Equipment Focus: Vertical Shredders ‚Äč

Apr 23, 2020, 17:11 PM
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March/April 2020

By Ken McEntee

Vertical shredders excel at size reduction and liberation of materials, manufacturers say. Although this equipment is not very well known in North America,the quality demands of today’s scrap buyers might lead scrap processors to give it a look.

Equipment Focus Vertical ShreddersAbout six years ago, MetalX (Waterloo, Ind.) funded a full-scale test that paired a low-speed, high-torque shredder with a vertical shredder at its Waterloo facility, says the owner of the Chicago-area company that manufactured the machines. MetalX sold the low-speed, high-torque shredder, but it kept the vertical shredder, installing it in a different location, he says.

About three years ago, A&E Auto Electric (Spartanburg, S.C.), a 40-year-old family company that makes automobile starters and alternators, decided that it wanted to break apart “meatballs”—scrap motors that consist of steel cores wound with copper wire, with or without a steel housing—to segregate the copper and steel, optimizing the value of the scrap. It invested in a 600-hp vertical shredder to do the job.

Vertical shredders—also called vertical mills, vertical ring mills, or vertical grinders—“are designed to take whole or pre-shredded materials down to smaller, and often significantly more densified, fractions in one progressive step, using gravity rather than grates,” the Chicago-area owner says. They offer a greater degree of size reduction and material liberation than hammermill shredders or slow-speed, high-torque shredders, and the processing “seems to offer low wear costs due to the design,” he and other manufacturers say. But the two vertical shredders mentioned above are among just a half-dozen newly built machines known to have been installed at metal recycling yards in North America in recent years.

The Chicago-area owner says that his firm owns the brand that patented the original vertical shredder design in 1966. That brand licensed the technology to numerous other companies in Europe and now builds vertical shredders in the United States and Asia. “Up until about 1995, these older, pioneering machines were all over the place, and a lot are still out there,” he says. “It’s hard to keep track of them because they’ve been sold into the secondary market. They were popular at one time, then the big companies that were behind their use pulled their marketing, and the hammermill guys won out in the scrap metal industry.”

Other manufacturers say their vertical shredders differ significantly in design and application from the older generation of vertical shredders. They agree, however, that vertical shredders of any kind are rare in North American scrapyards. They are far more abundant in Europe and Asia, they say. Japan has more than 500 of them, one company reports, while other sources estimate that between 350 and 400 vertical shredders are operating in Europe. “In China, we’re building 10 machines a month just for the Chinese scrap metal market,” the Chicago-area owner says.

The North American prospects for this equipment could be looking up, however. Inquiries about vertical shredders have increased over the past year or two, manufacturers say, and they believe that as many as a dozen are likely to start up over the next couple of years. “It’s an expensive piece of equipment, so I don’t expect to see every scrap processing yard in the country buying one,” says the founder of a Connecticut-based metals processing and trading firm. His company operates a vertical shredder and sells a brand of them it contracts out for manufacturing. “But I predict that within the next 10 years, there will be a couple of them running in every state.”

In 1983, Leonard Schnitzer—then chairman and CEO of Schnitzer Steel Industries (Portland, Ore.)—said vertical shredders would become prevalent in scrapyards in the future, the Chicago-area owner says. “Now, 50 years later, that may come true.”

Vertical shredding benefits

Driving increased demand for vertical shredders in North America, these sources say, is the desire to liberate and segregate specific scrap commodities to sell to end users. “Liberation is really the key,” says the CEO of a German company with its U.S. headquarters in Georgia. “If you lose copper in the ferrous because they are still entangled, there is a loss of value of the material you want to sell.”

The president of a New Hampshire-based U.S. subsidiary of a Swiss company agrees. When potential customers “see the final product that they can get with a vertical shredder, and the subsequent separation, they suddenly realize that they can have a much wider customer base.”

An example is a company that’s currently exporting meatballs, he says. “If you process the meatballs further, and you have a clean copper and aluminum product and a clean ferrous product, you can directly [sell] to foundries or to smelters, and you can better influence the value of the material. It is beneficial for business development and to get more independence.”

Versatility is another advantage, the Georgia CEO says. A vertical shredder “has flexibility to run different materials. … Not a lot of people have 4,000 or 5,000 tons of meatballs per year,” he says. “Maybe they have 500 tons [of meatballs], and they have 6 tons of small radiators, and a certain quantity of iron or aluminum. These are all materials which can be processed with a vertical shredder.”

Vertical shredders provide “excellent liberation of composite material such as electric motors, meatballs, wire harnesses, [automobile shredder residue], shredder wire, e-scrap, large and small domestic appliances,” and other items, the New Hampshire company president says. They have proved their value in shredding construction and demolition materials, too, other sources say.

