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Lai Z.,South China University of Technology | Lai Z.,GuangDong International Engineering Consultant Corporation | Ma X.,South China University of Technology | Tang Y.,South China University of Technology | And 2 more authors.
Applied Thermal Engineering | Year: 2014

To understand the deposition mechanism and determine the factors influencing corrosion, a municipal solid waste grate incinerator with the steam parameter of 6.5 MPa, 450 C was investigated. Deposits from the first pass as well as fly ash were characterized by SEM-EDS, XRF and XRD. Deposits contained more or less molten or semi-molten materials, due to the chemical reaction heat during sulfation, low melting point compounds and molecular cramming. The content of K, Na, Cl or Fe in the deposits was bigger than fly ash, but fly ash contained more Ca, S, Si and Al, due to their different source and deposition mechanism. Chlorides and alkali metal compounds were identified. The molten deposits increased the corrosion because liquid phase had faster chemical reactions and also provided an electrolyte for ionic transport or electrochemical attack. The chlorides and alkali metal compounds accelerated corrosion not only by lowering the melting temperature of the deposits, but also by attacking the metal surface with active oxidation mechanism. Moreover, entirety of deposits had a high strength, therefore, deposits were subject to stress impact and resulted in the metal defect on the heating tubes. © 2014 Elsevier Ltd. All rights reserved.

Tang Y.,South China University of Technology | Ma X.,South China University of Technology | Yu Q.,South China University of Technology | Zhang C.,South China University of Technology | And 2 more authors.
Waste Management | Year: 2015

This paper investigated the behavior of six heavy metals (Cd, Pb, Cu, Cr, Ni and Zn) in the bottom ashes of recycled polyvinyl chloride pellets (PVC), wood sawdust (WS) and paper mixture (PM), representing the common components of municipal solid waste (MSW), obtained during combustion in CO2/O2 atmosphere in a lab-scale electrically heated tube furnace. Replacement of N2 by CO2 did not obviously change the shape of relative enrichment factor (RE) curves and subsequent order of heavy metals, but increased enrichment of these heavy metals in bottom ashes of WS, PM and PVC. The increment of O2 concentration in CO2/O2 atmosphere further increased RE values. It was only when the temperature was higher than or equal to 700°C that the increment of the combustion temperature reduced the RE values of heavy metals. The effect of temperature on heavy metals evaporation was the most pronounced for the medium volatile metal Pb, and the least for the low volatiles Cr and Ni. The effect of temperature was more pronounced for PVC ash than for WS and PM ashes. This paper contributes to the control of heavy metals during MSW incineration and management of MSW oxy-fuel residues. © 2015 Elsevier Ltd.

Tang Y.T.,South China University of Technology | Ma X.Q.,South China University of Technology | Lai Z.Y.,Guangdong International Engineering Consultant Corporation | Fan Y.,Boston University
Energy | Year: 2015

The combustion of plastic (PVC), rubber (TR) and leather (L) in different atmospheres (80N2/20O2, 80CO2/20O2, 70CO2/30O2, 60CO2/40O2, 50CO2/50O2) was analyzed thermogravimetrically. Regardless of individual material or blend, the replacement of N2 only by CO2 resulted in smaller weight loss rates, a change in reactions occurring above 600°C and a worse burnout, and the oxygen-enriched combustion technology could alleviated the inhibitory effects to some extent. Above 600°C, the effect of O2 concentration on the weight loss rate in CO2/O2 atmosphere depended on the given operating conditions, but still postponed the location of the peaks. The characteristics of blends could be predicted roughly by the individual fuels and blending ratio. The addition of TR to L or PVC (polyvinyl chloride) hindered the burnout, and the addition of PVC to L or TR hindered the char-CO2 reaction. For the same individual material or blend, the apparent activation energies for the first two reactions in 70CO2/30O2 approximately equal to those in 80N2/20O2, while that the value for the third reactions in two atmospheres differed greatly. This work contributes to the understanding of MSW (municipal solid waste) oxygen-enriched combustion and development of MSW oxy-fuel combustion. © 2015 Elsevier Ltd.

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