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Alonso, Lozano Alvaro. "Coal gasification in entrained flow gasifiers simulation & comparison". Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-12726.
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RAKHSHI, AALIA. "A COMPUTATIONAL STUDY OF DEVOLATILIZATION AND KINETICS IN ENTRAINED FLOW COAL GASIFICATION". OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1534.
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Computational fluid dynamics (CFD) modeling is an integral part of the design cycle of modern entrained flow gasifiers. Gasification modeling considers an interacting multi-phase media in a turbulent environment. Several gasification sub-models have been developed and validated over the last thirty five years related to turbulence, gaseous combustion, devolatilization and char reactions. The CFD model of gasification must be valid for a range of operating conditions, reactor designs and feedstock compositions. Although tremendous strides have been made in every aspect of gasification modeling, shortcomings do exist in many of the sub-models. Two problems of practical significance are studied in this dissertation. The first is related to devolatilization and the second deals with the accuracy of the gaseous and char combustion models. A focus and consideration of the two problems will improve the predictive capability of the gasification model. In the first, a new framework for volatile breakdown is developed for entrained flow gasification modeling. The framework is based on an optimized solution of an under-determined system of equations formulated using a two-step Moore-Penrose generalized matrix approach. The approach permits the determination of the volatile composition using just the Proximate-Ultimate analysis data of coal. The method can be utilized for all coal types irrespective of origin.The accuracy and consistency of the framework is demonstrated by direct comparison with available devolatilization breakdown data. The overall performance of the framework is also appraised by incorporating it in a CFD simulation of an actual entrained flow gasifier, the 2550 TPD ConocoPhillips EGas technology based two stage oxygen blown gasifier. The reactor exit syngas composition from the simulation is favorably compared with available experimental data. In the second problem, a kinetics assessment of the quasi-global homogeneous and heterogeneous reaction mechanisms is carried out for entrained flow coal gasification modeling. Accurate closure of the chemical source term in gasification modeling necessitates a detailed study of turbulence-chemistry interaction. Towards this end, time-scale analysis of the homogeneous reactions is discussed using eigenvalue analysis of the reaction rate Jacobian matrix. A singular value decomposition of the stoichiometric reaction matrix is performed to assess the behavior of the homogeneous reactions in a reduced species vector space. The significant factors affecting the heterogeneous char reactions is assessed and the relative importance of bulk diffusion and inherent char kinetics is analyzed in a gasifier. The overall study is carried out using numerical and experimental results of an actual pilot scale gasifier, the 200 TPD (tons per day) Mitsubishi Heavy Industries (MHI) pilot scale air blown gasifier.
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Silaen, Armin. "Comprehensive Modeling and Numerical Investigation of Entrained-Flow Coal Gasifiers". ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/1148.
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Numerical simulations of coal gasification process inside a generic 2-stage entrainedflow gasifier are carried out using the commercial CFD solver ANSYS/FLUENT. The 3-D Navier-Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and one thermal cracking equation of volatiles. Finite rates are used for the heterogeneous solid-gas reactions. Both finite rate and eddy-breakup combustion models are calculated for each homogeneous gas-gas reaction, and the smaller of the two rates is used. Lagrangian-Eulerian method is employed. The Eulerian method calculates the continuous phase while the Lagrangian method tracks each coal particle. Fundamental study is carried out to investigate effects of five turbulence models (standard k-ε, k-ω, RSM, k-ω SST, and k-ε RNG) and four devolatilization models (Kobayashi, single rate, constant rate, and CPD) on gasification simulation. A study is also conducted to investigate the effects of different operation parameters on gasification process including coal mixture (dry vs. slurry), oxidant (oxygen-blown vs. air-blown), and different coal distributions between two stages. Finite-rate model and instantaneous gasification model are compared. It is revealed that the instantaneous gasification approach can provide an overall evaluation of relative changes of gasifier performance in terms of temperature, heating value, and gasification efficiency corresponding to parametric variations, but not adequately capture the local gasification process predicted by the finite rate model in most part of the gasifier. Simulations are performed to help with design modifications of a small industrial demonstration entrained-flow gasifier. It is discovered that the benefit of opening the slag tap on the quench-type gasifier wider by allowing slag to move successfully without clogging is compromised by increased heat losses, reduced gasification performance, downgraded syngas heating value, and increased unburned volatiles. The investigation of heat transfer on fuel injectors shows that blunt tip fuel injector is less likely to fail compared to conical tip fuel injector because the maximum high temperature on the injector is scattered. Two concentric fuel/oxidant injections provide better fuel-oxidant mixing and higher syngas heating value than four separate fuel and oxidant injections.
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Lu, Xijia. "An Applied Numerical Simulation of Entrained-Flow Coal Gasification with Improved Sub-models". ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1696.
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The United States holds the world's largest estimated reserves of coal and is also a net exporter of it. Coal gasification provides a cleaner way to utilize coal than directly burning it. Gasification is an incomplete oxidation process that converts various carbon-based feedstocks into clean synthetic gas (syngas), which can be used to produce electricity and mechanical power with significantly reduced emissions. Syngas can also be used as feedstock for making chemicals and various materials.
A Computational Fluid Dynamics (CFD) scheme has been used to simulate the gasification process for many years. However, many sub-models still need to be developed and improved. The objective of this study is to use the improved CFD modeling to understand the thermal-flow behavior and the gasification process and to provide guidance in the design of more efficient and cheaper gasifiers.
Fundamental research has been conducted to improve the gasification sub-models associated with the volatile thermal cracking, water-gas-shift (WGS) reaction, radiation effect, low-rank-coal gasification, coal to synthetic-natural-gas (SNG), and ash deposition mechanisms. The improved volatile thermal cracking model includes H2S and COS contents. A new empirical WGS reaction model is developed by matching the result with experimental data. A new coal demoisturization model is developed for evaporating the inherent moisture inside the coal particles during low-rank-coal gasification. An ash deposition model has also been developed. Moreover, the effect of different radiation models on the simulated result has been investigated, and the appropriate models are recommended.
Some improved model tests are performed to help modify an industrial entrained-flow gasifier. A two-stage oxygen feeding scheme and a unique water quench design are investigated. For the two-stage oxygen feeding design, both experimental data and CFD predictions verify that it is feasible to reduce the peak temperature and achieve a more uniform temperature distribution in the gasifier by controlling the injection scheme without changing the composition and production rate of the syngas. Furthermore, the CFD simulation can acceptably approximate the thermal-flow and reaction behaviors in the coal gasification process, which can then be used as a preliminary screening tool for improving existing gasifiers’ performance and designing new gasifiers.
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Young, Christopher Michael. "Pressure Effects on Black Liquor Gasification". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11539.
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Gasification of black liquor is an alternative to the combustion of black liquor, which is currently the dominant form of chemical recovery in the paper industry. Gasification of black liquor offers the possibility of higher thermal efficiencies than combustion, reducing manufacturing costs and creating new revenue streams through a forest biorefinery. Pressurizing the gasification reactor further enhances the efficiency advantage of gasification over combustion.
This study uses a pressurized entrained flow reactor (PEFR) to study black liquor gasification behavior under pressures, temperatures, and heating rates similar to those of next-generation high-temperature black liquor gasifiers. The effects of pressure on black liquor char morphology, gasification rates, pyrolysis carbon yields, and sulfur phase distribution were studied. These characteristics were investigated in three main groups of experiments at 900oC: pyrolysis (100% N2), gasification with constant partial pressure (0.25 bar H2O and 0.50 bar CO2), and gasification with constant mole fraction (10% CO2, 2% H2O, 1.7% CO, 0.3% H2), under five, ten, and fifteen bar total pressure.
It was found that pressure had an impact on the char physical characteristics immediately after the char entered the reactor. Increasing pressure had the effect of decreasing the porosity of the chars. Pressure also affected particle destruction and reagglomeration mechanisms. Surface areas of gasification chars decreased with increasing pressures, but only at low carbon conversions.
