【作者】 孙会兰；

【导师】 涂赣峰； 毕诗文；

【作者基本信息】 东北大学 ， 有色金属冶金， 2009， 博士

【摘要】 铝土矿和铁矿资源在我国属于紧缺资源,目前,这两种矿石储量不足的问题日益突出,而高铁铝土矿的合理综合利用可大大缓解这一问题。就当前较为合理可行的处理该矿的“烧结—高炉冶炼—提取氧化铝”工艺来看,尚存在一些问题有待于进一步完善。这些亟待解决的问题是：实际铝酸钙炉渣的氧化铝溶出率低、溶出时间长、碳碱浓度高等。基于上述问题,本文针对铝酸钙渣系的两种主要物相组成12CaO·7Al203和γ-2CaOSiO2进行了系统研究,主要研究结果如下。研究了12CaO·7Al203的合成条件及溶出性能,结果表明：当CaO:Al2O3摩尔比12：7、合成温度1773K和保温时间120min时,可得到纯度较高和氧化铝溶出率较高的12CaO·7Al203；溶出温度是影响12CaO·7Al203的氧化铝溶出性能的主要因素,其次为溶出时间和碳碱浓度,且二者的影响程度基本相同；12Ca0·7Al203的最佳溶出条件为：溶出温度363K、溶出时间120min和碳碱浓度120g·L-1,相应的氧化铝溶出率为98.69%。对1773K下保温60min以上合成的12Ca0·7Al203的微观结构和表面形貌进行了研究,利用Bragg方程和立方晶系晶格常数计算公式计算了晶格常数,通过相关公式计算了晶体的择优取向因子,采用Scherrer公式计算了平均晶粒大小和通过SEM研究了晶体的表面形貌,结果表明晶格常数随着保温时间的延长而增大,420晶面的择优取向因子随着保温时间延长而减小,平均晶粒大小不受保温时间的影响,表面形貌随着保温时间的延长逐渐出现较多和较大的孔洞结构。γ-2CaO·SiO2的自粉性和稳定性对铝酸钙炉渣溶出性能有较大影响,因此本文对γ-2CaO·SiO2的合成及其稳定性进行了研究,结果表明CaO:SiO2的摩尔比为2：1的混合物料在1773K下保温60min以上,可获得自粉良好的γ-2CaO·SiO2;γ-2CaO·SiO2在富含碳碱的铝酸钠溶液中有一定程度的分解反应,通过二次回归正交试验法得出了其分解率与碳碱浓度、分解温度、分解时间以及氧化铝浓度之间的关系式。在CaO-Al2O3-SiO2三元体系中合成了12CaO·7Al203和γ-2CaO·SiO2的混合物料,最佳合成条件为：CaO:Al2O3:SiO2摩尔比2.38：1：0.77,合成温度1773K,出炉温度373K,保温时间30min。合成产物除12CaO·7Al203和γ-2CaO·SiO2外基本不含其它物相,将该混合物料简称为CAS烧结产物。通过研究12Ca0·7Al203和γ-2CaO·SiO2的机械混合物料与CAS烧结产物的溶出性能差异,借助EDS分析,初步确定了烧结产物中12CaO·7Al203和γ-2CaO·SiO2各自以独立物相形式存在。采用二次回归正交试验法研究了CAS烧结产物的溶出性能,得出了氧化铝溶出率与溶出温度、碳碱浓度、溶出时间和液固比的关系式。通过研究CAS溶出渣的物相组成,初步探讨了溶出过程中的二次反应机理：当溶出时间较短,溶出温度和碳碱浓度(Na20C)较低时生成水化石榴石和钠硅渣；当溶出时间较长,溶出温度和碳碱浓度较高时水化石榴石被分解成钠硅渣或硅酸钙水合物。采用超声波强化溶出方式和二段溶出方式研究了12CaO·7Al2O3和CAS烧结产物的溶出性能,研究发现两种方式均可起到强化溶出的效果。达到相同的氧化铝溶出率时,单频超声波作用可降低12CaO·7A1203的溶出用液的碳碱浓度40g·L-1和溶出温度10K,双频协同的超声波作用方式可降低CAS烧结产物的溶出用液的碳碱浓度60g·L-1或溶出温度30K；采用二段溶出时,当溶出过程中的溶出时间分别为15min和20min,碳碱浓度为60g·L-1时,可使12CaO·7Al203和CAS烧结产物的氧化铝溶出率均达95%以上,并使溶出液中氧化铝含量分别升高约7g·L-1和16g·L-1。研究了12CaO·7Al203、CAS烧结产物和超声波作用下CAS烧结产物的溶出动力学,得出了各自的宏观动力学方程、表观活化能,对于CAS烧结产物及其超声波作用下的动力学还得出了频率因子、扩散方程和有效扩散系数。结果表明12Ca0·7Al203的溶出过程受表面化学反应控制,CAS烧结产物及其在超声波作用下的溶出过程受固膜内扩散控制。通过计算三个溶出过程中的表观活化能和推导溶出速率与溶出温度的关系对所得结论进行了验证。结合超声波作用前后溶液的拉曼光谱、电导率和有无超声波作用时溶出渣的表面形貌的研究,给出了超声波强化溶出的机理：超声波的作用加强了溶液中离子运动和C032-的伸缩振动和反对称伸缩振动,超声波空化作用强化了机械搅拌,阻碍了颗粒之间的团聚,促进了液固传质的进行,超声波提高了有效扩散系数,降低了反应的表观活化能,使固相扩散更顺利进行。此外,超声波也能在一定程度上抑制CAS烧结产物中γ-2CaO·SiO2的分解。更多还原

