Coal Contamination Research Articles

Assessment of the Influence of Sulfuric Acid/Hydrogen Peroxide Mixture on Organic Sulfur Reduction of High Sulfur Coals and Their Chemical Composition

One of the contaminants in coal is sulphur. The adverse impact of sulfur on coal, such as environmental pollution, degradation of steel quality, and reduction of coal’s thermal value, has led to the attention of sulfur separation methods in recent decades. Leaching (chemical dissolution) is one of the best methods for desulfurising coal, reducing sulfur in coal. In this study, hydrogen peroxide as an oxidising agent on sulfuric acid yield in reducing sulfur types of coal and chemical structure and the organic texture of high sulfur coal was investigated. The experiments were designed using a three-level response surface methodology with four duplicate points and 27 experiments. The independent variables studied were temperature, time, stirring speed and ratio of sulfuric acid to hydrogen peroxide. Dependent variables included reduction percentage of total, pyritic and organic sulfur. This study showed that 99.99% of total sulfur, 30.11% of pyritic sulfur and 69.08% of organic sulfur were reduced. These values were obtained at a temperature of 60°C, time 120 min, stirring speed 200 rpm and 3:1 ratio of sulfuric acid to hydrogen peroxide. Significant changes were observed by infrared spectroscopy (FTIR) of the coal structure before and after desulphurisation. On the other hand, the studies showed no specific changes in the bonds related to the organic coal matrix. The results showed that this method could be used as a secure process for removing inorganic and organic sulfur without destroying the organic coal matrix.

SO2 electrooxidation reaction on Pt single crystal surfaces in acidic media: Electrochemical and in situ FTIR studies

SO2 is a poisonous and anthropogenic gas generated by fossil fuel burning due to the common presence of S-containing contaminants in oil and coal. As a strategy to handle this pollutant and to increase H2 generation, the electrocatalytic SO2 oxidation reaction (SO2OR) is considered. In this way, SO2 is converted to H2SO4, while hydrogen gas is generated at the cathode. To better understand the mechanism and its dependence on the surface crystallography and electrolyte composition, electrochemical and in situ spectroscopic measurements using Pt single crystal electrodes were performed. The crystallographic orientation of the electrode is shown to be critical not only to the SO2OR activity but also to the resulting mechanism. The Pt(100) face is found to be the most active electrode in both H2SO4 and HClO4 aqueous electrolytes, and S2O62− appears as a key intermediate for the mechanism. Volcano plots, drawn considering the Stark tuning slope as a quantity proportional to the adsorption energy, show the importance of S2O62− in the electrode catalytic activity.

Effects of suspended coal particles on gill structure and oxygen consumption rates in a coral reef fish

Large quantities of coal are transported through tropical regions; however, little is known about the sub-lethal effects of coal contamination on tropical marine organisms, including fish. Here, we measured aerobic metabolism and gill morphology in a planktivorous coral reef damselfish, Acanthochromis polyacanthus to elucidate the sub-lethal effects of suspended coal particles over a range of coal concentrations and exposure durations. Differences in the standard oxygen consumption rates (MO2) between control fish and fish exposed to coal particles (38 and 73 mg L−1) were minimal and generally not dose dependent; however, the MO2 of fish exposed to 38 mg coal L−1 (21 days) and 73 mg coal L−1 (31 days) were both significantly higher than the MO2 of control fish. Chronic coal exposure (31 days) altered gill structure in the higher coal treatments (73 and 275 mg L−1), with fish exposed to 275 mg L−1 exhibiting significant reductions in gill mucous and thinning of lamellar and filament epithelium. These findings contribute to our limited understanding of the potential impacts of coal on tropical reef species; however, most of the observed effects occurred at high coal concentrations that are unlikely under most coal spill scenarios. Future studies should investigate other contamination scenarios such as the impacts of chronic exposures to lower concentrations of coal.

