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Статті в журналах з теми "Coal liquefaction Mathematical models"
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Wu, Chunlai, Shidong Shi, Xiaosu Zhu, and Ming Zhou. "A mathematical model for tubular reactors in direct coal liquefaction." Energy 18, no. 8 (August 1993): 815–25. http://dx.doi.org/10.1016/0360-5442(93)90060-q.
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Bongers, Geoffrey D., John S. T. Chan, W. Roy Jackson, Antonio F. Patti, Marc Marshall, and Pavla Meakin. "Reactions of montan wax fractions as models of brown coal liquefaction." Fuel 75, no. 10 (August 1996): 1161–66. http://dx.doi.org/10.1016/0016-2361(96)00078-6.
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Williams, B. C., and J. T. McMullan. "Development of computer models for the simulation of coal liquefaction processes." International Journal of Energy Research 18, no. 2 (March 1994): 117–22. http://dx.doi.org/10.1002/er.4440180209.
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Ji, Jie, Hui Yao, Di Wang, Zhi Suo, Luhou Liu, and Zhanping You. "Properties of Direct Coal Liquefaction Residue Modified Asphalt Mixture." Advances in Materials Science and Engineering 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/2473283.
Повний текст джерелаАнотація:
The objectives of this paper are to use Direct Coal Liquefaction Residue (DLCR) to modify the asphalt binders and mixtures and to evaluate the performance of modified asphalt mixtures. The dynamic modulus and phase angle of DCLR and DCLR-composite modified asphalt mixture were analyzed, and the viscoelastic properties of these modified asphalt mixtures were compared to the base asphalt binder SK-90 and Styrene-Butadiene-Styrene (SBS) modified asphalt mixtures. The master curves of the asphalt mixtures were shown, and dynamic and viscoelastic behaviors of asphalt mixtures were described using the Christensen-Anderson-Marasteanu (CAM) model. The test results show that the dynamic moduli of DCLR and DCLR-composite asphalt mixtures are higher than those of the SK-90 and SBS modified asphalt mixtures. Based on the viscoelastic parameters of CAM models of the asphalt mixtures, the high- and low-temperature performance of DLCR and DCLR-composite modified asphalt mixtures are obviously better than the SK-90 and SBS modified asphalt mixtures. In addition, the DCLR and DCLR-composite modified asphalt mixtures are more insensitive to the frequency compared to SK-90 and SBS modified asphalt mixtures.
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Kirca, V. S. Ozgur, and B. Mutlu Sumer. "Sinking Failure of Drag Embedment Anchors Due to Wave-Induced Seabed Liquefaction." International Journal of Ocean and Coastal Engineering 01, no. 04 (December 2018): 1850006. http://dx.doi.org/10.1142/s2529807018500069.
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This paper presents the results of an integrated mathematical modeling exercise for sinking of Drag Embedment Anchors (DEA) in a seabed liquefied by waves. The mathematical model consists of three elements (sub-models): (1) Mathematical model for residual liquefaction under waves; (2) Mathematical model for sinking of DEAs in the liquefied soil; and (3) Mathematical model for upward progression of compaction front in the post-liquefaction stage. The study demonstrates the implementation of the model with reference to a selected group of real-life DEAs. The results generally show that the ultimate sinking depths of DEAs are rather large (tens of centimeters short of the liquefaction depth), and accordingly, the ultimate sinking times of DEAs are rather small (O(10[Formula: see text]min)) as a result of the massive weights of these anchors. The paper presents a parametric study carried out in a systematic way to understand the influence of parameters such as the relative density of soil, the soil depth, and the grain size on the end results.
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Sato, Shimio. "Remarks on rate analysis of coal liquefaction using kinetic models involving multimolecular reaction paths." JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 23, no. 2 (1990): 249–50. http://dx.doi.org/10.1252/jcej.23.249.
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Şimşek, Emir Hüseyin, Fatih Güleç, and Hakan Kavuştu. "Application of Kalman filter to determination of coal liquefaction mechanisms using discrete time models." Fuel 207 (November 2017): 814–20. http://dx.doi.org/10.1016/j.fuel.2017.06.004.
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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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Yang, Lanhe. "Nonlinear coupling mathematical models on percolation-patterned underground coal gasification." International Journal of Energy Research 29, no. 15 (2005): 1331–53. http://dx.doi.org/10.1002/er.1067.
