Abstract: In view of the technical parameters of cumulative blasting to improve the permeability of coal seams with low permeability, under the condition of constant charge diameter, blast holes were designed with different charge coefficients and blast spacings, and then field test was carried out. The variation of gas drainage pure quantity before and after blasting was comparatively analyzed in blasting influence area, and the influence of blasting parameters on the permeability-increasing effect of coal seams was investigated on the basis of experimental data. It is shown that the permeability-increasing effect of coal seams can be improved by controlling blast-hole radial charge decoupling coefficient, axial charge length, sealing reliability, and blasting times.
Considering the actual situation of mines, the microseismic event probability factor, the monitoring area importance factor and the network layout feasibility factor were introduced to rebuild the objective function of monitoring network optimization based on the theory of D-optimal design. Taking microseismic monitoring in a phosphate ore for example, the mining area was zoned according to the importance of the monitoring area, the feasibility of the network layout, etc., and then the reference values of relevant factors were given by the expert investigation weight method. The monitoring region was rezoned according to the differences of these influence factors, and the integral form of the objective function was given with the control point coordinates of the monitoring region as the corresponding range of integration. The dynamic optimization design principles of microseismic monitoring were proposed, and the optimal plan of a microseismic monitoring network in this phosphate ore was established finally based on the above study. Field blasting test shows that the monitoring network is rational and valid to a certain degree, the average error of the three coordinate directions is 6.74 m, the maximum error is 10.05 m, and the spatial positioning error is 12.51 m. This positioning accuracy can satisfy the field engineering demand.
Abstract: This article introduces a mine fire visualization simulation method based on cellular automata. On the basis of mine tunnel visualization, a tunnel fire combustion model for expressing cellular temperature and a tunnel fire smoke spread model for expressing cellular concentration were built by fire cell characterization. In these models the influence of fuel type and input density, ventilation and roadway slope on mine fire ignition and the effect of double diffusion, ventilation, buoyancy and throttling on fire smoke spread were taken into account, and a probability function was used for cellular automata modelling. Then according to the fire cellular combustion evolution rules and smoke cellular spreading evolution rules, the spatial changes of tunnel fire burning and harmful gas concentration were demonstrated through visualization means. Actual data from a mine proves the feasibility and effectiveness of tunnel fire simulation based on cellular automata.
The reasons for the pressure rake of deep cone thickeners were studied On the basis of deep cone model dynamic settlement test and rheological parameters measurement. It is found that there are two reasons leading to the pressure rake of deep cone thickeners. The first is poor flocculation sedimentation caused by the fluctuations of incoming tailing concentration and flocculant dosage; and the second is the slurry's rheological parameters mutation resulting from the difference of deep cone slurry concentration distribution caused by intermittent filling discharge. This research on the pressure rake of deep cone thickeners can provide a theoretic basis for deep cone normal operation, accident forecasting and getting rid of accidents.
Abstract: Separation of nickel and cobalt from bioleaching solution was studied using a synergistic extraction system of P507 and Cyanex272. Test results indicate that the system has a better extraction effect. Combined with the system characteristic of high acidity and low cobalt-to-nickel ratio, the separation effect of nickel and cobalt was compared in three extraction systems of P507, Cyanex272, and P507-Cyanex272. P507-Cyanex272 was identified to have a good separation effect of nickel and cobalt at the initial pH value of 1.5 to 2.2 and the balance pH value of 4.00 to 5.25. Influence factors on separation of nickel and cobalt in the extraction system at 28℃ were examined systematically, and the best processes for this synergistic extraction are the P507/Cyanex272 mole ratio of 3:2, the saponification rate of 60%, the extractant volume fraction of 10%, and the organic to aqueous phase ratio of 1:4. Under these conditions, the first extraction rate of cobalt is 99.16%, and the separation factor of nickel and cobalt is 932.59.
Abstract: Oxygen partial pressure has important effect on the sintering process of iron ores. Sintering experiments were carried out in different atmosphere conditions. It is found that the mineral composition of the sinter is mainly hematite and calcium ferrite, and acicular calcium ferrite appears in a stronger oxidation atmosphere. No obvious difference in mineral composition while the oxygen partial pressure is in the range of 7.10×10-4 to 7.89×10-5 Pa, but magnetite appears in local region. When the oxygen partial pressure decreases from 4.44×10-5 Pa, magnetite obviously increases but hematite simultaneously decreases. To achieve an appropriate mineral composition and structure of high basicity sinter, the oxygen partial pressure should be controlled in the range of 2.12 ×104 to 7.10×10-4 Pa.
