| 1. |
- Burström, Per, et al.
(författare)
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A CFD-based evaluation of Selective Non-Catalytic Reduction of Nitric Oxide in iron ore grate-kiln plants
- 2015
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Ingår i: Progress in Computational Fluid Dynamics, An International Journal. - 1468-4349 .- 1741-5233. ; 15:1, s. 32-46
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Tidskriftsartikel (refereegranskat)abstract
- The overall goal of this study is to explore the function of selective non-catalytic reduction of nitric oxide (NO) in iron ore grate-kiln plants. Computational fluid dynamics is used to model the flow and the injection of urea and cyanuric acid reagents. Temperature, residence time and inlet NO content are varied, and the effects on the reduction of NO are studied. The simulations show that the use of urea results in a higher reduction of NO within the temperature window investigated as compared to cyanuric acid; however, urea cannot be used for NO reduction over the entire range of applicable temperatures. Cyanuric acid is usable within the entire temperature range for high NO content (i.e., 300 ppm) in the flue gas, but it is not effective for low NO concentration (i.e., 150 ppm). Moreover, the simulations indicate that temperature has a larger influence on the NO reduction than the residence time.
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| 2. |
- Burström, Per, et al.
(författare)
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A validated CFD model for prediction of selective non-catalytic reduction of nitric oxide by cyanuric acid
- 2016
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Ingår i: Progress in Computational Fluid Dynamics, An International Journal. - 1468-4349 .- 1741-5233. ; 16:2, s. 108-117
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Tidskriftsartikel (refereegranskat)abstract
- A CFD model for selective non-catalytic reduction of nitric oxide by cyanuric acid (RAPid REduction of Nitrogen Oxides, RAPRENOx process) is compared against reactor experiments. The numerical simulations were carried out solving the flow field. A model for the RAPRENOx chemistry was then included in the model enabling a study of the chemistry in the reactor. The simulations showed that the proposed chemistry model is valid under certain conditions. There is an especially good agreement for high O2 concentrations while the model failed in reproducing the experimental data for 0% H2O
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| 3. |
- Burström, Per, et al.
(författare)
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CFD-modelling of selective non-catalytic reduction of NOx in grate-kiln plants
- 2009
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Ingår i: Seventh International Conference on CFD in the Minerals and Process Industries. - : CSIRO Publishing. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- The overall goal of this project is to find out if selective non-catalytic reduction (SNCR) technologies can be used in grate-kiln plants for NOx reduction. The technique has, to the best knowledge of the authors, never been used in this context before despite that it is commonly used in cement and waste incineration plants. A Computational Fluid Dynamic model of parts of a real grate was created and numerical simulations with a commercial code was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The simulations show promising results for SNCR with urea but not with ammonia.
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| 4. |
- Burström, Per, et al.
(författare)
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CFD-modelling of selective non-catalytic reduction of NOx in grate-kiln plants
- 2010
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Ingår i: Progress in Computational Fluid Dynamics, An International Journal. - 1468-4349 .- 1741-5233. ; 10:5/6, s. 284-291
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Tidskriftsartikel (refereegranskat)abstract
- The overall goal of this project is to find out if Selective Non-Catalytic Reduction (SNCR) technologies can be used in grate-kiln plants for NOx reduction. The technique has, to the best knowledge of the authors, never been used in this context before, despite that it is commonly used in cement and waste incineration plants. A model for spray injection into the grate was included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The simulations indicate that the SNCR-technique works with urea, but not with ammonia.
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| 5. |
- Burström, Per, et al.
