The business of recycling scrap tires is
evolving. Until more recently, most processors performed
just primary reduction – reducing whole scrap tires
to various size strips of rough shred. But rough tire shred
is co-mingled waste – a blend of rubber, steel wire
and synthetic fiber. In some cases, over 25% of the weight
of the tire can be steel wire and non-rubber content. Removing
the steel and non-rubber components creates a host of new
market opportunities for reclaimed rubber.
Markets such as rubber mats, sports and
recreational playing surfaces or raw materials for rubber
compression molding are just a few of these newer applications.
To tap these higher value-added opportunities, scrap tire
processors need the right equipment to extract the steel
from rubber shred. Enter…the primary rubber granulator.
In conversation, there are several terms
for this product category. Trade names such as “rasper,”
“grizzly” or “liberator” are often
used interchangeably to describe equipment that performs
the function of a primary granulator. Semantics aside, it’s
the machines that strip steel wire from recycled tire rubber
that are the focus of this month’s spotlight.
Choosing a primary granulator
Astafan, general manager of Columbus-McKinnon
Corporation’s Sarasota, Florida operations said, “There
are essentially two kinds of customers in the market for
a primary rubber granulator. First, there’s the provider
of higher grade TDF that needs a smaller, cleaner, more
wire-free product. Other customers are typically involved
in civil engineering applications.” Both are part
of a growing market for higher-grade reclaimed rubber.
There are a number of points to consider
when choosing the right primary granulator for your needs.
Charlie Astafan points out, “We like to begin by asking
a lot of questions. Questions such as what volume of tires
a customer may be processing in a single shift, or 24-hour
period. We also need to know what percentage of the inbound
material is passenger car, truck or specialty tires, and
if they plan to process mixed material or run each type
separately. That tells us how large the infeed throat must
be, and gives us some insight as to whether single pass
or multiple pass configurations are necessary at different
points in the line. There are a lot of numbers to gather,”
Other points are less simple to quantify.
Questions such as training, start-up and post-sale support,
parts availability, warranty and brand preference come into
play. Invariably, price and financing are important as well.
Mr. Astafan notes, “Provided the right equipment is
in place for the need, customers should be looking at the
lowest total cost over time. Depreciation is an operator’s
single largest expense. Given volumes and mix of material
processed, it’s important to know how long a granulator
will run before a rebuild may be needed. Other costs such
as electricity, blade life, screens and routine maintenance
will vary. All of these expenses should be considered to
arrive at the best possible fit for each customer,”
Due to the steel wire content of passenger
car tires in particular, primary granulators can generate
a lot of heat while in operation. As an optional safeguard,
some manufacturers offer on-board fire detection and suppression
capabilities. In conjunction with sprinklers, these options
may result in cost savings on business insurance as well.
According to Columbus-McKinnon Corporation, fire detection/suppression
options would typically run less than 5% of the initial
cost of the granulator.
How they work
the tire recycling process, primary granulators are positioned
just downstream from the shredder, or primary reducer –
in some cases, several steps downstream. There’s a
lot of variety in how a tire recycling line may be configured,
due in large part to differing needs of the operation and
its customers, and the inherent differences in available
equipment. Typical set-ups include a primary reducer, a
secondary shredder, a classifier to remove synthetic fibers,
etc., and a primary granulator. Some operations include
secondary granulators or grinders for crumb rubber production
at the end of the process.
In most tire recycling operations, infeed
material to the granulator ranges in size from four inch
to six-inch shred. Once in the feed hopper, rubber shred
enters the rotor chamber where rubber and steel separation
Wendt, Jr., sales manager of Wendt Corporation,
Tonawanda, New York said, “The granulator is a relatively
low speed horizontal rotor. It turns at about 120 rpm and
strips the steel wire from reclaimed rubber. It’s
the special shape and relief angle of the knives that makes
this process so effective.”
Balancing throughput, or infeed material
with finished product is accomplished by way of more sophisticated
electrical controls. “Sensors in the rotor measure
the amperage draw, which reflects load on the machine,”
said Tom Wendt, Jr. “As material passes through the
screen and exits the rotor chamber, the amperage draw for
the rotor drops and a signal is sent to the feed conveyor.
That starts or speeds up material delivery to the rotor,
keeping the process balanced,” he added.
Keeping a granulator in top running condition
isn’t terribly difficult. John
Crowley, director of sales & marketing
for Granutech-Saturn Corporation in Grand Prairie, Texas,
makers of the popular “Grizzly” granulators
observes, “Aside from cleaning and lubrication, it’s
a matter of paying attention to blades (knives). Our machine
features a combination of 10 stationary blades and 50 rotary
blades. We recommend that on average, the blade gap be checked
and adjusted every 40 – 60 hours of operation. It’s
something that takes an experienced technician no longer
than 45 minutes to do. Depending on the quality and cleanliness
of the infeed material, the blade service interval can extend
out as far as every 120 hours of operation.”
Granutech-Saturn further recommends that
blades be rotated every other time the gap is checked and
set. John Crowley continues, “There are four cutting
surfaces to every blade, each with a 90 degree edge. Granulator
blades are rotated to keep the cutting edges fresh and sharp.
That keeps the product size consistent and keeps the quality
of the output material as high as possible.”
As a simple precaution, most customers
prefer to keep several sets of blades on hand. Tom Wendt,
Jr. observes, “It’s not uncommon for customers
to have three sets of knives – one set in use, one
set on the shelf and a third set out for refurbishing.”
Rotary knives wear a bit more quickly than the stationary
knives. Refurbishing usually involves welding, heat-treating
and quenching for hardness and durability.
Screens are another wear item that must
be checked periodically and replaced as needed. Operators
should be sure all screens are open, free of blockage and
within tolerance to size finished product as specified.
In tire recycling, the North American market
is about 10 years ahead of what’s going on in Europe.
It was just July of 2003 that whole scrap tires were banned
from most EU member landfills. In contrast, the U.S. processes
about 80% of the scrap tires generated each year. Charlie
Astafan notes, “We’ve seen a spike in export
activity for tire recycling equipment during the past year.
Exchange rates are favorable for many overseas customers
and there’s a lot of U.S. built product going to Europe
and South America right now,” he said. As more and
more applications for recycled tire rubber are developed
overseas, this trend is expected to continue.