Knowledge Management System Of Institute of process engineering,CAS
|Thesis Advisor||张懿, 周建军|
我国铝土矿资源储量丰富，每年资源消耗量也十分巨大。随着我国铝土矿需求量日益增长，且国内高品位铝土矿资源日趋枯竭，通过预脱硅手段提高低品位矿铝硅比，使之可用于拜耳法生产，将是解决铝土矿重大战略需求的关键所在。本文针对河南某典型低品位一水硬铝石型铝土矿(A/S = 2-3)难以直接利用的问题，采用焙烧-碱浸的方法进行预脱硅，有效地提升了矿物铝硅比，处理后的铝土矿A/S最高可达7.55。此外，由于脱硅液中碱浓度较高、成分较复杂，导致硅资源化利用困难。针对这一问题，本文采用种子诱导和循环碱液诱导两种方法，均成功地制备出了一类粒度分布较为集中的硅酸钙，可用于造纸填料。除硅后的碱液可进入预脱硅工序重复循环使用，进而实现了整个工艺流程的绿色与可持续循环。本论文主要研究内容与成果如下： （1）针对品位极低的铝土矿(A/S = 2.26)，通过焙烧-碱浸法，在1000 °C下焙烧1 h后，在95 °C 下200 g/L氢氧化钠溶液（以Na2O计）中浸出40 min，液固比为8，精矿铝硅比最高可提升至7.55。采用收缩模型，对焙烧矿浸出过程进行动力学分析，结果表明100 g/L和200 g/L碱浓度下的反应均属于化学反应速率控制过程，反应活化能分别是59.49 kJ/mol和51.61 kJ/mol。 （2）研究发现引入少量硅酸钙作种子（0.4 g/L）以及氧化钙预先在100 g/L的碱液中水化，可以从脱硅液中诱导合成粒度分布集中在10 µm左右的锡箔状硅酸钙。实验证实，三种不同性质的硅酸钙种子对产物粒径分布的影响不同。与seed-2或者seed-3相比，反应温度在90 °C下seed-1诱导效果最好。 （3）研究发现氧化钙预先在带有0.59 g/L硅酸根的100 g/L的碱液中水化同样可以从脱硅液中制备出粒度分布集中在10 µm左右的硅酸钙产物。通过FBRM在线监测以及其他表征手段证实CaO的缓慢水化以及硅酸根的诱导反应结晶共同促进了此类产物的生成。与文献报道的造纸填料硅酸钙以及沉淀碳酸钙（PCC）相比，此类硅酸钙在保证纸张强度的情况下可以极大提高纸张的松厚度。与传统研磨碳酸钙（GCC）相比，此填料磨耗率更低。说明其具有潜在的工业应用价值。;China is pretty rich in bauxite resources but large amounts of these bauxites are consumed each year. With the increasing demand for bauxite and the depletion of high-grade bauxite resources in our country, the key to solve the significant strategic demand of bauxite is to improve the mass ratio of alumina and silica of low-grade bauxite through pre-desilication so that it can be used in Bayer process. In this paper, targeting at a typical diaspore bauxite in Henan Province (A/S = 2-3), the method of roasting and alkali leaching was adopted to effectively improve the mass ratio of alumina and silica of the minerals. The A/S of bauxite after treatment was up to 7.55. In addition, due to the high alkali concentration and complex impurities in desilication solution, the utilization of silicon in the solution is still difficult to be solved. This goal could also be achieved by seed induction and circulating alkali solution induction put forward in this paper. And a kind of calcium silicate with concentrated particle size distribution (PSD) was successfully prepared, which could be used as paper filler. The alkali solution after silicon removal can be reused in the pre-desilication process, thus realizing the green and sustainable circulation of the whole process. The achievements and innovative results are exhibited as follows:(1) For the low-grade bauxite (A/S = 2.26), it was firstly roasted at 1000 °C for 1 h, and then leached in 200 g/L alkali solution at 95 °C for 40 min with liquid-solid ratio of 8. And the highest A/S of the product was increased to 7.55. And the kinetics of the leaching process was carried out by shrinking model. The results showed that the reactions with alkali concentration of 100 g/L and 200 g/L were both controlled by chemical reaction rate. And the activation energy was 59.49 kJ/mol and 51.61 kJ/mol, respectively.(2) It was found that the foil-shaped calcium silicate with narrow PSD centered at 10 µm could be synthesized from desilication solution, by the introduction of tiny amounts of calcium silicate seed (0.4 g/L) and pre-hydration of calcium oxide in 100 g/L alkali solution. Further experiments showed that different seeds had different effects on the PSD of products. Compared with seed-2 or seed-3, seed-1 had the best induction effect at 90 °C. (3) It was found that the pre-hydration of calcium silicate in 100 g/L alkali solution with tiny amounts of silicate (0.59 g/L) could also result in the calcium silicate product with controllable PSD centered at 10 µm. The online focused beam reflectance measurement (FBRM) and other measurements showed that the calcium silicate with narrow PSD could be obtained by the combined approaches of the slow hydration of CaO and the induced reaction crystallization of silicate. Compared with larger calcium silicate and PCC, the obtained product used as paper filler could greatly improve the bulk of paper while maintaining similar tensile strength. And compared with GCC, the wear rate of this filler is lower, which shows great potential in industrial application.
|邱怡锦. 低品位铝土矿的化学预脱硅与硅的资源化利用[D]. 中国科学院大学,2020.|
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