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。     

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。     

外包法直接还原钛铁矿过程的动力学研究

采用外包还原剂的方法对钛铁矿进行直接还原试验,研究了直接还原钛铁矿的动力学。结果表明,半焦粉直接还原钛铁矿分为两个阶段,第一阶段是升温阶段和恒温的初始阶段,受界面化学反应控制,表观活化能为113.14kJ/mol;第二阶段为恒温阶段,受固相中气体的内扩散控制,表观活化能为180.13kJ/mol。温度对还原度和还原速率的影响显著。随着温度的升高,还原度随之升高,反应速率加快;延长恒温时间也可以提高还原度,但恒温阶段反应速率增加缓慢     

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。     

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。     

用硫酸从电炉粉尘中浸出锌、铁试验研究

研究了用硫酸从电炉粉尘中浸出锌、铁,考察了温度、硫酸浓度、固液质量体积比及反应时间对锌、铁浸出率的影响,分析了浸出反应动力学。结果表明：在温度85℃、硫酸浓度1.0 mol/L、固液质量体积比20 g/1 L、反应时间60 min条件下,锌、铁浸出率分别为94.8%和95.68%;浸出反应符合收缩核模型,反应表观活化能分别为49.08 kJ/mol和58.00 kJ/mol,表明均受界面化学反应控制。根据线性拟合结果确定了锌、铁浸出过程半经验参数方程。     

铜冶炼酸性废水浸出废旧三元锂离子电池正极材料中Co的动力学研究

采用铜冶炼酸性废水浸出废旧三元锂离子电池正极材料,考察了浸出温度、酸性废水中初始H₂SO₄浓度、搅拌速度对Co浸出率的影响。结果表明,当浸出时间150 min、浸出温度363 K、液固比12.5、还原剂淀粉用量10 g/L、酸性废水中初始H₂SO₄浓度1.5 mol/L时,正极材料中Co的浸出率可达99.12%。利用未反应收缩核模型分析了还原浸出过程中Co的动力学。结果表明,Co的浸出过程受内扩散和界面化学反应混合控制,表观活化能为23.657 kJ/mol,动力学方程为：■     

真空碳热还原氧化锶动力学研究

在真空条件下,采用等温法对碳热还原氧化锶的动力学进行了研究。研究结果表明:还原温度对碳热还原氧化锶的还原速度影响较大,温度越高,还原速度越大,在温度高于1573 K时,还原较快。根据Arrhenius方程计算出,在1473～1673 K范围内,当碳的气化反应为控制环节时,反应活化能为163.39 kJ·mol-1;界面化学反应为控制环节时,反应活化能为212.29 kJ·mol-1;气相扩散为控制环节时的活化能为315.00～384.46 kJ·mol-1。扩散控制反应时活化能最大,真空条件下碳热还原氧化锶的还原速度由气相扩散控制。     

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。     

用草酸从赤泥中浸出钪、镧试验研究

研究了用草酸从赤泥中浸出钪和镧,考察了草酸用量、反应时间、温度、液固体积质量比对浸出的影响,分析了浸出动力学。结果表明：在赤泥质量1 g、草酸用量4.5 g,反应时间120 min、温度90℃、液固体积质量比12/1条件下,钪、镧平均浸出率分别为66.68%和78.23%;钪浸出过程符合多相液-固反应模型,反应受扩散控制,表观活化能为25.68 kJ/mol;镧浸出过程符合未反应收缩核模型,受化学反应控制,表观活化能为55.10 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.     

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.     

高磷鲕状赤铁矿酸浸脱磷动力学

在HSC6.0计算软件热力学分析的基础上,采用正交实验确定了高磷鲕状赤铁矿酸浸脱磷保铁的最佳工艺,并以最佳工艺为基础进行了酸浸过程中脱磷和铁损反应的动力学研究。热力学分析表明H_2SO_4为最佳酸浸用酸。正交实验得出最佳酸浸条件为:H+浓度为0.5mol/L的H_2SO_4溶液、酸浸时间40min、温度298K、液固比200mL∶14g、搅拌速度100r/min。在该条件下,脱磷率可达98.89%,铁损率仅为0.51%。通过SEM-EDS对酸浸前后高磷鮞状赤铁块矿试样分析表征得出:经H_2SO_4浸出后,磷灰石基本完全溶解,含铁矿相未发生明显反应。动力学分析显示:优化条件下,酸浸脱磷反应在298~328K内符合收缩未反应核模型,浸出过程主要受内扩散控制,表观活化能为11.24kJ/mol;铁损反应在298~328K内遵循收缩未反应核模型,浸出过程主要受化学反应控制,表观活化能为42.24kJ/mol。     

