Recycling waste bakelite as an alternative carbon resource for ironmaking applications

In-depth investigations were carried out on the thermal degradation and structural evolution of bakelite by heat treatment at different temperatures; the structural transformation to graphitic carbon at 1 450°C was confirmed through X-ray diffraction. High amounts of residual carbon were obtained after the high temperature charring of bakelite. The reduction behavior of iron oxide/bakelite composite pellets was studied at 1 450°C to investigate waste bakelite as a carbon resource in ironmaking towards a partial replacement of traditional carbon sources. These studies were carried out for raw bakelite as well as for bakelite char. The reduction of iron oxide by raw bakelite resulted in the non-separation of metal, slag and in the formation of direct reduced iron pellets. On the other hand, bakelite char pellet showed clear separation of iron nuggets from slag. This study has established bakelite as an alternative carbonaceous resource for reduction reactions in new ironmaking processes. © 2014 ISIJ

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

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 334 m2/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. © 2014 Elsevier Ltd. All rights reserved

Characterisation of gas evolution and char structural change during pyrolysis of waste CDs

The purpose of this study is to determine the characteristics of gas evolution and char structural change during pyrolysis of waste compact disc (CD). A combination of Thermogravimtetry-Fourier Transform Infrared spectroscopy (TG-FTIR) and Thermogravimtetry-Gas Chromatography/Mass Spectrometry (TG-GCMS) techniques are employed for this study. The thermal characteristics, temperature trend of evolving gas species and gas characteristics are investigated by TG-FTIR and TG-GCMS techniques. From the results, the waste CD degradation is divided into three stages (a) main gaseous compounds in first stage (<500 °C) are CO2, CO, CH4 and H2O (b) organic species including aromatic hydrocarbons, phenols and its derivatives are evolved between 500 and 600 °C. (c) Temperature above 600 °C, carbonisation and char formation occurred. The char chemical structure and physical characteristics are investigated by Scanning Electron Microscopy, FTIR spectroscopy, Raman spectroscopy and X-ray diffraction techniques. This fundamental study provides basic insight of waste CD pyrolysis and also indicates that very high valuable carbon product (90% carbon in residue) with good crystallinity is achievable

Irradiation induced effects on Ni<SUB>3</SUB>N/Si bilayer system

The irradiation effect in Ni3N/Si bilayers induced by 100 MeV Au ions at fluence 1.5 × 1014 ions/cm2 was investigated at room temperature. Grazing incidence X-ray diffraction determined the formation of Ni2Si and Si3N4 phases at the interface. The roughness of the thin film was measured by atomic force microscopy. X-ray reflectivity was used to measure the thickness of thin films. X-ray photoelectron spectroscopy has provided the elemental binding energy of Ni3N thin films. It was observed that after irradiation (Ni 2p3/2) peak shifted towards a lower binding energy. Optical properties of nickel nitride films, which were deposited onto Si (100) by ion beam sputtering at vacuum 1.2 × 10-4 torr, were examined using Au ions. In-situ I-V measurements on Ni3N/Si samples were also undertaken at room temperature which showed that there is an increase in current after irradiation

The power of steelmaking-harnessing high-temperature reactions to transform waste into raw material resources

Iron- and steelmaking processes present a largely untapped opportunity to transform some of the world's most problematic waste streams into raw materials for production. This opportunity lies in their high-temperature environments, which offer sustainable pathways for utilizing chemical reactions to repurpose waste materials as resources, such as reducing iron oxide to iron and dissolving the carbon in waste materials into metal. High- Temperature environments can be leveraged to revolutionize the role steelmakers play in globally significant, large-scale recycling, without making fundamental changes to manufacturing processes. This presentation describes the broad opportunities available to iron- and steelmakers to utilize waste streams - ranging from polymeric materials to agricultural wastes - as raw materials. The potential to implement such novel recycling solutions are not generally available to many other materials industries because they operate at relatively lower temperatures, which may not be suitable for triggering useful chemical transformations. Recycling waste polymeric materials in steelmaking is one solution for end-of-life products, which currently impose a serious burden on overstretched landfills, as is the case with some plastics. Specifically, this lecture presents fundamental understanding of different plastic wastes - melamine, high-density polyethylene, polycarbonate and Bakelite, as well as agricultural waste and tires - and their transformations and chemical reactions at high temperatures. Plant results from EAF steelmaking in Sydney, Australia, where recycling waste is now standard practice, will also be included