Pre-reduction of WO_(3)-Co_(3)O_(4)by H_(2)-C_(2)H_4 in a fluidized bed

In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)

Effect of CaO and CaCO3 on Reduction Rate of Iron Ore Pellets Containing Carbon

The effect of metallurgical fluxes CaO and CaCO3 on the reduction rate of iron ore pellets containing carbon in nitrogen atmosphere has been studied by a weight-loss thermal balance. The experimental results showed that adding CaO or CaCO3 can promote reduction reaction as the added CaO or CaCO3 probably decrease the apparent activation energy of iron ore concentrate-carbon-CaO or CaCO3 reaction, and the reduction rate constant changes with mass percent of CaO and CaCO3. The kinetic analysis also showed that the rate-controlling step of the reaction is inner gas diffusion.

放射性废阳离子树脂原位Fe_(2)O_(3)催化裂解减容研究

催化裂解能够有效减小放射性废树脂的体积,但温度过高有可能导致裂解过程中核素挥发。为降低裂解温度,本文采用原位Fe_(2)O_(3)对放射性废阳离子树脂进行催化裂解。结果表明,通过离子交换法将Fe^(3+)负载至阳离子树脂上,在裂解过程中原位生成Fe_(2)O_(3),能够使树脂的裂解温度降至650℃左右,比直接热裂解低130~150℃,且残渣率降低至15%(650℃)。对裂解残渣进行FT-IR、XRD、XPS和元素分析,结果发现Fe^(3+)原位生成的Fe_(2)O_(3)有效促进了磺酸基(-SO_(3)H)的转化及硫键(-S-)的断裂,树脂中83.1%的硫元素转化为SO_(2),16.9%的硫元素以硫酸盐的形式进入残渣中。上述实验结果表明,原位生成的Fe_(2)O_(3)能显著降低阳离子树脂的裂解温度和残渣率,能够实现放射性废树脂的有效减容。

Kinetics of Reduction of Iron Oxide in CaO-SiO_2-Al_2O_3-Fe_tO Slags with Graphite Powder

The reduction rate of Fe^tO in CaOSiO_2Al_2O_3Fe_tO slags with graphite powder has been determined in an alumina crucible at 1 673-1 823 K. The effects of temperature, slag basicity and Fe_tO content on the reduction rate have also been discussed. Test results show that the reduction rate increases with the increase of temperature or Fe_tO concentration in slags, and the reduction rate has a parabolic relation with slag simple basicity or optical basicity. The maximum reduction rate is observed around CaO/SiO_2=1.5 of molten slags. The reaction order is 1.26 or 1.31, and the reduction activation energy is 126.8 or 129.7 kJ/mol respectively in regard to Fe_tO content or Fe_tO activity calculated by using regular solution model. The reduction rate of Fe_tO in CaOSiO_2Al_2O_3Fe_tO slags with graphite powder is in the range of 0.15×10^-4-0.86×10^-4 molO/cm^2·s.

阪崎克洛诺菌还原蒙脱石中Fe^(3+)实验研究

为研究阪崎克洛诺菌(Cronobacter Sakazakii)还原普通钙基蒙脱石中Fe3+的过程与机理,测定了体系中总蛋白与Fe2+含量变化,应用同步辐射XRD(SRXRD)与X射线吸收近边结构(XANES)研究反应产物。总蛋白与Fe2+数据表明在厌氧条件下Cronobacter sakazakii以乙酸作为电子供体,利用钙基蒙脱石中Fe3+作为电子受体进行生长代谢,还原蒙脱石中Fe3+形成Fe2+。反应中蒙脱石晶体结构部分破坏,原始的d001峰消失,出现一系列与新生矿物有关的衍射峰。XANES结果显示蒙脱石中Fe主吸收峰向低能量方向移动0.5 e V,边前峰峰位中心向低能量方向移动且峰面积减小,Fe氧化态降低,蒙脱石晶体结构发生变化。研究探讨了自然界中广泛分布的钙基蒙脱石可能受到的微生物还原作用。

Efficient electrocatalytic conversion of N_(2) to NH_(3) using oxygen-rich vacancy lithium niobate cubes