The rate of carbon conversion in gasification was shown to be a function of the gas composition near the particle, with higher levels of inhibiting gases slowing carbon conversion. The same phenomenon of product gas inhibition observed in gasification was used to explain carbon conversions in pyrolysis reactions.
Sulfur distribution between condensed and gas phases was unaffected by increasing total pressure in the residence times investigated. Significant amounts of sulfur are lost during initial devolatilization. With water present this gas phase sulfur forms H2S and did not return to the condensed phase.
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Duchesne, Marc A. "Slagging in Entrained-flow Gasifiers". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23353.
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Gasification is a flexible technology which is applied in industry for electricity generation, hydrogen production, steam raising and liquid fuels production. Furthermore, it can utilize one or more feedstocks such as coal, biomass, municipal waste and petroleum coke. This versatility, in addition to being adaptable to various emissions control technologies (including carbon capture) renders it an attractive option for years to come. One of the most common gasifier types is the entrained-flow slagging gasifier. The behaviour of inorganic fuel components in these gasifiers is still ill-understood even though it can be the determining factor in their design and operation. A literature review of inorganic matter transformation sub-models for entrained-flow slagging gasifiers is provided. Slag viscosity was identified as a critical property in the sub-models. Slag viscosity models are only applicable to a limited range of slag compositions and conditions, and their performance is not easily assessed. An artificial neural network model was developed to predict slag viscosity over a broad range of temperatures and slag compositions. Furthermore, a toolbox was developed to assist slag viscosity model users in the selection of the best model for given slag compositions and conditions, and to help users determine how well the best model will perform. The slag viscosities of coal, petroleum coke and coal/petroleum coke blends were measured in the temperature range of 1175-1650ºC. Interaction of vanadium-rich slags with various materials was investigated. The results from the first two parts of a three-part research program which involves fuel characterization, testing in a 1 MWth gasifier, and computational fluid dynamics (CFD) modeling for entrained-flow slagging gasification are presented. The end goal is to develop a CFD model which includes inorganic matter transformations. Fuel properties were determined with prioritization based on their application; screening of potential fuels, ensuring proper gasifier operation, gasifier design and/or CFD modeling. Using CanmetENERGY’s 1 MWth gasifier, five gasification tests were completed with the characterized coals. Solid samples from the refractory liners, in-situ gas sampling probe sheaths and impingers, the slag tap, the slag pot, quench discharge water and scrubber water were collected and characterized.
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Kumar, Mayank Ph D. Massachusetts Institute of Technology. "Multiscale CFD simulations of entrained flow gasification". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69495.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references.
The design of entrained flow gasifiers and their operation has largely been an experience based enterprise. Most, if not all, industrial scale gasifiers were designed before it was practical to apply CFD models. Moreover, gasification CFD models developed over the years may have lacked accuracy or have not been tested over a wide range of operating conditions, gasifier geometries and feedstock compositions. One reason behind this shortcoming is the failure to incorporate detailed physics and chemistry of the coupled non-linear phenomena occurring during solid fuel gasification. In order to accurately predict some of the overall metrics of gasifier performance, like fuel conversion and syngas composition, we need to first gain confidence in the sub-models of the various physical and chemical processes in the gasifier. Moreover, in a multiphysics problem like gasification modeling, one needs to balance the effort expended in any one submodel with its effect on the accuracy of predicting some key output parameters. Focusing on these considerations, a multiscale CFD gasification model is constructed in this work with special emphasis on the development and validation of key submodels including turbulence, particle turbulent dispersion and char consumption models. The integrated model is validated with experimental data from various pilot-scale and laboratory-scale gasifier designs, further building confidence in the predictive capability of the model. Finally, the validated model is applied to ascertain the impact of changing the values of key operating parameters on the performance of the MHI and GE gasifiers. The model is demonstrated to provide useful quantitative estimates of the expected gain or loss in overall carbon conversion when critical operating parameters such as feedstock grinding size, gasifier mass throughput and pressure are varied.
by Mayank Kumar.
Ph.D.
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Rasid, Ruwaida Abdul. "Modelling and simulation of entrained flow gasification processes". Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595675.
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Depletion of conventional fossil fuel resources, as well as concerns regarding their environmental impact is a driving factor in the search for cleaner alternative fuels. Through the gasification of solid fuels, the produced syngas can be reacted to produce a cleaner, alternative liquid fuel. This thesis presents the development and use of a combination of fundamental and process models to evaluate alternative fuel production through a pressurised entrained flow gasification process. These include an equilibrium model, a one dimensional model and a process model. An equilibrium model using the non-stoichiometric approach based on the minimisation of Gibbs free energy and the Lagrange multipliers was established. A series of evaluations were performed to study the impact of the process conditions related to the entrained flow gasification, at the same time validating the model through comparisons with commercial software. It was shown that the model was not only quick to be developed, the results were also in excellent agreement with the commercial software it was compared to. A detailed one dimensional model of an entrained flow gasifier was developed from first principles. It is more complex than the equilibrium model, as it allows for evaluation of the variables along the length of the gasifier. Review of the available one-dimensional models of entrained flow gasifiers in the literature revealed inconsistent implementation of heat transfer mechanisms. The study showed that the solid-wall radiation along with the heterogeneous heat of reactions were the dominant heat transfer mechanisms in the entrained flow gasifier. In addition, although this model was developed specifically for a coal gasification process, assessment of biomass addition was also studied. ]t was shown that the best biomass mixtures were between 25% - 50%. A process model was developed in AspenHYSYS, which has enabled the entrained flow gasifier to be integrated with related auxiliary process equipment to model desired operating conditions. Implementation of the coal and biomass gasification for a polygeneration process is promising. Technoeconomic studies reveal that although biomass introduction may increase the costs of fuel, they are more environmentally-friendly as negative carbon emission can be achieved.
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Gibbs, Laura Anne. "Coal devolatilization in an entrained flow reactor". Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/6029.
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Joyce, James Alexander. "Pressurised entrained flow gasification of sugar cane wastes for cogeneration /". [St. Lucia, Qld.], 2006. http://adt.library.uq.edu.au/public/adt-QU20060713.095935/index.html.
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Hägglund, Philip. "Commissioning of Entrained Flow Reactor for Combustion and Gasification Research". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66204.
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Carlsson, Per. "Entrained flow black liquor gasification : detailed experiments and mathematical modelling". Licentiate thesis, Luleå : Luleå university of technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3076792.
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Tremel, Alexander [Verfasser]. "Reaction Kinetics of Solid Fuels during Entrained Flow Gasification / Alexander Tremel". München : Verlag Dr. Hut, 2013. http://d-nb.info/1031843787/34.
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Ma, Charlie. "Slag Formation During Pilot-Scale Pressurised Entrained-Flow Gasification of Woody Biomass". Licentiate thesis, Luleå tekniska universitet, Energivetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18723.
