Hydrocarbon condensates and argillites in the Eliška Mine burnt coal waste heap of the Žacléř coal district (Czech Republic): Products of high- and low-temperature stages of self-ignition
Introduction
Generally, three key factors should co-exist to accelerate coal oxidation, self-heating and self-combustion: 1), the presence of abundant organic matter, 2), easy access of oxygen and moisture, and 3), the ability to accumulate heat (Van Krevelen, 1993, Sracek et al., 2004, Misz et al., 2007, Pone et al., 2007, Misz-Kennan and Fabiańska, 2011, Kus and Misz-Kennan, 2017). A diverse spectrum of solid, liquid and gaseous products is formed as a result of burning conditions.
Gaseous products of burning have caused atmospheric pollution and environmental degradation in a number of coalfields. During combustion processes, greenhouse and others gases are formed (H2O, CO2, CO, CH4, H2S, H2, SO2, SO3, HCl, NH3; Carras et al., 2009, Stracher and Taylor, 2004), including a number of lighter volatile organic compounds such as n-alkanes, isoalkanes, n-alkenes, halohydrocarbons and benzene derivatives (Fabiańska et al., 2013). The organic substances are emitted into the atmosphere, but partial condensates from flue gas are deposited onto vent surfaces or pebbles (Pone et al., 2007, Querol et al., 2008, Querol et al., 2011, Ribeiro et al., 2013). Once condensation on surfaces occurs, these compounds can be also washed out from the burning heaps into local streams or ground waters (Skręt et al., 2010). In relation to burning conditions, bulk carbonaceous matter in burnt heaps includes a mixture of unburnt and thermally altered coal particles with high reflectance, reaction rims, fissures and devolatilization pores, cokes with porous or massive textures, and HCC that may be enriched in many trace elements (Ciesielczuk et al., 2014, Misz et al., 2007, Pone et al., 2007, Ribeiro et al., 2010, Suárez-Ruiz et al., 2012, Sýkorová et al., 2016). During combustion, some volatile coal-derived organic compounds (pyrolysates) may be formed. They can condense on colder places of burning heaps, especially on surfaces or just below the surface of the heap. A variety of organic solvent-soluble organic compounds were identified in pyrolysates, the most important being alkanes, alkenes, acyclic isoprenoids, alkylcyclohexanes, polycyclic aromatic hydrocarbons (PAHs) and their derivatives, oxygen-bearing compounds (furane derivatives, carboxylic acids, and aromatic ketones) and functional nitrogen compounds (organic amines, amides and imides (Jehlička et al., 2007, Misz-Kennan and Fabiańska, 2011, Nasdala and Pekov, 1993, Witzke et al., 2015, Žáček and Ondruš, 1997)). The greatest mass of organic pyrolysates, however, is represented by organic solvent-insoluble compounds that originate through condensation and oxidation of simple organic molecules (Misz-Kennan and Fabiańska, 2010). The chemical composition and physical properties of the insoluble part of HCC have not been studied in detail.
Together with volatile organic components, highly volatile elements (e.g., B, N, F, S, Cl, Se, As, Br, I and Hg) can be released into the atmosphere (Carras et al., 2009, Hower et al., 2009, Ribeiro et al., 2013, Ribeiro et al., 2016a, Ribeiro et al., 2016b, Zhao et al., 2008), and less volatile elements (Se, Ge, Zn, Mo, Cd, Sb, Tl and Pb) can accumulate in surface eflorescents of burning-mine heaps (Stracher et al., 2015), together with soluble and insoluble sulfates, aluminosulfates, sulfides or selenides (Pone et al., 2007, Witzke et al., 2015, Žáček and Skála, 2015). On the other hand, Mg, Al, Si, K, Ca, Sc, Ti, Fe, Sr, Ce, La, Sm, Eu, Hf and Th are essentially immobile during coal combustion, and Be, Na, P, V, Cr, Mn, Co, Ni, Cu, Rb, Ba, W and U display only limited mobility (Meij and te Winkel, 2009). They occur as oxides or form an admixture in pyrometamorphic (alumino) silicates, in amorphous meta-clay compounds, or in glass (Dai et al., 2014, Kříbek et al., 2017). The leaching of elements may be a significant environmental consequence of burnt coal wastes because some of them can be retained in fire-affected material, and others can become leachable to the environment (Querol et al., 2008, Querol et al., 2011, Ward et al., 2009, Ribeiro et al., 2010, Ribeiro et al., 2016b, Zhang et al., 2016, Kříbek et al., 2017).