Abstract: The defined oxidation ability of metallurgical slag based on the ion and molecule coexistence theory (IMCT), i.e., the comprehensive mass action concentration of iron oxides NFetO, was verified by comparing the calculated NFetO and the reported activity of iron oxides αFetO in selected 14 slag systems. To calculate NFetO in the selected slag systems, a thermodynamic model for calculating the mass action concentrations of structural units in CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 type slag systems, i.e., the IMCT-Ni thermodynamic model was developed. NFetO in the other 13 slag systems can be obtained by simplifing this IMCT-Ni. It is shown that the defined comprehensive mass action concentration of iron oxides NFetO is more accurate than the measured activity of iron oxides aFetO in characterizing the oxidation ability of the selected FetO-containing slag systems.
Abstract: A comprehensive mathematical model was established to develop and deeper understand direct reduction technology for rotary hearth furnaces (RHF). The model consists of the overall thermal and chemical balance model, the calculation model of heat balance at different zones, the waste heat recovery process model, the drying model of green pellets, the checking model of furnace box temperature and waste gas dew point, and the RHF process model. The basic process parameters of RHF were calculated by the model. Calculation results show that the overall energy consumption is effected by gas calorific value, waste gas temperature, and the recycling scheme of waste heat recovery. When the gas calorific value increases by 50 kJ·m-3, the theoretical combustion temperature increases by 22 to 25℃, and the gas consumption decreases by 41 to 47 m3·t-1. But when the preheating temperature increases by 100℃, the theoretical combustion temperature increases by 35 to 40℃, and the gas consumption decreases by 90 to 103 m3·t-1. Furthermore, the model can be applied to calculate technical parameters when the raw materials and fuel conditions are different, and the change laws of these technical parameters under different waste heat recovery processes can also be studied by this model.
Abstract: Solid-state decarburization kinetics of high-carbon ferrochrome powders was investigated by microwave heating. Calcium carbonate powders were used as a solid decarburizer. The high-carbon ferrochrome powders and calcium carbonate powders were mixed at the mole ratio between carbon in the high-carbon ferrochrome powders and CO2 decomposed from the calcium carbonate powders of 1:1 and 1:1.4. Then the mixtures were heated at different temperatures and decarburized in a microwave heating field. The carbon content of decarburized materials was measured and the apparent activation energy of decarburization reaction was calculated. Experimental results show that as the proportion of calcium carbonate in the mixtures enlarges, the decarburization rate increases, but the heating rate of the mixtures decreases. The decarbonization rate is higher at a higher temperature and for a longer holding time at the same mole ratio. The highest decarbonization rates are 65.56% and 82.96% for both the mixtures decarburized at 1200℃ for 60 min, respectively. Carbon activation diffusion and CO2 adsorption diffusion in the high-carbon ferrochrome powders are enhanced in a microwave heating field. Solid-phase decarburization approximates the first-order reaction and the apparent activation energy of decarburization reaction is 68.43 kJ·mol-1.
Abstract: The distribution behavior of bubbles in consideration of casting speed and electromagnetic braking in a slab continuous casting mold was investigated by the method of sampling statistics. The effects of electromagnetic braking and casting speed on the size, number and distribution of small bubbles were analyzed in detail. Experimental results show that bubbles with the diameter less than 0.1 mm account for 57%, 0.1-0.5 mm for 42.5%, and bigger than 0.5 mm for 0.5%. The deeper the subcutaneous distance is, the smaller the bubble size is. The number of bubbles in the narrow side is 50% more than that in the 1/4 position, and the number of bubbles in the 1/4 position is the least. With increasing casting speed, the size of bubbles decreases and the position of clusters moves from 9 to 12 mm in the slab subsurface at the 1/4 position and the narrow side, but bubbles gather at 3 mm of subsurface at the low and high casting speeds. When electromagnetic braking is applied, the size of bubbles becomes big in the center, but small in the 1/4 position and the narrow side, and the number of bubbles overall declines, significantly the number of cluster bubbles.
