高硫铝土矿氧化钙焙烧脱硫研究

针对一水硬铝石高硫型铝土矿,以河南矿石为原料,在马弗炉进行焙烧除硫的研究,重点研究了氧化钙在焙烧过程中的作用,并通过对焙烧矿进行X射线衍射来进行理论上的探讨,在此基础上,在熔盐炉中对焙烧矿和原矿进行高压溶出试验,研究溶出液中S2-含量的变化以及焙烧过程对溶出性能的影响。研究结果表明:矿石经焙烧后,硫化物型硫含量降低,加CaO焙烧效果更好;同时CaO起到固硫的作用而降低焙烧过程散于空气中的SO2的含量,原矿在600℃,45min条件下焙烧时,硫化物型硫含量S1%为0.10%,散于空气中的硫含量S3%为0.51%,而加了1%的CaO后,则S1%下降为0.07%,S3%下降为0.31%;焙烧过程中黄铁矿发生反应生成了赤铁矿Fe2O3。原矿经焙烧后进行溶出能显著降低溶出液中S2-的含量,改善矿石的溶出性能。最佳的焙烧温度为600℃,用1%CaO焙烧矿进行溶出,此时相对溶出率为95.35%,二价硫离子含量为0.16 g/L。     

Progress in flotation de-silica

1　INTRODUCTIONBayer sprocessisatypicalmethodtoproducea luminumoxidefrombauxite .Forthediasporic baux ite ,theBayer sprocesscaneconomicallyproducealu minumoxideonlywhenthemassratioofAl2 O3toSiO2 >10 .However ,inChina ,thealuminumoxidewasmainlyproducedbyusing“sinteringprocess”or“in parallelBayer sinteringcombination process”technologiesbecausethediasporic bauxiteischarac terizedbyhighcontentofaluminumoxideandsilicabutlowAl2 O3/SiO2 (average 5 6 ) .Thesetwotech nologieshavetheproble…     

Intensifying digestion of diaspore and separation of alumina and silica

1　INTRODUCTIONDespitetheabundantdepositofbauxitesinChi na ,ofthosepredominantisthediasporictypewithhighalumina ,highsilicaandlowferricoxides .Thebauxitedeposit,withthemassratioofaluminatosil ica(A/S)between 4and 8,accountsfor 80 %ofallthebauxitedeposit.Thenatureofhighsilicacontentdeterminesthatthemainlyadoptedtechniquetopro ducealuminainChinashouldbeBayer sinteringcom binationprocessorevenpuresinteringprocess .Althoughadramaticadvancementinaluminaproductionhasbeenachievedandthetechnolo…     

Effect of hydroxamic acid starch on reverse flotation desilicate from diasporic bauxite

It is important to depress diaspore effectively in order to remove silicates from diasporic bauxite.A new water soluble polymer hydroxamic acid starch(HA-starch)was prepared.The effects of the product on the diaspore and kaolinite flotation were investigated and its reactive mechanism was studied by zeta potential measurement and FTIR.The results show that HA-starch can depress diaspore while make positive effect on kaolinite flotation at low pH value(pH below 6)The flotation recovery of diaspore was sharply decreased with the increase of concentration of HA-starch.The chemical adsorption of HA-starch on the surface of diaspore was revealed.     

中国拜耳法氧化铝生产技术的发展方向

应用一水硬铝石型铝生产溶出动力学及一水硬铝石型铝土矿中硅钛矿物的反应行为规律对现有的间接加强化溶出技术进行了技术上的剖析。认为现有的单流法溶出技术用于处理我国的一水硬铝石型铝土矿,都表现有某些方面的不足。我国自行开发成功的高温双流水溶出技术实现一水硬铝石矿间接加热强化溶出的适宜选择。     

Efficient separation of alumina and silica in reduction-roasted kaolin by alkali leaching

