查看更多>>摘要：Resistivity will have different response characteristics to the hydraulic fracture propagation process.In this work,a resistivity testing system for hydraulic fracturing specimens was established.Resistivity and acoustic emission(AE)information were jointly analysed to determine the dynamic response char-acteristics of resistivity during hydraulic fracture propagation.The results show that the water and frac-ture exert a competitive influence on the connection structure of the circuit,and there are two significant peak resistivity points in the curve,presenting a double peak therein.The peak resistivity data of the specimen with a larger fracture area are much different from the initial value.With the increase of the rate of injection,the range of variation of the highest value that can be reached with the specimen resistivity decreases.High resistivity rates or high resistivity fluctuations exhibit rapid a release of fracture energy.The fracture failure mode dominated by shear fractures makes the formation produce a"series+parallel"electrical connection structure;a calculation model of formation resistivity based on shear and tensile failure was proposed to characterize the proportion of different types of hydraulic frac-tures and elucidate the control effect of matrix resistivity on the electrical performance of the overall cir-cuit structure.
查看更多>>摘要：Horizon control,maintaining the alignment of the shearer's exploitation gradient with the coal seam gra-dient,is a key technique in longwall mining automation.To identify the coal seam gradient,a geological model of the coal seam was constructed using in-seam seismic surveying technology.By synthesizing the control resolution of the range arm and the geometric characteristics of the coal seam,a gradient iden-tification method based on piecewise linear representation(PLR)is proposed.To achieve the maximum exploitation rate within the shearer's capacity,the control resolution of the range arm is selected as the threshold parameter of PLR.The control resolution significantly influenced the number of line segments and the fitting error.With the decrease of the control resolution from 0.01 to 0.02 m,the number of line segments decreased from 65 to 15,which was beneficial to horizon control.However,the average fitting error increased from 0.055 to 0.14 m,which would induce a decrease in the exploitation rate.To avoid significant deviation between the cutting range and the coal seam,the control resolution of the range arm must be lower than 0.02 m.In a field test,the automated horizon control of the longwall face was realized by coal seam gradient identification.
查看更多>>摘要：The disintegration of granite residual soil is especially affected by variations in physical and chemical properties.Serious geologic hazards or engineering problems are closely related to the disintegration of granite residual soil in certain areas.Research on the mechanical properties and controlling mecha-nisms of disintegration has become a hot issue in practical engineering.In this paper,the disintegration characteristics of improved granite residual soil are studied by using a wet and dry cycle disintegration instrument,and the improvement mechanism is analyzed.The results show that the disintegration amounts and disintegration ratios of soil samples treated with different curing agents are obviously dif-ferent.The disintegration process of improved granite residual soil can be roughly divided into 5 stages:the forcible water intrusion stage,microcrack and fissure development stage,curing and strengthening stage,stable stage,and sudden disintegration stage.The disintegration of granite residual soil is caused by the weakening of the cementation between soil particles under the action of water.When the disin-tegration force is greater than the anti-disintegration force of soil,the soil will disintegrate.Cement and lime mainly rely on ion exchange agglomeration,the inclusion effect of curing agents on soil particles,the hard coagulation reaction and carbonation to strengthen granite residual soil.Kaolinite mainly depends on the reversibility of its own cementation to improve and strengthen granite residual soil.The reversibil-ity of kaolinite cementation is verified by investigating pure kaolinite with a tensile,soaking,drying and tensile test cycle.Research on the disintegration characteristics and disintegration mechanism of improved granite residual soil is of certain reference value for soil modification.
查看更多>>摘要：Pyrrhotite is an associated mineral that exists widely in sulfide ore.The presence of pyrrhotite will affect the recovery of platinum group minerals.Therefore,researchers have paid increasing attention to the flotation separation of pyrrhotite.Pyrrhotite superstructures owning different Fe/S ratios results in var-ious crystal structures,corresponding to different physical,chemical and electronic properties,and con-sequently different flotation behavior.In the present paper,a comprehensive review is conducted to discuss the influence of crystal structures on the natural floatability,mineral-reagent interaction,surface oxidation and flotation electrochemistry of pyrrhotite.The selective flotation process of pyrrhotite from its associated minerals is also reviewed in this paper.It is hoped that this review can summarize the newly published research results combined with some representative results from the past,to provide a theoretical basis for the study of the flotation mechanism of pyrrhotite and provide a new direction for future research on pyrrhotite.
查看更多>>摘要：A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size,high harmful impurity content and oolitic structure.To recover iron from oolitic hematite,we developed a novel multistage dynamic magnetizing roasting technology.Compared with traditional magnetizing roasting technologies,this novel technology has the following advantages:firstly,the oolitic hematite is dynamically reduced in a multi-stage roasting furnace,which shortens the reduction time and avoids ringing and over-reduction;secondly,the novel dynamic magnetizing roasting technology has strong raw material adaptability,and the size range of raw materials can be as wide as 0-15 mm;thirdly,the roasting furnace adopts a preheating-heating pro-cess,and the low-calorific value blast furnace gas can be used as the fuel and reductant,which greatly reduces the cost.The actual industrial production data showed that the energy consumption in the roast-ing process can be less than 35 kg of standard coal per ton of raw ore.The iron grade of the concentrate and iron recovery reached 65％and 90％,respectively.
