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1.
Fluorine in coal is important because of not only its association with indicators of mineralization, but also environmental concerns relevant to the health of plants, animals and humans. In order to analyze the fluorine emission characteristics, this paper summarizes the laboratory data from a number of Chinese literatures of fluorine emission of coal and clay minerals for high-temperature heating. The range of temperature to which specimens have been exposed is room temperature to 1200 °C. The variation of fluorine emission has a significant increase with increasing temperature between the ranges 400–1200 °C, especially above 600 °C. Besides, environmental humidity has obvious influence on fluorine releasing. 相似文献
2.
Binoy K. Saikia Arpita Sharma Kakoli Khound Bimala P. Baruah 《Journal of the Geological Society of India》2013,82(3):295-298
Five representative sub-bituminous coals from NE part of India have been analyzed with respect to their distribution of carbon functional groups through 13C solid state NMR experiments. The 13C Cross Polarised/Magic Angle Spinning NMR spectra of the coal samples were recorded at temperatures of 23°C, 50°C and 70°C respectively and the changes on their structures were interpreted. The NMR spectra of low rank coals were found to exhibit varying degrees of fine structures. The aromaticities of the coal were also determined from the C/H ratios of coal. Some changes in the peak positions along with the formation of simple aromatic units were observed on mild heating. 相似文献
3.
The Ruhuhu Basin in SW Tanzania contains several small coal basins (i.e. Mchuchuma, Ngaka North, Mbalawala, Lumecha), consisting of fault controlled half-grabens submitted to several stages of tectonic activation. All basins underwent fragmentation in the ? middle Jurassic and late Miocene to Pliocene. Palaeotopography of pre-Karoo basement was partly responsible for the development of coal seam thickness distribution. Facies characteristics of the lower/middle and upper Mchuchuma Formation and the »Scarp sandstone« of the overlying Ketewaka formation exhibit synsedimentary basin subsidence. Vitrinite reflectance data suggest similar temperature gradients and burial history for the Mchuchuma and Ngaka subbasins. The application of a computer simulation program revealed the considerable effect of post-sedimentary tilting of depositional surfaces. In the Mchuchuma basin the back rotation of the base of the economic coal seam was calculated at -2°, the Ngaka basin showed an even higher degree of back rotation of -6°. Cyclicity was determined by Markov chain analysis for both basins. Mainly fining upward cycles prevail being characteristic for a fluvial environment. The depositional model for the Mchuchuma basin represents a meandering river system with a lower basal channel fill and an upper suspension load dominated cycle with accompanying overbank and flood plain sediments. The Ngaka basin shows an environment tentatively attributed to a braided river system. Thinning of coal seams and increased ash values in upper stratigraphic units depict deteriorating peat forming and preserving conditions. Swamp water chemistry was responsible for peat preservation, channel configuration and to some degree differential compaction governed the coal seam geometry. A slightly warmer climate than usually described for the Gondwana coals is proposed for the Lower Permian Tanzania coals. The diversity of microfloral evolution, eustatic sea level rises in the Sakmarian of Australia and available palaeotemperature curves demonstrate a probable mean annual temperature of 10–12 °C for a palaeolatitude of 60° S for the Tanzania coal fields. 相似文献
4.