During low-temperature alterations of coal wastes, or in the final stages of burning, the pyrometamorphic minerals or amorphous meta-clay compounds can be transformed into hydrous silicates or clay minerals. An envelope of argilites is usually associated with low-temperature gas vents at the surface of burnt coal waste heaps This low-temperature “metasomatism” is attributed to hydrothermal alterations of original rocks or pyrometamorphic products due to the action of steam and gases produced during coal heating or burning (Stracher et al., 2005, Stracher et al., 2011, Stracher et al., 2013, Witzke et al., 2015).
Therefore, the aims of this study were: (1), to compare the organic petrography and geochemistry of unburnt coal with products of coal burning and (2), to evaluate the time relationship between burning processes and the formation of coal-derived HCC, cokes and associated argilites at the surface of the heap.
The Eliška Mine waste coal heap was burning mostly in 1960s to 1980s and therefore, an important aim was also to evaluate the possible impact of combustion products on local water streams after almost 50 years of weathering and leaching.
Section snippets
Geology and self-ignition of the Eliška coal waste heap
The Eliška Mine waste coal heap is located in the Czech part of the Intra-Sudetic Basin (CPISB) in the Žacléř coal district near the border with Poland (Fig. 1A, B). Coal seams in this area are confined to the Žacléř Fm. (Upper Bashkirian–Lower Moscovian) and to the overlying Odolov Fm. (Upper Moscovian–Lower Kasimovian; ICS, 2017). Sediments of the Žacléř Fm. consist mainly of siltstones, sandstones and conglomerates, and intermediate and acid effusives. The great majority of coal seams (> 60)
Sample collection
Burnt coal heap substrates for mineralogical and inorganic geochemical studies were collected from trenches Z1E, Z1W, Z2S, Z2N and Z3S (Figs 1B and 2) located in various parts of the heap. Samples were taken at intervals of 10–20 cm from Zone 1 (HCC-enriched material), Zone 2 (argilitized zone), Zone 3 (clinker zone), and Zone 4 (coke-enriched zone). A total of 64 samples (approx. 0.3 kg each) were collected. The samples were sieved, and the < 2 mm fraction was homogenized in an agate mill to a
Mineralogy of substrates of the burnt coal waste heap
The heap comprised: (1), a surficial black layer rich in coal-derived hydrocarbon condensates (HCC) 2–20 cm thick; (2), a layer of argillite (20–40 cm); and (3), the underlying substrate of the burnt heap (clinker).
- (1)
The surface layer (Zone 1, Fig. 2) consisted of a mixture of organic and inorganic components. These materials were either loose or compact. Loose materials prevailing on the surface were comprised of breccias, i.e., fragments of thermally altered coal macerals, coke particles, HCC and
Organic matter
Coal samples of the Eliška Mine waste heap can be classified as unburnt (reference sample EL-0), and, to varying degrees, affected by burning/smoldering processes in Zone 1 and Zone 4 (Fig. 2; samples EL-1 to EL-5).
Conclusions
This study showed that the association of inorganic phases and products of thermal alteration of coal on the surface of the Eliška Mine burnt coal waste heap is a result of successive high and low temperature processes. This is evidenced by variability in the self-combustion of organic products in the waste, as indicated by optical microscopy, Raman- and FTIR data: highly reflective coke particles, altered coal matter and two types of HCC that form a mixture in many places.
