铁矿石粉煤基直接还原的热重分析

对大同烟煤-铁矿石粉的混合物进行了非等温热重-红外联用实验与分析,确定了铁矿石粉发生还原反应的温度区间范围,并结合还原产物的XRD图谱以及热重的定量计算结果,揭示了每个还原阶段完成后产物的物相及相应的还原分数。为了比较,进一步用热重分析仪对大同烟煤、神木褐煤以及阳泉无烟煤与铁矿石粉的混合物进行了非等温失重特性的对比实验研究。结果表明,低温阶段(800～950℃)大同烟煤对铁矿石粉的还原性最好,而高温阶段(1000～1100℃)神木褐煤也表现出良好的还原性。     

Modeling and simulations of a reformer used in direct reduction of iron

This paper presents a detailed modeling and simulations of a reformer unit used in the direct reduction of iron (DRI) process. A one-dimensional heterogeneous model for the catalyst tubes which takes into account the intraparticle mass transfer resistance was developed, while the furnace was modeled with bottom firing configuration. Validation against data from a local iron/steel plant showed satisfactory results. The performance variables of the unit were the process gas temperature, wall temperature and conversions of hydrogen, methane and carbon dioxide. The profiles of these output variables along the distance were calculated. The effect of operating parameters such as inlet temperature, natural gas flow rate and gas composition was also determined.     

生物质活性炭负载零价铁纳米晶簇直接催化还原NO

采用等体积浸渍法制备以生物质活性炭为载体的纳米铁基催化剂，利用TG、SEM、XPS、Raman等分析仪器对催化剂进行表征，探讨了活性炭负载零价铁和铁氧化物在无氧条件下脱硝的机理。结果表明：在750℃热还原条件下制得的铁基催化剂具备较高的活性，其活性中心是分散均匀的零价铁纳米晶簇。在280℃无氧条件下对NO的脱除效率达100%，且避免了活性炭载体的损耗。研究发现，催化剂快速失活是由于零价Fe被氧化为Fe₃O₄，因而降低了脱硝剂的活性。直接对失活催化剂进行热还原可以完全恢复活性，但这种方法会消耗炭载体；利用CO作为还原剂进行制备与再生，可以有效提高纳米晶簇的分散性，延长脱硝寿命并减少炭载体的损失，为零价Fe催化剂在实际应用中提供了可能性。     

温度及气氛对半焦直接还原铁矿石的影响

利用热重分析(TGA)和实验装置进行了半焦直接还原铁矿石试验,对比了不同还原温度和气氛下还原产品的性质。由TGA,焦矿质量比为1∶1的半焦铁矿石混合物由室温加热至1 100℃,N_2,H_2和CO气氛下还原过程可分为3个阶段,其中N_2下3个阶段活化能随温度逐渐增加,而H_2和CO下则先增加后降低。由固定床还原产物分析结果,温度和气氛对半焦直接还原铁反应过程及反应程度均有一定影响。3种气氛下,900℃后产物中主要为金属Fe,但引入还原性气体H_2,CO可有利于低温下铁矿石的还原。N_2气氛下反应至900℃后半焦可对铁矿石进行还原,但得到的海绵铁金属化率低于90%,无法满足直接炼钢要求,可通入H_2、CO等活性气氛,提高还原产品的品质。     

2种气氛下铁矿石粉煤基直接还原的热重研究

采用热重分析仪对大同煤、神木煤以及阳泉煤分别与铁矿石粉的混合物进行了氮气和二氧化碳2种气氛下的非等温质量损失特性的对比实验研究.研究结果表明:二氧化碳气氛下3个煤种分别同铁矿石粉混合物的反应阶段均为扩散控速,其中大同烟煤-铁矿石粉混合物的反应起始温度较低,阳泉无烟煤-铁矿石粉混合物的反应温度范围较大,反应的起始温度、反...     

Prospects for the development of brown coal deposits in kazakhstan and their quality evaluation for the direct iron reduction process

The paper describes modern requirements on the quality of carbonaceous materials used in the direct iron reduction process. Complex investigations of the quality of brown coals of Kazakhstan with regard to the direct iron reduction process included study of the material composition of the general and mineral parts, petrographic composition, and physicochemical characteristics (density, porosity, CO₂ reactivity, structural strength, and heat resistance). Recommendations and ranking of the studied coals for use as carbon reducing agents are provided.     

