Sulfur Content Of Coal Research Articles

Probing coals for non-pyritic sulphur using sulphur-metabolizing mesophilic and hyperthermophilic bacteria

The presence of elemental sulphur in several coals from the midwestern US (Illinois No. 6, Indiana No. 5, and an Indiana refuse coal) as well as in an Australian brown coal was probed using specific microbial activity to this sulphur speciation. The objective of this work was to differentiate elemental sulphur from the apparent organic sulphur fraction in these coals. Two hyperthermophilic archaebacteria, Pyrodictium brockii and Pyrococcus furiosus, are known to specifically reduce elemental sulphur to sulphide seawater-based media. The eubacterium, Thiobacillus thiooxidans, is known to specifically oxidize elemental sulphur to sulphate. These biological activities were examined in aqueous solutions containing the above coal samples by comparing the biotic production of sulphide or sulphate with both the reduction of total coal sulphur content and the reduction in the sulphur extractable by carbon disulphide. Only the heavily weathered, refuse coal contained significant elemental sulphur (≈ 1%), by both biological assay and sulphur assay of carbon disulphide-extractable material. The elemental sulphur content of the refuse coal appeared as organic sulphur by conventional analytical methods (i.e., ASTM method for coal sulphur speciation). The results here point to the prospect of using biological probes for elemental sulphur determination in coals, thereby making organic sulphur content determination more specific.

The relationship between macerals and sulphur content of some South African Permian coals

There is a positive correlation between sulphur concentration and the vitrinite maceral group content in Permian Vryheid Formation coals in South Africa; the reverse is true for the inertinite maceral family. This relationship is evident at intraseam, interseam and intercoalfied levels. Vitrinite precursors formed where the water table in peat-forming environments was high and Eh low. These conditions favoured bacterial sulphate reduction and resulting H 2S reacted with Fe 2+ and organic peat compounds to form pyrite and organic sulphur components. Inertinite precursors formed when the water table was low and Eh high; aerobic respiration prevailed and little H 2S was produced. Organic sulphur derived from peat-forming plant tissue is dominant in intertinite-rich low-sulphur coal; pyritic sulphur exceeds organic sulphur in high-sulphur coals dur to preferential reaction of H 2S with Fe 2+.

The sulphur, ash relationship in coal seams and its implications in mine planning in the United Kingdom

The effect of sulphur dioxide emission associated with the combustion of fossil fuels in power generation and implications in the formation of acid rain, has focused attention on the desulphurisation of power station fuel, before burning. In this context one of the possible ways to alleviate the situation is to reduce the sulphur content of coal. In many coal seams initial sulphur contents are unacceptably high and blending with seams of low sulphur value is practised. However, in the future, blending on a large scale to reduce the sulphur content of many of the United Kingdom coals may not be possible due to the limited reserves of low sulphur coal. Currently, to obtain a low sulphur product, coal preparation treatment or some selective extraction is practised in certain seams, however, in many cases it is not possible to separate sulphur from coal in the pre-combustion stage. This paper discusses the sulphur, ash relationship in two seams, the Cannel Row in North Staffordshire and the Flockton Thin of the Yorkshire Coalfield, which are examined with a view to identifying patterns of regional variation. Once these are established the possibility of selective planning of mine workings to avoid the high sulphur areas in these seams is discussed.

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.

Sulphur in peat and coal

Abstract Coal sulphur content is a major consideration in coal marketing. To predict sulphur content and distribution in a coal basin, a sulphur geochemical model needs to be developed. A series of questions are posed regarding coal sulphur distribution, forms and origins. Salient aspects of literature on coal sulphur content and distribution are reviewed to establish a framework for developing a sulphur geochemical model. Some coal sulphur originates from peat-forming processes. Sulphate, ferrous iron, and microorganisms are key ingredients for the origins of coal pyrite and organic sulphur. Hydrogen sulphide is an important intermediate for pyrite and organic sulphur formation in peats. Sulphur isotope values for peat sulphate, plant sulphur, peat pyrite and peat organic sulphur corroborate the hypothesis that microorganisms reduce sulphate to hydrogen sulphide, which in turn reacts with available ferrous iron or organic matter to produce pyrite and organic sulphur respectively.

