氧化亚铁颗粒氢还原过程的结构演变

采用热重法实验研究了773~1273 K氧化亚铁的等温氢还原动力学,发现873 K温度以上,反应动力学曲线有明显转折,说明反应机理发生了变化.在973~1073 K的温度范围,出现了反常的温度效应,即反应速率随温度升高而减小.为讨论产物结构对反应动力学的影响,分别对不同温度的反应产物,以及一定温度不同还原状态(不同反应时间)的产物进行形貌观察.结果显示,随着反应温度升高,还原产物表面的孔洞增多,枝状特征显著增加,而973 K和1023 K时表面的烧结现象明显.一定温度下,随着反应进行,表面的孔洞增多,并逐渐出现烧结.973 K和1023 K温度条件下反应产物大体保留原来的大颗粒外形,而1173 K时还原2 min开始,就大量出现枝状产物,并逐渐烧结.结合产物形貌变化和反应动力学曲线,反应前期为界面化学反应控速,随着反应进行,还原的金属铁发生烧结现象,致密的结构阻碍了产物气体向外扩散,反应控速环节转变为产物气体的外扩散,还原速率也随之降低.     

颗粒粒径对流态化还原铁矿粉黏结失流的影响

采用热态可视化流化床装置，在一定表观气速条件下，研究1073 K温度时不同粒级铁矿粉的黏结失流。根据对黏结失流影响程度的不同，可将矿粉颗粒分为三个粒径区间：中性气氛升温过程中失流的小粒径颗粒；还原至较低金属化率发生失流的中间粒径颗粒；还原至高金属化率也不发生失流的大粒径颗粒。分别对他们不同的影响机理进行了分析。研究还发现在正常流化条件下，随着矿粉颗粒粒径的增大，还原失流后床层的膨胀幅度会减小。     

Reduction of 1-3 mm iron ore by H2 in a fluidized bed

The reduction of 1-3 mm fine powder of iron ore by H₂ was conducted in a lab-fabricated kg class high temperature fluidized bed. The results show that the differential pressure in the fluidized bed, which has small fluctuation with time, increases with the increase of gas flowing velocity. The utilization ratio of gas decreases when the reaction lasts longer time indicating that the reaction is faster at the beginning of reduction and becomes slower in the latter process. The higher the reaction temperature is, the higher the utilization ratio of gas is, but the difference of utilization ratio among the different temperatures becomes smaller with time. The utilization ratio of gas and the metallization ratio can reach 9% and 84% respectively at 750℃ for 20 min, which shows the reduction reaction by H₂ is very fast. The increase of metallization ratio with gas velocity performs quite good linearity, which shows that a higher velocity of reducing gas can be used to improve the productivity of the reactor when H₂ is used as reducing gas. With the increase of charge height, the metallization ratio decreases, but the utilization ratio of gas increases. The reaction temperature can be reduced to 700-750℃ from 800-850℃ when H₂ is used as reducing gas.     

含碳酸盐脉石氧化铜矿的酸浸动力学

针对碳酸盐脉石对氧化铜矿酸浸动力学的影响进行探讨,研究了温度、酸度、矿石粒径、液固质量比、振荡速度等因素对含碳酸盐脉石氧化铜矿浸出的影响.结果表明,高温、高酸度、高液固质量比、小粒径和高振荡速度利于矿石的浸出,但碳酸盐脉石使得酸耗增加.考虑浸出成本确定合理的浸出条件为温度303 K、酸度35 g·L-1、矿石粒径0.074~0.125 mm、液固质量比3﹕1以及振荡速度180 r·min-1,浸出180 min后铜浸出率达53.6%.对浸出前后矿石表面形貌进行分析.结果显示碳酸盐脉石与酸反应后在矿石表面形成CaSO4·2H2 O沉淀,覆盖在颗粒表面,限制了矿石颗粒孔裂隙的发育.基于收缩未反应核模型对浸出动力学进行分析,发现碳酸盐脉石反应生成的沉淀阻碍了浸出反应,固体产物层扩散为浸出反应的控制步骤,反应的表观活化能为8.65 kJ·mol-1.     