INVESTIGASI DAN REKAYASA TAPAK REKLAMASI: STATE OF ART SUATU SOLUSI UNTUK MENUNJANG PASCATAMBANG TIMAH ALLUVIAL YANG BERKELANJUTAN

Reklamasi pada area bekas tambang merupakan salah satu tantangan untuk merepresentasikan wujud nyata manajemen berkelanjutan pada sektor pertambangan Indonesia. Kerangka kerja peraturan reklamasi dan pasca tambang di Indonesia menetapkan berbagai persyaratan untuk melaksanakan kegiatan reklamasi dan pasca tambang. Sebagai langkah awal, para pemangku kepentingan diwajibkan untuk berkonsultasi secara detail tentang peraturan-peraturan yang berlaku. Reklamasi timah alluvial (dan kemungkinan endapan logam alluvial lainnya) merupakan masalah yang pelik dalam mewujudkan program reklamasi pasca tambang yang berkelanjutan. Sering kali program reklamasi gagal karena adanya proses penambangan kembali di lahan yang sudah direklamasi. Masalah utama dalam proses reklamasi timah alluvial adalah bahaya geologi, hidrologi, hidrogeologi dan penambangan kembali. Dengan adanya data-data yang baik maka akan dapat dilakukan rekayasa teknik yang baik untuk mewujudkan reklamasi yang berkelanjutan. Penerapan teknologi tepat guna untuk mengantisipasi bahaya geologi, hidrogeologi, hidrologi serta monitoringnya sehingga aspek yang akan mengurangi keberhasilan program reklamasi sudah dapat diantisipasi sejak awal sehingga program pencegahannya dapat dilakukan sejak dini. Proses sterilisasi yang baik dilakukan sejak awal proses penambangan ataupun dilakukan sebelum proses penutupan tambang agar proses reklamasi dapat berjalan secara berkelanjutan.

Identification of the featured-element in fine road dust of cities with coal contamination by geochemical investigation and isotopic monitoring

The exploitation of coal releases large amounts of contaminants into the environment. However, the featured pollutants of coal utilization as well as the scope and degree of their impact remain to be revealed. To identify the featured-element of coal contamination in a complex environment, a typical coal resource city was selected, and the major elements, 18 trace elements, as well as δ13C, δ15N, and δ34S in the fine road dust and certain source materials were analyzed. Through multiple analysis methods, the featured-element was determined step-by-step: firstly, elements with enrichment coefficients greater than two in road dust were focused: Zn, Hg, Pb, Cu, Cd, and Cr; secondly, difference analysis showed a significant difference (p < 0.05) of Hg and Cu concentration at different distance from the coal-fired power plant, making Hg and Cu the only candidates for the featured-element; finally, through coal-related source materials determination, Cu was not qualified as a featured-element. Therefore, Hg was the only left element to be considered as the featured-element. To be more convincing, more analyses were performed to support Hg as the featured-element: cluster analysis and isotope monitoring indicated Hg in road dust could originate from coal combustion; X-ray photoelectron spectroscopy was also conducted, where the forms of Hg in road dust with possible source materials were compared, and the presence of HgO and Hg only in the road dust near the power plant indicated the impact of the power plant on the surrounding dust. Through the health risk assessment, it was found that Hg in the road dust had no health risk, though the study area still had Pb, Cr, and As risks, which were not closely related to the pollutants released by coal-related sources.

Nanomineralogy of evaporative precipitation of efflorescent compounds from coal mine drainage

Efflorescent nanophases (NPs) are found as a transitory accumulation of potentially hazardous elements (PHEs), particularly in tropical climates. The central objective of this study was to investigate the distribution of PHEs with NPs through the evaporative formation structures (EFS) of enormously PHEs-rich coal-mine drainages (CMD). The EFS were studied in natural coal mine drainage for five months in order to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in nature. The largest coal-fired power plant in South America, located in south Brazil, is used as an example of such a problem. In this work, a novel methodology for the analysis of PHEs in CMD precipitates is proposed for this affected coal area. The analytical method, combining X-Ray Diffraction (XRD) and advanced electron microscopies, shows the importance of nanomineralogy in understanding different circumstances of coal contamination. Several ultrafine-nanoparticles (UNPs) were identified in the sampled soils and river sediments together with the PHEs. A decrease in PHEs was identified in association with UNPs. However, further investigations are required with regard to the mobility of PHEs in water, atmosphere, soils, and sediments. The EPS was thoroughly studied, acquiring suitable understanding with investigational facts for Ca and Fe-sulphates, pickeringite, and several amorphous phases.