Study of thermal decomposition reactions in coals by pyrolysis-gas chromatography-mass spectrometry

The thermal decomposition of heteroatom-containing segments occurring in coals has been studied by pyrolysing a series of synthetic polymers. The polymers contained aryl ether segments in various molecular surroundings, aryl sulphide and heteroaromatic with oxygen or sulphur atoms. The scission of aryl ether bonds results mainly in phenols at 500–800°C, and the temperature at which phenol production takes place depends on the nature of the bonds attaching the aryl ether segment to the macromolecular matrix. Almost no phenol formation from heteroaromatic segments was observed. The production of phenols from low-rank coals is similar to that from a polymer in which aryl ether segments are bonded through keto and methylene groups to the neighbouring segments. The scission of aryl sulphides results in the formation of hydrogen sulphide. Hydrogen sulphide is also produced from dibenzothiophene segments, although at a considerably higher pyrolysis temperature. The formation of hydrogen sulphide is similar from aryl sulphides and low-rank coals. The amount of hydrogen sulphide produced by pyrolysis proved to be directly proportional to the organic sulphur content of Hungarian low-rank coals.

Direct measurement of organic sulphur in coal

A method of direct determination of the organic sulphur content of coal has been developed using the transmission electron microscope. An electron beam is focussed on a thinned section of coal and X-rays emitted from the elements in the volume irradiated by the electrons are measured by X-ray emission spectroscopic methods. Both the characteristic K α line of sulphur and the bremsstrahlung from the material in the irradiated volume are detected by a solid-state detector. An analytical method has been developed which uses these two measurements for a direct determination of the organic sulphur concentration. Minerals can easily be avoided since they are plainly seen by conventional electron microscope techniques. Several measurements of the organic sulphur concentration in coals have been made; they agree with the conventional chemical values reported for these coals. Of most importance, though, is the use of this technique to detect spatial variations of sulphur over small distances within the coal maceral.

Development of an X-ray fluorescence method for on-line determination of sulphur in coal

An XRF method for determining sulphur content in coal via iron fluorescence measurement has been investigated. Factors limiting accuracy have been assessed and quantified. Results for 0.2 mm-0 coal on a laboratory analyser and for 5 mm-0 coal on a commercial on-line analyser show calibration accuracies (1σ) of ±0.02% to ±030% sulphur for individual coal types. Many of the values obtained, particularly for low ash coals, are acceptable for on-line monitoring purposes.

Low-Rank Coal: Its Present and Future Role in the United States

Resources of low-rank coals in the United States are comparable in quantity to available resources of bituminous coals but are found primarily in the western part of the country. With the exception of the Gulf region lignites, these coals are generally remote from major energy-consuming areas. In most cases, the relatively thick seams of low-rank coal found close to the surface can be strip-mined at a fraction of the cost required to produce US bituminous coals. The importance of low-rank coal in the US energy system increased dramatically in the 1970s. This increase resulted from a combination of factors, including the escalating prices of oil and natural gas, the possibility of using low-rank coal to comply with clean-air regulations in some regions, the development of improved combustion technology, and the increased wheeling of power from region to region. Low-rank coals are noted for causing ash-related problems during combustion. However, the high alkali and low sulfur contents of many lowrank coals make them attractive for reducing sulfur emissions without much addition of limestone or lime. Some low-rank coals are especially attractive for gasification and liquefaction and are likely to dominate the early development of synthetic fuels plants and coal gasification/combined-cycle utilitymore » power plants. With all these factors considered, the role of low-rank coals in the United States is likely to continue growing as process improvements are made.« less

Overview of US Department of Energy Coal Preparation Research

The principal thrust of the U.S. Department of Energy (DOE) Coal Preparation R and D Program is to develop technology to reduce the ash and sulfur contents of United States coals to levels such that the resultant product can be formulated into a high quality solid or slurry fuel that could replace oil or natural gas in both new and retrofit applications. Specifically, the objective is to develop and refine cost-effective physical and chemical beneficiation processes to extract 85-95 percent of the total sulfur and ash. The Coal Preparation program is implemented by the Pittsburgh Energy Technology Center (PETC) and is conducted both in-house and by a cross section of industrial organizations, universities, and national laboratories. Research is subdivided into three areas -coal characterization, beneficiation, and ancillary unit operations. This paper provides a brief overview of many of the research projects being carried out in these areas in fiscal year 1984.

Relationship Between Reflectivity and Organic Sulfur Content of Macerals with Respect to Total Organic Sulfur Content and Rank of Coals: ABSTRACT

