Kinetics of isothermal reduction of stainless steelmaking dust pellets

The stainless steelmaking dust pellets were reduced in isothermal temperature condition simulating the direct recycling practice in the stainless steel production and the kinetics of the reduction process was investigated.The pellets were formed after mixing the dust with carbon as the reducing agent and dolomite as the binder and smelting flux. An electric furnace was used to heat the pellets and an electrical microbalance was used to check the mass of the pellets in the reduction process. The reduction rate was calculated according to the data of pellet mass change in consideration of the evaporation of moisture, zinc and lead at high temperature. The results of the experi-ments show that the reduction process is in two consecutive stages. The reduction kinetic models were set up for each stage and the kinetic parameters such as activation energy and frequency factor were determined. The apparent activation energy of the first stage is 21.69 kJ/mol, and this stage is controlled by chemical reaction. The apparentactivation energy of the second stage is 17.35 kJ/mol, and this stage is controlled by the diffusion of carbon monox-ide through the resultants of reaction.     

高炉尘泥化学除锌

为了降低经物理分选后的高炉精泥中锌的含量,对高炉精泥进行化学浸出除锌研究,考察浸出剂、浸出时间、温度、液固比和搅拌速度等对浸出的影响,并进行理论分析。结果表明：硫酸对锌的浸出率最高,氯化铁次之,氨水最低;在合适的浸出条件下：液固比8-1,温度20℃,硫酸浓度125 g/L,浸出时间35 min和搅拌速度150 r/min,锌浸出率为73.9%,高炉精泥中的锌含量从1.46%降低到0.38%。对硫酸浸出脱锌的动力学和反应机制的研究表明,浸出过程遵从1-2α/3-（1-α）2/3=kt,浸出反应的活化能为8.89 kJ/mol,属于扩散控制过程。     

预氧化钒钛磁铁精矿的固态还原动力学及其机理

研究预氧化钒钛磁铁精矿固态还原反应的动力学,采用XRD、SEM和EDS等手段研究还原产物的显微结构和物相变化,在此基础上,对其固态还原机理进行研究。结果表明：以煤为还原剂,在还原温度为950~1100°C时,预氧化钒钛磁铁精矿的固态还原受界面化学反应控制,反应的表观活化能为67.719 k J/mol;预氧化钒钛磁铁精矿的还原历程可描述为：预氧化钒钛磁铁精矿→钛铁晶石→钛铁矿→亚铁板钛矿（Fe Ti2O5）→（FenTi1-n）Ti2O5。预氧化钒钛磁铁精矿在1050°C还原60 min后,还原产物中会形成M3O5型（M为Fe、Ti、Mg、Mn等）固溶体,存在于M3O5固溶体中铁的难还原性是限制预氧化钒钛磁铁矿还原的主要原因。     

烧结电除尘灰中钾盐的回收及其浸出动力学

为了研究烧结电除尘灰中回收钾盐的强化浸出措施,使用ICP-AES、SEM-EDS和XRD分析技术对除尘灰的表面和内部形态,特别是钾盐的赋存形式进行分析。结果表明,该电除尘灰的主要成分是铁氧化合物,在其表面裸露吸附着一定含量的KCl晶体。水浸实验表明,该粉尘中的KCl可以通过水浸出、蒸发结晶的方式回收,其收率为18.56%。结晶产物的分析结果表明,KCl占61.21%,NaCl占13.40%,CaSO4占14.62%,K2SO4占10.86%。其水浸出动力学符合外扩散控制模型控制。强化浸出实验表明,提高浸出温度、加强搅拌、增加液固比等措施可以提高钾盐的浸出率和浸出速率。     

铁矿粉烧结电除尘灰中氯化钾的赋存形态及其水浸动力学分析

为分析氯化钾从烧结电除尘灰中水浸出速率及浸出动力学,使用扫描电镜-线扫描分析氯化钾在烧结电除尘灰中的赋存状态及其与其它颗粒之间的赋存关系。实验发现烧结电除尘的平均粒径小于10μm,大多以团聚形式存在;氯化钾和氯化钠颗粒在烧结电除尘中的部分表面与其它粉尘颗粒如铁氧化物、钙镁化合物等有粘附连接。氯化钾在烧结电除尘中的存在形式表明其水浸出过程可视为可溶水的物质的溶解过程。借助于在线电导率测量手段分析烧结电除尘灰的水浸动力学。结果证明该粉尘的水浸过程符合扩散控制的溶解过程模型。浸出平衡在5min之内即可达到,同时氯化钾的浸出率达到 95%以上。     

Isothermal reduction kinetics of zinc calcine under carbon monoxide

The reduction kinetics of zinc calcine under a CO atmosphere was evaluated by isothermal reductive roasting in a temperature range of 600−800 °C. The extent of reaction of zinc calcine was measured using thermogravimetry (TG), and the decomposition mechanism of zinc ferrite in zinc calcine was analyzed based on variations in the soluble zinc and ferrous contents. The results indicate that the reaction was controlled by the nucleation of the products, with an apparent activation energy of 65.28 kJ/mol. The partial pressure of CO affected the reaction rate more strongly than the CO intensity (defined as P_CO/(P_CO+P_CO2)). The generation rate of zinc oxide was higher than that of ferrous oxide; therefore, the nucleation of ferrous oxide is the rate-determining step of the reaction.     

