亚熔盐法氧化铝清洁生产的过程节能与分离流程优化
文献类型：学位论文
| 作者 | 陈利斌 |
| 学位类别 | 硕士 |
| 答辩日期 | 2010-05-25 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 张懿 ; 张亦飞 |
| 关键词 | NaOH亚熔盐 氧化铝生产 溶出 脱硅 脱钠 |
| 其他题名 | Process energy saving and optimization on separation technology in cleaner alumina production by sub-molten salt process |
| 学位专业 | 化学工艺 |
| 中文摘要 | 我国用于生产氧化铝的铝土矿多为中低品位难溶的一水硬铝石型，无法直接用传统经济的拜耳法生产，为此中国科学院过程工程研究所提出了NaOH亚熔盐法氧化铝清洁生产新工艺，以实现资源高效利用、过程节能环保的氧化铝工业可持续发展的总体目标。针对新工艺的溶出与拜耳法种分系统高效衔接的要求，本论文开展了过程用能优化、铝酸钠粗液脱硅和赤泥常压脱碱的研究，主要进展如下： (1) 研究了溶出过程预热级数与新蒸汽用量、换热面积及各费用的关系，建立了以年总费用最小为目标、预热级数（n）为决策变量的优化计算模型。通过实例分析表明，当n由5增加至16，新蒸汽用量减少了20.4%，总换热面积增加了近29.0%，当n = 12时，溶出车间年操作和设备折旧维修的总费用最小，可认为是给定参数条件下的最经济级数。通过敏感性分析显示，新蒸汽单价对优化结果影响显著，其变化±50%会引起年总费用变化±22%以上，且随着新蒸汽单价从-50%变化至+50%，最经济级数从8变成了14。 (2) 对亚熔盐法氧化铝生产的溶出工序进行了物料和热量衡算。结果表明，对于Al2O3含量为57%、铝硅比为4.2的铝土矿，生产1 t氧化铝产品，需矿1.83 t，循环母液3.74 m3；当溶出温度为190℃时，采用8级自蒸发，可得预热终温为154.1℃，新蒸汽（250℃）用量约0.9 t，溶出赤泥近1 t，所得指标优于拜耳法。 (3) 采用有效能分析方法，对亚熔盐法氧化铝生产的溶出过程进行了研究，确定了能量利用的薄弱环节，提出了适当提高原矿浆进口温度、充分利用排出的二次蒸汽和冷凝水以减少有效能损失的途径，从而达到工程上进一步节能的目的。 (4) 研究了亚熔盐法氧化铝生产所得铝酸钠粗液的脱硅。实验表明，在相同条件下，以拜耳法赤泥作为晶种时的脱硅效果要好于以亚熔盐法溶出赤泥作为晶种时的效果，且随着反应时间的延长，精液硅量指数（A/S）均提高。Al2O3浓度为140 g/L，分子比为1.4的铝酸钠粗液加入100 g/L的拜耳法赤泥，在104℃常压反应6 h，其精液硅量指数可由44提高到300以上，满足了种分的要求。 (5) 系统考察了CaO用量、初始溶液Na2O浓度、反应温度及反应时间对亚熔盐法氧化铝生产所得赤泥常压脱碱效果的影响。在液固比为6、钙泥比为0.22、初始溶液Na2O浓度为60 g/L、反应温度95℃及反应时间10 h的条件下，亚熔盐法所得赤泥的Na2O含量可由12.47%减少至1.41%，钠硅比降到0.07，符合赤泥外排的要求，碱耗远低于拜耳法及烧结法。原赤泥中Na8Al6Si6O24(OH)2(H2O)2和部分NaCaHSiO4在稀碱溶液中被分解成了更稳定的硅酸钙相，终赤泥中的钠主要以残留的NaCaHSiO4的形式存在。 关键词：NaOH亚熔盐，氧化铝生产，溶出，有效能分析，脱硅，脱碱 |
| 英文摘要 | The diasporic bauxites for producing alumina in China are characterized as low grade and tough to leach, thus they can not be economically treated by Bayer process. Therefore, a new green process for extracting alumina from the bauxites by NaOH sub-molten salt was proposed by the Institute of Process Engineering, Chinese Academy of Sciences, with the aim to efficient use of resources and energy to achieve the sustainable development of alumina industry. In order to lower production cost and improve the new technology, this research was focused on energy optimization of digestion unit, desilication of sodium aluminate liquor and dealkalization of red mud. The main results are as follows: (1) Established a mathematical model for analyzing the total annual cost (TAC) of the digestion unit based on the preheating stage (n) as decision variable. The practical example indicated that when n increased from 5 to 16, the live steam consumptions decreased by 20.4%, however, the total heat transfer areas increased about 29.0%; while n=12, the TAC is minimum, which might be considered as the economical preheating stage (nopt) under the given conditions. Through sensitivity analysis, it was found that the live steam price significantly affected the result, which changed ±50% would cause the changes in TAC over ±22% and made nopt shift from 8 to 14. (2) The material and heat balances of the digestion process in alumina production by sub-molten salt method were carried out. The results showed that 1 ton alumina could be produced from 1.83 t diasporic bauxites with Al2O3 content of 57% and A/S of 4.2, and approximately 1 t red mud were generated; when the leaching temperature was 190℃, the live steam (250℃) calculated was 0.9 t, which was less than that of Bayer process. (3) Through exergy analysis, the weak links in energy utilization of the digestion unit from sub-molten salt process were identified, and increasing inlet slurry temperature as well as full using of exhaust steam and condensate was proposed to reduce exergy loss. (4) The desilication of the sodium aluminate liquor from sub-molten salt process was studied. Using red mud from Bayer process as seed was better than that from sub-molten salt process under the same conditions. The mass ratio of Al2O3 to SiO2 (A/S) in the solution after desilication increased from 44 to over 300 under the conditions of initial Al2O3 140 g/L, molar ratio of Na2O to Al2O3 (MR or αk) 1.40, seed addition (red mud from Bayer process) 100 g/L, temperature 104℃ and reaction time 6 h. The desilicated aluminate solution quite met the requirement of seed crystallization of Al(OH)3. (5) The content of Na2O and the mass ratio of Na2O to SiO2 (N/S) in the red mud from sub-molten salt process could be decreased to 1.41% and 0.07, respectively, when dealkalizing in 60 g/L Na2O solution with CaO-to-red mud mass ratio of 0.22 at 95℃ for 10 h. Na8Al6Si6O24(OH)2(H2O)2 and some of NaCaHSiO4 in the red mud changed to the new phase of calcium silicate after reaction, and the sodium in the residue existed as unreacted NaCaHSiO4. Key words: NaOH sub-molten salt, Alumina production, Digestion, Exergy analysis, Desilication, Dealkalization |
| 语种 | 中文 |
| 公开日期 | 2013-09-22 |
| 页码 | 80 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1613]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 陈利斌. 亚熔盐法氧化铝清洁生产的过程节能与分离流程优化[D]. 中国科学院研究生院. 2010. |
入库方式： OAI收割
来源：过程工程研究所
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