Strengthening iron enrichment and dephosphorization of high-phosphorus oolitic hematite using high-temperature pretreatment

The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.

Formation and characterization of metallic iron grains in coal-based reduction of oolitic iron ore

To reveal the formation and characteristics of metallic iron grains in coal-based reduction, oolitic iron ore was isothermally re- duced in various reduction times at various reduction temperatures. The microstructure and size of the metallic iron phase were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and a Bgrimm process mineralogy analyzer. In the results, the re- duced Fe separates from the ore and forms metallic iron protuberances, and then the subsequent reduced Fe diffuses to the protuberances and grows into metallic iron grains. Most of the metallic iron grains exist in the quasi-spherical shape and inlaid in the slag matrix. The cumula- tive frequency of metallic iron grain size is markedly influenced by both reduction time and temperature. With increasing reduction temperature and time, the grain size of metallic iron obviously increases. According to the classical grain growth equation, the growth kinetic parameters, i.e., time exponent, growth activation energy, and pre-exponential constant, are estimated to be 1.3759 ± 0.0374, 103.18 kJ·mol^-1, and 922.05, respec- tively. Using these calculated parameters, a growth model is established to describe the growth behavior of metallic iron grains.

Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore

To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,respectively.Experimental results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic interior.The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases.The P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually decreased.The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.

Application of suspension magnetization roasting as technology for high-efficiency separation of valuable iron minerals from high-iron bauxite

A technology for suspension magnetization roasting−magnetic separation was proposed to separate iron minerals for recovery.The optimum parameters were as follows:a roasting temperature of 650℃,a roasting time of 20 min,a CO concentration of 20%,and particles with a size less than 37μm accounting for 67.14%of the roasted product.The total iron content and iron recovery of the magnetic concentrate were 56.71%and 90.50%,respectively.The phase transformation,magnetic transition,and microstructure evolution were systematically characterized through iron chemical phase analysis,X-ray diffraction,vibrating sample magnetometry,X-ray photoelectron spectroscopy,and transmission electron microscopy.The results demonstrated the transformation of hematite to magnetite,with the iron content in magnetite increasing from 0.41%in the raw ore to 91.47%in the roasted product.

Properties of a reaction-bonded β-SiAlON ceramic doped with an FeMo alloy for application to molten aluminum environments

An FeMo-alloy-doped β-SiA1ON （FeMo/β-SiA1ON） composite was fabricated via a reaction-bonding method using raw materials of Si, Al2O3, A1N, FeMo, and Sm2O3. The effects of FeMo on the microstructure and mechanical properties of the composite were investi- gated. Some properties of the composite, including its bending strength at 700℃ and after oxidization at 700℃ for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion re- sistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiA1ON composite exhibits strong potential for application to molten aluminum environments.

Twinnability of Al-Mg alloys:A first-principles interpretation

Al-Mg alloys are considered to have potentials to form twins during deformation because Mg can reduce the intrinsicstacking fault energy?ISFE of Al.Nevertheless,twinning has rarely been found in Al-Mg alloys even subjected to various severeplastic deformation(SPD)techniques.In order to probe the twinning propensity of Al-Mg alloys,first-principles calculations werecarried out to investigate the effects of Mg and vacancies on the generalized planar fault energy(GPFE)of Al.It is found that bothMg and vacancies exhibit a Suzuki segregation feature to the stacking fault,and have the influence of decreasing the?ISFE of Al.However,?ISFE does not decrease and the twinnability parameterτa of Al does not increase monotonically with increasing Mgconcentration in the alloy.On the basis ofτa evaluated from the calculated GPFE of Al-Mg alloys,we conclude that deformationtwinning is difficult for Al-Mg alloys even with a high content of Mg.Besides,the decrease of?ISFE caused by the introduction ofMg and vacancies is supposed to have the effect of improving the work-hardening rate and facilitating the formation of bandstructures in Al-Mg alloys subjected to SPD.

