二次精还原工艺对铁粉化学成分的影响

研究了二次精还原温度、时间、生粉料层厚度等工艺因素对铁粉化学成分的影响，提出了工业生产高品位铁粉的合理工艺制度。

用黄崖洞高纯铁精矿制取还原铁粉

以对山西黎城黄崖洞铁矿石进行选矿试验获得的高纯铁精矿为原料,采用固体碳粗还原—氢气精还原常规工艺进行制取还原铁粉的试验研究,结果表明,选取产自黎城附近的无烟煤和产自黎城境内的石灰作还原剂和脱硫剂,在还原剂用量为铁精矿量的1.5倍、脱硫剂用量为还原剂量的14%、还原温度为1200℃、还原时间为3.5h、料罐出炉温度为400℃的条件下进行粗还原,粗还原铁粉在温度为850℃、时间为2.5h的条件下进行H2还原,可制得化学成分(除酸不溶物外)和工艺性能与瑞典霍格纳斯名牌NC100.24铁粉及国标一级FHY100.25铁粉相近的较优质还原铁粉。

三氯化铁浸出-重铬酸钾滴定法测定钛精粉还原产物中的金属铁

试样用三氯化铁溶液溶解,金属铁被氧化为二氯化铁,过滤分离,滤液酸化后以二苯铵磺酸钠为指示剂,用重铬酸钾标准溶液滴定,实现了钛精粉还原产物中金属铁含量的测定。结果表明,试样粒度在0.125mm以下时,FeCl3溶液浓度和用量分别为10g/L和100mL,采用电磁搅拌60min为最佳的实验条件。分别用HgCl2分析法、矿相法对方法正确度进行检测,其中F检验和t检验判定此法与HgCl2法无显著性差异,同时,浸出前后试样的X射线衍射图谱对照和金相照片对比进一步证明滤渣中没有金属铁相,铁浸出完全。方法用于测定钛精粉还原产物样品,结果的相对标准偏差小于2%。

高效液相色谱法测定还原固精丸中马钱苷的含量

目的建立还原固精丸中马钱苷的含量测定方法。方法采用Welch Materials XB-C18色谱柱(250 mm×4.6 mm,5μm),四氢呋喃-乙腈-甲醇-0.05%磷酸溶液(1∶6∶4∶89)为流动相,检测波长236 nm。结果马钱苷在0.040 52～4.052μg范围内与峰面积呈良好线性关系(r=1.000 0),平均加样回收率为101.04%,RSD为1.60%(n=9)。结论该法操作简便,结果准确,重复性好,可用于还原固经丸的质量控制。

精氨酸——还原糖体系中1,2-二羰基化合物的形成和抑制研究

建立精氨酸—还原糖体系,考察影响该体系中1,2-二羰基化合物形成的因素,并探究形成过程中反应物与产物变化的动力学以及抑制剂染料木黄酮抑制1,2-二羰基化合物的动力学。对建立的精氨酸—还原糖模拟体系,采用气相色谱法评价温度、还原糖种类、pH和抑制剂染料木黄酮等各种因素对1,2-二羰基化合物形成的影响,并分析其变化规律,进而分析了反应体系中染料木黄酮介入前后反应物精氨酸、葡萄糖及产物1,2-二羰基化合物的含量变化规律。结果显示:影响1,2-二羰基化合物形成的最主要因素是时间;该体系中精氨酸和葡萄糖的浓度随着反应时间的延长而降低,且随着温度升高快速下降;1,2-二羰基化合物含量随着温度的升高和反应时间的延长而不断升高。时间和温度对丙酮醛(MGO)和乙二醛(GO)的产生有一定的影响,染料木黄酮通过降低反应体系中1,2-二羰基化合物的反应速率常数而抑制其产生。当染料木黄酮的添加量为50mmol/L时,对1,2-二羰基化合物的抑制率最高,均>50%。LC-MS证实染料木黄酮在氨基酸体系中抑制1,2-二羰基化合物的机制是通过捕获MGO形成染料木黄酮-MGO加合产物,从而达到消除效果。

铁精矿粉粒度对精控还原工艺的影响

本文以河北承德地区的铁精矿粉为原料,选用模拟隧道窑还原工艺制备海绵铁粉,研究了铁精矿粉粒度对精控还原工艺的影响。结果表明：铁精矿粉粒度对其还原工艺影响很大,并直接影响海绵铁粉的产品性能。在既定试验条件下,随着铁精矿粉粒度的增大,其精控还原所需最优还原温度随着增加,最佳配碳量先减少后增大,而最佳还原时间随粒度的增大呈现出先增大后减小的变化趋势。究其原因为粒度过小导致的粉体烧结和粒度过大导致的粉体芯部不易还原均会阻碍还原过程的进行。45~75μm粒度区间铁精矿粉最适合作为制备优质海绵铁粉原料,其在配碳量0.8、还原温度1150℃、还原时间4.5 h的精控还原工艺下可制得的海绵铁粉的铁含量高达97.88%。