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Pressurised entrained‐flow gasification (PEFG) of sustainable woody biomass offers the opportunity for envi-ronmentally benign production of syngas that is suitable for synthesis of fuels and other chemicals. During the PEFG process, ash-forming matter in the fuel undergoes transformations. Slag formation is an important form of ash transformation that occurs inside a PEFG reactor. In most industrial-scale PEFG of coal, the ash-forming matter becomes predominately molten and flows down the side of the reactor wall to be continuously tapped and removed. The slagging behaviour of woody biomass fuels during PEFG is expected to be different to that of coal, due to significant differences in the amount, composition and reactivity of the ash-forming matter. The objective of this thesis study was to initiate the elucidation of slag formation during PEFG of woody biomass. This was carried out by obtaining and characterising ash deposits and slags from pilot-scale experimental cam-paigns. An oxygen-fired pilot-scale reactor (ETC Piteå, Sweden) was used for the study. A low reactor temperature (< 1200 °C) study was carried out with three different fuels fired in separate experimental campaigns: stem wood, bark and pulp mill debarking residue (PMDR). Deposits were taken from each of the campaigns from the reactor for chemical characterisation. The stem wood fuel resulted in very little deposit that exhibited only minor amounts of melt, or slag, formation with enrichment of Si. The bark and PMDR fuels resulted in larger amounts of deposits with greater amounts of melt formation that were also enriched in Si. It was found that silica-based fuel contaminants, e.g., quartz sand and feldspars, may have an important role in melt formation. Following on, high reactor temperature (> 1350 °C) experimental campaigns involving stem wood produced flowing slags that eventuated in blockages of the reactor outlet. These slags were also retrieved from the reactor and characterised. It was found that they likely comprised of products resulting from detrimental interactions between the fuel ash and the mullite-based refractory used for the reactor wall lining. Viscosity models and thermochemical equilibrium calculations (TECs) were utilised to offer an explanation for the behaviour of the slags. Additional TECs were carried out to investigate the propensity for melt formation between the main ash-forming elements of woody biomass, Ca, K and Si, under global reactor conditions with relevance to PEFG. The results showed that, in general, the conditions for melt formation are broadened with increasing pressure, increasing amounts of Si and increased concentrations of gaseous K species. Dissolution of Al₂O₃ from mullite (Al₆Si₂O₁₃) refractory due to ash deposits and the gasification atmosphere was also predicted by the calculations. A scheme of slag formation during PEFG of woody biomass in a reactor with mullite-based refractory lining was proposed in light of the experimental observations. Some practical suggestions to avoid ash-related problems during PEFG of woody biomass are also discussed. This work forms part of a broader study to elucidate the ash transformations that occur during PEFG of woody biomass, which is necessary in order to develop the process into commercial availability.Godkänd; 2014; 20141102 (chamaf); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Charlie Ma Ämne: Energiteknik/Energy Engineering Uppsats: Slag Formation During Pilot-Scale Pressurised Entrained-Flow Gasification of Woody Biomass Examinator: Professor Marcus Öhman, Institutionen för teknikvetenskap och matematik, Luleå Tekniska universitet Diskutant: Universitetslektor Christoffer Boman, Umeå Universitet Tid: Fredag den 12 december 2014 kl 10.00 Plats: E246, Luleå tekniska universitet
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Mackrory, Andrew John. "Characterization of Black Liquor Sprays for Application to Entrained-Flow Processes". Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1593.pdf.
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Jafri, Yawer. "Entrained-Flow Gasification of Black Liquor and Pyrolysis Oil : Experimental and Equilibrium Modelling Studies of Catalytic Co-gasification". Licentiate thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60342.
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The last couple of decades have seen entrained-flow gasification of black liquor (BL) undergo an incremental process of technical development as an alternative to combustion in a recovery boiler. The ability of the technology to combine chemical recovery with the production of clean syngas renders it a promising candidate for the transformation of chemical pulp mills into integrated forest biorefineries. However, techno-economic assessments have shown that blending BL with the more easily transportable pyrolysis oil (PO) can not only increase the system efficiency for methanol production but remove a significant roadblock to development by partially decoupling production capacity from limitations on black liquor availability. The verification and study of catalytic co-gasification in an industrially-relative scale can yield both scientifically interesting and practically useful results, yet it is a costly and time-consuming enterprise. The expense and time involved can be significantly reduced by performing thermodynamic equilibrium calculations using a model that has been validated with relevant experimental data. The main objective of this thesis was to study, understand, quantify and compare the gasification behaviour and process performance of black liquor and pyrolysis oil blends in pilot-scale. A secondary objective of this work was to demonstrate and assess the usefulness and accuracy of unconstrained thermodynamic equilibrium modelling as a tool for studying and predicting the characteristics of alkali-impregnated biomass entrained-flow gasification. The co-gasification of BL/PO blends was studied at the 3 MWth LTU Green Fuels pilot plant in a series of experimental studies between June 2015 and April 2016. The results of the studies showed that the blending of black liquor with the more energy rich pyrolysis oil increased the energetic efficiency of the BLG process without adversely affecting carbon conversion. The effect of blend ratio and reactor temperature on the gasification performance of PO and BL blends with up to 20 wt% PO was studied in order to assess the impact of alkali-dilution in fuel on the conversion characteristics. In addition to unblended BL, three blends with PO/BL ratios of 10/90, 15/85 and 20/80 wt% were gasified at a constant load of 2.75 MWth. The decrease in fuel inorganic content with increasing PO fraction resulted in more dilute green liquor (GL) and a greater portion of the feedstock carbon ended up in syngas as CO. As a consequence, the cold gas efficiency increased by about 5%-units. Carbon conversion was in the range 98.8-99.5% and did not vary systematically with either fuel composition or temperature. The validation of thermodynamic equilibrium simulation of black liquor and pyrolysis co-gasifications with experimental data revealed the need to be mindful of errors and uncertainities in fuel composition that can influence predictions of equilibrium temperature. However, provided due care is to taken to ensure the use of accurate fuel composition data, unconstrained TEMs can serve as a robust and useful tool for simulating catalytic entrained-flow gasification of biomass-based feedstocks.LTU Biosyngas (Catalytic Gasification)
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Eriksson, Anna-Maria. "Torrefaction and gasification of biomass. The potential of torrefaction combined with entrained-flow gasification for production of synthesis gas". Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-146313.
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Torrefaction of biomass together with gasification in entrained-flow reactors is a new possible way of producing synthesis gas. The synthesis gas can later be used for the production of renewable liquid fuels. This is highly desirable since the transport sector consumes a high amount of fossil fuels that has to be exchanged for renewable fuels in the future. It is hard to tell if the technology above is an advantageous way or not to produce synthesis gas since it is very newly developed. A lot of obstacles exist such as the injection of the torrefied wood into the gasifier, the optimization of the ash flow down the entrained flow reactor and the high energy consumption of the drying. Investigation in the form of material and energy balances shows that the system can have as high energy efficiency as 73% and cold gas efficiency of 74% which is only slightly less then what the fluid-bed gasification has. Torrefaction and gasification developers allocate huge amount of money to develop torrefaction and entrained-flow gasification units. Interviews show that many experts believe that the technology will be commercial and used to produce renewable liquid fuels in the future.
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Lee, Ching Yuan. "Problems involved in simulating the flash carbonization process". Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183048088.
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Blanchard, Ryan P. "Measurements and Modeling of Coal Ash Deposition in an Entrained-Flow Reactor". Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2376.pdf.
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DeYoung, Stefan [Verfasser]. "Numerical Simulation of Entrained Flow Gasification with Focus on Char Reaction Kinetics / Stefan DeYoung". München : Verlag Dr. Hut, 2019. http://d-nb.info/1188516086/34.
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Pugalia, Neeraj. "Numerical modeling of cold flow and hot gas desulfurization in a circulating fluidized bed". Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2056.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xvi, 119 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 103-106).
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Legonda, Isack Amos. "Biomass gasification using a horizontal entrained-flow gasifier and catalytic processing of the product gas". Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/39280/.
