Coal Contamination Research Articles

Influence of selected coal contaminants on graphitic carbon electro-oxidation for application to the direct carbon fuel cell

A novel method examining the fundamental electrochemical behaviour of carbon is outlined here involving the use of a half cell set-up and solid sacrificial anode. Using this method, electrochemical oxidation of graphite is assessed using selective contamination of a graphite electrode with major coal contaminants identified in selected Australian black coals using X-ray diffraction. Contaminants identified include anatase, alumina, pyrite, quartz, kaolin and montmorillonite. From the systematic introduction of these contaminants it is shown that clay materials, such as kaolin and montmorillonite, act catalytically to increase the rate of graphite oxidation. Metal oxides and sulfides such as anatase, alumina and pyrite give a limited increase in the normalised current, whereas quartz gives a significant decrease in performance. This demonstrates a clear effect of the solid phase interaction of these contaminants on the electrochemical oxidation of graphite since the same effect is not observed when the contaminants are added instead to the molten carbonate electrolyte.

Partitioning of coal contaminants in the components of liquid tin anode solid oxide fuel cells

Direct carbon fuel cells (DCFCs) electrochemically convert fossil fuels to electricity, resulting in higher efficiency and less pollution than traditional direct combustion technologies. This work focuses on direct use of coal in a liquid tin anode solid oxide fuel cell (LTA SOFC) where a layer of molten tin functions as the anode. In such a direct solid fueling scheme, a major technical concern is the ultimate disposition of trace materials naturally present in the coal. Trace contaminants introduced with the coal must be located in the functional portions of the LTA SOFC to ensure that any deleterious reactions are known and ultimately mitigated. This research effort determines the thermochemical contaminant partitioning between the tin anode, slag, or electrolyte material and examines the critical interfaces within the system. Contaminant partitioning was examined by TEM, SEM/EDS, and ICP–OES/MS. Sulfur is known to poison yttria-stabalized zirconia (YSZ) and appears to form a tin sulfide phase that is dispersed in the liquid tin during operation. Results show that tin oxide formed on and near the YSZ electrolyte, and could potentially degrade charge transfer. The slag was found to consist of the expected metal oxides, however, tin and tin oxide were intermixed with the slag component, indicating a probable need for a tin recovery process that will potentially increase the complexity of an LTA SOFC system.

Spectral characterization of soil and coal contamination on snow reflectance using hyperspectral analysis

Snow is a highly reflecting object found naturally on the Earth and its albedo is highly influenced by the amount and type of contamination. In the present study, two major types of contaminants (soil and coal) have been used to understand their effects on snow reflectance in the Himalayan region. These contaminants were used in two categories quantitatively – addition in large quantity and addition in small quantity. Snow reflectance data were collected between 350 and 2500 nm spectral ranges and binned at 10 nm interval by averaging. The experiment was designed to gather the field information in controlled conditions, and radiometric observations were collected. First derivative, band absorption depth, asymmetry, percentage change in reflectance and albedo in optical region were selected to identify and discriminate the type of contamination. Band absorption depth has shown a subtle increasing pattern for soil contamination, however, it was significant for small amounts of coal contamination. The absorption peak asymmetry was not significant for soil contamination but showed a nature towards left asymmetry for coal. The width of absorption feature at 1025 nm was not significant for both the contaminations. The percentage change in reflectance was quite high for small amount of coal contamination rather than soil contamination, however, a shift of peak was observed in soil-contaminated snow which was not present in coal contamination. The albedo drops exponentially for coal contamination rather than soil contamination.

The lack of microbial degradation of polycyclic aromatic hydrocarbons from coal-rich soils

Analytical techniques used to assess the environmental risk of contamination from polycyclic aromatic hydrocarbons (PAHs) typically consider only abiotic sample parameters. Supercritical fluid extraction and sorption enthalpy experiments previously suggested slow desorption rates for PAH compounds in two coal-contaminated floodplain soils. In this study, the actual PAH availability for aerobic soil microorganisms was tested in two series of soil-slurry experiments. The experimental conditions supported microbial degradation of phenanthrene if it was weakly sorbed onto silica gel. Native coals and coal-derived particles in two soils effectively acted as very strong sorbents and prevented microbial PAH degradation. The long history of PAH exposure and degree of coal contamination apparently had no influence on the capability of the microbial soil community to overcome constraints of PAH availability. Within the context of the experimental conditions and the compounds chosen, our results confirm that coal-bound PAHs are not bioavailable and hence of low environmental concern.

