Coal Occurrence Research Articles

Deformation and seepage characteristics of gas-containing coal under true triaxial stress

Conventional triaxial tests were mostly conducted to explore the coal and gas outburst mechanisms based on the moulded coal specimens, leading to the difference of three-dimensional unequal stress condition between the simulated coal seam and the real coal seams. A true triaxial gas-solid coupled coal seepage test system was developed to fulfil the gas seepage under the true triaxial stress. Moreover, the deformation-failure characteristics and gas seepage behaviours of moulded coal and raw coal were investigated under true triaxial stress. By analysing the relations among stress, strain and permeability in true triaxial tests, it has established the important effect of the intermediate principle stress (σ2) on the occurrence of coal and gas outburst. The coal’s yield strength increased and permeability decreased when σ2 was at the early and middle stage of the load, while the coal’s permeability increased and instable failure happened when σ2 was at the late stage of the load. Particle flow code software was applied innovatively to simulate the seepage experiment, proving the reliability of experimental results. Meanwhile, the test standard based on raw coal was proposed. Furthermore, the present research results provide a new insight and approach for the prevention and monitoring of coal and gas outburst.

Characteristics and precursor information of electromagnetic signals of mining-induced coal and gas outburst

Coal and gas outburst disasters can cause serious casualties and property losses, which can be effectively avoided by means of early warning. In this paper, based on the theoretical analysis of the electromagnetic radiation (EMR) response law of mining-induced coal and gas outburst, this paper studied the variation law and precursory characteristics of EMR signals before and after the outburst. The results show that: (1) Coal and gas outburst is induced under the disturbance of mining and promoted by gas pressure and highly concentrated mining stress. (2) The EMR signal is related to changes in stress state, fracturing activity and gas flow state in the process of mining, and the increase of the outburst danger will change characteristics of EMR signal in time and frequency domains. (3) In the time domain, the EMR intensity is positively correlated with the outburst danger of coal seam. The variable coefficient of EMR intensity is greater than 0.15 during the dynamic appearance. The peak value of variable coefficient of EMR intensity is positively correlated to the local instability of coal. (4) In the frequency domain, the amplitude of EMR grows, and the signal frequency moves toward a high level. The dominant frequency rises from 6.6 kHz to 17.4 kHz, and the EMR signal components become more complicated. In practical application, the evolution process of coal and gas outburst danger can be monitored in real time through a comprehensive use of EMR intensity value and its variable coefficient, waveform and frequency distribution characteristics, so that the occurrence of coal and gas outburst disasters can be eliminated.

Influence of soluble organic matter on mechanical properties of coal and occurrence of coal and gas outburst

Coal is a complex organic rock. A large number of soluble organic matters (SOMs) existing in pores of the coal matrix and even in the macromolecular network structure will inevitably have some impact on the coal seam gas occurrence, migration and outburst risk. From the perspective of structure and composition of coal, a series of experiments were carried out to reveal the mechanism of SOMs on the gas outbursts. The results show that SOMs can improve the coal adsorption ability due to the strongly adsorbent groups. Compared with the raw coal, the SOMs-extracted residual coal undergoes a decrease in specific surface area and an increase in total pore volume, average pore diameter and porosity. Furthermore, compressive strength, tensile strength and elastic modulus of the residual coal are all higher than that of the raw coal, while gas content, gas emission initial velocity, drill cuttings desorption indexes (K1 and Δh2) of the residual coal are all lower than that of the raw coal. In summary, the SOMs in coal can promote coal and gas outbursts. Research results of the project provide a new way of promoting gas extraction and outburst prediction.

Studies on mercury occurrence in inorganic constituents of Polish coking coals

During the cokemaking process, a significant amount of mercury occurring in a coal blend is released to the atmosphere. One of the ways of reducing this emission is to reduce mercury content in a coal blend. This could be obtained through the coal washing process. The optimization of this process requires the knowledge of mercury occurrence in coal, especially in its inorganic constituents. A qualitative analysis of mercury occurrence in the inorganic constituents of Polish coking coals was performed using an electron probe microanalyzer (EPMA). For that purpose, selected samples of rejects and middling products derived from the washing process in dense media separators and jig concentrators were examined. The obtained results have confirmed a strong connection between mercury occurrence and the presence of sulfides (pyrite, marcasite, and chalcopyrite) in Polish coking coals. Significant amounts of mercury were also noticed for barite, siderite, and aluminosilicates. The highest value of mercury content, at the level of 0.100%, was obtained for marcasite. For the analyzed coals, the effectiveness of mercury removal in the washing process was determined by the forms of pyrite occurring in coal. The highest values of effectiveness of mercury removal were obtained in the case of coals for which the large framboidal pyrite aggregates with chalcopyrite overgrowths were noticed. It was also found that middling products were characterized by the occurrence of the Hg-rich overgrowths of pyrite on organic matter. To achieve a significant reduction in mercury content in clean coal, it is necessary to develop an effective method of removing this form of pyrite from hard coal.