查看更多>>摘要：The iron tailings of Bayan Obo mines are solid waste,which occupies land area and also causes environ-mental pollution;however,this waste can be recycled.In this study,based on the characteristics of iron minerals and fluorocarbonate contained in Bayan Obo iron tailings,clean magnetization roasting of iron minerals by bastnaesite from iron tailings during in-situ suspension magnetization roasting in a neutral atmosphere was explored.The results show that for iron tailings with a mass of 12 g,a N2 gas flow rate of 600 mL/min,and roasting for 5 min at 800℃,iron concentrate with a 60.44％iron grade at an iron recov-ery of 76.04％could be obtained.X-ray diffraction analysis showed that the weak magnetic hematite was reduced to strong magnetic magnetite in the neutral atmosphere,without additional reductant.The kinetics of the magnetization roasting of mineral mixtures(bastnaesite and hematite)in a neutral atmo-sphere showed that the optimal reaction mechanism function was the three-dimensional diffusion model with activation energy of 161.8838 kJ.mol-1;this indicates that the reaction was a heterogeneous,diffusion-controlled solid-state reaction.
查看更多>>摘要：The utilization of Ca ion as assistant depressant of CMC on talc has been widely reported.Thus,the study on the adsorption mechanism of Ca ion on talc surface is very crucial for understanding the performance of CMC on talc depression.In this paper,mechanism insights into hydrated Ca ion adsorption on talc(001)basal surface were creatively provided using DFT calculation.[Ca(H2O)6]2+and[Ca(OH)(H2O)3]+were determined as the effective hydrate components for Ca ion adsorption,and the top O site was the most favorable position for their adsorptions on talc surface.Furthermore,the adsorption mecha-nisms of[Ca(H2O)6]2+and[Ca(OH)(H2O)3]+on talc surface were found to be not the Ca-O chemical bond,but the hydrogen bonding formed by the H atom of the H2O ligand and the surface O atom.H2O acted like a bridge to connect them to the talc surface.Moreover,the hydrogen bonding was formed due to the hybridization of H 1 s orbital with the O 2s,O 2p orbitals.Simultaneously,electrons transferred between the H atom and the surface O atom.This work provides theoretical insights into the Ca ion adsorption on talc surface,which can help deeply understand the talc flotation using CMC as depression.
查看更多>>摘要：Malachite is one of the main minerals used for the industrial enrichment and recovery of copper oxide resources,and copper ions are unavoidable metal ions in the flotation pulp.The microflotation,contact angle,and adsorption experiments indicated that pretreatment with an appropriate concentration of cop-per ions could improve the malachite recovery,and the addition of excess copper ions reduced the hydrophobicity of the malachite surface.The results of zeta potential tests indicated that sodium sulfide and butyl xanthate were also adsorbed on the surface of malachite pretreated with copper ions.X-ray photoelectron spectroscopy(XPS)results indicated that-Cu-O and-Cu-OH bonds were formed on the surface of the samples.After pretreatment with an appropriate concentration of copper ions,the number of-OH groups on the mineral surface decreased,whereas the number of Cu-S groups on the mineral surface increased,which was conducive to the sulfidization of malachite.After adding a high con-centration of copper ions,the-OH groups on the mineral surface increased,whereas the number of Cu-S groups decreased,which had an adverse effect on the sulfidization flotation of malachite.Time-of-flight secondary ion mass spectrometry showed that pretreatment with copper ions resulted in a thicker sul-fidization layer on the mineral surface.
查看更多>>摘要：In this study,chalcopyrite was oxidized in hydrogen peroxide(H2O2)solutions of different concentrations to simulate different degrees of oxidation in real ores,and the effects of H2O2 treatment on chalcopyrite surface properties and flotation performance were investigated by surface analysis techniques and floata-tion experiments,which implied the reason for the poor grade and recovery of oxidized chalcopyrite con-centrate in the production process of the ore.Flotation results showed that when the concentration of H2O2 increased from 0％(by weight)to 5％,the flotation recovery of chalcopyrite decreased sharply.However,with increasing H2O2 concentration from 5％to 30％,chalcopyrite recovery improved relatively to different degrees with different collector concentrations.Analyses of X-ray photoelectron spectroscopy(XPS)and inductively coupled plasma-atomic optical emission spectrophotometry(ICP-OES)results indi-cated that the pretreatment with H2O2 caused that hydrophilic substance formed on chalcopyrite surface with the dissolution of copper ions,and the dissolution amount of copper increased with the increase of H2O2 concentration.UV-visible spectrophotometer and Fourier transform infrared spectrum(FTIR)stud-ies indicated that the pretreatment of chalcopyrite with H2O2 had little effect on the adsorption amount of potassium butyl xanthate(PBX)on chalcopyrite surface.However,due to the dissolution of copper ions,PBX interacted with chalcopyrite mainly as buthyl dixanthogen(BX)2.
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