Dissertations / Theses on the topic 'Coal gasification'
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Батальцев, Євген Володимирович, Евгений Владимирович Батальцев, and Yevhen Volodymyrovych Bataltsev. "Environmental aspects of coal gasification." Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/33522.
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Consumption of solid fuels increases with the development of industry. Working with them is more difficult in terms of hardware and technical supply than with gaseous or liquid hydrocarbons. In addition, coal mining, its transportation, drying, grinding and burning in boilers, accompanied by the formation of solid waste (ash and slag) and significant air emissions of oxides of carbon, nitrogen and sulfur are taken into account. This requires the creation of new technology of solid fuels using to reduce the anthropogenic impact on the environment. This technology is called coal gasification.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/33522
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Perkins, Gregory Martin Parry Materials Science & Engineering Faculty of Science UNSW. "Mathematical modelling of underground coal gasification." Awarded by:University of New South Wales. Materials Science and Engineering, 2005. http://handle.unsw.edu.au/1959.4/25518.
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Mathematical models were developed to understand cavity growth mechanisms, heat and mass transfer in combination with chemical reaction, and the factors which affect gas production from an underground coal gasifier. A model for coal gasification in a one-dimensional spatial domain was developed and validated through comparison with experimental measurements of the pyrolysis of large coal particles and cylindrical coal blocks. The effects of changes in operating conditions and coal properties on cavity growth were quantified. It was found that the operating conditions which have the greatest impact on cavity growth are: temperature, water influx, pressure and gas composition, while the coal properties which have the greatest impact are: the thermo-mechanical behaviour of the coal, the coal composition and the thickness of the ash layer. Comparison of the model results with estimates from field scale trials, indicate that the model predicts growth rates with magnitudes comparable to those observed. Model results with respect to the effect of ash content, water influx and pressure are in agreement with trends observed in field trials. A computational fluid dynamics model for simulating the combined transport phenomena and chemical reaction in an underground coal gasification cavity has been developed. Simulations of a two-dimensional axi-symmetric cavity partially filled with an inert ash bed have shown that when the oxidant is injected from the bottom of the cavity, the fluid flow in the void space is dominated by a single buoyancy force due to temperature gradients established by the combustion of volatiles produced from the gasification of carbon at the cavity walls. Simulations in which the oxidant was injected from the top of the cavity reveal a weak fluid circulation due to the absence of strong buoyancy forces, leading to poor gasification performance. A channel model of gas production from underground coal gasification was developed, which incorporates a zero-dimensional cavity growth model and mass transfer due to natural convection. A model sensitivity study is presented and model simulations elucidate the effects of operating conditions and coal properties on gas production.
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Norman, Narcrisha S. "Catalytic coal gasification using calcium oxide /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1203573171&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2006."Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 62-66). Also available online.
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Quartermaine, R. E. "Microstructural aspects of catalytic coal gasification." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377237.
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Saha, Gautam. "The role of coal surface charge in catalyzed coal gasification." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1992. http://digitalcommons.auctr.edu/dissertations/2173.
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The influence of the electrokinetic properties of coal on the adsorption and gasification activities of calcium acetate and potassium carbonate has been studied. It has been found from zeta potential measurements on lignite, subbituminous and bituminous coals that the coal particles are negatively charged in both acidic and basic solutions, although the negative charge density is more pronounced in strongly alkaline media. In general, the extent of calcium or potassium adsorption correlated with the negative zeta potentials. Calcium or potassium adsorption followed the order lignite > subbituminous > bituminous coal. Increased char reactivities were observed with catalysts loaded from basic or neutral solutions compared to catalysts impregnated from acidic solutions. The enhanced activities are attributed to increased contact between the anionic coal surface and the metal ions during catalyst loading. It is suggested that the extent of coal-catalyst interaction during catalyst loading from solution plays an important role in coal char reactivity.
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Amure, Olushola Adenike. "Ammonia formation in air blown coal gasification." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395495.
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Neseyif, S. "Predicting corrosion rates within coal gasification environments." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309623.
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Halsall, I. L. "Coal gasification kinetics simulated in laminar flames." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233080.
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Duff, Alastair James. "The mechanism of the direct hydrogasification of coals and polymeric coal models." Thesis, Heriot-Watt University, 1988. http://hdl.handle.net/10399/965.
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Visagie, J. P. "Generic gasifier modelling evaluating model by gasifier type /." Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-07022009-133535.
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Turner, John Andrew. "The gasification of coal under conditions pertinent to blast furnace coal injection." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246107.
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Slezak, Andrew A. "Modeling of particle trajectories of coal size and density fractions in a gasifier." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=6016.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains x, 164 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 119-121).