Investigation on coal seam distribution and gas occurrence law in Guizhou, China

In order to enhance the management level of coal mine safety production and promote the “safe, accurate and efficient” preventive treatments for gas in Guizhou of China, the occurrence and other prominent features of coal and gas are investigated. The characteristics and regularities of coal mine accidents in Guizhou during 2001–2015 are summarized to analyze the commonness of gas accidents in general and determine the characteristics of gas preventive treatment. Geological data, gas basic parameters, and physical properties of coal of 386 mines and 761 sets of coal seams in Guizhou are also statistically analyzed. Based on step control theory of gas occurrence structure and the regionally tectonic regularity of coal-bearing stratum distribution, the deformations of coal measures in Guizhou mine area are mainly caused by great variation of stratigraphic occurrence, complicated geological structure, and high crustal stress. The regional occurrence of coal seam is obvious with the highest content of Tongzi–Zunyi–Liuzhi–Xingyi line, which gradually reduces to the both east and west sides. Influence factors and weights of gas occurrence are expounded from geological and coal factor by mathematical statistics, and the main influence factors of gas occurrence are the sedimentary environment, syncline structure, and metamorphic grade in proper sequence. Combined with the risk prediction of coal and gas outburst area, the prediction of gas pressure by gas content is not suitable under the special occurrence conditions. The initial velocity of gas emission, the solidity coefficient, and the damage type in more than 77% of minable seams all exceed the critical value. This work provides guidance in improvement of the governance situation for gas control in Guizhou. The index prediction system which is suitable for mining conditions of special coal mines in Guizhou should be established.

Vanadium Transitions during Roasting-Leaching Process of Vanadium Extraction from Stone Coal

The vanadium occurrence in stone coal, water leaching, and acid leaching residue was investigated by energy dispersive spectrometer (EDS) mapping and point analysis, and the vanadium transitions during roasting-leaching of stone coal were revealed. In the roasting process, vanadium-bearing muscovite is converted to K-Na-feldspar, accompanying the liberation of vanadium. Most liberated vanadium reacts with sodium salt to generate water-soluble sodium vanadate, some reacts with calcite in stone coal to form water-insoluble calcium vanadate, and other liberated vanadium exists as free vanadium oxide. However, for coarse muscovite grains, the reaction of muscovite converted to K-Na-feldspar only occurs at the outer margin of muscovite grains, and the vanadium in the interior of muscovite grains is not liberated. During water leaching, the sodium vanadate is leached out. The calcium vanadate and free vanadium oxide are dissolved out in the process of acid leaching, and the vanadium, presenting in muscovite grains surrounded by K-Na-feldspar, still remains in the acid leaching residue. Two suggestions, including optimization of grinding-classification process and adopting microwave roasting, were proposed for improving vanadium recovery according to the vanadium transition rules.

Использование вторичных энергоресурсов угольных шахт

Elements of coal mine power facilities are considered. The key consumers of electricity, fuel, thermal energy and service cooling water are identified. The coal mining process areas within which the potential of secondary energy resources and renewable energy sources can be utilized to the maximum extent are determined. The study is based on using simplified calculation correlations for the typical parameters of power and power supply equipment, as well as on synthesizing various well-known concepts about the use of heat pumps for recovering secondary low-grade heat. A calculation technique is presented, and the energy of secondary low-grade heat released by the lifting installation’s drive during its operation is preliminarily analyzed. The advisability of using this energy by means of an air-to-water heat exchanger is substantiated. The amount of secondary low-grade heat removed by the compressor unit cooling system in producing 1 m3 of compressed air is calculated. The advisability of using the system for recovering the heat obtained from cooling the compressor unit instead of a cooling tower is substantiated. The possibility of using secondary low-potential heat in ventilating mine workings is investigated, and it is proposed to install an air-to-water heat exchanger in the air-discharge shaft courtyard for subsequently taking secondary low-grade heat from the mine air and transporting it to the integral heat exchanger. The study results have shown that the amount of secondary low-grade heat available within a mine the coal bed occurrence depth in which is more than 800 m is estimated at 502.32 MWh/1000 t of coal.

