宣龙式铁矿焙烧还原-磁选工艺及其影响因素

基于煤基焙烧还原-磁选工艺,进行了宣龙式难选鲕状赤铁矿石提铁过程及其影响因素的实验研究.以铁精矿品位和铁回收率为评价指标,确定了适合于该类矿石的最佳工艺条件:焙烧还原温度为1 200℃,还原剂用量为30%,焙烧还原时间为60min,焙烧产物磁选前的磨矿细度为-45μm占96.19%,磁选的磁场强度为111kA.m-1.在该工艺条件下,可以使铁精矿品位达到92.53%,铁回收率达到90.78%.     

高压辊磨机粉碎贫赤铁矿产品粒度特性

研究了贫赤铁矿经高压辊磨机开路、边料循环闭路和筛分全闭路粉碎后产品的粒度特性.试验结果表明:随着辊面压力的增加,粉碎产品粒度降低,分布更加均匀,破碎比F50/P50的增长速率高于破碎比F80/P80和F20/P20的增长速率;随着边料循环量的增加,粉碎产品的粒度降低,分布更不均匀,破碎比F80/P80的增长速率高于破碎...     

煤的挥发分对高磷鲕状赤铁矿直接还原焙烧的影响

在相同还原焙烧条件和等量添加剂下,系统研究了煤基还原剂中的挥发分对鄂西高磷鲕状赤铁矿在直接还原焙烧过程中对含铁和磷矿物的影响.通过XRD及SEM分析对煤基中挥发分的作用机理进行初步阐述.研究结果表明,煤的挥发分有利于铁回收率的提高,对降低铁产品中磷不利.经过类高温干馏的两种煤种的原煤作为还原剂时,焙烧产品新生成脉石矿物不同,并且原矿中鲕绿泥石和石英等会与含铁矿物发生复杂的化学反应,原矿中含磷矿物大部分仍以氟磷灰石形式存在,但少部分含磷矿物仍会参与还原焙烧的反应.     

高压辊磨机操作因素对粉碎产品粒度特性的影响

采用高压辊磨机破碎贫赤铁矿,分别研究了辊面速度、辊面压力、矿石含水率等操作因素对中料和边料产品粒度特性的影响.结果表明:增加辊面压力,中料和边料产品粒度变细,中料产品粒度分布更加集中,边料产品粒度分布更加均匀;提升一定的辊面速度,中料产品粒度变细,粒度分布更加集中,继续提升辊面速度,中料产品粒度特性无明显变化,辊面速度变化对边料产品粒度特性影响不明显;提高给料矿石的含水率,中料和边料产品细度变化不明显,中料产品粒度分布更加集中,边料产品粒度分布更加均匀.     

高磷鲕状赤铁矿还原焙烧及微生物脱磷试验

以湖北鄂西某高磷鲕状赤铁矿为研究对象,采用还原焙烧-弱磁选方法进行试验,并用黑曲霉对磁选后精矿进行微生物浸出脱磷研究.试验结果表明,正交实验得出各因素对精矿品位的影响顺序从大到小依次为焙烧温度、焙烧时间、还原剂比例、磨矿粒度.最佳焙烧-弱磁选条件为焙烧温度900℃、焙烧时间25 min、还原剂配比6％、磨矿粒度-0.074 mm95.08％,在此条件下获得精矿品位57.25％、回收率90.20％的较好的选别指标.黑曲霉对精矿中的磷元素具有较强的脱除能力,微生物浸出作用8d后,在较低的矿浆浓度下矿石的脱磷率为79.68％,矿石中的含磷量由0.85％降低到0.17％.该研究为微生物用于铁矿石的脱磷提供了理论依据.     

微波预处理条件对鄂西鲕状赤铁矿磨矿效率的影响

以鄂西鲕状赤铁矿为研究对象,采用不同功率与加热时间对其进行微波预处理,研究矿样在微波场中的升温特性,考察预处理前后矿样形貌、比表面积及孔隙率变化,分析所得矿样的磨矿效率、邦德磨矿功指数及过程功耗。结果表明,当微波功率为1~3kW时,矿石可在90s内被迅速加热至400℃以上,且升温速率随功率的增大而增加;经不同条件微波预处理后,赤铁矿与脉石颗粒间出现明显裂缝,矿石比表面积与孔隙率分别提升43.8%~51.9%和20.9%~40.0%;相同磨矿条件下,经功率为2kW、时间为45s处理后的矿样,-0.038mm和-0.074 mm粒级产品产率最高可提升37.2%和43.4%,邦德磨矿功指数最多可下降13.6%;微波预处理有助于降低磨矿过程功耗,当磨矿产品中-0.038 mm粒级产率为49.2%时,最大能耗降幅为21.4%。     