Strengthening leaching effect of Carlin-type gold via high-voltage pulsed discharge pretreatment

A high-voltage pulsed discharge(HVPD)pretreatment was used to strengthen the leaching effect of Carlin-type gold ore containing arsenic.Optimal results of the pretreatment experiments were obtained at the following operating conditions:a spherical gap spacing of 20 mm,pulse number of 100,and voltage of 30 kV.The leaching rate of gold was increased by 15.65%via the HVPD pretreatment.The mass fraction of–0.5+0.35 mm and–0.35+0.1 mm was increased by 10.97%and 6.83%compared to the untreated samples,respectively,and the Au grade of–0.1 mm was increased by 22.84%.However,the superiority of the HVPD pretreatment would be weakened by prolonged grinding time.Scanning electron microscopy results indicated that the pretreated products presented as a melting state and then condensation,accompanying by some pore formation.More micro-cracks were generated at the interface of the ore and the original crack were expended via pulsed discharge pretreatment,with the contact area between the leaching reagent and ore increased,the leaching reaction rate enhanced and the leaching effect strengthened.

Comparisons of Image Quality and ADCs in Breath-Hold, Respiratory-Triggered and Free-Breathing DWI of Pancreas at 3-T

Objective: To compare image quality and apparent diffusion coefficients (ADC) of the normal pancreas parenchymas in breath-hold, respiratory-triggered and free-breathing diffusion weighted imaging (DWI) at 3.0-Tesla. Methods: DWI of the pancreas was performed at 3.0-Tesla in 21 healthy volunteers with breath-hold, respiratory-triggered and free-breathing using b-values of 0 and 500 s/mm2. For all three sequences, two readers assigned an image quality score to images at b0 and b500, and two independent readers measured ADCs for the head, body and tail of pancreas. Image quality scores and ADCs of pancreas in the three DWIs were compared. Results: For b0, image quality scores was not significantly different among the three sequences (p = 0.103). For b500, image quality score was significantly lower in free-breathing DWI than breath-hold or respiratory-triggered DWI (p = 0.000), and not significantly different between breath-hold and respiratory-triggered DWI (p = 0.212). Mean ADCs differed significantly among the anatomical regions with the lowest values measured in the pancreatic tail both at breath-hold and respiratory-triggered DWIs whereas no significant difference was found at free-breathing DWI. Conclusion: Breath-hold or respiratory-triggered technique provided DW images of pancreas with acceptable quality at 3.0-Tesla. Breath-hold is the preferred DWI technique for ADC measurements of pancreas.

Application of dexmedetomidine in different doses in combined with propofol in the painless colonoscopy in the elder patients

Objective:To explore the anesthetic effect of dexmedetomidine (Dex) in different doses in combined with propofol on the painless colonoscopy in the elder patients.Methods: A total of 60 elder patients who were admitted in our hospital from November 2016 to October 2017 for selective painless fiber colonoscopy were included in the study and divided into the low dose group and high dose group according to Dex dose. The micro-infusion pump was used to inject Dex 10 min before examination. The load capacity in the low dose group was 0.25 μg/kg, while in the high dose group was 0.75 μg/kg. The pump injection was completed within 10 min, then a continuous pump injection was performed in a speed of 0.5 μg/kg/h until the check off. After the completion of Dex pumping, propofol (1-1.5 mg/kg) was slowly injected. MAP, HR, and SpO2 before medication (T0), 5 min after inserting the endoscope (T1), and the time after the examination being finished (T2) were recorded, respectively. The bioelectrical impedance technique was used to continuously monitor SV, CO, and SVR. The awakening time, propofol dose, and discharge time were recorded.Results: The comparison of MAP, HR, and SpO2 at T0 between the two groups was not statistically significant. MAP, HR, SV, CO, and SVR at T1 and T2 were significantly lower than those at T0, while the comparison of SpO2 was not significantly changed. MAP at T1 in the high dose group was significantly higher than that in the low dose group, while HR at T1 and T2 was significantly lower than that in the low dose group. SV, CO, and SVR at T1 and T2 in the high dose group was significantly higher than those in the low dose group. The awakening time in the high dose group was significantly shorter than that in the low dose group, and the propofol dose was significantly less than that in the low dose group, while the comparison of discharge time was not significantly different. Conclusions: Application of Dex in a high dose in the painless colonoscopy in the elder patients can reduce the propofol dose, and will not increase the inhibiting effect on respiration and circulation.

