GB2104960A - Apparatus for conveying solid material - Google Patents

Abstract

Material such as sand, oil shale or coal is fed via an inlet 16 to a pump 10 provided with an outlet 18. The pump comprises a rotor 12 including spaced friction discs 26 (28), Fig. 2 (not shown), which define a passageway in conjunction with a pivotable shoe 20 for compacting the material. A torque or rotation monitor 78 controls a servo motor 76 which pivots the shoe inwards to increase the compaction until a preset torque load on the pump driving motor is reached whereupon the shoe is retracted. Alternatively the shoe may be moved manually, or, if gravitational forces provide sufficient compaction of the material, the shoe may be fixed. The provision of the pivotable shoe prevents jamming of the pump. <IMAGE>

Description

SPECIFICATION Method and apparatus for conveying and metering solid material BACKGROUND OF THE INVENTION The present invention relates generally to apparatus and methods for conveying particulate solid material in large scale industrial processes.

The present invention has particular application to large scale industrial processes for the treatment of coal, oil shale or the like where large amounts of solid material must be conveyed and metered to different processing apparatus and areas within a particular processing plant.

Presently, screw feeders are typically utilized throughout large scale industrial operations for transporting and metering solid material. For example, in the processing of oil shale and coal, screw feeders are often specified as the means for introducing the raw carbonaceous material into processing apparatus. Although conventional screw feeders are widely used in industry, they are notorious for problems resulting from jamming due to solid material wedging between the outside of the screw flights and the trough or enclosure within which the screw rotates. As solid material begins to wedge and jam within the typical screw feeder, continued rotation of the screw increases pressure and compaction of said material at the stoppage site until a highly compacted plug is formed.The screw feeder continues to turn until the compressed plug of solid material becomes so large that the power or torque capability of the driving motor is exceeded. At this point, the only means by which the plug can be removed from the typical screw feeder is to disassemble and remove the screw from its enclosure.

in order to prevent severe jamming in screw type feeders, shear pins have been inserted in the screw feed drive system to prevent excessive loading and jamming of the screw feed conveyor.

These pins are designed to shear prior to excessive screw loading to prevent severe compacting and plugging of the screw feeder trough or enclosure.

In this way, clean-out of the screw feed conveyor is made easier since severe compaction and plugging of the conveyor tube are eliminated due to shearing of the pin prior to development of excessive torque loading on the screw. Even so, the screw feeders are still prone to jamming and must be cleaned out every time a shear pin is broken. In addition, shear pins which are continually stressed and strained during operation of the screw feed conveyor are subject to premature failure at loads normally encountered during conveyance of the solid material.

The intermittent breakdown of screw feeders due to jamming and other system failures is not only time-consuming but is quite costly due to the shutdown of an entire processing plant resulting from such a conveyance system failure.

Accordingly, it is apparent that there is a present need for a non-jamming method and apparatus for conveying and metering solid material.

SUMMARY OF THE INVENTION In accordance with the present invention, an improved apparatus and method are provided for conveying and metering solid material, especially particulate solids, with decreased jamming of the apparatus. The present invention is based on a new conveyor apparatus or pump which comprises a pump housing having an inlet, an outlet and a passageway connecting the inlet to the outlet. The passageway is formed by a friction drive-wall which is movable relative to the pump housing from the inlet towards the outlet and by a wall opposite the friction drivewall. An important feature of the present invention is that the friction drivewall has a greater surface area for contacting and conveying material than the surface area of the opposite wall.Thus the friction drivewall exerts frictional drive forces on solid material introduced through the housing inlet which exceed the frictional drag force exerted thereon by the opposite wall, so that the net frictional drive force conveys the solid material in a forward direction toward the outlet.

