攀枝花氧化钛精矿碳热还原动力学

以焦粉为还原剂,开展了氧化钛精矿含碳球团等温碳热还原试验研究,采用积分法进行了碳热还原动力学分析,还原温度分别为1 000、1 100、1 200、1 300℃。氧化钛精矿中铁氧化物还原度随还原温度和时间增加而增加,还原度可达91%。氧化钛精矿在1 000~1 300℃固相还原前期(60 min)受界面化学反应控制,反应活化能为51.23 k J/mol;反应后期(60 min)受扩散控制,反应活化能为93.53 k J/mol。氧化钛精矿碳热还原过程物相转变历程为:Fe2Ti O5→Fe3Ti3O10→Fe Ti O3,物相转变过程增加颗粒内部空隙,增加还原比表面积,改善还原过程气体扩散条件,加快还原初期化学反应速率。     

多层含碳球团转底炉内直接还原行为

 为明确转底炉内多层布料下球团的还原规律,采用含碳球团直接还原钒钛铁精矿,研究了还原温度和还原时间对不同层球团金属化率的影响以及铁精矿中各铁矿物的还原顺序。结果表明:多层球团的还原不同步,在上层球团还原完成并发生再氧化时,下层球团的还原仍在继续。球团的平均金属化率会随着还原温度的增加而提高,随着还原时间的延长出现先增高后降低的现象。在还原过程中存在一个获得最大金属化率的最佳还原时间（本试验为25min）。钒钛铁精矿中各铁矿物还原的难易程度按下列顺序依次增加：Fe2TiO5→Fe3O4→FeO→Fe2TiO4→FeTiO3。     

赤铁矿内配兰炭生产球团矿固结机制研究

摘要：通过对不同温度、不同兰炭配入量的内配兰炭赤铁矿球团进行FeO含量检测和矿相结构分析,得出兰炭在赤铁矿球团焙烧过程中的作用机制。结果表明：兰炭含量较低时,主要发生燃烧反应,不利于赤铁矿向磁铁矿转变,且气孔率增大使球团抗压强度降低;兰炭含量过高,还原反应占主导,大量Fe2O3被还原为Fe3O4,甚至被还原为FeO,随之形成铁橄榄石;兰炭燃烧放热过多使球团内部熔化,导致球团抗压强度大幅降低。最终选择适宜的兰炭配比为1.5%,焙烧温度为1300℃,焙烧时间为18.5min,空气流量为3.2L/min, 抗压强度为2708.8N。     

白云鄂博铁矿球团富氢还原动力学研究

针对气固直接还原工艺中存在着气体利用率低和还原供热不足等问题,利用恒温热重分析(TG)法,研究了氢/碳比率对白云鄂博铁精矿还原速度的影响。结果表明,在还原试验开始后40 min内,还原速率随wH2/wCO比增加而增大,使得Fe2O3→Fe3O4反应时间缩短。基于气相内扩散和界面反应的球团还原速度方程均能较好地处理本研究的数据,得到了反应速度常数与wH2/wCO的关系为:k界面=-0.1975+0.3 575wH2/wCO,k扩散=0.171 01+0.269 7wH2/wCO。根据Arrhenius方程计算出界面反应和气相内扩散活化能分别为26 k J/mol和44 k J/mol,因此本研究条件下限制性环节为气体内扩散控制。     

SO2还原SeO2制备Se的工艺及动力学研究

考察了反应温度、硫酸浓度、SO₂流速及反应时间对SO₂还原SeO₂制备Se过程的影响,并对该过程进行动力学研究,得到了最佳工艺条件及动力学限制性控制环节。结果表明：在反应温度40℃、硫酸浓度1 mol/L、SO₂流速60 mL/min、反应时间30 min的条件下,Se还原率达到99.73%,制备出纯度99.85%的Se;控制条件能得到不同形态Se,低温下得到无定形红硒,高温下得到结晶良好的黑硒;SO₂还原SeO₂制备Se的过程符合Avrami模型,表观活化能为1.98 kJ/mol,受扩散控制,动力学方程为-ln(1-X)=0.178×e^-238/Tt^1.276。     

含碳球团气固协同还原特点及动力学研究

通过热重实验,从还原温度、还原气氛及还原时间三方面对含碳球团的还原特点和动力学进行了研究,采用界面反应模型、三维扩散模型等对含碳球团还原过程进行拟合.研究表明:在本实验条件下,当温度为1100℃、气氛为单一H2、还原时间为60 min时,反应分数达到最大值0.81,还原效果最佳;还原过程中,还原速率先迅速增大,随后逐渐减小;当假设扩散模型为还原过程的限制性环节时,得到的拟合效果最好,反应活化能为93.18 kJ/mol.     

LaCl3·7H2O晶体的热分解

采用TG-DTG方法,得到LaCl3*nH2O晶体在空气中热分解过程及相应分解反应的活化能,即在84～112℃时,LaCl3*7H2O失去4个结晶水,分解反应的活化能为133.2kJ/mol,在123.2～137.9℃时,LaCl3*3H2O失去2个结晶水,分解反应的活化能为153.9kJ/mol,在162.5～177.4℃时,LaCl3*H2O失去1个结晶水,分解反应的活化能为454.6kJ/mol,在397.7～464.5℃时,LaCl3气相水解为LaOCl,活化能为66kJ/mol.在温度低于900℃(最高测试温度)时,LaOCl能稳定存在.     

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。     

钒钛磁铁矿含碳球团的还原历程

 为实现钒钛磁铁矿资源的高效合理利用,对钒钛磁铁矿含碳球团的还原过程进行了解析,初步建立了动力学控制方程;利用差热分析方法对钒钛磁铁矿的还原熔分历程进行了分析与讨论,认为钒钛磁铁矿的还原可分为煤的氧化、钒钛磁铁矿的直接还原、借助碳的气化反应的直接还原和还原结束4个部分;以攀枝花钒钛磁铁矿为原料,煤为还原剂,考察了反应时间和温度对含碳球团还原度的影响,确定固体产物层内扩散是钒钛磁铁矿含碳球团直接还原反应的控制性环节,计算出其表观活化能为112.13 kJ/mol。     

富氢对块状带低钛球团矿还原的影响研究

在高炉喷吹煤造气冶炼条件下,研究在低温区块状带不同H2含量和不同温度对矿石还原情况的影响。试验结果表明:当还原温度为900℃时,还原速率随着H2含量的增加而逐渐变大,当还原气氛一定时,还原速率随着还原温度的增加而逐渐变大;还原后的球团主要物相是单质铁,并含有少量的镁钛铁矿(Mg,Fe)(Fe,Ti)O3、镁铝尖晶石(Mg Al2O4)和镁橄榄石(Mg2Si O4);随着还原温度的增加,镁钛铁矿(Mg,Fe)(Fe,Ti)O3首先开始消失,镁铝尖晶石(Mg Al2O4)和镁橄榄石(Mg2Si O4)逐渐减少,并且随着还原温度的增加,H2的还原能力显著加强,铁矿石失氧速率增加,生成的金属铁发生聚集,导致球团内部留下小细孔。     

Effect of Metal Additions to the Reduction of Iron Oxide Composite Pellets with Hydrogen at Moderate Temperatures

The hydrogen reduction behavior of iron oxide composite pellets containing Ni, Fe, and Mn from 973 K to 1173 K was compared with iron oxide and Al₂O₃ containing reference composite pellets to determine the effect of metallic species on the kinetics of iron oxide reduction. The Mn and Ni containing pellets showed slightly faster initial reduction rates compared to the Fe and Al₂O₃ containing pellets. The effect of the metal phases was found to be more significant at lower temperatures when chemical reaction at the interface is a slower and more controlling factor. From the SEM of partially reduced pellets, a wide intermediate region between an O rich unreacted core and an Fe rich outer shell was observed. Although an initially short topochemical receding interface controlled region exists, the mixed control between the topochemical receding interface and pore diffusion was prevalent. For Fe₂O₃/Mn composite pellets, the thermodynamic stability of the MnO is higher and Mn can act as a reductant for iron oxide. Thus, the overall metallization of the Fe₂O₃/Mn composite pellets decreased compared to the other Fe₂O₃/metal composite pellets. From the temperature dependence of the iron‐oxide/metal composite pellets, the apparent activation energy was calculated to be approximately between 15 to 20 kJ/mol, which is typical of a mixed control reduction mechanism of gas diffusion and interface reaction.     