A tool for realistic study of nanoparticulate coal rejects

Pollution caused by hazardous and carcinogenic inorganic elements and organic compounds from coal may be more severe when coupled by other sources of pollution. In addition, the modes of occurrence of potential hazardous elements (PHEs) in coal cleaning rejects (CCRs) have been widely investigated using different methods, including statistical methods, which, however, in some cases resulted in misleading interpretations. In order to verify this potential problem and find an effective solution, we selected a data set, which contained comprehensive analyses of CCRs. The secondary products in sulphides-bearing coal mine rejects were studied in demand to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in the nature. A zone located in south Brazil, which is the major coal power plant in South America, can be given as an example of such a problem. In this work, a novel methodology for the analysis of PHEs in soils and sediments is proposed for this affected coal area. The analytical method combining X-Ray Diffraction (XRD) and advanced electron microscopies shows the importance of nanomineralogy in understanding different circumstances of coal contamination. Several ultrafine-nanoparticles (UNPs) were identified in the sampled soils and river sediments together with the PHEs. A decrease in PHEs was identified in association with UNPs. However, still further investigations are required with regard to the mobility of PHEs in water, atmosphere, soils, and sediments. The site studied around the coal power plant showed the highest sorption capacity possibly due to the high retention ability of components of soil and sediments such as carbon and clay. These observations of the coal-derived nanoparticles confirm their capability of regulating the mobility of hazardous elements, implying the need for restoring complex abandoned coal areas.

Sulfur Transformation Behavior of Inorganic Sulfur-Containing Compounds in Chemical Looping Combustion

Chemical looping combustion (CLC) is a promising technology for fuel conversion with inherent carbon capture. Because sulfur is an integral part of coal, the existence of sulfur contaminants in coal may degrade the purity of CO₂ and deteriorate the performance of the oxygen carrier in the CLC process. To uncouple the complex behavior of inorganic sulfur in coal, sulfur release of three inorganic sulfur-containing compounds (FeS₂, FeSO₄, and CaSO₄) mixed with activated carbon during the temperature-programmed process and the CLC process using iron ore as an oxygen carrier were investigated in a batch fluidized bed reactor at 950 °C. The results showed that, in the temperature-programmed process, the initial decomposition temperatures of FeS₂, FeSO₄, and CaSO₄ were about 400, 500, and 650 °C, respectively. During the reduction and oxidation stages of CLC, SO₂ was the main sulfur-containing gaseous compound. The sulfur stability of CaSO₄ was higher than those of FeS₂ and FeSO₄. The fractions of sulfur converted to gaseous species in the reduction stage (XS,g,ᵣₑd) of FeS₂ and FeSO₄ reached 90.38 and 87.42%, respectively, within 20.5 min, while the corresponding value was 53.97% for CaSO₄. During 5 cyclic redox experiments at 950 °C, the fraction of sulfur converted to gas species was almost maintained stable, while the energy-dispersive X-ray spectroscopy analysis showed the accumulation of sulfur after the cyclic reaction.