Effect of lollipop sucking on the recovery of gastrointestinal function in children after congenital choledochal cyst excision: A randomized controlled trial

This study is aimed to evaluate the effect of lollipop sucking on the recovery of gastrointestinal function in children after congenital choledochal cyst excision.58 children who had undergone congenital choledochal cyst excision were randomly divided into two groups:the controlled group and the experimental group.Children in the experimental group were allowed to suck on strawberry lollipops for 20e30 min once every four hours beginning six hours after the operation.The recovery time of bowel sounds and anal defecation was recorded and compared between experimental and control groups.Compared with the controlled group the recovery times of bowel sounds(41.75±7.38 h vs.51.43±5.02;p<0.001)and anal defecation(64.32±14.69 h vs.79.17±14.91 h;p<0.001)were significantly shorter in the experimental group.Results of the present study indicate that Sucking of lollipops by children after choledochal cyst excision facilitates the recovery of bowel movement and relieves postoperative abdominal distension.

Accessory navicular in children

Accessory navicular(AN)is a developmental variation of the secondary ossification center of the navicular tuberosity.Ten percent of patients with AN will have pain symptoms that affect walking and life.As the AN changes the position of the posterior tibial tendon insertion,children with AN often have posterior tibial tendon function insufficiency and flexible flat foot.Surgical treatment is often required after failure of conservative treatment.This article reviewed the etiology,clinical manifestations,complications,and treatment methods of AN.

Efficient enrichment of nickel and iron in laterite nickel ore by deep reduction and magnetic separation

The process of deep reduction and magnetic separation was proposed to enrich nickel and iron from laterite nickel ores.Results show that nickel-iron concentrates with nickel grade of 6.96%,nickel recovery of 94.06%,iron grade of 34.74%,and iron recovery of 80.44% could be obtained after magnetic separation under the conditions of reduction temperature of 1275℃,reduction time of 50 min,slag basicity of 1.0,carbon-containing coefficient of 2.5,and magnetic field strength of 72 kA/m.Reduction temperature and time affected the possibility of deep reduction and reaction progress.Slag basicity affected the composition of slag in burden and the spilling and enriching rate of nickel-iron from a matrix to form nickel-iron particles.Nickel-iron particles were generated,aggregated,and grew gradually in the reduction process.Nickel-iron particles can be effectively separated from gangue minerals by magnetic separation.

Effects of welding parameters on weld shape and residual stresses in electron beam welded Ti_2AlNb alloy joints

In order to estimate the residual stresses in Ti2AlNb alloy jointed by electron beam welding (EBW), a computational approach based on finite element method was developed. Meanwhile, experiments were carried out to verify the numerical results. The comparison between the simulation results and measurements suggests that the developed computational approach has sufficient accuracy to predict the welding residual stress distributions. The results show that the central area of the fusion zone suffers tensile stresses in three directions. When the other parameters remain unchanged, the focus current has great impact on the weld shape and size, and then affects the residual stress level significantly. Moreover, the thick plate full-penetrated EBW weld suffers near 1000 MPa tensile stress of Z-direction in the center of the fusion zone. The wider weld has lower tensile stress in Z-direction, resulting in lower risk for cracking.

Mechanism of reheat cracking in electron beam welded Ti2Al Nb alloys

In order to clarify the characteristics and formation mechanism of the reheat cracking in Ti2AlNb weldments,a series of heat treatment conditions were performed to the circular joints welded by electron beam,and then the macrostructures and microstructures were investigated using optical microscopy,scanning electron microscopy,X-ray diffractometry,and transmission electron microscopy.The results show that the reheat cracking occurs primarily along the grain boundaries in the weld when the Ti2AlNb circular welded joints are heated up to about 700℃.During the heat treatment,an almost complete transformation of B2→O happens while the temperature goes up through the O single-phase region.Then,O→B2+O phase transformation occurs primarily along the grain boundaries as the weld metal continues to heat up to the B2+O dual-phase region.Under the high tension stress consisting of welding residual stress and phase transformation stress,reheat cracking occurs at the interface between the B2+O dual-phase layer and the O-phase matrix.

