| 1. |
- Andersson, Viktor, 1983, et al.
(författare)
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Alkali desorption from ilmenite oxygen carrier particles used in biomass combustion
- 2024
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Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 359
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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.
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| 2. |
- Andersson, Viktor, 1983, et al.
(författare)
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Gaseous alkali interactions with ilmenite, manganese oxide and calcium manganite under chemical looping combustion conditions
- 2024
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Ingår i: Fuel Processing Technology. - 0378-3820 .- 1873-7188. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- Alkali species present in biomass pose significant challenges in chemical looping combustion (CLC) processes and other thermal conversion applications. The interactions between different alkali species and three common oxygen carrier (OC) materials that are considered to be state of the art in CLC applications have been investigated. A dedicated fluidized bed laboratory reactor was used to study interactions of KCl, NaCl, KOH, NaOH, K2SO4 and Na2SO4 with manganese oxide, calcium manganite and ilmenite. Alkali vapor was generated by injecting alkali salts under reducing, oxidizing and inert conditions at 900 °C. Gaseous species were measured online downstream of the reactor, and the efficiency of alkali uptake was determined under different conditions. The result show significant alkali uptake by all OCs under the studied conditions. Ilmenite shows near complete alkali uptake in reducing conditions, while manganese oxide and calcium manganite exhibited less effective alkali uptake, but have advantages in terms of fuel conversion and oxidizing efficiency. Alkali chlorides, sulfates and hydroxides show distinctly different behavior, with alkali hydroxides being efficiently captured all three investigate OC materials. The findings contribute to a deeper understanding of alkali behavior and offer valuable guidance for the design and optimization of CLC with biomass.
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| 3. |
- Purnomo, Victor, 1992, et al.
(författare)
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Effect of oxidation degree of iron-based oxygen carriers on their mechanical strength
- 2024
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Ingår i: Powder Technology. - 1873-328X .- 0032-5910. ; 438
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Tidskriftsartikel (refereegranskat)abstract
- Iron-based oxygen carriers are currently one of the most popular choices for chemical looping processes. In order to minimize losses of oxygen carrier materials in the system, it is important to assess attrition characteristics. Furthermore, in chemical looping gasification where the oxygen transfer capacity needs to be limited, a higher reduction degree of oxygen carriers can be expected. As different oxidation degrees lead to different phase compositions, this study aimed to investigate the correlation between mechanical strength of iron-based oxygen carriers and the phase composition, which is the result of oxidation degree change. Our findings demonstrate that how the phase composition may affect the attrition rate of oxygen carriers depends largely on the type of the material itself. In this study, the presence of Fe-Ti and Fe-Si combinations contribute to a generally stable attrition rate, while Fe-Ca system exhibits a decreasing attrition rate. Furthermore, attrition rate shows a more conclusive trend compared to crushing strength. Among the investigated materials, both ilmenite ore and iron sand showed a robust, stable mechanical stability with an attrition rate of approximately 0.5–1 wt%/h, which is on par with that of sand (0.5 wt%/h). The attrition rates of LD slag and mill scale are lower, about 1–3 wt%/h.
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| 4. |
- Purnomo, Victor, 1992, et al.
(författare)
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New approach for particle size and shape analysis of iron-based oxygen carriers at different oxidation degrees
- 2024
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Ingår i: Particuology. - : Elsevier. - 2210-4291 .- 1674-2001. ; 90, s. 493-503
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Tidskriftsartikel (refereegranskat)abstract
- One of the crucial issues in the chemical looping technology lies in its bed material: the oxygen carrier. Particle size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size range. While the favorable size ranges for oxygen carrier materials have already been reported, none of the published studies has analyzed the particle size and shape of oxygen carriers in detail. Furthermore, the effect of oxygen carriers’ oxidation degree on such properties has not been considered either. This study aimed to report the particle size and shape analysis of five iron-based oxygen carriers, one natural ore, one synthetic material, and three residue products, at different oxidation degrees using dynamic image analysis (DIA). The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch reactor. The size distribution, sphericity, and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer instrument. Our results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for comparison. The oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor extent. However, exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.
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| 5. |
- Surywanshi, Gajanan Dattarao, 1989, et al.
(författare)
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Energy, Exergy, Economic and Exergoeconomic Analyses of Chemical Looping Combustion Plant Using Waste Bark for District Heat and Power Generation with Negative Emissions
- 2024
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Ingår i: Energy Technology. - : John Wiley and Sons Inc. - 2194-4296 .- 2194-4288. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- The greenhouse gas emissions from the boiler of pulp and paper industries can be minimized by adapting chemical looping combustion (CLC) technology. This work aims to analyze the energy, exergy, economic, and exergoeconomic performance of an industrial scale CLC plant for district heat and electricity generation using waste bark from the paper and pulp industry. The CLC plant with one natural ore and one industrial waste oxygen carrier (OC) is modeled using Aspen Plus. The performance of the CLC plant has been compared to Örtofta combined heat and power plant without CO2 capture and with post-combustion CO2 capture as the reference cases. Results showed that the CLC-based power plant is energetically, exegetically, and economically efficient compared to the reference cases. The circulating fluidized bed boiler unit contributes the highest exergy destruction (about 50–80%). Among the CO2 capture plants, the CLC plant with ilmenite has the lowest levelized cost of district heat (4.58 € GJ−1), and a payback period (9.69 years) followed by the CLC plant with LD slag (5.91 € GJ−1 and 11.84 years), and the plant with PCC (6.94 € GJ−1 and 13.58 years). The exergoeconomic analysis reveals that the CLC reactors have the highest cost reduction potential, followed by the steam turbine.
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| 6. |
- Yaqub, Zainab Temitope, et al.
(författare)
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Process optimization of chemical looping combustion of solid waste/biomass using machine learning algorithm
- 2024
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Ingår i: Renewable Energy. - 0960-1481 .- 1879-0682. ; 225
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Tidskriftsartikel (refereegranskat)abstract
- Chemical Looping Combustion (CLC) is a carbon capture technology that uses an oxygen carrier to transfer the oxidizing agent to the fuel for combustion. This study used different machine learning algorithms, Artificial neural network and Response surface methodology to estimate the surface region process performance and optimize the process condition for the CLC of different solid fuels waste paper, plastic waste, and sugarcane bagasse blends. Based on the combustion efficiency, CO2 yield and CO2 capture efficiency responses, A high performance correlation (R2 > 0.8) was obtained for all the combustion parameters analyzed. The perturbation plot derived from the RSM analysis indicated that the most significant input parameters include the steam to fixed carbon, blend ratio and the fuel reaction temperature. The CLC process was optimized using RSM. For blends of SCB/WP, the best operating conditions were found to be 800 °C, a solid flow rate of 197.7 kg/h, an oxygen carrier to fuel ratio of 1.1, a steam to fixed carbon ratio of 2.16, and a blend ratio of 1. Similarly, for blends of SCB/PW, the optimal operating conditions were 800 °C, a solid flow rate of 199.4 kg/h, an oxygen carrier to fuel ratio of 1.3, steam to fixed carbon ratio of 2, and a blend ratio of 0.3. The optimum combustion performance was found to be 0.98, 0.78, and 0.96 for SCB/WP and 0.99, 0.62, and 0.96 for SCB/PW, respectively.
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