Biogeochemical responses of soil ecosystems to raw coal pollution in Xuanhua, China

China is the world’s largest coal producer and consumer. Despite extensive studies on coal-burning pollution, the effect of raw coal pollutants caused by transportation and turnover on soil along the road received little attention. The main purpose of the study was to clarify the biogeochemical response of soil ecosystems to raw coal pollution. The raw coal and unpolluted soil from the coal distribution area in Xuanhua, China were collected for the incubation experiments. Combined with the determination of soil physicochemical properties, including pH, electric conductivity, soluble ions, dissolved organic carbon, and available heavy metals, the biogeochemical responses of soil to raw coal pollution, such as soil enzyme activities (β-glucosidase, alkaline phosphatase, and Urease), microbial community composition, and soil respiration, were systematically studied. In addition, a q-PCR analysis of the urease was performed to clarify the inhibitory mechanism of urease by coal pollution. Furthermore, a simple field investigation was carried out to confirm the incubation results. Raw coal pollution not only changed the soil physicochemical properties but also made the available Zn, Ni, and Co accumulate significantly. A positive priming effect in soil with the low-dose raw coal addition was trigged, but soil respiration rate and soil enzyme activity, such as β-glucosidase and alkaline phosphatase, were inhibited to different degrees with the increased pollution. Urease activity also decreased under the higher coal contamination, which was due to inhibition of ureC gene expression. In addition to the slight soil acidification caused by coal pollution, microbial communities and diversity was also found to be affected. The relative abundances of the microorganisms related to urease, alkaline phosphatase, and β-glucosidase changed accordingly. The incubation results are in good agreement with the field survey results. Low-dose raw coal pollution can trigger the soil positive priming effect. However, as the coal pollution increased, the β-glucosidase, alkaline phosphatase, and urease in the soil were inhibited to varying degrees. The compounding effects of soil acidification, increased electric conductivity, and the accumulation of available heavy metals such as Zn, Ni, and Co are the key causes for the biogeochemical response of soil to coal pollution.

Impacts of Kaolin on the Thermal and Electrochemical Properties of Ternary Eutectic Molten Carbonate Electrolyte in the Direct Carbon Fuel Cell (DCFC)

Coal is the second largest energy resource used for electricity production in the world and is expected remain unchanged through 2030. The main problem of using coal in conventional combustion power plants is serious environmental pollution due to CO2 emissions. In this context, electrochemical conversion of solid carbon to generate electricity is one of the most efficient technologies using liquid electrolyte at high temperature which is environmentally friendly. Raw coal as a fuel has some advantages and disadvantages in terms of mineral impurities inhabited in the coal which affect the DCFC performance. Kaolin is a common mineral found in coal fuels which has an advantage over other impurities. It was demonstrated that clay impurities in the coal such as kaolin and montmorillonite react catalytically to enhance graphite oxidation in a half-cell set up DCFC and improve the cell performance [1]. Although other impurities such as alumina, anatase and pyrite have limited impacts on the electrochemical oxidation of graphite, quartz was presented a decline in the current density of electro-oxidation of graphite. Thermal investigation of different coal impurities into ternary eutectic carbonate mixture has been done to show the impacts of these impurities on the melting process and kinetics of the melting process [2]. However it isn’t obvious yet what the impacts of these impurities have on the electrochemical performance of the cell and which disruption or modification will happen with addition of them on eutectic carbonate mixtures. In this work different ratios of kaolinite mineral were purposely added to the ternary eutectic carbonate electrolyte to investigate the thermal properties of the mixture and its melting behaviour. Particularly, DTA data were analysed in terms of changing melting temperature of the mixture and the determination of activation energy using different heating rates to asses these effects. The effect of kaolinite on the half-cell performance of a DCFC was also examined by adding kaolinite with different ratios into the eutectic carbonate electrolyte. The OCP, current density and polarization performance have been measured for the half-cell set up and results compared for different ratios of kaolinite and pure eutectic. Reference: 1-Tulloch, J.; Allen, J.; Wibberley, L.; Donne, S. et al. Influence of selected coal contaminants on graphitic carbon electro-oxidation for application to the direct carbon fuel cell. J. Power Sources 2014, 260,140−14910.1016/j.jpowsour.2014.03.026 2-M.J. Glenn, J.A. Allen, S.W. Donne Thermal investigation of a doped alkali-metal carbonate ternary eutectic for direct carbon fuel cell applications Energy Fuels, 29 (8) (2015), pp. 5423-5433

Influence on Zhundong Coal Slagging and Contamination Characteristics of Oil Shale Semi-Coke Blending Combustion

