| 1. |
- Haugen, N. E. L., et al.
(författare)
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Bed Model for Grate-Fired Furnaces : Computational Fluid Dynamics Modeling and Comparison to Experiments
- 2022
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Ingår i: Energy & Fuels. - : American Chemical Society. - 0887-0624 .- 1520-5029. ; 36:11, s. 5852-5867
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Tidskriftsartikel (refereegranskat)abstract
- A detailed but still central processing unit (CPU)-efficient bed model for grate-fired combustion of biomass and waste is developed. Simulations of wood chip combustion are performed, and the results are compared to experiments. The so-called layer model is used to track the development of the thermally thick representative fuel particles in the bed. As an efficient way of handling a large number of physical fuel particles, each representative fuel particle represents a number of physical particles with the exact same properties. The motion of the fuel bed is handled in a way that requires negligible CPU power, while for wastes and other fuels with less defined shapes and structure, it still yields accuracy similar to the much more CPU-intensive collision-based models. In this work, the bed model is coupled with ANSYS Fluent and used to simulate one of the test campaigns performed at the grate-fired pilot unit at the University of Stuttgart. It is found that for the test campaign of interest, burning wood chips, the fuel bed is ignited from below, and it is explained how this is due to the thermal properties of the grate and how important the numerical handling of the grate is for an accurate prediction of the bed behavior.
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| 2. |
- Wang, L., et al.
(författare)
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Effect of fuel mixing on melting behavior of spruce wood ash
- 2019
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 1342-1347
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Konferensbidrag (refereegranskat)abstract
- The aim of this work was to investigate effects of fuel mixing on melting behavior of spruce wood ash. Spruce bark was studied as additive fuel regarding its ability to lower the melting and flowing temperature of spruce wood ash. Standard ash fusion characterization tests were carried out on ashes from mixtures of spruce wood and bark after heating at 550 °C. The ash residues after the ash fusion tests were analyzed by using scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX). High melting temperature and low sintering tendency of spruce wood ash was observed. It is mainly attributed to formation of calcium rich silicates with high melting temperatures. Upon mixing with 10 wt% bark, the melting temperature of the spruce wood ash considerably decreased, which flowed completely after the ash fusion test. Compared to spruce wood ash, SEM images showed that the ash from the mixture of spruce wood and bark passed a molten stage with formation of slag. SEM-EDX revealed that the concentration of silicon in the spruce wood ash increased as a result of mixing with spruce bark. It favors formation of low temperature melting potassium silicates.
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| 3. |
- Wang, L., et al.
(författare)
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Sintering of rye straw ash and effect of additives
- 2014
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; , s. 2008-2011
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Konferensbidrag (refereegranskat)abstract
- The effects of kaolin and calcite additives on the rye straw ash sintering behaviors were investigated. The rye straw ash has a high sintering tendency, with observation of severe fusion during combustion. The formation and melting of potassium silicates play key roles in sintering of the rye straw ash at elevated temperatures. Fusion characteristics temperatures of the rye straw ash were significantly increased upon kaolin and calcite addition. Kaolin addition led to formation of high temperature melting potassium aluminum silicates, which were revealed by XRD analyses. Due to formation of high temperature melting species due to kaolin addition, the severe sintering of the rye straw ash was significantly reduced. Addition of calcite provided CaO to react with silica in the rye straw ash, causing generation of high temperature melting calcium rich silicates. In addition, the dilution effect from calcite is a main reason for improved rye straw sintering behaviors.
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| 4. |
- Xie, Y., et al.
(författare)
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A critical review on production, modification and utilization of biochar
- 2022
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier B.V.. - 0165-2370 .- 1873-250X. ; 161
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Tidskriftsartikel (refereegranskat)abstract
- There has been an increased interest in the production of sustainable biochar in the past years, as biochar shows versatile physicochemical properties and, can have a wide applicability in diverse fields. Comprehensive studies have been made to characterize biochar produced from various biomass materials, using different production technologies and under different process conditions. However, research is still lacking in correlating biochar properties needed for certain applications with (i) feedstock, (ii) biochar production processes and conditions and (iii) biochar upgrading and modification strategies. To produce biochar with desired properties, there is a great need to establish and clarify such correlations, which can guide the selection of feedstock, tuning and optimization of the production process and more efficient utilization of biochar. On the other hand, further elucidation of these correlations is also important for biochar-stakeholder and end-users for predicting physiochemical properties of biochar from certain feedstock and production conditions, assessing potential effects of biochar utilization and clearly address needs towards biochar critical properties. This review summarizes a wide range of literature on the impact of feedstocks and production processes and reactions conditions on the biochar properties and the most important biochar properties required for the different potential applications. Based on collected data, recommendations are provided for mapping out biochar production for different biochar applications. Knowledge gaps and perspectives for future research have also been identified regarding the characterization and production of biochar.
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