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MENDES, PAULO ROBERTO BUFACCHI. "ISOTHERMAL GASIFICATION STUDY OF A SPHERICAL COAL PARTICLE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1986. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20347@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA partir das equações fundamentais da teoria clássica das misturas, é proposto um modelo simplificado, em regime pseudo-estacionário e isotérmico, da gaseificação do carvão sofrendo gaseificação com vapor dágua é analisada por meio de balanços diferenciais de conservação de massa de cada espécie química. O modelo leva em conta as reações do vapor dágua com o carbono e o monóxido de carbono. Estas duas reações aparecem no modelo como condições de contorno lineares, que englobam fenômenos intraparticulares, os quais são agrupados à superfície. As condições ambientais são consideradas constantes. Também são incluídas equações diferenciais que permitem calcular a taxa de consumo de vapor dágua e calor, a taxa de gaseificação e a taxa de geração de monóxido de carbono, dióxido de carbono e hidrogênio. Por meio de simulação digital foi possível estudarem-se os efeitos, sobre o processo, da granulometria, temperatura e fração volumétrica de vapor dágua no meio ambiente. As equações cinéticas utilizadas neste trabalho são aquelas do carvão de charqueadas, Rio Grande do Sul, Brasil.
A simplified model for steady, isothermal diffusion in the layer surrounding a spherical carbon particle undergoing steam gasification process is considered by way of the classical theory of reacting fluid mixtures. The model accounts for the steam – carbon reaction and the steam – carbon monoxide reaction. These two reactions appear in the model as linear boundary conditions that comprise the intraparticle effects, which are lumped at the surface. The ambient conditions are assumed to be constant. Differential equations for the calculation of steam and heat rate consumption, carbon monoxide, carbon dioxide and hydrogen rate generation and rate of gasification are also included. By means of digital simulation it was possible to study the effects of particle radius, temperature and steam concentration on the process. The kinect equations used in this paper are those of coal from Charqueadas, State of Rio Grande do Sul, Brasil.
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Li, Fanxing. "CHEMICAL LOOPING GASIFICATION PROCESSES." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236704412.
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Ross, David. "Devolatilisation and volatile matter combustion during fluidised-bed gasification of low-rank coal." Title page, contents and summary only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phr823.pdf.
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Bibliography: leaves 234-252. The devolution times of seven coals were determined by measuring the centre temperature response for single particles held stationary in a bench scale atmospheric fluidised-bed reactor.
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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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Bu, Jiachuan. "Kinetic analysis of coal and biomass co-gasification with carbon dioxide." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10457.
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Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains vi, 184 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 82-84).
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Punjak, Wayne Andrew. "High temperature interactions of alkali vapors with solids during coal combustion and gasification." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184599.
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The high temperature interactions of alkali metal compounds with solids present in coal conversion processes are investigated. A temperature and concentration programmed reaction method is used to investigate the mechanism by which organically bound alkali is released from carbonaceous substrates. Vaporization of the alkali is preceded by reduction of oxygen-bearing groups during which CO is generated. A residual amount of alkali remains after complete reduction. This residual level is greater for potassium, indicating that potassium has stronger interactions with graphitic substrates than sodium. Other mineral substrates were exposed to high temperature alkali chloride vapors under both nitrogen and simulated flue gas atmospheres to investigate their potential application as sorbents for the removal of alkali from coal conversion flue gases. The compounds containing alumina and silica are found to readily adsorb alkali vapors and the minerals kaolinite, bauxite and emathlite are identified as promising alkali sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite and emathlite are compared and analyzed both experimentally and through theoretical modeling. The experiments were performed in a microgravimetric reactor system; the sorbents were characterized before and after alkali adsorption using scanning Auger microscopy, X-ray diffraction analysis, mercury porosimetry and atomic emission spectrophotometry. The results show that the process is not a simple physical condensation, but a complex combination of several diffusion steps and reactions. There are some common features among these sorbents in their interactions with alkali vapors: In all cases the process is diffusion influenced, the rate of adsorption decreases with time and there is a final saturation limit. However, there are differences in reaction mechanisms leading to potentially different applications for each sorbent. Bauxite and kaolinite react with NaCl and water vapor to form nephelite and carnegieite and release HCl to the gas phase. However, emathlite reacts to form albite and HCl vapor. Albite has a melting point significantly lower than nephelite and carnegieite; therefore, emathlite is more suitable for lower temperature sorption systems downstream of the combustors/gasifiers, while kaolinite and bauxite are suitable as in-situ additives.
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Chan, M.-L. "The gasification of some U.K. bituminous coals." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383899.
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Azhakesan, M. "An investigation of coal gasification by rapid heating techniques." Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/2081/.
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Velazquez-Vargas, Luis Gilberto. "Development of chemical looping gasification processes for the production of hydrogen from coal." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187199715.
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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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Sricharoenchaikul, Viboon. "Fate of carbon-containing compounds from gasification of kraft black liquor with subsequent catalytic conditioning of condensable organics." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/10145.
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Mortazavi, Hamid Reza. "Rubbling and structural stability of underground coal gasification reactors /." Thesis, Connect to this title online; UW restricted, 1989. http://hdl.handle.net/1773/7051.
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Heidenreich, Craig. "Mathematical modelling of large low-rank coal particle devolatilization /." Title page, summary and contents only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phh4653.pdf.
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Silaen, Armin. "Simulation of Coal Gasification Process Inside a Two-Stage Gasifier." ScholarWorks@UNO, 2004. http://scholarworks.uno.edu/td/198.
