| 1. |
- Rydén, Magnus, 1975, et al.
(författare)
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Novel oxygen-carrier materials for chemical-looping combustion and chemical-looping reforming; LaxSr1─xFeyCo1─yO3─δ perovskites and mixed-metal oxides of NiO, Fe2O3 and Mn3O4
- 2008
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 2:1, s. 21-36
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Tidskriftsartikel (refereegranskat)abstract
- Solid oxygen-carrier materials for chemical-looping applications have been examined by reduction with CH4 and oxidation with air in a fixed-bed quartz reactor at 900ºC. Four perovskite materials, three metal-oxide materials and four metal-oxide mixtures have been studied. It was found that LaxSr1─xFeO3─δ perovskites provided very high selectivity towards CO/H2 and should be well suited for chemical-looping reforming. Substituting La for Sr was found to increase the oxygen capacity of these materials, but reduced the selectivity towards CO/H2 and the reactivity with CH4. La0.5Sr0.5Fe0.5Co0.5O3─δ was found to be feasible for chemical-looping combustion applications. NiO/MgAl2O4 propagated formation of solid carbon, likely due to the catalytic properties of metallic Ni. Fe2O3/MgAl2O4 had properties that made it interesting both for chemical-looping combustion and chemical-looping reforming. Adding 1% NiO particles to a bed of Fe2O3-particles increased both reactivity with CH4 and selectivity towards CO/H2 for reforming applications. Mn3O4/MgZrO2 was found to be suitable for chemical-looping combustion applications, but it could not be verified that adding NiO produced any positive effects.
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| 2. |
- Abad, Alberto, 1972, et al.
(författare)
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Fuel reactor model validation: Assessment of the key parameters affecting the chemical-looping combustion of coal
- 2013
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 19, s. 541-551
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Tidskriftsartikel (refereegranskat)abstract
- The success of a Chemical Looping Combustion (CLC) system for coal combustion is greatly affected by the performance of the fuel reactor. When coal is gasified in situ in the fuel reactor, several parameters affect the coal conversion, and hence the capture and combustion efficiencies. In this paper, a mathematical model for the fuel reactor is validated against experimental results obtained in a 100 kW(th) CLC unit when reactor temperature, solids circulation flow rate or solids inventory are varied. This is the first time that a mathematical model for Chemical Looping Combustion of coal with in situ gasification (iG-CLC) has been validated against experimental results obtained in a continuously operated unit. The validated model can be used to evaluate the relevance of operating conditions on process efficiency. Model simulations showed that the reactor temperature, the solids circulation flow rate and the solids inventory were the most relevant operating conditions affecting the oxygen demand. However, high values of the solids circulation flow rate must be prevented because they cause a decrease in the CO2 capture. The high values of CO2 capture efficiency obtained were due to the highly efficient carbon stripper. The validated model is a helpful tool in designing the fuel reactor to optimize the CLC process. A CO2 capture efficiency of eta(CC) = 98.5% and a total oxygen demand of Omega(T) = 9.6% is predicted, operating at 1000 C and 1500 kg/MWth in the fuel reactor.
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| 3. |
- Abanades, J. C., et al.
(författare)
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Emerging CO2 capture systems
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 40, s. 126-166
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Tidskriftsartikel (refereegranskat)abstract
- In 2005, the IPCC SRCCS recognized the large potential for developing and scaling up a wide range of emerging CO2 capture technologies that promised to deliver lower energy penalties and cost. These included new energy conversion technologies such as chemical looping and novel capture systems based on the use of solid sorbents or membrane-based separation systems. In the last 10 years, a substantial body of scientific and technical literature on these topics has been produced from a large number of R&D projects worldwide, trying to demonstrate these concepts at increasing pilot scales, test and model the performance of key components at bench scale, investigate and develop improved functional materials, optimize the full process schemes with a view to a wide range of industrial applications, and to carry out more rigorous cost studies etc. This paper presents a general and critical review of the state of the art of these emerging CO2 capture technologies paying special attention to specific process routes that have undergone a substantial increase in technical readiness level toward the large scales required by any CO2 capture system.
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| 4. |
- Ahlström, Johan, et al.
