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Characteristics of transmitting channel wave in a coal seam
An embedded underground coal seam carries channel waves of low seismic velocity along a stratigraphic rock-coal-rock sequence. In a homogeneous and isotropic seam, seismic waves propagate as trapped waves within the seam, which leads to propagation of channel waves. We describe how to set up a field test for transmission in order to acquire channel waves in a coal seam. Because channel wave signals are non-stationary in their frequencies and amplitudes, a necessary velocity spectrum and wavelet transformation analysis are applied to interpret the characteristics of channel waves. The advantage of using a wavelet transformation is that different resolutions can be obtained at different times and different frequencies. According to analysis of the seismic signals acquired in the S7 sensor hole, it was clearly shown that the characteristics of channel waves are lower frequencies and attenuation which can guide an effective wave for detecting voids, boundaries and faults in coal seams with strong roofs and floors....
2020-06-12 16:16:39浏览：1429
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Catastrophic mechanism of coal and gas outbursts and their prevention and control
Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point (P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load.When the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented....
2020-06-12 16:16:37浏览：1394
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Monitoring in Building Road Tunnel Across Coal Measures
In some cases coal measures,goaf,big caves,and huge faults,as well as high initial stress cannot be avoided in road tunnel excavation.These geological features may make it more difficul practical tunnel construction. So it is necessary to take strong precautious measures against gas outburst,water bursting and roof fall in a tunnel across coal measures with risk of gas outburst.The techniques,such as advance drilling exploration,multiple-cycle shallow depth hole controlled blasting,reinforced supporting,which include concrete grouting and twice supporting,and monitoring measures are often applied in the construction of tunnels and satisfied results are achieved. Results in this paper can help others to get experiences in road tunnel construction with similar geological features....
2020-06-12 16:16:37浏览：1406
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Chemical looping combustion of coal in interconnected fluidized beds
Chemical looping combustion is the indirect combustion by use of oxygen carrier.It can be used for CO2 capture in power generating processes. In this paper,chemical looping combustion of coal in interconnected fluidized beds with inherent separation of CO2 is proposed. It consists of a high velocity fluidized bed as an air reactor in which oxygen carrier is oxidized, a cyclone, and a bubbling fluidized bed as a fuel reactor in which oxygen carrier is reduced by direct and indirect reactions with coal. The air reactor is connected to the fuel reactor through the cyclone. To raise the high carbon conversion efficiency and separate oxygen carrier particle from ash, coal slurry instead of coal particle is introduced into the bottom of the bubbling fluidized bed. Coal gasification and the reduction of oxygen carrier with the water gas take place simultaneously in the fuel reactor. The flue gas from the fuel reactor is CO2 and water. Almost pure CO2 could be obtained after the condensation of water. The reduced oxygen carrier is then returned back to the air reactor, where it is oxidized with air. Thermodyanmics analysis indicates that NiO/Ni oxygen carrier is the optimal one for chemical looping combustion of coal.Simulation of the processes for chemical looping combustion of coal, including coal gasification and reduction of oxygen carrier, is carried out with Aspen Plus software. The effects of air reactor temperature, fuel reactor temperature, and ratio of water to coal on the composition of fuel gas, recirculation of oxygen carrier particles, etc., are discussed. Some useful results are achieved. The suitable temperature of air reactor should be between 1050-1150Cand the optimal temperature of the fuel reactor be between 900-950℃....
2020-06-12 16:16:36浏览：1430
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Structure of different types of coal metamorphism by HTEM
In order to discuss the effect of tectonic stress on the structural evolution of coal,given the importance attached to High-resolution Transmission Electron Microscopy (HTEM),we investigated several aspects of material structures of high-rank Carboniferous period coal,located in the northern foreland basin of the Dabie orogenic belt in eastern China.High powered crystal lattice images of Bright Fields (BF) and Selected Area Diffraction patterns (SAD) of different types of metamorphism in coal were obtained.The results show that the Basic Structural Units (BSU) become increasingly more compact as a function of rising temperature and pressure.Under pressure,the local orientation of molecules is strengthened,the arrangement of BSU speeds up and the degree of order is clearly enhanced....
