Academic literature on the topic 'Fluidized-bed combustion Mathematical models'
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Journal articles on the topic "Fluidized-bed combustion Mathematical models"
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Saxena, S. "Mathematical models for fluidized-bed coal combustion and sulfur retention." Energy 13, no. 7 (July 1988): 557–607. http://dx.doi.org/10.1016/0360-5442(88)90011-4.
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Wang, Zhong Jie, Ning Han, and Jia Wang. "The Study on the Fuzzy Control Algorithm for Main Steam Pressure Control of Circulated Fluidized Bed Boiler." Advanced Materials Research 383-390 (November 2011): 2092–96. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.2092.
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The main steam Pressure is one of the most important guidelines on Circulating Fluidized Bed Boiler (CFBB) operation quality and an important part in control system of CFBB. However, It is very difficult to establish the exact mathematical models of controlled objects because the combustion system of circulating fluidized bed boiler is an object that has many features: distributed parameters, nonlinear, time-varying and long time-delaying. it is unfavorable to control it with traditional controller. Therefore , In this paper fuzzy controller is used in controlling main vapor pressure systems of CFBB, and the fuzzy cascade control system is designed. In computer simulation, the fuzzy cascade control system exert stably, and has perfect control effect to main vapor pressure systems of CFBB.
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Ma, Yunpeng, Chenheng Xu, Hua Wang, Ran Wang, Shilin Liu, and Xiaoying Gu. "Model NOx, SO2 Emissions Concentration and Thermal Efficiency of CFBB Based on a Hyper-Parameter Self-Optimized Broad Learning System." Energies 15, no. 20 (October 18, 2022): 7700. http://dx.doi.org/10.3390/en15207700.
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At present, establishing a multidimensional characteristic model of a boiler combustion system plays an important role in realizing its dynamic optimization and real-time control, so as to achieve the purpose of reducing environmental pollution and saving coal resources. However, the complexity of the boiler combustion process makes it difficult to model it using traditional mathematical methods. In this paper, a kind of hyper-parameter self-optimized broad learning system by a sparrow search algorithm is proposed to model the NOx, SO2 emissions concentration and thermal efficiency of a circulation fluidized bed boiler (CFBB). A broad learning system (BLS) is a novel neural network algorithm, which shows good performance in multidimensional feature learning. However, the BLS has several hyper-parameters to be set in a wide range, so that the optimal combination between hyper-parameters is difficult to determine. This paper uses a sparrow search algorithm (SSA) to select the optimal hyper-parameters combination of the broad learning system, namely as SSA-BLS. To verify the effectiveness of SSA-BLS, ten benchmark regression datasets are applied. Experimental results show that SSA-BLS obtains good regression accuracy and model stability. Additionally, the proposed SSA-BLS is applied to model the combustion process parameters of a 300MW circulating fluidized bed boiler. Experimental results reveal that SSA-BLS can establish the accurate prediction models for thermal efficiency, NOx emission concentration and SO2 emission concentration, separately. Altogether, SSA-BLS is an effective modelling method.
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Mladenovic, Milica, Stevan Nemoda, Mirko Komatina, and Dragoljub Dakic. "Numerical simulation of non-conventional liquid fuels feeding in a bubbling fluidized bed combustor." Thermal Science 17, no. 4 (2013): 1163–79. http://dx.doi.org/10.2298/tsci121116007m.
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The paper deals with the development of mathematical models for detailed simulation of lateral jet penetration into the fluidized bed (FB), primarily from the aspect of feeding of gaseous and liquid fuels into FB furnaces. For that purpose a series of comparisons has been performed between the results of in-house developed procedure- fluid-porous medium numerical simulation of gaseous jet penetration into the fluidized bed, Fluent?s two-fluid Euler-Euler FB simulation model, and experimental results (from the literature) of gaseous jet penetration into the 2D FB. The calculation results, using both models, and experimental data are in good agreement. The developed simulation procedures of jet penetration into the FB are applied to the analysis of the effects, which are registered during the experiments on a fluidized pilot furnace with feeding of liquid waste fuels into the bed, and brief description of the experiments is also presented in the paper. Registered effect suggests that the water in the fuel improved mixing of fuel and oxidizer in the FB furnace, by increasing jet penetration into the FB due to sudden evaporation of water at the entry into the furnace. In order to clarify this effect, numerical simulations of jet penetration into the FB with three-phase systems: gas (fuel, oxidizer, and water vapour), bed particles and water, have been carried out.
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Wang, Liu, Zhang, Zhang, and Jin. "Numerical Investigation of Solid-Fueled Chemical Looping Combustion Process Utilizing Char for Carbon Capture." Processes 7, no. 9 (September 6, 2019): 603. http://dx.doi.org/10.3390/pr7090603.
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The in-depth understanding of the gas–solid flow and reaction behaviors, and their coupling characteristics during the chemical looping combustion (CLC) process has the guiding significance for the operation and optimization of a chemical looping combustor. A three-dimensional numerical model is applied to investigate the char-fueled CLC characteristics in a fuel reactor for efficient CO2 separation and capture. Simulations are carried out in a bubbling fluidized bed fuel reactor with a height of 2.0 m and a diameter of 0.22 m. The initial bed height is 1.1 m, and hence the height–diameter ratio of the slumped bed is five. The oxygen carrier is prepared with 14 wt% of CuO on 86 wt% of inert Al2O3. In the process of mathematical modeling, a Eulerian-Eulerian two-fluid model is adopted for both of the gas and solid phases. Gas turbulence is modeled on the basis of a k–ε turbulent model. The reaction kinetics parameters are addressed based upon previous experimental investigations from literature. During the simulation, the gas–solid flow patterns, composition distributions, and reaction characteristics are obtained. Moreover, the effects of solids inventory and fluidizing number on the reaction performance are elucidated in-depth. The results have shown that the reaction rates have close relationship with the flow patterns and the distributions of gas concentrations. Compared to the steam-char gasification over sand, the application of char-fueled CLC can effectively promote the conversion of gasification products. In addition, higher CO2 concentration at the outlet can be achieved by increasing the initial solids inventory or decreasing the fluidizing number. Some calculated values are verified by the previous data, indicating that the current three-dimensional models are reasonable to study the process mechanism of char-fueled CLC.
