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钾系亚熔盐法处理钛资源的应用基础研究
刘玉民
学位类型博士
导师齐涛
2007-06-10
学位授予单位中国科学院过程工程研究所
学位授予地点过程工程研究所
学位专业化学工艺
关键词亚熔盐 钛铁矿 高钛渣 氧化钛 钛酸钾
摘要二氧化钛,俗称钛白,是一种重要的化工原料,是世界上性能最好的一种白色颜料,广泛应用于涂料﹑塑料﹑造纸等行业。硫酸法和氯化法是目前工业生产二氧化钛的两种工艺,但无论是硫酸法或氯化法,它们在生产过程中存在排废量大、废物毒性大、对环境污染重等问题。本论文针对我国钛资源特色,提出了一种生产二氧化钛的新工艺,该工艺以钛铁矿或高钛渣为原料,以无毒、无害的氢氧化钾亚熔盐为反应介质,从生产源头消除了对环境的污染,实现了钛资源有价组分的综合利用。氢氧化钾亚熔盐具有蒸气压低、沸点高、反应活性高及流动性能好等特性,为性能可控的高浓度非常规介质。 本研究作为中国科学院过程工程研究所亚熔盐化工冶金技术平台的重要组成部分,对钛铁矿和高钛渣亚熔盐分解工艺新过程进行了系统的基础研究,为工艺设计提供了理论依据。主要研究内容如下: (1)通过热力学计算对钛铁矿中主要组分在氢氧化钾亚熔盐体系中分解时的可能生成产物进行了分析。实验研究了氢氧化钾浓度为55~80 wt.%,反应温度为100~280 ℃时TiO2在氢氧化钾亚熔盐中的反应行为。结果表明:随碱浓度及反应温度的不同可生成K4Ti3O8、KTiO2(OH)及K2Ti2O5•0.5H2O三种不同的钛酸钾产物;K4Ti3O8及K2Ti2O5•0.5H2O的形貌均为片状结晶,KTiO2(OH)的形状为六方柱状,且三种钛酸钾在一定的温度煅烧后均转化为片状的二钛酸钾(K2Ti2O5)。 (2)研究了氢氧化钾亚熔盐分解钛铁矿的反应动力学,提高反应温度、碱矿质量比或者减小矿粒度均能提高钛铁矿的分解率,其中反应温度的影响尤为显著;钛铁矿在氢氧化钾亚熔盐中的分解过程符合收缩未反应核模型,受界面化学反应控制,其表观活化能为55.49 kJ/mol。 (3)对钛铁矿在氢氧化钾亚熔盐中的分解工艺条件进行了优化,实验结果表明,在优化的条件下,矿石的分解率在96%以上;添加KNO3、高温焙烧预处理及超声波预处理钛铁矿对矿石的分解率没有明显的提高。 (4)钛铁矿氢氧化钾亚熔盐反应产物(K4Ti3O8)能与溶液中H+发生离子交换反应,随溶液pH值的降低,K4Ti3O8中K+离子逐渐被交换出来,生成一系列无定形的钛酸盐中间体。一定条件下所得的钛酸盐中间体经合适的温度煅烧后可转化为TiO2或K2Ti6O13纤维。 (5)新工艺过程的研究表明,氢氧化钾亚熔盐分解钛铁矿后经稀释相分离可实现钛-碱的初步分离,液相经熬碱浓缩可实现反应介质的内循环,固相经深度脱钾、溶解、萃取、水解、煅烧后可得形状为球形,大小在1.0 μm左右,其纯度在97%以上的二氧化钛粗产品。 (6)高钛渣氢氧化钾亚熔盐分解工艺表明,当碱矿比为4.5:1,反应温度为270 ℃,反应时间为2 h,高钛渣在氢氧化钾亚熔盐中能完全分解,钛的转化率接近100%。亚熔盐反应结束后通过稀释相分离,实现了碱-钛的初步分离与富集,分离的碱通过蒸发浓缩可实现反应介质的内循环,固相经深度脱钾、溶解、水解、煅烧后可得纯度为97.8%的锐钛矿型二氧化钛,经过漂白、包膜等后处理可用于工业上广泛使用的钛白。
其他摘要Titanium dioxide, which is also named titanium white, is one of the important raw materials in the chemical industries. Titanium white is the best-performance pigment in the world and can be widely used in the industry such as coating material, plastic material and paper manufacture et al. The common manufacture methods of titanium dioxide can be summarized into sulphate route and chloride route, which discharge a large amount of toxic waste and severely pollute the environment. According to the characteristic titanium resources in China, a new process for production of titanium dioxide by decomposing ilmenite ore or titaniferous slag with nontoxic KOH sub-molten salt (SMS) was proposed in the present paper. The aim of this new process is to eliminate the pollution at the source and fully utilize the all valuable compounds in titanium resources. KOH SMS is unconventional concentrated medium with controllable properties such as low vapour pressure, high boiling point, high reaction activity and good fluidity. The present study was one of the important parts of the SMS metallurgical technology proposed by the Institute of Process Engineering, Chinese Academy of Sciences. Fundamental research have been carried out on the new process for decomposing ilmenite ore and titaniferous slag with KOH SMS , which forms a base for designing technological flow sheet. The main points are as follows: (1) By thermodynamic calculation, the possible products of the main compositions existed in ilmenite ore were investigated in the decomposing process with KOH SMS. The reaction behavior of TiO2 with KOH SMS was conducted when the KOH concentration was 55~80 wt.