Geochemical characteristics and genetic mechanism of the high-N2 shale gas reservoir in the Longmaxi Formation, Dianqianbei Area, China

As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration risk.Accordingly,this study explores the genesis of shale gas reservoir and the mechanism of nitrogen enrichment through investigating shale gas compositions,isotope features,and geochemical characteristics of associated gases.The high-nitrogen shale gas reservoir in the Longmaxi Formation is demonstrated to be a typical dry gas reservoir.Specifically,the alkane carbon isotope reversal is ascribed to the secondary cracking of crude oil and the Rayleigh fractionation induced by the basalt mantle plume.Such a thermogenic oil-type gas reservoir is composed of both oil-cracking gas and kerogen-cracking gas.The normally high nitrogen content(18.05%-40.92%) is attributed to organic matter cracking and thermal ammoniation in the high-maturity stage.Specifically,the high heat flow effect of the Emeishan mantle plume exacerbates the thermal cracking of organic matter in the Longmaxi Formation shale,accompanied by nitrogen generation.In comparison,the abnormally high nitrogen content(86.79%-98.54%) is ascribed to the communication between the atmosphere and deep underground fluids by deep faults,which results in hydrocarbon loss and nitrogen intrusion,acting as the key factor for deconstruction of the primary shale gas reservoir.Results of this study not only enrich research on genetic mechanism of high-maturity N_@ shale gas reservoirs,but also provide theoretical guidance for subsequent gas reservoir resource evaluation and well-drilling deployment in this area.

Flotation behaviors and mechanisms of chalcopyrite and galena after cyanide treatment

Adsorbing tests between CN? and chalcopyrite or galena were conducted firstly, and then flotation tests of the twocyaniding minerals were investigated in butyl xanthate (BX) system. Results showed that the interaction between CN? and the twomineral surfaces were both chemical adsorption and can be described by the Langmuir adsorption isotherm model. In the optimumcondition of pH 6.5 and 4.0 mg/L BX, the recovery of cyaniding chalcopyrite and galena reached 82.1% and 63.9%, respectively. BXimproved the hydrophobicity of the surfaces of the two minerals, although CN? reduced the contact angle on the surface of minerals.The inhibitory effect of CN? on chalcopyrite far outweighed galena. Electrostatic adsorption exists in the interaction between BX andthe surface of galena after cyanide treatment in the pH range of 4.2?8.4, while the interactions between BX and the surface ofchalcopyrite after cyanide treatment is chemical adsorption.

Puerarin exhibits greater distribution and longer retention time in neurons than astrocytes in a co-cultured system

The phytoestrogen puerarin has been shown to protect neurons and astrocytes in the brain, and is therefore an attractive drug in the treatment of Alzheimer’s disease, Parkinson’s disease and cerebral ischemia. Whether puerarin exhibits the same biological processes in neurons and astro-cytesin vitro has rarely been reported. In this study, cortical neurons and astrocytes of newborn Sprague-Dawley rats were separated, identiifed and co-cultured in a system based on Transwell membranes. The retention time and distribution of puerarin in each cell type was detected by lfuorescence spectrophotometry and lfuorescence microscope. The concentration of puerarin in both co-cultured and separately cultured neurons was greater than that of astrocytes. Puerarin concentration reached a maximum 20 minutes after it was added. At 60 minutes after its addi-tion, a scant amount of drug was detected in astrocytes; however in both separately cultured and co-cultured neurons, the concentration of puerarin achieved a stable level of about 12.8 ng/mL. The results indicate that puerarin had a higher concentration and longer retention time in neu-rons than that observed in astrocytes.

