| 1. |
- Stanicic, Ivana, 1994, et al.
(författare)
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Fate of lead, copper, zinc and antimony during chemical looping gasification of automotive shredder residue
- 2021
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 302
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Tidskriftsartikel (refereegranskat)abstract
- Gasification experiments in this study were performed in a 2–4 MW indirect gasifier coupled to a semi-commercial CFB combustor at Chalmers University of Technology. Experiments were carried out during 13 days with automotive shredder residue (ASR), giving a unique opportunity to investigate the bed material under realistic conditions and with long residence times. The metal rich ash was accumulated in the bed, gaining some oxygen carrying capabilities, creating a chemical looping gasification (CLG) process. This study aims to expand the knowledge about the chemistry of zinc, copper, lead and antimony during CLG of ASR. Several experimental methods have been utilized, such as XRD, SEM-EDX and XPS along with detailed thermodynamic calculations to study chemical transformations that can occur in the system. Thermodynamic calculations showed that the reduction potential affect the phase distribution of these elements, where highly reduction conditions result in heavy metals dissolving in the slag phase. Copper and zinc ferrites, lead silicates and antimony oxides were identified at the particle surfaces in the bottom ash. The formation of an iron rich ash layer plays an important role, especially for copper and zinc speciation. The main pathways in the complex CLG system have been discussed in detail.
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| 2. |
- Stanicic, Ivana, 1994
(författare)
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Fate of Trace Elements in Thermochemical Conversion of Waste Fuels Using Oxygen Carriers
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The metals zinc, copper and lead are amongst the more abundant trace elements in waste fuels. The fate of these elements is important to study because they can affect the thermochemical conversion process and end up in ashes. With respect to the latter, this could have environmental implications when the ashes are used or landfilled but may also open up for the possibility of recycling. Utilizing metal oxides, so called oxygen carriers, as bed material in fluidized bed combustion could affect the fate of these metals. The interaction between heavy metals and oxygen carriers is an unexplored field of research. In this thesis a combined theoretical and experimental approach is used to study the fate of Zn, Cu and Pb in presence of oxygen carriers. Analysis methods such as scanning electron microscopy and x-ray diffraction were utilized to study morphology and main crystalline phases. Due to low concentrations x-ray photoelectron spectroscopy (XPS) was also used to study the trace elements on the surface and cross section of oxygen carrier particles. Thermodynamic calculations and a user defined database were applied to study phase formation for a range of parameters. Solid samples were obtained from industrial fluidized bed applications using oxygen carriers. The availability of samples from commercial units burning wastes provided a unique opportunity to study the trace element chemistry, as the long residence times of solids will allow for sufficient trace element interaction to be able to characterize appropriately. Analyzing ilmenite particles revealed incorporation of Zn the ash layer and accumulation of Cu inside the particles. During chemical looping gasification of a metal rich fuel and olivine, one major observation related to the surface enrichment of Cu and Zn, also in the form of ferrites. Thus, Fe is shown to play an important role for the interaction between the bed material and Cu and Zn. Pb is mainly concentrated in the fly ashes, during both olivine and ilmenite operation, although some lead chlorides, silicates and/or titanates were identified on the particles. Experimental findings and thermodynamic calculations indicate that the trace element chemistry is not only dependent on the oxygen carrier but also other ash components, for example K, Si and Cl. The proposed methodology in this thesis and the knowledge gained, can be applicable for other technologies using oxygen carriers, for example chemical looping combustion.
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| 3. |
- Stanicic, Ivana, 1994, et al.
(författare)
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Oxygen carrier aided combustion (OCAC) of two waste fuels - Experimental and theoretical study of the interaction between ilmenite and zinc, copper and lead
- 2021
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 148
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Tidskriftsartikel (refereegranskat)abstract
- Zinc, copper and lead are amongst the more abundant trace metals in waste fuels such as municipal solid waste and recovered waste wood. The ashes from waste fuels could contain high contents of these metals, which could be valuable but also toxic in certain environments. Oxygen carrier aided combustion, OCAC, is a novel technology for combustion of biomass and waste. Utilizing oxygen carriers could affect the fate of these metals and have implications for stability and recycling. The aim of this work is to study the fate of zinc, copper and lead during oxygen carrier aided combustion of two waste fuels utilizing ilmenite as an oxygen carrier. In total, four samples have been obtained from two different industrial fluidized bed boilers using ilmenite as bed material. Due to low concentrations, bulk analysis methods are not suitable for speciation, i.e. SEM/EDX and XRD. Hence, this investigation utilizes high resolution x-ray photoelectron spectroscopy (XPS), coupled to detailed thermodynamic modelling, with the aim of understanding trace metal speciation, distribution and phase composition. Characterization of the four samples show that iron at the surface of ilmenite particles interact with both copper and zinc to form ferrites, CuFe O and ZnFe O . Lead, on the other hand, is more prone to end up in the fly ash as condensed PbCl , but the mixed oxide PbTiO could be identified at the oxygen carrier surface. Thermodynamic calculations were shown to be in line with the identified compounds.
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