Impedance Study of the Synergistic Effects of Coal Contaminants: Is Cl a Contaminant or a Performance Stabilizer?

Impedance spectroscopy and current–voltage measurements were used to study the synergistic effects of the coal gas contaminants As, P, S, and Cl at the parts per million level on the performance of the anode-supported Ni–yttria-stabilized zirconia (YSZ)/YSZ/lanthanum strontium manganese solid oxide fuel cells (SOFCs) at . Three semicircles were differentiated in cell impedance spectra. The results indicate that the effects of the contaminants are synergistic, can be destructive or constructive, and are not a simple addition of individual contaminants. Adding to As and P accelerated the performance degradation. The addition of also increased the charge-transfer resistance, whereas the removal of resulted in a substantial ohmic resistance increase. The presence of Cl could mitigate or prevent performance loss from an attack by As and P. Impedance spectra show that the presence of Cl species protected the electronic percolation and slowed the rate of the charge-transfer resistance increase. Therefore, the tolerance limit of SOFCs for each contaminant could be significantly increased with Cl species in the gas stream. It is speculated that Cl species could react with nickel phosphides and Ni–P alloy to form NiCl(g), resulting in the restructuring of the catalyst surface.

Liquid Tin Anode SOFC For Direct Fuel Conversion - Impact of Coal and JP-8 Impurities

The Liquid Tin Anode solid oxide fuel cell (LTA-SOFC) has a demonstrated capability for direct fuel conversion using virtually any carbonaceous fuel. Two most notable applications under development are direct logistic fuel JP-8 conversion and direct coal (and biomass) conversion. For example a Gen 3.1 cell using logistic fuel only without fuel processing or reforming, has demonstrated specific power of 170 mW/cm2, at least 30 full thermal cycles and less than 7 minutes start up. Direct logistic fuel or coal conversion without fuel reforming/gasification/purification may also bring contaminants or impurities without fuel value in direct contact with fuel cell components. The tin anode is a fluid and a non-structural cell component so it is tolerant of many impurities. However fuel contaminants dissolved in molten tin could have a critical impact on cell components such as the electrolyte that are in direct contact with the molten tin anode. Certain fuel (V, Mo, etc.) impurities had shown causing damage to fuel cell if they were in direct contact with cell components such as electrolyte. This paper will examine liquid tin (molten tin bath) as a potential media to attenuate/reduce/eliminate harmful coal contaminants, providing a mitigation strategy for reducing a key technical risk factor of direct coal conversion using a fuel cell.

Effect of various coal contaminants on the performance of solid oxide fuel cells: Part II. ppm and sub-ppm level testing

Abstract The poisoning effects of various trace contaminants in the coal-derived syngas stream at ppm and sub-ppm level on the performance of Ni-YSZ/YSZ/LSM solid oxide fuel cells were studied at extended duration. The thermochemical nature of impurities such as PH3(g) and CH3Cl(g) in presence and absence of water steam was analyzed by a high temperature mass spectrometer. Only less than half of PH3(g) is hydrolyzed, and CH3Cl(g) also co-exist with HCl(g). After a certain duration of exposure, 1 ppm AsH3(g), 0.5 ppm PH3(g), and 2.5 ppm CH3Cl(g) all caused some degree of degradation to the power density at 750 °C. Whereas 1 ppm of H2S(g) resulted in immediate performance loss. The mechanisms of degradation are mainly divided into two categories: surface adsorption effect (for S and Cl) and bulk reaction effect (for As and P). The controversies regarding the poisoning effect and mechanism of S are also discussed with the aid of thermodynamic equilibrium composition calculation.

