Thermal plasma pyrolysis of used tires for carbon black recovery

This letter reports on the gaseous and carbon black product characteristics from nitrogen thermal plasma pyrolysis of used tires. Recently the disposal of used tires has drawn considerable attention because of the large amount of used tires produced all over the world. Several options for dealing with waste tires exist, such as using as shielding in shipside, incineration and pyrolysis. Thermal plasma pyrolysis of used tire has several advantages over other alternative tire recycling methods. No toxic substances are emitted, no liquid product is generated in the process and various commercial applications for the gaseous and solid products obtained are possible. A number of studies [1–4] have shown the merits of the plasma pyrolysis technique dealing with some classes of waste material especially polymers. In plasma pyrolysis, the organic volatile matter of tires is decomposed to low-molecular-weight products, which are useful as fuels or chemical sources; the inorganic components and the carbon black filler are discharged as solid residue relatively unaltered and therefore can theoretically be recycled in carbon black related applications. In the current study, the used tire particle sample was provided by Guangzhou Resource Recycling Company. A fine fraction of particles between 30 and 80 mesh was used in the experiments. Detailed description of the reactor assembly has already been published [1]. Steam may be injected into the plasma reaction chamber with the feed particles. The gas products were collected in rubber bags and analyzed by gas chromatography (Shimadzu GC-20B-1). Solid residues were saved in the ash tank. Samples CBp1 and CBp2 were obtained from plasma pyrolysis of tires at 35.2 kVA, feed rate 80 g/min, without steam injection and with steam injection 80 × 10−6 m3/min, respectively. Since the solid residues were studied for substitution of commercial carbon black, the following analyses were carried out: BET surface area, ash-content, SEM, XPS and 13C-NMR. When tire particles are injected into the plasma, they are heated up very rapidly by the plasma, the volatile matter is released and cracked giving rise to H2, CO,