Ag_2O机械活化和热还原合成Ag的等温动力学(英文)

在氩气气氛下,将Ag2O与石墨通过机械活化或热还原反应生成Ag,对其等温还原过程的动力学进行研究。结果表明,采用Johnson-Mehl-Avrami模型能合理地解释Ag2O与石墨经机械活化和热还原合成Ag的过程。采用相同的模型来研究机械活化和热还原反应合成Ag的动力学时,机械活化还原过程中的Avrami指数比热还原的要高;热还原和机械活化过程中的晶核长大机制分别是扩散控制和界面控制。     

40Cr钢等温转变曲线与非等温冷却过程数值分析

建立连续冷却过程多相转变模型,并实现了对冷却过程中各相转变量的数值预测。用传统叠加模型和Cahn微分模型分别对40Cr钢连续冷却过程中组织分布进行了模拟计算,结果表明,考虑动力学参数n随温度变化的相变动力学微分方程计算结果与实际结果更为接近。为分析晶粒尺寸对相变过程的影响,结合不同奥氏体化温度下的等温膨胀实验,讨论了考虑晶粒尺寸时的相变动力学模型的应用范围,不同晶粒度下的相变参数n相同时,模型才能准确反应实际相变过程。     

Kinetics of non-isothermal precipitation process of perovskite phase in oxidized Ti-bearing blast furnace slag

Kinetics of non-isothermal precipitation process and crystal growth of perovskite phase in oxidized Ti-bearing slag were investigated. The oxidized slag was obtained by blowing the air into the molten Ti-bearing blast furnace slag through a lance. The experimental results show that the cooling rate has important effect on precipitation and growth of perovskite phase in oxidized slag; the lower cooling rate is in favor of not only the increase of the volume fraction of perovskite phase, but also the growth of perovskite phase grain sizes. The particle coarsening in non-isothermal process has important effect on the crystal growth of perovskite phase. The relative volume fraction of perovskite phase could be approximately described by JMAK equation, and the experiential expression of the average crystal radius of perovskite phase was also obtained.     

氢气还原-ICP-AES法测定化工炉灰中的铑含量

贵金属合金催化网在使用过程中产生含铑的化工炉灰中含有贵金属,具有较高的回收价值。由于其含有有机物及氧化态铑样品难以消解。本文采用灼烧后氢气还原,盐酸-过氧化氢溶液密闭消解,所得溶液使用ICP-AES测定。结果表明,测定铑含量为0.01%～5.0%的化工炉灰,相对标准偏差(RSD)<2%(n=7),加标回收率为95.50%～104.46%,测定结果与管理样名义值吻合,能够满足回收过程中贸易的分析要求。     

碳热还原法制取铝硅合金的反应机理及其动力学

利用XRD、TG/DTA技术分别分析真空碳管炉内不同反应温度下的物相组成和碳热共还原Al2O3、SiO2的反应过程,并在此基础上探讨碳热还原法制取铝硅合金的反应机理.分别采用10、15、20和25 K/min升温速率的差热分析,研究动态氩气气氛中碳热法制取铝硅合金的反应动力学.结果表明:碳热还原反应过程可分为4个阶段,其中,以碳化物的生成与分解阶段为主.碳热还原反应的4种还原机理中,碳化物的生成与分解理论能较好地解释反应过程中出现的反应现象.各个吸热峰的表观活化能分别为848.9、945.4、569.7、325.7、431.9和723.1 kJ/mol,给出了各个吸热峰的动力学方程.同时,利用XRF和红外定硫定碳仪对碳管炉和电炉所得产物组成的定量分析,验证了动力学分析结果的可行性.     

高炉出铁场除尘技术研究与应用

本文论述了出铁场烟气治理的必要性,介绍了武钢对出铁场烟尘的"全面控制”方法,总结了效果并指出了需进一步完善的措施.     

