US2830407A - Blower using slugs of granular material to cut deposits from heating surfaces - Google Patents

Description

R. M. HARDGROVE 2,830,407 anem a: usmc SLUGS OF GRANULAR MATERIAL TO @111 DEPOSITS FROM HEATING SURFACES Filed llay 16, 1955 3 Sheets-Sheet 1 April 15, 1958 dbo INVENTOR RALPH M. HARocRov:

ATTORNEY Apfil 15, 1958 M. HARDGROVE UGS OF GRANULAR MATERIAL CUT DEPOSITS FROM HEATING SURFACES R. BLOWER USING SL Filed May 16, 1955 Sheets-Sheet 2 INVENTOR RALPH M. HARDGROVE ATTORNEY Apnl 15, 1958 R. M. HARDGROVE 2,830,407

BLOWER USING SLUGS UF GRANULAR MATERIAL To CUT DEPOSITS FROM HEATING SURFACES Filed May 16, 1955 3 Sheets-Sheet 3 INVENTOR.

RALPH M. HARDGROVE ATTORNEY United States Patent BLOWER USING SLUGS or GRANULAR MATE-- RIAL TO CUT DEPOSITS FROM HEATING SUR- FACES Ralph M. 'Hardgrove, North Canton, Ohio, assignor to The Babcock '& Wilcox Company, New York, N. Y., a corporation of New .Iersey Application May 16, 1955, Serial No. 508,579

4 Claims. (CI. 51-8) ing relatively hard pellets toward such surfaces to dis- I lodge deposited solids therefrom, the pellets being pressure-fluid-borne to the projection zone. More particularly, the invention is directed to novel mechanism for conveying the pellets from a pellet supply means to the projection zone.

In one important class of tubular heat exchangers, heat transfer is effected by heated gases flowing over the exterior surfaces of metal tubes through which flow relatively cooler liquids or vapors. A typical example is a water tube steam boiler or vapor generator, in which heat from combustion gases flowing over the tubes is used to convert the liquid to vapor and frequently to superheat the vapor. The combustion gases may be further utilized to superheat vapor of a lower pressure, to preheat the combustion air, and to preheat the liquid entering the generator.

The heating gases are produced by the combustion of a suitable fuel, usually coal, gas, or fuel oil, in the presence of combustion supporting air. Depending upon the characteristics of the fuel and upon the combustion conditions, the resultant gaseous products ofcombustion flowing through the gas passes of the heat exchanger carry a certain amount of non-combustibles in suspension. A typical non-combustible customarily present is slag.

As the gases flow over the relatively cooler tubes, the non-combustibles tend to deposit on the tube surfaces. As these deposits build up, they correspondingly reduce the efiiciency of heat transfer from the heating gases to the tubes and, if not removed, may eventually bridgeinter-tube spaces and partially block the gas passes. Hence, it is desirable to remove these deposited non-combustibles either at intervals whose frequency is determined by the rate of growth of the deposits or at regular intervals.

One arrangement for removing these deposits from the tube surfaces involves projecting relatively hard pellets toward the tube surfaces to dislodge the deposited solids therefrom. As the pellets must strike the tube surfaces with considerable force to be effective, a convenient discharge arrangement comprises carrying the pellets to the projection point in a high velocity stream of fluid, such as air, under pressure. At the projection point or zone, suitable means are provided for directing pellets at high velocity in cleaning relation toward the tube surfaces.

The present invention is directed to mechanism for conveying apressure-fluid-borne stream of pellets from a pellet supply to the pellet projection zone. This mechanism comprises a first conduit means, or air conveyor, extending from a point outside the heat exchanger into the pellet projecting and directing means. This conveyor is connected to a source of fluid under pressure. A second conduit means is connected to the first means at a point outwardly, or upstream, of the pellet projecting means and has a portion extending in telescoped, concentrically spaced relation through the first conduit means into the pellet projecting means. A pellet feeding means is connected to this second conduit means downstream of such connection point, and preferably between such point and the telescoped portion, for feeding pellets into the pressure fluid stream confined by the second conduit means for pressure-fluid-borne delivery to the pellet projecting means.

In a preferred form of the invention, a pellet hopper is provided having a discharge trough extending along its bottom and in communication therewith. One end of this trough has a gravity connection to the second conduit means, and a conveyor, preferably of the screw type, extends along the trough to move the pellets to the discharge connection. This conveyor is driven by means mounted outside the hopper and having a driving connection, such as a shaft, extending through a bearing or stufling box mounted externally of the trough. To maintain the pressure sealing of the hopper, a conduit is connected between the source of fluid under pressure and the stuffing box. Preferably, an equalizing connection is provided between the pellet discharge connection and the hopper space above the pellets.

