Reduction of Norwegian and Indian ilmenite with carbon monoxide and hydrogen gas blends

Synthesis gas, produced from natural gas, can be used to minimise coal consumption and carbon dioxide emissions during the processing of ilmenite. Two different ilmenite ores have been reduced with carbon monoxide and hydrogen mixtures to investigate the effects of temperature and gas composition on the final product. Thermogravimetric analysis was used to observe the reaction progress. Experimental work revealed that between 900 and 1000?°C the hydrogen content in the gas has an equally significant effect as the temperature. Statistical analysis determined that the source of the ore did not have a significant effect on the reaction rate. Armalcolite is one of the main products of pre-reduction in addition to metallic iron and rutile from these ilmenite concentrates. There is also some indication that titanium dioxide is reduced. Optical microscope images revealed that increasing amounts of hydrogen resulted in smaller more uniformly distributed metallic iron particles.     

SLon-2500立环脉动高梯度磁选机的研制与应用

采用最新的先进技术和创新理念,研制了我国目前处理量最大的高梯度磁选机——SLon-2500立环脉动高梯度磁选机。该机具处理量大,选矿效率、设备作业率和自动化程度高,电耗低的优点,用于赤铁矿、钛铁矿的分选及石英砂的提纯,均可获得优良的技术指标。     

云南文山某细粒钛铁矿选矿试验研究

云南文山某钛铁矿原矿含TiO25.96%,以钛铁矿为主,还含有少量的金红石。原矿经磨矿分级控制入选粒度为-0.5 mm,采用水力分级后重选,水力分级粒度为0.038 mm,重选工艺流程为螺旋溜槽粗选、摇床精选,得到品位46.67%,回收率59.01%的钛精矿。该工艺流程简单,投资小、选矿成本低。     

Mechanical properties and microstructures of AlSi7 alloy cast in sand and in polystyrene-containing sand moulds

Experimental work has been undertaken to study the effects of polystyrene pattern material on the mechanical properties and microstructures of cast aluminium alloys. This paper reports results obtained using Al—Si 7% (LM25) alloy. Rectangular tensile test-pieces of various thickness were cast at different pouring temperatures into standard resin-bonded sand moulds. The experiments were then repeated with polystyrene patterns placed into the sand mould cavities. A direct comparison of the effects of polystyrene pattern material on the properties of the cast test-pieces with those obtained under identical conditions by a standard sand casting method has thus been obtained. Ultimate tensile strength, elongation, Vickers hardness, porosity volume, and dendrite arm spacing (DAS) values relating to both methods were evaluated for a range of casting section thickness (4–16 mm) and pouring temperature (690–780 °C). The microstructural differences observed between the test pieces obtained, with and without polystyrene patterns, were verified by the changes in the solidification cooling curves recorded simultaneously for both methods.

The results obtained show that an expanded polystyrene pattern contained within a sand mould, under the experimental conditions used, does not have an adverse effect on the as-cast mechanical properties of LM25 alloy. On the contrary, the presence of polystyrene in the sand moulds resulted in higher rather than lower tensile properties. These findings have been supported by microstructural observations which reveal finer microstructures and lower volumes of porosity in the test pieces produced with the use of polystyrene, rather than in the absence of it. These observations are further supported by the evidence obtained from the cooling curves which reveal that the presence of polystyrene in the sand mould results in a faster casting cooling rate compared with that when no polystyrene is present.     

Epitaxial growth of NiTiO3 with a distorted ilmenite structure

MTiO₃ (M = Fe, Mn, Ni) compounds have received recent attention as possible candidates for multiferroic materials capable of magnetization switching by application of an electric field. In an attempt to stabilize NiTiO₃ in the rhombohedral R3 structure, epitaxial Ni_1 − xTi_1 − yO₃ films of different thickness and composition were deposited on Al₂O₃(0001) by pulsed laser deposition, and characterized using several techniques. Structural parameters for ilmenite-type NiTiO₃ and the metastable LiNbO₃-type NiTiO₃ structure with the space group R3c were predicted using density functional theory calculations, and compared with the experimental results. Our structural data from X-ray diffraction and X-ray absorption spectroscopy indicate that epitaxial ilmenite-type NiTiO₃ films were grown. Furthermore, lattice strain exerted by the sapphire substrate results in a distorted ilmenite structure similar to the LiNbO₃-type one. While R3c NiTiO₃, the desired structure based on recent theory, cannot be claimed at this point, our results demonstrate the potential of oxide heteroepitaxy to stabilize metastable multiferroic phases that may be difficult to prepare or are inaccessible in the bulk.     