The potential exists for predicting organic sulfur (So) contents of specific macerals within a coal based on total So content of the coal, rank of the coal, and maximum reflectivity in oil (Ro) of the macerals in question. In the past, determination of So content of specific macerals necessitated either a microanalysis technique, such as electron probe microanalysis (EPM), or analysis of maceral separates. Ten coal samples ranging in rank from low volatile to lignite and total So content from 0.47 to 4.51 wt. % were studied. Within each of the 10 coals, approximately 100 macerals ranging from the lowest reflecting exinites to the highest reflecting inertinites were analyzed for So content (using EPM techniq es) and Ro (using petrographic techniques). For each coal, log of maceral So content was plotted versus log of maceral Ro, and a linear regression of the data points was performed. On a three-dimensional plot, slopes of the 10 linear regressions were plotted versus the respective coal ranks versus the respective coal total So contents. Results indicate that relationships between So content and Ro of macerals within a coal are dependent on both the rank and total So content of the coal. As total So content of a coal equals So content of the vitrinite in that coal, the results suggest that predictive relationships exist between maceral So content, maceral Ro, coal total o content, and coal rank that may allow determination of maceral So contents without the need for microanalysis. End_of_Article - Last_Page 946------------

Geologic Controls on Sulfur Content in Coal: ABSTRACT

One of the principal factors controlling sulfur content of coal is the pH of the ancestral peat-forming environment. Coals derived from peats are believed to have formed under highly acidic conditions (pH <4.5) are low in sulfur (<1%), whereas sulfur content in coals derived from peats formed under elevated pH conditions (pH 4.5 to 7.5) tends to increase where pH was higher. Maximum bacterial activity occurs where conditions are neutral, or nearly so; such conditions favor sulfate reduction and peat degradation. This pH model is consistent with Schopf's suggestion that the sulfur content of a coal may give an indirect indication of the extent of anaerobic decay. Also, the common occurrence of pyrite in fusain bands may be related to pH conditions (neutral to slightly alkaline) in the pre-fusain layer caused by hydrolysis of alkali and alkaline earth metal ions, which were concentrated by burning. Regional and stratigraphic differences in sulfur contents End_Page 689------------------------------ of Appalachian basin coals are related to differences in pH conditions of the peat-forming paleoenvironments. High-sulfur coals (1) are associated with calcareous sedimentary sequences (marine, nonmarine, or both), (2) have elevated calcium carbonate content, and (3) have a low kaolinite to illite ratio. The converse is true for low-sulfur coals. Exploration for low-sulfur coal should focus on coal-bearing sequences contain a paucity of calcareous sediments. End_of_Article - Last_Page 690------------

Cretaceous-Tertiary Versus Carboniferous Depositional Settings--Factors Affecting Coal Parameters: ABSTRACT

Recent studies in the coal measures of the Carboniferous, Cretaceous, and Tertiary have shown that one of the most critical determinants of seam parameters is the depositional environment of the coal and enclosing strata. Although some of the differences between the Cretaceous-Tertiary and Carboniferous coals can be explained by their different ages and depth of burial (Btu, moisture content), many of the coal parameters (thickness and continuity, sulfur and trace-element content, ash content, roof and floor conditions) can be attributed to their depositional setting and the effect of energy conditions in the depositional basin on the environments of peat accumulation. Because of the wave energy in the western Cretaceous seaway, many of the deltas have sandstones that were reworked into interchannel areas from contemporaneous distributary mouth bars. These delta-front sheet sandstones formed platforms upon which widespread coals developed. In contrast, the most laterally continuous Carboniferous coals of the Appalachians accumulated in the upper reaches of the lower delta plain. Because of the low wave energies at the delta front, the only sites for coals to amass were on the levee and splay deposits adjacent to distributary channels which were separated by large interdistributary bay sequences. Previous studies have related the sulfur content of coals to the occurrence of marine and brackish roof rock. Western coals are considered to be lower in sulfur than eastern coals. Since a significant part of the western reserves are in fluvially related Tertiary coals while most of the low-sulfur fluvial coals of the Appalachian Carboniferous have already been mined, this statement is true in generalities. However, the Cretaceous-Tertiary coals of the west that developed in marginal marine environments are as high in sulfur as the Appalachian Carboniferous coals that accumulated in similar environments. End_of_Article - Last_Page 724------------

Routine Energy Dispersive Analysis of Sulfur in Coal

The analysis of sulfur in coal has been brought to the attention of the general public in recent years primarily as it concerns the pollution problem with coal-fired electric generation. Although our application is different, some of the results would be equally applicable to that circumstance. The Cement Division of Florida Mining and Materials Corporation produces annually about 500,000 tons of both Portland and Pozzolanic cements, using a coal-fired rotary kiln. The sulfur content of coal used in the manufacture of clinker ranges from traces to as much as 6%. Sulfur content in a dry process plant such as ours (this is the modern energy-efficient type of cement plant) is very critical, and in our case must be limited to 1.2% max.

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.