非晶态高炉渣的非等温析晶动力学研究

 采用差示扫描量热法(DSC)对非晶态高炉渣的析晶过程进行研究,得出不同升温速率下非晶态高炉渣析晶过程的DSC曲线,并根据动态DSC曲线用Kissinger法求出了析晶反应的活化能、反应级数及动力学方程中的指前因子等参数,建立了非晶态高炉渣析晶反应动力学的数学模型。实验所用非晶态高炉渣的析晶反应活化能为376.466 kJ/mol,该反应为一级反应。非晶态高炉渣的DSC曲线在1130~1310 K的温度区间内呈现出单一的晶化放热峰,峰顶温度、析晶温度和反应级数随升温速率的提高而提高。     

首钢烧结矿还原动力学

采用热重法在1173~1373 K、全CO气氛条件下,对首钢烧结矿进行还原动力学实验,确定了还原反应的表观活化能,进而推断在还原反应的前期烧结矿还原速率均由界面反应控制,还原反应后期的控制环节为固相扩散.分别由未反应核模型和固相反应动力学模型,分段给出不同温度下控制环节突变的时间点;通过动力学公式计算,得出不同温度下的反应速率常数和固相扩散系数.利用光学显微镜观察了烧结矿在各还原阶段的微观形貌,验证了烧结矿还原动力学的机理,同时也证明了扩散控制阶段使用体积缩小的未反应核模型与实际情况是吻合的.      

氢气还原氧化铁动力学的非等温热重方法研究

 用非等温热重分析法对氢气还原不同粒度细微氧化铁的动力学进行了研究。研究表明：铁矿粉粒度越小,起始反应温度越低,反应速度越快,反应达到平台期时所对应的还原率越高;平均粒度为3.5 mm的铁矿粉在400 ℃还原反应开始,700 ℃左右开始反应加快,达到平台期时的还原率为77%,而平均粒度为2 μm的铁矿粉在100 ℃已经开始反应,350 ℃反应加快,达到平台期时的还原率为98%,而且在600 ℃时还原率就达到了100%;铁矿粉粒度从3.5 mm降到2 μm后,还原反应的表观活化能从73.3 kJ/mol降低到30.46 kJ/mol;同时通过分析氢气还原氧化铁的反应机理得出,内扩散和界面化学反应均对整个反应过程起限制作用。     

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 of Solid Iron Oxide by Carbon

The reduction of pre‐reduced iron oxide by carbon was investigated from a kinetic viewpoint. The experimental procedure included thermogravimetric analysis to measure the weight change of the iron oxide pellet. The activation energy of the overall reaction was calculated to be 210 kJ/mol in the temperature range from 1273 to 1573 K. The overall reduction rate of FeO by carbon is believed to be mixed‐controlled by the Boudouard reaction and by the FeO reduction by CO gas in the temperature range investigated. The critical carbon concentration for the FeO reduction was estimated under the assumption that the activities of FeO and Fe are unity.     

Kinetics of hexavalent chromium reduction by grey cast iron powder

The kinetics of Cr (VI) reduction by grey cast iron powder (HT250 as per Chinese standard GBT 9439-2010) was investigated in this paper. Factors such as pH, initial Cr (VI) concentration, particle size, stirring speed and temperature on Cr (VI) reduction were first examined at a moderate reducing agent dosage. It was found that Cr (VI) reduction could only occur at an initial pH of 2.0 and above this value, the reaction nearly stopped. Additionally, the obvious dependence of Cr (VI) reducibility on other parameters was also revealed. The changes of pH, ORP and the concentration of Fe ions during the reaction were investigated. The correlations between the experimental data and reaction models involving homogeneous and heterogeneous reactions were studied. The results indicated first-order kinetics for the Cr (VI) reduction, which was a homogeneous reaction with an apparent activation energy of 20.718 kJ/mol. A semi-empirical equation was proposed to describe the kinetics of Cr (VI) reduction by HT250 powder. It was concluded that HT250 powder was a promising zero-valency iron (ZVI) material offering excellent reducibility and its use can be extended to the pre-treatment of wastewater containing other heavy metal ions such as Cu(II) and Pb(II).