As another feature of the present invention, the solid material is compacted or compressed either prior to or within the passageway to a sufficient level so that the solid material exhibits some of the properties of a liquid. As a result, the solid material becomes semi-hydrostatic in nature so that the frictional forces exerted by the drivewall convey the entire mass of solid material through the passageway, and additionally, since there is little or no slippage between the friction drivewall and semi-hydrostatic solid mass, the amount of solid material flowing through the passageway may be metered according to conventional techniques.

The method and apparatus of the present invention is believed to be essentially nonjamming, since it does away with the crosscutting or cross-current blade action of a screw feeder. For example, in a screw feeder, as the amount of blockage increases, the amount of frictional force contrary to the flow of solid material is developed. In the present invention, as blockage begins to occur, frictional forces increase as in a screw feeder system; however, the increase in frictional force merely increases the drive force supplied by the friction drivewall resulting in the increase of forces applied to move the solid plug through the passageway. Of course, in severe cases blockage may be great enough so that the torque or power capabilities of the motor driving the friction drivewall will be exceeded.As a particular feature of the present invention, in situations where blockage does occur, instead of having to disassemble the entire pump apparatus, provision is made for adjusting the opposite wall relative to the friction drivewall to increase the cross-sectional area of the passageway so that the plug of solid material jamming the pump may be easily removed.

The present invention therefore provides a suitable apparatus and method for conveying solid material which is non-jamming, since the drivewall moves in the same direction as the solid material flow, as opposed to conventional screw feed apparatus having blades which continually cross cut this flow. Further, compaction of the solid material through the pump prevents any blow-by of gas or product material which may be lost during introduction of carbonaceous material into a preheat or retort system.

The above-discussed and many other features and attendant advantages of the present invention will become apparent as the invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial cross-sectional side view of a preferred solids pump in accordance with the present invention. The view is taken in the I plane of Figure 2.

Figure 2 is a sectional view of Figure 1 taken in the II II plane.

Figure 3 is a partial view of the preferred pump in accordance with the present invention showing an adjustable passageway shoe moved to its inward or high compaction position.

Figure 4 is a partial view similar to Figure 2 showing the pump in the high compaction position.

Figure 5 is a vertical section taken in the V-V plane of Figure 1.

Figure 6 is an exploded perspective view of the drive rotor and adjustable passageway shoe.

Figure 7 is an alternative adjustable shoe embodiment.

DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT A preferred pump in accordance with the present invention is shown generally at 10 in Figures 1 and 2. The pump 10, designed for conveying solid material, such as sand, oil shale, coal, and any other particulate solid material, includes basically a friction drive rotor 12 which is mounted within housing 14, inlet 16, outlet 18, and an opposite adjustable shoe 20. In use, solid material is fed by gravity or positive pressure means through inlet 1 6 into passageway 22 between the rotor 1 2 and the opposite adjustable shoe 20. The rotor 12 drives the solid material through passageway 22 and into outlet 1 8 and out of the pump 1 0.Having basically described the pump and its operation, a more detailed description of this preferred exemplary embodiment foilows.

Referring to Figure 6, a preferred friction drive rotor 12 is shown. The friction drive rotor 12 includes a hub portion 24 and two sidewalls 26 and 28 extending radially outward from the hub portion 24. The interior faces 30 and 32 of sidewalls 26 and 28 and exterior face 34 of hub portion 24 define a U-shaped channel providing the friction drivewall which contacts the solid material as the rotor 12 is rotated to convey material through the pump 10. The hub portion 24 is further provided with a hole 36 for mounting the drive rotor 12 to a suitable shaft. Preferably, the drive rotor 12 is made from a suitably tough material, such as iron or steel. The drive rotor 12 may be made from one integral piece of material or may be fabricated as desired.

