石煤提钒钠化焙烧与钙化焙烧工艺研究

调研了石煤提钒钠化焙烧和钙化焙烧两种工艺的发展现状。高硅低钙含量的石煤宜采用钠化焙烧,高钙含量的石煤宜采用钙化焙烧,两种工艺各有所长。归纳了两种工艺下石煤提钒的最佳焙烧条件,得出最佳焙烧条件分别为:钠化焙烧温度区间800～850℃,焙烧时间2.0～2.5h,磨矿粒度106～180um,氯化钠用量为矿石的10%～20%。钙化焙烧比钠化焙烧要高100℃,温度区间900～950℃,焙烧时间2～3h,磨矿粒度106～180um,石灰用量为矿石的6%～8%。两种焙烧都需要充足的氧化氛围,但钠化焙烧时氧气不宜过多。各最佳焙烧条件之间存在一定耦合关系,在生产实际中,宜针对不同石煤进行特定实验。最后,总结了石煤提钒的主要焙烧设备,其中流化床炉具有较好的发展前景。     

Development of an Inert Anode for Electrowinning in Calcium Chloride–Calcium Oxide Melts

Studies were performed investigating the anodic testing of calcium ruthenate for electrowinning in calcium chloride–calcium oxide melts. The results showed that calcium ruthenate may be suitable as an inert anode in calcium chloride containing melts as it exhibited a low rate of corrosion in melts containing a small amount of calcium oxide, capable of producing oxygen on its surface, and did not contaminate the melt. To reduce the amount of ruthenium in the anode, solid solutions of calcium ruthenate in calcium titanate were investigated. At low concentrations, the solid solution is a semiconductor with a relatively low conductivity at room temperature, but at the temperature of operation, 1173 K, the material is an excellent electronic conductor. The other way of reducing the amount of ruthenium is to coat the solid solution onto a substrate. In this way, the substrate would give the mechanical strength while the coating would give the electrical conductivity and corrosion protection. Calcium ruthenate-based anodes can endure long-term use in the laboratory under an applied electrical field with oxygen being liberated on the anode indicating that these materials are candidates for the electrowining in calcium chloride–calcium oxide melts.     

Effect of postmortem injection time and postinjection aging time on the calcium-activated tenderization process in beef

The objectives of this study were to determine 1) the effectiveness of calcium chloride when injected later than 2 d postmortem, 2) the effect of extended postinjection aging time, and 3) the tenderness response curve in calcium chloride-treated beef. In Exp. 1, the longissimus thoracis et lumborum was injected on either d 2 or 14 postmortem with 5% by weight of a 200 mM calcium chloride solution. Samples were aged (1 degree C) either 7 or 35 d after injection. The uninjected control longissimus from the contralateral side was aged for 9, 21, 37, or 49 d. In Exp. 2, the longissimus thoracis et lumborum was injected on d 2 postmortem with 5% by weight of a 200 m x M calcium chloride solution then sampled for shear force on d 1, 2, 6, 8, 12, and 14 after injection. Calcium chloride injection, regardless of injection time or postinjection aging time, had higher (P < .05) sensory tenderness rating than control with the same total aging time (5.2, 5.5, 5.8, and 6.1 vs 4.3, 4.8, 5.1, and 5.3, respectively). Calcium chloride injection at d 14 reduced shear force (.7 kg) and increased tenderness rating (.7 units) as effectively (P > .05) as injection at d 2 (1.2 kg and .8 units, respectively). Calcium chloride-injected steaks had higher (P < .05) juiciness ratings than control steaks. Postrigor calcium chloride injection reduced (P < .05) shear force within 1 d after injection and resulted in more tender meat through 14 d after injection. Extended postinjection aging (35 d) had little effect on color display stability. Calcium activated tenderization can be applied as late as 14 d postmortem and will reduce the occurrence of tough meat if aging is limited.     

