In this paper, the optimum process parameters were obtained through treating phenol of simulated semi-coking wastewater using heat, Fe2+, Fe0 and semi-coke to catalyze persulfate. The results of phenol decomposition using PS catalyzed by heating, Fe2+, Fe0 and semi-coke were compared for selecting a better activating way. The article investigated the effects of temperature, catalyzer dosage, pH value and reaction time. The experiment showed the four methods can all catalyzed the process. Under the experimental conditions of heating, Fe2+, Fe0 and semi-coke degradation rate could reach to 20.7%, 75.1%, 94.5% and 40.0%, respectively. On this basis, this study established an L16(45) table to analyze the main influencing factors in semi-coke/Fe0 catalyzing system. Under the optimum conditions, the degradation rate of Phenol reached to 93.6%. However, the PS dosage was reduced by 14.4%.
This paper will present a detailed analysis of the deformation mechanism and stability assessment of the slope through field investigations, numerical modeling and measurements. Field investigation indicated that three thin coal seams encountered large mined-out area at one side and free surface of hill slope at the other side, which lead to the caving of roof strata movement, ground movement and crown crack along the preferred orientations of joints. The three-dimensional numerical modeling study on the case demonstrated that the plasticity failure occurred gradually along with the extension of mined-out area in depth. When the depth of mining reached the verge defined by the seismic prospecting method, a large mount of tension failure occurred on the crown of the slope. The factor of safety was 1.36 calculated by the shear strength reduction technique, which indicated the slope was in stable state. The measurement showed that the residual deformation occurred before 1998 and became stable subsequently, which indicated that the residual deformation almost finished and the slope is in stable state.
For spontaneous combustion possibilities under large flux methane drainage in the goaf, dynamic permeability in combination with the Forchheimer nonlinear equation was used to solve the problem of 3D oxygen distribution, heating law in goaf and to forecast the effects of fire protection by taking the fifth section face of the No.18 coal seam in Nanshan Coal Mine as the basis for this study. The results demonstrate that if the vertical position of the drainage laneway is so low as to cause serious air leakage, a high oxygen concentration area exists in the return side of the goaf, and there is also a high temperature region which has faster heating rate than in the other areas. The effect of methane drainage on goaf heating can be alleviated dramatically by simultaneous plugging and nitrogen injection. The results show that gas data in the return side of the goaf must be detected carefully in the work face, which is of similar drainage arrangement. Therefore, comprehensive fire protection measures should be carried out if conditions permit.
The numerical simulation is used to research the influence of nitrogen injection on spontaneous combustion in goaf. The spontaneous combustion mathematical model on the coupling of air flow field, oxygen concentration field, and residual coal temperature field was established with nitrogen injection in goaf. Then the software of numerical computation was programmed by Finite Volume Method. Combined with the example, the distributions of air flow field, oxygen concentration field and residual coal temperature field at different nitrogen injection volume were obtained by the software. The results show that the nitrogen injection could effectively prevent the spontaneous combustion fire in goaf and the highest temperature in goaf decreased with the nitrogen injection volume increasing. Finally, the accuracy of the numerical simulation was verified by the temperature observation in field. The achievement of this research is of theoretical and practical significance for the prevention of coal spontaneous combustion in goaf.
To simulate the variety of big coal sample permeability during the rupture process under quasi-plane strain state, a series of experiments have been performed by a set of self-made coal-gas coupling test system. The test results indicate that the development trend between the permeability rate-strain curve and the stress-strain curve of big coal sample is almost consistent. The permeability rate-strain curve is general hysteretic to stress-strain curve, indicating the close relativity between the evolvement of damage and the development of permeability rate. However, there is time interval between them and the permeability rate peaks value when the sample reaches the softened stage after the peak stress. Based on the characteristics of permeability rate-strain curve, three stages were plotted out: the stage before minimum permeability rate (k 0), the stage between minimum and maximum of permeability rate and the stage after the maximum permeability rate (k max). According to the three stages of permeability rate, the segmental curve equations of permeability rate-strain were fitted: the first stage can be fitted with negative exponential function; the second stage can be fitted with Boltzmann equation; and the last stage can be fitted with multinomial equation.