Effects of mechanical activation on the digestion of ilmenite in dilute H2SO4

The commercial sulfate process for pigment production uses concentrated sulfuric acid(N 85 wt% H_2SO_4) as feeding material and discharges 8–10 tons of spend dilute acid(20 wt% H_2SO_4) per ton of product. Re-using spend acid to leach ilmenite can cut the waste emission and save fresh feeding acid. However, the leaching reaction with dilute acid is very slow and the digestion efficiency is fairly low. This paper describes a wet-milling process to enhance the dilute-acid leaching of ilmenite that makes it possible to produce TiO_2 pigment in a more environmentally benign routine. The leaching kinetic study of unmilled ilmenite, dry milled 60 min ilmenite and wet milled 60 min ilmenite was conducted by revision of the shrinking core model(SCM), incorporation of particle size distribution(PSD) into SCM. The results revealed that mechano-chemical activation method significantly increased the leaching efficiency of titanium from 36% to 76% by reducing the particle size and increasing the reaction contact area. On the other hand, the milling process increased the lattice deformation and amorphization of crystalline, which lowered the activation energies in the leaching process. Compared with dry milling operation, wet milling is more effective, the particle size distribution of wet-milled ilmenite was much narrower, smaller, and more uniform. Wet milling of ilmenite makes the leaching reaction with dilute acid(60 wt% H_2 SO_4) practicable and the re-use of spend acid becomes possible and economical.     

钛铁矿摩擦静电分选研究

为探究摩擦电选分选钛铁矿的可行性,对比了钛铁矿及长石、石英、云母等脉石矿物与不同材质进行摩擦后的荷电特性。结果表明,以PVC作为摩擦介质时,钛铁矿与脉石矿物荷电的极性相反,且钛铁矿荷电量最高,荷质比可达4 nC/g。在此基础上对不同粒级矿物颗粒进行了荷电效果比较,确定物料的最佳分选粒级为0.074~0.125mm。采用实验室锯齿形摩擦电选系统对粒度为0.074~0.125 mm的钛铁矿与长石、石英、云母脉石矿物组成的混合物料进行摩擦电选试验,考察分选电压、给料速度和风量对分选结果的影响。结果表明,物料的分选效率随着分选电压、给料速度和风量的增大均呈先增大后减小的趋势,在分选电压为20 kV、给料速度为4.7 g/s、风量为80 m3/h时,钛铁矿分选指标最佳。     

哈密钛铁矿选矿与综合利用研究

采用“阶段磨矿—阶段选别”的磁选、重选、浮选、电选联合流程对哈密低品位复杂钛铁矿矿石（含钛铁矿、磁铁矿、钛磁铁矿）进行了选矿试验研究，结果表明，对于含ＴｉＯ２６３８％的原矿，可以获得含ＴｉＯ２４２７３％，Ｆｅ３４１４％的钛铁矿产品，可作为生产人造金红石的原料。对产品采用选择性沸腾氯化法生产人造金红石，在技术和经济上是可行的。     

Preparation of porous rutile titania from ilmenite by mechanical activation and subsequent sulfuric acid leaching

Synthesis of porous titania via mechanical activation of natural ilmenite and subsequent simultaneous dissolution and hydrolysis in dilute solutions of sulfuric acid was investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), N₂ adsorption/desorption measurements, energy-dispersive X-ray spectrometry (EDX) and thermogravimetric analysis (TG). This is a novel template-free approach for synthesis of microporous, mesoporous and micro–mesoporous TiO₂ materials. Effects of sulfuric acid concentration and calcination temperature on physicochemical properties of the TiO₂ materials were examined systematically. The results show that both the factors considerably affected the porosity of the materials. In a 15% acid solution a microporous TiO₂ hydrolysate with BET surface area 109.3 m²/g was prepared. With a 10% H₂SO₄, we obtained a more pure micro/mesopore TiO₂ hydrolysate with BET area of 257.6 m²/g. Calcining the hydrolysate at 500 °C led to the formation of a mesopore TiO₂. The mesoporous TiO₂ generated at 600 °C still has a BET area of 92.1 m²/g. The high thermal stability is probably related to the presence of H₂SO₄ in the channel walls of hydrolysate. The XRD analysis indicated all the TiO₂ materials prepared in this study being rutile. The mechanism for formation of the porous rutile TiO₂ is mainly via in situ hydrolysis and precipitation of the dissolved titanium on the un-reacted ilmenite surface, where H₂SO₄ may play a very important role.     

多段螺旋溜槽回收钛的试验研究

多段螺旋溜槽的选别特点是在设备内部形成贫富分选和分级分选流程。利用φ６００ｍｍ多段螺旋溜槽处理攀钢选矿厂尾矿和承德华能矿业有限公司铁选厂尾矿回收钛的试验研究表明，其精矿ＴｉＯ２品位达４６％左右，流程简单、可行。