Effect and mechanism of siderite on reverse flotation of hematite

The effects of siderite on reverse flotation of hematite were investigated using micro flotation, adsorption tests, and Fourier transform infrared spectroscopy. The flotation results show that interactions between siderite and quartz are the main reasons that siderite significantly influences the floatability. The interactions are attributed to dissolved siderite species and fine siderite particles. The interaction due to the dissolved species is, however, dominant. Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical calculations reveal that adhesion on quartz increases when the siderite particle size decreases and that fine particles partly influence quartz floatability. Chemical solution calculations indicate that the dissolved species of siderite might convert the surface of active quartz to CaCO₃ precipitates that can be depressed by starch. The theoretical calculations are in good agreement with the results of adsorption tests and FTIR spectroscopy and explain the reasons why siderite significantly influences reverse flotation of hematite.     

高磷赤铁矿制备碳化铁的产物分离试验研究

利用高磷鲕状赤铁矿制备碳化铁,产物中含磷组分是影响碳化铁质量的关键因素。为了探究分离方式和添加剂对产物中含磷组分分离的影响,在1023K下分别用无添加、添加2%V2O5和添加5%Na2SO4的高磷鲕状赤铁矿制备碳化铁,将制得的产物球磨不同时间后采用磁选或离心+磁选的方式进行产物分离,最后分析产物中含磷组分的变化。结果表明,延长球磨时间可以提高产物的脱磷率,但球磨时间过长会降低产物的铁收得率,以球磨2h为宜;无添加剂时制备所得碳化铁试样球磨时间从1h延长至2h后,脱磷率从18.17%升至18.48%,再增加离心分离操作后,会进一步提升产物的脱磷率至23.04%;添加5%Na_2SO_4和2%V_2O_5均可破坏铁矿石的鲕状结构,有利于含Fe组分与脉石的分离,但添加Na_2SO_4会降低产物的碳化铁含量,而V_2O_5的添加则可同时促进碳化铁的生成以及提高产物的脱磷率,是一种较好的添加剂。     

Grate-kiln pelletization of Indian hematite fines and its industrial practice

Indian hematite fines normally have a high iron grade and minor impurities; they are usually used as sinter fines for feeding into a blast furnace. In this work, the grindability properties of two kinds of Indian hematite fines and the roasting behaviors and induration characteristics of pellets made from these fines were revealed through experiments involving dry ball milling and small-scale and pilot-scale tests. In addition, the microstructures of the particles of ground India hematite fines and fired pellets were investigated using optical microscopy. On the basis of the results, a grate-kiln production line with an annual output of 1.2 Mt of oxidized pellets was established in India. This pellet plant operates stably and reliably, further confirming that preparing high-quality pellets with Indian hematite fines pretreated by dry ball milling is an industrially feasible process.     

Study on the strength of cold-bonded high-phosphorus oolitic hematite-coal composite briquettes

Composite briquettes containing high-phosphorus oolitic hematite and coal were produced with a twin-roller briquette machine using sodium carboxymethyl cellulose, molasses, starch, sodium silicate, and bentonite as binders. The effect of these binders on the strength of the composite briquettes, including cold strength and high-temperature strength, was investigated by drop testing and compression testing. It was found the addition of Ca(OH)₂ and Na₂CO₃ not only improved the reduction of iron oxides and promoted dephosphorization during the reduction-separation process but also provided strength to the composite briquettes during the briquetting process; a compressive strength of 152.8 N per briquette was obtained when no binders were used. On this basis, the addition of molasses, sodium silicate, starch, and bentonite improved the cold strength of the composite briquettes, and a maximum compressive strength of 404.6 N per briquette was obtained by using starch. When subjected to a thermal treatment at 1200℃, all of the composite briquettes suffered from a sharp decrease in compressive strength during the initial reduction process. This decrease in strength was related to an increase in porosity of the composite briquettes. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the decrease in strength of the composite briquettes could be caused by four factors: decomposition of bonding materials, gasification of coal, transportation of byproduct gases in the composite briquettes, and thermal stress.