Showing papers on "Coal published in 1993"

Coal: Typology - Physics - Chemistry - Constitution

Abstract: Part 1 Coal Typology: Coal as an economic good Coal as fuel and raw material Coal as an organic sediment Coal as a rock Coal as a biological debris Coal as an evolving organic chemical complex Coal as a solid colloid Coal as an enigma in solid state physics Coal as an object of classical chemical analysis Coal as an object of physical analysis. Part 2 Coal Physics: Physical properties and the additivity concept Volumetric properties Optical properties Electrical properties Magnetic properties Mechanical properties Cohesive and interfacial energy properties Thermal properties. Part 3 Coal Chemistry: The action of solvents on coal The action of oxidizing agents on coal Action of air and molecular oxygen on coal The action of hydrogen on coal The action of heat on coals The "grand processes" of coal utilization. Part 4 Coal Constitution: The chemical and physical nature of coals Coal analogues Coalification revisited Coal research. Part 5 Compendium.

Ash deposition during biomass and coal combustion: A mechanistic approach

Abstract: The variability in both inorganic and organic properties of biomass fuels is large. This paper discusses combustion-driven transformations and deposition of inorganic material found in solid fuels, with a focus on the formation of deposits and their properties. A small number of mechanisms is used to describe both the transformations and deposition. The discussion below outlines this mechanistic approach to describing the fate of inorganic material in solid fuels with a particular focus on the mechanisms of ash deposition. This mechanistic approach has the potential of embracing a large range of fuel variations, combustor types, and operating conditions without the need of developing extensive databases or testing procedures for each new situation. The approach has been successfully demonstrated for coal combustion, and examples from coal experiments will be used as illustrations. The same methodology and logic can be applied to biomass combustion. A comparison of coal and biomass is briefly presented, including the chemical structures and the modes of occurrence of inorganic material in the fuels. The major mechanisms of ash deposition during combustion of coal and biomass are related to the types of inorganic material in the fuel and the combustion conditions. The effects of fuel (biomass or coal) characteristics and combustor operating conditions on ash deposit properties such as tenacity, emissivity, thermal conductivity, morphology, strength, chemical composition, viscosity, and rate of growth are discussed. A mechanistic model describing ash deposition in solid-fuel combustors is presented and used to postulate characteristics of ash deposits formed in biomass combustors.

Trace and Minor Elements in Coal

Abstract: Coal will be a major energy source in the United States and in many other countries well into the 21st century. Although coal is composed predominantly of organic matter, inorganic constituents in coal commonly attract more attention and can ultimately determine how the coal will be used.

Coal and Coal-bearing Strata: Recent Advances

Abstract: Recent advances in coal geology are highlighted. The increase in our knowledge of peat formation is emphasized and the application of hydrological models of mire systems to coal-bearing strata is advocated. The importance of coalification studies to the geological community as a whole should not be underestimated. Consideration of the original peat-forming vegetation by coal geologists is advocated. Both conceptual and technical advances in coal geology are reviewed. Integration of different disciplines is likely to yield further insights into the study of coal and coal-bearing strata.

Mechanistic Aspects of the Formation of Hydrocarbons and Alcohols from CO Hydrogenation

Abstract: In 1973 the oil crisis prompted considerable world interest in the production of synfuels which, as a result, led to the development of the Mobil Methanol to Gasoline Process [1] and more recently to the Shell Middle Distillate Process [2]. Synfuels have been a subject of both scientific and political interest for most of the 20th century. With the recent Gulf crisis, which has resulted in a surge in crude oil prices, it is clear that the search to find economic alternatives to the use of petroleum as an energy source will continue. This observation is based on the fact that the world reserves of coal and natural gas far exceed those of oil, and this fact alone implies that the conversion of coal and natural gas to transportation fuels is almost certain to become more widespread within the next 20 years.

Coalbed Methane Characteristics of Gates Formation Coals, Northeastern British Columbia: Effect of Maceral Composition