Abstract: The influence of the state of prior austenite grains before dynamic transformation on the multi-phase microstructure and mechanical properties of hot-rolled Nb-V-Ti microalloyed TRIP steel based on dynamic transforma-tion of undercooled austenite (DTUA) was investigated by uniaxial hot compression test, scanning electron microscopy, and X-ray diffraction. In comparison with that prior anstenite grains are equiaxed before DTUA, when prior austenite grains are elongated before DTUA, the volume fraction of ferrite obtained by DTUA is higher, the volume fractions of bainite and martensite are lower, and the average size of bainite packets is smaller in the final multi-phase microstructure. But the volume fraction of retained austenite and the carbon content of retained austenite are similar in both cases. Compared with hot-rolled TRIP steel based on DTUA without micro-alloying elements, hot-rolled Nb-V-Ti microalloyed TRIP steel based on DTUA demonstrate higher yield strength and tensile strength, but lower elongation.
Abstract: Continuous hot deformation testing of Inconel 690 cone samples at three different temperatures (1100, 1140 and 1180℃) was performed with a hydraulic press machine. Dynamic recrystallization in the alloy during con-tinuous hot deformation was studied by optical microscopy and back scattering diffraction. It is found that dynamic recrystallization in Inconel 690 happens during continuous hot compression deformation. The nucleation of dynamic recrystallization is in the order of triple junctions of grains → strain-induced boundary migration → twin boundaries → inside of grains, and the twin promotes the recrystallization process of Inconel 690.
Abstract: Tensile fatigue experiments were performed to study the characteristic of temporary stable magnetiza-tion states under fatigue loading, as well as the distribution and variation of magnetic memory signal in the process of fatigue. Experimental results were analyzed and discussed using the modified J-A model. It is found that the temporary stable magnetization state of magnetic signal varies along a loop in a stress cycle and the loop changes when the fatigue load type changes, which indicates that it is reasonable using the modified J-A model to describe the magnetic memory phenomenon of metal. The change of magnetic signal is divided into three stages in the process of fatigue, which is explained according to the change law of parameter ξ″ (the parameter expresses the obstruction to magnetic domain wall motion) using the modified J-A model. The magnetic signal distributing in a ‘⌒’ shape around a defect is explained according to the distribution law of ξ″ around the defect.
Abstract: TiAlSiN coating was prepared on the GH4169 alloy surface by cathodic arc ion plating, the morphologies and energy spectra of its surface and interface were analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively, and the surface roughness was tested by profilometry. Friction and wear test of the coating was performed on a reciprocating friction testing machine, the point energy spectra and plane energy spectra after wear were analyzed by energy dispersive spectroscopy, the friction coefficient and wear property of the coating were studied, and the wear mechanism was discussed. Experimental results show that the structure of the coating surface is compact and the surface roughness is 194.57 nm. The coating is mainly composed of Ti, Al, Si and N elements, and the grains of TiN and AlN are refined by Si atoms. Chemical reactions and mutual diffusion of elements occur in the coating interface, and the combining form is chemical bonding. The average friction coefficient of the coating is 0.493, and the wear form is abrasive wear. The plane scanning results of wear traces indicate that Al and Ti nitrides in the coating decreases after wear, Si and N atoms have no significant reduction, and the increase in wear resistance of the coatings is mainly dependent on the compound formed by Si and N atoms.
Abstract: Lime mediated sludge Was Used as partial replacement for cement raw materials to produce cement. The adding amount of lime mediated sludge ranges from 0 to 30%. The influence of lime mediated sludge on cement performance was investigated. It is shown that adding 15% of lime mediated sludge into cement raw materials can significantly improve the calcining performance, the mineral phase crystal structure and the clinker's morphology, and the cement strength is also remarkably enhanced. The improvement capability of lime mediated sludge gradually declines with the increase of lime mediated sludge. When 30% of lime mediated sludge is added, the properties of the obtained cement are similar to those without adding sludge. Toxicity characteristic leaching test results indicate that after lime mediated sludge addition, heavy metalconcentrations in clinker and cement are higher than those in clinker and cement without lime mediated sludge, while the leaching concentrations are very low, Cu, Zn, Pb, Cr and Ni contents in the leachate are all below 1 mg·L-1, which canmeet the People's Republic of China Standard GB 5085.3-2007, with no risks of secondary pollution.
