高杂质钛铁矿固态催化还原的热分析动力学研究

通过热重分析方法研究了固态条件下高杂质钛铁矿的催化碳热还原机理。结果表明：杂质会阻碍钛铁矿还原,无催化剂时还原率较低,加入少量催化剂可以获得较高的还原率和较快的还原速度。催化剂不同的阴离子基团对反应有着不同的影响,在钠离子摩尔浓度相同的情况下,催化效果：四硼酸钠(Na2B4O7)>氟化钠(NaF)>氯化钠(NaCl)>硅酸钠(Na2SiO3)。在温度860~1100℃范围内,钛铁矿碳热还原反应的主要控速环节是界面化学反应。无催化剂反应的表观活化能为260.976kJ/mol;添加四硼酸钠的一组表观活化能降低最多,为226.182 kJ/mol。     

1173～1473K下鲕状赤铁矿石墨还原动力学研究

采用热重法研究了1 173～1 373 K下鲕状赤铁矿的石墨还原动力学。研究了温度对还原度和还原速率的影响,采用不同固相反应机理函数对反应过程进行拟合,分析了不同还原阶段反应限制性环节,并对还原样品进行了XRD、SEM和EDX表征分析。结果表明,随着温度增加,还原度和还原反应速率增加,随着还原度增加,还原反应速率先增加后降低;在1 173～1 273 K和1 273～1 373 K两个阶段,反应过程分别符合界面化学反应1-(1-α)~(1/3)和杨德模型[1-(1-α)~(1/3)]~2,对应的表观活化能分别为60.657 kJ/mol和301.662 kJ/mol,反应的限制环节分别为界面化学反应和固态扩散;还原样品的物相组成和微观形貌分析结果与前述反应动力学机理分析结果相符合。     

不同形貌升华氧化钼的还原动力学研究

本文以2种不同形貌升华氧化钼为原料,采用TG-DTA法研究了不同升温速率(3℃/min、5℃/min、10℃/min)下氢气还原氧化钼的动力学。结果表明:2种不同形貌的升华氧化钼一段还原反应起止还原温度几乎相同。但失重速率480℃前1~#MoO_3高于2~#MoO_3,480℃后1~#MoO_3失重速率低于2~#MoO_3。二段还原反应1~#MoO_3的反应温度较2~#MoO_3低。再通过用Flynn-Wall-Ozawa和Kissinger动力学分析方法计算2种不同形貌升华氧化钼的一段平均表观活化能为1~#MoO_3为89. 26 kJ/mol,2~#MoO_3为79. 86 kJ/mol,而二段表观活化能1~#MoO_3平均为103. 53 kJ/mol,2~#MoO_3为93. 16 kJ/mol。     

废脱硝催化剂加盐焙烧-酸浸提钛的浸出动力学研究

采用加盐焙烧-酸浸法回收废脱硝催化剂中的钛,利用液-固多相反应的核收缩模型研究硫酸浸钛的浸出动力学,考察了硫酸浓度和酸浸温度对钛浸出反应速率的影响。结果表明,在温度低于60℃或硫酸质量分数小于45%时,浸出受化学反应和固膜扩散混合控制;升温和提高硫酸浓度浸出过程则转变为化学反应控制。低温受混合控制时的表观活化能为30.23 kJ/mol,升温后受化学反应控制时的表观活化能为92.92 kJ/mol,表观反应级数为4.932。提高反应温度和硫酸浓度均能加快钛的浸出速率,提高钛的浸出率。     

真空碳热还原制备碳氧钛的动力学研究

采用非等温固相模型对碳热还原TiO2历程和动力学条件进行研究。结果表明,真空碳热还原TiO2可分为四个阶段,第一阶段(1 373~1 523K)主要物相为C和TinO2n-1(n≥5),第二阶段(1 523~1 673K)主要物相为C、TiC0.5O0.5和TinO2n-1(2≤n≤4),第三阶段(1 673~1 833K)主要物相为C、Ti2O3和TiC0.5O0.5,第四阶段(1 833~1 973K)主要物相为TiC0.5O0.5;第一阶段动力学方程为α2=kt,受一维扩散控制,表观活化能为113.55kJ/mol,第二阶段动力学方程为(1-α)-1-1=kt,受二级化学反应控制,温度对还原率影响较大,表观活化能为303.36 kJ/mol,第三阶段动力学方程为2[(1-α)-1/2-1]=kt,受1.5级化学反应控制,还原剂不足对反应影响较大,表观活化能为53.93kJ/mol,第四阶段动力学方程为1-2α/3-(1-α)2/3=kt,受三维扩散控制,物料疏松成为晶核长大的限制环节,表观活化能为99.22kJ/mol。     