Instead of the energy-intensive Haber-Bosch process,the researchers proposed a way to produce ammonia using water and nitrogen as feedstock,powered by electricity,without polluting the environment.Nevertheless,how to design efficient electrocatalyst for electrocatalytic nitrogen reduction reaction(NRR)is still urgent and challenging.Herein,a strategy is proposed to adjust the morphology and surface electronic structure of electrocatalyst by optimizing material synthesis method.LiNbO3(lithium niobate,LN)cubes with oxygen-rich vacancy and regular morphology were synthesized by hydrothermal synthesis and followed molten salt calcination process,which were used for electrocatalytic NRR under mild conditions.Compared with LN nanoparticles synthesized by solid phase reaction,LN cubes exhibit better NRR performance,with the highest ammonia yield rate(13.74μg.h^(-1).mg^(-1))at the best potential of-0.45V(vs.reversible hydrogen electrode,RHE)and the best Faradaic efficiency(85.43%)at-0.4 V.Moreover,LN cubes electrocatalyst also demonstrates high stability in 7 cycles and 18 h current-time tests.Further investigation of the reaction mechanism confirmed that the structure of oxygen vacancy could adjust the electronic structure of the electrocatalyst,which was conducive to the adsorption and activation of N_(2) molecule and also increased the ECSA of electrocatalyst,thus providing more active sites for the NRR process.

无缝钢管张力减径工艺减径率分配修正模型理论研究

无缝钢管张力减径工艺减径率分配是孔型分配合理与否的关键步骤,但其分配仍依赖于经验公式。从金属流动的角度分析了减径率的分配规律,在经验的基础上提出了“三点两段统合式”减径率分配修正模型。将修正模型得到的结果与传统模型计算结果以及企业生产数据相比,发现变化趋势相近,减径率和减径量变化曲线更加光滑,应用于生产有利于金属流动。

不同热轧压下率对06Cr13/Q345R爆炸复合板微观组织和拉伸断口的影响

采用不同热轧压下率,对06Cr13/Q345R爆炸复合板进行了轧制实验。采用超景深显微镜和扫描电镜(SEM)分别对不同热轧压下率的06Cr13/Q345R爆炸+轧制复合板微观组织和拉伸断口进行了研究。结果表明:轧制后的06Cr13/Q345R爆炸复合板消除了爆炸产生的熔化区、空洞等缺陷;随着轧制压下率的增大,复合板的微观组织细化程度增加;热轧后,拉伸断口都是延性断裂,有非常明显的大量韧窝。

基于3×3高维核矩阵的终止极化码研究

针对高维核矩阵构造的极化码中为提升纠错性能而造成的复杂度增加的问题,提出了基于3×3高维核矩阵终止极化码的构造方案。首先筛选出极化率最高的核矩阵G531构造终止极化码,并在二进制擦除信道上证明了在不影响纠错性能的前提下终止极化码能够降低编译码计算复杂度,同时推导出终止极化码的复杂度降低比的上下界。仿真表明,终止极化码复杂度降低比与二进制擦除信道(binary erasure channel, BEC)的擦除概率有关,在擦除概率为0.5左右时,复杂度降低比最小,且目标误帧率(frame error rate, FER)越高,复杂度降低比越大,在目标误帧率为10;时,最高可实现71.43%的复杂度降低比。

不同碱度及含氧化镁球团矿实验研究

在实验室条件下 ,对不同碱度及不同氧化镁球团进行了试验研究。结果表明 :当碱度R≥ 1 0时 ,球团需高温焙烧才能满足生产要求 ;当碱度R <1 0时 ,其焙烧温度只需 12 5 0℃左右。对于含量MgO球团 ,随着MgO/SiO2 比值的增加 ,其焙烧温度显著提高 ,通过配加含硼矿物可降低含MgO球团的焙烧温度 ,即在 12 0 0～ 12 5 0℃之间就能满足球团生产工艺的要求。

12架微张力减径机壁厚变化数学模型的研究

在12架三辊式微张力减径机上,实测了增壁率、减径率、壁厚系数、减径温度、减径速度、张力等主要参数,分析研究了这些参数对生产典型品种无缝钢管壁厚精度的影响程度,通过计算机回归处理得出壁厚不均数学模型公式,经现场实践证明该数学模型是有效的。

Rapid degradation of dyes in water by magnetic Fe^0/Fe_3O_4/graphene composites

Magnetic Fe^0/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption–desorption, scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FT-IR）, vibrating-sample magnetometer（VSM） measurements and X-ray photoelectron spectroscopy（XPS）. The results indicated that Fe^0/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe^0/Fe3O4/graphene and pollutants. Fe^0/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe^0/Fe3O4/graphene rapidly. After 20 min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe^0/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe^0/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water.