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Mei, Joseph S., Esmail R. Monazam, and Lawrence J. Shadle. "Flow Regime Study of a Light Material in an Industrial Scale Cold Flow Circulating Fluidized Bed." Journal of Energy Resources Technology 128, no. 2 (March 22, 2006): 129–34. http://dx.doi.org/10.1115/1.2199566.
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A series of experiments was conducted in the 0.3meter diameter circulating fluidized bed test facility at the National Energy Technology Laboratory (NETL) of the U. S. Department of Energy. The particle used in this study was a coarse, light material, cork, which has a particle density of 189kg∕m3 and a mean diameter of 812μm. Fluidizing this material in ambient air approximates the same gas-solids density ratio as coal and coal char in a pressurized gasifier. The purpose of this study is twofold. First, this study is to provide a better understanding on the fundamentals of flow regimes and their transitions. The second purpose of this study is to generate reliable data to validate the mathematical models, which are currently under development at NETL. Utilization of such coarse, light material can greatly facilitate the computation of these mathematical models. Furthermore, the ratio of density of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. This paper presents and discusses the data, which covered operating flow regime from dilute phase, fast fluidization, and to dense phase transport by varying the solid flux, Gs at a constant gas velocity, Ug. Data are presented by mapping the flow regime for coarse cork particles in a ΔP∕ΔL‐Gs‐Ug plot. The coarse cork particles exhibited different behavior than the published literature measurements on heavier materials such as alumina, sand, FCC, silica gel, etc. A stable operation can be obtained at a fixed riser gas velocity higher than the transport velocity, e.g., at Ug=3.2m∕s, even though the riser is operated within the fast fluidization flow regime. Depending upon the solids influx, the riser can also be operated at dilute phase or dense phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries as well as solids fractions in the upper dilute and the lower dense regions for fast fluidization flow regime. Comparisons of measured data with these empirical correlations show rather poor agreements. These discrepancies, however, are not surprising since the correlations for these transitions were derived from experimental data of comparative heavier materials such as sands, FCC, iron ore, alumina, etc.
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Shimizu, Tadaaki, Mirko Peglow, Kazuaki Yamagiwa, and Masato Tanaka. "Comparison among attrition-reaction models of SO2 capture by uncalcined limestone under pressurized fluidized bed combustion conditions." Chemical Engineering Science 58, no. 13 (July 2003): 3053–57. http://dx.doi.org/10.1016/s0009-2509(03)00157-x.
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de Lasa, Hugo. "The CREC Fluidized Riser Simulator a Unique Tool for Catalytic Process Development." Catalysts 12, no. 8 (August 12, 2022): 888. http://dx.doi.org/10.3390/catal12080888.
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The CREC Riser Simulator is a mini-fluidized bench scale unit invented and implemented in 1992, at the CREC (Chemical Reactor Engineering Centre), University of Western Ontario The CREC Riser Simulator can be operated at short reaction times, in the 3 s to 20 s range. The present review describes and evaluates the original basic concept of the 1992-CREC Riser Simulator Unit, and the improved design of the 2019-CREC Riser Simulator. Both the initial and the enhanced units are specially engineered to allow the rigorous assessment of both catalyst performance and catalytic reaction kinetics. Kinetic parameters of relatively simple and accurate mathematical models can be calculated using experimental data from the CREC Riser Simulator. Since its inception in 1992, the CREC Riser Simulator has been licensed to and manufactured for a significant number of universities and companies around the world. Several examples of scenarios where the CREC Riser Simulator can be employed to develop fluidized bed catalytic and heterogeneous reactor simulations are reported in this review. Among others, they include (a) hydrocarbon catalytic cracking, (b) the catalytic conversion of tar derived biomass chemical species, (c) steam and dry catalytic methane reforming, (d) the catalytic oxydehydrogenation of light paraffins, (e) the catalytic desulfurization of gasoline, and (f) biomass derived syngas combustion via chemical looping. In this review, special emphasis is given to the application of the CREC Riser Simulator to TIPB (tri-iso-propyl-benzene) catalytic cracking and the light paraffins catalytic oxydehydrogenation (PODH).
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Hajra, Sugato, and Abhishek Aditya Patra. "STUDY OF CIRCULATING COAL FLUIDIZED BOILERS." International Journal of Students' Research in Technology & Management 3, no. 6 (September 30, 2015): 396. http://dx.doi.org/10.18510/ijsrtm.2015.363.
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In the days of modernization, industrialization, technological world we find out a new method of steam production with help of coal. This state of act systems are manufactured over a range of 500 TPH.This boilers are highly efficient, multi coal firing capacity, less emission of so2 and nox gases, utilize high ignite cokes, petcoats,washery rejects. This survey paper is intended to comprehensively give an account of domain knowledge related to CFBC boiler. The authors touch upon the design changes which are introduced in the component levels in order to ease the operation, enhance the performance and to meet the regulatory compliance. In addition, salient correlations related to hydrodynamics, heat transfer and combustion are narrated to facilitate the control and system engineers to develop mathematical models using conservation of mass, energy and momentum equations.
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Khasanov, I. R., A. V. Karpov, S. F. Lobova, and N. V. Petrova. "Field modeling of the fire dynamics as an answer to the question about the fire alarm performance." Pozharovzryvobezopasnost/Fire and Explosion Safety 29, no. 5 (December 2, 2020): 40–50. http://dx.doi.org/10.22227/pvb.2020.29.05.40-50.