What should not go in a vertical shredder? The Georgia-based CEO cautions against processing larger electric motors because “the shaft is made of hardened steel and cannot be crushed well. Depending on the size of the [shredder], motors up to 4 kW can be processed; bigger motors should be avoided or should [go through] pre-treatment (removal of the shaft).” Unshreddables include very large, dense items, like an anvil, the Chicago-area owner says. An eject door in the top knocker area and the main grinding section can prevent such items from causing harm, he says.

“The vertical shredder does not cut material,” the New Hampshire president says. “Disintegration, liberation, and grinding require a certain brittleness of the input material,” such as that found in wire or cable mixed with some ferrous and/or stainless particles that act as knives. Thus, vertical shredders work well for processing shredder wire, but not necessarily for processing clean wire.

For some forms of scrap, a preshredder is a useful addition to a vertical shredder, these manufacturers say. “Then the flexibility is increased significantly,” the Georgia CEO says. The area sales manager of an Italian firm with its U.S. headquarters in Pennsylvania says several of its European installations pair a preshredder with a vertical mill. “In these plants, the customer can also process [end-of-life vehicles] and baled material,” he says. When used with preshredded material, vertical shredders use less horsepower per ton to create end products, the Chicago-area owner says. They also create higher-density shred than hammermill shredders, he says.

Although A&E purchased its vertical shredder mainly to process meatballs, it also uses it to process shredder wire and ASR, says Operations Manager Angie Emory. Before installing the machine, A&E used a hammermill shredder at another location to process motors and transmissions. “We needed something to further process the meatballs, wire, and fluff that came out of that facility,” she says. “Later, we started looking to buy more of that material to … process here to recover the copper, aluminum, and steel.”

How it works

A vertical shredder is somewhat like a hammermill shredder placed on end. The conical or cylindrical shell around the rotor is made of strong steel plates with thick liners that endure enormous force. Inside the shell at the top is a knocker assembly that sits on top of the rotor, which typically spins at 300 to 550 rpm. Attached to the rotor are rotating hammers, gear-shaped grinders, flails, or chains.

Newer generations of vertical mills have variable-speed drives allowing operators to change the speed of the rotor, the Pennsylvania-based manager says. “This is particularly useful to maintain output density and size: You can start at a lower speed, when liners and stars are new, and then adjust the speed when the wear parts start wearing down,” he explains. “Our vertical mill also has the option to adjust the lower grinding plate to keep the same gap as it wears out.”

Typically, material enters the shredder from the top using a steel belt conveyor or a vibratory feeder. The infeed opening size often matches the diameter of the rotor. The Georgia-based CEO says his bigger machines can take roughly 40-inch by 40-inch sheets of material; the New Hampshire president says his company’s largest machines can take a full-size French door refrigerator.

The material falls into the shredding chamber, first hitting the top knocker area. Knocker designs vary by manufacturer, but they include a top knocker, a slide, and a hammerhead, the Chicago-area owner says. The material moves between the rotor and the shell liners, where the independently spinning rings, hammers, and the like break it apart as it flows toward the exit chamber. The progressive narrowing of the liners keeps the material close to the rotor for better liberation and size reduction, he says.

The continuous impact of shearing, compression, tearing, and grinding force the particles down to the bottom of the shredding chamber. In some designs, when the particles reach the proper size, they pass through a gap between the rotor and the choke rings. Operators can adjust the gap to a predetermined output size—generally from ½ inch to 4 inches—eliminating the need for a screen. Other designs don’t use a choke ring. “When [particles] reach the bottom of the unit, they are properly sized if the manufacturer designs for the proper drop height and rotor size,” the Chicago-area owner says. Either way, “in one pass, the vertical shredder takes bulky material down to an output fraction size of less than 1 inch, if required,” the New Hampshire president says.

The particles reach the discharge chamber, where the centrifugal force of the rotor or a rotating sweeper moves them out of the shredder and onto a discharge conveyor. They then can move into downstream processing equipment such as vertical granulators, magnets, eddy-current separators, sensor sorters, and density sorters. (The nonferrous output from a vertical shredder is quite abrasive, the Connecticut firm founder says, thus he recommends a vertical granulator over a regular granulator for additional processing.)

“An interesting part of the process is that when you run stainless steel through the vertical shredder, because of the tremendous amount of friction and impact that takes place, the stainless steel becomes slightly magnetic, which is beneficial for downstream separation,” the New Hampshire president says.

One South American customer uses a vertical mill exclusively for stainless steel, the Pennsylvania-based manager says. A U.S. customer interested in this equipment provided a sample of infeed material that contained stainless grades 410/430 and 304; after milling and processing through a high-gauss magnet, they had “very good results,” he says.

