Scrap processors have been using shredding plants for several decades to break down automobile hulks and other obsolete items into grades of scrap valued by melt shop managers. It is a form of technology that is far from standing still.

Many advances have been made downstream of the shredder, involving more rapidly and accurately sorting the different metals and materials after the shredding chamber has performed its work.

What is happening within the shredding plant also is far from static, with scrap recyclers and equipment providers constantly upgrading how metal enters the chamber and how it can leave it the optimal condition to be presented to downstream equipment.

Shredding plant engineers say more changes are in the works or about to be introduced.

ALONE OR TOGETHER

The term auto shredder as it evolved in the last several decades of the 20th century generally referred to large, high-horsepower hammer mill plants into which auto hulks could be fed directly.

These powerful machines continue to perform around the world, but scrap processors have options to add preshredding equipment to their size reduction lines.

Metso Recycling, a subsidiary of Finland-based Metso Corp. that has business and engineering offices in Europe, the United States and Asia, says its EtaRip preshredder “is typically installed in front of a typical hammer mill shredder.”

R. Keith Carroll, the U.S.-based director of global sales support for the Metso Recycling product line, says its “primary use is as a bale breaker, but it can also be used to partially preprocess end-of-life vehicles (ELVs).”

How can adding another piece of somewhat expensive capital equipment yield a return on investment (ROI)? “By breaking and loosening the bale or ELV prior to feeding the main shredder, the process rate and efficiency of the shredder and downstream [system] are increased by eliminating the surges and gaps typically faced when processing these types of feedstock,” Carroll says.

Italy-based Danieli Centro Recycling, which also has offices and engineers in the United States, United Kingdom and several other nations, offers a variety of preshredder options, some of them part of its Danieli Henschel line.

Jake Allen from Danieli’s U.K. office says preshredders can offer ROI in a number of ways. “The ROI itself is mainly linked to the size of shredder behind the preshredder (higher benefit with smaller shredder),” he comments. “In addition to 10% to 30% increased production in the shredder at the same level of electrical consumption, you can expect around 20% more anvil and wear parts life span and 20% more production with the same hammers in the shredder,” Allen says.

Other benefits Allen cites include reduced downtime for the hammer mill shredder because the likelihood of explosions has been reduced and less environmental impact (noise and emissions) and neighbourhood issues because the hammer mill now can operate with a lower-horsepower motor.

Carroll also says preshredders offer “safety and operational benefits” in auto shredding applications. “One issue that operators often face with purchased bales or ELVs is the possibility of unshreddables hidden inside. The EtaRip exposes these large pieces with much less risk than when discovered inside of a hammer mill,” he comments.

“Similarly, gas tanks, pressurized cylinders and other components that could cause explosions if directly fed into shredders are depressurized in a controlled manner, significantly reducing the safety and fire risks associated with the traditional shredding of such items,” Carroll adds.

Whether shredding their scrap with one machine or two, plant operators have numerous options to weigh when it comes to selecting the automation, wear parts and other variables that go into optimising their size reduction lines.

ADVANCED THINKING

For an operator to run an optimal system, introducing feedstock into the shredding chamber can be critical.

Carroll says automation controls, such as the Metso Autopilot system, are designed to provide guidance at this stage, as well as in several other aspects of shredder operation.

“By automating the decision-making process of feeding material into the shredder, the shredder will consistently produce at a maximum rate and at lower costs,” he says. “Motor load spikes are reduced as well, as is the risk of overfilling,” Carroll adds.

Allen says the Danieli Q-Shred “suite of technologies” is likewise “designed to optimise shredder operation and utilisation factors.” That includes the Q-Shred’s HMI system, which Allen describes as offering “single-point process overview and control over shredder and material handling to reduce manpower.”

Beyond achieving uniform initial feed rates, the suppliers say automation controls can play a role in preventing downtime and ensuring maintenance tasks are performed at the right time and in ways that prevent future trouble.

Carroll says Autopilot “maximises the capacity and output of the shredder without compromising main motor or hydraulic plant health; minimises the probability of overloading the main drive; and improves consistency of mill motor utilisation.”

Q-Shred, according to Allen, is designed to result in “a fully automated plant in which there is no more need for a full-time operator in the control cabin overviewing shredder operation.”

Among its features is a maintenance management tool that monitors the operating hours of motors and hammers “with a service of data logging and trending for the whole machine,” he says.

Components and wear parts also are subjects of ongoing research. “One improvement we are currently bringing to the industry is a better approach to grate design,” Carroll says.

He adds that a new line of Metso grates “in most cases will increase the open area by 15% to 30% or more, depending on the single-beam grate design [being replaced].”

Allen says Danieli finds that in many applications, a low-voltage variable-speed drive (LV VSD) motor “is a valid alternative to a direct online medium voltage system.”

Among the advantages of an LV VSD configuration, he says, are “a lower impact on the feeder line during startup; lower motor stress levels thanks to the continuous torque control; safer machine operation in the form of one minute versus 30 minutes for rotor stoppage; and the possibility to recover energy during the stopping phase with a regenerative converter.”

Between the introduction of preshredding devices, advances in automation and new alternatives for components or power sources, shredding plant operators likely will be well-served in 2016 to stay in touch with their equipment vendors about evolving shredding plant technology.

The author is editor of Recycling Today Global Edition and can be contacted at btaylor@gie.net.