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Introduction. The performance of a fire alarm needs to be analyzed to answer the question about its compliance with fire safety requirements. This type of research is frequently performed in the course of a forensic fire investigation. Therefore, it is necessary to identify conditions of fire escalation and safe evacuation of people to assess the fire alarm performance.Purposes and objectives. The purpose of this work is the numerical study of the impact, produced by mathematical models of combustion, characteristics of fire loads and locations of fire beds, on fire alarm performance. Methods. Fire dynamics was field modeled to achieve the goal of this research. The analysis of flame propagation was performed with regard for various fire bed locations to simulate the fire alarm operation.Results and discussion. The fulfillment of safe evacuation conditions for cases of irregular arrangement of smoke detectors was analyzed to develop and test the algorithm for the calculation of the evacuation start time. It is shown that the estimated time of fire detection depends on combustion models employed (their average or complex level), the size of the computational grid, fire load specifications and the location of the fire bed.Conclusions. It is shown that the results of the field modeling of fire propagation and detection time are influenced by combustion models used, fire load specifications and the location of the fire bed in relation to smoke detectors. If the fire alarm fails to perform its functions and, consequently, safe evacuation conditions are not fulfilled, it is necessary either to improve the combustion model or to compare the modeling results obtained for actual and standard smoke detector location patterns.
Dissertations / Theses on the topic "Fluidized-bed combustion Mathematical models"
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Wildegger-Gaissmaier, Anna Elisabeth. "Fluidized bed utilization of South Australian coals." Title page, contents and abstract only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phw672.pdf.
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Alagoz, Duriye Ece. "Mathematical Modeling Of Fluidized Bed Combustors With Radiation Model." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607489/index.pdf.
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Simultaneous solution of the conservation equations for energy and chemical species in conjunction with radiative transfer equation was carried out by coupling a previously developed and tested system model of fluidized bed combustion (FBC) to an existing radiation model.
The predictive accuracy of the coupled code was assessed by applying it to 0.3 MWt METU Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) Test Rig burning lignite in its own ash and comparing its predictions with the measured temperatures and concentrations of gaseous species along the combustor and radiative heat fluxes incident on the refractory-lined freeboard walls on two combustion tests, with and without recycle. The predictions of the coupled code were found to be in good agreement with the measurements.
For the investigation of the significance of coupling of the radiation model to the system model, temperature predictions of the coupled code were compared with those obtained by the original system model. It was found that the effect of incorporating a radiation model into the system model on the predictions was not significant because the high temperatures of refractory-lined freeboard walls and high surface to volume ratio of the test rig under consideration cause the incident radiative heat fluxes to be dominated by walls rather than the particle laden gas emissions. However, in industrial boilers, freeboard is surrounded by water-cooled membrane walls and boilers have much lower surface to volume ratio. In order to examine the effects of both on radiation in industrial boilers, an investigation was carried out on 16 MWt Stationary Fluidized Bed Boiler (SFBB) by applying radiation model, in isolation from the system model, to the freeboard of the boiler. It was found that in the boiler, incident radiative heat fluxes were dominated by particle laden gas emissions.
In brief, the coupled code proposed in this study proves to be a useful tool in qualitatively and quantitatively simulating the processes taking place in an atmospheric fluidized bed boilers.
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Bell, Robyn Anne, and Robyn Bell@csiro au. "Numerical modelling of multi-particle flows in bubbling gas-solid fluidised beds." Swinburne University of Technology, 2000. http://adt.lib.swin.edu.au./public/adt-VSWT20050902.132803.
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In Victoria, Australia, brown coal is utilised as a major source of energy for the power generation industry. Victorian and South Australian brown coals have a very high moisture content and therefore, the efficiencies of power generation in traditional pulverised fuel fired furnaces are low. Fluidised beds offer a number of advantages over conventional furnaces, leading to improvements in efficiency and environmental impact. A disadvantage with implementing fluidised bed technology is the issue of scale-up. Fluidised bed behaviour can alter significantly with changes in scale, because of their strong dependence on the bed hydrodynamics. Hence, there is a need to accurately model bed behaviour to ensure that the effect of changes in scale are well understood and will not become costly and time consuming.
Computational Fluid Dynamics (CFD) techniques can be applied to fluidised bed systems to gain a better understanding of the hydrodynamic behaviour involved. In the past, numerical models have considered only single particle sizes due to the added complexity of interaction between particles of differing sizes and densities. Industrial fluidised beds typically contain more than one particle size and density, therefore there is a need to develop a numerical model which takes this into account. The aim of this thesis is to develop and validate CFD techniques for modelling the behavior of a gas-solid fluidised bed containing more than one particle size and density.
To provide validation data for the numerical model, physical experiments are undertaken on a small two-dimensional bubbling gas-solid fluidised bed. Mixing and segregation behaviour of different materials are investigated. The experiments demonstrate that whilst only a small proportion of the bed consists of different size/density particles, significant changes in bed behaviour are apparent. Changes in bubble rise velocity, bubble size and bubble shape are observed.
A number of constitutive equations must be included in the numerical model, including relationships for the momentum transfer between various phases and solids pressure. Different combinations of these constitutive equations are investigated. A new equation for particle-particle interactions is derived and included in a CFD model. The CFD model is validated against both data in the literature and physical experiments. From the validation studies, an optimum equation set is identified. This optimum equation set produces numerical results that closely resemble experimental bed behaviour, thus bringing the goal of solving scale-up problems one step closer. The use of this type of CFD model will ultimately result in timely and cost effective solutions for both the power generation and chemical processing industries.
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Gogolek, Peter Edmund Gordon. "Mathematical modelling of fluctuations in fluidized bed combustion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0006/NQ31928.pdf.