泡沫Cu-Zn电极电催化还原硝酸盐氮

采用阴极电沉积法制备载锌泡沫铜双金属复合电极,并通过扫描电子显微镜(SEM)、能量色散光谱和X线衍射仪(XRD)对载锌泡沫铜(泡沫Cu-Zn)电极进行表征。将泡沫Cu-Zn电极作为阴极,Ir-Ru/Ti板作为阳极,在无隔膜反应器中进行废水中硝酸盐氮(NO_(3)^(-)-N)电化学还原实验,考察电流密度、溶液pH、Cl^(-)浓度对NO_(3)^(-)-N还原效果的影响,研究NO_(3)^(-)-N还原机制。结果表明:Zn纳米颗粒以不规则絮状结构成功地沉积在泡沫铜表面。对于质量浓度为700 mg/L的NO_(3)^(-)-N模拟废水,在电流密度为20 mA/cm^(2)、不调节废水pH和NaCl投加量为1.5 g/L条件下,电解6 h后,将NO_(3)^(-)-N质量浓度由初始的700 mg/L降至约4 mg/L,去除率达到99%左右,无副产物亚硝酸盐氮(NO_(2)^(-)-N)产生,最终副产物氨氮(NH_(4)^(+)-N)质量浓度约64 mg/L,N_(2)选择率约90%。

热轧酸洗板表面黑斑缺陷成因及机理研究

针对国内某钢厂生产的热轧酸洗板表面出现黑斑缺陷而严重影响后续酸洗质量的问题,对黑斑缺陷的形成原因及机理进行了研究。采用场发射扫描电镜和电子探针、X射线衍射仪、维式硬度计对黑斑缺陷的微观形貌、元素分布和相成分进行了分析,并对不同轧制工艺下残留氧化铁皮压入规律进行了研究。结果表明:黑斑缺陷部位与无缺陷部位氧化铁皮都为两层结构,但黑斑缺陷部位氧化铁皮更厚,并在交界处出现了“C”形厚度渐变趋势;黑斑内氧化层处Si元素以Fe_(2)SiO_(4)形式富集,Fe_(2)SiO_(4)对氧化铁皮产生钉扎作用导致除鳞困难,形成氧化铁皮压入缺陷,外侧更厚的Fe_(3)O_(4)层致使压入缺陷表面呈现黑色;在模拟残留氧化铁皮压入的实验中,残留氧化铁皮在粗轧和精轧温度下压入基体都会导致热轧板表面出现黑斑,随着压下率的增大,黑斑与基体结合会更紧密;黑斑缺陷表面微观形貌表现为氧化铁皮压入形式,并且表面硬度与残留氧化铁皮压入形成的黑斑表面硬度接近,都远大于基体硬度。出现黑斑缺陷的根本原因是Fe_(2)SiO_(4)引起的氧化铁皮压入,因此可以通过改进除鳞工艺以及控制Fe_(2)SiO_(4)的形成来降低黑斑缺陷的发生率。

不同掺气设施对一体化消能工负压及消能率的影响研究

为了研究阶梯溢流面前几级阶梯与前置掺气坎的不同布置,对宽尾墩+阶梯溢流面+消力池一体化消能工负压及消能率的影响,该文运用水汽两相VOF方法的三维RNGκ-ε模型,对无掺气坎的均匀阶梯、有掺气坎的均匀阶梯(原型方案)、无掺气坎的首级大台阶及有掺气坎的首级大台阶四种方案进行数值模拟,并采用原型方案的水工模型试验验证了模型计算结果的准确性。结果表明:无前置掺气坎的方案一及方案三的WES曲面及阶梯溢流面存在较大负压,无前置掺气坎条件下首级大台阶的设置能减小阶梯溢流面最大负压,但增大了WES曲面最大负压。其中方案一及方案三的WES曲面最大负压分别为-4.32 KPa和-5.03 KPa,阶梯溢流面最大负压分别为-11.1 KPa和-9.19 KPa。有前置掺气坎的方案二及方案四的WES曲面及阶梯溢流面下游不存在负压,最大负压出现在首级阶梯,分别为-9.52 KPa和-0.842 KPa。前置掺气坎与首级大台阶结合的方案四可有效提高消能率,显著减小溢流坝面负压分布范围及负压值。四种方案中,方案四消能率最大,为62.23%,比无前置掺气坎条件下均匀阶梯的方案一消能率58.52%,增大了6.34%。