Small-scale area survey and analysis of Xinjiang's coal field fire in China

In this paper, Xinjiang＇s coal field is selected as the investigation area. Through a series of field surveys in Xinjiang, we made the small-scale area analysis of coal field fire using the ground remote sensing technique, and presented the reasonable evaluation of thermal anomaly conditions of Xinjiang＇s coal field arising from coal self-ignition fires. The results show that the method of small-scale area analysis is available for examining the extinguished actuality of coal fires and detecting fire spots. Therefore, for the selected fire-extlngulshed coal field in Xinjiang, the fire extinguishing effect was effectively analyzed by the means, and the new hidden thermal dangers were sought and diagnosed. For the coal field where the fire has not been extinguished, the utilization of this means approximately identified the severity and range of the fire area, and provided the quantitative and ground references for extinguish engineering.

Spatio-temporal changes of underground coal fires during 2008-2016 in Khanh Hoa coal field(North-east of Viet Nam) using Landsat time-series data

Underground coal fires are one of the most common and serious geohazards in most coal producing countries in the world. Monitoring their spatio-temporal changes plays an important role in controlling and preventing the effects of coal fires, and their environmental impact. In this study, the spatio-temporal changes of underground coal fires in Khanh Hoa coal field(North-East of Viet Nam) were analyzed using Landsat time-series data during the 2008-2016 period. Based on land surface temperatures retrieved from Landsat thermal data, underground coal fires related to thermal anomalies were identified using the MEDIAN+1.5×IQR(IQR: Interquartile range) threshold technique. The locations of underground coal fires were validated using a coal fire map produced by the field survey data and cross-validated using the daytime ASTER thermal infrared imagery. Based on the fires extracted from seven Landsat thermal imageries, the spatiotemporal changes of underground coal fire areas were analyzed. The results showed that the thermalanomalous zones have been correlated with known coal fires. Cross-validation of coal fires using ASTER TIR data showed a high consistency of 79.3%. The largest coal fire area of 184.6 hectares was detected in 2010, followed by 2014(181.1 hectares) and 2016(178.5 hectares). The smaller coal fire areas were extracted with areas of 133.6 and 152.5 hectares in 2011 and 2009 respectively. Underground coal fires were mainly detected in the northern and southern part, and tend to spread to north-west of the coal field.

Vertical variation of trace elements and its relation to the water-bearing capacity of Ordovician strata,in Datun coal field

We tested for fourteen trace elements in samples collected from the Ordovician strata in Datun coal field. The vertical concentration variation of these trace dements is reported. The relationship of the variation to the water-bearing capacity of the Ordovician strata is discussed. The minimum concentration of eleven （of 14 total） trace elements appears in the lower Majiagou formation. The maximum concentrations mainly appear in the Badou and Jiawang formations： eight maxima are located in Badou and four more are in Jiawang. The study of karst development and the water-bearing capacity of Ordovician strata shows that karst is well developed in the Majiagou formation and there is a consequent high water-bearing capacity in this formation： Badou and Jiawang formations are contrary to this situation. The results illustrate that the minimum concentrations of most trace elements within certain Ordovician formations can be taken as strong evidence for the existence of a well developed karst and a high water-bearing capacity.

STUDY ON EXTRACTING METHODS OF BURIED GEOLOGICAL INFORMATION IN HUAIBEI COAL FIELD

It is discussed features and tbe producing mechanism of buried geological information in geological, geophysical and remote sensing data in Huaibei coal field, and studied the methods extracting buried tectonic and igneous rock information from various geologicaI data using digital image processing techoiques.

