US3817432A

US3817432A - Flow promoting device for batch hoppers

Info

Publication number: US3817432A
Application number: US00237316A
Authority: US
Inventors: I Szendroi
Original assignee: Bethlehem Steel Corp
Current assignee: Bethlehem Steel Corp
Priority date: 1972-03-23
Filing date: 1972-03-23
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18
Also published as: CA1009619A

Abstract

An apparatus for minimizing arching of granular material within a gravity operated, batch-type hopper. A plate rotatable about a horizontal shaft is mounted within the hopper above a bottom discharge opening. Prior to charging the plate is rotated to a horizontally extending position and during discharging to a vertically extending position.

Description

United States Pat nt [191 -Szendroi June 18, 1974 FLOW PROMOTING DEVICE FOR BATCH 2,710,117 6/1955 Fritz et al. 222/231 x HOPPERS y l [75] Inventor: Imre Szendro1, Allentown, Pa. Primary:Examl'.ner Stanley H. Tonberg [73] Assignee: Bethlehem Steel Corporation, Attorney, Agent, or Firm-Joseph J. OKeefe Bethlehem, Pa. [22] Filed: Mar. 23, 1972 pp 16 57 ABSTRACT [5 2] US. Cl. 222/564 An apparatus for minimizing arching of granular mate- [51] Int. Cl. B65g 65/70 i thin a gra i y p r t h-type hopper. A [58] Field of Search 222/564, 232, 235, 231, plate rotatable about a horizontal shaft is mounted 222/234, 452, 502, 503, 508; 259/39, 45, 46; within the hopper above a bottom discharge opening. 302/52, 53 Prior to charging the plate is rotated to a horizontally extending position and during discharging to a verti- [56] R f r Cit d T cally extending position.

UNITED STATES PATENTS V 1 547,263 10/1895 Hoyle 259/45 7 Claims, 3 Drawing Figures FLOW PROMOTING DEVICE FOR BATCH HOPPERS BACKGROUND OF THE INVENTION This invention relates to hoppers, and more particularly to flow' promoting devices, which are positioned inside gravity operated batch-type hoppers such as are used to handle bulk materials, e.g. hoppers used to charge coke ovens.

Hoppers which are charged with batch quantities of material are known as batch-type hoppers. If the hopper depends upon gravity to help material to discharge through an opening in its lower portion, it is referred to as gravity-operated. Such devices are commonly employed to handle bulk materials. As is well known in the art, bulk materials are granular solids-of various particle sizes as for example crushed coal, ore, cement, flour, clay and soil.

During the discharge of gravity operated hoppers, a

serious problem referred to as arching or bridging can occur. Arching occurs when a portion of the material in the hopper becomes consolidated and forms a stable arch which extends between the walls of the hopper and prevents or retards the discharge of the remaining material from the hopper. Consolidation is used in reference to the action of such material. Consolidation is influenced by many factors including moisture, the action caused by the weight of the material andcompaction of the material during charging of an empty hopper. Compaction refers to the condition which results from successive layers of material being charged layer upon layer into a hopper. Many approaches have been tried in order to eliminate arching. For example, selection of hopper construction material to minimize friction, design of hoppers to include steep walls, and use of vibrators. Each of these approaches has disadvantages.

Also, the size of the discharging opening can be carefully selected to take into consideration flow character istics of the particular material to be handled. It is well known in the art that flow characteristics of each particular granular material can-be measured and used to predict the minimum size of the bottom discharge opening which will prevent formation of a stable arch. This minimum size is also equal to the critical arching dimension. if the opening is larger than this critical arching dimension, a stable arch will not form in the hopper above it. On the other hand, if the opening is smaller than the critical arching dimension, a' stable arch can form. The disadvantage of this approach is that, frequently, the size of the discharge opening is smaller than the critical arching dimension and is fixed by external factors such as the size of a charging opening with which the hopper opening must correspond or the dimensions of a receptacle which is to be charged from the hopper.

Various types of internally mounted, static flow promoting devices have been tried. These devices have taken the form of flat plates, cones, and cylinders, to name a few, and are generally mounted inside the hopper, above the discharge opening. Such static devices help prevent arching by minimizing consolidation of material during and after charging. Material falling into an empty'hopper arrives at the bottom after being slowed down by striking the device. Thereafter, the device continues to absorb part of the kinetic energy of the falling material, as well as support part of the weight of the material after charging is completed.

