The Optimum Conditions Of Vacumm Distillation To Recover Sulfur From Lead-Zinc Tailings And Modeling

Sulfur is a critical industrial material. Recycling Sulfur from wet metallurgical slag can effectively alleviate the constraint of sulfur productivity on economy development. Compared with many other recycling methods, vacuum distillation is safe, efficient, pollution-free, and capable of accumulating noble metal from slag. However, most current researches focus on a single factor in vacuum distillation. The practical distillation process can be affected by many factors which constrains the extensive industrial applications of vacuum distillation. In this thesis, basing on the study of the influence of single impact factor on extracting sulfur from lead-zinc tailings by vacuum distillation, the influence of main factors the optimal technological condition combination were deducted by orthogonal experiments. The empirical mathematical model for recycling sulfur by vacuum distillation method was formulated. The main contributions include:1. In the single factor experiment, the influences of vacuum degree, slag particle size, time, extraction rate, distillation area, and slag amount on sulfur evaporating rate were examined respectively. Under certain conditions, the amount of evaporated sulfur increased with the growth of any single factor following the similar trend. In the experiment, under preferable distillation condition, the sulfur evaporating rate can reach over98%. The purity of the obtained sulfur product can reach over99%.2. The characterization results of x-ray fluorescence spectroscopy analysis, XRD and SEM before and slag distillation show that:The main component before reaction is elemental sulfur. Yet the characteristic diffraction peak of sulfur in the slag after distillation is disappeared. The emergent primary diffraction peaks belong to PbFe(SO4)4(OH)12、ZnSO4、FeS2、SiO2. This result indicates that:the remaining slag is a mixture of the afore mentioned substances and the elemental sulfur barely exists in it; Most of the particle sizes of the slag before distillation are over10μm and have smooth surfaces. The SEM image of slag sample after distillation shows coarse surface and particles with different sizes mostly under2μm and distinct shapes. This indirectly demonstrates that the sulfur in the slag has been totally distilled. 3. The result of orthogonal experiment and the analysis of primary and secondary factors denote that, in the four factors affecting the sulfur amount distilled from vacuum distillation, the order of influence is:reaction temperature> reaction time> extraction rate> mass of material. From the analysis of orthogonal experiment, the optimal technological condition combination is:the extraction rate of2L/S, the reaction temperature of300°C, the reaction time of35min and the material mass of30g. These conditions are verified by complementary experiment.4. Based on the experimental data above, and according to the growth mathematical model, we generalized the mathematical model for recycling sulfur by vacuum distillation method:y=(M×m)/(1+10k1+k2t). To prove the accuracy of the model prediction, we designed an experiment under the condition of the temperature280°C, the extraction rate2L/S, the material mass30g and the changeable reaction time. The calculation result of this model is identical with the experiment outcome. Therefore this model can predict the amount of sulfur distilled under given material amount, temperature and time.