Shaoping Zhou Kan Wu Dawei Zhou Liang Li Yuankun Xu 《Geotechnical and Geological Engineering》2016,34(6):1847-1856
To study the displacement caused by underground mining, the displacement field in the strata overlying the mine was simulated in nine similar-material models with coal seam dip angles of 0°–80°. Digital close-range photogrammetry was employed to observe the displacement in these models and produce displacement vector diagrams of observation points set on the model surfaces. The movement boundary of the rock mass was extracted and determined. According to the displacement vectors’ direction, the displacement field within the movement boundary was divided into five zones: two zones with displacement vectors pointing towards the goaf center, two zones with vectors pointing towards the coal pillar, and one zone with displacement vectors pointing vertically downward. A symmetry index was defined to analyze the symmetry of the displacement field, and the results show that as the coal seam dip angle increased from 0° to 80°, the displacement field in the strata changed according to the following pattern: symmetric → asymmetric → nearly symmetric, with a transition angle of about 45°. The percentage of the area of the above-defined five zones relative to the displacement field’s total area also changed, showing a regular pattern. This study also revealed that the movement boundary inside the overlaying rock layers is not a straight line, but an S-shaped curve. These findings can enhance our understanding of the internal mechanism of ground subsidence and contribute to more effective prediction of the deformation occurring inside a given rock mass. 相似文献
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利用MPV—COMPACT型显微光度计对峰峰矿区通二井田煤镜质组反射率进行较系统的测试,发现井田内煤 3个光轴体主轴互相垂直,最大反射率轴倾角多数集中在 68°～69°之间,倾伏向有 3个方向,即近 280°、近 90°和近 180°。测区内煤的镜质组反射率椭球体的变形特征属于拉长型应变和压扁型应变。该井田煤镜质组反射率椭球体有限应变特征分析结果表明在煤系地层中,煤的最大镜质组反射率的方位除与区域构造应力场的作用有关外,还与其所处的局部构造位置有关。在断层附近,反射率Romax和Romin的差值随着距断层的距离增加而减小,且在断层面的两盘发生突变。这一特征有助于煤矿井下构造的预测。 相似文献
8.
The Palaeogene sedimentary record in the Himalayan foreland basin contains palaeosols that are interpreted as reflecting changes in climate through time with the passage of the Indian Plate from the equator to 30° N latitude. To understand spatial and temporal variation in the occurrence of diagnostic palaeosol types, 12 exposed stratigraphic sections were investigated and studied in detail using petrographic and geochemical techniques, including scanning electron microscopy and X‐ray mineralogy. Oxisol (bauxite) is a karst bauxite that occurs in crudely bedded and laminated forms. It contains gibbsite, goethite and kaolinite and shows chemical index of alteration values close to 100, demonstrating intense weathering. No gradual change in the concentrations of trace and rare earth elements is recorded. However, their behaviour suggests that the Oxisol was produced by weathering of basalt under a warm and humid climate. Histosol (coal), found stratigraphically higher than Oxisols, contains woody structures dominated by vitrinite maceral. The Histosol is interpreted as having originated from an undisturbed peat developed in a swamp of high tree density under wet tropical climatic conditions. Up‐section, calcrete profiles of stages 3 and 4, containing rhizoliths, pellets, filamentous calcite and Microcodium, have developed by pedogenic processes. Large negative stable carbon (?8·5‰ to ?11·2‰) and oxygen isotope values (?8·5‰ to ?12·6‰) suggest that the studied calcretes formed under the influence of meteoric water and soil organic matter in dry sub‐tropical climatic conditions. The formation of Oxisol in a warm and humid climate was possible in the equatorial region when part of the Indian subcontinent was close to the equator. The coal developed under a humid climate when the northern tip of the Indian subcontinent reached the intertropical convergence zone, while the pedogenic calcrete formed once the sub‐tropical climatic zone was reached. Hence, it is suggested that these palaeosols formed in different climatic zones during northward drift of the Indian plate and that the drift brought them to their present positions between 30° N and 35° N within the sub‐tropical climatic zone. 相似文献
9.
《Geochimica et cosmochimica acta》1999,63(19-20):3301-3310
The weathering rate of sedimentary organic matter in the continental surficial environment is poorly constrained despite its importance to the geochemical carbon cycle. During this weathering, complete oxidation to carbon dioxide is normally assumed, but there is little proof that this actually occurs. Knowledge of the rate and mechanisms of sedimentary organic matter weathering is important because it is one of the major controls on atmospheric oxygen level through geologic time.We have determined the aqueous oxidation rates of pyrite-free bituminous coal at 24° and 50°C by using a dual-cell flow-through method. Coal was used as an example of sedimentary organic matter because of the difficulty in obtaining pyrite-free kerogen for laboratory study. The aqueous oxidation rate obtained in the present study for air-saturated water (270 μM O2) was found to be on the order of 2 × 10−12 mol O2/m2/s at 25°C, which is fast compared to other geologic processes such as tectonic uplift and exposure through erosion. The reaction order with respect to oxygen level is 0.5 on a several thousand hour time scale for both 24° and 50°C experiments. Activation energies, determined under 24° and 50°C conditions, were ≈40 kJ/mol O2 indicating that the oxidation reaction is surface reaction controlled.The oxygen consumption rate obtained in this study is two to three orders of magnitude smaller than that for pyrite oxidation in water, but still rapid on a geologic time scale. Aqueous coal oxidation results in the formation of dissolved CO2, dissolved organic carbon (DOC), and solid oxidation products, which are all quantitatively significant reaction products. 相似文献
10.