热重-质谱联用研究铁矿粉氢还原的动力学研究

采用热重-质谱联用技术,研究了1 023～1 373 K条件下H2还原铁矿粉的反应动力学。结果表明,铁氧化物的还原存在分段现象,两个阶段均符合界面化学控速的反应机制,表观反应活化能分别为37.40 kJ/mol和34.97 kJ/mol。由质谱分析数据可以计算得到反应的还原度和还原速率,与热重分析相比,结果基本一致,但存在细节丢失及迟后现象。     

从电炉烟尘中碱浸锌的动力学研究

用液-固多相反应的未反应核缩芯模型研究了用NaOH溶液从电炉烟尘中浸出锌的动力学。考察了浸出温度、NaOH浓度对锌浸出率的影响。结果表明:温度低于80℃时,锌浸出过程受固膜扩散控制,反应表观活化能为9.581 8kJ/mol;温度高于80℃时,锌浸出过程受界面化学反应控制,反应表观活化能为49.319kJ/mol;浸出反应的表观反应级数为0.983。     

高炉粉尘造泡沫渣过程中FeO还原动力学的研究

为了循环利用高炉粉尘,研究了用宝山钢铁股份有限公司高炉粉尘与沥青焦粉混合后加入电弧炉造泡沫渣过程中FeO的还原动力学。结果表明,随粉尘加入量的增加和温度的升高,FeO的还原速率加快;用固体碳还原渣中FeO的反应为表观二级反应,其表观活化能为276kJ／mol;用固体碳还原渣中FeO的反应总速率由CO还原FeO的界面化学反应和炉渣的流动传质共同控制。     

烧结钛精矿气基还原动力学研究

为揭示烧结钛精矿气基还原机理,在CO和N_2体积分数分别为30%和70%的还原气氛条件下,开展了烧结钛精矿等温气基还原试验研究,还原温度分别为800、900、1 000℃,对气基还原动力学进行了分析。结果表明:烧结钛精矿中铁氧化物还原度随还原温度和时间增加而增加,整体还原度偏低,还原度接近70%。烧结钛精矿在800～1 000℃气基还原大部分时间内(140 min)受界面化学反应控制,反应活化能为46.97 kJ/mol;反应后期(140 min)受扩散控制,反应活化能为99.27 kJ/mol。烧结钛精矿碳热还原过程物相转变历程为:Fe_2TiO_5→Fe_2TiO_4→FeTiO_3。相同还原时间,烧结钛精矿还原样品中金属铁粒尺寸随温度升高从4.46μm增至30.13μm。     

DIBK-P204体系萃取锆和铪的动力学

研究了DIBK-P204体系萃取锆和铪的动力学,采用恒界面池法考察搅拌速度、界面积和温度对锆和铪萃取速率的影响。结果表明,DIBK-P204体系对锆和铪萃取速率符合准一级反应,萃取反应的控制类型分别为相内反应控制和混合控制,对锆和铪萃取的表观活化能分别为-32.193kJ/mol和-18.984kJ/mol,升高温度不利于萃取反应的进行。     

Kinetics of iridium reduction by hydrogen in hydrochloric acid solution

The effects of stirring speed, initial iridium ion concentration, hydrogen pressure, hydrochloric acid, chloride concentrations, seeding, and temperature on the reduction rate of iridium ion by hydrogen have been investigated. The whole process of reduction occurs in a complicated heterogeneous stage. The reduced metallic Ir serves itself as a catalyst for the reduction. The rate in the earlier stage of the reduction (including the nucleation period) is controlled by chemical reaction; the apparent activation energy obtained in the temperature range of 363 to 423 K was 76.1 kJ/mol. The order of the reaction with respect to the iridium ion concentration and the hydrogen partial pressure was found to be one, and the reaction rate increased with the increase of HC1 and Cl concentrations. The rate in the later stage was controlled by diffusion, and the apparent activation energy was reduced to 25.5 kJ/mol. The reaction mechanism has been given by the analysis of experimental results. Formerly Graduate Student, Department of Extractive Metallurgy, Institute of Precious Metals     

