RESUMO
This work, carried out within the framework of the BlackCycle project, demonstrates the robustness of an auger reactor for the pyrolysis of end-of-life tires (ELTs) to be considered within the seventh level of technology readiness (TRL-7). For this purpose, the resulting pyrolysis products are compared with those obtained from a pilot scale facility ranging within the fifth technology readiness level (TRL-5). Using the same type of ELTs, tire trucks (TTs), operating conditions used at the TRL-5 plant are attempted to mimic those expected at a semi-industrial plant: tailored temperature profile (450, 550, and 775 °C) and residence time for vapors (30 s) and solids (15 min). The feed mass rate is 4 and 400 kg/h for the pilot and semi-industrial plants, respectively. The yields of tire pyrolysis oil (TPO), tire pyrolysis gas (TPG), and raw recovered carbon black (RRCB) from both plants, as well as their key properties and characteristics, are in good agreement with each other. The TPO produced by both plants contains comparable concentrations of value-added chemicals such as benzene, toluene, xylene, ethylbenzene, and limonene. There is also a very similar pattern between the simulated distillation curves. The TPG obtained from both plants is also very rich in H2 and CH4 and has a lower calorific value of 52-54 MJ/Nm3 (N2 free basis). Although the RRCBs produced by the two plants are more demanding and require more labor, they do have a number of comparable characteristics. All this information demonstrates not only the reliability of the experimental campaigns to scale up the pyrolysis process but also the robustness of the semi-industrial scale plant based on the auger technology to be classified at TRL-7.
RESUMO
Pyrolysis is a chemical recycling process of interest as a means to achieve a sustainable circular economy for end-of-life tyres (ELTs). In the pyrolysis process, ELTs are converted into tyre pyrolysis gas (TPG), tyre pyrolysis oil (TPO) and raw recovered carbon black (RRCB). This work investigates for the first time the effect of different temperature profiles by using a single-auger pyrolysis reactor in an industrially relevant scale (TRL-5). Since the development of this process at this representative scale is quite limited and the temperature profile has not been previously studied, the results achieved in this work can provide a useful database for the development of this process at industrial scale. For this purpose, two different sources of ELTs, commercial truck tyres (CTTs) and passenger car tyres (PCTs), were used. Accordingly, the experimental campaign was conducted using two different incremental temperature profiles (425-550-775 °C and 600-700-800 °C) based on those that can be replicated in an industrial-scale auger pyrolysis plant. For the sake of comparison, two isothermal heating conditions (500-500-500 °C and 600-600-600 °C) were also tested. The results confirmed the remarkable influence of temperature profile on both the distribution and properties of products. The 425-550-775 °C temperature profile was found to enhance limonene production, which is associated with the minimisation of secondary reactions in the first heating zone of the reactor. Additionally, there were very low carbonaceous deposits found in the RRCB because of the high severity of devolatilisation conditions in the third heating zone of the reactor. On the other hand, when the temperature profile was raised, the production of single-ring aromatics, particularly benzene, toluene, ethylbenzene and xylenes (BTEX) significantly increased in the TPO at the expense of limonene. Thus, from this strategy, it is possible to tune the properties of the products depending on the requirements of the application in a single step, getting closer for circular economy in the ELT recycling domain.