Wisconsin-based BCA Industries, a maker of industrial shredding and recycling equipment, says it has been working with customers to find optimal size reduction and screening methods to help recycle the world’s growing volume of discarded lithium-ion (Li-ion) batteries.
Although Li-ion batteries have been used for many years, destructive recycling “has not been accomplished on any kind of scale due to the explosive nature of the materials,” states the equipment maker. Among the problems, says the firm, is that Li-ion batteries can induce fires, explosions and thermal runaway, a condition where the release of heat triggers other cells or batteries to “rapidly release more heat and volatile organic compound (VOC) gases in a dangerous, quickly escalating cycle,” states BCA.
“Traditionally, the process of recycling Li-on batteries has been described as a scene from Dante’s Inferno,” says John Neuens, BCA’s sales director. “There are acid baths, toxic gases and fumes and fires and explosions when items are shredded, and everyone is walking around in a Hazmat suit. It is a nasty environment to try and process in.”
He continues, “The problem is when you put a large item like a battery into a high torque shredder at any moderate speed, you immediately have enormous flammability issues. This is a unique problem for lithium-ion batteries because of the explosiveness and the amount of toxicity that it gives off when it explodes – and they all explode. You have thermal runaway very quickly and atmospheric gases that have to be contained.”
As a result, companies tend to store lithium batteries in 55-gallon drums without recycling them. Neuens says, however, “Today there is a giant push by industry, including the car industry, to try to recycle those types of batteries and save the valuable, recyclable materials safely.”
In terms of shredding such batteries, one method is to pass the shredded material over a screen with the smaller size material falling through and the bigger material coming back and recirculating through the shredder repeatedly until it reaches its desired size.
Unfortunately, some wet battery material may clog or “blind” the screen to a point that it no longer functions. This also slows the process significantly, while increasing maintenance time and costs, according to BCA.
Another alternative for Li-ion batteries is to use a series of shredders to progressively reduce the size of the material. In some larger battery assemblies, battery recyclers may use several different shredders and then granulators to reach the desired size of less than 3/8-inch, suitable for further processing, says Neuens.
Instead of using many shredders to progressively reduce the size of battery scrap, new shredder “knife” technology can uniformly cut to any size in a single pass and not allow smaller batteries to “slip through” the cutting chamber, according to the sales director. This reduces battery scrap down to a reclaimable proportion very quickly while containing thermal run away and fires with a coolant while requiring significantly less processing, energy use, labor and maintenance, he adds.
BCA says its patented Triplus knife system technology uses a bed knife design in a dual-shaft shredder to cut the width of the material to any size in a single pass without requiring a screen. The size of the end product is based on the size and geometry of the rotary and fixed knives as well as their gap distances.
A shredder using this design can produce more than 85 percent correctly sized material in one pass with less than 10 percent oversized material, Neuens says. He adds that very large batteries or those with hard metal components such as metal casings or rods are best broken down with another primary shredder first.
With the right technology, approximately two to three tons of batteries an hour can be reduced to the proper size for further processing using such a shredder, he says.
Additionally, in place of heat tumble drying, often used as part of processing wet battery materials, much faster, less energy-intensive solutions have been developed. “Because batteries contain viscous fluids and powdered materials, a drying process must also be utilized before the desired metals can be reclaimed,” says Neuens. “The common process used, tumble drying, is very slow, requires tremendous energy and results in airborne dust that must be controlled and filtered out.”
Industry innovators have developed a drying system that eliminates the need for tumble drying, though the specific details of this are proprietary, Neuens says.
The shredder knife system can allow a 50-horsepower (hp) single-pass shredder to produce the same amount of recyclable product per hour as a standard 100-to-150-hp conventional system, according to BCA Industries. This can reduce recycler energy costs by $1,500 to $5,000 per month while producing a more consistently sized product, says Neuens.
The technology, he adds, is flexible enough to be installed in any size shredder that BCA builds, from 10 hp to 800 hp, from and from a 15-inch-by-12-inch cutting chamber to a 48-inch-by -72-inch cutting chamber, in both stationary and portable units.
This article was prepared by a freelance writer on behalf of BCA Industries.