US2937050A - Apparatus for conveying solid granular material - Google Patents

Description

May 17, 1960 L. W- YODER APPARATUS FOR CONVEYING SOLID GRANULAR MATERIAL Filed Feb. 29, 1956 3 Sheets-Sheet 1 FIG.1

' so P 61 32 2o i 51 if E II 13 34-J INVENTOR.

Lloyd W. Yoder AT TO RNEY y 1960 w. YODER 2,937,050

APPARATUS FOR CONVEYING SOLID GRANULAR MATERIAL AT TORNEY May 17, 1960 14w. YODER 2,937,050

APPARATUS FOR. EDFWEYING SOLID GRANULAR MATERIAL Filed Feb. 29. 1956 3 3 INVENTOR. Lloyd W. Yoder ATTORNEY United States Patent APPARATUS FOR CONVEYING SOL GRANULARMATERIAL Lloyd W. Yoder, Alliance, Ohio, assignor to The Babcock & Wilcox Company, New York, N.Y., a, corporation of New Jersey Application February 29, 1956, Serial No. 568,613

1 Claim. (Cl. 302-53) the solid granular material over the gas swept heat ex change surfaces.

In heat exchange apparatus such as, for example,

. vapor generating units fired byash containing fuel, it has been customary to utilize high pressure blowers to remove the dust accumulations from the gas-swept surfaces of the heat exchange elements. In recent years, cleaning of the surface hasbeen accomplished by the use of shot, or other solid particle form or granular materials, which is cascaded downwardly over the heat exchange surfaces with the impingement of the shot on the surfaces removing the dust accumulations. In shot cleaning systems, the shot is recycled and periodically introduced into the upper portion of the housing enclosing the heat exchange elements so that the shot is distributed over the entire cross-sectional area of the heating gas pass. Customarily the gravitation movement of the shot is concurrent with the movement of the heating gases over the heat exchange elements of the unit, although counterourrent or transverse gas flow may be used. Since shot may have an errosive eifect on the heat exchange elements if the impact velocity'of the shot is excessive, it is desirable to provide means for maintaining the initial velocity of the shot to a minimum value in initially contacting the heat exchange elements. It is also desirable to separate the dislodged dust. and ash from the shot before the shot is returned to the heat exchange elements for cleaning purposes.

In accordance with my invention, I provide a novel form of check valve which is positioned in a closed conduit in the gravitational flow path of a particle form solid material discharging to a pressure vessel. The check valve is constructed to provide an unobstructed opening to the pressure vessel when generally atmospheric pressure conditons are present Within the vessel. When a pressure fluid is admitted to the pressure vessel, the same fluid is simultaneously delivered to an actuator operative to close the check valve and to thereby prevent lossof pressure fluid through the solid material inlet conduit. The check valve opens when the pressure withinthe pressure vessel is returned to atmospheric pressure conditions. Closing of the check valve of the invention may be accomplished manually or automatically, as desired.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Of the drawings: v

Fig. 1 is a side elevation, in section, of .a steam gen- Fig. 6 is an elevation, in section, taken on line 6-6v of Fig. 5. p

In the embodiment of the invention shown in the drawings, a shot cleaning installation constructed and arranged according to the invention is applied to a vapor generating and superheating unit of the general type dis closed in US. Patent 2,687,708. As shown in Fig. 1, the vapor generating unit is supplied with heating gases resulting from the combustion of granular solid fuel. The solid fuel is burned in a cyclone type furnace 10 with the gases discharging from the" throat '1-1 of the cyclone into a primary furnace 12. Combustion of the fuel is sub.- stantially completed within the cyclone furnace 10 and the hot gases are partially cooled by the water cooled surfaces in the boundary walls of the primary furnace 12. The partially cooled hot gases of combustion pass upwardly through a bank of spaced tubes 13 into an upwardly elongated secondary furnace 14 where the gases are further cooled by heat exchange with fluid cooled tubes 15 in the walls of the secondary furnace.

Thereafter, the gases of combustion leave the upper end portion of the upwardly elongated furnace 14 to reverse their direction of flow and to move downwardly across convection heat exchange surfaces positioned in a vertically elongated convection gas pass 16. "Leaving the lower portion of the convection gas pass 16 the hot combustion products are discharged through a gas outlet 17 to a tubular air heater or the like and thence discharge to the atmosphere through a stack (not shown).

