Abstract:

Various harms on equipment and atmospheric environment, including low-temperature corrosion, fouling and blue plumes, can be caused by SO₃ in flue gas for a coal-fired boiler. To predict and control SO₃ concentration to meet the increasing demands for energy conservation and emission reduction, more accurate knowledge on the effect of the factors that influence SO₃ in flue gas is required. Thus, in present work, a kinetic model was built by optimizing the previously developed kinetic models. The effect of the factors that influence SO₃ in flue gas was studied by numerically calculating SO₃ concentration under different conditions. Moreover, SO₃ concentrations under the conditions mentioned above were measured using a perfectly stirred reactor measuring apparatus built in this work. It was found that SO₃ concentration was apparently affected by the factors, namely, the concentrations of SO₂, O₂ and H₂O, as well as temperature and residence time. SO₃ concentration was seemingly affected by the concentrations of CO and NO, while was less influenced by CO₂ concentration. In addition, SO₃ concentration underwent three stages of sharp increase, slow increase and gradual decrease with increasing residence time.

Key words: coal-fired boiler, reaction kinetics, experimental validation, sulfur trioxide, flue gas

摘要：

燃煤锅炉烟气中SO₃能对锅炉设备、大气环境造成包括低温腐蚀、粘污和蓝烟等一系列的危害。因而，对烟气中SO₃主要影响因素及其影响规律的研究对于预测和控制烟气中SO₃浓度以满足不断增长的节能减排标准有重要意义。基于文献中的C/H/O/N/S化学动力学模型的优化、整合建立了化学动力学模型，对烟气中SO₃主要影响因素及其影响规律进行计算研究。还基于自主设计搭建了全混流反应器测量装置，对上述计算工况中的SO₃浓度进行测量。研究发现，烟气中SO₃浓度主要受SO₂、O₂和H₂O的浓度，以及温度和反应停留时间等影响。SO₃浓度受烟气中CO、NO的影响也较为显著，但是受CO₂的影响不大。另外，随着反应停留时间的增加，烟气中SO₃浓度先后经历了3个不同阶段：急剧增加，增长趋势逐渐减缓和逐渐减少。

关键词: 燃煤锅炉, 反应动力学, 实验验证, 三氧化硫, 烟道气