Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
1999-03-09
2001-04-24
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C423S449100, C423S449600, C423S449700, C110S267000, C110S268000, C110S275000, C110S276000, C110S278000
Reexamination Certificate
active
06221329
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the production of carbon black through pyrolytic distillation of scrap tires. More specifically, the present invention relates to a used tire pyrolysis system and method that incorporates a novel feed tube and zoned heating of tire scrap material to extract carbon black, scrap steel, heating oil and gas.
As the supply of available landfill space decreases, environmentally sensitive disposal of consumed vehicle tires is become an ever-increasing problem. In the U.S. alone, over 280 million vehicle tires are scrapped and shipped to landfills each year. Although some of the used vehicle tires are recycled to be used in pavement and others are burned as boiler fuel, more than 80% of used vehicle tires end up being deposited in landfills. Discarding spent vehicle tires in landfills has been recognized as a significant waste of recyclable resources. For many years it has been known that used vehicle tires can be recycled by pyrolysis to obtain valuable by-products that can be sold and reused. Pyrolysis, generally speaking, is a thermal distillation or decomposition of a substance. In the case of used vehicle tires, this process is carried out in the absence of oxygen and at temperatures generally between 500° C. and 800° C.
The process of recycling used tires by pyrolysis allows the recovery of substantial amounts of oil, gas, carbon black and scrap steel. In particular, it is expected that using the apparatus described herein, it will be possible to recover approximately 35 tons of carbon black and 10 tons of scrap steel from 100 tons of shredded vehicle tires.
Although many machines have been designed to recycle used tires through pyrolysis, none have been entirely successful. One problem with many previous machines involves the presence of particulate matter in the gas that is evolved from the tires. Particulate matter—primary carbon dust and glass fiber, accumulates in fittings, vents and flame arrestors, which can obstruct passages and create substantial danger of explosion.
Another of the difficulties of the present methods to recycle used tires through pyrolysis is that the solid carbon product, carbon black, obtained is outside of the specification for most commercial grade carbon black and is therefore not commercially usable. Thus, in order to produce commercial grade carbon black it is necessary to invest thermal energy to the recovered oil obtained through pyrolysis. As can be understood, it would be much more energy efficient to directly recover a commercial grade carbon black through the pyrolysis of used vehicle tires.
Another drawback to known pyrolysis machines involves oil contamination in the carbon black which destroys the commercial value thereof. In order to produce high quality carbon black, virtually all oil must be removed. In known pyrolysis machines, the oil vapor released from the pyrolyzed material is drawn, at least partially, through or past the carbon black product, thus contaminating it with oil residue.
Handling the shredded tire pieces has also presented substantial challenges in known pyrolysis systems. The residual steel strands and natural stickiness of the heated rubber combine to make transporting the shredded tires to be pyrolyzed a significant challenge. For example, many known methods utilize a rotating screw to feed the shredded tires into a kiln in which the pyrolysis process occurs. Due to the inherent properties of the shredded tires, the persistent problem with known machines is “baling-up” of the shredded tires within the screw conveyor leading to jamming of the screw auger used to convey them
Therefore, it is an object of the present invention to provide a pyrolysis system that efficiently and effectively feeds shredded vehicle tires into a rotary kiln in which the pyrolysis process occurs. It is an additional object of the present invention to operate the process of the pyrolysis system in a separate zoned manner to most efficiently process the vehicle tires. It is another object of the invention to operate the process in separate zoned areas, each of which operates at a distinct temperature to maximize the efficiency of the pyrolysis process. It is a further object of the invention to efficiently separate the recovered carbon black from the scrap steel at the end of the rotary kiln. Further, it is an object of the present invention to evacuate the oil-containing producer gas from within the rotary kiln at a position spaced from the discharge end of the rotary kiln to prevent contamination of the carbon black.
SUMMARY OF THE INVENTION
The present invention is a processing system for the reclamation and recovery of desirable materials from shredded vehicle tires through pyrolysis. The process of the present invention involves initially receiving a supply of shredded vehicle tires in a feed chamber. The feed chamber generally includes a double-dumping arrangement to provide an air interlock to prevent air from entering into the feed chamber.
The feed chamber in turn is coupled to a first end of an infeed device that is positioned to transport the supply of vehicle tire pieces from the feed chamber. In the preferred embodiment of the invention, the infeed device is a rotatable feed cylinder that extends between a first end and a second end. The rotatable feed cylinder is defined by a generally cylindrical shell that extends between the first end and the second end. The feed cylinder includes a flight formed along the inner surface of the shell of the feed cylinder. The flight formed within the feed cylinder extends from the first end of the feed cylinder to the second end of the feed cylinder. The flight extends radially inward from the inner surface of the shell and forms a screw-like pattern from the first end of the feed cylinder to the second end of the feed cylinder. When the feed cylinder is rotated, the flight formed along the inner surface of the feed cylinder directs the tire pieces from the feed chamber coupled to the first end of the feed cylinder to the second end of the feed cylinder.
The second end of the feed cylinder, in turn, is coupled to a pyrolysis section in which the vehicle tire pieces are pyrolyzed into their constituent material, such as char and steel wire scrap. The pyrolysis section is generally devoid of oxygen to facilitate the pyrolysis process within the pyrolysis section. The pyrolysis section includes a rotary kiln having an infeed end and a discharge end. The infeed end of the rotary kiln is elevated relative to the discharge end such that the rotation and incline of the rotary kiln combine to transport the tire pieces through the rotary kiln. The infeed end of the rotary kiln is coupled to the second end of the feed cylinder to receive the supply of vehicle tire pieces from the feed cylinder. Preferably, the rotary kiln and the feed cylinder are joined to rotate together.
The rotary kiln in the pyrolysis section is divided into a plurality of individual heating zones. Each of the individual heating zones formed within the rotary kiln is heated to a distinct operating temperature that is independent of the operating temperatures of the other heating zones. Thus, as the rotary kiln rotates, the vehicle tire pieces are transferred between the heating zones from the infeed end to the discharge end of the rotary kiln. As the tire pieces traverse the rotary kiln, the tire pieces are pyrolyzed.
In one feature of the present invention, the rotary kiln is divided into three separate, distinct heating zones that each operate at a different operating temperature. Preferably, the operating temperatures of the heating zones decrease from the infeed end of the rotary kiln to the discharge end of the rotary kiln. In a preferred embodiment of the invention, the operating temperature of the first heating zone nearest to the infeed end of the rotary kiln is between 700° C. to 800° C. The operating temperature of the second heating zone positioned adjacent to the first feeding zone is preferably between 600° C. to 700° C., while the operating tempe
Faulkner Bobby P.
Hansen Roy W.
Unterweger Robert J.
Andrus Sceales Starke & Sawall LLP
Griffin Steven P.
Nave Eileen E.
Svedala Industries Inc.
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