【作者】 吴志颖；

【导师】 涂赣峰； 吴文远；

【作者基本信息】 东北大学 ， 有色金属冶金， 2008， 博士

【摘要】 含氟稀土精矿主要包括单一氟碳铈矿和氟碳铈矿与独居石共生的混合稀土精矿,是稀土工业中重要的原料。在对含氟稀土精矿的处理中,焙烧分解是普遍采用的主要工艺。焙烧过程中氟的逸出不仅对环境造成了严重的污染,而且浪费了很多有价资源。因此,研究含氟稀土精矿焙烧过程中氟的行为规律,包括氟的走向、存在状态、逸出条件和反应过程等,这对实现氟的控制和有效回收处理,形成针对不同矿物的全新的清洁生产工艺提供理论依据。论文主要分为四个部分：第一部分研究了含氟稀土矿物焙烧逸出气体中氟的测定方法。通过对现有方法的对比与分析,提出了通过碱液吸收—衍生气化—气相色谱分析方法,此方法具有方便、快捷地测量含氟稀土矿物焙烧逸出气体中的含氟量的特点。当吸收气体流量控制在3L·min-1,NaOH溶液的浓度为0.001mol·L-1时,吸收效率达96.1%；衍生气相色谱分析的相对标准偏差为1.43%,加标回收率在96.9%-103.3%之间,RSD为2.75%,具有较高的精密度和准确度。第二部分研究了氟碳铈矿焙烧过程中氟的行为规律。采用气相色谱法分别测定了氟碳铈矿在干燥空气、60%相对湿度空气和饱和水蒸汽不同气氛下焙烧过程气相中的氟含量,结果表明氟碳铈矿中的氟逸出的基本条件是焙烧气氛中水份的存在,并随着焙烧温度的升高,空气湿度的增加,焙烧时间的延长气相中的氟含量大量增加；在通入饱和水蒸汽、焙烧温度1000℃、焙烧时间120min的条件下,氟的逸出率可达到98.362%,焙烧尾气中的氟可以用0.001mol·L-1的NaOH溶液完全吸收,以方便吸收利用。第三部分研究了CaO-NaCl和CaO-NaCl-CaCl2焙烧氟碳铈矿过程中氟的行为规律。研究发现在氟碳铈矿焙烧过程中,CaO具有明显的固氟作用,氟在焙烧产物中以REOF和CaF2的形态存在,气相中的氟以HF的形式逸出；NaCl或NaCl-CaCl2没有参加氟碳铈矿的分解反应,但可使CaO与分解产物REOF的反应温度降低近50℃和100℃,增强了抑制气相氟逸出的能力。在60%空气相对湿度下,700℃焙烧120min时的固氟率为82.42%。第四部分研究了CaO-NaCl或CaO-NaCl-CaCl2体系焙烧混合稀土精矿过程中氟的行为规律。其结果表明：混合稀土精焙烧过程中,CaO具有抑制氟逸出和分解独居石的双重作用,CaO和分解产物CaF2共同作用分解REPO4的能力高于单独添加CaO,焙烧产物中氟主要以Ca5F(PO4)3的形态存在。添加NaCl或NaCl-CaCl2均可使CaO的固氟率达到92%以上,以NaCl-CaCl2为助剂时,CaO分解独居石的反应温度和表观活化能更低,在700℃、120min条件下,混合稀土精矿的分解率大于90%。动力学研究结果表明,添加NaCl或NaCl-CaCl2均使CaO分解混合稀土精矿的化学反应表观活化能降低,促使产物中独居石分解,其中NaCl-CaCl2更加明显。更多还原

【Abstract】 Rare earth concentrate with fluorine is major material in rare earth industry, including single bastnaesite and mixed rare earth concentrate with bastnaesite and monazite.Roasting is the major technology in the treating process of rare earth concentrate with fluorine.Escaping fluorine in roasting course not only seriously polluted the environment but also made the valuable resource wasted.For this reason, the behaviors of fluorine in roasting course of rare earth concentrate with fluorine was studied, including its trending, existing state, escaping condition and reacting process. It provided theory foundation for controlling fluorine and effectually recovery processing, building a new clean manufacturing technology directing at different rare earth mineral.The paper consists of four parts.In the first part, measuring method of fluorine in the gas from rare earth concentrate with fluorine was studied. By comparing and analyzing the current approaches, the method of using Lye absorption, derivative gasification and gas chromatography analysis was convenient and fast. When the absorption of gas flow was controlled in 3Lmin-1 and the concentration of NaOH was 0.001molL-1,the absorption efficiency was up to 96.1%, the relative standard deviation of the derivative gas chromatography analysis was 1.43% and the recoveries of standard were in range of 96.9%-103.3% and RSD was 2.75%.This method had higher precision and accuracy.In the second part, behavior rule of fluorine in roasting process of bastnaesite was investigated. Fluorine in the gas during roasting process of bastnaesite was determined by gas chromatography under the different conditions such as in dry air,60% relative humidity and saturated water vapor. The results showed that the basic condition for fluorine escaping was the presence of water vapor in the roasting atmosphere. With the increasing of roasting temperature, time and air humidity, the content of fluorine in gas was also increasing at a large amount. Under the conditions of saturated water vapor, roasting temperature at 1000℃and time for 120min, escaping ratio of fluorine was up to 98.362%, which can be completely absorbed in 0.001molL·-1 NaOH solution.In the third part, behavior rule of fluorine was studied during the bastnaesite was roasted in the system of CaO-NaCl and CaO-NaCl-CaCl2. During the bastnaesite roasting process, calcium oxide had an obvious function on fixation of fluorine; the fluorine existed in the form of REOF and CaF2 in the roasting products and in the form of HF in gas.Adding NaCl or NaCl-CaCl2 could not affect the bastnaesite decomposition, but could reduce the reaction temperature of CaO and the decomposition product REOF by nearly 50℃and 100℃,at the same time could restrain the fluorine escaping. When the relative humidity was 60% and bastnaesite roasted at 700℃for 120min, the fluorine fixation ratio was 82.42%.In the last part, behavior rule of fluorine was studied during the mixed rare earth concentrate roasting process in the system of CaO-NaCl and CaO-NaCl-CaCl2. During the roasting process of the mixed rare earth concentrate CaO could not only restrain the fluorine escaping but also decompose the monazite. CaO together with CaF2 could decompose REPO4 better than a single CaO, fluorine mainly existed in the form of Ca5F(PO4)3.Adding NaCl or NaCl-CaCl2 could make the fluorine fixation ratio of CaO reach above 92%.By using NaCl-CaCl2 as auxiliary agent, the reaction temperature and the apparent activation energy were lower when monazite was decomposed at 700℃and for 120 min.,the decomposition ratio of the mixed rare earth concentrate was more than 90%.The results of dynamics showed that the chemical reactions apparent activation energy reduced by adding NaCl and NaCl-CaCl2, it advanced the decomposition of monazite, and NaCl-CaCl2 was more obvious.更多还原