In order to investigate the effect of fine coal covering around the bottom of coal stockpile on spontaneous combustion prevention, a two-dimensional math model was established to numerically simulate the fine coal covering coal pile and a coal pile temperature-rising experimental system was setup to study the two-dimensional heat and mass transfer characteristics of air diffusion in the horizontal direction and air heat convection in the vertical direction inside coal stockpiles covered by different thicknesses of fine coal. The results showed that (1) the fine coal located at the bottom of the coal pile can effectively inhibit air convection and diffusion, cut off oxygen replenishment, and prevent the temperature rise inside coal pile, and (2) thicker fine coal has more obvious effect. Finally, the field experiments on the fine coal covering coal piles for preventing self-ignition of coal pile were carried out successfully. The results showed that the uncovered or exposed coal piles self-ignited rapidly within a very short period (18 days), while the coal pile covered with 1 m fine coal lasted for 123 days with a maximum coal temperature of only 59.9 °C. The characteristics of temperature distribution and diffusion inside coal stockpile were studied, and the high-temperature region was found in the region 1.3 m high and 2–3 m deep in the coal pile. The effects of environment temperature and precipitation on self-ignition of coal pile were also analyzed in field experiment. The experimental results proved that the fine coal covering technology can effectively prevent the spontaneous combustion of coal stockpiles. 相似文献
11.
A low-mature coal (Ro=0.4%, from the Manjia'er depression, Tarim Basin, China) was subjected to closed system pyrolysis, in sealed gold tubes,
under isothermal temperature conditions. The carbon isotopic compositions of the pyrolyst fractions (hydrocarbon, CO2, CO, etc.) at two temperature points (350°C and 550°C) were measured. The results showed that {ie359-1} value is generally
heavier at 350°C than that at 550°C, because the high abundance of CO generated at low temperature would greatly influence
{ie359-2} value, and the retention time of CO in gas chromatograph is close to that of CH4. But CO is formed through chemical reaction of the oxygen-containing functional group −C=O, e.g. lactones, ketones, ether,
etc. at low temperature, while CO2 comes mainly from decarboxylization.
The carbon isotopic composition of coal gas from Lanzhou Coal Gas Works was definitely different from that of thermally pyrolysed
products from coal. The {ie359-3} value of coal gas was abnormally heavier than {ie359-4}. At the same time, the reversed
sequence ({ie359-5}) of {ie359-6} and {ie359-7} happened. The bond energy of free ions generally decides the sequence of generation
of hydrocarbon fractions according to the chemical structure, whereas the stability of pyrolysate fractions and their carbon
isotope fractionation are affected by the C−C bond energy.
This study was supported by the National Basic Research (973) Program of China (No. 2001CB209102). 相似文献
12.
WU Guanghui YUAN Yajuan HUANG Shaoying Thomas Matthew Vandyk XIAO Yang CAI Quan LUO Bingxu 《《地质学报》英文版》2018,92(1):74-88
Recent studies, focused on dihedral angles and intersection processes, have increased understandings of conjugate fault mechanisms. We present new 3-D seismic data and microstructural core analysis in a case study of a large conjugate strike-slip fault system from the intracratonic Tarim Basin, NW China. Within our study area, "X" type NE and NW trending faults occur within CambrianOrdovician carbonates. The dihedral angles of these conjugate faults have narrow ranges, 19° to 62° in the Cambrian and 26° to 51° in the Ordovician, and their modes are 42° and 44° respectively. These data are significantly different from the ～60° predicted by the Coulomb fracture criterion. It is concluded that:(1) The dihedral angles of the conjugate faults were not controlled by confining pressure, which was low and associated with shallow burial;(2) As dihedral angles were not controlled by pressure they can be used to determine the shortening direction during faulting;(3) Sequential slip may have played an important role in forming conjugate fault intersections;(4) The conjugate fault system of the Tarim basin initiated as rhombic joints; these subsequently developed into sequentially active "X" type conjugate faults; followed by preferential development of the NW-trending faults; then reactivation of the NE trending faults. This intact rhombic conjugate fault system presents new insights into mechanisms of dihedral angle development, with particular relevance to intracratonic basins. 相似文献
13.
