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A Kinetic Study Of The Role Of Oxygen In Hydrogasification Of Saran Char And Coal Char
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Book Synopsis A Kinetic Study of the Role of Oxygen in Hydrogasification of Saran Char and Coal Char by : Michael Gerard Lussier
Download or read book A Kinetic Study of the Role of Oxygen in Hydrogasification of Saran Char and Coal Char written by Michael Gerard Lussier and published by . This book was released on 1992 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Role of Surface Oxidation in Enhancing the Hydrogasification Rate of Coal Char by : Martin Edward Toomajian
Download or read book The Role of Surface Oxidation in Enhancing the Hydrogasification Rate of Coal Char written by Martin Edward Toomajian and published by . This book was released on 1991 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Masters Abstracts International by :
Download or read book Masters Abstracts International written by and published by . This book was released on 1993 with total page 1040 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Enhanced Coal Hydrogasification Via Oxidative Pretreatment by :
Download or read book Enhanced Coal Hydrogasification Via Oxidative Pretreatment written by and published by . This book was released on 1992 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: The gasification of coal char by hydrogen is much slower than in steam or carbon dioxide; moreover, hydrogasification rate in pure hydrogen decreases sharply with conversion for most carbons. To overcome this kinetic behavior, the oxidation of the char prior to and during hydrogasification has been investigated as a means of enhancing hydro gasification rate. Kinetic rate studies under well-characterized conditions have been complemented by careful surface analyses to characterize oxygen on the char surface prior to and during hydrogasification.
Book Synopsis Enhanced Coal Hydrogasification Via Oxidative Pretreatment. Final Technical Report by :
Download or read book Enhanced Coal Hydrogasification Via Oxidative Pretreatment. Final Technical Report written by and published by . This book was released on 1992 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: The gasification of coal char by hydrogen is much slower than in steam or carbon dioxide; moreover, hydrogasification rate in pure hydrogen decreases sharply with conversion for most carbons. To overcome this kinetic behavior, the oxidation of the char prior to and during hydrogasification has been investigated as a means of enhancing hydro gasification rate. Kinetic rate studies under well-characterized conditions have been complemented by careful surface analyses to characterize oxygen on the char surface prior to and during hydrogasification.
Book Synopsis Hydrogen Inhibition in Steam Gasification of Annealed Saran Char by : Michael Gerard Lussier
Download or read book Hydrogen Inhibition in Steam Gasification of Annealed Saran Char written by Michael Gerard Lussier and published by . This book was released on 1998 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Thermochemistry and Kinetics of Oxygen Interaction with Microporous Chars. Technical Report 12. [199 References]. by :
Download or read book Thermochemistry and Kinetics of Oxygen Interaction with Microporous Chars. Technical Report 12. [199 References]. written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In processes involving the hydrogasification of coal, the coal is first exposed to hydrogen at elevated temperatures and pressures during which devolatilization and gasification of the more reactive parts of the coal occur. A microporous coal char, which is relatively unreactive, is also produced. The char, in turn, can be reacted with steam to generate the hydrogen needed in the first part of the process. Or the char, in part, can be used in a boiler to raise steam. In any case, characterization of coal chars and the relation of character to behavior during gasification and/or combustion is important. This report is primarily concerned with laying the experimental base for the measurement of the heat of interaction of a gas (oxygen in this case) with chars. Following the laying of this base, using a char produced from a reproducible polymer system, heats of interaction of oxygen with chars produced from American coals, ranging in rank from anthracite to lignite, were measured. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the exothermicity and kinetics of interaction between Saran chars and oxygen at selected isothermal temperatures in the range 75 to 850/sup 0/C. The combination of measuring heats of oxygen interaction with chars (using the DSC technique) and weight changes during the interaction opens up a valuable new technique to characterize coal chars. Heats of interaction at 100/sup 0/C are found to be related to rates of char gasification at higher temperatures. Both heats of interaction and gasification rates are, in turn, seen to increase sharply as the rank of coal from which the char is produced is decreased.
