Abstract:
A method and apparatus for automatically sorting and blending coal and other fuel stocks through a computer-controlled process in order to achieve a specified blend of materials. By sorting fuel stocks with different characteristics into different stacking points, an operator can then automatically combine and uniformly blend these sorted fuel stocks to create a variety of blended materials with different properties tailored to the specific needs of the operator or end user. The computer-controlled nature of the process allows for precise blending in an automated and more efficient and reproducible fashion.

Description:
FIELD OF INVENTION 
     The present invention generally relates to an apparatus and method for sorting and blending coal and other fuel stocks through an automated, computer-controlled process in order to achieve a specified blend of materials. 
     BACKGROUND OF THE INVENTION 
     Power stations, also known as power plants, serve as industrial facilities for generating electric power. In general, many of these power plants rely on coal as the source of energy to generate electricity. These power plants can burn a significant amount of coal per day, e.g. 15,000 tons, at a particular heat value, e.g. 12,200 BTU/pound (British Thermal Unit/pound) for a larger facility. Frequently, coal power plants are located at or near coal mines in order to reduce the costs of obtaining and transporting the coal to the power plant. Thus, these coal power plants are designed to burn coal with the particular characteristics of the nearby coal (e.g., heat value or sulfur content). However, when the coal power plant operations eventually exhaust the economically feasible onsite or nearby coal reserves, the power plants must begin to use coal delivered from other sources. The heat value of the offsite coal may differ drastically from the value of the onsite coal, and, thus, power plants are faced with the problem of using coal that does not match the design parameters of the power plant, which can either reduce the efficiency of the power plant if the offsite coal has a lower heat value or significantly increase the fuel costs by burning higher-than-necessary quality coals. 
     In addition to the differing heat values, the offsite coal may have differing levels of undesirable non-carbon based elements or other components that adversely affect either the operating efficiency of the boilers that produce the steam for the power plant or the emission limits for the permits held by the power plant. For instance, the presence of too much sulfur or mercury in the coal can cause the power plant emissions to exceed the allowable levels under the applicable permits. The presence of too much ash (and rock and other non-carbon based elements) or moisture can interfere with the efficiency of the boilers and cause a reduction in the overall efficiency of the power plant. 
     Power plant operators have partially solved these problems by bringing in various grades of offsite coal and manually blending them in order to crudely create a blended coal at roughly the desired heat value or properties for the particular plant. However, this blending is often done by manually mixing one type of offsite coal with another using bulldozers or other moving equipment, which lacks precision in uniformly blending the coal to a specific heat value or property. It also lacks the ability to precisely control the characteristics of the blended coal. Because of the crude nature of the mixing, different portions of the blended coal will have very different characteristics even if the average characteristics meet the desired target values. 
     Because coal from multiple sources can vary greatly in terms of quality and the mixing is imprecise and not uniform, most power plants will limit their intake and rely on two sources of offsite coal in order to reduce the need for blending the coal as much as possible, or the power plants may choose to procure a higher quality more expensive product that exceeds the optimum burn quality requirement to avoid coal quality issues. As a result, these coal power plants (a) rely on limited coal sources instead of being able to receive coal from any number of providers, (b) blend few types of coal on site manually without much precision or uniformity of the overall blended product, and (c) lack the capacity to blend coal from many sources in an efficient, precise, and uniform manner to meet varying fuel, efficiency, or regulatory requirements. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention employs a new and novel method for sorting and blending fuel stocks of varying quality or characteristics through an automated, computer-controlled process in order to combine multiple fuel stocks or qualities of fuel stocks to produce an acceptable product for consumption by power plants or other end users. Unlike prior methods, the invention provides for a precise, automated method of blending of fuel stocks to meet the end user&#39;s particular requirements or regulatory demands. The invention provides the ability for a facility to receive substantial quantities of fuel stocks with different properties, sort and store these fuel stocks in differing areas, blend different stored fuel stocks in specific proportions, and deliver the blended fuel stock (in a variety of different combinations) to the end user through an automated, computer-controlled process. 
