Author
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Anthony, William |
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Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/24/2006 Publication Date: 7/5/2006 Citation: Anthony, W.S. 2006. New technology to separate rubber crumb from fiber. Applied Engineering in Agriculture. Vol. 22(4): 563-570. Interpretive Summary: Over 285 million tires are discarded annually in the U. S. and between 1 and 3 billion are currently in landfills. About 75% of the discarded tires are placed in landfills annually, and although they represent only 1% of the municipal solid waste, they are not biodegradable and pose a significant environmental problem. The scrap tire recycling industry in the United States has grown rapidly since 1986. One of the more acceptable disposal practices which is estimated to use 18 million tires per year, the tires are cut into pieces and "pulverized" into rubber particulates and polyester/nylon fiber using either a cryogenic treatment (freezing to 300 °F with liquid nitrogen) and hammer mill or by ambient grinding. Unfortunately, from 10 to 50% of the tire is still discarded as waste called fluff. A new machine to separate the waste fluff produced by tire recycling plants into marketable products such as crumb rubber and fiber was developed and tested in laboratory and field recycling facilities. The new machine divided the fluff into 70% crumb, 13% clean fiber, 9% partially cleaned fiber, 5% large pieces of unground rubber, and 3% waste. Economic evaluation for three tire recycling plants that processed from 2 to 5 million tires annually indicated that their gross income could be increased nearly $2 million per year depending on the quantity of tires processed and the landfill costs. The machines cost about $100,000 and are now available for commercial use. Technical Abstract: Tests at a research laboratory and field evaluation at a commercial tire recycling facility demonstrated the viability and economic value of a new machine to separate the waste fluff produced by tire recycling plants into marketable products such as crumb rubber and fiber. Two new fluff recycling machines were designed, constructed, patented and tested in the lab (prototype and improved), and one (prototype) was tested in a commercial plant. Fluff from several recycling plants was processed with the machines. After processing with the prototype machine, the fluff differed substantially in composition and contained from 34 to 87% crumb by weight, and from 1 to 26% fiber. The crumb was mostly 300 microns or smaller. The quantity of unground rubber in the fluff ranged from 2 to 64% and greatly impacted the amount of recoverable crumb and fiber. About 1% of the input material was discharged as waste by the air collection system used to transport the fiber as it exited the machine. Field tests at a commercial tire recycling facility were successful and the prototype machine yielded 70% crumb, 13% clean fiber, 9% partially cleaned fiber, 5% large pieces of unground rubber, and 3% cyclone waste. Evaluation of the improved machine with fluff from five recycling plants produced 40 to 67% crumb, mostly 300 microns or smaller. The highly variable raw material yielded from 1 to 21% clean fiber, 9 to 30% rough fiber, and 3 to 48% unground rubber. Economic evaluation for three tire recycling plants that processed from 2 to 5 million tires annually indicated that their gross income can be increased from $0.672 to $1.935 million per year depending on the quantity of tires processed and the landfill costs. The machines process about 1,491 kg/hr per meter of width (1,000 lbs/hr/ft) and cost about $100,000. The machines are now available for commercial use. |
