铁矿--生物质复合球团还原行为及还原动力学

通过分析生物质合成气气氛下,不同组分复合球团(添加和未添加生物质)的还原速率、还原度、表面微观结构和失重变化规律,对球团中添加生物质的作用机理以及含生物质球团还原过程的限制性环节展开研究.添加生物质的复合球团表面结构比无生物质球团疏松,孔隙率高,有利于后续还原的热质传递,增加产物还原度,降低反应活化能;复合球团的还原以收缩核方式进行,在1123~1323 K温度范围内,界面化学反应是两种球团还原反应的主要控速环节;添加生物质后,有利于界面化学反应的进行,使得球团的还原表观活化能由95.448 kJ·mol-1降低到68.131 kJ·mol-1.     

Gas-based reduction of vanadium titano-magnetite concentrate: behavior and mechanisms

The reduction of vanadium titano-magnetite pellets by H₂-CO at temperatures from 850 to 1050℃ was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_H2/(V_H2 + V_CO) on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_H2/(V_H2 + V_CO). The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H₂ atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy (SEM) in conjunction with back scatter electron (BSE) imaging. The results show that the difference in thermodynamic reducing ability between H₂ and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_3-xTi_xO₄ cannot be reduced under a CO atmosphere because of the densification of particles' structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H₂ atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H₂ reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.     

Thermal performance and reduction kinetic analysis of cold-bonded pellets with CO and H<Subscript>2</Subscript> mixtures

Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H₂–CO mixtures with different H₂/CO molar ratios (1:0, 5:2, 1:1, 2:5, and 0:1) under various temperatures (1023, 1123, 1223, 1323, and 1423 K) in a thermogravimetric analysis apparatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstructure of reduced pellets was observed by scanning electron microscopy–energy-dispersive spectrometry (SEM-EDS). The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hinder effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could maintain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overall equilibrium constant to the promotion effect depends on the gas composition.     

含碳球团的还原性和还原冷却后的强度

在 １２７３～１５７３ Ｋ条件下研究了不同煤种、木炭和石墨与不同种类矿石制成含碳球团 的还原速度;进而讨论了温度、配碳比（Ｃ／Ｏ）、挥发分含量等因素对含碳球团还原所需时间和 金属化率的影响．通过测定含碳球团还原冷却后的强度,对影响强度因素进行了分析．还原冷 却后的强度在温度 １２７３ Ｋ时较低,配入含挥发分较高的气煤,可以使还原冷却后的强度提高, 加快反应速度．     

Hydrogen absorption behavior of TA15 alloy

The hydrogen absorption kinetics of TA15 titanium alloy at 973–1123 K was studied using a tube-type hydrogen treatment furnace. The hydrogen absorption kinetic curves obtained were analyzed according to a series of mechanism equations to reveal the kinetic parameters and mechanism of the hydrogen absorption process. The results show that both the hydrogen absorption rate and the equilibrium hydrogen pressure increase and the time to reach equilibrium is shortened with increasing temperature. It is found that only the second hydrogen absorption period exists in the hydrogen absorption process of TA15 alloy between 973 and 1123 K, and the activation energy is 54.889 kJ/mol for hydrogen absorption. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results demonstrate that δ hydride forms between 973 and 1123 K, and β phase decreases with the increase of temperature. Orthorhombic α″ martensite is generated at 1073-1123 K, and their amount increases with increasing temperature.     

Utilization of waste polyethylene terephthalate as a reducing agent in the reduction of iron ore composite pellets

The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate (PET), because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450°C for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron (iron nuggets) were reduction at 1450°C for 10 min using composite pellets containing 60% PET and 40% coke.     

Binary fire-extinguishing agent composed of halocarbons and inert gases

C₃H₂F₃Br (1323) is a new kind of Halon replacements developed by our research group. In order to improve the disperse capability of 1323, nitrogen was mixed with 1323 to form the binary fire-extinguishing agent. In this work, the binary fire-extinguishing agent of nitrogen and 1323 was used in experiment and the fire extinguishing efficiency was discussed. In addition, the fire suppression mechanism was investigated and the fire-extinguishing concentration of nitrogen and 1323 was also studied.     