     In addition, this method provides for the flexibility, if desired, to change the characteristics and properties of the blended fuel stock based on the current needs of the operator or end user. Thus, for example, the invention can automatically provide coal of one heat value at one time of the day and a different heat value at another time of day based on the needs of an end user, such as a coal power plant. This kind of flexibility can be important to coal power plant operators who may not need the highest efficiency coal during off-peak hours, and want to save the highest efficiency (and more expensive) coal for peak-hour usage. This flexibility can also be important to a coal supplier for the pre-blending of coals for various customers with different coal quality requirements. 
     Furthermore, this invention can be used to reduce the level of certain components or contaminants in the fuel stock to a desired level. For example, an operator can mix coal with high sulfur content and low sulfur content together to create a blended coal with sulfur content within the applicable regulatory limits. 
     The invention can also be used to eliminate certain types of waste by blending the waste with another fuel stock. For example, an operator can blend coal with wastes, such as tire chips or coal refuse, to form a blended fuel stock that can be used in a particular type of boiler or facility. 
     This invention could also be used to enhance fuel stocks by blending in additives to increase the performance of the fuel stock. For example, an operator could blend coal with petroleum coke to increase the heat value of the coal. 
     In one example, an apparatus for sorting and blending fuel stocks, comprising a plurality of intake points to receive the fuel stocks; a plurality of intake feeders coupled to the intake points and to an intake conveyor to transfer the fuel stocks to one of a plurality of stacking tubes; a plurality of transfer conveyors coupled to the intake conveyor to transfer the fuel stocks between the stacking tubes; a plurality of transfer gates coupled to the transfer conveyors to direct the fuel stocks to the stacking tubes; a covered reclaiming chase located below and coupled to the stacking tubes; a reclaiming chase conveyor located in and running within the reclaiming chase; a plurality of reclaiming gates located in a roof of the covered reclaiming chase and positioned to control a flow of the fuel stocks around the stacking tubes through a plurality of reclaiming feeders onto the reclaiming chase conveyor; a plurality of belt scales coupled to the intake conveyor, transfer conveyor, and reclaiming chase conveyor; and a computer system coupled to the intake feeders, transfer gates, reclaiming feeders, intake conveyor, transfer conveyors, and reclaiming chase conveyor to control and monitor the intake feeders, intake conveyor, transfer conveyors, reclaiming feeders, and reclaiming chase conveyor; to control and monitor an opening and closing of the transfer gates and reclaiming gates; and to monitor an amount of the fuel stock passing over the belt scales. 
     In another example, an apparatus for sorting and blending fuel stocks, comprising an intake point to receive the fuel stocks; an intake feeder coupled to the intake point and to an intake conveyor to transfer the fuel stocks to one of a plurality of stacking points; a transfer conveyor coupled to the intake conveyor to transfer the fuel stocks between the stacking points; a transfer gate coupled to the transfer conveyor to direct the fuel stocks to the stacking points; a reclaiming chase coupled to the stacking points; a reclaiming chase conveyor located in and running within the reclaiming chase; a plurality of reclaiming gates coupled to the reclaiming chase and positioned to control a flow of the fuel stocks around the stacking points through a plurality of reclaiming feeders onto the reclaiming chase conveyor; and a computer system coupled to the transfer gate, reclaiming feeders, intake conveyor, transfer conveyor, and reclaiming chase conveyor to control and monitor the intake conveyor, transfer conveyor, reclaiming feeders, and reclaiming chase conveyor, and to control and monitor an opening and closing of the transfer gate and reclaiming gates. 
     In a further example, a method for blending fuel stocks, comprising receiving a received fuel stock at an intake point; sorting the received fuel stock into a sorted fuel stock by sending the received fuel stock from the intake point to one of a plurality of stacking points through a coupled intake conveyor and a transfer conveyor; blending the sorted fuel stock into a blended fuel stock by transferring the sorted fuel stock to a reclaiming chase conveyor in a reclaiming chase coupled to the stacking points through a plurality of reclaiming gates and a plurality of reclaiming feeders; and controlling the receiving, sorting, sending, blending, and transferring of the fuel stocks by a computer system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawing illustrates an embodiment of the invention and explains the principles of the invention. 
         FIG. 1  shows a general schematic of the blending system. 