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Trokhymets, Mykola, Vira Maltseva, Yehor Vialushkin, Volodymyr Antonchik, Tetiana Moskalova, and Maryna Polushyna. "Method and equipment for the safe development of preparatory workings in the gas-bearing coal seams." E3S Web of Conferences 109 (2019): 00102. http://dx.doi.org/10.1051/e3sconf/201910900102.
Повний текст джерелаАнотація:
The article describes a method and equipment for the safe development of preparatory working on a gas-bearing, outburst hazardous coal seam by a heading machine. The described method significantly prevents the gas emission during mining operations. Determination of the amount of degassing and relief wells is performed according to the given in article mathematical formulas. This ensures a significant increase in the level of safety processing the preparatory roadway on a gas-bearing, prone to outbursts coal seam by a heading machine. Due to this, the speed of conducting excavation increases and the cost of mining is reduced. The proportionality coefficients of the mathematical models were determined. Mathematical models are used to calculate the number of relief and degassing wells, which are drilled during the impulse hydraulic loosing of the nearby part of the coal seam. Also the duration of liquid injection into a coal seam is also determined. Mathematical models for calculating the number of injection, unloading and degassing boreholes can be used in development of the passports for conducting preparatory workings on a gas-bearing, prone to outburst coal seam by a heading machine with a preliminary impulse hydraulic loosing of the nearby part of a coal seam.
Дисертації з теми "Coal liquefaction Mathematical models"
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Donskoi, Eugene. "The mathematical modelling of direct reduction in iron ore/coal composites including the modelling of coal pyrolysis." Thesis, Queensland University of Technology, 2000.
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Rahman, Md Mizanur Engineering & Information Technology Australian Defence Force Academy UNSW. "Modelling the influence of fines on liquefaction behaviour." Publisher:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/43920.
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Traditionally, void ratio, e has been used as a state variable for predicting the liquefaction behaviour of soils under the Critical State (Steady State) framework. Recent publications show that void ratio, e may not be a good parameter for characterizing sand with fines as the steady state, SS data points move downward in e-log(p) space up to certain fines content termed as threshold fines content, TFC. Thus, it was difficult to apply SS concept on sand with fines as a small variation of fines content may lead to different SS line. Many researchers proposed to used equivalent granular void ratio, e* as an alternative state variable (i.e. in lieu of void ratio, e) in attempt to obtain a narrow trend line for SS data points irrespective of fc provided fc TFC. The e* is obtained from e. For the conversion from e to e*, one need a parameter b which presents the active fraction of fines in overall force structure of sand. However, predicting the b is problematic. Most, if not all, of the b reported were determined by case-specific back-analysis, that is, the b-value was selected so that the test results for a given sand-fines type could be correlated with the equivalent granular void ratio, e* irrespective of fines content. This thesis examines the factors that affecting the b value by examining published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based onparticle size ratio, and fines content, fc. Published data and experimental results on Sydney sand appears to be in support of the proposed equation. The single relation of SS data points in e*-log(p) space for sand with fines is referred as Equivalent Granular Steady State Line, EG-SSL. The EG-SSL is then used to define the equivalent granular state parameter,*. A good correlation observed between * and q-p, q- q responses in undrained shearing. The e* and * are also used to modified a state dependent constitutive model. Seven model input parameters are needed in addition four to critical state input parameters. These parameters are obtained from drained test. The model is used to predict q-pand q- q responses for flow, non-flow and limited flow behaviour for 0% to 30% fines contents. The model predictions are in good agreement with experimental results. The effect of fines types (in terms of plasticity and angularity) on the prediction equation of b are also examined with four different types of fines. A negligible effect of fines type on the prediction equation of b is observed. The link between monotonic and cyclic loading behaviour for sand with fines are also examined with emphasis on cyclic instability and strain hardening behaviour after quasi steady state, QSS for a range of fines contents (provided that fc < TFC). It is found that a single set of rules could be used to correlate monotonic and cyclic behaviour for a range of fines contents at same *.
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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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Shen, Yansong Materials Science & Engineering Faculty of Science UNSW. "Mathematical modelling of the flow and combustion of pulverized coal injected in ironmaking blast furnace." Awarded by:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41108.