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Gasification is a very efficient method of producing clean synthetic gas (syngas) which can be used as fuel for electric generation or chemical building block for petrochemical industries. This study performs detailed simulations of coal gasification process inside a generic two-stage entrained-flow gasifier to produce syngas carbon monoxide and hydrogen. The simulations are conducted using the commercial Computational Fluid Dynamics (CFD) solver FLUENT. The 3-D Navier-Stokes equations and seven species transport equations are solved with eddy-breakup combustion model. Simulations are conducted to investigate the effects of coal mixture (slurry or dry), oxidant (oxygen-blown or air-blown), wall cooling, coal distribution between the two stages, and the feedstock injection angles on the performance of the gasifier in producing CO and H2. The result indicates that coal-slurry feed is preferred over coal-powder feed to produce hydrogen. On the other hand, coal-powder feed is preferred over coal-slurry feed to produce carbon monoxide. The air-blown operation yields poor fuel conversion efficiency and lowest syngas heating value. The two-stage design gives the flexibility to adjust parameters to achieve desired performance. The horizontal injection design gives better performance compared to upward and downward injection designs.
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Bibrzycki, Jakub [Verfasser]. "Investigations of coal particle combustion and gasification / Jakub Bibrzycki." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2015. http://d-nb.info/1070571792/34.
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Lachas, Herve Jean Marie Yves Robert. "Trace element partitioning and emission control during coal gasification." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/7143.
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Zhou, Lingmei. "Kinetic study on co-gasification of coal and biomass." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-154403.
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Thermal co-processing of coal and biomass has been increasingly focused for its environmental and economic benefits. In the present work, the experimental and kinetic study on co-pyrolysis and co-gasification of Rhenish brown coal (HKN) and wheat straw (WS) was made.
The pyrolysis behavior, especially for co-pyrolysis, was investigated in a thermogravimetric analyzer (TGA) and a small fixed bed reactor (LPA). In TGA, the mass loss and reaction rate of single and blend samples were studied under various experimental conditions, and their effects on synergy effects. The synergy effects on products yield and properties of chars were studied in LPA. The kinetics of pyrolysis was obtained based on data from TGA by using the Coats-Redfern method. For gasification with CO2, a small fixed bed reactor (quartz glass reactor), equipped with an online GC to monitor the gas composition, was used. The effects of processing conditions on gasification behavior and synergy effects for mixed chars and co-pyrolysis chars were investigated. The volume reaction model (VRM), shrinking core model (SCM) and random pore model (RPM), were applied to fit the experimental data. The model best fitting the experiments was used to calculate the kinetic parameters. The reaction orders of gasification reactions with single chars are also investigated.
The pyrolysis study showed that a small amount of wheat straw added to the brown coal promoted the decomposition better and showed more significant synergy effects. The synergy effects varied with increasing heating rates and pressures, especially at 40 bar. The kinetic parameters were inconsistent with experimental behavior during co-pyrolysis, since the reaction was also affected by heat transfer, contact time, particles distribution and so on. The gasification study on single chars showed that Rhenish brown coal chars had higher reactivity; chars pyrolyzed at higher temperatures showed lower reactivity; and higher gasification temperatures and CO2 partial pressures led to higher reactivity. For co-gasification process, there was no significant synergy effect for mixed chars. However, negative synergy effects (reactivity decreased compared to the calculated values based on rule of mixing) were observed for co-pyrolysis chars, caused by properties change by co-pyrolysis process. For kinetics, the reaction orders of chars ranged from 0.3 to 0.7. Only random pore model fitted most experiments at low and high temperatures. Synergy effects were also observed in kinetic parameters. The values of activation energy E and pre-exponential factor A for mixed chars and co-pyrolysis chars were lower than expected. The negative synergy effects showed the pre-exponential factor A had more effects. However, the higher reactivity of mixed chars than co-pyrolysis chars showed that the reaction was affected more by activation energy E. Therefore, only investigating E or A value was not enough. In addition, a marked compensation effect between activation energies and pre-exponential factors was found in the present study. The isokinetic temperature for the present study was 856 °C. This was close to the temperature at which the gasification reaction transforms from the chemical controlled zone to the diffusion controlled zone for most chars.
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Nel, Sansha. "Catalytic steam gasification of large coal particles / Sansha Nel." Thesis, North-West University, 2011. http://hdl.handle.net/10394/8510.
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Catalytic gasification has been studied extensively in order to develop more efficient and
economic coal conversion processes. Fundamental studies regarding catalytic gasification
have thus far focused on experimentation with small coal particles and powders. The lack of
knowledge regarding the application of large coal particles in steam gasification studies, in
particular catalytic steam gasification, is the motivation behind this investigation.
A washed bituminous, medium rank-C Highveld coal (seam 4) was selected for this study,
and a general characterisation of the coal was conducted. It was found that the ash content
of the washed coal is 12.6 wt.% (air-dried basis). Based on the gross calorific value of 26.6
MJ/kg (air-dried basis), the coal sample was graded as a grade B coal. XRF analysis of the
ash indicated that the coal is rich in SiO2 and Al2O3, with a low potassium oxide content
(0.53 wt.%) which is typical for South African coal.
