Showing papers on "Coal published in 1990"

Trace Elements in Coal

Abstract: Origin of trace elements in coal mode of occurrence of trace elements in coal methods of analysis contents of trace elements in coals comparisons of coal with shale and soil variations within seams radioactivity and coal relevance of trace elements in coal.

Chemical percolation model for devolatilization. 2. Temperature and heating rate effects on product yields

Abstract: The chemical percolation devolatilization (CPD) model previously developed to describe the devolatilization behavior of rapidly heated coal was based on the chemical structure of the parent coal. Percolation lattice statistics are employed to describe generation of finite tar clusters as labile bonds are cleaved in the infinite coal lattice. The model is used here to describe effects of heating rate and temperature on tar and gas release from coal. Results indicate that the CPD models predictions yied good agreement with published data for a wide range of coals and particle heating rates

Cross-linking reactions during coal conversion

Abstract: During coal conversion, the breakup of the coal macromolecular network and resulting product formation are controlled by the relative rates of bond breaking, cross-linking, and mass transport. THe objective of this work was to systematically study the variations in cross-linking with several parameters (rank, temperature, heating rate, pretreatment, etc.), to identify the factors that control cross-linking rates. This paper describes a study of cross-linking behavior in which chars of a number of coals (including the Argonne premium coal samples) have been pyrolyzed under a variety of temperature histories and analyzed at intermediate extents of pyrolysis for solvent swelling behavior and functionnal group compositions

Free-radical thermolysis and hydrogenolysis of model hydrocarbons relevant to processing of coal

Abstract: Mechanisms are reviewed for thermal decomposition of selected hydrocarbons that serve as models for processing of coal. The hydrocarbon classes emphasized are aromatics, alkylaromatics, α,ω-di-arylalkanes, and hydroaromatics, especially tetralin. Perturbations by added sources of hydrogen, especially H 2 and hydroaromatics, are also covered. Free-radical pathways dominate. Emphasis is placed on quantitative understanding of elementary radical processes for bond breaking, bond making, and hydrogen transfer and on the response of the competitions among these to hydrocarbon structure and reaction conditions. Selected implications for coal processing are drawn

Combustion and leaching behavior of elements in the Argonne Premium Coal Samples

Abstract: Eight Argonne Premium Coal samples and two other coal samples were used to observe the effects of combustion and leaching on 30 elements. The results were used to infer the modes of occurrence of these elements. Instrumental neutron activation analysis indicates that the effects of combustion and leaching on many elements varied markedly among the samples. As much as 90% of the selenium and bromine is volatilized from the bituminous coal samples, but substantially less is volatilized from the low-rank coals. We interpret the combustion and leaching behavior of these elements to indicate that they are associated with the organic fraction. Sodium, although nonvolatile, is ion-exchangeable in most samples, particularly in the low-rank coal samples where it is likely to be associated with the organic constituents. Potassium is primarily in an ion-exchangeable form in the Wyodak coal but is in HF-soluble phases (probably silicates) in most other samples. Cesium is in an unidentified HNO 3 -soluble phase in most samples. Virtually all the strontium and barium in the low-rank coal samples is removed by NH 4 OAc followed by HCl, indicating that these elements probably occur in both organic and inorganic phases. Most tungsten and tantalum are in insoluble phases, perhaps as oxides or in organic association. Hafnium is generally insoluble, but as much as 65% is HF soluble, perhaps due to the presence of very fine grained or metamict zircon. We interpret the leaching behavior of uranium to indicate its occurrence in chelates and its association with silicates and with zircon. Most of the rare-earth elements (REE) and thorium appear to be associated with phosphates. Differences in textural relationships may account for some of the differences in leaching behavior of the REE among samples. Zinc occurs predominantly in sphalerite. Either the remaining elements occur in several different modes of occurrence (scandium, iron), or the leaching data are equivocal (arsenic, antimon

Method of increasing the permeability of a coal seam

Abstract: A method of increasing the rate of methane production from a coal seam includes introducing a desired volume of a gas, that causes coal to swell, into the coal seam adjacent a wellbore, maintaining the coal seam adjacent the wellbore in a pressurized condition for a period of time to permit the gas to contact a desired area of the coal adjacent the wellbore, and relieving the pressure within the coal seam by permitting fluids to flow out from the wellbore at a rate essentially equivalent to the maximum rate permitted by the wellbore and any surface wellbore flow control equipment. Uneven stress fractures should be created in the coal by this method which will increase the near wellbore permeability of the coal seam.