Preliminary assessment of the possibility of mercury removal from hard coal with the use of air concentrating tables

Abstract Mercury is characterized by highly toxic properties. The natural biogeochemical cycle of mercury occurs in the environment, which results in the fact that even a small amount of mercury emitted to the environment is a potential threat to human health. The process of coal combustion is one of the main sources of anthropogenic mercury emissions. For this reason, on 31 July 2017 the European Commission has adopted the mercury emission standards for large combustion plants. The issue of mercury emissions is particularly important for Poland. Forecasts concerning energy consumption in Poland show that coal will be the main source for energy production in the coming decades. Therefore, actions enabling the reduction of mercury emissions from coal-fired power plants will have to be implemented. The mercury emissions from coal-fired power plants may be reduced through the application of a number of methods. These methods can be divided into two main groups: the post-combustion methods which allow for mercury removal from flue gases, and the pre-combustion methods which allow for mercury removal from coal before its combustion. The effectiveness of mercury removal from coal is determined by the mode of its occurrence in coal. In the case of mercury occurrence in the adventitious inorganic constituents of coal, high effectiveness will be obtained in the coal cleaning processes. In the case of mercury occurrence in the organic matter as well as in the inherent inorganic constituents of coal, the effectiveness of this method will be low. Mercury could be removed from such coals through the process of thermal pretreatment at the temperature of 200-400°C (mild pyrolysis). In the paper, the possibility of mercury removal from hard coal through the process of dry deshaling on an air concentrating table was examined. Six raw coals (coal feed), clean coals and the rejects derived from their dry deshaling were analyzed. The mercury content was measured in the examined samples. The content of mercury in raw coals and clean coals were compared. Additionally, the effectiveness of mercury removal from coal with rejects was determined. For the analyzed coals, the effectiveness of mercury removal from coal in the process of dry deshaling on an air concentrating table ranged from 9 to 96%. This effectiveness is similar to the effectiveness of mercury removal from coal in the processes of coal washing. It should be mentioned that, when compared to the coal washing processes, the dry deshaling process is characterized by lower investment and operating costs. Therefore, the dry deshaling process on an air concentrating table should be considered as a competitive method for the coal washing processes. There is also a possibility of an increase in the mercury removal efficiency from coal in the process of dry deshaling as a result of the thermal pretreatment of clean coal derived from dry deshaling. This solution is only recommended for coals in which mercury occurs in the organic matter as well as in the inorganic constituents characterized by a relatively low temperature of mercury release.It should be emphasized that the dry deshaling process allowed for a decrease of mercury content is not suitable for every coal. Although for five of the analyzed coals the mercury content in clean coal was lower in the range from 11 to 53%, for one coal the mercury content was higher by 19%. The effect of decreasing the mercury content in coal is more evident when it is related to the amount of energy contained in coal (i.e. for example to the lower heating value). For five of the analyzed coals mercury content expressed in such a way decreased in the range from 11 to 53 %, and for one coal the mercury content was, however, higher. Nevertheless, the difference was not very significant (ca. 5%).

Microscopic evaluation of inertinite in the coke micro-structure: A case study from Jharia Coalfield, India

ABSTRACTInertinite, a maceral group, which remains inert or partly fuses during the carbonization process, plays a vital role in coke making. During carbonization, vitrinite softens and resolidifies to form porous mosaic texture and loses its original identity whereas, inertinite gets filled up as filler form firmly implanted within different types of mosaic matrix. Their size and association with other maceral or minerals also modify their behavior in coke. Structured and unstructured, smaller and larger, high and low reflectance, oxidation or heat alteration, all behaves in a different manner. The Gondwana coals are characteristically rich in inertinite group of macerals, especially semifusinite which has a wide range of reflectance and morphology varying from vitrinite to fusinite. Present study deals with the behavior of inertinite in Gondwana coals during the carbonization process. Coke petrography is an important tool which gives an insight into the maceral interaction. Different macerals of the inertinite group have been analyzed in coke and compared with their occurrence in parent coal. The study reveals the influence of different inertinite macerals in determining the coke quality.