Abstract: The majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite-rich coals. However, western Canadian coals are more inertinite-rich than those of the western United States and are shown to differ in gas adsorption characteristics. The influence of maceral composition upon gas adsorption characteristics of medium-volatile coal samples from the middle Cretaceous Gates Formation of northeastern British Columbia was investigated. Lithotype (coal facies) samples were analyzed for surface area, maceral and mineral composition, and methane adsorption; standard coal analyses were also performed (proximate, low-temperature ash, and equilibrium moisture). The vitrinite content of the samples analyzed ranges from 18 to 95% (vol. %, min ral matter free); the ash yield varies from 4.4 to 33.7% (wt. %). Both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms. On a mineral matter-free basis, the amount of methane adsorbed generally increases with vitrinite enrichment. The lowest methane adsorption occurs in the sample with the highest inertinite content. Carbon dioxide surface areas of the lithotypes range from 87 to 176 m2/g on a raw-coal basis, and from 99 to 184 m2/g on a mineral matter-free basis. Surface area generally decreases with increased mineral matter content and increases with increased vitrinite content. The increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite: vitrinite is predominantly microporous whereas inertinite is meso- to macroporous. The monolayer volumes of carbon dioxide (as calculated from the DubininRadushkevich equation) are higher than those of methane (as determined from the Langmuir equation), but are correlated. The methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit.

Relation between functional forms of coal nitrogen and formation of nitrogen oxide (NOx) precursors during rapid pyrolysis

Abstract: The formation of NO x precursors during rapid pyrolysis was investigated for 20 coals covering wide ranks at temperatures of 853-1488 K to elucidate the influence of coal properties on NO x formation during coal combustion. It was found that the main compositions of volatile nitrogen are HCN, NH 3 , and N 2 under these experimental conditions. Their yields are strongly dependent on coal types and pyrolysis temperature. By analyzing functional forms of coal nitrogen in parent coals and chars after pyrolysis using X-ray photoelectron spectroscopy, the relation between nitrogen functionality and formation of nitrogen-containing species has been further demonstrated. Three nitrogen functional forms of pyrrole type, pyridine type, and quaternary nitrogen are observed for all coals

Hydrocarbons from Coal

Abstract: Coal, “the black rock that burns,” is the subject of song, story, and legend. The earliest literature citation of coal (combustible bodies, some of which by inference must be coal) is credited to Aristotle in his treatise “Meteorology,” which may date near the middle of the fourth century B.C. Theophrastus, a student of Aristotle, at what is probably a slightly later date provides descriptions of different forms of coal based on their behavior in combustion, identifies areas of occurrence, and states that it was used by smiths (footnote by Hoover to Agricola, 1556). Though the Greek philosophers are responsible for the earliest known literature citations, China and perhaps other parts of eastern Asia are usually believed to have preceded the Mediterranean area in recognition of coal as a peculiar material with usable properties. Inouye (1913) states that although there is no authentic record of the history of the Fu-shun coal field in southern Manchuria, “it is said that the coal was used as fuel … for copper smelting in times as remote as 2,000 or even 3,000 years ago.” Fires through most of man’s history have been fed by “traditional fuels"—wood, straw, dung, and other plant materials. That coal could be of complementary usage is recorded in the remains of funeral pyres in Wales, dated about 3,000 years ago (Lindbergh and Proverse, 1977). However, the versatility of coal was not widely appreciated, and the discovery and use of charcoal satisfied most needs of primitive metal-working. By the end of the

Fundamentals of coal combustion : for clean and efficient use

Abstract: 1. Coal Processes and Technologies (P.T. Radulovic, L.D. Smoot). Introduction. Entrained Beds. Fluidized Beds. Fixed Beds. Other Processes. 2. Process Data and Strategies (G.J. Germane, C.N. Eatough, J.N. Cannon). Introduction. Scale of Data. Instrumentation for Data Collection. Analysis of Process Data. Representative Data Sets. Coal Utilization Strategies. 3. Coal Characteristics, Structure, and Reaction Rates (K.L. Smith, L.D. Smoot, T.H. Fletcher). Introduction. Selection of a Suite of Commonly Used Research Coals. Petrology and Macromolecular Structures of Coal. Coal Structural Characterization. Coal Devolatization. Char Oxidation. 4. Ash Formation and Deposition (S.A. Benson, M.L. Jones, J.N. Harb). Introduction. Inorganic Constituents in Coals. Formation of Ash Intermediates. Deposit Initiation. Deposit Characteristics and Growth. Properties of Deposits. Model Development. 5. Radiative Heat Transfer (M.P. Menguc, B.W. Webb). Introduction. Fundamentals of Radiative Transfer. Solution Techniques for the RTE. Radiative Properties. Application to Practical Systems. 6. Pollutant Formation and Control (R. Boardman, L.D. Smoot). Introduction. Combustion Chemistry of Nitrogen Oxides. Modeling of Nitrogen Oxides. Nitrogen Oxide Control Technologies. Mechanisms of Sulfur Oxides Formation. Sulfur Pollutant Reduction Technologies. SO x , NO x Abatement Technology Demonstrations. 7. Turbulent Reacting Flows (P.A. McMurthy, M. Queiroz). Fundamentals. Modeling Techniques. Multi-Phase Reacting Flows. Higher Order Reacting Flows. Higher Order Simulations. 8. Comprehensive Modeling (B.S. Brewster et al.). Introduction. Entrained-Bed Models. Fixed-Bed Models. Fluidized-Bed Models. Abbreviations. Author Index. Subject Index. (A Summary, References and Nomenclature are included with each chapter).