Referring to Figures 1 and 2, the drive rotor 12 is mounted within housing 14. The housing 14 includes walls 38 and 40. The drive rotor 12 is mounted in between walls 38 and 40 by way of shaft 42. The shaft 42 is rotatably driven by a motor or gasoline engine (not shown) in the direction indicated by arrow 44. The shaft 42 is mounted within bearing housing 46 which includes bearings 48 and 50. The latter are sealed off from the housing 46 by seal 52 and are also sealed externally by seal 54. Further, the shaft 42 isjournaled within sealed bearing 56 which is mounted securely within housing wall 40. The drive rotor 1 2 is securely mounted to shaft 42 so that they rotate in unison only.

It is preferred that the drive rotor 12 and housing 14 be sized so as to minimize gaps 58 and 60 between rotor sidewalls 26 and 28 and housing walls 38 and 40.

The inlet 16 includes walls 62, 63, 64 and 65. The walls 62 and 64 are sized so that they fit between the sidewalls 26 and 28 of the drive rotor 1 2. The walls 63 and 65 terminate on their inner ends along the perimeter of drive rotor 12 as best shown in Figure 5. Preferably, gaps between the inlet walls 62 and 64 and drive rotor walls 26 and 28 and between inlet walls 63 and 65 and the rotor 12 perimeter are kept at a minimum to prevent solids from leaking out of the pump 10 while at the same time not being so close that binding occurs between the inlet walls 62, 63, 64 and 65 and drive rotor 12.

The outlet 1 8 includes walls 66 and 68 which are sized to fit within the U-shaped channel defined by rotor 12 and walls 67 and 69 which terminate on their inner ends along the perimeter of drive rotor 12 as shown in Figure 2. Again, it is desirable that the outlet walls 66 and 68 be sufficiently wide to prevent solid material from falling through gaps between the outlet walls 66 and 68 and the drive rotor walls 26 and 28 while not being so wide as to bind against the drive rotor 1 2. Also, the gaps between the outlet walls 67 and 69 and the rotor 12 perimeter should be kept art a minimum to prevent leakage of solid material.

Both inlet 16 and outlet 1 8 are secured to the housing 1 4 by such means as bolts or pins 70. The bolts 70 are additionally used for securing the housing sidewalls 38 and 40 in position; however, any suitable means may be used for fixing the position of the housing walls 38 and 40 securely relative each other.

As shown in Figure 1, the inlet wall 64 and outlet wall 66 each terminate on their inner ends adjacent the exterior face 34 of hub portion 24.

The inlet wall 62 and outlet wall 68 terminate on their inner end adjacent the adjustable shoe 20. In this way, a passageway 22 is defined by a portion of the rotor 1 2 and the opposite interior face 72 of adjustable shoe 20.

As an important aspect of the present invention, the surface area of opposite interior face 72 is less than the surface areas of the interior sidewall faces 30 and 32 and exterior face 34 of hub portion 24 which are located at any given time in passageway 22 between inlet 1 6 and outlet 1 8 as the drive rotor 1 2 is rotated. In accordance with the present invention, since the surface area of friction drive wall 30,32,34 exceeds that of the opposite shoe wall 72, the net frictional drive force conveys the particulate solid material through the passageway 22.

Since it is especially contemplated that particulate solid material will be conveyed through the pump 10, it is important that this material be compacted to differing degrees for conveyance by friction through the passageway 22. Specifically, if this material is not compacted to any degree, the frictional drive force exerted on the particles adjacent the friction drivewall will not be conveyed to the bulk of the particles thereby resulting in little or no friction drive or conveyance of the said material. In accordance with the present invention, the said material is compacted either prior to or within the passageway 22.

Compaction of the particulate solid material results in its taking on a semi-hydrostatic character so that frictional forces exerted by the friction drivewalls 30, 32, 34 and opposite shoe face 72 are distributed throughout the entire particulate solid material in the passageway 22 resulting in conveyance of the entire solid mass.

The amount of compaction necessary for preferred operation of the solids pump 10 in accordance with the present invention will vary greatly depending upon the particular material being conveyed. For many solids, the pressure head developed by gravitational forces exerted on particulate solids in inlet 1 6 would result in sufficient compaction for operation of the pump 10. In this type of situation, no additional compaction would be necessary and a completely stationary fixed non-adjustable shoe 20 and opposite wall would be sufficient for pump action.