Catalysts for oxygen reduction from heat-treated carbon-supported iron phenantroline complexes

Oxygen reduction catalysts were prepared by heat treatment of carbon supported iron phenantroline complexes in Ar or NH₃. The optimum carbon black loading with iron was found to be 2%, the optimum heat treatment temperature was about 800 °C. X-ray diffractogramms and TEM showed the occurrence of crystalline species at higher catalyst loadings; however, these species seem not to contribute significantly to the catalytic activity. From the slope of the Koutecky–Levich plot, an average number of 3.7 electrons transferred per oxygen molecule was calculated, which is consistent with RRDE data. A Tafel slope of about 120 mV (decade)^–1 indicates that the first electron transfer is rate determining.     

低阶煤热解与低品位铁矿直接还原一体化研究

为了开发以低阶煤为还原剂的直接还原铁技术,采用低阶末煤分级热解生产热解煤气、焦油和半焦,利用热解煤气经升温后作为末煤热解和热半焦再次热解的热载体,热半焦再次热解得到的富CH4、H2和CO煤气作为低品位铁矿直接还原的还原剂,生产海绵铁。研究表明:低阶末煤热解耦合低品位铁矿直接还原技术与传统的基于天然气的气基直接还原技术相比,具有生产成本低、原料来源广的特点,非常符合我国富煤、富低品位铁、少气的资源状况。     

氧化铁浸染型石英中性正浮选制备低铁石英砂

氧化铁含量是决定石英在不同领域应用的主要因素,尤其是氧化铁浸染型石英砂,因氧化铁的赋存状态、共伴生、浸染程度及粒度差异,常规擦洗、强磁选及酸法反浮选难以有效降低石英中三氧化二铁含量。中性条件下,以抑制剂抑制含铁矿物、采用捕收剂使充分解离的石英上浮,通过粗选、精选进一步降低石英精砂中三氧化二铁含量。研究表明：自然pH下,采用淀粉基抑制剂CTSS、两性捕收剂兼起泡剂ZD-3联合作用,可将此类石英砂三氧化二铁含量由130～150mg/kg降至60～100mg/kg,满足超白光伏玻璃用硅质原料的质量要求;入浮砂粒度上限为0.6mm,以≤0.5mm为宜;对含铁铝硅酸盐矿物、氧化铁浸染型石英砂,中性正浮选石英精砂三氧化二铁含量低于酸性反浮选石英精砂中该指标;热力学计算表明pH≥5.5时淀粉基抑制剂CTSS与氧化铁表面铁离子发生化学键合的标准自由能变化ΔG为负值,化学键合具有自发趋势,抑制剂CTSS与含铁矿物的优先吸附是实现石英中性正浮选提纯的关键之一。     

还原参数对铁基催化剂F—T合成性能的影响

在浆态床反应器中详细考察了还原参数对工业铁基催化剂在F—T合成反应中的影响。研究结果表明：提高还原气体中CO／H2的比值有助于提高烯烃的选择性;提高还原气体的空速可以提高催化剂的活性,但是烯烃的选择性有所降低;升高还原温度在一定程度上可以提高催化剂的活性,但是温度过高容易造成催化剂积炭活性下降,适宜的还原温度范围为210～260℃。     

Electrochemical reduction of chemically passivated iron

Iron passivated chemically in chromate solutions over a range of pH was electrochemically reduced in phosphate-borate buffer solution of pH 8.5. According to the chronopotentiometry, the passive film became thinner as the pH diminished, which was in agreement with the ellipsometric result. The rest potential became more positive with decreasing pH, and the pH dependence was ?0.11 V/pH and ?0.07 V/pH in acid and alkaline solutions, respectively. The shift of the rest potential towards more positive values did not lead to an increase in the thickness of the passive film, and in this it differs from the behaviour of the passive film formed anodically. This discrepancy can be rationalized by the idea that most of the potential drop appears not across the passive film, but at the passive film-solution interface. In chemical passivation, a positive shift of the electrode potential is not associated with the growth of the passive film, provided that the rest potential is more positive than the Flade potential. The most influential factor for passive film growth is the environment, in which the iron initially dissolves readily and the passive film retains its stability.     