Alkali leaching was employed to investigate the separation of alumina and silica in roasted kaolin obtained by roasting kaolin alone in air at 1273 K for 60 min and in clinker prepared by roasting the mixed raw meal of kaolin, ferric oxide and coal powder with Fe₂O₃/Al₂O₃/C molar ratio of 1.2:2.0:1.2 in reducing atmosphere at 1373 K for 60 min. The thermodynamic analyses and alkali leaching results show that the composition of the Al?Si spinel in roasted kaolin is close to that of 3Al₂O₃·2SiO₂ and the spinel is dissolved with increasing leaching time, resulting in difficulty in deeply separating alumina and silica in kaolin by the traditional roasting?leaching process. On the contrary, the efficient separation of alumina and silica in kaolin can be reached by fully converting kaolinite into insoluble hercynite and soluble free silica, namely quartz solid solution and cristobalite solid solution, during reduction roasting, followed by alkali leaching of the obtained clinker. Furthermore, experimental results from treating high-silica diasporic bauxite indicate that the reduction roasting?alkali leaching process is potential to separate silica and alumina in aluminosilicates.     

Technology and mechanism of desilication from roasted diasporic bauxite in atmosphere

The leaching desilication technology of roasted diasporic bauxite in atmosphere by caustic soda solution was investigated. The optimum parameters were: the grinding fineness of the roasted bauxite -0. 076 mm and 80 % -85 %,leaching time 2h, Na2Ok100-150g/L, L/S 4-5, leaching temperature 90-95℃. The desilication rate 55.20% and concentrate A/S (mass ratio of A12O3 to SiO2) 9.90, as good as those obtained at pressure, were obtained respectivdy.Investigation of two-stage leaching shows that it can both improve desilication rate of roasted ore and reduce leaching time.When time of the first stage and the second stage is 30 min and 30 min respectively, desilication rate can reach 59.65 %.X-ray diffraction analysis of the concentrate has proved that desilication procedure is accompanied with the formation of sodium aluminosilicate hydrate. X-ray spectra also show that silica removed during leaching is amorphous silica. SiO2 occurrina as ouartz in raw ore or mullite formed during roasting can not dissolve in alkali solution.     

铝土矿反浮选体系分散与凝聚理论

在铝土矿反浮选脱硅过程中,矿浆悬浮液的分散和凝聚状态对微细粒－水硬铝石的回收和精矿铝硅比有显著影响。要使各种硅酸盐矿物混合物达到有效的选择性分离,首先必需使矿浆悬浮液处于最佳分散状态,避免各种矿物细粒间的相互混杂和矿泥罩盖。针对高硅铝土矿反浮选脱硅过程,根据经典DLVO理论,从颗粒间的相互作用分析了微细粒－水硬铝石在各种含硅脉石矿物表面的粘附情况。结果表明：一水硬铝石与含硅脉石矿物颗粒间的范德化相互作用总是吸引;而它们间的静电相互作用在弱碱性条件下时为排斥,在弱酸性条件下时为吸引,一水硬铝石的夹带上浮较为严重,不利于铝土矿的反浮选。     

Correlation between spraying conditions and microcrack density and their influence on thermal cycling life of thermal barrier coatings

It is generally known that the porosity of thermal barrier coatings is essential to guarantee a sufficiently high strain tolerance of the coating during thermal cycling. However, much less is known about the influence of the specific morphology of porosity, such as microcracks and typically larger pores, on the performance of the coatings. Both features are usually formed during plasma spraying of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs). In this investigation, the influence of microcracks on the thermal cycling behavior was studied. The amount of microcracks within YSZ thermal barrier coatings was changed by changing the powder-feeding rate. Only small changes of the total porosity were observed. Mercury porosimetry served as a tool to investigate both the amount of microcracks and pores in the coating. Additionally, microcrack densities were determined from metallographical investigations. A linear dependence between the amount of fine pores determined by Hg porosimetry and the crack density was obtained for one set of coatings. Thermal cycling TBC specimens with different microcrack densities were produced and tested in a gas burner test facility. At high surface temperatures (above 1300 °C), failure occurred in the ceramic close to the surface. Under these conditions, the samples with increased horizontal microcrack densities showed a significant increase of thermal cycling life.     