影响精氨酸-还原糖模拟体系荧光性晚期糖基化终末产物形成的因素

目的:通过建立精氨酸-还原糖模拟体系,考察影响该体系荧光性晚期糖基化终末产物(advanced glycation end products,AGEs)形成的因素。方法:对建立的精氨酸-还原糖模拟体系,采用荧光光谱法(λ_(ex)/λ_(em)=370 nm/440 nm)检测反应温度、还原糖浓度、pH值、金属离子和抑制剂染料木黄酮对AGEs形成的影响;并分析各个影响因素的作用效果。结果:在单个影响因素:反应温度(121℃)、还原糖及其浓度(3mmol/L的核糖)、pH值(9.2)和金属离子(Fe^(3+))作用下,产生荧光性AGEs作用效果最强,9 mmol/L抑制剂染料木黄酮对荧光性AGEs的形成有抑制作用。结论:反应时间、反应温度、还原糖种类及其浓度、pH值、金属离子和抑制剂染料木黄酮均对精氨酸-还原糖模拟体系荧光性AGEs的形成有影响,在该模拟体系中,反应时间是影响荧光性AGEs产生最主要的因素,其次为还原糖的种类。

高温还原对水雾化铁粉压缩性的影响

以莱钢集团粉末冶金有限公司LAP100.29水雾化铁粉为原料,在900℃下进行高温氢气还原,研究高温还原处理对水雾化铁粉的显微硬度、化学成分、松装密度、流动性、压缩性等性质的影响,以期对实际生产起到一定的借鉴和指导作用。结果表明:经900℃高温氢气还原处理后的铁粉纯度提高,大部分样品的流动性提高约2 s/50 g,松装密度提高0.1 g/cm3左右,压制密度提高0.1 g/cm3以上,而粉末显微硬度大幅降低至69～89 HV。在600 MPa下铁粉压制密度大部分达到7.15 g/cm3以上。

三个对“氧化应激”的重新认识

生命离不开氧,细胞的氧化还原状态直接调控蛋白质等生物大分子功能,介导细胞信号转导以及衰老、神经退行性疾病、代谢病、肿瘤等许多生理和病理过程。鉴于20世纪50年代提出的自由基衰老学说,长期以来氧化应激常与氧化损伤混为一谈,“抗氧化”一度成为“抗衰老”的代名词。本文结合本实验室相关研究工作及领域前沿,提出三个对“氧化应激”的重新认识:第一,氧化应激不等于氧化损伤,具有重要生理功能;第二,氧化应激不是“万金油”,氧化还原调控具有特异性,氧化还原修饰是其作用机制;第三,不能泛泛抗氧化,氧化还原平衡具有精准属性,抗氧化要考虑5R(Right species,Right place,Right time,Right level,Right target)原则,精准氧化还原医药时代已开启。未来挑战体现在氧化还原生物学与医学基础研究、氧化应激在生理和病理过程及环境胁迫中的特异分子机制研究及精准氧化还原干预三大方面,需要多学科交叉、基础与临床研究深度合作、国际协同攻关,实现对生命过程氧化还原认识的突破、机理的突破、精准干预的突破!

Effect of milling time on carbothermic reduction of ilmenite

A systematic investigation on the effect of milling time on carbothermic reduction of ilmenite was carried out by a combination of thermal analysis, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and particle size analysis. It was shown that the graphite crystalline structure was easily destroyed along the（002） crystal plane during milling process. The particle size of ilmenite/graphite mixture was largely decreased and a fully mixed composite structure was obtained after milling for 4 h at high milling intensity. Milling exerts positive effect on the decreasing temperatures of ilmenite reduction and gradual deoxidizing of titanium oxides was completed.

Modified carbothermal reduction method for synthesis of LiFePO_4/C composite

With LiAc-2H2O as Li precursor,pure olivine phase LiFePO4/C was synthesized at a relatively low temperature（650 ℃） and short sintering period（4 h） by molten salt carbothermal reduction method.Scanning electron micrograph shows that particle size of the product is about 1μm,smaller than that of the sample synthesized with Li2CO3 as Li precursor.Electrochemical measurements prove that LiFePO4/C obtained from LiAc-2H2O shows high capacity.The initial discharge capacities are 148 mA-h/g at 0.5C rate and 115 mA-h/g at 5C rate,respectively.After 50 cycles,the capacity retention ratios are 93% and 89% at 0.5C rate and 5C rate,respectively.