However, it is preferred that the amount of compaction obtainable within passageway 22 be variable. To accomplish such variable compaction, shoe 20 is mounted within housing 14 by pivot bar 74. The pivot bar 74 fixes the location of the upper end of shoe 20 adjacent the inlet wall 62 while allowing pivoting of the lower end of the shoe 20 near wall 68 inward toward rotor hub portion 24 as restricted by pin 75 and slot 77. In Figures 1 and 2, the shoe 20 is shown in a fully retracted position where the interior face 72 of shoe 20 forms a continuous arc between inlet wall 62 and outlet wall 68. In Figures 3 and 4, the shoe 20 is shown in its fully inserted position where the cross-sectional area of passageway 22 is maximaily reduced.In this way, it is possible to provide a passageway 22 having cross-sectional areas which decrease from its inlet end to its outlet end so as to compact particulate solid material as it moves therethrough. In practice, the pump 10 will initially be operated with the adjustable shoe 20 in its fully retracted position as shown in Figure' 1. If sufficient compaction of the said material is available in this position to provide adequate conveyance of said material, the shoe 20 will remain in its fully retracted position.

Usually, however, compaction of the said material within the passageway 22 will be necessary in order to provide sufficient frictional forces to expel said material through outlet 1 8. Accordingly, the adjustable shoe 20 will be moved inward somewhere between the position shown in Figure 1 and the position shown in Figure 3 to provide the necessary compaction for adequate conveyance of the particulate solid material.

Movement of the adjustable shoe 20 inward and outward to adjust cross-sectional areas of passageway 22 may be accomplished in any number of ways. As shown in Figure 1, it is preferred that an electric servo motor 76 or suitable equivalent be provided to adjustably move the shoe 20 towards and away from the drive rotor 12. In one feature of the present invention, it is preferred that the amount of torque load or resistance experienced by the drive rotor 1 2 be monitored by a suitable torque or rotation monitor 78.In operation a metered servo switch 80 is provided which moves the adjustable shoe 20 inward until torque loads increase thereby increasing the frictional drive forces between the rotor 12 and the solid material and increasing the forward driving force towards outlet 1 8. The adjustable shoe 20 continues to move inward until a predetermined torque is reached, indicating sufficient compaction of the solid material to provide maximum conveying efficiency. The automatic adjustment system is designed so that once the torque load of the motor or engine is exceeded or the drive rotor 12 slows, the servo switch 80 will cause the servo motor 76 to retract the adjustable shoe 20 to thereby increase the cross-sectional area of passageway 22 to allow the solid material to more freely travel through the pump 10.Although this type of automatic selfregulating system is preferred, the present invention may also be carried out with the adjustable shoe 20 being moved manually between fixed positions, if desired.

Another embodiment in accordance with the present invention for continually adjusting the shoe 20 is shown in Figure 7. This particular embodiment utilizes a hydrostatic drive unit 92 which is designed to apply constant torque to shaft 42. The hydrostatic drive unit 82 includes a drive motor or engine 94 and a hydrostatic transmission or drive assembly 96. The hydrostatic transmission 96 is of conventional type wherein constant torque is applied to shaft 42 by varying the pressure of the hydraulic medium present within the transmission 96. For example, when the rotor 12 experiences increased pump loads, the hydraulic medium pressure will be lowered in hydrostatic transmission 96 in order to maintain constant torque to shaft 42.