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Pulverized coal injection (PCI) technology is widely practised in blast furnace ironmaking due to economic, operational and environmental benefits. High burnout of pulverized coal in the tuyere and raceway is required for high PCI rate operation. A comprehensive review reveals that although there have been a variety of PCI models, there is still an evident need for a more realistic model for PCI operation in blast furnace. Aiming to build a comprehensive PCI model of a full-scale blast furnace, this thesis presents a series of three-dimensional mathematical models, in terms of model development, validation and application, in a sequence from a pilot-scale to a full-scale, from a simple to complicated geometry, from a coal only system to a coupled coal/coke system. Firstly a three-dimensional model of pulverized coal combustion is developed and applied to a pilot-scale PCI test rig. This model is validated against the measurements from two pilot-scale test rigs in terms of gas species composition and coal burnout. The gas-solid flow and coal combustion are simulated and analysed. The results indicate that the model is able to describe the evolutions of coal particles and provide detailed gas species distributions. It is also sensitive to various parameters and hence robust in examining various blast furnace operations. This model is then extended to examine the combustion of coal blends. The coal blend model is also validated against the experimental results for a range of coal blends conditions. The overall performance of a coal blend and the individual behaviours of its component coals are analysed. More importantly, the synergistic effect of coal blending on overall burnout is examined and the underlying mechanisms are explored. It is indicated that such synergistic effect can be optimized by adjusting the blending fraction, so as to compensate for the decreased burnout under high coal rate operation. The model provides an effective tool for the optimum design of coal blends. As a scale-up phase, the coal combustion model is applied to the blowpipe-tuyereraceway region of a full-scale blast furnace, where the raceway is simplified as a tube with a slight expansion. The in-furnace phenomena are simulated and analysed, focusing on the main coal plume. The effect of cooling gas conditions on combustion behaviours is investigated. Among the three types of cooling gas (methane, air, and oxygen), oxygen gives the highest coal burnout. Finally, a three-dimensional integrated mathematical model of pulverized coaVcoke combustion is developed. The model is applied to the blowpipe-tuyere-raceway-coke bed region of a full-scale blast furnace, which features a complicated raceway geometry and coke bed properties. The model is validated against the measurements in terms of coal burnout from a test rig and gas composition from a blast furnace, respectively. The model gives a comprehensive full-scale picture of the flow and thermo-chemical characteristics of PCI process. The typical operational parameters are then examined in terms of coal burnout and gas composition. It is indicated that the final burnout along the tuyere axis is insensitive to some operational parameters. The average burnout over the raceway surface can better represent the amount of unburnt coal particles entering the surrounding coke bed and it is also found to be more sensitive to the changes of most parameters. In addition, the underlying mechanisms of coal combustion are obtained. The coal burnout strongly depends on both oxygen availability and residence time. The existence of recirculation region gives a more realistic coal particle residence time and burnout. Compared with the fore-mentioned two models, this model is considered as a more comprehensive model of PCI operation for understanding the infurnace behaviours and provides more reliable information for the design of operational parameters.
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West-Hansen, Jan. "Long-term scheduling in underground coal mining using mixed binary programming." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54807.
Повний текст джерелаАнотація:
Recognizing the complexity of coal mining management, e.g., the scarcity of financial resources and the high level of uncertainty, a mixed binary programming model has been developed as an aid for generating production schedules which maximize the associated net present value.
Defining the mine layout as a precedence network, with the nodes representing mining blocks, a solution procedure is developed, based on Benders' partitioning scheme. That is, the procedure iterates between two problems, namely, the master (primal) problem, solved by a combination of heuristic and exact methods, and the subproblem (dual problem), solved partly by inspection and partly as a minimal cost network flow problem. The heuristic methods are based on improvements of existing algorithms for scheduling precedence-related jobs on m processors.
Computational experiences are presented and the procedure is demonstrated on a mining case.Ph. D.
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Chakraborty, Amal. "An integrated computer simulator for surface mine planning and design." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/90920.
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In the increasingly competitive coal market, it is becoming more important for coal operators to develop mathematical models for surface mining which can estimate mining costs before the actual mining begins. The problem becomes even more acute with the new reclamation laws, as they affect surface coal mining methods, productivity, and costs.
This study presents a computer simulator for a mountaintop removal type of surface mining operation. It will permit users to compare the costs associated with different overburden handling and reclamation plans. It may be used to minimize productivity losses, and, perhaps, to increase productivity and consequently to reduce operating costs through design and implementation of modified mountain top removal methods.M.S.