Book Synopsis Importance of Active Sites for Char Gasification in Oxygen (air) and Carbon Dioxide by : Philip L. Walker
Download or read book Importance of Active Sites for Char Gasification in Oxygen (air) and Carbon Dioxide written by Philip L. Walker and published by . This book was released on 1980 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1992-03 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Chemisorption, Reaction and Desorption Studies of Coal Chars in Steam, Oxygen and Carbon Dioxide by : L. R. Radovic
Download or read book Chemisorption, Reaction and Desorption Studies of Coal Chars in Steam, Oxygen and Carbon Dioxide written by L. R. Radovic and published by . This book was released on 1990 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of a transient kinetics (TK) technique allowed a direct measurement of reactive surface area (RSA) for chars gasified in both CO2 and O2, i.e., gasification rates normalized with respect to RSA were essentially constant over the entire conversion range. A temperature-programmed desorption (TPD) technique was also used to determine the amount of reactive surface intermediate formed on these chars during gasification in CO2 and O2; the results were in good agreement with those obtained by TK. In addition, TPD allowed an important distriction to be made between the stable C-O complexes and reactive C(O) intermediates residing on the char surface during gasification in CO2 and O2. The application of these two independent but complementary techniques provided a satisfactory quantitative understanding of char reactivity variations with conversion in CO2 and O2. Both techniques possess the unique capability of separately determining the reaction rate constant (site reactivity or turnover frequency) and the number of active sites participating in the reaction (RSA). A comparison of turnover frequencies for different chars gasified in 1 atm CO2 suggested that char gasification may be a structure sensitive reaction. The concept of reactive surface area was also used to achieve a better quantitative understanding of catalyzed char reactivity variations with conversion in carbon dioxide.
Book Synopsis Structural Characteristics and CO2 Reactivity of Partially Gasified Pittsburgh No.8 Coal Chars Generated in a High-pressure, High-temperature Flow Reactor by : Vijayaragavan Krishnamoorthy
Download or read book Structural Characteristics and CO2 Reactivity of Partially Gasified Pittsburgh No.8 Coal Chars Generated in a High-pressure, High-temperature Flow Reactor written by Vijayaragavan Krishnamoorthy and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Integrated gasification combined cycle (IGCC) is an advanced power generation technology based on gasification of coal or solid fuels. Despite many commercial operations, the knowledge of char gasification rates at high pressures and temperatures, crucial to the design and troubleshooting of the gasifiers, are relatively unknown. While many kinetic studies have been performed at atmospheric pressure and low heating rates, there are few studies that examined the reactivity of chars generated at high temperatures and elevated pressuresGasification rate of chars in entrained-flow gasifiers is dependent on both intrinsic reactivity and the gas diffusion rate of reactants into pores. Therefore, the knowledge of intrinsic reaction rate and the structural features of the char are necessary for developing a kinetic model. The aim of the thesis is to determine the intrinsic reactivity and the structural features of the chars generated at elevated pressures and temperatures pertinent to conditions of the entrained-flow gasifiers. A series of interrelated studies were conducted to characterize the gasification behavior of a widely used Pittsburgh No,8 coal. To generate chars under conditions similar to that of the gasifier, a 20 kW high-pressure, high-temperature flow reactor (HPHTFR) was designed to operate up to 1650C and 30 bar. The chars obtained at various temperatures, pressures, and pyrolysis atmospheres were characterized for physical and chemical structure using surface area analyzer, XRD, Raman, and morphological analysis. The CO2 kinetics on chars were obtained using a high pressure thermogravimetric analyzer (HPTGA). The structural properties and intrinsic kinetics of chars widely reported in the literature were generated in inert atmospheres. However, the pyrolysis of feedstock occurs in the presence of reaction gas. This difference can affect char structural properties and intrinsic reactivity. To determine the role of pyrolysis atmosphere, chars were generated in three different atomspheres-CO2/N2, Ar and N2- at 1100C and 6.2 bar. The chars generated in the CO2/N2 atmosphere showed higher conversion compared to that of chars generated in N2 and Ar atmospheres. The increased conversion in the CO2/N2 atmosphere was attributed to increased gasification of tar/soot. While the volatile yield showed some difference, char properties such as surface area, swelling ratio, defects to graphitic band ratio and crystallite sizes showed no difference. The kinetic parameters of the chars were obtained