Experimental Study of Ferrous Calcium Silicate Slags: Phase Equilibria at {\text{P}}_{{{\text{O}}_{2} }} Between 10?5?atm and 10?7?atm

Ferrous calcium silicate slags, whose principal components are “FeO _x ”-CaO-SiO₂, are widely used in copper smelting and converting operations. In the current study, high-temperature equilibration and rapid quenching techniques were used to study the phase equilibria of the ferrous calcium silicate slags. The compositions of phases in the slags were measured accurately using electron probe X-ray microanalysis (EPMA). The phase equilibria of the system have been characterized at oxygen partial pressures between 10⁻⁵ atm and 10⁻⁷ atm at selected temperatures between 1473 K and 1623 K (1200 °C and 1350 °C). The effects of oxygen partial pressure and temperature on the compositions of phases in the slags are presented.     

The chemical diffusivity of oxygen in liquid iron oxide and a calcium ferrite

Measurements have been made of the chemical diffusion coefficient of oxygen in liquid iron oxide at temperatures from 1673 to 1888 K and in a calcium ferrite (Fe/Ca = 2.57) at temperatures from 1573 to 1873 K. A gravimetric method was used to measure the oxygen uptake during the oxidation of the melts by oxygen or CO₂-CO mixtures. The rate was shown to be controlled by mass transfer in the liquid melt. The chemical diffusivity of oxygen in liquid iron oxide at oxygen potential between air and oxygen was found to be 4.2±0.3 × 10⁻³ cm²/s at 1888 K. That in iron oxide at oxidation state close to iron saturation was established to be given by the empirical expression log D=−6220/T + 1.12 for temperatures between 1673 and 1773 K. For the calcium ferrite (Fe/Ca=2.57) at oxygen potential between air and oxygen, the diffusivity of oxygen was found to be given by log D=−1760/T−1.31 for temperatures between 1673 and 1873 K. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

Microsegregation of oxygen in Zr-2.5Nb alloy materials

Oxygen partitioning between the primary-a andβ phases during heating at an(α + β) temperature was investigated in a Zr-2.5Nb alloy containing about 1100 ppm (wt) oxygen. Standard pressure tubes used in CANDU reactors have been produced from this material by hot extrusion of billets after preheating in the (α + β) temperature range. Secondary ion mass spectroscopy (SIMS) was found most suitable for oxygen mapping and for determining quantitatively the extent of preferential oxygen enrichment of primary-a grains in pressure tube samples previously subjected to experimental preheat treatments at an (α +β) temperature of 870° for different soak times up to 24 hours. For the (α α β)-treated materials, the oxygen concentration in the primary-a grains increased with soak time, reaching up to about 8 times the concentration in the primary-β matrix region. Samples from two standard pressure tubes with different fracture toughness properties were also examined. Signi-ficant differences between these tubes were found in their primary-α grain size and in the levels of oxygen enrichment of the a grains, which could provide an explanation for the difference in the toughness of these tubes.     

Simulation of Slag Freeze Layer Formation: Part I. Experimental Study

This study was conducted to understand the freeze layer formation and heat transfer that is required to design cooling systems in pyrometallurgical operations in which a frozen slag layer is used to protect the furnace wall. Similar Grashof and Prandtl numbers for operating furnaces were obtained in a 200-mm square cavity differentially heated on the sides containing an aqueous solution of calcium chloride. The solid front was tracked using a digital camera, and the temperature field was measured with thermocouples. The flow velocity field was measured using the two-dimensional particle image velocimetry technique. Experiments were conducted over a range of superheat conditions, and the solidification front was planar (i.e., neither cellular nor dendritic) because the system slowly approached steady state. The two-phase zone comprised particles circulating slowly with the liquid in the bulk of the cavity; at the vertical walls, velocities were higher.     

Studies on Extraction of Potassium from Feldspar by Roast-leach Method Using Phosphogypsum and Sodium Chloride

The extractions of potassium value from feldspar via roasting and leaching route was studied with a focus on the effects of the roasting time, temperature, additives, and particle size. Sodium chloride and phosphogypsum (PG) were used as a source of chloride and calcium, respectively, and played the important role during the roasting of feldspar. When the feldspar sample was roasted at 900°C with sodium chloride alone, the extraction of potassium was limited to 61%. The extraction could go up to 92.5% by the addition of phosphogypsum along with sodium chloride. The optimum conditions of potassium extraction were found to be, particle size 100 µm, roasting temperature 900°C and roasting time of one hour. The X-ray diffraction study indicated the formation of sylvite (KCl) in the roasted product and its disappearance in roast-leach residue due to its high water solubility. The morphological changes during the roasting process were clearly observed by field emission scanning electron microscope (FESEM) images. The extraction of potassium from feldspar was best fitted by the Ginstling and Brounshtein kinetic model. The activation energy of 238.6 KJ/mole and 28.73 KJ/mole for low and high-temperature regions indicated that the overall extraction process follows two-steps reaction path.     

