Kinetic study on pressure leaching of high iron sphalerite concentrate

The kinetics of pressure leaching high iron sphalerite concentrate was studied.The effects of agitation rate,temperature, oxygen partial pressure,initial acid concentration,particle size,iron content in the concentrate and concentration of Fe2 added into the solution on the leaching rate of zinc were examined.The experiment results indicate that if the agitation rate is greater than 600 r/min,its influence on Zn leaching rate is not substantial.A suitable rise in temperature can facilitate the leaching reaction,and the temperature should be controlled at 140-150℃.The increase trend of Zn leaching rate becomes slow when pressure is greater than 1.2 MPa,so the pressure is controlled at 1.2-1.4 MPa.Under the conditions of this study,Zn leaching rate decreases with a rise in the initial sulfuric acid concentration;and Zn leaching rate increases with a rise of iron content in the concentrate and Fe 2 concentration in the solution.Moreover,the experiment demonstrates that the leaching process follows the surface chemical reaction control kinetic law of“shrinking of unreacted core”.The activation energy for pressure leaching high iron sphalerite concentrate is calculated,and a mathematical model for this pressure leaching is obtained.The model is promising to guide the practical operation of pressure leaching high iron sphalerite concentrate.     

Kinetics of iron removal from metallurgical grade silicon with pressure leaching

In this paper, the kinetics of pressure leaching for purification of metallurgical grade silicon with hydrochloric acid was investigated. The effects of particle size, temperature, total pressure, and concentration of hydrochloric acid on the kinetics and mechanism of iron removal were studied. It was found that the reaction kinetic model followed the shrinking core model, and the apparent activation energy of the leaching reaction was 46.908 kJ/mol. And the apparent reaction order of iron removal with pressure leaching was 0.899. The kinetic equation was ob-tained and the mathematical model of iron removal from metallurgical grade silicon (MG-Si) was given as follows: 1-2/3x-(1-x)2/3=exp(5.1654-4811.4591/T+1.287lnp+1.046ln[C])·t/r02· The values calculated from the equation were consistent with the experimental results.     

Kinetics of iron removal from metallurgical grade silicon with pressure leaching

In this paper, the kinetics of pressure leaching for purification of metallurgical grade silicon with hydrochloric acid was investigated. The effects of particle size, temperature, total pressure, and concentration of hydrochloric acid on the kinetics and mechanism of iron removal were studied. It was found that the reaction kinetic model followed the shrinking core model, and the apparent activation energy of the leaching reaction was 46.908 kJ/mol. And the apparent reaction order of iron removal with pres...     

FeNiAlGaPBSiC非晶合金的晶化动力学

采用单辊急冷法制备了Fe68Ni1Al5Ga2P9.65B4.6Si3C6.75非晶薄带.用XRD、DSC研究合金的晶化动力学过程.结果表明:合金的玻璃转变和晶化行为均具有动力学效应,其晶化类型为初晶型和随后的共晶型反应.用Kissinger法计算得到的Eg、Ex、Ep1、Ep2分别为703、373、446、723 kJ/mol,Eg远大于Ex,表明该合金具有较高的热稳定性.     

Nd—Dy—Fe—Co—B快淬非晶合金的晶化动力学

用差热分析（DTA）,结合X射线衍射（XRD）研究了Nd-Dy-Fe-Co-B非晶合金的晶化动力学。结果表明,温度低于800℃不同升温速率的升温过程中,合金Nd7.5Dy1.5Fe70Co16B5中先后出现三个晶化相：软磁相α-Fe相、亚稳相Nd2Fe23B3和硬磁相Nd2Fe14B。三个晶化相的晶化激活能随晶化份数的增加而降低。α－F的表面激活能为98.09kJ/mol,Nd2Fe23B3和Nd2Fe14B的分别为131．79kJ/mol和129．20kJ/mol.Nd2Fe14B和α－Fe相的晶化行为表明Nd7 .5Dy1.5Fe70Co16B5合金退火时容易形成晶粒粗大的Nd2Fe14B/α-Fe微结构的原因,是Nd2Fe14B和α-Fe相都容易长大造成的。     

石煤钒矿硫酸活化常压浸出提钒工艺

研究石煤钒矿的硫酸活化提钒方法。分别考察矿石粒度、硫酸浓度、活化剂用量、催化剂用量、反应温度、反应时间和浸出液固比等因素对钒浸出率的影响。结果表明:石煤提钒的优化条件为矿石粒度小于74μm的占80%、硫酸浓度150 g/L、活化剂CaF2用量(相对于矿石)60 kg/t、催化剂R用量20 g/L、反应温度90℃、反应时间6 h、液固比(体积/质量,mL/g)2:1,在此优化条件下,钒浸出率可达94%以上;在优化条件下,采用两段逆流浸出,可有效减少活化剂CaF2以及浸出剂硫酸的消耗量;经过两段逆流浸出萃取反萃氧化水解工艺,全流程钒资源总回收率可达86.9%;V2O5产品纯度高于99.5%。     

