Efficient shredding

For a snowboarder, “shredding” means making wonderful, athletic moves on the way down a ski hill. For a recycler, shredding is a profitable way to process plastic scrap into valuable pellets. However, recyclers must make some important moves to ensure that both their facilities and their end products represent peak performance.

With its processing plant in Charlotte, North Carolina, Engineered Recycling Co. (ERC) is among the leaders in the recycling of HDPE (high-density polyethylene) scrap, whether in the form of intermediate bulk containers (IBCs) or as loose or baled HDPE bottles.

The ERC-Charlotte facility is a 210,000-square-foot specialized industrial building. According to ERC, it is home to the two largest single-shaft shredders in North America, each capable of shredding or grinding as much as 20,000 pounds per hour or more, depending on product mix and sizing screen.

“In total we process a little under 6 million pounds per month,” says Peter Suttoni, president of ERC.

HDPE, fractional-melt HDPE and polypropylene (PP) are the main materials that go through ERC’s shredders.

The company bills itself not only as an expert in HDPE recycling but also in plastics processing. “We thoroughly understand what it takes to make premium plastic products,” Suttoni says.
 

The process

Among the products ERC produces are postindustrial, HMW (high molecular weight) 4 to 7 HDPE pellets; postconsumer, fractional melt HDPE; and postindustrial, HWM 9 to 12 HDPE pellets.

Scrap materials are shipped to the company’s recycling facility in bales. After the bales are broken open, the next step is to do an initial size reduction and liberation of foreign materials.

“We use powerful magnets for metal removal and trommel screens for polypropylene separation and removal,” Suttoni says of the company’s equipment.

“Our high-speed wash lines are custom engineered, and our extrusion lines are specially designed for the type of material they process,” he adds.

Until recently, the company had a second recycling operation in Chicago. However, the two operations were consolidated at the North Carolina location, and the equipment from the Chicago plant was relocated to Charlotte.

“That gives us three very large single-shaft shredders here in Charlotte,” Suttoni says of the consolidated operation.

Two of the shredders are set up to process HMW HDPE. A third is set up to process fractional-melt HDPE that is gathered from curbside collection programs.

A typical truckload of HDPE bales coming into ERC might have been purchased from anywhere in North America.

A hydraulic tipper allows the company to take in large quantities of product, push a button and have the rest of the system automated for proper handling. It is a bit more complicated than that, of course.

“Bales are broken in trommels,” Suttoni says. The material is processed under magnets to remove any ferrous metallic contamination and then enters the shredders unwashed.”

In addition, any foreign material or fines are liberated from the plastic. Paper labels are a major concern, and the system handles them after size reduction but before final processing. The aspirator pushes the paper scrap and fines out of the material flow. While not every piece of paper is caught at the beginning of the process, almost all of it is pulled away from the underlying plastic by the time the process concludes, Suttoni says.

“We aspirate all plastic and fill supersacks that we track by lot codes as we move the material through the plants,” he says. The end product is washed and extruded to pellets.”

He continues, “At the heart of the system are two Vecoplan VAZ 2500-T shredders.”

The size of the company’s shredded material is confidential. “We don’t normally identify the size of our shred material as we feel it is a competitive advantage,” Suttoni says.

What he will say, however, is, “We prefer the Vecoplan shredder. Their machines are durable, and service is strong.”

Suttoni says “size, throughput and price” are his primary considerations when designing a processing line for ERC and when shopping for shredding equipment for the operation.
 

Shredder details

The two VAZ 2500-T shredders from Vecoplan, Archdale, North Carolina, used at ERC’s Charlotte operation are identical. The shredders have rotors that are 98 inches wide and 25 inches in diameter. Each of the units is equipped with 171 cutters and each cutter is 40 millimeters square.

The drive on the shredders is the patented Vecoplan HiTorc electromagnetic drive.

“The drive will provide a speed range of 30 to 300 rpm,” says Bob Gilmore, sales director at Vecoplan LLC.

The preferred speed is selected by the operator. The faster the drive goes, the faster the rotor moves, and the faster the machine processes. However, many factors downstream from the shredder will guide the operator in selecting the ideal speed for the shredders on any given day. Since it offers a continuous range of speeds, the operator can set the process to run at the best rate for the equipment and the product being produced. The drive is designed to allow quick reversing action and controlled stopping.

“You get tremendous torque values from the HiTorc units,” Gilmore says. “It has all the advantages of a hydraulic drive without the disadvantages of a hydraulic drive,” he adds.
 

Operating efficiency

The HiTorc drive is designed to offer other advantages besides its speed range. As one example, the shredder is designed to be energy efficient. Any motor rates a minimal amount of amperage even when idle; while the HiTorc has a rating of 300 horsepower, it only pulls single-digit amps when it is idling, according to the manufacturer. “That’s similar to what a home hair dryer pulls,” Gilmore says.

The drive can be programmed to maximum ramp-up speed. Although not an overriding concern at ERC, in many areas of the country electricity is billed at peak usage. The units ERC uses can be programmed not to exceed a certain draw on the grid, thus operating at a cheaper rate.

The manufacturer claims a power savings of 58 percent, or $7 per hour. Here are the numbers: With the HiTorc drive operating on a grid billed at 8 cents per kilowatt hour, and figuring 250 kilowatts and 0.3 average loading, consumption would be 75 kilowatts. Running 24 hours per day, seven days per week, and figuring an 85 percent run time, the machine would consume 10,710 kilowatt hours per week at a cost of $857.

A conventional AC drive running at 223 kilowatts with an 0.8 average load would consume 178 kilowatts. With the same run time, the machine would consume 25,418 kilowatt hours per week at a cost of $2,033, more than twice the cost of the HiTorc drive.
 

Maintenance schedule

Of course, when handling the volumes of material that ERC processes, keeping the equipment up and running is vital.

One key to keeping the machinery in good shape, Suttoni says, is continual rotation of the cutters.

“Our people do a considerable amount of welding to keep the rotors and cutter holders in specification,” Suttoni adds.

On top of that, there is the usual maintenance to cutting teeth. However, maintenance on the drive is minimal.

“Compared to a typical drive system, the HiTorc system has no moving parts,” Gilmore says. In a usual operation, there is a motor, drive shaft, clutch, gear reducer and the like. Each of those parts has moving parts of its own. With the HiTorc drive, only the electromagnetic motor is connected directly to the rotor.

One benefit of the company’s shredder type and its maintenance program is that ERC easily can change from one material to another when necessary. This is just another example of the productivity built into ERC’s system—from material flow to energy savings, the shredders at ERC are able to handle a mountain of material effectively and efficiently.

The author is a freelance writer based in Cleveland and can be contacted via email at curt@curtharler.com.