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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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Skinner, William. "Optimering van Iscor Newcastle kooks-steenkool mengsel." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51865.
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Thesis (MBA)--Stellenbosch University, 2000.ENGLISH ABSTRACT: It was found that the hot metal cost of ISCOR Newcastle's single blast furnace can significantly be reduced by the correct use of an integrated model to predict reductant cost based mainly on coal blend. The model uses coal ash chemistry, fluiidity, vitrinite rank and volatile matter to predict coke strength after reaction (CSR), coke ash and coking yield. CSR is used to predict maximum allowable coke nut- and pea consumption in the furnace as well as hot blast temperature. Pitch injection levels are predicted using CSR and blast furnace production rates. Coke ash, pitch injection and hot blast temperature is used to predict the coke rate. The above is used with imported Chinese coke cost to accurately predict reductant cost. It was found that the current optimum blends should include Australian en Nieu Zeeland coals because of price and quality conciderations. Because of its low cost of production and low quality the optimum percentage of Grootegeluk in the blend is determined largely by its transfer price.
AFRIKAANSE OPSOMMING: Die vloeiyster koste van ISCOR Newcastle se enigste hoogoond kan drasties verlaag word deur die korrekte gebruik van 'n geïntegreerde model wat reduktant koste voorspel op grond van steenkoolmengsel. Die model gebruik die chemiese samestelling van steenkool-as, fluiiditeit, vitriniet rang en vlugstof om kooks warmsterkte (SNR), kooks-as en verkooksingsopbrengs te voorspel. SNR is gebruik om die maksimum kooksneute- en -erteverbruik in die hoogoond sowel as blaastemperatuur te voorspel. Pikinspuiting is bereken met SNR en hoogoond produksietempo's. Pikinspuiting en blaastemperatuur word saam met kooks-as gebruik om kookskoers te voorspel. Bogenoemde is saam met die koste van ingevoerde Chinese kooks gebruik om reduktant koste akkuraat te voorspel. Daar was bevind dat die huidige optimum mengsels Australiese en Nieu Zeelandse steenkool moet bevat as gevolg van huidige prys- en kwaliteitsoorwegings. As gevolg van sy lae produksiekoste en lae kwaliteit word die optimum hoeveelheid Grootegeluk bepaal deur sy oordragprys.
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Kumar, Arun. "Ground control ramifications and economic impact of retreat mining on room and pillar coal mines." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49815.
Повний текст джерелаАнотація:
As the coal reserves at shallow depths become exhausted companies have to develop deeper deposits and increase percentage extraction to maintain production levels. Total extraction for room and pillar mines can only be achieved by pillar extraction. The unsupported roof increases during pillar extraction and hence the cost of ground control also increases. Nevertheless, pillar extraction where possible has many potential advantages such as decreased operating cost, increased utilization of reserves, and extended life of the mine. There are several variables such as depth, mining height, rock strength, mining geometry, roof and floor conditions, and retreat mining methods, which affect pillar extraction cost. Cost components of pillar extraction are classified as direct, indirect, fixed, and subsidence compensation costs. A discounted cash flow pillar extraction cost simulator has been developed and used to compute total pillar extraction cost for a variety of conditions and to explore the possibilities of optimizing ground control and retreat mining techniques to maximize extraction ratio. The computer program computes the safe and optimum pillar dimensions and determines the suitable pillar extraction method for the computed pillar width. Pillar extraction cost components are generated and totalled using the net present value method by the simulator. The total extraction cost simulator evaluates the potential advantages of pillar extraction and tests individual variables for sensitivity to changes in other variables attributable to ground control and pillar extraction techniques. Cost of pillar extraction per ton of coal versus depth is presented in the form of a simple nomogram by the simulator. The simulator can be used to determine the economic feasibility of pillar extraction at a particular depth, geologic and mining environment when the market price of mined coal is known.Ph. D.
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Huber, Anita. "Internal mixing in a mine lake." University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0103.