(författare)
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Discrete and continuous modelling of convective heat transport in a thin porous layer of mono sized spheres
- 2017
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Ingår i: Heat and Mass Transfer. - : Springer. - 0947-7411 .- 1432-1181. ; 53:1, s. 151-160
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Tidskriftsartikel (refereegranskat)abstract
- Convective heat transport in a relatively thin porous layer of monosized particles is here modeled. The size of the particles is only one order of magnitude smaller than the thickness of the layer. Both a discrete three-dimensional system of particles and a continuous one-dimensional model are considered. The methodology applied for the discrete system is Voronoi discretization with minimization of dissipation rate of energy. The discrete and continuous model compares well for low velocities for the studied uniform inlet boundary conditions. When increasing the speed or for a thin porous layer however, the continuous model diverge from the discrete approach if a constant dispersion is used in the continuous approach. The new result is thus that a special correlation must be used when using a continuous model for flow perpendicular to a thin porous media in order to predict the dispersion in proper manner, especially in combination with higher velocities.
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| 6. |
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| 7. |
- Burström, Per, et al.
(författare)
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Modelling heat transfer during flow through a random packed bed of spheres
- 2018
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Ingår i: Heat and Mass Transfer. - : Springer. - 0947-7411 .- 1432-1181. ; 54:4, s. 1225-1245
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Tidskriftsartikel (refereegranskat)abstract
- Heat transfer in a random packed bed of monosized iron ore pellets is modelled with both a discrete three-dimensional system of spheres and a continuous Computational Fluid Dynamics (CFD) model. Results show a good agreement between the two models for average values over a cross section of the bed for an even temperature profiles at the inlet. The advantage with the discrete model is that it captures local effects such as decreased heat transfer in sections with low speed. The disadvantage is that it is computationally heavy for larger systems of pellets. If averaged values are sufficient, the CFD model is an attractive alternative that is easy to couple to the physics up- and downstream the packed bed. The good agreement between the discrete and continuous model furthermore indicates that the discrete model may be used also on non-Stokian flow in the transitional region between laminar and turbulent flow, as turbulent effects show little influence of the overall heat transfer rates in the continuous model.
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| 8. |
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| 9. |
- Granström, Reine, et al.
(författare)
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CFD modelling of the flow through a grate-kiln
- 2009
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Ingår i: Proceedings from Seventh International Conference on Computational Fluid Dynamics in Minerals and Process Industries.
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Konferensbidrag (refereegranskat)abstract
- As part of an investigation regarding secondary reduction of NOx emissions in a grate-kiln iron ore pelletizing plant, the aim of this specific research is to develop a CFD model that enhances the understanding of the aerodynamics and mixing of species inside the rotary kiln. At first, a parametric study of the pure airflow through the kiln is carried out and for certain conditions, a transient behaviour similar to that of vortex shedding was observed, with a dependence on momentum flux ratio between the secondary air jets. Further, the development of a preliminary coal combustion model is set out, which is in need of continued work in order to produce reliable predictions of various parameters relevant to the reduction process. However, the effect of the combustion on the flow field is limited, indicating that the pure airflow model can be used to broadly investigate the influence of the secondary air flow.
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| 10. |
- Hellström, Gunnar, et al.
(författare)
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Parallel CFD simulations of an original and redesigned hydraulic turbine draft tube
- 2007
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Ingår i: Advances in Engineering Software. - : Elsevier BV. - 0965-9978 .- 1873-5339. ; 38:5, s. 338-344
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Tidskriftsartikel (refereegranskat)abstract
- The design of hydraulic turbine draft tubes has traditionally been based on simplified analytic methods, model and full-scale experiments. In the recent years the use of numerical methods such as computational fluid dynamics (CFD) has increased in the design process, due to the rapid escalation in computer performance. Today with parallel computer architectures, new aspects of flow can be considered. However, several problems have still to be solved before CFD can routinely be applied in product development. This paper aims to investigate the parallel performance of commercial CFD software on homogeneous computer networks, as common solutions encountered in the industry today. In addition, the efficiency improvements obtained in earlier experiments by modifying the shape of the draft tube will be considered, to deduce if the improvements can be captured with aid of CFD. Results from both the steady and the unsteady CFD simulations show that almost full scalability is obtained with the commercial CFD software CFX-5.7.1. Furthermore, no noticeable improvement in the pressure recovery factor or the flow field is noticed in the CFD simulations as compared to experiments. The discrepancy may be to the applied inlet boundary conditions and/or the turbulence model.
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