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Altindag, Hakan. "Mathematical Modeling Of Sulfur Retention In Fluidized Bed Combustors." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1085661/index.pdf.
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A considerable number of modeling studies for the investigation of sulfur
retention in atmospheric bubbling fluidized bed combustors have been carried out
and well documented in the literature. Despite 30 years of intensive study of
sulfation process in fluidized bed combustors and numerous laboratory studies,
there are still many uncertainties and disagreements on the subject. In addition,
modeling sulfur retention performance of Turkish lignites with high sulfur, volatile
matter and ash contents has not drawn much attention to date. Recent trend in
utilization of indigenous lignites in fluidized bed boilers necessitated investigation of pollutant emissions and adaptation of fluidized bed combustion technology to
these lignites. In an attempt to achieve this objective, a system model, previously
developed and tested for the prediction of the combustion behavior of fluidized bed
combustors was extended to incorporate sulfur retention.
The predictive accuracy of the model was assessed by applying it to the
prediction of the behavior of METU 0.3 MWt ABFBC test rig burning indigenous
lignites in their own ashes, and comparing its predictions with measurements taken
on the same rig. Sulfur dioxide concentration predictions throughout the combustor
were found to be in good agreement with the experimental data except for the small
discrepancy between predictions and measurements in the bed section.
Measurements and model predictions revealed that recyling enhances calcium
utilization significantly by increasing the sorbent residence time leading to higher
sulfur retention efficiencies. The system model proposed in this study proves to be a
useful tool in qualitatively and quantitatively simulating the processes taking place
in an atmospheric fluidized bed combustor.
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Afacan, Onur M. "Mathematical Modeling Of Nox Emissions In Bubbling Fluidized Bed Combustors." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606463/index.pdf.
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A comprehensive model, previously developed and tested for prediction of behavior of continuous fluidized bed combustors is extended to incorporate NOx formation and reduction reactions and applied to the simulation of METU 0.3 MWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) burning lignites with high volatile matter in their own ashes.
The predictive accuracy of the model was assessed by comparing its predictions with measurements taken previously on the same rig. Favorable comparisons are obtained between the predicted and measured temperatures and concentrations of gaseous species along the combustor. Results show that determination of partitioning of coal nitrogen into char nitrogen and volatile nitrogen, and release of volatile nitrogen along the combustor are found to be the most important parameters that affect NOx formation and reduction in bubbling fluidized bed combustors. The system model proposed in this study proves to be a useful tool in qualitatively and quantitatively simulating the processes taking place in an atmospheric fluidized bed combustor.
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Chevrier, Solène. "Development of subgrid models for a periodic circulating fluidized bed of binary mixture of particles." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19905/1/CHEVRIER_Solene.pdf.
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Detailed sensitivity numerical studies have shown that the mesh cell-size may have a drastic effect on the modelling of circulating fluidized bed with small particles. Typically, the cell-size must be of the order of few particle diameters to predict accurately the dynamical behaviour of a fluidized bed. Hence, the Euler-Euler numerical simulations of industrial processes are generally performed with grids too coarse to allow the prediction of the local segregation effects. Appropriate modelling, which takes into account the influence of unresolved structures, have been already proposed for monodisperse simulations. In this work, the influence of unresolved structures on a binary mixture of particles is investigated and models are proposed to account for those effect on bidisperse simulations of bidisperse gas-solid fluidized bed. To achieve this goal, Euler-Euler reference simulations are performed with grid refinement up to reach a mesh independent solution. Such kind of numerical simulation is very expensive and is restricted to very simple configurations. In this work, the configuration consists of a 3D periodical circulating fluidized bed, that could represent the established zone of an industrial circulating fluidized bed. In parallel, a filtered approach is developed where the unknown terms, called sub-grid contributions, appear. They correspond to the difference between filtered terms, which are calculated with the reference results then filtered, and resolved contributions, calculated with the filtered fields. Then spatial filters can be applied to reference simulation results to measure each sub-grid contribution appearing in the theoretical filtered approach. A budget analysis is carried out to understand and model the sub-grid term. The analysis of the filtered momentum equation shows that the resolved fluid-particle drag and inter-particle collision are overestimating the momentum transfer effects. The analysis of the budget of the filtered random kinetic energy shows that the resolved production by the mean shear and by the mean particle relative motion are underestimating the filtered ones. Functional models are proposed for the subgrid contributions of the drag and the inter-particle collision.
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Asthana, Abhishek. "Modélisation mathématique de la formation des NOx et de la volatilisation des métaux lourds lors de l'incinération sur grille d'ordures ménagères." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL018N/document.