Recovery of fuel gases from underground deposits

Abstract: A fuel gas, typically methane, is produced from a coal seam penetrated by an injection well and a gas production well by first introducing liquefied or gaseous carbon dioxide through the injection well into the coal seam and subsequently introducing a weakly adsorbable gas, for example nitrogen, through the injection well and into the coal seam As the weakly adsorbable gas passes through the coal seam, it forces the carbon dioxide through the seam If the carbon dioxide is in liquefied form, it evaporates as it moves through the seam, and the carbon dioxide gas desorbs methane from the coal and sweeps it toward the production well The methane is withdrawn from the seam through the production well

Material-Balance Techniques for Coal-Seam and Devonian Shale Gas Reservoirs With Limited Water Influx

Abstract: This paper presents the development of two material-balance methods for unconventional gas reservoirs. One method is appropriate for estimating original gas in place; the second is appropriate for making reservoir predictions. These techniques differ from the material-balance methods for conventional gas reservoirs in that the effects of adsorbed gas are included. For estimating original gas in place, the assumption of equilibrium between the free- and adsorbed-gas phases is required. No additional assumptions are required for reservoir predictions

Role of moisture in coal structure and the effects of drying upon the accessibility of coal structure

Abstract: This paper is concerned with the colloidal gel nature of coals and what impacts this has upon several properties of practical significance. Water is shown to be a good swelling agent for coals ranging in rank from lignites up to high-volatile bituminous, and the coals shrink when dried from the as-mined state. Shrinkage upon drying is correlated by volumetric shrinkage (%) = 0.863 (moisture content, wt%)-0.162. Shrinkage of this magnitude suggests that measurements of «surface areas» of dried coals will provide an erroneous estimate of true accessibility of coal structure. In addition, the presence of moisture in the structure of coals serves to significantly enhance the rate of uptake of solvents by the coal

Pyrolytic Degradation Studies of a Coal-Derived and a Petroleum-Derived Aviation Jet Fuel

Abstract: The future high-Mach aircraft requires advanced jet fuel with high stability in rigorous thermal environments. In this work high-temperature thermal stability of two JP-8 type jet fuels, a petroleum-derived JP-8P and a coal-derived JP-8C was studied by stressing in closed reactors at 450°C under 0.7 MPa of N 2 for periods ranging from 0.5 to 16 h. The extents of fuel degradation in terms of liquid depletion, gas formation, and solid deposition were always higher with JP-8P than with JP-8C. There appeared an induction period for solid formation, which was longer for JP-8C than for JP-8P

Gaseous emissions from circulating fluidized bed combustion of wood

Abstract: The emissions of NO, N2O, CO and SO2 were investigated during combustion of wood in a circulating fluidized bed boiler as a function of various parameters, including bed temperature, air supply and load. Emissions from mixtures of wood and coal were also investigated. The results show that the nitrogen oxide emission is directly related to the nitrogen content of the wood. The small amount of char in the bed during combustion of wood results in a much smaller reduction in the NO formed in the case of wood compared to that during combustion of coal and reduces the impact of bed temperature and air supply on the NO emissions during combustion of wood as compared to coal. Emission of N2O during combustion of wood was negligible.

Process for removing carbon dioxide regeneratively from gas streams

Abstract: The invention relates to a process for removing carbon dioxide regeneratively from a hot gas stream, containing flue gases or fuel gases, wherein the gas stream is successively: a) used for heating (1) and/or desorbing (2) a solid absorbent loaded with carbon dioxide; b) optionally used for generating energy (12); c) passed through an absorber (3) in which carbon dioxide from the gas stream is absorbed on the absorbent, and: d) is discharged (11); and wherein: e) the absorbent from step c) is desorbed in a desorber (2) at least partially and optionally under elevated pressure and is then returned to step c). A system for carrying out said process is also described. The process and the system are suitable for removing carbon dioxide from combustion gases and for shifting (coal) gasification gases towards hydrogen.