Coarsening kinetics of silica in copper

Coarsening experiments have been conducted in the copper-silica system to study the aging behavior of compound precipitates in metallic systems under various conditions of temperature and atmosphere. Most of the experiments were conducted in a two-zone heating furnace, wherein a copper-cuprous oxide mixture was heated in one zone and the copper-silica sample was heated in the other zone, all enclosed in a quartz capsule. The temperature of the former zone determined the oxygen partial pressure in the system and the temperature of the latter zone determined the coarsening temperature. The silica particles from the coarsened samples were extraction-replicated and photographed in an electron microscope. The average radii obtained from these photographs were used to determine coarsening rate constants and activation energies. Isothermal coarsening kinetics followed the γ^-3 vs t law, indicating volume diffusion control. Activation energies were obtained for four different sets of experimental conditions. In each case the activation plot was linear. For coarsening under variable oxygen pressure the experimental activation energy of 530 kJ (127 Kcal) agrees fairly well with the predicted value of 514 kJ (123 Kcal) which takes into consideration the heats of solution and dissolution, as well as the activation energy for diffusion. For coarsening under constant oxygen pressures the experimental activation energies do not compare well with the predicted values, calculated on the basis of complete equilibration of oxygen between the gaseous phase and the sample. However, the experimental activation energies of 524 kJ (125 Kcal) and 447 kJ (107 Kcal) lie in the predicted range calculated on the basis of fixed amounts of oxygen in solution in copper. In no case is the activation energy for coarsening equal to that for diffusion of either species in the matrix as is sometimes assumed. Formerly DSR Staff Member.     

氯化挥发回收含锡尾矿中的有价金属

采用氯化挥发法在马弗炉和管式炉中处理含锡尾矿,探索还原剂(无烟煤)和氯化剂(CaCl2)的加入量对有价金属挥发的影响。结果表明,在无烟煤加入量8%,氯化钙加入量21%,石灰加入量5.21%,温度1 000℃,挥发时间3h的条件下,锡挥发率达到96.15%,铅和锌的挥发率分别为96.22%和73.51%。     

Fundamental studies on the deoxidation of low carbon steels with ferrosilicon

Laboratory size (4.6 kg) low carbon-iron melts were deoxidized using plain ferrosilicon, ferrosilicon with calcium aluminate flux, and ferrosilicon with calcium silicate flux. The dissolved oxygen and total oxygen contents in these heats were measured as a function of time and temperature using oxygen probes and quenched pin samples taken from the melts. The dissolved oxygen values, as measured by the oxygen probes, indicated that the iron-silicon deoxidation reaches equilibrium within five minutes of reaction time. However, the total oxygen (dissolved oxygen+oxygen in oxide inclusions), as measured from the quenched pin samples, took almost twenty minutes to reach a steady state. The two aforementioned features were common to all the experimental heats. Below 1978 K the ferrosilicon heats with calcium silicate or calcium aluminate flux had lower steady state total oxygen values as compared to the plain ferrosilicon heats; the difference was more significant at lower quenching temperatures. Also, below 1978 K, the dissolved oxygen-temperature relationship of flux heats was identical to their steady state total oxygen-temperature relationship, which indicated that the addition of fluxes leads to elimination of oxide inclusions. The performance of calcium aluminate and the calcium silicate fluxes in removing the oxide inclusions was found to be identical in these laboratorysize heats. U. B. PAL, formerly Senior Metallurgist, Melting and Primary Operations, Allegheny Ludlum Corporation, Technical Center, Brackenridge, PA 15014     

