Comparison of trace element mobility from MSWI ash before and after plasma vitrification

A common perception of plasma arc treatment systems for municipal solid waste incineration ash is that the resulting vitrified slag is inert from an environmental perspective. Research was conducted to examine this hypothesis and to assess whether reduced pollutant release results from pollutant depletion during the process of the ash with plasma, or encapsulation in the glassy vitrified matrix. The concentrations of four discrete municipal solid waste incineration ash samples before and after plasma arc vitrification in a bench-scale unit were compared. Slag and untreated ash samples were leached using several standardized approaches and mobility among the four metals of interest (e.g. As, Cd, Pb and Sb) varied across samples, but was generally high (as high as 100% for Cd). Comparison across methods did not indicate substantial encapsulation in the vitrified slag, which suggests that reduced pollutant release from plasma arc vitrified slag is due to pollutant depletion by volatilization, not encapsulation. This has significant implications for the management of air pollution control residues from waste-to-energy facilities using plasma arc vitrification.

Investigation of Environmental Leaching Behavior of an Innovative Method for Landfilling of Waste Incineration Air Pollution Control Residues

Waste incineration air pollution control (APC) residues require pretreatment before landfilling because these types of residues encompass pollutants from an incineration gas stream. The environmental concerns of APC residues consist of a risk of leaching and subsequent release of potentially harmful substances that occur under environmental exposure. The stabilization/solidification (S/S) method of incineration residues is one of the most applied technologies for hazardous incineration residues. Portland cement is commonly used as a binder material in S/S for pollutant encapsulation, in order to change the hydrological characteristics of the landfilled material. Based on previous research, an innovative S/S method for APC residues is investigated, meant to replace Portland cement with cement-like material made from lignite fly ash (FA). To do this, a lab-scale landfill was created through the promoted S/S method and exposed to the environment for 12 months. Thus, this article assesses the lab-scale leaching behavior of a landfill disposal material exposed to environmental conditions and attempts to prove the promoted innovative S/S method. The results show that the replacement of Portland cement with a substitute material for utilization in the S/S method can mitigate energy consumption in the industrial cement subsector.