Прогнозування ефективності роботи вугільних шахт України

Coal is at present and will remain in visible future the main fuel resource for thermal and electric generation. However, the complex mining and geological conditions of coal occurrence in Ukraine, the deterioration of mine equipment, and insufficient investments in the modernization of mines lead to a high cost of coal mined, especially at mines with state ownership. The income from the sale of products for the predominant majority of coal enterprises does not enable them to compensate expenditures. This article is devoted to the analytical assessment of technical-and-economic level of the work of coal enterprises in Ukraine, the forecasting of cost price of the coal products based on the construction of regression models, and the determination of break-even points of the coal industry enterprises. Based on the results of performed investigations, we drew a conclusion that, in the territory under Ukraine's control, provided that equipment of the new technical level will be installed at a series of enterprises, they will be able to reach the maximal volumes of production and the zero profitability level already in 2020.

Why do climate change scenarios return to coal?

The following article conducts a meta-analysis to systematically investigate why Representative Concentration Pathways (RCPs) in the Fifth IPCC Assessment are illustrated with energy system reference cases dominated by coal. These scenarios of 21st-century climate change span many decades, requiring a consideration of potential developments in future society, technology, and energy systems. To understand possibilities for energy resources in this context, the research community draws from Rogner (1997) which proposes a theory of learning-by-extracting (LBE). The LBE hypothesis conceptualizes total geologic occurrences of oil, gas, and coal with a learning model of productivity that has yet to be empirically assessed.This paper finds climate change scenarios anticipate a transition toward coal because of systematic errors in fossil production outlooks based on total geologic assessments like the LBE model. Such blind spots have distorted uncertainty ranges for long-run primary energy since the 1970s and continue to influence the levels of future climate change selected for the SSP-RCP scenario framework. Accounting for this bias indicates RCP8.5 and other ‘business-as-usual scenarios’ consistent with high CO2 forcing from vast future coal combustion are exceptionally unlikely. Therefore, SSP5-RCP8.5 should not be a priority for future scientific research or a benchmark for policy studies.

Mechanical failure mechanisms and forms of normal and deformed coal combination containing gas: Model development and analysis

Abstract In coal mining, coal seams often contain several normal coal layers and deformed coal layers in the same region. However, the existence of deformed coal may promote the occurrence of coal and gas outbursts. To analyze the role of failure of different combinations of deformed coal on coal and gas outbursts, force analysis of normal and deformed coal combinations containing gas was carried out, and the expressions of interfacial stress induced by uncoordinated horizontal deformation were first derived in this paper. The results showed that the additional interfacial stresses are affected by the external stresses, internal gas pressure, gas sorption-induced swelling deformation and mechanical parameters of coal and that the additional interfacial stresses on the normal coal and deformed coal are equal and opposite. Then, based on the Mohr-Coulomb criterion and uncoordinated deformation, the mechanical failure mechanisms and forms of combinations containing gas under ideal conditions were analyzed. We found that there are seven failure forms for the combination containing gas, and in most cases, the destruction of the combination is caused by the structural failure of deformed coal. Finally, the failure mechanisms of the combination due to mining were discussed using the parameters from the Qinshui Basin. The results showed that failure is more probable at the interface between the deformed coal and normal coal bodies and that the existence of deformed coal can promote the damage of normal coal. These research results can help us to better understand the role of mechanical failure in coal and gas outbursts within combinations, and provide a theoretical basis for the control of coal and gas outbursts.

An Overview of Elemental Modes of Occurrence in Coal

An Overview of Elemental Modes of Occurrence in Coal

Method selection for mercury removal from hard coal

Mercury is commonly found in coal and the coal utilization processes constitute one of the main sources of mercury emission to the environment. This issue is particularly important for Poland, because the Polish energy production sector is based on brown and hard coal. The forecasts show that this trend in energy production will continue in the coming years. At the time of the emission limits introduction, methods of reducing the mercury emission will have to be implemented in Poland. Mercury emission can be reduced as a result of using coal with a relatively low mercury content. In the case of the absence of such coals, the methods of mercury removal from coal can be implemented. The currently used and developing methods include the coal cleaning process (both the coal washing and the dry deshaling) as well as the thermal pretreatment of coal (mild pyrolysis). The effectiveness of these methods various for different coals, which is caused by the diversity of coal origin, various characteristics of coal and, especially, by the various modes of mercury occurrence in coal. It should be mentioned that the coal cleaning process allows for the removal of mercury occurring in mineral matter, mainly in pyrite. The thermal pretreatment of coal allows for the removal of mercury occurring in organic matter as well as in the inorganic constituents characterized by a low temperature of mercury release. In this paper, the guidelines for the selection of mercury removal method from hard coal were presented. The guidelines were developed taking into consideration: the effectiveness of mercury removal from coal in the process of coal cleaning and thermal pretreatment, the synergy effect resulting from the combination of these processes, the direction of coal utilization as well as the influence of these processes on coal properties.

