Photo: Drop in – The Zerma tyre recycling plant at which up to 45 tons of material are processed an hour is a substantial initiative, obviously, beginning with in-feed of tyre casings into a Zerma ZXS-T shredder for passenger car or truck tyres (up to 1500mm diameter) where material is reduced into strips and pieces of approx. 100 mm. The material then moves to a second-stage Zerma ZTTS shredder where it is reduced to approx. 20mm. Steel radial material is removed at this stage. Heavy-duty GSH granulators with a special closed H-rotor are used in the final stage, producing pieces down to less than 5mm or as required
WITH the Supreme Court of Appeal’s recent ruling in favour of REDISA, the likelihood that the South African tyre recycling sector may be able to regain momentum has increased, meaning that tyre recycling may become a reality in the country. With that in mind, Jeff Cawcutt of Zerma Africa was an interested participant at Zerma’s global sales meeting in Thailand at which one of the Zerma customers in that country showed delegates its expanded tyre recycling plant. The Thai cement manufacturer, one of the largest in South-East Asia, has expanded its tyre recycling plant from 25 to 45 tons per hour, which is substantial in anybody’s book.
The name of the game for tyre recyclers – as it is for anyone involved in plastic or rubber recycling – is economy of scale: that is to achieve volume throughput where unit cost is as low as possible. With tyre recycling, tonnages are substantial and – in order for plants to operate profitably – high efficiency technology needs to be utilized.
Due to the increasing number of cars and trucks all over the world, used tyres are available in large quantities at relatively low cost, currently. With a bit of clever recycling, you can get a whole lot out of used tyres: granule in various sizes, steel and profit. The sales income naturally depends on the quality of the output material, and the process obviously needs to be as efficient as possible.
Zerma used its experience gained in the development of recycling systems for plastics, wood and e-waste over more than 70 years in the design of its tyre recycling systems, which ultimately produce high quality materials for recycling. Final products could be either shreds for thermal recycling, predominantly in the cement industry, and crumb rubber of about 5mm size used in various applications.
Shredding and metal separation
The core of the line is the newly developed Zerma ZXS-T tyre shredder. The lines now running are shredding passenger car and other tyres up to 1500mm diameter into a final particle size of approximately 20mm, as required by this customers down-stream processes.
Zerma tyre shredders are heavy-duty single-shaft shredders with gravity infeed and hydraulic rams specifically designed for the grinding of tyres. They feature extensive wear protection compared to other shredders. The machine is equipped with a flat rotor made of highly wear resistant steel with added weld on hard-facing for longer lifetime.
The cutters used in these shredders are made from a newly designed, specialised material to ensure long life and optimal performance. As opposed to other systems, the Zerma technology does not require the tyres to be de-beaded.
The shredded material is removed by vibratory discharge and conveyor belt and transferred to the ZTTS second-stage tyre shredder. This shredder is then used to reduce the material into pieces of approximately 20mm. This step helps to separate the tyre rubber from the steel. A combination of cross belt magnetic separators and magnetic drums helps to split the various factions at this stage in the process.
During metal separation, about 99% of the total steel content is removed. The steel-free granule can then be packed and used as refuse derived fuel or transferred to the granulating process.
Granulating and sifting
After shredding and steel separation the tyre shreds are transferred to the granulation process. For granulating of the rubber shreds, Zerma recommends use of its heavy-duty GSH granulators with a special closed H-rotor to reduce the rubber down to a size of <5mm in two steps.
Throughout this process the material is classified on Zerma CS screening machines and the last metal contamination is eliminated by additional magnetic drums.