Potassium carbonate (K2CO3) was selected as catalyst, and the excess solution
impregnation method was used to impregnate large coal particles (5 mm, 10 mm, 20 mm
and 30 mm). The pH of the impregnation solution stabilised after three weeks, which led to
the assumption that impregnation is complete. Two methods were used to determine the
catalyst loading obtained after impregnation: XRF was used to determine the wt.% K in the
ash, while ion specific electrode (ISE) was used to measure the [K+] decrease in the
impregnation solution. XRF results indicated the maximum catalyst loading obtainable for
large coal particles, with the specific impregnation method, to be between 0.68 – 0.83 wt.%
K (coal basis). XRF can be used to determine the catalyst loading by measuring the K
content in the ash, while ISE can be used to semi-quantitatively predict the catalyst loadings
of large coal particles. The catalyst distribution was studied using SEM and tomography
analyses. SEM scans showed that the formation of cracks occurred as a result of
impregnation, and EDS analysis indicated that the majority of the catalyst is concentrated
around the outer surface of the particles. Tomography scans, and mineral volume analysis,
indicated that the mineral matter of the coal particles increased after impregnation.
The effect of catalyst addition on reactivity was investigated by conducting steam gasification
experiments with 5 mm and 10 mm particles, in a large particle TGA. The 20 mm and 30
mm particles did not remain intact after impregnation and were therefore not used for the
reactivity experiments. Reactivity experiments were performed at temperatures ranging from
800 °C to 875 °C, with a steam concentration of 80 mol%. Graphs illustrating conversion as a function of time indicated that the addition of K2CO3 to the coal samples increased the
reaction rate. This was quantified by determining the reactivities of the raw and catalysed
samples using linearised homogeneous model plots. The reaction rate was found to be
temperature sensitive, and independent of particle size, which indicated that experiments
were conducted in the chemical reaction control regime. A slight decrease in activation
energy was observed with the addition of K2CO3, from 191 kJ/mol (raw coal) to 179 kJ/mol
(catalysed coal). Microscope images of raw and catalysed chars indicated that the addition
of a catalyst may reduce agglomeration.Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012
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Simpson, Lori Allison. "The suitability of coal gasification in India's energy sector." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38569.
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Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2006.Includes bibliographical references (p. 83-86).
Integrated Gasification Combined Cycle (IGCC), an advanced coal-based power generation technology, may be an important technology to help India meet its future power needs. It has the potential to provide higher generating efficiency, can be adapted to efficiently burn India's high-ash coal, and has the potential to do so with greatly reduced emissions and offers the longer term potential to assist India to manage its C02 emissions. Efficient gasification technology also offers India the potential to produce a variety of fuels, particularly transportation fuels, and chemicals. These potential benefits would be useful in a country that has coal shortages, runs inefficient power plants, and imports the majority of its transportation fuels. Driven by these potential benefits the Central Government-owned power generating equipment manufacturing company (BHEL) is developing a fluid-bed gasifier designed for Indian coals, but has not yet demonstrated it at a size larger than 6 MW. Outside of BHEL, there are many factors holding this technology back. First, the technology is projected to be more expensive than pulverized coal (PC) power generation. In the Indian environment, the capital costs are estimated to be 1.5 times higher, and the levelized cost of electricity is estimated to be 33 % higher than for PC power generation.
(cont.) Further, there are other technology options, such as super-critical pulverized coal technology, which are cheaper, more proven, and can provide immediate higher generating efficiency. The first supercritical PC plant is currently being built in India. To overcome these barriers will take further research and development, as well as demonstration at a commercial scale. This all needs to occur at a greater speed and with a greater urgency than is now apparent. The demonstration and commercialization will require significant subsidies, which may come in different forms. The Central Government may wish to subsidize the technology development for the pollution control benefits that it offers and do so via its linkages to BHEL. Foreign governments and institutions may choose to subsidize the costs for the carbon dioxide reduction credits that it can produce. In the end, the challenges facing IGCC in India are great. The cost and generating efficiency will have to at least rival those for other advanced coal technologies, and coal production and mining policies will have to be effectively enacted to increase the supply of coal available for new coal plants.
by Lori Allison Simpson.
S.M.
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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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Roullier, Benjamin David. "Modelling the local environmental impact of underground coal gasification." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40878/.
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Underground coal gasification (UCG) has the potential to access vast resources of stored fossil energy in a safe, clean and environmentally sound manner. Previous experiments have however led to concerns around surface subsidence, groundwater pollution and water table lowering. These issues can be prevented through the use of appropriate site selection and an understanding of the processes which cause these effects. Numerical simulations provide a cost effective means of predicting these issues without the need for costly and publically opposed field trials. This work uses a commercially available discrete element code to simulate the coupled thermal, hydraulic and mechanical phenomena which cause environmental damage. Surface subsidence is predicted through the displacements of fully deformable discrete elements separated by a network of fractures. The flow of groundwater through these fractures is simulated in order to predict the effects of water table lowering and the inflow of groundwater into the UCG cavity. Heat conduction from the cavity walls is simulated using an explicit finite difference algorithm which predicts both thermal expansion effects and the influence of temperature on rock material properties. Comparison of results with experimental observations in the literature show good agreement for subsidence and groundwater behaviour, while initial predictions for a range of designs show clear relationships between environmental effects and operating conditions. Additional work is suggested to incorporate groundwater contaminant transport effects, and it is envisioned that the overall model will provide a valuable screening tool for the selection of appropriate site designs for the future development of UCG as an economically viable and environmentally sound source of energy.