2020-06-12 16:16:36浏览：1431
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An Entrapment Model of Water Flow on Fine Coal Flotation
Effect of entrapment of water flow on fine coal flotation was studied. The relation between constant of water flotation rate and flotation time was investigated and the water recycling model determined. The entrapment model of water flow about the relation between the recovery of fine particle and that of water in concentration was established. Finally, the equation about ash in fine clean coal at any time was derived by introducing a de-ashing coefficient....
2020-06-12 16:16:34浏览：1420
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Critical Value of CO of Forecasting Coal Spontaneous Combustion
CO has been used widely in the production process of colliery as an index gas to predict spontaneous combustion of coal. But in some collieries there are CO gas in the upper corner of the face all the times, sometime CO gas even exceeds the regulated critical index. This phenomenon is much more obvious in the fully-mechanized longwall face and fully-mechanized longwall and top-coal caving face. Although many measures of fire-proof and fire-extinguishing have been adopted, the flowing amount of CO gas can be only decreasd, but can not be eliminated completely. Using the different kinds of coal, the experiment of coal oxidation was made at the low temperature. The experiment indicates that some kinds of coal can produce CO under the condition of normal temperature oxidation, sometime the CO consistency is very high, and the intension of CO can be decreased with oxidation time prolonging. Selecting rational critical value of CO is the kev to predicting spontaneous combustion of coal correctly and reliably. The problem of selecting retional critical value of CO was studied. Finally, the amount of CO gas released by different kinds of coal was obtained under normal temperature condition....
2020-06-12 16:16:33浏览：1434
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Study of Constituents of Fractionated Extraction from Datong Coal
Datong coal was extracted with CS2, n-hexane, benzene, methanol, acetone, tetrahydro-furan(THF) and THF/methanol(1:3,v/v) mixed solvent sequentially. The extracts were analyzed with GC/MS. It is presented that group seperation of soluble organic compounds in the coal can be achieved by fractionated extraction using different solvents. The results show that CS2 was effective for extracting arenes from the coal sample. n-Hexane extractable fraction from Datong coal mainly consists of n-alkanes. A great variety of oxygen-containing compounds are dominant in the components of methanol-soluble fraction. Acyclic isoprenoids, pentecyclic triterpanes and a series of cyclohexanes with long-chain alkyl-substitutes are detected in acetone-soluble fraction. Dicyclic aramatic hydrocarbons are identified in benzene-soluble fraction and 4-6 cyclic condensed aramatic hydrocarbons are identified in THF-soluble fraction. The molecular structures detection of 1,2-dichlorobenzene, 2,4-dibromophnol, 2,4,6-tribromophenol and 4-chlorobenzophe-none firstly provide information for existence form of bromine and chlorine in coal....
2020-06-12 16:16:31浏览：1425
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New progress in the processing and efficient utilization of coal
Coal accounts for about 70％ of the primary energy sources in China.The environmental pollution and resources waste involved with coal processing and utilization are serious.It is therefore urgent to develop highly-efficient coal resources utilization theory and methods with low-carbon discharge.Based on our long-term basic research and technology development,the progress in beneficiation,cleaning,and transformation of coal,which includes dense phase fluidized bed dry beneficiation,deep screening of wet fine coal,micro-bubble flotation column separation,molecular coal chemistry,and transformation and separation of coal and its derivatives into value-added chemicals under mild conditions,is discussed....
2020-06-12 16:16:30浏览：1409
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Spontaneous coal combustion producing carbon dioxide and water
Gas products from the process of coal oxidization and spontaneous combustion have been studied at different temperatures with FTI spectroscopic tests. With temperatures rising to about 30～100 ℃, water and carbon dioxide gas were formed and from about 105～150 ℃, carbon monoxide was produced. Using the DFT B3LYP method with a 6-311G basis set, the reaction system, where spontaneous combustion between coal and oxygen occurs and produces water and monoxide, has been studied, with the geometric configuration for all stagnation points on the potential reaction energy surface optimized. With a frequency analysis and an IRC method, transient formations were tested. Our results indicate that in the reaction of coal oxidization and spontaneous combustion producing carbon dioxide and water, oxygen molecules attack carbon atoms of the terminal of the propyl alcohol group on the lateral chain of benzene rings, which causes this propyl alcohol group to produce the acid (-CH2-CH2-COOH) group and water. This acid group continues its break up into carbon dioxide and the (-CH2-CH3) ethyl group. We have come to the conclusion that this water-and-carbon dioxide-production reaction is spontaneous, based on the observation of the energy released by the reaction....