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Dans une optique de maîtrise du procédé d’incinération des ordures ménagères et de ses possibles émissions polluantes, nous avons développé un modèle mathématique qui simule un lit d’ordures ménagères en combustion sur une grille mobile. Ce modèle décrit la plupart des phénomènes physicochimiques et thermiques intervenant lors de l’incinération : séchage et pyrolyse de la charge, combustion et gazéification du carbone résiduel, transferts thermiques, effondrement du lit, brassage… Il intègre également une description des mécanismes de volatilisation des métaux lourds et de formation des NOx. La cinétique de départ des métaux lourds est modélisée en tenant compte des différentes étapes de transport (transfert externe, diffusion intraparticulaire, volatilisation) au moyen de l’approche des temps caractéristiques additifs. Dans le cas simulé du cadmium, la prédiction d’une volatilisation quasi-complète est conforme aux résultats de la littérature. Le sous-modèle NOx prend en compte les mécanismes de formation thermique, prompt, combustible, par l’intermédiaire de N2O, ainsi que les mécanismes de réduction homogène par recombustion et hétérogène par le carbone résiduel. Les calculs révèlent que prédominent la formation par le mécanisme combustible et la destruction par la réduction hétérogène. Enfin, le modèle de lit a été utilisé pour étudier l’influence des divers paramètres opératoires : température, débit et distribution d’air primaire, taille des particules de déchets, brassage et schéma de brassage. Les résultats sont présentés et discutés en détail. L’influence des conditions opératoires sur l’efficacité du procédé et sur les émissions de Cd et NOx est analyséeAs a tool for controlling the Municipal Solid Waste (MSW) incineration process and its possible pollutant emissions, a mathematical model of the MSW bed burning on travelling grate of an incinerator was developed. The model describes most of the physico-chemical and thermal phenomena taking place in incineration like the drying and pyrolysis of the feed, combustion and gasification of char, oxidation of pyrolysis gases, heat transfer, bed shrinking, feed stirring, etc. Also described in the model are the mechanisms of Heavy Metals (HM) volatilization and NOx formation. Kinetics of HM release was modelled using the approach of additive reaction times accounting for the various transport mechanisms involved: external transfer, intra-particle diffusion and actual volatilization. In the case simulated, i.e. of Cd, almost total volatilization is predicted, which is confirmed by literature findings. The NOx sub-model takes into account most of the common mechanisms of formation like thermal, prompt, fuel, N2O intermediate and also NOx reduction by homogeneous reburning and heterogeneous reduction by char. Calculations show that NOx formation is predominated by the fuel mechanism and destruction by the heterogeneous reduction. Finally, the bed model was applied to study the influence of various operating parameters like flow rate, temperature and distribution of air under grates, waste particle size, feed stirring and the stirring scheme. The results are presented and discussed in detail and the influence of operating conditions on process efficiency and on emissions of Cd and NOx is analyzed
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Wildegger-Gaissmaier, Anna Elisabeth. "Fluidized bed utilization of South Australian coals / Anna Elisabeth Wildegger-Gaissmaier." Thesis, 1988. http://hdl.handle.net/2440/18806.
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Chin, Ming Chu, and 秦銘助. "The Mathematical Model of Coal Combustion in the Vortexing Fluidized Bed Combustor." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/32302461555629449088.
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碩士中原大學
化學工程研究所
82
A novel dimensionless relationship for predicting the proportions of volatile combustion within different regions of the fluidized bed combustor was presented. The temperatures of different regions can be predicted by material and energy balance including the proportion of volatile combustion. Experiments were carried out in a 0.45m pilot vortexing fluidized bed combustor (VFBC) to obtain temperature data of the two coal particle sizes, 2.52mm and 6.68mm, with different operating conditions. By using the multiple linear regression, the constants of the dimension- less equation were calculated. This model was used to predict the temperature distribution of the 0.7m*1.4m prototype VFBC and the difference between the experimental and theoretical study was compared. When the primary air increases, the temperature distribution curve stays the same and the total temperature decreases; the temperature of the freeboard decreases as the secondary air increases and the temperature has little increase both in the bed and above bed surface. The 6.68mm coal particle's temperature in the freeboard is lower than in the bed and compared with the 2.52mm coal particle, it shows a higher proportion of volatile combustion in the bed. The 2.52mm coal particle's temperature is higher at the feed position than in the bed because the time of volatile release is short due to the small particle size. Although the theoretical temperature is sometimes higher or sometimes lower than the experimental value, but the tendency of both are the same. The difference is smaller than 20℃ and the average deviation of including operating condition of the pilot and prototype VFBC doesn't exceed 7% within the three regions. The predictions from the model of different primary/ theoretical air ratio and different particle size also coincide well.
Books on the topic "Fluidized-bed combustion Mathematical models"
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Hyppänen, Timo. An experimental and theoretical study of multiphase flow in a circulating fluidized bed. Lappeenranta: Lappeenranta University of Technology, 1989.
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Ko, Daekwun. A numerical study of solid fuel combustion in a moving bed. 1993.
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Rhee, Brian Kanghee. Enhancement of mass transfer coefficient in three-phase magnetically stabilized fluidized bed. 1998.
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Jovanovic, Zoran R. Kinetic study on the production of silicon nitride by direct nitridation of silicon in a fluidized bed: Experiment and modeling. 1994.
Find full textBook chapters on the topic "Fluidized-bed combustion Mathematical models"
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Steward, F. R. "Mathematical Model of a Circulating Fluidized Bed with Chemical Reaction." In Combustion Technologies for a Clean Environment, 509–28. London: CRC Press, 2022. http://dx.doi.org/10.1201/9780367810597-40.
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de Vicente, S., G. Galiano, J. Velasco, and J. M. Aróstegui. "Mathematical Description of the Hydrodynamic Regimes of an Asymptotic Model for Two-Phase Flow Arising in PFBC Boilers." In Proceedings of the 20th International Conference on Fluidized Bed Combustion, 870–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-02682-9_135.
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Yang, Chunzhen, Yufeng Duan, and Haitao Hu. "DEM-Based Models for Solids Exchange in a Pant Leg Fluidized Bed." In Cleaner Combustion and Sustainable World, 641–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-30445-3_89.
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Butt, A. R., M. G. Jepson, and J. Moodie. "Communicating Chemical Processes — A Transputer Model of the British Coal Twin-Bed Pyrolyser/Combustor." In European Consortium for Mathematics in Industry, 95–98. Wiesbaden: Vieweg+Teubner Verlag, 1992. http://dx.doi.org/10.1007/978-3-663-09834-8_14.
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Weiß, V., J. Schöler, and F. N. Fett. "MATHEMATICAL MODELING OF COAL COMBUSTION IN A CIRCULATING FLUIDIZED BED REACTOR." In Circulating Fluidized Bed Technology, 289–98. Elsevier, 1988. http://dx.doi.org/10.1016/b978-0-08-036225-0.50032-0.
