超纯铁精矿粉直接还原制备超细铁粉

将超纯铁精矿粉气流粉碎到微米级,用氢气直接还原制备超细铁粉,利用正交实验法研究还原温度、时间、氢气流量等工艺参数对还原率的影响。结果表明:对超纯铁精矿粉还原率的影响程度从大到小依次为温度、时间、氢气流量,综合考虑生产成本,确定最佳的还原工艺参数为温度780℃、时间60 min、氢气流量0.3 L/min。在此工艺条件下得到的超细铁粉,全铁含量为98.58%,氢损0.45%,酸不溶物含量为0.19%,其化学成分符合粉末冶金用铁粉标准,一次粒度小于5μm。     

Interrelation between kinetics of reduction and volume change during formation of directly reduced iron rod

A kinetic study on reduction has been carried out by heating a central column of blue dust (a fine variety of iron ore) surrounded by a concentric layer of non-coking coal fines in the temperature range of 1173- 1323 K. The temperature of the periphery of blue dust column is kept constant at the temperature of experimentation, however, the temperature of the interior of the cylindrical column increases with time of residence and the change in volume of the reaction mass occurs. The loose column of blue dust gets reduced, consolidated and sintered to produce directly reduced iron rod (DRIR). The work also comprises studies concerning the effect of volume change on the reduction kinetics. The reduction phenomena are very much influenced by the change in volume of reaction mass. The kinetics of reduction shows an agreement with Ginstling-Brounshtein model whereas the kinetics of change in volume is interpreted using Johnson-Mehl equation. The rate constants k₁ and k₂ derived from kinetic analysis of reduction and volume change respectively are shown to be linearly interrelated till the change in volume with respect to the original volume becomes more or less constant.     

The kinetics of magnesium vapour dissolution into pig iron

Abstract

Magnesium injections are used extensively in the iron and steel industry for the production of ductile iron, and for the desulphurization of blast furnace pig iron. However, little is currently known about the kinetic mechanisms involved in either of these two cases. In the present work, a magnesium vaporizer was used to inject pure magnesium vapour into 60-kg pig iron melts (1250°C) at rates of between 0.7 and 12 gm/min for bubbling periods of 20 to 60 minutes. The efficiency of magnesium dissolution ranged between 20 and 80%. A mass transfer model, based on single bubbles, was used, to interpret the results. In addition, residual magnesium concentrations following holding times of up to 60 minutes after bubbling compared reasonably well with those predicted on the basis of theoretical evaporation rates.

Résumé

L'injection de magnésium est utilisée intensivement dans l'industrie siderurgique pour la production de fonte ductile et pour la désulfuration de la fonte en gueuse provenant du haut-fourneau. Cependant, il y a présentement peu dapos;informations sur les mécanismes de réactions impliqués dans l'un ou l'autre des deux cas. Dans ce présent travail, un va porisateur de magnésium a été utilise afin d'introduire la vapeur de magnésium pur dans un bain de 60 kg de fonte liquide à 1250°C, a des taux variant entre 0.7 et 12 gn/min pour des durées d'injection variant de 20 à 60 minutes. L'efficacité de la dissolution du magnésium dans la fonte liquide était comprise entre 20 et 80%.

Un modele de transfert de masse a été utilisé pour interpréter les résultats. Il est à noter que les concentrations résiduelles de magnésium correspondant à des temps de bouillonnement allant jusqu'à 60 minutes se comparent raisonnablement bien avec les valeurs prédites théoriquement à partir des taux d' évaporation du Mg.     

三氯化铁分解重铬酸钾滴定法测定直接还原铁中金属铁

试样用三氯化铁溶液溶解,金属铁被氧化为二氯化铁,过滤分离,滤液酸化后以二苯铵磺酸钠为指示剂,用重铬酸钾标准溶液滴定。确定了试样粒度在0.125 mm以下、三氯化铁溶液浓度和用量分别为100 g/L和40 mL、搅拌时间为30 min的最佳实验条件。用本法测定直接还原铁样品,相对标准偏差小于2%,加标回收率在99.5%~101.2%之间。     

Inhibition of the reoxidation of the secondary electron acceptor of photosystem II by bicarbonate depletion

Intravenous infusion of 600 ng/kg/min of 1-sarcosine, 8-isoleucine-angiotensin II, an angiotensin II antagonist, caused a marked blood pressure fall and a decrease in plasma aldosterone in 3 patients with Bartter's syndrome. These results indicate that proximal cause of Bartter's syndrome is an arteriolar hyporesponsiveness to angiotensin II and that this angiotensin II analogue has an antagonist activity on peripheral arterioles as well as adrenal cortex.     

Some aspects on porous properties of iron oxides containing foreign oxides reduced by hydrogen

The objective of this study is to prepare suitable iron ores for industrial reduction processes. Therefore, the properties of porous, green and indurated hematite compacts as well as iron ore were investigated by quantitatively measuring pore volume, BET surface area and pore size distribution. Furthermore, the influence of foreign oxides on porous properties was investigated. Based on these data, the mechanism of sintering process of the compacts was discussed. The results obtained here suggest that the porosity of the compacts after almost 100 pct reduction does not depend upon whether the compacts were indurated or not. Therefore, it would be concluded that indurating the compact is not necessary for pulverized iron ores containing foreign oxides when reduced in the process such as a fluidized bed system.     