using the nth order model. The activation energy was found to be independent of pyrolysis atmospheres. The order of reaction was found to be significantly affected by the pyrolysis atmosphere. The order of reaction followed the trend: CO2/N2> N2 Ar. The order of the reaction was found to correlate with surface area evolution.Gasification of coal can be impacted by the organic and inorganic compositional heterogeneity, which further impact the char morphology, and the intrinsic reactivity. To account for the compositional heterogeneity, chars were generated from various size fractions (-106+75, -150+106, -212+150, -420+212 m at 1300C and 11.3 bar) and density fractions (1.3 g/cc, 1.3-1.6 g/cc, 1.6g/cc of -106+75 m at 1300C and 11.3 bar). Chars were also generated over a range of temperatures (1100, 1300, and 1400C at 11.3 bar for the -150+106 m fraction), pressures (3.4, 6.2, 11.3, 15.5, and 21.7 bar at 1300C for -150+106 m fraction) to study the effect of temperature and pressure on char structures and reactivity. Chars were characterized for morphology, pore structure (i.e. surface area and pore volume), reflectance, and reactivity using oil immersion microscopy, N2 adsorption technique, reflectance microscopy, and thermogravimetric analyzer, respectively. The swelling ratio, pore volume, and surface area increased up to certain pressure while these parameters decreased with particle size and density fraction. The intrinsic reactivity of chars increased with inorganic matter and feed particle size, while it decreased with increase in char generation temperature. The intrinsic gasification rate is an important parameter for designing a kinetic model. Chars were obtained by partially gasifying Pittsburgh No.8 coal in CO2 atmosphere at 1300C and over a range of pressures (3.4, 6.2, 11.3, 15.5, and 21.7 bar) in the HPHTFR. The intrinsic reaction rate of those chars with CO2 was obtained at the char generation pressure using the HPTGA. The kinetic parameters were obtained using the nth order model. The intrinsic reaction rate, and activation energy were found to be independent of the char generation pressure. The order of reaction was obtained by varying CO2 partial pressures. The order of reaction decreased with increase in char generation pressure. The comparison of initial char with the char obtained at ~20% conversion in the HPTGA for surface area and pore volume showed that the reaction primarily occurs in microporous regions. The order of reaction also closely followed the surface area during gasification in the HPTGA.Through this research, a comprehensive assessment of the entrained-flow gasification behavior of Pittsburgh No.8 coal has been performed using proven experimental techniques under conditions of industrial interest. The structural features and kinetics were obtained. The generated data provide optimum, and trends that can be used as direct inputs to kinetic modelling and gasifier design applications.
Book Synopsis Intrinsic Reaction Kinetics of Coal Chars with Oxygen, Carbon Dioxide and Steam at Elevated Pressures by : Daniel Geoffrey Roberts
Download or read book Intrinsic Reaction Kinetics of Coal Chars with Oxygen, Carbon Dioxide and Steam at Elevated Pressures written by Daniel Geoffrey Roberts and published by . This book was released on 2000 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coal Combustion written by and published by . This book was released on 1992 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past quarter, we carried out a study of the kinetics of char combustion, assessed the reproducibility error of our experiments, and continued our systematic study of the effects of particle size and oxygen concentration on the reactivity of chars. The results from the kinetic study indicated that the rate expression for combustion of Illinois No. 6 chars is first order with respect to the oxygen concentration. The activation energy and the preexponential factor for this reaction were also calculated. The reproducibility error assessment shows that the average relative error increases with increasing particle size. Thus, the number of combustion runs needed for accurate measurements of the reaction rate increases with increasing particle size. For combustion in the regime of diffusional limitations, our results show the ignition temperature decreases with increasing pyrolysis heating rates, increasing coal particle size, decreasing heat treatment temperatures and increasing oxygen concentrations. The kinetic parameters (activation energy, preexponential rate factor, and order of reaction) for the combustion of Illinois No. 6 coal were determined using our thermogravimetric reactor with video microscopy imaging (TGA/VMI). In order to obtain a constant slope from the Arrhenius plot, the experiments were performed in the kinetic control regime. Our previous results demonstrated that in this regime char reactivity is independent of pyrolysis heating rate, heat treatment temperature (HTT), soak time and particle size. For this study therefore, we chose to pyrolyze and combust particles from the 28--32 mesh (500--600 [mu]m) fraction of Illinois No. 6 coal.
