Applied Mechanics and Materials Vols. 448-453

Abstract: Multi-level mining caused confusion of air return of overall ventilation system in Jinshandian Iron Mine. Based on fluid simulation software ANSYS-CFX, a modeling method of replacing fans with negative pressure section was proposed to build accurate 3D global model of mine ventilation network. Four feasible ventilation network optimization schemes were proposed. Airflow speed of inlet and air pressure of outlet was simulated in each scheme. To the principle of minimum ventilation energy, the scheme of return air through out3 and-270m level was determined as the optimal scheme. Using orthogonal experiment, three factors and three levels of variance analysis of airflow speed in each return air shaft was carried on. The functions of negative pressure of fans to airflow speed of outlet was built to calculate the optimal negative pressure parameter of each fan, which could realize the optimal allocation of air quantity and pressure in ventilation system.

Abstract: Based on analysis of water inrush coefficients developed and applied in deep coal mining with high water pressure, the author proposes that there are some defects of water inrush coefficients in calculation and application. By simulation experiments on the water resistance properties of the aquiclude in a coal seam floor, the author arrived at the distribution and digital characteristics of residual pressure in the course of high-pressure water rising in the water-resisting floor. The formula for a water inrush coefficient has been further revised.

Abstract: In this paper, the author investigated the research on coalbed methane and water two phase flow, from microscale to macroscale and field engineering studies. The literature research shown that the microflow in pore scale should pay more attention, especially the mechanism of interaction between gas and water, interaction between fluid flow, adsorption, deformation and even thermal field.

Abstract: In this paper, the extraction of vanadium from Chinese black shale by roasting with mixture salt addition was studied. The effect of salt additions, temperature and time on the recovery of vanadium were investigated by mixture salt roasting and 2% H₂SO₄ leaching. The mixture additions of Na₂CO₃-BaSO₄ was used in the roasting process. The optimal roasting conditions for black shale were determined to be 2.5 hours roasting at 760 °C with the mixture additive SB of 10-15%. After being leached with 2% sulphuric acid, the leaching efficiency of vanadium was obtained in 85%. The pollution of waste gas was decreased in the presence of BaSO₄-Fe₂O₃.

Abstract: Based on systematic experiments in the 20-L Siwek sphere, the explosion behaviors of bituminous coal dust were investigated by changing the strength of pyrotechnic ignitor. The effect on the maximum explosion pressure (P_ex) and maximum rate of pressure rise ((dp/dt)_ex) of the ignitor strength is analyzed. Due to the under-or over-driven phenomena, the overly low or high ignitor strength may result in unrealistic P_ex and (dp/dt)_ex, especially for lower dust concentration. To evaluate the suitability of ignitor strength, the time scales (i.e. the effective action time, t_eff, and the induction time, t_i,) of the ignitor combustion and flame kernel development are introduced by analyzing the ignition process of dust cloud. It can be found that the t_eff significantly heightens and the t_i gradually decreases with the rise of ignitor strength. Moreover, when the t_eff is much lower than the t_i, the under-driven phenomenon will occur, which leads to the underestimated P_ex and (dp/dt)_ex. Conversely, when the t_eff is much higher than the t_i, the explosion tests may be over-driven to cause the overestimated P_ex and (dp/dt)_ex. For ideal ignitor strength, the t_eff would be comparable to the t_i. Based on these facts, the under-and over-driven phenomena can be effectively verified by comparing the t_eff and the t_i. As a result, when the dimensionless time ratio t_eff/t_i is 0.52 or 1.42, the explosion tests in the 20-L sphere would be, respectively, under-driven or over-driven. To obtain the realistic test results in the 20-L sphere, it is suggested that the t_eff/t_i value should be in the range of 0.8~1.2 as much as possible.

Abstract: Some of the most classical technologies and equipment for coal mine water hazards prevention and control are prevented in this paper. In addition, the application of these technologies and equipment is introduced. The typical technologies and equipment for coal mine water hazards prevention and control can be divided into four groups: exploration technology and equipment; monitoring technology and equipment; forecasting technology and equipment; groundwater inrush controlling technology and equipment.

Abstract: Coalbed methane (CBM) resources are abundant on the earth. CBM brings man-kind harm but its also a clean type of resource. This article based on the analysis of CBM exploitation and utilization at home and abroad, analyzed the key issues for the slow development of CBM industry in China combining the domestic practical situation of coal mine gas drainage, and also proposed suggestions of reasonably exploiting and utilizing CBM.

Abstract: The neutral grounding mode through resistance and the grounding resistance value of 1140V coal mining distribution system are studied and simulated in this paper. According to the 1140V power supply system parameter of the underground mining area of a coal mine, the PACAD software is used to establish the simulation model of power system. The single-phase ground fault caused by the insulation deterioration of the load equipment is simulated through setting single-phase ground fault in charge line of load side. The advantage of neutral grounding mode through resistance is analyzed through the simulation result. According to the distributed capacitance over the ground of simulation data and power network, the value range of the neutral point grounding resistance can be obtained.

Abstract: To improve the power quality of power grid in coal mine, a kind of detection and control method for unified power quality controller (UPQC) without phase locked loop (PLL) is put forward. It can get the positive-sequence component of unity fundamental voltage through Park transformation,and then obtains the positive-sequence active component of fundamental current after proper operation . The PLL or filtering of three-phase voltage and the synchronous coordinates transformation for current are cancelled. The control strategy of the system is studied and the effectiveness and validity of UPQC are verified by simulation results.

Abstract: The binary polymer AA/SAS was synthesized by acrylic acid (AA) and sodium allylsulfonate (SAS), named as AS and its structure was characterized. Its scale inhibition performance was also investigated for single CaCO₃, CaSO₄ scales, and composite scales in simulated formation water containing Ca²⁺, Mg²⁺, Ba²⁺ and Sr²⁺. The results indicate that when adding 50mg/L of the inhibitor, it is 85.05% efficient for CaCO₃ inhibition and 98.85% for CaSO₄, but only 49.05% and 51.58% for BaSO₄ and SrSO₄ separately. The scale inhibition performance is obvious in the simulated formation water with high concentration of calcium (1300mg/L) and low barium ion (100mg/L ), the inhibition efficiency are both above 85% at a dosage of 80mg/L. And it can fairly satisfy the demand of inhibiting composite scales (CaCO₃ scale, CaSO₄ scale, BaSO₄ scale and SrSO₄ scale), when AS and CT was combined at a mass ratio of 2:1 in high calcium , barium and strontium ions contained formation water, being 95.3% efficient at the dosage of 100mg/L.