The uptake of ethyl iodide on black carbon surface

The importance of the iodine chemistry in the atmosphere has been demonstrated by recent obserations. The uptake of ethyl iodine on black carbon surface was inestigated at 298 K for the first time. Degussa FW2 （an amorphous black carbon comprising medium oxides） was used as black carbon sample. Black carbon surface was found to be deactiated in reaction with C2H51, and the uptake coefficient （r） was dependent on the time of exposure. The alue of （2.3±0.9）×10^-2 was determined for the initial uptake coefficient （No）. The result suggests that the heterogeneous loss of C2H51 on carbonaceous aerosols may be important under the atmospheric conditions.     

Effects of the hierarchical pyrolysis polyaniline on reversible hydrogen storage of LiBH4

In this work,LiBH_4–20 wt%PP composite was prepared by ball-milling with as-synthesized hierarchical pyrolysis polyaniline(PP)and LiBH_4,and the hydrogen sorption performance as well as catalytic mechanism of the composite was studied.It is found that the onset desorption temperature of the composite decreases to 75°C,almost 235°C lower than that of the milled LiBH_4.Moreover,the composite could release 4.1 wt%H_2and rehydrogenate a total of 4.4 wt%H_2when the temperature raiseds up to 400°C,showing an outstanding reversibility,which even 3.9 wt%H_2can be kept after five cycles.Through scanning electron microscopy(SEM)observation and X-ray diffraction(XRD)analysis,we found that the PP surface forms some nanoholes after hydrogenation-dehydrogenation cycles,which leads to the confinement of some LiBH_4in the PP nanoporous structure,therefore,the hydrogen sorption kinetics and reversibility are significantly enhanced.In addition,we also found the oxygenic groups of the PP can react with LiBH_4forming LiBO_2and Li_3BO_3,where the containing Li–B–O bonds loaded in the porous structure of the PP catalyze the hydrogenation reaction of LiBH_4.     

Martensitic transformation and magnetic properties of aged Ni-Fe-Ga-Ti shape memory alloy

This article reports the effect of ageing on the microstructure, martensitic transformation, magnetic properties, and mechanical properties of Ni₅₁Fe₁₈Ga₂₇Ti₄ shape memory alloy. There are five specimens of this alloy aged at 573 up to 973 K for 3 h per each. This range of ageing temperature greatly affects the microstructure of the alloy. As the ageing temperature increased from 573 up to 973 K, the microstructure of Ni₅₁Fe₁₈Ga₂₇Ti₄ alloy gradually changed from the entirely martensitic matrix at 573 K to the fully austenitic microstructure at 973 K. The volume fraction of precipitated Ni₃Ti particles increased with the ageing temperature increasing from 573 to 773 K. Further increasing the ageing temperature to 973 K decreased the content of Ni₃Ti in the microstructure. The martensitic transformation temperature was decreased steadily by increasing the ageing temperature. The magnetization saturation, remnant magnetization, and coercivity increased with the ageing temperature increasing up to 773 K. A further increase in ageing temperature decreased these magnetic properties. Moreover, the hardness values were gradually increased at first by increasing the ageing temperature to 773 K, and then dramatically decreased to the lowest value at 973 K.     

Study on the strength of cold-bonded high-phosphorus oolitic hematite-coal composite briquettes

Composite briquettes containing high-phosphorus oolitic hematite and coal were produced with a twin-roller briquette machine using sodium carboxymethyl cellulose, molasses, starch, sodium silicate, and bentonite as binders. The effect of these binders on the strength of the composite briquettes, including cold strength and high-temperature strength, was investigated by drop testing and compression testing. It was found the addition of Ca(OH)₂ and Na₂CO₃ not only improved the reduction of iron oxides and promoted dephosphorization during the reduction-separation process but also provided strength to the composite briquettes during the briquetting process; a compressive strength of 152.8 N per briquette was obtained when no binders were used. On this basis, the addition of molasses, sodium silicate, starch, and bentonite improved the cold strength of the composite briquettes, and a maximum compressive strength of 404.6 N per briquette was obtained by using starch. When subjected to a thermal treatment at 1200℃, all of the composite briquettes suffered from a sharp decrease in compressive strength during the initial reduction process. This decrease in strength was related to an increase in porosity of the composite briquettes. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the decrease in strength of the composite briquettes could be caused by four factors: decomposition of bonding materials, gasification of coal, transportation of byproduct gases in the composite briquettes, and thermal stress.     

