Bulk material storage and reclaim system

Systems and methods for reclaiming bulk solid material from storage stockpiles or from watercraft. A storage and reclaim system includes a support surface for supporting a stockpile of bulk material. The support surface is defined by a plurality of individual material support structures geometrically arranged and positioned with reference to each other so that the support surface is essentially continuous. Each of the material support structures in turn includes a dish or funnel-like structure having a generally conical floor surface sloping towards an individual discharge opening fitted with a discharge control gate. An array of vibrators is mechanically connected to each of the material support structures so as to introduce vibrational energy into the dish or funnel-like structures sufficient to either avoid a stable reclaim cone or to destabilize a stable reclaim cone which may form in order to maintain material discharge flow.

BACKGROUND OF THE INVENTION

The invention relates generally to reclaiming bulk solid material, such as coal, from storage stockpiles or from watercraft such as barges and ships used to transport bulk material.

Bulk material reclaim is a serious concern, and typically requires costly equipment. As examples, on land, coal may be stored in piles next to a power plant, and must somehow be made to enter a conveyor system. Similarly, bulk material must be rapidly removed or “reclaimed” from piles to load a ship or a barge. Conversely, a ship or a barge, once it reaches its destination, must be unloaded. All sorts of processing plants store raw material in piles, which must efficiently be “reclaimed,” typically onto conveyors, for actual use. Thus, coal is just one example; the material can be any bulk material. Other examples are ore, wood chips, grain, and various food products.

In the field of bulk material reclaim, a term of art is “live” reclaim. “Live” reclaim refers to the material which comes out when a discharge gate is opened at the bottom of a stockpile. In most cases, due to “angle of reclaim,” material stops flowing long before the entire stockpile is recovered, forming a “reclaim cone” of empty space. The amount of material which inherently flows before a stable “reclaim cone” is formed and flow stops is referred to as the “live” reclaim. After that, a mechanical device must be employed to move the stored material towards the opening (such as a mechanical rake, or a bulldozer), or vibration applied to assist in the flow. Prior art vibration systems, such as “vibrating drawdown hoppers” from Carman Industries, are only a partial solution.

More particularly, storage and reclaim of large quantities of bulk material on land is presently handled by several general methods, each of which has its advantages, costs, and limitations.

A first method may be described as Open or Enclosed Storage with Under-storage Reclaim. Conical, windrow, kidney shaped, and other types of material piles are formed by a number of different methods. A reclaim tunnel is provided under the stored material, with openings on top of the reclaim tunnel through which the material falls onto a reclaim conveyor below. This method has the advantage of low capital cost. Its main disadvantage is that mobile equipment is required to move the material not directly over the openings into the openings. This is a time consuming, costly and hazardous activity.

A second method may be described as Covered Slot or Inverted Cone. Slot or inverted cone storage usually requires a cover to prevent the introduction of water. The inverted cone must be steep enough to allow the material to “self clean” and be equipped with a reclaim device. The slot must also be steep enough to “self clean” but, due to the geometry, the slot can be less steep than the cone. The slot requires a reclaim rotary plow. To achieve significant storage volume, both of these structures must be very large, require significant excavation, and significant capital cost. Due to the depth of inverted cones and slots, the reclaim conveyor is also usually expensive.

A third method may be described as On Grade Storage with Mechanical Reclaimers. This type of storage can be open or covered. Some of the mechanical reclaimers in use are (1) bucket wheel reclaimers, (2) portal reclaimers, and (3) drum type reclaimers. All of these reclaimers have a relatively high capital cost and significant operating cost. Very large storage areas make covered storage not practical, which can lead to environmental issues.

Reclaim of bulk material from barges and ships has always been a capital intensive, labor intensive, and time consuming activity. Recently, self unloading ships and barges with partial reclaim systems have been developed. The systems in use are very complicated and costly requiring a large number of drawdown points and a multitude of conveyors to maintain a reasonable ship or barge capacity.

SUMMARY OF THE INVENTION

In one aspect a storage and reclaim system for bulk material is provided, including a support surface for supporting a stockpile of bulk material. The support surface is defined by a plurality of individual material support structures geometrically arranged and positioned with reference to each other so that the support surface is essentially continuous. Each of the material support structures in turn includes a dish or funnel-like structure having a generally conical floor surface sloping towards an individual discharge opening fitted with a discharge control gate. There is an array of vibrators for each of the material support structures mechanically connected to the material support structures so as to introduce vibrational energy into the dish or funnel-like structures sufficient to either avoid a stable reclaim cone or to destabilize a stable reclaim cone which may form in order to maintain material discharge flow while the discharge control gate is open.