Zhundong coal has the advantages of low ignition temperature and high burning rate etc,but the high content of alkali metal in coal leads to slagging and fouling problems in the combustion process. In order to improve the coal’s slagging and fouling problems and the combustion efficiency of oil shale semi coke, XRF was used to determine the ash content of the sample to show high sodium content in coal has reached 6.41% and high silicon, aluminum content in the oil shale semi coke and alkali metal content decreased obviously after mixing. By calculating the index of slagging and contamination showed that blending oil shale semi-coke makes slagging, contamination index of Zhundong coal decrease for higher, moderate and slight degree by severity, and semi-coke mixing proportion reached more than 30%, oil shale semi-coke greatly improve the coal contamination problem.

Reassessment of dibenzothiophene as marker for petroleum and coal contamination in sediments from Imo River, SE Nigeria

ABSTRACTDistributions of dibenzothiophene (DBT) and its historical trends of deposition in sediments from Afam, mangrove, estuary, and illegal petroleum refinery sites of Imo River, southeast Nigeria over the past approximately five decades were evaluated in order to reassess the compound's potential as a marker for petroleum and/or coal combustion emission source(s). The spatial distributions in the concentrations of DBT varied from 12.46 ng/g dry weight (dw) to 1,720.42 ng/g dw (mean 454.77±14 ng/g dw), maximizing and minimizing at locations adjacent to an illegal petroleum refinery site. There was no strong geographic element that influenced DBT distribution across the river. The concentrations of DBT down cores ranged from 13.54 ng/g dw at the middle layer (15–20 cm, approximately 1981–1989) of the Afam site to a maximum of 470.43 ng/g dw at near-top layer (5–10 cm) of the illegal petroleum refinery site. The later layer corresponds to a depositional time frame of approximately 1997–2005, coinciding with the period of intensive illegal petroleum refinery operations when coal was used as a refinery fuel in the illegal processing and oil bunkering/pipeline vandalization were at their peaks. The general decline in DBT levels from near-top layers (5–10 cm) to the most recent top layers (0–5 cm) was linked to the recent offer of amnesty to the Niger Delta militant groups by the Nigerian government and subsequent clamp down on economic saboteurs by the Nigerian joint armed forces. Due to its extra stability to microbial degradation relative to polycyclic aromatic hydrocarbons (PAHs), the study illustrated the greater potential of DBT as a marker for petroleum and/or coal combustion emission source contaminations than the commonly used markers such as PAHs.

Micro-flotation removal of coal contaminants from archaeological radiocarbon samples from Chaco Canyon, New Mexico, USA

Micro-flotation, a specific gravity separation technique, was successfully used to remove coal contaminants from radiocarbon samples obtained from profiles, unit excavations, and solid sediment cores in Chaco Canyon, New Mexico, USA. Coal from the Cretaceous Menefee Formation occurs throughout Chaco Canyon in aeolian, alluvial, colluvial, and anthropogenic sediments. The Menefee Formation contains carbonized broadleaf angiosperm and gymnosperm plants and, as such, paleobotanical analysis was not effective in the identification and removal of coal contaminants. The effectiveness of micro-flotation as a pretreatment procedure was evaluated by: i) comparing AMS radiocarbon ages on processed and unprocessed samples from the same archaeological contexts; ii) comparing a processed sample of carbonized hardwood charcoal with a sample of uncarbonized hardwood from the same archaeological context; and iii) comparing radiocarbon ages on a split sample of processed bulk carbon. The comparisons confirmed the effectiveness of micro-flotation in processing samples for radiocarbon dating in Chaco Canyon and would be applicable for similar locations elsewhere in the world.

