posted on 2021-05-11, 19:08authored byFelipe Campuzano, Natalia Cardona-Uribe, Andrés F. Agudelo, S. Mani Sarathy, Juan Daniel Martínez
This work assesses the effect of
adding CaO during the pyrolysis
of waste tires (WT) using a twin-auger reactor on the properties of
the pyrolysis derived products. Pyrolysis was conducted in a lab-scale
facility at a reactor temperature of 475 °C, solid residence
time of 3.5 min, WT mass flow rate of 1.16 kg/h, and N2 flow rate of 300 mL/min. CaO was continuously fed at ratios of 10,
15, and 20 wt %, according to the WT mass flow rate, using two particle
size ranges: fine (105–149 μm) and coarse (149–841
μm). The resulting tire pyrolysis oil (TPO) was initially characterized
in terms of sulfur content, and the sample with the lowest sulfur
content, named TPO[CaO], was further studied by different analytical
techniques, including GC–MS and 1H NMR. The tire
pyrolysis gas (TPG) and the tire pyrolysis solid (TPS) related to
TPO[CaO], so-called TPG[CaO] and TPS[CaO], respectively, were also
characterized by gas chromatography, and elemental, proximate, and
XRF analyses, respectively. Lastly, an acid demineralization process
was carried out to remove some of the inorganic elements in the TPS[CaO].
The addition of 15 wt % of coarse CaO during the pyrolysis of WT resulted
in a sulfur reduction in TPO of 26.10%, while viscosity and water
content were significantly reduced. The GC–MS analysis revealed
a significant presence of benzene, toluene, xylene, and limonene in
both TPO and TPO[CaO]. Likewise, 1H NMR suggested an increase
of hydrogen atoms in aromatic, naphthenic, and olefin structures in
the TPO[CaO], and a decrease of these atoms in paraffinic structures.
Similarly, H2 and some CxHy compounds increased, while CO2, CO, and H2S decreased in TPG[CaO], which supports the
hypothesis of the participation of CaO in several reactions during
the pyrolysis of WT. Although the ash content in TPS[CaO] was significantly
high after pyrolysis (57.5 wt %), the acid demineralization process
was effective at removing 80% of its inorganic content, improving
its surface area and porosity. The information presented in this work
aims at providing some insights toward the advancement of in situ upgrading strategies for the resulting products
derived from pyrolysis of WT.