Abstract: A pure polyurethane film and a modified polyurethane film containing ultraviolet light absorber UV-531 were prepared by spin-coating. Accelerated aging tests of the films exposed to ozone atmosphere, UV radiation, and UV/ozone atmosphere, were performed by using self-designed aging equipment. The aging behaviors of the films exposed to different atmospheres were evaluated by color difference, yellowness index, UV-Vis spectra, and Fourier transform infrared spectra. There is distinct synergistic aging effect between ozone-aging and UV-aging on both PU and M-PU films. The yellowing resistance properties of the polyurethane film in UV radiation atmosphere, UV/O3 atmosphere, and short-time ozone atmosphere can be improved by adding 0.2570 UV-531 into the film. The urethane structures in the two films decrease with increasing exposure time during exposure to the studied three atmospheres.
Abstract: A bell-less blast furnace charging model was established by using 3D discrete element method. The flow behavior of particles in the hopper and rotating chute, the falling trajectory and heaping process of particles discharged from the rotating chute were modeled and analyzed by using this model. Consequently, the charging process was reproduced visually. It is found that size segregation is always prevalent throughout the flow process of particles. The discharging flow from the hopper is funnel flow, and small particles tend to be discharged in the later stage due to size segregation. It is proved that the influence of chute inclination angle on the particle behavior and heaping process is very significance. The granular flow in the chute deviates upward to one side and tumbles attributing to rotation. Small particles close to the chute wall surface move to the inside of the stream, while large ones staying at the upper part of the chute flow move to the outside. The falling trajectory of particles is affected by particle size segregation, deflection and tumbling, and velocity distribution. During the process of burden falling and heaping, large particles are apt to segregate to the center and periphery of the furnace throat, while small particles locate under the pile top and they are partial to the center due to locating inside the stream and permeation. The applicability of the model has been verified by the measurement results of burden trajectories based on the laser grid in-furnace measure technology.
Abstract: To accurately measure target surface heat flux under water jet impinging, a new experimental method to calculate the heat flux of a target plate was introduced, which included adding a heat adiabatic material under the target plate, measuring the target plate temperature at one-point only, and using a one-dimensional inverse heat transfer. Experimental data analysis indicates that the probability of the relative error within ±5% is 93%. Because the bottom surface of the target plate is approximated to adiabatic condition, the inverse heat transfer calculated temperature of the bottom surface is slightly higher than the measured one. It is concluded that by adding a heat adiabatic material under the target plate, the accurate results of temperature and heat flux distribution of the target plate can be obtained easily even using a single-point temperature measurement method.
Abstract: The digital speckle correlation method was used to achieve fast and high-precision measurement of in-plane displacement under high temperature conditions. A plane array 532 nm laser used as the light source and an optical processing system which is composed of a 532 nm narrow band filter and an adjustable attenuator were a good solution to the imaging problem in this high-temperature case. An artificial speckle making method was described. In this method, high temperature ink resisting about 1000℃ was used as the speckle material, the artificial speckle under this situation was clear and good to image correlation calculation. An in-plane displacement detection system was built under high temperature conditions, micrometer moving displacement detection tests were carried out under different brightness values at room temperature, and thermal deformation field measurement tests of steel locally heated continuously to 1000℃ by blowtorch was also made. Test results show that the system can be used for the measurement of object displacement or deformation field at room temperature and high temperature conditions with the advantages of strong anti-jamming capability, high accuracy, and easy realizing.
Abstract: The temperature field and stress field of friction discs with circumferential and radial grooves during sliding processes were simulated and analyzed by direct coupled finite element method on the ANSYS platform. During this simulation the following factors were taken into account:the heat produced during the rubbing transfer of the friction disc and the separator disc, the heat transfer between the friction disc and lubrication or outside air, and displacement constraints. Simulation results reveal that the highest temperature and the biggest stress are 148.1℃ on the friction disc surface and 146 MPa in the groove, respectively, and they both appear in the earlier process. An ellipse hot spot forms on every small friction surface, and temperature in the middle is higher than that in the surrounding. Along the radius direction, the larger the radius is, the higher the temperature is, and the temperature distribution is a convex parabolic profile on the small friction surface and a concave parabolic profile on the small groove surface.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