In another aspect, a watercraft for transporting bulk material cargo is provided. The watercraft includes a hull defining an interior space having a bottom, and a storage and reclaim system supported within the hull. The storage and reclaim system includes a support surface for supporting a stockpile of bulk material, the support surface being defined by a plurality of individual material support structures geometrically arranged and positioned with reference to each other so that the support surface is essentially continuous. Each of the material support structures in turn includes a dish or funnel-like structure having a generally conical floor surface sloping towards an individual discharge opening fitted with a discharge control gate. There is an array of vibrators for each of the material support structures mechanically connected to the material support structures so as to introduce vibrational energy into the dish or funnel-like structures sufficient to either avoid a stable reclaim cone or to destabilize a stable reclaim cone which may form in order to maintain material discharge flow while the discharge control gate is open. The dish or funnel-like structures are supported within the hull in a manner such that there is a space below the dish or funnel-like structures and above the interior space bottom so as to accommodate vibration of the dish or funnel-like structures. At least one reclaim conveyor is located below the support surface and above the interior space bottom so as to receive bulk material discharged through at least one of the discharge openings and to convey the bulk material to another location for unloading the watercraft.

In yet another aspect, a method for storing and reclaiming bulk material is provided. The method includes the step of providing a storage and reclaim system, the storage and reclaim system including a support surface for supporting a stockpile of bulk material. The support surface is defined by a plurality of individual material support structures geometrically arranged and positioned with reference to each other so that the support surface is essentially continuous. Each of the material support structures in turn includes a dish or funnel-like structure having a generally conical floor surface sloping towards an individual discharge opening fitted with a discharge control gate. There is an array of vibrators for each of the material support structures mechanically connected to the material support structures so as to introduce vibrational energy into the dish or funnel-like structures. The method further includes building a stockpile of bulk material on the support surface, opening the discharge control gates when it is desired to reclaim bulk material, and conveying away bulk material discharged through the discharge openings. The vibrators are operated as needed in order to either avoid a stable reclaim cone or to destabilize a stable reclaim cone which may form in order to maintain material discharge flow while the discharge control gates are open.

DETAILED DESCRIPTION

In overview, embodiments of the invention provide systems and methods by which an essentially unlimited amount of bulk material of many types can be stored over storage areas essentially unlimited in area and reclaimed without the use of mobile equipment or expensive prior-art reclaimers. Extensive excavation during the construction of storage and reclaim systems embodying the invention is not required. The invention may be embodied in self-unloading ships and barges which are uncomplicated and relatively inexpensive. Embodiments of the invention allow ships and barges transporting bulk material to self-unload while maintaining lateral and longitudinal trim, and moreover allow barges to be unloaded while rafted.

Embodiments of the invention thus provide a relatively large, approximately flat, storage area, for a single large stockpile of bulk material. The storage area takes the form of what is herein termed a support surface, which is in turn made up of or defined by a plurality of individual material support structures geometrically arranged and positioned with reference to each other so that the support surface is essentially continuous. In the disclosed embodiments, the individual material support structures are simply square in plan view, and the support surface is rectangular in plan view.

Referring now to the drawings,FIG. 1is a three-dimensional representation of a land-based storage and reclaim system20embodying the invention, andFIGS. 2-6illustrate another land-based storage and reclaim system22embodying the invention. The storage and reclaim system20ofFIG. 1and the storage and reclaim system22ofFIGS. 2-6differ primarily in the number of individual material support structures defining the overall storage area. In the system20ofFIG. 1, nine material support structures are arranged in a 3×3 pattern. In the system22ofFIGS. 2-6, four material support structures are arranged in a 2×2 pattern. In view of the similarities, the system20ofFIG. 1and the system22ofFIGS. 2-6are generally described together hereinbelow, generally employing identical reference numbers for corresponding elements, and with differences noted where applicable.

InFIG. 1, the storage and reclaim system20includes an overall support surface24supporting a single stockpile26of bulk material, shown partially broken away. Likewise, the storage and reclaim system22ofFIGS. 2-6includes an overall support surface28supporting a single stockpile30of bulk material. The system22includes a roof32protecting the stockpile30, supported on longitudinal sidewalls34and36. Endwalls38aid in containing the stockpile30.