Reduction behavior and mechanism of Hongge vanadium titanomagnetite pellets by gas mixture of H2 and CO

Hongge vanadium titanomagnetite(HVTM)pellets were reduced by H_2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ(H_2)toφ(CO),and pellet size on the reduction of HVTM pellets were evaluated in detail and the reduction reaction kinetics was investigated.The results show that both the reduction degree and reduction rate can be improved with increasing the reduction temperature and the H_2 content as well as decreasing the pellet size.The rational reduction parameters are reduction temperature of 1050°C,ratio ofφ(H_2)toφ(CO)of 2.5,and pellet diameter in the range of 8-11 mm.Under these conditions(pellet diameter of 11mm),final reduction degree of 95.51% is achieved.The X-ray diffraction(XRD)pattern shows that the main phases of final reduced pellets under these conditions(pellet diameter of 11 mm)are reduced iron and rutile.The peak intensity of reduced iron increases obviously with the increase in the reduction temperature.Besides,relatively high reduction temperature promotes the migration and coarsening of metallic iron particles and improves the distribution of vanadium and chromium in the reduced iron,which is conducive to subsequent melting separation.At the early stage,the reduction process is controlled by interfacial chemical reaction and the apparent activation energy is 60.78kJ/mol.The reduction process is controlled by both interfacial chemical reaction and internal diffusion at the final stage,and the apparent activation energy is 30.54kJ/mol.     

铜渣直接还原动力学

我国铜渣资源储量丰富,渣中含有多种有价金属,具有很高的二次利用价值.为了揭示铜渣提铁的碳热还原机理,以无烟煤为还原剂,进行铜渣含碳球团等温还原实验,并对其进行动力学分析.实验设定的还原温度为1 000 ℃、1 050 ℃、1 100 ℃、1 150 ℃和1 200 ℃,碳氧比即n_c/n_o=1.0.结果表明,对于铜渣含碳球团等温还原实验,温度对反应速率有重要影响;该反应主要限速环节为气相扩散,活化能数值为118.059 kJ/mol;对其进行阶段性动力学分析,其活化能在61.54~146.98 kJ/mol范围内,且活化能的数值随着还原度的变化而变化,具体表现为:第1阶段反应活化能数值较小,原因可能是该阶段反应刚开始,原铜渣中含有一些铁氧化物（Fe₃O₄）先参与了反应;第2阶段反应活化能较高,此时原铜渣中的铁氧化物已基本反应,铁以橄榄石的状态存在,且橄榄石呈液态,致使球团孔隙度降低,气体在球团内的扩散受阻.      

旋转床CO还原澳大利亚PB粉特性及动力学研究

采用自主研制的小型旋转床反应器,结合化学分析和X射线衍射分析等技术对CO还原澳大利亚PB粉进行了直接还原实验研究。结果表明:CO流量为200 mL/min,矿粉粒径范围为0.044~0.089 mm,还原时间为60 min,还原温度为1 000℃时,还原产物还原度和金属化率达到最大值,分别为92.70%和86.28%;在700~1 000℃内基于收缩未反应核模型对澳大利亚PB粉还原反应进行动力学分析,得出反应前期(t30 min)还原过程由气体内扩散和界面化学反应混合控制;反应后期(t30 min)还原反应的限制性环节为气体内扩散,指前因子A为0.006 72 s~(-1),表观活化能E为10.043 kJ/mol。     

Non-Isothermal Kinetics of Reduction Reaction of Oxidized Pellet Under Microwave Irradiation

 The microwave heating characteristics of the mixture with oxidized pellet and coal was studied, and the non-isothermal reduction dynamics is discussed. The results show that, the slow-heating stage of the temperature rising process can be segmented into two heating temperature curves approximately that have good linear relationship. They can be seen as temperature programming. In the first stage, between 827 and 1073 K, the reaction mechanism obeys diffusion controlled model. In the second stage, between 1093 and 1323 K, the reaction mechanism also obeys diffusion controlled model. The apparent activation energies are found to be 7513 kJ/mol for the first stage and 5317 kJ/mol for the second stage. That is lower than the apparent activation energy under conventional heating. The microstructure of the reduced pellets shows that microwave can improve the kinetics of the reduction. Microwave has anxo-action to the reaction obviously.     