A back analysis of the temperature field in the combustion volume space during underground coal gasification

The exact shape and size of the gasification channel during underground coal gasification(UGC) are of vital importance for the safety and stability of the upper parts of the geological formation.In practice existing geological measurements are insufficient to obtain such information because the coal seam is typically deeply buried and the geological conditions are often complex.This paper introduces a cylindrical model for the gasification channel.The rock and soil masses are assumed to be homogeneous and isotropic and the effect of seepage on the temperature field was neglected.The theory of heat conduction was used to write the equation predicting the temperature field around the gasification channel.The idea of an excess temperature was introduced to solve the equations.Applying this model to UCG in the field for an influence radius,r,of 70 m gave the model parameters,u1,2,3...,of 2.4,5.5,8.7...By adjusting the radius(2,4,or 6 m) reasonable temperatures of the gasification channel were found for 4 m.The temperature distribution in the vertical direction,and the combustion volume,were also calculated.Comparison to field measurements shows that the results obtained from the proposed model are very close to practice.

Research and application of strip mining of village coal pillar at coal field of the north of the Yellow River in Shandong Province

This paper focuses on the village coal pillar under huge thick loose bed and thin bedrock over high prelatic water level at the north of the Yellow River. The strip mining technology was used to protect the village houses. The stratum structure control action of mining subsidence was used to design the mining and pillar width. To further raise resources recovery, we adopted the mutative scheme of mining and pillar width. Observation was carried out while mining. Research shows there is feasibility of the strip mining technology to protecting the village buildings of the village coal pillar under huge thick loose bed and thin bedrock over high prelatic water level at the north of the Yellow River. Finally, subsidence parameters of strip mining were obtained. It is the basic data of the strip mining of the coal field at the north of the Yellow River.

Application of axiomatic approach to coal mine design field

Two design axioms and axiomatic approach were discussed. As an example of application, design process of a new style single prop was illustrated in term of axi- oms.

THE REMOTE SENSING IN COAL GEOLOGY——A study on detection of coal spontanous burning by remote sensing in the coal fields in the north of China

The spontaneous burning has been lasting for thousands of years in the coal fields in the north of China. It spreads from the west (Tianshan coal field) to the east (Huolinhe coal field). Its E-W extension is up to 3750km, concentrating in N35°toN45°, its vertical depth up to 260m, and the surface temprature locally up to 270℃. Annually, it burns out 0, 250-300 million tones of coal, causing economic loss equivalent to 2-3 billion R.M.B. Yuan.It destroies coal resources and causes hazards in coal mines. In order to locate the extent and the direction in coal burning areas, the remote sensing technique has heen used and has produced an obvious benefit.

基于改进Node2vec算法的锅炉温度场分割方法研究

针对温度场特征参数差异引发的锅炉温度场分割准确性的问题,以维持温度场特征为目标,引入图结构表达场数据,通过改进Node2vec算法进行聚类分析,进而实现锅炉温度场的最佳分割。该方法基于多维度的特征信息对锅炉温度场实现分割,能够更准确地保留流场特征。在标准数据集上进行了实验验证,结果表明在具有多维度特征的数据集上,所提方法相比其他对比算法在分割效果方面有提升显著。最后将提出的方法用于分割电站锅炉温度场,结果表明该方法可以很好地捕捉温度场数据中的局部和全局特征,且结果具有较好的精确性。

Polycyclic aromatic hydrocarbon formation under simulated coal seam pyrolysis conditions

Coal seam pyrolysis occurs during coal seam fires and during underground coal gasification. This is an important source of polycyclic aromatic hydrocarbon （PAH） emission in China. Pyrolysis in a coal seam was simulated in a tubular furnace. The 16 US Environmental Protection Agency priority controlled PAHs were analyzed by HPLC. The effects of temperature, heating rate, pyrolysis atmosphere, and coal size were investigated. The results indicate that the 3-ring PAHs AcP and AcPy are the main species in the pyrolysis gas. The 2-ring NaP and the 4-ring Pyr are also of concern. Increasing temperature caused the total PAH yield to go through a minimum. The lowest value was obtained at the temperature of 600℃. Higher heating rates promote PAH formation, especially formation of the lower molecular weight PAHs. The typical heating rate in a coal seam, 5 ℃/min, results in intermediate yields of PAHs. The total PAHs yield in an atmosphere of N2 is about 1.81 times that seen without added N2, which indicates that an air flow through the coal seam accelerates the formation of PAHs. An increase in coal particle size reduces the total PAHs emission but promotes the formation of 5- and f-ring PAHs.