Effects of coal contamination on early life history processes of a reef-building coral, Acropora tenuis

Successful reproduction and larval dispersal are important for the persistence of marine invertebrate populations, and these early life history processes can be sensitive to marine pollution. Coal is emerging as a contaminant of interest due to the proximity of ports and shipping lanes to coral reefs. To assess the potential hazard of this contaminant, gametes, newly developed embryos, larvae and juveniles of the coral Acropora tenuis were exposed to a range of coal leachate, suspended coal, and coal smothering treatments. Fertilisation was the most sensitive reproductive process tested. Embryo survivorship decreased with increasing suspended coal concentrations and exposure duration, effects on larval settlement varied between treatments, while effects on juvenile survivorship were minimal. Leachate exposures had negligible effects on fertilisation and larval settlement. These results indicate that coral recruitment could be affected by spills that produce plumes of suspended coal particles which interact with gametes and embryos soon after spawning.

New improvements to MFIRE to enhance fire-modeling capabilities

NIOSH's mine fire simulation program, MFIRE, is widely accepted as a standard for assessing and predicting the impact of a fire on the mine ventilation system and the spread of fire contaminants in coal and metal/nonmetal mines, which has been used by U.S. and international companies to simulate fires for planning and response purposes. MFIRE is a dynamic, transient-state, mine ventilation network simulation program that performs normal planning calculations. It can also be used to analyze ventilation networks under thermal and mechanical influence such as changes in ventilation parameters, external influences such as changes in temperature, and internal influences such as a fire. The program output can be used to analyze the effects of these influences on the ventilation system. Since its original development by Michigan Technological University for the Bureau of Mines in the 1970s, several updates have been released over the years. In 2012, NIOSH completed a major redesign and restructuring of the program with the release of MFIRE 3.0. MFIRE's outdated FORTRAN programming language was replaced with an object-oriented C++ language and packaged into a dynamic link library (DLL). However, the MFIRE 3.0 release made no attempt to change or improve the fire modeling algorithms inherited from its previous version, MFIRE 2.20. This paper reports on improvements that have been made to the fire modeling capabilities of MFIRE 3.0 since its release. These improvements include the addition of fire source models of the t-squared fire and heat release rate curve data file, the addition of a moving fire source for conveyor belt fire simulations, improvement of the fire location algorithm, and the identification and prediction of smoke rollback phenomena. All the improvements discussed in this paper will be termed as MFIRE 3.1 and released by NIOSH in the near future.

Simulated coal spill causes mortality and growth inhibition in tropical marine organisms.

Coal is a principal fossil fuel driving economic and social development, and increases in global coal shipments have paralleled expansion of the industry. To identify the potential harm associated with chronic marine coal contamination, three taxa abundant in tropical marine ecosystems (the coral Acropora tenuis, the reef fish Acanthochromis polyacanthus and the seagrass Halodule uninervis) were exposed to five concentrations (0–275 mg coal l−1) of suspended coal dust (<63 μm) over 28 d. Results demonstrate that chronic coal exposure can cause considerable lethal effects on corals, and reductions in seagrass and fish growth rates. Coral survivorship and seagrass growth rates were inversely related to increasing coal concentrations (≥38 mg coal l−1) and effects increased between 14 and 28 d, whereas fish growth rates were similarly depressed at all coal concentrations tested. This investigation provides novel insights into direct coal impacts on key tropical taxa for application in the assessment of risks posed by increasing coal shipments in globally threatened marine ecosystems.

Genotoxic and biochemical changes in Baccharis trimera induced by coal contamination

The processing and combustion of coal in thermal power plants release anthropogenic chemicals into the environment. Baccharis trimera is a common plant used in folk medicine that grows readily in soils degraded by coal mining activities. This shrub bioaccumulates metals released into the environment, and thus its consumption may be harmful to health. The purpose of this study was to investigate the phytochemical profile, antioxidant capacity (DPPH), genotoxic (comet assay) and mutagenic potential (CBMN-cyt) in V79 cells of B. trimera aqueous extracts in the coal-mining region of Candiota (Bt-AEC), and in Bagé, a city that does not experience the effects of exposure to coal (Bt-AEB, a reference site). In the comet assay, only Bt-AEC was genotoxic at the highest doses (0.8mg/mL and 1.6mg/mL), compared to the control. For extracts from both areas, mutagenic effects were observed at higher concentrations compared to the control. The cell damage parameters were significantly high in both extracts; however, more striking values were observed for Bt-AEC, up to the dose of 0.8mg/mL. In chemical analysis, no variation was observed in the contents of flavonoids and phenolic compounds, neither the antioxidant activity, which may suggest that DNA damage observed in V79 cells was induced by the presence of coal contaminants absorbed by the plant

