Re-designing a viable ELTs depolymerization in circular economy: Pyrolysis prototype demonstration at TRL 7, with energy optimization and carbonaceous materials production

Publication date: 10 February 2018
Source:Journal of Cleaner Production, Volume 174
Author(s): N. Antoniou, A. Zabaniotou
The present study aims to demonstrate challenge-based innovations of ELTs depolymerization, show evidence of promising developments and improve pyrolysis performance towards its economic viability. A pyrolysis prototype, with a ELTs mass flow rate of 20 kg h⁻¹ was designed, constructed, and demonstrated. Up to 100 kg h⁻¹ of steel-free tyre granulates were pyrolyzed for up to 100 h continuous operation. The tests were carried out at 550 °C, under atmospheric pressure and residence time ∼12 min with good reliability and reproducibility. All three pyrolysis products showed good fuel characteristics. The LHV of the obtained producer gas estimated to 23.5 MJ Nm⁻³ and 26% of the prototype energy requirements were provided by using the producer gas as fuel. Pyro-oil showed high carbon content (86.04 wt%), GCV of 44.2 MJ kg⁻¹ and H/C ratio (1.74). Despite its higher sulphur content, pyro-oil is comparable to diesel fuel in all other characteristics. Chars exhibited high percentage of fixed carbon (>80 wt %) and a high GCV = 30.3 MJ kg⁻¹. S, Zn and Si were detected in chars, at low concentration. Based on surface and structural characteristics, chars were considered comparable to carbon blacks of N400-N500 series. Upgrading of char to activated carbon by physical and chemical activation, increased N2 surface area to 589 m² g⁻¹ and 402 m² g⁻¹, respectively. The study contributes significantly to increase knowledge on the viability of pyrolysis, providing to the recycling sector an opportunity for the deployment of take-off systems, within a Circular Economy. End of Life Tyres (ELTs) pyrolysis can be viable, if all produced streams are valorized.

Graphical abstract

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