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- Eliasson Störner, Felicia, 1994, et al.
(författare)
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An improved method for feeding ash model compounds to a bubbling fluidized bed – CLC experiments with ilmenite, methane, and K 2 CO 3
- 2023
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Ingår i: Greenhouse Gases: Science and Technology. - 2152-3878. ; 13:4, s. 546-564
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Tidskriftsartikel (refereegranskat)abstract
- Biomass conversion with carbon capture and storage (Bio-Energy CCS; BECCS) is one of the options considered for mitigating climate change. In this paper, the carbon capture technology chemical-looping combustion (CLC) is examined in which the CO2 is produced in a stream separate from the combustion air. A central research topic for CLC is oxygen carriers; solid metal oxides that provide oxygen for the conversion process. Biomass and waste-derived fuels contain reactive ash compounds, such as potassium, and interactions between the oxygen carrier and the ash species are critical for the lifetime and performance of the oxygen carrier. This work develops and demonstrates an improved method for studying the interactions between ash species and oxygen carriers. The method uses a lab-scale reactor operating under fluidized conditions, simulating CLC batch-wise by switching between feed gas. The novelty of the setup is the integrated system for feeding solid particles of ash model compounds, enabling the simulation of ash species accumulating in the bed. Ilmenite is a benchmark oxygen carrier for solid fuel conversion and was used in this study to evaluate the method using K2CO3 as a model ash compound. Experiments were done at 850 and 950°C. Methane conversion in CLC cycles and fluidization was evaluated with gas analysis and pressure drop measurements. Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD) analysis of bed particles were done after the experiments to establish changes in the morphology and composition of the ilmenite. The method for feeding the ash model compound was concluded to be satisfactory. At 950°C, K accumulated in the particles forming K-titanates and agglomeration was enhanced with K2CO3 addition. The agglomeration mechanism was solid-state sintering between the Fe-oxides forming on the particle surfaces. The bed defluidized at 950°C, but no such effect was seen at 850°C. The method is suitable for studying the Fe-Ti-K system with ilmenite and potassium without the influence of other ash species. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.
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| 2. |
- Eliasson Störner, Felicia, 1994, et al.
(författare)
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Oxygen Carrier Aided Combustion in Fluidized Bed Boilers in Sweden - Review and Future Outlook with Respect to Affordable Bed Materials
- 2021
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 11:17
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Forskningsöversikt (refereegranskat)abstract
- Oxygen carriers are metal oxide particles that could potentially enhance both fuel conversion and heat distribution in fluidized bed combustion, resulting in e.g., lowered emissions of unconverted species and better possibilities to utilize low‐grade fuels. A related technology based on fluidized beds with oxygen carriers can separate CO2 without large energy penalties. These technologies are called oxygen carrier aided combustion (OCAC) and chemical‐looping combustion (CLC), respectively. In the past few years, a large number of oxygen carriers have been suggested and evaluated for these purposes, many of which require complex production processes making them costly. Affordable metal oxide particles are, however, produced in large quantities as products and byproducts in the metallurgical industries. Some of these materials have properties making them potentially suitable to use as oxygen carriers. Uniquely for Sweden, the use of oxygen carriers in combustion have been subject to commercialization. This paper reviews results from utilizing low‐cost materials emerging from metallurgical industries for conversion of biomass and waste in semi‐commercial and commercial fluidized bed boilers in Sweden. The paper further goes on to discuss practical aspect of utilizing oxygen carriers, such as production and transport within the unique conditions in Sweden, where biomass and waste combustion as well as metallurgical industries are of large scale. This study concludes that utilizing metal oxides in this way could be technically feasible and beneficial to both the boiler owners and the metallurgical industries.
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| 3. |
- Eliasson Störner, Felicia, 1994, et al.
