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01413 Petrographic and geophysical assessment of coal quality as related to briquetting: The Miocene lignite of the Lower Rhine Basin, Germany
01 Solid fuels (derived solid fuels) 05/01409 Effect of hydrothermal treatment of coal on the oxidation susceptibility and electrical resistivity of HTT coke Sarkar, N. B. et al. Fuel Processing Technology, 2005, 86, (5), 487 497. The influence of hydrothermal treatment of coal prior to carbonization, on the oxidation susceptibility of resultant coke/char, calcined at 1350, 1800 and 2200°C has been investigated. The non-isothermal thermogravimetric analysis technique has been employed, and parameters such as onset, D T G peak temperatures, and cumulative oxidation loss (wt%) at different temperatures have been utilized to compare proneness to oxidation with respective untreated samples apart from electrical resistivity. Data suggest that all the cokes/chars samples produced from hydrothermally treated coals are less reactive and more electrically conductive (less resistive) than their respective untreated counterparts. But the extent of improvement of oxidation resistance and electrical conductivity appears to be coal-specific. The kinetic parameters obtained by non-linear regression analysis on multicurve reveal that the nth order reaction model (where 'n' was found to vary from 0.9 to 1.3) is the best-fitted model. The higher activation energy values observed for hydrothermally treated coke samples are in agreement with the observation of TG analysis data. Overall results indicate the importance of introducing a hydrothermal treatment step for the improvement of oxidation resistance as well as electrical conductivity of the coke samples.
05/01410 Evolution of active species of nanostructured anatase-supported V - O - M o catalyst in the course of reduction and oxidation Kornelak, P. et al. Catalysis Today, 2004, 90, (1-2), 103 107. A nanostructured anatase supported V - O - M o catalyst with V : Mo : Ti = 1 : 9 : 90, obtained by sol-gel method from inorganic substrates, was investigated. The structure of the species formed on the catalyst surface in the course of synthesis was determined and its evolution during oxidation and reduction was studied by the FT Raman spectroscopy. Vanadia-like monolayer islands with some molybdenum atoms substituted for vanadium ones were found to prevail on the surface of the catalyst. Oxidation was revealed to cause monolayer islands to join through monolayer bridges formed by vanadium segregating on the surface. However, reduction of the oxidized catalyst was shown to result in the splitting of the monolayer islands into smaller ones with higher molybdenum content. During the strong reduction irreversible transformation of the vanadia-like surface species into the resembling molybdena ones was observed.
05•01411 Modeling the development of char structure during the rapid heating of pulverized coal Yu, J. et al. Combustion andFlame, 2004, 136, (4), 519 532. A mathematical model for the swelling of a coal and the formation of a char structure during devolatilization is developed, based on a simplified multibubble mechanism. The formation of a char has been considered as having two successive steps: a multibubble stage, followed by a single-bubble stage. During the multibubble stage, the rupture of bubbles is governed by a force balance and the release of volatile matter is determined by the rate at which bubbles rupture. When a cenospheric structure has formed, the single-bubble model applies. During this stage, the rupture of a bubble is determined by its wall stress, and volatile species are released through both bubbles rupturing and direct diffusion of volatile species to the particle's surface. A sensitivity study has been carried out, based on which parameters have been determined for the present modelling work. The model predicts experimental trends for the swelling of a coal and the structural characteristics of chars under different heating conditions. The model is the first to provide a complete quantitative description of the evolution of a char's structure for a pulverized coal during rapid heating. Using standard properties of density fractions of a coal, the model predicts the heterogeneity of a char's structure and quantifies the distribution of different structures. The results predicted by the model agree with experimental measurements.
05•01412
Nanocarbons - recent research in Japan
Inagaki, M. et al. Carbon, 2004, 42, (8-9), 1401-1417. The definition and classification of nanocarbons are briefly discussed and proposed based mainly on their preparation methods. Recent research related to the preparation of nanocarbons and their applications in Japan is reviewed. This includes nanotube preparation by the template method, the polymer blend method coupled with spinning, heating a Si substrate under a steep temperature gradient in alcohol and the decomposition of a SiC single crystal wafer, and preparation of single-wall carbon nanohorns, cup-stacked-type nanofibres and exfoliated carbon fibres. Nano-structured carbons include the preparation of microporous carbons through PTFE decomposition, carbonization of organic aerogels and the zeolite template method, and preparation of nano-structured carbons through structure control of precursors, carbonization of polyimides, pitch with iodine complexes, and precursor design for high carbon yield.