Determination of Forms of Sulfur in Coal

Abstract Widespread interest in reducing the sulfur content of coal has increased the need for chemical determinations of the forms of sulfur: sulfate, pyritic, and organic. The proper use and application of methods of determining the forms of sulfur in coal and coal refuse, including interpretation of results, can pose serious problems; consequently, a report and discussion of current methods of analysis, including instrumental methods, should prove helpful. A review of the evolution of current ASTM sulfur standards is presented, and a critical examination is made of problems associated with the determination of the varieties of sulfur in coal. Results of instrumental, oxidation, and reduction methods are given to show that close agreement among the three can be obtained and that calculation of organic sulfur by difference is reasonably accurate. The dangers of applying these methods to the determination of forms of sulfur in coal-related materials (e.g., high-ash fractions from float-sink procedures) are illustrated by data from a washability study of 64 coals.

Determination of Sulfur, Ash, and trace Element Content of Coal, Coke, and Fly Using Multielement Tube-Excied X-ray Fluorescence Analsis

A procedure using tube excited energy dispersive x-ray fluorescence analysis with interelement corrections has been developed for multielement analysis of major and trace elements and ash content of coal, coke, and fly ash. The procedure uses pressed pellets and an exponential correction for interelement effects. The average deviations ranged from about 0.0003% for V at an average concentration of about .003% to 0.1% for S at an average concentration of 4%. About 25 elements were measured and 100 second minimum detectable concentrations ranged from about one part per million for elements near arsenic to about one tenth of one percent for sodium.

Use of Published Wyoming Coal Analyses: ABSTRACT

Published proximate analyses, heat values, and sulfur contents of representative Wyoming coals were compared by sample types (face, tipple, and delivered) and by mining methods (underground and strip). These comparisons suggest that the quality of thick, potentially strippable Wyoming coals should not be characterized too stringently from published proximate analyses and heat values without consideration of detailed background information on each analysis. Minimally, the type of sample, date of analysis, sizes sampled, description of coal, thickness and part of coal sampled and/or discarded, type of mine, mining equipment, preparation facility, processing, and even customer identification should be known. This precaution is deemed necessary for the following reasons. 1. Although analyses of face samples best characterize a coal bed in its natural state, most published analyses of Wyoming coals are either very old face samples from abandoned underground mines or they are tipple and delivered samples. 2. Most available face, tipple, and delivered samples of thick coals (35-118 ft thick) are only representative of one fourth to one half of the entire thickness of such beds. 3. For a given coal bed, there are not enough surface mines for which analyses are available to characterize End_Page 907------------------------------ reliably the quality of strippable reserves. 4. For a given coal bed, tipple and delivered samples from strip mines tend to exhibit lower average moisture contents (as-received basis), higher average ash contents (dry basis), as well as greater ranges in ash contents, and less predictable average heat values (dry basis) than expected. 5. Although for many coals tipple and delivered samples are available from both surface and deep mines, analyses of these types of samples are so dependent on the type and use of mining equipment, preparation facilities, processing, and contract specifications that they may only by chance bear a close resemblance to the coal in its natural state. Apparently only a coal's sulfur content can be characterized accurately from existing published analyses of face, tipple, or delivered samples, as no significant differences were noted in any of the comparisons. End_of_Article - Last_Page 908------------

Sulfur dioxide standards: primary more restrictive than secondary?

The fuel shortage has encouraged the utilization of high sulfur fuels in those facilities where they can be used in an environmentally safe manner. A study was undertaken by the State of Iowa to correlate sulfur content of coals, stack heights, and maximum ground level concentrations from power plants. This study revealed that the primary National Ambient Air Quality Standards for SO2 are more restrictive than the secondary standard in almost all cases. This conclusion is contrary to the position that the attainment of the secondary standard could beata later date than the attainment of the primary standards.

Price Elasticities of Demand and Air Pollution Control

IN the economic lilterature on externalities, two separate approaches to pollution control are distinguished; (1) government regulations to enforce control and (2) tax and subsidy schemes to stimulate voluntary abatement.' The dichotomy, however, is not always sharp. Enforced con'trols impose changes on economic activities which may increase costs and induce voluntary shifts away from pollution intensive activities. For example, a limitation on the sulfur content of industrial coal might stimulate the substitution of cleaner burning natural gas. In addition, the higher production costs associated with the shift to low sulfur coal or to natural gas may add to the prices of related outputs, reducing the demand for these products. In turn, substitutions among outputs may occur which will further alter the levels of production and consumption activities from what they would be in the absence of pollution control. Cost-effectiveness models for achieving environmental goals generally ignore induced voluntary abatement. As a consequence, the proposed solutions may be incorrect in that (a) the environmental goals would be exceeded and (b) the total cost of control would not be a minimum cost. This paper presents an air pollution control model in which both required control activity and the induced voluntary adjustments in consumption and production levels are taken into account. II The Cost-effectiveness Model with Fixed Production and Consumption Levels