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Alexander, Steven Ray. "Electrochemical removal of H₂S from fuel gas streams." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/11733.
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Park, Tae-Jun. "Factors affecting the reactivity of coal derived chars during gasification." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277379.
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Maxwell, Stuart. "An investigation into the gasification of coals, coal macerals and chars at high pressure." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/35384.
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A suite of coals covering a range of properties was gasified in a pressurised thermogravimetric analyser (PTGA) at 950°C and 2.5 MPa. The reactivities of the coals to steam were measured to determine any relationships between coal properties and reactivity. Some of the coals were pre-pyrolysed to produce chars, and the reactivity of these chars was measured both in steam and CO2. The results show that no simple relationships exist but trends can be shown whereby reactivity increases with decreasing carbon content, increasing volatile matter and decreasing mean vitrinite reflectance. Coal minerals, notably CaO, also increased reactivity to some extent in coals of low carbon content, yet carbon content itself influenced reactivity more than mineral content. The effect of pre-pyrolysis of the coals on reactivity appears to be dependent on coal rank, with higher rank coals (carbon content above 83%) showing an increase in reactivity whereas lower rank coals show a marked decrease.
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Man, Chi-Keung. "Some properties of cokes produced from high pressure carbonisation of coals." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/11844.
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The British Gas Lurgi slagging gasifier is a counter-current fixed bed gasifier operating at high pressure. Coal descending the gasifier is pyrolysed to form coke which is then gasified. Properties of such coke affect the gasifier in its efficiency of operation. This thesis describes a) the carbonisation of cokes from coal under simulated gasifier conditions, b) the characterisation of the resultant cokes in terms of structure and physical properties and, c) the formulation of relationships between coal thermoplasticity and coke properties. Three high-volatile bituminous coals Manvers Barnburgh NCB 702, and Gedling (Manton NCB 502, NCB 802) were carbonised in an autoclave under a range of pressures (0.5- 8.0 MPa), using two different heating regimes, shock heating to 700 °c and slow heating to 700 °c at 5 °C/min. Physical characterisation of the resultant cokes was carried out using optical and mechanical techniques. Optical anisotropy and image analysis were used to determine coke structure and porosity respectively. Tensile strength, microstrength and abrasion resistance were measured to establish the cokes' resistance to various forms of breakage. High pressure dilatometry and plastometry were used to measure the effects of pressure and heating rate on coal thermoplastic properties. Relationships between coal thermoplastic properties and coke properties are very complex. This work has shown that these relationships are highly dependent on carbonisation conditions with heating rate rather than pressure being the more dominant parameter.
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Xu, Qixiang. "Investigation of Co-Gasification Characteristics of Biomass and Coal in Fluidized Bed Gasifiers." Thesis, University of Canterbury. Chemical and Process, 2013. http://hdl.handle.net/10092/8399.
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This thesis presents research on the co-gasification characteristic of biomass and coal, and mathematical modelling of the co-gasification process in two main parts: i) experimental investigation and mathematical modelling of reaction kinetics of steam gasification of single char particles of pure coal, pure biomass, and blended coal and biomass; and ii) Experimental investigation and mathematical modelling of gasification characteristics of biomass, coal and their blends in pilot scale gasifiers. From the char reactivity study, the instinct difference in gasification characteristics of the two chars has been explained and reactivity of blended char can be predicted. In the pilot scale gasifier study, effects of blending ratio in feedstock and operating conditions on co-gasification of biomass and coal were investigated.
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Li, Jian 1957. "Pyrolysis and CO2 gasification of black liquor." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65338.
Full text
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Long, Henry A. III. "Analysis of Biomass/Coal Co-Gasification for Integrated Gasification Combined Cycle (IGCC) Systems with Carbon Capture." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/1371.
Full textAbstract:
In recent years, Integrated Gasification Combined Cycle Technology (IGCC) has become more common in clean coal power operations with carbon capture and sequestration (CCS). Great efforts have been spent on investigating ways to improve the efficiency, reduce costs, and further reduce greenhouse gas emissions. This study focuses on investigating two approaches to achieve these goals. First, replace the subcritical Rankine steam cycle with a supercritical steam cycle. Second, add different amounts of biomass as feedstock to reduce emissions. Finally, implement several types of CCS, including sweet- and sour-shift pre-combustion and post-combustion.
Using the software, Thermoflow®, this study shows that utilizing biomass with coal up to 50% (wt.) can improve the efficiency, and reduce emissions: even making the plant carbon-negative when CCS is used. CCS is best administered pre-combustion using sour-shift, and supercritical steam cycles are thermally and economically better than subcritical cycles. Both capital and electricity costs have been presented.
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Sloan, Elizabeth Patricia. "The influence of feedstock properties on gasification plant performance." Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241681.