高炉热储备区温度对煤气利用率的影响

研究了高炉热储备区内温度与煤气利用率的关系.结合热力学和实际情况,热储备区内只发生氧化亚铁的还原.因此需要利用吉布斯自由能计算和单界面未反应核模型对热储备区内还原反应进行热力学和动力学分析.结果表明:只有在H₂+H₂O体积分数小于0.3时降低热储备区温度才能提高煤气利用率.从1273K降温到1223K,氢气还原速率降低得比CO还原速率降低得多,说明温度对氢气还原的影响更大.对一般高炉来说,炉料在热储备区中还原所需的时间比其停留时间长或接近,说明热储备区内的还原反应没有达到平衡,降低温度不利于提高煤气利用率.     

Synthesis of TiO2 supported on activated carbon by MOCVD： operation parameters study

The metallo-organic chemical vapor deposition (MOCVD) technique has been applied to the preparation of the photocatalyst titanium dioxide supported on activated carbon. The effects of various condition parameters such as carrier gas flow rate, source temperature and deposition temperature on the deposition rate were investigated. The maximum deposition rate of 8.2 mg/(g x h) was obtained under conditions of carrier gas flow rate of 400 ml/min, source temperature of 423 K and deposition temperature of 913 K. The deposition rate followed Arrhenius behavior at temperature of 753 K to 913 K, corresponding to activation energy E(a) of 51.09 kJ/mol. TiO(2) existed only in anatase phase when the deposition temperature was 773 K to 973 K. With increase of deposition temperature from 1073 K to 1273 K, the rutile content sharply increased from 7% to 70%. It was found that a deposition temperature of 773 K and a higher source temperature of 448 K resulted in finely dispersed TiO(2) particles, which were mainly in the range of 10-20 nm.     

Kinetic study on the reaction between CO2-CO and wustite using the isotope exchange method

To investigate the reaction between CO₂-CO and wustite using the isotope exchange method at 1073, 1173, 1273, and 1373 K, the experiment apparatus was designed to simulate the fluidized bed. The chemical rate constant was estimated by considering the effect of gas phase mass transfer on the reaction. It is found that the chemical rate constant is inversely decreased with the increase in the ratio of CO₂/CO by volume. The activation energy of reaction is in a linear relationship with the ratio of CO₂/CO by volume, and the average activation energy is 155.37 kJ/mol.     

Cost-effective integrated strategy for the fabrication of hard-magnet barium hexaferrite powders from low-grade barite ore

Ultrafine barium hexaferrite (BaFe₁₂O₁₉) powders were synthesized from the metallurgical extracts of low-grade Egyptian barite ore via a co-precipitation route. Hydrometallurgical treatment of barite ore was systematically studied to achieve the maximum dissolution efficiency of Fe (~99.7%) under the optimum conditions. The hexaferrite precursors were obtained by the co-precipitation of BaS produced by the reduction of barite ore with carbon at 1273 K and then dissolved in diluted HCl and FeCl₃ solution at pH 10 using NaOH as a base; the product was then annealed at 1273 K in an open atmosphere. The effect of Fe3+/Ba2+ molar ratio and the addition of hydrogen peroxide (H₂O₂) on the phase structure, crystallite size, morphology, and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. Single-phase BaFe₁₂O₁₉ powder was obtained at an Fe3+/Ba2+ molar ratio of 8.00. The formed powders exhibited a hexagonal platelet-like structure. Good maximum magnetization (48.3 A·m2·kg–1) was achieved in the material prepared at an Fe3+/Ba2+ molar ratio of 8.0 in the presence of 5% H₂O₂ as an oxidizer and at 1273 K because of the formation of a uniform, hexagonal-shaped structure.     

氢气还原褐铁矿实验研究与动力学分析

本文旨在研究不同温度下氢气对褐铁矿还原度和还原速率的影响,并以此为基础分析动力学相关问题.通过热重分析深入了解褐铁矿失水状况.使用粒度为8~12 mm褐铁矿焙烧后,分别在750~950℃五个不同温度下使用4 L·min-1 H2进行还原,并分析还原率和还原速率随时间的变化关系.研究发现：随着反应进行,试样还原率逐渐增大,五条还原率曲线在t>28 min后与还原温度排序一致.通过动力学研究计算得反应表观活化能E=15.323 kJ·mol-1,从而确定扩散为还原反应的限制环节.     