Each support surface24or28is defined by a plurality of individual material support structures40geometrically arranged and positioned with reference to each other so that the support surfaces24(FIG. 1) and28(FIGS. 2-6) are essentially continuous. Thus, the individual material support structures40are at least adjacent and close enough to each other so the material does not fall between the individual material support structures40. Preferably, in order to accommodate expansion and contraction, the edges of the individual material support structures40overlap each other in a sliding manner (not shown).

In the particular embodiments illustrated herein, the individual material support structures40are square in plan view. In the system20ofFIG. 1, the individual material support structures40are arranged in a 3×3 configuration so that the overall support surface24is also square in plan view. Similarly, in the system22ofFIGS. 2-6, the individual material support structures40are arranged in a 3×3 configuration so that the overall support structure28is square in plan view. These are examples only; various rectangular configurations of overall material support structures can be constructed.

Typical dimensions for the individual material support structures40are 200 feet by 200 feet (approximately 60 meters by 60 meters) square to 300 by 300 feet (approximately 90 meters by 90 meters square). Accordingly, the overall material support surface24in the system ofFIG. 1may be 900 by 900 feet (approximately 270 by 270 meters) square. The overall material support surface28in the embodiment ofFIGS. 2-6may be 400 feet by 400 feet (approximately 120 by 120 meters) square. It will be appreciated that the 3×3 and 2×2 configurations, as well as the particular dimensions, are by way of example only; greater or smaller numbers of individual material support structures40may be provided. Accordingly, the stockpile26or30can be quite large, and conceptually is unlimited in area, as additional individual material support structures40are provided.

Although the individual material support structures40in the embodiments disclosed herein are square in plan view, it will be appreciated that other geometric shapes may be employed, so long as an essentially continuous support surface is defined when the individual material support structures are fitted together. For example, individual material support structures which are triangular in plan view may be employed. Related to that, depending upon the particular geometrical configuration employed, the individual material support structures do not all need to be the same size and shape.

Each of the individual material support structures40takes the form of a dish or funnel-like structure40having a generally conical floor surface42sloping towards an individual discharge opening44. (Since the material support structures40are square in plan view, more accurately intersections of the material support structures with horizontal planes define circles of increasing diameter as plane height increases, becoming arcuate segments of circles near the corners.) The slope of the conical floor surface42is relatively shallow, at an angle of between 5° to 12° relative to horizontal. The surface42preferably is made of a material which has a relatively low coefficient of friction, such as polished stainless steel, or a plastic material such as TIVAR® 88 Ultra High Molecular Weight Polyethylene (UHMWPE).

As employed herein, the terminology “generally conical” refers to any approximation of a cone. Thus, the generally conical floor surface may be fabricated as a plurality of planar pieces, such as a plurality of sloping planar triangular pieces, with as few as four sloping planar triangular pieces where the individual material support structures are square in plan view, although not presently preferred. (In that case intersections of the material support structures with horizontal planes define squares of increasing size as plane height increases.) In the example (not illustrated) of individual material support structures which are triangular in plan view, each individual material support structure may be made of three sloping planar triangular pieces. Related to this discussion of approximations of a cone, a circle can be approximated by a plurality of straight line segments, with the limiting case of an actual circle being an infinite number of infinitely short line segments. Typically the material support structures40are fabricated of sheet material cut and bent as required.

Whatever the particular configuration of the individual material support structures40, a structural support system, generally designated50, is provided below each of the individual support structures40, defining a space52below the material support structures40and above an underlying base54, representing, in the case of the land-based systems20and22, ground or a stable structure built on the ground, such as a concrete slab56(FIGS. 3 and 4).

In the system20ofFIG. 1, a structural support system60more particularly is represented as a plurality of pillars62extending upwardly from a support base64.

In the system22ofFIGS. 2-6, a structural support system70takes the form of spaced support beams72(FIG. 6) supported on pillars74. (For clarity of illustration, the spaced support beams72are omitted fromFIGS. 3 and 4, although the pillars74are shown inFIGS. 3 and 4.) The pillars74extend upwardly from a support base76, for example the concrete slab56.

