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Black end of life tires piled in a group

Sustainable industrial opportunities for carbon black

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The tire industry is a major consumer of Carbon Black, using 70 per cent of the material

The disruptions to Carbon Black supply chains, rising costs of the typical feedstock fossil fuels for producing Carbon Black, sustainability regulations, and stakeholder pressure have industry leaders concerned about the future of Carbon Black.

Luckily, there are sustainable options like a Carbon Black alternative, not as a direct replacement but with similar properties to Carbon Black, available on the market. In this article, you will learn about recovered Carbon Black as a sustainable option for several industries and use cases.

Types of Carbon Black

Carbon Black is a synthetic material made of 98 per cent carbon. Petroleum oil, gas, and coal tar are the common raw ingredients used to produce virgin Carbon Black (vCB) by burning the feedstocks at very high temperatures in reactors to vaporise the carbon. After cooling, the result is a paracrystalline spherical substance available as a powder.

Different manufacturing processes and feedstocks produce varying particle sizes, surface area, and aggregate structure, which define the properties of the vCB. So there are many grades of Carbon Black.

Tire manufacturing uses most vCB grades to stabilise and strengthen rubber products, such as tire treads, sidewalls, tubes, belts, and carcasses:

  • Grades with smaller particles, such as N110, N220, and N234, have high reinforcing, abrasion resistance, and tear strength. These grades are used as reinforcing filler materials to make rubber elastomers that form tread.
  • Medium to high reinforcing grades like N330, N339, and N550 are found in treads, inner liners, carcasses, and sidewalls.
  • Medium reinforcing vCB grades like N660 and N770 have low heat build-up and prevent tire deformation. They’re suitable for sidewalls, inner liners, and sealing rings.
  • Low reinforcing vCBs with high loading capacity and elongation are suitable for inner liners and belts.
  • Carbon Black is also a pigment that colors the tires black. It also protects the tires from the harmful effects of ultra-violet (UV) light and ozone to extend tire lifespan.

The cumulative effect of vCBs makes tires safer and more durable for driving. There are 21.5 per cent and 22 per cent of vCBs in passenger and truck tires. 

The use of fossil fuels to provide feedstock and energy for the manufacture of vCBs has increasingly become an image and compliance issue for the tire industry. Moreover, each ton of vCB produces around 3 tonnes of greenhouse emissions.

Recovered Carbon Black: a sustainable option

The tire industry needs new Carbon Black options that are sustainable to avoid the environmental problems created by vCB manufacturing and meet consumer demands for green products.

Recovered Carbon Black (rCB) can be a sustainable alternative to vCBs. Instead of new fossil fuels, rCB production uses end-of-life tires (ELTs) as feedstock in pyrolysis. 

However, rCB is not a 1:1 replacement for any particular vCB grade.

rCB is a new, unique grade with its own set of properties. The American Society for Testing and Materials (ASTM) International workgroup 36, set up in 2017, is still developing quality standards for rCB.

The properties of rCB reflect the mix of passenger and truck ELTs used in pyrolysis. It’s close in its properties to N660 because this grade is found in significant quantities in tires of all vehicles. However, minor amounts of high reinforcing vCB grades found in tire components will also be part of rCB. Moreover, the chemicals in the waste tires will also make their way into the rCB affecting its properties.

rCB is a sustainable Carbon Black option because of its small carbon footprint and circularity. The manufacturing process of Contec rCB produces 2 tonnes fewer carbon emissions than vCBs. Whereas vCB requires 2 tonnes of sulphur-rich fossil fuels, 1 tonne of rCB can be made from just three ELTs. 

Tire producers can solve their waste problems and use recycled materials in their tires to meet requirements set by the EU End-of-life Vehicles Directive by using pyrolytic products.

Pyrolysis at Contec

There are around 20 to 30 types of pyrolysis processes, but not all are created equal. 

Conventional pyrolysis systems can’t guarantee consistency in the quality of rCB. Contec has improved the pyrolysis process with several innovations to make rCB of a consistent quality that meets stringent industry requirements.

The Contec pyrolysis process, which is a continuous type, can guarantee a high-quality Carbon Black option due to multiple strategies in the various stages of the process:

  • The company has its own collection system to ensure that the ELTs are clean.
  • The process uses a fixed mix of truck and passenger tires to maintain product consistency with 15 per cent of truck tires.
  • Contec uses best-in-class industry shredder machines to shred the tires to get even small rubber granulates and remove steel to improve processing.
  • Contec is the only rCB producer to use molten salts as a heat transfer medium to provide even, controlled heating of the tire scrap.
  • A rotating auger makes sure that the waste tires have a similar residency time, which further improves quality. The uniform heating and residence time are responsible for the high and consistent quality of Contec’s rCB.
  • Contec has a strict protocol of checking the plant before and during the operation to ensure there are no pressure buildups or gas leaks to prevent explosions and fire hazards.
  •  There is strict and continuous monitoring of the temperature and heating of molten salts, with a single switch control to quickly stop the process.
  • Quality control is part of the process. The measures include sampling every 1-3 hours to check the operation and onsite-laboratory testing to ensure product quality.
  • Finally, the rCB is milled to get the recommended size and later pelletized to produce 0.5 to 1 mm pellets that make handling easy and pollution-free.
  • The pyrolysis process that Contec uses recovers 85 per cent of materials and produces only 439 KgCO2e/1 tonne of rCB.

So what is pyrolysis? It’s a thermo-chemical process, and the technique is several decades old. But its application to recycle tire waste to recover materials is new.

The tire rubber is separated from other components like steel, wires, and fabrics as part of the process. The shredded tires are then sent into a reactor, where Contec uses temperatures up to 510oC in an oxygen-free atmosphere to decompose the complex polymers in tires into simpler components.

The pyrolytic products of commercial interest are recovered gas, oil, Carbon Black, and steel.

Common recovered products from ELTs

Each of these four recovered products has a place in the tire industry’s circular economy.

  1. Recovered Carbon Black — Contec’s ‘ConBlack’ is a Carbon Black sustainable option. It can replace up to 30 per cent of semi-reinforcing vCBs, such as N550 and N660, to make new tires. These can produce inner liners, sidewalls, sealing rings, heavy-duty conveyors and transmission belts, and hoses. It can replace vCB up to 100 per cent for UV protection and produce non-tire items like rubber sheeting, roofing, cables, geomembranes, pigments, paints, and plastic items.
  2. Recovered gas — Gas is one of the first products formed in pyrolysis. Part of it condenses into liquids during cooling, but one part remains as gas. Contec has achieved fuel self-sufficiency using its recovered gas as fuel for heating the plant.
  3. Recovered Oil — Contec’s ‘ConPyro’ is the oil after refining and can equal virgin fossil fuels in quality. These sulphur and aromatic hydrocarbon-rich end-of-life tires derived pyrolysis oil (TDO) can replace fossil-based oil as feedstocks to produce high reinforcing vCBs. These vCBs can further increase the proportion of recovered materials in tires.
  4. Recovered steelContec’s ‘ConWire’ is retrieved before and after pyrolysis and can also be used again for producing new tires without loss of quality.

The tire industry is considering various options, including biological materials and recycled products, to replace fossil fuel feedstocks to produce Carbon Black alternatives. 

Contec’s ‘ConBlack’, using ELTs as feedstock, can be a sustainable and circular Carbon Black option to traditional vCB because of its various proven uses and applications. Get in touch to learn more about our sustainable solutions.

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