Some properties of reduced iron powder manufactured from Mill-scale

Conclusions Some key data are presented on the properties of iron powder reduced with a solid reducing agent from low-carbon steel mill-scale and on the mechanical characteristics of specimens pressed from this powder and sintered in hydrogen and dissociated ammonia atmospheres. The properties of iron powder manufactured by the process described meet the requirements of powder metallurgy.Translated from Poroshkovaya Metallurgiya, No. 3 (135), pp. 102–106, March, 1974.     

Dermal uptake of solvents from the vapour phase: an experimental study in humans

An overview of computer models developed since the late seventies, which enable the simulation of the primary effects of spinal cord stimulation (SCS) on nerve fibres, is presented. These models consist of a 3-dimensional volume conductor model, representing anatomical structures and their electrical conductivities, and cable models representing the electrical behaviour of nerve fibres. The characteristics of these models and their relation to anatomy and physiology, as well as the calculation of stimulation-induced electrical fields and their effect on nerve fibre models, are reviewed. It is shown that most characteristics of SCS as predicted by computer modelling correspond well with empirical data. Accordingly, a theoretical framework describing the relations between relevant parameters in SCS is presented. Finally, it is shown how theory and computer modeling are applied to improve the efficacy of SCS by the optimization of its technique, primarily by the design of new epidural electrodes.     

直接还原铁在转炉的应用效果分析

太钢二炼钢在80 t转炉上采用直接还原铁代替专用废钢冶炼品种钢的试验并推广使用,结果表明,直接还原铁代替废钢合适的比例为35%～50%,使用部分直接还原铁后转炉脱磷能力增加,脱磷率提高2.4%;80 t转炉配加5 t直接还原铁,石灰消耗增加9.3 kg/t;使用直接还原铁代替部分专用废钢,钢中残余元素及有害元素含量都很低.     

FeS-MnS phase relationships in the presence of excess iron

The FeS-MnS system is reexamined, both with and without excess iron. When excess iron is present, as is true for sulfide inclusions within steel, the pseudobinary reveals a peritectic rather than the previously assumed eutectic invariant. The maximum solubility limits (997 ± 3°C, or 1270 K) in the two solid phases are: a) 7.5 wt pct MnS in FeS, and b) 73.5 wt pct FeS in MnS. The peritectic liquid contains 66 wt pct Fe, ∼34 wt pct S, and ∼0.4 wt pct Mn. The two solid sulfide phases are nearly stoichiometric in the presence of excess iron; the Fe-richer sulfide is metal-deficient in the absence of a metallic iron phase. Based on this study, it is possible to be more specific than heretofore about the Fe-FeS-MnS-Mn region of the Fe-Mn-S ternary. In addition to the presence of a peritectic, it was concluded that the miscibility gap does not cross the univariant line between primary metal and (Mn,Fe)S phases. The peritectic liquid and the Mn-richer solid sulfide equilibrate with a metal containing ≤ 0.36 wt pct Mn. These data help explain the Mn/s ratios required to avoid hot-shortness in regular and resulfurized plain-carbon steels. G. S. MANN, formerly Graduate Student This is a part of the dissertation submitted by G. S. Mann for his Ph.D. at the University of Michigan     

FeSe-MnSe phase relationships in the presence of excess iron

The subsolidus phase relationships of iron selenide and manganese selenide are examined both with and without excess metallic iron. In the presence of excess metal, where the situation is similar to that existing in steels, the FeSe-MnSe pseudobinary has a peritectic at 976 ±3°C (1249 K) with the following phases: Fe (<0.3 wt pctMn) (s), (Fe,Mn)Se(2.5 wt pet MnSe) (s), (Mn,Fe)Se(48.5 wt pct FeSe) (s), and a selenidiliquid (4.3Mn, 37.7Fe, 58 wt pet Se). A minimum is observed in the liquidus surface at ∼920°C and FeSe-9 wt pet MnSe. A qualitative liquidus surface is proposed for the Fe-FeSe-MnSe-Mn section on the basis of these results. This is a part of the Dissertation submitted by G. S. Mann for his Ph.D. at the University of Michigan.     

离子交换树脂相分光光度法测定水中痕量铁

提出了利用离子交换树脂相分光光度法测定痕量铁的方法。在中性介质中,铁离子与邻苯二酚紫形成有色络合物,将其富集在粒径为0.177~0.250 mm的201×4苯乙烯阴离子交换树脂上,制作成薄层树脂,于波长648 nm处光度法直接测定。铁含量在0.004~0.24μg/mL范围内符合比尔定律,方法检出限为4.1μg/L。加入2,3-二巯基丙醇掩蔽超过允许量的Bi3+,Sn4+等离子的干扰,其余共存离子基本无干扰。方法用于水中痕量铁的测定,相对标准偏差为2.0%~2.3%,回收率在98%~99%之间。