一种检测电芬顿体系下DNA损伤的电化学生物传感器的研制

为了检测电芬顿体系下DNA的损伤,先采用石墨烯制备了一种致密的rGO/Fe₃O₄复合材料;再将复合材料和DNA修饰到玻碳电极上,利用电化学还原作用释放游离态Fe²⁺,并加入H₂O₂形成电芬顿体系;最后构建了一种检测电芬顿体系下DNA损伤的新型电化学生物传感器。检测结果表明,检测DNA损伤的最佳时间为30 min,最佳pH值为7.0。     

内配煤团块直接还原法制备铁粒技术研究

根据我国现阶段直接还原状况及国内能源的结构特点，提出利用舍碳团块直接还原制备铁颗粒的技术思想；通过调整团矿的内配碳比、温度、碱度及添加剂配入量来优化渣铁的分离和提高铁粒质量，找到最佳的配比方案。铁的收得率达到90％以上，铁粒中wFe〉96％，ws=0．02％～0．05％，wc〈4．0％；分离出的铁粒可直接作为电炉炼钢的优质原料。     

低配碳比含碳球团直接还原的实验研究

根据低配碳比含碳球团还原熔分工艺制备粒铁的技术思想,对低配碳比含碳球团的直接还原进行实验研究.结果表明,这种低配碳比的含碳球团还原速度较快,还原反应进行了10 min时表观还原度为84%,20min时表观还原度可达88%;继续延长反应时间,球团表层还原得到的少量金属铁会再次被氧化成FeO.还原反应结束后,球团内仍存在少量尚未还原的FeO,它们与脉石中的SiO2形成低熔点的铁橄榄石,有利于工艺后期渣铁的熔化及分离.     

A novel Pd/silicalite-1 composite membrane for hydrogen separation

A novel Pd/silicalite-1 composite membrane supported on the macroporous tubular stainless steel substrate was successfully fabricated by electroless plating at 303 K. The structure, morphology and gaseous permeability of the membrane were detected by X-ray diffractiometry （XRD）, scanning electron microscopy （SEM） and single-gas permeation test, respectively. Results confirm the formation of a thin, smooth, and continuous Pd/silicalite-1 composite membrane. The obtained composite membrane shows a high H2 permeance of 1.15×10^-6 mol. m^-2. s^-1. Pa^-1 with moderate H2 selectivity of 250 for H2/N2 at 773 K, at 0.1 MPa pressure drop, suggesting the potential application for H2 separation.     

Hydrogen storage properties of MgH<Subscript>2</Subscript> co-catalyzed by LaH<Subscript>3</Subscript> and NbH

To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH₂ + 10wt%LaH₃ + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H₂ within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH₃ and NbH upon dehydriding of MgH₂. By contrast, pure MgH₂, an MgH₂ + 20wt%LaH₃ composite, and an MgH₂ + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H₂, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH₂ + 10wt%LaH₃ + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH₂. The introduction of LaH₃ and NbH was beneficial to the hydrogen storage performance of MgH₂.     

Extraction of Aluminum and Iron from Boiler Slag by Sulfuric Acid

This paper presents a new method of recycling aluminum and iron in boiler slag derived from plants that use coal as fuel. The new method integrates efficient extraction and reuse of the leached pellets together. An elemental analysis of aqueous solutions leached by sulfuric acid was determined by EDTA-Naz-ZnCl2 titration method. The components and microstructures of the samples were examined by means of XRF, XRD and SEM. An aluminum extraction efficiency of 86.50% was achieved when the sintered pellets were leached using 4 mol · L^- 1 H2SO4 at solid/ liquid [m（g）/V（mL）] ratio of 1 ： 5 at 80 ℃ for 24 h. An iron extraction efficiency of 94.60% was achieved in the same conditions for the maximum extraction efficiency of Al. The extraction efficiencies of Al and Fe increased with an increase in temperature, leaching time and acidity. The concentration of alumina and iron hydroxide in the final product was determined to be 99.12% and 92.20% respectively. This product of alumina would be used directly for the production of metallic aluminum.     