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Trangmar, D. T. "The kinetics of combustion and gasification of some coal chars." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236930.
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Ong, Katherine M. (Katherine Mary). "Modeling of solid oxide fuel cell performance with coal gasification." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104226.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Growing concern over greenhouse gas emissions has driven research into clean coal power production alternatives. Novel coal power plant designs that lower CO2 emissions are imperative in the coming decades to mitigate global temperature rise. High-efficiency stationary power systems that integrate coal gasification with solid oxide fuel cells (SOFCs) have been championed by the Department of Energy for the past couple of decades. However, many fundamental questions about this system still need to be addressed by modeling the complex coupling between SOFC's and gasification. More specifically, work is needed to characterize SOFC performance with a range of syngas (H₂+CO) mixtures produced by coal gasification. This thesis used a multiscale modeling approach to analyze SOFC performance with coal syngas at both the systems level and at the surface reaction scale. The first investigation in this thesis couples an equilibrium gasifier model to a detailed ID SOFC model to study the theoretical performance of the coupled system run on steam or carbon dioxide. The results of this study indicate that the system performs substantially better with steam gasification than with CO₂ gasification as a result of the faster electro-oxidation kinetics of H₂ relative to CO. The coupled system is then shown to reach higher current densities and efficiencies when the heat released by the fuel cell is sent to the gasifier instead of a bottoming cycle. 55-60% efficiency is then predicted for the system with heat transfer and steam gasification, making this technology competitive with other advanced system designs and almost twice as efficient as conventional coal-fired power plants. The second study in this thesis investigates SOFC behavior with H₂ and CO (syngas) mixtures that come from coal gasification. SOFC models typically neglect CO electrochemistry in the presence of H₂ and H₂0, assuming that the water-gas-shift reaction proceeds faster than CO electrooxidation. The results of this study show, however, that CO electro-oxidation cannot be neglected in syngas mixtures, particularly at high current densities for high CO-content syigas. First the simulations demonstrate that incoming CO is not all shifted to form H₂ by reforming reactions before reaching the electrochemical reaction sites. Furthermore, the results of this 'study confirm that direct electro-oxidation of CO contributes non-negligible current relative to H₂ at high anode overpotentials. Together these results show that CO electro-oxidation plays an important role in SOFC performance not only via water-gas-shift reforming, but also via direct electro-oxidation when H₂ is also present. This work suggests that accurate models for both surface reforming and direct electro-oxidation of CO in SOFC anodes must be included in order to capture performance when using coal syngas mixtures. Finally, a multi-step mechanism for the simultaneous electro-oxidation of H₂ and CO in SOFCs is implemented and studied. This mechanism combines a couple of reaction pathways: hydrogen (H) spillover to the electrolyte, and oxygen (O) spillover to hydrogen and CO on the anode. This mechanism is successfully verified in the model against a wide range of experimental data for mixtures of CO/CO₂, H₂/N₂, H₂/H₂0, H₂/CO, and H₂/CO₂ . The simulations show that H spillover is the dominant source of current at low anode activation overpotentials, but also demonstrate that the currents produced by 0 spillover are non-negligible at high overpotentials. Furthermore, it is shown that the current produced by 0 spillover to CO is not limited by the rate of CO adsorption on nickel, which leads CO to contribute more to cell performance at high currents. Together these three modeling studies demonstrate how coal can be efficiently converted to electricity via gasification and the simultaneous electro-oxidation of H₂ and CO in a solid oxide fuel cell.
by Katherine M. Ong.
Ph. D.
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Botros, Barbara Brenda. "Improving heat capture for power generation in coal gasification plants." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69493.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 181-187).
Improving the steam cycle design to maximize power generation is demonstrated using pinch analysis targeting techniques. Previous work models the steam pressure level in composite curves based on its saturation temperature alone. The present work examines the effect of including both sensible and latent heating of steam in the composite curve. It is shown that including sensible heating allows for better thermal matching between the process and steam system which results in improving the overall efficiency while minimizing the capital cost. Additionally, fixed steam headers, such as assumed in total site analysis, give no allowance for reheating before turbine expansion, which can be valuable to consider when optimizing the steam system for certain plant configurations. A case study using an integrated gasification combined cycle (IGCC) plant with carbon capture and sequestration (CCS) is analyzed to assess changes in steam cycle design on the plant efficiency and cost. In addition to improving the steam system within an IGCC plant to improve efficiency, losses within the radiant heat exchanger can also be reduced. Instead of using high temperature syngas, cooling from 1300°C to 760°C, to boil steam at 330°C, another heat transfer fluid can be used and heated to higher temperatures. Material constraints restrict the maximum allowable temperature of the heat transfer fluid. To maintain high heat transfer coefficients in the heat transfer fluid, a fluid with high thermal conductivity, such as a liquid metal, can be used and heated to high temperatures (~700°C). Liquid metals can then act as an intermediate heat transfer medium, absorbing heat from high temperature syngas and rejecting it to steam at temperatures in excess of 500°C. The use of liquid metals leads to a 0.75 point increase in plant efficiency. Gases, such as carbon dioxide and helium, are also considered as potential heat transfer fluids in the radiant heat exchanger. These gases can be at equal pressure to the syngas pressure in the radiant heat exchanger, reducing the tensile stress in tube walls, but their low thermal conductivities still necessitate high strength materials at high temperature. A Brayton power cycle with recuperation is considered in this work, absorbing heat from the hot syngas and rejecting it to steam. Over a range of different Brayton cycle pressure ratios and maximum temperatures, no improvement in plant efficiency was found with respect to the case where steam is boiled in the same sized heat exchanger.
by Barbara Brenda Botros.