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[Truncated abstract] Mine lakes are a water body created after an open-cut mine ceases operating. The lakes develop in the former mine-pit due to the combination of groundwater inflow, surface run-off and, in some cases, due to rapid filling from river diversion. While potentially valuable water resources, these lakes often have poor water quality and managing the water body is an important part of the overall process of mine site rehabilitation. As mine lakes form in man-made pits, they have a bathymetry that is typically quite distinct from natural lakes and this can, in turn, strongly influence the hydrodynamics and hence the water quality of the water body. Despite the potential importance of these water bodies, there have been very few studies on the hydrodynamics of mine lakes. This study describes a field investigation of the hydrodynamics of a former coal mine lake, Lake Kepwari, in south-western Western Australia. In particular, this study examines the hydrodynamic processes in both the surface mixing layers and the internal mixing in the density stratified lake. Wind sheltering in the surface mixing layer occurs due to the presence of the steep walls and lake embankments. A week long field experiment was conducted in December 2003 using a combination of moored thermistor chains with meteorological stations and the deployment of rapid vertical profiling turbulent microstructure instruments and CTD drops from two boats operating on the lake. ... Simulations indicated that inclusion of a site specific sheltering effect, based on the results of the field campaign, significantly improved the models‘ performance in capturing the surface mixed layer deepening associated with episodic strong wind events that occur on the lake. Considerable internal mixing was indicated by the high dissipation rates observed, particularly near the boundaries. Large basin-wide diffusivities were also calculated from the heat budget method over long periods, showed a consistency with time, and were slightly higher in summer than during the Autumn Winter period. Although light, there are persistent winds over the lake and yet little basin-scale internal wave activity or seiching. It is hypothesized that any seiching motion was rapidly damped by strong mixing over the hydraulically rough bathymetry bathymetry created by the remnant benches from the open cut mining operation itself. This boundary mixing, in turn, drives secondary relaxation currents that transport mixed fluid from the boundaries to the interior, resulting in high effective basin-wide diffusivities. A simple boundary mixing model is proposed to describe this process.
Книги з теми "Coal liquefaction Mathematical models"
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Hynes, Mary Ellen. Probabilistic liquefaction analysis. Washington, DC: Division of Engineering Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1999.
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Hynes, M. E. Probabilistic liquefaction analysis. Washington, D.C: U.S. Nuclear Regulatory Commission, 1990.
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The outlook for thermal coal. Washington, D.C., U.S.A: World Bank, 1985.
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Suwała, Wojciech. Modeling transition in the Polish coal industry. Cracow: Instytut Gospodarki Surowcami Mineralnymi i Energią PAN, 1998.
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Domestic coal distribution: An interregional programming model for the U.S. coal industry. Greenwich, Conn: JAI Press, 1985.
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Edwards, John C. Mathematical modeling of spontaneous heating of a coalbed. Pgh. [i.e. Pittsburgh] Pa: U.S. Dept. of the Interior, Bureau of Mines, 1990.
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Edwards, John C. Mathematical modeling of spontaneous heating of a coalbed. Washington, DC: Dept. of the Interior, 1990.
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Ponomarev, V. P. Vosproizvodstvo ėkonomicheskogo potent͡s︡iala dobychi ugli͡a︡ v sisteme TĖK Rossii: Metodologii͡a︡ perekhodnoĭ ėkonomiki. Moskva: In-t konʺi͡u︡nktury rynka ugli͡a︡, 1997.
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Finkelman, Robert B. Development and evaluation of deterministic models for predicting the weight of fouling deposits from coal combustion. Reston, VA: U.S. Geological Survey, 1989.
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Sams, James I. Simulation of streamflow and sediment transport in two surface-coal-mined basins in Fayette County, Pennsylvania. Lemoyne, Pa: U.S. Dept. of the Interior, U.S. Geological Survey, 1995.
Знайти повний текст джерелаЧастини книг з теми "Coal liquefaction Mathematical models"
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Sarker, Ruhul A. "Alternative Mathematical Programming Models: A Case for a Coal Blending Decision Process." In Springer Optimization and Its Applications, 383–99. New York, NY: Springer New York, 2009. http://dx.doi.org/10.1007/978-0-387-98096-6_21.
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Hnydiuk-Stefan, Anna. "Methodology and Mathematical Models with Continuous Time for Technical and Economic Analysis of Effectiveness Modernization of Existing Coal Blocks for Dual-Fuel Gas-Steam Systems." In Dual-Fuel Gas-Steam Power Block Analysis, 81–98. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-03050-6_5.
Повний текст джерелаТези доповідей конференцій з теми "Coal liquefaction Mathematical models"
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Coelho, P. J., J. L. T. Azevedo, and L. M. R. Coelho. "The Mathematical Modeling of Utility Boilers at IST." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1554.