While these static devices help prevent arching, they also cause problems. Arching of material tends to occur in the area betweensuch devices and the hopper wall. Thus, the static device, while preventing arching in one area of the hopper, actually creates the structure which can lead to arching in another location. Also, the static devices affect the downward flow of material directly above the device. This effect can have the result of slowingthe speed of discharge of the hopper as a whole. ln operations which require rapid emptying of the hopper, anything which retards the emptying is a,

disadvantage.

Since, as is well known in the art, gravity-operated batch-type hoppers form a part of the charging machine used to charge coke ovens, the arching problems associated with these hoppers are not only present but are aggravated by conditions found in coke oven operations.

For instance, arching can result from compaction due to charging of crushed coal from the storage bin into the hopper carried on a larry car charging machine. in addition, increased consolidation takes place due to vibration when the larry car moves from the charging bin to a charging hole in the coke oven furnace. As an increasing amount of moisture is present in the coal, the danger of arching increases considerably.

Also, larry cars commonly contain four hoppers which simultaneously charge into four coke oven openings. The hoppers can only be closed simultaneously, and should one or more hoppers require a prolonged discharging time, the remaining already empty hoppers are exposed to escaping furnace gases laden with volatiles which can condense on the hopper interior. Such condensation can increase. friction between the hopper wall and coal in the next charge, thereby increasing the risk of arching.

ln addition, arching can cause insufficient material to be charged into the coke oven, resulting in loss of production and less uniform coke quality.

Finally, prolonged hopper discharge time, due to arching, can result in increased amounts of pollutant gases escaping from the furnace interior.

OBJECTS It is therefore an object of this invention to provide an improved gravity-operated batch-type hopper which minimizes arching of material over the discharge opening, by minimizing compaction of material during charging of the hopper;

lt is a further object of this invention to provide an improved gravity-operated batch-type hopper which prevents arching between the hopper walls and a flow promoting device.

it is also an object of this invention to provide an improved gravity-operated batch-type hopper containing a flow promoting device which avoids retarding material flow during discharge of the hopper.

It is also an object of this invention to provide an improved coke oven larry car which greatly minimizes arching of crushed coal above the discharge opening by minimizing consolidation of coal during charging and movement of the larry car.

SUMMARY OF THE INVENTION I have discovered that the aforementioned objects can be obtained by providing a rotatable flow promoting device positioned within a gravity-operated batchtype hopper, which is mounted on a movable coke oven larry car frame. Means are provided in the rotatable device by which it is locked into a horizontally extending position above the discharge opening so that it minimizes consolidation of material during charging and moving of the hopper. The device is mounted eccentrically which form contributes to the rotation during every discharge of the hopper, thereby minimizing interference with downward material flow. The rotatable action of the device prevents arching of material between the hopper walls and the device, and enhances discharge under certain conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 isa partial cross sectional view of a hopper embodying the invention mounted on a coke oven larry car.

FIG. 1.

FIG. 3 is an isometric schematic view of a locking means used on a plurality of hoppers embodying the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring more particularly to the. drawings, FIG. 1 shows a coke oven roof 1 which is provided with a rail structure 3 for supporting wheels 5 of a coke oven larry car shown generally as 7. The wheels 5 are driven by any suitable drive means, not shown, and depend from charging car 7.

One of the conical batch type coal hoppers 17 is mounted on larry car 7, by means of support member 19 which is fastened to channels 21 which are fastened to support member 11. A volume regulating device 23 supported by brackets 25 defines a top charging opening 27. A bottom discharging opening 29 is closed by any suitable gate means, which in this case is a sliding plate 31. Beneath sliding plate 31 and bottom opening 29 is an extension 33 which carries a sliding sleeve 35. In charging a coke oven, lower extension 33 and sliding sleeve 35 are positioned over a coke oven charging hole (not shown) before sliding plate 31 is retracted, permitting coal to pass through the bottom discharge opening 29.

Extending through the interior of hopper 17, and above the discharge opening 29 and sliding plate 31, is horizontal shaft 37. The shaft is retained in position by bearings 39 which also permit the shaft to rotate. For best results, the shaft is located at or above an elevation at which the minimum horizontal distance between opposing hopper walls is equal to the critical arching dimension of the material being processed, in this case crushed coal. The critical arching dimension of the material can be calculated from the theory and information reported by Andrew Jenike, in Storage and Flow of Solids", Bulletin No. 123 of the Utah Engineering Experiment Station, Vol. 53, No. 26, November 1964. In FIG. 1, 41 represents the critical arching dimension for the coal processed in hopper l7. Shaft 37 is shown located at an elevation where the interior hopper clearance is not less than the critical arching dimension 41 FIG. 2 is a cross sectional plan view of the hopper of I of the coal. Preferably shaft 37 is positioned at or just above the elevation wherein the distance between opposing wall portions of the hopper is equal to the critical arching dimension so that secondary consolidation of the coal does not occur when coal particles fall from the horizontally extending plate 43 to the bottom of hopper 17 during charging.