真空铝热炼锂还原渣回收氢氧化铝的研究

碳酸锂、氧化铝和氧化钙混合常压煅烧可获得LiAlO₂熟料,经真空铝热还原可得金属锂,同时得到铝酸钙系还原渣,主要成分为CaO·Al₂O₃和12CaO·7Al₂O₃.为综合利用该还原渣,通过混合碱液溶出、碳酸化分解回收氢氧化铝.研究溶出温度、溶出时间、还原渣粒度、碳酸钠质量浓度、氢氧化钠质量浓度、金属锂还原率对氧化铝溶出率的影响.结果表明:以锂还原率97%的炼锂还原渣为原料,粒度分布d_○90 74μm、溶出温度95℃、溶出时间120min、碳酸钠质量浓度240g/L及氢氧化钠质量浓度8.9g/L的条件下,氧化铝的溶出率为80.73%.溶出的铝酸钠溶液经碳分可获得体积平均粒径6.50μm及白度值96.9的氢氧化铝.     

硼铁矿石固相还原动力学

用热重法研究了硼铁矿石氢气还原动力学。氢气流量600ml/min,温度600～1000℃。实验结果表明,矿石结构、孔隙度和颗粒的大小对还原率有明显的影响。单一方向还原实验表明,气体在产物层孔隙的扩散对还原速度影响显著,是还原的控制步骤。将实验数据用TURK-DOGAN内扩散速度方程处理,求出H_2-H_2O气体在产物层孔隙中有效扩散系数D_o值随还原温度下降而明显减小。     

（光）助电-Fenton降解有机染料罗丹明B

以高纯石墨电极为阴极,铁片为阳极,Na2SO4溶液为支持电解质,通过阳极氧化提供Fe^2＋/Fe^3＋和阴极还原溶解氧转化为H2O2而形成Fenton体系,以降解有机染料罗丹明B（RhodamineB,RhB）为探针反应,研究了外加电压、铁电极面积（电荷密度）、极间距、电解质溶液浓度及外加紫外光照射（300 nm〈λ〈380n m）等因素对RhB降解反应的影响.结果表明：外加电压为7 V,铁片面积为3 cm^2（电荷密度为0.045 A/cm^2）,电极之间距离为4 cm,Na2SO4质量浓度为10 g/L时,反应100 min后RhB褪色完全.采用过氧化物酶催化反应吸光光度法和苯甲酸荧光分析法分别跟踪测定RhB降解反应过程中H2O2和羟基自由基（·OH）,表明RhB降解过程涉及·OH历程.通过分析测定RhB降解过程TOC变化和红外光谱分析,表明染料降解反应不仅仅为简单褪色而且深度氧化,180 min矿化率为73.0%.     

气相质谱法研究 Fe 与 CO2-- CO 氧化反应动力学

采用气相质谱在线监测反应气体成分变化的方法,研究了1273~1473 K 范围内,不同比例 CO2- CO 混合气体对铁片恒温氧化的反应动力学.结果表明,氧化反应速率与二氧化碳分压呈线性关系,反应速率常数随 CO2/ CO 体积比值增大而减小,铁片氧化反应的表观活化能为(137.7±15.8) kJ·mol -1.该方法得到的结果与文献相比较,结果是可靠的,表明该方法可以用来在线研究气-固反应的动力学.     

喷动流化床气固流动特性的三维数值模拟

采用离散元方法（DEM）,在用欧拉方法处理气相场的同时用拉格朗日方法处理离散颗粒场,对喷动流化床煤部分气化炉内的气固流动进行了三维数值模拟．直接跟踪床内每一个离散颗粒,考虑了碰撞力、携带力、重力、剪切提升力和Magnus升力,颗粒碰撞采用软球模型．获得了喷动流化床典型操作参数下的流动结构、颗粒的受力、颗粒的速度分布、气体和颗粒的湍流强度等结果．结果表明,颗粒之间碰撞率随着喷动气速的增大而增大,随粒径的增大而减小,然而颗粒与壁面的碰撞率受喷动气速和粒径的影响不明显．颗粒的运动受重力、携带力和碰撞力主导,除喷动区与环形区交界外,Magnus力和Saffman力可以忽略．气体湍流强度是颗粒湍流强度的2～3倍,近壁面区的气体和颗粒的湍流强度均较小．     