Towards understanding the influence of Mg content on phase transformations in the La3-xMgxNi9 alloys by in-situ neutron powder diffraction study

The present work is focused on the studies of the phase-structural transformations in the La_3-xMg_xNi₉ (x ​= ​1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride (Ni/MH) batteries. The phase equilibria and phase-structural transformations in the alloys were probed by in situ neutron powder diffraction (NPD) at the temperatures ranging from 300 ​K to 1273 ​K using the measurements of the equilibrated alloys at 8 setpoint temperatures of 300, 973, 1073, 1123, 1173, 1223, 1248 and 1273 ​K.Prepared by induction melting initial alloys were found to be multi-phase structured, containing up to 6 individual intermetallic compounds with different stoichiometric compositions. With the increase of the temperature and holding time, various transformations took place in the studied alloys. These included the formations and transformations of super-stacking intermetallics with variable ratios (La ​+ ​Mg)/Ni, 1:3, 2:7 and 5:19.With increasing temperatures, several systematic changes took place. (a) Abundances of (La,Mg)₂Ni₄ AB₂ and (La,Mg)Ni₃ AB₃ type intermetallics gradually decreased before they melted/decomposed above 1073 ​K; (b) The (La,Mg)₂Ni₇ A₂B₇ type intermetallics began to decrease in abundances above 1123 ​K; (c) The transformation in the (La,Mg)₅Ni₁₉ intermetallics from 3R to 2H proceeded above 1223 ​K.The increase of Mg content had no obvious influence on (La,Mg)₂Ni₄ and (La,Mg)₂Ni₇ phases, and corresponding reactions R1 and R3 took place at the same temperatures as in the La–Ni system. However, with increasing Mg content the melting point of (La,Mg)₅Ni₁₉ phase increased while the melting point of the (La,Mg)Ni₃ phase it decreased, leading to the variation of the reaction temperatures of the corresponding processes.The present study will assist in optimizing phase-structural composition of the alloys in the La–Mg–Ni system which contain Mg-modified layered structures by tailoring the high temperature annealing conditions.     

真空碳热还原过程中二氧化硅的挥发行为

为了解在真空碳热还原过程中SiO2的还原特性以及还原过程中的主要影响因素,对二氧化硅的还原过程进行热力学分析,得出化学反应自由能和临界温度。在系统压力为2~200 Pa条件下,以分析纯SiO2和Fe2O3为原料,采用XRD,SEM,EDS和化学成分分析等手段,研究Fe/Si摩尔比、配碳量、反应时间、还原剂粒度和升温速率对硅的挥发率和还原反应速率的影响。实验结果表明:在100 Pa条件下,SiO2的临界反应温度为1 330~1 427 K。SiO2发生气化反应生成的SiO气体挥发至石墨冷凝系统歧化生成Si和SiO2,造成硅的损失,且有部分SiO气体和石墨反应生成SiC;增大Fe/Si摩尔比和配碳量以及减小还原剂粒度均降低了硅的挥发率,提高了SiO2还原反应速率;延长反应时间和提高升温速率增加了硅的挥发率。     

Direct electrochemical reduction of solid vanadium oxide to metal vanadium at low temperature in molten CaCl2-NaCl

V₂O₅ sintered pellets and graphite rods were employed as the cathode and the anode, respectively; a molten CaCl₂-NaCl salt was used as the electrolyte. Then, V₂O₅ was directly reduced to metal vanadium by the Fray-Farthing-Chen (FFC) method at 873 K to realize low-temperature electrolysis. Two typical experimental conditions, electrolysis time and voltage, were taken into account to investigate the current efficiency and remaining oxygen content in electrolyzed products. The composition and microstructure of the products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). SEM observations show that a higher voltage (1.8?C3.4 V) and a longer electrolysis time (2?C5 h) can improve the product quality separately, that is, a lower remaining oxygen content and a more uniform microstructure. The products with an oxygen content of 0.205wt% are successfully obtained below 3.4 V for 10 h. However, the current efficiency is low, and further work is required.