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高铝粉煤灰低温液相法制备高白氢氧化铝的基础研究
Alternative TitleFundamental Research on Recovering Alumina from High-alumina Fly Ash to Produce High-white Aluminium
孙振华
Subtype硕士
Thesis Advisor李会泉 ; 唐清 ; 包炜军
2013-05-01
Degree Grantor中国科学院研究生院
Degree Discipline材料工程
Keyword高铝粉煤灰   低温液相法   物相转变   铝酸钠晶体   高白氢氧化铝
Abstract高铝粉煤灰是内蒙中西部、山西北部等地区的一种新型资源,其A12O3含量通常可达50%左右,相当于我国中低品位铝土矿中A12O3的含量,年排放量巨大。利用高铝粉煤灰提取氧化铝可以有效缓解我国氧化铝行业的优质资源短缺瓶颈。高白氢氧化铝作为特殊化学品氢氧化铝,附加值高,市场容量大。本文基于研究团队在亚熔盐清洁生产方面的研究积累,提出了高铝粉煤灰低温液相法制备高白氢氧化铝工艺路线,针对低碱预脱硅、高碱浸出提铝、高苛性比铝酸钠结晶、高白氢氧化铝种分分解四个主要过程,开展了深入的基础研究。取得主要成果如下: (1) 开展了高铝粉煤灰低温液相法提取氧化铝工艺过程条件优化研究。考察了高铝粉煤灰原料矿相组成,发现高铝粉煤灰主要为非晶态玻璃相包裹针状莫来石结构。采用单因素实验,考察工艺条件对稀碱预脱硅、浓碱浸出提铝过程的影响规律,研究发现浓碱浸出提铝过程氧化铝浸出率随反应温度增加、反应时间延长、碱灰比增加、以及钙硅比增大均先增加而后保持不变;在溶出温度280℃,溶出时间2h,碱灰比6:1,钙硅比1.0的优化工艺条件下,氧化铝溶出率大于85%。 (2)采用ICP-OES、XRF、XRD、FT-IR、SEM-EDS等手段,对稀碱预脱硅-浓碱浸出提铝过程的物相转变以及调控进行了深入研究。结果表明脱硅粉煤灰在浓碱溶液提取氧化铝过程中,通过添加氧化钙可以同时沉淀析出具有规则杆状或棒状形貌的NaCaHSiO4物相,以及较为细小的副产物类沸石相(1.2Na2O?0.8CaO?Al2O3?2SiO2?H2O);通过调控碱灰比、钙硅比可以控制脱铝尾灰的物相生成,碱灰比低于4或钙硅比低于0.5时,可以定向调控生成六面或八面沸石结构类沸石相;碱灰比大于6或钙硅比大于1.0时,可以定向调控生成棒状或杆状的硅酸钠钙相;碱灰比与钙硅比介于两者之间时,两种物相均有生成。 (3) 初步开展了高苛性比铝酸钠溶液结晶制备铝酸钠晶体、低苛性比铝酸钠溶液种分制备高白氢氧化铝的工艺过程研究。结果表明,温度升高、氧化钠含量降低、以及氧化硅含量升高,均不利用铝酸钠结晶过程的进行,优化条件下所得结晶产物为水合铝酸钠晶体,结晶率可达76.4%;低苛性比铝酸钠溶液种分结晶可以获得高白氢氧化铝,分解初温、分解原液苛性比对高白氢氧化铝产品的质量影响较大。
Other AbstractLarge amounts of high alumina fly ash, in which A12O3 content generally can reach 50%, equivalent to the content of A12O3 in low and medium grade bauxite, is found in the central and western Inner Mongolia and northern Shanxi regions of China. Producing alumina from high alumina fly ash can effectively relieve the stress of resource bottleneck of alumina industry in China. High white aluminum hydroxide, as a special chemical aluminum hydroxide with special performance, is considered as a high added value production with good market prospect. Based on the research on sub-molten developed by Institute of Process Engineering, Chinese Academy of Sciences, a new method and further fundamental research to produce high white aluminum hydroxide from high alumina fly ash by low temperature liquid method was carried out. The innovative results were summarized as follows: (1) The optimal conditions of low temperature liquid method to digest silica and alumina was investigated. Mineral phase researches of high alumina fly ash showed that high alumina fly ash was mainly acicular mullite coated by amorphous glass phase. The single factor experiments were carried out to figure out effects of dilute alkali pre-desilication and concentrated alkali leaching process of aluminum. The result showed that, the leaching rate of alumina increased with the prolongation of reaction time, increase of reaction temperature, alkali to ash ratio and Ca/Si(mol) were increased at first and then basically stable. The dissolution rate of alumina was greater than 85% at the optimal condition of dissolution temperature 280 ° C, the dissolution time 2h, alkali cement ratio 6:1, Ca/Si(mol) 1.0; (2) The phase transformation and regulation of desilicated and dealuminated reactions were investigated to support alumina dissolution process by ICP-OES, XRF, XRD, FT-IR, SEM-EDS. The results showed that desilicated fly ash digested in concentrated alkali solution can precipitate out rod-like or rod-like shape NaCaHSiO4 phase after adding Ca(OH)2,as well as the by-product of unnamed zeolite (1.2Na2O?0.8CaO?Al2O3?2SiO2?H2O). When the alkali to ash ratio was less than 4, or Ca/Si(mol) was less than 0.5, the dealuminated fly ash almost was unnamed zeolite phase , however , when the alkali to ash ratio was greater than 6, or Ca/Si(mol) was greater than 1.0 the dealuminated fly ash almost was NaCaHSiO4,The two phases were both generated in the other case. (3)The influential experiments factors on crystallization of sodium aluminate from high caustic ratio sodium aluminate solution,and seed precipitation of high white aluminum hydroxide from low caustic ratio sodium solution, were studied preliminarily. The result showed: the crystallization rate decreased with the increasing of elevated temperatures, reducing content of sodium oxide content and increasing content of silicon oxide, and under optimized conditions, the crystallization rate of up to 76.4%. High white aluminum hydroxide produced from low caustic sodium aluminate solution was investigated. The experiments showed that both of the decomposition original temperation and caustic ratio had a directly affect on the quality indicators of high white aluminum hydroxide products.
Pages97
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8343
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
孙振华. 高铝粉煤灰低温液相法制备高白氢氧化铝的基础研究[D]. 中国科学院研究生院,2013.
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