Abstract
Oxygen Carrier Aided Combustion is a novel fluidized bed concept for burning waste. This study analyzed solid samples from an industrial OCAC application using municipal solid waste and the oxygen carrier ilmenite. The presence of oxygen carriers impacts the ash chemistry, which can influence corrosion and ash characteristics. By investigating samples obtained from industrial applications, unique and highly relevant information on the solid-state chemistry and the fate of important elements can be obtained. In total, 20 bottom ashes and 17 fly ashes were sampled over a period of 38 days. In a preceding study, the surface interaction between ilmenite and Zn, Cu and Pb was investigated. In this paper, the distribution of these elements throughout the particle cross-section and the influence of residence time has been studied using XRD, SEM-EDX and XPS. The results show that Zn is incorporated in the Fe-rich ash layer over time in the form of Zn ferrites, while Cu accumulates inside the ilmenite particles with time, and Cr is enriched in the magnetically separated bottom ash. Low concentrations of Pb were detected in the bottom ashes, suggesting that a significant part is released in the gas phase. The influence of temperature, bed material and reduction potential were evaluated using multicomponent, multiphase equilibrium calculations. It is shown that an ilmenite bed is less prone to form melts in comparison to a bed of silica sand and that the addition of sulfur could decrease the volatilization of Pb.
Highlights
The concentrations of greenhouse gases in the atmosphere are increasing as a result of anthropogenic activities
This work aims to study a time series of solid industrial samples derived from OCAC of municipal solid waste (MSW) using the oxygen carrier ilmenite
While the pre ceding paper [48] focused on surface speciation for one sample, this study has elaborated on the trace element distribution throughout the particle cross-section, evaluated during a longer time series spanning 893 h with continuous ilmenite addition
Summary
The concentrations of greenhouse gases in the atmosphere are increasing as a result of anthropogenic activities. The global mean tem perature has increased with subsequent climate change. The warming from these anthropogenic emissions will persist from centuries to millennia and cause long-term changes in the climate system [2]. The second-largest contributor to greenhouse gas emissions is methane, which has a global warming potential of GWP100 = 28 [3,4]. One of the largest anthropogenic sources of methane emissions origi nates from waste landfills [5]. When municipal solid waste (MSW) is landfilled, the biodegradable portion releases methane and CO2 into the atmosphere. Recycling and composting of solid waste have increased by a factor of three, and incineration with energy recovery has increased fourfold [6]
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