2020-06-12 16:16:29浏览：1419
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Analysis and Research of Factors Affecting Coal Mining with Plough
Coal mining with ploughs is an ideal coal mining technology for thin a nd thinner coal seams. The existence conditions of coal seams are different for each other, which affects coal mining with ploughs to different degrees, and the application results are also different. The authors analyze the affecting factors by means of mathematical methods. The research is useful to the wide appli cation of ploughs....
2020-06-12 16:16:29浏览：1424
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Determination of coal mine mechanization using fuzzy logic
Two of the most important tasks in coal mines are to improve efficiency and to increase production besides keeping safety constantly in mind. In order to obtain these goals, mine mechanization is required. Mine mechanization needs high levels of investment and should therefore be studied carefully before final decisions about mechanization are made. When analysizing the potential for mechanization the following, rather imprecise, factors should be considered: seam inclination and thickness, geologi-cal disturbances, seam floor conditions, roof conditions, water at the working face and the extension of seams. In our study we have used fuzzy logic, membership functions and created fuzzy rule - based methods and to considered the ultimate objective: mechanization of mining. As a case study, the mechanization of the Takht coal seams in Iran was investigated. The results show a high potential for mechanization in most of the Takht coal seams....
2020-06-12 16:16:28浏览：1432
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Fractal desulfurization kinetics of high-sulfur coal
The pore structure characteristics of high-sulfur coal from Wansheng in Chongqing have been studied by a nitrogen adsorption method (BET).The effects of grinding and pre-treating with nitric acid on the inorganic sulfur content of coal have been investigated.Organic sulfur in coal pretreated with nitric acid was desulfurized by using propylene-glycol-KOH (PG-KOH).Fractal kinetic properties of these two desulfurization procedures were investigated by using fractal geometric theory.The results show that both the specific surface area and pore volume increased with the decrease in particle diameter.The microspore surface of coal had fractal characteristics; the fractal dimension was 2.48.The sulfur content decreased with the decrease in particle diameter by grinding.After pretreatment with nitric acid,the desulfurization ratio (DFR) of inorganic sulfur increased to over 99％ and the DFR of total sulfur to over 70％.The desulfurization procedure of inorganic sulfur had fractal kinetic characteristics; its reactive fractal dimension was 2.94.The organic sulfur desulfurization procedure by PG-KOH was also tallied with fractal kinetic properties; the reactive fractal dimension was 2.57.The effect of temperature on the desulfurization ratio of organic sulfur can be described with an Arrhenius empirical equation.The rate constant,pre-exponential factor and the activation energy of the reaction increased with the decrease in particle diameter....
2020-06-12 16:16:27浏览：1408
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Flow Simulation and Optimization of Plasma Reactors for Coal Gasification
This paper reports a 3-d numerical simulation system to analyze the complicatedflow in plasma reactors for coal gasification, which involve complex chemical reaction, two-phaseflow and plasma effect. On the basis of analytic results, the distribution of the density, tempera-ture and components' concentration are obtained and a different plasma reactor configuration isproposed to optimize the flow parameters. The numerical simulation results show an improvedconversion ratio of the coal gasification. Different kinds of chemical reaction models are used tosimulate the complex flow inside the reactor. It can be concluded that the numerical simulationsystem can be very useful for the design and optimization of the plasma reactor....
2020-06-12 16:16:26浏览：1406
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Blended coals for improved coal water slurries
Three coal samples of different ranks were used to study the effect of coal blending on the preparation of Coal Water Slurry (CWS). The results show that by taking advantage of two kinds of coal, the coal concentration in slurry made from hard-to-pulp coal can be effectively improved and increased by 3%-5% generally. DLT coal (DaLiuTa coal mine) is very poor in slurryability and the stability and rheology of the resulting slurry are not very good. When the amount of easily slurried coal is more than 30%, all properties of the CWS improve and the CWS meets the requirements for use as fuel. Coalification, porosity, surface oxygenic functional groups, zeta potential and grindability have a great effect on the performance of blended coal CWS. This leads to some differences in performance between the slurry made from a single coal and slurry made from blended coal....
2020-06-12 16:16:25浏览：1434
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