高温下金与石英的相互作用及其对浸金过程的影响

金在高温下可能与石英及硅酸盐类矿物相互作用,导致焙烧后矿石中金回收难度增大。于不同温度(600℃~750℃)和时间(1~4 h)条件下对石英-硫化矿-金粉混合物进行焙烧,考察焙烧渣中金的氰化浸出率。结果表明,高温会活化石英并与金相互作用,导致焙烧渣中的金难以被氰化物浸出。第一性原理计算表明,金原子在石英(101)表面的吸附能为-300.01 kJ/mol,Au-1与石英表面的Si-12距离为0.2264 nm,石英表面Si-12的电子转换到Au-1原子上,布居值和键长数据显示金原子与石英(101)表面的硅原子存在键合作用,印证了焙烧试验结果。     

Production of TiO_2 from CaTiO_3 by alkaline roasting method

CaTiO3 was decomposed by alkaline roasting method for the production of TiO2.The process included alkaline roasting, water leaching and acid leaching steps.In the alkaline roasting step, the factors such as roasting temperature and NaOH/CaTiO3 molar ratio were investigated and 99.5% TiO2 could be extracted from CaTiO3.In addition, it is believed that only ion-exchange between Ca2+ and Na+ takes place, while the structure of TiO 32-in CaTiO3 was not destroyed during the roasting process.In the acid leaching step, Ca(OH)2 could be completely leached at pH = 6-7 and Na2TiO3 was completely hydrolyzed simultaneously.The crystal structure of the leached sample seemed to be affected by pH and sequent calcination temperature.Finally, a flowsheet was proposed for the extraction of TiO2 from perovskite.     

Preparation of Ti-rich material from titanium slag by activation roasting followed by acid leaching

A method of activation roasting followed by acid leaching using titanium slag was introduced to prepare Ti-rich material. The effects of H₃PO₄ dosage, roasting temperature, and roasting time on TiO₂ grade were investigated. A Ti-rich material containing 88.54% TiO₂, 0.42% (CaO+MgO) was obtained when finely ground titanium slag was roasted with 7.5% H₃PO₄ at 1000 °C for 2 h, followed by a two-stage leaching in boiling dilute sulfuric acid for 2 h. The XRD patterns show that the product is titanium dioxide with a rutile structure. Mechanism studies show that structures of anosovite solid solution and silicate minerals are destroyed in the roasting process. As a result, titanium components in titanium slag are transformed into TiO₂ (rutile) while impurities are transformed into acid-soluble phosphate and quartz.     

Leaching of vanadium from stone coal with sulfuric acid

The effects of roasting, mass ratio of H2SO4 to stone coal, leaching temperature, liquid-to-solid ratio, grinding fineness of stone coal, and two-stage counter-current leaching on the vanadium leaching ratio were studied. The results show that the vanadium leaching ratio of roasted stone coal through two-stage counter-current leaching can reach 65.1% at the mass ratio of H2SO4 to stone coal of 20%, leaching temperature for the production of vanadium from stone coal.     

Fractal model for evaluating heat transfer of high temperature porous corundum shell in vacuum investment casting

The thin shell used in investment casting is a kind ofsemi-continuous porous stuff that consists of solid framewith fluid in the hole. Its thermal conductivity can directlyaffect the solidification of metal and thus affect the qualityof castings. Many people studied thermal conductivity andderived different models, in which only the pore size butnot the spatial structure of the pores were being taken careof [1]. Difference between these models is that the poresmay be considered as continuous o…     

