Research progress and prospects of coal petrology and coal quality in China

Clean utilization of coal depends on the quality of raw coal,which depends on the coal-forming parent materials(petrology and chemical composition of coal),the multiple media of the coal-forming environment,and some epigenetic conditions,such as thermal evolution(coalification),magmatic hydrothermal fluid,groundwater.Based on the research results of predecessors and prediction studies of coal resources since the founding of China,the present status of research on coal petrology,coal quality,coal metamorphism,and coal geochemistry in China is discussed in detail,with emphasis on research progress and the general situation of highly efficient and clean utilization of coal in the technical fields of coking,pyrolysis,combustion,gasification,and liquefaction,and the development prospects of coal petrology and coal quality in China are prospected.

Coal petrology and facies of No.6 coal of the Haerwusu Mine, Jungar Coalfield, Inner Mongolia

This paper discussed the petrological characteristics and coal facies of No.6 coal seam from the Haerwusu Mine, Jungar Coalfield, Inner Mongolia by using of coal petrology and geochemistry. No.6 coal facies can be divided into 3 types, arid forest peat swamp （including two subfacies） and reed peat swamp, respectively. From bottom to top, the development of peat swamps present wavy changes, and three coal facies types appear alternately, with obvious thyme. According to the parameters, 11 secondary sequences were identified of the peat swamps of No.6 coal seam. The results indicate that the mire formed in brackish water-fresh water weak regression environment, changed in excess oxygen and poor oxygen, and reflected the characteristics of transition phase.

Coal petrology,sedimentology and depositional environment of the Parvadeh coais in the Upper Triassic,Tabas Block of Central-East Iran

Peat forming environment strongly influences the economic value of any coal seam and coal-bearing strata.Hence,pal-aeoenvironmental studies provide important information for coal resource exploration.In this context,detailed studies on selected coals from the Parvadeh Area,Iran,were conducted using sedimentology,coal petrology,X-ray diffraction(XRD),scanning electron microscopy-energy dispersive X-ray analyzer(SEM-EDX),and proximate analysis.The sedi-mentary facies above and below the coal seams are mainly marine or marine-influenced facies,supporting that the coal-forming mires in the Parvadeh Area developed in a paralic environment,where the base level must be closely related to sea level.Sulfur contents are moderate to high and mark the influence of brackish/marine water,especially during transgres-sion after peat growth in a lower delta plain environment.The peat-forming mires extended on coastal/delta plain lobes.The lower delta plain/coastal plain coals are characterized by lateral continuity and substantial thickness,whereas few coals possibly representing the upper delta plain are thin and more discontinuous.The detrital nature and composition of the numerous partings and the overall high ash yield in the coal seams indicate an active tectonic area with high rates of creation of accommodation space over peat growth.Coal petrology and coal facies analysis exhibits a permanently high water table within a forest swamp and mostly rheotrophic conditions,sometimes with connection to the seawater.Accord-ing to paleoenvironmental reconstructions,it seems that coal layers may be thicker,with less sulfur(pyrite),but more clastic minerals and partings toward the western part of the area.Although these coal seams presently have low economic potential for the mining operation,partly due to great depth,this humic,high-volatile to medium-volatile bituminous coal may be suitable for exploration of coal bed methane resources.

Depositional Environment and Origin of Inertinite-rich Coal in the Ordos Basin

Inertinite-rich coal is widely distributed in the Ordos Basin,represented by the No.2 coal seam of the Middle Jurassic Yan'an Formation.This paper combined coal petrology and geochemistry to analyze the origin of inertinite,changes in the coal-forming environment and control characteristics of wildfire.Research has shown that there are two forms of inertinite sources in the study area.Alongside typical fusinization,wildfire events also play a substantial role in inertinite formation.There are significant fluctuations in the coal-forming environment of samples at different depths.Coal samples were formed in dry forest swamp with low water levels and strong oxidation,which have a high inertinite content,and the samples formed in wet forest swamp and limnic showed low inertinite content.Conversely,the inertinite content of different origins does not fully correspond to the depositional environment characterized by dryness and oxidation.Nonpyrogenic inertinites were significantly influenced by climatic conditions,while pyrofusinite was not entirely controlled by climatic conditions but rather directly impacted by wildfire events.The high oxygen level was the main factor causing widespread wildfire events.Overall,the combination of wildfire activity and oxidation generates a high content of inertinite in the Middle Jurassic coal of the Ordos Basin.

Geochemical and petrological studies of high sulfur coal and overburden from Makum coalfield (Northeast India) towards understanding and mitigation of acid mine drainage

Opencast coal mining produces trash of soil and rock containing various minerals,that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage(AMD)through oxidation pyrite minerals.The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India.In order to have a comprehensive overview of the AMD problem in Makum coalfield,the physico-chemical,geochemical,and petrological characteristics of the coal and overburden(OB)samples collected from the Makum coalfield(Northeast India)were thoroughly investigated.The maceral compositions reveal that coal features all three groups of macerals(liptinite,vitrinite,and inertinite),with a high concentration of liptinite indicating the coal of perhydrous,thereby rendering it more reactive.Pyrite(FeS_(2))oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and(OB)samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods,and to replicate the actual mine site leaching.Inductively coupled plasma-optical emission spectroscopy(ICP-OES)was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment.The Rare earth element(REE)enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB.These experiments reveal the change in conductivity,acid producing tendency,total dissolved solid(TDS),total Iron(Fe)and dissolved Sulfate(SO_(4)^(2−))ions on progress of the leaching experiments.Moreover,the discharge of FeS_(2) via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics.A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station.Apart from neutralisation of AMD water,this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water.

