According to the U.S. Department of Transportation, approximately 280 million tires are discarded in the U.S. each year. While as many as 30 million are reused, the majority are scrapped, with approximately 45 percent of them being landfilled and the rest recycled.
For recycling, steel, rubber, and fiber must be separated. A primary shredder reduces whole tires to large shreds, then a secondary shredder or granulator reduces the tire further and begins the process of separation. A third stage finishes the separation.
State Rubber and Environmental Solutions, LLC, (SRES) in Denver City, Texas processes about 300 scrap tires per hour, which translates to about 16 tons of material in an eight-hour shift. Dan Swanson, plant manager, said that reclaiming wire from scrap tires “has been attempted on and off over the last fifteen years,” but that it wasn’t until recently that it has been completely successful.
The problem, he said, “was getting enough of the rubber off of the wire.” Over the last two to three years, it has finally gotten to a point where the wire is clean enough, with rubber contaminants “two percent, if that much,” Swanson said. “It’s virtually nil.”
While the point of recycling tires is rubber reclamation, Swanson estimated that rubber is only about 65 percent of an average tire. Twenty percent is steel, and the last fifteen percent is fiber.
Reclaiming wire “is worth it because of the landfill costs,” Swanson explained. If the wire wasn’t clean enough for recycling, it would be landfilled. With landfill costs rising, steel prices good, and a viable market for the rubber, it makes sense to clean the steel. “The market has changed drastically over the last fifteen years,” Swanson said.
SRES receives whole tires and shreds them, using primary and secondary shredders from Granutech-Saturn Systems (GSS). The primary shredder is the Model 7240 BGHT and the secondary shredder is the Model 80 Grizzly.
Mike Hinsey, sales manager at GSS described the Model 80 Grizzly as a “300 horsepower, medium-speed grinder.” The Grizzly uses both fixed and rotating knives to shear and impact the tire shreds. It processes an average of three to four tons of material per hour, and up to five tons per hour, depending on the material.
The knife arrangement on the Grizzly is designed for efficient cutting, high production, and easy maintenance. An internal screen separates the clean granules from the larger pieces which require further processing.
Hinsey said that a 3/4” screen is average, but can be customized. The resulting rubber chips are nearly steel-free, while the mixed rubber and steel will generally have no more than ten to thirteen percent rubber.
After the Grizzly does its job at SRES, the contaminated wire goes to the Free Wire Reclaimer (FWR) manufactured by Action Equipment Company, Inc. (AEC) which uses a combination of vibration and inline magnetic separators to clean and separate the wire from the rubber.
Andy LaVeine, president of AEC explained that any unclean wire could go back to the granulating machine for further processing. At this point, the wire would have no more than ten percent contamination, and the final result is usually much less, as Swanson is experiencing.
Truck tires, LaVeine said, are easier to process and result in cleaner wire than passenger tires. While passenger tires might retain five to seven percent rubber contamination, truck tires average three to five percent.
When it comes to cleaning after granulating the tires, “rubber recovery alone justifies the machine,” LaVeine said, but explained that there are other savings as well. “If you can reclaim this stuff and you don’t have to re-circulate it to your granulator, you save on cutter wear with the granulator.”
The FWR’s input can sit directly under the granulator’s output or positioned elsewhere. The wire, which “looks like a wiry bird’s nest” travels on a vibrating conveyor, with clean rubber falling through a gap and wire going over the gap and coming off the end of the conveyor. The FWR can process two to three tons per hour.
LaVeine estimated that a tire recycler that ran a single shift and processed one ton of material per hour with the FWR could save as much as a half-million dollars per year. Besides the obvious landfill savings, LaVeine pointed out that freight would be reduced, and more rubber is reclaimed. He said the FWR could pay for itself in six months or less.
In business since 1872, Williams Patent Crusher & Pulverizer Co. Inc. (WPC) manufactures custom shredders. They manufacture a primary shredder, the Ripshear, which reduces whole tires to 2” x 12” strips.
The Nife Hog from WPC is designed to reduce shredded tires to a 5/8” to 3/4” size. The granulated rubber will be 95 to 98 percent steel-free while the steel wire will have from 10 to 15 percent rubber contamination remaining after processing.
The Nife Hog is available in several sizes and capacities, ranging from 150 to 300 horsepower, which process from 2,000 to 6,000 pounds of shredded tires per hour.
The Clean Wire System (CWS) from Bi-Metal Corporation (BMC) is a third-stage separator that is “designed to remove rubber and contaminants from steel wire extracted from tires,” according to Mark Bielicki, president of BMC. He described the process as “a combination of classification, agitation and magnetic separation.”
The CWS comes in a range of sizes and capacities, from the CWS Model 5800 up to the CWS Model 9160 which can process over 4,000 pounds of material per hour. BMC has been in the scrap business for 30 years, so along with selling the CWS, they provide a marketing plan for the reclaimed wire.
The CWS uses both a patented flexible membrane for classification, and both magnetic and air separation. Wire emerging from the Clean Wire System has less than two percent contamination. “It’s the cleanest in the industry,” Bielicki said.
No matter how it’s done, there’s no doubt that wire separation makes economic sense.