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A novel study on biomass-air gasification using a horizontal entrained-flow gasifier and catalytic processing of the product gas has been conducted. The study was designed to investigate the effect of catalyst loading on the product gas. The use of a horizontal entrained-flow gasifier reactor was used to assess the effect of the gasifier reactor orientation on the gasification process. Both experimental and computational fluid dynamics (CFD) approaches were employed. The gasification tests were conducted at 800 oC and equivalence ratio of 0.23 while the product gas was catalysed at 350-400 oC and a gas hourly space velocity (GHSV) of 8000 h-1. Preparation and characterisation of wood powder and catalysts were performed using classical methods. Moreover, the syngas and tar composition were analysed using a gas chromatograph (GC) and GC-mass spectrometer (GC-MS) respectively. The research findings showed that maximum fuel conversion and cold gas efficiency using a horizontal entrained-flow gasifier were 99 % and 70 % respectively. The gasifier length can also be reduced from the common 1000-2000 mm to 500 mm. The catalysis study showed that pumice and kaolin have limited catalytic effect on the product gas. However, doping with CeO2, ZrO2, CuO and NiO improved the syngas heating value, coking resistance and tar conversion. A notable increase in syngas LHV was achieved using ceria doped pumice (8.97 MJ/Nm3) and copper doped pumice (8.66 MJ/Nm3) compared to 6.67 MJ/Nm3 of non-catalytic test. For the tested catalysts, CeO2 doped pumice exhibited highest coking resistance. Furthermore, catalytic tar conversion was mainly through cracking and partial oxidation reactions. The lowest tar yield was found to be 3.55 g/Nm3 using kaolin-ceria-zirconia catalyst compared to 14.92 g/Nm3 of non-catalytic gasification. Tar reduction using untreated pumice was through adsorption and ranged 4-6 g/Nm3. In general, the results of this study suggest that there exist a sensitivity to the gasifier orientation on the overall gasification process. It has also shown that metal oxides have both beneficial and detrimental effects of syngas composition. Although syngas heating value increased with increasing catalyst loading, H2 showed a decreasing trend highlighting that further catalyst modification is required. Furthermore, pumice and kaolin can be utilised as catalyst support in the gasification technology. However, further experimental investigation on doping various catalytic metals and testing at different operating conditions are hereby proposed.
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Ma, Charlie. "Aspects of Ash Transformations in Pressurised Entrained-Flow Gasification of Woody Biomass : Pilot-scale studies". Doctoral thesis, Luleå tekniska universitet, Energivetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62914.
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Pressurised entrained-flow gasification (PEFG) of woody biomass has the potential to produce high purity syngas for the production of vital chemicals, e.g., biofuels. However, ash-related issues such as reactor blockages and refractory corrosion need to be addressed before this potential can be realised from a technical perspective. These undesirable consequences can be brought about by slag formation involving inorganic ash-forming elements and the chemical transformations that they undergo during fuel conversion. The objective of this study was to elucidate the ash transformations of the major ash-forming elements and the slag formation process. A pilot-scale PEFG reactor was used as the basis of the study, gasifying different woody biomass-based fuels including wood, bark, and a bark/peat mixture. Different ash fractions were collected and chemically analysed. Reactor slags had elemental distributions differing from that of the fuel ash, indicating the occurrence of fractionation of ash material during fuel conversion. Fly ash particles from a bark campaign were also heterogeneous with particles exhibiting differing compositions and physical properties; e.g., molten and crystalline formations. Si was consistently enriched in the reactor slags compared to other major ash-forming elements, while analyses of other ash fractions indicated that K was likely volatilised to a significant extent. In terms of slag behaviour, near-wall temperatures of approximately 1050-1200 °C inside the reactor were insufficient to form flowing ash slag for continuous extraction of ash material during firing the woody biomass fuels alone. However, fuel blending of a bark fuel with a silica-rich peat changed the chemical composition of the reactor slags and bulk slag flow behaviour was evident. Thermochemical equilibrium calculations supported the importance of Si in melt formation and in lowering solidus and liquidus temperatures of Ca-rich slag compositions that are typical from clean wood and bark. Viscosity estimations also showed the impact that solids have upon slag flow behaviour and corresponded qualitatively to the experimental observations. Corrosion of reactor refractory was observed. The mullite-based refractory of the reactor formed a slag with the fuel ash slag, which caused the former to flux away. Reactor blockages were also resultant because of the high viscosity of this slag near the outlet. A preliminary study into the corrosion of different refractories was also carried out, based on firing a bark/peat mixture. Alumina-rich refractories consisting of corundum, hibonite, mullite, and andalusite tended to form anorthite and exhibited varying degrees of degradation. Infiltration of slag was evident for all the samples and was a severe mode of degradation for some refractories. For fused-cast periclase and spinel-based refractories, slag infiltration was limited to voids and no extensive signs of refractory dissolution were found. This is also supported by a thermochemical equilibrium calculations mimicking slag infiltration that incorporated viscosity estimations. The findings from this thesis contribute towards the development of woody biomass PEFG by highlighting issues concerning ash fractionation, slag behaviours and ash\slash refractory interaction that should be investigated further.
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Soncini, Ryan Michael. "Computational Simulation of Coal Gasification in Fluidized Bed Reactors". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/78733.
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The gasification of carbonaceous fuel materials offers significant potential for the production of both energy and chemical products. Advancement of gasification technologies may be expedited through the use of computational fluid dynamics, as virtual reactor design offers a low cost method for system prototyping. To that end, a series of numerical studies were conducted to identify a computational modeling strategy for the simulation of coal gasification in fluidized bed reactors.
The efforts set forth by this work first involved the development of a validatable hydrodynamic modeling strategy for the simulation of sand and coal fluidization. Those fluidization models were then applied to systems at elevated temperatures and polydisperse systems that featured a complex material injection geometry, for which no experimental data exists. A method for establishing similitude between 2-D and 3-D multiphase systems that feature non-symmetric material injection were then delineated and numerically tested.
Following the development of the hydrodynamic modeling strategy, simulations of coal gasification were conducted using three different chemistry models. Simulated results were compared to experimental outcomes in an effort to assess the validity of each gasification chemistry model. The chemistry model that exhibited the highest degree of agreement with the experimental findings was then further analyzed identify areas of potential improvement.Ph. D.
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Fradet, Quentin [Verfasser], i Uwe [Akademischer Betreuer] Riedel. "Novel modeling approaches for the entrained-flow gasification of bio-slurries / Quentin Fradet ; Betreuer: Uwe Riedel". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1217253424/34.
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Panday, Rupendranath. "Modeling, identification and control of a cold flow circulating fluidized bed". Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5833.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains xiii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 94-99).
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Wu, Chunyang. "Fuel-NOx Formation during Low-Grade Fuel Combustion in a Swirling-Flow Burner". Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1165.pdf.
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Vargas, Duarte Gerardo. "An experimental study of the hydrodynamics of multiphase flow in fluidized beds". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Marklund, Magnus. "Pressurized entrained-flow high temperature black liquor gasification : CFD based reactor scale-up method and spray burner characterization /". Luleå : Division of Fluid Mechanics, Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1544/2006/42LTU-DT-0642-SE.pdf.
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Kestel, Matthias. "Numerical modeling of moving carbonaceous particle conversion in hot environments". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-204732.
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The design and optimization of entrained flow gasifiers is conducted more and more via computational fluid dynamics (CFD). A detailed resolution of single coal particles within such simulations is nowadays not possible due to computational limitations. Therefore the coal particle conversion is often represented by simple 0-D models. For an optimization of such 0-D models a precise understanding of the physical processes at the boundary layer and within the particle is necessary.
In real gasifiers the particles experience Reynolds numbers up to 10000. However in the literature the conversion of coal particles is mainly regarded under quiescent conditions. Therefore an analysis of the conversion of single particles is needed. Thereto the computational fluid dynamics can be used.
For the detailed analysis of single reacting particles under flow conditions a CFD model is presented. Practice-oriented parameters as well as features of the CFD model result from CFD simulations of a Siemens 200MWentrained flow gasifier. The CFD model is validated against an analytical model as well as two experimental data-sets taken from the literature. In all cases good agreement between the CFD and the analytics/experiments is shown.
The numerical model is used to study single moving solid particles under combustion conditions. The analyzed parameters are namely the Reynolds number, the ambient temperature, the particle size, the operating pressure, the particle shape, the coal type and the composition of the gas. It is shown that for a wide range of the analyzed parameter range no complete flame exists around moving particles. This is in contrast to observations made by other authors for particles in quiescent atmospheres. For high operating pressures, low Reynolds numbers, large particle diameters and high ambient temperatures a flame exists in the wake of the particle. The impact of such a flame on the conversion of the particle is low. For high steam concentrations in the gas a flame appears, which interacts with the particle and influences its conversion.