Reduction Characteristics and Kinetics of Bayanobo Complex Iron Ore Carbon Bearing Pellets

 The kinetics of isothermal reduction of the carbon bearing pellets, which were mainly composed of Bayanobo complex iron ore and pulverized coal, was investigated by thermogravimetry at the temperature of 1273-1673 K. The effects of xC/xO and the atmospheres on the extent of reduction also were investigated. The results indicate that the fractional reaction increased proportionally with temperature increasing and heating temperature is the significant influence factor to the reaction of carbon bearing pellets. The optimum xC/xO is 1. 2 and the effect of atmosphere on the reduction of iron oxides is almost negligible. The results can be interpreted that the reaction was initially controlled by a mixed controlled mechanism of carbon gasification and interface chemical reaction, and in the later stage, interface chemical reaction became the rate-controlling step. Apparent activation energy values of reduction at different levels of fractional reaction were calculated. Before F (fraction of reaction)=0. 5, the apparent activation energy ranges from 66. 39 to 75. 64 kJ/mol, while after F=0. 5, the apparent activation energy is 80. 98 to 85. 37 kJ/mol.     

DIBK-TBP体系萃取铪和锆的动力学研究

在恒界面池中研究DIBK-TBP协同萃取体系萃取铪、锆的动力学,考察了温度、界面积和搅拌强度等对萃取速率的影响。结果显示,DIBK-TBP体系萃取铪和锆的过程符合一级动力学反应;对铪的萃取为相内反应和扩散共同影响的混合控制类型,表观活化能-43.106kJ/mol;对锆的萃取与搅拌强度、比界面积无关,为相内反应控制类型,表观活化能-16.024kJ/mol。     

Fe3O4内配石墨球团的还原动力学

开展了Fe3O4内配石墨球团还原试验,以考察球团的中温还原性。设定温度950～1 100℃,时间低于35min。并采用新建立的还原动力学方程(PKV方程)计算球团的动力学参数。结果表明,球团的还原能力随时间、温度的提高而增加,初始时间段及较低温度下增加幅度相对较大;温度对球团的还原影响很大。球团在19min前后的活化能分别为102.046kJ/mol和86.872kJ/mol。控制环节为界面化学反应,前19min为碳的气化反应,后19min为CO还原Fe3O4。     

Reduction kinetics of molybdenum oxide in slag

The reduction rate of Mo oxide in slag by iron-carbon melt under different stirring conditions, reaction temperatures and slag composition has been investigated. Results indicate that the reduction of Mo oxide is a fast reaction; both stirring and temperature have evident influence upon the reaction; while the initial concentration of Mo oxide and content of fluoride in slag have also some influence upon the reaction. The reduction of Mo oxide is an apparent first order reaction. At 1440–1500°C, the reduction rate of Mo oxide is mainly controlled by Mo transfer in slag, with its diffusion activation energy of 223 kJ/mol. At 1500–1590°C, the transfer of Mo in metal turns to be the main limiting step, with its diffusion activation energy of 81.5 kJ/mol.     

高磷铁矿石含碳球团等温还原动力学

 为了研究高磷铁矿石含碳球团等温还原动力学在温度为1 173、1 273、1 323、1 373、1 423和1 473 K时,采用界面化学反应模型、Jander方程、Ginstling-Broushtein方程、G Valensi-R E Carter方程等固-固/气反应机理函数对反应过程进行拟合,并采用XRD、SEM、EDX等对样品的物相组成、微观形貌和元素分布进行表征分析。研究结果表明,随着还原程度提高,反应速率由0迅速增至最大值,随后逐渐减小并趋于平缓;当温度为1 173～1 373 K时,反应过程符合界面化学反应,表观活化能为70.02 kJ/mol,线性相关系数为0.948 1;当温度为1 373～1 473 K时,反应过程符合Jander方程,限制步骤为铁离子固相扩散,表观活化能为215.36 kJ/mol,线性相关系数为0.991 2。