Shredding tires for cement fuel production
October, 16th 2024
The Dual-Shear® M120 two-shaft shredder with a trommel screen system efficiently handles the tire shredding process, providing a cost-effective, space-saving solution that converts waste tires into energy.
Senegal, like the rest of West Africa, is experiencing a period of rapid urban development and economic growth. A region rich in natural resources is increasing its materials production to match the needs of its growing industry. Large deposits of limestone in Senegal and high demand have led to an organically expanding cement industry.
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 use tire chips or tire derived fuel (TDF) as a supplemental fuel source.
Dual-Shear® M120 with trommel screen processing truck tires.
In designing this expanded facility, Les Ciments Du Sahel partnered with Chinese based engineering firm CBMI Construction Co., Ltd (CBMI). CBMI has over 60 years of experience developing solutions for waste to energy and power generation plants.
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. To add to the difficulty, tires can contain high levels contaminants like dirt and sand that accelerate wear on cutters and screening equipment.
To find the best solution, CBMI reached out to Shredding Systems Inc (SSI) a US 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 an M120 two-shaft shredder with a trommel screen enclosure. SSI was confident in the system with experience building trommel systems since the mid ‘90s.
“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.”
Inside the cutting chamber of the M120.
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. Due to their design dirt can pass easily out of the screen as it spins.
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 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.
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 300ft2.
The small footprint does not mean small power. The 250hp M120, powered by a direct drive electric motor, is capable of shredding 6 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 industry leading 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.