锌浸渣还原焙烧-磁选回收铁

在查明锌浸渣工艺矿物学的基础上,采用还原焙烧将铁酸锌分解为氧化锌和磁性氧化铁,再通过磁选的方法回收铁,达到锌、铁分离的目的。实验考查了焙烧温度、焙烧时间、还原剂用量对铁酸锌分解率、铁回收率和铁品位的影响。结果表明:在焙烧温度为950℃、焙烧时间为1 h及还原剂添加量为10%和5%的条件下,铁酸锌分解率达到72.05%,铁回收率可达到91.79%,精矿中铁的品位为50%左右。焙烧及磁选过程中颗粒的团聚包裹是铁精矿品位不高的主要原因。     

Roasting metallic sulphides in a fluid column

The development of a new metallurgical roasting device is described. It consists of a refractory column into which air is injected at various levels, forming several superimposed fluidized beds with no supporting grates. When pelleted zinc sulphide concentrates are charged, the roasted product needs no further sintering before reduction to metal.     

Application of suspension magnetization roasting as technology for high-efficiency separation of valuable iron minerals from high-iron bauxite

A technology for suspension magnetization roasting?magnetic separation was proposed to separate iron minerals for recovery. The optimum parameters were as follows: a roasting temperature of 650 °C, a roasting time of 20 min, a CO concentration of 20%, and particles with a size less than 37 μm accounting for 67.14% of the roasted product. The total iron content and iron recovery of the magnetic concentrate were 56.71% and 90.50%, respectively. The phase transformation, magnetic transition, and microstructure evolution were systematically characterized through iron chemical phase analysis, X-ray diffraction, vibrating sample magnetometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results demonstrated the transformation of hematite to magnetite, with the iron content in magnetite increasing from 0.41% in the raw ore to 91.47% in the roasted product.     

变性淀粉在铝硅矿物浮选分离中的作用机理

通过浮选实验、动电位和红外光谱测定,详细考察了变性淀粉在铝硅矿物浮选分离中的作用效果和机理。浮选实验显示：非离子淀粉和阴离子淀粉在pH＜6时,抑制一水硬铝石的浮选,但当pH＞6时,却对一水硬铝石浮选有活化作用;阳离子淀粉在较宽pH值范围内对一水硬铝石均有抑制作用;3种淀粉化合物在pH＜6时均活化高岭石的浮选,当pH＞6时活化作用较微。结果表明：变性淀粉是一水硬铝石型铝土矿反浮选中实现一水硬铝石和高岭石分离的有效调整剂,阴离子淀粉使矿物表面ζ电位更负,阳离子淀粉使矿物质表面ζ电位更正,非离子淀粉使矿物表面电位绝对值减小。由实验结果结合药剂与矿物作用前后的红外光谱分析,得出结论：非离子淀粉主要通过氢键作用吸附于矿物表面,而静电力和化学键合力在阴离子淀粉和阳离子淀粉吸附中发挥着重要作用。     

低品位赤铁矿的磁化焙烧—磁选工艺研究

采用自行设计的非标管式气氛炉对低品位赤铁矿在中低温下进行预还原,然后在弱磁场下进行磁选.实验结果表明,在还原温度为800℃、还原粒度小于100 μm、还原时间30 min、磁选粒度为30 μm、磁选强度为150 mT时,经过二次磁选可获得品位61.13％、回收率76.28％的铁精矿.     

Reaction mechanism of roasting Zn2SiO4 using NaOH

The reaction kinetics of roasting zinc silicate using NaOH was investigated. The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows: molar ratio of NaOH to Zn₂SiO₄ of 16:1, reaction temperature of 550 °C, and reaction time of 2.5 h. In order to ascertain the phases transformation and reaction processes of zinc oxide and silica, the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures. The final phases of the specimen roasted at 600 °C were Na₂ZnO₂, Na₄SiO₄, Na₂ZnSiO₄ and NaOH. The reaction kinetic equation of roasting was determined by the shrinking unreacted core model. Aiming to investigate the reaction mechanism, two control models of reaction rate were applied: chemical reaction at the particle surface and diffusion through the product layer. The results indicated that the diffusion through the product layer model described the reaction process well. The apparent activation energy of the roasting was 19.77 kJ/mol.