Analysis of the Deoxidation Process of Copper using an Electrochemical Cell

A solid electrolyte oxygen sensing cell employing yttria‐stabilized zirconia (YSZ) was used to determine the oxygen content and activity in molten copper on a laboratory scale at temperatures between 1200 and 1400 °C. The effects of temperature and time of treatment were investigated on the deoxidizing process with Cu₃P. The amount of Cu₃P added ranged from 1 to 3% of the mass of molten copper. At 1200 and 1300°C, fair agreement was obtained between the oxygen contents calculated from the measured probe EMF and those obtained by chemical analysis. It was found that the oxygen is more efficiently removed at lower temperatures. A metallographic analysis of rapidly cooled samples showed that oxygen and phosphorus are present in the copper mainly as oxide dendrites.     

钙锶氯化物体系中钙和锶的重量法分析

针对氯化钙氯化锶混合体系,探索出能够准确分析该体系中钙和锶含量的分析方法。首先,用碳酸盐重量法分别对氯化钙和氯化锶单盐溶液进行分析,能够获得比较准确的测定结果且确定了碳酸盐沉淀适宜的烘干温度和烘干时间分别为200 ℃和20 h。在此基础上,结合碳酸盐重量法和经典的氯化银重量法对氯化钙和氯化锶的混合溶液进行准确地分析,分别获得碳酸盐沉淀的总质量和总氯的物质的量,再通过联立方程组求解得到钙锶氯化物共存体系中各组分的含量。最后,将实验方法用于分析钙和锶物质的量之比YB(YB=nCa∶nSr)为49、9.4、0.98、0.10和0.030的氯化物体系中氯化钙和氯化锶的组分含量时,测定结果比较准确,绝对误差小于0.5%。     

双环己酮草酰二腙光度法测定合金中高含量铜

以双环己酮草酰二腙（BCO）光度法快速测定合金中高含量铜,并对最佳显色条件进行了探讨。结果表明：在pH 8.5~10.0的氨水-氯化铵缓冲溶液中,铜与BCO形成蓝色络合物,该络合物的最大吸收波长为600 nm;BCO浓度为0.1 g/L;显色温度为20 ℃;显色时间是10 min;柠檬酸铵用量为1 mL。铜在0.4~4.0 μg/mL范围内符合比尔定律,表观摩尔吸光系数ε=1.6×10⁴ L·mol^-1·cm^-1。方法应用于高温合金及铜合金标准样品中高含量铜的测定,测定值与认定值相符,相对误差＜1.0%,相对标准偏差＜6.5%。     

Sulfur Transfer at Slag/Metal Interface—Impact of Oxygen Potential

In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/metal interface was monitored by X-ray sessile drop method in dynamic mode at temperature 1873 K (1600 °C) under nonequilibrium conditions. The experiments were carried out with pure iron and CaO-SiO₂-Al₂O₃-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. The impact of oxygen potential on the droplet oscillation as sulfur from the gas phase reaches the metal drop through the intermediate slag phase was monitored. The interfacial velocity was investigated. It was found that the increases of interfacial velocity and the maximum oscillation time were mainly attributed to the partial pressure of oxygen increases. The experiment results were explained by previous ab initio calculations. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.     

二次铝灰酸浸制备聚合氯化铝的研究

二次铝灰中仍含大量铝,对其进行回收具有重要意义。文中以二次铝灰为原料,通过盐酸浸出处理后再添加铝酸钙制备聚合氯化铝（PAC）,研究了HCl浓度、浸出温度、时间、液固比,铝酸钙添加量等因素的影响。综合考虑,适合二次铝灰酸浸制备聚合氯化铝的较优条件为:水洗后的二次铝灰在HCl浓度为6 mol/L,液固比为4∶1 mL/g,温度为85 ℃条件下酸浸2 h,此时的酸浸液中加入12 g/80 mL的铝酸钙,温度为85 ℃条件下反应1.5 h。该条件下酸浸过程中铝的浸出率为48.67%,且制得的液体PAC完全符合国家标准。      