         FIG. 2  shows a generalized schematic of the connections between a computer system and various subsystems of a blending system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An exemplary embodiment of the invention is described below. It will be understood by those skilled in the art that variants of this exemplary embodiment can be used to practice the inventions claimed. 
     Described below is an exemplary system for automatically sorting and blending coal using a computer-controlled assembly of hoppers, conveyors, gates, stacking tubes, chutes, and belt scales. As shown in  FIG. 1 , the blending system  10  is comprised of three drive-over intake hoppers  12  that receive coal  14  from dump trucks. Although the intake points in this particular exemplary embodiment are drive-over intake hoppers in which dump trucks can directly dump their loads of received coal  14  into the drive-over hoppers  12 , other numbers and types of intake points (such as back-up dumps and dozer traps) and other types of delivery mechanisms (such as barges, train cars, or conveyor belts) could be used instead and fall within the scope of the invention. 
     Beneath each of the drive-over intake hoppers  12  are intake weigh feeders  16  controlled by a computer system  18 . Other intake feeders, such as belt feeders or vibratory feeders, could be used and fall within the scope of the invention. Computer system  18  can independently stop, start, and regulate each weigh feeder  16  to control the amount of coal from each intake hopper  12  that is transferred to the intake conveyor  20 . In this way, the blending system operator can premix the received coal  14  before transferring it to the rest of the system. For example, if the operator knows it will be receiving loads of 11,000 and 13,000 BTU/pound coal during the day, it can hold the loads in two of the drive-over intake hoppers  12  and then open the respective weigh feeders  16  to mix the two loads to create a 12,000 BTU/pound blend of coal to be transferred to the rest of the system. While the blending system  10  can process coal of nearly any heat value, it typically receives coal with heat values ranging from 9,000 to 13,000 BTU/pound. 
     Coal from the intake conveyor  20  is then transferred through a series of connected or linked transfer conveyors  30  to the top of one of six stacking points—in this case, stacking tubes  22 . A stacking tube is a structure by which the received coal  14  can be sorted in piles  24  of sorted coal  26 . The received coal  14  enters at the top of the stacking tube  22  and falls inside the tube. Openings  28  in the sides of the stacking tube  22  allow the received coal  14  to exit the stacking tube  22  in a controlled manner to form piles  24  of sorted coal  26  surrounding the stacking tube  22 . Some additional advantages of stacking tubes  22  are that they reduce the amount of dust created when piling the sorted coal  26  and that they facilitate the stacking of sorted coal  26  without employing a bull dozer or other similar equipment. Given the particular needs and geography of the facility, the particular stacking tubes  22  used in this exemplary embodiment are square in cross section with each side being ten feet long and range in height from 56 to 88 feet. As shown in  FIG. 1 , these particular stacking tubes  22  contain a series of 4 by 4 feet square openings  28  in each of the sides in order to allow coal placed in the stacking tubes  22  to fall into conical piles  24  around the base of each stacking tube  22 . Again, the particular number, dimensions, and geometry of stacking tubes  22  and openings  28  used in this exemplary embodiment are not critical to this invention, and an individual of ordinary skill in the art would recognize that the number, dimensions, and geometry of stacking tubes  22  and openings  28  could be varied and still fall within the scope of this invention. In addition, stacking points other than stacking tubes (such as silos or radial or stationary stacking conveyors) could be used and still fall within the scope of this invention. 
     Each stacking tube  22  is connected or linked at the top by a series of transfer conveyors  30 . In addition, at the top of stacking tubes  22  are transfer gates  32 . This exemplary embodiment uses gravity flow diverters or flop gates as transfer gates  32 , but one skilled in the art would recognize that other transfer gates could be used and still fall within the scope of this invention. Transfer conveyors  30  and transfer gates  32  are connected and controlled by computer system  18 . By controlling which transfer conveyors  30  are on and which transfer gates  32  are open, incoming coal from intake conveyor  20  can be directed to different stacking tubes  22 . In this way, the received coal  14  can be sorted into piles  24  corresponding to different qualities or characteristics, such as the heat value (BTU/pound) or the sulfur or mercury content of the coal. In general, the coal that is used more often in the blending process is directed to the taller stacking tubes  22 , which have a larger capacity to pile and store the coal. By having multiple stacking tubes  22 , the operator can receive, sort, and store a variety of different types of coal that can later be blended in multiple different ways, depending on the operator&#39;s needs. In addition, the operator can store the same type of coal in more than one stacking tube, if desired. 
