【作者】 薛天艳；

【导师】 刘长厚； 齐涛；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 博士

【摘要】 我国蕴藏丰富的钛资源达9.65亿吨（以TiO₂计）,占世界总储量的38.85%,居首位,其中90.5%分布在攀枝花-西昌地区,主要赋存在多金属钒钛磁铁矿中,是国家重大特色金属资源。因钒钛磁铁矿资源组成复杂、品位低、钙镁含量高、难选冶,钛资源综合利用率仅为14.5%。钛白粉作为白色颜料和填料已成为世界上第三大无机化工产品,仅次于合成氨和磷酸。目前,钛白粉的工业生产方法为硫酸法工艺和氯化法工艺,存在废物量大、毒性强、环境污染重等问题。本论文针对我国钛资源特色,在中科院过程工程研究所研发的亚熔盐化工冶金技术的基础上,提出了低温熔盐钛白清洁生产技术,该工艺以高钛渣为原料,以氢氧化钠熔盐为反应介质,拟从生产源头消除环境污染,实现钛资源有价组分的高效-清洁-综合利用。主要研究内容和成果如下:（1）构建了氢氧化钠熔盐-高钛渣反应新体系。通过热力学计算,对高钛渣主要组分在氢氧化钠熔盐中分解可能生成的产物进行分析;考察了反应温度、反应时间、碱渣质量比及高钛渣粒径对钛转化率的影响,结果表明,在优化的分解条件下钛转化率达到98%以上,XRD表征为单一晶相的Na₂TiO₃;宏观反应动力学研究表明,分解过程符合未反应收缩核模型,过程速度受界面化学反应控制,其表观活化能为40.84 kJ/mol。（2）熔盐反应产物Na₂TiO₃经多级逆流洗涤可再生反应介质NaOH。Na₂TiO₃中Na⁺离子可与水溶液中H⁺发生离子交换,经多级逆流洗涤可将90%Na⁺离子浸出至碱液中,碱液经净化、蒸发浓缩可实现反应介质内循环;同时杂质铬、铝、锰、硅浸出至碱液中,而杂质铁、钙、镁随钛进入固相水洗产物,实现杂质离子与钛的高效高选择性分离;得到的水洗中间产物主要组成为钛65%～70%（以TiO₂计）、钠10%～12%。（3）液固相离子交换制备偏钛酸并高效分离杂质离子。水洗产物直接在硫酸或盐酸介质中经过液固相离子交换-水解可分别制得球形及针状偏钛酸;铁、钙、镁等杂质溶解进入酸液,钛以偏钛酸的形式沉淀,过滤后实现钛与杂质离子的高效高选择性二次分离;添加还原剂可以促进杂质离子的浸出;实验结果表明,盐酸体系产品纯度优于硫酸体系。（4）系统研究了硫酸钛溶液低浓度水解制备偏钛酸过程。水洗产物在稀硫酸中酸解形成硫酸钛溶液,过滤除去未反应的高钛渣及钙、镁、硅等杂质,滤液（硫酸钛溶液）经高温液相水解制备偏钛酸。实验结果表明,在优化条件下制备的偏钛酸经洗涤、盐处理、高温煅烧后可得到球形度高、平均粒径为150nm、分布均匀的二氧化钛粒子;XRF、XRD及白度分析表明,产品中TiO₂含量为98.6%,Fe₂O₃含量为0.002%,Hunter白度W_h为97.84,金红石含量R%为97.64%,经包膜粉碎后可用作钛白粉。更多还原

【Abstract】 Tititanium reserves in China are 965 million tons（TiO₂）,accounting for 38.85%of the total in the world,ranked the first place,of which 90.5%occurs in Panzhihua-Xichang region, present as multi-component associated magnetite containing vanadium and titanium.Due to the complexity and lower grade of resource,the comprehensive utilization of titanium is only 14.5%.Titanium dioxide pigment white,used as coatings,fillers for plastic and paper,has been the third most important raw material in chemical industry,following ammonia and phosphoric acid.Industrial production methods of titanium dioxide pigments include the sulfate process and the chloride process,which discharge a large amount of toxic waste,resulting in serious environmental problems.According to the characteristic of titanium resources in China,a novel metallurgical clean process for production of titanium dioxide by decomposing titanium slag with NaOH molten salt was proposed in the present paper.The aim of this process is to eliminate the pollution at the source and to fully utilize valuable compounds in titanium slag. The main points are as follows:（1） A novel reaction system of molten NaOH and titanium slag was established.By thermodynamic calculation,the possible products of the main compositions existed in titanium slag were investigated in the decomposition process with molten NaOH.Effects of reaction temperature,time,NaOH-to-slag mass ratio and particle size on titanium fractional conversion were studied.Approximately 98%of titanium in the slag could be converted under the optimal reaction conditions,and the product was characterized to be Na₂TiO₃ by XRD. The decomposition kinetics of titanium slag with molten NaOH under optimal reaction conditions indicates that the shrinking core model with chemical reaction controlled process is most applicable for the decomposition of titanium slag,with the apparent activation energy of 40.84kJ mol^-1.（2） The recycle of NaOH reaction medium could be carried out by multi-stage countercurrent wash of molten reaction product.Approximately 90%of the Na⁺ in molten product could be leached at the optimal conditions by multi-stage countercurrent washing, and the lye obtained could be recycled by further purification and evaporation.The impurities of Cr,Al,Mn and Si were leached to the alkaline solution,while titanium and impurities of Fe、Ca、Mg remained in the solid intermediate,thus,titanium was initially separated from impurities effectively and selectively.The chemical composition of solid intermediate after wash is TiO₂ 65%～70%,Na 10%～12%.（3） Preparation of hydrous titanium oxides by ion-exchange and separation of impurities were studied.The solid intermediate with high content of titanium was transferred to spherical and needle-like hydrous titanium oxides particles by ion-exchange at boiling point in diluted H₂SO₄ and HCl solutions,respectively.The impurities of Fe,Ca and Mg were leached to the acid solution,while titanium precipitated in the form of hydrous titanium oxides and subsequently effectively separated from impurities by filtration.The leaching rate of impurities can be improved by adding reductants during ion-exchange process.Experimental results show that the purity of product obtained in HCl medium is superior to that in H₂SO₄ medium.（4） Prepartation of hydrous titanium oxides by thermal hydrolysis of titanium sulfate solution was investigated.The solid intermediate was first digested in diluted sulfuric acid, forming titanium sulfate solution,which was subsequently hydrolyzed at boiling point, yielding hydrous titanium oxides precipitate.The unreacted titanium slag and impurities such as Ca,Mg and Si can be removed by filtration from titanium sulfate solution before its thermal hydrolysis.The data of thermal hydrolysis of titanium（Ⅳ） ions show that well dispersed spherical titanium dioxide particles with average size of 150 nm can be obtained under optimal reaciton condition.The results analyzed by XRF,XRD and whiteness show that chemical composition of the product is TiO₂ 98.6%,Fe₂O₃ 0.002%with Hunter white （W_h） 97.84 and rutile content（R%） 97.64%.After further treatment of coating and crush,the product can be used as pigment.更多还原