The performance of long term contracts : further evidence from coal markets

Abstract: This article extends my previous work on price adjustment in long-term coal contracts to cover a period in which the nominal market prices for coal were below the prices specified in the preexisting long-term contracts. Two related sets of questions are explored. First, did actual transactions prices for coal delivered pursuant to old contracts follow contractual pricing formulas, leading to higher rather than lower prices, or did they adapt quickly to changing market conditions? Second, what were the relative roles offormal contractual provisions, voluntary renegotiation, and breach of contractual promises in determining actual transactions prices, quantities, and the durability of contractual relations. It appears that actual transactions prices for coal delivered pursuant to old contracts were rigid downward, following written contractual provisions rather than changes in current market values. Changing economic conditions led to an increase in renegotiation, breach, and litigation, but the vast majority of existing long-term contracts endured through the market downturn without major changes in prices or quantities from those previously agreed to by contract. The threat of legal sanctions appears to have played an important role in sustaining contractual promises.

Analysis of the argonne premium coal samples by thermogravimetric fourier transform infrared spectroscopy

Abstract: This paper describes the most recent improvements in the apparatus and presents its application in characterizing the Argonne premium coal samples. The TG-FTIR apparatus for pyrolysis, oxidation of pyrolysis products, and oxidation of the sample is described. To analyze coal, a sequence of drying, pyrolysis, and combustion is employed to obtain proximate analysis, volatile composition, volatile kinetics, and relative char reactivity. Pyrolysis results are presented for the eight Argonne coals, several demineralized coals, and two oxidized samples of Pittsburgh Seam coal. A kinetic analysis was applied to species evolution data collected at several different heating rates. There is a systematic variation in rate with rank

Fuel Science and Technology Handbook

Abstract: The focus here is on new methods and known technologies that assist in the development of unconventional worldwide fossil fuel resources comparing petroleum to other fossil fuels, such as tar sands and heavy oils, bitumen, coal, oil shale, and natural gas. The contributions contrast scientific and t

A Laboratory Study of the Effect of Coal Selection on the Amount and Composition of Combustion Generated Submicron Particles

Abstract: Eleven selected coals were burned under controlled conditions in a laboratory combustion furnace to determine the effect of coal type on the amount and composition of combustion generated inorganic submicron particles. Significant differences in both the amount and composition of submicron particles were found between coals and particularly between rank of coals. In most cases, however, the extent to which an element appeared in the submicron fume could be correlated on the basis of its occurrence and distribution in the coals.

Co-generation system for co-producing clean, coal-based fuels and electricity

Abstract: A method for preparing coal-derived fuel compositions while simultaneously producing electricity by utilizing a novel co-generation configuration employing the hydrodisproportionation of coal. Hydrodisproportionation is the short residence time decomposition and volatilization of coal to produce liquid coproducts, minimizing char and gas production without utilization of external hydrogen, that is, hydrogen other than that contained in the coal feedstock. The char produced is gasified to simultaneously produce steam for electrical power generation and syngas to produce methanol in a once-through process. The methanol purge gas is used as a fuel gas for a gas-driven power generating turbine. The waste heat from the power generation is used as the process heat for hydrodisproportionation.