Furthermore the impact of the Stefan-flow on the boundary layer of the particle is studied. It is demonstrated that the Stefan-flow can reduce the drag coefficient and the Nusselt number for several orders of magnitude. On basis of the CFD results two new correlations are presented for the drag coefficient and the Nusselt number. The comparison between the correlations and the CFD shows a significant improvement of the new correlations in comparison to archived correlations.
The CFD-model is further used to study moving single porous particles under gasifying conditions. Therefore a 2-D axis-symmetric system of non-touching tori as well as a complex 3-D geometry based on the an inverted settlement of monodisperse spheres is utilized. With these geometries the influence of the Reynolds number, the ambient temperature, the porosity, the intrinsic surface and the size of the radiating surface is analyzed. The studies show, that the influence of the flow on the particle conversion is moderate. In particular the impact of the flow on the intrinsic transport and conversion processes is mainly negligible. The size of the radiating surface has a similar impact on the conversion as the flow in the regarded parameter range.
On basis of the CFD calculations two 0-D models for the combustion and gasification of moving particles are presented. These models can reproduce the results predicted by the CFD sufficiently for a wide parameter range.
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Tremel, Alexander [Verfasser], Hartmut [Akademischer Betreuer] Spliethoff i Thomas [Akademischer Betreuer] Kolb. "Reactions Kinetics of Solid Fuels during Entrained Flow Gasification / Alexander Tremel. Gutachter: Hartmut Spliethoff ; Thomas Kolb. Betreuer: Hartmut Spliethoff". München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1031550658/34.
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Strandberg, Martin. "From torrefaction to gasification : Pilot scale studies for upgrading of biomass". Doctoral thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-103046.
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Increasing the share of biomass, preferably by replacing fossil fuels, is one way to mitigate the present climate change. Fossil coal can be directly replaced by co-combustion of coal and biomass and fossil engine fuels (gasoline and diesel) could potentially partly be replaced by synthetic renewable fuels produced via entrained flow gasification of biomass. The use of biomass in these processes is so far limited, partly because of the fibrous and hygroscopic nature of biomass which leads to problem in storing, transportation, handling and feeding. This thesis demonstrates how the challenging characteristics of raw biomass are mitigated by the pretreatment method torrefaction. Torrefaction is a process where biomass is heated in an oxygen deficient atmosphere to typically between 240 and 350°C for a time period of 2 minutes to 1 hour. Most of the torrefaction R&D in the literature have so far been performed with bench-scale batch reactors. For the purpose of carefully studying continuous torrefaction, a 20 kg/h torrefaction pilot plant was therefore designed, constructed and evaluated. The overall conclusion from this thesis is that the many benefits of torrefied biomass are valid also when produced with a continuous pilot plant and for typically Swedish forest biomasses. Some of the documented improved biomass properties are increased heating value, increased energy density, higher friability (lower milling energy) and less hydrophilic biomass (less moisture uptake). Most of the improvements can be attributed to the decomposition of hemicellulose and cellulose during torrefaction. The most common variables for describing the torrefaction degree are mass yield or anhydrous weight loss but both are challenging to determine for continuous processes. We therefore evaluated three different methods (one existing and two new suggestions) to determine degree of torrefaction that not require measurement of mass loss. The degree of torrefaction based on analyzed higher heating value of the raw and torrefied biomass (DTFHHV) predicted mass yield most accurate and had lowest combined uncertainty. Pelletizing biomass enhance transportation and handling but results from pelletization of torrefied biomass is still very limited in the literature and mainly reported from single pellet presses. A pelletization study of torrefied spruce with a ring die in pilot scale was therefore performed. The bulk energy density was found to be 14.6 GJ/m3 for pelletized torrefied spruce (mass yield 75%), a 40% increase compared to regular white pellets and therefore are torrefied pellets more favorable for long distance transports. More optimization of the torrefied biomass and the pelletization process is though needed for acquiring industrial quality pellets with lower amount of fines and higher pellet durability than attained in the present study. Powders from milled raw biomass are generally problematic for feeding and handling and torrefied biomass has been proposed to mitigate these issues. The influence of torrefaction and pelletization on powder and particle properties after milling was therefore studied. The results show that powder from torrefied biomass were enhanced with higher bulk densities, lower angle of repose as well as smaller less elongated particles with less surface roughness. Even higher powder qualities were achieved by pelletizing the torrefied biomass before milling, i.e. another reason for commercial torrefied biomass to be pelletized. Entrained flow gasification (EFG) is a promising option for conversion of biomass to other more convenient renewable energy carriers such as electricity, liquid biofuels and green petrochemicals. Also for EFGs are torrefied fuels very limited studied. Raw and torrefied logging residues were successfully gasified in a pilot scale pressurized entrained flow biomass gasifier at 2 bar(a) with a fuel feed corresponding to 270 kWth. Significantly lower methane content (50% decrease) in the syngas was also demonstrated for the torrefied fuel with mass yield 49%. The low milling energy consumption for the torrefied fuels compared to the raw fuel was beneficial for the gasification plant efficiency.
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Septien, Stringel Joël. "High temperature gasification of millimetric wood particles between 800°C and 1400°C". Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0125/document.
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La gazéification de la biomasse a été étudiée dans les conditions d'un réacteur à flux entraîné, à savoir à vitesse de chauffage et à température élevées. Des expériences ont été réalisées dans un four à chute entre 800°C et 1400°C, à partir de particules de bois de taille 0,35 mm et 0,80 mm, dans une atmosphère inerte (100% molaire de N2), ou contenant de la vapeur d’eau (25% molaire). Les expériences ont également été simulées grâce à un modèle 1D avec des résultats positifs, ce qui a permis de mieux comprendre les phénomènes mis en jeu. Les solides obtenus (suies et char) ont été analysés et caractérisés. Des rendements élevés en gaz et goudrons, et un faible rendement en char ont été mesurés. Par conséquent, l'évolution de la phase volatile est déterminante pour les rendements des produits finaux. Au-dessus de 1000°C, la formation de suies devient importante. Les suies sont formées à partir de C2H2 et de HAP. En présence de vapeur d’eau, le rendement en suies est nettement moins élevé, ce qui s’explique essentiellement par le vaporeformage des précurseurs de suie, mais aussi par leur gazéification. La réaction de water-gas shift joue un rôle important dans la distribution des gaz majoritaires. La gazéification du char a été mise en évidence à 1200°C et 1400°C sous atmosphère humide. L'ensemble de ces réactions conduit à un gaz riche en H2, CO et CO2. L'équilibre thermodynamique est presque atteint à 1400°C avec une concentration de 25% molaire de H2O dans l’atmosphère. La graphitisation et la désactivation du char porté à haute température ont été mises en évidence expérimentalement. Néanmoins, ces phénomènes ont une influence négligeable sur l’évolution du rendement en char lors des expériences en four à chute. Enfin, la taille des particules n’a presque aucune influence sur les résultats expérimentauxBiomass gasification was studied in the conditions of an entrained flow reactor, namely at high heating rate and temperature. Experiments in a drop tube reactor were performed between 800°C and 1400°C, with wood particles of 0.35 mm and 0.80 mm size, under inert and steam containing - 25 mol% of H2O - atmospheres. These experiments were also simulated with a 1D model which gave good predictions. The collected solids, soot and char, were analyzed and characterized. This study highlights the importance of gas phase reactions on the yields of the final products, mainly gaseous compounds, in these conditions. These reactions are hydrocarbons cracking, reforming and polymerization, leading to soot formation, and water-gas shift. Char graphitization and deactivation were experimentally demonstrated. However, these phenomena have a negligible influence on char evolution in the drop tube reactor. Finally, the particle size was shown to have almost no influence on experimental results
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Bayham, Samuel C. "Iron-Based Coal Direct Chemical Looping Process for Power Generation: Experimental Aspects, Process Development, and Considerations for Commercial Scale". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1425759077.
