| 1. |
- Kong, Xiangrui, et al.
(författare)
-
Phase recognition in SEM-EDX chemical maps using positive matrix factorization
- 2023
-
Ingår i: Methodsx. - 2215-0161. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- Images from scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spec- troscopy (EDX) are informative and useful to understand the chemical composition and mixing state of solid materials. Positive matrix factorization (PMF) is a multivariate factor analysis tech- nique that has been used in many applications, and the method is here applied to identify factors that can describe common features between elemental SEM-EDX maps. The procedures of con- verting both graphics and digital images to PMF input files are introduced, and the PMF analysis is exemplified with an open-access PMF program. A case study of oxygen carrier materials from oxygen carrier aided combustion is presented, and the results show that PMF successfully groups elements into factors, and the maps of these factors are visualized. The produced images provide further information on ash interactions and composition of distinct chemical layers. The method can handle all types of chemical maps and the method is not limited solely to SEM-EDX although these images have been used as an example. The main characteristics of the method are:center dot Adapting graphics and digital images ready for PMF analysis.center dot Conversion between 1-D and 2-D datasets allows visualization of common chemical maps of elements grouped in factors.center dot Handles all types of chemical mappings and large data sets.
|
|
| 2. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Combined manganese oxides as oxygen carriers for biomass combustion — Ash interactions
- 2019
-
Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 149, s. 104-120
-
Tidskriftsartikel (refereegranskat)abstract
- © 2019 Institution of Chemical Engineers Carbon capture and storage (CCS) has been acknowledged as an important strategy for mitigation of climate change. Although highly applicable for fossil fuels, CCS with biomass could have the added advantage of resulting in negative emissions of carbon dioxide. One promising carbon capture technology is chemical-looping combustion (CLC). In CLC the reactors are filled with metal oxide bed material called oxygen carriers. Before CLC can be implemented for biomass combustion at a large scale, biomass ash components interaction with oxygen carriers needs to be further understood. Four combined manganese oxides Mn3O4-SiO2, Mn3O4-SiO2-TiO2, Mn3O4-Fe2O3 and Mn3O4-Fe2O3-Al2O3 were exposed to common biomass ash components K, Ca and P. The ash components can exist in many forms, but here the compounds CaCO3, K2CO3 and CaHPO4 were used. Exposures were performed at 900 °C for six hours in oxidising, reducing and inert conditions. Crystalline phases were analysed by XRD and morphology examined with SEM-EDX. Results show that oxygen carrier particles containing silicon were more likely to form agglomerates, especially in combination with potassium, whereas the particles including iron were more stable. MnFeAl was the oxygen carrier that showed least agglomerating behaviour while simultaneously showing a propensity to absorb some ash components. Some inconsistencies between thermodynamic predictions and experimental results is observed. This may be explained by lack of relevant data in the used databases, were only a few of the oxygen carrier-ash systems and subsystems have been optimised. Further optimisation related to manganese rich systems should be performed to obtain reliable results.
|
|
| 3. |
- Andersson, Viktor, 1983, et al.
(författare)
-
Alkali desorption from ilmenite oxygen carrier particles used in biomass combustion
- 2024
-
Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 359
-
Tidskriftsartikel (refereegranskat)abstract
- Oxygen-carrying fluidized bed materials are increasingly used in novel technologies for carbon capture and storage, and to improve the efficiency of fuel conversion processes. Potassium- and sodium-containing compounds are released during biomass combustion and may have both negative and positive effects on conversion processes. Ilmenite is an important oxygen carrier material with the ability to capture alkali in the form of titanates. This is a desirable property since it may reduce detrimental alkali effects including fouling, corrosion, and fluidized bed agglomeration. This study investigates the interactions of alkali-containing compounds with ilmenite particles previously used in an industrial scale (115 MWth) oxygen carrier aided combustion system. The ilmenite samples were exposed to temperatures up to 1000 °C under inert and oxidizing conditions while the alkali release kinetics were characterized using online alkali monitoring. Alkali desorption occurs between 630 and 800 °C, which is attributed to loosely bound alkali at or near the surface of the particles. Extensive alkali release is observed above 900 °C and proceeds during extended time periods at 1000 °C. The release above 900 °C is more pronounced under oxidizing conditions and approximately 9.1 and 3.2 wt% of the alkali content is emitted from the ilmenite samples in high and low oxygen activity, respectively. Detailed material analyses using scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were conducted before and after temperature treatment, which revealed that the concentrations of potassium, sodium and chlorine decrease at the outermost surface of the ilmenite particles during temperature treatment, and Cl is depleted to a deeper level in oxidizing conditions compared to inert. The implications for ilmenite-ash interactions, oxygen carrier aided combustion and chemical looping systems are discussed.
|
|
| 4. |
- Brorsson, Joakim, 1988, et al.
