High temperature properties of by-product cold bonded pellets containing blast furnace flue dust

In this investigation, the fundamental reactions occurring during the heat treatment of cold bonded pellets (CBP) comprised of iron and steelmaking by-products have been studied. Blast furnace (BF) flue dust, which contains fractions of coal and coke particles, has been included in the CBP blend as a source of solid reductant. Thermal analysis was performed on CBP samples in inert atmosphere at a heating rate of 10 °C/min in order to observe their high temperature properties, specifically, the mechanisms of self-reduction within CBPs. Both endothermic and exothermic reactions were observed during heating. The gases generated during thermal analysis were analyzed using a quadropole mass spectrometer (QMS). Furthermore, CBP samples heated to several different temperatures and quenched in argon were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results from this investigation demonstrate that the decomposition of hydrates and carbonates in CBP samples contribute, as gaseous intermediates, to an earlier reduction of contained iron oxides. The gaseous intermediates are responsible for an initial gasification of carbon contained in blast furnace flue dust leading to low temperature iron oxide reduction. The step-wise reduction of iron oxides in CBPs at the given conditions begins at ∼500 °C and is nearly completed at 1200 °C. This work can help to provide a fundamental understanding of the reduction characteristics of iron and steelmaking by-product agglomerates.     

Determination of minor elements in steelmaking flue dusts using laser ablation inductively coupled plasma mass spectrometry

Element determination in solid waste products from the steel industry usually involves the time-consuming step of preparing a solution of the solid. Laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to the analysis of Cr, Ni, Cu, As, Cd and Sn, elements of importance from the point of view of their impact on the environment, in electric arc furnace flue dust (EAFD). A simple method of sample preparation as pressed pellets using a mixture of cellulose and paraffin as binder material was applied. Calibration standards were prepared spiking multielement solution standards to a 1:1 ZnO + Fe₂O₃ synthetic matrix. The wet powder was dried and mechanically homogenised. Quantitative analysis were based on external calibration using a set of matrix matched calibration standards with Rh as a internal standard. Results obtained using only one-point for calibration without matrix matched, needing less time for standardization and data processing, are also presented. Data are calculated for flue dust reference materials: CRM 876-1 (EAFD), AG-6203 (EAFD), AG-6201 (cupola dust) and AG-SX3705 (coke ashes), and for two representative electrical arc furnace flue dusts samples from Spanish steelmaking companies: MS-1 and MS-2. For the reference materials, an acceptable agreement with certificate values was achieved, and the results for the MS samples matched with those obtained from conventional nebulization solutions (CN). The analytical precision was found to be better than 7% R.S.D. both within a single pellet and between several pellets of the same sample for all the elements.     

Surface area development of three cokes in relation to the zinc–lead blast furnace

The development of surface area on burn-off for three metallurgical cokes has been studied and correlated with rates of oxidation in carbon dioxide. The role of boric oxide, B₂O₃, as inhibitor of oxidation is discussed. The effect of ash build-up in the later stages of coke burn-off is evaluated in relation to surface area changes.     

Thermal characteristics of aged granulated blast furnace slags

A series of aged granulated blast furnace slags were investigated by DTA. Devitrification characteristics were found to change as a function of age, and regular trends could be established. XRD showed the devitrification process to result predominantly in melilite formation and minor amounts of merwinite, depending on slag age.Hydration of fresh slags resulted in the gradual formation of hydrated species and calcite. DTA indicated that the devitrification profile also changed with the extent of hydration.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthdayThe author acknowledges the assistance of Ms S. Bell and M. Venour (BHP) in this study.     

熔融X射线荧光光谱法测定高炉返粉组份

建立了X射线荧光光谱法测定高炉返粉中化学成分的方法,采用高温熔融法将试样制成玻璃状体,消除了基体干扰;通过对熔样条件、干扰元素、仪器参数、工作曲线拟合方式等方面进行实验研究,确定了最佳分析条件,实现了高炉返粉中主要成分SiO2等8种成分的同时测定,方法具有准确度高、同时测定多元素、分析速度快等特点。     

含钛高炉渣对水中氨氮的吸附特性

选用含钛高炉渣作为吸附剂,研究渣的投加量、粒径大小、温度以及溶液初始pH等因素对含钛高炉渣吸附水中氨氮的影响及吸附特性。动力学数据分析表明,准二级动力学模型能更好地描述含钛高炉渣对氨氮的吸附;颗粒内扩散方程拟合结果发现,含钛高炉渣对氨氮的吸附包括表面吸附和颗粒内扩散两个阶段。吸附等温线拟合表明Langmiur方程能够更好地模拟含钛高炉渣对氨氮的吸附过程。在20℃、反应时间4h的条件下,对于100mL浓度为100mg/L的氨氮溶液,8g粒径为80~120目的含钛高炉渣对氨氮的去除率可以达到32%;随着温度的升高,去除率基本呈上升趋势;溶液初始pH对氨氮的去除有一定的影响,在碱性条件下有较好的去除效果。     

Determination of chrysotile content of asbestos cement dusts by IR-spectroscopy

Summary A new pellet preparation technique was developed for the quantitative determination of chrysotile in samples of asbestos cement. Ethanol was used for preventing agglomeration of ground primary particles during pellet preparation. It has been proved that after alcohol treatment the particle size in the pellet remained small and the absorbance values of 5 parallel pellets agreed better than 95% relative. 10–500 g Chrysotile/mg sample were found in actually deposited samples taken from various sites in an asbestos cement factory.