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Abstract The mathematical modeling of utility boilers is a difficult problem due to the multiplicity of physical phenomena involved and to the interaction between different phenomena. However, reliable models are extremely useful since they can be used to design new equipment, and to optimize and retrofit units in operation. In this paper a survey of the work carried out at Institute superior Técnico (IST) in Lisbon is reported. Only the work based on comprehensive models, i.e., those accounting for all the relevant physical phenomena taking place in the combustion chamber is addressed. The models employed are briefly outlined. Then, four examples of application are given, two of them for coal-fired boilers where the effect of low NOx burners and coal over coal reburning is investigated, and the other two for oil-fired boilers where parallelization of the code and simulation of the convection chamber are reported.
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Slavinskaya, N. A. "Chemical Kinetic Modeling in Coal Gasification Processes: An Overview." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23362.
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Coal is the fuel most able to cover world deficiencies in oil and natural gas. This motivates the development of new and more effective technologies for coal conversion into other fuels. Such technologies are focused on coal gasification with production of syngas or gaseous hydrocarbon fuels, as well as on direct coal liquefaction with production of liquid fuels. The benefits of plasma application in these technologies is based on the high selectivity of the plasma chemical processes, the high efficiency of conversion of different types of coal including those of low quality, relative simplicity of the process control, and significant reduction in the production of ashes, sulphur, and nitrogen oxides. In the coal gasifier, two-phase turbulent flow is coupled with heating and evaporation of coal particles, devolatilization of volatile material, the char combustion (heterogeneous/porous oxidation) or gasification, the gas phase reaction/oxidation (homogeneous oxidation) of gaseous products from coal particles. The present work reviews literature data concerning modelling of coal gasification. Current state of related kinetic models for coal particle gasification, plasma chemistry and CFD tools is reviewed.
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Ghenai, C., and I. Janajreh. "Numerical Modeling of Coal/Biomass Co-Firing." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55204.
Повний текст джерелаАнотація:
Biomass co-firing within existing infrastructure of pulverized coal utility boilers is viewed as a practical near-term means of encouraging renewable energy while minimizing capital requirements, maintaining the high efficiency of pulverized coal boilers and reducing the emissions. Numerical investigation of coal/biomass co-firing is presented in this study. Co-combustion of biomass and coal is a complex problem that involves gas and particle phases, along with the effect of the turbulence on the chemical reactions. The transport equations for the continuous phase (gas) and discrete phase (spherical particles) are solved respectively in the Eulerian and Lagrangian frame of reference. The mathematical models used for co-pulverized coal/biomass particles combustion consist of models for turbulent flow (RNG k-ε model); gas phase combustion (two mixture fractions/PDF model: one mixture fraction is used for the fuel (char) and the second for the volatiles); particles dispersion by turbulent flow (stochastic tracking model); coal/biomass particles devolatilization (two competing rates Kobayashi model); heterogeneous char reaction (kinetics/diffusion limited rate model); and radiation (P-1 radiation model). The coal used is a Canadian high sulfur bituminous coal. The coal was blended with 5 to 20% wheat straw (thermal basis) for co-firing. The effect of the percentage of biomass blended with coal on the velocity field, temperature distribution, particles trajectories and pollutant emissions at the exit of the furnace is presented in this paper. One important result is the reduction of NO and CO2 emissions when using co-combustion. This reduction depends on the proportion of biomass (wheat straw) blended with coal.
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Al-Abdulkarem, Abdullah, Yunho Hwang, and Reinhard Radermacher. "Efficiency Improvement of Natural Gas Combined Cycle Power Plant With CO2 Capturing and Sequestration." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87436.