Geochemistry of vanadium (V) in Chinese coals.

Vanadium in coals may have potential environmental and economic impacts. However, comprehensive knowledge of the geochemistry of V in coals is lacking. In this study, abundances, distribution and modes of occurrence of V are reviewed by compiling >2900 reported Chinese coal samples. With coal reserves in individual provinces as the weighting factors, V in Chinese coals is estimated to have an average abundance of 35.81μg/g. Large variation of V concentration is observed in Chinese coals of different regions, coal-forming periods, and maturation ranks. According to the concentration coefficient of V in coals from individual provinces, three regions are divided across Chinese coal deposits. Vanadium in Chinese coals is probably influenced by sediment source and sedimentary environment, supplemented by late-stage hydrothermal fluids. Specifically, hydrothermal fluids have relatively more significant effect on the enrichment of V in local coal seams. Vanadium in coals is commonly associated with aluminosilicate minerals and organic matter, and the modes of V occurrence in coal depend on coal-forming environment and coal rank. The Chinese V emission inventory during coal combustion is estimated to be 4906mt in 2014, accounting for 50.55% of global emission. Vanadium emissions by electric power plants are the largest contributor.

Influence of Hg occurrence in coal on accuracy of Hg direct measurement based on thermal decomposition

To better monitor and control Hg emissions from coal-fired power plants, quantification of Hg contents in coal is essential. Thermal decomposition is widely used to pretreat solid samples. The complete thermal release of Hg in coal samples is a premise for obtaining accurate results of measured Hg contents. The recommended heating temperature is 800°C for coal samples. The research work in this paper has verified the existence of an abnormal phenomenon, where some Hg occurrences in typical coal at 800°C could not fully decompose. The temperature-programmed pyrolysis was designed to validate the assumption and determine the optimum decomposition temperature. The results demonstrate that Hg combined with montmorillonite mineral fully decomposes at temperatures above 800°C. The obtained results help to clarify the relationship between the decomposition temperature and Hg occurrence. The study offers good guidance to improve the accuracy of measured Hg contents by thermal decomposition, thus expanding the laboratory and industrial application.

Cisuralian coals of the Mullaley Sub-basin, northern New South Wales

ABSTRACTThe Mullaley Sub-basin of the Gunnedah Basin extends from Quirindi in the southeast, to north of Narrabri, to west of Dunedoo in northern New South Wales. There have been more than 100 boreholes sunk to basement investigating the (lower Permian) Cisuralian coal and coal seam gas resources of the Mullaley Sub-basin since the early 1990s. A desktop review of this open file information has allowed the formal correlation and naming of six Cisuralian coal members attaining a maximum 35 m of cumulative thickness within an upward coarsening sedimentary package totalling no more than 150 m. In ascending order, the coal members are: Bibblewindi (0–10 m), Bohena (3–18 m), Collygra (0.5–3 m), Coxs (1.5–4 m), Tullamullen (0.5–4 m) and Mooki (0.5–3 m).Cisuralian coal seams in the Maules Creek Formation of the southern Mullaley Sub-basin are here correlated with those of the Greta Coal Measures at Werris Creek and Muswellbrook. It is apparent that basement paleotopography played a significant role in the Cisuralian coal development as coals are best developed where the sedimentary sequence is greater than 60 m thick, as there the thick seams (Bohena and Bibblewindi coal members) occur towards the base of the sequence. The maximum western limit of the Cisuralian coals (Rocky Glen Ridge) is further east than previously inferred with new drilling information showing the Porcupine Formation directly overlying the barren pelletoidal claystones of the Leard Formation or the underlying volcanics (Boggabri Volcanics/Werrie Basalt). Early marine transgressions at the top of the Maules Creek Formation have stopped development of the Mooki, Tullamullen and Coxs coal members in the northern and eastern Mullaley Sub-basin and allowed the development of localised paraconglomerate (diamictite) intervals up to 10 m thick. Thick (>20 m cumulative) coal occurrences are localised to the Jacks Creek and Pilliga East State Forest areas southwest of Narrabri. The coal resource potential of the Mullaley Sub-basin is estimated at 13–28 billion tonnes.

