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Eddy current separators have made manual removal of nonferrous
materials from recycling waste streams a thing of the past.
As they’ve become standard equipment for recyclers,
the machines have become more powerful with larger magnetics
and capacity. The result is increased efficiency and improved
operating margins for recyclers handling incinerated, industrial
and household waste.
Eddy current separators apply to a wide range of materials,
including electronics, plastics, auto and white goods shredding,
foundry sand, and wood and medical waste. Specific applications
work to remove aluminum from plastic bottles, gold and silver
from computers, and stainless steel and ferrous metal from
wood waste, depending on the grade of the material.
Manufacturers offer separators as discrete units or as part
of a system that includes conveyors, splitters and vibrators.
Prices range from $30,000 to $140,000 for the whole package.
industry likes eddy current separators because they’re
versatile machines that offer a more economical method to
capturing nonferrous metal from different types of waste.
Compared to other metal separation processes, eddy current
separators are simple, stand-alone units that cost less. Many
consider the end product to have better quality than possible
with other separation techniques thanks to a higher degree
of separation and efficiency. For example, the purity of nonferrous
auto scrap has increased to 85 and 95 percent due to improvements
in eddy current separator technology.
“There’s a continuous requirement for cleaner
materials,” says Richard Bergan, sales manager of eddy
current separators at Magnetic Products, Inc., in Highland,
Michigan. “Eddy current separators are not just recovering
aluminum and tin cans now, they help to purify products also.”
Manufacturers continue to tweak eddy current separators
so volume and efficiency continues to increase. For recyclers,
Bergan says, it’s a matter of “how big a burden
can I put on this machine and how fine a product will I get
and still be efficient.”
Saving energy is another way separators have become more
efficient. Machines from Magnetic Products, for example, work
on a soft-start power supply that builds to maximum speed
gradually. “You don’t need as much draw that way,”
The drive toward more efficiency is apparently showing results.
“You see a lot more metal retrieved from the waste stream
now,” says Ben Davis, general manager at Huron Valley
Steel Corp., in Belleville, Michigan.
With only minor variations, most eddy current separators
are made with high-speed magnetic rotors that can spin up
to 3,000 RPM within a nonmetallic drum that spins at a slower
speed. The speed variance creates an electrical charge that
captures and expels nonferrous metallic elements thinly laid
out on a conveyor belt equipped with two to four pulleys.
A splitter at the end of the separator propels the nonferrous
metal into a collecting bin in the last fundamental step of
Because the metal particles come in various sizes, the short
circuit current flows irregularly around the objects as they
move along the conveyor belt. That jumpy current is what gives
the separator the name of eddy current.
the separator that works best for a specific recycling operation
depends on a number of variables. Some manufacturers suggest
owning units of different sizes to handle the variety of nonferrous
elements to be separated. Factors to consider before purchasing
include particle size and shape, conductivity, density, moisture
content, stickiness, size distribution, and fibrous and metallic
content. A combination of these factors will determine the
optimum rotor for efficiently handling of these materials
as well as determine the optimum machine settings for belt
and rotor speed, feed method and splitter operation.
“Magnetic separation is an art, not a science,”
says Don Morgan, the product manager for eddy current separators
at Walker Magnetics Group in Worcester, Massachusetts, “which
means your selection of equipment for the appropriate application
The rotor’s magnetic blocks are made with rare earth
magnets or standard ferrite ceramic. Most recyclers prefer
the rare earth magnet because they’re considered to
have a stronger magnetic field than ceramics. Ceramic magnets
do offer a somewhat higher depth of field that some say is
better for handling larger size objects, but most vendors
consider the advantage marginal. “Rare earth is much
more mainstream,” says Davis at Huron Valley Steel.
“The only reason someone would choose ceramic is because
can range from 20 to 80 inches, which in turn determines the
volume of material moving over the conveyor belts. Capacity
can range widely, from 4 tons an hour to as much as 60 tons
an hour. A 7-inch long, 36-inch wide rotor works best for
low-volume loads while a 13-inch long, 48-inch wide rotor
can handle heavy-duty loads like shredded cars.
Separators made by Eriez Manufacturing Co. in Erie, Pennsylvania,
exemplify the variety of features that adapt an eddy current
separator to each scrap load. Splitters, which are an option
on some units, are positioned higher and closer to the drum
for smaller particles while a rear splitter captures materials
with weaker magnetic content. Separators today can capture
particles as small as 3/32 inches or 2 mm.
Not only do today’s separators do more, but they last
longer too. Dings Magnetic Group in Milwaukee, Wisconsin,
makes eddy current separators with a triple shell design it
says increases strength and durability while producing a deeper
field that lets recyclers process more tons per hour with
better recovery rates.
In general, today’s eddy current separators can recover
up to 95 percent of recyclable materials from metallic-contaminated
waste. From such a simple, straightforward technology, that’s
a percentage that looks good in an increasingly refined marketplace.