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At least 19 recordsLinked to original sources
USGS2021

Geochemical data for Illinois Basin coal samples, 2015–2018

Researchers at the U.S. Geological Survey (USGS) and their collaborators conducted a study of the geochemical properties of coals currently produced for electric power generation in the Illinois Basin in Illinois and Indiana. The study follows from recommendations by an expert panel for the USGS to investigate the distribution and controls of trace constituents such as mercury (Hg) in Illinois Basin coals and the behavior of these constituents in coal preparation. A total of 72 new samples were collected by USGS collaborators between 2015 and 2017. These samples include raw coals, prepared coals, and waste coals from coal preparation. To understand the geochemistry and cleaning behavior of these coals, these samples were subjected to an integrated series of analyses described here, including microanalysis of coal constituents and bulk sample chemical analysis. Of the procedures used, whole-sample Hg analysis quantified overall mercury contents and its reduction by coal preparation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of pyrite in coal quantified Hg and other potentially harmful elements contained in pyrite, the most likely host of these constituents. Trace elements investigated include those whose emissions are regulated under the U.S. Environmental Protection Agency Mercury and Air Toxics Standards. This report and the corresponding data release, serve as an archive for geochemical data obtained in our study of the geochemistry of Illinois Basin coals. Material included in this report also define approaches used by the USGS over the period of study to characterize coal samples, requiring combined use of results from USGS and non-USGS laboratories.

Illinois↗
USGS2024

Energy-related rare earth element sources

Energy-related materials such as coal, coal-bearing wastes, and coal combustion products are traditionally thought of as sources or by-products of electric power generation. Increasingly, these materials are considered resources for their content of rare earth elements (REEs) and other useful constituents. In this chapter, we examine the distribution, modes of occurrence, and relative extractability of REEs from coal-derived materials. We also consider economic factors associated with recovery of REEs from these sources. While several coal-derived sources show promise for REE recovery at the pilot scale, in all cases, REE contents are much below those of primary ores, such that extraction and concentrating the REEs require new and innovative approaches that are largely developmental. Among coal-related sources, fly ash is the most REE-enriched, as REEs from coal are strongly retained in these refractory solids remaining after coal combustion. Partitioning of coal-derived elements into fly ash has been known for decades but this has yet to be commercially exploited. A key drawback shown in this chapter is that a significant fraction of REEs in fly ash is contained in highly insoluble aluminosilicate glasses that make up the largest portion of this material. In addition to testing chemical or physical pretreatment approaches to help improve the extractability of REEs from fly ash, current research is applying modern analytical approaches to better understand the distribution of REEs on increasingly smaller scales, in the interest of targeting their recovery. Next-most REE-enriched among coal-related materials are solid waste products of coal mining and wastes from coal preparation, both of which are REE-enriched relative to coal itself. These waste coals concentrate mineralogical constituents that are excluded during mining or removed during coal preparation because they do not contribute to the heating value of coal for power generation. Recovery of REEs from coal waste has shown promise at the pilot scale and has the added benefit of converting a waste into useful constituents. Total REE contents of commercial coals are, on average, much below the 300 parts per million interest level for REE recovery set by the U.S. Department of Energy (DOE). However, as reviewed in this chapter, certain horizons within coal beds show preferential REE enrichment and could be targeted by selective mining. Beyond this, certain coals are REE-enriched overall due to their unique geologic histories involving derivation from REE-enriched sediment sources, deposition of volcanic ash during coal formation, or interaction of coal with REE-bearing fluids. Acidic drainage from abandoned coal mines is produced by the breakdown of pyrite (FeS 2 ), which is unstable in oxygenated conditions. While these acidic fluids have lower REE contents than any of the coal-based solids described above, they are proportionally enriched in certain heavy rare earths, especially yttrium (Y). Precipitates from coal-based acid-mine drainage concentrate REEs to levels that are of interest for recovery, and these are also promising sources for extraction at the pilot scale.

Book chapter↗
USGS2017

Mercury and trace element distribution in density separates of a South African Highveld (#4) coal: Implications for mercury reduction and preparation of export coal

Eight density separates of Permian Highveld (#4) coal were investigated for partitioning of Hg and trace elements. The separates include float fractions obtained in heavy media having densities of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 g/cm 3 , and the sink fraction for 2.0 g/cm 3 . Bulk analysis of the separates shows strong (R 2 ≥ 0.80) positive correlations between pyritic sulfur and mercury, and between ash yield and both pyritic sulfur and mercury. Laser ablation (LA) ICP-MS analysis of individual pyrite grains in the separates confirms association of Hg and As with pyrite as indicated by bulk analysis. Other elements detected in pyrite by LA-ICP-MS include Mn, Co, Ni, Tl, and Pb. Results for the separates allow prediction of Hg, trace elements, and ash yields expected in specific South African coal products. These range from 0.06 ppm Hg and an ash yield of 11.5% ash for the export fraction to 0.47 ppm Hg and an ash yield of 60.9% for the discard (stone) fraction (dry basis). Results show pronounced differences expected between coal used for domestic power generation and coal which is exported.