Effects of mechanical activation and oxidation-reduction on hydrochloric acid leaching of Panxi ilmenite concentration

The effects of oxidation-reduction treatment and mechanical activation on the hydrochloric acid leaching performance of Panxi ilmenite concentration were investigated.The results show that both of oxidation-reduction treatment and mechanical activation significantly accelerate the extraction of Fe,Ca and Mg from Panxi ilmenite concentration;however,the CaO and MgO contents of the calcined residues obtained from oxidized-reduced ilmenite concentration are higher than the standard values required by chlorination process.The Ca and Mg in oxidized-reduced ilmenite concentration can be leached much faster after mechanical activation,yielding a synthetic rutile which meets the requirements of chlorination process containing 90.50% TiO2 and 1.37% total iron as well as combined CaO and MgO of 1.00%.The optimum oxidation and reduction conditions are as follows：oxidization at 900 ℃ in the presence of oxygen for 15 min and reduction at 750 ℃ by hydrogen for 30 min.

Behaviors of vanadium and chromium in coal-based direct reduction of high-chromium vanadium-bearing titanomagnetite concentrates followed by magnetic separation

The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.

Preparation of V-Ti-Fe master alloys by metallothermic reduction method

V-Ti-Fe master alloys were prepared by metaUothermic reduction method, and the influences of the mass ratio of V205 to TiO2, Al and Al-Mg alloy addition amounts on the metal recovery rates and alloy compositions were investigated. The results show that appropriate technological parameters are： the mass ratio of V205 to TiO2 is 0.5：1, Al addition represents 95% of the theoretical value, and the Al-Mg alloy addition amount is one third that of the Al addition. The results from energy spectrum analysis show that V and Fe distribute uniformly in the prepared alloy, while the segregation for Ti, i.e. Ti-rich phase is detected. A spray refming process was carried out to reduce the impurity contents of Al and O in the prepared alloys. The Al content drops from 4.27% to 1.86%, and the O content drops from 2.10% to 0.91% after the refining process.

精准氧化还原调控

生命离不开氧,氧化还原应激是细胞信号转导的重要调控方式,介导衰老、神经退行性疾病、代谢病、肿瘤等许多生理和病理过程。氧化还原平衡调控是促进生命健康的重要方面。本文分析了抗氧化剂研发和应用中长期面临的挑战和背后的三方面主要原因:对氧化还原应激的生理功能认识不足;抗氧化过度,引起还原应激;抗氧化策略缺乏特异性和精准性。作者提出细胞和机体具有精准氧化还原属性,抗氧化等氧化还原干预策略要考虑五个合适,即:合适的干预分子、时间、空间、水平、靶点,简称“5R”原则(right species、right time、right place、right level、right target)。精准氧化还原调控是未来发展方向,精准氧化还原医药研发正在开启。

Efficient enrichment of nickel and iron in laterite nickel ore by deep reduction and magnetic separation

The process of deep reduction and magnetic separation was proposed to enrich nickel and iron from laterite nickel ores.Results show that nickel-iron concentrates with nickel grade of 6.96%,nickel recovery of 94.06%,iron grade of 34.74%,and iron recovery of 80.44% could be obtained after magnetic separation under the conditions of reduction temperature of 1275℃,reduction time of 50 min,slag basicity of 1.0,carbon-containing coefficient of 2.5,and magnetic field strength of 72 kA/m.Reduction temperature and time affected the possibility of deep reduction and reaction progress.Slag basicity affected the composition of slag in burden and the spilling and enriching rate of nickel-iron from a matrix to form nickel-iron particles.Nickel-iron particles were generated,aggregated,and grew gradually in the reduction process.Nickel-iron particles can be effectively separated from gangue minerals by magnetic separation.

Direct carbothermic reduction of ilmenite concentrates by adding high dosage of Na_(2)CO_(3) in microwave field

A clean and efficient route for the utilization of ilmenite concentrates was proposed by direct carbothermic reduction in microwave field.High dosage of Na_(2)CO_(3),which can be recycled,was added to accelerate the reduction reaction of ilmenite concentrates.After microwave heating in the temperature range of 1073−1123 K for 20 min,the main products were Na_(2)TiO_(3) and metallic Fe with the metallization ratios being as high as 92.67%−93.21%.The reduction products were processed by water leaching,ball-milling in CO2 atmosphere and magnetic separation in turn.The final products after magnetic separation were Fe-rich materials and Ti-rich materials(90.04 wt.%TiO2),which can be used to produce iron and TiCl4 or TiO2.The optimized heating temperature was 1123 K in terms of metallization ratios,magnetic separation and caking property of the reduction products.Besides,the reduction mechanism of ilmenite concentrates with the addition of Na_(2)CO_(3) in microwave field was also proposed.