【作者】 徐冬；

【导师】 赵中伟； 陈爱良；

【作者基本信息】 中南大学 ， 有色金属冶金， 2011， 硕士

【摘要】 随着我国锌的需求量的增大以及硫化锌矿资源的日趋紧缺,氧化锌矿资源正逐步得到开发和利用。本文针对碱浸氧化锌矿的新工艺,对其做了部分的基础理论研究。具体内容如下：(一)研究了ZnO在不同Na20浓度下的溶解平衡时间,绘制了25℃、50℃、75℃和100℃四个温度下Na2O-ZnO-H2O体系的平衡相图,发现Na2O-ZnO-H2O体系平衡相图包括上升曲线段(左支)、最大溶解度点和下降曲线段(右支)；曲线左支平衡固相是ZnO,右支平衡固相是NaZn(OH)3; Na2O-ZnO-H2O体系在25℃、50℃、75℃和100℃低碱浓度下(Na20%<29%)的氧化锌溶解曲线相差不大,对左支体系进行稀释可以达到分离氧化锌的目的。但在较高碱浓度(Na20%>29%)时,氧化锌的溶解度随温度有较大的区别,可通过降温来实现NaZn(OH)3的提取分离。(二)研究发现100℃Na2O-ZnO-H2O体系在高碱浓度(Na20%>29%)下降温过程中析出针状NaZn(OH)3晶体；同一体系随着降温速度增加,其析晶速率增大,达到平衡需要的时间越短；降温速度越大,降到同一温度时析晶率越低；同一体系,不同降温速度达到最终温度足够长时间析晶率相等；通过四种降温速度作了非等温结晶实验,并用动力学结晶模型对其进行表征,得到三种动力学方程的参数,发现Avrami和R-t关系法适合描述非等温结晶动力学,Ozawa方程也可以得出比较好的线性关系,但不适用于描述Na2O-ZnO-H2O体系的非等温结晶动力学。(三)对Na2O-ZnO-H2O平衡体系(Na2O浓度小于29%)用水进行稀释,析出棒状的ZnO晶体；稀释倍数增大时,ZnO晶体变细,ZnO的析出率增大,而且随着稀释倍数的增大,析出率增大的幅度减少；稀释温度越高,ZnO晶体越粗,析出速度越大。(四)研究了Na2O-ZnO-H2O体系中分别添加Si02和CaO后对体系平衡的影响,发现Na2O-ZnO-SiO2-H2O体系的ZnO的最大溶解度点随着n(Na2O)/n(SiO2)的增大朝更高的Na20浓度和ZnO浓度移动,随着n(Na2O)/n(SiO2)值的增大,对应的平衡相图右支的下降幅度增大；往Na2O-ZnO-H2O体系中加入Ca(OH)2后,氧化锌在Na20浓度小于15%的氢氧化钠溶液中的溶解度降低,且这种差值随着温度的升高而缩小；CaO比Ca(OH)2对饱和锌酸钠溶液中ZnO溶解度影响更大。(五)研究发现添加CaO脱除Na2O-ZnO-SiO2-H2O体系中SiO2的效率随着CaO加入量的增大而提高,但是溶液中锌的损失率也与之俱升,1.5倍理论量的CaO加入量比较合适；CaO的除硅效果受温度影响显著,温度越高脱硅率也越高,且锌的损失率也有所下降。75℃下CaO的除硅率随着时间而迅速提高,在90分钟左右能达到较好的效果。更多还原

【Abstract】 With the increase of China’s demand of zinc source and the increasingly shortage of zinc sulfide, zinc oxide ore resources are gradually getting developed and utilized. This article carried out some basic theory research to the new of technology of zinc oxide alkaline leaching. The specific research content are as follows.1) The article investigated the dissolving balance time of ZnO in different Na2O concentration, plotted Na2O-ZnO-H2O system equilibrium diagram at 25℃,50℃,75℃and 100℃, and found Na2O-ZnO-H2O system equilibrium diagram is component of rising curve segment (the left half curve) maximum solubility point and the decline curve segment(the right half curve). The solid-phase on the left half curve of Na2O-ZnO-H2O system equilibrium diagram is ZnO while the one of the right half curve is NaZn(OH)3. There is little difference in ZnO solubility of Na2O-ZnO-H2O system among 25℃,50℃,75℃and 100℃in low alkali concentration (Na2O%< 29%) and it is possible to realize the separation of ZnO by diluting. But ZnO solubility differs quite a lot with temperature in high alkali concentration and it’s also possible to separate NaZn(OH)3 from the equilibrium system by cooling down.2) Results showed it is able to get needle-like NaZn(OH)3 crystals when Na2O-ZnO-H2O system in high alkali concentration cools down. Cooling crystallization changes with the initial alkali concentration. With the cooling rate increasing, the crystallization rate of the same system also increases and gets to equilibrium state earlier; however, when it gets to the same temperature, the crystallization ratio becomes lower, but the gap gets narrower as temperature cools down and disappears finaly at the end temperature for enough long time. Research investigated isothermal crystallization through four cooling rate experiments, characterized it with dynamics crystallization model and got 3 series dynamic parameters. Results shows Avrami and R-t methods are able to describe isothermal crystallization. Although Ozawa equation can also get good linear relation for this reaseach, it is not applicable to describe the isothermal crystallization of Na2O-ZnO-H2O system. 3) Research declared Na2O-ZnO-H2O system crystallizes virgate ZnO crystal by diluting with water. The larger the dilution factor is, the thinner ZnO crystal is and the crystallization ratio will also increase though the increasing scope decreases. As the diluting temperature goes up, ZnO crystal becomes thicker and the crystallization rate goes up too.4) Research discussed the effection of SiO2 and CaO on Na2O-ZnO-H2O system, found that the ZnO maximum solubility point of Na2O-ZnO-SiO2-H2O system moves toward higher Na2O and ZnO concentration point and the decline rate of the corresponding right half curve reduces as the n(Na2O)/n(SiO2) value grows up. After Ca(OH)2 is added to Na2O-ZnO-H2O system, ZnO solubility in alkali solution of which the Na2O concentration is under 15% reduces and the decline becomes narrow along with the temperature. Results show CaO does greater influence to ZnO solubility in Saturated zinc sodium solution than Ca(OH)2 does.5) Research showed the efficiency of CaO removing SiO2 from Na2O-ZnO-SiO2-H2O system rises with amount of CaO, but the zinc loss ratio goes up too.1.5 times of theoretical additive amount of CaO is most suitable. Desilication efficiency of CaO is remarkablely influenced by temperature:the higher, the better. Meanwhile zinc loss ratio declines. Desilication efficiency of CaO increases with time and it achieves a good result in 90 minutes or so.更多还原