Effect of various coal contaminants on the performance of solid oxide fuel cells: Part I. Accelerated testing

The contaminants that are potentially present in the coal-derived gas stream and their thermochemical nature are discussed. Accelerated testing was carried out on Ni–YSZ/YSZ/LSM solid oxide fuel cells (YSZ: yttria stabilized zirconia and LSM: lanthanum strontium manganese oxide) for eight main kind of contaminants: CH 3 Cl, HCl, As, P, Zn, Hg, Cd and Sb at the temperature range of 750–850 °C. The As and P species, at 10 and 35 ppm, respectively, resulted in severe power density degradation at temperatures 800 °C and below. SEM and EDX analysis indicated that As attacked the Ni region of the anode surface and the Ni current collector, caused the break of the current collector and the eventual cell failure at 800 °C. The phosphorous containing species were found in the bulk of the anode, they were segregated and formed “grain boundary” like phases separating large Ni patches. These species are presumably nickel phosphide/phosphate and zirconia phosphate, which could break the Ni network for electron transport and inhibit the YSZ network for oxygen ion transport. The presence of 40 ppm CH 3 Cl and 5 ppm Cd only affected the cell power density at above 800 °C and Cd caused significant performance loss. Whereas the presence of 9 ppm Zn, 7 ppm Hg and 8 ppm Sb only degraded the cell power density by less than 1% during the 100 h test in the temperature range of 750–850 °C.

Synergetic Effect of Various Coal Contaminants on the Performance of Solid Oxide Fuel Cells

not Available.

Elevated Rates of Neuroblastoma Associated with Exposure to Coal Tar from a Former Manufactured Gas Plant (MGP) Site

Purpose Extensive coal tar-related contamination from a former MGP site occurred in Taylorville, Illinois, including extremely high levels of polynuclear aromatic hydrocarbons, volatile organic compounds, and inorganic compounds in multiple on- and off-site environmental media. Coal tar has been classified as a known human carcinogen by numerous scientific and governmental panels of experts. Community concerns were raised regarding neuroblastoma risk given the proximity of a large, open pit with coal tar to the town playground, and known heightened fetal nervous system sensitivity to carcinogens. Methods A Standardized Incidence Ratio (SIR) analysis for the period 1986-1991 was conducted, comparing Taylorville and Christian County, IL with four comparison groups: 1) demographically-similar zip codes and counties; 2) demographically-similar zip codes without MGP sites; 3) the state of Illinois; and 4) the entire U.S. Confounding variables were accounted for by stratification or indirect adjustment. Disturbance and remediation of the site exacerbated the release of contaminants. Incident case data for the state of Illinois was obtained from the Illinois State Cancer Registry; population data was obtained from the 1990 U.S Census; and national reference rates were obtained from SEER. Results In all comparison groups, the SIR for neuroblastoma ranged from 9.9 to 24.3, with a lower-bounded 95% confidence interval (CI) that did not include 1. Comparisons using the four control groups provided comparable results, with higher SIRs generally seen in the comparison to the demographically similar, non-MGP site zip codes, which may imply an effect of the MGP sites on cancer incidence. Conclusion There was a significantly elevated incidence rate of neuroblastoma in children during a time period of heightened ambient exposure to coal tar-related contaminants relative to all comparison populations. There are 52,000 former MGP sites in the U.S. alone; thus, environmental exposure to coal tar is a continuing public health concern.

Development of an accurate, sensitive, and robust isotope dilution laser ablation ICP-MS method for simultaneous multi-element analysis (chlorine, sulfur, and heavy metals) in coal samples

A method for the direct multi-element determination of Cl, S, Hg, Pb, Cd, U, Br, Cr, Cu, Fe, and Zn in powdered coal samples has been developed by applying inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with laser-assisted introduction into the plasma. A sector-field ICP-MS with a mass resolution of 4,000 and a high-ablation rate laser ablation system provided significantly better sensitivity, detection limits, and accuracy compared to a conventional laser ablation system coupled with a quadrupole ICP-MS. The sensitivity ranges from about 590 cps for (35)Cl+ to more than 6 x 10(5) cps for (238)U+ for 1 microg of trace element per gram of coal sample. Detection limits vary from 450 ng g(-1) for chlorine and 18 ng g(-1) for sulfur to 9.5 pg g(-1) for mercury and 0.3 pg g(-1) for uranium. Analyses of minor and trace elements in four certified reference materials (BCR-180 Gas Coal, BCR-331 Steam Coal, SRM 1632c Trace Elements in Coal, SRM 1635 Trace Elements in Coal) yielded good agreement of usually not more than 5% deviation from the certified values and precisions of less than 10% relative standard deviation for most elements. Higher relative standard deviations were found for particular elements such as Hg and Cd caused by inhomogeneities due to associations of these elements within micro-inclusions in coal which was demonstrated for Hg in SRM 1635, SRM 1632c, and another standard reference material (SRM 2682b, Sulfur and Mercury in Coal). The developed LA-ICP-IDMS method with its simple sample pretreatment opens the possibility for accurate, fast, and highly sensitive determinations of environmentally critical contaminants in coal as well as of trace impurities in similar sample materials like graphite powder and activated charcoal on a routine basis.