Book Synopsis Gasification of Coal Char in Oxygen and Carbon Dioxide at High Temperatures by : Gerald Mandel
Download or read book Gasification of Coal Char in Oxygen and Carbon Dioxide at High Temperatures written by Gerald Mandel and published by . This book was released on 1977 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Combustion Kinetics of Coal Chars in Oxygen-Enriched Environments by : J. J. Murphy
Download or read book Combustion Kinetics of Coal Chars in Oxygen-Enriched Environments written by J. J. Murphy and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Temperature Trends in Coal Char Combustion Under Oxy-fuel Conditions for the Determination of Kinetics by :
Download or read book Temperature Trends in Coal Char Combustion Under Oxy-fuel Conditions for the Determination of Kinetics written by and published by . This book was released on 2014 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis STUDY OF ACTIVATION OF COAL CHAR. by : E. M. Suuberg
Download or read book STUDY OF ACTIVATION OF COAL CHAR. written by E. M. Suuberg and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the final report on a project whose aim is to explore in a fundamental manner the factors that influence the development of porosity in coal chars during the process of activation. It is known that choices of starting coal, activating agent and conditions can strongly influence the nature of an activated carbon produced from a coal. This project has been concerned mainly with the process of physical activation, which in fact involves the gasification of a char produced from a coal by oxidizing gases. This is of interest for two reasons. One is that there is commercial interest in production of activated carbons from coal, and therefore, in the conditions that can best be used in producing these materials. Much is already known about this, but there is a great deal that is in the realm of ''trade secret'' or just ''industry lore''. The second reason for interest in these processes is that they shed light on how porosity develops during any gasification process involving oxidizing gases. This has implications for understanding the kinetics and the role that ''surface area'' may play in determining kinetics. In earlier reports from this project, several conclusions had been reached upon which the present results rest. There is an often-cited difference in use of nitrogen and carbon dioxide as molecular probes of carbon porosity when using vapor adsorption techniques. Carbon dioxide is often ''preferred'' since it is argued that it offers greater access to fine microporosity, due to the higher temperature of carbon dioxide as opposed to nitrogen measurements. The early phases of this work revealed that the extreme differences are observed only in chars which are not much activated, and that by a few weight percent burnoff, the difference was negligible, provided a consistent theoretical equation was used in calculating uptake or ''surface area''. In another phase of this study, it was noted in a preliminary way how the use of different oxidizing environments would lead to very different porosity development in the same char. There did not seem to be a link to the overall inherent reactivity of the gas-char combination to the pattern of porosity development. In another portion of this study, it was observed that the expected pattern of porosity development could be seen, as a function of whether the process was carried out in a pure chemical kinetic control regime (Zone I) or in a partially mass transfer control regime (Zone II). This portion of the study was useful in suggesting that the unburned carbon from many practical pulverized coal combustion processes had actually emerged from a Zone II environment. This confirms other published hypotheses, and strongly suggests that the material does not survive the boiler environment because it was produced in a purely oxygen mass transfer limited zone (so-called Zone III) or because it was simply so unreactive that it could not burn up in the allotted time (a pure Zone I argument). Moreover, it is believed that the very rapid initial opening of porosity that is revealed by the rapid disappearance of nitrogen and carbon dioxide accessible porosity may be associated with a very thin surface layer of pyrolytically-formed carbon that effectively blocks the bulk char structure from nitrogen. Once removed by low extent of burn-off this phenomenon disappears. Finally, the project turned to comparing the relative influences of the starting coal and the oxidizing environment on the nature of porosity that was developed. Once again, the Argonne Premium coal suite served as a source of chars that would be representative of the broad range of coals found an utilized in the US. The conclusion is that the starting coal has a profound influence upon the ability of an oxidizing agent to develop porosity in the char. This is the single most important factor. Beyond this, however, there was a surprise to the extent that the ordering of porosity development did not follow a simply predictable pattern related to the reactivity of the activating agents. Oxygen is a very effective activating agent, if operation can be kept under control under so-called Zone I conditions. Its effectiveness is comparable to that of the more widely-employed steam.
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