Abstract:

Na₂S₂O₃ is the main byproduct salt in the waste liquid discharged from the wet desulfurization process. Reducing the amount of Na₂S₂O₃ is important for green production. Firstly, the key factors affecting the production of Na₂S₂O₃ were screened out by Plackett-Burman test, i.e. pH, sulfur concentration and temperature. On this basis, the response surface methodology is used to optimize the design of three factors and three levels with the production of Na₂S₂O₃ as the objective function. The results show that pH has the greatest influence on Na₂S₂O₃, followed by temperature and sulfur concentration. And the interaction between factors is small. The optimal operating conditions are pH 8.25, sulfur concentration 0.47 g/L, temperature 31.80℃, PDS concentration 90 mg/L, oxygen-sulfur ratio 1.2 mmol/mmol, and Na₂S₂O₃ production is 1.838 mmol/L. The influence of various factors is explained by the reaction kinetics from Na₂S₂O₃ and the equilibrium reaction of polysulfide ions. Finally, the actual production process was analyzed and it was found that the pH obtained by the experiment was too low, which was not conducive to the stability of the absorption process. The existing elemental sulfur melt separation method is not conducive to reducing the content of elemental sulfur in the desulfurization solution, and accelerates the formation of byproduct salts. Some suggestions for improvement are put forward and remarkable results are obtained.

Key words: desulfurization, oxidation regeneration, sodium thiosulfate, optimization, analysis

摘要：

Na₂S₂O₃是湿法脱硫过程外排废液中最主要的副盐，降低Na₂S₂O₃的生成量对绿色生产具有重要意义。首先采用Plackett-Burman实验筛选出影响Na₂S₂O₃生成量的关键因素，即pH、单质硫浓度、温度。在此基础上运用响应曲面法，以Na₂S₂O₃生成量为目标函数，进行三因素三水平的优化设计分析。研究结果表明，pH对Na₂S₂O₃的影响最大，其次是温度和单质硫浓度，因子间交互作用的影响很小。得到最优的操作条件为pH 8.25，单质硫浓度0.47 g/L，温度31.80℃，PDS浓度90 mg/L，氧硫比1.2 mmol/mmol，此时Na₂S₂O₃生成量为1.838 mmol/L。从Na₂S₂O₃反应动力学和多硫离子的平衡反应两方面对各因素的影响规律进行了解释。最后对实际生产过程进行分析，发现实验得出的pH过低，不利于吸收过程的稳定，现有单质硫熔融分离方法不利于降低脱硫液中的单质硫含量，加速了副盐的生成等问题，对此提出了改进意见，并取得了显著效果。

关键词: 脱硫, 氧化再生, 硫代硫酸钠, 优化, 分析