Incorporating the recovered carbon black produced in an industrial-scale waste tire pyrolysis plant into a natural rubber formulation.

This paper presents the experimental results obtained after incorporating the recovered Carbon Black (rCB) produced in an industrial-scale waste tire pyrolysis plant into a Natural Rubber (NR) formulation. The purpose of this study is to increase the technical knowledge on the use of rCB as a sustainable raw material in the rubber industry. The rCB and virgin Carbon Black (vCB) (ref. N550) under study were characterized using elemental and proximate analyses, X-Ray Fluorescence (XRF), Fourier Transform Infrared (FTIR) spectroscopy, and Scanning Electron Microscopy (SEM) were used, and different measures, including the Brunauer-Emmett-Teller (BET) surface area (SBET), particle size distribution (PSD), specific gravity, and pH, were estimated. The effect of rCB incorporation on the rheological, thermal, structural, and mechanical properties of the NR composites was assessed and compared to those obtained with vCB alone. The NR composites were prepared using different loads of vCB (20, 30, 40, and 50 phr), which was also replaced with rCB at different proportions (0, 50, and 100%). According to the characterization results, rCB offers lower reinforcement properties than vCB, which is attributable to its higher volatile matter and ash contents, higher apparent PSD, lower presence of acidic functional groups, and lower SBET. Despite this, interesting performances can be achieved when rCB is partially incorporated into the formulations or by increasing its load in the composites. For instance, when 50% of vCB was replaced with rCB, the values of the aforementioned properties were found to be between those obtained with the NR composites prepared with vCB and rCB. In addition, when increasing the rCB loading, some properties matched the behavior exhibited by vCB alone, thus compensating for the low reinforcement properties of rCB. These results are expected to provide an important impetus to move towards circular economy strategies having very positive impacts from the sustainable perspective.

Waste tire valorization by intermediate pyrolysis using a continuous twin-auger reactor: Operational features.

Pyrolysis can be regarded as a roadmap towards a circular and sustainable economy for waste tires (WT). This work investigates the operational characteristics of a novel twin-auger reactor to transform WT by intermediate pyrolysis into tire pyrolysis oil (TPO), recovery carbon black (rCB), and tire pyrolysis gas (TPG). The influence of four operating parameters: reactor temperature (X1), WT mass flow rate (X2), solid residence time (X3) and N2 volumetric flow rate (X4), was assessed in order to maximize the TPO yield (Y1), while keeping the rCB one (Y2) as low as possible. The experimental campaign was conducted based on central composite design (CCD). The analysis of variance (ANOVA) showed that X1 and X2 exhibit the highest statistical influence. An optimization of both responses resulted in TPO, rCB, and TPG yields of 45, 40 and 15 wt%, respectively, when the pyrolyzer is operated at 475 °C, 1.16 kg/h, 3.5 min and 300 mL/min. At these conditions, the resulting TPO showed contents of C, H, S, N and O around 88.2, 9.7, 1.3, 0.7 and <0.1 wt%, respectively, along with a heating value of 42.02 MJ/kg. The rCB is comprised of moisture, volatile matter, fixed carbon, and ash around 2.5, 3.7, 75.5, and 18.3 wt%, respectively; while the TPG was mainly composed of H2 (23.7 vol%) and CH4 (28.2 vol%). Overall, these results suggest that twin-auger pyrolyzers are well suited for valorizing WT by intermediate pyrolysis.

Carbon black recovery from waste tire pyrolysis by demineralization: Production and application in rubber compounding.

Pyrolysis offers the possibility to convert waste tires into liquid and gaseous fractions as well as a carbon-rich solid (CBp), which contains the original carbon black (CB) and the inorganic compounds used in tire manufacture. Whilst both liquid and gaseous fractions can be valorized without further processing, there is a general consensus that CBp needs to be improved before it can be considered a commercial product, seriously penalizing the pyrolysis process profitability. In this work, the CBp produced in a continuous pyrolysis process was demineralized (chemical leaching) with the aim of recovering the CB trapped into the CBp and thus, producing a standardized CB product for commercial purposes. The demineralization process was conducted by using cheap and common reagents (HCl and NaOH). In this sense, the acid treatment removed most of the mineral matter contained in the CBp and concentration was the main parameter controlling the demineralization process. An ash content of 4.9 wt% was obtained by using 60 min of soaking time, 60 °C of temperature, 10 mL/g of reagent/CBp ratio and HCl 4 M. The demineralized CBp (dCBp) showed a carbon content of 92.9 wt%, while the FRX analysis indicated that SiO2 is the major component into the ash. The BET surface area was 76.3 m2/g, and textural characterizations (SEM/EDX and TEM) revealed that dCBp is composed by primary particles lower than 100 nm. Although dCBp showed a low structure, the surface chemistry was rich in surface acidic groups. Finally, dCBp was used in Styrene Butadiene Rubber (SBR) compounding, probing its technical feasibility as substitute of commercial CB N550.