Conversely, when lower loads are being driven by the rotor 12, the hydraulic medium pressure is increased to higher levels. As a particular feature of this embodiment, a hydraulic fluid line 98 is connected between the hydrostatic transmission 96 and a hydraulic cylinder 100. The hydraulic cylinder drives piston 102 against the adjustable shoe 20. In this manner, constant pressure is exerted on shoe 20. The amount of pressure will vary according to the torque load experienced by rotor 12. More particularly, as torque loads on the rotor 12 increase, the hydraulic medium pressure will decrease in hydrostatic transmission 96 to provide constant torque to shaft 42.Concurrently, the pressure of the hydraulic medium in cylinder 100 will also decrease proportionally thereby decreasing the force exerted on the solid material and allowing easier pumping of the solid material through the pump 1 0. Conversely, when easily pumped solid material passes through pump 10, the pressure in the hydrostatic transmission 96 will increase thereby increasing the pressure of the hydraulic medium in cylinder 100 resulting in increased pressure exerted on adjustable shoe 20.

As will be realized, by choosing suitable hydrostatic pressures utilizing suitable valves etc., a particularly useful pump may be produced wherein the pressure applied to the adjustable shoe 20 is self-compensating and operates continually in response to loads experienced by shaft 42.

Although as shown in the preferred embodiment, particulate solid material is compacted within passageway 22, compaction may also be accomplished by sloping the walls of inlet 1 6 inward as they approach passageway 22.

In this way, a certain amount of compaction will take place which may be all that is necessary for suitable conveyance of certain solids.

As can be seen, the present pump is an improvement over prior screw-type feeders which continually must cut through the solid material and carry it in a direction opposed by frictional forces generated by the screw blades. This invention, by compacting the particulate solid material sufficiently and introducing it into a passageway where the surface area of the friction drivewall is larger than the opposite wall's surface area, results in forces being generated on the particulate solid material for the most part only in that material's direction of travel. The pump, therefore, is less likely to plug, and when it does, the plug may easily be removed by increasing the cross-section of the passageway through which the solid material passes.

Since there will be very little if any slippage between the drivewall and the solid material conveyed through passageway 22, the pump of the present invention may also be used as a meter to measure the amount of solid material conveyed through it. Since the volume of the passageway is known, conventional techniques involving measurements of the drive rotor rotational speed can easily be used to determine the flow rate of solid material through the pump.

Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention.

For example, although a drive rotor is the preferred form of drivewall, it is not essential. Any type of conveyor belt or other system may be utilized so long as the requisite compaction and ratio of drivewall area to opposite wall area is present.

Accordingly, the present invention is not limited to the specific embodiments as illustrated herein.

Claims (10)

1. An apparatus for conveying solid material, characterized by a pump housing having an inlet, an outlet and a passageway connecting the inlet to the outlet, the passageway being formed by a friction drivewall movable relative to the pump housing from the inlet towards the outlet and by a wall opposite the friction drivewall, the friction drivewall having a greater surface area for contacting and conveying the solid material than the surface area of the opposite wall.

2. An apparatus according to claim 1, characterized by the inlet has walls which slope towards the passageway for compacting the solid material prior to entering the passageway.

3. An apparatus according to claim 1 or 2, characterized by the opposite wall is adjustable relative to the friction drivewall for narrowing the passageway and compacting the solid material therein.

4. An apparatus according to claim 3, characterized by the opposite wall is adjustable by pivoting towards the drivewall adjacent the outlet.

5. An apparatus according to claim 1 or 2, characterized by the opposite wall is a fixed stationary non-adjustable wall.

6. An apparatus according to claim 1,2,3,4 or 5, characterized by the friction drivewall is a conveyor belt.

7. An apparatus according to claim 1 , 2, 3 or 4, characterized by the friction drivewall is a drive rotor rotatable within the pump housing.

8. An apparatus according to claim 7, characterized by the drive rotor has radially extending sidewalls on its hub portion forming a U-shaped channel.

9. An apparatus according to claim 7, characterized by the drive rotor is connected to a torque monitor which is connected to a servo motor for adjusting the opposite wall.

10. An apparatus according to claim 1, substantially as described with reference to any Figure or Figures of the accompanying drawings.