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Miccio, Francesco. "A mathematical model of a fluidized bed combustor coupled with a Stirling engine." In Computer Aided Chemical Engineering, 775–80. Elsevier, 2010. http://dx.doi.org/10.1016/s1570-7946(10)28130-0.
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Doraiswamy, L. K. "Reactor Design for Solid-Catalyzed Fluid-Phase Reactions." In Organic Synthesis Engineering. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195096897.003.0019.
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Catalytic reactions are carried out in reactors with a fixed, fluidized, or moving bed of catalyst. Although the chemical kinetics of the reaction obviously remains the same for all these reactors, the hydrodynamic features vary considerably. Because no complete description of these features is possible, it is convenient to postulate different situations and develop mathematical models to represent these situations for each type of reactor. It is also important to note that wherever solid catalysts are used, the question of catalyst deactivation cannot be ignored. Several books and reviews covering a variety of situations have been written, including those marked with an asterisk in the list of references. They are recommended for general reading. Our intention in this chapter is limited, however: formulate approaches to the design of two main classes of catalytic reactors, fixed and fluidized bed; briefly describe selected procedures along with a few numerical (or methodological) examples to illustrate their use; and outline a procedure for incorporating the effects of catalyst deactivation in reactor design and operation. There are basically two types of fixed-bed reactors: (1) multitubular, in which tubes of approximately 1.5 to 4.0 cm in diameter are placed as a bundle within a shell through which a heat exchange fluid is circulated to control the temperature profile within the reactor; and (2) adiabatic, in which the catalyst is placed directly inside a reactor (with no a priori limitation to the diameter), and heat removal is accomplished by multistaging the bed and removing the heat of reaction by heat exchange between stages. Four major models have been proposed for describing the behavior of a packed tubular reactor (see Doraiswamy and Sharma, 1984). Of these, the most extensively used is the quasi-continuum model in which the fluid-solid system is assumed to act as a single pseudohomogeneous phase with effective properties of its own (as for any true single phase). Thus the procedures developed in Chapters 4 and 10 for the homogeneous model can be used to determine the axial profiles of concentration and temperature. One can also allow for radial transport gradients within each tube [two-dimensional (2-D) models], as opposed to the simpler models in which these gradients are neglected—the one-dimensional (1-D) models.
Conference papers on the topic "Fluidized-bed combustion Mathematical models"
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Mei, Joseph S., Esmail R. Monazam, and Lawerence J. Shadle. "The Mapping of Flow Regimes for a Light Material: Cork." In 17th International Conference on Fluidized Bed Combustion. ASMEDC, 2003. http://dx.doi.org/10.1115/fbc2003-014.
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A series of experiments was conducted in the 0.3-meter diameter circulating fluidized bed test facility at the U.S. Department of Energy’s National Energy Technology Laboratory (NETL). Cork, the bed material used in this study, is a coarse, light material, with a particle density of 189 kg/m3 and a mean diameter of 1007 μm. Fluidizing this material in ambient air provides approximately the same gas to solids density ratio as coal and coal char in a pressurized gasifier. Furthermore, the density ratio of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. The purpose of this study is to generate reliable data to validate the mathematical models currently under development at NETL. Using such coarse, light material can greatly facilitate the computation of these mathematical models. This paper presents and discusses data for the operating flow regimes of dilute-phase, fast-fluidization, and dense-phase transport by varying the solid flux (Gs) at a constant gas velocity (Ug). Data are presented by mapping the flow regime for coarse cork particles in a ΔP/ ΔL-Gs-Ug plot. The coarse cork particles exhibited different behavior than the measurements on heavier materials found in published literature, such as alumina, sand, FCC, and silica gel. Stable operation can be obtained at a fixed riser gas velocity that is higher than the transport velocity (e.g. at Ug = 3.2 m/sec), even though the riser is operating within the fast fluidization flow regime. Depending upon the solid influx, the riser can also be operated at dilute-phase or dense-phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries, and solid fractions in the upper-dilute and the lower-dense regions of a fast fluidization flow regime. Comparisons of measured data show rather poor agreement with these empirical correlations. Xu et al. (2000) have observed this lack of agreement in their study of the effect of bed diameter on the saturation carrying capacity. The basis of empirical correlations depends on bed diameter and particle type, and are generally not well understood.
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Mueller, Christian, Anders Brink, and Mikko Hupa. "Numerical Simulation of the Combustion Behavior of Different Biomasses in a Bubbling Fluidized Bed Boiler." In 18th International Conference on Fluidized Bed Combustion. ASMEDC, 2005. http://dx.doi.org/10.1115/fbc2005-78138.
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Solid fuels currently used for energy production in thermal power plants are characterized by a large variety ranging from different coals to biomasses and wastes. This manifold of fuels offers opportunities to the energy producers and nowadays many power plants do not fire single fuels but fuel mixtures. While this procedure may lead to overall economic and environmental advantages it is very demanding for the boiler operators to maintain boiler performance and availability and to meet emission limits. The development of mathematical models that are capable of predicting the combustion behavior of fuel mixtures and provide guidelines for operators and manufacturers has been a challenge over the last years. Since bubbling fluidized beds are frequently used for firing fuel mixtures and especially biomass mixtures, current CFD based BFB models, such as the A˚bo Akademi Furnace Model, have been used widely over the last years to predict emission tendencies and ash deposition behavior. However, due to the complexity of the processes during combustion of fuel mixtures and the combustion process in the bubbling fluidised bed itself, the models are characterized by strong simplifications. This is especially true for the description of the lower part of the furnace, the region of fuel intake and bubbling bed. Recently, the A˚bo Akademi Furnace Model has been extended by a more detailed description of the fuel conversion by considering the combustion of individual biomass particles and a first simplified approach describing heat and mass transfer processes between the bubbling bed and the freeboard. Both submodels guarantee a closed mass and energy balance over the bed-freeboard region. In the current study the new submodels have been used to investigate the combustion conditions in a 290 MW bubbling fluidized bed boiler firing peat and forest residue. Clear differences in the simulation results for the both fuels can be found with regard to the specific combustion characteristics, the location of the main combustion zone and the total heat generated during combustion.