     Beneath stacking tubes  22  and located in the ground is an 850 foot covered reinforced concrete reclaiming chase  34  that has a 10 by 11 foot internal cross section. Inside this reclaiming chase  34  is a forty-eight inch-wide reclaiming chase conveyor  36  that runs the entire length of the reclaiming chase  34 . There are sixteen 6 by 6 foot reclaiming chase openings  38  (not all are shown in  FIG. 1 ) in the roof of the reclaiming chase  34  that have been placed in such a fashion as to allow the sorted coal  26  surrounding each stacking tube  22  to be directed onto the reclaiming chase conveyor  36 . Again, the particular dimensions of the reclaiming chase  34 , the reclaiming chase conveyor  36 , and reclaiming chase openings  38  described in this exemplary embodiment can vary depending on the needs of the operator, the volume of the coal being processed, the location of the blending system  10 , and other parameters of the blending system  10  and still fall within the scope of the invention. 
     As the sorted coal  26  in piles  24  is used, bulldozers or other coal-moving equipment are used to move the sorted coal  26  to make sure that a sufficient amount of sorted coal  26  remains over the reclaiming chase openings  38 . Reclaiming gates  40  are placed in the reclaiming chase openings  38  in order to control the flow of the sorted coal  26  onto the reclaiming chase conveyor  36 . Each reclaiming gate  40  is independently controlled by computer system  18 . In this exemplary embodiment, reclaiming gates  40  are gravity flow slide gates, but other types of gates or diverters could be used and fall within the scope of the invention. Sorted coal  26  from piles  24  can only fall onto reclaiming chase conveyor  36  when computer system  18  opens the appropriate reclaiming gate  40 . Reclaiming feeders  42  are located below each reclaiming gate  40  to direct and regulate the flow rate of the sorted coal  26  onto the reclaiming chase conveyor  36 . While this exemplary embodiment uses vibratory feeder pans as the reclaiming feeders  42 , other types of feeders, such as belt feeders and auger screw feeders, could be used and fall within the scope of this invention. The angle of the discharge end  43  of each reclaiming feeder  42  can be adjusted in order to assist the flow of sorted coal  26  onto the reclaiming chase conveyor  36 . In addition, air cannons  44  are connected to each reclaiming feeder  42  in order to dislodge any of the sorted coal that may at times bridge the opening and create blocking of the reclaiming feeder  42 . 
     By opening only certain reclaiming gates  40 , sorted coal  26  with different qualities (such as heat value, sulfur content, or mercury content) can be combined together onto the reclaiming chase conveyor  36  to create a blended coal  46  with certain desired characteristics. For example, if the sorted coal  26  around one stacking tube  22  has a heat value of 12,000 BTU/pound and the sorted coal  26  from around another stacking tube  22  has a heat value of 10,000 BTU/pound, computer system  18  can open a reclaiming gate  40  under each of these piles  24  to create an 11,000 BTU/pound blended coal  46 . Alternatively, computer system  18  could open one reclaiming gate  40  under the 10,000 BTU/pound pile  24  and three reclaiming gates  40  under the 12,000 BTU/pound pile  24  to create an 11,500 BTU/pound blended coal  46 . 
     By utilizing the various conveyors, feeders, stacking points, and gates, the coal is repeatedly folded and mixed as it passes through the blending system  10 , thereby creating a more uniformly blended coal  46  than would be obtained by simply mixing piles of coal with bulldozers or other manual means. 
     In addition, computer system  18  can control the amount of blended coal  46  exiting the reclaiming chase conveyor  36  by opening multiple reclaiming gates  40  (e.g., doubling the flow by opening twice the number of reclaiming gates  40 ), by changing the amount the reclaiming gates  40  are opened, by adjusting the angle of the reclaiming feeders  42 , and by increasing or decreasing the intensity of the vibration of the reclaiming feeders  42 . 