Below the shaft 37, and conforming to the interior wall of the hopper 17 is a stainless steel liner 38 which functions to minimize friction between the coal and hopper 17, thereby enhancing flow of coal during discharge of hopper l7.

Securely mounted on the shaft 37, as by welding, and directly above the bottom opening 29 and sliding plate 31 is flat plate 43 which turns with shaft 37 when it rotates. During charging, plate 43 is placed in a horizontal position as shown in the FIGURE. During discharge of hopper 17, plate 43 gradually rotates as material is discharged from the hopper and eventually plate 43 is in the vertically extending position 43' shown in phantom in FIG. 1. The plate 43 is mounted eccentrically on the shaft 37 so that the weight or coal acting on the plate 43 in the horizontally extending position exerts a torque on it causing the plate 43 to rotate to a vertically extending position upon discharge of the hopper. In FIG. 1, in the horizontal position, plate 43 intersects and substantially overlaps the vertical projection 45 of the discharge opening 29. TI-Iis overlapping is better shown in phantom wherein the plate is in the vertically extending position 43' in FIG. 1 and with this plate in the horizontal position in FIG. 2.

Referring to FIG. 2, the plate 43 is shown to overlap the discharge opening 29, and the cross sectional area of the plate 43 is not less than the horizontal cross sectional area of the discharge opening 29. The shape of the plate 43 can vary, and preferably it should intercept the entire width of the column of falling coal when the plate is horizontal. In the preferred embodiment of hopper 17 is circular in cross section and the flat plate 43 is circular in shape. For best results, the dimensions of the plate 43 are not less than the corresponding dimension of the bottom opening 29 measured on a horizontal plane through the opening 29. However, it should be understood that the plate size should be small enough so that it does not come into contact with the hopper 17 when the plate 43 is horizontal but large enough to completely shield the bottom opening 29 from direct impact of falling coal.

Referring to FIG. 3, outside the hopper 17, one end of shaft 37 forms a angle making a handle portion 45. Attached to the end of the handle 45 is a wedge shaped block 47, which is supported below by a spring mounted pin 49. The pin 49 prevents the wedge shaped block 47 from moving downward, thereby preventing rotation of shaft 37, and locking plate 43 into a horizontally extending position suitable for the charging of the hopper l7.

Attached to the outward end of the pin 49 is a cable 51 which passes over

pulleys

53 and 55 and attaches to linkage arm 57 which is pivotably connected at one end to sliding plate 31. Pivotably connected to the other end of linkage arm 57 is a horizontal shaft 59 which connects with a driving means (not shown) to open and close sliding plate 31. Where necessary, the driving means can open and close a plurality of hoppers simultaneously. Opening of sliding plate 31 to discharge the hopper 17 is accompanied by movement of linkage arm rupted into the bottom of hopper 17.

Connected to handle 45 iscable 61 which passes over pulleys 63 and 65 and is fastened to rotatable wheel 67.

Rotation of wheel 67 in the direction indicated by the arrow 68 pulls on cable 61 which pulls handle 45 up ward causing shaft 37 and plate 43 to rotate from a vertically extending discharging position to a horizontally extending charging position. As wedge shaped block 47 presses upwardly against spring mounted pin 49, the

wedge 47 forces the pin 49 inwardly until the wedge 47 passes the pin 49. Immediately, the spring mounted pin extends outwardly under the wedge shaped block 47 and locks it into place until the closure device sliding plate 31 is again moved to an open position.

In hoppers in which the charging opening 27 is not directly aligned over the discharge opening 29, a deflector chute can be positioned between the charging opening 27 and the plate 43 to assure that all incoming coal will fall against the plate 43.

OPERATION The empty larry car-7 is charged with crushed coal through the top charging opening 27. The plate 43, locked into a horizontally extending charging position, above the bottom discharging opening 28, is struck by the falling coal. The plate 43 substantially slows thefalling coal which then gently flows off the plate 43 and settles into the bottom of the hopper 17 which is closed by sliding plate 31. By'absorbing the impact of the falling coal, the plate 43 minimizes consolidation of the coal in the hopper 17 below the plate 43 thereby minimizing the possibility of arching below the plate 43.