(författare)
-
Thermodynamic properties for metal oxides from first-principles
- 2024
-
Ingår i: Computational Materials Science. - 0927-0256. ; 233
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, an efficient first-principles approach for calculating the thermodynamic properties of mixed metal oxides at high temperatures is demonstrated. More precisely, this procedure combines density functional theory and harmonic phonon calculations with tabulated thermochemical data to predict the heat capacity, formation energy, and entropy of important metal oxides. Alloy cluster expansions are, moreover, employed to represent phases that display chemical ordering as well as to calculate the configurational contribution to the specific heat capacity. The methodology can, therefore, be applied to compounds with vacancies and variable site occupancies. Results are, moreover, presented for a number of systems of high practical relevance: Fe–K–Ti–O, K–Mn–O, and Ca–Mn–O. For the reference materials, the agreement with experimental measurements is exceptional in the case of ilmenite (FeTiO3) and good for CaMnO3. When the generated data is used in multi-phase thermodynamic calculations to represent materials for which experimental data is not available, the predicted phase-diagrams for the K–Mn–O and K–Ti–O systems change dramatically. The demonstrated methodology is highly useful for obtaining approximate values on key thermodynamic properties in cases where experimental data is hard to obtain, inaccurate or missing.
|
|
| 5. |
|
|
| 6. |
- Purnomo, Victor, 1992, et al.
(författare)
-
Effect of the Conversion Degree on the Apparent Kinetics of Iron-Based Oxygen Carriers
- 2024
-
Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- The role of the oxygen carrier is important in energy conversion processes with fluidized beds, particularly chemical looping technology. It is necessary to establish the relevant kinetics of oxygen carriers that can be applicable for various chemical looping processes. In this study, we analyzed the apparent kinetics of three iron-based oxygen carriers, namely, ilmenite, iron sand, and LD slag, during the conversion of CO, H2, and CH4 in a fluidized bed batch reactor. The effect of both the oxidation degree, presented as the mass conversion degree, and temperature was considered. The results show that the changing grain size (CGS) model is generally applicable in predicting the apparent kinetics of reactions between the investigated iron oxygen carriers and gaseous fuels even at lower oxidation degrees (3-5 wt % reduction). The activation energies of the investigated materials in the conversions of CO, H2, and CH4 obtained from the fittings of the CGS model are about 51-92, 55-251, and 72-211 kJ/mol, respectively. Both the mass conversion degree and temperature influence the reactivity of oxygen carriers in a directly proportional way, especially at temperatures higher than 925 °C. The results of this study are useful for reaction engineering purposes, such as designing a reactor, in chemical looping units, or in any other processes that use oxygen carriers as a bed material.
|
|
| 7. |
- Purnomo, Victor, 1992, et al.
(författare)
-
Performance of iron sand as an oxygen carrier at high reduction degrees and its potential use for chemical looping gasification
- 2023
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 339
-
Tidskriftsartikel (refereegranskat)abstract
- Iron sand as an industrial by-product has a reasonable iron content (35 wt% Fe) and low economical cost. The reactivity of iron sand as an oxygen carrier was examined in a bubbling fluidized bed reactor using both gaseous and solid fuels at 850–975 °C. Pre-reductions of iron sand were performed prior to fuel conversion to adapt the less-oxygen-requiring environment in chemical looping gasification (CLG). Based on the investigations using CO and CH4, iron sand has an oxygen transfer capacity of around 1 wt%, which is lower than that of ilmenite. The conversion of pine forest residue char to CO and H2 was higher when using iron sand compared to ilmenite. Depending on the mass conversion degree of iron sand, the activation energy of pine forest residue char conversion using iron sand was between 187 and 234 kJ/mol, which is slightly lower than that of ilmenite. Neither agglomeration nor defluidization of an iron sand bed occurred even at high reduction degrees. These suggests that iron sand can be utilized as an oxygen carrier in CLG. Furthermore, this study presents novel findings in the crystalline phase transformation of iron sand at various degrees of oxidation, altogether with relevant thermodynamic stable phases.