铁粉矿在HIsarna工艺中预还原行为的研究

通过高温实验与理论分析研究了铁粉矿颗粒在高温下的热分解和熔化行为,以及熔化后气体与熔融粉矿液滴之间的还原动力学.当温度高于FeO熔点且产物层中有FeO生成时,铁粉矿颗粒会出现熔化现象.还原反应前210 ms伴随着剧烈的热分解反应,主要是Fe_2O_3分解成Fe_3O_4.熔化后的铁粉矿颗粒产物层是液态的FeO,颗粒中心是未反应的固态Fe_3O_4,还原反应发生在颗粒表面.Fe~(3+)在产物层中的扩散是还原反应的限制性环节,通过计算得到气体与熔融铁粉矿颗粒还原反应的表观活化能约为141 kJ/mol.     

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 Kinetics of Vanadium Titano-Magnetite Carbon Composite Pellets Adding Catalysts Under High Temperature

Experiments were carried out by adding CaF2 and NaF as catalysts in an Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from 1 473 to 1 673 K. The scanning electron microscope (SEM) was used to characterize the microstructure of product. By analyzing reduction mechanism, it was found that the rate controlling step was gas diffusion, and the activation energy was 178.39 kJ/mol without adding any catalysts. Adding CaF2 or NaF of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 14.95 and 15.79 kJ/mol, respectively. In addition, temperature was an important factor influencing on reaction rate.     

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。     

Morphology of Oxide Scale and Oxidation Kinetics of Low Carbon Steel

The oxidation kinetics and composition of oxide scales on low carbon steel(SPHC)were studied during isothermal oxidation.Thermogravimetric analyzer(TGA)was used to simulate isothermal oxidation process of SPHC for 240min under air condition,and the temperature range was from 500to 900 ℃.Scanning electron microscope(SEM)was used to observe cross-sectional scale morphology and analyze composition distribution of oxide scales.The morphology of oxide scale was classical three-layer structure.Fe2O3developed as whiskers at the outermost layer,and interlayer was perforated-plate Fe3O4 while innermost layer was pyramidal FeO.From the oxidation curves,the oxidation mass gain per unit area with time was of parabolic relation and oxidation rate slowed down.On the basis of experimental data,the isothermal oxidation kinetics model was derived and oxidation activation energy of SPHC steel was 127.416kJ/mol calculated from kinetics data.     

Fe(Ⅲ)/Fe(Ⅱ)在[Bmim]BF_4-FeCl_3-H_2O体系中的电化学行为

采用循环伏安法研究了Fe(Ⅲ)/Fe(Ⅱ)在[Bmim]BF4-FeCl3-H2O体系中的电化学行为。研究表明,在[Bmim]BF4-FeCl3-H2O体系中只观察到Fe(Ⅲ)/Fe(Ⅱ)的氧化还原反应,没有观察到Fe(Ⅱ)/Fe的氧化还原;Fe(Ⅲ)/Fe(Ⅱ)的氧化还原反应是扩散控制的可逆过程。还原峰值电流随扫描速率增大而增大,并符合Randles-Sevcik方程。Fe(Ⅲ)在[Bmim]BF4-FeCl3-H2O体系中的扩散系数与温度的关系符合Arrhenius公式,其扩散活化能为41.432 kJ/mol。     

微波加热配碳还原分解铁酸锌的工艺及机理研究

研究了利用微波配碳还原焙烧分解铁酸锌的工艺及机理。利用碳气化控制、化学控制及扩散控制模型研究了样品中铁酸锌分解的动力学行为,并考察了微波功率、反应温度、配碳比和粒度对铁酸锌分解率的影响。结果表明,样品的微波加热碳热还原试验的控制步骤为碳气化控制,活化能为39.21kJ/mol,在微波加热温度850℃、C/ZnFe2O4质量比为1∶4、粒径74～89μm、微波功率1.8kW、加热时间60min的条件下,铁酸锌的分解率达到90%。     

高铝铁矿石球团气基还原物相状态研究

在温度为950℃、还原气氛为纯CO条件下,对高铝铁矿石球团进行气基还原,还原时间分别为0、5、10、 20、40、60、80 min以及110 min,以明确各时间段内物相的变化情况。研究结果表明,还原5 min时即出现金属铁、 FeAl 2 O 4 和Fe 2 SiO 4 3种物相,10 min以至更长时间时金属铁峰强度有所增强,而其他2相变化并不明显;另外,该 种铁矿石中氧化铁的逐级还原规律并不明显,当金属铁相过早出现时,Fe 3 O 4 相以及独立存在的浮士体相未检测到。