% and the reaction temperature was 100~280 ℃. Based on the experimental results, it could be concluded that three kinds of potassium titanates, namely K4Ti3O8、KTiO2(OH) and K2Ti2O5•0.5H2O could be synthesized under the different temperature and KOH concentration. The morphology of K4Ti3O8 and K2Ti2O5•0.5H2O synthesized under the different conditions showed plate-like style and KTiO2(OH) showed hexagonal columnar. After the calcination at appropriate temperature, the three kinds of potassium titanates above could be transformed to K2Ti2O5. (2) The decomposing kinetics of ilmenite ore with KOH SMS was studied. It was indicated that increasing the reaction temperature and KOH concentration or decreasing the particle size of the ore could improve the decomposing rate, and the effect of reaction temperature was the most significant factor. The decomposing process of ilmenite ore with KOH SMS was well interpreted with a shrinking core model under chemical reaction control. According to the Arrhenius expression, the apparent activation energy for the decomposing of ilmenite was estimated to be 55.49 kJ/mol. (3) The technical parameters of the decomposing ilmenite ore with KOH SMS were optimized. The results showed that the decomposing ratio of ilmenite ore was above 96% under the optimum conditions. The addition of KNO3、high temperature calcination and ultrasonic treatment of ilmenite showed no obvious effect on the decomposing ratio of ilmenite. (4) The potassium titanate K4Ti3O8, which was the products of the reaction between ilmenite and KOH SMS, could exchange its K+ with H+ in the solution. With the decrease of pH value, the K+ existed in K4Ti3O8 could be gradually exchanged by H+ and a series of amorphous phase intermediates were obtained. Furthermore, titanium dioxide and K2Ti6O13 fibers could be obtained by calcining the intermediates at suitable temperature. (5) The study of the new technology process showed that the preliminary separation of Ti-KOH could be fulfilled by dilution after the decomposing ilmenite ore with KOH SMS. Excessive KOH solution could be recycled to the ore decomposition process after concentration by vaporization. After the high-degree removal of potassium, dissolution, extraction, hydrolysis and calcination of the solid, the raw product was obtained and the content of titanium dioxide was above 97%. The particle size of the product was about 1.0 μm and its morphology exhibited spherical. (6) The decomposing technology of titaniferous slag showed that the titaniferous slag could be decomposed completely in KOH SMS and the titanium conversion was almost 100% when the reaction conditions are: the alkali-to-ore 4.5:1, the reaction temperature 270 ℃ and the reaction time 2 h. The preliminary separation and concentration of Ti-KOH could be fulfilled by dilution after the SMS reaction. Excessive KOH solution could be recycled to the ore decomposition process after concentration by vaporization. After the high-degree removal of potassium, dissolution, hydrolysis and calcination of the solid, the raw product was obtained and the content of titanium dioxide was 97.8%. After the treatment of blanching and integument, the obtained product could be widely used in the industry as white titanium.
页数125
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/1108
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刘玉民. 钾系亚熔盐法处理钛资源的应用基础研究[D]. 过程工程研究所. 中国科学院过程工程研究所,2007.
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