While the hot products of combustion leaving the cyclone furnace 10 are largely free of entrained non-combustible materials, the entrained solids in the gases may be in a sticky state and are apt to be deposited on any cooling surfaces they may encounter. The bank of tubes 13 positioned across the lower portion of the furnace 14 and the tubes 15 in the furnace generally cools the combustion gases below the temperature at which the noncombustible solids therein aremolten, or in a sticky form. Thus, the gases turning into the convection gaspass 16 will contain a relatively minor amount of generally dry suspended solid materials. However, the suspended solids will have a tendency to deposit on the convection heating surfaces in the convection gas-pass, such as on the banks of superheating and economizer tubes indicated generally at 18 and it is desirable to maintain these surfaces as clean as possible for high heat transfer rates between the heating gases and the fluid within the tubes, 'as well as to maintain draft losses at a low value. As illustrated in thedrawings, a shotcleaning system is installed in the convection gas-pass 16 of the vapor generating and superheating unit. The shot may consist or irregular shape capable of withstanding the temperature shock and erosive conditions encountered in the service indicated. Steel particles in theform of spheres or cylinders of 1/8 to inchdimensions has proven satisfactory in actual service; As shown the system consists of an upper storage reservoir 20 from whichthe shot gravitates through a plurality of downwardly extending tubes 21. The lower ends of the distributing tubes 21 are provided with shotarresters 22 which reduce' the downward component of motion of at the level of the arresters.

Patented May 17, 1360 the shot,

Leaving the arrester, the shot. moves by gravity through'a generally vertical section of pipe 26 to encounter a distribution head 27 at the lower end of the pipe. The distributor head may be of hemispherical configuration, for example, with the shot falling thereon discharged outwardly to cascade downwardly over and against the tubular surfaces. of the convection'heating banks 18 of the unit. The number, surface configuration and position of the distributor heads is determined by the cross-sectional dimensions of the convection gas pass 16 and the distributor heads are constructed and arranged in their assembled position so as to distribute the shot substantially throughout the cross-sectional area of the gas pass.

The cascading action of the shot impacting the heat exchange surfaces 18 in the convection gas pass 16 re moves the ash deposited on the surfaces, with the shot and dislodged ash falling downwardly to the lower portion thereof. A row of spaced hoppers 29 are positioned across the bottom of the gas pass 16, downwardly adjacent the gas outlet 17 through which the gases and entrained ash passes toward the atmosphere. The change in the direction of flow of the combustion gases in move ing through the gas outlet 17 from the gas pass 16 separates the shot from the gases, so that the shot continues downwardly into the hoppers. The smaller particles of the dislodged ash will generally follow the movement of the gases while the larger particles of dislodged ash will fall to the hoppers 29 with the shot.

As hereinafter described, the shot is conveyed to the top of the unit for reuse as a heat exchanger cleaning medium. According to the invention the shot conveying is accomplished by a fluent lift mechanism of the dense phase type wherein a low volume of the fluent conveying medium, at a relatively high pressure, moves the shot through a pipe as a substantially solid mass having subst-antially' the same density as an equal volume of the shot without the conveying medium. In such a lift system, it has been found desirable to remove the dust and ash particles from the mass of shot before the shot is subjected to the action of the conveying fluid.

The separation of foreign particle material, such as ash, from the shot is accomplished in a elutriator 30.

The elutriator is disclosed and claimed in a copending application of Robert W. Curtis, Serial No. 565,576, filed February 15, 1956. The finer particles of dust dislodged from the banks ofthe economizer is entrained with the gases of combustion leaving the unit through the outlet 17 while the larger particles, which is of a high density, will be separated from the gases of combustion and tend to follow the shot into the hoppers 23 at the bottom of the unit.

In operation, each of the elutriators 30 is provided with a flow of compressed air, or other pressure fluid, so

that the velocity of the air passing upwardly through theelutriator is suflicient to entrain relatively large particles of dust dislodged from the heat exchange elements-18 without entraining the shot. Thus, the shot discharging downwardly from the elutriator 30 will be substantially clean, and when delivered to the conveying mechanism will not interfere with the transportation thereof.