Influence of mechanical activation on leaching kinetics of arsenopyrite

The influence of mechanical activation on the leaching kinetics of arsenopyrite was studied using a planetary centrifugal mill. It shows that mechanical activation can enhance the leaching process of arsenopyrite in a nitric-sulfate acidic solution. The leaching ratio within 20 min leaching time can increase from 2 % to 80 %～ 100 % ; 10 and 20 minties‘ activation can depress the apparent activation energy of leaching reaction from 54.5 kJ/mol to 39.0 kJ/mol and 34.0 kJ/mol, respectively. This means that the leaching reaction becomes little dependent on tempeerature, and arsenopyrite can change from refractory to flexible one; mechanical activation also increases the interplanar distance between crystal faces. The displacement of atoms from its equilibrium position indicates the increase in inner energy.     

Co基非晶软磁合金的制备与晶化动力学行为研究

采用旋铸急冷工艺在大气环境中制备出Co6.85Fe4Si10B17.5非晶合金带材.XRD分析表明:样品为完全非晶.用DiamondTG/DTA差热分析仪在高纯氩气保护下测量了非晶薄带的等温晶化动力学曲线.采用JMA方程计算出了合金的晶化动力学参数,在不同的晶化温度下,Avrami指数的值在2.11～2.58之间,晶化激活能Ec为113.67 kJ/mol.Co6.85Fe4Si10B17.5非晶合金的晶化方式是初晶型(761、791、803 K)和共晶型晶化(813 K),合金的晶化百分比与退火时间的关系曲线均为S型曲线.     

熔融镍渣等温氧化动力学研究

研究了富铁熔融镍渣在空气气氛下的等温氧化动力学行为。利用高温激光共聚焦显微镜(HT-CLSM)确定三元碱度0.6调质镍渣的实际熔融温度(液相线温度)为1488℃。通过管式炉等温氧化试验,获取温度1500～1575℃下熔融镍渣氧化过程Fe²⁺浓度-时间曲线,采用微分法和Arrhenius方程计算出熔渣中Fe²⁺的氧化反应级数为1.45～1.26,表观活化能为286.83 k J/mol,明确熔融镍渣氧化动力学主要受扩散传质控速。基于双膜理论和渗透理论,估算出1500～1575℃熔渣中氧的扩散系数分别为2.02×10^-9～4.42×10^-9 m²/s和0.50×10^-9～2.19×10^-9 m²/s,双膜理论估算出的氧扩散系数更具参考意义。     

纳米Eu0.12Y1.78La0.10O3-δ荧光粉的合成动力学

利用不同升温速率的差热-热重分析(DTA-TG)研究纳米Eu0.12Y1.78La0.10O3-δ荧光粉的合成动力学。研究表明,纳米Eu0.12Y1.78La0.10O3-δ荧光粉的前驱体为六方相Y(OH)3,利用Doyle-Ozawa法和Kissinger法计算得到前驱体2个分解阶段的表观活化能平均值分别为699.40、362.81kJ.mol-1。用Kissinger法确定反应级数和频率因子,确定纳米Eu0.12Y1.78La0.10O3-δ荧光粉2个合成阶段的反应速率方程分别为dα/dt=1.94×1046e-84120/T(1-α)1.17;dα/dt=5.89×1020e-43640/T(1-α)1.14。     

W17.9Ni65.6B13.5V3非晶合金的非等温晶化动力学研究

采用单辊急冷法制备了W17.9Ni65.6B13.5V3非晶薄带,并用X射线衍射(XRD)和示差扫描量热分析仪(DSC)研究了该非晶合金的变温晶化动力学。结果表明：玻璃转变温度Tg、晶化起始温度Tx和晶化峰值温度Tp均随着升温速率的增加而提高,具有明显的动力学效应;利用Kissinger方程和Ozawa方程求出的W17.9Ni65.6B13.5V3非晶合金的晶化激活能Ex分别达456.9kJ/mol和471.1kJ/mol,非晶合金具有较强的热稳定性;利用Kissinger方程和Ozawa方程计算得到的晶化激活能Ex均小于晶体长大激活能Ep,表明形核过程比晶粒长大过程更容易,该非晶合金在一定条件下退火容易获得超细晶粒组织。     

Kinetics of oxidative leaching of ocean polymetallic nodules in molten potassium hydroxide medium

The kinetics of oxidative leaching of ocean polymetallic nodules in molten potassium hydroxide medium was investigated in terms of the gas-flow rate, stirring rate, reaction time, reaction temperature and partial pressure of oxygen on the ratio of manganese conversion in ocean polymetallic nodules. The category of the rate controlling step was determined. The process of the liquid-phase oxidation reaction can be described by surface chemical reaction-controlled non-reaction shrinking core model(SCM), the apparent activation energy was achieved and the rate equation was put forward. From the equation, it can be concluded that the reaction rate mainly depends on the reaction temperature and the partial pressure of oxygen.     