中贫品位软锰矿直接还原为硫酸锰工艺研究

将生产硫酸锰传统法中的炭还原－硫酸提取工序合二为一,使二氧化锰直接转化为稳定的硫酸锰,重金属盐及可溶性硅酸盐转化为水难溶氧化物,提高了锰的利用率,水浸取硫酸锰的一次性收率可达90％左右,硫酸锰的纯度达到98．5％以上。     

Synthesis of mesoporous flower-like iron oxide nanostructures from iron alkoxide precursor and their application in the catalytic reduction of 4-nitrophenol

Journal of Porous Materials - Mesoporous flower-like FeOOH nanostructure was synthesized via hydrolysis of flower-like iron glycolate in aqueous methylamine solution and ethanol as a solvent with a...     

盘北选煤厂降低精煤水分的实践

盘北选煤厂由于原煤中-0.5mm粒级含量高,脱水设备处理量低,浮选及重介精煤水分高,导致最终精煤水分高、回收率低;通过改造工艺设备,采用加压过滤机,降低了精煤水分,提高了回收率,取得了显著的经济效益与社会效益。     

Hydrogen reduction of the chlorides of bi-valent chromium and iron

Previous work on the topochemical reduction of chromous and ferrous chlorides has been extended to include investigations carried out at elevated pressures. The kinetics are explained on the basis of heat and mass transfer processes involving vaporization of the metal chloride. Some of the problems encountered in the industrial application of these reactions are discussed.     

Effect of reduction temperature on the preparation of zero-valent iron aerogels for trichloroethylene dechlorination

Zero-valent iron (ZVI) aerogels have been synthesized by sol-gel method and supercritical CO₂ drying, followed by H₂ reduction in the temperature range of 350–500 °C. When applied to trichloroethylene (TCE) dechlorination, the ZVI aerogel reduced at 370 °C showed the highest performance in the conditions employed in this study. Thus, the effect of reduction temperature in preparing ZVI aerogels has been investigated by several characterizations such as BET, XRD, TPR, and TEM analyses. As the reduction temperature decreased from 500 to 350 °C, the BET surface area of the resulting aerogels increased from 6 to 30 m²/g, whereas their Fe⁰ content decreased up to 64%. It was also found that H₂ reduction at low temperatures such as 350 and 370 °C leads to the formation of ZVI aerogel particles consisting of both Fe⁰ and FeO _x in the particle cores with a different amount ratio, where FeO _x is a mixture of maghemite and magnetite. It is, therefore, suggested that reduction at 370 °C for ZVI aerogel preparation yielded particles homogeneously composed of Fe⁰ and FeO _x in the amount ratio of 87/13, resulting in high TCE dechlorination rate. On the other hand, when Pd- and Ni-ZVI aerogels were prepared via cogellation and then applied for TCE dechlorination, we also observed a similar effect of reduction temperature. However, the reduction at 350 or 370 °C produced Pd- or Ni-ZVI aerogel particles in which Fe⁰ and Fe₃O₄ co-exist homogeneously. Since both Fe⁰ and Fe₃O₄ are advantageous in TCE dechlorination, the activities of Pd- and Ni-ZVI aerogels reduced at 350 °C were comparable to those of both aerogels reduced at 370 °C, although the former aerogels have less Fe⁰ content.     

骆驼山矿选煤厂降低介质消耗的措施

通过分析骆驼山煤矿选煤厂在实际生产中介耗居高不下的原因,采取了建立介质档案,加强密度控制司机与相关人员的管理,加强脱介筛的喷水,用好磁选机等一系列有效措施,使选煤厂介耗降到1.5 kg/t以下。     

A procedure for the reduction and sintering of agglomerated,finely divided iron oxide to give porous iron pellets suitable for infiltration

The break-up of a stream of liquid metal by high-velocity gas jets is an important technique for the production of metal powders. For a reasonably complex atomization geometry using four nitrogen jets, high-speed and schlieren photography have been used to gain an understanding of the influence on the disintegration of streams of lead and tin of variables such as metal and gas flow rates and the nature of flow in the gas and metal streams. The actual mechanism of disintegration and the resulting particle size distributions have been discussed by use of detailed experimental information on the velocity distributions in the system of four nitrogen jets. The process of disintegration may be divided into three stages: primary disintegration, secondary disintegration and solidification. The conditions for each of these stages are discussed.