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

Fig. 1 is a partial schematic and partial sectional view of tube cleaning apparatus embodying the invention as arranged in operative association with a portion of a tubular heat exchanger;

Fig. 2 is an enlarged side elevation view, partly in section, of the pellet feeding hopper and its connection to the pellet conveying means and associatedcomponents;

Fig. 3 is a transverse sectional view of the hopper on the line 3-3 of Fig. 2;

Fig. 4 is an axially sectional view of the hearing or stufling box;

Fig. 5 is a sectional view on the line 5-5 of Fig. 2; and

Figs. 6 and 7 are, respectively, side and end elevation views of drive mechanism for reciprocating and rotating the pellet blowing tube, Fig. 6 being partly in section.

Referring to Figs. 1 through 4 of the drawings, the invention cleaning apparatus is illustrated as in operative relation with a tubular heat exchanger 10 comprising a side wall 11 along which extend wall protecting water tubes Hand 13. While the water tubes are generally in uniformly spaced parallel relation along wall 11, a pair of tubes 13 are bent away from each other at a pointalong their length to define a port 14 in wall 11, which port may be referred to as a blower tube port. The portion of the heat exchanger 10 shown in Fig. 1 is comprised between side wall 11 and a tube-formed division wall 15 which may likewise comprise water tubes. In the gas pass defined by wall 11, tubes 12 and 13, and division wall 15, are disposed tubes 16 of a superheater, for example.

The gas flow over the superheater tubes is as indicated by the arrow, and the flowing gaseous products of combustion carry solids in suspension, such as slag particles, unburned fuel particles and fly ash, which solids tend to deposit upon the surfaces of the tubes 12, 13, 15 and 16, particularly the tubes 16. These deposits, if not checked, build up to the point where they may eventually bridge or close the spaces between adjacent tubes and thus obstruct the gas flow through the gas pass. In addition, the deposits on the tube surfaces decrease the efficiency of heat transfer from the heating gas to the tube walls. Consequently, it is important that these deposits be cleaned from the tubes at least periodically.

Fig. 1 illustrates schematically'one type of cleaning arrangement which is effective in cleaning the tube sur- Patented Apr. 15, 19 58 conconnection 38 to a main air'tube telescopedwithin' a blower tube 45 extending into port 14.

Upstream of valve 37, a conveying air line or second conduitmeans41isbranchedolffrommainairline34 at a point 21 and has a portion extending in concentric spaced relationtthrough the air tube 46 to a point in advance of the discharge end of the latter. Air line 41 is centrally supported in air tube 40 by means of radial lugs 44 welded to circumferentially spaced points on line 41 and slidsbly engaging tube 40. A gravity discharge connection 42extends from the end ot trough 27 or screwhousingtoairline4l,wherebypelietsfromtank may be delivered into the stream of pressure air flowing along conveying air tube 41. A pressure equalin'ng connection 43 extends between the discharge end of trough 27 and the tiller neck 22, so that the air pr essures abovethegranularmaterialchargeinthetankfland in the trough 27 at the discharge end of screw are equalized by the tubular connection 43.

a converging bottom formed by sloping side plates 51 welded to side walls 48 and to screw housing 27. Flow restrictors or equalizers 52 extend through and interconnect sloping walls 51.

A cup-shaped member as an over and closes one end of screw housing 27 and supports the sleeve bearing 24 for one end of screw conveyor 25. The latter has a driving shaft 55 extending through an annular end plate 56 (Fig. 4) welded into the opposite end of trough 27. This shaft extends through the stuliing box or bearing 31 'and into the second bearing 29 mounted on an angular moisture separating chamber 65. Conduit 33 interconnects chamber 65 and motor through valve 39.

.0 The hearing or stufling box 31 includes trv sleeve 66 Blower-tubeistelescoped ontubeflsndismounted for axial reciprocation and simultaneous rotation rela-' tive to port 14. Such reciprocation and vr'otation'of tube 45 is provided by asuitable drive mechanism schematically illustrated at and described more fully hereinafter. 'Ihisdrivemechaniam,withthetube45rigidly' attached thereto, is reciprocated axially of the air tube controls are provided for eflecting automatic reciprocawelded to plate 56 and having studs 67 welded thereto and extending longitudinally therefrom. These studsreceive nuts 68 which force a packing flange 70 inwardly through sleeve '66 to compress packing 71 against a ring 15 which in turn presses packing 72 against end plate 56. The ring 75 has a circumferential channel 76 which is in communication with a port 77 in sleeve 66. Air

from line 33 is delivered to port 77 through a threaded I nipple 78, flows into channel 76, and thence through ports 79 to shaft 55. This maintains a pressure seal pressure'from the conduit and trough.

'preventing loss of Thedischargeconnection 42isconnectedtoa1'litting 40 interposed in second conduit means 4land having its end opposite connection 42 closed by an access plug 81.