The chemical
Acknowledgements
This study was carried out within the Czech Science Foundation grant project “A model of mobilization and geochemical cycles of potentially hazardous elements and organic compounds in burnt coal heaps” (GACR 15-11674S panel P210). Our thanks to the Operational Program Prague - Competitiveness, project “Centre for Texture Analysis” (No. CZ.2.16/3.1.00/21538), and the long-term conceptual development of the research organization RVO: 67985891. The authors of the paper would like to express their
References (138)
- et al.
Acid alteration in the fumarolic environment of Usu Volcano, Hokkaido
Japan J. Volcanol. Geotherm. Res.
(2000) - et al.
Distribution of n-paraffins as a clue to recognition of source beds
Geochim. Cosmochim. Acta
(1961) - et al.
Greenhouse gas emissions from low temperature oxidation and spontaneous combustion at open-cut coal mines in Australia
Int. J. Coal Geol.
(2009) - et al.
Gas evolution kinetics of two coal samples during rapid pyrolysis
Fuel Process. Technol.
(2010) - et al.
Mineralogy and geochemistry of coal wastes from the Starzykowiec coal-waste dump (Upper Silesia, Poland)
Int. J. Coal Geol.
(2014) - et al.
The properties of the nano-minerals and hazardous elements: potential environmental impacts of Brazilian coal waste fire
Sci. Total Environ.
(2016) - et al.
Composition and modes of occurrence of minerals and elements in coal combustion products derived from high-Ge coals
Int. J. Coal Geol.
(2014) - et al.
Gas emmisions, minerals, and tars associated with three coal fires, Powder River Basin, USA
Sci. Total Environ.
(2012) - et al.
Gaseous compounds and efflorescence generated in self heating coal-waste-dumps – a case study from the Upper and Lower Silesian Coal basins (Poland)
Int. J. Coal Geol.
(2013) - et al.
Organic petrology of a self-burning coal wastepile from Coleman, Alberta, Canada
Int. J. Coal Geol.
(1989)
Differences in bitumen and kerogen-bound fatty acid fractions during diagenesis and early catagenesis in a maturity series of New Zealand coals
Int. J. Coal Geol.
Influence of heating-rate variation on the anisotropy of carbonized vitrinites
Fuel
The role of magnesium in the formation of smectite minerals
Chem. Geol.
A multi-instrumental geochemical study of anomalous uranium enrichment in coal
J. Environ. Radioactiv.
The tiptop coal mine-fire, Kentucky: Preliminary investigation of the measurement of mercury and other hazardous gases from coal-fire gas vents
Int. J. Coal Geol.
Kinetics of montmorillonite dissolution in granitic solutions
Appl. Geochem.
Raman spectra of organic compound kladnoite (C6H4(CO2NH)) and hoelite (C14H8O2) – rare products of crysatllization on self-ignioted coal heaps
Spectrochim. Acta A
Toxicity of and metals in coal combustion ash leachate
J. Hazard. Mater.
Geochemistry, mineralogy, and isotope composition of Pb, Zn, and Cu in primary ores, gossan and barren ferruginous crust from the Perkoa base metal deposit, Burkina Faso
J. Geochem. Explor.
Trace element geochemistry of self-burning and weathering of a mineralized coal waste dump: The Novátor Mine, Czech Republic
Int. J. Coal Geol.
Low-temperature oxidation of coal. 3. Modelling spontaneous combustion in coal stockpiles
Fuel
Coal weathering and laboratory (artificial) coal oxidation
Int. J. Coal Geol.
The procedure used to develop a coal char classification – Commission III combustion working Group of the International Committee for coal and organic petrology
Int. J. Coal Geol.
Trace elements in world steam coal and their behaviour in Dutch coal-fired power stations: a review
Int. J. Coal Geol.
The role of carbon black/coal-tar pitch interactions in the early stage of carbonization
Carbon
Organic components in thermally altered coal waste: preliminary petrographic and geochemical investigation
Int. J. Coal Geol.
