Exploration on the Principle of ECMB

ECMB, which is developed by Amoco company in USA, has very prospective. On the basis of the study on adsorption characteristics of mixture gas in coal, the principle of ECMB has been explored. The order of adsorption capacities of coal for several gases is: CO 2>CH 4>N 2>H 2 when coal adsorbs gas. In 2 member mixture gases, adsorption capacities of coal for mixed gases, methane and carbon dioxide tally with Langmuir equation, but not does for nitrogen and hydrogen. The substance of the increasing drawing ratio of coal seam gas by using ECBM is decreasing adsorption amount of methane in coal by emptying the other gas or gases into coal seam. N 2 is better gas than CO 2 in the process of using ECMB.     

The Influence of In-situ Stress Gradient and Geothermal Temperature on The Calculation of Coalbed Gas Pressure

On the basis of coal seam having outcrop of coal seam and outlet on ground,the method for calculating coalbed gas pressure from the one-dimensional stable gas flow equation by considering deeply the influence of in-situ stress gradient and geothermal temperature is presented. In some mine, the theoretically computing and measuring results of coalbed gas pressure show that the in-situ stress gradient and the geothermal temperature have important influence on the calculation of coalbed gas pressure, and if the factors are drew into the calculation of coaled gas pressure,it will make the results much more accurate.     

Numerical simulation of seepage field of gas extraction drilling of single bedding of mining-coal bed

Aiming at the problem of reasonable decorate of coal gas extraction drilling, combining with the initial and boundary condition of borehole extraction, the solid and gas coupling mathematical model of gas seepage of borehole extraction is deduced based on established control equations of seepage field and deformation field. Taking gas extraction of stone coal slit as an example, according to the characteristics of coal seam in the research, the numerical simulation method is used to obtain the distribution rule of gas pressure, coalbed gas permeability, and coalbed gas seepage velocity as well as seam deformation. The effective radius of gas extraction drilling of single bedding about mining-coal bed is determined, which provides the basis for optimum arrangement of gas extraction drilling of single bedding. The results show that the effective radius of stone coal is about 4 m. If the prolonging drilling drainage time is less than 20%, the drilling quantities would reduce by about 50%.     

Analysis and numerical simulation of fluid-structure coupling of gas drainage from boreholes

Gas drainage from boreholes is main method of utilization and management of Chinese coal seam gas. As the exploitation depth increases, stress field and other factors on the impact of gas seepage are increasingly apparent. Based on the basis of a series of assumptions of coal seam gas, porosity and permeability equations are described by considering stress, coal seam gas pressure change on the coal produced by deformation of the skeleton. The fluid-structure coupling equations are derived by using the basic theorem of porous media flow and the fluid structure coupling theory. The gas seepage field is simulated and analyzed by using multi-physics coupling analysis software. The effect of gas pressure distribution, different burial depths and different drilling parameters (drainage negative pressure, drilling radius) on gas seepage field is obtained. Analysis of simulation results can provide theoretical guidance for on-site gas drainage.     

Study on Adsorption Characteristics of Coal to Gas in Geophysical Field

It is very important to mine safe exploitation, gas drawing and predict of coal and gas outburst that adsorption characteristics of coal to gas in geophysical field are studied. Adsorption and desorption characteristics of coal to gas in geophysical field have been reviewed in detail, then it is obtained that adsorption characteristics of coal to gas in electromagnetic field should be further studied . Adsorption and desorption characteristics of coal to methane in alternating electric field (AEF) have been studied mainly. Adsorption characteristics of three coal samples in AEF have been studied by means of Volume Method. The result shows that chemical properties and matter constituent of coal surface are no changed , adsorption and desorption of the coal samples in AEF well accord with Langmuir equation and two constants empirical formula, and because coal potential energy is increased and coal temperature is raised caused by Joule heat effect , adsorption ability of coal is decreased, and the desorption process is slowed down in AEF.     

Mechanism analysis of permeability based on promoting coal matrix shrinkage by water jet

High pressure pulsed water jet (HPWJ) is a new technology of effectively improving coal seam permeability. However, the mechanism of increased permeability is not yet clear, which restricts the application of HPWJ in different coal seams. From the perspective of improving permeability by coal matrix shrinkage, the impelled dynamic equations is established based on analysis of coal dynamic effects by water jet. According to theoretical analysis of the stress state of coal matrix, it is concluded that HPWJ can promote coal matrix shrinkage, and the relationship equation between jet impact-coal matrix is derived. Besides, the gas seepage function in the coal slotted by the HPWJ is gained by using PM model, which provides theoretical support for generalizing the technology in the coal mine.     

