改性淀粉抑制赤铁矿反浮选石英的作用机理研究

通过矿物浮选试验、动电位测定以及吸附量测试,考察了4种淀粉抑制剂对赤铁矿和石英浮选性能的影响,并探讨了其作用机理。在碱性条件下,改性淀粉抑制剂对赤铁矿抑制效果明显,且以改性玉米淀粉效果最佳,改性磷酸酯淀粉、改性羧甲基淀粉的抑制效果次之,而普通淀粉抑制作用一般。同时4种淀粉抑制剂对主要脉石矿物石英的抑制效果均不明显。pH=10~12.5条件下,改性玉米淀粉因其羟基氧和裸露在赤铁矿表面的铁元素发生了化学键合,因而选择性抑制能力最佳。分子动力学模拟表明,改性玉米淀粉片段与赤铁矿作用更为紧密,验证了改性淀粉能更好地抑制赤铁矿。     

高磷鲕状赤铁矿金属化还原焙烧-磁选-熔分新工艺研究

针对高磷鲕状赤铁矿中有价组元铁与杂质元素磷、硅、铝的分离难题,提出了低温选择性金属化还原—磁选—熔分处理新工艺,添加复合促进剂强化还原并促进金属铁微粒迁移、聚集、长大。研究了焙烧温度、促进剂用量、煤量、焙烧时间等条件对焙砂磨矿磁选后精矿铁品位、铁回收率及脱杂效果的影响。结果表明,添加剂对铁的富集及脱杂影响显著。优化的焙烧工艺条件下,原矿加入6%促进剂、25%的煤,975℃下恒温焙烧150 min,焙砂中铁主要以单质铁呈棒条状、蠕虫状产出,利于磨矿解离;磷仍主要以磷灰石存在;焙砂经磨矿—磁选,可获得含Fe 86.77%、P0.20%、Al_2O_3 1.81%、SiO_2 3.86%的精矿类海绵铁粉,Fe回收率88%;类海绵铁粉在1 550℃下熔分,可以得到含磷小于0.01%、含铁大于99%的优质铁水,全流程Fe回收率85%,杂质磷、硅、铝脱除率99%,实现了铁的高效回收和铁与磷、硅、铝组元的深度分离。     

Synthetic fayalite Fe2SiO4 by kinetically controlled reaction between hematite and silicon carbide

The present work explores the preparation of fayalite α-Fe₂SiO₄, the iron-rich end-member of the olivine solid-solution series, as a tar removal catalyst for biomass gasification. The synthetic procedure was developed starting from the stoichiometric mixture of hematite and micrometer size silicon carbide and employing thermal treatments in controlled atmospheres at 1000-1100°C supported by thermodynamic modeling to assess the required redox conditions. The treatments in dry and humidified inert gas yielded phase mixtures containing metallic Fe as one of the main phases, thus emphasizing a shortage of oxygen supply. XRD and TGA studies of precursor mixtures on heating in dry CO₂ demonstrated a multistep mechanism of the overall reaction including (a) fast reactivity between silicon carbide and hematite at ~920°C with formation of metallic Fe and amorphous silica followed by (b) formation of fayalite involving oxygen supplied in the form of CO₂ and competing with (c) over-oxidation to thermodynamically favorable Fe₃O₄+SiO₂ mixture. Comparative studies of reactivity in powdered and pelletized samples emphasized the importance of the kinetic factor in the formation of Fe₂SiO₄ while preventing further oxidation. The preferential formation of fayalite in the CO₂ atmosphere is shown to be favored by shorter treatments of compacted samples at higher temperatures. The procedure was designed (2-step heating to 1100°C in CO₂ followed by fast cooling) for the preparation of pelletized fayalite α-Fe₂SiO₄ catalyst with only minor traces of surface over-oxidation which can be suppressed by adding 10 vol.% of forming gas to CO₂ flow.     

油酸钠体系下细粒赤铁矿精矿过滤影响因素研究

油酸钠浮选的细粒赤铁矿精矿存在过滤困难问题，为找到解决问题的办法，以巴西某细粒赤铁矿精矿（-75 μm占96.90%）为研究对象，考察了油酸钠用量、矿浆pH、矿浆温度以及淀粉用量等对赤铁矿精矿过滤效果的影响。结果表明：①油酸钠用量对细粒赤铁矿精矿的过滤有显著影响，随着油酸钠用量的增加，赤铁矿精矿滤饼比阻增大。②矿浆pH对赤铁矿精矿滤饼比阻的影响较大，强酸性条件能减弱甚至消除油酸钠对赤铁矿精矿过滤的阻碍作用，近中性环境下赤铁矿精矿滤饼比阻变化不大，强碱性条件下赤铁矿精矿的过滤效果变差。③矿浆温度对赤铁矿精矿滤饼比阻的影响较小，随着温度的升高滤饼比阻减小。④添加少量的淀粉可促进赤铁矿精矿的过滤，过量的淀粉会增大赤铁矿精矿滤饼比阻。     