Hydrocarbon—Generating Characteristics of Barkinite—Rich Colas from Late Permian Longtan Formation ,South China 总被引：1，自引：0，他引：1
孙旭光 《中国地球化学学报》2000,19(3):227-232
Leping coal (including barkinite-rich coal) is a unique kind of coal,which is widely distrbuted in the Late Permian Longan Formation,South China,In this paper,ROck-Eval,Py-GC and simulation experiment via an open-system were used to study the hydrocarbon-generating potential,hydrocarbon composition.and hydrocarbon-generating model of barkiniterich coals from the shuicheng coal field of Guizhou Province,Southwest China.The results show that barkinite-rich coals have high hydrocarbon-generating potential,with S1 S2 being 211-311mg/g,and can produce large amounts of hydrocorbon at the high-maturity stage,mostly within the temperature range of 420-450℃(corresponding to VR0 1.1-1.5%);barkinite-rich coal is one of the better oil sources and light hydrocarbon and wet gas are the major hydrocarbon components,which account for 45% and 33% of the total hydrocarbons.respectively.These characteristics are of importance for exploring oil and gas resources in the Late permian Longtan Formation coals,southwest China. 相似文献
14.
Dynamics of catagenetic changes in the structure of humic coals in the Earth's interior can quantitatively be described using X-ray indices of components (phases), redistribution of which is determined by a system of differential equations in geological time. The system describes changes in the main formation parameters of coal seams in the Earth's interior (subsidence depth, temperature, pressure, and catagenesis index), on the one hand, and kinetics of catagenetic transformation of organic matter (OM), on the other. Such model makes it possible to establish regular changes in the phase composition of humic coals at different stages of coal basin formation. Using Paleozoic (Middle Carboniferous) coals of the Donets Basin as an example, it is established that main changes in the OM structure took place during the maximal subsidence of coal seams at maximal temperatures ranging from 110–15°C (for slightly metamorphosed coals of the L and G ranks) to 28°C (for anthracites) and pressures ranging from 55–74 to 146 MPa, respectively. Major processes leading to the observed X-ray phase composition of coals during the maximal subsidence of sedimentary sequences lasted approximately 40 Ma regardless of the geological age of sediments (Middle Carboniferous or Permian coal seams of the Donets or Kuznetsk coal basins, respectively). 相似文献
15.
The Erkovtsy brown coal field in the northwestern Zeya-Bureya sedimentary basin (129°–130° E, 46°–47° N) is structurally confined to southern flank of the Mesozoic-Cenozoic Belogor’e depression. The verified stratigraphic scheme of the coalfield sedimentary sequence is substantiated by palynological data on core samples from 18 boreholes sampled in the course of detailed prospecting and by paleobotanical analysis of sections in the Yuzhnyi sector of the coalfield (data of 1998 by M.A. Akhmetiev and S.P. Manchester). Sections of the Erkovtsy, Arkhara-Boguchan, and Raichikha brown-coal mines are correlated. Stratigraphic subdivisions distinguished in the studied sedimentary succession are the middle and upper Tsagayan subformations (the latter incorporating the Kivda Beds), Raichikha, Mukhino, Buzuli, and Sazanka formations. 相似文献
16.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(5):455-459
Based on the MAGSAT magnetic anomaly fields over Europe and the adjacent areas spherical cap models have been derived. The method of spherical cap harmonic analysis, due to Haines (1985), has been applied for the modelling of the MAGSAT magnetic anomalies. The data set used in the analysis included the 1 ° × 1 ° gridded values of the MAGSAT anomaly fields between latitudes ϑ = 6 ° to 60 °N and longitudes λ = 19 °W to 70 °E. The pole of the cap is at ϑ = 33 °N and λ = 26 °E and its half-angle is 40 ° . The maximum index (Km) of the model is 18 and the total number of model coefficients is 361. A minimum wavelength corresponding to this index at the Earth's surface is ~ 1000 km. The RMS deviations between the calculated and observed values are ~ 4 nT for δX, ~ 3 nT for ΔY and 3,5 nT for ΔZ respectively. The spherical cap harmonic model was used for the construction of magnetic anomaly maps for all components and at different altitudes. 相似文献
17.