With particular reference toFIG. 6, the spaced support beams72are arranged in a grid78of sloped radial beams80having a slope corresponding to the slope of the conical floor surface42, and a plurality of generally concentric beams82lying in individual horizontal planes. The support beams72and pillars74are structurally engineered so as to support the material support structure under the weight of the stockpile26.

Each discharge opening44is fitted with a discharge control gate90(FIGS. 3 and 4) of conventional construction which is opened and closed to selectively allow material to flow out through the respective discharge opening44.

In the storage and reclaim system20ofFIG. 1, three reclaim conveyors92,94and96are provided, located so as to receive bulk material discharged through the discharge openings44when the discharge control gates90are opened. Each of the three reclaim conveyors,92,94and96conveys material discharged through three of the nine discharge openings44in the system20ofFIG. 1. Likewise, in the storage and reclaim system22ofFIGS. 2-6, two reclaim conveyors98and100are provided, again located so as to receive bulk material discharged through the discharge openings44when the discharge control gates90are opened. Each of the two reclaim conveyors98and100conveys material discharged through two of the four discharge openings44in the system22ofFIGS. 2-6. The reclaim conveyors92,94,96or98,100convey bulk material to another location (not shown) in a conventional matter. InFIGS. 3 and 4, the reclaim conveyors98and100are shown installed in respective troughs102and104, the troughs102and104being formed in the concrete slab56.

With particular reference toFIGS. 2-4, for building the stockpile26of bulk material, an overhead storage tripper feed conveyor system generally designated110is provided, which receives feed stock from a storage feed conveyor112. For clarity of illustration, structural support for the conveyor system110is not shown. In order to fully utilize the capacity of the storage and reclaim system22, it is necessary to load the support surface24(FIG. 1) or support surface28(FIGS. 2-4) with material in the manner shown inFIG. 1with reference to the stockpile26. This allows material to be stored over a large area with a reasonable elevation of the top of the stored material stockpile26or30. By way of example and not limitation of a system for building a stockpile, the overhead storage tripper feed conveyor system110includes a series of conventional mobile trippers mounted on traversing conveyors. This allows the discharge point of each tripper to be located anywhere over the entire area where the stockpile26or30is to be built. In the event columns (not shown) are required to support the roof32, multiple mobile trippers and mobile tripper conveyors may be required. All the mobile tripper conveyors are fed by one storage conveyor equipped with mobile trippers to feed the mobile tripper conveyors.

As thus far described, the “live” reclaim capacity of the systems20and22ofFIG. 1andFIGS. 2-6is limited. Thus, and with reference toFIG. 7, due to the “angle of reclaim” there is a limit on how much of the stockpile26or30can be recovered onto the reclaim conveyors92,94,96or98,100simply by opening the discharge control gates90. “Angle of reclaim” is a well-known engineering property of granular materials, defined as the angle of a stable slope, generally determined by friction, cohesion, and the shapes of the particles, achieved while withdrawing material from the bottom of a pile of stored material.FIG. 7illustrates a situation where the discharge control gate90has been opened by an actuator120, thereby allowing material to flow through the discharge opening44onto an exemplary reclaim conveyor122. An exemplary angle of reclaim is represented inFIG. 7as angle124.

In the particular condition illustrated inFIG. 7, bulk material from a stockpile126representative of either of the stockpiles26or30has stopped flowing, resulting in a stable reclaim cone128surrounding empty air space. The amount of material which previously occupied the space within theFIG. 7stable reclaim cone128, in other words the material which comes out when the discharge control gate90is opened, is what is known as “live” reclaim from a pile of stored bulk material, and is less than the entire stockpile126.

Embodiments of the invention employ an array130of vibrators132for each of the material support structures40mechanically connected to the material support structures40so as to introduce vibrational energy into the dish or funnel-like structures40sufficient to either avoid a stable reclaim cone, or to destabilize a stable reclaim cone which may form, in order to maintain material discharge flow while the discharge control gate90is open. The vibrators132are visible and represented inFIGS. 2, 4, 6 and 7. Vibration of the dish or funnel-like structures40is accommodated by the spaces52below the dish or funnel-like structures40and above the underlying base54. Typically, the vibrators132are operated only as needed to destabilize a stable reclaim cone which has formed, although continuous or other intermittent operation is possible. In typical embodiments a flow switch (not shown) is employed to recognize a non-flow condition and activate the vibrators132.