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Bestimmung des Chrysotilgehaltes von Asbestzement-Staub mit Hilfe der IR-Spektroskopie

Zusammenfassung Zur Chrysotilbestimmung in Asbestzement wurde eine neue Methode zur Herstellung des Preßlings für die IR-Spektroskopie ausgearbeitet. Dabei wurde Ethanol eingesetzt, um ein Zusammenballen der Primärteilchen zu verhindern. Nach der Alkoholbehandlung blieb die Teilchengröße im Preßling klein, und die Extinktionswerte für 5 Preßlinge stimmten zu 95% überein. In Proben, die von verschiedenen Stellen einer Asbestzement-Fabrik genommen waren, konnten 10–500 g Chrysotil/mg gefunden werden.

     

EDTA滴定法测定再生锌原料中的锌含量

采用氟化铵-盐酸-硝酸-硫酸分解样品,氨水沉淀分离铁、锰、铅等共存元素,滤液中加入掩蔽剂掩蔽少量干扰元素,在pH=5～6的乙酸-乙酸钠缓冲溶液中,以二甲酚橙为指示剂,用EDTA标准滴定溶液滴定。测得结果为锌、镉合量,扣除镉量,即为锌量。方法用于测定再生锌原料中锌,结果的相对标准偏差(RSD,n=11)为0.15%～1.0%。按照实验方法对再生锌原料样品进行加标回收实验,回收率为99.1%～102%。能满足日常对再生锌原料中锌含量的检测要求。     

Application of thermal analysis to study of phase composition changes in blast furnace sinters

Application of thermal analysis to determine a quantity portion of iron oxides in symmetric blast furnace sinters is presented. In the multicomponent sample, calcium ferrites and many silicate phases beside doped iron oxides phases were observed. The dependence of sinter phase composition from basicity and relation with physicochemical properties is defined.     

Deposition of cesium and cobalt sorbed on zeolite in matrices of blast furnace slag

¹³⁷Cs and⁶⁰Co were sorbed from model solutions and waste water on chemically treated granular zeolite. The zeolite was incorporated into cement slurries based on blast furnace slag (BFS). The compressive and bending strength were measured after different times of hydration. The leaching tests were performed in water, base and acid solutions. The leachability was more pronounced only for samples in acidic solutions.     

Effects of pyrolysis upgrading temperature on semi-coke explosibility for blast furnace injection

Journal of Thermal Analysis and Calorimetry - The purpose of this work is to understand the semi-coke explosion issues and to improve the safety in semi-coke injection. It shows that the higher...     

电感耦合等离子体原子发射光谱测定钒钛高炉渣中钪镓铬镍钴

建立电感耦合等离子体原子发射光谱法(ICP-AES)同时测定钒钛高炉渣中0005%～0.3%的贵金属元素钪、镓、钴和0.0005%～0.6%铬、镍的检测方法。样品前处理方法采用氢氟酸、盐酸、硝酸和硫酸消解钒钛高炉渣,高温加热至硫酸分解产生三氧化硫浓白烟为此,直接以水稀释定容制备样品溶液,不仅快速完全消解高钛基样品,而且通过挥发除去高含量二氧化硅基体和反应残余的氢氟酸,减少溶液共存组分有效降低基体效应影响以及避免腐蚀检测仪器;而且依靠残余硫酸根与高钛基体络合生成硫酸氧钛离子,解决了高浓度钛基体在低酸度介质中易水解问题,无需补充加入大剂量酸以限制钛水解,直接以水稀释制备样品溶液,从而降低溶液酸度减少酸度效应影响。方法重点试验考察了钒钛高炉渣中钒钛铁钙镁铝等共存介质下基体效应、光谱干扰等干扰影响因素,优选了元素的分析谱线、背景校正区域以及光谱仪工作参数等检测条件,采用基体匹配和同步背景校正法消除基体效应影响。验证表明方法的技术性能指标：校准曲线相关系数>0.999,背景等效浓度0.0001%～0.0002%,元素检出限0.0001%～0.0002%,检测范围内RSD＜15%,回收率90%～114%     

Gaseous carbide mechanism of the reduction of oxides by carbon: from a graphite furnace to a blast furnace

The gaseous carbide mechanism of oxide reduction by carbon is described. This mechanism is based on two concurrent reactions: M_(g) + zC_(s) = MC_z(g) and MC_z(g) + (z/y) M_xO_y(s) = (1 + xz/y)M_(g) + zCO. The first of these reactions occurs on the surface of graphite, and the second on that of the oxide. Two assumptions had to be introduced to validate this mechanism. First, one had to postulate the presence of defects on the graphite surface favoring the formation of excess gaseous carbides. Second, it had to be assumed that irrespective of the saturated metal vapor pressure, the oxide is reduced via a stage of formation of gaseous metal atoms. This paper is devoted to the substantiation of these assumptions. We use for this purpose the results of our experiments, as well as the literature data. The results of practical application of the gaseous carbide theory in electrothermal atomic absorption spectrometry are discussed, as well as in other areas of science and technology dealing with the interaction of oxides with carbon, among them pyrometallurgy, carbide production, catalytic processes of graphitization and carbon gasification.     