Organic matter in constructed soils from a coal mining area in southern Brazil

In southern Brazil, the landscape restoration after the exhaustion of open cast coal mines involves the filling of mine cavities with both pedogenic and geological material. The objective of this work was to determine the content and chemical composition of the organic matter of two constructed soils (24 years and 2 years) in a coal mining area in southern Brazil. An undisturbed Acrisol and geological material from three sites were also sampled. Samples were analyzed for carbon and nitrogen contents by dry combustion and for chemical composition of the organic matter by 13C NMR CPMAS and FTIR spectroscopies. Prior to the spectroscopic analyses, the samples were treated with 10% (m/m) hydrofluoric acid solution, which lead to a carbon enrichment in the sample of 2–46 times. The three coal samples were mainly composed of aromatic C (46–63%) and alkyl C (10–28%), and differed largely in the carbon content (18–312 g kg −1). The C/N ratio of 27 and the proportions of O-alkyl C (26%) and aromatic C (29%) found in the native soil (18 g C kg −1 soil) suggest a coal contamination of the native site. The proportions of O/N-alkyl C (15–17%), alkyl C (22–23%) and aromatic C (39–41%) observed in the organic matter of the A1 horizon of the two constructed soils were intermediate to those of the coal samples and the native soil. In the younger constructed soil the proportion of O/N-alkyl diminished and that of aromatic C increased with depth, whereas in the older constructed soil this trend was less evident. Our results show that, during the 24 years after site reconstruction, the input of vegetation residues diluted the proportion of recalcitrant organic matter. The aromaticity index calculated from the FTIR data ( I 1620/ I 2920) correlated positively with the aryl C/alkyl C ratio, obtained from the NMR data, evidencing the applicability of the FTIR index for geological and coal contaminated samples.

05/00017 Technical progress in the development of zero emission coal technologies: Ziock, H.-J. et al. Proceedings of the International Technical Conference on Coal Utilization & Fuel Systems, 2003, 28, (2), 1199–1210

We present an update on the development of technologies required for the Zero Emission Carbon (ZEC) concept being pursued by ZECA Corporation. The concept has a highly integrated design involving hydrogasification, a calcium oxide driven reforming step that includes simultaneous C02 separation, coal compatible fuel cells for electricity production and heat recovery, and a closed loop gas system in which coal contaminants are removed either as liquids or solids. The process does not involve any combustion and as such has neither smokestack nor air emissions. An independent assessment of the concept by Nexant, a Bcchtel affiliated company, suggests a net efficiency of approximately 70% for conversion of the higher heat value fuel energy into electrical output. This is even after the penalties of carbon dioxide separation and pressurization to 1000 psi are taken into account. For carbon dioxide sequestration a variety of options are being considered, which include enhanced oil recovery in the near-term and mineral carbonation as a long-term approach. We report on our early results in the development of sulfur tolerant anode materials for solid oxide fuel cells; a critical analysis of the calcium oxide - calcium carbonate cycle; trace element removal; and the recent results of hydrogasification tests.

Fingerprinting of Gasoline and Coal Tar NAPL Volatile Hydrocarbons Dissolved in Groundwater

