Production of hydrogen-rich gases in the recycling process of residual carbon fiber reinforced polymers by pyrolysis.

In this work, a novel method to valorize the polymeric matrix of residual carbon fiber reinforced polymers (CFRP) in the recycling process of carbon fibers by pyrolysis is presented. The experiments have been carried out with an expired epoxy-based pre-preg and in a lab-scale installation composed of two reactors. In the first one, pyrolysis and oxidation have been carried out, while in the second one, the gases and vapors resulting from the thermal decomposition of the polymeric resin have been thermally treated. The following operating parameters have been studied in the pyrolysis step: dwell time, the use of N2 (N2 flow, no N2 flow and not even to inert the reaction medium) and the solid bed material of the second reactor. In the oxidation step, temperature and time have been optimized by using the theory of experiments based on 2 k factorial design was used. It has been demonstrated that clean carbon fibers and a gaseous fraction with 75% by volume of H2 can be obtained. This is possible through a combined process of (1) CFRP thermal decomposition at 500 °C, (2) thermal treatment of gases and vapors at 900 °C in a solid bed tubular reactor filled with a waste refractory material and (3) oxidation of pyrolysis solid at 500 °C during 165 min in presence of 1.3 L air min-1.

Possibilities and limits of pyrolysis for recycling plastic rich waste streams rejected from phones recycling plants.

The possibilities and limits of pyrolysis as a means of recycling plastic rich fractions derived from discarded phones have been studied. Two plastic rich samples (⩾80wt% plastics) derived from landline and mobile phones provided by a Spanish recycling company, have been pyrolysed under N2 in a 3.5dm3 reactor at 500°C for 30min. The landline and mobile phones yielded 58 and 54.5wt% liquids, 16.7 and 12.6wt% gases and 28.3 and 32.4wt% solids respectively. The liquids were a complex mixture of organic products containing valuable chemicals (toluene, styrene, ethyl-benzene, etc.) and with high HHVs (34-38MJkg-1). The solids were composed of metals (mainly Cu, Zn, and Al) and char (≈50wt%). The gases consisted mainly of hydrocarbons and some CO, CO2 and H2. The halogens (Cl, Br) of the original samples were mainly distributed between the gases and solids. The metals and char can be easily separated and the formers may be recycled, but the uses of the char will be restricted due to its Cl/Br content. The gases may provide the energy requirements of the processing plant, but HBr and HCl must be firstly eliminated. The liquids could have a potential use as energy or chemicals source, but the practical implementation of these applications will be no exempt of great problems that may become insurmountable (difficulty of economically recovering pure chemicals, contamination by volatile metals, etc.).