The shot receiving tanks 51 are each equipped with a check valve 52 which is positioned in the discharge pipe 31 between each hopper 2.9 and a tank 51. The check valves are shown in detail in Figs. 4, 5, and 6 and close the granular solid material inlet to the tanks simultaneously with the delivery of high pressure conveying air to the tanks. As shown particularly in Fig. 3, a duct 53 is supplied with high pressure fluid, for example compressed air, from an external source (not shown), and is connected with a tank 51A through a valved pipe 63. A pipe 64 is connected at one end between the tank 51A and the valve 62 in the pipe 63 to open to a power piston associated with each of the check valves 52. In view of the relatively small volumecf a power piston in comparison with the volume of the receiving tank 51, the valve is actuated to its closed position before the pressure in the tank has built up more than a minor amount.

Under, these conditions very'little pressure fluid, as used for conveying purposes, will escape upwardly through the pipe 31 into the flue gas outlet 17 from the steam generating unit.

As shown in Figs. 4, 5, and 6, each check valve 52-is constructed of a section of pipe 67 of greater diameter than the diameter of the discharge pipe 31. At its upper end the pipe 67 is attached to a flange 68, and at its lower end to an eccentric reducer which has a reduced diameter substantially equal to the diameter of the pipe 31. The reduced diameter of the reducer is attached to a flange 71, so that the check valve assembly may be bolted directly to the tank 51 or an intervening length of the pipe 31 may be interposed'between the valve and tank. A blank flange 72 of the same outer diameter as the flange 68 is eccentrically drilled to accommodate a short section of pipe 73 having the same diameter as that of the pipe 31. The pipe 73 is welded into the flange 72 and extends downwardly to a position spaced from the flange. The lower end portion of the pipe 73 is cut at an angle with respect to its axis so as to form a substantially elliptical opening in the end of the pipe. When the flanges 68 and 72are bolted togethenthe pipe 73 is positioned in alignment with the outlet of the eccentric reducer 70 and a space 74 is provided between one side of the pipe 73 and the inner surface of the pipe 67. The flanges '68 and 72 may be bolted, or otherwise at tached to the pipe 31 leading downwardly from the upwardly adjacent hopper 29.

A plate of generally the same elliptical dimensions as the lower end of the pipe 73 is pivotally mounted about a horizontal shaft 76 which is disposed in the space 74 generally at the level of the lower end of the pipe 73.. The plate 75 in its pivotal movement about the shaft 76 to a closed position engages the lower edge surface of the pipe 73 so as to prevent downward flow of shot or upward flow of pressure fluid therethrough.

The plate 75 is engaged by an arm 77 keyed to a shaft 78 which is horizontally disposed in the space 74 and spaced downwardly and outwardly of the shaft 76. The arm 77 has a rounded upper surface 80 to contact the lower side of the plate. The shaft 78 is mounted in bearings mounted Within and supported by the pipe 67 and one end of the shaft extends through the side wall of the pipe to be keyed to a clevis 82 which is pivotally connected with the piston shaft 83 of a pneumatic power element 8 4. With the construction described, movement of the piston shaft 83 of. the piston will move the arm 77 through an arc of, for example, 70 and Will correspondingly move the plate 75. The power element is pivotally mounted by a pin 85 to a depending clevis 86 which is in turn welded to an outwardly extending shelf 87 attached to the flange 68.

Thus, when the pressure fluid is admitted to the receiving tank 51A, some of the air passes through the pipe 64 to actuate the power element 84 to positively close the check valve. When the conveying air utilized in the system is cut oil, and the pressure within the receiving tanks has been evacuated through the conveying system to substantially atmospheric pressure the weight of the plate 7 5 and the arm 77 will move the piston of the power clement so that the check valves 52 will open for discharge of shot through the pipes 31 intothe receiving tanks 51. it will be noted that the valve will remain in a closed condition until the weight of the plate 75 and any material accumulated above the I plate surface is greater than the effective force exerted upon the lower surface of the plate bythe pressure Within the tank. This condition will be true even though the power element has been actuated to retract the arm 77.

With the check valve 52 closed the compressed air enters the tank 51A and moves the shot in the tank discharge end of the pipes 55 open to the upper end portion of the adjacent tank 51. The tank 51 furtherest removed from the air inlet connection is provided with a lift pipe 56, the lower end of which opens to the tank adjacent the bottom thereof while the upper end opens to the reservoir 20. The pipe 56 may have a number of bendsptherein such as shown in the pipe 56' in Fig. 2,

depending upon the layout of the steam generating and superheating unit. The pipe 56 discharges into the reservoir 20 where the conveying fluid is separated from the shot and the fluid thereafter vented to the atmosphere through a vent pipe 57 as shown in Fig. 2; or, as shown in Fig. 1, the carrier air from the conveying system may be vented through the pipes 21 to the gas pass 16.