Effect of serpentine and sodium hexametaphosphate on ascharite flotation

Sodium hexametaphosphate(SHMP)was used to minimize the adverse effect of serpentine for improving aschariterecovery.The effects of particle size and content of SHMP,and serpentine on ascharite flotation process were investigated throughflotation,zeta potential tests,FT-IR analysis,XPS analysis and DLVO theory.Particles interaction and mechanism of SHMP werealso discussed.It was found that aggregation between serpentine and ascharite particles easily happened,and the particle size ofserpentine had a profound impact on the ascharite recovery.In particular,the fine serpentine with size less than38μm had thegreatest contribution to the deterioration of ascharite flotation performance.After SHMP treatment,the adverse effect of serpentinewas significantly reduced.The mechanism of SHMP showed that it could alter the surface charges of serpentine and ascharite toprevent severe interparticle aggregation,which resulted in a well-dispersed pulp and benefited ascharite flotation process.Theadsorption of SHMP on serpentine was due to hydrogen bonding and chemical adsorption,resulting in the formation of complex onserpentine surface to decrease its floatability.

Effect of dexmedetomidine on inflammatory factors and immune function in elderly patients undergoing laparoscopic radical resection of colorectal cancer

Objective:To investigate the effect of dexmedetomidine on inflammatory factors and immune function in elderly patients undergoing laparoscopic radical resection of colorectal cancer. Methods: From April 2016 to April 2017, 86 cases of elderly laparoscopic radical resection of colorectal cancer in our hospital were selected and randomly divided into the observation group and the control group. 2 groups of patients were open venous access, oxygen mask, monitoring heart rate (HR), blood pressure (BP), electrocardiogram (ECG), oxygen saturation (SpO2), bispectral index (BIS), after induction of anesthesia, the observation group was given dexmedetomidine 0.4 g/kg to 20 mL of normal saline control. Group of 20 mL saline, 15 min infusion is completed, and the observation group of dexmedetomidine in 0.4 g/kg - h continuous infusion of normal saline control group, continuous infusion, until the end of surgery. Before induction of anesthesia (T0), 2 h after operation beginning (T1), at the end of operation (T2), 24 h after operation (T3) in venous blood, using ELISA method for the determination of serum interleukin-2 receptor (sIL-2R) and interleukin-6 (IL-6), tumor necrosis factor alpha (the level of TNF-alpha);on preoperative and postoperative 4 h, 12 h, 24 h after operation in venous blood serum epinephrine ELISA method (E), norepinephrine (NE), endothelin-1 (ET-1) level;on preoperative and postoperative 4 h, 12 h after surgery, 24 h venous blood flow cytometry determination of CD3+, CD4+, CD8+, CD4+/CD8+.Results:compared with before operation, the observation group after 4 h, 12 h, 24 h NE, and the lower control group E, NE and ET-1 increased, the observation group after 4 h, 12 h, 24 h E, NE, ET-1 lower than that of the control group;compared with T0, 2 patients in group T2, T3 sIL-2R, IL-6, TNF-alpha were increased, the observation group T2, T3 sIL-2R, IL-6, TNF- were lower than that of the control group;compared with the preoperative, 2 group after 4 h, 12 h, 24 h CD3+, CD4+, CD8+ and CD4+/CD8+ decreased, the observation group after 4 h, 12 h, 24 h CD3+, CD4+, CD8+, CD4+/CD8+ higher than those in the control group.Conclusion: Dexmedetomidine has a good analgesic effect on elderly patients undergoing laparoscopic radical resection of colorectal cancer. It can effectively relieve the stress reaction and inflammatory reaction during perioperative period, and effectively improve the immune function of the patients.

气凝胶隔热层隔热性能计算与试验验证

为了研究气凝胶隔热层的隔热效果,首先基于三维热流固耦合分析方法,通过数值计算手段对气凝胶隔热层的隔热性能进行了计算,随后在进口为高温条件下进行了隔热性能试验,获得了隔热层在不同温度、不同燃气流量下的隔热特性规律。采用Matlab软件对内外壁温度之间的关联关系进行了数学公式拟合,并对前期数值计算结果和试验结果进行了对比,证明数值计算的正确性。