Kinetics of SiO2 leaching from Al2O3 extracted slag of fly ash with sodium hydroxide solution

Kinetics of SiO₂ leaching from Al₂O₃ extracted slag of fly ash with sodium hydroxide solution was studied. The effect of leaching temperature, mass ratio of NaOH to SiO₂ and stirring speed on SiO₂ leaching rate was investigated. The results show that increasing leaching temperature, mass ratio of NaOH to SiO₂ and stirring speed increases SiO₂ leaching rate. The SiO₂ leaching rate is 95.66% under the optimized conditions. There are two stages for the SiO₂ leaching process, and the leaching reaction is very rapid in the first stage but quite slow in the second stage. The whole leaching process follows the shrinking core model, and the outer diffusion of no product layer is the rate-controlling step. The activation energies of the first and second stages are calculated to be 8.492 kJ/mol and 8.668 kJ/mol, respectively. The kinetic equations of the first and the second stages were obtained, respectively.     

焙烧氟碳铈矿硫酸浸出稀土的动力学(英文)

研究了硫酸浸出德昌稀土与天青石共伴生矿的焙烧矿过程。考查粒度、搅拌速度、硫酸浓度和温度对稀土浸出率的影响,并对稀土的浸出动力学进行分析。在选定的浸出条件下:粒径0.074～0.100mm、硫酸浓度1.5mol/L、液固比8:1、搅拌速度500r/min,稀土浸出反应受内扩散控制,表观活化能为9.977kJ/mol。     

AZ31B镁合金再结晶过程的动力学

对AZ31B镁合金热轧板材退火处理的静态再结晶进行了动力学分析。结果表明:AZ31B镁合金再结晶晶粒分数与退火时间的关系可以用JMAK方程进行描述,由实验数据计算得到AZ31B镁合金再结晶激活能为59.6~69.3 kJ/mol,在200,250,300,350℃和400℃时再结晶完成的时间分别为373~389,72.1~87.2,18.0~26.3,5.6~9.6 min和2.1~4.1 min,计算同时得到AZ31B镁合金再结晶动力学曲线,该曲线可以为制定AZ31B镁合金退火处理工艺提供参考。     

硅粉常压直接氮化合成氮化硅粉的动力学研究

以平均粒径为2.8 μm的硅粉为原料,添加氮化硅粉作为稀释剂,对常压氮气下直接氮化制各Si3N4粉的工艺进行了研究,氮化温度范围为1623～1823 K,氮化时间范围为0～20 min.借助XRD、SEM等检测方法,分析了氮化温度和氮化时间等因素对氮化过程的影响.基于不同氮化温度下硅的转化率与氮化时间的关系,利用粒径不变的缩芯模型,建立了一种简化的硅氮反应模型,该模型显示出硅的转化率随时间呈渐近线指数趋势.并利用该模型计算得出了硅粉常压直接氮化合成氮化硅粉的一些反应动力学参数:Arrhenius公式中指前因子为5.56×1012cm/s;活化能为534 kJ/mol;有效扩散系数为6.2×10-8cm2/s;以及反应速率常数的计算公式.     

强界面能各向异性下二元Ni-Cu合金枝晶生长过程的相场法模拟

基于Wheeler模型和Eggleston修正强界面能各向异性的方法,建立耦合溶质场和温度场的相场模型,模拟强界面能各向异性下Ni-Cu合金枝晶生长过程.结果表明:在强界面能各向异性作用下,界面方向枝晶生长不连续且枝晶出现棱角;由于枝晶尖端温度梯度和溶质梯度较大,枝晶生长迅速.当界面能各向异性强度低于临界值时,枝晶尖端生长速度随界面能各向异性强度的增加而增大;当界面能各向异性强度等于临界值时,枝晶尖端生长速度下降4.34％;当界面能各向异性强度大于临界值时,枝晶尖端生长速度随界面能各向异性强度的增加先增大到极大值后逐渐减小.当无量纲热过冷度较小时,晶体平衡形貌为类矩形;随着无量纲热过冷度的增加,晶体平衡形貌向枝晶转变,枝晶尖端生长速度先呈幂指数增加,然后呈线性增加,枝晶生长由扩散控制转变为动力学控制.     

钽钛合金的再结晶动力学研究

对不同变形量的合金丝进行了再结晶退火试验。根据Arrhenius公式计算出再结晶激活能Q＊结果表明，TaTi合金的再结晶速率随变形的增加而增大，这种情况是由于再结晶形核激活能（Q）的降低所致。     

TB8钛合金板材再结晶动力学

对TB8合金冷轧板材在770~820℃温度范围内的再结晶动力学研究表明:试验用TB8钛合金冷轧板材的再结晶最佳退火温度为790~810℃。采用Avrami方程可以较好的描述冷轧TB8合金板材退火过程的再结晶情况。800℃退火处理动力学拟合方程为:lnln[1/(1?x?t?)]??2.38?0.86lnt。由实验数据计算得到合金再结晶激活能为102.87 k J/mol。