizontal cross-sectional area of a vertically extending zone without the dynamic balancing and other problems pertinent to involute periphery distributors.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. Apparatus for distributing material substantially uni formly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination a centrifugal distribution disk rotatable about a vertical axis substantially centrally of such cross-sectional area to distribute material in all radial directions from such axis, the peripheral portions of said distributor being equi-radially distant from its axis of rotation; means operable to feed material to said distributor substantially at its center of rotation; and driving means for rotating said distributor constructed and arranged to continuously cyclically vary the angular velocity of said distributor to correspondingly vary the radius of distribution of the material; the circumferential periphery of the upper, material distributing surface of said disk being unobstructed throughout its entire length whereby, when the disk is rotated, material is distributed therefrom in all directions radially of the disk.

2. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a centrifugal distribution disk rotatable about a vertical axis substantially centrally of such cross-sectional area to distribute material in all radial directions from such axis; means operable to feed material to said disk; and driving means for rotating said disk constructed and arranged to continuously cyclically vary the angular velocity of said disk to correspondingly vary the radius of distribution of the material; the circumferential periphery of the upper, material distributing surface of said disk being unobstructed throughout its entire length whereby, when the disk is rotated, material is distributed therefrom in all directions radially of the disk.

3. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a centrifugal distribution disk rotatable about a vertical axis substantially centrally of such cross-sectional area to distribute material in all radial directions from such axis; means operable to feed material to said disk substantially at its center of rotation; and driving means for rotating said disk constructed and arranged to continuously cyclically vary the angular velocity of said disk to correspondingly vary the radius of distribution of the material; the circumferential periphery of the upper, material distributing surface of said disk being unobstructed throughout its entire length whereby, when the disk is rotated, material is distributed therefrom in all directions radially of the disk.

4. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical axis; means operable to feed material to said disk; and driving means for rotating said disk constructed and arranged to continuously cyclically vary the angular velocity of said disk to correspondingly vary the radius of distribution of the material; the circumferential periphery of the upper, material distributing surface of said disk being unobstructed throughout its entire length whereby, when the disk is rotated, material is distributed therefrom in all directions radially of the disk.

5. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical axis; means operable to feed material to said disk substantially at its center of rotation; and driving means for rotating said disk constructed and arranged to continuously cyclically vary the angular velocity of said disk to correspondingly vary the radius of distribution of the material; the circumferential periphery of the upper, material distributing surface of said disk being unobstructed throughout its entire length whereby, when the disk is rotated, material is distributed therefrom in all directions radially of the disk.

6. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical axis; means operable to feed material to said disk substantially axially to its apex; a constant speed driving means; a variable speed transmission connecting said driving means to rotate said disk; speed selector means for said transmission; and a control element driven by said driving means and operatively associated with said speed selector means, said control element cyclically operating said speed selector means to periodically vary the angular velocity of said disk.

7. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially "ertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical axis; means operable to feed material to said disk substantially axially to its apex; at constant speed motor; a variable speed transmission connecting said motor to rotate said disk; speed selector means for said transmission; and a control element driven by said motor and operatively associated with said speed selector means, said control element cyclically operating said speed selector means to periodically vary the angular velocity of said disk.

8. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical axis; means operable to feed material to said disk substantially axially to its apex; a constant speed driving means; a variable speed transmission connecting said driving means to rotate said disk and having a speed selecting lever; and a rotatable cam driven at a uniform angular velocity by said motor and engaged with said lever, said cam cyclically positioning said lever to periodically vary the angular velocity of said disk.

9. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical .axis; means operable to feed material to said disk substantially axially to its apex; at constant speed driving means; a variable speed transmission connecting said driving means to rotate said disk and having a speed selecting lever; and a rotatable cam driven at a uniform angular velocity by said motor and engaged with said lever, said cam cyclically positioning said lever to periodically vary the angular velocity of said disk; said cam being so constructed and arranged that the time period of the lever at a given angular velocity is proportional to the value of the angular velocity.

10. Apparatus for distributing material substantially uniformly over a horizontal cross-sectional area of a substantially vertically extending zone comprising, in combination, a conical centrifugal distribution disk rotatable about a vertical axis; means operable to feed material to said disk substantially axially to its apex; a constant speed driving means; :a variable speed transmission connecting said driving means to rotate said disk and having a speed selecting lever; and a rotatable cam driven at a uniform angular velocity by said motor and engaged with said lever, said cam cyclically positioning said lever to periodically vary the angular velocity of said disk; said disk having holes substantially at its axis for flow of material to the center of said cross-sectional area.

References Cited in the file of this patent UNITED STATES PATENTS 1,764,108 Kennedy June 17, 1930 2,274,172 Swisher Feb. 24, 1942 2,468,712 Kohler Apr. 26, 1949 2,507,166 Lehman May 9, 1950 2,532,136 Zahn Nov. 28, 1950 2,561,258 Wolf July 17, 1951 2,665,118 Broman Jan. 5, 1954