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Lu, You. "Computational Scheme Guided Design of a Hybrid Mild Gasifier". ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1526.
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A mild gasification method has been developed to provide an innovative clean coal technology. The objectives of this study are to (a) incorporate a fixed rate devolatilization model into the existing 2D multiphase reaction model, (b) expand the 2D model to 3D and (c) utilize the improved model to investigate the mild-gasification process and guide modification of the mild-gasifier design. The Eulerain-Eulerian method is employed to calculate both the primary phase (air) and secondary phase (coal particles). The improved 3D simulation model, incorporated with a devolatilization model, has been successfully developed and employed to determine the appropriate draft tube dimensions, entrained flow residence time, The simulations also help determine the appropriate operating fluidization velocity range to sustain the fluidized bed depth without depleting the chars or blowing the char away. The results are informative, but require future experimental data for verification.
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Schrier, Loren Clare. "Identification of by-products and investigation into the dechlorination mechanism of the Chemchar cocurrent flow gasification process by gas chromatography-mass selective detection /". free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9904867.
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Thesis (Ph. D.)--University of Missouri-Columbia, 1998.Trademark symbol follows Chemchar in title. Typescript. Vita. Includes bibliographical references (leaf 130). Also available on the Internet.
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Mazumder, AKM Monayem Hossain. "Development of a Simulation Model for Fluidized Bed Mild Gasifier". ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/101.
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A mild gasification method has been developed to provide an innovative clean coal technology. The objective of this study is to developed a numerical model to investigate the thermal-flow and gasification process inside a specially designed fluidized-bed mild gasifier using the commercial CFD solver ANSYS/FLUENT. Eulerain-Eulerian method is employed to calculate both the primary phase (air) and secondary phase (coal particles). The Navier-Stokes equations and seven species transport equations are solved with three heterogeneous (gas-solid), two homogeneous (gas-gas) global gasification reactions. Development of the model starts from simulating single-phase turbulent flow and heat transfer to understand the thermal-flow behavior followed by five global gasification reactions, progressively with adding one equation at a time. Finally, the particles are introduced with heterogeneous reactions. The simulation model has been successfully developed. The results are reasonable but require future experimental data for verification.
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Gärtner, Lars-Erik. "Modellierung und Simulation der Vergasung von Brennstoffmischungen". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-184350.
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Mit Hilfe eines variabel einsetzbaren Reaktornetzwerkmodells (RNM) wird in der vorliegenden Dissertation der Prozess der Vergasung von Brennstoffmischungen in der Fließbildsimulation beschrieben. Neben der Untersuchung von gestuften Prozessketten zur Veredelung von kohlenstoffhaltigen Energieträgern ist damit auch die differenzierte Analyse von Effekten während der Vergasung von binären und ternären Brennstoffmischungen möglich. Die Erstellung sowie Validierung des RNM wird anhand des PEFR-Vergasers, des SFGT-Vergasers und des Hybridwandvergaser vorgenommen. Die anschließende Analyse der Vergasung von Brennstoffmischungen zeigt, dass in ihren Eigenschaften sehr heterogene Brenn¬stoffmischungen Synergieeffekte bei der Vergasung hervorrufen. Diese sind in der Literatur schon oft beschrieben worden, eine systematische Analyse wird jedoch erst in der vorliegenden Dissertation durchgeführtWithin this document the modeling and simulation of fuel blend gasification is investigated based on a variably applicable Reduced Order Model (ROM) developed for the flowsheet simulation of entrained-flow gasification reactors and processes. On one hand this enables the investigation of cascaded solid fuel conversion technologies and on the other hand effects during gasification of binary and ternary fuel blends are describable. The development as well as the validation of the ROM has been carried out for the SFGT gasifier, the PEFR gasifier and the hybrid-wall gasifier. The subsequent analysis of binary and ternary fuel blend gasification shows that fuel blends with very heterogeneous component properties induce synergy effects which have been reported in various peer review publications
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Billaud, Joseph. "Gazéification de la biomasse en réacteur à flux entrainé : études expérimentales et modélisation". Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0010/document.
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Ce travail porte sur l'étude de la gazéification de biomasse en Réacteur à Flux Entrainé (RFE), dans le contexte du développement de procédés pour la production de biocarburants de deuxième génération. L'objectif de cette thèse est de modéliser les différents phénomènes qui régissent la conversion de la biomasse dans des conditions représentatives d'un RFE. La pyrolyse et la gazéification de particules de hêtre de taille comprise entre 315 et 415 µm ont été étudiées entre 800 et 1400°C en four à chute de laboratoire. L'influence de l'ajout de H2O, de CO2 et de O2 sur les produits de gazéification a été explorée, et les essais ont été simulés à partir d'un modèle 1D. L'ajout de H2O ou de CO2 permet de diminuer les rendements en char de manière significative. En phase gaz, l'influence principale de ces deux espèces est la modification de la composition en espèces majoritaires avec la réaction de gaz à l'eau. L'ajout de O2 a pour effet d'améliorer la conversion du carbone de la biomasse en gaz, et de réduire de manière significative la production de suies et de char. Le modèle, basé sur une chimie détaillée, permet de simuler ces essais de façon très satisfaisante sur toute la gamme de variation des conditions opératoires. La pyrolyse et la gazéification de particules de hêtre tamisées entre 1,12 et 1,25 mm a été étudiée en présence de O2. À 800, 1000 et 1200°C, la conversion de ces « grosses » particules est plus faible que celles des petites particules, mais à 1400°C la taille de particule n'a pas d'influence. Enfin, une étude expérimentale a été menée dans un RFE pilote pour étudier l'influence de la quantité de O2, de la taille de particule et de la pression sur la gazéification de particules de bois. Ces essais ont été simulés de façon satisfaisante en adaptant le modèle 1DThe present work deals with biomass gasification in Entrained Flow Reactor (EFR) in the context of the development of new Biomass-to-Liquid processes. The objective of this study is to develop a comprehensive model to better understand the phenomena controlling biomass gasification in conditions representative of an EFR. Biomass pyrolysis and gasification of beech particles sieved between 315 and 450 µm have been studied between 800 and 1400°C in a drop tube furnace. The influence of H2O, CO2 and O2 addition on gasification products has been investigated and the tests have been simulated with a 1D model. The addition of H2O or CO2 leads to a significantly lower char yield. The main influence of these two oxidants in gas phase is the modification of major species composition with water gas shift reaction. With the addition of O2, the carbon conversion into gas is improved and the char and soot yields are significantly lower. The simulations are in very good agreement with the experimental results. Biomass pyrolysis and gasification of beech particles sieved between 1.12 and 1.25 mm have been studied in presence of O2. Between 800 and 1200°C the carbon conversion into gas is lower than with the smaller particles but at 1400°C the particle size has no influence. At last, the influence of O2 addition, particle size and pressure on biomass gasification has been studied in a pilot scale EFR. These experimental results have been satisfactorily simulated by adapting the 1D model
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Meillot, Erick. "Contribution a l'etude d'un plasma d'arc de vapeur d'eau : application a la gazeification de charbon pulverise en plasma d'arc". Toulouse 3, 1988. http://www.theses.fr/1988TOU30030.
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On presente le developpement d'un prototype preindustriel d'une torche a plasma d'arc de vapeur d'eau. Calcul des proprietes thermodynamiques (composition chimique, enthalpie massique, chaleur specifique) du systeme ar/h::(2)o, a pression constante, entre 700 et 15000 k. On presente les evolutions des coefficients de transport du systeme ar/h::(2)o en fonction de la temperature. La thermolyse de l'eau est abordee a l'aide d'un modele numerique. Dimensionnement d'un reacteur plasma pour la synthese de gaz produit sont calcules pour differents types de charbon. Modele numerique de simulation de la gazeification de charbon pulverise dans un reacteur a lit entraine avec prise en compte de la granulometrie
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Boigelot, Romain. "Gazéification de déchets organiques dans un réacteur à flux entrainé : impact des inorganiques sur le fonctionnement du réacteur et choix des céramiques réfractaires". Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00835075.