热浮力驱动下地下煤火阴燃蔓延模型与机制

地下煤火蔓延模型与机制研究对我国煤炭资源绿色安全开采具有重要意义。目前地下煤火阴燃正向蔓延模型主要存在问题:简化的煤燃烧单步反应忽略了水分蒸发和热解吸热反应对蔓延的重要影响作用;缺乏实验数据验证模型的有效性。为此,构建了包含水分蒸发、煤热解和碳氧化三步反应体系的地下煤火阴燃正向蔓延数学模型;采用COMSOL Multiphysics有限元软件数值计算了该理论模型;开展了不同地裂缝渗透性条件下热浮力驱动地下煤火阴燃正向蔓延实验,进行对比实验和数值计算。结果表明:构建的模型揭示了地下煤火阴燃蔓延供氧控制机制,不仅能预测地下煤火阴燃正向蔓延高温区域的温度和蔓延速率,而且还能合理地预测阴燃多步反应速率以及氧气、煤、碳和灰分质量分数的时空演化。

基于炉膛气氛场的锅炉燃烧区域风量调节与控制技术及应用

讨论了锅炉风量控制的重要性,阐述了常规锅炉风量控制技术的现状,提出了基于炉膛气氛场的燃烧区域局部风量调节与控制技术,并重点介绍了该技术中CO及H2S测量等炉膛气氛场测量技术以及风量控制原理。介绍了在某600MW火电机组上的应用情况,并进行了经济性分析。结果表明,该技术能有效减少锅炉的化学不完全燃烧和机械不完全燃烧损失,避免非停损失和爆管维修损失,具有较好的经济性。

复采掘进工作面综合防灭火技术及实践

为确保复采掘进工作面的安全生产,针对复采工作面煤层易自燃的问题,在对运河煤矿F1301复采工作面现场条件以及遗煤自然发火风险分析的基础上,提出了适用于矿井复采掘进工作面的综合防灭火技术。采用风流场调控、均压堵漏、惰化处理、监测探测等有效手段,定性分析了复采条件下的防灭火机理,规范了防灭火技术工艺,量化了防灭火技术参数。通过实施综合防灭火技术,有效控制了掘进期间采空区煤层自然发火风险,使得F1301复采掘进工作得以顺利进行,同时也为工作面的回采创造了良好的防火条件,实践经验可为类似条件下工作面开采提供工程经验支撑。

Application of coal mine roof rating in Chinese coal mines

The coal mine roof rating(CMRR) is a measure of roof quality or structure competency for bedded roof types typically of underground coal mines. The CMRR has been used widely in the US, South Africa,Canada and Australia. In order to investigate the application of the CMRR system in Chinese coal mines,two coal mines in China located in Panjiang Coal Field in Guizhou Province were investigated. Field data were collected which is required to calculate the CMRR value based on underground exposure. The CMRR values of 11 locations in two coal mines were calculated. The investigations demonstrated that the chance of mine roof failure is very low if the CMRR value is more than 50, given adequate support is installed in mine. It was found that the CMRR guideline are useful to preliminarily investigate stability in Panjiang Coal Field mines.