Comprehensive Technical Support for High-Quality Anthracite Production: A Case Study in the Xinqiao Coal Mine, Yongxia Mining Area, China

The effective production of high-quality anthracite has attracted increasing global attention. Based on the coal occurrence in Yongxia Mining Area and mining conditions of a coalface in Xinqiao Coal Mine, we proposed a systematic study on the technical support for the production of high-quality anthracite. Six key steps were explored, including coal falling at the coalface, transport, underground bunker storage, main shaft hoisting, coal preparation on the ground, and railway wagon loading. The study resulted in optimized running parameters for the shearers, and the rotating patterns of the shearer drums was altered (one-way cutting was employed). Mining height and roof supporting intensity were reduced. Besides, loose presplitting millisecond blasting and mechanized mining were applied to upgrade the coal quantity and the lump coal production rate. Additionally, the coalface end transloading, coalface crush, transport systems, underground storage, and main shaft skip unloading processes were improved, and fragmentation-prevention techniques were used in the washing and railway wagon loading processes. As a result, the lump coal production rate was maintained at a high level and fragmentation was significantly reduced. Because of using the parameters and techniques determined in this research, high-quality coal production and increased profits were achieved. The research results could provide theoretical guidance and methodology for other anthracite production bases.

Studies of the correlation between mercury content and the content of various forms of sulfur in Polish hard coals

Similarities concerning the occurrence of mercury and sulfur in coal are the reasons for studying the correlation between mercury content and the content of the various forms of sulfur such as: total sulfur, pyritic sulfur, sulfate sulfur, and organic sulfur. For this purpose a wide range of different coals and rejects were used. Selected samples differed significantly in the content of ash, mercury, sulfur and its various forms. In the examinations, both steam and coking coals were studied. For coking coals, samples of raw coals, clean coals, middling products and rejects derived from coal preparation plants were examined. To verify the correlation a statistical analysis was performed. The Spearman’s rank correlation coefficient and the correlation coefficients R for polynomial functions of degree 1 and 2 were determined.Based on the obtained results, it can be concluded, that mercury occurs in Polish hard coals both in the organic matter and the inorganic constituents. For the organic matter a significant correlation between the content of mercury and the content of total sulfur and organic sulfur was obtained for subset of examined samples characterized by a relatively low ash yield (clean coals derived from the coal cleaning process). In the case of the inorganic constituents a significant correlation between the content of mercury and the content of pyritic sulfur was obtained for the examined subset of samples characterized by a very high ash yield (rejects derived from the coal cleaning process). An analysis of the subsets of samples derived from individual mines showed that the modes of occurrence of mercury in coal were different for various Polish mines. These differences may be explained by the genetic diversity of coal i.e. various diagenetic, coalification and post-diagenetic conditions, including such phenomena as mineralization that post-dates coal formation and magmatic intrusion, etc.In order to explain the mercury and sulfur behavior in the analyzed processes of coal cleaning the percentage share of those elements in rejects in relation to raw coal was also determined. The mercury removal efficiencies recorded for the cleaning process of Polish hard coals ranged from about 33% to as much as 67%.Results of the statistical analyses did not, however, provide necessary evidence allowing for the formulation of final conclusions regarding the modes of occurrence of mercury in Polish coals, its association with sulfur present in coal as well as proportioning of mercury in the processes of coal cleaning. The results did make it possible, though, to identify the major scientific problems, which, if solved by relevant methods (e.g. XRD, SEM, EPMA), will facilitate the understanding of the Hg-modes of occurrence in various Polish hard coals. The results of the statistical analyses will also make it easier to appropriately select samples in order to explain these scientific problems.

Types of Coal-Bearing Basin and Tectonic Unit in the Northwest Coal Hosting Area

Coal is typical of sedimentary deposits, Occurrence in a coal basin. The original nearly horizontal continuous coal seam was divided into different size; different depth containing coal segment by late tectonic movement, but its scope is not affected by today's "basin" restrictions. With the concept of coal occurrence tectonic unit to reflect the current Coal Occurrence Characteristics and build a prototype coal basin types that prototype into a coal basin tectonic movement after the formation of today's coal occurrence tectonic unit. In Northwest coal hosting area, the main coal bearing strata include Carboniferous-Permian, Upper Triassic, Lower-Middle Jurassic and Lower Cretaceous, and its distribution is regular; the center and strength of coal accumulation were variation in different coal-forming period; the types of basin are multiple, including Passive Margins, Peripheral Foreland, Intracontinental Rift, Intermontane, Strike-slip pull-apart, Strike-slip pull-apart, Inter-montane; moreover, one belt and two rings constitute the tectonic framework of Northwest coal hosting area.