“This test simulated processing the Zurik fraction of the ASR in a grinder mill, then [recovering] the stainless steel from this fraction,” he says. “The material remained magnetized … after the 30-plus days it took for shipping via boat,” he adds.

After the shredder

Downstream milling and separation of the nonferrous fraction is essential for maximizing the value of materials coming out of a vertical shredder, just as it is for materials coming out of a hammermill shredder. The Connecticut firm’s founder wonders whether that has been a barrier to vertical shredders’ use in the North American market. “When they first came to market, some [people] were representing them to be a one-piece solution,” he says. “Buyers now know that they also need a subsequent milling and downstream solution to polish the nonferrous portion.”

A&E sends materials coming out of the shredder through a series of ferrous and stainless steel magnets, shaker tables, and eddy-currents to segregate marketable materials and remove contaminants, Emory says. Optical sorting equipment and robotic pickers also could be a part of downstream separation, the Georgia-based CEO notes.

The Pennsylvania-based company manager points out a potential exception to the need for downstream separation: One customer “wants to process slitter trimmings to reduce size and increase density. In this case, the material is already clean, and no separation equipment is needed,” he says. “A simple inclined conveyor works as quality control: Balled-up material rolls down the conveyor into the radial stack; flat pieces are conveyed back to be re-run.”

In terms of performance and upkeep, A&E has been happy with the machine, Emory says. “We haven’t had any major problems.” Routine maintenance involves replacing the rings and hammers, replacing the wear plates on the knocker and sweepers, and refacing the shell liners, manufacturers say. “It’s been about a year since we’ve done major maintenance to take care of all of those things, so we plan to do that soon,” says Sales Manager Paul Willis. “Doing it all will probably cost between $20,000 and $25,000.” A&E plans to save some money and speed the process by having wear parts fabricated locally instead of ordering them from Japan, he adds.

“Wear parts such as grinders and various liners in the shredding chamber need to be replaced when they’re worn out,” the New Hampshire company president says. “Most customers have two rotors per shredder on site. Once grinders and liners need to be replaced, the worn rotor is removed and replaced with a freshly tooled one. Then the customer has time to work on the worn rotor while operation is ongoing with hardly any interruption. Replacement of the rotor can be accomplished in less than half a day” in his machines, with others saying it takes up to two days. The breaker body and rotor are hard faced and can be refaced, he adds. Rebuilds can range from $20,000 to $40,000, or $80,000 to $100,000 if the rotor is replaced, the Chicago-area owner says.

With proper maintenance, vertical shredders can last almost indefinitely, the Georgia CEO says. He credits improved wear part quality and automation, plus the ability to retrofit older machines. “We have seen some older machines in the U.S. which can operate only in one direction,” he says. “The newer ones operate in both directions, which reduces the [operating expense] and increases the uptime.” Others measure the lifespan, with proper maintenance, at 20 to 30 years. “Vertical mills are built strong and to last,” the Pennsylvania-based company manager says.

Making the purchasing decision

A&E’s biggest challenge since installing the shredder has been getting enough input material to make the operation cost-effective. “We’re just now getting all the material we need,” says owner Don Willis. Indeed, a vertical shredder is a worthwhile investment only if you have sufficient throughput volume, the Connecticut company founder says. These manufacturers and sellers estimate that 3 to 6 tons of material per hour would be adequate volume to optimize your return on investment, depending on factors such as what materials you’re shredding and how you’re separating them downstream. Others say 15 to 30 tons per hour would justify the investment.“Processing capacity on our machines ranges from less than a ton up to 30 tons per hour,” the New Hampshire company president says. Factors that affect throughput are the required output particle size, the input material size, the density and moisture content of input material, and any limitations of downstream equipment, he says.

Vendors were reluctant to provide the exact prices of their vertical shredders, but some gave ranges between $200,000 and $400,000 for just the shredder and up to $5 million for the vertical shredder plus a full array of downstream separation equipment. The machine and installation cost A&E about $1 million, including the cost of a concrete foundation, Willis says; the Chicago-area owner says the MetalX two-shredder installation also was about $1 million.

The Chicago-area owner is optimistic that vertical shredders will again become common in North American scrap facilities. They are “the machine of the future,” he says. “The future of vertical shredders goes beyond processing meatballs and coolant scrap. In America, there are big groups that are looking at transitioning from [operating] large megashredders to having multiple boutique operations or auxiliary satellite operations for rough shredding. The shear-type shredder and the vertical shredder are the machines they will use.”

Ken McEntee is a freelance writer based in Strongsville, Ohio, and publisher of Composting News and The Paper Stock Report.

These machines’ size reduction and material liberation abilities can help processors meet higher quality standards, manufacturers say.

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