Available online at www.sciencedirect.com Journal of Hazardous Materials 151 (2008) 473–480 Analysis of results from the operation of a pilot plasma gasification/vitrification unit for optimizing its performance K. Moustakas ∗ , G. Xydis, S. Malamis, K.-J. Haralambous, M. Loizidou National Technical University of Athens, School of Chemical Engineering, Unit of Environmental Science and Technology, 9, Heroon Polytechniou Street, Zografou Campus, 15773 Athens, Greece Received 18 January 2006; received in revised form 2 June 2007; accepted 6 June 2007 Available online 8 June 2007 Abstract Plasma gasification/vitrification is an innovative and environmentally friendly method of waste treatment. A demonstration plasma gasifica- tion/vitrification unit was developed and installed in Viotia region in order to examine the efficiency of this innovative technology in dealing with hazardous waste. The preliminary results from the trial runs of the plasma unit, as well as the study of the influence of certain parameters in the system performance are presented and analyzed in this paper, contributing to the improvement of the operation performance. Finally, data on the final air emissions and the vitrified ash toxicity characteristic leaching procedure (TCLP) results are provided in order to assess the environmental performance of the system. The produced slag was found to be characterized by extremely low leaching properties and can be utilized as construction material, while the values of the polluting parameters of the air emissions were satisfactory. © 2007 Elsevier B.V. All rights reserved. Keywords: Plasma technology; Gasification; Vitrification process; Slag 1. Introduction The operation of a large number of industries located in Vio- tia region is a great source of waste with high polluting load. More particularly, about 18,000 t of hazardous waste are gen- erated every year, and unfortunately, nonproper management practices are followed in some cases, which can constitute a danger for public health and environment. Moreover, as more and more wastewater treatment plants are applied for the effec- tive management of the generated wastewater, the quantities of the generated sludge are substantially increasing. Thermal waste treatment is attracting increasing attention as a viable alternative to landfill disposal. It reduces the volume of solid waste significantly but suffers from a bad reputation with the public, representing one of the top industries no one wants “in their backyard”. Some of this fear stems from a lack of information about the process, but more justified concerns over emissions remain. Depending on the type and age of the tech- ∗ Corresponding author. Tel.: +30 210 7723108/2334/3106; fax: +30 210 7723285. E-mail address: konmoust@central.ntua.gr (K. Moustakas). nology applied, potential emissions include dangerous organic molecules, like furans and dioxins, incomplete combustion prod- ucts, such as carbon monoxide, large amounts of particulates, as well as acid rain precursors like nitrogen oxides and sulfurous compounds. Furthermore, the management of the large amounts of bottom ash and potentially toxic fly ash can cause significant disposal problems in countries where landfill has already been banned [1]. The good news is that the technologies needed to remove the pollutants from the stack gas and clean the ashes are getting better [2,3]. Yet, they remain quite expensive. A promis- ing method that can destroy waste at high temperatures is plasma gasification, which uses electricity to convert waste into a fuel gas and an inert rock. In this framework, the scientific project entitled ‘development of a demonstration plasma gasification/vitrification unit for the treatment of hazardous waste’ aimed at studying the potential of plasma gasification and vitrification of waste (PGVW) tech- nology [4]. This paper obviously constitutes continuation of the work described in Ref. [4]. The theoretical basis of plasmas and gasification/vitrification process, as well as different applications [5,6] in various coun- tries were thoroughly investigated and led to the design of a pilot plasma unit, vitrifying the inorganic portion of the hazardous 0304-3894/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2007.06.006