Dear Readers,Weiboold Academy Logo

This is the tenth article of our monthly blog series “weibold! Academy”. As we have mentioned before, with these articles we try to provide our readers and our newsletter subscribers with valuable knowledge about the tire recycling industry. We believe that a basic knowledge foundation might be beneficial for everyone involved in the industry and each month we cover different topics, thus providing you with important know-how for the tire recycling industry. Month by month we together dwell deeper into the world of tires and the ways of recycling them. In case you have missed our first seven W! Academy articles, you can find them here:

  1. Welcome to weibold! Academy
  2. weibold! Academy: Recycled Rubber Output Spectrum and Rubber Granulates
  3. weibold! Academy: Rubber Granulates, Rubber Powder, Tire Derived Steel and Tire Derived Fiber
  4. weibold! Academy: Tyre Recycling Value Chain
  5. weibold! Academy: Applications for Tyre Recycling Plant Output
  6. weibold! Academy: Rubber Granulate Applications
  7. weibold! Academy: Rubber Powder Applications – Rubber Industry
  8. weibold! Academy: Rubber Powder Applications – Surface Coatings
  9. weibold! Academy: Success Factors in the Tire Recycling Industry 

This month we begin dwelling into how it helps to properly understand tire recycling technology.

Processing of Post-Consumer Tires

To meet the different requirements of potential applications for the rubber recovered from scrap tires, processing and recycling systems must be able to produce goods with clearly defined characteristics, which are suitable for use in a wide range of applications.

In this context, shredding, grinding and milling technologies are crucially important as they are the core of the recycling process. High quality equipment broadens scope of application of the recycled material.

The choice of technology affects the quality of the rubber granulate and powders:

  • the size
  • the shape
  • the surface
  • the purity
  • the output volume and therewith (most importantly)
  • the cost of the final product.

Size, shape, surface and purity are quality aspects that cause material acceptance with customers. Output quantity and cost are aspects that influence the customers’ willingness to purchase the material, hence they are the long term success of a tire recycling company.

Basically, there are two available technologies to transform used tires into rubber granulates and powders which can show a successful history in the industry:

  1. Normal Temperature (Ambient) Process

Ambient grinding comprises all sorts of mechanical shredding operations, which are carried out at room temperature. Knife shredding operations are predominant, whereby the input material is reduced during several stages to smaller and smaller sizes. Sieving technology is used to classify the various sizes according to the required applications. Lately roller mills became a preferred choice for tire recyclers to produce rubber powders.

  1. Cold Temperature (Cryogenic) Process

The input material is cooled down to approx. minus 90 degrees Celsius by means of liquid nitrogen until the rubber reaches a “glassy” state. “Glassy” is not really a technical term but shall only express the fact that the frozen rubber can easily be broken apart by means of e.g. hammer mills or desintegrators with very high impact energy.

Currently an estimated one percent of rubber granulates and powders are produced by means of cryogenic technology. Despite the few installations there are some good reasons for using cryogenic processes for certain applications.

Although we are not aware of any industrialized setup we need to mention a third way of recycling tires.

  1. Waterjet Milling Process

The process applies UHP (Ultra-High Pressure) waterjetting to pulverize the rubber with rotojetters in a single operation without any mechanical grinding or the use of  chemicals. This process is designed for large and very large tires which cannot be recycled in a conventional way, such as normal OTR (off-the-road) tyres or even the open-mining tyres of dia 4m.

Please feel free to contact us for more information anytime.