Ph.D.
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Ivanov, Georgi Pavlov. "Fabry-Perot Sapphire Temperature Sensor for Use in Coal Gasification." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32931.
Full textAbstract:
Sapphire fiber based temperature sensors are exceptional in their ability to operate at temperatures above 1000ºC and as high as 1800ºC. Sapphire fiber technology is emerging and the fiber is available commercially. Sapphire fiber has a high loss, is highly multi-mode and does not have a solid cladding, but it is nonetheless very useful in high temperature applications. Of the available interferometer configurations, Fabry-Perot interferometers are distinguished in their high accuracy and great isolation from sources of error.
In this thesis, improvements are reported to an existing design to enhance its reliability and to reduce possible modes of failure. The existing high temperature sensor design has shown a lot of potential in the past by continuously measuring the temperature in a coal gasifier for 7 months, but its true potential has not yet been realized. The goal of this work and the work of many others is to extend the working life and reliability of high-temperature optical sapphire temperature sensors in harsh environments by exploring a solid cladding for sapphire fiber, improved fringe visibility sapphire wafers and a new sensor design. This project is supported by the National Energy and Technology Laboratory of the Department of Energy.Master of Science
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Nyendu, Guevara Che. "Non-Catalytic Co-Gasification of Sub-Bituminous Coal and Biomass." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4233.
Full textAbstract:
Fluidization characteristics and co-gasification of pulverized sub-bituminous coal, hybrid poplar wood, corn stover, switchgrass, and their mixtures were investigated. Co-gasification studies were performed over temperature range from 700°C to 900°C in different media (N2, CO2, steam) using a bubbling fluidized bed reactor.
In fluidization experiments, pressure drop (ΔP) observed for coal-biomass mixtures was higher than those of single coal and biomass bed materials in the complete fluidization regime. There was no systematic trend observed for minimum fluidization velocity (Umf) with increasing biomass content. However, porosity at minimum fluidization (εmf) increased with increasing biomass content. Channeling effects were observed in biomass bed materials and coal bed with 40 wt.% and 50 wt.% biomass content at low gas flowrates. The effect of coal pressure overshoot reduced with increasing biomass content.
Co-gasification of coal and corn stover mixtures showed minor interactions. Synergetic effects were observed with 10 wt.% corn stover. Coal mixed with corn stover formed agglomerates during co-gasification experiments and the effect was severe with increase in corn stover content and at 900°C. Syngas (H2 + CO) concentrations obtained using CO2 as cogasification medium were higher (~78 vol.% at 700°C, ~87 vol.% at 800°C, ~93 vol.% at 900°C) than those obtained with N2 medium (~60 vol.% at 700°C, ~65 vol.% at 800°C, ~75 vol.% at 900°C).
Experiments involving co-gasification of coal with poplar showed no synergetic effects. Experimental yields were identical to predicted yield. However, synergetic effects were observed on H2 production when steam was used as the co-gasification medium. Additionally, the presence of steam increased H2/CO ratio up to 2.5 with 10 wt.% hybrid poplar content. Overall, char and tar yields decreased with increasing temperature and increasing biomass content, which led to increase in product gas.
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Parenti, Joshua A. "Thermo-gravimetric analysis of CO₂ induced gasification upon selected coal/biomass chars and blends." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10229.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains v, 126 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 59-69).
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SAMS, DAVID ALAN. "THE KINETICS AND MECHANISM OF THE POTASSIUM-CATALYZED CARBON/CARBON DIOXIDE GASIFICATION REACTION." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188012.
Full textAbstract:
The catalytic effect of potassium on the rate of CO₂ gasification of a bituminous coal char and a pure carbon substrate is investigated. The gasification rate depends on both the catalyst concentration (K/C atomic ratio) and the internal porous structure of the solid. For low values of the K/C atomic ratio, the initial gasification rate (mg carbon gasified per initial gram carbon per min) increases sharply with the addition of catalyst; at higher values, the rate profile levels off. The sharp increase in rate is due to the activation of reaction sites while the plateau is attributed to the saturation of the surface with active sites. The variation of the instantaneous gasification rate (based on remaining carbon) with carbon conversion at various initial K/C ratios is studied. The important reasons for the change in rate are the change in the solid surface area, the loss of active sites, the loss of catalyst by vaporization and the change in the K/C ratio due to carbon depletion. The loss of catalyst from the pure carbon substrate by vaporization is also determined. The extent of this loss depends primarily on the reaction start-up procedure. Temperature programmed experiments show that under inert atmospheres, both KOH and K₂CO₃ react with carbon to give a reduced form of the catalyst which appears to be a prerequisite for the rapid vaporization of potassium. The effect of catalyst loss on both the initial gasification rate and the variation in rate with conversion is determined. The reaction mechanism is studied by a temperature and concentration programmed reaction technique. The proposed redox mechanism contains three surface complexes: -CO₂K, -COK and -CK. The oxide groups are the intermediates during C/CO₂ gasification. The completely reduced form, -CK, is the end product of catalyst reduction and is the precursor for K loss. The stoichiometries of these surface groups are confirmed by oxygen and potassium balance.