Petrography and geochemistry of exported Colombian coals:Implications from correlation and regression analyses

The petrology of coal,as determined by the microscopic analysis of organic and inorganic elemental constituents of coal,provides information on its nature and characteristics.Coal is used worldwide in the production of thermal energy and coke.In the case of high-quality Colombian coals,only limited studies have been carried out.The present study presents the geochemical,mineralogical,and petrological characteristics of coal samples collected from Puerto Drummond in Cienaga,Colombia,to predict their potential uses.Therefore,the ultimate,proximate,petrographic,gross calorific value(GCV),ash fusion temperature,Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),X-ray fluorescence(XRF),and Thermogravimetric(TG)analyses were employed in this study.The petrological analysis reveals that Colombian coals are naturally more abundant in vitrinite(72%)than inertinite(14e23%)macerals.Silicates and aluminosilicate are the main minerals present as fine particles mixed with macerals.The XRD and FTIR analyses show that the most common and dominant minerals are quartz,while gypsum,hematite,calcite and mica occur in lesser amounts.The oxide composition of the coal ashes consists of 51e58%SiO2 and 18e25%Al2O3 as determined by XRF analysis.In correlation and regression analysis,the moisture content shows a reverse correlation with GCV(Regression value of R2¼0.68).This study helps researchers to comprehend the importance of Colombian coals and presents various techniques for characterisation of coals.

Petrology and geochemistry of the Carboniferous cutinite-rich coals from the Hequ area of Shanxi Province, China

Coal samples taken from the Taiyuan Formation in the Hequ area, China, for this study are typical cutinite-rich coals.The petrology and geochemistry of the samples were analyzed using microscopic examination, proximate and ultimate analysis,rock pyrolysis, and gas chromatography-mass spectrometry(GC-MS). The cutinites in Haochuan(HC) coals are predominantly of the thin-walled type, whereas those in the Jingzigou(JZG) coals are predominantly thick-walled. The variable thickness of cutinites in different coals is related to the environment in which the coal-forming plants grew. Compared with typical Ⅲ kerogens, HC and JZG bituminous coals are characterized by high volatile matter yields and hydrogen contents due to the elevated hydrogen-rich cutinite content. Pyrolysis data indicate that these cutinite-rich coals can be expected to generate commercial liquid and gaseous hydrocarbons. Pristane(Pr) and phytane(Ph) are both abundant in the samples, with the Pr/Ph ratios for both the HC and JZG coals being >3.0, indicating moderate maturity and oxic peat depositional conditions. The C>>C>Cnormalized relative abundance of regular steranes is consistent with a dominant contribution from higher plants.Abundant hopanes in the coals also suggest a substantial organic matter input from bacteria, which are common inhabitants of peat and coal. Palynology studies indicate that pteridophytes are likely to be the most common coal-forming plants. A gymnosperm contribution is also indicated by the presence of tetracyclic diterpenes. Massive accumulations of cuticles as cutinite in coal are rare and account for only a small proportion of coals worldwide. However, cutinite-rich coals are found in the northern margin of the North China Craton, in the Taiyuan Formation. The accumulation of cutinite in this area is the result of distinctive peat deposition conditions. Frequent marine transgression was an important contributing factor.

Discovery of cutinitic liptobiolith in northwestern China and a comparative study with Luquan Devonian coal

Devonian cutinitic liptobiolith is a special cuticle-rich coal formed during the early stage of land plant evolution. In China, this special coal has previously only been reported in the Yangtze area, with the Luquan Devonian cutinitic liptobiolith of Yunnan Province being the most well-known. Recently, this type of coal was first discovered in the Bulonggoer Sag, to the northwest of the Junggar Basin, NW Xinjiang. Its geological age is regarded as the Givetian period of the late Middle Devonian,which is equivalent to the age of the Luquan Devonian coal. The cutinitic liptobiolith from NW Xinjiang has a distinct sheet-like texture resembling a stack of paper or leaf sheets in appearance, and so it is commonly called "paper coal" or "leaf coal". Ribbonlike cutinite(thick-walled type) is the most abundant maceral in the coal(>60% and up to 80%, on a mineral-free basis), followed by ribbon-like collotelinite. The NW Xinjiang and Luquan cutinitic liptobioliths share similar maceral compositions;while their coal-forming plants and depositional conditions are distinct. The NW Xinjiang cutinitic liptobiolith was deposited in a regional fluvial or flood plain condition, with lycopsids as the dominant coal-forming plants. In contrast, the Luquan cutinitic liptobiolith formed in a coastal-lagoon environment, with primitive ferns as the predominant coal-forming plants, followed by lycopsids. The saturated fractions of the NW Xinjiang and Luquan liptobioliths are mainly composed of tetracyclic diterpanes. However, the tetracyclic diterpane compositions in the NW Xinjiang cutinitic liptobiolith are distinct from those in the Luquan Devonian coal:The former is dominated by atisanes and the latter is mainly composed of phyllocladanes. Different coal-forming plants may have contributed to the distinct tetracyclic diterpane compositions.