ELT UTILIZATION METHODS
-
No recovery at all: The end-of-life tires are used, for example, in agriculture, on competition tracks, in playgrounds.
-
Landfill: This occurs in countries where it is still permitted.
-
Incineration: Broken down, or sometimes whole, tires are burned to produce energy.The majority of all end-of-life tires are incinerated.
-
Energy recovery will likely remain the primary recovery method in large parts of the world due to the absence of alternative treatment methods.
-
Granulation: The tires are cut up and the steel and textile fiber removed before being granulated. The granulate can then becast into different shock-absorbing products, such as running tracks or playground safety surfacing.
-
Retreading: Tires can be retreaded at most three or four times, depending on wear and tear. Accordingly, the method does not provide a long-term circular solution to close the loop.
-
Cryo-technology: The tire is frozen and broken down into small fragments. These fragments can be used in tires and other rubber applications. It is, however, a relatively expensive process. Furthermore, since the material comprises complete rubber fragments from the recovered tires, the stability of the raw materials for use in new products is uncertain.
-
Devulcanisation: This process makes possible to vulcanize the material a new. Since this material also comprises entire fragments of rubber from the recovered tires, the method generates uncertainty in variations in the raw materials.
-
Pyrolysis: Only a few of multiple operators can manufacture high-quality rCB.
PYROLYSIS PROCESS
Pyrolysis is the thermal decomposition of organic substances under inert conditions (absence of oxygen) at high temperatures, usually between 400 and 800 degrees Celsius. Consequently, solid materials are con-verted into volatile gases and a carbonaceous solid residue (char) that contains most of the fixed carbon and inorganic materials (metals, salts, etc.). After being extracted from the pyrolysis reactor, the volatile gas is separated by condensation and distillation into a condensable fraction (i.e., heavier molecules) and a non-condensable fraction (i.e., low-molecular-weight gases and hydrocarbons, commonly referred to as syngas or pyrogas). Pyrolysis offers several operational, economic, and environmental advantages over other ELT management strategies. For instance, it is more energetically efficient and produces fewer emis-sions than incineration. After steel removal, the rubber fraction of ELT enables the production of three distinct pyrolysis products: syngas (gaseous low-molecular-weight compounds), fuel (liquid compounds), and recovered carbon black (rCB).
GASEOUS PRODUCT
The pyrolysis gas product mainly consists of low molecular weight hydrocarbons called syngas. The syngas produced by ELT pyrolysis include CO and CO₂, each in the range of 1–2 vol.%, along with other hydro-carbons, sulfur-containing compounds, and nitrogen-containing compounds (each < 0.1 vol.%). Typically, the syngas accounts for 10–30 wt.% of the pyrolysis products. Producing syngas with a higher heating value (HHV) is beneficial for pyrolysis systems because it can be directly utilised in the process, making it energy efficient.
LIQUID PRODUCT
The liquid resulting from ELT pyrolysis is a brown-coloured fuel resembling a petroleum fraction. The pyrolysis yield for the liquid product (34–42 wt.%) is higher than that of the other products. Pyrolysis oil is a very complex mixture of compounds, as more than 100 molecules have been identified. Solid Product.