【Abstract】 Bauxite and iron ore resources are short in China, and this problem become increasingly serious. The reasonable and comprehensive utilization of high-iron bauxite will relief the problem greatly. The reasonable process to deal with the high-iron bauxite is "sintering-blast furnace smelting-alumina leaching"process, but there are some problems need to be improved, such as lowing alumina leaching ratio, long leaching time and high concentration of sodium carbonate. So this thesis studied the main phases of calcium aluminate slag,12CaO·7Al2O3 and y-2CaO·SiO2. The results are as follows.Synthesizing and leaching property of 12CaO·7Al2O3 were studied, and the results showed that 12CaO·7Al2O3 which doesn’t have other phases but has high leaching alumina ratio can be obtained under 1773K for 120min from the mixture of CaO:Al2O3=12:7(mol ratio). The main factor which affect alumina leaching ratio is leaching temperature and the next two are leaching time and sodium carbonate concentration, what’s more, the degree of the two factors’ effects are similar. The optimum conditions for leaching 12CaO·7Al2O3 are leaching temperature 363K, leaching time 120min and sodium carbonate concentration 120 g·L-1, the alumina leaching ratio that obtained under these conditions is 98.69%.Micro-structure and surface morphology of 12CaO·7Al2O3 synthesized under 1773K during more than 60min were researched. Bragg equation and calculating formula of lattice constant in cubic system were used to calculate the lattice constants. Related formula was used to calculate crystal’s preferred orientation factor. Scherrer formula was used to calculate the average grain size. SEM was used to study crystal’s surface morphology. The results are: lattice constants increase, preferred orientation factors of 420 crystal face decrease and surfaces appear more and bigger lacunal structure as holding time become longer. But the average grain sizes don’t change with holding time.The self-disintegrating property and stability ofγ-2CaO·SiO2 are important to leaching property of calcium aluminate slag, so the synthesizing and stability of it were studied. The results showed thatγ-2CaO·SiO2 which has better self-disintegrating property can be obtained under 1773K for more than 60min from mixture of CaO:SiO2=2:1(mol ratio). y-2CaO·SiO2 will react in sodium aluminate solution which is rich in sodium carbonate and the relationship between decomposition ratio and sodium carbonate concentration, temperature, time and alumina concentration was obtained.The mixture of 12CaO·7Al2O3 and y-2CaO·SiO2 were obtained from CaO-Al2O3-SiO2 system. The optimal conditions for synthesizing are CaO:Al2O3:SiO2=2.38:1:0.77(mol ratio), synthesizing temperature 1773K, tapping temperature 373K and holding time 30min. The product doesn’t have other phases except 12CaO·7Al2O3 and y-2CaO·SiO2, and this mixture is called CAS sinter for short.12CaO·7Al2O3 and y-2CaO·SiO2 in CAS sinter were proved to be self-existent in basically by comparison of mechanically mixed mixture of 12CaO·7Al2O3 and y-2CaO·SiO2 and CAS sinter with the assistant of EDS. Relationship equation between alumina leaching ratio and leaching temperature, sodium carbonate concentration, leaching time and solid to liquid ratio was obtained by quadratic regression orthogonal method to study the leaching property of CAS sinter. Secondary reaction mechanism was also preliminary discussed by the phase research of slag after leaching. The research showed that the products are hydro-garnet and sodium-silicon residue when leaching time is short, leaching temperature and Na2Oc are low and that the hydro-garnet will transform to sodium-silicon residue and hydrate-calcium-silicate as leaching time become longer, temperature and Na2Oc become higher.Ultrasonic wave and two-stage leaching method were used to enhance leaching property of 12CaO·7Al2O3 and CAS sinter, and the results showed that both the two method are effective. When leaching time in the two-stage leaching method are 15min and 20min respectively and Na2Oc 60 g·L-1, the alumina leaching ratio of both 12CaO·7Al2O3 and CAS sinter can reach above 95% and alumina concentration in solution after leaching will be increased by about 7g·L-1and 16g·L-1. Na2Oc in the solution to leach 12CaO·7Al2O3 can be reduce by 40 g·L-1 and the temperature can be reduced by 10K with the action of single frequency ultrasonic wave, but 60 g·L-1 and 40K will be reduced by under double frequency collaborative ultrasonic wave when alumina leaching ratio is the same with the traditional method.Leaching dynamics of 12CaO·7Al2O3 and CAS sinter both with and without ultrasonic wave were researched. Macro-kinetics equation and apparent active energy were obtained. As to CAS sinter’s leaching dynamics both with and without ultrasonic wave, frequency factors, diffusion equations and effective diffusion coefficients were also obtained. The results showed that 12CaO·7Al2O3’s leaching is controlled by surface chemical reaction, CAS sinter’s leaching both with and without ultrasonic wave are controlled by solid film inter diffusion.The conclusion was validated by calculation of apparent active energy and derivation of leaching ratio and temperature.The mechanism of enhancement of ultrasonic wave was concluded with the assistant of Raman spectra, conductivity research before and after ultrasonic wave and surface appearance (SEM) both with and without ultrasonic wave. The mechanism can be described as follows: irons’ movement and CO32-’s stretching vibration and stretch vibration are enhanced, mechanical stirring was strengthened so that agglomeration of grains was hindered to promote transformation between liquid and solid, effective diffusion coefficient was increased and apparent active energy was reduced to facilitate solid diffusion in dynamics. Besides, decomposing of y-2CaO·SiO2 in CAS sinter is inhibited by little degree.更多还原