Thermal transformation of organic matter in coal waste from Rymer Cones (Upper Silesian Coal Basin, Poland)
Int. J. Coal Geol.
Application of organic petrology and geochemistry to coal waste studies
Int. J. Coal Geol.
The influence of heating rates on organic matter in laboratory and natural environments
Int. J. Coal Geol.
The impact of water-washing, biodegradation and self-heating processes on coal waste dumps in the Rybnik Industrial Region (Poland)
Int. J. Coal Geol.
Use of geochemical analysis and vitrinite reflectance to assess different self-heating processes in coal-waste dumps (Upper Silesi, Poland)
Fuel
Climatic vs. tectonic controls on peat accretion in non-marine setting; an example from the Žacléř Formation (Yeadonian-Bolsovian) in the Intra-Sudetic Basin (Czech Republic)
Int. J. Coal Geol.
Kerogen pyrolysis in the presence andabsence of water and minerals: amounts and compositions of bitumen and liquid hydrocarbons
Fuel
Kerogen pyrolysis in the presence and absenceof water and minerals: steranes and triterpenoids
Fuel
Microstructural characteristics of toluene and quinolone-insolubles from coal tar pitch and their cokes
Int. J. Coal Geol.
Classification of liptinite – ICCP system 1994
Int. J. Coal Geol.
The spontaneous combustion of coal and its by-products in the Witbank and Sasolburg coalfields of South Africa
Int. J. Coal Geol.
Alteration halos in the Tordillos sediment-hosted copper deposit of the Neuquén Basin, Argentina
Ore Geol. Rev.
Environment characterization of burnt coal gangue banks at Yangquan, Shanxi Province, China
Int. J. Coal Geol.
Influence of soil cover on reducing the environmental impact of spontaneous coal combustion in coal waste gobs: a review and new experimental data
Int. J. Coal Geol.
Aromatic components of coal: relation of distribution pattern to rank
Geochim. Cosmochim. Acta
Alkyldibenzofurans in terrestrial rocks: Influence of organic facies and maturation
Geochim. Cosmochim. Acta
Burning of coal waste piles from Douro Coalfield (Portugal): petrological, geochemical and mineralogical characterization
Int. J. Coal Geol.
Petrographic and geochemical characterization of coal waste piles from Douro Coalfield (NW Portugal)
Int. J. Coal Geol.
Mineral speciation and fate of some hazardous contaminants in coal waste pile from anthracite mining in Portugal
Int. J. Coal Geol.
Geochemistry of self-burning coal mining residues from El Bierzo Coalfield (NW Spain): environmental implications
Int. J. Coal Geol.
Petrography and mineralogy of self-burning coal wastes from anthracite mining in the El Bierzo Coalfield (NW Spain)
Int. J. Coal Geol.
The geochemistry, mineralogy and maturity of gossans derived from volcanogenic Zn-Pb-Cu deposits of the eastern Lachlan Fold Belt, NSW, Australia
J. Geochem. Explor.
Microstructures and microtextures of natural cokes: a study of heat-affected coking coals from the Jharia coalfield, India
Int. J. Coal Geol.
Standard Methods for the Examination of Water and Wastewater, 19th Edition APHA, AWWA
Cited by (11)
Organic minerals in a self-heating coal-waste dump in Upper Silesia, Poland: Structure, formation pathways and environmental issues
2024, International Journal of Coal GeologyThe geochemistry and hydrology of coal waste rock dumps: A systematic global review
2021, Science of the Total EnvironmentCitation Excerpt :Water levels in dumps may also rise due to run-on water from the adjacent catchment, laterally flushing COIs and increasing COI loads, and resulting in a hysteretic relationship between water discharge and COI loading (Villeneuve et al., 2017; Wellen et al., 2018). Typically, COI concentrations decrease over the flushing season (Søndergaard et al., 2008; Søndergaard et al., 2007; Sýkorová et al., 2018). In contrast, increasing precipitation and associated discharge may reduce environmental loads by altering chemistry such that precipitates are formed and deposited on the dump surface rather than released in effluent (e.g., as rainfall raises the pH, Al hydroxides are deposited at Green Valley, thereby temporarily removing Al from dump effluent (Brake et al., 2001a)).