According to the positive correlation of coal ash content and natural gamma, using a new coal core reposition method, which is ordered by global and local extreme, coal samples from medium-thickness seam are reasonably located. Integrated the data of coal macrostructure characteristics, coal petrography analysis and coal gas production test, it studies the relationship between coalbody structure and amplitude variation of different well logging data, and the tectonic coal recognition method with well logging data in fresh-water mud invasion. The results show that: the anomalous response of natural gamma ray, neutron, density and apparent resistivity does not reflect the coalbody structure type. In fresh-water drilling mud invasion, using the crossplot technique of dual-lateral, RXO resistivity response and the coalbody structure can classify granulated coal accurately; the proposed method is of good practicability and high reliability.
Double-layer, multi-roller plate crusher is a new device, that uses a multi-stage series crushing style to break particles, with the crushing ratio distribution directly influencing the machine’s performance. Three crushing ratios of 2.25, 2.15 and 2.01, used for fuzzy physical programming, were determined. The comparison of the optimized result between the double-layer multi-roller plate crusher and a high pressure roll grinder showed that the double-layer multi-roller plate crusher had a better performance, reducing crushing force and wear.
When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system.
Experiments simulating the effect of coal mine stopping through a fault zone were designed based on a working face of the Qianqiu coal mine in Yima, China. Through simulation of the physical process of fault reactivation and coal bumps, the displacement of the surrounding strata and evolution characteristics of fault stress under the effect of mining were studied. The mechanism of fault reactivation induced by coal mining was analyzed. The results show that shortly before fault reactivation, the normal stress and shear stress increased rapidly and the risk of a fault slip occurring was also increased. The fault reactivation, caused by the mining activity, occurred when the working face was 25–35 m from the fault along the hanging wall. The influence of mining increased the possibility of fault reactivation, while the local failure of the bearing capacity of the working face was the direct cause of the fault slip. Our results indicate that the influence of fault slip on the coal of the working face had a transient impact and acted as a loading-unloading function.
The importance of simultaneous coal and methane extraction and its significance on green exploitation is stated, and current research situation of simultaneous coal and methane and faced new problems are introduced. The research progress on movement of overlying strata and stresses change in them, cracks development during mining in overlying strata and methane emission under disturbance of mining as well as the changing rules of permeability and methane flow under the disturbance of mining is analyzed. The progress on practice of simultaneous coal and methane extraction is analyzed. The deficiencies of current research and further researching fields on simultaneous coal and methane extraction are pointed out.
Aspen plus software was employed to simulate the opposed multi-burner gasifier (OMB) methanol production process. The system concludes gasification scrubbing system and purification shift system. The distributions of ammonia concentration in streams were obtained. The study demonstrates that ammonium crystallization problem caused by ammonia accumulation, and if the process has ammonia exports its concentration will greatly reduced and the ammonia salt problem will effectively alleviate. Aspen plus simulation is a useful tool for improving water quality, maintaining stable production, strengthening the ammonia recycling use and reducing pollutant emissions.
Hydraulic fracturing is designed to form a high-conductivity fracture. The proppant will embed into the formation rock, especially in soft rock, owing to the interaction between proppant and fracture surface after fracture closure. Proppant embedment would reduce the fracture width and then lower the fracture conductivity. According to dimensional analysis, the rock is assumed to be an elastic material. Using the theory of elasticity to describe the stage of elastic deformation and analysis of the corresponding simplified embedding process, the study establish the static computation model of the two-dimensional infinite half plane and three-dimensional infinite half space model of the proppant embedment. According to laboratory results, the calculation model was modified, got an effective correction factor and analyzed the causes of errors, then discussed the factors which have impact on proppant embedment. The result calculated by the model in this paper can be reference of proppant optimization in on-site fracturing for a certainty degree.
Based on the engineering background of double-unit face mining under complicated geological conditions and the lagging fully-mechanized face surpassing the fore mechanized face of double-unit face in Zhou Yuanshan coal mine, strata-pressure behavior in the process was analyzed based on FLAC 3D and on-site measurement. The results show that the stress concentration factor of superposition abutment pressure and the alternate distance of double-unit face are meeting gauss function, the relationship between the depth of stress concentration point and alternate distance also meets gaussian function. When the alternate distance is larger than 24 m, the superimposition of pilot support pressure in the double-unit face is weak. When the alternate distance is more than 12–15 m, the changes of the roof subsidence coefficient and the depth of stress concentration point are stabilized; when the alternate distance is 3–6 m, the fore working face end is in the greatest impact area of superposition abutment pressure, this area should be avoided in determining the reasonable alternate distance.