Accidental spills and chronic leaks of fuel oil or other hydrocarbon material (e.g., coal tar) often result in subsurface accumulation of nonaqueous phase liquid (NAPL), which can be a subsequent source of contamination in groundwater. Linking hydrocarbons in groundwater to a source NAPL has been difficult when using standard target analytes (e.g., BTEX) because of differences in partitioning properties of the analytes between the source NAPL and groundwater. Because aqueous solubility is predicted to be the controlling influence in the partitioning of hydrocarbons from NAPL to groundwater, a solubility-based approach to matching dissolved hydrocarbons in groundwater to their source NAPL has been developed and validated for two sites with commonly encountered types of NAPL contamination. Specifically, a gasoline LNAPL and a coal tar DNAPL from two separate sites (West Virginia and California) and groundwater interfaced with these NAPLs were analyzed for approximately 50 gasoline-range hydrocarbons consisting of paraffin, isoparaffin, (mono-) aromatic, naphthene, and olefin compounds (PIANO). Solubility characteristics of selected alkyl aromatic hydrocarbons from the PIANO analysis were used to identify a set of diagnostic hydrocarbons, expressed as hydrocarbon ratios, which were found to be useful in distinguishing the source(s) of hydrocarbons in groundwater. At the West Virginia site, the diagnostic ratios in a downgradient groundwater sample were similar to those of a gasoline NAPL at that site, indicating the source of hydrocarbons to the groundwater was the upgradient gasoline NAPL. The diagnostic ratios of the groundwater in contact with the gasoline NAPL and the remote groundwater were also similar, providing evidence that the diagnostic ratios were retained during transport in the aquifer. At the California site, diagnostic ratios in a cross-gradient groundwater sample differed from those of the coal tar NAPL at that site, indicating that the remote groundwater hydrocarbons did not originate from the coal tar contamination. Environmental factors such as selective degradation of specific isomers and various geological conditions (e.g., soil mineralogy, and organic content) may confound the application of this solubility-based fingerprinting approach. Thus, it is recommended that multiple diagnostic pairs be simultaneously evaluated when considering this fingerprinting approach for specific sites and product types.

Coal Slag Reaction with High Chrome Refractories

Abstract ABSTRACT: Coal gasifiers are required to operate at very high temperatures, >1600°C, for long periods of time, > 13 months (10,000 hours) Fig.1. Under these conditions the refractory lining of choice is high chrome refractory. During operation coal contaminants form a liquid slag that run down the chamber walls which can react with the refractory walls. Albany Research Center has designed a series of experiments to understand the slag-refractory interactions, with the intent of eventually being able to reduce or minimize the problem and thereby extending the gasifier operation time before relining. To understand the slag-refractory interaction, elemental components of the slag have been allowed to react with the refractory under simulated gasifying conditions. The interactions have been characterized using X-ray diffraction, electron microscopy, elemental x-ray mapping, and quantitative microanalysis.

Preparation of a coal surface for contact angle measurements

Coal specimens of different ranks were polished using silicon carbide abrasive papers (with a grit from #60 to #1200) and alumina powder of varying size (from 5 to 0.05 μm). The coal surface roughness and contamination (by alumina powder) were examined with both scanning electron microscopy and atomic force microscopy. The water advancing and receding contact angles were measured on such surfaces by varying the bubble size, using the captive-bubble technique. It was found that silicon carbide paper abraded all components of the coal surface, i.e. both organic and inorganic matter, to a similar depth. The roughness of the coal surface due to polishing with silicon carbide abrasive papers affected the contact angle hysteresis and the contact angle vs. bubble size relationship. Polishing of coal specimens with alumina powder reduced the microroughness of the coal surface but produced rough features at the macro level and caused mineral inclusions rising above the smooth organic matter. This phenomenon results from the heterogeneity of coal specimens consisting of minerals and macerals with different hardness values. The roughness at the macro level was easily distinguishable and had a significant impact on the measured contact angles when the coal surface was polished with coarse alumina powders, 5 and 1 μm in diameter. The effect of surface roughness on the advancing and receding water contact angles was significantly reduced (if not completely eliminated) when the coal surface was polished with a fibrous cloth (CHEMOMET) in the final step, after having been polished with 0.05 (0.06) μm alumina powder. Microscopic observation of the coal surfaces revealed that an appropriate ultrasonic treatment (8-10 min in an ultrasonic bath filled with water) and mechanical cleaning (polishing with a CHEMOMET cloth) of coal samples were required to remove the alumina particles left on the surface due to the previous polishing procedure. An improved methodology for coal surface preparation, prior to contact angle measurements, as proposed in this paper, includes polishing with a series of abrasive papers and 0.05 (0.06) μm alumina powder, polishing and cleaning with a fibrous cloth (e.g. CHEMOMET), and, finally, an extended cleaning in an ultrasonic bath filled with water.