Experimental pyrolysis of metalliferous coal: A contribution to the understanding of pyrometamorphism of organic matter and sulfides during coal waste heaps fires
2021, International Journal of Coal GeologyCitation Excerpt :This non-oxidized environment during the heating of mineralized coal in the studied heaps is also indicated by the common presence of pyrrhotite or magnetite (not hematite) in pyrolysis products of coal (Kříbek et al., 2017; Sýkorová et al., 2018). In addition, the burnt waste heaps contain significant amounts of coke, semi-coke, bitumen, and thermally altered coal macerals, which also show limited access of oxygen in some parts of burnt waste heaps (Sýkorová et al., 2016, 2018). Therefore, the aim of this paper is the experimental modeling of processes that occur during the pyrometamorphism of organic matter and sulfides in burning heaps at temperatures of 200 °C, 500 °C, 700 °C and 900 °C, and the assessment of the volatility of inorganic and organic constituents during fires of coal waste heaps.
A review on the impact of mining operation: Monitoring, assessment and management
2020, Results in EngineeringCitation Excerpt :Burnt dumps have all likelihood to generate acid water than unburnt dumps due to the existence of water-soluble sulphates that are very much amenable to leaching and oxidation [16]. Furthermore, atmospheric contamination and environmental degradation in several minefields take place due to the occurrence of gaseous products in the course of burning dumps [17]. In the course of the combustion processes, greenhouse and some other gases suchlike H2O, CO2, CO, CH4, H2S, H, SO2, SO3, HCl, NH4 are formed [18,19].
Development of a petrographic classification system for organic particles affected by self-heating in coal waste. (An ICCP Classification System, Self-heating Working Group – Commission III)
2020, International Journal of Coal GeologyCitation Excerpt :Two types of bitumen were distinguished here: (1) bitumen of various shape, e.g., droplets, thread-like structures or bitumen of irregular appearance that commonly co-occurs with minerals and have strong yellowish fluorescence (Figs. 6CF), (Alpern et al., 1992; Gentzis and Goodarzi, 1989; Sýkorová et al., 2018) and (2) bitumen that commonly fills in cracks and various empty spaces within coal wastes and has elevated reflectance, pale grey colour and lack of fluorescence (Figs. 6G,H), (Alpern et al., 1992; Jacob, 1993; Gentzis and Goodarzi, 1989; Sýkorová et al., 2018). Similar forms like tar, pitch-like solid (Gentzis and Goodarzi, 1989; Engle et al., 2012) and as hydrocarbon condensates (Sýkorová et al., 2018) were reported in the literature; Char – derived largely from vitrinite and inertinite as product of self-heating or spontaneous combustion; organic particles with pyrolysis and/or combustion char morphology characterised by randomly distributed pores, shape, and size; their colour in reflected white light is light grey to white, and the reflectance is always higher than that of huminite/vitrinite in a non-altered coal waste sample; they were likely formed at temperature range 400–900 °C (Kwiecińska and Petersen, 2004; Lester et al., 2010; Suárez-Ruiz et al., 2015, 2017).
Comparison of organic compounds in char and soot from the combustion of biomass in boilers of various emission classes
2019, Journal of Environmental ManagementCitation Excerpt :Dibenzofuran and methyldibenzofuran usually make up a major proportion of the macromolecular structure of bituminous coals (Radke et al., 2000). They condense during cooling of flue gases below their boiling points of 285 and 306 °C respectively (Sýkorová et al., 2018). Human exposure, however, occurs mainly via food (Scholz and Stadler, 2018).