(författare)
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Potassium Ash Interactions with Oxygen Carriers Steel Converter Slag and Iron Mill Scale in Chemical-Looping Combustion of Biomass - Experimental Evaluation Using Model Compounds
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:2, s. 2304-2314
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is a combustion technology in which a solid oxygen carrier is used to convert fuel. The oxygen carrier is oxidized in air and subsequently transferred to a separate reactor in which it reacts with the fuel. The produced CO2 is inherently separated from the air components, making CLC a promising technology for carbon capture and storage (CCS). CLC of biomass combined with CCS (bioenergy CCS; BECCS) is a way to generate negative CO2 emissions and thus interesting for climate change mitigation. Undesirable chemical reactions between ash and oxygen carriers are a challenge in BECCS because of the reactive nature of biomass ash. This article examines two low-cost steel industry byproducts that have shown desirable fuel conversion properties in CLC: iron mill scale (Glödskal B) and steel converter slag (LD-slag). Their interactions with potassium ash model compounds (KCl, K2CO3,K2SO4, and KH2PO4) in a reducing atmosphere have been investigated. Mixtures of oxygen carriers and potassium salt have been reduced for 6 h in CO and steam in a laboratory-scale fixed-bed reactor at 850 °C. The reduced samples have been analyzed with SEM/EDS and XRD. The reactivity of the mixtures during reduction and oxidation has also been examined by thermogravimetric analysis (TGA). K2CO3 increased the reaction rate for the reduction of Glödskal and inhibited the reactivity of LD-slag. KH2PO4 formed a K−P−Fe component with apparent low melting temperature with Glödskal, causing agglomeration, and decreased the reduction/oxidation rate in TGA. KH2PO4 formed a K−P−Ca component with apparent high melting temperature with LD-slag causing agglomeration but the reduction rate was not affected. The study suggests that the iron mill scale and LD-slag should not be rejected as oxygen carriers for CLC based on potassium ash interaction.
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| 4. |
- Eliasson Störner, Felicia, 1994
(författare)
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Using affordable materials from metallurgical industries in Oxygen Carrier Aided Combustion and Chemical-Looping Combustion
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxygen carriers are solid oxides of transition metals that can be used to convert fuel in the absence of gaseous oxygen in a process called Chemical-Looping Combustion (CLC). The use of oxygen carriers makes it possible to produce undiluted CO2 without expensive gas separation. High-concentration CO2 is a requirement in carbon capture and storage (CCS), which is considered a promising path for climate change mitigation. Oxygen carriers can also be used as bed material in fluidized bed conversion, and in that case provides enhanced oxygen distribution in the furnace. The concept is called Oxygen Carrier Aided Combustion (OCAC), and has been implemented in several existing biomass-, or municipal solid waste-fired boilers with ilmenite as oxygen carrier. This thesis examines utilizing oxygen carriers for the conversion of biomass and waste-derived fuels. Such fuels contain reactive ash species, which cause operational problems in the boiler such as corrosion, bed agglomeration, and slagging. Historically, much of the CLC-research has been on synthetic oxygen carriers with high reactivity. However, since the lifetime is expected to become quite low due to contamination of ash, they are likely not economically viable with these low-grade fuels. Here, the focus instead is on low-cost materials. The situation in Sweden is quite unique, since affordable metal oxide particles are produced in large quantities in our metallurgical industries. Several products and by-products from these industries are potential oxygen carriers. This thesis summarizes and discusses the large-scale utilization of oxygen carriers for OCAC in Sweden. Ilmenite is the most studied oxygen carrier for this purpose, but some other low-cost materials have also been tested in semi-industrial scale. The general findings are that implementing OCAC in already existing fluidized bed boilers is possible and enables a decrease in air-to-fuel ratio. Since biomass and waste fuels have complex and reactive ash compositions, they react with, and affect the lifetime of oxygen carriers. This thesis, therefore, also discusses ash interactions with some low-cost materials. Potassium is considered the most problematic ash element. Potassium is reactive with bed material and causes deposit formation and corrosion on the boiler, among other problems. Fixed bed interaction experiments have been conducted in this work with different potassium salts and oxygen carriers to study the changes in the materials with respect to composition and reactivity. Two by-products from steelmaking (LD-slag and iron mill scale) were studied in fixed bed interactions experiments. Also, as part of the work, a new lab-scale method which allows for improved experiments in a fluidized bed reactor has been developed. The method was used to study the effect of the accumulation of potassium on reactivity and fluidization of oxygen carriers. The study was conducted with ilmenite as oxygen carrier and K2CO3 as ash model compound. The addition of K2CO3 caused defluidization in ilmenite and diffusion of K into the particles.
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