International Journal of Coal Geology↗
USGS2012

Minor element distribution in iron disulfides in coal: a geochemical review

Electron beam microanalysis of coal samples in U.S. Geological Survey (USGS) labs confirms that As is the most abundant minor constituent in Fe disulfides in coal and that Se, Ni, and other minor constituents are present less commonly and at lower concentrations than those for As. In nearly all cases, Hg occurs in Fe disulfides in coal at concentrations below detection by electron beam instruments. Its presence is shown by laser ablation ICP-MS, by selective leaching studies of bulk coal, and by correlation with Fe disulfide proxies such as total Fe and pyritic sulfur. Multiple generations of Fe disulfides are present in coal. These commonly show grain-to-grain and within-grain minor- or trace element compositional variation that is a function of the early diagenetic, coalification, and post-coalification history of the coal. Framboidal pyrite is almost always the earliest Fe disulfide generation, as shown by overgrowths of later Fe disulfides which may include pyrite or marcasite. Cleat- (or vein) pyrite (or marcasite) is typically the latest Fe disulfide generation, as shown by cross-cutting relations. Cleat pyrite forms by fluid migration within a coal basin and consequently may be enriched in elements such as As by deposition from compaction-driven fluids, metal enriched basinal brines or hydrothermal fluids. In some cases, framboidal pyrite shows preferential Ni enrichment with respect to co-occurring pyrite forms. This is consistent with bacterial complexing of metals in anoxic sediments and derivation of framboidal pyrite from greigite (Fe 3 S 4 ), an Fe monosulfide precursor to framboidal pyrite having the thio-spinel structure which accommodates transition metals. Elements such as As, Se, and Sb substitute for S in the pyrite structure whereas metals, including transition metals, Hg and Pb, are thought to substitute for Fe. Understanding the distribution of minor and trace elements in Fe disulfides in coal has important implications for their availability to the environment through coal mining and use, as well as for potential reduction by coal preparation, and for delineating diagenetic compositional changes throughout and after coal formation.

International Journal of Coal Geology↗
USGS2000

Direct comparison of XAFS spectroscopy and sequential extraction for arsenic speciation in coal

The speciation of arsenic in an Ohio bituminous coal and a North Dakota lignite has been examined by the complementary methods of arsenic XAFS spectroscopy and sequential extraction by aqueous solutions of ammonium acetate, HCl, HF, and HNO3. In order to facilitate a more direct comparison of the two methods, the arsenic XAFS spectra were obtained from aliquots of the coal prepared after each stage of the leaching procedure. For the aliquots, approximately linear correlations (r2 > 0.98 for the Ohio coal, > 0.90 for the ND lignite) were observed between the height of the edge-step in the XAFS analysis and the concentration of arsenic measured by instrumental neutron activation analysis. Results from the leaching sequence indicate that there are two major arsenic forms present in both coals; one is removed by leaching with HCl and the other by HNO3. Whereas the XAFS spectral signatures of the arsenic leached by HCl are compatible with arsenate for both coals, the arsenic leached by HNO3 is identified as arsenic associated with pyrite for the Ohio coal and as an As3+ species for the North Dakota lignite. Minor arsenate forms persist in both coals after the final leaching with nitric acid. The arsenate forms extracted in HCl are believed to be oxidation products derived from the other major arsenic forms upon exposure of the pulverized coals to air.

ACS Division of Fuel Chemistry, Preprints↗
USGS2011

Assessment and distribution of antimony in soils around three coal mines, Anhui, China

Thirty-three soil samples were collected from the Luling, Liuer, and Zhangji coal mines in the Huaibei and Huainan areas of Anhui Province, China. The samples were analyzed for antimony (Sb) by inductively coupled plasma-optical emission spectrometry (ICP-OES) method. The average Sb content in the 33 samples was 4 mg kg −1 , which is lower than in coals from this region (6.2 mg kg −1 ). More than 75% of the soils sampled showed a significant degree of Sb pollution (enrichment factors [EFs] 5–20). The soils collected near the gob pile and coal preparation plant were higher in Sb content than those collected from residential areas near the mines. The gob pile and tailings from the preparation plant were high in mineral matter content and high in Sb. They are the sources of Sb pollution in surface soils in the vicinity of coal mines. The spatial dispersion of Sb in surface soil in the mine region shows that Sb pollution could reach out as far as 350 m into the local environment conditions. Crops in rice paddies may adsorb some Sb and reduce the Sb content in soils from paddyfields. Vertical distribution of Sb in two soil profiles indicates that Sb is normally relatively immobile in soils.