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Sun, Tawei. "Alkali attack of coal gasifier refractory linings." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/94471.
Full textAbstract:
Thermodynamic calculations are used to study the alkali reactions in coal gasifier atmospheres. The reactive alkali and sulfur species released from coal are first calculated at temperatures from 800 K to 1900 K and pressures from 1 atm to 100 atm. Four P-T diagrams are constructed for the stable alkali and/or alkali-sulfur species at differ-ent temperatures and pressures. Alkali vapors are generated by the reactions
Na₂CO₃(s) + 2C(s) = 2Na(g) + 3CO(g)
Na₂CO₃(s) + H₂O(g) + C(s) = 2NaOH(g) + 2CO(g)
or
K₂CO₃(s) + 2C(s) = 2K(g) + 3CO(g)
K₂CO₃(s) + H₂O(g) + C(s) = 2KOH(g) + 2CO(g)
The phases formed from alkali-cement, and alkali-sulfur-cement reaction are also predicted. For both 53% and 72% alumina cement, calcium aluminate (CaO•Al₂O₃) is decomposed by the reactions
CaO•Al₂O₃ + 2Na + 1/20₂ = Na₂O•Al₂O₃ + CaO
CaO•Al₂O₃ + 2K + 1/20₂ = K₂O•Al₂O₃ + CaO
or
CaO•Al₂O₃ + 2Na + l/2S₂ = Na₂0•Al₂O₃ + CaS
CaO•Al₂O₃ + 2K + 1/2S₂ = K₂•Al₂O₃ + CaSM.S.
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Nguyen, Quoi The. "Kinetics of gasification and sulphur capture of oil sand cokes." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29041.
Full textAbstract:
Kinetics of steam gasification of both delayed and fluid cokes, byproducts from thermal cracking processes of Athabasca bitumen, have been studied in laboratory-size stirred and fixed bed reactors. The hydrogen sulphide in the product gas was captured in-situ using calcined dolomite and limestones as acceptors.
Experiments were carried out at atmospheric pressure and at temperatures between 800°C and 930°C. The coke particle size ranged from 0.1 to 3.5 mm, and the steam partial pressure was varied from 15.15 to 60.6 kPa. The carbon and sulphur conversions were computed from the knowledge of gas compositions and flowrates and the gasification kinetics of both species established. The effects of sorbent type, particle size, calcination conditions, and Ca/S molar ratios on the extent of sulphur capture during gasification were examined in separate series of experiments.
Scanning electron microscopy, surface area analysis, and mercury porosimetry were employed to relate physical structure changes in the solids to experimental kinetic data.
The rate of gasification for the delayed coke was generally higher than that for the fluid coke, and both cokes were almost unreactive to steam gasification at temperatures below 800°C. Increased reaction temperatures or reduced particle sizes increased both carbon as well as sulphur conversion. The carbon conversion rates were found to go through maxima as the time of reaction and extent of conversion increased. As the reaction proceeded the surface area of the coke increased to a maximum of about five times its initial value and thenfell off sharply. The extent of carbon conversion alone dictated the specific surface area irrespective of temperature, particle size and steam partial pressure.
Both calcined dolomite and calcined limestone were found to be effective in removing sulphur from the product gas. Sorbents possessing a larger specific area or smaller grain size had higher capacity to accept sulphur. At a Ca/S molar ratio of 2.0, the overall sulphur removal was approximately 90% for the first 3 hrs and the H₂S concentration in the produced gas was reduced to about 200 ppm from nearly 1250 ppm. The rate of sorbent conversion from CaO to CaS decreased monotonically with time.
Three available kinetic models for gasification - the Random Capillary Model, the Random Pore Model and the Modified Volumetric Model, were tested with the experimental gasification data. Although reasonable fits were obtained for Xc-t results, the sharp drop in rate at high conversion could not be adequately modelled. Rate constants were established for the initial stage of reaction only.
The Grain model and Continuous reaction models were tested with the
experimental sulphidation results. The sulphidation process was controlled by chemical reaction at low sorbent conversion, and subsequently by diffusion through the product layer at higher conversions. The reaction rate constant and the effective diffusivity were accordingly established as functions of temperature. Values compared favourably with results of sulphidation kinetics done without simultaneous gasification reported in the literature.
The results suggest that the gasification process and the sulphur capture process, which occur together in gasifiers with sorbent injection, can be treated independently.
Indexing terms: Gasification, Carbon Conversion, Sulphur Conversion,
Sulphur Removal, Calcine, Limestone, Dolomite, Hydrogen Sulphide, Sulphidation.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate