Pyritic Sulfur Content Research Articles

Seasonal Distribution of Sulfur Fractions in Louisiana Salt Marsh Soils

The profile distributions of specific sulfur forms were examined at a site in a Louisiana salt marsh over a 1-yr period. Soil samples were fractionated into acid-volatile sulfides, HCl-soluble sulfur, elemental sulfur, pyrite sulfur, ester-sulfate sulfur, carbon-bonded sulfur, and total sulfur. Inorganic sulfur constituted 16% to 36% of total sulfur, with pyrite sulfur representing <2%. Pyrite sulfur content in marsh soil was relatively high in winter. Pyrite sulfur and elemental sulfur together accounted for 4% to 24% of the inorganic sulfur fraction. Between 74% and 95% of inorganic sulfur was present as the HCl-soluble sulfur form. A significant negative correlation between acid-volatile sulfides and elemental sulfur observed in summer suggested the transformation of fulfides to elemental sulfur. Organic sulfur, in the forms of ester-sulfate sulfur and carbon-bonded sulfur, predominated in all sampling periods, comprising 64% to 84% of total sulfur. The conversion of ester-sulfate sulfur into carbon-bonded sulfur was more likely to occur in winter than in other seasons. Carbon-bonded sulfur accounted for 53% to 89% of the organic sulfur. Organic sulfur was the major contributor to the variation of total sulfur in all seasons studied. Total sulfur concentration showed a statistically significant increase with depth.

Sulfur distribution and isotopic composition in peats from the Okefenokee Swamp, Georgia and the Everglades, Florida

Peat cores from three aquatic environments (freshwater, brackish and marine have been analyzed for organic, pyritic and sulfatic sulfur contents and isotope ratios. Peat collected from each environment has a unique combination of sulfur content, distribution and isotope ratio. Freshwater peat from the Okefenokee Swamp contains the least sulfur (0.26 to 0.48%, primarily organic sulfur) and is vertically uniform in sulfur content and isotope ratio. The organic sulfur isotope ratio of the Okefenokee pear (+ 12.3 to + 12.8 per mil) is similar to that of sulfate in associated surface waters. Cores from presently brackish and marine peats from the Florida Everglades have high organic, pyritic and sulfatic sulfur contents with vertical variability in sulfur content and isotope ration. The isotope ratio of organic sulfur in the brackish and marine peat is lighter than that of sulfate associated with their respective peat-forming environments. Organic sulfur in the marine peat is isotopically lighter than in the brackish peat. Freshwater peats subsequently overlain by sediment associated with brackish to marine waters may have a sulfur content, distribution and isotopic ratio indistinguishable from peats derived under brackish or marine conditions. The primary source of sulfur in peats is dissolved sulfate associated with the peat-forming system. The sulfate concentration of the waters in which a peat forms is of major importance in determining the isotopic composition of the sulfur form found in peat. The content, distribution and isotopic ratio of low and high sulfur peats are similar to those reported for coals, indicating that the fundamental sulfur geochemistry of coals may have been established during the peat-forming stage of coalification. The organic sulfur content and isotope ratio of a coal may be useful in estimating the relative sulfate ion concentration of the waters present during the peat-forming stage of coalification where transgressive sequences are not involved. The sulfate ion concentration of paleowaters could be used to interpret the paleoenvironment during the peat-forming stage of coalification and thus, information about the organic sulfur content and isotope ratio of coals may prove useful in helping to assess coal quality in advance of mining.

Sulfur sources and sulfur bonding of some central European attrital brown coals

The Tertiary attrital brown coals of Central Europe contain usually between 0.2 and about 5% sulfur. It is well known that the sulfur content consists of sulfide (mostly pyrite), sulfates (gypsum and other sulfates), organic sulfur, and a low percentage of elemental sulfur. Usually, the pyrite sulfur content is said to be the highest, but recently more and more authors have published data showing a high percentage of organic sulfur for several coals. Investigating samples of coals from about 50 deposits from several central European countries, we also obtained such data. By means of a glow discharge-excited, low-temperature ashing technique, we got low-temperature ashes (LTA) containing a wide variety of minerals of different origin, Pyrite, which was shown to be stable during the LTA treatment used, was found only in a few specimens with remarkable amounts. Therefore, it is necessary to search for the bonding and the source of the sulfur in the coals and the LTAs. The LTAs investigated contain a number of detrital minerals (syndeposiionally transported into the coal-forming environment in solid state) which are mostly silicates and do not contain any sulfur. The authigenic minerals (postdepositionally crystallized in the coal) are rare but show a wide variety in their chemical composition. Most of them contain sulfur bound to the common metals of the coal, e.g., calcium, magnesium, iron, and others. In addition, there is a high mineral content in the LTAs, which was formed during the ashing run and these are called artifacts. These artificial minerals frequently have the same chemical composition as the authigenic material but are different in their structural properties. Therefore, the artifacts are qualitatively distinguishable from the authigenic minerals. Both the anions and the cations of the artificial minerals stem from the organic substance of the coal which is slowly destroyed during the LTA process (Fig. 1). Due to the instability of the structural properties of the sulfate artifacts, the detectable differences between them and the authigenic minerals are lost soon

A comparison of methods for the determination of the pyritic sulfur content of coal

The accurate determination of the concentration of inorganic sulfur in coal is of major environmental importance. With few exceptions, unless the coal is weathered, the inorganic sulfur present within the coal is iron disulfide minerals, chiefly pyrite and to a lesser extent, marcasite. The accuracy of the presently used ASTM procedure for the determination of iron disulfide sulfur can be questioned because various quantities of the mineral grains encapsulated by the coal matrix are not available to the acid-leaching reaction utilized in the procedure. The goal of this study was to test this hypothesis and to devise a procedure which would give analytical results in agreement with a matrix-independent analytical procedure, namely Mossbauer spectroscopy. The concentration of inorganic sulfur was determined for a suite of coal samples varying in sulfur abundance by the ASTM D2492 procedure on two particle sizes of coal, −60 mesh and −220 mesh. The coal samples were subjected to low-temperature ashing and the resultant ashes were leached with 0.5 N hydrochloric acid. The total weight loss from the ashing process was made up by adding sulfur-free spectrographic grade carbon and the sulfur content of the mixture was determined using a LECO 1R32 sulfur analyzer. The inorganic sulfur contents as determined by the three methods were then compared to the sulfur concentrations as calculated from the iron disulfide abundance as determined by Mossbauer spectroscopy. The data show that the sulfur analysis using ASTM D2492 and the −60 mesh coal sample is unsatisfactory. Acceptable sulfur data can, however, be determined using the ASTM method and −220 mesh coal. The best comparison of data was obtained with the sulfur content obtained by the LECO analysis of the acid-leached low-temperature ash. These results strongly suggest a significant error in inorganic sulfur analysis due to the encapsulation of iron disulfide grains within the organic matrix of the coal when a procedure is used based upon the leaching of the coal sample. The problem can be minimized by utilizing fine-grained coal (−325 mesh) and essentially eliminated by utilizing an hydrochloric acid-leached low-temperature ash.

Dependence of the liquefaction behaviour of some high-sulphur Turkish lignites on their properties

The liquefaction potential of seven high sulphur lignite samples from Middle, Western and Northwestern Anatolia were investigated by hydrogen-donor solvent extraction. The dependence of the conversion and individual fractions and gas yields on their properties are discussed. The lignites, especially those with high sulphur and volatile matter contents, were found to be suitable for liquefaction. By the application of simple linear regression, total sulphur content alone is observed to be a very good measure of the total benzene-soluble extract yield, the correlation coefficient of the regression, r, being equal to 0.99. Similarly, the hexane-soluble extract and the preasphaltene yields could best be predicted by regressions based on the pyritic sulphur content ( r=0.98) and the H/C atomic ratio ( r=0.96), respectively. The property of the lignites that explains the variations in the gas yield best is observed to be their carbon content ( r = −0.81). While no single property gives a strong correlation with asphaltene yield, volatile carbon content is still the best among the others. Geological homogeneity of our sample set is implied by these strong correlations.

Prediction of sulphur distribution in products during low temperature coal pyrolysis and gasification

During devolatilization of coal, the sulphur present is distributed into solid, liquid, and gaseous products depending on the type and quantity of the coal sulphur and the processing conditions (e.g., temperature, pressure, and heating rate) used. In this study, a series of coals (mainly high volatile bituminous) was devolatilized at a relatively low temperature (500 °C) in a fixed-bed reactor in an inert atmosphere. Primarily bituminous coals were used in this study as these are shown to yield the most liquid product during pyrolysis. The distribution of sulphur in solid, liquid, and gaseous products was monitored. Influence of peak devolatilization temperature on sulphur distribution in products was determined for a high volatile bituminous coal (Pittsburgh No. 8). The sulphur content of the pyrolysis liquids generated at 500 °C correlates well with the total coal sulphur. The total sulphur of the char can be correlated with the pyritic sulphur content of the coal. Total gaseous sulphur content (sum of H 2S and COS) or sulphur content of tar increases with increase in organic sulphur of coal, and relatively good correlations were obtained. An increase in pyrolysis temperature increases the total gaseous sulphur yield at the expense of char sulphur. Based on sulphur distribution data for 32 bituminous coals, equations have been developed to correlate the sulphur yield in products with the total sulphur of the feed coal. The correlations developed in this study are expected to be applicable for predicting the sulphur distribution in products during conversion of bituminous coals using low temperature pyrolysis technology, and to estimate sulphur products in the exit gases and tars when coal is converted in a fixed-bed gasifier in which initial devolatilization occurs at a relatively low temperature.

Sulfur groups in the cokes obtained from coals of different ranks

Coals of different ranks having their sulfur content distributed in different forms were heated up to 1000°C. It was shown that the higher the rank of the coal the more sulfur remained in the coke. The retention of sulfur in the coke is strongly dependent on the proportion of the thiophenic sulfur in the organic coal sulfur. The sulfur in the cokes examined was mainly organic in form. Iron sulfide, FeS, constituted most of the inorganic sulfur. A correlation was observed between the sulfide sulfur content in coke and the pyritic sulfur content in coal. The form and size of the iron sulfide present in the coke were determined by microscopic examination.

C-S-Fe relationships and the isotopic composition of pyrite in the New Albany Shale of the Illinois Basin, U.S.A.

The relationship between pyritic sulfur content (S pyr) and organic carbon content (C org) of shales analyzed from the New Albany Group depends upon C org. For samples of <6 wt.% C org, S pyt, and C org are strongly correlated ( r = 0.85). For C org-“rich” shales (>6 wt.%), no S pty-C org, correlation is apparent. The degree of Fe pyritization (DOP) shows similar relationships to C org. These C-S-Fe relationships suggest that pyrite formation was limited by the availability of metabolizable organic carbon in samples where C org < 6 wt.% and by the availability of reactive Fe for samples where C org > 6 wt.%. Apparent sulfur isotope fractionations relative to contemporaneous seawater sulfate (Δ 34S) for pyrite formation average −40% for non-calcareous shales and −25%. for calcareous shales. Δ 34 S values become smaller with increasing C org, S pyt, and DOP for all C org-“poar” (<6 wt%) and some C org-“nch” (<6 wt.%) shales. These trends suggest that pyrite formation occurred in a closed system or that instantaneous bacterial fractionation for sulfate reduction decreased in magnitude with increasing organic carbon content. The isotopic trends observed in the New Albany Group are not necessarily representative of other shales having a comparable range of organic carbon content, e.g. Cretaceous shales and mudstones from the western interior of North America ( GAUTIER, 1986). Δ 34 S values in the remainder of the C org-rich New Albany Group shales are relatively large (−38 to −47%.) and independent of C org, S pyr, and DOP, which suggests that pyrite in these shales formed mostly at or above the sediment-water interface by precipitation from an isotopically uniform reservoir of dissolved H 2S.

芦別炭鉱炭層内の硫黄の分布

The distribution of forms of sulfur in five palaeogene coal seams of the Ashibetsu colliery in the Ishikari coalfield was investigated in relation to the depositional environment of coal. The main parts of these coal seams contain low amounts of total sulfur. Sulfate and pyritic sulfur contents are very low in the middle part and increase sharply near the top of every coal seam. Some coal seams contain high or somewhat high amounts of inorganic sulfur near the floor. The distribution of organic sulfur is not so simple as that of inorganic sulfur, but there is a tendency for the content of organic sulfur to be high towards the roof. It is not clear why the content of organic sulfur in the lower part of one coal seam is high although the content of inorganic sulfur is very low in the same part.The variations in sulfur of coal seams are interpreted to depend on whether the coal formation developed under marine condition or fresh water condition. Especially pyritic sulfur content can be one of the important indicators of the depositional environment. It is estimated from the distribution of forms of sulfur in five coal seams of the Ashibetsu colliery that these coal formations began on the way to limnic environment or under fresh water condition influenced by marine regression, developed fundamentally in limnic basins and terminated under brackish water condition influenced by marine incursion. This transition is clearly in harmony with the cyclothem, sand→mud→coal→mud, as seen at the time of the deposition of coal seams in the Ishikari coalfield.

Size and maceral association of pyrite in Illinois coals and their float-sink fractions

The amount of pyrite (FeS 2) removed by physical cleaning varies with differences in the amount of pyrite enclosed within minerals and of free pyrite in feed coals. A microscopic procedure for characterizing the size and maceral association of pyrite grains was developed and evaluate by testing three coals and their washed products. The results yield an index to the cleanability of pyrite. The index is dependent upon particle size and has intermediate values for feed coals, lower values for cleaned fractions, and higher values for refuse fractions; furthermore, it correlates with pyritic sulfur content. In the coals examined, the summed percentage of grain diameters of pyrite enclosed in vitrinite, liptinite, and bi- and trimacerite provides a quantitative measure of the proportion of early diagenetic deposition of pyrite.

Coal Quality in Area of Sand Mountain and Lookout Mountain, Southern Appalachian Mountains, Georgia, Tennessee, and Alabama: ABSTRACT

More than 10 coal beds of Pennsylvanian age crop out around Sand Mountain and Lookout Mountain in Georgia, Tennessee, and Alabama. These beds were deposited in barrier and fluvial environments. Few determinations of modern coal-quality data have been made for these coals, although they have been mined for more than 100 years. To evaluate their quality, 47 coal samples from beds 1, 2, 3, 4, 5, 5A, 6, 8, 9, 9A, and 10 were analyzed for ultimate and proximate values, calorific values, forms of sulfur, ash-fusion temperatures, free-swelling indices, and 60 major and minor, and trace-element concentrations. Most samples have less than 1% total sulfur and have low pyritic and organic sulfur contents. The ash content has geometric mean value of about 8%. The mean calorific value is just above 13,000; some samples have values above 15,000 Btu. The calculated coal rank ranges from low to medium volatile bituminous. However, the rank reverses in the Lookout Mountain coal, suggesting possible tectonic intervention. Because of high free-swelling indices and low concentrations of volatiles, sulfur, and as, most of these coal beds contain premium quality metallurgical or metallurgical-blend coal. In some coal beds, the concentrations of CaO, Na/sub 2/O, P/sub 2/O/sub 5/,more » MgO, and chlorine show wide differences from the overall geometric mean, indicating changing deposition or tectonic conditions. The geometric mean concentrations of minor and trace lithophile elements do not display large differences when compared to other eastern US bituminous coal samples. Chalcophile elements such as silver, arsenic, cobalt, mercury, selenium, and zinc are present in concentrations that may be related to depositional or diagenetic processes. Antimony content is high in some samples.« less

Formula omitted] ratios of low sulfur permian Australian coals in relation to depositional environments

Previous studies of the distribution and isotopic composition of sulfur in coal have been largely concerned with variations in relation to gross differences in environments of deposition and maturation. In this study attention is focussed on the composition of sulfur in low-sulfur coals deposited in fluvio-deltaic environments. By selecting samples with total sulfur contents ⩽ 1.0% and with pyritic sulfur contents ⩽ 0.2%, the effects of direct marine influences were minimized. Within these constraints total sulfur contents and δ 34 S-values of both total and organically bound sulfur increase downslope in fluvio-deltaic systems. These trends are attributed to increase downslope in the concentration of terrestrial sulfate available during plant growth, to the preferred reduction and assimilation of the 32S sulfate during bacterial attack and plant growth and to marginal marine influences.

Effect of Wyodak coal properties on hydroliquefaction reactivity

The effect of Wyodak coal properties on liquefaction reactivity as measured by distillate yield and cyclohexane conversion has been investigated. Spot samples of four Wyodak subbituminous coals from the Anderson and Canyon coal seams in the Powder River Basin of NE Wyoming were liquefied in microautoclave and batch reactor experiments. Runs were made using two different Wyodak coal-derived solvents. Emphasis in this work was directed toward correlation of C 4-700 K distillate yield and cyclohexane conversion as functions of measurable physical, chemical and petrographic properties of the feed coal. Reactivity rankings were found to be the same using either measure of coal reactivity. However, the data indicated that distillate yields were a function of both solvent quality and feed coal properties. For each solvent studied, selected coal properties, including carbon content, total and organic sulphur content, vitrinite content and total reactive maceral (vitrinite plus exinite) content, were found to give statistically significant correlations with distillate production and cyclohexane conversion. Pyritic and sulphate sulphur contents did not appear to enhance liquefaction yield or conversion at the reaction conditions studied. However, any catalytic effects due to pyrite or sulphate sulphur may have been masked by the use of two high quality liquefaction solvents.

Pyrite-organic matter relationships: Currant Bush Limestone, Georgina Basin, Australia

The relationship between the TOC (total organic carbon) and S (pyritic sulphur) contents of some organic-rich (TOC 3–14%) silty limestones and calcareous siltstones from the Cambrian Currant Bush Limestone of the Georgina Basin, Australia, is similar to that of euxinic sediments, but could also indicate deposition in a non-saline environment. However, such conditions are not easily reconciled with the shallow equatorial epeiric sea in which the formation is considered to have been deposited. The relationship can alternatively be explained by the relatively low Fe content of the sediment being the main limiting factor in pyrite generation, coupled with a slightly increased degree of pyritization with increased TOC. The relationship between the TOC and S contents of organic-poor (TOC 0.2–2.4%) samples from the same formation is similar to that of normal marine sediments, but the Fe content is probably also the major controlling factor on pyrite generation. These interpretations demonstrate that in using TOC and S contents to aid in reconstruction of depositional environments, it is important to check whether Fe content could have been the limiting factor in the formation of pyrite, even in sediments with only moderate carbonate contents.

Heavy media separation of SRC-II feedstocks: 1. Effect on coal properties

The objectives of this investigation were to determine the effects of coal preparation on the properties of Run-of-Mine (ROM) and washed Powhatan and Ireland Mine coals and to assess the potential effects on SRC-II liquefaction yields. The effect of washing on the two coals was found to be quite similar. For both coals, the properties were altered more significantly by changes in separation media gravity than by changes in the coal size. The elemental composition of the Powhatan and Ireland washed coals was correlated with carbon content. It was shown that both the hydrogen and oxygen levels increased linearly with the carbon content of the coal samples. However, the H C and O C ratios were not changed significantly by coal cleaning. Only small variations in the nitrogen and organic sulphur levels were observed while the sulphate sulphur and chlorine levels were not affected by coal cleaning. The major impact of the coal cleaning was to reduce the pyritic sulphur (and hence the total sulphur) content of the coals. Most of the pyritic sulphur was shifted into the middling coal and refuse fractions while the clean coals had much lower contents and the pyritic sulphur level decreased with increasing carbon content. Coal cleaning did not significantly alter the maceral contents of vitrinite, exinite, total reactive macerals (TRM), or the reflectance of vitrinite; all these parameters varied over a very narrow range, probably within the precision of the measurement technique.

Reactions of small covalent molecules with coal: trifluoroacetic acid

Anhydrous ammonia, methanol, and other protonic reagents have been utilized for the chemical comminution of coal. In this investigation, subbituminous, low-volatile bituminous and high-volatile bituminouscoals have been comminuted readily by trifluoroacetic acid. Approximately 5% of the original coal dissolves during the trifluoroacetic acid treatment leaving a material which has a high calorific value. The pyritic and organic sulphur contents and the ash yields are greatly reduced. Micrographs after treatment show the layered structure of the coal.

Sulphur removal potential of American coals as a determinant of sulphur dioxide emissions from coal-fired power plants

The presence of sulphur in coals is a major obstacle to their use in coal-fired power plants because of the restrictions placed on sulphur dioxide emitted from such plants. In this study, it has been found that the recently imposed sulphur dioxide emission standards in the United States are unrealistic because they are not consonant with the reserve base of U.S. coals by total and pyritic sulphur contents, and with factors influencing the removal of pyrite by physical methods. Since cleaning of coal by physical means is inexpensive compared with converting coals into clean-burning fuels before burning them in the boilers or reverting to stack-gas clean-up, and since direct firing of coal conserves the coal if the end product is electricity, it is recommended that the standards to be imposed should be consonant with the reserve base and the potential of physical methods.

Mossbauer studies of coal and coke: quantitative phase identification and direct determination of pyritic and iron sulphide sulphur content

Mössbauer spectroscopy has been used to analyse the included minerals and mineral-derived phases of a large suite of coal, coke, and other coal-related samples. Scanning electron microscopy, chemical analysis, and X-ray diffraction were used as supplementary techniques. Most of the samples studied were bituminous coals, and the dominant Fe-bearing minerals observed were pyrite, carbonate phases (siderite, ankerite), and ferrous silicates (principally illite). Pyrite was present in all coals investigated and was the dominant Fe-bearing phase in approximately 70% of the samples. Absorption peaks from ferrous Fe contained in illite and other clay minerals were observed for 90% of the coals, and were dominant for approximately 20% of the samples. The carbonates siderite and ankerite were present in approximately half of the coals, and siderite was the dominant Fe-bearing phase in four samples. In weathered coals and coal refuse, Fe sulphates, oxides and oxyhydroxides were also observed. Mössbauer data obtained from numerous coals before and after coking established that the following transformations occur during high-temperature carbonization: 1. (1) pyrite → troilite ( FeS) + pyrrhotite ( Fe 1 − x S); 2. (2) illite + other silicates → ferrous glass; 3. (3) siderite → metallic Fe. A new method was developed for making direct, quantitative determinations of the amount of pyritic sulphur in coal, which involves comparing the observed Mössbauer mass absorption coefficient for pyrite in coal to a standard calibration curve. Preliminary data for coke samples show that the same technique can be applied to determine the amount of sulphur contained in the Fe sulphide phases, troilite and pyrrhotite.

Desulfurization of Coal by Flotation of Coal in a Single-Stage Process

Abstract A single-stage flotation process was developed in which coal was floated out and pyrite was depressed. Up to 90% of the pyritic sulfur content of bituminous coal could be removed at 75% coal recovery. The process was applied to three Canadian and two United States coals. Higher coal recoveries were obtained for low sulfur coals; up to 94.4% coal recovery was possible with 18.2% pyritic sulfur removal. Sulfate sulfur, trace elements, and ash were also removed. The effects of particle size, temperature, slurry density, and flotation time were studied. From a simplified rate equation a nonintegral order was obtained for the flotation process.

Removal of Sulfur from Coal by Treatment with Hydrogen

Abstract The Colorado School of Mines is performing a research contract under the sponsorship of the Office of Coal Research, the State of Colorado, and the Office of Research Services of the Colorado School of Mines to determine the importance of operating variables and raw material properties on coal desulfurization via the solvent refining process. The solvent refining process is being studied in bench-scale, high-pressure, high-temperature, rocking-bomb autoclave batch reactors. The liquid product from the reactor is vacuum distilled to give a solvent refined coal, and the refined coal product is analyzed for sulfate, pyritic, and total sulfur content, with organic sulfur content being determined by difference. Initially five variables were studied: temperature, partial pressure of hydrogen, solvent-to-coal ratio, solvent type, and reaction time. The reaction time was determined to be statistically unimportant, and anthracene was shown to be the better solvent. Further experimental work has been completed to investigate the three remaining operating variables. Statistical analysis of experimental data is now being performed to investigate the nonlinearity of sulfur removal from coal as influenced by the operating variables.