Anhui↗
USGS1998

Preparation and evaluation of coal-derived activated carbons for removal of mercury vapor from simulated coal combustion flue fases

Coal-derived activated carbons (CDACs) were tested for their suitability in removing trace amounts of vapor-phase mercury from simulated flue gases generated by coal combustion. CDACs were prepared in bench-scale and pilot-scale fluidized-bed reactors with a three-step process, including coal preoxidation, carbonization, and then steam activation. CDACs from high-organicsulfur Illinois coals had a greater equilibrium Hg0 adsorption capacity than activated carbons prepared from a low-organic-sulfur Illinois coal. When a low-organic-sulfur CDAC was impregnated with elemental sulfur at 600 ??C, its equilibrium Hg0 adsorption capacity was comparable to the adsorption capacity of the activated carbon prepared from the high-organicsulfur coal. X-ray diffraction and sulfur K-edge X-ray absorption near-edge structure examinations showed that the sulfur in the CDACs was mainly in organic forms. These results suggested that a portion of the inherent organic sulfur in the starting coal, which remained in the CDACs, played an important role in adsorption of Hg0. Besides organic sulfur, the BET surface area and micropore area of the CDACs also influenced Hg0 adsorption capacity. The HgCl2 adsorption capacity was not as dependent on the surface area and concentration of sulfur in the CDACs as was adsorption of Hg0. The properties and mercury adsorption capacities of the CDACs were compared with those obtained for commercial Darco FGD carbon.

Energy and Fuels↗
USGS1999

From in situ coal to the final coal product: A case study of the Danville Coal Member (Indiana)

A surface coal mine operation and preparation plant in southwestern Indiana was sampled to examine variations in coal quality and coal petrography parameters for the Danville Coal Member of the Dugger Formation (Pennsylvanian-Desmoinesian, Westphalian D). Representative samples from in situ coal, preparation plant feeds, and a final coal product were collected in order to compare coal quality, coal petrography, trace element concentrations, and ash chemistry of the coal to those of the product. Coal quality parameters of the in situ samples and various feeds, coarse refuse, and final product were variable. The quality of the final coal product was best predicted by the coal quality of the clean coal feed (from the middle portions of the seam). Some trace element contents, especially lead and arsenic, varied between the coal feeds and the product. Lead contents increased in the feeds and product compared to the channel sample of the raw coal, possibly due to contamination in the handling process.A surface coal mine operation and preparation plant in southwestern Indiana was sampled to examine variations in coal quality and coal petrography parameters for the Danville Coal Member of the Dugger Formation (Pennsylvanian-Desmoinesian, Westphalian D). Representative samples from in situ coal, preparation plant feeds, and a final coal product were collected in order to compare coal quality, coal petrography, trace element concentrations, and ash chemistry of the coal to those of the product. Coal quality parameters of the in situ samples and various feeds, coarse refuse, and final product were variable. The quality of the final coal product was best predicted by the coal quality of the clean coal feed (from the middle portions of the seam). Some trace element contents, especially lead and arsenic, varied between the coal feeds and the product. Lead contents increased in the feeds and product compared to the channel sample of the raw coal, possibly due to contamination in the handling process.

International Journal of Coal Geology↗
USGS1950

Spectrographic analysis of coal and coal ash

Coal can be analyzed on the spectrograph for per cent ash and composition of ash in a matter of a few minutes, using the total energy method. The composition of the ash so determined can be used to calculate ash softening temperatures. This analysis can be made in sufficiently short a time to control tipple and washing operations for preparation of coal to meet specifications. This spectrographic method can be readily adapted to the analysis of rocks, minerals, and inorganic chemicals of all kinds.