'Salem Box Test' to predict the suitability of metallurgical coke for blast furnace ironmaking

Synopsis Blast furnace performance depends strongly on the coke reactivity index (CRI) and coke strength after reaction (CSR) properties. An innovative and cost-effective method, known as the Salem Box Test, has been developed to prevent the mass production of inferior coke unsuitable for blast furnace use. This method consists of coal carbonization on a microscale and involves charging approximately 18 kg of coal blend in a stainless steel box, carbonizing it together with coal cake in the plant coke ovens, and testing the coke produced for CRI and CSR to determine its suitability for blast furnace use. Only coal blends that yield coke with CRI 64% are permitted for mass production, and other coal blends are either rejected or the blending ratios adjusted in an attempt to upgrade them. The experimental results reveal that, for a given coal blend, the quality of coke produced by the Salem Box Test is comparable with that produced by bulk production, indicating that the test is acceptable as a screening tool for regular use. The present paper describes the methodology and application of Salem Box Test to predict the suitability of coke for blast furnace use at JSW Steel Limited, Salem Works (JSWSL), and illustrates its advantages in adjusting the coal blending ratio to produce superior coke, in detecting coal contamination, and in preventing bulk production of inferior coke.

Dry separation on coal–silica mixture using rotary triboelectrostatic separator

Silica minerals are one of the major contaminants in coal. They significantly deteriorate the coal quality and need to be removed before the use of coal. Conventional coal preparation techniques are wet processing methods that require huge quantities of water and chemical reagents, which induce high operation cost and environmental pollution. Therefore, dry separation technique to preconcentrate coal before the wet processing or even substitute the wet processing is required. In this study, the coal–silica mixture was beneficiated using a novel rotary triboelectrostatic separator (RTS). This new type of electrostatic separator is characterized with high particle charging efficiency, good separation environment and high throughput. The experiment result shows the surface charge densities of the coal, and the silica particles are greatly enhanced and the ash rejection of coal–silica mixture is achieved using the RTS. The ideal coal–silica mixture electrostatic separation characteristic using the RTS was determined. The charge density difference between coal and silica particles is distinct after the charging process. Better separation efficiency could be obtained when an industrial size RTS is available to use.

Recent history of sediment metal contamination in Lake Macquarie, Australia, and an assessment of ash handling procedure effectiveness in mitigating metal contamination from coal-fired power stations

This study assessed historical changes in metal concentrations in sediments of southern Lake Macquarie resulting from the activities of coal-fired power stations, using a multi-proxy approach which combines 210Pb, 137Cs and metal concentrations in sediment cores. Metal concentrations in the lake were on average, Zn: 67mg/kg, Cu: 15mg/kg, As: 8mg/kg, Se: 2mg/kg, Cd: 1.5mg/kg, Pb: 8mg/kg with a maximum of Zn: 280 mg/kg, Cu: 80 mg/kg, As: 21 mg/kg, Se: 5 mg/kg, Cd: 4 mg/kg, Pb: 48 mg/kg. The ratios of measured concentrations in sediment cores to their sediment guidelines were Cd 1.8, As 1.0, Cu 0.5, Pb 0.2 and Zn 0.2, with the highest concern being for cadmium. Of special interest was assessment of the effects of changes in ash handling procedures by the Vales Point power station on the metal concentrations in the sediments. Comparing sediment layers before and after ash handling procedures were implemented, zinc concentrations have decreased 10%, arsenic 37%, selenium 20%, cadmium 38% and lead 14%. An analysis of contaminant depth profiles showed that, after implementation of new ash handling procedures in 1995, selenium and cadmium, the main contaminants in Australian black coal had decreased significantly in this estuary.