|
|
| 8. |
- Stanicic, Ivana, 1994
(författare)
-
Chemical Transformation of Inorganic Species in Thermochemical Conversion of Waste-Derived Fuels - The Role of Oxygen Carriers
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Waste-derived fuels are used increasingly in heat and power production systems in Sweden. Thermal conversion of waste-derived and biomass fuels offers the possibility of achieving carbon dioxide-neutral or even negative emissions. To limit global warming, it is essential to integrate these systems with carbon capture and storage. However, using alternative fuels raises challenges due to their complex compositions and their contents of heavy metals and other inorganic species. Chemical looping technologies have great potential for lowering costs for CO2 capture and reducing emissions of pollutants, such as NOx. These processes utilize metal oxides, or oxygen carriers (OCs), to transfer oxygen from air to fuel. However, the fates of the inorganic ash species in the presence of OCs are not well understood. The aim of this thesis is to provide a better understanding of the chemical transformations that occur in chemical looping applications, focusing on the heavy metals Zn, Cu, and Pb. In this thesis, the reaction pathways of Zn, Cu and Pb are studied using combined theoretical and experimental approaches. Samples derived from combustion and gasification processes that utilize OCs are studied in detail by XRD, SEM-EDX and XPS. Zn and Cu are observed to interact with the OC and form ferrites under both combustion and gasification conditions. The formation of ferrites is shown to play an important role in the pathways for these elements. For the Fe-Ti-based OC ilmenite, Zn is incorporated into the ash layer while Cu is found to accumulate inside the ilmenite particles. The interaction between Zn and ilmenite is studied in greater detail in laboratory-scale experiments. It is observed that reaction with Zn is promoted after ilmenite has undergone consecutive reduction and oxidation cycles, owing to the formation of an Fe-rich layer on the external surface. Pb is concentrated in the fly ash regardless of the chemical looping technology and OC types investigated in this thesis. The chemical speciation of Zn, Cu, and Pb in chemical looping processes is further considered with respect to the oxygen carrier type, temperature, reduction potential, and other ash components. The correlation of theoretical and experimental observations enables the identification of systems that were not well-described by thermodynamic equilibrium calculations (TECs). To improve the predictive potentials of TECs, thermodynamic databases are expanded by incorporating data i) available in the literature, and ii) from first principle calculations. For the latter, thermodynamic data is obtained for experimentally identified crystalline phases that are not available in the literature. This expansion has contributed to the updated and most comprehensive thermodynamic database for combined OC and ash systems. The database was implemented to study the phase stability during chemical looping combustion (CLC) of waste-derived fuels, providing the first insights into the chemical speciation of inorganic ash species. The results indicate that a major fraction of the problematic compounds exits the fuel reactor with the gas, preventing corrosion of the heat transfer surfaces in the air reactor.
|
|
| 9. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Fate of lead, copper, zinc and antimony during chemical looping gasification of automotive shredder residue
- 2021
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 302
-
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.
|
|
| 10. |
|
|
| 11. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Fate of trace elements in Oxygen Carrier Aided Combustion (OCAC) of municipal solid waste
- 2022
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 311
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 12. |
- Stanicic, Ivana, 1994
(författare)
-
Fate of Trace Elements in Thermochemical Conversion of Waste Fuels Using Oxygen Carriers
- 2021
-
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.
|
|
| 13. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Interaction of oxygen carriers with common biomass ash components
- 2020
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 200
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon capture and storage (CCS) has been proposed as a bridging technology between the current energy production and a future renewable energy system. One promising carbon capture technology is chemical-looping combustion (CLC). In CLC the reactors are filled with metal oxide bed material called oxygen carriers. The interaction between oxygen carriers and biomass ashes is a poorly explored field. To make CLC a viable process, and thereby creating carbon emission reductions, more knowledge about the interactions between biomass ashes and oxygen carriers is needed. This study investigated solid-state reactions of three promising oxygen carriers, hematite, hausmannite and synthesised ilmenite with different biomass ash components. Oxygen carriers were exposed with the ash components: calcium carbonate, silica and potassium carbonate at 900 °C and at different reducing potentials. Crystalline phases of the exposed samples were determined using powder x-ray diffraction (XRD). Results showed that the oxygen carriers hausmannite and hematite interact to a higher extent compared to synthesised ilmenite regarding both physical characteristics and detectable phases. Synthesised ilmenite formed new phases only in systems including potassium. Thermodynamic calculations were performed on the multicomponent system and compared with experimental results. The results suggest that optimisation of systems involving manganese and potassium should be performed.
|
|
| 14. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Investigating the Interaction between Ilmenite and Zinc for Chemical Looping
- 2023
-
Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 37:11, s. 7856-7870
-
Tidskriftsartikel (refereegranskat)abstract
- The iron and titanium oxide ilmenite is a benchmark oxygen carrier for chemical looping combustion (CLC) and oxygen carrier-aided combustion (OCAC). Both of them are combustion technologies for biomass and waste fuels with lower emissions and low costs for carbon capture. Here, the interaction between the ash component zinc and oxygen carrier ilmenite is studied in a two-staged vertical tube reactor. Three types of ilmenites─Norwegian rock ilmenite, synthesized ilmenite, and ilmenite extracted after 200 h of OCAC in a full-scale fluidized bed unit─were exposed to gas-phase Zn and ZnCl2. Following the exposure, samples were analyzed concerning morphology, chemical distribution, composition, and crystalline phases. The observations were complemented with thermodynamic equilibrium calculations. It is observed that the iron-rich layer formed on the external surface of rock ilmenite after activation promotes the reaction with both gaseous zinc compounds, with zinc ferrite formed in the external Fe-rich layer. In contrast, ilmenite with no segregation of Fe and Ti showed to interact less with zinc species. Metallic Zn penetrated the particles, while the interaction depth was shallow with ZnCl2 for all investigated ilmenite oxygen carriers. The gaseous conditions, particle ash layer composition, and iron availability are shown to play an important role in the interaction between zinc compounds and ilmenite particles. Based on these results, interaction mechanisms for Zn and ZnCl2 are proposed. This interaction could have environmental implications for the toxicity of ash streams from waste combustion in addition to possibilities for Zn recycling.
