Knowledge Management System Of Institute of process engineering,CAS
|Thesis Advisor||段东平 ; 周娥|
|Place of Conferral||北京|
|Keyword||Carbonization Process 碳酸锂 Dry Milling 碳化反应 Pressurized Carbonization 干磨 加压碳化 Lithium Carbonate|
锂产品日益重要的战略地位逐渐推进盐湖提锂技术的蓬勃发展。碳酸锂是盐湖提锂工艺可直接制备的主要锂盐产品，更是目前锂电池行业的基础原材料。从盐湖中的锂资源制备成碳酸锂产品主要通过除杂富集过程和碳化沉锂过程，其中除杂富集过程是近年来的研究热点，且已经形成成熟的生产工艺，而碳化沉锂过程则生产工艺单一且研究少。本文从盐湖提锂工艺中的碳化沉锂过程出发，研究工业碳化沉锂过程中各关键因素对产率、颗粒形貌和杂质含量的影响规律。之后为优化工业碳化沉锂过程的不足，提出两类新的反应体系即球磨干磨体系和加压反应体系，并考察主要因素在两种体系下的碳化过程产率、产品形貌和杂质含量的影响。本论文研究内容包括三部分：（1）模拟工业碳化沉锂过程，分析对比正向加料和反向加料两种加料方式下反应物摩尔比、氯化锂浓度、温度以及加料速率对碳化过程的影响。实验结果为温度对碳化反应产率、碳酸锂产品形貌和杂质含量影响最大。在低温下制备的碳酸锂产品微观形貌趋近于片状交错聚集体，在高温下则趋近于棒状穿插聚集体，两类碳酸锂颗粒均易携带杂质，前者杂质含量更高。在优化条件下，两种加料方式制备碳酸锂的产率分别为78.43%和78.46%，洗涤后碳酸锂产品中Na+含量仅为0.130%和0.167%，优于工业级碳酸锂标准。因此，工业碳化过程的不足表现为碳化反应产率低小于80%，初制产物需多次洗涤才能达到工业级碳酸锂标准，但残留杂质含量仍较高，难以达到电池级碳酸锂标准。（2）球磨干磨法制备碳酸锂新工艺研究。实验确定碳酸钠和氯化锂机械化学反应的优化条件为：反应物摩尔比为1 : 2，反应时间为15 min，球磨转速为600 rpm，球样比为5 : 1，通过XRD分析反应直接产物，其转化率近100%。经一次水洗除杂得到碳酸锂产品，其颗粒微观形貌主要为块状和无定形小颗粒团聚体，杂质Na+含量低于0.1%，最小为0.076%，优于工业碳化过程制备的碳酸锂产品。该碳化方法尤其适宜在我国西北干旱缺水地区实现产业化。（3）加压釜中加压碳化制备碳酸锂的过程研究。在优化条件下，通入CO2加压条件下碳酸锂产率可达92.79%，通入N2加压条件下碳酸锂产率可达92.13%，两者产率远高于工业碳化过程。两种气体加压条件下制备的碳酸锂颗粒经洗涤后均呈棒状和无定型小颗粒聚集体，洗涤后碳酸锂产品中Na+含量最低为0.114%和0.128%，优于工业碳化沉锂过程制备的碳酸锂产品。同时为避免钠杂质带入，以碳酸铵作为碳化剂与氯化锂溶液在加压釜中进行碳化沉锂反应，但是碳酸锂产率极低，低于40%。以上研究为碳化沉锂过程的工艺优化及新工艺开发提供了可靠的数据支持，对盐湖锂资源的高效提取利用具有一定的参考意义。
Increasingly important strategic position of lithium products gradually led to the rapid development of salt lake lithium technology. Lithium carbonate as a salt lithium can be directly prepared from lithium salt using salt lake lithium technology, also is the basic raw materials of newly developing lithium battery industry. Lithium resources in the salt lake convert into lithium carbonate products mainly by impurity removal and carbonization reaction. The first step as research hotspot applied in industry frequently, and carbonization process according little research and simple industrial application need more investigated. In this paper, the effects of various factors on the conversion, crystal morphology and impurity content in the industrial carbonization process were studied. Then, according to the shortcomings of the process of industrial carbonization process, two new systems as ball milling and autoclave pressurized reaction systems were proposed, and the effects of the main factors on the conversion, crystal morphology and impurity content of the carbonation process were investigated.There are mainly three sections in this dissertation.(1) The effects of the molar ratio of reactants, the concentration of lithium chloride, the temperature and the rate of feeding on the carbonization process in the process of regular and reverse feeding were investigated. The experimental results show that the reaction temperature has the greatest effect on the conversion, crystal morphology and impurity content of target Li2CO3 products. The microstructure of the target Li2CO3 products prepared at low temperature is close to the flaky intercalation aggregates, and it tend to reach the rod-like interspersed aggregates at high temperature. The two kinds of target Li2CO3 particles are both easy to carry impurities and the former impurity content is higher. The conversion under regular and reverse feeding ways were 78.43% and 78.46% under the optimized conditions. And the Na+ content of the target Li2CO3 product was only 0.130% and 0.167%, which was better than that of the industrial grade lithium carbonate. The shortcomings of industrial carbonization process are low conversion and high impurity content of several-times washed products.(2) A technique for preparing Li2CO3 was developed through dry milling mechanochemical process instead of industrial carbonization process. The XRD patterns of primary Li2CO3 powders indicate that mechanochemical reaction of both Na2CO3 and LiCl can be completed in 15 min under the optimal conditions at rotation speed as 600 rpm, ball–to–sample mass ratio as 5/1, and molar ratio of Na2CO3 to LiCl as 1/2. The after one-time washing products of Li2CO3 contain impurity of Na+ less than 0.1% with the minimum values as 0.076% which is better than that of industrial carbonization reaction. Two shapes of massive particles and smaller grains less than 1 μm in nano scale can be observed in the target products of Li2CO3 powders. The developed technique for preparing Li2CO3 products can be applied in insufficient water areas such as northwestern China especially in Qinghai–Tibet plateau.(3) The carbonation process of sodium carbonate and lithium chloride solution under the pressure of CO2 and N2 in the autoclave was investigated. Under the optimal reaction conditions, the conversion ware 92.79% with CO2 pressurization and 92.13% with N2 pressurization, and the conversion were much higher than that of industrial carbonation. The microstructure of target Li2CO3 products under both gas pressurized were accumulation of rod-like particles and amorphous small particles. And the contents of Na+ in the Li2CO3 products were 0.114% and 0.128%. In order to avoid the introduction of Na+ impurities, using ammonium carbonate as a carbonation agent in the autoclave react with lithium chloride. The reaction conversion is very low and the highest is only 36.38%. So it’s not suitable for industrial application.The above research provides reliable data support for the process optimization and new process development of the carbonization process, which has certain reference significance for the efficient extraction and utilization of salt resources.
|陈宁. 盐湖卤水碳化沉锂的过程研究及工艺优化[D]. 北京. 中国科学院研究生院,2017.|
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