Industrial shredders transform used tires into fuel for concrete production
The dual-shear M120 two-shaft shredder with a trommel screen system shreds end-of-life tires, providing a cost-effective way to turn waste into energy
Senegal is experiencing a period of rapid urban development and economic growth. Large deposits of limestone in Senegal and a growing construction industry have led to a high demand for domestically produced cement.
A key process in cement production involves heating crushed limestone in a kiln to produce an intermediary product known as clinker. To generate the immense amount of heat required in clinker production, kilns are super-heated with coal. To reduce the cost and carbon emissions of coal-fired kilns, clinker factories often use tire chips or tire derived fuel (TDF) as a supplemental fuel source.
Senegalese cement producer Les Ciments Du Sahel is located 30 miles outside of the capital city of Dakar, and produces 600,000 tons of cement annually. The company recently added an in-house TDF line to produce their own tire chips.
To design this expanded facility, Les Ciments Du Sahel partnered with Chinese engineering firm CBMI Construction (CBMI). Tires are a difficult material to shred due to their thick rubber treads inlaid with high tensile steel wire.
For long term success, a shredder with a large enough throat, specialized internal parts, and enough power is required. Compounding the challenges, tires can contain high levels of contaminants like dirt and sand that accelerate wear on cutters and screening equipment.
Shredding Systems Inc. joins the project
To find the best solution, CBMI reached out to Shredding Systems Inc. (SSI) a U.S.-based shredder manufacturer with decades of experience designing systems for tire processing. After considering the conditions of the operation, as well as the budget, SSI designed and manufactured a M120 two-shaft shredder with a trommel screen enclosure.
"Trommel systems are a great option for companies who are considering starting a TDF line," explains Rich Ellis, Asia sales manager at SSI. "It is a cost-effective option that is easy to maintain, has a small footprint, and produces a good quality fuel chip."
A trommel is a rotating drum screen that captures the tire pieces as they leave the shredder. Fingers on the screen recirculate the pieces until gravity drops them back into the cutting chamber. Once the pieces reach the desired size, they will pass effortlessly through the screen and onto a conveyor. Trommel systems excel in conditions with high levels of dirt and sand, according to SSI. Due to their design, dirt can pass easily out of the screen as it spins.
Trommel systems are a practical design for TDF production
On a trommel system, the screen is separated from the cutting chamber, allowing material to freely drop onto the screen. The result is a clean sheared tire piece that can flow easily into an incinerator.
In a shredder with an internal screen, the minimal clearance between the screen and cutters causes tire chips to rub, fraying the metal wires. This scrubbing action is great for liberating wire from rubber in metal recovery applications. However, in TDF production this process is less desirable. The frayed wires tangle with one another causing tire pieces to cling together. These balled up tire chips are harder to feed into the incinerator and can cause the system to slow or jam.
An economical and space-efficient solution
Relative to their vibratory screen counterparts, trommel systems are considerably more economical and space efficient solutions. Instead of requiring multiple conveyors and lots of floor space, the trommel system at Les Ciments Du Sahel fits snuggly into the corner of their facility taking up floor space only slightly larger than the footprint of the shredder itself, around 300 square feet.
Small but powerful electric motor
The small footprint does not mean small power. The 250 horsepower M120, powered by a direct-drive electric motor, is capable of shredding six tons of mixed auto and over-the-road truck tires an hour. The M120 is a low speed, high torque shredder built with SSI's technology and can handle the challenges of tire shredding with ease.
A trommel system is a viable solution for turning a waste product, like end-of-life tires, into a fuel source. Providing reliable and economical shredding solutions to companies in emerging markets like Senegal is an essential part of sustainable urban and industrial development.