Coal pillar mechanics of violent failure in U.S. Mines

This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitoring and numerical modeling in bump-prone U.S. mines. The focus is on induced horizontal stress in mine pillars and surrounding strata as highly stressed pillars punch into the roof and floor, causing shear failure and buckling of strata; under stiff stratigraphic units of some western US mines, these events could be accompanied by violent failure of pillar cores. Pillar punching eventually results in tensile stresses at the base of the pillar, facilitating transition into the post-failure regime; this transition will be nonviolent if certain conditions are met, notably the presence of interbedded mudstones with low shear strength properties and proper mine designs for controlling seismicity and dynamic loads. The study clearly shows high confining stress build-up in coal pillars resulting in up to twice higher peak vertical stress and high strain energy accumulations in some western US mines in comparison with peak stresses predicted using common empirical pillar design methods. It is the unstable release of this strain energy that can cause significant damage resulting from pillar dilation and ground movements. These forces are much greater than the capacity of most common internal support systems, resulting in horizontal stressinduced roof falls locally, in mines under unremarkable far-field horizontal stress. Attention should be placed on pillar designs as increasing support density may prove to be ineffective. This mechanism is analyzed using field measurements and generic finite-difference stress analyses. The study confirms the higher load carrying capacity of confinement-controlled coal seams in comparison with structurally controlled coal seams. Such significant differences in confining stresses are not taken into account when estimating peak pillar strength using most common empirical techniques such as those proposed by Bieniawski and Salamon. While using lower pillar strength estimates may be considered conservative,it underestimates the actual capacity of pillars in accumulating much higher stress and strain energies,misleading the designer and inadvertently diminishing mine safety. The role of induced horizontal stress in mine pillars and surrounding strata is emphasized in coal pillar mechanics of violent failure. The triggering mechanism for the violent events is sudden loss of pillar confinement due to dynamic loading resulting from failure of overlying stiff and strong strata. Evidence of such mechanism is noted in the field by observed red-dust at the coal-rock interfaces at the location of coal bumps and irregular, periodic caving in room-and-pillar mines quantified through direct pressure measurements in the gob.

Prospecting for coal in China with remote sensing

With the rapid development of China＇s economy, coal resources are increasingly in great demand. As a result, the remaining coal reserves diminish gradually with large-scale exploitation of coal resources. Easily-found mines which used to be identified from outcrops or were buried under shallow overburden are decreasing, especially in the prosperous eastern regions of China, which experience coal shortages. Currently the main targets of coal prospecting are concealed and unidentified underground coal bodies, making it more and more difficult for coal prospecting. It is therefore important to explore coal prospecting by taking advantage of modern remote sensing and geographic information system technologies. Given a theoretical basis for coal prospecting by remote sensing, we demonstrate the methodologies and existing problems systematically by summarizing past practices of coal prospecting with remote sensing. We propose a new theory of coal prospecting with remote sensing. In uncovered areas, coal resources can be prospected for by direct interpretation. In coal beating strata of developed areas covered by thin Quaternary strata or vegetation, prospecting for coal can be carried out by indirect interpretation of geomorphology and vegetation. For deeply buried underground deposits, coal prospecting can rely on tectonic structures, interpretation and analysis of new tectonic clues and regularity of coal formation and preservation controlled by tectonic structures. By applying newly hyper-spectral, multi-polarization, multi-angle, multi-temporal and multi-resolution remote sensing data and carrying out integrated analysis of geographic attributes, ground attributes, geophysical exploration results, geochemical exploration results, geological drilling results and remote sensing data by GIS tools, coal geology resources and mineralogical regularities can be explored and coal resource information can be acquired with some confidence.

CLAY MINERAL ASSEMBLAGES AND THEIR IMPLICATIONS IN SHIHEZI FORMATION FROM THE HUAIBEI COAL-BEARING STRATA

Clay mineral assemblages in Shihezi Formation of Huaibei coal-bearing strata are determined by X-ray diffraction and Differential Thermal Analyzer, that is restated to the sediment faces and climatic changes in the source area, and to a lesser extent, alterations during burial diagenesis. In the Upper Shihezi Formation, the clay fraction is dominated by kaolinite in northern part of the coal field, which was formed in alluvial sediment environment. But in the South of Huaibei coal field, the clay mineral assemblage consists of mainly illite that reflects the influence of sea water. The predominately kaolinite and sederite composition of the clay fraction in the lower Shihezi Formation sediments documents less relief and gentle erosion of kaolinite rich soils developing under warm source area. In the lower part of Shihezi Formation, some chlorite is detected, which suggests transformation of illite or kaolinite to chlorite under conditions of burial diagenesis.