Measurement of parameters impacting methane recovery from coal seams

Abstract: This paper describes the behaviour of coalbeds as gas reservoirs and discusses the results of a study carried out to establish the effect of release of methane on gas flow behaviour of coal. Experimental work consisted of microscopy, establishing adsorption/desorption isotherms, and monitoring changes in the volume of coal matrix with increasing and decreasing gas pressure. Micrographs obtained using small pieces of coal indicated that coal is made up of blocks, containing matrix and pores, separated by microfractures. This confirms the dual porosity model of coal structure with a primary porosity, and a fracture/cleat porosity-physical model used in coalbed methane simulators developed recently. Isotherms suggested that for the samples tested, a major part of the gas is released only after pressure falls below 600 psi, and this is primarily due to desorbing gas. Results of the volumetric strain experiments indicated that there is an increase in matrix volume with increase in gas pressure, in spite of matrix compressibility. Adsorption, therefore, induces swelling of the matrix. With decrease in gas pressure from 1000 psi to atmospheric, the matrix volume shrunk by 0.5%. These experimental results were inputted in a reservoir model and simulation runs made to determine the effect of pore volume and matrix shrinkage compressibilities on gas production. Over a five year period 60% more gas was produced when matrix shrinkage was used as an input parameter.

Mouse skin tumorigenicity studies of indoor coal and wood combustion emissions from homes of residents in Xuan Wei, China with high lung cancer mortality

Abstract: The rural Xuan Wei County, Yunnan Province, China, has an unusually high lung cancer mortality rate that cannot be attributed to tobacco smoke or occupational exposure. The lung cancer rate is associated with 'smoky' coal, in contrast to wood or 'smokeless' coal burned in unventilated homes. This study was conducted to characterize and compare mouse skin tumorigenicity of the coal and the wood combustion emissions and to link the animal data to human lung cancer. Indoor air particles (less than 10 microns) were collected from a central commune where the lung cancer mortality rate is high and smoky coal is the major fuel used and also from a south-western commune where lung cancer mortality rate is low and where wood or smokeless coal are the major fuels used. The organic extracts of these indoor air particles from smoky coal, smokeless coal and wood combustion were analysed for polycyclic aromatic hydrocarbons and assayed for skin tumor initiation activity and complete carcinogenicity in SENCAR mice. The results showed that the organic extract of the emission particles from smoky coal combustion is the most active in tumor initiation among the three combustion emission samples followed by smokeless coal and then wood. The organic extract of the particles from smoky coal combustion was shown to be a potent complete carcinogen, whereas the wood extract was relatively inactive as a complete carcinogen. The extract of particles from the smokeless coal combustion was not tested for complete carcinogenicity because of inadequate supply. Eighty-eight percent of the mice treated with the smoky coal extract showed carcinomas, averaging 1.1 carcinomas per tumor-bearing mouse at the end of the 77 week study. These findings were in agreement with the epidemiological data, which showed that the Xuan Wei residents using smoky coal as a major fuel in homes had a high lung cancer mortality rate. This study demonstrates that the results of the tumorigenicity assays in mice were in agreement with human lung cancer data.

Hydrothermal alteration in anthracite from eastern Pennsylvania: Implications for mechanisms of anthracite formation

Abstract: Orthogonal joint sets (cleat) in anthracite-rank coal beds from eastern Pennsylvania contain two mineralogically and chemically different authigenic clay mineral assemblages In localities from all four anthracite fields, the systematic cleat contains significant quantities (20 to 95 wt%) of authigenic rectorite, sudoite, or tosudite, which are clay minerals primarily associated with hydrothermal veins and ore deposits The strike of systematic cleat in this region roughly parallels the inferred direction of lateral compressive stress during the Alleghany orogeny The opposing nonsystematic cleat contains mostly authigenic NH 4 -illite, a clay that also occurs in the coal matrix All of these authigenic clay minerals formed during anthracitization (T> 200 °C) by replacement of kaolinite and quartz, both of which formed during an earlier stage of coalification and are present in the joints and matrix of nearly all coal samples These distinct mineralogical-structural relations are observed throughout the Anthracite region and suggest that (1) mineralogical variations in the coal joints are related primarily to permeability variations that were controlled by the orientation of Alleghanian stress fields, (2) hydrothermal fluids passed through the systematic cleat during anthracitization, and (3) hydrothermal alteration influenced diagenesis in this region Hydrothermal alteration may be related to basin-wide fluid migrations that were driven by Alleghanian-age uplift Basinal fluid flow, concentrated along permeable joints and detachment zones, could have efficiently transported heat from depth and thereby increased the rate of coalification and decreased the postulated minimum depths at which anthracitization occurred (perhaps ≤5km vs 6-10 km)