214
Fuel and Energy Abstracts July 2005
05•01413 Petrographic and geophysical assessment of coal quality as related to briquetting" the Miocene lignite of the Lower Rhine Basin, Germany Naeth, J. et al. International Journal of Coal Geology, 2004, 60, (1), 1741. In the Lower Rhine Basin, Germany, Tertiary lignites are mined primarily for electrical power generation and briquetting purposes. Until 2000, when the mine was closed, coals from the Bergheim open pit mine were used for briquetting. After 2000, briquettes were produced from the Hambach open pit mine but did not show the same quality and hardness as those from the Bergheim pit. In this context, the macropetrographic and microlithotype composition of the Hambach lignites was studied in detail. Samples were taken from the three profiles, $1, $2 and $3, and a well, R1. All of the samples were macropetrographically described, analysed in their microlithotype composition, and coals from profile $3 were analysed for their briquetting compression strength. Three horizons of high gelite content were detected in the Main Seam, two of them with negligible thickness and one with a thickness of up to 1 m. Briquettes produced from these horizons are characterized by significantly reduced hardness. By careful interpretation of subtle changes in geophysical log data, it was possible to map the occurrence of these gelite horizons. As a consequence of these studies, an excavation plan was set up by the R W E Rheinbraun to avoiding mining of critical strata for briquetting purposes.
05/01414 Synthesis of carbon nanotubes by detonation of 2,4,6-triazido-l,3,5-triazine in the presence of transition metals Utschig, T. et al. Carbon, 2004, 42, (4), 823-828. The formation of carbon nanotubes via explosive decomposition of an energetic precursor, 2,4,6-triazido-s-triazine C3N12, was investigated with respect to the presence of the transition metals Fe, Ni, Cu, Ti and the degree of confinement of the explosive charge. The carbonaceous detonation products were characterized by transmission and scanning electron microscopy, energy dispersive X-ray analysis and infrared absorption spectroscopy. Multi-walled carbon nanotubes with diameters from 50 to 150 nm and a variety of morphologies were found. Metal particles in the tubes and at some of the tube ends indicate a catalytic growth mechanism.
05101415 The physical character of coal char formed during rapid pyrolysis at high pressure Matsuoka, K. et al. Fuel, 2005, 84, (1), 63-69. Rapid pyrolysis was conducted in a drop tube reactor using seven coals under various operating conditions. In addition to dense char, porous chars (network char and cenospheric char) were formed by the rapid pyrolysis under certain conditions. Porous char was mainly composed of film-like carbon and skeleton carbon. The pyrolyzed coal char particles were characterized in detail. Morphology and bulk density of porous char were quite different from the dense char formed under the same conditions, but elemental composition and BET surface area were similar to each other. Carbon dioxide gasification reactivity of porous char was lower than dense char in the later gasification stage, and this was ascribed to the low reactivity of skeleton carbon.
05•01416 The structure of prospective denox catalysts based on carbon-montmorillonite nanocomposites Grzybek, T. et al. Catalysis" Today, 2004, 90, (1 2), 69-76. Montmorillonites modified with carbon deposits were reported to be promising catalysts of NO reduction with ammonia (SCR). The influence of different preparation methods on structural, textural and sorption properties were discussed. Three preparation methods were considered, differing in the pretreatment of the clay preceding the introduction of carbon precursor (polymer soluble in water). The structure was studied by XRD, texture by sorption of argon, benzene and carbon tetrachloride and surface composition by XPS. The obtained nanocomposites had different textural properties, depending on pretreatment. XPS, TPD and textural data suggest different mechanisms of formation of nanocomposites on untreated and acidic pretreated clays. The introduction of carbon deposits influenced hydrophilic properties. The number of ammonia sites changed after each preparative step: acidic pretreatment, pillaring and the formation of carbon deposits.
05/01410 Evolution of active species of nanostructured anatase-supported V - O - M o catalyst in the course of reduction and oxidation Kornelak, P. et al. Catalysis Today, 2004, 90, (1-2), 103 107. A nanostructured anatase supported V - O - M o catalyst with V : Mo : Ti = 1 : 9 : 90, obtained by sol-gel method from inorganic substrates, was investigated. The structure of the species formed on the catalyst surface in the course of synthesis was determined and its evolution during oxidation and reduction was studied by the FT Raman spectroscopy. Vanadia-like monolayer islands with some molybdenum atoms substituted for vanadium ones were found to prevail on the surface of the catalyst. Oxidation was revealed to cause monolayer islands to join through monolayer bridges formed by vanadium segregating on the surface. However, reduction of the oxidized catalyst was shown to result in the splitting of the monolayer islands into smaller ones with higher molybdenum content. During the strong reduction irreversible transformation of the vanadia-like surface species into the resembling molybdena ones was observed.
05•01411 Modeling the development of char structure during the rapid heating of pulverized coal Yu, J. et al. Combustion andFlame, 2004, 136, (4), 519 532. A mathematical model for the swelling of a coal and the formation of a char structure during devolatilization is developed, based on a simplified multibubble mechanism. The formation of a char has been considered as having two successive steps: a multibubble stage, followed by a single-bubble stage. During the multibubble stage, the rupture of bubbles is governed by a force balance and the release of volatile matter is determined by the rate at which bubbles rupture. When a cenospheric structure has formed, the single-bubble model applies. During this stage, the rupture of a bubble is determined by its wall stress, and volatile species are released through both bubbles rupturing and direct diffusion of volatile species to the particle's surface. A sensitivity study has been carried out, based on which parameters have been determined for the present modelling work. The model predicts experimental trends for the swelling of a coal and the structural characteristics of chars under different heating conditions. The model is the first to provide a complete quantitative description of the evolution of a char's structure for a pulverized coal during rapid heating. Using standard properties of density fractions of a coal, the model predicts the heterogeneity of a char's structure and quantifies the distribution of different structures. The results predicted by the model agree with experimental measurements.