湿化学法制备ZnO纳米流体

采用湿化学法成功制备了氧化锌（ZnO）纳米流体。用X射线衍射仪（XRD）、透射电子显微镜（TEM）对ZnO纳米颗粒的成分、分散性、形貌和粒径进行了分析表征;研究了醇水比（丙二醇（PG）／水）、乙酸锌浓度、反应时间、分散剂等因素对纳米流体分散稳定性和ZnO粒径的影响。结果表明,以乙酸锌（（CH3COO）2Zn·2H2O）为锌源,以氢氧化钠（NaOH）为碱源,V（丙二醇）：V（水）=3：2,乙酸锌浓度为0．1mol·L^-1,反应时间0．5h,聚乙二醇2000（PEG2000）加入1％（m（PEG2000）／m（乙酸锌）=1％）时为最佳工艺条件,产物氧化锌颗粒大小在20～30nm,分散性好,解决了团聚问题,可以稳定较长时间。     

Basic properties of steel plant dust and technological properties of direct reduction

Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas (OG) sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 μm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces (BF) if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250℃ for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the briquettes were kept at 1250℃ for 6 min.     

普鲁士蓝对罗丹明B的光催化降解研究

用普鲁士蓝与过氧化氢作为类-Fenton试剂,在波长大于420 nm的可见光辐射下研究了罗丹明B的光催化降解规律。实验表明：普鲁士蓝与过氧化氢形成的Fenton体系对罗丹明B有显著的降解作用,在没有电解质存在下,9.0 mg·L-1的罗丹明B经过120 min的降解,其降解率达到64.0%,其降解动力学符合一级反应动力学方程。加入KNO3,KCl,KBr,K2SO4电解质后,反应速率有不同程度的影响,在保持钾离子浓度相同的情况下,阴离子对罗丹明B降解速率的影响从大到小的顺序是SO42-〉Br-〉Cl-〉NO3-,其中在0.05 mol·L-1硫酸钾溶液中40 min时罗丹明B的降解率达到了97.0%。     

铁基载氧体化学链燃烧还原过程的数学模型

为了研究铁基载氧体的反应特性,基于未反应缩核模型建立了移动床内铁基载氧体颗粒还原过程的一维数学模型.模型中考虑了铁基载氧体与H2、CO的多级还原反应,气体组分体积分数模拟值与实验值的平均误差为6.9％,总还原度的平均误差为11.2％.研究表明:铁基载氧体在移动床反应器内最终还原度约为23％,主要进行的反应是第一级和第二级还原反应,第一级和第二级还原度分别为95％和40％;提高反应器内温度、选择合适的载氧体粒径及气固比有助于增加反应的深度,提高合成气及铁基载氧体的利用率,载氧体粒径建议取1 ～2mm.     

聚溴酚蓝过氧化氢传感器的研究

通过电聚合溴酚蓝于铂丝电极上,利用该聚合膜对H2O2直接催化制得无酶过氧化氢传感器.实验结果表明该聚合膜对H2O2呈现出良好的催化特性,并对该传感器性能及影响该传感器性能的因素作了详细的研究.在优化的条件下,该传感器的线性响应范围为5.6×10-8~1.4×10-5mol/L,检测线为3.1×10-8mol/L.并且,该传感器灵敏度较高、重现性好、稳定性较长.     

DO对短程反硝化过程中N2O产量的影响

利用SBR反应器,考察不同溶解氧(DO)条件下NO2-反硝化过程中N2O产生及释放过程。研究结果表明:控制曝气量为0.3 L/min,进水NO2--N质量浓度为40 mg/L,体系DO质量浓度分别为0,0.1,0.3,0.5和0.7 mg/L时,反硝化过程N2O释放量分别为0.41,0.60,2.62,4.98,6.83 mg/L;随DO质量浓度的增加,反硝化速率明显降低;当DO质量浓度由0 mg/L增至0.7 mg/L时,每克混合液悬浮固体(MLSS)的NO2-反硝化速率由14.9 mg/(L.h)降至10.2 mg/(L.h),每克MLSS的N2O产生速率由0.2 mg/(L.h)增至1.9 mg/(L.h)。其原因为:高DO质量浓度对氧化亚氮还原酶具有较强的毒性,抑制了N2O的进一步还原过程;高NO2-的存在导致抑制了氧化亚氮还原酶的活性。降低A/O和A2/O等生物脱氮过程中缺氧反应器内部DO质量浓度,保证严格缺氧条件,是减少短程生物反硝化过程中N2O产量的关键因素。