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Devaraj A.R.,Imperial College London | Cheeseman C.R.,Imperial College London | Boccaccini A.R.,Imperial College London | Deegan D.,Tetronics Ltd.
International Journal of Applied Ceramic Technology | Year: 2010

Air pollution control (APC) residues produced from cleaning gas emissions at energy from waste (EfW) plants processing municipal solid waste are a problematic hazardous waste. In this research they have been treated using DC plasma technology and this produces an inert glass. Glass-ceramic tiles were prepared by powder pressing and sintering fritted APC residue-derived glass. Tile samples prepared with high levels of plasma treated APC residue glass had comparable physical properties to commercially available ceramics such as porcelain and monoporosa, with high bulk density (2.4 g/cm3), low water absorption (<6%) and high flexural strength (∼60 MPa). © 2009 The American Ceramic Society.

Tang K.M.,University of Liverpool | Yan J.D.,University of Liverpool | Chapman C.,Tetronics Ltd. | Fang M.T.C.,University of Liverpool
Journal of Physics D: Applied Physics | Year: 2010

A three-dimensional steady-state arc model has been developed for simulating the behaviour of a twin-torch plasma system operating in an atmospheric argon environment. The governing equations for plasma flow, electric and magnetic fields are solved in a Cartesian coordinate system with suitable domain size and appropriate boundary conditions. Radiation from the arc is accounted for using the concept of net emission coefficient. Results over the current range 300-900A suggest that the two arc columns attached, respectively, to anode and cathode are coupled by a thin tissue-like conducting layer with a thickness in the range 3-6 mm, serving as a critical part of the current path. Lorentz force resulting from the arc's current interacting with its own magnetic field plays a decisive role in bending the two arc columns and shaping the coupling zone. Turbulence is introduced to account for the effect resulting from instability of the coupling zone as observed in experiment and its effectiveness is analysed in detail usingdifferent length scale parameters. Suggestions to further improve the model are proposed. © 2010 IOP Publishing Ltd.

Roether J.A.,Imperial College London | Daniel D.J.,Imperial College London | Amutha Rani D.,Imperial College London | Deegan D.E.,Tetronics Ltd. | And 2 more authors.
Journal of Hazardous Materials | Year: 2010

Air pollution control (APC) residues, obtained from a major UK energy from waste (EfW) plant, processing municipal solid waste, have been blended with silica and alumina and melted using DC plasma arc technology. The glass produced was crushed, milled, uni-axially pressed and sintered at temperatures between 750 and 1150 °C, and the glass-ceramics formed were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties assessed included Vickers's hardness, flexural strength, Young's modulus and thermal shock resistance. The optimum sintering temperature was found to be 950 °C. This produced a glass-ceramic with high density (∼2.58 g/cm3), minimum water absorption (∼2%) and relatively high mechanical strength (∼81 ± 4 MPa). Thermal shock testing showed that 950 °C sintered samples could withstand a 700 °C quench in water without micro-cracking. The research demonstrates that glass-ceramics can be readily formed from DC plasma treated APC residues and that these have comparable properties to marble and porcelain. This novel approach represents a technically and commercially viable treatment option for APC residues that allow the beneficial reuse of this problematic waste. © 2009 Elsevier B.V. All rights reserved.

Kourti I.,Imperial College London | Deegan D.,Tetronics Ltd. | Boccaccini A.R.,Friedrich - Alexander - University, Erlangen - Nuremberg | Boccaccini A.R.,Imperial College London | Cheeseman C.R.,Imperial College London
Waste and Biomass Valorization | Year: 2013

Air pollution control (APC) residues are hazardous waste generated from the air pollution abatement systems operating at energy from waste plants processing municipal solid waste. APC residues can be blended with glass forming additives and treated by direct current (DC) plasma technology, producing a stable, non-hazardous inert glass slag. This research has characterised the pozzolanic activity of this glass slag. The effects of glass cooling rate (quenched or air cooled) and particle size distribution have been investigated. The results show that quenched or fritted APC glass is significantly more pozzolanic than air-cooled glass. The optimum blended Portland cement paste, which maximises APC glass utilization and has the best properties, contained 20 wt % fritted APC glass slag. This blended Portland cement paste had low water demand, developed a dense microstructure and had high compressive strength (*100 MPa). The research has demonstrated that the glass slag resulting from DC plasma treatment of APC residues is pozzolanic and has potential to be beneficially reused in blended cements. © Springer Science+Business Media Dordrecht 2013.

Kourti I.,Imperial College London | Rani D.A.,Imperial College London | Deegan D.,Tetronics Ltd. | Boccaccini A.R.,Imperial College London | Cheeseman C.R.,Imperial College London
Journal of Hazardous Materials | Year: 2010

Air pollution control (APC) residues are the hazardous waste produced from cleaning gaseous emissions at energy-from-waste (EfW) facilities processing municipal solid waste (MSW). APC residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium alumino-silicate glass. This research has investigated the optimisation and properties of geopolymers prepared from this glass. Work has shown that high strength geopolymers can be formed and that the NaOH concentration of the activating solution significantly affects the properties. The broad particle size distribution of the APC residue glass used in these experiments results in a microstructure that contains unreacted glass particles included within a geopolymer binder phase. The high calcium content of APC residues may cause the formation of some amorphous calcium silicate hydrate (C-S-H) gel. A mix prepared with S/L = 3.4, Si/Al = 2.6 and [NaOH] = 6 M in the activating solution, produced high strength geopolymers with compressive strengths of ∼130 MPa. This material had high density (2070 kg/m3) and low porosity. The research demonstrates for the first time that glass derived from DC plasma treatment of APC residues can be used to form high strength geopolymer-glass composites that have potential for use in a range of applications. © 2009 Elsevier B.V. All rights reserved.

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