05•01412
Nanocarbons - recent research in Japan
Inagaki, M. et al. Carbon, 2004, 42, (8-9), 1401-1417. The definition and classification of nanocarbons are briefly discussed and proposed based mainly on their preparation methods. Recent research related to the preparation of nanocarbons and their applications in Japan is reviewed. This includes nanotube preparation by the template method, the polymer blend method coupled with spinning, heating a Si substrate under a steep temperature gradient in alcohol and the decomposition of a SiC single crystal wafer, and preparation of single-wall carbon nanohorns, cup-stacked-type nanofibres and exfoliated carbon fibres. Nano-structured carbons include the preparation of microporous carbons through PTFE decomposition, carbonization of organic aerogels and the zeolite template method, and preparation of nano-structured carbons through structure control of precursors, carbonization of polyimides, pitch with iodine complexes, and precursor design for high carbon yield.
214
Fuel and Energy Abstracts July 2005
05•01413 Petrographic and geophysical assessment of coal quality as related to briquetting" the Miocene lignite of the Lower Rhine Basin, Germany Naeth, J. et al. International Journal of Coal Geology, 2004, 60, (1), 1741. In the Lower Rhine Basin, Germany, Tertiary lignites are mined primarily for electrical power generation and briquetting purposes. Until 2000, when the mine was closed, coals from the Bergheim open pit mine were used for briquetting. After 2000, briquettes were produced from the Hambach open pit mine but did not show the same quality and hardness as those from the Bergheim pit. In this context, the macropetrographic and microlithotype composition of the Hambach lignites was studied in detail. Samples were taken from the three profiles, $1, $2 and $3, and a well, R1. All of the samples were macropetrographically described, analysed in their microlithotype composition, and coals from profile $3 were analysed for their briquetting compression strength. Three horizons of high gelite content were detected in the Main Seam, two of them with negligible thickness and one with a thickness of up to 1 m. Briquettes produced from these horizons are characterized by significantly reduced hardness. By careful interpretation of subtle changes in geophysical log data, it was possible to map the occurrence of these gelite horizons. As a consequence of these studies, an excavation plan was set up by the R W E Rheinbraun to avoiding mining of critical strata for briquetting purposes.
05/01414 Synthesis of carbon nanotubes by detonation of 2,4,6-triazido-l,3,5-triazine in the presence of transition metals Utschig, T. et al. Carbon, 2004, 42, (4), 823-828. The formation of carbon nanotubes via explosive decomposition of an energetic precursor, 2,4,6-triazido-s-triazine C3N12, was investigated with respect to the presence of the transition metals Fe, Ni, Cu, Ti and the degree of confinement of the explosive charge. The carbonaceous detonation products were characterized by transmission and scanning electron microscopy, energy dispersive X-ray analysis and infrared absorption spectroscopy. Multi-walled carbon nanotubes with diameters from 50 to 150 nm and a variety of morphologies were found. Metal particles in the tubes and at some of the tube ends indicate a catalytic growth mechanism.
05101415 The physical character of coal char formed during rapid pyrolysis at high pressure Matsuoka, K. et al. Fuel, 2005, 84, (1), 63-69. Rapid pyrolysis was conducted in a drop tube reactor using seven coals under various operating conditions. In addition to dense char, porous chars (network char and cenospheric char) were formed by the rapid pyrolysis under certain conditions. Porous char was mainly composed of film-like carbon and skeleton carbon. The pyrolyzed coal char particles were characterized in detail. Morphology and bulk density of porous char were quite different from the dense char formed under the same conditions, but elemental composition and BET surface area were similar to each other. Carbon dioxide gasification reactivity of porous char was lower than dense char in the later gasification stage, and this was ascribed to the low reactivity of skeleton carbon.
05•01416 The structure of prospective denox catalysts based on carbon-montmorillonite nanocomposites Grzybek, T. et al. Catalysis" Today, 2004, 90, (1 2), 69-76. Montmorillonites modified with carbon deposits were reported to be promising catalysts of NO reduction with ammonia (SCR). The influence of different preparation methods on structural, textural and sorption properties were discussed. Three preparation methods were considered, differing in the pretreatment of the clay preceding the introduction of carbon precursor (polymer soluble in water). The structure was studied by XRD, texture by sorption of argon, benzene and carbon tetrachloride and surface composition by XPS. The obtained nanocomposites had different textural properties, depending on pretreatment. XPS, TPD and textural data suggest different mechanisms of formation of nanocomposites on untreated and acidic pretreated clays. The introduction of carbon deposits influenced hydrophilic properties. The number of ammonia sites changed after each preparative step: acidic pretreatment, pillaring and the formation of carbon deposits.