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Although natural gas is considered as a clean fuel compared to coal, natural gas combined cycles (NGCC) emit high amounts of CO2 at the plant site. To mitigate global warming caused by the increase in atmospheric CO2, CO2 capture and sequestration (CCS) using amine absorption is proposed. However, implementing this CCS system increases the energy consumption by about 15–20%. Innovative processes integration and waste heat utilization can be used to improve the energy efficiency. Four waste heat sources and five potential uses were uncovered and compared using a parameter defined as the ratio of power gain to waste heat. A new integrated CCS configuration is proposed, which integrates the NGCC with the CO2 removal and CO2 compression cycles. HYSYS simulation software was used to simulate the CO2 removal cycle using monoethanolamine (MEA) solution, NGCC, CO2 compression cycle, CO2 liquefaction cycles and Organic Rankine Cycle (ORC). The developed models were validated against experimental data from the literature with good agreements. Two NGCC with steam extraction configurations were optimized using Matlab GA tool coupled with HYSYS simulation software. Efficiency improvement in one of the proposed CCS configurations that uses the available waste heat in absorption chillers to cool the inlet-air to the gas turbine and to run an ORC, and uses the developed CO2 liquefaction and pumping instead of multistage compression is 6.04 percent point, which represents 25.91 MW more power than the conventional CCS configuration.
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Honegger, Douglas G. "Considerations for Selecting Approaches to Estimate Lateral Spread Displacements for Assessing Pipeline Performance." In 2006 International Pipeline Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/ipc2006-10337.
Повний текст джерелаАнотація:
Liquefaction hazards, specifically lateral spread displacement resulting from liquefaction, are the most pervasive and often the most severe earthquake hazards to buried oil and natural gas transmission pipelines. While the potential threat of lateral spread displacements to buried pipelines has long been recognized, the availability of approaches and tools to assess the likelihood of liquefaction and estimate of the severity of the lateral spread hazard has improved significantly in the past 10 to 15 years. The most significant areas of improvements have focused on the development of probabilistic approaches, the use of alternatives to standard penetration tests such as cone penetrometer tests and shear wave velocity measurements, and methods to combine the results of dynamic site response analyses with what remains an empirical approach to liquefaction assessment. Approaches available for estimating lateral spread displacements can be generally divided into two categories, empirical methods and analytical methods. Empirical methods are generally limited to estimating the magnitude of lateral spread displacements at the ground surface and must rely upon judgment in defining ground displacements at depth, the size of the lateral spread, and the variation of lateral spread displacement both within and at the margins of the lateral spread zone. Current advanced analytical methods range from relatively simple mathematical analogs to finite element continuum models using either Eulerian or Lagrangian formulations. In addition, many researchers have developed specialty codes for assessing lateral spread displacement. As analytical methods have increased in complexity, there has been a commensurate increase in the cost to undertake these methods because of additional subsurface information requirements and the engineering effort to implement the analyses. Despite the significant advances in the ability to estimate lateral spread displacements, engineering assessment of pipeline performance for potential lateral spread hazards remains an approximate proposition requiring considerable judgment owing to practical limitations with respect to available information, modeling capabilities, and interpretation of modeling results. In many instances, these limitations raise questions regarding whether or not the added value provided by more sophisticated lateral spread modeling techniques justifies the substantial increase in costs. These questions are explored by comparing the advantages and constraints related to common approaches for estimating lateral spread hazard with respect to the ultimate goal of assessing the adequacy of a pipeline river crossing. The comparisons support a conclusion that the most advanced methods may not necessarily lead to a more reliable design solution.
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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.
Повний текст джерелаАнотація:
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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Pacio, Julio C., and Carlos A. Dorao. "Modelling Two-Phase Heat Exchanger Performance in the Annular-Mist Flow Regime Considering Entrainment and Deposition Phenomena." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-10013.
Повний текст джерелаАнотація:
Two-phase flow heat exchangers are main components of large cryogenics, power generation, refrigeration and liquefaction of natural gas plants, both in terms of capital cost and technical challenges. A major challenge in their design is the prediction of local heat transfer coefficients and pressure gradients for the evaporating or condensing fluids. Traditional heat exchanger models are based on one single correlation for predicting the heat transfer in the entire saturated boiling regime, disregarding the flow structure. However, the structure of the flow dictates how the different physical processes (nucleate boiling, convective heat transfer to the liquid and vapour phase, thin film evaporation) interact and contribute to the total heat transfer. In particular, a relevant flow-regime transition for the sizing of heat exchangers is the occurrence of dryout during the evaporation process in the annular-mist flow regime. The objective of this work is to present a three-field model for describing the annular-mist flow considering a liquid film, liquid droplets and a vapor phase, and predicting the occurrence of dryout. The flow structure is affected by the entrainment, deposition and evaporation. These processes are studied on the base of semi-empirical models. The final mathematical model is implemented into an in-house solver. The model is validated with uniform heat flux data available in the open literature. While the model performs well in the case of water flows (within 10% error), the uncertainties are larger for other fluids, probably due to the applicability range of the empirical models. Finally, two numerical examples considering the sensitivity of the input parameters and axial power distribution are studied.
