CROSS-REFERENCE TO RELATED APPLICATIONS
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This application claims priority to U.S. Provisional Patent Application Ser. No. 62/197,432, filed on Jul. 27, 2015, which is incorporated herein by reference in its entirety.
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1. Field of the Invention
The present invention relates generally to systems and methods for pyrolyzing carbon-containing materials.
2. Description of Related Art
In general, pyrolysis is a process of thermochemically decomposing carbon-containing materials at an elevated temperature and in the absence of oxygen. Pyrolysis may be used to convert carbon-containing materials including, for example, rubber-containing composites such as tires and other industrial rubber and rubber-based items, into other materials, including carbon- and hydrocarbon-containing compounds like pyrolysis oils, residue gases, and carbonaceous solids. In addition to providing a more environmentally-benign method of disposing of various carbon-containing waste materials, such as, for example, used tires, pyrolysis also provides an opportunity to create valuable end products, which may themselves be further usable, salable, and/or recyclable. To date, a commercial-scale pyrolysis facility capable of efficiently and predictably recovering valuable products from various carbon-containing feedstocks has yet to be provided.
Therefore, a need exists for systems and method of pyrolyzing carbon-containing material to create valuable end products. Ideally, such systems and methods could be employed on a commercial scale and could be configured to process a wide variety of feedstocks, while still providing products with predictable and desirable properties.
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One aspect of the present invention concerns a method for pyrolyzing a rubber-containing material. The method comprises the steps of (a) selecting a target value for a property of a pyrolysis product; (b) based on the target value, obtaining a heating profile for the pyrolysis of the rubber-containing material, wherein the heating profile includes a range of prescribed pyrolysis temperatures as a function of time; (c) heating a crucible containing a first quantity of the rubber-containing material to a temperature sufficient to pyrolyze at least a portion of the first quantity of the rubber-containing material to thereby provide pyrolysis vapor and pyrolysis solids; and (d) recovering at least a portion of the pyrolysis vapor or at least a portion of the pyrolysis solids in at least one downstream processing zone to thereby provide the pyrolysis product. During the heating, heating, the actual value of the pyrolysis temperature varies by not more than 20° F. from the prescribed pyrolysis temperature provided by the heating profile.
Another aspect of the present invention concerns a method of pyrolyzing a pyrolyzable material. The method includes the steps of (a) pyrolyzing a first quantity of pyrolyzable material under conditions sufficient to form a first amount of pyrolysis vapor and pyrolysis solids; (b) recovering a first product from the first amount of the pyrolysis vapor or the pyrolysis solids; (c) measuring the value of at least one property of the first product; (d) based on steps (a) through (c), constructing an operating profile that comprises a prescribed value, or ranges of values, for at least one operating parameter of the pyrolysis of step (a) and/or the recovering of step (b), wherein the operating profile further comprises a target value, or range of values, for the property measured in step (c); (e) at least partially filling a crucible with a second quantity of pyrolyzable material; (f) pyrolyzing at least a portion of the second quantity of pyrolyzable material under conditions sufficient to form a second amount of pyrolysis vapor and pyrolysis solids; and (g) recovering a second product from the second amount of the pyrolysis vapor or the pyrolysis solids. The pyrolyzing of step (f) and/or the recovering of step (g) are performed according to the operating profile.
BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1 is a schematic diagram of an exemplary pyrolysis facility 10, particularly illustrating various areas within the facility and the relationships between these areas;
FIG. 2 is a schematic diagram of a pyrolysis zone 214 suitable for use in the pyrolysis facility 10 shown in FIG. 1, particularly illustrating the processing steps of crucibles 250a-250l during a portion of the overall heating cycle shown in FIGS. 3a-c;
FIG. 3a is a chart illustrating the overall heating cycle of crucibles 250a-250l in the pyrolysis zone 214 shown in FIG. 2, particularly illustrating the processing steps for each of crucibles 250a-250l during the first eight hours of a 24-hour cycle;
FIG. 3b is a chart illustrating the overall heating cycle of crucibles 250a-250l in the pyrolysis zone 214 shown in FIG. 2, particularly illustrating the processing steps for each of crucibles 250a-250l during the second eight hours of a 24-hour cycle;
FIG. 3c is a chart illustrating the overall heating cycle of crucibles 250a-250l in the pyrolysis zone 214 shown in FIG. 2, particularly illustrating the processing steps for each of crucibles 250a-250l during the last eight hours of a 24-hour cycle;
FIG. 4 is a schematic diagram of an exemplary pyrolysis zone 414 and a separation zone 416 suitable for use in pyrolysis facility 10, particularly showing the use of a single separation zone to process pyrolysis vapor from multiple crucibles heated in more than one pyrolysis furnace;
FIG. 5 is a schematic diagram of an exemplary solids processing system 518 suitable for use in pyrolysis facility 10 shown in FIG. 1, particularly illustrating various areas of the solids processing zone 518 and the relationships between these areas;
FIG. 6 is a schematic diagram of an exemplary solids processing system 618 suitable for use in pyrolysis facility 10 shown in FIG. 1, particularly illustrating one example of a dust collection system 650 and its related components; and
FIG. 7 is an exemplary yield curve, particularly showing the yield of pyrolysis gas, pyrolysis oil, and carbon black as a function of pyrolysis temperature during pyrolysis of a rubber-containing material.
Turning initially to FIG. 1, a schematic depiction of a pyrolysis facility 10 capable of pyrolyzing rubber and other carbon-containing materials to form a variety of valuable end products is provided. As shown in FIG. 1, pyrolysis facility 10 includes a feed preparation zone 12, a pyrolysis zone 14, a separation zone 16, and a solids processing zone 18. During pyrolysis of a carbon-containing material, larger carbon-containing molecules may be thermally decomposed and chemically modified in order to provide a lighter hydrocarbon pyrolysis vapor and a carbon-rich residual solid material. In some cases, the pyrolysis performed in pyrolysis facility 10 may be low temperature pyrolysis, which is generally carried out at temperatures less than about 1,000° F., or it may be high temperature pyrolysis, which is generally performed at temperatures exceeding 1,000° F. Additional details regarding the operation of pyrolysis facility 10 will be described herein, with respect to the Figures.
Pyrolysis facility 10 shown in FIG. 1 can be configured to process one or more types of feed. Any pyrolyzable carbon-containing materials may be used, including, for example, rubber and rubber-containing materials, plastics, wood, paper, biomass such as agricultural and forestry waste materials, coal, oils, including waste oil, and the like. Examples of suitable rubber-containing materials can include, but not limited to, tires, rubber-coated chains, reinforced rubber belts, mats, hoses, tubing, and combinations thereof. The pyrolyzable feed introduced into pyrolysis facility 10 can include one or more types of waste materials, including industrial waste materials, consumer waste materials, and/or agricultural waste materials, that otherwise have limited or no further use. Although generally described herein with respect to rubber-containing materials, it should be understood that pyrolysis facility 10 may additionally, or alternatively, be configured to process any suitable pyrolyzable material, including one or more of the carbon-containing materials listed above. In some cases, pyrolysis facility 10 may be configured to process a single feedstock, or a limited number of feedstocks, while, in other cases, pyrolysis facility 10 may be capable of pyrolyzing a wide range of feedstocks.
The feedstock introduced into facility 10 can be in any size and of any shape capable of being pyrolyzed within the facility. The feedstock may be introduced into facility 10 in a ready-to-process form, or it may require additional treatment prior to pyrolysis. When the feedstock includes tires, the tires delivered to facility 10 may be whole tires or the tires may be pre-shredded or ground into smaller pieces. When shredded, the average length, or longest dimension, of the tire feedstock can be at least about 0.5 inches, at least about 1 inch, or at least about 2 inches and/or not more than about 15 inches, not more than about 10 inches, not more than about 8 inches, not more than about 6 inches, or not more than about 5 inches. The tire feedstock may be pre-sorted, for example, by manufacturer, by type of tire (e.g., road tire, agricultural tire, heavy equipment tire, etc.), and/or by specific tire component (e.g., sidewall, bead, tread, etc.). Alternatively, the feedstock may include a mixture of tires from several manufacturers, it may include several types of tires, and/or it may include multiple tire components.