(författare)
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Sustainable aviation fuels – Options for negative emissions and high carbon efficiency
- 2023
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier Ltd. - 1750-5836 .- 1878-0148. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- Mitigating the climate impact from aviation remains one of the tougher challenges in adapting society to fulfill stated climate targets. Long-range aviation cannot be electrified for the foreseeable future and the effects of combusting fuel at high altitude increase the climate impact compared to emissions of green-house gasses only, which further limits the range of sustainable fuel alternatives. We investigate seven different pathways for producing aviation biofuels coupled with either bio-energy carbon capture and storage (BECCS), or bio-energy carbon capture and utilization (BECCU). Both options allow for increased efficiency regarding utilization of feedstock carbon. Our analysis uses process-level carbon- and energy balances, with carbon efficiency, climate impact and levelized cost of production (LCOP) as primary performance indicators. The results show that CCS can achieve a negative carbon footprint for four out of the seven pathways, at a lower cost of GHG reduction than the base process option. Conversely, as a consequence of the electricity-intensive CO2 upgrading process, the CCU option shows less encouraging results with higher production costs, carbon footprints and costs of GHG reduction. Overall, pathways with large amounts of vented CO2, e.g., gasification of black liquor or bark, as well as fermentation of forest residues, reach a low GHG reduction cost for the CCS option. These are also pathways with a larger feedstock and corresponding production potential. Our results enable a differentiated comparison of the suitability of various alternatives for BECCS or BECCU in combination with aviation biofuel production. By quantifying the relative strengths and weaknesses of BECCS and BECCU and by highlighting cost, climate and carbon-efficient pathways, these results can be a source of support for both policymakers and the industry. © 2023 The Author(s)
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| 5. |
- Ahmad, Nawaz, et al.
(författare)
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Injection of CO2-saturated brine in geological reservoir : A way to enhanced storage safety
- 2016
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier. - 1750-5836 .- 1878-0148. ; 54, s. 129-144
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Tidskriftsartikel (refereegranskat)abstract
- Injection of free-phase supercritical CO2 into deep geological reservoirs is associated with risk of considerable return flows towards the land surface due to the buoyancy of CO2, which is lighter than the resident brine in the reservoir. Such upward movements can be avoided if CO2 is injected in the dissolved phase (CO2aq). In this work, injection of CO2-saturated brine in a subsurface carbonate reservoir was modelled. Physical and geochemical interactions of injected low-pH CO2-saturated brine with the carbonate minerals (calcite, dolomite and siderite) were investigated in the reactive transport modelling. CO2-saturated brine, being low in pH, showed high reactivity with the reservoir minerals, resulting in a significant mineral dissolution and CO2 conversion in reactions. Over the injection period of 10 yr, up to 16% of the injected CO2 was found consumed in geochemical reactions. Sorption included in the transport analysis resulted in additional quantities of CO2 mass stored. However, for the considered carbonate minerals, the consumption of injected CO2aq was found mainly in the form of ionic trapping.
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| 6. |
- Ahmad, Nawaz, et al.
(författare)
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Reactive transport modeling of leaking CO2-saturated brine along a fractured pathway
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier. - 1750-5836 .- 1878-0148. ; 42, s. 672-689
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Tidskriftsartikel (refereegranskat)abstract
- One concern regarding the underground storage of carbon dioxide (CO2) is its potential leakage from reservoirs. Over short period of time, the leakage risk is related mainly to CO2 as a separate supercritical fluid phase. However, over longer periods upon complete dissolution of injected CO2 in the fluid, the leakage risk is associated with dissolved phase CO2. Over the geological time scales, large-scale groundwater motion may cause displacement of brine containing dissolved CO2 along the conducting pathways. In this paper, we present a comprehensive modeling framework that describes the reactive transport of CO2-saturated brine along a fracture in the clay caprock based on the future, hypothetical leakage of the dissolved phase CO2. This study shows that the transport of leaked dissolved CO2 is significantly retarded by a combination of various physical and geochemical processes, such as mass exchange between conducting fracture and the neighboring rock matrix through molecular diffusion, sorption and calcite dissolution in the rock matrix. Mass stored in aqueous and adsorbed states in the rock matrix caused retention of dissolved CO2 along the leakage pathway. Calcite dissolution reaction in the rock matrix resulted in consumption of leaking dissolved CO2 and reduced its mass along the leakage pathway. Consumption and retention of dissolved CO2 along the leakage pathway have important implications for analyzing the potential reduction of CO2 fluxes from storage reservoirs over large periods and long travel pathways.
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| 7. |
- Alcalde, J., et al.
(författare)
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Active seismic characterization experiments of the Hontomin research facility for geological storage of CO2, Spain
- 2013
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 19:0, s. 785-795
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Tidskriftsartikel (refereegranskat)abstract
- An active source seismic experiment was carried out as part of the subsurface characterization study of the first Spanish Underground Research Facility for Geological Storage of CO2 in Hontomín (Burgos, Spain). The characterization experiment included a 36 km2 3D seismic reflection survey and two three-component seismic profiles. The target reservoir is a saline aquifer located at 1450 m depth within Lower Jurassic carbonates (Lias). The main seal is formed by interlayered marlstones and marly limestones of Early to Middle Jurassic age (Dogger and Lias). The seismic images obtained allow defining the 3D underground architecture of the reservoir site. The structure consists of an asymmetric dome crosscut by a relatively complex fault system. The detailed characterization of the fracture system is currently under study to unravel the geometric distribution of the faults and their extent within the different formations that form the structure. The constrained model has guided the design of the injection and monitoring boreholes and provided the data for the baseline study. The resultant high resolution seismic model will be used as a reference in future monitoring stages.
