Thermal plasma processing of high temperature insulation wools

Abstract

High temperature insulation wool (HTIW) wastes, generated in large volume as a part of demolition and construction processes, are difficult to recycle and pose significant hazards to health and environment. Alkaline earth silicate wools (AESW) and alumino silicate wools (ASW) are the two major types. Typical constituents include silica and oxides of Ca, Al and Mg etc. in varying ratios, giving rise to their specific colours and inherited thermo-physical properties. Successful mitigation and reuse of such wools have not been explored enough. Possibly for the first time, the study makes an extensive investigation on air plasma mitigation of four most commonly used HTIW, namely, fresh rock wool, waste rock wool, waste stone wool and waste ceramic wool. This is a single step dry process. Use of freely available ambient air to generate plasma, extremely high enthalpy, presence of nascent atomic and ionic species and extremely high temperature make the process fast, efficient, economic and unique one to convert such wastes into valorised product. While the thermal field delivered by an air plasma torch has been derived from magneto-hydrodynamic simulation, the study makes a direct in-situ investigation of the evolution of thermal field in the melting zone using two colour pyrometer, and characterises the vitreous solidified end product using X-diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Analysis, Energy Dispersive X-ray Fluorescence Spectroscopy and Neutron Activation Analysis. Possible valorisation and use of the end product have been discussed in light of their observed elemental composition.

Keywords: Air plasma; Insulation wool; Plasma melting; Plasma waste management; Vitrification.