The reservoir illustrated in the drawings consists of a cylindrical or polygonal vessel of considerably greater cross-sectional area than the diameter of the pipe 56 (or 56') connected thereto. The pipe 56 (or 56) may terminate at the bottom of the reservoir 20 or may extend upwardly into the reservoir. The type of construction will determine whether or not the discharge end of the pipe is submerged in shot. Either form of construction is satisfactory for the purposes of the shot conveying system illustrated. The reservoir 20 may have suflicient volume to store all of the shot such as indicated at 20' in Fig.2, or the shot may be stored in the tanks 51 and delivered to the reservoir 20 substantially as needed for cleaning purposes, as indicated at-20 in Figs. 1 and 3,

As shown in Fig. 2, the upper end portion of the shot reservoir 20 may be provided with'a frusto-conical cone section 60 which is supplied with a screen 61 extend- As an illustration of the operation of the shot creaning apparatusrlet it be assumed that a complete charge of shot for each cleaning cycle amounts to one ton. After cascadingthrough the gas pass, the shot will accumulate in the shot receiving tanks 51. Compressed air, at a pressure of from 75 to 150 pounds per square inch. and in a volume of from 100 to 300 cubic feet per minute is delivered to the shot receiving tanks. The admission of compressed air to the tanks 51 will close thecheck valves 52, and the shot will move in series through each of the tanks and the transport pipe 56 to. the reservoir 20. With a 3" diameter shottransport pipe, the shot will be transported from the tanks 51 to the reservoir 20 in a matter of 1 or 2 minutes. During transportation of the shot, the shot conveying pipe 56 will be filled with the shot which has a transport density substantially equal to the static density of the shot without the addition of the transporting air. In this type of shot transportation equipmentthe mass of shot moves upwardly substantially as a solid mass and at a slow rate with minimum wear on the walls of the confining transport line, and on the shot.

ing across the entire cross-section'of the reservoir. The r upper end of the cone 60 is provided with a carrier fluid outlet opening for the discharge of the separated carrier fluid through the vent 57. The screen is used to prevent discharge of-shot through the carrier medium outlet during periods when a surge occurs in the transport line.

In the arrangementsillustrated, the shot cleaning equipment is intended for periodic operation. For example, the shot may be discharged across the heat exchange surfaces of the unit for a period of, for example, 5 or 10 minutes during each hour. The frequency of operation of shot cleaning equipment is dependent upon the operating characteristics of the particular unit in which the cleaning system is installed. For example, when handling an extremely dirty fuel it may be necessaryto operate the shot cleaning apparatus as frequently as 3 or 4 times during each hour. With anintermittent type of opera tion, a charge of shot may be delivered to the reservoir 20 (or 20') at the top of the unit and the entire charge cascaded over the heat exchange surface. The shot gravitates downwardly until all of it has accumulated in the shot receiving tanks 51 at the bottom of the installation. The shot may then return to the reservoir 20' until the next cycle of shot cleaning is desired.

While in accordance with the provisions of the statutes, I have illustrated and described'herein the best form and mode of operation of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claim, and that certain features of my invention may sometimes be used to advantage Without a corresponding use of other features. r

The claim is:

A check valve comprising a closed body having an inlet and an outlet in the opposite ends thereof for the movement of materials therethrough, said inlet and outlet being eccentrically arranged with respect to said closed body to define a space out of the path of material flow through said closed body, a tubular extension of said inlet projecting into said closed body, a closure plate rotatable about a transverse axis, said transverse axis being disposed in said space, a pivotable arm positioned and arranged within said closed body to engage said closure plate and to move said plate into closing position with respect to the end of said tubular extension,'and power actuated means for rotating said pivotable arm in direct responseto achange in the pressure delivered thereto.

References Cited in the file of this patent UNITED STATES PATENTS 186,832

Greenwood Jan. 30, 1877 795,591 Eastburn July 24, 1905 1,309,671 Weaver July 15, 1919 1,577,637 Hess Mar. 23, 1926 1,706,861 Pokorny Mar. 26, 1929 1,980,495 Muir Nov. 13, 1934 2,565,946 Bozich; Aug. 28, 1951 2,684,929 Schutte July 27, 1954 2,703,732 Schutte Mar. 8, 1955 2,739,742

Anderson Mar. 27, 1956

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