As shown in FIG. 1, the pyrolyzable feedstock introduced into pyrolysis facility 10 is initially introduced into a pretreatment and storage zone 20, wherein the feedstock may be pretreated, as needed, and/or stored prior to pyrolysis. In pretreatment and storage zone 20, the feedstock can be prepared, as needed, for subsequent pyrolysis by, for example, washing, drying, sorting, and/or shredding the feedstock into a more processable form. When, for example, the feedstock includes a mixture of tires, the tires may be sorted in pretreatment and storage zone 20 by manufacturer and/or by type, as discussed above. Alternatively, or in addition, whole tires may be shredded and, optionally separated into component parts, within pretreatment and storage zone 20, using suitable equipment. Pretreatment and storage zone 20 may also include one or more storage containers, areas, bunkers, or silos for storing the feed prior to pyrolysis.
As shown in FIG. 1, the feed exiting pretreatment and storage zone 20 can be transferred to a filling zone 22 via line 110. Any suitable transfer device can be used to move the feed from pretreatment and storage zone 20 to filling zone 22. Examples of transfer devices can include, but are not limited to, convey devices like conveyor belts and walking floors, or mobile vehicles such as a cart, trailer, or fork lift.
In filling zone 22, the pyrolyzable feed transferred from pretreatment and storage zone 20 via line 110 is loaded into one or more crucibles. A crucible can be any sealable container, capable of withstanding elevated temperatures, that is able to facilitate pyrolysis of the materials contained therein. Crucibles can be formed of any suitable material that is inert to the contents and capable of withstanding elevated pyrolysis temperatures. Such materials include, but are not limited to, steel or other similar metal. Crucibles can have any desirable size and/or shape and may, for example, have an internal volume of at least about 15 cubic feet, at least about 25 cubic feet, or at least about 30 cubic feet and/or not more than about 150 cubic feet, not more than about 100 cubic feet, not more than about 75 cubic feet, or not more than about 50 cubic feet. In some cases, the crucibles may be cylindrical and may have a diameter of at least about 2 feet, at least about 2.5 feet, or at least about 3 feet and/or not more than about 6 feet, not more than about 5 feet, or not more than about 4 feet, with a length of at least about 3 feet, at least about 3.5 feet, or at least about 4 feet and/or not more than about 8 feet, not more than about 7 feet, or not more than about 6 feet. The exact size and shape of the crucible may depend, in part, on the specific furnace configuration and desired batch size.
In filling zone 22, one or more crucibles may be at least partially filled with pyrolyzable feedstock which, can, for example, comprise a rubber-containing material. The amount of feed introduced into the crucible may vary depending on several factors, including the total production capacity of the facility, the size and shape of the crucibles, the type and form of the feed, the configuration of the furnace, and combinations thereof. In some cases, each crucible may be placed on a scale, tared, and filled with at least about 250, at least about 350, at least about 450, at least about 500 pounds, at least about 600 pounds, or at least about 700 pounds and/or not more than about 1,000 pounds, not more than about 900 pounds, or not more than about 800 pounds of pyrolyzable feed. Depending on the size of the crucible, this may result in at least 50 percent, at least 75 percent, at least 85 percent, or at least 90 percent of the total internal volume of the crucible being filled with pyrolyzable feed. The crucibles can be filled individually in sequence, or two or more crucibles may be filled simultaneously. Additionally, each crucible may be filled on an as-needed basis, or one or more crucibles may be pre-filled and held in a holding area (not shown) to await transfer into pyrolysis zone 14, which will be discussed in detail shortly. The crucibles can be filled according to any suitable method, including manually, by forklift, or by a hydraulic device.
Once filled, the crucible may be sealed by placing and securing a removable cover to the top of the crucible. Optionally, prior to securing the cover onto the crucible, a gasket may be inserted between the crucible and the cover in order to facilitate a better seal between the two components and prevent outward leakage or oxygen ingress during heating. When used, the gasket may be a high temperature reusable gasket capable of being exposed to multiple temperature cycles without losing functionality. After placement of the gasket, if any, the cover may then be secured onto the crucible in any suitable manner and can, for example, be bolted onto an upper flange surface of the crucible. In this way, the cover may be removably coupled to the crucible so that it may be subsequently removed, after pyrolysis, to facilitate emptying and refilling of the crucible for further pyrolysis cycles. In some cases, an overhead transport crane or other lift device may be used to place the cover onto the crucible and/or to transport the cover to and from a cover storage area (not shown).