Because the size of the plate 43 exceeds the corresponding size of the bottom discharge opening 29 as measured on a horizontal plane through the opening 29, the plate 43 prevents coal from falling uninter- When the hopper 17 is fully charged, theplate 43 supports the weight of the overlying coal, lessening consolidation of the coal below plate 43. Also, as the loaded larry car 7, moves along the rails 3 on the coke oven roof 1, the plate 43 minimizes additional consolidation of the coal below the plate which consolidation arises due to movement and vibration of the hopper 17.

As the hopper 17 is discharged, sliding plate 31 retracts to open the discharge opening 29. Simultaring between the plate 43 and the hopper 17. With the flat plate 43 in the vertically extending discharge position blockage to coal flow is minimal and the hopper 17 is emptied rapidly.

After discharge of hopper 17, the plate 43 is locked into a horizontally extending charging position by rotating wheel 67 to raise wedge shaped block 47 past spring'mounted pin 49, as previously described.

In actual practice, a larry car frame carrying four hoppers as described was put into service charging crushed coal having a critical arching dimension of 48 inches as calculated in accordance within the aforementioned report by Andrew Jenike. The diameter of the hopper at which the shaft was located, was 51 inches. The total time required for complete discharge of the four hoppers on the larry car averaged 50 seconds as compared to a normal range of I80 to 300 seconds, with extreme cases due to arching up to 900 secthrough a top charging opening batch quantities of -granular material and to discharge said material through a bottom discharge opening, the improvement comprising:

a. a plate eccentrically mounted on a rotatable shaft within said hopper above said bottom discharge opening and adapted to be placed in a position during charging of said material into said hopper to absorb the impact of said material to minimize consolidation and be rotatedduring discharge of said material from said hopper to minimize arching of said material;

b. the dimensions of said plate being not less than the corresponding dimensions of said discharge opening measured in a horizontal plane through said discharge opening;

c. means for blocking said plate into a horizontally extending charging position; and

(1. means for unlocking said plate for rotation to a vertically extending discharging position.

2. Apparatus according to claim 1 in which the plate is substantially flat.

3. In combinationwith a hopper adapted to receive through a top charging opening batch quantities of granular material and to discharge said material through a bottom dischargeopening, the improvement comprising:

a. gate means associated with said discharge opening and adapted to be closed when said hopper is being charged and opened when said hopper is being discharged,

b. a rotatable shaft extending horizontally within said h pp c. plate means eccentrically secured on said shaft means, and

1. having a cross sectional area greater than the horizontal cross sectional area of said discharge opening, and

2. in a horizontal position intersecting and substantially overlapping a vertical projection of said discharge opening, and adapted to be placed in a position during charging of said material into said hopper'to absorb the impact of said material to minimize consolidation and be rotated during discharging of said material from said hopper to minimize arching of said material.

shaft is located at an elevation wherein the minimum horizontal dimension between said wall portions is not less than the critical arching dimension of said granular material.

7. Apparatus according to claim 6 in which the plate is substantially flat.

Claims

1. In combination with a hopper adapted to receive through a top charging opening batch quantities of granular material and to discharge said material through a bottom discharge opening, the improvement comprising: a. a plate eccentrically mounted on a rotatable shaft within said hopper above said bottom discharge opening and adapted to be placed in a position during charging of said material into said hopper to absorb the impact of said material to minimize consolidation and be rotated during discharge of said material from said hopper to minimize arching of said material; b. the dimensions of said plate being not less than the corresponding dimensions of said discharge opening measured in a horizontal plane through said discharge opening; c. means for blocking said plate into a horizontally extending charging position; and d. means for unlocking said plate for rotation to a vertically extending discharging position.

2. Apparatus according to claim 1 in which the plate is substantially flat.

2. in a horizontal position intersecting and substantially overlapping a vertical projection of said discharge opening, and adapted to be placed in a position during charging of said material into said hopper to absorb the impact of said material to minimize consolidation and be rotated during discharging of said material from said hopper to minimize arching of said material.

3. In combination with a hopper adapted to receive through a top charging opening batch quantities of granular material and to discharge said material through a bottom discharge opening, the improvement comprising: a. gate means associated with said discharge opening and adapted to be closed when said hopper is being charged and opened when said hopper is being discharged, b. a rotatable shaft extending horizontally within said hopper, c. plate means eccentrically secured on said shaft means, and

4. Apparatus according to claim 3 with means operably connected to the rotatable shaft to lock the plate into a horizontally extending position.

5. Apparatus according to claim 4 with means to automatically unlock said plate for rotation during discharge of said hopper.

6. Apparatus according to claim 5 in which said hopper comprises opposite wall portions and in which said shaft is located at an elevation wherein the minimum horizontal dimension between said wall portions is not less than the critical arching dimension of said granular material.

7. Apparatus according to claim 6 in which the plate is substantially flat.