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La gazéification de la biomasse permet d'obtenir un gaz de synthèse riche en CO et H2 utilisable pour la production d'électricité, de biocarburants ou de composés chimiques. Ce procédé permet de palier à l'épuisement des ressources fossiles. L'utilisation de boues d'épuration comme ressources de biomasse assurerait à ce type de déchets organiques une valorisation énergétique. Cependant, les boues contiennent une forte charge minérale (entre 30 et 50% massique). Cette fraction est composée d'une vingtaine d'oxyde notamment la silice, la chaux et l'oxyde de phosphore, P2O5 (plus de 15%).Les boues sont des systèmes complexes très peu étudiés jusqu'à présent. Il est donc nécessaire de connaitre le comportement en température des inorganiques afin de mesurer leur impact lors du processus de gazéification et de se prémunir contre les risques de corrosion et de pollution du gaz liés à leur présence. - Dans un premier temps, les températures de liquidus de deux fractions minérales de boues ont été déterminées. Il s'avère que celles-ci, comprises entre 1257°C et 1358°C, sont dans la plage opératoire d'un gazéifieur à lit entrainé. De plus, une étude menée sur le binaire SiO2-P2O5 a permis d'améliorer les bases de données thermodynamiques. - Dans un second temps, les études thermodynamiques et cinétiques de volatilisation du phosphore ont mis en évidence le faible relâchement en température du phosphore grâce à la formation de phases réfractaires associant l'oxyde de phosphore et la chaux tel que Ca3(PO4)2 et Ca9Fe(PO4)7. La volatilité des inorganiques des boues est inférieure à 0.5% massique. - Enfin, l'interaction entre les inorganiques liquides et plusieurs céramiques réfractaires a été étudiée, par des essais de corrosion statique et dynamique. Un matériau, constitué d'alumine et d'oxyde de chrome, s'est révélé être un excellent candidat pour le garnissage du réacteur de gazéification.
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Beath, Andrew Charles. "Mathematical Modelling of Entrained Flow Coal Gasification". Thesis, 1996. http://hdl.handle.net/1959.13/24844.
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A mathematical model for entrained flow coal gasification was developed with the objective of predicting the influence of coal properties and gasification conditions on the performance of entrained flow gasifiers operating at pressures up to 21 atmospheres (2.1MPa). The model represents gasifiers as plug flow reactors and therefore neglects any mixing or turbulence effects. Coal properties were predicted through use of correlations from a variety of literature sources and others that were developed from experimental data in the literature. A sensitivity analysis of the model indicated that errors in the calculated values of coal volatile yield, carbon dioxide gasification reactivity and steam gasification may significantly affect the model predictions. Similarly errors in the input values for gasifier wall temperatures and gasifier diameter, when affected by slagging, can cause model prediction errors. Model predictions were compared with experimental gasification results for a range of atmospheric and high pressure gasifiers, the majority of the results being obtained by CSIRO at atmospheric pressure for a range of coals. Predictions were accurate for the majority of atmospheric pressure results over a large range of gas feed mixtures. Due to the limited range of experimental data available for high pressure gasification the capability of the model is somewhat uncertain, although the model provided accurate predictions for the majority of the available results. The model was also used to predict the trends in particle reactions with gasification and the influence of pressure, gasifier diameter and feed coal on gasifier performance. Further research on coal volatile yields, gasification reactivities and gas properties at high temperatures and pressures was recommended to improve the accuracy of model inputs. Additional predictions and model accuracy improvements could be made by extending the model to include fluid dynamics and slag layer modelling.PhD Doctorate
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Beath, Andrew Charles. "Mathematical Modelling of Entrained Flow Coal Gasification". Diss., 1996. http://hdl.handle.net/1959.13/24844.
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A mathematical model for entrained flow coal gasification was developed with the objective of predicting the influence of coal properties and gasification conditions on the performance of entrained flow gasifiers operating at pressures up to 21 atmospheres (2.1MPa). The model represents gasifiers as plug flow reactors and therefore neglects any mixing or turbulence effects. Coal properties were predicted through use of correlations from a variety of literature sources and others that were developed from experimental data in the literature. A sensitivity analysis of the model indicated that errors in the calculated values of coal volatile yield, carbon dioxide gasification reactivity and steam gasification may significantly affect the model predictions. Similarly errors in the input values for gasifier wall temperatures and gasifier diameter, when affected by slagging, can cause model prediction errors. Model predictions were compared with experimental gasification results for a range of atmospheric and high pressure gasifiers, the majority of the results being obtained by CSIRO at atmospheric pressure for a range of coals. Predictions were accurate for the majority of atmospheric pressure results over a large range of gas feed mixtures. Due to the limited range of experimental data available for high pressure gasification the capability of the model is somewhat uncertain, although the model provided accurate predictions for the majority of the available results. The model was also used to predict the trends in particle reactions with gasification and the influence of pressure, gasifier diameter and feed coal on gasifier performance. Further research on coal volatile yields, gasification reactivities and gas properties at high temperatures and pressures was recommended to improve the accuracy of model inputs. Additional predictions and model accuracy improvements could be made by extending the model to include fluid dynamics and slag layer modelling.PhD Doctorate
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Hong, Mong Yie, i 洪孟逸. "Simulation of coal gasification in entrained-flow bed". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/67925215174649839003.
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Chih-JungChen i 陳致融. "Numerical Simulation and Optimization of Coal and Biomass Gasification in an Entrained-bed Gasifier". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/99171288255043145063.
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博士國立成功大學
機械工程學系碩博士班
101
Gasification plays an important role in the development of clean coal technology. In addition, not only coal but also other materials can be employed as feedstocks in gasification. Biomass is an important source of renewable energy in the world. It can also be gasified with coal through co-gasification. Therefore, the objective of this study is to seek appropriate operations for gasification process, the present study develops a numerical method to predict coal gasification phenomena in an entrained-flow gasifier. Particular emphasis is placed on the influence of injection pattern upon synthesis gas (syngas) production. The parameter of steam/coal ratio is also taken into account to evaluate its impact on hydrogen generation. With oxygen injected from the center inlet and coal from the middle ring inlet of the reactor, the operating pattern gives the best performance of coal gasification where the carbon conversion (CC) and coal gas efficiency (CGE) are 89 and 72%, respectively. Increasing steam into the reactor reduces CC and less CO is generated. For the results of gasaification by different feeds, the obtained results suggest that in all cases, the carbon conversions of the three fuels are higher than 90%. However, the cold gasification efficiency for raw bamboo is low, mainly due to the relatively lower calorific value of the material. In the case of the torrefied bamboo fuel, the gasification performance is enhanced significantly and is quite similar to the coal gasification under the same conditions. It appears that the optimum oxygen-to-fuel mass flow ratios for the gasification of raw bamboo, torrefied bamboo, and coal are 0.9, 0.7, and 0.7, and their equivalence ratios are 0.692, 0.434, and 0.357, respectively. On the other hand, Gasification is a very complex thermal conversion process. The result of gasification is influenced by many factors. Hence, the present study was conducted to optimize the gasification process in an entrained-flow gasifier through the application of the Taguchi method. Results suggest that the optimum conditions are a wall temperature of 1500 K, an O/F ratio of 0.6, coal feed type and a gasifier pressure of 3 MPa. The influence strength order of each control condition is feed type＞O/F ratio＞wall temperature＞pressure. The value of the S/N ratio for the optimum case is 13.40, which is the highest value compared to other cases. The simulations suggest that the developed numerical method is able to provide an accurate prediction on syngas formation. With oxygen injected from the center inlet and coal from the middle ring inlet of the reactor, the operating pattern gives the best performance of coal gasification. Analysis of the Taguchi method was used to evaluate the calculation results. Results show that the Taguchi method is able to investigate the gasification process well.