RESEARCH ON THE MECHANISM OF GAS OUTBURST INITATION IN MINES

The mechanism of coal-gas outburst iniration is comprehensively analysed. The direct courses of initating coal-gas outburst are the sudden loss of confining stresses and the gas pressure gradient in coal seam. The effects of working face's advancing rate, geological conditions and gas pressure gradient as well as mechanical & physical characteristics of coal on outburst initation are expounded by means of mathematic analyses about gas seepage which takes place in coal seams. The results are of certain practical significance and reference value to further quantitive study of outburst and its predication.     

Analysis on rock cross-cut coal uncovering using high pressure water jet slotting in close distance seam group

Safe production and procedures at the driving face are restricted in mines of Guizhou province by the long periods required for rock cross-cut coal uncovering in high gas coal seam group. A new method is proposed to solve this problem using high pressure water jet slotting in penetration boreholes. This is proposed to increase the gas desorption rate and reduce drilling hole, which will shorten the cycle of rock cross-cut coal uncovering. Numerical simulation is used to compare the pressure relief effects of different slotting methods in penetration boreholes. The results show that the pressure relief effect of slotting all coal seams is more ideal. Field application indicates that high pressure water jet slotting has good effect of the pressure relief in coal seam group. The drilling number is reduced by 30, the drilling length is shortened by 610 m and the standard time of gas pre-pumping decreases by 39 days.     

Mathematical Model of Methane Transport in Coal Seam

This paper studies the effects of ground stress and ground electrical field onmethane transpont in coal seam. A gas seepage equation is set up based on the principles of seepagetheory,which takes the ground stress and ground electrical field into considerationz     

Experimental analysis of matrix shrinkage’s influence on mechanical permeability of gas filled coal

Based on the coal seam of Zhao zhuang coal mine and Si he coal mine belong to Jin cheng anthracite Mining Group in Shanxi province, by using the self developed three axial servo controlled seepage equipment for hot fluid solid coupling of coal containing methane, parallel experiments for permeability of helium and methane under different gas pressures are carried out to quantitatively study the influence of Klinkenberg effects on the permeability of coal. Meanwhile, the problem of permeability decreasing caused by fluid pressure decreasing and gas desorption is eliminated by controlling the effective stress. The results show thatthe Klinkenberg effect is obvious under low gas pressure. With the increase of gas pressure, the permeability of coal decreases at first and then increases. The inflection points of gas pressure for Klinkenberg effect are about 0.9 MPa both for coal samples in Zhao zhuang coal mine and Si he coal mine. When the effective stress is constant, with the increase of gas pressure, the permeability increment caused by Klinkenberg effect decreases, while permeability increment caused by coal matrix shrinkage increases. Coal matrix shrinkage has a close relationship with the mechanical properties of coal rock mass. For the coal sample with a poor mechanical property, coal matrix shrinkage is more obvious.     

Theoretical Analysis on 13-Bit Lattice Gas Automata Model with Poly-velocity and its Simulation

An 13 bit lattice gas automata model has been investigated from fluid discrete dynamics. By gaining the moment equations from lattice Boltzmann equation and using Chapman Enskog expansion, the fluid dynamics equation and energy equation of 13 bit lattice gas automata model with polyvelocity have been deduced. The validity of the model using for non isothermal fluid dynamics has been proved . Finally, simulation results for non isothermal flow pass plate have been shown     

STUDY ABOUT FLOW THEORY AND GOVERNING EQUATION OF GAS SEEPAGE FLOW IN COAL BEDS

This paper analyzes comprehensively the present approaches about the flow theory and governing equation of the gas seepage in China from the equations of the gas flow continuity, motion, state ane content. The viewpoint is put forward in the paper that the gas amount taking part in seepage flow is only a part of the whole gas content. The governing equation, of gas seepage flow in coal seams is set up on condition that procedures of adsorption and desorption are convertible completely.     

The application of deep hole pre-split blasting to gas improved extraction in high hydrogen sulphide mine

As the present result of gas extraction by conventional methods in soft low permeability of high-gas mine is not satisfying, deep hole presplitting controlling blasting technology is adopted in Changwu Tingnan coal mine, Shaanxi province. The amount of a single drilling gas extraction increases by 1.36 times, face gas extraction rate edges up to 50% and seam permeability coefficient increases by 9 times. By taking some comprehensive measures, such as enhancing ventilation, drainage, extraction of hydrogen sulfide and lime slurry injection in the blast holes, the hydrogen sulphide is controlled in advanced and the concentration is controlled blow 2×10 -6~4×10 -6, thus the working environment is effectively improved and the safety in production is ensured.     

Triaxial creep model and its stability analysis of gas containing coal 

Investigation on the creep property of coal containing gas is an effective means for understanding the mechanism of delay outburst of coal and gas in a coal mine. This paper conducts triaxial creep tests on the specimens of gas containing coal using a self made creep experimental apparatus to determine the creep law for coal containing gas. An improved triaxial creep model is developed for containing gas by coupling a Nishihara model with another visco elasto plastic body which can describe the deformation property of non Newtonian fluids. The parameter fittings are conducted based on the experimental dada.The present model is examined in terms to the results of triaxial creep tests in various stress level cases. The result shows that the proposed model for gas containing coal can properly represent the creep deformation at different creep stages, especially at the accelerating stage. The instability condition of the model for coal containing gas is also discussed according to stability theories of differential equation solution.     