Determination of cadmium,zinc, and lead by non-dispersive atomic fluorescence spectrometry with a new graphite furnace atomizer

A new graphite furnace atomizer has been developed and applied to the determination of cadmium, zinc, and lead by non-dispersive atomic fluorescence spectrometry. A solar-blind photomultiplier, a lock-in amplifier, and microwave-excited electrodeless discharge lamps are used. The detection limits for cadmium, zinc, and lead in the non-dispersive atomic fluorescence mode are 1·10^?13g, 2·10^?13g, and 2·10^?11g, respectively, which are 20-, 10-, and 2-fold better than those in the atomic absorption mode. The analytical working curves are linear over about three decades of concentration from the detection limits.     

The atomic absorption determination of zinc with a graphite furnace

The use of a heated graphite furnace has been evaluated for the atomic absorption determination of zinc. Interferences were found to occur with most elements when present in large amounts; solvent extraction procedures have been investigated to avoid such effects. Results are reported for the solvent extraction and determination of zinc in the range 0.002–1 p.p.m.     

焦炭溶损反应动力学及其模型研究

利用未反应核收缩模型对高炉焦炭与CO2的反应动力学进行了研究,建立了以可测参数（R）表达的焦炭与CO2的反应动力学关系式。并对反应速率常数和有效扩散系数、表观反应活化能和有效扩散活化能及反应过程中各步骤阻力进行了分析。结果表明,（1）焦炭与CO2的反应符合未反应核收缩模型。（2）反应的表观活化能Ea=124.5kJ/mol,有效扩散活化能ED=642.4 kJ/mol;界面化学反应的阻力随反应温度升高而增加;残余灰层内的内扩散传质阻力相对比例随温度升高而下降。（3）焦炭溶损反应在低温区主要受内扩散控制,随着温度升高,反应由外扩散、化学反应和内扩散三步控制;当进入高温区,反应进行一段时间后主要受内扩散控制。     

粗锌中镉的测定方法研究

样品用硝酸-盐酸分解,采用扣除背景的方式消除高含量的锌对低含量镉测定的影响。优化了镉测定的仪器条件,建立了粗锌中镉含量的测定方法。用于测定粗锌中镉,结果的相对标准偏差(RSD,n=11)为0.95%～6.3%。按照实验方法对粗锌样品进行加标回收实验,加标回收率为98.0%～102%。与ICP-AES法测定结果基本一致,能满足日常对粗锌中镉含量的测定要求。     

Determination of zinc dialkyldithiocarbamates in latex condoms

A simple high-performance liquid chromatographic (HPLC) assay is developed for measuring zinc dialkyldithiocarbamate (DTC) levels in latex condoms. After extraction of 14 different brands of latex condoms in acetonitrile, aliquots of the extracts are subjected to a preliminary screening assay by treatment with cobalt chloride and measurement of UV absorption at 320 nm, which results in the identification of 6 DTC-containing samples. Prior to analysis by HPLC, zinc dimethyldithiocarbamate (ZDMC) or zinc diethyldithiocarbamate (ZDEC) is added to the extracts in order to block transmetalation reactions with the analytes of interest. A reversed-phase C(18) column, with gradient elution and UV detection at 260 nm, is used to measure the zinc DTCs. The limits of detection for ZDEC and zinc dibutyldithiocarbamate (ZDBC) are 5 and 10 micro g/mL. Levels of ZDBC and ZDEC range from not detectable to 3.31 and 1.79 mg/condom, respectively. Total protein and latex allergenic protein levels are determined and range from 98 to 776 and 0.01 to 14.04 micro g/unit, respectively, but are not related to the level of ZDBC or ZDEC. This methodology provides both screening and specific tools for the determination of unstable zinc DTC complexes in latex products.     

粗锌中镉的测定方法研究

采用火焰原子荧光法（FAFS）和电感耦合等离子体质谱法（ICP-MS）测定铅锌矿中的镉. 通过对比研究,两种方法的校准曲线相关系数良好（r>0.999 5）,方法检出限、准确度和精密度均符合质量规范要求. 经过铅锌矿实际样品的比对,两种方法不存在显著性差异. FAFS法比ICP-MS法测定时间短,精密度高,适用于大批量铅锌矿样品的测定.