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

What is claimed is:

1. In combination with means'constructed to project relatively hard pellets to dislodge deposited solids from theexteriortubesurfacesotaheatexchangertubebankcontacted by gases carrying solids in suspension which deposit on such surfaces; mechanism for conveying a high velocity stream of such pellets to such pellet projecting means comprising, in combination, first conduit means extending into the pellet projecting means front/a point spacedfrosnthelattenmeansforconnectingasourceof lluidunderpressuretotheouterendofsaidflrstconduit means for delivery of fluid at high velocityvto the pellet projecting means; second conduit means connected to said first conduit means at a point spaced from such pellet projecting means and extending into said first conduit means; a pressure scalable hopper arranged to receive 1 a supply of the pellets; a conveyor housing extending along the bottom of said hopper and in communication therewith; a gravity discharge connection interconnecting oneend otsaidhousing andsaidsecondconduitmeans downstream of said point for feeding of pellets into the high velocity pressure fluid stream confined by said second conduit means for high velocity delivery of pellets to such pellet projecting means; a conveyor extending along said housing to move the pellets to said discharge connection; conveyor driving means mounted outside said pressureairflowingthroughvtheairmbefiembracing I'lhopperandhousimadrivingconnectionbetweensaid driving means and said conveyor extending through a bearing mounted externally of said housing; and a pressure connection extending between said first conduit means and said bearing.

2. In combination with means constructed to project relatively hard pellets to dislodge deposited solids from the exterior tube surfaces of a heat exchanger tube bank contacted by gases carrying solids in suspension which deposit on such surfaces; mechanism for conveying a high velocity stream of such pellets to such pellet projecting means comprising, in combination, first conduit means extending into the pellet projecting means from a point spaced from the latter; means for connecting a source of fluid under pressure to the outer end of said first conduit means for delivery of fluid at high velocity to the pellet projecting means; second conduit means connected to said first conduit means at a point spaced from such pellet projecting means and extending into said first conduit means; a pressure scalable hopper arranged to receive a supply of the pellets; a screw housing extending along the bottom of said hopper and in communication therewith; a gravity discharge connection interconnecting one end of said housing and said second conduit means downstream of said point for feeding of pellets into the high velocity pressure fluid stream confined by said second conduit means for high velocity delivery of pellets to such pellet projecting means; a screw conveyor extending along said housing to move the pellets to said discharge connection; conveyor driving means mounted outside said hopper and housing; a driving shaft connecting said driving means and said conveyor extending through a bearing mounted externally of said housing; and a pressure connection extending between said first conduit means and said bearing.

3. In combination with means constructed to project relatively hard pellets to dislodge deposited solids from the exterior tube surfaces of a heat exchanger tube bank contacted by gases carrying solids in suspension which deposit on such surfaces; mechanism for conveying a high velocity stream of such pellets to such pellet projecting means comprising, in combination, first conduit means extending into the pellet projecting means from a point spaced from the latter; means for connecting a source of fluid under pressure to the outer end of said first conduit means for delivery of fluid at high velocity to the pellet projecting means; second conduit means connected to said first conduit means at a point spaced from such pellet projecting means and having a portion extending into said first conduit means; a pressure scalable hopper arranged to receive a supply of the pellets; a conveyor housing extending along the bottom of said hopper and n communication therewith; a gravity discharge consection interconnecting one end of said housing and said second conduit means between said point and said portion for feeding of pellets into the high velocity pressure fluid stream confined by said second conduit means for high velocity delivery of pellets to such pellet projecting means; a conveyor extending along said housing to move the pellets to said discharge connection; conveyor driving means mounted outside said hopper and housing; a driving connection between said driving means and said conveyor extending through a bearing mounted externally of said housing; and a pressure connection extending between said first conduit means and said bearing.

4. In combination with means constructed to project relatively hard pellets to dislodge deposited solids from the exterior tube surfaces of a heat exchanger tube bank contacted by gases carrying solids in suspension which deposit on such surfaces; mechanism for conveying a high velocity stream of such pellets to such pellet projecting means comprising, in combination, first conduit means extending into the pellet projecting means from a point spaced from the latter; means for connecting a source of fluid under pressure to the outer end of said first co'n-' duit means for delivery of fluid at high velocity to the pellet projecting means; second conduit means connected to said first conduit means at a point spaced from such pellet projecting means and having a portion extending into said first conduit means; a pressure scalable hopper arranged to receive a supply of the pellets; a screw housing extending along the bottom of said hopper and in communication therewith; a gravity discharge connection interconnecting one end of said housing and said second conduit means between said point and said portion for feeding of pellets into the high velocity pressure fluid stream confined by said second conduit means for high velocity delivery of pellets to such pellet projecting means; a screw conveyor extending along said housing to move the pellets to said discharge connection; conveyor driving means mounted outside said-hopper and housing; a driving shaft connecting said driving means and said conveyor extending through a bearing mounted externally of said housing; and a pressure connection extending between said first conduit means and said bearing.

References Cited in the file of this patent UNITED STATES PATENTS 1,454,979 Muhlfeld et al. May 15, 1923 2,477,334 Hibner et al July 26, 1949 2,497,021 Stems Feb. 7, 1950 2,569,952 Ridley Oct. 2, 1951 FOREIGN PATENT 628,434 Germany Apr. 4, 1936 636,052 Great Britain Apr. 19, 1950 1,088,479 France Sept. 8, 1954

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