Coal and gas outburst disaster early warning andemergency response decision support technology

In order to realize early warning of coal and gas outbursts, and take timely emergency response, the technology of coal and gas outburst early warning and emergency response decision support is brought forward. The characteristics of abnormal gas outburst are specially analyzed, thus methods are given to monitor and identify the coal and gas outburst disaster. Combined with existing safety monitoring system in the mine, researches of such techniques are carried out as outburst gas content predicting, spread range forecasting and regions of power cutoff. Through those techniques, the Daping coal mine gas explosion disaster is retrieved. In the process of simulation, gas spreading early warning and related emergency response proposals can be issued before the gas arrive.     

Experiments on triaxial mechanical properties of soft coal containing gas

Taking briquette specimens composed by soft coal with outbursting trends as research object, systematic research of the influence on triaxial mechanical properties of soft coal containing gas caused by confining pressure and gas pressure is done. The results show that confining pressure can significantly affect mechanical properties of soft coal containing gas, the compression phase of soft coal containing gas is obvious and the triaxial strength is increased gradually as confining pressure is increased; the influence on elastic modulus and shape of stress-strain curve is not obvious. The triaxial strength of soft coal containing gas shows decrease trend as gas pressure is increased; the influence on strength of soft coal containing gas caused by gas pressure is obvious when the confining pressure is smaller, but it is not obvious when the confining pressure is bigger. the influence caused by gas pressure on elastic modulus and deformation of yield step is not obvious; gas pressure has not only obvious mechanical effects,but also have chemical action on soft coal containing gas; stress-strain curve of soft coal containing gas can be expressed by conic, the influence caused by gas pressure can be considered as equivalent confining pressure effects.     

DEVELOPMENT AND EXPERIMENTAL ANALYSIS OF HYDRAULIC LOCK OF THE THINNEST COAL SEAM SHEARER

The structure and work theory of a new type of hydraulic lock of the thinnest coal seam shearer is described in this paper. Its performance tests have been done the test results show that the performance of hydraulic lock is satisfactory and can be fit for the needs of locking and floating of the cutting drum of the thinnest coal seam shearer     

Establishment and analysis of dynamic mathematical model for coal gasifier

Based on the analysis of flowing combustion, gasification reaction, and lumped parameter, a three region model is established to predict the temperature and gas components of Texaco coal gasifier. Using mass balance and energy balance equations to each zone, the model takes account of gas solid two phase flow, coal pyrolysis, radiation heat transfer, and heterogeneous and homogeneous kinetic chemical reactions. Based on the model, a program is developed for dynamic and static simulation. After parameterization and simulation analysis, some important trends and conclusions are attained. Because the model can accurately predict the temperature and gas components in jet region, it has widespread engineering application value.     

Recent Research on Supervision Running State of the Tuyere and Raceway in Blast Furnace

The manipulators pay fully attention to the running state of raceway looked into tuyere peehole in blast furnace in its production process. And it is important for judgement and control the blast furnace. The pulverized coal feeding and burning cases can be supervised by peehole in tuyere. Temperature distribution can be studied by brightness and numerical simulation of pulverized coal combustion. The recent research of temperature examined and supervision technique of the tuyere and raceway in blast furnace are set forth at home and abroad. A method settling supervision and control the state of tuyere and raceway in blast furnace is put forward by coalescent numeric image process technique to numeric simulate two dimensional imaging technique.     

Analysis on the mechanical model in gob-side entry retaining of inclined coal seam

When gob-side roadways in inclined coal seam are retained by strike long wall mining method, the conveyor roadway are retained under ascending mining and the ventilation roadway is retained under underhand mining. In order to research the differences of roof activity in the two conditions, stack continuous layer boards model and load strips segmentation method are used and the influence of the coal seam dip angle is considered. Then the solving formulas of roadside support resistance under such conditions are obtained. Through comparison and analysis, it shows that roadside support resistance of conveyor roadway gob-side entry retaining is much greater than ventilation roadway gob-side entry retaining. When ventilation roadway gob-side entry retaining is used, roadside support resistance reduces with the coal seam dip angle increases. While conveyor roadway gob-side entry retaining is adoptel, roadside support resistance increases with the coal seam dip angle increases. But when the coal seam dip angle is larger than the natural repose angle of goaf caving gangue, the resistance can be reduced by considering the effect of goaf gangue accumulation. The conclusion provides reference for choosing mining sections order of gob-side entry retaining in inclined coal seam.