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摘要:
四川甲基卡、李家沟等地锂辉石储量丰富,为下游锂电池储能材料等领域提供了重要的原料来源。传统锂辉石制碳酸锂工艺中,采用氢氧化钠中和法除去铁、铝等杂质,但是副产硫酸钠附加值低,导致生产成本较高,本论文研究了以氨气替代强氧化钠中和法除杂制碳酸锂工艺,发现在精制锂溶液沉淀结晶过程中存在LiNH4SO4复盐产生,影响了锂的收率和碳酸锂产品品质。为解决此问题,本论文采用等温溶解平衡法研究了三元体系Li+,NH4+ //SO42--H2O在298 K下的稳定相平衡关系,测定了平衡液相中各组分溶解度、密度和折光率数据,并绘制了该体系的相图、密度-组成图和折光率-组成图。结果表明该三元体系为复杂三元体系,有复盐LiNH4SO4形成;其稳定相图由3个固相结晶区,3条单变量曲线和2个共饱点组成,3个结晶区分别为(NH4)2SO4,Li2SO4·H2O和LiNH4SO4,且LiNH4SO4复盐的结晶区较大。研究结果表明,为了避免LiNH4SO4复盐的产生,需在锂辉石制工业级碳酸锂工艺前端通过钙离子沉淀法将锂溶液中锂硫比[Li2SO4·H2O/(NH4)2SO4]降到1.6以下,研究结果为四川锂辉石湿法冶金工艺中采用氨中和除杂提供了理论指导。
Abstract:Sichuan Jiajika, Lijiagou and other places have rich spodumene reserves, it provides an important source of raw materials for downstream lithium battery energy storage materials and other fields.In the traditional spodumene production process of lithium carbonate, sodium hydroxide neutralization method is used to remove impurities such as iron and aluminum. However, the added value of by-product sodium sulfate is low, resulting in high production costs. This paper studies the process of replacing strong sodium oxide with ammonia gas to neutralize impurities to prepare lithium carbonate, it was found that LiNH4SO4 double salt was produced during the precipitation and crystallization process of refined lithium solution, which affected the yield of lithium and the quality of lithium carbonate products.In order to solve the problem, the stable phase equilibrium relationship of the ternary system Li+, NH4+//SO42--H2O at 298 K was studied by the isothermal dissolved equilibrium method. The solubility, density and refractive index data of each component of the equilibrium liquid phase were measured, and the phase diagram, density-composition diagram and refractive index composition diagram of the system were drawn. The results show that this system is a complex ternary system, with the formation of LiNH4SO4 double salt; its stable phase diagram consists of 3 solid phase crystallization regions, 3 univariate curves, 2 invariant points, 3 crystallization regions corresponding to (NH4)2SO4, Li2SO4·H2O and LiNH4SO4, And double salt LiNH4SO4 crystallization area is the largest.The research results show that in order to avoid the production of LiNH4SO4 double salt, It is necessary to reduce the lithium-sulfur ratio (w(Li2SO4)·H2O/w(NH4)2SO4) in the lithium solution to less than 1 through the calcium ion precipitation method at the front end of the spodumene-made industrial-grade lithium carbonate process, the research results provide theoretical guidance for the use of ammonia neutralization and impurity removal in the Sichuan spodumene hydrometallurgical process.
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表 1 实验试剂
Table 1. Experimental reagents
序号 名称 规格 厂家 1 一水硫酸锂 AR250 g 成都科隆化学品有限公司 2 硫酸铵 AR500 g 成都金山化学试剂有限公司 3 氯化钡 AR500 g 成都金山化学试剂有限公司 4 茜素红 AR 25 g 成都科隆化学品有限公司 5 硫酸钠 UG500 g 成都科隆化学品有限公司 表 2 实验仪器
Table 2. laboratory apparatus
序号 设备 型号 厂家 1 电子分析天平 FA1204N型 JINGHAI公司 2 恒温振荡器 HZ-9613Y 金坛市杰瑞尔电器有限公司 3 恒温磁力水浴锅 DF-101S 上海兴创科学仪器设备有限公司 4 原子吸收光谱仪 赛默飞iCE3300 赛默飞世尔科技有限公司 5 超纯水机 CD-UPT-Ⅱ-20L型 成都超越科技有限责任公司 6 阿贝斯折光仪 WYA型 仪电物光有限公司 7 X-ray射线衍射仪 Ultima-Ⅳ型 日本理学 表 3 三元体系Li+, NH4+//SO42--H2O在298 K下溶解度、密度、折光率测定值
Table 3. Expem values of solubility, density and refractive index of ternary system Li+, NH4+ //SO42--H2O at 298 K
序号 密度/(g·cm-3) 折光率/ nD 液相组成/% 固相组成/% 平衡固相 w(Li2SO4) w((NH4)2SO4) w(Li2SO4) w((NH4)2SO4) 1, A 1.2471 1.3981 0.00 43.22 0.00 73.51 NS 2 1.2620 1.4001 3.75 39.85 1.60 70.00 NS 3 1.2660 1.4003 5.04 40.34 1.75 74.03 NS 4, C 1.2815 1.4013 7.12 39.11 33.93 51.01 NS+LNS 5 1.2714 1.3994 8.65 34.94 29.67 46.53 LNS 6 1.2604 1.3959 10.03 31.70 32.47 46.24 LNS 7 1.2571 1.3927 11.64 28.45 37.55 48.73 LNS 8 1.2545 1.3904 15.31 20.83 26.74 35.35 LNS 9 1.2538 1.3884 17.24 18.97 38.40 45.06 LNS 10 1.2584 1.3888 20.84 14.39 32.66 34.34 LNS 11, D 1.2624 1.3872 22.02 13.17 34.79 34.70 LNS+LS 12 1.2620 1.3880 23.53 11.92 54.28 6.16 LS 13 1.2457 1.3823 24.80 5.92 56.02 2.89 LS 14 1.2256 1.3785 25.82 2.81 58.30 2.35 LS 15, B 1.2175 1.3748 26.53 0.00 60.53 0.00 LS 注:NS—(NH4)2SO4;LS—Li2SO4·H2O;LNS—LiNH4SO4。 -
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