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Monazam, Esmail R., and Lawrence J. Shadle. "Fuel Gas Clean-Up in a Transport Reactor: Model Development and Analysis." In 18th International Conference on Fluidized Bed Combustion. ASMEDC, 2005. http://dx.doi.org/10.1115/fbc2005-78082.
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Integrated Gasification Combined Cycle (IGCC) is the leading coal-fired system being developed by the U. S. Department of Energy to produce clean electricity from coal. One of the key components of this IGCC is fuel gas desulfurization (HGD) which is used to remove sulfurous compounds from coal gases with efficient, regenerable, mixed-metal oxide sorbents. Previous commercial desulfurization processes are based on wet scrubbing at or below ambient temperatures, resulting in considerable thermal efficiency loss as well as costly wastewater treatment. This has led to the development of gas-solid processes using transport reactors above the dew point of water. These systems offer the advantages of high throughput, continuous operation, and efficiency gains over low-temperature scrubbing of H2S. The National Energy Technology Laboratory (NETL) is developing a simplified transport reactor mathematical model to provide a quick estimation of pressure drops and conversions as a function of riser dimensions, sorbent properties and gas velocity. Hydrodynamics and a solid conversion model, together with a transport reactor mass balance, are used to predict the performance of a fuel gas desulfurization reactor. Experimental data collected at NETL’s Gas Process Development Unit (GPDU) are used to provide an initial assessment of the model.
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Ada´nez, Juan, Francisco Garci´a-Labiano, Luis F. de Diego, Ainhoa Plata, Javier Celaya, Pilar Gaya´n, and Alberto Abad. "Optimizing the Fuel Reactor for Chemical Looping Combustion." In 17th International Conference on Fluidized Bed Combustion. ASMEDC, 2003. http://dx.doi.org/10.1115/fbc2003-063.
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A mathematical model for a bubbling fluidized bed has been developed to optimize the performance of the fuel reactor in chemical looping combustion systems. This model considers both the hydrodynamic of the fluidized bed (dense bed and freeboard) and the kinetics of the oxygen carrier reduction. Although the model is valid for any of the possible oxygen carriers and fuels, the present work has been focused in the use of a carrier, CuO-SiO2, and CH4 as fuel. The shrinking core model has been used to define the particle behavior during their reduction. The simulation of the fuel reactor under different operating conditions was carried out to set the operating conditions and optimize the process. The effect of different design or operating variables as the bed height, the oxygen carrier/fuel ratio, and the gas throughput was analyzed. Finally, a sensitivity analysis to the solid reactivity, the bubble diameter, and to the gas/solid contact efficiency in the freeboard was done. At vigorous fluidization, solid present in the freeboard can strongly contribute to the gas conversion in the fuel reactor. However, the gas/solid contact efficiency in this zone must be determined for each particular case.
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Ada´nez, Juan, Luis F. de Diego, Pilar Gaya´n, Francisco Garci´a-Labiano, Andre´s Cabanillas, and Alberto Bahillo. "Co-Combustion of Biomass and Coal in Circulating Fluidized Bed: Modeling and Validation." In 17th International Conference on Fluidized Bed Combustion. ASMEDC, 2003. http://dx.doi.org/10.1115/fbc2003-064.
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In this work carbon combustion efficiencies in circulating fluidized bed combustion (CFBC) when co-firing biomass and coal mixtures were studied. Experimental results were obtained from the combustion of two kind of coals with a forest residue (Pine bark) in a CBF pilot plant (0.3MWth) with 20-cm i.d. and 6.5-m height. The effect of operating conditions such as percentage of biomass in the feed, temperature, excess air, air velocity and percentage of secondary air on carbon combustion efficiency was studied. A mathematical model for the co-combustion of coal and biomass in a circulating fluidized bed boiler has been developed. The riser is divided in three zones with different hydrodynamic characteristics: bottom, splash and freeboard. The bottom bed has a constant voidage, determined by a modified two-phase theory. The solids are considered in perfect mixing and the gas in plug flow. The voidage in the splash region follows an exponential decay model. In the freeboard region, the solids and the gas are in plug flow, and a core-annulus structure is considered. Devolatilization of solid fuels is modeled with a particle reaction model which allows to determine the volatiles generation rate as a function of time and operating conditions. Kinetics of char combustion is modeled with the shrinking particle model with mixed control by chemical reaction and gas film diffusion, assuming that the ashes separate once formed. To consider that the char particles are a mixture of coal and biomass char particles, a weighted average combustion rate is defined taking into account the individual combustion rates. Population balances of char particles in the different regions were developed to calculate carbon concentrations. The developed model can predict the different gas concentrations along the riser, such as oxygen, SO2, CO, CH4, etc..., and the carbon combustion efficiency. The experimental results of carbon combustion efficiencies and gas emissions were compared with those predicted by the model and a good correlation was found for all the conditions used.
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Z˙ukowski, Witold. "Methane and Ethane Combustion in an Inert Fluidized Bed." In 18th International Conference on Fluidized Bed Combustion. ASMEDC, 2005. http://dx.doi.org/10.1115/fbc2005-78100.