Electrochemical reduction of CO2: Two- or three-electrode configuration

Electrocatalytical conversion of CO₂ into various chemicals like hydrocarbons and CO is regarded as a promising approach to mitigate carbon emission and, meanwhile, to provide sustainable energy and value-added chemicals. Two different reactors are used in this work. One is based upon the two-electrode configuration powered by a DC power supply or Si solar cell, which is suitable for practical applications. Another is three-electrode one powered by a potentiostat, which is feasible to study the electrode performance. Polycrystalline Cu electrode is used as the cathode, and hematite is the anode. Performance of CO₂ reduction using the two- and three-electrode configurations is studied by measuring electrode potential, cell voltage, current density, Faradaic efficiency, and reduction selectivity of CO₂. Cu cathode used here exhibits a low overpotential for CO₂ reduction, specifically for the cell with two-electrode configuration. No obvious difference can be observed between the two types of configurations at a low bias like −0.3 and −0.4 V; while the reactor with two-electrode configuration exhibits better performance at a high bias like −0.8 V than the one with three-electrode configuration. Thus, the reactors with two-electrode configuration are desirable for practical applications, specifically considering solar cells can be used as the power source to provide green and sustainable energy.     

非洲某特大型铁矿工艺矿物学研究

非洲某特大型铁矿高品位赤褐铁矿矿石铁品位为52.73%,铁主要以赤铁矿、褐铁矿的形式存在,铁在赤褐铁矿中的分布率为90.06%。矿石主要有用矿物为赤褐铁矿,脉石矿物主要为黏土、石英、辉石、水铝氧石。为了给选矿工艺流程的确定提供依据,对高品位赤褐铁矿的矿石进行了工艺矿物学研究。矿石构造主要为块状构造和层状构造,矿石结构主要为斑状结构、粒状结构、针状结构、脉状结构、包含结构。赤铁矿、褐铁矿和含铁黏土工艺嵌布粒度分布较细,在-0.07 mm分布率分别为79.26%、62.93%和58.42%。褐铁矿颗粒中常包裹一些细粒脉石矿物,包体粒径30μm的颗粒占到70%,这部分褐铁矿与脉石关系紧密,不利于褐铁矿的单体解离。通过对高品位赤褐铁矿矿石的工艺矿物学研究可知,样品属于较难选矿石。采用物理选矿方法,回收率应在75%～80%之间,精矿品位很难超过64%。     

油酸钠作捕收剂时变性淀粉对赤铁矿、石英可浮性的影响

以油酸钠为捕收剂,以木薯原淀粉、取代度为0.026和0.21的羧甲基淀粉、取代度为0.0065和0.055的磷酸酯淀粉作为抑制剂,考察了赤铁矿和石英的可浮性。重点研究了变性淀粉基团取代度对其抑制性能的影响。浮选试验结果表明,原淀粉与变性淀粉对赤铁矿的抑制作用规律一致,提高变性淀粉的取代度可增强其对赤铁矿的抑制能力;对于Ca~(2+)活化的石英,在较低的Ca~(2+)用量时,原淀粉和变性淀粉均没有明显的抑制作用,但是随着Ca~(2+)用量的增加,变性淀粉表现出一定的抑制作用、且取代度越高越显著。这种抑制作用与油酸钠、Ca~(2+)及变性淀粉三者的用量有关。Ca~(2+)以Ca(OH)+的形式吸附于石英表面,油酸钠或变性淀粉再与Ca(OH)+作用,如果油酸钠用量较大,全部Ca(OH)+优先与油酸钠作用,则石英被捕收;如果油酸钠用量相对较小,变性淀粉与剩余的Ca(OH)+作用,则对石英产生抑制作用。控制Ca~(2+)和油酸钠的用量在最佳范围,增加变性淀粉的取代度可提高其在赤铁矿脱硅反浮选中的抑制性能。     

一种超细粒嵌布铁矿石的选矿研究与评价

青海某地含少量氧化矿的磁铁矿，矿物组成简单、有用矿物嵌布极细，属于难选矿石。采用阶段性磨矿、阶段性弱磁选及反浮选工艺后，磨矿细度-500目达到95％以上，铁精矿TFe61．11％，回收率为45．98％，产率为24．74％。     

我国难选铁矿石的研究现状及利用途径

介绍了我国在难选红铁矿方面所作的研究，并且重点介绍了国内外难选鲕状赤铁矿的研究现状以及在红铁矿选矿方面进步较快的鞍山式赤铁矿的研究现状，并对鲕状赤铁矿选矿研究提出了对其利用的新途径--直接冶炼并用其渣制造微晶玻璃。     

氟硅酸铵在赤铁矿与含铁硅酸盐浮选分离中的选择性抑制作用

研究了油酸钠为捕收剂的赤铁矿浮选中，水玻璃与氟化物等抑制剂对含铁硅酸盐脉石矿物霓石（NaFe2SiO6）的浮选抑制行为。单矿物浮选试验结果表明，以氟硅酸铵对霓石的抑制效果最好，在pH=4～5的弱酸性条件下具有最佳的选择性。人工混合矿浮选分离试验结果表明，油酸钠（NaOL）与十二烷基磺酸钠（SDS）组合使用分选效果更佳。通过对矿物表面ξ电位与油酸钠吸附量的测定以及红外光谱分析，初步讨论了氟硅酸铵对霓石选择性抑制作用的机理。