     Belt scales  48  are placed throughout the blending system  10  in order for the computer system  18  to monitor the amount or weight of coal travelling on the various conveyors in the system. In this way, computer system  18  recognizes how much coal has been received at the drive-over intake hoppers  12 , how much coal is being placed into each stacking tube  22 , how much coal is being blended onto the reclaiming chase conveyor  36 , and how much blended coal  46  is exiting the blending system  10 . 
     The discharge end of the reclaiming chase conveyor  36  is connected or linked to an output conveyor  50  and sent to transfer point  52 , the site at which the blended coal  46  can be directed to a coal-fired boiler facility at electrical power plant  54 . The exemplary embodiment described above can receive more than 5 million tons of coal annually and deliver as much as 1,200 tons of blended coal  46  (at, for example, 12,200 BTU/pound) to power plant  54 . The exemplary embodiment can change both the amount and characteristics of blended coal  46  based on the current needs of power plant  54 . 
     Once the blending system  10  creates blended coal  46 , one of ordinary skill in the art would recognize that blended coal  46  can be directed to a variety of destinations, such as storage silos, boiler facilities, trucks, vehicles, barges, ships, train cars, stacking tubes, piles, or other conveyors, depending on the application or the operator&#39;s needs. 
     Computer system  18  is a series of computers and programmable logic controllers connected or linked by fiber-optic or wire cabling throughout blending system  10 . As shown in  FIG. 2 , Computer system  18  receives inputs from a variety of sensors and detectors, such as interlocks, sensors, belt scales  48 , and flow meters. Based on the parameters set by the operator, computer system  18  can control the various subsystems in blending system  10 , including conveyors  20 ,  30 ,  36 , and  50 , feeders  16  and  42 , gates  32  and  40 , and air cannons  44 . Computer system  18  can open and close the various gates, turn on and off the various conveyors, and adjust the vibration of the feeders. Computer system  18  also maintains information about what type and amount of coal is available in each location of blending system  10 , including what type of coal has been received at each drive-over intake hopper  12 , what type of coal is being transported by intake conveyor  20 , what type of coal is being transported by transfer conveyors  30 , what type of coal is in each pile  24  around each stacking tube  22 , and what type of coal is being blended onto reclaiming chase conveyor  36 . The precise connections and programming of computer system  18  depends on the equipment being used and how it has been located and configured. One of ordinary skill in the art would recognize that the computer system  18  could be configured in a variety of different manners, depending on the equipment used and the control desired by the user. 
     In another embodiment, an end user, such as power plant  54 , could send a signal to the blending system  10  directing that a certain quality of coal (for example, a heat value of 12,200 BTU/pound) be delivered to the end user. Computer system  18  would then make the appropriate calculations based on the sorted coal  26  that is present and automatically adjust the blending system  10  to deliver the requested blended coal  46  directly to the end user. This could also be accomplished by installing a coal analyzer that instantaneously samples and analyzes the blended product and then relays that information to computer system  18  that then adjusts the blend ratios accordingly. 
     While the exemplary embodiment of blending system  10  blends various types and grades of coal as its fuel stock, the invention is not limited to just blending coal. Rather, one of ordinary skill in the art would recognize that other fuel stocks may be blended, including but not limited to biomass, coke, sawdust, tire scrap, filter cake (pod fines), and coal refuse. By blending various materials together in blending system  10 , an operator may create a blended material that has specific desired properties, such as a particular heat value (BTU/pound) or sulfur content at or below a specified level. Blending system  10  may also be used to eliminate less desirable materials by combining them in appropriate quantities with other materials. For example, an operator could still utilize low heat value coal that would otherwise not be suitable for the operator&#39;s desired application by combining it with higher heat valued coal to form a blend of coal with an acceptable or useful heat value. An operator could also still utilize coal with an inappropriately high contaminant by blending it with a purer coal such that the average contaminant content fell below acceptable levels. 
     The foregoing description has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The descriptions were selected to explain the principles of the invention and their practical application to enable others skilled in the art to utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. Although particular constructions of the present invention have been shown and described, other alternative constructions will be apparent to those skilled in the art and are within the intended scope of the present invention.