Study of structural evolution of chars during rapid pyrolysis of waste CDs at different temperatures

Abstract

In this paper, the work dealt with the characterisation of chars obtained by rapid pyrolysis of waste compact discs (CDs) at different temperatures and its application as reductant in ironmaking industries. The rapid pyrolysis was performed at atmospheric pressure and temperatures ranging from 550 to 1550°C. The obtained chars were characterised by ultimate analysis, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photon spectroscopy (XPS), N2 isothermal adsorption method and scanning electron microscopy (SEM). The results indicated that char structure changed upon different pyrolysis temperature. The char yield decreased from 22% to 18% and gradual increase in carbon/oxygen ratio was observed with increase in pyrolysis temperature from 550 to 1550°C. The porosity in chars increased progressively with pyrolysis temperature, and maximum development of pores appeared at 850°C with surface area 334m2/g. At higher pyrolysis temperature, the chars became more aromatic and ordered, and aliphatic structures decreased significantly. The loss of functional groups at higher temperature such as carbonyl, aliphatic CH was evident by FTIR, XPS and Raman results. The ordered char structure obtained at 1550°C was used as reductant carbon for iron oxide reduction process, and 90% reduction was achieved. The waste CD char obtained during pyrolysis indicates as a valuable supplementary carbon source for ironmaking industries.