Reduction mechanism of stainless steelmaking dust and carbon pellets

1 INTRODUCTIONThe smelting temperature generally reaches1 600 ℃or higher in stainless steel making opera-tion. Under this condition,approxi mately 1 % 2 %(mass fraction) of the scrap charged into the fur-nace is converted to dust[1]as by-product of steel-making process .It has been assigned as a hazard-ous waste and banned from landfills by variousgovernment regulatory agencies because it containsa lot of heavy metals such as zinc ,lead,cadmium,chromium and nickel , which will be leached …     

镀锌基板氧化铁皮在还原过程中的组织演变

氢气还原氧化铁皮无酸洗热镀锌技术具有清洁、环保、低成本的优点。为了促进该技术的推广应用,采取5％压下率冷轧作为预处理工艺,并利用真空管式炉和扫描电镜,研究了不同还原温度对经预处理和未预处理镀锌基板SPHC带钢氧化铁皮还原产物、还原效率和还原机制的影响规律。结果表明:SPHC带钢在30%H₂浓度下,不同温度下还原机制有较大差异,最终产生3种不同的还原产物,500~600 ℃时还原产物为多孔铁,经过预处理的试样多孔铁更致密;700 ℃时还原产物由多孔铁与致密铁共同组成,经过预处理的试样氧化铁皮残留量小于未预处理的试样;800 ℃时还原产物为致密铁,未预处理的试样氧化铁皮中间层依旧存在氧化物残留,经预处理的试样几乎看不见氧化物残留;900 ℃时还原产物为致密铁,预处理和未预处理试样还原效果几乎相同。     

Leaching process of germanium oxide dust

A thermodynamic analysis on the acid leaching process of germanium oxide dust and discussion on the behaviors of main substances of the dust in the leaching process were carried out. The effects of temperature, acid concentration, leaching time and stirring speed on the leaching rate of germanium were investigated. Based on the characteristic of the dust, the kinetics and reactive mechanism of acid leaching were stud- ied. The results show that the leaching of the dust by acid belonged to "the unreacted core shrinking model" of producing solid outgrowth layer. The chemical reaction was controlled by inner diffusion process. The apparent activation energy of leaching process was 12.60 kJ/mol. The leaching reaction of germanium was determined to be mainly second order reaction. The optimum conditions were the reaction tem- perature of 363 K, the leaching time of 2.5 h, the stirring speed of 120 r/min, the solid-to-liquid ratio of 1/8 and the acid concentration of 120 g/L. Under these conditions, the leaching rate of germanium can come up to more than 87%.     

烟化炉产氧化锌烟尘的介电特性及温升特性

为了研究微波焙烧脱除氧化锌烟尘中氟氯的可行性以及氧化锌烟尘的吸波特性,采用谐振腔微扰法对不同物料密度氧化锌烟尘的介电特性（ε′,ε″和tanδ）进行测定。氧化锌烟尘的介电常数、介电损耗和损耗角正切值与氧化锌烟尘的表观密度成正比。在微波场下研究物料质量和微波功率对氧化锌烟尘升温特性的影响。结果表明,氧化锌烟尘对微波具有较强的吸波能力,其表观升温速率与微波焙烧功率成正比,与质量成反比,在8 min内温度可到达800℃。     

回收铝电解炭渣中电解质的研究

研究了回收铝电解炭渣中电解质的焙烧工艺,重点探讨了焙烧温度、停留时间、添加剂加入量对炭渣焙烧工艺的影响,分析了各影响因子与反应率之间的变化关系.在细粒料-回转窑焙烧条件下获得了较高的反应率,回收电解质纯度大干99%,杂质含量低于0.5%,可直接作为铝电解原料.     

密闭直流电弧炉冶炼钛渣热量平衡研究

密闭直流电弧炉冶炼生产钛渣利用输入电能进行加热,在高温情况下,钛精矿中的FeO和TiO2发生还原反应.反应进行程度影响熔池内渣的粘度,进而影响炉壁挂渣层的厚度和排渣排铁的难易程度,故还原反应过程必须控制输入能量使DC炉系统达到热量平衡；输入能量过高会使熔池内的渣过热,挂渣层变薄,造成炉壁腐蚀；输入能量过低,会导致渣的粘度明显增大,造成排渣困难,并产生泡沫渣.根据理论计算,每冶炼1t钛精矿需要消耗约911.55kWh的能量,云南某公司加料速率为5t钛精矿/h,钛精矿碳热还原,理论上需要消耗约4557.734kWh的电耗.能量支出方面有物料带走的物理热、炉壁和炉顶冷却水热损失、炉底风冷热损失、电力设备热损失以及少量未预见热损失,钛精矿冶炼过程中,能量的输出和输入是基本相等的,热量处于平衡状态.     

新型硅热法炼镁还原炉的设计开发

分析了蓄热燃烧技术应用于我国镁还原工业的必要性,设计开发了70罐的新型金属镁还原炉,利用蓄热燃烧技术达到大幅节能降耗的目的。通过弥散燃烧、多点供热以及炉体结构的设计实现炉膛温度的三维均匀,达到炉体新型化、提高产镁率、延长还原罐及炉体寿命、缩短还原周期等目的。