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Burning premixed fuel-air mixtures in a bubbling fluidized bed is accompanied by some characteristic phenomena. The most striking one is the production of acoustic effects, indicating that combustion is not really continuous. A second, less obvious effect, is the NOx concentration in the flue gases falling with increasing bed temperature, observed above a certain critical mean bed temperature. To investigate the periodic burning of portions of methane-air mixture, photometric and acoustic signals were recorded simultaneously. Using a laboratory quartz reactor, explosions could be optically recorded in the bed, millimeters above distributor. With ethane fuel, the effective “combustion zone” in the reactor was also located by determining vertical temperature profiles, using eight thermocouples. When the bed temperature rises, maxima in the vertical temperature profiles associated with the “reaction zone” move from above the bubbling bed to the distributor. A mathematical model of unsteady combustion in a single bubble surrounded by bed material was used to simulate the process. Computed temperature maxima were compared with the experimental profiles. This meant finding the region where bubbles of premixed gases exploded, experimentally and from the model. A correlation between the NOx concentration and the location of the explosions (and diameter of the exploding bubbles) has also been found.
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Yusof, Nurul Syazwani, Sumarni Abu Bakar, and Razidah Ismail. "Modified graphical autocatalytic set model of combustion process in circulating fluidized bed boiler." In PROCEEDINGS OF THE 21ST NATIONAL SYMPOSIUM ON MATHEMATICAL SCIENCES (SKSM21): Germination of Mathematical Sciences Education and Research towards Global Sustainability. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4887567.
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Nakamura, Masato, Hanwei Zhang, Karsten Millrath, and Nickolas J. Themelis. "Modeling of Waste-to-Energy Combustion With Continuous Variation of the Solid Waste Fuel." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-55342.
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A mathematical model of a mass-burn, waste-to-energy combustion chamber has been developed that includes stochastic representation of the variability of the fuel (municipal solid waste, MSW). The drying, pyrolysis, gasification and combustion processes on the moving grate are governed by several factors such as proximate and ultimate analysis, particle size, moisture, heating value, and bulk density, all of which change continuously. This extreme variability has not been considered in past mathematical models of WTE combustion that used mean values of the MSW properties. The Monte Carlo stochastic method has been applied to provide a time series description of the continuous variation of solid wastes at the feed end of the traveling grate. The combustion of the solid particles on the grate is simulated using percolation theory. The feed variation and the percolation theory models are combined with the FLIC two-dimensional bed model developed by Sheffield University to project the transient phenomena in the bed, such as the break-up of waste particles and the channeling of combustion air throughout the bed, and their effects on the combustion process.
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Mastrovito, M., S. M. Camporeale, A. Forte, and B. Fortunato. "Analysis of Pressure Oscillations Data in Gas Turbine Annular Combustion Chamber Equipped With Passive Damper." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-69056.
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Growing environmental awareness, the current legislations, and the increasing competition in the energy market lead gas turbine manufacturers to develop combustion chambers that have to guarantee low NOx emissions, low pressure drop and high combustor outlet temperature. Modern annular and can-type gas turbine combustion chambers, able to work in lean premixed mode, show a remarkable attitude to produce flame instabilities, well known as humming. Many theoretical approaches have been proposed in order to describe the phenomenon and predict the stability margin of the burner. Experimental tests are needed to assess mathematical models and to evaluate the effects of either active or passive methodologies adopted to reduce combustion driven instabilities. Tests have been carried out at the Ansaldo Caldaie test bed on a real-size annular combustion chamber, equipped with a certain number of Helmholtz resonators. The combustion chamber has been instrumented with piezoelectric and opto-electronic transducers in order to determine the pressure field both in proximity of the instability limit and in humming condition. When pressure data are collected before than humming appears, pressure oscillations are much lower than those gathered in humming conditions; therefore, by using sensors designed to work under the pressure levels characterising the humming conditions, difficulties arise in proximity of the stability limit due the low signal-to-noise ratio. In this paper some techniques used to analyse the data gathered from the tests will be shown. Moreover, a simple algorithm capable to analyse a large amount of data and to synthesise them into a few significant parameters useful for the spectral analysis of the pressure field, has been validated by means of both real and simulated signals.
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Yue, Guangxi, Junfu Lu, Hai Zhang, Hairui Yang, Jiansheng Zhang, Qing Liu, Zheng Li, Eric Joos, and Philippe Jaud. "Design Theory of Circulating Fluidized Bed Boilers." In 18th International Conference on Fluidized Bed Combustion. ASMEDC, 2005. http://dx.doi.org/10.1115/fbc2005-78134.
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Studies on circulating fluidized bed (CFB) boilers have being conducted at the Tsinghua University (TH) for about two decades and much of works are done to link the fundamentals with practical application. A full set of design theory was developed and some key elements of this theory are presented in this paper. First, a classification of state of the solid-gas two-phase flow in CFB boiler is given. TH’s studies validated that a CFB boiler can be generally described as the superposition of a fast bed in the upper part with a bubbling bed or turbulent bed in the bottom part. A concept model of material balance for the open system of CFB boiler was developed and later improved as a more comprehensive 1-D model taking ash formation, particle attrition and segregation in bed into account. Some results of the models are discussed. Then the concept of State Specification of a CFB boiler is defined and discussed. The State Specification is regarded as the first step to design a CFB and a base to classify different style of CFB boiler technologies for various CFB boiler manufacturers. The State Specification adopted by major CFB boiler makers is summarized and associated importance issues are addressed. The heat transfer model originally developed by Leckner and his coworkers is adopted and improved. It is further calibrated with experimental data obtained on the commercial CFB boiler measurements. The principle, improvements and application of the model are introduced. Some special tools developed for heat transfer field test are also given. Also, combustion behaviors of char and volatile content are studied, and the combustion difference between a CFB boiler and a bubbling bed is analyzed. The influence of volatile content and size distribution is discussed. The concept of vertical distribution of combustion and heat in CFB boiler furnace is introduced and discussed as well. In the last, the suggested design theory of CFB boiler is summarized.
Reports on the topic "Fluidized-bed combustion Mathematical models"
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Preto, F. A mathematical model for fluidized bed coal combustion. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1985. http://dx.doi.org/10.4095/302616.
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