In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal mining industry. However, during the engineering applications, it is observed that the efficiency of gas drainage initially improves, but reduces thereafter. Thus, it is speculated that the contrasts in coalbed methane drainage efficiency may reflect variation of the closure behavior of the artificial fracture created. Based on comprehensive gas drainage monitoring data in underground coal mines, the work presented herein uses numerical simulation to show the behavior of the time-dependent closure of coal seam fractures associated with various levels of waterjet fracturing parameters and geomechanical conditions.
Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation. A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission. The test comparison analyzes the acoustic emission load and CT images for an effective observation on the entire process, from crack propagation to the samples’ destruction. The box dimension of the coal samples’ acoustic emission series and the CT images were obtained through calculations by using the authors’ own program. The results show that the fractal dimension of both the acoustic emission energy and CT image increase rapidly, indicating coal and rock mass has entered a dangerous condition. Hence, measures should be taken to unload the pressure of the coal and rock mass. The test results provide intuitive observation data for the coal meso-damage model. The test contributes to in-depth studies of coal or rock crack propagation mechanisms and provides a theoretical basis for rock burst mechanism.
Based on the features and requirements of gas drainage system, an optimized explosion resistance technology is done after a comprehensive analysis and research about the triple IR (Infrared Ray) flame detection technology, explosion resistance valve technology and explosion resistance control technology. An intelligent PLC (Programmable Logic Controller) resistance control system is designed which can cut off the gas branch quickly and accurately, and the controller have automatic pressure maintaining function, valve rotation limit function, remote and local control interlock function. The reliability and rationality of explosion resistance technology is verified by gas pipeline explosion propagation and resistance simulation test. Overall response time of explosion resistance system is less than 100ms, and the spread of fire in gas pipeline can be prevented effectively.
Through the montmorillonite settlement experiment in the clear water and electrolyte solution, the influence of slime water settling character was studied in clear water and different electrolyte solution, the montmorillonite’s hydration expansion effectively restrained was verified, the process method to wash coal with the electrolyte was put forward, and the results indicate that the solution of 10 g/L KCl is optimal inhibitor on the montmorillonite in the tested three kinds of electrolyte solution. With the contrast test in clear water and electrolyte solution, two reagent adding way can be selected in KCl solution: one way is to add PAM separately, the effectively sedimentation can be made with simply 0.1% anion; the other way is the coordination with polymeric aluminum and PAM, the anionic of PAM and polymeric aluminum are 0.02% and 0.5% respectively. However, in clear water, the polymeric aluminum must be joined together with the anionic PAM, and the amount of the PAM reaches 0.5%, which is 25 times as great as that in KCL solution. The field work with raw coal further verifies the above conclusions further.
Via multi-dimensional gas chromatography, configured with parallel dual-channel, double detectors, valves switching and back flushing, rapid analysis of the gas compositions consisting of C1–C5 hydrocarbons and permanent gases, such as CO2, H2S, H2, and CO, for direct coal liquefaction has been realized. With four packed chromatographic columns, which are Hayesep-Q pre-column, Hayesep-Q column, molecular sieve 5A column and one PLOT Al2O3 S capillary column, the gas compositions for direct coal liquefaction are analyzed qualitatively and quantitatively by the external standard method. The determination method has such advantages as excellent separation, simple operation, rapid analysis and accurate results.
The reaction characteristics of phenolic hydroxyl group were studied under the conditions of direct coal liquefaction. 2-naphthol was used as a coal model compound in this study. Under the conditions of with and without catalysts, a series of experiments were conducted at different temperatures, pressures and reaction time. Gas chromatography-mass spectrometry and gas chromatography were used to identify and quantify the reactants and products respectively. The conversion of 2-naphthol rises with the increase of reaction temperature, initial pressure and catalyst amount. The results indicated that temperature had a significant effect on 2-naphthol conversion, which promoted the dehydroxylation reaction. However, initial pressure had an important influence on the hydrogenation of 2-naphthol and naphthalene. The iron catalyst plays a significant role of cracking instead of hydrogenation. It is concluded that the harsh reaction conditions of high temperature, high pressure, and more catalyst are conducive to promoting dehydroxylation of 2-naphthol. The reaction mechanism was put forward based the experimental results, in which 2-tetralone was an intermediate.