Analytical Chemistry↗
USGS1998

Potentially hazardous elements in coal: Modes of occurrence and summary of concentration data for coal components

Mode-of-occurrence data are summarized for 13 potentially hazardous elements (Be, Cr, Mn, Co, Ni, As, Se, Cd, Sb, Hg, Pb, Th, U) in coal. Recent work has refined mode-of-occurrence data for Ni, Cr, and As, as compared to previous summaries. For Cr, dominant modes of occurrence include the clay mineral iliite, an amorphous CrO(OH) phase, and Cr-bearing spinels. Nickel is present in Fe-sulfides (pyrite and marcasite) and is also organically bound. Arsenic-bearing pyrite may be the dominant host of As in bituminous coals. Concentration data for the 13 HAPs, obtained primarily by quantitative microanalysis techniques, are compiled for mineral and organic portions of coal. HAPs element concentrations are greatest in Fe-sulfides, and include maxima of 2,300 ppm (Co), 4,500ppm (Ni), 4.9wt.% (As), 2,000ppm (Se), 171 ppm (Hg), and 5,500ppm (Pb). Trace-element microanalysis is a significant refinement over bulk methods, and shows that there is considerable trace-element variation on a fine scale for a given coal, and from one coal to another.

Coal Preparation↗
USGS2011

Study relationship between inorganic and organic coal analysis with gross calorific value by multiple regression and ANFIS

The relationship between maceral content plus mineral matter and gross calorific value (GCV) for a wide range of West Virginia coal samples (from 6518 to 15330 BTU/lb; 15.16 to 35.66 MJ/kg) has been investigated by multivariable regression and adaptive neuro-fuzzy inference system (ANFIS). The stepwise least square mathematical method comparison between liptinite, vitrinite, plus mineral matter as input data sets with measured GCV reported a nonlinear correlation coefficient ( R 2 ) of 0.83. Using the same data set the correlation between the predicted GCV from the ANFIS model and the actual GCV reported a R 2 value of 0.96. It was determined that the GCV-based prediction methods, as used in this article, can provide a reasonable estimation of GCV.

International Journal of Coal Preparation and Util↗
USGS2001

Coal combustion products

Coal-burning powerplants, which supply more than half of U.S. electricity, also generate coal combustion products, which can be both a resource and a disposal problem. The U.S. Geological Survey collaborates with the American Coal Ash Association in preparing its annual report on coal combustion products. This Fact Sheet answers questions about present and potential uses of coal combustion products.

Fact Sheet↗
USGS2006

Mercury in coal and the impact of coal quality on mercury emissions from combustion systems

The proportion of Hg in coal feedstock that is emitted by stack gases of utility power stations is a complex function of coal chemistry and properties, combustion conditions, and the positioning and type of air pollution control devices employed. Mercury in bituminous coal is found primarily within Fe-sulfides, whereas lower rank coal tends to have a greater proportion of organic-bound Hg. Preparation of bituminous coal to reduce S generally reduces input Hg relative to in-ground concentrations, but the amount of this reduction varies according to the fraction of Hg in sulfides and the efficiency of sulfide removal. The mode of occurrence of Hg in coal does not directly affect the speciation of Hg in the combustion flue gas. However, other constituents in the coal, notably Cl and S, and the combustion characteristics of the coal, influence the species of Hg that are formed in the flue gas and enter air pollution control devices. The formation of gaseous oxidized Hg or particulate-bound Hg occurs post-combustion; these forms of Hg can be in part captured in the air pollution control devices that exist on coal-fired boilers, without modification. For a given coal type, the capture efficiency of Hg by pollution control systems varies according to type of device and the conditions of its deployment. For bituminous coal, on average, more than 60% of Hg in flue gas is captured by fabric filter (FF) and flue-gas desulfurization (FGD) systems. Key variables affecting performance for Hg control include Cl and S content of the coal, the positioning (hot side vs. cold side) of the system, and the amount of unburned C in coal ash. Knowledge of coal quality parameters and their effect on the performance of air pollution control devices allows optimization of Hg capture co-benefit.

Applied Geochemistry↗
USGS2004

Application of SAXS and SANS in evaluation of porosity, pore size distribution and surface area of coal

This paper discusses the applicability of small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) techniques for determining the porosity, pore size distribution and internal specific surface area in coals. The method is noninvasive, fast, inexpensive and does not require complex sample preparation. It uses coal grains of about 0.8 mm size mounted in standard pellets as used for petrographic studies. Assuming spherical pore geometry, the scattering data are converted into the pore size distribution in the size range 1 nm (10 A??) to 20 ??m (200,000 A??) in diameter, accounting for both open and closed pores. FTIR as well as SAXS and SANS data for seven samples of oriented whole coals and corresponding pellets with vitrinite reflectance (Ro) values in the range 0.55% to 5.15% are presented and analyzed. Our results demonstrate that pellets adequately represent the average microstructure of coal samples. The scattering data have been used to calculate the maximum surface area available for methane adsorption. Total porosity as percentage of sample volume is calculated and compared with worldwide trends. By demonstrating the applicability of SAXS and SANS techniques to determine the porosity, pore size distribution and surface area in coals, we provide a new and efficient tool, which can be used for any type of coal sample, from a thin slice to a representative sample of a thick seam. ?? 2004 Elsevier B.V. All rights reserved.