Spatial variability in the naphthalene mineralization response to oxygen, nitrate, and orthophosphate amendments in MGP aquifer sediments

The feasibility of aerobic in situ bioremediation isbeing investigated for use in a strategy to controlsubsurface coal tar contamination at the site of aformer manufactured gas plant. As part of thisinvestigation, anoxic aquifer sands collected between11 and 25 m below ground surface were assayed in batchmicrocosms to measure the singular and combinedeffects of O2, NO3 -, andPO4 3- on 14C-naphthalenemineralization. The influence of these additivesvaried considerably between sediments. A high initialconcentration of O2 (21 mg/L) promoted thegreatest extent of mineralization in the majority ofactive sediments. NO3 - (85 mg/L) wasobserved to enhance, inhibit, or have no effect on therate of naphthalene mineralization, althoughsignificant denitrification was observed in nearly allthe active sediments. Data suggest thatPO4 3- complexation and/or precipitation withsediment cations limited P bioavailability. Thesediments that were incapable of mineralizingnaphthalene were characterized by low pH (< 4.1),high SO4 2- (> 500 mg/L), and moderate tohigh dissolved Fe(II) (30–265 mg/L) whenequilibrated aerobically with water. Fe(II) likelyexerted a significant O2 demand that reduced theO2 available as an electron acceptor forbiodegradation. These experiments demonstrate thatwhile aeration/oxygenation can be an effectivestrategy for enhancing subsurface bioremediation ofaromatic hydrocarbons, the biodegradation response toaeration/oxygenation and nutrient addition may varyconsiderably within an aquifer.

AMS-radiocarbon dating of organic-poor lake sediment, an example from Linnévatnet, Spitsbergen, Svalbard

AMS-radiocarbon dating of specific organic fractions is used to evaluate sources of errors in dating of organic-poor lake sediment from Linnévatnet, a proglacial arctic lake. Dates on un differentiated (bulk) organic matter are much too old because of contamination from detrital coal. Attempts to remove coal from other organic matter were only partially successful, a consequence of the wide grain-size distribution of the coal. Even if coal contamination is fully removed, the bulk of the remaining organic matter is of aquatic origin and is unsuitable for 14C dating because the lake waters are depleted in 14 C due to dissolution of carbonate minerals. Terrestrial plant macrofossils provide the only reliable material to date the lake sediment; however, this material is present in sufficient quantity for AMS-radiocarbon dating only in cores proximal to the main inlet streams. Paired dates on terrestrial plants and aquatic insects from the same core level and paired dates on modern aquatic and terrestrial vegetation indicate differences in carbon reservoir activities of 1000 and 3000 years. In hard-water lakes, coring is recommended in inlet-proximal areas where inwashed terrestrial vegetation is most concen trated. Chronologies established in proximal cores can be transferred to central-basin cores using litho or chemo-stratigraphic indices.

Effect of Pressure on Second-Generation Pressurized Fluidized Bed Combustion Plants

In the search for a more efficient, less costly, and more environmentally responsible method for generating electrical power from coal, research and development has turned to advanced pressurized fluidized bed combustion (PFBC) and coal gasification technologies. A logical extension of this work is the second-generation PFBC plant, which incorporates key components of each of these technologies. In this new type of plant, coal is devolatilized/carbonized before it is injected into the PFB combustor bed, and the low-Btu fuel gas produced by this process is burned in a gas turbine topping combustor. By integrating coal carbonization with PFB coal/char combustion, gas turbine inlet temperatures higher than 1149°C (2100°F) can be achieved. The carbonizer, PFB combustor, and particulate-capturing hot gas cleanup systems operate at 871°C (1600°F), permitting sulfur capture by time-based sorbents and minimizing the release of coal contaminants to the gases. This paper presents the performance and economics of this new type of plant and provides a brief overview of the pilot plant test programs being conducted to support its development.

Comments on the Meadowcroft Rockshelter Radiocarbon Chronology and the Recognition of Coal Contaminants

Early 14C dates from Meadowcroft Rockshelter have engendered debate on the antiquity of human occupation in North America. Although the investigators of this important site conclude that particulate and nonparticulate contamination have not affected the radiocarbon dates, several points of confusion remain in regard to the question of coal contamination. We clarify these issues, provide comparative data from other sites, and recommend specific tests that are necessary to negate or support the issue of "dead carbon" contamination of radiocarbon samples.