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Cheng-RungLei i 雷政融. "Influences of Different Combustion Models on the Coal-Gasification Simulation of an Entrained-Bed Gasifier". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/56615855879415291703.
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碩士國立成功大學
航空太空工程學系碩博士班
101
In the present study, a numerical model has been developed for an up-flow entrained-bed gasifier by the commercial CFD software, ANSYS-FLUENT. The accuracy for the predicted composition of the outlet syngas and temperature distribution is compared for different turbulent combustion models. Two different combustion models including non-premixed flamelet model, and finite-rate/eddy dissipation model, are investigated. The results obtained from the present computations show that the predicted syngas composition by the finite-rate/eddy dissipation model is in better agreement with the experimental data. However, the concentration of H2 is under-estimated by the non-premixed flamelet model. Regarding the outlet temperature and the temperature distribution, the predictions by the finite-rate/eddy dissipation model are also in better agreement with the experiment. The temperature is overestimated by the non-premixed flamelet model. As far as the carbon conversion and cold gas efficiency are concerned, the predictions by the finite-rate/eddy dissipation model are close to the experimental data, while those by the non-premixed flamelet model are underestimated. On the whole, the finite-rate/eddy dissipation model is superior to the non-premixed flamelet model in the accuracy of predictions.
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Pan, Ze-Wei, i 潘則瑋. "Numerical Simulation Study of Gasification Characteristics in Entrained Bed Gasifier with Coal Water Slurry and Bio-slurry". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/27u523.
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碩士國立虎尾科技大學
機械與機電工程研究所
101
Coal is the largest stock of the fossil fuel around the world, that was about 72%. It content high energy density to own high potential performance of economics. It emitted large amount the pollutions in the coal using process directly, that reduced the competitiveness of coal. Therefore, how to make the coal to be a clean energy for using is an important issue in the world, IGCC is an opportunity of clean coal using that couple with capture carbon dioxide technology (CCS) and other pollution controller unit to reduce pollution in the process. The products of IGCC are hydrogen and carbon monoxide (syngas) mainly. Syngas was employed to burn in gas turbine to generate the electrical power. The gasification process is an important process in IGCC, in that dominates the efficiency of clean coal technology. , There are several sub-reactions and phase reactions in coal gasification such as evaporation, pyrolysis, combustion, reforming and homogenous and heterogeneous reaction, respectively. Coal-water slurry and bio-char slurry were employed to investigate the gasification process by numerical methods in this study. SIMPLE methods and standards k-ε model were employed to solve problems of pressure-velocity and turbulence, respectively. To track droplet via phase change used the discrete phase model and the DO model was for radiation characteristics calculation in droplet. The carbon conversion efficiency and cold gas efficiency were the performance index of gasifier in this study. These results of study showed that the efficiencies of combustion in gasification were optimized when O/C ratio were between 0.5 to 0.8. Therefore, we investigated the pressure and droplet size effect in coal water slurry in O/C ratio of 0.8. The evaluated pressure in gasifier confined the combustion regime to increase the flame temperature and reduce the transport of heat and mass of slurry and oxidizer in pressure of 1 to 20 atm. In addition, the evaluated pressure effect affected the penetration length and droplet residence time that were parameters of gasifier. operating parameters of In the pressure 1bar, droplet 400 μm and concentration 55% have better gasification. By the above conditions, 5% -20% of the coffee grounds char are mixed into the slurry, made into a bio-slurry and analyzed. There results show that char is added to improve levels of volatile matter. Carbon conversion rate is better, but cold gas efficiency decreases.
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Yang, Yao-Wei, i 楊曜維. "Experimental Study of the Gasification Characteristics of Bio-Char Slurry and Coal Water Slurry in Entrained Bed Gasfier". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/yg38sd.
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碩士國立虎尾科技大學
機械與機電工程研究所
101
The purpose of this paper is to design a nozzle suitable for coal water slurry entrained bed gasifier, in which the most suitable nozzle is found through characteristics measurement of atomized cold flow field of the nozzle and gasification of entrained bed gasifier. For measurement of atomized cold flow field, the optical measurement technique and image observation are used to explore characteristics of nozzle atomization, where particle image velocimetry (PIV) is mainly used to measure the atomized flow field and make related calculations. Malvern spray laser particle size analyzer is used for atomized particle size analysis. The particle size is measured 10cm, 15cm and 20cm respectively below the spray. The nozzle is an internally-mixing air atomizing one. The atomization characteristics are judged at different nozzle assemblies (single-hole and four-hole), liquid concentrations (10%-30%), spray cone angles, particle size analysis and mass distribution. This lab established a 10kg/gr coal-water slurry entrained bed gasifier in Nanzih District, Kaohsiung City. The reaction zone of the entrained bed is 1020mm long and 200m in diameter. The effects of different parameters on gasification results are explored at different nozzle assemblies, bio-coal slurry and O/C (mole/mole); the reaction is explored based on the temperature records of gasifier and output of main gaseous products (H2, CO, CO2); the measurement of atomization characteristics of cold flow field and the result of gasification are compared for verification. The experimental result shows that the single-hole air atomizing nozzle needs higher energy output when high flow working gas is operating. When the liquid-gas ratio is different, the operating range of the multihole nozzle is wider than that of the single-hole nozzle. However, these do not happen for the multihole nozzle. As for particle size analysis, the particle size of the atomized liquid drop of the single-hole nozzle is smaller than that of the atomized liquid drop of the multihole nozzle. With the increase of the impact gas flow, the atomized particle size reduces gradually; when it reaches a certain value, the changes of the atomized particle size become unobvious. In the experiment of the coal-water slurry entrained bed gasifier, the single-hole internally-mixing nozzle has higher reaction of combustion than the single-hole externally-mixing nozzle. This research will improve the nozzle in the future so as to improve gasification reaction efficiency and carbon conversion efficiency.
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Yin-ChuChen i 陳映竹. "Numerical Analyses of an Entrained-Flow Coal Slurry Gasifier with Separate Oxygen-Feeding Streams". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/55770534076970252779.
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碩士國立成功大學
航空太空工程學系
102
The characteristic design of a Texaco gasifier, with a coaxial coal-slurry oxygen-jet nozzle and an outer annular oxygen-jet, has a significant influence on the gasification process. For the fuel-oxidant coaxial jet nozzle, the central oxygen-jet flow impinges on the coal-slurry stream and assists in the atomization of the coal slurry. The outer oxygen-jet, which splits the oxygen intake stream into two, makes an influence of the flame position and causes an effect of the gasification efficiency and coal conversion rate. In the study, numerical simulations of the coal slurry gasification process inside an entrained-flow gasifier with separate oxygen feeding streams are investigated using the commercial computational fluid dynamic software, ANSYS/ FLUENT. Three parameters, namely, positions of the outer annulus feeding tunnel, oxygen/carbon ratio, and oxygen feeding velocity of the outer annulus streams, have been examined to determine the effects of operating conditions on the gasification process. The numerical results show that the flame distribution is affected by the positions of the outer tunnel. As the outer tunnel is moved away from the central axis, the flame surface is extended and leads to a higher temperature in the downstream of the gasifier. In the investigations of the oxygen/carbon ratio, the lower the oxygen/carbon ratio is, the lower outlet temperature and the poorer the coal conversion rate. The distribution of the combustion region and the coal conversion rate is strongly affected by the feeding velocity of the outer annulus stream. The coal conversion rate and the cold gas efficiency are in a descending trend when the oxidant feeding is operated in high velocity. The compositions of the product gases are affected by the WGS. Moreover, the reaction rate of the WGS reaction is sensitive to the temperature of the gasification chamber.