|
|
| 15. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Oxygen carrier aided combustion (OCAC) of two waste fuels - Experimental and theoretical study of the interaction between ilmenite and zinc, copper and lead
- 2021
-
Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 148
-
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.
|
|
| 16. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Thermodynamic Analysis on the Fate of Ash Elements in Chemical Looping Combustion of Solid Fuels Iron-Based Oxygen Carriers
- 2022
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 36:17, s. 9648-9659
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion (CLC) enables efficient combustion of hydrocarbon fuels while also producing a gas stream with high CO2 concentrations, suitable for carbon capture and storage (CCS). CLC of biomass in combination with CCS results in efficient removal of carbon dioxide from the atmosphere, i.e., negative emissions. However, biomass and waste-derived fuels can contain significant fractions of aggressive ash precursors, which can affect the operability and functionality of oxygen carriers. In this paper, the fate of common ash elements will be investigated thermodynamically in a system utilizing iron-based oxygen carriers: ilmenite and iron oxide. Multiphase, multicomponent equilibrium calculations were performed using databases from FACT and a user-defined database, with a specific focus on alkali (K and Na) and heavy metals (Cu, Zn, and Pb). A detailed and comprehensive comparison with available literature data from experimental investigations was performed, and compounds not available in the databases were identified. Due to a lack of thermodynamic data in the literature, thermodynamic properties for four compounds, K0.85Fe0.85Ti0.15O2, K0.4Fe0.4Ti0.6O2, KTi8O16, and KTi8O16.5, were obtained from first-principles calculations. The fate of ash elements is studied for CLC of three biomass and waste-derived solid fuels under relevant CLC conditions: 950 °C in the fuel reactor and 1050 °C in the air reactor. Results show that the choice of the oxygen carriers largely influences the behavior of the ash elements. Compared to CLC with iron oxide, ilmenite is more beneficial with respect to high-temperature corrosion since less potassium is released into the gas phase since the titanium content in ilmenite immobilizes both potassium and calcium. For both oxygen carriers, the most corrosive compounds are expected to leave with the gas in the fuel reactor, keeping the air reactor free from chlorides. It was found that the compound KTi8O16 is stable in reducing conditions and low potassium concentrations. This is in conformity with previous experimental data, where this phase has been identified in the interior of ilmenite particles used in oxygen carrier aided combustion of wood chips.
|
|
| 17. |
- Stanicic, Ivana, 1994, et al.
(författare)
-
Thermodynamic analysis on the fate of ash elements in chemical looping combustion of solid fuels – Manganese-Based oxygen carriers
- 2024
-
Ingår i: Fuel. - 0016-2361. ; 369
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion (CLC) is an innovative technology suitable for converting waste-derived fuels into heat and power. The process inherently produces pure CO2, which is highly favorable for carbon capture and storage and could be instrumental for achieving negative emissions. CLC operates by utilizing solid oxygen carriers (OCs) to transfer heat and oxygen between two reactors. The OC play a crucial role in achieving an efficient combustion. Manganese-based OCs are particularly interesting, due to their ability to release gaseous oxygen. However, ash components from solid fuels could alter their oxygen transfer capacity, and cause problems related to corrosion and agglomeration. The objective of this work is to obtain in-depth insights about Mn-based OCs for CLC of waste-derived fuels. This is achieved by investigating phase transitions during CLC of solid fuels when utilizing two manganese-based OCs: manganese oxide and a representative manganese ore. For this purpose, thermodynamic modeling is employed, and a specific focus is given to K, Na, Cu, Zn, and Pb, due to their important role in corrosion and/or agglomeration. Thermodynamic databases are expanded by calculating properties from first-principles. It is shown that Mn-based OCs are suitable for effectively converting waste-derived fuels while limiting corrosion. Furthermore, the iron in manganese ores is found to have positive implications for oxygen-transfer reactions. In terms of alkali release to the gas phase, manganese ore seems to be a more promising material compared to manganese oxide. The pathways for the heavy metals Zn, Cu, and Pb were, meanwhile, independent of the OC type.
|
|
| 18. |
|
|
| 19. |
|
|