International Journal of Coal Geology↗
USGS1997

Adsorption of SO 2 on bituminous coal char and activated carbon fiber

The SO 2 adsorption behaviors of activated carbons produced from Illinois coal and of commercially prepared activated carbon fibers (ACFs) were compared. There was no relation between surface area of coal-based carbons and SO 2 adsorption, whereas adsorption of SO 2 on the series of ACFs was inversely proportional to N 2 BET surface area. Higher surface area ACFs had wider pores and adsorbed less SO 2 ; thus, pore size distribution is thought to play a significant role in SO 2 adsorption for these materials. Oxidation with HNO 3 and/or H 2 SO 4 , followed by heat treatment at 700−925°C to remove carbon−oxygen complexes, resulted in increased SO 2 adsorption for both coal chars and ACFs. This behavior was explained by an increase in the available number of free sites, previously occupied by oxygen and now available for SO 2 adsorption. The use of nitrogen-containing functional groups on ACFs of proper pore size shows promise for further increasing SO 2 adsorption capacities. Knowledge of the relationship among the number of free sites, pore size, and surface chemistry on corresponding SO 2 adsorption should lead to the development of more efficient adsorbents prepared from either coal or ACFs.

Energy and Fuels↗
USGS2005

Appalachian coal assessment: Defining the coal systems of the Appalachian basin

The coal systems concept may be used to organize the geologic data for a relatively large, complex area, such as the Appalachian basin, in order to facilitate coal assessments in the area. The concept is especially valuable in subjective assessments of future coal production, which would require a detailed understanding of the coal geology and coal chemistry of the region. In addition, subjective assessments of future coal production would be enhanced by a geographical information system that contains the geologic and geochemical data commonly prepared for conventional coal assessments. Coal systems are generally defined as one or more coal beds or groups of coal beds that have had the same or similar genetic history from their inception as peat deposits, through their burial, diagenesis, and epigenesis to their ultimate preservation as lignite, bituminous coal, or anthracite. The central and northern parts of the Appalachian basin contain seven coal systems (Coal Systems A-G). These systems may be defined generally on the following criteria: (1) on the primary characteristics of their paleopeat deposits, (2) on the stratigraphic framework of the Paleozoic coal measures, (3) on the relative abundance of coal beds within the major stratigraphic groupings, (4) on the amount of sulfur related to the geologic and climatic conditions under which paleopeat deposits accumulated, and (5) on the rank of the coal (lignite to anthracite). ??2005 Geological Society of America.

Special Paper of the Geological Society of America↗
USGS1950

Coal resources of the United States, A progress report, November 1, 1950

Interest in the quantity and quality of the coal reserves of the United States has increased greatly since the end of World War II, principally because of the growing realization that the ultimate reserves of petroleum and natural gas, although largely undefined, still. have finite limits. With the greatly increased use of petroleum and natural gas, it has become further apparent that the reserves of these two fuels, whatever their ultimate limits may prove to be, are being consumed at a rate far surpassing that anticipated a few years ago. At some time in the future, therefore, the contribution of coal to the total production of energy in this country must inevitably be enlarged to include some of the needs now served by petroleum and natural gas. Although coal-bearing rocks cover 14 percent of the total area of the United States (fig. 1) and contain enormous reserves, it is equally apparent that reserves of coal also have limits. In the extensively mined sections in the East it is already increasingly difficult to locate new areas containing thick beds of high-rank and high-quality coal to replace areas that have been mined out. Furthermore, a considerable part of the total reserves of the United States consists of coal of lignite and subbituminous ranks and coal contained in thin beds that can be mined only with great difficulty and expense. At the present time, therefore, the depletion of reserves of high-rank and high-quality coal, particularly the Eastern coal that is suitable for the manufacture of metallurgical coke, is a more serious problem than the percentage depletion of the total coal reserves. Recognizing the need for more detailed estimates of coal reserves than those that have been available in the past, the U. S. Geological Survey is now preparing a reappraisal of the coal reserves of the United States in which primary emphasis is placed on the amounts of coal in separate categories according to rank,thickness of coal, and thickness of overburden. Many of the state geological surveys in coal-producing areas are also preparing new appraisals of coal reserves. The increasing volume of geologic data available on the occurrence of coal and the detailed and careful methods now employed in calculating reserves should ultimately provide a more reliable estimate for the coal reserves of the United States than has been obtainable previously, although much additional work remains to be done.

Circular↗