As the stockpile26,30or124is nearly recovered, leaving just a small quantity of bulk material on the support surface24or28, the operation reduces to that of a vibrating feeder, allowing substantially all of the bulk material to pass through the discharge openings44. However, prior to that point, the mode of operation is distinct from that of a vibrating feeder.

As illustrated inFIG. 6, in the disclosed embodiment the vibrators132are mechanically connected to the undersides of the dish or funnel-like structures40at selected locations intermediate the pillars74and intermediate the support beams72. The vibrators132more particularly are rotary electric vibrators such as a Model Number RE 13-6 Rotary Electric Vibrator manufactured by The Cleveland Vibrator Company. This vibrator rotates at 1,145 RPM, is powered by a 1.1 HP motor and produces 2,860 lbs of force. Different installations of varying geometry and storage capacities require different vibrators. It will be appreciated that the vibrators may be powered by energy sources other than electricity.

Referring now toFIGS. 8-11, a watercraft embodying the invention is generally designated140and more particularly is illustrated as an inland hopper barge142having a bow144and a stern146. The watercraft140may also be an ocean-going ship. InFIG. 11, the barge146is illustrated as floating in water148at an unloading dock150equipped with a receiving conveyor system152.

The barge142has a hull160defining an interior space162having a bottom164. The interior space162is divided into compartments166,168and170by bulkheads172,174and176. InFIG. 10, a watertight access hatch178is visible in the bulkhead172.

Supported within the hull160is a storage and reclaim system180, essentially identical to the storage and reclaim systems20and22described hereinabove, except for being part of the watercraft150. Thus, the storage and reclaim system180includes an overall support surface182supporting a single stockpile186of bulk material, such as coal. The support surface182is defined by a plurality of individual material support structures188,190and192each corresponding to the material support structures40described in detail hereinabove, geometrically arranged and positioned with reference to each other so that the support surface182is essentially continuous. In the system180ofFIGS. 8-11, the material support structures188,190and192are arranged in a 1×3 pattern, in other words, in a straight line, consistent with the usual shape of an inland hopper barge. The overall support surface accordingly is rectangular but not square.

As in the embodiments described hereinabove, each of the individual material support structures188,190and192takes the form of a dish or funnel-like structure having a generally conical floor surface194,196or198sloping towards individual discharge openings200,202and204. The discharge openings200,202and204are fitted with corresponding discharge control gates206,208and210.

The dish or funnel-like structures188,190and192are supported within the hull160in a manner such that there are spaces212,214and216below the dish or funnel-like structures194,196and198and above the bottom164. With particular reference toFIG. 9, structural support systems220are provided, each more particularly comprising a grid222of sloped radial beams224having a slope corresponding to the slope of the conical floor surfaces194,196and198, and a plurality of generally concentric beams226lying in individual horizontal planes.

With reference toFIGS. 10 and 11, a single reclaim conveyor230is located within a reclaim conveyor tunnel232(FIG. 10) which is provided with a sump pump (not shown). The reclaim conveyor230is located below the discharge openings200,202and204so as to receive bulk material discharged when the discharge control gates206,208and210are opened.

With particular reference toFIG. 11, the reclaim conveyor230discharges into a transfer chute234, which in turn transfers material to an unloading conveyor236, which in turn unloads material onto the receiving conveyor system152of the dock156.

In the same manner as described hereinabove with reference to the systems20and22, an array250of vibrators252is provided for each of the material support structures188,190and192mechanically connected to the material support structures188,190and192so as to introduce vibrational energy into the dish or funnel-like structures188,190and192so as to introduce vibrational energy sufficient to either avoid a stable reclaim cone, or to destabilize a stable reclaim cone which may form, in order to maintain material discharge flow while the discharge control gates206,208and210are open with particular reference toFIG. 9.

During the unloading process, longitudinal trim of the barge152can be maintained by individual control of the discharge control gates206,208and210. Lateral trim is maintained automatically.

Moreover, barges can be arranged so that, during unloading, bulk material discharge at the bow144of one barge is fed into the stern146of the barge ahead. By using a collecting conveyor (not shown) parallel to the bow of a raft of barge (not shown), an entire raft can be unloaded without breaking the raft.

When a storage and reclaim system embodying the invention is installed in a ship, it is anticipated that a 100,000 ton vessel can be unloaded in less than eighteen hours.

While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.