T. J. Rawling M. Sandiford G. R. Beardsmore S. Quenette S. H. Goyen B. Harrison 《Australian Journal of Earth Sciences》2013,60(8):817-830
Coal-bearing basins have increased economic potential for enhanced geothermal systems owing to thermal insulation provided by the coal and associated organic-rich sediments. In such insulation-dominated prospects, heat refraction effects associated with buried insulators can produce negative surface heat-flow anomalies in the most prospective areas. The Latrobe Valley in Victoria, Australia, is an archetypal coal basin. Using numerical simulations incorporating the coal geometries, we show that the Latrobe Valley coals might elevate the temperature of the rocks at 4 km depth by some 30–35°C relative to a ‘base’ condition with no coal. This effectively boosts the average geothermal gradient by about 30%, with a corresponding improvement in the economic case for geothermal energy in the Latrobe Valley. 相似文献
18.
为查明径向井分支在煤层中的施工轨迹是否与设计轨迹一致,保障煤储层的增透改造效果。采用地面小型试验与现场测试相结合的手段,先对煤储层径向井井眼轨迹的影响因素展开研究,并基于电位法监测技术分析该方法用于煤层气径向井轨迹监测的可行性,在此基础上建立了基于电位法的煤储层径向井井眼轨迹监测方法与工艺,并进行现场监测分析。研究结果表明,煤层中径向井井眼轨迹主要受原始裂隙、地应力、结构薄弱面等因素共同控制,导致煤层气径向井在喷射施工过程中井眼方位通常会发生不同程度的偏转,角度在15°~30°间,径向井分支长度也均小于设计的喷射长度。电位法煤层气径向井轨迹监测方法可以清晰地监测到方位、长度等径向井轨迹参数的变化情况,研究结果可以有效地指导煤储层径向井的设计与施工。 相似文献
19.
《International Journal of Coal Geology》1987,7(2):195-208
The Arauco Sedimentary basin of Chile (37° −37° 45′S, 73° 08′ −73° 41′W) contains the most important reserves of bituminous coals of Chile. These are concentrated in two Formations: Curanilahue (Lower Eocene) and Trihueco (Middle Eocene). Five coal seams from the Lota Member of the Curanilahue Formation have been studied from the stratigraphic, palynologic and geochemical point of view. These coals were formed during a regressive stratigraphic episode; the palynological assemblage indicates that the climatic conditions prevailing at the time were of high humidity and temperature. These coals from a geochemical point of view are characterized by high sulphur (2.02%), ash (11.9%) and Ge (67.5 ppm; 1224.3 ppm in ash). 相似文献
20.
Evaluation of coal as adsorbent for phosphate removal 总被引：1，自引：1，他引：0
Sabir Khan M. Ishaq Imtiaz Ahmad Sajjad Hussain Hameed Ullah 《Arabian Journal of Geosciences》2013,6(4):1113-1117
This paper reports the adsorption of phosphate ions on coal, charcoal, and coal ash. The influences of factors such as contact time, and initial adsorbate concentration have been studied. Adsorption of phosphate ions on virgin coal was significant compared to charcoal, coal and coal ash evacuated at 200°C. The significant adsorption capability of coal is due to the porosity as well as due to organic carbon and inorganic elements present in coal. The evacuation of coal proved to be ineffective in enhancing its capability for phosphate ions retention. The adsorption behaviors of all the three adsorbent used was conformed using Freundlich’s adsorption model. The results suggest that coal could be used as an efficient adsorbent for removing phosphate ions from wastewater. 相似文献