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| 8. |
- Ali, Hassan, et al.
(författare)
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Cost Estimation of CO2 Absorption Plants for CO2 Mitigation – Method and Assumptions
- 2019
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 88, s. 10-23
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Tidskriftsartikel (refereegranskat)abstract
- The estimates of post combustion CO2 capture costs reported in the literature range from 50 €/tCO2 to 128 €/tCO2, reflecting differences in the cost estimation methods used, scopes of the analyses, and assumptions made. This variation in calculated costs is important when evaluating the feasibility of a technology and highlights the importance of ensuring consistency and transparency in cost estimations. This study establishes a cost estimation tool that highlights the effects of different assumptions on the overall cost of a capture plant and identifies the crucial technical and economic factors. The input is a simplified process flow diagram and equipment list. Detailed installation factors and the equipment cost are the two main elements used to derive the capital expenditures (CAPEX), which represent a fundamental component of the cost estimation approach. A detailed installation factor sheet is used for the capital cost estimation. The method is applied to a Base case that involves the capture of CO2 from the flue gas of a process industry, giving a capture cost of 62.5 €/tCO2. The Base case results reveal that the steam cost, electricity cost, and capital cost are the main contributors. This method can provide an overview of the main cost drivers, and a sensitivity analysis of the variable input parameters can be performed simply and quickly. The results obtained using this method can be valuable in the early phase of the project and contribute to decision making.
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| 9. |
- Ali, Hassan, et al.
(författare)
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Cost estimation of heat recovery networks for utilization of industrial excess heat for carbon dioxide absorption
- 2018
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 74, s. 219-228
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Tidskriftsartikel (refereegranskat)abstract
- The absorption of CO 2 using solvents (e.g., amines) is considered a state-of-the-art, albeit energy-intensive process for CO 2 capture. While it is generally recognized that the utilization of waste heat has potential to reduce the energy-associated costs for CO 2 capture, the cost of waste heat recovery is seldom quantified. In this work, the cost of heat-collecting steam networks for waste heat recovery for solvent regeneration is estimated. Two types of networks are applied to waste heat recovery from the flue gases of four process industries (cement, silicon, iron & steel, and pulp & paper) via a heat recovery steam generator (HRSG). A novel approach is presented that estimates the capital and operational expenditures for waste heat recovery from process industries. The results show that the overall cost (CAPEX + OPEX) of steam generated from one hot flue gas source is in the range of 1.1–4.1 €/t steam. The cost is sensitive to economic parameters, installation factors, the overall heat transfer coefficient, steam pressure, and to the complexity of the steam network. The cost of steam from an existing natural gas boiler is roughly 5–20-times higher than that of steam generated from recovered waste heat. The CAPEX required to collect the heat is the predominant factor in the cost of steam generation from waste heat. The major contributor to the CAPEX is the heat recovery steam generator, although the length of the steam pipeline (when heat is collected from two sources or over long distances) is also important for the CAPEX.
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| 10. |
- Andersson, Klas, 1977, et al.
(författare)
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Thermal radiation in oxy-fuel flames
- 2011
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 5:suppl. 1, s. S58-S65
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates thermal radiation in oxy-fuel flames, based on experiments and modelling. Experiments were conducted in a 100 kW test facility in air and oxy-fuel combustion atmospheres, using two different types of fuels, lignite and propane. In-flame measurements of gas composition, temperature and total radiation intensity, were performed and used as input to radiation modelling to examine the influence of oxy-fuel conditions on gas and particle radiation characteristics. In the modelling, the spectral properties of CO(2) and H(2)O are treated by means of a statistical narrow band model and particle radiation is modelled for both scattering and non-scattering particles. Experiments on the propane flame show that the flame radiation conditions are drastically influenced by the recycling conditions. With OF 27 conditions (27% oxygen in the feed gas) and dry recycling, the temperature is slightly lower compared to air-fired conditions, but the emitted intensity is significantly increased. Modelling shows that this is mainly caused by a significantly increased soot radiation. Propane flame images show that the presence of soot in oxy-fuel conditions varies strongly with recycling conditions. The contribution due to an increased emission by CO(2) is of minor importance. In the lignite experiments similar flame temperatures were kept during air and oxy-fuel combustion (OF 25 conditions with dry recycling). The measurements show that the intensity levels in both flames are similar which is due to a strong particle radiation in both environments. The modelling reveals that the dominance by particle radiation contra gas radiation is closely related to whether the particles are scattering or non-scattering.
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