煤田火区氧化煤分阶催化气化及作用机理

煤田火区热量较大,火区高温会对周围煤体造成影响,在火区受到有效控制或蔓延至其他区域后,往往在火区边缘或邻近煤层形成数量较大的氧化煤。与原始煤炭相比,氧化煤热值低、灰分高,难以作为常规燃煤利用,目前多与优质煤混合利用,导致混煤整体燃烧热值降低且炉渣量增加,严重影响电厂锅炉运行效率。为了更好地利用氧化煤,实现资源利用最大化,提出了氧化煤的分阶催化气化思路,并提出使用价格低廉的膨润土作为高温阶段的催化芯材,通过分阶式催化剂分别实现氧化煤气化过程的初期快速活化和后期催化气化,从而实现氧化煤高效气化利用。采用X射线衍射、扫描电子显微镜和孔隙分析表征氧化煤催化气化过程中关键结构演变特征,并利用热重质谱联用开展气化实验,通过特征参数分析气化前期和后期反应特点。结果表明:分阶式催化剂由外层K_(2)CO_(3)和内层膨润土构成,其表层K_(2)CO_(3)能明显促进氧化煤初期热解过程中孔隙结构的形成,在气化初期产生大量微孔结构,增加氧化煤与气化剂CO_(2)的接触面积,提高氧化煤反应活性;含Na+阳离子的膨润土可以在高温阶段发挥稳定催化作用,弥补了K_(2)CO_(3)在高温阶段易挥发和失活的缺陷。在分阶式催化剂作用下,碳晶格单元的生长速度减小。这表明分阶式催化剂可以插入碳芳环的边缘,导致内部晶格出现缺陷,从而有效抑制氧化煤焦的石墨化进程,保证连续催化气化反应。当K_(2)CO_(3)和钠基膨润土的质量比达到1∶1,整体催化气化效果最佳。分阶式催化剂在热解阶段也起到一定的催化作用,能促进氧化煤热解脱挥发分释放出氢气。在气化反应阶段,分阶式催化剂能有效降低氧化煤气化反应温度以及合成气产率峰值温度,提高气化反应速率。CO和H_(2)体积分数峰值对应温度的降低幅度分别达到97.4、129.1℃,具有明显的催化效果。氧化煤的分阶式催化气化高效制取合成气为火区氧化煤高效利用提供了新思路,可避免大量火区滞留煤炭资源的浪费。

燃煤机组SCR烟气脱硝系统流场均布一体化建模与性能优化

选择性催化还原(SCR)烟气脱硝效率与其内部烟气和还原剂流动的均匀性密切相关。在建立SCR脱硝反应数学模型基础上,采用用户自定义子程序耦合了多组分烟气流动与反应过程;通过比较不同负荷下330 MW等级燃煤机组脱硝性能的实测与模拟数据验证了模型的可靠性和有效性,基于对反应器内烟气和还原剂流动及其反应特性的数值模拟分析,提出了喷氨格栅上游导流板结构优化方案,进而考察了操作条件对NO和NH3排放质量浓度的影响。结果表明:喷氨格栅来流烟气速度分布的非均匀性是导致烟气与还原剂混合效果较差的主要原因,进而通过调整喷氨格栅上游导流板结构并在烟道壁面增设挡板可将脱硝效率提高约3.37%;为满足NO_(x)质量浓度为50 mg/m^(3)及NH3质量浓度为2.5 mg/m^(3)的排放限值需选取适宜喷氨量,以所选取SCR脱硝装置为例,当烟气初始NO质量浓度为650 mg/m^(3),SCR脱硝系统适宜氨氮摩尔比应约为0.94。