Electrochemical Reduction of Tungsten Compounds to Produce Tungsten Powder

The production of tungsten by direct current reduction has been investigated. Experimental studies involved the electrochemical reduction of the solid tungsten compounds tungsten trioxide (WO₃) and calcium tungstate (CaWO₄) in the form of an assembled cathode of porous pellets attached to a current collector. Molten calcium chloride and a molten solution of calcium chloride and sodium chloride at eutectic composition, 48 pct mol NaCl, were used as the electrolytes. Reduced samples were characterized by means of X-ray diffraction analyses and scanning electron microscopy. The results of X-ray analyses, supported with thermodynamic computations, showed that WO₃ cannot be used without loss in processes that involve the use of CaCl₂ at high temperatures because it reacts with CaCl₂ by releasing volatile tungsten oxychloride. In the electrochemical reduction of CaWO₄, X-ray diffraction results indicated the presence of tungsten with significant concentrations of calcium compounds. Metallic tungsten was obtained after treating the reduced samples with dilute hydrochloric acid solutions.     

Oxidation of ferrous sulfate in weakly acidic solution by gas bubbling

The oxidation of Fe²⁺ ion in aqueous solution in a pH region between 4.7 and 5.5 was studied. By supplying dilute NaOH solution from an automatic titrator, pH of the solution was maintained constant during the oxidation. The reaction is comprised of the sequential steps of the dissolution of gaseous oxygen and the oxidation of Fe²⁺ ion by dissolved oxygen. The latter reaction proceeds along two paths: homogeneous reaction in the solution (rate constant:k) and heterogeneous reaction on the surface of ferric hydroxide precipitate (rate constant:ks). The measured time variation of the concentrations of Fe²⁺ ion and dissolved oxygen was explained by simultaneous rate equations. Linear relationships were found between logk and pH and between logks and pH having slopes of 2 and unity, respectively. An activation energy of 103 kJ/mol was obtained fork. The overall rate of oxidation of Fe²⁺ ion was chemically controlled at pH lower than 5.0 and temperature lower than 298 K. On the other hand, it was controlled by both chemical reactions and the dissolution of oxygen at higher pH and temperature.     

The oxidation behavior of some Ni-Cr-Al alloys at high temperatures

Oxidation of ternary Ni-Cr-Al alloys containing different Cr/Al ratios has been studied in the temperature range 800° to 1300°C. Most of the studies were performed in 1 atm oxygen or air, but the oxygen pressure dependence for one of the alloys was also investigated. The experimental methods included thermogravimetric measurements of oxidation rates and studies on reacted specimens by means of X-ray diffraction, metallographic techniques, electron microprobe analysis, and electron microscopy. In general, the oxidation rates decrease faster with time than that for an ideal parabolic behavior. The major reaction products were NiO, Cr₂O₃,α-Al₂O₃, and Ni(Cr,Al)₂O₄. The relative amounts of these were a function of composition, temperature, oxygen pressure, and reaction time. The Ni-9Cr-6Al alloy has the best oxidation resistance due to the formation ofα-Al₂O₃ at all temperatures investigated. The oxidation mechanism of the alloy is discussed.     

On the calculations of the diffusion coefficients of oxygen and nitrogen in niobium

The Snoek peaks for oxygen and nitrogen in niobium have been remeasured using a torsion pendulum equipped with LVDT transducers connected to an oscillograph for automatic data recording. The peak temperatures were determined using a new numerical analysis of the peak shape. These new low temperature data have been combined with high temperature direct data and intermediate temperature high frequency internal friction data reported in the literature. When it is assumed that the oxygen and nitrogen] occupied octahedral positions in the niobium matrix, the diffusion coefficients for both oxygen and nitrogen atoms follow a simple Arrhenius behavior. In the temperature range of this analysis (140 to 1000°C for oxygen and 270 to 1800°C for nitrogen) the equationsD = (5.3E - 7) exp - (1.095E5)/RT andD = (2.6E - 6) exp - (1.523E5)/RT apply for the diffusion of oxygen and nitrogen, respectively. Entropy of activation calculations were made using the above activation energies and frequency factors, and the results agree well with reported values for other systems as well as with the theory of Keyes. This good agreement suggests that the assumption that oxygen and nitrogen prefer octahedral sites is probably correct.