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Tipa, Andrea, Alessandro Sorce, Matteo Pascenti, and Alberto Traverso. "A New Sensor Diagnostic Technique Applied to a Micro Gas Turbine Rig." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68580.
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This paper describes the development and testing of a new algorithm to identify faulty sensors, based on a statistical model using quantitative statistical process history. Two different mathematical models were used and the results were analyzed to highlight the impact of model approximation and random error. Furthermore, a case study was developed based on a real micro gas turbine facility, located at the University of Genoa. The diagnostic sensor algorithm aims at early detection of measurement errors such as drift, bias, and accuracy degradation (increase of noise). The process description is assured by a database containing the measurements selected under steady state condition and without faults during the operating life of the plant. Using an invertible statistical model and a combinatorial approach, the algorithm is able to identify sensor fault. This algorithm could be applied to plants in which historical data are available and quasi steady state conditions are common (e.g. Nuclear, Coal Fired, Combined Cycle).
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Portacha, Józef, Idris A. Elfeituri, Adam Smyk, and Jerzy K. Fiszdon. "Effects of Variation of the Overall Heat Transfer Coefficient in the Feedwater Heaters on the Thermodynamic and Economic Performance of Power Stations." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1355.
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Abstract This paper examines the effect of the variation of the overall heat transfer coefficient (U) in feedwater heaters on the thermodynamic and economic performance of a coal-fired steam power plant. The changes in the values of U are caused by the heat transfer surface fouling or by errors in the power plant design. These errors often result from the use of approximate heat transfer equations when selecting power plants elements. Low and high pressure feedwater heaters of a power plant equipped with a condensing turbine and a natural circulation steam generator with one reheat stage are considered in this work. The research was conducted using the overall heat transfer coefficients from 50% to 150% of the nominal value. The thermodynamic and economic effects on the power plant were calculated using the mathematical model of the power plant. The power plant components’ mathematical models evaluate the influence of the changes in the heaters’ overall heat transfer coefficient on the thermodynamic (especially exergetic) losses and economic effects. They take into account off-design operating conditions. The decomposition method and multi-level iterative process was used to solve the problem. The research proved that, during operation, the capacity of the power plant might change by up to 2% due to above-mentioned variations. For a 600 MW power plant that means variation of the electric power delivery of approximately 12 MW and increase of the operating costs of up to 4 million dollars per year. The obtained results are particularly useful in the decision-making process in planning renovation and feedwater heaters’ replacement periods.
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Khadem-Sameni, Melody, John Preston, and John Armstrong. "Railway Capacity Challenge: Measuring and Managing in Britain." In 2010 Joint Rail Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/jrc2010-36280.
Повний текст джерелаАнотація:
In the European Union, the total length of railway lines has decreased since 1970, mainly by abandoning very old routes such as those to coal mines. However, there has been huge growth in the transport of goods and passengers due to economic growth and globalization. Accommodating more passengers and goods on less infrastructure has resulted in the railway capacity challenge. The highest rate of growth in passenger kilometres in Europe belongs to Britain, where a rise of 42.2 percent has been achieved in the period 1995–2006 while the total length of railway lines has decreased from 19,330 route km in 1970 to 16,321 km in 2008. Railways originated from Great Britain therefore old tracks along with huge growth in railway transportation in recent years and inadequate infrastructure have resulted in a serious railway capacity challenge. This paper reviews different definitions of railway capacity, discusses issues for it (including having one degree of freedom for movement, constant need for maintenance due to wear caused by wheel-rail interaction and domino effect) and examines underlying infrastructure, traffic and operating parameters that affect capacity utilisation. Current methods for analyzing capacity utilisation are investigated: theoretical formulae, parametric and mathematical models and various simulation software. For tackling the capacity challenge, a hierarchy of soft and hard measures that can be deployed to increase capacity is proposed. Some of the latest initiatives in Britain to tackle railway capacity challenge and using the current infrastructure efficiently are analyzed including Network Modeling Framework (NMF), Delivering a Sustainable Railway, High Level Output Statement (HLOS) and Route Utilisation Strategies (RUSs). In the end, five policies that can contribute to better utilising capacity in Britain are suggested.